ALBERT

Description: Chemical analyses returned by Mars Pathfinder indicate that some rocks may be high in silica, implying differentiated parent materials. Rounded pebbles and cobbles and a possible conglomerate suggest fluvial processes that imply liquid water in equilibrium with the atmosphere and thus a warmer and wetter past. The moment of inertia indicates a central metallic core of 1300 to 2000 kilometers in radius. Composite airborne dust particles appear magnetized by freeze-dried maghemite stain or cement that may have been leached from crustal materials by an active hydrologic cycle. Remote-sensing data at a scale of generally greater than approximately 1 kilometer and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catastrophic floods that are relatively dust-free.

Description: An annual whiting event occurs each year in late May to early June in Fayetteville Green Lake, New York. The initiation of this event correlates with exponential growth of the Synechococcus population within the lake. Synechococcus is the dominant (by approximately 4 orders of magnitude) autotrophic organism owing to the oligotrophic condition of the lake. The delta 13C values of the dissolved inorganic C range seasonally from -9.5% in winter to -6.2% in summer due to photosynthetic activity. Calcite precipitates principally in the microenvironment surrounding Synechococcus because of a photosynthetically driven alkalization process and the availability of the cells as nucleation sites. This calcite has a heavier delta 13C value (〉4%) than does the dissolved inorganic C of the lake water owing to the cells' preferential uptake of 12C. A conceptual model suggests that photosynthetic activity and cell surface chemistry, together with the substantial surface area that arises from the great abundance of micron-sized cells, allow Synechococcus to dominate the annual whiting events in Fayetteville Green Lake.

Description: The Rotating-Wall Vessel (RWV) is a novel in vitro cell culture system used to successfully culture a cell line derived from a heterologous mixed mullerian tumor cell of the ovary. Although the original tumor was comprised of both epithelial and mesodermal components, long-term culture in conventional flasks established a cell line from this tumor with homogeneous epitheliallike growth characteristics (1). Cells from Passage 36 were seeded into a Rotating-Wall Vessel containing Cytodex-3 microcarrier beads. Scanning electron micrographs of tumor cells cultured for 32 d in the RWV showed the presence of heterogeneous cell populations organized into three-dimensional tissuelike architecture. Immunocytochemical analysis confirmed the cellular heterogeneity, as demonstrated by expression of both epithelial and mesenchymal antigens. Reverse transcription polymerase chain reaction amplification demonstrated the presence of mRNA for cellular oncogenes HER-2/neu, H-ras, K-ras, and tumor suppressor p53. Thus, there are two advantages to propagation of tissue in the RWV culture system:(a) tissue diversification representing populations present in the original tumor, and (b) the three-dimensional freedom to organize tissues morphologically akin to those observed in vivo. These data indicate that the RWV culture system is suitable for generating large quantities of ovarian tumor cells in vitro that are amenable to immunocytochemical, oncogenic, morphologic characteristics demonstrated in vivo.

Description: Immunity relies on the circulation of lymphocytes through many different tissues including blood vessels, lymphatic channels, and lymphoid organs. The ability of lymphocytes to traverse the interstitium in both nonlymphoid and lymphoid tissues can be determined in vitro by assaying their capacity to locomote through Type I collagen. In an attempt to characterize potential causes of microgravity-induced immunosuppression, we investigated the effects of simulated microgravity on human lymphocyte function in vitro using a specialized rotating-wall vessel culture system developed at the Johnson Space Center. This very low shear culture system randomizes gravitational vectors and provides an in vitro approximation of microgravity. In the randomized gravity of the rotating-wall vessel culture system, peripheral blood lymphocytes did not locomote through Type I collagen, whereas static cultures supported normal movement. Although cells remained viable during the entire culture period, peripheral blood lymphocytes transferred to unit gravity (static culture) after 6 h in the rotating-wall vessel culture system were slow to recover and locomote into collagen matrix. After 72 h in the rotating-wall vessel culture system and an additional 72 h in static culture, peripheral blood lymphocytes did not recover their ability to locomote. Loss of locomotory activity in rotating-wall vessel cultures appears to be related to changes in the activation state of the lymphocytes and the expression of adhesion molecules. Culture in the rotating-wall vessel system blunted the ability of peripheral blood lymphocytes to respond to polyclonal activation with phytohemagglutinin. Locomotory response remained intact when peripheral blood lymphocytes were activated by anti-CD3 antibody and interleukin-2 prior to introduction into the rotating-wall vessel culture system. Thus, in addition to the systemic stress factors that may affect immunity, isolated lymphocytes respond to gravitational changes by ceasing locomotion through model interstitium. These in vitro investigations suggest that microgravity induces non-stress-related changes in cell function that may be critical to immunity. Preliminary analysis of locomotion in true microgravity revealed a substantial inhibition of cellular movement in Type I collagen. Thus, the rotating-wall vessel culture system provides a model for analyzing the microgravity-induced inhibition of lymphocyte locomotion and the investigation of the mechanisms related to lymphocyte movement.

