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Query: CAS:7440-44-0 (Carbon)
 10,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carbon/silica (carbosil) samples prepared utilizing mesoporous silica gel (Si-60) modified by methylene chloride pyrolysis were studied by nitrogen adsorption, quasi-isothermal thermogravimetry, p-nitrophenol adsorption from aqueous solution, and (1)H NMR methods. The structural characteristics and other properties of carbosils depend markedly on the synthetic conditions and the amount of carbon deposited. The changes in the pore size distribution with increasing carbon concentration suggest grafting of carbon mainly in pores, leading to diminution of the mesopore radii. However, heating pure silica gel at the pyrolysis temperature of 550 degrees C leads to an increase in the pore radii. The quasi-isothermal thermogravimetry and (1)H NMR spectroscopy methods used to investigate the water layers on carbosils showed a significant capability of carbosils to adsorb water despite a relatively large content of the hydrophobic carbon deposit, which represents a nonuniform layer incompletely covering the oxide surface. Copyright 2000 Academic Press.
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PMID:Surface Properties of Mesoporous Carbon-Silica Gel Adsorbents. 1068 74

Oligotrophic PYGV medium, inoculated with soils from Linnaeus Terrace (1600 m, Antarctica), yielded four aerobic actinomycetes with short rods, multiple and irregular septa and often motile buds. Cells were 1.0-2.8 x 1.0-3.0 microm and colonies were beige to pink. The isolates were nearly identical in physiological and biochemical tests. Three strains grew from 0 degrees C to 25-28 degrees C, but one was psychrophilic with a maximum growth temperature of 20 degrees C. Carbon sources utilized were D-glucose, D-galactose, lactose, sucrose or mannitol; malate, succinate, fumarate, pyruvate or glutarate were decarboxylated aerobically. Peptone and yeast extract were the preferred nitrogen sources. Nitrate was reduced aerobically or anaerobically. Cell walls contained meso-diaminopimelic acid, glutamate, alanine, glycine, galactose, glucose and ribose. Major fatty acids of strains AA-802, -824, -825 and -826T were n18:1, i16:0 and ai17:0. Major respiratory quinones were MK-9(H4) and MK-8(H4). Polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. Phosphatidylglycerol was found in most strains. The DNA G+C contents were 68-70 mol%. In 16S rDNA analyses, similarity values obtained for 500 nucleotides from the 5' terminus were > 99.5%. Almost complete sequences from AA-826T and -825 were 99.9% similar. Strain AA-826T belonged to a novel cluster of desert soil and rock isolates within the Geodermatophilaceae and was equidistantly related to members of Geodermatophilus and to a Blastococcus lineage. The four isolates represent a new genus, Modestobacter gen. nov., with Modestobacter multiseptatus sp. nov. as the type species. The type strain, Modestobacter multiseptatus AA-826T, was deposited in the DSMZ as DSM 44406T.
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PMID:Modestobacter multiseptatus gen. nov., sp. nov., a budding actinomycete from soils of the Asgard Range (Transantarctic Mountains). 1082 21

The nodulating soybean (Enrei) and its non-nodulating mutant (EN 1282) were grown in outdoor plots for 2 years (1994: extraordinary dry, high temperature, 1995: ordinary year). Carbon and nitrogen accumulation, delta 13C and delta 15N values in plant parts and xylem fluids and delta 15N values in the water-extractable soil N were analysed throughout the growing period. Plant growth in 1994 was rapid during the early growth stages, but no pods were produced. In 1995, plant growth was normal and pods were formed. The delta 13C values of the leaves were less negative in 1994 than in 1995 and the nodulated plants showed less negative delta 13C values than non-nodulated plants in both years. The delta 13C values of the leaves during the vegetative phase were positively correlated to the leaf N concentrations. Leaf N concentrations in their turn were influenced by nodulation and weather conditions and/or soil available N. The delta 15N values in the plants and xylem fluids were lower in the nodulated soybean than in non-nodulated soybean in both years, and estimates of the contribution of N2 fixation in nodulated plants based on plant top delta 15N values were 7-14% in 1994 and 37-63% in 1995. The delta 13C values of xylem fluids did not differ between nodulated and non-nodulated plants. Thus, the expected contribution by phosphopenolpyruvate carboxylase-mediated CO2 fixation in the root nodules to plant C-incorporation could not have been significant.
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PMID:Weather and nodule mediated variations in delta 13C and delta 15N values in field-grown soybean (Glycine max L.) with special interest in the analyses of xylem fluids. 1093 12

