6,440 research outputs found
The finite temperature QCD using 2+1 flavors of domain wall fermions at N_t = 8
We study the region of the QCD phase transition using 2+1 flavors of domain
wall fermions (DWF) and a lattice volume with a fifth dimension
of . The disconnected light quark chiral susceptibility, quark number
susceptibility and the Polyakov loop suggest a chiral and deconfining crossover
transition lying between 155 and 185 MeV for our choice of quark mass and
lattice spacing. In this region the lattice scale deduced from the Sommer
parameter is GeV, the pion mass is MeV
and the kaon mass is approximately physical. The peak in the chiral
susceptibility implies a pseudo critical temperature MeV
where the first error is associated with determining the peak location and the
second with our unphysical light quark mass and non-zero lattice spacing. The
effects of residual chiral symmetry breaking on the chiral condensate and
disconnected chiral susceptibility are studied using several values of the
valence .Comment: 41 pages, 10 tables, 13 figure
The microbiome in bronchiectasis
Bronchiectasis is increasing in prevalence worldwide, yet current treatments available are limited to those alleviating symptoms and reducing exacerbations. The pathogenesis of the disease and the inflammatory, infective and molecular drivers of disease progression are not fully understood, making the development of novel treatments challenging. Understanding the role bacteria play in disease progression has been enhanced by the use of next-generation sequencing techniques such as 16S rRNA sequencing. The microbiome has not been extensively studied in bronchiectasis, but existing data show lung bacterial communities dominated by Pseudomonas, Haemophilus and Streptococcus, while exhibiting intraindividual stability and large interindividual variability. Pseudomonas- and Haemophilus-dominated microbiomes have been shown to be linked to severe disease and frequent exacerbations. Studies completed to date are limited in size and do not fully represent all clinically observed disease subtypes. Further research is required to understand the microbiomes role in bronchiectasis disease progression. This review discusses recent developments and future perspectives on the lung microbiome in bronchiectasis
Zebrafish Comparative Genomics and the Origins of Vertebrate Chromosomes
To help understand mechanisms of vertebrate genome evolution, we have compared zebrafish and tetrapod gene maps. It has been suggested that translocations are fixed more frequently than inversions in mammals. Gene maps showed that blocks of conserved syntenies between zebrafish and humans were large, but gene orders were frequently inverted and transposed. This shows that intrachromosomal rearrangements have been fixed more frequently than translocations. Duplicated chromosome segments suggest that a genome duplication occurred in ray-fin phylogeny, and comparative studies suggest that this event happened deep in the ancestry of teleost fish. Consideration of duplicate chromosome segments shows that at least 20% of duplicated gene pairs may be retained from this event. Despite genome duplication, zebrafish and humans have about the same number of chromosomes, and zebrafish chromosomes are mosaically orthologous to several human chromosomes. Is this because of an excess of chromosome fissions in the human lineage or an excess of chromosome fusions in the zebrafish lineage? Comparative analysis suggests that an excess of chromosome fissions in the tetrapod lineage may account for chromosome numbers and provides histories for several human chromosomes
Hadron Structure on the Lattice
A few chosen nucleon properties are described from a lattice QCD perspective:
the nucleon sigma term and the scalar strangeness in the nucleon; the vector
form factors in the nucleon, including the vector strangeness contribution, as
well as parity breaking effects like the anapole and electric dipole moment;
and finally the axial and tensor charges of the nucleon. The status of the
lattice calculations is presented and their potential impact on phenomenology
is discussed.Comment: 17 pages, 9 figures; proceedings of the Conclusive Symposium of the
Collaborative Research Center 443 "Many-body structure of strongly
interacting systems", Mainz, February 23-25, 201
In Vivo and In Vitro Pharmacological Studies of Methoxycarbonyl-Carboetomidate
Background—We previously developed two etomidate analogs that retain etomidate’s favorable hemodynamic properties, but whose adrenocortical effects are reduced in duration or magnitude. Methoxycarbonyl-etomidate (MOC-etomidate) is rapidly metabolized and ultra-short acting whereas (R)-ethyl 1-(1-phenylethyl)-1H-pyrrole-2-carboxylate (carboetomidate) does not potently inhibit 11?