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NASA NTRS1996

Differences in Femoral Geometry and Structure Due to Immobilization

Reduction in bone mass of the lower extremity is well documented in individuals with paralysis resulting from spinal cord injury (SCI). The consequent osteopenia leads to elevated fracture risk with fractures occurring more commonly in the femoral shaft and supracondylar regions than the hip. A model has recently been described to estimate geometry and structure of the femoral midshaft from whole body scans by dual X-ray absorptiometry (DXA). Increases in femoral geometric and structural properties during growth were primarily related to mechanical loading as reflected by body mass. In this study, we investigate the relationship between body mass and femoral geometry and structure in adults with normal habitual mechanical loading patterns and those with severely reduced loading. The subjects were 78 ambulatory men (aged 20-72 yrs) and 113 men with complete paralysis from SCI of more than 4 years duration (aged 21 73 yrs). Subregional analysis was performed on DXA whole body scans to obtain bone mineral content (BMC, g), cortical thickness (cm), crosssectional moment of inertia (CSMI, cm4), and section modulus (cm3) of the femoral midshaft. All measured bone variables were significantly lower in SCI compared with ambulatory subjects: -29% (BMC), -33% (cortical thickness), -23% (CSMI), and -22% (section modulus) while body mass was not significantly different. However, the associations between body mass and bone properties were notably different; r2 values were higher for ambulatory than SCI subjects in regressions of body mass on BMC (0.48 vs 0.20), CSMI (0.59 vs 0.32), and section modulus (0.59 vs 0.31). No association was seen between body mass and cortical thickness for either group. The greatest difference between groups is in the femoral cortex, consistent with reduced bone mass via endosteal expansion. The relatively lesser difference in geometric and structural properties implies that there is less effect on mechanical integrity than would be expected from bone mass results alone. The reduced association in SCI subjects between body mass and bone properties is not unexpected. Although mean body mass differs little between ambulatory and SCI individuals, the association between body mass and in vivo skeletal loading is no longer present, as mechanical influences are removed except for transfer activities. The residual association is probably attributable to the strength of this influence during growth. These results highlight the importance of examining geometry and structure in conjunction with bone mass.

Kiratli, Beatrice Jenny↗

NASA NTRS2017

Imprint of the Sun’s Evolving Polar Winds on IBEX Energetic Neutral Atom All-sky Observations of the Heliosphere

With 7 years of Interstellar Boundary Explorer (IBEX) measurements of energetic neutral atoms (ENAs), IBEX has shown a clear correlation between dynamic changes in the solar wind and the heliosphere’s response in the formation of ENAs. In this paper, we investigate temporal variations in the latitudinal-dependent ENA spectrum from IBEX and their relationship to the solar wind speed observed at 1 au. We find that the variation in latitude of the transition in ENA spectral indices between low (≲1.8) and high (≳1.8) values, as well as the distribution of ENA spectral indices at high and low latitudes, correlates well with the evolution of the fast and slow solar wind latitudinal structure observed near 1 au. This correlation includes a delay due to the time it takes the solar wind to propagate to the termination shock and into the inner heliosheath, and for ENAs to be generated via charge-exchange and travel back toward 1 au. Moreover, we observe a temporal asymmetry in the steepening of the ENA spectrum in the northern and southern hemispheres, consistent with asymmetries observed in the solar wind and polar coronal holes. While this asymmetry is observed near the upwind direction of the heliosphere, it is not yet observed in the tail direction, suggesting a longer line-of-sight integration distance or different processing of the solar wind plasma downstream of the termination shock.

Local interstellar matter↗

NASA NTRS2004

The Severe Weather Outbreak of 10 November 2002: Lightning and Radar Analysis of Storms in the Deep South

On the afternoon and evening of 10 November 2002, the Midwest and Deep South were struck by a major outbreak of severe storms that produced some 80 tornadoes. In terms of number of tornadoes, this was the largest outbreak in the United States since November 1992. Some 32 of the tornadoes occurred in Tennessee, Mississippi, Alabama and Georgia, including several long-track killers. We use the North Alabama Lightning Mapping Array (LMA) and other data sources to perform a comprehensive analysis of the structure and evolution of the outbreak. Most of the Southern tornadoes occurred in isolated, fast-moving supercell storms that formed in warm, moist air ahead of a major cold front. Storms tended to form in lines parallel to storm cell motion, resulting in many communities being hit multiple times by severe storms that evening. Supercells in Tennessee produced numerous strong tornadoes with short to medium-length track paths, while the supercells further south produced several very long-track tornadoes. Radar data indicate that the Tennessee storms tended to split frequently, apparently limiting their ability to sustain long-lived tornadoes, while storms further south split at most one time. The differences between these storms appear to be related to the presence of stronger jetstream winds in Tennessee relative to those present in Mississippi, Alabama and Georgia. LMA-derived flash rates associated with most of the supercell storm cores were about 1-2 flashes per second. Rapid increases in lightning rates (or "jumps") occurred prior to tornado touchdown in many instances. Lightning "holes" (lightning-free regions associated with the echo-free vault) occurred in two of the Tennessee supercells. The complexity of the relationship between lightning and storm severity is revealed by the behavior of one Alabama supercell, which produced a peak flash rate of nearly 14 flashes per second, well after the end of its long-track tornado, while interacting and ultimately merging with a daughter supercell on its southwest flank. Close examination of this powerful storm indicates that its prodigious flash rate was the result of strong flash activity over an unusually large area, rather than a concentrated core of extremely high flash rate activity.

