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At least 361 records · Page 20

Carbon Dioxide: Surprising Effects on Decision Making and Neurocognitive Performance

The occupants of modern submarines and the International Space Station (ISS) have much in common as far as their air quality is concerned. Air is polluted by materials offgassing, use of utility compounds, leaks of systems chemicals, and anthropogenic sources. The primary anthropogenic compound of concern to submariners and astronauts has been carbon dioxide (CO2). NASA and the US Navy rely on the National Research Council Committee on Toxicology (NRC-COT) to help formulate exposure levels to CO2 that are thought to be safe for exposures of 3-6 months. NASA calls its limits Spacecraft Maximum Allowable Concentrations (SMACs). Years of experience aboard the ISS and a recent publication on deficits in decision making in ground-based subjects exposed briefly to 0.25% CO2 suggest that exposure levels that have been presumed acceptable to preserve health and performance need to be reevaluated. The current CO2 exposure limits for 3-6 months set by NASA and the UK Navy are 0.7%, and the limit for US submariners is 0.5%, although the NRC-COT recommended a 90-day level of 0.8% as safe a few years ago. NASA has set a 1000-day SMAC at 0.5% for exploration-class missions. Anecdotal experience with ISS operations approaching the current 180-day SMAC of 0.7% suggest that this limit is too high. Temporarily, NASA has limited exposures to 0.5% until further peer-reviewed data become available. In the meantime, a study published last year in the journal Environmental Health Perspectives (Satish U, et al. 2012) demonstrated that complexdecision- making performance is somewhat affected at 0.1% CO2 and becomes "dysfunctional" for at least half of the 9 indices of performance at concentrations approaching 0.25% CO2. The investigators used the Strategic Management Simulation (SMS) method of testing for decisionmaking ability, and the results were so surprising to the investigators that they declared that their findings need to be independently confirmed. NASA has responded to the findings on decision making by developing a study to either confirm or refute the published results. In addition, other neurocognitive tests that have been and will be used aboard the ISS will be part of the ground-based study. Further evaluations during the exposures will include ocular and cardiovascular effects of CO2 exposure. In addition, the 1- carbon genetics of the test subjects will be evaluated to determine if any individual subjects are unusually susceptible to CO2 exposure because of genetic factors. Our plan is to extend the published study from Satish by employing a wider series of CO2 exposures to include concentrations of 0.06, 0.12, 0.25, and 0.50%. We believe that our findings will be of keen interest to submariners and to those designing "tight" buildings.

James, John T.↗

Countermeasure for Radiation Protection and Repair

Exposure to ionizing radiation during long-duration space missions is expected to cause short-term illness and increase long-term risk of cancer for astronauts. Radiation-induced free radicals overload the antioxidant defense mechanisms and lead to cellular damage at the membrane, enzyme, and chromosome levels. A large number of radioprotective agents were screened, but most had significant side effects. But there is increasing evidence that significant radioprotective benefit is achieved by increasing the dietary intake of foods with high antioxidant potential. Early plant-growing systems for space missions will be limited in both size and volume to minimize power and mass requirements. These systems will be well suited to producing plants containing high concentrations of bioprotective antioxidants. This project explored whether the production of bioprotective compounds could be increased by altering the lighting system, without increasing the space or power requirements for production, and evaluated the effects of environmental conditions (light quantity, light quality, and carbon dioxide [CO2] concentration) on the production of bioprotective compounds in lettuce, which provide a biological countermeasure for radiation exposure. The specific deliverables were to develop a database of bioprotectant compounds in plants that are suitable for use on longduration space missions, develop protocols for maintaining and increasing bioprotectant production under light emitting diodes (LEDs), recommend lighting requirements to produce dietary countermeasures of radiation, and publish results in the Journal of the American Society for Horticultural Science.

