Early-Time Energy Loss in a Strongly-Coupled SYM Plasma

We carry out an analytic study of the early-time motion of a quark in a strongly-coupled maximally-supersymmetric Yang-Mills plasma, using the AdS/CFT correspondence. Our approach extracts the first thermal effects as a small perturbation of the known quark dynamics in vacuum, using a double expansion that is valid for early times and for (moderately) ultrarelativistic quark velocities. The quark is found to lose energy at a rate that differs significantly from the previously derived stationary/late-time result: it scales like T^4 instead of T^2, and is associated with a friction coefficient that is not independent of the quark momentum. Under conditions representative of the quark-gluon plasma as obtained at RHIC, the early energy loss rate is a few times smaller than its late-time counterpart. Our analysis additionally leads to thermally-corrected expressions for the intrinsic energy and momentum of the quark, in which the previously discovered limiting velocity of the quark is found to appear naturally.Comment: 39 pages, no figures. v2: Minor corrections and clarifications. References added. Version to be published in JHE

Tourism Life Cycle Assessment (LCA): Proposal of a New Methodological Framework for Sustainable Consumption and Production

Tourism has become an important part of modern life styles, besides being one of the largest and fastest growing economic sectors worldwide, in spite of occasional shocks over the last decade (UNWTO 2010). Tourism’s contribution to the gross domestic product (GDP) is – when direct contribution and multipliers are included - estimated at up to 10% in some advanced, diversified economies. However, this strong growth also implies an increase of undesired environmental impacts. Tourism is globally responsible for 5% of all carbon dioxide emissions, the most important greenhouse gas causing climate change (UNWTO UNEP WMO 2008). However, in terms of radiative forcing, the direct measure for contribution to climate change, tourism even could have share of up to 12.5% (Scott et al., 2010). Also, the greenhouse gas emissions of tourism are estimated to grow at a rather large rate, while a globally emissions should be reduced with up to 80% by 2050 (e.g. Scott et al., 2010). Finally, it has been shown that the eco-efficiency – the economic contribution per ton emissions – of tourism is rather low (Gössling et al., 2005). Theses data totally clash with the view, actually slightly common to many re¬searchers in the past, according to which tourism is a low environmental impact industry (McCrory 2006). Now, it is a shared concept that tourist activities are strongly related to the environment, since, on the one hand, the natural environment itself may be consid¬ered as a major input resource to the processes of tourism industries, and, on the other hand, the development of tourism as a mass industry may severely increase its overall impact on the environment (Butler 2004; Raggi and Petti 2006; Romeril 1989). Given the predictions of an increased role of tourism industries in the world economy, the environmental aspects of, and impacts gen¬erated by tourist activities should be accurately considered according to a Life Cycle Thinking perspective. This concept has been extensively advocated as the proper way of addressing the challenges linked with sustainable development, and, in particular, with those measures for enhancing sustainable consumption and production. In the framework of sustainable development policies, the “Sustainable Consumption and Production and Sustainable Industrial Policy (SCP) Action Plan” (European Commission 2008) is a building block in the EU. In line with this policy, a wide range of environmental instruments have been developed so far for assessment and labelling/certification purposes of travel and tourist services. This ongoing proliferation of different initiatives shows a high degree of diversity in terms of scope, assessment methodologies and means and tools of communication. Although this proliferation reflects the vast variety of travel and tourist products and the complicated nature in assessing their environmental performance, these environmental instruments seem to suffer from a lack of integration and standardisation or quality control. This situation has the potential to confuse or even mislead travellers and the stakeholders within the industry. Research questions were: - What environmental instruments and initiatives are currently supporting the application of the European Sustainable Consumption and Production (SCP) Action Plan in the travel and tourism industry? - What are their key characteristics and how do they stand in relation to Life Cycle Assessment (LCA) principles? - How can these instruments be combined in a general framework capable to render this industry low carbon and more sustainable from an environmental point of view?JRC.H.8-Sustainability Assessmen

Effect of adaptive abilities on utilities, direct or mediated by mental health?

<p>Abstract</p> <p>Background</p> <p>In cost-utility analyses gain in health can be measured using health state utilities. Health state utilities can be elicited from members of the public or from patients. Utilities given by patients tend to be higher than utilities given by members of the public. This difference is often suggested to be explained by adaptation, but this has not yet been investigated in patients. Here, we investigate if, besides health related quality of life (HRQL), persons' ability to adapt can explain health state utilities. Both the direct effect of persons' adaptive abilities on health state utilities and the indirect effect, where HRQL mediates the effect of ability to adapt, are examined.</p> <p>Methods</p> <p>In total 125 patients with Rheumatoid Arthritis were interviewed. Participants gave valuations of their own health on a visual analogue scale (VAS) and time trade-off (TTO). To estimate persons' ability to adapt, patients filled in questionnaires measuring Self-esteem, Mastery, and Optimism. Finally they completed the SF-36 measuring HRQL. Regression analyses were used to investigate the direct and mediated effect of ability to adapt on health state utilities.</p> <p>Results</p> <p>Persons' ability to adapt did not add considerably to the explanation of health state utilities above HRQL. In the TTO no additional variance was explained by adaptive abilities (Δ R²= .00, β = .02), in the VAS a minor proportion of the variance was explained by adaptive abilities (Δ R²= .05, β = .33). The effect of adaptation on health state utilities seems to be mediated by the mental health domain of quality of life.</p> <p>Conclusions</p> <p>Patients with stronger adaptive abilities, based on their optimism, mastery and self-esteem, may more easily enhance their mental health after being diagnosed with a chronic illness, which leads to higher health state utilities.</p

Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal