1,413 research outputs found

    Sustainable operations and maintenance of water supplies: a conceptual model for engineers and development workers : a thesis submitted in partial fulfilment of the requirement for the degree of Master of Philosophy in Development Studies and Agricultural Engineering at Massey University

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    There have been major problems with the sustainability of many water supply projects in the Developing World. One major area that influences this sustainability is the ongoing operation and maintenance of the water supply. A number of different surveys have shown that within 12 months of a water project being constructed and handed over to the community or government water dept. between 30-70% are not functioning at all or are not producing their original design supply. The purpose of the research was to produce a conceptual model that could be used by development agencies and engineers to increase the sustainability of water supplies. A review of the literature revealed that the major factors influencing sustainable operation and maintenance of water supplies were, technology, infrastructure for parts, training of both agency and community in maintenance of the water supply, the source of funding for O & M, design, ownership and responsibility, and management. These factors were incorporated into a conceptual model, each factor fitting into one or more of the different stages of a water supply project, namely: 1. Planning; 2. Design; 3. Construction; 4. Transfer Ceremony; and 5. Operations. There were up to four major groups of people involved in this process, namely, an International Development Agency, a Government Water Dept., a Community Water Committee, and a Community or Users. Surveys were conducted in Ethiopia, looking at both urban and rural water projects. The results were used to substantiate the model and/or to revise the model. It was concluded from the survey that the following were influential upon sustainable operation and maintenance in Ethiopia: Community ownership does not equate to community responsibility for O & M; Training of the individual or group responsible for O & M is essential; A lack of infrastructure leds to O & M problems; And, community involvement in all stages of the water supply project is essential. The revised conceptual model presents the processes and factors needed to instigate sustainable O & M of water supply projects in developing countries

    Evidence for Nodal Superconductivity in LaFePO from Scanning SQUID Susceptometry

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    We measure changes in the penetration depth λ\lambda of the Tc6T_c \approx 6 K superconductor LaFePO. In the process scanning SQUID susceptometry is demonstrated as a technique for accurately measuring {\it local} temperature-dependent changes in λ\lambda, making it ideal for studying early or difficult-to-grow materials. λ\lambda of LaFePO is found to vary linearly with temperature from 0.36 to \sim2 K, with a slope of 143±\pm15 \AA/K, suggesting line nodes in the superconducting order parameter. The linear dependence up to Tc/3\sim T_c/3 is similar to the cuprate superconductors, indicating well-developed nodes.Comment: 4 pages, 5 figure

    The Association of Long-Term Exposure to Particulate Matter Air Pollution with Brain MRI Findings: The ARIC Study.

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    BACKGROUND: Increasing evidence links higher particulate matter (PM) air pollution exposure to late-life cognitive impairment. However, few studies have considered associations between direct estimates of long-term past exposures and brain MRI findings indicative of neurodegeneration or cerebrovascular disease. OBJECTIVE: Our objective was to quantify the association between brain MRI findings and PM exposures approximately 5 to 20 y prior to MRI in the Atherosclerosis Risk in Communities (ARIC) study. METHODS: ARIC is based in four U.S. sites: Washington County, Maryland; Minneapolis suburbs, Minnesota; Forsyth County, North Carolina; and Jackson, Mississippi. A subset of ARIC participants underwent 3T brain MRI in 2011-2013 (n=1,753). We estimated mean exposures to PM with an aerodynamic diameter less than 10 or 2.5μm (PM RESULTS: In pooled analyses, higher mean PM CONCLUSIONS: Long-term past PM exposure in was not associated with markers of cerebrovascular disease. Higher long-term past PM exposures were associated with smaller deep-gray volumes overall, and higher P

    Local measurement of the superfluid density in the pnictide superconductor Ba(Fe1x_{1-x}Cox_{x})2_2As2_2 across the superconducting dome

