439 research outputs found
Is there evidence to support multidisciplinary healthcare working in rheumatology? A systematic review of the literature
Plastic Flow, Voltage Bursts, and Vortex Avalanches in Superconductors
We use large-scale parallel simulations to compute the motion of
superconducting magnetic vortices during avalanches triggered by small field
increases. We find that experimentally observable voltage bursts correspond to
pulsing vortex movement along branched channels or winding chains, and relate
vortex flow images to features of statistical distributions. As pin density is
increased, a crossover occurs from interstitial motion in narrow easy-flow
winding channels with typical avalanche sizes, to pin-to-pin motion in broad
channels, characterized by a very broad distribution of sizes. Our results are
consistent with recent experiments.Comment: 4 pages, Latex, 4 figures included. Movies available at
http://www-personal.engin.umich.edu/~nor
Internal avalanches in a pile of superconducting vortices
Using an array of miniature Hall probes, we monitored the spatiotemporal
variation of the internal magnetic induction in a superconducting niobium
sample during a slow sweep of external magnetic field. We found that a sizable
fraction of the increase in the local vortex population occurs in abrupt jumps.
The size distribution of these avalanches presents a power-law collapse on a
limited range. In contrast, at low temperatures and low fields, huge avalanches
with a typical size occur and the system does not display a well-defined
macroscopic critical current.Comment: 5 pages including 5 figure
Rectification and Flux Reversals for Vortices Interacting with Triangular Traps
We simulate vortices in superconductors interacting with two-dimensional
arrays of triangular traps. We find that, upon application of an ac drive, a
net dc flow can occur which shows current reversals with increasing ac drive
amplitude for certain vortex densities, in agreement with recent experiments
and theoretical predictions. We identify the vortex dynamics responsible for
the different rectification regimes. We also predict the occurrence of a novel
transverse rectification effect in which a dc flow appears that is transverse
to the direction of the applied ac drive.Comment: 4 pages, 4 postscript figure
Prenatal micronutrient supplementation and postpartum depressive symptoms in a pregnancy cohort
Background Postpartum depression is a serious problem for women and their offspring. Micronutrient supplements are recommended for pregnant women because of their documented protective effects for the offspring, but their potential beneficial effects on maternal mental health are unknown. This study investigated the association between prenatal micronutrient supplementation and the risk for symptoms of postpartum depression in a longitudinal pregnancy cohort from the Alberta Pregnancy Outcomes and Nutrition (APrON) study. Methods Participants came from a cohort of the first 600 APrON women. Supplemental nutrient intake and symptoms of depression (measured with the Edinburgh Postnatal Depression Scale (EPDS)) were collected at each trimester and 12 weeks postpartum. Results Of the 475 participants who completed the EPDS at least twice in pregnancy and at 12 weeks postpartum, 416 (88%) scored <10 and 59 (12%) scored â„10, where an EPDS â„10 is considered to be âat least probable minor depressionâ. Mean nutrient intakes from supplements were higher in women with lower EPDS scores, particularly selenium (p = 0.0015) and omega-3s (p = 0.01). Bivariate analyses showed that several demographic and social/lifestyle variables were associated with EPDS â„10: not having been born in Canada (p = 0.01), greater number of chronic conditions (p = 0.05), greater number of stressful life events during this pregnancy (p = 0.02), and lower prenatal and postnatal support (p = 0.0043 and p = 0.0001, respectively). Adjusting for covariates and nutrients known to be associated with postpartum depression, logistic regression showed that having a prenatal EPDS â„ 10 increased the odds of postpartum depressive symptoms (second and third trimester OR = 3.29, 95% CI = 1.55 - 7.01, p = 0.004 and OR = 4.26, 95% CI = 2.05 - 8.85, p < 0.0001, respectively), while prenatal supplemental selenium (per 10 mcg, OR = 0.76, 95% CI = 0.74 - 0.78, p = 0.0019) and postnatal social support (OR = 0.87, 95% CI = 0.78 - 0.97, p = 0.0015) were protective. Conclusions Multiple factors, including supplementary selenium intake, are associated with the risk of postpartum depressive symptoms. Future research on dietary supplementation in pregnancy with special attention to selenium intake is warranted. Keywords: Postpartum depression, Dietary supplements, Selenium, Omega-
Scalar and Pseudoscalar Higgs Boson Plus One Jet Production at the LHC and Tevatron
The production of the Standard Model (SM) Higgs boson (H) in association with
a jet is compared with that of the lightest scalar Higgs boson (h^0) and the
pseudoscalar Higgs boson (A^0) of the Minimal Supersymmetric Model (MSSM) at
both the CERN Large Hadron Collider (LHC) and the Fermilab Tevatron. We include
both top and bottom quark loops to lowest order in QCD and investigate the
limits of zero quark mass and infinite quark mass.Comment: 14 pages, REVTeX4, 14 eps figures v2: Version accepted for
publication in PR
Meson Cloud of the Nucleon in Polarized Semi-Inclusive Deep-Inelastic Scattering
We investigate the possibility of identifying an explicit pionic component of
the nucleon through measurements of polarized baryon fragments
produced in deep-inelastic leptoproduction off polarized protons, which may
help to identify the physical mechanism responsible for the breaking of the
Gottfried sum rule. The pion-exchange model predicts highly correlated
polarizations of the and target proton, in marked contrast with
the competing diquark fragmentation process. Measurement of asymmetries in
polarized production may also reveal the presence of a kaon cloud in
the nucleon.Comment: 23 pages REVTeX, 7 uuencoded figures, accepted for publication in
Zeit. Phys.
