316 research outputs found
Results of Universal Prenatal Screening for Hepatitis C Infection in a Remote American Indian Primary Care Population
BACKGROUND: Although chronic liver disease remains a major area of health disparity for American Indian (AI) people, the epidemiology of hepatitis C virus (HCV) infection among AI people is poorly documented. Because of suspected high local prevalence, two remote AI clinics in the Northern Plains implemented universal prenatal HCV screening in 2005. When this screening program reported an unexpectedly high prenatal anti-HCV (anti-HCV antibody) positivity rate, we conducted a case-control study to determine risks for infection and opportunities for community intervention.
MAIN FINDINGS: The clinics screened a total of 205 pregnant women (median age, 22 years). Of these 205 women, a total of 13 (6.3%; 95% confidence interval, 3.4â10.6) had anti-HCV confirmed. Of the anti-HCV-positive women, 10 (76.9%) were aged 15â24 years. We included 10 cases and 40 anti-HCV-negative prenatal controls in a case-control study. On multivariate analysis, only injection-drug use (IDU) remained associated with HCV seropositivity.
CONCLUSIONS: Universal prenatal screening revealed a high prevalence of anti-HCV at these remote AI clinics. This population has not been previously described at being at elevated risk for HCV infection. In order to reduce health disparities, young, rural AI populations seeking prenatal care need to be included in interventions to reduce HCV transmission
Rescue of TRAF3-null mice by p100 NF-ÎșB deficiency
Proper activation of nuclear factor (NF)âÎșB transcription factors is critical in regulating fundamental biological processes such as cell survival and proliferation, as well as in inflammatory and immune responses. Recently, the NF-ÎșB signaling pathways have been categorized into the canonical pathway, which results in the nuclear translocation of NF-ÎșB complexes containing p50, and the noncanonical pathway, which involves the induced processing of p100 to p52 and the formation of NF-ÎșB complexes containing p52 (Bonizzi, G., and M. Karin. 2004. Trends Immunol. 25:280â288). We demonstrate that loss of tumor necrosis factor (TNF) receptorâassociated factor 3 (TRAF3) results in constitutive noncanonical NF-ÎșB activity. Importantly, TRAF3â/â B cells show ligand-independent up-regulation of intracellular adhesion molecule 1 and protection from spontaneous apoptosis during in vitro culture. In addition, we demonstrate that loss of TRAF3 results in profound accumulation of NF-ÎșBâinducing kinase in TRAF3â/â cells. Finally, we show that the early postnatal lethality observed in TRAF3-deficient mice is rescued by compound loss of the noncanonical NF-ÎșB p100 gene. Thus, these genetic data clearly demonstrate that TRAF3 is a critical negative modulator of the noncanonical NF-ÎșB pathway and that constitutive activation of the noncanonical NF-ÎșB pathway causes the lethal phenotype of TRAF3-deficient mice
Nonequilibrium Phase Transitions in Models of Aggregation, Adsorption, and Dissociation
We study nonequilibrium phase transitions in a mass-aggregation model which
allows for diffusion, aggregation on contact, dissociation, adsorption and
desorption of unit masses. We analyse two limits explicitly. In the first case
mass is locally conserved whereas in the second case local conservation is
violated. In both cases the system undergoes a dynamical phase transition in
all dimensions. In the first case, the steady state mass distribution decays
exponentially for large mass in one phase, and develops an infinite aggregate
in addition to a power-law mass decay in the other phase. In the second case,
the transition is similar except that the infinite aggregate is missing.Comment: Major revision of tex
Slow relaxation due to optimization and restructuring: Solution on a hierarchical lattice
Motivated by the large strain shear of loose granular materials we introduced
a model which consists of consecutive optimization and restructuring steps
leading to a self organization of a density field. The extensive connections to
other models of statistical phyics are discussed. We investigate our model on a
hierarchical lattice which allows an exact asymptotic renormalization
treatment. A surprisingly close analogy is observed between the simulation
results on the regular and the hierarchical lattices. The dynamics is
characterized by the breakdown of ergodicity, by unusual system size effects in
the development of the average density as well as by the age distribution, the
latter showing multifractal properties.Comment: 11 pages, 7 figures revtex, submitted to PRE see also:
cond-mat/020920
Spin Hall conductivity in BiSb as an experimental test of bulk-boundary correspondence
Bulk-boundary correspondence is a foundational principle underlying the
electronic band structure and physical behavior of topological quantum
materials. Although it has been rigorously tested in topological systems where
the physical properties involve charge currents, it remains unclear whether
bulk-boundary correspondence should also hold for non-conserved spin currents.
