177 research outputs found
Cardy-Verlinde formula of Kehagias-Sfetsos black hole
In this paper, we have shown that the entropy of the Kehagias-Sfetsos black
hole in Hoava-Lifshitz (HL) gravity can be expressed by the
Cardy-Verlinde formula. The later is supposed to be an entropy formula of
conformal field theory in any dimension.Comment: 10 pages, accepted by IJT
Critical points and supersymmetric vacua, III: String/M models
A fundamental problem in contemporary string/M theory is to count the number
of inequivalent vacua satisfying constraints in a string theory model. This
article contains the first rigorous results on the number and distribution of
supersymmetric vacua of type IIb string theories compactified on a Calabi-Yau
3-fold with flux. In particular, complete proofs of the counting formulas
in Ashok-Douglas and Denef-Douglas are given, together with van der Corput
style remainder estimates. We also give evidence that the number of vacua
satisfying the tadpole constraint in regions of bounded curvature in moduli
space is of exponential growth in .Comment: Final revision for publication in Commun. Math. Phys. Minor
corrections and editorial change
Small Horizons
All near horizon geometries of supersymmetric black holes in a N=2, D=5
higher-derivative supergravity theory are classified. Depending on the choice
of near-horizon data we find that either there are no regular horizons, or
horizons exist and the spatial cross-sections of the event horizons are
conformal to a squashed or round S^3, S^1 * S^2, or T^3. If the conformal
factor is constant then the solutions are maximally supersymmetric. If the
conformal factor is not constant, we find that it satisfies a non-linear vortex
equation, and the horizon may admit scalar hair.Comment: 21 pages, latex. Typos corrected and reference adde
Physical properties of FeSeTe single crystals grown under different conditions
We report on structural, magnetic, conductivity, and thermodynamic studies of
FeSeTe single crystals grown by self-flux and Bridgman methods.
The samples were prepared from starting materials of different purity at
various temperatures and cooling rates. The lowest values of the susceptibility
in the normal state, the highest transition temperature of 14.5 K, and
the largest heat-capacity anomaly at were obtained for pure (oxygen-free)
samples. The critical current density of A/cm (at 2
K) achieved in pure samples is attributed to intrinsic inhomogeneity due to
disorder at the cation and anion sites. The impure samples show increased
up to A/cm due to additional pinning centers of
FeO. The upper critical field of kOe is estimated
from the resistivity study in magnetic fields parallel to the \emph{c}-axis.
The anisotropy of the upper critical field reaches a value at . Extremely low values of the residual Sommerfeld coefficient for pure
samples indicate a high volume fraction of the superconducting phase (up to
97%). The electronic contribution to the specific heat in the superconducting
state is well described within a single-band BCS model with a temperature
dependent gap K. A broad cusp-like anomaly in the electronic
specific heat of samples with suppressed bulk superconductivity is ascribed to
a splitting of the ground state of the interstitial Fe ions. This
contribution is fully suppressed in the ordered state in samples with bulk
superconductivity.Comment: 11 pages, 11 figures, 3 table
Lrp Acts as Both a Positive and Negative Regulator for Type 1 Fimbriae Production in Salmonella enterica Serovar Typhimurium
Leucine-responsive regulatory protein (Lrp) is known to be an indirect activator of type 1 fimbriae synthesis in Salmonella enterica serovar Typhimurium via direct regulation of FimZ, a direct positive regulator for type 1 fimbriae production. Using RT-PCR, we have shown previously that fimA transcription is dramatically impaired in both lrp-deletion (Δlrp) and constitutive-lrp expression (lrpC) mutant strains. In this work, we used chromosomal PfimA-lacZ fusions and yeast agglutination assays to confirm and extend our previous results. Direct binding of Lrp to PfimA was shown by an electrophoretic mobility shift assay (EMSA) and DNA footprinting assay. Site-directed mutagenesis revealed that the Lrp-binding motifs in PfimA play a role in both activation and repression of type 1 fimbriae production. Overproduction of Lrp also abrogates fimZ expression. EMSA data showed that Lrp and FimZ proteins independently bind to PfimA without competitive exclusion. In addition, both Lrp and FimZ binding to PfimA caused a hyper retardation (supershift) of the DNA-protein complex compared to the shift when each protein was present alone. Nutrition-dependent cellular Lrp levels closely correlated with the amount of type 1 fimbriae production. These observations suggest that Lrp plays important roles in type 1 fimbriation by acting as both a positive and negative regulator and its effect depends, at least in part, on the cellular concentration of Lrp in response to the nutritional environment