Power corrections to the transition form factor and pion distribution amplitudes
Employing the standard hard-scattering approach and the running coupling
method we calculate a class of power-suppressed corrections to the electromagnetic transition form
factor (FF) arising from the end-point
integration regions. In the investigations we use a hard-scattering amplitude
of the subprocess , symmetrized under
exchange important for exclusive
processes containing two external photons. In the computations the pion model
distribution amplitudes (DA's) with one and two non-asymptotic terms are
employed. The obtained predictions are compared with the CLEO data and
constraints on the DA parameters and at the
normalization point are extracted. Further restrictions on
the pion DA's are deduced from the experimental data on the electromagnetic FF
.Comment: 23 pages, 6 figures; the version published in Phys. Rev. D69, 094010
(2004
On-disk coronal rain
Small and elongated, cool and dense blob-like structures are being reported
with high resolution telescopes in physically different regions throughout the
solar atmosphere. Their detection and the understanding of their formation,
morphology and thermodynamical characteristics can provide important
information on their hosting environment, especially concerning the magnetic
field, whose understanding constitutes a major problem in solar physics. An
example of such blobs is coronal rain, a phenomenon of thermal non- equilibrium
observed in active region loops, which consists of cool and dense chromospheric
blobs falling along loop-like paths from coronal heights. So far, only off-limb
coronal rain has been observed and few reports on the phenomenon exist. In the
present work, several datasets of on-disk H{\alpha} observations with the CRisp
Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST) are
analyzed. A special family of on-disk blobs is selected for each dataset and a
statistical analysis is carried out on their dynamics, morphology and
temperatures. All characteristics present distributions which are very similar
to reported coronal rain statistics. We discuss possible interpretations
considering other similar blob-like structures reported so far and show that a
coronal rain interpretation is the most likely one. Their chromospheric nature
and the projection effects (which eliminate all direct possibility of height
estimation) on one side, and their small sizes, fast dynamics, and especially,
their faint character (offering low contrast with the background intensity) on
the other side, are found as the main causes for the absence until now of the
detection of this on-disk coronal rain counterpart.Comment: 18 pages, 10 figures. Accepted for Solar Physic
Transverse Phase Locking for Vortex Motion in Square and Triangular Pinning Arrays
We analyze transverse phase locking for vortex motion in a superconductor
with a longitudinal DC drive and a transverse AC drive. For both square and
triangular arrays we observe a variety of fractional phase locking steps in the
velocity versus DC drive which correspond to stable vortex orbits. The locking
steps are more pronounced for the triangular arrays which is due to the fact
that the vortex motion has a periodic transverse velocity component even for
zero transverse AC drive. All the steps increase monotonically in width with AC
amplitude. We confirm that the width of some fractional steps in the square
arrays scales as the square of the AC driving amplitude. In addition we
demonstrate scaling in the velocity versus applied DC driving curves at
depinning and on the main step, similar to that seen for phase locking in
charge-density wave systems. The phase locking steps are most prominent for
commensurate vortex fillings where the interstitial vortices form symmetrical
ground states. For increasing temperature, the fractional steps are washed out
very quickly, while the main step gains a linear component and disappears at
melting. For triangular pinning arrays we again observe transverse phase
locking, with the main and several of the fractional step widths scaling
linearly with AC amplitude.Comment: 10 pages, 14 postscript figure
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