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NASA NTRS1994

A multi-ion generalized transport model of the polar wind

The higher-order generalizations of the equations of standard hydrodynamics, known collectively as generalized transport theories, have been used since the early 1980s to describe the terrestrial polar wind. Inherent in the structure of generalized transport theories is the ability to describe not only interparticle collisions but also certain non-Maxwellian processes, such as heat flow and viscous stress, that are characteristic of any plasma flow that is not collision dominated. Because the polar wind exhibits a transition from collision-dominated to collisionless flow, generalized transport theories possess advantages for polar wind modeling not shared by either collision-dominated models (such as standard hydrodynamics) or collisionless models (such as those based on solving the collisionless Boltzmann equation). In general, previous polar wind models have used generalized transport equations to describe electrons and only one species of ion (H(+)). If other ion species were included in the models at all, it was in a simplified or semiempirical manner. The model described in this paper is the first polar wind model that uses a generalized transport theory (bi-Maxwellian-based 16-moment theory) to describe all of the species, both major and minor, in the polar wind plasma. In the model, electrons and three ion species (H(+), He(+), O(+)) are assumed to be major and several ion species are assumed to be minor (NO(+), Fe(+), O(++)). For all species, a complete 16-moment transport formulation is used, so that profiles of density, drift velocity, parallel and perpendicular temperatures, and the field-aligned parallel and perpendicular energy flows are obtained. In the results presented here, emphasis is placed on describing those constituents of the polar wind that have received little attention in past studies. In particular, characteristic solutions are presented for supersonic H(+) outflow and for both supersonic and subsonic outflows of the major ion He(+). Solutions are also presented for various minor ions, both atomic and molecular and both singly and multiply charged.

Demars, H. G.↗

NASA NTRS1996

Howard University Energy Expert Systems Institute Summer Program (EESI)

Howard University, under the auspices of the Center for Energy Systems and Controls runs the Energy Expert Systems Institute (EESI) summer outreach program for high school/pre-college minority students. The main objectives are to introduce precollege minority students to research in the power industry using modern state-of-the-art technology such as Expert Systems, Fuzzy Logic and Artificial Neural Networks; to involve minority students in space power management, systems and failure diagnosis; to generate interest in career options in electrical engineering; and to experience problem-solving in a teamwork environment consisting of faculty, senior research associates and graduate students. For five weeks the students are exposed not only to the exciting experience of college life, but also to the inspiring field of engineering, especially electrical engineering. The program consists of lectures in the fundamentals of engineering, mathematics, communication skills and computer skills. The projects are divided into mini and major. Topics for the 1995 mini projects were Expert Systems for the Electric Bus and Breast Cancer Detection. Topics on the major projects include Hybrid Electric Vehicle, Solar Dynamics and Distribution Automation. On the final day, designated as 'EESI Day' the students did oral presentations of their projects and prizes were awarded to the best group. The program began in the summer of 1993. The reaction from the students has been very positive. The program also arranges field trips to special places of interest such as the NASA Goddard Space Center.

Momoh, James A.↗

NASA NTRS1997

Symposium on Career Opportunities in Biomedical and Public Health Sciences

The goal of the Symposium on Career Opportunities in Biomedical and Public Health Sciences is to encourage minority collegiate and junior and senior high school students to pursue careers in biomedical and public health sciences. The objectives of the Symposium are to: (1) Provide information to participants concerning biomedical and public health science careers in government, academe and industry; (2) Provide information to minority students about training activities necessary to pursue a biomedical or public health science career and the fiscal support that one can obtain for such training; and (3) Provide opportunities for participating minority biomedical and public health role models to interact with participants.

