11,986 research outputs found
Symmetry Analysis of Multiferroic Co_3TeO_6
A phenomenological explanation of the magnetoelectric behavior of Co_3TeO_6
is developed. We explain the second harmonic generation data and the magnetic
field induced spontaneous polarization in the magnetically ordered phase below
20K.Comment: Phys rev B Rapids, to appea
Towards a Microscopic Model of Magnetoelectric Interactions in Ni3V2O8
We develop a microscopic magnetoelectric coupling in NiVO (NVO)
which gives rise to the trilinear phenomenological coupling used previously to
explain the phase transition in which magnetic and ferroelectric order
parameters appear simultaneously. Using combined neutron scattering
measurements and first-principles calculations of the phonons in NVO, we
determine eleven phonons which can induce the observed spontaneous
polarization. Among these eleven phonons, we find that a few of them can
actually induce a significant dipole moment. Using the calculated atomic
charges, we find that the required distortion to induce the observed dipole
moment is very small (~0.001 \AA) and therefore it would be very difficult to
observe the distortion by neutron-powder diffraction. Finally, we identify the
derivatives of the exchange tensor with respect to atomic displacements which
are needed for a microscopic model of a spin-phonon coupling in NVO and which
we hope will be obtained from a fundamental quantum calculation such as LDA+U.
We also analyze two toy models to illustrate that the Dzyaloskinskii-Moriya
interaction is very important for coexisting of magnetic and ferroelectric
order but it is not the only mechanism when the local site symmetry of the
system is low enough.Comment: 20 pages, 10 figure
Extended X-ray emission around four 3C quasars at 0.55<z<0.75 observed with Chandra
We report on the detection of a soft spatially-extended component of X-ray
emission around four intermediate-redshift 3C quasars observed with Chandra:
3C254, 3C263, 3C275.1 and 3C281. The bolometric luminosity of this emission
ranges over 0.3-1.6 times 10^{44}erg/s, and extends to lengthscales of over 350
kpc at the redshift of the quasar. The X-rays are most likely thermal emission
from the intracluster medium of a cluster of galaxies around each quasar, which
provides the working surface for the powerful radio lobes. Some X-ray emission
is also seen to be associated with the radio plasma.Comment: 8 pages, 4 panelled figures, MNRAS in pres
Liberation Kitchen: Annotating Intergenerational Conversations Among Black Women in Art and Education
In this essay, we, four Black women art educators, draw from Black feminisms and Afrofemcentrism. Our practice considers nuanced ways that Black women curate spaces of communal care, which position forms of dialogic encounters with one another. We put forward aspects of Black life, as lived in and through sharing intimacies of the geospatial and as continuation of Black radical traditions. We argue that a kitchenspace indexes a Black praxis, centering intergenerational knowledge-sharing and methodology toward liberation. We think with Black feminist scholar/artists and insist a method of self-annotating, indexing our lives into the otherwise absences of Black women’s narratives in the field of art education. We practice the theorization and method of using images of personal artwork and our dialogues. These annotations realign new centers of knowledge and refuse cannibalization by Euro-dominant narratives
Polarization restricts hepatitis C virus entry into HepG2 hepatoma cells
The primary reservoir for hepatitis C virus (HCV) replication is believed to be hepatocytes, which are highly polarized with tight junctions (TJ) separating their basolateral and apical domains. HepG2 cells develop polarity over time, resulting in the formation and remodeling of bile canalicular (BC) structures. HepG2 cells expressing CD81 provide a model system to study the effects of hepatic polarity on HCV infection. We found an inverse association between HepG2-CD81 polarization and HCV pseudoparticle entry. As HepG2 cells polarize, discrete pools of claudin-1 (CLDN1) at the TJ and basal/lateral membranes develop, consistent with the pattern of receptor staining observed in liver tissue. The TJ and nonjunctional pools of CLDN1 show an altered association with CD81 and localization in response to the PKA antagonist Rp-8-Br-cyclic AMPs (cAMPs). Rp-8-Br-cAMPs reduced CLDN1 expression at the basal membrane and inhibited HCV infection, supporting a model where the nonjunctional pools of CLDN1 have a role in HCV entry. Treatment of HepG2 cells with proinflammatory cytokines, tumor necrosis factor alpha and gamma interferon, perturbed TJ integrity but had minimal effect(s) on cellular polarity and HCV infection, suggesting that TJ integrity does not limit HCV entry into polarized HepG2 cells. In contrast, activation of PKC with phorbol ester reduced TJ integrity, ablated HepG2 polarity, and stimulated HCV entry. Overall, these data show that complex hepatocyte-like polarity alters CLDN1 localization and limits HCV entry, suggesting that agents which disrupt hepatocyte polarity may promote HCV infection and transmission within the liver