The Signaling Petri Net-Based Simulator: A Non-Parametric Strategy for Characterizing the Dynamics of Cell-Specific Signaling Networks
Reconstructing cellular signaling networks and understanding how they work are major endeavors in cell biology. The scale and complexity of these networks, however, render their analysis using experimental biology approaches alone very challenging. As a result, computational methods have been developed and combined with experimental biology approaches, producing powerful tools for the analysis of these networks. These computational methods mostly fall on either end of a spectrum of model parameterization. On one end is a class of structural network analysis methods; these typically use the network connectivity alone to generate hypotheses about global properties. On the other end is a class of dynamic network analysis methods; these use, in addition to the connectivity, kinetic parameters of the biochemical reactions to predict the network's dynamic behavior. These predictions provide detailed insights into the properties that determine aspects of the network's structure and behavior. However, the difficulty of obtaining numerical values of kinetic parameters is widely recognized to limit the applicability of this latter class of methods
Electromagnetic Field Effect or Simply Stress? Effects of UMTS Exposure on Hippocampal Longterm Plasticity in the Context of Procedure Related Hormone Release
Harmful effects of electromagnetic fields (EMF) on cognitive and behavioural features of humans and rodents have been controversially discussed and raised persistent concern about adverse effects of EMF on general brain functions. In the present study we applied radio-frequency (RF) signals of the Universal Mobile Telecommunications System (UMTS) to full brain exposed male Wistar rats in order to elaborate putative influences on stress hormone release (corticosteron; CORT and adrenocorticotropic hormone; ACTH) and on hippocampal derived synaptic long-term plasticity (LTP) and depression (LTD) as electrophysiological hallmarks for memory storage and memory consolidation. Exposure was computer controlled providing blind conditions. Nominal brain-averaged specific absorption rates (SAR) as a measure of applied mass-related dissipated RF power were 0, 2, and 10 W/kg over a period of 120 min. Comparison of cage exposed animals revealed, regardless of EMF exposure, significantly increased CORT and ACTH levels which corresponded with generally decreased field potential slopes and amplitudes in hippocampal LTP and LTD. Animals following SAR exposure of 2 W/kg (averaged over the whole brain of 2.3 g tissue mass) did not differ from the sham-exposed group in LTP and LTD experiments. In contrast, a significant reduction in LTP and LTD was observed at the high power rate of SAR (10 W/kg). The results demonstrate that a rate of 2 W/kg displays no adverse impact on LTP and LTD, while 10 W/kg leads to significant effects on the electrophysiological parameters, which can be clearly distinguished from the stress derived background. Our findings suggest that UMTS exposure with SAR in the range of 2 W/kg is not harmful to critical markers for memory storage and memory consolidation, however, an influence of UMTS at high energy absorption rates (10 W/kg) cannot be excluded
Ethnobotany genomics - discovery and innovation in a new era of exploratory research
We present here the first use of DNA barcoding in a new approach to ethnobotany we coined "ethnobotany genomics". This new approach is founded on the concept of 'assemblage' of biodiversity knowledge, which includes a coming together of different ways of knowing and valorizing species variation in a novel approach seeking to add value to both traditional knowledge (TK) and scientific knowledge (SK). We employed contemporary genomic technology, DNA barcoding, as an important tool for identifying cryptic species, which were already recognized ethnotaxa using the TK classification systems of local cultures in the Velliangiri Hills of India. This research is based on several case studies in our lab, which define an approach to that is poised to evolve quickly with the advent of new ideas and technology. Our results show that DNA barcoding validated several new cryptic plant species to science that were previously recognized by TK classifications of the Irulas and Malasars, and were lumped using SK classification. The contribution of the local aboriginal knowledge concerning plant diversity and utility in India is considerable; our study presents new ethnomedicine to science. Ethnobotany genomics can also be used to determine the distribution of rare species and their ecological requirements, including traditional ecological knowledge so that conservation strategies can be implemented. This is aligned with the Convention on Biological Diversity that was signed by over 150 nations, and thus the world's complex array of human-natural-technological relationships has effectively been re-organized
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