WorldWideScience

Sample records for dynamic carbon content

  1. Effect of Charcoal Volatile Matter Content and Feedstock on Soil Microbe-Carbon-Nitrogen Dynamics

    Science.gov (United States)

    McClellan, T.; Deenik, J. L.; Hockaday, W. C.; Campbell, S.; Antal, M. J., Jr.

    2010-12-01

    Charcoal has important biogeochemical implications in soil—first as a means to sequester carbon, and second as a soil conditioner to potentially enhance soil quality and fertility. Volatile matter (VM) content is a property of charcoal which describes its degree of thermal alteration, or carbonization. Results from greenhouse experiments have shown that plant growth can be negatively affected by charcoals with high VM content (20-35%), with and without fertilizer supplements, whereas low VM charcoal (6-9%) increased plant growth when combined with fertilizer. We conducted two laboratory studies to characterize the VM content of charcoals derived from two feedstocks (corncob and kiawe) and relate observed differences to key aspects of soil fertility. Using Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (NMR), total phenol content (using a Prussian blue colorimetric assay), and gas chromatography-mass spectrometry (GC-MS), we found that the VM content of charcoal primarily consisted of alkanes, oxygen-substituted alkanes, and phenolic compounds. However, the GC-MS data indicated that charcoals can differ vastly in their extractable fraction, depending upon both VM content and feedstock. In a second set of experiments, we examined the effect of VM content and feedstock on soil microbial activity, available nitrogen (N), and soluble carbon (C). High VM corncob charcoals significantly enhanced microbial activity, coupled with net reduction in available N and soluble C. For a given feedstock, the extent of this effect was dependent upon VM content. However, the overall effect of VM content on microbial dynamics was apparently related to the composition of the acetone-extractable fraction, which was particularly important when comparing two charcoals derived from different feedstocks but with the equivalent VM contents. Removing the acetone-extractable fraction from the 23% VM corncob charcoal significantly reduced the enhancement of

  2. Coupled land surface-subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra

    Science.gov (United States)

    Phuong Tran, Anh; Dafflon, Baptiste; Hubbard, Susan S.

    2017-09-01

    Quantitative characterization of soil organic carbon (OC) content is essential due to its significant impacts on surface-subsurface hydrological-thermal processes and microbial decomposition of OC, which both in turn are important for predicting carbon-climate feedbacks. While such quantification is particularly important in the vulnerable organic-rich Arctic region, it is challenging to achieve due to the general limitations of conventional core sampling and analysis methods, and to the extremely dynamic nature of hydrological-thermal processes associated with annual freeze-thaw events. In this study, we develop and test an inversion scheme that can flexibly use single or multiple datasets - including soil liquid water content, temperature and electrical resistivity tomography (ERT) data - to estimate the vertical distribution of OC content. Our approach relies on the fact that OC content strongly influences soil hydrological-thermal parameters and, therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. We employ the Community Land Model to simulate nonisothermal surface-subsurface hydrological dynamics from the bedrock to the top of canopy, with consideration of land surface processes (e.g., solar radiation balance, evapotranspiration, snow accumulation and melting) and ice-liquid water phase transitions. For inversion, we combine a deterministic and an adaptive Markov chain Monte Carlo (MCMC) optimization algorithm to estimate a posteriori distributions of desired model parameters. For hydrological-thermal-to-geophysical variable transformation, the simulated subsurface temperature, liquid water content and ice content are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using different numerical experiments and evaluate the influence of measurement errors and benefit of joint inversion on the

  3. Coupled land surface–subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra

    Directory of Open Access Journals (Sweden)

    A. P. Tran

    2017-09-01

    Full Text Available Quantitative characterization of soil organic carbon (OC content is essential due to its significant impacts on surface–subsurface hydrological–thermal processes and microbial decomposition of OC, which both in turn are important for predicting carbon–climate feedbacks. While such quantification is particularly important in the vulnerable organic-rich Arctic region, it is challenging to achieve due to the general limitations of conventional core sampling and analysis methods, and to the extremely dynamic nature of hydrological–thermal processes associated with annual freeze–thaw events. In this study, we develop and test an inversion scheme that can flexibly use single or multiple datasets – including soil liquid water content, temperature and electrical resistivity tomography (ERT data – to estimate the vertical distribution of OC content. Our approach relies on the fact that OC content strongly influences soil hydrological–thermal parameters and, therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. We employ the Community Land Model to simulate nonisothermal surface–subsurface hydrological dynamics from the bedrock to the top of canopy, with consideration of land surface processes (e.g., solar radiation balance, evapotranspiration, snow accumulation and melting and ice–liquid water phase transitions. For inversion, we combine a deterministic and an adaptive Markov chain Monte Carlo (MCMC optimization algorithm to estimate a posteriori distributions of desired model parameters. For hydrological–thermal-to-geophysical variable transformation, the simulated subsurface temperature, liquid water content and ice content are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using different numerical experiments and evaluate the influence of measurement errors and

  4. Dynamic carbon content as an indicator of desertification processes in soils developed from volcanic parental material in the Region of Murcia

    International Nuclear Information System (INIS)

    Martinez-Martinez, S.; Faz Cano, A.; Acosta Aviles, J. A.

    2009-01-01

    Soil Organic Carbon (SOC is an essential components of the global carbon cycle, especially in soils developed from volcanic rocks, due to these soils does not have inorganic carbon. In arid and semiarid areas mineralization of organic carbon is very intense due to climatic conditions, causing soils depletion and therefore desertification. The objective of this study is to determine the content of OC, as a first step in the assessment of desertification. The objective of this study is to determine the content of OC, as a first step in the assessment of desertification processes affecting this area of the southeast of Spain. (Author) 7 refs.

  5. Organic carbon content of tropical zooplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.

    In the Zuari and Mandovi estuaries variations in organic carbon of zooplankton are 26.4-38.8 and 24-39.9% of dry weight respectively. Maximum carbon content of estuarine zooplankton is observed in November. Organic carbon in nearshore and oceanic...

  6. Determination of low carbon content in uranium

    International Nuclear Information System (INIS)

    Champeix, L.; Chevilliard, H.; Ponty, J.

    1960-01-01

    The method of carbon determination previously used for low carbon steels has been applied to uranium. Carbon contents down to a few tens p.p.m. and probably to a few p.p.m., can be determined with satisfactory precision, sensibility and accuracy. Reprint of a paper published in 'Memoires Scientifiques Rev. Metallurg.', LVI, n. 7, 1959, p. 657-662 [fr

  7. Carbon, chromium and molybdenum contents

    International Nuclear Information System (INIS)

    Sinatora, A; Goldenstein, H.; Mei, P.R.; Albertin, E.; Fuoco, R.; Mariotto, C.L.

    1992-01-01

    This work describes solidification experiments on white cast iron, with 15 and 20% of chromium, 2.3, 3.0 and 3.6 % of carbon and 0.0, 1.5 and 2.5 % of molybdenum in test de samples with 30 mm diameter. Measurements were performed on the austenite and eutectic formation arrests, the number of the eutectic carbide particles relative to the total and the eutectic volumes, and the volume fraction of the primary austenite

  8. Carbon fiber content measurement in composite

    Science.gov (United States)

    Wang, Qiushi

    Carbon fiber reinforced polymers (CFRPs) have been widely used in various structural applications in industries such as aerospace and automotive because of their high specific stiffness and specific strength. Their mechanical properties are strongly influenced by the carbon fiber content in the composites. Measurement of the carbon fiber content in CFRPs is essential for product quality control and process optimization. In this work, a novel carbonization-in-nitrogen method (CIN) is developed to characterize the fiber content in carbon fiber reinforced thermoset and thermoplastic composites. In this method, a carbon fiber composite sample is carbonized in a nitrogen environment at elevated temperatures, alongside a neat resin sample. The carbon fibers are protected from oxidization while the resin (the neat resin and the resin matrix in the composite sample) is carbonized under the nitrogen environment. The residue of the carbonized neat resin sample is used to calibrate the resin carbonization rate and calculate the amount of the resin matrix in the composite sample. The new method has been validated on several thermoset and thermoplastic resin systems and found to yield an accurate measurement of fiber content in carbon fiber polymer composites. In order to further understand the thermal degradation behavior of the high temperature thermoplastic polymer during the carbonization process, the mechanism and the kinetic model of thermal degradation behavior of carbon fiber reinforced poly (phenylene sulfide) (CPPS) are studied using thermogravimetry analysis (TGA). The CPPS is subjected to TGA in an air and nitrogen atmosphere at heating rates from 5 to 40°C min--1. The TGA curves obtained in air are different from those in nitrogen. This demonstrates that weight loss occurs in a single stage in nitrogen but in two stages in air. To elucidate this difference, thermal decomposition kinetics is analyzed by applying the Kissinger, Flynn-Wall-Ozawa, Coat-Redfern and

  9. Cast Iron With High Carbon Content

    Science.gov (United States)

    Curreri, P. A.; Hendrix, J. C.; Stefanescu, D. M.

    1986-01-01

    Method proposed for solidifying high-carbon cast iron without carbon particles segregating at upper surface. Solidification carried out in low gravity, for example on airplane flying free-fall parabolic trajectory. Many different microstructures obtained by proposed technique, and percentage by weight of carbon retained in melt much higher than at present.

  10. Terahertz Dynamics in Carbon Nanomaterials

    Science.gov (United States)

    Kono, Junichiro

    2012-02-01

    This NSF Partnerships for International Research and Education (PIRE) project supports a unique interdisciplinary and international partnership investigating terahertz (THz) dynamics in nanostructures. The 0.1 to 10 THz frequency range of the electromagnetic spectrum is where electrical transport and optical transitions merge, offering exciting opportunities to study a variety of novel physical phenomena in condensed matter. By combining THz technology and nanotechnology, we can advance our understanding of THz physics while improving and developing THz devices. Specifically, this PIRE research explores THz dynamics of electrons in carbon nanomaterials, namely, nanotubes and graphene --- low-dimensional, sp^2-bonded carbon systems with unique finite-frequency properties. Japan and the U.S. are global leaders in both THz research and carbon research, and stimulating cooperation is critical to further advance THz science and to commercialize products developed in the lab. However, obstacles exist for international collaboration --- primarily linguistic and cultural barriers --- and this PIRE project aims to address these barriers through the integration of our research and education programs. Our strong educational portfolio endeavours to cultivate interest in nanotechnology amongst young U.S. undergraduate students and encourage them to pursue graduate study and academic research in the physical sciences, especially those from underrepresented groups. Our award-winning International Research Experience for Undergraduates Program, NanoJapan, provides structured research internships in Japanese university laboratories with Japanese mentors --- recognized as a model international education program for science and engineering students. The project builds the skill sets of nanoscience researchers and students by cultivating international and inter-cultural awareness, research expertise, and specific academic interests in nanotechnology. U.S. project partners include Rice

  11. Inter-relationships between hydrogen and carbon contents of ...

    African Journals Online (AJOL)

    Empirical relationships between hydrogen and carbon contents and the calorific values of rice husks, cotton see-ds, jatropha seeds, palm kernel shells and cashew shells were investigated. The experimental data indicated higher correlation coefficient between calorific values and hydrogen content than between calorific ...

  12. Integrating plant carbon dynamics with mutualism ecology.

    Science.gov (United States)

    Pringle, Elizabeth G

    2016-04-01

    Plants reward microbial and animal mutualists with carbohydrates to obtain nutrients, defense, pollination, and dispersal. Under a fixed carbon budget, plants must allocate carbon to their mutualists at the expense of allocation to growth, reproduction, or storage. Such carbon trade-offs are indirectly expressed when a plant exhibits reduced growth or fecundity in the presence of its mutualist. Because carbon regulates the costs of all plant mutualisms, carbon dynamics are a common platform for integrating these costs in the face of ecological complexity and context dependence. The ecophysiology of whole-plant carbon allocation could thus elucidate the ecology and evolution of plant mutualisms. If mutualisms are costly to plants, then they must be important but frequently underestimated sinks in the terrestrial carbon cycle. © 2015 The Author. New Phytologist © 2015 New Phytologist Trust.

  13. Seasonal dynamic of content of 137Cs in mushrooms

    International Nuclear Information System (INIS)

    Zarubina, N.E.

    2007-01-01

    Researches of seasonal dynamics of content of 137 Cs in mushrooms were carried out. Under condition of selection, mushrooms of different kinds only 2 times in one year - in the beginning and in the end of vegetative period - are marked with increase of levels of specific activity of 137 Cs by autumn. During monthly selection of mushrooms, dynamics of the contents of 137 Cs carries spasmodic character. Seasonal dynamics of the contents of 137 Cs varies for mushrooms of different kinds

  14. Effect of carbon content on the mechanical properties of medium carbon steels

    Energy Technology Data Exchange (ETDEWEB)

    Calik, Adnan [Dept. of Mechanical Education, Suleyman Demirel Univ., Isparta (Turkey); Duzgun, Akin [Civil Engineering Dept., Ataturk Univ., Erzurum (Turkey); Sahin, Osman [Physics Dept., M. Kemal Univ., Hatay (Turkey); Ucar, Nazim [Physics Dept., Suleyman Demirel Univ., Isparta (Turkey)

    2010-05-15

    The mechanical properties of medium-carbon steels with a carbon content ranging from 0.30 to 0.55 wt.% were investigated by tensile and microhardness tests at room temperature. It was observed that the higher carbon content results in an increase in yield stress and ultimate tensile stress, while the elongation remains essentially constant. The results were explained by the hindering of dislocation motion associated with solid solution hardening. (orig.)

  15. Determination of free carbon content in boron carbide ceramic powders

    International Nuclear Information System (INIS)

    Castro, A.R.M. de; Lima, N.B. de; Paschoal, J.O.A.

    1990-01-01

    Boron carbide is a ceramic material of technological importance due to its hardness and high chemical and thermal stabilities. Free carbon is always found as a process dependent impurity in boron carbide. The development of procedures for its detection is required because its presence leads to a degradation of the boron carbide properties. In this work, several procedures for determining free carbon content in boron carbide specimens are reported and discussed for comparison purposes. (author) [pt

  16. Content of nitrogen in waste petroleum carbon for steel industries

    International Nuclear Information System (INIS)

    Rios, R.O; Jimenez, A.F; Szieber, C.W; Banchik, A.D

    2004-01-01

    Steel industries use refined carbon as an alloy for steel production. This alloy is produced from waste carbon from the distillation of the petroleum. The refined carbon, called recarburizer, is obtained by calcination at high temperature. Under these thermal conditions the organic molecules decompose and a fraction of the N 2 , S and H 2 , volatile material and moisture are released; while the carbon tends to develop a crystalline structure similar to graphite's. The right combination of calcinations temperature and time in the furnace can optimize the quality of the resulting product. The content of S and N 2 has to be minimized for the use of calcined carbon in the steel industry. Nitrogen content should be reduced by two orders of magnitude, from 1% - 2% down to hundreds of ppm by weight. This work describes the activities undertaken to obtain calcined coke from petroleum from crude oil carbon that satisfies the requirements of the Mercosur standard 02:00-169 (Pending) for use as a carborizer in steels industries. To satisfy the requirements of the Mercosur standards NM 236:00 IRAM-IAS-NM so that graphite is used as a carburizer a content of 300 ppm maximum weight of nitrogen has to be obtained. So the first stage in this development is to define a production process for supplying calcined coke in the range of nitrogen concentrations required by the Mercosur standards (CW)

  17. Caffeine content of energy drinks, carbonated sodas, and other beverages.

    Science.gov (United States)

    McCusker, Rachel R; Goldberger, Bruce A; Cone, Edward J

    2006-03-01

    The caffeine content of 10 energy drinks, 19 carbonated sodas, and 7 other beverages was determined. In addition, the variability of the caffeine content of Coca-Cola fountain soda was evaluated. Caffeine was isolated from the samples by liquid-liquid extraction and analyzed by gas chromatography with nitrogen-phosphorus detection. The caffeine concentration of the caffeinated energy drinks ranged from none detected to 141.1 mg/serving. The caffeine content of the carbonated sodas ranged from none detected to 48.2 mg/serving, and the content of the other beverages ranged from < 2.7 to 105.7 mg/serving. The intra-assay mean, standard deviation, and % coefficient of variation for the Coca-Cola fountain samples were 44.5, 2.95, and 6.64 mg/serving, respectively.

  18. Carbon dynamics in wetland restoration

    Energy Technology Data Exchange (ETDEWEB)

    Kovalenko, K.; Ciborowski, J.; Gardner-Costa, J.; Slama, C. [Windsor Univ., ON (Canada); Daly, C.; Hornung, J. [Suncor Energy, Calgary, AB (Canada); Dixon, G.; Farwell, A. [Waterloo Univ., ON (Canada); Foote, L.; Frederick, K.; Roy, M. [Alberta Univ., Edmonton, AB (Canada); Liber, K. [Saskatchewan Univ., Saskatoon, SK (Canada); Smits, J. [Calgary Univ., AB (Canada); Wytrykush, C. [Syncrude Canada Ltd., Edmonton, AB (Canada)

    2010-07-01

    This study focused on the reclamation of wetland ecosystems impacted by oil sands development in the boreal wetlands. Although these wetlands play an important role in global carbon balance, their ecosystem function is compromised by direct and regional anthropogenic disturbance and climate change. Large oil sand mining areas that require reclamation generate substantial quantities of extraction process-affected materials. In order to determine if the reclaimed wetlands were restored to equivalent ecosystem function, this study evaluated carbon flows and food web structure in oil sands-affected wetlands. The purpose was to determine whether a prescribed reclamation strategy or topsoil amendment accelerates reclaimed wetland development to produce self-sustaining peatlands. In addition to determining carbon fluxes, this study measured compartment standing stocks for residual hydrocarbons, organic substrate, bacterioplankton, phytoplankton, biofilm, macrophytes, detritus, zoobenthos and aquatic-terrestrial exports. Most biotic 28 compartments differed between oil-sands-affected and reference wetlands, but the difference lessened with age. Macroinvertebrate trophic diversity was lower in oil sands-affected wetlands. Peat amendment seemed to speed convergence for some compartments but not others. These results were discussed in the context of restoration of ecosystem function and optimization of reclamation strategies.

  19. Deforestation in Amazonia impacts riverine carbon dynamics

    Science.gov (United States)

    Langerwisch, Fanny; Walz, Ariane; Rammig, Anja; Tietjen, Britta; Thonicke, Kirsten; Cramer, Wolfgang

    2016-12-01

    Fluxes of organic and inorganic carbon within the Amazon basin are considerably controlled by annual flooding, which triggers the export of terrigenous organic material to the river and ultimately to the Atlantic Ocean. The amount of carbon imported to the river and the further conversion, transport and export of it depend on temperature, atmospheric CO2, terrestrial productivity and carbon storage, as well as discharge. Both terrestrial productivity and discharge are influenced by climate and land use change. The coupled LPJmL and RivCM model system (Langerwisch et al., 2016) has been applied to assess the combined impacts of climate and land use change on the Amazon riverine carbon dynamics. Vegetation dynamics (in LPJmL) as well as export and conversion of terrigenous carbon to and within the river (RivCM) are included. The model system has been applied for the years 1901 to 2099 under two deforestation scenarios and with climate forcing of three SRES emission scenarios, each for five climate models. We find that high deforestation (business-as-usual scenario) will strongly decrease (locally by up to 90 %) riverine particulate and dissolved organic carbon amount until the end of the current century. At the same time, increase in discharge leaves net carbon transport during the first decades of the century roughly unchanged only if a sufficient area is still forested. After 2050 the amount of transported carbon will decrease drastically. In contrast to that, increased temperature and atmospheric CO2 concentration determine the amount of riverine inorganic carbon stored in the Amazon basin. Higher atmospheric CO2 concentrations increase riverine inorganic carbon amount by up to 20 % (SRES A2). The changes in riverine carbon fluxes have direct effects on carbon export, either to the atmosphere via outgassing or to the Atlantic Ocean via discharge. The outgassed carbon will increase slightly in the Amazon basin, but can be regionally reduced by up to 60 % due to

  20. Soil organic carbon dynamics jointly controlled by climate, carbon inputs, soil properties and soil carbon fractions.

    Science.gov (United States)

    Luo, Zhongkui; Feng, Wenting; Luo, Yiqi; Baldock, Jeff; Wang, Enli

    2017-10-01

    Soil organic carbon (SOC) dynamics are regulated by the complex interplay of climatic, edaphic and biotic conditions. However, the interrelation of SOC and these drivers and their potential connection networks are rarely assessed quantitatively. Using observations of SOC dynamics with detailed soil properties from 90 field trials at 28 sites under different agroecosystems across the Australian cropping regions, we investigated the direct and indirect effects of climate, soil properties, carbon (C) inputs and soil C pools (a total of 17 variables) on SOC change rate (r C , Mg C ha -1  yr -1 ). Among these variables, we found that the most influential variables on r C were the average C input amount and annual precipitation, and the total SOC stock at the beginning of the trials. Overall, C inputs (including C input amount and pasture frequency in the crop rotation system) accounted for 27% of the relative influence on r C , followed by climate 25% (including precipitation and temperature), soil C pools 24% (including pool size and composition) and soil properties (such as cation exchange capacity, clay content, bulk density) 24%. Path analysis identified a network of intercorrelations of climate, soil properties, C inputs and soil C pools in determining r C . The direct correlation of r C with climate was significantly weakened if removing the effects of soil properties and C pools, and vice versa. These results reveal the relative importance of climate, soil properties, C inputs and C pools and their complex interconnections in regulating SOC dynamics. Ignorance of the impact of changes in soil properties, C pool composition and C input (quantity and quality) on SOC dynamics is likely one of the main sources of uncertainty in SOC predictions from the process-based SOC models. © 2017 John Wiley & Sons Ltd.

  1. Stable isotope compositions of organic carbon and contents of ...

    African Journals Online (AJOL)

    The stable isotope compositions of organic carbon (OC), and contents of OC and nitrogen for four sediment cores recovered from lakes Makat (located in the Ngorongoro Crater), Ndutu and Masek (located in the Serengeti Plains) are used to document sources of organic matter (OM) and climatic changes in sub-arid ...

  2. Method for creating high carbon content products from biomass oil

    Science.gov (United States)

    Parker, Reginald; Seames, Wayne

    2012-12-18

    In a method for producing high carbon content products from biomass, a biomass oil is added to a cracking reactor vessel. The biomass oil is heated to a temperature ranging from about 100.degree. C. to about 800.degree. C. at a pressure ranging from about vacuum conditions to about 20,700 kPa for a time sufficient to crack the biomass oil. Tar is separated from the cracked biomass oil. The tar is heated to a temperature ranging from about 200.degree. C. to about 1500.degree. C. at a pressure ranging from about vacuum conditions to about 20,700 kPa for a time sufficient to reduce the tar to a high carbon content product containing at least about 50% carbon by weight.

  3. Determination of contents of carbonate and hydrogen carbonate in solutions for alkaline leading of uranium ores

    International Nuclear Information System (INIS)

    Radil, V.

    1988-01-01

    The new analytical method is based on the determination of the molar ratio carbonate - hydrogen carbonate using the measured concentration of hydrogen ions, the determination of the dissociation constant of carbonic acid for different values of ionic strength. The concentration of hydrogen ions was measured with a Metrohm 632 pH meter with the use of a combined glass electrode. The content of total carbonate carbon was determined coulometrically and the uranium content was determined by extraction with tributyl phosphate and by spectrometry of the complex of uranyl ions with Arsenazo III. Model solutions were used for the experiments which contained a high concentration of sulfate ions, thiosulfate ions, uranium and various proportions of carbonate and hydrogen carbonate. The composition of the individual samples of the extraction solutions are tabulated. The calibration was made of the glass combined electrode at different ionic strength, the values determined of dissociation constants of carbonic acid for different ionic strength. The mathematical procedure is described for the calculation of molar concentrations of carbonate and hudrogen carbonate and the results are presented of the analysis of model solutions. (E.S.). 5 tabs., 1 fig., 5 refs

  4. Denuded zone in Czochralski silicon wafer with high carbon content

    International Nuclear Information System (INIS)

    Chen Jiahe; Yang Deren; Ma Xiangyang; Que Duanlin

    2006-01-01

    The thermal stability of the denuded zone (DZ) created by high-low-high-temperature annealing in high carbon content (H[C]) and low carbon content (L[C]) Czochralski silicon (Cz-Si) has been investigated in a subsequent ramping and isothermal 1050 deg. C annealing. The tiny oxygen precipitates which might occur in the DZ were checked. It was found in the L[C] Cz-Si that the DZ shrank and the density of bulk micro-defects (BMDs) reduced with the increase of time spent at 1050 deg. C. Also, the DZs above 15 μm of thickness present in the H[C] Cz-Si wafers continuously and the density and total volume of BMDs first decreased then increased and finally decreased again during the treatments. Moreover, tiny oxygen precipitates were hardly generated inside the DZs, indicating that H[C] Cz-Si wafers could support the fabrication of integrated circuits

  5. Denuded zone in Czochralski silicon wafer with high carbon content

    Science.gov (United States)

    Chen, Jiahe; Yang, Deren; Ma, Xiangyang; Que, Duanlin

    2006-12-01

    The thermal stability of the denuded zone (DZ) created by high-low-high-temperature annealing in high carbon content (H[C]) and low carbon content (L[C]) Czochralski silicon (Cz-Si) has been investigated in a subsequent ramping and isothermal 1050 °C annealing. The tiny oxygen precipitates which might occur in the DZ were checked. It was found in the L[C] Cz-Si that the DZ shrank and the density of bulk micro-defects (BMDs) reduced with the increase of time spent at 1050 °C. Also, the DZs above 15 µm of thickness present in the H[C] Cz-Si wafers continuously and the density and total volume of BMDs first decreased then increased and finally decreased again during the treatments. Moreover, tiny oxygen precipitates were hardly generated inside the DZs, indicating that H[C] Cz-Si wafers could support the fabrication of integrated circuits.

  6. Validity of estimating the organic carbon content of basin sediment using color measurements

    International Nuclear Information System (INIS)

    Sasaki, Toshinori; Sugai, Toshihiko; Ogami, Takashi; Yanagida, Makoto; Yasue, Ken-ichi

    2010-01-01

    Psychometric lightness (L* value) measured by a colorimeter offers a rapid means of obtaining the organic carbon content of sediment. We measured peat and lacustrine sediments covering the past 300 ka - 106 samples for L* value and 197 samples for organic carbon content. L* values are highly correlated with organic carbon contents. Therefore, L* values are a convenient alternative to measuring organic carbon contents. (author)

  7. Dynamic replacement and loss of soil carbon on eroding cropland

    Science.gov (United States)

    Harden, J.W.; Sharpe, J.M.; Parton, W.J.; Ojima, D.S.; Fries, T.L.; Huntington, T.G.; Dabney, S.M.

    1999-01-01

    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.

  8. Measurement of carbon storage in landfills from the biogenic carbon content of excavated waste samples.

    Science.gov (United States)

    De la Cruz, Florentino B; Chanton, Jeffrey P; Barlaz, Morton A

    2013-10-01

    Landfills are an anaerobic ecosystem and represent the major disposal alternative for municipal solid waste (MSW) in the U.S. While some fraction of the biogenic carbon, primarily cellulose (Cel) and hemicellulose (H), is converted to carbon dioxide and methane, lignin (L) is essentially recalcitrant. The biogenic carbon that is not mineralized is stored within the landfill. This carbon storage represents a significant component of a landfill carbon balance. The fraction of biogenic carbon that is not reactive in the landfill environment and therefore stored was derived for samples of excavated waste by measurement of the total organic carbon, its biogenic fraction, and the remaining methane potential. The average biogenic carbon content of the excavated samples was 64.6±18.0% (average±standard deviation), while the average carbon storage factor was 0.09±0.06g biogenic-C stored per g dry sample or 0.66±0.16g biogenic-C stored per g biogenic C. Published by Elsevier Ltd.

  9. Modelling and mapping the topsoil organic carbon content for Tanzania

    Science.gov (United States)

    Kempen, Bas; Kaaya, Abel; Ngonyani Mhaiki, Consolatha; Kiluvia, Shani; Ruiperez-Gonzalez, Maria; Batjes, Niels; Dalsgaard, Soren

    2014-05-01

    Soil organic carbon (SOC), held in soil organic matter, is a key indicator of soil health and plays an important role in the global carbon cycle. The soil can act as a net source or sink of carbon depending on land use and management. Deforestation and forest degradation lead to the release of vast amounts of carbon from the soil in the form of greenhouse gasses, especially in tropical countries. Tanzania has a high deforestation rate: it is estimated that the country loses 1.1% of its total forested area annually. During 2010-2013 Tanzania has been a pilot country under the UN-REDD programme. This programme has supported Tanzania in its initial efforts towards reducing greenhouse gas emission from forest degradation and deforestation and towards preserving soil carbon stocks. Formulation and implementation of the national REDD strategy requires detailed information on the five carbon pools among these the SOC pool. The spatial distribution of SOC contents and stocks was not available for Tanzania. The initial aim of this research, was therefore to develop high-resolution maps of the SOC content for the country. The mapping exercise was carried out in a collaborative effort with four Tanzanian institutes and data from the Africa Soil Information Service initiative (AfSIS). The mapping exercise was provided with over 3200 field observations on SOC from four sources; this is the most comprehensive soil dataset collected in Tanzania so far. The main source of soil samples was the National Forest Monitoring and Assessment (NAFORMA). The carbon maps were generated by means of digital soil mapping using regression-kriging. Maps at 250 m spatial resolution were developed for four depth layers: 0-10 cm, 10-20 cm, 20-30 cm, and 0-30 cm. A total of 37 environmental GIS data layers were prepared for use as covariates in the regression model. These included vegetation indices, terrain parameters, surface temperature, spectral reflectances, a land cover map and a small

  10. Sequestration of organochlorine pesticides in soils of distinct organic carbon content

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Na [Laboratory for Earth Surface Processing, College of Urban and Environmental Sciences, Peking University, Beijing 100871 (China); State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); Yang Yu [Laboratory for Earth Surface Processing, College of Urban and Environmental Sciences, Peking University, Beijing 100871 (China); Tao Shu, E-mail: taos@urban.pku.edu.cn [Laboratory for Earth Surface Processing, College of Urban and Environmental Sciences, Peking University, Beijing 100871 (China); Liu Yan; Shi Kelu [Laboratory for Earth Surface Processing, College of Urban and Environmental Sciences, Peking University, Beijing 100871 (China)

    2011-03-15

    In the present study, five soil samples with organic carbon contents ranging from 0.23% to 7.1% and aged with technical dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) for 15 months were incubated in a sealed chamber to investigate the dynamic changes of the OCP residues. The residues in the soils decreased over the incubation period and finally reached a plateau. Regression analysis showed that degradable fractions of OCPs were negatively correlated with soil organic carbon (SOC) except for {alpha}-HCH, while no correlation was found between degradation rate and SOC, which demonstrated that SOC content determines the OCP sequestration fraction in soil. Analysis of the ratio of DDT and its primary metabolites showed that, since it depends on differential sequestration among them, magnitude of (p,p'-DDE + p,p'-DDD)/p,p'-DDT is not a reliable criterion for the identification of new DDT sources. - Research highlights: > Soil organic carbon content determines the OCP sequestration fraction in soil. > Magnitude of (p,p'-DDE + p,p'-DDD)/p,p'-DDT is not a reliable criterion for the identification of new DDT sources. > The more hydrophobic compounds have relatively higher sequestration fractions in soils with SOC contents >2%. > DDD may have higher sorption by soil organic matter than DDE. - The effect of soil organic matter on the sequestration of organochlorine pesticides (HCHs and DDTs) in soils was investigated in an innovative microcosm chamber.

  11. Aggregate and soil organic carbon dynamics in South Chilean Andisols

    Science.gov (United States)

    Huygens, D.; Boeckx, P.; Van Cleemput, O.; Oyarzún, C.; Godoy, R.

    2005-06-01

    Extreme sensitivity of soil organic carbon (SOC) to climate and land use change warrants further research in different terrestrial ecosystems. The aim of this study was to investigate the link between aggregate and SOC dynamics in a chronosequence of three different land uses of a south Chilean Andisol: a second growth Nothofagus obliqua forest (SGFOR), a grassland (GRASS) and a Pinus radiata plantation (PINUS). Total carbon content of the 0-10cm soil layer was higher for GRASS (6.7 kg C m-2) than for PINUS (4.3 kg C m-2, while TC content of SGFOR (5.8 kg C m-2) was not significantly different from either one. High extractable oxalate and pyrophosphate Al concentrations (varying from 20.3-24.4 g kg-1, and 3.9-11.1 g kg-1, respectively) were found in all sites. In this study, SOC and aggregate dynamics were studied using size and density fractionation experiments of the SOC, δ13C and total carbon analysis of the different SOC fractions, and C mineralization experiments. The results showed that electrostatic sorption between and among amorphous Al components and clay minerals is mainly responsible for the formation of metal-humus-clay complexes and the stabilization of soil aggregates. The process of ligand exchange between SOC and Al would be of minor importance resulting in the absence of aggregate hierarchy in this soil type. Whole soil C mineralization rate constants were highest for SGFOR and PINUS, followed by GRASS (respectively 0.495, 0.266 and 0.196 g CO2-Cm-2d-1 for the top soil layer). In contrast, incubation experiments of isolated macro organic matter fractions gave opposite results, showing that the recalcitrance of the SOC decreased in another order: PINUS>SGFOR>GRASS. We deduced that electrostatic sorption processes and physical protection of SOC in soil aggregates were the main processes determining SOC stabilization. As a result, high aggregate carbon concentrations, varying from 148 till 48 g kg-1, were encountered for all land use sites. Al

  12. Determination of moisture content of single-wall carbon nanotubes.

    Science.gov (United States)

    Sturgeon, Ralph E; Lam, Joseph W; Windust, Anthony; Grinberg, Patricia; Zeisler, Rolf; Oflaz, Rabia; Paul, Rick L; Lang, Brian E; Fagan, Jeffrey A; Simard, Benoit; Kingston, Christopher T

    2012-01-01

    Several techniques were evaluated for the establishment of reliable water/moisture content of single-wall carbon nanotubes. Karl Fischer titration (KF) provides a direct measure of the water content and was used for benchmarking against results obtained by conventional oven drying, desiccation over anhydrous magnesium perchlorate as well as by thermogravimetry and prompt gamma-ray activation analysis. Agreement amongst results was satisfactory with the exception of thermogravimetry, although care must be taken with oven drying as it is possible to register mass gain after an initial moisture loss if prolonged drying time or elevated temperatures (120 °C) are used. Thermogravimetric data were precise but a bias was evident that could be accounted for by considering the non-selective loss of mass as volatile carbonaceous components. Simple drying over anhydrous magnesium perchlorate for a minimum period of 8-10 days is recommended if KF is not available for this measurement.

  13. Impact of Carbon Nanoparticle Shape on Polymer Dynamics in Nanocomposites

    Science.gov (United States)

    Miller, Brad; Dadmun, Mark

    2012-02-01

    In forming quality nanocomposites of carbon-based nanoparticles (CNPs) in a polymer matrix, achieving and maintaining a high degree of dispersion is a crucial problem. One method to attain well-dispersed CNP nanocomposites is to incorporate non-covalent interactions between the CNP and matrix, which also impacts the dynamics of the polymer chain. In this work, T2 NMR relaxometry (T2 NMR) examines the effect on polymer chain dynamics of incorporating CNPs into polystyrene-co-acrylonitrile (SAN) random copolymer matrices. In SAN-CNP composites, the segmental-chain dynamics can be influenced by the non-covalent interactions formed with the nanoparticle (interacting), but are also influenced by the CNP steric bulk alone (non-interacting). The use of T2 NMR allows for the examination of the influence of the extent of non-covalent interactions on this segmental chain level. This segmental level view also allows for the distinction between relaxation dynamics of the interacting and non-interacting regimes. Current data indicates that increased acrylonitrile content in the copolymer results in increased non-covalent interactions and overall slowing of chain dynamics.

  14. Microbial carbon recycling: an underestimated process controlling soil carbon dynamics

    Science.gov (United States)

    Basler, A.; Dippold, M.; Helfrich, M.; Dyckmans, J.

    2015-07-01

    The mean residence times (MRT) of different compound classes of soil organic matter (SOM) do not match their inherent recalcitrance to decomposition. One reason for this is the stabilisation within the soil matrix, but recycling, i.e. the reuse of "old" organic material to form new biomass may also play a role as it uncouples the residence times of organic matter from the lifetime of discrete molecules in soil. We analysed soil sugar dynamics in a natural 30 years old labelling experiment after a~wheat-maize vegetation change to determine the extent of recycling and stabilisation in plant and microbial derived sugars: while plant derived sugars are only affected by stabilisation processes, microbial sugars may be subject to both, stabilisation and recycling. To disentangle the dynamics of soil sugars, we separated different density fractions (free particulate organic matter (fPOM), light occluded particulate organic matter (≤1.6 g cm-3; oPOM1.6), dense occluded particulate organic matter (≤2 g cm-3; oPOM2) and mineral-associated organic matter (>2 g cm-3; Mineral)) of a~silty loam under long term wheat and maize cultivation. The isotopic signature of sugars was measured by high pressure liquid chromatography coupled to isotope ratio mass spectrometry (HPLC/IRMS), after hydrolysis with 4 M Trifluoroacetic acid (TFA). While apparent mean residence times (MRT) of sugars were comparable to total organic carbon in the bulk soil and mineral fraction, the apparent MRT of sugars in the oPOM fractions were considerably lower than those of the total carbon of these fractions. This indicates that oPOM formation was fuelled by microbial activity feeding on new plant input. In the bulk soil, mean residence times of the mainly plant derived xylose (xyl) were significantly lower than those of mainly microbial derived sugars like galactose (gal), rhamnose (rha), fucose (fuc), indicating that recycling of organic matter is an important factor regulating organic matter dynamics

  15. Fast analysis of carbon content by inelastic scattering of neutrons

    International Nuclear Information System (INIS)

    Heinrich, B.; Irmer, K.; Poetschke, R.

    1986-01-01

    The direct measurement of carbon concentration of conveyor belts is a difficult problem. The great penetration depth by the fast neutrons and the 4.43 MeV γ-radiation gives an especially suitable method. The measurement were performed by the following methods: excitation of γ-radiation by a Pu-Be neutron source, excitation of γ-radiation by DT-neutron generator in stationary regime, in pulse regime, or coupled with time correlated associated particle method. Furthermore, a special Monte Carlo code in which the geometry of the measuring equipment could be specified, was written to calculate the 4.43 MeV γ counting rate for backscatter geometries and for penetration geometries. The influence of conveyor belt, of content of H, O, Fe and of mass by surface for 4.43 MeV γ-radiation was calculated for application brown coal in industry. (author)

  16. Responses of Carbon Dynamics to Nitrogen Deposition in Typical Freshwater Wetland of Sanjiang Plain

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2014-01-01

    Full Text Available The effects of nitrogen deposition (N-deposition on the carbon dynamics in typical Calamagrostis angustifolia wetland of Sanjiang Plain were studied by a pot-culture experiment during two continuous plant growing seasons. Elevated atmospheric N-deposition caused significant increases in the aboveground net primary production and root biomass; moreover, a preferential partition of carbon to root was also observed. Different soil carbon fractions gained due to elevated N-deposition and their response intensities followed the sequence of labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between N-deposition and flooded condition facilitated the release of different carbon fractions. Positive correlations were found between CO2 and CH4 fluxes and liable carbon contents with N-deposition, and flooded condition also tended to facilitate CH4 fluxes and to inhibit the CO2 fluxes with N-deposition. The increases in soil carbon fractions occurring in the nitrogen treatments were significantly correlated with increases in root, aboveground parts, total biomass, and their carbon uptake. Our results suggested that N-deposition could enhance the contents of active carbon fractions in soil system and carbon accumulation in plant of the freshwater wetlands.

  17. Total content of carbon monoxide in the atmosphere over Russian regions according to satellite data

    Science.gov (United States)

    Sitnov, S. A.; Mokhov, I. I.; Dzhola, A. V.

    2017-01-01

    Carbon monoxide (CO) total columns over European Russia (ER) and western Siberia (WS) have been analyzed using MOPITT (V5, TIR/NIR, L3) IR-radiometer data obtained in 2000-2014. High CO contents are revealed over large urban and industrial agglomerations and over regions of oil-and-gas production. A stable local CO maximum is observed over the Moscow agglomeration. Statistical characteristics of CO total columns observed in the atmosphere over ER and WS in 2000-2014 are presented. An analysis of long-term changes in CO content reveals nonlinear changes in the CO total column over northern Eurasia in 2000-2014. Results of a comparative analysis of annual variations in atmospheric CO contents over ER and WS are given. Based on Fourier analysis, empirical models of annual variations in total CO contents over ER and WS are proposed. Relations between regional CO contents and fire characteristics and between spatial CO distributions and features of large-scale atmospheric dynamics under conditions of weather and climate anomalies in the summers of 2010 in ER and 2012 in WS are analyzed. Data on total CO contents measured with a MOPITT satellite radiometer and a ground-based spectrometer operating at the Zvenigorod Scientific Station of the Obukhov Institute of Atmospheric Physics are compared.

  18. Socio-functional dynamics of the mathematical contents

    Directory of Open Access Journals (Sweden)

    Isabel Alonso-Berenguer

    2018-01-01

    Full Text Available The article presents a model of the socio-functional dynamics of the mathematical contents that offers a novel theoretical-methodological basement for the development of the process of teaching-learning of the mathematical one. The investigation, of theoretical character, used the methods of analysis-synthesis, inductive-deductive and historical-logical to elaborate the one mentioned model that leaves of considering that the future professors have appropriated previously of the mathematical contents, foreseen in the curriculum, and they are, therefore, under conditions of understanding the potentialities of the same ones to facilitate the formation of socio-functional values.   

  19. Low carbon content NiTi shape memory alloy produced by electron beam melting

    Directory of Open Access Journals (Sweden)

    Otubo Jorge

    2004-01-01

    Full Text Available Earlier works showed that the use of electron beam melting is a viable process to produce NiTi shape memory alloy. In those works a static and a semi-dynamic processes were used producing small shell-shaped and cylindrical ingots respectively. The main characteristics of those samples were low carbon concentration and good composition homogeneity throughout the samples. This paper presents the results of scaling up the ingot size and processing procedure using continuous charge feeding and continuous casting. The composition homogeneity was very good demonstrated by small variation in martensitic transformation temperatures with carbon content around 0.013wt% compared to 0.04 to 0.06wt% of commercial products.

  20. Clay content drives carbon stocks in soils under a plantation of Eucalyptus saligna Labill. in southern Brazil

    Directory of Open Access Journals (Sweden)

    Tanise Luisa Sausen

    2014-06-01

    Full Text Available Soil carbon accumulation is largely dependent on net primary productivity. To our knowledge, there have been no studies investigating the dynamics of carbon accumulation in weathered subtropical soils, especially in managed eucalyptus plantations. We quantified the seasonal input of leaf litter, the leaf decomposition rate and soil carbon stocks in an commercial plantation of Eucalyptus saligna Labill. in southern Brazil. Our goal was to evaluate, through multiple linear regression, the influence that certain chemical characteristics of litter, as well as chemical and physical characteristics of soil, have on carbon accumulation in soil organic matter fractions. Variables related to the chemical composition of litter were not associated with the soil carbon stock in the particulate and mineral fractions. However, certain soil characteristics were significantly associated with the carbon stock in both fractions. The concentrations of nutrients associated with plant growth and productivity, such as phosphorus, sulfur, copper and zinc, were associated with variations in the labile carbon pool (particulate fraction. Clay content was strongly associated with the carbon stock in the mineral fraction. The carbon accumulation and stabilization in weathered subtropical Ultisol seems to be mainly associated with the intrinsic characteristics of the soil, particularly clay content, rather than with the quantity, chemical composition or decomposition rate of the litter.

  1. Socio-functional dynamics of the mathematical contents

    OpenAIRE

    Isabel Alonso-Berenguer; María Elena Pardo-Gómez; Alexander Gorina-Sánchez; Rosa Cova-Vallejo

    2018-01-01

    The article presents a model of the socio-functional dynamics of the mathematical contents that offers a novel theoretical-methodological basement for the development of the process of teaching-learning of the mathematical one. The investigation, of theoretical character, used the methods of analysis-synthesis, inductive-deductive and historical-logical to elaborate the one mentioned model that leaves of considering that the future professors have appropriated previously of the mathematical c...

  2. Management Impacts on Carbon Dynamics in a Sierra Nevada Mixed Conifer Forest.

    Science.gov (United States)

    Dore, Sabina; Fry, Danny L; Collins, Brandon M; Vargas, Rodrigo; York, Robert A; Stephens, Scott L

    2016-01-01

    Forest ecosystems can act as sinks of carbon and thus mitigate anthropogenic carbon emissions. When forests are actively managed, treatments can alter forests carbon dynamics, reducing their sink strength and switching them from sinks to sources of carbon. These effects are generally characterized by fast temporal dynamics. Hence this study monitored for over a decade the impacts of management practices commonly used to reduce fire hazards on the carbon dynamics of mixed-conifer forests in the Sierra Nevada, California, USA. Soil CO2 efflux, carbon pools (i.e. soil carbon, litter, fine roots, tree biomass), and radial tree growth were compared among un-manipulated controls, prescribed fire, thinning, thinning followed by fire, and two clear-cut harvested sites. Soil CO2 efflux was reduced by both fire and harvesting (ca. 15%). Soil carbon content (upper 15 cm) was not significantly changed by harvest or fire treatments. Fine root biomass was reduced by clear-cut harvest (60-70%) but not by fire, and the litter layer was reduced 80% by clear-cut harvest and 40% by fire. Thinning effects on tree growth and biomass were concentrated in the first year after treatments, whereas fire effects persisted over the seven-year post-treatment period. Over this period, tree radial growth was increased (25%) by thinning and reduced (12%) by fire. After seven years, tree biomass returned to pre-treatment levels in both fire and thinning treatments; however, biomass and productivity decreased 30%-40% compared to controls when thinning was combined with fire. The clear-cut treatment had the strongest impact, reducing ecosystem carbon stocks and delaying the capacity for carbon uptake. We conclude that post-treatment carbon dynamics and ecosystem recovery time varied with intensity and type of treatments. Consequently, management practices can be selected to minimize ecosystem carbon losses while increasing future carbon uptake, resilience to high severity fire, and climate related

  3. Effect of carbon content on friction and wear of cast irons

    Science.gov (United States)

    Buckley, D. H.

    1977-01-01

    Friction and wear experiments were conducted with cast irons and wrought steels containing various amounts of carbon in the alloy structure in contact with 52100 steel. Gray cast irons were found to exhibit lower friction and wear characteristics than white cast irons. Further, gray cast iron wear was more sensitive to carbon content than was white. Wear with gray cast iron was linearly related to load, and friction was found to be sensitive to relative humidity and carbon content. The form, in which the carbon is present in the alloy, is more important, as the carbon content and no strong relationship seems to exist between hardness of these ferrous alloys and wear.

  4. Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests

    Science.gov (United States)

    Talhelm, Alan F; Pregitzer, Kurt S; Kubiske, Mark E; Zak, Donald R; Campany, Courtney E; Burton, Andrew J; Dickson, Richard E; Hendrey, George R; Isebrands, J G; Lewin, Keith F; Nagy, John; Karnosky, David F

    2014-01-01

    Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2) and tropospheric ozone (O3) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3. Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r2 = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m−2) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (ΔNPP/ΔN) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2. Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. PMID:24604779

  5. Looking skyward to study ecosystem carbon dynamics

    Science.gov (United States)

    Dye, Dennis G.

    2012-01-01

    Between May and October 2011 the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program, conducted a field campaign at the ARM Southern Great Plains site in north central Oklahoma to evaluate a new instrument for quantitative image-based monitoring of sky conditions and solar radiation. The High Dynamic Range All-Sky Imaging System (HDR-ASIS) was developed by USGS to support studies of cloud- and aerosol-induced variability in the geometric properties of solar radiation (the sky radiance distribution) and its effects on photosynthesis and uptake of carbon dioxide (CO2) by terrestrial ecosystems. Under a clean, cloudless atmosphere when the Sun is above the horizon, most of the solar radiation reaching an area of the Earth's surface is concentrated in a beam coming directly from the Sun; a relatively small proportion arrives as diffuse radiation from the rest of the sky. Clouds and atmospheric aerosols cause increased scattering of the beam radiation, which increases the proportion of diffuse radiation at the surface.

  6. Effects of organic matter, calcium carbonates and moisture content ...

    African Journals Online (AJOL)

    When the organic matter was removed, reactive calcium carbonate concentrations in dry sediment became several times greater than those in the wet sediment. In other way, when calcium carbonates were removed, organic carbon concentrations decreased especially in B horizon of the wet sediment. On the opposite, OC ...

  7. Global workspace dynamics: Cortical "binding and propagation enables conscious contents.

    Directory of Open Access Journals (Sweden)

    Bernard J Baars

    2013-05-01

    Full Text Available A global workspace is a hub of binding and propagation in a population of loosely coupled signaling elements. Global workspace (GW architectures recruit many distributed, specialized agents to help resolve focal ambiguities. In the brain, conscious experiences may reflect a global workspace function. For animals the natural world is full of fitness-related ambiguities, suggesting a general adaptive pressure for brains to resolve focal ambiguities quickly and accurately. In humans and related species the cortico-thalamic (C-T core is believed to underlie conscious aspects of perception, thinking, learning, feelings of knowing, emotions, imagery, working memory and executive control. The C-T core has many anatomical hubs, but conscious percepts are unitary and internally consistent at any given moment. The repertoire of conscious contents is a large, open set. These points suggest that a brain-based GW capacity cannot be localized in a single anatomical hub. Rather, it should be sought in a dynamic capacity for adaptive binding and propagation of neural signals over multi-hub networks. We refer to this as dynamic global workspace theory (dGW. In this view, conscious contents can arise in any region of the C-T core when multiple signal streams settle on a winner-take-all equilibrium. The resulting bound gestalt may ignite an any-to-many broadcast, lasting ~100-200 ms, and trigger widespread adaptation in established networks. Binding and broadcasting may involve theta/gamma or alpha/gamma phase coupling. Conscious contents (qualia may reflect their sources in cortex. Sensory percepts may bind and broadcast from posterior regions, while non-sensory feelings of knowing (FOKs may be frontotemporal. The small focal capacity of conscious contents may be the biological price to pay for global access. We propose that in the intact brain the hippocampal/rhinal complex may support conscious event organization as well as episodic memory coding.

  8. Understanding the spatial distribution of factors controlling topsoil organic carbon content in European soils.

    Science.gov (United States)

    Rial, M; Martínez Cortizas, A; Rodríguez-Lado, L

    2017-12-31

    Soil Organic Carbon (SOC) constitutes the largest terrestrial carbon pool. The understanding of its dynamics and the environmental factors that influence its behaviour as sink or source of atmospheric CO 2 is crucial to quantify the carbon budget at the global scale. At the European scale, most of the existing studies to account for SOC stocks are centred in the fitting of predictive model to ascertain the distribution of SOC. However, the development of methodologies for monitoring and identifying the environmental factors that control SOC storage in Europe remains a key research challenge. Here we present a modelling procedure for mapping and monitoring SOC contents that uses Visible-Near Infrared (VNIR) spectroscopic measurements and a series of environmental covariates to ascertain the key environmental processes that have a major contribution into SOC sequestration processes. Our results show that it follows a geographically non-stationary process in which the influencing environmental factors have different weights depending on the spatial location. This implies that SOC stock modelling should not rely on a single model but on a combination of different statistical models depending on the environmental characteristics of each area. A cluster classification of European soils in relation to those factors resulted in the determination of four groups for which specific models have been obtained. Differences in climate, soil pH, content of coarse fragments or land cover type are the main factors explaining the differences in SOC in topsoil from Europe. We found that climatic conditions are the main driver of SOC storage at the continental scale, but we also found that parameters like land cover type influence SOC content found at the local scales in certain areas. Our methodology developed at continental scale could be used in future research aimed to improve the predictive performance of SOC assessments at European scale. Copyright © 2017 Elsevier B.V. All

  9. Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Igor Konyashin

    2018-03-01

    Full Text Available Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures.

  10. Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide.

    Science.gov (United States)

    Konyashin, Igor; Zaitsev, Alexander; Meledin, Alexander; Mayer, Joachim; Loginov, Pavel; Levashov, Evgeny; Ries, Bernd

    2018-03-09

    Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures.

  11. Interfaces between Model Co-W-C Alloys with Various Carbon Contents and Tungsten Carbide

    Science.gov (United States)

    Konyashin, Igor; Zaitsev, Alexander; Mayer, Joachim; Loginov, Pavel; Levashov, Evgeny; Ries, Bernd

    2018-01-01

    Interfaces between alloys simulating binders in WC-Co cemented carbides and tungsten carbide were examined on the micro-, nano-, and atomic-scale. The precipitation of fine WC grains and η-phase occurs at the interface of the alloy with the low carbon content. The precipitation of such grains almost does not occur in the alloy with the medium-low carbon content and does not take place in the alloy with the high carbon content. The formation of Co nanoparticles in the binder alloy with the medium-low carbon content was established. Interfaces in the alloy with the medium-low carbon content characterized by complete wetting with respect to WC and with the high carbon content characterized by incomplete wetting were examined at an atomic scale. The absence of any additional phases or carbon segregations at both of the interfaces was established. Thus, the phenomenon of incomplete wetting of WC by liquid binders with high carbon contents is presumably related to special features of the Co-based binder alloys oversaturated with carbon at sintering temperatures. PMID:29522437

  12. Relating black carbon content to reduction of snow albedo

    Science.gov (United States)

    Brandt, R. E.; Warren, S. G.; Clarke, A. D.

    2011-12-01

    In remote snow of the Northern Hemisphere, the levels of soot pollution are in the parts-per-billion (ppb) range, where the effect on albedo is at the level of a few percent. A reduction of albedo by 1-2% is significant for climate but is difficult to detect experimentally, because snow albedo depends on several other variables. In our work to quantify the climatic effect of black carbon (BC) in snow, we therefore do not directly measure the albedo reduction. Instead, we use a two-step procedure: (1) We collect snow samples, melt and filter them, and analyze the filters spectrophotometrically for BC concentration. (2) We use the BC amount from the filter measurement, together with snow grain size, in a radiative transfer model to compute the albedo reduction. Our radiative transfer model uses the discrete ordinates algorithm DISORT 2.0. We have chosen a representative BC size distribution and optical constants, and have incorporated those of mineral dust as well. While a given mass of BC causes over an order of magnitude more snow albedo reduction compared to dust, a snowpack containing dust mutes the albedo-reducing effect of BC. Because the computed reduction of snow albedo is model-based, it requires experimental verification. We doubt that direct measurement of albedo-reduction will be feasible in nature, because of the vertical variation of both snow grain size and soot content, and because the natural soot content is small. We conclude that what is needed is an artificial snowpack, with uniform grain size and large uniform soot content (ppm not ppb), to produce a large signal on albedo. We have chosen to pursue this experiment outdoors rather than in the laboratory, for the following reasons: (1) The snowpack in the field of view is uniformly illuminated if the source of radiation is the Sun. (2) Visible radiation penetrates into the snow, so photons emerge horizontally distant from where they entered. In the limited width of a laboratory snowpack, radiation

  13. Terrestrial carbon storage dynamics: Chasing a moving target

    Science.gov (United States)

    Luo, Y.; Shi, Z.; Jiang, L.; Xia, J.; Wang, Y.; Kc, M.; Liang, J.; Lu, X.; Niu, S.; Ahlström, A.; Hararuk, O.; Hastings, A.; Hoffman, F. M.; Medlyn, B. E.; Rasmussen, M.; Smith, M. J.; Todd-Brown, K. E.; Wang, Y.

    2015-12-01

    Terrestrial ecosystems have been estimated to absorb roughly 30% of anthropogenic CO2 emissions. Past studies have identified myriad drivers of terrestrial carbon storage changes, such as fire, climate change, and land use changes. Those drivers influence the carbon storage change via diverse mechanisms, which have not been unified into a general theory so as to identify what control the direction and rate of terrestrial carbon storage dynamics. Here we propose a theoretical framework to quantitatively determine the response of terrestrial carbon storage to different exogenous drivers. With a combination of conceptual reasoning, mathematical analysis, and numeric experiments, we demonstrated that the maximal capacity of an ecosystem to store carbon is time-dependent and equals carbon input (i.e., net primary production, NPP) multiplying by residence time. The capacity is a moving target toward which carbon storage approaches (i.e., the direction of carbon storage change) but usually does not attain. The difference between the capacity and the carbon storage at a given time t is the unrealized carbon storage potential. The rate of the storage change is proportional to the magnitude of the unrealized potential. We also demonstrated that a parameter space of NPP, residence time, and carbon storage potential can well characterize carbon storage dynamics quantified at six sites ranging from tropical forests to tundra and simulated by two versions (carbon-only and coupled carbon-nitrogen) of the Australian Community Atmosphere-Biosphere Land Ecosystem (CABLE) Model under three climate change scenarios (CO2 rising only, climate warming only, and RCP8.5). Overall this study reveals the unified mechanism unerlying terrestrial carbon storage dynamics to guide transient traceability analysis of global land models and synthesis of empirical studies.

  14. Inferring absorbing organic carbon content from AERONET data

    Directory of Open Access Journals (Sweden)

    A. Arola

    2011-01-01

    Full Text Available Black carbon, light-absorbing organic carbon (often called "brown carbon" and mineral dust are the major light-absorbing aerosols. Currently the sources and formation of brown carbon aerosol in particular are not well understood. In this study we estimated the amount of light–absorbing organic carbon and black carbon from AERONET measurements. We find that the columnar absorbing organic carbon (brown carbon levels in biomass burning regions of South America and Africa are relatively high (about 15–20 mg m−2 during biomass burning season, while the concentrations are significantly lower in urban areas in US and Europe. However, we estimated significant absorbing organic carbon amounts from the data of megacities of newly industrialized countries, particularly in India and China, showing also clear seasonality with peak values up to 30–35 mg m−2 during the coldest season, likely caused by the coal and biofuel burning used for heating. We also compared our retrievals with the modeled organic carbon by the global Oslo CTM for several sites. Model values are higher in biomass burning regions than AERONET-based retrievals, while the opposite is true in urban areas in India and China.

  15. Inferring absorbing organic carbon content from AERONET data

    Science.gov (United States)

    Arola, A.; Schuster, G.; Myhre, G.; Kazadzis, S.; Dey, S.; Tripathi, S. N.

    2011-01-01

    Black carbon, light-absorbing organic carbon (often called "brown carbon") and mineral dust are the major light-absorbing aerosols. Currently the sources and formation of brown carbon aerosol in particular are not well understood. In this study we estimated the amount of light-absorbing organic carbon and black carbon from AERONET measurements. We find that the columnar absorbing organic carbon (brown carbon) levels in biomass burning regions of South America and Africa are relatively high (about 15-20 mg m-2 during biomass burning season), while the concentrations are significantly lower in urban areas in US and Europe. However, we estimated significant absorbing organic carbon amounts from the data of megacities of newly industrialized countries, particularly in India and China, showing also clear seasonality with peak values up to 30-35 mg m-2 during the coldest season, likely caused by the coal and biofuel burning used for heating. We also compared our retrievals with the modeled organic carbon by the global Oslo CTM for several sites. Model values are higher in biomass burning regions than AERONET-based retrievals, while the opposite is true in urban areas in India and China.

  16. Carbon stocks and dynamics under improved tropical pasture and silvopastoral

    NARCIS (Netherlands)

    Mosquera Vidal, O.; Buurman, P.; Ramirez, B.L.; Amezquita, M.C.

    2012-01-01

    To evaluate the effect of land use change on soil organic carbon, the carbon contents and stocks of primary forest, degraded pasture, and four improved pasture systems in Colombian Amazonia were compared in a flat and a sloping landscape. The improved pastures were Brachiaria humidicola, and

  17. Stable carbon isotope depth profiles and soil organic carbon dynamics in the lower Mississippi Basin

    Science.gov (United States)

    Wynn, J.G.; Harden, J.W.; Fries, T.L.

    2006-01-01

    Analysis of depth trends of 13C abundance in soil organic matter and of 13C abundance from soil-respired CO2 provides useful indications of the dynamics of the terrestrial carbon cycle and of paleoecological change. We measured depth trends of 13C abundance from cropland and control pairs of soils in the lower Mississippi Basin, as well as the 13C abundance of soil-respired CO2 produced during approximately 1-year soil incubation, to determine the role of several candidate processes on the 13C depth profile of soil organic matter. Depth profiles of 13C from uncultivated control soils show a strong relationship between the natural logarithm of soil organic carbon concentration and its isotopic composition, consistent with a model Rayleigh distillation of 13C in decomposing soil due to kinetic fractionation during decomposition. Laboratory incubations showed that initially respired CO 2 had a relatively constant 13C content, despite large differences in the 13C content of bulk soil organic matter. Initially respired CO2 was consistently 13C-depleted with respect to bulk soil and became increasingly 13C-depleted during 1-year, consistent with the hypothesis of accumulation of 13C in the products of microbial decomposition, but showing increasing decomposition of 13C-depleted stable organic components during decomposition without input of fresh biomass. We use the difference between 13C / 12C ratios (calculated as ??-values) between respired CO 2 and bulk soil organic carbon as an index of the degree of decomposition of soil, showing trends which are consistent with trends of 14C activity, and with results of a two-pooled kinetic decomposition rate model describing CO2 production data recorded during 1 year of incubation. We also observed inconsistencies with the Rayleigh distillation model in paired cropland soils and reasons for these inconsistencies are discussed. ?? 2005 Elsevier B.V. All rights reserved.

  18. [Seasonal dynamics of soil organic carbon and active organic carbon fractions in Calamagrostis angustifolia wetlands topsoil under different water conditions].

    Science.gov (United States)

    Hou, Cui-Cui; Song, Chang-Chun; Li, Ying-Chen; Guo, Yue-Dong

    2011-01-01

    The experiment was carried in Sanjiang Plain in the northeast of China during the growing season in 2009. Soil organic carbon (SOC), as well as the soil active organic carbon fractions in the 0-20 cm soil layer of Calamagrostis angustifolia wetland under different water conditions were on monthly observation. Based on the research and indoor analysis, the seasonal dynamics of light fractions of soil organic carbon (LFOC) and microbial biomass carbon (MBC) were analyzed. The results indicated that the SOC contents had significantly seasonal dynamics, and the hydrological circle had apparently driving effect on LFOC and MBC during the growing season, especially under the seasonal flooded condition. The freeze-thaw process reduced the SOC, LFOC, MBC contents, with the decreases of 74.53%, 80.93%, 83.09%, while both carbon contents of light and heavy fractions were reduced at the same time. The result also showed that the seasonal flooding condition increased the proportion of LFOC in topsoil, which was larger in marsh meadow (13.58%) than in wet meadow (11.96%), whilst the MBC in marsh meadow (1 397.21 mg x kg(-1)) was less than the latter (1 603.65 mg x kg(-1)), proving that the inundated environment inhibited the mineralization and decomposition of organic matter. But the microbial activity could be adaptive to the flooding condition. During the growing season the MBC soared to 1 829.21 mg x kg(-1) from 337.56 mg x kg(-1) in July, and the microbial quotient was 1.51 times higher than that in June, indicating the high microbial efficacy of soil organic matter. Meanwhile, there was a significant correlation between the contents of LFOC and SOC (r = 0.816), suggesting that higher LFOC content was favorable to the soil carbon accumulation. Moreover, in the seasonal flooded Calamagrostis angustifolia wetland the soil LFOC content was significantly correlated with MBC (r = 0.95), implying that the available carbon source had more severe restriction on the microbial

  19. The use of soil monitoring networks to detect changes in soil organic carbon content

    Science.gov (United States)

    Keller, A.; Schwierz, C.; Schwab, P.; Ammann, S.; Meuli, R.; Rossier, N.; Papritz, A.

    2010-05-01

    Process-based carbon dynamic models are widely used to estimate and forecast temporal changes in soil organic carbon content (SOC). Often, these models are calibrated against measurements from long-term field experiments with controlled treatments at a local scale. Repeated SOC inventories at the sites of a soil monitoring network may provide additional valuable information about temporal changes at a regional scale for a broader range of environmental conditions (land use, soil type, climate, etc.). Recently, Saby et al. (2008) assessed the adequacy of European soil monitoring networks to detect changes in SOC. The minimum detectable changes (MDC) differed considerably among the networks, and the design turned out to be an important factor. However, Saby et al. derived their results from scenarios because the majority of the European monitoring networks performed only one sampling campaign so far. Data on SOC changes, gathered by repeated sampling at monitoring sites under controlled conditions including strict quality assurance protocols, are still rare, and little is known about random and systematic errors in the estimated changes. Furthermore, suitable (geo-) statistical procedures are required to extrapolate the SOC measurements and their change from the surveyed sites to the regional scale. In our presentation, we report (i) our experiences on MDC gained by repeated SOC measurements at selected sites of the Swiss Soil Monitoring Network (NABO), and (ii) we show how the SOC measurements recorded at the sites of the soil monitoring network of Canton Fribourg can be used for a mapping SOC and its change at the regional scale. For this purpose we a use robust geostatistical kriging approach which exploits the dependence of SOC on land use, altitude and climate. Saby P.A. et al. (2008). Will European soil-monitoring networks be able to detect changes in topsoil organic carbon content? Global Change Biology 14: 2432-2442.

  20. Dynamic characteristics of multi-walled carbon nanotubes under a ...

    Indian Academy of Sciences (India)

    Abstract. This paper reports the results of an investigation into the effect of transverse magnetic fields on dynamic characteristics of multi-walled carbon nanotubes (MWNTs). Couple dynamic equations of MWNTs subjected to a transverse magnetic field are derived and solved by considering the Lorentz magnetic forces ...

  1. Dynamics of carbon 14 in soils: a review

    International Nuclear Information System (INIS)

    Tamponnet, C.

    2004-01-01

    In terrestrial ecosystems, soil is the main interface between atmosphere, hydrosphere, lithosphere and biosphere. Its interactions with carbon cycle are primordial. Information about carbon 14 dynamics in soils is quite dispersed and an up-to-date status is therefore presented in this paper. Carbon 14 dynamics in soils are governed by physical processes (soil structure, soil aggregation, soil erosion) chemical processes (sequestration by soil components either mineral or organic), and soil biological processes (soil microbes, soil fauna, soil biochemistry). The relative importance of such processes varied remarkably among the various biomes (tropical forest, temperate forest, boreal forest, tropical savannah, temperate pastures, deserts, tundra, marshlands, agro ecosystems) encountered in the terrestrial eco-sphere. Moreover, application for a simplified modelling of carbon 14 dynamics in soils is proposed. (author)

  2. Digital Mapping of Soil Organic Carbon Contents and Stocks in Denmark

    DEFF Research Database (Denmark)

    Adhikari, Kabindra; Hartemink, Alfred E.; Minasny, Budiman

    2014-01-01

    Estimation of carbon contents and stocks are important for carbon sequestration, greenhouse gas emissions and national carbon balance inventories. For Denmark, we modeled the vertical distribution of soil organic carbon (SOC) and bulk density, and mapped its spatial distribution at five standard...... soil depth intervals (025, 5215, 15230, 30260 and 602 100 cm) using 18 environmental variables as predictors. SOC distribution was influenced by precipitation, land use, soil type, wetland, elevation, wetness index, and multi-resolution index of valley bottom flatness. The highest average SOC content...

  3. Integrating microbial diversity in soil carbon dynamic models parameters

    Science.gov (United States)

    Louis, Benjamin; Menasseri-Aubry, Safya; Leterme, Philippe; Maron, Pierre-Alain; Viaud, Valérie

    2015-04-01

    Faced with the numerous concerns about soil carbon dynamic, a large quantity of carbon dynamic models has been developed during the last century. These models are mainly in the form of deterministic compartment models with carbon fluxes between compartments represented by ordinary differential equations. Nowadays, lots of them consider the microbial biomass as a compartment of the soil organic matter (carbon quantity). But the amount of microbial carbon is rarely used in the differential equations of the models as a limiting factor. Additionally, microbial diversity and community composition are mostly missing, although last advances in soil microbial analytical methods during the two past decades have shown that these characteristics play also a significant role in soil carbon dynamic. As soil microorganisms are essential drivers of soil carbon dynamic, the question about explicitly integrating their role have become a key issue in soil carbon dynamic models development. Some interesting attempts can be found and are dominated by the incorporation of several compartments of different groups of microbial biomass in terms of functional traits and/or biogeochemical compositions to integrate microbial diversity. However, these models are basically heuristic models in the sense that they are used to test hypotheses through simulations. They have rarely been confronted to real data and thus cannot be used to predict realistic situations. The objective of this work was to empirically integrate microbial diversity in a simple model of carbon dynamic through statistical modelling of the model parameters. This work is based on available experimental results coming from a French National Research Agency program called DIMIMOS. Briefly, 13C-labelled wheat residue has been incorporated into soils with different pedological characteristics and land use history. Then, the soils have been incubated during 104 days and labelled and non-labelled CO2 fluxes have been measured at ten

  4. Dynamic simulation of the carbon-in-pulp and carbon-in-leach processes

    Directory of Open Access Journals (Sweden)

    L. R. P. de Andrade Lima

    2007-12-01

    Full Text Available Carbon-in-leach and carbon-in-pulp are continuous processes that use activated carbon in a cascade of large agitated tanks, which have been widely used to recover or concentrate precious metals in gold extraction plants. In the carbon-in-pulp process adsorption occurs after the leaching cascade section of the plant, and in the carbon-in-leach process leaching and adsorption occur simultaneously. In both processes the activated carbon is moved from one tank to another in countercurrent with the ore pulp until the recovery of the loaded carbon in the first tank. This paper presents a dynamic model that describes, with minor changes, the carbon-in-leach, the carbon-in-pulp, and the gold leaching processes. The model is numerically solved and calibrated with experimental data from a plant and used to perform a study of the effect of the activated carbon transfer strategy on the performance of the adsorption section of the plant. Based on the calculated values of the gold loss in the liquid and of the gold recovered in the loaded activated carbon that leaves the circuit, the results indicate that strategies in which a significant amount of activated carbon is held in the first tank and the contact time between the carbon and the pulp is longer are the best carbon transfer strategies for these processes.

