@article{ZaikinKurthsSaparinetal.2005, author = {Zaikin, Alexei and Kurths, J{\"u}rgen and Saparin, Peter and Gowin, W. and Prohaska, Steffen}, title = {Modeling bone resorption in 2D CT and 3D mu CT images}, issn = {0218-1274}, year = {2005}, abstract = {We study several algorithms to simulate bone mass loss in two-dimensional and three-dimensional computed tomography bone images. The aim is to extrapolate and predict the bone loss, to provide test objects for newly developed structural measures, and to understand the physical mechanisms behind the bone alteration. Our bone model approach differs from those already reported in the literature by two features. First, we work with original bone images, obtained by computed tomography (CT); second, we use structural measures of complexity to evaluate bone resorption and to compare it with the data provided by CT. This gives us the possibility to test algorithms of bone resorption by comparing their results with experimentally found dependencies of structural measures of complexity, as well as to show efficiency of the complexity measures in the analysis of bone models. For two-dimensional images we suggest two algorithms, a threshold algorithm and a virtual slicing algorithm. The threshold algorithm simulates bone resorption on a boundary between bone and marrow, representing an activity of osteoclasts. The virtual slicing algorithm uses a distribution of the bone material between several virtually created slices to achieve statistically correct results, when the bone-marrow transition is not clearly defined. These algorithms have been tested for original CT 10 mm thick vertebral slices and for simulated 10 mm thick slices constructed from ten I mm thick slices. For three-dimensional data, we suggest a variation of the threshold algorithm and apply it to bone images. The results of modeling have been compared with CT images using structural measures of complexity in two- and three-dimensions. This comparison has confirmed credibility of a virtual slicing modeling algorithm for two-dimensional data and a threshold algorithm for three-dimensional data}, language = {en} } @phdthesis{Zaikin2002, author = {Zaikin, Alexei}, title = {Noise-induced transitions and resonant effects in nonlinear systems}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0000761}, school = {Universit{\"a}t Potsdam}, year = {2002}, abstract = {Unsere allt{\"a}gliche Erfahrung ist mit verschiedenen akustischen Einfluessen wie L{\"a}rm, aber auch Musik verbunden. Jeder weiss, wie L{\"a}rm st{\"o}ren kann und Kommunikation behindert oder gar unterbindet. {\"A}hnliche optische Effekte sind bekannt: starkes Schneetreiben oder Regeng{\"u}sse verschlechtern die Sicht und lassen uns Umrisse nur noch schemenhaft erkennen. Jedoch koennen {\"a}hnliche Stimuli auch sehr positive Auswirkungen haben: Autofahrer fahren bei leiser Musik konzentrierter -- die Behauptung von Schulkindern, nur bei dr{\"o}hnenden B{\"a}ssen die Mathehausaufgaben richtig rechnen zu k{\"o}nnen, ist allerdings nicht wissenschaftlich erwiesen. Außerordentlich interessant aus dieser Sicht sind auch Reizleitungsprozesse: Reize werden nur weitergleitet, wenn die strukturlosen Signale der Neuronen mit ausreichend starker Intensit{\"a}t erfolgen, also ein Schwellwert {\"u}berschritten ist. Der Physiker Dr. Alexei Zaikin von der Universit{\"a}t Potsdam besch{\"a}ftigt sich mit sogenannten rauschinduzierten Ph{\"a}nomenen aus theorischer Sicht. Sein Forschungsgebiet sind Prozesse, bei denen Rauschen mehrfach das Systemverhalten beeinflusst: ist es ausreichend gross, d.h. gr{\"o}ßer als ein kritischer Wert, wird eine regul{\"a}re Struktur gebildet, die durch das immernoch vorhandene Rauschen mit der Struktur des Nachbarsystems synchronisiert. Um ein solches System mit kritischem Wert zu erhalten, bedarf es einer weiteren Rauschquelle. Herr Zaikin analysierte noch weitere Beispiele solcher doppelt stochastischen Effekte. Die Ausarbeitung derartiger theoretischer Grundlagen ist wichtig, da diese Prozesse in der Neurophysik, in technischen Kommunikationssystemen und in den Lebenswissenschaften eine Rolle spielen.}, language = {en} } @article{UllnerAresMorellietal.2012, author = {Ullner, E. and Ares, S. and Morelli, L. G. and Oates, A. C. and J{\"u}licher, F. and Nicola, E. and Heussen, R. and Whitmore, D. and Blyuss, K. and Fryett, M. and Zakharova, A. and Koseska, A. and Nene, N. R. and Zaikin, Alexei}, title = {Noise and oscillations in biological sysems multidisciplinary approach between experimental biology, theoretical modelling and synthetic biology}, series = {International journal of modern physics : B, Condensed matter physics, statistical physics, applied physics}, volume = {26}, journal = {International journal of modern physics : B, Condensed matter physics, statistical physics, applied physics}, number = {25}, publisher = {World Scientific}, address = {Singapore}, issn = {0217-9792}, doi = {10.1142/S0217979212460095}, pages = {12}, year = {2012}, abstract = {Rapid progress of experimental biology has provided a huge flow of quantitative data, which can be analyzed and understood only through the application of advanced techniques recently developed in theoretical sciences. On the other hand, synthetic biology enabled us to engineer biological models with reduced complexity. In this review we discuss that a multidisciplinary approach between this sciences can lead to deeper understanding of the underlying mechanisms behind complex processes in biology. Following the mini symposia "Noise and oscillations in biological systems" on Physcon 2011 we have collected different research examples from theoretical modeling, experimental and synthetic biology.}, language = {en} } @article{SaparinThomsenProhaskaetal.2005, author = {Saparin, P. I. and Thomsen, J. S. and Prohaska, Steffen and Zaikin, Alexei and Kurths, J{\"u}rgen and Hege, H. C. and Gowin, W.}, title = {Quantification of spatial structure of human proximal tibial bone biopsies using 3D measures of complexity}, issn = {0094-5765}, year = {2005}, abstract = {Changes in trabecular bone composition during development of osteoporosis are used as a model for bone loss in microgravity conditions during a space flight. Symbolic dynamics and measures of complexity are proposed and applied to assess quantitatively the structural composition of bone tissue from 3D data sets of human tibia bone biopsies acquired by a micro-CT scanner. In order to justify the newly proposed approach, the measures of complexity of the bone architecture were compared with the results of traditional 2D bone histomorphometry. The proposed technique is able to quantify the structural loss of the bone tissue and may help to diagnose and to monitor changes in bone structure of patients on Earth as well as of the space-flying personnel. © 2005 Elsevier Ltd. All rights reserved}, language = {en} } @article{PoschelBrilliantovZaikin2005, author = {Poschel, T. and Brilliantov, Nikolai V. and Zaikin, Alexei}, title = {Bistability and noise-enhanced velocity of rolling motion}, year = {2005}, abstract = {We investigate the motion of a hard cylinder rolling down a soft, inclined plane. The cylinder is subjected to a viscous drag force and stochastic fluctuations due to the surrounding rnedium. In a wide range of parameters we observe bistability of the rolling velocity. In dependence on the parameters, increasing noise level may lead to increasing or decreasing average velocity of the cylinder. The approximative analytical theory agrees with numerical results}, language = {en} }