Online Annual Review 2016: Scientific highlights
- Better quantification of tumor metabolism
- Creating diamond and lonsdaleite using shock-compression
- Magnetic vortex cores as tunable spin-wave emitters
- Researchers establish connection between solar cycle and planetary constellation
- Better understanding of geothermal ore forming processes
Better quantification of tumor metabolism
A new parameter which can be determined from PET images could be an important building block for customized cancer treatment. Researchers at HZDR have developed the Standard Uptake Ratio (SUR), with which tumor metabolism can be quantified more accurately than with the methods currently employed. This facilitates better prognoses for treatment and could be of use in the future for individualized treatment.
Up to now a parameter known as a Standard Uptake Value (SUV) has been used to quantify the tumor metabolism. However, it is very imprecise. Several studies have proven that a considerably better quantification can be achieved using SUR. Whether this also has benefits for patients was investigated by HZDR scientists in collaboration with clinics. Together with the Dresden OncoRay Center they evaluated the clinical data of 130 patients with a carcinoma of the esophagus. To do this, they correlated the PET parameters and further clinical features of the tumor with how the treatment was progressing.
The study revealed that the use of SUR allowed conclusions to be drawn regarding patients’ chances of survival, the risk of remote metastases or the development of a local recurrence. If prognoses like these were possible before the start of treatment, the treatment could be tailored accordingly, for example by using intensified chemotherapy or a higher dose of radiation. As a PET examination is carried out in any case, the SUR evaluation does not add any extra burden. Before the new technique can benefit patients it needs to be tested on a large number of patients in a prospective validation.
- Publication: F. Hofheinz et al., “An investigation of the relation between tumor-to-liver ratio (TLR) and tumor-to-blood standard uptake ratio (SUR) in oncological FDG PET“, in: EJNMMI Research, 2016 (DOI: 10.1186/s13550-016-0174-y)
- Contact: Dr. Frank Hofheinz, Institute of Radiopharmaceutical Cancer Research
Creating diamond and lonsdaleite using shock-compression
The transformation of graphite into diamond is of major scientific and technological interest. For the first time, HZDR researchers have managed to observe this very fast process, which takes place under extreme conditions. In order to simulate this special form of matter, a graphite sample was bombarded with high-intensity laser pulses. The experiment took place in Stanford, California with the X-ray laser at the Linac Coherent Light Source.
The surface of the material sample is heated extremely quickly by the laser pulses. This generates a shock wave which vigorously compresses and heats the material. For a couple of nanoseconds a warm, dense matter is created that otherwise only occurs in the center of planets or on Earth during a meteorite impact. During the analysis of the experiment at HZDR, clues were found which indicate diamond was formed - or even lonsdaleite, an exotic crystalline carbon which, in its pure form, would be harder than diamond. This structure would result from a shock-compression of around two million atmospheres. The "Helmholtz Young Investigator Group “Dynamic Warm Dense Matter Research with HIBEF”, led by Dr. Dominik Kraus, is currently researching how much of the structure remains following the bombardment. As nano-diamonds are used in medicine, amongst other industries, the controlled creation of diamonds and lonsdaleite has a considerable application potential.
For this kind of research, the HZDR is building the Helmholtz International Beamline for Extreme Fields (HIBEF) at the European XFEL in Schenefeld, near Hamburg. From 2018, scientists there will carry out investigations under extreme conditions, such as high pressures, temperatures or electromagnetic fields. Two new lasers will then be ready, with which material samples can be effectively compressed and heated.
Publication: D. Kraus, A. Ravasio, M. Gauthier, D. O. Gericke, J. Vorberger, S. Frydrych, J. Helfrich, L. B. Fletcher, G. Schaumann, B. Nagler , B. Barbrel, B. Bachmann, E. J. Gamboa, S. Göde, E. Granados, G. Gregori, H. J. Lee, P. Neumayer, W. Schumaker, T. Döppner, R. W. Falcone, S. H. Glenzer, M. Roth, "Nanosecond formation of diamond and lonsdaleite by shock compression of graphite", in: Nature Communications, 2016 (DOI-Link: 10.1038/ncomms10970)
- Contact: Dr. Dominik Kraus, Helmholtz Young Investigator Group "Dynamic Warm Dense Matter Research with HIBEF" / Institute of Radiation Physics
Magnetic vortex cores as tunable spin-wave emitters
Spin waves correspond to the collective fundamental excitations of magnetically ordered spin systems. The use of such spin waves as signal carriers in future spintronic information processing devices can substantially reduce power consumption compared to contemporary charge-based technologies, by preventing ohmic losses during the transmission of data. Yet, the coherent excitation of short-wavelength spin waves remained a significant challenge so far.
In this work, it was shown that the nanoscale cores of a stacked magnetic vortex pair can be driven to excite spin waves with wavelengths as short as 100 nm. We directly imaged this process of coherent spin-wave generation and subsequent radial propagation by means of time-resolved x-ray microscopy at the BESSY II synchrotron of the Helmholtz Zentrum Berlin. Thereby, it was also found that the emitted wavelengths can be directly and continuously tuned by the driving signal over a wide range of GHz frequencies. Furthermore, we determined the underlying spin-wave dispersion relation to be linear, gapless in frequency, and strongly non-reciprocal. The magnetic vortex pairs investigated in this study were induced prior to the microscopy experiments by applying ion beam modifications at the Ion Beam Center of HZDR.
