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Online Annual Report 2015

Scientific Highlights

New method for improved tumor diagnosis successfully tested on preclinical scale

Tracking the tumor: PNA-antibodies detect initially the diseased cells (red) and accumulate at the tumor site. Afterwards the radioactively labeled probes (blue) selectively bind to them by specific base pairing. Modern imaging methods allow the scientists thus to visualize the tumor. Foto: HZDR/Pfefferkorn

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in cooperation with colleagues at the Universities of Zurich and Bochum, have successfully tested a new tumor diagnosis method on mice under near-real conditions for the first time. For several years, cancer research has relied on radioactively labeled antibodies to diagnose and fight malignant tumors. Because they specifically interact with certain target structures, the diseased cells can be detected and treated with high precision.

One problem has thus far been their large molecular mass resulting in long circulation in the patient’s body for a relatively long period of time before they bind to the tumor cells. They thus also accumulate in healthy tissue. This substantially delays detection of the tumor and leads to detrimental radiation exposure of healthy organs. The researchers from Dresden, Zurich and Bochum have therefore chosen an alternative strategy, the so-called pretargeting approach. In this multistep process, unlabeled antibodies specific for the epidermal growth factor receptor – a cancer biomarker – are administrated in the first step. Upon injection, sufficient time is allowed for circulation, tumor accumulation and clearance of excess antibodies from the body.

In order to later deliver a radionuclide of choice to the tumor-bound antibodies, the researchers combined them with derivatives of the peptide nucleic acid (PNA) – a stable, synthetic DNA analog. The complementary PNA counterparts were radiolabeled with the diagnostic radionuclide technetium-99m and injected in a second step. These small molecules reach the malignant tissue quickly and bind the local antibody-PNA conjugates with minimal accumulation elsewhere. And indeed, the researchers were able to clearly visualize the tumor in a short period of time while minimizing the risk of radiation exposure of healthy tissues. Using this pretargeting approach, the researchers can overcome limitations of conventional radiolabeled antibodies, which is particularly important for therapeutic applications.

  • Press release: Molecular Spies to Fight Cancer
  • Publication: A. Leonidova, C. Foerster, K. Zarschler, M. Schubert, H. Pietzsch, J. Steinbach, R. Bergmann, N. Metzler-Nolte, H. Stephan, G. Gasser, „In vivo demonstration of an active tumor pretargeting approach with peptide nucleic acid bioconjugates as complementary system”, in: Chemical Science (2015), DOI: 10.1039/c5sc00951k
  • Contact: Dr. Holger Stephan, Institute of Radiopharmaceutical Cancer Research

Particle accelerator at the underground laboratory in Gran Sasso shows rare event

Entrance to the Gran Sasso laboratory of the Italian National Institute for Nuclear Physics. Foto: INFN

An international research group, in which scientists from the HZDR played a leading role, has demonstrated a nuclear reaction for the first time that only occurs in what are known as red giants. Many chemical elements that make up the matter in our surroundings are created within these enormous stars. At the end of the red giants’ lifecycle, these elements are hurled into the cosmos by means of gigantic explosions. The researchers at the Laboratory for Underground Nuclear Astrophysics (LUNA) in the Gran Sasso laboratory explore the processes that occur within stars. LUNA is part of the Italian National Institute for Nuclear Physics.

LUNA lies one-and-a-half kilometers beneath the Gran Sasso mountains. This thick rock cover protects the experiments from the disruptive influences of cosmic radiation. This enables the researchers to recreate conditions similar to those within stars. At the LUNA accelerator, the scientists could measure three hitherto unobserved “resonances” for the first time in the neon-sodium cycle, which is vital for sodium production. Particle physicists use the term "resonance" to denote interaction rate increases that only occur at very specific energies. If atomic nuclei collide, an excited nuclear state - a “resonance” - can form when the energy levels are right.

To carry out their studies, the researchers accelerated hydrogen nuclei and used them to bombard the neon-22 noble gas isotope. Using special detectors, they could subsequently observe the extremely rare process. The observed increase in sodium production may help explain the so-called neon-sodium anticorrelation observed in some stars.

  • Press release: The Puzzle of the Origin of Elements in the Universe
  • Publication: F. Cavanna, R. Depalo, M. Aliotta, M. Anders, D. Bemmerer, A. Best, A. Boeltzig, C. Broggini, C.G. Bruno, A. Caciolli, P. Corvisiero, T. Davinson, A. di Leva, Z. Elekes, F. Ferraro, A. Formicola, Z. Fülöp, G. Gervino, A. Guglielmetti, C. Gustavino, G. Gyürky, G. Imbriani, M. Junker, R. Menegazzo, V. Mossa, F. R. Pantaleo, P. Prati, D. A. Scott, E. Somorjai, O. Straniero, F. Strieder, T. Szücs, M.P. Takács, D. Trezzi, „Three new low-energy resonances in the 22Ne(p,gamma)23Na reaction“, in: Physical Review Letters, 115, 252501 (2015), DOI: 10.1103/PhysRevLett.115.252501
  • Contact: PD Dr. Daniel Bemmerer, Institute of Radiation Physics

Researchers discover giant magnetoresistance in new material

Giant magnetoresistance in niobum phosphide Illustration: Yulin Chen

Information technology is expected to process and save larger amounts of data faster and in a smaller amount of space. Engineers have therefore been exploiting physical effects such as giant magnetoresistance for quite a long time. This phenomenon describes the great alteration of the electrical resistance of a material when exposed to a magnetic field. This is how an increase in storage density could be achieved in modern hard drives. In order to attain this effect, the computer industry has relied on various delicately layered materials. The production of such systems is highly complex.