-hydroxylase. We hypothesized that MOC-etomidate’s labile ester could be incorporated into carboetomidate to produce a new agent that possesses favorable properties individually found in each agent. We describe the synthesis and pharmacology of methoxycarbonyl-(R)-ethyl 1-(1-phenylethyl)-1H-pyrrole-2-carboxylate (MOC-carboetomidate), a “soft” analog of carboetomidate. Methods—MOC-carboetomidate’s octanol:water partition coefficient was determined chromatographically and compared with those of etomidate, carboetomidate, and MOC-etomidate. MOC-carboetomidate’s EC50 and ED50 for loss of righting reflexes (LORR) were measured in tadpoles and rats, respectively. Its effect on gamma-aminobutyric acid A (GABAA) receptor function was assessed using two-microelectrode voltage clamp electrophysiological techniques and its metabolic stability was determined in pooled rat blood using high performance liquid chromatography. Its duration of action and effects on arterial blood pressure and adrenocortical function were assessed in rats. Results—MOC-carboetomidate’s octanol:water partition coefficient was 3300 ± 280, whereas those for etomidate, carboetomidate, and MOC-etomidate were 800 ± 180, 15000 ± 3700, and 190 ± 25, respectively. MOC-carboetomidate’s EC50 for LORR in tadpoles was 9 ± 1 µM and its EC50 for LORR in rats was 13 ± 5 mg/kg. At 13 µM, MOC-carboetomidate enhanced GABAA receptor currents by 400 ± 100%. Its metabolic half-life in pooled rat blood was 1.3 minutes. The slope of a plot of the duration of LORR in rats versus the logarithm of the hypnotic dose was significantly shallower for MOC-carboetomidate than for carboetomidate (4 ± 1 vs. 15 ± 3, respectively; p = 0. 0004123). At hypnotic doses, the effects of MOC-carboetomidate on arterial blood pressure and adrenocortical function were not significantly different from those of vehicle alone. Conclusions—MOC-carboetomidate is a GABAA receptor modulator with potent hypnotic activity that is more rapidly metabolized and cleared from the brain than carboetomidate, maintains hemodynamic stability similar to carboetomidate, and does not suppress adrenocortical function
Additive and multiplicative hazards modeling for recurrent event data analysis
<p>Abstract</p> <p>Background</p> <p>Sequentially ordered multivariate failure time or recurrent event duration data are commonly observed in biomedical longitudinal studies. In general, standard hazard regression methods cannot be applied because of correlation between recurrent failure times within a subject and induced dependent censoring. Multiplicative and additive hazards models provide the two principal frameworks for studying the association between risk factors and recurrent event durations for the analysis of multivariate failure time data.</p> <p>Methods</p> <p>Using emergency department visits data, we illustrated and compared the additive and multiplicative hazards models for analysis of recurrent event durations under (i) a varying baseline with a common coefficient effect and (ii) a varying baseline with an order-specific coefficient effect.</p> <p>Results</p> <p>The analysis showed that both additive and multiplicative hazards models, with varying baseline and common coefficient effects, gave similar results with regard to covariates selected to remain in the model of our real dataset. The confidence intervals of the multiplicative hazards model were wider than the additive hazards model for each of the recurrent events. In addition, in both models, the confidence interval gets wider as the revisit order increased because the risk set decreased as the order of visit increased.</p> <p>Conclusions</p> <p>Due to the frequency of multiple failure times or recurrent event duration data in clinical and epidemiologic studies, the multiplicative and additive hazards models are widely applicable and present different information. Hence, it seems desirable to use them, not as alternatives to each other, but together as complementary methods, to provide a more comprehensive understanding of data.</p
Electronic and nuclear contributions to time-resolved optical and X-ray absorption spectra of hematite and insights into photoelectrochemical performance
Ultrafast time-resolved studies of photocatalytic thin films can provide a wealth of information crucial for understanding and thereby improving the performance of these materials by directly probing electronic structure, reaction intermediates, and charge carrier dynamics. The interpretation of transient spectra, however, can be complicated by thermally induced structural distortions, which appear within the first few picoseconds following excitation due to carrier–phonon scattering. Here we present a comparison of ex situ steady-state thermal difference spectra and transient absorption spectra spanning from NIR to hard X-ray energies of hematite thin films grown by atomic layer deposition. We find that beyond the first 100 picoseconds, the transient spectra measured for all excitation wavelengths and probe energies are almost entirely due to thermal effects as the lattice expands in response to the ultrafast temperature jump and then cools to room temperature on the microsecond timescale. At earlier times, a broad excited state absorption band that is assigned to free carriers appears at 675 nm, and the lifetime and shape of this feature also appear to be mostly independent of excitation wavelength. The combined spectroscopic data, which are modeled with density functional theory and full multiple scattering calculations, support an assignment of the optical absorption spectrum of hematite that involves two LMCT bands that nearly span the visible spectrum. Our results also suggest a framework for shifting the ligand-to-metal charge transfer absorption bands of ferric oxide films from the near-UV further into the visible part of the solar spectrum to improve solar conversion efficiency