Buechler, D. E.↗

NASA NTRS2011

Achievable Performance and Effective Interrogator Design for SAW RFID Sensor Tags

For many NASA missions, remote sensing is a critical application that supports activities such as environmental monitoring, planetary science, structural shape and health monitoring, non-destructive evaluation, etc. The utility of the remote sensing devices themselves is greatly increased if they are passive that is, they do not require any on-board power supply such as batteries and if they can be identified uniquely during the sensor interrogation process. Additional passive sensor characteristics that enable greater utilization in space applications are small size and weight, long read ranges with low interrogator power, ruggedness, and operability in extreme environments (vacuum, extreme high/low temperature, high radiation, etc.) In this paper, we consider one very promising passive sensor technology, called surface acoustic wave (SAW) radio-frequency identification (RFID), that satisfies all of these criteria. Although SAW RFID tags have great potential for use in numerous space-based remote sensing applications, the limited collision resolution capability of current generation tags limits the performance in a cluttered sensing environment. That is, as more SAW-based sensors are added to the environment, numerous tag responses are superimposed at the receiver and decoding all or even a subset of the telemetry becomes increasingly difficult. Background clutter generated by reflectors other than the sensors themselves is also a problem, as is multipath interference and signal distortion, but the limiting factor in many remote sensing applications can be expected to be tag mutual interference. This problem may be greatly mitigated by proper design of the SAW tag waveform, but that remains an open research problem, and in the meantime, several other related questions remain to be answered including: What are the fundamental relationships between tag parameters such as bit-rate, time-bandwidth-product, SNR, and achievable collision resolution? What are the differences in optimal or near-optimal interrogator designs between noise-limited environments and interference-limited environments? What are the performance characteristics of different interrogator designs in term of parameters such as transmitter power level, range, and number of interfering tags? In this paper, we present the results of a research effort aimed at providing at least partial answers to all of these questions.

Barton, Richard J.↗

NASA NTRS2005

A Preliminary Investigation of the E-Beam Induced Polymerization of Maleimide and Norbornene End-capped Polyimides

A research area of high activity in connection with aerospace engineering has been the development of polymer thermosetting resins that can resist temperature as high as 300 C while maintaining adequate toughness, and providing ease of processing to enable low temperature and low cost composite fabrication methods. In order to meet such requirements, sequential interpenetrating polymer networks (IPNs) based on bismaleimide (BMI) and cyanate ester (CE) monomers were investigated. In these systems, a polycyanurate network is first formed in the presence of BMI and appropriate reactive diluent monomers and in a second step, a network based on the BMI is created in the presence of a fully formed polycyanurate network. The materials developed can be processed at relatively low temperature (less than 150 C) and with the aid of electron beam (EB) curing. Of major importance to the success of this work was the identification of a reactive diluent that improves ease of processing and has tailored reactivity to allow for the controlled synthesis of CE-BMI sequential IPNs. Based on solubility and reactivity of a number of reactive diluents, N-acryloylmorpholine (AMP) was selected as a comonomer for BMI copolymerization. A donor-acceptoreaction mechanism was suggested to explain the relative reactivity of a variety of reactive diluents towards maleimide functionality. The optimum processing parameters for the formation of the first network were determined through the study of metal catalyzed cure and hydrolysis of cyanate esters, whereas the reaction behavior for second network formation in terms of the influence of EB dose rate and temperature was elucidated through an in-situ kinetics study of maleimide and AMP copolymerization. Structure-property relationships were developed which allowed for the design of improved resin systems. In particular, appropriate network coupler possessing cyanate ester and maleimide functionality was synthesized to link the polycyanurate first network to the BMI/AMP second network and thus form linked sequential IPNs (LIPNs). Consequently, Tg as high as 370 C was achieved and a fracture toughness of 120 Joules per square meters was obtained for resin systems that possess adequately low viscosity for processing using liquid molding techniques at low temperature.

Palmese, Giuseppe R.↗

NASA NTRS1996

Ceruloplasmin enhances smooth muscle cell- and endothelial cell-mediated low density lipoprotein oxidation by a superoxide-dependent mechanism

Cultured vascular smooth muscle cells (SMC) and endothelial cells (EC) stimulate low density lipoprotein (LDL) oxidation by free radical-mediated, transition metal-dependent mechanisms. The physiological source(s) of metal ions is not known; however, purified ceruloplasmin, a plasma protein containing 7 coppers, oxidizes LDL in vitro. We now show that ceruloplasmin also increases LDL oxidation by vascular cells. In metal ion-free medium, human ceruloplasmin increased bovine aortic SMC- and EC-mediated LDL oxidation by up to 30- and 15-fold, respectively. The maximal response was at 100-300 microg ceruloplasmin/ml, a level at or below the unevoked physiological plasma concentration. Oxidant activity was dependent on protein structure as a specific proteolytic cleavage or removal of one of the seven ceruloplasmin copper atoms inhibited activity. Three lines of evidence indicated a critical role for cellular superoxide (O2.) in ceruloplasmin-stimulated oxidation. First, the rate of production of O2. by cells correlated with their rates of LDL oxidation. Second, superoxide dismutase effectively blocked ceruloplasmin-stimulated oxidation by both cell types. Finally, O2. production by SMC quantitatively accounted for the observed rate of LDL oxidation. To show this, the course of O2. production by SMC was simulated by repeated addition of xanthine and xanthine oxidase to culture medium under cell-free conditions. Neither ceruloplasmin nor O2. alone increased LDL oxidation, but together they completely reconstituted the oxidation rate of ceruloplasmin-stimulated SMC. These results are the first to show that ceruloplasmin stimulates EC- and SMC-mediated oxidation of LDL and that cell-derived O2. accounts quantitatively for metal-dependent, free radical-initiated oxidation of LDL by these cells.

