Local Structure of Alkaline-Earth Boroaluminate Crystals and Glasses: II, 11B and 27Al MAS NMR Spectroscopy of Alkaline-Earth Boroaluminate Glasses

¹¹B and ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra of alkaline-earth boroaluminate glasses show that the structure of these glasses are far more complicated than previously thought. The relative concentrations of 3- and 4-coordinated boron vary as found by previous investigators using continuous-wave NMR methods, but the ²⁷Al NMR spectra indicate the presence of Al in 4-, 5-, and 6-fold coordination, in contrast to previous assignments. Analysis of the data based on local charge balance considerations provides a qualitative model that correctly predicts compositional variations of the NMR peak intensities and ²⁷Al chemical shifts for a wide range of boroaluminate glass compositions.     

The separation of coal fines using flowing-film gravity concentration

This paper reviews the results of a broadly based investigation into the possible merits of treating coal fines using flowing-film gravity separators such as Reichert cones, trays and spirals. The work was carried out in the test facilities maintained by Mineral Deposits Limited (MDL) both within Australia and in several overseas locations. In the initial phase, the cost of the work was borne by MDL, but funding for the second phase, which had wider terms of reference, was supplied by a grant from the National Energy Research, Development and Demonstration Council (NERDDC). The project is expected to continue until mid-1984, but the assessments of the tray and spiral separators are complete and form the main subject of this paper.     

A comparison of sequential extraction procedures for measuring phosphate rock residues in soils

Laboratory studies have been undertaken to evaluate sequential extraction procedures to measure phosphate rock (PR) residues in a range of temperate (New Zealand) and tropical (Indonesian) soils. The amounts of soil and PR-P were measured by using a sequential procedure which involved pre-extraction with either 1M NaCl or 0.5M NaCl/TEA (pH 7), followed by 1M NaOH and mineral acids. The acids included varying concentrations of HCl or H₂SO₄ (0.5–4M) and a tri-acid mixture of HCl, HNO₃ and HClO₄ (5:5:7). Amounts of PR residues in the soil were estimated from increases in amounts of the acid-extractable P (acid-P) or Ca (acid-Ca) in the PR-treated over untreated soil.Amounts of PR-P residues (measured by HCl-P) in New Zealand soils varying in pH and Ca levels were completely recovered (±5%) when the soils were pre-extracted with 0.5M NaCl/TEA, rather than 1M NaCl (or no pre-extraction). Pre-extraction of acid soil/PR mixtures with 1M NaCl caused dissolution of PR during the extraction. Although the HCl-Ca also estimated the amount of PR residues well, particularly after a 0.5M NaCl/TEA pre-extraction, this method was less sensitive than the HCl-P method, particularly in the soils with high native Ca saturation.In contrast to the high recovery obtained from the New Zealand soils, the recovery of the PR-P residues in the Indonesian soils in the HCl extracts following the 0.5M NaCl/TEA and 1M NaOH extractions were low ranging from 62 to 86%. Although increasing the concentration of HCl (upto 4M) did not cause any improvement in the recovery of PR-P, extraction with H₂SO₄ achieved complete recovery of PR-P. For all soils, a sequential extraction involving 0.5M NaCl/TEA-1M NaOH-0.5M H₂SO₄ is recommended for measuring PR residues in pairs of PR-treated and untreated field or laboratory incubated soils.     

The mechano-sorptive behavior of flexible water-blown polyurethane foams

Samples of flexible water-blown slabstock polyurethane foams were compressed under constant load to study the effects of cycling moisture content on creep behavior and compare this behavior with the creep response where either a constant high or low moisture environment existed at the same temperature. Three sets of foams were tested: (1) 4 pph water content slabstock foam; (2) 5 pph water content slabstock foam; and (3) 2 pph water content molded foam. As the moisture conditions were cycled from low to high humidity while maintaining constant temperature in an environmental chamber, the compressive strain increased in subsequent steps with larger increases observed during the desorption portion of the humidity cycling. All three sets of foams showed similar behavior at a given temperature. At a temperature of 40°C, the strain levels under cyclic moisture conditions surpassed those levels observed at the highest constant relative humidity. During the first absorption step, the creep level increased. During any subsequent absorption step, the creep level either increased very little or none at all. Finally, during any desorption step, the creep level increased. This overall phenomenon of enhanced creep under cyclic moisture levels is attributed to water interacting with the hydrogen bonded structure within the foam. These hydrophillic interactions, principally promoted within the hard segment regions due to high hydrogen bonding, are disrupted causing slippage and increased in strain. As the foam is rapidly dired, regions of free volume are induced by the loss of water thus causing further increases in strain Prior to the reestablishment of well ordered hydrogen bonding. Further support to this proposition was given by the results obtained at a temperature of 90° C where it is well known that hydrogen bonds are much more mobile. Here, the strain levels under cyclic moisture conditions were nearly the same as those under constant high relative humidity. Weakening of the hydrogen bonds by means such as increased temperature resulted in similar strain levels to those under cyclic moisture levels. © 1993 John Wiley & Sons, Inc.     