Sullivan, Walter W.↗

NASA NTRS1998

Aeronautics and Aviation Science: Careers and Opportunities Project

The National Aeronautics and Space Administration funded project, Aeronautics and Aviation Science: Careers and Opportunities has been in operation since July, 1995. This project operated as a collaboration with Massachusetts Corporation for Educational Telecommunications, the Federal Aviation Administration, Bridgewater State College and four targeted "core sites" in the greater Boston area. In its first and second years, a video series on aeronautics and aviation science was developed and broadcast via "live, interactive" satellite feed. Accompanying teacher and student supplementary instructional materials for grades 6-9 were produced and disseminated by the Massachusetts Corporation for Educational Telecommunications (MCET). In the MCET grant application it states that project Take Off! in its initial phase would recruit and train teachers at "core" sites in the greater Boston area, as well as opening participation to other on-line users of MCET's satellite feeds. "Core site" classrooms would become equipped so that teachers and students might become engaged in an interactive format which aimed at not only involving the students during the "live" broadcast of the instructional video series, but which would encourage participation in electronic information gathering and sharing among participants. As a Take Off! project goal, four schools with a higher than average proportion of minority and underrepresented youth were invited to become involved with the project to give these students the opportunity to consider career exploration and development in the field of science aviation and aeronautics. The four sites chosen to participate in this project were: East Boston High School, Dorchester High School, Randolph Junior-Senior High School and Malden High School. In year 3 Dorchester was unable to continue to fully participate and exited out. Danvers was added to the "core site" list in year 3. In consideration of Goals 2000, the National Science Foundation standards for quality of teaching, and an educational agenda that promotes high standards for all students, Aeronautics and Aviation Science: Careers and Opportunities had as its aim to deliver products to schools, both in and outside the project sites, which attempt to incorporate multi-disciplined approaches in the presentation of a curriculum which would be appropriate in any classroom, while also aiming to appeal to young women and minorities. The curriculum was developed to provide students with fundamentals of aeronautics and aviation science. The curriculum also encouraged involving students and teachers in research projects, and further information gathering via electronic bulletin boards and internet capabilities. Though not entirely prescriptive, the curriculum was designed to guide teachers through recommended activities to supplement MCET's live telecast video presentations. Classroom teachers were encouraged to invite local pilots, meteorologists, and others from the field of aviation and aeronautics, particularly women and minorities to visit schools and to field questions from the students.

Texter, P. Cardie↗

NASA NTRS1999

Containerless, Low-Gravity Undercooling of Ti-Ce Alloys in the MSFC Drop Tube

Previous tests of the classical nucleation theory as applied to liquid-liquid gap miscibility systems found a discrepancy between experiment and theory in the ability to undercool one of the liquids before the L1-L2 separation occurs. To model the initial separation process in a two-phase liquid mixture, different theoretical approaches, such as free-energy gradient and density gradient theories, have been put forth. If there is a large enough interaction between the critical liquid and the crucible, both models predict a wetting temperature (T(sub w)) above which the minority liquid perfectly wets and layers the crucible interface, but only on one side of the immiscibility dome. Materials with compositions on the other side of the dome will have simple surface adsorption by the minority liquid before bulk separation occurs when the coexistence (i.e., binoidal) line in reached. If the interaction between the critical liquid and the crucible were to decrease, T(sub w) would increase, eventually approaching the critical consolute temperature (T(sub cc)). If this situation occurs, then there could be large regions of the miscibility gap where non-perfect wetting conditions prevail resulting in droplets of L1 liquid at the surface having a non-zero contact angle. The resulting bulk structure will then depend on what happens on the surface and the subsequent processing conditions. In the past several decades, many experiments in space have been performed on liquid metal binary immiscible systems for the purpose of determining the effects that different crucibles may have on the wetting and separation process of the liquids. Potard performed experiments that showed different crucible materials could cause the majority phase to preferentially wet the container and thus produce a dispersed microstructure of the minority phase. Several other studies have been performed on immiscibles in a semi-container environment using an emulsion technique. Only one previous study was performed using completely containerless processing of immiscible metals and the results of that investigation are similar to some of the emulsion studies. In all the studies, surface wetting was attributed as the cause for the similar microstructures or the asymmetry in the ability to undercool the liquid below the binoidal on one side of the immiscibility dome. By removing the container completely from the separation process, it was proposed that the loss of the crucible/liquid interaction would produce a large shift in T(sub w) and thus change the wetting characteristics at the surface. By investigating various compositions across the miscibility gap, a change in the type and amount of liquid wetting at the surface of a containerless droplet should change the surface nucleating behavior of the droplet - whether it be the liquid-liquid wetting or the liquid-to-solid transition. Undercooling of the liquid into the metastable region should produce significant differences in the separation process and the microstructure upon solidification. In this study, we attempt to measure these transitions by monitoring the temperature of the sample by optical pyrometry. Microstructural analysis will be made to correlate with the degree of undercooling and the separation mechanisms involved.

