453 research outputs found
Overt and subtle discrimination and psychological well-being:Examining the mediating and moderating role of ethnic-racial identity among emerging adults
Ethnic-racial identity (ERI) has been reported as mediator and moderator of the relation between discrimination and psychological well-being. However, it remains unclear how different forms of discrimination (i.e., overt and subtle) predict well-being over time, and whether ERI exploration and commitment mediate or moderate this association. This preregistered study explored the associations of overt and subtle discrimination with well-being (i.e., depression, substance use, life satisfaction) in a sample of 323 ethnic-racial minoritized college students (M age W1 = 18.03, 62.7% female) from longitudinal data collected in the US. Cross-lagged panel models across three waves indicated no associations of overt discrimination, but participants experiencing more subtle discrimination during their transition to college reported more depressive symptoms after four months. Ethnic-racial identity did not function as mediator or moderator. Findings indicate the need for a more nuanced understanding of the role of ERI during emerging adulthood.</p
Statistical mechanics of RNA folding: importance of alphabet size
We construct a minimalist model of RNA secondary-structure formation and use
it to study the mapping from sequence to structure. There are strong,
qualitative differences between two-letter and four or six-letter alphabets.
With only two kinds of bases, there are many alternate folding configurations,
yielding thermodynamically stable ground-states only for a small set of
structures of high designability, i.e., total number of associated sequences.
In contrast, sequences made from four bases, as found in nature, or six bases
have far fewer competing folding configurations, resulting in a much greater
average stability of the ground state.Comment: 7 figures; uses revtex
Tunneling spectra of submicron BiSrCaCuO intrinsic Josephson junctions: evolution from superconducting gap to pseudogap
Tunneling spectra of near optimally doped, submicron
BiSrCaCuO intrinsic Josephson junctions are presented,
and examined in the region where the superconducting gap evolves into
pseudogap. The spectra are analyzed using a self-energy model, proposed by
Norman {\it et al.}, in which both quasiparticle scattering rate and
pair decay rate are considered. The density of states derived
from the model has the familiar Dynes' form with a simple replacement of
by = ( + )/2. The
parameter obtained from fitting the experimental spectra shows a roughly linear
temperature dependence, which puts a strong constraint on the relation between
and . We discuss and compare the Fermi arc behavior
in the pseudogap phase from the tunneling and angle-resolved photoemission
spectroscopy experiments. Our results indicate an excellent agreement between
the two experiments, which is in favor of the precursor pairing view of the
pseudogap.Comment: 7 pages, 6 figure
Dipeptidyl peptidase 4 inhibitors and risk of inflammatory bowel disease: Real-world evidence in U.S. Adults
OBJECTIVE A recent study raises concerns that dipeptidyl peptidase 4 inhibitors (DPP4i) are associated with increased risk of inflammatory bowel disease (IBD). We evaluated the association between new use of DPP4i and IBD risk compared with other secondline antihyperglycemics. RESEARCH DESIGN AND METHODS We implemented an active-comparator, new-user cohort design using two U.S. administrative claims databases for commercially insured (MarketScan) and older adult (Medicare fee-for-service, 20% random sample) patients from January 2007 to December 2016.We identified patients, aged ≥18 years, who initiated DPP4i versus sulfonylureas (SUs) or initiated DPP4i versus thiazolidinediones (TZDs) and were without prior diagnosis, treatment, or procedure for IBD. The primary outcome was incident IBD, defined by IBD diagnosis preceded by colonoscopy and biopsy and followed by IBD treatment. We performed propensity score weighting to control for measured baseline confounding, estimated adjusted hazard ratios (aHRs [95% CI]) using weighted Cox proportional hazards models, and used randomeffects meta-analysis models to pool aHRs across cohorts. RESULTS We identified 895,747 eligible patients initiating DPP4i, SU, or TZD; IBD incidence rates ranged from 11.6 to 32.3/100,000 person-years. Over a median treatment duration of 1.09-1.69 years, DPP4i were not associated with increased IBD risk across comparisons. The pooled aHRs for IBD were 0.82 (95% CI 0.41-1.61) when comparing DPP4i (n 5 161,612) to SU (n 5 310,550) and 0.76 (0.46-1.26) when comparing DPP4i (n 5 205,570) to TZD (n 5 87,543). CONCLUSIONS Our population-based cohort study of U.S. adults with diabetes suggests that shortterm DPP4i treatment does not increase IBD risk
Stripes, Pseudogaps, and Van Hove Nesting in the Three-band tJ Model
Slave boson calculations have been carried out in the three-band tJ model for
the high-T_c cuprates, with the inclusion of coupling to oxygen breathing mode
phonons. Phonon-induced Van Hove nesting leads to a phase separation between a
hole-doped domain and a (magnetic) domain near half filling, with long-range
