2,443 research outputs found
Artificial Topological Superconductor by the Proximity Effect
published_or_final_versio
Monitoring of particulate matter concentrations at high altitude ecosystems of Pakistan and China
Particulate matter exhibits different behavior with altitude. A comparative analysis was carried out to monitor PM1, PM2.5, PM4, PM10 and PMTotal at elevations above 3000 m in both China and Pakistan. Real time monitoring of PM was carried out at both sites using a DustTrak DRX (model 8533, TSI Inc.) for 24 hours each. In Pakistan, the average value of PMTotal was 415 ± 16 μg/m3 while in China the value was considerably lower i.e. 110 ± 57 μg/m3. The 24-hour mean values recorded were well above the WHO recommended limit of 25 μg/m3. These results indicate that, even at sites some distance from anthropogenic sources, PM concentrations still pose a health risk
A transient homotypic interaction model for the influenza A virus NS1 protein effector domain
Influenza A virus NS1 protein is a multifunctional virulence factor consisting of an RNA binding domain (RBD), a short linker, an effector domain (ED), and a C-terminal 'tail'. Although poorly understood, NS1 multimerization may autoregulate its actions. While RBD dimerization seems functionally conserved, two possible apo ED dimers have been proposed (helix-helix and strand-strand). Here, we analyze all available RBD, ED, and full-length NS1 structures, including four novel crystal structures obtained using EDs from divergent human and avian viruses, as well as two forms of a monomeric ED mutant. The data reveal the helix-helix interface as the only strictly conserved ED homodimeric contact. Furthermore, a mutant NS1 unable to form the helix-helix dimer is compromised in its ability to bind dsRNA efficiently, implying that ED multimerization influences RBD activity. Our bioinformatical work also suggests that the helix-helix interface is variable and transient, thereby allowing two ED monomers to twist relative to one another and possibly separate. In this regard, we found a mAb that recognizes NS1 via a residue completely buried within the ED helix-helix interface, and which may help highlight potential different conformational populations of NS1 (putatively termed 'helix-closed' and 'helix-open') in virus-infected cells. 'Helix-closed' conformations appear to enhance dsRNA binding, and 'helix-open' conformations allow otherwise inaccessible interactions with host factors. Our data support a new model of NS1 regulation in which the RBD remains dimeric throughout infection, while the ED switches between several quaternary states in order to expand its functional space. Such a concept may be applicable to other small multifunctional proteins
Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay
The decay channel
is studied using a sample of events collected
by the BESIII experiment at BEPCII. A strong enhancement at threshold is
observed in the invariant mass spectrum. The enhancement can be fit
with an -wave Breit-Wigner resonance function with a resulting peak mass of
and a
narrow width that is at the 90% confidence level.
These results are consistent with published BESII results. These mass and width
values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics
Ultrasensitive force detection with a nanotube mechanical resonator
Since the advent of atomic force microscopy, mechanical resonators have been
used to study a wide variety of phenomena, such as the dynamics of individual
electron spins, persistent currents in normal metal rings, and the Casimir
force. Key to these experiments is the ability to measure weak forces. Here, we
report on force sensing experiments with a sensitivity of 12 zN Hz^(-1/2) at a
temperature of 1.2 K using a resonator made of a carbon nanotube. An
ultra-sensitive method based on cross-correlated electrical noise measurements,
in combination with parametric downconversion, is used to detect the
low-amplitude vibrations of the nanotube induced by weak forces. The force
sensitivity is quantified by applying a known capacitive force. This detection
method also allows us to measure the Brownian vibrations of the nanotube down
to cryogenic temperatures. Force sensing with nanotube resonators offers new
opportunities for detecting and manipulating individual nuclear spins as well
as for magnetometry measurements.Comment: Early version. To be published in Nature Nanotechnolog
High magnetic field scales and critical currents in SmFeAs(O,F) crystals: promising for applications
Superconducting technology provides most sensitive field detectors, promising
implementations of qubits and high field magnets for medical imaging and for
most powerful particle accelerators. Thus, with the discovery of new
superconducting materials, such as the iron pnictides, exploring their
potential for applications is one of the foremost tasks. Even if the critical
temperature Tc is high, intrinsic electronic properties might render
applications rather difficult, particularly if extreme electronic anisotropy
prevents effective pinning of vortices and thus severely limits the critical
current density, a problem well known for cuprates. While many questions
concerning microscopic electronic properties of the iron pnictides have been
successfully addressed and estimates point to a very high upper critical field,
their application potential is less clarified. Thus we focus here on the
critical currents, their anisotropy and the onset of electrical dissipation in
high magnetic fields up to 65 T. Our detailed study of the transport properties
of optimally doped SmFeAs(O,F) single crystals reveals a promising combination