Source record↗

Enzyme-based CO2 capture for advanced life support

Elevated CO2 levels in air can lead to impaired functioning and even death to humans. Control of CO2 is critical in confined spaces that have little physical or biological buffering capacity (e.g., spacecraft, submarines, or aircraft). A novel enzyme-based contained liquid membrane bioreactor was designed for CO2 capture and certain application cases are reported in this article. The results show that the liquid layer accounts for the major transport resistance. With addition of carbonic anhydrase, the transport resistance decreased by 71%. Volatile organic compounds of the type and concentration expected to be present in either the crew cabin or a plant growth chamber did not influence carbonic anhydrase activity or reactor operation during 1-day operation. Alternative sweep method studies, examined as a means of eliminating consumables, showed that the feed gas could be used successfully in a bypass mode when combined with medium vacuum pressure (-85 kPa) to achieve CO2 separation comparable to that with an inert sweep gas. The reactor exhibited a selectivity for CO2 versus N2 of 1400:1 and CO2 versus O2 is 866:1. The CO2 permeance was 1.44 x 10(-7) mol m-2 Pa-1 s-1 (4.3 x 10(-4) cm3 cm-2 s-1 cmHg-1) at a feed concentration of 0.1% CO2. These data show that the enzyme-based contained liquid membrane is a promising candidate technology that may be suitable for NASA applications to control CO2 in the crew or plant chambers.

NASA Discipline Life Support Systems↗

Investigations on the system boron-carbon silicon

The above elements form with each other binary compounds which are very interesting from the point of view of their structure and their chemistry and which are important for technology. The present investigation is concerned with the three-component system and the behavior of the binary compounds occurring in it. Investigations employing various techniques, such as X-ray, chemical analysis, microscopy and fusion experiments showed that no ternary phase exists within the boundary of the ternary system. There is no compound with a higher abrasion capacity than boron carbide. The probable phase field divisions at two isothermic intersections and the fusion isotherms are indicated.

Kieffer, R.↗

Decoding the Domino: The Dark Side of Iapetus

We present new spectra of the leading and trailing hemispheres of Iapetus from 2.4 to 3.8 micron. We have combined the leading hemisphere spectra with previous observations by others to construct a composite spectrum of the dark side (leading) hemisphere from 0.3 to 3.8 gm. We review attempts to deduce the composition of the dark material from previously available spectrophotometry. None of them (numbering more than 20 million!) leads to a synthetic spectrum that matches the new data. An intimate mixture of water ice, amorphous carbon and a nitrogen-rich organic compound (modeled here as Triton tholin) can fit the entire composite dark side spectrum. Observations in this spectral region have not revealed this mix of material on any other object observed thus far. We propose that this dark material may have originated on Titan, where atmospheric photochemistry has been producing nitrogen-rich organic compounds for 4.5 GY.

Owen, Tobias C.↗

An Explorer-Class Astrobiology Mission

In this paper we describe a potential new Explorer-class space mission, the AstroBiology Explorer (ABE), consisting of a relatively modest dedicated space observatory having a 50 cm aperture primary mirror which is passively cooled to T less than 65 K, resides in a low-background orbit (heliocentric orbit at 1 AU, Earth drift-away), and is equipped with a suite of three moderate order (m approx. 10) dispersive spectrographs equipped with first-order cross-dispersers in an "echellette" configuration and large format (1024xl024 pixel) near- and mid-IR detector arrays cooled by a modest amount of cryogen. Such a system would be capable of addressing outstanding problems in Astrochemistry and Astrophysics that are particularly relevant to Astrobiology and addressable via astronomical observation. The observational program of this mission would make fundamental scientific progress in each of the key areas of the cosmic history of molecular carbon, the distribution and chemistry of organic compounds in the diffuse and dense interstellar media, and the evolution of ices and organic matter in young planetary systems. ABE could make fundamental progress in all of these areas by conducting an approximately one year mission to obtain a coordinated set of infrared spectroscopic observations over the 2.5-20 micrometers spectral range at spectral resolutions of R greater than or equal to 1000 of approximately 1000 galaxies, stars, planetary nebulae, and young star planetary systems.

