Effects of several factors on chemical condensation of mixed amino acid adenylates
Protein synthesis, dialysis and Mg ion concentration effects on chemical condensation of mixed amino acid adenylates
Fox, S. W.↗
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Results for “CHEMICAL EFFECT”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Climate-chemical interactions and greenhouse effects of trace gases
A completely coupled one-dimensional radiative-convective (RC) and photochemical-diffusion (PC) model has been developed recently and used to study the climate-chemical interactions. The importance of radiative-chemical interactions within the troposphere and stratosphere has been examined in some detail. We find that increases of radiatively and/or chemically active trace gases such as CO2, CH4 and N2O have both the direct effects and the indirect effects on climate change by changing the atmospheric O3 profile through their interaction with chemical processes in the atmosphere. It is also found that the climatic effect of ozone depends strongly on its vertical distribution throughout the troposphere and stratosphere, as well on its column amount in the atmosphere.
Shi, Guang-Yu↗
Nonequilibrium effects on the aerothermodynamics of transatmospheric and aerobraking vehicles
A 3D CFD algorithm is used to study the effect of thermal and chemical nonequilibrium on slender and blunt body aerothermodynamics. Both perfect gas and reacting gas air models are used to compute the flow over a generic transatmospheric vehicle and a proposed lunar transfer vehicle. The reacting air is characterized by a translational-rotational temperature and a vibrational-electron-electronic temperature and includes eight chemical species. The effects of chemical reaction, vibrational excitation, and ionization on lift-to-drag ratio and trim angle are investigated. Results for the NASA Ames All-body Configuration show a significant difference in center of gravity location for a reacting gas flight case when compared to a perfect gas wind tunnel case at the same Mach number, Reynolds number, and angle of attack. For the same center of gravity location, the wind tunnel model trims at lower angle of attack than the full-scale flight case. Nonionized and ionized results for a proposed lunar transfer vehicle compare well to computational results obtained from a previously validated reacting gas algorithm. Under the conditions investigated, effects of weak ionization on the heat transfer and aerodynamic coefficients were minimal.
Hassan, Basil↗
A numerical study of shock wave/boundary layer interaction in nonequilibrium chemically reacting air - The effects of catalytic walls
This paper presents a numerical study that investigate the effects of nonequilibrium chemistry, and in particular, wall catalycity on the separated flow region generated by an oblique shock wave impinging upon a flat plate boundary layer. To obtain a solution to this problem, the full two dimensional Navier-Stokes equations were solved using MacCormack's predictor-corrector time dependent technique on a rectangular grid. Nonequilibrium chemistry was included by utilizing the 5 species, 17 reaction modified Dunn-Kang chemical kinetics model. Separate results were obtained for: calorically perfect, chemically reacting - noncatalytic wall, and chemically reacting - fully catalytic wall cases, for a given set of flow conditions. A direct comparison of all three cases revealed a slight decrease in the peak heat transfer for the noncatalytic wall case, as compared to the calorically perfect case. On the other hand, the fully catalytic wall case had a tremendous increase in the peak surface heat transfer. It is concluded that, for the particular conditons treated here (nearly frozen flow in the free stream), the effects of the nonequilibrium chemically reacting flow on the shock-wave/boundary-layer interaction depend critically on the catalycity of the wall, having virtually no effect for the case of a noncatalytic wall, and exerting a tremendous effect for a fully catalytic wall.
Grumet, Adam A.↗
Effects of Temperature on Polymer/Carbon Chemical Sensors
Experiments were conducted on the effects of temperature, polymer molecular weight, and carbon loading on the electrical resistances of polymer/carbon-black composite films. The experiment were performed in a continuing effort to develop such films as part of the JPL Electronic Nose (ENose), that would be used to detect, identify, and quantify parts-per-million (ppm) concentration levels of airborne chemicals in the space shuttle/space station environments. The polymers used in this study were three formulations of poly(ethylene oxide) [PEO] that had molecular weights of 20 kilodaltons, 600 kilodaltons, and 1 megadalton, respectively. The results of one set of experiments showed a correlation between the polymer molecular weight and the percolation threshold. In a second set of experiments, differences among the temperature dependences of resistance were observed for different carbon loadings; these differences could be explained by a change in the conduction mechanism. In a third set of experiments, the responses of six different polymer/carbon composite sensors to three analytes (water vapor, methanol, methane) were measured as a function of temperature (28 to 36 C). For a given concentration of each analyte, the response of each sensor decreased with increasing temperature, in a manner different from those of the other sensors.
Manfireda, Allison↗
Chemical release and radiation effects experiment advanced planned
A summary of the efforts conducted to provide assessments and planning support for the Chemical Release and Radiation Experiment Satellite (CRRES) is reported. Included are activities regarding scientific working group and workshop development including the preparation of descriptive information on the CRRES project.
