1,398 research outputs found
Quasiparticle transport and localization in high-T_c superconductors
We present a theory of the effects of impurity scattering in d_{x^2-y^2}
superconductors and their quantum disordered counterparts, based on a
non-linear sigma model formulation. We show the existence, in a
quasi-two-dimensional system, of a novel spin-metal phase with a non-zero spin
diffusion constant at zero temperature. With decreasing inter-layer coupling,
the system undergoes a quantum phase transition (in a new universality class)
to a localized spin-insulator. Experimental implications for spin and thermal
transport in the high-temperature superconductors are discussed.Comment: 4 pages, 1 figur
A note on Friedmann equation of FRW universe in deformed Horava-Lifshitz gravity from entropic force
With entropic interpretation of gravity proposed by Verlinde, we obtain the
Friedmann equation of the Friedmann-Robertson-Walker universe for the deformed
Ho\v{r}ava-Lifshitz gravity. It is shown that, when the parameter of
Ho\v{r}ava-Lifshitz gravity , the modified Friedmann
equation will go back to the one in Einstein gravity. This results may imply
that the entropic interpretation of gravity is effective for the deformed
Ho\v{r}ava-Lifshitz gravity.Comment: 9 pages, no figure
A parabolic solar collector for harnessing solar energy in Bucaramanga, Colombia
In this work, a solar energy collection system based on a parabolic solar collector adjusted to the conditions and availability of energy was designed to examine this type of collection device and evaluate the energy potential when installed in an educational institution. To do this, data from the historical series of solar radiation compiled by the POWER project (Prediction of Worldwide Energy Resources) were analyzed and compared with data from the Institute of Hydrology, Meteorology and Environmental Studies in Colombia (IDEAM)
Performance of a HER2 testing algorithm specific for p53-abnormal endometrial cancer
Aims Human epidermal growth factor receptor 2 (HER2) amplification in endometrial cancer (EC) is almost completely confined to the p53-abnormal (p53abn) molecular subtype and independent of histological subtype. HER2 testing should therefore be molecular subtype-directed. However, the most optimal approach for HER2 testing in EC has not been fully established. Therefore, we developed an EC-specific HER2 immunohistochemistry (IHC) scoring method and evaluated its reproducibility and performance to establish an optimal diagnostic HER2 testing algorithm for p53abn EC. Methods and results HER2 IHC slides of 78 p53abn EC were scored by six gynaecopathologists according to predefined EC-specific IHC scoring criteria. Interobserver agreement was calculated using Fleiss' kappa and the first-order agreement coefficient (AC1). The consensus IHC score was compared with HER2 dual in-situ hybridisation (DISH) results. Sensitivity and specificity were calculated. A substantial interobserver agreement was found using three- or two-tiered scoring [kappa = 0.675, 95% confidence interval (CI) = 0.633-0.717; AC1 = 0.723, 95% CI = 0.643-0.804 and kappa = 0.771, 95% CI = 0.714-0.828; AC1 = 0.774, 95% CI = 0.684-0.865, respectively]. Sensitivity and specificity for the identification of HER2-positive EC was 100 and 97%, respectively, using a HER2 testing algorithm that recommends DISH in all cases with moderate membranous staining in >10% of the tumour (IHC+). Performing DISH on all IHC-2+ and -3+ cases yields a sensitivity and specificity of 100%. Conclusions Our EC-specific HER2 IHC scoring method is reproducible. A screening strategy based on IHC scoring on all cases with subsequent DISH testing on IHC-2+/-3+ cases has perfect test accuracy for identifying HER2-positive EC.Biological, physical and clinical aspects of cancer treatment with ionising radiatio
The 2HWC HAWC Observatory Gamma Ray Catalog
We present the first catalog of TeV gamma-ray sources realized with the
recently completed High Altitude Water Cherenkov Observatory (HAWC). It is the
most sensitive wide field-of-view TeV telescope currently in operation, with a
1-year survey sensitivity of ~5-10% of the flux of the Crab Nebula. With an
instantaneous field of view >1.5 sr and >90% duty cycle, it continuously
surveys and monitors the sky for gamma ray energies between hundreds GeV and
tens of TeV.
