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Search Results: 1 - 10 of 130499 matches for " V. Vasilyev "
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Discrete singular integrals in a half-space
Alexander V. Vasilyev,Vladimir B. Vasilyev
Mathematics , 2014,
Abstract: We consider Calderon -- Zygmund singular integral in the discrete half-space $h{\bf Z}^m_{+}$, where ${\bf Z}^m$ is entire lattice ($h>0$) in ${\bf R}^m$, and prove that the discrete singular integral operator is invertible in $L_2(h{\bf Z}^m_{+}$) iff such is its continual analogue. The key point for this consideration takes solvability theory of so-called periodic Riemann boundary problem, which is constructed by authors.
Triangular Wavelets: An Isotropic Image Representation with Hexagonal Symmetry
Kensuke Fujinoki,Oleg V. Vasilyev
EURASIP Journal on Image and Video Processing , 2009, DOI: 10.1155/2009/248581
Abstract: This paper introduces triangular wavelets, which are two-dimensional nonseparable biorthogonal wavelets defined on the regular triangular lattice. The construction that we propose is a simple nonseparable extension of one-dimensional interpolating wavelets followed by a straightforward generalization. The resulting three oriented high-pass filters are symmetrically arranged on the lattice, while low-pass filters have hexagonal symmetry, thereby allowing an isotropic image processing in the sense that three detail components are distributed uniformly. Applying the triangular filter to images, we explore applications that truly benefit from the triangular wavelets in comparison with the conventional tensor product transforms.
Conditins for the Time Dissipative Structure Formation at Nonequilibrium Transitions
A.V. Dvornichenko,A.A. Vasilyev,V.О. Kharchenko
Journal of Nano- and Electronic Physics , 2011,
Abstract: We discuss processes of the dissipative structure formation when the nonequilibrium phase transition takes place. The model is considered under assumptions that dispersion of the relaxation time of the order parameter and influence of the external force present. It was found that self-organization occurs through the Hopf bifurcation and results in the dissipative structure formation. Analysis was performed according to the Lyapunov and Floquet exponent investigation. It was found that the complex picture of ordering with two reentrant Hopf bifurcations occurs.
A quantum volume hologram
Denis V. Vasilyev,Ivan V. Sokolov,Eugene S. Polzik
Physics , 2009, DOI: 10.1103/PhysRevA.81.020302
Abstract: We propose a new scheme for parallel spatially multimode quantum memory for light. The scheme is based on counter-propagating quantum signal wave and strong classical reference wave, like in a classical volume hologram, and therefore can be called a quantum volume hologram. The medium for the hologram consists of a spatially extended ensemble of atoms placed in a magnetic field. The write-in and read-out of this quantum hologram is as simple as that of its classical counterpart and consists of a single pass illumination. In addition we show that the present scheme for a quantum hologram is less sensitive to diffraction and therefore is capable of achieving higher density of storage of spatial modes as compared to previous proposals. A quantum hologram capable of storing entangled images can become an important ingredient in quantum information processing and quantum imaging.
Quantum memory for images - a quantum hologram
Denis V. Vasilyev,Ivan V. Sokolov,Eugene S. Polzik
Physics , 2007, DOI: 10.1103/PhysRevA.77.020302
Abstract: Matter-light quantum interface and quantum memory for light are important ingredients of quantum information protocols, such as quantum networks, distributed quantum computation, etc. In this Letter we present a spatially multimode scheme for quantum memory for light, which we call a quantum hologram. Our approach uses a multi-atom ensemble which has been shown to be efficient for a single spatial mode quantum memory. Due to the multi-atom nature of the ensemble it is capable of storing many spatial modes, a feature critical for the present proposal. A quantum hologram has a higher storage capacity compared to a classical hologram, and is capable of storing quantum features of an image, such as multimode superposition and entangled quantum states, something that a standard hologram is unable to achieve. Due to optical parallelism, the information capacity of the quantum hologram will obviously exceed that of a single-mode scheme.
