Deep Reactive Ion Etching (DRIE) of High Aspect Ratio SiC Microstructures using a Time-Multiplexed Etch-Passivate Process

High aspect ratio silicon carbide (SiC) microstructures are needed for microengines and other harsh environment micro-electro-mechanical systems (MEMS). Previously, deep reactive ion etching (DRIE) of low aspect ratio (AR less than or = 1) deep (greater than 100 micron) trenches in SiC has been reported. However, existing DRIE processes for SiC are not well-suited for definition of high aspect ratio features because such simple etch-only processes provide insufficient control over sidewall roughness and slope. Therefore, we have investigated the use of a time-multiplexed etch-passivate (TMEP) process, which alternates etching with polymer passivation of the etch sidewalls. An optimized TMEP process was used to etch high aspect ratio (AR greater than 5) deep (less than 100 micron) trenches in 6H-SiC. Power MEMS structures (micro turbine blades) in 6H-SiC were also fabricated

Development of an Extreme High Temperature n-type Ohmic Contact to Silicon Carbide

We report on the initial demonstration of a tungsten-nickel (75:25 at. %) ohmic contact to silicon carbide (SiC) that performed for up to fifteen hours of heat treatment in argon at 1000 C. The transfer length method (TLM) test structure was used to evaluate the contacts. Samples showed consistent ohmic behavior with specific contact resistance values averaging 5 x 10-4 -cm2. The development of this contact metallization should allow silicon carbide devices to operate more reliably at the present maximum operating temperature of 600 C while potentially extending operations to 1000 C. Introduction Silicon Carbide (SiC) is widely recognized as one of the materials of choice for high temperature, harsh environment sensors and electronics due to its ability to survive and continue normal operation in such environments [1]. Sensors and electronics in SiC have been developed that are capable of operating at temperatures of 600 oC. However operating these devices at the upper reliability temperature threshold increases the potential for early degradation. Therefore, it is important to raise the reliability temperature ceiling higher, which would assure increased device reliability when operated at nominal temperature. There are also instances that require devices to operate and survive for prolonged periods of time above 600 oC [2, 3]. This is specifically needed in the area of hypersonic flight where robust sensors are needed to monitor vehicle performance at temperature greater than 1000 C, as well as for use in the thermomechanical characterization of high temperature materials (e.g. ceramic matrix composites). While SiC alone can withstand these temperatures, a major challenge is to develop reliable electrical contacts to the device itself in order to facilitate signal extractio

A Sr-Rich Star on the Main Sequence of Omega Centauri

Abundance ratios relative to iron for carbon, nitrogen, strontium and barium are presented for a metal-rich main sequence star ([Fe/H]=--0.74) in the globular cluster omega Centauri. This star, designated 2015448, shows depleted carbon and solar nitrogen, but more interestingly, shows an enhanced abundance ratio of strontium [Sr/Fe] ~ 1.6 dex, while the barium abundance ratio is [Ba/Fe]<0.6 dex. At this metallicity one usually sees strontium and barium abundance ratios that are roughly equal. Possible formation scenarios of this peculiar object are considered.Comment: 13 pages, 3 figures. Accepted to ApJ

Economic evaluation of short treatment for multidrugresistant tuberculosis, Ethiopia and South Africa : the STREAM trial

