Combined Effect Of Carbon Research Articles

Carbon encapsulated CdTe nanorods to execute the enhanced and photo corrosion free hydrogen production

We present carbon-encapsulated CdTe nanorods synthesized through a well-established hydrothermal method. The impact of varying weight percentages of carbon on CdTe nanorods has been explored. XRD, HR-TEM, XPS, Raman and UV-Vis characterization techniques are used to examine the physicochemical and optical properties of prepared compounds. The loading of the carbon layer can be regulated by varying the quantity of sucrose utilized during the synthesis process. The optimized photocatalyst exhibits a superior rate of hydrogen evolution at 247.7 mmol. h−1. g−1cat compared to bare CdTe nanorods. Here, the carbon layer serves a dual purpose as a photocorrosion inhibitor and facilitates electron tunneling for surface reactions. This combined effect of carbon on CdTe is responsible for the observed improvement in the hydrogen evolution rate. As the loading of carbon varies, the activity is aligning closely with the light penetration effect in photocatalysis. Furthermore, we investigated the durability of the optimized photocatalyst, revealing that it retains 89 % of its initial activity even after five cycles. After the activity experiments, essential characterizations such as XRD, Raman and XPS were also analyzed, and the solar to H2 conversion efficiency was computed.

Arsenic resistance and horizontal gene transfer are associated with carbon and nitrogen enrichment in bacteria

Coastal waters are confluences receiving large amounts of point and non-point sources of pollution. An attempt was made to explore microbial community interactions in response to carbon, nitrogen and metal pollution. Additionally, experiments were designed to analyze the influence of these factors on horizontal gene transfer (HGT). Shift in bacterial diversity dynamics by arsenic stress and nutrient addition in coastal waters was explored by metagenomics of microcosm setups. Phylogenetic analysis revealed equal distribution of Gammaproteobacteria (29%) and Betaproteobacteria (28%) in control microcosm. This proportional diversity from control switched to unique distribution of Gammaproteobacteria (44.5%)> Flavobacteria (17.7%)> Bacteriodia (11.92%)> Betaproteobacteria (11.52%) in microcosm supplemented with carbon, nitrogen and metal (C + N + M). Among metal-stressed systems, alpha diversity analysis indicated highest diversity of genera in C + N + M followed by N + M > C+M> metal alone. Arsenic and ampicillin sensitive E. coli XL1 blue and environmental strains (Vibrio tubiashii W85 and E. coli W101) were tested for efficiency of uptake of plasmid (P) pUCminusMCS (arsBRampR) under varying stress conditions. Transformation experiments revealed that combined effect of carbon, nitrogen and metal on horizontal gene transfer (HGT) was significantly higher (p < 0.01) than individual factors. The effect of carbon on HGT was proved to be superior to nitrogen under metal stressed conditions. Presence of arsenic in experimental setups (P + M, P + N + M and P + C + M) enhanced the HGT compared to non-metal counterparts supplemented with carbon or nitrogen. Arsenic resistant bacterial isolates (n = 200) were tested for the ability to utilize various carbon and nitrogen substrates and distinct positive correlation (p < 0.001) was found between arsenic resistance and utilization of urea and nitrate. However, evident positive correlation was not found between carbon sources and arsenic resistance. Our findings suggest that carbon and nitrogen pollution in aquatic habitats under arsenic stress determine the microbial community dynamics and critically influence uptake of genetic material from the surrounding environment.

The combined effect of carbon and chromium enrichment on 〈1 0 0〉 loop absorption in iron

In this work we study the effects of C and Cr enrichment of 〈100〉 dislocation loops (DL) on their absorption and obstacle strength when interacting with an edge dislocation. To do so, we have i) developed a C-Cr cross potential based on density functional theory data as part of a ternary FeCrC interatomic potential; ii) performed exchange Monte Carlo simulations employing the developed interatomic potential to obtain the distribution of the solutes enriching the DL in the energetically optimum configurations; iii) performed large scale molecular dynamics simulations employing the interatomic potential to characterize the interaction between an edge dislocation line and the decorated DL. We found that the obstacle stress scales to the same obstacle strength regardless the DL density. On the other hand, we found that C, the level of Cr enrichment, loop size and interaction temperature have a significant impact on the obstacle strength and level of absorption of the loops. The presented results can be used to help parameterize and validate discrete dislocation dynamics codes and therein integrated constitutive laws to enable accounting for irradiation-induced chemical segregation effects.

