Equation of state and initial temperature of quark gluon plasma at RHIC

In gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) a perfect fluid of quarks, sometimes called the strongly interacting quark gluon plasma (sQGP) is created for an extremely short time. The time evolution of this fluid can be described by hydrodynamical models. After expansion and cooling, the freeze-out happens and hadrons are created. Their distribution reveals information about the final state of the fluid. To investigate the time evolution one needs to analyze penetrating probes, such as direct photon observables. Transverse momentum distributions of low energy direct photons were mesured in 2010 by PHENIX, while azimuthal asymmetry in 2011. These measurements can be compared to hydrodynamics to determine the equation of state and the initial temperature of sQGP. In this paper we analyze an 1+3 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution, azimuthal asymmetry and momentum correlations of direct photons. Based on earlier fits to hadronic spectra, we compare photon calculations to measurements to determine the equation of state and the initial temperature of sQGP. We find that the initial temperature in the center of the fireball is 507+-12 MeV, while for the sound speed we get a speed of sound of 0.36+-0.02. We also estimate a systematic error of these results. We find that the measured azimuthal asymmetry is also not incompatible with this model, and predict a photon source that is significantly larger in the out direction than in the side direction.Comment: 12 pages, 4 figures. This work was supported by the OTKA grant NK-73143 and NK-101438 and M. Csanad's Bolyai scholarshi

Five-year follow-up of participants diagnosed with chronic airflow obstruction in a South African Burden of Obstructive Lung Disease (BOLD) survey

Background. A community-based prevalence survey performed in two suburbs in Cape Town, South Africa (SA), in 2005, using the international Burden of Obstructive Lung Disease (BOLD) method, confirmed a prevalence of chronic airflow obstruction (CAO) in 23.1% of adults aged >40 years.Objectives. To study the clinical course and prognosis over 5 years of patients with CAO identified in the 2005 survey.Methods. Patients with CAO in 2005 were invited to participate. Standard BOLD and modified questionnaires were completed. Spirometry was performed using spirometers of the same make as in 2005.Results. Of 196 eligible participants from BOLD 2005, 45 (23.0%) had died, 8 from respiratory causes, 10 from cardiovascular causes and 6 from other known causes, while in 21 cases the cause of death was not known. On multivariate analysis, only age and Global initiative for Obstructive Lung Disease (GOLD) stage 4 disease at baseline were significantly associated with death. Of the 151 survivors, 11 (5.6% of the original cohort) were unavailable and 33 (16.8%) declined or had medical exclusions. One hundred and seven survivors were enrolled in the follow-up study (54.6%, median age 63.1 years, 45.8% males). Post-bronchodilator spirometry performed in 106 participants failed to confirm CAO, defined as a forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio of <0.7, in 16 participants (15.1%), but CAO was present in 90. The median decline in FEV1 was 28.9 mL/year (interquartile range –54.8 - 0.0) and was similar between GOLD stages. The median total decline in FVC was 75 mL, and was significantly greater in GOLD stage 1 (–350 mL) than in stages 2 or 3 (–80 mL and +140 mL, respectively; p<0.01). Fifty-eight participants with CAO in 2005 (64.4%) remained in the same GOLD stage, while 21 (23.3%) deteriorated and 11 (12.2%) improved by ≥1 stage. Only one-third were receiving any treatment for chronic obstructive pulmonary disease (COPD).Conclusions. The prevalence, morbidity and mortality of CAO and COPD in SA are high and the level of appropriate treatment is very low, pointing to underdiagnosis and inadequate provision of and access to effective treatments and preventive strategies for this priority chronic non-communicable disease

Control of Autophagosome Axonal Retrograde Flux by Presynaptic Activity Unveiled Using Botulinum Neurotoxin Type A

Botulinum neurotoxin type A (BoNT/A) is a highly potent neurotoxin that elicits flaccid paralysis by enzymatic cleavage of the exocytic machinery component SNAP25 in motor nerve terminals. However, recent evidence suggests that the neurotoxic activity of BoNT/A is not restricted to the periphery, but also reaches the CNS after retrograde axonal transport. Because BoNT/A is internalized in recycling synaptic vesicles, it is unclear which compartment facilitates this transport. Using live-cell confocal and single-molecule imaging of rat hippocampal neurons cultured in microfluidic devices, we show that the activity-dependent uptake of the binding domain of the BoNT/A heavy chain (BoNT/A-Hc) is followed by a delayed increase in retrograde axonal transport of BoNT/A-Hc carriers. Consistent with a role of presynaptic activity in initiating transport of the active toxin, activity-dependent uptake of BoNT/A in the terminal led to a significant increase in SNAP25 cleavage detected in the soma chamber compared with nonstimulated neurons. Surprisingly, most endocytosed BoNT/A-Hc was incorporated into LC3-positive autophagosomes generated in the nerve terminals, which then underwent retrograde transport to the cell soma, where they fused with lysosomes both in vitro and in vivo. Blocking autophagosome formation or acidification with wortmannin or bafilomycin A1, respectively, inhibited the activity-dependent retrograde trafficking of BoNT/A-Hc. Our data demonstrate that both the presynaptic formation of autophagosomes and the initiation of their retrograde trafficking are tightly regulated by presynaptic activity

