862 research outputs found
Slowly rotating charged black holes in anti-de Sitter third order Lovelock gravity
In this paper, we study slowly rotating black hole solutions in Lovelock
gravity (n=3). These exact slowly rotating black hole solutions are obtained in
uncharged and charged cases, respectively. Up to the linear order of the
rotating parameter a, the mass, Hawking temperature and entropy of the
uncharged black holes get no corrections from rotation. In charged case, we
compute magnetic dipole moment and gyromagnetic ratio of the black holes. It is
shown that the gyromagnetic ratio keeps invariant after introducing the
Gauss-Bonnet and third order Lovelock interactions.Comment: 14 pages, no figur
Colliding plane wave solution in F(R)=R^{N} gravity
We identify a region of F(R)=R^{N} gravity without external sources which is
isometric to the spacetime of colliding plane waves (CPW). From the derived
curvature sources, N (N>1) measures the strength (i.e. the charge) of the
source. The analogy renders construction and collision of plane waves in
F(R)=R^{N} gravity possible, as in the Einstein-Maxwell (EM) theory, simply
because R=0. A plane wave in this type of gravity is equivalent to a Weyl
curvature plus an electromagnetic energy-momentum-like term (i.e. 'source
without source'). For N=1 we recover naturally the plane waves (and their
collision) in Einstein's theory. Our aim is to find the effect of an expanding
universe by virtue of F(R)=R^{N} on the colliding gravitational plane waves of
Einstein.Comment: 9 pages, 2 figure
Phenotype and differentiation potential of a novel rat tracheal epithelial cell line.
In this report we described the establishment and characterization of a continuous rat tracheal epithelial (RTE) cell line spontaneously derived from secondary RTE cell cultures. Designated SPOC1, this cell line is nontumorigenic and maintains a diploid karyotype with specific, nonrandom chromosomal alterations involving chromosomes 1, 3, and 6. SPOC1 cells demonstrate decreased requirements for peptide growth factors, compared with primary RTE cells. Upon inoculation into denuded rat tracheas, which are then implanted into syngeneic hosts, SPOC1 cells initially form a stratified squamous epithelium, which becomes less stratified with time and forms glandlike invaginations into the surrounding lamina propria. No evidence of ciliated cell differentiation is detected. The epithelium formed by SPOC1 cells in tracheal grafts reacts with antibodies specific for keratin 14, 13, and 19 (but not keratin 18) at both early and late time points, although the localization of antibody staining changes as the epithelium becomes less stratified with time. The suprabasal epithelial cells become positive for alcian blue-periodic acid-Schiff staining at later time points. The near-normal karyotype and differentiation potential of SPOC1 cells make this cell line a unique window into early changes occurring during immortalization of airway epithelial cells and will allow studies of relationships between differentiation state and neoplastic transformation
Inflation and Brane Gases
We investigate a new way of realizing a period of cosmological inflation in
the context of brane gas cosmology. It is argued that a gas of co-dimension one
branes, out of thermal equilibrium with the rest of the matter, has an equation
of state which can - after stabilization of the dilaton - lead to power-law
inflation of the bulk. The most promising implementation of this mechanism
might be in Type IIB superstring theory, with inflation of the three large
spatial dimensions triggered by ``stabilized embedded 2-branes''. Possible
applications and problems with this proposal are discussed.Comment: 7 pages, uses REVTeX, version to appear in Phys. Rev.
Resolvent estimates for normally hyperbolic trapped sets
We give pole free strips and estimates for resolvents of semiclassical
operators which, on the level of the classical flow, have normally hyperbolic
smooth trapped sets of codimension two in phase space. Such trapped sets are
structurally stable and our motivation comes partly from considering the wave
equation for Kerr black holes and their perturbations, whose trapped sets have
precisely this structure. We give applications including local smoothing
effects with epsilon derivative loss for the Schr\"odinger propagator as well
as local energy decay results for the wave equation.Comment: Further changes to erratum correcting small problems with Section 3.5
and Lemma 4.1; this now also corrects hypotheses, explicitly requiring
trapped set to be symplectic. Erratum follows references in this versio
Noise Sources in Photometry and Radial Velocities
The quest for Earth-like, extrasolar planets (exoplanets), especially those
located inside the habitable zone of their host stars, requires techniques
sensitive enough to detect the faint signals produced by those planets. The
radial velocity (RV) and photometric transit methods are the most widely used
and also the most efficient methods for detecting and characterizing
exoplanets. However, presence of astrophysical "noise" makes it difficult to
detect and accurately characterize exoplanets. It is important to note that the
amplitude of such astrophysical noise is larger than both the signal of
Earth-like exoplanets and state-of-the-art instrumentation limit precision,
making this a pressing topic that needs to be addressed. In this chapter, I
present a general review of the main sources of noise in photometric and RV
observations, namely, stellar oscillations, granulation, and magnetic activity.
