Influence of Gamma-Ray Emission on the Isotopic Composition of Clouds in the Interstellar Medium

We investigate one mechanism of the change in the isotopic composition of cosmologically distant clouds of interstellar gas whose matter was subjected only slightly to star formation processes. According to the standard cosmological model, the isotopic composition of the gas in such clouds was formed at the epoch of Big Bang nucleosynthesis and is determined only by the baryon density in the Universe. The dispersion in the available cloud composition observations exceeds the errors of individual measurements. This may indicate that there are mechanisms of the change in the composition of matter in the Universe after the completion of Big Bang nucleosynthesis. We have calculated the destruction and production rates of light isotopes (D, 3He, 4He) under the influence of photonuclear reactions triggered by the gamma-ray emission from active galactic nuclei (AGNs). We investigate the destruction and production of light elements depending on the spectral characteristics of the gamma-ray emission. We show that in comparison with previous works, taking into account the influence of spectral hardness on the photonuclear reaction rates can increase the characteristic radii of influence of the gamma-ray emission from AGNs by a factor of 2-8. The high gamma-ray luminosities of AGNs observed in recent years increase the previous estimates of the characteristic radii by two orders of magnitude. This may suggest that the influence of the emission from AGNs on the change in the composition of the medium in the immediate neighborhood (the host galaxy) has been underestimated.Comment: 13 pages, 13 figures, 3 table

Fragmentation channels of relativistic 7^7Be nuclei in peripheral interactions

Nuclei of $^7$Li were accelerated at the JINR Nuclotron. After the charge-exchange reaction involving these nuclei at an external target a second $^7$Be beam of energy 1.23A GeV was formed. This beam was used to expose photo-emulsion chambers. The mean free path for inelastic $^7$Be interactions in emulsion $\lambda$=14.0$\pm$0.8 cm coincides within the errors with those for $^6$Li and $^7$Li nuclei. More than 10% of the $^7$Be events are associated with the peripheral interactions in which the total charge of the relativistic fragments is equal to the charge of the $^7$Be and in which charged mesons are not produced. An unusual ratio of the isotopes is revealed in the composition of the doubly charged $^7$Be fragments: the number of $^3$He fragments is twice as large as that of $^4$He fragments. In 50% of peripheral interactions, a $^7$Be nucleus decays to two doubly charged fragments. The present paper gives the channels of the $^7$Be fragmentation to charged fragments. In 50% of events, the $^7$Be fragmentation proceeds only to charged fragments involving no emission of neutrons. Of them, the $^3$He+$^4$He channel dominates, the $^4$He+d+p and $^6$Li+pchannels constitute 10% each. Two events involving no emission of neutrons are registered in the 3-body $^3$He+t+p and $^3$He+d+d channels. The mean free path for the coherent dissociation of relativistic $^7$Be nuclei to $^3$He+$^4$He is 7$\pm$1 m. The particular features of the relativistic $^7$Be fragmentation in such peripheral interactions are explained by the $^3$He+$^4$He 2-cluster structure of the $^7$Be nucleus.Comment: 10 pages, 3 figures, 3 tables, conference: Conference on Physics of Fundamental Interactions, Moscow, Russia, 5-9 Dec 200

Role of the Nuclear and Electromagnetic Interactions in the Coherent Dissociation of the Relativistic 7^7Li Nucleus into the 3^3H + 4^4He Channel

The differential cross section in the transverse momentum $Q$ and a total cross section of $(31\pm4)$ mb for the coherent dissociation of a 3-A-GeV/$c$ $^7$Li nucleus through the $^3$H$+^4$He channel have been measured on emulsion nuclei. The observed $Q$ dependence of the cross section is explained by the predominant supposition of the nuclear diffraction patterns on light (C, N, O) and heavy (Br, Ag) emulsion nuclei. The contributions to the cross section from nuclear diffraction ($Q\le400$ MeV/$c$) and Coulomb $(Q\le50$ MeV/$c$) dissociations are calculated to be 40.7 and 4 mb, respectively.Comment: ISSN 0021-3640, Pleiades Publishing, Ltd., 200

