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All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Theoretical studies of the marine sulfur cycle

Several reduced sulfur compounds are produced by marine organisms and then enter the atmosphere, where they are oxidized and ultimately returned to the ocean or the land. The oceanic dimethyl sulfide (DMS) flux, in particular, represents a significant fraction of the annual global sulfur input to the atmosphere. In the atmosphere, this gas is converted to sulfur dioxide (SO2), methane sulfonic acid, and other organic acids which are relatively stable and about which little is known. SO2 is a short lived gas which, in turn, is converted to sulfuric acid and other sulfate compounds which contribute significantly to acid rain. Because of the complexity of the sulfur system, it is not well understood even in the unperturbed atmosphere. However, a number of new observations and experiments have led to a significant increase in the understanding of this system. A number of one dimensional model experiments were conducted on the gas phase part of the marine sulfur cycle. The results indicate the measured concentration of DMS and the amplitude of its diurnal cycle are in agreement with estimates of its global flux. It was also found that DMS can make a large contribution to the background SO2 concentration in the free troposphere. Estimates of CS2 concentrations in the atmosphere are inconsistent with estimated fluxes; however, measured reaction rates are consistent with the observed steep tropospheric gradient in CS2. Observations of CS2 are extremely sparse. Further study is planned.

Toon, Owen B.↗
NASA NTRS2005

Journal of Gravitational Physiology, Volume 12, Number 1

The following topics were covered: System Specificity in Responsiveness to Intermittent -Gx Gravitation during Simulated Microgravity in Rats; A Brief Overview of Animal Hypergravity Studies; Neurovestibular Adaptation to Short Radius Centrifugation; Effect of Artificial Gravity with Exercise Load by Using Short-Arm Centrifuge with Bicycle Ergometer as a Countermeasure Against Disused Osteoporosis; Perception of Body Vertical in Microgravity during Parabolic Flight; Virtual Environment a Behavioral and Countermeasure Tool for Assisted Gesture in Weightlessness: Experiments during Parabolic Flight; Artificial Gravity: Physiological Perspectives for Long-Term Space Exploration; Comparison of the Effects of DL-threo-Beta-Benzyloxyaspartate on the Glutamate Release from Synaptosomes before and after Exposure of Rats to Artificial Gravity; Do Perception and Postrotatory Vestibulo-Ocular Reflex Share the Same Gravity Reference?; Vestibular Adaptation to Changing Gravity Levels and the Orientation of Listing's Plane; Compound Mechanism Hypothesis on +Gz - Induced Brain Injury and Dysfunction of Learning and Memory; Environmental Challenge Impairs Prefrontal Brain Functions; Effect of 6-Days of Support Withdrawal on Characteristics of Balance Function; Hypergravity-Induced Changes of Neuronal Activities in CA1 Region of Rat Hippocampus; Audiological Findings in Antiorthostatic Position Modelling Microgravitation; Investigating Human Cognitive Performance during Spaceflight; The Relevance of the Minimization of Torque Exchange with the Environment in Weightlessness is Confirmed by Asimulation Study; Characteristics of the Eyes Pursuit Function during Readaptation to Terrestrial Gravity after Prolonged Flights Aboard the International Space Station; Comparison of Cognitive Performance Tests for Promethazine Pharmacodynamics in Human Subjects; Structural Reappraisal of Dendritic Tree of Cerebellar Purkinje Cell for Novel Functional Modeling of Elementary Sensorimotor Adaptive Processes; Orpheus 0 G or Ear in Microgravity to Establish Symptoms Concomittant of Inner and Middle Ear and Osteoporosis in Microgravity; Understanding Visual Perception in the Perspective of Gravity; Cortical Regions Associated with Orthostatic Stress in Conscious Humans; Restoration of Central Blood Volume: Application of a Simple Concept and Simple Device to Counteract Cardiovascular Instability in Syncope and Hemorrhage; WISE-2005: Integrative Cardiovascular Responses with LBNP during 60-Day Bed Rest in Women; Intracranial Pressure Increases during Weightlessness. A Parabolic Flights Study; Lower Limb & Portal Veins Echography for Predicting Risk of Thrombosis during a 90-D Bed Rest; Calf Tissue Liquid Stowage and Muscular and Deep Vein Distension in Orthostatic Tests after a 90-Day Head Down Bed Rest; Morphology of Brain Vessels in the Tail Suspended Rats Exposed to Intermittent 2 G; Alterations in Vasoreactivity of Femoral Artery Induced by Hindlimb Unweighting are Related to the Changes of Contractile Protein in Rats; and Respiratory Sinus Arrhythmia: A Marker of Decreased Parasympathetic Modulation after Short Duration.

