Replacement Of Carbon Research Articles

Uniform stable-isotope labeling in mammalian cells: formulation of a cost-effective culture medium

Uniform stable-isotope labeling of mammalian cells is achieved via a novel formulation of a serum-free cell culture medium that is based on stable-isotope-labeled autolysates and lipid extracts of various microbiological origin. Yeast autolysates allow complete replacement of individual amino acids and organic acids in a chemically defined medium (DMEM/F12), enabling a cost-effective formulation of a stable-isotope-labeled culture medium for mammalian cells. In addition, biomass-derived hydrolysates, autolysates, and lipid extracts of various classes of algae were explored as cell culture components, both separately and in combination with yeast autolysates. Optimal autolysate concentrations were established. Such novel medium formulations were tested on mammalian cell lines, often used for recombinant protein production, i.e., Chinese hamster ovary (CHO) and human embryonic kidney (HEK 293). Special attention was paid to the adaptation of these mammalian cell lines to serum-free media. Formulation of the novel proprietary cell culture medium PLIm, based on yeastolates instead of individual amino acids and organic acids, allows a four- to eightfold cost reduction for (15)N and (13)C,(15)N stable-isotope-labeling, respectively, in CHO cells and a three- to sixfold cost reduction in HEK 293 cells. A high level of stable-isotope enrichment of mammalian cells (>90%) was achieved within four passages by complete replacement of carbon and nitrogen sources in the medium with their stable-isotope-labeled analogs. These conditions can be used to more cost-effectively produce labeled recombinant proteins in mammalian cells.

ChemInform Abstract: Synthesis and Radioprotective Properties of 9a-Homo-13-thiaprostanoids.

Among bioregulators used in treatment of irradiationinduced diseases [I] a special position belongs to prostaglandins (and especially to their analogs) [2, 3]. These compounds, even taken at extremely low doses, exhibit a combination of therapeutic properties (cytoprotective activity with respect to epithelium of gastroenteric tract, endothelium of blood vessels, thrombocytes, tissue basophils, immunocompetent cells, etc.). In this connection, we may expect that prostaglandin-based radioprotectors would combine various mechanisms in protecting organism, together with low toxicity and absence of side effects. One of most justified approaches to modification of prostaglandins, which proved to provide an increase in their efficiency, selectivity, and chemical and metabolic stability, is that based on replacement of carbon by heteroatoms (N, S, O) [4] and introduction of alkyi substituents into various sites of prostanic skeleton [5]. in this work we used both methods for synthesis of previously unreported 9a-homo-13-thiaprostanoids l l a h and llla d. We have also studied radioprotective properties of these compounds and some other biological effects that can be used in prophylaxis and therapy of radiation damage. The key compounds for synthesis of these 13-thiaprostanoids are previously described vinyl analogs ofcarboxylic acid chloroanhydrides ( l a d), which were used for obtaining 13-azaprostanoids by interaction with amines [6]. Proceeding from these data and using results reported by Kirchlechner [7], we expected that interaction of chlorovinyldiketones l a d with thiols would also follow the scheme of vinyl substitution to yield 13-thiaprostanoids corresponding to structures of thiols employed. For thiophenol and thiooctanol, it was found that this reaction actually takes place upon treatmem of [a d with a two-fold excess of thiol in a THF solution in presence of a ten-fold excess of triethylamine.

Impurity seeding and scaling of edge parameters in ITER

ITER divertor and edge modelling with the ITER B2–EIRENE code including neutral–neutral and molecule–ion collisions has led to updated scaling of the helium density and flux and the DT flux with the pumping speed and the divertor neutral pressure. The replacement of carbon by the addition of seeded impurities (neon) strongly modifies the upstream DT density and DT neutral influx at constant detachment state, i.e. divertor neutral pressure and has a smaller influence on the peak divertor power load. The core plasma performance is modelled with the integrated core-pedestal–SOL (ICPS) model implemented in ASTRA; the operating window with seeded impurities is smaller than with DT injection alone.

