Water Mobility in Glassy and Rubbery Solids as Determined by Oxygen-17 Nuclear Magnetic Resonance: Impact on Chemical Stability

Although chemical reactivity in solid food systems has been studied as a function of water activity and glass transition, the possible effects of water mobility on chemical reactions have not been investigated. The effect of the glass transition on water mobility at constant temperature and water content was determined. The relationship between the experimentally determined water mobility in polyvinylpyrrolidone (PVP) systems and chemical reactivity data from the same PVP systems was evaluated. Water mobility, as determined via ¹⁷O-NMR, was not affected by the glass transition; PVP systems at constant water activities and water contents, but different physical states (glassy and rubbery), had the same water mobility. An evaluation of four chemical reactions showed no relation between water mobility and kinetic data. The effect of water on chemical reactions is multidimensional and cannot be reduced to a single physicochemical parameter.     

Novel Calibration Technique for a Coulometric Evolved Vapor Analyzer for Measuring Water Content of Materials

Evolved vapor coulometry is a measurement technique that selectively detects water and is used to measure water content of materials. The basis of the measurement is the quantitative electrolysis of evaporated water entrained in a carrier gas stream. Although this measurement has a fundamental principle—based on Faraday’s law which directly relates electrolysis current to amount of substance electrolyzed—in practice it requires calibration. Commonly, reference materials of known water content are used, but the variety of these is limited, and they are not always available for suitable values, materials, with SI traceability, or with well-characterized uncertainty. In this paper, we report development of an alternative calibration approach using as a reference the water content of humid gas of defined dew point traceable to the SI via national humidity standards. The increased information available through this new type of calibration reveals a variation of the instrument performance across its range not visible using the conventional approach. The significance of this is discussed along with details of the calibration technique, example results, and an uncertainty evaluation.     

Effect of surge voltage risetime on the insulation of low-voltagemachines fed by PWM converters

This paper investigates the repetitive surge-voltage withstand of low-voltage mush-wound machines operated on adjustable-speed drives (ASDs) using insulated gate bipolar transistor (IGBT) semiconductor technology. Historical work on surge testing of motor insulation has focused on one or more of the following aspects: (1) large horsepower motors; (2) medium-voltage form-wound motors; (3) single-shot impulse-type transients; or (4) low-voltage machines with surge risetimes >200 ns. IGBT drives can have risetimes of 50-200 ns. Thus, a new study on electrical stress of insulation systems due to the nonlinear voltage distribution of mush-wound motors when subjected to repetitive steep dV/dt square-pulse waveforms (rather than impulse wave testing) is presented. Magnitude and risetime of the repetitive ASD surge-voltage transient induced on the machine terminals is reviewed first. Next, surge propagation into the winding was investigated to identify maximum voltage stress points on the conductor insulation. Potential failure mechanisms observed at these points are then discussed. The significance of decreasing surge risetime and increasing cable lengths on internal nonlinear voltage distribution is studied with experimental results from a 7.5-hp motor with a tapped stator winding     

Barriers to social services for HIV-infected urban migrators

Anecdotal accounts suggest that residency requirements often lead to denial of services at a time when HIV positive migrators are most in need of these services. However, this suspicion has never been empirically tested. Using needs assessment data collected for Harris County, Texas, this article examines eligibility and knowledge barriers faced by HIV positive recent migrators into Harris County. Results indicated that migration into the county was a significant predictor of failure to receive government-administered basic services such as food services but was not a significant predictor of failure to receive community based organization (CBO)-administered "specialized" services targeted specifically to HIV positive individuals. Results also indicated that migration was associated with knowledge barriers for all types of services.     

Development and initial assessment of objective fatigue measures for apple harvest work

Previous research has shown that neck, back and shoulder musculoskeletal strain is a major occupational health problem affecting migrant orchard harvest workers. Researchers seek to measure the effect of an ergonomic modification to the apple picking bucket on muscle fatigue, however objective measures for use in the orchard are not yet available.

