Computer Sciences Corporation

About: Computer Sciences Corporation is a based out in . It is known for research contribution in the topics: Spacecraft & Software development. The organization has 1916 authors who have published 2389 publications receiving 62729 citations. The organization is also known as: CSC.

Far-Ultraviolet Imagery of the Edge-on Spiral Galaxy NGC 4631

Abstract: Far-ultraviolet (FUV) imagery of the edge-on, Sc/SBd galaxy NGC 4631 reveals very strong FUV emission, resulting from active star formation, uniformly distributed along the galactic midplane. Multiband imagery, H I and H II position-velocity curves, and extinction considerations all imply that the emission is from the outer edges of the visible galaxy. The overall FUV morphology of this edge-on disk system is remarkably similar to those of the "chain galaxies" evident at high redshift, thus suggesting a similar interpretation for at least some of those distant objects. FUV, U, B, and V magnitudes, measured for 48 star-forming regions, along with corresponding Hα and Hβ measurements are used to construct diagnostic color-color diagrams. Although there are significant exceptions, most of the star-forming regions are less massive and older than 30 Doradus. Comparison with the expectations from two star formation models yields ages of 2.7 to 10 Myr for the instantaneous burst (IB) model and star formation cutoff ages of 0 to 9 Myr for the continuous star formation (CSF) model. Interpreted in terms of the IB model the photometry implies a total created mass in the 48 star-forming regions of 2.5 × 107 M☉. When viewed as resulting from constant star formation the photometry implies a star formation rate of 0.33 M☉ yr-1. These results are compared to those derived from FIR and radio observations. Corrections for FUV emission reprocessed by interstellar grains are estimated. A large ring, ~3 kpc in diameter, of 14 star-forming regions is concentrically located with an expanding H I shell toward the eastern end of the galaxy. Our observations imply that the shell may have been generated primarily by supernovae arising from 5.3 × 104 OB stars in a massive star-forming region beginning about 20 Myr ago, and that the presently observed FUV bright emission is due to second generation stars.

Genotoxic activity detected in soils from a hazardous waste site by the Ames test and an SOS colorimetric test.

Abstract: Ten soil samples from a hazardous waste site were compared for their genotoxic activity by the Ames test (Salmonella reverse mutation assay) and a modified SOS colorimetric test. Polynuclear aromatic hydrocarbons known to produce frameshift mutations were found in high levels in the soils. Salmonella typhimurium TA98, sensitive to frameshift mutations, was selected as the Ames tester strain. Escherichia coli K12 PQ37 (sulA::lacZ) was the SOS tester strain. Organic extracts were prepared from the soil samples by Soxhlet extraction. One set of the soil samples was extracted with methylene chloride and a second set with cyclohexane. Two criteria from reproducible dose-related increases in response to the soil were used to compare the positive responses: 1) the concentrations required for doubling responses and 2) a minimum concentration required to produce statistically significant increases from background controls. Analysis of variance indicated that with S9 mix, Ames and SOS results were similar for the same soils and solvent extractions. However, without S9 mix, the SOS test was significantly more sensitive than the Ames test to the genotoxins extracted from the soils. Both the Ames and SOS tests detected lower concentrations of genotoxins in methylene chloride than in cyclohexane extracts. The simplicity of the method, reduction in expenses, and results within 1 working day all contribute to the advantages of the SOS test.

Unstructured Grids on NURBS Surfaces

Abstract: A simple and efficient computational method is presented for unstructured surface grid generation. This method is built upon an advancing front technique combined with grid projection. The projection technique is based on a Newton-Raphson method. This combined approach has been successfully implemented for structured and unstructured grids. In this paper, the implementation for unstructured grid is discussed.

Empirical relationship of ultraviolet extinction and the interstellar diffuse bands

Abstract: New ultraviolet colors are presented for 110 hot stars. These data are combined with infrared colors and diffuse-band measurements to study the relationship of diffuse interstellar bands (4430, 5780, 6284 A) to the overall extinction curve. Equivalent widths of 5780 A and 6284 A are not well correlated with infrared, visible, or ultraviolet extinction measurements for stars in this sample. The central depth of 4430 A is well correlated with visible and infrared extinction, but less well correlated with UV extinction at 1800 A. The wavelength 4430 A is strongly correlated with the strength of the 2200-A bump. The data suggest that if small grains account for the general rise in UV extinction, the diffuse bands are not formed in these grains. The wavelength 4430 A may well arise in large grains and/or in the material responsible for the 2200-A bump. Correlations with UV extinctions derived by other authors are discussed in detail. It is suggested that definitions of extinction parameters and band shapes, as well as selection effects in small samples of stars, may still compromise conclusions based on correlation studies such as are being attempted.

Determining Metrics for Systems Engineering

Abstract: Systems Engineering Metrics are not easy to establish, perhaps that is why ineffective Systems Engineering is so prevalent. This paper discusses suggested metrics to measure the degree of effectiveness of both the Systems Engineering product and process. Metrics are suggested for reviews and documentation as examples of measuring the quality of the products, and for the effectiveness of Systems Engineers as examples of measuring the quality of the process.