407 research outputs found
Electronic structure of multiquantum giant vortex states in mesoscopic superconducting disks
We report self-consistent calculations of the microscopic electronic
structure of the so-called giant vortex states. These novel multiquantum vortex
states, detected by recent magnetization measurements on submicron disks, are
qualitatively different from the Abrikosov vortices in the bulk. We find that,
in addition to multiple branches of bound states in the core region, the local
tunneling density of states exhibits Tomasch oscillations due to the
single-particle interference arising from quantum confinement. These features
should be directly observable by scanning tunneling spectroscopy.Comment: 5 pages, 4 figure
5-Hydroxy-1-aryl-4-pyridone-2-carboxylic Acid Esters as Chelating and Extracting Agents. I. Extraction and Separation of Tantalum(V) and Niobium(V) from Oxalate Solutions
The extraction of niobium and tantalum from oxalate solution
has been studied using the esters of 5-hydroxy-l-aryl-4-pyridone-
2-carboxylic acid as extractants. The influence of the concentration
of hydrochloric, sulphuric, hydrofluoric and oxalic acids on the
extraction of niobium and tantalum has been investigated. The
dependence of the extraction of these metals upon the concentration
of the extractant in the organic phase was also studied. A
procedure for the separation of niobium from tantalum directly
from oxalate solution is described. The radionuclides 95Nb and 182Ta
were used for the determination of the distribution coefficients
5-Hydroxy-1-aryl-4-pyridone-2-carboxylic Acid Esters as Chelating and Extracting Agents. I. Extraction and Separation of Tantalum(V) and Niobium(V) from Oxalate Solutions
The extraction of niobium and tantalum from oxalate solution
has been studied using the esters of 5-hydroxy-l-aryl-4-pyridone-
2-carboxylic acid as extractants. The influence of the concentration
of hydrochloric, sulphuric, hydrofluoric and oxalic acids on the
extraction of niobium and tantalum has been investigated. The
dependence of the extraction of these metals upon the concentration
of the extractant in the organic phase was also studied. A
procedure for the separation of niobium from tantalum directly
from oxalate solution is described. The radionuclides 95Nb and 182Ta
were used for the determination of the distribution coefficients
Phase Fluctuations and Pseudogap Properties: Influence of Nonmagnetic Impurities
The presence of nonmagnetic impurities in a 2D ``bad metal'' depresses the
superconducting Berezinskii-Kosterlitz-Thouless transition temperature, while
leaving the pairing energy scale unchanged. Thus the region of the pseudogap
non-superconducting phase, where the modulus of the order parameter is non-zero
but its phase is random, and which opens at the pairing temperature is
substantially bigger than for the clean system. This supports the premise that
fluctuations in the phase of the order parameter can in principle describe the
pseudogap phenomena in high- materials over a rather wide range of
temperatures and carrier densities. The temperature dependence of the bare
superfluid density is also discussed.Comment: 11 pages, LaTeX, 1 EPS figure; final version to appear in
Low.Temp.Phy
Probing superconducting phase fluctuations from the current noise spectrum of pseudogaped metal-superconductor tunnel junctions
We study the current noise spectra of a tunnel junction of a metal with
strong pairing phase fluctuation and a superconductor. It is shown that there
is a characteristic peak in the noise spectrum at the intrinsic Josephson
frequency when is smaller than the pairing gap but
larger than the pairing scattering rate. In the presence of an AC voltage, the
tunnelling current noise shows a series of characteristic peaks with increasing
DC voltage. Experimental observation of these peaks will give direct evidence
of the pair fluctuation in the normal state of high- superconductors and
from the half width of the peaks the pair decay rate can be estimated.Comment: 4 pages, 3 figure
False-negative malaria rapid diagnostic test results and their impact on community-based malaria surveys in sub- Saharan Africa
Surveillance and diagnosis of Plasmodium falciparum malaria relies predominantly on rapid diagnostic tests (RDTs). However, false-negative RDT results are known to occur for a variety of reasons, including operator error, poor storage conditions, pfhrp2/3 gene deletions, poor performance of specific RDT brands and lots, and low-parasite-density infections. We used RDT and microscopy results from 85,000 children enrolled in Demographic Health Surveys and Malaria Indicator Surveys from 2009 to 2015 across 19 countries to explore the distribution of and risk factors for false-negative RDTs in Sub40 Saharan Africa, where malaria’s impact is greatest. We sought to (i) identify spatial and demographic patterns of false-negative RDT (FN-RDT) results, defined as a negative RDT but positive gold-standard microscopy test, and (ii) estimate the percentage of infections missed within community-based malaria surveys due to FN-RDT results. Across all studies, 19.9% [95% CI: 19.0 – 20.9] of microscopy-positive subjects were negative by RDT. The distribution of FN-RDT results was spatially heterogeneous. The variance in FN-RDT results was best explained by the prevalence of malaria, with an increase in FN46 RDT results observed at lower transmission intensities, among younger subjects, and in urban areas. The observed proportion of FN-RDT results was not predicted by differences in RDT brand or lot performance alone. These findings characterise how the probability of detection by RDTs varies in different transmission settings and emphasize the need for careful interpretation of prevalence estimates based on surveys employing RDTs alone. Further studies are needed to characterise the cost-effectiveness of improved malaria diagnostics (e.g. PCR or highly sensitive RDTs) in community52 based surveys, especially in regions of low transmission intensity or high urbanicity
Neutrophil extracellular traps formation and clearance is enhanced in fever and attenuated in hypothermia
Fever and hypothermia represent two opposite strategies for fighting systemic inflammation. Fever results in immune activation; hypothermia is associated with energy conservation. Systemic Inflammatory Response Syndrome (SIRS) remains a significant cause of mortality worldwide. SIRS can lead to a broad spectrum of clinical symptoms but importantly, patients can develop fever or hypothermia. During infection, polymorphonuclear cells (PMNs) such as neutrophils prevent pathogen dissemination through the formation of neutrophil extracellular traps (NETs) that ensnare and kill bacteria. However, when dysregulated, NETs also promote host tissue damage. Herein, we tested the hypothesis that temperature modulates NETs homeostasis in response to infection and inflammation. NETs formation was studied in response to infectious (Escherichia coli, Staphylococcus aureus) and sterile (mitochondria) agents. When compared to body temperature (37°C), NETs formation increased at 40°C; interestingly, the response was stunted at 35°C and 42°C. While CD16+ CD49d+ PMNs represent a small proportion of the neutrophil population, they formed ~45-85% of NETs irrespective of temperature. Temperature increased formyl peptide receptor 1 (FPR1) expression to a differential extent in CD16+ CD49d- vs. CD49d+ PMNSs, suggesting further complexity to neutrophil function in hypo/hyperthermic conditions. The capacity of NETs to induce Toll-like receptor 9 (TLR9)-mediated NF-κB activation was found to be temperature independent. Interestingly, NET degradation was enhanced at higher temperatures, which corresponded with greater plasma DNase activity in response to temperature increase. Collectively, our observations indicate that NETs formation and clearance are enhanced at 40°C whilst temperatures of 35°C and 42°C attenuate this response. Targeting PMN-driven immunity may represent new venues for intervention in pathological inflammation
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