Miniature Oil-less Reciprocating Compressor for High-Lift, High-Temperature Heat Pump Applications

In the extreme temperature environment of the moon, the regolith surface temperature can reach 100°C during the 354-hour lunar day. This often exceeds the maximum allowable temperature of critical electronics onboard small lunar rovers designed for long-term science missions. In environments with such high heat sink temperatures, active vapor compression cooling solutions allow greater mission flexibility than traditional passive spacecraft thermal control. The objective of this research was to design and experimentally evaluate a critical enabling technology for effective lunar rover class heat pumps: the high-lift, high-temperature, microgravity compressor. The main technical challenges in the design of a compressor for these conditions include operation in a microgravity environment, relatively high compression ratio requirements, extreme temperatures during transport and operation in space and on the moon, and the low equipment vibration requirements for small lunar rovers. A twin-piston oil-less reciprocating compressor was designed to meet these requirements. The oil-less design mitigates the challenges of oil distribution in microgravity environments. A twin-piston configuration was designed to balance the dynamic forces and lower the vibration of the compressor. Compressor components were sized to operate with new high-temperature, environmentally friendly refrigerants at compression ratios between 3 and 7. The compressor was designed for a cooling capacity on the order of 100 W. A prototype compressor was fabricated and experimentally evaluated. The total mass of the compressor was 2.86 kg. Maximum exported vibration was estimated to be 0.04 N at the base of the compressor based on kinematic calculations and measured motor torque. Experimental capacity and efficiency measurements were lower than predicted. This was likely due to manufacturing and tolerance deficiencies in the first prototype compressor resulting in blowback around the piston seal, higher friction than predicted, suboptimal bearing performance, suboptimal reed valve design, and tolerance stack up in the crankshaft and cylinders. These manufacturing issues can be overcome in next generation prototypes

Selective laser melting and tempering of H13 tool steel for rapid toolingg applications

H13 components with a relative density of ∼99% were additively manufactured using the selective laser melting (SLM) process. The highest density part (relevant density 99%) with the lowest level of porosity (<0.01%) was made with a volumetric energy density of 760 J/mm3 (152 W laser power, 100 mm/s scanning speed, 40 μm hatch spacing, and 50 μm layer thickness). Wrought and additively manufactured samples underwent tempering at 550, 600, and 650 °C for 2 h followed by furnace cooling. Additively manufactured samples and wrought H13 samples that were austenitized followed by water quenching were martensitic with similar microhardness values of 708.4 ± 25.0 HV and 708.1 ± 12.6 HV, respectively. A tempered martensitic structure was observed in SLM-manufactured and tempered samples. Samples that were additively manufactured and tempered at 550 °C showed higher microhardness (728.5 ± 28.2 HV) than non-tempered SLM-manufactured samples due to an upward shift in the secondary hardening phase. Tempering at 600 and 650 °C resulted in coarsening of the carbides and martensite, which led to a reduction in microhardness. Additively manufactured samples maintained higher microhardness values than wrought H13 samples at all tempering temperatures, likely because of higher dislocation density, finer grains present, and higher volume fraction of carbide nanoparticles

A framework for human microbiome research

A variety of microbial communities and their genes (the microbiome) exist throughout the human body, with fundamental roles in human health and disease. The National Institutes of Health (NIH)-funded Human Microbiome Project Consortium has established a population-scale framework to develop metagenomic protocols, resulting in a broad range of quality-controlled resources and data including standardized methods for creating, processing and interpreting distinct types of high-throughput metagenomic data available to the scientific community. Here we present resources from a population of 242 healthy adults sampled at 15 or 18 body sites up to three times, which have generated 5,177 microbial taxonomic profiles from 16S ribosomal RNA genes and over 3.5 terabases of metagenomic sequence so far. In parallel, approximately 800 reference strains isolated from the human body have been sequenced. Collectively, these data represent the largest resource describing the abundance and variety of the human microbiome, while providing a framework for current and future studies

Charged extracellular residues, conserved throughout a G-protein-coupled receptor family, are required for ligand binding, receptor activation, and cell-surface expression