We study charge-to-spin conversion in a canonical topological insulator,
BiSb, to address this fundamentally unresolved question. We use
spin-torque ferromagnetic resonance measurements to accurately probe the
charge-to-spin conversion efficiency in epitaxial BiSb~thin films
of high structural quality spanning the entire range of composition, including
both trivial and topological band structures, as verified using {\it in vacuo}
angle-resolved photoemission spectroscopy. From these measurements, we deduce
the effective spin Hall conductivity (SHC) and find excellent agreement with
the values predicted by tight-binding calculations for the intrinsic SHC of the
bulk bands. These results provide strong evidence that the strong spin-orbit
entanglement of bulk states well below the Fermi energy connects directly to
the SHC in epitaxial BiSb~films interfaced with a metallic
ferromagnet. The excellent agreement between theory and experiment points to
the generic value of analyses focused entirely on bulk properties, even for
topological systems involving non-conserved spin currents
Phase Transition in the Takayasu Model with Desorption
We study a lattice model where particles carrying different masses diffuse,
coalesce upon contact, and also unit masses adsorb to a site with rate or
desorb from a site with nonzero mass with rate . In the limit (without
desorption), our model reduces to the well studied Takayasu model where the
steady-state single site mass distribution has a power law tail for large mass. We show that varying the desorption rate induces
a nonequilibrium phase transition in all dimensions. For fixed , there is a
critical such that if , the steady state mass distribution,
for large as in the Takayasu case. For , we
find where is a new exponent, while for
, for large . The model is studied
analytically within a mean field theory and numerically in one dimension.Comment: RevTex, 11 pages including 5 figures, submitted to Phys. Rev.
Persistence properties of a system of coagulating and annihilating random walkers
We study a d-dimensional system of diffusing particles that on contact either
annihilate with probability 1/(q-1) or coagulate with probability (q-2)/(q-1).
In 1-dimension, the system models the zero temperature Glauber dynamics of
domain walls in the q-state Potts model. We calculate P(m,t), the probability
that a randomly chosen lattice site contains a particle whose ancestors have
undergone exactly (m-1) coagulations. Using perturbative renormalization group
analysis for d < 2, we show that, if the number of coagulations m is much less
than the typical number M(t), then P(m,t) ~ m^(z/d) t^(-theta), with theta=d Q
+ Q(Q-1/2) epsilon + O(epsilon^2), z=(2Q-1) epsilon + (2 Q-1) (Q-1)(1/2+A Q)
epsilon^2 +O(epsilon^3), where Q=(q-1)/q, epsilon =2-d and A =-0.006. M(t) is
shown to scale as t^(d/2-delta), where delta = d (1 -Q)+(Q-1)(Q-1/2) epsilon+
O(epsilon^2). In two dimensions, we show that P(m,t) ~ ln(t)^(Q(3-2Q))
ln(m)^((2Q-1)^2) t^(-2Q) for m << t^(2 Q-1). The 1-dimensional results
corresponding to epsilon=1 are compared with results from Monte Carlo
simulations.Comment: 12 pages, revtex, 5 figure
Shearing of loose granular materials: A statistical mesoscopic model
A two-dimensional lattice model for the formation and evolution of shear
bands in granular media is proposed. Each lattice site is assigned a random
variable which reflects the local density. At every time step, the strain is
localized along a single shear-band which is a spanning path on the lattice
chosen through an extremum condition. The dynamics consists of randomly
changing the `density' of the sites only along the shear band, and then
repeating the procedure of locating the extremal path and changing it. Starting
from an initially uncorrelated density field, it is found that this dynamics
leads to a slow compaction along with a non-trivial patterning of the system,
with high density regions forming which shelter long-lived low-density valleys.
Further, as a result of these large density fluctuations, the shear band which
was initially equally likely to be found anywhere on the lattice, gets
progressively trapped for longer and longer periods of time. This state is
however meta-stable, and the system continues to evolve slowly in a manner
reminiscent of glassy dynamics. Several quantities have been studied
numerically which support this picture and elucidate the unusual system-size
effects at play.Comment: 11 pages, 15 figures revtex, submitted to PRE, See also:
cond-mat/020921
Pattern Formation in Interface Depinning and Other Models: Erratically Moving Spatial Structures
We study erratically moving spatial structures that are found in a driven
interface in a random medium at the depinning threshold. We introduce a
bond-disordered variant of the Sneppen model and study the effect of extremal
dynamics on the morphology of the interface. We find evidence for the formation
of a structure which moves along with the growth site. The time average of the
structure, which is defined with respect to the active spot of growth, defines
an activity-centered pattern. Extensive Monte Carlo simulations show that the
pattern has a tail which decays slowly, as a power law. To understand this sort
of pattern formation, we write down an approximate integral equation involving
the local interface dynamics and long-ranged jumps of the growth spot. We
clarify the nature of the approximation by considering a model for which the
integral equation is exactly derivable from an extended master equation.
Improvements to the equation are considered by adding a second coupled equation
which provides a self-consistent description. The pattern, which defines a
one-point correlation function, is shown to have a strong effect on ordinary
space-fixed two-point correlation functions. Finally we present evidence that
this sort of pattern formation is not confined to the interface problem, but is
generic to situations in which the activity at succesive time steps is
correlated, as for instance in several other extremal models. We present
numerical results for activity-centered patterns in the Bak-Sneppen model of
evolution and the Zaitsev model of low-temperature creep.Comment: RevTeX, 18 pages, 19 eps-figures, To appear in Phys. Rev.
Self-Reported Cognitive Function and Mental Health Diagnoses among Former Professional American-Style Football Players
Clinical practice strongly relies on patients' self-report. Former professional American-style football players are hesitant to seek help for mental health problems, but may be more willing to report cognitive symptoms. We sought to assess the association between cognitive symptoms and diagnosed mental health problems and quality of life among a cohort of former professional players. In a cross-sectional design, we assessed self-reported cognitive function using items from the Quality of Life in Neurological Disorders (Neuro-QOL) Item Bank. We then compared mental health diagnoses and quality of life, assessed by items from the Patient-Reported Outcome Measurement Information System (PROMIS Âź), between former professional players reporting daily problems in cognitive function and former players not reporting daily cognitive problems. Of the 3758 former professional players included in the analysis, 40.0% reported daily problems due to cognitive dysfunction. Former players who reported daily cognitive problems were more likely to also report depression (18.0% vs. 3.3%, odds ratio [OR] = 6.42, 95% confidence interval [CI] [4.90-8.40]) and anxiety (19.1% vs. 4.3%, OR = 5.29, 95% CI [4.14-6.75]) than those without daily cognitive problems. Further, former players reporting daily cognitive problems were more likely to report memory loss and attention deficit(/hyperactivity) disorder and poorer general mental health, lower quality of life, less satisfaction with social activities and relationships, and more emotional problems. These findings highlight the potential of an assessment of cognitive symptoms for identifying former players with mental health, social, and emotional problems
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