2,256 research outputs found
kHz Quasi-Periodic Oscillations in the low-mass X-ray binary 4U 0614+09
We report on a comprehensive analysis of the kilohertz (above 300 Hz)
quasi-periodic oscillations (kHz QPOs) detected from the neutron star low-mass
X-ray binary 4U0614+09 with the Rossi X-ray Timing Explorer (RXTE). With a much
larger data set than previously analyzed (all archival data from February 1996
up to October 2007), we first investigate the reality of the 1330 Hz QPO
reported by van Straaten et al. (2000). This QPO would be of particular
interest since it has the highest frequency reported for any source. A thorough
analysis of the same observation fails to confirm the detection. On the other
hand, over our extended data set, the highest QPO frequency we measure for the
upper kHz QPO is at about 1224 Hz; a value which is fully consistent with the
maximum values observed in similar systems. Second, we demonstrate that the
frequency dependence of the quality factor and amplitude of the lower and upper
kHz QPOs follow the systematic trends seen in similar systems (Barret et al.,
2006). In particular, 4U0614+09 shows a drop of the quality factor of the lower
kHz QPO above 700 Hz. If this is due to an approach to the innermost stable
circular orbit, it implies a neutron star mass of about 1.9 solar masses.
Finally, when analyzing the data over fixed durations, we have found a gap in
the frequency distribution of the upper QPO, associated with a local minimum of
its amplitude. A similar gap is not present in the distribution of the lower
QPO frequencies, suggesting some cautions when interpreting frequency ratio
distributions, based on the occurrence of the lower QPO only.Comment: 10 pages, 6 color figures, 2 tables, Accepted for publication in
MNRA
Validity and reliability of the Chinese critical thinking disposition inventory
2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Symbolic Partial-Order Execution for Testing Multi-Threaded Programs
We describe a technique for systematic testing of multi-threaded programs. We
combine Quasi-Optimal Partial-Order Reduction, a state-of-the-art technique
that tackles path explosion due to interleaving non-determinism, with symbolic
execution to handle data non-determinism. Our technique iteratively and
exhaustively finds all executions of the program. It represents program
executions using partial orders and finds the next execution using an
underlying unfolding semantics. We avoid the exploration of redundant program
traces using cutoff events. We implemented our technique as an extension of
KLEE and evaluated it on a set of large multi-threaded C programs. Our
experiments found several previously undiscovered bugs and undefined behaviors
in memcached and GNU sort, showing that the new method is capable of finding
bugs in industrial-size benchmarks.Comment: Extended version of a paper presented at CAV'2
Flexibility in the perceptual span during reading: evidence from Mongolian
Readers can acquire useful information from only a narrow region of text around each fixation (the perceptual span), which extends asymmetrically in the direction of reading. Studies with bilingual readers have additionally shown that this asymmetry reverses with changes in horizontal reading direction. However, little is known about the perceptual span's flexibility following orthogonal (vertical vs. horizontal) changes in reading direction, because of the scarcity of vertical writing systems and because changes in reading direction often are confounded with text orientation. Accordingly, we assessed effects in a language (Mongolian) that avoids this confound, in which text is conventionally read vertically but can also be read horizontally. Sentences were presented normally or in a gaze-contingent paradigm in which a restricted region of text was displayed normally around each fixation and other text was degraded. The perceptual span effects on reading rates were similar in both reading directions. These findings therefore provide a unique (nonconfounded) demonstration of perceptual span flexibility
Enhanced Luminescence of Eu-Doped TiO2Nanodots
Monodisperse and spherical Eu-doped TiO2nanodots were prepared on substrate by phase-separation-induced self-assembly. The average diameters of the nanodots can be 50 and 70 nm by changing the preparation condition. The calcined nanodots consist of an amorphous TiO2matrix with Eu3+ions highly dispersed in it. The Eu-doped TiO2nanodots exhibit intense luminescence due to effective energy transfer from amorphous TiO2matrix to Eu3+ions. The luminescence intensity is about 12.5 times of that of Eu-doped TiO2film and the luminescence lifetime can be as long as 960 μs
Differential Detection of Genetic Loci Underlying Stem and Root Lignin Content in Populus