Sandford, Scott↗

Mineralogy of Meteorite Groups

Approximately 275 mineral species have been identified in meteorites, reflecting diverse redox environments, and, in some cases, unusual nebular formation conditions. Anhydrous ordinary, carbonaceous and R chondrites contain major olivine, pyroxene and plagioclase; major opaque phases include metallic Fe-Ni, troilite and chromite. Primitive achondrites are mineralogically similar. The highly reduced enstatite chondrites and achondrites contain major enstatite, plagioclase, free silica and kamacite as well as nitrides, a silicide and Ca-, Mg-, Mn-, Na-, Cr-, K- and Ti-rich sulfides. Aqueously altered carbonaceous chondrites contain major amounts of hydrous phyllosilicates, complex organic compounds, magnetite, various sulfates and sulfides, and carbonates. In addition to kamacite and taenite, iron meteorites contain carbides, elemental C, nitrides, phosphates, phosphides, chromite and sulfides. Silicate inclusions in IAB/IIICD and lIE iron meteorites consist of mafic silicates, plagioclase and various sulfides, oxides and phosphates. Eucrites, howardites and diogenites have basaltic to orthopyroxenitic compositions and consist of major pyroxene and calcic plagioclase and several accessory oxides. Ureilttes .are made up mainly of calcic, chromian olivine and low-Ca clinopyroxene embedded in a carbonaceous matrix; accessory phases include the C polymorphs graphite, diamond, lonsdaleite and chaoite as well as metallic Fe-Ni, troilite and halides. Angrites are achondrites rich in fassaitic pyroxene (i.e. , AI-Ti diopside); minor olivine with included magnesian kirschsteinite is also present. Martian meteorites comprise basalts, Iherzolites, a dunite and an orthopyroxenite. Major phases include various pyroxenes and olivine; minor to accessory phases include various sulfides, magnetite, chromite and Ca-phosphates. Lunar meteorites comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase. Several meteoritic phases were formed by shock metamorphism. Martensite (a2-fe,Ni) has a distorted body-centered-cubic structure and formed by a shear transformation from taenite during shock reheating and rapid cooling. The C polymorphs diamond, lonsdaleite and chaoite formed by shock from graphite. Suessite formed in the North Haig ureilite by reduction of Fe and Si (possibly from olivine) via reaction with carbonaceous matrix material. Ringwoodite, the spinel form of (Mg,Fe)2Si04, and majorite, a polymorph of (Mg,Fe)Si03 with the garnet structure, formed inside shock veins in highly shocked ordinary chondrites. Secondary minerals in meteorite finds that formed during terrestrial weathering include oxides and hy-. droxides formed directly from metallic Fe-Ni by oxidation, phosphates formed by the alteration of schreibersite, and sulfates formed by alteration of troilite.

Rubin, Alan E.↗

Spectral Aerosol Extinction (SpEx): A New Instrument for In situ Ambient Aerosol Extinction Measurements Across the UV/Visible Wavelength Range

We introduce a new instrument for the measurement of in situ ambient aerosol extinction over the 300-700 nm wavelength range, the Spectral Aerosol Extinction (SpEx) instrument. This measurement capability is envisioned to complement existing in situ instrumentation, allowing for simultaneous measurement of the evolution of aerosol optical, chemical, and physical characteristics in the ambient environment. In this work, a detailed description of the instrument is provided along with characterization tests performed in the laboratory. Measured spectra of NO2 and polystyrene latex spheres agreed well with theoretical calculations. Good agreement was also found with simultaneous aerosol extinction measurements at 450, 530, and 630 nm using CAPS PMex instruments in a series of 22 tests including non-absorbing compounds, dusts, soot, and black and brown carbon analogs. SpEx can more accurately distinguish the presence of brown carbon from other absorbing aerosol due to its 300 nm lower wavelength limit compared to measurements limited to visible wavelengths. In addition, the spectra obtained by SpEx carry more information than can be conveyed by a simple power law fit that is typically defined by the use of Angstrom Exponents. Future improvements aim at lowering detection limits and ruggedizing the instrument for mobile operation.

Jordan, C. E.↗

Combustion Studies of MMA/GOx for a Hybrid Rocket Motor

Poly(methyl methacrylate) (PMMA) is the synthetic polymer of methyl methacrylate (MMA), used in a multitude of applications, including as a solid fuel in hybrid rockets. PMMA undergoes pyrolysis into gaseous MMA (C5H8O2), which then undergoes combustion into carbon dioxide, water, carbon monoxide and low-molecular-weight compounds, including formaldehyde. Hybrid rocket motors as seen in the schematic in Fig. 1, contains the oxidizer in a pressurized tank, which is released through a port in the solid fuel grain in the combustion chamber, after which the combustion products are exhausted through a converging diverging nozzle.