Bacteria in a water‐damaged building: associations of actinomycetes and non‐tuberculous mycobacteria with respiratory health in occupants

We examined microbial correlates of health outcomes in building occupants with a sarcoidosis cluster and excess asthma. We offered employees a questionnaire and pulmonary function testing and collected floor dust and liquid/sludge from drain tubing traps of heat pumps that were analyzed for various microbial agents. Forty‐nine percent of participants reported any symptom reflecting possible granulomatous disease (shortness of breath on exertion, flu‐like achiness, or fever and chills) weekly in the last 4 weeks. In multivariate regressions, thermophilic actinomycetes (median = 529 CFU/m²) in dust were associated with FEV₁/FVC [coefficient = ?2.8 per interquartile range change, P = 0.02], percent predicted FEF_25–75% (coefficient = ?12.9, P = 0.01), and any granulomatous disease‐like symptom [odds ratio (OR) = 3.1, 95% confidence interval (CI) = 1.45?6.73]. Mycobacteria (median = 658 CFU/m²) were positively associated with asthma symptoms (OR = 1.5, 95% CI = 0.97?2.43). Composite score (median = 11.5) of total bacteria from heat pumps was negatively associated with asthma (0.8, 0.71?1.00) and positively associated with FEV₁/FVC (coefficient = 0.44, P = 0.095). Endotoxin (median score = 12.0) was negatively associated with two or more granulomatous disease‐like symptoms (OR = 0.8, 95% CI = 0.67?0.98) and asthma (0.8, 0.67?0.96). Fungi or (1→3)‐β‐D‐glucan in dust or heat pump traps was not associated with any health outcomes. Thermophilic actinomycetes and non‐tuberculous mycobacteria may have played a role in the occupants' respiratory outcomes in this water‐damaged building.     

Catalytic and inhibitory effects of dissolved Cd2+ on C3H8 electro-oxidation

Studies have been made of the effect of Cd²⁺ on the oxidation rate of C₃H₈ in 80% H₃PO₄ at 130 C on platinized Pt electrodes.Dissolved Cd²⁺ discharges, probably as Cd⁰, and forms a stable sub-monolayer on a Pt electrode at potentials as high as 0·5 V versus RHE. Although this Cd⁰ layer is apparently substantially desorbed in favor of adsorbed hydrocarbon, C₃H₈ adsorption is inhibited in its presence. C₃H₈ oxidation is also inhibited. However, the C₃H₈ oxidation rate is observed to increase under some circumstances, and this appears to be because Cd isabsorbed into the Pt lattice. Co-plating of Cd and Pt leads to an electrode which, once the excess Cd has been removed, appears to be stable, and which catalyses C₃H₈ oxidation by about a factor of three at 0·25 V. Above 0·3 V, this absorbed Cd somewhat inhibits C₃H₈ oxidation.     

PMO managers' self-determined participation in a purposeful virtual community-of-practice

Communities-of-practice (CoPs) have received significant attention within a variety of literatures but we remain largely ignorant of the potential of purposefully-created CoPs in global organisations. In this context, the challenge is likely to be convincing ‘masters’ (Wenger, 1998) on the merits of joining the conversation on practice at a distance, thus making the willingness for exchange a key to the quality and longevity of the community. We posed the question “Why would busy, dispersed, knowledgeable professionals want to join and participate in a deliberately-organised CoP?” Our 2-year collaborative action study allowed us to observe the CoP and its membership at close range. We conclude that autonomy, competence and belonging underscore participation, co-production and diffusion of innovative problem-solving and practice beyond the CoP. The study will inform organisations contemplating similar interventions and also serves as a basis for further investigation and theory building on organized CoPs by the research community.     

