Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The effects of hydrocarbon reactions and diamond precipitation on the internal structure and evolution of icy giant planets such as Neptune and Uranus have been discussed for more than three decades. Inside these celestial bodies, simple hydrocarbons such as methane, which are highly abundant in the atmospheres, are believed to undergo structural transitions that release hydrogen from deeper layers and may lead to compact stratified cores. Indeed, from the surface towards the core, the isentropes of Uranus and Neptune intersect a temperature–pressure regime in which methane first transforms into a mixture of hydrocarbon polymers, whereas, in deeper layers, a phase separation into diamond and hydrogen may be possible. Here we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene, PET ant PMMA samples dynamically compressed to conditions around 150 GPa and 5,000 K; these conditions resemble the environment around 10,000 km below the surfaces of Neptune and Uranus. Our findings demonstrate the necessity of high pressures for initiating carbon–hydrogen separation and imply that diamond precipitation may require pressures about ten times as high as previously indicated by static compression experiments. Our results will inform mass–radius relationships of carbon-bearing exoplanets, provide constraints for their internal layer structure and improve evolutionary models of Uranus and Neptune, in which carbon–hydrogen separation could influence the convective heat transport. In addition to their relevance for planetary modelling, by showing the formation of diamonds that are possibly a few nanometers in size from laser-irradiated plastic, our results may identify a new method to produce diamond nanoparticles for material science and industrial applications.

*We acknowledge support by the U.S. DOE under awards DE-FG52-10NA29649 and DE-NA0001859 as well as the Helmholtz Association under award VH-NG-1141.

High-energy laser systems can be used to mimic extreme states of matter, as found in the interior of various celestial bodies, in the laboratory. Combining such laser systems with extremely bright X-ray sources, particularly X-ray free electron lasers (XFELs), allows for studying exotic physical processes in real-time. This includes high-pressure phase separation reactions, such as diamond precipitation from liquid hydrocarbons, which has been predicted to happen deep inside Neptune and Uranus, and many other interesting phenomena.

At the Linac Coherent Light Source (LCLS), we obtained experimental results from hydrocarbon samples that were laser-compressed to the extreme pressure and temperature conditions found in the deep interiors of such ‘icy’ giant planets [1]. The extreme brightness of the XFEL source enables unprecedented in situ snapshots of the induced chemical reactions and shows that diamond nucleation is initiated on sub-nanosecond timescales at ~150 GPa and ~5000 K. Combining several X-ray and optical diagnostic methods, we obtain high-quality constraints for theoretical models of the involved physical processes: X-ray diffraction records the formation of solid diamond structures, Small angle X-ray scattering determines the size distribution of the growing nanodiamonds while spectrally resolved X-ray scattering provides an absolute scale for the diffraction pattern giving the absolute amount of the reacting material that undergoes species separation. Optical velocimetry is used to characterize and optimize the laser-driven compression waves and optical reflectometry indicates that the isolated hydrogen produced by the phase separation reaction is in a metallic state. All these diagnostics can be used with single-shot quality in the same experiment and provide unprecedented insights into the nanosecond kinetics of chemical reactions at extreme pressures and temperatures.

Besides underlining the general importance of chemical processes inside giant planets, our results
will inform mass-radius relationships of carbon-bearing exoplanets, provide constraints for their internal layer structure and improve evolutionary models of Uranus and Neptune, where carbon-hydrogen separation could significantly influence the convective heat transport. Finally, our experiments may identify a new method to produce diamond nanoparticles for material science and
industrial applications.

[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017)

The paper reports on first attempts to prove the concept of Single Plane Compton Imaging (SPCI), recently proposed on the basis of simulations, in practice. SPCI combines electronic collimation as known from conventional Compton cameras with a much simpler detector design: Multiple scintillator pixels are arranged alongside in a single detection plane. Imaging information is encoded in a set of ‘conditional’ spectra meaning energy deposition distributions in single pixels obliged with the condition of a coincident detection in another (adjacent) pixel. The activity distribution is iteratively reconstructed from the measured projections (the bin contents of the conditional spectra) by using Maximum Likelihood Expectation Maximization (MLEM) algorithms.
This concept has been approached experimentally with two distinct setups addressing the application fields of radionuclide imaging in nuclear medicine, and of prompt-gamma based range verification in radiooncology with proton beams. The first setup consists of a 4×4 array of about 7 × 7 × 20 mm3 GAGG scintillator pixels read out with a Philips STEK module comprising 4×4 digital silicon photomultiplier dies. Data were taken with radioactive point sources arranged in few-cm distance from the scintillator pixels. The second setup consists of much larger monolithic cerium bromide scintillation detectors arranged head-to-head in pairs. Those were exposed to prompt gamma radiation produced by a 90 MeV proton beam in a beam-stopping polymethyl acrylate (PMMA) target. Though data analyses are not yet finished, the effects enabling imaging are clearly visible. Preliminary plots exemplify the applicability of SPCI in both applications. The experimental activities have been closely accompanied with appropriate modeling using the Geant4 toolkit

Timing resolution in time-of-flight (TOF) PET is known to be to a different extend count-rate dependent, while using the actual timing resolution during TOF-PET image reconstruction is crucial for achieving high contrast recovery. However, a count-rate dependent TOF-resolution calibration procedure is usually not provided by the vendor. We therefore developed such a procedure which is compatible with clinical routine and is also applicable retrospectively to existing data.

We propose a novel Maximum-Likelihood Timing Resolution Estimation algorithm that maximizes likelihood by updating activity image and TOF-kernel width alternately. For activity update TOF-MLEM was used and quadratic surrogate based maximization of the likelihood was performed to update timing resolution.

The algorithm was integrated into our previously developed reconstruction tool THOR, see ref. (1), and evaluated using the Philips Ingenuity TF PET/MR scanner and phantom and patient studies covering a large range of count-rates. Studies were grouped by imaging protocol ("brain" and "whole-body", covering different transaxial fields of view). Within each group a linear dependency of timing resolution on count-rate was observed which is in correspondence with reports by other groups. The timing resolution degradation value approaches 150 ps (~25% of initial TOF-kernel width) for clinical relevant count-rates. No difference in estimated timing resolution between the study groups was encountered.

Our preliminary results indicate that the proposed algorithm is capable of realistic timing resolution estimation. The timing resolution of the Philips Ingenuity TF PET/MR degrades rapidly with count-rate. This should be accounted for during image reconstruction.

(1) A. Lougovski, F. Hofheinz, J. Maus, et al., Physics in Medicine and Biology 59(3), 561 (2014)

In order to determine the cross section of the ¹²C(α,γ)¹⁶O reaction at astrophysically relevant energies, an accelerator with a stable and intensive ¹²C ion beam in an ultra low background environment is needed. For this purpose a 134-MC-SNICS cesium sputter ion source is going to be part of the Felsenkeller shallow underground accelerator facility. To determine the characteristics of this ion source overground tests were undertaken at HZDR. The contribution will report on long time measurements of the ion current and the beam emittance.

Due to modern society’s high demand for raw materials and the gradual depletion of low-cost mineral ores, mineral exploration campaigns and geological mapping increasingly require the development of sustainable, cost-efficient and easily applicable methods. Sustainability is a critical issue especially for exploration in Arctic regions with their unique and sensitive ecosystems. This study validates the potential of a newly developed multi-source and multi-scale remote sensing approach and will showcase how spectral imaging supports less invasive geological exploration work. Our workflow brings traditional 2D hyperspectral data into the third dimension with the help of SfM-MVS (Structure from Motion-Multi View Stereo) derived pointclouds, which provide a basis for evaluation of material properties and geological structures in a geometrically accurate virtual environment. This approach can be used to guide the geologist in the field and thus decreases the geologist’s personal risk in the field, is less invasive than traditional mapping and may even reduce the number of required boreholes. The case study area is located in Central West Greenland and hosts the Black Angel Pb-Zn deposit. Central West Greenland is characterized by Arctic climate conditions and alpine terrain, which prevents the growth of vegetation, but makes access for field campaigns extremely difficult. Thus, a ground-based hyperspectral imaging system was employed to highlight small mineralogical differences in rocks that cannot be recognised in traditional RGB images and associated photogeological models. Based on well-defined absorption features of the carbonates within the Shortwave-Infrared (SWIR; 970–2500 nm), the marbles of the Paleoproterozoic Mârmorilik Formation can be divided into calcite- and dolomite-rich units. As a result, previously unknown deformation structures (faults and folds) and lithological boundaries within the apparently homogeneous marbles are clearly revealed. Additional mineral mapping procedures such as Spectral Feature Fitting highlight gypsum occurrences related to deformation and ore emplacement. The lithological boundaries and tectonic structures extracted from the hyperspectral 3D surface model are then extrapolated into the subsurface using existing well data. The proposed workflow is fast, efficient, and fully validated and should be considered as a viable alternative to traditional techniques in exploration mapping.

Für die Auswertung und das Zusammenführen mehrerer Messungen eines Myonenteleskops wurde eine Software entwickelt. Diese wurde benutzt, um zwei Messreihen am Helmholtz-Zentrum Dresden-Rossendorf zu analysieren. Dabei wurde unter anderem die Polarwinkelabhängigkeit des Myonenflusses bestätigt.
Nachfolgend wurden Messungen in den Stollen des Felsenkellers durchgeführt. Hier wurde an mehreren Positionen in den Stollen 4, 8 und 9 gemessen. Auffälligkeiten im Myonenfluss der oberen Hemisphäre wurden analysiert und im Falle eines Standortes mit früheren Messungen und einer Simulation verglichen, wobei sich eine starke Diskrepanz zu den in dieser Arbeit gewonnenen Messergebnissen zeigte. Auch die Abhängigkeiten des Myonenflusses vom Polarwinkel und der Atmosphärentemperatur wurden betrachtet.

Sedimentary facies exert a primary control on sandstone diagenesis and reservoir quality. The Namib Sand Sea with its Sossusvlei playa-lake is often considered as a modern analogue for sandstone reservoirs. Remote sensing in combination with ground observations allowed us to map the facies distribution pattern of associated fluvial and aeolian sediments. Laboratory spectral signature measurements were used to further improve the separability of six major facies: modern aeolian sand, bypass surface, mud pool/mud drapes, heavy mineral lag, aeolian reworked and fossil dune remnant. Using a supervised classification algorithm trained by field observations, a combination of Principal Component Analysis, band ratios, texture and geomorphologic indices has shown the best result. This made it possible to create a map outlining the facies distribution pattern of the Sossusvlei area at a scale of 1:10 000. We propose this as a possible workflow to efficiently map and monitor desert environments and to investigate the interplay of aeolian and fluvial sediments, including their linked implications on diagenesis. This could improve paleoclimate modelling and even allow facies mapping on other planets.

Experimental results were obtained at the Mini-LIMMCAST facility [1], an experimental setup to model continuous casting of steel operated continuously as a loop with the cold liquid metal alloy GaInSn. The setup consists of a round mould with an inner diameter of 80 mm, representing a mould used in industrial bloom casting in a scale of 1:3. A mould-electromagnetic-stirrer (M-EMS) generated a rotating magnetic field (RMF) with different magnetic flux densities. Velocity profiles inside the mould were measured by Ultrasound Doppler Velocimetry (UDV). The experiments revealed an unexpected behaviour of the submerged jet: for medium magnetic field strengths of the RMF it can be observed, that the jet stops circling and stays at one position in the mould, bearing the risk of breakout due to continuous impingement of superheated material to one position of the solidified shell.

Ziel/Aim:

Die Asphärizität (ASP) des Somatostatinrezeptors kann bei Patienten mit GEP-NEN zur prätherapeutischen Prognoseabschätzung vor Lu-177-DOTATATE-Peptidrezeptor-Radionuklidtherapie (PRRT) herangezogen werden [1, 2]. Ziel der Studie war es, die Korrelation zwischen der intratherapeutisch mittels SPECT/CT bestimmten ASP und dem Ki-67 Index zu überprüfen.

Methodik/Methods:

Retrospektive Analyse von 31 Patienten (m=19; w=12; medianes Alter 72,6 [45-87] Jahre) mit einer GEP-NEN. Die ASP wurde läsionsbasiert aus SPECT/CT-Daten im Rahmen einer Dosimetrie (24h p.i.) im 1. Zyklus der PRRT erhoben. Der Ki-67 Index (Median 4; Spannweite 1-20) wurde mittels Stanzbiopsie oder chirurgischer Sicherung bestimmt. Spearmans-Rangkorrelationskoeffizient rho sowie Bland-Altman-Diagramme wurden zur statistischen Auswertung verwendet, als Konkordanz wurde eine Abweichung von <=5% definiert.

Ergebnisse/Results:

Insgesamt wurden 62 hepatische Läsionen analysiert. Der Ki-67 Index wurde histologisch aus dem Primarius (n=22) oder aus hepatischen Läsionen (n=9) ermittelt. Die G1-Tumorläsionen zeigten eine mediane ASP von 2,2% (IQR: 1,1-5,2) und die G2-Läsionen eine mediane ASP von 2,8 (IQR: 0,78-6,0; p>0,05). Der Korrelationskoeffizient betrug rho=0,51 (p<0,01). Die mittlere absolute Differenz zwischen ASP und Ki-67 Index betrug 0,66 (95% Limits of Agreement, -9,2–10,5). Hierbei verhielten sich 4/62 Läsionen diskordant.

Schlussfolgerungen/Conclusions:

Es zeigte sich eine signifikante Korrelation zwischen dem Anstieg des Ki-67 Index sowie dem Anstieg der ASP der Somatostatinrezeptorverteilung, welche somit ein Prädiktor für eine Entdifferenzierung von GEP-NEN darstellen könnte. Eine Klassifizierung der NEN in G1 oder G2 war durch die ASP jedoch nicht möglich.

Ziel/Aim:

In der Bildgebung von gastroenteropankreatischen NEN (GEP-NEN) kann die Heterogenität der Somatostinrezeptorverteilung als prognostischer Parameter vor einer PRRT herangezogen werden [1, 2]. Ziel der Studie war die Validierung der Asphärizität (ASP) zur prätherapeutischen Prognoseabschätzung mittels In-111-DTPA-Octreotid-SPECT/CT (OctreoScan®) in Korrelation zum intratherapeutischem SPECT/CT bei Lu-177-DOTATATE-Peptidrezeptor-Radionuklidtherapie (PRRT).

Methodik/Methods:

Retrospektive Analyse von 20 Patienten (m=14; w=6; medianes Alter, 72,6 [54-87] Jahre) mit einer GEP-NEN. Die ASP wurde läsionsbasiert im OctreoScan® (ASPIn) und im Rahmen der Dosimetrie (24h p.i.) im 1. Zyklus der PRRT (ASPLu) bestimmt. Die Korrelation wurde mittels Spearmans-Rangkorrelationskoeffizient rho verglichen und die Übereinstimmung mit Bland-Altman-Diagrammen ermittelt. Konkordanz lag bei einer Abweichung von <=5% vor.

Ergebnisse/Results:

Insgesamt wurden 77 Läsionen (Leber: n=60, Lymphknoten: n=11, Knochen: n=4, Pankreas: n=2) analysiert. Läsionen mit hoher ASP zeigten ein signifikant schlechteres Ansprechen auf eine PRRT. Der optimale Schwellenwert lag für die ASPIn bei <5,12% (Sensitivität 90% und Spezifität 93%) und für die ASPLu bei <5,02% (Sensitivität 92% und Spezifität 89%). Der Korrelationskoeffizient betrug rho=0,72 (p<0,01). Die mittlere absolute Differenz zwischen ASPIn und ASPLu betrug -0,04 (95% Limits of Agreement, -6,1–6,0). 10/77 Läsionen (7/60 Leber, 1/10 Lymphknoten, 2/6 Sonstige) verhielten sich diskordant.

Schlussfolgerungen/Conclusions:

Trotz unterschiedlichem Rezeptoraffinitätsprofil und anderem Radionuklid zeigt die prä-/intratherapeutische Asphärizität auf Basis der Rezeptorexpression eine hohe Korrelation. Dies unterstreicht den Stellenwert der prätherapeutischen ASP in der Prädiktion des Ansprechens auf eine PRRT und sollte als weiteres Kriterium für die Patientenauswahl prospektiv validiert werden.

