The scaling of exploding liquid jets under intense X-ray pulses

A general scaling of the evolution of an exploding liquid jet under an ultra short and intense X-ray pulse from a X-ray free electron laser (XFEL) is proposed. A general formulation of the conservation of energy for blasts in vacuum partially against a deformable object leads to a compact expression that governs the evolution of the gap produced by the explosion. The theoretical analysis contemplates two asymptotic stages for small and large times from the initiation of the blast. A complete dimensional analysis of the problem and an optimal collapse of experimental data reveal that the universal approximate analytical solution proposed is in remarkable agreement with experiments

Kinetic approach to the cluster liquid-gas transition

The liquid-gas transition in free atomic clusters is investigated theoretically based on simple unimolecular rate theories and assuming sequential evaporations. A kinetic Monte Carlo scheme is used to compute the time-dependent properties of clusters undergoing multiple dissociations, and two possible definitions of the boiling point are proposed, relying on the cluster or gas temperature. This numerical approach is supported by molecular dynamics simulations of clusters made of sodium atoms or C60 molecules, as well as simplified rate equation

Theoretical study of finite temperature spectroscopy in van der Waals clusters. II Time-dependent absorption spectra

Using approximate partition functions and a master equation approach, we investigate the statistical relaxation toward equilibrium in selected CaAr$_n$ clusters. The Gaussian theory of absorption (previous article) is employed to calculate the average photoabsorption intensity associated with the 4s^2-> 4s^14p^1 transition of calcium as a function of time during relaxation. In CaAr_6 and CaAr_10 simple relaxation is observed with a single time scale. CaAr_13 exhibits much slower dynamics and the relaxation occurs over two distinct time scales. CaAr_37 shows much slower relaxation with multiple transients, reminiscent of glassy behavior due to competition between different low-energy structures. We interpret these results in terms of the underlying potential energy surfaces for these clusters.Comment: 10 pages, 9 figure

Social Networks in Labor Markets

Research in sociology and economics point to important role for social networks in labor markets. Social contacts mediate propagation of rich and reliable information among indi- viduals and thus help workers find jobs and employers find employees. Recent theoretical advances show that for agents connected through networks employment is positively cor- related across time and agents, unemployment exhibits duration dependence, and inequal- ity can persist. Recent empirical findings underscore nonlinearities in social interactions and potentially important effects of self-selection. Socioeconomic characteristics can explain substantial spatial dependence in unemployment.networks, labor markets, social connections, unemployment, proximity, spatial dependence, information networks, neighborhoods and jobs

Fixing for Your Life

The Asian crisis took place against a background of exchange rate regimes that were characterized as soft pegs. This has led many analysts to conclude that the peg did it' and that emerging markets (EMs) should just say no' to pegged exchange rates. We present evidence that EMs are very different from developed economies in key dimensions that play a key role when it comes to the choice of exchange rate regime--floating for EMs is no panacea. In EMs currency crashes are contractionary, the adjustments in the current account are far more acute. Credibility and market access, as captured in the behavior of credit ratings and interest rates, is adversely affected by devaluations or depreciations. Exchange rate volatility is more damaging to trade and the passthrough from exchange rate swings to inflation is far higher in EMs. These differences between emerging and developed economies may explain EMs reluctance to tolerate large exchange rate movements. In a simple framework we illustrate why large exchange rate swings are feared when access to international credit may be lost.

Fear of Floating

In recent years, many countries have suffered severe financial crises, producing a staggering toll on their economies, particularly in emerging markets. One view blames fixed exchange rates-- soft pegs'--for these meltdowns. Adherents to that view advise countries to allow their currency to float. We analyze the behavior of exchange rates, reserves, the monetary aggregates, interest rates, and commodity prices across 154 exchange rate arrangements to assess whether official labels' provide an adequate representation of actual country practice. We find that, countries that say they allow their exchange rate to float mostly do not--there seems to be an epidemic case of fear of floating.' Since countries that are classified as having a free or a managed float mostly resemble noncredible pegs--the so-called demise of fixed exchange rates' is a myth--the fear of floating is pervasive, even among some of the developed countries. We present an analytical framework that helps to understand why there is fear of floating.