1,476 research outputs found
Preliminary isotope heater locations and masking pattern Passive Seismic Experiment Package Central Station
No full textA series of parametric thermal studies have been carried out to determine the optimum locations for the two heaters and the optimum masking pattern.prepared by R. J. Simms
Final isotope heater locations and masking pattern -- Passive Seismic Experiment Package Central Station
No full textThe parametric studies have been completed. Since the thermal characteristics of the three configurations were so similar, the selection was primarily based upon mechanical considerations. A unique rectangular masking pattern has been found which, within the assumptions discussed, satisfy the specified thermal plate average temperature limits, of -65 F to +140 F.prepared by R. J. Simms
Degradation of Environmental Protection Coatings for Gas Turbine Materials
No full textNowadays, problems of component materials reliability in gas and oil-fired gas turbines focus on assessing the potential behaviour of commonly employed coatings, in order to avoid expensive and unpredictable failure in service and producing new materials whose performance meets life time and manufacturing/ repairing requirements.
This MPhil project has investigated the oxidative and corrosive degradation mechanisms for some of the alloy/coatings systems (CMSX-4, CMSX-4/ RT22, CMSX-4/ CN91 and CMSX-4/ “LCO22”), which are currently used for turbines blades and vanes, in order to achieve a better knowledge of materials behaviour and to improve models for the prediction of turbine components’ lives. To achieve this target the study has made use of realistic simulations of turbine exposure conditions in combined with pre- and post-exposure metrology of bar shape materials samples, while optical microscopy has been applied to describe the microstructural evolution during the exposure and the products of the degradation for the hot corrosion.
For high temperature oxidation, over extended periods of time (up to 10,000 hours), the research has allowed to describe the morphological changes in respect of the exposure time and temperature and to determine the oxidation kinetics experienced by the alloy and coatings. A model has been presented for predicting θ- α-Al2O3 growth. Moreover, using NASA COSP spalling model, with rate constants values coming from this study, a comparison between experimental mass change data and prediction has been shown.
The hot corrosion study has provided new quantitative metal loss data and observations that extend/validate an existing model for materials life prediction, based on defining the severity of the corrosion conditions through measures of gas composition and contaminant deposition flux
Randomised controlled trial of screening for Chlamydia trachomatis to prevent pelvic inflammatory disease: the POPI (prevention of pelvic infection) trial.
No full textOBJECTIVE: To determine whether screening and treating women for chlamydial infection reduces the incidence of pelvic inflammatory disease over the subsequent 12 months.
DESIGN: Randomised controlled trial.
SETTING: Common rooms, lecture theatres, and student bars at universities and further education colleges in London. PARTICIPANTS: 2529 sexually active female students, mean age 21 years (range 16-27).
INTERVENTION: Participants completed a questionnaire and provided self taken vaginal swabs, with follow-up after one year. Samples were randomly allocated to immediate testing and treatment for chlamydial infection, or storage and analysis after a year (deferred screening controls).
MAIN OUTCOME MEASURE: Incidence of clinical pelvic inflammatory disease over 12 months.
RESULTS: Baseline prevalence of chlamydia was 5.4% (68/1254) in screened women and 5.9% (75/1265) in controls. 94% (2377/2529) of women were followed up after 12 months. The incidence of pelvic inflammatory disease was 1.3% (15/1191) in screened women compared with 1.9% (23/1186) in controls (relative risk 0.65, 95% confidence interval 0.34 to 1.22). Seven of 74 control women (9.5%, 95% confidence interval 4.7% to 18.3%) who tested positive for chlamydial infection at baseline developed pelvic inflammatory disease over 12 months compared with one of 63 (1.6%) screened women (relative risk 0.17, 0.03 to 1.01). However, most episodes of pelvic inflammatory disease occurred in women who tested negative for chlamydia at baseline (79%, 30/38). 22% (527/2377) of women reported being tested independently for chlamydia during the trial.
CONCLUSION: Although some evidence suggests that screening for chlamydia reduces rates of pelvic inflammatory disease, especially in women with chlamydial infection at baseline, the effectiveness of a single chlamydia test in preventing pelvic inflammatory disease over 12 months may have been overestimated
Quality of life and wellbeing among HIV outpatients in East Africa: a multicentre observational study.
No full textBACKGROUND: Global health investment has reduced HIV mortality and transmission. However, little is known of patient-reported outcomes alongside ART rollout. This study aimed to measure wellbeing using patient-reported outcome measures (PROMS) among outpatients at PEPFAR-funded facilities. METHODS: In a multicentre 2 country cross-sectional study, adults attending 12 facilities in Kenya and Uganda gave self-reported data on quality of life (physical and mental wellbeing dimensions), functional and a measure of multidimensional problems (physical, psychological, social and spiritual). RESULTS: Among the 1,337 participants, multidimensional problems were more common in psychological, spiritual and social domains than in physical. In multivariable analysis using GEE to adjust for facility effect, the mental health subscale of quality of life was lower for people with limited functional status (B = -5.27, 95% CI -5.99, 1. -4.56 p < 0.001) and higher for wealthier people (B = 0.91, 95% CI 0.48, 1.33, p < 0.001). The physical health subscale of quality of life was lower for those with limited functional status (B = -8.58, 95% CI -9.46 to -7.70, p < 0.001) and those who had a caregiver present (B = -1.97, 95% CI -3.72 to -0.23, p = 0.027), higher for wealthier people (B = 1.14, 95% CI 0.65, 1.64, p < 0.001), and positively associated with CD4 count (B = 1.61, 95% CI 1.08-2.14, p < 0.001). Multidimensional problems were more burdensome for people with limited functional status (B = -2.06, 95% CI -2.46 to -1.66, p < 0.001), and less burdensome with more education (B = 0.63, 95% CI 0.25-1.00, p = 0.001) or ART use (B = 0.94, 95% CI 0.34-1.53, p = 0.002). CONCLUSIONS: Multidimensional problems are highly prevalent, and worse with declining function. Importantly, ART use does not appear to be protective for self-reported physical and mental dimensions of quality of life. Assessment and management of self-reported wellbeing must form part of HIV care and treatment services to ensure maximum benefit from ART investment
Heavy water lattice project annual report / editors: Irving Kaplan, A.E. Profio [and] T.J. Thompson ; contributors P.S. Brown ... [et al.]