  5. Thallium and its contents in Remata carbonate rocks

    Directory of Open Access Journals (Sweden)

    Kondelová Marcela

    1996-09-01

    Full Text Available The article presents at first the list of thallium own minerals and its isomorphic content in other minerals, especially in Slovakian ore deposits. This trace element was found in numerous dolomite-rock samples from Remata massif near Handlová. An interesting level of Tl content was analyzed in nonsilicified rocks; the highest content of Tl (and Ag are along the E – W line of disturbance. The presence of thallium in some limonitic aggregates in close Kremnica-gold deposit indicate any continuous relation. Some similarities to type gold deposits Carlin ( USA are discussed, even if no gold and discrete thallium phases were in Remata determined yet.

  6. Electrical properties of multiphase composites based on carbon nanotubes and an optimized clay content

    Science.gov (United States)

    Egiziano, Luigi; Lamberti, Patrizia; Spinelli, Giovanni; Tucci, Vincenzo; Guadagno, Liberata; Vertuccio, Luigi

    2016-05-01

    The experimental results concerning the characterization of a multiphase nanocomposite systems based on epoxy matrix, loaded with different amount of multi-walled carbon nanotubes (MWCNTs) and an optimized Hydrotalcite (HT) clay content (i.e. 0.6 wt%), duly identified by an our previous theoretical study based on Design of Experiment (DoE), are presented. Dynamic-mechanical analysis (DMA) reveal that even the introduction of higher HT loading (up to 1%wt) don't affect significantly the mechanical properties of the nanocomposites while morphological investigations show an effective synergy between clay and carbon nanotubes that leads to peculiar micro/nanostructures that favor the creation of the electrical conductive network inside the insulating resin. An electrical characterization is carried out in terms of DC electrical conductivity, percolation threshold (EPT) and frequency response in the range 10Hz-1MHz. In particular, the measurements of the DC conductivity allow to obtain the typical "percolation" curve also found for classical CNT-polymer mixtures and a value of about 2 S/m for the electrical conductivity is achieved at the highest considered CNTs concentration (i.e. 1 wt%). The results suggest that multiphase nanocomposites obtained incorporating dispersive nanofillers, in addition to the conductive one, may be a valid alternative to the polymer blends, to improve the properties of the polymeric materials thus able to meet high demands, particularly concerning their mechanical and thermal stability and electrical features required in the aircraft engineering.

  7. Mapping soil organic carbon content by geographically weighted regression

    NARCIS (Netherlands)

    Song, Xiao Dong; Brus, Dick J.; Liu, Feng; Li, De Cheng; Zhao, Yu Guo; Yang, Jin Ling; Zhang, Gan Lin

    2016-01-01

    In large heterogeneous areas the relationship between soil organic carbon (SOC) and environmental covariates may vary throughout the area, bringing about difficulty for accurate modeling of the regional SOC variation. The benefit of local, geographically weighted regression (GWR) coefficients was

  8. carbonate microfacies and major element content of the paleocene

    African Journals Online (AJOL)

    DJFLEX

    The Paleocene-Eocene limestone and shale units exposed at the Sagamu quarry, southwestern Nigeria, were investigated for the carbonate microfacies and major geochemical elements to deduce the depositional environment and the diagenetic history of the limestone. From field observations the limestone is generally ...

  9. Nuclear Fermi Dynamics: physical content versus theoretical approach

    International Nuclear Information System (INIS)

    Griffin, J.J.

    1977-01-01

    Those qualitative properties of nuclei, and of their energetic collisions, which seem of most importance for the flow of nuclear matter are listed and briefly discussed. It is suggested that nuclear matter flow is novel among fluid dynamical problems. The name, Nuclear Fermi Dynamics, is proposed as an appropriate unambiguous label. The Principle of Commensurability, which suggests the measurement of the theoretical content of an approach against its expected predictive range is set forth and discussed. Several of the current approaches to the nuclear matter flow problem are listed and subjected to such a test. It is found that the Time-Dependent Hartree-Fock (TDHF) description, alone of all the major theoretical approaches currently in vogue, incorporates each of the major qualitative features within its very concise single mathematical assumption. Some limitations of the conventional TDHF method are noted, and one particular defect is discussed in detail: the Spurious Cross Channel Correlations which arise whenever several asymptotic reaction channels must be simultaneously described by a single determinant. A reformulated Time-Dependent-S-Matrix Hartree-Fock Theory is proposed, which obviates this difficulty. It is noted that the structure of TD-S-HF can be applied to a more general class of non-linear wave mechanical problems than simple TDHF. Physical requirements minimal to assure that TD-S-HF represents a sensible reaction theory are utilized to prescribe the definition of acceptable asymptotic channels. That definition, in turn, defines the physical range of the TD-S-HF theory as the description of collisions of certain mathematically well-defined objects of mixed quantal and classical character, the ''TDHF droplets.''

  10. The role of vegetation dynamics in the control of atmospheric CO{sub 2} content

    Energy Technology Data Exchange (ETDEWEB)

    Sitch, Stephen

    2000-04-01

    This thesis contains a description of the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM) and its application to infer the role of vegetation dynamics on atmospheric CO{sub 2} content at different time-scales. The model combines vegetation dynamics and biogeochemistry in a modular framework. Individual modules describe ecosystems processes, including vegetation resource competition and production, tissue turnover, growth, fire and mortality, soil and litter biogeochemistry, including the effects of CO{sub 2} on these processes. The model simulates realistic post-disturbance succession in different environments. Seasonal exchange of H{sub 2}O and CO{sub 2} between the terrestrial biosphere and the atmosphere is modelled in reasonable agreement with observation. Global estimates of carbon stocks in soil, litter and vegetation are within their acceptable ranges and the model captures the present-day patterns in vegetation. Fire return intervals are simulated correctly in most regions. Results emphasise the important role of the terrestrial biosphere in both the seasonal cycle and in the inter-annual variability in the growth rate of atmospheric CO{sub 2}. LPJ successfully reproduced both the amplitude and phase of the seasonal cycle of atmospheric CO{sub 2} content as measured at a global network of monitoring stations. The model predicted a small net terrestrial biosphere uptake of CO{sub 2} during the 1980s with a strong CO{sub 2} fertilisation effect, which enhances plant production, reduced by the effects of climate and land use change. Historical land use change and CO{sub 2} fertilisation have been the dominant, albeit opposing factors governing the response of the terrestrial biosphere with respect to carbon storage during the 20th century. LPJ is run using one future climate and atmospheric CO{sub 2} scenario until 2200. Enhanced production due to the CO{sub 2} fertilisation effect eventually reaches an asymptote, and consequently the ability of

  11. Temporal carbon dynamics of forests in Washington, US: implications for ecological theory and carbon management

    Science.gov (United States)

    Crystal L. Raymond; Donald. McKenzie

    2014-01-01

    We quantified carbon (C) dynamics of forests in Washington, US using theoretical models of C dynamics as a function of forest age. We fit empirical models to chronosequences of forest inventory data at two scales: a coarse-scale ecosystem classification (ecosections) and forest types (potential vegetation) within ecosections. We hypothesized that analysis at the finer...

  12. [Seasonal dynamics of carbon and nitrogen in fine roots and their differences between successive rotation poplar plantations].

    Science.gov (United States)

    Wang, Yan-ping; Xu, Tan; Zhu, Wan-rui; Wang, Hua-tian; Zhang, Guang-can; Li, Chuan-rong; Jiang, Yue-zhong

    2015-11-01

    In this study, poplar fine roots in two successive rotation plantations were sampled over seasons. Root samples were grouped from first to five orders to examine the seasonal dynamics of carbon and nitrogen contents of poplar fine roots with orders, and compared their differences between two successive rotation plantations, and finally to find the relationships between the fine root growth and the productivity decline of successive rotation poplar plantations. The results showed that non-structure carbohydrates (NSC) content increased significantly with root orders, while nitrogen content decreased. The contents of total carbon and NSC were significantly related to total nitrogen content. Root orders explained 98.2% variance of carbon and nitrogen contents of poplar fine roots, and the difference between rotations only explained 1.7% of variance. Poplar fine roots consisted of more carbon and less nitrogen with root orders, and the seasonal changes in contents of total carbon, total nitrogen and NSC showed significant difference between rotations, while.that of the C:N ratio didn' t show significant difference. Root order and season showed interaction effect on carbon and nitrogen dynamic. The C:N ratio was about 20:1 in lower order roots, and more than 30:1 in higher order roots. The C:N ratio in summer and autumn was significantly less than those in other seasons, while NSC content was the highest in November. This study indicated that the allocation of carbon and nitrogen in fine roots was closely correlated with fine root orders. Both NSC content and C:N ratio were of greatly important ecological significance in fine root turnover and growth regulation.

  13. Biobased carbon content of resin extracted from polyethylene composite by carbon-14 concentration measurements using accelerator mass spectrometry.

    Science.gov (United States)

    Taguchi, Kazuhiro; Kunioka, Masao; Funabashi, Masahiro; Ninomiya, Fumi

    2014-01-01

    An estimation procedure for biobased carbon content of polyethylene composite was studied using carbon-14 ((14)C) concentration ratios as measured by accelerated mass spectrometry (AMS). Prior to the measurement, additives and fillers in composites should be removed because they often contain a large amount of biobased carbon and may shift the estimation. Samples of resin with purity suitable for measurement were isolated from composites with a Soxhlet extractor using heated cyclohexanone. After cooling of extraction solutions, the resin was recovered as a fine semi-crystalline precipitate, which was easily filtered. Recovery rates were almost identical (99%), even for low-density polyethylene and linear low-density polyethylene, which may have lower crystallinity. This procedure could provide a suitable approach for estimation of biobased carbon content by AMS on the basis of the standard ASTM D 6866. The biobased carbon content for resin extracted from polyethylene composites allow for the calculation of biosynthetic polymer content, which is an indicator of mass percentage of the biobased plastic resin in the composite.

  14. Molecular dynamics analysis on axial buckling of functionalized carbon nanotubes in thermal environment.

    Science.gov (United States)

    Mehralian, Fahimeh; Tadi Beni, Yaghoub

    2017-11-04

    Molecular dynamics simulations are conducted to investigate the buckling characteristics of functionalized carbon nanotubes (f-CNTs) under axial compression at various temperatures. The influences of functionalization, content of functional groups, chirality and diameter, as well as temperature on buckling response of pristine and functionalized CNTs are investigated. It is found that the buckling capacity of CNTs deteriorates drastically by functionalization, though the increase in the content of functional groups slightly enhances their stability. Besides, the results show that temperature considerably contributes to the stability of nanotubes but interestingly it has the most pronounced impact on pristine CNTs than functionalized ones, as defective CNTs.

  15. Carbon dynamics of contrasting agricultural practices

    Science.gov (United States)

    Ghee, Claire; Hallett, Paul; Neilson, Roy; Robinson, David; Paterson, Eric

    2013-04-01

    Application of organic amendments can improve soil quality and provide crop nutrients. To optimise these agricultural benefits from organic applications, the capacity of microbe-driven nutrient and carbon cycling must be understood and exploited. Consideration is therefore required of the complex interactions between the rhizosphere, microbial biomass and organic amendment. We hypothesise that the labile C present in root exudates of plants increases the mineralisation of organic matter in soil, constituting a mechanism to promote nutrient acquisition. This mechanism is known as the 'priming effect', but is poorly understood in the context of agricultural carbon and nutrient management. Field data from the Centre of Sustainable Cropping (CSC) research platform (Dundee, Scotland, UK) are utilised to build an understanding of soil C and N fluxes between contrasting agricultural practices. The field site uses a split-plot design to compare (i) compost amended soils with reduced tillage and chemical inputs and (ii) conventionally managed soils, reflective of current UK commercial arable practice. Significant differences (p= compost amended and conventionally managed soils at field-scale with respect to soil microbial biomass (SMB), total organic carbon (TOC) and mineral nitrogen. Investigation into the priming effect within compost amended soils was subsequently undertaken under laboratory conditions. Stable isotope analysis and measurements of soil biotic parameters were used to quantify priming resulting from Spring Barley (Hordeum vulgare cv. Optic) cultivation for (i) unamended and (ii) municipal compost incorporated soils. Compost treatments comprised amendments of 25, 50 and 150 t/Ha and planted soils were compared with unplanted controls. Soil mesocosms were maintained under controlled environmental conditions within labelling chambers supplied continuously with 13C-depleted CO2. Throughout a 41-day incubation period, soil CO2 efflux and dissolved organic carbon

  16. Remote Sensing of Vegetation Nitrogen Content for Spatially Explicit Carbon and Water Cycle Estimation

    Science.gov (United States)

    Zhang, Y. L.; Miller, J. R.; Chen, J. M.

    2009-05-01

    Foliage nitrogen concentration is a determinant of photosynthetic capacity of leaves, thereby an important input to ecological models for estimating terrestrial carbon and water budgets. Recently, spectrally continuous airborne hyperspectral remote sensing imagery has proven to be useful for retrieving an important related parameter, total chlorophyll content at both leaf and canopy scales. Thus remote sensing of vegetation biochemical parameters has promising potential for improving the prediction of global carbon and water balance patterns. In this research, we explored the feasibility of estimating leaf nitrogen content using hyperspectral remote sensing data for spatially explicit estimation of carbon and water budgets. Multi-year measurements of leaf biochemical contents of seven major boreal forest species were carried out in northeastern Ontario, Canada. The variation of leaf chlorophyll and nitrogen content in response to various growth conditions, and the relationship between them,were investigated. Despite differences in plant type (deciduous and evergreen), leaf age, stand growth conditions and developmental stages, leaf nitrogen content was strongly correlated with leaf chlorophyll content on a mass basis during the active growing season (r2=0.78). With this general correlation, leaf nitrogen content was estimated from leaf chlorophyll content at an accuracy of RMSE=2.2 mg/g, equivalent to 20.5% of the average measured leaf nitrogen content. Based on this correlation and a hyperspectral remote sensing algorithm for leaf chlorophyll content retrieval, the spatial variation of leaf nitrogen content was inferred from the airborne hyperspectral remote sensing imagery acquired by Compact Airborne Spectrographic Imager (CASI). A process-based ecological model Boreal Ecosystem Productivity Simulator (BEPS) was used for estimating terrestrial carbon and water budgets. In contrast to the scenario with leaf nitrogen content assigned as a constant value without

  17. Dual-shale-content method for total organic carbon content evaluation from wireline logs in organic shale

    Directory of Open Access Journals (Sweden)

    Nie Xin

    2017-05-01

    Full Text Available Organic shale is one of the most important unconventional resources all around the world. Total organic carbon (TOC content is an important evaluation parameter of reservoir hydrocarbon source quality. The regular evaluation methods have higher requirements of well logs and core experiment data for statistical regression. Through analyzing the resistivity and gamma ray logging response characteristics of shale content and organic matters, combined with digital rock physics experiment simulation, we put forward and improve the dual-shale-content method for TOC content logging evaluation. The accuracy of this method is verified by actual data processing. The result shows the dual-shale-content method is simple to use and the error is small. And by comparing with the calculation results by using the ΔLogR method, it is revealed that the trend of the TOC content calculated by our method agrees with the core results better. This new method is suitable for the evaluation of TOC content in the area or interval where there is only conventional logs.

  18. Applications of Remote Sensing for Studying Lateral Carbon Fluxes and Inundation Dynamics in Tidal Wetlands

    Science.gov (United States)

    Lamb, B. T.; Tzortziou, M.; McDonald, K. C.

    2017-12-01

    Wetlands play a key role in Earth's carbon cycle. However, wetland carbon cycling exhibits a high level of spatiotemporal dynamism, and thus, is not as well understood as carbon cycling in other ecosystems. In order to accurately characterize wetland carbon cycling and fluxes, wetland vegetation phenology, seasonal inundation dynamics, and tidal regimes must be understood as these factors influence carbon generation and transport. Here, we use radar remote sensing to map wetland properties in the Chesapeake Bay, the largest estuary in the United States with more than 1,500 square miles of tidal wetlands, across a range of tidal amplitudes, salinity regimes, and soil organic matter content levels. We have been using Sentinel-1 and ALOS PALSAR-1 radar measurements to characterize vegetation and seasonal inundation dynamics with the future goal of characterizing salinity gradients and tidal regimes. Differences in radar backscatter from various surface targets has been shown to effectively discriminate between dry soil, wet soil, vegetated areas, and open water. Radar polarization differences and ratios are particularly effective at distinguishing between vegetated and non-vegetated areas. Utilizing these principles, we have been characterizing wetland types using supervised classification techniques including: Random Forest, Maximum Likelihood, and Minimum Distance. The National Wetlands Inventory has been used as training and validation data. Ideally, the techniques we outline in this research will be applicable to the characterization of wetlands in coastal areas outside of Chesapeake Bay.

  19. Soil Organic Carbon dynamics in agricultural soils of Veneto Region

    Science.gov (United States)

    Bampa, F. B.; Morari, F. M.; Hiederer, R. H.; Toth, G. T.; Giandon, P. G.; Vinci, I. V.; Montanarella, L. M.; Nocita, M.

    2012-04-01

    One of the eight soil threats expressed in the European Commission's Thematic Strategy for Soil Protection (COM (2006)231 final) it's the decline in Soil Organic Matter (SOM). His preservation is recognized as with the objective to ensure that the soils of Europe remain healthy and capable of supporting human activities and ecosystems. One of the key goals of the strategy is to maintain and improve Soil Organic Carbon (SOC) levels. As climate change is identified as a common element in many of the soil threats, the European Commission (EC) intends to assess the actual contribution of the soil protection to climate change mitigation and the effects of climate change on the possible depletion of SOM. A substantial proportion of European land is occupied by agriculture, and consequently plays a crucial role in maintaining natural resources. Organic carbon preservation and sequestration in the EU's agricultural soils could have some potential to mitigate the effects of climate change, particularly linked to preventing certain land use changes and maintaining SOC stocks. The objective of this study is to assess the SOC dynamics in agricultural soils (cropland and grassland) at regional scale, focusing on changes due to land use. A sub-objective would be the evaluation of the most used land management practices and their effect on SOC content. This assessment aims to determine the geographical distribution of the potential GHG mitigation options, focusing on hot spots in the EU, where mitigation actions would be particularly efficient and is linked with the on-going work in the JRC SOIL Action. The pilot area is Veneto Region. The data available are coming from different sources, timing and involve different variables as: soil texture, climate, soil disturbance, managements and nutrients. The first source of data is the LUCAS project (Land Use/Land Cover Area Frame statistical Survey). Started in 2001, the LUCAS project aims to monitor changes in land cover/use and

  20. Carbon content of austenite in austempered ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Chang, L.C. [Kuang Wu Inst. of Tech. and Commerce, Taipei (Taiwan, Province of China). Dept. of Mechanical Engineering

    1998-06-05

    The development of austempered ductile iron (ADI) is a major achievement in cast iron technology. The austempering heat treatment enables the ductile cast iron containing mainly strong bainitic ferrite and ductile carbon-enriched austenite, with some martensite transforms from austenite during cooling down to room temperature. A key factor controlling the stability of the retained austenite can be evaluated soundly using the thermodynamics principles. It is the purpose here to demonstrate that the data of ADI from numerous sources have a similar trend.

  1. 1 Soil Organic Carbon Dynamics under different plantation crops of ...

    African Journals Online (AJOL)

    Using the SOC as indicator, the soil organic matter content needs to be improved upon for sustainable productivity. ... microorganisms which are involved in litter degradation process. However, there. J S Ogeh* ... by the linear regression study. Keywords: Soil organic carbon, plantation crops, different ages, tropics, cashew,.

  2. Contemporary carbon content of bis (2-ethylhexyl) phthalate in butter.

    Science.gov (United States)

    Tong, T; Ondov, J M; Buchholz, B A; VanDerveer, M C

    2016-01-01

    The fraction of naturally produced bis (2-ethylhexyl) phthalate (DEHP), a ubiquitous plasticizer known to contaminate packaged foods, was determined for each of five 1.10 kg samples of unsalted market butter by accelerator mass spectrometry (AMS). After extraction and concentration enrichment with liquid-liquid extraction, flash column chromatography, and preparative-scale high performance liquid chromatography, each sample provided ≈ 250 μg extracts of DEHP with carbon purity ranging from 92.5 ± 1.2% (n = 3, 1σ) to 97.1 ± 0.8% (n = 3, 1σ) as measured with gas chromatography mass spectrometry (GC-MS). After corrections for method blank DEHP, co-eluting compounds, and unidentified carbon, the mean fraction of naturally produced DEHP in butter was determined to be 0.16 ± 0.12 (n = 5, 1σ). To our knowledge, this is the first report of the contemporary fraction of DEHP isolated from market butter in the U.S. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Global workspace dynamics: cortical "binding and propagation" enables conscious contents.

    Science.gov (United States)

    Baars, Bernard J; Franklin, Stan; Ramsoy, Thomas Zoega

    2013-01-01

    A global workspace (GW) is a functional hub of binding and propagation in a population of loosely coupled signaling elements. In computational applications, GW architectures recruit many distributed, specialized agents to cooperate in resolving focal ambiguities. In the brain, conscious experiences may reflect a GW function. For animals, the natural world is full of unpredictable dangers and opportunities, suggesting a general adaptive pressure for brains to resolve focal ambiguities quickly and accurately. GW theory aims to understand the differences between conscious and unconscious brain events. In humans and related species the cortico-thalamic (C-T) core is believed to underlie conscious aspects of perception, thinking, learning, feelings of knowing (FOK), felt emotions, visual imagery, working memory, and executive control. Alternative theoretical perspectives are also discussed. The C-T core has many anatomical hubs, but conscious percepts are unitary and internally consistent at any given moment. Over time, conscious contents constitute a very large, open set. This suggests that a brain-based GW capacity cannot be localized in a single anatomical hub. Rather, it should be sought in a functional hub - a dynamic capacity for binding and propagation of neural signals over multiple task-related networks, a kind of neuronal cloud computing. In this view, conscious contents can arise in any region of the C-T core when multiple input streams settle on a winner-take-all equilibrium. The resulting conscious gestalt may ignite an any-to-many broadcast, lasting ∼100-200 ms, and trigger widespread adaptation in previously established networks. To account for the great range of conscious contents over time, the theory suggests an open repertoire of binding coalitions that can broadcast via theta/gamma or alpha/gamma phase coupling, like radio channels competing for a narrow frequency band. Conscious moments are thought to hold only 1-4 unrelated items; this small

  4. Properties of welded joints of 2,25Cr-1Mo steel with various carbon content

    International Nuclear Information System (INIS)

    Vornovitskij, I.N.; Brodetskaya, E.Z.; Pozdnyakova, A.S.

    1980-01-01

    Properties of welded joints of 2,25 Cr - 1 Mo steel pipelines with different carbon content are considered. It is shown that application of electrodes developed in some countries for welding permits in many cases to exclude heat treatment of welded joints owing to high ductility of weld deposited metal. To improve the ductility, it is necessary to limit both carbon content down to 0,03-0,06% and detrimental elements (sulfur, phosphorus). Heat affected zone hardness may be increased at the expense of carbon. Weld deposited metal possesses the highest long-term strength at the given test temperature; in this case long-term strength of welded joints and base metal is practically the same. The long-term strength of high-carbon steel is higher at the test temperature of 565 deg C as compared to mean-carbon and low-carbon steels, whose long-term strength is practically equal at this temperature. The long-term strength of high-carbon and mean-carbon steels is practically the same and higher as compared with low-carbon one at the test temperature of 510 deg C

  5. Simulated impacts of insect defoliation on forest carbon dynamics

    Science.gov (United States)

    D. Medvigy; K.L. Clark; N.S. Skowronski; K.V.R. Schäfer

    2012-01-01

    Many temperate and boreal forests are subject to insect epidemics. In the eastern US, over 41 million meters squared of tree basal area are thought to be at risk of gypsy moth defoliation. However, the decadal-to-century scale implications of defoliation events for ecosystem carbon dynamics are not well understood. In this study, the effects of defoliation intensity,...

  6. Carbon-14 Content of Carbonaceous Deposits in Oldbury Core Graphite

    International Nuclear Information System (INIS)

    Metcalfe, M.P.; Tzelepi, A.; Gill, J.

    2016-01-01

    Graphite specimens taken from the surface of Magnox reactor core components have been studied by differential thermal oxidation and counting of off-gases to quantify the contribution or otherwise of carbonaceous deposits to the C-14 inventory of the core graphite. While present within the open porosity of the graphite, such deposits formed from polymerization reactions in the CO 2 /CO atmosphere of the reactor and from the decomposition of methane are concentrated predominantly on the outer surfaces of components. An improved understanding of their C-14 content could influence handling of material during decommissioning and could influence treatment options. (author)

  7. Dynamic energy models and carbon mitigation policies

    Science.gov (United States)

    Tilley, Luke A.

    In this dissertation I examine a specific class of energy models and their implications for carbon mitigation policies. The class of models includes a production function capable of reproducing the empirically observed phenomenon of short run rigidity of energy use in response to energy price changes and long run exibility of energy use in response to energy price changes. I use a theoretical model, parameterized using empirical data, to simulate economic performance under several tax regimes where taxes are levied on capital income, investment, and energy. I also investigate transitions from one tax regime to another. I find that energy taxes intended to reduce energy use can successfully achieve those goals with minimal or even positive impacts on macroeconomic performance. But the transition paths to new steady states are lengthy, making political commitment to such policies very challenging.

  8. Application of Fast Pyrolysis Biochar to a Loamy soil - Effects on carbon and nitrogen dynamics and potential for carbon sequestration

    DEFF Research Database (Denmark)

    Bruun, Esben

    and at the same time mitigate climate change by sequestering carbon in the soil. In general, the inherent physicochemical characteristics of biochars make these materials attractive agronomic soil conditioners. However, different pyrolysis technologies exist, i.e. slow pyrolysis, fast pyrolysis, and full...... gasification systems, and each of these influence the biochar quality differently. As of yet, there is only limited knowledge on the effect of applying fast pyrolysis biochar (FP-biochar) to soil. This PhD project provides new insights into the short-term impacts of adding FP-biochar to soil on the greenhouse...... gas (GHG) emissions and on soil carbon and nitrogen dynamics. The FP-biochars investigated in the thesis were generated at different reactor temperatures by fast pyrolysis of wheat straw employing a Pyrolysis Centrifuge Reactor (PCR). The carbohydrate content ranged from more than 35 % in FP...

  9. Relation between PAH and black carbon contents in size fractions of Norwegian harbor sediments

    International Nuclear Information System (INIS)

    Oen, Amy M.P.; Cornelissen, Gerard; Breedveld, Gijs D.

    2006-01-01

    Distributions of total organic carbon (TOC), black carbon (BC), and polycyclic aromatic hydrocarbons (PAH) were investigated in different particle size fractions for four Norwegian harbor sediments. The total PAH (16-EPA) concentrations ranged from 2 to 113 mg/kg dry weight with the greatest fraction of PAH mass in the sand fraction for three of the four sediments. TOC contents ranged from 0.84% to 14.2% and BC contents from 0.085% to 1.7%. This corresponds to organic carbon (OC = TOC - BC) contents in the range of 0.81-14% and BC:TOC ratios of 1.3-18.1%. PAH isomer ratios suggested that the PAH in all four sediments were of pyrogenic origin. Furthermore, stronger correlations between PAH versus BC (r 2 = 0.85) than versus OC (r 2 = 0.15) were found. For all size fractions and bulk sediments, the PAH-to-BC ratios for the total PAHs were on average 6 ± 3 mg PAH/g BC. These results suggest that PAH distributions were dominated by the presence of BC, rather than OC. As sorption to BC is much stronger than sorption to OC, this may result in significantly lower dissolved concentrations of PAH than expected on the basis of organic carbon partitioning alone. - PAH contents correlated better with black carbon than organic carbon for four Norwegian harbor sediments

  10. Estimation of black carbon content for biomass burning aerosols from multi-channel Raman lidar data

    Science.gov (United States)

    Talianu, Camelia; Marmureanu, Luminita; Nicolae, Doina

    2015-04-01

    Biomass burning due to natural processes (forest fires) or anthropical activities (agriculture, thermal power stations, domestic heating) is an important source of aerosols with a high content of carbon components (black carbon and organic carbon). Multi-channel Raman lidars provide information on the spectral dependence of the backscatter and extinction coefficients, embedding information on the black carbon content. Aerosols with a high content of black carbon have large extinction coefficients and small backscatter coefficients (strong absorption), while aerosols with high content of organic carbon have large backscatter coefficients (weak absorption). This paper presents a method based on radiative calculations to estimate the black carbon content of biomass burning aerosols from 3b+2a+1d lidar signals. Data is collected at Magurele, Romania, at the cross-road of air masses coming from Ukraine, Russia and Greece, where burning events are frequent during both cold and hot seasons. Aerosols are transported in the free troposphere, generally in the 2-4 km altitude range, and reaches the lidar location after 2-3 days. Optical data are collected between 2011-2012 by a multi-channel Raman lidar and follows the quality assurance program of EARLINET. Radiative calculations are made with libRadTran, an open source radiative model developed by ESA. Validation of the retrievals is made by comparison to a co-located C-ToF Aerosol Mass Spectrometer. Keywords: Lidar, aerosols, biomass burning, radiative model, black carbon Acknowledgment: This work has been supported by grants of the Romanian National Authority for Scientific Research, Programme for Research- Space Technology and Advanced Research - STAR, project no. 39/2012 - SIAFIM, and by Romanian Partnerships in priority areas PNII implemented with MEN-UEFISCDI support, project no. 309/2014 - MOBBE

  11. Coupled Land Surface-Subsurface Hydrogeophysical Inverse Modeling to Estimate Soil Organic Carbon Content in an Arctic Tundra

    Science.gov (United States)

    Tran, A. P.; Dafflon, B.; Hubbard, S.

    2017-12-01

    Soil organic carbon (SOC) is crucial for predicting carbon climate feedbacks in the vulnerable organic-rich Arctic region. However, it is challenging to achieve this property due to the general limitations of conventional core sampling and analysis methods. In this study, we develop an inversion scheme that uses single or multiple datasets, including soil liquid water content, temperature and ERT data, to estimate the vertical profile of SOC content. Our approach relies on the fact that SOC content strongly influences soil hydrological-thermal parameters, and therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. The scheme includes several advantages. First, this is the first time SOC content is estimated by using a coupled hydrogeophysical inversion. Second, by using the Community Land Model, we can account for the land surface dynamics (evapotranspiration, snow accumulation and melting) and ice/liquid phase transition. Third, we combine a deterministic and an adaptive Markov chain Monte Carlo optimization algorithm to better estimate the posterior distributions of desired model parameters. Finally, the simulated subsurface variables are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using synthetic experiments. The results show that compared to inversion of single dataset, joint inversion of these datasets significantly reduces parameter uncertainty. The joint inversion approach is able to estimate SOC content within the shallow active layer with high reliability. Next, we apply the scheme to estimate OC content along an intensive ERT transect in Barrow, Alaska using multiple datasets acquired in the 2013-2015 period. The preliminary results show a good agreement between modeled and measured soil temperature, thaw layer thickness and electrical resistivity. The accuracy of estimated SOC content

  12. Cement content influence in rebar corrosion in carbonated mortars

    Directory of Open Access Journals (Sweden)

    Américo, P. O.

    2003-12-01

    Full Text Available The cement hydration products protect the concrete rebars of the reinforced concrete due to the production of Ca(OH2, NaOH, and KOH that, upon dissolving in the concrete s aqueous phase, generate a pH above 12.5. However, reinforced concrete structures are exposed to pollutant gases, such as, CO2 which upon penetrating the concrete, reacts with the alkaline components, consequently reducing the pH of the aqueous phase causing the loss of passivity by the rebar and as a consequence its corrosion when there is the presence of humidity and oxygen. The objective of the current paper is the analysis of the alkaline reserve influence, measured by the cement content, in the corrosion of rebars employing the polarization resistance technique for determining the corrosion intensity. Results for corrosion intensity of rebars embedded in prismatic mortar test specimens are produced with three cement content levels, with equal water/cement ratio. Cylindrical test specimens were also used for verification of the capillary absorption and the porosity by means of mercury porosymetry The results show that the initiation period is shorter and the corrosion intensity of the rebars is higher when the cement content is lower However, there is also an alteration in the microstructure upon altering the cement content, and far this reason one cannot conclude that the alkaline reserve alone is responsible for these results.

    Los productos de hidratación del cemento protegen las armaduras embebidas en el hormigón debido a la gran cantidad de Ca(OH2, NaOH y KOH disueltos en la fase acuosa del hormigón que proporcionan un pH mayor que 12,5. Sin embargo, las estructuras de hormigón armado están expuestas a los gases contaminantes como el CO2, que al penetrar en el hormigón reacciona con los compuestos alcalinos, se reduce el pH de la fase acuosa y provocan la despasivación de la armadura. Posteriormente, si hay

  13. Determination of the carbon content of domestic farm produces to estimate offsite C-14 ingestion dose

    International Nuclear Information System (INIS)

    Jung, Y. G.; Kim, M. J.; Lee, G. B.

    2003-01-01

    The carbon content of grains, leafy and root vegetables, and fruits which the Koreans usually eat were calculated to use in the estimation of offsite C-14 ingestion dose. With the data of food intake per day in the Report on 1998 national health and nutrition survey- dietary intake survey, 5 age-group integrate d intake of the 4 farm produce groups were extracted for food items and the amount. Intake percentage in each food group were taken as food weighing factor for the foods. Carbon content was calculated using protein, fat, and carbohydrate content of the foods, and multiplied by the corresponding food weighing factor to derive the content of the food groups. The calculated carbon content of grains, leafy and root vegetables, and fruits were 39.%, 4.2%, 8.0%, and 5.9% respectively. Grains and fruits were not much different from ODCM for carbon content, but vegetables were higher by 0.7%∼4.5%

  14. Incorporating microbial dormancy dynamics into soil decomposition models to improve quantification of soil carbon dynamics of northern temperate forests

    Energy Technology Data Exchange (ETDEWEB)

    He, Yujie [Purdue Univ., West Lafayette, IN (United States). Dept. of Earth, Atmospheric, and Planetary Sciences; Yang, Jinyan [Univ. of Georgia, Athens, GA (United States). Warnell School of Forestry and Natural Resources; Northeast Forestry Univ., Harbin (China). Center for Ecological Research; Zhuang, Qianlai [Purdue Univ., West Lafayette, IN (United States). Dept. of Earth, Atmospheric, and Planetary Sciences; Purdue Univ., West Lafayette, IN (United States). Dept. of Agronomy; Harden, Jennifer W. [U.S. Geological Survey, Menlo Park, CA (United States); McGuire, Anthony D. [Alaska Cooperative Fish and Wildlife Research Unit, U.S. Geological Survey, Univ. of Alaska, Fairbanks, AK (United States). U.S. Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit; Liu, Yaling [Purdue Univ., West Lafayette, IN (United States). Dept. of Earth, Atmospheric, and Planetary Sciences; Wang, Gangsheng [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Climate Change Science Inst. and Environmental Sciences Division; Gu, Lianhong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division

    2015-11-20

    Soil carbon dynamics of terrestrial ecosystems play a significant role in the global carbon cycle. Microbial-based decomposition models have seen much growth recently for quantifying this role, yet dormancy as a common strategy used by microorganisms has not usually been represented and tested in these models against field observations. Here in this study we developed an explicit microbial-enzyme decomposition model and examined model performance with and without representation of microbial dormancy at six temperate forest sites of different forest types. We then extrapolated the model to global temperate forest ecosystems to investigate biogeochemical controls on soil heterotrophic respiration and microbial dormancy dynamics at different temporal-spatial scales. The dormancy model consistently produced better match with field-observed heterotrophic soil CO2 efflux (RH) than the no dormancy model. Our regional modeling results further indicated that models with dormancy were able to produce more realistic magnitude of microbial biomass (<2% of soil organic carbon) and soil RH (7.5 ± 2.4 PgCyr-1). Spatial correlation analysis showed that soil organic carbon content was the dominating factor (correlation coefficient = 0.4-0.6) in the simulated spatial pattern of soil RH with both models. In contrast to strong temporal and local controls of soil temperature and moisture on microbial dormancy, our modeling results showed that soil carbon-to-nitrogen ratio (C:N) was a major regulating factor at regional scales (correlation coefficient = -0.43 to -0.58), indicating scale-dependent biogeochemical controls on microbial dynamics. Our findings suggest that incorporating microbial dormancy could improve the realism of microbial-based decomposition models and enhance the integration of soil experiments and mechanistically based modeling.

  15. Measuring quality of omnidirectional high dynamic range content

    Science.gov (United States)

    Perrin, Anne-Flore; Bist, Cambodge; Cozot, Rémi; Ebrahimi, Touradj

    2017-09-01

    Although HDR content processing, coding and quality assessment have been largely addressed in the last few years, little to no work has been concentrating on how to assess quality in HDR for 360° or omnidirectional content. This paper is an attempt to answer to various questions in this direction. As a minimum, a new data set for 360° HDR content is proposed and a new methodology is designed to assess subjective quality of HDR 360° content when it is displayed on SDR HMD after applying various tone mapping operators. The results are then analyzed and conclusions are drawn.

  16. FP corrosion dependence on carbon and chromium content in Fe-Cr steel

    International Nuclear Information System (INIS)

    Sasaki, Koei; Tanigaki, Takanori; Fukumoto, Ken-ichi; Uno, Masayoshi

    2015-01-01

    In an attempt to investigate Cs or Cs-Te corrosion dependence on chromium or carbon content in Fe-Cr steel, cesium and Cs-Te corrosion test were performed to three specimens, Fe-9Cr-0C, Fe-9Cr-0.14C and Fe-13Cr-0.14C, for 100 hours at 973K in simulated high burn-up fuel pin environment. Cesium corrosion depth has no dependence on chromium or carbon content in Fe-Cr steel. Cs-Te corrosion was appeared in only Fe-13Cr-0.14C which has chromium carbides ranged along grain boundary. Appearance of the Cs-Te corrosion was determined by distribution or arrangement of chromium carbides which depends on chromium and carbon content. (author)

  17. Modeling Potential Carbon Monoxide Exposure Due to Operation of a Major Rocket Engine Altitude Test Facility Using Computational Fluid Dynamics

    Science.gov (United States)

    Blotzer, Michael J.; Woods, Jody L.

    2009-01-01

    This viewgraph presentation reviews computational fluid dynamics as a tool for modelling the dispersion of carbon monoxide at the Stennis Space Center's A3 Test Stand. The contents include: 1) Constellation Program; 2) Constellation Launch Vehicles; 3) J2X Engine; 4) A-3 Test Stand; 5) Chemical Steam Generators; 6) Emission Estimates; 7) Located in Existing Test Complex; 8) Computational Fluid Dynamics; 9) Computational Tools; 10) CO Modeling; 11) CO Model results; and 12) Next steps.

  18. Radiocarbon Content of Dissolved Organic Carbon in the South Indian Ocean

    Science.gov (United States)

    Bercovici, S. K.; McNichol, A. P.; Xu, L.; Hansell, D. A.

    2018-01-01

    We report four profiles of the radiocarbon content of dissolved organic carbon (DOC) spanning the South Indian Ocean (SIO), ranging from the Polar Front (56°S) to the subtropics (29°S). Surface waters held mean DOC Δ14C values of -426 ± 6‰ ( 4,400 14C years) at the Polar Front and DOC Δ14C values of -252 ± 22‰ ( 2,000 14C years) in the subtropics. At depth, Circumpolar Deep Waters held DOC Δ14C values of -491 ± 13‰ ( 5,400 years), while values in Indian Deep Water were more depleted, holding DOC Δ14C values of -503 ± 8‰ ( 5,600 14C years). High-salinity North Atlantic Deep Water intruding into the deep SIO had a distinctly less depleted DOC Δ14C value of -481 ± 8‰ ( 5,100 14C years). We use multiple linear regression to assess the dynamics of DOC Δ14C values in the deep Indian Ocean, finding that their distribution is characteristic of water masses in that region.

  19. Influence of legume crops on content of organic carbon in sandy soil

    Directory of Open Access Journals (Sweden)

    Hajduk Edmund

    2015-06-01

    Full Text Available The paper presents the results of a 3-year field experiment designed to evaluate the content of organic carbon in brown soil (Haplic Cambisol Dystric developed from a light loamy sand under legumes cultivation. Experimental factors were: species of legume crop (colorful-blooming pea (Pisum sativum, chickling vetch (Lathyrus sativus, narrow-leafed lupin (Lupinus angustifolius, methods of legumes tillage (legumes in pure culture and in mixture with naked oats and mineral N fertilization (0, 30, 60, 90 kg N·ha−1. Cultivation of legumes on sandy soil did not result in an increase of organic carbon content in the soil after harvest as compared to the initial situation, i.e. 7.39 vs. 7.76 g·kg−1 dry matter (DM, on average, respectively. However, there was the beneficial effect of this group of plants on soil abundance in organic matter, the manifestation of which was higher content of organic carbon in soils after legume harvest as compared to soils with oats grown (7.21 g·kg−1 DM, on average. Among experimental crops, cultivation of pea exerted the most positive action to organic carbon content (7.58 g·kg−1, after harvest, on average, whereas narrow-leaved lupin had the least effect on organic carbon content (7.23 g·kg−1, on average. Pure culture and greater intensity of legume cultivation associated with the use of higher doses of mineral nitrogen caused less reduction in organic carbon content in soils after harvest.

  20. Dynamics of soil organic carbon and microbial biomass carbon in relation to water erosion and tillage erosion.

    Science.gov (United States)

    Xiaojun, Nie; Jianhui, Zhang; Zhengan, Su

    2013-01-01

    Dynamics of soil organic carbon (SOC) are associated with soil erosion, yet there is a shortage of research concerning the relationship between soil erosion, SOC, and especially microbial biomass carbon (MBC). In this paper, we selected two typical slope landscapes including gentle and steep slopes from the Sichuan Basin, China, and used the (137)Cs technique to determine the effects of water erosion and tillage erosion on the dynamics of SOC and MBC. Soil samples for the determination of (137)Cs, SOC, MBC and soil particle-size fractions were collected on two types of contrasting hillslopes. (137)Cs data revealed that soil loss occurred at upper slope positions of the two landscapes and soil accumulation at the lower slope positions. Soil erosion rates as well as distribution patterns of the erosion is the major process of soil redistribution in the gentle slope landscape, while tillage erosion acts as the dominant process of soil redistribution in the steep slope landscape. In gentle slope landscapes, both SOC and MBC contents increased downslope and these distribution patterns were closely linked to soil redistribution rates. In steep slope landscapes, only SOC contents increased downslope, dependent on soil redistribution. It is noticeable that MBC/SOC ratios were significantly lower in gentle slope landscapes than in steep slope landscapes, implying that water erosion has a negative effect on the microbial biomass compared with tillage erosion. It is suggested that MBC dynamics are closely associated with soil redistribution by water erosion but independent of that by tillage erosion, while SOC dynamics are influenced by soil redistribution by both water erosion and tillage erosion.

  1. Dynamics of Soil Organic Carbon and Microbial Biomass Carbon in Relation to Water Erosion and Tillage Erosion

    Science.gov (United States)

    Xiaojun, Nie; Jianhui, Zhang; Zhengan, Su

    2013-01-01

    Dynamics of soil organic carbon (SOC) are associated with soil erosion, yet there is a shortage of research concerning the relationship between soil erosion, SOC, and especially microbial biomass carbon (MBC). In this paper, we selected two typical slope landscapes including gentle and steep slopes from the Sichuan Basin, China, and used the 137Cs technique to determine the effects of water erosion and tillage erosion on the dynamics of SOC and MBC. Soil samples for the determination of 137Cs, SOC, MBC and soil particle-size fractions were collected on two types of contrasting hillslopes. 137Cs data revealed that soil loss occurred at upper slope positions of the two landscapes and soil accumulation at the lower slope positions. Soil erosion rates as well as distribution patterns of the erosion is the major process of soil redistribution in the gentle slope landscape, while tillage erosion acts as the dominant process of soil redistribution in the steep slope landscape. In gentle slope landscapes, both SOC and MBC contents increased downslope and these distribution patterns were closely linked to soil redistribution rates. In steep slope landscapes, only SOC contents increased downslope, dependent on soil redistribution. It is noticeable that MBC/SOC ratios were significantly lower in gentle slope landscapes than in steep slope landscapes, implying that water erosion has a negative effect on the microbial biomass compared with tillage erosion. It is suggested that MBC dynamics are closely associated with soil redistribution by water erosion but independent of that by tillage erosion, while SOC dynamics are influenced by soil redistribution by both water erosion and tillage erosion. PMID:23717530

  2. Dynamic topography and the Cenozoic carbonate compensation depth

    Science.gov (United States)

    Campbell, S. M.; Moucha, R.; Raymo, M. E.; Derry, L. A.

    2015-12-01

    The carbonate compensation depth (CCD), the ocean depth at which the calcium carbonate accumulation rate goes to zero, can provide valuable insight into climatic and weathering conditions over the Cenozoic. The paleoposition of the CCD can be inferred from sediment core data. As the carbonate accumulation rate decreases linearly with depth between the lysocline and CCD, the CCD can be calculated using a linear regression on multiple sediment cores with known carbonate accumulation rates and paleodepths. It is therefore vital to have well-constrained estimates of paleodepths. Paleodepths are typically calculated using models of thermal subsidence and sediment loading and compaction. However, viscous convection-related stresses in the mantle can warp the ocean floor by hundreds of meters over broad regions and can also vary significantly over millions of years. This contribution to paleobathymetry, termed dynamic topography, can be calculated by modeling mantle flow backwards in time. Herein, we demonstrate the effect dynamic topography has on the inference of the late Cenozoic CCD with an example from the equatorial Pacific, considering sites from IODP Expeditions 320/321. The equatorial Pacific, given its large size and high productivity, is closely tied to the global carbon cycle. Accordingly, long-term changes in the equatorial Pacific CCD can be considered to reflect global changes in weathering fluxes and the carbon cycle, in addition to more regional changes in productivity and thermohaline circulation. We find that, when the dynamic topography contribution to bathymetry is accounted for, the equatorial Pacific CCD is calculated to be appreciably shallower at 30 Ma than previous estimates would suggest, implying a greater deepening of the Pacific CCD over the late Cenozoic.

  3. Size-dependence of volatile and semi-volatile organic carbon content in phytoplankton cells

    Directory of Open Access Journals (Sweden)

    Sergio eRuiz-Halpern

    2014-07-01

    Full Text Available The content of volatile and semivolatile organic compounds (VOC and SOC, measured as exchangeable dissolved organic carbon (EDOC, was quantified in 9 phytoplanktonic species that spanned 4 orders of magnitude in cell volume, by disrupting the cells and quantifying the gaseous organic carbon released. EDOC content varied 4 orders of magnitude, from 0.0015 to 14.12 pg C cell-1 in the species studied and increased linearly with increasing phytoplankton cell volume following the equation EDOC (pg C cell-1 = -2.35 x cellular volume (CV, µm3 cell-1 0.90 (± 0.3, with a slope (0.90 not different from 1 indicating a constant increase in volatile carbon as the cell size of phytoplankton increased. The percentage of EDOC relative to total cellular carbon was small but varied 20 fold from 0.28 % to 5.17 %, and no obvious taxonomic pattern in the content of EDOC was appreciable for the species tested. The cell release rate of EDOC is small compared to the amount of carbon in the cell and difficult to capture. Nonetheless, the results point to a potential flux of volatile and semivolatile phytoplankton-derived organic carbon to the atmosphere that has been largely underestimated and deserves further attention in the future.

  4. Carbon Prices: Dynamic analysis of European and Californian markets

    Science.gov (United States)

    Sousa, Rita Mafalda Dionisio de

    Carbon markets' goal is to promote the reduction of emissions of greenhouse gases where it is most cost-efficient. This makes the price of the tradable good - carbon dioxide equivalent (CO2e) - a key variable in management and risk decisions, in markets related to activities connected with the burning of fossil fuels, such as power generation. This work aims to improve the analysis of carbon prices' dynamics, considering the possibility of multidirectional effects between prices of CO2e, energy (primary and final), offsets licenses and the economy performance, in various frequencies. The two main research questions are: (i) what drives carbon price variations? (ii) what variations do carbon prices drive? We used two comple-mentary methodologies: (a) a vector autoregression model (of common use in macroeconomics and financial markets but not in carbon-energy relations), which allows the analysis of causality and of impulse-response functions of daily prices; and (b) an innovative multivariate wavelet analysis, which allows us to understand the relationship and causal link between the variables in the time and frequency dimensions, particularly in longer cycles (4 8 and 8 20 months), not perceived in previous studies. As case studies we considered the European (EU ETS) and Califor-nia (AB32) carbon markets. This is the first research to present the analysis of the referred US market. The analysis covers the 2008-2013 period, intentionally excluding the EU ETS phase I, for greater consistency of results. Results suggest that the economy and electricity drive the price of European carbon, while gas and oil have a greater role in California. So, there is a greater influence of final energy prices in the most mature market. We also observe that the price of CERs does not affect the European carbon price. On the other hand, this study shows for the first time that carbon prices have impacts on electricity prices over longer cycles (8 20 months) and in coal over short

  5. Observations and assessment of forest carbon dynamics following disturbance in North America

    Science.gov (United States)

    S. J. Goetz; B. Bond-Lamberty; B. E. Law; J. A. Hicke; C. Huang; R. A. Houghton; S. McNulty; T. O’Halloran; M. Harmon; A. J. H. Meddens; E. M. Pfeifer; D. Mildrexler; E. S. Kasischke

    2012-01-01

    Disturbance processes of various types substantially modify ecosystem carbon dynamics both temporally and spatially, and constitute a fundamental part of larger landscape-level dynamics. Forests typically lose carbon for several years to several decades following severe disturbance, but our understanding of the duration and dynamics of post-disturbance forest carbon...

  6. Effect of carbon black content on the microwave absorbing properties of CB/epoxy composites

    Directory of Open Access Journals (Sweden)

    Pourya Mehdizadeh

    2016-04-01

    Full Text Available To prevent serious electromagnetic interference, a single-layer and double layer wave-absorbing coating employing complex absorbents composed of carbon black with epoxy resin as matrix was prepared. The morphologies of carbon black /epoxy composites were characterized by scanning electron microscope  and atomic force microscope, respectively. The carbon black  particles exhibit obvious polyaromatic were characterized by X-ray diffraction. The electromagnetic parameters of carbon black  were measured in the frequency range of 8–12 GHz by transmission/reflection technology, and the electromagnetic loss mechanisms of the two particles were discussed, respectively. The microwave absorption properties of the coatings were investigated by measuring reflection loss  using arch method. The effects of carbon black  mass ratio, thickness and double-layer on the microwave absorption properties were discussed, respectively. The results showed that the higher thickness, higher ratio and double-layer of carbon black /epoxy content could make the absorption band shift towards the lower frequency range. Significantly, the wave-absorbing coating could be applied in different frequency ranges according to actual demand by controlling the content of carbon black  in composites.

  7. Insights into soil carbon dynamics across climatic gradients from carbon-pool specific radiocarbon analyses

    Science.gov (United States)

    van der Voort, Tessa Sophia; Hagedorn, Frank; McIntyre, Cameron; Zell, Claudia; Eglinton, Timothy Ian

    2017-04-01

    Soil carbon constitutes the largest terrestrial reservoir of organic carbon, and therefore understanding the mechanisms and drivers of carbon stabilization is crucial, especially in the framework of climate change. The understanding of the dependence of soil organic turnover in specific carbon pools as related to e.g. climate, soil texture and mineralogy is limited. In this framework, radiocarbon constitutes a uniquely powerful tool that help to unravel carbon dynamics from decadal to millennial timescales. This project combines bulk and pool-specific radiocarbon analyses in the top and deep soil on a wide range of forested soils that span a large climatic gradient (MAT 1.3-9.2°C, MAP 600 to 2100 mm m-2y-1). These well-studies sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). This study aims to combine the insights gained from bulk and pool-specific turnover to environmental conditions and molecular composition of soil carbon. The pools investigated span the mineral-associated (occluded and heavy fractions from density fractionation) and potentially water-soluble (free light fractions from density fractionation and water extractable organic carbon) organic carbon fractions. Pool-specific radiocarbon work is augmented by the measurement of abundance of compounds such as alkanes, fatty acids and lignin phenols on a subset of samples. Initial results show disparate patterns depending on soil type and in particular soil texture, which could be indicative of various stabilization mechanisms in different soils. Overall, this study provides new insights into the controls of soil organic matter dynamics as related to environmental conditions, in particular in specific sub-pools of carbon.

  8. Variations and determinants of carbon content in plants: a global synthesis

    Directory of Open Access Journals (Sweden)

    S. Ma

    2018-02-01

    Full Text Available Plant carbon (C content is one of the most important plant traits and is critical to the assessment of global C cycle and ecological stoichiometry; however, the global variations in plant C content remain poorly understood. In this study, we conducted a global analysis of the plant C content by synthesizing data from 4318 species to document specific values and their variation of the C content across plant organs and life forms. Plant organ C contents ranged from 45.0 % in reproductive organs to 47.9 % in stems at global scales, which were significantly lower than the widely employed canonical value of 50 %. Plant C content in leaves (global mean of 46.9 % was higher than that in roots (45.6 %. Across life forms, woody plants exhibited higher C content than herbaceous plants. Conifers, relative to broad-leaved woody species, had higher C content in roots, leaves, and stems. Plant C content tended to show a decrease with increasing latitude. The life form explained more variation of the C content than climate. Our findings suggest that specific C content values of different organs and life forms developed in our study should be incorporated into the estimations of regional and global vegetation biomass C stocks.

  9. Northern peatland carbon stocks and dynamics: a review

    Directory of Open Access Journals (Sweden)

    Z. C. Yu

    2012-10-01

    Full Text Available Peatlands contain a large belowground carbon (C stock in the biosphere, and their dynamics have important implications for the global carbon cycle. However, there are still large uncertainties in C stock estimates and poor understanding of C dynamics across timescales. Here I review different approaches and associated uncertainties of C stock estimates in the literature, and on the basis of the literature review my best estimate of C stocks and uncertainty is 500 ± 100 (approximate range gigatons of C (Gt C in northern peatlands. The greatest source of uncertainty for all the approaches is the lack or insufficient representation of data, including depth, bulk density and carbon accumulation data, especially from the world's large peatlands. Several ways to improve estimates of peat carbon stocks are also discussed in this paper, including the estimates of C stocks by regions and further utilizations of widely available basal peat ages.

    Changes in peatland carbon stocks over time, estimated using Sphagnum (peat moss spore data and down-core peat accumulation records, show different patterns during the Holocene, and I argue that spore-based approach underestimates the abundance of peatlands in their early histories. Considering long-term peat decomposition using peat accumulation data allows estimates of net carbon sequestration rates by peatlands, or net (ecosystem carbon balance (NECB, which indicates more than half of peat carbon (> 270 Gt C was sequestrated before 7000 yr ago during the Holocene. Contemporary carbon flux studies at 5 peatland sites show much larger NECB during the last decade (32 ± 7.8 (S.E. g C m−2 yr–1 than during the last 7000 yr (∼ 11 g C m−2 yr–1, as modeled from peat records across northern peatlands. This discrepancy highlights the urgent need for carbon accumulation data and process understanding, especially at decadal and centennial timescales

  10. The effect of carbon content on mechanical properties, failure and corrosion resistance of deposited chromium metal

    Directory of Open Access Journals (Sweden)

    Леонід Кімович Лещинськiй

    2017-06-01

    Full Text Available It has been shown that if choosing a metal composition for surfacing rolls and rollers of continuous casting machines, both the carbon impact on the mechanical and functional properties and the critical values of the chromium concentration, which determine the corrosion resistance of the metal with regard to electrochemical corrosion theory, should be considered as well. The paper studied the effect of chromium and carbon steel the X5-X12 type on the structure, technological strength, mechanical properties, fracturing resistance and corrosion resistance of the weld metal. The composition of chromium tool steels (deposited metal (X5-used for the rolls of hot rolling mills and (X12-used for continuous casting machines rollers correspond to these values. The impact of carbon on the properties of the deposited metal containing chromium was considered by comparing the data for both types of the deposited metal. It was found that for both types of the deposited metal (X5 and X12, the limiting value of the carbon content, providing an optimal combination of strength, ductility, failure resistance is the same. If the carbon content is more than the limiting value – (0,25% the technological strength and failure resistance of the deposited metal significantly reduce. With increasing carbon content from 0,18 to 0,25% the martensite structure has a mixed morphology – lath and plate. The strength and toughness of the deposited metal grow. Of particular interest is simultaneous increase in the specific work of failure resulted from crack inhibition at the boundary with far less solid and more ductile ferrite. As for the 5% chromium metal, the X12 type composition with 0,25% C, is borderline. With a further increase in the carbon content of the metal both ductility and failure resistance sharply decrease and with 0,40% C the growth rate of fatigue crack increases by almost 1,5 times

  11. DYNAMICS OF CARBON SEQUESTRATION IN ABANDONED GRASSLANDS OF NORTHEASTERN MEXICO

    Directory of Open Access Journals (Sweden)

    José Israel Yerena Yamallel

    2014-04-01

    Full Text Available Livestock activities due to the improper handling of the load capacity, suffer from low productivity in their grasslands, which are abandoned giving rise to the appearance of species considered invasive and undesirable for producers, without knowing the qualities of these as mitigating of climate change. The objective of the present study was to estimate the carbon content in tamaulipan thornscrub and three abandoned grasslands with a time of abandonment of 10, 20 and 30 years. For the estimation of the carbon content was used a systematic sampling design, in each area were established four sampling sites of 1,600 m2. The primary scrub is the system that resulted in the largest value of carbon content of 14.25 Mg ha-1, followed by the grasslands of 30, 20 and 10 years with 8.03, 7.33 and 4.13 Mg ha-1 respectively. It was concluded that recovering the initial state of the primary scrub take many years, as can be seen in the grasslands system 30 years reaching only 56% of what it had in reserves of primary scrub.

  12. The effect of empirical potential functions on modeling of amorphous carbon using molecular dynamics method

    International Nuclear Information System (INIS)

    Li, Longqiu; Xu, Ming; Song, Wenping; Ovcharenko, Andrey; Zhang, Guangyu; Jia, Ding

    2013-01-01

    Empirical potentials have a strong effect on the hybridization and structure of amorphous carbon and are of great importance in molecular dynamics (MD) simulations. In this work, amorphous carbon at densities ranging from 2.0 to 3.2 g/cm 3 was modeled by a liquid quenching method using Tersoff, 2nd REBO, and ReaxFF empirical potentials. The hybridization, structure and radial distribution function G(r) of carbon atoms were analyzed as a function of the three potentials mentioned above. The ReaxFF potential is capable to model the change of the structure of amorphous carbon and MD results are in a good agreement with experimental results and density function theory (DFT) at low density of 2.6 g/cm 3 and below. The 2nd REBO potential can be used when amorphous carbon has a very low density of 2.4 g/cm 3 and below. Considering the computational efficiency, the Tersoff potential is recommended to model amorphous carbon at a high density of 2.6 g/cm 3 and above. In addition, the influence of the quenching time on the hybridization content obtained with the three potentials is discussed.

  13. Soil organic matter dynamics and the global carbon cycle

    International Nuclear Information System (INIS)

    Post, W.M.; Emanuel, W.R.; King, A.W.

    1992-01-01

    The large size and potentially long residence time of the soil organic matter pool make it an important component of the global carbon cycle. Net terrestrial primary production of about 60 Pg C·yr -1 is, over a several-year period of time, balanced by an equivalent flux of litter production and subsequent decomposition of detritus and soil organic matter. We will review many of the major factors that influence soil organic matter dynamics that need to be explicitly considered in development of global estimates of carbon turnover in the world's soils. We will also discuss current decomposition models that are general enough to be used to develop a representation of global soil organic matter dynamics

  14. Current-induced dynamics in carbon atomic contacts

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Gunst, Tue; Brandbyge, Mads

    2011-01-01

    carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias...... of molecular-scale contacts. Systems based on molecules bridging electrically gated graphene electrodes may offer an interesting test-bed for these effects. Results: We employ a semi-classical Langevin approach in combination with DFT calculations to study the current-induced vibrational dynamics of an atomic...... voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed...

  15. Contents

    Directory of Open Access Journals (Sweden)

    Editor IJRED

    2012-11-01

    Full Text Available International Journal of Renewable Energy Development www.ijred.com Volume 1             Number 3            October 2012                ISSN 2252- 4940   CONTENTS OF ARTICLES page Design and Economic Analysis of a Photovoltaic System: A Case Study 65-73 C.O.C. Oko , E.O. Diemuodeke, N.F. Omunakwe, and E. Nnamdi     Development of Formaldehyde Adsorption using Modified Activated Carbon – A Review 75-80 W.D.P Rengga , M. Sudibandriyo and M. Nasikin     Process Optimization for Ethyl Ester Production in Fixed Bed Reactor Using Calcium Oxide Impregnated Palm Shell Activated Carbon (CaO/PSAC 81-86 A. Buasri , B. Ksapabutr, M. Panapoy and N. Chaiyut     Wind Resource Assessment in Abadan Airport in Iran 87-97 Mojtaba Nedaei       The Energy Processing by Power Electronics and its Impact on Power Quality 99-105 J. E. Rocha and B. W. D. C. Sanchez       First Aspect of Conventional Power System Assessment for High Wind Power Plants Penetration 107-113 A. Merzic , M. Music, and M. Rascic   Experimental Study on the Production of Karanja Oil Methyl Ester and Its Effect on Diesel Engine 115-122 N. Shrivastava,  , S.N. Varma and M. Pandey  

  16. Using elevation gradients to study climate controls on soil carbon dynamics

    Science.gov (United States)

    Trumbore, S.; Marzaioli, F.; Castanha, C.; Amundson, R.

    2009-04-01

    Elevation gradients provide the opportunity to study vegetation and climate gradients in a setting where other soil forming factors such as parent material and soil age are held constant. We use the observed changes in radiocarbon content of organic matter fractionated by density and other methods to infer the dynamics of soil carbon and how it varies with elevation along transects in the Sierra Nevada mountains in California, USA. In surface litter layers, changes in the radiocarbon content from 1992 to 2006 in litter layers show that these layers are more dynamic than originally inferred from a comparison based on changes between the 1950s and the 1990s. In mineral soils, fractions often considered to be the most slowly cycling (hydrolysis residue) showed large changes in 14C in the last decade. We use incubations to determine the mean age of carbon respired by microbes along the same gradients; these data are compared to incubations from other sites and show that climate and vegetation are a major controls of the mean age of fast-cycling carbon in litter and soils.

  17. Simulated impacts of insect defoliation on forest carbon dynamics

    International Nuclear Information System (INIS)

    Medvigy, D; Clark, K L; Skowronski, N S; Schäfer, K V R

    2012-01-01

    Many temperate and boreal forests are subject to insect epidemics. In the eastern US, over 41 million meters squared of tree basal area are thought to be at risk of gypsy moth defoliation. However, the decadal-to-century scale implications of defoliation events for ecosystem carbon dynamics are not well understood. In this study, the effects of defoliation intensity, periodicity and spatial pattern on the carbon cycle are investigated in a set of idealized model simulations. A mechanistic terrestrial biosphere model, ecosystem demography model 2, is driven with observations from a xeric oak–pine forest located in the New Jersey Pine Barrens. Simulations indicate that net ecosystem productivity (equal to photosynthesis minus respiration) decreases linearly with increasing defoliation intensity. However, because of interactions between defoliation and drought effects, aboveground biomass exhibits a nonlinear decrease with increasing defoliation intensity. The ecosystem responds strongly with both reduced productivity and biomass loss when defoliation periodicity varies from 5 to 15 yr, but exhibits a relatively weak response when defoliation periodicity varies from 15 to 60 yr. Simulations of spatially heterogeneous defoliation resulted in markedly smaller carbon stocks than simulations with spatially homogeneous defoliation. These results show that gypsy moth defoliation has a large effect on oak–pine forest biomass dynamics, functioning and its capacity to act as a carbon sink. (letter)

  18. Irradiation of carbon nanotubes with carbon projectiles: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Denton, Cristian D. [Departamento de Fisica Aplicada, Universidad de Alicante, 03080 Alicante (Spain); Heredia-Avalos, Santiago; Moreno-Marin, Juan Carlos [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, 03080 Alicante (Spain)

    2013-04-15

    The irradiation of carbon based nanostructures with ions and electrons has been shown to be an appropriate tool to tailor their properties. The defects induced in the nanostructures during irradiation are able to modify their mechanical and electronic properties. Here we simulate the irradiation of carbon nanotubes with carbon ions using a molecular dynamics code. We use the Tersoff potential joined smoothly to the Universal Ziegler-Biersack-Littmark potential at short distances. We study the number of defects produced after irradiation with a single carbon ion finding a saturation with its energy at {proportional_to} 3 keV. We observe, after continuum irradiation with low energy ions, the formation of bumps in the irradiated region. For larger energy ions we find that the diameter of the nanotube shrinks as shown in previous works. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Carbon and nitrogen in Danish forest soils - Contents and distribution determined by soil order

    DEFF Research Database (Denmark)

    Vejre, Henrik; Callesen, Ingeborg; Vesterdal, Lars

    2003-01-01

    Increasing atmospheric CO2 concentrations, and widespread deposition of N to terrestrial ecosystems has increased the focus on soil C and N pools. The aim of this study was to estimate the size and distribution of organic C and N pools in well-drained Danish forest soils. We examined 140 forest......)) and least in Spodosols (0.51 kg m(-2)). The main contributor to the high C content in Spodosols is the spodic horizons containing illuvial humus, and thick organic horizons. Carbon and N concentrations decreased with soil depth. Soil clay content was negatively correlated to C content and positively...

  20. Properties of carbon composite paper derived from coconut coir as a function of polytetrafluoroethylene content

    Science.gov (United States)

    Destyorini, Fredina; Indriyati; Indayaningsih, Nanik; Prihandoko, Bambang; Zulfia Syahrial, Anne

    2018-03-01

    The carbon composite papers were produced by utilizing carbon materials from coconut coir. In the present work, carbon composite papers (CCP) were prepared by mixing carbon materials in the form of powder and fibre with polymer (ethylene vinyl acetate and polyethylene glycol) in xylene at 100°C. Then, polytetrafluoroethylene (PTFE) with different content was used to treat the surface of CCP. The properties of PTFE-coated CCP were analysed by means of contact angle measurement, tensile testing, porosity, density, and electrical conductivity measurements. As expected, all CCP’s surfaces treated with PTFE were found to be hydrophobic with contact angle >120° and relatively constant during 60 minutes measurement. Furthermore, water contact angle, density, and mechanical properties of CCP generally increase with increasing PTFE content. However, the porosity and electrical conductivity of CCP decrease slightly as the PTFE content increased from 0 wt% to 30 wt%. Based on the observation and analysis, the optimum PTFE content on CCP was 20 %, in which the mechanical properties and hydrophobicity behaviour were improved significantly, but it was only caused a very small drop in porosity and electrical conductivity

  1. Size distribution and carbonate content of the sediments of the western shelf of India

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Pylee, A.

    Sediment samples collected during the 25th cruise of I.N.S. KISTNA (Indian Programme of I.I.O.E.) were analysed for grain size and carbonate content. The shelf sediments show well defined zonation, except where river-borne sediments tend to mask...

  2. Organic carbon content of zooplankton from the nearshore waters of Bombay

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.; Gajbhiye, S.N.; Sayed, F.Y.

    Organic carbon content of zooplankton in the Versova Creek and Thana Creek (polluted areas), off Versova and off Mahim, Bombay, India (relatively unpolluted areas) varied respectively from 21.4-30, 13.2-38.4, 21.6-30 and 25.8-39.6% dry weight...

  3. A study of the carbon dynamics of Japanese grassland and forest using 14C and 13C

    International Nuclear Information System (INIS)

    Katsuno, Kazumi; Miyairi, Yosuke; Tamura, Kenji; Matsuzaki, Hiroyuki; Fukuda, Kenji

    2010-01-01

    We quantified the carbon contents of grassland and forest soil using conventional methods and studied the changes in their dynamics by measuring δ 13 C and Δ 14 C. Soil samples were taken from a neighboring Miscanthus sinensis grassland and Pinus densiflora forest in central Japan. Both had been maintained as grassland until the 1960s, when the latter was abandoned and became a pine forest by natural succession. The soil carbon content of the forest was much lower than that of the grassland, implying that the soil carbon decreased as the grassland became forest. The δ 13 C values were very similar in the grassland and forest, at approximately -20 per mille , suggesting that M. sinensis (a C4 plant) contributed to carbon storage, whereas there was little carbon accumulation from P. densiflora (a C3 plant) in forest soil. The Δ 14 C values and calculated soil carbon mean residence time (MRT) showed that the soil carbon in the upper A horizon was older, and that in the lower A horizon was younger in forest than in grassland. From these results, we conclude that young, fast-MRT soil carbon is decomposed in the upper A horizon, and old, stable soil carbon was decomposed in the lower A horizon after the pine invasion.

  4. Dynamic Content in Future Internet Opportunities Grad Course

    DEFF Research Database (Denmark)

    Frick, Jan; Pedersen, Jens Myrup

    2017-01-01

    and digital content: Videos, quizzes, articles to read, assignments, etc. In addition to making it all available on online platforms, we are also experimenting with making it available offline as e-books. This has several advantages, e.g. it can be accessed offline, and it is not depending on platforms...

  5. An objective method for High Dynamic Range source content selection

    DEFF Research Database (Denmark)

    Narwaria, Manish; Mantel, Claire; Da Silva, Matthieu Perreira

    2014-01-01

    component of such validation studies is the selection of a challenging and balanced set of source (reference) HDR content. In order to facilitate this, we present an objective method based on the premise that a more challenging HDR scene encapsulates higher contrast, and as a result will show up more...

