Radio-frequency discharges in Oxygen. Part 1: Modeling

In this series of three papers we present results from a combined experimental and theoretical effort to quantitatively describe capacitively coupled radio-frequency discharges in oxygen. The particle-in-cell Monte-Carlo model on which the theoretical description is based will be described in the present paper. It treats space charge fields and transport processes on an equal footing with the most important plasma-chemical reactions. For given external voltage and pressure, the model determines the electric potential within the discharge and the distribution functions for electrons, negatively charged atomic oxygen, and positively charged molecular oxygen. Previously used scattering and reaction cross section data are critically assessed and in some cases modified. To validate our model, we compare the densities in the bulk of the discharge with experimental data and find good agreement, indicating that essential aspects of an oxygen discharge are captured.Comment: 11 pages, 10 figure

The adenosine generating enzymes CD39/CD73 control microglial processes ramification in the mouse brain

Microglial cells invade the brain as amoeboid precursors and acquire a highly ramified morphology in the postnatal brain. Microglia express all essential purinergic elements such as receptors, nucleoside transporters and ecto-enzymes, including CD39 (NTPDase1) and CD73 (5'-nucleotidase), which sequentially degrade extracellular ATP to adenosine. Here, we show that constitutive deletion of CD39 and CD73 or both caused an inhibition of the microglia ramified phenotype in the brain with a reduction in the length of processes, branching frequency and number of intersections with Sholl spheres. In vitro, unlike wild-type microglia, cd39-/- and cd73-/- microglial cells were less complex and did not respond to ATP with the transformation into a more ramified phenotype. In acute brain slices, wild-type microglia retracted approximately 50% of their processes within 15 min after slicing of the brain, and this phenomenon was augmented in cd39-/- mice; moreover, the elongation of microglial processes towards the source of ATP or towards a laser lesion was observed only in wild-type but not in cd39-/- microglia. An elevation of extracellular adenosine 1) by the inhibition of adenosine transport with dipyridamole, 2) by application of exogenous adenosine or 3) by degradation of endogenous ATP/ADP with apyrase enhanced spontaneous and ATP-induced ramification of cd39-/- microglia in acute brain slices and facilitated the transformation of cd39-/- and cd73-/- microglia into a ramified process-bearing phenotype in vitro. These data indicate that under normal physiological conditions, CD39 and CD73 nucleotidases together with equilibrative nucleoside transporter 1 (ENT1) control the fate of extracellular adenosine and thereby the ramification of microglial processes

Comparative study of semiclassical approaches to quantum dynamics

Quantum states can be described equivalently by density matrices, Wigner functions or quantum tomograms. We analyze the accuracy and performance of three related semiclassical approaches to quantum dynamics, in particular with respect to their numerical implementation. As test cases, we consider the time evolution of Gaussian wave packets in different one-dimensional geometries, whereby tunneling, resonance and anharmonicity effects are taken into account. The results and methods are benchmarked against an exact quantum mechanical treatment of the system, which is based on a highly efficient Chebyshev expansion technique of the time evolution operator.Comment: 32 pages, 8 figures, corrected typos and added references; version as publishe

Buckling of Cylindrical Shells of Variable Thickness, Loaded by External Uniform Pressure

From the mathematical standpoint one has a partial  differential equation with variable coefficients. Perturbation procedure gives the possibilityfor an analytical solution of this eigenvalue problem. Self-adjoint equations and Padé approximants are used for improving the obtained results

On the Wake Structure in Streaming Complex Plasmas

The theoretical description of complex (dusty) plasmas requires multiscale concepts that adequately incorporate the correlated interplay of streaming electrons and ions, neutrals, and dust grains. Knowing the effective dust-dust interaction, the multiscale problem can be effectively reduced to a one-component plasma model of the dust subsystem. The goal of the present publication is a systematic evaluation of the electrostatic potential distribution around a dust grain in the presence of a streaming plasma environment by means of two complementary approaches: (i) a high precision computation of the dynamically screened Coulomb potential from the dynamic dielectric function, and (ii) full 3D particle-in-cell simulations, which self-consistently include dynamical grain charging and non-linear effects. The applicability of these two approaches is addressed

Поляризационно-модуляционная методика определения абсолютных значений механических напряжений в сапфировых оптических окнах

