443 research outputs found
Development of procedures for calculating stiffness and damping properties of elastomers in engineering applications. Part 4: Testing of elastomers under a rotating load
A test rig designed to measure stiffness and damping of elastomer cartridges under a rotating load excitation is described. The test rig employs rotating unbalance in a rotor which runs to 60,000 RPM as the excitation mechanism. A variable resonant mass is supported on elastomer elements and the dynamic characteristics are determined from measurements of input and output acceleration. Five different cartridges are considered: three of these are buttons cartridges having buttons located in pairs, with 120 between each pair. Two of the cartridges consist of 360 elastomer rings with rectangular cross-sections. Dynamic stiffness and damping are measured for each cartridge and compared with predictions at different frequencies and different strains
Development of procedures for calculating stiffness and damping of elastomers in engineering applications. Part 5: Elastomer performance limits and the design and test of an elastomer damper
Tests were performed on elastomer specimens of the material polybutadiene to determine the performance limitations imposed by strain, temperature, and frequency. Three specimens were tested: a shear specimen, a compression specimen, and a second compression specimen in which thermocouples were embedded in the elastomer buttons. Stiffness and damping were determined from all tests, and internal temperatures were recorded for the instrumented compression specimen. Measured results are presented together with comparisons between predictions of a thermo-viscoelastic analysis and the measured results. Dampers of polybutadiene and Viton were designed, built, and tested. Vibration measurements were made and sensitivity of vibration to change in unbalance was also determined. Values for log decrement were extracted from the synchronous response curves. Comparisons were made between measured sensitivity to unbalance and log decrement and predicted values for these quantities
Mechanical design handbook for elastomers
A comprehensive guide for the design of elastomer dampers for application in rotating machinery is presented. Theoretical discussions, a step by step procedure for the design of elastomer dampers, and detailed examples of actual elastomer damper applications are included. Dynamic and general physical properties of elastomers are discussed along with measurement techniques
Evolving forms of manufacturing strategy development:evidence and implications
This paper outlines, using evidence from several case studies, the use of alternative forms of manufacturing strategy processes. Our investigation shows that the manufacturing strategy development practices of manufacturers are evolving in many directions; we found several alternatives to the formal top-down planning process. Manufacturers use one or more of the following alternatives with or without the top-down manufacturing strategy process: a coherent pattern of actions; manufacturing/process improvement programs; or the pursuit of core manufacturing capabilities. It appears that the various manufacturing strategy development processes may be tied to the strategic role of manufacturing in a company. This paper offers a framework that captures the relationship between the strategic role of manufacturing and the process of manufacturing strategy development. An in-depth case from a UK company illustrates the evolving forms of manufacturing strategy development processes
Researching Bradford: A review of social research on Bradford District
A synthesis of findings from social research on the District of Bradford. This report synthesises the findings from a wide range of social research undertaken on the District of Bradford, primarily between 1995 and 2005. The researchers reviewed almost 200 pieces of work. The key results are summarised under thematic headings: - The social, economic and institutional context - Community cohesion - Housing, neighbourhoods and regeneration - Business and enterprise - Health, disability and social care - Children and young people - Education, skills and the labour market - Crime and community safety It also identifies a future research agenda. The main purpose of the review was to provide the Joseph Rowntree Foundation and local organisations in Bradford with a firm basis upon which to build future work in the District
Barriers and facilitators experienced by osteopaths in implementing a biopsychosocial (BPS) framework of care when managing people with musculoskeletal pain – a mixed methods systematic review
