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At least 487 records · Page 27

Small passive student experiments on G324 261 individual quests for student knowledge

The Charleston County School District CAN DO Project payload on STS-57 had a primary goal of photographing the Earth with the GeoCam camera system. In addition, the payload carried 261 passive student experiments representing the efforts of several thousand students throughout the district and in four other states. These experiments represented the individual concepts of teams ranging in age from pre-school to high school. Consequently, a tremendous variety of samples from collard green seeds to microscopic 'water bears' were flown. Each prospective team was provided a simple kit equipped with five vials. Each student team submitted five coded samples, one for space flight and four control samples. The control samples were exposed to radiation, cold and centrifugation respectively while one negative control sample was passively stored. The students received the samples back still coded so that they were unaware of which samples were flown. They then investigated their samples according to their individual research protocols. The results were presented in poster and platform form at a student research symposium. Space Trees grown from tree seeds flown in the payload have been planted at all district schools, and at many guest schools. These seeds represented another way in which to involve additional classes and students. Both the passive experiments and the space trees were housed in what otherwise would have been wasted space within the payload. They extended the GAS programs worthwhile ballast concept to another level. The opportunity to fly an experiment in space is too previous not to be extended to the greatest number of students possible.

Nicholson, James H.↗

Laser diagnostics for microgravity droplet studies

An instrument has been designed, built, and tested for performing laser diagnostic measurements of droplet combustion in low-gravity-flight aircraft. Nonintrusive measurements are of particular importance for droplet combustion (the simplest example of non-premixed combustion) and transport in microgravity environments, where physical contact would introduce an unacceptable level of perturbations. The resolution of these diagnostics can also isolate transport to length scales much smaller than the droplet diameter. These techniques can be configured to instantaneously map an entire flow field in two and three dimensions, providing either qualitative or quantitative information on the distribution of a desired scalar or vector quantity. Detailing the gas-phase flow field and position of the flame front can be achieved using planar laser-induced fluorescence (PLIF) of OH or another flame front marker. An alternative approach is to obtain LIF from a diagnostic seed included in the liquid phase fuel; it would be consumed at the flame front. The main advantage to this approach is that it is easier to choose the wavelength of the molecular absorption which coincides with convenient laser wavelengths rather than finding lasers which can be configured to access OH. Our present method uses a nitrogen-pumped dye laser tuned to a sodium absorption and addition of small concentrations of NaCl to the fuel. Particle image velocimetry (PIV) is a laser-based technique which has recently had its practicality greatly enhanced by the development of high-resolution CCD cameras and the increase in speed and capacity of computer systems. With this technique, a seeded flow is illuminated with a double-pulsed laser sheet to generate a double exposure image on a film or CCD camera. Computer analysis of the image is used to determine the particle velocity vectors and, thus, the gas velocity within the plane of the laser sheet. Our current experiment uses PIV for measuring relative droplet gas-phase velocities in a parabolic flight environment. The results show successful application of PLIF relative to luminosity and radical emission near 308 nm. PIV results are less successful due to gas thermal expansion deflecting the seed particles away from the measurement volume. PIV is applicable for measurements in the absence of combustion.

Winter, Michael↗

Method and apparatus for producing a substrate with low secondary electron emissions

The present invention is directed to a method and apparatus for producing a highly-textured surface on a copper substrate with only extremely small amounts of texture-inducing seeding or masking material. The texture-inducing seeding material is delivered to the copper substrate electrically switching the seeding material in and out of a circuit loop.