При вирощуванні зливків монокристалічного сапфіру в ньому виникають дефекти у вигляді мікробульбашок, границь блоків і зумовлені ними механічні напруження, які суттєво впливають на функціональні властивості кристалу. Проблему контролю якості сапфірових структур вирішують багатьма способами, але вони не є достатньо чутливими для потреб сучасної оптики та мікроелектроніки, або є складними у використанні (рентгенівські методи). Традиційний контроль внутрішніх механічних напружень здійснюють візуально на полярископі-поляриметрі ПКС-250, в основу якого покладено метод подвійного променезаломлення Сенармона. Проте технічні можливості цього традиційного методу не здатні виконувати високочутливий кількісний контроль зразків монокристалів сапфіру з мікронапруженнями. Тому актуальною задачею сучасного приладобудування є розроблення нових високочутливих методів технічної діагностики та неруйнівного контролю якості деталей із сапфіру. Автори роботи досліджували можливість використання методу модуляційної поляриметрії для вирішення поставленої задачі. Однак стан поляризації як характеристики випромінювання має з огляду на диференціальну спектроскопію суттєву відмінність від інших способів модуляції. Вона полягає, перш за все, у тому, що поляризація, як просторова характеристика хвилі, залежить від сукупності значень – компонент вектора Максвела-Джонса або вектора Стокса. Отже, на відміну від модуляцій інших фізичних величин, що оперують із єдиним параметром, поляризаційна модуляція (ПМ) характеризується двомірним впливом на хвилю. Метою роботи було розроблення методики визначення абсолютних величин внутрішніх механічних напружень у локальних точках сапфірових оптичних вікон за допомогою модуляційної поляриметрії. У результаті проведених досліджень полірованих зразків сапфіру (типу оптичних вікон) було розроблено методику визначення абсолютних значень внутрішніх механічних напружень у матеріалах, прозорих в оптичному діапазоні випромінювання на основі модуляційної поляриметрії. Розроблена методика дозволила виявити внутрішні механічні напруження у сапфірових вікнах і визначити причину невідповідності досліджених зразків щодо вимог лазерних систем. Розроблено методику експериментального визначення величини абсолютних значень внутрішніх механічних напружень у сапфірових оптичних вікнах за допомогою використання модуляційної поляриметрії. Встановлено розподіл у двомірному просторі внутрішніх напружень у полірованих зразках сапфіру та їх абсолютні значення.There are defects such as microbubbles and boundaries of blocks appears in monocrystalline sapphire bars when they growing due to mechanical stresses that significantly affect the functional properties of the crystal. The quality control structures sapphire problem is solved in many ways, but they are not sufficiently sensitive to the needs of modern optics and microelectronics, or difficult to use (X-ray methods). Traditional control internal mechanical stresses perform visually on polariscope-polarimeter PKS-250, which is based on the double refraction Senarmona. However, the traditional method technical capability is not able to perform highly quantitative control samples of single crystal sapphire with mikrostresses. Therefore, the actual problem of modern instrumentation is the development of new highly sensitive methods of non-destructive quality diagnostics and control of parts of the sapphire. The authors of investigated the possibility of using the method of modulation polarimetry to solve this problem. However, this characteristic radiation as the state of polarization has in terms of differential spectroscopy substantial difference from other methods of modulation. It is, above all, that the polarization as spatial characteristics of the wave reflected set of values - the components of the vector Maxwell Jones or Stokes vector. Thus, unlike the modulation of other physical quantities that operate with a single parameter, polarization modulation (PM) is characterized by two-dimensional effects on the wave. The purpose of the work was the development of methods for determining the absolute values of the internal stresses in local points of sapphire optical windows using modulation polarimetry. The polished sapphire samples (such as optical windows) studies has developed a method of determining the absolute values of the internal stresses in materials transparent in the optical radiation through modulation polarimetry. The identification of internal stresses in the sapphire windows and determine the cause of inconsistency of the samples with the requirements of laser systems are enabled in this method. The determination of the absolute values of internal mechanical stresses in sapphire optical windows through the use of modulation polarimetry experimental method is developed. The distribution in two-dimensional space of internal stresses in polished sapphire samples and their absolute values are established.При выращивании слитков монокристаллического сапфира в нем возникают дефекты в виде микропузырьков, границ блоков и обусловленные ими механические напряжения, которые существенно влияют на функциональные свойства кристалла. Проблему контроля качества сапфировых структур решают различными способами, но они не достаточно чувствительны для нужд современной оптики и микроэлектроники, или сложны в использовании (рентгеновские методы). Традиционный контроль внутренних механических напряжений осуществляют визуально на полярископе-поляриметре ПКС-250, в основу которого положен метод двойного лучепреломления Сенармона. Однако технические возможности этого традиционного метода не способны выполнять высокочувствительный количественный контроль образцов монокристаллов сапфира с микронапряжениями. Поэтому актуальной задачей современного приборостроения является разработка новых высокочувствительных методов технической диагностики и неразрушающего контроля качества деталей из сапфира. Авторы работы исследовали возможность использования метода модуляционной поляриметрии для решения поставленной задачи. Однако такая характеристика излучения как состояние поляризации, имеет с точки зрения дифференциальной спектроскопии существенное отличие от других способов модуляции. Она заключается, прежде всего, в том, что поляризация, как пространственная характеристика волны, выражается совокупностью значений - компонентами вектора Максвелла-Джонса или вектора Стокса. Таким образом, в отличие от модуляций других физических величин, оперирующих с единственным параметром, поляризационная модуляция (ПМ) характеризуется двухмерным влиянием на волну. Целью работы была разработка методики определения абсолютных величин внутренних механических напряжений в локальных точках сапфировых оптических окон с помощью модуляционной поляриметрии. В результате проведенных исследований полированных образцов сапфира (типа оптических окон) была разработана методика определения абсолютных значений внутренних механических напряжений в материалах, прозрачных в оптическом диапазоне излучения на основе модуляционной поляриметрии. Разработанная методика позволила выявить внутренние механические напряжения в сапфировых окнах и определить причину несоответствия исследованных образцов требованиям лазерных систем. Разработана методика экспериментального определения величины абсолютных значений внутренних механических напряжений в сапфировых оптических окнах за счет использования модуляционной поляриметрии. Установлено распределение в двухмерном пространстве внутренних напряжений в полированных образцах сапфира и их абсолютные значения

