Transient color sensitivity of the Hill reaction during the disintegration of chloroplasts
Hill reaction color sensitivity in red and blue light during chloroplast disintegration, considering oxygen evolution capacity
Gaffron, H.↗
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Absolute rate parameters for the reaction of ground state atomic oxygen with dimethyl sulfide and episulfide
It is pointed out that the investigated reaction of oxygen with dimethyl sulfide may play an important role in photochemical smog formation and in the chemical evolution of dense interstellar clouds. Kinetic data were obtained with the aid of the flash photolysis-resonance fluorescence method. The photodecomposition of molecular oxygen provided the oxygen atoms for the experiments. The decay of atomic oxygen was studied on the basis of resonance fluorescence observations. Both reactions investigated were found to be fast processes. A negative temperature dependence of the rate constants for reactions with dimethyl sulfide was observed.
Lee, J. H.↗
Electrochemical approach for passivating steel and other metals and for the simultaneous production of a biocide to render water potable
Potentiostatic polarization curves indicated that the cathodic reactions in deaerated KI-I2 water solutions were due to iodine reduction and hydrogen evolution. In the presence of oxygen an additional reduction wave appeared. Anodic polarization curves revealed that iodine could be produced in the region of potential from +600 to +1000 nv vs. SCE.
Source record↗
The reducing power generated in photoact I of photosynthesis.
Photoreduction of viologen dyes analyzed with chloroplasts, noting oxygen evolution and photophosphorylation efficiency, reduction potentials, etc
PHOTOSYNTHESIS↗
Atmosphere revitalization for manned spacecraft - An assessment of technology readiness
The level of proficiency attained by the most effective physical and chemical regenerative processes capable of providing a habitable atmospheric environment in a spacecraft is assessed. It is shown that both the Sabatier and Bosh reactions are in a mature stage of technological readiness and can effectively reduce the carbon dioxide in a spacecraft. An electrochemical method for concentrating CO2 from an air environment offers promise to approach low levels of pCO2 control. Technological advances in the fields of solid polymer electrolytes and oxygen evolution electrocatalysts have led to a water electrolysis system that can maintain efficient performance for several years. Nitrogen supply and control of the composition of the spacecraft atmosphere is effectively provided by the circulating electrolyte technique.
Samonski, F. H., Jr.↗
Catalysts for electrochemical generation of oxygen
Several aspects of the electrolytic evolution of oxygen for use in life support systems are analyzed including kinetic studies of various metal and nonmetal electrode materials, the formation of underpotential films on electrodes, and electrode surface morphology and the use of single crystal metals. In order to investigate the role of surface morphology to electrochemical reactions, a low energy electron diffraction and an Auger electron spectrometer are combined with an electrochemical thin-layer cell allowing initial characterization of the surface, reaction run, and then a comparative surface analysis.
Hagans, P.↗
A model for the evolution of opaques in mare lavas
The apparent 'reduced' state of the opaque mineral assemblages of mare basalts has led to various hypotheses on their origin through reduction by various media. A model is developed whereby the presence of trivalent titanium (Ti/3+/) and metallic iron in mare lavas at low oxygen fugacities automatically leads to the production of the observed assemblages by cooling near the mare basalt solidus. The 'reduced' assemblages may evolve isochemically at oxygen fugacities near the iron-ilmenite-ferropseudobrookite buffer by a reaction of the form Fe(2+)+2 Ti(3+) = metallic iron +2 Ti(4+).
Haselton, J. D.↗
CNO isotope production in nova outbursts
A current model of novae is presented which explains their outbursts assuming that the progenitor of a common nova is a carbon-oxygen dwarf. This white dwarf accretes H-rich material from its companion which produces strong shock waves at its surface; as the amount of accreted material increases later, its bottom ignites. The nova outburst is then triggered by CNO-Ne reactions which favor the formation of rare isotopes with proton-rich radioactive parents such as C-13, N-15, O-17, and Ne-21. The production of such nuclear species is examined in different nova models, and conclusions are drawn concerning the importance of novae in models of chemical evolution of the galaxy.
Audouze, J.↗
The chemical evolution of molecular clouds
The nonequilibrium chemistry of dense molecular clouds (10,000 to 1 million hydrogen molecules per cu cm) is studied in the framework of a model that includes the latest published chemical data and most of the recent theoretical advances. In this model the only important external source of ionization is assumed to be high-energy cosmic-ray bombardment; standard charge-transfer reactions are taken into account as well as reactions that transfer charge from molecular ions to trace-metal atoms. Schemes are proposed for the synthesis of such species as NCO, HNCO, and CN. The role played by adsorption and condensation of molecules on the surface of dust grains is investigated, and effects on the chemical evolution of a dense molecular cloud are considered which result from varying the total density or the elemental abundances and from assuming negligible or severe condensation of gaseous species on dust grains. It is shown that the chemical-equilibrium time scale is given approximately by the depletion times of oxygen and nitrogen when the condensation efficiency is negligible; that this time scale is probably in the range from 1 to 4 million years, depending on the elemental composition and initial conditions in the cloud; and that this time scale is insensitive to variations in the total density.
Iglesias, E.↗
The chemical activities of the Viking biology experiments and the arguments for the presence of superoxides, peroxides, gamma-Fe2O3 and carbon suboxide polymer in the Martian soil
The evolution of N2, Ar, O2, and CO2 from Martian soil as a function of humidity in the Gas Exchange Experiment are correlated with the mean level of water vapor in the Martian atmosphere. All but O2 are associated with desorption. The evolution of oxygen is consistent with the presence of alkaline earth and alkali metal superoxides; and their peroxides and the gamma-Fe2O3 in the soil can account for the generation of radioactive gas in the Labeled Release Experiment. The slower evolution of CO2 from both the Gas Exchange Experiment and the Labeled Release Experiment are associated with the direct oxidation of organics by gamma-Fe2O3. The Pyrolytic Release Experiment's second peak may be carbon suboxide as demonstrated by laboratory experiments. A necessary condition is that the polymer exists in the Martian soil. We ascribe the activity of the surface samples to the reaction of Martian particulates with an anhydrous CO2 atmosphere activated by uv and ionizing radiations. The surface particles are ultimately altered by exposure to small but significant amounts of water at the sites. From the working model, we have predicted the peculiar nature of the chemical entities and demonstrated that the model is justified by laboratory data. The final confirmation of this model will entail a return to Mars, but the nature and implications of this chemistry for the Martian surface is predicted to reveal even more about Mars with further simulations in the laboratory.
long duration↗