Homogeneous nucleation of quark-gluon plasma, finite size effects and long-lived metastable objects

The general formalism of homogeneous nucleation theory is applied to study the hadronization pattern of the ultra-relativistic quark-gluon plasma (QGP) undergoing a first order phase transition. A coalescence model is proposed to describe the evolution dynamics of hadronic clusters produced in the nucleation process. The size distribution of the nucleated clusters is important for the description of the plasma conversion. The model is most sensitive to the initial conditions of the QGP thermalization, time evolution of the energy density, and the interfacial energy of the plasma-hadronic matter interface. The rapidly expanding QGP is first supercooled by about $\Delta T = T - T_c = 4-6$. Then it reheats again up to the critical temperature T_c. Finally it breaks up into hadronic clusters and small droplets of plasma. This fast dynamics occurs within the first $5-10 fm/c$. The finite size effects and fluctuations near the critical temperature are studied. It is shown that a drop of longitudinally expanding QGP of the transverse radius below 4.5 fm can display a long-lived metastability. However, both in the rapid and in the delayed hadronization scenario, the bulk pion yield is emitted by sources as large as 3-4.5 fm. This may be detected experimentally both by a HBT interferometry signal and by the analysis of the rapidity distributions of particles in narrow p_T-intervals at small p_T on an event-by-event basis.Comment: 29 pages, incl. 12 figures and 1 table; to be published in Phys. Rev.

Electromagnetic form factors of light vector mesons

The electromagnetic form factors G_E(q^2), G_M(q^2), and G_Q(q^2), charge radii, magnetic and quadrupole moments, and decay widths of the light vector mesons rho^+, K^{*+} and K^{*0} are calculated in a Lorentz-covariant, Dyson-Schwinger equation based model using algebraic quark propagators that incorporate confinement, asymptotic freedom, and dynamical chiral symmetry breaking, and vector meson Bethe-Salpeter amplitudes closely related to the pseudoscalar amplitudes obtained from phenomenological studies of pi and K mesons. Calculated static properties of vector mesons include the charge radii and magnetic moments: r_{rho+} = 0.61 fm, r_{K*+} = 0.54 fm, and r^2_{K*0} = -0.048 fm^2; mu_{rho+} = 2.69, mu_{K*+} = 2.37, and mu_{K*0} = -0.40. The calculated static limits of the rho-meson form factors are similar to those obtained from light-front quantum mechanical calculations, but begin to differ above q^2 = 1 GeV^2 due to the dynamical evolution of the quark propagators in our approach.Comment: 8 pages of RevTeX, 5 eps figure

Increasing Seed Viability of Maize Haploid Inducing Lines by Genetic and Non-Genetic Approaches

Some haploid inducing lines used in the production of maize doubled haploids (DHs), express germination problems and reduced vigor. In this study, haploid inducing lines RWS, RWK-76 and their reciprocal hybrids RWS/RWK-76 and RWK-76/RWS were examined for viability by Tetrazolium (TZ) and germination ability by standard germination tests. Evaluation based on TZ tests showed that 59% of the seed of RWK-76/RWS were not viable, compared with only 12% dead seed in RWS/RWK-76. Similarly, the percentage and speed of germination in RWK- 76/RWS (25%, 1.53) was lower than for RWS/RWK-76 (74%, 4.30). In an effort to develop a quick method for assessing seed viability in these lines, the TZ test was repeated in a different way. Seed from each genotype was placed in beakers containing distilled water.Seed would either float or sink. Subsequent TZ testing confirmed that seed that floated was dead, and seed that sank was alive, although some of them had defective embryos. The dead seed in both genotypes failed to develop an embryo, leaving an empty cavity that would fill with air and cause seed to float on water. This feature can be exploited for a simple and practical method to separate living from dead seed. In addition, we surveyed theig1 (indeterminate gametophyte) gene as a candidate for germination problems in inducer lines.Sequencing data from theig1 region showed that RWS and RWK-76 differed in one nucleotide and amino acidin the firstexon of ig1.Segregation of ig1 alleles from RWS and RWK-76 wassignificantly (P=0.01) distortedin the respectiveF2 population relative to the expected Mendelian segregation ratio (1:2:1). Thus, either ig1 or a linked gene in the ig1 region affect seed viability

Some Consequences of Thermosolutal Convection: The Grain Structure of Castings

The essential principles of thermosolutal convection are outlined, and how convection provides a transport mechanism between the mushy region of a casting and the open bulk liquid is illustrated. The convective flow patterns which develop assist in heat exchange and macroscopic solute segregation during solidification; they also provide a mechanism for the transport of dendritic fragments from the mushy region into the bulk liquid. Surviving fragments become nuclei for equiaxed grains and so lead to blocking of the parental columnar, dendritic growth front from which they originated. The physical steps in such a sequence are considered and some experimental data are provided to support the argument

A study of the reaction pim p --> omega pim p at 18 GeV/c: The D and S decay amplitudes for b1(1235) --> omega pi

The reaction pim p --> omega pim p, omega --> pip pim pi0 has been studied at 18 GeV/c. The omega pim mass spectrum is found to be dominated by the b1(1235). Partial Wave Analysis shows that b1 production is dominated by natural parity exchange. The S-wave and D-wave amplitudes for b1(1235) --> omega pi have been determined, and it is found that the amplitude ratio, |D/S| = 0.269 +/- (0.009)stat +/- (0.01)sys and the phase difference, phi(D-S) = 10.54 deg +/- (2.4)stat +/- (3.9)sys.Comment: 7 pages, 9 figures, revtex4 format, to be published in Physics Letters

Prospects for e+e- physics at Frascati between the phi and the psi

We present a detailed study, done in the framework of the INFN 2006 Roadmap, of the prospects for e+e- physics at the Frascati National Laboratories. The physics case for an e+e- collider running at high luminosity at the phi resonance energy and also reaching a maximum center of mass energy of 2.5 GeV is discussed, together with the specific aspects of a very high luminosity tau-charm factory. Subjects connected to Kaon decay physics are not discussed here, being part of another INFN Roadmap working group. The significance of the project and the impact on INFN are also discussed. All the documentation related to the activities of the working group can be found in http://www.roma1.infn.it/people/bini/roadmap.html.Comment: INFN Roadmap Report: 86 pages, 25 figures, 9 table

The psychological science accelerator’s COVID-19 rapid-response dataset

In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data

A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic

The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world