545 research outputs found

    Formation of bound states of electrons in spherically symmetric oscillations of plasma

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    We study spherically symmetric oscillations of electrons in plasma in the frame of classical electrodynamics. Firstly, we analyze the electromagnetic potentials for the system of radially oscillating charged particles. Secondly, we consider both free and forced spherically symmetric oscillations of electrons. Finally, we discuss the interaction between radially oscillating electrons through the exchange of ion acoustic waves. It is obtained that the effective potential of this interaction can be attractive and can transcend the Debye-Huckel potential. We suggest that oscillating electrons can form bound states at the initial stages of the spherical plasma structure evolution. The possible applications of the obtained results for the theory of natural plasmoids are examined.Comment: 9 pages in LaTeX2e, no figures; paper was significantly modified, 2 new references added, some inessential mathematics was removed, many typos were corrected; final variant to be published in Physica Script

    Diurnal variations of cosmic ray geomagnetic cut-off threshold rigidities

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    The spectrographic global survey method was used to investigate the rigidity variations Rc of geomagnetic cut-off as a function of local time and the level of geomagnetic disturbance for a number of stations of the world wide network. It is shown that geomagnetic cut-off threshold rigidities undergo diurnal variations. The diurnal wave amplitude decreases with increasing threshold rigidity Rc, and the wave maximum occurs at 2 to 4 hr LT. The amplitude of diurnal variations increases with increasing geomagnetic activity. The results agree with those from trajectory calculations made for an asymmetric model of the magnetosphere during different geomagnetic disturbance conditions

    Effective attraction between oscillating electrons in a plasmoid via acoustic waves exchange

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    We consider the effective interaction between electrons due to the exchange of virtual acoustic waves in a low temperature plasma. Electrons are supposed to participate in rapid radial oscillations forming a spherically symmetric plasma structure. We show that under certain conditions this effective interaction can result in the attraction between oscillating electrons and can be important for the dynamics of a plasmoid. Some possible applications of the obtained results to the theory of natural long-lived plasma structures are also discussed.Comment: 14 pages in LaTeX2e, two columns, 3 eps figures; minimal changes, some typos are corrected; version published on-line in Proc. R. Soc.

    Spin-down of neutron stars by neutrino emission

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    We study the spin-down of a neutron star during its early stages due to the neutrino emission. The mechanism we consider is the subsequent collisions of the produced neutrinos with the outer shells of the star. We find that this mechanism can indeed slow down the star rotation but only in the first tens of seconds of the core formation, which is when the appropriate conditions of flux and collision rate are met. We find that this mechanism can extract less than 1 % of the star angular momentum, a result which is much less than previously estimated by other authors.Comment: 9 pages, 2 eps figures, RevTeX 4-1. The paper was significantly modified. Now it addresses only the issues of a neutron star spin-down. Version to be published in Phys. Rev.

    EXPERIENCE OF SUCCESSFUL ACNEFORM ERUPTIONS TREATMENT IN PATIENT WITH MULTIPLE MELANOMA

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    Objective: to describe the results of the joint monitoring and diversified treatment of oncologists and dermatologists those patient with multiple recurrent melanoma who received over a long period a targeted anti-cancer therapy, which was complicated by side-effect as widespread acneform rush, resistant to traditional treatment. Patient A., born in 1988, was followed up and got a treatment more than 2 years in oncology out-patient clinic diagnosed with “Melanoma of the front surface of the left leg T2bN0M0 IIA”. Subsequently, the patient was verified metastasis in the inginal lymph nodes, in the soft tissues of the hips, to liver. Acute adverse reaction has developed in a short time after getting the anti-tumor target therapy as generalized acneform rush and itching of the skin. Skin symptoms accompanied by pronounced psychological and emotional stress, therefore, dermatologists have been invited to provide additional medical assistance to this patient. Due to the fact that subsequent traditional anti-acne algorithms of topical and oral treatment was not such effective, there was made a decision to use an alternative supporting external therapy, which did not have similar examples of usage previously. Results. External application of tacrolimus ointment in combination with other drugs and then as a mono-therapy, allows us in a rather short period achieve a stable and pronounced regression of skin pathological lesions, to return to the previously cancelled initial drug dose of the anti-tumor target therapy, to change significantly components of the patient’s quality of life. Conclusion. The search for additional and alternative treatment approaches for similar patients, as in our case, remains relevant for specialists and patients themselves. This case is an example of alternative approach to the tacrolimus topical application in patient with drug-mediated acneform rush

