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Sample records for carbon regimes results

  1. Changes in Soil Carbon and Enzyme Activity As a Result of Different Long-Term Fertilization Regimes in a Greenhouse Field

    PubMed Central

    Zhang, Lili; Chen, Wei; Burger, Martin; Yang, Lijie; Gong, Ping; Wu, Zhijie

    2015-01-01

    In order to discover the advantages and disadvantages of different fertilization regimes and identify the best management practice of fertilization in greenhouse fields, soil enzyme activities involved in carbon (C) transformations, soil chemical characteristics, and crop yields were monitored after long-term (20-year) fertilization regimes, including no fertilizer (CK), 300 kg N ha-1 and 600 kg N ha-1 as urea (N1 and N2), 75 Mg ha-1 horse manure compost (M), and M with either 300 or 600 kg N ha-1 urea (MN1 and MN2). Compared with CK, fertilization increased crop yields by 31% (N2) to 69% (MN1). However, compared with CK, inorganic fertilization (especially N2) also caused soil acidification and salinization. In the N2 treatment, soil total organic carbon (TOC) decreased from 14.1±0.27 g kg-1 at the beginning of the long-term experiment in 1988 to 12.6±0.11 g kg-1 (P<0.05). Compared to CK, N1 and N2 exhibited higher soil α-galactosidase and β-galactosidase activities, but lower soil α-glucosidase and β-glucosidase activities (P<0.05), indicating that inorganic fertilization had different impacts on these C transformation enzymes. Compared with CK, the M, MN1 and MN2 treatments exhibited higher enzyme activities, soil TOC, total nitrogen, dissolved organic C, and microbial biomass C and N. The fertilization regime of the MN1 treatment was identified as optimal because it produced the highest yields and increased soil quality, ensuring sustainability. The results suggest that inorganic fertilizer alone, especially in high amounts, in greenhouse fields is detrimental to soil quality. PMID:25706998

  2. Changes in soil carbon and enzyme activity as a result of different long-term fertilization regimes in a greenhouse field.

    PubMed

    Zhang, Lili; Chen, Wei; Burger, Martin; Yang, Lijie; Gong, Ping; Wu, Zhijie

    2015-01-01

    In order to discover the advantages and disadvantages of different fertilization regimes and identify the best management practice of fertilization in greenhouse fields, soil enzyme activities involved in carbon (C) transformations, soil chemical characteristics, and crop yields were monitored after long-term (20-year) fertilization regimes, including no fertilizer (CK), 300 kg N ha-1 and 600 kg N ha-1 as urea (N1 and N2), 75 Mg ha-1 horse manure compost (M), and M with either 300 or 600 kg N ha-1 urea (MN1 and MN2). Compared with CK, fertilization increased crop yields by 31% (N2) to 69% (MN1). However, compared with CK, inorganic fertilization (especially N2) also caused soil acidification and salinization. In the N2 treatment, soil total organic carbon (TOC) decreased from 14.1±0.27 g kg-1 at the beginning of the long-term experiment in 1988 to 12.6±0.11 g kg-1 (P<0.05). Compared to CK, N1 and N2 exhibited higher soil α-galactosidase and β-galactosidase activities, but lower soil α-glucosidase and β-glucosidase activities (P<0.05), indicating that inorganic fertilization had different impacts on these C transformation enzymes. Compared with CK, the M, MN1 and MN2 treatments exhibited higher enzyme activities, soil TOC, total nitrogen, dissolved organic C, and microbial biomass C and N. The fertilization regime of the MN1 treatment was identified as optimal because it produced the highest yields and increased soil quality, ensuring sustainability. The results suggest that inorganic fertilizer alone, especially in high amounts, in greenhouse fields is detrimental to soil quality.

  3. Changes in soil carbon and enzyme activity as a result of different long-term fertilization regimes in a greenhouse field.

