Modular and Reusable Miniature Subsystems for Small Satellites: An Example Describing Surrey’s Nanosatellite S-Band Downlink

For more than a decade, engineers at Surrey and elsewhere have been advocating a modular approach to satellite engineering, and demonstrating this approach with practical missions. The electro-mechanical modularity pioneered by Surrey and AMSAT on their microsatellites has been emulated by many groups building satellites in the faster, better, cheaper paradigm. Paradoxically, the technique is now being applied to both larger satellites (minisatellites) and smaller satellites (nanosatellites). Simultaneously, the underlying technology is advancing and functional density is increasing rapidly. The standard 330 x 330 x 30 mm module characteristic of Surrey’s early satellites is inappropriate both for nanosatellites and for the increasingly dense electronics now available. As part of the Surrey Nanosatellite Applications Program (SNAP), we have investigated a smaller, more modern modular unit based on the “Eurocard” standard. This paper describes the new modular approach, and some of the subsystem functions which can now be embedded in the 120 x 160 x 20 mm unit. Using modules based on the in-house SNAP standard, Surrey can now design minisatellites, microsatellites and nanosatellites sharing common subsystem designs where appropriate. This updated modular approach still confers benefits in flight heritage, technology insertion, redundancy, system design and analysis and manufacturing

Full surface examination of small spheres with a computer controlled scanning electron microscope

This report discusses a computer automated stage and Scanning Electron Microscopy (SEM) system for detecting defects in glass spheres for inertial confinement laser fusion experiments. This system detects submicron defects and permits inclusion of acceptable spheres in targets after examination. The stage used to examine and manipulate the spheres through 4..pi.. steradians is described. Primary image recording is made on a roster scanning video disc. The need for SEM stability and methods of achieving it are discussed

Validity of a pictorial perceived exertion scale for effort estimation and effort production during stepping exercise in adolescent children

This is the author's PDF version of an article published in European Physical Education Review ©2002. The definitive version is available at http://epe.sagepub.com.Recent developments in the study of paediatric effort perception have continued to emphasise the importance of child-specific rating scales. The purpose of this study was to examine the validity of an illustrated 1 – 10 perceived exertion scale; the Pictorial Children’s Effort Rating Table (PCERT). 4 class groups comprising 104 children; 27 boys and 29 girls, aged 12.1±0.3 years and 26 boys, 22 girls, aged 15.3±0.2 years were selected from two schools and participated in the initial development of the PCERT. Subsequently, 48 of these children, 12 boys and 12 girls from each age group were randomly selected to participate in the PCERT validation study. Exercise trials were divided into 2 phases and took place 7 to 10 days apart. During phase 1, children completed 5 x 3-minute incremental stepping exercise bouts interspersed with 2-minute recovery periods. Heart rate (HR) and ratings of exertion were recorded during the final 15 s of each exercise bout. In phase 2 the children were asked to regulate their exercising effort during 4 x 4-minute bouts of stepping so that it matched randomly prescribed PCERT levels (3, 5, 7 and 9). Analysis of data from Phase 1 yielded significant (P<0.01) relationships between perceived and objective (HR) effort measures for girls. In addition, the main effects of exercise intensity on perceived exertion and HR were significant (P<0.01); perceived exertion increased as exercise intensity increased and this was reflected in simultaneous significant rises in HR. During phase 2, HR and estimated power output (POapprox) produced at each of the four prescribed effort levels were significantly different (P<0.01). The children in this study were able to discriminate between 4 different exercise intensities and regulate their exercise intensity according to 4 prescribed levels of perceived exertion. In seeking to contribute towards children’s recommended physical activity levels and helping them understand how to self-regulate their activity, the application of the PCERT within the context of physical education is a desirable direction for future research

Putative ammonia-oxidizing Crenarchaeota in suboxic waters of the Black Sea : a basin-wide ecological study using 16S ribosomal and functional genes and membrane lipids

