28,035 research outputs found
Quantum Wire-on-Well (WoW) Cell With Long Carrier Lifetime for Efficient Carrier Transport
A quantum wire-on-well (WoW) structure, taking advantage of the layer undulation of an In- GaAs/GaAs/GaAsP superlattice grown on a vicinal substrate, was demonstrated to enhance the carrier collection from the confinement levels and extend the carrier lifetime (220 ns) by approximately 4 times as compared with a planar reference superlattice. Strained InGaAs/GaAs/GaAsP superlattices were grown on GaAs substrates under exactly the same condition except for the substrate misorientation (0o- and 6o- off). The growth on a 6o-off substrate induced significant layer undulation as a result of step bunching and non-uniform precursor incorporation between steps and terraces whereas the growth on a substrate without miscut resulted in planar layers. The undulation was the most significant for InGaAs layers, forming periodically aligned InGaAs nanowires on planar wells, a wire-on-well structure. As for the photocurrent corresponding to the sub-bandgap range of GaAs, the light absorption by the WoW was extended to longer wavelengths and weakened as compared with the planar superlattice, and almost the same photocurrent was obtained for both the WoW and the planar superlattice. Open-circuit voltage for the WoW was not affected by the longer-wavelength absorption edge and the same value was obtained for the two structures. Furthermore, the superior carrier collection in the WoW, especially under forward biases, improved fill factor compared with the planer superlattice
Comparison of the extended linear sigma model and chiral perturbation theory
The pion-nucleon scattering amplitudes are calculated in tree approximation
with the use of the extended linear sigma model (ELSM) as well as heavy baryon
chiral perturbation theory (HBPT), and the non-relativistic forms of the
ELSM results are compared with those of HBPT. We find that the amplitudes
obtained in ELSM do not agree with those derived from the more fundamental
effective approach, HBPT.Comment: 7 page
Reduction of Dilute Ising Spin Glasses
The recently proposed reduction method for diluted spin glasses is
investigated in depth. In particular, the Edwards-Anderson model with \pm J and
Gaussian bond disorder on hyper-cubic lattices in d=2, 3, and 4 is studied for
a range of bond dilutions. The results demonstrate the effectiveness of using
bond dilution to elucidate low-temperature properties of Ising spin glasses,
and provide a starting point to enhance the methods used in reduction. Based on
that, a greedy heuristic call ``Dominant Bond Reduction'' is introduced and
explored.Comment: 10 pages, revtex, final version, find related material at
http://www.physics.emory.edu/faculty/boettcher
Synthesis of SmFeAsO by an Easy and Versatile Route and its Physical Property Characterization
We report synthesis, structure, electrical transport and heat capacity of
SmFeAsO. The title compound is synthesized by one-step encapsulation of
stoichiometric FeAs, Sm, and Sm2O3 in an evacuated (10-5 Torr) quartz tube by
prolong (72 hours) annealing at 1100oC. The as synthesized compound is
crystallized in tetragonal structure with P4/nmm space group having lattice
parameters a = 3.93726(33) A and c = 8.49802(07) A. The resistance (R-T)
measurements on the compound exhibited ground state spin-density-wave
(SDW)-like metallic steps below 140 K. Heat capacity CP(T) measurements on the
title compound, showed an anomaly at around 140 K, which is reminiscent of the
SDW ordering of the compound. At lower temperatures the CP(T) shows a clear
peak at around 4.5 K. At lower temperature below 20 K, Cp(T) is also measured
under an applied field of 7 Tesla. It is concluded that the CP(T) peak at 4.5 K
is due to the anti-ferromagnetic(AFM) ordering of Sm3+ spins. These results are
in confirmation with ordering of Sm in Sm2-xCexCuO4.Comment: 9 pages Text + Figs Contact Author ([email protected]
Using Flow Cytometry to Analyze Cryptococcus Infection of Macrophages.
