On the numerical solution of the three-dimensional advection-diffusion equation

A new approach is proposed for the numerical solution of three-dimensional advection-diffusion equations, which arise, among others, in air pollution modelling. The technique is based on directional operator splitting, which results in one-dimensional advection-diffusion equations. Then upstream-type difference approximations are applied for the first-order derivatives and non-standard difference approximations for the second-order derivatives. This approach leads to significant qualitative improvements in the behaviour of the numerical solutions

Четверта міжнародна наукова-практична конференція «Комп’ютерне моделювання в хімії і технологіях та системах сталого розвитку»

Основу сучасних метеорологічних моделей складають нелінійні тривимірні рівняння конвективної дифузії. Задача реалізації цих рівнянь є обчислювально складною. В даній роботі пропонується застосування розпаралелювання на відеографічних процесорах при реалізації метеорологічних моделей. Представлено результати розв'язання тестової задачі за допомогою технології CUDA та графічного прискорювача. Проведено аналіз отриманих результатів.The basis of modern meteorological models are nonlinear three-dimensional convection diffusion equations. The problem of realization of these equations is computationally complex. In this paper the application of parallelization with graphics processors for meteorological models implementation is proposed. The results of solving the test problem using CUDA technology with graphics processing unit are presented. An analysis of the obtained results provided.Основу современных метеорологических моделей составляют нелинейные трехмерные уравнения конвективной диффузии, реализация которых является вычислительно сложной задачей. В работе предлагается применение распараллеливания на видеографических процессорах при реализации метеорологических моделей. Представлены результаты решения тестовой задачи с помощью технологии CUDA с их анализом

Модифицирование литейных алюминиевых сплавов системы Al–Mg–Si обработкой жидкой фазы наносекундными электромагнитными импульсами

The AA 511 alloy of the Al–Mg–Si system was used as an example to demonstrate that aluminum melt irradiation with nanosecond electromagnetic pulses (NEPs) leads to a significant change in the nature of structure formation during crystallization. It was found that an increase in the frequency of melt irradiation with NEPs is accompanied by the refinement of the alloy structural components, while the greatest grain size reduction of the α-solid solution and intergranular inclusions of the eutectic Mg2Si phase is observed at a NEPs frequency f = 1000 Hz. An increase in the NEPs frequency leads to a significant increase in the concentration of magnesium in the α-solid solution and the fragmentation of Mg2Si phase intergranular inclusions, which is released in the form of compact isolated inclusions when the melt is irradiated at a frequency of 1000 Hz. It was shown that melt processing with NEPs leads to an increase in the Brinell hardness of as-cast specimens, as well as to a significant increase in the microhardness of α-solid solution grains (from 38.21 HV in the initial state to 61.85 HV after irradiation with a frequency of 1000 Hz). It was assumed that the effect of a pulsed electromagnetic field leads to a decrease in the critical values of the Gibbs free energy required to initiate nucleation processes, and to a decrease in the surface tension at the «growing crystal – molten metal» interface, which causes a modifying effect on the alloy structure due to a decrease in the critical size of crystal nuclei.На примере сплава АА 511 системы Al–Mg–Si показано, что облучение алюминиевых расплавов наносекундными электромагнитными импульсами (НЭМИ) приводит к существенному изменению характера структурообразования при кристаллизации. Установлено, что повышение частоты облучения расплавов НЭМИ сопровождается измельчением структурных составляющих сплава и перераспределением в них легирующих элементов. При этом наибольшая степень уменьшения размеров зерен α-твердого раствора и межзеренных включений эвтектической фазы Mg2Si наблюдается при частоте НЭМИ f = 1000 Гц. Повышение частоты НЭМИ приводит к значительному увеличению концентрации магния в α-твердом растворе и фрагментации межзеренных включений фазы Mg2Si, которая при облучении расплава с f = 1000 Гц выделяется в форме компактных изолированных включений. Показано, что обработка расплавов НЭМИ приводит к повышению твердости (по Бринеллю) образцов в литом состоянии, а также к увеличению микротвердости зерен α-твердого раствора (с 38,21 HV в исходном состоянии до 61,85 HV после облучения с частотой 1000 Гц). Было сделано предположение, что воздействие импульсного электромагнитного поля приводит к понижению критических значений свободной энергии Гиббса, необходимых для инициации процессов зародышеобразования, и снижению поверхностного натяжения на границах раздела «растущий кристалл – металлический расплав», что обусловливает модифицирующее воздействие на структуру сплава за счет уменьшения критического размера зародышей кристаллизации

