Engineering Papers⌕ Search

Engineering topics

Evans, R. H.

Publications and source records attributed to Evans, R. H..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Extracellular calcium elicits a chemokinetic response from monocytes in vitro and in vivo

Recruitment of macrophages to sites of cell death is critical for induction of an immunologic response. Calcium concentrations in extracellular fluids vary markedly, and are particularly high at sites of injury or infection. We hypothesized that extracellular calcium participates in modulating the immune response, perhaps acting via the seven-transmembrane calcium-sensing receptor (CaR) on mature monocytes/macrophages. We observed a dose-dependent increase in monocyte chemotaxis in response to extracellular calcium or the selective allosteric CaR activator NPS R-467. In contrast, monocytes derived from mice deficient in CaR lacked the normal chemotactic response to a calcium gradient. Notably, CaR activation of monocytes bearing the receptor synergistically augmented the transmigration response of monocytes to the chemokine MCP-1 in association with increased cell-surface expression of its cognate receptor, CCR2. Conversely, stimulation of monocytes with MCP-1 or SDF-1alpha reciprocally increased CaR expression, suggesting a dual-enhancing interaction of Ca(2+) with chemokines in recruiting inflammatory cells. Subcutaneous administration in mice of Ca(2+), MCP-1, or (more potently) the combination of Ca(2+) and MCP-1, elicited an inflammatory infiltrate consisting of monocytes/macrophages. Thus extracellular calcium functions as an ionic chemokinetic agent capable of modulating the innate immune response in vivo and in vitro by direct and indirect actions on monocytic cells. Calcium deposition may be both consequence and cause of chronic inflammatory changes at sites of injury, infection, and atherosclerosis.

Non-NASA Center↗
NASA NTRS1995

TRISTAR 1: Evaluation methods for testing head-up display (HUD) flight symbology

The first in a series of piloted head-up display (HUD) flight symbology studies (TRISTAR) measuring pilot task performance was conducted at the NASA Ames Research Center by the Tri-Service Flight Symbology Working Group (FSWG). Sponsored by the U.S. Army Aeroflightdynamics Directorate, this study served as a focal point for the FSWG to examine HUD test methodology and flight symbology presentations. HUD climb-dive marker dynamics and climb-dive ladder presentations were examined as pilots performed air-to-air (A/A), air-to-ground (A/G), instrument landing system (ILS), and unusual attitude (UA) recover tasks. Symbolic presentations resembled pitch ladder variations used by the U.S. Air Force (USAF), U.S. Navy (USN), and Royal Air Force (RAF). The study was initiated by the FSWG to address HUD flight symbology deficiencies, standardization, issue identification, and test methodologies. It provided the mechanism by which the USAF, USN, RAF, and USA could integrate organizational ideas and reduce differences for comparisons. Specifically it examined flight symbology issues collectively identified by each organization and the use of objective and subjective text methodology and flight tasking proposed by the FSWG.

Newman, R. L.↗
NASA NTRS1993

Comment on 'Aerosol and Rayleigh radiance contributions to Coastal Zone Colour Scanner images' by Eckstein and Simpson

In a recent paper Eckstein and Simpson describe what they believe to be serious difficulties and/or errors with the CZCS (Coastal Zone Color Scanner) processing algorithms based on their analysis of seven images. Here we point out that portions of their analysis, particularly those dealing with multiple scattered Rayleigh radiance, are incorrect. We also argue that other problems they discuss have already been addressed in the literature. Finally, we suggest that many apparent artifacts in CZCS-derived pigment fields are likely to be due to inadequacies in the sensor band set or to poor radiometric stability, both of which will be remedied with the next generation of ocean color sensors.

Gordon, H. R.↗
NASA NTRS1985

Chronology of warm-core ring 82B

The chronology presently derived from satellite thermal imagery to describe the formation and life history of the warm core ring 82B furnishes insight into a classification of features and discrete events associated with Gulf Stream warm core rings; these events are thereby put in a broader spatial and temporal context. The interactions of the ring with surrounding waters are noteworthy, and the existence of vortex-vortex interactions is shown to be a significant cause of local water advection through streamer activity. Acoustic velocity profiling and drifter trajectories have been used to corroborate hydrographic features of the ring and its environs.

Evans, R. H.↗
NASA NTRS1985

Small-scale cyclones on the periphery of a Gulf Stream warm-core ring

Small-scale cyclones found around Gulf Stream warm-core ring 82B are investigated by using infrared satellite images and current information obtained with an acoustic-Doppler velocimeter. Currents in these cyclones reveal speeds ranging from 20 to 80 cm/s. One small cyclone or 'ringlet' found in June 1982 was studied extensively by removing the basic rotational velocities of 82B. The azimuthal velocity field for this ringlet was used with the gradient current equation to calculate the absolute dynamic topography at 100 dbar. It was found that the ringlet was 13 dyn-cm lower than its surroundings. In addition, neglect of the centrifugal term would have changed the dynamic topography of the ringlet by 30 percent. From a comparison with CTD data the absolute reference level was determined, and a vertical profile of horizontal currents was calculated for the ringlet. Other cyclones were found throughout the slope water region around warm-core ring 82B with observable lifetimes of 1 to 2 weeks. The northeast quadrant of 82B was a favored generation site for ringlets. Two cyclones were observed to form in this region and were advected anticyclonically around 82B. Typically, at any one time, six cyclones with diameters of approximately 40 to 50 km can be detected north of the Gulf Stream by using satellite images.