Vaughan, William W.↗
Effect of temperature oscillation on chemical reaction rates in the atmosphere
The effect of temperature fluctuations on atmospheric ozone chemistry is examined by considering the Chapman photochemical theory of ozone transport to calculate globally averaged ozone production rates from mean reaction rates, activation energies, and recombination processes.
Eberstein, I. J.↗
Use of the Magnetic Isotope Effect for Silicon Isotopomer Chemical Separation
The goal of the Phase I work was to develop a novel approach to silicon isotope separation that will use the difference in chemical reactivity of the three naturally-occurring silicon isotopes. The 'magnetic isotope effect' (MIE) will be employed to differentially react 29Si from 28Si and 30Si. The difference in reactivity to either directly deplete 29Si to the required sub-ppm levels or deplete 29Si sufficiently to allow final purification with distillation or centrifugation.
36 MATERIALS SCIENCE↗
Investigating the Effects of Gamma Radiation on Selected Chemicals for Use in Biosignature Detection Instruments on the Surface of Jupiter's Moon Europa
Jupiter's moon Europa is a prime target for the search for potential signs of life in the solar system. The Europa Lander Science Definition Team Report outlined investigations and measurement requirements on a future Europa Lander and has led us to consider application of powerful techniques such as pyrolysis and derivatization gas chromatography mass spectrometry (GC-MS) and laser desorption mass spectrometry (LD-MS) to elucidate the organic composition of near-surface ice and minerals. Definitive identification of chemical biosignatures using such techniques is strongly enabled by the use of various chemicals, such as perfluorotributylamine (PFTBA) for the MS calibration, α-cyano-hydroxycinnamic acid (CHCA) for matrix-assisted laser desorption and ionization (MALDI) and N,N-dimethylformamide dimethyl acetal (DMF-DMA), N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) and tetramethylammonium hydroxide (TMAH) for wet chemistry GC-MS protocols. The jovian radiation environment is known to represent a uniquely challenging risk to mission performance and lifetime, principally due to high radiation levels. To assess the potential ionizing radiation damage to these important chemicals, we tested their effectiveness following gamma radiation exposure doses up to the anticipated Europa Lander rating requirement of 300 krad(Si). The chemicals were sealed in glass ampules under vacuum (<10 mTorr), to reduce trapped oxygen gas, as the oxidation by O2 may be enhanced in the presence of radiation. We report that all five chemicals exposed to total ionizing doses of 0, 150 and 300 krad(Si) maintained their full effectiveness, and no significant degradation was observed.
Radiation↗
Chemical Interface Damping Revealed by Single-Particle Absorption Spectroscopy
Plasmon-induced interfacial charge separation is a promising way to efficiently extract energetic carriers through direct plasmon decay. This mechanism of charge transfer has been investigated by single-particle scattering spectroscopy, which measures the homogeneous plasmon line width. The line width is broadened by charge transfer, generally known as chemical interface damping. However, conflicting reports exist regarding the effect of chemical interface damping on the corresponding single-particle absorption spectrum, which is needed to accurately determine absolute light conversion efficiencies. This work aims to resolve this question by directly correlating absorption and scattering spectra of individual gold nanorods in the presence and absence of a charge-accepting interface. We find that for TiO 2 coated nanorods, the absorption line width is indeed broadened due to chemical interface damping but is overall narrower than the scattering line width. Here, chemical interface damping is furthermore found to increase with larger resonance energies. The observed differences in line widths between absorption and scattering are elucidated within the context of an analytically tractable model describing the lowest energy optically bright and higher-order optically dark plasmon modes of the nanorod, including bulk, radiative, and chemical interface damping effects. Taken together, these results establish that single-particle absorption spectroscopy is capable of revealing interfacial charge injection by direct plasmon decay.
absorption↗
Effects of lubricants - General background
Oil viscosity and chemical composition effects on roller bearing lubricant efficiency
Appeldoorn, J. K.↗
Chemical Analyses
As a preliminary study on the effects of chemical aging of polymer materials MERL and TRI have examined two polymeric materials that are typically used for offshore umbilical applications. These two materials were Tefzel, a copolymer of ethylene and tetrafluoroethylene, and Coflon, polyvinylidene fluoride. The Coflon specimens were cut from pipe sections and exposed to H2S at various temperatures and pressures. One of these specimens was tested for methane permeation, and another for H2S permeation. The Tefzel specimens were cut from .05 mm sheet stock material and were exposed to methanol at elevated temperature and pressure. One of these specimens was exposed to methanol permeation for 2 days at 100 C and 2500 psi. An additional specimen was exposed to liquid methanol for 3 days at 150 C and 15 Bar. Virgin specimens of each material were similarly prepared and tested.