Jensen, Kenneth A.↗

Alexandrite laser transmitter development for airborne water vapor DIAL measurements

In the DIAL technique, the water vapor concentration profile is determined by analyzing the lidar backscatter signals for laser wavelengths tuned 'on' and 'off' a water vapor absorption line. Desired characteristics of the on-line transmitted laser beam include: pulse energy greater than or equal to 100 mJ, high-resolution tuning capability (uncertainty less than 0.25 pm), good spectral stability (jitter less than 0.5 pm about the mean), and high spectral purity (greater than 99 percent). The off-line laser is generally detuned less than 100 pm away from the water vapor line. Its spectral requirements are much less stringent. In our past research, we developed and demonstrated the airborne DIAL technique for water vapor measurements in the 720-nm spectral region using a system based on an alexandrite laser as the transmitter for the on-line wavelength and a Nd:YAG laser-pumped dye laser for the off-line wavelength. This off-line laser has been replaced by a second alexandrite laser. Diode lasers are used to injection seed both lasers for frequency and linewidth control. This eliminates the need for the two intracavity etalons utilized in our previous alexandrite laser and thereby greatly reduces the risk of optical damage. Consequently, the transmitted pulse energy can be substantially increased, resulting in greater measurement range, higher data density, and increased measurement precision. In this paper, we describe the diode injection seed source, the two alexandrite lasers, and the device used to line lock the on-line seed source to the water vapor absorption feature.

Chyba, Thomas H.↗

Effects of stress ethylene inhibitors on sweet clover (Melilotus Alba L.) seedling growth in microgravity

Previous experiments from our lab have shown that seeds of sweet clover, when germinated and grown within the Fluid Processing Apparatus (FPA) on a slow rotating clinostat produce significantly greater levels of the volatile stress hormone, ethylene, when compared to seeds treated the same but without clinorotation. In both conditions, carbon dioxide levels reached high levels and seedling growth was inhibited. However, clinorotation inhibited growth to a greater extent. To help determine to what extent microgravity influences stress ethylene production and to what extent ethylene inhibits seedling growth, we have extended the above experiments by growing sweet clover in the presence of aminooxyacetic acid (AOA) and silver nitrate (AgNO3), inhibitors of stress ethylene biosynthesis and action, respectively. Seeds of sweet clover were germinated and grown for five days in the FPA under two gravity conditions: under stationary conditions on Earth and in microgravity onboard the space shuttle, Discovery (STS-63), which launched Feb. 3, 1995. Upon recovery, gas samples were aspirated from the growth chambers and carbon dioxide and ethylene concentrations were measured using a gas chromatograph. Then the tissue was weighed, photographed and fixed, and is current undergoing further morphological and microscopic characterization.

Gallegos, Gregory L.↗

Method and Apparatus for Producing a Substrate with Low Secondary Electron Emissions

The present invention is directed to a method and apparatus for producing a highly-textured surface on a copper substrate with only extremely small amounts of texture-inducing seeding of masking material. The texture-inducing seeding material is delivered to the copper substrate electrically switching the seeding material in and out of a circuit loop.

Jensen, Kenneth A.↗

Performance Improvements to the Lidar Atmospheric Sensing Experiment (LASE)

Lidar Atmospheric Sensing Experiment (LASE) is the first fully-engineered, modular, tunable, autonomous Differential Absorption Lidar (DIAL) system for the remote measurement of water vapor, aerosols and clouds across the troposphere. It was designed, built and environmentally tested at LARC. LASE was designed to fly aboard a NASA/Ames ER-2 aircraft (NASA's high altitude aircraft) and operate at altitudes from 58,000 to 70,000 feet. Since its first flight on May 11, 1994, it has flown 28 total missions on board the ER-2. LASE has been validated with results showing an accuracy better than the initial requirement for vertical profiles of water vapor in the troposphere. LASE can also deploy on several other aircraft including the NASA P-3 and will fly aboard the NASA DC-8 during the Convection And Moisture EXperiment (CAMEX) in July-September 1998. The tunable laser system of LASE was designed to operate in a double-pulse mode at 5Hz, with energy outputs of up to 15OmJ per pulse in the 813 to 819nm wavelength region and with 99% of the output energy within a spectral interval of 1.06 pm. Sixteen wavelengths were selected to cover the various water vapor absorption cross sections needed for the DIAL measurement. The Ti:Sapphire laser was constructed using a frequency-doubled Nd:YAG laser as the pump source and a single mode diode laser as a injection seeder for the Ti:Al2O3 laser. We have improved the LASE instrument in several important ways. Improvements to the seed source have demonstrated that DFB laser diodes can be used as reliable seed sources on airborne DIAL instruments. The DFB diode has enabled LASE to gather more data and significantly reduced the maintenance required to insure that the system performance requirements are met. The multiwavelength sequential seeding technique is the current method of data collection for LASE. It has the advantages of providing an entire atmospheric coverage of H2O(v) from the ground to the aircraft altitude along a single ground track. The development of a flight deployable system to measure spectral purity will insure that the LASE instrument or any future flight based DIAL system can meet the performance specifications to insure data accuracy.