    PubMed

    Zhang, Lili; Chen, Wei; Burger, Martin; Yang, Lijie; Gong, Ping; Wu, Zhijie

    2015-01-01

    In order to discover the advantages and disadvantages of different fertilization regimes and identify the best management practice of fertilization in greenhouse fields, soil enzyme activities involved in carbon (C) transformations, soil chemical characteristics, and crop yields were monitored after long-term (20-year) fertilization regimes, including no fertilizer (CK), 300 kg N ha-1 and 600 kg N ha-1 as urea (N1 and N2), 75 Mg ha-1 horse manure compost (M), and M with either 300 or 600 kg N ha-1 urea (MN1 and MN2). Compared with CK, fertilization increased crop yields by 31% (N2) to 69% (MN1). However, compared with CK, inorganic fertilization (especially N2) also caused soil acidification and salinization. In the N2 treatment, soil total organic carbon (TOC) decreased from 14.1±0.27 g kg-1 at the beginning of the long-term experiment in 1988 to 12.6±0.11 g kg-1 (P<0.05). Compared to CK, N1 and N2 exhibited higher soil α-galactosidase and β-galactosidase activities, but lower soil α-glucosidase and β-glucosidase activities (P<0.05), indicating that inorganic fertilization had different impacts on these C transformation enzymes. Compared with CK, the M, MN1 and MN2 treatments exhibited higher enzyme activities, soil TOC, total nitrogen, dissolved organic C, and microbial biomass C and N. The fertilization regime of the MN1 treatment was identified as optimal because it produced the highest yields and increased soil quality, ensuring sustainability. The results suggest that inorganic fertilizer alone, especially in high amounts, in greenhouse fields is detrimental to soil quality. PMID:25706998

  4. A universal model for nanoporous carbon supercapacitors applicable to diverse pore regimes, carbon materials, and electrolytes.

    PubMed

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent

    2008-01-01

    Supercapacitors, commonly called electric double-layer capacitors (EDLCs), are emerging as a novel type of energy-storage device with the potential to substitute batteries in applications that require high power densities. In response to the latest experimental breakthrough in nanoporous carbon supercapacitors, we propose a heuristic theoretical model that takes pore curvature into account as a replacement for the EDLC model, which is based on a traditional parallel-plate capacitor. When the pore size is in the mesopore regime (2-50 nm), counterions enter mesoporous carbon materials and approach the pore wall to form an electric double-cylinder capacitor (EDCC); in the micropore regime (<2 nm), solvated/desolvated counterions line up along the pore axis to form an electric wire-in-cylinder capacitor (EWCC). In the macropore regime (>50 nm) at which pores are large enough so that pore curvature is no longer significant, the EDCC model can be reduced naturally to the EDLC model. We present density functional theory calculations and detailed analyses of available experimental data in various pore regimes, which show the significant effects of pore curvature on the supercapacitor properties of nanoporous carbon materials. It is shown that the EDCC/EWCC model is universal for carbon supercapacitors with diverse carbon materials, including activated carbon materials, template carbon materials, and novel carbide-derived carbon materials, and with diverse electrolytes, including organic electrolytes, such as tetraethylammonium tetrafluoroborate (TEABF(4)) and tetraethylammonium methylsulfonate (TEAMS) in acetonitrile, aqueous H(2)SO(4) and KOH electrolytes, and even an ionic liquid electrolyte, such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI). The EDCC/EWCC model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration and dielectric constant, and solute ion size It

  5. A Universal Model for Nanoporous Carbon Supercapacitors Applicable to Diverse Pore Regimes, Carbons, and Electrolyte

    SciTech Connect

    Sumpter, Bobby G; Huang, Jingsong; Meunier, Vincent

    2008-01-01

    Supercapacitors, commonly called electric double-layer capacitors (EDLCs), are emerging as a novel type of energy storage device with the potential to substitute batteries in applications requiring high power densities. In response to the latest experimental breakthrough in nanoporous carbon supercapacitors, we propose a heuristic theoretical model that takes pore curvature into account as a replacement for the EDLC model which is based on a traditional parallel-plate capacitor. When the pore size is in the mesopore regime (2-50 nm), counterions enter mesoporous carbons and approach the pore wall to form an electric double-cylinder capacitor (EDCC); in the micropore regime (< 2 nm), solvated/desolvated counterions line up along the pore axis to form an electric wire-in-cylinder capacitor (EWCC). In the macropore regime (> 50 nm) where pores are large enough so that the pore curvature is no longer significant, the EDCC model can be reduced naturally to the EDLC model. We present density functional theory calculations and detailed analyses of available experimental data in various pore regimes, showing the significant effects of pore curvature on the supercapacitor properties of nanoporous carbons. It is shown that the EDCC/EWCC model is universal to carbon supercapacitors with diverse carbon materials including activated carbons, template carbons, and novel carbide-derived carbons, and with diverse electrolytes including organic electrolytes such as tetraethylammonium tetrafluoroborate (TEABF4), tetraethylammonium methyl-sulfonate (TEAMS) in acetonitrile, aqueous H2SO4 and KOH electrolytes, and even ionic liquid electrolyte such as 1-ethyl-3-methylimmidazolium bis(trifluromethane-sulfonyl)imide (EMI-TFSI). The EDCC/EWCC model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration and dielectric constant, and solute ion size, and may lend a support for the systematic optimization of the

