5,292 research outputs found
The Quantum States and the Statistical Entropy of the Charged Black Hole
We quantize the Reissner-Nordstr\"om black hole using an adaptation of
Kucha\v{r}'s canonical decomposition of the Kruskal extension of the
Schwarzschild black hole. The Wheeler-DeWitt equation turns into a functional
Schroedinger equation in Gaussian time by coupling the gravitational field to a
reference fluid or dust. The physical phase space of the theory is spanned by
the mass, , the charge, , the physical radius, , the dust proper time,
, and their canonical momenta. The exact solutions of the functional
Schroedinger equation imply that the difference in the areas of the outer and
inner horizons is quantized in integer units. This agrees in spirit, but not
precisely, with Bekenstein's proposal on the discrete horizon area spectrum of
black holes. We also compute the entropy in the microcanonical ensemble and
show that the entropy of the Reissner-Nordstr\"om black hole is proportional to
this quantized difference in horizon areas.Comment: 31 pages, 3 figures, PHYZZX macros. Comments on the wave-functional
in the interior and one reference added. To appear in Phys. Rev.
Mouse tafazzin is required for male germ cell meiosis and spermatogenesis
Barth syndrome is an X-linked mitochondrial disease, symptoms of which include neutropenia and cardiac myopathy. These symptoms are the most significant clinical consequences of a disease, which is increasingly recognised to have a variable presentation. Mutation in the Taz gene in Xq28 is thought to be responsible for the condition, by altering mitochondrial lipid content and mitochondrial function. Male chimeras carrying a targeted mutation of Taz on their X-chromosome were infertile. Testes from the Taz knockout chimeras were smaller than their control counterparts and this was associated with a disruption of the progression of spermatocytes through meiosis to spermiogenesis. Taz knockout ES cells also showed a defect when differentiated to germ cells in vitro. Mutant spermatocytes failed to progress past the pachytene stage of meiosis and had higher levels of DNA double strand damage and increased levels of endogenous retrotransposon activity. Altogether these data revealed a novel role for Taz in helping to maintain genome integrity in meiosis and facilitating germ cell differentiation. We have unravelled a novel function for the Taz protein, which should contribute to an understanding of how a disruption of the Taz gene results in the complex symptoms underlying Barth Syndrome
Non-Markovian Dynamics of Charge Carriers in Quantum Dots
We have investigated the dynamics of bound particles in multilevel
current-carrying quantum dots. We look specifically in the regime of resonant
tunnelling transport, where several channels are available for transport.
Through a non-Markovian formalism under the Born approximation, we investigate
the real-time evolution of the confined particles including transport-induced
decoherence and relaxation. In the case of a coherent superposition between
states with different particle number, we find that a Fock-space coherence may
be preserved even in the presence of tunneling into and out of the dot.
Real-time results are presented for various asymmetries of tunneling rates into
different orbitals.Comment: 9 pages, 3 figures, International Workshop on Physics-Based
Mathematical Models for Low-Dimensional Semiconductor Nanostructures. BIRS,
November 18-23, 200
Does land use and landscape contribute to self-harm? A sustainability cities framework
Self-harm has become one of the leading causes of mortality in developed countries.
The overall rate for suicide in Canada is 11.3 per 100,000 according to Statistics Canada in 2015.
Between 2000 and 2007 the lowest rates of suicide in Canada were in Ontario, one of the most
urbanized regions in Canada. However, the interaction between land use, landscape and self-harm
has not been significantly studied for urban cores. It is thus of relevance to understand the impacts of
land-use and landscape on suicidal behavior. This paper takes a spatial analytical approach to assess
the occurrence of self-harm along one of the densest urban cores in the country: Toronto. Individual
self-harm data was gathered by the National Ambulatory Care System (NACRS) and geocoded into
census tract divisions. Toronto’s urban landscape is quantified at spatial level through the calculation
of its land use at di erent levels: (i) land use type, (ii) sprawl metrics relating to (a) dispersion and
(b) sprawl/mix incidence; (iii) fragmentation metrics of (a) urban fragmentation and (b) density and
(iv) demographics of (a) income and (b) age. A stepwise regression is built to understand the most
influential factors leading to self-harm from this selection generating an explanatory model.This research was supported by the Canadian Institutes of
Health Research Strategic Team Grant in Applied Injury Research # TIR-103946 and the Ontario Neurotrauma
Foundation grantinfo:eu-repo/semantics/publishedVersio
Entropy from the foam II
A simple model of spacetime foam, made by two different types of wormholes in
a semiclassical approximation, is taken under examination: one type is a
collection of Schwarzschild wormholes, while the other one is made by
Schwarzschild-Anti-de Sitter wormholes. The area quantization related to the
entropy via the Bekenstein-Hawking formula hints a possible selection between
the two configurations. Application to the charged black hole are discussed.Comment: Revtex 3.0, 10 pages, Replaced version with minor changes and one
ref. adde
The Quantum Stress-Tensor in Self-Similar Spherical Dust Collapse
We calculate the quantum stress tensor for a massless scalar field in the 2-d
self-similar spherical dust collapse model which admits a naked singularity. We
find that the outgoing radiation flux diverges on the Cauchy horizon. This may
have two consequences. The resultant back reaction may prevent the naked
singularity from forming, thus preserving cosmic censorship through quantum
effects. The divergent flux may lead to an observable signature differentiating
naked singularities from black holes in astrophysical observations.Comment: Latex File, 19 page
Quantum general relativity and Hawking radiation
In a previous paper we have set up the Wheeler-DeWitt equation which
describes the quantum general relativistic collapse of a spherical dust cloud.
In the present paper we specialize this equation to the case of matter
perturbations around a black hole, and show that in the WKB approximation, the
wave-functional describes an eternal black hole in equilibrium with a thermal
bath at Hawking temperature.Comment: 13 pages, minor revisions in: (i) para 5 of Introduction, (ii) para
following Eqn. (10). Revised version to appear in Phys. Rev.
Novel Approaches for Fungal Transcriptomics from Host Samples.
Candida albicans adaptation to the host requires a profound reprogramming of the fungal transcriptome as compared to in vitro laboratory conditions. A detailed knowledge of the C. albicans transcriptome during the infection process is necessary in order to understand which of the fungal genes are important for host adaptation. Such genes could be thought of as potential targets for antifungal therapy. The acquisition of the C. albicans transcriptome is, however, technically challenging due to the low proportion of fungal RNA in host tissues. Two emerging technologies were used recently to circumvent this problem. One consists of the detection of low abundance fungal RNA using capture and reporter gene probes which is followed by emission and quantification of resulting fluorescent signals (nanoString). The other is based first on the capture of fungal RNA by short biotinylated oligonucleotide baits covering the C. albicans ORFome permitting fungal RNA purification. Next, the enriched fungal RNA is amplified and subjected to RNA sequencing (RNA-seq). Here we detail these two transcriptome approaches and discuss their advantages and limitations and future perspectives in microbial transcriptomics from host material
- …