Lifshitz/Schr\"odinger D-p-branes and dynamical exponents

We extend our earlier study of special double limits of `boosted' $AdS_5$ black hole solutions to include all black D$p$-branes of type II strings. We find that Lifshitz solutions can be obtained in generality, with varied dynamical exponents, by employing these limits. We then study such double limits for `boosted' D$p$-brane bubble solutions and find that the resulting non-relativistic solutions instead describe Schr\"odinger like spacetimes, having varied dynamical exponents. We get a simple map between these Lifshitz & Schr\"odinger solutions and a relationship between two types of dynamical exponents. We also discuss about the singularities of the Lifshitz solutions and an intriguing thermodynamic duality.Comment: 20 pages; 3 figures; v3: similar to JHE

Vortex detection and quantum transport in mesoscopic graphene Josephson-junction arrays

We investigate mesoscopic Josephson junction arrays created by patterning superconducting disks on monolayer graphene, concentrating on the high-$T/T_c$ regime of these devices and the phenomena which contribute to the superconducting glass state in diffusive arrays. We observe features in the magnetoconductance at rational fractions of flux quanta per array unit cell, which we attribute to the formation of flux-quantized vortices. The applied fields at which the features occur are well described by Ginzburg-Landau simulations that take into account the number of unit cells in the array. We find that the mean conductance and universal conductance fluctuations are both enhanced below the critical temperature and field of the superconductor, with greater enhancement away from the graphene Dirac point.This work was financially supported by the Engineering and Physical Sciences Research Council, and an NPL/EPSRC Joint Postdoctoral Partnership (RG61493).This is the accepted manuscript. The final version is available at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.245418

Radio pulsar populations

The goal of this article is to summarize the current state of play in the field of radio pulsar statistics. Simply put, from the observed sample of objects from a variety of surveys with different telescopes, we wish to infer the properties of the underlying sample and to connect these with other astrophysical populations (for example supernova remnants or X-ray binaries). The main problem we need to tackle is the fact that, like many areas of science, the observed populations are often heavily biased by a variety of selection effects. After a review of the main effects relevant to radio pulsars, I discuss techniques to correct for them and summarize some of the most recent results. Perhaps the main point I would like to make in this article is that current models to describe the population are far from complete and often suffer from strong covariances between input parameters. That said, there are a number of very interesting conclusions that can be made concerning the evolution of neutron stars based on current data. While the focus of this review will be on the population of isolated Galactic pulsars, I will also briefly comment on millisecond and binary pulsars as well as the pulsar content of globular clusters and the Magellanic Clouds.Comment: 16 pages, 6 figures, to appear in Proceedings of ICREA Workshop on The High-Energy Emission from Pulsars and their Systems, Sant Cugat, Spain, 2010 April 12-16 (Springer

Accretion Disks Around Black Holes: Twenty Five Years Later

We study the progress of the theory of accretion disks around black holes in last twenty five years and explain why advective disks are the best bet in explaining varied stationary and non-stationary observations from black hole candidates. We show also that the recently proposed advection dominated flows are incorrect.Comment: 30 Latex pages including figures. Kluwer Style files included. Appearing in `Observational Evidence for Black Holes in the Universe', ed. Sandip K. Chakrabarti, Kluwer Academic Publishers (DORDRECHT: Holland

Ultrahard carbon film from epitaxial two-layer graphene

Atomically thin graphene exhibits fascinating mechanical properties, although its hardness and transverse stiffness are inferior to those of diamond. To date, there hasn't been any practical demonstration of the transformation of multi-layer graphene into diamond-like ultra-hard structures. Here we show that at room temperature and after nano-indentation, two-layer graphene on SiC(0001) exhibits a transverse stiffness and hardness comparable to diamond, resisting to perforation with a diamond indenter, and showing a reversible drop in electrical conductivity upon indentation. Density functional theory calculations suggest that upon compression, the two-layer graphene film transforms into a diamond-like film, producing both elastic deformations and sp2-to-sp3 chemical changes. Experiments and calculations show that this reversible phase change is not observed for a single buffer layer on SiC or graphene films thicker than 3 to 5 layers. Indeed, calculations show that whereas in two-layer graphene layer-stacking configuration controls the conformation of the diamond-like film, in a multilayer film it hinders the phase transformation.Comment: Published online on Nature Nanotechnology on December 18, 201

Lifshitz spacetimes from AdS null and cosmological solutions

We describe solutions of 10-dimensional supergravity comprising null deformations of $AdS_5\times S^5$ with a scalar field, which have $z=2$ Lifshitz symmetries. The bulk Lifshitz geometry in 3+1-dimensions arises by dimensional reduction of these solutions. The dual field theory in this case is a deformation of the N=4 super Yang-Mills theory. We discuss the holographic 2-point function of operators dual to bulk scalars. We further describe time-dependent (cosmological) solutions which have anisotropic Lifshitz scaling symmetries. We also discuss deformations of $AdS\times X$ in 11-dimensional supergravity, which are somewhat similar to the solutions above. In some cases here, we expect the field theory duals to be deformations of the Chern-Simons theories on M2-branes stacked at singularities.Comment: Latex, 29pgs, v3. references, minor clarifications (subsection on Lifshitz geometry seen by scalar probes) added, to appear in JHE

