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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Collagen Turnover in Relation to Risk Factors and Hemodynamics in Human Intracranial Aneurysms

Determinants for molecular and structural instability, that is, impending growth or rupture, of intracranial aneurysms (IAs) remain uncertain. To elucidate this, we endeavored to estimate the actual turnover rates of the main molecular constituent in human IA (collagen) on the basis of radiocarbon ( 14 C) birth dating in relation to IA hemodynamics. Collagen turnover rates in excised human IA samples were calculated using mathematical modeling of 14 C birth dating data of collagen in relation to risk factors and histological markers for collagen maturity/turnover in selected IA. Hemodynamics were simulated using image-based computational fluid dynamics. Correlation, logistic regression, and receiver operating characteristic analyses were performed. Collagen turnover rates were estimated in 46 IA (43 patients); computational fluid dynamics could be performed in 20 IA (20 patients). The mean collagen turnover rate (γ) constituted 126% (±1% error) per year. For patients with arterial hypertension, γ was greater than 2600% annually, whereas γ was distinctly lower with 32% (±1% error) per year for patients without risk factors, such as smoking and hypertension. There was a distinct association between histological presence of rather immature collagen in human IA and the presence of modifiable risk factors. Spatial-temporal averaged wall shear stress predicted rapid collagen turnover (odds ratio, 1.6 [95% CI, 1.0–2.7]). Receiver operating characteristic analysis demonstrated a good test accuracy (area under the curve, 0.798 [95% CI, 0.598–0.998]) for average wall shear stress with a threshold ≥4.9 Pa for rapid collagen turnover. Our data indicate that turnover rates and stability of collagen in human IA are strongly associated with the presence of modifiable risk factors and aneurysmal hemodynamics. Finally, these findings underline the importance of strict risk factor modification in patients with unruptured IA. Future should include more detailed risk factor data to establish a more causal understanding of hemodynamics and the rupture risk of individual IA.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Science & Technology Review: Climate Change Comes into Focus

At Lawrence Livermore National Laboratory, we focus on science and technology research to ensure our nation’s security. We also apply that expertise to solve other important national problems in energy, bioscience, and the environment. Science & Technology Review is published eight times a year to communicate, to a broad audience, the Laboratory’s scientific and technological accomplishments in fulfilling its primary missions. The publication’s goal is to help readers understand these accomplishments and appreciate their value to the individual citizen, the nation, and the world. The cover image shows a simulation run on the Department of Energy’s (DOE’s) state-of-the-science Energy Exascale Earth Systems Model (E3SM), which leverages DOE’s advanced supercomputers for climate and earth science research. As the article beginning on p. 4 describes, the newly released version 2 will be used to simulate aspects of Earth’s variability at weather-scale resolution and investigate decadal changes in climate that will critically impact the United States in coming years.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

CT584 Is Not a Protective Vaccine Antigen against Respiratory Chlamydial Challenge in Mice

Background: Chlamydia trachomatis is the most prevalent bacterial sexually transmitted pathogen in humans worldwide. Since chlamydial infection is largely asymptomatic with the potential for serious complications, a preventative vaccine is likely the most viable long-term answer to this public health threat. Cell-free protein synthesis (CFPS) utilizes the cellular protein manufacturing machinery decoupled from the requirement for maintaining cellular viability, offering the potential for flexible, rapid, and decentralized production of recombinant protein vaccine antigens. Methods: Here, we use CFPS to produce the full-length putative chlamydial type three secretion system (T3SS) needle-tip protein, CT584, for evaluation as a vaccine antigen in mouse models. High-speed atomic force microscopy (HS-AFM) (RIBM, Tsukuba, Japan) imaging and computer simulations confirm that CFPS-produced CT584 retains a native-like structure prior to immunization. Female mice were primed with CT584 adjuvanted with CpG-1826 intranasally (i.n.) or CpG-1826 + Montanide ISA 720 intramuscularly (i.m.), followed four weeks later by an i.m. boost before respiratory challenge with 10 4 inclusion forming units (IFU) of Chlamydia muridarum. Results: Immunization with CT584 generated robust antibody responses but weak cell-mediated immunity and failed to protect against i.n. challenge as demonstrated by body weight loss, increased lung weights, and the presence of high numbers of IFUs in the lungs. Conclusion: While CT584 was not a protective vaccine candidate, the speed and flexibility with which CFPS can be used to produce other potential chlamydial antigens make it an attractive technique for antigen production.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1974

