380 research outputs found
The Combined Release and Radiation Effects Satellite (CRRES) program: A unique series of scientific experiments
The Defense Department and NASA have joined in a program to study the space environment which surrounds the earth and the effects of space radiation on modern satellite electronic systems. The Combined Release and Radiation Effects Satellite (CRRES) will carry an array of active experiments including chemical releases and a complement of sophisticated scientific instruments to accomplish these objectives. Other chemical release active experiments will be performed with sub-orbital rocket probes. The chemical releases will 'paint' the magnetic and electric fields of earthspace with clouds of glowing ions. Earthspace will be a laboratory, and the releases will be studied with an extensive network of ground-, aircraft-, and satellite-based diagnostic instruments. Some of the topics discussed include the following: the effects of earthspace; the need for active experiments; types of chemical releases; the CRRES program schedule; international support and coordinated studies; photographing chemical releases; information on locating chemical releases for observation by the amateur; and CRRES as a program
Eclipsing Binaries as Astrophysical Laboratories: Internal Structure, Convective Core Overshooting and Evolution of the B-star Components of V380 Cygni
New photometric solutions have been carried out on the important eccentric
eclipsing system V380 Cygni (B1.5II-III + B2V) from UBV differential
photoelectric photometry obtained by us. The photometric elements obtained from
the analysis of the light curves have been combined with the spectroscopic
solution recently published by Popper & Guinan and have led to the physical
properties of the system components. The effective temperature of the stars has
been determined by fitting IUE UV spectrophotometry to Kurucz model atmospheres
and compared with other determinations from broad-band and intermediate-band
standard photometry. The values of mass, absolute radius, and effective
temperature, for the primary and secondary stars are: 11.1+/-0.5 Mo, 14.7+/-0.2
Ro, 21350+/-400 K, and 6.95+/-0.25 Mo, 3.74+/-0.07 Ro, 20500+/-500 K,
respectively. In addition, a re-determination of the system's apsidal motion
rate has been done from the analysis of 12 eclipse timings obtained from 1923
to 1995. Using stellar structure and evolutionary models with modern input
physics, tests on the extent of convection in the core of the more massive star
of the system have been carried out. Both the analysis of the log g-log Teff
diagram and the apsidal motion study indicate a star with a larger convective
core, and thus more centrally condensed, than currently assumed. This has been
quantified in form of an overshooting parameter with a value of 0.6+/-0.1.
Finally, the tidal evolution of the system (synchronization and circularization
times) has also been studied.Comment: 23 pages, 5 figures, version accepted for publication in Ap
Spitzer 24 um Images of Planetary Nebulae
Spitzer MIPS 24 um images were obtained for 36 Galactic planetary nebulae
(PNe) whose central stars are hot white dwarfs (WDs) or pre-WDs with effective
temperatures of ~100,000 K or higher. Diffuse 24 um emission is detected in 28
of these PNe. The eight non-detections are angularly large PNe with very low
H-alpha surface brightnesses. We find three types of correspondence between the
24 um emission and H-alpha line emission of these PNe: six show 24 um emission
more extended than H-alpha emission, nine have a similar extent at 24 um and
H-alpha, and 13 show diffuse 24 um emission near the center of the H-alpha
shell. The sizes and surface brightnesses of these three groups of PNe and the
non-detections suggest an evolutionary sequence, with the youngest ones being
brightest and the most evolved ones undetected. The 24 um band emission from
these PNe is attributed to [O IV] 25.9 um and [Ne V] 24.3 um line emission and
dust continuum emission, but the relative contributions of these three
components depend on the temperature of the central star and the distribution
of gas and dust in the nebula.Comment: 24 pages, 8 figures, to appear in the Astronomical Journal, September
issue. Relace previous file; two references are added and typos are correcte
The Torino Observatory Parallax Program: White Dwarf Candidates
We present parallax determinations for six white dwarf candidates in the
Torino Observatory Parallax Program. The absolute parallaxes are found with
precisions at the 2-3 milliarcsecond level. For WD 1126+185 we find a distance
incompatible with being a white dwarf, implying an incorrect classification.
