Collapse of a Bose-Einstein condensate induced by fluctuations of the laser intensity

The dynamics of a metastable attractive Bose-Einstein condensate trapped by a system of laser beams is analyzed in the presence of small fluctuations of the laser intensity. It is shown that the condensate will eventually collapse. The expected collapse time is inversely proportional to the integrated covariance of the time autocorrelation function of the laser intensity and it decays logarithmically with the number of atoms. Numerical simulations of the stochastic 3D Gross-Pitaevskii equation confirms analytical predictions for small and moderate values of mean field interaction.Comment: 13 pages, 7 eps figure

Simulation of a stationary dark soliton in a trapped zero-temperature Bose-Einstein condensate

We discuss a computational mechanism for the generation of a stationary dark soliton, or black soliton, in a trapped Bose-Einstein condensate using the Gross-Pitaevskii (GP) equation for both attractive and repulsive interaction. It is demonstrated that the black soliton with a "notch" in the probability density with a zero at the minimum is a stationary eigenstate of the GP equation and can be efficiently generated numerically as a nonlinear continuation of the first vibrational excitation of the GP equation in both attractive and repulsive cases in one and three dimensions for pure harmonic as well as harmonic plus optical-lattice traps. We also demonstrate the stability of this scheme under different perturbing forces.Comment: 7 pages, 15 ps figures, Final version accepted in J Low Temp Phy

Modulational and Parametric Instabilities of the Discrete Nonlinear Schr\"odinger Equation

We examine the modulational and parametric instabilities arising in a non-autonomous, discrete nonlinear Schr{\"o}dinger equation setting. The principal motivation for our study stems from the dynamics of Bose-Einstein condensates trapped in a deep optical lattice. We find that under periodic variations of the heights of the interwell barriers (or equivalently of the scattering length), additionally to the modulational instability, a window of parametric instability becomes available to the system. We explore this instability through multiple-scale analysis and identify it numerically. Its principal dynamical characteristic is that, typically, it develops over much larger times than the modulational instability, a feature that is qualitatively justified by comparison of the corresponding instability growth rates

Inheritance of juvenile resistance to powdery mildew in barley accessions from Ethiopia

Background. Barley (Hordeum vulgare L.) is one of the key food crops, ranking fourth in the world in terms of sown area and production among cereals. Often, one of the main factors that reduces yield and product quality is the spread of fungal pathogens in commercial crops. Powdery mildew (causative agent: Blumeria graminis (DC.) Golovin ex Speer f. sp. hordei Marchal) is considered one of the most common and harmful among barley diseases. Plant resistance to B. graminis limits the spread of the disease, and the development of resistant cultivars prevents a decrease in plant productivity. The specificity of the host–pathogen relationship and the loss of efficiency in many genes determine the need for a continuous study of previously unexplored local barley forms and a search for new, most effective resistance genes.Materials and methods. The genetic control of juvenile resistance to B. graminis was studied in 14 accessions of spring barley from the Ethiopian (Abyssinian) center of crop origin. The natural population of the pathogen served as infectious material for infecting barley. The intensity and nature of sporulation as well as the qualitative reactions of plant tissues in response to the penetration of the fungus (necrosis and chlorosis) were accepted as indicators of resistance in the accessions. Powdery mildew resistance was assessed under laboratory and field conditions. The genetic control of the resistance trait was studied using the method of hybridological analysis followed by statistical processing.Results and conclusions. Barleys from the Ethiopian center of morphogenesis are characterized by great genetic diversity. Studying the inheritance of juvenile resistance to powdery mildew made it possible to ascertain the monogenic control of the trait in all studied forms. Ten barley accessions with one effective recessive resistance allele and four with the dominant control of the trait may be recommended for immunity-targeted breeding

An instability criterion for nonlinear standing waves on nonzero backgrounds

A nonlinear Schr\"odinger equation with repulsive (defocusing) nonlinearity is considered. As an example, a system with a spatially varying coefficient of the nonlinear term is studied. The nonlinearity is chosen to be repelling except on a finite interval. Localized standing wave solutions on a non-zero background, e.g., dark solitons trapped by the inhomogeneity, are identified and studied. A novel instability criterion for such states is established through a topological argument. This allows instability to be determined quickly in many cases by considering simple geometric properties of the standing waves as viewed in the composite phase plane. Numerical calculations accompany the analytical results.Comment: 20 pages, 11 figure

