5,126 research outputs found
LANDSAT/coastal processes
The author has identified the following significant results. Correlations between the satellite radiance values water color, Secchi disk visibility, turbidity, and attenuation coefficients were generally good. The residual was due to several factors including systematic errors in the remotely sensed data, errors, small time and space variations in the water quality measurements, and errors caused by experimental design. Satellite radiance values were closely correlated with the optical properties of the water
Prosthesis coupling
A coupling for use in an apparatus for connecting a prosthesis to the bone of a stump of an amputated limb is described which permits a bio-compatible carbon sleeve forming a part of the prosthesis connector to float so as to prevent disturbing the skin seal around the carbon sleeve. The coupling includes a flexible member interposed between a socket that is inserted within an intermedullary cavity of the bone and the sleeve. A lock pin is carried by the prosthesis and has a stem portion which is adapted to be coaxially disposed and slideably within the tubular female socket for securing the prosthesis to the stump. The skin around the percutaneous carbon sleeve is able to move as a result of the flexing coupling so as to reduce stresses caused by changes in the stump shape and/or movement between the bone and the flesh portion of the stump
Analysis of surface tris (2,3-dibromopropyl) phosphate on chlorobutyl rubber SCAPE suits
Tris (2,30-dibromopropyl) phosphate was used to confer flame retardant properties on butyl rubber formulations used in protective clothing such as the self-contained atmospheric protective ensembles (SCAPE suits) worn at Kennedy Space Center in support of Apollo, Skylab, and Apollo-Soyuz missions since 1966. Because tris (2,3-dibromopropyl) phosphate is mutagenic, surface concentrations of the compound in SCAPE suits were investigated as were as potential methods of removing or isolating it. Analytical procedures for determining surface concentrations of the tris compound on non-porous materials are described. Soap-and-water washing is the most efficient method of removing the compound from fabricated SCAPE suits and unused material
High-precision ID-TIMS cassiterite UāPb systematics using a low-contamination hydrothermal decomposition: implications for LA-ICP-MS and ore deposit geochronology
Cassiterite (SnO2) is the most common ore phase of Sn. Typically
containing 1ā100āĀµgāgā1 of uranium and relatively low concentrations of common
Pb, cassiterite has been increasingly targeted for UāPb geochronology,
principally via microbeam methods, to understand the timing and durations
of granite-related magmaticāhydrothermal systems throughout geological time.
However, due to the extreme resistance of cassiterite to most forms of acid
digestion, there has been no published method permitting the complete,
closed-system decomposition of cassiterite under conditions in which the basic
necessities of measurement by isotope dilution can be met, leading to a
paucity of reference and validation materials. To address this a new low
blank (<ā1āpgāPb) method for the complete acid decomposition of
cassiterite utilising HBr in the presence of a mixed UāPb tracer, U and Pb
purification, and thermal ionisation mass
spectrometry (TIMS) analyses has been developed. Decomposition rates have
been experimentally evaluated under a range of conditions. A careful balance
of time and temperature is required due to competing effects (e.g. HBr
oxidation), yet the decomposition of 500āĀµm diameter fragments of
cassiterite is readily achievable over periods comparable to zircon
decomposition. Its acid-resistant nature can be turned into an advantage by
leaching common Pb-bearing phases (e.g. sulfides, silicates) without
disturbing the UāPb systematics of the cassiterite lattice. The archetypal
SnāW greisen deposit of Cligga Head, SW England, is used to define accuracy
relative to chemical abrasionāisotope dilutionāthermal ionisation mass
spectrometry (CA-ID-TIMS) zircon UāPb ages and demonstrates the potential of
this new method for resolving high-resolution timescales (<0.1ā%) of magmaticāhydrothermal systems. However, data also indicate that the
isotopic composition of initial common Pb varies significantly, both between
crystals and within a single crystal. This is attributed to significant
fluidārock interactions and the highly F-rich acidic nature of the
hydrothermal system. At microbeam precision levels, this issue is largely
unresolvable and can result in significant inaccuracy in interpreted ages.
The ID-TIMS UāPb method described herein can, for the first time, be used to
properly characterise suitable reference materials for microbeam
cassiterite UāPb analyses, thus improving the accuracy of the UāPb
cassiterite chronometer as a whole.</p
The RCB star V854 Cen is surrounded by a hot dusty shell
Aims : The hydrogen-deficient supergiants known as R Coronae Borealis (RCB)
stars might be the result of a double-degenerate merger of two white dwarfs
(WDs), or a final helium shell flash in a planetary nebula central star. In
this context, any information on the geometry of their circumstellar
environment and, in particular, the potential detection of elongated
structures, is of great importance. Methods : We obtained near-IR observations
of V854 Cen with the AMBER recombiner located at the Very Large Telescope
Interferometer (VLTI) array with the compact array (B35m) in 2013 and the
long array (B140m) in 2014. At each time, V854 Cen was at maximum light.