Combined effect of Fe-Si alloys and carbon on Si3N4 stability at elevated temperatures

The combined effect of carbon and Fe-Si alloys on Si3N4 was explored by heat treating Si3N4 materials at 1500 °C and 1600 °C in flowing nitrogen. The phase compositions and microstructures were characterized by XRD and SEM, respectively. The reaction degree was analysed based on the mass variation in the system. Combined with a thermodynamic assessment, the reaction mechanism was studied and proposed. The results show that the coexistence of Fe-Si alloys and carbon accelerates the phase transformation from Si3N4 to SiC and worsens the strength of Si3N4 materials. Fe-Si alloys accelerate the deposition of CO gas to free carbon and accelerate the decomposition of Si3N4 to Si. The in situ-formed Si can react with carbon, thus accelerating the thermodynamic and kinetic formation of SiC. Along with the growth of pores and the deterioration of the wettability of Fe-Si alloys during this process, the microstructure changes from a network constituted by Si3N4 columns/whiskers to porous SiC particles with weak linkages, which leads to the failure of Si3N4 materials. Therefore, the combined effect of Fe-Si alloys and carbon is harmful for Si3N4 materials at 1500–1600 °C.

Carbon and nitrogen inputs differentially affect priming of soil organic matter in tropical lowland and montane soils

Microbial decomposition of soil organic matter (SOM) can be accelerated or reduced by the combined effects of carbon (C) and nutrient inputs through a phenomenon known as ‘priming’. Tropical lowland and montane soils contain large stores of C and may undergo substantial future changes in C and nutrient inputs due to global change, yet how these inputs might interact to influence priming is poorly understood in these ecosystems. We addressed this question using soils from a 3400 m tropical elevation gradient which vary strongly in nitrogen (N) and phosphorus (P) availability. To determine how existing nutrient availability in different tropical soils regulates microbial activity, and whether microbial demand for nutrients leads to priming, soils were amended with simple and more complex 13C-labelled substrates in combination with inorganic N, P and N + P. Isotopic partitioning (13C in CO2 and in phospholipid fatty acids; PLFA) was used to identify sources of C (substrate- or SOM-derived) in respiration and in microbial communities. Nutrient treatments did not influence the amount of substrate-respired C for any of the soils, but did affect the direction and magnitude of priming effects. For the upper montane forest and grassland soils, C addition had a relatively minor influence on the turnover of SOM, but N addition (with or without C) reduced SOM mineralisation (negative priming), suggesting reduced microbial N-mining from SOM when N was externally supplied. By contrast, in the lower montane and lowland forest soils, C addition increased SOM mineralisation (positive priming), but the response was unaffected by nutrient additions. The assimilation of 13C substrates into functionally active microorganisms revealed that C substrate complexity, but not added nutrients, strongly affected C-use within the microbial community: in both lowland and montane forest soils, fungi assimilated a greater proportion of the simple C substrate, while gram-positive bacteria assimilated a greater proportion of the more complex C substrate. Overall, our results have contrasting implications for the response of soil C cycling in tropical montane and lowland ecosystems under future global change.

A study on the combined effects of carbon and nitrogen source on high added value products synthesis by Nannochloropsis oceanica CCMP1779 using response surface methodology

Response surface methodology (RSM) was used to evaluate the combined effect of the initial carbon (NaHCO3) and nitrogen (NaNO3) source concentration on the synthesis of high added value products by Nannochloropsis oceanica CCMP1779, applying a 22 full-factorial central composite design with four axial points. Biomass and lipid production were influenced by the variations of the tested parameters. Highest biomass production (0.581 g/L) and specific growth rate (0.279 d−1) were obtained at high carbon concentration, while low nitrogen concentration favors the lipids accumulation (highest lipid content 44.65 g/100 g DCW). The fatty acids (FAs) profile of N. oceanica CCMP1779 was dominated by saturated (SFAs) and monounsaturated fatty acids (MUFAs), comprising 88–95% of the total FAs, while polyunsaturated acids (PUFAs) accounted for 5–11%. Palmitic (C16:0), palmitoleic (C16:1 n-7), oleic acid (C18:1 n-9), myristic (C14:0) and eicosapentaenoic acid (C20:5 n-3) (EPA) were the major FAs detected and their content depended on the (NaHCO3) and nitrogen (NaNO3) combination. Optimization of through RSM indicated that a combination of 1.3 g/L NaHCO3 and 0.06 g/L NaNO3 maximizes the FAs accumulation and MUFAs content, while the above conditions have the exact opposite effect on PUFAs and EPA content.

