LIGA micro-openings for coherence characterization of X-rays

Infinitely thin opaque screens serving for diaphragms as defined in the visible-light optics are not feasible for operation with X-ray beams due to their high penetrability. Micro-openings of predicted sidewall shape in a gold layer up to 140 μm thick which would provide low transparency, are proposed. The proposed micro-openings were made using the LIGA technique and tested successfully at photon energies of up to 25 keV. The micro-openings can be used as targets for coherence X-ray pattern or, if long interference tails are avoided by means of the advanced sidewall shape, as X-ray beam collimators.     

SLIGA Based underwater weapon safety and arming system

 The Naval Surface Warfare Center, Indian Head Division (NSWCIHD) is applying microelectromechanical system (MEMS) technology to underwater weapon Safety and Arming (S&A) system development. MEMS technology provides an opportunity to develop a miniaturized S&A system that is more sophisticated with improved safety and reliability at a lower cost compared to current systems. An S&A system prevents premature initiation of the weapon while reliably ensuring initiation at the appropriate time. An S&A system uses multiple sensors and devices. In comparison with other weapon S&A systems, a critical aspect of underwater weapon S&A systems is the mechanical interlock system utilizing actuators and mechanical sensors. This paper describes the design, development and fabrication of S&A SLIGA device prototypes and of a SLIGA based S&A system. NSWCIHD worked with members of the HI-MEMS Alliance during design, development and fabrication. Advancements achieved by the HI-MEMS Alliance and SLIGA S&A design issues are discussed. Received: 25 August 1997/Accepted: 10 September 1997     

Global radionavigation and location systems for tracking marine mammals

Over the past decade the Argos System has become a widely used tool for animal tracking. This paper investigates whether lower costs and energy requirements could be achieved by alternative techniques. These include the global radionavigation systems GPS and Omega which employ low-powered receivers rather than the high-powered transmitters of Argos. A variety of systems are studied and their costs and energy requirements modelled within specific marine mammal tracking scenarios. This paper presents a fundamental analysis exploring current and future options available to researchers who need to track marine mammals.     

Relative sensitivity of Loran-C phase tracking and cycle selection to CWI

Carrier-wave interference (CWI) is the most significant source of disturbance affecting the operation of the Loran-C radionavigation systems now being introduced into Europe. The article presents novel results of a study into the relative sensitivity to CWI of the phase-tracking and cycle-selection operations of Loran-C receivers.<>     

Centriacinar remodeling and sustained procollagen gene expression after exposure to ozone and nitrogen dioxide

Sprague-Dawley rats were exposed to 0.8 ppm ozone (O3), to 14.4 ppm nitrogen dioxide (NO2), or to both gases simultaneously for 6 h per day for up to 90 d. The extent of histopathologic changes within the central acinus of the lungs was compared after 7 or 78 to 90 d of exposure using morphometric analysis by placement of concentric arcs radiating outward from a single reference point at the level of the bronchiole- alveolar duct junction. Lesions in the lungs of rats exposed to the mixture of gases extended approximately twice as far into the acinus as in those exposed to each individual gas. The extent of tissue involvement was the same at 78 to 90 d as noted at 7 d in all exposure groups. At the end of exposure, in situ hybridization for procollagen types I and III demonstrated high levels of messenger RNA within central acini in the lungs of animals exposed to the combination of O3 and NO2. In contrast, animals exposed to each individual gas had a similar pattern of message expression compared with that seen in control animals, although centriacinar histologic changes were still significantly different from control animals. We conclude that the progressive pulmonary fibrosis that occurs in rats exposed to the combination of O3 and NO2 is due to sustained, elevated expression of the genes for procollagen types I and III. This effect at the gene level is correlated with the more severe histologic lesions seen in animals exposed to both O3 and NO2 compared with those exposed to each individual gas. In contrast, the sustained expression of the procollagen genes is not associated with a shift in the distribution of the lesions because the area of change in each group after 7 d of exposure was the same as after 78 to 90 d of exposure.     

Radionavigation in a time of change

The dramatic reductions in the cost, size, weight and power consumption of electronic equipment during the last decade have had an especially profound effect on the practice of radionavigation. Traditional users of radio aids now have equipment of smaller size and increased reliability and performance which provide many additional functions by virtue of their greatly enhanced computing power. At the same a completely new consumer market has been created which has come to dominate the entire radionavigation industry. This process of change is illustrated by examining the development of low-cost receivers for three radionavigation systems: direction-finding, Loran-C and Decca Navigator. The paper then shows how the use of other marine and aeronautical navigation aids has changed and describes novel applications of radio techniques made possible by these technical developments     

Design and implementation of a web mining system for organizing search engine results

We present the design and implementation of a web mining system that creates a hierarchical clustering of web documents retrieved by commercial web search engines. The cluster hierarchy is produced by a novel method called the Cluster Hierarchy Construction Algorithm (CHCA) and it can be used to explore the topics of interest related to the search query and their relationships. We discuss important design issues for our system, including stemming and dimensionality reduction, as well as some implementation details. We show examples of system results, compare them with results from similar systems, and analyze the responses to a survey of the system's users. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 607–625, 2005.     

Quantum Effects in Three-Dimensional H + D2 Reaction at High Energies

The H + D₂ reactive system was studied in the energy range 0.84 < E_tr < 2.70 eV employing the ordinary Quasi-Classical Trajectory Approach (QCTA), the Classical and the Quantum Reactive Infinite Order Sudden Approximations (CRIOSA and QRIOSA), and the Angle-Oriented Transition State Theory (AOTST). From a detailed analysis of the various integral cross-sections and opacity functions, it was concluded that pronounced quantum effects ( > 10%) are expected in the high-energy region (≤ 2 eV).     

Local Hall Effect and Ballistic Transport in Multi-terminal InAs-Based Lateral Spin-Valve Tunnelling Devices

A multi-terminal InAs-based lateral spin-valve tunnelling device is presented, which enables individual electrical characterization of all spin-valve components in two-terminal configuration. Both the spin-valve and the non-local geometry are available for studying spin-dependent transport. Furthermore, we propose a measurement geometry in which the spin-dependent contact resistance of the sensor electrode can be measured in three-terminal configuration. Longitudinal magnetoresistance in spin-valve geometry reveal hysteresis loops of 1 mΩ deflection as known from Hall magnetometry. In non-local geometry a polarity-dependent current–voltage characteristic at 2 K is observed. This can be understood in terms of a superposition of a diffusive resistive component with a polarity-dependent ballistic component.     

The volatiles of off-flavoured unblanched green peas (Pisum sativum)

Volatile extracts of moderately off-flavoured frozen peas, prepared by vacuum sublimation followed by concentration of the sublimate by low temperature vacuum distillation, were examined by gas chromatography, silica gel chromatography and combined gas chromatography–mass spectrometry. The constituents identified included alcohols (29), carbonyls (31), esters (12), hydrocarbons (19), terpenes (6) and 3-alkyl-2-methoxypyrazines (3). Olfactory monitoring of the gas chromatographic column effluent indicated that most of the strong odours were associated with alkanals, alk-2-enals, alka-2,4- and 2,6-dienals, octa-3,5-dien-2-ones, 3-alkyl-2-methoxypyrazines and hexanol. However, no compound which, by itself, could account for the “hay-like” off-flavour of peas was evident. The off-flavour is considered to be complex and composed largely of the more odorous unsaturated carbonyls derived from the enzymic breakdown of the unsaturated pea lipids. The volatiles of pea shells similarly examined were found to contain many of the compounds present in peas.