  6. Importance of vegetation dynamics for future terrestrial carbon cycling

    Science.gov (United States)

    Ahlström, Anders; Xia, Jianyang; Arneth, Almut; Luo, Yiqi; Smith, Benjamin

    2015-05-01

    Terrestrial ecosystems currently sequester about one third of anthropogenic CO2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand

  7. Importance of vegetation dynamics for future terrestrial carbon cycling

    International Nuclear Information System (INIS)

    Ahlström, Anders; Smith, Benjamin; Xia, Jianyang; Luo, Yiqi; Arneth, Almut

    2015-01-01

    Terrestrial ecosystems currently sequester about one third of anthropogenic CO 2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO 2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand

  8. Caffeine content of prepackaged national-brand and private-label carbonated beverages.

    Science.gov (United States)

    Chou, K-H; Bell, L N

    2007-08-01

    Caffeine is a well-known stimulant that is added as an ingredient to various carbonated soft drinks. Due to its stimulatory and other physiological effects, individuals desire to know the exact amount of caffeine consumed from these beverages. This study analyzed the caffeine contents of 56 national-brand and 75 private-label store-brand carbonated beverages using high-performance liquid chromatography. Caffeine contents ranged from 4.9 mg/12 oz (IGA Cola) to 74 mg/12 oz (Vault Zero). Some of the more common national-brand carbonated beverages analyzed in this study with their caffeine contents were Coca-Cola (33.9 mg/12 oz), Diet Coke (46.3 mg/12 oz), Pepsi (38.9 mg/12 oz), Diet Pepsi (36.7 mg/12 oz), Dr Pepper (42.6 mg/12 oz), Diet Dr Pepper (44.1 mg/12 oz), Mountain Dew (54.8 mg/12 oz), and Diet Mountain Dew (55.2 mg/12 oz). The Wal-Mart store-brand beverages with their caffeine contents were Sam's Cola (12.7 mg/12 oz), Sam's Diet Cola (13.3 mg/12 oz), Dr Thunder (30.6 mg/12 oz), Diet Dr Thunder (29.9 mg/12 oz), and Mountain Lightning (46.5 mg/12 oz). Beverages from 14 other stores were also analyzed. Most store-brand carbonated beverages were found to contain less caffeine than their national-brand counterparts. The wide range of caffeine contents in carbonated beverages indicates that consumers would benefit from the placement of caffeine values on food labels.

  9. Ameliorant Application on Variation of Carbon Stock and Ash Content on Peatland South Kalimantan

    Directory of Open Access Journals (Sweden)

    Siti Nurzakiah

    2013-03-01

    Full Text Available Carbon stock on peatlands are large and will be easily emitted if the land is opened or drained, therefore the measurements of carbon stocks and ash content are important to know the amount of emissions and agricultural sustainability in peatlands. This study aimed to determine carbon stock and ash content on peatlands in the Indonesia Climate Change Trust Fund (ICCTF located in South Kalimantan on the geographic position S. 03°25’52" and E. 114°47’6.5". The experiment consisted of six treatments of ameliorant materials namely; mineral soil, peat fertilizer A, peat fertilizer T, manure, ash, and control. The results showed that the variation of peat soil properties was very high at this location. Peat thickness ranged from 36-338 cm, and this led to high variations in carbon stocks ranged between 161.8 – 1142.2 Mg ha-1. Besides ash contents of the soil were also highly varied ranged from 3.4 – 28.5%. This natural variation greatly affected the ICCTF study design. Mineral soil treatment had a mean carbon stock (961.3 ± 61.5 Mg ha-1 which was higher and different from other treatments. High ash content was obtained in the ash treatment (18.6 ± 2.5% and manure (15.7 ± 3.6%. It is recommended that the analysis of plant responses and greenhouse gas emissions using a single regression analysis and multiple regression with ash content as one of the independent variables are needed.

  10. Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests

    Science.gov (United States)

    Alan F. Talhelm; Kurt S. Pregitzer; Mark E. Kubiske; Donald R. Zak; Courtney E. Campany; Andrew J. Burton; Richard E. Dickson; George R. Hendrey; J. G. Isebrands; Keith F. Lewin; John Nagy; David F. Karnosky

    2014-01-01

    Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2) and tropospheric ozone (O3) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment...

  11. Molten carbonate fuel cell: dynamic numerical modeling and experimental investigation

    Energy Technology Data Exchange (ETDEWEB)

    Leal, Elisangela Martins [National Institute for Space Research, Cachoeira Paulista, SP (Brazil). Combustion and Propulsion Lab.], e-mail: elisangela@lcp.inpe.br; Jabbari, Faryar [University of California, Irvine, CA (United States). Mechanical and Aerospace Engineering Dept.], e-mail: fjabbari@uci.edu; Brouwer, Jacob [University of California, Irvine, CA (United States). National Fuel Cell Research Center], e-mail: jb@nfcrc.uci.edu

    2006-07-01

    In this paper, a detailed model incorporating simplified geometric resolution of a molten carbonate fuel cell (MCFC) with detailed and dynamic simulation of all physical, chemical, and electrochemical processes in the stream-wise direction is presented. The model was developed using mass and momentum conservation, electrochemical and chemical reaction mechanisms, and heat transfer. Results from the model are compared with data from an experimental MCFC unit. Furthermore, the model was applied to predict dynamic variations of voltage, current and temperature in an MCFC as it responds to varying load demands. The voltage was evaluated by applying a model developed by Yu h and Selman (1991a, 1991b). The results show that the model can be used to predict voltage and dynamic response characteristics of an MCFC accurately and consistently for a variety of temperatures and pressures. (author)

  12. The dynamic response of carbon fiber-filled polymer composites

    Science.gov (United States)

    Dattelbaum, D. M.; Gustavsen, R. L.; Sheffield, S. A.; Stahl, D. B.; Scharff, R. J.; Rigg, P. A.; Furmanski, J.; Orler, E. B.; Patterson, B.; Coe, J. D.

    2012-08-01

    The dynamic (shock) responses of two carbon fiber-filled polymer composites have been quantified using gas gun-driven plate impact experimentation. The first composite is a filament-wound, highly unidirectional carbon fiber-filled epoxy with a high degree of porosity. The second composite is a chopped carbon fiber- and graphite-filled phenolic resin with little-to-no porosity. Hugoniot data are presented for the carbon fiber-epoxy (CE) composite to 18.6 GPa in the through-thickness direction, in which the shock propagates normal to the fibers. The data are best represented by a linear Rankine-Hugoniot fit: Us = 2.87 + 1.17 ×up(ρ0 = 1.536g/cm3). The shock wave structures were found to be highly heterogeneous, both due to the anisotropic nature of the fiber-epoxy microstructure, and the high degree of void volume. Plate impact experiments were also performed on a carbon fiber-filled phenolic (CP) composite to much higher shock input pressures, exceeding the reactants-to-products transition common to polymers. The CP was found to be stiffer than the filament-wound CE in the unreacted Hugoniot regime, and transformed to products near the shock-driven reaction threshold on the principal Hugoniot previously shown for the phenolic binder itself. [19] On-going research is focused on interrogating the direction-dependent dyanamic response and dynamic failure strength (spall) for the CE composite in the TT and 0∘ (fiber) directions.

  13. The dynamic response of carbon fiber-filled polymer composites

    Directory of Open Access Journals (Sweden)

    Patterson B.

    2012-08-01

    Full Text Available The dynamic (shock responses of two carbon fiber-filled polymer composites have been quantified using gas gun-driven plate impact experimentation. The first composite is a filament-wound, highly unidirectional carbon fiber-filled epoxy with a high degree of porosity. The second composite is a chopped carbon fiber- and graphite-filled phenolic resin with little-to-no porosity. Hugoniot data are presented for the carbon fiber-epoxy (CE composite to 18.6 GPa in the through-thickness direction, in which the shock propagates normal to the fibers. The data are best represented by a linear Rankine-Hugoniot fit: Us = 2.87 + 1.17 ×up(ρ0 = 1.536g/cm3. The shock wave structures were found to be highly heterogeneous, both due to the anisotropic nature of the fiber-epoxy microstructure, and the high degree of void volume. Plate impact experiments were also performed on a carbon fiber-filled phenolic (CP composite to much higher shock input pressures, exceeding the reactants-to-products transition common to polymers. The CP was found to be stiffer than the filament-wound CE in the unreacted Hugoniot regime, and transformed to products near the shock-driven reaction threshold on the principal Hugoniot previously shown for the phenolic binder itself. [19] On-going research is focused on interrogating the direction-dependent dyanamic response and dynamic failure strength (spall for the CE composite in the TT and 0∘ (fiber directions.

  14. Dynamics of myelin content decrease in the rat stroke model

    Science.gov (United States)

    Kisel, A.; Khodanovich, M.; Atochin, D.; Mustafina, L.; Yarnykh, V.

    2017-08-01

    The majority of studies were usually focused on neuronal death after brain ischemia; however, stroke affects all cell types including oligodendrocytes that form myelin sheath in the CNS. Our study is focused on the changes of myelin content in the ischemic core and neighbor structures in early terms (1, 3 and 10 days) after stroke. Stroke was modeled with middle cerebral artery occlusion (MCAo) in 15 male rats that were divided into three groups by time points after operation. Brain sections were histologically stained with Luxol Fast Blue (LFB) for myelin quantification. The significant demyelination was found in the ischemic core, corpus callosum, anterior commissure, whereas myelin content was increased in caudoputamen, internal capsule and piriform cortex compared with the contralateral hemisphere. The motor cortex showed a significant increase of myelin content on the 1st day and a significant decrease on the 3rd and 10th days after MCAo. These results suggest that stroke influences myelination not only in the ischemic core but also in distant structures.

  15. Current-induced dynamics in carbon atomic contacts

    Directory of Open Access Journals (Sweden)

    Jing-Tao Lü

    2011-12-01

    Full Text Available Background: The effect of electric current on the motion of atoms still poses many questions, and several mechanisms are at play. Recently there has been focus on the importance of the current-induced nonconservative forces (NC and Berry-phase derived forces (BP with respect to the stability of molecular-scale contacts. Systems based on molecules bridging electrically gated graphene electrodes may offer an interesting test-bed for these effects.Results: We employ a semi-classical Langevin approach in combination with DFT calculations to study the current-induced vibrational dynamics of an atomic carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed. Molecular dynamics including current-induced forces enables an energy redistribution mechanism among the modes, mediated by anharmonic interactions, which is found to be vital in the description of the electrical heating.Conclusion: We have developed a semiclassical Langevin equation approach that can be used to explore current-induced dynamics and instabilities. We find instabilities at experimentally relevant bias and gate voltages for the carbon-chain system.

  16. Diurnal fluctuations in cotton leaf carbon export, carbohydrate content, and sucrose synthesizing enzymes.

    Science.gov (United States)

    Hendrix, D L; Huber, S C

    1986-06-01

    In fully expanded leaves of greenhouse-grown cotton (Gossypium hirsutum L., cv Coker 100) plants, carbon export, starch accumulation rate, and carbon exchange rate exhibited different behavior during the light period. Starch accumulation rates were relatively constant during the light period, whereas carbon export rate was greater in the afternoon than in the morning even though the carbon exchange rate peaked about noon. Sucrose levels increased throughout the light period and dropped sharply with the onset of darkness; hexose levels were relatively constant except for a slight peak in the early morning. Sucrose synthase, usually thought to be a degradative enzyme, was found in unusually high activities in cotton leaf. Both sucrose synthase and sucrose phosphate synthetase activities were found to fluctuate diurnally in cotton leaves but with different rhythms. Diurnal fluctuations in the rate of sucrose export were generally aligned with sucrose phosphate synthase activity during the light period but not with sucrose synthase activity; neither enzyme activity correlated with carbon export during the dark. Cotton leaf sucrose phosphate synthase activity was sufficient to account for the observed carbon export rates; there is no need to invoke sucrose synthase as a synthetic enzyme in mature cotton leaves. During the dark a significant correlation was found between starch degradation rate and leaf carbon export. These results indicate that carbon partitioning in cotton leaf is somewhat independent of the carbon exchange rate and that leaf carbon export rate may be linked to sucrose formation and content during the light period and to starch breakdown in the dark.

  17. Variation of total organic carbon content along the stream Harsit, Eastern Black Sea Basin, Turkey.

    Science.gov (United States)

    Bayram, Adem; Önsoy, Hizir; Akinci, Görkem; Bulut, Volkan Numan

    2011-11-01

    The TOC in surface waters and wastewater is an important analytical parameter describing the total content of all organic substances containing carbon. In practice, the TOC originated from natural and anthropogenic sources, and even if it is not directly responsible for dangers on human health, its determination is important for any kind of water that is used by public. The aim of this study was to determine variation of total organic carbon (TOC) and total carbon (TC) content in the stream Harsit, which courses in Eastern Black Sea Region, Turkey. Sampling was fortnightly conducted in each of the four seasons between March 2009 and February 2010. A total of 230 water samples were collected from ten sampling stations along the main branch of the stream Harsit with 143 km of length. Obtained TOC values were evaluated and used to classify the water quality of stream Harsit, according to the Turkish Water Pollution Control Regulation (TWPCR). The annual average TOC content values for the stations were found between 2.33 and 6.97 mg/L. It was seen that the TOC content have increased along the streamcourse of Harsit until the fourth station, where reaches its maximum value. The TOC content, then, has decreased and the minimum value was observed in the eighth station. The results showed that, except in winter season, maximum TOC content observed in many of the water samples were above Class I water standard indicated in TWPCR, which classifies the water resources according to the different area of uses. It was also found that TOC has a small contribution to TC and the highest TOC content in stream waters were measured in Gumushane station where direct discharge of city wastewaters and solid waste dumping to the stream were observed.

  18. Determination of fossil carbon content in Swedish waste fuel by four different methods.

    Science.gov (United States)

    Jones, Frida C; Blomqvist, Evalena W; Bisaillon, Mattias; Lindberg, Daniel K; Hupa, Mikko

    2013-10-01

    This study aimed to determine the content of fossil carbon in waste combusted in Sweden by using four different methods at seven geographically spread combustion plants. In total, the measurement campaign included 42 solid samples, 21 flue gas samples, 3 sorting analyses and 2 investigations using the balance method. The fossil carbon content in the solid samples and in the flue gas samples was determined using (14)C-analysis. From the analyses it was concluded that about a third of the carbon in mixed Swedish waste (municipal solid waste and industrial waste collected at Swedish industry sites) is fossil. The two other methods (the balance method and calculations from sorting analyses), based on assumptions and calculations, gave similar results in the plants in which they were used. Furthermore, the results indicate that the difference between samples containing as much as 80% industrial waste and samples consisting of solely municipal solid waste was not as large as expected. Besides investigating the fossil content of the waste, the project was also established to investigate the usability of various methods. However, it is difficult to directly compare the different methods used in this project because besides the estimation of emitted fossil carbon the methods provide other information, which is valuable to the plant owner. Therefore, the choice of method can also be controlled by factors other than direct determination of the fossil fuel emissions when considering implementation in the combustion plants.

  19. Forest structure and carbon dynamics in Amazonian tropical rain forests.

    Science.gov (United States)

    Vieira, Simone; de Camargo, Plinio Barbosa; Selhorst, Diogo; da Silva, Roseana; Hutyra, Lucy; Chambers, Jeffrey Q; Brown, I Foster; Higuchi, Niro; dos Santos, Joaquim; Wofsy, Steven C; Trumbore, Susan E; Martinelli, Luiz Antonio

    2004-08-01

    Living trees constitute one of the major stocks of carbon in tropical forests. A better understanding of variations in the dynamics and structure of tropical forests is necessary for predicting the potential for these ecosystems to lose or store carbon, and for understanding how they recover from disturbance. Amazonian tropical forests occur over a vast area that encompasses differences in topography, climate, and geologic substrate. We observed large differences in forest structure, biomass, and tree growth rates in permanent plots situated in the eastern (near Santarém, Pará), central (near Manaus, Amazonas) and southwestern (near Rio Branco, Acre) Amazon, which differed in dry season length, as well as other factors. Forests at the two sites experiencing longer dry seasons, near Rio Branco and Santarém, had lower stem frequencies (460 and 466 ha(-1) respectively), less biodiversity (Shannon-Wiener diversity index), and smaller aboveground C stocks (140.6 and 122.1 Mg C ha(-1)) than the Manaus site (626 trees ha(-1), 180.1 Mg C ha(-1)), which had less seasonal variation in rainfall. The forests experiencing longer dry seasons also stored a greater proportion of the total biomass in trees with >50 cm diameter (41-45 vs 30% in Manaus). Rates of annual addition of C to living trees calculated from monthly dendrometer band measurements were 1.9 (Manaus), 2.8 (Santarém), and 2.6 (Rio Branco) Mg C ha(-1) year(-1). At all sites, trees in the 10-30 cm diameter class accounted for the highest proportion of annual growth (38, 55 and 56% in Manaus, Rio Branco and Santarém, respectively). Growth showed marked seasonality, with largest stem diameter increment in the wet season and smallest in the dry season, though this may be confounded by seasonal variation in wood water content. Year-to-year variations in C allocated to stem growth ranged from nearly zero in Rio Branco, to 0.8 Mg C ha(-1) year(-1) in Manaus (40% of annual mean) and 0.9 Mg C ha(-1) year(-1) (33% of

  20. Airborne Measurement of Ecosystem Carbon Dynamics over Heterogeneous Landscapes

    Science.gov (United States)

    Wade, T. J.; Hill, T. C.; Clement, R.; Moncrieff, J.; Disney, M.; Nichol, C. J.; Williams, M. D.

    2009-12-01

    Terrestrial carbon sinks are currently believed to account for the removal and storage of approximately 25% of anthropogenic carbon emissions from the atmosphere. The processes involved are numerous and complex and many feedbacks are at play. The ability to study the dynamics of different ecosystems at scales meaningful to climatic forcing is essential for understanding the key processes involved and identifying crucial sensitivities and thresholds. Airborne platforms with the requisite instrumentation offer the opportunity to directly measure biological processes and atmospheric structures at scales that are not achievable by ground measurements alone. The current generation of small research aircraft such as the University of Edinburgh’s Diamond HK36TTC ECO Dimona present excellent platforms for measurement of both the atmosphere and terrestrial surface. In this study we present results from airborne CO2/H2O flux measuring campaigns in contrasting climatic systems to quantify spatial patterns in ecosystem photosynthesis. Several airborne campaigns were undertaken in Arctic Finland, as part of the Arctic Biosphere Atmosphere Coupling at Multiple Scales (ABACUS) project (2008), and mainland UK as part of the UK Population Biology Network (UKPopNet) 2009 project, to explore the variability in surface CO2 flux across spatial scales larger than captured using conventional ground based eddy covariance. We discuss the application of our aircraft platform as a tool to address the challenge of understanding carbon dynamics within landscapes of heterogeneous vegetation class, terrain and hydrology using complementary datasets acquired from airborne eddy covariance and remote sensing.

  1. Dynamics of maize carbon contribution to soil organic carbon in association with soil type and fertility level.

    Science.gov (United States)

    Pei, Jiubo; Li, Hui; Li, Shuangyi; An, Tingting; Farmer, John; Fu, Shifeng; Wang, Jingkuan

    2015-01-01

    Soil type and fertility level influence straw carbon dynamics in the agroecosystems. However, there is a limited understanding of the dynamic processes of straw-derived and soil-derived carbon and the influence of the addition of straw carbon on soil-derived organic carbon in different soils associated with different fertility levels. In this study, we applied the in-situ carborundum tube method and 13C-labeled maize straw (with and without maize straw) at two cropland (Phaeozem and Luvisol soils) experimental sites in northeast China to quantify the dynamics of maize-derived and soil-derived carbon in soils associated with high and low fertility, and to examine how the addition of maize carbon influences soil-derived organic carbon and the interactions of soil type and fertility level with maize-derived and soil-derived carbon. We found that, on average, the contributions of maize-derived carbon to total organic carbon in maize-soil systems during the experimental period were differentiated among low fertility Luvisol (from 62.82% to 42.90), high fertility Luvisol (from 53.15% to 30.00%), low fertility Phaeozem (from 58.69% to 36.29%) and high fertility Phaeozem (from 41.06% to 16.60%). Furthermore, the addition of maize carbon significantly decreased the remaining soil-derived organic carbon in low and high fertility Luvisols and low fertility Phaeozem before two months. However, the increasing differences in soil-derived organic carbon between both soils with and without maize straw after two months suggested that maize-derived carbon was incorporated into soil-derived organic carbon, thereby potentially offsetting the loss of soil-derived organic carbon. These results suggested that Phaeozem and high fertility level soils would fix more maize carbon over time and thus were more beneficial for protecting soil-derived organic carbon from maize carbon decomposition.

  2. Global investigation of the nonlinear dynamics of carbon nanotubes

    KAUST Repository

    Xu, Tiantian

    2016-11-17

    Understanding the complex nonlinear dynamics of carbon nanotubes (CNTs) is essential to enable utilization of these structures in devices and practical applications. We present in this work an investigation of the global nonlinear dynamics of a slacked CNT when actuated by large electrostatic and electrodynamic excitations. The coexistence of several attractors is observed. The CNT is modeled as an Euler–Bernoulli beam. A reduced-order model based on the Galerkin method is developed and utilized to simulate the static and dynamic responses. Critical computational challenges are posed due to the complicated form of the electrostatic force, which describes the interaction between the upper electrode, consisting of the cylindrically shaped CNT, and the lower electrode. Toward this, we approximate the electrostatic force using the Padé expansion. We explore the dynamics near the primary and superharmonic resonances. The nanostructure exhibits several attractors with different characteristics. To achieve deep insight and describe the complexity and richness of the behavior, we analyze the nonlinear response from an attractor-basins point of view. The competition of attractors is highlighted. Compactness and/or fractality of their basins are discussed. Both the effects of varying the excitation frequency and amplitude are examined up to the dynamic pull-in instability.

  3. Future active layer dynamics and carbon dioxide production from thawing permafrost layers in Northeast Greenland

    DEFF Research Database (Denmark)

    Hollesen, Jørgen; Elberling, Bo; Jansson, P.E.

    2011-01-01

    from a moist permafrost soil in High-Arctic Greenland with observed heat production and carbon dioxide (CO2) release rates from decomposition of previously frozen organic matter. Observations show that the maximum thickness of the active layer at the end of the summer has increased 1 cm yr-1 since 1996......Thawing permafrost and the resulting mineralization of previously frozen organic carbon (C) is considered an important future feedback from terrestrial ecosystems to the atmosphere. Here, we use a dynamic process oriented permafrost model, the CoupModel, to link surface and subsurface temperatures......–105 cm as a result of a 2–6 °C warming. An additional increase in the maximum active layer thickness of a few centimetres may be expected due to heat production from decomposition of organic matter. Simulated future soil temperatures and water contents are subsequently used with measured basal soil...

  4. Satellite observation of particulate organic carbon dynamics in ...

    Science.gov (United States)

    Particulate organic carbon (POC) plays an important role in coastal carbon cycling and the formation of hypoxia. Yet, coastal POC dynamics are often poorly understood due to a lack of long-term POC observations and the complexity of coastal hydrodynamic and biogeochemical processes that influence POC sources and sinks. Using field observations and satellite ocean color products, we developed a nw multiple regression algorithm to estimate POC on the Louisiana Continental Shelf (LCS) from satellite observations. The algorithm had reliable performance with mean relative error (MRE) of ?40% and root mean square error (RMSE) of ?50% for MODIS and SeaWiFS images for POC ranging between ?80 and ?1200 mg m23, and showed similar performance for a large estuary (Mobile Bay). Substantial spatiotemporal variability in the satellite-derived POC was observed on the LCS, with high POC found on the inner shelf (satellite data with carefully developed algorithms can greatly increase

  5. Application of laser-produced-plasmas to determination of carbon content in steel

    International Nuclear Information System (INIS)

    Ortiz, M.; Aragon, C.; Aguilera, J.A.; Campos, J.

    1994-01-01

    This paper describes an analytical method to determine carbon content in solid and molten steel. It is based on the study of the emission spectrum from a Nd-YAG laser produced plasma. The light emitted from the plasma is focused to the entrance slit of a spectrometer and detected by an OMA III system. For every laser pulse an spectral range of 100 A are recorded. With the use of time-resolved spectroscopy a precision of 1.6% and a detection limit of 65 ppm of carbon content in steel have been obtained. These values are similar to those of other accurate conventional techniques but using optics fiber and laser excitation it is possible to made sample calibrations in hostile environments. Also, as the analysis are made in real time changes in sample composition can be measured without stopping production processes. (Author) 26 refs

  6. Application of laser-produced-plasmas to determination of carbon content in steel

    International Nuclear Information System (INIS)

    Ortiz, M.; Aragon, C.; Aguilera, J. A.; Campos, J.

    1994-01-01

    This paper describes an analytical method to determine carbon content in solid and molten steel. It is based on the study of the emission spectrum from a Nd-YAG laser produced plasma. The light emitted from the plasma is focused to the entrance slit of a spectrometer and detected by an OMA III system. For every laser pulse an spectral range of 100 A are recorded. With the use of time-resolved spectroscopy a precision of 1.6 % and a detection limit of 65 ppm of carbon content in steel have been obtained. These values are similar to those of other accurate conventional techniques but using optics fiber and laser excitation it is possible to made sample calibrations in hostile environments. Also, as the analysis are made in real time changes in sample composition can be measured without stopping production processes. (Author) 26 refs

  7. Linear Theory of Soil Organic Carbon Dynamics: Implications in Modeling Soil Respiration and Carbon Sequestration

    Science.gov (United States)

    Porporato, A.; Manzoni, S.; Katul, G.

    2008-12-01

    The long-term, large-scale soil organic carbon dynamics are typically described by mathematical models based on networks of linear reservoirs. Properties of these networks can be diagnosed from linear system theory (i.e. impulse-response transformations), which is seldom used in soil biogeochemistry, although it can be used to compare and test different models in the context of long-term carbon sequestration in soils. In this work, the general theory of linear impulse-response systems is briefly reviewed and linked to the theory of stochastic point processes. Two characteristic times are considered, the residence time (i.e., the time spent by a molecule in the system) and age (the time elapsed since the molecule entered the system). Both are represented through their probability density functions, which are computed explicitly as a function of model structure. Different cases are analyzed and compared, ranging from a simple individual-pool model, to feedback models involving loops (as in models of soil organic carbon-microbial interactions and physical adsorption-desorption), and to more complex networks often used to simulate in the details the soil organic carbon processes. As examples for these complex networks, the compartmental model CENTURY (Parton et al., 1987), and the continuum-quality Q-model (Agren and Bosatta, 1996) are considered. We assess the relative importance of model structural characteristics to determine the organic carbon residence time and age distributions.

  8. A Molecular Dynamics Study on the Confinement of Carbon Dioxide Molecules in Carbon Nanotubes

    Science.gov (United States)

    Lazor, Meagan; Rende, Deniz; Baysal, Nihat; Ozisik, Rahmi

    2012-02-01

    The influence of atmospheric carbon dioxide (CO2) concentration on global warming is considered as one of the primary environmental issues of the past two decades. The main source of CO2 emission is human activity, such as the use of fossil fuels in transportation and industrial plants. Following the release of Kyoto Protocol in 1997, effective ways of controlling CO2 emissions received much attention. As a result, various materials such as activated carbon, zeolites, and carbon nanotubes (CNTs) were investigated for their CO2 adsorbing properties. CNTs were reported to have CO2 adsorption capability twice that of activated carbon, hence they received the most attention. In the current study, single walled carbon nanotubes (SWNTs) were used as one dimensional nanoporous materials and their CO2 adsorption capacity was analyzed with Molecular Dynamics simulations. Results indicated that SWNTs are excellent CO2 adsorbers and their effectiveness increase at low CO2 concentrations. In addition, we showed that by varying temperature, CO2 can be removed from the SWNTs, providing a simple method to reuse SWNTs.

  9. Size and Carbon Content of Sub-seafloor Microbial Cells at Landsort Deep, Baltic Sea

    DEFF Research Database (Denmark)

    Braun, Stefan; Morono, Yuki; Littmann, Sten

    2016-01-01

    small cell sizes as adaptation to the long-term subsistence at very low energy availability in the deep biosphere. We present for the first time depth-related data on the cell volume and carbon content of sedimentary microbial cells buried down to 60 m below the seafloor. Our data enable estimates...... of volume- and biomass-specific cellular rates of energy metabolism in the deep biosphere and will improve global estimates of microbial biomass....

  10. Trace elements contents of carbonate sediments from the Mazagan Escarpment off central Morocco (CYAMAZ, 1982)

    OpenAIRE

    Renard, M

    1985-01-01

    Trace element analysis (Mg, Sr, Na, K, Mn, Fe, Ni, Cr, and Zn) of CYAMAZ carbonates shows that a geochemical characterization of platform and post-platform sediments is possible. Platform sediments geochemical study leads to precise the paleoenvironment and shows that late oceanic diagenesis (which take place after subsidence of the platform) does not alter trace element contents of rocks. An attempt of geochemical dating (chemostratigraphy) of post-platform sediments is made.

  11. Influence of Carbon Content on the Crystallographic Structure of Boron Carbide Films

    OpenAIRE

    Conde, O.; Silvestre, A. J.; Oliveira, J. C.

    2002-01-01

    Boron carbide thin films were synthesised by laser-assisted chemical vapour deposition (LCVD), using a CO2 laser beam and boron trichloride and methane as precursors. Boron and carbon contents were measured by electron probe microanalysis (EPMA). Microstructural analysis was carried out by Raman microspectroscopy and glancing incidence X-ray diffraction (GIXRD) was used to study the crystallographic structure and to determine the lattice parameters of the polycrystalline films. The rhombohedr...

  12. Main Feedbacks Between Oxidizable Carbon Content and Selected Soil Characteristic of Chernozem

    Directory of Open Access Journals (Sweden)

    Vítězslav Vlček

    2015-01-01

    Full Text Available Anthropogenic pressure on our agricultural land is culminating last hundred years, especially after 1948, not only because of only massive application of mineral fertilizers but also because of land consolidation and subsequent accelerated water and wind erosion and use of mechanization. This article focuses on main demonstration of feedbacks especially with oxidizable carbon which can negatively affect soil as a homeostatic system. Oxidizable carbon, as the basis of soil humus, is crucial for maintaining soil fertility and for its resistance to further degradation factors affecting the soil. 35 chernozem sites were selected in South Moravia region. These soils had been probably used for their fertility and availability before the turn of the AD. Unfortunately, their long-term agricultural use has resulted in adverse impact on their quality.This way, shallower forms of erosion were often formed. These erosion forms are omitted for the purposes of our study there. For this work, locations with preserved chernic (i.e. diagnostic horizon, as the horizon with less anthropogenic influence, were selected. Relations between a grain size (clay, silt and sand particles, exchange reaction in soil, sorption capacity, oxidizable carbon content, total nitrogen content and content of selected potentially acceptable elements (Ca, Mg were monitored.

  13. Organic carbon determination in histosols and soil horizons with high organic matter content from Brazil

    Directory of Open Access Journals (Sweden)

    Pereira Marcos Gervasio

    2006-01-01

    Full Text Available Soil taxonomy systems distinguish mineral soils from organic soils based on the amount of soil organic carbon. Procedures adopted in soil surveys for organic carbon measurement are therefore of major importance to classify the soils, and to correlate their properties with data from other studies. To evaluate different methods for measuring organic carbon and organic matter content in Histosols and soils with histic horizons, from different regions of Brazil, 53 soil samples were comparatively analyzed by the methods of Walkley & Black (modified, Embrapa, Yeomans & Bremner, modified Yeomans & Bremner, muffle furnace, and CHN. The modified Walkley & Black (C-W & B md and the combustion of organic matter in the muffle furnace (OM-Muffle were the most suitable for the samples with high organic carbon content. Based on regression analysis data, the OM-muffle may be estimated from C-W & B md by applying a factor that ranges from 2.00 to 2.19 with 95% of probability. The factor 2.10, the average value, is suggested to convert results obtained by these methods.

  14. Nonlinear Dynamics of Carbon Nanotubes Under Large Electrostatic Force

    KAUST Repository

    Xu, Tiantian

    2015-06-01

    Because of the inherent nonlinearities involving the behavior of CNTs when excited by electrostatic forces, modeling and simulating their behavior is challenging. The complicated form of the electrostatic force describing the interaction of their cylindrical shape, forming upper electrodes, to lower electrodes poises serious computational challenges. This presents an obstacle against applying and using several nonlinear dynamics tools typically used to analyze the behavior of complicated nonlinear systems undergoing large motion, such as shooting, continuation, and integrity analysis techniques. This works presents an attempt to resolve this issue. We present an investigation of the nonlinear dynamics of carbon nanotubes when actuated by large electrostatic forces. We study expanding the complicated form of the electrostatic force into enough number of terms of the Taylor series. Then, we utilize this form along with an Euler-Bernoulli beam model to study for the first time the dynamic behavior of CNTs when excited by large electrostatic force. The geometric nonlinearity and the nonlinear electrostatic force are considered. An efficient reduced-order model (ROM) based on the Galerkin method is developed and utilized to simulate the static and dynamic responses of the CNTs. Several results are generated demonstrating softening and hardening behavior of the CNTs near their primary and secondary resonances. The effects of the DC and AC voltage loads on the behavior have been studied. The impacts of the initial slack level and CNT diameter are also demonstrated.

  15. NONLINEAR DYNAMICS OF CARBON NANOTUBES UNDER LARGE ELECTROSTATIC FORCE

    KAUST Repository

    Xu, Tiantian

    2015-06-01

    Because of the inherent nonlinearities involving the behavior of CNTs when excited by electrostatic forces, modeling and simulating their behavior is challenging. The complicated form of the electrostatic force describing the interaction of their cylindrical shape, forming upper electrodes, to lower electrodes poises serious computational challenges. This presents an obstacle against applying and using several nonlinear dynamics tools typically used to analyze the behavior of complicated nonlinear systems undergoing large motion, such as shooting, continuation, and integrity analysis techniques. This works presents an attempt to resolve this issue. We present an investigation of the nonlinear dynamics of carbon nanotubes when actuated by large electrostatic forces. We study expanding the complicated form of the electrostatic force into enough number of terms of the Taylor series. Then, we utilize this form along with an Euler-Bernoulli beam model to study for the first time the dynamic behavior of CNTs when excited by large electrostatic force. The geometric nonlinearity and the nonlinear electrostatic force are considered. An efficient reduced-order model (ROM) based on the Galerkin method is developed and utilized to simulate the static and dynamic responses of the CNTs. Several results are generated demonstrating softening and hardening behavior of the CNTs near their primary and secondary resonances. The effects of the DC and AC voltage loads on the behavior have been studied. The impacts of the initial slack level and CNT diameter are also demonstrated.

  16. Digital mapping of soil organic carbon contents and stocks in Denmark.

    Science.gov (United States)

    Adhikari, Kabindra; Hartemink, Alfred E; Minasny, Budiman; Bou Kheir, Rania; Greve, Mette B; Greve, Mogens H

    2014-01-01

    Estimation of carbon contents and stocks are important for carbon sequestration, greenhouse gas emissions and national carbon balance inventories. For Denmark, we modeled the vertical distribution of soil organic carbon (SOC) and bulk density, and mapped its spatial distribution at five standard soil depth intervals (0-5, 5-15, 15-30, 30-60 and 60-100 cm) using 18 environmental variables as predictors. SOC distribution was influenced by precipitation, land use, soil type, wetland, elevation, wetness index, and multi-resolution index of valley bottom flatness. The highest average SOC content of 20 g kg(-1) was reported for 0-5 cm soil, whereas there was on average 2.2 g SOC kg(-1) at 60-100 cm depth. For SOC and bulk density prediction precision decreased with soil depth, and a standard error of 2.8 g kg(-1) was found at 60-100 cm soil depth. Average SOC stock for 0-30 cm was 72 t ha(-1) and in the top 1 m there was 120 t SOC ha(-1). In total, the soils stored approximately 570 Tg C within the top 1 m. The soils under agriculture had the highest amount of carbon (444 Tg) followed by forest and semi-natural vegetation that contributed 11% of the total SOC stock. More than 60% of the total SOC stock was present in Podzols and Luvisols. Compared to previous estimates, our approach is more reliable as we adopted a robust quantification technique and mapped the spatial distribution of SOC stock and prediction uncertainty. The estimation was validated using common statistical indices and the data and high-resolution maps could be used for future soil carbon assessment and inventories.

  17. Fluoride content in bottled drinking waters, carbonated soft drinks and fruit juices in Davangere city, India.

    Science.gov (United States)

    Thippeswamy, H M; Kumar, Nanditha; Anand, S R; Prashant, G M; Chandu, G N

    2010-01-01

    The regular ingestion of fluoride lowers the prevalence of dental caries. The total daily intake of fluoride for optimal dental health should be 0.05-0.07 mg fluoride/kg body weight and to avoid the risk of dental fluorosis, the daily intake should not exceed a daily level of 0.10 mg fluoride/kg body weight. The main source of fluoride is from drinking water and other beverages. As in other countries, consumption of bottled water, juices and carbonated beverages has increased in our country. To analyze the fluoride content in bottled water, juices and carbonated soft drinks that were commonly available in Davangere city. Three samples of 10 commercially available brands of bottled drinking water, 12 fruit juices and 12 carbonated soft drinks were purchased. Bottled water and carbonated soft drinks were stored at a cold place until fluoride analysis was performed and a clear juice was prepared using different fruits without the addition of water. Then, the fluoride analysis was performed. The mean and standard deviation of fluoride content of bottled water, fruit juices and carbonated soft drinks were measured, which were found to be 0.20 mg (±0.19) F/L, 0.29 mg (±0.06) F/L and 0.22 mg (±0.05) F/L, respectively. In viewing the results of the present study, it can be concluded that regulation of the optimal range of fluoride in bottled drinking water, carbonated soft drinks and fruit juices should be drawn for the Indian scenario.

  18. Fluoride content in bottled drinking waters, carbonated soft drinks and fruit juices in Davangere city, India

    Directory of Open Access Journals (Sweden)

    Thippeswamy H

    2010-01-01

    Full Text Available Background: The regular ingestion of fluoride lowers the prevalence of dental caries. The total daily intake of fluoride for optimal dental health should be 0.05-0.07 mg fluoride/kg body weight and to avoid the risk of dental fluorosis, the daily intake should not exceed a daily level of 0.10 mg fluoride/kg body weight. The main source of fluoride is from drinking water and other beverages. As in other countries, consumption of bottled water, juices and carbonated beverages has increased in our country. Objective: To analyze the fluoride content in bottled water, juices and carbonated soft drinks that were commonly available in Davangere city. Materials and Methods: Three samples of 10 commercially available brands of bottled drinking water, 12 fruit juices and 12 carbonated soft drinks were purchased. Bottled water and carbonated soft drinks were stored at a cold place until fluoride analysis was performed and a clear juice was prepared using different fruits without the addition of water. Then, the fluoride analysis was performed. Results: The mean and standard deviation of fluoride content of bottled water, fruit juices and carbonated soft drinks were measured, which were found to be 0.20 mg (±0.19 F/L, 0.29 mg (±0.06 F/L and 0.22 mg (±0.05 F/L, respectively. Conclusion: In viewing the results of the present study, it can be concluded that regulation of the optimal range of fluoride in bottled drinking water, carbonated soft drinks and fruit juices should be drawn for the Indian scenario.

  19. Assembling content into dynamic learning objects versus authoring of e-learning courses.

    Directory of Open Access Journals (Sweden)

    Jeanne Schreurs

    2008-09-01

    Full Text Available It is our goal to assemble the content into dynamic learning objects (LO, to make the content adaptable to the learners prefernces and to all kinds of used appliances by the learner. A three layer e-learning course development model has been defined based on the “conceptual model of content object”. It starts by decomposing the learning content into small chunks which are initially placed in a hierarchic structure of units and blocks. The raw content components, being the atomic learning objects (ALO, were linked to the blocks and are structured in the database. We set forward a dynamic generation of LO's customised to the learner group on point of content and customised on point of presentation, fitting the preferences and the used appliances of the learner. In that view we need a LO assembling system fitting the requirements of interoperability and reusability and starting from selecting the raw learning content from the learning materials content database. The company AGFA Healthcare is using an authoring system that creates SCO’s being interoperable. Thanks to a good management is the solution a best practice, even it is not based on a database. Though they can not create dynamic solutions and cannot customise the e-learning module on the fly to the learners preference and the used appliance by the learner.

  20. Thermokarst dynamics and soil organic matter characteristics controlling initial carbon release from permafrost soils in the Siberian Yedoma region

    DEFF Research Database (Denmark)

    Weiss, Niels; Blok, Daan; Elberling, Bo

    2016-01-01

    This study relates soil organic matter (SOM) characteristics to initial soil incubation carbon release from upper permafrost samples in Yedoma region soils of northeastern Siberia, Russia. Carbon (C) and nitrogen (N) content, carbon to nitrogen ratios (C:N), δ13C and δ15N values show clear trends...... that correspond with SOM age and degree of decomposition. Incubation results indicate that older and more decomposed soil material shows higher C respiration rates per unit incubated C than younger and less decomposed samples with higher C content. This is important as undecomposed material is often assumed...... to be more reactive upon thawing. Large stocks of SOM and their potential decomposability, in combination with complex landscape dynamics that include one or more events of Holocene thaw in most of the landscape, are of consequence for potential greenhouse gas release from permafrost soils in the Yedoma...

  1. Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Meareg Amare

    2017-01-01

    Full Text Available Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6×10-6 to 100×10-6 mol L−1 with determination coefficient and method detection limit (LoD = 3 s/slope of 0.99925 and 8.37×10-7 mol L−1, respectively, supplemented by recovery results of 93.79–102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w% of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users’ highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

  2. Dynamic Changes of Soil Surface Organic Carbon under Different Mulching Practices in Citrus Orchards on Sloping Land.

    Science.gov (United States)

    Gu, Chiming; Liu, Yi; Mohamed, Ibrahim; Zhang, Runhua; Wang, Xiao; Nie, Xinxin; Jiang, Min; Brooks, Margot; Chen, Fang; Li, Zhiguo

    2016-01-01

    Mulching management has been used in many places all over the world to improve agricultural sustainability. However, the cycling of carbon in the soil under applications of mulch on sloping arable land is not yet fully understood. A four-year field experiment was carried out in Xiaofuling watershed of Danjiangkou reservoir in China. The object was to evaluate the effects of the application of straw mulch (ST) and grass mulch (GT) on dynamic changes in soil organic carbon and its fractions. Results showed that mulch applied on the soil surface increased the contents of SOC and its active fractions in the soil. Compared to the control without cover (CK), ST and GT treatments increased the contents of SOC, LOC, DOC, POC and EOC by 14.73%, 16.5%, 22.5%, 41.5% and 21%, respectively, in the 0-40 cm soil layer, and by 17%, 14%, 19%, and 30%, respectively, in the 0-100 cm soil layer. The contents of organic carbon and its active fractions decreased with increasing soil depth in all of the treatments. SOC was accumulated in the period of December to the following March. The contents of soil DOC and LOC were high in January to March, while the contents of soil POC and EOC were high in June to September. The relative contents of soil organic carbon fractions were POC > EOC > LOC > DOC over the four years. Straw mulching had no significant effect on the changes in soil organic carbon active fractions during the different periods. Based on this long-term field experiment in Danjiangkou reservoir, we found that straw mulching had a significant effect on soil, increasing SOC content and stock in slopping arable land, and that live grass mulching was more effective than rice straw mulching. We discuss possible optimal periods for the implementation of mulching practices on sloping land.

  3. Individual Nanoporous Carbon Spheres with High Nitrogen Content from Polyacrylonitrile Nanoparticles with Sacrificial Protective Layers.

    Science.gov (United States)

    Zhang, Jianan; Yuan, Rui; Natesakhawat, Sittichai; Wang, Zongyu; Zhao, Yepin; Yan, Jiajun; Liu, Siyuan; Lee, Jaejun; Luo, Danli; Gottlieb, Eric; Kowalewski, Tomasz; Bockstaller, Michael R; Matyjaszewski, Krzysztof

    2017-11-01

    Functional nanoporous carbon spheres (NPC-S) are important for applications ranging from adsorption, catalysis, separation to energy storage, and biomedicine. The development of effective NPC-S materials has been hindered by the fusion of particles during the pyrolytic process that results in agglomerated materials with reduced activity. Herein, we present a process that enables the scalable synthesis of dispersed NPC-S materials by coating sacrificial protective layers around polyacrylonitrile nanoparticles (PAN NPs) to prevent interparticle cross-linking during carbonization. In a first step, PAN NPs are synthesized using miniemulsion polymerization, followed by grafting of 3-(triethoxysilyl)propyl methacrylate (TESPMA) to form well-defined core-shell structured PAN@PTESPMA nanospheres. The cross-linked PTESPMA brush layer suppresses cross-linking reactions during carbonization. Uniform NPC-S exhibiting diameters of ∼100 nm, with relatively high accessible surface area (∼424 m 2 /g), and high nitrogen content (14.8 wt %) was obtained. When compared to a regular nanoporous carbon monolith (NPC-M), the nitrogen-doped NPC-S demonstrated better performance for CO 2 capture with a higher CO 2 /N 2 selectivity, an increased efficiency in catalytic oxygen reduction reactions, as well as improved electrochemical capacitive behavior. This miniemulsion polymerization-based strategy for the preparation of functional PAN NPs provides a new, facile approach to prepare high-performance porous carbon spheres for diverse applications.

  4. A facile method of synthesizing uniform resin colloidal and microporous carbon spheres with high nitrogen content.

    Science.gov (United States)

    Song, Jing-Chuan; Lu, Zhong-Yuan; Sun, Zhao-Yan

    2014-10-01

    3-Aminophenol/formaldehyde (AF) resin colloidal spheres with narrow size distribution and high nitrogen content are synthesized in the presence of urea. The obtained particles that indicated by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) are spherical morphology and uniform. It can be further carbonized into carbon spheres preserving high nitrogen percent. The particle size is tunable from 300 nm to 850 nm by appropriately varying the concentration of precursor or water/ethanol volume ratio. Even using the water as an only solvent, we can also obtain spherical particles with different size. Typically, the nitrogen percent in the obtained polymer and carbon particles is as high as 10.39 wt% and 8.95 wt%, respectively. The typical surface area of resulted carbon particles obtained from nitrogen adsorption measurement is 459 m(2) g(-1). X-ray diffraction demonstrates the obtained carbon spheres are amorphous, which are expected to have practical application in the field of energy devices. The method can be considered as a low cost and facile method for mass production. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Adsorption of ionizable organic contaminants on multi-walled carbon nanotubes with different oxygen contents

    Energy Technology Data Exchange (ETDEWEB)

    Li Xiaona; Zhao Huimin [Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Liaoning Province, Dalian 116024 (China); Quan Xie, E-mail: quanxie@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Liaoning Province, Dalian 116024 (China); Chen Shuo; Zhang Yaobin; Yu Hongtao [Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Liaoning Province, Dalian 116024 (China)

    2011-02-15

    Multi-walled carbon nanotubes (MWNTs), which are considered to be promising candidates for the adsorption of toxic organics, are released into aqueous environment with their increasing production and application. In this study, the adsorption behaviors of five structurally related ionizable organic contaminants namely perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonamide (PFOSA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-n-nonylphenol (4-NP) onto MWNTs with different oxygen contents (3.84-22.85%) were investigated. The adsorption kinetics was investigated and simulated with pseudo-second-order model. The adsorption isotherms were found to be fitted with Freundlich model and influenced by both the properties of organic chemicals and the oxygen contents of MWNTs. As adsorption capacity decreases dramatically with the increasing of oxygen contents, the MWNTs with the lowest oxygen contents possess the highest adsorption capacity among four MWNTs. For the MWNTs with the oxygen contents of 3.84%, the adsorption affinity related with hydrophobic interaction and {pi}-electron polarizability decreased in the order of 4-NP > PFOSA > PFOS > 2,4-D > PFOA. Furthermore, the adsorption characters of five contaminants were affected by solution pH and solute pK{sub a} considering electrostatic repulse force and hydrogen bonding, which showed the adsorption of MWNTs with lower oxygen content is much sensitive to solution chemistry.

  6. Adsorption of ionizable organic contaminants on multi-walled carbon nanotubes with different oxygen contents

    International Nuclear Information System (INIS)

    Li Xiaona; Zhao Huimin; Quan Xie; Chen Shuo; Zhang Yaobin; Yu Hongtao

    2011-01-01

    Multi-walled carbon nanotubes (MWNTs), which are considered to be promising candidates for the adsorption of toxic organics, are released into aqueous environment with their increasing production and application. In this study, the adsorption behaviors of five structurally related ionizable organic contaminants namely perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonamide (PFOSA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-n-nonylphenol (4-NP) onto MWNTs with different oxygen contents (3.84-22.85%) were investigated. The adsorption kinetics was investigated and simulated with pseudo-second-order model. The adsorption isotherms were found to be fitted with Freundlich model and influenced by both the properties of organic chemicals and the oxygen contents of MWNTs. As adsorption capacity decreases dramatically with the increasing of oxygen contents, the MWNTs with the lowest oxygen contents possess the highest adsorption capacity among four MWNTs. For the MWNTs with the oxygen contents of 3.84%, the adsorption affinity related with hydrophobic interaction and π-electron polarizability decreased in the order of 4-NP > PFOSA > PFOS > 2,4-D > PFOA. Furthermore, the adsorption characters of five contaminants were affected by solution pH and solute pK a considering electrostatic repulse force and hydrogen bonding, which showed the adsorption of MWNTs with lower oxygen content is much sensitive to solution chemistry.

  7. Effects of carbon content on high-temperature mechanical and thermal fatigue properties of high-boron austenitic steels

    Directory of Open Access Journals (Sweden)

    Xiang Chen

    2016-01-01

    Full Text Available High-temperature mechanical properties of high-boron austenitic steels (HBASs were studied at 850 °C using a dynamic thermal-mechanical simulation testing machine. In addition, the thermal fatigue properties of the alloys were investigated using the self-restraint Uddeholm thermal fatigue test, during which the alloy specimens were cycled between room temperature and 800°C. Stereomicroscopy and scanning electron microscopy were used to study the surface cracks and cross-sectional microstructure of the alloy specimens after the thermal fatigue tests. The effects of carbon content on the mechanical properties at room temperature and high-temperature as well as thermal fatigue properties of the HBASs were also studied. The experimental results show that increasing carbon content induces changes in the microstructure and mechanical properties of the HBASs. The boride phase within the HBAS matrix exhibits a round and smooth morphology, and they are distributed in a discrete manner. The hardness of the alloys increases from 239 (0.19wt.% C to 302 (0.29wt.% C and 312 HV (0.37wt.% C; the tensile yield strength at 850 °C increases from 165.1 to 190.3 and 197.1 MPa; and the compressive yield strength increases from 166.1 to 167.9 and 184.4 MPa. The results of the thermal fatigue tests (performed for 300 cycles from room temperature to 800 °C indicate that the degree of thermal fatigue of the HBAS with 0.29wt.% C (rating of 2–3 is superior to those of the alloys with 0.19wt.% (rating of 4–5 and 0.37wt.% (rating of 3–4 carbon. The main cause of this difference is the ready precipitation of M23(C,B6-type borocarbides in the alloys with high carbon content during thermal fatigue testing. The precipitation and aggregation of borocarbide particles at the grain boundaries result in the deterioration of the thermal fatigue properties of the alloys.

  8. Tillage, cropping sequence, and nitrogen fertilization effects on dryland soil carbon dioxide emission and carbon content.

    Science.gov (United States)

    Sainju, Upendra M; Jabro, Jalal D; Caesar-Tonthat, Thecan

    2010-01-01

    Management practices are needed to reduce dryland soil CO(2) emissions and to increase C sequestration. We evaluated the effects of tillage and cropping sequence combinations and N fertilization on dryland crop biomass (stems + leaves) and soil surface CO(2) flux and C content (0- to 120-cm depth) in a Williams loam from May to October, 2006 to 2008, in eastern Montana. Treatments were no-tilled continuous malt barley (Hordeum vulgaris L.) (NTCB), no-tilled malt barley-pea (Pisum sativum L.) (NTB-P), no-tilled malt barley-fallow (NTB-F), and conventional-tilled malt barley-fallow (CTB-F), each with 0 and 80 kg N ha(-1). Measurements were made both in Phase I (malt barley in NTCB, pea in NTB-P, and fallow in NTB-F and CTB-F) and Phase II (malt barley in all sequences) of each cropping sequence in every year. Crop biomass varied among years, was greater in the barley than in the pea phase of the NTB-P treatment, and greater in NTCB and NTB-P than in NTB-F and CTB-F in 2 out of 3 yr. Similarly, biomass was greater with 80 than with 0 kg N ha(-1) in 1 out of 3 yr. Soil CO(2) flux increased from 8 mg C m(-2) h(-1) in early May to 239 mg C m(-2) h(-1) in mid-June as temperature increased and then declined to 3 mg C m(-2) h(-1) in September-October. Fluxes peaked immediately following substantial precipitation (>10 mm), especially in NTCB and NTB-P. Cumulative CO(2) flux from May to October was greater in 2006 and 2007 than in 2008, greater in cropping than in fallow phases, and greater in NTCB than in NTB-F. Tillage did not influence crop biomass and CO(2) flux but N fertilization had a variable effect on the flux in 2008. Similarly, soil total C content was not influenced by treatments. Annual cropping increased CO(2) flux compared with crop-fallow probably by increasing crop residue returns to soils and root and rhizosphere respiration. Inclusion of peas in the rotation with malt barley in the no-till system, which have been known to reduce N fertilization rates and

  9. Correlation Lengths for Estimating the Large-Scale Carbon and Heat Content of the Southern Ocean

    Science.gov (United States)

    Mazloff, M. R.; Cornuelle, B. D.; Gille, S. T.; Verdy, A.

    2018-02-01

    The spatial correlation scales of oceanic dissolved inorganic carbon, heat content, and carbon and heat exchanges with the atmosphere are estimated from a realistic numerical simulation of the Southern Ocean. Biases in the model are assessed by comparing the simulated sea surface height and temperature scales to those derived from optimally interpolated satellite measurements. While these products do not resolve all ocean scales, they are representative of the climate scale variability we aim to estimate. Results show that constraining the carbon and heat inventory between 35°S and 70°S on time-scales longer than 90 days requires approximately 100 optimally spaced measurement platforms: approximately one platform every 20° longitude by 6° latitude. Carbon flux has slightly longer zonal scales, and requires a coverage of approximately 30° by 6°. Heat flux has much longer scales, and thus a platform distribution of approximately 90° by 10° would be sufficient. Fluxes, however, have significant subseasonal variability. For all fields, and especially fluxes, sustained measurements in time are required to prevent aliasing of the eddy signals into the longer climate scale signals. Our results imply a minimum of 100 biogeochemical-Argo floats are required to monitor the Southern Ocean carbon and heat content and air-sea exchanges on time-scales longer than 90 days. However, an estimate of formal mapping error using the current Argo array implies that in practice even an array of 600 floats (a nominal float density of about 1 every 7° longitude by 3° latitude) will result in nonnegligible uncertainty in estimating climate signals.

  10. Fructose content and composition of commercial HFCS-sweetened carbonated beverages

    Science.gov (United States)

    White, J S; Hobbs, L J; Fernandez, S

    2015-01-01

    Objective: The obesigenic and related health effects of caloric sweeteners are subjects of much current research. Consumers can properly adjust their diets to conform to nutritional recommendations only if the sugars composition of foods and beverages is accurately measured and reported, a matter of recent concern. We tested the hypothesis that high-fructose corn syrup (HFCS) used in commercial carbonated beverages conforms to commonly assumed fructose percentages and industry technical specifications, and fulfills beverage product label regulations and Food Chemicals Codex-stipulated standards. Design: A high-pressure liquid chromatography method was developed and verified for analysis of sugars in carbonated beverages sweetened with HFCS-55. The method was used to measure percent fructose in three carbonated beverage categories. Method verification was demonstrated by acceptable linearity (R2>0.99), accuracy (94–104% recovery) and precision (RSDbeverages sweetened with HFCS-55. The difference in fructose measurements between laboratories was significant but small (0.1%), and lacked relevance. Differences in fructose by product category or by product age were not statistically significant. Total sugars content of carbonated beverages showed close agreement within product categories (95% confidence interval=0.01–0.54%). Conclusions: Using verified analytical methodology for HFCS-sweetened carbonated beverages, this study confirmed the hypothesis that fructose as a percentage of total sugars is in close agreement with published specifications in industry technical data sheets, published literature values and governmental standards and requirements. Furthermore, total sugars content of commercial beverages is consistent with common industry practices for canned and bottled products and met the US Federal requirements for nutritional labeling and nutrient claims. Prior concerns about composition were likely owing to use of improper and unverified methodology. PMID

  11. Priming alters soil carbon dynamics during forest succession

    Science.gov (United States)

    Qiao, Na; Xu, Xingliang; Wang, Juan; Kuzyakov, Yakov

    2017-04-01

    The mechanisms underlying soil carbon (C) dynamics during forest succession remain challenged. We examined priming of soil organic matter (SOM) decomposition along a vegetation succession: grassland, young and old-growth forests. Soil C was primed much more strongly in young secondary forest than in grassland or old-growth forest. Priming resulted in large C losses (negative net C balance) in young-forest soil, whereas C stocks increased in grassland and old-growth forest. Microbial composition assessed by phospholipid fatty acids (PLFA) and utilization of easily available organics (13C-PLFA) indicate that fungi were responsible for priming in young-forest soils. Consequently, labile C inputs released by litter decomposition and root exudation determine microbial functional groups that decompose SOM during forest succession. These findings provide novel insights into connections between SOM dynamics and stabilization with microbial functioning during forest succession and show that priming is an important mechanism for contrasting soil C dynamics in young and old-growth forests.

  12. Effect of water content and organic carbon on remote sensing of crop residue cover

    Science.gov (United States)

    Serbin, G.; Hunt, E. R., Jr.; Daughtry, C. S. T.; McCarty, G. W.; Brown, D. J.; Doraiswamy, P. C.

    2009-04-01

    Crop residue cover is an important indicator of tillage method. Remote sensing of crop residue cover is an attractive and efficient method when compared with traditional ground-based methods, e.g., the line-point transect or windshield survey. A number of spectral indices have been devised for residue cover estimation. Of these, the most effective are those in the shortwave infrared portion of the spectrum, situated between 1950 and 2500 nm. These indices include the hyperspectral Cellulose Absorption Index (CAI), and advanced multispectral indices, i.e., the Lignin-Cellulose Absorption (LCA) index and the Shortwave Infrared Normalized Difference Residue Index (SINDRI), which were devised for the NASA Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor. Spectra of numerous soils from U.S. Corn Belt (Indiana and Iowa) were acquired under wetness conditions varying from saturation to oven-dry conditions. The behavior of soil reflectance with water content was also dependent on the soil organic carbon content (SOC) of the soils, and the location of the spectral bands relative to significant water absorptions. High-SOC soils showed the least change in spectral index values with increase in soil water content. Low-SOC soils, on the other hand, showed measurable difference. For CAI, low-SOC soils show an initial decrease in index value followed by an increase, due to the way that water content affects CAI spectral bands. Crop residue CAI values decrease with water content. For LCA, water content increases decrease crop residue index values and increase them for soils, resulting in decreased contrast. SINDRI is also affected by SOC and water content. As such, spatial information on the distribution of surface soil water content and SOC, when used in a geographic information system (GIS), will improve the accuracy of remotely-sensed crop residue cover estimates.

  13. Endotoxemia reduces cerebral perfusion but enhances dynamic cerebrovascular autoregulation at reduced arterial carbon dioxide tension*

    DEFF Research Database (Denmark)

    Brassard, Patrice; Kim, Yu-Sok; van Lieshout, Johannes

    2012-01-01

    OBJECTIVE:: The administration of endotoxin to healthy humans reduces cerebral blood flow but its influence on dynamic cerebral autoregulation remains unknown. We considered that a reduction in arterial carbon dioxide tension would attenuate cerebral perfusion and improve dynamic cerebral autoreg...

  14. Content

    DEFF Research Database (Denmark)

    Keiding, Tina Bering

    Aim, content and methods are fundamental categories of both theoretical and practical general didactics. A quick glance in recent pedagogical literature on higher education, however, reveals a strong preoccupation with methods, i.e. how teaching should be organized socially (Biggs & Tang, 2007......, is subordinating content to methods as seen in modern didactics, hereby transforming content to a medium for achievement of learning-to-learn skills rather than something valuable in its own right. At the level of general didactics quite few attempts have been made to formulate criteria and categories...... secondary levels. In subject matter didactics, the question of content is more developed, but it is still mostly confined to teaching on lower levels. As for higher education didactics, discussions on selection of content are almost non-existent on the programmatic level. Nevertheless, teachers are forced...

  15. Improving Spectral Estimation of Soil Organic Carbon Content through Semi-Supervised Regression

    Directory of Open Access Journals (Sweden)

    Huizeng Liu

    2017-01-01

    Full Text Available Visible and near infrared (VIS-NIR spectroscopy has been applied to estimate soil organic carbon (SOC content with many modeling strategies and techniques, in which a crucial and challenging problem is to obtain accurate estimations using a limited number of samples with reference values (labeled samples. To solve such a challenging problem, this study, with Honghu City (Hubei Province, China as a study area, aimed to apply semi-supervised regression (SSR to estimate SOC contents from VIS-NIR spectroscopy. A total of 252 soil samples were collected in four field campaigns for laboratory-based SOC content determinations and spectral measurements. Semi-supervised regression with co-training based on least squares support vector machine regression (Co-LSSVMR was applied for spectral estimations of SOC contents, and it was further compared with LSSVMR. Results showed that Co-LSSVMR could improve the estimations of SOC contents by exploiting samples without reference values (unlabeled samples when the number of labeled samples was not excessively small and produce better estimations than LSSVMR. Therefore, SSR could reduce the number of labeled samples required in calibration given an accuracy threshold, and it holds advantages in SOC estimations from VIS-NIR spectroscopy with a limited number of labeled samples. Considering the increasing popularity of airborne platforms and sensors, SSR might be a promising modeling technique for SOC estimations from remotely sensed hyperspectral images.

  16. Soil carbon dynamics inferred from carbon isotope compositions of soil organic matter and soil respiration

    International Nuclear Information System (INIS)

    Koarashi, Jun; Asano, Tomohiro; Iida, Takao; Moriizumi, Jun

    2004-01-01

    To better understand 14 C cycling in terrestrial ecosystems, 14 C abundances were evaluated for fractionated soil organic matter (SOM) and soil respiration in an urban forest. In 2001 soil profile, Δ 14 C values of litter and bulk SOM increased rapidly from litter surface (62.7 per mille) to uppermost mineral soil layer (244.9 per mille), and then decreased sharply to 6 cm depth of mineral soil (125.0 per mille). Carbon enriched in 14 C by atmospheric nuclear weapons testing had penetrated to at least 16 cm depth of mineral soil. The average Δ 14 C in atmospheric CO 2 was 58.8 per mille in August 2001, suggesting recent carbon input to the topmost litter layer. Although a similar depth distribution was observed for Δ 14 C values of residual SOM after acid hydrolysis, the Δ 14 C values were slightly lower than those in bulk SOM. This indicates input of 'bomb' C into this organic fraction and higher 14 C abundance in acid-soluble SOM. The most of CO 2 may be derived from the microbial decomposition of the acid-soluble, or labile, SOM. Therefore, the labile SOM may become most influential pool for soil carbon cycling. In contrast, carbon in base-insoluble SOM remained considerably low in 14 C abundance at all depths, suggesting no or little incorporation of 'bomb' C to this fraction. Values of Δ 14 C in soil respiration ranged from 91.9 to 146.4 per mille in August 2001, showing a significant contribution from decomposition of SOM fixed over past 2-40 years. These results indicate that the use of bulk SOM as a representative of soil carbon pool would lead to severe misunderstand of the soil C dynamics on decadal and shorter time scales. (author)

  17. Topsoil organic carbon content of Europe, a new map based on a generalised additive model

    Science.gov (United States)

    de Brogniez, Delphine; Ballabio, Cristiano; Stevens, Antoine; Jones, Robert J. A.; Montanarella, Luca; van Wesemael, Bas

    2014-05-01

    There is an increasing demand for up-to-date spatially continuous organic carbon (OC) data for global environment and climatic modeling. Whilst the current map of topsoil organic carbon content for Europe (Jones et al., 2005) was produced by applying expert-knowledge based pedo-transfer rules on large soil mapping units, the aim of this study was to replace it by applying digital soil mapping techniques on the first European harmonised geo-referenced topsoil (0-20 cm) database, which arises from the LUCAS (land use/cover area frame statistical survey) survey. A generalized additive model (GAM) was calibrated on 85% of the dataset (ca. 17 000 soil samples) and a backward stepwise approach selected slope, land cover, temperature, net primary productivity, latitude and longitude as environmental covariates (500 m resolution). The validation of the model (applied on 15% of the dataset), gave an R2 of 0.27. We observed that most organic soils were under-predicted by the model and that soils of Scandinavia were also poorly predicted. The model showed an RMSE of 42 g kg-1 for mineral soils and of 287 g kg-1 for organic soils. The map of predicted OC content showed the lowest values in Mediterranean countries and in croplands across Europe, whereas highest OC content were predicted in wetlands, woodlands and in mountainous areas. The map of standard error of the OC model predictions showed high values in northern latitudes, wetlands, moors and heathlands, whereas low uncertainty was mostly found in croplands. A comparison of our results with the map of Jones et al. (2005) showed a general agreement on the prediction of mineral soils' OC content, most probably because the models use some common covariates, namely land cover and temperature. Our model however failed to predict values of OC content greater than 200 g kg-1, which we explain by the imposed unimodal distribution of our model, whose mean is tilted towards the majority of soils, which are mineral. Finally, average

  18. Novel porous carbon materials with ultrahigh nitrogen contents for selective CO 2 capture

    KAUST Repository

    Zhao, Yunfeng

    2012-01-01

    Nitrogen-doped carbon materials were prepared by a nanocasting route using tri-continuous mesoporous silica IBN-9 as a hard template. Rationally choosing carbon precursors and carefully controlling activation conditions result in an optimized material denoted as IBN9-NC1-A, which possesses a very high nitrogen doping concentration (∼13 wt%) and a large surface area of 890 m 2 g -1 arising from micropores (<1 nm). It exhibits an excellent performance for CO 2 adsorption over a wide range of CO 2 pressures. Specifically, its equilibrium CO 2 adsorption capacity at 25 °C reaches up to 4.50 mmol g -1 at 1 bar and 10.53 mmol g -1 at 8 bar. In particular, it shows a much higher CO 2 uptake at low pressure (e.g. 1.75 mmol g -1 at 25 °C and 0.2 bar) than any reported carbon-based materials, owing to its unprecedented nitrogen doping level. The high nitrogen contents also give rise to significantly enhanced CO 2/N 2 selectivities (up to 42), which combined with the high adsorption capacities, make these new carbon materials promising sorbents for selective CO 2 capture from power plant flue gas and other relevant applications. © 2012 The Royal Society of Chemistry.

  19. Influence of the Mg-content on ESR-signals in synthetic calcium carbonate

    International Nuclear Information System (INIS)

    Barabas, M.; Bach, A.; Mudelsee, M.; Mangini, A.

    1989-01-01

    Carbonate crystals doped with various concentrations of Mg 2+ -ions have been grown by a gel-diffusion method. An increase of the Mg/Ca-ratio to more than about 1 caused a phase change in the crystal lattice from calcite to aragonite. The properties of the ESR-signals of the synthetic carbonates were studied and compared with natural marine carbonates. The following results were derived: (a) In the presence of Mg 2+ -ions the synthetic carbonates display the same ESR-signals as natural calcites of marine origin with similar properties (thermal stability, radiation sensitivity). (b) The saturation value of the signal at g=2.0006 in synthetic calcites was found to be strongly related with the Mg-content in the crystals. (c) The signal at g=2.0036 (axial symmetry) which is present in calcite was not influenced by the Mg-concentration. Its saturation value decreases when the crystal phase changed from calcite to aragonite and in complement the signal at g=2.0031 appeared. (d) The signals at g=2.0057 and g=2.0031 are most probably not of organic origin. (author)

  20. Carbon Content of the Core through New Windows on the Earth's Interior

    Science.gov (United States)

    Li, J.; Gao, L.; Chen, B.; Zhao, J.; Alp, E. E.; Sturhahn, W.; Lavina, B.; Dera, P. K.

    2011-12-01

    The global carbon cycle may involve iron carbide as a component of the Earth's inner core. Placing constraints on the core's carbon content requires knowledge on the phase stability, density, and sound velocities of relevant iron-carbon alloys under the corresponding pressure and temperature conditions. Recent technological advances have opened new windows on viewing the structure and vibrational properties of iron-rich materials under megabar pressure and high temperature. Here we report new experimental results on the equations-of-state and phonon density-of-states of compressed Fe3C and Fe7C3 under core pressures and elevated temperatures. The measurements use specialized diamond-anvil cell designs and newly developed single-crystal X-ray diffraction (SXD) and nuclear resonant inelastic X-ray scattering (NRIXS) techniques. Our data reveal intriguing behavior of the two carbides under extreme conditions, including pressure-induced magnetic transitions, "invar-like" compressiblity, and significant phonon softening under high temperature. The results bear on the presence and role of carbon in the Earth's core.

  1. Thermal Transport in Carbon Nanotubes using Molecular Dynamics

    Science.gov (United States)

    Moore, Andrew; Khatun, Mahfuza

    2011-10-01

    We will present results of thermal transport phenomena in Carbon Nanotube (CNT) structures. CNTs have many interesting physical properties, and have the potential for device applications. Specifically, CNTs are robust materials with high thermal conductance and excellent electrical conduction properties. A review of electrical and thermal conduction of the structures will be discussed. The research requires analytical analysis as well as simulation. The major thrust of this study is the usage of the molecular dynamics (MD) simulator, LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). A significant investigation using the LAMMPS code is conducted on the existing Beowulf Computing Cluster at BSU. NanoHUB, an open online resource to the entire nanotechnology community developed by the researchers of Purdue University, is used for further supplementary resources. Results will include the time-dependence of temperature, kinetic energy, potential energy, heat flux correlation, and heat conduction.