Robinson, M. B.↗

NASA NTRS1999

Wetting Characteristics of Immiscibles

Early microgravity experiments with immiscible alloys were usually carried out with the intent of forming dispersed microstructures. By processing under microgravity conditions, the main mechanism leading to gross phase separation could be eliminated. However, analysis of flight samples revealed a separated structure where the minor phase was present along the outer surface, while the major phase was present in the center. The Wetting Characteristics of Immiscibles (WCI) project, which flew aboard the USMP-4 (United States Microgravity Payload) mission in November of 1997, was designed to gain insight into the mechanisms causing segregation of these alloys. This investigation utilized an immiscible transparent organic alloy system and a transparent container in order to facilitate direct observation of the separation process. A range of immiscible alloy compositions was utilized in order to obtain variations in the minor and major phases present and observe the influence on the segregation processes. A small composition range was found where the minor liquid phase perfectly wet the cell gasket. Unexplained observations were made at the extremes of the composition range.

Andrews, J. B.↗

NASA NTRS2000

The Rural Outreach Project

The Rural Outreach Project was designed to increase the diversity of NASA's workforce by: 1) Conducting educational research designed to investigate the most effective strategies for expanding innovative, NASA-sponsored pre-college programs into rural areas; 2) Field-testing identified rural intervention strategies; 3) Implementing expanded NASA educational programs to include 300 rural students who are disabled, female and/or minority; and 4) Disseminating project strategies. The Project was a partnership that included NASA Langley Research Center's Office of Education, Norfolk State University, Cooperative Hampton Roads Organizations for Minorities in Engineering (CHROME) and Paul D. Camp Community College. There were four goals and activities identified for this project; 1) Ascertain effective strategies for expanding successful NASA-sponsored urban-based, pre-college programs into rural settings; 2) Field test identified rural intervention strategies; 3) Publish or disseminate two reports, concerning project research and activities at a national conference; 4) Provide educational outreach to 300, previously underserved, rural students who are disabled, female and /or minority.

Coleman, Clarence D.↗

NASA NTRS2000

Student Outreach with Renewable Energy Technology

The Student Outreach with Renewable Energy Technology (SORET) program is an education program involving three Historically Black Colleges and Universities and NASA's John H. Glenn Research Center at Lewis Field. These three universities; Central State University (CSU), Savannah State University (SSU) and Wilberforce University (WU) are working together with NASA Glenn to use the theme of renewable energy to improve the science, engineering and technology education of minority students and to attract minority students to these fields. In this vein, a renewable energy laboratory course is being offered at WU with the goal of giving the students of WU and CSU hands on experiences. As part of this course, the students are constructing solar light posts for a local high school with a high minority population. A Physics teacher from this school and some of his high school students are involved with this project. A lecture course on energy systems and sustainability is being developed by SSU to be delivered via distance reaming to the other institutions. Summer activities are being planned at all three institutions involving student projects in renewable energy. For example, WU students will work on a study of the synthesis and properties of photovoltaic materials. In addition, CSU will present a weeklong summer program to high school students with the assistance of WU. This presentation will focus on the student involvement and achievements in the educational area to date and plot the future course of this program.

Buffinger, D. R.↗

NASA NTRS2000

Conference Summary

Celebrations and special events were in order this year as the Minority University-Space Interdisciplinary Network (MU-SPIN) Program and NASA's Minority University Research and Education Division (MURED) both reached their 10th anniversaries. In honor of this occasion, the 2000 Annual Users' Conference held at Morris Brown College (MBC) in Atlanta, Georgia, September 11-15, 2000, was the first to be jointly hosted by MU-SPIN and MURED. It was particularly fitting that this anniversary should fall in the year 2000. The start of the new millennium propelled us to push bold new ideas and renew our commitment to minority university participation in all areas of NASA. With the theme 'Celebrating Our Tenth Year With Our Eyes on the Prize,' the conference provided a national forum for showcasing successful MU-SPIN and MURED Program (MUREP) experiences to enhance faculty/student development in areas of scientific and technical research and education. Our NASA-relevant conference agenda resulted in a record-breaking 220 registered attendees. Using feedback from past participants, we designed a track of student activities closely tailored to their interests. The resulting showcase of technical assistance and best practices set a new standard for our conferences in the years to come. This year's poster session was our largest ever, with over 50 presentations from students, faculty, and teachers. Posters covered a broad range of NASA activities from 'A Study of the Spiral Galaxy M101' to 'Network Cabling Characteristics.'