Standardized treatment in pediatric patients with Hodgkin’s lymphoma (HL) follows risk stratification by tumor stage, erythrocyte sedimentation rate and tumor bulk. We aimed to identify quantitative parameters from pretherapeutic FDG-PET to assist prediction of response to induction chemotherapy.

Methodik/Methods:

Retrospective analysis in 50 children with HL (f:18; m:32; median age, 14.8 [4-18] a) consecutively treated according to EuroNet-PHL-C1 (n=42) or -C2 treatment protocol (n=8). Total metabolic tumor volume (MTV) in pretherapeutic FDG-PET was defined using a semi-automated, background adapted threshold. Metabolic (SUVmax/mean/peak, total lesion glycolysis [MTV*SUVmean]) and heterogeneity parameters (asphericity [ASP], entropy, contrast, local homogeneity, energy, and cumulative SUV-volume histograms) were derived. Early response assessment (ERA) was performed after 2 cycles of induction chemotherapy according to treatment protocol and verified by reference rating. Prediction of inadequate response (IR) in ERA was based on ROC analysis separated by stage 1/2 (1 and 26 patients) and stage 3/4 disease (7 and 16 patients) or treatment group/level (TG/TL) 1 to 3.

Ergebnisse/Results:

IR was seen in 28/50 patients (TG/TL1, 6/12 patients; TG/TL2, 10/17; TG/TL3, 12/21). Among all PET parameters, MTV best predicted IR; ASP was the best heterogeneity parameter. AUC of MTV was 0.84 (95%-confidence interval, 0.69-0.99) in stage 1/2 and 0.86 (0.7-1.0) in stage 3/4. In patients of TG/TL1, AUC of MTV was 0.92 (0.74-1.0); in TG/TL2 0.71 (0.44-0.99), and in TG/TL3 0.85 (0.69-1.0). Patients with high vs. low MTV had IR in 86 vs. 0% in TG/TL1, 80 vs. 29% in TG/TL2, and 90 vs. 27% in TG/TL3 (cut-off, >80 ml, >160 ml, >410 ml).

Schlussfolgerungen/Conclusions:

In this explorative study, high total MTV best predicted inadequate response to induction therapy in pediatric HL of all pretherapeutic FDG-PET parameters – in both low and high tumor stages as well as the 3 different TG/TL.

Ziel/Aim:

Ziel der retrospektiven Studie war die Evaluation der prognostischen Relevanz der FDG-PET/CT-basierten Biomarker maximaler und mittlerer SUV (SUVmax, SUVmean), metabolisches Tumorvolumen (MTV) und total lesion glycolysis (TLG) im Primarius bei Erstdiagnose eines oralen Plattenepithelkarzinoms (OSSC). Der Einfluss auf das Gesamtüberleben (OS) wurde mit etablierten Prognoseparametern verglichen.

Methodik/Methods:

Einschluss von 127 Patienten mit zwischen 2006 und 2013 bioptisch gesichertem OSCC und präoperativer FDG-PET/CT (3 MBq/kg Körpergewicht, Start 60 min p.i., Biograph 16, Siemens). Messung von SUVmax, SUVmean, MTV (Schwellenwert: 41% SUVmax) und TLG im Primarius mittels ROVER (ABX, Radebeul). Berechnung des OS nach Kaplan-Meier. Analyse prognostischer Parameter mit uni-/multivariater Cox-Regression.

Ergebnisse/Results:

In der Nachbeobachtung starben 52 (41%) der Patienten (Status aller Patienten über mindestens 36 Monate bekannt). Das mediane OS war länger bei geringerem MTV (≤5,3 ml: >95 Monate; >5,3 ml: 59 Monate; p=0,006) oder TLG (≤38,7 g: 95 Monate; >38,7 g: 47 Monate; p<0,001). SUVmax und SUVmean hatten keinen Einfluss auf das OS (p>0,05). Die univariate Cox-Regression identifizierte MTV (Hazard Ratio [HR]=2,260, p=0,005), TLG (HR=2,808, p=0,001), Lymphknoten (LK)-Status (HR=2,234, p=0,005) und UICC-Stadium (HR=2,095, p=0,021) als Prognosefaktoren, nicht jedoch Geschlecht, Alter (>60 J), oder Tabak-/Alkoholabusus. Multivariat erwiesen sich nur MTV (HR=1,991, p=0,019) und TLG (HR=2,808, p=0,001) als unabhängige Prognosefaktoren.

Schlussfolgerungen/Conclusions:

MTV und TLG des Primarius sind Prognosefaktoren für das OS bei Patienten mit Erstdiagnose eines OSCC. TLG ist der stärkste unabhängige Prognosefaktor für das OS und übertrifft etablierte klinische Parameter.

Ziel/Aim:

Estimation of tumor load in multiple myeloma (MM) is challenging. The biomarker ß2 microglobulin (ß2M) is widely used to estimate myeloma cell mass and prognosis, but serum levels are influenced by a variety of factors such as varying secretion by myeloma cell clones and renal function. High serum levels of lactic dehydrogenase (LDH) have been shown to identify high-grade lymphoma-like myeloma. PET/CT is a useful tool for assessment of MM, particularly by identifying prognostically relevant, metabolically active disease.Aim of this study was to further characterize the association between whole-body metabolic tumor burden and serum markers in MM.

Methodik/Methods:

We retrospectively recruited 31 patients (55.7± 9.2 y) who had underwent whole-body FDG PET/CT (48 scans) for assessment of relapse or progressive disease after hematopoietic stem cell transplantation. Patients with at least one FDG-positive lesion were included. Metabolic tumor burden (MTV) was determined using an automatic segmentation algorithm (Rover ABX GmbH), and was tested for correlation with serum ß2M (primary hypothesis) as well as with LDH, albumin, creatinine, calcium and gamma globulin (explorative tests).

Ergebnisse/Results:

Median metabolic tumor burden was 71.4ml (range: 5-1318ml). ß2M did not demonstrate a significant correlation with metabolic tumor burden (Spearman rho=0.070, p=0.649). PET-defined myeloma burden was significantly correlated with LDH (rho=0.388, p=0.006). There was a tendency towards correlation with albumin (rho=-0.270, p=0.063). None of the other serum markers correlated with MTV.

Schlussfolgerungen/Conclusions:

PET-defined tumor burden provides incremental information over ß2M. FDG-uptake and ß2M define only partly overlapping measures of myeloma cell mass. PET may preferably identify high-grade lymphoma-like myeloma.

Ziel/Aim:

Accurate calibration is a prerequisite for SUV quantification in PET and usually performed via phantom measurements. However, such a calibration is only valid for the used phantom since attenuation and scatter correction limitations affect quantification accuracy (QA) in-vivo. In recent studies in-vivo QA was assessed using bladder image vs. urine samples comparisons and showed a systematic underestimate of SUVs when relying on phantom-based calibration. A notable disadvantage of this approach is that it requires additional effort, making it unattractive for clinical use. The goal of this work was evaluation of an alternative method utilizing image-derived arterial blood SUVs (BSUV) averaged over a sufficiently large number of subjects.

Methodik/Methods:

We analyzed 681 patient scans from 3 sites which underwent routine 18F-FDG PET/CT or PET/MR. BSUVs were determined in the descending aorta using a roughly cylindrical ROI (delineated in the attenuation image and spatially transferred to PET). Minimum ROI volume was 5 ml and a safety margin used to avoid partial volume effects. Mean BSUVs, standard deviation (SD), and standard error of the mean (SEM) were computed for subgroups corresponding to 3 scanner calibrations of each site (9 subgroups, n=54-100). Intra- and inter-site variability was computed.

Ergebnisse/Results:

Relative SD (SEM) of BSUV in the subgroups ranged 14.3%–20.7% (2.8%–4.8%). BSUV-differences between intra-site groups were 1.8%–6.4% and mostly (5/6) insignificant. Inter-site BSUV-differences were significant and much larger (12.6%–25.1%, P<0.001).

Schlussfolgerungen/Conclusions:

Due to low inter-site BSUV-variability, group-averages can be computed with high statistical accuracy (<5%) in groups of ~70 patients and used for comparison of relative in-vivo QA. For multi-center trials this method can reveal inter-site differences at the 10% level and might even be used to calibrate image data between sites.

Aim: Accurate calibration is a prerequisite for SUV quantification in PET and usually performed via phantom measurements. However, such a calibration is only valid for the used phantom since attenuation and scatter correction limitations affect quantification accuracy (QA) in-vivo. In recent studies in-vivo QA was assessed using bladder image vs. urine samples comparisons and showed a systematic underestimate of SUVs when relying on phantom-based calibration. A notable disadvantage of this approach is that it requires additional effort, making it unattractive for clinical use. The goal of this work was evaluation of an alternative method utilizing image-derived arterial blood SUVs (BSUV) averaged over a sufficiently large number of subjects.

Methods: We analyzed 681 patient scans from 3 sites which underwent routine 18F-FDG PET/CT or PET/MR. BSUVs were determined in the descending aorta using a roughly cylindrical ROI (delineated in the attenuation image and spatially transferred to PET). Minimum ROI volume was 5 mL and a safety margin used to avoid partial volume effects. Mean BSUVs, standard deviation (SD), and standard error of the mean (SEM) were computed for subgroups corresponding to 3 scanner calibrations of each site (9 subgroups, n=54–100). Intra- and inter-site variability was computed.

Results: Relative SD (SEM) of BSUV in the subgroups ranged 14.3%–20.7% (2.8%–4.8%). BSUV-differences between intra-site groups were 1.8%–6.4% and mostly (5/6) insignificant. Inter-site BSUV-differences were significant and much larger (12.6%–25.1%, P<0.001).

Conclusions: Due to low inter-site BSUV-variability, group-averages can be computed with high statistical accuracy (<5%) in groups of ~70 patients and used for comparison of relative in-vivo QA. For multi-center trials this method can reveal inter-site differences at the 10% level and might even be used to calibrate image data between sites.

The reality of the development of scientific software is often far from the clearly structured, cascading work packages that grant applications require, but rather in the spirit of agile programming: Start from a working minimal prototype, always have running code, work in sprints (typically towards the end of reporting periods). Those characteristics actually match rather well onto the concept of agile programming. This talk will explain the principles of agile software development, the exisiting software tool support using the free-of-charge GitLab Libre Edition as an example, and the implementation of the processes, including team communication, continuous integration and publication of documentation.

This talk will give an overview of high energy density (HED) researches in the frame of Helmholtz International Beamline for Extreme Fields (HiBEF) project leading by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The HiBEF user consortium is aiming to contribute and operate different experimental setups at the HED beamline of the European XFEL with worldwide unique ultrashort and extremely bright X-ray flashes.
Three main kinds of HED experiments including relativistic laser solid targets interactions to understand the plasma heating and ionization dynamics, high energy long pulse laser shocked warm dense matters to understand the stellar structures, intense XFEL-matter interactions to understand the effect of crystal structure on the rapidly melting and heating process performed by our group at LCLS and SACLA will be reviewed in this talk. All these experiments take advantages of the ultra-short and intense coherent XFEL beam as a probe to achieve nanometer and femtosecond resolutions simultaneously. Furthermore, to design and under the HED experiments, we will also present the theoretical and simulation studies based on the particle-in-cell (PIC) code, atomic collisional- radiative code and density function theory (DFT) code.

In this paper, we report the magnetic and electrical properties of Mn implanted nearly intrinsic Si wafers after subsecond thermal treatment. Activation of acceptors is realized in pulsed laser annealing (PLA) films with a free hole concentration of 6.29  ×  10^20 cm−3 while the sample annealed by rapid thermal annealing (RTA) shows n-type conductivity with a much smaller free electron concentration in the order of 10^15 cm−3. Ferromagnetism is probed for all films by a SQUID magnetometer at low temperatures. The formation of ferromagnetic MnSi1.7 nanoparticles which was proven in RTA films can be excluded in Mn implanted Si annealed by PLA.

On the basis of a pyrazine core structure, three new adenosine A2B receptor ligands (7a – 7c) were synthesized containing a 2-fluoropyridine moiety suitable for 18F-labeling. Compound 7a was docked into a homology model of the A2B receptor based on X-ray structures of the related A2A receptor, and its interactions with the adenosine binding site were rationalized. Binding affinity data were determined at the four human adenosine receptor subtypes. Despite a rather low selectivity regarding the A1 receptor, 7a was radiolabeled as the most suitable candidate (Ki(A2B) = 4.24 nM) in order to perform in vivo studies with the aim to estimate fundamental pharmacokinetic characteristics of the compound class. Organ distribution studies and a single PET study demonstrated brain uptake of [18F]7a with a standardized uptake value (SUV) of ≈1 at 5 min post injection followed by a fast wash out. Metabolism studies of [18F]7a in mice revealed the formation of a blood-brain barrier penetrable radiometabolite, which could be structurally identified. The results of this study provide an important basis for the design of new derivatives with improved binding properties and metabolic stability in vivo.

The classical constant deflection rate Small Punch (SP) test is a miniature technique that can provide estimates on the material tensile properties. Linear correlations are usually used for relating the maximum force and displacement at maximum force, recorded during the SP test, to the ultimate tensile strength. Fitting coefficients used in the correlations are calibrated on data from flat SP specimens. SP test requires only a small amount of testing material which represents a clear benefit when irradiated samples have to be tested. Therefore, there is a considerable interest in using SP for testing fuel cladding material properties. In this work we show that the same correlation equations, albeit with adjusted fitting coefficients, can be used to estimate the ultimate tensile strength from tube SP specimens. The calculated fitting coefficients lead to reasonable estimates of the ultimate tensile strength at temperatures of up to 650oC although the coefficients themselves have been computed at the room temperature. The coefficients are more suited for assessing ductile materials as the models used for computing the coefficients do not account for damage/cracking, observed during the SP tests of brittle material. Finally, using the calculated ratios of maximum forces and displacements at maximum forces, one can map the two values of a given curved SP test to the equivalent flat SP values.

The stability of the martensitic microstructure in ferritic/martensitic G91 steel at operating temperatures up to 700 ºC might be improved by means of ausforming thermomechanical treatments. The goal sought is to promote the formation of a high number density of MX nanoprecipitates in the martensitic microstructure obtained after a subsequent tempering. This work is focused on the effect of the ausforming temperature. The results show that the lower the ausforming temperature is the higher is the dislocation density obtained in ausformed fresh martensite and the larger the number density of MX carbonitrides after tempering are. Creep strength, evaluated by Small Punch Creep Tests has allowed us to conclude that the best creep behavior was obtained for the steel ausformed at lower the temperature due to the higher pinning force for dislocation motion triggered by the distribution of MX. The creep results obtained on the ausformed samples were compared with those after the conventional heat treatment, showing that the high density of MX carbonitrides after an ausforming thermomechanical treatment is a promising processing to raise the operation temperature of this steel.

Small Punch Creep technique was used as a screening procedure to evaluate the creep properties of different microstructures developed in a thermomechanical simulator. The goal seek was to generate alternative microstructures in a conventional ferritic-martensitic G91 steel grade which boost thermal stability at temperatures as high as 700ºC. The developed microstructures allow studying the effect of the austenitization temperature optimized by thermodynamic calculations and the ausforming on the creep strength and ductility. The improvement in creep strength recorded was attributable to a higher number density of MX precipitates. By contrast, these microstructures showed an important reduction in creep ductility.

I will introduce the superconducting electron accelerator ELBE (Electron Linear accelerator with high Brilliance and low Emittance) as a source for different types of secondary radiation, including low- (meV) and high- (MeV) energy photons, positrons and neutrons. Being a solid-state spectroscopist, I will then focus on research we have performed using the terahertz free-electron laser FELBE. Here the high peak power can be employed for nonlinear optical experiments in the THz range, whereas the picosecond pulse structure enables time-resolved studies of relaxation processes.

