Circumbinary disk evolution

We study the evolution of circumbinary disks surrounding classical T Tau stars. High resolution numerical simulations are employed to model a system consisting of a central eccentric binary star within an accretion disk. The disk is assumed to be infinitesimally thin, however a detailed energy balance including viscous heating and radiative cooling is applied. A novel numerical approach using a parallelized Dual-Grid technique on two different coordinate systems has been implemented. Physical parameters of the setup are chosen to model the close systems of DQ Tau and AK Sco, as well as the wider systems of GG Tau and UY Aur. Our main findings are for the tight binaries a substantial flow of material through the disk gap which is accreted onto the central stars in a phase dependent process. We are able to constrain the parameters of the systems by matching both accretion rates and derived spectral energy distributions to observational data where available

Electronic structure of intermetallics based on a rare earth element and a transition or noble metal

The results of ab initio study of resonant surface states genesis in the vicinity of Γ point for GdRh[2]Si[2] are presented in this work. Our electronic band structure calculations have shown that the resonant surface states are already formed in three atomic layer slab Si-Rh-Si. The states localization within three layer slab causes its resonant nature and presence of these states on Si- and Gd- termination surfaces

Разработка способов, алгоритмов и программ обнаружения и исправления пакетных или независимых ошибок при передаче данных по каналам связи

Настоящая научно-квалификационная работа посвящена разработке способов, алгоритмов и программ обнаружения и исправления ошибок при передаче данных по каналам связи для обеспечения целостности и надёжности передаваемых команд и данных между устройствами вычислительно техники, а также при считывании данных из запоминающих устройств.The present scientific and qualification work is devoted to the development of methods, algorithms and programs for detecting and correcting errors in the transmission of data over communication channels to ensure the integrity and reliability of the transmitted commands and data between computing devices, as well as when reading data from memory devices

Temozolomide induces apoptosis and senescence in glioma cells cultured as multicellular spheroids

Temozolomide is an alkylating cytostatic drug that finds increasing application in the treatment of melanoma, anaplastic astrocytoma and glioblastoma multiforme. The compound is a prodrug that decomposes spontaneously, independent of an enzymatic activation step. DNA methylation induces futile mismatch repair cycles and depletion of the DNA repair enzyme O6-methylguanine-DNA methyltransferase should then initiate programmed cell death. We show drug-dependent inhibition of tumour growth in a three-dimensional cell culture model of the glioma cell lines U87MG and GaMG. Migrational behaviour of the glioblastoma cells remained unaltered. However, coincubation of tumour spheroids with primary brain aggregates showed reduced tumour cell invasion into brain tissue in the presence of temozolomide. This was not achieved by slowing cellular migration, as temozolomide-treated cells displayed no reduced motility. By transferase-mediated dUTP nick-end labelling (TUNEL) of apoptotic nuclei, we found that the drug was able to induce apoptosis throughout the tumour cell spheroids. Apoptosis was highest in the core region of the spheroids. Repetitive application of sublethal doses of temozolomide to multicellular spheroids resulted in the development of drug resistance in GaMG cells. We suggest that temozolomide is a strong initiator of apoptosis in glioblastoma tumour cells in a spheroid cell culture system, when cells are already in a stressful environment

Huygens' Principle for the Klein-Gordon equation in the de Sitter spacetime

In this article we prove that the Klein-Gordon equation in the de Sitter spacetime obeys the Huygens' principle only if the physical mass $m$ of the scalar field and the dimension $n\geq 2$ of the spatial variable are tied by the equation $m^2=(n^2-1)/4$. Moreover, we define the incomplete Huygens' principle, which is the Huygens' principle restricted to the vanishing second initial datum, and then reveal that the massless scalar field in the de Sitter spacetime obeys the incomplete Huygens' principle and does not obey the Huygens' principle, for the dimensions $n=1,3$, only. Thus, in the de Sitter spacetime the existence of two different scalar fields (in fact, with m=0 and $m^2=(n^2-1)/4$), which obey incomplete Huygens' principle, is equivalent to the condition $n=3$ (in fact, the spatial dimension of the physical world). For $n=3$ these two values of the mass are the endpoints of the so-called in quantum field theory the Higuchi bound. The value $m^2=(n^2-1)/4$ of the physical mass allows us also to obtain complete asymptotic expansion of the solution for the large time. Keywords: Huygens' Principle; Klein-Gordon Equation; de Sitter spacetime; Higuchi Boun

Особенности формирования сварного шва в изделиях из титанового сплава Ti-6Al-4V, полученных аддитивными методами

В данной работе проводился сравнительных анализ микроструктуры и микротвердости сварных соединений, полученных методом электроннолучевой сварки (ЭЛС). В качестве образцов исследовались пластины, полученные прокаткой и аддитивным методом EBF{3} (electronbeam freeform fabrication - электронно-лучевое изготовление свободной формы). Выявлено аналогичное формирование трех сварочных зон после ЭЛС в 3D-напечатанных образцах. Показано влияние исходной структуры на процесс формирования сварного соединения. Из результатов дюрометрического анализа следует, что зона плавления (FZ) характеризуется повышенной микротвердостью относительно основного материала. Однако в случае образцов, полученных методом EBF{3}, характер повышения отличается, что связано с особенностями формирования сварного шва.Comparing analysis of the microstructure and microhardness has been investigated in electron-beam welded Ti-6Al-4V alloy parts obtained by rolling and additive manufacturing. Electron-beam welding produced three distinct zones (FZ - the fusion zone, HAZ - the heat affected zone, BM - the base metal) in the welded material. The influence of the BM on the structure of welded joint is shown. According to the results of microhardness testing, it follows that in the FZ the microhardness is higher than in the BM. However, for samples obtained by EBF{3}, the nature of the increase is different due to the features of the formed microstructure during welding

Повышение энергетических характеристик органоводоугольных топлив за счет добавления металлических частиц

В научно-квалификационной работе представлены результаты экспериментальных исследований процессов, протекающих при зажигании органоводоугольных топлив с добавлением металлических частиц.По результатам экспериментальных исследований установлены отличия стадий зажигания металлизированных составов ВУТ и ОВУТ от исходных. Выделены температурные диапазоны зажигания топлив с добавлением частиц металла, определены размеры частиц металла, наиболее эффективно влияющие на энергетические характеристики топлив.The scientific qualification work show the results of experimental studies of the processes occurring during the ignition of organic coal-water slurry with the addition of metal particles. identified differences of the ignition stages of metallized compositions of CWS and OCWS from the initial. The temperature ranges of ignition of fuels with the addition of metal particles are identified, the sizes of metal particles that most effectively affect the energy characteristics of the fuel are determined