Fuller, Charles A.↗
NASA NTRS2007

In-situ micro-FTIR Study of Thermal Changes of Organics in Tagish Lake Meteorite: Behavior of Aliphatic Oxygenated Functions and Effects of Minerals

Systematic in-situ FTIR heating experiments of Tagish Lake meteorite grains have been performed in order to study thermal stability of chondritic organics. Some aliphatic model organic substances have also been used to elucidate effects of hydrous phyllosilicate minerals on the thermal stability of organics. The experimental results indicated that organic matter in the Tagish Lake meteorite might contain oxygenated aliphatic hydrocarbons which are thermally stable carbonyls such as ester and/or C=O in ring compounds. The presence of hydrous phyllosilicate minerals has a pronounced effect on the increase of the thermal stability of aliphatic and oxygenated functions. These oxygenated aliphatic organics in Tagish Lake can be formed during the aqueous alteration in the parent body and the formation temperature condition might be less than 200 C, based especially on the thermal stability of C-O components. The hydrous phyllosilicates might provide sites for organic globule formation and protected some organic decomposition

Kebukawa, Yoko↗
NASA NTRS2016

Visible-Light-Responsive Photocatalysis: Ag-Doped TiO2 Catalyst Development and Reactor Design Testing

In recent years, the alteration of titanium dioxide to become visible-light-responsive (VLR) has been a major focus in the field of photocatalysis. Currently, bare titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Hg-vapor fluorescent light sources are used in photocatalytic oxidation (PCO) reactors to provide adequate levels of ultraviolet light for catalyst activation; these mercury-containing lamps, however, hinder the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. VLR-TiO2 would allow for use of ambient visible solar radiation or highly efficient visible wavelength LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Over the past three years, Kennedy Space Center has developed a VLR Ag-doped TiO2 catalyst with a band gap of 2.72 eV and promising photocatalytic activity. Catalyst immobilization techniques, including incorporation of the catalyst into a sorbent material, were examined. Extensive modeling of a reactor test bed mimicking air duct work with throughput similar to that seen on the International Space Station was completed to determine optimal reactor design. A bench-scale reactor with the novel catalyst and high-efficiency blue LEDs was challenged with several common volatile organic compounds (VOCs) found in ISS cabin air to evaluate the system's ability to perform high-throughput trace contaminant removal. The ultimate goal for this testing was to determine if the unit would be useful in pre-heat exchanger operations to lessen condensed VOCs in recovered water thus lowering the burden of VOC removal for water purification systems.

Photocatalysis↗
NASA NTRS2016

Tropospheric Ozone Change from 1980 to 2010 Dominated by Equatorward Redistribution of Emissions

Ozone is an important air pollutant at the surface, and the third most important anthropogenic greenhouse gas in the troposphere. Since 1980, anthropogenic emissions of ozone precursors methane, non-methane volatile organic compounds, carbon monoxide and nitrogen oxides (NOx) have shifted from developed to developing regions. Emissions have thereby been redistributed equatorwards, where they are expected to have a stronger effect on the tropospheric ozone burden due to greater convection, reaction rates and NOx sensitivity. Here we use a global chemical transport model to simulate changes in tropospheric ozone concentrations from 1980 to 2010, and to separate the influences of changes in the spatial distribution of global anthropogenic emissions of short-lived pollutants, the magnitude of these emissions, and the global atmospheric methane concentration. We estimate that the increase in ozone burden due to the spatial distribution change slightly exceeds the combined influences of the increased emission magnitude and global methane. Emission increases in Southeast, East and South Asia may be most important for the ozone change, supported by an analysis of statistically significant increases in observed ozone above these regions. The spatial distribution of emissions dominates global tropospheric ozone, suggesting that the future ozone burden will be determined mainly by emissions from low latitudes.