Holographic Fermi and Non-Fermi Liquids with Transitions in Dilaton Gravity

We study the two-point function for fermionic operators in a class of strongly coupled systems using the gauge-gravity correspondence. The gravity description includes a gauge field and a dilaton which determines the gauge coupling and the potential energy. Extremal black brane solutions in this system typically have vanishing entropy. By analyzing a charged fermion in these extremal black brane backgrounds we calculate the two-point function of the corresponding boundary fermionic operator. We find that in some region of parameter space it is of Fermi liquid type. Outside this region no well-defined quasi-particles exist, with the excitations acquiring a non-vanishing width at zero frequency. At the transition, the two-point function can exhibit non-Fermi liquid behaviour.Comment: 52 pages, 6 figures. v3: Appendix F added showing numerical interpolation between the near-horizon region and AdS4. Additional minor comments also adde

Vulval elephantiasis as a result of tubercular lymphadenitis: two case reports and a review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Elephantiasis as a result of chronic lymphedema is characterized by gross enlargement of the arms, legs or genitalia, and occurs due to a variety of obstructive diseases of the lymphatic system. Genital elephantiasis usually follows common filariasis and lymphogranuloma venereum. It may follow granuloma inguinale, carcinomas, lymph node dissection or irradiation and tuberculosis but this happens rarely. Vulval elephantiasis as a consequence of extensive lymph node destruction by tuberculosis is very rare. We present two very unusual cases of vulval elephantiasis due to tuberculous destruction of the inguinal lymph nodes.</p> <p>Case presentation</p> <p>Two Indian women - one aged 40 years and the other aged 27 years, with progressively increasing vulval swellings over a period of five and four years respectively - presented to our hospital. In both cases, there was a significant history on presentation. Both women had previously taken a complete course of anti-tubercular treatment for generalized lymphadenopathy. The vulval swellings were extremely large: in the first case report, measuring 35 × 25 cm on the right side and 45 × 30 cm on the left side, weighing 20 lb and 16 lb respectively. Both cases were managed by surgical excision with reconstruction and the outcome was positive. Satisfactory results have been maintained during a follow-up period of six years in both cases.</p> <p>Conclusions</p> <p>Elephantiasis of the female genitalia is unusual and it has rarely been reported following tuberculosis. We report two cases of vulval elephantiasis as a consequence of extensive lymph node destruction by tuberculosis, in order to highlight this very rare clinical scenario.</p

BPS Spectrum, Indices and Wall Crossing in N=4 Supersymmetric Yang-Mills Theories

BPS states in N=4 supersymmetric SU(N) gauge theories in four dimensions can be represented as planar string networks with ends lying on D3-branes. We introduce several protected indices which capture information on the spectrum and various quantum numbers of these states, give their wall crossing formula and describe how using the wall crossing formula we can compute all the indices at all points in the moduli space.Comment: LaTeX file, 33 pages, 15 figure

Informing patients of familial diabetes mellitus risk: How do they respond? A cross-sectional survey

<p>Abstract</p> <p>Background</p> <p>A strong family history of type 2 diabetes mellitus (DM) confers increased DM risk. This survey analysis determined whether patients who were informed by their doctors of familial DM risk acknowledged that risk and took steps to reduce it.</p> <p>Methods</p> <p>We conducted an analysis of the National <it>Health Styles 2004 </it>mail survey. All non-diabetic participants who responded to the question of whether their doctor had or had not informed them of their familial DM risk (<it>n </it>= 3,323) were compared for their risk-reducing behaviour and attitude to DM risk.</p> <p>Results</p> <p>Forty-one percent (<it>n </it>= 616) of the question responders that had DM family histories were informed by their doctors of their familial risk; the chance of being informed increased with the number of relatives that had the disease. Members of the informed group were more likely than those in the non-informed group to report lifestyle changes to prevent DM (odds ratio [OR] 4.3, 95% confidence interval [CI] 3.5–5.2) and being tested for DM (OR 2.9, 95% CI 2.4–3.6), although no significant improvement occurred in their U.S.-recommended exercise activity (OR 0.9, 95% CI 0.7–1.1). Overall, informed responders recognised both their familial and personal DM risk; most discussed diabetes with their family (69%), though less so with friends (42%); however, 44% of them still did not consider themselves to be at risk.</p> <p>Conclusion</p> <p>Responders who were informed by their doctors of being at familial DM risk reported greater incidences of lifestyle changes, DM screening, and awareness of risk than non-informed responders. Doctors were more likely to inform patients with stronger DM family histories. Identifying this higher risk group, either in isolation or in combination with other recognised risk factors, offers doctors the opportunity to target limited health promotion resources efficiently for primary DM prevention.</p