Pyrochlore Phases in the System ZnO–Bi2O3–Sb2O5: I. Stoichiometries and Phase Equilibria

Two cubic pyrochlore phases exist in the system ZnO–Bi₂O₃–Sb₂O₅. Neither has the supposed "ideal" stoichiometry, Zn₂Bi₃Sb₃O₁₄. One, P ₁, is a solid solution phase, Zn_{2+ x} Bi_{2.96−( x − y )}Sb_{3.04− y} O_14.04+δ where 0< x <0.13(1), 0< y <0.017(2) and a =10.4285(9)−10.451(1) Å. The other, P ₂, is a line phase, Zn₂Bi_3.08Sb_2.92O_13.92 with a =10.462(2) Å. Subsolidus phase relations at 950°C involving phases P ₁ and P ₂ in the ZnO–Bi₂O₃–Sb₂O₅ phase diagram have been determined.     

Geochemical Fractionation of Stream Sediments Impacted by Pb-Zn Mining Wastes: Missouri,USA

Mine Water and the Environment - Stream sediments affected by historic mining in Aurora, Missouri, were digested via sequential extraction to determine the amount of Zn, Pb, and Cd bound to each of...     

Developing monitoring indicators for urban micro contracts in South Asia

The growing emphasis in many low-income countries on community-based infrastructure means that more programmes are being implemented through micro contracts. The advantages of this approach are that it encourages:

participative negotiation of activities and speedier implementation;

the use of local resources, skills and appropriate technology; and

entrepreneurship in communities.

For client organisations, however, large numbers of very small contracts are much harder to monitor, supervise and evaluate. This paper draws upon recent research in India, Pakistan and Sri Lanka to develop a ‘benchmarking framework' to study the time and cost performance of 162 small-scale contracts for urban infrastructure. The study found that costs were normally very close to target, but project duration generally far exceeded the target. There is only a weak association between the cost and time growth.     

A quasi-experimental assessment of the effect of computerizing noncognitive paper-and-pencil measurements: A test of measurement equivalence.

Previous studies have provided evidence to question the equivalence of data gathered by different administration modes and to suggest that noncognitive instruments validated for paper-and-pencil administration may not be valid for computerized administration. In this study, a series of analyses of the variance–covariance matrices tested the measurement equivalence of data collected from paper-and-pencil and computerized formats. Four work-related noncognitive psychological measures were tested in this study. There was no evidence that administration mode had an effect on measurement equivalence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of waterbeds on heart rate in preterm infants

The purpose of this study was to investigate the effects of waterbeds on heart rate (HR) in preterm infants. Subjects were 22 medically stable preterm infants. Across a 10-day study, HR was determined for a 1-hour period on each day. Baseline HRs with infants on the standard incubator mattress were obtained on the first 2 days of the study. They were then placed on the waterbed for 4 days. They were then returned to the incubator mattress and studied for 4 more days. Infants served as their own controls among baseline, on-waterbed (On-WB) and off-waterbed (Off-WB) periods. HR was determined by using a heart beat counting feature of the neonatal cardio-respiratory monitors. Analysis of variance revealed significant HR variability among subjects. There was no difference between baseline HR and on-waterbed HR. The HR increased when infants were transferred back to the standard mattress. The possibility that theophylline acted as a confound existed because doses were changed and levels varied for some subjects within the study period. Eight infants responded to the waterbed with lower HR during the On-WB period compared to the baseline (mean reduction = 5.7 bpm). The findings that HRs rose when the infants were returned to the incubator mattress are similar to those of a previous study. The subjects' reactivity to changes in treatment condition continues to confound the question as to whether waterbed therapy effects a reduction in HR. Since waterbeds have consistently resulted in soothing effects such as improved sleep and lowered activity, failure to produce a concomitant reduction in HR warrants attention toward other factors that may be determinants of heart rate. The high variability within and among subjects raises questions as to the usefulness of the HR variable for determining energy costs.     

