956 research outputs found
Strains and pseudo-magnetic fields in circular graphene rings
We demonstrate that circular graphene ring under a shear stress displays
strong pseudo-magnetic fields. We calculate the pseudo-magnetic field both from
continuum elasticity theory as well as molecular dynamics simulations. Stable
wrinkles are induced by shear deformations and lead to enhancement of the
pseudo-magnetic field. The strong pseudo-magnetic field found here can be
observed by imaging graphene flake at the atomic level e.g. through scanning
tunneling microscope.Comment: 11 pages, 8 figures. (Appendixes A and B are added) To appear in
Phys. Rev.
The effect of sublattice symmetry breaking on the electronic properties of a doped graphene
Motivated by a number of recent experimental studies, we have carried out the
microscopic calculation of the quasiparticle self-energy and spectral function
in a doped graphene when a symmetry breaking of the sublattices is occurred.
Our systematic study is based on the many-body GW approach that is
established on the random phase approximation and on graphene's massive Dirac
equation continuum model. We report extensive calculations of both the real and
imaginary parts of the quasiparticle self-energy in the presence of a gap
opening. We also present results for spectral function, renormalized Fermi
velocity and band gap renormalization of massive Dirac Fermions over a broad
range of electron densities. We further show that the mass generating in
graphene washes out the plasmaron peak in spectral weight.Comment: 22 Pages, 10 Figure
Many-body effective mass enhancement in a two-dimensional electron liquid
Motivated by a large number of recent magnetotransport studies we have
revisited the problem of the microscopic calculation of the quasiparticle
effective mass in a paramagnetic two-dimensional (2D) electron liquid (EL). Our
systematic study is based on a generalized approximation which makes use
of the many-body local fields and takes advantage of the results of the most
recent QMC calculations of the static charge- and spin-response of the 2D EL.
We report extensive calculations for the many-body effective mass enhancement
over a broad range of electron densities. In this respect we critically examine
the relative merits of the on-shell approximation, commonly used in
weak-coupling situations, {\it versus} the actual self-consistent solution of
the Dyson equation. We show that already for and higher, a
solution of the Dyson equation proves here necessary in order to obtain a well
behaved effective mass. Finally we also show that our theoretical results for a
quasi-2D EL, free of any adjustable fitting parameters, are in good qualitative
agreement with some recent measurements in a GaAs/AlGaAs heterostructure.Comment: 12 pages, 3 figures, CMT28 Conference Proceedings, work related to
cond-mat/041226
Ground-state properties of gapped graphene using the random phase approximation
We study the effect of band gap on the ground-state properties of Dirac
electrons in a doped graphene within the random phase approximation at zero
temperature. Band gap dependence of the exchange, correlation and ground-state
energies and the compressibility are calculated. We additionally show that the
conductance in the gapped graphene is smaller than gapless one. We also
calculate the band gap dependence of charge compressibility and it decreases
with increasing the band gap values.Comment: 11 pages, Final version. To appear in Phys. Rev.
The study of the rate of convergence in the stock exchange market of the persian gulf countries
Stock exchange is one of the main pillars and principles of the country’s economy and paying attention to this organization not only flourishes and promotes it, but also causes the growth and development of the national economy. For this reason, the factors that affect this organization should be analyzed to develop it through the obtained results. Sudden shocks of the market, global financial crises and the increase of vitality of stock returns at an international level during the past years have created some concerns to managers and investors. The study of the presenceand absence of the effectiveness of global financial markets from each other can significantly help the prediction of global crises and timely performance to these crises. This study used the stock price index of the Persian Gulf countries available on formal informational databases for 5 years (2005-2010) as daily in order to study the long-term convergence between the price index of the stock exchange in the Persian Gulf countries. In this study, the relationship between the indices was examined by correlation analysis method and the stationary of series related to each country by the Augmented Dicky Fuller test and the long term convergence by Johansson cointegration method. The study results show the most of these countries have a high correlation and the relationship between these countries is significant. The results of Johansson cointegration test in the both tested methods of max-Eigenvalue proved 3 long term convergence equations and Static Traceproved 6 long term convergence equations at 0/05 significance level.Keywords: correlation, long term convergence, cointegration, price inde
The Role of Electron-electron Interactions in Graphene ARPES Spectra
We report on a theoretical study of the influence of electron-electron
interactions on ARPES spectra in graphene that is based on the
random-phase-approximation and on graphene's massless Dirac equation continuum
model. We find that level repulsion between quasiparticle and plasmaron
resonances gives rise to a gap-like feature at small k. ARPES spectra are
sensitive to the electron-electron interaction coupling strength and might enable an experimental determination of this material parameter.Comment: 5 Pages, 4 Figures, Submitte
Determination of mebudipine in human plasma by liquid chromatography�tandem mass spectrometry
In previous studies, mebudipine, a dihydropyridine calcium channel blocker, showed a considerable potential to be used in cardiovascular diseases. The aim of the current study was to develop a valid method using reversed-phase high performance liquid chromatography coupled with electrospray ionization mass spectrometry to assay mebudipine in the human plasma. Separation was achieved on a Zorbax Eclipse® C18 analytical column using a mobile phase consisted of methanol/water (90:10, v/v). The flow rate was 0.6 mL/min and carbamazepine was used as an internal standard (IS). This method involved the use of M +Na+ ions of mebudipine and IS at m/z 411 and 259, respectively with the selected ion monitoring (SIM) mode. There were no interfering peaks from endogenous components in blank plasma chromatograms. Standard curves were linear (r2>0.99) between 5 to 100 ng/mL. The mean extraction efficiency was about 84% and the limit of quantification for mebudipine was 5 ng/mL in plasma. The coefficient of variation and error at all of the intra-day and inter-day assessments were less than 11%. The results indicated that this method is a fast, accurate, sensitive, selective and reliable method for the determination of mebudipine in the human plasma. The assay method has been successfully used to estimate plasma concentration of mebudipine after the oral administration of 2.5 mg tablet in healthy adults. © 2015 by School of Pharmacy Shaheed Beheshti University of Medical Sciences and Health Services
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