For G-protein-coupled receptors (GPCRs) in general, the roles of extracellular residues are not well defined compared with residues in transmembrane helices (TMs). Nevertheless, extracellular residues are important for various functions in both peptide-GPCRs and amine-GPCRs. In this study, the V1a vasopressin receptor was used to systematically investigate the role of extracellular charged residues that are highly conserved throughout a subfamily of peptide-GPCRs, using a combination of mutagenesis and molecular modeling. Of the 13 conserved charged residues identified in the extracellular loops (ECLs), Arg116 (ECL1), Arg125 (top of TMIII), and Asp204 (ECL2) are important for agonist binding and/or receptor activation. Molecular modeling revealed that Arg125 (and Lys 125) stabilizes TMIII by interacting with lipid head groups. Charge reversal (Asp125) caused re-ordering of the lipids, altered helical packing, and increased solvent penetration of the TM bundle. Interestingly, a negative charge is excluded at this locus in peptide-GPCRs, whereas a positive charge is excluded in amine-GPCRs. This contrasting conserved charge may reflect differences in GPCR binding modes between peptides and amines, with amines needing to access a binding site crevice within the receptor TM bundle, whereas the binding site of peptide-GPCRs includes more extracellular domains. A conserved negative charge at residue 204 (ECL2), juxtaposed to the highly conserved disulfide bond, was essential for agonist binding and signaling. Asp204 (and Glu204) establishes TMIII contacts required for maintaining the α-hairpin fold of ECL2, which if broken (Ala204 or Arg204) resulted in ECL2 unfolding and receptor dysfunction. This study provides mechanistic insight into the roles of conserved extracellular residues

Systematic review with meta-analysis of the epidemiological evidence relating smoking to COPD, chronic bronchitis and emphysema

<p>Abstract</p> <p>Background</p> <p>Smoking is a known cause of the outcomes COPD, chronic bronchitis (CB) and emphysema, but no previous systematic review exists. We summarize evidence for various smoking indices.</p> <p>Methods</p> <p>Based on MEDLINE searches and other sources we obtained papers published to 2006 describing epidemiological studies relating incidence or prevalence of these outcomes to smoking. Studies in children or adolescents, or in populations at high respiratory disease risk or with co-existing diseases were excluded. Study-specific data were extracted on design, exposures and outcomes considered, and confounder adjustment. For each outcome RRs/ORs and 95% CIs were extracted for ever, current and ex smoking and various dose response indices, and meta-analyses and meta-regressions conducted to determine how relationships were modified by various study and RR characteristics.</p> <p>Results</p> <p>Of 218 studies identified, 133 provide data for COPD, 101 for CB and 28 for emphysema. RR estimates are markedly heterogeneous. Based on random-effects meta-analyses of most-adjusted RR/ORs, estimates are elevated for ever smoking (COPD 2.89, CI 2.63-3.17, n = 129 RRs; CB 2.69, 2.50-2.90, n = 114; emphysema 4.51, 3.38-6.02, n = 28), current smoking (COPD 3.51, 3.08-3.99; CB 3.41, 3.13-3.72; emphysema 4.87, 2.83-8.41) and ex smoking (COPD 2.35, 2.11-2.63; CB 1.63, 1.50-1.78; emphysema 3.52, 2.51-4.94). For COPD, RRs are higher for males, for studies conducted in North America, for cigarette smoking rather than any product smoking, and where the unexposed base is never smoking any product, and are markedly lower when asthma is included in the COPD definition. Variations by sex, continent, smoking product and unexposed group are in the same direction for CB, but less clearly demonstrated. For all outcomes RRs are higher when based on mortality, and for COPD are markedly lower when based on lung function. For all outcomes, risk increases with amount smoked and pack-years. Limited data show risk decreases with increasing starting age for COPD and CB and with increasing quitting duration for COPD. No clear relationship is seen with duration of smoking.</p> <p>Conclusions</p> <p>The results confirm and quantify the causal relationships with smoking.</p

