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ePaper created 2013-04-09, 17:43:56 | version 1.25.6
concrete terms, this could help doctors to deal more effectively with a wide- spread problem in cancer treatment. “Many drugs have only a limited effect. The blood that transports the drugs flows in a different way in tumours than in healthy tissue,” says the mathemati- cian. Medical scientists have studied cancerous tissue and discovered special properties of the blood vessels. How- ever, the treatment generally remains the same. “The dose is increased to in- crease the effect – but then the side ef- fects also become more severe.” In order to develop more efficient and less damaging methods we need to know more. How does the structure of the vessels affect the behaviour of blood cells? How does the efficacy of the drugs change if certain nanoparti- cles are added? Such questions can hardly be an- swered without a sophisticated model of the microcirculation. Fedosov is convinced that he can provide such a model. “We intend to simulate the blood flow in a cubic millimetre of tissue. That would represent great progress.” A cubic millimetre sounds tiny but its micro- circulation represents a gigantic world with a dazzling array of events. A MADDING CROWD Many millions of blood cells swim around in the blood plasma in one cubic millimetre of tissue. About five million blood cells release oxygen there, take up carbon dioxide and change their shape; white blood cells pass through the walls of the blood vessels and pass over into the tissue as antibodies. The blood cells are in constant motion, they repel each other and form clumps; the flows be- come incessantly thinner, thicker, slower or faster. In short, there is a madding crowd of blood cells. The simulation of blood flows therefore represents a great challenge for fluid dynamics. As one of only a few scientists world- wide, Dmitry A. Fedosov has risen to the challenge. In his award-winning PhD the- sis, he presented a method of simulating blood flows. “From existing knowledge, I develop a model, from which I form algo- rithms and translate these into software codes. I then check my model against data from experiments. Once the model is verified I expand it.” He can thus push forward into fields which are inaccessible to experiments for ethical or technical reasons. In his PhD thesis, for example, he was able to predict how red blood cells behave in the case of malaria. The results are one reason why the Humboldt Foundation awarded him one of the most valuable German science prizes, the Sofja Kovalevskaja Award. This award is intended to attract top- class researchers to Germany. The mathematician will receive € 1.3 million over a period of five years to set up and direct his own working group. GEOMETRY OF THE BLOOD VESSELS What Fedosov has now set his sights on goes far beyond his PhD thesis. He intends to raise the level of his modelling from the vessels to a network. This is more than a quantitative leap. He will not only have to simulate more blood cells but also the complex geometry of the network of blood vessels and the flu- id dynamics of blood at branches in the network. If he is to succeed the model must be as simple as possible. The trick is to rec- ognize what is indispensable for repre- senting the system and get rid of everything else. At Jülich, Fedosov is currently mainly concerned with techni- cal aspects. For example, he is distribut- ing the calculations between the proces- sors of the supercomputers so that as many as possible are in operation. At the moment, due to the complex geometry of the model a large number of proces- sors are idle. However, Fedosov is mak- ing rapid progress and he is sure that in spring he will be able to simulate a net- work with simple branches. That would be a great step forward. :: Christoph Mann Dmitry A. Fedosov has already lived in Siberia and the USA. At Jülich, the thirty-year-old mathe- matician heads a group working on the simulation of blood flow. 1|2013 Research in Jülich 21 EARLY-CAREER SCIENTISTS | Simulation Institute Dr. Dmitry A. Fedosov