Dhandapani, Chandru↗

In Situ Chemical Reduction Interim Measures Work Plan Hot Spot 3 Mobile Launcher Platform Rehabilitation Sites / Vehicle Assembly Building Area (SWMU 056) Kennedy Space Center, Florida

This document presents the design details of an In Situ Chemical Reduction (ISCR) Interim Measures Work Plan for Hot Spot 3 within Mobile Launcher Platform Rehabilitation Sites/Vehicle Assembly Building Area, Solid Waste Management Unit (SWMU) 056 (SWMU 056), located at the John F. Kennedy Space Center, Florida. The interim measures (IM) treatment zone encompasses an area identified as the High Concentration Plume (HCP), which is defined as the area with chlorinated volatile organic compound (CVOC) groundwater concentrations greater than their respective Natural Attenuation Default Concentration (NADC). The objective of the IM is to remove CVOC mass within the treatment area to levels that facilitate a transition to natural attenuation monitoring. The IM design consists of the selected ISCR amendment, Provect-IR, which is a mixture of solid reagents in a single product that promotes enhanced reductive dechlorination and ISCR. ProvectIR includes natural antimethanogenic compounds; multiple hydrophilic, nutrient-rich organic carbon sources; zero valent iron; chemical oxygen scavengers; and vitamin and mineral sources. The proposed treatment area for this IM encompasses less than 1 acre and includes three vertical treatment intervals to reach the NADC plumes that vary per CVOC and depth: 4 to 10 feet below land surface (bls), 10 to 18 feet bls, and 42 to 52 feet bls. The amendment will be distributed through 16 injection points (IP01 through IP16) using dosing rates ranging from 0.4% to 0.6% of soil mass within the treatment interval and a 15% or 20% slurry strength. Dosage rates and slurry strength are based on groundwater geochemistry, soil characteristics, and contaminant concentrations. To aid in the evaluation of the ISCR IM performance, six performance monitoring wells will be installed following injections and sampled semiannually. CVOC parameters will be sampled until concentrations reduce to below their NADC. Underground Injection Control parameters will be sampled until concentrations decrease to background levels or to levels that meet respective groundwater standards. Sampling frequency will be evaluated annually and modified as needed. The path forward for the ISCR IM implementation includes preparing the IM Implementation Work Plan, ISCR injections, monitoring well installation, performance monitoring, and reporting.

Randall K. Sillan↗

Stable hydrogen and carbon isotope ratios of extractable hydrocarbons in the Murchison meteorite

A fairly fool-proof method to ensure that the compounds isolated from meteorites are truly part of the meteorites and not an artifact introduced by exposure to the terrestrial environment, storage, or handling is presented. The stable carbon and hydrogen isotope ratios in several of the chemical compounds extracted from the Murchison meteorite were measured. The results obtained by studying the amino acids in this meteorite gave very unusual hydrogen and carbon isotope ratios. The technique was extended to the different classes of hydrocarbons and the hydrocarbons were isolated using a variety of separation techniques. The results and methods used in this investigation are described in this two page paper.

Krishnamurthy, R. V.↗

Airborne Measurements of Western U.S. Wildfire Emissions: Comparison with Prescribed Burning and Air Quality Implications

Wildfires emit significant amounts of pollutants that degrade air quality. Plumes from three wildfires in the western U.S. were measured from aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) and the Biomass Burning Observation Project (BBOP), both in summer 2013. This study reports an extensive set of emission factors (EFs) for over 80 gases and 5 components of submicron particulate matter (PM1) from these temperate wildfires. These include rarely, or never before, measured oxygenated volatile organic compounds and multifunctional organic nitrates. The observed EFs are compared with previous measurements of temperate wildfires, boreal forest fires, and temperate prescribed fires. The wildfires emitted high amounts of PM1 (with organic aerosol (OA) dominating the mass) with an average EF that is more than 2 times the EFs for prescribed fires. The measured EFs were used to estimate the annual wildfire emissions of carbon monoxide, nitrogen oxides, total non methane organic compounds, and PM1 from 11 western U.S. states. The estimated gas emissions are generally comparable with the 2011 National Emissions Inventory (NEI). However, our PM1 emission estimate (1530 +/- 570 Gg/yr) is over 3 times that of the NEI PM2.5 estimate and is also higher than the PM2.5 emitted from all other sources in these states in the NEI. This study indicates that the source of OA from biomass burning in the western states is significantly underestimated. In addition, our results indicate that prescribed burning may be an effective method to reduce fine particle emissions.

