2,911 research outputs found

    Integrated orbital servicing study for low-cost payload programs. Volume 2: Technical and cost analysis

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    Orbital maintenance concepts were examined in an effort to determine a cost effective orbital maintenance system compatible with the space transportation system. An on-orbit servicer maintenance system is recommended as the most cost effective system. A pivoting arm on-orbit servicer was selected and a preliminary design was prepared. It is indicated that orbital maintenance does not have any significant impact on the space transportation system

    Study of several factors affecting crew escape trajectories from the Space Shuttle Orbiter at low-subsonic speeds

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    Factors affecting the bailout characteristics from the space shuttle orbiter at low-subsonic speeds were investigated. In the 12-foot low-speed tunnel and the 4 by 7-meter tunnel with 0.03-scale models. The effect of crew-model exit velocity, body position, and body weight were studied with egress from the main side hatch with the orbiter upright and from the upper cabin hatch with the orbiter inverted. Crew model drag and flow field measurements around the orbiter were estimated. The high-angle-of-attack trim characteristics of the orbiter was determined by force tests in an attempt to improve bailout conditions. A computer simulation was made to evaluate the maneuver necessary to attain the high-angle-of-attack trim

    Stability and Reversibility of Lithium Borohydrides Doped by Metal Halides and Hydrides

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    In an effort to develop reversible metal borohydrides with high hydrogen storage capacities and low dehydriding temperature, doping LiBH4 with various metal halides and hydrides has been conducted. Several metal halides such as TiCl3, TiF3, and ZnF2 effectively reduced the dehydriding temperature through a cation exchange interaction. Some of the halide doped LiBH4 are partially reversible. The LiBH4 + 0.1TiF3 desorbed 3.5 wt % and 8.5 wt % hydrogen at 150 and 450 °C, respectively, with subsequent reabsorption of 6 wt % hydrogen at 500 °C and 70 bar observed. XRD and NMR analysis of the rehydrided samples confirmed the reformation of LiBH4. The existence of the (B12H12)−2 species in dehydrided and rehydrided samples gives insight into the resultant partial reversibility. A number of other halides, MgF2, MgCl2, CaCl2, SrCl2, and FeCl3, did not reduce the dehydriding temperature of LiBH4 significantly. XRD and TGA-RGA analyses indicated that an increasing proportion of halides such as TiCl3, TiF3, and ZnCl2 from 0.1 to 0.5 mol makes lithium borohydrides less stable and volatile. Although the less stable borohydrides such as LiBH4 + 0.5TiCl3, LiBH4 + 0.5TiF3, and LiBH4 + 0.5ZnCl2 release hydrogen at room temperature, they are not reversible due to unrecoverable boron loss caused by diborane emission. In most cases, doping that produced less stable borohydrides also reduced the reversible hydrogen uptake. It was also observed that halide doping changed the melting points and reduced air sensitivity of lithium borohydrides

    Sex differences in mathematics and reading achievement are inversely related: within- and across-nation assessment of 10 years of PISA data

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    We analyzed one decade of data collected by the Programme for International Student Assessment (PISA), including the mathematics and reading performance of nearly 1.5 million 15 year olds in 75 countries. Across nations, boys scored higher than girls in mathematics, but lower than girls in reading. The sex difference in reading was three times as large as in mathematics. There was considerable variation in the extent of the sex differences between nations. There are countries without a sex difference in mathematics performance, and in some countries girls scored higher than boys. Boys scored lower in reading in all nations in all four PISA assessments (2000, 2003, 2006, 2009). Contrary to several previous studies, we found no evidence that the sex differences were related to nations’ gender equality indicators. Further, paradoxically, sex differences in mathematics were consistently and strongly inversely correlated with sex differences in reading: Countries with a smaller sex difference in mathematics had a larger sex difference in reading and vice versa. We demonstrate that this was not merely a between-nation, but also a within-nation effect. This effect is related to relative changes in these sex differences across the performance continuum: We did not find a sex difference in mathematics among the lowest performing students, but this is where the sex difference in reading was largest. In contrast, the sex difference in mathematics was largest among the higher performing students, and this is where the sex difference in reading was smallest. The implication is that if policy makers decide that changes in these sex differences are desired, different approaches will be needed to achieve this for reading and mathematics. Interventions that focus on high-achieving girls in mathematics and on low achieving boys in reading are likely to yield the strongest educational benefits

