Exact results for static and radiative fields of a quark in N=4 super Yang-Mills

In this work (which supersedes our previous preprint arXiv:1112.2345) we determine the expectation value of the N=4$ SU(N) SYM Lagrangian density operator in the presence of an infinitely heavy static particle in the symmetric representation of SU(N), by means of a D3-brane probe computation. The result that we obtain coincides with two previous computations of different observables, up to kinematical factors. We argue that these agreements go beyond the D-brane probe approximation, which leads us to propose an exact formula for the expectation value of various operators. In particular, we provide an expression for the total energy loss by radiation of a heavy particle in the fundamental representation.Comment: 14 pages. This submission supersedes our previous preprint arXiv:1112.2345. v2: numerical factors fixed, minor clarifications, added reference

Geometry of open strings ending on backreacting D3-branes

We investigate open string theory on backreacting D3-branes using a spacetime approach. We study in detail the half-BPS supergravity solutions describing open strings ending on D3-branes, in the near horizon of the D3-branes. We recover quantitatively several non-trivial features of open string physics including the appearance of D3-brane spikes, the polarization of fundamental strings into D5-branes, and the Hanany-Witten effect. Finally we detail the computation of the gravitational potential between two open strings, and contrast it with the holographic computation of Wilson lines. We argue that the D-brane backreaction has a large influence on the low-energy gravity, which may lead to experimental tests for string theory brane-world scenarios.Comment: 64 pages, 20 figure

Thermal photons in QGP and non-ideal effects

We investigate the thermal photon production-rates using one dimensional boost-invariant second order relativistic hydrodynamics to find proper time evolution of the energy density and the temperature. The effect of bulk-viscosity and non-ideal equation of state are taken into account in a manner consistent with recent lattice QCD estimates. It is shown that the \textit{non-ideal} gas equation of state i.e $\epsilon-3\,P\,\neq 0$ behaviour of the expanding plasma, which is important near the phase-transition point, can significantly slow down the hydrodynamic expansion and thereby increase the photon production-rates. Inclusion of the bulk viscosity may also have similar effect on the hydrodynamic evolution. However the effect of bulk viscosity is shown to be significantly lower than the \textit{non-ideal} gas equation of state. We also analyze the interesting phenomenon of bulk viscosity induced cavitation making the hydrodynamical description invalid. We include the viscous corrections to the distribution functions while calculating the photon spectra. It is shown that ignoring the cavitation phenomenon can lead to erroneous estimation of the photon flux.Comment: 11 pages, 13 figures; accepted for publication in JHE

Holographic flows and thermodynamics of Polyakov loop impurities

We study holographic probes dual to heavy quark impurities interpo- lating between fundamental and symmetric/antisymmetric tensor representations in strongly coupled N = 4 supersymmetric gauge theory. These correspond to non- conformal D3- and D5-brane probe embeddings in AdS_5 × S^5 exhibiting flows on their world-volumes. By examining the asymptotic regimes of the embeddings and the one-point function of static fields sourced by the boundary impurity, we con- clude that the D5-brane embedding describes the screening of fundamental quarks in the UV into an antisymmetric source in the IR, whilst the non-conformal, D3- brane solution interpolates between the symmetric representation in the UV and fundamental sources in the IR. The D5-brane embeddings exhibit nontrivial ther- modynamics with multiple branches of solutions, whilst the thermal analogue of the interpolating D3-brane solution does not appear to exist

Beyond R0 : demographic models for variability of lifetime reproductive output

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 6 (2011): e20809, doi:10.1371/journal.pone.0020809.The net reproductive rate measures the expected lifetime reproductive output of an individual, and plays an important role in demography, ecology, evolution, and epidemiology. Well-established methods exist to calculate it from age- or stage-classified demographic data. As an expectation, provides no information on variability; empirical measurements of lifetime reproduction universally show high levels of variability, and often positive skewness among individuals. This is often interpreted as evidence of heterogeneity, and thus of an opportunity for natural selection. However, variability provides evidence of heterogeneity only if it exceeds the level of variability to be expected in a cohort of identical individuals all experiencing the same vital rates. Such comparisons require a way to calculate the statistics of lifetime reproduction from demographic data. Here, a new approach is presented, using the theory of Markov chains with rewards, obtaining all the moments of the distribution of lifetime reproduction. The approach applies to age- or stage-classified models, to constant, periodic, or stochastic environments, and to any kind of reproductive schedule. As examples, I analyze data from six empirical studies, of a variety of animal and plant taxa (nematodes, polychaetes, humans, and several species of perennial plants).Supported by National Science Foundation Grant DEB-0816514 and by a Research Award from the Alexander von Humboldt Foundation

TRPA1 is essential for the vascular response to environmental cold exposure

This work was supported by the British Heart Foundation and a Capacity Building Award in Integrative Mammalian Biology. It was also supported by Arthritis Research UK and XK is supported by a British Pharmacological Society AJ Clark studentship

