5,963 research outputs found
A Paclitaxel-Eluting Stent for the Prevention of Coronary Restenosis
Background Intimal hyperplasia and resulting restenosis limit the efficacy of coronary stenting. We studied a coronary stent coated with the antiproliferative agent paclitaxel as a means of preventing restenosis.
Methods We conducted a multicenter, randomized, controlled, triple-blind study to evaluate the ability of a paclitaxel-eluting stent to inhibit restenosis. At three centers, 177 patients with discrete coronary lesions (<15 mm in length, 2.25 to 3.5 mm in diameter) underwent implantation of paclitaxel-eluting stents (low dose, 1.3 µg per square millimeter, or high dose, 3.1 µg per square millimeter) or control stents. Antiplatelet therapies included aspirin with ticlopidine (120 patients), clopidogrel (18 patients), or cilostazol (37 patients). Clinical follow-up was performed at one month and four to six months, and angiographic follow-up at four to six months.
Results Technical success was achieved in 99 percent of the patients (176 of 177). At follow-up, the high-dose group, as compared with the control group, had significantly better results for the degree of stenosis (mean [±SD], 14±21 percent vs. 39±27 percent; P<0.001), late loss of luminal diameter (0.29±0.72 mm vs. 1.04±0.83 mm, P<0.001), and restenosis of more than 50 percent (4 percent vs. 27 percent, P<0.001). Intravascular ultrasound analysis demonstrated a dose-dependent reduction in the volume of intimal hyperplasia (31, 18, and 13 mm3, in the high-dose, low-dose, and control groups, respectively). There was a higher rate of major cardiac events in patients receiving cilostazol than in those receiving ticlopidine or clopidogrel. Among patients receiving ticlopidine or clopidogrel, event-free survival was 98 percent and 100 percent in the high-dose and control groups, respectively, at one month, and 96 percent in both at four to six months.
Conclusions Paclitaxel-eluting stents used with conventional antiplatelet therapy effectively inhibit restenosis and neointimal hyperplasia, with a safety profile similar to that of standard stents.published_or_final_versio
MERS-CoV antibody responses 1 Year after symptom onset, South Korea, 2015
We investigated the kinetics of the Middle East respiratory syndrome coronavirus (MERS-CoV) neutralizing and spike protein antibody titers over the course of 1 year in 11 patients who were confirmed by reverse transcription PCR to have been infected during the outbreak in South Korea in 2015. Robust antibody responses were detected in all survivors who had severe disease; responses remained detectable, albeit with some waning, for <1 year. The duration of viral RNA detection (but not viral load) in sputum significantly correlated with the antibody response magnitude. The MERS S1 ELISA antibody titers correlated well with the neutralizing antibody response. Antibody titers in 4 of 6 patients who had mild illness were undetectable even though most had evidence of pneumonia. This finding implies that MERS-CoV seroepidemiologic studies markedly underestimate the extent of mild and asymptomatic infection. Obtaining convalescent-phase plasma with high antibody titers to treat MERS will be challenging.published_or_final_versio
Comparison of serological assays in human Middle East respiratory syndrome (MERS)-coronavirus infection
Plaque reduction neutralisation tests (PRNT), microneutralisation (MN), Middle East respiratory syndrome (MERS)-spike pseudoparticle neutralisation (ppNT) and MERS S1-enzyme-linked immunosorbent assay (ELISA) antibody titres were compared using 95 sera from 17 patients with MERS, collected two to 46 days after symptom onset. Neutralisation tests correlated well with each other and moderately well with S1 ELISA. Moreover to compare antigenic similarity of genetically diverse MERS-CoV clades, the response of four sera from two patients sampled at two time periods during the course of illness were tested by 90% PRNT. Genetically diverse MERS-CoV clades were antigenically homogenous.published_or_final_versio
Coffee consumption and prostate cancer risk: further evidence for inverse relationship
<p>Abstract</p> <p>Background</p> <p>Higher consumption of coffee intake has recently been linked with reduced risk of aggressive prostate cancer (PC) incidence, although meta-analysis of other studies that examine the association between coffee consumption and overall PC risk remains inconclusive. Only one recent study investigated the association between coffee intake and grade-specific incidence of PC, further evidence is required to understand the aetiology of aggressive PCs. Therefore, we conducted a prospective study to examine the relationship between coffee intake and overall as well as grade-specific PC risk.</p> <p>Methods</p> <p>We conducted a prospective cohort study of 6017 men who were enrolled in the Collaborative cohort study in the UK between 1970 and 1973 and followed up to 31st December 2007. Cox Proportional Hazards Models were used to evaluate the association between coffee consumption and overall, as well as Gleason grade-specific, PC incidence.</p> <p>Results</p> <p>Higher coffee consumption was inversely associated with risk of high grade but not with overall risk of PC. Men consuming 3 or more cups of coffee per day experienced 55% lower risk of high Gleason grade disease compared with non-coffee drinkers in analysis adjusted for age and social class (HR 0.45, 95% CI 0.23-0.90, p value for trend 0.01). This association changed a little after additional adjustment for Body Mass Index, smoking, cholesterol level, systolic blood pressure, tea intake and alcohol consumption.</p> <p>Conclusion</p> <p>Coffee consumption reduces the risk of aggressive PC but not the overall risk.</p
Quantum phase transition in a single-molecule quantum dot
Quantum criticality is the intriguing possibility offered by the laws of
quantum mechanics when the wave function of a many-particle physical system is
forced to evolve continuously between two distinct, competing ground states.