The purpose of this study is to develop simple back, shoulder or arm strength measures, which detect statistically significant drops in strength over one workday. Candidate muscle strength measures were piloted in the laboratory, adapted for the orchard and evaluated (n=102). Data were analyzed for morning to afternoon fatigue, and for correlation between fatigue score and hours worked.

In the laboratory, the timed arm hold (35.7% time reduction, 95% CI: 21.81–49.61), and the timed spinal extension (31.8% time reduction, 95% CI: 23.54–39.96) showed significant fatigue. In the orchard (n=102), only the timed arm hold showed significant (11.4%, p<.0001) fatigue. The potential effect of field conditions and subject motivation on these results needs further exploration.     

Forecasting the pattern of urban growth with PUP: a web-based model interfaced with GIS and 3D animation

This paper describes a model (PUP — Projections for Urban Planning) implemented to forecast the location of housing development and population growth on the fringes of large cities. The model couples the land use and housing unit methods of population forecasting in a GIS framework that delivers a seamless interface between data assembly, modelling, visualisation and analysis. Work has focussed on incorporating spatial relationships, calibration, and visualisation. Three factors are accounted for: land availability; accessibility to facilities and other stimuli; and adjacency to existing development. These are weighted and combined to determine the probable location of future development. Forecasts are available as: GIS compatible files; tables; or 3D animations with interactive querying. The model has been implemented in Adelaide but its generic structure yields a flexible, interactive forecasting system that can be adapted to provide decision support for urban planning in a range of urban settings.     

Improving patient compliance--a multicentre evaluation of the 'DDS tile test'

The feasibility and utility of the "DDS tile test" under field conditions was assessed in 112 leprosy centres in Maharashtra. About 10% of the 2952 urine samples tested negative for dapsone. Feed back information from 54 centres one year later showed that the test could be performed easily under field conditions and also that counselling of patients showing poor compliance helped to improve drug compliance in over 80% of cases.     

Influence of light dark cycles on estradiol-17 beta induced luteinizing hormone patterns of the prepuberal gilt

Two groups of Yorkshire gilts (110 d of age) were maintained in two light regimens. Both light regimens consisted of 14 h of light and 10 h of darkness, but were 180 degrees out of phase. Gilts in Group 1 received light from 1200 to 0200 and gilts in Group 2 from 2400 to 1400. At approximately 140 d of age each group was divided into four subgroups of eight gilts each (1A, 1B, 1C, 1D or 2A, 2B, 2C, 2D). All gilts were blood sampled at 2-h intervals for 5 d commencing on d 142. The four subgroups received a single injection of estradiol (15 micrograms/kg body weight) on d 143 at either 2400 (A), 0600 (B), 1200 (C), or 1800 (D). For pigs in Groups 1A and 1D, the injection of estradiol coincided with the animals' "subjective day" and the injections given to Groups 1B and 1C with their "subjective night." When estradiol-17 beta (E2) was administered to the gilts during their subjective day the LH profile showed one peak, whereas when E2 was administered during dark hours the profile exhibited two peaks (P < .0001). In Group 2 for which the light cycle was reversed, the well-defined spikes of LH were found to coincide with the injections of estradiol administered during the dark hours. Smaller biphasic peaks of LH occurred when injections of estradiol coincided with the light hours.(ABSTRACT TRUNCATED AT 250 WORDS)     

Profiles of chicken macrophage effector functions

In contrast to the mammalian system, avian species lack the so-called "resident" or "harvestable" macrophage population in the abdominal exudate. However, macrophages can be recruited into the chicken's abdominal cavity (presumably from the blood monocyte pool) if an inflammatory agent such as Sephadex is injected. The kinetics of inflammatory cell recruitment in terms of time, cell type, and state of activation to perform a particular effector function is currently an active area of research. This report will provide information on several chicken macrophage effector functions, including in vivo chemotaxis, phagocytosis, bacterial uptake and killing, biosynthesis of nitric oxide and various enzymes, and monokines such as interleukin-1 and granulocyte colony-stimulating factor.