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Maltsev T. | Maltsev A. Ya. | Maltsev Anna | Maltsev I. A. | Maltsev A. | Maltsev Andrei Ya. | Maltsev Valeri P. | Maltsev P. P. | Maltsev Roman V. | Maltsev Andrei

Valeri Daniele | Valeri Mauro | Valeri Linda | Valeri Sergio | Valeri Alessandro | Valeri D. | Valeri Fabio M. | Valeri Luca | Valeri S. | Valeri Tioukov

P Deepak | P Bharath K | P Kirana Kumara | P Arun Kumar S | P Balamuralidhar | P Chithrabhanu | P Prathosh A. | P Preejith S. | p | P C.

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Kinetics of the initial stage of immunoagglutionation studied with the scanning flow cytometer

Surovtsev Ivan V., Yurkin Maxim A., Shvalov Alexander N., Nekrasov Vyacheslav M., Sivolobova Galina F., Grazhdantseva Antonina A., Maltsev Valeri P., Chernyshev Andrey V.
29 Jul 2008 physics.optics physics.bio-ph arxiv.org/abs/0807.4645

The use of a scanning flow cytometer (SFC) to study the evolution of monomers, dimers and higher multimers of latex particles at the initial stage of the immunoagglutination is described. The SFC can measure the light-scattering pattern (indicatrix) of an individual particle over an angular range of 10-60 deg. A comparison of the experimentally measured and theoretically calculated indicatrices allows one to discriminate different types of latex particles (i.e. monomers, dimers, etc.) and, therefore, to study the evolution of immunoagglutination process. Validity of the approach was verified by simultaneous measurements of light-scattering patterns and fluorescence from individual polymer particles. Immunoagglutination was initiated by mixing bovine serum albumin (BSA)-covered latex particles (of 1.8 um in diameter) with anti-BSA IgG. The analysis of experimental data was performed on the basis of a mathematical model of diffusion-limited immunoagglutination aggregation with a steric factor. The steric factor was determined by the size and the number of binding sites on the surface of a latex particle. The obtained data are in good agreement with the proposed mathematical modeling.

Determination of volume, shape and refractive index of individual blood platelets

Kolesnikova Irina V., Potapov Sergei V., Yurkin Maxim A., Hoekstra Alfons G., Maltsev Valeri P., Semyanov Konstantin A.
29 Jul 2008 physics.optics physics.bio-ph arxiv.org/abs/0807.4673

Light scattering patterns (LSP) of blood platelets were theoretically and experimentally analyzed. We used spicular spheroids as a model for the platelets with pseudopodia. The discrete dipole approximation was employed to simulate light scattering from an individual spicular spheroid constructed from a homogeneous oblate spheroid and 14 rectilinear parallelepipeds rising from the cell centre. These parallelepipeds have a weak effect on the LSP over the measured angular range. Therefore, a homogeneous oblate spheroid was taken as a simplified optical model for platelets. Using the T-matrix method, we computed the LSP over a range of volumes, aspect ratios and refractive indices. Measured LSPs of individual platelets were compared one by one with the theoretical set and the best fit was taken to characterize the measured platelets, resulting in distributions of volume, aspect ratio and refractive index.

Experimental and theoretical study of light scattering by individual mature red blood cells by use of scanning flow cytometry and discrete dipole approximation

Yurkin Maxim A., Semyanov Konstantin A., Tarasov Peter A., Chernyshev Andrei V., Hoekstra Alfons G., Maltsev Valeri P.
09 Apr 2007 physics.optics physics.med-ph arxiv.org/abs/0704.1134

Elastic light scattering by mature red blood cells (RBCs) was theoretically and experimentally analyzed with the discrete dipole approximation (DDA) and the scanning flow cytometry (SFC), respectively. SFC permits measurement of angular dependence of light-scattering intensity (indicatrix) of single particles. A mature RBC is modeled as a biconcave disk in DDA simulations of light scattering. We have studied the effect of RBC orientation related to the direction of the incident light upon the indicatrix. Numerical calculations of indicatrices for several aspect ratios and volumes of RBC have been carried out. Comparison of the simulated indicatrices and indicatrices measured by SFC showed good agreement, validating the biconcave disk model for a mature RBC. We simulated the light-scattering output signals from the SFC with the DDA for RBCs modeled as a disk-sphere and as an oblate spheroid. The biconcave disk, the disk-sphere, and the oblate spheroid models have been compared for two orientations, i.e. face-on and rim-on incidence. Only the oblate spheroid model for rim-on incidence gives results similar to the rigorous biconcave disk model.