Moreover, for each noise source I discuss the techniques and observational
strategies which allow us to mitigate their impact.Comment: 11 pages, 2 tables, Lecture presented at the IVth Azores
International Advanced School in Space Sciences on "Asteroseismology and
Exoplanets: Listening to the Stars and Searching for New Worlds"
(arXiv:1709.00645), which took place in Horta, Azores Islands, Portugal in
July 201
Feasibility and Acceptability of Maternal Choline Supplementation in Heavy Drinking Pregnant Women: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial
Background: Choline, an essential nutrient, serves as a methyl-group donor for DNA methylation and is a constituent of the neurotransmitter acetylcholine and a precursor to major components of cell membranes. Findings from animal studies suggest that choline supplementation during pregnancy can mitigate adverse effects of prenatal alcohol exposure on growth and neurocognitive function. We conducted a randomized, double-blind exploratory trial to examine feasibility and acceptability of a choline supplementation intervention during pregnancy. Methods: Seventy heavy drinkers, recruited in mid-pregnancy, were randomly assigned to receive a daily oral dose of 2 g of choline or a placebo from time of enrollment until delivery. Each dose consisted of an individually wrapped packet of powder that, when mixed with water, produced a sweet tasting grape-flavored drink. Adherence was assessed by collecting used and unused drink packets on a monthly basis and tabulating the number used. Side effects were assessed in monthly interviews. Blood samples obtained at enrollment and at 4 and 12 weeks after randomization were assayed for plasma choline concentration. Results: Adherence was good-to-excellent (median doses taken = 74.0%; interquartile range = 53.9 to 88.7%) and was not related to a range of sociodemographic characteristics or to alcohol consumption ascertained using a timeline follow-back interview. By 4 weeks, plasma choline concentrations were significantly higher in the choline supplementation than the placebo arm, and this group difference continued to be evident at 12 weeks. The only side effect was a small increase in nausea/dyspepsia. No effects were seen for diarrhea, vomiting, muscle stiffness, blood pressure, or body odor changes. Conclusions: This study demonstrated that a choline supplementation program with very heavy drinkers during pregnancy is feasible even among highly disadvantaged, poorly educated women. The broad acceptability of this intervention is indicated by our finding that adherence was not related to maternal education, intellectual function, depression, nutritional status, or alcohol use
Database for mRNA Half-Life of 19 977 Genes Obtained by DNA Microarray Analysis of Pluripotent and Differentiating Mouse Embryonic Stem Cells
Degradation of mRNA is one of the key processes that control the steady-state level of gene expression. However, the rate of mRNA decay for the majority of genes is not known. We successfully obtained the rate of mRNA decay for 19 977 non-redundant genes by microarray analysis of RNA samples obtained from mouse embryonic stem (ES) cells. Median estimated half-life was 7.1 h and only <100 genes, including Prdm1, Myc, Gadd45 g, Foxa2, Hes5 and Trib1, showed half-life less than 1 h. In general, mRNA species with short half-life were enriched among genes with regulatory functions (transcription factors), whereas mRNA species with long half-life were enriched among genes related to metabolism and structure (extracellular matrix, cytoskeleton). The stability of mRNAs correlated more significantly with the structural features of genes than the function of genes: mRNA stability showed the most significant positive correlation with the number of exon junctions per open reading frame length, and negative correlation with the presence of PUF-binding motifs and AU-rich elements in 3′-untranslated region (UTR) and CpG di-nucleotides in the 5′-UTR. The mRNA decay rates presented in this report are the largest data set for mammals and the first for ES cells
Matching and surface barrier effects of the flux-line lattice in superconducting films and multilayers.
The flux-line lattice dissipation and the pinning force of Bi2Sr2CaCu2O8 and YBa2Cu3O7 films and a Nb/Cu multilayer are investigated with the vibrating reed technique. In magnetic fields oriented under a small angle with respect to the film surfaces the Bi-2:2:1:2 film shows a series of pronounced dissipation maxima at matching fields BN in the irreversible region of the magnetic phase diagram. The Y-1:2:3 film shows tiny damping maxima, whereas no structure in the dissipation of the Nb/Cu multilayer is detected below the upper critical field. The comparison of the matching fields to an anisotropic London model shows that the dissipation maxima are caused by rearrangements of the flux-line lattice configuration due to interactions with the sample surface. The different behavior of the high-temperature superconductors and the Nb/Cu multilayer is understood by explicitly taking the surface barrier into account. Deviations from the surface induced commensurability of the flux-line lattice due to the intrinsic pinning are discussed. Our results indicate that pancake vortices in the Bi-2:2:1:2 film should be coupled below the irreversibility line and below magnetic fields B??0.5 T perpendicular to the film surface
Orbital state and magnetic properties of LiV_2 O_4
LiV_2 O_4 is one of the most puzzling compounds among transition metal oxides
because of its heavy fermion like behavior at low temperatures. In this paper
we present results for the orbital state and magnetic properties of LiV_2 O_4
obtained from a combination of density functional theory within the local
density approximation and dynamical mean-field theory (DMFT). The DMFT
equations are solved by quantum Monte Carlo simulations. The trigonal crystal
field splits the V 3d orbitals such that the a_{1g} and e_{g}^{pi} orbitals
cross the Fermi level, with the former being slightly lower in energy and
narrower in bandwidth. In this situation, the d-d Coulomb interaction leads to
an almost localization of one electron per V ion in the a_{1g} orbital, while
the e_{g}^{pi} orbitals form relatively broad bands with 1/8 filling. 2The
theoretical high-temperature paramagnetic susceptibility chi(T) follows a
Curie-Weiss law with an effective paramagnetic moment p_{eff}=1.65 in agreement
with the experimental results.Comment: 11 pages, 10 figures, 2 table
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