Natural Convection Cooling of the Advanced Stirling Radioisotope Generator Engineering Unit

After fueling and prior to launch, the Advanced Stirling Radioisotope Generator (ASRG) will be stored for a period of time then moved to the launch pad for integration with the space probe and mounting on the launch vehicle. During this time, which could be as long as 3 years, the ASRG will operate continuously with heat rejected from the housing and fins. Typically, the generator will be cooled by forced convection using fans. During some of the ground operations, maintaining forced convection may add significant complexity, so allowing natural convection may simplify operations. A test was conducted on the ASRG Engineering Unit (EU) to quantify temperatures and operating parameters with natural convection only and determine if the EU could be safely operated in such an environment. The results show that with natural convection cooling the ASRG EU Stirling convertor pressure vessel temperatures and other parameters had significant margins while the EU was operated for several days in this configuration. Additionally, an update is provided on ASRG EU testing at NASA Glenn Research Center, where the ASRG EU has operated for over 16,000 hr and underwent extensive testing

Identification of domains of the Tomato spotted wilt virus NSm protein involved in tubule formation, movement and symptomatology

AbstractDeletion and alanine-substitution mutants of the Tomato spotted wilt virus NSm protein were generated to identify domains involved in tubule formation, movement and symptomatology using a heterologous Tobacco mosaic virus expression system. Two regions of NSm, G19-S159 and G209-V283, were required for both tubule formation in protoplasts and cell-to-cell movement in plants, indicating a correlation between these activities. Three amino acid groups, D154, EYKK205–208 and EEEEE284–288 were linked with long-distance movement in Nicotiana benthamiana. EEEEE284–288 was essential for NSm-mediated long-distance movement, whereas D154 was essential for tubule formation and cell-to-cell movement; indicating separate genetic controls for cell-to-cell and long-distance movement. The region I57-N100 was identified as the determinant of foliar necrosis in Nicotiana benthamiana, and mutagenesis of HH93–94 greatly reduced necrosis. These findings are likely applicable to other tospovirus species, especially those within the ‘New World’ group as NSm sequences are highly conserved

Design, Qualification and Integration Testing of the High-Temperature Resistance Temperature Device for Stirling Power System

The Advanced Stirling Radioisotope Generator (ASRG), developed from 2006 to 2013 under the joint sponsorship of the United States Department of Energy (DOE) and National Aeronautics and Space Administration (NASA) to provide a high-efficiency power system for future deep space missions, employed Sunpower Incorporated's Advanced Stirling Convertors (ASCs) with operating temperature up to 840 C. High-temperature operation was made possible by advanced heater head materials developed to increase reliability and thermal-to-mechanical conversion efficiency. During a mission, it is desirable to monitor the Stirling hot-end temperature as a measure of convertor health status and assist in making appropriate operating parameter adjustments to maintain the desired hot-end temperature as the radioisotope fuel decays. To facilitate these operations, a Resistance Temperature Device (RTD) that is capable of high-temperature, continuous long-life service was designed, developed and qualified for use in the ASRG. A thermal bridge was also implemented to reduce the RTD temperature exposure while still allowing an accurate projection of the ASC hot-end temperature. NASA integrated two flight-design RTDs on the ASCs and assembled into the high-fidelity Engineering Unit, the ASRG EU2, at Glenn Research Center (GRC) for extended operation and system characterization. This paper presents the design implementation and qualification of the RTD, and its performance characteristics and calibration in the ASRG EU2 testing