Non-NASA Center↗

NASA NTRS1998

Test Standard Developed for Determining the Slow Crack Growth of Advanced Ceramics at Ambient Temperature

The service life of structural ceramic components is often limited by the process of slow crack growth. Therefore, it is important to develop an appropriate testing methodology for accurately determining the slow crack growth design parameters necessary for component life prediction. In addition, an appropriate test methodology can be used to determine the influences of component processing variables and composition on the slow crack growth and strength behavior of newly developed materials, thus allowing the component process to be tailored and optimized to specific needs. At the NASA Lewis Research Center, work to develop a standard test method to determine the slow crack growth parameters of advanced ceramics was initiated by the authors in early 1994 in the C 28 (Advanced Ceramics) committee of the American Society for Testing and Materials (ASTM). After about 2 years of required balloting, the draft written by the authors was approved and established as a new ASTM test standard: ASTM C 1368-97, Standard Test Method for Determination of Slow Crack Growth Parameters of Advanced Ceramics by Constant Stress-Rate Flexural Testing at Ambient Temperature. Briefly, the test method uses constant stress-rate testing to determine strengths as a function of stress rate at ambient temperature. Strengths are measured in a routine manner at four or more stress rates by applying constant displacement or loading rates. The slow crack growth parameters required for design are then estimated from a relationship between strength and stress rate. This new standard will be published in the Annual Book of ASTM Standards, Vol. 15.01, in 1998. Currently, a companion draft ASTM standard for determination of the slow crack growth parameters of advanced ceramics at elevated temperatures is being prepared by the authors and will be presented to the committee by the middle of 1998. Consequently, Lewis will maintain an active leadership role in advanced ceramics standardization within ASTM. In addition, the authors have been and are involved with several international standardization organizations including the Versailles Project on Advanced Materials and Standards (VAMAS), the International Energy Agency (IEA), and the International Organization for Standardization (ISO). The associated standardization activities involve fracture toughness, strength, elastic modulus, and the machining of advanced ceramics.

Choi, Sung R.↗

NASA NTRS2016

Aerosol Meteorology of Maritime Continent for the 2012 7SEAS Southwest Monsoon Intensive Study - Part 2: Philippine Receptor Observations of Fine-Scale Aerosol Behavior

The largest 7 Southeast Asian Studies (7SEAS) operations period within the Maritime Continent (MC) occurred in the August-September 2012 biomass burning season. Data included were observations aboard the MY Vasco, dispatched to the Palawan Archipelago and Sulu Sea of the Philippines for September 2012. At these locations, the Vasco observed MC smoke and pollution entering the southwest monsoon (SWM) monsoonal trough. Here we describe the research cruise findings and the finer-scale aerosol meteorology of this convectively active region. This 2012 cruise complemented a 2-week cruise in 2011 and was generally consistent with previous findings in terms of how smoke emission and transport related to monsoonal flows, tropical cyclones (TC), and the covariance between smoke transport events and the atmosphere's thermodynamic structure. Biomass burning plumes were usually mixed with significant amounts of anthropogenic pollution. Also key to aerosol behavior were squall lines and cold pools propagating across the South China Sea (SCS) and scavenging aerosol particles in their path. However, the 2012 cruise showed much higher modulation in aerosol frequency than its 2011 counterpart. Whereas in 2011 large synoptic-scale aerosol events transported high concentrations of smoke into the Philippines over days, in 2012 measured aerosol events exhibited a much shorter-term variation, sometimes only 312h. Strong monsoonal flow reversals were also experienced in 2012. Nucleation events in cleaner and polluted conditions, as well as in urban plumes, were observed. Perhaps most interestingly, several cases of squall lines preceding major aerosol events were observed, as opposed to 2011 observations where these lines largely scavenged aerosol particles from the marine boundary layer. Combined, these observations indicate pockets of high and low particle counts that are not uncommon in the region. These perturbations are difficult to observe by satellite and very difficult to model. Indeed, the Navy Aerosol Analysis and Prediction System (NAAPS) simulations captured longer period aerosol events quite well but largely failed to capture the timing of high-frequency phenomena. Ultimately, the research findings of these cruises demonstrate the real world challenges of satellite-based missions, significant aerosol life cycle questions such as those the future Aerosol/Clouds/Ecosystems (ACE) will investigate, and the importance of small-scale phenomena such as sea breezes, squall lines, and nucleation events embedded within SWM patterns in dominating aerosol life cycle and potential relationships to clouds.

Reid, Jeffrey S.↗

NASA NTRS1988

Cytoplasmic membrane changes during adaptation of the fresh water cyanobacterium Synechococcus 6311 to salinity

In this investigation, changes were characterized in cell structure and cytoplasmic membrane organization that occur when the freshwater cyanobacterium Synechococcus 6311 is transferred from 'low salt' (0.03 molar NaCl) to 'high salt' (0.5 molar NaCl) media (i.e. sea water concentration). Cells were examined at several time points after the imposition of the salt stress and compared to control cells, in thin sections and freeze fracture electron microscopy, and by flow cytometry. One minute after exposure to high salt, i.e. 'salt shock', virtually all intracellular granules disappeared, the density of the cytoplasm decreased, and the appearance of DNA material was changed. Glycogen and other granules, however, reappeared by 4 hours after salt exposure. The organization of the cytoplasmic membrane undergoes major reorganization following salt shock. Freeze-fracture electron microscopy showed that small intramembrane particles (diameter 7.5 and 8.5 nanometers) are reduced in number by two- to fivefold, whereas large particles, (diameters 14.5 and 17.5 nanometers) increase two- to fourfold in frequency, compared to control cells grown in low salt medium. The changes in particle size distribution suggest synthesis of new membrane proteins, in agreement with the known increases in respiration, cytochrome oxidase, and sodium proton exchange activity of the cytoplasmic membrane.

