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At least 307 records · Page 17

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NASA NTRS1993

Upper tropospheric ozone production following mesoscale convection during STEP/EMEX

The chemistry and dynamics of a convective system observed on February 2, 1987 in the EMEX and STEP campaigns are analyzed. Chemical and thermodynamic profiles in undisturbed air near the EMEX 9 system indicate that the troposphere was well mixed by previous convection. As a consequence there was little direct transport from the boundary layer to the upper troposphere and air transported upward was detrained throughout the middle and upper troposphere. There was minimal effect on O3 production. Other convective complexes located 800-900 km upstream produced greater perturbations on trace gas profile immediately below the tropopause. Ozone production was reduced by about 0.25 ppbv/d at these altitudes, representing a reduction in P(O3) of 15-20 percent over the column from 14.5 to 17 km. P(O3) from 12 to 17 km in a region distant from active convection and subject to lightning was 2-3 times higher than it would have been without lightning.

Pickering, Kenneth E.↗

NASA NTRS2006

Mathematical Modeling of the Origins of Life

The emergence of early metabolism - a network of catalyzed chemical reactions that supported self-maintenance, growth, reproduction and evolution of the ancestors of contemporary cells (protocells) was a critical, but still very poorly understood step on the path from inanimate to animate matter. Here, it is proposed and tested through mathematical modeling of biochemically plausible systems that the emergence of metabolism and its initial evolution towards higher complexity preceded the emergence of a genome. Even though the formation of protocellular metabolism was driven by non-genomic, highly stochastic processes the outcome was largely deterministic, strongly constrained by laws of chemistry. It is shown that such concepts as speciation and fitness to the environment, developed in the context of genomic evolution, also held in the absence of a genome.

Pohorille, Andrew↗

NASA NTRS2007

Spacecraft Water Exposure Guidelines for Selected Contaminants

The International Space Station is a closed and complex environment, so some contamination of its internal atmosphere and water system is expected. To protect space crews from contaminants in potable and hygiene water, the National Aeronautics and Space Administration (NASA) requested that the National Research Council (NRC) provide guidance on how to develop water exposure guidelines and review NASA s development of the exposure guidelines for specific chemicals. NASA selects water contaminants for which spacecraft water exposure guidelines (SWEGs) will be established; this involves identifying toxicity effects relevant to astronauts and calculating exposure concentrations on the basis of those end points. SWEGs are established for exposures of 1, 10, 100, and 1,000 days. This report is the second volume in the series, Spacecraft Water Exposure Guidelines for Selected Chemicals. SWEG reports for acetone, alkylamines, ammonia, barium, cadmium, caprolactam, formate, formaldehyde, manganese, total organic carbon, and zinc are included in this report. The committee concludes that the SWEGs developed for these chemicals are scientifically valid based on the data reviewed by NASA and are consistent with the NRC (2000) report, Methods for Developing Spacecraft Water Exposure Guidelines. SWEG reports for additional chemicals will be presented in a subsequent volume.

Source record↗

NASA NTRS2016

Filled Nd(z)Fe(x)Co(4-x)Sb(12-y)Ge(y) Skutterudites: Processing and Thermoelectric Properties

Skutterudites have proven to be a useful thermoelectric system as a result of their enhanced figure of merit (ZT1), cheap material cost, favorable mechanical properties, and good thermal stability. The majority of skutterudite interest in recent years has been focused on binary skutterudites like CoSb3. Binary skutterudites are often double and triple filled, with a range of elements from the lanthanide series, in order to reduce the lattice component of thermal conductivity. Ternary and quaternary skutterudites, such as Co4Ge6Se6 or Ni4Sb8Sn4, provide additional paths to tune the electronic structure. The thermal conductivity can further be improved in these complex skutterudites by the introduction of fillers. The Nd(z)Fe(x)Co(4-x)Sb(12-y)Ge(y) system has been investigated as a p-type thermoelectric material, and is stable up to 600 C. The influence of Fe and Ge content, along with filler Nd, was investigated on thermoelectric transport properties. In addition to the chemical influence on properties, some processing details of the system will also be addressed.