The value of a desk study for building a national river obstacle inventory

This study evaluates two desk‐based approaches for building an inventory of man‐made river obstacles. The creation of a river obstacle inventory is a vital first step in developing a prioritization process for obstacle removal and/or modification. In this study, a desktop geographical information system analysis of two rivers and their tributary network was undertaken, using two different approaches. The first involved analysing historical maps, satellite imagery, and Ordnance Survey Ireland Discovery Series maps and producing a geo‐referenced layer of all the potential river obstacles. The second involved developing a geo‐referenced layer of potential river obstacles based on the intersections between elements of the transport network (roads and railways) and river systems. To determine the effectiveness of the desk studies, the located obstacles were cross‐referenced with actual obstacles verified through a field survey. The desk studies identified several thousand potential obstacles. The study utilizing a range of maps consistently located a greater number of actual obstacles than the desk study based on intersections between the transport and river networks. The results indicate that desk‐based research offers an efficient and effective method for locating river obstacles and can guide subsequent field surveys aimed at confirming the presence of obstacles. This is particularly useful for eliminating from study large stretches of rivers that would otherwise need to be walked to confirm the presence, or otherwise, of potential river obstacles. In this regard, desk‐based exercises can offer opportunities to save on both time and cost in larger river assessments.     

Simulated recruitment of riparian trees and shrubs under natural and regulated flow regimes on the Wisconsin River,USA

Models that link ecological responses to hydrologic changes are important for assessing the effects of flow regulation on aquatic and riparian ecosystems. Based on the Recruitment Box Model, a graphical model used to prescribe environmental flows for cottonwood (Populus spp.) recruitment, we designed a simulation model to represent the influence of river flow dynamics on seedling recruitment of riparian pioneer woody plants. The model simulates the influence of temporal patterns of river stage on dispersal, germination, initial recruitment and over‐winter survival of first‐year seedlings of riparian pioneer shrubs and trees. We used the model to simulate seedling recruitment patterns for five species (Acer saccharinum, Betula nigra, Populus deltoides, Salix nigra and Salix exigua) on the Wisconsin River (Wisconsin, USA) under three flow scenarios: historic (1935–2002), simulated natural (1915–1975) and simulated regulated flows (1915–1975). Simulation results agreed well with field‐observed relative differences among years (1997–2000) in seedling densities for the five focal species. Simulated successful recruitment years were highly synchronous among species, but species differed in their sensitivity to flows at different times during the growing season, consistent with among‐species differences in seed dispersal timing. Comparison of simulated natural and regulated flows for 1915–1975 showed that flow regulation decreased monthly flow variability, increased late summer to winter baseflow and reduced the magnitude of spring peaks. Simulated recruitment and over‐winter survival of tree seedlings of all species was enhanced under the regulated flow scenario, likely due to increased summer baseflow and reductions in peak flood magnitude. Our analyses show the utility of extending the Recruitment Box Model to include multiple species of riparian shrubs and trees, and the effects of post‐colonization flows on their recruitment success. However, some key functional relationships between flow patterns and woody seedling demography (e.g. shear stress thresholds for seedling mortality) have not been adequately quantified and merit further study. Copyright © 2006 John Wiley & Sons, Ltd.     

Historical and contemporary movement and survival rates of walleye (Sander vitreus) in Lake Winnipeg,Canada

Understanding patterns of fish movement in large lake ecosystems is essential for determining appropriate management actions as differences in movement behaviour can influence life history traits such as growth and survival. Lake Winnipeg in Manitoba, Canada supports the 2nd largest walleye (Sander vitreus) commercial fishery in North America. We used mark-recapture models to determine movement and estimate survival of walleye between basins of Lake Winnipeg in historical and contemporary contexts, comparing a tag-recovery study completed historically during 1974–1977 with a contemporary (2017–2019) acoustic telemetry study. Mark-recapture models revealed comparably low but detectable annual transitions between basins from historical (0.3–1.2%) and contemporary datasets (7–8.5%). Historically, fish > 300 mm more frequently moved in a south to north direction. Contemporary estimates suggest similar length-based directionality in that fish > 350 mm were always more likely to move in a south-north direction. Contemporary annual survival derived from mark-recapture models ranged between 27 and 45% and 64.3% when derived from catch curve analysis, while independently derived annual historical survival estimates ranged between 50 and 69% and 45.5% from catch curve analysis. Using the contemporary dataset, we also observed seasonal variation in movement and survival between basins, with the greatest movement across the lake occurring during the fall. Our results demonstrate a persisting pattern of low but measurable movement, suggesting between basin movement is not unusual for Lake Winnipeg. Further, low walleye survival rates reported here for the two time periods studied, support recent management actions to reduce fishing pressure across the lake.