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Joel Wells, NASA Public Affairs, introduces Steve Altemus, NASA Test Director, Glenn Chin, STS-105 Mission Manager, and Ed Priselac, Shuttle Weather Officer, in this STS-105 prelaunch press conference. An overview is given of the launch countdown, payload status (Leonardo Multipurpose Logistics Module), and weather forecast. The men then answer questions from the press.
George Diller, NASA Public Affairs, introduces Pete Nickolenko, NASA Test Director, Scott Higginbotham, STS-104 Mission Manager, and Ed Priselac, Shuttle Weather Officer, in this STS-104 launch minus two days press conference. An overview is given of the launch vehicle status, countdown procedures, payload status, and weather forecast. The men then answer questions from the press.
George Diller, NASA Public Affairs, introduces Jeff Spaulding, NASA Test Director, Louie Garcia, STS-104 Operations Engineer, and Ed Priselac, Shuttle Weather Officer, in this launch minus one day press conference. An overview is given of the launch vehicle status, countdown procedures, payload status, and weather forecast. The men then answer questions from the press.
Joel Wells, NASA Public Affairs, introduces Jeff Spaulding, NASA Test Director, Gregory Horvath, STS-104 Mission Integration Engineer, and Ed Priselac, Shuttle Weather Officer, in this STS-104 prelaunch press conference. An overview is given of the launch countdown, payload status, and weather forecast. The men then answer questions from the press.
Joel Wells, NASA Public Affairs, introduces Pete Nickolenko, NASA Test Director, Glen Chin, STS-105 Mission Manager, and Ed Priselac, Shuttle Weather Officer. They give an overview of the countdown to the STS-105 Discovery Orbiter launch, including details on prelaunch tests (activate and check on-board avionics software, payload bay closeout, prepare and clear launch pad, etc.), payload bay status (Leonardo Multipurpose Logistics Module), and the weather forecast. The men then answer questions from the press.
The Dead Sea is located on the northern branch of the African-Levant Rift systems. The rift system, according to one model, was formed by a series of strike slip faults, initially forming approximately two million years ago. The Dead Sea is an evaporite basin that receives freshwater from springs and from the Jordan River. The Dead Sea is different from other evaporite basins, such as the Great Salt Lake, in that it possesses high concentrations of magnesium and has an average pH of 6.1. The dominant cation in the Great Salt Lake is sodium, and the pH is 7.7. Calcium concentrations are also higher in the Dead Sea than in the Great Salt Lake. Both basins are similar in that the dominant anion is chlorine and the salinity levels are approximately 20 %. Other common cations that have been identified from the waters of the Dead Sea and the Great Salt Lake include sodium and potassium. A variety of Archea, Bacteria, and a single genus of a green algal, Dunaliella, has been described from the Dead Sea. Earlier studies concentrated on microbial identification and analysis of their unique physiology that allows them to survive in this type of extreme environment. Potential microbial fossilization processes, microbial fossils, and the metallic ions associated with fossilization have not been studied thoroughly. The present study is restricted to identifying probable microbial morphologies and associated metallic ions. XRD (X Ray Diffraction) analysis indicates the presence of halite, quartz, and orthoclase feldspar. In addition to these minerals, other workers have reported potassium chloride, magnesium bromide, magnesium chloride, calcium chloride, and calcium sulfate. Halite, calcium sulfate, and orthoclase were examined in this report for the presence of microbes, microbially induced deposits or microbial alteration. Neither the gypsum nor the orthoclase surfaces possesses any obvious indications of microbial life or fossilization. The sand-sized orthoclase particles are weathered with 122 extensive fan-shaped mineral deposits. The gypsum deposits are associated with halite minerals and also exhibit extensive weathering. Halite minerals represent the only substrates that have probable rod-shaped microbial structures with long, filamentous, apical extensions. EDS (energy dispersive x-ray) analysis of the putative microbes indicates elevated calcium levels that are enriched with magnesium. The rod-shaped structures exhibit possible fossilization stages. Rhombohedralshaped minerals of magnesium-enriched calcium carbonate are deposited on the microbial surfaces, and eventually coat the entire microbial surface. The sodium chloride continues to crystallize on nearby halite surface and even crystallizes on the fossilized microbial remains. The putative fossils are found exclusively on halite surfaces, and all contained elevated levels of calcium magnesium cations. Both of these metallic cations are associated with microbial activity and fossilization. Their morphological diversity is low in comparison with the reported living Dead Sea microbial population. If we examine the fossil record for multicellular organisms, fossilization rates are lower for soft-bodied organisms than for those possessing hard parts, i.e. shells, bones. For example, smaller, single celled organisms would have a smaller chance of fossilization; their fossilized shapes could be mistaken for abiotic products. Another consideration is that dead organisms in the water column are probably utilized as a food source by other microbes before fossilization processes are completed. This may be an important consideration as we attempt to model and interpret ancient microbial environments either on Earth or on Mars.
