Essential self-adjointness of magnetic Schr\"odinger operators on locally finite graphs

We give sufficient conditions for essential self-adjointness of magnetic Schr\"odinger operators on locally finite graphs. Two of the main theorems of the present paper generalize recent results of Torki-Hamza.Comment: 14 pages; The present version differs from the original version as follows: the ordering of presentation has been modified in several places, more details have been provided in several places, some notations have been changed, two examples have been added, and several new references have been inserted. The final version of this preprint will appear in Integral Equations and Operator Theor

Strain Hardening of Polymer Glasses: Entanglements, Energetics, and Plasticity

Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are pulled taut between entanglements rather than a change in entropy. A weak entropic stress is only observed in shape recovery of deformed samples when heated above the glass transition. While short chains do not form an entangled network, they exhibit partial shape recovery, orientation, and strain hardening. Stresses for all chain lengths collapse when plotted against a microscopic measure of chain stretching rather than the macroscopic stretch. The thermal contribution to the stress is directly proportional to the rate of plasticity as measured by breaking and reforming of interchain bonds. These observations suggest that the correct microscopic theory of strain hardening should be based on glassy state physics rather than rubber elasticity.Comment: 15 pages, 12 figures: significant revision

Muon pair creation from positronium in a circularly polarized laser field

We study elementary particle reactions that result from the interaction of an atomic system with a very intense laser wave of circular polarization. As a specific example, we calculate the rate for the laser-driven reaction $e^+e^- \to \mu^+\mu^-$, where the electron and positron originate from a positronium atom or, alternatively, from a nonrelativistic $e^+e^-$ plasma. We distinguish accordingly between the coherent and incoherent channels of the process. Apart from numerical calculations, we derive by analytical means compact formulas for the corresponding reaction rates. The rate for the coherent channel in a laser field of circular polarization is shown to be damped because of the destructive interference of the partial waves that constitute the positronium ground-state wave packet. Conditions for the observation of the process via the dominant incoherent channel in a circularly polarized field are pointed out

Tumor microenvironment: the formation of the immune profile

Tumor microenvironment (TME) is formed as a result of interaction and cross-linking between the tumor cell and different types of surrounding cells. Recent studies have shown that the tumor reprograms the microenvironment so that TME promotes the development of primary tumors, their metastasis and becomes an important regulator of oncogenesis. Under the influence of the tumor, the immune profile in the TME undergoes significant changes, “editing". An immunosuppressive network is formed, which suppresses the activity of the main effector of cellular immunity — T lymphocytes. T cells in TMA are in a state of anergy and exhaustion. T cells in TME are characterized by increased expression of inhibitory receptors, decreased secretion of cytokines and cytolytic activity. Blocking inhibitory receptors with specific antibodies can lead to the restoration of the functions of exausted T cells. Therefore, the restoration of the functional activity of T lymphocytes is one of the important strategies in cancer immunotherapy. The formation of the immune profile is influenced by genetic aberrations accumulating in the tumor. They play an important role in creating a specific, characteristic only for this tumor immune environment in the TME. Genetic changes in tumor cells lead to phenotypic and functional rearrangements of lymphocytes, which allows the tumor to escape the reaction of immune cells. Since many tumors occur after prolonged inflammation or exhibit characteristics of chronic inflammation as they progress, inflammation is considered an important factor in the formation of immune profile in TME. Immune infiltrates from different human tumors associated with inflammation may contain valuable prognostic and pathophysiological information. Macrophages in the TME now began to be regarded as descriptive marker and as a therapeutic target. One of the main mechanisms by which tumor cells reprogram surrounding cells is the release of exosomes — small vesicles that carry and deliver proteins and nucleic acids to other cells. When exosomal cargo is absorbed, molecular, transcriptional and translational changes occur in the recipient non-tumor cells in the TME. Therefore, tumor exosomes are an effective means by which the functions of immune cells in TME are purposefully changed. Thus, along with individual molecular and genomic testing of the tumor, attention should be paid to a deeper analysis of the immune profile of TME. It is a large resource of biomarkers and targets for immunotherapy

