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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
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NASA NTRS1975

The 1973 solar occultation of the Crab Nebula pulsar

The mean electron density of the solar corona was determined by measuring the dispersion of radiofrequency pulses from pulsar NP 0532 during the June 1973 solar occultation. Trends continued which were noticed in 1971 as solar activity declined. Model fitting results suggest that the corona continued to become even more concentrated toward the equator in 1973 than in 1971. The number density of electrons in most regions decreased. The best model of the distribution of corona electrons is suggested to be one with zero density at the poles. K-corona isophotes and contours of equal path-integrated density are presented for several models. Electron density versus date and position in the corona are tabulated. It is seen that there is no simple relationship between the onset of major solar activity and density or scattering enhancements.

Weisberg, J. M.↗
NASA NTRS1977

The rhesus (Macaca mulatta) and crab-eating (Macaca fascicularis) monkeys in cardiovascular and aerospace research

Two nonhuman primate species were used to investigate the effects of gravitoinertial forces on pilot incapacitation and performance impairment, to define human physiologic tolerance and safe exposure limits to these environments, and to obtain data which can be used to evolve new methods to improve man's G tolerance to match the structural capability of new generation aircraft. The macaca fascicularis was used to study the effects of environmental stress and atheroscelerosis on cerebral blood flow and function agents on myocardial and cardiovascular function were studied in the macaca mulatta.

Erickson, H. H.↗
NASA NTRS1983

Gamma rays from the Crab Pulsar 0531+21

Results are reported for observations of PSR 0531 + 21 performed with a gamma ray double Compton scatter telescope launched on a balloon. The operation of the telescope and the handling of the data are described. Phase diagrams for the pulsar and energy distributions for gamma rays from the primary and secondary pulses are shown and discussed. The results indicate that these observations are the first of gamma ray lines from neutrons captured on protons or iron in pulsars. Arguments supporting this interpretation are given.

Long, J. L.↗
NASA NTRS1997

Study of the Polarization Properties of the Crab Nebula and Pulsar with BATSE

Activities carried out under this proposal included: 1) development and refinements of Monte Carlo simulations of the atmospheric reflected albedo hard x-ray emissions, both unpolarized and polarized, 2) modeling and simulations of the off-axis response of the BATSE LAD detectors, and 3) comparison of our simulation results with numerous BATSE flare and cosmic burst data sets.

Forrest, David J.↗
NASA NTRS2001

Observation of Crab-Like Supernova Remnants

The purpose of this program was to observe the supernova remnants 3C58 and G21.5-0.9 and to search for pulsed emission. If a pulsar were to be found, the period derivative and inferred magnetic field would have extreme values if pulsar evolution had followed the standard model. If this is not the case, the standard model must be revised. We also sought to obtain very accurate measurement of the synchrotron emission spectrum of each remnant.

Seward, Frederick D.↗
NASA NTRS1997

Mitochondrial gene arrangement of the horseshoe crab Limulus polyphemus L.: conservation of major features among arthropod classes

Numerous complete mitochondrial DNA sequences have been determined for species within two arthropod groups, insects and crustaceans, but there are none for a third, the chelicerates. Most mitochondrial gene arrangements reported for crustaceans and insect species are identical or nearly identical to that of Drosophila yakuba. Sequences across 36 of the gene boundaries in the mitochondrial DNA (mtDNA) of a representative chelicerate. Limulus polyphemus L., also reveal an arrangement like that of Drosophila yakuba. Only the position of the tRNA(LEU)(UUR) gene differs; in Limulus it is between the genes for tRNA(LEU)(CUN) and ND1. This positioning is also found in onychophorans, mollusks, and annelids, but not in insects and crustaceans, and indicates that tRNA(LEU)(CUN)-tRNA(LEU)(UUR)-ND1 was the ancestral gene arrangement for these groups, as suggested earlier. There are no differences in the relative arrangements of protein-coding and ribosomal RNA genes between Limulus and Drosophila, and none have been observed within arthropods. The high degree of similarity of mitochondrial gene arrangements within arthropods is striking, since some taxa last shared a common ancestor before the Cambrian, and contrasts with the extensive mtDNA rearrangements occasionally observed within some other metazoan phyla (e.g., mollusks and nematodes).

Non-NASA Center↗
NASA NTRS2005

An XMM-Newton Search for Crab-like Supernova Remnants

The primary goals of the study are to search for evidence of non-thermal emission that would suggest the presence of a pulsar in this compact SNR. We have performed the reduction of the EPIC data for this observation, cleaning the data to remove time intervals of enhanced particle background, and have created maps in several energy bands, and on a variety of smoothing scales. We find no evidence for emission from the SNR. Given the small angular size of the SNR, we conclude that rather than being a young remnant, it is actually fairly old, but distant. At its current stage of evolution, the remnant shell has apparently entered the radiative phase, wherein the shell temperature has cooled sufficiently to be either below X-ray-emitting temperatures or at temperatures easily absorbed the foreground interstellar material. We have thus concluded that this SNR is not a viable candidate for a young ejecta-rich or pulsar-driven SNR.

Mushotzky, Richard↗