The selective attachment of molecular or cellular biological elements on flat substrates plays a critical role towards advancements in the field of biotechnology. As majority of the available market for biotech products (e.g. biosensors) is based on the functionalization of substrates, new approaches offering carriers with superior performance i.e. with easy-to-control immobilization of the target bio-elements are desirable. Though, many fabulous developments have been witnessed over the past decades, the controlled entrapment of biomolecules remains an unsolved problem. The frequently utilized routes of chemical-covalent or biological immobilization suffer from limited control and tendency to deactivate. Consequently, new carrier designs with alternative mechanisms of entrapment are of considerable interest. Following this trend, herein we present a promising concept for selective biomolecule assembly onto the bulk-functionalized PolCarr-BioChip. PolCarr-BioChip consists of a doped Si-wafer with an ultra-thin insulating film and a characteristic patter of surface near electrostatic forces (SNEF). The binding of the electrically polarizable bio-element onto PolCarr is purely driven by SNEF, offering an excellent degree of control on the mm-µm-nm scale. By varying the doping conditions, the SNEF can be readily altered. This, in turn, allows for optimization of binding efficacy of the PolCarr-BioChip. Finally, the design of PolCarr can be adjusted to the individual target application (e.g. directed nerve cell growth). The examples of the application-tailored PolCarr templates will be demonstrated in the presentation. We believe the unique features of the PolCarr-BioChip make it a promising alternative to the challenges faced by variety of state-of-the-art biotech products.

The selective attachment of molecular or cellular biological elements on flat substrates plays a critical role towards advancements in the field of biotechnology. As majority of the available market for biotech products (e.g. biosensors) is based on the functionalization of substrates, new approaches offering carriers with superior performance i.e. with easy-to-control immobilization of the target bio-elements are desirable. Though, many fabulous developments have been witnessed over the past decades, the controlled entrapment of biomolecules remains an unsolved problem. The frequently utilized routes of chemical-covalent or biological immobilization suffer from limited control and tendency to deactivate. Consequently, new carrier designs with alternative mechanisms of entrapment are of considerable interest. Following this trend, herein we present a promising concept for selective biomolecule assembly onto the bulk-functionalized PolCarr-BioChip. PolCarr-BioChip consists of a doped Si-wafer with an ultra-thin insulating film and a characteristic patter of surface near electrostatic forces (SNEF). The binding of the electrically polarizable bio-element onto PolCarr is purely driven by SNEF, offering an excellent degree of control on the mm-µm-nm scale. By varying the doping conditions, the SNEF can be readily altered. This, in turn, allows for optimization of binding efficacy of the PolCarr-BioChip. Finally, the design of PolCarr can be adjusted to the individual target application (e.g. directed nerve cell growth). The examples of the application-tailored PolCarr templates will be demonstrated in the presentation. We believe the unique features of the PolCarr-BioChip make it a promising alternative to the challenges faced by variety of state-of-the-art biotech products.

The selective attachment of molecular or cellular biological elements on flat substrates plays a critical role towards advancements in the field of biotechnology. As majority of the available market for biotech products (e.g. biosensors) is based on the functionalization of substrates, new approaches offering carriers with superior performance i.e. with easy-to-control immobilization of the target bio-elements are desirable. Though, many fabulous developments have been witnessed over the past decades, the controlled entrapment of biomolecules remains an unsolved problem. The frequently utilized routes of chemical-covalent or biological immobilization suffer from limited control and tendency to deactivate. Consequently, new carrier designs with alternative mechanisms of entrapment are of considerable interest. Following this trend, herein we present a promising concept for selective biomolecule assembly onto the bulk-functionalized PolCarr substrate. PolCarr consists of a doped Si-wafer with an ultra-thin insulating film and a characteristic patter of surface near electrostatic forces (SNEF). The binding of the electrically polarizable bio-element onto PolCarr is purely driven by SNEF, offering an excellent degree of control on the mm-µm-nm scale. By varying the doping conditions, the SNEF can be readily altered. This, in turn, allows for optimization of binding efficacy of the PolCarr substrate. Finally, the design of PolCarr can be adjusted to the individual target application (e.g. directed nerve cell growth). The examples of the application-tailored PolCarr templates will be demonstrated in the presentation. We believe the unique features of the PolCarr carrier make it a promising alternative to the challenges faced by variety of state-of-the-art biotech products.

Der PolCarr-BioChip besteht aus Silizium mit implantiertem Ladungsmuster und ermöglicht eine kontrollierte Anhaftung von elektrisch polarisierbaren Biomaterialien. Die Anhaftung wird durch oberflächennahe, elektrostatische Kräfte (SNEF) ermöglicht. Die SNEF über PolCarr-BioChips sind unabhängig von den Umgebungsbedingungen und auch stabil während Sterilisation, Schockgefrieren und Inkubation.

Mass transfer of surface-active substances across fluidic interfaces is frequently accompanied by Marangoni instability [1]. Marangoni convection can show a temporal periodicity in the form of relaxation oscillations due to subsequent consumption and regeneration of its driving force. Contrary to the complex behavior of strong surfactants or reactive mass transfer, a simple two-phase-system consisting of paraffin oil and water is employed in our study. Due to mass transfer of isopropanol as a weak surfactant, concentration gradients and, by implication, density gradients are produced in-situ.
We have first studied single small droplets, placed in the concentration gradient, by means of a combination of experiments and simulations. The experiments are conducted in a Hele-Shaw experiment in which the droplets are visualized by shadowgraphy [2]. The 2D numerical simulations are based on a diffusiveinterface approach and assume a linear concentration and density gradient. We show that the single droplets perform about hundred periods of regular ROs over almost one hour. By analyzing their characteristics, the underlying mechanism can be attributed to the interaction between the mixing by Marangoni convection and the restoring effects of diffusion and buoyant convection on the driving concentration gradients. In the next step, ensembles of droplet comprising droplet pairs as well as linear or circular chains of droplets are investigated. If the spatial distance between the droplets in within the propagation depth of the relaxation oscillations, we observe an excitation of the relaxation oscillation from one droplet to its neighbor [3]. As a result, neighboring droplets are forced to oscillate with the same frequency. On arranging the droplets in chains, an efficient transmission of the relaxation oscillation can be achieved.
References
[1] K. Eckert, T. K¨ollner, K. Schwarzenberger, T. Boeck, Transport Processes at Fluidic Interfaces, Eds: D. Bothe, A. Reusken, Springer (2017).
[2] Schwarzenberger, S Aland, H Domnick, S Odenbach, K Eckert, Colloids and Surfaces A: Physicochemical and Engineering Aspects 481, 633-643 (2015).
[3] M. Mokbel, K. Schwarzenberger, K. Eckert, S. Aland (2017), in preparation.

Introduction
A wealth of preclinical experiments has clearly demonstrated that site-specific protein modification results in a more homogenous product population with defined and tunable properties compared to traditional bioconjugation techniques (1, 2). This is of particular importance for antibodies and their fragments as random conjugation strategies can compromise their functionality and interfere with or abolish their immunoreactivity (3). That specifically applies to small-sized antibody formats such as single chain variable fragments and single-domain antibody-fragments due to their compact structure and limited number of available functional reactive residues outside the antigen-binding site (4-6). Here, we describe a versatile two-step approach for site-specific introduction of bifunctional radiometal-chelating agents into antibody-derived fragments for the generation of highly defined radioimmunotracers.

Methods
The first step of this approach uses enzyme-mediated bioconjugation for regioselective incorporation of an azide-containing linker into an antibody fragment. The second step of this modular approach involves the modification of the azide-tagged antibody fragment with dibenzocyclooctyne (DBCO)-containing fluorescent dyes or DBCO-modified bispidine via Cu-free strain-promoted alkyne-azide cycloaddition.

Results
In an exemplary way, we demonstrate the versatility of this two-step approach by the site-specific incorporation of fluorescent dyes or radiometal chelators for fluorescence or positron emission tomographic imaging at physiological conditions. In vitro binding studies on different human cancer cell lines using dye- or 64Cu-labeled antibody fragments showed high specificity, co-localization and a receptor-mediated cellular uptake of the EGFR-specific probes. Noteworthy, we did not observe any detrimental effect to the functionality of the antibody fragments.

Discussion and Conclusion
The site-specific insertion of a bioorthogonal handle into the targeting moiety allows the subsequent convenient and straightforward incorporation of a variety of complementary probes. In addition, the heterogeneity of the conjugate population is substantially reduced as the conjugation site is defined and maximally one probe is attached per antibody fragment.

References
1. Agarwal P, Bertozzi CR. Site-specific antibody-drug conjugates: the nexus of bioorthogonal chemistry, protein engineering, and drug development. Bioconjug Chem. 2015;26(2):176-92.
2. Sletten EM, Bertozzi CR. Bioorthogonal chemistry: fishing for selectivity in a sea of functionality. Angew Chem Int Ed Engl. 2009;48(38):6974-98.
3. Schumacher D, Hackenberger CP, Leonhardt H, Helma J. Current Status: Site-Specific Antibody Drug Conjugates. J Clin Immunol. 2016;36 Suppl 1:100-7.
4. Meyer JP, Adumeau P, Lewis JS, Zeglis BM. Click Chemistry and Radiochemistry: The First 10 Years. Bioconjug Chem. 2016;27(12):2791-807.
5. Massa S, Xavier C, Muyldermans S, Devoogdt N. Emerging site-specific bioconjugation strategies for radioimmunotracer development. Expert Opin Drug Deliv. 2016;13(8):1149-63.
6. Schumacher D, Helma J, Schneider AFL, Leonhardt H, Hackenberger CPR. Nanobodies: Chemical Functionalization Strategies and Intracellular Applications. Angew Chem Int Ed Engl. 2018;57(9):2314-33.

Trivalent lanthanides and actinides (Ln3+/Ac3+) are mostly non-essential metal ions and, in case of trivalent actinides, also not naturally occurring elements. Nonetheless, both lanthanides and actinides can be found in significant quantities in our environment. Trivalent lanthanides have a geogenic origin and get further into the environment during mining, processing and subsequent disposal caused by their intensive use for modern high-tech products. In contrast, trivalent actinides can be unintentionally released by for example the failure of nuclear power plants or during their long-term disposal. Even though they are typically non-essential elements their chemical similarity to calcium (Ca) justifies a detailed investigation of their physiological relevance to organisms and in particular regarding to their interference with the Ca metabolism. In literature an accumulation of lanthanides and actinides in organisms is reported as a function of concentration. Thus, specific or nonspecific transport of these elements in cells can be expected. Possible pathways are via the Na-Ca antiporter, bio-ligand mediated endocytosis or via ionophores. Furthermore, a metal induced permeabilization is described in literature. At least some of these processes can lead to accumulation of these lanthanides or actinides in the food chain.
To study the interaction of lanthanides with Brassica napus on a cellular level, callus and suspension cells were exposed to Eu3+. Besides the kinetics of the bio-association, the amount of associated Eu3+ and its effect on cell growth and viability was determined. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used as direct speciation technique to determine the Eu3+ species on callus cells and cell compartments after the cell fractionation. The latter showed that 95 % of the Eu3+ can be found on large cell fragments, e.g. the cell membrane, whereas 5 % can be found in the cytoplasm and the residual plasma and intracellular membranes.
Not only the uptake routes for these elements are unknown but also the molecular mechanism of toxicity is not yet fully understood. An interference with metal ion channels, transporters and/or an interaction with other proteins is possible. In this study calmodulin (CaM) was used as Ca-binding protein relevant for all eukaryotes and as protein with a well-established crystal structure. As such, CaM plays a key role in the Ca metabolism and interacts with more than 350 cellular targets. Combining enzymology, calorimetry, spectroscopy and computational modeling allowed a structural and mechanistic understanding of the effects of Eu3+ and Cm3+ cations on the CaM protein structure and function. The analyses proved that Eu3+ binds CaM with high affinity and displaces Ca2+. Additional experiments demonstrated that the latter applies also for Cm3+. In addition, the stronger binding and different chemical environment of Eu3+/Cm3+ leads to structural distortion and disorder of CaM, which is associated with a reduced enzymatic activity of CaM.

This talk presents how the GitLab Community Edition installation at HZDR is used to map components of agile programming and also motivates why most scientific programming is agile.

The helium ion microscope is well known for its imaging with spot sizes below 0.5 nm, its nano-fabrication capabilities, the small energy spread of less than 1 eV and the extremely high brightness. This is not only possible for conducting but also insulating samples without the need for a conductive coating.
This relatively new device still suffers from the lack of a well integrated material analysis. Past and ongoing activities of various labs for in situ analysis will be summarized. Recently we implemented time-of-flight spectrometry to measure the energy of backscattered helium, the mass of sputtered ions and in future the energy loss of transmitted particles [1].
The focus will be on the technical realization of the significantly improved time-of-flight secondary ion mass spectrometry setup. New results, drawbacks and derive conclusions for the practical use of this promising technique will be presented [2]. Similarities and differences to the also recently developed system using a magnetic sector will be shown [3].
For m/q ≤ 80 u a mass resolution delta m ≤ 0.3 u has been achieved. This is sufficient for many life science applications that rely on the isotope identification of light elements (e.g.: C14, N15). The lateral resolution of 8 nm has been evaluated using the knife edge method and represents a world record for spatially resolved secondary ion mass spectrometry.
[1] N. Klingner, R. Heller, G. Hlawacek, J. von Borany, J.A. Notte, J. Huang, S. Facsko. Ultramicroscopy 162 (2016), pp 91-97
[2] N. Klingner, R. Heller, G. Hlawacek, et al. (2018), in preparation
[3] D. Dowsett, T. Wirtz. Analytical Chemistry, 2017, 89 (17), pp 8957–8965

Securing economically and ecologically viable sources of certain strategic elements, such as chromium and vanadium, represents an important challenge facing Europe currently.[1] The CHROMIC project seeks to address this issue by developing novel processes for the procurement of such metals from secondary resources. Solvent extraction (SX) is a well-known method which can separate and concentrate such chemical species, and which can provide numerous advantages over more established pyrometallurgical processes for metal purification.[2] This present work aims to construct a solvent extraction process applicable to highly alkaline slag-leach-solutions for the selective recovery of chromium, vanadium, and eventually niobium.
The extractant used in this study is Aliquat 336, an ionic liquid composed of quaternary ammonium salt, dissolved in diluents such as kerosene and methyl isobutyl ketone.[3] Model feed solutions have been created based on the most probable leach solutions for this process, with pH in the range of 12 – 13 and chromate as the major species with an approximate chromium concentration of 1 g/L. Radiolabelling samples with the isotopes chromium-51 (half-life 27.7 days) and vanadium-48 (half-life 16.0 days) allows determination of the metal content in each phase, without the need for any sample preparation of the sort which is required for other analytical techniques such as ICP-OES or ICP-MS. To the best of our knowledge, this work represents the first use of ⁴⁸V radiotracer individually (and the first use of ⁵¹Cr radiotracer in combination) analysis for a solvent extraction study.[4]
Thus far experiments have principally been carried out on single-element solutions containing only one of the desired target elements. In this way we have elucidated the influence of various factors on the efficiency of extraction. The pH of extraction medium plays an important role, not just on the extractability where increasing pH causes a decrease in metal extraction, but also on the stability of the extracted solution. Similarly, the concentration of competing anions such as chloride, sulphate, or nitrate has a strong negative influence on the amount of metal extracted. For example, addition of 0.5 M sodium sulphate will in general reduce extraction of chromium to half the salt-free value. Kinetics of mass transport were determined to be rapid, a significant factor when it comes to scaling up the process from laboratory to industrial scale (mixer-settler unit). Extraction isotherms have been constructed for different possible sets of extraction conditions, and used to guide our continuing research into these systems. Preliminary experiments on mixed-element solutions seem to show coextraction of chromium and vanadium together; in future experiments a suitable scrubbing technique will be employed to attempt to fully separate and purify these elements.
The results obtained thus far indicate the viability of Aliquat 336 as extractant for these key strategic metals from expected leach solutions of industrial slags. The continuation of the project will focus on optimising the process under realistic industrial conditions.
1. Communication from the European commission to the European Parliament on Critical Raw Materials, 13.09.2017
http://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:52017DC0490&from=EN
2. Weinhardt et al, Industrial and Engineering Chemistry,43(7), 1676-1684, (1951)
3. Wionczyk et al, Hydrometallurgy, 78, 116-128, (2005)
4. Katsuta et al, Journal of Radioanalytical and Nuclear Chemistry, 222(1-2), 45-50, (1997)

A three-dimensional (3D) network of interconnected nanowires of functional materials possesses huge potential for device fabrication since it hinders sluggish interfacial charge carrier transport owing to reduced contact resistance. In the present work, the formation of a highly porous 3D interconnected nano-network by Na+ ion irradiation is demonstrated. The mechanism of solid junction formation at very low energy is established using the results obtained from TRI3DYN computer simulation studies. The formation of a 3D interconnected network resulted in a significant improvement in the electrical conduction as compared to that observed for the pristine nanotube mesh. Further, contact angle measurement shows a transition from "superhydrophilic" nature, as observed for pristine nanotubes, to "superhydrophobic" nature for the 3D nano-network. The superhydrophobicity of the 3D nano-network is expected to find application in miniaturized electronic devices, wherein water condensation and related effects such as short-circuits and erroneous signal output can be significantly minimized.