Femtometer Toroidal Structures in Nuclei

The two-nucleon density distributions in states with isospin $T=0$, spin $S$=1 and projection $M_S$=0 and $\pm$1 are studied in $^2$H, $^{3,4}$He, $^{6,7}$Li and $^{16}$O. The equidensity surfaces for $M_S$=0 distributions are found to be toroidal in shape, while those of $M_S$=$\pm$1 have dumbbell shapes at large density. The dumbbell shapes are generated by rotating tori. The toroidal shapes indicate that the tensor correlations have near maximal strength at $r<2$ fm in all these nuclei. They provide new insights and simple explanations of the structure and electromagnetic form factors of the deuteron, the quasi-deuteron model, and the $dp$, $dd$ and $\alpha d$ $L$=2 ($D$-wave) components in $^3$He, $^4$He and $^6$Li. The toroidal distribution has a maximum-density diameter of $\sim$1 fm and a half-maximum density thickness of $\sim$0.9 fm. Many realistic models of nuclear forces predict these values, which are supported by the observed electromagnetic form factors of the deuteron, and also predicted by classical Skyrme effective Lagrangians, related to QCD in the limit of infinite colors. Due to the rather small size of this structure, it could have a revealing relation to certain aspects of QCD.Comment: 35 pages in REVTeX, 25 PostScript figure

Electromagnetic response functions of few-nucleon systems

Inclusive electromagnetic reactions in few-nucleon systems are studied basing on accurate three- and four-body calculations. The longitudinal 4He(e,e') response function obtained at q\le 600 MeV/c completely agrees with experiment. The exact 4He spectral function obtained in a semirealistic potential model is presented, and the accuracy of the quasielastic response calculated with its help is assessed, as well as the accuracy of some simpler approximations for the response. The photodisintegration cross section of 3He obtained with the realistic AV14 NN force plus UrbanaVIII NNN force agrees with experiment. It is shown that this cross section is very sensitive to underlying nuclear dynamics in the E_\gamma\simeq 70-100 MeV region. In particular, the NNN nuclear force clearly manifests itself in this region.Comment: 10 pages, Latex, style file is included, 7 ps figures, to appear in Proc. of the 2nd Int. Conf. on Perspectives in Hadronic Physics, ITCP, Triest, May 1999, World Sci., Singapor

ЗАЩИТНЫЕ ПОКРЫТИЯ La–Mn–Cu–O НА СТАЛИ-ИНТЕРКОННЕКТОРЕ 08Х17Т ДЛЯ ТВЕРДООКСИДНЫХ ТОПЛИВНЫХ ЭЛЕМЕНТОВ, ПОЛУЧЕННЫЕ МЕТОДОМ ЭЛЕКТРОКРИСТАЛЛИЗАЦИИ ИЗ НЕВОДНЫХ РАСТВОРОВ ЭЛЕКТРОЛИТОВ

A novel method was developed to form a protective layer on 08KhG17T stainless steel used to make interconnectors for solid oxide fuel cells. The method was based on the electrocrystallization of metals from non-aqueous electrolyte solutions on the stainless-steel interconnector surface with subsequent thermal treatment. Chemical composition of electrolyte was selected so that the surface is coated with an oxide protective layer of the following composition: LaMn0,9Cu0,1O3. As a result, a uniform oxide layer was formed on the stainless steel interconnector surface to protect stainless steel against high-temperature oxidation resulting in degraded functional properties of the interconnector. The coatings formed were characterized by means of grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy from the surface and in the cross section. Elemental and phase composition analyses have shown that the main components of the protective coatings are compounds with perovskite and spinel structures. The protective coating in contact with cathode material based on lanthanum strontium manganite have shown significantly lowered chromium penetration from steel as a result of diffusion annealing in comparison with the sample without the protective coating. Interconnector bonding to the protective coating has shown no noticeable degradation during at least 500 h at 850 °C in ambient air.Разработан новый метод формирования защитного покрытия на нержавеющей стали марки 08Х17Т, используемой для изготовления интерконнекторов твердооксидных топливных элементов. Он основан на электрокристаллизации металлов из неводных растворов электролитов на поверхности интерконнектора из нержавеющей стали с последующей термической обработкой. Химический состав электролита подбирался из расчета получения на поверхности оксидного слоя состава LaMn0,9Cu0,1O3. В результате на поверхности нержавеющей стали-интерконнера сформировался сплошной оксидный слой, защищающий сталь от высокотемпературного окисления, ведущего к деградации функциональных свойств интерконнектора. Полученные покрытия исследованы методами рентгенофазового анализа в геометрии скользящего пучка, рентгенофотоэлектронной спектроскопии и растровой электронной микроскопии с поверхности и в поперечном сечении. Анализ элементного и фазового составов покрытия показал, что основными его компонентами являются соединения со структурой перовскита и шпинели. В контакте с катодным материалом на основе манганита лантана–стронция защитное покрытие показало заметное ухудшение проникновения хрома из стали в результате диффузионного обжига по сравнению с образцом без покрытия. Соединение интерконнектора с покрытием не показывает заметной деградации в течение не менее 500 ч при температуре 850 °C в воздушной атмосфере