Isotopic turnover rate and fractionation in multiple tissues of red rock lobster (Jasus edwardsii) and blue cod (Parapercis colias): Consequences for ecological studies

This study experimentally determined the turnover rates of δ 13C and δ 15N as a function of growth and metabolism and isotopic fractionation for different tissues in captive populations of red rock lobster ( Jasus edwardsii) and blue cod ( Parapercis colias). Isotopic turnover was estimated using the model of Hesslein et al. [Hesslein, R., Hallard, K., Ramlal, P., 1993. Replacement of sulfur, carbon, and nitrogen in tissue of growing broad whitefish ( Coregonus nasus) in response to a change in diet traced by δ 34S, δ 13C, and δ 15N. Can. J. Fish. Aquat. Sci. 50, 2071–2076.]. Isotopic fractionations relative to diet differed among tissues and isotopes. Lobster muscle was more enriched than hemolymph and blue cod fin tissue was more enriched than blood for δ 13C and δ 15N. The metabolic component of turnover accounted for > 90% of the total isotopic turnover in lobster tissues and 30%–60% in blue cod tissues. Lobster muscle (half-life 147 d) and hemolymph (half-life 117 d) turnover rates were not significantly different but were faster than turnover rates of blue cod tissues. Whole blood, blood plasma fraction, and the blood cellular fraction had similar turnover rates; the whole blood half-life was 240 d for blue cod. Measuring turnover in larger, slower growing animals allowed for a more precise estimate of the metabolic component of isotopic turnover than in fast growing animals in which change is predominantly the result of dilution through growth. The differences in fractionation values among tissues observed here demonstrate that using generic trophic fractionation values would introduce error into diet reconstruction or migration studies. We demonstrate that a modified version of Hesslein et al.'s [Hesslein, R., Hallard, K., Ramlal, P., 1993. Replacement of sulfur, carbon, and nitrogen in tissue of growing broad whitefish ( Coregonus nasus) in response to a change in diet traced by δ 34S, δ 13C, and δ 15N. Can. J. Fish. Aquat. Sci. 50, 2071–2076.] turnover model could be used to estimate the temporal component of migration.

Synthesis and study of new liquid crystalline compounds with an epoxy group

The influence of the transformation of a terminal double bond to an epoxide group in the series of compounds containing phenyl benzoate moiety as the mesogenic rigid core is investigated. The epoxide derivatives are obtained by biotransformation methods. The double bond or epoxide ring are separated by different numbers of methylene units from the phenyl ring of benzoic acid in its methoxy or decyloxyphenyl esters. The mesogenic properties of the synthesised compounds are investigated by optical microscopy, calorimetric and X‐ray methods. In contrast to methoxyphenyl esters most of decyloxyphenyl esters showed enantiotropic liquid crystalline behaviour. The replacement of the double carbon–carbon bond by the polar and bulky epoxy group destabilises the mesophase in almost all cases.

Novel therapeutics with enhanced biological activity generated by the strategic introduction of silicon isosteres into known drug scaffolds

AbstractThe strategic replacement of carbon with silicon within biologically prevalidated drug scaffolds can generate focused libraries of pharmaceutically relevant agents with novel, durable and marketable intellectual property. This approach can be cost‐effective and of lower developmental risk because known drugs have recognized pharmacology and toxicity profiles, proven safety in humans, and established manufacturing and formulation methods. The change in shape, charge, and lipophilicity that can result from the addition of silicon can favorably alter the biological activity and toxicology of the parent drug. Silicon‐containing derivatives of indomethacin are COX‐2 selective, suggesting they will not be associated with the classical toxicities associated with nonselective inhibition of the cyclooxygenases. The silicon‐indomethacin derivatives also demonstrated superior anti‐cancer activity at clinically achievable concentrations when tested in vitro against a human pancreatic cancer cell line, MiaPaCa‐2, and a panel of 14 human multiple myeloma cell lines. Bioorganosilicon chemistry represents an attractive approach for emerging biopharmaceutical organizations seeking to rapidly develop a portfolio of novel pharmacological agents that have the potential for enhanced therapeutic and pharmacological benefit. Drug Dev Res 68:156–163, 2007. ©2007 Wiley‐Liss, Inc.