A programmed cell death pathway in the malaria parasite Plasmodium falciparum has general features of mammalian apoptosis but is mediated by clan CA cysteine proteases

Several recent discoveries of the hallmark features of programmed cell death (PCD) in Plasmodium falciparum have presented the possibility of revealing novel targets for antimalarial therapy. Using a combination of cell-based assays, flow cytometry and fluorescence microscopy, we detected features including mitochondrial dysregulation, activation of cysteine proteases and in situ DNA fragmentation in parasites induced with chloroquine (CQ) and staurosporine (ST). The use of the pan-caspase inhibitor, z-Val-Ala-Asp-fmk (zVAD), and the mitochondria outer membrane permeabilization (MOMP) inhibitor, 4-hydroxy-tamoxifen, enabled the characterization of a novel CQ-induced pathway linking cysteine protease activation to downstream mitochondrial dysregulation, amplified protease activity and DNA fragmentation. The PCD features were observed only at high (μM) concentrations of CQ. The use of a new synthetic coumarin-labeled chloroquine (CM-CQ) showed that these features may be associated with concentration-dependent differences in drug localization. By further using cysteine protease inhibitors z-Asp-Glu-Val-Asp-fmk (zDEVD), z-Phe-Ala-fmk (zFA), z-Phe-Phe-fmk (zFF), z-Leu-Leu-Leu-fmk (zLLL), E64d and CA-074, we were able to implicate clan CA cysteine proteases in CQ-mediated PCD. Finally, CQ induction of two CQ-resistant parasite strains, 7G8 and K1, reveals the existence of PCD features in these parasites, the extent of which was less than 3D7. The use of the chemoreversal agent verapamil implicates the parasite digestive vacuole in mediating CQ-induced PCD

Current infestation status of Atlantic salmon with Anisakis simplex larvae in the River Ponoi (the Murmansk region)

The infestation of Atlantic salmon with larvae of nematode Anisakis simplex has been studied in recreational catches in the River Ponoi of the Murmansk Region by using data from field research. The level and dynamics of infestation of autumn Atlantic salmon in 2009–2016 have been determined in comparison with the historical data. The results of research have shown that the proportion of salmon infested with parasite (extensiveness of infestation) varied from 2,1 to 59,8 % and a number of parasites in a single fish (intensity of infestation) – from 0–1 to 0–28. Indexes of infestation have varied also among different groups of autumn salmon but related neither with a number of years salmon spent at sea nor with salmon run timing into the river. The Red Vent Syndrome (RVS) has never been confirmed for Ponoi Atlantic salmon. The larvae of nematode have been found only in the mesentery and on the internal organs of the abdominal cavity of salmon and never in the muscles. Observations of the behavior of parasite larvae found in the abdominal cavity of the salmon have shown that when storing unbetted fish during the day at different ambient temperatures, migration of larvae to muscle tissue has not been observed. These findings have an important practical application as larvae of nematode Anisakis simplex are infective to humans and cause Anisakidosis. After having analyzed the data on dynamics of salmon infestation the assumption has been made that the level of Atlantic salmon infestation with Anisakis simplex larvae depends mostly on the role of different salmon food species in the parasite life cycle and their availability in different years of salmon feeding migration in ocean

Characterization of Tobacco Mosaic Virus Virions and Repolymerized Coat Protein Aggregates in Solution by Small-Angle X-Ray Scattering

The structure of tobacco mosaic virus (TMV) virions and stacked disk aggregates of TMV coat protein (CP) in solution was analyzed by synchrotron-based small-angle X-ray scattering (SAXS) and negative contrast transmission electron microscopy (TEM). TMV CP aggregates had a unique stability but did not have helical symmetry. According to the TEM data, they were stacked disks associated into transversely striated rod-shaped structures 300 to 800 Å long. According to modeling based on the crystallographic model of the 4-layer TMV CP aggregate (PDB: 1EI7), the stacked disks represented hollow cylinders. The calculated SAXS pattern for the disks was compared to the experimental one over the entire measured range. The best correlation with the SAXS data was found for the model with the repeating central pair of discs; the SAXS curves for the stacked disks were virtually identical irrespectively of the protein isolation method. The positions of maxima on the scatter curves could be used as characteristic features of the studied samples; some of the peaks were assigned to the existing elements of the quaternary structure (periodicity of aggregate structure, virion helix pitch). Low-resolution structural data for the repolymerized TMV CP aggregates in solution under conditions similar to natural were produced for the first time. Analysis of such nano-size objects is essential for their application in biomedicine and biotechnology