TY  - JOUR
A1  - Poschel, T.
A1  - Brilliantov, Nikolai V.
A1  - Zaikin, Alexei
T1  - Bistability and noise-enhanced velocity of rolling motion
N2  - 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
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Saparin, P. I.
A1  - Thomsen, J. S.
A1  - Prohaska, Steffen
A1  - Zaikin, Alexei
A1  - Kurths, Jürgen
A1  - Hege, H. C.
A1  - Gowin, W.
T1  - Quantification of spatial structure of human proximal tibial bone biopsies using 3D measures of complexity
N2  - 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
Y1  - 2005
SN  - 0094-5765
ER  - 
TY  - JOUR
A1  - Zaikin, Alexei
A1  - Kurths, Jürgen
A1  - Saparin, Peter
A1  - Gowin, W.
A1  - Prohaska, Steffen
T1  - Modeling bone resorption in 2D CT and 3D mu CT images
N2  - 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
Y1  - 2005
SN  - 0218-1274
ER  -