    The La Prele Mammoth Site, Converse County, Wyoming, USA

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    The La Prele Mammoth site is a Clovis archaeolog- ical site in Converse County, Wyoming (U.S.A.) that preserves chipped stone artifacts in spatial as- sociation with the remains of a subadult Columbi- an mammoth (Mammuthus columbi). The site was discovered in 1986 and initially tested by George Frison in 1987, but work ceased there until 2014 due to a disagreement with the landowner. In the intervening years, questions arose as to whether the artifacts and mammoth remains were truly associated, and the site was largely dismissed by American archaeologists. Recent excavations have not only demonstrated that La Prele was the loca- tion of a mammoth kill by Clovis hunters around 12,850 years ago, but it also preserves a campsite in close proximity to the kill. The camp includes multiple hearth-centered activity areas that appear to represent domestic spaces, reflected by the pres- ence of a diversity of stone tool forms, bone nee- dles, a bone bead, a large area of hematite-stained matrix, and the butchered and cooked remains of at least one other large mammal species. The site has the potential to inform us about aspects of the social organization of Clovis bands, particularly with respect to mammoth hunting and butchery.The symposium and the volume "Human-elephant interactions: from past to present" were funded by the Volkswagen Foundation

    Personalised asthma action plans for adults with asthma

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    BACKGROUND: A key aim of asthma care is to empower each person to take control of his or her own condition. A personalised asthma action plan (PAAP), also known as a written action plan, an individualised action plan, or a self-management action plan, contributes to this endeavour. A PAAP includes individualised self-management instructions devised collaboratively with the patient to help maintain asthma control and regain control in the event of an exacerbation. A PAAP includes baseline characteristics (such as lung function), maintenance medication and instructions on how to respond to increasing symptoms and when to seek medical help. OBJECTIVES: To evaluate the effectiveness of PAAPs used alone or in combination with education, for patient-reported outcomes, resource use and safety among adults with asthma. SEARCH METHODS: We searched the Cochrane Airways Group Specialised Register of trials, clinical trial registers, reference lists of included studies and review articles, and relevant manufacturers' websites up to 14 September 2016. SELECTION CRITERIA: We included parallel randomised controlled trials (RCTs), both blinded and unblinded, that evaluated written PAAPs in adults with asthma. Included studies compared PAAP alone versus no PAAP, and/or PAAP plus education versus education alone. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted study characteristics and outcome data and assessed risk of bias for each included study. Primary outcomes were number of participants reporting at least one exacerbation requiring an emergency department (ED) visit or hospitalisation, asthma symptom scores on a validated scale and adverse events (all causes). Secondary outcomes were quality of life measured on a validated scale, number of participants reporting at least one exacerbation requiring systemic corticosteroids, respiratory function and days lost from work or study. We used a random-effects model for all analyses and standard Cochrane methods throughout. MAIN RESULTS: We identified 15 studies described in 27 articles that met our inclusion criteria. These 15 included studies randomised a total of 3062 participants (PAAP vs no PAAP: 2602 participants; PAAP plus education vs education alone: 460 participants). Ten studies (eight PAAP vs no PAAP; two PAAP plus education vs education alone) provided outcome data that contributed to quantitative analyses. The overall quality of evidence was rated as low or very low.Fourteen studies lasted six months or longer, and the remaining study lasted for 14 weeks. When reported, mean age ranged from 22 to 49 years and asthma severity ranged from mild to severe/high risk. PAAP alone compared with no PAAPResults showed no clear benefit or harm associated with PAAPs in terms of the number of participants requiring an ED visit or hospitalisation for an exacerbation (odds ratio (OR) 0.75, 95% confidence interval (CI) 0.45 to 1.24; 1385 participants; five studies; low-quality evidence), change from baseline in asthma symptoms (mean difference (MD) -0.16, 95% CI -0.25 to - 0.07; 141 participants; one study; low-quality evidence) or the number of serious adverse events, including death (OR 3.26, 95% CI 0.33 to 32.21; 125 participants; one study; very low-quality evidence). Data