Thermoelectric↗

NASA NTRSDate not supplied

Acid Alteration of Clay Minerals With Implication for Mars’ Surface Processes

The co-occurrence of phyllosilicates (clays) and sulfate stratigraphies at many locations on Mars are associated with a sharp change in surface conditions from neutral/alkaline pH during the Noachian (4.1-3.7 Ga) which favored the formation of clays to acidic conditions during the Hesperian (3.7-2.9 Ga) which favored the formation of sulfates. Yet, if these two contrasting geosystems were temporarily sequential, it is unknown how the Hesperian acidic conditions altered the previously formed clay units. We performed laboratory batch experiments to fingerprint the diagnostic features produced during interactions of Mars-analog clays and acidic solutions. Two clays, and silicon (IV) oxide, were reacted with solution of either sulfuric acid or filtered natural acid rock drainage (ARD) in plastic bottles. The solutions were adjusted at four pH values (1, 3, 5, and 7) and reacted at 4, 30, and 80°C for 3, 7, and 14 days. At the end of the experiments, the filtered supernatants were analyzed by ICP-MS while the solids were characterized by X-Ray Diffraction; Energy-Dispersive X-Ray Fluorescence analyses; Raman and Short-Wave Infrared spectroscopies and Scanning Electron Microscopy. Results show that the solution chemistry played a key role in the evolution of the clay-solution systems. In H2SO4 systems, the solution pH steadily increased due to partial clay dissolution with no secondary phase formation detected. Contrary, in the ARD systems, the pH decreased due to the ample presence of Fe which controlled both the reactivity of clays by the growth of protecting surface coatings and the solution pH by the precipitation of Fe nanophases; secondary phase detected included goethite, jarosite, gypsum, and siderite. These results indicate that, on Mars, the chemical interaction between clays and acidic solutions was complex and dependent on the solution chemistry. Acidic, sulfate-rich solutions have a high dissolution capacity and could have induced widespread clay disintegration. Notably, if Fe-rich ARD was involved, the clays on Mars could have remained stable during acidic Hesperian period due to formation of protective coatings. Comparison of our results with martian observations will be performed to determine how acidic conditions could potentially affect clays in sedimentary settings, including the Gale crater.

L. Lefticariu↗

NASA NTRS1988

Gneiss-charnockite transformation at Kottavattam, Southern Kerala (India)

At Kottavattam, leucocratic granitic garnet-biotite gneisses (age less than 2 Ga) were partially transformed to coarse-grained charnockite along a system of conjugate fractures (N70E and N20W) and the foliation planes (N60 to 80W; dip 80 to 90 SW) about 550 m.y. ago. To examine and quantify changes in fabric, mineralogy, pore fluids and chemical composition associated with this process, large rock specimens showing gneiss-charnockite transition were studied in detail. The results of the present study corroborate the concept that charnockite formation at Kottavattam is an internally-generated phenomenon and was not triggered by the influx of carbonic fluids from a deep-seated source. It is suggested that charnockitization was caused by the following mechanism: (1) near-isothermal decompression during uplift of the gneiss complex led to an increase of the pore fluid pressure (P sub fluid greater than P sub lith) which - in a regime of anisotropic stress - triggered or at least promoted the development of conjugate fractures; (2) the simultaneous release of pore fluids from bursting fluid inclusions and their escape into the developing fracture system resulted in a drop of fluid pressure; and (3) the internal generation and buffering of the fluids and their, probably, limited migration in an entirely granitic rock system explains the absence of any significant metasomatic mass transfer.

