Successful completion of a cyclic ground test of a mercury ion auxiliary propulsion system

An engineering model Ion Auxiliary Propulsion System (IAPS) 8-cm thruster (S/N 905) has completed a life test at NASA Lewis Research Center. The mercury ion thruster successfully completed and exceeded the test goals of 2557 on/off cycles and 7057 hr of operation at full thrust. The final 1200 cycles and 3600 hr of the life test were conducted using an engineering model of the IAPS power electronics unit (PEU) and breadboard digital controller and interface unit (DCIU). This portion of the test is described in this paper with a charted history of thruster operating parameters and off-normal events. Performance and operating characteristics were constant throughout the test with only minor variations. The engineering model power electronics unit operated without malfunction; the flight software in the digital controller and interface unit was exercised and verified. Post-test inspection of the thruster revealed facility enhanced accelerator grid erosion but overall the thruster was in good condition. It was concluded that the thruster performance was not drastically degraded by time or cycles. Additional cyclic testing is currently under consideration

A Hybrid Sequencing Approach Completes the Genome Sequence of Thermoanaerobacter ethanolicus JW 200

Thermoanaerobacter ethanolicus JW 200 has been identified as a potential sustainable biofuel producer due to its ability to readily ferment carbohydrates to ethanol. A hybrid sequencing approach, combining Oxford Nanopore and Illumina DNA sequence reads, was applied to produce a single contiguous genome sequence of 2,911,280 bp

Metagenetic analysis of patterns of distribution and diversity of marine meiobenthic eukaryotes

AimMeiofaunal communities that inhabit the marine benthos offer unique opportunities to simultaneously study the macroecology of numerous phyla that exhibit different life-history strategies. Here, we ask: (1) if the macroecology of meiobenthic communities is explained mainly by dispersal constraints or by environmental conditions; and (2) if levels of meiofaunal diversity surpass existing estimates based on morphological taxonomy. LocationUK and mainland European coast. MethodsNext-generation sequencing techniques (NGS; Roche 454 FLX platform) using 18S nuclear small subunit ribosomal DNA (rDNA) gene. Pyrosequences were analysed using AmpliconNoise followed by chimera removal using Perseus. ResultsRarefaction curves revealed that sampling saturation was only reached at 15% of sites, highlighting that the bulk of meiofaunal diversity is yet to be discovered. Overall, 1353 OTUs were recovered and assigned to 23 different phyla. The majority of sampled sites had c. 60-70 unique operational taxonomic units (OTUs) per site, indicating high levels of beta diversity. The environmental parameters that best explained community structure were seawater temperature, geographical distance and sediment size, but most of the variability (R-2=70%-80%) remains unexplained. Main conclusionsHigh percentages of endemic OTUs suggest that meiobenthic community composition is partly niche-driven, as observed in larger organisms, but also shares macroecological features of microorganisms by showing high levels of cosmopolitanism (albeit on a much smaller scale). Meiobenthic communities exhibited patterns of isolation by distance as well as associations between niche, latitude and temperature, indicating that meiobenthic communities result from a combination of niche assembly and dispersal processes. Conversely, isolation-by-distance patterns were not identified in the featured protists, suggesting that animals and protists adhere to radically different macroecological processes, linked to life-history strategies.Natural Environment Research Council (NERC) [NE/E001505/1, NE/F001266/1, MGF-167]; Portuguese Foundation for Science and Technology (FCT) [SFRH/BD/27413/2006, SFRH/BPD/80447/2014]; EPSRC [EP/H003851/1]; BBSRC CASE studentship; Unilever; Biotechnology and Biological Sciences Research Council [987347]; Engineering and Physical Sciences Research Council [EP/H003851/1]; Natural Environment Research Council [NE/F001290/1, NE/F001266/1, NE/E001505/1, NBAF010002]info:eu-repo/semantics/publishedVersio

Use of the Dexamethasone-Corticotrophin Releasing Hormone Test to Assess Hypothalamic-Pituitary-Adrenal Axis Function in Rheumatoid Arthritis

Objectives. Hypothalamic-Pituitary-Adrenal axis function may be abnormal in rheumatoid arthritis (RA). A pilot study in 7 patients suggested impaired glucocorticoid feedback in some patients after the dexamethasone-corticotrophin releasing hormone (CRH) test. This study aimed to investigate the dexamethasone-corticotrophin releasing factor test in a larger group of patients and relate the results to characteristics of the disease. Methods. Outpatients with active RA (≥3 swollen and tender joints and C-reactive protein > 10 mg/L) took dexamethasone (1.5 mg) at 23:00 hour in the evening. Next day, baseline saliva and plasma samples were collected, CRH was infused at 11:00 hour, and 4 serial blood and saliva samples were collected. Plasma samples were stored at −80°C and a radioimmunoassay performed for saliva and plasma cortisol. Results. All 20 participants showed normal dexamethasone suppression and mounted no response to the CRH challenge. In samples with measurable cortisol, there was a strong correlation between saliva and plasma values (r = 0.876, n = 26, P < .01). Conclusion. No abnormalities were found in the Dexamethasone-CRH test in RA patients in contrast to a previous pilot study. Salivary cortisol measurement may offer an alternative noninvasive technique to plasma cortisol in RA patients in future studies