This phenomenon, often related to a zero-temperature magnetic phase transition,
can be observed in several strongly correlated materials such as heavy fermion
compounds or possibly high-temperature superconductors, and is believed to
govern many of their fascinating, yet still unexplained properties. In contrast
to these bulk materials with very complex electronic structure, artificial
nanoscale devices could offer a new and simpler vista to the comprehension of
quantum phase transitions. This long-sought possibility is demonstrated by our
work in a fullerene molecular junction, where gate voltage induces a crossing
of singlet and triplet spin states at zero magnetic field. Electronic tunneling
from metallic contacts into the quantum dot provides here the
necessary many-body correlations to observe a true quantum critical behavior.Comment: 8 pages, 5 figure
Pseudogap temperature as a Widom line in doped Mott insulators
The pseudogap refers to an enigmatic state of matter with unusual physical
properties found below a characteristic temperature in hole-doped
high-temperature superconductors. Determining is critical for
understanding this state. Here we study the simplest model of correlated
electron systems, the Hubbard model, with cluster dynamical mean-field theory
to find out whether the pseudogap can occur solely because of strong coupling
physics and short nonlocal correlations. We find that the pseudogap
characteristic temperature is a sharp crossover between different
dynamical regimes along a line of thermodynamic anomalies that appears above a
first-order phase transition, the Widom line. The Widom line emanating from the
critical endpoint of a first-order transition is thus the organizing principle
for the pseudogap phase diagram of the cuprates. No additional broken symmetry
is necessary to explain the phenomenon. Broken symmetry states appear in the
pseudogap and not the other way around.Comment: 6 pages, 4 figures and supplementary information; published versio
Effective action of three-dimensional extended supersymmetric matter on gauge superfield background
We study the low-energy effective actions for gauge superfields induced by
quantum N=2 and N=4 supersymmetric matter fields in three-dimensional Minkowski
space. Analyzing the superconformal invariants in the N=2 superspace we propose
a general form of the N=2 gauge invariant and superconformal effective action.
The leading terms in this action are fixed by the symmetry up to the
coefficients while the higher order terms with respect to the Maxwell field
strength are found up to one arbitrary function of quasi-primary N=2
superfields constructed from the superfield strength and its covariant spinor
derivatives. Then we find this function and the coefficients by direct quantum
computations in the N=2 superspace. The effective action of N=4 gauge multiplet
is obtained by generalizing the N=2 effective action.Comment: 1+27 pages; v2: minor corrections, references adde
Hidden Magnetism and Quantum Criticality in the Heavy Fermion Superconductor CeRhIn5
With understood exceptions, conventional superconductivity does not coexist
with long-range magnetic order[1]. In contrast, unconventional
superconductivity develops near a boundary separating magnetically ordered and
magnetically disordered phases[2,3]. A maximum in the superconducting
transition temperature Tc develops where this boundary extrapolates to T=0 K,
suggesting that fluctuations associated with this magnetic quantum-critical
point are essential for unconventional superconductivity[4,5]. Invariably
though, unconventional superconductivity hides the magnetic boundary when T <
Tc, preventing proof of a magnetic quantum-critical point[5]. Here we report
specific heat measurements of the pressure-tuned unconventional superconductor
CeRhIn5 in which we find a line of quantum-phase transitions induced inside the
superconducting state by an applied magnetic field. This quantum-critical line
separates a phase of coexisting antiferromagnetism and superconductivity from a
purely unconventional superconducting phase and terminates at a quantum
tetracritical point where the magnetic field completely suppresses
superconductivity. The T->0 K magnetic field-pressure phase diagram of CeRhIn5
is well described with a theoretical model[6,7] developed to explain
field-induced magnetism in the high-Tc cuprates but in which a clear
delineation of quantum-phase boundaries has not been possible. These
experiments establish a common relationship among hidden magnetism, quantum
criticality and unconventional superconductivity in cuprate and heavy-electron
systems, such as CeRhIn5.Comment: journal reference adde
Block of NMDA receptor channels by endogenous neurosteroids: implications for the agonist induced conformational states of the channel vestibule
N-methyl-D-aspartate receptors (NMDARs) mediate synaptic plasticity, and their dysfunction is implicated in multiple brain disorders. NMDARs can be allosterically modulated by numerous compounds, including endogenous neurosteroid pregnanolone sulfate. Here, we identify the molecular basis of the use-dependent and voltage-independent inhibitory effect of neurosteroids on NMDAR responses. The site of action is located at the extracellular vestibule of the receptor's ion channel pore and is accessible after receptor activation. Mutations in the extracellular vestibule in the SYTANLAAF motif disrupt the inhibitory effect of negatively charged steroids. In contrast, positively charged steroids inhibit mutated NMDAR responses in a voltage-dependent manner. These results, in combination with molecular modeling, characterize structure details of the open configuration of the NMDAR channel. Our results provide a unique opportunity for the development of new therapeutic neurosteroid-based ligands to treat diseases associated with dysfunction of the glutamate system
Spectroscopic analysis of finite size effects around a Kondo quantum dot
We consider a simple setup in which a small quantum dot is strongly connected
to a finite size box. This box can be either a metallic box or a finite size
quantum wire.The formation of the Kondo screening cloud in the box strongly
depends on the ratio between the Kondo temperature and the box level spacing.
By weakly connecting two metallic reservoirs to the quantum dot, a detailed
spectroscopic analysis can be performed. Since the transport channels and the
screening channels are almost decoupled, such a setup allows an easier access
to the measure of finite-size effects associated with the finite extension of
the Kondo cloud.Comment: contribution to Les Houches proceeding, ``Quantum magnetism'' 200
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