Structure, function and diversity of the healthy human microbiome

Author Posting. © The Authors, 2012. This article is posted here by permission of Nature Publishing Group. The definitive version was published in Nature 486 (2012): 207-214, doi:10.1038/nature11234.Studies of the human microbiome have revealed that even healthy individuals differ remarkably in the microbes that occupy habitats such as the gut, skin and vagina. Much of this diversity remains unexplained, although diet, environment, host genetics and early microbial exposure have all been implicated. Accordingly, to characterize the ecology of human-associated microbial communities, the Human Microbiome Project has analysed the largest cohort and set of distinct, clinically relevant body habitats so far. We found the diversity and abundance of each habitat’s signature microbes to vary widely even among healthy subjects, with strong niche specialization both within and among individuals. The project encountered an estimated 81–99% of the genera, enzyme families and community configurations occupied by the healthy Western microbiome. Metagenomic carriage of metabolic pathways was stable among individuals despite variation in community structure, and ethnic/racial background proved to be one of the strongest associations of both pathways and microbes with clinical metadata. These results thus delineate the range of structural and functional configurations normal in the microbial communities of a healthy population, enabling future characterization of the epidemiology, ecology and translational applications of the human microbiome.This research was supported in part by National Institutes of Health grants U54HG004969 to B.W.B.; U54HG003273 to R.A.G.; U54HG004973 to R.A.G., S.K.H. and J.F.P.; U54HG003067 to E.S.Lander; U54AI084844 to K.E.N.; N01AI30071 to R.L.Strausberg; U54HG004968 to G.M.W.; U01HG004866 to O.R.W.; U54HG003079 to R.K.W.; R01HG005969 to C.H.; R01HG004872 to R.K.; R01HG004885 to M.P.; R01HG005975 to P.D.S.; R01HG004908 to Y.Y.; R01HG004900 to M.K.Cho and P. Sankar; R01HG005171 to D.E.H.; R01HG004853 to A.L.M.; R01HG004856 to R.R.; R01HG004877 to R.R.S. and R.F.; R01HG005172 to P. Spicer.; R01HG004857 to M.P.; R01HG004906 to T.M.S.; R21HG005811 to E.A.V.; M.J.B. was supported by UH2AR057506; G.A.B. was supported by UH2AI083263 and UH3AI083263 (G.A.B., C. N. Cornelissen, L. K. Eaves and J. F. Strauss); S.M.H. was supported by UH3DK083993 (V. B. Young, E. B. Chang, F. Meyer, T. M. S., M. L. Sogin, J. M. Tiedje); K.P.R. was supported by UH2DK083990 (J. V.); J.A.S. and H.H.K. were supported by UH2AR057504 and UH3AR057504 (J.A.S.); DP2OD001500 to K.M.A.; N01HG62088 to the Coriell Institute for Medical Research; U01DE016937 to F.E.D.; S.K.H. was supported by RC1DE0202098 and R01DE021574 (S.K.H. and H. Li); J.I. was supported by R21CA139193 (J.I. and D. S. Michaud); K.P.L. was supported by P30DE020751 (D. J. Smith); Army Research Office grant W911NF-11-1-0473 to C.H.; National Science Foundation grants NSF DBI-1053486 to C.H. and NSF IIS-0812111 to M.P.; The Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231 for P.S. C.; LANL Laboratory-Directed Research and Development grant 20100034DR and the US Defense Threat Reduction Agency grants B104153I and B084531I to P.S.C.; Research Foundation - Flanders (FWO) grant to K.F. and J.Raes; R.K. is an HHMI Early Career Scientist; Gordon&BettyMoore Foundation funding and institutional funding fromthe J. David Gladstone Institutes to K.S.P.; A.M.S. was supported by fellowships provided by the Rackham Graduate School and the NIH Molecular Mechanisms in Microbial Pathogenesis Training Grant T32AI007528; a Crohn’s and Colitis Foundation of Canada Grant in Aid of Research to E.A.V.; 2010 IBM Faculty Award to K.C.W.; analysis of the HMPdata was performed using National Energy Research Scientific Computing resources, the BluBioU Computational Resource at Rice University

Selective Laser Melting of H13 Tool Steel for Rapid Tooling

The current knowledge on the microstructural evolutions and mechanical properties of selective laser melting (SLM) produced H13 tool steel components is limited. This research is focused on optimization of SLM processing parameters for H13 tool steel and investigation of microstructure and mechanical properties of H13 tool steel components after SLM and heat treatment. H13 components with a relative density of ~99% were additively manufactured using the SLM process. The highest density part (relevant density 99%) with the lowest level of porosity (<0.01%) was made with a volumetric energy density (VED) of 760 J/mm3 (152 W laser power, 100 mm/s scanning speed, 40 m hatch spacing, and 50 m layer thickness). Wrought and SLM produced samples underwent tempering at 550, 600, and 650°C for two hours followed by furnace cooling. Both SLMed samples and austenitized followed by water quenched wrought samples presented martensitic microstructures with similar microhardness values of ~708 HV. No obvious trend was observed between VED and microhardness values. SLMed and tempered samples showed high microhardness value of 728.5±28.2 HV due to presence of high dislocation density caused by rapid solidification during SLM, finer grains and microstructure, and precipitation of second phase (carbides) during tempering. Tempered martensitic structure was observed in SLMed and tempered samples. These precipitates showed coarsening at 600 and 650°C leading to a decrease in microhardness. SLMed samples maintained higher microhardness values than wrought H13 samples at each tempering temperature likely due to higher dislocation density and finer grains present in SLMed parts (rapid solidification characteristics). High relative densities (99.9% or greater) were not achieved in SLMed parts, and further optimization deemed necessary to achieve full density parts. Furthermore, presence of cracks in the SLMed H13 tool steel parts is a problem that needs to be addressed before implementation of SLMed molds in applications that require high thermal fatigue resistance such as like plastic injection molding