Raith, M.↗

NASA NTRS1981

Safety management of complex research operations

Complex research and technology operations present many varied potential hazards which must be addressed in a disciplined independent safety review and approval process. The research and technology effort at the Lewis Research Center is divided into programmatic areas of aeronautics, space and energy. Potential hazards vary from high energy fuels to hydrocarbon fuels, high pressure systems to high voltage systems, toxic chemicals to radioactive materials and high speed rotating machinery to high powered lasers. A Safety Permit System presently covers about 600 potentially hazardous operations. The Safety Management Program described in this paper is believed to be a major factor in maintaining an excellent safety record at the Lewis Research Center.

Brown, W. J.↗

NASA NTRS1994

Organic Chemistry of Meteorites

Studies of the molecular structures and C,N,H-isotopic compositions of organic matter in meteorites reveal a complex history beginning in the parent interstellar cloud which spawned the solar system. Incorporation of interstellar dust and gas in the protosolar nebula followed by further thermal and aqueous processing on primordial parent bodies of carbonaceous, meteorites have produced an inventory of diverse organic compounds including classes now utilized in biochemistry. This inventory represents one possible set of reactants for chemical models for the origin of living systems on the early Earth. Evidence bearing on the history of meteoritic organic matter from astronomical observations and laboratory investigations will be reviewed and future research directions discussed.

Chang, S.↗

NASA NTRS1998

Mesoscale Variability in SUCCESS Data

Analysis of meteorological, chemical and microphysical data from the airborne SUCCESS (SUbsonic aircraft Contrail and Cloud Effects Special Study) mission is reported. Careful analysis of the complex DC-8 flight pattern of May 2, 1996 reveals 19 linear flight segments within six main geographical areas, which we have analyzed. Significant mountain wave activity is revealed in the data from the MMS (Meteorology Measurement System) and MTP (Microwave Temperature Profiler) instruments on the DC-8, which resembles previous observations of mountain wave structures near Boulder, Colorado. Strong mountain-wave-induced upwelling downwind of the Rockies is noted. Turbulence is also noted in regions of the mountain wave consistent with overturning near the tropopause. Zonal winds recorded on the ER-2 are shown to be consistent with mountain wave breaking at or near critical levels in the stratosphere, consistent with the strong turbulence reported by the pilot during the ER-2 flight. These observations have been supported with spectral analyses and modeling studies. 'Postcasts' of mountain wave activity on May 2, 1996 using the Naval Research Laboratory Mountain Wave Forecast Model predicts both strong mountain wave activity near the tropopause and strong mountain-wave-induced turbulence in the stratosphere.

Eckermann, Stephen D.↗

NASA NTRSDate not supplied

Spectroscopic Investigation of Ungrouped Carbonaceous Chondrites

Carbonaceous (C) chondrites are the most primitive meteorite samples of our solar system. They retain records of their origin, formation mechanisms, evolution and secondary processes. This makes them excellent samples for studies to better understand and shed light on the early history of the solar system. A small fraction of C chondrites is type 2 ungrouped (C2-ung) chondrites. These meteorites could not be easily classified into one of the well-established groups due to compositional/petrological differences and other anomalies [1]. Different starting materials and/or complex post-accretionary processes in the parent bodies may have caused their anomalous compositional properties. As such, chemical characterization of C2-ung chondrites can potentially enable us to differentiate between processes and shed light onto the cosmochemical processes/events that cause such incompatibilities. In this work, we present detailed spectroscopic and imaging data on multiple C2-ung chondrites and compare them with various members of well-established C chondrite groups.

M. Yesiltas↗

NASA NTRS1986

Thermodynamic Calculations for Complex Chemical Mixtures

General computer program, CECTRP, developed for calculation of thermodynamic properties of complex mixtures with option to calculate transport properties of these mixtures. Free-energy minimization technique used in equilibrium calculation. Rigorous equations used in transport calculations. Program calculates equilibrium compositions and corresponding thermodynamic and transport properties of mixtures. CECTRP accommodates up to 24 reactants, 20 elements, and 600 products, 400 of which are condensed. Written in FORTRAN IV for any large computer system.