Electroluminescence of several pyrazoloquinoline and quinoksaline derivatives

Experimental investigations of electroluminescent spectra for several pyrazoloquinoline and quinoksaline derivatives have been performed. The investigations have shown that replacement of carbon by nitrogen in the middle aromatic rings and replacement of aromatic ring by methyl group shift the main spectral maxima from 404 up to 455 nm for photoluminescence and from 450 up to 560 nm for electroluminescence. Such wide range of the spectral shift of the luminescence and electroluminescence opens a possibility of using the materials like new electroluminophore. The experimental data show sufficient agreement with semi-empirical quantum-chemical calculations. The observed long-range wavelength spectral shift of the theoretically calculated and experimentally observed maxima is caused by electron-vibration shift.

Soil organic matter dynamics in lands continuously cultivated with maize and soybean in Heilongjiang Province, Northeast China: Estimation from natural 13C abundance

Northeast China is the main production area of maize and soybean in China. In the present study, the rates of decomposition and replacement of soil organic carbon (SOC) were estimated using the soil inventory collected since 1991 from long-term maize and soybean cultivation plots in Heilongjiang Province, Northeast China, to evaluate the sustainability of the present cultivation system. The total carbon (C) content in soil was stable without any significant changes in the plots (approximately 28.5 g C kg−1). The δ13C value of soil organic matter under continuous maize cultivation increased linearly with an annual increment of 0.07 from −23.9 in 1991, which indicated that approximately 13% of the initial SOC was decomposed during the 13-year period of maize cultivation, with a half-life of 65 years. Slow decomposition of SOC was considered to result from the low annual mean temperature (1.5°C) and long freezing period (170–180 days year−1) in the study area. In contrast, the amount of organic C derived from maize increased in the soil with a very slow annual increment of 0.17 g C kg−1, probably because of the removal of all the plant residues from the plots. Based on the soil organic matter dynamics observed in the study plots, intentional recycling/maintenance of plant residues was proposed as a way of increasing soil fertility in maize or soybean cultivation.

Modeling carbon sequestration and timber production in a regional case study

Forests make up large ecosystems and by the uptake of carbon dioxide can play an important role in mitigating the greenhouse effect. In this study, mitigation of carbon emissions through carbon uptake and storage in forest biomass and the use of forest biofuel for fossil fuel substitution were considered. The analysis was performed for a 3.2 million hectare region in northern Sweden. The objective was to maximize net present value for harvested timber, biofuel production and carbon sequestration. A carbon price for build-up of carbon storage and for emissions from harvested forest products was introduced to achieve an economic value for carbon sequestration. Forest development was simulated using an optimizing stand-level planning model, and the solution for the whole region was found using linear programming. A range of carbon prices was used to study the effect on harvest levels and carbon sequestration. At a zero carbon price, the mean annual harvest level was 5.4 million m, the mean annual carbon sequestration in forest biomass was 1.48 million tonnes and the mean annual replacement of carbon from fossil fuel with forest biofuel was 61 000 tonnes. Increasing the carbon price led to decreasing harvest levels of timber and decreasing harvest levels of forest biofuel. Also, thinning activities decreased more than clear-cut activities when the carbon prices increased. The level of carbon sequestration was governed by the harvest level and the site productivity. This led to varying results for different parts of the region.3

Improving the creep properties of 9Cr-3W-3Co-NbV steels and their weld joints by the addition of boron