NASA Discipline Number 61-10↗

NASA NTRS2003

Fundamental space radiobiology

The unique feature of the space radiation environment is the dominance of high-energy charged particles (HZE or high LET radiation) emitted by the Sun and galactic sources, or trapped in the Van Allen radiation belts. These charged particles present a significant hazard to space flight crews, and accelerator-based experiments are underway to quantify the health risks due to unavoidable radiation exposure. There are three principal properties of charged particles that distinguish them from conventional radiation, i.e. gamma rays and x-rays. First, they have a defined range in matter rather than an exponential absorption profile. Second, they undergo nuclear reactions to produce secondary particles. Third, and most important, they deposit their energy along well-defined linear paths or tracks rather than diffuse fields. The structured energy deposition pattern interacts on multiple scales with the biological structures of DNA, cells and tissues to produce correlated patterns of damage that evade repair systems. Traditional concepts of dose and its associated normalization parameter, RBE (relative biological effectiveness), break down under experimental scrutiny, and probabilistic models of risk based on the number of particle traversals per cell may be more appropriate. Unique patterns of DNA damage, gene expression, mobilization of repair proteins, activation of cytokines and remodeling of cellular microenvironment are observed following exposure to high LET radiation. At low levels of exposure the communication of bioactive substances from irradiated to unirradiated "bystander" cells can amplify the damage and cause a significant deviation from linearity in dose vs. response relations. Under some circumstances, there is even a multigenerational delay in the expression of radiation-induced genetic damage (genomic instability) which is not strictly dose dependent. These issues and the experimental evidence derived from ground based experiments at particle accelerators are presented along with speculation about how modified inertial conditions might perturb homeostatic responses to radiation to further complicate risk assessment for space flight.

NASA Discipline Radiation Health↗

NASA NTRS2001

A Structural and Molecular Approach for the Study Biomarkers

Investigation of the nucleation and growth of crystals in both abiotic and biotic systems is critical to seemingly diverse disciplines of geology, biology, environmental science, and astrobiology. While there are abundant studies devoted to the determination of the structure and composition of inorganic crystals, as well as to the development of thermodynamic and kinetic models, it is only recently that research efforts have been directed towards understanding mineralization in biological systems (i.e., biomineralization). Biomineralization refers to the processes by which living organisms form inorganic solids. Studies of the processes of biomineralization under low temperature aqueous conditions have focused primarily on magnetite forming bacteria and shell forming marine organisms. Many of the biological building materials consist of inorganic minerals (calcium carbonate, calcium phosphate, silica or iron oxide) intricately combined with organic polymers (like proteins). More recently, efforts have been undertaken to explore the nature of biological activities in ancient rocks. In the absence of well-preserved microorganisms or genetic material required for the polmerase chain reaction (PCR) method in molecular phylogenetic studies, using biominerals as biomarkers offers an alternative approach for the recognition of biogenic activity in both terrestrial and extraterrestrial environments. The primary driving force in biomineralization is the interaction between organic and inorganic phases. Thus, the investigation of the ultrastructure and the nature of reactions at the molecular level occurring at the interface between inorganic and organic phases is essential to understanding the processes leading to the nucleation and growth of crystals. It is recognized that crystal surfaces can serve as the substrate for the organization of organic molecules that lead to the formation of polymers and other complex organic molecules, and in discussions of the origins of life, is referred to as organic synthesis on mineral surfaces. Furthermore, it is suggested that the interaction between mineral surfaces and simple organic molecules resulted in the formation of amino acids, RNA, and perhaps other more complex molecules such as proteins. On the other hand, in natural systems, it is recognized that functional groups on cell walls or membranes of microorganisms serve as sites of nucleation and crystallization. The precise replication of biominerals with controlled structure, morphology, size and texture is not confined to higher organisms as it also occurs in primitive prokaryotic cells such as magnetotactic bacteria and cyanobacteria. This suggests that the principal strategies of biomineralization were established early on in the evolutionary history of organisms. It is critical, therefore, to search for common mechanisms within diverse biological systems. One such common factor is the capability for organization and self-assembly. Organic macromolecules such as proteins and lipids can aggregate and polymerize forming membranes or extracellular matrix. At the organic-inorganic interface, several factors such as lattice geometry, polarity, stereochemistry and topography may act in concert to control nucleation and growth of crystals. Although several models have been proposed that discuss the significance of these factors for biomineralization, no comprehensive experimental data are available. In contrast to crystallization in exclusively inorganic systems, the kinetics of reaction and structural relationships between organic and inorganic phases in biominerals or biomimetic material is poorly understood. For example, it is not clear if the concept of epitactic growth (geometrical matching of unit cells at the interface of a secondary crystal growing on a primary crystal) applies to organic-inorganic systems. In contrast to inorganic templates that often have a smooth and rigid surface that promotes epitactic growth, biological substrates are usually rough and result in a large degree of mismatch. It is apparent that factors controlling the reaction at the crystal-matrix interface are strongly dependent upon the nature of the substrate. Therefore, characterization of the assembled organic surface and surface structure of the inorganic phase is crucial to understanding the processes of biomineralization. The focus of our research is the investigation of the processes leading to the nucleation and growth of crystals on both natural and synthetic systems through an interdisciplinary approach that integrates molecular biology, morphology and mineralogy using advanced preparation and analytical techniques. We have studied run-products, particularly magnetite, siderite and other carbonates, that resulted from extracellular biomineralization by extremophiles isolated from a variety of extreme environments ranging from permafrost to hydrothermal vent systems. The results of this study are critical to recognizing biomarkers in terrestrial and extraterrestrial environments.