Interpretation of chemically created periapical lesions using direct digital imaging

Perchloric acid (70%) was used to create simulated periapical lesions in tooth sockets of 15 dentate cadaver jaw specimens. Using the Trophy USA direct digital radiographic system, linear images were captured at selected time intervals after initial acid application and altered by contrast reversal, pseudocolor enhancement, and two forms of histogram equalization. The 525 total images were randomized for display on a computer monitor for evaluation by five endodontists. Images were evaluated twice by each rater, with viewings 1 to 2 wk apart. Statistical analysis determined interrater variability, intrarater reproducibility, and the relative merits of each enhancement technique. At 8, 12, 16, and 24 h after acid application, both techniques of histogram equalization yielded a statistically significant improvement over reverse contrast in perception of periapical patholais. Linear and pseudocolor-enhanced images were also significantly more diagnostic than reverse contrast at 12, 16, and 24 h. Intrarater reproducibility showed moderate agreement, but analysis showed only a fair level of interrater agreement.     

Role of primate medial vestibular nucleus in long-term adaptive plasticity of vestibuloocular reflex

1. Fifteen hundred and thirty cells were recorded in the medial vestibular nucleus (MVN) of alert monkeys whose vestibuloocular reflex (VOR) had been adapted to one of two kinds of spectacles. The "high-gain" sample was recorded from monkeys that had worn 2.0 x telescopic spectacles; the gain of the VOR in the dark (eye velocity divided by head velocity) was greater than 1.5. The "low-gain" sample was recorded from monkeys that had worn goggles providing a visual field that was fixed with respect to the freely turning head; the gain of the VOR was less than 0.4. 2. Cells showing modulation of firing rate related to imposed head velocity were grouped into four categories: pure vestibular (10), vestibular-plus-saccade (10), vestibular-plus-position (10), and vestibular-plus-head/body (24). Sensitivity to head velocity was measured from averaged responses to sinusoidal, 0.4-Hz whole-body oscillation in the horizontal plane. Almost all cells (98%) having increased firing during ipsilateral head rotation received inputs from the horizontal semicircular canals. Conversely, 82% of cells having increased firing during contralateral head rotation received inputs from the vertical canals. 3. There were no statistically significant differences in resting discharge rate, phase shift, or sensitivity to head velocity between the high- and low-gain samples of any of the cell types. Nonetheless, there was a consistent tendency, evident in all the functionally defined cell groups, for the sensitivity to be about 20% greater in the high-gain samples. However, this difference is small by comparison with the fourfold difference in VOR gain. 4. Detailed scrutiny of the response properties of individual cells suggested that the small differences in sensitivity reflect small changes distributed throughout the population, rather than large and potentially significant changes within a small sub-population. 5. Our data indicate that large, adaptive changes in the gain of the VOR are accompanied by only minor changes in the vestibular sensitivity and no changes in the phase shift or resting discharge rates of cells in the MVN. It remains possible that large changes in vestibular sensitivity occurred in cells we did not sample or in subgroups we could not identify. We argue that this is unlikely and that the major changes underlying VOR plasticity occur after the first central synapse in the VOR pathways.     

THE EXTRACTION OF RHODIUM FROM AQUEOUS HITRIC ACID BY ORGANOPHOSPHINE SULPHIDES

The organophosphine sulphides, tri-phenyl phosphine sulphide (TPPS), tri-n-butyl phosphine sulphide (TBPS) and N,N',N"-tri-n-hexyl phosphorothioic-triamide (THPS) have been investigated for their potential use as extractants for the recovery of fission product rhodium from aqueous nitric acid solutions. The ease with which the extractions proceed can be rationalised in terms of the polarisability of the P=S bond, and in the case of THPS, the extraction is shown to proceed via a solvating type mechanism. Equilibration times for the extraction are of the order of 3-6 hours.     

Hydration of Nafion® studied by AFM and X-ray scattering

Nafion® is a commercially available perfluorosulphonate cation exchange membrane commonly used as a perm-selective separator in chlor-alkali electrolysers and as the electrolyte in solid polymer fuel cells. This usage arises because of its high mechanical, thermal and chemical stability coupled with its high conductivity and ionic selectivity, which depend strongly on the water content. The membrane was therefore studied in different states of hydration with two complementary techniques: atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) combined with a maximum entropy (MaxEnt) reconstruction. Tapping mode phase imaging was successfully used to identify the hydrophobic and hydrophilic regions of Nafion. The images support the MaxEnt interpretation of a cluster model of ionic aggregation, with spacings between individual clusters ranging from 3 to 5 nm, aggregating to form cluster agglomerates with sizes from 5 to 30 nm. Both techniques indicate that the number density of ionic clusters changes as a function of water content, and this explains why the bulk volumetric swelling in water is observed to be significantly less than the swelling inferred from scattering measurements.