The subpopulation of microglia sensitive to neurotransmitters/neurohormones is modulated by stimulation with LPS, interferon-γ, and IL-4

Recently, neurotransmitters/neurohormones have been identified as factors controlling the function of microglia, the immune competent cells of the central nervous system. In this study, we compared the responsiveness of microglia to neurotransmitters/neurohormones. We freshly isolated microglia from healthy adult C57Bl/6 mice and found that only a small fraction (1-20%) responded to the application of endothelin, histamine, substance P, serotonin, galanin, somatostatin, angiotensin II, vasopressin, neurotensin, dopamine, or nicotine. In cultured microglia from neonatal and adult mice, a similarly small population of cells responded to these neurotransmitters/neurohormones. To induce a proinflammatory phenotype, we applied lipopolysaccaride (LPS) or interferon-gamma (IFN-{gamma}) to the cultures for 24 h. Several of the responding populations increased; however, there was no uniform pattern when comparing adult with neonatal microglia or LPS with IFN-{gamma} treatment. IL-4 as an anti-inflammatory substance increased the histamine-, substance P-, and somatostatin-sensitive populations only in microglia from adult, but not in neonatal cells. We also found that the expression of different receptors was not strongly correlated, indicating that there are many different populations of microglia with a distinct set of receptors. Our results demonstrate that microglial cells are a heterogeneous population with respect to their sensitivity to neurotransmitters/neurohormones and that they are more responsive in defined activation states

Mitochondrial exchanger NCLX plays a major role in the intracellular Ca(2+) signaling, gliotransmission, and proliferation of astrocytes

