Changes in the phase structure and formation of chemical compounds by ion implantation of tantalum thin films

Evaporated films of tantalum+tantalum oxide, 500 Å thick, were implanted with argon, oxygen and nitrogen ions. The phase structure of the films was determined by transmission electron microscopy and the dose dependence of resistivity and thermal coefficient of resistivity was satisfactorily explained in terms of the precipitation of compounds formed in the film. Argon bombardment had little effect on the structure of a film until sputter etching had reduced the film thickness considerably, when precipitates of TaO₂ in the form of rounded islands were created. Oxygen bombardment resulted in the precipitation of the b.c.c. phase of tantalum, and at higher doses precipitates of TaO₂ were formed. Nitrogen bombardment resulted in a sudden phase change and the precipitation of Ta₄N₅ in the form of hexagonal platelets; the conduction process in these films was highly activated, probably as a result of the presence of an amorphous oxide matrix. The dependence of changes in electrical properties on oxygen content of the film is explained by this phase structure.     

Thin films of triglycine sulfate by laser evaporation

Thin films of triglycine sulfate were prepared by laser evaporation. The properties of these films were evaluated by electrical measurements, x-ray diffraction and IR spectrometry. The deposited material was found to be essentially triglycine sulfate with some glycine present as a decomposition product. The deposited material was also found to be highly oriented with the pyroelectric direction lying in the plane of the film.     

Coded excitation with spectrum inversion (CEXSI) for ultrasound array imaging

In this paper, a scheme called coded excitation with spectrum inversion (CEXSI) is presented. An established optimal binary code whose spectrum has no s and possesses the least variation is encoded as a burst for transmission. Using this optimal code, the decoding filter can be derived directly from its inverse spectrum. Various transmission techniques can be used to improve energy coupling within the system pass-band. We demonstrate its potential to achieve excellent decoding with very low (<80 dB) side-lobes. For a 2.6 /spl mu/s code, an array element with a center frequency of 10 MHz and fractional bandwidth of 38%, range side-lobes of about 40 dB have been achieved experimentally with little compromise in range resolution. The signal-to-noise ratio (SNR) improvement also has been characterized at about 14 dB. Along with simulations and experimental data, we present a formulation of the scheme, according to which CEXSI can be extended to improve SNR in sparse array imaging in general.     

Moondyne Joe probably slept here

This paper explores the 'place' of Glenhourne farmhouse in the southwest of Western Australia as a construct of memory, myth and story. Framing this is a discussion of the role that memory and myth has in the anchorage of our present society and Glenhourne as a heritage place.     

Longitudinal patterns of risk for depression in dementia caregivers: Objective and subjective primary stress as predictors.

The present study examined how patterns of risk for depression over 1 year in 188 dementia caregivers (consistently asymptomatic, n ?=?88; consistently symptomatic, n ?=?40; changing risk, n ?=?60) could be predicted by objective (behavior problems of the relative) and subjective (role captivity and overload) primary stress. Results reveal that all primary stressors differentiated caregivers who remained at low levels of symptomatology over the course of 1 year from those who were at risk for experiencing a depressive disorder. In addition, caregivers' subjective experience of role captivity predicted the chronicity of risk. Findings extend prior caregiving research on patterns of depressive symptomatology by highlighting the relationship between subjective primary stressors and stability and change in caregivers' mental health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A psychophysical study to determine acceptable limits for repetitive hand impact severity during automotive trim installation

The purpose of the current study was to use a psychophysical methodology to establish acceptable impact severity levels for this automotive trim installation. Two studies were conducted. In the first study, 17 male and 12 female subjects (6 assembly line workers and 23 students) performed 5 hand impacts/min on a device that simulated the process of seating push pins during door trim panel installation. In both studies, subjects were asked to impact the simulation device as hard as they found acceptable without causing injury, numbness or pain. Subjects were trained for 11 h. Force and hand acceleration time-histories were recorded from the simulation device and a hand-mounted accelerometer, respectively. The magnitude of each impact was quantified with eight dependent measures: peak, time-to-peak, load rate and impulse, from both the force and acceleration transducers. Statistics were used to determine the effects of gender, skill level and impact location on acceptable impact severity. In the second study, 8 male and 8 female subjects performed repeated hand impacts on a wall-mounted force plate at three different frequencies (2, 5 and 8 impacts/min) over three separate sessions. Force measures and statistics were the same as in Study 1. In the first study, impact location did not appear to have a consistent effect on the acceptable impact severities and there was no significant differences observed between male and female values. For both force and acceleration, impulse was the most reliable variable followed by the peak. In the second study an increase in impact frequency was observed to result in a significant decrease in the acceptable levels of peak force and force impulse. This effect was largest when going from 2 to 5 impacts/min and was less pronounced when going from 5 to 8 impacts/min (especially for force impulse). Male subjects demonstrated significantly higher acceptable impulse levels. Based on the combined results from both studies, acceptable limits were recommended for peak force and impulse that would be acceptable to 75% of the population for a range of frequencies. These limits were observed to range from 181 (8/min) to 259 N (2/min) for peak force and 2.53 (8/min) to 3.52 N s (2/min) for force impulse. It was concluded that force impulse and peak force were the variables most likely being controlled by the subjects.

Relevance to industry

Automotive assembly includes a number of tasks that involve hand impacts within the manufacturing process. One such task is the door trim panel installation process where the base of the hand is used to impact the door trim panel and drive fastening push pins through holes in the metal door frames. The current study provides tolerance limits so that industrial tasks involving hand impacts can be evaluated for their injury risk.     

Stressed Salmonella are exposed to reactive oxygen species from two independent sources during recovery in conventional culture media

Previously, Stephens et al. [J. Appl. Microbiol. 83 (1997) 445–455] developed a sensitive technique for studying the resuscitation of low levels of stressed Salmonella. Using this technique the influence on recovery performance of the peptone component of buffered peptone water was investigated. Within 12 different peptone types as much as 3.5 log₁₀ cells/ml difference was observed between the best and worst performing formulations. Poor recovery performance was linked to reactive oxygen species (ROS) generation through auto-oxidation of reducing sugars and photo-sensitisation of sensitive components such as riboflavin. Supplementary recovery agents were explored with only Oxyrase^®, which has both enzymes to degrade ROS and the ability to rapidly turn a medium anaerobic, having any significant effect. It improved the speed of recovery and increased, by up to 100-fold, the number of stressed cells recovered. Stressed cells were further studied by flow cytometry with cell sorting, based on the staining pattern from a novel fluorochrome combination, into good and poor recovery media. It was identified that within a stressed population the removal of all oxygen protected actively respiring cells the most by forcing them to generate energy from anaerobic metabolism thus avoiding any risk from accidental endogenous ROS generation. The recognition of two independent sources of oxidative stress in the routine use of conventional culture media is discussed in relation to pathogen detection and other areas of food microbiology.     

Random Sampling of States in Dynamic Programming

We combine three threads of research on approximate dynamic programming: sparse random sampling of states, value function and policy approximation using local models, and using local trajectory optimizers to globally optimize a policy and associated value function. Our focus is on finding steady-state policies for deterministic time-invariant discrete time control problems with continuous states and actions often found in robotics. In this paper, we describe our approach and provide initial results on several simulated robotics problems.      

Optical homodyne receiver with a six-port fibre coupler

The performance of a PSK optical homodyne system based on a six-port fibre coupler, which avoids the need for an optical 90° hybrid device, is determined. Depending on the actual receiver implementation using the coupler, the receiver sensitivity is shown to be about 0.5?3 dB from ideal and local laser excess intensity noise can be cancelled.