During this talk I will first briefly introduce the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Institute of Ion Beam Physics and Materials Research as well as the Ion Beam Centre as a user facility run by the Institute.

Next, I will present some of the equipment available at the nanofabrication facility in Rossendorf (NanoFaRo), in particular electron beam lithography (EBL) systems as well as tools for thin film deposition and reactive ion etching (RIE), paying special attention on their capabilities.

I will then go through the most important nanofabrication projects, both internal and external, run lately at NanoFaRo, including top-down fabrication and electrical characterisation of silicon (Si) nanowire (NW) reconfigurable field effect transistors (RFETs) together with detailed study of nickel (Ni) silicidation of Si NWs; top-down fabrication of a large number of gratings with different periodicity on 2 µm thick Si membranes for laser targets; electrical contacting of randomly distributed nanostructures (bottom-up grown VO2 and hyperdoped Si NWs, DNA origami, flakes of 2D materials, etc.); top-down fabrication of four-terminal Si NW test devices for modulation doping experiments; nanopatterning of polymer brushes by reactive writing with EBL; bevel formation by EBL and RIE for dopant/conductance profiling of thin films and NWs by conductive atomic force microscopy (C-AFM); top-down fabrication of Si NWs hyperdoped with selenium (Se) as well as of plasmonic antennas on Si hyperdoped with tellurium (Te); fabrication and electrical characterisation of FETs on 2D materials, etc. Concluding this part of my talk, I will draw your attention to some highlights of our activities, focussing mostly on processes for high-resolution patterning as well as on high-precision electrical contacting of randomly distributed nanostructures.

Finally, I will discuss possibilities for collaboration between HZDR and UCC/Tyndall in the field of our activities.

During the last decade, semiconductor nanowires (NWs) have received significant academic and commercial attention due to their attractive electrical and mechanical properties and large surface area to volume ratios. They have a variety of possible applications including nanoelectronics, nanophotonics, photovoltaics, sensorics, etc. Among all semiconductor NWs the ones based on group IV materials have the added value of being the most silicon (Si) compatible. This would allow their relatively easy integration into the existing semiconductor technology platform.

In my talk I will first present the NWs that we are working with. These include top-down fabricated Si and germanium (Ge) NWs having widths down to 6-7 nm as well as bottom-up grown alloyed germanium-tin (Ge1-xSnx) NWs with x = 0.07-0.1, diameters of 50-70 nm and lengths of 1 to 3 µm. In the future we plan to work also with alloyed SiGe and SiGeSn NWs with varying content of the different materials.

I will next discuss the innovative devices that we are targeting, namely junctionless nanowire transistors (JNTs) and reconfigurable field effect transistors (RFETs). In particular, we are interested in Si JNTs for sensing application as well as in Ge and GeSn JNTs for digital logic. Concerning RFETs, we are currently working on Si RFETs and commencing activities on Ge RFETs. In the future we are planning to work also on GeSn RFETs.

Finally, I will pay a special attention to a novel device that we recently invented: group IV heterostructure band-to-band tunnel FET (TFET). We are planning to fabricate this device with a scalable and fully CMOS compatible process and expect it to demonstrate high Ion together with low Ioff and hence steep subthreshold slopes.

A new strategy for the synthesis of large poly-oxo cluster bearing 38 tetravalent uranium atoms {U38} has been developed by controlling the water release from the esterification reaction between carboxylic acid and alcohol. The molecular entity [U38O56Cl40(H2O)2(ipa)20]·(ipa)x (ipa = isopropanol) was crystallized from the solvothermal reaction of the mixture of UCl4 and benzoic acid in isopropanol at temperature ranging from 70 to 130°C. Its crystal structure reveals the molecular assembly of the UO2 fluorite-like inner core {U14} with oxo groups bridging the uranium centers. The {U14} core is further surrounded by six tetrameric sub-units of {U4} to form the {U38} cluster. Its surface is decorated by either bridging- and terminal chloride anions or terminal isopropanol molecules. Another synthesis using the same reactant mixture at a room temperature resulted in the crystallization of discrete dinuclear complex [U2Cl4(bz)4(ipa)4] (bz = benzoate), in which each uranium center is coordinated by two chlorine atoms, four oxygen atoms from carboxylate groups and two additional oxygen atoms from isopropanol. The slow production of water released from the esterification of isopropanol allows the formation of the giant cluster with oxo bridges linking the uranium atoms at a temperature above 70°C, whereas no such oxo groups are present in the dinuclear complex formed at a room temperature. The kinetic of {U38} crystallization as well as the ester formation are analyzed and discussed. SAXS experiments indicate that the {U38} species are not dominant in the supernatant, but hexanuclear entities which are closely related to the [U6O8] type are formed.

Since the 1940s, great amounts of Plutonium (Pu) have been produced for both military and civil purposes. Until now, the standard therapy for decorporation following inhalation has been the intravenous injection of diethylenetriaminepentaacetic acid ligand (Ca-DTPA form). This method offers a strong complexing constant for Pu(iv) but has poor chemical specificity, therefore its efficacy is limited to actinides present in the blood. Consequently, there is no decorporation treatment currently available which efficiently removes the intracellular Pu(iv) trapped in the pulmonary macrophages. Our research shows that a nanoparticle approach could be of particular interest due to large contact area and ability to target the retention compartments of the lungs. In this study, we have focused on the inhalation process involving forms of Pu(iv) with poor solubility. We explored the design of biocompatible nanoparticles able to target the macrophages in the lung alveoli and to chelate the forms of Pu(iv) with poor solubility. Nanoparticle formation was achieved through an ionic cross-linking concept using a polycationic polymer and an anionic chelate linker. We chose N-trimethyl chitosan, for its biocompatibility, as the polycationic polymer base of the nanoparticle and the phosphonic analogue of DTPA, diethylenetriamine-pentamethylenephosphonic acid (DTPMP) as the anionic chelating linker in forming NPs TMC-DTPMP. The synthesis and physico-chemical characterization of these NPs are presented. Secondly, the complexation mechanisms of TMC-DTPMP NPs with Thorium (Th(iv)) are discussed in terms of efficiency and structure. The Extended X-Ray Absorption Fine Structure (EXAFS) of the TMC-DTPMP complex with Th(iv) as well as Pu(iv) are defined and completed with DFT calculations to further delineate the plutonium coordination sphere after complexation. Finally, preliminary cytotoxicity tests onto macrophages were assayed.

Lipid bilayers and lipid-associated proteins play crucial roles in biology. As in vivo studies and manipulation are inherently difficult, membrane-mimetic systems are useful for the investigation of lipidic phases, lipid-protein interactions, membrane protein function and membrane structure in vitro. In this work, we describe a route to leverage the programmability of DNA nanotechnology and create DNA-encircled bilayers (DEBs). DEBs are made of multiple copies of an alkylated oligonucleotide hybridized to a single-stranded minicircle, in which up to two alkyl chains per helical turn point to the inside of the toroidal DNA ring. When phospholipids are added, a bilayer is observed to self-assemble within the ring such that the alkyl chains of the oligonucleotides stabilize the hydrophobic rim of the bilayer to
prevent formation of vesicles and support thermotropic lipid phase transitions. The DEBs are completely free of protein and can be synthesized from commercially available components using routine equipment. The diameter of DEBs can be varied in a predictable manner. The well-established toolbox from structural DNA nanotechnology, will ultimately enable the rational design of DEBs so that their size, shape or functionalization can be adapted to the specific needs of biophysical investigations of lipidic phases and the properties of membrane proteins embedded into DEB nanoparticle bilayers.

Lipid bilayers and lipid-associated proteins play a crucial role in biology. Since studies and manipulation in vivo are inherently challenging, several in vitro membrane-mimetic systems have been developed to enable the study of lipidic phases, lipid-protein interactions and membrane protein function. Controlling the size and shape or introducing functional elements in a programmable way is, however, difficult to achieve with common systems based on polymers, peptides or membrane scaffolding proteins. In this work we describe a route leveraging the unique programmability of DNA nanotechnology to create DNA-encircled bilayers (DEBs) as a novel nano-scaled membrane-mimetic. For this, alkylated oligonucleotides are hybridized to a single-stranded minicircle (ssMC) such that all alkyl chains point to the inside stabilizing the lipid bilayer. Atomic force microscopy (AFM), transmission electron microscopy (TEM) and coarse grain molecular dynamics (CGMD) simulations confirm the formation of discoidal lipid bilayer structures. Fluorescence spectroscopy was used to monitor lipid phase transitions and revealed head group-dependent lipid-DNA interactions at the bilayer rim. The DEB technology described herein provides unprecedented control of size, shape, stability and functionalization of engineered membrane nanoparticles and will become a valuable tool for biophysical investigation of lipid phases and lipid-associated proteins and complexes.

In order to analyze the potential influence of natural occuring microorganisms within the bentonite on the properties of the bentonite barrier, we set up microcosm-experiments. Two different Bavarian bentonites (a natural and an industrial one) were supplied with an anaerobic, synthetic Opalinus-clay pore water solution under an N2/CO2-atmosphere and were incubated for one year at 30 °C and 60 °C. To some set ups organics (acetate or lactate) or H2 were supplemented. During the incubation time samples were analyzed for several biogeochemical parameters and the evolution of microbial community.
Our results clearly demonstrate, that natural occuring microbes affect geochemical parameters. Set ups containing the industrial bentonite supplemented with lactate or H2 show the most striking effects. The respective batches were dominated (up to 81 %) by Desulfosporosinus spp. after 6 months – spore-forming, strictly anaerobic, sulfate-reducing organisms, able to survive under very harsh conditions. Concomitantly, an increase of ferrous iron and a simoultaneous decrease of ferric iron was observed as well as a decrease in sulfate – alterations that could effect different properties of and reactions within the barrier system of an HLW.

We carried out ultrasonic Doppler measurements of a precession driven flow in a cylindrical cavity. The experimental studies were conducted in a downscaled water experiment to analyze the possibility of hydrodynamic dynamo action in a planned large-scale liquid sodium experiment. The azimuthal and axial mode decomposition close to the outer rim reveals a significant peak for the axi-symmetric flow component with axial wavenumber k=2 in a narrow region of the precession ratio. At this peak, dynamo action is predicted for the DRESDYN sodium experiment. Specifically we analyze the ultrasonic measurement data which were transferred via slip rings from the vessel rotating about two axes. By post-processing the azimuthal dependence of the flow was extracted from the ultrasonic data. The utilized workflow eliminates the slight variations over time of the operating conditions and of the frame rate of the data acquisition. The downscaled water experiment was operated in a wide range from Re=10000 to 1.6·106, showing a very good agreement with direct numerical simulations at their upper limit of Re=10000.

The shibboleth-authenticator module for Invenio provides web browser single sign-on via the SAML protocol. It is based on the python3-saml module and supports the usage of multiple identity providers at the same time.

Because of its chemo- and radiotoxicity, the incorporation of uranium into human body via ingestion potentially poses a
serious health risk. When ingested, the gastrointestinal fluids are the primary media to interact with uranium, eventually influencing and even determining its biochemical behavior in the gastrointestinal tract and thereafter. The chemical interactions between uranium and the components of gastrointestinal fluids are, however, poorly understood to date. In this study, the complexation of uranium(VI) (as the uranyl ion, UO22+) with the protein α-amylase, one of the major enzymes in saliva and pancreatic juices, was investigated over a wide range of pH or uranium/α-amylase concentrations covering physiological conditions. Macroscopic sorption experiments suggested a strong and fast complexation of UO22+ to α-amylase between pH 5 and 7. Potentiometric titration was employed to determine the complex stability constants for the relevant UO22+ α-amylase complexes, which is crucial for reliable thermochemical modeling to assess the potential health risk of uranium. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that α-amylase is interacting with UO22+ primarily via its carboxylate groups presumably from the aspartic acid and glutamic acid side chains. The effect of UO22+ on the enzyme activity was also investigated to understand the potential implication of uranium for the in vivo functions of the digestive fluids, indicating that the presence of uranium inhibits the enzyme activity. This inhibitory effect can be, however, suppressed by an excess of calcium.

Background:

The current de facto standard for quantification of tumor metabolism in oncological whole-body PET is the standardized uptake value (SUV) approach. SUV determination requires accurate scanner calibration. Residual inaccuracies of the calibration lead to biased SUV values. Especially, this can adversely affect multicenter trials where it is difficult to ensure reliable cross-calibration across participating sites. The goal of the present work was the evaluation of a new method for monitoring scanner calibration utilizing the image-derived arterial blood SUV (BSUV) averaged over a sufficiently large number of whole-body FDG-PET investigations.

Data of 681 patients from three sites which underwent routine 18F-FDG PET/CT or PET/MR were retrospectively analyzed. BSUV was determined in the descending aorta using a three-dimensional ROI concentric to the aorta’s centerline. The ROI was delineated in the CT or MRI images and transferred to the PET images. A minimum ROI volume of 5 mL and a concentric safety margin to the aortic wall was observed. Mean BSUV, standard deviation (SD), and standard error of the mean (SE) were computed for three groups of patients at each site, investigated 2 years apart, respectively, with group sizes between 53 and 100 patients. Differences of mean BSUV between the individual groups and sites were determined.

Results: SD (SE) of BSUV in the different groups ranged from 14.3 to 20.7% (1.7 to 2.8%). Differences of mean BSUV between intra-site groups were small (1.1–6.3%). Only one out of nine of these differences reached statistical significance. Inter-site differences were distinctly larger (12.6–25.1%) and highly significant (P<0.001).

Conclusions: Image-based determination of the group-averaged blood SUV in modestly large groups of whole-body FDG-PET investigations is a viable approach for ensuring consistent scanner calibration over time and across different sites. We propose this approach as a quality control and cross-calibration tool augmenting established phantom-based procedures.

Graphics processing units (GPU) have evolved to massively parallel processors for general-purpose computing during the last couple of years. They are now available in small and energy-efficient embedded systems, too. This talk gives a brief overview about GPU computing and introduces the NVIDIA Jetson platform as an example for a GPU powered embedded system.

The importance of research data and research data management (RDM) in the research lifecycle is growing. This talk provides an overview about data management in research projects. The goal is to make research data FAIR (Findable, Accessible, Interoperable and Retrievable) by starting early with a Data Management Plan (DMP) and making research data available in appropriate data repositories.

We have designed and synthesized a series of cyclopentadienyl tricarbonyl 99mTc/Re complexes containing a spirocyclic piperidine moiety as sigma receptor ligands. Rhenium compound 3a (4-(3H-spiro(2-benzofuran-1,4’-piperidin)-1’-yl)butylcarbonylcyclopentadienyl tricarbonyl rhenium) showed high affinity for both sigma-1 (Ki = 13.8 ± 0.7 nM) and sigma-2 (Ki = 15.1 ± 3.5 nM) receptors. In the MTT assay, 3a displayed significant and comparable antiproliferative activity in DU145, MCF7 and MCF7/Adr tumor cells to siramesine, indicating 3a is an agonist of sigma-2 receptors and a potential antitumor agent. The corresponding radiolabeled compound [99mTc]3b was prepared via double-ligand-transfer reaction from the corresponding ferrocene precursor with a radiochemical yield of 48% and a radiochemical purity of more than 99%. Studies of the cellular accumulation of [99mTc]3b in C6 and DU145 tumor cells indicated that the total binding and the intracellular association is notably high.
Incubation with haloperidol significantly reduced the radiotracer accumulation dose-dependently. The biodistribution of [99mTc]3b in nude mice bearing DU145 tumor xenografts showed high tumor uptake (4.27%ID/g) and high tumor-to-blood (12) and tumor-to-muscle (5) ratios at 2 h postinjection. Pretreatment with haloperidol resulted in a remarkable reduction of tumor accumulation, indicating the specific binding of [99mTc]3b to sigma receptors in the tumor. These findings highlight the further evaluation of cyclopentadienyl tricarbonyl 99mTc/Re complexes and prospectively the 188Re-labeled analogs containing a spirocyclic piperidine moiety as sigma ligands for tumor imaging and therapy.