Thomas-Keprta, Kathie↗

NASA NTRS2018

From Apollo to the Future, the NASA Curation Model for Engaging the Sample Science Community Maximizes Science on Extraterrestrial Samples

The Astromaterials Acquisition and Curation Office at Johnson Space Center (JSC) has enjoyed a long-term partnership (50 years!) with a broad community of planetary sample scientists. This partnership has enabled the curators of planetary samples to plan for and enact evolving requirements for preservation of sample scientific integrity and for handling and long-term storage. The basis for this relationship is a standing peer review advisory committee composed of leading scientists who are recognized for achievements in sample analysis. The committee and its descendants have brought familiarity with the most relevant scientific investigations and the associated analytical and contamination challenges. Beginning with Apollo, the review committee was charged with oversight of curatorial operations and with ensuring fair access to samples. As additional samples from other planetary bodies were acquired, the committee evolved, taking on new responsibilities, reflected in committee name changes. However, oversight of curatorial operations and fair allocation of samples remain basic responsibilities. Committee recommendations are sent to the NASA Headquarters Discipline Scientist for approval. To minimize conflict of interest and maximize fair access, the rules governing the make-up of the committee is structured. Systematic rotation of leadership and staggered terms of membership allow the committee to retain expertise while bringing in fresh ideas. The first peer review committee was called the Lunar Sample Analysis and Planning Team (LSAPT) and was formalized in early 1968 with about 15 members. Their function was to review a) the equipment and procedures used in the new Lunar Receiving Laboratory (LRL); b) the proficiency and capability of the LRL staff; c) the sequence of sample analysis and allocation after quarantine release; and d) the findings of the Preliminary Examination Team (PET). According to LSAPT member Gerald Wasserburg, one of the first issues they faced was deciding whether to have most of the sample analyses performed in house at the LRL or to distribute samples to members of the scientific community. LSAPT concluded that the major scientific investigations should be carried out externally to the LRL by scientists chosen for their expertise in specific disciplines. Further they recommended that the PET's basic characterization of samples be circulated to the broad scientific community. LSAPT set its own agenda, paid attention to facility details, closely monitored the move of samples from the LRL to the interim curatorial facility in 1973, and was active in inspecting curation facilities. Between 1975 and 1979, a Facility Subcommittee of LSAPT oversaw the design and construction of a permanent facility for preservation of lunar samples. The result was an outstanding facility still in use today. In 1977, a separate peer review committee, the Meteorite Working Group (MWG), was formed to evaluate requests for new meteorites then being collected in Antarctica under what would in 1980 become a 3-agency agreement (National Science Foundation, NASA, Smithsonian Institution). By 1979, after lunar samples were moved into the new permanent facility, the vacated gloveboxes and laboratory were prepared for meteorite curation. Recognizing that LSAPT had been helpful in setting up the JSC curatorial facility for Antarctic meteorites, JSC recommended the review committee be given expanded duties, including advice on curation and analysis of materials from other planetary bodies and the name be changed to Lunar and Planetary Sample Team (LAPST). In 1993, LAPST was renamed the Curation and Analysis Planning Team for Extraterrestrial Materials (CAPTEM) to reflect additional functions. CAPTEM is chartered to be (1) a community-based, interdisciplinary forum for discussion and analysis of matters concerning the collection and curation of extraterrestrial samples, including planning future sample return missions and (2) a standing review panel, charged with evaluating proposals requesting allocation of all extraterrestrial samples contained in NASA collections. Efficiency and flexibility are gained through use of subcommittees, both ad hoc and standing. Transition of the MWG to a subcommittee of CAPTEM was completed in 2017. Today subcommittees review allocation requests for lunar samples, Antarctic meteorites, cosmic dust, Stardust cometary samples, Genesis solar wind samples, and samples returned from asteroids. Other subcommittees address facilities, informatics, and micro-cratered substrates. Planetary samples have been sent to research teams in over 30 countries world-wide. The expertise in the care and fair distribution of astromaterials by NASA using this model spans generations of planetary sample scientists and is a valuable resource to be tapped for future sample returns - OSIRIS-REx, Hayabusa 2, and Mars 2020.