  2. Dynamic simulation of a direct carbonate fuel cell power plant

    Energy Technology Data Exchange (ETDEWEB)

    Ernest, J.B. [Fluor Daniel, Inc., Irvine, CA (United States); Ghezel-Ayagh, H.; Kush, A.K. [Fuel Cell Engineering, Danbury, CT (United States)

    1996-12-31

    Fuel Cell Engineering Corporation (FCE) is commercializing a 2.85 MW Direct carbonate Fuel Cell (DFC) power plant. The commercialization sequence has already progressed through construction and operation of the first commercial-scale DFC power plant on a U.S. electric utility, the 2 MW Santa Clara Demonstration Project (SCDP), and the completion of the early phases of a Commercial Plant design. A 400 kW fuel cell stack Test Facility is being built at Energy Research Corporation (ERC), FCE`s parent company, which will be capable of testing commercial-sized fuel cell stacks in an integrated plant configuration. Fluor Daniel, Inc. provided engineering, procurement, and construction services for SCDP and has jointly developed the Commercial Plant design with FCE, focusing on the balance-of-plant (BOP) equipment outside of the fuel cell modules. This paper provides a brief orientation to the dynamic simulation of a fuel cell power plant and the benefits offered.

  3. The influence of land use on soil organic carbon and nitrogen content and redox potential

    DEFF Research Database (Denmark)

    Kusliene, Gedrime

    2010-01-01

    The aim of the research was to evaluate organic matter status in the soil according to the organic carbon content, total and mineral nitrogen amounts, carbon to nitrogen (C:N) ratio and redox potential depending on land usage and plant spieces. Soil samples were taken from the fields under...... different farming systems (conventional and organic) as well as abandoned lands. We choose the plants of two botanical species (Poaceae and Fabaceae) in organic and conventional farming systems as well as abandoned lands. Experimental results show that the best soil organic matter status according...... to the investigated indexes is in the soils of conventional and orgaic farming systems occupied with mixtures of Poaceae and Fabaceae and the worst - in the soils of abandoned Poaceae meadowa. In the abandoned lands, Fabaceae (galega) had better influence on soil organic matter status than Poaceae....

  4. Effect of Carbon and Nitrogen Content on Deformation and Fracture of AISI 304 Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    C. Menapace

    2008-04-01

    Full Text Available The effect of small differences in the content of carbon and nitrogen on the room temperature tensile deformation and fracture behaviour of an AISI 304 stainless steel was studied. In the steel containing the lower amount of carbon and nitrogen, a higher amount of strain induced alfa’ martensite is formed, which increases strain hardening rate and both uniform and total elongation at fracture. The presence of large martensitic areas in the cross section causes strain localization at the austenite/martensite interface, which promotes the nucleation of cracks and their propagation along the interface. This results in a decrease of Ultimate Tensile Strength. Strain induced transformation slightly reduces strain rate sensitivity, as well.

  5. Using DayCENT and CN-CLASS to simulate carbon dynamics in C3 and C4 agricultural crop

    Science.gov (United States)

    Chang, K.; Warland, J. S.; Bartlett, P. A.; Arain, M. A.; Voroney, P.; Wagner-Riddle, C.

    2009-12-01

    This study validated and compared the modeling mechanism of carbon fixation in two different models: DayCENT(daily time-step of agroecosystem model) and CN-CLASS(half-hourly time-step of Carbon and Nitrogen coupled Canadian Land Surface Scheme for GCMS) in a corn(2005) and soybean(2006) year in southern Ontario, Canada. The purpose of this study was to evaluate the sensitivity of modeling parameters that related to carbon fixation and further to examine the relationship of carbon dynamics and environmental factors. We validated two models with field measurements of soil water content, soil temperature, latent heat and sensible heat. In addition, above-ground biomass measurements and leaf area index inventory data were used to ensure the modeling carbon allocation for the plant structure. The two different photosynthesis-stomatal conductance subroutines: Collatz's and Bonan's in CN-CLASS were also evaluated with field measurements. Our simulations suggests that both models had a general good control on environmental factors and carbon dynamics. Our sensitivity analysis indicated that further modification of leaf area index, specific leaf area, Q10 and base rate for the various respiration subroutines in CN-CLASS are required.

  6. Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy

    OpenAIRE

    Agustina, Elsye; Goak, Jeungchoon; Lee, Suntae; Seo, Youngho; Park, Jun-Young; Lee, Naesung

    2015-01-01

    Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red–orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship ...

  7. The carbon isotopes ratio and trace metals content determinations in some Transylvanian fruit juices

    Science.gov (United States)

    Dehelean, A.; Magdas, D. A.; Cristea, G.

    2012-02-01

    This work presents a preliminary study on the carbon isotope signature and trace metal content investigated on the soil-plant-fruit pulp chain. The samples were collected from two Transylvanian areas namely Alba and Salaj. The average value of the δ13C at the soil surface was around δ13C ≈ -27%° and important differences of the δ13C values between the two studied areas were not observed. Meanwhile, differences between fruit pulp of grape juice and the pulp of pear juice relived a difference of about 1.5%° for δ13C values.

  8. Effects of Soil Compaction and Organic Carbon Content on Preferential Flow in Loamy Field Soils

    DEFF Research Database (Denmark)

    Soares, Antonio; Moldrup, Per; Vendelboe, Anders Lindblad

    2015-01-01

    . Tritium breakthrough experiments were conducted at constant flow rates and obtained breakthrough curves were analyzed for 5% tracer arrival time and dispersivity. Both soils showed strong correlations between soil compaction, expressed in terms of bulk density, and preferential flow. Interestingly......, the relationships between bulk density and tritium transport parameters were markedly different for the two soils although the relationship between bulk density and macroporosity was nearly identical. The difference was likely caused by the higher organic carbon content of one soil leading to a more pronounced pipe...

  9. Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers

    Science.gov (United States)

    Culebras, Mario; Madroñero, Antonio; Cantarero, Andres; Amo, José Maria; Domingo, Concepción; López, Antonio

    2012-10-01

    Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditions: surface tension, mass density, and Raman measurements. A discussion on the validity of the results obtained through the correlation between them is the purpose of the present work.

  10. Determination of local carbon content in austenite during intercritical annealing of dual phase steels by PEELS analysis

    International Nuclear Information System (INIS)

    Garcia-Junceda, A.; Caballero, F.G.; Capdevila, C.; Garcia de Andres, C.

    2007-01-01

    Parallel electron energy loss spectroscopy has allowed to analyse and quantify local variations in the carbon concentration of austenite islands transformed during the intercritical annealing treatment of commercial dual-phase steels. These changes in the carbon content of different austenite regions are responsible for the different volume fractions of tempered martensite, martensite and retained austenite obtained after intercritical annealing and overaging treatment. This technique reveals how carbon distribution in austenite evolves as the transformation process advances

  11. The effects of permafrost thaw on soil hydrologic, thermal, and carbon dynamics in an Alaskan peatland

    Science.gov (United States)

    Jonathan A. O' Donnell; M.Torre Jorgenson; Jennifer W. Harden; A.David McGuire; Mikhail Z. Kanevskiy; Kimberly P. Wickland

    2012-01-01

    Recent warming at high-latitudes has accelerated permafrost thaw in northern peatlands, and thaw can have profound effects on local hydrology and ecosystem carbon balance. To assess the impact of permafrost thaw on soil organic carbon (OC) dynamics, we measured soil hydrologic and thermal dynamics and soil OC stocks across a collapse-scar bog chronosequence in interior...

  12. The efficiency of different types of wood charcoal on increasing carbon content on surfaces of low carbon steel in the pack carburizing process

    Directory of Open Access Journals (Sweden)

    Narongsak Thammachot

    2014-09-01

    Full Text Available The purpose of this research is to compare the efficiency of five types of wood charcoal, eucalyptus, coconut shell, tamarind, bamboo and cassava root in increasing carbon content on surfaces of low carbon steel by the pack carburizing process. The experiment for pack carburized low carbon steel (grade AISI 1020 was conducted by using the different wood charcoals as carburizers, mixed with 10% limestone (by weight as the energizer. The carburizing temperature of 950°C, and carburizing times of 2, 4 and 6 hours were used in the experiment. After grinding, the specimens in each case were checked for carbon content by optical emission spectroscopy. Micro-Vickers hardness testing and microstructure inspections were carried out. The results of the experiment showed that the efficiency of eucalyptus charcoal as the carburizer (for increasing carbon content on surfaces of low carbon steel was higher than that of tamarind, cassava root, coconut shell and bamboo charcoals. The averages for carbon content were: 1.16, 1.06, 0.97, 0.83 and 0.77% respectively.

  13. Ganglion dynamics and its implications to geologic carbon dioxide storage.

    Science.gov (United States)

    Wang, Yifeng; Bryan, Charles; Dewers, Thomas; Heath, Jason E; Jove-Colon, Carlos

    2013-01-02

    Capillary trapping of a nonwetting fluid phase in the subsurface has been considered as an important mechanism for geologic storage of carbon dioxide (CO(2)). This mechanism can potentially relax stringent requirements for the integrity of cap rocks for CO(2) storage and therefore can significantly enhance storage capacity and security. We here apply ganglion dynamics to understand the capillary trapping of supercritical CO(2) (scCO(2)) under relevant reservoir conditions. We show that, by breaking the injected scCO(2) into small disconnected ganglia, the efficiency of capillary trapping can be greatly enhanced, because the mobility of a ganglion is inversely dependent on its size. Supercritical CO(2) ganglia can be engineered by promoting CO(2)-water interface instability during immiscible displacement, and their size distribution can be controlled by injection mode (e.g., water-alternating-gas) and rate. We also show that a large mobile ganglion can potentially break into smaller ganglia due to CO(2)-brine interface instability during buoyant rise, thus becoming less mobile. The mobility of scCO(2) in the subsurface is therefore self-limited. Vertical structural heterogeneity within a reservoir can inhibit the buoyant rise of scCO(2) ganglia. The dynamics of scCO(2) ganglia described here provides a new perspective for the security and monitoring of subsurface CO(2) storage.

  14. Mapping soil organic carbon content and composition across Australia to assess vulnerability to climate change

    Science.gov (United States)

    Viscarra Rossel, R. A.

    2015-12-01

    We can effectively monitor soil condition—and develop sound policies to offset the emissions of greenhouse gases—only with accurate data from which to define baselines. Currently, estimates of soil organic C for countries or continents are either unavailable or largely uncertain because they are derived from sparse data, with large gaps over many areas of the Earth. Here, we derive spatially explicit estimates, and their uncertainty, of the distribution and stock of organic C content and composition in the soil of Australia. The composition of soil organic C may be characterized by chemical separation or physical fractionation based on either particle size or particle density (Skjemstad et al., 2004; Gregorich et al., 2006; Kelleher&Simpson, 2006; Zimmermann et al., 2007). In Australia, for example, Skjemstad et al. (2004) used physical separation of soil samples into 50-2000 and <50-μm particle-size fractions followed by the measurement of char-carbon using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, giving the three OC pools, particulate organic carbon (POC), humic organic carbon (HOC) and resistant organic carbon (ROC; charcoal or char-carbon). We assembled and harmonized data from several sources to produce the most comprehensive set of data on the current stock of organic C in soil of the continent. Using them, we have produced a fine spatial resolution baseline map of organic C, POC, HOC and ROC at the continental scale. In this presentation I will describe how we made the maps and how we use them to assess the vulnerability of soil organic C to for instance climate change.

  15. Fluid Dynamics of Carbon Dioxide Disposal into Saline Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Julio Enrique [Univ. of California, Berkeley, CA (United States)

    2003-01-01

    Injection of carbon dioxide (CO2) into saline aquifers has been proposed as a means to reduce greenhouse gas emissions (geological carbon sequestration). Large-scale injection of CO2 will induce a variety of coupled physical and chemical processes, including multiphase fluid flow, fluid pressurization and changes in effective stress, solute transport, and chemical reactions between fluids and formation minerals. This work addresses some of these issues with special emphasis given to the physics of fluid flow in brine formations. An investigation of the thermophysical properties of pure carbon dioxide, water and aqueous solutions of CO2 and NaCl has been conducted. As a result, accurate representations and models for predicting the overall thermophysical behavior of the system CO2-H2O-NaCl are proposed and incorporated into the numerical simulator TOUGH2/ECO2. The basic problem of CO2 injection into a radially symmetric brine aquifer is used to validate the results of TOUGH2/ECO2. The numerical simulator has been applied to more complex flow problem including the CO2 injection project at the Sleipner Vest Field in the Norwegian sector of the North Sea and the evaluation of fluid flow dynamics effects of CO2 injection into aquifers. Numerical simulation results show that the transport at Sleipner is dominated by buoyancy effects and that shale layers control vertical migration of CO2. These results are in good qualitative agreement with time lapse surveys performed at the site. High-resolution numerical simulation experiments have been conducted to study the onset of instabilities (viscous fingering) during injection of CO2 into saline aquifers. The injection process can be classified as immiscible displacement of an aqueous phase by a less dense and less viscous gas phase. Under disposal conditions (supercritical CO2) the viscosity of carbon

  16. Pore-Scale Transport of Strontium During Dynamic Water Content Changes in the Unsaturated Zone

    Science.gov (United States)

    Weaver, W.; Kibbey, T. C. G.; Papelis, C.

    2016-12-01

    Dynamic water content changes in the unsaturated zone caused by natural and manmade processes, such as evaporation, rainfall, and irrigation, have an effect on contaminant mobility. In general, in the unsaturated zone, evaporation causes an increase in contaminant concentrations, potentially leading to sorption of contaminants on aquifer materials or precipitation of crystalline or amorphous phases. On the other hand, increase of water content may result in dissolution of precipitated phases and increased mobility of contaminants. The objective of this study was to develop a quantitative model for the transport of strontium through sand under dynamic water content conditions, as a function of strontium concentration, pH, and ionic strength. Strontium was selected as a surrogate for strontium-90, a by-product of nuclear reactions. The dynamic water content was determined using an automated device for rapidly measuring the hysteretic capillary pressure—saturation relationship, followed by ambient air evaporation, and gravimetric water content measurement. Strontium concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS). Flow interruption experiments were conducted to determine whether equilibrium conditions existed for a given flowrate. Scanning electron microscopy (SEM) was used to visualize the treated quartz sand particles and the distribution of strontium on sand grains was determined using elemental maps created by energy-dispersive x-ray spectroscopy (EDX). Strontium behavior appears to be pH dependent as well as ionic strength dependent under these conditions.

  17. The topology of non-linear global carbon dynamics: from tipping points to planetary boundaries

    International Nuclear Information System (INIS)

    Anderies, J M; Carpenter, S R; Steffen, Will; Rockström, Johan

    2013-01-01

    We present a minimal model of land use and carbon cycle dynamics and use it to explore the relationship between non-linear dynamics and planetary boundaries. Only the most basic interactions between land cover and terrestrial, atmospheric, and marine carbon stocks are considered in the model. Our goal is not to predict global carbon dynamics as it occurs in the actual Earth System. Rather, we construct a conceptually reasonable heuristic model of a feedback system between different carbon stocks that captures the qualitative features of the actual Earth System and use it to explore the topology of the boundaries of what can be called a ‘safe operating space’ for humans. The model analysis illustrates the existence of dynamic, non-linear tipping points in carbon cycle dynamics and the potential complexity of planetary boundaries. Finally, we use the model to illustrate some challenges associated with navigating planetary boundaries. (letter)

  18. Ameliorated Austenite Carbon Content Control in Austempered Ductile Irons by Support Vector Regression

    Directory of Open Access Journals (Sweden)

    Chan-Yun Yang

    2013-01-01

    Full Text Available Austempered ductile iron has emerged as a notable material in several engineering fields, including marine applications. The initial austenite carbon content after austenization transform but before austempering process for generating bainite matrix proved critical in controlling the resulted microstructure and thus mechanical properties. In this paper, support vector regression is employed in order to establish a relationship between the initial carbon concentration in the austenite with austenization temperature and alloy contents, thereby exercising improved control in the mechanical properties of the austempered ductile irons. Particularly, the paper emphasizes a methodology tailored to deal with a limited amount of available data with intrinsically contracted and skewed distribution. The collected information from a variety of data sources presents another challenge of highly uncertain variance. The authors present a hybrid model consisting of a procedure of a histogram equalizer and a procedure of a support-vector-machine (SVM- based regression to gain a more robust relationship to respond to the challenges. The results show greatly improved accuracy of the proposed model in comparison to two former established methodologies. The sum squared error of the present model is less than one fifth of that of the two previous models.

  19. Biomass Carbon Content in Schima- Castanopsis Forest of Midhills of Nepal: A Case Study from Jaisikuna Community Forest, Kaski

    Directory of Open Access Journals (Sweden)

    Sushma Tripathi

    2018-01-01

    Full Text Available Community forests of Nepal’s midhills have high potentiality to sequester carbon. This paper tries to analyze the biomass carbon stock in Schima-Castanopsis forest of Jaisikuna community forests of Kaski district, Nepal. Forest area was divided into two blocks and 18 sample plots (9 in each block which were laid randomly. Diameter at Breast Height (DBH and height of trees (DBH≥5cm were measured using the DBH tape and clinometer. Leaf litter, herbs, grasses and seedlings were collected from 1*1m2 plot and fresh weight was taken. For calculating carbon biomass is multiplied by default value 0.47. The AGTB carbon content of Chilaune, Katus and other species were found 19.56 t/ha, 18.66 t/ha and 3.59 t/ha respectively. The AGTB of Chilaune dominated, Katus dominated and whole forest was found 43.78 t/ha, 39.83 t/ha and 41.81 t/ha respectively. Carbon content at leaf litter, herbs, grasses and seedlings was found 2.73 t/ha. Below ground biomass carbon at whole forest was found 6.27 t/ha. Total biomass and carbon of the forest was found 108.09 t/ha and 50.80 t/ha respectively. Difference in biomass and carbon content at Chilaune dominated block and Katus dominated block was found insignificant. This study record very low biomass carbon content than average of Nepal's forest but this variation in carbon stock is not necessarily due to dominant species present in the forest. Carbon estimation at forest of different elevation, aspect and location are recommended for further research. International Journal of EnvironmentVolume-6, Issue-4, Sep-Nov 2017, page: 72-84

  20. Static and Dynamic Mechanical Properties of Graphene Oxide-Incorporated Woven Carbon Fiber/Epoxy Composite

    Science.gov (United States)

    Adak, Nitai Chandra; Chhetri, Suman; Kim, Nam Hoon; Murmu, Naresh Chandra; Samanta, Pranab; Kuila, Tapas

    2018-01-01

    This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 °C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young's modulus, toughness, flexural strength and flexural modulus by 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tanδ), respectively, at its glass transition temperature. The fiber-matrix interaction was studied using a Cole-Cole plot analysis.

  1. Improved dynamic properties of natural rubber filled with irradiation-modified carbon black

    Science.gov (United States)

    Wu, Yongpeng; Wen, Shipeng; Shen, Jing; Jiang, Jian; Hu, Shui; Zhang, Liqun; Liu, Li

    2015-06-01

    In this work, carbon black particles (CBs) were modified by high-energy electron beam (EB) irradiation at different doses. The influence of EB irradiation on the surface and particle size of CBs was investigated. Then, the CBs were compounded with natural rubber (NR), and the mechanical properties and dynamic properties of CBs/NR composite were further researched. The results showed that the irradiated CBs had more oxygen-containing groups and smaller particle sizes than original CBs. After irradiation, the content of bound rubber around the irradiated CBs increased, and the mechanical properties of CBs/NR composite were improved. Most importantly, NR filled with irradiated CBs has lower abrasion, higher wet skid resistance, and lower rolling resistance than NR filled with untreated CBs.

  2. Carbon and Nitrogen dynamics in deciduous and broad leaf trees under drought stress

    Science.gov (United States)

    Joseph, Jobin; Schaub, Marcus; Arend, Matthias; Saurer, Matthias; siegwolf, Rolf; Weiler, Markus; Gessler, Arthur

    2017-04-01

    , we labelled the soil with 15N nitrate by injecting nitrate solution into the soil without strongly changing the water content for investigating nitrogen uptake and distribution along different compartments of the plant soil continuum. We observed a distinct difference in the carbon and nitrogen dynamics and allocation pattern between broad leaf and conifer seedlings. Broad leaf species showed a lower reduction of CO2 assimilation under drought and still allocated significant amounts of the new assimilates to the roots. Especially in maple and oak the belowground transfer of assimilates was kept at high levels even under severe drought stress, while there was a reduction in assimilation transport in beech. Instead, only small amounts of 13C labelled new assimilates arrived in the roots of conifers in the drought treatments. In the deciduous species 15N taken up the roots was more intensively allocated to aboveground tissues compared to conifers under control conditions, which retained the largest amounts within the fine roots. 15N uptake was reduced in the drought treatments in all species assessed. There was, however, no clear relation of this reduction to changes in 13C allocation to the roots. We thus cannot conclude that the reduction of nitrogen uptake is due to reduced transport of new assimilates belowground. We thus need to assume that carbon storage is sufficient to provide energy and carbon for nitrogen uptake and assimilation at least over the short-term. During longer drought periods, however, depletion of carbon stores might adversely affect the nutrient uptake and balance of trees.

  3. Primary Nutritional Content of Bio-Flocs Cultured with Different Organic Carbon Sources and Salinity

    Directory of Open Access Journals (Sweden)

    JULIE EKASARI

    2010-09-01

    Full Text Available Application of bio-flocs technology (BFT in aquaculture offers a solution to avoid environmental impact of high nutrient discharges and to reduce the use of artificial feed. In BFT, excess of nutrients in aquaculture systems are converted into microbial biomass, which can be consumed by the cultured animals as a food source. In this experiment, upconcentrated pond water obtained from the drum filter of a freshwater tilapia farm was used for bio-flocs reactors. Two carbon sources, sugar and glycerol, were used as the first variable, and two different levels of salinity, 0 and 30 ppt, were used as the second variable. Bio-flocs with glycerol as a carbon source had higher total n-6 PUFAs (19.1 ± 2.1 and 22.3 ± 8.6 mg/g DW at 0 and 30 ppt, respectively than that of glucose (4.0 ± 0.1 and 12.6 ± 2.5 mg/g DW at 0 and 30 ppt. However, there was no effect of carbon source or salinity on crude protein, lipid, and total n-3 PUFAs contents of the bio-flocs.

  4. Productivity, carbon utilization, and energy content of mass in scalable microalgae systems.

    Science.gov (United States)

    Murray, Kyle E; Shields, Jeremy A; Garcia, Nicholas D; Healy, Frank G

    2012-06-01

    This study was designed to examine carbon utilization within scalable microalgae production systems. Neochloris oleoabundans was produced in replicated troughs containing BG11 nutrient formulation. Atmospheric CO(2) was supplemented with ∼5% CO(2) or with NaHCO(3), and the pH of troughs receiving NaHCO(3) was adjusted with HCl or H(3)PO(4). Peak biomass concentrations reached 950, 1140, or 850 mg L(-1) and biomass productivities of 109, 96, and 74 mg L(-1) day(-1) were achieved in the CO(2), NaHCO(3):HCl and NaHCO(3):H(3)PO(4) troughs, respectively. The highest productivity is expected in a scaled-up continuous batch process of the CO(2) supplemented system, which was projected to yield 8948 L lipids ha(-1)yr(-1). Carbon utilization in the CO(2), NaHCO(3):HCl and NaHCO(3):H(3)PO(4) systems was ∼0.5, 15.5, and 12.9%, while the energy content of the combustible biomass was 26.7, 13.2, and 15.4 MJ kg(-1), respectively. Techno-economic analyses of microalgal production systems should consider efficiencies and cost-benefit of various carbon sources. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. [Soil organic carbon content and its distribution pattern in Hangzhou Bay coastal wetlands].

    Science.gov (United States)

    Shao, Xue-xin; Yang, Wen-ying; Wu, Ming; Jiang, Ke-yi

    2011-03-01

    In this paper, the soil organic carbon (SOC) content and its distribution pattern in the natural intertidal zones and reclaimed wetlands of Hangzhou Bay were studied, aimed to explore the effects of vegetation succession, exotic species invasion, and reclamation on the SOC in costal wetlands of the Bay. In intertidal zones, the surface SOC content ranged from 4.41 to 8.58 g x kg(-1), with an average of 6.45 g x kg(-1), and differed significantly under different vegetations, with a tendency of under Phragmites australis (8.56 +/- 0.04 g x kg(-1)) > Spartina alterniflora (7.31 +/- 0.08 g x kg(-1)) > Scirpus mariqueter (5.48 +/- 0.29 g x kg(-1)) > mudflats (4.47 +/- 0.09 g x kg(-1)); in reclaimed wetlands, the surface SOC content was 7.46 +/- 0.25 g x kg(-1) in the 1960s, 1.96 +/- 0.46 g x kg(-1) in the 1980s, and 5.12 +/- 0.16 g x kg(-1) in 2003, showing a trend of increased after an initial decrease with increasing reclamation year. The SOC in the profiles all showed a decreasing trend from the surface to the bottom. The SOC in intertidal zones and reclaimed wetlands was significantly negatively correlated with soil pH, and positively correlated with soil total nitrogen (TN), suggesting a large reserve of organic nitrogen in TN. The correlation between SOC and soil C/N ratio was not obvious in intertidal zones, but significantly positive in reclaimed wetlands, indicating that reclamation affected soil C/N ratio to a certain extent. This study showed that in the intertidal zones, soil carbon sequestration capacity increased gradually with plant community succession. However, the invasion of exotic species Spartina alternflora might decrease the capacity of carbon sequestration in intertidal zones. It was also found that the changes of soil moisture content, particle composition, vegetation coverage, and reclamation history were the main factors affecting the SOC distribution in reclaimed wetlands.

  6. Highly ordered macroporous woody biochar with ultra-high carbon content as supercapacitor electrodes

    International Nuclear Information System (INIS)

    Jiang, Junhua; Zhang, Lei; Wang, Xinying; Holm, Nancy; Rajagopalan, Kishore; Chen, Fanglin; Ma, Shuguo

    2013-01-01

    Woody biochar monolith with ultra-high carbon content and highly ordered macropores has been prepared via one-pot pyrolysis and carbonization of red cedar wood at 750 °C without the need of post-treatment. Energy-dispersive spectroscope (EDX) and scanning electron microscope (SEM) studies show that the original biochar has a carbon content of 98 wt% with oxygen as the only detectable impurity and highly ordered macroporous texture characterized by alternating regular macroporous regions and narrow porous regions. Moreover, the hierarchically porous biochar monolith has a high BET specific surface area of approximately 400 m 2 g −1 . We have studied the monolith material as supercapacitor electrodes under acidic environment using electrochemical and surface characterization techniques. Electrochemical measurements show that the original biochar electrodes have a potential window of about 1.3 V and exhibit typical rectangular-shape voltammetric responses and fast charging–discharging behavior with a gravimetric capacitance of about 14 F g −1 . Simple activation of biochar in diluted nitric acid at room temperature leads to 7 times increase in the capacitance (115 F g −1 ). Because the HNO 3 -activation slightly decreases rather than increases the BET surface area of the biochar, an increase in the coverage of surface oxygen groups is the most likely origin of the substantial capacitance improvement. This is supported by EDX, X-ray photoelectron spectroscopy (XPS), and Raman measurements. Preliminary life-time studies show that biochar supercapacitors using the original and HNO 3 -activated electrodes are stable over 5000 cycles without performance decays. These facts indicate that the use of woody biochar is promising for its low cost and it can be a good performance electrode with low environmental impacts for supercapacitor applications

  7. Quantifying terrestrial ecosystem carbon dynamics in the Jinsha watershed, Upper Yangtze, China from 1975 to 2000

    Science.gov (United States)

    Zhao, Shuqing; Liu, Shuguang; Yin, Runsheng; Li, Zhengpeng; Deng, Yulin; Tan, Kun; Deng, Xiangzheng; Rothstein, David; Qi, Jiaguo

    2010-01-01

    Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial biosphere and the atmosphere is critical to our understanding of regional patterns of carbon budgets. Here we use the General Ensemble biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China’s upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces, such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975–2000, with an average rate of 0.36 Mg/ha/yr, primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to a lower net gain of carbon in the watershed, and after that soils became a small sink. Ecosystem carbon sink/source patterns showed a high degree of spatial heterogeneity. Carbon sinks were associated with forest areas without disturbances, whereas carbon sources were primarily caused by stand-replacing disturbances. It is critical to adequately represent the detailed fast-changing dynamics of land use activities in regional biogeochemical models to determine the spatial and temporal evolution of regional carbon sink/source patterns.

  8. Predicting Reactive Transport Dynamics in Carbonates using Initial Pore Structure

    Science.gov (United States)

    Menke, H. P.; Nunes, J. P. P.; Blunt, M. J.

    2017-12-01

    Understanding rock-fluid interaction at the pore-scale is imperative for accurate predictive modelling of carbon storage permanence. However, coupled reactive transport models are computationally expensive, requiring either a sacrifice of resolution or high performance computing to solve relatively simple geometries. Many recent studies indicate that initial pore structure many be the dominant mechanism in determining the dissolution regime. Here we investigate how well the initial pore structure is predictive of distribution and amount of dissolution during reactive flow using particle tracking on the initial image. Two samples of carbonate rock with varying initial pore space heterogeneity were reacted with reservoir condition CO2-saturated brine and scanned dynamically during reactive flow at a 4-μm resolution between 4 and 40 times using 4D X-ray micro-tomography over the course of 1.5 hours using μ-CT. Flow was modelled on the initial binarized image using a Navier-Stokes solver. Particle tracking was then run on the velocity fields, the streamlines were traced, and the streamline density was calculated both on a voxel-by-voxel and a channel-by-channel basis. The density of streamlines was then compared to the amount of dissolution in subsequent time steps during reaction. It was found that for the flow and transport regimes studied, the streamline density distribution in the initial image accurately predicted the dominant pathways of dissolution and gave good indicators of the type of dissolution regime that would later develop. This work suggests that the eventual reaction-induced changes in pore structure are deterministic rather than stochastic and can be predicted with high resolution imaging of unreacted rock.

  9. Chemical method for determination of carbon dioxide content in egg yolk and egg albumen.

    Science.gov (United States)

    Keener, K M; LaCrosse, J D; Babson, J K

    2001-07-01

    The safety, quality, and shelf life of shell eggs is a function of carbon dioxide content. A commercial process was recently developed for rapidly cooling shell eggs by using cryogenic CO2. The benefit of this new process over existing cooling processes is that the CO2 addition during cryogenic cooling provides additional safety and quality enhancements. In order for these benefits to be fully developed into a process that can be adopted by the egg industry, and thus realized by the consumer, the amount of CO2 absorbed by the egg during this process needs to be quantified. Because the albumen pH of rapidly cooled eggs was reduced to pH neutralization. A simple and accurate method for determining CO2 content in acidified egg albumen and yolk samples was developed. This method involves the liberation of CO2 from an acidified egg sample into a standardized, dilute sodium hydroxide solution inside a sealed jar. The egg sample and a small beaker containing the standardized sodium hydroxide solution are placed in a glass jar and sealed. Next, a concentrated acid phosphate solution is injected through a rubber septum in the cap of the jar onto the egg sample, while avoiding contact with the sodium hydroxide solution. The sample is then stored at 37 C for 24 h. During this storage period, the carbon dioxide is released from the egg sample and is absorbed into the sodium hydroxide solution. Afterwards, the dilute sodium hydroxide solution is removed and titrated to the phenolphthalein endpoint using a dilute, standardized hydrochloric acid solution. The amount of hydrochloric acid solution required for neutralization can be directly related to CO2 content in the sample.

  10. Content modification attacks on consensus seeking multi-agent system with double-integrator dynamics

    Science.gov (United States)

    Dong, Yimeng; Gupta, Nirupam; Chopra, Nikhil

    2016-11-01

    In this paper, vulnerability of a distributed consensus seeking multi-agent system (MAS) with double-integrator dynamics against edge-bound content modification cyber attacks is studied. In particular, we define a specific edge-bound content modification cyber attack called malignant content modification attack (MCoMA), which results in unbounded growth of an appropriately defined group disagreement vector. Properties of MCoMA are utilized to design detection and mitigation algorithms so as to impart resilience in the considered MAS against MCoMA. Additionally, the proposed detection mechanism is extended to detect the general edge-bound content modification attacks (not just MCoMA). Finally, the efficacies of the proposed results are illustrated through numerical simulations.

  11. [Dynamic change of active component content in different parts of Prunella vulgaris].

    Science.gov (United States)

    Wang, Yuxia; Yin, Jinbao; Guo, Qiaosheng; Xiao, Yunhua

    2011-03-01

    Through determination of the dynamic change of the active component in different parts of Prunella vulgaris at different growth stages, to find the optimal harvest time. Total flavonoids content was determined by using the spectrophotometric method, and the content of ursolic acid and oleanolic acid was determined by HPLC. The contents of ash and extract were determined according to the methods in Chinese Pharmacopeia (2005 edition). There existed the active components in all parts of P. vulgaris, but the active component contents in different parts of P. vulgaris of at different growth stages, changed very obviously. In Yangtze-Huaihai region, the optimal harvest time of Prunella spike best harvest is at the end of June, and Prunellastem at the end of May. All parts of P. vulgaris have medicinal value.

  12. The influence of saltmarsh restoration on sediment dynamics and the potential impact on carbon sequestration

    Science.gov (United States)

    Taylor, Benjamin; Paterson, David

    2017-04-01

    Coastal wetland ecosystems can act as large-capacity carbon sinks, providing a valuable climate change mitigation function. Globally, saltmarshes are estimated to accumulate an average of 244.7g C m-2 yr-1 (Ouyang & Lee 2014). Saltmarsh areas have experienced rapid loss in the recent past of approximately 1-2% per year (Duarte et al. 2008). Efforts to restore these areas could result in additional carbon storage due to extended vegetation cover and altered burial due to changing sediment dynamics. The influence of restoration through transplantation on sediment dynamics within a small estuary on the east coast of Scotland was assessed. Restoration efforts have been implemented since the early 2000s providing examples of old established sites ("old", >10years), young recently planted sites ("young", percentage organic matter content of deposited material is significantly lower in mudflat and young areas (3.78 ± 0.59% and 3.66 ± 0.79% respectively) versus those of natural and old areas (12.08 ± 2.27% and 6.70 ± 1.30% respectively). This relationship suggests that older restored areas are potentially offering the most potential benefit in terms of carbon sequestration, due to higher rates of deposition from the potential load and higher percentage organic content of those deposits. Furthermore, measurements of sediment accretion rates over the same period show natural and old areas to be the most effective at retaining sediment, with average elevation changes of 6.99 ± 1.64mm and 6.56 ± 0.94mm respectively, in comparison to young areas, 4.44 ± 1.58mm, and mudflats, 1.51 ± 1.23mm. Factors influencing these differences could be attributed to type and density of vegetation present and elevation of each area (or immersion period). However, the data suggests restoration could play an important role, which once established, appears to facilitate efficient sediment deposition from potential sediment load and crucially the effective accumulation of organic rich

  13. Application of fast pyrolysis biochar to a loamy soil - Effects on carbon and nitrogen dynamics and potential for carbon sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Bruun, E.W.

    2011-05-15

    Thermal decomposition of biomass in an oxygen-free environment (pyrolysis) produces bio-oil, syngas, and char. All three products can be used to generate energy, but an emerging new use of the recalcitrant carbon-rich char (biochar) is to apply it to the soil in order to enhance soil fertility and at the same time mitigate climate change by sequestering carbon in the soil. In general, the inherent physicochemical characteristics of biochars make these materials attractive agronomic soil conditioners. However, different pyrolysis technologies exist, i.e. slow pyrolysis, fast pyrolysis, and full gasification systems, and each of these influence the biochar quality differently. As of yet, there is only limited knowledge on the effect of applying fast pyrolysis biochar (FP-biochar) to soil. This PhD project provides new insights into the short-term impacts of adding FP-biochar to soil on the greenhouse gas (GHG) emissions and on soil carbon and nitrogen dynamics. The FP-biochars investigated in the thesis were generated at different reactor temperatures by fast pyrolysis of wheat straw employing a Pyrolysis Centrifuge Reactor (PCR). The carbohydrate content ranged from more than 35 % in FP-biochars made at a low reactor temperature (475 deg. C) down to 3 % in FP-biochars made at high temperatures (575 deg. C). The relative amount of carbohydrates in the FP-biochar was found to be correlated to the short-term degradation rates of the FP-biochars when applied to soil. Fast and slow pyrolysis of wheat straw resulted in two different biochar types with each their distinct physical structures and porosities, carbohydrate contents, particle sizes, pH values, BET surface areas, and elemental compositions. These different physicochemical properties obviously have different impacts on soil processes, which underscores that results obtained from soil studies using slow pyrolysis biochars (SP-biochar) are not necessarily applicable for FP-biochars. For example, the incorporation

  14. Soil respiration and organic carbon dynamics with grassland conversions to woodlands in temperate china.

    Directory of Open Access Journals (Sweden)

    Wei Wang

    Full Text Available Soils are the largest terrestrial carbon store and soil respiration is the second-largest flux in ecosystem carbon cycling. Across China's temperate region, climatic changes and human activities have frequently caused the transformation of grasslands to woodlands. However, the effect of this transition on soil respiration and soil organic carbon (SOC dynamics remains uncertain in this area. In this study, we measured in situ soil respiration and SOC storage over a two-year period (Jan. 2007-Dec. 2008 from five characteristic vegetation types in a forest-steppe ecotone of temperate China, including grassland (GR, shrubland (SH, as well as in evergreen coniferous (EC, deciduous coniferous (DC and deciduous broadleaved forest (DB, to evaluate the changes of soil respiration and SOC storage with grassland conversions to diverse types of woodlands. Annual soil respiration increased by 3%, 6%, 14%, and 22% after the conversion from GR to EC, SH, DC, and DB, respectively. The variation in soil respiration among different vegetation types could be well explained by SOC and soil total nitrogen content. Despite higher soil respiration in woodlands, SOC storage and residence time increased in the upper 20 cm of soil. Our results suggest that the differences in soil environmental conditions, especially soil substrate availability, influenced the level of annual soil respiration produced by different vegetation types. Moreover, shifts from grassland to woody plant dominance resulted in increased SOC storage. Given the widespread increase in woody plant abundance caused by climate change and large-scale afforestation programs, the soils are expected to accumulate and store increased amounts of organic carbon in temperate areas of China.

  15. Effect of variation in argon content of calibration gases on determination of atmospheric carbon dioxide.

    Science.gov (United States)

    Min, Deullae; Kang, Namgoo; Moon, Dong Min; Lee, Jin Bok; Lee, Dong Soo; Kim, Jin Seog

    2009-12-15

    Carbon dioxide (CO(2)) is a greenhouse gas that makes by far the largest contribution to the global warming of the Earth's atmosphere. For the measurements of atmospheric CO(2) a non-dispersive infrared analyzer (NDIR) and gas chromatography are conventionally being used. We explored whether and to what degree argon content can influence the determination of atmospheric CO(2) using the comparison of CO(2) concentrations between the sample gas mixtures with varying Ar amounts at 0 and 18.6 mmol mol(-1) and the calibration gas mixtures with Ar at 8.4, 9.1, and 9.3 mmol mol(-1). We newly discovered that variation of Ar content in calibration gas mixtures could undermine accuracy for precise and accurate determination of atmospheric CO(2) in background air. The differences in CO(2) concentration due to the variation of Ar content in the calibration gas mixtures were negligible (<+/-0.03 micromol mol(-1)) for NDIR systems whereas they noticeably increased (<+/-1.09 micromol mol(-1)) especially for the modified GC systems to enhance instrumental sensitivity. We found that the thermal mass flow controller is the main source of the differences although such differences appeared only in the presence of a flow restrictor in GC systems. For reliable monitoring of real atmospheric CO(2) samples, one should use calibration gas mixtures that contain Ar content close to the level (9.332 mmol mol(-1)) in the ambient air as possible. Practical guidelines were highlighted relating to selection of appropriate analytical approaches for the accurate and precise measurements of atmospheric CO(2). In addition, theoretical implications from the findings were addressed.

  16. Organic carbon dynamics in mangrove ecosystems: a review

    NARCIS (Netherlands)

    Kristensen, E.; Bouillon, S.; Dittmar, T.; Marchand, C.

    2008-01-01

    Our current knowledge on production, composition, transport, pathways and transformations of organic carbon in tropical mangrove environments is reviewed and discussed. Organic carbon entering mangrove foodwebs is either produced autochthonously or imported by tides and/or rivers. Mangrove litter

  17. Parametric studies on iron-carbon composite nanoparticles synthesized by laser pyrolysis for increased passivation and high iron content

    Science.gov (United States)

    Dumitrache, F.; Morjan, I.; Fleaca, C.; Birjega, R.; Vasile, E.; Kuncser, V.; Alexandrescu, R.

    2011-04-01

    Iron/iron carbide core and carbon shell nanoparticles with improved magnetic properties were successfully synthesized by laser pyrolysis. As iron and carbon precursors, iron pentacarbonyl and pure or argon-diluted acetylene/ethylene mixtures, respectively, were used. The aim of the present optimization is the improvement of the magnetic properties of the nanomaterials by the increase of the iron percent in powders simultaneously to the maintaining of the protective character of the carbon coverage of nanoparticles. The chemical content and the crystalline structure were monitored by EDX, XRD and TEM techniques. In the first study, the content of acetylene as carbon source was diminished from 75% to 0%. Consequently the percent iron increased from 10 at.% to 28 at.% while oxygen remained relatively constant (around 5 at.%). In the second step, only diluted ethylene was used (maximum 87.5 vol.% Ar). In this case, an increase of iron to 46 at.% is observed. An optimum 50% carbon source dilution was found. Above this value, the carbon content increases and below it, superficial oxidation increases through the diminishing of the carbon shell. The magnetic properties and the Fe phase composition of the Fe-C samples were analyzed by temperature dependent Mössbauer spectroscopy.

  18. Using LUCAS topsoil database to estimate soil organic carbon content in local spectral libraries

    Science.gov (United States)

    Castaldi, Fabio; van Wesemael, Bas; Chabrillat, Sabine; Chartin, Caroline

    2017-04-01

    The quantification of the soil organic carbon (SOC) content over large areas is mandatory to obtain accurate soil characterization and classification, which can improve site specific management at local or regional scale exploiting the strong relationship between SOC and crop growth. The estimation of the SOC is not only important for agricultural purposes: in recent years, the increasing attention towards global warming highlighted the crucial role of the soil in the global carbon cycle. In this context, soil spectroscopy is a well consolidated and widespread method to estimate soil variables exploiting the interaction between chromophores and electromagnetic radiation. The importance of spectroscopy in soil science is reflected by the increasing number of large soil spectral libraries collected in the world. These large libraries contain soil samples derived from a consistent number of pedological regions and thus from different parent material and soil types; this heterogeneity entails, in turn, a large variability in terms of mineralogical and organic composition. In the light of the huge variability of the spectral responses to SOC content and composition, a rigorous classification process is necessary to subset large spectral libraries and to avoid the calibration of global models failing to predict local variation in SOC content. In this regard, this study proposes a method to subset the European LUCAS topsoil database into soil classes using a clustering analysis based on a large number of soil properties. The LUCAS database was chosen to apply a standardized multivariate calibration approach valid for large areas without the need for extensive field and laboratory work for calibration of local models. Seven soil classes were detected by the clustering analyses and the samples belonging to each class were used to calibrate specific partial least square regression (PLSR) models to estimate SOC content of three local libraries collected in Belgium (Loam belt

  19. Tritium- and carbon-14-contents of wines of different vintage from the northern and southern hemisphere

    International Nuclear Information System (INIS)

    Fischer, E.; Mueller, H.

    1980-01-01

    The carbon-14 and tritium radioactivity contents of up to 19 vintages of German and Southafrican wines were compared. A similar large dependence of the 14 C- and of the 3 H-activity in the German wine on the nuclear weapon tests of the years 1962/63 was found out. The radioactivity level is also 1977/78 still essentially higher than before 1950. The Southafrican wines have been influenced considerably less by nuclear explosions. The highest 3 H-values were found in the vintage 1963 of the German wine with 5910 pCi/litre and in the vintage 1964 of the Southafrican wine with 510 pCi/litre. (orig.) [de

  20. Determination of Elements and Carbon Content of Stainless Steel Welded Pipeline

    Directory of Open Access Journals (Sweden)

    Pavel Hudeček

    2016-01-01

    Full Text Available Find out defects or problems of welds are not so simple from time to time. Specially, if weld has been made in rough environmental conditions like high temperature, dusty wind and humidity. It is important to assure have good conditions to realize basic step of welding. For welding, have been used welding procedures specification and procedure qualification record. However, difficult conditions, documentations rightness or human errors are always here. Common weld defects like cracks, porosity, lack of penetration and distortion can compromise the strength of the base metal, as well as the integrity of the weld. According of site inspection, there were suspicion of inclusions, leaker or segregation in root of weld. Surface treatment after welding and keep the intervals between single welds to not overheat the pipes. To recognize those suspicions, mechanical testing around weld joint, determination of carbon content and inductively coupled plasma atomic emission spectroscopy will be done.

  1. Modeling vegetation and carbon dynamics of managed grasslands at the global scale with LPJmL 3.6

    Directory of Open Access Journals (Sweden)

    S. Rolinski

    2018-02-01

    Full Text Available Grassland management affects the carbon fluxes of one-third of the global land area and is thus an important factor for the global carbon budget. Nonetheless, this aspect has been largely neglected or underrepresented in global carbon cycle models. We investigate four harvesting schemes for the managed grassland implementation of the dynamic global vegetation model (DGVM Lund–Potsdam–Jena managed Land (LPJmL that facilitate a better representation of actual management systems globally. We describe the model implementation and analyze simulation results with respect to harvest, net primary productivity and soil carbon content and by evaluating them against reported grass yields in Europe. We demonstrate the importance of accounting for differences in grassland management by assessing potential livestock grazing densities as well as the impacts of grazing, grazing intensities and mowing systems on soil carbon stocks. Grazing leads to soil carbon losses in polar or arid regions even at moderate livestock densities (<  0.4 livestock units per hectare – LSU ha−1 but not in temperate regions even at much higher densities (0.4 to 1.2 LSU ha−1. Applying LPJmL with the new grassland management options enables assessments of the global grassland production and its impact on the terrestrial biogeochemical cycles but requires a global data set on current grassland management.

  2. Modeling vegetation and carbon dynamics of managed grasslands at the global scale with LPJmL 3.6

    Science.gov (United States)

    Rolinski, Susanne; Müller, Christoph; Heinke, Jens; Weindl, Isabelle; Biewald, Anne; Bodirsky, Benjamin Leon; Bondeau, Alberte; Boons-Prins, Eltje R.; Bouwman, Alexander F.; Leffelaar, Peter A.; te Roller, Johnny A.; Schaphoff, Sibyll; Thonicke, Kirsten

    2018-02-01

    Grassland management affects the carbon fluxes of one-third of the global land area and is thus an important factor for the global carbon budget. Nonetheless, this aspect has been largely neglected or underrepresented in global carbon cycle models. We investigate four harvesting schemes for the managed grassland implementation of the dynamic global vegetation model (DGVM) Lund-Potsdam-Jena managed Land (LPJmL) that facilitate a better representation of actual management systems globally. We describe the model implementation and analyze simulation results with respect to harvest, net primary productivity and soil carbon content and by evaluating them against reported grass yields in Europe. We demonstrate the importance of accounting for differences in grassland management by assessing potential livestock grazing densities as well as the impacts of grazing, grazing intensities and mowing systems on soil carbon stocks. Grazing leads to soil carbon losses in polar or arid regions even at moderate livestock densities (management options enables assessments of the global grassland production and its impact on the terrestrial biogeochemical cycles but requires a global data set on current grassland management.

  3. Modelling the influence of carbon content on material behavior during forging

    Science.gov (United States)

    Korpała, G.; Ullmann, M.; Graf, M.; Wester, H.; Bouguecha, A.; Awiszus, B.; Behrens, B.-A.; Kawalla, R.

    2017-10-01

    Nowadays the design of single process steps and even of whole process chains is realized by the use of numerical simulation, in particular finite element (FE) based methods. A detailed numerical simulation of hot forging processes requires realistic models, which consider the relevant material-specific parameters to characterize the material behavior, the surface phenomena, the dies as well as models for the machine kinematic. This data exists partial for several materials, but general information on steel groups depending on alloying elements are not available. In order to generate the scientific input data regarding to material modelling, it is necessary to take into account the mathematical functions for deformation behavior as well as recrystallization kinetic, which depends alloying elements, initial microstructure and reheating mode. Besides the material flow characterization, a detailed description of surface changes caused by oxide scale is gaining in importance, as these phenomena affect the material flow and the component quality. Experiments to investigate the influence of only one chemical element on the oxide scale kinetic and the inner structure at high temperatures are still not available. Most data concerning these characteristics is provided for the steel grade C45, so this steel will be used as basis for the tests. In order to identify the effect of the carbon content on the material and oxidation behavior, the steel grades C15 and C60 will be investigated. This paper gives first approaches with regard to the influence of the carbon content on the oxide scale kinetic and the flow stresses combined with the initial microstructure.

  4. Desorption behaviors of BDE-28 and BDE-47 from natural soils with different organic carbon contents.

    Science.gov (United States)

    Liu, WenXin; Cheng, FangFang; Li, WeiBo; Xing, BaoShan; Tao, Shu

    2012-04-01

    Desorption kinetic and isothermal characteristics of BDE-28 and BDE-47 were investigated using natural soils with different organic carbon fractions. The results indicated that a two-compartment first-order model with dominant contribution of slow desorption could adequately describe the released kinetics of studied PBDEs. Desorption isotherms of different samples could be fitted well by linear distribution model or nonlinear Freundlich model. Moreover, most desorption procedures roughly exhibited hysteresis with respect to preceding sorption ones. At the statistically significant level of 0.05 or 0.1, total organic carbon content (f(OC)) exhibited significant correlations with the fitted parameters by the isothermal models. The correlations of f(OC) and SOM fractions (e.g., fulvic acid and humin) with the single point desorption coefficients at lower aqueous concentrations of studied PBDEs were significant; while at higher aqueous concentrations, the relationships were less significant or insignificant. Our findings may facilitate a comprehensive understanding on behaviors of PBDEs in soil systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Toxicity of ethylene combustion condensates is directly proportional to their carbon content.

    Science.gov (United States)

    Stojicic, Nevena; Baumstark-Khan, Christa; Hellweg, Christine E; Grotheer, Horst-Henning; Reitz, Günther; Kolanus, Waldemar; Hemmersbach, Ruth

    2010-02-28

    Numerous epidemiological studies have shown a strong link between air pollution and human morbidity and mortality. Combustion sources are most significant contributors to the urban air pollution. So far, toxicological research has focused predominantly on combustion generated particulate matter, thereby neglecting chemical complexity of combustion exhausts. The aim of this study was to assess toxic potential of ethylene combustion condensates, containing both particulate and gaseous combustion by-products, by means of a recombinant bacterial assay called the SWITCH (Salmonella Weighting of Induced Toxicity (Genotoxicity) and Cytotoxicity for Human Health) test. Thereby, the suitability of total organic carbon (TOC) as a parameter for toxicity assessment was also investigated. Ethylene was combusted in a low-pressure burner under controlled laboratory conditions by only varying the carbon/oxygen ratio (C/O=0.63-0.93). Ethylene combustion condensates were generated by drawing 10 l of combustion exhaust at constant flow rate (0.4 l/min) and collecting it in condensated form in glass bottles cooled by liquid nitrogen. Genotoxic and cytotoxic potency of combustion condensates was analyzed with the SWITCH test, based on sequential measurements of luminescence, absorbance and fluorescence outputs of treated bacterial cultures. Our results show correlation between TOC content of combustion condensates and their genotoxicity/cytotoxicity. Moreover, combustion condensates of same TOC concentration exert the same toxic effect regardless of the used C/O ratios during their generation. Our results revealed that toxicologically relevant component(s) of the ethylene combustion exhausts is/are being produced during highly, mildly and non-sooting combustion conditions, only in different proportions. Thereby, total organic carbon proved to be a suitable parameter for the assessment of the toxicity of combustion condensates. (c) 2010 Elsevier Ireland Ltd. All rights reserved.

  6. Sources and Dynamics of Inorganic Carbon within the Upper Reaches of the Xi River Basin, Southwest China.

    Directory of Open Access Journals (Sweden)

    Junyu Zou

    Full Text Available The carbon isotopic composition (δ13C of dissolved and particulate inorganic carbon (DIC; PIC was used to compare and analyze the origin, dynamics and evolution of inorganic carbon in two headwater tributaries of the Xi River, Southwest China. Carbonate dissolution and soil CO2 were regarded as the primary sources of DIC on the basis of δ13CDIC values which varied along the Nanpan and Beipan Rivers, from -13.9‰ to 8.1‰. Spatial trends in DIC differed between the two rivers (i.e., the tributaries, in part because factors controlling pCO2, which strongly affected carbonate dissolution, differed between the two river basins. Transport of soil CO2 and organic carbon through hydrologic conduits predominately controlled the levels of pCO2 in the Nanpan River. However, pCO2 along the upper reaches of the Nanpan River also was controlled by the extent of urbanization and industrialization relative to agriculture. DIC concentrations in the highly urbanized upper reaches of the Nanpan River were typical higher than in other carbonate-dominated areas of the upper Xi River. Within the Beipan River, the oxidation of organic carbon is the primary process that maintains pCO2 levels. The pCO2 within the Beipan River was more affected by sulfuric acid from coal industries, inputs from a scenic spot, and groundwater than along the Nanpan River. With regards to PIC, the contents and δ13C values in the Nanpan River were generally lower than those in the Beipan River, indicating that chemical and physical weathering contributes more marine carbonate detritus to the PIC along the Beipan River. The CO2 evasion flux from the Nanpan River was higher than that in the Beipan River, and generally higher than along the middle and lower reaches of the Xi River, demonstrating that the Nanpan River is an important net source of atmospheric CO2 in Southwest China.

  7. Dynamic viscosities of the ternary liquid mixtures (dimethyl carbonate + methanol + ethanol) and (dimethyl carbonate + methanol + hexane) at several temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, A. [Chemical Engineering Department, Vigo University, 36310 Vigo (Spain); Pereiro, A.B. [Chemical Engineering Department, Vigo University, 36310 Vigo (Spain); Canosa, J. [Chemical Engineering Department, Vigo University, 36310 Vigo (Spain); Tojo, J. [Chemical Engineering Department, Vigo University, 36310 Vigo (Spain)]. E-mail: jtojo@uvigo.es

    2006-05-15

    Densities, {rho} speeds of sound, u and dynamic viscosities, {eta} of the ternary mixtures {l_brace}dimethyl carbonate (DMC) + methanol + ethanol{r_brace} and (dimethyl carbonate + methanol + hexane) were gathered at T = (293.15, 298.15, 308.15, and 313.15) K. From experimental data viscosity deviations, {delta}{eta} of the ternary mixtures were evaluated. These results have been correlated using the Cibulka equation. The fitting parameters and the standard deviations of the ternary viscosity deviations are given. UNIFAC-VISCO group contribution method was used to predict the dynamic viscosities of the ternary mixtures at several temperatures.

  8. Carbon content and C:N ratio of transparent exopolymeric particles (TEP) produced by bubbling exudates of diatoms

    DEFF Research Database (Denmark)

    Mari, Xavier

    1999-01-01

    The carbon content of transparent exopolymeric particles (TEP) was measured in the laboratory in particles produced by bubbling exudates of the diatom Thalassiosira weissflogii, grown under nitrogen non-limited conditions (N:P = 7). The carbon content of these particles (TEP-C) appears to vary...... for dissolved organic carbon in coastal seas. The carbon to nitrogen ratio of TEP was measured from particles formed by bubbling exudates of the diatoms T. weissflogii, Skeletonema costatum, Chaetoceros neogracile and C. affinis. Each of these diatom species was grown under various N:P ratios, from N......-non-limited to N-limited conditions. While the C:N ratio of the diatom cells grown under N-limited conditions was high (C:N >= 14), the TEP aggregates formed by coagulation of the extracellular release produced by these cells exhibited a C:N ratio relatively constant (C:N = 7.3 ± 2.6) and apparently independent...

  9. Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy.

    Science.gov (United States)

    Agustina, Elsye; Goak, Jeungchoon; Lee, Suntae; Seo, Youngho; Park, Jun-Young; Lee, Naesung

    2015-10-01

    Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red-orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship between optical absorbance and Fe concentration. Many Fe catalysts were microscopically observed to be encased by graphitic layers, thus preventing their extraction. Fe catalyst dissolution from CNTs was investigated with various single and mixed acids, and Fe concentration was found to be highest with CNTs being held at reflux in HClO4/HNO3 and H2SO4/HNO3 mixtures. This novel colorimetric method to measure Fe concentrations by UV/Vis spectroscopy was validated by inductively coupled plasma optical emission spectroscopy, indicating its reliability and applicability to asses Fe content in CNTs.

  10. Can mud (silt and clay) concentration be used to predict soil organic carbon content within seagrass ecosystems?

    KAUST Repository

    Serrano, Oscar

    2016-09-07

    The emerging field of blue carbon science is seeking cost-effective ways to estimate the organic carbon content of soils that are bound by coastal vegetated ecosystems. Organic carbon (C-org) content in terrestrial soils and marine sediments has been correlated with mud content (i.e., silt and clay, particle sizes <63 mu m), however, empirical tests of this theory are lacking for coastal vegetated ecosystems. Here, we compiled data (n = 1345) on the relationship between C-org and mud contents in seagrass ecosystems (79 cores) and adjacent bare sediments (21 cores) to address whether mud can be used to predict soil C-org content. We also combined these data with the delta C-13 signatures of the soil C-org to understand the sources of Corg stores. The results showed that mud is positively correlated with soil C-org content only when the contribution of seagrass-derived C-org to the sedimentary C-org pool is relatively low, such as in small and fast-growing meadows of the genera Zostera, Halodule and Halophila, and in bare sediments adjacent to seagrass ecosystems. In large and long-living seagrass meadows of the genera Posidonia and Amphibolis there was a lack of, or poor relationship between mud and soil C-org content, related to a higher contribution of seagrass-derived C-org to the sedimentary C-org pool in these meadows. The relatively high soil C-org contents with relatively low mud contents (e.g., mud-C-org saturation) in bare sediments and Zostera, Halodule and Halophila meadows was related to significant allochthonous inputs of terrestrial organic matter, while higher contribution of seagrass detritus in Amphibolis and Posidonia meadows disrupted the correlation expected between soil C-org and mud contents. This study shows that mud is not a universal proxy for blue carbon content in seagrass ecosystems, and therefore should not be applied generally across all seagrass habitats. Mud content can only be used as a proxy to estimate soil C-org content for

  11. Effects of long-term compost application on carbon content and soil physical properties

    Science.gov (United States)

    Eden, Marie; Houot, Sabine

    2013-04-01

    Biological treatment through composting of organic wastes fulfils multiple purposes: it not only reduces the amount of waste stored in landfills but can also provide agricultural soils with organic amendments, which affect physicochemical soil properties and reduce the use of mineral fertilizers. However, the impacts of different types of amendments are not yet fully understood, as quantity and quality of the exogenous organic matter (EOM) applied vary greatly and numerous other parameters are affected as well, such as pH, heavy metal content, or nutrient availability. The objective of this project was to investigate the effect of different organic amendments - via simulations - on water holding capacity (WHC) and particularly plant available water (PAW), in regard to irrigation needs. The long-term field experiment "Qualiagro" (INRA - Veolia Environment collaboration) was established in Feucherolles, France in 1998, where five treatments were designed, each with two levels of mineral nitrogen (N) addition: minimal and optimal. Farmyard manure (FYM) and three types of compost - all applied every other year at a rate of 4 t carbon ha-1 - gave rise to varying organic carbon (OC) contents and were compared to a control treatment. The treatments changed the soil's OC content from initially ~10.5 g kg-1 to a range of 9.35 to 15.58 g kg-1. An increased OC content can enhance WHC by increasing total porosity/ reducing bulk density. The PAW - the difference between field capacity (FC) and permanent wilting point (WP); predicted with pedotransfer functions related to OC - increases, if the increase at FC is larger than that at WP. With a higher amount of PAW, the need to irrigate fields - to ensure sufficient water availability for plant growth - decreases. At the same time, soil bulk density (ρd) affects root growth; denser soils can lead to reduced rooting depth. Both of these effects were considered when employing a simple soil water balance model (BUDGET; http

  12. Total carbon content and humic substances quality in selected subtypes of Cambisols

    Directory of Open Access Journals (Sweden)

    Veronika Petrášová

    2009-01-01

    Full Text Available Cambisols cover an estimated 45% of agricultural soils in the Czech Republic. We aimed our work at stabile forms of organic carbon and humic substances quality in Cambisols under different types of soil management (grassland and arable soil. Object of our study were the following subtypes of Cambisols: Eutric Cambisol (locality Vatín – arable soil, Eutric Cambisol (locality Vatín – grassland, Haplic Cambisol (locality Náměšť n/Oslavou – arable soil, Leptic Cambisol (locality Ocmanice – grassland, Haplic Cambisol (locality Nové Město na Moravě – arable soil, Haplic Cambisol (locality Přemyslov – Tři Kameny – grassland, Arenic Cambisol (locality Pocoucov – arable soil, Dystric Cambisol (locality Sněžné – arable soil, Dystric Cambisol (locality Velká Skrovnice – arable soil, Dystric Cambisol (locality Vojnův Městec – arable soil. Non-destructive spectroscopic methods such as UV-VIS spectroscopy, synchronous fluorescence spectroscopy (SFS and 13C NMR spectroscopy for humic substances (HS quality assessment were used. Total organic carbon (TOC content was determined by oxidimetric titration. Fractionation of HS was made by short fractionation method. Isolation of pure humic ­acids (HA preparation was made according to the standard IHSS method.Results showed that TOC and humus content varied from 2.70 % (grassland to 1.3 % (arable soil. Ave­ra­ge HS sum was 8.4 mg / kg in grassland and 6.4 mg / kg in arable soil. Average HA sum was 3.6 mg / kg in grassland and 3 mg / kg in arable soil. Fulvic acids (FA content was 4.7 mg / kg in grassland and 3.7 mg / kg in arable soil. HS quality was low and very similar for all studied samples. HA/FA ratio low (< 1. HS absorbance in UV-VIS spectral range was low and similar in all studied samples. Higher absorption in this spectral range was closely connected with higher HS content. Also in 2D-synchronous fluorescence scan spectra

  13. Preface: Impacts of extreme climate events and disturbances on carbon dynamics

    Science.gov (United States)

    Xiao, Jingfeng; Liu, Shuguang; Stoy, Paul C.

    2016-01-01

    The impacts of extreme climate events and disturbances (ECE&D) on the carbon cycle have received growing attention in recent years. This special issue showcases a collection of recent advances in understanding the impacts of ECE&D on carbon cycling. Notable advances include quantifying how harvesting activities impact forest structure, carbon pool dynamics, and recovery processes; observed drastic increases of the concentrations of dissolved organic carbon and dissolved methane in thermokarst lakes in western Siberia during a summer warming event; disentangling the roles of herbivores and fire on forest carbon dioxide flux; direct and indirect impacts of fire on the global carbon balance; and improved atmospheric inversion of regional carbon sources and sinks by incorporating disturbances. Combined, studies herein indicate several major research needs. First, disturbances and extreme events can interact with one another, and it is important to understand their overall impacts and also disentangle their effects on the carbon cycle. Second, current ecosystem models are not skillful enough to correctly simulate the underlying processes and impacts of ECE&D (e.g., tree mortality and carbon consequences). Third, benchmark data characterizing the timing, location, type, and magnitude of disturbances must be systematically created to improve our ability to quantify carbon dynamics over large areas. Finally, improving the representation of ECE&D in regional climate/earth system models and accounting for the resulting feedbacks to climate are essential for understanding the interactions between climate and ecosystem dynamics.

  14. Regional prediction of soil organic carbon content over croplands using airborne hyperspectral data

    Science.gov (United States)

    Vaudour, Emmanuelle; Gilliot, Jean-Marc; Bel, Liliane; Lefebvre, Josias; Chehdi, Kacem

    2015-04-01

    This study was carried out in the framework of the Prostock-Gessol3 and the BASC-SOCSENSIT projects, dedicated to the spatial monitoring of the effects of exogenous organic matter land application on soil organic carbon storage. It aims at identifying the potential of airborne hyperspectral AISA-Eagle data for predicting the topsoil organic carbon (SOC) content of bare cultivated soils over a large peri-urban area (221 km2) with both contrasted soils and SOC contents, located in the western region of Paris, France. Soils comprise hortic or glossic luvisols, calcaric, rendzic cambisols and colluvic cambisols. Airborne AISA-Eagle data (400-1000 nm, 126 bands) with 1 m-resolution were acquired on 17 April 2013 over 13 tracks which were georeferenced. Tracks were atmospherically corrected using a set of 22 synchronous field spectra of both bare soils, black and white targets and impervious surfaces. Atmospherically corrected track tiles were mosaicked at a 2 m-resolution resulting in a 66 Gb image. A SPOT4 satellite image was acquired the same day in the framework of the SPOT4-Take Five program of the French Space Agency (CNES) which provided it with atmospheric correction. The land use identification system layer (RPG) of 2012 was used to mask non-agricultural areas, then NDVI calculation and thresholding enabled to map agricultural fields with bare soil. All 18 sampled sites known to be bare at this very date were correctly included in this map. A total of 85 sites sampled in 2013 or in the 3 previous years were identified as bare by means of this map. Predictions were made from the mosaic spectra which were related to topsoil SOC contents by means of partial least squares regression (PLSR). Regression robustness was evaluated through a series of 1000 bootstrap data sets of calibration-validation samples. The use of the total sample including 27 sites under cloud shadows led to non-significant results. Considering 43 sites outside cloud shadows only, median

  15. Modelling global change impacts on soil carbon contents of agro-silvo-pastoral Mediterranean systems

    Science.gov (United States)

    Lozano-García, Beatriz; Muñoz-Rojas, Miriam; Parras-Alcántara, Luis

    2016-04-01

    total of 38 sampling points were selected under two management practices and six different land uses: (1) MEOW-dehesa (D); (2) MEOW-dehesa + some pine trees (D+P); (3) MEOW-dehesa + some cork oaks (D+C); (4) MEOW-dehesa + some gall oaks (D + G); (5) MEOW-dehesa after a clarified process and transformed to olive grove but maintaining isolated oaks (OG) and (6) MEOW-dehesa after a clarified process and transformed to cereal pasture with isolated oaks (C). Preliminary results showed a high heterogeneity of SOC contents along the soil profile for different climate and land use scenarios. The methods used here can be easily implemented in other Mediterranean areas with available information on climate, site, soil and land use. Keywords: CarboSOIL model, land use change, climate change, soil depth, dehesa References: Abd-Elmabod, S.K., Muñoz-Rojas, M., Jordán, A., Anaya-Romero, M., De la Rosa, D., 2014. Modelling soil organic carbon stocks along topographic transects under climate change scenarios using CarboSOIL. Geophys. Res. Abstr. vol. 16 EGU2014-295-1, EGU General Assembly.) Álvaro-Fuentes, J., Easter, M., Paustian, K., 2012. Climate change effects on organic carbon storage in agricultural soils of northeastern Spain. Agric. Ecosyst. Environ. 155, 87-94. Corral-Fernández, R., Parras-Alcántara, L., Lozano-García, B. 2013. Stratification ratio of soil organic C, N and C:N in Mediterranean evergreen oak woodland with conventional and organic tillage. Agric. Ecosyst. Environ. 164, 252-259. Francaviglia, R., Coleman, K., Whitmore, A.P., Doro, L., Urracci, G., Rubino, M., Ledda, L., 2012. Changes in soil organic carbon and climate change - application of the RothC model in agrosilvo-pastoral Mediterranean systems. Agric. Syst. 112, 48- 54. IPCC, 2007. Technical summary. In: Climate Change 2007. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change http://www.ipcc.ch/. Lozano-García, B., Parras-Alcántara, L

  16. PnET Models: Carbon, Nitrogen, Water Dynamics in Forest Ecosystems (Vers. 4 and 5)

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: PnET (Photosynthetic / EvapoTranspiration model) is a nested series of models of carbon, water, and nitrogen dynamics in forest ecosystems. The models can...

  17. PnET Models: Carbon, Nitrogen, Water Dynamics in Forest Ecosystems (Vers. 4 and 5)

    Data.gov (United States)

    National Aeronautics and Space Administration — PnET (Photosynthetic / EvapoTranspiration model) is a nested series of models of carbon, water, and nitrogen dynamics in forest ecosystems. The models can be used to...

  18. LBA-ECO ND-11 Litter Decomposition, Carbon, and Nitrogen Dynamics in Agroforestry

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains the results of an experiment to determine litter decomposition and dynamics of carbon and nitrogen release from plant litter of differing...

  19. LBA-ECO ND-11 Litter Decomposition, Carbon, and Nitrogen Dynamics in Agroforestry

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains the results of an experiment to determine litter decomposition and dynamics of carbon and nitrogen release from plant litter of...

  20. Introducing litter quality to the ecosystem model LPJ-GUESS: Effects on short- and long-term soil carbon dynamics

    Science.gov (United States)

    Portner, Hanspeter; Wolf, Annett; Rühr, Nadine; Bugmann, Harald

    2010-05-01

    and 2007 [Rühr(2009)] and present soil carbon stocks [Heim et al.(2009)]. Our Results show, that for short-term soil carbon dynamics, e.g. estimates of heterotrophic soil respiration on an annual basis, the inclusion of the dependency on litter quality is not necessary, as the differences are minor only. However, when considering long-term soil carbon dynamics, e.g. simulated estimates of present soil carbon content, the dependency on litter quality shows effect, as there are correlations with specific site factors such as site location and forest type. The inclusion of the dependence on litter quality therefore may be of importance for the projection of future soil carbon dynamics, as forest types may well be altered due to climatic change. References [Heim et al.(2009)] A. Heim, L. Wehrli, W. Eugster, and M.W.I. Schmidt. Effects of sampling design on the probability to detect soil carbon stock changes at the swiss CarboEurope site Lägeren. Geoderma, 149(3-4):347-354, 2009. [Rühr(2009)] Nadine Katrin Rühr. Soil respiration in a mixed mountain forest : environmental drivers and partitioning of component fluxes. PhD thesis, ETH, 2009. [Smith et al.(2001)] Benjamin Smith, I. Colin Prentice, and Martin T. Sykes. Representation of vegetation dynamics in the modelling of terrestrial ecosystems: comparing two contrasting approaches within european climate space. Global Ecology and Biogeography, 10(6):621-637, 2001. [Tuomi et al.(2008)] Mikko Tuomi, Pekka Vanhala, Kristiina Karhu, Hannu Fritze, and Jari Liski. Heterotrophic soil respiration-Comparison of different models describing its temperature dependence. Ecological Modelling, 211(1-2): 182-190, 2008.

