4,979 research outputs found

    LANDSAT/MMS propulsion module design. Volume 1: Task 4.3, trade studies

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    Evaluations are presented of alternative LANDSAT follow-on launch configurations to derive the propulsion requirements for the multimission modular spacecraft (MMS). Two basic types were analyzed including use of conventional launch vehicles and shuttle-supported missions. It was concluded that two sizes of modular hydrazine propulsion modules would provide the most cost-effective combination for future missions of this spacecraft. Conceptual designs of the selected propulsion modules were performed to the depth permitting determination of mass properties and estimated costs

    Measurement of focusing properties for high numerical aperture optics using an automated submicron beamprofiler

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    The focusing properties of three aspheric lenses with numerical aperture (NA) between 0.53 and 0.68 were directly measured using an interferometrically referenced scanning knife-edge beam profiler with sub-micron resolution. The results obtained for two of the three lenses tested were in agreement with paraxial gaussian beam theory. It was also found that the highest NA aspheric lens which was designed for 830nm was not diffraction limited at 633nm. This process was automated using motorized translation stages and provides a direct method for testing the design specifications of high numerical aperture optics.Comment: 6 pages 4 figure

    A simplicial gauge theory

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    We provide an action for gauge theories discretized on simplicial meshes, inspired by finite element methods. The action is discretely gauge invariant and we give a proof of consistency. A discrete Noether's theorem that can be applied to our setting, is also proved.Comment: 24 pages. v2: New version includes a longer introduction and a discrete Noether's theorem. v3: Section 4 on Noether's theorem has been expanded with Proposition 8, section 2 has been expanded with a paragraph on standard LGT. v4: Thorough revision with new introduction and more background materia

    Nitric oxide, a survival factor for lens epithelial cells

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    Purpose: Nitric oxide (NO) is capable of promoting either cell death or cell survival depending on cell type and experimental conditions. In this study, the possible effects of NO on the viability of lens epithelial cells were investigated in an explant model used previously to identify cellular changes associated with posterior capsule opacification following cataract surgery. Methods: Rat lens epithelial explants prepared from weanling rats were cultured in a serum-free medium for five days with or without the addition of the nitric oxide synthase inhibitor, L-Nω-nitro-L-arginine methyl ester (L-NAME), using the inactive enantiomer D-NAME as a control. Alternatively, explants were cultured for nine days with or without the NO donor, sodium nitroprusside. Explants were assessed morphologically and immunohistochemically or by determining DNA content. Results: In the presence of L-NAME but not in controls, progressive rounding up and detachment of cells from the lens capsule occurred, leading to extensive cell loss. Affected cells showed apoptosis-like cell-surface blebbing and nuclear fragmentation. Conversely, inclusion of sodium nitroprusside suppressed the morphological changes and spontaneous cell loss that occurred when sparsely covered explants were cultured for nine days, increased cell coverage fourfold during that period, and prevented the expression of the transdifferentiation markers α-smooth muscle actin and fibronectin. In addition, whereas L-NAME exacerbated cell loss induced by culturing with 50 pg/ml transforming growth factor-β2, sodium nitroprusside offered protection. Conclusions: This study points to a previously unidentified role for NO as an endogenously produced survival factor for lens epithelial cells, raising the possibility of using NO deprivation as a means of removing residual lens cells following cataract surgery and thereby preventing posterior capsule opacification

    Is there an association between metabolic syndrome and rotator cuff related shoulder pain? A systematic review

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    Objectives Rotator cuff related shoulder pain (RCRSP) is a common upper limb complaint. It has been suggested that this condition is more common among people with cardiometabolic risk factors. This systematic review has synthesised evidence from case-control, cross-sectional and cohort studies on the association between metabolic syndrome (MetS) and RCRSP. Design and Data Sources Five medical databases (MEDLINE, EMBASE, SCOPUS, CINAHL and AMED) and reference checking methods were used to identify all relevant English articles that considered MetS and RCRSP. Studies were appraised using the Newcastle Ottawa Scale (NOS). Two reviewers performed critical appraisal and data extraction. Narrative synthesis was performed via content analysis of statistically significant associations . Results Three cross-sectional, two case-control and one cohort study met the inclusion criteria, providing a total of 1,187 individuals with RCRSP. Heterogeneity in methodology and RCRSP or MetS definition precluded a meaningful meta-analysis. Four of the included studies identified associations between the prevalence of MetS and RCRSP. Studies consistently identified independent cardiometabolic risk factors associated with RCRSP. All studies were level III evidence. Summary and Conclusion The low-moderate quality evidence included in this review suggests an association between MetS and RCRSP. Most studies demonstrated moderate quality on appraisal. The direction of association and cardiometabolic factors influencing should be investigated by longitudinal and treatment studies. These preliminary conclusions and clinical utility should be treated with caution due to limitations of the evidence bas

    Quantitative molecular assessment of chimerism across tissues in marmosets and tamarins