of high (>2 x 10^6 A/cm^2) and nearly isotropic critical current densities
along all crystal directions. This favorable intragrain current transport in
SmFeAs(O,F), which shows the highest Tc of 54 K at ambient pressure, is a
crucial requirement for possible applications. Essential in these experiments
are 4-probe measurements on Focused Ion Beam (FIB) cut single crystals with
sub-\mu\m^2 cross-section, with current along and perpendicular to the
crystallographic c-axis and very good signal-to-noise ratio (SNR) in pulsed
magnetic fields. The pinning forces have been characterized by scaling the
magnetically measured "peak effect"
Electronic Origin of High Temperature Superconductivity in Single-Layer FeSe Superconductor
The latest discovery of high temperature superconductivity signature in
single-layer FeSe is significant because it is possible to break the
superconducting critical temperature ceiling (maximum Tc~55 K) that has been
stagnant since the discovery of Fe-based superconductivity in 2008. It also
blows the superconductivity community by surprise because such a high Tc is
unexpected in FeSe system with the bulk FeSe exhibiting a Tc at only 8 K at
ambient pressure which can be enhanced to 38 K under high pressure. The Tc is
still unusually high even considering the newly-discovered intercalated FeSe
system A_xFe_{2-y}Se_2 (A=K, Cs, Rb and Tl) with a Tc at 32 K at ambient
pressure and possible Tc near 48 K under high pressure. Particularly
interesting is that such a high temperature superconductivity occurs in a
single-layer FeSe system that is considered as a key building block of the
Fe-based superconductors. Understanding the origin of high temperature
superconductivity in such a strictly two-dimensional FeSe system is crucial to
understanding the superconductivity mechanism in Fe-based superconductors in
particular, and providing key insights on how to achieve high temperature
superconductivity in general. Here we report distinct electronic structure
associated with the single-layer FeSe superconductor. Its Fermi surface
topology is different from other Fe-based superconductors; it consists only of
electron pockets near the zone corner without indication of any Fermi surface
around the zone center. Our observation of large and nearly isotropic
superconducting gap in this strictly two-dimensional system rules out existence
of node in the superconducting gap. These results have provided an unambiguous
case that such a unique electronic structure is favorable for realizing high
temperature superconductivity
Clinical Implication of Targeting of Cancer Stem Cells
The existence of cancer stem cells (CSCs) is receiving increasing interest particularly due to its potential ability to enter clinical routine. Rapid advances in the CSC field have provided evidence for the development of more reliable anticancer therapies in the future. CSCs typically only constitute a small fraction of the total tumor burden; however, they harbor self-renewal capacity and appear to be relatively resistant to conventional therapies. Recent therapeutic approaches aim to eliminate or differentiate CSCs or to disrupt the niches in which they reside. Better understanding of the biological characteristics of CSCs as well as improved preclinical and clinical trials targeting CSCs may revolutionize the treatment of many cancers. Copyright (c) 2012 S. Karger AG, Base
Care Seeking Behavior of Chest Symptomatics: A Community Based Study Done in South India after the Implementation of the RNTCP
INTRODUCTION: With the creation of the Revised National TB Control Programme (RNTCP), tuberculosis services have become decentralized and more accessible. A 1997 study prior to RNTCP implementation reported that most chest symptomatics accessed first private health care facilities and a general dissatisfaction with government health facilities. The study was repeated post-RNTCP implementation to gain insight into the current care seeking behavior of chest symptomatics. METHODOLOGY: A cross-sectional community-based study carried out between March-August 2008 in 4 sites (2 rural [R] and 2 urban [U]) from the same two districts of Chennai and Madurai, southern India, as in the 1997 study. Six hundred and forty chest symptomatics were identified (R 314; U 326), and detailed interviews were done for 606 (R311; U295). RESULTS: Prevalence of chest symptomatics in the urban and rural areas were 2.7% and 4.9% respectively (p<0.01), and was found to increase with age (Chi-square for trend, p<0.01). Longer delays in seeking care were seen amongst symptomatics above 45 years of age (p 0.01), and those who had taken previous TB treatment (p=0.05). Overall, 50% (222/444) of the chest symptomatics approached a government health care facility first (R 142 (61%); U 80 (38%), p=or  <0.001). This was significantly (p<0.001) more than were observed in the 1997 study, where only 38.4% approached a government facility first. Sixty two (28%) of the 222 made a second visit to a government facility (R26%; U31%), while 17% shifted to a private facility (R14%; U21%). Dissatisfaction with the health care facility was one of the major reasons expressed. CONCLUSIONS: It appears that the RNTCP has had an impact in the community with regard to the availability and accessibility of TB services in government health facilities. However the relatively high levels of subsequent shifting to private health facilities calls for urgent action to make government facilities more patients friendly with quality care facilities in the delivery of RNTCP services
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