measured oxygenated volatile organic compounds↗

Synthesizing Diamond from Liquid Feedstock

A relatively economical method of chemical vapor deposition (CVD) has been developed for synthesizing diamond crystals and films. Unlike prior CVD methods for synthesizing diamond, this method does not require precisely proportioned flows of compressed gas feedstocks or the use of electrical discharges to decompose the feedstocks to obtain free radicals needed for deposition chemical reactions. Instead, the feedstocks used in this method are mixtures of common organic liquids that can be prepared in advance, and decomposition of feedstock vapors is effected simply by heating. The feedstock used in this method is a solution comprising between 90 and 99 weight percent of methanol and the balance of one or more other oxyhydrocarbons that could include ethanol, isopropanol, and/or acetone. This mixture of compounds is chosen so that dissociation of molecules results in the desired proportions of carbon-containing radicals (principally, CH3) and of OH, H, and O radicals. Undesirably, the CVD temperature and pressure conditions thermodynamically favor the growth of graphite over the growth of diamond. The H radicals are desirable because they help to stabilize the growing surface of diamond by shifting the thermodynamic balance toward favoring the growth of diamond. The OH and O radicals are desirable because they preferentially etch graphite and other non-diamond carbon, thereby helping to ensure the net deposition of pure diamond. The non-methanol compounds are included in the solution because (1) methanol contains equal numbers of C and O atoms; (2) an excess of C over O is needed to obtain net deposition of diamond; and (3) the non-methanol molecules contain multiple carbon atoms for each oxygen atom and thus supply the needed excess carbon A typical apparatus used in this method includes a reservoir containing the feedstock liquid and a partially evacuated stainless-steel reaction chamber. The reservoir is connected to the chamber via tubing and a needle valve or other suitable flow controller. When the liquid enters the low-pressure environment inside the chamber, it evaporates to form a vapor mixture of the same chemical composition. In addition to the inlet for the feedstock liquid, the chamber is fitted with an outlet connected to a vacuum pump (not shown) through a throttle valve (also not shown) that is automatically controlled to keep the pressure at or near the required value throughout the deposition process. Inside the chamber, a spiral filament made of tungsten, tantalum, graphite, or other high-melting-temperature material is electrically heated to a temperature >2,000 C high enough to cause dissociation of vapor molecules into the aforementioned radicals. A deposition substrate typically, a diamond-polished silicon wafer about 2.5 cm square is positioned about 2 cm away from the filament. The exact location of the substrate is chosen so that the substrate becomes heated by the filament to a deposition temperature in the approximate range of 800 to 1,000 C.

Tzeng, Yonhua↗

Functionalization of Single-Wall Carbon Nanotubes by Photo-Oxidation

new technique for carbon nanotube oxidation was developed based upon the photo-oxidation of organic compounds. The resulting method is more benign than conventional oxidation approaches and produces single-wall carbon nanotubes (SWCNTs) with higher levels of oxidation. In this procedure, an oxygen saturated suspension of SWNTs in a suitable solvent containing a singlet oxygen sensitizer, such as Rose Bengal, is irradiated with ultraviolet light. The resulting oxidized tubes are recovered by filtering the suspension, followed by washing to remove any adsorbed solvent and sensitizer, and drying in a vacuum oven. Chemical analysis by FT-infrared and x-ray photoelectron spectroscopy revealed that the oxygen content of the photo-oxidized SWCNT was 11.3 atomic % compared to 6.7 atomic % for SWCNT that had been oxidized by standard treatment in refluxing acid. The photo-oxidized SWCNT produced by this method can be used directly in various polymer matrixes, or can be further modified by chemical reactions at the oxygen functional groups and then used as additives. This method may also be suitable for use in oxidation of multiwall carbon nanotubes and graphenes.