Harrington, James L., Jr.↗

NASA NTRS2006

Pyroxenes in Martian meteorites as petrogenetic indicators

Pyroxenes in Martian meteorites are important recorders of petrogenetic processes. Understanding the details of pyroxene major and minor element compositional variations can provide important insights into those processes. A combination of careful petrographic analysis of natural samples and experimental crystallization studies can lead to better understanding of the processes that gave rise to these samples on Mars. In addition, experimentally determined major, minor and trace element partition coefficients are important for using natural pyroxenes to estimate the compositions of the melts from which they crystallized and the oxidation conditions that prevailed during crystallization. We will report on minor element (Al, Ti, Cr) zoning in nakhlite pyroxenes and in synthetic pyroxenes that we have grown for the purposes of determining pyroxene/melt partition coefficients for Sr and REE. The natural pyroxenes have patchy Al zoning that, by analogy with our experimental pyroxenes, we interpret as sector zoning. The irregular patchy nature of the zoning is probably the result of the vagaries of growth kinetics and local environment during crystal growth. More slowly cooled nakhlites have the most distinct bimodal zoning, with one mode having Al2O3 around 0.5-0.6 wt%, and the other around 0.9 %. Average Al content increases with increasing cooling rate. This feature is puzzling, since the cumulus pyroxenes were almost certainly present at the time of eruption. Al and Ti are strongly correlated, but Cr is completely decoupled from those elements. The synthetic pyroxenes are distinctly sector zoned in Al and Ti, and the sector-to-sector variation in Al within a single crystal has important effects on trace element partition coefficients. Trivalent REE are strongly correlated with Al, while divalent elements (Sr, Eu+2) show a significantly weaker correlation. For example, as the Al2O3 content varies from 0.3 to 0.6 wt % from one sector to another, D(Gd) increases by approx.80% while D(Sr) and D(Eu) only increase by 20-30% at oxygen fugacities near IW. The different Al dependency of D for trivalent REE vs. divalent Eu and Sr considerably complicates the calibration of the Eu oxybarometer.

McKay, Gordon↗

NASA NTRS1995

The Three Sources of Gas in the Comae of Comets

Surface water ice on a comet nucleus is the major source of coma gas. Dust, entrained by coma gas, fragments and vaporizes, forming a second, distributed source of coma gas constituents. Ice species more volatile than water ice below the surface of the nucleus are a third source of coma gas. Vapors from these ices, produced by heat penetrating into the nucleus, diffuse through pores outward into the coma. The second and third sources provide minor, but sometimes easily detectible, gaseous species in the coma. We present mixing ratios of observed minor coma constituents relative to water vapor as a function of heliocentric and cometocentric distances and compare these ratios with model predictions, assuming the sources of the minor species are either coma dust or volatile ices in the nucleus.

Three Sources Comets↗

NASA NTRS2006

Additional Complexities in Nakhlite Pyroxenes: A Progress (?) Report

Nakhlites are olivine-bearing clinopyroxene cumulates [e.g., 1]. Based on petrographic characteristics, they may be divided into groups that cooled at different rates and may have been formed at different depths in a single flow [e.g., 2, 3]. The order of cooling rate is Lafayette < Governador Valadares ~ Nakhla < Yamato000593 < NWA817 ~ MIL03346. Nakhlite cumulus pyroxene grains consist of large cores that are nearly homogeneous in major element composition surrounded by thin rims that are zoned to Fe-rich compositions. Detailed study of these pyroxenes is important because they retain a record of the crystallization history of the nakhlite magma. Moreover, because the composition of the nakhlite parent melt cannot be directly determined, inversion of the major and minor element composition of the cumulate pyroxene cores can be used to estimate the composition of that melt. Thus it is important to understand the major and minor element zoning in the cumulus pyroxenes. We recently reported complications in the minor element zoning of nakhlite pyroxenes, especially for Al and Cr [4]. This abstract reports additional complications noted since that report.