Health for sale: the medicinal plant markets in Trujillo and Chiclayo, Northern Peru

Traditional methods of healing have been beneficial in many countries with or without access to conventional allopathic medicine. In the United States, these traditional practices are increasingly being sought after for illnesses that cannot be easily treated by allopathic medicine. More and more people are becoming interested in the knowledge maintained by traditional healers and in the diversity of medicinal plants that flourish in areas like Northern Peru. While scientific studies of medicinal plants are underway, concern has arisen over the preservation of both the large diversity of medicinal plants and the traditional knowledge of healing methods that accompanies them. To promote further conservation work, this study attempted to document the sources of the most popular and rarest medicinal plants sold in the markets of Trujillo (Mayorista and Hermelinda) and Chiclayo (Modelo and Moshoqueque), as well as to create an inventory of the plants sold in these markets, which will serve as a basis for comparison with future inventories. Individual markets and market stalls were subjected to cluster analysis based on the diversity of the medicinal plants they carry. The results show that markets were grouped based on the presence of: (1) common exotic medicinal plants; (2) plants used by laypeople for self-medication related to common ailments ("everyday remedies"); (3) specialized medicinal plants used by curanderos or traditional healers; and (4) highly "specialized" plants used for magical purposes. The plant trade in the study areas seems to correspond well with the specific health care demands from clientele in those areas. The specific market patterns of plant diversity observed in the present study represent a foundation for comparative market research in Peru and elsewhere

Metal release from contaminated estuarine sediment under pH changes in the marine environment

The contaminant release from estuarine sediment due to pH changes was investigated using a modified CEN/TS 14429 pH-dependence leaching test. The test is performed in the range of pH values of 0-14 using deionised water and seawater as leaching solutions. The experimental conditions mimic different circumstances of the marine environment due to the global acidification, carbon dioxide (CO2) leakages from carbon capture and sequestration technologies, and accidental chemical spills in seawater. Leaching test results using seawater as leaching solution show a better neutralisation capacity giving slightly lower metal leaching concentrations than when using deionised water. The contaminated sediment shows a low base-neutralisation capacity (BNCpH 12 = -0.44 eq/kg for deionised water and BNCpH 12 = -1.38 eq/kg for seawater) but a high acid-neutralisation capacity when using deionised water (ANCpH 4 = 3.58 eq/ kg) and seawater (ANCpH 4 = 3.97 eq/kg). Experimental results are modelled with the Visual MINTEQ geochemical software to predict metal release from sediment using both leaching liquids. Surface adsorption to iron- and aluminium- (hydr)oxides was applied for all studied elements. The consideration of the metal-organic matter binding through the NICA-Donnan model and Stockholm Humic Model for lead and copper, respectively, improves the former metal release prediction. Modelled curves can be useful for the environmental impact assessment of seawater acidification due to its match with the experimental values.This work was supported by the Spanish Ministry of Economy and Competitiveness, Project No. CTM 2011-28437-C02-01, ERDF included. M. C. Martı´n-Torre was funded by the Spanish Ministry of Economy and Competitiveness by means of FPI. Fellowship No. BES-2012-053816

Mutations in Eml1 lead to ectopic progenitors and neuronal heterotopia in mouse and human.

Neuronal migration disorders such as lissencephaly and subcortical band heterotopia are associated with epilepsy and intellectual disability. DCX, PAFAH1B1 and TUBA1A are mutated in these disorders; however, corresponding mouse mutants do not show heterotopic neurons in the neocortex. In contrast, spontaneously arisen HeCo mice display this phenotype, and our study revealed that misplaced apical progenitors contribute to heterotopia formation. While HeCo neurons migrated at the same speed as wild type, abnormally distributed dividing progenitors were found throughout the cortical wall from embryonic day 13. We identified Eml1, encoding a microtubule-associated protein, as the gene mutated in HeCo mice. Full-length transcripts were lacking as a result of a retrotransposon insertion in an intron. Eml1 knockdown mimicked the HeCo progenitor phenotype and reexpression rescued it. We further found EML1 to be mutated in ribbon-like heterotopia in humans. Our data link abnormal spindle orientations, ectopic progenitors and severe heterotopia in mouse and human

Infinitesimal Idealization, Easy Road Nominalism, and Fractional Quantum Statistics

It has been recently debated whether there exists a so-called “easy road” to nominalism. In this essay, I attempt to fill a lacuna in the debate by making a connection with the literature on infinite and infinitesimal idealization in science through an example from mathematical physics that has been largely ignored by philosophers. Specifically, by appealing to John Norton’s distinction between idealization and approximation, I argue that the phenomena of fractional quantum statistics bears negatively on Mary Leng’s proposed path to easy road nominalism, thereby partially defending Mark Colyvan’s claim that there is no easy road to nominalism