Flow cytometry is a powerful analytical technique, which is increasingly being used to study the interaction between host cells and intracellular pathogens. Flow cytometry is capable of measuring a greater number of infected cells within a sample compared to alternative techniques such as fluorescence microscopy. This means that robust quantification of rare events during infection is possible. Our lab and others have developed flow cytometry methods to study interactions between host cells and intracellular pathogens, such as Cryptococcus neoformans, to quantify phagocytosis, intracellular replication, and non-lytic expulsion or "vomocytosis" from the phagosome. Herein we describe these methods and how they can be applied to the study of C. neoformans as well as other similar intracellular pathogens
Using Flow Cytometry to Analyze Cryptococcus Infection of Macrophages.
Flow cytometry is a powerful analytical technique, which is increasingly being used to study the interaction between host cells and intracellular pathogens. Flow cytometry is capable of measuring a greater number of infected cells within a sample compared to alternative techniques such as fluorescence microscopy. This means that robust quantification of rare events during infection is possible. Our lab and others have developed flow cytometry methods to study interactions between host cells and intracellular pathogens, such as Cryptococcus neoformans, to quantify phagocytosis, intracellular replication, and non-lytic expulsion or "vomocytosis" from the phagosome. Herein we describe these methods and how they can be applied to the study of C. neoformans as well as other similar intracellular pathogens
Diffusive energy transport in the S=1 Haldane chain compound AgVP2S6
We present the results of measurements of the thermal conductivity
of the spin S=1 chain compound AgVP_2S_6 in the temperature range between 2 and
300 K and with the heat flow directed either along or perpendicular to the
chain direction. The analysis of the anisotropy of the heat transport allowed
for the identification of a small but non-negligible magnon contribution
along the chains, superimposed on the dominant phonon contribution
. At temperatures above about 100 K the energy diffusion constant
D_E(T), calculated from the data, exhibits similar features as
the spin diffusion constant D_S(T), previously measured by NMR. In this regime,
the behaviour of both transport parameters is consistent with a diffusion
process that is caused by interactions inherent to one-dimensional S=1 spin
systems.Comment: 6 pages, 4 figure
New Luttinger liquid physics from photoemission on LiMoO
Temperature dependent high resolution photoemission spectra of quasi-1
dimensional LiMoO evince a strong renormalization of its
Luttinger liquid density-of-states anomalous exponent. We trace this new effect
to interacting charge neutral critical modes that emerge naturally from the
two-band nature of the material. LiMoO is shown thereby to
be a paradigm material that is capable of revealing new Luttinger physics.Comment: 4 pages, 3 figures. Accepted for publication by Phys. Rev. Let
Relaxational behavior of the infinite-range Ising spin-glass in a transverse field
We study the zero-temperature behavior of the infinite-ranged Ising spin
glass in a transverse field. Using spin summation techniques and Monte Carlo
methods we characterize the zero-temperature quantum transition. Our results
are well compatible with a value for the correlation length
exponent, for the dynamical exponent and an algebraic decay for
the imaginary-time correlation function. The zero-temperature relaxation of the
energy in the presence of the transverse field shows that the system
monotonically reaches the ground state energy due to tunneling processes and
displays strong glassy effects.Comment: 15 pages + 5 Figures, Revte
Tau Polarization in Tau-Neutrino Nucleon Scattering
We investigate the spin polarization of \tau^{\pm} leptons produced in
\nu_{\tau} and \bar{\nu}_{\tau} nucleon scattering via charged currents.
Quasi-elastic scattering, \Delta resonance production and deep inelastic
scattering processes are studied. The polarization information is essential for
measuring the \tau^{\pm} appearance rate in long baseline neutrino oscillation
experiments, because the decay particle distributions depend crucially on the
\tau^{\pm} spin. In this article, we calculate the spin density matrix of each
process and estimate the spin polarization vector in medium and high neutrino
energy interactions. We find that the produced \tau^{\pm}'s have high degree of
polarization, and their spin direction depends non-trivially on the energy and
the scattering angle of \tau^{\pm} in the laboratory frame.Comment: 23 pages, 35 figures; compile errors corrected; notation errors in
Eq.(30) and (31) corrected, typo error in Eq.(40) corrected, references and
comments in footnote adde
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