29,958 research outputs found
The fatigue behavior of materials for the supersonic transport
Crack propagation behavior, residual static strength, and base fatigue strength of supersonic transport skin materia
Persistent Sunward Flow of ~1.6 MeV Protons at 1 Au
The anisotropy of 1.3 to 2.3 MeV protons has been measured with the Caltech Electron/Isotope
Spectrometer aboard IMP-7 for periods between prompt solar particle events from 72/273 to
74/2. The diffusive anisotropy, which has been computed by subtracting the independently determined.
convective anisotropy from the observed anisotropy, is predominantly directed toward the sun with a typical radial component
of 14%
Monitoring and Discovering X-ray Pulsars in the Small Magellanic Cloud
Regular monitoring of the SMC with RXTE has revealed a huge number of X-ray
pulsars. Together with discoveries from other satellites at least 45 SMC
pulsars are now known. One of these sources, a pulsar with a period of
approximately 7.8 seconds, was first detected in early 2002 and since discovery
it has been found to be in outburst nine times. The outburst pattern clearly
shows a period of 45.1 +/- 0.4 d which is thought to be the orbital period of
this system. Candidate outburst periods have also been obtained for nine other
pulsars and continued monitoring will enable us to confirm these. This large
number of pulsars, all located at approximately the same distance, enables a
wealth of comparative studies. In addition, the large number of pulsars found
(which vastly exceeds the number expected simply by scaling the relative mass
of the SMC and the Galaxy) reveals the recent star formation history of the SMC
which has been influenced by encounters with both the LMC and the Galaxy.Comment: 5 pages, 4 figures, AIP conference proceedings format. Contribution
to "X-ray Timing 2003: Rossi and Beyond." meeting held in Cambridge, MA,
November, 200
Isolation of microsatellite loci in the Capricorn silvereye, Zosterops lateralis chlorocephalus (Aves : Zosteropidae)
The Capricorn silvereye (Zosterops lateralis chlorocephalus
) is ideally suited to investigating the genetic basis of body size evolution. We have isolated and characterized a set of microsatellite markers for this species. Seven out of 11 loci were polymorphic. The number of alleles
detected ranged from two to five and observed heterozygosities between 0.12 and 0.67. One locus, ZL49, was found to be sex-linked. This moderate level of diversity is consistent with that expected in an isolated, island population
Laser Guide Star Adaptive Optics Integral Field Spectroscopy of a Tightly Collimated Bipolar Jet from the Herbig Ae star LkHa 233
We have used the integral field spectrograph OSIRIS and laser guide star
adaptive optics at Keck Observatory to obtain high angular resolution (0.06"),
moderate spectral resolution (R ~ 3800) images of the bipolar jet from the
Herbig Ae star LkHa 233, seen in near-IR [Fe II] emission at 1.600 & 1.644
microns. This jet is narrow and tightly collimated, with an opening angle of
only 9 degrees, and has an average radial velocity of ~ 100 km/s. The jet and
counterjet are asymmetric, with the red-shifted jet much clumpier than its
counterpart at the angular resolution of our observations. The observed
properties are in general similar to jets seen around T Tauri stars, though it
has a relatively large mass flux of (1.2e-7 +- 0.3e-7) M_sun/year, near the
high end of the observed mass flux range around T Tauri stars. We also
spatially resolve an inclined circumstellar disk around LkHa 233, which
obscures the star from direct view. By comparison with numerical radiative
transfer disk models, we estimate the disk midplane to be inclined i = 65 +- 5
degrees relative to the plane of the sky. Since the star is seen only in
scattered light at near-infrared wavelengths, we detect only a small fraction
of its intrinsic flux. Because previous estimates of its stellar properties did
not account for this, either LkHa 233 must be located closer than the
previously believed, or its true luminosity must be greater than previously
supposed, consistent with its being a ~4 M_sun star near the stellar birthline.Comment: Accepted for publication in the Ap
Interpreting the extended emission around three nearby debris disc host stars
Cool debris discs are a relic of the planetesimal formation process around
their host star, analogous to the solar system's Edgeworth-Kuiper belt. As
such, they can be used as a proxy to probe the origin and formation of
planetary systems like our own. The Herschel Open Time Key Programmes "DUst