Carbon catabolite repression of several catabolic operons in Bacillus subtilis is mediated by the repressor CcpA. An inactivation of the ccpA gene has two distinct phenotypes: (i) catabolite repression of catabolic operons is lost and (ii) the growth of bacteria on minimal medium is severely impaired. We have analyzed the physiological properties of a ccpA mutant strain and show that the ccpA mutation does not affect sugar transport. We have isolated extragenic suppressors of ccpA that suppress the growth defect (sgd mutants). Catabolite repression of beta-xylosidase synthesis was, however, not restored suggesting that the suppressor mutations allow differentiation between the phenotypes of the ccpA mutant. A close inspection of the growth requirements of the ccpA mutant revealed the inability of the mutant to utilize inorganic ammonium as a single source of nitrogen. An intact ccpA gene was found to be required for expression of the gltAB operon encoding glutamate synthase. This enzyme is necessary for the assimilation of ammonium. In a sgd mutant, gltAB operon expression was no longer dependent on ccpA, suggesting that the poor expression of the gltAB operon is involved in the growth defect of the ccpA mutant.
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PMID:The catabolite control protein CcpA controls ammonium assimilation in Bacillus subtilis. 1094 96

The responses of gas exchange and water use efficiency to nitrogen nutrition for winter wheat were investigated under well-watered and drought conditions. The photosynthetic gas exchange parameters of winter wheat are remarkably improved by water and nitrogen nutrition and the regulative capability of nitrogen nutrition is influenced by water status. The effects of nitrogen nutrition on photosynthetic characteristics and on the limited factors to photosynthesis are not identical under different water status. Intrinsic water use efficiency (WUE(i)) of the plants at the high-N nutrition was decreased by a larger value than that of the plants in the low-N treatment due to a larger decrease in photosynthetic rate than in transpiration rate. Carbon isotope composition of plant material (delta(p)) is increased by the increase of drought intensity. The delta(p) at a given level of C(i)/C(a) is reduced by nitrogen deficiency. Leaf carbon isotope discrimination (Delta) is increased by the increase of nitrogen nutrition and decreased by the increase of drought intensity. Transpirational water use efficiency (WUE(t)) is negatively correlated with Delta in both nitrogen supply treatments and increased with the nitrogen supply.
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PMID:Nitrogen nutrition and water stress effects on leaf photosynthetic gas exchange and water use efficiency in winter wheat. 1099 67

Carbon accumulation in the terrestrial biosphere could partially offset the effects of anthropogenic CO2 emissions on atmospheric CO2. The net impact of increased CO2 on the carbon balance of terrestrial ecosystems is unclear, however, because elevated CO2 effects on carbon input to soils and plant use of water and nutrients often have contrasting effects on microbial processes. Here we show suppression of microbial decomposition in an annual grassland after continuous exposure to increased CO2 for five growing seasons. The increased CO2 enhanced plant nitrogen uptake, microbial biomass carbon, and available carbon for microbes. But it reduced available soil nitrogen, exacerbated nitrogen constraints on microbes, and reduced microbial respiration per unit biomass. These results indicate that increased CO2 can alter the interaction between plants and microbes in favour of plant utilization of nitrogen, thereby slowing microbial decomposition and increasing ecosystem carbon accumulation.
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PMID:Nitrogen limitation of microbial decomposition in a grassland under elevated CO2. 1119 41

Carbon fiber platinized ultramicroelectrodes placed within micrometres of a single living cell are used to monitor cellular events. This artificial synapse is used here to collect and examine the very nature of the massive oxidative bursts produced by human fibroblasts when their membrane is locally depolarized by a puncture made with a micrometre sized sealed pipette. The electrochemical analysis of the response indicates that oxidative bursts consist of a mixture of a few femtomoles of highly cytotoxic chemicals: hydrogen peroxide, nitrogen monoxide and peroxynitrite, together with nitrite ions, which may result from a partial spontaneous decomposition of peroxynitrite prior to its release by the cell.
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PMID:Analysis of individual biochemical events based on artificial synapses using ultramicroelectrodes: cellular oxidative burst. 1119 88

