检索结果-南通市图书馆

Two loop low temperature corrections to electron self energy

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics C 2011年第7期35卷 608-611页

作者： Mahnaz Q. Haseeb samina s. masood Department of Physics COMSATS Institute of Information Technology Islamabad Pakistan Department of Physics University of Houston Clear Lake Houston TX 77058

We recalculate the two loop corrections in the background heat bath using real time formalism. The procedure of the integrations of loop momenta with dependence on finite temperature before the momenta without it has been followed. We determine the mass and wavefunction renormalization constants in the low temperature limit of QED, for the first time with this preferred order of integrations. The correction to electron mass and spinors in this limit is important in the early universe at the time of primordial nucleosynthesis as well as in astrophysics.

关键词： renormalization finite temperature field theory electron self energy two-loop corrections

Magnetic Dipole Moment of Neutrino

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of High Energy Physics, Gravitation and Cosmology 2015年第1期1卷 1-13页

作者： samina s. masood Department of Physics University of Houston Clear Lake Houston USA

We recalculate the magnetic moment of neutrinos in a hot and dense medium. The magnetic dipole moment of neutrinos is modified at high temperature and chemical potential. We show that the magnetic dipole moment of electron neutrino does not get a significant contribution from thermal background to meet the cosmological bound. However, chemical potential contribution to the magnetic moment is non-ignorable even when chemical potential is an order of magnitude greater than the electron mass. It is demonstrated that this effect is more significant in the models with an extended Higgs sector through neutrino mixing.

关键词： Neutrino Magnetic Moment Hot and Dense Medium

Nucleosynthesis in Hot and Dense Media

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Physics 2014年第5期5卷 296-308页

作者： samina s. masood Department of Physics University of Houston Clear Lake Houston USA

We study the finite temperature and density effects on beta decay rates to compute their contributions to nucleosynthesis. QED type corrections to beta decay from the hot and dense background are estimated in terms of the statistical corrections to the self-mass of an electron. For this purpose, we re-examine the hot and dense background contributions to the electron mass and compute its effect to the beta decay rate, helium yield, energy density of the universe as well as the change in neutrino temperature from the first order contribution to the self-mass of electrons during these processes. We explicitly show that the thermal contribution to the helium abundance at T = m of a cooling universe (0.045 percent) is higher than the corresponding contribution to helium abundance of a heating universe (0.031 percent) due to the existence of hot fermions before the beginning of nucleosynthesis and their absence after the nucleosynthesis, in the early universe. Thermal contribution to helium abundance was a simple quadratic function of temperature, before and after the nucleosynthesis. However, this quadratic behavior was not the same before the decoupling temperature due to weak interactions;so the nucleosynthesis did not even start before the universe had cooled down to the neutrino decoupling temperatures and QED became a dominant theory in the presence of a high concentration of charged fermions. It is also explicitly shown that the chemical potential in the core of supermassive and superdense stars affect beta decay and their helium abundance but the background contributions depend on the ratio between temperature and chemical potential and not the chemical potential or temperature only. We calculate the hot and dense background contributions for m = T = μ. It has been noticed that temperature plays a role in regulating parameter in an extremely dense systems. Therefore, for extremely dense systems, temperature has to be large enough to get the expected value of heli

关键词： Nucleosynthesis Beta Decay Compact stars Hot and Dense Media

首要诊断为高血压的患者急诊就诊结局的人群研究分析

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中华高血压杂志 2016年第12期24卷 1185-1186页

作者： masood s Austin P C Atzema C L 曲浥晨机构不详

尽管已有大量针对非急诊、门诊高血压的远期预后及治疗方案的研究,但对急诊高血压,尤其是无明显靶器官损害的急诊高血压的相关研究却很少,缺乏高血压急诊患者短期及长期预后的研究。一份发表于1967年的研究是少数对急诊高血压患者短、... 详细信息

尽管已有大量针对非急诊、门诊高血压的远期预后及治疗方案的研究,但对急诊高血压,尤其是无明显靶器官损害的急诊高血压的相关研究却很少,缺乏高血压急诊患者短期及长期预后的研究。一份发表于1967年的研究是少数对急诊高血压患者短、长期预后进行调查的研究之一,结果显示：在143例舒张压显著升高[115~129 mm Hg（1mm Hg=0.133kPa）]并随机分配至降压治疗组或安慰剂组的男性患者中，安慰剂组有21例患者出现高血压并发症或死亡，而降压治疗组则均未发现上述情况。

关键词：急诊科靶器官损害急性心肌梗死住院率自测血压就诊量就诊率血压测量安大略省肾脏衰竭

Preparation of Nanoporous Carbonaceous Promoters for Enhanced CO2 Absorption in Tertiary Amines

在线全文

学校读者我要写书评

暂无评论

Engineering 2020年第12期6卷 1381-1394页

作者： masood s.Alivand Omid Mazaheri Yue Wu Geoffrey W.stevens Colin A.scholes Kathryn A.Mumford Department of Chemical Engineering The University of MelbourneParkvilleVIC 3010Australia Peter Cook Centre for CCs Research The University of MelbourneParkvilleVIC 3010Australia school of Agriculture and Food Faculty of Veterinary and Agricultural SciencesThe University of MelbourneParkvilleVIC 3010Australia

