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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

HST image restoration: A comparison of pre- and post-servicing mission results

A variety of image restoration techniques (e.g., Wiener filter, Lucy-Richardson, MEM) have been applied quite successfully to the aberrated HST images. The HST servicing mission (scheduled for late 1993 or early 1994) will install a corrective optics system (COSTAR) for the Faint Object Camera and spectrographs and replace the Wide Field/Planetary Camera with a second generation instrument (WF/PC-II) having its own corrective elements. The image quality is expected to be improved substantially with these new instruments. What then is the role of image restoration for the HST in the long term? Through a series of numerical experiments using model point-spread functions for both aberrated and unaberrated optics, we find that substantial improvements in image resolution can be obtained for post-servicing mission data using the same or similar algorithms as being employed now to correct aberrated images. Included in our investigations are studies of the photometric integrity of the restoration algorithms and explicit models for HST pointing errors (spacecraft jitter).

Hanisch, R. J.↗
NASA NTRS1993

Polarization analysis of a balloon-borne solar magnetograph

The 10(exp -5) polarization specification for the Balloon-borne Vector Magnetograph (BVM) can be met. The 10(exp -5) specification is shown to be a limitation on the diattenuation and retardance along the chief ray path through the optical system, such that the magnitude of the polarization aberration piston term is constrained to be less than .5(10)(exp -5). Coating specification sheets are provided which will ensure that the polarization sensitivity of the BVM will be less than 10(exp -5). An optical design is provided for a vector magnetograph. Finally, to provide a concrete mathematical meaning for polarization sensitivity, the polarization aberration matrix is averaged of the exit pupil. This shows that the coupling between circular and linear states depends only on the magnitude of the polarization aberration piston term.

Reiley, Daniel J.↗
NASA NTRS1994

Chromosomal damage observed in first postirradiation metaphases of repair-proficient and -deficient cell lines

Investigation of radiation induced damage in mutant strains of mammalian cells which show a defect in the rejoining of DNA double strand breaks provides an unique opportunity to examine the role of double strand breaks and the mechanisms of double strand break rejoining in the production of chromosome aberrations. This is particularly important, because there is increasing evidence that the DNA double strand break is the major lesion responsible for the formation of chromosome aberrations. To address this issue, we studied the induction of chromosome aberrations in xrs-5 cells, an x-ray sensitive strain of a Chinese hamster ovary cell line, which shows a defect in the rejoining of double strand breaks and their wild-type parent CHO-cells. Because radiosensitivity depends strongly on cellular age, the experiments were performed with synchronous cells.

Ritter, S.↗
NASA NTRS1996

Advanced Orion Optimized Laser System Analysis

Contractor shall perform a complete analysis of the potential of the solid state laser in the very long pulse mode (100 ns pulse width, 10-30 hz rep-rate) and in the very short pulse mode (100 ps pulse width 10-30 hz rep rate) concentrating on the operation of the device in the 'hot-rod' mode, where no active cooling the laser operation is attempted. Contractor's calculations shall be made of the phase aberrations which develop during the repped-pulse train, and the results shall feed into the adaptive optics analyses. The contractor shall devise solutions to work around ORION track issues. A final report shall be furnished to the MSFC COTR including all calculations and analysis of estimates of bulk phase and intensity aberration distribution in the laser output beam as a function of time during the repped-pulse train for both wave forms (high-energy/long-pulse, as well as low-energy/short-pulse). Recommendations shall be made for mitigating the aberrations by laser re-design and/or changes in operating parameters of optical pump sources and/or designs.

Source record↗
NASA NTRS2003

Truly incomplete and complex exchanges in prematurely condensed chromosomes of human fibroblasts exposed in vitro to energetic heavy ions

