83,259 research outputs found
Further Series Studies of the Spin-1/2 Heisenberg Antiferromagnet at T=0: Magnon Dispersion and Structure Factors
We have extended our previous series studies of quantum antiferromagnets at
zero temperature by computing the one-magnon dispersion curves and various
structure factors for the linear chain, square and simple cubic lattices. Many
of these results are new; others are a substantial extension of previous work.
These results are directly comparable with neutron scattering experiments and
we make such comparisons where possible.Comment: 15 pages, 12 figures, revised versio
Spin-wave excitation spectra and spectral weights in square lattice antiferromagnets
Using a recently developed method for calculating series expansions of the
excitation spectra of quantum lattice models, we obtain the spin-wave spectra
for square lattice, Heisenberg-Ising antiferromagnets. The calculated
spin-wave spectrum for the Heisenberg model is close to but noticeably
different from a uniformly renormalized classical (large-) spectrum with the
renormalization for the spin-wave velocity of approximately . The
relative weights of the single-magnon and multi-magnon contributions to neutron
scattering spectra are obtained for wavevectors throughout the Brillouin zone.Comment: Two postscript figures, 4 two-column page
The role of cultural values in understanding the challenges faced by female entrepreneurs in Nigeria
This article is (c) Emerald Group Publishing and permission has been granted for this version to appear here (http://bura.brunel.ac.uk/handle/2438/4036). Emerald does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from Emerald Group Publishing Limited.Purpose: This paper examines the challenges female entrepreneurs face in the development of their business in the context of Nigeria. In so doing, it addresses a gap in the literature on the experiences of female entrepreneurs in a non-Western context and acknowledges the contribution that women make in this area of work.
Design: It draws on survey data from 274 female entrepreneurs currently engaged in their businesses in three statesâLagos (Nigeriaâs largest city), Ogun, and Oyo within the south west of Nigeria.
Findings: Results indicate that female entrepreneurs are generally confident and resourceful and that they enjoy the challenge of entrepreneurial activity. As in the West, they experience difficulties relating to family commitments and access to finance â as well as problems gaining acceptance and accessing networks.
Originality: It is argued that cultural values specific to the situation mean that these challenges, while common to female entrepreneurs in other national contexts, âplay outâ differentially and that they are experienced with different levels of depth and âintensityâ. It is also argued that future research might uncover at a deeper level and drawing on qualitative methodology how some of the factors identified are experienced in womenâs day to day lives. The paper suggests some policy implications in the form of support for female entrepreneurs in this context
Interface driven reentrant superconductivity in HoNi-NbN-HoNi nanostructures
Superconductivity (S) and ferromagnetism (F) are probed through transport and
magnetization measurements in nanometer scale HoNi-NbN (F-S) bilayers and
HoNi-NbN-HoNi (F-S-F) trilayers. The choice of materials has been made
on the basis of their comparable ordering temperatures and strong magnetic
anisotropy in HoNi. We observe the normal state reentrant behavior in
resistance vs. temperature plots of the F-S-F structures just below the
superconducting transition in the limited range of HoNi layer thickness
d (20 nm d 80 nm) when d is fixed at 10
nm. The reentrance is quenched by increasing the out-of-plane (H)
magnetic field and transport current where as in-plane (H) field
of 1500 Oe has no effect on the reentrance. The thermally activated flux
flow characteristics of the S, F-S and F-S-F layers reveal a transition from
collective pinning to single vortex pinning as we place F layers on both sides
of the S film. The origin of the reentrant behavior seen here in the range of
0.74 T/T 0.92 is attribute to a delicate balance
between the magnetic exchange energy and the condensation energy in the
interfacial regions of the trilayer.Comment: 13 pages and 5 figure
Magnetotransport in polycrystalline LaSrMnO thin films of controlled granularity
Polycrystalline LaSrMnO (LSMO) thin films were
synthesized by pulsed laser ablation on single crystal (100) yttria-stabilized
zirconia (YSZ) substrates to investigate the mechanism of magneto-transport in
a granular manganite. Different degrees of granularity is achieved by using the
deposition temperature (T) of 700 and 800 C. Although no
significant change in magnetic order temperature (T) and saturation
magnetization is seen for these two types of films, the temperature and
magnetic field dependence of their resistivity ((T, H)) is strikingly
dissimilar. While the (T,H) of the 800 C film is comparable to that
of epitaxial samples, the lower growth temperature leads to a material which
undergoes insulator-to-metal transition at a temperature (T 170
K) much lower than T. At T T, the resistivity is characterized by
a minimum followed by ln \emph{T} divergence at still lower temperatures. The
high negative magnetoresistance ( 20) and ln \emph{T} dependence
below the minimum are explained on the basis of Kondo-type scattering from
blocked Mn-spins in the intergranular material. Further, a striking feature of
the T = 700 C film is its two orders of magnitude larger anisotropic
magnetoresistance (AMR) as compared to the AMR of epitaxial films. We attribute
it to unquenching of the orbital angular momentum of 3d electrons of Mn ions in
the intergranular region where crystal field is poorly defined.Comment: 26 pages, 7 figure
RTP control protocol (RTCP) extended report (XR) block for independent reporting of burst/fgp discard metrics
This document defines an RTP Control Protocol (RTCP) Extended Report
(XR) block that allows the reporting of burst/gap discard metrics
independently of the burst/gap loss metrics for use in a range of RTP
applications
Random sampling of an AC source: A tool to teach probabilistic observations
An undergraduate level experiment is described to demonstrate the role of
probabilistic observations in physics. A capacitor and a DC voltmeter are used
to randomly sample an AC voltage source. The resulting probability distribution
is analyzed to extract information about the AC source. Different
characteristic probability distributions arising from various AC waveforms are
calculated and experimentally measured. The reconstruction of the AC waveform
is demonstrated from the measured probability distribution under certain
restricted circumstances. The results are also compared with a simulated data
sample. We propose this as a pedagogical tool to teach probabilistic
measurements and their manipulations.Comment: Revtex4 file, 10 pages with 8 figure
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