Energy loss in perturbative QCD

We review the properties of energetic parton propagation in hot or cold QCD matter, as obtained in recent works. Advances in understanding the energy loss - collisional and radiative - are summarized, with emphasis on the latter: it features very interesting properties which may help to detect the quark-gluon plasma produced in heavy ion collisions. We describe two different theoretical approaches, which lead to the same radiated gluon energy spectrum. The case of a longitudinally expanding QCD plasma is investigated. The energy lost by a jet with given opening angle is calculated in view of making predictions for the suppression (quenching) of hard jet production. Phenomenological implications for the difference between hot and cold matter are discussed. Numerical estimates of the loss suggest that it may be significantly enhanced in hot compared to cold matter.Comment: 49 pages latex file with 11 embedded PS figures. Uses ar.sty (included), one equation revised. submitted to Annual Review of Nuclear and Particle Scienc

On the regularity of the Hausdorff distance between spectra of perturbed magnetic Hamiltonians

We study the regularity properties of the Hausdorff distance between spectra of continuous Harper-like operators. As a special case we obtain H\"{o}lder continuity of this Hausdorff distance with respect to the intensity of the magnetic field for a large class of magnetic elliptic (pseudo)differential operators with long range magnetic fields.Comment: to appear in the Proceedings of the 'Spectral Days' conference, Santiago de Chile 201

Replacing smoking with vaping during pregnancy: Impacts on metabolic health in mice.

Smoking is a significant risk factor for the development of metabolic diseases. Due to social pressures to quit smoking, many pregnant women are vaping as an alternative nicotine source. However, the metabolic consequences of replacing tobacco cigarettes with e-cigarettes during pregnancy are unknown. Therefore, in the mothers and their offspring, we investigated the metabolic and hepatic impacts of replacing cigarette smoke with e-vapour during pregnancy. Female BALB/c mice were either air-exposed or cigarette smoke-exposed (SE) from six weeks before pregnancy until lactation. At mating, a subset of the SE mice were instead exposed to e-vapour. Markers of glucose and lipid metabolism were measured in the livers and plasma, from the mothers and their male offspring (13 weeks). In the SE mothers, plasma insulin levels were reduced, leading to downstream increases in hepatic gluconeogenesis and plasma non-esterified fatty acids (NEFA). In the e-vapour replacement mothers, these changes were not as significant. In the SE offspring, there was impaired glucose tolerance, and increased plasma NEFA and liver triglyceride concentrations. E-vapour replacement restored lipid homeostasis but did not improve glucose tolerance. Therefore, in a murine model, low dose e-cigarette replacement during pregnancy is less toxic than cigarette smoke

Properties of humic substances isolated from different natural sources

The purpose of study was to determine properties of humic substances by combination of modern and traditional methods. Humic substances isolated from three different sources from Mongolia such as peloid from Lake Gurban nuur, coal from Baganuur deposit and oil shale from Shine khudag deposit. On the basis of determination H/C and O/C atomic ratios in humic substances by elemental analysis, confirmed existing of aromatic structures in the molecules and oxidized functional groups. Have been studied the structure of humic substances by spectral method. For example infrared spectrums showed that humic substances are characterizing with poly-structural components, with different quantity in the samples. Light adsorption of samples in the UV-Vis region, a decrease on the absorption intensity with an increase of the wave length was observed (Fig. 2). The high ratio Н/С, attributed to stretching of C=C bond of aromatic rings in IR spectrums, the high content of functional groups, lower extinction coefficients, confirmed that aromatic fragments to prevail than aliphatic chain fragments in structure of all studied HS. DOI: http://dx.doi.org/10.5564/mjc.v14i0.199 Mongolian Journal of Chemistry 14 (40), 2013, p51-5

High star formation rates as the origin of turbulence in early and modern disk galaxies

High spatial and spectral resolution observations of star formation and kinematics in early galaxies have shown that two-thirds are massive rotating disk galaxies with the remainder being less massive non-rotating objects. The line of sight averaged velocity dispersions are typically five times higher than in today's disk galaxies. This has suggested that gravitationally-unstable, gas-rich disks in the early Universe are fuelled by cold, dense accreting gas flowing along cosmic filaments and penetrating hot galactic gas halos. However these accreting flows have not been observed, and cosmic accretion cannot power the observed level of turbulence. Here we report on a new sample of rare high-velocity-dispersion disk galaxies we have discovered in the nearby Universe where cold accretion is unlikely to drive their high star-formation rates. We find that the velocity dispersion is most fundamentally correlated with their star-formation rates, and not their mass nor gas fraction, which leads to a new picture where star formation itself is the energetic driver of galaxy disk turbulence at all cosmic epochs.Comment: 9 pages, 2 figures, Supplimentary Info available at: http://pulsar.swin.edu.au/~agreen/nature/sigma_mean_arXiv.pdf. Accepted for publication in Natur

