4,963 research outputs found
Dipole-interacting Fermionic Dark Matter in positron, antiproton, and gamma-ray channels
Cosmic ray signals from dipole-interacting dark matter annihilation are
considered in the positron, antiproton and photon channels. The predicted
signals in the positron channel could nicely account for the excess of positron
fraction from Fermi LAT, PAMELA, HEAT and AMS-01 experiments for the dark
matter mass larger than 100 GeV with a boost (enhancement) factor of 30-80. No
excess of antiproton over proton ratio at the experiments also gives a severe
restriction for this scenario. With the boost factors, the predicted signals
from Galactic halo and signals as mono-energetic gamma-ray lines (monochromatic
photons) for the region close to the Galactic center are investigated. The
gamma-ray excess of recent tentative analyses based on Fermi LAT data and the
potential probe of the monochromatic lines at a planned experiment, AMS-02, are
also considered.Comment: Version to be published in PRD(2013), Title changed, text modifie
A cohort study of the associations between udder conformation, milk somatic cell count, and lamb weight in suckler ewes
A cohort study of 67 suckler ewes from 1 farm was carried out from January to May 2010 to investigate associations between udder conformation, udder half milk somatic cell count (SCC), and lamb weight. Ewes and lambs were observed at lambing. Ewe health and teat condition and lamb health and weight were recorded on 4 to 5 further occasions at 14-d intervals. At each observation, a milk sample was collected from each udder half for somatic cell counting. Two weeks after lambing, ewe udder conformation and teat placement were scored. Low lamb weight was associated with ewe SCC >400,000 cells/mL (−0.73kg), a new teat lesion 14 d previously (−0.91kg), suboptimal teat position (−1.38kg), rearing in a multiple litter (−1.45kg), presence of diarrhea at the examination (−1.19kg), and rearing by a 9-yr-old ewe compared with a 6-yr-old ewe (−2.36kg). High lamb weight was associated with increasing lamb age (0.21kg/d), increasing birth weight (1.65kg/kg at birth), and increasing number of days the ewe was given supplementary feed before lambing (0.06kg/d). High udder half SCC was associated with pendulous udders (9.6% increase in SCC/cm of drop) and greater total cross-sectional area of the teats (7.2% increase of SCC/cm2). Low SCC were associated with a heavier mean litter weight (6.7% decrease in SCC/kg). Linear, quadratic, and cubic terms for days in lactation were also significant. We conclude that poor udder and teat conformation are associated with high levels of intramammary infection, as indicated by increased SCC and that both physical attributes of the udder and SCC are linked to lamb growth, suggesting that selection of suckler ewes with better udder and teat conformation would reduce intramammary infection and increase lamb growth rate
Bioactive composites for bone tissue engineering
One of the major challenges of bone tissue engineering is the production of a suitable scaffold material. In this review the current composite materials options available are considered covering both the methods of both production and assessing the scaffolds. A range of production routes have been investigated ranging from the use of porogens to produce the porosity through to controlled deposition methods. The testing regimes have included mechanical testing of the materials produced through to in vivo testing of the scaffolds. While the ideal scaffold material has not yet been produced, progress is being made
Non-monotonic temperature dependent transport in graphene grown by Chemical Vapor Deposition
Temperature-dependent resistivity of graphene grown by chemical vapor
deposition (CVD) is investigated. We observe in low mobility CVD graphene
device a strong insulating behavior at low temperatures and a metallic behavior
at high temperatures manifesting a non-monotonic in the temperature dependent
resistivity.This feature is strongly affected by carrier density modulation. To
understand this anomalous temperature dependence, we introduce thermal
activation of charge carriers in electron-hole puddles induced by randomly
distributed charged impurities. Observed temperature evolution of resistivity
is then understood from the competition among thermal activation of charge
carriers, temperature-dependent screening and phonon scattering effects. Our
results imply that the transport property of transferred CVD-grown graphene is
strongly influenced by the details of the environmentComment: 7 pages, 3 figure