    A Line Through the Sacred Lands of the Altai Mountains: Perspectives on the Altai Pipeline Project

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    In 2006 preliminary plans were made public showing that Gazprom intended to construct a pipeline through the Altai republic (Russia, south-west Siberia). Unfortunately, there was almost no attention to integrating the conservation of cultural heritage (both archaeological and landscape) into the planning of the pipeline, though the Altai is well-known for its rich cultural heritage. Hitherto, no assessment has been made of the potential impact of the project, nor did Gazprom release detailed information about the exact course of the route. The present article aims to illustrate the potential impact of the pipeline based on a detailed study of a small segment of the route, using remote sensing images and data gathered during fieldwork. This assessment underlines the need for a well-thought-out strategy, which is required if sustainable integration of heritage conservation into the construction plan is to be realized. If such a balance is not found, thousands of archaeological monuments could disappear, which would result in a huge cultural and scientific loss. As a possible solution, an integrative strategy founded on a desk-based study of remote sensing images and a well-directed field survey is suggested

    Улучшенная модель двухзатворного JFET для аналоговых интегральных микросхем

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    A double gate JFETs are often used in analog integrated circuits to provide an extremely low input current and capacitance when the top gate is controlled. Circuit synthesis and modeling of analog IC with such a field-effect transistor are possible only if there are models that adequately describe the features of its operation, namely, changing of the current-voltage characteristics by the top gate controlling when a constant reverse voltage is applied to the bottom gate. The article considers the modernization of the well-known electrical model of the double gate field-effect transistor for the LTSpice software, which includes taking into account the influence of the top gate voltage by connecting two series-connected functional voltage sources to the top gate, one of which ensures the coincidence of the measurement results and the simulation of the drain current at a low voltage between the top gate and the source, and the second – when the voltage between the top gate and the source is close to the cutoff voltage. A method for identifying the parameters of functional voltage sources is presented. The proposed model of a double gate field-effect transistor is advisable to use in the IC design of various analog devices, especially electrometric operational amplifiers and charge-sensitive amplifiers.Двухзатворные полевые транзисторы с управляющим p-n-переходом часто применяются в аналоговых интегральных микросхемах для обеспечения предельно малого входного тока и емкости при управлении верхним затвором. Схемотехнический синтез и моделирование аналоговых микросхем с таким полевым транзистором возможны только при наличии моделей, адекватно описывающих особенности его работы, а именно – изменение вольт-амперных характеристик, управляя верхним затвором при подаче постоянного обратного напряжения на нижний затвор. В статье рассмотрена модернизация известной электрической модели двухзатворного полевого транзистора для программы LTSpice, заключающаяся в учете влияния напряжения на нижнем затворе путем включения в цепь верхнего затвора двух последовательно соединенных функциональных источников напряжения, один из которых обеспечивает совпадение результатов измерений и моделирования тока стока при малом напряжении между верхним затвором и истоком, а второй – при напряжении между верхним затвором и истоком, близком к напряжению отсечки. Приведена методика идентификации параметров функциональных источников напряжения. Предложенную модель двухзатворного полевого транзистора целесообразно использовать при схемотехническом проектировании различных аналоговых устройств, особенно электрометрических операционных усилителей и зарядочувствительных усилителей

    СРЕДСТВА РЕГИСТРАЦИИ ИМПУЛЬСНОГО ВИДИМОГО ИЗЛУЧЕНИЯ МАЛОЙ ИНТЕНСИВНОСТИ. ЧАСТЬ 1. ОСОБЕННОСТИ И ВОЗМОЖНОСТИ МНОГОКАНАЛЬНЫХ ФОТОПРИЕМНИКОВ С ВНУТРЕННИМ УСИЛЕНИЕМ. ОБЗОР

