Efficiency of linked cell algorithms

The linked cell algorithm is an essential part of molecular simulation software, both molecular dynamics and Monte Carlo. Though it scales linearly with the number of particles, there has been a constant interest in increasing its performance, because a large part of CPU time is spent to identify the interacting particles. Several recent publications proposed improvements to the algorithm and investigated their efficiency by applying them to particular setups. Here we develop a general method to evaluate the efficiency of these algorithms which is mostly independent of the parameters of the simulation, and test it for a number of linked cell algorithms. We also propose a combination of linked cell reordering and interaction sorting that performs well for a broad range of simulation setups.     

Recombination Centers in Gamma-Irradiated Arsenic-Doped Germanium

A comprehensive investigation has been performed of the properties of recombination centers introduced in As-doped Ge by Co60 gamma rays. Materials of three resistivities were used: ~0.2, ~1 and ~8 ?-cm. Measurements of lifetime versus temperature were made at low excess densities following various anneals. Numerous measurements of lifetime as a function of excess density with temperature as a parameter and with different annealing histories were performed. The position of the recombination center was observed to shift slightly with anneal temperature from Ev + 0. 346 ±.005 eV for room temperature stable defects to 0. 322 ±0.003 eV for samples which have been annealed in the range of ~70°C to ~120°C. These values are based on excess density measurements and assume unity statistical weight. The possible error from this assumption is estimated to be ±0.02 eV. The variation of electron capture probability with temperature was indicated by comparison with temperature dependence data; it varies approximately as T3/4. The hole-to-electron capture probability ratio near room temperature is 400 ±30 %. The arsenic atom appears to play no significant role in the process of recombination center creation or annihilation.     

Transplacentally induced neuronal migration disorders: an animal model for the study of the epilepsies

OBJECTIVES: This investigation examined whether, despite the Tobacco Institute's Voluntary Cigarette Advertising and Promotion Code, current cigarette print advertising communicates culturally positive messages to youth about smoking. METHODS: Nine hundred thirteen students in grades 6-8 (ages 10-15) were shown a sample of four contemporary cigarette print ads (Camel, Marlboro, Newport, and Virginia Slims) and completed structured written assessments designed to capture their perceptions of each ad. RESULTS: Across the four ads, between 37% and 84% of the students reported that the ads communicated to them that smoking will make people popular, cool, successful in life, sexy, attractive, and healthy. Sizeable percentages of students reported that the ads show people using the product in an "exaggerated" way, and that what people in the ads are doing requires "exercise and physical energy." The median estimated age of the models in the ads was under age 25 for four out of the six models. CONCLUSIONS: As perceived by adolescents, current cigarette print advertising violates basic tenets of the Voluntary Code, thus bringing into question the tobacco industry's ability to self-regulate image advertising. These findings suggest that the FDA ruling to prohibit image advertising for tobacco in publications with significant youth readership deserves serious consideration.     

Toward a sentient environment: real-time wide area multiple human tracking with identities

In this paper, we presented a fully integratedreal-time computer vision system that can detect and track multiple humans in a wide-area using a network of stereo cameras. Continuous human identities are achieved by fusing video tracking with different kinds of biometric devices. The system also provides immersive visualization which enables the users to conveniently navigate through space and time and query useful events. The key innovations include stereo-based multi-object detection and tracking, a unified approach for fusing multiple sensors of different modalities, visualization and user interface design.     

Authoring and Searching in Dynamically Growing Hypertext Databases

In this paper we show how an application in the domain of Office Information Systems can be modelled so that a dynamically growing database of hypertext documents is created and automatically extended, as well as easily searched. We propose a method for analyzing office applications which relies on a model based on statecharts to record the flow of documents within the system. A prototype implementation is described of a hypertext system to support the creation, storage and retrieval of documents associated to formal face to face meetings. Special features to be incorporated into hypertext systems aimed at supporting the storage and retrieval of office documents are also identified.     