Magnetic interactions in transition metal doped ZnO : An abinitio study
We calculate the nature of magnetic interactions in transition-metal doped
ZnO using the local spin density approximation and LSDA+\textit{U} method of
density functional theory. We investigate the following four cases: (i) single
transition metal ion types (Cr, Mn, Fe, Co, Ni and Cu) substituted at Zn sites,
(ii) substitutional magnetic transition metal ions combined with additional Cu
and Li dopants, (iii) substitutional magnetic transition metal ions combined
with oxygen vacancies and (iv) pairs of magnetic ion types (Co and Fe, Co and
Mn, etc.). Extensive convergence tests indicate that the calculated magnetic
ground state is unusually sensitive to the k-point mesh and energy cut-off, the
details of the geometry optimizations and the choice of the
exchange-correlation functional. We find that ferromagnetic coupling is
sometimes favorable for single type substitutional transition metal ions within
the local spin density approximation. However, the nature of magnetic
interactions changes when correlations on the transition-metal ion are treated
within the more realistic LSDA + \textit{U} method, often disfavoring the
ferromagnetic state. The magnetic configuration is sensitive to the detailed
arrangement of the ions and the amount of lattice relaxation, except in the
case of oxygen vacancies when an antiferromagnetic state is always favored.Comment: 11 pages, 17 figure
Atomic Layer Deposition of Ni Thin Films and Application to Area-Selective Deposition
Ni thin films were deposited by atomic layer deposition (ALD) using bis(dimethylamino-2-methyl-2-butoxo)nickel [Ni(dmamb)(2)] as a precursor and NH3 gas as a reactant. The growth characteristics and film properties of ALD Ni were investigated. Low-resistivity films were deposited on Si and SiO2 substrates, producing high-purity Ni films with a small amount of oxygen and negligible amounts of nitrogen and carbon. Additionally, ALD Ni showed excellent conformality in nanoscale via holes. Utilizing this conformality, Ni/Si core/shell nanowires with uniform diameters were fabricated. By combining ALD Ni with octadecyltrichlorosilane (OTS) self-assembled monolayer as a blocking layer, area-selective ALD was conducted for selective deposition of Ni films. When performed on the prepatterned OTS substrate, the Ni films were selectively coated only on OTS-free regions, building up Ni line patterns with 3 mu m width. Electrical measurement results showed that all of the Ni lines were electrically isolated, also indicating the selective Ni deposition. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3504196] All rights reserved.ope
Dirty Black Holes and Hairy Black Holes
An approach based on considerations of the non-classical energy momentum
tensor outside the event horizon of a black hole provides additional physical
insight into the nature of discrete quantum hair on black holes and its effect
on black hole temperature. Our analysis both extends previous work based on the
Euclidean action techniques, and corrects an omission in that work. We also
raise several issues related to the effects of instantons on black hole
thermodynamics and the relation between these effects and results in two
dimensional quantum field theory.Comment: 13 pages, Latex, submitted to Physical Review Letter
Mono-allelic retrotransposon insertion addresses epigenetic transcriptional repression in human genome
Background: Retrotransposons have been extensively studied in plants and animals and have been shown to have an impact on human genome dynamics and evolution. Their ability to move within genomes gives retrotransposons to affect genome instability. Methods: we examined the polymorphic inserted AluYa5, evolutionary young Alu, in the progesterone receptor gene to determine the effects of Alu insertion on molecular environment. We used mono-allelic inserted cell lines which carry both Alu-present and Alu-absent alleles. To determine the epigenetic change and gene expression, we performed restriction enzyme digestion, Pyrosequencing, and Chromatin Immunoprecipitation. Results: We observed that the polymorphic insertion of evolutionally young Alu causes increasing levels of DNA methylation in the surrounding genomic area and generates inactive histone tail modifications. Consequently the Alu insertion deleteriously inactivates the neighboring gene expression. Conclusion: The mono-allelic Alu insertion cell line clearly showed that polymorphic inserted repetitive elements cause the inactivation of neighboring gene expression, bringing aberrant epigenetic changes
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