Combined effects of carbon, nitrogen and phosphorus on CH4 production and denitrification in wetland sediments

Anthropogenic impacts and associated climate change are anticipated to change nutrient availability in wetlands. Changes in nutrient availability can affect major biogeochemical reactions (i.e., methanogenesis, denitrification) which impact greenhouse gas emissions and trophic status of ecosystems. However, the modulating role of nutrients in C and N cycles, and their resulting effects on interactions between methanogenesis and denitrification are poorly understood. Here, anaerobic slurry incubations were carried out to test the sole and combined effects of C, N and P on methanogenesis and denitrification in wetland sediments. Three levels of N (as KNO3) were added, and three levels of P (as KH2PO4), either with or without C (as CH3COOH) additions during laboratory slurry incubations. We investigated potential CH4 production, denitrification, physico-chemical properties of sediment and pore water and abundances of methanogens and denitrifiers by using functional genes (mcrA and nirS). N addition significantly inhibited CH4 production (Mean 8.6±10.8μmolg−1 d.w) compared to the treatment without N addition (Mean 28.2±18.1μmolg−1 d.w) during incubation, irrespective of C addition. P addition did not directly influence methanogenesis. However, combined N and P addition decreased CH4 production (Mean 7.2±10.2μmolg−1 d.w) to a larger extent than sole N addition (Mean 11.3±11.9μmolg−1 d.w) due to increased substrate competition with denitrifiers. Interestingly, N and P addition in combination with C addition led to inhibition of CH4 production as well as denitrification. Combined with increasing ammonium and accumulating nitrite (NO2−), the observed inhibition suggests that a change of electron flow towards dissimilatory nitrate reduction to ammonium (DNRA) consumed more electron donors (i.e., acetate) in the process, reducing methanogenesis and denitrification. Our result suggests that P, especially in combination with other substrates, should be considered as an important modulating factor in greenhouse gas emissions (in particular CH4 and N2O) from wetlands.

Combined effects of carbon, phosphorus and nitrogen on lipid accumulation of Chlorella vulgaris in mixotrophic culture

AbstractBACKGROUNDMicroalgae biodiesel has attracted considerable attention, however, low lipid content has significantly restricted its development. Many research studies have demonstrated that nutrient deficiency is an important factor stimulating lipid accumulation in algal cells. This present study investigated the combined effects of nitrogen, phosphorus, and carbon on algal lipid accumulation by Chlorella vulgaris in mixotrophic culture.RESULTSPhosphorus at 0.2 g L−1 concentration inhibited Chlorella vulgaris growth but did not influence lipid accumulation. High concentration of NaNO3 (3.75 g L−1) inhibited both algal growth and lipid accumulation. Nitrogen sufficiency can stimulate lipid accumulation. Glucose limitation restricted both biomass production and lipid accumulation, resulting in lipid content decrease even under nitrogen sufficiency. CO2 was unable to satisfy the carbon demand for lipid accumulation when glucose was exhausted in mixotrophic culture. The initial C:N ratio of culture medium played an important role in algal lipid accumulation. Lipid content was maintained at 7.6–11.3% when the initial C:N of culture was less than 50, while it increased significantly to 23.9% with initial C:N of culture increased to 92.7.CONCLUSIONSuperior lipid accumulation requires limiting nitrogen concentration in the medium solution. High initial C:N ratio greater than 86 was found to be beneficial for algal lipid accumulation. © 2014 Society of Chemical Industry

Combined effects of carbon and phosphorus levels on the invasive cyanobacterium, Cylindrospermopsis raciborskii