Edwards, W. C.↗

Substrate With Low Secondary Emissions

The present invention is directed to a method and apparatus for producing a highly -textured surface on a copper substrate -with only extremely small amounts of texture-inducing seeding or masking material. The texture-inducing seeding material is delivered to the copper substrate electrically switching the seeding material in and out of a circuit loop.

Jensen, Kenneth A.↗

Paleoenvironmental History of JoCo Marsh, Jamaica Bay, New York

Sediment cores from JoCo Marsh, located in Jamaica Bay, NY were analyzed for plant macrofossil and foraminifera records. These records reflect changes in vegetation, sea level, climate and human intervention. Better understanding of past environmental changes provides information for future preservation and protection of the estuary. A 2.81 m core was retrieved from JoCo, a high marsh area located on the eastern side of Jamaica Bay. The lithology of the core differs from high levels of sand, with small amounts of clay, in the bottom 0.8 meters, to salt marsh peat in the upper 2 meters of the core. Basal wood in the sand was dated to about 2060 yr BP. Elphidium foraminifera dominate the basal sands, along with Scirpus seeds, wood, and charcoal. These sands include fish scales which are tentatively identified as killifish, suggesting shallow pools. The transition to marsh peat is dominated by sedge seeds, and declines in charcoal. The peat appears to be dominated by salt marsh grasses. At 2 m the foraminifera change to include mainly Trochammina species and other undifferentiated agglutinates. The upper portion of the core is dominated by Salicornia seeds along with Trochammina and Miliammina or Quinqueloculia. The history of this marsh will be integrated with other records of marsh environmental change along the US eastern seaboard.

Liberman, Louisa↗

Seedless Laser Velocimetry Using Heterodyne Laser-Induced Thermal Acoustics

A need exists for a seedless equivalent of laser Doppler velocimetry (LDV) for use in low-turbulence or supersonic flows or elsewhere where seeding is undesirable or impractical. A compact laser velocimeter using heterodyne non-resonant laser-induced thermal acoustics (LITA) to measure a single component of velocity is described. Neither molecular (e.g. NO2) nor particulate seed is added to the flow. In non-resonant LITA two beams split from a short-pulse pump laser are crossed; interference produces two counterpropagating sound waves by electrostriction. A CW probe laser incident on the sound waves at the proper angle is directed towards a detector. Measurement of the beating between the Doppler-shifted light and a highly attenuated portion of the probe beam allows determination of one component of flow velocity, speed of sound, and temperature. The sound waves essentially take the place of the particulate seed used in LDV. The velocimeter was used to study the flow behind a rearward-facing step in NASA Langley Research Center's Basic Aerodynamics Research Tunnel. Comparison is made with pitot-static probe data in the freestream over the range 0 m/s - 55 m/s. Comparison with LDV is made in the recirculation region behind the step and in a well-developed boundary layer in front of the step. Good agreement is found in all cases.

