7,797 research outputs found
Results of tests OA26 and IA16 in the NASA/ARC 3.5-foot hypersonic wind tunnel on an 0.015-scale model (36-OTS) of the space shuttle configuration 140A/B to obtain pressures for venting analysis
Tests were conducted, from November 15 to December 4, 1973, to obtain surface pressure data on an 0.015-scale replica of the Space Shuttle Vehicle 4. Data were obtained at Mach numbers of 5.3, 7.4, and 10.3, to support the venting analysis for both launch and entry conditions. These tests were the final tests in a series covering a Mach number range from 0.6 to 10.3. The model was instrumented with pressure orifices in the vicinity of the cargo bay door hinge and parting lines, and on the side of the fuselage at the crew compartment, and below the orbital maneuvering system pods at the aft compartment. The model was tested at angles of attack and sideslip consistent with expected divergencies from the nominal trajectory
Landscape of standing variation for tandem duplications in Drosophila yakuba and Drosophila simulans
We have used whole genome paired-end Illumina sequence data to identify
tandem duplications in 20 isofemale lines of D. yakuba, and 20 isofemale lines
of D. simulans and performed genome wide validation with PacBio long molecule
sequencing. We identify 1,415 tandem duplications that are segregating in D.
yakuba as well as 975 duplications in D. simulans, indicating greater variation
in D. yakuba. Additionally, we observe high rates of secondary deletions at
duplicated sites, with 8% of duplicated sites in D. simulans and 17% of sites
in D. yakuba modified with deletions. These secondary deletions are consistent
with the action of the large loop mismatch repair system acting to remove
polymorphic tandem duplication, resulting in rapid dynamics of gain and loss in
duplicated alleles and a richer substrate of genetic novelty than has been
previously reported. Most duplications are present in only single strains,
suggesting deleterious impacts are common. D. simulans shows larger numbers of
whole gene duplications in comparison to larger proportions of gene fragments
in D. yakuba. D. simulans displays an excess of high frequency variants on the
X chromosome, consistent with adaptive evolution through duplications on the D.
simulans X or demographic forces driving duplicates to high frequency. We
identify 78 chimeric genes in D. yakuba and 38 chimeric genes in D. simulans,
as well as 143 cases of recruited non-coding sequence in D. yakuba and 96 in D.
simulans, in agreement with rates of chimeric gene origination in D.
melanogaster. Together, these results suggest that tandem duplications often
result in complex variation beyond whole gene duplications that offers a rich
substrate of standing variation that is likely to contribute both to
detrimental phenotypes and disease, as well as to adaptive evolutionary change.Comment: Revised Version- Accepted at Molecular Biology and Evolutio
Investigation of fatigue strength of multilayer advanced fiber composites
The analytical characterization of a multilayer fiber composite plate (without hole) was accomplished for both static and dynamic loading conditions using the finite difference technique. Thornel 300/5208 composites with and without holes were subjected to static and tensile fatigue testing. Five (5) fiber orientations were submitted to test. Tensile fatigue testing also included three (3) loading conditions and two (2) frequencies. The low-cycle test specimens demonstrated a shorter tensile fatigue life than the high-cycle test specimens. Failure surfaces demonstrated effect of testing conditions. Secondary failure mechanisms, such as: delamination, fiber breakage, and edge fiber delamination were present. Longitudinal delamination between plies also occurred in these specimens
THE PSOCOPTERA OF THE KRAKATAU ISLANDS, INDONESIA
At least 80 species of Psocoptera are represented in recent collections from the Krakatau Islands, Sunda Strait. They represent 15 families, and 29 species are described tu new. Twenty four species are known only from the Krahataus but. others are widespread in nearby regions of Sumatra and Java and a few are known to be more broadly distributed. Numbers of species recorded from each of the Krahatau Islands are : Rakata 58, Panjang 48, Sertung 27, Anak Krakatau 27
Timing analysis techniques at large core distances for multi-TeV gamma ray astronomy
We present an analysis technique that uses the timing information of
Cherenkov images from extensive air showers (EAS). Our emphasis is on distant,
or large core distance gamma-ray induced showers at multi-TeV energies.
Specifically, combining pixel timing information with an improved direction
reconstruction algorithm, leads to improvements in angular and core resolution
as large as ~40% and ~30%, respectively, when compared with the same algorithm
without the use of timing. Above 10 TeV, this results in an angular resolution
approaching 0.05 degrees, together with a core resolution better than ~15 m.
The off-axis post-cut gamma-ray acceptance is energy dependent and its full
width at half maximum ranges from 4 degrees to 8 degrees. For shower directions
that are up to ~6 degrees off-axis, the angular resolution achieved by using
timing information is comparable, around 100 TeV, to the on-axis angular
resolution. The telescope specifications and layout we describe here are geared
towards energies above 10 TeV. However, the methods can in principle be applied
to other energies, given suitable telescope parameters. The 5-telescope cell
investigated in this study could initially pave the way for a larger array of
sparsely spaced telescopes in an effort to push the collection area to >10 km2.
These results highlight the potential of a `sparse array' approach in
effectively opening up the energy range above 10 TeV.Comment: Published in Astroparticle Physic
Understanding the effect resonant magnetic perturbations have on ELMs
All current estimations of the energy released by type I ELMs indicate that,
in order to ensure an adequate lifetime of the divertor targets on ITER, a
mechanism is required to decrease the amount of energy released by an ELM, or
to eliminate ELMs altogether. One such amelioration mechanism relies on
perturbing the magnetic field in the edge plasma region, either leading to more
frequent, smaller ELMs (ELM mitigation) or ELM suppression. This technique of
Resonant Magnetic Perturbations (RMPs) has been employed to suppress type I
ELMs at high collisionality/density on DIII-D, ASDEX Upgrade, KSTAR and JET and
at low collisionality on DIII-D. At ITER-like collisionality the RMPs enhance
the transport of particles or energy and keep the edge pressure gradient below
the 2D linear ideal MHD critical value that would trigger an ELM, whereas at
high collisionality/density the type I ELMs are replaced by small type II ELMs.
Although ELM suppression only occurs within limitied operational ranges, ELM
mitigation is much more easily achieved. The exact parameters that determine
the onset of ELM suppression are unknown but in all cases the magnetic
perturbations produce 3D distortions to the plasma and enhanced particle
transport. The incorporation of these 3D effects in codes will be essential in
order to make quantitative predictions for future devices.Comment: 32 pages, 9 figure
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