5,809 research outputs found

    Renormalization-group anatomy of transverse-momentum dependent parton distribution functions in QCD

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    The ultraviolet and rapidity divergences of transverse-momentum dependent parton distribution functions with lightlike and transverse gauge links is studied, also incorporating a soft eikonal factor. We find that in the light-cone gauge with qq^--independent pole prescriptions extra divergences appear which amount, at one-loop, to a cusp-like anomalous dimension. We show that such contributions are absent when the Mandelstam-Leibbrandt prescription is used. In the first case, the soft factor cancels the anomalous-dimension defect, while in the second case its ultraviolet-divergent part reduces to unity.Comment: 10 pages, 3 figures; needs ws-mpla-hep.cls (supplied). Talk presented by the first author at Workshop on "Recent Advances in Perturbative QCD and Hadronic Physics", 20--25 July 2009, ECT*, Trento, Italy, in Honor of Prof. Anatoly Efremov's 75th birthda

    Polystyrene microplastics ingestion induced behavioral effects to the cladoceran Daphnia magna

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    Microplastic (\u3bcPs) contamination represents a dramatic environmental problem threatening both aquatic and terrestrial organisms. Although several studies have highlighted the presence of \u3bcPs in aquatic environments, the information regarding their toxicity towards organisms is still scant. Moreover, most of the ecotoxicological studies of \u3bcPs have focused on marine organisms, largely neglecting the effects on freshwater species. The present study aimed at exploring the effects caused by 21-days exposure to three concentrations (0.125, 1.25 and 12.5 \u3bcg/mL) of two differently sized polystyrene microplastics (P\u3bcPs; 1 and 10 \u3bcm) to the Cladoceran Daphnia magna. The ingestion/egestion capability of daphnids (<24 h) and adults, the changes in individual growth and behavior, in terms of changes in swimming activity, phototactic behavior and reproduction, were investigated. Both particles filled the digestive tract of daphnids and adults within 24 h of exposure at all the tested concentrations. Ingested P\u3bcPs remained in the digestive tract even after 96 h in a clean medium. For both particles, an overall increase in body size of adults was noted at the end of the exposure to the highest tested concentrations, accompanied by a significant increase in swimming activity, in terms of distance moved and swimming velocity, and by an alteration of the phototactic behavior. A significant increase in the mean number of offspring after the exposure to the highest P\u3bcPs concentrations of different size was recorded. Polystyrene \u3bcPs can affect behavioral traits of D. magna leading to potentially harmful consequences on population dynamics of this zooplanktonic species

    Restoration of kTk_T factorization for low pTp_T hadron hadroproduction

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    We discuss the applicability of the kTk_T factorization theorem to low-pTp_T hadron production in hadron-hadron collision in a simple toy model, which involves only scalar particles and gluons. It has been shown that the kTk_T factorization for high-pTp_T hadron hadroproduction is broken by soft gluons in the Glauber region, which are exchanged among a transverse-momentum-dependent (TMD) parton density and other subprocesses of the collision. We explain that the contour of a loop momentum can be deformed away from the Glauber region at low pTp_T, so the above residual infrared divergence is factorized by means of the standard eikonal approximation. The kTk_T factorization is then restored in the sense that a TMD parton density maintains its universality. Because the resultant Glauber factor is independent of hadron flavors, experimental constraints on its behavior are possible. The kTk_T factorization can also be restored for the transverse single-spin asymmetry in hadron-hadron collision at low pTp_T in a similar way, with the residual infrared divergence being factorized into the same Glauber factor.Comment: 12 pages, 2 figures, version to appear in EPJ

    An outlook on modern and sustainable approaches to the management of grape pomace by integrating green processes, biotechnologies and advanced biomedical approaches

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    Grape pomace is the main solid residue of wine industry, mainly composed of seeds, skins and stalks, all containing high amounts of valuable phytochemicals. Considering its high potential, in this review, an outlook on different resources and products, which can be obtained by the recovery of grape pomace is provided. Special attention has been devoted to the analysis of chemical, physical and biotechnological processes to be applied and also to the high value compounds and products, such as supplements, nutraceuticals and cosmeceuticals, that can be manufactured. In particular, in the first part of the review, an update on the composition of grape pomace has been provided along with the analysis of its traditional fate. In the second part, the more modern and green approaches tested to the sustainable management of grape pomace are reported and discussed

    Semi-inclusive vector meson production in DIS

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    We analyze one-particle inclusive DIS in the case when a spin-1 hadron (such as a vector meson) is observed in the final state. We consider only leading order contributions in 1/Q, but we include transverse momentum of partons. Several new fragmentation functions appear in cross sections. One of them can be measured in connection with the transverse-spin disbtribution function h_1.Comment: 3 pages, uses sprocl.sty, talk given at the DIS2000 conference, Liverpool, England, April 2000, to appear in the conference proceeding

