Derivative-free Gauss-Newton-like Algorithm for Parameter Estimation

This paper develops the idea of parameter estimation using the derivative-free nonlinear least-squares algorithm. The algorithm was found efficient and convenient for many applications

Possible Effects of the Existence of the 4th Generation Neutrino

The 4th generation of fermions predicted by the phenomenology of heterotic string models can possess new strictly conserved charge, which leads, in particular, to the hypothesis of the existence of the 4th generation massive stable neutrino. The compatibility of this hypothesis with the results of underground experiment DAMA searching for weakly interactive particles of dark matter and with the EGRET measurements of galactic gamma--background at energies above 1 GeV fixes the possible mass of the 4th neutrino at the value about 50 GeV. The possibility to test the hypothesis in accelerator experiments is considered. Positron signal from the annihilation of relic massive neutrinos in the galactic halo is calculated and is shown to be accessible for planned cosmic ray experiments.Comment: 10 pages, 4 PostScript figure, Latex2

Using the associative method of studying the text during university classes in literary disciplines

The article deals with the productive possibilities of the associative method of studying a literary text at university classes in literary disciplines. The student's creative thinking is characterized by the ability to generate new and sometimes unexpected semantic connections. Creative thinking largely depends on the so-called associative flexibility. There are several areas in the university teaching of literary studies in which the associative method of studying the text is effective. These are areas determined by the specifics of the type of artistic thinking, the specifics of a particular genre, and the individual manner of the writer. The method of developing associative thinking is important in the study of lyrical prose, where the specific weight of subtextual semantic nuances is high. Another area of literary studies in which an associative method of understanding a text is appropriate is the study of irony, including parody as ironic stylization. The very process of laughable reinterpretation of a foreign word implies the presence of a potential arsenal of situational associative references. At the same time, classes in literary studies use not only literary texts that are part of the main body of Russian literature, but also the range of phenomena that belongs to the so-called creative laboratory of the writer: writer's diaries, notebooks, work records, epistolary heritage. The method of associative study of the text can be used in the course of classes on practical poetics, where students comprehend all the complexities of the artistic form of a literary work. Using the associative method of studying a literary text helps to better understand the nature of the dialogical interaction between the writer and the reader, because a literary work is nothing more than a replica in the ongoing communication between the author and the recipient of his creation. This communication has its own hidden languages. A literary work can be called a meaning-intensive space of meeting and touching the associative fields of the writer and the reader. The educational tasks that can be solved by the associative method of learning are diverse. This technology helps to effectively assimilate special terminology; understand internal system connections in a literary text; establish significant connections between a specific literary phenomenon and the historical and literary context, cultural epoch; form and enrich connections between a specific writer's manner (stylistic originality) and the national Fund of the Russian language; identify cross-references between a specific literary phenomenon and the national cultural code; to determine the balance of traditional and innovative in relation to a specific literary text

Size-dependent bandgap and particle size distribution of colloidal semiconductor nanocrystals

A new analytical expression for the size-dependent bandgap of colloidal semiconductor nanocrystals is proposed within the framework of the finite-depth square-well effective mass approximation in order to provide a quantitative description of the quantum confinement effect. This allows one to convert optical spectroscopic data (photoluminescence spectrum and absorbance edge) into accurate estimates for the particle size distributions of colloidal systems even if the traditional effective mass model is expected to fail, which occurs typically for very small particles belonging to the so-called strong confinement limit. By applying the reported theoretical methodologies to CdTe nanocrystals synthesized through wet chemical routes, size distributions are inferred and compared directly to those obtained from atomic force microscopy and transmission electron microscopy. This analysis can be used as a complementary tool for the characterization of nanocrystal samples of many other systems such as the II-VI and III-V semiconductor materials.Comment: 9 pages, 5 figure

Self-consistency over the charge-density in dynamical mean-field theory: a linear muffin-tin implementation and some physical implications

We present a simple implementation of the dynamical mean-field theory approach to the electronic structure of strongly correlated materials. This implementation achieves full self-consistency over the charge density, taking into account correlation-induced changes to the total charge density and effective Kohn-Sham Hamiltonian. A linear muffin-tin orbital basis-set is used, and the charge density is computed from moments of the many body momentum-distribution matrix. The calculation of the total energy is also considered, with a proper treatment of high-frequency tails of the Green's function and self-energy. The method is illustrated on two materials with well-localized 4f electrons, insulating cerium sesquioxide Ce2O3 and the gamma-phase of metallic cerium, using the Hubbard-I approximation to the dynamical mean-field self-energy. The momentum-integrated spectral function and momentum-resolved dispersion of the Hubbard bands are calculated, as well as the volume-dependence of the total energy. We show that full self-consistency over the charge density, taking into account its modification by strong correlations, can be important for the computation of both thermodynamical and spectral properties, particularly in the case of the oxide material.Comment: 20 pages, 6 figures (submitted in The Physical Review B

Biotic interactions, energy pathways and trigger factors of ecosystem dynamics in shallow saline lakes

Environmental variables, food-web dynamics, and energy pathways were investigated in ecosystems of six shallow lakes of the Crimea with salinity ranging from 24 to 340‰. There were considerable inter- and intra-annual #uctuations in the abiotic characteristics of the lakes. All the lakes had a very high concentration of total phosphorus in the water (up to 5.6 gP m-3) due to a great influence of the watershed on the lakes. A high level of primary production (up to 14.9 gC m-2 d-1) was found in the most of the lakes. The lowest primary production was found in the most saline lake with a dense population of the filtrator, Artemia urmiana. Grazing benthic energy pathways were dominant at salinities between 24 and 58‰. Greater levels of salinity led to a gradual reduction of benthic and increase of planktonic energy pathways. A fast shift from turbid to the clear-water regime was observed in one of the lakes, caused by annual variations in weather conditions

Observation of the parallel-magnetic-field-induced superconductor-insulator transition in thin amorphous InO films

We study the response of a thin superconducting amorphous InO film with variable oxygen content to a parallel magnetic field. A field-induced superconductor-insulator transition (SIT) is observed that is very similar to the one in normal magnetic fields. As the boson-vortex duality, which is the key-stone of the theory of the field-induced SIT, is obviously absent in the parallel configuration, we have to draw conclusion about the theory insufficiency.Comment: 3 pages, 4 figure