An alternative could arise from combining niobium and phosphorus: niobium phosphate. Researchers from the Max Planck Institute for Chemical Physics of Solids together with scientists from the Dresden High Magnetic Field Laboratory at the HZDR observed an approximately 10,000-fold resistance increase in this material. The reason for the drastic change is attributed to what is known as relativistic electrons within the niobium phosphate. These are superfast charge carriers, which move at approximately three hundred kilometers per second. The influence of the applied magnetic field in turn depends on the velocity of the electrons.

This phenomenon is due to the deflection of the charge carriers through the Lorentz force. This leads to the fact that with rising magnetic field an ever larger portion of the electrons flows in the wrong direction. The electrical resistance thus increases. The faster the electrons, the greater the effect of the magnetic field. As the researchers managed to demonstrate, the exotic characteristics of niobium phosphate are based on some electrons that behave as if they had no mass. They can thus move exceptionally fast. The material therefore may be highly suitable for future applications in information technology.

  • Press release: With 300 Kilometers per Second to New Electronics
  • Publication: C. Shekhar, A.K. Nayak, Y. Sun, M. Schmidt, M. Nicklas, I. Leermakers, U. Zeitler, Y. Skourski, J. Wosnitza, Z. Liu, Y. Chen, W. Schnelle, H. Borrmann, Y. Grin, C. Felser, B. Yan, „Extremely large magnetoresistance and ultrahigh mobility in the topological Weyl semimetal candidate NbP”, in: Nature Physics, 11, 645 (2015), DOI: 10.1038/nphys3372
  • Contact: Prof. Joachim Wosnitza, Dresden High Magnetic Field Laboratory

New model calculations predict the most economically efficient metal processing

Foto: TUBAF / Detlev Müller

One of the most important processes in extracting precious metals from deposits lies in the processing. This involves crushing the rock and separating the ore from the unusable waste rock, through an array of various methods. Which specific methods come into use depends on the ore properties, such as the mineralogical composition or the concentration of precious elements contained within.

HZDR researchers from the Helmholtz Institute Freiberg for Resource Technology have developed an adaptive method with which they can predict how processing methods must be combined and how equipment must be adjusted to achieve the most economically efficient yield. The development of such model calculations is particularly important for extracting economically strategic high-tech metals such as germanium, gallium, indium or rare earths. Due to their low concentration in mostly complex composite ores, they are often mined as by-products.

During the exploratory phase, an ore deposit is divided into several blocks of rock measuring approximately 1,000 cubic meters each. Based on drill core data and statistical methods, the mathematicians from Freiberg create series of alternative three-dimensional models with possible properties of these blocks. The researchers can thus derive what methods and settings are most likely to be suitable for the processing of each individual block. What is new within these computations is that the scientists can account for the fact that the ore properties of each block are not truly observed, but rather guessed from boreholes on its surroundings. The separation processes thus can be adjusted in the processing plant according to the locally changing ore properties and the data we have about them.

  • Publication: R. Tolosana-Delgado, U. Mueller, K.G. van den Boogaart, C Ward, J. Gutzmer, „Improving processing by adaptation to conditional geostatistical simulation of block compositions”, in: The Journal of the Southern African Institute of Mining and Metallurgy 115 (2015)
  • Contact: Dr. Raimon Tolosana Delgado, Helmholtz Institute Freiberg for Resource Technology

Better understanding emergency scenarios in nuclear reactors

The multipurpose thermalhydraulic test facility TOPFLOW is designed for the investigation of stationary and transient phenomena in two phase flows as well as for the development and validation of models used in computational fluid dynamic codes. Foto: HZDR / Rainer Weisflog

In nuclear reactors fission heat is used to heat water at high pressure, for example to about 300 degree Celsius in a pressurized water reactor. This way steam for operation of a turbine is generated in a secondary loop. In case of an emergency shut-down continuous cooling of fuel rods, which still produce decay heat, is essential for the safety of the nuclear reactor. If the emergency was caused by a leak in the primary loop, the loss of coolant has to be compensated by feeding additional water from extra reservoirs.

This water is, however, much colder than the reactor components. The difference in temperature due to insufficient mixing of hot and cold water could in turn cause thermomechanical strains in the reactor wall with the danger of crack initiation. Hence good mixing of hot water in the loop and cold feed water is essential. For this, scientists need to simulate the fluid flow and mixing by advanced and complex computer simulations.

Experimental data at plant conditions for validation of such computational fluid dynamics simulations are, however, scarce. Researchers from the HZDR Institute of Fluid Dynamics have now managed to separate different partial effects of the feed water injection process for the first time and observed them with high resolution measurement techniques. With a high-speed camera as well as mobile pressure and temperature sensors, they could precisely observe the behavior of the cold water jets when penetrating the hot water. The HZDR test facility TOPFLOW was used to carry out the measurements under realistic temperature and pressure conditions.

This globally unique data set is not only relevant for safety measures in reactor plants, but can also be transferred to chemical engineering processes. The results could then contribute to an increase in efficiency.

  • Publication: T. Seidel, „Direct condensation and entrainment steam experiments at the TOPFLOW-DENISE facility“, atw – International Journal for Nuclear Power, 2015
  • Contact: Matthias Beyer, Institute of Fluid Dynamics