The yeast Cryptococcus sp. UFMG-Y28 can utilize benzonitrile as a nitrogen and possible additional carbon source. The kinetics of growth on Yeast Carbon Base (YCB) added of benzonitrile as sole nitrogen source showed that benzonitrile was metabolized to benzoic acid and ammonia. Liquid chromatography analysis indicated that Cryptococcus sp. UFMG-Y28 metabolized 12 mM benzonitrile to 10 mM benzoic acid. Resting cells cultivated on YCB-propionitrile medium showed nitrilase activity against benzonitrile. This strain appears to be promising for bioconversion of nitriles to high value acids and for bioremediation of sites contaminated with aliphatic and aromatic nitriles.
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PMID:Metabolism of benzonitrile by Cryptococcus sp. UFMG-Y28. 1119

A lab-scale hybrid upflow sludge bed-filter (USBF) reactor was employed to carry out methanogenesis and denitrification of the effluent from an anaerobic industrial reactor (EAIR) in a fish canning industry. The reactor was initially inoculated with methanogenic sludge and there were two different operational steps. During the first step (Step I: days 1-61), the methanogenic process was carried out at organic loading rates (OLR) of 1.0-1.25 g COD l-1 d-1 reaching COD removal percentages of 80%. During the second step (Step II: days 62-109) nitrate was added as KNO3 to the industrial effluent and the OLR was varied between 1.0 and 1.25 g COD l-1 d-1. Two different nitrogen loads of 0.10 and 0.22 g NO3(-)-N l-1 d-1 were applied and these led to nitrogen removal percentages of around 100% in both cases and COD removal percentages of around 80%. Carbon to nitrogen ratio (C:N) in the influent was maintained at 2.0 and eventually it was increased to 3.0, by means of glucose addition, to control the denitrification process. From these results it is possible to establish that wastewater produced in a fish canning industry can be used as a carbon source for denitrification and that denitrifying microorganisms were present in the initially methanogenic sludge. Biomass productions of 0.23 and 0.61 g VSS:g TOC fed for Steps I and II, respectively, were calculated from carbon global balances, showing an increase in biomass growth due to denitrification.
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PMID:Simultaneous methanogenesis and denitrification of pretreated effluents from a fish canning industry. 1122 93

Carbon assimilation by Cedrela odorata L. (Meliaceae) seedlings was investigated in ambient and elevated CO2 concentrations ([CO2]) for 119 days, using small fumigation chambers. A solution containing macro- and micronutrients was supplied at two rates. The 5% rate (high rate) was designed to avoid nutrient limitation and allow a maximum rate of growth. The 1% rate (low rate) allowed examination of the effect of the nutrient limitation-elevated CO2 interaction on carbon assimilation. Root growth was stimulated by 23% in elevated [CO2] at a high rate of nutrient supply, but this did not lead to a change in the root:shoot ratio. Total biomass did not change at either rate of nutrient supply, despite an increase in relative growth rate at the low nutrient supply rate. Net assimilation rates and relative growth rates were stimulated by the high rate of nutrient addition, irrespective of [CO2]. We used a biochemical model of photosynthesis to investigate assimilation at the leaf level. Maximum rate of electron transport (Jmax) and maximum velocity of carboxylation (Vcmax) did not differ significantly with CO2 treatment, but showed a substantial reduction at the low rate of nutrient supply. Across both CO2 treatments, mean Jmax for seedlings grown at a high rate of nutrient supply was 75 micromol m(-2) s(-1) and mean Vcmax was 27 micromol m(-2) s(-1). The corresponding mean values for seedlings grown at a low rate of nutrient supply were 36 micromol m(-2) s(-1) and 15 micromol m(-2) s(-1), respectively. Concentrations of leaf nitrogen, on a mass basis, were significantly decreased by the low nutrient supply rate, in proportion to the observed decrease in photosynthetic parameters. Chlorophyll and carbohydrate concentrations of leaves were unaffected by growth [CO2]. Because there was no net increase in growth in response to elevated [CO2], despite increased assimilation of carbon at the leaf level, we hypothesize that the rate of respiration of non-photosynthetic organs was increased.
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PMID:Interaction of nutrient limitation and elevated CO2 concentration on carbon assimilation of a tropical tree seedling (Cedrela odorata). 1130 73


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