Bulluck, J. W.↗
Negative Electron Affinity Effect on the Surface of Chemical Vapor Deposited Diamond Polycrystalline Films
Strong negative electron affinity effects have been observed on the surface of as-grown chemical vapor deposited diamond using Secondary Electron Emission. The test samples were randomly oriented and the surface was terminated with hydrogen. The effect appears as an intensive peak in the low energy part of the spectrum of the electron energy distribution and may be described in the model of effective negative electron affinity.
Krainsky, I. L.↗
Large Electrically and Chemically Tunable Rashba–Dresselhaus Effects in Ferroelectric CsGeX 3 (X = Cl, Br, I) Perovskites
Rashba–Dresselhaus effects, which originate from spin–orbit coupling and allow for spin manipulations, are actively explored in materials, following the pursuit of spintronics and quantum computing. However, materials that possess practically significant Rashba–Dresselhaus effects often contain toxic elements and offer little opportunity for the tunability of the effects. We used first-principles simulations to reveal that the recently discovered halide ferroelectrics in the CsGeX 3 (X = Cl, Br, I) family possess large and tunable Rashba-Dresselhaus effects. In particular, they give origin to the spin splitting of up to 171 meV in the valence band of CsGeI 3 . The value is chemically tunable and can decrease by 25% and 70% for CsGeBr 3 and CsGeCl 3 , respectively. Such chemical tunability could result in the engineering of desired values through a solid solution technique. Application of an electric field was found to result in structural changes that could decrease and increase spin splitting, leading to electrical tunability of the effect. In the vicinity of conduction and valence band extrema, the spin textures are mostly of the Rashba type, which is promising for spin-to-charge conversion applications. The spin directions are coupled with the polarization direction, leading to Rashba-ferroelectricity cofunctionality. Furthermore, our work identifies lead-free perovskite halides as excellent candidates for spin-based applications and is likely to stimulate further research in this direction.
Electric fields↗
Ionizing particle radiations effects and simulation consideration
Proton accelerator, electron accelerators, and beam transport system of NASA space radiation effects laboratory - transient, permanent, surface, and chemical radiation effects
NASA PROGRAM↗
Microcoupon Assay Of Adhesion And Growth Of Bacterial Films
Microbiological assay technique facilitates determination of some characteristics of sessile bacteria like those that attach to and coat interior walls of water-purification systems. Biofilms cause sickness and interfere with purification process. Technique enables direct measurement of rate of attachment of bacterial cells, their metabolism, and effects of chemicals on them. Used to quantify effects of both bactericides and growth-stimulating agents and in place of older standard plate-count and tube-dilution techniques.
Pierson, Duane L.↗
GCKP84--General Chemical Kinetics Code for Gas-Phase Flow and Batch Processes Including Heat Transfer Effects
A general chemical kinetics code is described for complex, homogeneous ideal gas reactions in any chemical system. The main features of the GCKP84 code are flexibility, convenience, and speed of computation for many different reaction conditions. The code, which replaces the GCKP code published previously, solves numerically the differential equations for complex reaction in a batch system or one dimensional inviscid flow. It also solves numerically the nonlinear algebraic equations describing the well stirred reactor. A new state of the art numerical integration method is used for greatly increased speed in handling systems of stiff differential equations. The theory and the computer program, including details of input preparation and a guide to using the code are given.
David A Bittker↗
Chemical versus physical pressure effects on the structure transition of bilayer nickelates
The observation of high-T c superconductivity (HTSC) in concomitant with pressure-induced orthorhombic-tetragonal structural transition in bilayer La 3 Ni 2 O 7 has sparked hopes of achieving HTSC by stabilizing the tetragonal phase at ambient pressure. Chemical pressure, introduced by replacing La 3+ with smaller rare-earth R 3+ has been considered as a potential route. However, our experimental and theoretical investigation reveals that such substitutions, despite causing lattice contraction, actually produce stronger orthorhombic distortions, requiring higher pressures for the structural transition. A linear extrapolation of P c versus the average size of A-site cations (<$r_A$>), yields a putative critical value of (<$r_A$>) ≈ 1.23 Å for P c ≈ 1 bar. The negative correlation between P c and (<$r_A$>) indicates that replacing La 3+ with smaller R 3+ ions is unlikely to reduce P c to ambient pressure. Instead, substituting La 3+ with larger cations like Sr 2+ or Ba 2+ might be a feasible approach. Our results provide guidance for realizing ambient-pressure HTSC in bilayer nickelates.
36 MATERIALS SCIENCE↗