697 research outputs found
Colliding AdS gravitational shock waves in various dimensions and holography
The formation of marginally trapped surfaces in the off-center collision of
two shock waves on AdS_D (with D=4,5,6,7 and 8) is studied numerically. We
focus on the case when the two waves collide with nonvanishing impact parameter
while the sources are located at the same value of the holographic coordinate.
In all cases a critical value of the impact parameter is found above which no
trapped surface is formed. The numerical results show the existence of a simple
scaling relation between the critical impact parameter and the energy of the
colliding waves. Using the isometries of AdS_D we relate the solutions obtained
to the ones describing the collision of two waves with a purely holographic
impact parameter. This provides a gravitational dual for the head-on collision
of two lumps of energy of unequal size.Comment: 25 pages, 11 figures. v2: minor changes, typos corrected. To appear
in JHE
Critical Trapped Surfaces Formation in the Collision of Ultrarelativistic Charges in (A)dS
We study the formation of marginally trapped surfaces in the head-on
collision of two ultrarelativistic charges in space-time. The metric of
ultrarelativistic charged particles in is obtained by boosting
Reissner-Nordstr\"om space-time to the speed of light. We show that
formation of trapped surfaces on the past light cone is only possible when
charge is below certain critical - situation similar to the collision of two
ultrarelativistic charges in Minkowski space-time. This critical value depends
on the energy of colliding particles and the value of a cosmological constant.
There is richer structure of critical domains in case. In this case
already for chargeless particles there is a critical value of the cosmological
constant only below which trapped surfaces formation is possible. Appearance of
arbitrary small nonzero charge significantly changes the physical picture.
Critical effect which has been observed in the neutral case does not take place
more. If the value of the charge is not very large solution to the equation on
trapped surface exists for any values of cosmological radius and energy density
of shock waves. Increasing of the charge leads to decrease of the trapped
surface area, and at some critical point the formation of trapped surfaces of
the type mentioned above becomes impossible.Comment: 30 pages, Latex, 7 figures, Refs. added and typos correcte
Combining Anomaly and Z' Mediation of Supersymmetry Breaking
We propose a scenario in which the supersymmetry breaking effect mediated by
an additional U(1)' is comparable with that of anomaly mediation. We argue that
such a scenario can be naturally realized in a large class of models. Combining
anomaly with Z' mediation allows us to solve the tachyonic slepton problem of
the former and avoid significant fine tuning in the latter. We focus on an
NMSSM-like scenario where U(1)' gauge invariance is used to forbid a tree-level
mu term, and present concrete models, which admit successful dynamical
electroweak symmetry breaking. Gaugino masses are somewhat lighter than the
scalar masses, and the third generation squarks are lighter than the first two.
In the specific class of models under consideration, the gluino is light since
it only receives a contribution from 2-loop anomaly mediation, and it decays
dominantly into third generation quarks. Gluino production leads to distinct
LHC signals and prospects of early discovery. In addition, there is a
relatively light Z', with mass in the range of several TeV. Discovering and
studying its properties can reveal important clues about the underlying model.Comment: Minor changes: references added, typos corrected, journal versio
The Hawking-Page crossover in noncommutative anti-deSitter space
We study the problem of a Schwarzschild-anti-deSitter black hole in a
noncommutative geometry framework, thought to be an effective description of
quantum-gravitational spacetime. As a first step we derive the noncommutative
geometry inspired Schwarzschild-anti-deSitter solution. After studying the
horizon structure, we find that the curvature singularity is smeared out by the
noncommutative fluctuations. On the thermodynamics side, we show that the black
hole temperature, instead of a divergent behavior at small scales, admits a
maximum value. This fact implies an extension of the Hawking-Page transition
into a van der Waals-like phase diagram, with a critical point at a critical
cosmological constant size in Plank units and a smooth crossover thereafter. We
speculate that, in the gauge-string dictionary, this corresponds to the
confinement "critical point" in number of colors at finite number of flavors, a
highly non-trivial parameter that can be determined through lattice
