A non-perturbative estimate of the heavy quark momentum diffusion coefficient

We estimate the momentum diffusion coefficient of a heavy quark within a pure SU(3) plasma at a temperature of about 1.5Tc. Large-scale Monte Carlo simulations on a series of lattices extending up to 192^3*48 permit us to carry out a continuum extrapolation of the so-called colour-electric imaginary-time correlator. The extrapolated correlator is analyzed with the help of theoretically motivated models for the corresponding spectral function. Evidence for a non-zero transport coefficient is found and, incorporating systematic uncertainties reflecting model assumptions, we obtain kappa = (1.8 - 3.4)T^3. This implies that the "drag coefficient", characterizing the time scale at which heavy quarks adjust to hydrodynamic flow, is (1.8 - 3.4) (Tc/T)^2 (M/1.5GeV) fm/c, where M is the heavy quark kinetic mass. The results apply to bottom and, with somewhat larger systematic uncertainties, to charm quarks.Comment: 18 pages. v2: clarifications adde

Critical point and scale setting in SU(3) plasma: An update

We explore a method developed in statistical physics which has been argued to have exponentially small finite-volume effects, in order to determine the critical temperature Tc of pure SU(3) gauge theory close to the continuum limit. The method allows us to estimate the critical coupling betac of the Wilson action for temporal extents up to Nt ~ 20 with < 0.1% uncertainties. Making use of the scale setting parameters r0 and sqrt{t0} in the same range of beta-values, these results lead to the independent continuum extrapolations Tc r0 = 0.7457(45) and Tc sqrt{t0} = 0.2489(14), with the latter originating from a more convincing fit. Inserting a conversion of r0 from literature (unfortunately with much larger errors) yields Tc / LambdaMSbar = 1.24(10).Comment: 12 pages. v2: clarifications and references added, published versio

Medicinal plants used in the management of diabetes mellitus 2015

Diabetes mellitus is one of the common endocrine disorders prevalent in almost all of the countries. This chronic pathology is characterized by hyperglycemia caused by defective insulin action, insulin secretion, or the combination of both. Prolonged persistence of elevated blood glucose level consequently caused a series of complications such as nephropathy, retinopathy, and cardiomyopathy. Currently available synthetic drugs for treating this disease are found to be associated with many adverse effects. The use of plants in medicine is an age-long practice in various parts of the globe for both preventive and curative purposes. Several warnings have been issued over lack of quality control, scientific evidence for the efficacy, and potential adverse effects of herbal remedies including hepatotoxicity, nephrotoxicity, cardiotoxicity, and reproductive toxicity among others. Despite all of these, reliance on herbs as medicine for the management of diabetes mellitus is still much practiced by a large proportion of the world population because they are readily available and affordable with perceived reduced toxicity. Therefore, with the upsurge of interests in medicinal plants, there is a need for thorough scientific investigations of these plants for both efficacy and potential toxicity. In this issue, we present some recent advances in the use of medicinal plants for treating diabetes mellitus. B. Pang et al. (“Innovative Thoughts of Treating Diabetes from the Perspective of Traditional Chinese Medicine”)presented a review article on the contribution of traditional Chinese medicine to the development of alternative and complementary medicine for the treatment and prevention of diabetes mellitus. In another paper (“Effect of Rhizoma Coptidis (Huang Lian) on Treating Diabetes Mellitus”), B. Pang et al. discussed the efficacy and safety of Rhizoma Coptidis in the treatment of diabetes mellitus. In another study (“Evaluation of the Effects of Cornus mas L. Fruit Extract on Glycemic Control and Insulin Level in Type 2 Diabetic Adult Patients: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial”), R. Soltani et al. reported the results of a clinical trial on the effect of Cornus mas L. fruit extract on hyperglycemia in type 2 diabetic patients. In addition, W. Liu et al. (“The Effects of Chinese Medicine on Activation of Wnt/β-Catenin Signal Pathway under High Glucose Condition”) present a valuable review on some compounds implicated in the regulation of Wnt/β-catenin signal pathway as a mechanism of action involved in the antihyperglycemic activity from Chinese medicine. Furthermore, A. O. T. Ashafa and M. I. Kazeem (“Toxicopathological Evaluation of Hydroethanol Extract of Dianthus basuticus in Wistar Rats”) reported on the effects of Dianthus basuticus (a Basotho plant with acclaimed antidiabetic activity) on some biochemical parameters and histology of Wistar rats. Finally, X.-J. Li et al. (“TCM Formula Xiaoyaosan Decoction Improves Depressive-Like Behaviors in Rats with Type 2 Diabetes”) evaluated the effect of traditional medicine formula, Xiaoyaosan, on the cognitive function of diabetic rats. After the first volume of this special issue that was published in 2014, we hope that this issue will present additional valuable information for scientists and clinicians