No full textStatement of responsibility on title-page reads: editors: Irving Kaplan A.E. Profio, T.J. Thompson; contributors: P.S. Brown, W.H. D'Ardenne, J.Harrington, III, I.Kaplan, B.K. Malaviya, P.F. Palmedo, J.C. Peak. A.E. Profio. R. Simms. T.J. Thompson. A. Weitzberg. J,R. Wolberg"September 30, 1962""NYO-10, 208."Includes bibliographical referencesAnnual report; September 30, 1962U.S. Atomic Energy Commission contract AT(30-1)234
sj-pdf-1-asm-10.1177_10731911221143343 – Supplemental material for Structure of Pathological Personality Traits Through the Lens of the CAT-PD Model
No full textSupplemental material, sj-pdf-1-asm-10.1177_10731911221143343 for Structure of Pathological Personality Traits Through the Lens of the CAT-PD Model by Whitney R. Ringwald, Leah Emery, Shereen Khoo, Lee Anna Clark, Yuliya Kotelnikova, Matthew D. Scalco, David Watson, Aidan G. C. Wright and Leonard J. Simms in Assessment</p
The hot corrosion of nickel-base disc alloys
No full textThe efficiency of a jet’s engines has a direct affect on its economic and environmental
impact through the quantity of aviation fuel consumed and CO2 emitted. These factors are
becoming increasingly important due to higher fuel costs and a greater global awareness of
environmental issues.
To date, most of the corrosion research work concerning jet turbines has focused on the
hottest parts, the turbine blades vanes and combustion chamber. However, as the engines
run hotter and with more stress, new superalloys have also been developed for the turbine
disc. Although extensive research has been carried out with regard to the mechanical
properties of these alloys, relatively little research has been done into their corrosion
resistance.
The aim of this research is to investigate the hot corrosion characteristics of both the
existing and more recently developed disc alloys. Based on these data, the corrosion
performance of these alloys was modelled and compared.
These aims have been achieved using data from a series of “deposit recoat” corrosion tests
on the relevant alloys carried out at Cranfield during the last 6 years. The alloys that are the
focus of this study are: Waspaloy, Inconel 718, U720, and RR1000. RR1000 is of particular
interest since it is the most recently developed alloy and relatively little is known about its
corrosion properties. The tests have been carried over a range of temperatures relevant to
the current operating temperatures and the desired higher operating temperatures of the
turbine discs. The effects of deposition flux, deposit composition and exposure time have
also been investigated as part of this study.
A quantitative assessment of the corrosion damage has been carried out and provided
metal loss data which has been used to generate empirical models and to compare the
effects of variables. The data generated suggest that in the propagation stage of hot
corrosion the rate of corrosion is approximately the same between alloys. Therefore the
important factor when modelling a disc alloy’s corrosion behaviour is the length of the
incubation period.
The changes in elemental composition undergone at the alloy surface during corrosion have
been investigated using a scanning electron microscope (SEM) equipped with an energy
dispersive X-ray spectroscopy (EDX). The results support the literature in that type II
corrosion exhibits no preferential alloy depletion underneath the corrosion deposits
Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis
No full textMultiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis
Population Structure and Life History Connectivity of Antarctic Silverfish (Pleuragramma antarctica) in the Southern Ocean Ecosystem
No full textAntarctic silverfish (Pleuragramma antarctica) are the most important pelagic forage fish on the Antarctic continental shelf. They have an exclusively pelagic life history, including cryopelagic eggs and early larvae. The discovery of extensive distributions of eggs and larvae under fast-ice inside Terra Nova Bay, and the revelation that the aggregates were stable between years, suggested dispersal over the continental shelf by older larvae and juveniles and a return as adults to spawning areas, consistent with observations from the Antarctic Peninsula of large-scale adult movement inshore. This life history hypothesis holds promise for understanding population structure in silverfish found around the Antarctic continental shelf. However, the hypothesis is challenged by inconsistencies concerning the distribution of spawning and feeding areas, a low-energy life strategy, and lack of phylogenetic diversification.
We review recent and past population and genetic studies in the context of published literature on the physical environment, including hydrography and a recent geological reconstruction of Antarctic Ice Sheet deglaciation. We suggest physical-biological interactions between glacial trough systems, circulation, and life history processes in shaping distributions of silverfish along and across the shelf. We discuss how these processes may result in a richly diverse population structure around the Antarctic and over time, and show how the synthesis can help account for (1) variability in spawning and feeding areas over succeeding glacial cycles, (2) connectivity without invoking active migration on large spatial scales, and (3) persistence over successive glacial cycles without further phylogenetic diversification. Based on this synthesis, we make predictions concerning population structuring and genetic signatures of paleo-climatic events, and suggest multi-disciplinary approaches to test these in future research
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