revealed a statistically significant improvement in quality of life scores for those receiving PAAP compared with no PAAP (MD 0.18, 95% CI 0.05 to 0.30; 441 participants; three studies; low-quality evidence), but this was below the threshold for a minimum clinically important difference (MCID). Results also showed no clear benefit or harm associated with PAAPs on the number of participants reporting at least one exacerbation requiring oral corticosteroids (OR 1.45, 95% CI 0.84 to 2.48; 1136 participants; three studies; very low-quality evidence) nor on respiratory function (change from baseline forced expiratory volume in one second (FEV1): MD -0.04 L, 95% CI -0.25L to 0.17 L; 392 participants; three studies; low-quality evidence). In one study, PAAPs were associated with significantly fewer days lost from work or study (MD -6.20, 95% CI -7.32 to - 5.08; 74 participants; low-quality evidence). PAAP plus education compared with education aloneResults showed no clear benefit or harm associated with adding a PAAP to education in terms of the number of participants requiring an ED visit or hospitalisation for an exacerbation (OR 1.08, 95% CI 0.27 to 4.32; 70 participants; one study; very low-quality evidence), change from baseline in asthma symptoms (MD -0.10, 95% CI -0.54 to 0.34; 70 participants; one study; low-quality evidence), change in quality of life scores from baseline (MD 0.13, 95% CI -0.13 to 0.39; 174 participants; one study; low-quality evidence) and number of participants requiring oral corticosteroids for an exacerbation (OR 0.28, 95% CI 0.07 to 1.12; 70 participants; one study; very low-quality evidence). No studies reported serious adverse events, respiratory function or days lost from work or study. AUTHORS' CONCLUSIONS: Analysis of available studies was limited by variable reporting of primary and secondary outcomes; therefore, it is difficult to draw firm conclusions related to the effectiveness of PAAPs in the management of adult asthma. We found no evidence from randomised controlled trials of additional benefit or harm associated with use of PAAP versus no PAAP, or PAAP plus education versus education alone, but we considered the quality of the evidence to be low or very low, meaning that we cannot be confident in the magnitude or direction of reported treatment effects. In the context of this caveat, we found no observable effect on the primary outcomes of hospital attendance with an asthma exacerbation, asthma symptom scores or adverse events. We recommend further research with a particular focus on key patient-relevant outcomes, including exacerbation frequency and quality of life, in a broad spectrum of adults, including those over 60 years of age

    Connected parents: combining online and off-line parenthood in vlogs and blogs

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    This article explores evaluative discourse in a corpus sample of parents' vlogs (video blogs) and blogs (henceforth v/ blogs) dealing with family tasks and responsibilities, as a reflection of underlying values concerning parenthood. It pays special attention to the important role played by the expression of attitude, understood as "ways of feeling" and including the meanings of affect, judgement and appreciation, together with positive politeness in the social practices of the discursive construction of online and off-line parenthood. Analysis and description of the data show two main patterns in parents' practices, either aiming at perfection through juggling and multi-tasking or building resistance to the demands of families and society. Results show that parents frequently exploit the system of affect for building positive face and rapport, while indirectly expressing judgement of social esteem and social sanction, which construct their identities as mothers and fathers and those of the members of their communities of practice. The corpus for the study consists of a random sample of 400 evaluative units in posts and comments on v/ blogs dealing with family tasks and responsibilities (200 in English and 200 in Spanish, with half the sample being drawn from fathers' and the other half from mothers' v/ blogs). I will approach the analysis of the data from appraisal (Martin and White 2005, Bednarek 2008) and politeness theory (Brown and Levinson 1987) in order to explore the features of evaluative discourse and the management of face. The methodology for processing the data borrows quantitative techniques from Corpus Linguistics, including the coding and statistical treatment of the sample with UAM Corpus Tools (O'Donnell 2011), together with Pragmatics and Discourse Analysis (DA), as done in some previous research (SantamarĂ­a-GarcĂ­a 2011, 2014).Project "EMO-FUNDETT: EMOtion and language at work", I+D FFI2013-47792-C2-1-P, sponsored by the Spanish Ministry of Science and Innovatio