OBJECTIVE STREAM was a phase-III non-inferiority randomised controlled trial (RCT) to evaluate a shortened regimen for multi-drug resistant tuberculosis (MDR-TB), and included the first-ever within-trial economic evaluation of such regimens, reported here. METHODS We compared the costs of ‘Long’ (20-22 months) and ‘Short’ (9-11 months) regimens in Ethiopia and South Africa. Cost data were collected from trial participants, and health system costs estimated using ‘bottom-up’ and ‘top-down’ costing approaches. A cost-effectiveness analysis was conducted with the trial primary outcome as the measure of effectiveness, including a probabilistic sensitivity analysis (PSA) to illustrate decision uncertainty. FINDINGS The Short-regimen reduced healthcare costs per case by 21% in South Africa (US$8,341 Long vs US$6,619 Short) and 25% in Ethiopia (US$6,097 Long vs US$4,552 Short). The largest component of this saving was medication in South Africa (67%) and social support in Ethiopia (35%). In Ethiopia, participants on the Short-regimen reported reductions in dietary supplementation expenditure (US$225 per case (95$13 (95%CI 11-14), South Africa US$64 (95$19,000 (Ethiopia) or <US$14,500 (South Africa). CONCLUSION The Short-regimen provided substantial health system cost savings and reduced financial burden on participants. Shorter regimens are likely to be cost-effective in most settings, and an effective strategy to support the WHO goal of eliminating catastrophic costs in T

Avifauna and urban encroachment in time and space

AIM: Urban expansion significantly alters fringe environments often with unde-sirable impacts on biodiversity. Consequently, there is a need to define clearconservation objectives for areas subject to urban encroachment. Urban fringe development is a highly dynamic process, both spatially and temporally, but few studies are equipped to examine its temporal effects on biota. We aimed to explore the impacts of urban encroachment on avifauna through space and time.LOCATION: The Australian Capital Territory, Australia. METHODS: We used records from an extensive 14-year monitoring programme undertaken in temperate woodland. We fitted hierarchical generalized linear models to assess individual species responses to the distance from monitoring sites to the urban boundary, and the temporal rate of change in this distance through time. We used factorial analysis on mixed data to examine trait group responses to these predictors.RESULTS: Our results indicated that the occurrence of approximately half of the study region’s avifauna is strongly linked to the proximity of their habitat to the urban fringe, but that the impact of urban fringe development on the occurrence of some species changed through time. We identified several species of conservation concern that respond negatively to large annual increases in urban fringe development, irrespective of its proximity to suitable habitat. Species responses to urban proximity were linked to life history traits, with small,migratory, woodland-dependent species that rely on mid- and upper-canopy structures, clearly disadvantaged by urban environments.MAIN CONCLUSIONS: Our findings demonstrate the breadth of species responses to urban encroachment over much larger distances than is typically investigated in urban ecological studies. We identify guilds vulnerable to the impacts of urban fringe development and therefore in need of ecologically sensitive urban design. We argue that future urban expansion towards important fringe habitats will need to be planned strategically through space and time.This research received funding support from Conservation Planning and Research, Environment and Sustainable Devel-opment Directorate ACT Government and the Fenner Schoolof Environment and Society. DBL, PG and KI were sup-ported by the National Environmental Research Program. ADM was supported by an ARC Future Fellowship (FT100100358)

Bite force and cranial bone strain in four species of lizards

In vivo bone strain data provide direct evidence of strain patterns in the cranium during biting. Compared to mammals, in vivo bone strains in lizard skulls are poorly documented. This paper presents strain data from the skulls of Anolis equestris, Gekko gecko, Iguana iguana and Salvator merianae during transducer biting. Analysis of variance was used to investigate effects of bite force, bite point, diet, cranial morphology and cranial kinesis on strain magnitudes. Within individuals the most consistent determinants of variance in bone strain magnitudes are gage location and bite point, with the importance of bite force varying between individuals. Inter-site variance in strain magnitudes—strain gradient—is present in all individuals, and varies with bite point. Between individuals within species, variance in strain magnitude is driven primarily by variation in bite force, not gage location or bite point, suggesting that inter-individual variation in patterns of strain magnitude is minimal. Between species, variation in strain magnitudes is significantly impacted by bite force and species membership, as well as by interactions between gage location, species, and bite point. Independent of bite force, species differences in cranial strain magnitudes may reflect selection for different cranial morphology in relation to feeding function, but what these performance criteria are is not clear. The relatively low strain magnitudes in Iguana and Uromastyx compared to other lizards may be related to their herbivorous diet. Cranial kinesis and the presence or absence of postorbital and supratemporal bars are not important determinants of inter-specific variation in strain magnitudes

