Reversible combination of carbon monoxide with a synthetic oxygen carrier complex

Chlorocarbonyl-bis(triphenylphosphine)iridium(I), in solution, reacts reversibly with carbon monoxide under normal conditions, one molecule per metal atom. Formation of a 1 : 1 metal complex-CO adduct is verified by CO absorption measurements and the infrared spectrum of the adduct measured in situ. The spectrum suggests that the metal-C-O bonding is of the type found in conventional metal carbonyl.     

Dynamics of carbon monoxide binding by heme proteins

Rebinding of carbon monoxide to myoglobin and to cytochrome P-450 after removal by a light flash occurs down to 50 degrees K for myoglobin and 25 degrees K for cytochrome P-450 in glycerol-water solution. Above 240 degrees K the reaction is second order; between 240 degrees and 200 degrees K the rebinding becomes exponential and independent of the carbon monoxide concentration. Below 150 degrees K the reaction follows a power law and is approximately 10(3) times faster for cytochrome P-450 than for myoglobin.     

Microwave measurement of mesospheric carbon monoxide

Ground-based observation of atmospheric absorption of solar radiation at a wavelength of 2.6 millimeters has provided the first measurement of mesospheric carbon monoxide. The measurement agrees with photochemical predictions of a carbon monoxide source in the lower thermosphere due to dissociation of carbon dioxide by solar radiation, and has implications for the magnitude of vertical transport in the mesosphere.     

Prenatal exposure to carbon monoxide: learning and memory deficits

Exposing pregnant rats to carbon monoxide (150 parts per million) produced only minor reductions in the birth weights of the pups and gave no evidence of overt teratogenesis. However, behavioral evaluation of learning and memory processes in a two-way avoidance task suggested a functional deficit in the central nervous system of the exposed offspring. Multiple dependent measures and specific control groups confirmed that this deficit was independent of nonassociative or motivational alterations.     

Production of carbon monoxide and gaseous hydrocarbons in seawater: relation to dissolved organic carbon

Carbon monoxide, ethylene, and propylene were produced in illuminated, cell-free distilled water or natural seawater systems to which dissolved organic matter produced by phytoplankton had been added. Methane and the higher saturated gaseous hydrocarbons were not produced. In the dark, little or no carbon monoxide and no hydrocarbons were produced in the distilled water systems; only carbon monoxide was produced in natural seawater, but less was produced than in the light.     

Argonne intense pulsed neutron source used to solve the molecular structure of a novel organometallic complex

The single-crystal structure of Mn(CO)(3)(C(7)H(11)) is the first to be solved by direct methods based on time-of-flight neutron diffraction data obtained at the Argonne Intense Pulsed Neutron Source. The molecule contains an unusual three-center, two-electron manganese-hydrogen-carbon interaction.     

Microwave measurements of carbon monoxide on titan

The ratio of the flux density of Titan was measured in two 200-megahertz bands, one centered on the (1-0) rotation line of carbon monoxide at 115.3 gigahertz and the other 2600 megahertz lower. The measurements were made with a complex-correlation technique on the new millimeter-wavelength interferometer at the Owens Valley Radio Observatory, Big Pine, California. The excess flux in the carbon monoxide band is interpreted as a strong detection of carbon monoxide and a mixing ratio, assumed constant, of 6 x 10(-5). The brightness temperature of Titan at 112.6 gigahertz is 69 +/- 10 kelvins, consistent with atmospheric emission from just below the tropopause.     

Mars: microwave detection of carbon monoxide

The 115-gigahertz microwave line of carbon monoxide has been detected in the spectrum of Mars. The measurement is sensitive to carbon monoxide between the surface and an altitude of approximately 50 kilometers in the martian atmosphere. This extends the altitude region to well above that previously sensed.     

Venus: microwave detection of carbon monoxide

The 115-gigahertz microwave line of carbon monoxide has been detected in the spectrum of Venus. The measurement proves that the carbon monoxide mixing ratio increases above an altitude of 85 kilometers in the Venus stratosphere and provides quantitative information on carbon monoxide in the altitude region from 80 to 110 kilometers. This altitude region is well above that which has been previously sensed.     

Air pollution: sensitive detection of ten pollutant gases by carbon monoxide and carbon dioxide lasers

Detection sensitivities of a few parts per billion for ten gaseous pollutants have been evaluated by measuring the strength of the absorption of infrared radiation from carbon monoxide and carbon dioxide lasers. Ethylene concentrations as small as 5 parts per billion have been detected in air. The measured absorption strengths indicate that in mixtures of pollutants, such as nitrogen dioxide and water vapor, the sensitivity is reduced by overlapping absorption bands. However, calculations indicate that it should be possible to detect nitrogen dioxide concentrations of 0.01 part per million in the presence of water vapor concentrations of 105 parts per million.     

Titan: discovery of carbon monoxide in its atmosphere

The 3-0 rotation-vibration band of carbon monoxide in the near-infrared spectrum of Titan has been identified, and a reflecting layer model mixing ratio of carbon monoxide to molecular nitrogen of 6 x 10(-5) has been determined. This result supports the probable detection of carbon dioxide by Samuelson and his co-workers and strengthens possible analogies between the atmosphere of Titan and conditions on primitive Earth.     