Magnetotactic bacteria are a heterogeneous group of motile, mainly aquatic procaryotes that align and swim along geomagnetic field lines. They are of interest to astrobiologists because of the magnetite crystals found in the Mars meteorite ALH84001 which share many characteristics with the magnetite produced intracellularly by magnetotactic bacteria. These bacteria are diverse morphologically, physiologically and phylogenetically, sharing a few key characteristics: 1) the presence of intracellular membrane-bound magnetic crystals (magnetosomes), usually but not always arranged in chains; 2) motility by means of flagella; and 3) microaerophillic or anaerobic physiology. The bilophotrichous (having two flagella bundles) magnetotactic cocci (MC) are ubiquitous in aquatic habitats but have proven extremely difficult to cultivate. Because only several marine strains have been isolated and grown in axenic culture, little is known about the physiology and the biogeochemical roles of the MC. We studied the composition and distribution of intracellular structures in an uncultured MC, designated ARB-1. To do this, a combination of light microscopy, environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) were used. Cells of ARB-1 were separated from sediments collected from Baldwin Lake (Los Angeles Arboretum, Arcadia, CA). They are large spherical to oblate spheroidal Gram-negative cells, ranging from 1 to 4 micrometers along the maximum dimension, which is perpendicular to the direction of swimming. Cells have two large phosphorus-containing inclusions that comprise a large percentage of the cell volume. Many smaller sulfur inclusions are located at the convex end of the cell. Most of the cellular Fe is present in the magnetosomes. These may be arranged as a clump at the concave end of the cell, near the two flagella bundles, or as chains, or as both a clump and chains. The magnetosomes were identified as magnetite (Fe3O4) by selected area electron diffraction (SAED) and high resolution TEM. We saw a trend between cell size and organization of the magnetosomes. Smaller, more spherical cells were more likely to have chains than were larger, more oblate cells. This may indicate different populations of cells, or it may be attributed to variations in cell growth cycle. The size distribution (length) of magnetosomes in chains was similar to that of magnetosomes in clusters, except that there was a larger size range for clustered magnetosomes. Magnetosomes from ARB-1 cells average 82 nm in length. If plotted on a graph of length as a function of aspect ratio, they fall within the single domain region of the plot. If compared with the size distributions of magnetite from ALH84001 and magnetosomes from the cultured magnetotactic vibrio MV-1, the magnetites produced by ARB-1 cells are, on average, larger and have a wider range of aspect ratio. ARB-1 cells have a specific organization of the P, S, and Fe inclusions. The P inclusions always occupy the majority of the cell volume and separate the S inclusions from the disorganized clumps of magnetosomes and the flagella bundles. The P inclusions may contain polyphosphate, which could play several roles in motility, adaptation to stress, growth and division, buoyancy, and energy. The S inclusions might be a way to store S, a potential energy source, when the cells move from sulfide to oxygen zones. The consistency of P, S, and Fe organization in ARB-1 cells suggests that these inclusions have some specific and interactive functions.
Molecular engineering of ternary single source precursors based on the [{PBu3}2Cu(SR')2In(SR')2] architecture have afforded the first liquid CIS ternary single source precursors (when R = Et, n-Pr), which are suitable for low temperature deposition (< 350 C). Thermogravimetric analyses (TGA) and modulated-differential scanning calorimetry (DSC) confirm their liquid phase and reduced stability. X-ray diffraction studies, energy dispersive analyzer (EDS), and scanning electron microscopy (SEM) support the formation of the single-phase chalcopyrite CuInS2 at low temperatures.
Pleistocene volcanic centers in NW Spitsbergen, Norway host one of the world's richest occurrences of mantle xenoliths. The xenoliths comprise varieties of spinel lherzolites and pyroxenites. Some of these xenoliths (and their host basalts) contain 10-100 micrometer globules of ankedtic-magnesitic carbonates (AMC). In composition, mineralogy and petrology the AMC globules from Spitsbergen are strikingly similar to the carbonate globules in ALH84001. The AMC globules occur within interstitial quenched glass and as fracture fillings, although we have not seen replacement fabrics analogous to carbonate rosettes replacing glass in ALH84001. Siderite/ankerite forms the core of these concentrically zoned globules while rims are predominantly magnesite. Clay minerals can occasionally be found within and around the globules. Aside from the clay minerals, the principal mineralogical difference between the AMCs and the ALH84001 carbonate rosettes is the presence of concentrated zones of nanophase magnetite in the rosettes, notably absent in the AMCs. However, carbonate globules containing nanophase magnetite have been produced inorganically by hydrothermal precipitation of carbonates and subsequent heating. We heated Spitsbergen AMC at 585 C in a reducing atmosphere to determine whether magnetite could be produced. Optical micrographs of the heated Spitsbergen AMC show dark concentric zones within the AMC. High resolution SEM images of those areas reveal 150-200 nm euhedral crystals that exhibit various morphologies including octahedra and elongated prisms. EDS analyses of areas where the crystals occur contain Fe, O, and minor Si, and P. However, the probe integrates over volumes of material, which also include the surrounding matrix. We have begun TEM observations of both the heated and unheated Spitsbergen AMC to characterize the microstructures of the carbonates, establish the presence/absence of magnetite and determine the relationship of the clay minerals to the carbonates and host rock.
