A socially aware caching mechanism for encounter networks

Managing community content in mobile communities is challenging, since informal groups may emerge spontaneously whenever opportunities exist. To deal with group dynamics, encounter based community support systems can be a solution. In encounter networks, peers exchange content whenever they physically meet, i.e., whenever peers are near to each other. To assure content availability within the community network, content needs to be replicated (cached) and continuously updated. A?well known drawback of this scheme is the fact that the resource usage can be quite high. In this paper we present new caching strategies based on sociological knowledge, aiming at improving the overall content quality. We derive mobility and connectivity aware cache policies and simulate their benefit for knowledge building with urban life simulations. Results show that context precision and recall can be greatly improved in comparison to traditional cache strategies applied in the majority of encounter networks.     

Monte Carlo simulation of boron implantation into single-crystalsilicon

An improved Monte Carlo simulation model has been developed for boron implantation into single-crystal silicon. This model is based on the Marlowe Monte Carlo code and contains significant improvements for the modeling of ion implantation, including a newly developed local electron concentration-dependent electronic stopping model and a newly developed cumulative damage model. These improvements allow the model to reliably predict boron implant profiles not only as a function of energy, but also as a function of other important implant parameters such as tilt angle, rotation angle, and dose. In addition, profiles of implant generated point defects (silicon interstitials and vacancies) can be calculated     

Recent advances in amplify-and-forward two-hop relaying [Accepted from Open Call]

In this article we review an important class of wireless cooperation protocols known as amplify-and-forward relaying. One or more low-complexity relay nodes assist the communication between sources and destinations without having to decode the signal. This makes AF relaying transparent to modulation and coding of the source/destination communication protocol. It is therefore a highly flexible technology that also qualifies for application in heterogeneous networks comprising many nodes of different complexity or even standards. Recently, two-way relaying was introduced, which is readily combined with AF relaying. It is a spectrally efficient protocol that allows for bidirectional communication between sources and destinations. In order to investigate the potential of wireless AF relaying, we introduce three distributed network scenarios that differ in the amount of cooperation between nodes. New challenges arise in those networks, and we discuss approaches to overcome them. For the most general case of a completely distributed system, we present coherent relaying solutions that offer a distributed spatial multiplexing gain even for single-antenna nodes. Based on real-world experiments, we validate the feasibility of all schemes in our laboratory.     

Microwave cavity perturbation technique: Part I: Principles

This report reviews the analysis used to extract the complex conductivity of a compound from a microwave cavity perturbation measurement. We intend to present a generalized treatment valid for any spheroidally shaped sample of arbitrary conductivity which is placed at either the electric or magnetic field antinode of the cavity. To begin with, we establish the relationship between the measured parameters and the conductivity for a spherical sample. Next, we extend these results to the case of spheroids; and for the first time, we cover all different configurations that one can possibly use to study an arbitrary conducting sample inside a cavity: in particular, all possible orientations of the sample with respect to the applied field are solved.     

Engineering a heavy atom derivative for the X-ray structure analysis of cyclodextrin glycosyltransferase

Based on a preliminary structural model of cyclodextrin glycosyltransferasefrom Bacillus circulans (EC 2.4.1.19 [EC] ), Ser428 and Ser475 ofthe enzyme were mutated to cysteines in order to produce suitableheavy atom derivatives. Mutant Ser475 - Cys could not be expressedas protein. Mutant Ser428 - Cys was expressed in Escherichiacoli and purified. It crystallized isomorphously and gave riseto a mercury derivative that improved the electron density map.The structural results show that the new mercury-binding siteis in a pocket at the protein surface.     

FISHER'S INFORMATION MATRIX FOR SEASONAL AUTOREGRESSIVE-MOVING AVERAGE MODELS

Abstract. Two procedures are described for obtaining Fisher's information matrix of a multiplicative seasonal autoregressive-moving average process. They can be useful in determining the asymptotic covariance matrix of Gaussian maximum likelihood estimators of the parameters. Components of the information matrix are expressed in the first procedure as integrals of rational functions. The second procedure makes use of the autocorrelation function of several autoregressive processes.     

Development of organosilicone–polyurethanes as stone preservation and consolidation materials

Two organosilicone-modified polyurethanes are investigated as potential materials for the conservation and consolidation of natural stones. The materials are low molecular weight oligomers at the application stage and react with the humidity of the air to give polymers, forming continuous microlayers. The two differ in the length of the organosilicone chain, resulting in pronounced differences in their physical state: one forms a brittle glassy material (T_g ≈ 70°C). and the other, a soft rubbery material (T_g ≈ −100°C). The rate of the polymerization of the prepolymers was investigated at different conditions, showing a strong dependence on the presence of a catalyst and air humidity. Both these favorable conditions exist probably in the natural stone pores, enhancing the formation of the protective hydrophobic internal microlayer. © 1996 John Wiley & Sons, Inc.