  1. Baseline-Dependent Responses of Soil Organic Carbon Dynamics to Climate and Land Disturbances

    Directory of Open Access Journals (Sweden)

    Zhengxi Tan

    2013-01-01

    Full Text Available Terrestrial carbon (C sequestration through optimizing land use and management is widely considered a realistic option to mitigate the global greenhouse effect. But how the responses of individual ecosystems to changes in land use and management are related to baseline soil organic C (SOC levels still needs to be evaluated at various scales. In this study, we modeled SOC dynamics within both natural and managed ecosystems in North Dakota of the United States and found that the average SOC stock in the top 20 cm depth of soil lost at a rate of 450 kg C ha−1 yr−1 in cropland and 110 kg C ha−1 yr−1 in grassland between 1971 and 1998. Since 1998, the study area had become a SOC sink at a rate of 44 kg C ha−1 yr−1. The annual rate of SOC change in all types of lands substantially depends on the magnitude of initial SOC contents, but such dependency varies more with climatic variables within natural ecosystems and with management practices within managed ecosystems. Additionally, soils with high baseline SOC stocks tend to be C sources following any land surface disturbances, whereas soils having low baseline C contents likely become C sinks following conservation management.

  2. Baseline-dependent responses of soil organic carbon dynamics to climate and land disturbances

    Science.gov (United States)

    Tan, Zhengxi; Liu, Shuguang

    2013-01-01

    Terrestrial carbon (C) sequestration through optimizing land use and management is widely considered a realistic option to mitigate the global greenhouse effect. But how the responses of individual ecosystems to changes in land use and management are related to baseline soil organic C (SOC) levels still needs to be evaluated at various scales. In this study, we modeled SOC dynamics within both natural and managed ecosystems in North Dakota of the United States and found that the average SOC stock in the top 20 cm depth of soil lost at a rate of 450 kg C ha−1 yr−1 in cropland and 110 kg C ha−1 yr−1 in grassland between 1971 and 1998. Since 1998, the study area had become a SOC sink at a rate of 44 kg C ha−1 yr−1. The annual rate of SOC change in all types of lands substantially depends on the magnitude of initial SOC contents, but such dependency varies more with climatic variables within natural ecosystems and with management practices within managed ecosystems. Additionally, soils with high baseline SOC stocks tend to be C sources following any land surface disturbances, whereas soils having low baseline C contents likely become C sinks following conservation management.

  3. ORCHIDEE-SOM: modeling soil organic carbon (SOC) and dissolved organic carbon (DOC) dynamics along vertical soil profiles in Europe

    Science.gov (United States)

    Camino-Serrano, Marta; Guenet, Bertrand; Luyssaert, Sebastiaan; Ciais, Philippe; Bastrikov, Vladislav; De Vos, Bruno; Gielen, Bert; Gleixner, Gerd; Jornet-Puig, Albert; Kaiser, Klaus; Kothawala, Dolly; Lauerwald, Ronny; Peñuelas, Josep; Schrumpf, Marion; Vicca, Sara; Vuichard, Nicolas; Walmsley, David; Janssens, Ivan A.

    2018-03-01

    Current land surface models (LSMs) typically represent soils in a very simplistic way, assuming soil organic carbon (SOC) as a bulk, and thus impeding a correct representation of deep soil carbon dynamics. Moreover, LSMs generally neglect the production and export of dissolved organic carbon (DOC) from soils to rivers, leading to overestimations of the potential carbon sequestration on land. This common oversimplified processing of SOC in LSMs is partly responsible for the large uncertainty in the predictions of the soil carbon response to climate change. In this study, we present a new soil carbon module called ORCHIDEE-SOM, embedded within the land surface model ORCHIDEE, which is able to reproduce the DOC and SOC dynamics in a vertically discretized soil to 2 m. The model includes processes of biological production and consumption of SOC and DOC, DOC adsorption on and desorption from soil minerals, diffusion of SOC and DOC, and DOC transport with water through and out of the soils to rivers. We evaluated ORCHIDEE-SOM against observations of DOC concentrations and SOC stocks from four European sites with different vegetation covers: a coniferous forest, a deciduous forest, a grassland, and a cropland. The model was able to reproduce the SOC stocks along their vertical profiles at the four sites and the DOC concentrations within the range of measurements, with the exception of the DOC concentrations in the upper soil horizon at the coniferous forest. However, the model was not able to fully capture the temporal dynamics of DOC concentrations. Further model improvements should focus on a plant- and depth-dependent parameterization of the new input model parameters, such as the turnover times of DOC and the microbial carbon use efficiency. We suggest that this new soil module, when parameterized for global simulations, will improve the representation of the global carbon cycle in LSMs, thus helping to constrain the predictions of the future SOC response to global

  4. Influence of moisture content and temperature on degree of carbonation and the effect on Cu and Cr leaching from incineration bottom ash.

    Science.gov (United States)

    Lin, Wenlin Yvonne; Heng, Kim Soon; Sun, Xiaolong; Wang, Jing-Yuan

    2015-09-01

    This study investigated the influence of moisture content and temperature on the degree of carbonation of municipal solid waste (MSW) incineration bottom ash (IBA) from two different incineration plants in Singapore. The initial rate of carbonation was affected by the nominal moisture content used. Carbonation temperature seemed to play a part in changing the actual moisture content of IBA during carbonation, which in turn affected the degree of carbonation. Results showed that 2h of carbonation was sufficient for the samples to reach a relatively high degree of carbonation that was close to the degree of carbonation observed after 1week of carbonation. Both Cu and Cr leaching also showed significant reduction after only 2h of carbonation. Therefore, the optimum moisture content and temperature were selected based on 2h of carbonation. The optimum moisture content was 15% for both incineration plants while the optimum temperature was different for the two incineration plants, at 35°C and 50°C. The effect on Cu and Cr leaching from IBA after accelerated carbonation was evaluated as a function of carbonation time. Correlation coefficient, Pearson's R, was used to determine the dominant leaching mechanism. The reduction in Cu leaching was found to be contributed by both formation of carbonate mineral and reduction of DOC leaching. On the other hand, Cr leaching seemed to be dominantly controlled by pH. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Comparing soil organic carbon dynamics in plantation and secondary forest in wet tropics in Puerto Rico

    Science.gov (United States)

    LI YIQING; MING XU; ZOU XIAOMING; PEIJUN SHI§; YAOQI ZHANG

    2005-01-01

    We compared the soil carbon dynamics between a pine plantation and a secondary forest, both of which originated from the same farmland abandoned in 1976 with the same cropping history and soil conditions, in the wet tropics in Puerto Rico from July 1996 to June 1997. We found that the secondary forest accumulated the heavy-fraction organic carbon (HF-OC) measured by...

  6. Stream carbon dynamics in low-gradient headwaters of a forested watershed

    Science.gov (United States)

    April Bryant-Mason; Y. Jun Xu; Johnny M. Grace

    2013-01-01

    Headwater streams drain more than 70 percent of the total watershed area in the United States. Understanding of carbon dynamics in the headwater systems is of particular relevance for developing best silvicultural practices to reduce carbon export. This study was conducted in a low-gradient, predominantly forested watershed located in the Gulf Coastal Plain region, to...

  7. Satellite observation of particulate organic carbon dynamics on the Louisiana continental shelf

    Science.gov (United States)

    Particulate organic carbon (POC) plays an important role in coastal carbon cycling and the formation of hypoxia. Yet, coastal POC dynamics are often poorly understood due to a lack of long-term POC observations and the complexity of coastal hydrodynamic and biogeochemical process...

  8. Initial Soil Organic Matter Content Influences the Storage and Turnover of Litter-, Root- and Soil Carbon in Grasslands

    Science.gov (United States)

    Liu, L.; Xu, S.; Li, P.; Sayer, E. J.

    2017-12-01

    Grassland degradation is a worldwide problem that often leads to substantial loss of soil organic matter (SOM). Understanding how SOM content influences the stabilization of plant carbon (C) to form soil C is important to evaluate the potential of degraded grasslands to sequester additional C. We conducted a greenhouse experiment using C3 soils with six levels of SOM content and planted the C4 grass Cleistogenes squarrosa and/or added its litter to investigate how SOM content regulates the storage of new soil C derived from litter and roots, the decomposition of extant soil C, and the formation of soil aggregates. We found that microbial biomass carbon (MBC) increased with SOM content, and increased the mineralization of litter C. Both litter addition and planted treatments increased the amount of new C inputs to soil. However, litter addition had no significant impacts on the mineralization of extant soil C, but the presence of living roots significantly accelerated it. Thus, by the end of the experiment, soil C content was significantly higher in the litter addition treatments, but was not affected by planted treatments. The soil macroaggregate fraction increased with SOM content and was positively related to MBC. Overall, our study suggests that as SOM content increases, plant growth and soil microbes become more active, which allows microbes to process more plant-derived C and increases new soil C formation. The interactions between SOM content and plant C inputs should be considered when evaluating soil C turnover in degraded grasslands.

  9. Round Robin Tests to Determine Fiber Content of Carbon Fiber-Reinforced Thermoplastic Composites by Combustion and Thermogravimetry

    Directory of Open Access Journals (Sweden)

    Masahiro Funabashi

    2017-01-01

    Full Text Available To propose methods to determine the fiber content of carbon fiber-reinforced plastics (CFRP for the International Organization for Standardization, the fiber contents of CFRP with polyamide-6 were measured using a combustion method based on ISO 14127 and a thermogravimetry method based on the modified ISO 9924-3 under a round robin test managed by the Polymer Subcommittee of the Industrial Technology Cooperative Promotion Committee in Japan. In the combustion method, the fiber contents of the CFRTP (~0.3 g were determined by the mass of carbon fiber remaining after burning (ISO 14127. The fiber contents in weight of the CFRTP with 8, 9, or 10 plies were determined to be 55.720%, 61.088%, or 65.326%, respectively, by 17 research institutes. In the thermogravimetry method, the fiber contents of the CFRTP (~10 mg were determined by the mass of carbon fiber remaining after heating it to 600°C in nitrogen gas using thermogravimetry apparatus (modified ISO 9924-3. The fiber contents of the CFRTP with 8, 9, or 10 plies were determined to be 56.908%, 61.579%, or 64.819%, respectively, by 8 research institutes. It was confirmed that thermogravimetry method was as accurate as the combustion method based on ISO 14127.

  10. Effect of organic carbon content of the domestic bentonite on the performance of buffer material in a high-level waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung [Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-12-01

    The organic carbon content of the domestic bentonite have been measured, and its effects on the performance of buffer are analyzed. The total carbon content and the organic carbon content were in the range of 3160 to 3600 and 2400 to 2800 ppm, respectively. The aqueous phase equilibrium concentrations of total carbon and organic carbon in bentonite-water mixture were in the range of 25 to 50 ppm and 4 to 18 ppm, respectively. The results indicate that the effect of organic matter in the domestic bentonite on the performance of buffer material were insignificant. 33 refs., 15 figs., 10 tabs. (Author)

  11. Carbon Dynamics and Export from Flooded Wetlands: A Modeling Approach

    Science.gov (United States)

    Described in this article is development and validation of a process based model for carbon cycling in flooded wetlands, called WetQual-C. The model considers various biogeochemical interactions affecting C cycling, greenhouse gas emissions, organic carbon export and retention. ...

  12. Carbon dioxide and methane emission dynamics in central London (UK)

    Science.gov (United States)

    Helfter, Carole; Nemitz, Eiko; Barlow, Janet F.; Wood, Curtis R.

    2013-04-01

    National Atmospheric Emissions Inventory (NAEI) for the flux footprint estimated using a simple Kormann-Meixner model. Methane emissions from central London exhibit diurnal trends both for concentrations and fluxes. The former is consistent with cycles of growth and shrinkage of the urban boundary layer. Methane fluxes are strongly correlated with those of carbon dioxide. Work is ongoing to establish to what extent the diurnal cycles reflect dynamic changes in ground sources (emissions from road traffic, commercial/ domestic heating, variations in flux footprint) and to what extent they are affected by transport efficiency between street level and the top of the tower and storage in between, given the high measurement height.

  13. Functional differences in the allometry of the water, carbon and nitrogen content of gelatinous organisms

    KAUST Repository

    Molina-Ramírez, Axayacatl

    2015-05-19

    We have supplemented available, concurrent measurements of fresh weight (W, g) and body carbon (C, g) (46 individuals, 14 species) and nitrogen (N, g) (11 individuals, 9 species) of marine gelatinous animals with data obtained during the global ocean MALASPINA 2010 Expedition (totalling 267 individuals and 33 species for the W versus C data; totalling 232 individuals and 31 species for the N versus C data). We then used those data to test the allometric properties of the W versus C and N versus C relationships. Overall, gelatinous organisms contain 1.13 ± 1.57% of C (by weight, mean ± SD) in their bodies and show a C:N of 4.56 ± 2.46, respectively, although estimations can be improved by using separate conversion coefficients for the carnivores and the filter feeders. Reduced major axis regression indicates that W increases isometrically with C in the carnivores (cnidarians and ctenophores), implying that their water content can be described by a single conversion coefficient of 173.78 gW(g C)-1, or a C content of 1.17 ± 1.90% by weight, although there is much variability due to the existence of carbon-dense species. In contrast, W increases more rapidly than C in the filter feeders (salps and doliolids), according to a power relationship W = 446.68C1.54. This exponent is not significantly different from 1.2, which is consistent with the idea that the watery bodies of gelatinous animals represent an evolutionary response towards increasing food capture surfaces, i.e. a bottom-up rather than a top-down mechanism. Thus, the available evidence negates a bottom-up mechanism in the carnivores, but supports it in the filter feeders. Last, N increases isometrically with C in both carnivores and filter feeders with C:N ratios of 3.89 ± 1.34 and 4.38 ± 1.21, respectively. These values are similar to those of compact, non-gelatinous organisms and reflect a predominantly herbivorous diet in the filter feeders, which is confirmed by a difference of one trophic level

  14. A dynamic mathematical model for packed columns in carbon capture plants

    DEFF Research Database (Denmark)

    Gaspar, Jozsef; Jørgensen, John Bagterp; Fosbøl, Philip Loldrup

    2015-01-01

    is suitable for gas-liquid packed columns, e.g. for CO2 absorption and desorption. The model is based on rigorous thermodynamic and conservation principles and it is set up to preserve these properties upon numerical integration in time. The developed model is applied for CO2 absorption and desorption......In this paper, we present a dynamic mathematical model for the absorption and desorption columns in a carbon capture plant. Carbon capture plants must be operated in synchronization with the operation of thermal power plants. Dynamic and flexible operation of the carbon capture plant is important...

  15. Carbon Dynamics of a Boreal Logging Age Sequence in Northern Manitoba

    Science.gov (United States)

    Plaut, J.; Martin, J.; Weber, J.; Gower, S. T.

    2001-12-01

    Increasing pressure has been put on boreal forests to meet the growing demand for timber products. Boreal forests contain a disproportionately large amount of carbon in the soil and are believed to play an important role in carbon sequestration, but the effects of disturbance, such as harvesting, on the carbon budget are poorly understood. The objective of this study was to compare the carbon content and aboveground net primary production for a mixed species (Picea mariana, Pinus banksiana, and Populus tremuloides) boreal forest logging age sequence in northern Manitoba. The age sequence consisted of replicated, even-aged stands that originated from clear-cut harvests in 1990, 1983, 1971, and 1935. Carbon content of aboveground vegetation increased significantly during stand recovery, and was significantly greater than similar-aged black spruce stands recovering from wildfire. Distribution of coarse woody debris (CWD) was bimodal, with greater mass per hectare at the 1990 and 1935 sites, and a minimum at the 1971 site. Trends in CWD distribution, as well as forest floor carbon and soil carbon content are used to establish decomposition rates and consequences for the carbon budget.

  16. Biomass, organic carbon and calorific content of zooplankton from the Arabian Sea off Central West coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnakumari, L.; Nair, V.R.

    Organic carbon content and calorific values of zooplankton varied from 18.35 to 32.49% (av. 27.8%) and from 2.56 to 4.71 k cal. g-1 dry wt (av. 3.99) respectively. Areawise off Gujarat sustained higher standing stock of zooplankton (77.18 mg m-3...

  17. Rust Layer Formed on Low Carbon Weathering Steels with Different Mn, Ni Contents in Environment Containing Chloride Ions

    Directory of Open Access Journals (Sweden)

    Gui-qin FU

    2016-11-01

    Full Text Available The rusting evolution of low carbon weathering steels with different Mn, Ni contents under a simulated environment containing chloride ions has been investigated to clarify the correlation between Mn, Ni and the rust formed on steels. The results show that Mn contents have little impact on corrosion kinetics of experimental steels. Content increase of Ni both enhances the anti-corrosion performance of steel substrate and the rust. Increasing Ni content is beneficial to forming compact rust. Semi-quantitative XRD phase analysis shows that the quantity ratio of α/γ*(α-FeOOH/(γ-FeOOH+Fe3O4 decreases as Mn content increases but it increases as Ni content increases. Ni enhances rust layer stability but Mn content exceeding 1.06 wt.% is disadvantageous for rust layer stability. The content increase of Mn does not significantly alter the parameters of the polarization curve. However, as Ni contents increases, Ecorr has shifted to the positive along with decreased icorr values indicating smaller corrosion rate especially as Ni content increases from 0.42 wt.% to 1.50 wt.%.DOI: http://dx.doi.org/10.5755/j01.ms.22.4.12844

  18. Evidence on dynamic effects in the water content – water potential relation of building materials

    DEFF Research Database (Denmark)

    Scheffler, Gregor Albrecht; Plagge, Rudolf

    2008-01-01

    the required material functions, i.e. the moisture storage characteristic and the liquid water conductivity, from measured basic properties. The current state of the art in material modelling as well as the corresponding transport theory implies that the moisture transport function is unique...... and that the moisture storage characteristic is process dependent with varying significance for the numerical simulation. On the basis of different building materials, a comprehensive instantaneous profile measurement study has been accomplished. Profiles of water content and relative humidity were obtained during...... a series of adsorption and desorption processes. The data provides clear evidence that the water content – water potential relationship is not only dependent on the process history, but also on the process dynamics. The higher moisture potential gradients were induced, the larger was the deviation between...

  19. Luminescence dynamics in AlGaN with AlN content of 20%

    KAUST Repository

    Soltani, Sonia

    2016-12-15

    Optical properties and carrier dynamics of an AlGaN layer with an AlN content of 20% have been studied using time-resolved photoluminescence (TR-PL). Despite the high density of defects due to the relatively high AlN content, an intense PL emission from the sample has been detected. Low-temperature PL spectra exhibit several features, accompanied by a strong emission-wavelength dependence of the PL decay time. A significant red-shift of more than 200 meV from the band edge is recorded for the PL emission from localized states. Temperature-dependent PL spectra of the sample are dominated by the emission from localized states and, furthermore, show a relatively slight decrease by almost an order of magnitude with increasing temperature from 45 to 300 K. Our observations indicate strong, spatial localization effects of carriers, resulting in an increase in the radiative recombination rate.

  20. Dynamic and Static Exercises Differentially Affect Plasma Cytokine Content in Elite Endurance- and Strength-Trained Athletes and Untrained Volunteers.

    Science.gov (United States)

    Kapilevich, Leonid V; Zakharova, Anna N; Kabachkova, Anastasia V; Kironenko, Tatyana A; Orlov, Sergei N

    2017-01-01

    Extensive exercise increases the plasma content of IL-6, IL-8, IL-15, leukemia inhibitory factor (LIF), and several other cytokines via their augmented transcription in skeletal muscle cells. However, the relative impact of aerobic and resistant training interventions on cytokine production remains poorly defined. In this study, we compared effects of dynamic and static load on cytokine plasma content in elite strength- and endurance-trained athletes vs. healthy untrained volunteers. The plasma cytokine content was measured before, immediately after, and 30 min post-exercise using enzyme-linked immunosorbent assay. Pedaling on a bicycle ergometer increased IL-6 and IL-8 content in the plasma of trained athletes by about 4- and 2-fold, respectively. In contrast to dynamic load, weightlifting had negligible impact on these parameters in strength exercise-trained athletes. Unlike IL-6 and IL-8, dynamic exercise had no impact on IL-15 and LIF, whereas static load increases the content of these cytokines by ~50%. Two-fold increment of IL-8 content seen in athletes subjected to dynamic exercise was absent in untrained individuals, whereas the ~50% increase in IL-15 triggered by static load in the plasma of weightlifting athletes was not registered in the control group. Thus, our results show the distinct impact of static and dynamic exercises on cytokine content in the plasma of trained athletes. They also demonstrate that both types of exercises differentially affect cytokine content in plasma of athletes and untrained persons.

  1. Disentangling the counteracting effects of water content and carbon mass on zooplankton growth

    DEFF Research Database (Denmark)

    Mcconville, Kristian; Atkinson, Angus; Fileman, Elaine S.

    2017-01-01

    inclusion improves zooplankton growth models. We found that carbon percentage is continuous, but that species are not distributed homogenously along this axis. To assess variability of this trait in situ, we investigated the distribution of biomass across the range of carbon percentage for a zooplankton......Zooplankton vary widely in carbon percentage (carbon mass as a percentage of wet mass), but are often described as either gelatinous or non-gelatinous. Here we update datasets of carbon percentage and growth rate to investigate whether carbon percentage is a continuous trait, and whether its...... time series at station L4 off Plymouth, UK. This showed separate biomass peaks for gelatinous and crustacean taxa, however, carbon percentage varied 8-fold within the gelatinous group. Species with high carbon mass had lower carbon percentage, allowing separation of the counteracting effects...

  2. Hydrogen content and density in nanocrystalline carbon films of a predominant diamond character

    International Nuclear Information System (INIS)

    Hoffman, A.; Heiman, A.; Akhvlediani, R.; Lakin, E.; Zolotoyabko, E.; Cyterman, C.

    2003-01-01

    Nanocrystalline carbon films possessing a prevailing diamond or graphite character, depending on substrate temperature, can be deposited from a methane hydrogen mixture by the direct current glow discharge plasma chemical vapor deposition method. While at a temperature of ∼880 deg. C, following the formation of a thin precursor graphitic film, diamond nucleation occurs and a nanodiamond film grows, at higher and lower deposition temperatures the films maintain their graphitic character. In this study the hydrogen content, density and nanocrystalline phase composition of films deposited at various temperatures are investigated. We aim to elucidate the role of hydrogen in nanocrystalline films with a predominant diamond character. Secondary ion mass spectroscopy revealed a considerable increase of the hydrogen concentration in the films that accompanies the growth of nanodiamond. It correlates with near edge x-ray adsorption spectroscopy measurements, that showed an appearance of spectroscopic features associated with the diamond structure, and with a substantial increase of the film density detected by x-ray reflectivity. Electron energy loss spectroscopy showed that nanocrystalline diamond films can be deposited from a CH 4 /H 2 mixture with hydrogen concentration in the 80%-95% range. For a deposition temperature of 880 deg. C, the highest diamond character of the films was found for a hydrogen concentration of 91% of H 2 . The deposition temperature plays an important role in diamond formation, strongly influencing the content of adsorbed hydrogen with an optimum at 880 deg. C. It is suggested that diamond nucleation and growth of the nanodiamond phase is driven by densification of the deposited graphitic films which results in high local compressive stresses. Nanodiamond formation is accompanied by an increase of hydrogen concentration in the films. It is suggested that hydrogen retention is critical for stabilization of nanodiamond crystallites. At lower

  3. The effects of burning and grazing on soil carbon dynamics in managed Peruvian tropical montane grasslands

    Science.gov (United States)

    Oliver, Viktoria; Oliveras, Imma; Kala, Jose; Lever, Rebecca; Arn Teh, Yit

    2017-12-01

    Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long-term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands, an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A density fractionation method was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free light fraction (LF), especially at the lower depths (10-20 and 20-30 cm). In the control soils, 20 % of the material recovered was in the free LF, which contained 30 % of the soil C content. In comparison, the burnt-grazed soil had the smallest recovery of the free LF (10 %) and a significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the not-burnt soils (7 %) and there was no significant difference among the treatments in the heavy fraction (F) ( ˜ 70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2 fluxes were increased and the dominant

  4. Soil aggregation and associated microbial communities modify the impact of agricultural management on carbon content.

    Science.gov (United States)

    Trivedi, Pankaj; Delgado-Baquerizo, Manuel; Jeffries, Thomas C; Trivedi, Chanda; Anderson, Ian C; Lai, Kaitao; McNee, Matthew; Flower, Kenneth; Pal Singh, Bhupinder; Minkey, David; Singh, Brajesh K

    2017-08-01

    Soil carbon (C) stabilisation is known to depend in part on its distribution in structural aggregates, and upon soil microbial activity within the aggregates. However, the mechanisms and relative contributions of different microbial groups to C turnover in different aggregates under various management practices remain unclear. The aim of this study was to determine the role of soil aggregation and their associated microbial communities in driving the responses of soil organic matter (SOM) to multiple management practices. Our results demonstrate that higher amounts of C inputs coupled with greater soil aggregation in residue retention management practices has positive effects on soil C content. Our results provide evidence that different aggregate size classes support distinct microbial habitats which supports the colonisation of different microbial communities. Most importantly our results indicate that the effects of management practices on soil C is modulated by soil aggregate sizes and their associated microbial community and are more pronounced in macro-aggregate compared with micro-aggregate sizes. Based on our findings we recommend that differential response of management practices and microbial control on the C turnover in macro-aggregates and micro-aggregate should be explicitly considered when accounting for management impacts on soil C turnover. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  5. Laboratory studies on effect of fiber content on dynamic characteristics of municipal solid waste.

    Science.gov (United States)

    Alidoust, P; Keramati, M; Shariatmadari, N

    2018-02-27

    The dynamic characterization of municipal solid waste (MSW), especially in regions with high seismicity, is of considerable importance in the stability assessment of landfills. Additionally, findings indicated that the response of MSW under dynamic loadings is significantly affected by fibrous material. Therefore, a comprehensive strain-controlled cyclic triaxial testing program was performed on MSW samples retrieved from a landfill in the Kahrizak area, Tehran province. The tests were conducted on fresh MSW specimens (with a diameter of 100 mm) with different percentage of fibers in the consolidated undrained condition. The potential reinforcing capability of fibers and their impacts on changes in the MSW composition were investigated under variations of different factors including confining pressure, loading frequency, Poisson's ratio, and loading cycles. From the results of the study, increasing fiber content in specimens resulted in improved elastic behavior of MSW under dynamic loadings, irrespective of the test conditions, such that the normalized shear modulus reduction curves shifted to the right, while the damping ratio curves exhibited no specific trend. However, it is necessary to simultaneously consider the impact of fiber contents, confining stress and shear strain on the variation rates of normalized shear modulus reduction values. This trend is attributed to the greater values of stiffness from changing the composition when compared with the one generated by obtained reinforcement within the studied strain range. Given the lack of systematic evaluations on the effect of the fibrous waste materials on the dynamic response of MSW, the results of this study provide additional insight into the seismic analysis of landfills. Copyright © 2018. Published by Elsevier Ltd.

  6. Carbon dynamics in topsoil and subsoil along a cultivated toposequence

    DEFF Research Database (Denmark)

    Chirinda, Ngoni; Elsgaard, Lars; Thomsen, Ingrid Kaag

    2014-01-01

    Topography-induced spatial heterogeneity influences soil organic carbon (SOC) stocks and microbial degradation (respiration) both in topsoil and subsoil compartments. However, the interaction between topographic position and soil horizons has rarely been assessed. This study aimed to investigate ...

  7. Holocene carbon dynamics at the forest-steppe ecotone of southern Siberia.

    Science.gov (United States)

    Mackay, Anson William; Seddon, Alistair W R; Leng, Melanie J; Heumann, Georg; Morley, David W; Piotrowska, Natalia; Rioual, Patrick; Roberts, Sarah; Swann, George E A

    2017-05-01

    The forest-steppe ecotone in southern Siberia is highly sensitive to climate change; global warming is expected to push the ecotone northwards, at the same time resulting in degradation of the underlying permafrost. To gain a deeper understanding of long-term forest-steppe carbon dynamics, we use a highly resolved, multiproxy, palaeolimnological approach, based on sediment records from Lake Baikal. We reconstruct proxies that are relevant to understanding carbon dynamics including carbon mass accumulation rates (CMAR; g C m -2  yr -1 ) and isotope composition of organic matter (δ 13 C TOC ). Forest-steppe dynamics were reconstructed using pollen, and diatom records provided measures of primary production from near- and off-shore communities. We used a generalized additive model (GAM) to identify significant change points in temporal series, and by applying generalized linear least-squares regression modelling to components of the multiproxy data, we address (1) What factors influence carbon dynamics during early Holocene warming and late Holocene cooling? (2) How did carbon dynamics respond to abrupt sub-Milankovitch scale events? and (3) What is the Holocene carbon storage budget for Lake Baikal. CMAR values range between 2.8 and 12.5 g C m -2  yr -1 . Peak burial rates (and greatest variability) occurred during the early Holocene, associated with melting permafrost and retreating glaciers, while lowest burial rates occurred during the neoglacial. Significant shifts in carbon dynamics at 10.3, 4.1 and 2.8 kyr bp provide compelling evidence for the sensitivity of the region to sub-Milankovitch drivers of climate change. We estimate that 1.03 Pg C was buried in Lake Baikal sediments during the Holocene, almost one-quarter of which was buried during the early Holocene alone. Combined, our results highlight the importance of understanding the close linkages between carbon cycling and hydrological processes, not just temperatures, in southern Siberian environments

  8. Carbon dynamics in an Imperata grassland in Northeast India

    Directory of Open Access Journals (Sweden)

    Amrabati Thokchom

    2016-01-01

    Full Text Available Carbon stocks and soil CO2 flux were assessed in an Imperata cylindrica grassland of Manipur, Northeast India. Carbon stocks in the vegetative components were estimated to be 11.17 t C/ha and soil organic carbon stocks were 55.94 t C/ha to a depth of 30 cm. The rates of carbon accumulation in above-ground and below-ground biomass were estimated to be 11.85 t C/ha/yr and 11.71 t C/ha/yr, respectively. Annual soil CO2 flux was evaluated as 6.95 t C/ha and was highly influenced by soil moisture, soil temperature and soil organic carbon as well as by C stocks in above-ground biomass. Our study on the carbon budget of the grassland ecosystem revealed that annually 23.56 t C/ha was captured by the vegetation through photosynthesis, and 6.95 t C/ha was returned to the atmosphere through roots and microbial respiration, with a net balance of 16.61 t C/ha/yr being retained in the grassland ecosystem. Thus the present Imperata grassland exhibited a high capacity to remove atmospheric CO2 and to induce high C stocks in the soil provided it is protected from burning and overgrazing.Keywords: Above-ground biomass, below-ground biomass, carbon stocks, carbon storage, net primary productivity, soil CO2 flux.DOI: 10.17138/TGFT(419-28  

  9. An H-infinity approach to optimal control of oxygen and carbon dioxide contents in blood

    Science.gov (United States)

    Rigatos, Gerasimos; Siano, Pierluigi; Selisteanu, Dan; Precup, Radu

    2016-12-01

    Nonlinear H-infinity control is proposed for the regulation of the levels of oxygen and carbon dioxide in the blood of patients undergoing heart surgery and extracorporeal blood circulation. The levels of blood gases are administered through a membrane oxygenator and the control inputs are the externally supplied oxygen, the aggregate gas supply (oxygen plus nitrogen), and the blood flow which is regulated by a blood pump. The proposed control method is based on linearization of the oxygenator's dynamical model through Taylor series expansion and the computation of Jacobian matrices. The local linearization points are defined by the present value of the oxygenator's state vector and the last value of the control input that was exerted on this system. The modelling errors due to linearization are considered as disturbances which are compensated by the robustness of the control loop. Next, for the linearized model of the oxygenator an H-infinity control input is computed at each iteration of the control algorithm through the solution of an algebraic Riccati equation. With the use of Lyapunov stability analysis it is demonstrated that the control scheme satisfies the H-infinity tracking performance criterion, which signifies improved robustness against modelling uncertainty and external disturbances. Moreover, under moderate conditions the asymptotic stability of the control loop is also proven.

  10. Multi-factor controls on terrestrial carbon dynamics in urbanized areas

    Science.gov (United States)

    Zhang, C.; Tian, H.; Pan, S.; Lockaby, G.; Chappelka, A.

    2014-12-01

    As urban land expands rapidly across the globe, much concern has been raised that urbanization may alter the terrestrial carbon cycle. Urbanization involves complex changes in land structure and multiple environmental factors. Little is known about the relative contribution of these individual factors and their interactions to the terrestrial carbon dynamics, however, which is essential for assessing the effectiveness of carbon sequestration policies focusing on urban development. This study developed a comprehensive analysis framework for quantifying relative contribution of individual factors (and their interactions) to terrestrial carbon dynamics in urbanized areas. We identified 15 factors belonging to five categories, and we applied a newly developed factorial analysis scheme to the southern United States (SUS), a rapidly urbanizing region. In all, 24 numeric experiments were designed to systematically isolate and quantify the relative contribution of individual factors. We found that the impact of land conversion was far larger than other factors. Urban managements and the overall interactive effects among major factors, however, created a carbon sink that compensated for 42% of the carbon loss in land conversion. Our findings provide valuable information for regional carbon management in the SUS: (1) it is preferable to preserve pre-urban carbon pools than to rely on the carbon sinks in urban ecosystems to compensate for the carbon loss in land conversion. (2) In forested areas, it is recommendable to improve landscape design (e.g., by arranging green spaces close to the city center) to maximize the urbanization-induced environmental change effect on carbon sequestration. Urbanization-induced environmental change will be less effective in shrubland regions. (3) Urban carbon sequestration can be significantly improved through changes in management practices, such as increased irrigation and fertilizer and targeted use of vehicles and machinery with least

  11. Nonzero-Sum Relationships in Mitigating Urban Carbon Emissions: A Dynamic Network Simulation.

    Science.gov (United States)

    Chen, Shaoqing; Chen, Bin; Su, Meirong

    2015-10-06

    The "stove-pipe" way of thinking has been mostly used in mitigating carbon emissions and managing socioeconomics because of its convenience of implementation. However, systems-oriented approaches become imperative in pursuit of an efficient regulation of carbon emissions from systems as complicated as urban systems. The aim of this paper is to establish a dynamic network approach that is capable of assessing the effectiveness of carbon emissions mitigation in a more holistic way. A carbon metabolic network is constructed by modeling the carbon flows between economic sectors and environment. With the network shocked by interventions to the sectoral carbon flows, indirect emissions from the city are accounted for under certain carbon mitigation strategies. The nonzero-sum relationships between sectors and environmental components are identified based on utility analysis, which synthesize the nature of direct and indirect network interactions. The results of the case study of Beijing suggest that the stove-pipe mitigation strategies targeted the economic sectors might be not as efficient as they were expected. A direct cutting in material or energy import to the sectors may result in a rebound in indirect emissions and thus fails to achieve the carbon mitigation goal of the city as a whole. A promising way of foreseeing the dynamic mechanism of emissions is to analyze the nonzero-sum relationships between important urban components. Thinking cities as systems of interactions, the network approach is potentially a strong tool for appraising and filtering mitigation strategies of carbon emissions.

  12. Ignoring detailed fast-changing dynamics of land use overestimates regional terrestrial carbon sequestration

    Directory of Open Access Journals (Sweden)

    S. Q. Zhao

    2009-08-01

    Full Text Available Land use change is critical in determining the distribution, magnitude and mechanisms of terrestrial carbon budgets at the local to global scales. To date, almost all regional to global carbon cycle studies are driven by a static land use map or land use change statistics with decadal time intervals. The biases in quantifying carbon exchange between the terrestrial ecosystems and the atmosphere caused by using such land use change information have not been investigated. Here, we used the General Ensemble biogeochemical Modeling System (GEMS, along with consistent and spatially explicit land use change scenarios with different intervals (1 yr, 5 yrs, 10 yrs and static, respectively, to evaluate the impacts of land use change data frequency on estimating regional carbon sequestration in the southeastern United States. Our results indicate that ignoring the detailed fast-changing dynamics of land use can lead to a significant overestimation of carbon uptake by the terrestrial ecosystem. Regional carbon sequestration increased from 0.27 to 0.69, 0.80 and 0.97 Mg C ha−1 yr−1 when land use change data frequency shifting from 1 year to 5 years, 10 years interval and static land use information, respectively. Carbon removal by forest harvesting and prolonged cumulative impacts of historical land use change on carbon cycle accounted for the differences in carbon sequestration between static and dynamic land use change scenarios. The results suggest that it is critical to incorporate the detailed dynamics of land use change into local to global carbon cycle studies. Otherwise, it is impossible to accurately quantify the geographic distributions, magnitudes, and mechanisms of terrestrial carbon sequestration at the local to global scales.

  13. Modeling compositional dynamics based on GC and purine contents of protein-coding sequences

    KAUST Repository

    Zhang, Zhang

    2010-11-08

    Background: Understanding the compositional dynamics of genomes and their coding sequences is of great significance in gaining clues into molecular evolution and a large number of publically-available genome sequences have allowed us to quantitatively predict deviations of empirical data from their theoretical counterparts. However, the quantification of theoretical compositional variations for a wide diversity of genomes remains a major challenge.Results: To model the compositional dynamics of protein-coding sequences, we propose two simple models that take into account both mutation and selection effects, which act differently at the three codon positions, and use both GC and purine contents as compositional parameters. The two models concern the theoretical composition of nucleotides, codons, and amino acids, with no prerequisite of homologous sequences or their alignments. We evaluated the two models by quantifying theoretical compositions of a large collection of protein-coding sequences (including 46 of Archaea, 686 of Bacteria, and 826 of Eukarya), yielding consistent theoretical compositions across all the collected sequences.Conclusions: We show that the compositions of nucleotides, codons, and amino acids are largely determined by both GC and purine contents and suggest that deviations of the observed from the expected compositions may reflect compositional signatures that arise from a complex interplay between mutation and selection via DNA replication and repair mechanisms.Reviewers: This article was reviewed by Zhaolei Zhang (nominated by Mark Gerstein), Guruprasad Ananda (nominated by Kateryna Makova), and Daniel Haft. 2010 Zhang and Yu; licensee BioMed Central Ltd.

  14. Structure and dynamics of European sports science textual contents: Analysis of ECSS abstracts (1996-2014).

    Science.gov (United States)

    Hristovski, Robert; Aceski, Aleksandar; Balague, Natalia; Seifert, Ludovic; Tufekcievski, Aleksandar; Cecilia, Aguirre

    2017-02-01

    The article discusses general structure and dynamics of the sports science research content as obtained from the analysis of 21998 European College of Sport Science abstracts belonging to 12 science topics. The structural analysis showed intertwined multidisciplinary and unifying tendencies structured along horizontal (scope) and vertical (level) axes. Methodological (instrumental and mode of inquiry) integrative tendencies are dominant. Theoretical integrative tendencies are much less detectable along both horizontal and vertical axes. The dynamic analysis of written abstracts text content over the 19 years reveals the contextualizing and guiding role of thematic skeletons of each sports science topic in forming more detailed contingent research ideas and the role of the latter in stabilizing and procreating the former. This circular causality between both hierarchical levels and functioning on separate characteristic time scales is crucial for understanding how stable research traditions self-maintain and self-procreate through innovative contingencies. The structure of sports science continuously rebuilds itself through use and re-use of contingent research ideas. The thematic skeleton ensures its identity and the contingent conceptual sets its flexibility and adaptability to different research or applicative problems.

  15. Stress wave velocity and dynamic modulus of elasticity of yellow-poplar ranging from 100 to 10 percent moisture content

    Science.gov (United States)

    Jody D. Gray; Shawn T. Grushecky; James P. Armstrong

    2008-01-01

    Moisture content has a significant impact on mechanical properties of wood. In recent years, stress wave velocity has been used as an in situ and non-destructive method for determining the stiffness of wooden elements. The objective of this study was to determine what effect moisture content has on stress wave velocity and dynamic modulus of elasticity. Results...

  16. Effect of Carbon Content on the Properties of Iron-Based Powder Metallurgical Parts Produced by the Surface Rolling Process

    Directory of Open Access Journals (Sweden)

    Yan Zhao

    2018-01-01

    Full Text Available In recent years, the rolling densification process has become increasingly widely used to strengthen powder metallurgy parts. The original composition of the rolled powder metallurgy blank has a significant effect on the rolling densification technology. The present work investigated the effects of different carbon contents (0 wt. %, 0.2 wt. %, 0.45 wt. %, and 0.8 wt. % on the rolling densification. The selection of the raw materials in the surface rolling densification process was analyzed based on the pore condition, structure, hardness, and friction performance of the materials. The results show that the 0.8 wt. % carbon content of the surface rolling material can effectively improve the properties of iron-based powder metallurgy parts. The samples with 0.8 wt. % carbon have the highest surface hardness (340 HV0.1 and the lowest surface friction coefficient (0.35. Even if the dense layer depth is 1.13 mm, which is thinner than other samples with low carbon content, it also meets the requirements for powder metallurgy parts such as gears used in the auto industry.

  17. Microscale characterisation of stochastically reconstructed carbon fiber-based Gas Diffusion Layers; effects of anisotropy and resin content

    Science.gov (United States)

    Yiotis, Andreas G.; Kainourgiakis, Michael E.; Charalambopoulou, Georgia C.; Stubos, Athanassios K.

    2016-07-01

    A novel process-based methodology is proposed for the stochastic reconstruction and accurate characterisation of Carbon fiber-based matrices, which are commonly used as Gas Diffusion Layers in Proton Exchange Membrane Fuel Cells. The modeling approach is efficiently complementing standard methods used for the description of the anisotropic deposition of carbon fibers, with a rigorous model simulating the spatial distribution of the graphitized resin that is typically used to enhance the structural properties and thermal/electrical conductivities of the composite Gas Diffusion Layer materials. The model uses as input typical pore and continuum scale properties (average porosity, fiber diameter, resin content and anisotropy) of such composites, which are obtained from X-ray computed microtomography measurements on commercially available carbon papers. This information is then used for the digital reconstruction of realistic composite fibrous matrices. By solving the corresponding conservation equations at the microscale in the obtained digital domains, their effective transport properties, such as Darcy permeabilities, effective diffusivities, thermal/electrical conductivities and void tortuosity, are determined focusing primarily on the effects of medium anisotropy and resin content. The calculated properties are matching very well with those of Toray carbon papers for reasonable values of the model parameters that control the anisotropy of the fibrous skeleton and the materials resin content.

  18. Carbon diffusion in molten uranium: an ab initio molecular dynamics study

    Science.gov (United States)

    Garrett, Kerry E.; Abrecht, David G.; Kessler, Sean H.; Henson, Neil J.; Devanathan, Ram; Schwantes, Jon M.; Reilly, Dallas D.

    2018-04-01

    In this work we used ab initio molecular dynamics within the framework of density functional theory and the projector-augmented wave method to study carbon diffusion in liquid uranium at temperatures above 1600 K. The electronic interactions of carbon and uranium were described using the local density approximation (LDA). The self-diffusion of uranium based on this approach is compared with literature computational and experimental results for liquid uranium. The temperature dependence of carbon and uranium diffusion in the melt was evaluated by fitting the resulting diffusion coefficients to an Arrhenius relationship. We found that the LDA calculated activation energy for carbon was nearly twice that of uranium: 0.55 ± 0.03 eV for carbon compared to 0.32 ± 0.04 eV for uranium. Structural analysis of the liquid uranium-carbon system is also discussed.

  19. Modelling temperature acclimation effects on the carbon dynamics of forest ecosystems in the conterminous United States

    Directory of Open Access Journals (Sweden)

    Min Chen

    2013-01-01

    Full Text Available The projected rise in temperature in the 21st century will alter forest ecosystem functioning and carbon dynamics. To date, the acclimation of plant photosynthesis to rising temperature has not been adequately considered in earth system models. Here we present a study on regional ecosystem carbon dynamics under future climate scenarios incorporating temperature acclimation effects into a large-scale ecosystem model, the terrestrial ecosystem model (TEM. We first incorporate a general formulation of the temperature acclimation of plant photosynthesis into TEM, and then apply the revised model to the forest ecosystems of the conterminous United States for the 21st century under the future Intergovernmental Panel on Climate Change (IPCC Special Report on Emissions Scenarios (SRES climate scenarios A1FI, A2, B1 and B2. We find that there are significant differences between the estimates of carbon dynamics from the previous and the revised models. The largest differences occur under the A1FI scenario, in which the model that considers acclimation effects predicts that the region will act as a carbon sink, and that cumulative carbon in the 21st century will be 35 Pg C higher than the estimates from the model that does not consider acclimation effects. Our results further indicate that in the region there are spatially different responses to temperature acclimation effects. This study suggests that terrestrial ecosystem models should take temperature acclimation effects into account so as to more accurately quantify ecosystem carbon dynamics at regional scales.

  20. Retraction Note to: Effect of Carbon Content on the Electrical Conductivity of Carbon Black-Filled PMC with Various Matrices

    Science.gov (United States)

    Shin, Soon-Gi

    2018-02-01

    The Editor-in-Chief and Editorial Board of Electronic Materials Letters have retracted this article [1] because its contents have been previously published by Miyasaka et al. [2]. The contents of this article are therefore redundant. Author Soon-Gi Shin has not responded to correspondence from the Editor about this retraction.

  1. Fusion of electroencephalographic dynamics and musical contents for estimating emotional responses in music listening.

    Science.gov (United States)

    Lin, Yuan-Pin; Yang, Yi-Hsuan; Jung, Tzyy-Ping

    2014-01-01

    Electroencephalography (EEG)-based emotion classification during music listening has gained increasing attention nowadays due to its promise of potential applications such as musical affective brain-computer interface (ABCI), neuromarketing, music therapy, and implicit multimedia tagging and triggering. However, music is an ecologically valid and complex stimulus that conveys certain emotions to listeners through compositions of musical elements. Using solely EEG signals to distinguish emotions remained challenging. This study aimed to assess the applicability of a multimodal approach by leveraging the EEG dynamics and acoustic characteristics of musical contents for the classification of emotional valence and arousal. To this end, this study adopted machine-learning methods to systematically elucidate the roles of the EEG and music modalities in the emotion modeling. The empirical results suggested that when whole-head EEG signals were available, the inclusion of musical contents did not improve the classification performance. The obtained performance of 74~76% using solely EEG modality was statistically comparable to that using the multimodality approach. However, if EEG dynamics were only available from a small set of electrodes (likely the case in real-life applications), the music modality would play a complementary role and augment the EEG results from around 61-67% in valence classification and from around 58-67% in arousal classification. The musical timber appeared to replace less-discriminative EEG features and led to improvements in both valence and arousal classification, whereas musical loudness was contributed specifically to the arousal classification. The present study not only provided principles for constructing an EEG-based multimodal approach, but also revealed the fundamental insights into the interplay of the brain activity and musical contents in emotion modeling.

  2. Fusion of Electroencephalogram dynamics and musical contents for estimating emotional responses in music listening

    Directory of Open Access Journals (Sweden)

    Yuan-Pin eLin

    2014-05-01

    Full Text Available Electroencephalography (EEG-based emotion classification during music listening has gained increasing attention nowadays due to its promise of potential applications such as musical affective brain-computer interface (ABCI, neuromarketing, music therapy, and implicit multimedia tagging and triggering. However, music is an ecologically valid and complex stimulus that conveys certain emotions to listeners through compositions of musical elements. Using solely EEG signals to distinguish emotions remained challenging. This study aimed to assess the applicability of a multimodal approach by leveraging the EEG dynamics and acoustic characteristics of musical contents for the classification of emotional valence and arousal. To this end, this study adopted machine-learning methods to systematically elucidate the roles of the EEG and music modalities in the emotion modeling. The empirical results suggested that when whole-head EEG signals were available, the inclusion of musical contents did not improve the classification performance. The obtained performance of 74~76% using solely EEG modality was statistically comparable to that using the multimodality approach. However, if EEG dynamics were only available from a small set of electrodes (likely the case in real-life applications, the music modality would play a complementary role and augment the EEG results from around 61% to 67% in valence classification and from around 58% to 67% in arousal classification. The musical timbre appeared to replace less-discriminative EEG features and led to improvements in both valence and arousal classification, whereas musical loudness was contributed specifically to the arousal classification. The present study not only provided principles for constructing an EEG-based multimodal approach, but also revealed the fundamental insights into the interplay of the brain activity and musical contents in emotion modeling.

  3. Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland.

    Directory of Open Access Journals (Sweden)

    Xuexin Shao

    Full Text Available Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC and dissolved organic carbon (DOC, excepting for that of microbial biomass carbon (MBC. The P. australis soil was with the highest content of both SOC (7.86 g kg-1 and DOC (306 mg kg-1, while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg-1, and the bare mudflat was with the lowest content of DOC (270 mg kg-1. Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg-1 h-1, and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg-1 h-1 and invertase (9.81 mg g-1 24h-1; however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg-1 h-1, β-glycosidase (2.87 mg kg-1 h-1, and invertase (8.02 mg g-1 24h-1. Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands.

  4. Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland.

    Science.gov (United States)

    Shao, Xuexin; Yang, Wenying; Wu, Ming

    2015-01-01

    Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg-1) and DOC (306 mg kg-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg-1), and the bare mudflat was with the lowest content of DOC (270 mg kg-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg-1 h-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg-1 h-1) and invertase (9.81 mg g-1 24h-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg-1 h-1), β-glycosidase (2.87 mg kg-1 h-1), and invertase (8.02 mg g-1 24h-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands.

  5. Dynamic Contention Window Control Scheme in IEEE 802.11e EDCA-Based Wireless LANs

    Science.gov (United States)

    Abeysekera, B. A. Hirantha Sithira; Matsuda, Takahiro; Takine, Tetsuya

    In the IEEE 802.11 MAC protocol, access points (APs) are given the same priority as wireless terminals in terms of acquiring the wireless link, even though they aggregate several downlink flows. This feature leads to a serious throughput degradation of downlink flows, compared with uplink flows. In this paper, we propose a dynamic contention window control scheme for the IEEE 802.11e EDCA-based wireless LANs, in order to achieve fairness between uplink and downlink TCP flows while guaranteeing QoS requirements for real-time traffic. The proposed scheme first determines the minimum contention window size in the best-effort access category at APs, based on the number of TCP flows. It then determines the minimum and maximum contention window sizes in higher priority access categories, such as voice and video, so as to guarantee QoS requirements for these real-time traffic. Note that the proposed scheme does not require any modification to the MAC protocol at wireless terminals. Through simulation experiments, we show the effectiveness of the proposed scheme.

  6. Fire and Microtopography in Peatlands: Feedbacks and Carbon Dynamics

    Science.gov (United States)

    Benscoter, B.; Turetsky, M. R.

    2011-12-01

    Fire is the dominant natural disturbance in peatland ecosystems. Over the past decade, peat fires have emerged as an important issue for global climate change, human health, and economic loss, largely due to the extreme peat fire events in Indonesia and Russia that severely impacted metropolitan areas and social infrastructure. However, the impact and importance of fire in peatland ecosystems are more far-reaching. Combustion of vegetation and soil organic matter releases an average of 2.2 kg C m-2 to the atmosphere, primarily as CO2, as well as a number of potentially harmful emissions such as fine particulate matter and mercury. Additionally, while peatlands are generally considered to be net sinks of atmospheric carbon, the removal of living vegetation by combustion halts primary production following fire resulting in a net loss of ecosystem carbon to the atmosphere for several years. The recovery of carbon sink function is linked to plant community succession and development, which can vary based on combustion severity and the resulting post-fire microhabitat conditions. Microtopography has a strong influence on fire behavior and combustion severity during peatland wildfires. In boreal continental peatlands, combustion severity is typically greatest in low-lying hollows while raised hummocks are often lightly burned or unburned. The cross-scale influence of microtopography on landscape fire behavior is due to differences in plant community composition between microforms. The physiological and ecohydrological differences among plant communities result in spatial patterns in fuel availability and condition, influencing the spread, severity, and type of combustion over local to landscape scales. In addition to heterogeneous combustion loss of soil carbon, this differential fire behavior creates variability in post-fire microhabitat conditions, resulting in differences in post-fire vegetation succession and carbon exchange trajectories. These immediate and legacy

  7. Carbon budget estimation of a subarctic catchment using a dynamic ecosystem model at high spatial resolution

    Science.gov (United States)

    Tang, J.; Miller, P. A.; Persson, A.; Olefeldt, D.; Pilesjo, P.; Heliasz, M.; Jackowicz-Korczynski, M.; Yang, Z.; Smith, B.; Callaghan, T. V.; Christensen, T. R.

    2015-05-01

    A large amount of organic carbon is stored in high-latitude soils. A substantial proportion of this carbon stock is vulnerable and may decompose rapidly due to temperature increases that are already greater than the global average. It is therefore crucial to quantify and understand carbon exchange between the atmosphere and subarctic/arctic ecosystems. In this paper, we combine an Arctic-enabled version of the process-based dynamic ecosystem model, LPJ-GUESS (version LPJG-WHyMe-TFM) with comprehensive observations of terrestrial and aquatic carbon fluxes to simulate long-term carbon exchange in a subarctic catchment at 50 m resolution. Integrating the observed carbon fluxes from aquatic systems with the modeled terrestrial carbon fluxes across the whole catchment, we estimate that the area is a carbon sink at present and will become an even stronger carbon sink by 2080, which is mainly a result of a projected densification of birch forest and its encroachment into tundra heath. However, the magnitudes of the modeled sinks are very dependent on future atmospheric CO2 concentrations. Furthermore, comparisons of global warming potentials between two simulations with and without CO2 increase since 1960 reveal that the increased methane emission from the peatland could double the warming effects of the whole catchment by 2080 in the absence of CO2 fertilization of the vegetation. This is the first process-based model study of the temporal evolution of a catchment-level carbon budget at high spatial resolution, including both terrestrial and aquatic carbon. Though this study also highlights some limitations in modeling subarctic ecosystem responses to climate change, such as aquatic system flux dynamics, nutrient limitation, herbivory and other disturbances, and peatland expansion, our study provides one process-based approach to resolve the complexity of carbon cycling in subarctic ecosystems while simultaneously pointing out the key model developments for capturing

  8. Dynamics of dissolved organic carbon in the northwestern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.; Rajendran, A; Somasundar, K.; Haake, B.; Jenisch, A; Shuo, Z.; Ittekkot, V.; Desai, B.N.

    and fate of DOC in relation to other carbon and nitrogen components in a region with variable productivity. MATERIAL AND METHODS All the samplings were carried out on board R/V "Sonne" during cruise No. 42 (April-June 1986) as part of the Indo... of the former (Fukami et al., 1981; Cho and Azam, 1988). Using a factor of 0.75 for CO2/O2 and the equation for skeletal carbonate dissolution (ICO2) by Kroopnick (1985), we evaluate the relative significance of or- ganic and inorganic matter decomposition...

  9. The changing global carbon cycle: Linking plant-soil carbon dynamics to global consequences

    Science.gov (United States)

    Chapin, F. S.; McFarland, J.; McGuire, David A.; Euskirchen, E.S.; Ruess, Roger W.; Kielland, K.

    2009-01-01

    Most current climate-carbon cycle models that include the terrestrial carbon (C) cycle are based on a model developed 40 years ago by Woodwell & Whittaker (1968) and omit advances in biogeochemical understanding since that time. Their model treats net C emissions from ecosystems as the balance between net primary production (NPP) and heterotrophic respiration (HR, i.e. primarily decomposition).

  10. The changing global carbon cycle: linking local plant-soil carbon dynamics to global consequences

    Science.gov (United States)

    F. Stuart Chapin; Jack McFarland; A. David McGuire; Eugenie S. Euskirchen; Roger W. Ruess; Knut. Kielland

    2009-01-01

    Most current climate-carbon cycle models that include the terrestrial carbon (C) cycle are based on a model developed 40 years ago by Woodwell & Whittaker (1968) and omit advances in biogeochemical understanding since that time. Their model treats net C emissions from ecosystems as the balance between net primary production (NPP) and heterotrophic respiration (HR,...

  11. Challenges and Opportunities assessing Methane and Carbon Dioxide dynamics in Tidal Wetlands - the Blue Carbon Perspective

    Science.gov (United States)

    Schafer, K. V.; Duman, T.; Kurepa, S.

    2016-12-01

    Blue carbon as the new currency for wetland carbon accounting has gained traction and will be incorporated into the new State of the Carbon Cycle Report (SOCCR2). In this analysis, an example of an urban tidal estuary will highlight some of the challenges that lie ahead. The bottom up approach of estimating methane budgets is highly uncertain and does not match top down approaches of methane emission estimates. Bottom up scaling relies on patchy, partly non-representative chamber measurements that are also not capable of measuring methane ebullition events. Fast methane (CH4) gas analyzers such as the LI7700 are now enabling continuous ecosystem scale (eddy flux) measurements and assessment in conjunction with carbon dioxide (CO2) measurements, avoiding the patchy up-scaling from chamber measurements. Reconciling small scale, patchy chamber measurements with ecosystem fluxes and subsequent regional analysis are still challenging and hamper accurate assessment of coastal wetland carbon fluxes and thus "Blue Carbon" accounting. A long-term assessment at a tidal wetland in the Northeastern US showed large interannual variations in net ecosystem exchange and methane emission, further illustrating difficulties in assessing "additionality" of blue carbon credits. Likewise, current modeling strategies do not account for ebullitive methane fluxes. We will contextualize the research findings of a tidal wetland with current efforts in carbon accounting.

  12. Influence of dissolved organic carbon content on modelling natural organic matter acid-base properties.

    Science.gov (United States)

    Garnier, Cédric; Mounier, Stéphane; Benaïm, Jean Yves

    2004-10-01

    Natural organic matter (NOM) behaviour towards proton is an important parameter to understand NOM fate in the environment. Moreover, it is necessary to determine NOM acid-base properties before investigating trace metals complexation by natural organic matter. This work focuses on the possibility to determine these acid-base properties by accurate and simple titrations, even at low organic matter concentrations. So, the experiments were conducted on concentrated and diluted solutions of extracted humic and fulvic acid from Laurentian River, on concentrated and diluted model solutions of well-known simple molecules (acetic and phenolic acids), and on natural samples from the Seine river (France) which are not pre-concentrated. Titration experiments were modelled by a 6 acidic-sites discrete model, except for the model solutions. The modelling software used, called PROSECE (Programme d'Optimisation et de SpEciation Chimique dans l'Environnement), has been developed in our laboratory, is based on the mass balance equilibrium resolution. The results obtained on extracted organic matter and model solutions point out a threshold value for a confident determination of the studied organic matter acid-base properties. They also show an aberrant decreasing carboxylic/phenolic ratio with increasing sample dilution. This shift is neither due to any conformational effect, since it is also observed on model solutions, nor to ionic strength variations which is controlled during all experiments. On the other hand, it could be the result of an electrode troubleshooting occurring at basic pH values, which effect is amplified at low total concentration of acidic sites. So, in our conditions, the limit for a correct modelling of NOM acid-base properties is defined as 0.04 meq of total analysed acidic sites concentration. As for the analysed natural samples, due to their high acidic sites content, it is possible to model their behaviour despite the low organic carbon concentration.

  13. A one-step carbonization route towards nitrogen-doped porous carbon hollow spheres with ultrahigh nitrogen content for CO 2 adsorption

    KAUST Repository

    Wang, Yu

    2015-01-01

    © The Royal Society of Chemistry 2015. Nitrogen doped porous carbon hollow spheres (N-PCHSs) with an ultrahigh nitrogen content of 15.9 wt% and a high surface area of 775 m2 g-1 were prepared using Melamine-formaldehyde nanospheres as hard templates and nitrogen sources. The N-PCHSs were completely characterized and were found to exhibit considerable CO2 adsorption performance (4.42 mmol g-1).

  14. Calculation of diffusion coefficients for carbon dioxide + solute system near the critical conditions by non-equilibrium molecular dynamics simulation

    OpenAIRE

    Higashi, Hidenori; Oda, Tsuyoshi; Iwai, Yoshio; Arai, Yasuhiko

    2004-01-01

    A non-equilibrium molecular dynamics simulation was adopted to calculate the diffusion coefficients for a pseudo-binary system of carbon dioxide and for a carbon dioxide + solute system at 308.2 and 318.2K. The calculated results were compared with the self- and tracer diffusion coefficients calculated by an equilibrium molecular dynamics simulation. The simulated results for the pseudo-binary system of carbon dioxide by the non-equilibrium molecular dynamics simulation are in good agreement ...

  15. Risks attributable to water quality changes in shallow potable aquifers from geological carbon sequestration leakage into sediments of variable carbonate content

    DEFF Research Database (Denmark)

    Cahill, Aaron Graham; Jakobsen, Rasmus; Mathiesen, Tina Bay

    2013-01-01

    The consequences of CO2 leakage from geological sequestration into shallow aquifers must be fully understood before such geo-engineering technology can be implemented. A series of CO2 exposure batch reactor experiments were conducted utilizing 8 sediments of varying composition obtained from across...... Denmark including; siliceous, carbonate and clay materials. Sediments were exposed to CO2 and hydro-geochemical effects were observed in order to improve general understanding of trace metal mobility, quantify carbonate influence, assess risks attributable to fresh water resources from a potential leak...... and aid monitoring measurement and verification (MMV) program design. Results demonstrate control of water chemistry by sediment mineralogy and most significantly carbonate content, for which a potential semi-logarithmic relationship with pH and alkalinity was observed. In addition, control of water...

  16. Modeling terrestrial carbon and water dynamics across climatic gradients: does plant trait diversity matter?

    Science.gov (United States)

    Pappas, Christoforos; Fatichi, Simone; Burlando, Paolo

    2016-01-01

    Plant trait diversity in many vegetation models is crudely represented using a discrete classification of a handful of 'plant types' (named plant functional types; PFTs). The parameterization of PFTs reflects mean properties of observed plant traits over broad categories ignoring most of the inter- and intraspecific plant trait variability. Taking advantage of a multivariate leaf-trait distribution (leaf economics spectrum), as well as documented plant drought strategies, we generate an ensemble of hypothetical species with coordinated attributes, rather than using few PFTs. The behavior of these proxy species is tested using a mechanistic ecohydrological model that translates plant traits into plant performance. Simulations are carried out for a range of climates representative of different elevations and wetness conditions in the European Alps. Using this framework we investigate the sensitivity of ecosystem response to plant trait diversity and compare it with the sensitivity to climate variability. Plant trait diversity leads to highly divergent vegetation carbon dynamics (fluxes and pools) and to a lesser extent water fluxes (transpiration). Abiotic variables, such as soil water content and evaporation, are only marginally affected. These results highlight the need for revising the representation of plant attributes in vegetation models. Probabilistic approaches, based on observed multivariate whole-plant trait distributions, provide a viable alternative. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  17. Accounting for forest carbon pool dynamics in product carbon footprints: Challenges and opportunities

    International Nuclear Information System (INIS)

    Newell, Joshua P.; Vos, Robert O.

    2012-01-01

    Modification and loss of forests due to natural and anthropogenic disturbance contribute an estimated 20% of annual greenhouse gas (GHG) emissions worldwide. Although forest carbon pool modeling rarely suggests a ‘carbon neutral’ flux profile, the life cycle assessment community and associated product carbon footprint protocols have struggled to account for the GHG emissions associated with forestry, specifically, and land use generally. Principally, this is due to underdeveloped linkages between life cycle inventory (LCI) modeling for wood and forest carbon modeling for a full range of forest types and harvest practices, as well as a lack of transparency in globalized forest supply chains. In this paper, through a comparative study of U.S. and Chinese coated freesheet paper, we develop the initial foundations for a methodology that rescales IPCC methods from the national to the product level, with reference to the approaches in three international product carbon footprint protocols. Due to differences in geographic origin of the wood fiber, the results for two scenarios are highly divergent. This suggests that both wood LCI models and the protocols need further development to capture the range of spatial and temporal dimensions for supply chains (and the associated land use change and modification) for specific product systems. The paper concludes by outlining opportunities to measure and reduce uncertainty in accounting for net emissions of biogenic carbon from forestland, where timber is harvested for consumer products. - Highlights: ► Typical life cycle assessment practice for consumer products often excludes significant land use change emissions when estimating carbon footprints. ► The article provides a methodology to rescale IPCC guidelines for product-level carbon footprints. ► Life cycle inventories and product carbon footprint protocols need more comprehensive land use-related accounting. ► Interdisciplinary collaboration linking the LCA and

  18. Adsorption dynamics of copper ion by low cost activated carbon

    International Nuclear Information System (INIS)

    Arivoli, S.; Saravanan, S.; Nandhakumar, V.; Nagarajan, Sulochana

    2009-01-01

    The activated carbon was prepared using solid waste called Terminalia Catappa Linn shell and the physicochemical properties of carbon were investigated to explore the adsorption process. The effectiveness of such carbon in adsorbing copper ion from aqueous solution has been studied as a function of agitation time, adsorbent dosage, initial metal ion concentration, temperature, pH, and desorption. Adsorption equilibrium studies were carried out in order to optimize the experimental conditions. The adsorption of copper ion onto carbon followed a first order kinetic model. Adsorption data were modeled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacity Qm was 30.60, 33.85, 35.87, and 38.35 at initial PH 7.0. The equilibrium time was found to be 40 min for all initial concentrations studied. Desorption studies were performed with dilute HCl and show that ion exchange is the predominant copper ion adsorption mechanism. The adsorbent was found to be both effective and economically viable. (author)

  19. Colossal carbon! Disturbance and biomass dynamics in Alaska's national forests

    Science.gov (United States)

    John Kirkland; Tara Barrett

    2016-01-01

    The Chugach and Tongass National Forests are changing, possibly in response to global warming. Forested areas within Alaska's temperate rain forests are creeping into areas that were previously too cold or too wet. These forests are also becoming denser. As biomass increases, the amount of carbon stored in the forest also increases. Tara Barrett, a...

  20. Temperate forest dynamics and carbon storage: A 26-year case ...

    African Journals Online (AJOL)

    Overall, these results suggest that the forest is in a post-disturbance recovery phase, although favourable climatic conditions over the last three decades may also have had an influence on AGB accumulation. Keywords: aboveground biomass, carbon sequestration, forest conservation, long-term monitoring, succession ...

  1. Effects of tillage on contents of organic carbon, nitrogen, water-stable aggregates and light fraction for four different long-term trials

    Science.gov (United States)

    Andruschkewitsch, R.; Geisseler, D.; Koch, H.-J.; Ludwig, B.

    2012-04-01

    Despite increasing interest in tillage techniques as a factor affecting organic carbon (Corg) dynamics and stabilization mechanisms little is known about the underlying processes. Our objectives were (i) to quantify the impact of different tillage treatments on the amount and distribution of of labile Corg pools, on the water-stable macro-aggregate (>250 µm) contents and on organic carbon (Corg) storage and (ii) to quantify the ability of soils under different tillage treatments, light fraction (LF) inputs and clay contents in macro-aggregate formation. Therefore four long-term tillage trials on loess soil in Germany with regular conventional tillage (CT, to 30 cm), mulch tillage (MT, to 10 cm), and no-tillage (NT) treatments. Samples were taken in 0-5 cm, 5-25 cm and 25-40 cm depth after 18-25 years of different tillage treatments and investigated on free and occluded LF (fLF and oLF, respectively) and on macro-aggregate contents. Furthermore an incubation experiment for the quantifcation of macro-aggregate formation was conducted. Macro-aggregates in soils from CT and NT treatments (0-5 and 5-25 cm soil depth) were destroyed and different amounts of light fraction (LF) and clay were applied. The four long-term tillage trials, differing in texture and climatic conditions, revealed consistent results in Corg storage among each other. Based on the equivalent soil mass approach (CT: 0-40, MT: 0-38, NT: 0-36 cm) the Corg stocks in the sampled profile were significantly higher for the MT treatment than for the CT and NT treatments. Significantly lower Corg, fLF, oLF, and macro-aggregate contents for the soils under CT treatment in comparison with the soils under NT and MT treatments were restricted on the top 5 cm. The correlation of the macro-aggregate content against the fLF and oLF contents suggested that the macro-aggregate content is influenced to a lesser extent directly by the physical impact of the different tillage treatments but by the contents of available

  2. [Dynamic change of four triterpenic acids contents in different organs of loquat (Eriobotrya japonica) and phenology].

    Science.gov (United States)

    Li, Ji-yang; Xie, Xiao-mei; Li, Qian-wen; Zhang, Qi; Chen, Sheng-lin; Wang, He-qun; Yu, Wen-xia; Yang, Mo

    2015-03-01

    The loquat is widely cultivated in China, its succulent fruits, leaves and flower are used as a traditional medicine for the treatment of many diseases. The study is aimed to analyse the content of the four triterpene compounds ( ursolic acid, corosolic acid, maslinic acid, oleanolic acid) in different organs, and investigate the dynamic changes in different phenological period. The triterpenic acids content in the samples was measured by HPLC based on the plant phenological observations. The results showed that order of four triterpenic acids content in different organs from high to low was defoliation (23.2 mg x g(-1)) > mature leaves (21.7 mg x g(-1)) > young leaves (17.5 mg x g(-1)) > fruits (7.36 mg x g(-1)) > flowers (6.40 mg x g(-1)). The triterpenic acids were not detected in the seeds. The total amount of the four triterpenic acids in the loquat leaves collected in the different phenological stages of sprout, flower bud, blossom and fruit varied between 17.8 and 26.2 mg x g(-1) (defoliation), 16.5 and 23.5 mg x g(-1) (mature leaves), 14.7 and 21.5 mg x g(-1) (young leaves), respectively. The content increased progressively with the leaf development, maturation and aging. There was a higher level of the dry material and triterpenic acids accumulation in the mature leaves during fruit enlargement. This paper attempts to present the case for medicinal plants of a broad geographical distribution to study on the secondary metabolites and harvesting time.