Wu Z., Zeng B., Li R. and Song L. 2012. Combined effects of carbon and phosphorus levels on the invasive cyanobacterium, Cylindrospermopsis raciborskii. Phycologia 51: 144–150. DOI: 10.2216.10.87.1The invasive cyanobacterium, Cylindrospermopsis raciborskii, was cultured semicontinuously for 18 days at different carbon and phosphorus levels. Growth and photosynthesis were measured to study the combined effects of CO2 and phosphorus availabilities. The results showed that enrichment of CO2 or inorganic phosphorus (Pi) levels in the culture medium significantly increased specific growth rate (μ), light-saturated photosynthesis (Pm) and photosynthetic efficiency (α), but tended to decrease dark respiratory rate (Rd), saturating irradiance for photosynthesis (Ek) and the light compensation point (Ec). However, photosynthetic responses to inorganic carbon concentration in C. raciborskii were affected by interactions between CO2 and Pi. At high Pi concentration, elevated CO2 significantly increased the inorganic carbon-saturated photosynthesis rate (Vmax) and substrate concentration giving half-maximal photosynthetic rate [K0.5 (DIC)], whereas at low Pi levels, elevated CO2 slightly decreased the values of Vmax and K0.5 (DIC). Additionally, enrichment with Pi significantly increased K0.5 (DIC) and Vmax regardless of the CO2 level, suggesting that Pi plays a role in photosynthetic carbon fixation in C. raciborskii. Furthermore, when C. raciborskii was batch cultured in different carbon and phosphorus concentrations for 72 h, the uptake rate of nitrogen increased with enrichment of both CO2 and Pi, while the uptake rate of phosphorus was enhanced only by increases in Pi concentration. The results suggest that the availability of CO2 and phosphorus have combined and independent effects on photosynthesis and nutrient uptake in C. raciborskii, reflecting that changes in environmental factors could influence the dominance of this invasive cyanobacterium. These combined effects need to be considered when generalizing this species response to changing CO2 levels.

The Stacking Fault Energy and its Dependence on the Interstitial Content in Various Austenitic Steels

The stacking fault energy (SFE) is an intrinsic property of metals and is involved in the deformation mechanism of different kind of steels, such as TWIP (twinning induced plasticity), TRIP (transformation induced plasticity), HNS (high nitrogen), and high strength steels. The dependence of the SFE on the content of interstitial elements (C, N) is not yet fully understood, and different tendencies have been found by different authors. In order to study the influence of the interstitial elements on the SFE, experimental measurements extracted from literature were collected and analyzed to predict the individual and combined effect of carbon and nitrogen in different systems. The referenced austenitic steels are Fe-22Mn-C, Fe-30Ni-C, Fe-15Cr-17Mn-N, Fe-18Cr-16Ni-10Mn-N, Fe-18Cr-9Mn-C-N, Fe-18Mn-18Cr-C-N and Fe-(20-30)Mn-12Cr-C-N. The calculation of the SFE is based on the Gibbs free energy of the austenite to ε-martensite transformation (ΔGγàε), which is calculated by means of the Calphad method. The revision of the measured values reveals that on different ranges of interstitial contents the SFE behaves differently. At lower values (C, N or C+N up to 0.4%), a local minimum or maximum is found in most of the systems. At higher concentration levels, a proportional dependence seems to occur. These observations agree with the theory of the dependence of SFE on the free electron concentration. Alloying with Mn or Ni has a strong influence on the electronic configuration and magnetic properties of the austenite and therefore on the SFE. The results of this study provide valuable information for materials design, especially in the context of alloying with C, N or C+N.

Seasonal and inter-annual variability of air–sea CO 2 fluxes and seawater carbonate chemistry in the Southern North Sea

A 3D coupled biogeochemical–hydrodynamic model (MIRO-CO 2&CO) is implemented in the English Channel (ECH) and the Southern Bight of the North Sea (SBNS) to estimate the present-day spatio-temporal distribution of air–sea CO 2 fluxes, surface water partial pressure of CO 2 (pCO 2) and other components of the carbonate system (pH, saturation state of calcite ( Ω ca) and of aragonite ( Ω ar)), and the main drivers of their variability. Over the 1994–2004 period, air–sea CO 2 fluxes show significant inter-annual variability, with oscillations between net annual CO 2 sinks and sources. The inter-annual variability of air–sea CO 2 fluxes simulated in the SBNS is controlled primarily by river loads and changes of biological activities (net autotrophy in spring and early summer, and net heterotrophy in winter and autumn), while in areas less influenced by river inputs such as the ECH, the inter-annual variations of air–sea CO 2 fluxes are mainly due to changes in sea surface temperature and in near-surface wind strength and direction. In the ECH, the decrease of pH, of Ω ca and of Ω ar follows the one expected from the increase of atmospheric CO 2 (ocean acidification), but the decrease of these quantities in the SBNS during the considered time period is faster than the one expected from ocean acidification alone. This seems to be related to a general pattern of decreasing nutrient river loads and net ecosystem production (NEP) in the SBNS. Annually, the combined effect of carbon and nutrient loads leads to an increase of the sink of CO 2 in the ECH and the SBNS, but the impact of the river loads varies spatially and is stronger in river plumes and nearshore waters than in offshore waters. The impact of organic and inorganic carbon (C) inputs is mainly confined to the coast and generates a source of CO 2 to the atmosphere and low pH, of Ω ca and of Ω ar values in estuarine plumes, while the impact of nutrient loads, highest than the effect of C inputs in coastal nearshore waters, also propagates offshore and, by stimulating primary production, drives a sink of atmospheric CO 2 and higher values of pH, of Ω ca and of Ω ar.