simulations.Comment: 24 pages, 6 figure, 1 table, version matching that published on JHE
Potentiation of thrombus instability: a contributory mechanism to the effectiveness of antithrombotic medications
Š The Author(s) 2018The stability of an arterial thrombus, determined by its structure and ability to resist endogenous fibrinolysis, is a major determinant of the extent of infarction that results from coronary or cerebrovascular thrombosis. There is ample evidence from both laboratory and clinical studies to suggest that in addition to inhibiting platelet aggregation, antithrombotic medications have shear-dependent effects, potentiating thrombus fragility and/or enhancing endogenous fibrinolysis. Such shear-dependent effects, potentiating the fragility of the growing thrombus and/or enhancing endogenous thrombolytic activity, likely contribute to the clinical effectiveness of such medications. It is not clear how much these effects relate to the measured inhibition of platelet aggregation in response to specific agonists. These effects are observable only with techniques that subject the growing thrombus to arterial flow and shear conditions. The effects of antithrombotic medications on thrombus stability and ways of assessing this are reviewed herein, and it is proposed that thrombus stability could become a new target for pharmacological intervention.Peer reviewedFinal Published versio
Kretzoiarctos gen. nov., the Oldest Member of the Giant Panda Clade
The phylogenetic position of the giant panda, Ailuropoda melanoleuca (Carnivora: Ursidae: Ailuropodinae), has been one of the most hotly debated topics by mammalian biologists and paleontologists during the last century. Based on molecular data, it is currently recognized as a true ursid, sister-taxon of the remaining extant bears, from which it would have diverged by the Early Miocene. However, from a paleobiogeographic and chronological perspective, the origin of the giant panda lineage has remained elusive due to the scarcity of the available Miocene fossil record. Until recently, the genus Ailurarctos from the Late Miocene of China (ca. 8â7 mya) was recognized as the oldest undoubted member of the Ailuropodinae, suggesting that the panda lineage might have originated from an Ursavus ancestor. The role of the purported ailuropodine Agriarctos, from the Miocene of Europe, in the origins of this clade has been generally dismissed due to the paucity of the available material. Here, we describe a new ailuropodine genus, Kretzoiarctos gen. nov., based on remains from two Middle Miocene (ca. 12â11 Ma) Spanish localities. A cladistic analysis of fossil and extant members of the Ursoidea confirms the inclusion of the new genus into the Ailuropodinae. Moreover, Kretzoiarctos precedes in time the previously-known, Late Miocene members of the giant panda clade from Eurasia (Agriarctos and Ailurarctos). The former can be therefore considered the oldest recorded member of the giant panda lineage, which has significant implications for understanding the origins of this clade from a paleobiogeographic viewpoint
Allosteric Analysis of Glucocorticoid Receptor-DNA Interface Induced by Cyclic Py-Im Polyamide: A Molecular Dynamics Simulation Study
Background: It has been extensively developed in recent years that cell-permeable small molecules, such as polyamide, can be programmed to disrupt transcription factor-DNA interfaces and can silence aberrant gene expression. For example, cyclic pyrrole-imidazole polyamide that competes with glucocorticoid receptor (GR) for binding to glucocorticoid response elements could be expected to affect the DNA dependent binding by interfering with the protein-DNA interface. However, how such small molecules affect the transcription factor-DNA interfaces and gene regulatory pathways through DNA structure distortion is not fully understood so far. Methodology/Principal Findings: In the present work, we have constructed some models, especially the ternary model of polyamides+DNA+GR DNA-binding domain (GRDBD) dimer, and carried out molecular dynamics simulations and free energy calculations for them to address how polyamide molecules disrupt the GRDBD and DNA interface when polyamide and protein bind at the same sites on opposite grooves of DNA. Conclusions/Significance: We found that the cyclic polyamide binding in minor groove of DNA can induce a large structural perturbation of DNA, i.e. a.4 A Ë widening of the DNA minor groove and a compression of the major groove by more than 4A Ë as compared with the DNA molecule in the GRDBD dimer+DNA complex. Further investigations for the ternary system of polyamides+DNA+GRDBD dimer and the binary system of allosteric DNA+GRDBD dimer revealed that the compression o
Aspects of Non-minimal Gauge Mediation