Confluent human fibroblast cells (AG1522) were irradiated with gamma rays, 490 MeV/nucleon silicon ions, or iron ions at either 200 or 500 MeV/nucleon. The cells were allowed to repair at 37 degrees C for 24 h after exposure, and a chemically induced premature chromosome condensation (PCC) technique was used to condense chromosomes in the G2 phase of the cell cycle. Incomplete and complex exchanges were analyzed in the irradiated samples. To verify that chromosomal breaks were truly unrejoined, chromosome aberrations were analyzed using a combination of whole-chromosome specific probes and probes specific for the telomere region of the chromosome. Results showed that the frequency of unrejoined chromosome breaks was higher after irradiation with the heavy ions of high LET, and consequently the ratio of incomplete to complete exchanges increased steadily with LET up to 440 keV/microm, the highest LET included in the present study. For samples exposed to 200 MeV/nucleon iron ions, chromosome aberrations were analyzed using the multicolor FISH (mFISH) technique, which allows identification of both complex and truly incomplete exchanges. Results of the mFISH study showed that 0.7 and 3 Gy iron ions produced similar ratios of complex to simple exchanges and incomplete to complete exchanges; these ratios were higher than those obtained after exposure to 6 Gy gamma rays. After 0.7 Gy of iron ions, most complex aberrations were found to involve three or four chromosomes, which is a likely indication of the maximum number of chromosome domains traversed by a single iron-ion track.

NASA Discipline Radiation Health↗
NASA NTRS2006

Stability of Radiation Induced Chromosome Damage in Human Peripheral Blood Lymphocytes

Chromosome damage in an individual's peripheral blood lymphocytes can be an indicator of radiation exposure and this data can be used to evaluate dose after accidental or occupational exposure. Evidence suggests that the yield of chromosome damage in lymphocytes is also a relevant biomarker of cancer risk in humans that reflects individual cancer susceptibility. It follows that biomonitoring studies can be used to uncover subjects who are particularly susceptible to radiation damage and therefore at higher risk of cancer. Translocations and other stable aberrations are commonly believed to persist in peripheral blood cells for many years after exposure, and it has been suggested that translocations can be used for assessing retrospective radiation doses or chronic exposures. However, recent investigations suggest that translocations might not always persist indefinitely. We measured chromosome aberrations in the blood lymphocytes of six astronauts before their respective missions of approximately 3 to 6 months onboard the international space station, and again at various intervals up to 5 years after flight. In samples collected a few days after return to earth, the yield of chromosome translocations had significantly increased compared with preflight values, and results indicate that biodosimetry estimates lie within the range expected from physical dosimetry. However, for five of the astronauts, follow up analysis revealed a temporal decline in translocations with half-lives ranging from 10 to 58 months. The yield of exchanges remained unchanged for the sixth astronaut during an observation period of 5 months post-flight. These results may indicate complications with the use of stable aberrations for retrospective dose reconstruction and could affect cancer risk predictions that are estimated from yields of chromosome damage obtained shortly after exposure.

Cucinotta, F. A.↗
NASA NTRS2007

The Influence of Shielding on the Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage

Chromosome damage was assessed in human peripheral blood lymphocytes after in vitro exposure to the either Si-28 (490 or 600 MeV/n), Ti-48 (1000 MeV/n), or Fe-56 (600, 1000, or 5000 MeV/n). LET values for these ions ranged from 51 to 184 keV/micron and doses ranged from 10 to 200 cGy. The effect of either aluminum or polyethylene shielding on the induction of chromosome aberrations was investigated for each ion. Chromosome exchanges were measured using fluorescence in situ hybridization (FISH) with whole chromosome probes in cells collected at G2 and mitosis in first division post irradiation after chromosomes were prematurely condensed using calyculin-A. The yield of chromosomal aberrations increased linearly with dose and the relative biological effectiveness (RBE) for the primary beams, estimated from the initial slope of the dose response curve for total chromosomal exchanges with respect to gamma-rays, ranged from 9 to 35. The RBE values increased with LET, reaching a maximum for the 600 MeV/n Fe ions with LET of 184 keV/micron. When the LET of the primary beam was below approximately 100 keV/micron, the addition of shielding material increased the effectiveness per unit dose. Whereas shielding decreased the effectiveness per unit dose when the LET of primary beams was higher than 100 keV/micron. The yield of aberrations correlated with the dose-average LET of the beam after traversal through the shielding.