To the problems of modeling the brain ischemia in small animals

In the review article the problems of modeling cerebral ischemia in small mammals are consecrated. The advantages of experimental studies that are based on the similarity of the blood circulation of the brain in humans and animals are indicated. Classification of experimental models for the study of acute and chronic disorders of cerebral circulation, mechanisms of their development and preclinical approbation of new drugs is given. The authors indicate that all experimental models of brain ischemia can be divided into two groups: to study risk factors and pathophysiological studies of brain ischemia. And in the second case, the models of focal and global ischemia are described. In conclusion, the authors point out the difficulties and shortcomings of certain methods of ischemia reproduction, which await researchers to solve the above problems

INVESTIGATION ON THE DISCRETIZATION OF THE REALISTIC IRREGULAR WAVE GENERATION REGION THROUGH THE WAVEMIMO METHODOLOGY

Aiming to contribute to the research related to the sea wave energy conversion, the present paper approaches an investigation of the discretization used in the region of imposition of the prescribed velocity boundary condition, which is necessary for the WaveMIMO methodology. This methodology is employed for the numeric generation of irregular waves based on realistic sea state data. These data (obtained from TOMAWAC software in the present study) are treated to obtain orbital profiles of wave propagation velocity, which are imposed as boundary conditions on the wave channel. In this study, the realistic data considered refers to a point close to the Molhes da Barra, located on the coast of the municipality of Rio Grande, Rio Grande do Sul, Brazil. The numerical simulations were performed in Fluent, a computational fluid dynamics (CFD) software based on the finite volume method (FVM). The volume of fluid (VOF) multiphase model was used on the treatment of the water-air interface. Free surface elevation data obtained when the region of imposition of the prescribed velocity boundary condition was subdivided into 8, 11 and 14 segments were compared. The results found show that the 14 segments discretization represents more precisely the free surface elevation of irregular waves

Перспективи створення противірусного лікарського препарату на основі сировини синтетичного походження