The talk will provide an overview of the liquid metal battery (LMB) related activities at Helmholtz-Zentrum Dresden - Rossendorf (HZDR) with a focus on magnetohydrodynamic aspects of future large scale LMBs. High current densities in the range of 4 up to 130 kA/m^-2, as typical for LMBs, together with cells of large cross section will result in substantial currents accompanied by considerable magnetic fields. Thus electromagnetically driven flows and instabilities should be of concern for large enough installations, especially when the thin electrolyte layers necessitated by the limited open circuit voltages are taken into account. Beneficial effects of mild electromagnetically driven flows are to be expected for the cathodes were mixing should improve cell performance.

Liquid metal batteries are introduced as a potential means to future economic large-scale electricity storage indispensable for energy systems with high penetration of fluctuating sources. The talk will concentrate on the role of electrodynamics and fluid mechanics in the design of large single cells, discussing a few instability mechanisms that should be taken into account.

We investigated the utility of a heparin/peptide-polyethylene glycol conjugate system to build Layer-by-Layer (LbL) structures, to assemble tailored multilayer-biomatrices for cell culture. The LbL assembly balances the advantages of polyelectrolyte systems and protein-based systems. Human umbilical vein endothelial cells showed distinct responses to: the film thickness and structure; the presence, density and spatial arrangement of a cell adhesion ligand within the nanothin film; and the pretreatment of the film with morphogens. The LbL technique presents a versatile tool for modifying cell culture substrates with defined and diverse biochemical and structural features, for investigating cell-material interactions.

Flow measurements by means of the Ultrasound Doppler Velocimetry (UDV) have been carried out in a cold liquid metal mockup experiment to model the continuous casting process of steel. The setup was realized in the mini-LIMMCAST facility and represents a 1:3 scale model of a typical industrial bloom caster. An arrangement of ten individual ultrasonic sensors attached to a commercial system and an academic UDV system with linear ultrasound array was mounted along the mold to capture the velocity distribution near the meniscus and the submerged entry nozzle (SEN). The results obtained by the two measurement systems are compared and show the superiority of the academic system due to its higher spatial resolution.

Arterial spin labeling (ASL) is a non-invasive MRI modality that can provide insight in brain hemodynamics. One main limiting factor of ASL is its relatively low signal-to-noise ratio (SNR). New technical developments like 3D readouts and background suppression have improved SNR [1] and additional post processing steps including noise regression methods can further improve temporal SNR (tSNR) [2]. We hypothesize that Independent Component Analysis (ICA) should provide separation of physiological noise from signal and thus improving SNR and cerebral blood flow (CBF) quantification as has been shown for BOLD fMRI. Therefore, in this study, we evaluated the use of ICA to separate perfusion signal from noise in ASL data.

Temozolomide-based radiochemotherapy (RCT) is a treatment standard for glioblastoma patients. However, RCT is associated with risks of neurocognitive decline. Perfusion is a possible early marker of tissue damage and has been shown to correlate with cognitive changes in many diseases. Perfusion decrease at 3 to 6 months after RT was recently reported in glioblastoma patients. However, it remains unclear whether the decrease is reversible and thus possibly a precursor of the late-delayed cognitive changes. In this study, we have measured perfusion changes up to 18 months following RCT. No further progress of perfusion deficits was found indicating that the early perfusion decrease is predictive of late perfusion decrease and might thus be connected with cognitive decline.

It was recognized early on in the development of ASL that the contribution of the vascular signal was a confound in measuring tissue perfusion. To this end, Alsop et al. proposed introducing a post-label delay (PLD) to allow for the blood to arrive at the microvasculature level and preferably wash-out from the macro-vasculature1. Considering, however, that the ASL signal decays during the PLD, a compromise is typically made between the need to minimize the effect of the vascular signal and optimum SNR. The choice of PLD becomes more complex in clinical applications where the arterial transit time (ATT) is expected to vary considerable across patients as well as within a patient, such as in carotid occlusive disease. In such applications, a concomitant measurement of both CBF and ATT would be ideal. However, ATT acquisition leads to longer scanning time, lower SNR, and higher motion sensitivity. To this end, Mutsaerts et al. have recently shown that spatial coefficient of variation (sCoV) of the ASL signal can be used as a proxy for the ATT measurement2. In this study, we tested whether an asymmetry in sCoV in carotid occlusive patients could predict the side of the occlusion with higher sensitivity than the CBF asymmetry. We also investigated the temporal variance of the ASL signal and tested its feasibility to detect the vascular signal in the ASL data from this patient population.

We have compared CBF value agreement in healthy subjects across two readouts, 3D-GraSE and 2D-EPI, and two field strength, 1.5 and 3T, and investigated for which acquisition parameters we can reach the best agreement. Significantly higher GM CBF was observed with a 2D-EPI readout compared to a 3D-GraSE readout with equivalent acquisition resolution (p < 0.005 for 1.5T and p < 0.05 for 3T). A better agreement was observed between 3D-GraSE and 2D-EPI on 3T systems when the resolution of the 3D-GraSE readout was increased to match the effective resolution to the 2D-EPI scan (ICC = 0.772 and ICC = 0.932 respectively).

This pCASL and 31P/1H-MRS study explored the cerebrovascular reactivity (CVR) and its efficacy on brain metabolic stability during a five-minute breathhold in fifteen experienced freedivers. Cerebral blood flow (CBF) increase occurred later than the decrease of the recently discovered arterial transit time correlate, spatial CoV. The latter may thus be an early CVR biomarker. CBF varied between vessel territories, gray and white matter and usually lowered with more experience. MRS showed near stable physiological cerebral ATP and pH concentrations despite peripheral lactate acidosis. In conclusion, this trial revealed that CVR sufficiently compensates the metabolic challenge of a five minute breath-hold.
In conclusion, this trial revealed that cerebral perfusion increase sufficiently compensates the metabolic challenge of a five-minute breath-hold.

We have compared CBF value agreement in healthy subjects across two readouts, 3D-GraSE and 2D-EPI, and two field strength, 1.5 and 3T, and investigated for which acquisition parameters we can reach the best agreement. Significantly higher GM CBF was observed with a 2D-EPI readout compared to a 3D-GraSE readout with equivalent acquisition resolution (p < 0.005 for 1.5T and p < 0.05 for 3T). A better agreement was observed between 3D-GraSE and 2D-EPI on 3T systems when the resolution of the 3D-GraSE readout was increased to match the effective resolution to the 2D-EPI scan (ICC = 0.772 and ICC = 0.932 respectively).

Background: In elderly populations, cerebral blood perfusion (CBF) measurements with arterial spin labelling (ASL) are affected by macro-vascular artefacts as a result of prolonged arterial transit time (ATT) [Figure 1]. The spatial coefficient of variance (CoV) provides a robust indirect estimate of ATT, hence it might be used as a proxy of the vascular health of the subject2, alone or in conjunction with other measures such as white matter hyperintensities (WMH) volume. The goal of this study was to compare spatial CoV between healthy controls (HCs) and subjects with Alzheimer’s (AD) or Parkinson’s (PD) disease. Methods: We analysed the scans of 143 participants from the APGeM study, in which a 3D GRASE pulsed ASL protocol was added to the Siemens 3T MRI protocol for degenerative diseases. Healthy controls (HC, n=56) and participants with AD- or PD-related mild cognitive impairment or dementia (AD, n=41; PD, n=46) were included [Table 1]. We calculated grey matter (GM) CBF, spatial CoV, and WMH volume using ExploreASL [ref]. Pearson’s correlation was used to calculate the correlation of spatial CoV with age and WMH volume. Student’s-test was performed to check differences in spatial CoV between sexes. A linear regression model was built to investigate whether spatial CoV could discriminate between HC vs. AD, HC vs. PD, and AD vs. PD after correction for age and sex. WMH and spatial CoV were logtransformed.
Results: Spatial CoV showed a positive correlation with age (cor=0.35, p<0.001) and with WMH volume (cor=0.38, p <0.001) [Figure 2]. A difference in spatial CoV of 0.12 was reported (p<0.001). Spatial CoV differences were detected between HC and AD (ß=0.08, p=0.004) and between HC and PD (ß=0.09, p=0.0002) subjects [Figure 3]. However, spatial CoV was not able to discriminate between AD and PD. Conclusions: The relatively strong correlation between spatial CoV and WMH volume make ASL a promising marker to investigate the interplay between large and small vessel disease. These results suggest that cerebrovascular health is reduced in AD and PD patients. Validation studies in larger cohorts and across a wider range of disorders could provide further insight in the relation between vascular disorders and neurodegeneration.

Background:

Arterial Spin Labelling (ASL) is a technique for measuring cerebral blood flow (CBF)1,2 and has shown promising results for discriminating Alzheimer’s disease patients from mild cognitive impairment and controls1. ASL is commercially available on all major MRI vendors; however, it has been shown that CBF values are sequence and scanner-dependent, due to variability of the acquisition methods used by each vendor. In this study, we compare the latest generation of pseudo-continuous ASL (pCASL) vendor-provided sequences to quantify between-vendor variability of whole-brain and regional CBF estimation.
Methods:
Eight healthy volunteers (4/4 M/F; mean/SD/median age=47/12/48 years) were scanned on three 3T MR systems with pCASL matched acquisition parameters (Table 1) and ADNI-2 3D-T1weighted (MPRAGE). CBF quantification and post-processing was performed using ExploreASL3 in conjunction with SPM124. Post-processing included registration of the T1-MPRAGE and ASL to MNI space, parcellation of the T1-MPRAGE to grey matter (GM), white matter (WM), and regions affected in dementia (ROI_dem). Quantification was performed according to the ASL consensus paper5. Mean-CBF was calculated in ROI_dem and in the whole-brain within a standard (GM+WM>70%) and expanded (GM+WM>5%) mask. Spatial coefficient of variation (sCoV)6 was calculated for GM(>70%) and whole-brain (GM+WM>70%). Statistical significances were calculated using repeated measure ANOVA (P<0.05).
Results:
Whole-brain CBF values using the expanded mask showed better agreement between three vendors than the standard mask (Figure 1). There was no significant difference in mean-CBF of ROI_dem for Philips and Siemens, while GE showed significantly lower mean-CBF in these regions (Figure 2). sCoV also showed a similar trend, with GE having the lowest sCoV relative to Philips and Siemens for both whole-brain and GM (Figure 3).
Conclusions:
Whole-brain CBF was similar across vendors when an expanded mask was applied. However, there was a difference between GE and Philips/Siemens in CBF and sCoV in grey matter regions. We hypothesize that the differences are related to between-scanner differences in effective spatial resolution, in particular the lower effective resolution of GE’s spiral readout7. Future work will investigate whether smoothness equalization8 can account for this. We anticipate that this work will increase the utility of ASL as a perfusion biomarker in multi-center dementia studies.

Rare earth elements are an essential part of high-tech devices in the entertainment, automotive and aerospace industry, which is why there is a growing demand for these elements. However, benefication and processing of rare earths is difficult. Thus, there are several studies concerning with the reaction chemistry and the finding of more economical extraction methods for rare earth metals. This study concerns with the liberation and reaction chemistry of a silicate rare earth ore, from the mine Strange Lake, in Canada. The chemical kinetics are focused in order to investigate the chemical behavior of rare earth elements. Therefore, a kinetic model, suggested frequently in literature, is applied and the study’s objective is the examination of the practicality of this model for this specific material. The concentrate was therefore leached for four hours at elevated temperature (50 to 90°C) and with concentrated sulfuric acid (1M to 3M H2SO4). The influence of temperature, acid concentration and pulp density was studied.
It was found that the recovery of the measured rare earth elements could be optimized from around 50 to about 80 Wt% by a temperature increase of 40°C. Hence, it is considered that leaching of rare earth elements is an endothermic process. The highest recovery could be determined for europium and yttrium with around 80 Wt% (90°C, 3M H2SO4). Besides that, a raise in sulfuric acid concentration of 2 mol/l resulted in an increase of recovery of 20 Wt% for the totality of the measured rare earth elements. Aside from agitation and particle size, also the pulp density has important impacts on the leaching process concerning retention time and throughput. In this study pulp density was raised from 5 to 25% (w/v), thereby enhancing the recovery from about 80 Wt% to about 95 Wt%. The kinetic mechanisms are described by the shrinking core model. The rate of reaction versus time and the Arrhenius plots were determined for the measured elements. It was observed that leaching of rare earth elements is controlled by transport mechanisms, which occur by inner diffusion through a porous ash layer. The activation energy EA for the measured rare earth species was respectively determined and it was found that most of these EA values are in the range of 25 kJ/mol to 50 kJ/mol. This order of magnitude allows the assumption, that the rate limiting step of leaching rare earths is inner diffusion.

The Helmholtz-Center at Dresden-Rossendorf operates several user beamlines for materials research using positron annihilation energy and lifetime spectroscopy. A superconducting electron LINAC [1] serves as a driver for hard X-ray production from electron-bremsstrahlung which in turn generates positrons through pair production. GiPS, the Gamma-induced Positron Source directly generates electron-positron pairs inside the sample under investigation [2]. The source is especially suited for materials which are not qualified for vacuum conditions or because they are imposing hazardous conditions or intrinsic radioactivity. Some exemplary defect studies [3] will be presented. MePS, the Monoenergetic Positron Source utilizes positrons with discrete energies ranging from 500 eV to 16 keV [4] for thin film studies. A magnetic beam transport system guides positrons to the sample under investigation. Applications of porosimetry studies in low-k dielectrics [5] and polymer brushes [6] will be presented. The MePS facility is currently complemented by the AIDA-II - Apparatus for in-situ Defect Analysis - where defect studies can be performed in a wide temperature range during thin film growth and ion irradiation. The precedent setup AIDA-I is in operation at a 22Na-based mono-energetic continuous positron beam [7] used for Doppler-broadening spectroscopy experiments [8,9].
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). AIDA-I was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox). The AIDA-II facility was funded through the Helmholtz Energy Materials Characterization Platform.

[1] F. Gabriel, et al., Nucl. Instr. Meth. B 161, 1143 (2000).
[2] M. Butterling, et al., Nucl. Instr. Meth. B 269, 2623 (2011).
[3] M. Reiner, et al., Scientific Reports 6, 29109 (2016).
[4] A. Wagner, et al., Journal of Physics: Conference Series 791, 012004 (2017).
[5] A. Uedono, et al., Applied Surface Science 368, 272 (2016).
[6] G. Panzarasa, et al., Macromolecules 50, 5574 (2017).
[7] W. Anwand, et al., Defect and Diffusion Forum Vl. 331, 25 (2012).
[8] M. O. Liedke, et al., Journal of Applied Physics 117 163908 (2015).
[9] T. Kosub, et al., Nature Communications 8, 13985 (2017).