Λc+\Lambda^+_c- and Λb\Lambda_b-hypernuclei

$\Lambda^+_c$- and $\Lambda_b$-hypernuclei are studied in the quark-meson coupling (QMC) model. Comparisons are made with the results for $\Lambda$-hypernuclei studied in the same model previously. Although the scalar and vector potentials felt by the $\Lambda$, $\Lambda_c^+$ and $\Lambda_b$ in the corresponding hypernuclei multiplet which has the same baryon numbers are quite similar, the wave functions obtained, e.g., for $1s_{1/2}$ state, are very different. The $\Lambda^+_c$ baryon density distribution in $^{209}_{\Lambda^+_c}$Pb is much more pushed away from the center than that for the $\Lambda$ in $^{209}_\Lambda$Pb due to the Coulomb force. On the contrary, the $\Lambda_b$ baryon density distributions in $\Lambda_b$-hypernuclei are much larger near the origin than those for the $\Lambda$ in the corresponding $\Lambda$-hypernuclei due to its heavy mass. It is also found that level spacing for the $\Lambda_b$ single-particle energies is much smaller than that for the $\Lambda$ and $\Lambda^+_c$.Comment: Latex, 14 pages, 4 figures, text was extended, version to appear in Phys. Rev.

Plasmonic excitations in noble metals: The case of Ag

The delicate interplay between plasmonic excitations and interband transitions in noble metals is described by means of {\it ab initio} calculations and a simple model in which the conduction electron plasmon is coupled to the continuum of electron-hole pairs. Band structure effects, specially the energy at which the excitation of the $d$-like bands takes place, determine the existence of a subthreshold plasmonic mode, which manifests itself in Ag as a sharp resonance at 3.8 eV. However, such a resonance is not observed in the other noble metals. Here, this different behavior is also analyzed and an explanation is provided.Comment: 9 pages, 8 figure

Knowledge network modelling to support decision-making for strategic intervention in IT project-oriented change management

This is the Accepted Manuscript version of an article published by Taylor & Francis in Journal of Decision Systems on 20 March 2014, available online: http://www.tandfonline.com/doi/abs/10.1080/12460125.2014.886499.This paper focuses on knowledge management to enhance decision support systems for strategic intervention in information technology (IT) project-oriented change management. It proposes a model of change management knowledge networks (CMKNM) to support decision by tackling three existing issues: insufficient knowledge traceability based on the relationships between knowledge elements and key factors, lack of procedural knowledge to provide adequate policies to guide changes, and lack of ‘lessons learned’ documentation in knowledge bases. A qualitative method was used to investigate issues surrounding knowledge mobilisation and knowledge networks. Empirical study was undertaken with industries to test the CMKNM. Results are presented from the empirical study on the key factors influencing knowledge mobilisation in IT project-oriented change management, knowledge networks and connections. The CMKNM model allows key knowledge mobilisation factors to be aligned with each other; it also defines the connections between knowledge networks allowing knowledge to be mobilised by tracing knowledge channels to support decision.Peer reviewe

Bound state solutions of the Dirac-Rosen-Morse potential with spin and pseudospin symmetry

The energy spectra and the corresponding two- component spinor wavefunctions of the Dirac equation for the Rosen-Morse potential with spin and pseudospin symmetry are obtained. The $s-$wave ($\kappa = 0$ state) solutions for this problem are obtained by using the basic concept of the supersymmetric quantum mechanics approach and function analysis (standard approach) in the calculations. Under the spin symmetry and pseudospin symmetry, the energy equation and the corresponding two-component spinor wavefunctions for this potential and other special types of this potential are obtained. Extension of this result to $\kappa \neq 0$ state is suggested.Comment: 18 page

Observables from a solution of 1+3 dimensional relativistic hydrodynamics

In this paper we analyze a 1+3 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution and other observables from the solution and compare them to measurements from the Relativistic Heavy Ion Collider (RHIC). We find that the solution we analyze is compatible with the data. In the last several years many numerical models were tested, but it is the first time that an exact, parametric, 1+3 dimensional relativistic solution is compared to data.Comment: 6 pages, 6 figures. Published in EPJ A. This work was supported by the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi

Spin-Charge Separation in the t−Jt-J Model: Magnetic and Transport Anomalies

A real spin-charge separation scheme is found based on a saddle-point state of the $t-J$ model. In the one-dimensional (1D) case, such a saddle-point reproduces the correct asymptotic correlations at the strong-coupling fixed-point of the model. In the two-dimensional (2D) case, the transverse gauge field confining spinon and holon is shown to be gapped at {\em finite doping} so that a spin-charge deconfinement is obtained for its first time in 2D. The gap in the gauge fluctuation disappears at half-filling limit, where a long-range antiferromagnetic order is recovered at zero temperature and spinons become confined. The most interesting features of spin dynamics and transport are exhibited at finite doping where exotic {\em residual} couplings between spin and charge degrees of freedom lead to systematic anomalies with regard to a Fermi-liquid system. In spin dynamics, a commensurate antiferromagnetic fluctuation with a small, doping-dependent energy scale is found, which is characterized in momentum space by a Gaussian peak at ($\pi/a$, $\pi/a$) with a doping-dependent width ($\propto \sqrt{\delta}$, $\delta$ is the doping concentration). This commensurate magnetic fluctuation contributes a non-Korringa behavior for the NMR spin-lattice relaxation rate. There also exits a characteristic temperature scale below which a pseudogap behavior appears in the spin dynamics. Furthermore, an incommensurate magnetic fluctuation is also obtained at a {\em finite} energy regime. In transport, a strong short-range phase interference leads to an effective holon Lagrangian which can give rise to a series of interesting phenomena including linear-$T$ resistivity and $T^2$ Hall-angle. We discuss the striking similarities of these theoretical features with those found in the high-$T_c$ cuprates and give aComment: 70 pages, RevTex, hard copies of 7 figures available upon request; minor revisions in the text and references have been made; To be published in July 1 issue of Phys. Rev. B52, (1995