Transverse energy fluctuations and the pattern of J/Psi suppression in Pb-Pb collisions

The NA50 collaboration has recently observed that the J/psi production rate in Pb-Pb collisions decreases more rapidly as a function of the transverse energy for the most central collisions than for less central ones. We show that this phenomenon can be understood as an effect of transverse energy fluctuations in central collisions. A good fit of the data is obtained using a model which relates J/psi suppression to the local energy density. Our results suggest that the J/psi is completely suppressed at the highest densities achieved in Pb-Pb collisions.Comment: v2, 4 pages, LaTeX, 3 eps figures include

J/Psi suppression in central Pb-Pb collisions

We discuss the recent NA50 J/Psi production data in Pb--Pb collisions, in particular the second drop at high transverse energies which correspond to the most central collisions. Using a model which relates the J/Psi suppression to the local energy density, we show that the data can be explained by taking into account transverse energy fluctuations at a given impact parameter. Predictions of this model for RHIC are briefly discussed.Comment: to appear in the Proceedings of Quark Matter'200

Stochastic TDHF in an exactly solvable model

We apply in a schematic model a theory beyond mean-field, namely Stochastic Time-Dependent Hartree-Fock (STDHF), which includes dynamical electron-electron collisions on top of an incoherent ensemble of mean-field states by occasional 2-particle-2-hole ($2p2h$) jumps. The model considered here is inspired by a Lipkin-Meshkov-Glick model of $\Omega$ particles distributed into two bands of energy and coupled by a two-body interaction. Such a model can be exactly solved (numerically though) for small $\Omega$. It therefore allows a direct comparison of STDHF and the exact propagation. The systematic impact of the model parameters as the density of states, the excitation energy and the bandwidth is presented and discussed. The time evolution of the STDHF compares fairly well with the exact entropy, as soon as the excitation energy is sufficiently large to allow $2p2h$ transitions. Limitations concerning low energy excitations and memory effects are also discussed.Comment: 23 pages, 8 figures, accepted in Annals of Physic

Interview with Lee Pao Xiong

Born in Long Tieng, Laos in 1966, Lee Pao Xiong lived with his father, who had already been recruited into the Hmong army at age 12. His mother and grandparents lived nearby. After the fall of Long Tieng in May 1975, Xiong and his family spent more than a year in Thai refugee camps before migrating to the United States in 1976. Settling first in Indiana, his family moved to the Twin Cities in 1979. Xiong earned a B.S. in Political Science from the University of Minnesota, an M.A. from Hamline University, and is currently pursuing his Ph.D. He has held a variety of important positions, including: Executive Director of Hmong-American Partnership; Executive Director, State Council on Asian-Pacific Minnesotans; Director, Government & Community Relations, Concordia University; President & CEO, Urban Coalition. In 2000 he became the first Hmong American presidential appointee when Bill Clinton named him to serve on the President’s Advisory Commission on Asian Americans and Pacific Islanders. He is currently the Director of the Center for Hmong Studies at Concordia University – St. Paul. **Editor’s note: One should note that laughter can express a wide range of emotions. In Mr. Xiong’s case, laughter is often used to defuse a tense or even tragic story he is relating

Influential Article Review - The Importance of Humility and Trust in the Workplace

This paper examines leadership. We present insights from a highly influential paper. Here are the highlights from this paper: Leader humility has emerged as an important topic in understanding the role of leadership in organizations in recent years. Though it was found to enhance subordinates’ work performance and positive work behaviors, we are unaware of the psychological mechanism and boundary conditions underlying leader humility and employees’ negative behaviors toward leaders. Drawing on social exchange theory and using a multistage sample including 273 employees and 55 supervisors in China, we demonstrated a negative indirect effect between leader humility and subordinates’ counterproductive work behaviors toward supervisors (CWB-S) via interpersonal justice and trust in supervisors. Furthermore, we find that a leader's political skill moderates the effect of leader humility on interpersonal justice and trust in the supervisor. The indirect effect of leader humility on subordinates’ CWB-S through interpersonal justice is stronger when leader political skill is high, suggesting a moderated mediation model. Finally, we discuss the theoretical contributions and practical implications of this study, and highlight future directions for research on leader humility. For our overseas readers, we then present the insights from this paper in Spanish, French, Portuguese, and German

Boosting heritability : estimating the genetic component of phenotypic variation with multiple sample splitting

Background Heritability is a central measure in genetics quantifying how much of the variability observed in a trait is attributable to genetic differences. Existing methods for estimating heritability are most often based on random-effect models, typically for computational reasons. The alternative of using a fixed-effect model has received much more limited attention in the literature. Results In this paper, we propose a generic strategy for heritability inference, termed as "boosting heritability", by combining the advantageous features of different recent methods to produce an estimate of the heritability with a high-dimensional linear model. Boosting heritability uses in particular a multiple sample splitting strategy which leads in general to a stable and accurate estimate. We use both simulated data and real antibiotic resistance data from a major human pathogen, Sptreptococcus pneumoniae, to demonstrate the attractive features of our inference strategy. Conclusions Boosting is shown to offer a reliable and practically useful tool for inference about heritability.Peer reviewe