4,228 research outputs found

    AGB subpopulations in the nearby globular cluster NGC 6397

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    It has been well established that Galactic Globular clusters (GCs) harbour more than one stellar population, distinguishable by the anti-correlations of light element abundances (C-N, Na-O, and Mg-Al). These studies have been extended recently to the asymptotic giant branch (AGB). Here we investigate the AGB of NGC 6397 for the first time. We have performed an abundance analysis of high-resolution spectra of 47 RGB and 8 AGB stars, deriving Fe, Na, O, Mg and Al abundances. We find that NGC 6397 shows no evidence of a deficit in Na-rich AGB stars, as reported for some other GCs - the subpopulation ratios of the AGB and RGB in NGC 6397 are identical, within uncertainties. This agrees with expectations from stellar theory. This GC acts as a control for our earlier work on the AGB of M 4 (with contrasting results), since the same tools and methods were used.Comment: 10 pages, 7 figures, 8 tables (2 online-only). Accepted for publication in MNRA

    Energy Dependent Tunneling in a Quantum Dot

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    We present measurements of the rates for an electron to tunnel on and off a quantum dot, obtained using a quantum point contact charge sensor. The tunnel rates show exponential dependence on drain-source bias and plunger gate voltages. The tunneling process is shown to be elastic, and a model describing tunneling in terms of the dot energy relative to the height of the tunnel barrier quantitatively describes the measurements.Comment: 4 pages, 4 figure

    Assessment of the variability of airborne contamination levels in an intensive care unit over a 24 hour period

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    Introduction: The objective of this study was to evaluate the variability in the dynamics and levels of airborne contamination within a hospital ICU in order to establish an improved understanding of the extent to which airborne bioburden contributes to cross-infection of patients. Microorganisms from the respiratory tract or skin can become airborne by coughing, sneezing and periods of increased activity such as bed changes and staff rounds. Current knowledge of the clinical microflora is limited however it is estimated that 10-33% of nosocomial infections are transmitted via air. Methods: Environmental air monitoring was conducted in Glasgow Royal Infirmary ICU, in the open ward and in patient isolation rooms. A sieve impactor air sampler was used to collect 500 L air samples every 15 minutes over 10 hour (08:00-18:00 h) and 24 hour (08:00-08:00 h) periods. Samples were collected, room activity logged and the bacterial contamination levels were recorded as CFU/m3 of air. Results: A high degree of variability in levels of airborne contamination was observed over the course of a 10 hour day and a 24 period in a hospital ICU. Counts ranged from 12-510 CFU/m3 over 24 hours in an isolation room occupied for 10 days by a patient with C. difficile infection. Contamination levels were found to be lowest during the night and in unoccupied rooms, with an average value of 20 CFU/m3. Peaks in airborne contamination showed a direct relation to an increase in room activity. Conclusions: This study demonstrates the degree of airborne contamination that can occur in an ICU over a 24 hour period. Numerous factors were found to contribute to microbial air contamination and consideration should be given to potential improved infection control strategies and decontamination technologies which could be deployed within the clinical environment to reduce the airborne contamination levels, with the ultimate aim of reducing healthcare-associated infections from environmental sources

    Analysis of Kelly-optimal portfolios

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    We investigate the use of Kelly's strategy in the construction of an optimal portfolio of assets. For lognormally distributed asset returns, we derive approximate analytical results for the optimal investment fractions in various settings. We show that when mean returns and volatilities of the assets are small and there is no risk-free asset, the Kelly-optimal portfolio lies on Markowitz Efficient Frontier. Since in the investigated case the Kelly approach forbids short positions and borrowing, often only a small fraction of the available assets is included in the Kelly-optimal portfolio. This phenomenon, that we call condensation, is studied analytically in various model scenarios.Comment: 15 pages, 7 figures; extended list of references and some minor modification

