520 research outputs found
Composition of Near-Earth Asteroid 2008 EV5: Potential target for Robotic and Human Exploration
We observed potentially hazardous asteroid (PHA) 2008 EV5 in the visible
(0.30-0.92 microns) and near-IR (0.75-2.5 microns) wavelengths to determine its
surface composition. This asteroid is especially interesting because it is a
potential target for two sample return mission proposals (Marco Polo-R and
Hayabusa-2) and human exploration due to its low delta-v for rendezvous. The
spectrum of 2008 EV5 is essentially featureless with exception of a weak
0.48-microns spin-forbidden Fe3+ absorption band. The spectrum also has an
overall blue slope. The albedo of 2008 EV5 remains uncertain with a lower limit
at 0.05 and a higher end at 0.20 based on thermal modeling. The Busch et al.
(2011) albedo estimate of 0.12 is consistent with our thermal modeling results.
The albedo and composition of 2008 EV5 are also consistent with a C-type
taxonomic classification (Somers et al. 2008). The best spectral match is with
CI carbonaceous chondrites similar to Orgueil, which also have a weak
0.48-microns feature and an overall blue slope. This 0.48-microns feature is
also seen in the spectrum of magnetite. The albedo of CI chondrites is at the
lower limit of our estimated range for the albedo of 2008 EV5.Comment: Pages: 19 Figures: 6 Tables:
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Sexual well-being and diurnal cortisol after prostate cancer treatment.
Sexual dysfunction and psychological distress are common after prostate cancer. Research has not examined the role of neuroendocrine markers of stress (e.g. cortisol). This study examines whether sexual functioning or sexual bother is associated with diurnal cortisol. Men treated for prostate cancer completed the University of California-Los Angeles Prostate Cancer Index and provided saliva samples four times daily for cortisol assessment. Higher sexual bother, but not sexual functioning, was associated with steeper cortisol slope. Better sexual functioning, and not sexual bother, was significantly associated with the cortisol awakening response. Assessment of stress and stress-reducing interventions might be warranted in sexual rehabilitation after prostate cancer
On the survivability and detectability of terrestrial meteorites on the moon
Materials blasted into space from the surface of early Earth may preserve a unique record of our planet's early surface environment. Armstrong et al. (2002) pointed out that such materials, in the form of terrestrial meteorites, may exist on the Moon and be of considerable astrobiological interest if biomarkers from early Earth are preserved within them. Here, we report results obtained via the AUTODYN hydrocode to calculate the peak pressures within terrestrial meteorites on the lunar surface to assess their likelihood of surviving the impact. Our results confirm the order-of-magnitude estimates of Armstrong et al. (2002) that substantial survivability is to be expected, especially in the case of relatively low velocity (ca. 2.5 km/s) or oblique (≤45°) impacts, or both. We outline possible mechanisms for locating such materials on the Moon and conclude that searching for them would be a scientifically valuable activity for future lunar exploration
Characterization of Asteroidal Basalts through Reflectance Spectroscopy and Implications for the Dawn Mission
There are currently five known groups of basaltic achondrites that represent material from distinct differentiated parent bodies. These are the howardite-eucrite-diogenite (HED) clan, mesosiderite silicates, angrites, Ibitira, and Northwest Africa (NWA) 011 [1]. Spectroscopically all these basaltic achondrite groups have absorption bands located near 1 and 2 microns due to the presence of pyroxene. Some of these meteorite types have spectra that are quite similar, but nevertheless have characteristics (e.g. spectral slope, band depths, etc.) that may be used to differentiate them from each other
Calibrations of phase abundance, composition, and particle size distribution for olivine-orthopyroxene mixtures from reflectance spectra
Spectral reflectance measurements of characterized (phase abundance, particle size) mixtures of olivine and orthopyroxene were utilized to define the correlations between spectral and albedo parameters of such assemblages and their mineralogical or textural properties. Thirty-three different spectral parameters falling into three general classes (relative or ratioed, absolute or albedo, and wavelength) were investigated for empirical sensitivity to one or more of the mixture properties. Theoretical considerations and previous experimental observations were utilized to understand their functional relationships. The ratio of areas for the 1- and 2-3µm absorption bands is shown to be a sensitive indicator of the olivine-orthopyroxene abundance and is very nearly independent of particle size and mineral composition. In conjunction with an abundance determination, the wavelength position of the 1-3tm absorption feature can be utilized to determine the molar iron contents of the olivine and orthopyroxene phases. This calibration is insensitive to particle size but will produce systematic deviations if the phases have significantly different iron contents or if more than a few percent of a clinopyroxene component is present. The spectral albedo in the 0.6- to 0.7-µm region is relatively insensitive to phase abundance and can be used to constrain particle size if phase composition has been determinedVarious portions of this work were supported at the University of Hawaii by NASA grant NSG-7312 and by a Sigma Xi Foundation grant to E.A.C. and at Rensselaer Polytechnic Institute by NASA grant NAGW-642. Planetary Geosciences Division, Hawaii Institute of Geophysics, University of Hawaii, publication4 70