Statistical Mechanics and the Physics of the Many-Particle Model Systems

The development of methods of quantum statistical mechanics is considered in light of their applications to quantum solid-state theory. We discuss fundamental problems of the physics of magnetic materials and the methods of the quantum theory of magnetism, including the method of two-time temperature Green's functions, which is widely used in various physical problems of many-particle systems with interaction. Quantum cooperative effects and quasiparticle dynamics in the basic microscopic models of quantum theory of magnetism: the Heisenberg model, the Hubbard model, the Anderson Model, and the spin-fermion model are considered in the framework of novel self-consistent-field approximation. We present a comparative analysis of these models; in particular, we compare their applicability for description of complex magnetic materials. The concepts of broken symmetry, quantum protectorate, and quasiaverages are analyzed in the context of quantum theory of magnetism and theory of superconductivity. The notion of broken symmetry is presented within the nonequilibrium statistical operator approach developed by D.N. Zubarev. In the framework of the latter approach we discuss the derivation of kinetic equations for a system in a thermal bath. Finally, the results of investigation of the dynamic behavior of a particle in an environment, taking into account dissipative effects, are presented.Comment: 77 pages, 1 figure, Refs.37

Гипоксические белки VEGF A и CA IX и резистентность клеток сарком мягких тканей к химиопрепаратам: пилотный опыт ex vivo анализа

Introduction. The identification of predictive factors is a cornerstone task of modern oncology. The development of new targeted drugs determines the need for prediction of chemosensitivity of each patient to the prescribed therapy, in this regard, the search for biomarkers of predictive response to therapy is actively conducted.The study objective to investigate the relationship between tumor cell resistance and the expression levels of CA IX (carbonic anhydrase IX) and VEGF A (vascular endothelial growth factor А) in patient-derived cultures of soft tissue sarcomas.Materials and methods: ex vivo soft tissue sarcoma cell culture, resazurin test, immunoblotting.Results. We obtained 46 ex vivo samples of soft tissue sarcoma cultures for which chemosensitivity to doxorubicin, ifosfamide, docetaxel, gemcitabine, and their combinations was assessed by the resazurin cytotoxicity test. We analyzed the relationship between the expression of hypoxic proteins VEGF A and CA IX and the resistance to drugs. A correlation between the CA IX expression in hypoxia and cell resistance to ifosfamide and its combination with doxorubicin was found. Soft tissue sarcomas with high VEGF A index were resistant to doxorubicin, docetaxel, and its combination with gemcitabine (p &lt;0.05).Conclusion. The data obtained on patient-derived cultures indicate the relationship between hypoxic signaling and resistance of soft tissue sarcomas to chemotherapeutics.Введение. Поиск предиктивных факторов является краеугольной задачей современной онкологии. Разработка большого числа новых таргетных препаратов определяет необходимость четкого предсказания хемочувствительности конкретного пациента к назначаемой терапии. В связи с этим активно ведется поиск биомаркеров прогноза ответа на терапию.Цель исследования – изучение взаимосвязи между резистентностью опухолевых клеток и уровнем экспрессии CA IX (карбоангидразы IX) и VEGF A (фактора роста эндотелия сосудов А) в ex vivo культурах сарком мягких тканей.Материалы и методы. В исследование были включены ex vivo культуры сарком мягких тканей, использованы резазуриновый тест, иммуноблоттинг.Результаты. Получено 46 ex vivo образцов культур сарком мягких тканей, для которых с помощью резазуринового теста на цитотоксичность определена хемочувствительность к доксорубицину, ифосфамиду, доцетакселу, гемцитабину и их комбинациям. Проведен анализ связи экспрессии гипоксических белков VEGF A и CA IX с резистентностью к химиопрепаратам. Обнаружена корреляция уровня экспрессии CA IX в гипоксии с резистентностью клеток к ифосфамиду и его комбинации с доксорубицином. Образцы сарком мягких тканей, обладающие высоким индексом VEGF A, были резистентны к доксорубицину, доцетакселу и его комбинации с гемцитабином (p &lt;0,05).Заключение. Полученные на ex vivo культурах данные свидетельствуют о взаимосвязи гипоксического сигналинга и резистентности сарком мягких тканей к химиотерапии

