Population of higher-energy levels in LiY_(1-x)Er_xF_4 (x=O.003 ÷1) crystals under CW IR laser-diode pumping

Steady-state population of 7 lowest excited erbium. levels in LiY¬¬_(1-x)Er_xF_4 (YLF:Er^(3+) (x=0.003-1) crystals was studied under upconversion. CW InGaAs laser-diode pumping with varied power density. Theoretical and experimental concentration and power dependencies of population of higher-energy radiative levels were obtained. Relative changes in populations of studied levels in YLF:Er^(3+) crystals were experimentally controlled by visible spectra of steady-state luminescence in the wavelength ranges corresponding to transitions ^4S_(3/2) --> ^4I(15/2) (0.52--0.57) mum and ^4 F_(9/2) --> ^I_(15/2) (0.64--0.68) µm. IR-pumped luminescence kinetic curves of higher-energy transitions ^4S_(3/2) --> ^4I_(15/2) (0.55 µm) and ^2H_(9/2) --> ^4I_(15/2) (0.41 µm) were recorded. The energy-transfer mechanisms were determined, and the predominant mechanisms responsible for upconversion excitation were elucidated. Microparameters of energy transfer and concentration dependencies of the selfquenching rates and non-linear coupling were obtained on the basis of theoretical and experimental estimates of the rates of intra- and intercenter relaxation processes (migration, selfquenching, and upconversion) allowing for statistics of coupling between the impurity centers in the system. The steady-state dependencies of population on the erbium concentration and pumping power density were calculated within the framework of rate balance equations. Good agreement between the theory and experimental data was obtained

Concentration and power dependences of level population of 2.8-mu m laser transition in YLF : Er crystals under CW laser diode pumping

An influence of interionic cross relaxation processes (upconversion, selfquenching) on concentration and power dependences of the inverse population of ^4I_(11/2) and ^4I_(13/2) laser levels in YLF:Er crystals under CW laser-diode pumping were studied both theoretically and experimentally. Computer simulations were carried out taking into account not only pair interaction but also the multi-ion interaction in the whole system. Optimal Er concentration for 3 - µm CW lasing was estimated as 10 - 15%

The Synthesis of Nanocomposites with Use of Cellulose

This work studied the synthesis of nanocomposites with cellulose use as crystallizing polymer on the basis of its ability to form crystalline particles with various parameters of an elementary cell – nanoparticles of a metal or oxide origin. The authors obtained high dispersed systems by dispersion of volume phases from solutions using condensation method. At using of this method, depending on the conditions of the formation process of the new phase can be obtained as systems with a size of several nanometers as well as more coarsely dispersed systems. The dispersiveness of a system, arising during formation of new phases, is determined by ratio speed of formation and nucleus growth of new phase a phase transition. The condensation process involves the formation of new phase according the heterogeneous or homogeneous mechanisms. The kinetics formation of new phase is determined by two stages: the formation of  condensation centers (nucleus) and nucleus growth. In formation process of nanocomposite materials the natural polymer with known molecular structure is used as matrix, in which we can put desired nanoparticles in the form of filler. In this work the authors used cellulose which has developed capillary-porous structure, including in-fibrillar porous with the size of 1.5-10 nm, and which is able to form crystallites with different parameters of lattice cell

Фауна и экология Spirurida у крупного рогатого скота Узбекистана

Objective of research: The objective of this study was to investigate the fauna, features of distribution and ecology of nematodes of the order Spirurida - parasites of cattle from Uzbekistan. Material and methods. Cattle and isolated animal organs were investigated by the method of complete and incomplete autopsies. Blood samples and animal skin biopsies were studied. Flies (Diptera) and beetles, intermediate hosts of nematodes, were collected and studied in places of cattle concentration, in spring, summer and autumn. Results and discussion: In animals of Uzbekistan 11 species of Spirurida nematodes belonging to two suborders were identified. Spirurata are represented by 7 species, Filariata by 4. The landscape distribution of the mentioned species of Spirurida and their biocenotic connections to corresponding hosts under conditions of Uzbekistan were determined.Цель исследования - изучение фауны, особенностей распространения и экологии нематод отряда Spirurida -паразитов крупного рогатого скота Узбекистана. Материалы и методы. Методом полных и неполных вскрытий исследованы крупный рогатый скот и отдельные органы животных. Исследованы пробы крови и проведена биопсия кожи животных. В местах концентрации крупного рогатого скота собраны и исследованы весной, летом и осенью двукрылые и жуки - промежуточные хозяева изучаемых нематод. Результаты и обсуждение. У исследованных животных Узбекистана выявлено 11 видов нематод отряда Spirurida, принадлежащих к двум подотрядам. Spirurata представлены 7 видами, Filariata - 4. Определено ландшафтное распределение отмеченных видов спирурид и их биоценотические связи с соответствующими хозяевами в условиях Узбекистана

Fauna and ecology of Spirurida in cattle of Uzbekistan

Objective of research: The objective of this study was to investigate the fauna, features of distribution and ecology of nematodes of the order Spirurida - parasites of cattle from Uzbekistan. Material and methods. Cattle and isolated animal organs were investigated by the method of complete and incomplete autopsies. Blood samples and animal skin biopsies were studied. Flies (Diptera) and beetles, intermediate hosts of nematodes, were collected and studied in places of cattle concentration, in spring, summer and autumn. Results and discussion: In animals of Uzbekistan 11 species of Spirurida nematodes belonging to two suborders were identified. Spirurata are represented by 7 species, Filariata by 4. The landscape distribution of the mentioned species of Spirurida and their biocenotic connections to corresponding hosts under conditions of Uzbekistan were determined

Opportunities of Innovation Technologies in Higher Education

This article highlights the benefits of continuing education, including the use of innovative technologies in higher education. The role of the “Economic Theory” science in developing the knowledge and understanding of economic laws in society, the understanding of the processes of market economy reform, the formation of creative ideas in the younger generation, the enhancement of economic culture. the importance of this discipline through the implementation of important tasks. Knowledge is a multi-tiered, complex process of perception of object properties, highlighting important aspects of it and expressing it in conclusions, comparing it with other objects and making judgments, and generalizing them