Description: Airborne microwave radiometric measurements in the framework of the HAPEX-Sahel Experiment were performed by the Push Broom Microwave Radiometer (PBMR) and the PORTOS radiometer. The flights of both radiometers produced an original set of data covering the 1.4-90 GHz range of frequency. The East and West Central Super Sites were the areas most intensively observed by the microwave radiometers. Over those sites, several brightness temperature (TB) maps are available at seven dates distributed over a 1 month period in the middle of the rainy season. A comparison of the two radiometers demonstrates their radiometric quality and the precision of the localization of the microwave observations. At 1.4 GHz, the vegetation had very little effect on the soil microwave emission. Maps of soil moisture were developed using a single linear relationship between TB and the surface soil moisture. There is an important spatial heterogeneity in the soil moisture distribution, which is explained by both the soil moisture hydrodynamic properties and the localization of the precipitation fields. At 5.05 GHz, the vegetation must be accounted for to infer soil moisture from the microwave observations. A method based on a simple radiative transfer model and on microwave data has shown encouraging results.

Description: Despite significant achievements in computational fluid dynamics, there still remain many fluid flow phenomena not well understood. For example, the prediction of temperature distributions is inaccurate when temperature gradients are high, particularly in shock wave turbulent boundary layer interactions close to the wall. Complexities of fluid flow phenomena include transition to turbulence, relaminarization separated flows, transition between viscous and inviscid incompressible and compressible flows, among others, in all speed regimes. The purpose of this paper is to introduce a new approach, called the Flowfield-Dependent Mixed Explicit-Implicit (FDMEI) method, in an attempt to resolve these difficult issues in Computational Fluid Dynamics (CFD). In this process, a total of six implicitness parameters characteristic of the current flowfield are introduced. They are calculated from the current flowfield or changes of Mach numbers, Reynolds numbers, Peclet numbers, and Damkoehler numbers (if reacting) at each nodal point and time step. This implies that every nodal point or element is provided with different or unique numerical scheme according to their current flowfield situations, whether compressible, incompressible, viscous, inviscid, laminar, turbulent, reacting, or nonreacting. In this procedure, discontinuities or fluctuations of an variables between adjacent nodal points are determined accurately. If these implicitness parameters are fixed to certain numbers instead of being calculated from the flowfield information, then practically all currently available schemes of finite differences or finite elements arise as special cases. Some benchmark problems to be presented in this paper will show the validity, accuracy, and efficiency of the proposed methodology.

Description: Eliminating or reducing current restrictions in the air traffic control system due to wake vortex considerations would yield increased capacity, decreased delays, and cost savings. Current wake vortex separation standards are widely viewed as very conservative under most conditions. However, scientific uncertainty about wake vortex behavior under different atmospheric conditions remains a barrier to development of an adaptive vortex spacing system. The objective of the wake vortex field measurement efforts during December, 1994 and August, 1995 at Memphis, TN were to record wake vortex behavior for varying atmospheric conditions and types of aircraft. This effort is part of a larger effort by the NASA Langley Research Center to develop an Aircraft Vortex Spacing System (AVOSS) as an element of the Terminal Area Productivity (TAP) program. The TAP program is being performed in concert with the FAA Terminal Air Traffic Control Automation (TATCA) program and ATC Automation. Wake vortex behavior was observed using a mobile continuous-wave (CW) coherent laser Doppler radar (lidar) developed at Lincoln Laboratory. This lidar features a number of improvements over previous systems, including the first-ever demonstration of an automatic wake vortex detection and tracking algorithm.