Seltene Erdelemente (SEE), eine Gruppe aus 17 chemisch sehr ähnlichen Metallen, sind in der heutigen Zeit ein wichtiger Bestandteil unserer technologischen Entwicklung. Wichtige Anwendungen stellen beispielsweise die Herstellung von starken Dauermagneten (Neodym-Eisen-Bor, Samarium-Kobalt), Katalysatoren und Elektronik (LCD, Laser, optische Temperatursensoren) dar. Die verwendeten Mengen in den einzelnen Applikationen sind meist gering, dennoch ist die Nachfrage an diesen Metallen hoch. Dies ist darauf zurückzuführen, dass der Einsatz der SEE in manchen Anwendungsgebieten alternativlos ist.
Die Lage auf dem Weltmarkt ist problematisch, denn China besitzt derzeit das Monopol der Seltenen-Erden-Produktion. Um auch in Zukunft die Industrie mit diesen begehrten Metallen versorgen und das Chinamonopol umgehen zu können, ist es wichtig neue Ressourcen ausfindig zu machen und Technologien zur Verarbeitung zu entwickeln. Einer dieser möglichen neuen Ressourcen ist die Eudialyt-Lagerstätte Norra Kärr.
Diese Studienarbeit soll mögliche Verarbeitungsmethoden des Eudiaylt-Erzes untersuchen. Ein Teil dieser Arbeit befasst sich mit der Laugung des Erzes durch Schwefelsäure bei unterschiedlichen Laugungstemperaturen sowie Säurekonzentrationen. In der Auswertung wurde dabei auf den Laugungsverlauf und Laugungsausbeuten eingegangen. Des Weiteren sind die Säureverbräuche bestimmt und die Laugungsrückstände mittels Mineral Liberation Analysis (MLA) untersucht worden, um die mineralogische Zusammensetzung nach der Laugung beurteilen zu können. Problematisch bei der Verarbeitung des silikatischen Eudialyts ist die Entstehung von Kieselsäure in der Laugungslösung. Diese bedingt eine schlechte Filtrierbarkeit, wodurch sich der 2. Teil der Studienarbeit mit einem Verfahren zur Unterdrückung des Kieselgels befasst. Hierfür wurde ein 2-stufiger Aufschluss verwendet. Der 1. Schritt besteht aus einem Aufschluss des Erz-Säure-Gemisches bei 105 °C, der 2. Schritt aus einer Laugung mit Wasser. Die durch die Kieselgelbildung beeinflussbare Filtrationsgeschwindigkeit wurde anhand der unterschiedlichen Aufschlusszeiten verglichen. Außerdem konnte ein Vergleich der Laugungsausbeuten zwischen konventioneller und dem 2-stufigen Verfahren erfolgen. Ebenfalls geht diese Arbeit auf das Silizium als Störelement sowie Zirkonium, Hafnium und Mangan als weitere Wertelemente ein.

Proton radiotherapy (PT) requires accurate target alignment before each treatment fraction, ideally utilizing 3D in-room X-ray computed tomography imaging (CT). Typically, the optimal patient position is determined on the basis of anatomical landmarks or implanted markers. In the presence of non-rigid anatomical changes, however, the planning scenario cannot be exactly reproduced and positioning should rather aim at finding the optimal position in terms of the actually applied dose.
In this work, dose-guided patient alignment, implemented as multicriterial optimization (MCO) problem, has been investigated in the scope of intensity modulated and double scattered proton therapy (IMPT and DSPT) for the first time. A method for automatically determining the optimal patient position with respect to pre-defined clinical goals was implemented. Linear dose interpolation was used to access a continuous space of potential patient shifts. Fourteen head and neck (H&N) and eight prostate cancer patients with repeated CT data (up to 5 control CTs) were included in this study. Dose interpolation accuracy was evaluated and the potential dosimetric advantages of dose-guided over anatomy-based patient alignment investigated by comparison of clinically relevant target and organ-at-risk (OAR) dose-volume histogram (DVH) parameters.
Dose interpolation was found sufficiently accurate with average pass-rates of 90% and 99% for an exemplary H&N and prostate patient, respectively, using a 2% dose-difference criterion. Compared to anatomy-based alignment, the main impact of automated MCO-based dose-guided positioning was a reduced dose to the serial OARs (spinal cord and brain stem) for the H&N cohort. For the prostate cohort, under-dosage of the target structures could also be efficiently diminished. Limitations of dose-guided positioning were mainly found in reducing target over-dosage due to weight loss for H&N patients, which might require adaptation of the treatment plan.
Since labor-intense online quality-assurance is not required for dose-guided patient positioning, it might, nevertheless, be considered an interesting alternative to full online re-planning.

Metal-induced crystallization with layer exchange (MIC w LE) reduces the crystallization temperature of group 14 elements significantly. This is especially interesting for device fabrication on substrates with limited thermal stability. In this contribution, MIC w LE is applied on Ni and C thin film stacks with different stacking sequences. The influence of the thin film morphology and stacking on the layer exchange degree αLE and the graphitic ordering is studied comprehensively in situ and ex situ.
During annealing of the thin films at up to 700 °C, film morphology and stacking sequence had a significant impact on αLE, showing an incomplete LE for the C/Ni stack. The highest αLE of 96%, determined by RBS and ERDA, was achieved for the smoothest samples and Ni/C stacking sequence. Raman spectroscopy and TEM demonstrated the formation of 2D crystalline carbon structures independently of the stacking sequence, while the degree of graphitic ordering increased with decreasing surface roughness. The simultaneous occurrence of LE and graphitization has been demonstrated in situ by RBS and Raman, giving insights into mechanism responsible for carbon crystallization in this system.

Rock salt formations are considered as potential host rocks for the long-term storage of highly radioactive waste in a deep geological repository. A combination of culture-dependent and culture-independent methods was used to investigate the microbial diversity in rock salt. Extremely halophilic archaea, e.g. Halobacterium species, dominate this habitat. For long-term risk assessment it is of high interest to study how these microorganisms can interact with radionuclides if released from the waste repository. Therefore, the interactions of different extremely halophilic Halobacterium species with uranium, one of the major radionuclides of concern in the geological repository, were investigated in detail in batch experiments. A multi-spectroscopic and microscopic approach was used to decipher the interaction mechanisms on a molecular level. Depending on the used initial uranium concentration the different Halobacterium species showed a different bioassociation behaviour of uranium. By using time-resolved laser-induced fluorescence spectroscopy the formation of U(VI) phosphate minerals, such as meta-autunite, as well as the complexation with carboxylate groups was observed as a function of the uranium concentration and the Halobacterium species. Furthermore, the presence of U(VI)-phosphate minerals could be visualized by scanning electron microscopy. These findings highlight the potential significance of the microbial life in deep geological hypersaline environments and offer new insights into the microbe-actinide interactions at highly saline conditions relevant to the disposal of highly radioactive waste as well as bioremediation.

Y128- and Y36-cut single-crystalline lithium niobate (LN) thin films are fabricated by the crystal-ion-slicing (CIS) technique onto LN substrates. The conditions for the successful exfoliation of submicron-thick LN thin films are independent of the wafer orientation used in the present work. Wafer bonding using benzocyclobutene (BCB) is adopted to transfer LN thin films onto substrates, instead of the generally used hydrophilic bonding, which does not need a strict surface polishing process before the bonding. A noncontact polishing method involving low-energy Ar+ irradiation is adopted to treat the sliced LN thin films. The atomic force microscopy result shows that the surface roughness of the LN thin film is reduced from 10.6 to 6.4nm.

Implantation of bulk CdTe single crystals with high fluences of 500 keV Cr+ ions was performed to achieve Cr concentration above the equilibrium solubility limit of this element in CdTe lattice. The structure and composition of the implanted samples were studied using secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) to characterize the incorporation of chromium into the host lattice and to investigate irradiation-induced damage build-up. It was found that out-diffusion of Cr atoms and sputtering of the targets alter the depth distribution and limit concentration of the projectile ions in the as-implanted samples. Appearance of crystallographically oriented, metallic α-Cr nanoparticles inside CdTe matrix was found after implantation, as well as a strong disorder at the depth far beyond the projected range of the implanted ions.

Computed tomography (CT) is known for giving cross-sectional images of a body. As tomographic scans require mechanical movement of components, data acquisition is commonly too slow to capture dynamic processes, which are faster than the acquisition time for a single image. Time-averaged angle-resolved CT imaging is a more recent method, which has demonstrated a capability to sharply image fast rotating machinery components by synchronizing data acquisition with rotation. However, in this modality all information on static parts disappear. In this paper, a novel data acquisition approach is introduced that combines both CT imaging methods. Eventually, the developed method is exemplarily applied to the study of gas-liquid flow in an industrial centrifugal pump using high-resolution gamma-ray tomography imaging.

Helium Ion Microscopy is a relatively young imaging and nanofabrication technique which is based on a gas field ionization source.
It rasters a narrow beam of helium ions as across the surface of the specimen to obtain high resolution surface sensitive images.
Usually secondary particles such as electrons are collected for image formation but also photons, backscattered atoms or sputtered sample atoms can be used for image formation.
Thanks to the very high brightness of the source a lateral resolution as small as 0.5\,nm can be achieved.
The method is in particular suitable for obtaining high resolution images of insulating samples (such as ceramic materials and biological samples) as the built in charge compensation allows to observe such specimen with out any additional conductive coatings.
In this contribution I will introduce the method and briefly introduce the underlying physics.
In the rest of the chapter a number of imaging modes will be discussed and selected examples will be presented.
Finally, an outlook is presented on the ongoing efforts to add analytical capabilities to the method.

The depth resolution of mono-energetic positron annihilation spectroscopy using a positron beam is shown to improve by concurrently removing the sample surface layer during positron beam spectroscopy. During ion beam sputtering with argon ions, Doppler-broadening spectroscopy is performed with energies ranging from 3 keV to 5 keV allowing for high-resolution defect studies just below the sputtered surface. With this technique, significantly improved depth resolutions could be obtained even at larger depths when compared to standard positron beam experiments which suffer from extended positron implantation profiles at higher positron energies. Our results show that it is possible to investigate layered structures with a thickness of about 4 microns with significantly improved depth resolution. We demonstrated that a purposely generated ion-beam induced defect profile in a silicon sample could be resolved employing the new technique. A depth resolution of less than 100 nm could be reached.

Magnetic and microstructural properties of <111> textured Cu/Nx[Co/Ni] films are studied as a function of the number of bilayer repeats N and annealing temperature. M(H) loop measurements show that coercivity, H_c, increases with annealing temperature and that the slope of the saturation curve at H_c has a larger reduction for smaller N. An increase of the magnetic anisotropy (K_u) to saturation magnetization (M_s) ratio after annealing Nx[Co/Ni] with N < 15 only partially describes the increase to H_c. Energy-dispersive X-ray spectroscopy analyses performed in scanning transmission electron microscopy mode across cross-sections of as-deposited and annealed Cu/16x[Co/Ni] films show that Cu diffuses from the seed layer into grain boundaries of Co/Ni. Diffusion of Cu reduces exchange coupling (H_ex) between the magnetic grains and explains the increase in H_c. Additionally, the difference in the slope of the M(H) curves at H_c between the thick (N = 16) and thin (N = 4) magnetic multilayers is due to Cu diffusion more effectively decoupling magnetic grains in the thinner multilayer.

The prognosis of patients with esophageal carcinoma remains dismal despite ongoing efforts to improve treatment options. For locally advanced tumors, several randomized trials have shown the benefit of neoadjuvant chemoradiation followed by surgery compared to surgery alone. The aim of this exploratory study was to evaluate the prognostic value of different baseline positron emission tomography (PET) parameters and their potentially additional prognostic impact at the end of neoadjuvant radiochemotherapy. Furthermore, the standard uptake ratio (SUR) as a new parameter for quantification of tumor metabolism was compared to the conventional PET parameters metabolic active volume (MTV), total lesion glycolysis (TLG), and standardized uptake value (SUV) taking into account known basic parameters.

Methods: 18F-FDG-PET/CT was performed in 76 consecutive patients ((60±10) years, 71 males) with newly diagnosed esophageal cancer before and during the last week of neoadjuvant radiochemotherapy. MTV of the primary tumor was delineated with an adaptive threshold method. The blood SUV was determined by manually delineating the aorta in the low dose CT. SUR values were computed as scan time corrected ratio of tumor SUVmax and mean blood SUV. Univariate Cox regression and Kaplan-Meier analysis with respect to locoregional control (LRC), freedom from distant metastases (FFDM), and overall survival (OS) was performed. Additionally, independence of PET parameters from standard clinical factors was analyzed with multivariate Cox regression.

Results: In multivariate analysis two parameters showed a significant correlation with all endpoints: restaging MTV and restaging SUR. Furthermore, restaging TLG was prognostic for LCR and FFDM. For all endpoints the largest effect size was found for restaging SUR. The only basic factors remaining significant in multivariate analyses were histology for OS and FFDM and age for LRC.

Conclusion: PET provides independent prognostic information for OS, LRC, and FFDM in addition to standard clinical parameters in this patient cohort. Our results suggest that the prognostic value of tracer uptake can be improved when characterized by SUR rather than by SUV. Overall, our investigation revealed a higher prognostic value of restaging parameters compared to baseline PET; therapy-adjustments would still be possible at this point of time. Further investigations are required to confirm these hypothesis-generating results.

Purpose: 18F-fluorodeoxyglucose (FDG) uptake within irradiated non-tumor affected oesophagus (NTO) at re-staging positron emission tomography (PET) is a potential surrogate to measure radiation induced inflammation (RIF). RIF itself was shown to be of high prognostic relevance in patients undergoing preoperative radiochemotherapy (RCT) for locally advanced oesophageal cancer. We assessed the prognostic relevance of NTO uptake in an independent cohort of patients treated with definitive RCT.

Methods: Seventy-two patients with oesophageal squamous cell carcinomas treated with curative intent definitive RCT were retrospectively evaluated. All patients underwent pre-treatment and re-staging FDG-PET after 40-50 Gray radiation dose. Standardized uptake values (SUVmax/SUVmean), metabolic tumor volume (MTV) and relative changes between pre-treatment and re-staging PET (∆SUVmax/∆SUVmean) were determined within tumor and NTO. Univariate Cox regression with respect to overall survival (OS), local control (LC), distant metastases (DM) and treatment failure (TF) was performed. Independence of parameters was tested in multivariate Cox regression.

Results: ∆SUVmax NTO and MTV were prognostic factors for all investigated clinical endpoints (OS, LC, DM, TF). Inclusion of clinical and PET tumor parameters in multivariate analysis showed ∆SUVmax NTO as an independent prognostic factor. Furthermore, multivariate analysis of ∆SUVmax NTO with previously published cutoffs from the preoperatively treated patients revealed ∆SUVmax NTO as independent prognostic factor for OS (HR=1.88, p=0.038), TF (HR=2.11, p=0.048) and DM (HR=3.02, p=0.047).

Conclusions: NTO-related tracer uptake during course of treatment in patients suffering from esophageal carcinoma was proven to be of high prognostic relevance. Thus, metabolically activity of NTO measured by ∆SUVmax NTO is a potential candidate for future treatment individualization (i.e. organ preservation).

Objectives: Partial volume (PV) correction is an important step in arterial spin labeling (ASL) MRI used to separate perfusion effects from structural, and to calculate the mean gray-matter (GM) perfusion. There are currently three main methods to perform that: (1) including only voxels with GM volume above a preset threshold (GM-Threshold); (2) using weighted voxel contribution combined with thresholding (GM-Weighted); or (3) applying a spatial linear regression algorithm (PVEc). In all cases, GM volume is obtained from PV maps extracted from T1w images. As such, PV maps contain errors due to the difference in readout-type (a major source of geometric distortions) and spatial resolution between ASL and T1w images. Here, we estimated these errors and evaluated their effect on the performance of each PV-correction method.
Materials and Methods: Twenty-two volunteers were scanned using 2D EPI and 3D spiral ASL. For each PV-correction method, GM CBF was computed using PV maps simulated to contain estimated errors due to geometric distortions and resolution mismatch. Results were analyzed to assess the effect of each error on extraction of GM CBF from ASL data.
Results: Geometric distortion had the largest effect on the 2D EPI data whereas resolution mismatch on the 3D spiral. The PVEc method outperformed the GM-Threshold even in the presence of combined errors. The quantitative advantage of PVEc was 16% without and 10% with the combined errors for both readouts. Consistent with theoretical expectations, for error-free PV maps, PVEc method extracted the true GM CBF. In contrast, GM-Weighted overestimated GM CBF by 5% whereas GM-Threshold underestimated it by 16%. The presence of PV-map errors decreased the calculated GM CBF for all methods.
Conclusion: The quality of PV maps presents no argument for preferring the GM-Threshold method to PVEc in clinical applications of ASL.