Hart, Roger C.↗

Analysis of the Spaceflight Effects on Growth and Development of Super Dwarf Wheat Grown on the Space Station Mir

The hypothesis being tested is that Super Dwarf wheat, Triticum aestivum L., plants in the Svet Greenhouse onboard the Russian Space Station Mir will complete a life cycle in spaceflight, providing that the environmental conditions necessary for adequate growth on Earth are supplied. Twenty six seeds of wheat were planted in each of 2 rows of 2 root compartments for a total of 104 seeds in Svet. Germination rate at 7 d was 56 and 73% on Mir and 75 and 90% in ground-based controls. Plants were grown throughout the whole cycle of ontogenesis (123 d) with samples gathered at different times to validate the morphological and reproductive stages of the plants. Young plants showed vigorous early seedling growth, with large biomass production, including the formation of 280 floral spikes. Upon return to Earth, comparative analyses showed that the number of tillers and flowers per spikelet were 63.2% and 40% greater, respectively, in Mir-grown plants than in the controls. By contrast, the stem length (52.4%), spike mass (49.2%) and length (23.1%), awn length (75.7%), number of spikelets per spike (42.8%) and number of seeds per spike (100% sterile) from Mir-grown plants were substantially less than the controls. Distribution of moisture and roots throughout the substrate was very good. All florets on Mir-grown spikes ceased development at the same stage of ontogeny. Lack of caryopses formation was attributed to male sterility occurring at different stages of staminal development. Anthers failed to dehisce and pollen grains were smaller and shriveled compared to the controls, suggesting a chronic stress had occurred in the Svet growth chamber. Recent ground-based studies indicated that ethylene, which was measured at 0.3 to 1.8 mg per kilogram in the Mir, almost certainly could have induced male sterility in the wheat plants grown on the Mir.

Levinskikh, M. A.↗

Space Age Spuds

American Ag-Tech International, Ltd. developed a system called Quantum Tubers through the Wisconsin Center for Space Automation and Robotics (a NASA-sponsored Commercial Space Center). Using computerization and technologies originally intended for growing plants in space, the company developed a growth chamber that accelerates plant growth and is free of plant pathogens. The chamber is used to grow minitubers, which serve as nuclear seed stock for potatoes. Using lighting technology, temperature and humidity controls, and automation technology, the minituber can be generated in one closed facility with out much labor handling. This means they can be grown year round in extreme environments. The system eliminates the need for multiple generations of seed and eliminates exposure to pathogens, disease and pests. The Quantum Tubers system can produce 10-20 million tubers throughout the year, about equal to the world's supply of this generation seed stock.

Source record↗

Composition and physiological profiling of sprout-associated microbial communities

The native microfloras of various types of sprouts (alfalfa, clover, sunflower, mung bean, and broccoli sprouts) were examined to assess the relative effects of sprout type and inoculum factors (i.e., sprout-growing facility, seed lot, and inoculation with sprout-derived inocula) on the microbial community structure of sprouts. Sprouts were sonicated for 7 min or hand shaken with glass beads for 2 min to recover native microfloras from the surface, and the resulting suspensions were diluted and plated. The culturable fraction was characterized by the density (log CFU/g), richness (e.g., number of types of bacteria), and diversity (e.g., microbial richness and evenness) of colonies on tryptic soy agar plates incubated for 48 h at 30 degrees C. The relative similarity between sprout-associated microbial communities was assessed with the use of community-level physiological profiles (CLPPs) based on patterns of utilization of 95 separate carbon sources. Aerobic plate counts of 7.96 +/- 0.91 log CFU/g of sprout tissue (fresh weight) were observed, with no statistically significant differences in microbial cell density, richness, or diversity due to sprout type, sprout-growing facility, or seed lot. CLPP analyses revealed that the microbial communities associated with alfalfa and clover sprouts are more similar than those associated with the other sprout types tested. Variability among sprout types was more extensive than any differences between microbial communities associated with alfalfa and clover sprouts from different sprout-growing facilities and seed lots. These results indicate that the subsequent testing of biocontrol agents should focus on similar organisms for alfalfa and clover, but alternative types may be most suitable for the other sprout types tested. The inoculation of alfalfa sprouts with communities derived from various sprout types had a significant, source-independent effect on microbial community structure, indicating that the process of inoculation alters the dynamics of community development regardless of the types of organisms involved.

