Phase transition and critical end point driven by an external magnetic field in asymmetric quark matter

The location of the critical end point (CEP) in the QCD phase diagram is determined under different scenarios. The effect of strangeness, isospin/charge asymmetry and an external magnetic field is investigated. The discussion is performed within the 2+1 flavor Nambu--Jona-Lasinio model with Polyakov loop. It is shown that isospin asymmetry shifts the CEP to larger baryonic chemical potentials and smaller temperatures. At large asymmetries the CEP disappears. However, a strong enough magnetic field drives the system into a first order phase transition.Comment: 7 pages, 3 figures; PRD versio

Jogadores patológicos online e offline: caracterização e comparação

Face ao grande desenvolvimento do jogo ao nível mundial, o problema colocado foi: perceber quais são as características, os fatores de risco, perigosidade e respetivas diferenças entre jogadores patológicos online (JPON) e offline (JPOF); que permitirão a posteriori a elaboração de programas de prevenção e tratamento adequados à cultura portuguesa, assim como indicar novas linhas de investigação. Com este mesmo intuito, tentou-se responder a três questões centrais da literatura científica atual: i) Serão os jogadores patológicos online diferentes dos offline? (Griffiths, 2011); ii) Será o jogo online mais atractivo e prejudicial que o jogo offline? (Shaffer, 2009); e iii) existe um continuum de risco e de consequências negativas uso-abuso-dependência em ambos os modos? (Orford, 2011) Os instrumentos utilizados neste estudo, quantitativo, transversal e exploratório de caráter descritivo e comparativo-correlacional foram: um questionário sociodemográfico, outro sobre comportamentos de jogo, o South Oaks Gambling Screen (lesieur & Blume, 1987) para avaliar o tipo de jogador − recreativo, abusivo ou patológico −, e ainda um questionário sobre estratégias de coping, tendo a amostra contado com 342 jogadores patológicos, 776 jogadores abusivos e 481 recreativos, repartidos pelos modos offline e online, com idades entre os 16 e os 80 anos. Os participantes respondiam diretamente a um questionário para jogadores online ou offline, mediante o seu modo preferencial de apostar. Pode concluir-se do estudo que existem diferenças entre JPOF e JPON, que existe um continuum de risco em ambos os modos, sendo mais rápido e intenso no modo online. Pode considerar-se que o modo online apresenta um risco de danos superior, pois os resultados nos fatores de risco situacionais e estruturais foram mais elevados nos JPON, apesar de nos fatores de risco das características individuais surgirem relativamente superiores nos JPOF, sendo, todavia, e muito provavelmente em grande medida, devido à média de idades destes últimos ser superior em mais de dez anos. Realça-se a tendência para haver cada vez mais jogadores patológicos mistos, ou seja: que apostam tanto no modo offline como online. Existe hoje em Portugal uma base científica para construir programas de prevenção e tratamento baseados no perfil quer dos JPOF quer dos JPON, mas deverão ser elaborados novos estudos para aquilatar sobre a influência dos fatores de riscos situacionais e estruturais no jogador misto e qual a relação que este estabelece com cada um dos modos, online e offline. Ao nível sociodemográfico e de comportamentos, o perfil do jogador online consiste em: ser do género masculino; média de idade de 30 anos; formação escolar completa superior; vivem em meio urbano; mais profissões “intelectuais/científicas”; e jogam sobretudo poker e apostas desportivas mais motivados por fácil acessibilidade e disponibilidade no horário 17h-21h, cinco vezes por semana, gastam menos dinheiro e têm historial de relação com jogos e computadores que remonta em média aos 16 anos. O perfil do jogador offline é: masculino; 40 anos (nas mulheres 50 anos); licenciado; com actividade profissional (área de gestores e empreendedores); com relações conjugais de compromisso; com gastos de dinheiro e tempo mais significativos. Jogam sobretudo a slotmachines, mais motivados por divertimento e ganhar dinheiro, com mais ideação suicida e mais problemas ligados ao stresse, depressão e ansiedade, fazendo mais apostas online do que os jogadores online apostam offline. Idade e género influenciam fortemente estes perfis

