Abstract
Laminated composites have so far received little attention as a potential material for gear drive applications. In the presented study, the thermomechanical performance of a newly developed ...type of epoxy impregnated, autoclave-cured carbon fibre-reinforced polymer gear—running in pair with a steel pinion—was analysed, using a combination of experimental and numerical approaches. The employed methods enabled the identification of the composite’s mechanical, thermal, and tribological characteristics, as related to the studied gear pair application. A newly proposed, finite-element-analysis-based iterative procedure enabled an implicit evaluation of the analysed material pair’s coefficient of friction (COF), which is a key parameter in determining the gear pair’s thermomechanical characteristics. For the considered material pair, a value of 0.34 was identified for the coefficient in the quasi-steady region. As the coefficient is strongly correlated with frictional heat generation and significantly affects the surface shear stress, it can consequently have a meaningful influence on the composite’s wear rate. The developed COF identification procedure was validated using a reciprocating cylinder-on-flat tribological test method. The composite gear’s service life was additionally tested at various running loads, resulting in pitch contact pressures ranging between 400 and 540 MPa. Lifetime gear test results showed a markedly superior performance compared to the high-temperature thermoplastic polyether ether ketone, which is typically employed in the most demanding polymer gear applications. Several methods are additionally proposed that could further improve the developed composite gears’ performance.
Graphical Abstract
Graphical Abstract
Summary Background It is well known that citizens of developed countries are more likely to be overweight than they were 20 years ago. The most serious health problems are not associated with ...overweight or moderate obesity, however, but with clinically severe or morbid obesity (e.g. more than 100 pounds (45 kg) overweight). There is no reason to expect that morbid obesity trends parallel overweight or moderate obesity. If morbid obesity is a rare pathological condition that has biological causes, the more than 10-fold increase in bariatric surgery procedures over the past eight years in the USA could have even lowered the prevalence of morbid obesity—and may very well stem the problem in other countries. Objective To estimate trends for extreme weight categories (BMI>40 and >50) for the period between 1986 and 2005 in the USA, and to investigate whether trends have changed since 2000. Methods Data from The Behavioral Risk Factor Surveillance System (a random-digit telephone survey of the household population of the USA), for the period from 1986 to 2005, were analysed. The main outcome measure was body mass index (BMI), calculated from self-reported weight and height. Results From 2000 to 2005, the prevalence of obesity (self-reported BMI over 30) increased by 24%. However, the prevalence of a (self-reported) BMI over 40 (about 100 pounds (45 kg) overweight) increased by 50% and the prevalence of a BMI over 50 increased by 75%, two and three times faster, respectively. The heaviest BMI groups have been increasing at the fastest rates for 20 years. Conclusions The prevalence of clinically severe obesity is increasing at a much faster rate among adults in the USA than is the prevalence of moderate obesity. This is consistent with the public health idea that the population weight distribution is shifting, which disproportionately increases extreme weight categories. Because comorbidities and resulting service use are much higher among severely obese individuals, the widely published trends for overweight/obesity underestimate the consequences for population health. The aggressive and costly expansion of bariatric surgery in recent years has had no visible effect on containing morbid obesity rates in the USA.
Clinically severe or morbid obesity (body mass index (BMI) >40 or 50 kg m(-2)) entails far more serious health consequences than moderate obesity for patients, and creates additional challenges for ...providers. The paper provides time trends for extreme weight categories (BMI >40 and >50 kg m(-2)) until 2010, using data from the Behavioral Risk Factor Surveillance System. Between 2000 and 2010, the prevalence of a BMI >40 kg m(-2) (type III obesity), calculated from self-reported height and weight, increased by 70%, whereas the prevalence of BMI >50 kg m(-2) increased even faster. Although the BMI rates at every point in time are higher among Hispanics and Blacks, there were no significant differences in trends between them and non-Hispanic Whites. The growth rate appears to have slowed down since 2005. Adjusting for self-report biases, we estimate that in 2010 15.5 million adult Americans or 6.6% of the population had an actual BMI >40 kg m(-2). The prevalence of clinically severe obesity continues to be increasing, although less rapidly in more recent years than prior to 2005.
