3,155 research outputs found
High resolution global gridded data for use in population studies
Recent years have seen substantial growth in openly available satellite and other geospatial data layers, which represent a range of metrics relevant to global human population mapping at fine spatial scales. The specifications of such data differ widely and therefore the harmonisation of data layers is a prerequisite to constructing detailed and contemporary spatial datasets which accurately describe population distributions. Such datasets are vital to measure impacts of population growth, monitor change, and plan interventions. To this end the WorldPop Project has produced an open access archive of 3 and 30 arc-second resolution gridded data. Four tiled raster datasets form the basis of the archive: (i) Viewfinder Panoramas topography clipped to Global ADMinistrative area (GADM) coastlines; (ii) a matching ISO 3166 country identification grid; (iii) country area; (iv) and slope layer. Further layers include transport networks, landcover, nightlights, precipitation, travel time to major cities, and waterways. Datasets and production methodology are here described. The archive can be downloaded both from the WorldPop Dataverse Repository and the WorldPop Project websit
Controls upon the location and size of glacial overdeepenings
Overdeepening is an important glaciological and geomorphological process that has the potential to influence the response of ice masses to climatic changes. We have examined several hundred glacial overdeepenings proximal to/ within Labrador, Canada, to investigate the controls upon overdeepening location and size. Our analyses show that overdeepening appears to correlate strongly with glacial confluence and, importantly, the correlation is strongest where confluence-geometry indicates the speed up of ice-flow. Further, we find that the magnitude of ice-flow speed up correlates with overdeepening depth only for confluences situated in or near major geological fault-zones. Our findings therefore support the hypothesis that overdeepening can be initiated by an increase in ice velocity. Further, we conclude that overdeepening is most efficacious where fractured bedrock enables efficient quarrying
Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind are Dominated by Kinetic Instabilities
We use magnetic helicity to characterise solar wind fluctuations at
proton-kinetic scales from Wind observations. For the first time, we separate
the contributions to helicity from fluctuations propagating at angles
quasi-parallel and oblique to the local mean magnetic field, . We
find that the helicity of quasi-parallel fluctuations is consistent with
Alfv\'en-ion cyclotron and fast magnetosonic-whistler modes driven by proton
temperature anisotropy instabilities and the presence of a relative drift
between -particles and protons. We also find that the helicity of
oblique fluctuations has little dependence on proton temperature anisotropy and
is consistent with fluctuations from the anisotropic turbulent cascade. Our
results show that parallel-propagating fluctuations at proton-kinetic scales in
the solar wind are dominated by proton temperature anisotropy instabilities and
not the turbulent cascade. We also provide evidence that the behaviour of
fluctuations at these scales is independent of the origin and macroscopic
properties of the solar wind.Comment: Accepted for publication in ApJL. 6 Pages, 3 figures, 1 tabl
The Role of Proton-Cyclotron Resonance as a Dissipation Mechanism in Solar Wind Turbulence: A Statistical Study at Ion-Kinetic Scales
We use magnetic field and ion moment data from the MFI and SWE instruments
onboard the Wind spacecraft to study the nature of solar wind turbulence at
ion-kinetic scales. We analyze the spectral properties of magnetic field
fluctuations between 0.1 and 5.5 Hz over 2012 using an automated routine,
computing high-resolution 92 s power and magnetic helicity spectra. To ensure
the spectral features are physical, we make the first in-flight measurement of
the MFI `noise-floor' using tail-lobe crossings of the Earth's magnetosphere
during early 2004. We utilize Taylor's hypothesis to Doppler-shift into the
spacecraft frequency frame, finding that the spectral break observed at these
frequencies is best associated with the proton-cyclotron resonance scale,
, compared to the proton inertial length and proton gyroscale
. This agreement is strongest when we consider periods where
, and is consistent with a spectral break at for
and for . We also find that
the coherent magnetic helicity signature observed at these frequencies is
bounded at low frequencies by and its absolute value reaches a maximum
at . These results hold in both slow and fast wind streams, but with a
better correlation in the more Alfv\'enic fast wind where the helicity
signature is strongest. We conclude that these findings are consistent with
proton-cyclotron resonance as an important mechanism for dissipation of
turbulent energy in the solar wind, occurring at least half the time in our
selected interval. However, we do not rule out additional mechanisms.Comment: 16 pages, 11 figures. Accepted for publication in The Astrophysical
Journal. Please contact authors to obtain WIND MFI 'noise-floor' for use in
other studie
A critical ethnographic study of discriminatory social practice during clinical practice in emergency medical care