  6. A universal model for nanoporous carbon supercapacitors applicable to diverse pore regimes, carbon materials, and electrolytes.

    PubMed

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent

    2008-01-01

    Supercapacitors, commonly called electric double-layer capacitors (EDLCs), are emerging as a novel type of energy-storage device with the potential to substitute batteries in applications that require high power densities. In response to the latest experimental breakthrough in nanoporous carbon supercapacitors, we propose a heuristic theoretical model that takes pore curvature into account as a replacement for the EDLC model, which is based on a traditional parallel-plate capacitor. When the pore size is in the mesopore regime (2-50 nm), counterions enter mesoporous carbon materials and approach the pore wall to form an electric double-cylinder capacitor (EDCC); in the micropore regime (<2 nm), solvated/desolvated counterions line up along the pore axis to form an electric wire-in-cylinder capacitor (EWCC). In the macropore regime (>50 nm) at which pores are large enough so that pore curvature is no longer significant, the EDCC model can be reduced naturally to the EDLC model. We present density functional theory calculations and detailed analyses of available experimental data in various pore regimes, which show the significant effects of pore curvature on the supercapacitor properties of nanoporous carbon materials. It is shown that the EDCC/EWCC model is universal for carbon supercapacitors with diverse carbon materials, including activated carbon materials, template carbon materials, and novel carbide-derived carbon materials, and with diverse electrolytes, including organic electrolytes, such as tetraethylammonium tetrafluoroborate (TEABF(4)) and tetraethylammonium methylsulfonate (TEAMS) in acetonitrile, aqueous H(2)SO(4) and KOH electrolytes, and even an ionic liquid electrolyte, such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI). The EDCC/EWCC model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration and dielectric constant, and solute ion size It

  7. Ecosystem carbon storage capacity as affected by disturbance regimes: A general theoretical model

    SciTech Connect

    Weng, Ensheng; Luo, Yiqi; Wang, Weile; Wang, Han; Hayes, Daniel J; McGuire, A. David; Hastings, Alan; Schimel, David

    2012-01-01

    Disturbances have been recognized as a key factor shaping terrestrial ecosystem states and dynamics. A general model that quantitatively describes the relationship between carbon storage and disturbance regime is critical for better understanding large scale terrestrial ecosystem carbon dynamics. We developed a model (REGIME) to quantify ecosystem carbon storage capacities (E[x]) under varying disturbance regimes with an analytical solution E[x] = U {center_dot} {tau}{sub E} {center_dot} {lambda}{lambda} + s {tau} 1, where U is ecosystem carbon influx, {tau}{sub E} is ecosystem carbon residence time, and {tau}{sub 1} is the residence time of the carbon pool affected by disturbances (biomass pool in this study). The disturbance regime is characterized by the mean disturbance interval ({lambda}) and the mean disturbance severity (s). It is a Michaelis-Menten-type equation illustrating the saturation of carbon content with mean disturbance interval. This model analytically integrates the deterministic ecosystem carbon processes with stochastic disturbance events to reveal a general pattern of terrestrial carbon dynamics at large scales. The model allows us to get a sense of the sensitivity of ecosystems to future environmental changes just by a few calculations. According to the REGIME model, for example, approximately 1.8 Pg C will be lost in the high-latitude regions of North America (>45{sup o} N) if fire disturbance intensity increases around 5.7 time the current intensity to the end of the twenty-first century, which will require around 12% increases in net primary productivity (NPP) to maintain stable carbon stocks. If the residence time decreased 10% at the same time additional 12.5% increases in NPP are required to keep current C stocks. The REGIME model also lays the foundation for analytically modeling the interactions between deterministic biogeochemical processes and stochastic disturbance events.