  3. Analysis of carbon and nitrogen dynamics in riparian soils: model development.

    Science.gov (United States)

    Brovelli, A; Batlle-Aguilar, J; Barry, D A

    2012-07-01

    The quality of riparian soils and their ability to buffer contaminant releases to aquifers and streams are connected intimately to moisture content and nutrient dynamics, in particular of carbon (C) and nitrogen (N). A multi-compartment model-named the Riparian Soil Model (RSM)-was developed to help investigate the influence and importance of environmental parameters, climatic factors and management practices on soil ecosystem functioning in riparian areas. The model improves existing tools, in particular regarding its capability to simulate a wide range of temporal scales, from days to centuries, along with its ability to predict the concentration and vertical distribution of dissolved organic matter (DOM). It was found that DOM concentration controls the amount of soil organic matter (SOM) stored in the soil as well as the respiration rate. The moisture content was computed using a detailed water budget approach, assuming that within each time step all the water above field capacity drains to the layer underneath, until it becomes fully saturated. A mass balance approach was also used for nutrient transport, whereas the biogeochemical reaction network was developed as an extension of an existing C and N turnover model. Temperature changes across the soil profile were simulated analytically, assuming periodic temperature changes in the topsoil. To verify the consistency of model predictions and to illustrate its capabilities, a synthetic but realistic soil profile in a deciduous forest was simulated. Model parameters were taken from the literature, and model predictions were consistent with experimental observations for a similar scenario. Modelling results stressed the importance of environmental conditions on SOM cycling in soils. The mineral and organic C and N stocks fluctuate at different time scales in response to oscillations in climatic conditions and vegetation inputs/uptake. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Investigation of the interfacial properties of polyurethane/carbon nanotube hybrid composites: A molecular dynamics study

    Science.gov (United States)

    Goclon, Jakub; Panczyk, Tomasz; Winkler, Krzysztof

    2018-03-01

    Considering the varied applications of hybrid polymer/carbon nanotube composites and the constant progress in the synthesis methods of such materials, we report a theoretical study of interfacial layer formation between pristine single-wall carbon nanotubes (SWCNTs) and polyurethane (PU) using molecular dynamic simulations. We vary the SWCNT diameter and the number of PU chains to examine various PU-SWCNT interaction patterns. Our simulations indicate the important role of intra-chain forces in PU. No regular polymeric structures could be identified on the carbon nanotube surface during the simulations. We find that increasing the SWCNT diameter results in stronger polymer binding. However, higher surface loadings of PU lead to stronger interpenetration by the polymeric segments; this effect is more apparent for SWCNTs with small diameters. Our core finding is that the attached PU binds most strongly to the carbon nanotubes with the largest diameters. Polymer dynamics reveal the loose distribution of PU chains in these systems.

  5. Physicochemical characteristics and droplet impact dynamics of superhydrophobic carbon nanotube arrays.

    Science.gov (United States)

    Aria, Adrianus I; Gharib, Morteza

    2014-06-17

    The physicochemical and droplet impact dynamics of superhydrophobic carbon nanotube arrays are investigated. These superhydrophobic arrays are fabricated simply by exposing the as-grown carbon nanotube arrays to a vacuum annealing treatment at a moderate temperature. This treatment, which allows a significant removal of oxygen adsorbates, leads to a dramatic change in wettability of the arrays, from mildly hydrophobic to superhydrophobic. Such change in wettability is also accompanied by a substantial change in surface charge and electrochemical properties. Here, the droplet impact dynamics are characterized in terms of critical Weber number, coefficient of restitution, spreading factor, and contact time. Based on these characteristics, it is found that superhydrophobic carbon nanotube arrays are among the best water-repellent surfaces ever reported. The results presented herein may pave a way for the utilization of superhydrophobic carbon nanotube arrays in numerous industrial and practical applications, including inkjet printing, direct injection engines, steam turbines, and microelectronic fabrication.

  6. Molecular dynamics study of cavitation in carbon nanotube reinforced polyethylene nanocomposite

    Science.gov (United States)

    Logunov, M. A.; Orekhov, N. D.

    2018-01-01

    Carbon nanotubes (CNTs) have proved to be very promising fillers for polymer nanocomposites. However, because of the lack of a detailed understanding of the principles of the nanoinclusion interaction with polymer matrixes, the properties of such materials are poorly understood. In the present study, within the coarse-grained molecular-dynamics methods, aspects of the interaction of amorphous polyethylene matrix with carbon nanotubes and the influence of CNTs on the cavitation during the nanocomposite deformation are studied.

  7. A 6 year longitudinal study of post-fire woody carbon dynamics in California's forests

    Science.gov (United States)

    Bianca N.I. Eskelson; Vicente J. Monleon; Jeremy S. Fried

    2016-01-01

    We examined the dynamics of aboveground forest woody carbon pools — live trees, standing dead trees, and down wood—during the first 6 years following wildfire across a wide range of conditions, which are characteristic of California forest fires. From repeated measurements of the same plots, we estimated change in woody carbon pools as a function of crown fire severity...

  8. Nearshore Carbon and Sediment Dynamics of an Eroding Permafrost Coast: Herschel Island, Yukon Territory, Canada

    OpenAIRE

    Radosavljevic, Boris; Lantuit, Hugues; Fritz, Michael

    2012-01-01

    The study presented herein seeks to determine the fate of sediment and carbon supplied into the nearshore zone by coastal erosion and thermokarst in permafrost landscapes. To accomplish this, the sediment and carbon sources and sinks will be identified and quantified using remotely sensed imagery, bathymetric and sidescan surveys, shallow seismic profiles, and the interpretation of sediment cores. Coastal dynamics on arctic coasts are characterized by a seasonal dichotomy. Sea ice and land...

  9. Analysis of Static and Dynamic E-Reference Content at a Multi-Campus University Shows, that Updated Content is Associated with Greater Annual Usage

    Directory of Open Access Journals (Sweden)

    Laura Costello

    2016-03-01

    Full Text Available Objective – To discover whether there is a difference in use over time between dynamically updated and changing subscription e-reference titles and collections, and static purchased e-reference titles and collections. Design – Case study. Setting – A multi-campus Canadian university with 9,200 students enrolled in both graduate and undergraduate programs. Subjects – E-reference book packages and individual e-reference titles. Methods – The author compared data from individual e-reference books and packages. First, individual subscription e-reference books that periodically added updated content were compared to individually purchased e-reference books that remained static after purchase. The author then compared two e-reference book packages that provided new and updated content to two static e-reference book packages. The author compared data from patron usage to new content added over time using regression analysis. Main Results – As the library acquired e-reference titles, dynamic title subscriptions added to the collection were associated with 2,246 to 4,635 views per subscription while static title additions were associated with 8 to 123 views per purchase. The author also found that there was a strong linear relationship between views and dynamic titles added to the collection (R2=0.79 and a very weak linear relationship (R2=0.18 with views when static titles are added to the collection. Regression analysis of dynamic e-reference collections revealed that the number of titles added to each collection was strongly associated with views of the material (R2=0.99, while static e-reference collections were less strongly linked (R2=0.43. Conclusion – Dynamic e-reference titles and collections experienced increases in usage each year while static titles and collections experienced decreases in usage. This indicates that collections and titles that offer new content to users each year will continue to see growth in usage while static

  10. Determination of oxygen content and carbonate impurity in YBa2Cu3O7-x by diffuse reflectance infrared spectroscopy

    International Nuclear Information System (INIS)

    Merzbacher, C.I.; Bonner, B.P.

    1991-01-01

    Samples of YBa 2 Cu 3 O 7-x with x ranging from ∼0 to 0.65 have been analyzed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in the midinfrared region (400--6000 cm -1 ). Spectral line shapes vary gradually as a function of oxygen stoichiometry, and the reflectance at 400 and 1000 cm -1 decreases linearly with decreasing oxygen content. Spectra of samples that were incompletely synthesized or exposed to a 4% CO 2 atmosphere at 650 degree C clearly indicated the presence of carbonate. DRIFTS is therefore a quick, nondestructive method for determining oxygen content in YBa 2 Cu 3 O 7-x powders, and for detecting carbonate species due to synthesis error or reaction with CO 2 -bearing atmosphere

  11. Effects of carbon nanofiller characteristics on PTT chain conformation and dynamics: A computational study

    International Nuclear Information System (INIS)

    Asadinezhad, Ahmad; Kelich, Payam

    2017-01-01

    Highlights: • Poly (trimethylene terephthalate) (PTT) conformation adopts a folded shape near nanofiller surface. • Graphene and carbon nanotube with different size and chemistry were simulated. • Graphene functionalization induces stronger confinement on PTT chain conformation. • PTT chain motion alters in dynamics mode as it becomes adsorbed onto nanofillers. • PTT reveals further changes near graphene than carbon nanotube surface. - Abstract: The effects of nanofiller chemistry and geometry on static and dynamic properties of an aromatic polyester, poly (trimethylene terephthalate), were addressed thanks to long-run classical molecular dynamics simulation. Two carbon nanofillers, graphene and carbon nanotube, were employed, where graphene was used in pristine and functionalized forms and carbon nanotube was used in two different diameters. The nanofiller geometry and chemistry were found to exert significant effects on conformation and dynamic behavior of PTT chain at the interface within the time scale the simulation was performed. It was found that PTT chain underwent interaction of van der Waals type with nanofiller via two subsequent phases, adsorption and orientation. The former stage, with definite characteristic time, involved translation of polymer chain toward interface while the latter was controlled by vibrational motions of chain atoms. The consequence of interaction was an increase in conformational order of polymer chain by transition to folded shape being favorable for any subsequent structural ordering (crystallization). The interaction of polymer with nanofiller gave rise to a reduction in overall mobility of polymer chain characterized by crossover from normal diffusive motion to subdiffusive mode.

  12. Carbon Dynamics in Heathlands in Response to a Changing Climate

    DEFF Research Database (Denmark)

    Nielsen, Pia Lund

    Climate is changing, and more adverse changes are expected in the future. Changes, caused by continuously rising atmospheric concentrations of greenhouse gasses as CO2, will affect ecosystem processes and functions in the future and hence the cycling of carbon. The vaste amount of studies have...... focused on effects of climate change on aboveground biomass, less have been conducted on belowground biomass, and the thesis is one of few studies comprising both above- and belowground biomass and take interactions of climate change factors into account. To follow the fate of carbon in the ecosystem we...... no persistent changes over the years. Responses of aboveground and belowground biomass were coupled, and Deschampsia flexuosa showed high ability to adapt to treatments. As the major response was observed belowground, I further studied decomposition of fine roots. Fine roots of Deschampsia flexuosa from deep...

  13. Simulation of a dynamical ecotourism system with low carbon activity: A case from western China.

    Science.gov (United States)

    He, Yuan; Huang, Ping; Xu, Hong

    2018-01-15

    Currently, sustainable tourism is becoming more and more important in developing ecological economies. To achieve low-carbon development, some industries, such as logistics and municipal solid waste, have already taken action, but tourism has not attached sufficient importance to this issue. This paper designs an ecotourism system including tourism, carbon waste (solid waste and sewage), and ecology (water supply and green areas) to simulate low-carbon ecotourism through a quantitative approach. This paper explores the tourism system as well as some interactive factors and studies their quantitative relationship based on historical data. A feedback-loop dynamical system model is designed to simulate tourism, waste carbon, and ecology simultaneously. Finally, a case study applying the feedback-loop dynamical system model to Leshan City, a typical travel destination with colorful natural resources in western China, is conducted to indicate the development of ecotourism in an environmentally friendly economy, which verifies the positive effects of the model. Results show a coordinating upward tendency of tourism, solid waste carbon, and ecology from the dynamical model. When tourism increases, solid waste accumulation increases; however, the amount of sewage dumped directly into nature decreases sharply. After analysis of investment policy scenarios, the research indicates that more funds for sewage treatment will attract more tourists. To maintain the equilibrium of carbon waste, more funds shall be invested in solid waste treatment in the long term. Some discussions about local policy are included. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Revision of Fontes & Garnier's model for the initial 14C content of dissolved inorganic carbon used in groundwater dating

    Science.gov (United States)

    Han, Liang-Feng; Plummer, Niel

    2013-01-01

    The widely applied model for groundwater dating using 14C proposed by Fontes and Garnier (F&G) (Fontes and Garnier, 1979) estimates the initial 14C content in waters from carbonate-rock aquifers affected by isotopic exchange. Usually, the model of F&G is applied in one of two ways: (1) using a single 13C fractionation factor of gaseous CO2 with respect to a solid carbonate mineral, εg/s, regardless of whether the carbon isotopic exchange is controlled by soil CO2 in the unsaturated zone, or by solid carbonate mineral in the saturated zone; or (2) using different fractionation factors if the exchange process is dominated by soil CO2 gas as opposed to solid carbonate mineral (typically calcite). An analysis of the F&G model shows an inadequate conceptualization, resulting in underestimation of the initial 14C values (14C0) for groundwater systems that have undergone isotopic exchange. The degree to which the 14C0 is underestimated increases with the extent of isotopic exchange. Examples show that in extreme cases, the error in calculated adjusted initial 14C values can be more than 20% modern carbon (pmc). A model is derived that revises the mass balance method of F&G by using a modified model conceptualization. The derivation yields a “global” model both for carbon isotopic exchange dominated by gaseous CO2 in the unsaturated zone, and for carbon isotopic exchange dominated by solid carbonate mineral in the saturated zone. However, the revised model requires different parameters for exchange dominated by gaseous CO2 as opposed to exchange dominated by solid carbonate minerals. The revised model for exchange dominated by gaseous CO2 is shown to be identical to the model of Mook (Mook, 1976). For groundwater systems where exchange occurs both in the unsaturated zone and saturated zone, the revised model can still be used; however, 14C0 will be slightly underestimated. Finally, in carbonate systems undergoing complex geochemical reactions, such as oxidation of

  15. Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon bonds

    Science.gov (United States)

    Guan, Zhibin; Lu, Yixuan

    2015-09-15

    A method of preparing a malleable and/or self-healing polymeric or composite material is provided. The method includes providing a polymeric or composite material comprising at least one alkene-containing polymer, combining the polymer with at least one homogeneous or heterogeneous transition metal olefin metathesis catalyst to form a polymeric or composite material, and performing an olefin metathesis reaction on the polymer so as to form reversible carbon-carbon double bonds in the polymer. Also provided is a method of healing a fractured surface of a polymeric material. The method includes bringing a fractured surface of a first polymeric material into contact with a second polymeric material, and performing an olefin metathesis reaction in the presence of a transition metal olefin metathesis catalyst such that the first polymeric material forms reversible carbon-carbon double bonds with the second polymeric material. Compositions comprising malleable and/or self-healing polymeric or composite material are also provided.

  16. Dynamic and inertial controls on forest carbon-water relations

    Science.gov (United States)

    Maxwell, T.; Silva, L.; Horwath, W. R.

    2017-12-01

    This study fuses theory, empirical measurements, and statistical models to evaluate multiple processes controlling coupled carbon-water cycles in forest ecosystems. A series of latitudinal and altitudinal transects across the California Sierra Nevada was used to study the effects of climatic and edaphic gradients on intrinsic water-use efficiency (iWUE) - CO2 fixed per unit of water lost via transpiration - of nine dominant trees species. Transfer functions were determined between leaf, litter, and soil organic matter stable isotope ratios of carbon, oxygen, and nitrogen, revealing causal links between the physiological performance of tree species and stand-level estimations of productivity and water balance. Our results show that species iWUE is governed both by leaf traits (24% of the variation) and edaphic properties, such as parent material and soil development (3% and 12% of the variation, respectively). We show that soil properties combined with isotopic indicators can be used to explain constraints over iWUE by regulating water and nutrient availability across elevation gradients. Based on observed compositional shifts likely driven by changing climates in the region, encroachment of broad leaf trees could lead to an 80% increase in water loss via transpiration for each unit of CO2 fixed in Sierra mixed conifer zones. A combination of field-based, laboratory, and remote sensed data provide a useful framework for differentiating the effect of multiple controls of carbon and water cycles in temperate forest ecosystems.

  17. WIMP detection and slow ion dynamics in carbon nanotube arrays

    CERN Document Server

    Cavoto, G.; Cocina, F.; Ferretti, J.; Polosa, A.D.

    2016-06-24

    Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (~ 10 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with ...

  18. Dynamics of carbon sequestration in a coastal wetland using radiocarbon measurements

    Science.gov (United States)

    Choi, Yonghoon; Wang, Yang

    2004-12-01

    Coastal wetlands are sensitive to global climate change and may play an important role in the global carbon cycle. However, the dynamics of carbon (C) cycling in coastal wetlands and its response to sea level change associated with global warming is still poorly understood. In this study, we estimated the long-term and short-term rates of C accumulation, using C and C isotopic measurements of peat cores collected along a soil chronosequence, in a coastal wetland in north Florida. The long-term C accumulation rates determined by examining the C inventory and the radioactive decay of radiocarbon as a function of depth in the peat cores decrease with time from ˜130 ± 9 g C/m2/yr over the last century to ˜13 ± 2 g C/m2/yr over the millennium timescale. The short-term C accumulation rates estimated by examining the differences in the radiocarbon and C contents of the surfacial peat between archived (1985, 1988) and present (1996 and 1997) samples range from 42 to 193 g C/m2/yr in low marsh, from 18 to 184 g C/m2/yr in middle marsh, and from -50 to 181 g C/m2/yr in high marsh. The high end-values of our estimated short-term C accumulation rates are comparable to the estimated rates of C sequestration in coastal wetlands reported by [2003], but are significantly higher than our estimated long-term rates in the marshes and are also much higher than the published rates of C sequestration in northern peatlands. The higher recent rates of C accumulation in coastal marshes, in comparison with the longer-term rates, are due to slow but continuous decomposition of organic matter in the peat over time. However, other factors such as increased primary production in the coastal wetland over the last decades or century, due to a rise in mean sea level and/or CO2 and nitrogen fertilization effect, could also have contributed to the large difference between the recent and longer-term rates. Our data indicate that salt marshes in this area have been and continue to be a sink for

  19. The application of Car-Parrinello molecular dynamics to the study of tetrahedral amorphous carbon

    International Nuclear Information System (INIS)

    McKenzie, D.R.; McCulloch, D.G.; Goringe, C.M.

    1998-01-01

    The Car-Parrinello method for carrying out molecular dynamics enables the forces between atoms to be calculated by solving Schroedinger's equation for the valence electrons using Density Functional Theory. The method is capable of giving good structural predictions for amorphous network solids by quenching from the melt, even in situations where the bonding changes from one site to another. In amorphous carbon where, depending on its environment, carbon may show sp 2 or sp 3 bonds. The method is applied here to the study of network solids using the example of tetrahedral amorphous carbon

  20. Visualizing the growth dynamics of individual single-wall carbon nanotubes

    DEFF Research Database (Denmark)

    Wagner, Jakob Birkedal; Zhang, Lili; He, Maoshuai

    In order to meet the increasing demand of faster and more flexible electronics and optical devices and at the same time decrease the use of the critical metals, carbon based devices are in fast development. Single walled carbon nanotube (SWCNT) based electronics is a way of addressing...... around the studied sample at elevated temperature gives a unique way of monitoring gas-solid interactions such as CNT growth. Here we show the direct experimental evidence on the growth dynamics of SW-CNTs from Co/MgO catalysts using CO as carbon source inside the environmental TEM. The evolution...

  1. [XPS and Raman spectral analysis of nitrogenated tetrahedral amorphous carbon (ta-C : N) films with different nitrogen content].

    Science.gov (United States)

    Chen, Wang-Shou; Zhu, Jia-Qi; Han, Jie-Cai; Tian, Gui; Tan, Man-Lin

    2009-01-01

    Nitrogenated tetrahedral amorphous carbon (ta-C : N) films were prepared on the polished C--Si substrates by introducing highly pure nitrogen gas into the cathode region and the depositing chamber synchronously using filtered cathodic vacuum arc (FCVA) technology. The nitrogen content in the films was controlled by changing the flow rate of nitrogen gas. The configuration of ta-C : N films was investigated by means of X-ray photoelectron spectroscopy (XPS) and visible Raman spectroscopy. It was shown that the nitrogen content in the films increased from 0.84 at% to 5.37 at% monotonously when the nitrogen flow rate was varied from 2 seem to 20 sccm. The peak position of C (1s) core level moved towards higher binding energy with the increase in nitrogen content. The shift of C (1s) peak position could be ascribed to the chemical bonding between carbon and nitrogen atoms even though more three-fold coordinated sp2 configuration as in graphite was formed when the films were doped with more nitrogen atoms. Additionally, the half width of C(1s) peak gradually was also broadened with increasing nitrogen content. In order to discover clearly the changing regularities of the microstructure of the films, the XPS C(1s) spectra and Raman spectra were deconvoluted using a Gaussian-Lorentzian mixed lineshape. It was shown that the tetrahedral hybridization component was still dominant even though the ratio of sp2/sp3 obtained from C(1s) spectra rose with the increase in nitrogen content. The Raman measurements demonstrated that the G peak position shifted towards higher frequency from 1,561 to 1,578 cm(-1) and the ratio of ID/IG also rose with the increase in nitrogen content. Both results indicated that the graphitizing tendency could occur with the increase in nitrogen content in the films.

  2. Dynamics of intracellular polymers in enhanced biological phosphorus removal processes under different organic carbon concentrations.

    Science.gov (United States)

    Xing, Lizhen; Ren, Li; Tang, Bo; Wu, Guangxue; Guan, Yuntao

    2013-01-01

    Enhanced biological phosphorus removal (EBPR) may deteriorate or fail during low organic carbon loading periods. Polyphosphate accumulating organisms (PAOs) in EBPR were acclimated under both high and low organic carbon conditions, and then dynamics of polymers in typical cycles, anaerobic conditions with excess organic carbons, and endogenous respiration conditions were examined. After long-term acclimation, it was found that organic loading rates did not affect the yield of PAOs and the applied low organic carbon concentrations were advantageous for the enrichment of PAOs. A low influent organic carbon concentration induced a high production of extracellular carbohydrate. During both anaerobic and aerobic endogenous respirations, when glycogen decreased to around 80 ± 10 mg C per gram of volatile suspended solids, PAOs began to utilize polyphosphate significantly. Regressed by the first-order reaction model, glycogen possessed the highest degradation rate and then was followed by polyphosphate, while biomass decay had the lowest degradation rate.

  3. Advanced in-situ measurement of soil carbon content using inelastic neutron scattering

    Science.gov (United States)

    Measurement and mapping of natural and anthropogenic variations in soil carbon stores is a critical component of any soil resource evaluation process. Emerging modalities for soil carbon analysis in the field is the registration of gamma rays from soil under neutron irradiation. The inelastic neutro...

  4. SCREENING OF CONTENT AND DYNAMIC OF ACCUMULATION OF POLYPHENOLS IN SOME BASIDIOMYCETES SPECIES

    Directory of Open Access Journals (Sweden)

    Veligodska A. K.

    2015-12-01

    Full Text Available The aim of the study was to investigate the total content of polyphenolic substances in Basidiomycetes carpophores from 50 species, of which 27 belong to the order Polyporales and 23 to the order Agaricales. Introduced 23 strains of 8 species of Basidiomycetes. Methods. Gathered wild carpophores dried and crushed to a particle size of 0,1 till 0,01 mm and searching strains were cultured in Erlenmeyyers flasks by surface method on standard glucose-peptone culture medium. Determination of total content of polyphenolic compounds was carried out in ethanol extracts of mycological material by a modified method of Folin-Chokalteu. Completely dry biomass of carpophores and mycelium was determined gravimetrically. Results. There was identified the species of polyporal fungi Ganoderma applanatum, Ganoderma lucidum, Laetiporus sulphureus and Fomes fomentarius and types of agarical mushrooms Stropharia rugosoannulata, Agrocybe cylindracea, Tricholoma flavovirens, Flammulina velutipes, Pleurotus ostreatus and Fistulina hepatica high in polyphenolic compounds. It was determined the content of polyphenols ranging from more than 60 mg / g completely dry biomass. For introduced strains established dynamics of growth and accumulation of polyphenolic compounds in the mycelium and culture filtrate during fermentation on glucose-peptone medium. All cultures reach a maximum accumulation of biomass on the 12th day of growth. Shizophyllum commune Sc-1101 and 10 and F. velutipes F-202 have been identified as the most productive strains. The lowest accumulation of absolutely dry biomass was recorded for strain P. ostreatus P-192 and strain F. fomentarius Ff-09. Cultures have investigated individual value growth such as biomass accumulation in the applied cultivation conditions, which probably reflects the suitability of the medium for their growth and genotypic characteristics. Strains are overwhelmingly able to accumulate polyphenolic compounds in both mycelium and

  5. SCREENING OF CONTENT AND DYNAMIC OF ACCUMULATION OF POLYPHENOLS IN SOME BASIDIOMYCETES SPECIES

    Directory of Open Access Journals (Sweden)

    A. K. Veligodska

    2015-11-01

    Full Text Available The aim of the study was to investigate the total content of polyphenolic substances in Basidiomycetes carpophores from 50 species, of which 27 belong to the order Polyporales and 23 to the order Agaricales. Introduced 23 strains of 8 species of Basidiomycetes. Methods. Gathered wild carpophores dried and crushed to a particle size of 0,1 till 0,01 mm and searching strains were cultured in Erlenmeyyers flasks by surface method on standard glucose-peptone culture medium. Determination of total content of polyphenolic compounds was carried out in ethanol extracts of mycological material by a modified method of Folin-Chokalteu. Completely dry biomass of carpophores and mycelium was determined gravimetrically. Results. There was identified the species of polyporal fungi Ganoderma applanatum, Ganoderma lucidum, Laetiporus sulphureus and Fomes fomentarius and types of agarical mushrooms Stropharia rugosoannulata, Agrocybe cylindracea, Tricholoma flavovirens, Flammulina velutipes, Pleurotus ostreatus and Fistulina hepatica high in polyphenolic compounds. It was determined the content of polyphenols ranging from more than 60 mg / g completely dry biomass. For introduced strains established dynamics of growth and accumulation of polyphenolic compounds in the mycelium and culture filtrate during fermentation on glucose-peptone medium. All cultures reach a maximum accumulation of biomass on the 12th day of growth. Shizophyllum commune Sc-1101 and 10 and F. velutipes F-202 have been identified as the most productive strains. The lowest accumulation of absolutely dry biomass was recorded for strain P. ostreatus P-192 and strain F. fomentarius Ff-09. Cultures have investigated individual value growth such as biomass accumulation in the applied cultivation conditions, which probably reflects the suitability of the medium for their growth and genotypic characteristics. Strains are overwhelmingly able to accumulate polyphenolic compounds in both mycelium and

  6. Beyond the electronic textbook model: software techniques to make on-line educational content dynamic.

    Science.gov (United States)

    Frank, M S; Dreyer, K

    2001-06-01

    . This technology enables the educator to choreograph a stylized, interactive delivery of his or her message using multimedia components assembled in virtually any order, spanning any number of web pages for a given case or theme. An educator can thus exercise precise influence on specific learning objectives, embody his or her personal teaching style within the content, and ultimately enhance its educational impact. The described technology amplifies the efforts of the educator and provides a more dynamic and enriching learning environment for web-based education.

  7. Dynamic Self-Stiffening and Structural Evolutions of Polyacrylonitrile/Carbon Nanotube Nanocomposites.

    Science.gov (United States)

    Li, Yinhui; Zhou, Pucha; An, Feng; Liu, Yaodong; Lu, Chunxiang

    2017-02-15

    The self-stiffening under external dynamic strain has been observed for some artificial materials, especially for nanocomposites. However, few systematic studies have been carried out on their structural evolutions, and the effect of the types of nanofillers was unclear. In this study, we used a semicrystalline polymer, polyacrylonitrile (PAN), and various types of carbon nanomaterials including C 60 , carbon nanotube (CNT), and graphene oxide (GO). An external uniaxial dynamic strain at small amplitude of 0.2% was applied on the prepared nanocomposite films. It was observed that PAN/CNT exhibited significant self-stiffening behavior, whereas PAN/GO showed no response. Systematic characterizations were performed to determine the structural evolutions of PAN/CNT film during dynamic strain testing, and it was found that the external dynamic strain not only induced the crystallization of PAN chains but also aligned CNT along the strain direction.

  8. Estimating soil organic carbon content with visible-near-infrared (vis-NIR) spectroscopy.

    Science.gov (United States)

    Gao, Yin; Cui, Lijuan; Lei, Bing; Zhai, Yanfang; Shi, Tiezhu; Wang, Junjie; Chen, Yiyun; He, Hui; Wu, Guofeng

    2014-01-01

    The selection of a calibration method is one of the main factors influencing measurement accuracy with visible-near-infrared (Vis-NIR, 350-2500 nm) spectroscopy. This study, based on both air-dried unground (DU) and air-dried ground (DG) soil samples, used nine spectral preprocessing methods and their combinations, with the aim to compare the commonly used partial least squares regression (PLSR) method with the new machine learning method of support vector machine regression (SVMR) to find a robust method for soil organic carbon (SOC) content estimation, and to further explore an effective Vis-NIR spectral preprocessing strategy. In total, 100 heterogeneous soil samples collected from Southeast China were used as the dataset for the model calibration and independent validation. The determination coefficient (R(2)), root mean square error (RMSE), residual prediction deviation (RPD), and ratio of performance to interquartile range were used for the model evaluation. The results of this study show that both the PLSR and SVMR models were significantly improved by the absorbance transformation (LOG), standard normal variate with wavelet detrending (SW), first derivative (FD), and mean centering (MC) spectral preprocessing methods and their combinations. SVMR obtained optimal models for both the DU and DG soil, with R(2), RMSE, and RPD values of 0.72, 2.48 g/kg, and 1.83 for DU soil and 0.86, 1.84 g/kg, and 2.60 for DG soil, respectively. Among all the PLSR and SVMR models, SVMR showed a more stable performance than PLSR, and it also outperformed PLSR, with a smaller mean RMSE of 0.69 g/kg for DU soil and 0.50 g/kg for DG soil. This study concludes that PLSR is an effective linear algorithm, but it might not be sufficient when dealing with a nonlinear relationship, and SVMR turned out to be a more suitable nonlinear regression method for SOC estimation. Effective SOC estimation was obtained based on the DG soil samples, but the accurate estimation of SOC with DU soil

  9. Non-Equilibrium Molecular Dynamics Simulation of Poiseuille Flow in a Carbon Nanochannel

    OpenAIRE

    Ni, Guo Liang; He, Ming Li; Hua, Yao Zu; Abareshi, Bagher

    2017-01-01

    International audience; The numerical simulation of a Poiseuille flow in a narrow channel using the molecular dynamics simulation (MDS) is performed. Poiseuille flow of liquid Argon in a carbon nanochannel is simulated by embedding the fluid particles in a uniform force field. Density, velocity and Temperature profiles across the channel are investigated. When particles will be inserted into the flow, it is expected that the dynamics of flow will depend on the thermostat chosen. To obtain a m...

  10. Strongly Nonlinear Dependence of Energy Transfer Rate on sp(2) Carbon Content in Reduced Graphene Oxide-Quantum Dot Hybrid Structures.

    Science.gov (United States)

    Dong, Yitong; Son, Dong Hee

    2015-01-02

    The dependence of the energy transfer rate on the content of sp(2)-hybridized carbon atoms in the hybrid structures of reduced graphene oxide (RGO) and Mn-doped quantum dot (QD(Mn)) was investigated. Taking advantage of the sensitivity of QD(Mn)'s dopant luminescence lifetime only to the energy transfer process without interference from the charge transfer process, the correlation between the sp(2) carbon content in RGO and the rate of energy transfer from QD(Mn) to RGO was obtained. The rate of energy transfer showed a strongly superlinear increase with increasing sp(2) carbon content in RGO, suggesting the possible cooperative behavior of sp(2) carbon domains in the energy transfer process as the sp(2) carbon content increases.

  11. Empirical observations offer improved estimates of forest floor carbon content across in the United States

    Science.gov (United States)

    Perry, C. H.; Domke, G. M.; Walters, B. F.; Smith, J. E.; Woodall, C. W.

    2014-12-01

    The Forest Inventory and Analysis (FIA) program of the United States Forest Service reports official estimates of national forest floor carbon (FFC) stocks and stock change to national and international parties, the US Environmental Protection Agency (USEPA) and the United Nations Framework Convention on Climate Change (UNFCCC), respectively. These estimates of national FFC stocks are derived from plot-level predictions of FFC density. We suspect the models used to predict plot-level FFC density are less than ideal for several reasons: (a) they are based upon local studies that may not reflect FFC dynamics at the national scale, (b) they are relatively insensitive to climate change, and (c) they reduce the natural variability of the data leading to misplaced confidence in the estimates. However, FIA has measured forest floor attributes since 2001 on a systematic 1/16th subset of a nation-wide array of inventory plots (7 800 of 125 000 plots). Here we address the efficacy of replacing plot-level model predictions with empirical observations of FFC density while assessing the impact of imputing FFC density values to the full plot network on national stock estimates. First, using an equivalence testing framework, we found model predictions of FFC density to differ significantly from the observations in all regions and forest types; the mean difference across all plots was 21 percent (1.81 Mg·ha-1). Furthermore, the model predictions were biased towards the lower end of extant FFC density observations, underestimating it while greatly truncating the range relative to the observations. Second, the optimal imputation approach (k-Nearest Neighbor, k-NN) resulted in values that were equivalent to observations of FFC density across a range of simulated missingness and maintained the high variability seen in the observations. We used the k-NN approach to impute FFC density values to the 94 percent of FIA inventory plots without soil measurements. Third, using the imputed

  12. Graphene and carbon nanotubes ultrafast relaxation dynamics and optics

    CERN Document Server

    Malic, Ermin

    2013-01-01

    The book introduces the reader into the ultrafast nanoworld of graphene and carbon nanotubes, including their microscopic tracks and unique optical finger prints. The author reviews the recent progress in this field by combining theoretical and experimental achievements. He offers a clear theoretical foundation by presenting transparently derived equations. Recent experimental breakthroughs are reviewed. By combining both theory and experiment as well as main results and detailed theoretical derivations, the book turns into an inevitable source for a wider audience from graduate students to researchers in physics, materials science, and electrical engineering who work on optoelectronic devices, renewable energies, or in the semiconductor industry.

  13. Carbon dioxide and methane dynamics in Russian tundra

    DEFF Research Database (Denmark)

    Johansson, Paul Torbjörn; Kiepe, Isabell; Herbst, Mathias

    Russia. The area is situated at 67°N in the European part of northeast Russia within the Pechora basin. The Russian tundra region is an area which has recently been subject to many speculations in relation to climatic change effects and greenhouse gas (GHG) exchange but still little scientific......, and discuss possible implications of climatic change on this lowland tundra ecosystem. This study have been conducted as a part of the CARBO-North project (2006-2010), a project within the EU 6th framework programme, aiming at quantifying the carbon budget in Northern Russia across temporal and spatial scales....

  14. The effect of cyclic and dynamic loads on carbon steel pipe

    International Nuclear Information System (INIS)

    Rudland, D.L.; Scott, P.M.; Wilkowski, G.M.

    1996-02-01

    This report presents the results of four 152-mm (6-inch) diameter, unpressurized, circumferential through-wall-cracked, dynamic pipe experiments fabricated from STS410 carbon steel pipe manufactured in Japan. For three of these experiments, the through-wall crack was in the base metal. The displacement histories applied to these experiments were a quasi-static monotonic, dynamic monotonic, and dynamic, cyclic (R = -1) history. The through-wall crack for the third experiment was in a tungsten-inert-gas weld, fabricated in Japan, joining two lengths of STS410 pipe. The displacement history for this experiment was the same history applied to the dynamic, cyclic base metal experiment. The test temperature for each experiment was 300 C (572 F). The objective of these experiments was to compare a Japanese carbon steel pipe material with US pipe material, to ascertain whether this Japanese steel was as sensitive to dynamic and cyclic effects as US carbon steel pipe. In support of these pipe experiments, quasi-static and dynamic, tensile and fracture toughness tests were conducted. An analysis effort was performed that involved comparing experimental crack initiation and maximum moments with predictions based on available fracture prediction models, and calculating J-R curves for the pipe experiments using the η-factor method

  15. A Simple Beta-Function Model for Soil-Water Repellency as a Function of Water and Organic Carbon Contents

    DEFF Research Database (Denmark)

    Karunarathna, Anurudda Kumara; Kawamoto, Ken; Møldrup, Per

    2010-01-01

    WR(θ) models is still lacking. In this study, a simple empirical beta function was suggested to describe the effect of changing soil-water content on the change of WR given as apparent contact angle (α) measured by the molarity of ethanol droplet (MED) method. The beta function for predicting α......Soil-water content (θ) and soil organic carbon (SOC) are key factors controlling the occurrence and magnitude of soil-water repellency (WR). Although expressions have recently been proposed to describe the nonlinear variation of WR with θ, the inclusion of easily measurable parameters in predictive......(θ) is based on measurement of WR on air-dry soil and three additional model parameters: the water contents at which the maximum WR (highest α) occurs and where WR ceases (α = 90 degrees), and the maximum α value. The MED data for three data sets from literature comprising WR measurements across moisture...

  16. Incorporating microbial dormancy dynamics into soil decomposition models to improve quantification of soil carbon dynamics of northern temperate forests

    Science.gov (United States)

    He, Yujie; Yang, Jinyan; Zhuang, Qianlai; Harden, Jennifer W.; McGuire, A. David; Liu, Yaling; Wang, Gangsheng; Gu, Lianhong

    2015-01-01

    Soil carbon dynamics of terrestrial ecosystems play a significant role in the global carbon cycle. Microbial-based decomposition models have seen much growth recently for quantifying this role, yet dormancy as a common strategy used by microorganisms has not usually been represented and tested in these models against field observations. Here we developed an explicit microbial-enzyme decomposition model and examined model performance with and without representation of microbial dormancy at six temperate forest sites of different forest types. We then extrapolated the model to global temperate forest ecosystems to investigate biogeochemical controls on soil heterotrophic respiration and microbial dormancy dynamics at different temporal-spatial scales. The dormancy model consistently produced better match with field-observed heterotrophic soil CO2 efflux (RH) than the no dormancy model. Our regional modeling results further indicated that models with dormancy were able to produce more realistic magnitude of microbial biomass (dormancy, our modeling results showed that soil carbon-to-nitrogen ratio (C:N) was a major regulating factor at regional scales (correlation coefficient = −0.43 to −0.58), indicating scale-dependent biogeochemical controls on microbial dynamics. Our findings suggest that incorporating microbial dormancy could improve the realism of microbial-based decomposition models and enhance the integration of soil experiments and mechanistically based modeling.

  17. Spatiotemporal visualization of subcellular dynamics of carbon nanotubes

    KAUST Repository

    Serag, Maged F.

    2012-12-12

    To date, there is no consensus on the relationship between the physicochemical characteristics of carbon nanotubes (CNTs) and their biological behavior; however, there is growing evidence that the versatile characteristics make their biological fate largely unpredictable and remain an issue of limited knowledge. Here we introduce an experimental methodology for tracking and visualization of postuptake behavior and the intracellular fate of CNTs based on the spatial distribution of diffusion values throughout the plant cell. By using raster scan image correlation spectroscopy (RICS), we were able to generate highly quantitative spatial maps of CNTs diffusion in different cell compartments. The spatial map of diffusion values revealed that the uptake of CNTs is associated with important subcellular events such as carrier-mediated vacuolar transport and autophagy. These results show that RICS is a useful methodology to elucidate the intracellular behavior mechanisms of carbon nanotubes and potentially other fluorescently labeled nanoparticles, which is of relevance for the important issues related to the environmental impact and health hazards. © 2012 American Chemical Society.

  18. Climate policies between carbon prices, oil rents and urban dynamics

    International Nuclear Information System (INIS)

    Waisman, H.

    2012-01-01

    This thesis investigates the effects of constraints imposed on economic interactions by limitations due to natural resources, among which oil and urban land play a crucial role in the context of climate change. These dimensions, often neglected in existing analyses, have an ambiguous effect since they suggest both the risk of enhanced costs if carbon limitations reinforce the sub-optimalities caused by pre-existing constraints, but also, conversely, the possibility of co-benefits if the climate policy helps to correct some pre-existing imperfections of socio-economic trajectories. To investigate this issue, an innovative modeling framework of the energy-economy interactions is elaborated that embarks the specificities of the deployment of oil production capacities and the issues related to the spatial organization in urban areas. We demonstrate that, beyond the carbon price, the costs of climate policy essentially depend on the sequencing of complementary measures, with a crucial role of spatial policy designed to control transport-related emissions through mobility. (author)

  19. Social Network and Content Analysis of the North American Carbon Program as a Scientific Community of Practice

    Science.gov (United States)

    Brown, Molly E.; Ihli, Monica; Hendrick, Oscar; Delgado-Arias, Sabrina; Escobar, Vanessa M.; Griffith, Peter

    2015-01-01

    The North American Carbon Program (NACP) was formed to further the scientific understanding of sources, sinks, and stocks of carbon in Earth's environment. Carbon cycle science integrates multidisciplinary research, providing decision-support information for managing climate and carbon-related change across multiple sectors of society. This investigation uses the conceptual framework of com-munities of practice (CoP) to explore the role that the NACP has played in connecting researchers into a carbon cycle knowledge network, and in enabling them to conduct physical science that includes ideas from social science. A CoP describes the communities formed when people consistently engage in shared communication and activities toward a common passion or learning goal. We apply the CoP model by using keyword analysis of abstracts from scientific publications to analyze the research outputs of the NACP in terms of its knowledge domain. We also construct a co-authorship network from the publications of core NACP members, describe the structure and social pathways within the community. Results of the content analysis indicate that the NACP community of practice has substantially expanded its research on human and social impacts on the carbon cycle, contributing to a better understanding of how human and physical processes interact with one another. Results of the co-authorship social network analysis demonstrate that the NACP has formed a tightly connected community with many social pathways through which knowledge may flow, and that it has also expanded its network of institutions involved in carbon cycle research over the past seven years.

  20. Carbon Dynamics of Reclaimed Coal Mine Soil under Agricultural Use: A Chronosequence Study in the Dongtan Mining Area, Shandong Province, China

    Directory of Open Access Journals (Sweden)

    Jun-Feng Qu

    2017-04-01

    Full Text Available Soil organic carbon (SOC plays an essential role in the early stages of pedogenisis and ecological restoration in reclaimed mine soils. Dynamic changes in the SOC content are essential for assessing the quality of reclaimed mine soils and the effect of ecological restoration. To objectively assess the carbon dynamics of reclaimed soils, we selected the surface (0–20 cm soil of farmland under agricultural use (soybean–wheat rotation from a reclamation chronosequence (R4: 4 years of reclamation, R7: 7 years of reclamation, R10: 10 years of reclamation and R13: 13 years of reclamation in the Dongtan Mining Area, Shandong Province, China. The adjacent normal, unaffected farmland was used as a control (CK. The results showed that the SOC content gradually increased with the reclamation age until it reached 7.98 g·kg−1 for R13, which accounted for 76% of that of the CK. However, the total carbon contents of the reclaimed soils did not significantly differ from and even appeared higher than that of the CK. This is mainly because the inorganic carbon contents of the reclaimed soils ranged from 2.98 to 12.61 g·kg−1, all of which were significantly higher than the 0.87 g·kg−1 obtained for the CK. The microbial biomass carbon (MBC content and the microbial quotient significantly increased with the reclamation age of the soil, and both parameters were markedly higher for R13 than for the CK. The dissolved organic carbon (DOC content and its ratio to the SOC were significantly higher for R4–R13 than for the CK and DOC/SOC gradually decreased with the reclamation age. Both the reclamation age and the temperature had positive effects on the soil basal respiration (SBR. The SBR rate constantly increased with the reclamation age and was markedly higher at 25 °C than at 15 °C. The temperature sensitivity (Q10 of the SBR showed a clearly decreasing trend for the reclamation chronosequence, but its value remained higher for R13 than for the CK (2

  1. Fluido-Dynamic and Electromagnetic Characterization of 3D Carbon Dielectrophoresis with Finite Element Analysis

    Directory of Open Access Journals (Sweden)

    Rodrigo Martinez-Duarte

    2008-12-01

    Full Text Available The following work presents the fluido-dynamic and electromagnetic characterization of an array of 3D electrodes to be used in high throughput and high efficiency Carbon Dielectrophoresis (CarbonDEP applications such as filters, continuous particle enrichment and positioning of particle populations for analysis. CarbonDEP refers to the induction of Dielectrophoresis (DEP by carbon surfaces. The final goal is, through an initial stage of modeling and analysis, to reduce idea-to-prototype time and cost of CarbonDEP devices to be applied in the health care field. Finite Element Analysis (FEA is successfully conducted to model flow velocity and electric fields established by polarized high aspect ratio carbon cylinders, and its planar carbon connecting leads, immersed in a water-based medium. Results demonstrate correlation between a decreasing flow velocity gradient and an increasing electric field gradient toward electrodes’ surfaces which is optimal for selected CarbonDEP applications. Simulation results are experimentally validated in the proposed applications.

  2. Young's moduli of carbon materials investigated by various classical molecular dynamics schemes

    Science.gov (United States)

    Gayk, Florian; Ehrens, Julian; Heitmann, Tjark; Vorndamme, Patrick; Mrugalla, Andreas; Schnack, Jürgen

    2018-05-01

    For many applications classical carbon potentials together with classical molecular dynamics are employed to calculate structures and physical properties of such carbon-based materials where quantum mechanical methods fail either due to the excessive size, irregular structure or long-time dynamics. Although such potentials, as for instance implemented in LAMMPS, yield reasonably accurate bond lengths and angles for several carbon materials such as graphene, it is not clear how accurate they are in terms of mechanical properties such as for instance Young's moduli. We performed large-scale classical molecular dynamics investigations of three carbon-based materials using the various potentials implemented in LAMMPS as well as the EDIP potential of Marks. We show how the Young's moduli vary with classical potentials and compare to experimental results. Since classical descriptions of carbon are bound to be approximations it is not astonishing that different realizations yield differing results. One should therefore carefully check for which observables a certain potential is suited. Our aim is to contribute to such a clarification.

  3. Land-use dynamics influence estimates of carbon sequestration potential in tropical second-growth forest

    Science.gov (United States)

    Schwartz, Naomi B.; Uriarte, María; DeFries, Ruth; Gutierrez-Velez, Victor H.; Pinedo-Vasquez, Miguel A.

    2017-07-01

    Many countries have made major commitments to carbon sequestration through reforestation under the Paris Climate Agreement, and recent studies have illustrated the potential for large amounts of carbon sequestration in tropical second-growth forests. However, carbon gains in second-growth forests are threatened by non-permanence, i.e. release of carbon into the atmosphere from clearing or disturbance. The benefits of second-growth forests require long-term persistence on the landscape, but estimates of carbon potential rarely consider the spatio-temporal landscape dynamics of second-growth forests. In this study, we used remotely sensed imagery from a landscape in the Peruvian Amazon to examine patterns of second-growth forest regrowth and permanence over 28 years (1985-2013). By 2013, 44% of all forest cover in the study area was second growth and more than 50% of second-growth forest pixels were less than 5 years old. We modeled probabilities of forest regrowth and clearing as a function of landscape factors. The amount of neighboring forest and variables related to pixel position (i.e. distance to edge) were important for predicting both clearing and regrowth. Forest age was the strongest predictor of clearing probability and suggests a threshold response of clearing probability to age. Finally, we simulated future trajectories of carbon sequestration using the parameters from our models. We compared this with the amount of biomass that would accumulate under the assumption of second-growth permanence. Estimates differed by 900 000 tonnes, equivalent to over 80% of Peru’s commitment to carbon sequestration through ‘community reforestation’ under the Paris Agreement. Though the study area has more than 40 000 hectares of second-growth forest, only a small proportion is likely to accumulate significant carbon. Instead, cycles between forest and non-forest are common. Our results illustrate the importance of considering landscape dynamics when assessing

  4. Content and carbon stocks in labile and recalcitrant organic matter of the soil under crop-livestock integration in Cerrado

    Directory of Open Access Journals (Sweden)

    Itaynara Batista

    2013-12-01

    Full Text Available The study of organic matter and its compartments and their relationship with management, aims to develop strategies for increasing their levels in soils and better understanding of its dynamics. This work aimed to evaluate the fractions of soil organic matter and their carbon stocks in different soil cover system in crop-livestock integration and native Cerrado vegetation. The study was conducted at the farm Cabeceira, Maracajú – MS, sample area have the following history: soybean/corn + brachiaria/cotton/oat + pasture/soybean/formation of pasture/grazing, sampling was carried out in two seasons, dry (May/2009 and rainy (March 2010, in the dry season, crops present were: pasture, corn and cotton + brachiaria and in the rainy season were corn, cotton and soybeans, so the areas in the two evaluation periods were: pasture / maize + brachiaria / cotton, cotton / soybean area and a native of Savanna. Was performed to determine the exchangeable cations, particle size analysis, bulk density, organic carbon, particle size fractionation of organic matter of the soil with the quantification of particulate organic carbon (POC and organic carbon associated with minerals (OCam. Was also quantified the carbon stock and size fractions. The area of pasture / maize showed higher carbon stock in the particulate fraction in the topsoil. The area of cotton / soy due to its lower clay, showed the greatest loss of carbon. Because of the areas have the same history, the stock of more recalcitrant fraction was not sensitive to variations in coverage. The POC fraction appears more sensitive to different soil covers and seasonality.

  5. Calcium content of different compositions of gallstones and pathogenesis of calcium carbonate gallstones

    Directory of Open Access Journals (Sweden)

    Ji-Kuen Yu

    2013-01-01

    Conclusion: From our study, we found chronic and/or intermittent cystic duct obstructions and low-grade GB wall inflammation lead to GB epithelium hydrogen secretion dysfunction. Increased calcium ion efflux into the GB lumen combined with increased carbonate anion presence increases SI_CaCO3 from 1 to 22.4. Thus, in an alkaline milieu with pH 7.8, calcium carbonate begins to aggregate and precipitate.

  6. Modeling water, carbon, and nitrogen dynamics for two drained pine plantations under intensive management practices

    Science.gov (United States)

    Shiying Tian; Mohamed A. Youssef; R. Wayne Skaggs; Devendra Amatya; George M. Chescheir

    2012-01-01

    This paper reports results of a study to test the reliability of the DRAINMOD-FOREST model for predicting water, soil carbon (C) and nitrogen (N) dynamics in intensively managed forests. The study site, two adjacent loblolly pine (Pinus taeda L.) plantations (referred as D2 and D3), are located in the coastal plain of North Carolina, USA. Controlled drainage (with weir...

  7. Amazon forest carbon dynamics predicted by profiles of canopy leaf area and light environment

    Science.gov (United States)

    S. C. Stark; V. Leitold; J. L. Wu; M. O. Hunter; C. V. de Castilho; F. R. C. Costa; S. M. McMahon; G. G. Parker; M. Takako Shimabukuro; M. A. Lefsky; M. Keller; L. F. Alves; J. Schietti; Y. E. Shimabukuro; D. O. Brandao; T. K. Woodcock; N. Higuchi; P. B de Camargo; R. C. de Oliveira; S. R. Saleska

    2012-01-01

    Tropical forest structural variation across heterogeneous landscapes may control above-ground carbon dynamics. We tested the hypothesis that canopy structure (leaf area and light availability) – remotely estimated from LiDAR – control variation in above-ground coarse wood production (biomass growth). Using a statistical model, these factors predicted biomass growth...

  8. BACTERIOPLANKTON DYNAMICS IN PENSACOLA BAY, FL, USA: ROLE OF PHYTOPLANKTON AND DETRIAL CARBON SOURCES

    Science.gov (United States)

    Bacterioplankton Dynamics in Pensacola Bay, FL, USA: Role of Phytoplankton and Detrital Carbon Sources (Abstract). To be presented at the16th Biennial Conference of the Estuarine Research Foundation, ERF 2001: An Estuarine Odyssey, 4-8 November 2001, St. Pete Beach, FL. 1 p. (ER...

  9. Effects of harvest on carbon and nitrogen dynamics in a Pacific Northwest forest catchment

    Science.gov (United States)

    Alex Abdelnour; Robert B. McKane; Marc Stieglitz; Feifei Pan; Yiwei. Cheng

    2013-01-01

    We used a new ecohydrological model, Visualizing Ecosystems for Land Management Assessments (VELMA), to analyze the effects of forest harvest on catchment carbon and nitrogen dynamics. We applied the model to a 10 ha headwater catchment in the western Oregon Cascade Range where two major disturbance events have occurred during the past 500 years: a stand-replacing fire...

  10. Carbon respiration and nitrogen dynamics in Corsican pine litter amended with aluminium and tannins

    NARCIS (Netherlands)

    Kraal, P.; Nierop, K.G.J.; Kaal, J.; Tietema, A.

    2009-01-01

    We investigated the carbon (C) mineralisation and nitrogen (N) dynamics in litter from a Corsican pine forest in response to individual and combined additions of aluminium (M), condensed tannin (extracted from fresh Corsican pine needles) and hydrolysable tannin (commercial tannic acid). Production

  11. An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems

    Science.gov (United States)

    Yu Zhang; Changsheng Li; Carl C. Trettin; Harbin Li; Ge Sun

    2002-01-01

    Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global clinlate change. Predictions of C dynamics require us to consider interactions among many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. In this paper, we report a simulation model...

  12. Burrowing herbivores alter soil carbon and nitrogen dynamics in a semi-arid ecosystem, Argentina

    Science.gov (United States)

    Kenneth L. Clark; Lyn C. Branch; Jose L. Hierro; Diego. Villarreal

    2016-01-01

    Activities of burrowing herbivores, including movement of soil and litter and deposition of waste material, can alter the distribution of labile carbon (C) and nitrogen (N) in soil, affecting spatial patterning of nutrient dynamics in ecosystems where they are abundant. Their role in ecosystem processes in surface soil has been studied extensively, but effects of...

  13. Dynamic mechanical and dielectric properties of ethylene vinyl acetate/carbon nanotube composites

    Czech Academy of Sciences Publication Activity Database

    Valentová, H.; Ilčíková, M.; Czaniková, K.; Špitalský, Z.; Šlouf, Miroslav; Nedbal, J.; Omastová, M.

    2014-01-01

    Roč. 53, č. 3 (2014), s. 496-512 ISSN 0022-2348 R&D Projects: GA TA ČR TE01020118 Institutional support: RVO:61389013 Keywords : carbon nanotubes * dielectric relaxation spectroscopy * dynamic mechanical analysis Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.740, year: 2014

  14. Clinical significance of dynamic measurements of serum and urinary TNF-α contents in patients receiving kidney transplantation

    International Nuclear Information System (INIS)

    Wu Cuihua; Xu Jun; Zhang Daojie

    2004-01-01

    Objective: To investigate the clinical significance of dynamic measurements of serum and urinary TNF-α contents in patients following kidney transplantation. Methods: Serum and urinary TNF-α contents were measured with RIA in 45 patients receiving kidney transplantation (both before and 2 day after operation) and 45 controls. In the group of 33 patients without rejection, serial dynamic measurements of serum and urinary TNF-α content were repeatedly performed on d7, d14, d21 and d28 postoperatively. Results: Serum TNF-α levels in all the patients groups were significantly higher than those in the controls (P 0.05). Urinary TNF-α levels dropped even faster and approached control values by d7. Conclusion: Continuous monitoring of post-operative serum and urinary TNF-α contents serves as an important indicator of the function of the transplanted kidney

  15. Dynamics in carbon exchange fluxes for a grazed semi-arid savanna ecosystem in West Africa

    DEFF Research Database (Denmark)

    Tagesson, Torbern; Fensholt, Rasmus; Cropley, Ford

    2015-01-01

    The main aim of this paper is to study land-atmosphere exchange of carbon dioxide (CO2) for semi-arid savanna ecosystems of the Sahel region and its response to climatic and environmental change. A subsidiary aim is to study and quantify the seasonal dynamics in light use efficiency (ε) being a key...... variable in scaling carbon fluxes from ground observations using earth observation data. The net ecosystem exchange of carbon dioxide (NEE) 2010-2013 was measured using the eddy covariance technique at a grazed semi-arid savanna site in Senegal, West Africa. Night-time NEE was not related to temperature...... (C) MJ-1 for the dry season and 2.27gCMJ-1 for the peak of the rainy season, and its seasonal dynamics was governed by vegetation phenology, photosynthetically active radiation, soil moisture and vapor pressure deficit (VPD). The CO2 exchange fluxes were very high in comparison to other semi...

  16. Carbon dioxide and methane dynamics in Russian tundra

    DEFF Research Database (Denmark)

    Johansson, Paul Torbjörn; Kiepe, Isabell; Herbst, Mathias

    Russia. The area is situated at 67°N in the European part of northeast Russia within the Pechora basin. The Russian tundra region is an area which has recently been subject to many speculations in relation to climatic change effects and greenhouse gas (GHG) exchange but still little scientific......, and discuss possible implications of climatic change on this lowland tundra ecosystem. This study have been conducted as a part of the CARBO-North project (2006-2010), a project within the EU 6th framework programme, aiming at quantifying the carbon budget in Northern Russia across temporal and spatial scales....... evidence is available from this region. At present, there are fundamental questions to answer about the CH4 concentration in the atmosphere and its oscillations and what role CH4 exchange may have under future climatic conditions, To do so, we need to better understand the ecosystem- atmosphere...

  17. Nitrogen Deposition Effects on Soil Carbon Dynamics in Temperate Forests

    DEFF Research Database (Denmark)

    Ginzburg Ozeri, Shimon

    edges were used to study the effects of varying N deposition load on SOC stocks and fluxes as well as on the temperature sensitivity of SOM respiration. In a third study, the effects of 20 years of continuous experimental N addition (35 kg N ha-1 year-1) on soil C budget were investigated. Our general...... incubated in litterbags had significantly lower late-stage decomposition rates compared with control litter. However, potential respiration of forest floor and mineral soil was overall unaffected by the experimental N-additions. A temperature treatment of forest floor samples taken from one edge site......Soils contain the largest fraction of terrestrial carbon (C). Understanding the factors regulating the decomposition and storage of soil organic matter (SOM) is essential for predictions of the C sink strength of the terrestrial environment in the light of global change. Elevated long-term nitrogen...

  18. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    Science.gov (United States)

    Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

    2016-07-01

    The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

  19. Carbon and nutrient contents in soils from the Kings River Experimental Watersheds, Sierra Nevada Mountains, California

    Science.gov (United States)

    D.W. Johnson; C.T. Hunsaker; D.W. Glass; B.M. Rau; B.A. Roath

    2011-01-01

    Soil C and nutrient contents were estimated for eight watersheds in two sites (one high elevation, Bull, and one low elevation, Providence) in the Kings River Experimental Watersheds in the western Sierra Nevada Mountains of California. Eighty-seven quantitative pits were dug to measure soil bulk density and total rock content, while three replicate surface samples...

  20. Carbon value dynamics for France: A key driver to support mitigation pledges at country scale

    Energy Technology Data Exchange (ETDEWEB)

    Assoumou, Edi, E-mail: edi.assoumou@mines-paristech.fr [Centre for Applied Mathematics, MINES ParisTech (France); Maizi, Nadia [Centre for Applied Mathematics, MINES ParisTech (France)

    2011-07-15

    The climate agenda in France and several other countries is a complex combination of unilateral commitments with regional and international objectives. When analyzing national policies, the findings of worldwide analyses are of limited accuracy and the large aggregates on which they are built level out most local specificities and inertia. Specific assessments are hence needed. This paper quantifies the dynamic evolution of carbon values for French climate and energy policy. Its time dependency over successive periods and the effects of setting intermediate targets are evaluated using a long-term optimization model. Addressing critical issues for France, we produce consistent energy, emissions and carbon value estimates with a 5-year time step. Our results are situated above the upper range of carbon value estimates of world models with an overlapping zone. We show that the official policy guideline value is only consistent with an optimistic combination of assumptions. The central estimates are 4 times greater than the guideline carbon value for 2050 and up to 14 times greater in 2020 because of short-term inertia that are costly to move. We also find that with intermediate objectives, the carbon value's dynamic is more than a simple upward curve and that its variability is itself time dependent. - Highlights: > We quantify the dynamic evolution of carbon values for France. > We use a long-term optimization energy model from the MARKAL family. > We compute consistent energy balances for different climate and energy policy. > We show that the official guideline is only consistent with optimistic assumptions. > The dynamic is not a simple upward curve and influencing parameters are analyzed.

  1. Electrochemical Glucose Oxidation Using Glassy Carbon Electrodes Modified with Au-Ag Nanoparticles: Influence of Ag Content

    Directory of Open Access Journals (Sweden)

    Nancy Gabriela García-Morales

    2015-01-01

    Full Text Available This paper describes the application of glassy carbon modified electrodes bearing Aux-Agy nanoparticles to catalyze the electrochemical oxidation of glucose. In particular, the paper shows the influence of the Ag content on this oxidation process. A simple method was applied to prepare the nanoparticles, which were characterized by transmission electron microscopy, Ultraviolet-Visible spectroscopy, X-ray diffraction spectroscopy, and cyclic voltammetry. These nanoparticles were used to modify glassy carbon electrodes. The effectiveness of these electrodes for electrochemical glucose oxidation was evaluated. The modified glassy carbon electrodes are highly sensitive to glucose oxidation in alkaline media, which could be attributed to the presence of Aux-Agy nanoparticles on the electrode surface. The voltammetric results suggest that the glucose oxidation speed is controlled by the glucose diffusion to the electrode surface. These results also show that the catalytic activity of the electrodes depends on the Ag content of the nanoparticles. Best results were obtained for the Au80-Ag20 nanoparticles modified electrode. This electrode could be used for Gluconic acid (GA production.

  2. The effects of burning and grazing on soil carbon dynamics in managed Peruvian tropical montane grasslands

    Directory of Open Access Journals (Sweden)

    V. Oliver

    2017-12-01

    Full Text Available Montane tropical soils are a large carbon (C reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long-term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands, an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A density fractionation method was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free light fraction (LF, especially at the lower depths (10–20 and 20–30 cm. In the control soils, 20 % of the material recovered was in the free LF, which contained 30 % of the soil C content. In comparison, the burnt–grazed soil had the smallest recovery of the free LF (10 % and a significantly lower C content (14 %. The burnt soils had a much higher proportion of C in the occluded LF (12 % compared to the not-burnt soils (7 % and there was no significant difference among the treatments in the heavy fraction (F ( ∼  70 %. The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2

  3. Human impacts on soil carbon dynamics of deep-rooted Amazonian forests and effect of land use change on the carbon cycle in Amazon soils

    Science.gov (United States)

    Nepstad, Daniel; Stone, Thomas; Davidson, Eric; Trumbore, Susan E.

    1992-01-01

    The main objective of these NASA-funded projects is to improve our understanding of land-use impacts on soil carbon dynamics in the Amazon Basin. Soil contains approximately one half of tropical forest carbon stocks, yet the fate of this carbon following forest impoverishment is poorly studied. Our mechanistics approach draws on numerous techniques for measuring soil carbon outputs, inputs, and turnover time in the soils of adjacent forest and pasture ecosystems at our research site in Paragominas, state of Para, Brazil. We are scaling up from this site-specific work by analyzing Basin-wide patterns in rooting depth and rainfall seasonality, the two factors that we believe should explain much of the variation in tropical soil carbons dynamics. In this report, we summarize ongoing measurements at our Paragominas study site, progress in employing new field data to understand soil C dynamics, and some surprising results from our regional, scale-up work.

  4. Trends in nanoscale mechanics mechanics of carbon nanotubes, graphene, nanocomposites and molecular dynamics

    CERN Document Server

    2014-01-01

    This book contains a collection of the state-of-the-art reviews written by the leading researchers in the areas of nanoscale mechanics, molecular dynamics, nanoscale modeling of nanocomposites and mechanics of carbon nanotubes. No other book has reviews of the recent discoveries such as a nanoscale analog of the Pauli’s principle, i.e., effect of the spatial exclusion of electrons or the SEE effect, a new Registry Matrix Analysis for the nanoscale interfacial sliding and new data on the effective viscosity of interfacial electrons in nanoscale stiction at the interfaces. This volume is also an exceptional resource on the well tested nanoscale modeling of carbon nanotubes and nanocomposites, new nanoscale effects, unique evaluations of the effective thickness of carbon nanotubes under different loads, new data on which size of carbon nanotubes is safer and many other topics. Extensive bibliography concerning all these topics is included along with the lucid short reviews. Numerous illustrations are provided...

  5. Reconstruction of annual carbon dynamics and balance for an oligotrophic pine fen

    Energy Technology Data Exchange (ETDEWEB)

    Alm, J.; Silvola, J.; Aaltonen, H. [Joensuu Univ. (Finland). Dept. of Biology; Talanov, A.; Ikkonen, E. [Karelian Research Centre of Russian Academy of Sciences (Russian Federation). Inst. of Biology; Nykaenen, H.; Martikainen, P.J. [National Public Health Inst. Kuopio (Finland). Dept. of Environmental Microbiology

    1996-12-31

    Atmospheric carbon dioxide (CO{sub 2}) is bound by mire vegetation in photosynthesis during the growing season, and is re-released by respiration of plants, soil animals and microorganisms consuming dead organic matter. A small proportion of annual primary production may fall below the water table to anoxic conditions and thus escapes the oxidative decomposition. Also from anoxic peat, carbon is released with clear seasonal and spatial variation as methane (CH{sub 4}.). The rate of carbon accumulation in peat depends on the annual inbalance of plant production and litter decomposition. Exchange of CO{sub 2} and CH{sub 4} between peat, vegetation and the atmosphere thus reflects the dynamics of carbon flows in the ecosystem. Net ecosystem CO{sub 2} exchange (PN), total CO{sub 2} release (RTOT) and CH{sub 4} release (D) from different treeless surfaces of low-sedge Sphagnum papillosum pine fen was studied in eastern Finland. (8 refs.)

  6. Modelling carbon dynamics from urban land conversion: fundamental model of city in relation to a local carbon cycle

    Directory of Open Access Journals (Sweden)

    Schellnhuber Hans-Joachim

    2006-08-01

    Full Text Available Abstract Background The main task is to estimate the qualitative and quantitative contribution of urban territories and precisely of the process of urbanization to the Global Carbon Cycle (GCC. Note that, on the contrary to many investigations that have considered direct anthropogenic emission of CO2(urbanized territories produce ca. 96–98% of it, we are interested in more subtle, and up until the present time, weaker processes associated with the conversion of the surrounding natural ecosystems and landscapes into urban lands. Such conversion inevitably takes place when cities are sprawling and additional "natural" lands are becoming "urbanized". Results In order to fulfil this task, we first develop a fundamental model of urban space, since the type of land cover within a city makes a difference for a local carbon cycle. Hence, a city is sub-divided by built-up, „green" (parks, etc. and informal settlements (favelas fractions. Another aspect is a sub-division of the additional two regions, which makes the total number reaching eight regions, while the UN divides the world by six. Next, the basic model of the local carbon cycle for urbanized territories is built. We consider two processes: carbon emissions as a result of conversion of natural lands caused by urbanization; and the transformation of carbon flows by "urbanized" ecosystems; when carbon, accumulated by urban vegetation, is exported to the neighbouring territories. The total carbon flow in the model depends, in general, on two groups of parameters. The first includes the NPP, and the sum of living biomass and dead organic matter of ecosystems involved in the process of urbanization, and namely them we calculate here, using a new more realistic approach and taking into account the difference in regional cities' evolution. Conclusion There is also another group of parameters, dealing with the areas of urban territories, and their annual increments. A method of dynamic forecasting

  7. Dynamics of content of some minerals in teenagers’ organisms with cardiovascular system pathology and chronic tonsillitis

    Directory of Open Access Journals (Sweden)

    O. I. Smiyan

    2017-08-01

    Full Text Available The article presents basic features of the mineral metabolism in adolescent children suffering from chronic tonsillitis and secondary affection of the cardiovascular system in disease dynamics. Aim of this work was to study the dynamics of zinc, iron, potassium and magnesium in adolescents with disorders of the cardiovascular system and chronic tonsillitis. Materials and methods. 63 patients with chronic tonsillitis were examined, among them – 31 children suffered from chronic tonsillitis without pathology of the cardiovascular system (I group, 32 – were patients with disorders of the cardiovascular system on the background of chronic tonsillitis (II group. Determination of concentration of trace elements of iron, zinc, potassium, magnesium in blood serum was measured by atomic absorption spectrophotometry. Results. The content of trace elements zinc, iron, minerals potassium and magnesium was analyzed. It breaches of macro- and trace element composition in the blood serum of children with chronic tonsillitis in the form of lower concentrations of iron and zinc in patients with damage to the cardiovascular system, and in patients without cardiac disease. It should be noted that children with tonsillogenyc cardiac lesions had a significant decrease in the level of macro-magnesium during hospitalization compared to children without cardiovascular pathology. After treatment, levels of such elements as iron, zinc, magnesium were not normalized. Moreover, significant changes were observed in patients with heart disease on the background of chronic tonsillitis. After the standard treatment, concentrations of iron and zinc in both groups, and magnesium in children from the second group remained at a low level, compaed with children without cardiac disease. Conclusion. The analysis of micro and macro elements in the serum of children with chronic tonsillitis, showed a significant decrease of iron and zinc concentration in the first days of

  8. Biometrics in Laminaria digitata: A useful tool to assess biomass, carbon and nitrogen contents

    Science.gov (United States)

    Gevaert, F.; Janquin, M.-A.; Davoult, D.

