Tungsten carbide is more oxidation resistant than tungsten when processed to full density

AbstractPrevious studies report that WC oxidises in air more readily than W. However, systematic thermogravimetric studies reveal considerably slower oxidation kinetics in WC samples, which outperform previous measurements by 1–2 orders of magnitude. By combining X-ray diffraction and electron microscopy, the enhanced stability in WC is explained by a dense interlayer of sub-stoichiometric WO3, approximately 10μm in thickness, which forms adjacent to the substrate/oxide interface. The faster oxidation kinetics from previous studies are explained by the comparatively low densities of samples used

Thermal shock of tungsten carbide in plasma-facing conditions

Tungsten carbide (WC) has been found to have higher resistance to plasma-induced thermal shock compared to rolled tungsten. The electron beam device JUDITH 1 was used to simulate likely thermal shock conditions induced by edge localised modes and plasma disruptions. Loading conditions of 100–1000 cycles, heat fluxes of 0.19–1.13 GW/m2 and base temperatures of 400–1000 °C were employed on two candidate WC-based materials: a monolithic WC ceramic, and a WC-FeCr composite. Surprisingly, the monolith outperformed the composite under all conditions. This was unexpected, particularly at 400 °C, based on the calculated thermal shock resistance parameters. The result was explained by preferential melting of the metallic FeCr binder. Compared to available data collected under identical conditions on rolled tungsten plate, monolithic WC had lower surface roughness from thermal shock damage, particularly when tested at 400 °C. This shows promise for its use as a plasma facing material. Strategies for further improving performance are discussed

Diversity in the organization of elastin bundles and intramembranous muscles in bat wings

Unlike birds and insects, bats fly with wings composed of thin skin that envelops the bones of the forelimb and spans the area between the limbs, digits, and sometimes the tail. This skin is complex and unusual; it is thinner than typical mammalian skin and contains organized bundles of elastin and embedded skeletal muscles. These elements are likely responsible for controlling the shape of the wing during flight and contributing to the aerodynamic capabilities of bats. We examined the arrangement of two macroscopic architectural elements in bat wings, elastin bundles and wing membrane muscles, to assess the diversity in bat wing skin morphology. We characterized the plagiopatagium and dactylopatagium of 130 species from 17 families of bats using cross‐polarized light imaging. This method revealed structures with distinctive relative birefringence, heterogeneity of birefringence, variation in size, and degree of branching. We used previously published anatomical studies and tissue histology to identify birefringent structures, and we analyzed their architecture across taxa. Elastin bundles, muscles, neurovasculature, and collagenous fibers are present in all species. Elastin bundles are oriented in a predominantly spanwise or proximodistal direction, and there are five characteristic muscle arrays that occur within the plagiopatagium, far more muscle than typically recognized. These results inform recent functional studies of wing membrane architecture, support the functional hypothesis that elastin bundles aid wing folding and unfolding, and further suggest that all bats may use these architectural elements for flight. All species also possess numerous muscles within the wing membrane, but the architecture of muscle arrays within the plagiopatagium varies among families. To facilitate present and future discussion of these muscle arrays, we refine wing membrane muscle nomenclature in a manner that reflects this morphological diversity. The architecture of the constituents of the skin of the wing likely plays a key role in shaping wings during flight

Editor\u27s Introduction to the 10th Anniversary Volume of the Journal of Southeast Asian American Education and Advancement

Editor\u27s Introduction to the 10th Anniversary Volum

Gestational diabetes in a rural setting.

Women who are already diabetic and become pregnant, as well as women who develop gestational diabetes, have increased risks of complications to both fetus and mother. These risks in gestational diabetes mellitus (GDM) can be reduced to near that of a non-diabetic mother by normalizing the blood sugar. The current recommended standards are reviewed. Utilizing a team approach, care was provided to patients with GDM in a rural primary care setting in order to attempt to normalize the blood sugar to the recommended level. Review of the outcomes of these pregnancies supports the conclusion that acceptable care for patients with GDM can be provided away from the tertiary care centers and in the primary care setting

Thermophysical properties of Co-free WC-FeCr hardmetals

Fe-Cr alloys can potentially replace carcinogenic Co as the binder system in WC-hardmetals. Furthermore, they may be used in emerging applications such as nuclear fusion reactor shielding, where use of Co is forbidden due to the formation of hazardous activated species. In such applications, a good understanding of thermophysical properties is critical to predicting high temperature performance. By combining several thermal analysis techniques (dilatometry, laser flash and calorimetry) we have determined the thermal conductivity and thermal expansivity of several grades of WC-FeCr hardmetals between room temperature and 1200 °C. In these materials the WC grain size was varied between 0.2 and 5 microns. The binder content was kept constant at 10 wt.%, and the nominal binder composition was Fe-8 wt.% Cr. The room temperature thermal conductivities of these materials varied between about 50 and 110 W/m-K, which are similar values to analogous WC-Co materials. Thermal expansion curves exhibited discontinuous shrinkage events at about 850 °C, due to an allotropic phase transition within the FeCr binder between its BCC and FCC structures. The magnitude of the shrinkage was about a third that predicted by the rule-of-mixtures, suggesting significant internal stresses could be generated during the transformation. Such internal stresses could affect the properties of WC-FeCr hardmetals when operating at high temperature