  8. Tundra carbon balance under varying temperature and moisture regimes

    NASA Astrophysics Data System (ADS)

    Huemmrich, K. F.; Kinoshita, G.; Gamon, J. A.; Houston, S.; Kwon, H.; Oechel, W. C.

    2010-12-01

    To understand the effects of environmental change on tundra carbon balance, a manipulation experiment was performed in wet sedge tundra near Barrow, Alaska. Three replicates of six environmental treatments were made: control, heating, raising or lowering water table, and heating along with raising or lowering water table. Carbon fluxes were measured using a portable chamber for six days during the 2001 growing season. Spectral reflectance and meteorological measurements were also collected. Empirical models derived from flux measurements were developed for daily gross ecosystem production (GEP) and ecosystem respiration (Re). The amount of photosynthetically active radiation absorbed by the plants was strongly correlated with GEP. This relationship was not affected by treatment or time during the growing season. Re was related to soil temperature with a different relationship for each water level treatment. Re in the lowered water table treatment had a strong response to temperature changes, while the raised water table treatment showed little temperature response. These models calculated daily net ecosystem exchange for all of the treatments over the growing season. Warming increased both the seasonal carbon gain and carbon loss. By the end of summer the lowered water table treatments, both heated and unheated, were net carbon sources while all other treatments were sinks. Warming and/or raising the water table increased the strength of the net sink. Over the timescale of this experiment, water table primarily determined whether the ecosystem was a source or sink, with temperature modifying the strength of the source or sink.

  9. Regime Shifts in Lakes: Organic Carbon Dynamics and Whole Ecosystem Responses

    NASA Astrophysics Data System (ADS)

    Anderson, N. J.

    2015-12-01

    The concept of using sediment records to identify regime shifts in lakes has largely focussed on biological proxies, such as diatoms and chironomids. In this approach, long-term records of rapid ecological change are compared with independent proxies of the variables driving ecosystem change, for example, climate or catchment disturbance processes (hydrological budgets, deforestation, fire etc.). One of the main problems with this approach is that the sediment cores upon which the data analyses are made are taken from the central part of lakes, often at the deepest point. As a result, the ecological changes observed reflect pelagic (open water) processes rather than whole-lake responses. As most lakes (apart from hypertrophic systems) are dominated by benthic production it is unclear whether palaeolimnological assessments of regime shifts are representative of the whole lake response. Theoretically, this question can be addressed simply by using cores from shallow water. There are a number of problems with this approach, most notably the loss of temporal resolution in shallow water cores (due to the slower sediment accumulation rate) and the different biological assemblages in the shallow water (littoral) cores. There is a strong effect of water depth on the zonation and distribution of biological remains across any lake. An alternative approach therefore is to use total organic carbon [OC] accumulation rate as a measure of the whole lake response to see if there is, in fact, a regime shift at the whole lake scale. Here I present examples of Holocene OC accumulation rate responses to external forcing from shallow eutrophic and boreal lakes and compare them to biological records of structural ecological change to determine whether there has been a whole-lake regime shift.

  10. Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes

    NASA Astrophysics Data System (ADS)

    Portner, H.; Wolf, A.; Bugmann, H.

