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31.
We consider the tachyon-brane inflationary universe model in the context of a polytropic gas equation of state. In slow-roll approximation, we discuss general conditions of this model. For exponential potential, in high-energy limit the characteristics of the model are presented. By using the seven-year Wilkinson Microwave Anisotropy Probe (WMAP7) observational data, we constrain the cosmological parameters of the model. 相似文献
32.
Distinguishing and quantification of the human visual pathways using high-spatial-resolution diffusion tensor tractography 总被引:1,自引:0,他引:1
Arash Kamali Khader M. Hasan Pavani Adapa Azadeh Razmandi Zafer Keser John Lincoln Larry A. Kramer 《Magnetic resonance imaging》2014
Quantification of the living human visual system using MRI methods has been challenging, but several applications demand a reliable and time-efficient data acquisition protocol. In this study, we demonstrate the utility of high-spatial-resolution diffusion tensor fiber tractography (DTT) in reconstructing and quantifying the human visual pathways. Five healthy males, age range 24–37 years, were studied after approval of the institutional review board (IRB) at The University of Texas Health Science Center at Houston. We acquired diffusion tensor imaging (DTI) data with 1-mm slice thickness on a 3.0-Tesla clinical MRI scanner and analyzed the data using DTT with the fiber assignment by continuous tractography (FACT) algorithm. By utilizing the high-spatial-resolution DTI protocol with FACT algorithm, we were able to reconstruct and quantify bilateral optic pathways including the optic chiasm, optic tract, optic radiations free of contamination from neighboring white matter tracts. 相似文献
33.
We investigate some aspects of black hole (BH) thermodynamics in the framework of a modified dispersion relation. We calculate a minimal length and a maximal momentum to find a relation between spacetime dimensions and the presence of logarithmic prefactor in the black hole entropy relation. We show that the logarithmic prefactor appears not only in an even number of dimensions but also in an odd number of dimensions. In addition, the sign of the logarithmic factor is different for positive values of α in all dimensions. Using the corrected entropy, the black hole radiation probability is calculated in the tunneling formalism, which is corrected up to the same order of the Planck length and shows a more probable quantum tunneling. 相似文献
34.
Nitrosylation of Nitric‐Oxide‐Sensing Regulatory Proteins Containing [4Fe‐4S] Clusters Gives Rise to Multiple Iron–Nitrosyl Complexes
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Pauline N. Serrano Dr. Hongxin Wang Dr. Jason C. Crack Christopher Prior Prof. Matthew I. Hutchings Prof. Andrew J. Thomson Dr. Saeed Kamali Dr. Yoshitaka Yoda Dr. Jiyong Zhao Dr. Michael Y. Hu Dr. Ercan E. Alp Dr. Vasily S. Oganesyan Prof. Nick E. Le Brun Prof. Stephen P. Cramer 《Angewandte Chemie (International ed. in English)》2016,55(47):14575-14579
The reaction of protein‐bound iron–sulfur (Fe‐S) clusters with nitric oxide (NO) plays key roles in NO‐mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe‐S clusters has been hampered by a lack of information about the nature of the iron‐nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe‐4S] cluster to sense NO. This work reveals that nitrosylation yields multiple products structurally related to Roussin's Red Ester (RRE, [Fe2(NO)4(Cys)2]) and Roussin's Black Salt (RBS, [Fe4(NO)7S3]. In the latter case, the absence of 32S/34S shifts in the Fe?S region of the NRVS spectra suggest that a new species, Roussin's Black Ester (RBE), may be formed, in which one or more of the sulfide ligands is replaced by Cys thiolates. 相似文献
35.
S. L. Chin H. L. Xu Q. Luo F. Théberge W. Liu J. F. Daigle Y. Kamali P. T. Simard J. Bernhardt S. A. Hosseini M. Sharifi G. Méjean A. Azarm C. Marceau O. Kosareva V. P. Kandidov N. Ak?zbek A. Becker G. Roy P. Mathieu J. R. Simard M. Chateauneuf J. Dubois 《Applied physics. B, Lasers and optics》2009,95(1):1-12
All matters in the path of filaments induced by an intense femtosecond laser pulse propagating in air could be fragmented
and result in the emission of characteristic fluorescence spectra from the excited fragments. The fluorescence spectra exhibit
specific signatures (fingerprints) that can be used for the identification of various substances including chemical and biological
species. In this paper, we present an overview of the recent progress in our laboratory concerning the “remote” sensing of
chemical and biological agents/pollutants in air using filamentation-induced nonlinear fluorescence techniques. 相似文献
36.