Coulomb forces limiting the separation to a nanoscopic scale. Strong
correlation effects pin the Fermi level close to, but not precisely at the Van
Hove singularity (VHS), which can enhance the tendency to phase separation. The
resulting dispersions have been calculated, both in the uniform phases and in
the phase separated regime. In the latter case, distinctly different
dispersions are found for large, random domains and for regular (static)
striped arrays, and a hypothetical form is presented for dynamic striped
arrays. The doping dependence of the latter is found to provide an excellent
description of photoemission and thermodynamic experiments on pseudogap
formation in underdoped cuprates. In particular, the multiplicity of observed
gaps is explained as a combination of flux phase plus charge density wave (CDW)
gaps along with a superconducting gap. The largest gap is associated with VHS
nesting. The apparent smooth evolution of this gap with doping masks a
crossover from CDW-like effects near optimal doping to magnetic effects (flux
phase) near half filling. A crossover from large Fermi surface to hole pockets
with increased underdoping is found. In the weakly overdoped regime, the CDW
undergoes a quantum phase transition (), which could be obscured
by phase separation.Comment: 15 pages, Latex, 18 PS figures Corrects a sign error: major changes,
esp. in Sect. 3, Figs 1-4,6 replace
Measurement of the nuclear multiplicity ratio for hadronization at CLAS
The influence of cold nuclear matter on lepto-production of hadrons in
semi-inclusive deep inelastic scattering is measured using the CLAS detector in
Hall B at Jefferson Lab and a 5.014 GeV electron beam. We report the
multiplicity ratios for targets of C, Fe, and Pb relative to deuterium as a
function of the fractional virtual photon energy transferred to the
and the transverse momentum squared of the . We find that the
multiplicity ratios for are reduced in the nuclear medium at high
and low , with a trend for the transverse momentum to be
broadened in the nucleus for large .Comment: Submitted to Phys. Lett.
Coherent Photoproduction of pi^+ from 3^He
We have measured the differential cross section for the
He reaction. This reaction was studied using
the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons
produced with the Hall-B bremsstrahlung tagging system in the energy range from
0.50 to 1.55 GeV were incident on a cryogenic liquid He target. The
differential cross sections for the He
reaction were measured as a function of photon-beam energy and pion-scattering
angle. Theoretical predictions to date cannot explain the large cross sections
except at backward angles, showing that additional components must be added to
the model.Comment: 11 pages, 16 figure
Demonstration of a novel technique to measure two-photon exchange effects in elastic scattering
The discrepancy between proton electromagnetic form factors extracted using
unpolarized and polarized scattering data is believed to be a consequence of
two-photon exchange (TPE) effects. However, the calculations of TPE corrections
have significant model dependence, and there is limited direct experimental
evidence for such corrections. We present the results of a new experimental
technique for making direct comparisons, which has the potential to
make precise measurements over a broad range in and scattering angles. We
use the Jefferson Lab electron beam and the Hall B photon tagger to generate a
clean but untagged photon beam. The photon beam impinges on a converter foil to
generate a mixed beam of electrons, positrons, and photons. A chicane is used
to separate and recombine the electron and positron beams while the photon beam
is stopped by a photon blocker. This provides a combined electron and positron
beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen
target. The large acceptance CLAS detector is used to identify and reconstruct
elastic scattering events, determining both the initial lepton energy and the
sign of the scattered lepton. The data were collected in two days with a
primary electron beam energy of only 3.3 GeV, limiting the data from this run
to smaller values of and scattering angle. Nonetheless, this measurement
yields a data sample for with statistics comparable to those of the
best previous measurements. We have shown that we can cleanly identify elastic
scattering events and correct for the difference in acceptance for electron and
positron scattering. The final ratio of positron to electron scattering:
for GeV and
Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive production
We present studies of single-spin asymmetries for neutral pion
electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV
polarized electrons from an unpolarized hydrogen target, using the CEBAF Large
Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator
Facility. A substantial amplitude has been measured in the
distribution of the cross section asymmetry as a function of the azimuthal
angle of the produced neutral pion. The dependence of this amplitude
on Bjorken and on the pion transverse momentum is extracted with
significantly higher precision than previous data and is compared to model
calculations.Comment: to be submitted PL
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