Photochemistry of HOx in the upper troposphere at northern midlatitudes

The factors controlling the concentrations of HOx radicals (= OH + peroxy) in the upper troposphere (8-12 km) are examined using concurrent aircraft observations of OH, HO2, H2O2, CH3OOH, and CH2O made during the Subsonic Assessment Ozone and Nitrogen Oxide Experiment (SONEX) at northern midlatitudes in the fall. These observations, complemented by concurrent measurements of O3, H2O, NO, peroxyacetyl nitrate (PAN), HNO3, CH4, CO, acetone, hydrocarbons, actinic fluxes, and aerosols, allow a highly constrained mass balance analysis of HOx and of the larger chemical family HOy (= HOx + 2 H2O2 + 2 CH3OOH + HNO2 + HNO4). Observations of OH and HO2 are successfully simulated to within 40% by a diel steady state model constrained with observed H2O2 and CH3OOH. The model captures 85% of the observed HOx variance, which is driven mainly by the concentrations of NOx (= NO + NO2) and by the strength of the HOx primary sources. Exceptions to the good agreement between modeled and observed HOx are at sunrise and sunset, where the model is too low by factors of 2-5, and inside cirrus clouds, where the model is too high by factors of 1.2-2. Heterogeneous conversion of NO2 to HONO on aerosols (γNO2=10-3) during the night followed by photolysis of HONO could explain part of the discrepancy at sunrise. Heterogeneous loss of HO2 on ice crystals (γice_HO2=0.025) could explain the discrepancy in cirrus. Primary sources of HOx from O(1D)+H2O and acetone photolysis were of comparable magnitude during SONEX. The dominant sinks of HOy were OH+HO2 (NOx<50 parts per trillion by volume (pptv)) and OH+HNO4 (NOx>50 pptv). Observed H2O2 concentrations are reproduced by model calculations to within 50% if one allows in the model for heterogeneous conversion of HO2 to H2O2 on aerosols (γHO2=0.2). Observed CH3OOH concentrations are underestimated by a factor of 2 on average. Observed CH2O concentrations were usually below the 50 pptv detection limit, consistent with model results; however, frequent occurrences of high values in the observations (up to 350 pptv) are not captured by the model. These high values are correlated with high CH3OH and with cirrus clouds. Heterogeneous oxidation of CH3OH to CH2O on aerosols or ice crystals might provide an explanation (γice_CH3OH∼0.01 would be needed). Copyright 2000 by the American Geophysical Union

X-Ray Measurement of Material Properties in Composites

Advanced materials for use in the aerospace industry are presently being developed and applied at an astonishing rate. This pace is driven by the need for materials that can withstand higher operating temperatures and loads, yet remain cost competitive. As the performance demands of aerospace materials push nearer and nearer the theoretical limit for strength, the allowed flaw size in traditional materials is driven smaller, making quality control more stringent. This demand for improved performance characteristics is also generating strong interest in other materials such as: exotic alloys, ceramics and reinforced composites. A need exists for characterizing these advanced materials for composition variations, flaw content, inclusions and porosity using nondestructive techniques at all stages of the materials life cycle. These stages include initial characterization of a new material, process control during the manufacturing of the material, quality control of incoming material, and the in service inspection of the final part

E-cigarettes damage the liver and alter nutrient metabolism in pregnant mice and their offspring.

Approximately 15% of pregnant women vape electronic cigarettes (e-cigarettes), exposing the fetus to a range of toxic compounds, including nicotine and by-products of e-cigarette liquid (e-liquid) pyrolysis. Owing to the recent emergence of these products, research mainly focuses on immediate users, and not on in utero exposure. Therefore, this study aimed to understand the impact of intrauterine e-cigarette vapor (e-vapor) exposure, with and without nicotine, on liver metabolic markers in the male offspring. E-vapor was generated using an e-cigarette filled with tobacco-flavored e-liquid (18 or 0 mg/mL nicotine). Female Balb/c mice were exposed to e-vapor for 6 weeks before mating, through gestation and lactation, without direct exposure to the offspring. Livers and plasma from dams and male offspring (13 weeks old) were examined. Exposure to nicotine-free e-vapor promoted metabolic changes and liver damage in both the dams and their offspring. Furthermore, exposure to nicotine-containing e-vapor did not cause liver damage but induced hepatic steatosis in the adult offspring. Therefore, maternal vaping is detrimental to both the dams and their offspring, with nicotine providing a potential protective effect

Bright spots, physical activity investments that work : sweatcoin : a steps generated virtual currency for sustained physical activity behaviour change

Sweatcoin converts the step count recorded on smartphones into a virtual currency. Using this app, users generate financial rewards through physical activity, with higher levels of activity creating a higher ‘income’. Sweatcoins can subsequently be used to purchase commercially available products from an in-app marketplace

A transient homotypic interaction model for the influenza A virus NS1 protein effector domain

Influenza A virus NS1 protein is a multifunctional virulence factor consisting of an RNA binding domain (RBD), a short linker, an effector domain (ED), and a C-terminal 'tail'. Although poorly understood, NS1 multimerization may autoregulate its actions. While RBD dimerization seems functionally conserved, two possible apo ED dimers have been proposed (helix-helix and strand-strand). Here, we analyze all available RBD, ED, and full-length NS1 structures, including four novel crystal structures obtained using EDs from divergent human and avian viruses, as well as two forms of a monomeric ED mutant. The data reveal the helix-helix interface as the only strictly conserved ED homodimeric contact. Furthermore, a mutant NS1 unable to form the helix-helix dimer is compromised in its ability to bind dsRNA efficiently, implying that ED multimerization influences RBD activity. Our bioinformatical work also suggests that the helix-helix interface is variable and transient, thereby allowing two ED monomers to twist relative to one another and possibly separate. In this regard, we found a mAb that recognizes NS1 via a residue completely buried within the ED helix-helix interface, and which may help highlight potential different conformational populations of NS1 (putatively termed 'helix-closed' and 'helix-open') in virus-infected cells. 'Helix-closed' conformations appear to enhance dsRNA binding, and 'helix-open' conformations allow otherwise inaccessible interactions with host factors. Our data support a new model of NS1 regulation in which the RBD remains dimeric throughout infection, while the ED switches between several quaternary states in order to expand its functional space. Such a concept may be applicable to other small multifunctional proteins