J.-F. Daigle O. Kosareva N. Panov M. Bégin F. Lessard C. Marceau Y. Kamali G. Roy V. P. Kandidov S. L. Chin 《Applied physics. B, Lasers and optics》2009,94(2):249-257
A simple method to produce longer filaments with higher ionization density in air by controlling the diameter of an aperture
in the laser beam path is studied via an analysis of the backscattered N2 fluorescence collected by LIDAR. Significant increase in the fluorescence signal (approximately by a factor of five depending
on the conditions) and an increased filament length was observed at an optimum diameter. 3D + time stochastic numerical simulations
have shown that the optimum aperture size corresponds to the case of multiple filament ‘squeezing’ around the propagation
axis forming the regularized elongated structure with higher overall amount of plasma. The optimum range of aperture sizes
is the same for the initial transverse perturbation scale variation at least within a factor of three. 相似文献
37.
Kinetic studies of the oxidative coupling of methane over the Mn/Na2WO4/SiO2 catalyst 总被引:1,自引:0,他引:1
Oxidative coupling of methane is a direct way to obtain C2 hydrocarbon,and Mn-Na-W/SiO2 catalyst is the most promising among all the catalysts.The 2%Mn/5%Na2WO4/SiO2 catalyst was prepared by the incipient wetness impregnation method.A 7-step heterogeneous reaction model of the oxidative coupling of methane to C2 hydrocarbons was conducted by co-feeding methane and oxygen at a total pressure of 1 bar over the catalyst.The kinetic measurements were carried out in a micro-catalytic fixed bed reactor.The kinetic data were obtained at the appropriate range of reaction conditions (4 kPa<Po2 <20 kPa,20 kPa<PCZH4 <80 kPa,800℃<T<900℃).The proposed reaction kinetic scheme consists of three primary and four consecutive reaction steps.The conversions of hydrocarbons and carbon oxides were evaluated by applying Langrnuir-Hinshelwood type rate equations.Power-law rate equation was applied only for the water-gas shift reaction.In addition,the effects of operating conditions on the reaction rate were studied.The proposed kinetic model can predict the conversion of methane and oxygen as well as the yield of C2 hydrocarbons and carbon oxides with an average accuracy of ±15%. 相似文献
38.
The reaction of dithiocarbamate salts ( IV a − c ) with bis(naphthalene chloroacetates) ( II a,b ) and bis(naphthalene ethoxybromide) ( II c ) in dimethylformamide (DMF) furnished corresponding podands as V a − i in high to excellent yields. Three reacting ligands, ( II a,b ) and ( II c ), were obtained in the reaction of bis(naphthalene) ( I a,b ) with chloroacetylchloride and 1,2‐dibromoethane. Dynamic NMR spectroscopic data of three series of podands ( V a − c , V d−f , and V g − i ) are discussed, and their free energy of activation (Δ GC≠) at coalescence temperatures are figured out. The Δ GC≠ s of these podands were attributed to conformational isomerization in the range of 14.5–18.3 kcal mol−1 due to rotation and resonance effects about thioamide C N bond. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:659–668, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20730 相似文献
39.
Sergei Gukov Amer Iqbal Can Koz?az Cumrun Vafa 《Communications in Mathematical Physics》2010,298(3):757-785
We establish a direct map between refined topological vertex and sl(N) homological invariants of the of Hopf link, which include Khovanov-Rozansky homology as a special case. This relation provides
an exact answer for homological invariants of the Hopf link, whose components are colored by arbitrary representations of
sl(N). At present, the mathematical formulation of such homological invariants is available only for the fundamental representation
(the Khovanov-Rozansky theory) and the relation with the refined topological vertex should be useful for categorizing quantum
group invariants associated with other representations (R
1, R
2). Our result is a first direct verification of a series of conjectures which identifies link homologies with the Hilbert
space of BPS states in the presence of branes, where the physical interpretation of gradings is in terms of charges of the
branes ending on Lagrangian branes. 相似文献
40.
This paper presents an output-feedback adaptive controller for a class of linear systems with unknown time-varying state delay
and in the presence of actuator failures. We consider a common type of actuator failure in which some unknown system inputs
may be stuck at some unknown fixed values and at unknown time instants. The adaptive controller is designed based on SPR–Lyapunov
approach for relative degree one and two cases. Closed-loop system stability and asymptotic output tracking are proved using
suitable Lyapunov–Krasovskii functional for each case. Simulation results are provided to demonstrate the effectiveness of
the proposed results. 相似文献