For WD 2216+484 we find our distance is consistent with a simple DA white dwarf
rather than a composite system as previously proposed in the literature. In
general it is found that the published photometric distance is an overestimate
of the distance found here.Comment: AA paper, 7 pages, 4 figure
The stellar content of the Hamburg/ESO survey. I. Automated selection of DA white dwarfs
We describe automatic procedures for the selection of DA white dwarfs in the
Hamburg/ESO objective-prism survey (HES). For this purpose, and the selection
of other stellar objects (e.g., metal-poor stars and carbon stars), a flexible,
robust algorithm for detection of stellar absorption and emission lines in the
digital spectra of the HES was developed. Broad band (U-B, B-V) and narrow band
(Str\"omgren c_1) colours can be derived directly from HES spectra, with
precisions of sigma(U-B)=0.092mag; sigma(B-V)=0.095mag; sigma(c_1)=0.15mag.
We describe simulation techniques that allow to convert model or slit spectra
to HES spectra. These simulated objective-prism spectra are used to determine
quantitative selection criteria, and for the study of selection functions. We
present an atlas of simulated HES spectra of DA and DB white dwarfs.
Our current selection algorithm is tuned to yield maximum efficiency of the
candidate sample (minimum contamination with non-DAs). DA candidates are
selected in the B-V versus U-B and c_1 versus W_\lambda(Hbeta+Hgamma+Hdelta)
parameter spaces. The contamination of the resulting sample with hot subdwarfs
is expected to be as low as ~8%, while there is essentially no contamination
with main sequence or horizontal branch stars. We estimate that with the
present set of criteria, ~80% of DAs present in the HES database are recovered.
A yet higher degree of internal completeness could be reached at the expense of
higher contamination. However, the external completeness is limited by
additional losses caused by proper motion effects and the epoch differences
between direct and spectral plates used in the HES.Comment: A&A in press. 15 pages, 15 figures. Includes table with coordinates
and magnitudes for 46 spectroscopically confirmed DA white dwarfs and hot
subdwarf
Interactions between a Trawl Fishery and Spatial Closures for Biodiversity Conservation in the Great Barrier Reef World Heritage Area, Australia
Background\ud
The Queensland East Coast Otter Trawl Fishery (ECOTF) for penaeid shrimp fishes within Australia's Great Barrier Reef World Heritage Area (GBRWHA). The past decade has seen the implementation of conservation and fisheries management strategies to reduce the impact of the ECOTF on the seabed and improve biodiversity conservation. New information from electronic vessel location monitoring systems (VMS) provides an opportunity to review the interactions between the ECOTF and spatial closures for biodiversity conservation.\ud
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Methodology and Results\ud
We used fishing metrics and spatial information on the distribution of closures and modelled VMS data in a geographical information system (GIS) to assess change in effort of the trawl fishery from 2001–2009 and to quantify the exposure of 70 reef, non-reef and deep water bioregions to trawl fishing. The number of trawlers and the number of days fished almost halved between 2001 and 2009 and new spatial closures introduced in 2004 reduced the area zoned available for trawl fishing by 33%. However, we found that there was only a relatively minor change in the spatial footprint of the fishery as a result of new spatial closures. Non-reef bioregions benefited the most from new spatial closures followed by deep and reef bioregions.\ud
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Conclusions/Significance\ud
Although the catch of non target species remains an issue of concern for fisheries management, the small spatial footprint of the ECOTF relative to the size of the GBRWHA means that the impact on benthic habitats is likely to be negligible. The decline in effort as a result of fishing industry structural adjustment, increasing variable costs and business decisions of fishers is likely to continue a trend to fish only in the most productive areas. This will provide protection for most benthic habitats without any further legislative or management intervention
Doom and Boom on a Resilient Reef: Climate Change, Algal Overgrowth and Coral Recovery
