Coherent lidars based on intracavity heterodyning of echo signals

The development and technical realization of the method of laser sounding of the atmosphere based on the effects of mixing of reference and external fields of scattering inside a laser cavity are presented. An approximate theory of the method was developed on the basis of the investigations using the model of a three-mirror laser. The nonlinear effect of a wideband laser on frequency-dependent external influences of the atmosphere was investigated. The field measurements of gaseous composition of the atmosphere were performed on the basis of a given method of coherent reception using a tunable CO2 laser

Rapid assessment of nonlinear optical propagation effects in dielectrics

Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrödinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process

Ion beam irradiation of ABO4 compounds with the fergusonite, monazite, scheelite, and zircon structures

The effects of irradiation on CaWO4, SrWO4, BaWO4, YVO4, LaVO4, YNbO4, and LaNbO4 were investigated on thin crystals using 1.0 MeV Kr ions at 50-1000 K. All of the ABO4 compounds can be amorphized with calculated damage cross sections (σa = 1/Fc0) in the range of ~ 0.30-1.09 × 10-14 cm2 ion-1 at zero Kelvin. Analysis of fluence-temperature data returned critical temperatures for amorphization (Tc) of 311 ± 1, 358 ± 90, 325 ± 19, 415 ± 17, 541 ± 6, 636 ± 26, and 1012 ± 1 K, respectively for the compounds listed above. Compared with previous in situ irradiation of ABO4 orthophosphate samples using 0.8 MeV Kr ions, the Tc values of LaVO4 and YVO4 are higher than those of LaPO4 and YPO4 by 82 K and 124 K, respectively. The Tc values of the three scheelite structures, CaWO4, SrWO4, and BaWO4, indicate that they are the most radiation tolerant compounds under these conditions. The A-B cation anti-site energies, EfAB, determined by DFT range from 2.48 to 10.58 eV and are highly correlated with the A-B cation ionic radius ratio, rA/rB, but are not correlated with Tc across the different structure types, suggesting that the formation and migration energies of Frenkel defects play a more important role in damage recovery in these compounds. We also discuss the role of cation and anion charge/iconicity as determined by DFT. ABO4 compounds with the zircon structure and B = P or V have a distinct advantage over those with B = Si as the damaged regions do not appear to be significantly affected by polymerization of (PO4)3- or (VO4)3- groups which might stabilize the amorphous fraction and ultimately lead to phase separation as observed in zircon (ZrSiO4)

Взаимосвязь цен на нефть и макроэкономических показателей в России

One of the most important external factors affecting the exchange rate of the US dollar to the Russian rouble has been the global oil price. Russia, whose economy is mainly associated with oil production, is one of the world’s largest oil suppliers. Therefore, the slightest fluctuations in oil prices can have a significant effect on its economy. The aim of the article is to study the relationship between macroeconomic parameters and oil prices. The objectives of the study are to identify factors having a long-term positive relationship with oil prices based on a mathematical approach, as well as to propose improvements for Russian macroeconomic indicators. The authors use modern mathematical methods of vector autoregression (VAR-model), the Granger method and the Dickey-Fuller test to study the long-term and shortterm relationships between the relevant time series for the period from 2014 to 2016. On this basis, it was calculated that a 1% increase in GDP leads to a strengthening of the national currency by 1.47%. This fact can be explained by the overall growth of the national economy. The Granger test results for the model show that global oil price (and Russian GDP) has the greatest impact on the exchange rate in the short term. The following actions are proposed for improving macroeconomic indicators: stabilisation of foreign economic policy; diversification of exports (although oil revenues can serve as a tool for improving the quality of Russian economic development and public life in general); development of the Russian ‘Urals’ benchmark and increasing its trading volumes on the world market; transition to rubles for settlements of Russian oil and gas; use of a ruble indicator (ruble barrel) of the ‘Urals’ oil price to support the development of Russia’s financial and economic policy.Одним из важнейших внешних факторов, влияющих на курс доллара к рублю, продолжает оставаться мировая цена на нефть. Россия — один из крупнейших в мире поставщиков «черного золота», ее экономика в основном связана с нефтедобычей. Поэтому малейшие колебания цен на нефть оказывают на нее сильнейшее влияние. Цель работы — изучение взаимосвязи между макроэкономическими параметрами и ценами на нефть. Задачи исследования: выявление факторов, имеющих долгосрочную положительную связь с ценами на нефть на основе математического подхода и подготовка предложений по улучшению макроэкомических индикаторов России. Авторы используют современные математические методы векторной авторегрессии (VAR-модель), метод Грэнджера, тест Дики-Фуллера для исследования долгосрочных и краткосрочных отношений между временными рядами за период c 2014 по 2016 г. Рассчитано, что рост ВВП на 1% приводит к укреплению национальной валюты на 1,47%. Этот факт можно объяснить ростом экономики страны в целом. Результаты теста Грейнджера для модели показывают, что цена на нефть (как и ВВП) оказывает наибольшее влияние на валютный курс в краткосрочной перспективе. Предложены следующие действия по улучшению макроэкономических показателей: стабилизация внешнеэкономической политики; диверсификация экспорта: нефтяные доходы могут превратиться в инструмент повышения качества развития российской экономики и жизни общества в целом; формирование российского бэнчмарка Urals и повышение объемов торгов по нему до мирового уровня; перевод расчетов за российскую нефть и газ в рубли; использование рублевого индикатора (рублевый баррель) цены на нефть марки Urals при формировании финансово-экономической политики России