Goeorge, Kerry↗
NASA NTRS2007

Break Point Distribution on Chromosome 3 of Human Epithelial Cells exposed to Gamma Rays, Neutrons and Fe Ions

Most of the reported studies of break point distribution on the damaged chromosomes from radiation exposure were carried out with the G-banding technique or determined based on the relative length of the broken chromosomal fragments. However, these techniques lack the accuracy in comparison with the later developed multicolor banding in situ hybridization (mBAND) technique that is generally used for analysis of intrachromosomal aberrations such as inversions. Using mBAND, we studied chromosome aberrations in human epithelial cells exposed in vitro to both low or high dose rate gamma rays in Houston, low dose rate secondary neutrons at Los Alamos National Laboratory and high dose rate 600 MeV/u Fe ions at NASA Space Radiation Laboratory. Detailed analysis of the inversion type revealed that all of the three radiation types induced a low incidence of simple inversions. Half of the inversions observed after neutron or Fe ion exposure, and the majority of inversions in gamma-irradiated samples were accompanied by other types of intrachromosomal aberrations. In addition, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosome exchanges. We further compared the distribution of break point on chromosome 3 for the three radiation types. The break points were found to be randomly distributed on chromosome 3 after neutrons or Fe ions exposure, whereas non-random distribution with clustering break points was observed for gamma-rays. The break point distribution may serve as a potential fingerprint of high-LET radiation exposure.

Hada, M.↗
NASA NTRS2007

Utility of DF-1 for Radioprotection in Lymphocytes

The development of degenerative changes in the vasculature, such as atherosclerosis, is a known consequence of exposure to ionizing radiation, and is thus a concern for astronaut health following long duration space flight. Cellular damage caused by radiation is due to free radical generation and DNA damage. The goal of this project was to assess the ability of a C60-derivative, DF-1, to mitigate cellular damage resulting from radiation exposure in primary human lymphocytes. DF-1 is a water-soluble C60 fullerene encapsulated in dendrimeric functional groups that is proposed to exhibit antioxidant properties. Human lymphocytes are radiosensitive and travel throughout the body potentially causing bystander effects in any tissues they contact. These cells were subjected to varying doses of gamma radiation in the presence or absence of DF-1. Cells were collected at 48 hours post-irradiation for chromosomal aberration studies and at 72 hours post-irradiation for micronuclei studies. These studies showed that the irradiated cells contained more chromosomal aberrations and micronuclei than the control cells. Addition of the DF-1 reduced the amount of observed DNA damage in the irradiated cells. Growth curves were measured for the lymphocytes exposed to 0 and 4 Gray gamma irradiations, and we observed less growth in the cells irradiated at 4 Gy. 2,7-dichlorofluorescein diacetate was used to detect reactive oxygen species production, and increased production of ROS was observed in the irradiated lymphocytes. Human lymphocytes were subjected to varying doses of gamma or photon radiation in the presence and absence of DF-1 and a known radioprotectant, amifostine. After irradiation, the production of reactive oxygen species, growth curves and cell viability were measured. These cells were also collected to quantify chromosomal aberrations and micronuclei formation. We predict that irradiated cells will show the most damage and that DF-1 will provide protective effects similar to those of amifostine, an established radioprotectant.

Reynolds, Julia↗
NASA NTRS2008

Persistence of Space Radiation Induced Cytogenetic Damage in the Blood Lymphocytes of Astronauts

Cytogenetic damage in astronaut's peripheral blood lymphocytes is a useful in vivo marker of space radiation induced damage. Moreover, if radiation induced chromosome translocations persist in peripheral blood lymphocytes for many years, as has been assumed, they could potentially be used to measure retrospective doses or prolonged low dose rate exposures. However, as more data becomes available, evidence suggests that the yield of translocations may decline with time after exposure, at least in the case of space radiation exposures. We present our latest follow-up measurements of chromosome aberrations in astronauts blood lymphocytes assessed by FISH painting and collected a various times beginning directly after return from space to several years after flight. For most individuals the analysis of individual time-courses for translocations revealed a temporal decline of yields with different half-lives. Since the level of stable aberrations depends on the interplay between natural loss of circulating T-lymphocytes and replenishment from the stem or progenitor cells, the differences in the rates of decay could be explained by inter-individual variation in lymphocyte turn over. Biodosimetry estimates derived from cytogenetic analysis of samples collected a few days after return to earth lie within the range expected from physical dosimetry. However, a temporal decline in yields may indicate complications with the use of stable aberrations for retrospective dose reconstruction, and the differences in the decay time may reflect individual variability in risk from space radiation exposure. In addition, limited data on multiple flights show a lack of correlation between time in space and translocation yields. Data from one crewmember who has participated in two separate long-duration space missions and has been followed up for over 10 years provides limited information on the effect of repeat flights and show a possible adaptive response to space radiation exposure.

