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Search Results: 1 - 10 of 6063 matches for " Igor Shevchenko "
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Absorbing boundary conditions for the Westervelt equation
Barbara Kaltenbacher,Igor Shevchenko
Mathematics , 2014,
Abstract: The focus of this work is on the construction of a family of nonlinear absorbing boundary conditions for the Westervelt equation in one and two space dimensions. The principal ingredient used in the design of such conditions is pseudo-differential calculus. This approach enables to develop high order boundary conditions in a consistent way which are typically more accurate than their low order analogs. Under the hypothesis of small initial data, we establish local well-posedness for the Westervelt equation with the absorbing boundary conditions. The performed numerical experiments illustrate the efficiency of the proposed boundary conditions for different regimes of wave propagation.
A Dual Origin of the Xist Gene from a Protein-Coding Gene and a Set of Transposable Elements
Eugeny A. Elisaphenko, Nikolay N. Kolesnikov, Alexander I. Shevchenko, Igor B. Rogozin, Tatyana B. Nesterova, Neil Brockdorff, Suren M. Zakian
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002521
Abstract: X-chromosome inactivation, which occurs in female eutherian mammals is controlled by a complex X-linked locus termed the X-inactivation center (XIC). Previously it was proposed that genes of the XIC evolved, at least in part, as a result of pseudogenization of protein-coding genes. In this study we show that the key XIC gene Xist, which displays fragmentary homology to a protein-coding gene Lnx3, emerged de novo in early eutherians by integration of mobile elements which gave rise to simple tandem repeats. The Xist gene promoter region and four out of ten exons found in eutherians retain homology to exons of the Lnx3 gene. The remaining six Xist exons including those with simple tandem repeats detectable in their structure have similarity to different transposable elements. Integration of mobile elements into Xist accompanies the overall evolution of the gene and presumably continues in contemporary eutherian species. Additionally we showed that the combination of remnants of protein-coding sequences and mobile elements is not unique to the Xist gene and is found in other XIC genes producing non-coding nuclear RNA.
Combined Transfer of Human VEGF165 and HGF Genes Renders Potent Angiogenic Effect in Ischemic Skeletal Muscle
Pavel Makarevich, Zoya Tsokolaeva, Alexander Shevelev, Igor Rybalkin, Evgeny Shevchenko, Irina Beloglazova, Tatyana Vlasik, Vsevolod Tkachuk, Yelena Parfyonova
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038776
Abstract: Increased interest in development of combined gene therapy emerges from results of recent clinical trials that indicate good safety yet unexpected low efficacy of “single-gene” administration. Multiple studies showed that vascular endothelial growth factor 165 aminoacid form (VEGF165) and hepatocyte growth factor (HGF) can be used for induction of angiogenesis in ischemic myocardium and skeletal muscle. Gene transfer system composed of a novel cytomegalovirus-based (CMV) plasmid vector and codon-optimized human VEGF165 and HGF genes combined with intramuscular low-voltage electroporation was developed and tested in vitro and in vivo. Studies in HEK293T cell culture, murine skeletal muscle explants and ELISA of tissue homogenates showed efficacy of constructed plasmids. Functional activity of angiogenic proteins secreted by HEK293T after transfection by induction of tube formation in human umbilical vein endothelial cell (HUVEC) culture. HUVEC cells were used for in vitro experiments to assay the putative signaling pathways to be responsible for combined administration effect one of which could be the ERK1/2 pathway. In vivo tests of VEGF165 and HGF genes co-transfer were conceived in mouse model of hind limb ischemia. Intramuscular administration of plasmid encoding either VEGF165 or HGF gene resulted in increased perfusion compared to empty vector administration. Mice injected with a mixture of two plasmids (VEGF165+HGF) showed significant increase in perfusion compared to single plasmid injection. These findings were supported by increased CD31+ capillary and SMA+ vessel density in animals that received combined VEGF165 and HGF gene therapy compared to single gene therapy. Results of the study suggest that co-transfer of VEGF and HGF genes renders a robust angiogenic effect in ischemic skeletal muscle and may present interest as a potential therapeutic combination for treatment of ischemic disorders.
Infinite statistics, symmetry breaking and combinatorial hierarchy
Shevchenko, V.
High Energy Physics - Phenomenology , 2008, DOI: 10.1142/S0217732309030825
Abstract: The physics of symmetry breaking in theories with strongly interacting quanta obeying infinite (quantum Boltzmann) statistics known as quons is discussed. The picture of Bose/Fermi particles as low energy excitations over nontrivial quon condensate is advocated. Using induced gravity arguments it is demonstrated that the Planck mass in such low energy effective theory can be factorially (in number of degrees of freedom) larger than its true ultraviolet cutoff. Thus, the assumption that statistics of relevant high energy excitations is neither Bose nor Fermi but infinite can remove the hierarchy problem without necessity to introduce any artificially large numbers. Quantum mechanical model illustrating this scenario is presented.
On the pattern of Casimir scaling violation in gluodynamics
V. Shevchenko
Physics , 2002, DOI: 10.1016/S0370-2693(02)02968-4
Abstract: Results of lattice analysis indicate that the static potential in SU(3) gauge theory is proportional to eigenvalue of quadratic Casimir operator for the corresponding representation with a good accuracy. We discuss the mechanism of possible deviations from the Casimir scaling in gluodynamics in terms of correlators of path-ordered gauge-invariant operators defined on the worldsheet of the confining string.
Mixed stochastic delay differential equations
Georgiy Shevchenko
Mathematics , 2013,
Abstract: We consider a stochastic delay differential equation driven by a Holder continuous process and a Wiener process. Under fairly general assumptions on its coefficients, we prove that this equation is uniquely solvable. We also give sufficient conditions for finiteness of its moments and establish a limit theorem.
Convergence of hitting times for jump-diffusion processes
Georgiy Shevchenko
Mathematics , 2015, DOI: 10.15559/15-VMSTA32
Abstract: We investigate the convergence of hitting times for jump-diffusion processes. Specifically, we study a sequence of stochastic differential equations with jumps. Under reasonable assumptions, we establish the convergence of solutions to the equations and of the moments when the solutions hit certain sets.
Local times for multifractional square Gaussian processes
Georgiy Shevchenko
Mathematics , 2013,
Abstract: We consider multifractional process given by double Ito--Wiener integrals, which generalize the multifractional Rosenblatt process. We prove that this process is continuous and has a square integrable local time.
Fractional Brownian motion in a nutshell
Georgiy Shevchenko
Mathematics , 2014,
Abstract: This is an extended version of the lecture notes to a mini-course devoted to fractional Brownian motion and delivered to the participants of 7th Jagna International Workshop.
Integrability of solutions to mixed stochastic differential equations
Georgiy Shevchenko
Mathematics , 2013,
Abstract: We prove that the standard conditions that provide unique solvability of a mixed stochastic differential equations also guarantee that its solution possesses finite moments. We also present conditions supplying existence of exponential moments. For a special equation whose coefficients do not satisfy the linear growth condition, we find conditions for integrability of its solution.
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