Combined effects of carbon, nitrogen and phosphorus substrates on D‐ribose production via transketolase deficient strain of Bacillus pumilus

AbstractBACKGROUND: D‐ribose, a five carbon sugar, can be produced via mutant strains with impairment in the non‐oxidative part of the pentose phosphate pathway (PPP). D‐ribose is an important intermediate in the pharmaceutical industry. This work focuses on the effect of various substrates on D‐ribose production with a transketolase deficient strain of Bacillus pumilus IFO13322.RESULT: D‐ribose titer is found to increase with a concomitant decrease in the yield (on a g product g−1 substrate basis) with increasing glucose concentration. Likewise, higher concentration of ammonium sulfate led to lower product yield while glucose and corn steep liquor concentrations were kept unaltered. Among the complex nitrogen substrates, cas amino acids showed better product yield than corn steep liquor. When tested for supplements of defined amino acids, media supplemented with tyrosine, phenylalanine, tryptophan and histidine gave better yields and higher biomass growth. This is possibly due to the fact that mutant strain is an aromatic amino acids auxotroph owing to impairment in aromatic amino acid biosynthesis. Further, higher phosphate concentrations in the media led to greater biomass formation and lower D‐ribose yield.CONCLUSIONS: At higher glucose or ammonium sulfate concentrations, a greater proportion of the carbon was channeled toward byproducts such as acetate, and acetoin and biomass formation. Thus, the relative rates of PPP and in turn the D‐ribose yield were dependent on not only the carbon substrate concentration but also the nitrogen and phosphorus substrates. Copyright © 2008 Society of Chemical Industry

Influence of alloying element additions on tribological behaviour of sintered steels with high content in manganese–nickel

Manganese and nickel are alloying elements with a high hardenability. Manganese is an excellent substitute for nickel due to its low cost but presents a great affinity for oxygen. In this work, the friction and wear behaviour of sintered manganese–nickel steels, by a pin-on-disk test has been studied. The tests were made under dry conditions, 0.1 m/s and 10 N as linear speed and applied load, respectively. Wear behaviour was evaluated against spherical pin of martensitic stainless steel (49 HRC). High manganese–nickel sintered steels were manufactured with two levels of carbon: 0.3 and 0.7% by weight. The unique level of addition of pure electrolytic manganese and different prealloyed manganese–nickel (80Mn/20Ni, 55Mn/45Ni and 25Mn/75Ni) was 4% by weight. All the compositions were prepared by dry mixing in ball mill and compacted at 700 MPa using uniaxial pressing. The sintering was carried out at 1230 °C in 90N 2/10H 2 as protective atmosphere. Density, porosity and hardness were evaluated. After sintering, all samples were polished at the same surface conditions and friction coefficients and wear rates have been measured. A complete microstructural study of the different steels and their transversal wear tracks was carried out. Deformations of ferritic areas, closed surface porosity and austenite–martensite transformation during wear test were detected. For materials with 0.7% C, the combined effect of carbon and manganese increases wear resistance.

The combined effect of carbon and neutron radiation on molybdenum

The formation of defect clusters, spots and loops, in molybdenum due to neutron irradiation at 40°C was studied by transmission electron microscopy. Carbon promotes the heterogeneous nucleation of clusters and is responsible for the formation of resolvable dislocation loops. A saturation level in the density of spots and loops is attained after an exposure of approximately 10 19 nvt, independent of the carbon concentration and further irradiation produces defect interaction and a complex damage state. Annealing of the irradiated samples results in a decrease in the density of small spots and an increase in the density and size of the resolvable dislocation loops. The loops were identified as being interstitial in character; the spot clusters were inferred to be interstitial also.