Building and Refining Abstract Planning Cases by Change of Representation Language

ion is one of the most promising approaches to improve the performance of problem solvers. In several domains abstraction by dropping sentences of a domain description -- as used in most hierarchical planners -- has proven useful. In this paper we present examples which illustrate significant drawbacks of abstraction by dropping sentences. To overcome these drawbacks, we propose a more general view of abstraction involving the change of representation language. We have developed a new abstraction methodology and a related sound and complete learning algorithm that allows the complete change of representation language of planning cases from concrete to abstract. However, to achieve a powerful change of the representation language, the abstract language itself as well as rules which describe admissible ways of abstracting states must be provided in the domain model. This new abstraction approach is the core of Paris (Plan Abstraction and Refinement in an Integrated System), a system in which abstract planning cases are automatically learned from given concrete cases. An empirical study in the domain of process planning in mechanical engineering shows significant advantages of the proposed reasoning from abstract cases over classical hierarchical planning.Comment: See http://www.jair.org/ for an online appendix and other files accompanying this articl

The Economic Consequences of the Decline of Marriage

The institution of marriage has served to funnel economic resources from fathers to children. Its continued decline in the countries of the developed world threatens the adequacy of the economic support of human reproduction, now increasingly provided by women. Its decline is also probably implicated in the low birth rates now being registered. The rise of cohabitation has not prevented a rise in the proportion of lone parents, and their numbers are growing rapidly. The children of lone parents are relatively deprived, both in terms of income and adults’ time for child care and housekeeping. Government-supported programs in the United States aimed at rescuing marriage have not been proven effective. Ways need to be explored to get a return of men’s economic support for reproduction. But the most likely way of repairing at least some of the damage to children is a big increase in government provision to the entire population of goods and services that children need: health care, high-quality education, child care, decent housing, university education. This will require in most countries a big rise in taxes and government expenditure.

The Conductance of a Perfect Thin Film with Diffuse Surface Scattering

The conductance of thin films with diffusive surface scattering was solved semi-classically by Fuchs and Sondheimer. However, when the intrinsic electron mean free path is very large or infinite their conductance diverges. In this letter a simple diffraction picture is presented. It yields a conductance which corresponds to a limiting mean free path. PACS: 73.50.-h, 73.50.Bk, 73.23.-b, 73.25.+i, B14

Coherent population transfer beyond the adiabatic limit: generalized matched pulses and higher-order trapping states

We show that the physical mechanism of population transfer in a 3-level system with a closed loop of coherent couplings (loop-STIRAP) is not equivalent to an adiabatic rotation of the dark-state of the Hamiltonian but coresponds to a rotation of a higher-order trapping state in a generalized adiabatic basis. The concept of generalized adiabatic basis sets is used as a constructive tool to design pulse sequences for stimulated Raman adiabatic passage (STIRAP) which give maximum population transfer also under conditions when the usual condition of adiabaticty is only poorly fulfilled. Under certain conditions for the pulses (generalized matched pulses) there exists a higher-order trapping state, which is an exact constant of motion and analytic solutions for the atomic dynamics can be derived.Comment: 15 pages, 9 figure

Bifurcation discovery tool

Motivation: Biochemical networks often yield interesting behavior such as switching, oscillation and chaotic dynamics. This article describes a tool that is capable of searching for bifurcation points in arbitrary ODE-based reaction networks by directing the user to regions in the parameter space, where such interesting dynamical behavior can be observed. Results: We have implemented a genetic algorithm that searches for Hopf bifurcations, turning points and bistable switches. The software is implemented as a Systems Biology Workbench (SBW) enabled module and accepts the standard SBML model format. The interface permits a user to choose the parameters to be searched, admissible parameter ranges, and the nature of the bifurcation to be sought. The tool will return the parameter values for the model for which the particular behavior is observed. Availability: The software, tutorial manual and test models are available for download at the following website: http:/www.sys-bio.org/ under the bifurcation link. The software is an open source and licensed under BSD

Transition (LINER/HII) nuclei as evolved Composite (Seyfert 2/Starburst) nuclei

We compare the circumnuclear stellar population and environmental properies of Seyfert and Composite (Seyfert + Starburst) nuclei with those of LINERs and LINER/HII transition galaxies (TOs), and discuss evidences for evolution from Seyfert/Composite to LINER/TO nuclei.Comment: 2 pages, 1 figure; to appear in the Proceedings of IAU Symp. No. 222: The Interplay among Black Holes, Stars and ISM in Galactic Nuclei, CUP, eds. T. Storchi-Bergmann, L. Ho and H. R. Schmit

Measuring a coherent superposition

We propose a simple method for measuring the populations and the relative phase in a coherent superposition of two atomic states. The method is based on coupling the two states to a third common (excited) state by means of two laser pulses, and measuring the total fluorescence from the third state for several choices of the excitation pulses.Comment: 7 pages, 1 figure, twocolumn REVTe