Photoacoustic cell for ultrasound contrast agent characterization

Photoacoustics has emerged as a tool for the study of liquid gel suspension behavior and has been recently employed in a number of new biomedical applications. In this paper, a photoacoustic sensor is presented which was designed and realized for analyzing photothermal signals from solutions filled with microbubbles, commonly used as ultrasound contrast agents in echographic imaging techniques. It is a closed cell device, where photothermal volume variation of an aqueous solution produces the periodic deflection of a thin membrane closing the cell at the end of a short pipe. The cell then acts as a Helmholtz resonator, where the displacement of the membrane is measured through a laser probe interferometer, whereas photoacoustic signal is generated by a laser chopped light beam impinging onto the solution through a glass window. Particularly, the microbubble shell has been modeled through an effective surface tension parameter, which has been then evaluated from experimental data through the shift of the resonance frequencies of the photoacoustic sensor. This shift of the resonance frequencies of the photoacoustic sensor caused by microbubble solutions is high enough for making such a cell a reliable tool for testing ultrasound contrast agent, particularly for bubble shell characterization.     

A New Intelligent System Methodology for Time Series Forecasting with Artificial Neural Networks

The Time-delay Added Evolutionary Forecasting (TAEF) approach is a new method for time series prediction that performs an evolutionary search for the minimum number of dimensions necessary to represent the underlying information that generates the time series. The methodology proposed is inspired in Takens theorem and consists of an intelligent hybrid model composed of an artificial neural network combined with a modified genetic algorithm. Initially, the TAEF method finds the best fitted model to forecast the series and then performs a behavioral statistical test in order to adjust time phase distortions that may appear in the representation of some series. An experimental investigation conducted with relevant time series show the robustness of the method through a comparison, according to several performance measures, to previous results found in the literature and those obtained with more traditional methods.     

Improvement on direct ethanol fuel cell performance by using doped-Nafion 117 membranes with Pt and Pt–Ru nanoparticles

Nafion^® 117 membranes doped with Pt (4 × 10⁻⁴ mol L⁻¹ or 8 × 10⁻⁴ mol L⁻¹ H₂PtCl₆ solution), and with Pt–Ru (4 × 10⁻⁴ mol L⁻¹ H₂PtCl₆ and 2 × 10⁻⁴ mol L⁻¹ RuCl₃ solutions) nanoparticles have been synthesized using a simple and scalable absorption-reduction method. The chemical integrity of the membranes was confirmed by ¹³C and ¹⁹F solid-state NMR. The pore microstructure of the membranes was preserved after the doping process, according to SAXS measurements. The tests of the direct ethanol fuel cells (DEFC) performance at 90 °C exhibited up to 38% and 56% increase at the maximum power densities for Pt doped-Nafion^® membrane from lower and higher concentration of H₂PtCl₆ solution, respectively, compared to bare Nafion^® membranes. Additionally, a Pt–Ru doped-membrane tested at 110 °C exhibited the highest power density. Such superior performances may be attributed to a synergistic effect between the extra amount of active catalytic sites inside the pore structure for the electrochemical oxidation of ethanol, thus preventing ethanol crossover, and the excellent proton migration properties conferred by the pore microstructure of Nafion^®. These results demonstrate that the doped-Nafion^® membrane has a good capacity to improve the performance of DEFC, and provided further clarification on the synthesis process of polymer electrolyte doped-membranes in fuel cell technology.     

Effect of drying and storage time on the physico-chemical properties of mango leathers

Fruit leathers are made by drying a very thin layer of fruit puree to obtain a chewy product. The objective of this work was to minimise the drying time required to produce mango leathers with no preservatives and no sugar added, and to evaluate their acceptance and storage stability. Mango puree was spread on Petri dishes and oven‐dried according to a central composite design with two independent variables: drying temperature (60–80 °C) and puree load (0.4–0.6 g cm^?2). The minimum drying time (120 min) resulted from drying a puree load of 0.5 g cm^?2 at 80 °C. The product was well accepted, especially in terms of flavour. The mango leathers were packed in polypropylene buckets and stored at 25 °C. The combination between low water activity (0.62) and low pH (3.8) allowed the product to be microbiologically stable for at least 6 months, without the need for chemical preservatives.