862 research outputs found
OGO-6 gas-surface energy transfer experiment
The kinetic energy flux of the upper atmosphere was analyzed using OGO-6 data. Energy transfer between 10 microwatts/sq cm and 0.1 W/sq cm was measured by short-term frequency changes of temperature-sensitive quartz crystals used in the energy transfer probe. The condition of the surfaces was continuously monitored by a quartz crystal microbalance to determine the effect surface contamination had on energy accommodation. Results are given on the computer analysis and laboratory tests performed to optimize the operation of the energy transfer probe. Data are also given on the bombardment of OGO-6 surfaces by high energy particles. The thermoelectrically-cooled quartz crystal microbalance is described in terms of its development and applications
Localization of Interaction using Fibre-Optic Shape Sensing in Soft-Robotic Surgery Tools
Minimally invasive surgery requires real-time tool tracking to guide the surgeon where depth perception and visual occlusion present navigational challenges. Although vision-based and external sensor-based tracking methods exist, fibre-optic sensing can overcome their limitations as they can be integrated directly into the device, are biocompatible, small, robust and geometrically versatile. In this paper, we integrate a fibre Bragg grating-based shape sensor into a soft robotic device. The soft robot is the pneumatically attachable flexible (PAF) rail designed to act as a soft interface between manipulation tools and intra-operative imaging devices. We demonstrate that the shape sensing fibre can detect the location of the tools paired with the PAF rail, by exploiting the change in curvature sensed by the fibre when a strain is applied to it. We then validate this with a series of grasping tasks and continuous US swipes, using the system to detect in real-time the location of the tools interacting with the PAF rail. The overall location-sensing accuracy of the system is 64.6%, with a margin of error between predicted location and actual location of 3.75 mm
Evaluating Genetic Viability of Pronghorn in Wind Cave National Park
The pronghorn (Antilocapra americana) was reintroduced into Wind Cave National Park, South Dakota, in 1914 and thus, has inhabited the Park for almost a century. A decline in the population has raised concern for the continued existence of pronghorn inside Wind Cave National Park. Historically, pronghorn numbers reached greater than 300 individuals in the 1960\u27s but declined to about 30 individuals by 2002. The primary objective of our study was to evaluate genetic characteristics of pronghorn to determine if reduced heterozygosity contributed to the decline of pronghorn in Wind Cave National Park. Microsatellite DNA was collected from 75 pronghorn inhabiting Wind Cave National Park in western South Dakota (n = 11), northwestern South Dakota (n = 33), and southwestern South Dakota (n = 31). Pronghorn in Wind Cave National Park had similar levels of observed heterozygosity (0.473 to 0.594) and low inbreeding coefficients (-0.168 to 0.037) when compared with other populations in western South Dakota. Furthermore, indices of population structure indicated no differentiation occurred among pronghorn populations. Results indicated that genetic variability was not a primary factor in the decline of pronghorn in Wind Cave National Park
Far Ultraviolet Absolute Flux of alpha Virginis
We present the far ultraviolet spectrum of alpha Virginis taken with EURD
spectrograph on-board MINISAT-01. The spectral range covered is from ~900 to
1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE
spectra of alpha Vir and compared the extension of the model to our wavelengths
with EURD data. This comparison shows that EURD fluxes are consistent with the
prediction of the model within 20-30%, depending on the reddening assumed. EURD
fluxes are consistent with Voyager observations but are ~60% higher than most
previous rocket observations of alpha Vir.Comment: 13 pages, 4 figures. Submitted to The Astrophysical Journa
Unveiling the Active Nucleus of Centaurus A
We report new HST WFPC2 and NICMOS observations of the center of the nearest
radio galaxy Centaurus A (NGC 5128) and discuss their implications for our
understanding of the active nucleus and jet. We detect the active nucleus in
the near-IR (K and H) and, for the first time, in the optical (I and V),
deriving the spectral energy distribution of the nucleus from the radio to
X-rays. The optical and part of the near-IR emission can be explained by the
extrapolation of the X-ray power law reddened by A_V~14mag, a value consistent
with other independent estimates.
The 20pc-scale nuclear disk discovered by Schreier et al. (1998) is detected
in the [FeII] 1.64mic line and presents a morphology similar to that observed
in Pa alpha with a [FeII]/Pa alpha ratio typical of low ionization Seyfert
galaxies and LINERs. NICMOS 3 Pa alpha observations in a 50"x50" circumnuclear
region suggest enhanced star formation (~0.3Msun/yr) at the edges of the
putative bar seen with ISO, perhaps due to shocks driven into the gas.
The light profile, reconstructed from V, H and K observations, shows that
Centaurus A has a core profile with a resolved break at ~4" and suggests a
black--hole mass of ~10^9 Msun. A linear blue structure aligned with the
radio/X-ray jet may indicate a channel of relatively low reddening in which
dust has been swept away by the jet.Comment: 19 pages, 13 figures, Astrophysical Journal, in press. High quality
figures available at http://www.arcetri.astro.it/~marconi/colpic.htm
The Coronae of AR Lac
We observed the coronally active eclipsing binary, AR Lac, with the High
Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five
orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV
spectra and photometry were also obtained with the Extreme Ultraviolet
Explorer. Significant variability in both X-ray and EUV fluxes were observed,
dominated by at least one X-ray flare and one EUV flare. We saw no evidence of
primary or secondary eclipses. X-ray flux modulation was largest at high
temperature, indicative of flare heating of coronal plasma. Line widths
interpreted in terms of Doppler broadening suggest that both binary stellar
components are active. From line fluxes obtained from total integrated spectra,
we have modeled the emission measure and abundance distributions. A strong
maximum was found in the differential emission measure, characterized by peaks
at log T = 6.9 and 7.4, together with a weak but significant cooler maximum
near log T=6.2, and a moderately strong hot tail from log T= 7.6-8.2. Coronal
abundances have a broad distribution and show no simple correlation with first
ionization potential. While the resulting model spectrum generally agrees very
well with the observed spectrum, there are some significant discrepancies,
especially among the many Fe L-lines. Both the emission measure and abundance
distributions are qualitatively similar to prior determinations from other
X-ray and ultraviolet spectra, indicating some long-term stability in the
overall coronal structure.Comment: 31 pages, 8 figures, 3 tables; Accepted for publication in the
Astrophysical Journal (tentatively October 1, 2003
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