Aqueous solutions of tertiary amines are promising absorbents for CO2 capture,as they are typically characterized by a high absorption capacity,low heat of reaction,and low ***,tertiary amines also exhibit very low kinetics of CO2 absorption,which has made them unattractive options for large-scale ***,a series of novel nanoporous carbonaceous promoters(NCPs)with different properties were synthesized,characterized,and used as rate promoters for CO2 absorption in aqueous N,N-diethylethanolamine(DEEA)*** prepare a DEEA–NCP nanofluid,NCPs were dispersed into aqueous 3 mol∙L1 DEEA solution using *** results revealed that among microporous(GC)and mesoporous(Gs)carbonaceous structures functionalized with ethylenediamine(EDA)and polyethyleneimine(PEI)molecules,the GC–EDA promoter exhibited the best performance.A comparison between DEEA–GC–EDA nanofluid and typical aqueous DEEA solutions highlighted that the GC-EDA promoter enhances the rate of CO2 absorption at 40C by 38.6%(36.8–50.7 kPamin1)and improves the equilibrium CO2 absorption capacity(15 kPa;40C)by 13.2%(0.69–0.78 mol of CO2 per mole of DEEA).Moreover,the recyclability of DEEA–GC–EDA nanofluid was determined and a promotion mechanism is *** outcomes demonstrate that NCP–GC–EDA in tertiary amines is a promising strategy to enhance the rate of CO2 absorption and facilitate their large-scale deployment.

关键词： CO2 absorption Nanofluid N,N-diethylethanolamine Nanoporous carbonaceous promoters Polyamine functionalization

stokes' First Problem for an MHD Burgers Fluid

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2013年第1期59卷 99-104页

作者： masood Khan Department of Mathematics Quaid-i-Azam University

This work is related to the flow of a magnetohydrodynamic Burgers *** flow of an incompressible conducting Burgers fluid in the presence of a uniform transverse magnetic field over a plate that is moved suddenly is *** the application of the Laplace and Fourier sine transforms techniques,the exact analytical expressions for the velocity field and associated shear stress are determined in simple *** are written as a sum of steady-state and transient *** graphical results are plotted for different values of indispensable parameters and some interesting results are *** corresponding solutions for the hydrodynamic Burgers fluid appear as the limiting cases of the obtained solutions.

关键词： stokes' first problem Burgers fluid Laplace and Fourier sine transforms exact solutions

MHD Flow of an Oldroyd-B Fluid through a Porous space Induced by sawtooth Pulses

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2011年第8期28卷 161-164页

作者： masood Khan Zeeshan Department of Mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan

We investigate the unsteady magnetohydrodynamic(MHD)flow of an Oldroyd-B fluid through a porous space induced by sawtooth *** fluid is assumed to be electrically conducting in the presence of a transverse uniform magnetic *** porous space is taken into account using modified Darcy's law for the Oldroyd-B *** solutions of the governing problem are obtained by using the Laplace transform *** effects of the magnetic parameter,the permeability of the porous space and the elasticity parameter of the fluid are studied on the flow characteristics.

关键词： method field porous

Influence of Cu doping in Magnesium Hydroxide Nanoparticles for Bandgap Engineering

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials science) 2023年第3期38卷 485-489页

作者： sYED masood Raza s NAsEEM shah ADEEL Tahir YAsMEEN Bibi Department of Physics Federal Urdu University of ArtsScience&TechnologyKarachiPakistan Department of Chemistry Federal Urdu University of ArtsScience&TechnologyKarachiPakistan

Cu doped Mg(OH)_(2) nanoparticles were synthesized with varying concentrations from 0 to 10%by a chemical synthesis technique of coprecipitation.X-rays diffraction (XRD) of the samples confirms that all the samples acquire the hexagonal crystal *** results indicated the solubility limit of dopant in the host material and the secondary phase of CuO was observed beyond 3%Cu doping in Mg(OH)_(2).The reduction in the size of nanoparticles was observed from 166 to 103 nm for Mg(OH)_(2) and 10% Cu doped Mg(OH)_(2)samples,*** shift in absorption spectra exhibited the systematical enhancement in optical bandgap from 5.25 to 6.085 eV.A good correlation was observed between the bandgap energy and crystallite size of the nanocrystals which confirmed the size induced effect in the *** transformation in the sample morphology was observed from irregular spherical particles to sepals like shapes with increasing the Cu concentration in the host *** energy dispersive X-Ray (EDX) analysis confirmed the purity of mass percentage composition of the elements present in the samples.

关键词： Cu doped Mg(OH)_(2) nanoparticles phase purity optical band gap morphologies

EXACT sOLUTIONs FOR MAGNETOHYDRODYNAMIC FLOW IN A ROTATING FLUID

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica sinica 2002年第3期18卷 244-251页

作者： s. Asghar masood Khan A.M. siddiqui T. Hayat Department of Mathematics Quaid-i-Azam University Islamabad Pakistan Department of Mathematics Pennsylvania State University York Campus 1031 Edgecomb Avenue New York PA 17403 USA

An analytical solution is obtained for the flow due to solid-body rotations an oscillating porous disk and of a fluid at infinity. Neglecting the induced magnetic field, the effects of the transversely applied magnetic field on the flow are studied. Further, the flow confined between two disks is also discussed. It is found that an infinite number of solutions exist for the flow confined between two disks.

关键词： rotating fluid porous disk double disks magnetohydrodynamic flow