    2009-04-01

    Many biogeochemical models have been applied to study the response of the carbon cycle to changes in climate, whereby the process of carbon uptake (photosynthesis) has usually gained more attention than the equally important process of carbon release by respiration. The decomposition of soil organic matter is driven by a combination of factors with a prominent one being soil temperature [Berg and Laskowski(2005)]. One uncertainty concerns the response function used to describe the sensitivity of soil organic matter decomposition to temperature. This relationship is often described by one out of a set of similar exponential functions, but it has not been investigated how uncertainties in the choice of the response function influence the long term predictions of biogeochemical models. We built upon the well-established LPJ-GUESS model [Smith et al.(2001)]. We tested five candidate functions and calibrated them against eight datasets from different Ameriflux and CarboEuropeIP sites [Hibbard et al.(2006)]. We used a simple Exponential function with a constant Q10, the Arrhenius function, the Gaussian function [Tuomi et al.(2008), O'Connell(1990)], the Van't Hoff function [Van't Hoff(1901)] and the Lloyd&Taylor function [Lloyd and Taylor(1994)]. We assessed the impact of uncertainty in model formulation of temperature response on estimates of present and future long-term carbon storage in ecosystems and hence on the CO2 feedback potential to the atmosphere. We specifically investigated the relative importance of model formulation and the error introduced by using different data sets for the parameterization. Our results suggested that the Exponential and Arrhenius functions are inappropriate, as they overestimated the respiration rates at lower temperatures. The Gaussian, Van't Hoff and Lloyd&Taylor functions all fit the observed data better, whereby the functions of Gaussian and Van't Hoff underestimated the response at higher temperatures. We suggest, that the

  11. Watershed Fire Regime Effects On Particulate Organic Carbon Composition in Oregon and California Coast Range Rivers

    NASA Astrophysics Data System (ADS)

    Hatten, J. A.; Goni, M. A.; Wheatcroft, R. A.; Borgeld, J. C.; Padgett, J. S.; Pasternack, G. B.; Gray, A. B.; Watson, E. B.; Warrick, J. A.

    2010-12-01

    Fire causes major changes to organic carbon, converting biological organic materials to pyrogenic-derived organic carbon (Py-OC), including black carbon. Wildfire also dramatically affects hydrological and erosion processes within watersheds, potentially increasing the erosion and discharge of Py-OC as particulate organic carbon (POC). We hypothesize that the proportion of the POC being discharged as Py-OC will be affected by the watershed’s fire regime, increasing with annual proportion of the watershed burned. During the 2008 and 2009 water years, suspended sediment samples were collected from the Alsea, Umpqua, Eel, Salinas, and Arroyo Seco Rivers draining the Coast Ranges of Oregon and California. Events and discharges of various magnitudes were captured in this sample set. This sample set also included suspended sediment collected from the Arroyo Seco River after a 2008 wildfire burned through a large portion of its watershed. Fine (<63 μm) and coarse (>63 μm) particulate material was analyzed for OC and N. We used cupric oxide oxidation to determine the contribution of Py-OC and unburned organic matter to the POC load of these rivers. The area weighted mean fire return interval decreases from the Douglas fir dominated forests in the Alsea River watershed in the north to the chaparral dominated Arroyo Seco River watershed in the south (Alsea > Umpqua > Eel > Salinas > Arroyo Seco). This translated into an increase in the proportion of each watershed burned from north to south. With the increase in annual proportion of watershed burned we found that the Py-OC content of coarse and fine POC increased from north to south. These results suggest that fire plays an important role in delivering POC to long-term carbon sinks in the coastal and ocean environment.

  12. Thermal effects on mass detection sensitivity of carbon nanotube resonators in nonlinear oscillation regime

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Keun; Yang, Hyun-Ik; Kim, Chang-Wan

    2015-11-01

    A mass sensor using a nano-resonator has high detection sensitivity, and mass sensitivity is higher with smaller resonators. Therefore, carbon nanotubes (CNTs) are the ultimate materials for these applications and have been actively studied. In particular, CNT-based nanomechanical devices may experience high temperatures that lead to thermal expansion and residual stress in devices, which affects the device reliability. In this letter, to demonstrate the influence of the temperature change (i.e., thermal effect) on the mass detection sensitivity of CNT-based mass sensor, dynamic analysis is carried out for a CNT resonator with thermal effects in both linear and nonlinear oscillation regimes. Based on the continuum mechanics model, the analytical solution method with an assumed deflection eigenmode is applied to solve the nonlinear differential equation which involves the von Karman nonlinear strain-displacement relation and the additional axial force associated with thermal effects. A thermal effect on the fundamental resonance behavior and resonance frequency shift due to adsorbed mas, i.e., mass detection sensitivity, is examined in high-temperature environment. Results indicate a valid improvement of fundamental resonance frequency by using nonlinear oscillation in a thermal environment. In both linear and nonlinear oscillation regimes, the mass detection sensitivity becomes worse due to the increasing of temperature in a high-temperature environment. The thermal effect on the detection sensitivity is less effective in the nonlinear oscillation regime. It is concluded that a temperature change of a mass sensor with a CNT-based resonator can be utilized to enhance the detection sensitivity depending on the CNT length, linear/nonlinear oscillation behaviors, and the thermal environment.