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    We measure the penetration depth λab(T)\lambda_{ab}(T) in Ba(Fe1x_{1-x}Cox_{x})2_2As2_2 using local techniques that do not average over the sample. The superfluid density ρs(T)1/λab(T)2\rho_s(T)\equiv1/\lambda_{ab}(T)^2 has three main features. First, ρs(T=0)\rho_s(T=0) falls sharply on the underdoped side of the dome. Second, λab(T)\lambda_{ab}(T) is flat at low TT at optimal doping, indicating fully gapped superconductivity, but varies more strongly in underdoped and overdoped samples, consistent with either a power law or a small second gap. Third, ρs(T)\rho_s(T) varies steeply near TcT_c for optimal and underdoping. These observations are consistent with an interplay between magnetic and superconducting phases

    Local measurement of the penetration depth in the pnictide superconductor Ba(Fe0.95_{0.95}Co0.05_{0.05})2_2As2_2

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    We use magnetic force microscopy (MFM) and scanning SQUID susceptometry to measure the local superfluid density ρs\rho_{s} in Ba(Fe0.95_{0.95}Co0.05_{0.05})2_2As2_2 single crystals from 0.4 K to the critical temperature Tc=18.5T_c=18.5 K. We observe that the penetration depth λ\lambda varies about ten times more slowly with temperature than previously published, with a dependence that can be well described by a clean two-band fully gapped model. We demonstrate that MFM can measure the important and hard-to-determine absolute value of λ\lambda, as well as obtain its temperature dependence and spatial homogeneity. We find ρs\rho_{s} to be uniform despite the highly disordered vortex pinning

    Ecophysiological investigations of understory eastern redcedar in central Missouri

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    Eastern redcedar (Juniperus virginiana) is a sun-adapted, drought-resistant pioneer species common to pastures, abandoned fields, fence rows, and calcareous rock outcrops throughout the eastern United States. However, it is also a frequent component of the understory in mature oakhickory forests in central Missouri, where light levels are typically < 10% of full sunlight during much of the growing season. This is below eastern redcedar's reported optimum for photosynthesis. The competitive survival of understory eastern redcedar under such environmental conditions was apparently due to it being an evergreen conifer in a deciduous forest. Hence, its foliage was able to maintain a positive carbon dioxide balance throughout much of the year, with maximum net photosynthetic rates occurring during periods when the overstory was leafless. The greatest daily average net photosynthetic rates (Ph,) occurred during overstory leaf emergence when temperatures were moderate and light levels to the understory trees were annually the highest. Furthermore, since leaf temperatures and tree water deficits were relatively low at this time, daily gas exchange rates were not greatly limited by midday stomatal closure. After the overstory foliage had fully developed, understory light levels averaged -S50-800o below levels observed in early spring. Thus, photosynthesis was severely light limited during the day, resulting in Ph, that were 15-45% of the springtime maxima. The greatest daily average transpiration rates (TR) occurred during the summer due to the high evaporative demand. Increasing leaf temperatures and tree water deficits became more important by late summer, causing stomatal closure during some afternoons, which reduced Ph,, and TR to :730 and 40%, respectively, of the early summer levels. During the autumn, winter, and early spring, understory light levels were normally above the saturation point for photosynthesis. The light saturation point for an understory study tree (expressed as flux of photosynthetically active photons) was ;800 Armol m--2 s1, less than half of that reported for open-grown eastern redcedar. This relatively lower light saturation point suggested an adjustment to shade conditions. During the autumn overstory defoliation period, light levels to understory trees progressively increased, and Ph, eventually reached 80W of the springtime maximum. In contrast, TR only reached ;25% of the summer maximum, owing to relatively low evaporative demands. During the late autumn and winter, low leaf and soil temperatures combined to limit gas exchange severely. The major controlling factors seemed to be cold air temperatures directly inhibiting Ph, and cold soil temperatures indirectly producing tree water deficits due to reduced water uptake at the soil-root interface. Such conditions promoted persistent stomatal closure, resulting in Ph, near zero. However, a temporary warming trend during the winter caused an increase in Ph,, to a level -301O of the springtime maximum. Higher net photosynthetic rates probably were not possible due to the effects of low soil and air temperatures on the stomatal mechanism and on the photosynthetic apparatus