Background: Post-apartheid, South Africa adopted an inclusive education system that was intended to be free of unfair discrimination. This qualitative study examines the experiences and perceptions of racial discrimination between Emergency Medical Care (EMC) students, clinical mentors, and patients within an Emergency Medical Service (EMS) during clinical practice. Understanding the nature of such discrimination is critical for redress. Methods: Within the conceptual framework of Critical Race Theory, critical ethnographic methodology explored how discriminatory social practice manifests during clinical practice. Semi-structured interviews enabled thematic analysis. We purposively sampled 13 undergraduate EMC students and 5 Emergency Care (EC) providers. Results: EMC student participants reported experiences of racial and gender discrimination during work-integrated learning (WIL) as they were treated differently on the basis of race and gender. Language was used as an intentional barrier to isolate students from the patients during WIL because EC providers would intentionally speak in a language not understood by the student and failed to translate vital medical information about the case. This conduct prevented some students from engaging in clinical decision-making. Conclusions: Unfair discrimination within the pre-hospital setting have an impact on the learning opportunities of EMC students. Such practice violates basic human rights and has the potential to negatively affect the clinical management of patients, thus it has the potential to violate patient’s rights. This study confirms the existence of discriminatory practices during WIL which is usually unreported. The lack of a structured approach to redress the discrimination causes a lack of inclusivity and unequal access to clinical education in a public clinical platform
Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2
We demonstrate the continuous and reversible tuning of the optical band gap
of suspended monolayer MoS2 membranes by as much as 500 meV by applying very
large biaxial strains. By using chemical vapor deposition (CVD) to grow
crystals that are highly impermeable to gas, we are able to apply a pressure
difference across suspended membranes to induce biaxial strains. We observe the
effect of strain on the energy and intensity of the peaks in the
photoluminescence (PL) spectrum, and find a linear tuning rate of the optical
band gap of 99 meV/%. This method is then used to study the PL spectra of
bilayer and trilayer devices under strain, and to find the shift rates and
Gr\"uneisen parameters of two Raman modes in monolayer MoS2. Finally, we use
this result to show that we can apply biaxial strains as large as 5.6% across
micron sized areas, and report evidence for the strain tuning of higher level
optical transitions.Comment: Nano Lett., Article ASA
High-Density Lipoprotein Cholesterol and Particle Concentrations, Carotid Atherosclerosis, and Coronary Events MESA (Multi-Ethnic Study of Atherosclerosis)
ObjectivesThe purpose of this study was to evaluate independent associations of high-density lipoprotein cholesterol (HDL-C) and particle (HDL-P) concentrations with carotid intima-media thickness (cIMT) and incident coronary heart disease (CHD).BackgroundHDL-C is inversely related to CHD, and also to triglycerides, low-density lipoprotein particles (LDL-P), and related metabolic risk. HDL-P associations with CHD may be partially independent of these factors.MethodsIn a multiethnic study of 5,598 men and women ages 45 to 84 years old, without baseline CHD, excluding subjects on lipid-lowering medications, triglycerides >400 mg/dl, or missing values, we evaluated associations of HDL-C and nuclear magnetic resonance spectroscopy-measured HDL-P with cIMT and incident CHD (myocardial infarction, CHD death, and angina, n = 227 events; mean 6.0 years follow-up). All models were adjusted for age, sex, ethnicity, hypertension, and smoking.ResultsHDL-C and HDL-P correlated with each other (ρ = 0.69) and LDL-P (ρ = −0.38, −0.25, respectively, p < 0.05 for all). For (1 SD) higher HDL-C (15 mg/dl) or HDL-P (6.64 μmol/l), cIMT differences were − 26.1 (95% confidence interval [CI]: −34.7 to −17.4) μm and −30.1 (95% CI: −38.8 to − 21.4) μm, and CHD hazard ratios were 0.74 (95% CI: 0.63 to 0.88) and 0.70 (95% CI: 0.59 to 0.82), respectively. Adjusted for each other and LDL-P, HDL-C was no longer associated with cIMT (2.3; 95% CI: − 9.5 to 14.2 μm) or CHD (0.97; 95% CI: 0.77 to 1.22), but HDL-P remained independently associated with cIMT (−22.2; 95% CI: − 33.8 to −10.6 μm) and CHD (0.75; 95% CI: 0.61 to 0.93). Interactions by sex, ethnicity, diabetes, and high-sensitivity C-reactive protein were not significant.ConclusionsAdjusting for each other and LDL-P substantially attenuated associations of HDL-C, but not HDL-P, with cIMT and CHD. Potential confounding by related lipids or lipoproteins should be carefully considered when evaluating HDL-related risk
Au-catalyzed biaryl coupling to generate 5- to 9-membered rings: turnover-limiting reductive elimination versus π-complexation
The intramolecular gold–catalyzed arylation of arenes by aryltrimethylsilanes has been investigated from both a mechanistic and preparative aspect. The reaction generates five to nine membered rings, and of the 44 examples studied, ten include a heteroatom (N, O). The tethering of the arene to the arylsilane not only provides a tool to probe the impact of the conforma-tional flexibility of Ar–Au–Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes - substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facili-tated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron-demand and conformational freedom on the rate of reductive elimination from diaryl gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the electronics of the arene and changes from reductive elimination to π-complexation for arenes bearing strongly electron-withdrawing substitu-ents (σ >0.43). Reductive elimination is accelerated by electron-donating substituents (□ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings results in faster reductive elimination from Ar-Au(X)-Ar, and to the π-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step
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