George, Kerry↗
NASA NTRS2009

Altered Gene Expressions and Cytogenetic Repair Efficiency in Cells with Suppressed Expression of XPA after Proton Exposure

Cellular responses to damages from ionizing radiation (IR) exposure are influenced not only by the genes involved in DNA double strand break (DSB) repair, but also by non- DSB repair genes. We demonstrated previously that suppressed expression of several non-DSB repair genes, such as XPA, elevated IR-induced cytogenetic damages. In the present study, we exposed human fibroblasts that were treated with control or XPA targeting siRNA to 250 MeV protons (0 to 4 Gy), and analyzed chromosome aberrations and expressions of genes involved in DNA repair. As expected, after proton irradiation, cells with suppressed expression of XPA showed a significantly elevated frequency of chromosome aberrations compared with control siRNA treated (CS) cells. Protons caused more severe DNA damages in XPA knock-down cells, as 36% cells contained multiple aberrations compared to 25% in CS cells after 4Gy proton irradiation. Comparison of gene expressions using the real-time PCR array technique revealed that expressions of p53 and its regulated genes in irradiated XPA suppressed cells were altered similarly as in CS cells, suggesting that the impairment of IR induced DNA repair in XPA suppressed cells is p53-independent. Except for XPA, which was more than 2 fold down regulated in XPA suppressed cells, several other DNA damage sensing and repair genes (GTSE1, RBBP8, RAD51, UNG and XRCC2) were shown a more than 1.5 fold difference between XPA knock-down cells and CS cells after proton exposure. The possible involvement of these genes in the impairment of DNA repair in XPA suppressed cells will be further investigated.

Zhang, Ye↗
NASA NTRS2009

Cytogenetic Response to Ionizing Radiation Exposure in Human Fibroblasts with Suppressed Expression of Non-DSB Repair Genes

Changes of gene expression profile are one of the most important biological responses in living cells after ionizing radiation (IR) exposure. Although some studies have shown that genes up-regulated by IR may play important roles in DNA damage repair, the relationship between the regulation of gene expression by IR, particularly genes not known for their roles in double-strand break (DSB) repair, and its impact on cytogenetic responses has not been well studied. The purpose of this study is to identify new roles of IR inducible genes in radiation-induced chromosome aberrations and micronuclei formation. In the study, the expression of 25 genes selected on the basis of their transcriptional changes in response to IR was individually knocked down by small interfering RNA in human fibroblast cells. Frequencies of micronuclei (MN) formation and chromosome aberrations were measured to determine the efficiency of cytogenetic repair, and the fraction of bi-nucleated cells in the MN analysis was used as a marker for cell cycle progression. In response to gamma radiation, the formation of MN was significantly increased by suppressed expression of five genes: Ku70 (DSB repair pathway), XPA (nucleotide excision repair pathway), RPA1 (mismatch repair pathway), RAD17 and RBBP8 (cell cycle control). Knocked-down expression of four genes (MRE11A, RAD51 in the DSB pathway, SESN1, and SUMO1) significantly inhibited cell cycle progression, possibly because of severe impairment of DNA damage repair. Moreover, decreased XPA, p21, or MLH1 expression resulted in both significantly enhanced cell cycle progression and increased yields of chromosome aberrations, indicating that these gene products modulate both cell cycle control and DNA damage repair. Nine of these eleven genes, whose knock-down expression affected cytogenetic repair, were up-regulated in cells exposed to gamma radiation, suggesting that genes transcriptionally modulated by IR were critical to regulate IR-induced biological consequences. Furthermore, eight non-DBS repair genes showed involvement in regulating DSB repair, indicating that successful DSB repair requires both DSB repair mechanisms and non-DSB repair systems.