    Detectors for the James Webb Space Telescope Near-Infrared Spectrograph I: Readout Mode, Noise Model, and Calibration Considerations

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    We describe how the James Webb Space Telescope (JWST) Near-Infrared Spectrograph's (NIRSpec's) detectors will be read out, and present a model of how noise scales with the number of multiple non-destructive reads sampling-up-the-ramp. We believe that this noise model, which is validated using real and simulated test data, is applicable to most astronomical near-infrared instruments. We describe some non-ideal behaviors that have been observed in engineering grade NIRSpec detectors, and demonstrate that they are unlikely to affect NIRSpec sensitivity, operations, or calibration. These include a HAWAII-2RG reset anomaly and random telegraph noise (RTN). Using real test data, we show that the reset anomaly is: (1) very nearly noiseless and (2) can be easily calibrated out. Likewise, we show that large-amplitude RTN affects only a small and fixed population of pixels. It can therefore be tracked using standard pixel operability maps.Comment: 55 pages, 10 figure

    Re-evaluation of low intensity pulsed ultrasound in treatment of tibial fractures (TRUST): Randomized clinical trial

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    Objective: To determine whether low intensity pulsed ultrasound (LIPUS), compared with sham treatment, accelerates functional recovery and radiographic healing in patients with operatively managed tibial fractures. Design: A concealed, randomized, blinded, sham controlled clinical trial with a parallel group design of 501 patients, enrolled between October 2008 and September 2012, and followed for one year. Setting: 43 North American academic trauma centers. Participants: Skeletally mature men or women with an open or closed tibial fracture amenable to intramedullary nail fixation. Exclusions comprised pilon fractures, tibial shaft fractures that extended into the joint and required reduction, pathological fractures, bilateral tibial fractures, segmental fractures, spiral fractures \u3e7.5 cm in length, concomitant injuries that were likely to impair function for at least as long as the patient\u27s tibial fracture, and tibial fractures that showed 1 cm gap after surgical fixation. 3105 consecutive patients who underwent intramedullary nailing for tibial fracture were assessed, 599 were eligible and 501 provided informed consent and were enrolled. Interventions: Patients were allocated centrally to self administer daily LIPUS (n=250) or use a sham device (n=251) until their tibial fracture showed radiographic healing or until one year after intramedullary fixation. Main outcom e measures: Primary registry specified outcome was time to radiographic healing within one year of fixation; secondary outcome was rate of non-union. Additional protocol specified outcomes included short form-36 (SF-36) physical component summary (PCS) scores, return to work, return to household activities, return to ≥80% of function before injury, return to leisure activities, time to full weight bearing, scores on the health utilities index (mark 3), and adverse events related to the device. Results: SF-36 PCS data were acquired from 481/501 (96%) patients, for whom we had 2303/2886 (80%) observations, and radiographic healing data were acquired from 482/501 (96%) patients, of whom 82 were censored. Results showed no impact on SF-36 PCS scores between LIPUS and control groups (mean difference 0.55, 95% confidence interval -0.75 to 1.84; P=0.41) or for the interaction between time and treatment (P=0.30); minimal important difference is 3-5 points) or in other functional measures. There was also no difference in time to radiographic healing (hazard ratio 1.07, 95% confidence interval 0.86 to 1.34; P=0.55). There were no differences in safety outcomes between treatment groups. Patient compliance was moderate; 73% of patients administered ≥50% of all recommended treatments. Conclusions: Postoperative use of LIPUS after tibial fracture fixation does not accelerate radiographic healing and fails to improve functional recovery. Study registration: ClinicalTrialGov Identifier: NCT00667849
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