Mitochondria not only provide cells with energy, but are central to Ca(2+) signaling. Powered by the mitochondrial membrane potential, Ca(2+) enters the mitochondria and is released into the cytosol through a mitochondrial Na(+)/Ca(2+) exchanger. We established that NCLX, a newly discovered mitochondrial Na(+)/Ca(2+) exchanger, is expressed in astrocytes isolated from mice of either sex. Immunoblot analysis of organellar fractions showed that the location of NCLX is confined to mitochondria. Using pericam-based mitochondrial Ca(2+) imaging and NCLX inhibition either by siRNA or by the pharmacological blocker CGP37157, we demonstrated that NCLX is responsible for mitochondrial Ca(2+) extrusion. Suppression of NCLX function altered cytosolic Ca(2+) dynamics in astrocytes and this was mediated by a strong effect of NCLX activity on Ca(2+) influx via store-operated entry. Furthermore, Ca(2+) influx through the store-operated Ca(2+) entry triggered strong, whereas ER Ca(2+) release triggered only modest mitochondrial Ca(2+) transients, indicating that the functional cross talk between the plasma membrane and mitochondrial domains is particularly strong in astrocytes. Finally, silencing of NCLX expression significantly reduced Ca(2+)-dependent processes in astrocytes (i.e., exocytotic glutamate release, in vitro wound closure, and proliferation), whereas Ca(2+) wave propagation was not affected. Therefore, NCLX, by meditating astrocytic mitochondrial Na(+)/Ca(2+) exchange, links between mitochondria and plasma membrane Ca(2+) signaling, thereby modulating cytoplasmic Ca(2+) transients required to control a diverse array of astrocyte functions

Spontaneous Ca(2+) transients in mouse microglia

Microglia are the resident immune cells in the central nervous system and many of their physiological functions are known to be linked to intracellular calcium (Ca2+) signaling. Here we show that isolated and purified mouse microglia-either freshly or cultured-display spontaneous and transient Ca2+ elevations lasting for around ten to twenty seconds and occurring at frequencies of around five to ten events per hour and cell. The events were absent after depletion of internal Ca2+ stores, by phospholipase C (PLC) inhibition or blockade of inositol-1,4,5-trisphosphate receptors (IP3Rs), but not by removal of extracellular Ca2+, indicating that Ca2+ is released from endoplasmic reticulum intracellular stores. We furthermore provide evidence that autocrine ATP release and subsequent activation of purinergic P2Y receptors is not the trigger for these events. Spontaneous Ca2+ transients did also occur after stimulation with Lipopolysaccharide (LPS) and in glioma-associated microglia, but their kinetics differed from control conditions. We hypothesize that spontaneous Ca2+ transients reflect aspects of cellular homeostasis that are linked to regular and patho-physiological functions of microglia

Employing an open-source tool to assess astrocyte tridimensional structure

Astrocytes display important features that allow them to maintain a close dialog with neurons, ultimately impacting brain function. The complex morphological structure of astrocytes is crucial to the role of astrocytes in brain networks. Therefore, assessing morphologic features of astrocytes will help provide insights into their physiological relevance in healthy and pathological conditions. Currently available tools that allow the tridimensional reconstruction of astrocytes present a number of disadvantages, including the need for advanced computational skills and powerful hardware, and are either time-consuming or costly. In this study, we optimized and validated the FIJI-ImageJ, Simple Neurite Tracer (SNT) plugin, an open-source software that aids in the reconstruction of GFAP-stained structure of astrocytes. We describe (1) the loading of confocal microscopy Z-stacks, (2) the selection criteria, (3) the reconstruction process, and (4) the post-reconstruction analysis of morphological features (process length, number, thickness, and arbor complexity). SNT allows the quantification of astrocyte morphometric parameters in a simple, efficient, and semi-automated manner. While SNT is simple to learn, and does not require advanced computational skills, it provides reproducible results, in different brain regions or pathophysiological states.The authors acknowledge funding from national funds through the FCT—Foundation for Science and Technology—project (PTDC/SAU-NSC/118194/2010) to G.T., V.M.S., S.G.G. and J.F.O., and fellowships (SFRH/BD/89714/2012 to V.M.S., SFRH/BPD/97281/2013 to J.F.O., SFRH/BD/101298/2014 to S.G.G., PD/BD/114120/2015 to S.P.N, and PD/BD/127822/2016 to G.T.); Marie Curie Fellowship FP7-PEOPLE-2010-IEF 273936 and BIAL Foundation Grants and 207/14 to J.F.O.; QREN and FEDER funds through Operational program for competitiveness factors—COMPETE, “ON.2 SR&TD Integrated Program—NORTE-07-0124-FEDER-000021”; National and European funds through FCT, and FEDER through COMPETE (PEst-C/SAU/LA0026/2011 and FCOMP-01-0124-FEDER-022724; PEst-C/SAU/LA0026/2013 and FCOMP-01-0124-FEDER-037298, respectively)info:eu-repo/semantics/publishedVersio