    2008-10-01

    Sporophytes of Laminaria digitata (Hudson) J.V. Lamouroux (Ochrophyta: Phaeophyceae) were haphazardly collected seasonally from September 1996 to March 1999 in the rocky shore of the eastern English Channel in order to conduct a biometrical study relating fresh weight (FW), dry weight (DW), carbon and nitrogen masses to the length of the thalli. The aim was to create a tool that allows estimation of the weight of the algae by a simple, rapid and non destructive morphological measurement of the total length of the sporophyte. The highly significant and lasting relationships obtained appeared very useful to express the standing biomass of L. digitata in terms of carbon or nitrogen. Variations in tissue carbon (C) and nitrogen (N) were examined over a complete seasonal cycle and showed clear patterns, ranged from 26.8 to 33.1% of the total dry weight for carbon and 1.87 to 3.20% for nitrogen. The seasonal variations in C/N ratio corresponded to a winter nitrogen uptake from the medium and to high spring carbon assimilation due to photosynthesis.

  9. The global distribution of leaf chlorophyll content and seasonal controls on carbon uptake

    Science.gov (United States)

    Croft, H.; Chen, J. M.; Luo, X.; Bartlett, P. A.; Staebler, R. M.; He, L.; Mo, G.; Luo, S.; Simic, A.; Arabian, J.; He, Y.; Zhang, Y.; Beringer, J.; Hutley, L. B.; Noland, T. L.; Arellano, P.; Stahl, C.; Homolová, L.; Bonal, D.; Malenovský, Z.; Yi, Q.; Amiri, R.

    2017-12-01

    Leaf chlorophyll (ChlLeaf) is crucial to biosphere-atmosphere exchanges of carbon and water, and the functioning of terrestrial ecosystems. Improving the accuracy of modelled photosynthetic carbon uptake is a central priority for understanding ecosystem response to a changing climate. A source of uncertainty within gross primary productivity (GPP) estimates is the failure to explicitly consider seasonal controls on leaf photosynthetic potential. Whilst the inclusion of ChlLeafinto carbon models has shown potential to provide a physiological constraint, progress has been hampered by the absence of a spatially-gridded, global chlorophyll product. Here, we present the first spatially-continuous, global view of terrestrial ChlLeaf, at weekly intervals. Satellite-derived ChlLeaf was modelled using a physically-based radiative transfer modelling approach, with a two stage model inversion method. 4-Scale and SAIL canopy models were first used to model leaf-level reflectance from ENIVSAT MERIS 300m satellite data. The PROSPECT leaf model was then used to derive ChlLeaf from the modelled leaf reflectance. This algorithm was validated using measured ChlLeaf data from 248 measurements within 26 field locations, covering six plant functional types (PFTs). Modelled results show very good relationships with measured data, particularly for deciduous broadleaf forests (R2 = 0.67; ppigment status in modelling photosynthetic carbon uptake. We anticipate that the global ChlLeaf product will make an important step towards improving the accuracy of global carbon budgets.

  10. Morphology, Microstructure, and Hydrogen Content of Carbon Nanostructures Obtained by PECVD at Various Temperatures

    Directory of Open Access Journals (Sweden)

    M. Acosta Gentoiu

    2017-01-01

    Full Text Available Carbon nanostructures were obtained by acetylene injection into an argon plasma jet in the presence of hydrogen. The samples were synthesized in similar conditions, except that the substrate deposition temperatures TD were varied, ranging from 473 to 973 K. A strong dependence of morphology, structure, and graphitization upon TD was found. We obtained vertical aligned carbon nanotubes (VA-CNTs at low temperatures as 473 K, amorphous carbon nanoparticles (CNPs at temperatures from about 573 to 673 K, and carbon nanowalls (CNWs at high temperatures from 773 to 973 K. Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, elastic recoil detection analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to substantiate the differences in these material types. It is known that hydrogen concentration modifies strongly the properties of the materials. Different concentrations of hydrogen-bonded carbon could be identified in amorphous CNP, VA-CNT, and CNW. Also, the H : C ratios along depth were determined for the obtained materials.

  11. Nexus Thinking on Soil Carbon Dynamics and Soil Health

    Science.gov (United States)

    Lal, R.

    2016-12-01

    Anthropocene is driven by global population of 7.5 billion in 2016, increasing annually by 80 million and projected to be 9.7 billion by 2050. The ecological impact (I=PAT, where P is population, A is affluence, and T is technology) of the population is similar to that of a geological force. Thus, humanity's impact is driven by demands for food, water, energy, and services derived from soil. Soil health, its capacity to function as a vital living system, is determined by quantity and quality of soil organic carbon (SOC) in the root zone ( 50cm). Maintenance of SOC at above the threshold level (1.5 to 2.0% by weight in the root zone) is critical to performing numerous ecosystem services for human wellbeing and nature conservancy. These services and functions strongly depend on nexus or inter-connectivity of biological processes within the pedosphere. The nexus is strongly governed by coupled biogeochemical cycling of water (H2O), carbon (C), nitrogen (N), phosphorus (P) and sulfur (S). Further, it is the nexus between pedological and biological processes that renews and purifies water by denaturing and filtering pollutants; circulates C among biotic and abiotic pools in close association with other elements (N, P, S); provides habitat and energy source for soil biota (macro, meso, and micro flora and fauna), facilitates exchanges of gases between soil and the atmosphere and moderates climate, and creates favorable rhizospheric processes that promote plant growth and enhance net primary productivity. Soil health, governed by SOC quality and quantity, determines the provisioning of numerous ecosystem services and the importance of nexus thinking is highlighted by the truism that "health of soil, plants, animals, human and ecosystem is one and indivisible." The sequestration of SOC depends on land use and soil management strategies which create a positive C budget. Thus, input of biomass-C into the soil must exceed the losses by erosion, mineralization and leaching

  12. Molecular Dynamics Simulation Study of Carbon Dioxide, Methane, and Their Mixture in the Presence of Brine

    KAUST Repository

    Yang, Yafan

    2017-10-03

    We perform molecular dynamics simulation study of CO2, methane, and their mixture in the presence of brine over a broad range of temperature (311–473 K), pressure (up to about 100 MPa), and NaCl concentration (up to about 14 wt %). The general decrease in the interfacial tension (IFT) values of the CH4–brine system with pressure and temperature is similar to that obtained for the corresponding CH4–water system. The IFT of methane and brine is a linearly increasing function of salt concentration, and the resulting slopes are dependent on the pressure. A similar behavior as methane is observed for such systems containing CO2 and CO2–CH4 mixture. The IFT of CO2 and brine increases linearly with increasing salt content; however, the resulting slopes are independent of pressure. The simulations show that the presence of CO2 decreases the IFT values of the CH4–water and CH4–brine systems, but the degree of reduction depends on the amount of CO2 in each sample, which is consistent with experimental evidence. These IFT values show a linear correlation with the amount of CO2, and the resulting slopes are dependent on the temperature and pressure. Furthermore, our results for the mole fractions of the different species in the CO2–CH4–water system at 323 K and 9 MPa are in agreement with those of experiments. The mole fractions of methane and CO2 in the water-rich phase decrease with increasing salt concentration, whereas that of H2O in the methane- or CO2-rich phases remains almost unaffected in all of the studied cases. Our results could be useful because of the importance of carbon dioxide sequestration and shale gas production.

  13. Modeling Coupled Landscape Evolution and Soil Organic Carbon Dynamics in Intensively Management Landscapes

    Science.gov (United States)

    Yan, Q.; Kumar, P.

    2017-12-01

    Soil is the largest reservoir of carbon in the biosphere but in agricultural areas it is going through rapid erosion due disturbance arising from crop harvest, tillage, and tile drainage. Identifying whether the production of soil organic carbon (SOC) from the crops can compensate for the loss due to erosion is critical to ensure our food security and adapt to climate change. In the U.S. Midwest where large areas of land are intensively managed for agriculture practices, predicting soil quantity and quality are critical for maintaining crop yield and other Critical Zone services. This work focuses on modeling the coupled landscape evolutions soil organic carbon dynamics in agricultural fields. It couples landscape evolution, surface water runoff, organic matter transformation, and soil moisture dynamics to understand organic carbon gain and loss due to natural forcing and farming practices, such as fertilizer application and tillage. A distinctive feature of the model is the coupling of surface ad subsurface processes that predicts both surficial changes and transport along with the vertical transport and dynamics. Our results show that landscape evolution and farming practices play dominant roles in soil organic carbon (SOC) dynamics both above- and below-ground. Contrary to the common assumption that a vertical profile of SOC concentration decreases exponentially with depth, we find that in many situations SOC concentration below-ground could be higher than that at the surface. Tillage plays a complex role in organic matter dynamics. On one hand, tillage would accelerate the erosion rate, on the other hand, it would improve carbon storage by burying surface SOC into below ground. Our model consistently reproduces the observed above- and below-ground patterns of SOC in the field sites of Intensively Managed Landscapes Critical Zone Observatory (IMLCZO). This model bridges the gaps between the landscape evolution, below- and above-ground hydrologic cycle, and

  14. Stored Carbon Dynamics are Controlled by a Combination of Evolutionary, Physiological, and Ecological Pressures

    Science.gov (United States)

    Aubrey, D. P.; Mims, J. T.; Oswald, S. W.; Teskey, R. O.; Mitchell, R. J.

    2016-12-01

    Allocation of assimilated carbon to storage provides a critical carbohydrate buffer when metabolic demands exceed current photosynthetic supply; however, our process-level understanding of controls on carbon storage pools and fluxes remains relatively poor. Recent studies have shifted the paradigm from the concept that stored carbon pools are a sink of low priority that accumulate passively when photosynthetic inputs exceed demand toward the concept that these pools are active sinks of high priority. It follows that allocation toward storage—at the expense of growth—is a trait that would be under selective pressure since species that allocate toward storage should be more resilient to disturbance. Using fire-dependent longleaf pine in a series of manipulative and observational studies, we explore how stored carbon dynamics are controlled by a combination of evolutionary, physiological, and ecological pressures. Our manipulative studies revealed large stored carbon pools in roots that maintained belowground metabolism for a year after current photosynthetic supply was restricted. Likewise, the concentration of stored carbon in the smallest, most metabolically active roots was not influenced until nearly one year later. Our observational studies indicated that stored carbon pools differ among closely related species with overlapping natural distributions, but evolutionary histories of different disturbance frequencies and thus, different selective pressures on carbon storage. Our comparisons of stored carbon pools between longleaf trees growing under xeric or mesic soil moisture regimes indicated that allocation toward storage exhibits plasticity through space and time in response to both short- and long-term variations in resource availability. We expect a continuum of responses to disturbances related to ecological niche and evolutionary adaptation that influence the availability of carbohydrates for metabolic demands. We also expect a continuum in stored

  15. Managed Scots pine forests in Central Spain: First results on soil carbon dynamics

    Science.gov (United States)

    Díaz-Pinés, Eugenio; Rubio, Agustín.; Vicente, Pablo; Montes, Fernando; Cañellas, Isabel

    2010-05-01

    Scots pine forests in Sierra de Guadarrama (Central Spain) cover thousands of hectares, and constitute the southern-western limit of the Scots pine's world distribution. It is worth noting that site and climate characteristics of Spanish Scots pine stands greatly vary from Scots pine areas in Central Europe. Specific forest management strategies may help to increase soil carbon sink strength, since further afforestation is constrained in mountain areas in Central Spain. In order to find and develop the most appropriate forest measures to optimize soil carbon sequestration, deeper understanding of forest management effects on soil carbon stocks and fluxes is needed. It is specially desirable in Mediterranean environments, where there is a important lack of information. Further relationships between soil carbon dynamics and different cutting regimes and length of rotation period would improve this understanding. Results found up to now are contradictory, and clearly vary depending on site and climatic conditions. Here, we present preliminary results focused on soil carbon dynamics from two managed Scots pine forests in Central Spain (Valsaín and Navafría), which differ in the cutting-regime intensity (Valsaín: group shelterwood; Navafría uniform shelterwood) and their rotation period length (Valsaín: 120 years; Navafría: 100 years). In each forest, we established one chronosequence, covering the whole stand ages along the rotation period (20 years interval). We estimated soil carbon stocks in the first 20 cm of the mineral soil, in order to detect long-term carbon sequestration, rather than carbon accumulation in the forest floor, which can be directly related to recent harvesting operations. In addition, we present our first results of soil respiration rates, covering the period May-December 2009.

  16. ASTECv2/MEDICIS computer code investigation of influence of water content and carbon dioxide content in the concrete on the kinetics of molten corium–concrete interaction

    International Nuclear Information System (INIS)

    Gencheva, R.; Stefanova, A.; Groudev, P.

    2013-01-01

    Highlights: • We model an ex-vessel MCCI severe accident with ASTECv2/MEDICIS computer code. • Represented NPP is VVER1000 nuclear power plant. • MCCI analyses concern different H 2 O and CO 2 contents in the reactor pit concrete. • Analyses demonstrate significant influence of H 2 O and CO 2 on the ablation kinetics. • Analyses demonstrate significant influence of H 2 O and CO 2 on the melt-through time. - Abstract: This investigation was done in the frame of SARNET2 European Network of Excellence on Severe Accidents project (6-th Framework Program of the European Commission), joint program activity JPA-2, WP6-4. ASTECv2/MEDICIS computer code was used to simulate the ex-vessel corium–concrete interaction cases. This code, jointly developed by the IRSN (France) and GRS (Germany) for simulation of severe accidents, is now considered as the European reference simulation tool. As a reference nuclear power plant for these ASTECv2/MEDICIS calculations the VVER1000 reactor type was used. The main goal of this paper is to investigate the influence of water content (H 2 O) and the content of carbon dioxide (CO 2 ) in the concrete on the kinetics of molten corium–concrete interaction (MCCI) between the molten corium and reactor basemat concrete. In this paper, there are investigated different concentrations of H 2 O and CO 2 in the concrete interacting with the corium poured after reactor vessel failure during a severe accident in VVER1000 nuclear power plant

  17. A molecular dynamics simulation study for the mechanical properties of different types of carbon nanotubes

    Science.gov (United States)

    Talukdar, Keka; Mitra, Apurba Krishna

    2012-09-01

    Carbon nanotubes have caught tremendous attention of the researchers during the last decade due to their excellent mechanical, electrical, optical and thermal properties. The exploitation of these fibers as reinforcing agents in making strong fiber composites has been a primary research topic in the recent investigations on composite materials. Although the theoretical results are rather optimistic, the goal of achieving high strength of the carbon nanotube composites is still not satisfactorily realized. We report here a comparative study of the mechanical properties of single-walled, multi-walled and bundle of single-walled carbon nanotubes. Their mechanical behavior is investigated by molecular dynamics simulation, considering Brenner's second generation reactive empirical bond order interatomic potential between the carbon atoms making a tube. For a long range interaction, we have defined a weak van der Waals force which acts between different layers of a multi-walled tube or between different tubes of a bundle. Samples of three isolated armchair single-wall carbon nanotubes of different diameters, a multi-wall armchair carbon nanotube and finally a bundle of three armchair single-walled nanotubes of same diameter are taken. Their fracture pattern and buckling behavior are modeled and compared. Significant changes are observed in the mechanical properties of the samples of different types of carbon nanotubes which arise due to the interaction between the shells of a multi-walled tube or the tubes in a bundle.

  18. [Design of dynamic simulation system for carbon cycle in forest ecosystem].

    Science.gov (United States)

    Zhu, Jian-Gang; Yu, Xin-Xiao; Zhang, Zhen-Ming; Wang, Chen; Gan, Jing; Wang, Xiao-Ping; Li, Jin-Hai

    2009-11-01

    Modeling techniques are indispensable for the researches on the carbon cycle of forest ecosystem. In this paper, a new general simulation system FORCASS (FORest CArbon Simulation System) was designed and developed under Simulink environment, with the objectives of modeling the carbon cycle dynamics of forest ecosystems. A comprehensive analysis on the framework, design solution, and development process showed that the FORCASS was feasible. This simulation system had the characteristics of 1) it divided the carbon storage in forest ecosystem into four compartments, i.e., vegetation, litter, soil, and animal, and took into account the carbon flows between the compartments, possessing high mechanism and easily to be comprehended, 2) it was a process-based system, taking the Richards growth function of vegetation component biomass carbon storage as the input to solve difference equations, and was easily to export the outputs such as net primary productivity (NPP) and net ecosystem productivity (NEP) at different stand ages, and 3) it had the explicit expansibility because it was developed based on a general framework for carbon cycle patterns.

  19. The Effect Of Carbon Concentration On The Retained Austenite Content And The Mechanical Properties Of TRIP Steel Wire Rod Obtained From The Stelmor Controlled Cooling Line

    Directory of Open Access Journals (Sweden)

    Muskalski Z.

    2015-09-01

    Full Text Available The austenite content of the multiphase TRIP-structure steels depends, inter alia, on the carbon concentration and the properly selected parameters of the two-stage heat treatment.

  20. Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode

    OpenAIRE

    Amare, Meareg; Aklog, Senait

    2017-01-01

    Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6 ? 10?6 to 100 ? 10?6?mol?L?1 with determination coefficient and method detection limit (LoD = 3?s/slope) of 0....

  1. Immediate analysis of the oil content of seeds by carbon-13 nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Leal, K.Z.; Costa, V.E.U.; Seidl, P.R.; Campos, M.P.A.; Colnago, L.A.

    1981-01-01

    The carbon 13 nuclear magnetic resonance (CMR) spectra of a series of Brazilian oilseeds was registered. The main constituents of the oils are identified and signals for each carbon atom are assigned. Chemical shifts are estimated for the free fatty acids and compared to those observed from the seeds, with good results. Besides being non-destructive, the RMC method proves to be fast and is useful in the determination of the principal components of the oil fraction of different types of seeds. (Author) [pt

  2. Where Does The Carbon Go? Carbon Dynamics And Fire of a North Australian Tropical Savanna

    Science.gov (United States)

    Hutley, L. B.; Beringer, J.; Tapper, N. J.; Cernusak, L.

    2007-12-01

    The role of fire as one of the primary natural carbon cycling mechanisms is a key issue in considering global change feedbacks. In north Australia, the dominant ecosystem is tropical savanna and for mesic savannas within 100 km of the northern coastline, fire, storms and cyclones all impact carbon stocks. Fire is the most frequent disturbance agent as fires burn with a near annual frequency in these systems. We aimed to determine the annual net ecosystem productivity (NEP) from these savannas and the impact of fire on productivity. We established a long-term eddy covariance flux tower at Howard Springs, Australia and present here 5 years of data from 2001 to 2005. Fire has direct impacts through emissions but also has indirect effects through the loss of productivity due to reduced functional leaf area index and the carbon costs of rebuilding the canopy. The impact of fire on the canopy latent energy exchange was evident for 40 days while the canopy was rebuilt; however, the carbon balance took approximately 70 days to recover. The annual fire free NEP at Howard Springs was estimated at -4.3 t C ha-1 y-1 with a range of -3.5 to -5.1 t C ha-1 y-1 across years. We calculated the average annual indirect fire effect as 0.7 t C ha-1 y-1 using a neural network model approach and estimated average emissions of fine and coarse fuels as 1.6 t C ha-1 y-1. This allowed us to calculate a net biome production of 2.0 t C ha-1 y-1. We then partitioned this remaining sink and suggest that most of this can be accounted for by woody increment (1.2 t C ha-1 y-1) and shrub encroachment (0.5 t C ha-1 y-1). Given the consistent sink at this site, even under an almost annual fire regime, there may be management options to increase carbon sequestration by reducing fire frequency.

  3. Plasma ATP concentration and venous oxygen content in the forearm during dynamic handgrip exercise

    Directory of Open Access Journals (Sweden)

    Askew Christopher D

    2009-12-01

    Full Text Available Abstract Background It has been proposed that adenosine triphosphate (ATP released from red blood cells (RBCs may contribute to the tight coupling between blood flow and oxygen demand in contracting skeletal muscle. To determine whether ATP may contribute to the vasodilatory response to exercise in the forearm, we measured arterialised and venous plasma ATP concentration and venous oxygen content in 10 healthy young males at rest, and at 30 and 180 seconds during dynamic handgrip exercise at 45% of maximum voluntary contraction (MVC. Results Venous plasma ATP concentration was elevated above rest after 30 seconds of exercise (P Conclusions Collectively these results indicate that ATP in the plasma originated from the muscle microcirculation, and are consistent with the notion that deoxygenation of the blood perfusing the muscle acts as a stimulus for ATP release. That ATP concentration was elevated just 30 seconds after the onset of exercise also suggests that ATP may be a contributing factor to the blood flow response in the transition from rest to steady state exercise.

  4. Effect of carbonate content on the mechanical behaviour of clay fault-gouges

    Science.gov (United States)

    Bakker, Elisenda; Niemeijer, André; Hangx, Suzanne; Spiers, Chris

    2015-04-01

    Carbon dioxide capture and storage (CCS) in depleted oil and gas reservoirs is considered to be the most promising technology to achieve large-scale reduction in anthropogenic emissions. In order to retain the stored CO2 from the atmosphere for the very long-term, i.e. on timescales of the order of 103-104 years, it is essential to maintain the integrity of the caprock, and more specifically of any faults penetrating the seal. When selecting suitable CO2-storage reservoirs, pre-exisiting faults within the caprock require close attention, as changes in the stress state resulting from CO2-injection may induce fault slip motion which might cause leakage. Little is known about the effect of fluid-rock interactions on the mineral composition, mechanical properties and the integrity and sealing capacity of the caprock. Previous studies on the effect of mineral composition on the frictional properties of fault gouges have shown that friction is controlled by the dominant phase unless there is a frictionally weak, through-going fabric. However, the effect on stability is less clear. Since long-term CO2-exposure might cause chemical reactions, potentially resulting in the dissolution or precipitation of carbonate minerals, a change in mineralogy could affect the mechanical stability of a caprock significantly. Calcite, for example, is known to be prone to micro-seismicity and shows a transition from velocity-strengthening to velocity-weakening behaviour around 100-150°C. Therefore, we investigated the effect of varying clay:carbonate ratios on fault friction behaviour, fault reactivation potential and slip stability, i.e. seismic vs. aseismic behaviour. Three types of simulated fault gouges were used: i) carbonate-free, natural clay-rich caprock samples, consisting of predominantly phyllosilicates (~80%) and quartz ~20%), ii) pure calcite, and iii) mixtures of carbonate-free clay-rich caprock and pure calcite, with predetermined clay:carbonate ratios. For the natural clay

  5. Compatible Models of Carbon Content of Individual Trees on a Cunninghamia lanceolata Plantation in Fujian Province, China.

    Directory of Open Access Journals (Sweden)

    Lin Zhuo

    Full Text Available We tried to establish compatible carbon content models of individual trees for a Chinese fir (Cunninghamia lanceolata (Lamb. Hook. plantation from Fujian province in southeast China. In general, compatibility requires that the sum of components equal the whole tree, meaning that the sum of percentages calculated from component equations should equal 100%. Thus, we used multiple approaches to simulate carbon content in boles, branches, foliage leaves, roots and the whole individual trees. The approaches included (i single optimal fitting (SOF, (ii nonlinear adjustment in proportion (NAP and (iii nonlinear seemingly unrelated regression (NSUR. These approaches were used in combination with variables relating diameter at breast height (D and tree height (H, such as D, D2H, DH and D&H (where D&H means two separate variables in bivariate model. Power, exponential and polynomial functions were tested as well as a new general function model was proposed by this study. Weighted least squares regression models were employed to eliminate heteroscedasticity. Model performances were evaluated by using mean residuals, residual variance, mean square error and the determination coefficient. The results indicated that models with two dimensional variables (DH, D2H and D&H were always superior to those with a single variable (D. The D&H variable combination was found to be the most useful predictor. Of all the approaches, SOF could establish a single optimal model separately, but there were deviations in estimating results due to existing incompatibilities, while NAP and NSUR could ensure predictions compatibility. Simultaneously, we found that the new general model had better accuracy than others. In conclusion, we recommend that the new general model be used to estimate carbon content for Chinese fir and considered for other vegetation types as well.

  6. Charge/discharge characteristics of sulfurized polyacrylonitrile composite with different sulfur content in carbonate based electrolyte for lithium batteries

    International Nuclear Information System (INIS)

    Wang Li; He Xiangming; Li Jianjun; Chen Min; Gao Jian; Jiang Changyin

    2012-01-01

    Highlights: ► The sulfurized polyacrylonitrile composite shows good performance. ► Stable cycling capacity over 700 mAh g −1 of the composite. ► Close to 100% utilization of elemental sulfur. ► Capacity retention over 97% after 80 cycles. ► Average capacity degradation rate less than 0.03% per cycle. - Abstract: The charge/discharge characteristics of sulfurized polyacrylonitrile composite (SPAN) cathodes with different sulfur content in conventional carbonate based electrolyte for rechargeable lithium batteries have been investigated. The good performance of SPAN in the carbonate based electrolyte indicates a material difference between SPAN and elemental sulfur/carbon composite materials. The SPAN with sulfur contents of 33.7%, 42.0% and 46.3% are prepared by control of heating time. The SPAN with sulfur content of 42.0% shows the best electrochemical performance, it can deliver stable cycling capacity over 700 mAh g −1 , and keep capacity retention over 97% after 80 cycles in the electrolyte of 1 M LiPF 6 /EC + DEC. The average capacity degradation rate is less than 0.03% per cycle excluding the first discharge capacity. Prototype 100 mAh Li/SPAN cell is assembled, showing energy density of 437 Wh kg −1 excluding the weight of package and capacity retention of 90.4% after 30 cycles at 100% depth of discharge. This study demonstrates that the sulfurized polyacrylonitrile composite in the electrolyte of 1 M LiPF 6 /EC + DEC is a promising battery chemistry, which materials are abundant, of low cost and easily available, to fabricate Li/SPAN batteries, paving an alternative avenue to develop high performance lithium batteries for energy storage and vehicular application.

  7. Impacts of Invasive Pests on Forest Carbon and Nitrogen Dynamics

    Science.gov (United States)

    Lovett, G. M.; Crowley, K. F.

    2014-12-01

    Forests of the U.S. have been subject to repeated invasions of destructive insects and diseases imported from other continents. Like other disturbances, these pests can produce short-term ecosystem effects due to tree mortality, but unlike other disturbances, they often target individual species and therefore can cause long-term species change in the forest. Because tree species vary in their influence on carbon (C) and nitrogen (N) cycles, pest-induced species change can radically alter the biogeochemistry of a forest. In this paper we use both data and modeling to examine how pest-induced species change may alter the C and N cycling in forests of the eastern U.S. We describe a new forest ecosystem model that distinguishes individual tree species and allows species composition to shift over the course of the model run. Results indicate that the mortality of eastern hemlock (Tsuga canadensis) by hemlock woolly adelgid and its replacement by faster-growing species such as black birch (Betula lenta) will reduce forest floor C stocks but increase productivity as the birch become established. Decline of American beech (Fagus grandifolia) from beech bark disease and its replacement by sugar maple (Acer saccharum) is likely to decrease soil C storage and increase N leaching from the ecosystem. Responses to other invasive pests will also be discussed. The magnitude of these species-specific effects on C and N cycling is in many cases larger than direct effects expected from changes in climate and atmospheric N deposition, indicating that species change should be included in models that predict forest ecosystem function under future environmental conditions.

  8. Convergence of carbon dioxide emissions in Chinese cities: A continuous dynamic distribution approach

    International Nuclear Information System (INIS)

    Wu, Jianxin; Wu, Yanrui; Guo, Xiumei; Cheong, Tsun Se

    2016-01-01

    This paper investigates the spatial dynamics of per capita carbon dioxide (CO 2 ) emissions in China. The analyses are conducted by employing a continuous dynamic distribution approach and panel data of 286 cities at the prefecture and above-prefecture level. The results show that per capita CO 2 emissions tend to converge during the sample period of 2002–2011. However, multimodality is found in the ergodic distribution of the full sample. It is also found that there is more persistence in cities with low per capita CO 2 emissions, and more mobility in cities with high per capita CO 2 emissions. The analyses also show that the dynamics of per capita CO 2 emissions are significantly different among various geographical, income and environmental policy groups. The conditional distribution analyses indicate that multimodality cannot be explained independently by any one of the two factors, namely geographical location or income level. The findings in this study may have important policy implications for CO 2 abatement in China. - Highlights: •Spatial dynamics of per capita carbon dioxide (CO 2 ) emissions in 286 Chinese cities. •A continuous dynamic distribution approach and panel data. •Multimodality is found in the ergodic distribution of the full sample. •Significantly different dynamics among various city groups.

  9. Seasonal dynamics of permafrost carbon emissions: A passive, quasi-continuous 14CO2 sampler

    Science.gov (United States)

    Pedron, S.; Xu, X.; Walker, J. C.; Welker, J. M.; Klein, E. S.; Euskirchen, E. S.; Czimczik, C. I.

    2017-12-01

    Millennia of carbon (C) fixation by tundra vegetation, coupled with low rates of C mineralization by soil microorganisms and preservation in permafrost, have allowed Arctic soils to accumulate vast quantities of organic C (1672 Pg C total). Today, the Arctic is rapidly warming (0.48oC decade-1) and widespread degradation of permafrost may subject permafrost C to microbial mineralization and fluxes to the atmosphere, accelerating climate change. Loss of permafrost C can be quantified in situ by measuring the radiocarbon (14C) content of soil and ecosystem respiration, because permafrost C is older (depleted in 14C) than current plant products and soil C cycling operates on timescales of years to centuries. Here, we use 14C analysis of CO2 respired from graminoid tundra in Arctic Alaska to 1) apportion how plant and microbial respiration contribute to ecosystem respiration in spring, summer, and fall, and 2) elucidate the C sources of microbial respiration throughout the year. We used a novel, passive sampling system, capable of trapping diffusive CO2 throughout the active layer of tussock sedge tundra (n=4, from mineral soil to air) over periods of 2 days to 3 weeks in June 2017. CO2 was collected into various sizes of canisters, ranging from 0.5-32 L, and analyzed for its 14C content at UC Irvine's KCCAMS laboratory. To evaluate the system's efficiency, and quantify the temporal and spatial variability of ecosystem respiration sources, we co-deployed 3 Vaisala Carbocap [CO2] and temperature probes, and traditional chambers (n=6) and gas wells (n=10) for sampling of ecosystem- and soil-respired 14CO2 over 15 min-24 hours. A comparison of traditional methods with our new sampler indicates that the system accurately sampled the expected [CO2] depth gradient. The CO2 sampling rate was positively correlated to soil [CO2] (R2=0.963), equivalent to 1.4*10-3±1.6*10-3 mg C/L/month/ppm (n=8). Gas well and probe concentrations were of the same order of magnitude on the same

  10. Reindeer grazing in subarctic boreal forest - influences on the soil carbon dynamics

    Science.gov (United States)

    Koster, Kajar; Berninger, Frank; Köster, Egle; Pumpanen, Jukka

    2015-04-01

    Reindeer (Rangifer tarandus L.) are the most important large mammalian herbivores in the northern ecosystems , which have many effects on plant diversity, soil nutrient cycling and soil organic matter decomposition. Changes caused by reindeer in vegetation have indirect effects on physical features of the soil e.g. soil microclimate, root biomass and also on soil C dynamics. Earlier, the role of reindeer grazing in ground vegetation dynamics and in soil carbon (C) dynamics has been mostly investigated in open tundra heaths. The objectives of this study were to examine if and how the reindeer grazing (and the possible temperature changes in soil caused by heavy grazing) is affecting the soil C dynamics (CO2 efflux from the soil, C storage in soil, microbial biomass in the soil). In a field experiment in Finnish Lapland, in Värriö Strict Nature Reserve (67° 46' N, 29° 35' E) we have assessed the changes occurring in above- and belowground biomasses, and soil C dynamics (CO2 efflux, soil C content, soil microbial biomass C) among areas grazed and ungrazed by reindeer. Our study areas are located in the northern boreal subarctic coniferous forest at the zone of the last intact forest landscapes in Fennoscandia, where large areas of relatively undisturbed subarctic Scots pine (Pinus sylvestris L.) forests can still be found. The sample plots located in the Värriö Strict Nature Reserve (10 sample plots in total established in year 2013) are situated along the borderline between Finland and Russia, where the ungrazed area was excluded from the reindeer grazing already in 1918, to prevent the Finnish reindeer from going to the Russian side and there are not many reindeer on Russian side of the area. To characterize the stands we have established circular sample plots on areas with a radius of 11.28 m, where different tree characteristics were measured (diameter at 1.3 m, height, height of a tree, crown height, crown diameter, stand age, etc.). On every sample plot

  11. Vegetation controls on carbon, water, and energy dynamics with implications for permafrost thaw

    Science.gov (United States)

    Loranty, M. M.; Berner, L. T.

    2013-12-01

    Changes in ecosystem structure and function characterized by climate induced alterations in vegetation communities will exert strong influence on the fate of permafrost carbon via controls on surface energy partitioning. These controls are likely to occur both directly through changes in ground heat fluxes and indirectly through climate feedbacks associated with changes in albedo and evapotranspiration. Larch forests of northeastern Siberia constitute the largest ecosystem type underlain by continuous permafrost and therefore warrant considerable attention in this regard. Here we report observations of carbon, water, and energy fluxes made using the static chamber method for three understory vegetation communities in a mature northeastern Siberian larch forest. We find that carbon and water fluxes tend to increase in magnitude with NDVI, with carbon fluxes exhibiting net uptake during the growing season in vegetation communities dominated by deciduous shrubs. Communities characterized by a combination of evergreen and deciduous shrubs and mosses, or by lichens we find lower water fluxes and carbon neutrality. In the case of lichens, water fluxes are low while surface and soil temperatures as well as thaw depths are relatively high. These results illustrate the potential for vegetation to influence permafrost dynamics through controls on surface energy partitioning. While our results stem from a relatively small spatial scale, they are a relevant analog for large-scale shifts in arctic and boreal vegetation communities as well as changes in successional dynamics associated with changing disturbance regimes, particularly fire.

  12. Theoretical studies of zirconium and carbon clusters with molecular dynamics simulations

    International Nuclear Information System (INIS)

    Zhang, B.

    1993-08-01

    In this dissertation, we will present a systematic study of structures of fullerenes ranging from C 20 to C 100 by introducing a novel scheme. Using our new scheme, we not only reproduce all known fullerene structures but also successfully predicted several other fullerene structures which were confirmed by experiments. By utilizing the tight-binding molecular-dynamic (TBMD) simulation, we also studied the dynamical behavior of fullerenes: Vibrations, thermal disintegration of individual clusters as well as collisions between fullerenes. If the beauty of carbon fullerene is not enough, people found that carbon can also form tubules and even speculated that they can form three-dimensional graphite-like networks. By extending our fullerene structure searching scheme, we performed a search for the ground-state structure of three dimensional carbon network. We found the most stable structure people ever proposed for simple cubic based networks. From the difference of this new form of carbon and graphite in the electronic and vibrational properties, we propose an experimental probe to identify these novel three-dimensional carbon networks

  13. A note on the molecular water content in uranyl carbonate mineral andersonite

    Czech Academy of Sciences Publication Activity Database

    Plášil, Jakub; Čejka, J.

    2015-01-01

    Roč. 60, č. 3 (2015), s. 181-187 ISSN 1802-6222 R&D Projects: GA ČR GP13-31276P Institutional support: RVO:68378271 Keywords : andersonite * uranyl carbonate * crystal structure * molecular water Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.326, year: 2015

  14. A review of volatile compounds in tektites, and carbon content and isotopic composition of moldavite glass

    Czech Academy of Sciences Publication Activity Database

    Žák, Karel; Skála, Roman; Řanda, Zdeněk; Mizera, Jiří

    2012-01-01

    Roč. 47, č. 6 (2012), s. 1010-1028 ISSN 1086-9379 R&D Projects: GA ČR GA205/09/0991 Institutional research plan: CEZ:AV0Z30130516; CEZ:AV0Z10480505 Keywords : moldavites * geochemistry * ries * carbon stable isotopes * moldavites (Germany) Subject RIV: DD - Geochemistry Impact factor: 2.800, year: 2012

  15. Deforestation, floodplain dynamics, and carbon biogeochemistry in the Amazon Basin

    Science.gov (United States)

    Bryan, M. L.; Dunne, T.; Richey, J.; Melack, J.; Simonett, D. S.; Woodwell, G.

    1984-01-01

    Three aspects of the physical geographic environment of the Amazon Basin are considered: (1) deforestation and reforestation, (2) floodplain dynamics, and (3) fluvial geomorphology. Three independent projects are coupled in this experiment to improve the in-place research and to ensure that the Shuttle Imaging Radar-B (SIR-B) experiment stands on a secure base of ongoing work. Major benefits to be obtained center on: (1) areal and locational information, (2) data from various depression angles, and (3) digital radar signatures. Analysis will be conducted for selected sites to define how well SIR-B data can be used for: (1) definition of extent and location of deforestation in a tropical moist forest, (2) definition and quantification of the nature of the vegetation and edaphic conditions on the (floodplain) of the Amazon River, and (3) quantification of the accuracy with which the geometry and channel shifting of the Amazon River may be mapped using SIR-B imagery in conjunction with other remote sensing data.

  16. Does drought legacy alter the recovery of grassland carbon dynamics from drought?

    Science.gov (United States)

    Bahn, Michael; Hasibeder, Roland; Fuchslueger, Lucia; Ingrisch, Johannes; Ladreiter-Knauss, Thomas; Lair, Georg; Reinthaler, David; Richter, Andreas; Kaufmann, Rüdiger

    2017-04-01

    Climate projections suggest an increase in the frequency and the severity of extreme climatic events, such as droughts, with consequences for the carbon cycle and its feedbacks to the climate system. An important implication of increasing drought frequency is that possible legacies of previous droughts may increasingly affect ecosystem responses to new drought events, though this has been rarely tested. Based on a series of severe experimental droughts performed during nine subsequent years on a mountain grassland in the Austrian Alps, we present evidence of effects of drought legacies on the recovery of grassland carbon dynamics from drought and analyse the underlying mechanisms. Both single and recurrent droughts led to increased aboveground productivity during drought recovery relative to control plots, favoring the biomass production and leaf area of grass species more strongly than of forbs. Belowground productivity was significantly increased during recovery. This led to higher total root length, even though specific root length was strongly reduced during recovery, particularly after recurrent drought events. Following rewetting, the temperature dependence of soil respiration was increasingly diminished and the Birch effect declined with progressive recurrence of droughts. This was paralleled by a change in soil aggregate stability and soil porosity in plots repeatedly exposed to drought. Isotopic pulse-labelling experiments revealed effects of drought legacy on plant carbon uptake and belowground allocation and altered microbial turnover of recent plant-derived carbon during and after a subsequent drought. Shifts in tissue nitrogen concentration indicate that drought effects on soil nitrogen turnover and availability could play an important role in the recovery of grassland carbon dynamics following both single and recurrent droughts. In conclusion, drought legacies can alter the recovery of grassland carbon dynamics from drought, the effects increasing

  17. Peatland Carbon Dynamics in Alaska During Past Warm Climates

    Science.gov (United States)

    Yu, Z.; Cleary, K.; Massa, C.; Hunt, S. J.; Klein, E. S.; Loisel, J.

    2013-12-01

    Peatlands represent a large belowground carbon (C) pool in the biosphere. However, how peatland C sequestration capacity varies with changes in climate and climate-induced disturbance is still poorly understood and debated. Here we summarize results from Alaskan peatlands to document how peat C accumulation has responded to past warm climate intervals. We find that the greatest C accumulation rates at sites from the Kenai Peninsula to the North Slope occurred during the Holocene thermal maximum (HTM) in the early Holocene. This time period also corresponds with explosive formation and expansion of new peatlands on the landscape across Alaska. In addition, we note that many peatlands that existed during the earlier Holocene on the North Slope have disappeared and are presently covered by mineral soils under tundra or sandy deposits. During the Medieval Climate Anomaly (MCA) around 1000-500 years ago, several peatlands in Alaska show high rates of C accumulation when compared to the period before the MCA during the Neoglacial or the following Little Ice Age period. Altogether, our results indicate that the Alaskan landscape was very different during the last 10,000 years and that peatlands can rapidly accumulate C under warm climatic conditions. We speculate that warmth-stimulated increase in plant production surpasses increase in peat decomposition during the early Holocene, and potentially also during the MCA. Other factors that might have contributed to rapid peat accumulation during the early Holocene include increased summer sunlight, lowered sea levels, and decreased sea-ice cover/duration. Summer insolation was ca. 8% higher than today during the early Holocene due to orbital variations, which likely promoted plant productivity by increasing growing seasons sunlight. Furthermore, lower sea levels and exposed shallow continental shelves in the Beaufort Sea (Arctic Ocean) would have made the present-day Arctic Coastal Plain more continental, with warmer summers

  18. Testing the performance of a Dynamic Global Ecosystem Model: Water balance, carbon balance, and vegetation structure

    Science.gov (United States)

    Kucharik, Christopher J.; Foley, Jonathan A.; Delire, Christine; Fisher, Veronica A.; Coe, Michael T.; Lenters, John D.; Young-Molling, Christine; Ramankutty, Navin; Norman, John M.; Gower, Stith T.

    2000-09-01

    While a new class of Dynamic Global Ecosystem Models (DGEMs) has emerged in the past few years as an important tool for describing global biogeochemical cycles and atmosphere-biosphere interactions, these models are still largely untested. Here we analyze the behavior of a new DGEM and compare the results to global-scale observations of water balance, carbon balance, and vegetation structure. In this study, we use version 2 of the Integrated Biosphere Simulator (IBIS), which includes several major improvements and additions to the prototype model developed by Foley et al. [1996]. IBIS is designed to be a comprehensive model of the terrestrial biosphere; the model represents a wide range of processes, including land surface physics, canopy physiology, plant phenology, vegetation dynamics and competition, and carbon and nutrient cycling. The model generates global simulations of the surface water balance (e.g., runoff), the terrestrial carbon balance (e.g., net primary production, net ecosystem exchange, soil carbon, aboveground and belowground litter, and soil CO2 fluxes), and vegetation structure (e.g., biomass, leaf area index, and vegetation composition). In order to test the performance of the model, we have assembled a wide range of continental and global-scale data, including measurements of river discharge, net primary production, vegetation structure, root biomass, soil carbon, litter carbon, and soil CO2 flux. Using these field data and model results for the contemporary biosphere (1965-1994), our evaluation shows that simulated patterns of runoff, NPP, biomass, leaf area index, soil carbon, and total soil CO2 flux agree reasonably well with measurements that have been compiled from numerous ecosystems. These results also compare favorably to other global model results.

  19. Dynamics of organic and inorganic carbon in surface sediments of the Yellow River Estuary

    Science.gov (United States)

    Yu, Z.; Wang, X.; Liu, X.; Zhang, E.; Hang, F.

    2017-12-01

    Estuarine sediment is an important carbon reservoir thus may play an important role in the global carbon cycle. However, little is known on the dynamics of organic carbon (OC) and inorganic carbon (IC) in the surface sediment of the Yellow River Estuary, a large estuary in northern China. In this study, we applied element analyses and isotopic approach to study spatial distribution and sources of OC and IC in the Yellow River Estuary. We found that TIC concentration (6.3-20.1 g kg-1) was much higher than TOC (0.2-4.4 g kg-1) in the surface sediment. There showed a large spatial variability in TOC and TIC and their stable isotopes. Both TOC and TIC were higher to the north (2.6 and 14.5 g kg-1) than to the south (1.6 and 12.2 g kg-1), except in the southern bay where TOC and TIC reached 2.7 and 15.4 g kg-1, respectively. Generally, TOC and TIC in our study area was mainly autochthonous. The lower TOC values in the south section were due to relatively higher kinetic energy level whereas the higher values in the bay was attributable to terrigenous matters accumulation and lower kinetic energy level. However, the southern bay revealed the most negative δ13Corg and δ13Ccarb, suggesting that there might exist some transfer of OC to IC in the section. Our study points out that the dynamics of sedimentary carbon in the Yellow River Estuary is influenced by multiple and complex processes, and highlights the importance of carbonate in carbon sequstration.

  20. Does carbon availability control temporal dynamics of radial growth in Norway spruce (Picea abies)?

    Science.gov (United States)

    Oberhuber, Walter; Gruber, Andreas; Swidrak, Irene

    2015-04-01

    Intra-annual dynamics of cambial activity and wood formation of coniferous species exposed to soil dryness revealed early culmination of maximum growth in late spring prior to occurrence of more favourable environmental conditions, i.e., repeated high rainfall events during summer (Oberhuber et al. 2014). Because it is well known that plants can adjust carbon allocation patterns to optimize resource uptake under prevailing environmental constraints, we hypothesize that early decrease in radial stem growth is an adaptation to cope with drought stress, which might require an early switch of carbon allocation to belowground organs. Physical blockage of carbon transport in the phloem through girdling causes accumulation and depletion of carbohydrates above and below the girdle, respectively, making this method quite appropriate to investigate carbon relationships in trees. Hence, in a common garden experiment we will manipulate the carbon status of Norway spruce (Picea abies) saplings by phloem blockage at different phenological stages during the growing season. We will present the methodological approach and first results of the study aiming to test the hypothesis that carbon status of the tree affects temporal dynamics of cambial activity and wood formation in conifers under drought. Acknowledgment The research is funded by the Austrian Science Fund (FWF): P25643-B16 "Carbon allocation and growth of Scots pine". Reference Oberhuber W, A Gruber, W Kofler, I Swidrak (2014) Radial stem growth in response to microclimate and soil moisture in a drought-prone mixed coniferous forest at an inner Alpine site. Eur J For Res 133:467-479.

  1. The effect of treatment with activated carbon on the metal content in reuse of lubricating oil waste

    Directory of Open Access Journals (Sweden)

    Riyanto

    2018-01-01

    Full Text Available The effect of treatment with activated carbon to the metal content in the reuse of lubricating oil waste has been done. Waste lubricating oil has treatment using 1-butanol and KOH as a solvent and coagulant. The research studies of the effect of activated carbon to the metals are Pb, Cr, Ca, Mg and Fe in lubrication oil waste after treatment. Waste lubricating oil treatment by the adsorption method using activated carbon with various weight are 0,5; 1,0; and 1,5 g. The metal concentrate was analysis after and before treatment using Atomic Adsorption Spectrophotometer (AAS. The analysis result shown the best weight of activated carbon for decreased of metals contains in lubricating oil waste is 1.5 g. Metal concentration of Pb, Cr, Ca, Mg and Fe in lubricating oil waste before treatment are 181.0002, 10.7198, 1019.0220, 325.8788 and 365.1329 mg/L (ppm, respectively. Metal concentration of Pb, Cr, Ca, Mg and Fe in lubricating oil waste after treatment are 47.5670, not detection, 2.6871, 44.3251 and 222.043 mg/L (ppm, respectively. Base on ASTM D5185 standard shown the Ca, Mg and Cr metals concentration according to the new lubricating oil quality standard. Pb and Fe metals concentration after process are still above the new lubricating oil quality standard. As a conclusion is activated carbon is a good material for treatment of waste lubricating oil, especially to reduce metal concentrations.

  2. Assessment of pre-industrial carbon dioxide content in the atmosphere using hydro-chemical data

    International Nuclear Information System (INIS)

    Heans, K.A.; Liaxin, Y.I.

    2001-01-01

    A hydrochemical method has been developed to calculate concentrations of carbon dioxide (CO 2 ) in the pre-industrial atmosphere and its relationship to climatic change. The following factors affect the Earth's climate: (1) the sun with all its processes, (2) the attraction of the moon that limits the axis of inclination of the Earth, and (3) the cycle of carbon dioxide and the greenhouse effect. An imbalance in the climate system would be a major global disaster that could be detrimental for life on Earth. Recent studies and temperature measurements have shown a trend in which air temperature has increased in the troposphere in the last 100 years, affecting the normal development of natural processes. Various phenomena result from climatic change, or the gradual heating of the Earth. These include the weakening of the glacial layer that covers the Earth's surface, cycles of prolonged slowing in freeze and thaw periods of aquatic surfaces, and increased air temperature in the troposphere which can also causes abnormal fluctuations of temperature in the atmosphere, resulting in heat waves and droughts. Gradual heating of the Earth can also result in rainy periods that produce devastating floods, hurricanes and extreme winds. Changes in water temperature can influence pH levels which affect certain marine species. An increase of 5 degrees C in the global average atmospheric temperature has created changes in 420 physical processes as well as in the behavior of plants and animals. The author stated that the most drastic factor that affects the balance of the Earth's climate is the actions of man interfering with the carbon cycle, as carbon dioxide plays a vital role in the formation of the greenhouse effect. The problem results from an imbalance of the carbon dioxide cycle when CO 2 emissions are increased through the combustion of fossil fuels. It was determined that before the beginning of the Industrial Revolution, carbon dioxide in the atmosphere was 256 ppm

  3. Investigation of WC-Co Electrospark Coatings with Various Carbon Contents

    Science.gov (United States)

    Burkov, A. A.; Pyachin, S. A.

    2014-06-01

    Electrospark deposition was employed to clad WC-10%Co, W/C1.6 -10%Co, and W/C0.5 -10%Co hard alloys on steel 1035, and the tribological properties of the coatings obtained were examined. The influence of the W/C ratio in the electrode materials on the decarburization of tungsten carbide was studied. It is shown that the degree of tungsten carbide degradation can be reduced by increasing the concentration of carbon in the WC-Co electrode materials, and also that the WC decarburization reaction is reversible on annealing. Coatings deposited using new electrode materials with an excess of carbon (W/C0.5) and/or tungsten (W/C1.6) have increased microhardness and improved frictional characteristics compared with the conventional coating.

  4. Dynamic modelling and humus balances as tools for estimating and upscaling soil carbon stock changes in temperate cropland

    Science.gov (United States)

    Oberholzer, Hans-Rudolf; Holenstein, Hildegard; Mayer, Jochen; Leifeld, Jens

    2010-05-01

    Humus balances are simple mathematical tools used by farmers for assessing the overall performance of their management in terms of soil organic matter changes. They are based on humus reproduction factors which themselves mainly depend on crop rotation, residue management, and amount and type of organic fertilization. Dynamic models, on the other hand, are typically complex and need more detailed input data and are designed to calculate the time course of soil carbon content. In both cases, thorough validation is needed to utilize their potential for estimating carbon stock changes. We compared the results of three humus balance methods SALCA-SQ (Neyroud 1997), VDLUFA method (VDLUFA 2004), Humod (Brock et al. 2008) and the RothC model with measured soil carbon stocks in a long-term experiment in Switzerland for the period 1977-2005 (Fliessbach et al 2007). The field trial comprises various minerally and organically fertilized treatments, the latter differing in the amount and composition of organics applied. All methods were able to distinguish systematic management effects on soil organic carbon (SOC). However, only those SOC trajectories calculated with the dynamic model RothC matched measured stocks quantitatively. For both, humus balances and dynamic modelling the result strongly depended on parameterization of organic fertilizers, i.e. its stability and organic matter content. Therefore, incomplete information on the amount and composition of organic fertilizer and lack of knowledge about its potential for humus reproduction is regarded an uncertainty in both dynamic modelling and humus balance calculation, and seems to be a major drawback for the reliable application of these approaches at the regional scale. Our results stress the need for more detailed and harmonized data bases of organic fertilizer composition and application rates. References Brock C., Hoyer U., Leithold G., Hülsbergen K.-J., 2008. Entwicklung einer praxisanwendbaren Methode der

  5. Simultaneous AMS determination of {sup 14}C content and total carbon mass in biological samples

    Energy Technology Data Exchange (ETDEWEB)

    Zoppi, U., E-mail: uzoppi@acciumbio.co [Accium BioSciences, 550 17th Avenue, Suite 550, Seattle, WA 98122 (United States); Arjomand, A. [Accium BioSciences, 550 17th Avenue, Suite 550, Seattle, WA 98122 (United States)

    2010-04-15

    Accelerator Mass Spectrometry (AMS) is now recognized as one of the most powerful techniques available for conducting ultrasensitive clinical studies. However, since for biological applications the relevant quantity is the total {sup 14}C activity (i.e. dpm/mL sample), AMS {sup 14}C measurements must be combined with total carbon concentrations measured on a separate instrument using a different sample aliquot. This procedure is inherently a source of large inaccuracies, especially in non-homogeneous samples such as urine and fecal blends. To overcome this limitation we developed a new measurement technique whereby a small amount of {sup 13}C-enriched carbon carrier is added to each sample. Accurate measurement of the {sup 13}C/{sup 12}C and {sup 14}C/{sup 13}C ratios of the mix can be used to simultaneously calculate total carbon mass and {sup 14}C concentration of the original sample. In this paper we present our first test runs including a detailed error analysis demonstrating that sample mass and {sup 14}C concentration of the original sample can be determined with a precision and accuracy of better than 3%, thus significantly reducing the final uncertainty due to sample in-homogeneities.

  6. International Student Carbon Footprint Challenge--Social Media as a Content and Language Integrated Learning Environment

    Science.gov (United States)

    Fauville, Géraldine; Lantz-Andersson, Annika; Säljö, Roger

    2012-01-01

    Environmental education (EE) is now clearly specified in educational standards in many parts of the world, and at the same time the view of language learning is moving towards a content and language integrated learning (CLIL) strategy, to make English lessons more relevant and attractive for students (Eurydice, 2006). In this respect,…

  7. Voltammetric determination of polyphenolic content in pomegranate juice using a poly(gallic acid/multiwalled carbon nanotube modified electrode

    Directory of Open Access Journals (Sweden)

    Refat Abdel-Hamid

    2016-07-01

    Full Text Available A simple and sensitive poly(gallic acid/multiwalled carbon nanotube modified glassy carbon electrode (PGA/MWCNT/GCE electrochemical sensor was prepared for direct determination of the total phenolic content (TPC as gallic acid equivalent. The GCE working electrode was electrochemically modified and characterized using scanning electron microscope (SEM, cyclic voltammetry (CV, chronoamperometry and chronocoulometry. It was found that gallic acid (GA exhibits a superior electrochemical response on the PGA/MWCNT/GCE sensor in comparison with bare GCE. The results reveal that a PGA/MWCNT/GCE sensor can remarkably enhance the electro-oxidation signal of GA as well as shift the peak potentials towards less positive potential values. The dependence of peak current on accumulation potential, accumulation time and pH were investigated by square-wave voltammetry (SWV to optimize the experimental conditions for the determination of GA. Using the optimized conditions, the sensor responded linearly to a GA concentration throughout the range of 4.97 × 10−6 to 3.38 × 10−5 M with a detection limit of 3.22 × 10−6 M (S/N = 3. The fabricated sensor shows good selectivity, stability, repeatability and (101% recovery. The sensor was successfully utilized for the determination of total phenolic content in fresh pomegranate juice without interference of ascorbic acid, fructose, potassium nitrate and barbituric acid. The obtained data were compared with the standard Folin–Ciocalteu spectrophotometric results.

  8. Selective optical switching of interface-coupled relaxation dynamics in carbon nanotube-Si heterojunctions

    KAUST Repository

    Ponzoni, Stefano

    2014-10-16

    By properly tuning the photon energy of a femtosecond laser pump, we disentangle, in carbon nanotube-Si (CNT/Si) heterojunctions, the fast relaxation dynamics occurring in CNT from the slow repopulation dynamics due to hole charge transfer at the junction. In this way we are able to track the transfer of the photogenerated holes from the Si depletion layer to the CNT layer, under the action of the built-in heterojunction potential. This also clarifies that CNT play an active role in the junction and do not act only as channels for charge collection and transport.

  9. Diameter-dependent bending dynamics of single-walled carbon nanotubes in liquids.

    Science.gov (United States)

    Fakhri, Nikta; Tsyboulski, Dmitri A; Cognet, Laurent; Weisman, R Bruce; Pasquali, Matteo

    2009-08-25

    By relating nanotechnology to soft condensed matter, understanding the mechanics and dynamics of single-walled carbon nanotubes (SWCNTs) in fluids is crucial for both fundamental and applied science. Here, we study the Brownian bending dynamics of individual chirality-assigned SWCNTs in water by fluorescence microscopy. The bending stiffness scales as the cube of the nanotube diameter and the shape relaxation times agree with the semiflexible chain model. This suggests that SWCNTs may be the archetypal semiflexible filaments, highly suited to act as nanoprobes in complex fluids or biological systems.

  10. The dynamically evolving nematocyst content of an anthozoan, a scyphozoan, and a hydrozoan.

    Science.gov (United States)

    Rachamim, Tamar; Morgenstern, David; Aharonovich, Dikla; Brekhman, Vera; Lotan, Tamar; Sher, Daniel

    2015-03-01

    Nematocytes, the stinging cells of cnidarians, are the most evolutionarily ancient venom apparatus. These nanosyringe-like weaponry systems reach pressures of approximately 150 atmospheres before discharging and punching through the outer layer of the prey or predator at accelerations of more than 5 million g, making them one of the fastest biomechanical events known. To gain better understanding of the function of the complex, phylum-specific nematocyst organelle, and its venom payload, we compared the soluble nematocyst's proteome from the sea anemone Anemonia viridis, the jellyfish Aurelia aurita, and the hydrozoan Hydra magnipapillata, each belonging to one of the three basal cnidarian lineages which diverged over 600 Ma. Although the basic morphological and functional characteristics of the nematocysts of the three organisms are similar, out of hundreds of proteins identified in each organism, only six are shared. These include structural proteins, a chaperone which may help maintain venon activity over extended periods, and dickkopf, an enigmatic Wnt ligand which may also serve as a toxin. Nevertheless, many protein domains are shared between the three organisms' nematocyst content suggesting common proteome functionalities. The venoms of Hydra and Aurelia appear to be functionally similar and composed mainly of cytotoxins and enzymes, whereas the venom of the Anemonia is markedly unique and based on peptide neurotoxins. Cnidarian venoms show evidence for functional recruitment, yet evidence for diversification through positive selection, common to other venoms, is lacking. The final injected nematocyst payload comprises a mixture of dynamically evolving proteins involved in the development, maturation, maintenance, and discharge of the nematocysts, which is unique to each organism and potentially to each nematocyst type. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved

  11. Coastal Wetland Carbon Dynamics Across a Sediment Delivery Gradient in the Atchafalaya and Terrebonne Basins, Louisiana

    Science.gov (United States)

    McCall, A.; Twilley, R.

    2017-12-01

    The Atchafalaya and Terrebonne Basins of the Mississippi River Deltaic Plain are examples of river-occupied and river-abandoned coastal basins that have undergone coupled natural and anthropogenic changes over time, especially in the last 100 years, influencing their respective coastal wetlands physically and ecologically. These basins provide unique, experimental units of sediment delivery to coastal wetlands to test hypotheses of ecosystem service functioning at multiple time and geographic scales. This study investigates wetland carbon dynamics over time at the basin scale and at the coastal-land margin. We are testing the hypotheses that sediment input via freshwater delivery to coastal deltaic floodplains allows for these systems to develop and perform ecosystem services such as biomass production, which promotes soil carbon accumulation that increases the marsh platform elevation, acting as a carbon sink. Meanwhile, decreased sediment supply to coastal deltaic wetlands in the Terrebonne Basin leads to degradation, subsidence of the marsh platform, and a landward migration of wetlands. This decreases the carbon storage capacity over time and leads to an increase in historic sequestered carbon fluxing out of the system and into coastal waters, thus acting as a carbon source. Using historic soil and vegetation data, we found that since 1949, the wetland soil carbon storage capacity has increased by 47% in the Atchafalaya Basin and decreased by 42% in the Terrebonne Basin. We also examined above and belowground productivity and biomass allocation of dominant emergent species of distinct hydrogeomorphic zones along the coastal-land margin. Soil characteristics have also been measured using short-term feldspar plots across these hydrogeomorphic zones. We also measured particulate carbon, dissolved organic carbon, and suspended sediment concentrations to determine the carbon flux in/out of these systems over a typical tidal cycle. These preliminary findings suggests

  12. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Directory of Open Access Journals (Sweden)

    X. Yang

    2010-10-01

    Full Text Available We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades

  13. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Science.gov (United States)

    Yang, X.; Richardson, T. K.; Jain, A. K.

    2010-10-01

    We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM) to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades. This study indicates

  14. High-efficient and high-content cytotoxic recording via dynamic and continuous cell-based impedance biosensor technology.

    Science.gov (United States)

    Hu, Ning; Fang, Jiaru; Zou, Ling; Wan, Hao; Pan, Yuxiang; Su, Kaiqi; Zhang, Xi; Wang, Ping

    2016-10-01

    Cell-based bioassays were effective method to assess the compound toxicity by cell viability, and the traditional label-based methods missed much information of cell growth due to endpoint detection, while the higher throughputs were demanded to obtain dynamic information. Cell-based biosensor methods can dynamically and continuously monitor with cell viability, however, the dynamic information was often ignored or seldom utilized in the toxin and drug assessment. Here, we reported a high-efficient and high-content cytotoxic recording method via dynamic and continuous cell-based impedance biosensor technology. The dynamic cell viability, inhibition ratio and growth rate were derived from the dynamic response curves from the cell-based impedance biosensor. The results showed that the biosensors has the dose-dependent manners to diarrhetic shellfish toxin, okadiac acid based on the analysis of the dynamic cell viability and cell growth status. Moreover, the throughputs of dynamic cytotoxicity were compared between cell-based biosensor methods and label-based endpoint methods. This cell-based impedance biosensor can provide a flexible, cost and label-efficient platform of cell viability assessment in the shellfish toxin screening fields.

  15. Global Workspace Dynamics: Cortical “Binding and Propagation” Enables Conscious Contents

    Science.gov (United States)

    Baars, Bernard J.; Franklin, Stan; Ramsoy, Thomas Zoega

    2013-01-01

    A global workspace (GW) is a functional hub of binding and propagation in a population of loosely coupled signaling elements. In computational applications, GW architectures recruit many distributed, specialized agents to cooperate in resolving focal ambiguities. In the brain, conscious experiences may reflect a GW function. For animals, the natural world is full of unpredictable dangers and opportunities, suggesting a general adaptive pressure for brains to resolve focal ambiguities quickly and accurately. GW theory aims to understand the differences between conscious and unconscious brain events. In humans and related species the cortico-thalamic (C-T) core is believed to underlie conscious aspects of perception, thinking, learning, feelings of knowing (FOK), felt emotions, visual imagery, working memory, and executive control. Alternative theoretical perspectives are also discussed. The C-T core has many anatomical hubs, but conscious percepts are unitary and internally consistent at any given moment. Over time, conscious contents constitute a very large, open set. This suggests that a brain-based GW capacity cannot be localized in a single anatomical hub. Rather, it should be sought in a functional hub – a dynamic capacity for binding and propagation of neural signals over multiple task-related networks, a kind of neuronal cloud computing. In this view, conscious contents can arise in any region of the C-T core when multiple input streams settle on a winner-take-all equilibrium. The resulting conscious gestalt may ignite an any-to-many broadcast, lasting ∼100–200 ms, and trigger widespread adaptation in previously established networks. To account for the great range of conscious contents over time, the theory suggests an open repertoire of binding1 coalitions that can broadcast via theta/gamma or alpha/gamma phase coupling, like radio channels competing for a narrow frequency band. Conscious moments are thought to hold only 1–4 unrelated items; this

  16. Dynamical and biogeochemical control on the decadal variability of ocean carbon fluxes

    Directory of Open Access Journals (Sweden)

    R. Séférian

    2013-04-01

    Full Text Available Several recent observation-based studies suggest that ocean anthropogenic carbon uptake has slowed down due to the impact of anthropogenic forced climate change. However, it remains unclear whether detected changes over the recent time period can be attributed to anthropogenic climate change or rather to natural climate variability (internal plus naturally forced variability alone. One large uncertainty arises from the lack of knowledge on ocean carbon flux natural variability at the decadal time scales. To gain more insights into decadal time scales, we have examined the internal variability of ocean carbon fluxes in a 1000 yr long preindustrial simulation performed with the Earth System Model IPSL-CM5A-LR. Our analysis shows that ocean carbon fluxes exhibit low-frequency oscillations that emerge from their year-to-year variability in the North Atlantic, the North Pacific, and the Southern Ocean. In our model, a 20 yr mode of variability in the North Atlantic air-sea carbon flux is driven by sea surface temperature variability and accounts for ~40% of the interannual regional variance. The North Pacific and the Southern Ocean carbon fluxes are also characterised by decadal to multi-decadal modes of variability (10 to 50 yr that account for 20–40% of the interannual regional variance. These modes are driven by the vertical supply of dissolved inorganic carbon through the variability of Ekman-induced upwelling and deep-mixing events. Differences in drivers of regional modes of variability stem from the coupling between ocean dynamics variability and the ocean carbon distribution, which is set by large-scale secular ocean circulation.

  17. Relating coccolithophore calcification rates to phytoplankton community dynamics: Regional differences and implications for carbon export

    Science.gov (United States)

    Poulton, Alex J.; Adey, Tim R.; Balch, William M.; Holligan, Patrick M.

    2007-03-01

    Recent measurements of surface coccolithophore calcification from the Atlantic Ocean (50°N-50°S) are compared to similar measurements from other oceanic settings. By combining the different data sets of surface measurements, we examine general and regional patterns of calcification relative to organic carbon production (photosynthesis) and other characteristics of the phytoplankton community. Generally, surface calcification and photosynthesis are positively correlated, although the strength of the relationship differs between biogeochemical provinces. Relationships between surface calcification, chlorophyll- a and calcite concentrations are also statistically significant, although again there is considerable regional variability. Such variability appears unrelated to phytoplankton community composition or hydrographic conditions, and may instead reflect variations in coccolithophore physiology. The contribution of inorganic carbon fixation (calcification) to total carbon fixation (calcification plus photosynthesis) is ˜1-10%, and we estimate a similar contribution from coccolithophores to total organic carbon fixation. However, these contributions vary between biogeochemical provinces, and occasionally coccolithophores may account for >20% of total carbon fixation in unproductive central subtropical gyres. Combining surface calcification and photosynthetic rates with standing stocks of calcite, particulate organic carbon, and estimated phytoplankton carbon allows us to examine the fates of these three carbon pools. The relative turnover times vary between different biogeochemical provinces, with no clear relationship to the overall productivity or phytoplankton community structure found in each province. Rather, interaction between coccolithophore physiology (coccolith production and detachment rates), species diversity (cell size), and food web dynamics (grazer ecology) may control the composition and turnover times of calcite particles in the upper ocean.

  18. Everglades peats: using historical and recent data to estimate predrainage and current volumes, masses and carbon contents

    Directory of Open Access Journals (Sweden)

    S.M. Hohner

    2015-01-01

    Full Text Available The Florida Everglades is a patterned peatland formed from sawgrass and other aquatic plant material that has accumulated over millennia. This peatland was initially drained in the late 1800s for agricultural and urban development and has been highly modified by the construction of canals and levées. Restoration plans include providing additional surface water flow which should help to prevent further peat loss by oxidation and encourage the accretion of peat that has been lost through drainage and peat fires. But how much peat has been lost? We know that about 50 % of the original surface area is gone; but what about the driver of ecological processes, the soil? Using Geographic Information Systems (GIS technology, we compared predrainage and current peat volumes using historical and recent datasets, spatially-referenced soil bulk density values and carbon content to determine peat mass and carbon mass for each Everglades region. Given the uncertainties in the datasets, this analysis should be viewed as providing rough order-of-magnitude values. Our calculations indicate that the current Everglades contains less than 24 % of the original peat volume, 17 % of its mass and 19 % of its carbon.

  19. Distributions of Manganese, Iron, and Manganese-Oxidizing Bacteria In Lake Superior Sediments of Different Organic Carbon Content

    Science.gov (United States)

    Richardson, Laurie L.; Nealson, Kenneth H.

    1989-01-01

    Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin in Lake Superior and the north and south ends of the Caribou trough, and brought to the surface for immediate analysis. Minielectrode profiles of oxygen concentration of the three cores were carried out using a commercially available minielectrode apparatus. Oxygen depletion to less than 1% occurred within 4 cm of the surface for two of the cores, but not until approximately 15 cm for the core from the south basin of the Caribou trough. The three cores exhibited very different profiles of soluble, as well as leachable, manganese and iron, suggesting different degrees of remobilization of these metals in the sediments. Vertical profiles of viable bacteria and Mn oxidizing bacteria, determined by plating and counting, showed that aerobic (and facultatively aerobic) heterotrophic bacteria were present at the highest concentrations near the surface and decreased steadily with depth, while Mn oxidizing bacteria were concentrations primarily at and above the oxic/anoxic interface. Soluble manganese in the pore waters, along with abundant organic carbon, appeared to enhance the presence of manganese oxidizing bacteria, even below the oxic/anoxic interface. Profiles of solid-phase leachable manganese suggested a microbial role in manganese reprecipitation in these sediments.

  20. Measurement of contemporary and fossil carbon contents of PM 2.5 aerosols: results from Turtleback Dome, Yosemite National Park

    International Nuclear Information System (INIS)

    Bench, G

    2003-01-01

    The impact of aerosol particulate matter of mean mass aerodynamic diameter (le) 2.5 ∝m (PM 2.5 aerosols), on health, visibility, and compliance with EPA's regional haze regulations is a growing concern. Techniques that can help better characterize particulate matter are required to better understand the constituents, causes and sources of PM 2.5 aerosols. Measurement of the 14 C/C ratio of the PM 2.5 aerosols, the absence of 14 C in fossil carbon materials and the known 14 C/C levels in contemporary carbon materials allows use of a two-component model to derive contemporary and fossil carbon contents of the particulate matter. Such data can be used to estimate the relative contributions of fossil fuels and biogenic aerosols to the total aerosol loading. Here, the methodology for performing such an assessment using total suspended particulate Hi-vol aerosol samplers to collect PM 2.5 aerosols on quartz fiber filters and the technique of accelerator mass spectrometry to measure 14 C/C ratios is presented and illustrated using PM 2.5 aerosols collected at Yosemite National Park

  1. The role of tropical deforestation in the global carbon cycle: Spatial and temporal dynamics

    Science.gov (United States)

    Houghton, R. A.; Skole, David; Moore, Berrien; Melillo, Jerry; Steudler, Paul

    1995-01-01

    'The Role of Tropical Deforestation in the Global Carbon cycle: Spatial and Temporal Dynamics', was a joint project involving the University of New Hampshire, the Marine Biological Laboratory, and the Woods Hole Research Center. The contribution of the Woods Hole Research Center consisted of three tasks: (1) assist University of New Hampshire in determining the net flux of carbon between the Brazilian Amazon and the atmosphere by means of a terrestrial carbon model; (2) address the spatial distribution of biomass across the Amazon Basin; and (3) assist NASA Headquarters in development of a science plan for the Terrestrial Ecology component of the NASA-Brazilian field campaign (anticipated for 1997-2001). Progress on these three tasks is briefly described.