Convergence of the discrete dipole approximation. I. Theoretical analysis

Yurkin Maxim A., Maltsev Valeri P., Hoekstra Alfons G.
31 Mar 2007 physics.optics physics.comp-ph arxiv.org/abs/0704.0033

We performed a rigorous theoretical convergence analysis of the discrete dipole approximation (DDA). We prove that errors in any measured quantity are bounded by a sum of a linear and quadratic term in the size of a dipole d, when the latter is in the range of DDA applicability. Moreover, the linear term is significantly smaller for cubically than for non-cubically shaped scatterers. Therefore, for small d errors for cubically shaped particles are much smaller than for non-cubically shaped. The relative importance of the linear term decreases with increasing size, hence convergence of DDA for large enough scatterers is quadratic in the common range of d. Extensive numerical simulations were carried out for a wide range of d. Finally we discuss a number of new developments in DDA and their consequences for convergence.

Convergence of the discrete dipole approximation. II. An extrapolation technique to increase the accuracy

Yurkin Maxim A., Maltsev Valeri P., Hoekstra Alfons G.
31 Mar 2007 physics.optics physics.comp-ph arxiv.org/abs/0704.0035

We propose an extrapolation technique that allows accuracy improvement of the discrete dipole approximation computations. The performance of this technique was studied empirically based on extensive simulations for 5 test cases using many different discretizations. The quality of the extrapolation improves with refining discretization reaching extraordinary performance especially for cubically shaped particles. A two order of magnitude decrease of error was demonstrated. We also propose estimates of the extrapolation error, which were proven to be reliable. Finally we propose a simple method to directly separate shape and discretization errors and illustrated this for one test case.

The discrete dipole approximation for simulation of light scattering by particles much larger than the wavelength

Yurkin Maxim A., Maltsev Valeri P., Hoekstra Alfons G.
31 Mar 2007 physics.optics physics.comp-ph arxiv.org/abs/0704.0037

In this manuscript we investigate the capabilities of the Discrete Dipole Approximation (DDA) to simulate scattering from particles that are much larger than the wavelength of the incident light, and describe an optimized publicly available DDA computer program that processes the large number of dipoles required for such simulations. Numerical simulations of light scattering by spheres with size parameters x up to 160 and 40 for refractive index m=1.05 and 2 respectively are presented and compared with exact results of the Mie theory. Errors of both integral and angle-resolved scattering quantities generally increase with m and show no systematic dependence on x. Computational times increase steeply with both x and m, reaching values of more than 2 weeks on a cluster of 64 processors. The main distinctive feature of the computer program is the ability to parallelize a single DDA simulation over a cluster of computers, which allows it to simulate light scattering by very large particles, like the ones that are considered in this manuscript. Current limitations and possible ways for improvement are discussed.

Schrodinger Operators on Graphs

P Novikov S.
11 Apr 2000 math-ph math.MP arxiv.org/abs/math-ph/0004013

This work is the direct continuation of the author's note published in Russian Math Surveys 52 (1997), no 6. Discrete Schrodinger operators on graphs and higher dimensional simplicial complexes are considered. A vector-valued symplectic form on the space of solutions is consructed. This form, "Symplectic Wronskian", takes value in the group of 1-dimensional cycles. This construction has important applications for the Scattering Theory on graphs with tails. Effective diagonalization of the real Fermionic quadratic form is presented in the Appendix. This construction appeared first time in 1987 in the author's paper dedicated to an analogue of Morse theory for vector fields (it was published as an Appendix to the author's joint paper with M.Shubin, Soviet Math Dokl 34 (1987) no 1).

On the local systems Hamiltonian in the weakly nonlocal Poisson brackets

Maltsev A. Ya., Novikov S. P.
19 Jun 2000 nlin.SI math-ph math.MP arxiv.org/abs/nlin/0006030

We study in this work the important class of nonlocal Poisson Brackets (PB) which we call weakly nonlocal. They appeared recently in some investigations in the Soliton Theory. However there was no theory of such brackets except very special first order case. Even in this case the theory was not developed enough. In particular, we introduce the Physical forms and find Casimirs, Momentum and Canonical forms for the most important Hydrodynamic type PB of that kind and their dependence on the boundary conditions.

IHEP Experience on Creation and Operation of RFQS

Belyaev O. K., Ershov O. V., Maltsev I. G., Stepanov V. B., Strekalovskikh S. A., Teplyakov V. A., Zherebtsov A. V.
08 Aug 2000 physics.acc-ph arxiv.org/abs/physics/0008020

The new 1.8 MeV proton RFQ was completed and started operation in the IHEP in 1997. It was built according to the plan of modernization of the injection system to the booster of the IHEP proton synchrotron.

An analogue of the Sommerfeld radiation condition for the Dirac operator

Kravchenko Vladislav V., P Raul Castillo
31 Aug 2000 math-ph math.AP math.MP arxiv.org/abs/math-ph/0008042

A simple radiation condition at infinity for time-harmonic massive Dirac spinors is proposed. This condition allows an analogue of the Cauchy integral formula in unbounded domains for null-solutions of the Dirac equation to be proved. The result is obtained with the aid of methods of quaternionic analysis.