New ferritic steels with a controlled addition of boron have been developed recently for ultrasuper-critical fossil power plants. These steels possess excellent creep resistance compared to conventional steels like P91, P92, P122, etc., and this has been attributed to the delay in coarsening of the carbides during creep owing to partial replacement of carbon by boron in these carbides. However, the susceptibility of the weld joints of the boron-containing ferritic steels to type IV cracking, which significantly brings down the rupture life of the weld joints, has not been investigated so far. In the present work, the creep properties of recently developed 9Cr-3W-3Co-NbV steels with boron contents varying from 47 to 180 ppm and of their weld joints have been studied. Creep tests were carried out at 923 K in the stress range of 140 to 80 MPa. Specimens were examined for particle coarsening using field-emission scanning electron microscopy, and the boron content in the precipitates was estimated using field-emission auger electron spectroscopy (FE-AES). The grain size of the parent metal and the heat-affected zone (HAZ) were estimated using electron backscattered pattern (EBSP) imaging. Results showed that the creep properties of the steels with 90 and 130 ppm boron and of their weld joints are superior to those of the P92 steels and its weld joints. Further, no weld joints exhibited type IV cracking. No significant coarsening of the carbides was observed, not only in the parent metal but also in the HAZ of the steels with ≥90 ppm of boron. In addition to the delay in carbide coarsening, the large prior-austenite grain size of the parent metal and the absence of a conventional fine-grained HAZ (FGHAZ) in the weld joints also seem to have a beneficial effect on improving the creep properties of these steels and their weld joints.

Passivation of metal carbide surfaces: relevance to carbon nanotube–metal interconnections

Transition metal carbides are known to be effective electrical contacts for carbon nanotubes in nanoelectronics devices. Three different approaches to modifying or capping molybdenum carbide are presented: deposition of carbon on the surface, replacement of interstitial carbon with nitrogen using NO, and functionalization of the surface with polymerization active sites.

Synthesis and Properties of the First Stable Neutral Germaaromatic Compound, 2-{2,4,6-Tris- [bis-(trimethylsilyl)methyl]phenyl}-2-germanaphthalene

The first stable neutral germaaromatic compound, 2-germanaphthalene 1a, was synthesized by taking advantage of an extremely bulky and efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). The molecular structure and aromaticity of 1a were discussed on the basis of its NMR, UV−vis, and Raman spectra, X-ray crystallographic analysis, and theoretical calculations. All the 1H and 13C NMR chemical shifts of the 2-germanaphthalene ring of 1a were in good agreement with the calculated values for 2-germanaphthalene and 2-phenyl-2-germanaphthalene. The patterns of UV−vis and Raman spectra of 1a were similar to those of naphthalene, although the shift to longer wavelength (in the UV−vis spectrum) and smaller wavenumber (in the Raman spectrum) resulting from the replacement of carbon with germanium were observed. X-ray crystallographic analysis of 1a revealed that the 2-germanaphthalene ring was almost planar and perpendicular to the benzene ring of the Tbt group. These experimental r...

液体急冷Fe-Nd-(C, B)合金の2-14-1相形成能

The forming ability of the Nd2Fe14(C, B) phase was investigated in melt-spun Fe90−zNd10(C, B)z (z=3, 5, 7, 9) alloys in which the ratio of carbon to boron was changed. The cooling rate of the molten sample was varied by changing the surface velocity of a single roller apparatus. It was confirmed that the substitution of a small amount of boron promotes the formation of the 2-14-1 phase in the samples z=3 to 7. The 2-14-1 phase is formed instead of Nd2Fe17CX phase with the substitution of 1 mol% boron abruptly. With increasing boron substitution, the Curie temperature of the 2-14-1 phase increases from 533 to 586 K, indicating the boron replacement of carbon in the 2-14-1 phase. On the other hand, in the alloys of the samples z=9, the volume fraction of the 2-14-1 phase increases with increasing boron substitution gradually, and the Curie temperature of the phase is almost constant (586 K) regardless of the ratio of carbon to boron in the alloys. The result indicates that carbon atoms are scarcely dissolved in the 2-14-1 phase. The magnetic properties are improved by the substitution of 15 to 40% carbon for boron as compared with the ternary Nd-Fe-B alloys. The (BH)max value reaches maximal 136 kJ/m3 in the sample Fe83Nd10CB6.

