26 research outputs found

    Extremal black holes in D=4 Gauss-Bonnet gravity

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    We show that four-dimensional Einstein-Maxwell-Dilaton-Gauss-Bonnet gravity admits asymptotically flat black hole solutions with a degenerate event horizon of the Reissner-Nordstr\"om type AdS2×S2AdS_2\times S^2. Such black holes exist for the dilaton coupling constant within the interval 0≤a2<acr20\leq a^2<a^2_{\rm cr}. Black holes must be endowed with an electric charge and (possibly) with magnetic charge (dyons) but they can not be purely magnetic. Purely electric solutions are constructed numerically and the critical dilaton coupling is determined acr≃0.488219703a_{\rm cr}\simeq 0.488219703. For each value of the dilaton coupling aa within this interval and for a fixed value of the Gauss--Bonnet coupling α\alpha we have a family of black holes parameterized by their electric charge. Relation between the mass, the electric charge and the dilaton charge at both ends of the allowed interval of aa is reminiscent of the BPS condition for dilaton black holes in the Einstein-Maxwell-Dilaton theory. The entropy of the DGB extremal black holes is twice the Bekenstein-Hawking entropy.Comment: New material and references added, errors corrected including higher decimals in a_cr, figures improve

    Global solutions for higher-dimensional stretched small black holes

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    Small black holes in heterotic string theory have vanishing horizon area at the supergravity level, but the horizon is stretched to the finite radius AdS2×SD−2AdS_2 \times S^{D-2} geometry once higher curvature corrections are turned on. This has been demonstrated to give good agreement with microscopic entropy counting. Previous considerations, however, were based on the classical local solutions valid only in the vicinity of the event horizon. Here we address the question of global existence of extremal black holes in the DD-dimensional Einstein-Maxwell-Dilaton theory with the Gauss-Bonnet term introducing a variable dilaton coupling aa as a parameter. We show that asymptotically flat black holes exist only in a bounded region of the dilaton couplings 0<a<acr0 < a < a_{\rm cr} where acra_{\rm cr} depends on DD. For D≥5D \geq 5 (but not for D=4D = 4) the allowed range of aa includes the heterotic string values. For a>acra > a_{\rm cr} numerical solutions meet weak naked singularities at finite radii r=rcuspr = r_{\rm cusp} (spherical cusps), where the scalar curvature diverges as ∣r−rcusp∣−1/2|r - r_{\rm cusp}|^{-1/2}. For D≥7D \geq 7 cusps are met in pairs, so that solutions can be formally extended to asymptotically flat infinity choosing a suitable integration variable. We show, however, that radial geodesics cannot be continued through the cusp singularities, so such a continuation is unphysical.Comment: 26 pages, 19 figures, minor correction

    Extremal dyonic black holes in D=4 Gauss-Bonnet gravity

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    We investigate extremal dyon black holes in the Einstein-Maxwell-dilaton (EMD) theory with higher curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. In the same theory without the Gauss-Bonnet term the extremal dyon solutions exist only for discrete values of the dilaton coupling constant aa. We show that the Gauss-Bonnet term acts as a dyon hair tonic enlarging the allowed values of aa to continuous domains in the plane (a,qm)(a, q_m) the second parameter being the magnetic charge. In the limit of the vanishing curvature coupling (a large magnetic charge) the dyon solutions obtained tend to the Reissner-Nordstr\"om solution but not to the extremal dyons of the EMD theory. Both solutions have the same values of the horizon radius as a function of charges. The entropy of new dyonic black holes interpolates between the Bekenstein-Hawking value in the limit of the large magnetic charge (equivalent to the vanishing Gauss-Bonnet coupling) and twice this value for the vanishing magnetic charge. Although an expression for the entropy can be obtained analytically using purely local near-horizon solutions, its interpretation as the black hole entropy is legitimate only once the global black hole solution is known to exist, and we obtain numerically the corresponding conditions on the parameters. Thus, a purely local analysis is insufficient to fully understand the entropy of the curvature corrected black holes. We also find dyon solutions which are not asymptotically flat, but approach the linear dilaton background at infinity. They describe magnetic black holes on the electric linear dilaton background.Comment: 19 pages, 3 figures, revtex

    Dysfunction in Ribosomal Gene Expression in the Hypothalamus and Hippocampus following Chronic Social Defeat Stress in Male Mice as Revealed by RNA-Seq