Peroral Endoscopic Myotomy in Diffuse Thickened Esophageal Wall in an Adolescent

Achalasia is an extremely rare pathology in children. Peroral endoscopic myotomy (POEM) is the gold standard for the surgical treatment of achalasia in adults, but only a limited number of cases of achalasia treatment using POEM in children have been published in the literature. Sometimes, high-resolution manometry signs of achalasia can mimic diffuse esophageal leiomyoma. This case report represents the first known successful performance of POEM on a 15-year-old female with diffuse thickening of the esophagus with signs and symptoms of achalasia and suspicion for Alport syndrome associated with diffuse esophageal leiomyoma

Finding the Cell Center by a Balance of Dynein and Myosin Pulling and Microtubule Pushing: A Computational Study

By comparing computer modeling predictions with observations, we conclude that strong dynein and weaker myosin-generated forces pull the microtubules inward competing with microtubule plus-ends pushing the microtubule aster outward and that the balance of these forces positions the centrosome at the cell center

Size-dependent stability of ultra-small α-/β-phase tin nanocrystals synthesized by microplasma

Key features of tin, including electronic band structure and opto-electronic properties, are influenced by the crystal structure. Here the authors report a microplasma process for the synthesis of ultra-small tin nanocrystals in which the crystal structure is dependent on crystallite size

An Experimental and Computational Study of Effects of Microtubule Stabilization on T-Cell Polarity

T-killer cells eliminate infected and cancerous cells with precision by positioning their centrosome near the interface (immunological synapse) with the target cell. The mechanism of centrosome positioning has remained controversial, in particular the role of microtubule dynamics in it. We re-examined the issue in the experimental model of Jurkat cells presented with a T cell receptor-binding artificial substrate, which permits controlled stimulation and reproducible measurements. Neither 1-µM taxol nor 100-nM nocodazole inhibited the centrosome positioning at the “synapse” with the biomimetic substrate. At the same time, in micromolar taxol but not in nanomolar nocodazole the centrosome adopted a distinct peripheral rather than the normally central position within the synapse. This effect was reproduced in a computational energy-minimization model that assumed no microtubule dynamics, but only a taxol-induced increase in the length of the microtubules. Together, the experimental and computational results indicate that microtubule dynamics are not essential for the centrosome positioning, but that the fit of the microtubule array in the deformed body of the conjugated T cell is a major factor. The possibility of modulating the T-cell centrosome position with well-studied drugs and of predicting their effects in silico appears attractive for designing anti-cancer and antiviral therapies