187 research outputs found
Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-Type Galaxies from the SMAKCED Project. I. Kinematically Decoupled Cores and Implications for Infallen Groups in Clusters
We present evidence for kinematically decoupled cores (KDCs) in two dwarf
early-type (dE) galaxies in the Virgo cluster, VCC 1183 and VCC 1453, studied
as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey.
These KDCs have radii of 1.8'' (0.14 kpc) and 4.2'' (0.33 kpc), respectively.
Each of these KDCs is distinct from the main body of its host galaxy in two
ways: (1) inverted sense of rotation; and (2) younger (and possibly more
metal-rich) stellar population. The observed stellar population differences are
probably associated with the KDC, although we cannot rule out the possibility
of intrinsic radial gradients in the host galaxy. We describe a statistical
analysis method to detect, quantify the significance of, and characterize KDCs
in long-slit rotation curve data. We apply this method to the two dE galaxies
presented in this paper and to five other dEs for which KDCs have been reported
in the literature. Among these seven dEs, there are four significant KDC
detections, two marginal KDC detections, and one dE with an unusual central
kinematic anomaly that may be an asymmetric KDC.The frequency of occurence of
KDCs and their properties provide important constraints on the formation
history of their host galaxies. We discuss different formation scenarios for
these KDCs in cluster environments and find that dwarf-dwarf wet mergers or gas
accretion can explain the properties of these KDCs. Both of these mechanisms
require that the progenitor had a close companion with a low relative velocity.
This suggests that KDCs were formed in galaxy pairs residing in a poor group
environment or in isolation whose subsequent infall into the cluster quenched
star formation.Comment: 14 pages, accepted for publication in Ap
Evolution of Microstructure and Texture during Warm Rolling Of a Duplex Steel
The effect of warm rolling on the evolution of microstructure and texture in a duplex stainless steel (DSS) was investigated. For this purpose, a DSS steel was warm rolled up to 90 pct reduction in thickness at 498 K, 698 K, and 898 K (225 °C, 425 °C, and 625 °C). The microstructure with an alternate arrangement of deformed ferrite and austenite bands was observed after warm rolling; however, the microstructure after 90 pct warm rolling at 498 K and 898 K (225 °C and 625 °C) was more lamellar and uniform as compared to the rather fragmented and inhomogeneous structure observed after 90 pct warm rolling at 698 K (425 °C). The texture of ferrite in warm-rolled DSS was characterized by the presence of the RD (〈011〉//RD) and ND (〈111〉//ND) fibers. However, the texture of ferrite in DSS warm rolled at 698 K (425 °C) was distinctly different having much higher fraction of the RD-fiber components than that of the ND-fiber components. The texture and microstructural differences in ferrite in DSS warm rolled at different temperatures could be explained by the interaction of carbon atoms with dislocations. In contrast, the austenite in DSS warm rolled at different temperatures consistently showed pure metal- or copper-type deformation texture which was attributed to the increase in stacking fault energy at the warm-rolling temperatures. It was concluded that the evolution of microstructure and texture of the two constituent phases in DSS was greatly affected by the temperature of warm rolling, but not significantly by the presence of the other phas
Promoting Resilience Among African American Girls: Racial Identity as a Protective Factor
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146551/1/cdev12995.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146551/2/cdev12995_am.pd
Electronic transport in EuB
EuB is a magnetic semiconductor in which defects introduce charge
carriers into the conduction band with the Fermi energy varying with
temperature and magnetic field. We present experimental and theoretical work on
the electronic magnetotransport in single-crystalline EuB. Magnetization,
magnetoresistance and Hall effect data were recorded at temperatures between 2
and 300 K and in magnetic fields up to 5.5 T. The negative magnetoresistance is
well reproduced by a model in which the spin disorder scattering is reduced by
the applied magnetic field. The Hall effect can be separated into an ordinary
and an anomalous part. At 20 K the latter accounts for half of the observed
Hall voltage, and its importance decreases rapidly with increasing temperature.
As for Gd and its compounds, where the rare-earth ion adopts the same Hund's
rule ground state as Eu in EuB, the standard antisymmetric
scattering mechanisms underestimate the of this contribution by several
orders of magnitude, while reproducing its almost perfectly. Well below
the bulk ferromagnetic ordering at = 12.5 K, a two-band model
successfully describes the magnetotransport. Our description is consistent with
published de Haas van Alphen, optical reflectivity, angular-resolved
photoemission, and soft X-ray emission as well as absorption data, but requires
a new interpretation for the gap feature deduced from the latter two
experiments.Comment: 35 pages, 12 figures, submitted to PR
Monte Carlo simulation of ice models
We propose a number of Monte Carlo algorithms for the simulation of ice
models and compare their efficiency. One of them, a cluster algorithm for the
equivalent three colour model, appears to have a dynamic exponent close to
zero, making it particularly useful for simulations of critical ice models. We
have performed extensive simulations using our algorithms to determine a number
of critical exponents for the square ice and F models.Comment: 32 pages including 15 postscript figures, typeset in LaTeX2e using
the Elsevier macro package elsart.cl
Quantum effects in the quasiparticle structure of the ferromagnetic Kondo lattice model
A new ``Dynamical Mean-field theory'' based approach for the Kondo lattice
model with quantum spins is introduced. The inspection of exactly solvable
limiting cases and several known approximation methods, namely the second-order
perturbation theory, the self-consistent CPA and finally a moment-conserving
decoupling of the equations of motion help in evaluating the new approach. This
comprehensive investigation gives some certainty to our results: Whereas our
method is somewhat limited in the investigation of the J<0-model, the results
for J>0 reveal important aspects of the physics of the model: The energetically
lowest states are not completely spin-polarized.A band splitting, which occurs
already for relatively low interaction strengths, can be related to distinct
elementary excitations, namely magnon emission (absorption) and the formation
of magnetic polarons. We demonstrate the properties of the ferromagnetic Kondo
lattice model in terms of spectral densities and quasiparticle densities of
states.Comment: 19 pages, 4 figure
Impact of FTO genotypes on BMI and weight in polycystic ovary syndrome : a systematic review and meta-analysis
Aims/hypothesis
FTO gene single nucleotide polymorphisms (SNPs) have been shown to be associated with obesity-related traits and type 2 diabetes. Several small studies have suggested a greater than expected effect of the FTO rs9939609 SNP on weight in polycystic ovary syndrome (PCOS). We therefore aimed to examine the impact of FTO genotype on BMI and weight in PCOS.