Mcbride, B. J.↗

NASA NTRS2004

Fossil Signatures Using Elemental Abundance Distributions and Bayesian Probabilistic Classification

Elemental abundances (C6, N7, O8, Na11, Mg12, Al3, P15, S16, Cl17, K19, Ca20, Ti22, Mn25, Fe26, and Ni28) were obtained for a set of terrestrial fossils and the rock matrix surrounding them. Principal Component Analysis extracted five factors accounting for the 92.5% of the data variance, i.e. information content, of the elemental abundance data. Hierarchical Cluster Analysis provided unsupervised sample classification distinguishing fossil from matrix samples on the basis of either raw abundances or PCA input that agreed strongly with visual classification. A stochastic, non-linear Artificial Neural Network produced a Bayesian probability of correct sample classification. The results provide a quantitative probabilistic methodology for discriminating terrestrial fossils from the surrounding rock matrix using chemical information. To demonstrate the applicability of these techniques to the assessment of meteoritic samples or in situ extraterrestrial exploration, we present preliminary data on samples of the Orgueil meteorite. In both systems an elemental signature produces target classification decisions remarkably consistent with morphological classification by a human expert using only structural (visual) information. We discuss the possibility of implementing a complexity analysis metric capable of automating certain image analysis and pattern recognition abilities of the human eye using low magnification optical microscopy images and discuss the extension of this technique across multiple scales.

Hoover, Richard B.↗

NASA NTRSDate not supplied

Nearest-Neighbor Machine Learning Feature Selection for Interpretation of Microbial Molecular Signatures from Isotope Ratio Mass Spectrometry Data

Mass spectrometry (MS) promises to be a powerful tool for potential biosignature detection during astrobiological missions on ocean worlds in our solar system. Accurate and generalizable machine learning methods could enhance science return on investment by predicting seawater chemistry and classifying isotopic biosignatures, either as a signature consistent with microbial life (biotic) or as a novelty (unclassified/unique). However, machine learning models are likely to be complex and involve interactions between MS features, making biosignatures difficult to interpret. Feature selection methods provide biological and chemical context that help interpret the mechanisms of machine learning models, but these methods also need the ability to detect complex interactions. Previously, we developed a machine learning feature selection algorithm called nearest-neighbor projected distance regression (NPDR) that has the ability to identify important model features that involve complex interactions and automatically reduce correlation and the dimensionality in a high-dimensional variable space. The standard distance metrics used in NPDR – Manhattan and Euclidean – assume the multivariate data are isotropic, which is often violated in real data due to differences in the covariance between variables. Thus, we extend NPDR to include a random forest distance, and other anisotropic distance metrics, for computing nearest neighbors. We also augment the isotope-ratio MS data with time-series features from the raw MS signal to improve biotic classification. We test NPDR on our novel experimental ocean world seawater analog MS data. We measure isotope fractionations of volatile CO 2 that could be measured in exospheres or plumes. Samples include baseline abiotic conditions using a range of possible seawater chemistry consistent with Europa and Enceladus, and biotic samples that include microbes in these seawaters. We use penalized NPDR with random forest proximity to identify interpretable microbial molecular signatures. We compare features with random forest importance, and we train a classifier that discriminates between biotic and abiotic samples with high accuracy. These ML-trained ocean-world analog MS data could be used to assist in identifying biosignatures during future missions.

geochemistry↗

NASA NTRS2024

Experimentally Modeling the Emergence of Prebiotically Plausible Phospholipid Vesicles

The prebiotic emergence of protocells is an important part of any origins of life scenario. Although fatty-acid-based vesicles are well studied, how they transitioned to phospholipid vesicles is uncertain. Herein, we show that cyclic-phospholipids formed from fatty acids and glycerol could have played a role by generating a heterogeneous library of vesicles with diverse morphologies and tolerance to a range of metal ions, temperature, and pH. The cyclic phosphate moiety facilitates the natural emergence of vesicles composed of diacyl-phospholipids to become part of the chemical evolutionary process. Competing emergent properties of the various systems (facilitated by additives) could have led to an early preference of the sn-1,2-acyl-substitution on the glycerol backbone coincidental with extant biology. Thus, cyclic-phospholipids could have played a significant role not only in early prebiotic protocellular chemistry but also in facilitating the chemical evolution of protocells from the structurally simple to the functionally more complex.