Evaluation of satellite remote sensing and automatic data techniques for characterization of wetlands and coastal marshlands

The author has identified the following significant results. The evaluation was conducted in a humid swamp and marsh area of southern Louisiana. ERTS digital multispectral scanner data was compared with similar data gathered by intermediate altitude aircraft. Automatic data processing was applied to several data sets to produce simulated color infrared images, analysis of single bands, thematic maps, and surface classifications. These products were used to determine the effectiveness of satellites to monitor accretion of land, locate aquatic plants, determine water characteristics, and identify marsh and forest species. The results show that to some extent all of these can be done with satellite data. It is most effective for monitoring accretion and least effective in locating aquatic plants. The data sets used show that the ERTS data is superior in mapping quality and accuracy to the aircraft data. However, in some applications requiring high resolution or maximum use of intermittent clear weather conditions, data gathering by aircraft is preferable. Data processing costs for equivalent areas are about three times greater for aircraft data than ERTS data. This is primarily because of the larger volume of data generated by the high resolution aircraft system.

Cartmill, R. H.↗
NASA NTRS1974

Internal Ultraviolet Explorer (IUE) study program. Volume 1: Technology discussion

The results of a simulation study to predict the IUE imaging chain performance are presented, including simulation photographs and transparencies of ultraviolet echelle spectra. Errors in wavelength determination and radiometric measurements due to system degradation are indicated to be minor. Some order overlap is predicted at the bottom of the echelle format.

Turner, T. S., Jr.↗
NASA NTRS1977

Meteorological radar facility (MRF) slot conductance investigations

A preliminary meteorological radar facility (MRF) array design was completed in support of the slot conductance measurement program. Three different slot measurement techniques were evaluated. The selection of the probe comparison measurement technique was selected as the principal experimental method with the impedance measurement technique chosen to measure a few higher conductance slots to be used as reference slots. The impedance of 43 slots in 0.9 x 0.4 inch standard waveguide and of 40 slots in 0.835 x 0.4 inch waveguide was measured. Also, impedance measurements were made of a few slots using image planes to simulate mutual coupling effects. The measured and theoretical conductance, susceptance, and radiation phase data are presented in graphic form as a function of slot displacement for constant slot length, and of slot length for constant slot displacement. It is concluded that the proposed MRF array design approach is a feasible one.

Ratkevich, A. E.↗
NASA NTRS1979

A model for testing centerfinding algorithms for automated optical navigation

An efficient software simulation of the imaging process for optical navigation is presented, illustrating results using simple examples. The problems of image definition and optical system modeling, including ideal image containing features and realistic models of optical filtering performed by the entire camera system, are examined. A digital signal processing technique is applied to the problem of developing methods of automated optical navigation and the subsequent mathematical formulation is presented. Specific objectives such as an analysis of the effects of camera defocusing on centerfinding of planar targets, addition of noise filtering to the algorithm, and implementation of multiple frame capability were investigated.

Griffin, M. D.↗
NASA NTRS1980

Crop classification with a Landsat/radar sensor combination

A combined Landsat/radar approach to classification of remotely sensed data, with emphasis on crops, was undertaken. Radar data were obtained by microwave radar spectrometers over fields near Eudora, Kansas and Landsat image data were obtained for the same test site. After Landsat digital images were registered and test-cells extracted, a comparable set of radar image pixels were simulated to match the Landsat pixels. The combined data set is then used for classification, and the results are examined with the best combination of sensor variables identified. Finally, the usefulness of radar in a simulated cloud-cover situation is demonstrated. The major conclusion derived from this study is that the combination of radar/optical sensors is superior to either one alone.

