552 research outputs found
Study of controlled diffusion stator blading. 1. Aerodynamic and mechanical design report
Pratt & Whitney Aircraft is conducting a test program for NASA in order to demonstrate that a controlled-diffusion stator provides low losses at high loadings and Mach numbers. The technology has shown great promise in wind tunnel tests. Details of the design of the controlled diffusion stator vanes and the multiple-circular-arc rotor blades are presented. The stage, including stator and rotor, was designed to be suitable for the first-stage of an advanced multistage, high-pressure compressor
The Possible White Dwarf-Neutron Star Connection
The current status of the problem of whether neutron stars can form, in close
binary systems, by accretion-induced collapse (AIC) of white dwarfs is
examined. We find that, in principle, both initially cold C+O white dwarfs in
the high-mass tail of their mass distribution in binaries and O+Ne+Mg white
dwarfs can produce neutron stars. Which fractions of neutron stars in different
types of binaries (or descendants from binaries) might originate from this
process remains uncertain.Comment: 6 pages. To appear in "White Dwarfs", ed. J. Isern, M. Hernanz, and
E. Garcia-Berro (Dordrecht: Kluwer
Blue carbon stocks in Baltic Sea eelgrass (Zostera marina) meadows
Although seagrasses cover only a minor fraction of the ocean seafloor, their
carbon sink capacity accounts for nearly one-fifth of the total oceanic
carbon burial and thus play a critical structural and functional role in
many coastal ecosystems. We sampled 10 eelgrass (<i>Zostera marina</i>) meadows in Finland and 10
in Denmark to explore seagrass carbon stocks (C<sub>org</sub> stock) and carbon
accumulation rates (C<sub>org</sub> accumulation) in the Baltic Sea area. The study
sites represent a gradient from sheltered to exposed locations in both
regions to reflect expected minimum and maximum stocks and accumulation. The
C<sub>org</sub> stock integrated over the top 25âŻcm of the sediment averaged 627âŻgâŻCâŻm<sup>â2</sup> in Finland, while in Denmark the average C<sub>org</sub> stock was over
6 times higher (4324âŻgâŻCâŻm<sup>â2</sup>). A conservative estimate of the total
organic carbon pool in the regions ranged between 6.98 and 44.9âŻtâŻCâŻha<sup>â1</sup>.
Our results suggest that the Finnish eelgrass meadows are minor carbon sinks
compared to the Danish meadows, and that majority of the C<sub>org</sub> produced in
the Finnish meadows is exported. Our analysis further showed that
>âŻ40âŻ% of the variation in the C<sub>org</sub> stocks was explained by
sediment characteristics, i.e. dry density, porosity and silt content. In
addition, our analysis show that the rootâŻ:âŻshoot ratio of <i>Z. marina</i> explained
>âŻ12âŻ% and the contribution of <i>Z. marina</i> detritus to the sediment surface
C<sub>org</sub> pool explained >âŻ10âŻ% of the variation in the C<sub>org</sub> stocks.
The mean monetary value for the present carbon storage and carbon sink
capacity of eelgrass meadows in Finland and Denmark, were 281 and 1809âŻEURâŻha<sup>â1</sup>, respectively. For a more comprehensive picture of
seagrass carbon storage capacity, we conclude that future blue carbon
studies should, in a more integrative way, investigate the interactions
between sediment biogeochemistry, seascape structure, plant species
architecture and the hydrodynamic regime
Galactic Cosmic Rays from Superbubbles and the Abundances of Lithium, Beryllium, and Boron
In this article we study the galactic evolution of the LiBeB elements within
the framework of a detailed model of the chemical evolution of the Galaxy that
includes galactic cosmic ray nucleosynthesis by particles accelerated in
superbubbles. The chemical composition of the superbubble consists of varying
proportions of ISM and freshly supernova synthesized material. The
observational trends of 6 LiBeB evolution are nicely reproduced by models in
which GCR come from a mixture of 25% of supernova material with 75% of ISM,
except for 6 Li, for which maybe an extra source is required at low
metallicities. To account for 7 Li evolution several additional sources have
been considered (neutrino-induced nucleosynthesis, nova outbursts, C-stars).
The model fulfills the energetic requirements for GCR acceleration.Comment: 25 pages, 9 figures. Accepted for publication in the Astrophysical
Journa
Effective Field Theory Program for Conformal Quantum Anomalies
The emergence of conformal states is established for any problem involving a
domain of scales where the long-range, SO(2,1) conformally invariant
interaction is applicable. Whenever a clear-cut separation of ultraviolet and
infrared cutoffs is in place, this renormalization mechanism produces binding
in the strong-coupling regime. A realization of this phenomenon, in the form of
dipole-bound anions, is discussed.Comment: 15 pages. Expanded, with additional calculational details. To be
published in Phys. Rev.
Impact of RNA Editing on Functions of the Serotonin 2C Receptor in vivo
Transcripts encoding 5-HT2C receptors are modified posttranscriptionally by RNA editing, generating up to 24 protein isoforms. In recombinant cells, the fully edited isoform, 5-HT2C-VGV, exhibits blunted G-protein coupling and reduced constitutive activity. The present studies examine the signal transduction properties of 5-HT2C-VGV receptors in brain to determine the in vivo consequences of altered editing. Using mice solely expressing the 5-HT2C-VGV receptor (VGV/Y), we demonstrate reduced G-protein coupling efficiency and high-affinity agonist binding of brain 5-HT2C-VGV receptors. However, enhanced behavioral sensitivity to a 5-HT2C receptor agonist was also seen in mice expressing 5-HT2C-VGV receptors, an unexpected finding given the blunted G-protein coupling. In addition, mice expressing 5-HT2C-VGV receptors had greater sensitivity to a 5-HT2C inverse agonist/antagonist enhancement of dopamine turnover relative to wild-type mice. These behavioral and biochemical results are most likely explained by increases in 5-HT2C receptor binding sites in the brains of mice solely expressing 5-HT2C-VGV receptors. We conclude that 5-HT2C-VGV receptor signaling in brain is blunted, but this deficiency is masked by a marked increase in 5-HT2C receptor binding site density in mice solely expressing the VGV isoform. These findings suggest that RNA editing may regulate the density of 5-HT2C receptor binding sites in brain. We further caution that the pattern of 5-HT2C receptor RNA isoforms may not reflect the pattern of protein isoforms, and hence the inferred overall function of the receptor
Detection of emerging parvoviruses and anellovirus in lung of captive wild boars.
Projeto/Plano de Ação: 02.11.10.600-03
Caracterização do perfil sorolĂłgico de nulĂparas suĂnas e da progĂȘnie frente ao parvovĂrus suĂno.
Projeto: 03.09.00.046
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