Changes in cardiovascular risk factors in relation to increasing ethnic inequalities in cardiovascular mortality:comparison of cross-sectional data in the Health Surveys for England 1999 and 2004

OBJECTIVES: Reducing disease inequalities requires risk factors to decline quickest in the most disadvantaged populations. Our objective was to assess whether this happened across the UK's ethnic groups. DESIGN: Secondary analysis of repeated but independent cross-sectional studies focusing on Health Surveys for England 1999 and 2004. SETTING: Community-based population level surveys in England. PARTICIPANTS: Seven populations from the major ethnic groups in England (2004 sample sizes): predominantly White general (6704), Irish (1153), Chinese (723), Indian (1184), Pakistani (941), Bangladeshi (899) and Black Caribbean (1067) populations. The numbers were smaller for specific variables, especially blood tests. OUTCOME MEASURES: Data on 10 established cardiovascular risk factors were extracted from published reports. Differences between 1999 and 2004 were defined a priori as occurring when the 95% CI excluded 0 (for prevalence differences), or 1 (for risk ratios) or when there was a 5% or more change (independent of CIs). RESULTS: Generally, there were reductions in smoking and blood pressure and increases in the waist–hip ratio, body mass index and diabetes. Changes between 1999 and 2004 indicated inconsistent progress and increasing inequalities. For example, total cholesterol increased in Pakistani (0.3 mmol/L) and Bangladeshi men (0.3 mmol/L), and in Pakistani (0.3 mmol/L), Bangladeshi (0.4 mmol/L) and Black Caribbean women (0.3 mmol/L). Increases in absolute risk factor levels were common, for example, in Pakistani (five risk factors), Bangladeshi (four factors) and general population women (four factors). For men, Black Caribbeans had the most (five factor) increases. The changes relative to the general population were also adverse for three risk factors in Pakistani and Black Caribbean men, four in Bangladeshi women and three in Pakistani women. CONCLUSIONS: Changes in populations with the most cardiovascular disease and diabetes did not decline the quickest. Cardiovascular screening programmes need more targeting

Abnormal WC crystal growth from liquid Co flux occurs via eta phase decomposition

The growth mechanism of large WC crystals from a liquid Co-based flux is identified. This is achieved by systematically varying the growth temperature and Co content from 1200 to 1400 °C and 70–83 at.% respectively. Crystal growth was characterised using metallography and X-ray diffraction. The WC grains were bimodally distributed, consisting of a smaller (10–20 μm) population of grains, which nucleated homogenously from the liquid, and a secondary population of abnormally large grains, several millimetres in size. The abnormal grains nucleated on the (W,Co)6C eta phase, and subsequently consumed it through a carburisation reaction. The size of abnormal grains was enhanced by adopting the eutectic composition, such that the first solid phase to form was the eta phase, whilst at the same time cooling slowly through the eta➔WC transformation temperature, at ~1300 °C. This growth mechanism could be exploited for a variety of metal carbides with similarly sluggish diffusion rates

The effect of sarcopenia on postoperative outcomes following emergency laparotomy: a systematic review and meta-analysis

Emergency laparotomy procedures have high rates of postoperative mortality and morbidity in older patient. Sarcopenia is associated with poor postoperative outcomes in elective surgeries and there is growing evidence for its use as a risk predictor in the emergency setting. The study aimed to evaluate the effect of sarcopenia on postoperative mortality and morbidity following emergency laparotomy. Five electronic databases were systematically searched (MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials, and Web of Science) from conception until the 14th February 2022. All prospective cohort studies were included. Risk of bias was assessed with the Newcastle-Ottawa score. Pooled meta-analyses were estimated using the Mantel-Haenszel and inverse-generic variance method for mortality and morbidity outcomes. Eleven retrospective cohort studies were included, of which ten were included in the meta-analysis comprising of 3492 patients (1027 sarcopenic, 2465 non-sarcopenic). The study level incidence of sarcopenia ranged from 24.6 to 50.3% with a median rate of 25.1%. Sarcopenia was associated with increased 30-day mortality (OR 2.36, 95% CI, 1.66, 3.37, I2 = 43%), 90-day mortality (OR 2.51, 95% CI, 1.79, 3.52, I2 = 0%), and length of hospital stay (in days) (MD 1.18, 95% CI, 0.42, 1.94, I2 = 0%, P=0.002), but not incidence of postoperative major complications (OR 1.49, 95% CI, 0.86, 2.56, I2 = 70%, P = 0.15). Sarcopenia predicts poor outcomes following emergency laparotomy. We suggest assessment of sarcopenia should be incorporated into acute surgical assessment to identify high risk patients and inform clinical decision-making prior to an emergency laparotomy