Dairy bioactives and functional ingredients with skin health benefits
The potential of whey from Italian cheese productions to support skin health and anti-ageing mechanism was studied. The effect of whey on dermal and epidermal cells was evaluated. Whey inhibited the activity of elastase and tyrosinase enzymes by 60% and 32%, respectively. Whey cytotoxicity against tested skin cell lines, human fibroblasts (HDFa) and keratinocytes (HaCaT) was not observed. Moreover, the antioxidant activity of the samples was noted, after treatment with whey intracellular ROS level was decreased by 87% in comparison with the hydrogen peroxide-treated cells. Fibroblasts produced a significant amount of extracellular matrix molecules, collagen I, elastin and glycosaminoglycans as a result of treatment with tested whey. In addition, the ability of samples to improve the cell barrier integrity of keratinocytes was proven. The obtained results indicate that pure whey supports skin health and shows potential to be used by the cosmetic industry
NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results
The NEOWISE dataset offers the opportunity to study the variations in albedo
for asteroid classification schemes based on visible and near-infrared
observations for a large sample of minor planets. We have determined the
albedos for nearly 1900 asteroids classified by the Tholen, Bus and Bus-DeMeo
taxonomic classification schemes. We find that the S-complex spans a broad
range of bright albedos, partially overlapping the low albedo C-complex at
small sizes. As expected, the X-complex covers a wide range of albedos. The
multi-wavelength infrared coverage provided by NEOWISE allows determination of
the reflectivity at 3.4 and 4.6 m relative to the visible albedo. The
direct computation of the reflectivity at 3.4 and 4.6 m enables a new
means of comparing the various taxonomic classes. Although C, B, D and T
asteroids all have similarly low visible albedos, the D and T types can be
distinguished from the C and B types by examining their relative reflectance at
3.4 and 4.6 m. All of the albedo distributions are strongly affected by
selection biases against small, low albedo objects, as all objects selected for
taxonomic classification were chosen according to their visible light
brightness. Due to these strong selection biases, we are unable to determine
whether or not there are correlations between size, albedo and space
weathering. We argue that the current set of classified asteroids makes any
such correlations difficult to verify. A sample of taxonomically classified
asteroids drawn without significant albedo bias is needed in order to perform
such an analysis.Comment: Accepted to Ap
A Spectral Analysis of the Massalia Asteroid Family to Evaluate the L-Chondrite Source Hypothesis
A major research objective within asteroid science is to identify the source bodies of the meteorites. So far, possible or probable parent bodies have only been identified for a few meteorite types. These meteorite types include the H-type ordinary chon-drites [1,2], HEDs [3,4], pallasites [3], and mesosider-ites [5]. Identifying the parent bodies of meteorites helps to determine the location within the solar nebula where the geochemical processes, recorded in meteorites, took place. This has significantly increased our understanding of the evolution of the solar nebula and the early so-lar system [6].
Among the many meteorite types whose parent bodies are unknown are the L-chondrites. L-chondrites exhibit evidence of a shock event that occurred around 470 Ma, which implies that the L-chondrites resulted from an impact event which may have disrupted the L-chondrite parent body. This evidence is corroborated by fossil L-chondrite meteorites found in Ordovician sedimentary rocks dating to the same time period [7-12]. This suggests that if the source outcrop of the L-chondrites stills exists today, it is within an asteroid family.
The Massalia asteroid family has been suggested to be a possible source of the L-chondrites [13]. We are currently testing this hypothesis. So far, we have observed fourteen Massalia family asteroids, analyzed their spectra, and interpreted their spectra to determine their meteorite analogues in an effort to see whether or not the analogues support our hypothesis. This abstract reports the initial results for seven of these bodies
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