Role of NADPH Oxidase versus Neutrophil Proteases in Antimicrobial Host Defense

NADPH oxidase is a crucial enzyme in mediating antimicrobial host defense and in regulating inflammation. Patients with chronic granulomatous disease, an inherited disorder of NADPH oxidase in which phagocytes are defective in generation of reactive oxidant intermediates (ROIs), suffer from life-threatening bacterial and fungal infections. The mechanisms by which NADPH oxidase mediate host defense are unclear. In addition to ROI generation, neutrophil NADPH oxidase activation is linked to the release of sequestered proteases that are posited to be critical effectors of host defense. To definitively determine the contribution of NADPH oxidase versus neutrophil serine proteases, we evaluated susceptibility to fungal and bacterial infection in mice with engineered disruptions of these pathways. NADPH oxidase-deficient mice (p47phox−/−) were highly susceptible to pulmonary infection with Aspergillus fumigatus. In contrast, double knockout neutrophil elastase (NE)−/−×cathepsin G (CG)−/− mice and lysosomal cysteine protease cathepsin C/dipeptidyl peptidase I (DPPI)-deficient mice that are defective in neutrophil serine protease activation demonstrated no impairment in antifungal host defense. In separate studies of systemic Burkholderia cepacia infection, uniform fatality occurred in p47phox−/− mice, whereas NE−/−×CG−/− mice cleared infection. Together, these results show a critical role for NADPH oxidase in antimicrobial host defense against A. fumigatus and B. cepacia, whereas the proteases we evaluated were dispensable. Our results indicate that NADPH oxidase dependent pathways separate from neutrophil serine protease activation are required for host defense against specific pathogens

Deletion of Internal Sequences Results in Tobacco Mosaic Virus Defective RNAs That Accumulate to High Levels without Interfering with Replication of the Helper Virus

AbstractDeletion of certain internal sequences of the tobacco mosaic tobamovirus (TMV) genome was required to create replication-defective RNAs (dRNA) that were replicatedin transby TMV. All dRNAs that accumulated to detectable levels were missing nucleotides 3420–4902, which appeared to constitute a core region that inhibited replicationin trans.Deletion of additional sequences resulted in dRNAs that varied tremendously in ability to be replicated from none to levels exceeding that of the helper viral RNA. Accumulation of dRNA negative- and positive-stranded RNAs of each dRNA paralleled those of the helper virus. Negative-stranded RNA accumulation of both helper and dRNA ceased at the same early time in the infection while synthesis of both positive-stranded RNAs continued, suggesting that both dRNAs and helper virus RNAs were synthesized from the same pool of replicase complexes. Positive- to negative-stranded RNA ratios for the dRNAs were similar to, or slightly greater than the wild-type helper virus. Full-length dRNAs were not supportedin transby a replication-competent helper virus. Even though some of the artificially constructed dRNAs accumulated to levels exceeding the level of the helper virus, none appreciably affected the replication of the helper virus, suggesting that the dRNAs are produced from “excess” replicase capacity

Common sense computing (episode 3): Concurrency and concert tickets

ABSTRACT As the third in a series of projects investigating commonsense computing -the relevant knowledge that students have before any formal study of computing -we examine students' commonsense understanding of concurrency. Specifically, we replicated (with modifications) an experiment by Ben-David Kolikant. [2] Ben-David Kolikant's data were gathered from high-school seniors who had previously studied computing, at the beginning of an advanced class in concurrent and distributed programming. Modifying one of her questions to reflect our students' lack of background, we asked students at five different institutions, in the first week of CS1, to describe in English the problems that might arise when more than one person is selling seats to a concert. Almost all students (97%) identified the problem of interest -that a race condition may occur between sellers. 73% of students identified at least one possible solution. We found that the categorizations developed by Ben-David Kolikant were also meaningful when applied to our data, that our beginning CS1 students are more likely to give centralized solutions (as opposed to decentralized ones) than Ben-David Kolikant's concurrency students, and that the granularity of solutions is finer among the more experienced students

Decomposition in Al-Zn alloys: Part II. Decomposition during continuous cooling

A small angle X-ray scattering study (SAS) has been made of decomposition during contin uous cooling in four binary Al-Zn alloys with compositions spanning the miscibility gap and in two ternary alloys, each containing 22 at. pct Zn plus small amounts of Sn and Mg. Plots of log λm (wavelength receiving maximum amplification during the quench)vs log Q (quench rate) yield slopes of approximately -1/3 for all alloys, indicating that coarsening plays an important role during the quench. In addition, measurements of integrated area under the SAS spectra indicate that decomposition is essentially complete in the quenched condition for all of the alloys studied