In this study, we established a comprehensive genetic map with a large number of progeny from a three-generation hybrid Populus intercross, and phenotyped the lignin content, S/G ratio and 28 cell wall subcomponents both in stems and roots for the mapping individuals. Phenotypic analysis revealed that lignin content and syringyl-to-guaiacyl (S/G) ratio using pyrolysis molecular beam mass spectroscopy (pyMBMS) varied among mapping individuals. Phenotypic analysis revealed that stem lignin content is significantly higher than that in root and the quantified traits can be classified into four distinct groups, with strong correlations observed among components within organs. Altogether, 179 coordinating QTLs were detected, and they were co-localized into 49 genetic loci, 27 of which appear to be pleiotropic. Many of the detected genetic loci were detected differentially in stem and root. This is the first report of separate genetic loci controlling cell wall phenotypes above and below ground. These results suggest that it may be possible to modify lignin content and composition via breed and/or engineer as a means of simultaneously improving Populus for cellulosic ethanol production and carbon sequestration
Myeloperoxidase gene-463G > A polymorphism and premature coronary artery disease
We investigated the association between myeloperoxidase gene -463G > A polymorphism and premature coronary artery disease (CAD) in two Chinese population samples: 229 patients and 230 controls. Genotypes were determined by ligase detection reaction-polymerase chain reaction sequencing and the grouping technique. We found lower frequencies of both the A/A genotype and the A allele in patients (p < 0.05). Multivariate logistic regression showed that the risk of premature CAD in subjects carrying the AA genotype was reduced by 83% in relation to individuals carrying the G/G genotype (OR = 0.172, 95% CI: 0.057-0.526, p = 0.002). Our results indicate that -463G > A polymorphism of the myeloperoxidase gene is associated with premature CAD in Chinese individuals, suggesting that the AA genotype is a protective factor against premature CAD
Low-Energy Probes of a Warped Extra Dimension
We investigate a natural realization of a light Abelian hidden sector in an
extended Randall-Sundrum (RS) model. In addition to the usual RS bulk we
consider a second warped space containing a bulk U(1)_x gauge theory with a
characteristic IR scale of order a GeV. This Abelian hidden sector can couple
to the standard model via gauge kinetic mixing on a common UV brane. We show
that if such a coupling induces significant mixing between the lightest U(1)_x
gauge mode and the standard model photon and Z, it can also induce significant
mixing with the heavier U(1)_x Kaluza-Klein (KK) modes. As a result it might be
possible to probe several KK modes in upcoming fixed-target experiments and
meson factories, thereby offering a new way to investigate the structure of an
extra spacetime dimension.Comment: 26 pages, 1 figure, added references, corrected minor typos, same as
journal versio
Structure and Luminescence Properties of Eu3+-Doped Cubic Mesoporous Silica Thin Films
Eu3+ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol–gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu3+ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of5D0-7F1 and 5D0-7F2 of Eu3+ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu3+ ions-doped mesoporous silica thin films increases linearly with increasing Eu3+ concentration
Genetic Variants in TGF-β Pathway Are Associated with Ovarian Cancer Risk
The transforming growth factor-β (TGF-β) signaling pathway is involved in a diverse array of cellular processes responsible for tumorigenesis. In this case-control study, we applied a pathway-based approach to evaluate single-nucleotide polymorphisms (SNPs) in the TGF-β signaling pathway as predictors of ovarian cancer risk. We systematically genotyped 218 SNPs from 21 genes in the TGF-β signaling pathway in 417 ovarian cancer cases and 417 matched control subjects. We analyzed the associations of these SNPs with ovarian cancer risk, performed haplotype analysis and identified potential cumulative effects of genetic variants. We also performed analysis to identify higher-order gene-gene interactions influencing ovarian cancer risk. Individual SNP analysis showed that the most significant SNP was SMAD6: rs4147407, with an adjusted odds ratio (OR) of 1.60 (95% confidence interval [CI], 1.14–2.24, P = 0.0066). Cumulative genotype analysis of 13 SNPs with significant main effects exhibited a clear dose-response trend of escalating risk with increasing number of unfavorable genotypes. In gene-based analysis, SMAD6 was identified as the most significant gene associated with ovarian cancer risk. Haplotype analysis further revealed that two haplotype blocks within SMAD6 were significantly associated with decreased ovarian cancer risk, as compared to the most common haplotype. Gene-gene interaction analysis further categorized the study population into subgroups with different ovarian cancer risk. Our findings suggest that genetic variants in the TGF-β signaling pathway are associated with ovarian cancer risk and may facilitate the identification of high-risk subgroups in the general population
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