Lebron-Colon, Marisabel↗

Synthesis and biological screening by novel hybrid fluorocarbon hydrocarbon compounds for use as artificial blood substitutes

A series of hybrid fluorochemicals of general structure R(1)R(2)R(3)CR(4) was prepared where the R(i)'s (i=1,2,3) is a saturated fluoroalkyl group of formula C sub N F sub 2n+1, and R(4) is an alkyl group C sub n H sub 2n+1 or a related moiety containing amino, ether, or ester functions but no CF bonds. Compounds of this class containing approximately eight to twenty carbons total have physical properties suitable for use as the oxygen carrying phase of fluorochemical emulsion artificial blood. The chemical synthesis, and physical and biological testing of pure single isomers of the proposed artificial blood candidate compounds are included. Significant results are given.

Moacanin, J.↗

Development of aircraft brake materials

The requirements of brake materials were outlined and a survey made to select materials to meet the needs of high temperature brakes. A number of metals and ceramic materials were selected and evaluated in sliding tests which simulated aircraft braking. Nickel, molybdenum tungsten, Zr02, high temperature cements and carbons were tested. Additives were then incorporated into these materials to optimize their wear or strength behavior with particular emphasis on nickel and molybdenum base materials and a high temperature potassium silicate cement. Optimum materials were developed which improved wear behavior over conventional brake materials in the simulated test. The best materials are a nickel, aluminum oxide, lead tungstate composition containing graphite or molybdenum disulphite; a molybdenum base material containing LPA100 (an intermetallic compound of cobalt, molybdenum, and silicon); and a carbon material (P5).

Ho, T. L.↗

Ocean Carbon From Space: Current Status and Priorities for the Next Decade

The ocean plays a central role in modulating the Earth’s carbon cycle. Monitoring how the ocean carbon cycle is changing is fundamental to managing climate change. Satellite remote sensing is currently our best tool for viewing the ocean surface globally and systematically, at high spatial and temporal resolutions, and the past few decades have seen an exponential growth in studies utilising satellite data for ocean carbon research. Satellite-based observations must be combined with in-situ observations and models, to obtain a comprehensive view of ocean carbon pools and fluxes. To help prioritise future research in this area, a workshop was organised that assembled leading experts working on the topic, from around the world, including remote-sensing scientists, field scientists and modellers, with the goal to articulate a collective view of the current status of ocean carbon research, identify gaps in knowledge, and formulate a scientific roadmap for the next decade, with an emphasis on evaluating where satellite remote sensing may contribute. A total of 449 scientists and stakeholders participated (with balanced gender representation), from North and South America, Europe, Asia, Africa, and Oceania. Sessions targeted both inorganic and organic pools of carbon in the ocean, in both dissolved and particulate form, as well as major fluxes of carbon between reservoirs (e.g., primary production) and at interfaces (e.g., air-sea and land–ocean). Extreme events, blue carbon and carbon budgeting were also key topics discussed. Emerging priorities identified include: expanding the networks and quality of in-situ observations; improved satellite retrievals; improved uncertainty quantification; improved understanding of vertical distributions; integration with models; improved techniques to bridge spatial and temporal scales of the different data sources; and improved fundamental understanding of the ocean carbon cycle, and of the interactions among pools of carbon and light. We also report on priorities for the specific pools and fluxes studied, and highlight issues and concerns that arose during discussions, such as the need to consider the environmental impact of satellites or space activities; the role satellites can play in monitoring ocean carbon dioxide removal approaches; economic valuation of the satellite based information; to consider how satellites can contribute to monitoring cycles of other important climatically-relevant compounds and elements; to promote diversity and inclusivity in ocean carbon research; to bring together communities working on different aspects of planetary carbon; maximising use of international bodies; to follow an open science approach; to explore new and innovative ways to remotely monitor ocean carbon; and to harness quantum computing. Overall, this paper provides a comprehensive scientific roadmap for the next decade on how satellite remote sensing could help monitor the ocean carbon cycle, and its links to the other domains, such as terrestrial and atmosphere.

oceanography↗

Removing Biostatic Agents From Fermentation Solutions

Liquid carbon dioxide inexpensive solvent. Inexpensive process proposed for removing such poisons as furfural and related compounds from fermentation baths of biomass hydrolysates. New process based on use of liquid carbon dioxide as extraction solvent. Liquid CO2 preferable to such other liquid solvents as ether or methylene chloride.

Du Fresne, E. R.↗