Zhang, Yuqiang↗
NASA NTRS1991

Aging commuter aeroplanes: Fatigue evaluation and control methods

The risks associated with old aeroplanes arise in the main from the difficulty of obtaining support from the manufacturer and other skilled people, and from a general loss of reliability caused by wear and other deterioration. The loss of reliability is caused by two broad classes of problem. There are those problems which are self evident, and hazardous rather than catastrophic. These are the problem areas where characteristically there have been multiple overhauls, repairs, and replacements, and where aging really means the results of repair ineffectiveness that accumulates. The other class of problem is the insidious and potentially catastrophic class. It includes the progressive deterioration of items which are not maintained, and often cannot be maintained because the deterioration cannot be seen. It includes loss of physical properties in adhesives and other organic compounds, corrosion, and the response to repeated loads. This paper deals with a currently unnecessarily troublesome aspect of that response. The present working definition of "commuter aeroplanes" encompasses a wide range of aging types, from the Fairchild F27, through deHavilland Canada Twin Otters to the smaller twin engined Piper and Cessna models. It includes such types as the Lockheed 10, the Beech 18, and the Grumman Mallard. Although we must remain concerned about those types which have been certificated under a design standard or operational rule which embodies the elementary fail-safe concept and which have not been subjected to a subsequent structural audit, this paper is directed, in the first instance, towards types for which fatigue and damage tolerance evaluation was not required as a condition of certification. It will be seen, however, that the principles are robust enough for more general application.

Aging Aircraft↗
NASA NTRS1993

Visible photoluminescence of porous Si(1-x)Ge(x) obtained by stain etching

We have investigated visible photoluminescence (PL) from thin porous Si(1-x)Ge(x) alloy layers prepared by stain etching of molecular-beam-epitaxy-grown material. Seven samples with nominal Ge fraction x varying from 0.04 to 0.41 were studied at room temperature and 80 K. Samples of bulk stain etched Si and Ge were also investigated. The composition of the porous material was determined using X-ray photoemission spectroscopy and Rutherford backscattering techniques to be considerably more Ge-rich than the starting epitaxial layers. While the luminescence intensity drops significantly with the increasing Ge fraction, we observe no significant variation in the PL wavelength at room temperature. This is clearly in contradiction to the popular model based on quantum confinement in crystalline silicon which predicts that the PL energy should follow the bandgap variation of the starting material. However, our data are consistent with small active units containing only a few Si atoms that are responsible for the light emission. Such units are present in many compounds proposed in the literature as the cause of the visible PL in porous Si.

Ksendzov, A.↗
NASA NTRS2012

Crystallographic Stability of Metastable Phase Formed by Containerless Processing in REFeO3 (RE: Rare-Earth Element)

Undercooling a melt often facilitates a metastable phase to nucleate preferentially. Although the classical nucleation theory shows that the most critical factor for forming a metastable phase is the interface free energy, the crystallographic stability is also indispensable for the phase to be frozen at ambient temperature. In compound materials such as oxides, authors have suggested that the decisive factors for forming a critical nucleus are not only the free energy difference but also the difference of the entropy of fusion between stable and metastable phases. In the present study, using REFeO3 (RE: rare-earth element) as a model material, we investigate the formation of a metastable phase from undercooled melts with respect to the competitive nucleation and crystallographical stabilities of both phases.

Kuribayashi, Kazuhiko↗
NASA NTRS1986

Infrared observations of small solar-system bodies

Observations of Europa using the Cooled Grating Array Spectrometer have resulted in the discovery of new absorption features in the spectrum of the trailing side of Europa which have been attributed to either magnetospherically implanted sulfur compounds or recently emplaced hydrates of ammonia. More observations are planned to determine which of these two classes of compounds are responsible. Two asteroid occultations have been observed so far, but with some negative results (the occultations paths shifted sufficiently that the groups responsible for timing the visual occultation got no data). High-quality data in the thermal infrared were obtained nevertheless; those data are useful for constraint of thermal models of asteroids and will be analyzed in that context. Work was completed to perfect a computer code that will fit a triaxial-ellipsoid thermal model to the IR data while constrained by the visual lightcurve.

Brown, R. H.↗
NASA NTRS1986

In search of stratospheric bromine oxide

The Imaging Spectrometric Observatory (ISO) is capable of recording spectra in the wavelength range of 200 to 12000 Angstroms. Data from a recent Spacelab 1 ATLAS mission has imaged the terrestrial airglow at tangent ray heights of 90 and 150 km. These data contain information about trace atmospheric constituents such as bromine oxide (BrO), hydroxyl (OH), and chlorine dioxide (OClO). The abundances of these species are critical to stratospheric models of catalytic ozone destruction. Heretofore, very few observations were made especially for BrO. Software was developed to purge unwanted solar features from the airglow spectra. The next step is a measure of the strength of the emission features for BrO. The final analysis will yield the scale height of this important compound.