Photoconductive antennas (PCAs) are among the most conventional devices used for emission as well as detection of terahertz (THz) radiation. However, due to their low optical-to-THz conversion efficiencies, applications of these devices in out-of-laboratory conditions are limited. In this paper, we report several factors of enhancement in THz emission efficiency from conventional PCAs by coating a nano-layer of dielectric (TiO2) on the active area between the electrodes of a semi-insulating GaAs-based device. Extensive experiments were done to show the effect of thicknesses of the TiO2layer on the THz power enhancement with different applied optical power and bias voltages. Multiphysics simulations were performed to elucidate the under-lying physics behind the enhancement of efficiency of the PCA. Additionally, this layer increases the robustness of the electrode gaps of the PCAs with high electrical insulation as well as protect it from external dust particles.

Photoconductive terahertz (THz) emitters have been fulfilling many demands required for table-top THz time-domain spectroscopy up to 3-4 THz. In contrast to the widely used photoconductive materials such as GaAs and InGaAs, Ge is a non-polar semiconductor characterized by a gapless transmission in the THz region due to absence of one-phonon absorption. We present here the realization of a Ge-based photoconductive THz emitter with a smooth broadband spectrum extending up to 13 THz and compare its performance with a GaAs-based analogue. We show that the spectral bandwidth of the Ge emitter is limited mainly by the laser pulse width (65 fs) and, thus, can be potentially extended to even much higher THz frequencies.

⁶⁴Cu wird für die nuklearmedizinische Anwendung diskutiert. Neben der Kernumwandlung über Elektroneneinfang werden auch Positronen und Auger-Elektronen (AE) emittiert. Um deren Wirkungspotential an DNA zu untersuchen, wurden zunächst zwei Pyrenderivate mit unterschiedlicher Spacerlänge zwischen Pyreneinheit und DOTA-Chelator mit [⁶⁴Cu]CuCl₂ radiomarkiert. Die induzierten Strahlenschäden an pUC19 Plasmid-DNA wurden in Abhängigkeit von der Dosis untersucht.

Bubble columns are widely applied reactors in the chemical process industry due to their excellent heat and mass transfer properties as well as their simple design and easy manufacturing without any moving part. Fischer-Tropsch and methanol syntheses are typical processes carried out in such columns. Most of the involved reactions are highly exothermic and require an efficient heat removal, for example, via internal tube bundle heat exchangers. Heat exchangers, with up to 60 m2 m-3 surface area, can be installed as dense tube bundles covering up to 60 % of the cross-sectional area, which accordingly, alter hydrodynamics, flow patterns, mixing and mass transfer significantly.
Therefore, this study aims at revealing the influence of common tube bundle layouts, i.e. triangular and square pitches, at various tube diameters at approx. 25 % cross-sectional area coverage. The studies were carried out using narrow and pilot-scale bubble columns with 100 and 400 mm diameter, respectively, operated with air and water. Ultrafast X-ray tomography as well as wire-mesh sensors were applied to study the columns’ hydrodynamics as well as the flow in individual sub-channels. In particular, holdup and bubble size distributions were measured and compared for both columns. Furthermore, it is discussed to which extend hydrodynamic parameters, such as radial holdup profiles and gas velocity profiles etc., can be utilized for scale-up purposes based on hydrodynamic similarity at both reactor scales.

Positron emission tomography (PET) is "an analytical imaging technology developed to use compounds labelled with positron-emitting radioisotopes as molecular probes to image and measure biochemical processes of mammalian biology in vivo" [1]. One outstanding feature of the PET technology is the ability to perform absolute quantification of regional perfusion, metabolism, and function [2]. There are clinical demands for quantification regarding description of biodistribution, dosimetry, intra- and inter-individual comparisons, and setup of age- and gender-specific (normal) databases. Notably, FDG PET allows diagnosis, differential diagnosis, assessment of prognosis, and patient stratification in malignant disease. Moreover, image guided therapy has been proven to improve tumour delineation and irradiation field definition regarding protection of normal tissue and dose escalation on tumour tissue [3]. After initial assessment, follow-up investigations describe the effect of therapy and influence therapeutic management regarding continuation or change of modality and intensification or de-escalation of therapy. In addition to qualitative description and quantification of tracer uptake or uptake changes during follow-up, more sophisticated kinetic modelling and analysis may be applied. However, reliability and significance of all derived numbers is influenced by technical factors and biological processes.

Synchrocyclotrons and laser based particle accelerators, developed with the goal to enable more compact particle therapy facilities, may bring highly pulsed radiation field to external beam radiation therapy. In addition, such highly pulsed fields may be desirable due to their potential clinical benefits regarding better healthy tissue sparing or improved gating for moving tumors. However, they pose new challenges for dosimetry, the corner stone of any application of ionizing radiation.
These challenges affect both clinical and radiation protection dosimetry. Air-filled ionization chambers, which dominate clinical dosimetry, face the problem of increased signal loss due to volume recombination when a highly pulsed field liberates a large amount of charge in a short time in the chamber. While well established descriptions exist for this volume recombination for the moderately pulsed fields in current use (Boag's formulas), the assumptions on which those descriptions are based will most likely not hold in the prospective, highly pulsed fields of future accelerators. Furthermore, ambient dose rate meters used in radiation protection dosimetry as survey meters or fixed installations are generally only tested for continuous fields, casting doubt on their suitability to measure pulsed fields.
This thesis investigated both these aspects of dosimetry - clinical as well as radiation protection - to enable the medical application of highly pulsed radiation fields. For a comprehensive understanding, experimental investigations were coupled with theoretical considerations and developments.
Pulsed fields, varying in both dose-per-pulse and pulse duration over a wide range, were generated with the ELBE research accelerator, providing a 20 MeV pulsed electron beam. Ionization chambers for clinical dosimetry were investigated using this electron beam directly, with an aluminium Faraday cup providing the reference measurement. Whereas the dose rate meters were irradiated in the photon field generated from stopping the electron beam in the Faraday cup. In those measurements, the reference was calculated from the ionization chamber, then serving a an electron beam monitor, cross-calibrated to the photon field with thermoluminescent dosimeters.
Three dose rate meters based on different operating principles were investigated, covering a large portion of the operating principles used in radiation protection: the ionization chamber based RamION, the proportional counter LB 1236-H10 and the scintillation detector AD-b. Regarding clinical dosimetry, measurements of two prominent ionization chamber geometries, plane-parallel (Advanced Markus chamber) and thimble type (PinPoint chamber), were performed. In addition to common air-filled chambers, chambers filled with pure nitrogen and two non-polar liquids, tetramethylsilane and isooctane, were investigated.
In conjunction with the experiments, a numerical solution of the charge liberation, transport, and recombination processes in the ionization chamber was developed to calculate the volume recombination independent of the assumptions necessary to derive Boag's formulas. Most importantly, the influence of the liberated charges in the ionization chamber on the electric field, which is neglected in Boag's formulas, is included in the developed calculation.
Out of the three investigated dose rate meters only the RamION could be identified as an instrument truly capable of measuring a pulsed field. The AD-b performed below expectations (principally, a scintillator is not limited in detecting pulsed radiation), which was attributed to the signal processing, emphasizing the problem of a typical black-box signal processing in commercial instruments. The LB 1236-H10, on the other hand, performed as expected of a counting detector. While this supports the recent effort to formalize these expectations and standardize testing for counting dosimeters in DIN IEC/TS 62743, it also highlights the insufficiency of counting detectors for highly pulsed fields in general and shows the need for additional normative work to establish requirements for dose rate meters not based on a counting signal (such as the RamION), for which no framework currently exists. With these results recognized by the German radiation protection commission (SSK) the first steps towards such a framework are taken.
The investigation of the ionization chambers used in radiation therapy showed severe discrepancies between Boag's formulas and the experimentally observed volume recombination. Boag's formulas describe volume recombination truly correctly only in the two liquid-filled chambers. All the gas-filled chambers required the use of effective parameters, resulting in values for those parameters with little to no relation to their original meaning. Even this approach, however, failed in the case of the Advanced Markus chamber for collection voltages ≥ 300 V and beyond a dose-per-pulse of about 100 mGy.
The developed numerical model enabled a much better calculation of volume recombination and allowed the identification of the root of the differences to Boag's formulas as the influence of the liberated charges on the electric field. Increased positive space charge due to increased dose-per-pulse slows the collection and reduces the fraction of fast, free electrons, which are unaffected by volume recombination. The resultant increase in the fraction of charge undergoing volume recombination, in addition to the increase in the total amount of charge, results in an increase in volume recombination with dose-per-pulse that is impossible to describe with Boag's formulas. It is particularly relevant in the case of high electric fields and small electrode distances, where the free electron fraction is large. In addition, the numerical calculation allows for arbitrary pulse durations, while Boag's formulas apply only to very short pulses.
In general, the numerical calculation worked well for plane-parallel chambers, including those filled with the very diverse media of liquids, nitrogen and air. Despite its increased complexity, the thimble geometry could be implemented as well, although, in the case of the PinPoint chamber, some discrepancies to the experimental data remained, probably due to the required geometrical approximations.
A possible future development of the numerical calculation would be an improved description of the voltage dependence of the volume recombination. At the moment it requires characterizing a chamber at each desired collection voltage, which could be eliminated by an improved modeling of the volume recombination's dependence on collection voltage. Nevertheless, the developed numerical calculation presents a marked improvement over Boag's formulas to describe the dose-per-pulse dependence and pulse duration dependence of volume recombination in ionization chambers, in principle enabling the application of ionization chambers in the absolute dosimetry of highly pulsed fields.

We report the first determination of the in-plane complex optical conductivity of 1111 high-Tc superconducting iron oxypnictide single crystals PrFeAs(O,F) and thin films SmFeAs(O,F) by means of conventional and microfocused infrared spectroscopy, ellipsometry, and time-domain THz transmission spectroscopy. A strong itinerant contribution is found to exhibit a dramatic difference in coherence between the crystal and the film. Using extensive temperature-dependent measurements of THz transmission, we identify a previously undetected 2.5-meV collective mode in the optical conductivity of SmFeAs(O,F), which is strongly suppressed at Tc and experiences an anomalous T-linear softening and narrowing below T∗≈110  K≫Tc. The suppression of the infrared absorption in the superconducting state reveals a large optical superconducting gap with a similar gap ratio 2Δ/kBTc≈7 in both materials, indicating strong pairing.

With ultra-high intensity short pulse lasers generating plasma, new extreme states of matter can be created, and new concepts for particle acceleration, material science, and fusion energy can be explored. A critical component is the characterization of relativistic electrons that are accelerated and transported in the material of the target, generating ultra-intense bremsstrahlung.
Measuring the bremsstrahlung spectrum is a crucial aspect of plasma diagnostics. In this work it is showed how calorimetric techniques, based on longitudinally resolved measurements of energy deposition, are especially suitable for the reconstruction of the photon spectra and how electron dynamics can be studied.
Multi-layered scintillator calorimeters with different readouts are under development at Helmholtz-Zentrum Dresden-Rossendorf for this purpose. Prototypes have been tested at the ELBE facility both at the gELBE beamline with a well-known bremsstrahlung spectrum and in a laser-plasma environment at DRACO.

GeoPET is the application of positron emission tomography (PET) for direct, non-destructive, quantitative spatiotemporal measurement and visualization of fluid transport in natural geological media on drill-core scale. Data on heterogeneous flow and diffusion can be extracted from PET experiments which can be used to parameterize reactive transport models that better reflect the heterogenous nature of geochemical transport processes.
GeoPET functions through the use of positron emitting radioactive isotopes. The emitted positron quickly annihalates with electrons inside the matrix setting the physical resolution limit of the PET technique at about 1 mm spatial resolution. Upon annihilation two gamma photons are sent out in opposite directions that are detected coincidentally and thus hold information about the location of the original decay. This can be used to keep track of solute species, particles and solids. Through the use of [F-18]KF (halflife: 1.8 h) we are able to visualize heterogenous flow in geological media on drill-core scale and to extract flow fields and porosity data from the yielded data. Using Na-22 (halflife: 250 d) longer-term diffusion experiments can be perfomed and matrix-diffusion coefficients can be extracted from the data. Furthermore, through the development of appropriate labeling strategies we have visualized the transport of [I-124]MWCNTs and the initial stages of [Cu-64]CuS leaching.
In case of the technologically interesting application of in-situ copper bioleaching we have imaged matrix diffusion and the heterogenous flow through a Kupferschiefer sandstone fractured core sample. The extracted flow velocity fields and diffusion coefficients were used to parameterize a reactive transport model in the COMSOL-PHREEQC interface (iCP) to simulate mineral dissolution/precipitation, porosity change, as well as, copper extraction in the sequential leaching process employed within the BIOMOre project including water washing, acid washing and ferric iron acid leaching.

We focus on the transport behaviour of Cu under conditions related to a biohydrometallurgical leaching approach using neutrophilic microorganisms in neutral to slightly alkaline solutions. The effect of the microbial siderophore desferrioxamineB (DFOB) as a model leaching organic ligand on mobility and transport of Cu in the presence of kaolinite was investigated in column experiments. A geochemical transport model was established to describe the results. It was found that DFOB strongly enhances Cu mobility. The reactive transport model (including a surface complexation model) shows good agreement with the experimental data and is suitable to predict the transport behaviour of Cu in dependence on geochemical conditions.
The results of modeling revealed that in the absence of the ligand, a pH increase from 6.5 to 8.5 significantly retarded Cu breakthrough, whereas in the presence of DFOB, Cu breakthrough curves were nearly insensitive to pH changes and close to the breakthrough curve of a non-reactive tracer.

A structural study of the surface complexation of Pb(II) on the (View the MathML source) surface of hematite was undertaken using crystal truncation rod (CTR) X-ray diffraction measurements under in situ conditions. The sorbed Pb was found to form inner sphere (IS) complexes at two types of edge-sharing sites on the half layer termination of the hematite (View the MathML source) surface. The best fit model contains Pb in distorted trigonal pyramids with an average Pbsingle bondO bond length of 2.27(4) Å and two characteristic Pb-Fe distances of 3.19(1) Å and 3.59(1) Å. In addition, a site coverage model was developed to simulate coverage as a function of sorbate-sorbate distance. The simulation results suggest a plausible Pb-Pb distance of 5.42 Å, which is slightly larger than the diameter of Pb’s first hydration shell. This relates the best fit surface coverage of 0.59(4) Pb per unit cell at monolayer saturation to steric constraints as well as electrostatic repulsion imposed by the hydrated Pb complex. Based on the structural results we propose a stoichiometry of the surface complexation reaction of Pb(II) on the hematite (1-102) surface and use bond valence analysis to assign the protonation schemes of surface oxygens. Surface reaction stoichiometry suggests that the proton release in the course of surface complexation occurs from the Pb-bound surface O atoms at pH 5.5.

In the framework of the EU Horizon 2020 research project “BIOMOre” we developed a benchmark 3D reactive transport model to evaluate and predict insitu leaching (ISL) of fractured calcareous Kupferschiefer ore deposites. A critical challenge of our tasks is the implementation of the feedback between the evolution of porosity due to mineral dissolution/precipitation and modifications of the hydrodynamics of the reacting fluid. The sequential leaching of a calcareous sulfidic sandstone core (D=6 cm, L=10 cm) sampled from Kupferschiefer ore formation (Rudna mine, Poland) was done in laborytory. Here we present simulated results of the leaching of the core sample.
Geochemical modeling was performed by means of the COMSOL-PHREEQC interface iCP. The governing equations for fluid flow and conservative tracer transport are solved within the finite element code Comsol Multiphysics®. The geochemical processes considered in the model are kinetically controlled mineral dissolution and precipitation and equilibrium aqueous complexation reactions based on mass action law simulated by means of PHREEQC using BRGM database and advective-dispersive transport in the fracture and matrix diffusion in the rock mass calculated by COMSOL Multiphysics.
Calculated solution concentration of the outflow compares fairly well with the variation in the measured concentrations. Results showed that Cl is mainly released from halite which is totally removed in the washing stages. In addition our results showed that in stages 1, 2, and 3 about 0.04, 0.21, and 8.3% of Cu was extracted from sample respectively.