Background: Coral reefs around the world are experiencing large-scale degradation, largely due to global climate change, overfishing, diseases and eutrophication. Climate change models suggest increasing frequency and severity of warming-induced coral bleaching events, with consequent increases in coral mortality and algal overgrowth. Critically, the recovery of damaged reefs will depend on the reversibility of seaweed blooms, generally considered to depend on grazing of the seaweed, and replenishment of corals by larvae that successfully recruit to damaged reefs. These processes usually take years to decades to bring a reef back to coral dominance
C-C Chemokine Receptor 5 on Pulmonary Mesenchymal Cells Promotes Experimental Metastasis via the Induction of Erythroid Differentiation Regulator 1
C-C Chemokine receptor five knockout (Ccr5-/-) mice develop fewer experimental pulmonary metastases than wild type (WT) mice. This phenomenon was explored by applying gene-expression profiling to the lungs of mice with these metastases. Consequently, Erythroid Differentiation Regulator 1 (Erdr1) was identified as upregulated in the WT mice. Though commonly associated with bone marrow stroma, Erdr1 was differentially expressed in WT pulmonary mesenchymal cells (PMCs) and murine embryonic fibroblasts (MEFs). Moreover, the Ccr5 ligand Ccl4 increased its expression by 3.36 ± 0.14 fold. Ccr5 signaling was dependent on the Map2k but not the Pi3k pathway since treatment with U0126 inhibited upregulation of Erdr1 but treatment with LY294002 increased the expression by 3.44 ± 0.92 fold (p < 0.05). Erdr1's effect on B16-F10 melanoma metastasis was verified by the adoptive transfer of WT MEFs into Ccr5-/- mice. In this model, MEFs that had been transduced with Erdr1 shRNA lowered metastasis by 33% compared to control transduced MEFs. The relevance of ERDR1 on human disease was assessed by co-culturing chronic lymphocytic leukemia (CLL) cells with M2-10B4 stromal cells that had been transfected with shRNA or control plasmids. After 96 hours of co-culture, the cell counts were higher with control cell lines compared with Erdr1 knockdown lines (OR 1.88 ± 0.27, 2.52 ± 0.66 respectively). This increase was associated with a decrease in apoptotic cells (OR 0.69 ± 0.18, 0.58 ± 0.12 respectively)
Effects of pretreatment hypothermia during resuscitated porcine hemorrhagic shock
OBJECTIVES: Accidental hypothermia increases mortality and morbidity after hemorrhage, but controversial data are available on the effects of therapeutic hypothermia. Therefore, we tested the hypothesis whether moderate pretreatment hypothermia would beneficially influence organ dysfunction during long-term, porcine hemorrhage and resuscitation. DESIGN: Prospective, controlled, randomized study. SETTING: University animal research laboratory. SUBJECTS: Twenty domestic pigs of either gender. INTERVENTIONS: Using an extracorporeal heat exchanger, anesthetized and instrumented animals were maintained at 38 degrees C, 35 degrees C, or 32 degrees C core temperature and underwent 4 hours of hemorrhage (removal of 40% of the blood volume and subsequent blood removal/retransfusion to maintain mean arterial pressure at 30 mm Hg). Resuscitation comprised of hydroxyethyl starch and norepinephrine infusion titrated to maintain mean arterial pressure at preshock values. MEASUREMENTS AND MAIN RESULTS: Before, immediately at the end of, and 12 and 22 hours after hemorrhage, we measured systemic and regional hemodynamics (portal vein, hepatic and right kidney artery ultrasound flow probes) and oxygen transport, and nitric oxide and cytokine production. Hemostasis was assessed by rotation thromboelastometry. Postmortem biopsies were analyzed for histomorphology (hematoxylin and eosin staining) and markers of apoptosis (kidney Bcl-xL and caspase-3 expression). Hypothermia at 32 degrees C attenuated the shock-related lactic acidosis but caused metabolic acidosis, most likely resulting from reduced carbohydrate oxidation. Although hypothermia did not further aggravate shock-related coagulopathy, it caused a transitory attenuation of kidney and liver dysfunction, which was ultimately associated with reduced histological damage and more pronounced apoptosis. CONCLUSIONS: During long-term porcine hemorrhage and resuscitation, moderate pretreatment hypothermia was associated with a transitory attenuation of organ dysfunction and less severe histological tissue damage despite more pronounced metabolic acidosis. This effect is possibly due to a switch from necrotic to apoptotic cell death, ultimately resulting from reduced tissue energy deprivation during the shock phase
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