Ionization of clusters in intense laser pulses through collective electron dynamics

The motion of electrons and ions in medium-sized rare gas clusters (1000 atoms) exposed to intense laser pulses is studied microscopically by means of classical molecular dynamics using a hierarchical tree code. Pulse parameters for optimum ionization are found to be wavelength dependent. This resonant behavior is traced back to a collective electron oscillation inside the charged cluster. It is shown that this dynamics can be well described by a driven and damped harmonic oscillator allowing for a clear discrimination against other energy absorption mechanisms.Comment: 4 pages (4 figures

A systematic review of pliance, tracking, and augmenting

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What is learning? On the nature and merits of a functional definition of learning

Learning has been defined functionally as changes in behavior that result from experience or mechanistically as changes in the organism that result from experience. Both types of definitions are problematic. We define learning as ontogenetic adaptation-that is, as changes in the behavior of an organism that result from regularities in the environment of the organism. This functional definition not only solves the problems of other definitions, but also has important advantages for cognitive learning research

Europe�s New Fiscal Rules

Europe has put in place a new system of complex fiscal rules. These include the so-called �six pack� to upgrade the Stability and Growth Pact and a new Treaty incorporating the �fiscal compact�. Much of the discussion about the new rules has been procedural or theoretical. This paper shows what the rules will mean in practice under a medium-term scenario developed by the OECD. So far, fiscal consolidation has largely been driven by the recent wave of Excessive Deficit Procedures. Only once these commitments have been fulfilled will the new system of rules come into action. Its pillar will be the requirement to balance budgets in structural terms. The rules imply a tight fiscal stance over the coming years for many European countries by historical standards. Almost all countries will have to be as disciplined as the few countries that managed to make meaningful progress in tackling high debt levels in the past. Over the very long term, the rules imply extremely low levels of debt. Thus, the requirements are not likely to be permanent. The rules are complex. The methodology to calculate the structural balance has a number of weaknesses and discretion will be needed in implementing the rules