BACKGROUND: Clinical practice guidelines commonly recommend adopting a biopsychosocial (BPS) framework by practitioners managing musculoskeletal pain. However, it remains unclear how osteopaths implement a BPS framework in the management of musculoskeletal pain. Hence, the objective of this review was to systematically appraise the literature on the current practices, barriers and facilitators experienced by osteopaths in implementing a BPS framework of care when managing people with musculoskeletal pain. METHODS: The following electronic databases from January 2005 to August 2020 were searched: PubMed, CINAHL, Science Direct, Google Scholar, ProQuest Central and SCOPUS. Two independent reviewers reviewed the articles retrieved from the databases to assess for eligibility. Any studies (quantitative, qualitative and mixed methods) that investigated the use or application of the BPS approach in osteopathic practice were included in the review. The critical appraisal skills program (CASP) checklist was used to appraise the qualitative studies and the Mixed Methods Appraisal Tool (MMAT) was used to appraise quantitative or mixed methods studies. Advanced convergent meta-integration was used to synthesise data from quantitative, qualitative and mixed methods studies. RESULTS: A total of 6 studies (two quantitative, three qualitative and one mixed methods) were included in the final review. While two key concepts (current practice and embracing a BPS approach) were generated using advanced meta-integration synthesis, two concepts (barriers and enablers) were informed from qualitative only data. DISCUSSION: Our review finding showed that current osteopathic practice occurs within in the biomedical model of care. Although, osteopaths are aware of the theoretical underpinnings of the BPS model and identified the need to embrace it, various barriers exist that may prevent osteopaths from implementing the BPS model in clinical practice. Ongoing education and/or workshops may be necessary to enable osteopaths to implement a BPS approach
Predicting the transition from acute to persistent low back pain
Background Most people experience low back pain (LBP) at least once in their lifetime. Only a minority of them go on to develop persistent LBP. However, the socioeconomic costs of persistent LBP significantly exceed the costs of the initial acute LBP episode. Aims To identify factors that influence the progression of acute LBP to the persistent state at an early stage. Methods Prospective inception cohort study of patients attending a health practitioner for their first episode of acute LBP or recurrent LBP after a pain free period of at least 6 months. Patients were assessed at baseline addressing occupational and psychological factors as well as pain, disability, quality of life and physical activity and followed up at 3, 6, 12 weeks and 6 months. Variables were combined to the three indices ‘working condition', ‘depression and maladaptive cognitions' and ‘pain and quality of life'. Results The index ‘depression and maladaptive cognitions' was found to be a significant baseline predictor for persistent LBP up to 6 months (OR 5.1; 95% CI: 1.04-25.1). Overall predictive accuracy of the model was 81%. Conclusions In this study of patients with acute LBP in a primary care setting psychological factors at baseline correlated with a progression to persistent LBP up to 6 months. The benefit of including factors such as ‘depression and maladaptive cognition' in screening tools is that these factors can be addressed in primary and secondary preventio
Effects of targeting lower versus higher arterial oxygen saturations on death or disability in preterm infants
Gene conversion in human rearranged immunoglobulin genes
Over the past 20 years, many DNA sequences have been published suggesting that all or part of the V<sub>H</sub> segment of a rearranged immunoglobulin gene may be replaced in vivo. Two different mechanisms appear to be operating. One of these is very similar to primary V(D)J recombination, involving the RAG proteins acting upon recombination signal sequences, and this has recently been proven to occur. Other sequences, many of which show partial V<sub>H</sub> replacements with no addition of untemplated nucleotides at the V<sub>H</sub>–V<sub>H</sub> joint, have been proposed to occur by an unusual RAG-mediated recombination with the formation of hybrid (coding-to-signal) joints. These appear to occur in cells already undergoing somatic hypermutation in which, some authors are convinced, RAG genes are silenced. We recently proposed that the latter type of V<sub>H</sub> replacement might occur by homologous recombination initiated by the activity of AID (activation-induced cytidine deaminase), which is essential for somatic hypermutation and gene conversion. The latter has been observed in other species, but not in human Ig genes, so far. In this paper, we present a new analysis of sequences published as examples of the second type of rearrangement. This not only shows that AID recognition motifs occur in recombination regions but also that some sequences show replacement of central sections by a sequence from another gene, similar to gene conversion in the immunoglobulin genes of other species. These observations support the proposal that this type of rearrangement is likely to be AID-mediated rather than RAG-mediated and is consistent with gene conversion
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