McKay, G.↗

NASA NTRS2011

Coordinated Analyses of Diverse Components in Whole Stardust Cometary Tracks

Analyses of samples returned from Comet 81P/Wild-2 by the Stardust spacecraft have resulted in a number of surprising findings that show the origins of comets are more complex than previously suspected. However, these samples pose new experimental challenges because they are diverse and suffered fragmentation, thermal alteration, and fine scale mixing with aerogel. Questions remain about the nature of Wild-2 materials, such as the abundances of organic matter, crystalline materials, and presolar grains. To overcome these challenges, we have developed new sample preparation and analytical techniques tailored for entire aerogel tracks. We have successfully ultramicrotomed entire "carrot" and "bulbous" type tracks along their axis while preserving their original shapes. This innovation allowed us to examine the distribution of fragments along the track from the entrance hole all the way to the terminal particle (TP). We will present results of our coordinated analysis of the "carrot" type aerogel tracks #112 and #148, and the "bulbous" type aerogel tracks #113, #147 and #168 from the nanometer to the millimeter scale. Scanning TEM (STEM) was used for elemental and detailed mineralogy characterization, NanoSIMS was used for isotopic analyses, and ultrafast two-step laser mass spectrometry (ultra L2MS) was used to investigate the nature and distribution of organic phases. The isotopic measurements were performed following detailed TEM characterization for coordinated mineralogy. This approach also enabled spatially resolving the target sample from fine-scale mixtures of compressed aerogel and melt. Eight of the TPs of track #113 are dominated by coarse-grained enstatite (En90) that is largely orthoenstatite with minor, isolated clinoenstatite lamellae. One TP contains minor forsterite (Fo88) and small inclusions of diopside with % levels of Al, Cr and Fe. Two of the TPs contain angular regions of fine-grained nepheline surrounded by enstatite. Their O isotopic compositions are in the range of meteoritic materials, implying that they originated in the inner Solar System. Complex aromatic hydrocarbons are distributed along aerogel tracks and in TPs. These organics are likely cometary but were affected by shock heating. Three TPs of track #147 and two of track 168 have completely different mineralogy. TP2 of track #147 entirely consists of Fe-Ni alloy (5 at% Ni) and TP3 contains Fa28 with partial olivine-pyroxene intergrowth and minor albite. TP4 contains pentlandite, Fe-olivine, albite and high Ca pyroxene with Na and Cr (kosmochlor component). TP1 of #168 contains Fe-olivine, albite and pentlandite, and the concentric TP2 has a core of olivine grains with co-existing indigenous amorphous SiO2 surrounded by a carbon mantle, which in turn is surrounded by a layer of compressed aerogel. The TP of the carrot track #112 is a (16)O-rich forsteritic olivine grain that likely formed in the inner Solar System. The track also contains submicron-sized diamond grains of likely Solar System origin.

Nakamura-Messenger, Keiko↗

NASA NTRS2012

Molecular Technique to Understand Deep Microbial Diversity

Current sequencing-based and DNA microarray techniques to study microbial diversity are based on an initial PCR (polymerase chain reaction) amplification step. However, a number of factors are known to bias PCR amplification and jeopardize the true representation of bacterial diversity. PCR amplification of the minor template appears to be suppressed by the exponential amplification of the more abundant template. It is widely acknowledged among environmental molecular microbiologists that genetic biosignatures identified from an environment only represent the most dominant populations. The technological bottleneck has overlooked the presence of the less abundant minority population, and underestimated their role in the ecosystem maintenance. To generate PCR amplicons for subsequent diversity analysis, bacterial l6S rRNA genes are amplified by PCR using universal primers. Two distinct PCR regimes are employed in parallel: one using normal and the other using biotinlabeled universal primers. PCR products obtained with biotin-labeled primers are mixed with streptavidin-labeled magnetic beads and selectively captured in the presence of a magnetic field. Less-abundant DNA templates that fail to amplify in this first round of PCR amplification are subjected to a second round of PCR using normal universal primers. These PCR products are then subjected to downstream diversity analyses such as conventional cloning and sequencing. A second round of PCR amplified the minority population and completed the deep diversity picture of the environmental sample.