We use the radioactive flux correlation for star forming galaxies in the local universe to derive their contribution to the cosmic radio background (CRB). The CRB from these galaxies is therefore determined by the evolution of the comoving infrared luminosity density with redshift, which is constrained by galaxy number counts at various infrared wavelengths and by the cosmic infrared background. The research of ED was supported by NASA NRA 99-OSS-01 Astrophysics Theory Program. MB acknowledges the support of the "Research Opportunities for Undergraduates in the Laboratory for Astronomy and Solar Physics" for the summer student internship program at NASA/GSFC.
Unweighting of the juvenile soleus muscle is characterized by an increased binding capacity for insulin relative to muscle mass due to sparing of the receptors during atrophy. Although carbohydrate metabolism and protein degradation in the unweighted muscle develop increased sensitivity to insulin in vivo, protein synthesis in vivo and system A amino acid transport in vitro do not appear to develop such an enhanced response. The long-term goal is to identify the precise nature of this apparent resistance in the insulin signal transduction pathway and to consider how reduced weight-bearing may elicit this effect, by evaluating specific components of the insulin signalling pathway. Because the insulin-signalling pathway has components in common with the signal transduction pathway for insulin-like growth factor (IGF-1) and potentially other growth factors, the study could have important implications in the role of weight-bearing function on muscle growth and development. Since the insulin signalling pathway diverges following activation of insulin receptor tyrosine kinase, the immediate specific aims will be to study the receptor tyrosine kinase (IRTK) and those branches, which lead to phosphorylation of insulin receptor substrate-1 (IRS-1) and of Shc protein. To achieve these broader objectives, we will test in situ, by intramuscular injection, the responses of glucose transport, system A amino acid transport and protein synthesis to insulin analogues for which the receptor has either a weaker or much stronger binding affinity compared to insulin. Studies will include: (1) estimation of the ED(sub 50) for each analogue for these three processes; (2) the effect of duration (one to four days) of unweighting on the response of each process to all analogues tested; (3) the effect of unweighting and the analogues on IRTK activity; and (4) the comparative effects of unweighting and analogue binding on the tyrosine phosphorylation of IRTK, IRS-1, and Shc protein.
Thermally sprayed coatings are being studied and developed as methods of enabling lightweight composites to be used more extensively as structural components in propulsion applications in order to reduce costs and improve efficiency through weight reductions. The primary goal of this work is the development of functionally graded material [FGM] polymer/metal matrix composite coatings to provide improved erosion/oxidation resistance to polyimide-based polymer matrix composite [PMC] substrates. The goal is to grade the coating composition from pure polyimide, similar to the PMC substrate matrix on one side, to 100 % WC-Co on the other. Both step-wise and continuous gradation of the loading of the WC-Co reinforcing phase are being investigated. Details of the coating parameter development will be presented, specifically the high velocity oxy-fuel [HVOF] combustion spraying of pure PMR-11 matrix material and layers of various composition PMR-II/WC-Co blends onto steel and PMR-15 composite substrates. Results of the HVOF process optimization, microstructural characterization, and analysis will be presented. The sprayed coatings were evaluated using standard metallographic techniques - optical and scanning electron microscopy [SEM]. An SEM + electron dispersive spectroscopy [EDS] technique has also been used to confirm retention of the PMR-II component. Results of peel/butt adhesion testing to determine adhesion will also be presented.
High-temperature slow-crack growth of single crystal 10 wt% Cr2O3 - Al2O3 (nominal composition) fibers has been studied by tensile rupture experiments at 1400 C, under different stressing rates (0.5 to 41.5 MPa/s). Slow-crack growth (SCG) is less pronounced with increasing Cr2O3. Rupture stresses increased with the stressing rate from 397 MPa to 515 MPa, resulting in a SCG exponent, N=19. The Cr2O3 composition was analyzed by Energy Dispersed X-Ray Spectra (EDS) and fracture surfaces were studied by scanning electron microscopy (SEM). Results are compared with previous studies on 100-300 ppm Cr3(+) doped sapphire fibers and on commercial sapphire fibers.