  13. Computational and Experimental Investigations Into the Mass Loss of a Carbon Material in the Sublimation Regime of its Thermochemical Destruction

    NASA Astrophysics Data System (ADS)

    Gorskii, V. V.; Zolotarev, S. L.; Olenicheva, A. A.

    2015-01-01

    The authors give results of an experimental investigation into the ablation characteristics of a modern fi ne granular carbon material in the high-enthalpy jet of a TT-1 arc-heated facility [1] ("TsNIImash" Federal State Unitary Enterprise), and also results of computational and experimental investigations into the parameters of the jet of this facility. Data given in the article provide a basis for studying the regularities of the mass loss of the carbon material in a sublimation regime of its thermochemical destructioncpb

  14. Relationships among precipitation regime, nutrient availability, and carbon turnover in tropical rain forests.

    PubMed

    Posada, Juan M; Schuur, Edward A G

    2011-03-01

    The effect of high precipitation regime in tropical forests is poorly known despite indications of its potentially negative effects on nutrient availability and carbon (C) cycling. Our goal was to determine if there was an effect of high rainfall on nitrogen (N) and phosphorous (P) availability and indexes of C cycling in lowland tropical rain forests exposed to a broad range of mean annual precipitation (MAP). We predicted that C turnover time would increase with MAP while the availability of N and P would decrease. We studied seven Neotropical lowland forests covering a MAP range between 2,700 and 9,500 mm. We used radiocarbon (∆(14)C) from the atmosphere and respired from soil organic matter to estimate residence time of C in plants and soils. We also used C, N, and P concentrations and the stable isotope ratio of N (δ(15)N) in live and dead plant tissues and in soils as proxies for nutrient availability. Negative δ(15)N values indicated that the wettest forests had N cycles that did not exhibit isotope-fractionating losses and were potentially N-limited. Element ratios (N:P and C:P) in senescent leaves, litter, and live roots showed that P resorption increased considerably with MAP, which points towards increasing P-limitation under high MAP regimes. Soil C content increased with MAP but C turnover time only showed a weak relationship with MAP, probably due to variations in soil parent material and age along the MAP gradient. In contrast, comparing C turnover directly to nutrient availability showed strong relationships between C turnover time, N availability (δ(15)N), and P availability (N:P) in senescent leaves and litter. Thus, an effect of MAP on carbon cycling appeared to be indirectly mediated by nutrient availability. Our results suggest that soil nutrient availability plays a central role in the dynamic of C cycling in tropical rain forests.

  15. Carbon rhizodeposition by plants of contrasting strategies for resource acquisition: responses to various nitrogen fertility regimes

    NASA Astrophysics Data System (ADS)

    Baptist, Florence; Aranjuelo, I.; Lopez-Sangil, L.; Rovia, P.; Nogués, S.

    2010-05-01

    Rhizodeposition by plants is one of the most important physiological mechanisms related to carbon and nitrogen cycling which is also believed to vary along the acquisition-conservation continuum. However, owing to methodological difficulties (i.e. narrow zone of soil around roots and rapid assimilation by soil microbes), root exudation and variations between species are one of the most poorly understood belowground process. Although previous approaches such as hydroponic culture based system, permit the chemical analysis of exudates, the fact that this protocol is qualitative, conditions its utility (see review in Phillips et al. 2008). Others techniques based on pulse-labelling approach have been developed to quantify rhizodeposition but are rarely sufficient to uniformly label all plant inputs to soil. Consequently with this typical pulse chase methods, recent assimilates are labeled but the recalcitrant carbon will not be labeled and therefore the contribution of this carbon will not be considered. Hence, traditional pulse labelling is not a quantitative means of tracing carbon due to inhomogeneous labelling and so limits greatly comparative studies of rhizodeposition fluxes at the interspecific level. In this study we developped a new protocole based on a long-term (3 months) steady state 13C labelling in order (1) to quantify rhizodeposition fluxes for six graminoid species caracterized by contrasted nutrient acquisition strategies and (2) to investigate to what extent various level of nitrogen fertility regimes modulate rhizodeposition fluxes. This method will enable to quantify under natural soil conditions both the accumulation of 13C in the soil but also the quantity that has been respired by the microorganisms during a given time and so will give an integrated picture of rhizodeposition fluxes for each species under each nitrogen fertility level. Results are currently being processed and will be presented at the conference. References: Phillips RP, Erlitz