Dynamic replacement and loss of soil carbon on eroding cropland

Links between erosion/sedimentation history and soil carbon cycling were examined in a highly erosive setting in Mississippi loess soils. We sampled soils on (relatively) undisturbed and cropped hillslopes and measured C, N, 14C, and CO2 flux to characterize carbon storage and dynamics and to parameterize Century and spreadsheet 14C models for different erosion and tillage histories. For this site, where 100 years of intensive cotton cropping were followed by fertilization and contour plowing, there was an initial and dramatic decline in soil carbon content from 1870 to 1950, followed by a dramatic increase in soil carbon. Soil erosion amplifies C loss and recovery: About 100% of the original, prehistoric soil carbon was likely lost over 127 years of intensive land use, but about 30% of that carbon was replaced after 1950. The eroded cropland was therefore a local sink for CO2 since the 1950s. However, a net CO2 sink requires a full accounting of eroded carbon, which in turn requires that decomposition rates in lower slopes or wetlands be reduced to about 20% of the upland value. As a result, erosion may induce unaccounted sinks or sources of CO2, depending on the fate of eroded carbon and its protection from decomposition. For erosion rates typical of the United States, the sink terms may be large enough (1 Gt yr−1, back‐of‐the‐envelope) to warrant a careful accounting of site management, cropping, and fertilization histories, as well as burial rates, for a more meaningful global assessment.

Nitrogen Alloyed 9-12% Chromium Steels with a Mertensitic-Austenitic Microstructure

In this work, a new alloy design for 9-12% chromium steels is proposed. The main objectives of the design are the replacement of the fully martensitic structure by a martensitic-austenitic microstructure and the replacement of carbon by nitrogen in order to obtain fine and stable precipitates of V-nitride instead of coarse Cr-carbide. The microstructure consists of lamellar austenite within a matrix of tempered martensite. Because of the fine distribution of austenite, this structure is referred to as microduplex structure. Microduplex steels provide a good combination of strength and toughness and especially high creep strength.

Improvement of Ionic Conductivity of Room Temperature Molten Salt Based on Quaternary Ammonium Cation and Imide Anion

The improvement of the conductivity of room temperature molten salt (RTMS) based on quaternary aliphatic ammonium cations (QA) and bis(trifluoromethanesulfon)imide was investigated. The conductivity was apparently increased with decreasing molecular weight of cation. The lightest cation was trimethylpropylammonium, which indicate relatively high conductivity of 4.0 mS cm−1 (30°C). Further improvement could be performed by slight modifications such as an addition of a methyl group and a replacement of carbon to oxygen in the alkyl side chain. The effect of such modifications to the conductivity was attributed to the difference of dipole moment of QA estimated by MOPAC. The electrochemical properties of RTMS based on QA were also investigated. The cathodic limits of RTMS based on QA were different according to the cationic structure. Since the most negative cathodic limit obtained was −0.4 V vs. Li/Li+, the plating and stripping behavior of lithium on Ni could be performed in the RTMS based on QA.

Formation of Si3N4 and SiC composite by nitrogen implantation

Silicon carbide was implanted with 50 keV nitrogen at elevated temperature up to 1100°C in order to form a composite of SiC and Si 3 N 4 . The depth profiles, the chemical state of the elements and the structure of the implanted surface were measured using Rutherford backscattering (RBS), nuclear resonance analysis (NRA), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and glancing angle X-ray diffraction (G-XRD). With increasing nitrogen fluence a replacement of carbon by nitrogen took place and β-Si 3 N 4 crystallites were formed on β-SiC surface at 1100°C, and the maximum concentration and halfwidth of the nitrogen profile implanted at 1100°C decreased in comparison with those implanted at <930°C. Preferential loss of graphite-like carbon produced by the nitrogen implantation was promoted by the irradiation with hydrogen radical beam during the nitrogen implantation, and the amount of β-Si 3 N 4 crystallites gradually increased