Zhang, Ye↗
NASA NTRS2007

Broadband Phase Retrieval for Image-Based Wavefront Sensing

A focus-diverse phase-retrieval algorithm has been shown to perform adequately for the purpose of image-based wavefront sensing when (1) broadband light (typically spanning the visible spectrum) is used in forming the images by use of an optical system under test and (2) the assumption of monochromaticity is applied to the broadband image data. Heretofore, it had been assumed that in order to obtain adequate performance, it is necessary to use narrowband or monochromatic light. Some background information, including definitions of terms and a brief description of pertinent aspects of image-based phase retrieval, is prerequisite to a meaningful summary of the present development. Phase retrieval is a general term used in optics to denote estimation of optical imperfections or aberrations of an optical system under test. The term image-based wavefront sensing refers to a general class of algorithms that recover optical phase information, and phase-retrieval algorithms constitute a subset of this class. In phase retrieval, one utilizes the measured response of the optical system under test to produce a phase estimate. The optical response of the system is defined as the image of a point-source object, which could be a star or a laboratory point source. The phase-retrieval problem is characterized as image-based in the sense that a charge-coupled-device camera, preferably of scientific imaging quality, is used to collect image data where the optical system would normally form an image. In a variant of phase retrieval, denoted phase-diverse phase retrieval [which can include focus-diverse phase retrieval (in which various defocus planes are used)], an additional known aberration (or an equivalent diversity function) is superimposed as an aid in estimating unknown aberrations by use of an image-based wavefront-sensing algorithm. Image-based phase-retrieval differs from such other wavefront-sensing methods, such as interferometry, shearing interferometry, curvature wavefront sensing, and Shack-Hartmann sensing, all of which entail disadvantages in comparison with image-based methods. The main disadvantages of these non-image based methods are complexity of test equipment and the need for a wavefront reference.

Dean, Bruce H.↗
NASA NTRS2009

Distribution of Chromosome Breakpoints in Human Epithelial Cells Exposed to Low- and High-LET Radiations

The advantage of the multicolor banding in situ hybridization (mBAND) technique is not only its ability to identify simultaneously both inter- and intrachromosome exchanges, but also the ability to measure the breakpoint location along the length of the chromosome in a precision that is unmatched with other traditional banding techniques. Breakpoints on specific regions of a chromosome have been known to associate with specific cancers. The breakpoint distribution in cells after low- and high-LET radiation exposures will also provide the data for biophysical modeling of the chromatin structure, as well as the data for the modeling the formation of radiation-induced chromosome aberrations. In a series of experiments, we studied low- and high-LET radiation-induced chromosome aberrations using the mBAND technique with chromosome 3 painted in 23 different colored bands. Human epithelial cells (CH1 84B5F5/M10) were exposed in vitro to Cs- 137 rays at both low and high dose rates, secondary neutrons with a broad energy spectrum at a low dose rate and 600 MeV/u Fe ions at a high dose rate. The data of both inter- and intrachromosome aberrations involving the painted chromosome have been reported previously. Here we present data of the location of the chromosome breaks along the length of chromosome 3 in the cells after exposures to each of the four radiation scenarios. In comparison to the expected breakpoint distribution based on the length of the bands, the observed distribution appeared to be non-random for both the low- and high-LET radiations. In particular, hot spots towards both ends of the chromosome were found after low-LET irradiations of either low or high dose rates. For both high-LET radiation types (Fe ions and neutrons), the breakpoint distributions were similar, and were much smoother than that for low-LET radiation. The dependence of the breakpoint distribution on the radiation quality requires further investigations.

Hada, Megumi↗
NASA NTRS2003

Truly Incomplete and Complex Chromosomal Exchanges in Human Fibroblast Cells Exposed In Situ to Energetic Heavy Ions