ВАРИАНТЫ И ПЕРСПЕКТИВЫ ПЕРЕПРОФИЛИРОВАНИЯ ЛЕКАРСТВЕННЫХ ПРЕПАРАТОВ ДЛЯ ИСПОЛЬЗОВАНИЯ В ТЕРАПИИ ОНКОЛОГИЧЕСКИХ ЗАБОЛЕВАНИЙ

Recently many new approaches for repurposing or repositioning of the clinically used drugs have been developed. Drug repurposing  allows not only to use known schemes for the synthesis of  biologically active compounds, but also to avoid multiple studies that  are necessary for drug approval process – analysis of  pharmacokinetics, carcinogenicity, acute and chronic toxicity,  including cardiotoxicity, nephrotoxicity, allergenicity etc. It makes  possible to reduce the number of experimental studies as well as  costs of investigations. In cancer research drug repurposing includes screening for medicines used nowadays for the treatment of patients with non-cancer diseases which possess anticancer activity or able to enhance the effects of the standard anticancer chemotherapy, and  search for new applications of known anticancer drugs for the  treatment of different cancer types. Scientific rationale for the search of the compounds with potential anticancer properties among drugs  with different applications is based on the multiple cross-talks of  signaling pathways, which can inhibit cell proliferation. Modern  advances in genomics, proteomics and bioinformatics, development  of permanently improving databases of drug molecular effects and  high throughput analytical systems allow researchers to analyze  simultaneously a large bulk of existing drugs and specific molecular targets. This review describes the main approaches and  resources currently used for the drug repurposing, as well as a  number of examples.В настоящее время появились новые программы по перепрофилированию или перепозиционированию лекарственных средств, используемых в медицинской практике.  Перепрофилирование препаратов позволяет не только использовать отработанные схемы  синтеза биологически активных соединений, но и избежать проведения исследований,  необходимых для внедрения новых лекарственных препаратов в медицинскую практику, по  фармакокинетике, канцерогенности, острой и хронической токсичности, в том числе  кардиотоксичности, нефротоксичности, аллергенности и т.д. Это создает возможность сократить объем необходимых исследований и снизить затраты на них. В онкологии  программы перепрофилирования лекарственных средств включают как поиск препаратов,  обладающих противоопухолевой активностью или потенцирующих действие  противоопухолевых препаратов, среди известных и широко применяемых лекарственных  средств, используемых для лечения неонкологических заболеваний, так и анализ  возможности использования уже известных противоопухолевых препаратов для лечения  каких-либо новых нозологических форм заболевания. Основанием для поиска  противоопухолевых свойств среди препаратов иного назначения является тот факт, что  сигнальные пути в клетке характеризуются большим количеством перекрестных  взаимодействий и некоторые из них могут ингибировать пролиферацию опухолевых клеток.  Современные достижения геномики, протеомики, биоинформатики, появление объемных баз данных по молекулярным эффектам лекарственных препаратов, мощных аналитических систем и их постоянное совершенствование уже позволяет исследователям  одновременно проанализировать большое количество существующих препаратов в  применении к конкретной молекулярной мишени. В обзоре рассмотрены основные подходы  и ресурсы, использующиеся в настоящее время для перепрофилирования лекарственных  препаратов, а также приведен ряд примеров