Sunil Pulletikurti↗

NASA NTRS1982

Criteria for the emergence and evolution of life in the solar system

It is proposed that there are at least 25 specific conditions or requirements which have to be fulfilled in order for life to appear and evolve in a planetary system such as ours. The criteria are grouped into five major general areas: (1) Planetary criteria relate to the physical properties of the planet as it is formed and as it becomes a cosmic body with the potential to provide an abode for life. (2) Chemical criteria concern the composition, availability of effective energy sources, and chemical constraints of the environment where reactions take place for the prebiological formation of biochemical compounds. (3) Protobiological criteria relate to the prebiologically synthesized oligomeric and polymeric biomolecules, how they interact cooperatively to form protobiological structures and functions, and self-assemble to give rise to a living system. (4) Evolutionary criteria are concerned with the processes responsible for the increase in complexity of organisms by genomic multiplication, symbiotic integration, and cellular differentiation, as well as with the negentropic ability of organisms to continuously recycle all the volatile biogenic elements. (5) Stellar criteria relate to the elemental composition mass, lifetime, and other features of Main Sequence stars which may be surrounded by planetary systems similar to our own.

Oro, J.↗

NASA NTRS1990

The 1990 update to strategy for exploration of the inner planets

The Committee on Planetary and Lunar Exploration (COMPLEX) has undertaken to review and revise the 1978 report Strategy for Exploration of the Inner Planets, 1977-1987. The committee has found the 1978 report to be generally still pertinent. COMPLEX therefore issues its new report in the form of an update. The committee reaffirms the basic objectives for exploration of the planets: to determine the present state of the planets and their satellites, to understand the processes active now and at the origin of the solar system, and to understand planetary evolution, including appearance of life and its relation to the chemical history of the solar system.

Esposito, Larry W.↗

NASA NTRS1997

Wing Flutter Control

Through Small Business Innovation Research (SBIR) contracts from Langley Research Center, Orbital Research Inc. developed the Orbital Research Intelligent Control Algorithm (ORICA), the first practical hardware-independent adaptive predictive control structure, specifically suited for optimal control of complex, time-varying systems. ORICA technology has been applied to the problem of controlling aircraft wing flutter. Coupled with NASA expertise, the technology has the possibility of making jet travel safer, more cost effective by extending distance range, and lowering overall aircraft operating costs. Future application areas for ORICA include control of robots, power trains, systems with arrays of sensors, or regulating chemical plants or electrical power plant control.

Source record↗

NASA NTRS1990

Microspheres

Vital information on a person's physical condition can be obtained by identifying and counting the population of T-cells and B-cells, lymphocytes of the same shape and size that help the immune system protect the body from the invasion of disease. The late Dr. Alan Rembaum developed a method for identifying the cells. The method involved tagging the T-cells and B-cells with microspheres of different fluorescent color. Microspheres, which have fluorescent dye embedded in them, are chemically treated so that they can link with antibodies. With the help of a complex antibody/antigen reaction, the microspheres bind themselves to specific 'targets,' in this case the T-cells or B-cells. Each group of cells can then be analyzed by a photoelectronic instrument at different wavelengths emitted by the fluorescent dyes. Same concept was applied to the separation of cancer cells from normal cells. Microspheres were also used to conduct many other research projects. Under a patent license Magsphere, Inc. is producing a wide spectrum of microspheres on a large scale and selling them worldwide for various applications.

Source record↗