Aims. The last comprehensive catalogue of high-mass X-ray binaries in the Small Magellanic Cloud (SMC) was published about ten years ago. Since then new such systems were discovered, mainly by X-ray ...observations with Chandra and XMM-Newton. For the majority of the proposed HMXBs in the SMC no X-ray pulsations were discovered as yet, and unless other properties of the X-ray source and/or the optical counterpart confirm their HMXB nature, they remain only candidate HMXBs. Methods. From a literature search we collected a catalogue of 148 confirmed and candidate HMXBs in the SMC and investigated their properties to shed light on their real nature. Based on the sample of well-established HMXBs (the pulsars), we investigated which observed properties are most appropriate for a reliable classification. We defined different levels of confidence for a genuine HMXB based on spectral and temporal characteristics of the X-ray sources and colour-magnitude diagrams from the optical to the infrared of their likely counterparts. We also took the uncertainty in the X-ray position into account. Results. We identify 27 objects that probably are misidentified because they lack an infrared excess of the proposed counterpart. They were mainly X-ray sources with a large positional uncertainty. This is supported by additional information obtained from more recent observations. Our catalogue comprises 121 relatively high-confidence HMXBs (the vast majority with Be companion stars). About half of the objects show X-ray pulsations, while for the rest no pulsations are known as yet. A comparison of the two subsamples suggests that long pulse periods in excess of a few 100 s are expected for the “non-pulsars”, which are most likely undetected because of aperiodic variability on similar timescales and insufficiently long X-ray observations. The highest X-ray variability together with the lowest observed minimum fluxes for short-period pulsars indicate that in addition to the eccentricity of the orbit, its inclination against the plane of the Be star circum-stellar disc plays a major role in determining the outburst behaviour. Conclusions. The large population of HMXBs in the SMC, in particular Be X-ray binaries, provides the largest homogeneous sample of such systems for statistical population studies.
Objective: To examine the link between childhood overweight status and elementary school outcomes. Design: Prospective study design: multivariate regression models examining the association between ...changes in overweight status and school outcomes between kindergarten entry and end of third grade, after controlling for various child, family and school characteristics. Subjects: Nationally representative sample of US children who entered kindergarten in 1998, with longitudinal data on body mass index (BMI) and school outcomes at kindergarten entry and end of third grade. Measurements: Wide range of elementary school outcomes collected in each wave including academic achievement (math and reading standardized test scores); teacher reported internalizing and externalizing behavior problems (BP), social skills (self-control, interpersonal skills) and approaches to learning; school absences; and grade repetition. Measurements of height and weight in each wave were used to compute BMI and indicators of overweight status based on CDC growth charts. A rich set of control variables capturing child, family, and school characteristics. Results: Moving from not-overweight to overweight between kindergarten entry and end of third grade was significantly associated (P<0.05) with reductions in test scores, and teacher ratings of social-behavioral outcomes and approaches to learning among girls. However, this link was mostly absent among boys, with two exceptions- boys who became overweight had significantly fewer externalizing BPs (P<0.05), but more absences from school compared to boys who remained normal weight. Being always-overweight was associated with more internalizing BP among girls but fewer externalizing BPs among boys. Conclusion: Change in overweight status during the first 4 years in school is a significant risk factor for adverse school outcomes among girls but not boys. Girls who become overweight during the early school years and those who start school being overweight and remain that way may need to be monitored carefully.
The behavior of bioaerosol particles with various size and shape in the human respiratory tract was simulated by using a probabilistic model of the lung and an almost realistic mathematical approach ...to particle deposition. Results obtained from the theoretical computations clearly show that biogenic particle deposition in different lung compartments does not only depend on physical particle properties, but also on breathing mode (nose or mouth breathing) and inhalative flow rate (=tidal volume×breathing frequency/30). Whilst ultrafine (<100nm) and large (>5μm) particles tend to accumulate in the extrathoracic region and the uppermost airways of the tracheobronchial tree, particles with intermediate size are characterized by higher penetration depth, leading to their possible accumulation in the lung alveoli. Due to their deposition in deep lung regions and insufficient clearance, some bioaerosol particles may induce severe lung diseases ranging from infections, allergies, and toxic reactions to cancer.
In an effort to unify the nomenclature of Trypanosoma cruzi, the causative agent of Chagas disease, an updated system was agreed upon at the Second Satellite Meeting. A consensus was reached that T. ...cruzi strains should be referred to by six discrete typing units (T. cruzi I-VI). The goal of a unified nomenclature is to improve communication within the scientific community involved in T. cruzi research. The justification and implications will be presented in a subsequent detailed report.
