26 research outputs found
Virginia Beach offshore sediment study
This investigation was initiated from discussions among members of the Minerals Management Service-Virginia Task Force in an effort to locate a nearby and offshore source of beach-quality sand for the resort strip at Virginia Beach. Because of the increasing difficulty of relying upon land-based material, attention has been focused on investigating offshore sources. Previous work (Kimball and others, 1991) suggests an offshore deposit of beach-quality sands is located on a shoal between 3 and 8 km east of Sandbridge. Planned vibracoring on this shoal during the fall of 1993 should establish the viability of the sand occurrence. Although material from this site could . be used to nourish the resort strip, the dredging and transportation costs for an offshore resource would be decreased if another source could be located closer to the strip
Characterization of the Differentiation and Leptin Secretion Profile of Adult Stem Cells on Patterned Polylactide Films
Several issues need to be better understood before breast tissue engineering becomes a clinically viable option. One of the most important aspects is the interaction between cells and the microtopography of the implant surface. The aim of this study was to evaluate the efficacy of D1 cells, multipotent mouse bone marrow stromal precursors, in differentiating to adipocytes and to characterize their metabolic activity (lactic acid released and glucose consumed), leptin secretion and lipid production when cultured on patterned poly(L-lactide) (PLLA) films. It was determined that, by appropriate stimulation, the D1 cells displayed morphological characteristics of adipocytes and produced lipid. The results showed that a patterned surface did affect the rate of lipid production. Polynomial models were proposed to predict the amount of leptin secreted by the cells over a period of time
Main Belt Asteroids with WISE/NEOWISE I: Preliminary Albedos and Diameters
We present initial results from the Wide-field Infrared Survey Explorer
(WISE), a four-band all-sky thermal infrared survey that produces data well
suited to measuring the physical properties of asteroids, and the NEOWISE
enhancement to the WISE mission allowing for detailed study of Solar system
objects. Using a NEATM thermal model fitting routine we compute diameters for
over 100,000 Main Belt asteroids from their IR thermal flux, with errors better
than 10%. We then incorporate literature values of visible measurements (in the
form of the H absolute magnitude) to determine albedos. Using these data we
investigate the albedo and diameter distributions of the Main Belt. As observed
previously, we find a change in the average albedo when comparing the inner,
middle, and outer portions of the Main Belt. We also confirm that the albedo
distribution of each region is strongly bimodal. We observe groupings of
objects with similar albedos in regions of the Main Belt associated with
dynamical breakup families. Asteroid families typically show a characteristic
albedo for all members, but there are notable exceptions to this. This paper is
the first look at the Main Belt asteroids in the WISE data, and only represents
the preliminary, observed raw size and albedo distributions for the populations
considered. These distributions are subject to survey biases inherent to the
NEOWISE dataset and cannot yet be interpreted as describing the true
populations; the debiased size and albedo distributions will be the subject of
the next paper in this series.Comment: Accepted to ApJ. Online table to also appear on the publisher's
websit
WISE/NEOWISE Observations of the Jovian Trojans: Preliminary Results
We present the preliminary analysis of over 1739 known and 349 candidate
Jovian Trojans observed by the NEOWISE component of the Wide-field Infrared
Survey Explorer (WISE). With this survey the available diameters, albedos and
beaming parameters for the Jovian Trojans have been increased by more than an
order of magnitude compared to previous surveys. We find that the Jovian Trojan
population is very homogenous for sizes larger than km (close to the
detection limit of WISE for these objects). The observed sample consists almost
exclusively of low albedo objects, having a mean albedo value of .