Submillimeter heterodyne detection of interstellar carbon monoxide at 434 micrometers

A submillimeter heterodyne radiometer, developed for astronomical applications, uses an optically pumped laser local oscillator and a quasi-optical Schottky diode mixer. The resultant telescope-mounted system, which has a noise temperature less than 4000 K (double sideband) and high frequency and spatial resolution, has been used to detect the J = 6 --> 5 rotational transition of carbon monoxide at 434 micrometers in the Orion molecular cloud. The measurements, when compared with previous millimeter-wave data, indicate that the broad carbon monoxide emission feature is produced by an optically thin gas whose temperature exceeds 180 K.     

Carbon dioxide activation at the Ni,Fe-cluster of anaerobic carbon monoxide dehydrogenase

Anaerobic CO dehydrogenases catalyze the reversible oxidation of CO to CO2 at a complex Ni-, Fe-, and S-containing metal center called cluster C. We report crystal structures of CO dehydrogenase II from Carboxydothermus hydrogenoformans in three different states. In a reduced state, exogenous CO2 supplied in solution is bound and reductively activated by cluster C. In the intermediate structure, CO2 acts as a bridging ligand between Ni and the asymmetrically coordinated Fe, where it completes the square-planar coordination of the Ni ion. It replaces a water/hydroxo ligand bound to the Fe ion in the other two states. The structures define the mechanism of CO oxidation and CO2 reduction at the Ni-Fe site of cluster C.     

黑麦草对铀胁迫的光合响应及铀吸收特性研究

为探究铀污染土壤下黑麦草光合特性和体内各部位铀积累分布特征的变化,本研究通过盆栽土培试验,研究了不同外源铀浓度处理(0、25、50、75、100 mg·kg~(-1))下黑麦草光合气体交换变化参数、光合荧光参数和黑麦草对铀的富集特征的影响。结果显示,铀胁迫会使植物的光合速率(A)和气孔导度(Gs)显著降低(P0.05),光合性能指数(PIabs)随外源铀浓度的增加呈先增后减的趋势,但未对黑麦草的胞间CO_2浓度(Ci)、最大光化学效率(Fv/Fm)和相对可变荧光(Vj)产生显著影响。随外源铀污染浓度的增加,土壤中铀残留量、黑麦草体内地上部和地下部的累积量显著增加(P0.05),且随着生长时间的增加,土壤中铀残留量显著减小、黑麦草体内地上部和地下部的累积量显著增加。生物富集系数(BCF)和铀总提取量分别在100 mg·kg~(-1)处理下达到最大值。结果表明,黑麦草的光合荧光参数对铀具有较好的耐受性,而光合速率的降低可能是光抑制引起的,黑麦草对铀有较高的富集能力,且随着生长时间和外源处理浓度的增加而增加。     

还原脱硝法去除二硝基甲苯研究现状

综述了还原脱硝法去除水中二硝基甲苯的研究现状,以及二硝基甲苯去除的影响因素;零价铁还原去除二硝基甲苯过程中,铁和杂质形成原电池,在原电池表面产生活性氢,二硝基甲苯与活性氢结合被还原,铁表面产生Fe（OH）2沉淀;分析并提出纳米铁、合金以及其他还原性物质还原去除二硝基甲苯的研究方法。     

Nitric oxide reduction coupled with carbon monoxide oxidation in the presence of soluble metal catalysts

Solutions of RhCl(3).xH(2)O in ethanol and Ru(NO)(2)[P(C(6)H(5))(3)](2) in benzene catalyze the reduction of nitric oxide to nitrous oxide concomitant with the oxidation of carbon monoxide to carbon dioxide at ambient temperature and atmospheric pressure. The reaction, which is followed by gas chromatography and by the decrease in pressure of the system, proceeds to 47 percent conversion of the reactants after 63 hours.     

Rare-earth oxides of manganese and cobalt rival platinum for the treatment of carbon monoxide in auto exhaust

The perovskite-like compounds RE(1-X)Pb(5)MnO(3) and RECoO(3), where RE (rare earth) is lanthanum, praseodymium, or neodymium, are active catalysts for the oxidation of carbon monoxide. Crushed single crystals of these compounds compare favorably with commercial platinum catalysts in initial activity and lifetime. Therefore, these compounds are promising substitutes for platinum in devices for the catalytic treatment of auto exhaust.     

Multifunctional carbon nanotube yarns by downsizing an ancient technology

By introducing twist during spinning of multiwalled carbon nanotubes from nanotube forests to make multi-ply, torque-stabilized yarns, we achieve yarn strengths greater than 460 megapascals. These yarns deform hysteretically over large strain ranges, reversibly providing up to 48% energy damping, and are nearly as tough as fibers used for bulletproof vests. Unlike ordinary fibers and yarns, these nanotube yarns are not degraded in strength by overhand knotting. They also retain their strength and flexibility after heating in air at 450 degrees C for an hour or when immersed in liquid nitrogen. High creep resistance and high electrical conductivity are observed and are retained after polymer infiltration, which substantially increases yarn strength.