Li, R. Y.↗
NASA NTRS1984

Rectification of single and multiple frames of satellite scanner imagery using points and edges as control

Rectification of single and overlapping multiple scanner frames produced by such satellite-borne scanners as the LANDSAT MSS was carried out using a newly developed comprehensive parametric model. Tests with both simulated and real image data demonstrate conclusively that this model in general is superior to the widely used polynomial model, and that the simultaneous rectification of overlapping frames using least squares techniques yields a high accuracy than sngle frame rectification due to the inclusion of tie points between the image frames. Used to control, edges or lines, whic are much more likely to be found in images, can replace conventional control points and can easily be implemented into the least squares approach. An efficient algorithm for findng corresponding points in image paris was developed which can be used for determining tie points between image frames and thus increase the ecnomy of the whole rectification procedure.

Paderes, F. C., Jr.↗
NASA NTRS1984

Thematic Mapper simulator research for forest resource mapping in the Clearwater National Forest, Idaho

Per-pixel maximum likelihood digital classification and photo interpretation of Thematic Mapper Simulator (TMS) composited images for a managed conifer forest were used to evaluate both land cover and forest structure characteristics. TMS channels 4, 7, 5 and 3, which were found to be optimal for forest vegetation analysis, used the full range of the Thematic Mapper's spectral capability. Photo interpretation results indicate that a false color composite from TMS channels 4, 7, and 2 provided the highest accuracies; the combination of improved spatial, spectral and radiometric resolution of the Thematic Mapper yielded greater sensitivity to forest structural characteristics.

Brass, J. A.↗
NASA NTRS1985

Spectroscopy of Moses Rock dike using remote sensing

Zeiss IR-photographs, NS0001 (TM simulator) and airborne imaging spectrometer (AIS) data were obtained for the Moses Rock kimberlite dike in southern Utah to identify and characterize the distinctive mafic mineralogy of the dike as well as the surrounding sedimentary rocks. The Zeiss and NS001 images provide information on the regional setting and allow units of the dike to be distinguished from the sediments. The AIS data are narrow images obtained in 128 near-infrared channels and provide characterizing information on the surface composition through. Three distinct spectroscopic units were found which have been tentatively identified as serpentized olivine-bearing soils found in the dike and two types of gypsum bearing soils found in the surrounding sedimentary soils.

Mustard, J. F.↗
NASA NTRS1986

Automation, robotics, and inflight training for manned Mars missions

The automation, robotics, and inflight training requirements of manned Mars missions will be supported by similar capabilities developed for the space station program. Evolutionary space station onboard training facilities will allow the crewmembers to minimize the amount of training received on the ground by providing extensive onboard access to system and experiment malfunction procedures, maintenance procedures, repair procedures, and associated video sequences. Considerable on-the-job training will also be conducted for space station management, mobile remote manipulator operations, proximity operations with the Orbital Maneuvering Vehicle (and later the Orbit Transfer Vehicle), and telerobotics and mobile robots. A similar approach could be used for manned Mars mission training with significant additions such as high fidelity image generation and simulation systems such as holographic projection systems for Mars landing, ascent, and rendezvous training. In addition, a substantial increase in the use of automation and robotics for hazardous and tedious tasks would be expected for Mars mission. Mobile robots may be used to assist in the assembly, test and checkout of the Mars spacecraft, in the handling of nuclear components and hazardous chemical propellent transfer operations, in major spacecraft repair tasks which might be needed (repair of a micrometeroid penetration, for example), in the construction of a Mars base, and for routine maintenance of the base when unmanned.

Holt, Alan C.↗
NASA NTRS1986

The Space Shuttle, fluid dynamics, and computer graphics

Several samples are presented of CFD-generated flow ribbon images of fuel flow in the SSME. The images result from simulations of H2 flow through a design iteration of the main injector, the hot gas manifold and the fuel bowl section. The color-coded ribbons provide three-dimensional perspectives which indicate the direction and orientation of the flow and the velocity magnitude in intervals along the flow path.