Aim. To determine the prospects for the creation of a drug based on inosine pranobex using scientific analysis of the characteristics and range of antiviral drugs at the pharmaceutical market ofUkraine.Materials and methods. The material of the article was literary sources of electronic and printed publications on the problems of the use of the substance of synthetic origin – inosine pranobex in modern pharmacotherapy of epidemic mumps, herpes virus human, cytomegalovirus, Epstein-Barr virus, chickenpox virus, influenza virus and parainfluenza. The results were collected and processed using the analytical-comparative, logical and systematic methods of research and the analysis of scientific publications of scientists from different countries of the world, explanation of the reasons and the conceptual position of the authors of the works analyzed on the development and application of antiviral drugs and systematization of the data collected.Results and discussion. The substance of synthetic origin, inosine pranobex, has a direct antiviral effect due to its ability to bind to the ribosomes of infected cells, slows down the synthesis of viral RNA (transcriptional and translational impairment) and leads to inhibition of replication of RNA and DNA-genomic viruses. Induction of interferon formation is also characteristic for the drugs on the basis of this substance. The immunomodulating properties of inosine pranobex are due to the ability of the substance to enhance the differentiation of pre-T-lymphocytes, stimulate mitogen-induced proliferation of T-and B-lymphocytes, increase the functional activity of T-lymphocytes, as well as their ability to form lymphokines. The synthesis of interleukin-1, the expression of membrane receptors and the ability to respond to lymphokines and chemotactic factors are stimulated. Due to the wide range of the pharmacological action, inosine pranobex stimulates mainly cellular immunity, which is especially effective under conditions of cellular immunodeficiency. It has been also found that the use of inosine pranobex helps to reduce the severity of symptoms of herpes infection, duration of the disease; in addition, the substance studied can enhance the antiviral effect of interferon, acyclovir and other antiviral drugs. The above facts prove the relevance of the use of inosine pranobex both for the treatment and prevention of acute and chronic viral infections.Conclusions. The article highlights the current issues of the treatment and prevention of acute respiratory viral infections at the present stage. The classification and features of the mechanism of action of common antiviral drugs are given. A comparison has been made between domestic and international data on the spectrum of application and the pharmacological safety of inosine pranobex. The studies indicate the prospects of creating production of the substance of synthetic origin – inosine pranobex inUkraine. The development of an antiviral drug based on it will significantly reduce the economic costs of industrial production and will be able to guarantee the quality of the medicinal product confirmed by clinical studies. Цель работы. Определение перспективы создания лекарственного препарата на основе инозита пранобекса путем научного анализа характеристики и ассортимента противовирусных препаратов на фармацевтическом рынке Украины.Материалы и методы. Материалом статьи служили литературные источники электронных и печатных изданий по проблематике применения вещества синтетического происхождения инозина пранобекса в современной фармакотерапии эпидемического паротита, вируса герпеса человека, цитомегаловируса, вируса Эпштейна-Барра, вируса ветряной оспы, вируса гриппа и парагриппа. Результаты собраны и обработаны с помощью аналитико-сравнительного, логического и системного методов исследования и анализа научных публикаций ученых разных стран мира, изложения соображений и концептуальной позиции авторов проанализированных работ по разработке и применению противовирусных препаратов и систематизации собранных данных.Результаты и их обсуждение. Вещество синтетического происхождения инозин пранобекс имеет прямое противовирусное действие, обусловленное способностью связываться с рибосомами пораженных вирусом клеток, замедляет синтез вирусной РНК (нарушение транскрипции и трансляции) и приводит к подавлению репликации РНК и ДНК-геномных вирусов. Также препаратам на основе этой субстанции свойственна индукция интерферонообразования. Иммуномодулирующие свойства инозина пранобекса обусловлены способностью субстанции усиливать дифференцирование пре-Т-лимфоцитов, стимулировать индуцированную митогенами пролиферацию Т- и В-лимфоцитов, повышать функциональную активность Т-лимфоцитов, а также их способность к образованию лимфокинов. Стимулируется синтез интерлейкина-1, экспрессия мембранных рецепторов и способность реагировать на лимфокины и хемотаксические факторы. За счет широкого спектра фармакологического действия инозин пранобекс стимулирует преимущественно клеточный иммунитет, что особенно эффективно в условиях клеточного иммунодефицита. Установлено также, что применение инозина пранобекса способствует уменьшению выраженности симптомов инфекции герпеса, длительности заболевания; кроме того, исследуемая субстанция способна усиливать противовирусное действие интерферона, ацикловира и других противовирусных препаратов. Вышеупомянутое доказывает актуальность использования инозина пранобекса как для лечения, так и для профилактики острых и хронических вирусных инфекций.Выводы. Освещены актуальные вопросы лечения и профилактики острых респираторных вирусных инфекций на современном этапе. Приведена классификация и особенности механизма действия распространенных противовирусных препаратов. Проведено сравнение отечественных и мировых данных по спектру применения и фармакологической безопасности инозина пранобекса. Освещенные исследования свидетельствуют о перспективности создания производства субстанции синтетического происхождения – инозина пранобекса в Украине. Разработка противовирусного препарата на его основе существенно сократит экономические затраты промышленного производства и сможет гарантировать качество лекарственного средства, подтвержденное клиническими исследованиями. Мета роботи. Визначення перспективи створення лікарського препарату на основі інозину пранобексу шляхом наукового аналізу характеристики та асортименту противірусних препаратів на фармацевтичному ринку України.Матеріали та методи. Матеріалом статті слугували літературні джерела електронних та друкованих видань з проблематики застосування речовини синтетичного походження інозину пранобексу в сучасній фармакотерапії епідемічного паротиту, вірусу герпесу людини, цитомегаловірусу, вірусу Епштейна-Барра, вірусу вітряної віспи, вірусу грипу та парагрипу. Результати зібрані та оброблені за допомогою аналітико-порівняльного, логічного і системного методів дослідження та аналізу наукових публікацій учених різних країн світу, викладення міркувань та концептуальної позиції авторів проаналізованих робіт стосовно розробки і застосування противірусних препаратів та систематизації зібраних даних.Результати та їх обговорення. Речовина синтетичного походження інозин пранобекс чинить пряму противірусну дію, зумовлену здатністю зв’язуватися із рибосомами вражених вірусом клітин, що уповільнює синтез вірусної РНК (порушення транскрипції та трансляції) і призводить до пригнічення реплікації РНК- та ДНК-геномних вірусів. Також препаратам на основі цієї субстанції властива індукція інтерфероноутворення. Імуномодулюючі властивості інозину пранобексу зумовлені здатністю субстанції підсилювати диференціювання пре-Т-лімфоцитів, стимулювати індуковану мітогенами проліферацію Т- та В-лімфоцитів, підвищувати функціональну активність Т-лімфоцитів, а також їх здатність до утворення лімфокінів. Стимулюється синтез інтерлейкіну-1, експресія мембранних рецепторів та здатність реагувати на лімфокіни і хемотаксичні фактори. За рахунок широкого спектра фармакологічної дії інозин пранобекс  стимулює переважно клітинний імунітет, що особливо ефективно в умовах клітинного імунодефіциту. Встановлено також, що застосування інозину пранобексу сприяє зменшенню вираженості симптомів інфекції герпесу, тривалості захворювання; крім того, досліджувана субстанція здатна потенціювати противірусну дію інтерферону, ацикловіру та інших противірусних препаратів. Вищезазначене доводить актуальність використання інозину пранобексу як для лікування, так і для профілактики гострих і хронічних вірусних інфекцій.Висновки. Висвітлені актуальні питання лікування і профілактики гострих респіраторних вірусних інфекцій на сучасному етапі. Наведено класифікацію та особливості механізму дії поширених противірусних препаратів. Проведено порівняння вітчизняних та світових даних щодо спектра застосування та фармакологічної безпеки інозину пранобексу. Висвітлені дослідження свідчать про перспективність створення виробництва субстанції синтетичного походження – інозину пранобексу в Україні. Розробка противірусного препарату на його основі суттєво скоротить економічні витрати промислового виробництва та зможе гарантувати якість лікарського засобу, підтверджену клінічними дослідженнями

