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CO Gas (co + gas)
Selected AbstractsGrowth of tungsten whiskers oriented in <111> directionCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2010V. G. Zavodinsky Abstract The electron micro diffraction technique and pseudopotential ab initio calculations were implemented to study in details the formation and mechanism of growth of the tungsten whiskers during the reduction of nickel tungstate by CO gas. It has been shown that the W whiskers prefer to grow as crystals oriented in the <111> direction, and this process may be considered as the epitaxial growth on the hexagonal planes of Ni4W particles. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Oxygen isotope analysis of phosphate: improved precision using TC/EA CF-IRMS,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2009D. F. LaPorte Abstract Oxygen isotope values of biogenic apatite have long demonstrated considerable promise for paleothermometry potential because of the abundance of material in the fossil record and greater resistance of apatite to diagenesis compared to carbonate. Unfortunately, this promise has not been fully realized because of relatively poor precision of isotopic measurements, and exceedingly small size of some substrates for analysis. Building on previous work, we demonstrate that it is possible to improve precision of ,18OPO4 measurements using a ,reverse-plumbed' thermal conversion elemental analyzer (TC/EA) coupled to a continuous flow isotope ratio mass spectrometer (CF-IRMS) via a helium stream [Correction made here after initial online publication]. This modification to the flow of helium through the TC/EA, and careful location of the packing of glassy carbon fragments relative to the hot spot in the reactor, leads to narrower, more symmetrically distributed CO elution peaks with diminished tailing. In addition, we describe our apatite purification chemistry that uses nitric acid and cation exchange resin. Purification chemistry is optimized for processing small samples, minimizing isotopic fractionation of PO4,3 and permitting Ca, Sr and Nd to be eluted and purified further for the measurement of ,44Ca and 87Sr/86Sr in modern biogenic apatite and 143Nd/144Nd in fossil apatite. Our methodology yields an external precision of ± 0.15, (1,) for ,18OPO4. The uncertainty is related to the preparation of the Ag3PO4 salt, conversion to CO gas in a reversed-plumbed TC/EA, analysis of oxygen isotopes using a CF-IRMS, and uncertainty in constructing calibration lines that convert raw ,18O data to the VSMOW scale. Matrix matching of samples and standards for the purpose of calibration to the VSMOW scale was determined to be unnecessary. Our method requires only slightly modified equipment that is widely available. This fact, and the demonstrated improvement in precision, should help to make apatite paleothermometry far more accessible to paleoclimate researchers. Copyright © 2009 John Wiley & Sons, Ltd. [source] Oxidation Protection of MgO,C Refractories by Means of Al8B4C7JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2001Tianming Wang The effect of Al8B4C7 used as an antioxidant in MgO,C refractories and the behavior of Al8B4C7 in CO gas were investigated in the present study. Al8B4C7 was found to react with CO gas, to form Al2O3(s), B2O3(l), and C(s), at temperatures >1100°C. The Al2O3 reacts with MgO to form MgAl2O4 near the surface of the material. At the same time, B2O3(l) evaporates and reacts with MgO, to form a liquid phase, at >1333°C, the eutectic point between 3MgO·B2O3 and MgO. The coexistence of the liquid and MgAl2O4 makes the protective layer more dense, thus inhibiting oxidation of the refractory. At >1333°C, the process apparently is controlled by oxygen diffusion, whereas it is controlled by chemical reaction when the temperature is <1333°C. [source] Increased intestinal luminal carbon monoxide gas in patients with ulcerative colitisALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 2006T. TAKAGI Summary Background Recent studies in models of inflammatory bowel disease have demonstrated that heme oxygenase-1 (HO-1) induction, or its by-products in this process such as carbon monoxide (CO), plays an important role in the intestinal inflammation. However, the distribution of HO-1 in intestinal mucosa and the concentration of intestinal luminal CO in humans have not yet been investigated. Aim To detect the HO-immunopositive cells in the intestine of normal subjects and in patients with ulcerative colitis (UC) and to measure intestinal luminal CO gas contents using gas chromatography. Materials and Methods The expression of HO-1 in the intestine was determined using immunohistochemistry. Human colonic gas was collected using colonoscopy from healthy volunteers and patients with UC. Analysis of intestinal luminal gas was performed using a newly developed portable gas chromatograph. Results Immunopositive staining for HO-1 was localized in the inflammatory cells, mainly mononuclear cells, and the number of cells that accepted stain was greater in patients with UC. CO level in the intestinal lumen significantly increased in patients in the active stage of UC. Conclusion