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Miller, R. C.

Publications and source records attributed to Miller, R. C..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Effect of track structure and radioprotectors on the induction of oncogenic transformation in murine fibroblasts by heavy ions

The oncogenic potential of high-energy 56Fe particles (1 GeV/nucleon) accelerated with the Alternating Gradient Synchrotron at the Brookhaven National Laboratory was examined utilizing the mouse C3H 10T1/2 cell model. The dose-averaged LET for high-energy 56Fe is estimated to be 143 keV/micrometer with the exposure conditions used in this study. For 56Fe ions, the maximum relative biological effectiveness (RBEmax) values for cell survival and oncogenic transformation were 7.71 and 16.5 respectively. Compared to 150 keV/micrometer 4He nuclei, high-energy 56Fe nuclei were significantly less effective in cell killing and oncogenic induction. The prostaglandin E1 analog misoprostol, an effective oncoprotector of C3H 10T1/2 cells exposed to X rays, was evaluated for its potential as a radioprotector of oncogenic transformation with high-energy 56Fe. Exposure of cells to misoprostol did not alter 56Fe cytotoxicity or the rate of 56Fe-induced oncogenic transformation.

NASA Discipline Radiation Health↗
NASA NTRS1994

Oncogenic transformation through the cell cycle and the LET dependent inverse dose rate effect

Synchronised populations of mouse C3H/10T-1/2 cells were obtained by a stringent mitotic dislodgment procedure. Mitotic cells rapidly attach and progress sequentially through the cell cycle. Irradiation (3 Gy of X rays) was carried out at intervals from 0 to 18 h after initiating cell cycle progression of the mitotic cells. Oncogenic transformation was enhanced 10-fold over cells irradiated soon after replating (G1 and S phases) for cells in a near 2 h period corresponding to cells in G2 phase but not in mitosis. The cell surviving fraction had a 2-1/2-fold variation with resistant peaks corresponding to the late G1 and late S phases. These findings provide experimental support for the hypothesis initiated by Rossi and Kellerer and developed by Brenner and Hall to explain the LET dependent inverse dose rate effect for oncogenic transformation.

NASA Discipline Radiation Health↗
NASA NTRS1986

The effects of stimulus modality and task integrality: Predicting dual-task performance and workload from single-task levels

The influence of stimulus modality and task difficulty on workload and performance was investigated. The goal was to quantify the cost (in terms of response time and experienced workload) incurred when essentially serial task components shared common elements (e.g., the response to one initiated the other) which could be accomplished in parallel. The experimental tasks were based on the Fittsberg paradigm; the solution to a SternBERG-type memory task determines which of two identical FITTS targets are acquired. Previous research suggested that such functionally integrated dual tasks are performed with substantially less workload and faster response times than would be predicted by suming single-task components when both are presented in the same stimulus modality (visual). The physical integration of task elements was varied (although their functional relationship remained the same) to determine whether dual-task facilitation would persist if task components were presented in different sensory modalities. Again, it was found that the cost of performing the two-stage task was considerably less than the sum of component single-task levels when both were presented visually. Less facilitation was found when task elements were presented in different sensory modalities. These results suggest the importance of distinguishing between concurrent tasks that complete for limited resources from those that beneficially share common resources when selecting the stimulus modalities for information displays.

Hart, S. G.↗
NASA NTRS1984

Assessing the Subjective Workload of Directional Orientation Tasks

The impact of various flight-related tasks on the workload imposed by the requirement to compute new headings, course changes, and reciprocal headings was investigated. Eight pilots were presented with a series of heading-change tasks in a laboratory setting. Two levels of difficulty of each of three tasks were presented verbally and spatially. Performance was measured by evaluating the speed and accuracy of the responses. The subjective responses and objective measures of performance reflected a strong association between subjective experience and objective behavior. The reciprocal calculations were performed quickly and accurately throughout and were considered to be minimally loading. Subjective workload, percent correct and response times for the two course-change tasks varied significantly as a function of level of difficulty and display format, with no discernable speed/accuracy trade off.

Miller, R. C.↗
NASA NTRS1976

Design and evaluation of thin metal surface insulation for hypersonic flight

An all-metal insulation was studied as a thermal protection system for hypersonic vehicles. Key program goals included fabricating the insulation in thin packages which are optimized for high temperature insulation of an actively cooled aluminum structure, and the use of state-of-the-art alloys. The insulation was fabricated from 300 series stainless steel in thicknesses of 0.8 to 12 mm. The outer, 0.127 mm thick, skin was textured to accommodate thermal expansion and oxidized to increase emittance. The thin insulating package was achieved using an insulation concept consisting of foil radiation shields spaced within the package, and conical foil supports to carry loads from the skin and maintain package dimensions. Samples of the metal-insulation were tested to evaluate thermal insulation capability, rain and sand erosion resistance, high temperature oxidation resistance, applied load capability, and high temperature emittance.

Miller, R. C.↗
NASA NTRS1974

Metal-wool heat shields for space shuttle

The packaging of metal wool for reusable thermal heat shields applied to aerodynamic and other surfaces for the space shuttle was analyzed and designed, and samples were fabricated and experimentally studied. Parametric trends were prepared for selected configurations. An all-metal thermally efficient, reliable, reusable and producible heat shield system was designed and structurally tested for use on spacecraft aerodynamic surfaces where temperatures do not exceed 810 K. Stainless steel sheet, primarily for structure and secondarily in the transverse plane for thermal expansion, was shown to accommodate thermal expansion in all directions when restrained at the edges and heated to 1360 K. Aerodynamic loads of 0.35 x 1000,000 newtons/sq meter, and higher, may be easily accepted by structures of this design. Seven all-metal thermal protection specimens, 12.7 cm square and 2.5 cm thick were fabricated and are being experimentally evaluated at simulated shuttle entry conditions in an arc jet facility.

Miller, R. C.↗
NASA NTRS1973

Acquisition and analysis of coastal ground truth data for correlation with ERTS-A imagery

The author has identified the following significant results. Examination of the digital image of Monterey Bay, California area indicates more resolution in all MSS bands than found in the film imagery. This inability to delineate subtle density variations may be similar to those difficulties encountered by some investigators at the light end of the spectrum. Because the digital image is large and only certain areas of the total image are enhanced at one time, the digital technique of presenting MSS imagery is complimentary with the supplied film imagery. Examination of selected film imagery of the Monterey Bay and Santa Barbara Channel areas raises more questions than can be answered at this time. Density variations over water areas could be of an oceanic or atmospheric origin, or both. The ground truth acquisition phase of this project will clear up some of the apparent ambiguities, but probably not completely. A more thorough examination of meteorological parameters is recommended.

Miller, R. C.↗
NASA NTRS1972

Acquisition and analysis of coastal ground-truth data for correlation with ERTS-A imagery

The author has identified the following significant results. Areas with high sediment loads and a wide range of water parameters (such as San Francisco Bay, an area not a target of this study but included in the imagery) show dramatic variations in the photographs. Open oceanic areas off California have relatively homogenous water and hence a much lower range of contrast. The mean shore coastal areas show an intermediate range.

Miller, R. C.↗