Competing field pulse induced dynamic transition in Ising models

The dynamic magnetization-reversal phenomena in the Ising model under a finite-duration external magnetic field competing with the existing order for $T<T_c^0$ has been discussed. The nature of the phase boundary has been estimated from the mean-field equation of motion. The susceptibility and relaxation time diverge at the MF phase boundary. A Monte Carlo study also shows divergence of relaxation time around the phase boundary. Fluctuation of order parameter also diverge near the phase boundary. The behavior of the fourth order cumulant shows two distinct behavior: for low temperature and pulse duration region of the phase boundary the value of the cumulant at the crossing point for different system sizes is much less than that corersponding to the static transition in the same dimension which indicate a new universality class for the dynamic transition. Also, for higher temperature and pulse duration, the transition seem to fall in a mean-field like weak-singularity universality class.Comment: 12 pages, 17 ps & eps figures, to appear in a Special Issue of Phase Transitions (2004), Ed. S. Pur

Economic Inequality: Is it Natural?

Mounting evidences are being gathered suggesting that income and wealth distribution in various countries or societies follow a robust pattern, close to the Gibbs distribution of energy in an ideal gas in equilibrium, but also deviating significantly for high income groups. Application of physics models seem to provide illuminating ideas and understanding, complimenting the observations.Comment: 7 pages, 2 eps figs, 2 boxes with text and 2 eps figs; Popular review To appear in Current Science; typos in refs and text correcte

Money in Gas-Like Markets: Gibbs and Pareto Laws

We consider the ideal-gas models of trading markets, where each agent is identified with a gas molecule and each trading as an elastic or money-conserving (two-body) collision. Unlike in the ideal gas, we introduce saving propensity $\lambda$ of agents, such that each agent saves a fraction $\lambda$ of its money and trades with the rest. We show the steady-state money or wealth distribution in a market is Gibbs-like for $\lambda=0$, has got a non-vanishing most-probable value for $\lambda \ne 0$ and Pareto-like when $\lambda$ is widely distributed among the agents. We compare these results with observations on wealth distributions of various countries.Comment: 4 pages, 2 eps figures, in Conference Procedings of International Conference on "Unconventional Applications of Statistical Physics", Kolkata, India, March 2003; paper published in Physica Scripta T106 (2003) 3

Back to the Future: Lessons Learned in Modern Target-based and Whole-Cell Lead Optimization of Antimalarials

Antimalarial drug discovery has historically benefited from the whole-cell (phenotypic) screening approach to identify lead molecules in the search for new drugs. However over the past two decades there has been a shift in the pharmaceutical industry to move away from whole-cell screening to target-based approaches. As part of a Wellcome Trust and Medicines for Malaria Venture (MMV) funded consortium to discover new blood-stage antimalarials, we used both approaches to identify new antimalarial chemotypes, two of which have progressed beyond the lead optimization phase and display excellent in vivo efficacy in mice. These two advanced series were identified through a cell-based optimization devoid of target information and in this review we summarize the advantages of this approach versus a target-based optimization. Although the each lead optimization required slightly different medicinal chemistry strategies, we observed some common issues across the different the scaffolds which could be applied to other cell based lead optimization programs