368 research outputs found
Study of an advanced General Aviation Turbine Engine (GATE)
The best technology program for a small, economically viable gas turbine engine applicable to the general aviation helicopter and aircraft market for 1985-1990 was studied. Turboshaft and turboprop engines in the 112 to 746 kW (150 to 1000 hp) range and turbofan engines up to 6672 N (1500 lbf) thrust were considered. A good market for new turbine engines was predicted for 1988 providing aircraft are designed to capitalize on the advantages of the turbine engine. Parametric engine families were defined in terms of design and off-design performance, mass, and cost. These were evaluated in aircraft design missions selected to represent important market segments for fixed and rotary-wing applications. Payoff parameters influenced by engine cycle and configuration changes were aircraft gross mass, acquisition cost, total cost of ownership, and cash flow. Significant advantage over a current technology, small gas turbine engines was found especially in cost of ownership and fuel economy for airframes incorporating an air-cooled high-pressure ratio engine. A power class of 373 kW (500 hp) was recommended as the next frontier for technology advance where large improvements in fuel economy and engine mass appear possible through component research and development
A Cropping System for Intensive Grain Production on Sloping Land
From the beginnings of Kentucky Agriculture, soil erosion and related losses in productivity have been major problems for Kentucky farmers. Improved soil conservation practices during the past forty years have been especially significant in the recovery and progress of our agricultural industry. No-tillage methods for crop production, which were pioneered in Kentucky, have proven useful in controlling erosion and holding production at high levels. During recent years, the marketplace has strongly encouraged grain production, with the unfortunate effect that many Kentucky hillsides have been returned to grain production without sufficient erosion control measures. This report describes innovations in use of no-tillage and other conservation practices to develop a system of grain production for sloping land, thus enabling increased income, and nearly eliminating erosion at the same time
Keck Cosmic Web Imager Observations of He II Emission in I Zw 18
With a metallicity of 12 + Log(O/H) ≍ 7.1-7.2, I Zw 18 is a canonical low-metallicity blue compact dwarf (BCD) galaxy. A growing number of BCDs, including I Zw 18, have been found to host strong, narrow-lined, nebular He II (λ4686) emission with enhanced intensities compared to Hβ (e.g., He II(λ4686)/Hβ > 1%). We present new observations of I Zw 18 using the Keck Cosmic Web Imager. These observations reveal two nebular He II emission regions (or He III regions) northwest and southeast of the He III region in the galaxy's main body investigated in previous studies. All regions exhibit He II(λ4686)/Hβ greater than 2%. The two newly resolved He III regions lie along an axis that intercepts the position of I Zw 18's ultraluminous X-ray (ULX) source. We explore whether the ULX could power the two He III regions via shock activity and/or beamed X-ray emission. We find no evidence of shocks from the gas kinematics. If the ULX powers the two regions, the X-ray emission would need to be beamed. Another potential explanation is that a class of early-type nitrogen-rich Wolf-Rayet stars with low winds could power the two He III regions, in which case the alignment with the ULX would be coincidental
Production of α1,3-galactosyltransferase-deficient pigs
The enzyme α1,3-galactosyltransferase (α1,3GT or GGTA1) synthesizes α1,3galactose (α1,3Gal) epitopes (Galα1,3Galβ1,4GlcNAc-R), which are the major xenoantigens causing hyperacute rejection in pig-to-human xenotransplantation. Complete removal of α1,3Gal from pig organs is the critical step toward the success of xenotransplantation. We reported earlier the targeted disruption of one allele of the α1,3GT gene in cloned pigs. A selection procedure based on a bacteria[toxin was used to select for cells in which the second allele of the gene was knocked out. Sequencing analysis demonstrated that knockout of the second allele of the α1,3GT gene was caused by a T-to-G single point mutation at the second base of exon 9, which resulted in inactivation of the α1,3GT protein. Four healthy α1,3GT double-knockout female piglets were produced by three consecutive rounds of cloning. The piglets carrying a point mutation in the α1,3GT gene hold significant value, as they would allow production of α1,3Gal-deficient pigs free of antibiotic-resistance genes and thus have the potential to make a safer product for human use
Towards norms for accreditation of biobanks for human health and medical research:Compilation of existing guidelines into an ISO certification/accreditation norm-compatible format
In recent years, biobanks have evolved into professional infrastructures that acquire, validate, process, store, manage and distribute biological material of human origin to public or private end-users/researchers. This article (a) highlights the importance of quality assurance for both the biobank basic processes and sample annotation in order to ensure reliable results of research based on these samples, (b) suggests that certification according to international standards can contribute to the organization of the biobanking processes while accreditation can contribute to the organization of sample characterization/validation, and (c) provides a compilation of all existing guidelines against an International Organization for Standardization (ISO) format.</p