Readability and content analysis of lifestyle education resources for weight management in Australian general practice
© 2016 El-Haddad et al. Background: Weight management education is one of the key strategies to assist patients to manage their weight. Educational resources provide an important adjunct in the chain of communication between practitioners and patients. However, one in five Australian adults has low health literacy. The purpose of this study was to assess the readability and analyse the content of weight management resources. Methods: This study is based on the analysis of 23 resources found in the waiting rooms of ten Sydney-based general practices and downloaded from two clinical software packages used at these practices. The reading grade level of these resources was calculated using the Flesch Reading Ease, Flesch-Kincaid Grade Level, Fry Readability Graph, and the Simplified Measure of Gobbledygook. Resources' content was analysed for the presence of dietary, physical activity, and behaviour change elements, as recommended by the Clinical practice guidelines for the management of overweight and obesity in adults, adolescents, and children in Australia. Results: The resources' average reading grade level was for a 10th grader (9.5 ± 1.8). These findings highlight that the average reading grade level was two grades higher than the recommended reading grade level for health education resources of 8th grade level or below. Seventy percent of resources contained dietary and behaviour change elements. Physical activity was included in half of the resources. Two messages were identified to be inconsistent with the guidelines and three messages had no scientific basis. Conclusion: A body of evidence now exists that supports the need to develop evidence-based education resources for weight management that place low demand on literacy, without compromising content accuracy. The findings from this study suggest that there is significant room for improvement in the educational resources provided in general practices
Variability Timescales in the M87 Jet: Signatures of E-Squared Losses, Discovery of a Quasi-period in HST-1, and the Site of TeV Flaring
We investigate the variability timescales in the jet of M87 with two goals.
The first is to use the rise times and decay times in the radio, ultraviolet
and X-ray lightcurves of HST-1 to constrain the source size and the energy loss
mechanisms affecting the relativistic electron distributions. HST-1 is the
first jet knot clearly resolved from the nuclear emission by Chandra and is the
site of the huge flare of 2005. We find clear evidence for a
frequency-dependent decrease in the synchrotron flux being consistent with
E-squared energy losses. Assuming that this behavior is predominantly caused by
synchrotron cooling, we estimate a value of 0.6 mG for the average magnetic
field strength of the HST-1 emission region, a value consistent with previous
estimates of the equipartition field. In the process of analyzing the first
derivative of the X-ray light curve of HST-1, we discovered a quasi-periodic
oscillation which was most obvious in 2003 and 2004 prior to the major flare in
2005. The four cycles observed have a period of order 6 months. The second goal
is to search for evidence of differences between the X-ray variability
timescales of HST-1 and the unresolved nuclear region (diameter <0.6"). These
features, separated by more than 60 pc, are the two chief contenders for the
origin of the TeV variable emissions observed by HESS in 2005 and by MAGIC and
VERITAS in 2008. The X-ray variability of the nucleus appears to be at least
twice as rapid as that of the HST-1 knot. However, the shortest nuclear
variability timescale we can measure from the Chandra data (<= 20 days) is
still significantly longer than the shortest TeV variability of M87 reported by
the HESS and MAGIC telescopes (1-2 days).Comment: Accepted for publication in the Astrophysical Journal. 16 pages
including 9 figures, some in colo
Symmetry Analysis for the Ruddlesden-Popper Systems, Ca3Mn2O7 and Ca3Ti2O7
We perform a symmetry analysis of the zero-temperature instabilities of the
tetragonal phase of Ca3Mn2O7 and Ca3Ti2O7 which is stable at high temperature.
We introduce order parameters to characterize each of the possible lattice
distortions in order to construct a Landau free energy which elucidates the
proposed group-subgroup relations for structural transitions in these systems.
We include the coupling between the unstable distortion modes and the
macroscopic strain tensor. We also analyze the symmetry of the dominantly
antiferromagnetic ordering which allows weak ferromagnetism. We show that in
this phase the weak ferromagnetic moment and the spontaneous ferroelectric
polarization are coupled, so that rotating one of these ordering by applying an
external electric or magnetic field one can rotate the other ordering. We
discuss the number of different domains (including phase domains) which exist
in each of the phases and indicate how these may be observed.Comment: 21 pages, 14 figure
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