A primarily silica-containing material with traces of organic compounds, as well as aluminum and calcium additions, was exposed to a Mach 0.3 burner rig at atmospheric pressure using jet fuel. The sample was exposed for 5 continuous hours at 1370 C. Post exposure x-ray diffraction analyses indicate formation of cristobalite, quartz, NiO and Spinel (Al(Ni)CR2O4). The rig hardware is composed of a nickel-based superalloy with traces of Fe. These elements are indicated in the energy dispersive spectroscopy (EDS) results. This material was studied as a candidate for high temperature applications under an engine technology program.
We have analyzed our 23-year merged ozone data set for variability and trends with a statistical time-series model. To assist in that analysis, we have analyzed the Goddard ED photochemical model for the same time period with the same time-series model. Multiple runs of the photochemical model allow us to separate the effects of various terms on ozone, such as solar cycle and volcanic eruptions. We use this to help us separate those signals from each other in the data. We also used a smoothed version of the photochemical model's prediction of global ozone change in place of a simple linear trend. We find a number of interesting results. This particular photochemical model is more sensitive to chlorine perturbations than the atmosphere appears to be. It is less sensitive to solar cycle. It predicts an effect from the Pinatubo eruption that is nearly symmetric in the two hemispheres, but the data appears to have not responded to Pinatubo in the southern mid-latitudes. These results and their uncertainties will be discussed.
The development of thin-film solar cells on flexible, lightweight, space-qualified durable substrates (i.e. Kapton) provides an attractive solution to fabricating solar arrays with high specific power, (W/kg). The syntheses and thermal modulation of ternary single source precursors, based on the [{LR}2Cu(SR')2In(SR')2] architecture in good yields are described. Thermogravimetric analyses (TGA) and Low temperature Differential Scanning Caloriometry, (DSC) demonstrate that controlled manipulation of the steric and electronic properties of either the group five-donor and/or chalcogenide moiety permits directed adjustment of the thermal stability and physical properties of the precursors. TGA-Evolved Gas Analysis, confirms that single precursors decompose by the initial extrusion of the sulphide moiety, followed by the loss of the neutral donor group, (L) to release the ternary chalcopyrite matrix. X-ray diffraction studies, EDS and SEM on the non-volatile pyrolized material demonstrate that these derivatives afford single-phase CuInS2/CuInSe2 materials at low temperature. Thin-film fabrication studies demonstrate that these single source precursors can be used in a spray chemical vapor deposition process, for depositing CuInS2 onto flexible polymer substrates at temperatures less than 400 C.
We have been investigating the synthesis of quantum dots of CdSe, CuInS2, and CuInSe2 for use in an intermediate bandgap solar cell. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Bawendi, et. al., in the early 1990's. However, unlike previous work in this area we have also utilized single-source precursor molecules in the synthesis process. We will present XRD, TEM, SEM and EDS characterization of our initial attempts at fabricating these quantum dots. Investigation of the size distributions of these nanoparticles via laser light scattering and scanning electron microscopy will be presented. Theoretical estimates on appropriate quantum dot composition, size, and inter-dot spacing along with potential scenarios for solar cell fabrication will be discussed.
Astrobiologists are working to develop methodologies for the recognition of bacterial microfossils, biominerals, and chemical biomarkers in terrestrial rocks, to provide a basis for the scientific assessment of possible microfossils in meteorites and other Astromaterials. During the past 5 years, we have conducted electron microscopy investigations to understand the morphology and chemical composition of microfossils in ancient terrestrial rocks and to search for microfossils presence in meteorites. We have detected evidence of indigenous microfossils and biominerals in-situ in every carbonaceous meteorite investigated but have found no evidence for microfossils in the nickel-iron and stony meteorites studied. In this paper, we provide a brief review of prior evidence for microfossils in meteorites and present Scanning and Environmental Scanning Electron Microscope (SEM and ESEM) and Field Emission Scanning Electron Microscope (FESEM) images of microfossils found in-situ in freshly fractured surfaces of the Murchison and Rainbow meteorites. We describe the techniques and methods used to protect the samples from contamination and for the discrimination of indigenous microfossils from recent terrestrial contaminants We provide data from Energy Dispersive Spectroscopy (EDS) and Link microprobe analysis of the chemical elements and 2D x-ray maps as strong evidence that these biogenic forms are indigenous to the meteorites and cannot logically be interpreted as recent bio-contaminants. We show evidence of framboidal magnetites and pyrites and compare them with framboidal magnetites and pyrites found in Cambrian richs from the Siberian Platform.