Vaishampayan, Parag A.↗

NASA NTRS2012

Molecular Technique to Reduce PCR Bias for Deeper Understanding of Microbial Diversity

Current planetary protection policies require that spacecraft targeted to sensitive solar system bodies be assembled and readied for launch in controlled cleanroom environments. A better understanding of the distribution and frequency at which high-risk contaminant microbes are encountered on spacecraft surfaces would significantly aid in assessing the threat of forward contamination. However, despite a growing understanding of the diverse microbial populations present in cleanrooms, less abundant microbial populations are probably not adequately taken into account due to technological limitations. This novel approach encompasses a wide spectrum of microbial species and will represent the true picture of spacecraft cleanroom-associated microbial diversity. All of the current microbial diversity assessment techniques are based on an initial PCR amplification step. However, a number of factors are known to bias PCR amplification and jeopardize the true representation of bacterial diversity. PCR amplification of a minor template appears to be suppressed by the amplification of a more abundant template. It is widely acknowledged among environmental molecular microbiologists that genetic biosignatures identified from an environment only represent the most dominant populations. The technological bottleneck overlooks the presence of the less abundant minority population and may underestimate their role in the ecosystem maintenance. DNA intercalating agents such as propidium monoazide (PMA) covalently bind with DNA molecules upon photolysis using visible light, and make it unavailable for DNA polymerase enzyme during polymerase chain reaction (PCR). Environmental DNA samples will be treated with suboptimum PMA concentration, enough to intercalate with 90 99% of the total DNA. The probability of PMA binding with DNA from abundant bacterial species will be much higher than binding with DNA from less abundant species. This will increase the relative DNA concentration of previously "shadowed" less abundant species available for PCR amplification. These PCR products obtained with and without PMA treatment will then be subjected to downstream diversity analyses such as sequencing and DNA microarray. It is expected that PMA-coupled PCR will amplify the "minority population" and help in understanding microbial diversity spectrum of an environmental sample at a much deeper level. This new protocol aims to overcome the major potential biases faced when analyzing microbial 16S rRNA gene diversity. This study will lead to a technological advancement and a commercial product that will aid microbial ecologists in understanding microbial diversity from various environmental niches. Implementation of this technique may lead to discoveries of novel microbes and their functions in sustenance of the ecosystem.

Vaishampayan, Parag A.↗

NASA NTRS2012

Deducing Wild 2 Components with a Statistical Dataset of Olivine in Chondrite Matrix

Introduction: A preliminary exam of the Wild 2 olivine yielded a major element distribution that is strikingly similar to those for aqueously altered carbonaceous chondrites (CI, CM, and CR) [1], in which FeO-rich olivine is preferentially altered. With evidence lacking for large-scale alteration in Wild 2, the mechanism for this apparent selectivity is poorly understood. We use a statistical approach to explain this distribution in terms of relative contributions from different chondrite forming regions. Samples and Analyses: We have made a particular effort to obtain the best possible analyses of both major and minor elements in Wild 2 olivine and the 5-30 micrometer population in chondrite matrix. Previous studies of chondrite matrix either include larger isolated grains (not found in the Wild 2 collection) or lack minor element abundances. To overcome this gap in the existing data, we have now compiled greater than 10(exp 3) EPMA analyses of matrix olivine in CI, CM, CR, CH, Kakangari, C2-ungrouped, and the least equilibrated CO, CV, LL, and EH chondrites. Also, we are acquiring TEM/EDXS analyses of the Wild 2 olivine with 500s count times, to reduce relative errors of minor elements with respect to those otherwise available. Results: Using our Wild 2 analyses and those from [2], the revised major element distribution is more similar to anhydrous IDPs than previous results, which were based on more limited statistics (see figure below). However, a large frequency peak at Fa(sub 0-1) still persists. All but one of these grains has no detectable Cr, which is dissimilar to the Fa(sub 0-1) found in the CI and CM matrices. In fact, Fa(sub 0-1) with strongly depleted Cr content is a composition that appears to be unique to Kakangari and enstatite (highly reduced) chondrites. We also note the paucity of Fa(sub greater than 58), which would typically indicate crystallization in a more oxidizing environment [3]. We conclude that, relative to the bulk of anhydrous IDPs, Wild 2 may have received a larger contribution from the Kakangari and/or enstatite chondrite forming regions. Alternatively, Wild 2 may have undergone accretion in an anomalously reducing region, marked by nebular condensation of this atypical forsterite. In [4], a similar conclusion was reached with an Fe-XANES study. We will also use similar lines of reasoning, and our previous conclusions in [5], to constrain the relative contributions of silicates that appear to have been radially transported from different ordinary and carbonaceous chondrite forming regions to the Kuiper Belt. In addition, the widespread depletion of Cr in these FeO-rich (Fa(sub greater than 20)) fragments is consistent with mild thermal metamorphism in Wild 2.

