STME Hydrogen Mixer Study

The hydrogen mixer for the Space Transportation Main Engine is used to mix cold hydrogen bypass flow with warm hydrogen coolant chamber gas, which is then fed to the injectors. It is very important to have a uniform fuel temperature at the injectors in order to minimize mixture ratio problems due to the fuel density variations. In addition, the fuel at the injector has certain total pressure requirements. In order to achieve these objectives, the hydrogen mixer must provide a thoroughly mixed fluid with a minimum pressure loss. The AEROVISC computational fluid dynamics (CFD) code was used to analyze the STME hydrogen mixer, and proved to be an effective tool in optimizing the mixer design. AEROVISC, which solves the Reynolds Stress-Averaged Navier-Stokes equations in primitive variable form, was used to assess the effectiveness of different mixer designs. Through a parametric study of mixer design variables, an optimal design was selected which minimized mixed fuel temperature variation and fuel mixer pressure loss. The use of CFD in the design process of the STME hydrogen mixer was effective in achieving an optimal mixer design while reducing the amount of hardware testing

Investigation of Transient CFD Methods Applied to a Transonic Compressor Stage

Understanding unsteady flow phenomena in compressor stages often requires the use of time-accurate CFD simulations. Due to the inherent differences in blade pitch between adjacent blade rows, the flow conditions at any given instant in adjacent blade rows differ. Simplified computation of the stage represented by a single blade in each row and simple periodic boundary conditions is therefore not possible. Depending on the blade counts, it may be necessary to model the entire annulus of the stage; however, this requires considerable computational time and memory resources. Several methods for modeling the transient flow in turbomachinery stages which require a minimal number of blade passages per row, and therefore reduced computational demands, have been presented in the literature. Recently, some of these methods have become available in commercial CFD solvers. This paper provides a brief description of the methods used, and how they are applied to a transonic compressor stage. The methods are evaluated and compared in terms of computational efficiency and storage requirements, and comparison is made to steady stage simulations. Comparisons to overall performance data and two-dimensional LDV measurements are used to assess the predictive capabilities of the methods. Computed flow features are examined, and compared with reported measurements.</jats:p

Arabidopsis Type III Gγ Protein AGG3 Is a Positive Regulator of Yield and Stress Responses in the Model Monocot Setaria viridis

Heterotrimeric G-proteins are key regulators of a multitude of growth and development pathways in eukaryotes. Along with the conserved G-protein components found in all organisms, plants have certain novel variants with unique architecture, which may be involved in the regulation of plant-specific traits. The higher plant-specific type III (or Class C) Gγ protein, which possesses a large C terminal extension, represented by AGG3 in Arabidopsis, is one such variant of canonical Gγ proteins. The type III Gγ proteins are involved in regulation of many agronomically important traits in plants, including seed yield, organ size regulation, abscisic acid (ABA)-dependent signaling and stress responses, and nitrogen use efficiency. However, the extant data, especially in the monocots, present a relatively complex and sometimes contradictory picture of the regulatory role of these proteins. It remains unclear if the positive traits observed in certain naturally occurring populations are due to the presence of specific allelic variants of the proteins or due to the altered expression of the gene itself. To address these possibilities, we have overexpressed the Arabidopsis AGG3 gene in the model monocot Setaria viridis and systematically evaluated its role in conferring agriculturally relevant phenotypes. Our data show that AtAGG3 is indeed functional in Setaria and suggest that a subset of the traits affected by the type III Gγ proteins are indeed positively correlated with the gene expression level, while others might have more complex, allele specific regulation

Effectiveness of strategies to encourage general practitioners to accept an offer of free access to online evidence-based information: a randomised controlled trial

Background: This study examined the effectiveness of seven different interventions designed to increase the proportion of general practitioners (GPs) accepting an offer of free access to an online evidence-based resource. Methods: Australian GPs (n = 14,000) were randomly selected and assigned to seven intervention groups, with each receiving a different letter. Seven different strategies were used to encourage GPs to accept an offer of two years free access to an online evidence-based resource (BMJ Clinical Evidence). The first group received a standard letter of offer with no experimental demands. Groups two to seven received a standard letter of offer outlining the requirements of the study. They were asked to complete an initial online questionnaire, agree to complete a 12-month follow-up questionnaire, and agree to having data about their usage of the online evidence-based resource provided to researchers. Groups three to seven also had additional interventions included in the letter of offer: access to an online tutorial in use of the resource (group three); provision of a pamphlet with statements from influential opinion leaders endorsing the resource (group four); offer of eligibility to receive professional development points (group five); offer of eligibility for a prize of $500 for registration at a medical conference of their choice (group six); and a combination of some of the above interventions (group seven). Results: In the group with no research demands, 27% accepted the offer. Average acceptance across all other groups was 10%. There was no advantage in using additional strategies such as financial incentives, opinion leader support, offer of professional development points, or an educational aid over a standard letter of offer to increase acceptance rates. Conclusion: This study showed low acceptance rates of the offer of access to the online resource when there was an associated requirement of response to a short online questionnaire and non-obtrusive monitoring of GP behaviour in terms of accessing the resource. If we are to improve care and encourage evidence-based practice, we need to find effective ways of motivating doctors and other health professionals to take part in research that can inform our implementation efforts

Optimising the use of electronic health records to estimate the incidence of rheumatoid arthritis in primary care:what information is hidden in free text?

Primary care databases are a major source of data for epidemiological and health services research. However, most studies are based on coded information, ignoring information stored in free text. Using the early presentation of rheumatoid arthritis (RA) as an exemplar, our objective was to estimate the extent of data hidden within free text, using a keyword search