Analytic Rank of Graph Algebras and Quantum Spaces

We show that the analytic rank, as defined by Murphy, of a unitalgraph C*-algebra is either 1 or 0, depending on whether or notthe underlying graph possesses an initial loop. As a corollary,we show that the analytic rank of certain quantum spaces (includingsome quantum spheres, projective spaces and lens spaces) is1. 2000 Mathematics Subject Classification 46L05, 46L65, 46L87.     

Structures and potential superconductivity in at high pressure: en route to "metallic hydrogen"

A way to circumvent the high pressures needed to metallize hydrogen is to "precompress" it in hydrogen-rich molecules, a strategy probed theoretically for silane. We show that phases with tetrahedral SiH4 molecules should undergo phase transitions with sixfold- and eightfold-coordinate Si appearing above 25 GPa. The most stable structure found can be metallized at under a megabar and at a compression close to the prediction of Goldhammer-Herzfeld criterion. According to a BCS-like estimate, metallic silane should be a high-temperature superconductor.     

1-Bromo-1-chloro-2,2,2-trifluoroethane (Halothane) as a building block for fluorine compounds

This review provides an overview of several synthetic applications of the first fluorinated anaestetic, 1-bromo-1-chloro-2,2,2-trifluoroethane, leading to convenient preparation of numerous fluorine, and particularly, CF₃ group containing compounds via organometallic (Mg, Zn) and free radical “sulphinatodehalogenation” reactions.     

Study of the elemental composition of wine stoppers using PIXE

Analysis of stoppers has been restricted mostly to the determination of organic compounds and microorganisms, but none of these studies aimed at the mineral contents of stoppers. Therefore, the aim of this work is to determine the elemental concentration of cork and synthetic stoppers. Wine, cork, and synthetic stoppers were analyzed through the particle‐induced X‐ray emission and micro‐particle‐induced X‐ray emission techniques. The analysis of the internal and external layers of cork and synthetic stoppers showed striking differences in their elemental composition and concentrations and depend on the nature of the stopper. For instance, Si, S, K, and Ca have higher concentrations in the external layer than in the inner portion of the stoppers. Moreover, our results show that elements are not distributed homogeneously throughout the surface of cork stoppers. This study provides, for the first time, data on the elemental composition of different stoppers, which could serve as a database for future research in this field. Finally, it is important to mention that wine and stoppers were analyzed with the same technique, which allows a straightforward comparison between them. Copyright © 2013 John Wiley & Sons, Ltd.     

A hyper-heuristic approach to sequencing by hybridization of DNA sequences

In this paper we investigate the use of hyper-heuristic methodologies for predicting DNA sequences. In particular, we utilize Sequencing by Hybridization. We believe that this is the first time that hyper-heuristics have been investigated in this domain. A hyper-heuristic is provided with a set of low-level heuristics and the aim is to decide which heuristic to call at each decision point. We investigate three types of hyper-heuristics. Two of these (simulated annealing and tabu search) draw their inspiration from meta-heuristics. The choice function hyper-heuristic draws its inspiration from reinforcement learning. We utilize two independent sets of low-level heuristics. The first set is based on a previous tabu search method, with the second set being a significant extension to this basic set, including utilizing a different representation and introducing the definition of clusters. The datasets we use comprises two randomly generated datasets and also a publicly available biological dataset. In total, we carried out experiments using 70 different combinations of heuristics, using the three datasets mentioned above and investigating six different hyper-heuristic algorithms. Our results demonstrate the effectiveness of a hyper-heuristic approach to this problem domain. It is necessary to provide a good set of low-level heuristics, which are able to both intensify and diversify the search but this approach has demonstrated very encouraging results on this extremely difficult and important problem domain.