Lestrade, John Patrick↗
NASA NTRS2004

Rotating Reverse Osmosis for Wastewater Reuse

Our previous work established the concept of a low-pressure rotating reverse osmosis membrane system. The rotation of the cylindrical RO filter produces shear and Taylor vortices in the annulus of the device that decrease the concentration polarization and fouling commonly seen with conventional RO filtration techniques. A mathematical model based on the film theory and the solution-diffusion model agrees well with the experimental results obtained using this first generation prototype. However, based on the model, the filtrate flux and contaminant rejection depend strongly on the transmembrane pressure. Therefore, the goal of our current work is to improve the flux of the device by increasing the transmembrane pressure by a factor of 3 to 4. In addition, the rejections for a wider variety of inorganic and organic compounds typically found in space mission wastewater are measured.

Lueptow, Richard M.↗
NASA NTRS2014

Investigation of Pyridine Carboxylic Acids in CM2 Carbonaceous Chondrites: Potential Precursor Molecules for Ancient Coenzymes

The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We also report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono- and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.

precursor molecules↗
NASA NTRS2014

Investigation of Pyridine Carboxylic Acids in CM2 Carbonaceous Chondrites: Potential Precursor Molecules for Ancient Coenzymes

The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We lso report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono- and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.

Pyridine Carboxylic↗
NASA NTRS1972

Predesign report for the rotor systems research aircraft

A conceptual predesign of a compound helicopter for conducting rotor research is presented. The aircraft was selected by the Government as the better of two concepts submitted. The helicopter is a three place vehicle in the 24,000 pound gross weight class. It has been determined that the helicopter satisfies the requirements for the rotor research mission. The model has been predesigned sufficiently to allow an assessment of its performance and stability and control characteristics. A brief treatment of these subjects is included.

Source record↗
NASA NTRS2007

NASA Tech Briefs, September 2007

Topics covered include; Rapid Fabrication of Carbide Matrix/Carbon Fiber Composites; Coating Thermoelectric Devices To Suppress Sublimation; Ultrahigh-Temperature Ceramics; Improved C/SiC Ceramic Composites Made Using PIP; Coating Carbon Fibers With Platinum; Two-Band, Low-Loss Microwave Window; MCM Polarimetric Radiometers for Planar Arrays; Aperture-Coupled Thin-Membrane L-Band Antenna; WGM-Based Photonic Local Oscillators and Modulators; Focal-Plane Arrays of Quantum-Dot Infrared Photodetectors; Laser Range and Bearing Finder With No Moving Parts; Microrectenna: A Terahertz Antenna and Rectifier on a Chip; Miniature L-Band Radar Transceiver; Robotic Vision-Based Localization in an Urban Environment; Programs for Testing an SSME-Monitoring System; Cathodoluminescent Source of Intense White Light; Displaying and Analyzing Antenna Radiation Patterns; Payload Operations Support Team Tools; Space-Shuttle Emulator Software; Soft Real-Time PID Control on a VME Computer; Analyzing Radio-Frequency Coverage for the ISS; Nanorod-Based Fast-Response Pressure-Sensitive Paints; Capacitors Would Help Protect Against Hypervelocity Impacts; Diaphragm Pump With Resonant Piezoelectric Drive; Improved Quick-Release Pin Mechanism; Designing Rolling-Element Bearings; Reverse-Tangent Injection in a Centrifugal Compressor; Inertial Measurements for Aero-assisted Navigation (IMAN); Analysis of Complex Valve and Feed Systems; Improved Path Planning Onboard the Mars Exploration Rovers; Robust, Flexible Motion Control for the Mars Explorer Rovers; Solar Sail Spaceflight Simulation; Fluorine-Based DRIE of Fused Silica; Mechanical Alloying for Making Thermoelectric Compounds; Process for High-Rate Fabrication of Alumina Nanotemplates; Electroform/Plasma-Spray Laminates for X-Ray Optics; An Automated Flying-Insect Detection System; Calligraphic Poling of Ferroelectric Material; Blackbody Cavity for Calibrations at 200 to 273 K; KML Super Overlay to WMS Translator; High-Performance Tiled WMS and KML Web Server; Modeling of Radiative Transfer in Protostellar Disks; Composite Pulse Tube; Photometric Calibration of Consumer Video Cameras; Criterion for Identifying Vortices in High- Pressure Flows; Amplified Thermionic Cooling Using Arrays of Nanowires; Delamination-Indicating Thermal Barrier Coatings; Preventing Raman Lasing in High-Q WGM Resonators; Procedures for Tuning a Multiresonator Photonic Filter; Robust Mapping of Incoherent Fiber-Optic Bundles; Extended-Range Ultrarefractive 1D Photonic Crystal Prisms; Rapid Analysis of Mass Distribution of Radiation Shielding; Modeling Magnetic Properties in EZTB; Deep Space Network Antenna Logic Controller; Modeling Carbon and Hydrocarbon Molecular Structures in EZTB; BigView Image Viewing on Tiled Displays; and Imaging Sensor Flight and Test Equipment Software.