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    Chronic social defeat stress leads to the development of anxiety-and depression-like states in male mice and is accompanied by numerous molecular changes in brain. The influence of 21-day period of social stress on ribosomal gene expression in five brain regions was studied using the RNA-Seq database. Most Rps, Rpl, Mprs, and Mprl genes were upregulated in the hypothalamus and downregulated in the hippocampus, which may indicate ribosomal dysfunction following chronic social defeat stress. There were no differentially expressed ribosomal genes in the ventral tegmental area, midbrain raphe nuclei, or striatum. This approach may be used to identify a pharmacological treatment of ribosome biogenesis abnormalities in the brain of patients with &quot;ribosomopathies.&quot

    Design, Performance, and Calibration of CMS Hadron Endcap Calorimeters

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    Detailed measurements have been made with the CMS hadron calorimeter endcaps (HE) in response to beams of muons, electrons, and pions. Readout of HE with custom electronics and hybrid photodiodes (HPDs) shows no change of performance compared to readout with commercial electronics and photomultipliers. When combined with lead-tungstenate crystals, an energy resolution of 8\% is achieved with 300 GeV/c pions. A laser calibration system is used to set the timing and monitor operation of the complete electronics chain. Data taken with radioactive sources in comparison with test beam pions provides an absolute initial calibration of HE to approximately 4\% to 5\%

    Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised protons

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    Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise. © 2015

    Application of Electrophoton Capture (EPC) Analysis Based on Gas Discharge Visualization (GDV) Technique in Medicine: A Systematic Review. The J of Alternative and Complementary

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    Abstract Objectives: The objective of this study was to evaluate the scale and scope of implementing electrophoton capture (EPC) analysis based on gas discharge visualization (GDV) technique in diverse medical applications and psychophysiology; to identify the range of applications in medicine; and to show in which areas the procedure can be useful to health professionals. Design: The design of the study is a systematic review. Methods: The database included articles published in peer-reviewed journals, proceedings of the international scientific congress &apos;&apos;Science, Information, Spirit &apos;&apos; (2003-2007), articles from the International Union of Medical and Applied Bioelectrography database, and proceedings of other conferences devoted to EPC or GDV, bioelectrography, and biophotonics. Search restrictions were human subjects, English or Russian language, and publication date from 2003 to 2007. All randomized controlled studies (RCTs) and systematic research reports (SRRs) were evaluated using Scottish Intercollegiate Guidelines Network and Jadad checklists. Results: The search yielded 136 articles addressing four different fields of medical and psychophysiologic applications of EPC (GDV). Among them were 26 SRR, 19 RCT, 18 case reports or case series, and 13 cohort studies. Thirteen (13) RCTs and 19 SRRs were rated &apos;&apos;high&apos;&apos; on the two conventional checklists. Conclusions: (1) The software and equipment EPC=GDV-complex is a convenient and easy-to-use device, easily allows examining patients with various pathologies and, therefore, offers a wide range of applications

    Dysfunction in Ribosomal Gene Expression in the Hypothalamus and Hippocampus following Chronic Social Defeat Stress in Male Mice as Revealed by RNA-Seq

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    Chronic social defeat stress leads to the development of anxiety- and depression-like states in male mice and is accompanied by numerous molecular changes in brain. The influence of 21-day period of social stress on ribosomal gene expression in five brain regions was studied using the RNA-Seq database. Most Rps, Rpl, Mprs, and Mprl genes were upregulated in the hypothalamus and downregulated in the hippocampus, which may indicate ribosomal dysfunction following chronic social defeat stress. There were no differentially expressed ribosomal genes in the ventral tegmental area, midbrain raphe nuclei, or striatum. This approach may be used to identify a pharmacological treatment of ribosome biogenesis abnormalities in the brain of patients with “ribosomopathies.

    Highly Sensitive Nanomagnetic Quantification of Extracellular Vesicles by Immunochromatographic Strips: A Tool for Liquid Biopsy

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    Extracellular vesicles (EVs) are promising agents for liquid biopsy—a non-invasive approach for the diagnosis of cancer and evaluation of therapy response. However, EV potential is limited by the lack of sufficiently sensitive, time-, and cost-efficient methods for their registration. This research aimed at developing a highly sensitive and easy-to-use immunochromatographic tool based on magnetic nanoparticles for EV quantification. The tool is demonstrated by detection of EVs isolated from cell culture supernatants and various body fluids using characteristic biomarkers, CD9 and CD81, and a tumor-associated marker—epithelial cell adhesion molecules. The detection limit of 3.7 × 105 EV/µL is one to two orders better than the most sensitive traditional lateral flow system and commercial ELISA kits. The detection specificity is ensured by an isotype control line on the test strip. The tool’s advantages are due to the spatial quantification of EV-bound magnetic nanolabels within the strip volume by an original electronic technique. The inexpensive tool, promising for liquid biopsy in daily clinical routines, can be extended to other relevant biomarkers
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