The - and -band continua were investigated by means of spectrally
dependant geometric models. These data were supplemented with mid-IR VISIR/VLT
images. Results : A dusty slightly elongated over density is discovered both in
the - and -band images. With the compact array, the central star is
unresolved (\,mas), but a flattened dusty environment of mas is discovered whose flux increases from about 20% in the
band to reach about 50% at 2.3\micron, which indicates hot
(T1500\,K) dust in the close vicinity of the star. The major axis is
oriented at a position angle (P.A.) of 12629. Adding the long-array
configuration dataset provides tighter constraints on the star diameter
( mas), a slight increase of the overdensity to
mas and a consistent P.A. of 13349. The closure phases, sensitive to
asymmetries, are null and compatible with a centro-symmetric, unperturbed
environment excluding point sources at the level of 3% of the total flux in
2013 and 2014. The VISIR images exhibit a flattened aspect ratio at the 15-20%
level at larger distances (1\arcsec) with a position angle of
9219, marginally consistent with the interferometric observations.
Conclusions : This is the first time that a moderately elongated structure has
been observed around an RCB star. These observations confirm the numerous
suggestions for a bipolar structure proposed for this star in the literature,
which were mainly based on polarimetric and spectroscopic observations.Comment: Accepted by A\&A, new version after language editing, Astronomy and
Astrophysics (2014
Effective Hamiltonian Approach to Hyperon Beta Decay with Final-State Baryon Polarization
Using an effective Hamiltonian approach, we obtain expressions for hyperon
beta decay final-state baryon polarization. Terms through second order in the
energy release are retained. The resulting approximate expressions are much
simpler and more compact than the exact expressions, and they agree closely
with them.Comment: 1 Figure Will appear in Phys Rev D 60 Article 117505 (Dec 1, 1999
Challenges and opportunities in the care of survivors of adolescent and young adult (AYA) cancers
Total column CO_2 measurements at Darwin, Australia ā site description and calibration against in situ aircraft profiles
An automated Fourier Transform Spectroscopic (FTS) solar observatory was established in Darwin, Australia in August 2005. The laboratory is part of the Total Carbon Column Observing Network, and measures atmospheric column abundances of CO_2 and O_2 and other gases. Measured CO_2 columns were calibrated against integrated aircraft profiles obtained during the TWP-ICE campaign in JanuaryāFebruary 2006, and show good agreement with calibrations for a similar instrument in Park Falls, Wisconsin. A clear-sky low airmass relative precision of 0.1% is demonstrated in the CO2 and O2 retrieved column-averaged volume mixing ratios. The 1% negative bias in the FTS X_(CO_2) relative to the World Meteorological Organization (WMO) calibrated in situ scale is within the uncertainties of the NIR spectroscopy and analysis
Dust around red supergiants in the Magellanic Clouds
It is both surprising and exciting to find that young galaxies at high redshift contain large dust masses. For galaxies at z \u3e 5, after only 1 Gyr, there has not been time for low-mass stars to have evolved to the AGB phase and produce dust. In such galaxies, Type II SNe and red supergiants (RSGs) may even dominate the dust production rate. It has long been known that RSG atmospheres produce dust, but little is known about it. We are pursuing three parallel studies to better understand RSG dust. First, we are using optical spectra and JHK photometry to characterize the optical and near-IR extinction curves of the RSGs. Second, we are using the optical spectra combined with 2MASS, IRAC and MIPS photometry to estimate the dust mass loss rates from Local Group RSGs. In addition, we will use our Monte Carlo radiative transfer models to analyze the emission from dust in the circumstellar shells. Third, the final piece of the puzzle is being provided by obtaining new IRS spectra of LMC and SMC RSGs. We plan to use the IRS to make a systematic study of the dust properties in RSG shells in the LMC and SMC so that we can probe how they may vary with a large range of galactic metallicities. The derived stellar SEDs and extinction curves will be combined with Spitzer IRAC and MIPS photometry and IRS spectra for use as inputs to our Monte Carlo codes which will be used to study the composition, size distributions and clumpiness of the dust. Ā© 2009 International Astronomical Union
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