Towards the continuum limit in transport coefficient computations

The analytic continuation needed for the extraction of transport coefficients necessitates in principle a continuous function of the Euclidean time variable. We report on progress towards achieving the continuum limit for 2-point correlator measurements in thermal SU(3) gauge theory, with specific attention paid to scale setting. In particular, we improve upon the determination of the critical lattice coupling and the critical temperature of pure SU(3) gauge theory, estimating r0*Tc ~ 0.7470(7) after a continuum extrapolation. As an application the determination of the heavy quark momentum diffusion coefficient from a correlator of colour-electric fields attached to a Polyakov loop is discussed.Comment: 7 pages. To appear in the Proceedings of the 31st International Symposium on Lattice Field Theory, July 29 - August 3, 2013, Mainz, German

Charmonium properties in hot quenched lattice QCD

We study the properties of charmonium states at finite temperature in quenched QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above $T_c$. Our analysis suggests that both S wave states ($J/\psi$ and $\eta_c$) and P wave states ($\chi_{c0}$ and $\chi_{c1}$) disappear already at about $1.5 T_c$. The charm diffusion coefficient is estimated through the Kubo formula and found to be compatible with zero below $T_c$ and approximately $1/\pi T$ at $1.5 T_c\lesssim T\lesssim 3 T_c$.Comment: 32 pages, 19 figures, typo corrected, discussions on isotropic vs anisotropic lattices expanded, published versio

Distribution of two species of Curly-tailed Lizards, genus Leiocephalus, in a metropolitan park, and the rediscovery of a nominate subspecies

Two Hispaniolan endemic species of lizards in the genus Leiocephalus (L. lunatus Cochran 1934 and L. personatus Cope 1862) are parapatric in an urban park in Santo Domingo, capital of the Dominican Republic. In the course of this study, we unexpectedly rediscovered the long-overlooked nominate subspecies of Leiocephalus lunatus 1 km inland from the vicinity of the type locality as what appears to be a relict population. Two congeners in the same urban setting within their natural ranges is an uncommon scenario. We provide detailed distributional data for both species within the Parque Mirador del Sur, and also report surviving populations of L. l. lunatus west of its type locality

Large magnetoresistance at room-temperature in semiconducting polymer sandwich devices

We report on the discovery of a large, room temperature magnetoresistance (MR) effect in polyfluorene sandwich devices in weak magnetic fields. We characterize this effect and discuss its dependence on voltage, temperature, film thickness, electrode materials, and (unintentional) impurity concentration. We usually observed negative MR, but positive MR can also be achieved under high applied electric fields. The MR effect reaches up to 10% at fields of 10mT at room temperature. The effect shows only a weak temperature dependence and is independent of the sign and direction of the magnetic field. We find that the effect is related to the hole current in the devices.Comment: 3 pages, 4 figure

Heavy Quark diffusion from lattice QCD spectral functions

We analyze the low frequency part of charmonium spectral functions on large lattices close to the continuum limit in the temperature region $1.5\lesssim T/T_c\lesssim 3$ as well as for $T \simeq 0.75T_c$. We present evidence for the existence of a transport peak above $T_c$ and its absence below $T_c$. The heavy quark diffusion constant is then estimated using the Kubo formula. As part of the calculation we also determine the temperature dependence of the signature for the charmonium bound state in the spectral function and discuss the fate of charmonium states in the hot medium.Comment: 4 pages, Proceedings for Quark Matter 2011 Conference, May 23-28, 2011, Annecy, Franc