Comparative study of the fluorescence spectrum of plasma proteins and red blood cells of blood in aging and drug addiction

Aging is accompanied by intensification of oxidative degradation of proteins, including lipoproteins, proteolytic system dysfunction and accumulation of oxidized proteins. Similar changes are found in drug addiction. In this regard, we carried out a comparative study of conformational changes of plasma proteins and red blood cells of people of different age groups and people who use drugs. The study was carried out with the use of fluorescence analysis to measure the spectra of fluorescence of amino acid residues in proteins (summary fluorescence and tryptophan). In the analysis of fluorescence spectra it is preferable to use the second derivative of the fluorescence spectra as it is the most informative. The application of this research method was chosen because it has high sensitivity. It provides information on the status of living systems without damaging them; it requires large quantities of biological material; it makes it possible to differentiate between the various stages of the disease. Changes in the general phase and tryptophan fluorescence plasma proteins in older people and drug addicts indicate increase in the availability of tryptophan residues to the aqueous environment as a result of conformational changes of macromolecules and the disruption of the lipid layer due to the intensification of free radical processes

Comparison of operating costs of reinforced concrete bridges and overpasses with different static schemes

The article considers two options for the design of an overpass with a beam-cut and a beam-continuous static scheme. An inspection of the technical condition of beam-cut reinforced concrete bridges in operation in Tashkent built in 1970-90 was conducted. Estimating the maintenance costs of overpasses with different static schemes operating for the last 50 years shows that the continuous reinforced concrete option drastically reduces the cost of repair work in operation. This, in turn, has a cumulative effect on the development of the bridge-building industry in the Republic of Uzbekistan. The predicted operating costs of overpasses with different static schemes during operation for 50 years showed that in a continuous reinforced concrete option, 435,803,803 soums are saved annually. The most important thing is that the proposed solution dramatically reduces the cost of repair work. This, in turn, has a cumulative effect on the development of the bridge-building industry in the Republic of Uzbekistan

Thermal diffusion of supersonic solitons in an anharmonic chain of atoms

We study the non-equilibrium diffusion dynamics of supersonic lattice solitons in a classical chain of atoms with nearest-neighbor interactions coupled to a heat bath. As a specific example we choose an interaction with cubic anharmonicity. The coupling between the system and a thermal bath with a given temperature is made by adding noise, delta-correlated in time and space, and damping to the set of discrete equations of motion. Working in the continuum limit and changing to the sound velocity frame we derive a Korteweg-de Vries equation with noise and damping. We apply a collective coordinate approach which yields two stochastic ODEs which are solved approximately by a perturbation analysis. This finally yields analytical expressions for the variances of the soliton position and velocity. We perform Langevin dynamics simulations for the original discrete system which fully confirm the predictions of our analytical calculations, namely noise-induced superdiffusive behavior which scales with the temperature and depends strongly on the initial soliton velocity. A normal diffusion behavior is observed for very low-energy solitons where the noise-induced phonons also make a significant contribution to the soliton diffusion.Comment: Submitted to PRE. Changes made: New simulations with a different method of soliton detection. The results and conclusions are not different from previous version. New appendixes containing information about the system energy and soliton profile

Electronic energy band parameters of CuInSe2 : Landau levels in magnetotransmission spectra

Magnetotransmission (MT) at magnetic fields up to 29 T was used to study the electronic structure of CuInSe2 in thin polycrystalline films. The zero field absorption spectra exhibited resolved A, B, and C free excitons. Quantum oscillations, due to diamagnetic excitons comprising electrons and holes from Landau levels quantized in the conduction and valence band, respectively, appeared in the MT spectra at fields over 5 T. Spectral energies of Landau levels and binding energies of the corresponding diamagnetic excitons, theoretically calculated assuming a quasicubic approximation of the CuInSe2 tetragonal lattice structure, helped to identify the character of the experimentally observed diamagnetic excitons. Spectral energies of diamagnetic excitons in the MT spectra with different circular polarizations were used to determine the electron and light hole effective masses, whereas heavy hole masses as well as the γ and γ1 Luttinger parameters, Ep Kane energy, and F parameter of the influence of remote bands, as well as their polaron values, were calculated using the Luttinger theory