Kennelly, M. A.↗
NASA NTRS1983

Nimbus 7 CZCS - Reduction of its radiometric sensitivity with time

Preliminary results are described for an effort to quantify the sensitivity decay of a radiometry sensor (the Coastal Zone Color Scanner or CZCS aboard Nimbus 7). The method used in the study is to (1) compute the water-leaving radiance for imagery acquired in regions where this radiance is known or can be independently estimated, and (2) adjust the sensor calibration to force agreement between the two radiances. Decay factors for orbit numbers from 0 to 20,000 are plotted, and surface and space measurements are compared for the Gulf Stream and the Northern Sargasso Sea at different seasons. The fact that a seasonal variability in the chlorophyll a concentration in the Sargasso Sea was found in the sensor analysis (apparently the first such satellite observation) increases confidence in the method.

Gordon, H. R.↗
NASA NTRS1983

DSN ground communications facility

A functional description of the GCF and its relationships with other elements of the DSN and NASCOM is presented together with development objectives and goals and comments on implementation activites in support of flight projects.

Evans, R. H.↗
NASA NTRS1983

Phytoplankton pigment concentrations in the Middle Atlantic Bight - Comparison of ship determinations and CZCS estimates

The processing algorithms used for relating the apparent color of the ocean observed with the Coastal-Zone Color Scanner on Nimbus-7 to the concentration of phytoplankton pigments (principally the pigment responsible for photosynthesis, chlorophyll-a) are developed and discussed in detail. These algorithms are applied to the shelf and slope waters of the Middle Atlantic Bight and also to Sargasso Sea waters. In all, four images are examined, and the resulting pigment concentrations are compared to continuous measurements made along ship tracks. The results suggest that over the 0.08-1.5 mg/cu m range, the error in the retrieved pigment concentration is of the order of 30-40% for a variety of atmospheric turbidities. In three direct comparisons between ship-measured and satellite-retrieved values of the water-leaving radiance, the atmospheric correction algorithm retrieved the water-leaving radiance with an average error of about 10%. This atmospheric correction algorithm does not require any surface measurements for its application.

Gordon, H. R.↗
NASA NTRS1981

DSN ground communication facility

A functional description of the GCF and its relationships with other elements of the DSN and NASCOM is presented together with development objectives and goals and comments on implementation activities in support of flight projects.

Evans, R. H.↗
NASA NTRS1980

DSN Ground Communications Facility

A functional description of the Ground Communications Facility (GCF) and its relationships with other elements of the Deep Space Network and the NASA Communications Network is presented together with development objectives and goals and comments on implementation activities in support of flight projects. The voice, teletype, high speed data, wideband data, monitor and control, data records, network log processor, and network communications equipment subsystems are individually examined.

Evans, R. H.↗
NASA NTRS1980

Satellite remote sensing facility for oceanograhic applications

The project organization, design process, and construction of a Remote Sensing Facility at Scripps Institution of Oceanography at LaJolla, California are described. The facility is capable of receiving, processing, and displaying oceanographic data received from satellites. Data are primarily imaging data representing the multispectral ocean emissions and reflectances, and are accumulated during 8 to 10 minute satellite passes over the California coast. The most important feature of the facility is the reception and processing of satellite data in real time, allowing investigators to direct ships to areas of interest for on-site verifications and experiments.

Evans, R. H.↗
NASA NTRS1979

DSN ground communications facility

A functional description of the Ground Communications Facilities and its relationships with other elements of the Deep Space Network and NASA Communications Network is presented together with development objectives and goals and comments on implementation activities in support of flight projects.

Evans, R. H.↗
NASA NTRS1978

DSN ground communications facility

A functional description of the ground communications facility and its relationships with other elements of the Deep Space network and the world-wide NASA communications network (NASCOM) is presented together with development activities and goals and comments on implementation activities in support of flight projects.

Evans, R. H.↗
NASA NTRS1971

Table look-up approach to pattern recognition.

The table look-up approach is based on prestoring in fast, random-access, core memory the desired answer (e.g., crop-type) for all combinations of multispectral scanner outputs from selected channels. Specifically, each set of measurements from a given point on the ground is interpreted as that address in core memory where the answer can be retrieved. Substituting the simple retrieval operation for the length y computations required by the conventional approach offers two advantages: (1) the processing time is reduced by more than an order of magnitude; (2) the multispectral scanner data can be processed by computers having minimal sophistication, complexity, and cost. These two advantages may make it possible to use an onboard computer to perform the classification function in flight.

Eppler, W. G.↗