981 research outputs found
Inner-shelf circulation and sediment dynamics on a series of shoreface-connected ridges offshore of Fire Island, NY
Locations along the inner-continental shelf offshore of Fire Island, NY, are characterized by a series of shoreface-connected ridges (SFCRs). These sand ridges have approximate dimensions of 10 km in length, 3 km spacing, and up to similar to 8 m ridge to trough relief and are oriented obliquely at approximately 30 degrees clockwise from the coastline. Stability analysis from previous studies explains how sand ridges such as these could be formed and maintained by storm-driven flows directed alongshore with a key maintenance mechanism of offshore deflected flows over ridge crests and onshore in the troughs. We examine these processes both with a limited set of idealized numerical simulations and analysis of observational data. Model results confirm that alongshore flows over the SFCRs exhibit offshore veering of currents over the ridge crests and onshore-directed flows in the troughs, and demonstrate the opposite circulation pattern for a reverse wind. To further investigate these maintenance processes, oceanographic instruments were deployed at seven sites on the SFCRs offshore of Fire Island to measure water levels, ocean currents, waves, suspended sediment concentrations, and bottom stresses from January to April 2012. Data analysis reveals that during storms with winds from the northeast, the processes of offshore deflection of currents over ridge crests and onshore in the troughs were observed, and during storm events with winds from the southwest, a reverse flow pattern over the ridges occurred. Computations of suspended sediment fluxes identify periods that are consistent with SFCR maintenance mechanisms. Alongshore winds from the northeast drove fluxes offshore on the ridge crest and onshore in the trough that would tend to promote ridge maintenance. However, alongshore winds from the southwest drove opposite circulations. The wind fields are related to different storm types that occur in the region (low-pressure systems, cold fronts, and warm fronts). From the limited data set, we identify that low-pressure systems drive sediment fluxes that tend to promote stability and maintain the SFCRs while cold front type storms appear to drive circulations that are in the opposite sense and may not be a supporting mechanism for ridge maintenance
Quantum whistling in superfluid 4He
Fundamental considerations predict that macroscopic quantum systems such as
superfluids and the electrons in superconductors will exhibit oscillatory
motion when pushed through a small constriction. Here we report the observation
of these oscillations between two reservoirs of superfluid 4He partitioned by
an array of nanometer-sized apertures. They obey the Josephson frequency
equation and are coherent amongst all the apertures. This discovery at the
relatively high temperature of 2K (2000 times higher than related phenomena in
3He) may pave the way for a new class of practical rotation sensors of
unprecedented precision.Comment: 6 pages, 3 figures, to be published in Natur
Evaluation of procalcitonin-guided antimicrobial stewardship in patients admitted to hospital with COVID-19 pneumonia
BACKGROUND: Procalcitonin is a biomarker that may be able to identify patients with COVID-19 pneumonia who do not require antimicrobials for bacterial respiratory tract co-infections. OBJECTIVES: To evaluate the safety and effectiveness of a procalcitonin-guided algorithm in rationalizing empirical antimicrobial prescriptions in non-critically ill patients with COVID-19 pneumonia. METHODS: Retrospective, single-site, cohort study in adults hospitalized with confirmed or suspected COVID-19 pneumonia and receiving empirical antimicrobials for potential bacterial respiratory tract co-infection. Regression models were used to compare the following outcomes in patients with and without procalcitonin testing within 72 h of starting antimicrobials: antimicrobial consumption (DDD); antimicrobial duration; a composite safety outcome of death, admission to HDU/ICU or readmission to hospital within 30 days; and length of admission. Procalcitonin levels of ≤0.25 ng/L were interpreted as negatively predictive of bacterial co-infection. Effects were expressed as ratios of means (ROM) or prevalence ratios (PR) accordingly. RESULTS: 259 patients were included in the final analysis. Antimicrobial use was lower in patients who had procalcitonin measured within 72 h of starting antimicrobials: mean antimicrobial duration 4.4 versus 5.4 days, adjusted ROM 0.7 (95% CI 0.6–0.9); mean antimicrobial consumption 6.8 versus 8.4 DDD, adjusted ROM 0.7 (95% CI 0.6–0.8). Both groups had similar composite safety outcomes (adjusted PR 0.9; 95% CI 0.6–1.3) and lengths of admission (adjusted ROM 1.3; 95% CI 0.9–1.6). CONCLUSIONS: A procalcitonin-guided algorithm may allow for the safe reduction of antimicrobial usage in hospitalized non-critically ill patients with COVID-19 pneumonia
Cataract surgery: expectations of patients assisted during a community project in SĂŁo Paulo, state of SĂŁo Paulo, Brazil
The role of clathrin in post-golgi trafficking in toxoplasma gondii
Apicomplexan parasites are single eukaryotic cells with a highly polarised secretory system that contains unique secretory organelles (micronemes and rhoptries) that are required for host cell invasion. In contrast, the role of the endosomal system is poorly understood in these parasites. With many typical endocytic factors missing, we speculated that endocytosis depends exclusively on a clathrin-mediated mechanism. Intriguingly, in Toxoplasma gondii we were only able to observe the endogenous clathrin heavy chain 1 (CHC1) at the Golgi, but not at the parasite surface. For the functional characterisation of Toxoplasma gondii CHC1 we generated parasite mutants conditionally expressing the dominant negative clathrin Hub fragment and demonstrate that CHC1 is essential for vesicle formation at the trans-Golgi network. Consequently, the functional ablation of CHC1 results in Golgi aberrations, a block in the biogenesis of the unique secretory microneme and rhoptry organelles, and of the pellicle. However, we found no morphological evidence for clathrin mediating endocytosis in these parasites and speculate that they remodelled their vesicular trafficking system to adapt to an intracellular lifestyle
Therapeutic hypothermia for acute ischaemic stroke. Results of a European multicentre, randomised, phase III clinical trial
Introduction:
We assessed whether modest systemic cooling started within 6 hours of symptom onset improves functional outcome at three months in awake patients with acute ischaemic stroke.
