Matter wave soliton bouncer

Dynamics of a matter wave soliton bouncing on the reflecting surface (atomic mirror) under the effect of gravity has been studied by analytical and numerical means. The analytical description is based on the variational approach. Resonant oscillations of the soliton's center of mass and width, induced by appropriate modulation of the atomic scattering length and the slope of the linear potential are analyzed. In numerical experiments we observe the Fermi type acceleration of the soliton when the vertical position of the reflecting surface is periodically varied in time. Analytical predictions are compared with the results of numerical simulations of the Gross-Pitaevskii equation and qualitative agreement between them is found.Comment: 8 pages, 5 figure

Resonances in a trapped 3D Bose-Einstein condensate under periodically varying atomic scattering length

Nonlinear oscillations of a 3D radial symmetric Bose-Einstein condensate under periodic variation in time of the atomic scattering length have been studied analytically and numerically. The time-dependent variational approach is used for the analysis of the characteristics of nonlinear resonances in the oscillations of the condensate. The bistability in oscillations of the BEC width is invistigated. The dependence of the BEC collapse threshold on the drive amplitude and parameters of the condensate and trap is found. Predictions of the theory are confirmed by numerical simulations of the full Gross-Pitaevski equation.Comment: 17 pages, 10 figures, submitted to Journal of Physics

Collapse and revival of oscillations in a parametrically excited Bose-Einstein condensate in combined harmonic and optical lattice trap

In this work, we study parametric resonances in an elongated cigar-shaped BEC in a combined harmonic trap and a time dependent optical lattice by using numerical and analytical techniques. We show that there exists a relative competition between the harmonic trap which tries to spatially localize the BEC and the time varying optical lattice which tries to delocalize the BEC. This competition gives rise to parametric resonances (collapse and revival of the oscillations of the BEC width). Parametric resonances disappear when one of the competing factors i.e strength of harmonic trap or the strength of optical lattice dominates. Parametric instabilities (exponential growth of Bogoliubov modes) arise for large variations in the strength of the optical lattice.Comment: 9 pages, 20 figure

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

Effects of plant growth regulators on callogenesis and embryogenesis in sarnav and desiree potato (Solanum tuberosum L.) varieties

Somatic embryos play a pivotal role in the production of high-quality potatoes and seed breeding. This study focused on determining the concentrations of 1-naphthaleneacetic acid (NAA) and 6-benzyl amino purine (BAP) in the formation of callus tissue and callus induction. Our goal was to assess the efficiency of potato explants with the highest potential for somatic embryo production. To achieve this, we cultivated Sarnav and Desiree potato varieties under in vitro tissue culture conditions, utilizing the obtained tissue cultures for subsequent experiments. The MS nutrient media were enriched with NAA and BAP at ratios of 1.5: 1, 1: 1.5, and 1: 1 mg/L, along with NAA concentrations of 1.5, 1, or 2 mg/L. Somatic embryogenesis experiments were conducted using various MS nutrient media, enriched with BAP and GA3 at concentrations of 1: 0.5, 0.4: 0.1, 0.5: 0.2, and 0.1: 0.1 mg/L of plant growth regulators. During the course of the study, diverse callus formations were observed in both leaf and internodal stem explants. Among the nutrient media, the M2 medium enriched with 1: 1.5 mg/L of NAA and BAP yielded the highest callus formation rates: 92% for the Desiree variety and 100% for the Sarnav variety, specifically in internodal stem explants. Notably, the index of embryo formation in leaf explants selected for somatic embryogenesis within the SE4 medium was 70% for the Sarnav variety and 65% for the Desiree variety. The inclusion of BAP and GA3 at a ratio of 0.1: 0.1 mg/l in the SE4 nutrient medium resulted in somatic embryogenesis in 80% of calli for the Sarnav variety and 78% for the Desiree variety. These findings underscore the potential for regenerating plants through somatic embryogenesis in the Sarnav potato variety, a significant development with implications for genetic transformation studies involving this particular variety

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

Stability analysis of the D-dimensional nonlinear Schroedinger equation with trap and two- and three-body interactions

Considering the static solutions of the D-dimensional nonlinear Schroedinger equation with trap and attractive two-body interactions, the existence of stable solutions is limited to a maximum critical number of particles, when D is greater or equal 2. In case D=2, we compare the variational approach with the exact numerical calculations. We show that, the addition of a positive three-body interaction allows stable solutions beyond the critical number. In this case, we also introduce a dynamical analysis of the conditions for the collapse.Comment: 6 pages, 7 figure

Negative thermal expansion of MgB2_{2} in the superconducting state and anomalous behavior of the bulk Gr\"uneisen function

The thermal expansion coefficient $\alpha$ of MgB$_2$ is revealed to change from positive to negative on cooling through the superconducting transition temperature $T_c$. The Gr\"uneisen function also becomes negative at $T_c$ followed by a dramatic increase to large positive values at low temperature. The results suggest anomalous coupling between superconducting electrons and low-energy phonons.Comment: 5 figures. submitted to Phys. Rev. Let

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

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