around NEarby Stars" (DUNES) and "Disc Emission via a Bias-free Reconnaissance
in the Infrared/Submillimetre" (DEBRIS) observed many nearby, sun-like stars at
far-infrared wavelengths seeking to detect and characterize the emission from
their circumstellar dust. Excess emission attributable to the presence of dust
was identified from around 20% of stars. Herschel's high angular
resolution ( 7" FWHM at 100 m) provided the capacity for resolving
debris belts around nearby stars with radial extents comparable to the solar
system (50 to 100 au). As part of the DUNES and DEBRIS surveys, we obtained
observations of three debris disc stars, HIP 22263 (HD 30495), HIP 62207 (HD
110897), and HIP 72848 (HD 131511), at far-infrared wavelengths with the
Herschel PACS instrument. Combining these new images and photometry with
ancilliary data from the literature, we undertook simultaneous multi-wavelength
modelling of the discs' radial profiles and spectral energy distributions using
three different methodologies: single annulus, modified black body, and a
radiative transfer code. We present the first far-infrared spatially resolved
images of these discs and new single-component debris disc models. We
characterize the capacity of the models to reproduce the disc parameters based
on marginally resolved emission through analysis of two sets of simulated
systems (based on the HIP 22263 and HIP 62207 data) with the noise levels
typical of the Herschel images. We find that the input parameter values are
recovered well at noise levels attained in the observations presented here.Comment: 13 pages, 5 figures, 5 tables, accepted for publication in A&
Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite
We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithiumâfluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and 11B nuclear magnetic resonance studies suggest that co-intercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties
An exploration of ebook selection behavior in academic library collections
Academic libraries have offered ebooks for some time, however little is known about how readers interact with them while making relevance decisions. In this paper we seek to address that gap by analyzing ebook transaction logs for books in a university library
Discovery of a Second Millisecond Accreting Pulsar: XTE J1751-305
We report the discovery by the RXTE PCA of a second transient accreting
millisecond pulsar, XTE J1751-305, during regular monitoring observations of
the galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it
one of the fastest pulsars. The pulsations contain the signature of orbital
Doppler modulation, which implies an orbital period of 42 minutes, the shortest
orbital period of any known radio or X-ray millisecond pulsar. The mass
function, f_x = (1.278 +/- 0.003) x 10^{-6} M_sun, yields a minimum mass for
the companion of between 0.013 and 0.017 M_sun, depending on the mass of the
neutron star. No eclipses were detected. A previous X-ray outburst in June,
1998, was discovered in archival All-Sky Monitor data. Assuming mass transfer
in this binary system is driven by gravitational radiation, we constrain the
orbital inclination to be in the range 30-85 deg, and the companion mass to be
0.013-0.035 M_sun. The companion is most likely a heated helium dwarf. We also
present results from the Chandra HRC-S observations which provide the best
known position of XTE J1751-305.Comment: Astrophysical Journal Letters, Accepted, (AASTeX
Stability of Ca-montmorillonite hydrates: A computer simulation study
Classic simulations are used to study interlayer structure, swelling curves,
and stability of Ca-montmorillonite hydrates. For this purpose, NPzzT$ and
MuPzzT ensembles are sampled for ground level and given burial conditions. For
ground level conditions, a double layer hydrate having 15.0 A of basal spacing
is the predominant state for relative vapor pressures (p/po) ranging in
0.6-1.0. A triple hydrate counting on 17.9 A of interlaminar distance was also
found stable for p/po=1.0. For low vapor pressures, the system may produce a
less hydrated but still double layer state with 13.5 A or even a single layer
hydrate with 12.2 A of interlaminar distance. This depends on the established
initial conditions. On the other hand, the effect of burial conditions is two
sided. It was found that it enhances dehydration for all vapor pressures except
for saturation, where swelling is promoted.Comment: 8 pages, 9 figure
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