Effect of interface bonding on spin-dependent tunneling from the oxidized Co surface

We demonstrate that the factorization of the tunneling transmission into the product of two surface transmission functions and a vacuum decay factor allows one to generalize Julliere's formula and explain the meaning of the ``tunneling density of states'' in some limiting cases. Using this factorization we calculate spin-dependent tunneling from clean and oxidized fcc Co surfaces through vacuum into Al using the principal-layer Green's function approach. We demonstrate that a monolayer of oxygen on the Co (111) surface creates a spin-filter effect due to the Co-O bonding which produces an additional tunneling barrier in the minority-spin channel. This changes the minority-spin dominated conductance for the clean Co surface into a majority spin dominated conductance for the oxidized Co surface.Comment: 7 pages, revtex4, 4 embedded eps figure

Observation of band structure and density of states effects in Co-based magnetic tunnel junctions

Utilizing Co/Al$_2$O$_3$/Co magnetic tunnel junctions (MTJs) with Co electrodes of different crystalline phases, a clear relationship between electrode structure and junction transport properties is presented. For junctions with one fcc(111) textured and one polycrystalline (poly-phase and poly-directional) Co electrode, a strong asymmetry is observed in the magnetotransport properties, while when both electrodes are polycrystalline the magnetotransport is essentially symmetric. These observations are successfully explained within a model based on ballistic tunneling between the calculated band structures (DOS) of fcc-Co and hcp-Co.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Influence of s-d interfacial scattering on the magnetoresistance of magnetic tunnel junctions

We propose the two-band s-d model to describe theoretically a diffuse regime of the spin-dependent electron transport in magnetic tunnel junctions (MTJ's) of the form F/O/F where F's are 3d transition metal ferromagnetic layers and O is the insulating spacer. We aim to explain the strong interface sensitivity of the tunneling properties of MTJ's and investigate the influence of electron scattering at the nonideal interfaces on the degradation of the TMR magnitude. The generalized Kubo formalism and the Green's functions method were used to calculate the conductance of the system. The vertex corrections to the conductivity were found with the use of "ladder" approximation combined with the coherent-potential approximation (CPA) that allowed to consider the case of strong electron scattering. It is shown that the Ward identity is satisfied in the framework of this approximation that provides the necessary condition for a conservation of a tunneling current. Based on the known results of ab-initio calculations of the TMR for ballistic junctions, we assume that exchange split quasi-free s-like electrons with the density of states being greater for the majority spin sub-band give the main contribution to the TMR effect. We show that, due to interfacial inter-band scattering, the TMR can be substantially reduced even down to zero value. This is related to the fact that delocalized quasi-free electrons can scatter into the strongly localized d sub-band with the density of states at the Fermi energy being larger for minority spins compared to majority spins. It is also shown that spin-flip electron scattering on the surface magnons within the interface leads to a further decrease of the TMR at finite temperature.Comment: REVTeX4, 20 pages, 9 figures, 1 table, submitted to Phys.Rev.B; In Version 2 the text is substantially improved, the main results and conclusions left the sam