Matter-positronium interaction: An exact diagonalization study of the He atom - positronium system

The many-body system comprising a He nucleus, three electrons, and a positron has been studied using the exact diagonalization technique. The purpose has been to clarify to which extent the system can be considered as a distinguishable positronium (Ps) atom interacting with a He atom and, thereby, to pave the way to a practical atomistic modeling of Ps states and annihilation in matter. The maximum value of the distance between the positron and the nucleus is constrained and the Ps atom at different distances from the nucleus is identified from the electron and positron densities, as well as from the electron-positron distance and center-of-mass distributions. The polarization of the Ps atom increases as its distance from the nucleus decreases. A depletion of the He electron density, particularly large at low density values, has been observed. The ortho-Ps pick-off annihilation rate calculated as the overlap of the positron and the free He electron densities has to be corrected for the observed depletion, specially at large pores/voids.Comment: 18 pages, 8 figure

The role of positronium decoherence in the studies of positron annihilation in matter

A small difference between the energy of the para-positronium (p-Ps) and ortho-positronium (o-Ps) states suggests the possibility of superposition of p-Ps and o-Ps during the formation of positronium (Ps) from pre-Ps terminating its migration in the matter in a void ('free volume'). It is shown that such a superposition decohere in the basis of p-Ps and o-Ps and the decoherence time is estimated. The time scale of the decoherence estimated here motivates respective correction in decomposition of the positron annihilation lifetime spectra. The way of the correction is sketched. The timescale of the decoherence suggests a need of awareness when experimental data from positron annihilation techniques are processed. More generally, the superposited state of Ps should contribute to the evolution theory of positronium in matter.Comment: 15 pages, 6 figure

Toward an Energy Efficient Language and Compiler for (Partially) Reversible Algorithms

We introduce a new programming language for expressing reversibility, Energy-Efficient Language (Eel), geared toward algorithm design and implementation. Eel is the first language to take advantage of a partially reversible computation model, where programs can be composed of both reversible and irreversible operations. In this model, irreversible operations cost energy for every bit of information created or destroyed. To handle programs of varying degrees of reversibility, Eel supports a log stack to automatically trade energy costs for space costs, and introduces many powerful control logic operators including protected conditional, general conditional, protected loops, and general loops. In this paper, we present the design and compiler for the three language levels of Eel along with an interpreter to simulate and annotate incurred energy costs of a program.Comment: 17 pages, 0 additional figures, pre-print to be published in The 8th Conference on Reversible Computing (RC2016

Photonic crystal resonator integrated in a microfluidic system

We report on a novel optofluidic system consisting of a silica-based 1D photonic crystal, integrated planar waveguides and electrically insulated fluidic channels. An array of pillars in a microfluidic channel designed for electrochromatography is used as a resonator for on-column label-free refractive index detection. The resonator was fabricated in a silicon oxynitride platform, to support electroosmotic flow, and operated at 1.55 microns. Different aqueous solutions of ethanol with refractive indices ranging from n = 1.3330 to 1.3616 were pumped into the column/resonator and the transmission spectra were recorded. Linear shifts of the resonant wavelengths yielded a maximum sensitivity of 480 nm/RIU and a minimum difference of 0.007 RIU was measured

Vermittlung von Schlüsselkompetenzen bei der Ausbildung im Ökologischen Landbau am Beispiel Polen

The aim of this paper is to analyze if non-formal education in folk high schools, based on the ideas of Grundtvig, combined with vocational training on organic farming is suited to build key competences recommended by the EU. A curriculum for a two year vocational training course on organic farming was developed and tested at a folk high school in Poland. Interviews with students and teachers give very positive feedback

Detecting Determinacy in Prolog Programs: 22nd International Conference, ICLP 2006, Seattle, WA, USA, August 17-20, 2006. Proceedings

In program development it is useful to know that a call to a Prolog program will not inadvertently leave a choice-point on the stack. Determinacy inference has been proposed for solving this problem yet the analysis was found to be wanting in that it could not infer determinacy conditions for programs that contained cuts or applied certain tests to select a clause. This paper shows how to remedy these serious deficiencies. It also addresses the problem of identifying those predicates which can be rewritten in a more deterministic fashion. To this end, a radically new form of determinacy inference is introduced, which is founded on ideas in ccp, that is capable of reasoning about the way bindings imposed by a rightmost goal can make a leftmost goal deterministic