The influence of dense vertical tube bundles in a batch bubble column reactor of 100 mm diameter and 1100 mm clear liquid height on liquid dispersion and gas-liquid mass transfer was studied. In particular, the effects of different tube patterns (triangular and square pitch), tube diameters (8 and 13 mm) and bottom end designs (flat and U-tube) having a tube diameter-to-pitch ratio of approx. 1.3 were investigated.
Dispersion coefficients were determined based on conductive tracer experiments recorded via wire-mesh sensors (WMS) with up to 90 measurement points distributed in the column’s cross-section in between the tubes. The gas-liquid mass transfer coefficient was determined via fast-responding oxygen needle probes. Tube pitch and pattern were identified as the most crucial design parameters for the extent of liquid dispersion. We found that particularly the U-tube bottom end design induces large liquid circulation patterns, which enhance dispersion. The presence of internals decreases the k_l a value as a consequence of turbulence damping, which is also confirmed by lower k_l values (e.g. 0.6 × 10-3 m s-1 for the empty BCR and 0.25 × 10-3 m s-1 for the square pitch with 8 mm tubes at 0.05 m s-1 superficial gas velocity), whereas the pitch is the most decisive design parameter. The U-tube bottom end design was identified as the most beneficial configuration with respect to liquid mixing and gas-liquid mass transfer.

We study the evolution of magnetoresistance with temperature in thin film bilayers consisting of platinum and antiferromagnet Cr2O3 with its easy axis out of the plane. We vary the temperature from 20 °C to 60 °C, in the vicinity of the Néel temperature of Cr2O3 of approximately 37 °C. The magnetoresistive response is recorded during rotations of the external magnetic field in three mutually orthogonal planes. A large magnetoresistance having a symmetry consistent with a positive spin Hall magnetoresistance is observed in the paramagnetic phase of Cr2O3, which however vanishes when cooling to below the Néel temperature. Compared to analogous experiments in a Gd3Ga5O12/Pt bilayer, we conclude that a paramagnetic moment in the insulator induced by an applied magnetic field is not sufficient to explain the observed magnetoresistance. We speculate that the type of magnetic moment at the interface qualitatively impacts the spin angular momentum transfer, with the 3d moments of Cr sinking angular momentum much more efficiently as compared to the more localized 4f moments of Gd.

Thorough understanding of the aqueous complexation of U(VI) with ubiquitous inorganic ligands, such as hydroxide and carbonate, is crucial for predicting U(VI) mobility in natural and engineered systems, since retardation processes largely depend on the metal speciation. U(VI) hydrolysis [1] and complexation with carbonate in weakly alkaline media [2] have been extensively studied. This work systematically elucidates the U(VI) speciation in (hyper)alkaline solutions, where OH- and CO32- can occur in approximately equimolar quantities and compete for the complexation with U(VI). Such (hyper)alkaline conditions can evolve within deep geological repositories for radioactive waste by degradation of concrete. The effect of pH-dependent changes on the U(VI) sorption affinity was investigated by batch sorption experiments with Ca-bentonite, which is considered as buffer and backfill material within such repositories. Spectroscopic measurements provide information on the underlying retention mechanisms on the molecular level.
Time-resolved laser-induced fluorescence spectroscopy (TRLFS) proofs the formation of (calcium) uranyl carbonate complexes in aqueous solution in the presence of carbonate. However, these complexes only form up to a certain pH. A sudden change of the speciation to uranyl hydroxides was detected above pH 10 at low carbonate concentrations (0.5 mM) and above pH 11 at high carbonate concentrations (100 mM).
Batch sorption experiments reveal that this ligand replacement of carbonate by hydroxide correlates with an increase in U(VI) retention by Ca-bentonite. The study shows that an almost complete sorption of U(VI) can be obtained in (hyper)alkaline repository environments, even though carbonate is present in substantial amounts.
In order to clarify the mechanisms responsible for the very strong U(VI) retention, uranyl complexes on the bentonite surface were examined directly, using X-ray absorption spectroscopy (Rossendorf Beamline (ROBL), ESRF, Grenoble). Extended X-ray absorption fine structure (EXAFS) spectra did not show any indication of precipitates, implying that adsorption is the dominant retention process. In all samples with high U(VI) retention, the derived uranium coordination is identical irrespective of the amount of contained carbonate. According to atomic distances and coordination numbers, the U(VI) surface complexes shift from a 5-fold to a 4-fold coordination in the equatorial plane with increasing pH. Attachment might be facilitated by charge balancing cations (i.e. Ca2+) that mediate between the negatively charged clay surface and the anionic aqueous U(VI)-hydroxide complexes.

Einleitung
Echtzeit-Magnetresonanztomographie kann die Präzision der Protonentherapie verbessern.
Ziel dieser Arbeit war die Charakterisierung der Bildqualität eines in-Beam MR-Scanners während der Bestrahlung.

Material & Methoden
Ein offener 0.22 T MR-Scanner (MrJ2200, Paramed) wurde im Isozentrum einer horizontalen Protonenstrahlanlage installiert. Die MR-Bildqualität wurde anhand zweier Komponenten beurteilt. Erstens wurde die Homogenität des Magnetfeldes des MR-Scanners innerhalb eines sphärischen Volumens von 22 cm Durchmesser mithilfe einer Magnetfeldkamera (MFC3045/48, Metrolab) vermessen. Dabei wurde der Einfluss der Strahlführungsmagnete, für Protonenenergien zwischen 70 und 220 MeV, untersucht. Zweitens wurde die Bildqualität ausgehend vom Protokoll des American College of Radiology (ACR) mittels des kleinen ACR Phantomes in einer dedizierten Kniespule untersucht. Hierzu wurden sowohl die vorgegebenen T1 und T2 Spin-Echo (SE) Sequenzen als auch zwei T1- und T2*-gewichtete Gradienten-Echo (GE) Sequenzen genutzt. Neben Referenzbildern mit ausgeschalteter Strahlanlage wurden Bilder in verschiedenen Szenarien sowohl unter dem Einfluss der Strahlführungsmagnete sowie unter direkter Bestrahlung aufgenommen. Hierfür wurde ein auf 10 mm Durchmesser kollimierter Strahl der Energie 125 MeV mit Dosisraten von 1 bzw. 80 Gy/min verwendet. ACR Bildparameter sowie Bildverschiebungen wurden mithilfe einer validierten Software (Matlab) ermittelt.

Ergebnisse
Die Magnetfeldhomogenität innerhalb des untersuchten Bereiches betrug 88 ppm (peak-to-peak). Unter dem Einfluss der Strahlführungsmagnete wurden Änderungen kleiner 3 ppm gemessen, weiterhin jedoch eine Verschiebung der mittleren Resonanzfrequenz, abhängig von der gewählten Strahlenergie, um 70 bis 110 Hz. Die T1-gewichteten GE Bilder enthalten Streifenartefakte; alle anderen SE und GE Bilder konnten ausgewertet werden. Es existieren keine signifikanten Unterschiede in den ACR Parametern zwischen den unterschiedlichen Szenarien. Bildverschiebungen in Frequenzkodierrichtung betrugen zwischen 0.5 und 3 mm und weisen eine indirekte Proportionalität zu den Gradientenstärken der einzelnen Sequenzen auf.

Zusammenfassung
Die Bildqualität des in-Beam MR-Scanners erfüllt die Spezifikationen des Herstellers sowie der ACR. Es wurde keine Änderung der MR-Bildqualität unter simultaner Bildgebung und Bestrahlung festgestellt, jedoch müssen Bildverschiebungen sequenzabhängig kompensiert werden.

Einleitung:

Falls bei der Therapieplanung CT-Kontrastmittel (KM) zur Diagnose und Konturierung eingesetzt wird, muss zur Dosisberechnung in der Regel ein weiteres, „natives“ CT-Bild ohne KM aufgenommen werden. Grund dafür ist der Einfluss der hohen Ordnungszahl des im KM enthaltenen Iods. Dieser kann durch den Einsatz von Dual-Energy-CT (DECT) korrigiert werden, was die Planung auf KM-angereicherten Bildern ermöglicht.

Material & Methoden:

Der Effekt eines gebräuchlichen KM (Imeron® 300, Bracco Imaging Deutschland GmbH) auf die ermittelte Elektronendichte wurde in CT-Bildern (a) einer Verdünnungsreihe in Wasser und (b) von 7 Hirntumorpatienten gemessen. Mit einem Somatom Definition Flash DECT-Scanner (Siemens Healthineers), ausgestattet mit zwei Röntgenröhren, wurden Bilder im 120 kVp Single-Energy-CT (SECT) Modus (nur a) und 80/140Sn kVp DECT-Modus (a und b) aufgenommen. Bei den Patienten (b) wurde jeweils ein Scan mit und ohne KM durchgeführt. Elektronendichte-Bilder wurden für SECT mit einer Hounsfield-Lookup-Tabelle und für DECT mit der Software Syngo.CT Rho/Z (Siemens Healthineers) erstellt.

Ergebnisse:

Bei der Verdünnungsreihe (a) führte der Einfluss des KM in den 120 kVp Bildern zu einer Überschätzung der Elektronendichte von 5-10% bei typischer Anreicherung (maximal 6 mg Iod/ml). Diese Verfälschung konnte durch den Einsatz von DECT auf unter 1% begrenzt werden. Bei den Patienten (b) betrug die mittlere Differenz zwischen den 120 kVp-äquivalenten Nativ- und KM-Bildern im Ganzhirn 1.5-4.4%, die entsprechende Differenz in den Elektronendichte-Bildern nur 0.2-0.6% (Abb. 1).

Zusammenfassung:

Der Einfluss von KM auf die Elektronendichte kann mittels DECT auf unter 1% reduziert werden. Dies ermöglicht den Verzicht auf einen zusätzlichen nativen Scan und somit eine Vereinfachung des klinischen Workflows und eine Reduktion der Strahlendosis auf die Hälfte.

Purpose/Objective:

Dual-spiral dual-energy CT (DECT) provides additional patient information to improve range accuracy in proton therapy, but is prone to motion between the two consecutively acquired scans. Here, the clinical feasibility of dual-spiral time-resolved DECT (4D-DECT) for proton treatment planning within the thoracic region was evaluated.

Material/Methods:

4D-DECT scans of three non-small-cell lung cancer (NSCLC) patients were acquired during the course of treatment with a Siemens single-source DECT scanner (Fig.1). For temporally averaged datasets and four breathing phases, the geometrical conformity of both 4D-DECT scans before (80kVp/140kVp) and after (58keV/79keV) image post-processing including deformable image registration (DIR) was assessed by normalized cross correlation (NCC).
To evaluate the reliability of dose calculation, clinical treatment plans were recalculated on DECT-derived 79keV MonoCT and 140kVp SECT datasets as reference using a heuristic conversion (HLUT) from CT number to stopping-power ratio (SPR). Dose distributions were compared with gamma analyses (0.1% dose-difference, 1mm distance-to-agreement criterion).
Finally, range differences between HLUT and patient-specific DECT-based SPR prediction were quantified.

Results:

Respiration changes during 4D-DECT acquisition resulted in NCCs>80%, indicating geometrical deviations of (1-2)mm. This was almost completely corrected by DIR leading to a high geometrical conformity with average NCC ± SD = (99.6±0.4)% corresponding to anatomical shifts below 0.2mm (not visually distinguishable). Even the impact of coughing could be corrected by DIR (Fig.2).
Clinical dose distributions on 140kVp and 79keV datasets were similar with average gamma passing rate of 99.9% and maximal dose difference of 0.8%.
Clinically relevant mean range shifts of (2.2±1.2)% were determined between patient-specific DECT-based SPR prediction and HLUT.

Conclusion:

Dual-spiral 4D-DECT is applicable for dose calculation on 79keV MonoCT datasets in NSCLC patients. Patient-specific DECT-based SPR prediction performed properly and revealed its potential for reducing range uncertainty. Even if large motion differences hamper 4D-DECT post-processing, only the 140kVp scan can be used and additional information on respiration variability and robustness is gathered.

Purpose/Objective
The sub-percentage accuracy in proton stopping-power prediction of patient-individualized range prediction (PIRP) using dual-energy CT (DECT) was demonstrated in recent studies. Although DECT-derived pseudo-monoenergetic CT scans have been introduced into clinical routine, a heuristic conversion (HLUT) from CT number to stopping power ratio (SPR) is still necessary, Fig.1(1). We propose a method to refine the clinical HLUT by applying PIRP on a broad patient cohort as a step towards its clinical implementation.

Materials/Methods
Voxelwise correlations of CT number and SPR were obtained using DECT scans of 102 brain-tumor and 25 prostate-cancer patients treated with protons. The clinical HLUT was then refined by performing a step-wise weighted linear fit of the SPR distribution in different tissue regions, Fig.1(2). Furthermore, the intra- and inter-patient variability was quantified. To assess dose differences and range shifts, proton treatment plans were recalculated using the clinical and refined HLUT as well as PIRP.

Results
Between clinical HLUT and PIRP, mean range differences (±1SD) of (1.2±0.7)% for brain-cancer and (1.7±0.5)% for prostate-tumor patients were determined. On average, the clinical HLUT predicted larger SPR for brain, muscle and trabecular bone, leading to the systematic range deviations. They were significantly reduced (p≪0.001, two-sample t-test) below 0.3% by using the refined HLUT. However, an observed intra-patient soft-tissue diversity of 6% as well as an inter-patient bone diversity of 5% cannot be considered by any generic HLUT-based range prediction.

Conclusion
Retrospective application of PIRP allows for a reduction of systematic deviations found in clinical HLUT. In principal, this can also be transferred to particle-therapy centers not using DECT routinely. The refined HLUT was implemented at our institution as a step towards the currently ongoing full integration of PIRP. This includes the calibration, an end-to-end test as well as the quantification of prospects in safety margin reduction.

Nachdem wir uns sehr ausführlich über Verbindungen unterhalten haben, die Kohlenstoff-Kohlenstoff-Mehrfachbindungen enthalten (Alkene, Alkine, Aromaten), wollen wir zu Verbindungsklassen und funktionellen Gruppen kommen, bei denen Kohlenstoff-Heteroatom-Doppelbindungen existieren. Das sind insbesondere Aldehyde, Ketone, Carbonsäuren und deren Derivate. Im Gegensatz zu den nichtaktivierten C=C-Doppelbindungen sind diese Kohlenstoff-Heteroatom-Doppelbindungen bereits durch die Unterschiede in den EN-Werten aktiviert. Wir finden ein elektronegatives Zentrum am Heteroatom (Sauerstoff, Stickstoff oder Schwefel) und ein elektropositives Zentrum am Kohlenstoff. Somit ist die Regioselektivität bei nucleophilen bzw. elektrophilen Angriffen vorgegeben. Wenn beispielsweise Nucleophile an diese Doppelbindung angreifen, werden sie spezifisch an den Kohlenstoff gebunden, wohingegen die Elektrophile den Sauerstoff angreifen. Neben der Carbonylgruppe, in der der Sauerstoff über eine Doppelbindung gebunden ist gibt es auch carbonylanaloge Verbindungen mit Stickstoff oder Schwefel, wobei die Elektronegativitätsdifferenz und damit die Polarisierung der Doppelbindung in der Richtung O > N > S abnimmt.

In den vergangenen Heften haben wir uns ausführlich über die Reaktionen an gesättigten und ungesättigten Kohlenstoffatomen unterhalten, wobei wir die aromatischen Vertreter geflissentlich ausgelassen haben. Außerdem haben wir geschaut, welche Effekte diese Aromaten bzw. aromatische Reste wie Phenylgruppen auf die Stabilität von Zwischenstufen wie Carbanionen, Carbokationen oder Radikalen ausüben und welche Konsequenzen sich aus diesem Einfluss dann auf die Reaktivität und /oder (Regio-)Selektivität der Derivate ergeben.

Additionen sind die mit Abstand wichtigsten Reaktionen von ungesättigten Verbindungen (Alkenen, Alkinen, aber auch Carbonylverbindungen). Formal handelt es sich dabei um die Umkehrung der Eliminierungsreaktionen. Additionsreaktionen können radikalisch oder ionisch verlaufen. Im Falle eines ionischen Verlaufs können wir noch zwischen einem elektrophilen oder einem nucleophilen ersten Angriff auf die Doppelbindung unterschieden. Der vierte Typ umfasst die große Gruppe der Cycloadditionen. Diese pericyclischen Reaktionen kommen ohne geladene Teilchen aus und verlaufen meist konzertiert. Somit sind vier Typen von Additionen an die Doppelbindung zu unterscheiden.