NASA Center KSC↗

Formation of three-dimensional cell/polymer constructs for bone tissue engineering in a spinner flask and a rotating wall vessel bioreactor

The aim of this study is to investigate the effect of the cell culture conditions of three-dimensional polymer scaffolds seeded with rat marrow stromal cells (MSCs) cultured in different bioreactors concerning the ability of these cells to proliferate, differentiate towards the osteoblastic lineage, and generate mineralized extracellular matrix. MSCs harvested from male Sprague-Dawley rats were culture expanded, seeded on three-dimensional porous 75:25 poly(D,L-lactic-co-glycolic acid) biodegradable scaffolds, and cultured for 21 days under static conditions or in two model bioreactors (a spinner flask and a rotating wall vessel) that enhance mixing of the media and provide better nutrient transport to the seeded cells. The spinner flask culture demonstrated a 60% enhanced proliferation at the end of the first week when compared to static culture. On day 14, all cell/polymer constructs exhibited their maximum alkaline phosphatase activity (AP). Cell/polymer constructs cultured in the spinner flask had 2.4 times higher AP activity than constructs cultured under static conditions on day 14. The total osteocalcin (OC) secretion in the spinner flask culture was 3.5 times higher than the static culture, with a peak OC secretion occurring on day 18. No considerable AP activity and OC secretion were detected in the rotating wall vessel culture throughout the 21-day culture period. The spinner flask culture had the highest calcium content at day 14. On day 21, the calcium deposition in the spinner flask culture was 6.6 times higher than the static cultured constructs and over 30 times higher than the rotating wall vessel culture. Histological sections showed concentration of cells and mineralization at the exterior of the foams at day 21. This phenomenon may arise from the potential existence of nutrient concentration gradients at the interior of the scaffolds. The better mixing provided in the spinner flask, external to the outer surface of the scaffolds, may explain the accelerated proliferation and differentiation of marrow stromal osteoblasts, and the localization of the enhanced mineralization on the external surface of the scaffolds. Copyright 2002 Wiley Periodicals, Inc.

NASA Discipline Cell Biology↗

High relative humidity increases yield, harvest index, flowering, and gynophore growth of hydroponically grown peanut plants

Growth chamber experiments were conducted to study the physiological and growth response of peanut (Arachis hypogaea L.) to 50% and 85% relative humidity (RH). The objective was to determine the effects of RH on pod and seed yield, harvest index, and flowering of peanut grown by the nutrient film technique (NFT). 'Georgia Red' peanut plants (14 days old) were planted into growth channels (0.15 x 0.15 x 1.2 m). Plants were spaced 25 cm apart with 15 cm between channels. A modified half-Hoagland solution with an additional 2 mM Ca was used. Solution pH was maintained between 6.4 and 6.7, and electrical conductivity (EC) ranged between 1100 and 1200 microS cm-1. Temperature regimes of 28/22 degrees C were maintained during the light/dark periods (12 hours each) with photosynthetic photon flux (PPF) at canopy level of 500 micromoles-m-2s-1. Foliage and pod fresh and dry weights, total seed yield, harvest index (HI), and seed maturity were greater at high than at low RH. Plants grown at 85% RH had greater total and individual leaflet area and stomatal conductance, flowered 3 days earlier and had a greater number of flowers reaching anthesis. Gynophores grew more rapidly at 85% than at 50% RH.