These findings indicate that the HO-CO system is induced in UC. [source] Ureilite petrogenesis: A limited role for smelting during anatexis and catastrophic disruptionMETEORITICS & PLANETARY SCIENCE, Issue 6 2006Paul H. Warren Several mass-balance problems arise from this hypothesis. Smelting inevitably consumes a large proportion of any plausible initial carbon while generating significant proportions of Fe metal and copious proportions of CO gas. The most serious problem concerns the yield of CO gas. If equilibrium smelting produced the ureilites' entire 21 mol% range in olivine-core mg, the proportion of gas within the asteroidal mantle (assuming plausibly low pressure <,80 bar) should have reached ,85 vol%. Based on the remarkably stepwise cooling history inferred from ureilite texture and mineralogy, a runaway, CO-leaky process that can loosely be termed smelting appears to have occurred, probably triggered by a major impact. The runaway scenario appears likely because, by Le Châtelier's principle, CO leakage would tend to accelerate the smelting process. Also, the copious volumes of gas produced by smelting would have led to explosive, mass-leaky eruptions into the vacuum surrounding the asteroid. Loss of mass would mean diminution of interior pressure, which would induce further smelting, leading to further loss of mass (basalt), and so on. Such a disruptive runaway process may have engendered the ureilites' distinctive reduced olivine rims. But the only smelting, according to this scenario, was a short-lived disequilibrium process that reduced only the olivine rims, not the cores; and the ureilites were cooling, not melting, during the abortive "smelting" episode. [source] Formation of TiC core-graphitic mantle grains from CO gasMETEORITICS & PLANETARY SCIENCE, Issue 5 2006Yuki KIMURA 1996). Carbonaceous materials can be formed from C2H2 and its derivatives, as well as from CO gas. In this paper, we will demonstrate that large-cage-structure carbon particles can be produced from CO gas by the Boudouard reaction. Since the sublimation temperature for such fullerenes is low, the large cages can be deposited onto previously nucleated TiC and produce TiC core-graphitic mantle spherules. New constraints for the formation conditions and the time scale for the formation of TiC core-graphitic mantle spherules are suggested by the results of this study. In particular, TiC core-graphitic mantle grains that are found in primitive meteorites that have never experienced hydration could be mantled by fullerenes or carbon nanotubes rather than by graphite. In situ observations of these grains in primitive anhydrous meteoritic matrix could confirm or refute this prediction and would demonstrate that the graphitic mantle on such grains is a metamorphic feature due to interaction of the presolar fullerenes with water within the meteorite matrix. [source] Determination of stability of MIG/MAG welding processesQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 5 2001Marjan Suban Abstract The paper treats several methods of evaluating the stability of MIG/MAG welding processes, which are based on measurement of time-varying welding-current intensity and welding voltage. The stability of the welding process is affected by numerous parameters. The most unfavourable result of poor stability are spatters, which are problematic in terms of material losses and extension of production times due to cleaning, as well as appearance. The experimental part of the paper is based on stability analyses carried out with three different gas-shielding atmospheres. Two different welding domains were compared. The first was short-circuit material transfer, and the second spraying material transfer. The results obtained in the analysis of the signals measured indicate a more stable short-circuit material transfer in the case of welding with the pure CO gas, and a more stable spray material transfer in the case of welding with the transferred ionized molten energy mixture. Copyright © 2001 John Wiley & Sons, Ltd. [source] Hydrogenogenic CO Conversion in a Moderately Thermophilic (55 °C) Sulfate-Fed Gas Lift Reactor: Competition for CO-Derived H2BIOTECHNOLOGY PROGRESS, Issue 5 2006Jan Sipma Thermophilic (55 °C) sulfate reduction in a gas lift reactor fed with CO gas as the sole electron donor was investigated. The reactor was inoculated with mesophilic granular sludge with a high activity of CO conversion to hydrogen and carbon dioxide at 55 °C. Strong competition for H2 was observed between methanogens and sulfate reducers, while the homoacetogens present consumed only small amounts of H2. The methanogens appeared to be more sensitive to pH and temperature shocks imposed to the reactor, but could not be completely eliminated. The fast growth rates of the methanogens (generation time of 4.5 h) enabled them to recover fast from shocks, and they rapidly consumed more than 90% of the CO-derived H2. Nevertheless, steep increases in sulfide production in periods with low methane production suggests that once methanogenesis is eliminated, sulfate reduction with CO-rich gas as electron donor has great potential for thermophilic biodesulfurization. [source] |