Integration of Nanostructures into Microsensor Devices on Whole Wafers

Chemical sensors are used in a wide variety of applications, such as environmental monitoring, fire detection, emission monitoring, and health monitoring. The fabrication of chemical sensors involving nanostructured materials holds the potential for the development of sensor systems with unique properties and improved performance. However, the fabrication and processing of nanostructures for sensor applications currently are limited in the ability to control their location on the sensor, which in turn hinders the progress for batch fabrication. This report discusses the advantages of using nanomaterials in sensor designs, some of the challenges encountered with the integration of nanostructures into microsensor / devices, and then briefly describes different methods attempted by other groups to address this issue. Finally, this report will describe how our approach for the controlled alignment of nanostructures onto a sensor platform was applied to demonstrate an approach for the mass production of sensors with nanostructures

The King–Devick test for sideline concussion screening in collegiate football

AbstractPurposeSports-related concussion has received increasing attention as a result of neurologic sequelae seen among athletes, highlighting the need for a validated, rapid screening tool. The King–Devick (K–D) test requires vision, eye movements, language function and attention in order to perform and has been proposed as a promising tool for assessment of concussion. We investigated the K–D test as a sideline screening tool in a collegiate cohort to determine the effect of concussion.MethodsAthletes (n=127, mean age 19.6±1.2 years) from the Wheaton College football and men's and women's basketball teams underwent baseline K–D testing at pre-season physicals for the 2012–2013 season. K–D testing was administered immediately on the sidelines for football players with suspected head injury during regular games and changes compared to baseline were determined. Post-season testing was also performed to compare non-concussed athletes’ test performance.ResultsConcussed athletes (n=11) displayed sideline K–D scores that were significantly higher (worse) than baseline (36.5±5.6s vs. 31.3±4.5s, p<0.005, Wilcoxon signed-rank test). Post-season testing demonstrated improvement of scores and was consistent with known learning effects (35.1±5.2s vs. 34.4±5.0s, p<0.05, Wilcoxon signed-rank test). Test-retest reliability was analyzed between baseline and post-season administrations of the K–D test resulting in high levels of test-retest reliability (intraclass correlation coefficient (ICC)=0.95 [95% Confidence Interval 0.85–1.05]).ConclusionsThe data show worsening of K–D test scores following concussion further supporting utility of the K–D test as an objective, reliable and effective sideline visual screening tool to help identify athletes with concussion

Comparison of a web-based 24-h dietary recall tool (Foodbook24) to an interviewer-led 24-h dietary recall

Web-based tools have the potential to reduce the cost of dietary assessment; however, it is necessary to establish their performance compared to traditional dietary assessment methods. This study aims to compare nutrient and food intakes derived from Foodbook24 to those obtained from an interview-led 24-h dietary recall (24HDR). Seventy-nine adult participants completed one self-administered 24HDR using Foodbook24 and one interviewer-led 24HDR on the same day. Following a 10 days wash-out period the same process was completed again in opposite order to the previous study visit. Statistical analysis including Spearman’s rank order correlation, Mann-Whitney U tests, cross-classification analysis, and “Match”, “Omission”, and “Intrusion” rates were used to investigate the relationship between both methods. Strong, positive correlations of nutrient intake estimated using both methods was observed (rs = 0.6–1.0; p < 0.001). The percentage of participants classified into the same tertile of nutrient intake distribution using both methods ranged from 58% (energy) to 82% (vitamin D). The overall match rate for food intake between both methods was 85%, while rates for omissions and intrusions were 11.5% and 3.5%, respectively. These results, alongside the reduced cost and participant burden associated with Foodbook24, highlight the tool’s potential as a viable alternative to the interviewer-led 24HDR