A large class of non-minimal gauge mediation models, such as (semi-)direct
gauge mediation, predict a hierarchy between the masses of the supersymmetric
standard model gauginos and those of scalar particles. We perform a
comprehensive study of these non-minimal gauge mediation models, including mass
calculations in semi-direct gauge mediation, to illustrate these features, and
discuss the phenomenology of the models. We point out that the cosmological
gravitino problem places stringent constraints on mass splittings, when the
Bino is the NLSP. However, the GUT relation of the gaugino masses is broken
unlike the case of minimal gauge mediation, and an NLSP other than the Bino
(especially the gluino NLSP) becomes possible, relaxing the cosmological
constraints. We also discuss the collider signals of the models.Comment: 56 pages, 8 figures; v2:minor corrections, references added; v3:minor
correction
New Insights into the Lake Chad Basin Population Structure Revealed by High-Throughput Genotyping of Mitochondrial DNA Coding SNPs
BACKGROUND: Located in the Sudan belt, the Chad Basin forms a remarkable ecosystem, where several unique agricultural and pastoral techniques have been developed. Both from an archaeological and a genetic point of view, this region has been interpreted to be the center of a bidirectional corridor connecting West and East Africa, as well as a meeting point for populations coming from North Africa through the Saharan desert. METHODOLOGY/PRINCIPAL FINDINGS: Samples from twelve ethnic groups from the Chad Basin (nâ=â542) have been high-throughput genotyped for 230 coding region mitochondrial DNA (mtDNA) Single Nucleotide Polymorphisms (mtSNPs) using Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF) mass spectrometry. This set of mtSNPs allowed for much better phylogenetic resolution than previous studies of this geographic region, enabling new insights into its population history. Notable haplogroup (hg) heterogeneity has been observed in the Chad Basin mirroring the different demographic histories of these ethnic groups. As estimated using a Bayesian framework, nomadic populations showed negative growth which was not always correlated to their estimated effective population sizes. Nomads also showed lower diversity values than sedentary groups. CONCLUSIONS/SIGNIFICANCE: Compared to sedentary population, nomads showed signals of stronger genetic drift occurring in their ancestral populations. These populations, however, retained more haplotype diversity in their hypervariable segments I (HVS-I), but not their mtSNPs, suggesting a more ancestral ethnogenesis. Whereas the nomadic population showed a higher Mediterranean influence signaled mainly by sub-lineages of M1, R0, U6, and U5, the other populations showed a more consistent sub-Saharan pattern. Although lifestyle may have an influence on diversity patterns and hg composition, analysis of molecular variance has not identified these differences. The present study indicates that analysis of mtSNPs at high resolution could be a fast and extensive approach for screening variation in population studies where labor-intensive techniques such as entire genome sequencing remain unfeasible
Correlating changes in lung function with patient outcomes in chronic obstructive pulmonary disease: a pooled analysis
Background
Relationships between improvements in lung function and other clinical outcomes in chronic obstructive pulmonary disease (COPD) are not documented extensively. We examined whether changes in trough forced expiratory volume in 1 second (FEV1) are correlated with changes in patient-reported outcomes.
Methods
Pooled data from three indacaterol studies (n = 3313) were analysed. Means and responder rates for outcomes including change from baseline in Transition Dyspnoea Index (TDI), St. George's Respiratory Questionnaire (SGRQ) scores (at 12, 26 and 52 weeks), and COPD exacerbation frequency (rate/year) were tabulated across categories of ÎFEV1. Also, generalised linear modelling was performed adjusting for covariates such as baseline severity and inhaled corticosteroid use.
Results
With increasing positive ÎFEV1, TDI and ÎSGRQ improved at all timepoints, exacerbation rate over the study duration declined (P < 0.001). Individual-level correlations were 0.03-0.18, but cohort-level correlations were 0.79-0.95. At 26 weeks, a 100 ml increase in FEV1 was associated with improved TDI (0.46 units), ÎSGRQ (1.3-1.9 points) and exacerbation rate (12% decrease). Overall, adjustments for baseline covariates had little impact on the relationship between ÎFEV1 and outcomes.
Conclusions
These results suggest that larger improvements in FEV1 are likely to be associated with larger patient-reported benefits across a range of clinical outcomes
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