  2. BEAM DYNAMICS STUDIES FOR A COMPACT CARBON ION LINAC FOR THERAPY

    Energy Technology Data Exchange (ETDEWEB)

    Plastun, A.; Mustapha, B.; Nassiri, A.; Ostroumov, P.

    2016-05-01

    Feasibility of an Advanced Compact Carbon Ion Linac (ACCIL) for hadron therapy is being studied at Argonne National Laboratory in collaboration with RadiaBeam Technologies. The 45-meter long linac is designed to deliver 109 carbon ions per second with variable energy from 45 MeV/u to 450 MeV/u. S-band structure provides the acceleration in this range. The carbon beam energy can be adjusted from pulse to pulse, making 3D tumor scanning straightforward and fast. Front end accelerating structures such as RFQ, DTL and coupled DTL are designed to operate at lower frequencies. The design of the linac was accompanied with extensive end-to-end beam dynamics studies which are presented in this paper.

  3. Carbon dynamics, food web structure and reclamation strategies in Athabasca oil sands wetlands (CRFAW)

    International Nuclear Information System (INIS)

    Ciborowski, J.; Dixon, G.; Foote, L.; Liber, K.; Smits, J.

    2010-01-01

    This abstract provided details of the Carbon Dynamics, Food Web Structure and Reclamation Strategies in Athabasca Oil Sands Wetlands (CFRAW) program, a collaboration between oil sands industry partners and university laboratories. CFRAW researchers are investigating the effects of mine tailings and process waters on the development, health, and function of wetland communities in post-mining landscapes. The aim of the program is to accurately predict how quickly the reclaimed wetlands will approach conditions seen in reference wetland systems. The program is also examining the effects of hydrocarbons as a surrogate source of carbon after they are metabolized by bacteria. The biological uptake, pathways, and movement through the food web of materials used by the biota in constructed wetlands are also being studied. Flux estimates will be used to determine if wetlands amended with peat will maintain their productivity. A conceptual model of carbon pathways and budgets is also being developed.

  4. Structure and dynamics of porcine submaxillary mucin as determined by natural abundance carbon-13 NMR spectroscopy

    International Nuclear Information System (INIS)

    Gerken, T.A.; Jentoft, N.

    1987-01-01

    Nearly all of the resonances in the 13 C NMR spectrum of porcine submaxillary mucin glycoprotein (PSM) have been assigned to the peptide core carbons and to the carbons in the eight different oligosaccharide side chains that arise from the incomplete biosynthesis of the sialylated A blood group pentasaccharide. By use of these assignments, a nearly complete structural analysis of intact PSM has been performed without resorting to degradative chemical methods. Considerable structural variability in the carbohydrate side chains was observed between mucins obtained from different animals, while no variability was observed between glands in a single animal. The dynamics of the PSM core and carbohydrate side chains were examined by using the carbon-13 nuclear magnetic resonance relaxation times and nuclear Overhauser enhancements of each assigned carbon resonance. The peptide core of PSM exhibits internal segmental flexibility that is virtually identical with that of ovine submaxillary mucin (OSM), whose carbohydrate side chain consists of the α-NeuNAc(2-6)α-Ga1NAc disaccharide. These results differ from most reports of glycoprotein dynamics, which typically find the terminal carbohydrate residues to be undergoing rapid internal rotation about their terminal glycosidic bonds. The results reported here are consistent with previous studies on the conformations of the A and H determinants derived from model oligosaccharides and further indicate that the conformations of these determinants are unchanged when covalently bound to the mucin peptide core. In spite of their carbohydrate side-chain heterogeneity, mucins appear to be ideal glycoproteins for the study of O-linked oligosaccharide conformation and dynamics and for the study of the effects of glycosylation on polypeptide conformation and dynamics

  5. In situ carbon and nitrogen dynamics in ryegrass-clover mixtures

    DEFF Research Database (Denmark)

    Rasmussen, J.; Eriksen, J.; Jensen, Erik Steen

    2007-01-01

    Carbon (C) and nitrogen (N) dynamics in a third production year ryegrass–clover mixture were investigated in the field. Cylinders (diameter 29.7 cm) were installed to depths of 20, 40 and 60 cm and equipped with suction cups to collect percolating pore water. Ryegrass and clover leaves were cross...... on the ratio between dry matter accumulated in the donating and receiving species, the 14C-allocation within the receiving species and the root turnover rate in the soil....

  6. Web Search Engines and Indexing and Ranking the Content Object Including Metadata Elements Available at the Dynamic Information Environments

    Directory of Open Access Journals (Sweden)

    Faezeh sadat Tabatabai Amiri

    2012-10-01

    Full Text Available The purpose of this research was to make exam the indexing and ranking of XML content objects containing Dublin Core and MARC 21 metadata elements in dynamic online information environments by general search engines and comparing them together in a comparative-analytical approach. 100 XML content objects in two groups were analyzed: those with DCXML elements and those with MARCXML elements were published in website http://www.marcdcmi.ir. from late Mordad 1388 till Khordad 1389. Then the website was introduced to Google and Yahoo search engines. Google search engine was able to retrieve fully all the content objects during the study period through their Dublin Core and MARC 21 metadata elements; Yahoo search engine, however, did not respond at all. The indexing of metadata elements embedded in content objects in dynamic online information environments and different between indexing and ranking of them were examined. Findings showed all Dublin Core and MARC 21 metadata elements by Google search engine were indexed. And there was not observed difference between indexing and ranking DCXML and MARCXML metadata elements in dynamic online information environments by Google search engine.

  7. Dynamics of the microaggregate composition of chernozem in relation to changes in the content of organic matter

    Science.gov (United States)

    Kryshchenko, V. S.; Zamulina, I. V.; Rybyanets, T. V.; Kravtsova, N. E.; Biryukova, O. A.; Golozubov, O. M.

    2016-06-01

    Monitoring of soil dispersivity and humus state has been performed in the stationary profile of ordinary chernozem in the Botanic Garden of the Southern Federal University in 2009-2014. The contents of physical clay and sand are almost stable in time, which indicates a quasi-static (climax) equilibrium in the soil. Another (reversible dynamic) process occurs simultaneously: seasonal and annual variation in the mass fractions of clay and silt in physical clay. Variations of humus content in the whole soil and in its physical clay are also observed on the background of seasonal changes in precipitation and temperature. A procedure has been developed for the analysis of the polydisperse soil system with consideration for the quasi-static and dynamic equilibriums. A two-vector coordinate system has been introduced, which consists of scales for changes in the contents of physical clay and physical sand in 100 g of soil and changes in the fractions of clay and silt in 100 g of physical clay. Co-measurements of two dispersivity series of soil samples—actual dynamic and calculated under quasi-static equilibrium (ideal)—have been performed. Dynamic equilibrium coefficients, which cumulatively reflect the varying proportions of physical clay and physical sand in the soil and the mass fractions of clay and silt in physical clay, have been calculated.

  8. The effect of soll water conditions on carbon isotope discrimination and minerals contents in spring-planted wheat

    International Nuclear Information System (INIS)

    Zhu Lin; Liang Zongsuo; Xu Xing; Li Shuhua

    2008-01-01

    Carbon isotope discrimination (triangle open 13 C) has been proposed as indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of high cost for triangle open 13 C analysis, attempts have been made to identify alternative screening criteria. Ash content (m a ) has been proposed as an alternative criterion for triangle open 13 C in wheat and barley. A pot experiment with three water treatments (45% ± 5% FC, 55% ± 5% FC and 75% ± 5%FC) was conducted and flag leaf triangle open 13 C (triangle openL a ), contents of ash, potassium (K), magnesium (Mg) and calcium (Ca) were measured to study the relationships between triangle open, mineral composition in spring planted bread wheat (Triticum aestivum L.). In the light of the results obtained in this research, the traits measured showed significant differences among the three water treatments. There were variations in triangle openL a between the genotypes derived from contrasting environments. The improved varieties or advanced lines bred in irrigated areas displayed higher triangle open 13 C values, while the improved and local varieties bred in rain-fed areas exhibited lower triangle open 13 C values Significant positive correlations were found between triangle open 13 C and m a in seedlings and second fully developed leaves at elongation stage and in flag leaves at anthesis stage in severe drought treatment (T 1 ) (r=0.790, P 13 C was negatively associated with potassium (K) content in flag leaves in T 2 (r=0.813, P 2 and T 3 (r=0.725, P 13 C and calcium (Ca) content in flag leaves in T 3 (r=0.708, P a is a possible alternative criterion of triangle open 13 C in vegetative organs especially in stressed environments. K, Mg and Ca contents in flag leaf under moderate water stress or feasible water conditions might be new predictive criteria of triangle openL a . (authors)

  9. Impacts of climatic and atmospheric changes on carbon dynamics in the Great Smoky Mountains National Park

    International Nuclear Information System (INIS)

    Zhang Chi; Tian Hanqin; Chappelka, Arthur H.; Ren Wei; Chen Hua; Pan Shufen; Liu Mingliang; Styers, Diane M.; Chen Guangsheng; Wang Yuhang

    2007-01-01

    We used the Dynamic Land Ecosystem Model (DLEM) to estimate carbon (C) storage and to analyze the impacts of environmental changes on C dynamics from 1971 to 2001 in Great Smoky Mountain National Park (GRSM). Our simulation results indicate that forests in GRSM have a C density as high as 15.9 kg m -2 , about twice the regional average. Total carbon storage in GRSM in 2001 was 62.2 Tg (T = 10 12 ), 54% of which was in vegetation, the rest in the soil detritus pool. Higher precipitation and lower temperatures in the higher elevation forests result in larger total C pool sizes than in forests at lower elevations. During the study period, the CO 2 fertilization effect dominated ozone and climatic stresses (temperature and precipitation), and the combination of these multiple factors resulted in net accumulation of 0.9 Tg C in this ecosystem. - Model simulations suggest that rising atmospheric CO 2 compensates for the adverse effects of ozone stress on ecosystem carbon dynamics in Great Smoky Mountain National Park

  10. Stable isotope compositions of organic carbon and contents of organic carbon and nitrogen of lacustrine sediments from sub-arid northern Tanzania

    International Nuclear Information System (INIS)

    Muzuka, A.N.N.

    2006-01-01

    The stable isotope compositions of organic carbon (OC), and contents of OC and nitrogen for four sediment cores recovered from lakes Makat (located in the Ngorongoro Crater), Ndutu and Masek (located in the Serengeti Plains) are used to document sources of organic matter (OM) and climatic changes in sub-arid northern Tanzania during the late Pleistocene-Holocene period. Accelerate mass spectrometer (AMS) 14 C ages on total OM for sediments collected from the Ngorongoro Crater Lake indicate that the sedimentation rate is approximately 17 cm/ka. The δ 13 C values from the 20 cm long core (short core) show a downcore increase, whereas that of 500 cm long core (long core), show two peaks enriched in 13 C and three peaks depleted in 13 C. A general downcore increase in the δ 13 C values for the short core suggests changes in the relative proportion of C 3 and C 4 fraction increasing downcore. Similarly, low and high peaks in the long core suggest changes in the relative proportion of C 3 and C 4 with low values having high proportion of C 3 type of material, probably indicating changes in precipitation and lake levels in the area. Deposition of OM depleted in 13 C took place during periods of high precipitation and high lake levels. Although high content of OC and nitrogen in some core sections are associated with elevated C/N ratio values, diagenetic alteration of isotope signature is unlikely to have caused OC and isotope enrichment in sections having high contents of OC and nitrogen. The OC isotope record from Lake Ndutu shows a general downcore decrease in δ 13 C values and contents of OC and nitrogen. (author)

  11. The interaction between land use change, sediment fluxes and carbon dynamics: evaluating an integrated soil-landscape model at the millennial time-scale.

    Science.gov (United States)

    Bouchoms, Samuel; Van Oost, Kristof; Vanacker, Veerle

    2015-04-01

    Soil-landscape modelling has received growing attention as it allows us to evaluate the interaction between earth surface and soil bio-physical processes. At the landscape scale, human-induced land use change has altered the balance between soil erosion and production, and largely modified sediment fluxes. Intensification in soil redistribution rates affects the interaction between soil chemical, physical and biological processes at the landscape scale. Here, we evaluate the SPEROS-LT model, a spatially explicit 3D model combining a dynamic representation of land use, soil erosion and deposition and the soil carbon cycle. We assess the impact of millennial-scale human-induced land use change on sediment fluxes and carbon dynamics in the Dijle catchement (central Belgium). The watershed has undergone a 3000 years continuous human-induced alteration of the vegetation covers for agricultural characterized by Our study is based on land use reconstructions for the last 3000 years, including massive deforestation for agriculture in Roman Times and the Middle Ages followed by urbanization in the last 150 years. Land use reconstructions rely on simple land use allocation rules based on slope gradients. SPEROS-LT is parametrized for erosion rates against available figures in the literature by changing the transport capacity and the transfer coefficient which defines the amount of flux transferred between different land uses. Carbon content profiles at steady state (i.e. without influence of erosion or deposition) are calibrated for each land use and for the first upper meter of soil by comparing modeled profiles to an averaged observed profiles in stable areas of the pedologic region. We present a model sensitivity analysis and a full validation of the predicted soil carbon storage (horizontally, i.e. in space, and vertically, i.e. with depth) using a large database of observational data. The results indicate (i) a good agreement of the erosion rates. Speros LT modeled

  12. Carbon dynamics after forest harvest in Central Siberia: the ZOTTO footprint area

    Science.gov (United States)

    Panov, Alexey; Zrazhevskaya, Galina; Shibistova, Olga; Onuchin, Alexander; Heimann, Martin

    2013-04-01

    Temperate and boreal forests of the Northern Hemisphere have been recognized as important carbon sinks. Accurate calculation of forest carbon budget and estimation of the temporal variations of forest net carbon fluxes are important topics to elucidate the ''missing sink'' question and follow up the changing carbon dynamics in forests. In the frame of the ongoing Russian-German partner project the Zotino Tall Tower Observatory (ZOTTO; www.zottoproject.org) a unique international research platform for large-scale climatic observations is operational about 20 km west of the Yenisei river (60.8°N; 89.35°E). The data of the ongoing greenhouse gas and aerosol measurements at the tall tower are used in atmospheric inversions studies to infer the distribution of carbon sinks and sources over the whole Northern Eurasia. The tall tower footprint area estimates of carbon stocks and fluxes are highly demanded for bottom-up validation of inversion estimates. The ZOTTO site lies in a vast region of forests and wetlands, still relatively undisturbed by anthropogenic influences, but a moderate human impact on vegetation, represented mainly by logging activities, becomes essential. Therefore, accurate estimates of carbon pools in vegetation and soil following harvesting are essential to inversion studies for ZOTTO and critical to predictions of both local ecosystem sustainability and global C exchange with the atmosphere. We present our investigation of carbon dynamics after forest harvest in the tall tower footprint area (~1000 km2). The changes in C pools and annual sequestration were quantified among several clear-cut lichen pine (Pinus sylvestris Lamb.) stands representing various stages of secondary succession with a "space-for-time substitution" technique. When viewed as a chronosequence, these stands represent snapshots showing how the effects of logging may propagate through time. The study concluded that ecosystems during the first 15 yrs after forest harvest become C

  13. Dynamics of phenanthrenequinone on carbon nano-onion surfaces probed by quasielastic neutron scattering.

    Science.gov (United States)

    Chathoth, Suresh M; Anjos, Daniela M; Mamontov, Eugene; Brown, Gilbert M; Overbury, Steven H

    2012-06-21

    We used quasielastic neutron scattering (QENS) to study the dynamics of phenanthrenequinone (PQ) on the surface of onion-like carbon (OLC), or so-called carbon onions, as a function of surface coverage and temperature. For both the high- and low-coverage samples, we observed two diffusion processes; a faster process and nearly an order of magnitude slower process. On the high-coverage surface, the slow diffusion process is of long-range translational character, whereas the fast diffusion process is spatially localized on the length scale of ∼4.7 Å. On the low-coverage surface, both diffusion processes are spatially localized; on the same length scale of ∼4.7 Å for the fast diffusion and a somewhat larger length scale for the slow diffusion. Arrhenius temperature dependence is observed except for the long-range diffusion on the high-coverage surface. We attribute the fast diffusion process to the generic localized in-cage dynamics of PQ molecules, and the slow diffusion process to the long-range translational dynamics of PQ molecules, which, depending on the coverage, may be either spatially restricted or long-range. On the low-coverage surface, uniform surface coverage is not attained, and the PQ molecules experience the effect of spatial constraints on their long-range translational dynamics. Unexpectedly, the dynamics of PQ molecules on OLC as a function of temperature and surface coverage bears qualitative resemblance to the dynamics of water molecules on oxide surfaces, including practically temperature-independent residence times for the low-coverage surface. The dynamics features that we observed may be universal across different classes of surface adsorbates.

  14. Dynamics of Phenanthrenequinone on Carbon Nano-Onion Surfaces Probed by Quasielastic Neutron Scattering

    International Nuclear Information System (INIS)

    Mamontov, Eugene; Brown, Gilbert M.; Overbury, Steven H.; Mavila Chathoth, Suresh

    2012-01-01

    We used quasielastic neutron scattering (QENS) to study the dynamics of phenanthrenequinone (PQ) on the surface of onion-like carbon (OLC), or so called carbon onions, as a function of surface coverage and temperature. For both the high- and low-coverage samples, we observed two diffusion processes; a faster process and nearly an order of magnitude slower process. On the high-coverage surface, the slow diffusion process is of long-range translational character, whereas the fast diffusion process is spatially localized on the length scale of ∼ 4.7. On the low-coverage surface, both diffusion processes are spatially localized; on the same length scale of ∼ 4.7 for the fast diffusion and a somewhat larger length scale for the slow diffusion. Arrhenius temperature dependence is observed except for the long-range diffusion on the high-coverage surface. We attribute the fast diffusion process to the generic localized in-cage dynamics of PQ molecules, and the slow diffusion process to the long-range translational dynamics of PQ molecules, which, depending on the coverage, may be either spatially restricted, or long-range. On the low-coverage surface, uniform surface coverage is not attained, and the PQ molecules experience the effect of spatial constraints on their long-range translational dynamics. Unexpectedly, the dynamics of PQ molecules on OLC as a function of temperature and surface coverage bears qualitative resemblance to the dynamics of water molecules on oxide surfaces, including practically temperature-independent residence times for the low-coverage surface. The dynamics features that we observed may be universal across different classes of surface adsorbates.

  15. Calibrating Carbon Measurements in Basaltic Glass Using SIMS and FTIR: The Effect of Variable H2O Contents

    Science.gov (United States)

    Hervig, R. L.; Moore, G. M.; Roggensack, K.

    2009-12-01

    The effect of mixed volatiles (H2O + CO2) dissolved in basaltic glass on the calibrations of Fourier transform infra-red spectrometry (FTIR) and secondary ion mass spectrometry (SIMS) for H2O and CO2 is assessed. A series of mixed volatile-bearing calc-alkaline basalts were synthesized and analyzed using high-T vacuum manometry, FTIR, and SIMS. No significant deviations from the single volatile component calibrations were found for the FTIR method. The SIMS analyses of these well-characterized basaltic glasses were conducted in three different analytical modes: 1) using a Cs+ primary beam and detection of negative secondary ions shows that the yield of negative carbon ions shows minor (if any) change for H2O contents up to ~3 wt.% but decreases by nearly two-fold in glasses containing ≥5.5 wt.% H2O, 2) using an O- primary beam and detection of negative or positive secondary ions provides linear calibrations for CO2 concentrations in basalts and does not show a significant effect of H2O on the carbon ion yield. Testing the above SIMS approaches for determining H2O in mixed-volatile basaltic glasses shows: a) no effect of carbon on the yield of hydrogen ions, and b) the lowest background levels are achieved by using Cs+ or O- primary beams and detection of negative secondary ions. The analyses using O- primary beams and detection of negative secondary ions results in high session-to-session reproducibility and are also very simple, allowing visitors to SIMS laboratories to obtain high-quality microanalyses for H and C (and F & Cl) with minimal training. Analyses for carbon using positive secondary ions shows low sensitivity, and requires operation of the SIMS at high enough mass resolving power to eliminate interfering 24Mg2+ ions, but does represent an approach for adding C measurements to SIMS analyses of lithophile elements in melt inclusions.

  16. Fluoride content in bottled waters, juices and carbonated soft drinks in Mexico City, Mexico.

    Science.gov (United States)

    Jimenez-Farfan, M D; Hernandez-Guerrero, J C; Loyola-Rodriguez, J P; Ledesma-Montes, C

    2004-07-01

    The objective of this study was to analyse 283 samples of soft drinks available in the metropolitan market of Mexico City, Mexico: 105 juices, 101 nectars, 57 carbonated drinks and 20 bottled waters. Samples of the beverages were analysed using an Orion 720A potentiometer and an Orion 9609BN F ion-specific electrode. Fluoride concentration in the above-mentioned products ranged from 0.07 to 1.42 p.p.m. It was found that fluoride concentrations varied according to the brand, flavour and presentation of the product. The highest mean concentration of fluoride was found in the juices and cola drinks (0.67 +/- 0.38 and 0.49 +/- 0.41 p.p.m., respectively). The mean fluoride concentration for carbonated drinks was 0.43 +/- 0.36 p.p.m. Bottled waters had a fluoride concentration of 0.21 +/- 0.08 p.p.m. The findings suggest that fluoride ingested through bottled drinks represents an important part of the total fluoride ingested by the population. In view of the wide variation of fluoride concentration in the tested products, it is necessary to implement regulatory guidelines for controlling its concentration in order to prevent dental fluorosis.

  17. Growing up with stress - carbon sequestration and allocation dynamics of a broadleaf evergreen forest

    Science.gov (United States)

    Griebel, Anne; Bennett, Lauren T.; Arndt, Stefan K.

    2016-04-01

    Evergreen forests have the potential to sequester carbon year-round due to the presence of leaves with a multi-year lifespan. Eucalypt forests occur in warmer climates where temperature and radiation are not imposing a strong seasonality. Thus, unlike deciduous or many coniferous trees, many eucalypts grow opportunistically as conditions allow. As such, many eucalypts do not produce distinct growth rings, which present challenges to the implementation of standard methods and data interpretation approaches for monitoring and explaining carbon allocation dynamics in response to climatic stress. As a consequence, there is a lack of detailed understanding of seasonal growth dynamics of evergreen forests as a whole, and, in particular, of the influence of climatic drivers on carbon allocation to the various biomass pools. We used a multi-instrument approach in a mixed species eucalypt forest to investigate the influence of climatic drivers on the seasonal growth dynamics of a predominantly temperate and moisture-regulated environment in south-eastern Australia. Ecosystem scale observations of net ecosystem exchange (NEE) from a flux tower in the Wombat forest near Melbourne indicated that the ecosystem is a year-round carbon sink, but that intra-annual variations in temperature and moisture along with prolonged heat waves and dry spells resulted in a wide range of annual sums over the past three years (NEE ranging from ~4 to 12 t C ha-1 yr-1). Dendrometers were used to monitor stem increments of the three dominant eucalypt species. Stem expansion was generally opportunistic with the greatest increments under warm but moist conditions (often in spring and autumn), and the strongest indicators of stem growth dynamics being radiation, vapour pressure deficit and a combined heat-moisture index. Differences in the seasonality of stem increments between species were largely due to differences in the canopy position of sampled individuals. The greatest stem increments were

  18. Land use and carbon dynamics in the southeastern United States from 1992 to 2050

    International Nuclear Information System (INIS)

    Zhao, Shuqing; Liu, Shuguang; Sohl, Terry; Werner, Jeremy; Young, Claudia

    2013-01-01

    Land use and land cover change (LUCC) plays an important role in determining the spatial distribution, magnitude, and temporal change of terrestrial carbon sources and sinks. However, the impacts of LUCC are not well understood and quantified over large areas. The goal of this study was to quantify the spatial and temporal patterns of carbon dynamics in various terrestrial ecosystems in the southeastern United States from 1992 to 2050 using a process-based modeling system and then to investigate the impacts of LUCC. Spatial LUCC information was reconstructed and projected using the FOREcasting SCEnarios of future land cover (FORE-SCE) model according to information derived from Landsat observations and other sources. Results indicated that urban expansion (from 3.7% in 1992 to 9.2% in 2050) was expected to be the primary driver for other land cover changes in the region, leading to various declines in forest, cropland, and hay/pasture. The region was projected to be a carbon sink of 60.4 gC m −2  yr −1 on average during the study period, primarily due to the legacy impacts of large-scale conversion of cropland to forest that happened since the 1950s. Nevertheless, the regional carbon sequestration rate was expected to decline because of the slowing down of carbon accumulation in aging forests and the decline of forest area. (letter)

  19. Evolutionarily stable strategy of carbon and nitrogen investments in forest leaves and its application in vegetation dynamic modeling

    Science.gov (United States)

    Weng, E.; Farrior, C.; Dybzinski, R.; Pacala, S. W.

    2015-12-01

    Leaf mass per area (LMA) and leaf lifespan (LL) are two highly correlated plant traits that are key to plant physiological and ecological properties. Usually, low LMA means short LL, high nitrogen (N) content per unit mass, and fast turnover rates of nutrients; high LMA leads to long LL, low N content, and slow turnover rates. Deciduous trees with low LMA and short lifespan leaves have low carbon cost but high nitrogen demand; and evergreen trees, with high LMA and long lifespan leaves, have high carbon cost but low nitrogen demand. These relationships lead to: 1) evergreen trees have higher leaf area index than deciduous trees; 2) evergreen trees' carbon use efficiency is lower than the deciduous trees' because of their thick leaves and therefore high maintenance respiration; 3) the advantage of evergreens trees brought by their extra leaves over deciduous trees diminishes with increase N in ecosystem. These facts determine who will win when trees compete with each other in a N-limited ecosystem. In this study, we formulate a mathematical model according to the relationships between LMA, LL, leaf nitrogen, and leaf building and maintenance cost, where LMA is the fundamental variable determining the other three. We analyze the evolutionarily stable strategies (ESSs) of LMA with this mathematical model by examining the benefits of carbon and nitrogen investments to leaves in ecosystems with different N. The model shows the ESS converges to low LMA at high N and high LMA at low N. At intermediate N, there are two ESSs at low and high ends of LMA, respectively. The ESS also leads to low forest productivity by outcompeting the possible high productive strategies. We design a simulation scheme in an individual-based competition model (LM3-PPA) to simulate forest dynamics as results of the competition between deciduous and evergreen trees in three different biomes, which are temperate deciduous forest, deciduous-evergreen mixed forest, and boreal evergreen forest. The

  20. Quasi-static and dynamic strain sensing using carbon nanotube/epoxy nanocomposite thin films

    International Nuclear Information System (INIS)

    Anand, Sandeep V; Roy Mahapatra, D

    2009-01-01

    Thin films are developed by dispersing carbon black nanoparticles and carbon nanotubes (CNTs) in an epoxy polymer. The films show a large variation in electrical resistance when subjected to quasi-static and dynamic mechanical loading. This phenomenon is attributed to the change in the band-gap of the CNTs due to the applied strain, and also to the change in the volume fraction of the constituent phases in the percolation network. Under quasi-static loading, the films show a nonlinear response. This nonlinearity in the response of the films is primarily attributed to the pre-yield softening of the epoxy polymer. The electrical resistance of the films is found to be strongly dependent on the magnitude and frequency of the applied dynamic strain, induced by a piezoelectric substrate. Interestingly, the resistance variation is found to be a linear function of frequency and dynamic strain. Samples with a small concentration of just 0.57% of CNT show a sensitivity as high as 2.5% MPa −1 for static mechanical loading. A mathematical model based on Bruggeman's effective medium theory is developed to better understand the experimental results. Dynamic mechanical loading experiments reveal a sensitivity as high as 0.007% Hz −1 at a constant small-amplitude vibration and up to 0.13%/μ-strain at 0–500 Hz vibration. Potential applications of such thin films include highly sensitive strain sensors, accelerometers, artificial neural networks, artificial skin and polymer electronics

  1. Organic Carbon Stocks, Dynamics and Restoration in Relation to Soils of Agroecosystems in Ethiopia: A Review

    Directory of Open Access Journals (Sweden)

    Getaneh Gebeyehu

    2017-02-01

    Full Text Available Soils represent the largest carbon pool and play important roles for carbon storage for prolonged periods in agroecosystems. A number of studies were conducted to quantify soil organic carbon (SOC worldwide. The objective of this review was to evaluate organic carbon stocks, dynamics and restoration in soils of agroecosystems in Ethiopia. Soil data from 32 different observations, representing four different agroecosystems, were analysed. The mean SOC stocks in the four agroecosystems varied and ranged from 25.66 (sub-humid agroecosystem to 113.17 (humid mid-highland agroecosystems Mg C ha-1 up to one meter depth. The trend of mean SOC followed (in descending order: humid mid-highland (113.17 Mg C ha-1 > per-humid highland (57.14 Mg C ha-1 > semi-arid (25.77 Mg C ha-1 > sub-humid (25.66 Mg C ha-1. Compared with soils of tropical countries, those in Ethiopian agroecosystems contained low SOC storage potential. This might be associated with differences in measurement and analysis methods as 53.1% of the studies employed the Walkley-Black Method, which is known to underestimate carbon stocks in addition to ecological and management effects. However, shifts of land management from rain-fed to irrigation farming systems exhibited progress in the improvement of mean SOC storage potential. The analyses showed that farming systems involving irrigation sequestered more carbon than rain-fed farm systems. The mean SOC in the various agricultural land uses followed the following trend (in descending order: agroforestry (153.57 Mg C ha-1 > grazing land (34.61 Mg C ha-1 > cereal cultivation (24.18 Mg C ha-1. Therefore, the possible solutions for improvement of organic carbon stocks would be implementation of appropriate restoration strategies based on agroecosystems.INTERNATIONAL JOURNAL OF ENVIRONMENT Volume-6, Issue-1, Dec-Feb 2016/17, page: 1-22 

  2. Projection of corn production and stover-harvesting impacts on soil organic carbon dynamics in the U.S. Temperate Prairies

    Science.gov (United States)

    Wu, Yiping; Liu, Shuguang; Young, Claudia J.; Dahal, Devendra; Sohl, Terry L.; Davis, Brian

    2015-01-01

    Terrestrial carbon sequestration potential is widely considered as a realistic option for mitigating greenhouse gas emissions. However, this potential may be threatened by global changes including climate, land use, and management changes such as increased corn stover harvesting for rising production of cellulosic biofuel. Therefore, it is critical to investigate the dynamics of soil organic carbon (SOC) at regional or global scale. This study simulated the corn production and spatiotemporal changes of SOC in the U.S. Temperate Prairies, which covers over one-third of the U.S. corn acreage, using a biogeochemical model with multiple climate and land-use change projections. The corn production (either grain yield or stover biomass) could reach 88.7–104.7 TgC as of 2050, 70–101% increase when compared to the base year of 2010. A removal of 50% stover at the regional scale could be a reasonable cap in view of maintaining SOC content and soil fertility especially in the beginning years. The projected SOC dynamics indicated that the average carbon sequestration potential across the entire region may vary from 12.7 to 19.6 g C/m2/yr (i.e., 6.6–10.2 g TgC/yr). This study not only helps understand SOC dynamics but also provides decision support for sustainable biofuel development.

  3. Comparative Environmental Life Cycle Assessment of Alternative Uses of Wastewater Carbon Content

    DEFF Research Database (Denmark)

    Kroghsbo, Nena; Nicolaisen, Janna; Wenzel, Henrik

    Alternative scenarios for the wastewater and sludge treatment configurations in urban wastewater treatment were studied with the aim of comparing their environmental aspects. As the reference, a conventional activated sludge treatment was chosen including a primary settling and biogas made from...... for assessing the environmental priorities between using the carbon for nutrient removal through denitrification and energy production/recovery through biogas or PHA. The preliminary results and conclusions of the study will be presented....... the mixed primary and secondary sludge. This reference was then compared to an alternative use of the mixed sludge for the fermentative generation of polyhydroxyalkanoates, PHA and subsequent use of the PHA to substitute polypropylene on the polymer markets. This comparison allows for assessing...

  4. Molecular dynamics investigation of carbon nanotube junctions in non-aqueous solutions

    KAUST Repository

    Gkionis, Konstantinos

    2014-07-23

    The properties of liquids in a confined environment are known to differ from those in the bulk. Extending this knowledge to geometries defined by two metallic layers in contact with the ends of a carbon nanotube is important for describing a large class of nanodevices that operate in non-aqueous environments. Here we report a series of classical molecular dynamics simulations for gold-electrode junctions in acetone, cyclohexane and N,N-dimethylformamide solutions and analyze the structure and the dynamics of the solvents in different regions of the nanojunction. The presence of the nanotube has little effect on the ordering of the solvents along its axis, while in the transversal direction deviations are observed. Importantly, the orientational dynamics of the solvents at the electrode-nanotube interface differ dramatically from that found when only the electrodes are present.

  5. Assessing the dynamic material criticality of infrastructure transitions: A case of low carbon electricity

    International Nuclear Information System (INIS)

    Roelich, Katy; Dawson, David A.; Purnell, Phil; Knoeri, Christof; Revell, Ruairi; Busch, Jonathan; Steinberger, Julia K.

    2014-01-01

    Highlights: • We present a method to analyse material criticality of infrastructure transitions. • Criticality is defined as the potential for, and exposure to, supply disruption. • Our method is dynamic reducing the probability of lock-in to at-risk technologies. • We show that supply disruption potential is reducing but exposure is increasing. - Abstract: Decarbonisation of existing infrastructure systems requires a dynamic roll-out of technology at an unprecedented scale. The potential disruption in supply of critical materials could endanger such a transition to low-carbon infrastructure and, by extension, compromise energy security more broadly because low carbon technologies are reliant on these materials in a way that fossil-fuelled energy infrastructure is not. Criticality is currently defined as the combination of the potential for supply disruption and the exposure of a system of interest to that disruption. We build on this definition and develop a dynamic approach to quantifying criticality, which monitors the change in criticality during the transition towards a low-carbon infrastructure goal. This allows us to assess the relative risk of different technology pathways to reach a particular goal and reduce the probability of being ‘locked in’ to currently attractive but potentially future-critical technologies. To demonstrate, we apply our method to criticality of the proposed UK electricity system transition, with a focus on neodymium. We anticipate that the supply disruption potential of neodymium will decrease by almost 30% by 2050; however, our results show the criticality of low carbon electricity production increases ninefold over this period, as a result of increasing exposure to neodymium-reliant technologies

  6. Fed-batch cultivation of baker's yeast followed by nitrogen or carbon starvation: effects on fermentative capacity and content of trehalose and glycogen

    DEFF Research Database (Denmark)

    Jørgensen, Henning; Olsson, Lisbeth; Rønnow, B.

    2002-01-01

    An industrial strain of Saccharomyces cerevisiae (DGI 342) was cultivated in fed-batch cultivations at a specific growth rate of 0.2 h(-1). The yeast was then exposed to carbon or nitrogen starvation for up to 8 h, to study the effect of starvation on fermentative capacity and content of protein...... of the yeast cells, and the fermentative capacity per gram dry-weight decreased by 40%. The protein content in the carbon-starved yeast increased as a result of starvation due to the fact that the content of glycogen was reduced. The fermentative capacity per gram dry-weight was, however, unaltered....... increased from 45 to 64 mg (g dry-weight)(-1), whereas the glycogen content in the same period was reduced from 55 to 5 mg (g dry-weight)(-1). Glycogen was consumed faster than trehalose during storage of the starved yeast for 1 month. Nitrogen starvation resulted in a decrease in the protein content...

  7. Carbon exchange in biological soil crust communities under differential temperatures and soil water contents: implications for global change

    Science.gov (United States)

    Grote, Edmund E.; Belnap, Jayne; Housman, David C.; Sparks, Jed P.

    2010-01-01

    Biological soil crusts (biocrusts) are an integral part of the soil system in arid regions worldwide, stabilizing soil surfaces, aiding vascular plant establishment, and are significant sources of ecosystem nitrogen and carbon. Hydration and temperature primarily control ecosystem CO2 flux in these systems. Using constructed mesocosms for incubations under controlled laboratory conditions, we examined the effect of temperature (5-35 1C) and water content (WC, 20-100%) on CO2 exchange in light cyanobacterially dominated) and dark cyanobacteria/lichen and moss dominated) biocrusts of the cool Colorado Plateau Desert in Utah and the hot Chihuahuan Desert in New Mexico. In light crusts from both Utah and New Mexico, net photosynthesis was highest at temperatures 430 1C. Net photosynthesis in light crusts from Utah was relatively insensitive to changes in soil moisture. In contrast, light crusts from New Mexico tended to exhibit higher rates of net photosynthesis at higher soil moisture. Dark crusts originating from both sites exhibited the greatest net photosynthesis at intermediate soil water content (40-60%). Declines in net photosynthesis were observed in dark crusts with crusts from Utah showing declines at temperatures 425 1C and those originating from New Mexico showing declines at temperatures 435 1C. Maximum net photosynthesis in all crust types from all locations were strongly influenced by offsets in the optimal temperature and water content for gross photosynthesis compared with dark respiration. Gross photosynthesis tended to be maximized at some intermediate value of temperature and water content and dark respiration tended to increase linearly. The results of this study suggest biocrusts are capable of CO2 exchange under a wide range of conditions. However, significant changes in the magnitude of this exchange should be expected for the temperature and precipitation changes suggested by current climate models.

  8. Designing a dynamic data driven application system for estimating real-time load of dissolved organic carbon in a river

    Science.gov (United States)

    Ying. Ouyang

    2012-01-01

    Understanding the dynamics of naturally occurring dissolved organic carbon (DOC) in a river is central to estimating surface water quality, aquatic carbon cycling, and global climate change. Currently, determination of the DOC in surface water is primarily accomplished by manually collecting samples for laboratory analysis, which requires at least 24 h. In other words...

  9. Effects of Subsetting by Carbon Content, Soil Order, and Spectral Classification on Prediction of Soil Total Carbon with Diffuse Reflectance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Meryl L. McDowell

    2012-01-01

    Full Text Available Subsetting of samples is a promising avenue of research for the continued improvement of prediction models for soil properties with diffuse reflectance spectroscopy. This study examined the effects of subsetting by soil total carbon (Ct content, soil order, and spectral classification with k-means cluster analysis on visible/near-infrared and mid-infrared partial least squares models for Ct prediction. Our sample set was composed of various Hawaiian soils from primarily agricultural lands with Ct contents from <1% to 56%. Slight improvements in the coefficient of determination (R2 and other standard model quality parameters were observed in the models for the subset of the high activity clay soil orders compared to the models of the full sample set. The other subset models explored did not exhibit improvement across all parameters. Models created from subsets consisting of only low Ct samples (e.g., Ct < 10% showed improvement in the root mean squared error (RMSE and percent error of prediction for low Ct soil samples. These results provide a basis for future study of practical subsetting strategies for soil Ct prediction.

  10. Contemporary carbon dynamics in terrestrial ecosystems in the Southeastern Plains of the United States

    Science.gov (United States)

    Liu, S.; Loveland, Thomas R.; Kurtz, R.M.

    2004-01-01

    Quantifying carbon dynamics over large areas is frequently hindered by the lack of consistent, high-quality, spatially explicit land use and land cover change databases and appropriate modeling techniques. In this paper, we present a generic approach to address some of these challenges. Land cover change information in the Southeastern Plains ecoregion was derived from Landsat data acquired in 1973, 1980, 1986, 1992, and 2000 within 11 randomly located 20-km × 20-km sample blocks. Carbon dynamics within each of the sample blocks was simulated using the General Ensemble Biogeochemical Modeling System (GEMS), capable of assimilating the variances and covariance of major input variables into simulations using an ensemble approach. Results indicate that urban and forest areas have been increasing, whereas agricultural land has been decreasing since 1973. Forest clear-cutting activity has intensified, more than doubling from 1973 to 2000. The Southeastern Plains has been acting as a carbon sink since 1973, with an average rate of 0.89 Mg C/ha/yr. Biomass, soil organic carbon (SOC), and harvested materials account for 56%, 34%, and 10% of the sink, respectively. However, the sink has declined continuously during the same period owing to forest aging in the northern part of the ecoregion and increased forest clear-cutting activities in the south. The relative contributions to the sink from SOC and harvested materials have increased, implying that these components deserve more study in the future. The methods developed here can be used to quantify the impacts of human management activities on the carbon cycle at landscape to global scales.

  11. Sediment deposition and associated organic carbon dynamics in a tropical River system; the Tana River (Kenya)

    Science.gov (United States)

    Omengo, Fred; Alleman, Tine; Geeraert, Naomi; Bouillon, Steven; Govers, Gerard

    2014-05-01

    Floodplains are known to play a potentially important role in regulating the downstream transport of sediments, carbon, and nutrients in river systems. We investigated sediment and carbon transport, retention and deposition in the floodplains of the lower Tana River (Kenya), between the two main downstream gauging stations Garissa and Garsen. The Tana River is the largest river in Kenya and runs for more than 1,000 km from Kenya's highlands (Mt Kenya and the Aberdare mountains). The catchment covers around 100,000km² and the hydrology is controlled by the shifting of intertropical convergence Zone (ITCZ), leading to a bimodal precipitation cycle. Sediment cores were taken at various sites within the floodplains, and analysed for bulk density, organic carbon (OC) and nitrogen content, stable isotope signatures (δ13C) of organic C, and grain size distribution. We determined 137Cs and 210Pbxs activities in order to estimate historical sedimentation rates and to quantify the post-depositional losses of organic carbon. In addition, we measured fresh sediment deposition rates immediately after an extended period of flooding, along with associated flood heights and the distance relative to the main River . Fresh sediment deposition rates ranged between 1mm and 15mm for the period of study at an average rate of 1.13 gcm-3 (dry weight). This varied with distance of the floodplain from the main river and its elevation relative to the full bank. The fresh deposited sediment had an average organic carbon content of 1.55 ± 0.42%. Sediment cores showed a strong downcore gradient in OC content, from 3 - 12%C in the top layers to typically less than 0.5 % below 50 cm. The C:N ratios varied from 8 to 16 with majority averaging 9-11. Stable isotope signatures (δ13C) of organic C varied between -28‰ to -16‰ for the deeper core samples. 137Cs and 210Pbxs profiles indicate a vertical accretion at an average rate of 0.6 cm per year in the sites measured so far. The Tana river

  12. Subsoil carbon accumulation on an arable Mollisol is retention dominated, in contrast to input driven carbon dynamics in topsoil

    Science.gov (United States)

    Beem-Miller, Jeffrey; Lehmann, Johannes

    2017-04-01

    The majority of the world's soil organic carbon (OC) stock is stored below 30 cm in depth, yet sampling for soil OC assessment rarely goes below 30 cm. Recent studies suggest that subsoil OC is distinct from topsoil OC in quantity and quality: subsoil OC concentrations are typically much lower and turnover times are much longer, but the mechanisms involved in retention and input of OC to the subsoil are not well understood. Improving our understanding of subsoil OC is essential for balancing the global carbon budget and confronting the challenge of global climate change. This study was undertaken to assess the relationship between OC stock and potential drivers of OC dynamics, including both soil properties and environmental covariates, in topsoil (0 to 30 cm) versus subsoil (30 to 75 cm). The performance of commonly used depth functions in predicting OC stock from 0 to 75 cm was also assessed. Depth functions are a useful tool for extrapolating OC stock below the depth of sampling, but may poorly model "hot spots" of OC accumulation, and be inadequate for modelling the distinct dynamics of topsoil and subsoil OC when applied with a single functional form. We collected two hundred soil cores on an arable Mollisol, sectioned into five depth increments (0-10, 10-20, 20-30, 30-50, and 50-75 cm), and performed the following analyses on each depth increment: concentration of OC, inorganic C, permanganate oxidizable carbon (POXC), and total N, as well as texture, pH, and bulk density; a digital elevation model was used to calculate elevation, slope, curvature, and soil topographic wetness index. We found that topsoil OC stocks were significantly correlated (p 7.0), flat topography, a high OC to total N ratio, and a high ratio of POXC to OC. These findings suggest that at this site, topsoil OC stock is input driven, while OC accumulation in the subsoil is retention dominated. Accordingly, a new depth function is proposed that uses a linear relationship to model OC stock

  13. The Role of Stream Water Carbon Dynamics and Export in the Carbon Balance of a Tropical Seasonal Rainforest, Southwest China

    Science.gov (United States)

    Zhou, Wen-Jun; Zhang, Yi-Ping; Schaefer, Douglas A.; Sha, Li-Qing; Deng, Yun; Deng, Xiao-Bao; Dai, Kai-Jie

    2013-01-01

    A two-year study (2009 ∼ 2010) was carried out to investigate the dynamics of different carbon (C) forms, and the role of stream export in the C balance of a 23.4-ha headwater catchment in a tropical seasonal rainforest at Xishuangbanna (XSBN), southwest China. The seasonal volumetric weighted mean (VWM) concentrations of total inorganic C (TIC) and dissolved inorganic C (DIC) were higher, and particulate inorganic C (PIC) and organic C (POC) were lower, in the dry season than the rainy season, while the VWM concentrations of total organic C (TOC) and dissolved organic C (DOC) were similar between seasons. With increased monthly stream discharge and stream water temperature (SWT), only TIC and DIC concentrations decreased significantly. The most important C form in stream export was DIC, accounting for 51.8% of the total C (TC) export; DOC, POC, and PIC accounted for 21.8%, 14.9%, and 11.5% of the TC export, respectively. Dynamics of C flux were closely related to stream discharge, with the greatest export during the rainy season. C export in the headwater stream was 47.1 kg C ha−1 yr−1, about 2.85% of the annual net ecosystem exchange. This finding indicates that stream export represented a minor contribution to the C balance in this tropical seasonal rainforest. PMID:23437195

  14. The role of stream water carbon dynamics and export in the carbon balance of a tropical seasonal rainforest, southwest China.

    Directory of Open Access Journals (Sweden)

    Wen-Jun Zhou

    Full Text Available A two-year study (2009 ~ 2010 was carried out to investigate the dynamics of different carbon (C forms, and the role of stream export in the C balance of a 23.4-ha headwater catchment in a tropical seasonal rainforest at Xishuangbanna (XSBN, southwest China. The seasonal volumetric weighted mean (VWM concentrations of total inorganic C (TIC and dissolved inorganic C (DIC were higher, and particulate inorganic C (PIC and organic C (POC were lower, in the dry season than the rainy season, while the VWM concentrations of total organic C (TOC and dissolved organic C (DOC were similar between seasons. With increased monthly stream discharge and stream water temperature (SWT, only TIC and DIC concentrations decreased significantly. The most important C form in stream export was DIC, accounting for 51.8% of the total C (TC export; DOC, POC, and PIC accounted for 21.8%, 14.9%, and 11.5% of the TC export, respectively. Dynamics of C flux were closely related to stream discharge, with the greatest export during the rainy season. C export in the headwater stream was 47.1 kg C ha(-1 yr(-1, about 2.85% of the annual net ecosystem exchange. This finding indicates that stream export represented a minor contribution to the C balance in this tropical seasonal rainforest.

  15. Respiratory Effects of Inhaled Single-Walled Carbon Nanotubes: The Role of Particle Morphology and Iron Content

    Science.gov (United States)

    Madl, Amy Kathleen

    Nanotechnology provides promise for significant advancements in a number of different fields including imaging, electronics, and therapeutics. With worldwide production of carbon nanotubes (CNTs) exceeding over 500 metric tons annually and industry growth expecting to double over the next 5 yr, there are concerns our understanding of the hazards of these nanomaterials may not be keeping pace with market demand. The physicochemical properties of CNTs may delineate the key features that determine either toxicity or biocompatibility and assist in evaluating the potential health risks posed in industrial and consumer product settings. We hypothesized that the iron content and morphology of inhaled single-walled carbon nanotubes (SWCNTs) influences the extent of cellular injury and alters homeostasis in the lung. To address this hypothesis, (1) an aerosol system was developed to deliver carbon-based nanomaterials in a manner of exposure that is physiologically and environmentally relevant (e.g., inhalation), (2) acute (1 d) and subacute (10 d) nose-only inhalation studies to a well-characterized aerosol of iron-containing (FeSWCNT) versus cleaned (iron removed, cSWCNTs) SWCNTs were conducted to evaluate the time-course patterns of possible injury through measurement of markers of cytotoxicity, inflammation, and cellular remodeling/homeostasis, and (3) the effects of SWCNTs were compared to other well-studied materials (e.g. non-fibrous, low-iron content ultrafine carbon black and fibrous, high-iron content, highly persistent, durable and potent carcinogen crocidolite) to offer insights into the relative toxicity of these nanomaterials as well as the possible mechanisms by which the effects occur. Rats (SD) were exposed to either aerosolized SWCNTs (raw FeSWCNT or purified cSWCNT), carbon black (CB), crocidolite, or fresh air via nose-only inhalation. Markers of inflammation and cytotoxicity in lung lavage, mucin in different airway generations, and collagen in the

  16. Dynamic contents of energy and organic nutrient in steppe growths of the Mohelenská Serpentine Steppe National Nature Reserve

    Directory of Open Access Journals (Sweden)

    Pavel Veselý

    2006-01-01

    Full Text Available The aim of the study was to determine the dynamics in the content of organic nutrients, ash and energy in dry matter of growths within the Mohelenská Serpentine Steppe National Nature Reserve (NPR, and to document their initial nutritive value before the intended grazing. Plant samples in 1995 and 1996 during the growing season in 14-days intervals from the area of 3 × 1 m2. Amounts of dry matter, fibre, nitrogen substances, fat and ashes were determined in growths according to the ANONYM (2001. Nitrogen-free extract substances (BNLV were determined by final calculating; BE, ME, NEL, NEV, PDIN and PDIE were calculated using the regression equations (VESELÝ and ZEMAN, 1995, 1997. Combining ratio (SP was calculated according to the relation: SP = PDIN (g/NEL (MJ. The dynamics of the contents of dry matter, organic nutrients, ashes and energy were assessed in the growth during the vegetation period and the dynamics was compared with standardized requirements of sheep (no pregnant ewe. Regression and correlation relations for nutrition value of the growths during vegetation period were calculated by use of mathematical-statistical analysis. Only statistically significantly (P<0.05 different parameters form the zero are presented in the paper. The content of dry matter in the growths culminated in summer months (places D8, E13, B17 and it was accompanied by depression in autumn months. After the highest content of crude protein, PDIN and PDIE recorded in spring months summer depression (August followed, this depression was partly balanced by autumn growth of vegetation. The content of ash in steppe growths increased during evaluated period. Similar tendency was registered for fat. Also the contents of fibre and BNLV linearly increased. The contents of nitrogen nutrients and energy corresponded with standardized requirements for sheep during whole vegetation period. Conversely the content of fibre highly exceeded the requirement except in spring

  17. Inferring brown carbon content from UV aerosol absorption measurements during biomass burning season

    Science.gov (United States)

    Mok, J.; Krotkov, N. A.; Arola, A. T.; Torres, O.; Jethva, H. T.; Andrade, M.; Labow, G. J.; Eck, T. F.; Li, Z.; Dickerson, R. R.; Stenchikov, G. L.; Osipov, S.

    2015-12-01

    Measuring spectral dependence of light absorption by colored organic or "brown" carbon (BrC) is important, because of its effects on photolysis rates of ozone and surface ultraviolet (UV) radiation. Enhanced UV spectral absorption by BrC can in turn be exploited for simultaneous retrievals of BrC and black carbon (BC) column amounts in field campaigns. We present an innovative ground-based retrieval of BC and BrC volume fractions and their mass absorption efficiencies during the biomass burning season in Santa Cruz, Bolivia in September-October 2007. Our method combines retrieval of BC volume fraction using AERONET inversion in visible wavelengths with the inversion of total BC+BrC absorption (i.e., column effective imaginary refractive index, kmeas) using Diffuse/Direct irradiance measurements in UV wavelengths. First, we retrieve BrC volume fraction by fitting kmeas at 368nm using Maxwell-Garnett (MG) mixing rules assuming: (1) flat spectral dependence of kBC, (2) known value of kBrC at 368nm from laboratory absorption measurements or smoke chamber experiments, and (3) known BC volume fraction from AERONET inversion. Next, we derive kBrC in short UVB wavelengths by fitting kmeas at 305nm, 311nm, 317nm, 325nm, and 332nm using MG mixing rules and fixed volume fractions of BC and BrC. Our retrievals show larger than expected spectral dependence of kBrC in UVB wavelengths, implying reduced surface UVB irradiance and inhibited photolysis rates of surface ozone destruction. We use a one-dimensional chemical box model to show that the observed strong wavelength dependence of BrC absorption leads to inhibited photolysis of ozone to O(1D), a loss mechanism, while having little impact or even accelerating photolysis of NO2, an ozone production mechanism. Although BC only absorption in biomass burning aerosols is important for climate radiative forcing in the visible wavelengths, additional absorption by BrC is important because of its impact on surface UVB radiation

  18. Dynamic hybrid life cycle assessment of energy and carbon of multicrystalline silicon photovoltaic systems.

    Science.gov (United States)

    Zhai, Pei; Williams, Eric D

    2010-10-15

    This paper advances the life cycle assessment (LCA) of photovoltaic systems by expanding the boundary of the included processes using hybrid LCA and accounting for the technology-driven dynamics of embodied energy and carbon emissions. Hybrid LCA is an extended method that combines bottom-up process-sum and top-down economic input-output (EIO) methods. In 2007, the embodied energy was 4354 MJ/m(2) and the energy payback time (EPBT) was 2.2 years for a multicrystalline silicon PV system under 1700 kWh/m(2)/yr of solar radiation. These results are higher than those of process-sum LCA by approximately 60%, indicating that processes excluded in process-sum LCA, such as transportation, are significant. Even though PV is a low-carbon technology, the difference between hybrid and process-sum results for 10% penetration of PV in the U.S. electrical grid is 0.13% of total current grid emissions. Extending LCA from the process-sum to hybrid analysis makes a significant difference. Dynamics are characterized through a retrospective analysis and future outlook for PV manufacturing from 2001 to 2011. During this decade, the embodied carbon fell substantially, from 60 g CO(2)/kWh in 2001 to 21 g/kWh in 2011, indicating that technological progress is realizing reductions in embodied environmental impacts as well as lower module price.

  19. Revealing the Dynamics of Platinum Nanoparticle Catalysts on Carbon in Oxygen and Water Using Environmental TEM

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Langli [Environmental; Engelhard, Mark H. [Environmental; Shao, Yuyan [Environmental; Wang, Chongmin [Environmental

    2017-10-02

    Deactivation of supported metal nanoparticle catalysts, especially in relevant gas condition, is a critical challenge for many technological applications, including heterogeneous catalysis, electrocatalysis, fuel cells, biomedical imaging and drug delivery. It has been far more commonly realized that deactivation of catalysts stems from surface area loss due to particle coarsening, however, for which the mechanism remains largely unclear. Herein, we use aberration corrected environmental transmission electron microscopy, at atomic level, to in-situ observe the dynamics of Pt catalyst in fuel cell relevant gas conditions. Particles migration and coalescence is observed to be the dominant coarsening process. As compared with the case of H2O, O2 promotes Pt nanoparticle migration on carbon surface. Surprisingly, coating Pt/carbon with a nanofilm of electrolyte (Nafion ionomer) leads to a faster migration of Pt in H2O than in O2, a consequence of Nafion-carbon interface water “lubrication” effect. Atomically, the particles coalescence is featured by re-orientation of particles towards lattice matching, a process driven by orientation dependent van der Waals force. These results provide direct observations of dynamics of metal nanoparticles at critical surface/interface under relevant conditions and yield significant insights into the multi-phase interaction in related technological processes.

  20. Human impacts on 20th century fire dynamics and implications for global carbon and water trajectories

    Science.gov (United States)

    Li, Fang; Lawrence, David M.; Bond-Lamberty, Ben

    2018-03-01

    Fire is a fundamental Earth system process and the primary ecosystem disturbance on the global scale. It affects carbon and water cycles through changing terrestrial ecosystems, and at the same time, is regulated by weather and climate, vegetation characteristics, and, importantly, human ignitions and suppression (i.e., the direct human effect on fire). Here, we utilize the Community Land Model version 4.5 (CLM4.5) to quantify the impacts of changes in human ignition and suppression on fire dynamics and associated carbon and water cycles. We find that the impact is to significantly reduce the 20th century global burned area by a century average of 38 Mha/yr and by 103 Mha/yr at the end of the century. Land carbon gain is weakened by 17% over the 20th century, mainly due to increased human deforestation fires and associated escape fires (i.e., degradation fires) in the tropical humid forests, even though the decrease in burned area in many other regions due to human fire suppression acts to increase land carbon gain. The direct human effect on fire weakens the upward trend in global runoff throughout the century by 6% and enhances the upward trend in global evapotranspiration since 1945 by 7%. In addition, the above impacts in densely populated, highly developed (if population density > 0.1 person/km2), or moderately populated and developed regions are of opposite sign to those in other regions. Our study suggests that particular attention should be paid to human deforestation and degradation fires in the tropical humid forests when reconstructing and projecting fire carbon emissions and net atmosphere-land carbon exchange and estimating resultant impacts of direct human effect on fire.

  1. Carbon Dynamics in the Hyporheic Zone of a Headwater Mountain Stream in the Cascade Mountains, Oregon

    Science.gov (United States)

    Wondzell, S. M.; Corson-rikert, H.; Haggerty, R.; Dosch, N.

    2015-12-01

    We investigated carbon dynamics in the hyporheic zone of a steep, forested, headwater catchment in the Cascade Mountains of western Oregon, USA. Water samples were collected monthly from the stream and a well network between July and December 2013 and again in March 2014. Samples collected from the well network showed that DOC concentrations decreased, and that DIC concentrations increased, with median travel time through the hyporheic zone on all sample dates. Further, the magnitude of the observed increase in DIC was approximately 10-times too large to be explained by metabolism of stream-source DOC. We examined two alternative explanations: 1) that different source waters - either groundwater rich in DIC or lateral inputs of soil water rich in labile DOC that was subsequently metabolized to DIC - mixed with stream water and thereby accounted for the high concentrations of DIC observed in the hyporheic zone, or 2) that changes in the concentrations of DOC and DIC were best explained by in-situ biogeochemical processing of buried particulate organic matter. End-member mixing analyses showed that neither groundwater nor lateral inputs of soil water influenced carbon chemistry within the hyporheic zone. The analyses could not rule out leaching from the overlying unsaturated riparian soils as a potential source of DOC, but the rate of input from this source would have to be much smaller than the rate at which DOC was metabolized in the hyporheic zone because concentrations of DOC in the hyporheic zone were always lower than in the stream. Overall, our results suggest that particulate organic carbon, perhaps augmented with DOC leached from the overlying soils, is the primary source of organic carbon to the hyporheic zone. Further, these measurements suggest that riparian zones supply, via hyporheic exchange, a disproportionately large fraction of carbon to headwater streams and may therefore play an outsized role in the global carbon cycle.

  2. Human impacts on 20th century fire dynamics and implications for global carbon and water trajectories

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fang; Lawrence, David M.; Bond-Lamberty, Ben

    2018-03-01

    Fire is a fundamental Earth system process and the primary ecosystem disturbance on the global scale. It affects carbon and water cycles through changing terrestrial ecosystems, and at the same time, is regulated by weather and climate, vegetation characteristics, and, importantly, human ignitions and suppression (i.e., the direct human effect on fire). Here, we utilize the Community Land Model version 4.5 (CLM4.5) to quantify the impacts of changes in human ignition and suppression on fire dynamics and associated carbon and water cycles. We find that the impact is to significantly reduce the 20th century global burned area by a century average of 38 Mha/yr and by 103 Mha/yr at the end of the century. Land carbon gain is weakened by 17% over the 20th century, mainly due to increased human deforestation fires and associated escape fires (i.e., degradation fires) in the tropical humid forests, even though the decrease in burned area in many other regions due to human fire suppression acts to increase land carbon gain. The direct human effect on fire weakens the upward trend in global runoff throughout the century by 6% and enhances the upward trend in global evapotranspiration since ~ 1945 by 7%. In addition, the above impacts in densely populated, highly developed (if population density > 0.1 person/km2), or moderately populated and developed regions are of opposite sign to those in other regions. Our study suggests that particular attention should be paid to human deforestation and degradation fires in the tropical humid forests when reconstructing and projecting fire carbon emissions and net atmosphere-land carbon exchange and estimating resultant impacts of direct human effect on fire.

  3. The Accumulation and Seasonal Dynamic of the Soil Organic Carbon in Wetland of the Yellow River Estuary, China

    Directory of Open Access Journals (Sweden)

    Xianxiang Luo

    2014-01-01

    Full Text Available The wetland of the Yellow River estuary is a typical new coastal wetland in northern China. It is essential to study the carbon pool and its variations for evaluating the carbon cycle process. The study results regarding the temporal-spatial distribution and influential factors of soil organic carbon in four typical wetlands belonging to the Yellow River estuary showed that there was no significant difference in the contents of the surface soil TOC to the same season among the four types of wetlands. For each type of wetlands, the TOC content in surface soils was significantly higher in October than that in both May and August. On the whole, the obvious differences in DOC contents in surface soils were not observed in the different wetland types and seasons. The peak of TOC appeared at 0–10 cm in the soil profiles. The contents of TOC and DOC were significantly higher in salsa than those in reed, suggesting that the rhizosphere effect of organic carbon in salsa was more obvious than that in reed. The results of the principal component analysis showed that the nitrogen content, salinity, bulk density, and water content were dominant influential factors for organic carbon accumulation and seasonal variation.

  4. Project Summary (2012-2015) – Carbon Dynamics of the Greater Everglades Watershed and Implications of Climate Change

    Energy Technology Data Exchange (ETDEWEB)

    Hinkle, Ross [University of Central Florida; Benscoter, Brian [Florida Atlantic University; Comas, Xavier [Florida Atlantic University; Sumner, David [USGS; DeAngelis, Donald [USGS

    2015-04-07

    Carbon Dynamics of the Greater Everglades Watershed and Implications of Climate Change The objectives of this project are to: 1) quantify above- and below-ground carbon stocks of terrestrial ecosystems along a seasonal hydrologic gradient in the headwaters region of the Greater Everglades watershed; 2) develop budgets of ecosystem gaseous carbon exchange (carbon dioxide and methane) across the seasonal hydrologic gradient; 3) assess the impact of climate drivers on ecosystem carbon exchange in the Greater Everglades headwater region; and 4) integrate research findings with climate-driven terrestrial ecosystem carbon models to examine the potential influence of projected future climate change on regional carbon cycling. Note: this project receives a one-year extension past the original performance period - David Sumner (USGS) is not included in this extension.

  5. Robbing Peter to Pay Paul: Modeling the Dynamic Evolution of the Coastal Carbon Sink Across Multiple Landforms

    Science.gov (United States)

    Herbert, E. R.; Walters, D.; Windham-Myers, L.; Kirwan, M. L.

    2016-12-01

    Evaluating the strength and long-term stability of the coastal carbon sink requires a consideration of the spatial evolution of coastal landscapes in both the horizontal and vertical dimensions. We present a model of the transformation and burial of carbon along a bay-marsh-upland forest complex to explore the response of the coastal carbon sink to sea level rise (SLR) and anthropogenic activity. We establish a carbon mass-balance by coupling dynamic biogeochemically-based models of soil carbon burial in aquatic, intertidal, and upland environments with a physically-based model of marsh edge erosion, vertical growth and migration into adjacent uplands. The modeled increase in marsh vertical growth and carbon burial at moderate rates of sea level rise (3-10 mm/yr) is consistent with a synthesis of 219 field measurements of marsh carbon accumulation that show a significant (ploss of forest carbon stocks. Coastlines with high relief or barriers to wetland migration can become sources of carbon through the erosion of buried carbon stocks, but we show that the recapture of eroded carbon through vertical growth can be an important mechanism for reducing carbon loss. Overall, we show that the coastal carbon balance must be evaluated in a landscape context to account for changes in the size and magnitude of both the stocks and sinks of marsh carbon and for the transfers of carbon between coastal habitats. These results may help inform current efforts to appraise coastal carbon sinks that are beset by issues of landscape heterogeneity and the provenance of buried carbon.

  6. Characterizing dynamic behavior of carbon dioxide nano-jets using molecular dynamics simulation

    Science.gov (United States)

    Huang, Pei-Hsing; Chou, Chuen-Shii; Hung, Shang-Chao; Jhan, Jhih-Wei

    2017-12-01

    This paper reports on the use of molecular dynamics (MD) simulations to elucidate the dynamic behavior of CO2 through a Graphene/Au(111) nano-injector. We investigated the effects of jet diameter ( d), system temperature ( T), and the extrusion velocity ( v) of a graphite piston plate on the jet pattern, system pressure ( P), and the number of molecules ( N m) in the outflow. Simulation results show that the combined effects of high v and small d induced a larger jet angle, resulting in an increase in the number of CO2 molecules attached to the surface of the outlet. Increasing d enhanced the formation of the T-junction molecular geometry of CO2 molecules, due to the effects of electrostatic attraction between C (0.5888 e) and O (- 0.2944 e) of CO2, which caused the formation of larger agglomerations of CO2 molecules in the vicinity of the nano-injector orifice in the final extrusion stage. The increase in P within the cylinder of the nano-injector was more pronounced during middle and final stages of extrusion, compared with the effects observed during the initial stages. Despite the fact that N m increased noticeably with an increase in T, the value of N m at d = 1.5 nm and T ≥ 300 K greatly exceeded that at d = 1.0 nm and T = 500 K, regardless of the value of v. The numerical simulations presented in this study could be helpful in the design of nano-injectors for a diversity of applications associated with engineering systems and biomedicine at the nano-scale.

  7. [Dynamics of carbon, nitrogen and phosphorus storage of three dominant marsh plants in Hangzhou Bay coastal wetland].

    Science.gov (United States)

    Shao, Xue-xin; Li, Wen-hua; Wu, Ming; Yang, Wen-ying; Jiang, Ke-yi; Ye, Xiao-qi

    2013-09-01

    Salt marshes perform important ecosystem functions in carbon, nitrogen and phosphorus recycling. The plant biomass, content and pools of C, N and P were measured seasonally in three marsh species Phragmites australis, Spartina alterniflora and Scirpus mariquezer in Hangzhou Bay coastal wetland for the dynamics of C, N and P storage. The results showed that seasonal variation of aboveground biomass displayed a unimodal curve. The seasonal variability of plant OC content in the aboveground part of the plants was not significant, while the TN and TP content decreased significantly from spring to winter. The seasonal variability of plant C, N and P pools was significant. And there was a significant relationship between plant C/N/P pools and biomass. The pools among plant species were significantly different. S. mariqueter had the lowest C/N/P pools. TN pool in the aboveground part of P. australis was higher than that of S. aterniflora, but its TP pool was lower than that of S. alterniflora, and there was no significant difference for OC pools between P. australis and S. alterniflora. C fixation of the three marsh species was 380%, 376% and 55.5% of the average C fixation of terrestrial vegetations in China, and 463%, 458% and 67.7% of the average C fixation of terrestrial vegetations of the world. Considering the purification capacity of N and P, July would be the best harvest time of the study area for three plants. And the harvest of S. alterniflora could remove the biggest amount of P, since P was a limiting nutrient for phytoplankton growth. In conclusion, the marsh plants had strong C fixation and N/P purification ability.

  8. Electrochemical oxidation of carbon-containing fuels and their dynamics in low-temperature fuel cells.

    Science.gov (United States)

    Krewer, Ulrike; Vidakovic-Koch, Tanja; Rihko-Struckmann, Liisa

    2011-10-04

    Fuel cells can convert the energy that is chemically stored in a compound into electrical energy with high efficiency. Hydrogen could be the first choice for chemical energy storage, but its utilization is limited due to storage and transport difficulties. Carbon-containing fuels store chemical energy with significantly higher energy density, which makes them excellent energy carriers. The electro-oxidation of carbon-containing fuels without prior reforming is a more challenging and complex process than anodic hydrogen oxidation. The current understanding of the direct electro-oxidation of carbon-containing fuels in low-temperature fuel cells is reviewed. Furthermore, this review covers various aspects of electro-oxidation for carbon-containing fuels in non-steady-state reaction conditions. Such dynamic investigations open possibilities to elucidate detailed reaction kinetics, to sense fuel concentration, or to diagnose the fuel-cell state during operation. Motivated by the challenge to decrease the consumption of fossil fuel, the production routes of the fuels from renewable resources also are reviewed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. An Atomistic Carbide-Derived Carbon Model Generated Using ReaxFF-Based Quenched Molecular Dynamics

    Directory of Open Access Journals (Sweden)

    Matthew W. Thompson

    2017-10-01

    Full Text Available We report a novel atomistic model of carbide-derived carbons (CDCs, which are nanoporous carbons with high specific surface areas, synthesis-dependent degrees of graphitization, and well-ordered, tunable porosities. These properties make CDCs viable substrates in several energy-relevant applications, such as gas storage media, electrochemical capacitors, and catalytic supports. These materials are heterogenous, non-ideal structures and include several important parameters that govern their performance. Therefore, a realistic model of the CDC structure is needed in order to study these systems and their nanoscale and macroscale properties with molecular simulation. We report the use of the ReaxFF reactive force field in a quenched molecular dynamics routine to generate atomistic CDC models. The pair distribution function, pore size distribution, and adsorptive properties of this model are reported and corroborated with experimental data. Simulations demonstrate that compressing the system after quenching changes the pore size distribution to better match the experimental target. Ring size distributions of this model demonstrate the prevalence of non-hexagonal carbon rings in CDCs. These effects may contrast the properties of CDCs against those of activated carbons with similar pore size distributions and explain higher energy densities of CDC-based supercapacitors.

  10. Monitoring and Modeling Carbon Dynamics at a