2,721 research outputs found
Vibration characteristics of 1/8-scale dynamic models of the space-shuttle solid-rocket boosters
Vibration tests and analyses of six 1/8 scale models of the space shuttle solid rocket boosters are reported. Natural vibration frequencies and mode shapes were obtained for these aluminum shell models having internal solid fuel configurations corresponding to launch, midburn (maximum dynamic pressure), and near endburn (burnout) flight conditions. Test results for longitudinal, torsional, bending, and shell vibration frequencies are compared with analytical predictions derived from thin shell theory and from finite element plate and beam theory. The lowest analytical longitudinal, torsional, bending, and shell vibration frequencies were within + or - 10 percent of experimental values. The effects of damping and asymmetric end skirts on natural vibration frequency were also considered. The analytical frequencies of an idealized full scale space shuttle solid rocket boosted structure are computed with and without internal pressure and are compared with the 1/8 scale model results
The presence of B7-H4+ macrophages and CD25+CD4+ and FOXP3+ regulatory T cells in the microenvironment of nasal polyps - a preliminary report.
The nasal polyp (NP) seems to represent the end-stage of longstanding inflammation in patients with chronic rhinosinusitis. The aim of our study has been to evaluate the presence of two regulatory cell populations in the microenvironment of NP: CD4+CD25high Foxp3+ (Treg) cells and B7-H4-expressing macrophages. Treg cells are actively able to inhibit T lymphocytes, while the population of B7-H4-expressing macrophages has recently been described as characterized by a regulatory function similar to that of Treg cells. For our study, we evaluated 14 NP tissue samples. The samples were divided into two main groups, eosinophilic (NP) and lymphocytic (NP), according to the predominant type of immune cell infiltration. The presence of Treg cells and B7-H4 positive macrophages in the samples was analyzed by FACS. Treg cells and B7-H4-expressing macrophages were identified in all the examined nasal polyps. The percentages of both Treg cells and of B7H4 positive cells found in the eosinophilic nasal polyps were higher than those found in the lymphocytic nasal polyps. Treg cells and B7H4+ macrophage subpopulations were present in the NP microenvironment and the alterations in their percentages were related to a distinct pattern of immune cell infiltration
Freeze-out configuration properties in the 197Au + 197Au reaction at 23 AMeV
Data from the experiment on the 197Au + 197Au reaction at 23 AMeV are
analyzed with an aim to find signatures of exotic nuclear configurations such
as toroid-shaped objects. The experimental data are compared with predictions
of the ETNA code dedicated to look for such configurations and with the QMD
model. A novel criterion of selecting events possibly resulting from the
formation of exotic freeze-out configurations, "the efficiency factor", is
tested. Comparison between experimental data and model predictions may indicate
for the formation of flat/toroidal nuclear systems
Laboratory Tests of Low Density Astrophysical Equations of State
Clustering in low density nuclear matter has been investigated using the
NIMROD multi-detector at Texas A&M University. Thermal coalescence modes were
employed to extract densities, , and temperatures, , for evolving
systems formed in collisions of 47 MeV Ar + Sn,Sn
and Zn + Sn, Sn. The yields of , , He, and
He have been determined at = 0.002 to 0.032 nucleons/fm and
= 5 to 10 MeV. The experimentally derived equilibrium constants for
particle production are compared with those predicted by a number of
astrophysical equations of state. The data provide important new constraints on
the model calculations.Comment: 5 pages, 3 figure
Experimental Determination of In-Medium Cluster Binding Energies and Mott Points in Nuclear Matter
In medium binding energies and Mott points for , , He and
clusters in low density nuclear matter have been determined at specific
combinations of temperature and density in low density nuclear matter produced
in collisions of 47 MeV Ar and Zn projectiles with Sn
and Sn target nuclei. The experimentally derived values of the in
medium modified binding energies are in good agreement with recent theoretical
predictions based upon the implementation of Pauli blocking effects in a
quantum statistical approach.Comment: 5 pages, 3 figure
Search for stable Strange Quark Matter in lunar soil
We report results from a search for strangelets (small chunks of Strange
Quark Matter) in lunar soil using the Yale WNSL accelerator as a mass
spectrometer. We have searched over a range in mass from A=42 to A=70 amu for
nuclear charges 5, 6, 8, 9, and 11. No strangelets were found in the
experiment. For strangelets with nuclear charge 8, a concentration in lunar
soil higher than is excluded at the 95% confidence level. The
implied limit on the strangelet flux in cosmic rays is the most sensitive to
date for the covered range and is relevant to both recent theoretical flux
predictions and a strangelet candidate event found by the AMS-01 experiment.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Towards the critical behavior for the light nuclei by NIMROD detector
The critical behavior for the light nuclei with A has been
investigated experimentally by the NIMROD multi-detectors. The wide variety of
observables indicate the critical point has been reached in the disassembly of
hot nuclei at an excitation energy of 5.60.5 MeV/u.Comment: 4 pages, 2 figures; Proceeding of 18th Nuclear Physics Division
Conference of the Euro. Phys. Society (NPDC18) "Phase transitions in strongly
interacting matter", Prague, 23.8.-29.8. 2004. To be published in Nuclear
Physics
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