The beaming parameter was also derived for a large fraction of the observed
sample, and it is also very homogenous with an observed mean value of
. Preliminary debiasing of the survey shows our observed sample is
consistent with the leading cloud containing more objects than the trailing
cloud. We estimate the fraction to be N(leading)/N(trailing) , lower than the value derived by others.Comment: Accepted for publication in Astrophysical Journal. Electronic table
will be available at the publishers websit
WISE/NEOWISE observations of Active Bodies in the Main Belt
We report results based on mid-infrared photometry of 5 active main belt
objects (AMBOs) detected by the Wide-field Infrared Survey Explorer (WISE)
spacecraft. Four of these bodies, P/2010 R2 (La Sagra), 133P/Elst-Pizarro,
(596) Scheila, and 176P/LINEAR, showed no signs of activity at the time of the
observations, allowing the WISE detections to place firm constraints on their
diameters and albedos. Geometric albedos were in the range of a few percent,
and on the order of other measured comet nuclei. P/2010 A2 was observed on
April 2-3, 2010, three months after its peak activity. Photometry of the coma
at 12 and 22 {\mu}m combined with ground-based visible-wavelength measurements
provides constraints on the dust particle mass distribution (PMD), dlogn/dlogm,
yielding power-law slope values of {\alpha} = -0.5 +/- 0.1. This PMD is
considerably more shallow than that found for other comets, in particular
inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. It
is similar to the PMD seen for 9P/Tempel 1 in the immediate aftermath of the
Deep Impact experiment. Upper limits for CO2 & CO production are also provided
for each AMBO and compared with revised production numbers for WISE
observations of 103P/Hartley 2.Comment: 32 Pages, including 5 Figure
NEOWISE Observations of Near-Earth Objects: Preliminary Results
With the NEOWISE portion of the \emph{Wide-field Infrared Survey Explorer}
(WISE) project, we have carried out a highly uniform survey of the near-Earth
object (NEO) population at thermal infrared wavelengths ranging from 3 to 22
m, allowing us to refine estimates of their numbers, sizes, and albedos.
The NEOWISE survey detected NEOs the same way whether they were previously
known or not, subject to the availability of ground-based follow-up
observations, resulting in the discovery of more than 130 new NEOs. The
survey's uniformity in sensitivity, observing cadence, and image quality have
permitted extrapolation of the 428 near-Earth asteroids (NEAs) detected by
NEOWISE during the fully cryogenic portion of the WISE mission to the larger
population. We find that there are 98119 NEAs larger than 1 km and
20,5003000 NEAs larger than 100 m. We show that the Spaceguard goal of
detecting 90% of all 1 km NEAs has been met, and that the cumulative size
distribution is best represented by a broken power law with a slope of
1.320.14 below 1.5 km. This power law slope produces 1,900
NEAs with 140 m. Although previous studies predict another break in the
cumulative size distribution below 50-100 m, resulting in an increase in
the number of NEOs in this size range and smaller, we did not detect enough
objects to comment on this increase. The overall number for the NEA population
between 100-1000 m are lower than previous estimates. The numbers of near-Earth
comets will be the subject of future work.Comment: Accepted to Ap
WISE/NEOWISE Observations of the Hilda Population: Preliminary Results
We present the preliminary analysis of 1023 known asteroids in the Hilda
region of the Solar System observed by the NEOWISE component of the Wide-field
Infrared Survey Explorer (WISE). The sizes of the Hildas observed range from
km. We find no size - albedo dependency as reported by other
projects. The albedos of our sample are low, with a weighted mean value , for all sizes sampled by the NEOWISE survey. We observed a
significant fraction of the objects in the two known collisional families in
the Hilda population. It is found that the Hilda collisional family is
brighter, with weighted mean albedo of , than the general
population and dominated by D-type asteroids, while the Schubart collisional
family is darker, with weighted mean albedo of (). Using
the reflected sunlight in the two shortest WISE bandpasses we are able to
derive a method for taxonomic classification of of the Hildas
detected in the NEOWISE survey. For the Hildas with diameter larger than 30km
there are D-type asteroids and C-/P-type
asteroids (with the majority of these being P-types).Comment: Accepted for publication in Astrophysical Journal. Electronic table
to be published on the publishers websit
Preliminary Results from NEOWISE: An Enhancement to the Wide-field Infrared Survey Explorer for Solar System Science
The \emph{Wide-field Infrared Survey Explorer} has surveyed the entire sky at
four infrared wavelengths with greatly improved sensitivity and spatial
resolution compared to its predecessors, the \emph{Infrared Astronomical
Satellite} and the \emph{Cosmic Background Explorer}. NASA's Planetary Science
Division has funded an enhancement to the \WISE\ data processing system called
"NEOWISE" that allows detection and archiving of moving objects found in the
\WISE\ data. NEOWISE has mined the \WISE\ images for a wide array of small
bodies in our Solar System, including Near-Earth Objects (NEOs), Main Belt
asteroids, comets, Trojans, and Centaurs. By the end of survey operations in
February 2011, NEOWISE identified over 157,000 asteroids, including more than
500 NEOs and 120 comets. The NEOWISE dataset will enable a panoply of new
scientific investigations.Comment: ApJ accepte