Apart from the fundamental importance of the phenomena observed, the obtained results will open a way for the development of new and efficient bias-free non-reciprocal microwave signal-processing devices. At the same time, these results comply with achieving MAG.4 (Characterization and ion beam modification of magnetic relaxation channels in a single sub-100nm nanostructure).
- Press release: A Mini-Antenna for the Data Processing of Tomorrow
- Publication: S. Wintz, V. Tiberkevich, M. Weigand, J. Raabe, J. Lindner, A. Erbe, A. Slavin, J. Fassbender, „Magnetic vortex cores as tunable spin-wave emitters“, in: Nature Nanotechnology, 2016 (DOI-Link: 10.1038/nnano.2016.117)
- Contact: Dr. Sebastian Wintz, Paul Scherrer Institut (PSI) / Institute of Ion Beam Physics and Materials Research
Researchers establish connection between solar cycle and planetary constellation
Over a 22-year cycle, solar activity first increases and then decreases. The reason for this is the Sun’s magnetic field which reverses polarity approximately every eleven years. HZDR researchers assume that a specific planetary constellation can set the rhythm for this. They have developed a new theory, according to which planetary tidal forces are sufficient to directly influence the Sun’s activity. Amazingly, the solar field reversal cycle coincides exactly with the periods in which the Sun, Venus, the Earth and Jupiter are in alignment.
The Sun’s magnetic field is generated by the so-called alpha-Omega dynamo. As a result of the differential rotation of the hot conductive plasma, the Omega Effect creates a magnetic field in the form of two rings to the north and to the south of the solar equator. In turn, the alpha effect uses this to generate a magnetic field which runs along the Sun’s lines of longitude, between its poles. Exactly where and how the alpha dynamo originates is currently unknown.
The research team discovered that the alpha effect is prone to oscillations under certain conditions. The Tayler instability, which arises in the Sun’s hot plasma due to the interaction of the magnetic field and the current, plays an important role in this. For the first time, the researchers have found evidence for the Tayler instability also oscillating back and forth between right- and left-handedness. What is special about this is that the reversal happens with no change to the flow energy. This means that small forces are enough to initiate an oscillation in the alpha effect. Calculations show that the very weak tidal forces of Venus, the Earth and Jupiter are sufficient for this.
- Press release: Are planets setting the Sun’s pace?
- Publication: F. Stefani et al., „Synchronized helicity oscillations: A link between planetary tides and the solar cycle?”, in: Solar Physics, 2016 (DOI-Link:10.1007/s11207-016-0968-0)
- Contact: Dr. Frank Stefani, Institute of Fluid Dynamics
Better understanding of geothermal ore forming processes
Most non-ferrous metal ore deposits (lead, copper, zinc, tin) are created by the circulation of hot, often high-saline waters in the Earth’s upper crust. Thanks to high temperatures and salinity these solutions can dissolve considerable amounts of different trace elements from rocks which are deep down. These are then precipitated close to the surface due to either cooling, boiling or being mixed with surface waters and form an ore deposit.
In order to detect the deposits deep underground, a good understanding of the geological control parameters which lead to their creation is required. Where did the ore forming waters come from? From which rocks are the metals they contain leached? Which mechanism led to the precipitation of the ore? These are all important factors which are of great significance for the precise localization of a deposit.
An important indication of the nature of the ore forming process is the temperature and the salinity of the waters involved. Geologists who study ore deposits generally use the smallest inclusions of these waters in transparent minerals (quartz, fluorite), so-called fluid inclusions, in order to determine both of these parameters. However, this technique has many limitations. Firstly, the minerals being studied often do not form at the same time as the actual ore minerals meaning that they possibly record different conditions. Secondly, initial investigations only allow for a very spatially restricted analysis as fluid inclusions often only occur along isolated growth areas.
The chemical composition of the ore mineral itself offers an alternative to fluid inclusions. For example, the incorporation of specific trace elements is strongly dependent on the formation temperature. One element - or a combination of elements - can be used to determine the formation temperature. This is generally referred to as a “geothermometer”.
Researchers at the HZDR’s Helmholtz Institute Freiberg for Resource Technology (HIF) have developed one such thermometer for sphalerite in a new study. Sphalerite, zinc sulfide (ZnS), is the most important zinc mineral and occurs in almost every sulfured non-ferrous metal deposit, usually together with other relevant ore minerals. By means of a meta-analysis of geochemical data it was possible to show that the concentrations of some elements in sphalerite are strongly dependent on temperature. Conversely, this means that it is possible to use these interdependencies as a geothermometer and to better understand ore forming systems by analyzing the ore. The researchers hope to be able to make further minerals, such as pyrite, useful for geothermometry.
- Publication: M. Frenzel, T. Hirsch, J. Gutzmer, “Gallium, germanium, indium, and other trace and minor elements in sphalerite as a function of deposit type - A meta-analysis”, in: Ore Geology Reviews, 2016 (DOI-Link: 10.1016/j.oregeorev.2015.12.017)
- Contact: Dr. Max Frenzel, until January 2018 at the University of Adelaide