Allton, Judith↗

NASA NTRS2012

Initial Observations by the Mars Exploration Rover Opportunity at Cape York, Meridiani Planum

Since the beginning of its mission, the MER rover Opportunity has visited a sequence of progressively larger impact craters in order to characterize rocks that represent an ever broader stratigraphic range. Endeavour Crater is by far the largest crater that this rover has visited, therefore the crater rim provides materials from strata that are much deeper and older than any materials yet sampled. Indeed, the Mars Reconnaissance Orbiter CRISM instrument detected spectral signatures of hydrated phyllosilicates in several rim segments, consistent with a Noachian provenance. In addition, the crater rim might have recorded the effects of the original impact as well as the thermal processes that occurred in its aftermath. This report summarizes initial observations of geologic structures and the fabrics, chemistry and mineralogy of rocks. Cape York is an N/NE - S/SW-trending segment of crater rim that is bounded by rim segments that are more deeply eroded, forming embayments. Opportunity drove onto the southwest margin of Cape York and has traversed across the Cape to a ridge near its northern end. The rim of Endeavour Crater was severely degraded and then on lapped by Meridiani sulfate-rich deposits, indicating that Cape York deposits experienced extensive erosion prior to the deposition of Meridiani Planum sulfate-rich sediments. Cape York consists of impact-uplifted rocks that are surrounded by a younger bedrock bench that might represent sediments shed from Cape York. The uplifted rock "Tisdale-2," located near the southern end of Cape York, is a polymict lithic breccia. Its elemental composition resembles a mixture of basalt plus bedrock encountered previously at Meridiani Planum, and it is relatively enriched in Ni, Zn, P, characteristic of hydrothermal fluids. "Chester Lake" and "Greeley Haven" are bedrock surfaces located near the southern and northern ends of Cape York, respectively, and they exhibit fabrics reminiscent of suevites. The rocks that were analyzed so far are quite different from any rocks previously encountered by Opportunity and Spirit. Several light-toned vein deposits (approx 1 cm) were discovered in the bench that borders the western flanks of Cape York. The vein "Homestake" is rich in Ca and S, and it exhibits a spectral feature near 1000 run caused by hydration, indicating that "Homestake" consists substantially of gypsum. The relationship(s) between these veins and the sulfate-rich layered deposits at Meridiani Planum remains uncertain. The veins might have been deposited by sulfate-rich fluids perhaps either in the immediate aftermath of the impact that formed Endeavour Crater or at some later time. Current uncertainties notwithstanding, the novel lithologies at Cape York are significantly older than the sulfate-rich sedimentary rocks at Meridiani Planum, and these lithologies have recorded episodes of aqueous activity from earlier epochs, perhaps during the Noachian. The author acknowledges the contributions of the Athena Science Team, the MER engineering team, JPL and NASA.

Marais, David J.↗

NASA NTRS1993

Relationships between pigment composition variation and reflectance for plant species from a coastal savannah in California

Advances in imaging spectroscopy have indicated that remotely sensed reflectance measurements of the plant canopy may be used to identify and qualify some classes of canopy biochemicals; however, the manner in which differences in biochemical compositions translate into differences is not well understood. Most frequently, multiple linear regression routines have been used to correlate narrow band reflectance values with measured biochemical concentrations. Although some success has been achieved with such methods for given data sets, the bands selected by multiple regression are not consistent between data sets, nor is it always clear what physical or biological basis underlies the correlation. To examine the relationship between biochemical concentration and leaf reflectance signal we chose to focus on the visible spectrum where the primary biochemical absorbances are due to photosynthetic pigments. Pigments provide a range of absorbance features, occur over a range of concentrations in natural samples, and are ecophysiologically important. Concentrations of chlorophyll, for example, have been strongly correlated to foliar nitrogen levels within a species and to photosynthetic capacity across many species. In addition pigments effectively absorb most of the photosynthetically active radiation between 400-700 nm, a spectral region for which silicon detectors have good signal/noise characteristics. Our strategy has been to sample a variety of naturally occurring species to measure leaf reflectance and pigment compositions. We hope to extend our understanding of pigment reflectance effects to interpret small overlapping absorbances of other biochemicals in the infrared region. For this reason, selected samples were also tested to determine total nitrogen, crude protein, cellulose, and lignin levels. Leaf reflectance spectra measured with AVIRIS bandwidths and wavelengths were compared between species and within species and for differences between seasons, for changes in the the shape of the spectra. We attempt to statistically correlate these shape changes with differences in pigment compositions. In parallel with our comparisons of pigment composition and leaf reflectance, we have modified the PROSPECT leaf reflectance model to test the contributions of pigments or pigment group concentrations. PROSPECT considers a leaf as a multi-layer dielectric plane with an uneven surface. Jacquemoud adapted the basic analysis of Allen for surface effects, a leaf thickness factor, and the absorption of water and chlorophyll (actually all pigments) and the plant matrix. Our modifications to PROSPECT in the forward direction include breaking out the pigment concentration parameter into separate components for chlorophyll a and b and a number of xanthophylls and carotenes, and introducing a shift and convolution function to model the spread and shift from their in vitro measurements to their in vivo state. Further, we have considered how the matrix elements (i.e., all biochemicals and structural effects not modeled explicity) vary with species.

Ustin, Susan L.↗

NASA NTRS1996

On the Relationship Between Transit Velocity of Interplanetary Shocks and Solar Active Processes