Patients and methods:
In this European randomised open-label clinical trial with blinded outcome assessment, adult patients with acute ischaemic stroke were randomised to cooling to a target body temperature of 34.0–35.0°C, started within 6 h after stroke onset and maintained for 12 or 24 h , versus standard treatment. The primary outcome was the score on the modified Rankin Scale at 91 days, as analysed with ordinal logistic regression.
Results:
The trial was stopped after inclusion of 98 of the originally intended 1500 patients because of slow recruitment and cessation of funding. Forty-nine patients were randomised to hypothermia versus 49 to standard treatment. Four patients were lost to follow-up. Of patients randomised to hypothermia, 15 (31%) achieved the predefined cooling targets. The primary outcome did not differ between the groups (odds ratio for good outcome, 1.01; 95% confidence interval, 0.48–2.13; p = 0.97). The number of patients with one or more serious adverse events did not differ between groups (relative risk, 1.22; 95% confidence interval, 0.65–1.94; p = 0.52).
Discussion:
In this trial, cooling to a target of 34.0–35.0°C and maintaining this for 12 or 24 h was not feasible in the majority of patients. The final sample was underpowered to detect clinically relevant differences in outcomes.
Conclusion:
Before new trials are launched, the feasibility of cooling needs to be improved
Stimulated optomechanical excitation of surface acoustic waves in a microdevice
Stimulated Brillouin interaction between sound and light, known to be the
strongest optical nonlinearity common to all amorphous and crystalline
dielectrics, has been widely studied in fibers and bulk materials but rarely in
optical microresonators. The possibility of experimentally extending this
principle to excite mechanical resonances in photonic microsystems, for sensing
and frequency reference applications, has remained largely unexplored. The
challenge lies in the fact that microresonators inherently have large free
spectral range, while the phase matching considerations for the Brillouin
process require optical modes of nearby frequencies but with different
wavevectors. We rely on high-order transverse optical modes to relax this
limitation. Here we report on the experimental excitation of mechanical
resonances ranging from 49 to 1400 MHz by using forward Brillouin scattering.
These natural mechanical resonances are excited in ~100 um silica microspheres,
and are of a surface-acoustic whispering-gallery type
Human Endometrial Side Population Cells Exhibit Genotypic, Phenotypic and Functional Features of Somatic Stem Cells
During reproductive life, the human endometrium undergoes around 480 cycles of growth, breakdown and regeneration should pregnancy not be achieved. This outstanding regenerative capacity is the basis for women's cycling and its dysfunction may be involved in the etiology of pathological disorders. Therefore, the human endometrial tissue must rely on a remarkable endometrial somatic stem cells (SSC) population. Here we explore the hypothesis that human endometrial side population (SP) cells correspond to somatic stem cells. We isolated, identified and characterized the SP corresponding to the stromal and epithelial compartments using endometrial SP genes signature, immunophenotyping and characteristic telomerase pattern. We analyzed the clonogenic activity of SP cells under hypoxic conditions and the differentiation capacity in vitro to adipogenic and osteogenic lineages. Finally, we demonstrated the functional capability of endometrial SP to develop human endometrium after subcutaneous injection in NOD-SCID mice. Briefly, SP cells of human endometrium from epithelial and stromal compartments display genotypic, phenotypic and functional features of SSC
An exploration into the impact of exposure to community violence and hope on children's perceptions of well-being: a South African perspective
The study aims to explore the relationship between exposure to community
violence, hope, and well-being. More specifically, the study aims to ascertain whether
hope is a stronger predictor of well-being than exposure to violence. Stratified
random sampling was used to select a sample of 566 adolescents aged 14–17 years,
from both high violence and low violence areas in Cape Town, South Africa. A
questionnaire consisting of Snyder’s Children’s Hope Scale, the Recent Exposure to
Violence Scale and the KIDSCREEN-52 was used. Data analysis techniques included
descriptive statistics, correlations, and multiple regression. A positive, significant
relationship was found between children’s hope and their well-being. Although
exposure to community violence was found to be significantly correlated with wellbeing,
the relationship was negligible.While exposure to community violence and hope
were found to be significant predictors of well-being, hope emerged as a stronger
predictor of child well-being than exposure to community violence.Department of HE and Training approved lis
Resonant Thermoelectric Nanophotonics
Photodetectors are typically based either on photocurrent generation from electron–hole pairs in semiconductor structures or on bolometry for wavelengths that are below bandgap absorption. In both cases, resonant plasmonic and nanophotonic structures have been successfully used to enhance performance. Here, we show subwavelength thermoelectric nanostructures designed for resonant spectrally selective absorption, which creates large localized temperature gradients even with unfocused, spatially uniform illumination to generate a thermoelectric voltage. We show that such structures are tunable and are capable of wavelength-specific detection, with an input power responsivity of up to 38 V W^(–1), referenced to incident illumination, and bandwidth of nearly 3 kHz. This is obtained by combining resonant absorption and thermoelectric junctions within a single suspended membrane nanostructure, yielding a bandgap-independent photodetection mechanism. We report results for both bismuth telluride/antimony telluride and chromel/alumel structures as examples of a potentially broader class of resonant nanophotonic thermoelectric materials for optoelectronic applications such as non-bandgap-limited hyperspectral and broadband photodetectors
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