Bursts of ULF noise excited by sudden changes of solar wind dynamic pressure
V. Safargaleev,J. Kangas,A. Kozlovsky,A. Vasilyev
Annales Geophysicae (ANGEO) , 2003,
Abstract: We present the results of analysis of the dayside magnetic pulsation response to a sudden change in solar wind dynamic pressure. We concentrate on the events when a burst or a series of short-lived bursts in the Pc1 frequency range with the repetition period of 7–15 min were observed on the ground around the local noon. Not every impulse of large amplitude caused this phenomenon. We have found that the ULF bursts were excited when the spectrograms of the DMSP satellites showed a signature of 10–30 keV ions in the vicinity of the magnetic flux tube of the ground observatory, that may be related to a geomagnetic storm preceding the event. In light of this finding a possible model of the phenomenon is suggested in which the hot protons influence significantly both the generation and modulation of Pc1 activity. Key words. Magnetospheric physics (solar wind – magnetosphere interaction; MHD waves and instabilities; storms and substorms)
Analysis of HIV-1 primary drug resistance in Kazakhstan
I Lapovok,V Laga,A Vasilyev,E Kazennova
Journal of the International AIDS Society , 2012, DOI: 10.7448/ias.15.6.18209
Abstract: Purpose of the study: Monitoring of primary resistance in HIV-1 variants circulating in Russia and FSU countries is the important task of HIV infection molecular epidemiology. The data of HIV molecular epidemiology are absent or limited in many FSU countries. IDU-A variant of HIV-1 subtype A has been dominating in Russia (>90%) and other FSU countries since 1996. Additionally, the Central Asian region (e.g. Kazakhstan and Uzbekistan) is characterized by relatively wide spread of CRF02_AG recombinant. The aim of our study was the analysis of HIV primary drug resistance in HIV-1 variants from Kazakhstan. Methods: Blood collection from the HIV-infected na ve patients was carried out by local specialists. The study was performed with the informed consent of patients. All sequences of pol gene were analyzed by COMETv0.1 and HIVdb on-line programs. The phylogenetic analysis and tropism testing were carried out by MEGA4.0 and geno2pheno. Summary of results: 51 PBMC samples were analyzed. According to pol gene phylogenetic analysis and genotyping 24 (47.0%) samples belonged to recombinant CRF02_AG; 25 (49.0%)-to subtype A1; 2 (3.9%)-to CRF03_AB circulating in Russia and some FSU countries. Only one subtype A1 sample had D30N mutation in Pro-region that cause high-level resistance to NFV. All AG-samples had K20I substitution which is characteristic for HIV-1 subtype A and G and is believed to be associated with resistance to LPV and NFV. In addition, we found that 2 AG-samples had L10V and L76I substitutions, accordingly. Two A1-subtype samples studied had L10I and K43T, accordingly. A62V characteristic mutation in RT-region was found in 12 (48%) subtype A1-samples. One of them had M184I mutation as well. Besides, we found 3 A1-samples harboring NNRTIs resistance mutations-K103N, G190S, K238N, accordingly. Further we analyzed IN region of pol-gene in 16 and env-gene in 23 samples studied. We found only one E157Q mutation (in CRF03_AB sample) in IN region. As to tropism, only two subtype A1 and 1 CRF03_AB samples belonged to X4/X4R5 variant, all these A1-subtype samples harbored A62V and one of them-G190S in RT region of pol-gene; the other samples were treated as R5 variants. Conclusions: Our data demonstrated the low level of HIV primary drug resistance in Kazakhstan. HIV-1 subtype A variant dominates on this territory, but CRF02_AG recombinant is rather widespread as well. CRF02_AG variant studied has characteristic features in Pro region compared with IDU-A.