    An economic survey of New Zealand wheatgrowers : survey no. 2

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    This is survey number 2. No. 1 was know as "National wheatgrowers' survey"This Report is the second in an annual series of economic surveys of New Zealand wheatgrowing farms. These surveys have been undertaken by the Agricultural Economics Research Unit at Lincoln College on behalf of Wheat Growers Sub-Section of Federated Farmers of New Zealand Inc. Specific attention has been focused on the physical characteristics of wheatgrowing farms, the area of wheat and other crops sown, wheat yields, cultural practices and costs and returns for the 1977/78 wheat crop. An attempt has also been made to allocate plant and machinery overhead costs to the wheat enterprise on both an historical and current cost basis. The need for current and detailed information from the Survey involved two visits to the farms in the sample; one in the spring following drilling and the second in the autumn after harvest

    Collaborating with individuals with lived experience to adapt CANMAT clinical depression guidelines into a patient treatment guide: The CHOICE‐D co‐design process

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    Effective treatment of depression involves collaboration with informed patients and families and appropriate knowledge sharing. We describe here our experience, as a case example, of a collaboration to “translate” a clinical guideline designed for practitioners into an accessible, plainlanguage version that patients and families can use during the care process, both to provide basic educational information and to foster informed discussions with their treatment providers. Content experts in knowledge translation, patient advocacy, patient‐oriented research, and psychiatry guided overall project design. Our first step was to identify lived experience writers to join in the codesign and co‐writing of the “CHOICE‐D Patient and Family Guide to Depression Treatment.” A national call for writers attracted 62 applicants, from whom eight individuals with lived experience of depression and writing experience were selected. Individuals subsequently attended a welcoming teleconference, followed by a 1‐day workshop designed to provide (a) a detailed overview of the clinician guideline, (b) an opportunity to select what should be included in the Guide, and (c) key principles of knowledge translation/lay writing. Both from the workshop and subsequently through the codesign process, lived experience writers recommended that the Guide address symptoms, effects of illness course on treatment, first‐line treatments, safety/side effects, and treatment misconceptions. To promote patient autonomy, question scripts (how and what to ask your treatment provider), self‐triaging resources, and treatment selection aids were suggested. Stylistic considerations included use of simple yet hopeful language, brevity, white space, key terms glossary, and graphics. Several strategies were particularly useful to optimize writer engagement in the codesign process: a pre‐workshop conference call and circulation of project resources, an in‐person workshop to increase content knowledge, structured discussion with co‐writers and project leads to develop ideas, and practical training exercises with the provision of feedback. Both during and at the end of the project, writers provided additional recommendations for improving the process, including more in‐person meetings, distribution of step‐by‐step instructions on the writing task, and a key terms glossary of technical terms to support their role. In conclusion, we describe a process with practical tips and reflective feedback on important considerations for engaging persons with lived experience as leaders in the codesign and writing process of lay treatment guidelines. These methods may serve as a model for similar projects in other areas of healthcare.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156154/2/jep13308.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156154/1/jep13308_am.pd

    ENVIRONMENTAL IMPACTS OF USING DESALINATED WATER IN CONCRETE PRODUCTION IN AREAS AFFECTED BY FRESHWATER SCARCITY

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    Up to 500 litres of water may be consumed at the batching plant per cubic meter of ready mix concrete, if water for washing mixing trucks and equipment is included. Demand for concrete is growing almost everywhere, regardless of local availability of freshwater. The use of freshwater for concrete production exacerbates stress on natural water resources. In water-stressed coastal countries such as Israel, desalinated seawater (DSW) is often used in the production of concrete. However, the environmental impacts of this practice have not yet been assessed. In this study the effect of using DSW on the water and carbon footprints of concrete was investigated using life cycle assessment. Water footprint results highlight the benefits of using DSW rather than freshwater to produce concrete in Israel. In contrast, because desalination is an energy intensive process, using DSW increases the greenhouse gas intensity of concrete. Nevertheless, this increase (0.27 kg CO2e/m3 concrete) is small, if compared to the life cycle greenhouse gas emissions of concrete. Our results show that using untreated seawater in the mix (transported by truck from the coast) in place of DSW, would be beneficial in terms of water and carbon footprints if the batching plant were located less than 13 km from the withdrawal point. However, use of untreated seawater increases steel reinforcement corrosion, resulting in loss of structural integrity of the reinforced concrete composite. Sustainability of replacing steel with non-corrosive materials should be explored as a way to reduce both water and carbon footprints of concrete
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