NASA Discipline Life Support Systems↗

Analysis of peg formation in cucumber seedlings grown on clinostats and in a microgravity (space) environment

In young cucumber seedlings, the peg is a polar out-growth of tissue that functions by snagging the seed coat, thereby freeing the cotyledons. Previous studies have indicated that peg formation is gravity dependent. In this study we analyzed peg formation in cucumber seedlings (Cucumis sativus L. cv Burpee Hybrid II) grown under conditions of normal gravity, microgravity, and simulated microgravity (clinostat rotation). Seeds were germinated on the ground, in clinostats and on board the space shuttle (STS 95) for 1-2 days, frozen and subsequently examined for their stage of development, degree of hook formation, number of pegs formed, and peg morphology. The frequency of peg formation in space grown seedlings was found to be nearly identical to that of clinostat grown seedlings and to differ from that of seedlings germinated under normal gravity only in a minority of cases; approximately 6% of the seedlings formed two pegs and nearly 2% of the seedlings lacked pegs, whereas such abnormalities did not occur in ground controls. The degree of hook formation was found to be less pronounced for space grown seedlings, compared to clinostat grown seedlings, indicating a greater degree of decoupling between peg formation and hook formation in space. Nonetheless, in all seedlings having single pegs and a hook, the peg was found to be positioned correctly on the inside of the hook, showing that there is coordinate development even in microgravity environments. Peg morphologies were altered in space grown samples, with the pegs having a blunt appearance and many pegs showing alterations in expansion, with the peg extending out over the edges of the seed coat and downwards. These phenotypes were not observed in clinostat or ground grown seedlings.

STS-95 Shuttle Project↗

The development of spaceflight experiments with Arabidopsis as a model system in gravitropism studies

Experiments with Arabidopsis have been developed for spaceflight studies in the European Space Agency's Biorack module. The Biorack is a multiuser facility that is flown on the United States Space Shuttle and serves as a small laboratory for studying cell and developmental biology in unicells, plants, and small invertebrates. The purpose of our spaceflight research was to investigate the starch-statolith model for gravity perception by studying wild-type (WT) and three starch-deficient mutants of Arabidopsis. Since spaceflight opportunities for biological experimentation are scarce, the extensive ground-based testing described in this paper is needed to ensure the success of a flight project. Therefore, the specific aims of our ground-based research were: (1) to modify the internal configuration of the flight hardware, which originally was designed for large lentil seeds, to accommodate small Arabidopsis seeds; (2) to maximize seed germination in the hardware; and (3) to develop favorable conditions in flight hardware for the growth and gravitropism of seedlings. The hardware has been modified, and growth conditions for Arabidopsis have been optimized. These experiments were successfully flown on two Space Shuttle missions in 1997.

STS-84 Shuttle Project↗

Seedborne fungal contamination: consequences in space-grown wheat

Plants grown in microgravity are subject to many environmental stresses that may promote microbial growth and result in disease symptoms. Wheat (cv. Super Dwarf) recovered from an 8-day mission aboard a NASA (National Aeronautics and Space Administration) space shuttle showed disease symptoms, including girdling of leaf sheaths and chlorosis and necrosis of leaf and root tissues. A Neotyphodium species was isolated from the seed and leaf sheaths of symptomatic wheat used in the spaceflight mission. Certain isozymes of a peroxidase unique to extracts from the microgravity-grown plants were observed in extracts from earth-grown Neotyphodium-infected plants but were not present in noninfected wheat. The endophytic fungus was eliminated from the wheat seed by prolonged heat treatment at 50 degrees C followed by washes with water at 50 degrees C. Plants from wheat seed infected with the Neotyphodium endophyte were symptomless when grown under greenhouse conditions, whereas symptoms appeared after only 4 days of growth in closed containers. Disease spread from an infected plant to noninfected plants in closed containers. Dispersion via spores was found on asymptomatic plants at distances of 7 to 18 cm from infected plants. The size and shape of the conidia, mycelia, and phialide-bearing structures and the ability to grow rapidly on carbohydrates, especially xylose, resembled the characteristics of N. chilense, which is pathogenic on orchard grass, Doctylis glomerati. The Neotyphodium wheat isolate caused disease symptoms on other cereals (wheat cv. Malcolm, orchard grass, barley, and maize) grown in closed containers.

NASA Discipline Plant Biology↗