Author Posting. © Blackwell, 2007. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Environmental Microbiology 9 (2007): 1001-1016, doi:10.1111/j.1462-2920.2006.01227.x.Within the upper 400 m at western, central, and eastern stations in the world’s largest stratified basin, the Black Sea, we studied the qualitative and quantitative distribution of putative nitrifying Archaea based on their genetic markers (16S rDNA, amoA encoding for the alfa-subunit of archaeal ammonia monooxygenase), and crenarchaeol, the specific glycerol diphytanyl glycerol tetraether (GDGT) of pelagic Crenarchaeota within the Group I.1a. Marine Crenarchaeota were the most abundant Archaea (up to 98% of the total archaeal 16S rDNA copies) in the suboxic layers with oxygen levels as low as 1 μM including layers where previously anammox bacteria were described (Kuypers et al., 2003). Different marine crenarchaeotal phylotypes (both 16S rDNA and amoA) were found at the upper part of the suboxic zone as compared to the base of the suboxic zone and the upper 15-30 m of the anoxic waters with prevailing sulfide concentrations of up to 30 μM. Crenarchaeol concentrations were higher in the sulfidic chemocline as compared to the suboxic zone. These results indicate an abundance of putative nitrifying Archaea at very low oxygen levels within the Black Sea and might form an important source of nitrite for the anammox reaction.This work was supported by a grant from the Netherlands Organization for Scientific Research (VENI Innovational Research Grant nr. 813.13.001 to MJLC), an U. S. National Science Foundation grant OCE0117824 to SGW and the Spinoza award to JSSD, which we greatly acknowledge

Creating sustainable value through food waste management: does retail customer value proposition matter?

Purpose This research aims to explore retail managers' views on how food waste (FW) management activities contribute to sustainable value creation and how the customer value proposition (CVP) for a given food retailer interacts with their approaches to FW management. Design/methodology/approach A three-stage exploratory qualitative approach to data collection and analysis was adopted, involving in-depth interviews with retail managers, documentary analysis of multiple years of relevant corporate reports and email validation by seven major UK grocery retailers. Thematic content analysis supplemented by word similarity cluster analysis, two-step cluster analysis and crisp-set qualitative comparative analysis was undertaken. Findings FW management practices have been seen by retail managers to contribute to all forms of sustainable value creation, as waste reduction minimises environmental impact, saves costs and/or serves social needs, whilst economic value creation lies at the heart of retail FW management. However, retail operations are also framed by CVP and size of a retailer that enable or inhibit the adoption of certain FW management practices. Low-price retailers were more likely to adopt practices enabling them to save costs. Complicated cost-incurring solutions to FW were more likely to be adopted by retailers associated with larger size, high quality and a range of services. Originality/value This study is the first of its kind to empirically explore retail managers' perception of sustainable value creation through FW management activities and to provide empirical evidence of the linkages between retail CVP and sustainable value creation in the context of retail FW management

Interaction of anions with the surface of a coordination cage in aqueous solution probed by their effect on a cage-catalysed Kemp elimination

An octanuclear M8L12 coordination cage catalyses the Kemp elimination reaction of 5-nitro-1,2-benzisoxazole (NBI) with hydroxide to give 2-cyano-4-nitrophenolate (CNP) as the product. In contrast to the previously-reported very efficient catalysis of the Kemp elimination reaction of unsubstituted benzisoxazole, which involves the substrate binding inside the cage cavity, the catalysed reaction of NBI with hydroxide is slower and occurs at the external surface of the cage, even though NBI can bind inside the cage cavity. The rate of the catalysed reaction is sensitive to the presence of added anions, which bind to the 16+ cage surface, displacing the hydroxide ions from around the cage which are essential reaction partners in the Kemp elimination. Thus we can observe different binding affinities of anions to the surface of the cationic cage in aqueous solution by the extent to which they displace hydroxide and thereby inhibit the catalysed Kemp elimination and slow down the appearance of CNP. For anions with a −1 charge the observed affinity order for binding to the cage surface is consistent with their ease of desolvation and their ordering in the Hofmeister series. With anions that are significantly basic (fluoride, hydrogen carbonate, carboxylates) the accumulation of the anion around the cage surface accelerates the Kemp elimination compared to the background reaction with hydroxide, which we ascribe to the ability of these anions to participate directly in the Kemp elimination. This work provides valuable mechanistic insights into the role of the cage in co-locating the substrate and the anionic reaction partners in a cage-catalysed reaction

A common genetic variant of a mitochondrial RNA processing enzyme predisposes to insulin resistance

Mitochondrial energy metabolism plays an important role in the pathophysiology of insulin resistance. Recently, a missense N437S variant was identified in the MRPP3 gene, which encodes a mitochondrial RNA processing enzyme within the RNase P complex, with predicted impact on metabolism. We used CRISPR-Cas9 genome editing to introduce this variant into the mouse Mrpp3 gene and show that the variant causes insulin resistance on a high-fat diet. The variant did not influence mitochondrial gene expression markedly, but instead, it reduced mitochondrial calcium that lowered insulin release from the pancreatic islet β cells of the Mrpp3 variant mice. Reduced insulin secretion resulted in lower insulin levels that contributed to imbalanced metabolism and liver steatosis in the Mrpp3 variant mice on a high-fat diet. Our findings reveal that the MRPP3 variant may be a predisposing factor to insulin resistance and metabolic disease in the human population