Mu and Delta opioid receptors activate the same G proteins in human neuroblastoma SH-SY5Y cells
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72251/1/sj.bjp.0704430.pd
On the Kinematics of Cold, Metal-enriched Galactic Fountain Flows in Nearby Star-forming Galaxies
We use medium-resolution Keck/Echellette Spectrograph and Imager spectroscopy
of bright quasars to study cool gas traced by CaII 3934,3969 and NaI 5891,5897
absorption in the interstellar/circumgalactic media of 21 foreground
star-forming galaxies at redshifts 0.03 < z < 0.20 with stellar masses 7.4 <
log M_*/M_sun < 10.6. The quasar-galaxy pairs were drawn from a unique sample
of Sloan Digital Sky Survey quasar spectra with intervening nebular emission,
and thus have exceptionally close impact parameters (R_perp < 13 kpc). The
strength of this line emission implies that the galaxies' star formation rates
(SFRs) span a broad range, with several lying well above the star-forming
sequence. We use Voigt profile modeling to derive column densities and
component velocities for each absorber, finding that column densities N(CaII) >
10^12.5 cm^-2 (N(NaI) > 10^12.0 cm^-2) occur with an incidence f_C(CaII) =
0.63^+0.10_-0.11 (f_C(NaI) = 0.57^+0.10_-0.11). We find no evidence for a
dependence of f_C or the rest-frame equivalent widths W_r(CaII K) or W_r(NaI
5891) on R_perp or M_*. Instead, W_r(CaII K) is correlated with local SFR at
>3sigma significance, suggesting that CaII traces star formation-driven
outflows. While most of the absorbers have velocities within +/-50 km/s of the
host redshift, their velocity widths (characterized by Delta v_90) are
universally 30-177 km/s larger than that implied by tilted-ring modeling of the
velocities of interstellar material. These kinematics must trace galactic
fountain flows and demonstrate that they persist at R_perp > 5 kpc. Finally, we
assess the relationship between dust reddening and W_r(CaII K) (W_r(NaI 5891)),
finding that 33% (24%) of the absorbers are inconsistent with the best-fit
Milky Way E(B-V)-W_r relations at >3sigma significance.Comment: 38 pages, 16 figures, 4 tables. Accepted to Ap
Changing a semantics: opportunism or courage?
The generalized models for higher-order logics introduced by Leon Henkin, and
their multiple offspring over the years, have become a standard tool in many
areas of logic. Even so, discussion has persisted about their technical status,
and perhaps even their conceptual legitimacy. This paper gives a systematic
view of generalized model techniques, discusses what they mean in mathematical
and philosophical terms, and presents a few technical themes and results about
their role in algebraic representation, calibrating provability, lowering
complexity, understanding fixed-point logics, and achieving set-theoretic
absoluteness. We also show how thinking about Henkin's approach to semantics of
logical systems in this generality can yield new results, dispelling the
impression of adhocness. This paper is dedicated to Leon Henkin, a deep
logician who has changed the way we all work, while also being an always open,
modest, and encouraging colleague and friend.Comment: 27 pages. To appear in: The life and work of Leon Henkin: Essays on
his contributions (Studies in Universal Logic) eds: Manzano, M., Sain, I. and
Alonso, E., 201
Aptamer-based multiplexed proteomic technology for biomarker discovery
Interrogation of the human proteome in a highly multiplexed and efficient manner remains a coveted and challenging goal in biology. We present a new aptamer-based proteomic technology for biomarker discovery capable of simultaneously measuring thousands of proteins from small sample volumes (15 [mu]L of serum or plasma). Our current assay allows us to measure ~800 proteins with very low limits of detection (1 pM average), 7 logs of overall dynamic range, and 5% average coefficient of variation. This technology is enabled by a new generation of aptamers that contain chemically modified nucleotides, which greatly expand the physicochemical diversity of the large randomized nucleic acid libraries from which the aptamers are selected. Proteins in complex matrices such as plasma are measured with a process that transforms a signature of protein concentrations into a corresponding DNA aptamer concentration signature, which is then quantified with a DNA microarray. In essence, our assay takes advantage of the dual nature of aptamers as both folded binding entities with defined shapes and unique sequences recognizable by specific hybridization probes. To demonstrate the utility of our proteomics biomarker discovery technology, we applied it to a clinical study of chronic kidney disease (CKD). We identified two well known CKD biomarkers as well as an additional 58 potential CKD biomarkers. These results demonstrate the potential utility of our technology to discover unique protein signatures characteristic of various disease states. More generally, we describe a versatile and powerful tool that allows large-scale comparison of proteome profiles among discrete populations. This unbiased and highly multiplexed search engine will enable the discovery of novel biomarkers in a manner that is unencumbered by our incomplete knowledge of biology, thereby helping to advance the next generation of evidence-based medicine
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