A colimit decomposition for homotopy algebras in Cat

Badzioch showed that in the category of simplicial sets each homotopy algebra of a Lawvere theory is weakly equivalent to a strict algebra. In seeking to extend this result to other contexts Rosicky observed a key point to be that each homotopy colimit in simplicial sets admits a decomposition into a homotopy sifted colimit of finite coproducts, and asked the author whether a similar decomposition holds in the 2-category of categories Cat. Our purpose in the present paper is to show that this is the case.Comment: Some notation changed; small amount of exposition added in intr

Evaluation of possible temperature fluctuations from proposed power modifications at Hoover Dam

There are several planned alternatives for increasing the generation capacity of Hoover Dam to help meet peak power demands. These alternatives include: (a) uprating the existing generating units, (b) replacing or adding one or more generating units and (c) adding reversible pumped-storage hydroelectric units. Since the existing generators are at the end of their economic life and have to be replaced, their uprating has been scheduled as routine maintenance. This will increase the generating capacity of the Hoover Dam powerplant from 1240 MW to 1810 MW, but the anticipated capacity for meeting power demand is 2300 MW. Therefore, modifications (alternatives B and C) are also being considered to obtain an additional 500 MW from Hoover Dam. The proposed modification of Hoover Dam will alter the existing daily discharge regime, but because of water requirements downstream, the total volume of water discharged over an annual period will remain the same. To meet peak power demands with the proposed alternatives, the daily discharge cycle will be changed to longer periods of low flow (evening-early morning)and shorter periods of peak flow (midafternoon-dusk). The peak discharge rate will increase to 76,000 ft3.sec-1 (Table l), but minimum flows of 2000 ft3.sec-1 will be maintained with alternatives A and B when the elevation of Lake Mohave is below 630 ft. Since the water of Lake Mohave extends to the tail race of Hoover Dam when lake elevations are greater than 630 ft., minimum flows of 2000 ft3.sec-1 will be unnecessary and hence zero discharge at night may occur. With reversible pumped-storage (alternative C), some of the water used for generating during peak power demands would also be pumped back to Lake Mead at night at a rate of up to 25,000 ft3.sec-1. This will cause reverse flows in the river section, and could pull Lake Mohave water to the dam. Hoover Dam has two sets of intake gates located at elevation 1045 ft. and 900 ft. on the four intake towers. The upper gates (1045 ft.), with few exceptions, have not been used since 1954, but, with the addition of generating units (alternative B) or the installation of reversible pumped-storage units (alternative C), one upper gate on the Arizona Tower would be used in conjunction with the four lower gates to facilitate the higher flows. We have previously reported (Paulson, Baker and Deacon 1980) that the discharge temperature could increase and undergo daily fluctuation due to withdrawal of increasing amounts of warmer water form Lake Mead at higher peak discharge. The U.S. Water and Power Resources Service therefore initiated this investigation to determine to what extent discharge temperature from Hoover Dam and thermal stratification in Lake Mead would change with discharges under the following conditions: (i) all four intakes on the upper gates (ii) all four intakes on the lower gates, (iii) from a combined use of one upper gate and four lower gates

Evaluation of impacts associated with reregulation of water levels in Lake Mohave

The U.S. Water and Power Resources Service is considering reregulating Lake Mohave water levels to increase the net power benefit from Hoover Dam. Reregulation will not increase the generation capacity of the Hoover powerplant but it will enable the plant operation to be increased when the energy has greater monetary value. Energy generated at different times of the year has different market value, the highest being in January-March and July- September. By generating more power during these periods more net monetary benefit can be derived from Hoover Dam. The total volume of water released from Hoover Dam over an annual period must remain unchanged due to downstream water requirements for irrigation. To obtain this power benefit, therefore, less water for generation would be discharged during the low market value periods to enable higher discharges during the high market value periods. The discharge regime at Davis Dam would also remain unchanged in order to meet downstream water requirements. Therefore more extreme fluctuations in Lake Mohave water levels would result in order to accommodate changes in the Hoover Dam discharge regime. Water levels in Lake Mohave presently fluctuate from a maximum elevation of about 647 ft. in February-April to a minimum of 630.5 ft. in September- November. The minimum elevation has been maintained to accommodate the marinas on the lake. To optimize power generation from Hoover Dam, water levels in Lake Mohave will fluctuate from elevations of 600 to 640 ft. The greatest power benefit would be derived from decreased Hoover Dam discharge in April-June and October-December and increased discharge in January-March and July-September… The proposed reregulation alternatives will alter environmental conditions in Lake Mohave because of the extreme variations in water level. The U.S. Water and Power Resources Service initiated this investigation to determine to what extent reregulation would affect limnological conditions and fisheries in Lake Mohave

e-Social Science and Evidence-Based Policy Assessment : Challenges and Solutions

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