    An assessment of temporal, spatial and taxonomic trends in harmful algal toxin exposure in stranded marine mammals from the US New England coast

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    © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fire, S. E., Bogomolni, A., DiGiovanni, R. A., Jr., Early, G., Leighfield, T. A., Matassa, K., Miller, G. A., Moore, K. M. T., Moore, M., Niemeyer, M., Pugliares, K., Wang, Z., & Wenzel, F. W. An assessment of temporal, spatial and taxonomic trends in harmful algal toxin exposure in stranded marine mammals from the US New England coast. Plos One, 16(1),(2021): e0243570, https://doi.org/10.1371/journal.pone.0243570.Despite a long-documented history of severe harmful algal blooms (HABs) in New England coastal waters, corresponding HAB-associated marine mammal mortality events in this region are far less frequent or severe relative to other regions where HABs are common. This long-term survey of the HAB toxins saxitoxin (STX) and domoic acid (DA) demonstrates significant and widespread exposure of these toxins in New England marine mammals, across multiple geographic, temporal and taxonomic groups. Overall, 19% of the 458 animals tested positive for one or more toxins, with 15% and 7% testing positive for STX and DA, respectively. 74% of the 23 different species analyzed demonstrated evidence of toxin exposure. STX was most prevalent in Maine coastal waters, most frequently detected in common dolphins (Delphinus delphis), and most often detected during July and October. DA was most prevalent in animals sampled in offshore locations and in bycaught animals, and most frequently detected in mysticetes, with humpback whales (Megaptera novaeangliae) testing positive at the highest rates. Feces and urine appeared to be the sample matrices most useful for determining the presence of toxins in an exposed animal, with feces samples having the highest concentrations of STX or DA. No relationship was found between the bloom season of toxin-producing phytoplankton and toxin detection rates, however STX was more likely to be present in July and October. No relationship between marine mammal dietary preference and frequency of toxin detection was observed. These findings are an important part of a framework for assessing future marine mammal morbidity and mortality events, as well as monitoring ecosystem health using marine mammals as sentinel organisms for predicting coastal ocean changes.S.F. - NOAA John H. Prescott Marine Mammal Rescue Assistance Grant Program #NA16NMF4390151 S.F. - NOAA John H. Prescott Marine Mammal Rescue Assistance Grant Program #NA17NMF4390082 S.F. - Florida Tech Department of Biological Sciences S.F. - Florida Tech John H. Evans Library Open Access Subvention Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

    Individual Actions as Community Informative Resources. A Collective Informative Systems Approach

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    This paper conceives communities (in this case, partnerships) as being able to become collective informative repositories of individual and collective actions that may better-inform their members. This paper presents one approach for studying if a community has become such an informative repository. The approach used here consists of introducing a formal language (Viable Systems Modelling, VSM) into one of the community nodes (a participant) and tracing if its use is seen in another node (another participant) - indicating the presence of a process of diffusion. This research design has been tested in a crime-reduction partnership in the UK. One of its members was asked to engage in the design and testing of this approach as a co-researcher. As a result, a questionnaire to map communication and control devices inside an organization was jointly developed. In keeping with VSM principles, the questionnaire encouraged participants to reflect on attenuation and amplification processes within their communications channels. To test the quality of the outcomes of this approach, members from another crime-reduction partnership were also invited to answer the survey; this was to confirm that VSM notions were not evident for those outside the development and testing of the questionnaire. The questionnaire indicated also its capability to make visible communication and organizational processes within collectives and its potential to stimulate self-organization, for those individuals who became familiar with VSM. Furthermore, this approach provided the authors with the capability to study information flows inside the two collectives, and contributed to an understanding of these flows as a model for building and maintaining a Community Informative System
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