Source record↗
NASA NTRS2010

Amino Acids from Icy Amines: A Radiation-Chemical Approach to Extraterrestrial Synthesis

Detections of amino acids in meteorites go back several decades, with at least 100 such compounds being reported for the Murchison meteorite alone. The presence of these extraterrestrial molecules raises questions as to their formation, abundance, thermal stability, racemization, and possible subsequent reactions. Although all of these topics have been studied in laboratories, such work often involves many variables and unknowns. This has led us to seek out model systems with which to uncover reaction products, test chemical predictions, and sited light on underlying reaction mechanisms. This presentation will describe one such study, focusing on amino-acid formation in ices.

Dworkin, J. P.↗
NASA NTRS1986

What predictions can be made on the nature of carbon and carbon-bearing compounds (hydrocarbons) in the interstellar medium based on studies of interplanetary dust particles?

The nature of hydrocarbons and properties of elemental carbon in circumstellar, interstellar, and interplanetary dust is a long standing problem in astronomy and meteorite research. The textures and crystallographical properties of poorly graphitized carbon (PGC) from carbonaceous chondrites and Chondritic Porous Aggregates (CPAs) are comparable with PGCs formed by dehydrogenation and carbonization of hydrocarbon precursors under natural terrestrial and experimental conditions. A multistage model of hydrocarbon diagenesis in CPA and carbonaceous chondrite (proto-) planetary parent bodies was proposed in which hydrocarbons are subjected to low temperature hydrous pyrolysis. Continued efforts to recognize hydrocarbons and elemental phases in CPAs may allow understanding of the multistage hydrocarbon/elemental carbon model.

Rietmeijer, F. J. M.↗
NASA NTRS1994

Two-dimensional simulation of Pinatubo aerosol and its effect on stratospheric ozone

This paper presents time-dependent simulations of the response of the stratosphere to the injection into the atmosphere of massive amounts of sulfur during the eruption of Mt. Pinatubo (The Philippines) in June 1991. The study is based on a coupled two-dimensional chemical-dynamical-radiative model to which a microphysical model for sulfate aerosol formation and fate has been added. The study suggests that, during the first year (July 1991 to June 1992) following the volcanic eruption, the observed changes in the ozone amount integrated between 65 deg S and 65 deg N were caused primarily by changes in the meridional circulation (associated with heating by the volcanic cloud in the tropics) and in the photolysis rate of molecules such as ozone (associated with backscattering of light by the cloud). During the second year after the eruption, as the aerosol was dispersed at all latitudes and, in particular, reached the polar region, the largest contribution to ozone reduction resulted from the heterogeneous chemical conversion of N2O5 and ClONO2 on the surface of the aerosol particles. The conversion of the latter compound, and hence the magnitude of the calculated ozone depletion, is highly dependent on the temperature in the lower stratosphere. Despite the fact that the surface area provided by aerosol particles decreased during the second year following the eruption, the calculated ozone depletion remained significant because the conversion of N2O5 is insensitive to the aerosol surface area density for values larger than 1-10 sq microns/cu cm (depending on latitude). The predicted reduction in ozone at 20 km in March during the third year (July 1993 to June 1994) of the model integration is smaller by a factor of 2 than it was during the second year.

Tie, Xuexi↗