Mendelian randomization evaluation of causal effects of fibrinogen on incident coronary heart disease

Background Fibrinogen is an essential hemostatic factor and cardiovascular disease risk factor. Early attempts at evaluating the causal effect of fibrinogen on coronary heart disease (CHD) and myocardial infraction (MI) using Mendelian randomization (MR) used single variant approaches, and did not take advantage of recent genome-wide association studies (GWAS) or multi-variant, pleiotropy robust MR methodologies. Methods and findings We evaluated evidence for a causal effect of fibrinogen on both CHD and MI using MR. We used both an allele score approach and pleiotropy robust MR models. The allele score was composed of 38 fibrinogen-associated variants from recent GWAS. Initial analyses using the allele score used a meta-analysis of 11 European-ancestry prospective cohorts, free of CHD and MI at baseline, to examine incidence CHD and MI. We also applied 2 sample MR methods with data from a prevalent CHD and MI GWAS. Results are given in terms of the hazard ratio (HR) or odds ratio (OR), depending on the study design, and associated 95% confidence interval (CI). In single variant analyses no causal effect of fibrinogen on CHD or MI was observed. In multi-variant analyses using incidence CHD cases and the allele score approach, the estimated causal effect (HR) of a 1 g/L higher fibrinogen concentration was 1.62 (CI = 1.12, 2.36) when using incident cases and the allele score approach. In 2 sample MR analyses that accounted for pleiotropy, the causal estimate (OR) was reduced to 1.18 (CI = 0.98, 1.42) and 1.09 (CI = 0.89, 1.33) in the 2 most precise (smallest CI) models, out of 4 models evaluated. In the 2 sample MR analyses for MI, there was only very weak evidence of a causal effect in only 1 out of 4 models. Conclusions A small causal effect of fibrinogen on CHD is observed using multi-variant MR approaches which account for pleiotropy, but not single variant MR approaches. Taken together, results indicate that even with large sample sizes and multi-variant approaches MR analyses still cannot exclude the null when estimating the causal effect of fibrinogen on CHD, but that any potential causal effect is likely to be much smaller than observed in epidemiological studies

Spinflation from Geometric Tachyon

We study the assisted inflation scenario from the rolling of $N$ BPS D3-brane into the NS5-branes, on a transverse geometry of $R^3 \times S^1$, coupled to four dimensional gravity. We assume that the branes are distributed along $S^1$ and the probe D3-branes spin along $R^3$ plane. Qualitatively this process is similar to that of N-tachyon assisted inflation on unstable D-branes. We further study the spinflation scenario numerically and analyze its effect.Comment: 18pages, 9 figures, added clarifications, to appear in JHE

Magnetic resonance for assessment of axillary lymph node status in early breast cancer: A systematic review and meta-analysis

Introduction Current methods of identifying axillary node metastases in breast cancer patients are highly accurate, but are associated with several adverse events. This review evaluates the diagnostic accuracy of magnetic resonance imaging (MRI) techniques for identification of axillary metastases in early stage newly diagnosed breast cancer patients. Methods Comprehensive searches were conducted in April 2009. Study quality was assessed. Sensitivity and specificity were meta-analysed using a bivariate random effects approach, utilising pathological diagnosis via node biopsy as the comparative gold standard. Results Based on the highest sensitivity and specificity reported in each of the nine studies evaluating MRI (n = 307 patients), mean sensitivity was 90% (95% CI: 78–96%; range 65–100%) and mean specificity 90% (95% CI: 75–96%; range 54–100%). Across five studies evaluating ultrasmall super-paramagnetic iron oxide (USPIO)-enhanced MRI (n = 93), mean sensitivity was 98% (95% CI: 61–100%) and mean specificity 96% (95% CI: 72–100%). Across three studies of gadolinium-enhanced MRI (n = 187), mean sensitivity was 88% (95% CI: 78–94%) and mean specificity 73% (95% CI: 63–81%). In the single study of in-vivo proton MR spectroscopy (n = 27), sensitivity was 65% (95% CI: 38–86%) and specificity 100% (95% CI: 69–100%). Conclusions USPIO-enhanced MRI showed a trend towards higher sensitivity and specificity and may make a useful addition to the current diagnostic pathway. Additional larger studies with standardised methods and standardised criteria for classifying a node as positive are needed. Current estimates of sensitivity and specificity do not support replacement of SLNB with any current MRI technology in this patient group