346 research outputs found
The electron density is smooth away from the nuclei
We prove that the electron densities of electronic eigenfunctions of atoms
and molecules are smooth away from the nuclei.Comment: 16 page
Black-hole quasinormal modes and scalar glueballs in a finite-temperature AdS/QCD model
We use the holographic AdS/QCD soft-wall model to investigate the spectrum of
scalar glueballs in a finite temperature plasma. In this model, glueballs are
described by a massless scalar field in an AdS_5 black hole with a dilaton
soft-wall background. Using AdS/CFT prescriptions, we compute the boundary
retarded Green's function. The corresponding thermal spectral function shows
quasiparticle peaks at low temperatures. We also compute the quasinormal modes
of the scalar field in the soft-wall black hole geometry. The temperature and
momentum dependences of these modes are analyzed. The positions and widths of
the peaks of the spectral function are related to the frequencies of the
quasinormal modes. Our numerical results are found employing the power series
method and the computation of Breit-Wigner resonances.Comment: Revision: Results unchanged. More discussions on the model and on the
results. References added. 28 pages, 7 figures, 5 table
An infinite family of magnetized Morgan-Morgan relativistic thin disks
Applying the Horsk\'y-Mitskievitch conjecture to the empty space solutions of
Morgan and Morgan due to the gravitational field of a finite disk, we have
obtained the corresponding solutions of the Einstein-Maxwell equations. The
resulting expressions are simply written in terms of oblate spheroidal
coordinates and the solutions represent fields due to magnetized static thin
disk of finite extension. Now, although the solutions are not asymptotically
flat, the masses of the disks are finite and the energy-momentum tensor agrees
with the energy conditions. Furthermore, the magnetic field and the circular
velocity show an acceptable physical behavior.Comment: Submitted to IJTP. This paper is a revised and extended version of a
paper that was presented at arXiv:1006.203
A review of the discovery reach of directional Dark Matter detection
Cosmological observations indicate that most of the matter in the Universe is Dark Matter. Dark Matter in the form of Weakly Interacting Massive Particles (WIMPs) can be detected directly, via its elastic scattering off target nuclei. Most current direct detection experiments only measure the energy of the recoiling nuclei. However, directional detection experiments are sensitive to the direction of the nuclear recoil as well. Due to the Sun’s motion with respect to the Galactic rest frame, the directional recoil rate has a dipole feature, peaking around the direction of the Solar motion. This provides a powerful tool for demonstrating the Galactic origin of nuclear recoils and hence unambiguously detecting Dark Matter. Furthermore, the directional recoil distribution depends on the WIMP mass, scattering cross section and local velocity distribution. Therefore, with a large number of recoil events it will be possible to study the physics of Dark Matter in terms of particle and astrophysical properties. We review the potential of directional detectors for detecting and characterizing WIMPs
Plasmonic excitations in noble metals: The case of Ag
The delicate interplay between plasmonic excitations and interband
transitions in noble metals is described by means of {\it ab initio}
calculations and a simple model in which the conduction electron plasmon is
coupled to the continuum of electron-hole pairs. Band structure effects,
specially the energy at which the excitation of the -like bands takes place,
determine the existence of a subthreshold plasmonic mode, which manifests
itself in Ag as a sharp resonance at 3.8 eV. However, such a resonance is not
observed in the other noble metals. Here, this different behavior is also
analyzed and an explanation is provided.Comment: 9 pages, 8 figure
Scientific Highlights of the HETE-2 Mission
The HETE-2 mission has been highly productive. It has observed more than 250
GRBs so far. It is currently localizing 25 - 30 GRBs per year, and has
localized 43 GRBs to date. Twenty-one of these localizations have led to the
detection of X-ray, optical, or radio afterglows, and as of now, 11 of the
bursts with afterglows have known redshifts. HETE-2 has confirmed the
connection between GRBs and Type Ic supernovae, a singular achievement and
certainly one of the scientific highlights of the mission so far. It has
provided evidence that the isotropic-equivalent energies and luminosities of
GRBs are correlated with redshift, implying that GRBs and their progenitors
evolve strongly with redshift. Both of these results have profound implications
for the nature of GRB progenitors and for the use of GRBs as a probe of
cosmology and the early universe. HETE-2 has placed severe constraints on any