Confluent human fibroblast cells (AG 1522) were irradiated with gamma rays, 490 MeV/nucleon Si, or with Fe ions at either 200 or 500 MeV/nucleon. The cells were allowed to repair at 37 C for 24 hours after exposure, and a chemically induced premature chromosome condensation (PCC) technique was used to condense chromosomes in the G2 phase of the cell cycle. Incomplete and complex exchanges were analyzed in the irradiated samples. In order to verify that chromosomal breaks were truly unrejoined, chromosome aberrations were analyzed using a combination of whole chromosome specific probes and probes specific for the telomere region of the chromosome. Results showed that the frequency of unrejoined chromosome breaks was higher after high-LET radiation, and consequently, the ratio of incomplete to complete exchanges increased steadily with LET up to 440 keV/micron, the highest LET value in the present study. For samples exposed to 200 MeV/nucleon Fe ions, chromosome aberrations were analyzed using the multicolor FISH (mFISH) technique that allow identification of both complex and truly incomplete exchanges. Results of the mFISH study showed that 0.7 and 3 Gy dose of the Fe ions produced similar ratios of complex to simple exchanges and incomplete to complete exchanges, values for which were higher than those obtained after a 6 Gy gamma exposure. After 0.7 Gy of Fe ions, most complex aberrations were found to involve three or four chromosomes, which is a likely indication of the maximum number of chromosome domains traversed by a single Fe ion track.

Wu, Honglu↗
NASA NTRS2014

Karyotyping of Chromosomes in Human Bronchial Epithelial Cells Transformed by High Energy Fe Ions

Lung cancer induced from exposure to space radiation is believed to be one of the most significant health risks for long-term space travels. In a previous study, normal human bronchial epithelial cells (HBECs), immortalized through the expression of Cdk4 and hTERT, were exposed to gamma rays and high energy Fe ions for the selection of transformed clones induced by low- and high-LET radiation. In this research, we analyzed chromosome aberrations in these selected clones for genomic instability using the multi-color fluorescent in situ hybridization (mFISH), as well as the multi-banding in situ hybridization (mBAND) techniques. In most of the clones, we found chromosomal aberrations involving translocations between different chromosomes, with several of the breaks occurred in the q-arm of chromosome 3. We also identified copy number variations between the transformed clones and the parental HBEC cells regardless of the exposure condition. Our results indicated that the chromosomal aberrations in low- and high radiation-induced transformed clones are inadequately different from spontaneous soft agar growth. Further analysis is underway to reveal the genomic instability in more transformed clones

Yeshitla, Samrawit↗
NASA NTRS2015

Simulation of DNA Damage in Human Cells from Space Radiation Using a Physical Model of Stochastic Particle Tracks and Chromosomes

The formation of double-strand breaks (DSBs) and chromosomal aberrations (CAs) is of great importance in radiation research and, specifically, in space applications. We are presenting a recently developed model, in which chromosomes simulated by NASARTI (NASA Radiation Tracks Image) is combined with nanoscopic dose calculations performed with the Monte-Carlo simulation by RITRACKS (Relativistic Ion Tracks) in a voxelized space. The model produces the number of DSBs, as a function of dose for high-energy iron, oxygen, and carbon ions, and He ions. The combined model calculates yields of radiation-induced CAs and unrejoined chromosome breaks in normal and repair deficient cells. The merged computational model is calibrated using the relative frequencies and distributions of chromosomal aberrations reported in the literature. The model considers fractionated deposition of energy to approximate dose rates of the space flight environment. The merged model also predicts of the yields and sizes of translocations, dicentrics, rings, and more complex-type aberrations formed in the G0/G1 cell cycle phase during the first cell division after irradiation.

Ponomarev, Artem↗
NASA NTRS2019

Design and Modeling of the Off-Axis Parabolic Deformable (OPD) Mirror Laboratory

Coronagraph-equipped direct imaging missions need an active wavefront control system to cancel out the optical aberrations that degrade the performance of the coronagraphs. A fast steering mirror is used to control Line-of-Sight (LoS) pointing error caused by the telescope jitter. In addition to controlling other low-order aberrations such as astigmatism and coma, high stroke, high actuator density deformable mirrors (DMs) are also used to control the electric field at the required high spatial frequencies. We are designing a testbed to verify a different deformable architecture, where the powered optic in the optical train are controllable and have lower actuator count compared to the existing DMs with flat nominal surfaces. This simplifies the packaging issue for space missions and reduces both cost and risk of having the entire coronagraph instrument's performance depending on one or two high-actuator count DMs. The testbed would also be capable of testing different low-order wavefront sensing algorithms, which focuses in the near-term on a new adaptive Kalman filtering and gradient decent method to estimate the harmonic LoS errors that affect space telescopes. In long run, we would test different machine learning techniques to estimate low-order aberrations and non-linear algorithms for digging the region of high contrast called the dark holes (DH).

Subedi, Hari↗