Methods
A systematic search of medical databases (PubMed, EMBASE and Cochrane CENTRAL) was conducted up to the end of April 2011. Seven studies describing eight distinct PCOS cohorts were retrieved; seven were genotyped for SNP rs9939609 and one for SNP rs1421085. The per allele effect on BMI and body weight increase was calculated and subjected to meta-analysis.
Results
A total of 2,548 women with PCOS were included in the study; 762 were TT homozygotes, 1,253 had an AT/CT genotype, and 533 were AA/CC homozygotes. Each additional copy of the effect allele (A/C) increased the BMI by a mean of 0.19 z score units (95% CI 0.13, 0.24; p = 2.26 × 10−11) and body weight by a mean of 0.20 z score units (95% CI 0.14, 0.26; p = 1.02 × 10−10). This translated into an approximately 3.3 kg/m2 increase in BMI and an approximately 9.6 kg gain in body weight between TT and AA/CC homozygotes. The association between FTO genotypes and BMI was stronger in the cohorts with PCOS than in the general female populations from large genome-wide association studies. Deviation from an additive genetic model was observed in heavier populations.
Conclusions/interpretation
The effect of FTO SNPs on obesity-related traits in PCOS seems to be more than two times greater than the effect found in large population-based studies. This suggests an interaction between FTO and the metabolic context or polygenic background of PCOS
Epidemiological and cohort study finds no association between COVID-19 and Guillain-Barré syndrome
Reports of Guillain-Barré syndrome (GBS) have emerged during the Coronavirus disease 2019 (COVID-19) pandemic. This epidemiological and cohort study sought to investigate any causative association between COVID-19 infection and GBS. The epidemiology of GBS cases reported to the UK National Immunoglobulin Database was studied from 2016 to 2019 and compared to cases reported during the COVID-19 pandemic. Data were stratified by hospital trust and region, with numbers of reported cases per month. UK population data for COVID-19 infection were collated from UK public health bodies. In parallel, but separately, members of the British Peripheral Nerve Society prospectively reported incident cases of GBS during the pandemic at their hospitals to a central register. The clinical features, investigation findings and outcomes of COVID-19 (definite or probable) and non-COVID-19 associated GBS cases in this cohort were compared. The incidence of GBS treated in UK hospitals from 2016 to 2019 was 1.65–1.88 per 100 000 individuals per year. GBS incidence fell between March and May 2020 compared to the same months of 2016–19. GBS and COVID-19 incidences during the pandemic also varied between regions and did not correlate with one another (r = 0.06, 95% confidence interval: −0.56 to 0.63, P = 0.86). In the independent cohort study, 47 GBS cases were reported (COVID-19 status: 13 definite, 12 probable, 22 non-COVID-19). There were no significant differences in the pattern of weakness, time to nadir, neurophysiology, CSF findings or outcome between these groups. Intubation was more frequent in the COVID-19 affected cohort (7/13, 54% versus 5/22, 23% in COVID-19-negative) attributed to COVID-19 pulmonary involvement. Although it is not possible to entirely rule out the possibility of a link, this study finds no epidemiological or phenotypic clues of SARS-CoV-2 being causative of GBS. GBS incidence has fallen during the pandemic, which may be the influence of lockdown measures reducing transmission of GBS inducing pathogens such as Campylobacter jejuni and respiratory viruses
A Wide Field, Low Frequency Radio Image of the Field of M31: II. -- Source Classification and Discussion
We have previously presented the results of a 325 MHz radio survey of M31,
conducted with the A-configuration of the Very Large Array. In this survey, a
total of 405 radio sources between <6" and 170" in extent were mapped with a
resolution of 6" and a sensitivity of ~0.6 mJy/beam. Here, we compare the
resultant source list and image with other radio, IR, optical, X-ray
observations and catalogs of the region. Through this, we were able to identify
five supernova remnant (SNR) candidates and three pulsar wind nebula (PWN)
candidates in M31, as well as three Milky Way radio stars, a possible Milky Way
Planetary Nebula, and a bevy of interesting extragalactic objects: a BL Lac, a
Giant Radio Galaxy, a galaxy merger, and several high-z radio galaxy
candidates. In addition, a large number of compact (<6") extremely steep
spectrum sources () were
detected whose nature is unknown.Comment: 30 pages, 23 tables, + 18 figures. Low-resolution figures are
available here in .jpg form. ApJS accepted, to be published in August 2005,
v159 2 issu
- …