HAWC is located in Mexico at a latitude of 19 degree North and was completed
in March 2015. Here, we present the 2HWC catalog, which is the result of the
first source search realized with the complete HAWC detector. Realized with 507
days of data and represents the most sensitive TeV survey to date for such a
large fraction of the sky. A total of 39 sources were detected, with an
expected contamination of 0.5 due to background fluctuation. Out of these
sources, 16 are more than one degree away from any previously reported TeV
source. The source list, including the position measurement, spectrum
measurement, and uncertainties, is reported. Seven of the detected sources may
be associated with pulsar wind nebulae, two with supernova remnants, two with
blazars, and the remaining 23 have no firm identification yet.Comment: Submitted 2017/02/09 to the Astrophysical Journa
A member of the TERMINAL FLOWER1/CENTRORADIALIS gene family controls sprout growth in potato tubers
Potato tuber bud dormancy break followed by premature sprouting is a major commercial problem which results in quality losses and decreased tuber marketability. An approach to controlling premature tuber sprouting is to develop potato cultivars with a longer dormancy period and/or reduced rate of sprout growth. Our recent studies using a potato diploid population have identified several quantitative trait loci (QTLs) that are associated with tuber sprout growth. In the current study, we aim to characterize a candidate gene associated with one of the largest effect QTLs for rapid tuber sprout growth on potato chromosome 3. Underlying this QTL is a gene encoding a TERMINAL FLOWER 1/CENTRORADIALIS homologue (PGSC0003DMG400014322). Here, we use a transgenic approach to manipulate the expression level of the CEN family member in a potato tetraploid genotype (cv. Désirée). We demonstrate a clear effect of manipulation of StCEN expression, with decreased expression levels associated with an increased rate of sprout growth, and overexpressing lines showing a lower rate of sprout growth than controls. Associated with different levels of StCEN expression were different levels of abscisic acid and cytokinins, implying a role in controlling the levels of plant growth regulators in the apical meristem
The Sensitivity of HAWC to High-Mass Dark Matter Annihilations
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view
detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in
central Mexico at 19 degrees North latitude and 4100 m above sea level, HAWC
will observe gamma rays and cosmic rays with an array of water Cherenkov
detectors. The full HAWC array is scheduled to be operational in Spring 2015.
In this paper, we study the HAWC sensitivity to the gamma-ray signatures of
high-mass (multi- TeV) dark matter annihilation. The HAWC observatory will be
sensitive to diverse searches for dark matter annihilation, including
annihilation from extended dark matter sources, the diffuse gamma-ray emission
from dark matter annihilation, and gamma-ray emission from non-luminous dark
matter subhalos. Here we consider the HAWC sensitivity to a subset of these
sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the
Galactic center. We simulate the HAWC response to gamma rays from these sources
in several well-motivated dark matter annihilation channels. If no gamma-ray
excess is observed, we show the limits HAWC can place on the dark matter
cross-section from these sources. In particular, in the case of dark matter
annihilation into gauge bosons, HAWC will be able to detect a narrow range of
dark matter masses to cross-sections below thermal. HAWC should also be
sensitive to non-thermal cross-sections for masses up to nearly 1000 TeV. The
constraints placed by HAWC on the dark matter cross-section from known sources
should be competitive with current limits in the mass range where HAWC has
similar sensitivity. HAWC can additionally explore higher dark matter masses
than are currently constrained.Comment: 15 pages, 4 figures, version to be published in PR
Observational constraints on Horava-Lifshitz cosmology
We use observational data from Type Ia Supernovae (SNIa), Baryon Acoustic
Oscillations (BAO), and Cosmic Microwave Background (CMB), along with
requirements of Big Bang Nucleosynthesis (BBN), to constrain the cosmological
scenarios governed by Horava-Lifshitz gravity. We consider both the detailed
and non-detailed balance versions of the gravitational sector, and we include
the matter and radiation sectors. We conclude that the detailed-balance
scenario cannot be ruled out from the observational point of view, however the
corresponding likelihood contours impose tight constraints on the involved
parameters. The scenario beyond detailed balance is compatible with
observational data, and we present the corresponding stringent constraints and
contour-plots of the parameters. Although this analysis indicates that
Horava-Lifshitz cosmology can be compatible with observations, it does not
enlighten the discussion about its possible conceptual and theoretical
problems.Comment: 11 pages, 6 figures, version published in JCA
Perturbative instabilities in Horava gravity
We investigate the scalar and tensor perturbations in Horava gravity, with
and without detailed balance, around a flat background. Once both types of
perturbations are taken into account, it is revealed that the theory is plagued
by ghost-like scalar instabilities in the range of parameters which would
render it power-counting renormalizable, that cannot be overcome by simple
tricks such as analytic continuation. Implementing a consistent flow between
the UV and IR limits seems thus more challenging than initially presumed,
regardless of whether the theory approaches General Relativity at low energies
or not. Even in the phenomenologically viable parameter space, the tensor
sector leads to additional potential problems, such as fine-tunings and
super-luminal propagation.Comment: 21 pages, version published at Class. Quant. Gra
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