Recently, it was reported that preferential relationships exist between the transit velocity V(sub T) of earthward-directed interplanetary shocks and solar active processes, in particular, eruptive filaments outside active regions (the size of the erupting filament L(sub f)) and solar flares (the value of the X-ray characteristic J). Unfortunately, statistical testing of the proposed associations was not accomplished, nor was the 'geo-effectiveness' of the events adequately described. Reported here are the results of a re-examination of the 21 eruptive filaments (SSC-EF events) and 26 X-ray flares (SSC-F events) that have been associated with storm sudden commencements (SSCs) at Earth. Simple statistical testing refutes the claim that a preferential relationship exists between V(sub T) and L(sub F), while it supports the claim that one exists between V(sub T) and J. More importantly, the inferred relationship between V(sub T) and J is found to be more complicated than previously thought. In particular, it now appears that SSC-F events may be separable into two groups, based on the value of J: a low-J group (J less than 56), in which V(sub T) varies directly with J, and a high-J group (J greater than 56), in which V(sub T) varies inversely with J. As a whole, high-J events are associated with shocks of higher average transit velocity than those of low-J events, and SSC-F events with shocks of higher average transit velocity than those of SSC-EF events. Further, high-J events tend to be of greater X-ray class ( greater than M3), longer duration (greater then 80 min), and are more likely to be associated with type II/IV radio emission (9 of 12) than low-J events. They also tend to occur in magnetically complex (gamma/delta configuration) active regions (10 of 12) that are large in area extent (area greater than 445 millionths of a solar hemisphere) on the day of flaring (9 of 12). Of the 9 solar proton events that affected the Earth's environment that were found to be associated with SSC-F events, six were high-J events. Concerning 'geo-effectiveness', there appears to be no preferential relationship between the value of the J-parameter and the most negative value of the Dst geomagnetic index Dst(min) following the SSC, which is found to usually occur at 6-14 h after SSC onset (18 of 26) and which ranged in value from -1 to -249 (having a median value of about -75). Of the 26 SSC-F events, only 14 can be associated with a Dst(min) less than or equal to -75, and of these only 7 were high-J events. Of the 14 storm-related events (i.e. Dst(min) less than or equal to -75), three have previously been identified as being either 'magnetic clouds' or 'bidirectional flows', both manifestations of earthward-directed coronal mass ejections (CMEs). Superposed epoch analyses of selected solar wind parameters and Dst during the interval of storm-related SSC-F events demonstrate that geoeffective SSC-F events tend to be associated with solar wind flows that are faster, greater in magnetic field strength, and have a rotating field which has a strong southward component shortly after SSC onset, in comparison to SSC-F events that do not have Dst(min) less than or equal to 75. Therefore, it is inferred that geoeffective SSC-F events are probably fast earthward-directed CMEs. Although no single parameter is found that can serve as a predictor of high-skill level for determining the geoeffectiveness of an SSC-F event prior to its occurrence at Earth, one finds that knowledge of the flare's hemispheric location and appearance or lack of appearance of a two-ribbon structure is sufficient to correctly predict the geoeffectiveness of 20 out of 25 of the SSC-F events (80%). Surprisingly, the association or lack of association of metric type II/IV radio emission as a characteristic for determining the geoeffectiveness of the SSC-F events proved unfruitful, as did, to a lesser extent, the duration of the X-ray emission.

Wilson, Robert M.↗

NASA NTRS2002

A Chandra X-ray Study of Cygnus A: The Nucleus - 2

We report Chandra Advanced CCD Imaging Spectrometer and quasi-simultaneous Rossi X-Ray Timing Explorer (RXTE) observations of the nearby, powerful radio galaxy Cygnus A, with the present paper focusing on the properties of the active nucleus. In the Chandra observation, the hard (less than a few keV) X-ray emission is spatially unresolved with a size is approximately 1" (1.5 kpc, H(sub 0) = 50 km/s/Mpc) and coincides with the radio and near-infrared nuclei. In contrast, the soft (less than 2 keV) emission exhibits a bipolar nebulosity that aligns with the optical bipolar continuum and emission-line structures and approximately with the radio jet. In particular, the soft X-ray emission corresponds very well with the [O III] (lambda)5007 and H(alpha) + [N II] lambda(lambda)6548, 6583 nebulosity imaged with Hubble Space Telescope. At the location of the nucleus, there is only weak soft X-ray emission, an effect that may be intrinsic or result from a dust lane that crosses the nucleus perpendicular to the source axis. The spectra of the various X-ray components have been obtained by simultaneous fits to the six detectors. The compact nucleus is detected to 100 keV and is well described by a heavily absorbed power-law spectrum with Gamma(sub h) = 1.52(sup + 0.12, sub -0.12) (similar to other 0.12 narrow-line radio galaxies) and equivalent hydrogen column N(sub H)(nuc) = 2.0(sup +0.1, sub -0.1) x 10(exp 23)/sq cm. This 0.2 column is compatible with the dust obscuration to the near-infrared source for a normal gas-to-dust ratio. The soft (less than 2 keV) emission from the nucleus may be described by a power-law spectrum with the same index (i.e., Gamma(sub l) = Gamma(sub h), although direct fits suggest a slightly larger value for Gamma(sub l). Narrow emission lines from highly ionized neon and silicon, as well as a "neutral" Fe K(alpha) line, are detected in the nucleus and its vicinity (r approximately less than 2 kpc). The equivalent width (EW) of the Fe K(alpha) line (182(sup +40, sub -54) eV) is in good agreement with theoretical predictions for the EW versus N(sub H)(nuc) relationship in various geometries. An Fe K edge is also seen. The RXTE observations indicate a temperature of kT = 6.9(sup +0., sub -1.0) keV for the cluster gas (discussed in Paper III of this series) and cluster emission lines of Fe K(alpha) and Fe K(beta) and/or Ni K(alpha). We consider the possibility that the extended soft X-ray emission is electron-scattered nuclear radiation. Given that 1% of the unabsorbed 2 - 10 keV nuclear radiation would have to be scattered, the necessary gas column [N(sub H)(Scattering) approx. = 3.5 x 10(exp 22)/sq cm] would absorb the X-rays rather than scatter them if the gas is cold. Thus, the scattering plasma must be highly ionized. If this ionization is achieved through photoionization by the nucleus, the ionization parameter zeta greater than 1 ergs cm/s and the electron density n(sub e) approx. = 6 cc given the observed distance of the soft X-ray emission from the nucleus. The electron column density inferred from the X-ray observations is much too low to account for the extended optical scattered light, strongly suggesting that the polarized optical light is scattered by dust. The presence of highly ionized Ne lines in the soft X-ray spectrum requires 20 ergs cm/s approximately less than zeta approximately less than 300 ergs cm/s these lines may originate closer to the nucleus than the extended soft continuum or in a lower density gas. A collisionally ionized thermal model of the extended soft X-rays cannot be ruled out but is unattractive in view of the low metal abundance required (Z = 0.03 Z(mass)). The hard X-ray to far-infrared ratio for the nucleus of Cygnus A is similar to that seen in Seyfert 1 and unobscured radio galaxies. By means of the correlation between hard X-ray luminosity and nuclear optical absolute magnitude for these classes of object, we estimate M(sub B) = -22.4 for Cygnus A, near the .borderline between Seyfert galaxies and QSOs.