The X-Ray Zurich Environmental Study (X-ZENS). I. Chandra and XMM-Newton observations of active galactic nuclei in galaxies in nearby groups
We describe X-ray observations with Chandra and XMM-Newton of 18 galaxy
groups (M_group ~ 1-6x10^13 Msolar, z~0.05) from the Zurich Environmental Study
(ZENS). We aim to establish the frequency and properties, unaffected by host
galaxy dilution and obscuration, of AGNs in central and satellite galaxy
members, also as a function of halo-centric distance. X-ray point-source
detections are reported for 22 of 177 observed galaxies, down to a limit of
f_(0.5-8 keV) ~ 5x10^-15 erg cm^-2 s^-1, corresponding to a limiting luminosity
of L_(0.5-8 keV)~3x10^40 erg s^-1. With the majority of the X-ray sources
attributed to AGNs of low-to-moderate levels (L/L_Edd>~10^-4), we discuss the
detection rate in the context of the occupation of AGNs to halos of this mass
scale and redshift, and compare the structural/morphological properties between
AGN-active and non-active galaxies of different rank and location within the
group halos. We see a slight tendency for AGN hosts to have either relatively
brighter/denser disks (or relatively fainter/diffuse bulges) than non-active
galaxies of similar mass. At galaxy mass scales <10^11 Msolar, central galaxies
appear to be a factor ~4 more likely to host AGNs than satellite galaxies of
similar mass. This effect, coupled with the tendency for AGNs to reside in
massive galaxies, explains the (weak) trend for AGNs to be preferentially found
in the inner regions of groups, with no detectable trend with halo-centric
distance in the frequency of AGNs within the satellite population. Finally, our
data support other analyses in finding that the rate of decline with redshift
of AGN activity in groups matches that of the global AGN population, indicating
that either AGNs occur preferentially in groups, or that the evolution rate is
independent of halo mass. These trends are of potential importance, and require
X-ray coverage of a larger sample to be solidly confirmed.Comment: 18 pages, 13 figures, submitted to The Astrophysical Journal, this is
a revised version that addresses the referee's comment
Robust Optical Richness Estimation with Reduced Scatter
Reducing the scatter between cluster mass and optical richness is a key goal
for cluster cosmology from photometric catalogs. We consider various
modifications to the red-sequence matched filter richness estimator of Rozo et
al. (2009), and evaluate their impact on the scatter in X-ray luminosity at
fixed richness. Most significantly, we find that deeper luminosity cuts can
reduce the recovered scatter, finding that sigma_lnLX|lambda=0.63+/-0.02 for
clusters with M_500c >~ 1.6e14 h_70^-1 M_sun. The corresponding scatter in mass
at fixed richness is sigma_lnM|lambda ~ 0.2-0.3 depending on the richness,
comparable to that for total X-ray luminosity. We find that including blue
galaxies in the richness estimate increases the scatter, as does weighting
galaxies by their optical luminosity. We further demonstrate that our richness
estimator is very robust. Specifically, the filter employed when estimating
richness can be calibrated directly from the data, without requiring a-priori
calibrations of the red-sequence. We also demonstrate that the recovered
richness is robust to up to 50% uncertainties in the galaxy background, as well
as to the choice of photometric filter employed, so long as the filters span
the 4000 A break of red-sequence galaxies. Consequently, our richness estimator
can be used to compare richness estimates of different clusters, even if they
do not share the same photometric data. Appendix 1 includes "easy-bake"
instructions for implementing our optimal richness estimator, and we are
releasing an implementation of the code that works with SDSS data, as well as
an augmented maxBCG catalog with the lambda richness measured for each cluster.Comment: Submitted to ApJ. 20 pages in emulateapj forma
EMPoWER Hybrid Networks: Exploiting Multiple Paths over Wireless and ElectRical Mediums
Several technologies, such as WiFi, Ethernet and power-line communications (PLC), can be used to build residential and enterprise networks. These technologies often co-exist; most networks use WiFi, and buildings are readily equipped with electrical wires that can offer a capacity up to 1 Gbps with PLC. Yet, current networks do not exploit this rich diversity and often operate far below the available capacity. We design, implement, and evaluate EMPoWER, a system that exploits simultaneously several potentially-interfering mediums. It operates at layer 2.5, between the MAC and IP layers, and combines routing (to find multiple concurrent routes) and congestion control (to efficiently balance traffic across the routes). To optimize resource utilization and robustness, both components exploit the heterogeneous nature of the network. They are fair and efficient, and they operate only within the local area network, without affecting remote Internet hosts. We demonstrate the performance gains of EMPoWER, by simulations and experiments on a 22-node testbed. We show that PLC/WiFi, benefiting from the diversity offered by wireless and electrical mediums, provides significant throughput gains (up to 10x) and improves coverage, compared to multi-channel WiFi
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