X-ray or optical afterglow of a short GRB. It is also solving the mystery of
"optically dark' GRBs, and revealing the nature of X-ray flashes.Comment: 10 pages, 9 figures, to appear in proc. "The Restless High-Energy
Universe", Royal Tropical Institute, Amsterdam; revised text, added ref
Impact of long-term erythromycin therapy on the oropharyngeal microbiome and resistance gene reservoir in non-cystic fibrosis bronchiectasis
Published 18 April 2018Long-term macrolide therapy reduces rates of pulmonary exacerbation in bronchiectasis. However, little is known about the potential for macrolide therapy to alter the composition and function of the oropharyngeal commensal microbiota or to increase the carriage of transmissible antimicrobial resistance. We assessed the effect of long-term erythromycin on oropharyngeal microbiota composition and the carriage of transmissible macrolide resistance genes in 84 adults with bronchiectasis, enrolled in the Bronchiectasis and Low-dose Erythromycin Study (BLESS) 48-week placebo-controlled trial of twice-daily erythromycin ethylsuccinate (400 mg). Oropharyngeal microbiota composition and macrolide resistance gene carriage were determined by 16S rRNA gene amplicon sequencing and quantitative PCR, respectively. Long-term erythromycin treatment was associated with a significant increase in the relative abundance of oropharyngeal Haemophilus parainfluenzae (P = 0.041) and with significant decreases in the relative abundances of Streptococcus pseudopneumoniae (P = 0.024) and Actinomyces odontolyticus (P = 0.027). Validation of the sequencing results by quantitative PCR confirmed a significant decrease in the abundance of Actinomyces spp. (P = 0.046). Erythromycin treatment did not result in a significant increase in the number of subjects who carried erm(A), erm(B), erm(C), erm(F), mef(A/E), and msrA macrolide resistance genes. However, the abundance of erm(B) and mef(A/E) gene copies within carriers who had received erythromycin increased significantly (P < 0.05). Our findings indicate that changes in oropharyngeal microbiota composition resulting from long-term erythromycin treatment are modest and are limited to a discrete group of taxa. Associated increases in levels of transmissible antibiotic resistance genes within the oropharyngeal microbiota highlight the potential for this microbial system to act as a reservoir for resistance.IMPORTANCE Recent demonstrations that long-term macrolide therapy can prevent exacerbations in chronic airways diseases have led to a dramatic increase in their use. However, little is known about the wider, potentially adverse impacts of these treatments. Substantial disruption of the upper airway commensal microbiota might reduce its contribution to host defense and local immune regulation, while increases in macrolide resistance carriage would represent a serious public health concern. Using samples from a randomized controlled trial, we show that low-dose erythromycin given over 48 weeks influences the composition of the oropharyngeal commensal microbiota. We report that macrolide therapy is associated with significant changes in the relative abundances of members of the Actinomyces genus and with significant increases in the carriage of transmissible macrolide resistance. Determining the clinical significance of these changes, relative to treatment benefit, now represents a research priority.Jocelyn M. Choo, Guy C. J. Abell, Rachel Thomson, Lucy Morgan, Grant Waterer, David L. Gordon, Steven L. Taylor, Lex E. X. Leong, Steve L. Wesselingh, Lucy D. Burr, Geraint B. Roger
Discovery and validation of plasma proteomic biomarkers relating to brain amyloid burden by SOMAscan assay.
Plasma proteins have been widely studied as candidate biomarkers to predict brain amyloid deposition to increase recruitment efficiency in secondary prevention clinical trials for Alzheimer's disease. Most such biomarker studies are targeted to specific proteins or are biased toward high abundant proteins.
4001 plasma proteins were measured in two groups of participants (discovery group = 516, replication group = 365) selected from the European Medical Information Framework for Alzheimer's disease Multimodal Biomarker Discovery study, all of whom had measures of amyloid.
A panel of proteins (n = 44), along with age and apolipoprotein E (APOE) ε4, predicted brain amyloid deposition with good performance in both the discovery group (area under the curve = 0.78) and the replication group (area under the curve = 0.68). Furthermore, a causal relationship between amyloid and tau was confirmed by Mendelian randomization.
The results suggest that high-dimensional plasma protein testing could be a useful and reproducible approach for measuring brain amyloid deposition
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
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