► We review the population structure of Trypanosoma cruzi, causative agent of Chagas disease. ► We provide information on the eco-epidemiology of T. cruzi discrete typing units (DTUs). ► We outline ...the correlation of DTU with clinical manifestations. ► We summarize methods for DTU genotyping. ► Understanding of T. cruzi genetic diversity will provide new insights to future interventions.
The protozoan Trypanosoma cruzi, its mammalian reservoirs, and vectors have existed in nature for millions of years. The human infection, named Chagas disease, is a major public health problem for Latin America. T. cruzi is genetically highly diverse and the understanding of the population structure of this parasite is critical because of the links to transmission cycles and disease. At present, T. cruzi is partitioned into six discrete typing units (DTUs), TcI–TcVI. Here we focus on the current status of taxonomy-related areas such as population structure, phylogeographical and eco-epidemiological features, and the correlation of DTU with natural and experimental infection. We also summarize methods for DTU genotyping, available for widespread use in endemic areas. For the immediate future multilocus sequence typing is likely to be the gold standard for population studies. We conclude that greater advances in our knowledge on pathogenic and epidemiological features of these parasites are expected in the coming decade through the comparative analysis of the genomes from isolates of various DTUs.
The aim of this study was to examine the association between food prices and food outlet density and changes in the body mass index (BMI) among elementary school children in the USA.
The Early ...Childhood Longitudinal Study followed a nationally representative sample of kindergarten children over 4 years. We merged individual-level data to (a) metropolitan data on food prices and (b) per capita number of restaurants, grocery stores and convenience stores in the child's home and school zip code. The dependent variables were BMI changes over 1 and 3 years. We analysed mean changes with least-squares regression, and median changes and 85th percentile changes with quantile regression. We controlled for baseline BMI, age, real family income and sociodemographic characteristics.
Lower real prices for vegetables and fruits were found to predict a significantly lower gain in BMI between kindergarten and third grade; half of that effect was found between kindergarten and first grade. Lower meat prices had the opposite effect, although this effect was generally smaller in magnitude and was insignificant for BMI gain over 3 years. Differences across subgroups were not statistically significant due to smaller sample sizes in subgroup analyses, but the estimated effects were meaningfully larger for children in poverty, children already at risk for overweight or overweight in kindergarten, and Asian and Hispanic children. There were no significant effects for dairy or fast-food prices, nor for outlet density, once we had controlled for individual characteristics and random intercepts to adjust standard errors for the sampling design.
The geographic variation in fruit and vegetable prices is large enough to explain a meaningful amount of the differential gain in BMI among elementary school children across metropolitan areas. However, as consumption information was not available, we cannot confirm that this is the actual pathway. We found no effects of food outlet density at the neighbourhood level, possibly because availability is not an issue in metropolitan areas.
The deepest XMM–Newton mosaic map of the central 1
$_{.}^{\circ}$
5 of the Galaxy is presented, including a total of about 1.5 Ms of EPIC-pn cleaned exposures in the central 15 arcsec and about 200 ...ks outside. This compendium presents broad-band X-ray continuum maps, soft X-ray intensity maps, a decomposition into spectral components and a comparison of the X-ray maps with emission at other wavelengths. Newly discovered extended features, such as supernova remnants (SNRs), superbubbles and X-ray filaments are reported. We provide an atlas of extended features within ±1° of Sgr A⋆. We discover the presence of a coherent X-ray-emitting region peaking around G0.1−0.1 and surrounded by the ring of cold, mid-IR-emitting material known from previous work as the ‘Radio Arc Bubble’ and with the addition of the X-ray data now appears to be a candidate superbubble. Sgr A's bipolar lobes show sharp edges, suggesting that they could be the remnant, collimated by the circumnuclear disc, of an SN explosion that created the recently discovered magnetar, SGR J1745−2900. Soft X-ray features, most probably from SNRs, are observed to fill holes in the dust distribution, and to indicate a direct interaction between SN explosions and Galactic centre (GC) molecular clouds. We also discover warm plasma at high Galactic latitude, showing a sharp edge to its distribution that correlates with the location of known radio/mid-IR features such as the ‘GC Lobe’. These features might be associated with an inhomogeneous hot ‘atmosphere’ over the GC, perhaps fed by continuous or episodic outflows of mass and energy from the GC region.
PDF