Frank, D. R.↗

NASA NTRS2013

Petrologic and In Situ Geochemical Constraints on Diogenite Genesis

Diogenites, members of the howardite, eucrite and diogenite (HED) clan, are orthopyroxenite, harzburgite and dunite meteorites [1-3]. Most are breccias, but remnant textures indicate they were originally coarse-grained rocks, with grain sizes of order of cm. Their petrography and compositions support an origin as crustal cumulates from a differentiated asteroid. Astronomical observations, and surface mineralogy and composition of Vesta determined by the Dawn spacecraft suggest that asteroid (4) Vesta is the parent object for HED meteorites [4-6]. The origin of diogenites is an unsettled issue. It is difficult to fit their bulk compositional characteristics into global magma ocean models that successfully describe the compositions of basaltic and cumulate eucrites [7]. Compositional analyses of acid-leached bulk samples have led to the hypothesis that many diogenites were formed late by interaction of their parent melts with a eucritic crust [8]. Those observations may alternatively be explained by subsolidus equilibration of trace elements between orthopyroxene and minor/ accessory phases in the rocks such as plagioclase and phosphate [7]. These competing hypotheses can be tested through in situ measurements of trace and minor elements in orthopyroxene. Our new petrologic observations and in situ minor and trace element data for a suite of diogenites are used to discuss the petrologic evolution of diogenites. Our preliminary data on two diogenites are consistent with the hypothesis that subsolidus element mobilization processes caused unusual trace element signatures seen in some diogenites [7]. We cannot stress strongly enough, however, that the sample set is too small and that additional data are required before definitive conclusions can be made.

Mittlefehldt, David W.↗

NASA NTRS2016

Dynamic Characterization of Galfenol (Fe81.6Ga18.4)

Galfenol has the potential to transform the smart materials industry by allowing for the development of multifunctional, load-bearing devices. One of the primary technical challenges faced by this development is the very limited experimental data on Galfenol's frequency-dependent response to dynamic stress, which is critically important for the design of such devices. This report details a novel and precise characterization of the constitutive behavior of polycrystalline Galfenol (Fe81.6Ga18.4) under quasi-static (1 Hz) and dynamic (4 to 1000 Hz) stress loadings. Mechanical loads are applied using a high-frequency load frame. Quasi-static minor and major hysteresis loop measurements of magnetic flux density and strain are presented for constant electromagnet currents (0 to 1.1 A) and constant magnetic fields 0 to 14 kA/m (0 to 180 Oe). The dynamic stress amplitude for minor and major loops is 2.88 and 31.4 MPa (418 and 4550 psi), respectively. Quasi-static material properties closely match published values for similar Galfenol materials. Quasi-static actuation responses are also measured and compared to quasi-static sensing responses; the high degree of reversibility seen in the comparison is consistent with published measurements and modeling results. Dynamic major and minor loops are measured for dynamic stresses up to 31 MPa (4496 psi) and 1 kHz, and the bias condition resulting in maximum, quasi-static sensitivity. Eddy current effects are quantified by considering solid and laminated Galfenol rods. Three key sources of error in the dynamic measurements are accounted for: (1) electromagnetic noise in strain signals due to Galfenol's magnetic response, (2) error in load signals due to the inertial force of fixturing, and (3) phase misalignment between signals due to conditioning electronics. For dynamic characterization, strain error is kept below 1.2 percent of full scale by wiring two collocated gauges in series (noise cancellation) and through leadwire weaving. Inertial force error is kept below 0.41 percent by measuring the dynamic force in the specimen using a nearly collocated piezoelectric load washer. The phase response of all conditioning electronics is explicitly measured and corrected for. In general, as frequency is increased, the sensing response becomes more linear because of an increase in eddy currents. As frequency increases above approximately 100 Hz, the elbow in the strain-versus-stress response disappears as the active (soft) regime stiffens toward the passive (hard) regime. Under constant-field conditions, the loss factors of the solid rod peak between 200 and 600 Hz, rather than exhibiting a monotonic increase. Compared to the solid rod, the laminated rod exhibits much slower increases in hysteresis with frequency, and its quasi-static behavior extends to higher frequencies. The elastic modulus of the laminated rod decreases between 100 and 300 Hz; this trend is currently unexplained.

Dynamic sensing↗