On the early stages of wind-wave generation under accelerated wind conditions

International audienceWhen wind starts to blow, a momentum transfer initiates through the air-water interface generating ocean wave. This transfer is usually characterized in terms of the drag coefficient, CD, but its dependency with wind speed still presents remarkable scatter in the experimental studies. Besides, Babanin and Makin (2008) found that gustiness were responsible to the most distant outliers in drag coefficient values. Also, several studies showed the influence of the sea state and wave age in the roughness and drag coefficient behavior (Smith et al. 1992; Donelan et al. 1993; Drennan 2003). Most of the past studies of wind-waves generation considered uniform and stationary wind speeds. However, in open field it is common to have conditions of wind blowing with a certain acceleration before the constant wind condition is reached. In order to study the early stages of the generation of waves under accelerated wind conditions, a total of five experiments with a characteristic wind speed acceleration were conducted in a large wind-wave facility at the Institut Pytheas (Marseille-France). Momentum fluxes were estimated from hot wire anemometry and, the free surface displacement was measured along the channel tank by resistance and capacitance wire probes. High resolution wind speed and water elevation measurements were acquired at a high resolution rate. During experiments the wind speed was increased with a constant acceleration over time, reaching a constant maximum intensity of 13 m/s. It was observed that during accelerated wind conditions, drag coefficient values depends on the degree of development of the flow regime in the air section and on wave field generation and evolution. The acceleration of wind speed has a direct influence on water surface roughness and water wave evolution in time and in space

Fluid Dynamics and Secondary Currents in an Asymmetrical Rectangular Canal with Sidewall Streamwise Rib

Channels with streamwise ribs have been studied for decades in chemical engineering, environmental and sanitary engineering, aeronautics, astronautics, biology and geology. Some designs have been used for close to a century in water treatment plants. Longitudinal ribs along channel walls have been successfully tested for the increased heat and mass transfer rates. In alluvial channels, long-lasting three-dimensional large-scale turbulent vortices may yield the development of longitudinal ridges on the mobile bed with preferential sediment transport in between. Herein a detailed hydrodynamic study was conducted in an asymmetrical rectangular channel equipped with a sidewall streamwise rib. Both free-surface, velocity and boundary shear stress measurements showed strong secondary currents of Prandtl's second kind. The sidewall rib and channel asymmetry contributed to very-strong secondary motion, associated with turbulent dissipation. A key feature of the channel design was the provision of a well-defined highly-turbulent low-velocity zone (LVZ) beneath the rib. The configuration might be applied to hydraulic structure design, but uttermost care must be considered. A number of practical considerations showed major technical challenges, and in many instances, alternative designs should be preferred, particularly in hydraulic structures. Altogether this detailed investigation demonstrated how the introduction of a seemingly simple streamwise shape, i.e. square rib, may induce a major change in hydrodynamic properties, in comparison to a simple rectangular channel flow

Phase diagram and critical properties within an effective model of QCD: the Nambu-Jona-Lasinio model coupled to the Polyakov loop

We investigate the phase diagram of the so-called Polyakov--Nambu--Jona-Lasinio model at finite temperature and non-zero chemical potential with three quark flavors. Chiral and deconfinement phase transitions are discussed and the relevant order-like parameters are analyzed. The results are compared with simple thermodynamic expectations and lattice data. We present the phase diagram in the ($T,\,\mu_B)$ plane, paying special attention to the critical end point: as the strength of the flavor-mixing interaction becomes weaker, the critical end point moves to low temperatures and can even disappear.Comment: 46 pages, 11 figures, 3 table

D-amino acids govern stationary phase cell wall remodeling in bacteria

4 pages, 4 figures.-- PMID: 19762646 [PubMed].-- Supporting information available at: http://www.sciencemag.org/cgi/content/full/sci;325/5947/1552/DC1In all known organisms, amino acids are predominantly thought to be synthesized and used as their L-enantiomers. Here, we found that bacteria produce diverse D-amino acids as well, which accumulate at millimolar concentrations in supernatants of stationary phase cultures. In Vibrio cholerae, a dedicated racemase produced D-Met and D-Leu, whereas Bacillus subtilis generated D-Tyr and D-Phe. These unusual D-amino acids appear to modulate synthesis of peptidoglycan, a strong and elastic polymer that serves as the stress-bearing component of the bacterial cell wall. D-Amino acids influenced peptidoglycan composition, amount, and strength, both by means of their incorporation into the polymer and by regulating enzymes that synthesize and modify it. Thus, synthesis of D-amino acids may be a common strategy for bacteria to adapt to changing environmental conditions.This work was supported by Howard Hughes Medical Institute (HHMI); NIH AI-R37-42347 (M.K.W.) and CA24487 and GM086258 (J.C.); Ministry of Education and Science, Spain (MEC) BFU2006-04574 and Fundación Ramón Areces (M.A.P.); Jane Coffin Childs Fellowship (H.L.); MEC Fellowship (F.C.); and HHMI Exceptional Research Opportunities (EXROP) (C.N.T.).Peer reviewe

Modulating the luminescence of an iridium(III) complex incorporating a di(2-picolyl)anilino-appended bipyridine ligand with Zn2+ cations

International audienceA novel iridium complex incorporating a di(2-picolyl)anilino-appended bipyridine ligand was synthesized and its optical properties studied. The presence of Zn2+ ions specifically perturbs the excited state, giving rise to a blue-shifted absorption and emission, and a shorter luminescence lifetime