514 research outputs found
Electric field dependence of thermal conductivity of a granular superconductor: Giant field-induced effects predicted
The temperature and electric field dependence of electronic contribution to
the thermal conductivity (TC) of a granular superconductor is considered within
a 3D model of inductive Josephson junction arrays. In addition to a
low-temperature maximum of zero-field TC K(T,0) (controlled by mutual
inductance L_0 and normal state resistivity R_n), the model predicts two major
effects in applied electric field: (i) decrease of the linear TC, and (ii)
giant enhancement of the nonlinear (i.e., grad T-dependent) TC with
[K(T,E)-K(T,0)]/K(T,0) reaching 500% for parallel electric fields E=E_T
(E_T=S_0|grad T| is an "intrinsic" thermoelectric field). A possiblity of
experimental observation of the predicted effects in granular superconductors
is discussed.Comment: 5 LaTeX pages (jetpl.sty included), 2 EPS figures. To be published in
JETP Letter
Inhaled nitric oxide for high-altitude pulmonary edema
BACKGROUND. Pulmonary hypertension is a hallmark of high-altitude pulmonary edema and may contribute to its pathogenesis. When administered by inhalation, nitric oxide, an endothelium-derived relaxing factor, attenuates the pulmonary vasoconstriction produced by short-term hypoxia. METHODS. We studied the effects of inhaled nitric oxide on pulmonary-artery pressure and arterial oxygenation in 18 mountaineers prone to high-altitude pulmonary edema and 18 mountaineers resistant to this condition in a high altitude laboratory (altitude, 4559 m). We also obtained lung-perfusion scans before and during nitric oxide inhalation to gain further insight into the mechanism of action of nitric oxide. RESULTS. In the high-altitude laboratory, subjects prone to high-altitude pulmonary edema had more pronounced pulmonary hypertension and hypoxemia than subjects resistant to high-altitude pulmonary edema. Arterial oxygen saturation was inversely related to the severity of pulmonary hypertension (r=-0.50, P=0.002). In subjects prone to high-altitude pulmonary edema, the inhalation of nitric oxide (40 ppm for 15 minutes) produced a decrease in mean (+/-SD) systolic pulmonary-artery pressure that was three times larger than the decrease in subjects resistant to such edema (25.9+/-8.9 vs. 8.7+/-4.8 mm Hg, P<0.001). Inhaled nitric oxide improved arterial oxygenation in the 10 subjects who had radiographic evidence of pulmonary edema (arterial oxygen saturation increased from 67+/-10 to 73+/-12 percent, P=0.047), whereas it worsened oxygenation in subjects resistant to high-altitude pulmonary edema. The nitric oxide-induced improvement in arterial oxygenation in subjects with high-altitude pulmonary edema was accompanied by a shift in blood flow in the lung away from edematous segments and toward nonedematous segments. CONCLUSIONS. The inhalation of nitric oxide improves arterial oxygenation in high-altitude pulmonary edema, and this beneficial effect may be related to its favorable action on the distribution of blood flow in the lungs. A defect in nitric nitric oxide synthesis may contribute to high-altitude pulmonary edema
Enhancing Resource Management through Prediction-based Policies
Task-based programming models are emerging as a promising alternative to make
the most of multi-/many-core systems. These programming models rely on runtime
systems, and their goal is to improve application performance by properly
scheduling application tasks to cores. Additionally, these runtime systems
offer policies to cope with application phases that lack in parallelism to fill
all cores. However, these policies are usually static and favor either
performance or energy efficiency. In this paper, we have extended a task-based
runtime system with a lightweight monitoring and prediction infrastructure that
dynamically predicts the optimal number of cores required for each application
phase, thus improving both performance and energy efficiency. Through the
execution of several benchmarks in multi-/many-core systems, we show that our
prediction-based policies have competitive performance while improving energy
efficiency when compared to state of the art policies.Comment: Postprint submitted and published at Euro-Par2020: International
European Conference on Parallel and Distributed Computing (Springer)
(https://link.springer.com/chapter/10.1007%2F978-3-030-57675-2_31
Current-voltage characteristics of diluted Josephson-junction arrays: scaling behavior at current and percolation threshold
Dynamical simulations and scaling arguments are used to study the
current-voltage (IV) characteristics of a two-dimensional model of resistively
shunted Josephson-junction arrays in presence of percolative disorder, at zero
external field. Two different limits of the Josephson-coupling concentration
are considered, where is the percolation threshold. For
and zero temperature, the IV curves show power-law behavior above a disorder
dependent critical current. The power-law behavior and critical exponents are
consistent with a simple scaling analysis. At and finite temperature ,
the results show the scaling behavior of a T=0 superconducting transition. The
resistance is linear but vanishes for decreasing with an apparent
exponential behavior. Crossover to non-linearity appears at currents
proportional to , with a thermal-correlation length exponent
consistent with the corresponding value for the diluted XY model at
.Comment: Revtex, 9 postscript pages, to appear in Phys. Rev.