Belie, R. G.↗
NASA NTRS1990

RLE progress report no. 133, 1 January - 31 December 1990

Activities of the Research Laboratory of Electronics at MIT are summarized. NASA-sponsored research in the area of synthetic aperture radar image interpretation and simulation is described. Other government-sponsored and industry-sponsored studies are also described which address the following topics: microwave and millimeter wave integrated circuits, high-speed integrated circuit interconnects, Instrument Landing System/Microwave Landing System frequency management assessment, and superconducting electronics.

Allen, Jonathan↗
NASA NTRS1993

Analysis of rocket beacon transmissions for computerized reconstruction of ionospheric densities

Three methods are described to obtain ionospheric electron densities from transionospheric, rocket-beacon TEC data. First, when the line-of-sight from a ground receiver to the rocket beacon is tangent to the flight trajectory, the electron concentration can be obtained by differentiating the TEC with respect to the distance to the rocket. A similar method may be used to obtain the electron-density profile if the layer is horizontally stratified. Second, TEC data obtained during chemical release experiments may be interpreted with the aid of physical models of the disturbed ionosphere to yield spatial maps of the modified regions. Third, computerized tomography (CT) can be used to analyze TEC data obtained along a chain of ground-based receivers aligned along the plane of the rocket trajectory. CT analysis of TEC data is used to reconstruct a 2D image of a simulated equatorial plume. TEC data is computed for a linear chain of nine receivers with adjacent spacings of either 100 or 200 km. The simulation data are analyzed to provide an F region reconstruction on a grid with 15 x 15 km pixels. Ionospheric rocket tomography may also be applied to rocket-assisted measurements of amplitude and phase scintillations and airglow intensities.

Bernhardt, P. A.↗
NASA NTRS1994

AXAF VETA-I mirror ring focus measurements

The AXAF VETA-I mirror ring focus measurements were made with an HRI (microchannel plate) X-ray detector. The ring focus is a sharply focused ring formed by X-rays before they reach the VEAT-I focal plane. It is caused by spherical aberrations due to the finite source distance and the despace in the VETA-I test. The ring focus test reveals some aspects fo the test system distortions and the mirror surface figure which are difficult or impossible to detect at the focal plane. The test results show periodic modulations of the ring radius and width which could be caused by gravity, thermal, and/or epoxy shrinkage distortions. The strongest component of the modulation had a 12-fold symmetry, because these distortions were exerted on the mirror through 12 flexures of the VETA-I mount. Ring focus models were developed to simulate the ring image. The models were compared with the data to understand the test system distortions and the mirror glass imperfection. Further studies will be done to complete this work. The ring focus measurement is a very powerful test. We expect that a similar test for the finally assembled mirror of AXAD-I will be highly valuable.

Tananbaum, H. D.↗
NASA NTRS1992

Optimizing binary phase and amplitude filters for PCE, SNR, and discrimination

Binary phase-only filters (BPOFs) have generated much study because of their implementation on currently available spatial light modulator devices. On polarization-rotating devices such as the magneto-optic spatial light modulator (SLM), it is also possible to encode binary amplitude information into two SLM transmission states, in addition to the binary phase information. This is done by varying the rotation angle of the polarization analyzer following the SLM in the optical train. Through this parameter, a continuum of filters may be designed that span the space of binary phase and amplitude filters (BPAFs) between BPOFs and binary amplitude filters. In this study, we investigate the design of optimal BPAFs for the key correlation characteristics of peak sharpness (through the peak-to-correlation energy (PCE) metric), signal-to-noise ratio (SNR), and discrimination between in-class and out-of-class images. We present simulation results illustrating improvements obtained over conventional BPOFs, and trade-offs between the different performance criteria in terms of the filter design parameter.

Downie, John D.↗