HIV-1 genetic variants in Kyrgyzstan
V Laga,E Kazennova,A Vasilyev,I Lapovok
Journal of the International AIDS Society , 2012, DOI: 10.7448/ias.15.6.18229
Abstract: Objectives: During the last two decades, HIV-1 has been spreading rapidly in former Soviet Union republics including Kyrgyzstan. The current molecular monitoring of HIV-infection epidemic is carried out in Russia only with no or limited data from the other FSU countries. The aim of this work was to investigate the prevalence of HIV-1 genetic variants circulating in Kyrgyzstan. Methods: Blood collection from the HIV-infected patients was carried out by local specialists with the informed consent and the questionnaire was answered by each of the patients. The total number of samples was 100. The washed cell pellets were transferred to Moscow following with proviral DNA extraction, PCR amplification and gag, pol and env genes sequencing. The phylogenetic analysis of nucleotide sequences using neighbor-joining method was carried out by MEGA 3 program. The preliminary data were obtained in 22 samples isolated from PBMC of HIV-infected patients from Kyrgyzstan. Results: Among the samples studied 6 (27.3%) samples belonged to a subtype CRF02_AG, 16 samples - to subtype A (A1). One of the samples belonging to CRF02_AG, probably, is a recombinant between CRF02_AG and A1. There was no major drug resistance mutations in the samples studied. The minor mutations were presented in small proportions: 1 in PR (L10I), 6 in RT (A62V - in 3 samples, V108G, E138A, Y181F, M184I, L210M - on one sample) and 1 in IN (L74M). It was impossible to associate the distribution of mutations with HIV-1 genetic variant. The V3 loop (env gene) in 17 samples was analyzed for tropism using geno2pheno program; all samples were found to be R5-viruses. Conclusion: The HIV-1 subtype A seems to dominate in Kyrgyzstan like in other FSU countries. The recombinant CRF02_AG epidemiologically linked to Uzbekistan is quite widespread. The rest of Kyrgyzstan collection is under investigation and the data will be refined soon.
Large-scale fluctuations in the distribution of galaxies from the Two Degree Field Galaxy Redshift Survey
Francesco Sylos Labini,Nikolay L. Vasilyev,Yurij V. Baryshev
Physics , 2009, DOI: 10.1051/0004-6361:200810575
Abstract: We study statistical properties of galaxy structures in several samples extracted from the 2dF Galaxy Redshift Survey. In particular, we measured conditional fluctuations by means of the scale-length method and determined their probability distribution. In this way we find that galaxy distribution in these samples is characterized by large amplitude fluctuations with a large spatial extension, whose size is only limited by the sample's boundaries. These fluctuations are quite typical and persistent in the sample's volumes, and they are detected in two independent regions in the northern and southern galactic caps. We discuss the relation of the scale-length method to several statistical quantities, such as counts of galaxies as a function of redshift and apparent magnitude. We confirm previous results, which have determined by magnitude and redshift counts that there are fluctuations of about 30% between the southern and the northern galactic caps and we relate explicitly these counts to structures in redshift space. We show that the estimation of fluctuation amplitude normalized to the sample density is biased by systematic effects, which we discuss in detail. We consider the type of fluctuations predicted by standard cosmological models of structure formation in the linear regime and, to study nonlinear clustering, we analyze several samples of mock-galaxy catalogs generated from the distribution of dark matter in cosmological N-body simulations. In this way we conclude that the galaxy fluctuations present in these samples are too large in amplitude and too extended in space to be compatible with the predictions of the standard models of structure formation.
Persistent fluctuations in the distribution of galaxies from the Two degree Field Galaxy Redshift Survey
Francesco Sylos Labini,Nikolay L. Vasilyev,Yurij V. Baryshev
Physics , 2008, DOI: 10.1209/0295-5075/85/29002
Abstract: We apply the scale-length method to several three dimensional samples of the Two degree Field Galaxy Redshift Survey. This method allows us to map in a quantitative and powerful way large scale structures in the distribution of galaxies controlling systematic effects. By determining the probability density function of conditional fluctuations we show that large scale structures are quite typical and correspond to large fluctuations in the galaxy density field. We do not find a convergence to homogeneity up to the samples sizes, i.e. ~ 75 Mpc/h. We then measure, at scales r <~ 40 Mpc/h, a well defined and statistically stable power-law behavior of the average number of galaxies in spheres, with fractal dimension D=2.2 +- 0.2. We point out that standard models of structure formation are unable to explain the existence of the large fluctuations in the galaxy density field detected in these samples. This conclusion is reached in two ways: by considering the scale, determined by the linear perturbation analysis of a self-gravitating fluid, below which large fluctuations are expected in standard models and through the determination of statistical properties of mock galaxy catalogs generated from cosmological N-body simulations of the Millenium consortitum.
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