Young, Andrew J.↗

NASA NTRS1997

Carbon in the Former Soviet Union: The Current Balance

This work has been carried out in a period of great changes in Russia that have brought extreme hardships to the scientific community. We have been fortunate in establishing excellent relationships with the Russian scientific community and believe we have helped to retain coherence in circumstances where the continuation of research was in doubt. We have learned much and have been effective in advancing, even establishing, scholars and programs in Russia that might not otherwise have survived the transition. The vigor of the International Boreal Forest Research Association (IBFRA) is one sign of the value and success of these activities. Largely due to the current political and economic transitions in the former Soviet Union, the forests of much of the FSU are under reduced logging pressure. In addition, there is a decline in air pollution as heavy industry has waned, at least for now. Russian forestry statistics and our personal experience indicate a decline, perhaps as high as 60%, in forest harvesting over the last few years. But, new international market pressures on the forests exist in European Russia and in the Far East. The central government, still the "owner" of Russian forests, is having difficulty maintaining control over forest use and management particularly in the Far East and among the southern territories that have large, nonRussian ethnic populations. Extraordinarily large areas of mixed forest and grasslands, sparse or open forests, and mixed forests and tundra must be considered when calculating forest area It is insufficient to think of Russia as simply forest and nonforest Forest productivity, measured as growth of timber, appears to be in decline in all areas of Russia except in European Russia. Most information and publications on the recent history of these forests is heavily dependent on statistical data from the Soviet era. The interpretation of these data is very much open to debate. Anatoly Shwidenko, a long term collaborator and former senior scientist (mensuration) for the Soviet Committee on Forests, now a scholar at the International Institute of Applied Systems Analysis (IIASA), Vienna, has provided abundant contributions from the data available to him and from his experience. Forest stand carbon is concentrated in the Russian Far East (i.e. Primorski Kray), Central-Southern Siberia and European Russia But, soil carbon can be 10 times forest stand C. Our efforts in mapping the area and changes in area (as well as the internal structure) of forests have made major contributions to our joint understanding of the scale and status of these forests. To realize the importance of this contribution one needs only to recognize that any large scale Soviet-era maps of the area did not include latitude and longitude. Even today, there is great reluctance to provide these data, the basis of any GIS.

Woodwell, G. M.↗

NASA NTRS2008

Temporal Stability of Surface Roughness Effects on Radar Based Soil Moisture Retrieval During the Corn Growth Cycle

A representative soil surface roughness parameterization needed for the retrieval of soil moisture from active microwave satellite observation is difficult to obtain through either in-situ measurements or remote sensing-based inversion techniques. Typically, for the retrieval of soil moisture, temporal variations in surface roughness are assumed to be negligible. Although previous investigations have suggested that this assumption might be reasonable for natural vegetation covers (Moran et al. 2002, Thoma et al. 2006), insitu measurements over plowed agricultural fields (Callens et al. 2006) have shown that the soil surface roughness can change considerably over time. This paper reports on the temporal stability of surface roughness effects on radar observations and soil moisture retrieved from these radar observations collected once a week during a corn growth cycle (May 10th - October 2002). The data set employed was collected during the Optimizing Production Inputs for Economic and Environmental Enhancement (OPE3) field campaign covering this 2002 corn growth cycle and consists of dual-polarized (HH and VV) L-band (1.6 GHz) acquired at view angles of 15, 35, and 55 degrees. Cross-polarized L baud radar data were also collected as part of this experiment, but are not used in the analysis reported on here. After accounting for vegetation effects on radar observations, time-invariant optimum roughness parameters were determined using the Integral Equation Method (IEM) and radar observations acquired over bare soil and cropped conditions (the complete radar data set includes entire corn growth cycle). The optimum roughness parameters, soil moisture retrieval uncertainty, temporal distribution of retrieval errors and its relationship with the weather conditions (e.g. rainfall and wind speed) have been analyzed. It is shown that over the corn growth cycle, temporal roughness variations due to weathering by rain are responsible for almost 50% of soil moisture retrieval uncertainty depending on the sensing configuration. The effects of surface roughness variations are found to be smallest for observations acquired at a view angle of 55 degrees and HH polarization. A possible explanation for this result is that at 55 degrees and HH polarization the effect of vertical surface height changes on the observed radar response are limited because the microwaves travel parallel to the incident plane and as a result will not interact directly with vertically oriented soil structures.

Joseph, A.T.↗