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    The main types of the modern photo detectors applied to single photon registration are analyzed. It is offered to use silicon photomultipliers for production of multi-channel optoelectronic systems with the single photon resolution.Проанализированы основные типы современных фотоприемников, применяемых для регистрации импульсного оптического излучения видимой области спектра. Сделан вывод о том, что для создания многоканальных оптико-электронных систем с однофотонным разрешением целесообразно использовать кремниевые фотоэлектронные умножители

    СРЕДСТВА РЕГИСТРАЦИИ ИМПУЛЬСНОГО ВИДИМОГО ИЗЛУЧЕНИЯ МАЛОЙ ИНТЕНСИВНОСТИ. Часть 2. ПРЕДВАРИТЕЛЬНАЯ ОБРАБОТКА СИГНАЛОВ КРЕМНИЕВЫХ ФОТОЭЛЕКТРОННЫХ УМНОЖИТЕЛЕЙ. ОБЗОР

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    Bias circuits, output signals and readout electronics of silicon photomultipliers are considered. Requirements to analog IC for SiPM signal preliminary processing are formulated. According to requirements the set of radiation hardened analog ICs including the comparator and transresistance amplifiers with different gain and speed is produced.Рассмотрены схемы включения, выходные сигналы и считывающая электроника кремниевых фотоэлектронных умножителей. Сформулированы требования к аналоговым устройствам для предварительной обработки их сигналов, в соответствии с которыми создана серия радиационно-стойких аналоговых микросхем, включающая компаратор напряжения и трансрезистивные усилители с разным коэффициентом преобразования и быстродействием

    Проектирование BJT-JFET операционных усилителей на базовом матричном кристалле

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    The use of dual-gate field-effect transistors located on the base matrix crystal MH2XA031, controlled by a p–n junction needed to reduce the input current of operational amplifiers is studied. Typical circuits of operational amplifiers, containing: source repeaters connected to the inputs of the operational amplifier on complementary bipolar transistors; input differential stage on p-JFET with a “current mirror” load on n–p–n-transistors; input differential in the form of a “folded cascode” on a p-JFET are analyzed. To minimize the input current, it is re commended to use bootstrapped feedback to keep the drain-to-source voltage of the input JFETs low, independent of the input common-mode voltage, and to connect only the top gate of the dual-gate JFET to the op-amp input. The electrical circuits for MH2XA031 elements and the results of circuit simulation of the developed amplifiers, called OAmp10J, OAmp11.1, OAmp11.2, are presented. Accounting the established features of the input stages and operating modes of active elements in circuit design will allow to create an operational amplifier with the required combination of basic parameters.Рассмотрено применение расположенных на базовом матричном кристалле МН2ХА031 двухзатворных полевых транзисторов, управляемых p–n-переходом, для уменьшения входного тока операционных усилителей. Проанализированы типовые схемы операционных усилителей, содержащие: истоковые повторители, соединенные с входами операционного усилителя на комплементарных биполярных транзисторах; входной дифференциальный каскад на p-JFET с нагрузкой в виде «токового зеркала» на n–p–n-транзисторах; входной дифференциальный каскад в виде «перегнутого каскода» на p-JFET. Для максимального уменьшения входного тока рекомендовано применение следящей обратной связи, поддерживающей напряжение сток-исток входных JFET на малом уровне, не зависящем от входного синфазного напряжения, и соединение с входом операционного усилителя только верхнего затвора двухзатворного полевого транзистора. Приведены электрические схемы для элементов МН2ХА031 и результаты схемотехнического моделирования разработанных усилителей, названных OAmp10J, OAmp11.1, OAmp11.2. Учет при схемотехническом проектировании установленных особенностей входных каскадов и режимов работы активных элементов позволит создать операционный усилитель с требуемым сочетанием основных параметров
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