Causes of death and associated factors over a decade of follow-up in a cohort of people living with HIV in rural Tanzania
BACKGROUND: Nearly half of HIV-related deaths occur in East and Southern Africa, yet data on causes of death (COD) are scarce. We determined COD and associated factors among people living with HIV (PLHIV) in rural Tanzania. METHODS: PLHIV attending the Chronic Diseases Clinic of Ifakara, Morogoro are invited to enrol in the Kilombero and Ulanga Antiretroviral Cohort (KIULARCO). Among adults (>/= 15 years) enrolled in 2005-2018, with follow-up through April 2019, we classified COD in comprehensive classes and as HIV- or non-HIV-related. In the subset of participants enrolled in 2013-2018 (when data were more complete), we assessed cause-specific mortality using cumulative incidences, and associated factors using proportional hazards models. RESULTS: Among 9871 adults (65% female, 26% CD4 count < 100 cells/mm(3)), 926 (9%) died, among whom COD were available for 474 (51%), with missing COD mainly in earlier years. The most common COD were tuberculosis (N = 127, 27%), non-AIDS-related infections (N = 72, 15%), and other AIDS-related infections (N = 59, 12%). Cardiovascular and renal deaths emerged as important COD in later calendar years, with 27% of deaths in 2018 attributable to cardiovascular causes. Most deaths (51%) occurred within the first six months following enrolment. Among 3956 participants enrolled in 2013-2018 (N = 203 deaths, 200 with COD ascertained), tuberculosis persisted as the most common COD (25%), but substantial proportions of deaths from six months after enrolment onwards were attributable to renal (14%), non-AIDS-related infections (13%), other AIDS-related infections (10%) and cardiovascular (10%) causes. Factors associated with higher HIV-related mortality were sex, younger age, living in Ifakara town, HIV status disclosure, hospitalisation, not being underweight, lower CD4 count, advanced WHO stage, and gaps in care. Factors associated with higher non-HIV-related mortality included not having an HIV-positive partner, lower CD4 count, advanced WHO stage, and gaps in care. CONCLUSION: Incidence of HIV-related mortality was higher than that of non-HIV-related mortality, even in more recent years, likely due to late presentation. Tuberculosis was the leading specific COD identified, particularly soon after enrolment, while in later calendar years cardiovascular and renal causes emerged as important, emphasising the need for improved screening and management
Dynamic transition in vortex flow in strongly disordered Josephson junction arrays and superconducting thin films
We study the dynamics of vortices in strongly disordered Josephson
junction arrays and superconducting films driven by a current. We find a
dynamic phase transition in vortex flow at a current . Below
there is plastic flow characterized by an average-velocity correlation length
scale in the direction of motion, which diverges when approaching
. Above we find a moving vortex phase with homogeneous flow and
short range smectic order. A finite size analysis shows that this phase becomes
asymptotically a liquid for large length scales.Comment: 4 pages, 4 figure
Diluted Josephson-junction arrays in a magnetic field: phase coherence and vortex glass thresholds
The effects of random dilution of junctions on a two-dimensional
Josephson-junction array in a magnetic field are considered. For rational
values of the average flux quantum per plaquette , the superconducting
transition temperature vanishes, for increasing dilution, at a critical value
, while the vortex ordering remains stable up to , much
below the value corresponding to the geometric percolation threshold. For
, the array behaves as a zero-temperature vortex-glass.