    Investigation of single spin asymmetries in pi^{+} electroproduction

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    The azimuthal single target-spin asymmetries for pi^{+} production in semi-inclusive deep inelastic scattering of leptons off longitudinally polarized protons are evaluated using two main approaches available in the literature. It is shown that the approximation where the twist-2 transverse quark spin distribution in the longitudinally polarized nucleon is small enough to be neglected leads to a consistent description of all existing asymmetries observed by the HERMES experiment.Comment: 11 pages with 4 figures, LaTe

    Electron-Ion Collider: The Next QCD Frontier

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    This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on Gluons and quark sea at high energies at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier

    A Decolonial Critique of the Racialized “Localwashing” of Extraction in Central Africa

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    Responding to calls for increased attention to actions and reactions “from above” within the extractive industry, we offer a decolonial critique of the ways in which corporate entities and multinational institutions propagate racialized rhetoric of “local” suffering, “local” consultation, and “local” fault for failure in extractive zones. Such rhetoric functions to legitimize extractive intervention within a set of practices that we call localwashing. Drawing from a decade of research on and along the Chad-Cameroon Oil Pipeline, we show how multi-scalar actors converged to assert knowledge of, responsibility for, and collaborations with “local” people within a racialized politics of scale. These corporate representations of the racialized “local” are coded through long-standing colonial tropes. We identify three interrelated and overlapping flexian elite rhetoric(s) and practices of racialized localwashing: (a) anguishing, (b) arrogating, and (c) admonishing. These elite representations of a racialized “local” reveal diversionary efforts “from above” to manage public opinion, displace blame for project failures, and domesticate dissent in a context of persistent scrutiny and criticism from international and regional advocates and activists

    Mechanical stress causes microplastic release from PET mineral water bottles

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    Plastic particle ingestion has become of concern as a possible threat to human health. Previous works have already explored the presence of microplastic (MP) in the bottled drinking water as a source of MP intake. Here, we consider the release of MP particles from single-use PET mineral water bottles upon exposure to mechanical stress utilizing scanning electron microscopy (SEM), which allows the implementation of morphological and elemental analysis of the plastic material surface and quantification of MP concentrations in sample water. The aim of this study is to better evaluate the sources of MP intake from plastic bottles, especially considering the effect of daily use on these bottles such as the abrasion of the PET and PE material. For that, we analysed MP release of PET-bottlenecks and PE-caps on their surfaces after a series of bottle openings/closings (one time, ten times, 100 times). Furthermore, we will investigate the occurrence of MP particles on the inner wall surface of the PET bottles and measure MP concentrations of the water after exposing the bottles to mechanical stress (squeezing treatment; none, one minute, ten minutes). All investigated bottles were purchased in Italian supermarkets and included different brands and water types. An in-house manufactured filtration apparatus was used to filter the sample water. To assess sample contamination or particle loss during the procedure in the lab, blank and positive control samples were included. The first results show a considerable increase of MP particles occurrence on the surface of PET and PE material (bottleneck and caps) after opening and closing the bottles 100 times. Considering these findings, MP concentrations in the bottled mineral water are expected to increase after exposure to mechanical stress (squeezing treatment). More information about MP concentration in mineral water - possibly increased through release of particles from the bottle inner wall - will be presented in the conference. In addition to the implications of the results, also the applicability of the used filtration and analysis technique will be discussed

    Generation of Potent and Stable Human CD4+ T Regulatory Cells by Activation-independent Expression of FOXP3

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    Therapies based on enhancing the numbers and/or function of T regulatory cells (Tregs) represent one of the most promising approaches to restoring tolerance in many immune-mediated diseases. Several groups have investigated whether human Tregs suitable for cellular therapy can be obtained by in vitro expansion, in vitro conversion of conventional T cells into Tregs, or gene transfer of the FOXP3 transcription factor. To date, however, none of these approaches has resulted in a homogeneous and stable population of cells that is as potently suppressive as ex vivo Tregs. We developed a lentivirus-based strategy to ectopically express high levels of FOXP3 that do not fluctuate with the state of T-cell activation. This method consistently results in the development of suppressive cells that are as potent as Tregs and can be propagated as a homogeneous population. Moreover, using this system, both naive and memory CD4+ T cells can be efficiently converted into Tregs. To date, this is the most efficient and reliable protocol for generating large numbers of suppressive CD4+ Tregs, which can be used for further biological study and developed for antigen-specific cellular therapy applications
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