Fluorophores of lipofuscin granules responsible for human eye fundus autofluorescence

Individual fluorophores and/or their groups contained in a chloroform extract of lipofuscin granules isolated from retinal pigment epithelium of human cadaver eyes were studied by HPLC. Their spectral characteristics were studied, which made it possible to evaluate the contribution of particular fluorophores and/or their groups to the general image of human eye fundus autofluorescence. Many components, being conjugates of all-trans-retinal of different nature, contribute to the total fluorescence spectrum of the chloroform extract. The fluorophore A2E is not predominant.     

Effect of coherence and polarization on frequency resolution in optical Fourier transforming system

Using an example of vector Gaussian Schell-model beam, we demonstrate and analyze the dependence of the spatial frequency resolution in optical Fourier transforming system on the intrinsic coherence-polarization structure of illumination.     

Density of prelocalized states in mesoscopic NS systems

The semiclassical theory of the proximity effect predicts the formation of a gap E _g ～?D/L ² in the excitation spectrum of a diffusive contact between a normal metal and a superconductor (NS). Mesoscopic fluctuations lead to the emergence of states localized anomalously in the normal metal and weakly linked with the superconducting bank, creating a nonzero density of states for energies lower than E _g . In this review, the behavior of the density of quasiparticle states below a quasi-classical gap is considered for various geometries of the NS system (special attention is paid to SNS junctions) and for the problem of a superconductor with a low concentration of magnetic impurities, in which a similar effect is observed. Analysis is mainly carried out on the basis of a fully microscopic method of the supermatrix σ model; in this method, a nonzero density of states emerges due to instanton configurations with broken supersymmetry. In addition, the results of an alternative approach proceeding from the idea of universality of the spectra of random Hamiltonians with the given symmetry are reviewed. In situations studied using both methods, the results are identical. They include the exact expression for the mean density of states of an NS system in the vicinity of E _g . In the framework of 1D and 2D σ models, the subgap density of states is determined with an exponential accuracy. The contacts with a poor transparency of the NS interface are also considered. It is shown that the number of subgap states in the case of low transparency is much greater than unity.

     

Coulomb effects in a nanoscale SINIS junction

We study a system of two superconductors connected by a small normal grain. We consider the modification of the Josephson effect by the Coulomb interaction on the grain. Coherent charge transport through the junction is suppressed by Coulomb repulsion. An optional gate electrode may relax the charge blocking and enhance the current leading to the single Cooper pair transistor effect. Temperature dependences of critical current and of the minigap induced in the normal grain by the proximity to superconductor are studied. Both temperature and Coulomb interaction suppress critical current and minigap, but their interplay may lead to the nonmonotonic and even reentrant temperature dependence.     

Functional Feynman-Kac Equations for Limit Lognormal Multifractals

A novel technique of functional Feynman-Kac equations is developed for the probability distribution of the limit lognormal multifractal process introduced by Mandelbrot [in Statistical Models and Turbulence, M. Rosenblatt and C. Van Atta, eds., Springer, New York (1972)] and constructed explicitly by Bacry, Delour, and Muzy [Phys. Rev. E 64:026103 (2001)]. The distribution of the process is known to be determined by the complicated stochastic dependence structure of its increments (SDSI). It is shown that the SDSI has two separate layers of complexity that can be captured in a precise way by a pair of functional Feynman-Kac equations for the Laplace transform. Exact solutions are obtained as power series expansions in the intermittency parameter using a novel intermittency differentiation rule. The expansion of the moments gives a new representation of the Selberg integral. The author wishes to express gratitude to the Mathematics Department of Lehigh University for generous support during his stay at Lehigh University, where this article was written.     

Wannier-Type Threshold Laws for Multifragmentation and Thomson’s Problem

Wannier-type threshold theory for multiple break-up processes is based on the existence of special classical trajectories which represent partial fixed points of the equations of motion in a system of charged particles. These trajectories preserve the shape of the initial configuration while only changing its overall size in time. The relation between such scaling configurations and Thomson’s (or surface Coulomb) problem is analyzed. In particular, it is shown that for eight electrons the twisted cube configuration solves Thomson’s problem and also governs the threshold break-up of eight electrons receding from a charged core. The relevant exponents for the threshold power law are evaluated.     

Threshold Laws for Multiparticle Fragmentation

 The threshold behaviour of the cross section for break-up of an atomic particle into N charged fragments is described by a power law, , where E is the energy excess above the threshold. The threshold index μ reflects the dynamics of long-range Coulomb correlation. The general features of the theory are discussed. The charge and mass dependence of the threshold index is analyzed for some particular systems. Received October 29, 2001; accepted for publication November 9, 2001     

Angular pattern of minijet transverse energy flow in hadron and nuclear collisions

bstract The azimuthal asymmetry of a minijet system produced at the early stage of nucleon-nucleon and nuclear collisions in a central rapidity window is studied. We show that, in pp collisions, the minijet-transverse-energy production in a central rapidity window is essentially unbalanced in azimuth because of asymmetric contributions in which only one minijet hits the acceptance window. We further study the angular pattern of the transverse-energy flow generated by semihard degrees of freedom at the early stage of high-energy nuclear collisions and its dependence on the number of semihard collisions in the models either including or neglecting soft contributions to the inelastic cross section at RHIC and LHC energies, as well as on the choice of infrared cutoff. From Yadernaya Fizika, Vol. 65, No. 5, 2002, pp. 918–929. Original English Text Copyright ? 2002 by Leonidov, Ostrovsky. This article was submitted by the authors in English.     

Flexibility Analysis in the Case of Incomplete Information about Uncertain Parameters

In recent years the flexibility analysis of chemical processes has attracted a significant amount of attention among researchers in the chemical engineering community. Flexibility analysis permits to identify/create chemical processes, which can satisfy all design specifications in spite of process and parametric uncertainty (from several sources) at the operation stage. All formulations of the flexibility problem are based on the supposition that during the operation stage there is enough experimental data from which exact values of the uncertain parameters can be obtained. However, in practice this assumption is often not met. Here in this paper, we consider the case when the uncertain parameters can be divided into two sets, namely a set that can be estimated with sufficient accuracy (at the operation stage) and a set that cannot be. Based on this view, we have developed extensions of the feasibility test and two-stage optimization problem to handle the two sets of uncertainty. We have developed the relevant split and bound algorithm for solving the new two-step optimization problem.