Numerical results for from defect energy calculations are presented
which are consistent with this scenario.Comment: 4 pages, 4 figures, to appear in Phys. Rev.
Stigma-directed services (Stig2Health) to improve 'linkage to care' for people living with HIV in rural Tanzania: study protocol for a nested pre-post implementation study within the Kilombero and Ulanga Antiretroviral Cohort
Background: HIV-related stigma is a major barrier to the timely linkage and retention of patients in HIV care in sub-Saharan Africa, where most people living with HIV/AIDS reside. In this implementation study we aim to evaluate the effect of stigma-directed services on linkage to care and other health outcomes in newly diagnosed HIV-positive patients. Methods: In a nested project of the Kilombero and Ulanga Antiretroviral Cohort in rural Tanzania, we conduct a prospective observational pre-post study to assess the impact of a bundle of stigma-directed services for newly diagnosed HIV positive patients. Stigma-directed services, delivered by a lay person living with HIV, are i) post-test counseling, ii) post-test video-assisted teaching, iii) group support therapy and group health education, and iv) mobile health. Patients receiving stigma services (enrolled from 1 (st) February 2020 to 31 (st) August 2021) are compared to a historical control receiving the standard of care (enrolled from 1 (st) July 2017 to 1 (st) February 2019). The primary outcome is 'linkage to care'. Secondary endpoints are retention in care, viral suppression, death and clinical failure at 6-12 months (up to 31 (st) August 2022). Self-reported stigma and depression are assessed using the Berger Stigma scale and the PHQ-9 questionnaire, respectively. The sample size calculation was based on cohort data from 2018. Assuming a pre-intervention cohort of 511 newly diagnosed adults of whom 346 (68%) were in care and on antiretroviral treatment (ART) at 2 months, a 10% increase in linkage (from 70 to 80%), a two-sided type I error rate of 5%, and 90% power, 321 adults are required for the post-implementation group. Discussion: We expect that integration of stigma-directed services leads to an increase of proportions of patients in care and on ART. The findings will provide guidance on how to integrate stigma-directed services into routine care in rural sub-Saharan Africa
Phase-coherence threshold and vortex-glass state in diluted Josephson-junction arrays in a magnetic field
We study numerically the interplay of phase coherence and vortex-glass state
in two-dimensional Josephson-junction arrays with average rational values of
flux quantum per plaquette and random dilution of junctions. For ,
we find evidence of a phase coherence threshold value , below the
percolation concentration of diluted junctions , where the superconducting
transition vanishes. For the array behaves as a
zero-temperature vortex glass with nonzero linear resistance at finite
temperatures. The zero-temperature critical currents are insensitive to
variations in in the vortex glass region while they are strongly
dependent in the phase coherent region.Comment: 6 pages, 4 figures, to appear in Phys. Rev.
Peptides derived from hookworm anti-inflammatory proteins suppress inducible colitis in mice and inflammatory cytokine production by human cells
A decline in the prevalence of parasites such as hookworms appears to be correlated with the rise in non-communicable inflammatory conditions in people from high- and middle-income countries. This correlation has led to studies that have identified proteins produced by hookworms that can suppress inflammatory bowel disease (IBD) and asthma in animal models. Hookworms secrete a family of abundant netrin-domain containing proteins referred to as AIPs (Anti-Inflammatory Proteins), but there is no information on the structure-function relationships. Here we have applied a downsizing approach to the hookworm AIPs to derive peptides of 20 residues or less, some of which display anti-inflammatory effects when co-cultured with human peripheral blood mononuclear cells and oral therapeutic activity in a chemically induced mouse model of acute colitis. Our results indicate that a conserved helical region is responsible, at least in part, for the anti-inflammatory effects. This helical region has potential in the design of improved leads for treating IBD and possibly other inflammatory conditions
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