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    <p>Abstract</p> <p>Background</p> <p>Marmosets are playing an increasingly large and important role in biomedical research. They share genetic, anatomical, and physiological similarities with humans and other primate model species, but their smaller sizes, reproductive efficiency, and amenability to genetic manipulation offer an added practicality. While their unique biology can be exploited to provide insights into disease and function, it is also important that researchers are aware of the differences that exist between marmosets and other species. The New World monkey family Callitrichidae, containing both marmoset and tamarin species, typically produces dizygotic twins that show chimerism in the blood and other cells from the hematopoietic lineage. Recently, a study extended these findings to identify chimerism in many tissues, including somatic tissues from other lineages and germ cells. This has raised the intriguing possibility that chimerism may play an increasingly pervasive role in marmoset biology, ranging from natural behavioral implications to increased variability and complexity in biomedical studies.</p> <p>Results</p> <p>Using a quantitative PCR based methodology, Y-chromosomes can be reliably detected in the females with male fraternal twins allowing for a relative quantification of chimerism levels between individuals and tissues. With this approach in common marmosets (<it>Callithrix jacchus</it>) and cotton-top tamarins (<it>Saguinus oedipus</it>), chimerism was detected across a broad array of tissues. Chimerism levels were significantly higher in tissues primarily derived from the hematopoietic lineage, while they were lower, though still detectable, in tissues with other origins. Interestingly, animals with a characteristic marmoset wasting disease show higher levels of chimerism in those tissues affected. Fibroblast cell lines from chimeric individuals, however, are not found to be chimeric themselves.</p> <p>Conclusion</p> <p>Taken together, the levels of chimerism in tissues of different origins coupled with other lines of evidence suggest that indeed only hematopoietic cell lineages are chimeric in callitrichids. The chimerism detected in other tissues is likely the result of blood or lymphocytic infiltration. Using molecular methods to detect chimerism in a tissue sample seems to have allowed a substantial increase in the ability to detect these minor cell populations.</p

    Light-Cone Quantization of the Liouville Model

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    We present the quantization of the Liouville model defined in light-cone coordinates in (1,1) signature space. We take advantage of the representation of the Liouville field by the free field of the Backl\"{u}nd transformation and adapt the approch by Braaten, Curtright and Thorn. Quantum operators of the Liouville field +ϕ\partial_{+}\phi, ϕ\partial_{-}\phi, egϕe^{g\phi}, e2gϕe^{2g\phi} are constructed consistently in terms of the free field. The Liouville model field theory space is found to be restricted to the sector with field momentum P+=PP_{+}=-P_{-}, P+>0P_{+}> 0 , which is a closed subspace for the Liouville theory operator algebra.Comment: 16 p, EFI-92-6

    Applying psychological type theory to cathedral visitors : a case study of two cathedrals in England and Wales

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    This study employs Jungian psychological type theory to profile visitors to Chester Cathedral in England and St Davids Cathedral in Wales. Psychological type theory offers a fourfold psychographic segmentation of visitors, distinguishing between introversion and extraversion, sensing and intuition, thinking and feeling, and judging and perceiving. New data provided by 157 visitors to Chester Cathedral (considered alongside previously published data provided by 381 visitors to St Davids Cathedral) demonstrated that these two cathedrals attract more introverts than extraverts, more sensers than intuitives, and more judgers than perceivers, but equal proportions of thinkers and feelers. Comparison with the population norms demonstrated that extraverts and perceivers are significantly under-represented among visitors to these two cathedrals. The implications of these findings are discussed both for maximising the visitor experiences of those already attracted to these cathedrals and for discovering ways of attracting more extraverts and more perceivers to explore these cathedrals

    Does physical activity change following hip and knee replacement? Matched case-control study evaluating Physical Activity Scale for the Elderly data from the Osteoarthritis Initiative

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    Objectives: To determine whether physical activity measured using the Physical Activity Scale for the Elderly (PASE), changes during the initial 24 months post-total hip (THR) or knee replacement (TKR), and how this compares to a matched non-arthroplasty cohort. Design: Case-controlled study analysis of a prospectively collected dataset. Setting: USA community-based. Participants: 116 people post-THR, 105 people post-TKR compared to 663 people who had not undergone THR or TKR, or had hip or knee osteoarthritis. Cohorts were age-, gender- and BMI-matched. Main outcome measures: Physical activity assessed using the 12-item PASE at 12 and 24 months post-operatively. Results: There was no significant difference in total PASE score between pre-operative to 12 months (mean: 136 vs. 135 points; p=0.86) or 24 months following THR (mean: 136 vs 132 points; p=0.95). Whilst there was no significant difference in total PASE score from pre-operative to 12 months post-TKR (126 vs. 121 points; p=0.93), by 24 months people following TKR reported significantly greater physical activity (126 vs. 142 points; p=0.04). There was no statistically significant difference in physical activity between the normative matched and THR (p≥0.14) or TKR (p≥0.06) cohorts at 12 or 24 months post-joint replacement. Conclusions: Physical activity is not appreciably different to pre-operative levels at 12 or 24 months post-THR, but was greater at 24 months following TKR. Health promotion strategies are needed to encourage greater physical activity participation following joint replacement, and particularly targeting those who undergo THR
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