Effect of fiber coating on lifetime of Nicalon fiber-silicon carbide composites in air

Studies of the lifetime of Nicalon fiber-reinforced SiC matrix composites subjected to flexural stresses were conducted at temperatures of 600 and 950°C in air. The objective of this study was to evaluate the effectiveness of selected fiber coatings; i.e., carbon, boron-doped carbon (B-doped C), and boron nitride (BN), on the time-to-failure of Nicalon-SiC composites. Results at 600 and 950°C showed that the composite having a B-doped C fiber coating exhibited lifetimes that depend upon stress and temperature as found earlier for a composite with a carbon fiber coating. However, the replacement of the undoped carbon with a B-doped C fiber coating increased the lifetime by 10–100-fold and the apparent fatigue limit by a factor of two (to ≈150 MPa). On the other hand, the lifetime of composites at 950°C with a BN fiber coating was insensitive to the applied stress for levels up to ≈200 MPa (fatigue limit level) and was up to a thousand-fold longer than those composites having either B-doped C or undoped carbon fiber coatings. However, at 600°C, the composite with a BN fiber coating did exhibit a stress-dependent lifetime with an apparent fatigue limit of ≈150 MPa. The lifetime-limiting process in both of these composites is due to the progressive oxidation of the interface region and formation of boron-containing silicate glass, which forms a strong interfacial bond between fiber and matrix, (thus, high debond stress and interfacial shear stress), resulting in embrittlement of the composites.

Compositional changes of silicon carbide induced by nitrogen implantation

In order to form a composite of SiC and Si 3N 4 on a SiC surface polycrystalline SiC was irradiated with a 50-keV nitrogen ion beam with or without a hydrogen radical beam at elevated temperature up to 1100°C. The depth profiles, the chemical state of elements and the structure of the implanted surface were measured using RBS, NRA, AES, XPS and G-XRD. It was found that graphite-like carbon produced by the nitrogen implantation at 1100°C segregated at the surface and carbon depletion layer are formed beneath the surface. With increasing nitrogen fluence the replacement of carbon by nitrogen took place and β-Si 3N 4 crystallites were formed on the SiC surface. Preferential loss of carbon atoms in the implanted layer was promoted by irradiation with a hydrogen radical beam during the nitrogen implantation, and the amount of β-Si 3N 4 crystallites gradually increased.

Elevated temperature solid particle erosion of silicon carbide continuous fibre reinforced calcium aluminosilicate glass-ceramic matrix composite

A unidirectional silicon carbide continuous fibre reinforced calcium aluminusilicate (CAS/SiC) glass-ceramic matrix composite has been subjected to silica sand solid particle erosion over the temperature range 20 to 726 °C. At room temperature, tests were conducted at two velocities. The lower (7 m s −1) did not generate lateral cracks and a wear rate of 0.004 mg g −1 was observed. At the higher velocity (24 m s −1), lateral cracking was the main mechanism of material removal and an increased wear rate was found. The higher velocity wear rate of 0.16 mg g −1 at room temperature increased to 0.26 ± 0.02 mg g −1 at all other temperatures. Increasing the temperature of the test leads to smoother wear surfaces exhibiting an increasing contribution from plasticity. The reasons for the increase in wear rate from room temperature to 400 °C are unclear. They are not consistent with the release of residual axial tensile stresses in the matrix resulting from mismatches in the coefficients of thermal expansion of the two phases on cooling down from the processing temperature. Above 400 °C the changes are broadly consistent with the replacement of carbon by silica at the fibre-matrix interface, release of residual stress and softening of the glass-ceramic matrix.