  16. The influence of hydrodynamic regime on infaunal assemblages inhabiting carbonate sediments on central Pacific seamounts

    NASA Astrophysics Data System (ADS)

    Levin, Lisa A.; Thomas, Cynthia L.

    1989-12-01

    We investigated the following hypotheses for deep seamounts in the central Pacific Ocean: (1) infaunal and microbial abundances are elevated in regions of current intensification, (2) infaunal lifestyles reflect variation in hydrodynamic conditions and (3) bioturbation is more intense in high-energy regimes. Our studies were carried out at three sites: the northwest perimeter of the Horizon Guyot sediment cap (1840 m), which is characterized by strong bottom currents and rippled foraminiferan sands, and the central summits of Horizon Guyot (1480 m) and Magellan Rise (3150 m), whose sediments are unrippled and finer grained. Contrary to our first hypothesis, the high-energy, Horizon perimeter sediments exhibited lower biological activity than the summit sites, as reflected in lower organic nitrogen (0.011% vs. 0.015-0.017%), higher C/N ratios (19 vs 11), lower bacterial counts (1.21 vs 2.03-2.15 × 10 8ml -1) and lower macrofaunal abundances (255 vs 388-829 m -2). Sediment organic carbon values (0.14-0.19%) and meiofaunal abundances (2866-5150 m -2) did not differ significantly among the three sites. Infaunal life habits varied among sites but sediment mixing did not. Macrofauna were found deeper in rippled perimeter sediments than in the cap sediments. Sessility and surface-feeding modes dominated among polychaetes at the higher-energy Horizon perimeter, while motility and subsurface feeding were common in the quieter, finer-grained regimes. Significant sediment mixing takes place on 100-year time scales a all three sites, probably a result of large, infaunal bioturbators at the cap sites and physical sediment instability at the perimeter site. Excess 210Pb exhibited moderately high inventories (38-59 dpm cm -2) and deep penetration (15 cm). Estimated mixing coefficients (D b) ranged from 0.6 to 3.0 cm 2y -1 at the three sites. Our findings indicate that hydrodynamic differences can lead to greater variation in sediment and faunal characteristics on a single

  17. Effects of Successive Rotation Regimes on Carbon Stocks in Eucalyptus Plantations in Subtropical China Measured over a Full Rotation.

    PubMed

    Li, Xiaoqiong; Ye, Duo; Liang, Hongwen; Zhu, Hongguang; Qin, Lin; Zhu, Yuling; Wen, Yuanguang

    2015-01-01

    Plantations play an important role in carbon sequestration and the global carbon cycle. However, there is a dilemma in that most plantations are managed on short rotations, and the carbon sequestration capacities of these short-rotation plantations remain understudied. Eucalyptus has been widely planted in the tropics and subtropics due to its rapid growth, high adaptability, and large economic return. Eucalyptus plantations are primarily planted in successive rotations with a short rotation length of 6~8 years. In order to estimate the carbon-stock potential of eucalyptus plantations over successive rotations, we chose a first rotation (FR) and a second rotation (SR) stand and monitored the carbon stock dynamics over a full rotation from 1998 to 2005. Our results showed that carbon stock in eucalyptus trees (TC) did not significantly differ between rotations, while understory vegetation (UC) and soil organic matter (SOC) stored less carbon in the SR (1.01 vs. 2.76 Mg.ha(-1) and 70.68 vs. 81.08 Mg. ha(-1), respectively) and forest floor carbon (FFC) conversely stored more (2.80 vs. 2.34 Mg. ha(-1)). The lower UC and SOC stocks in the SR stand resulted in 1.13 times lower overall ecosystem carbon stock. Mineral soils and overstory trees were the two dominant carbon pools in eucalyptus plantations, accounting for 73.77%~75.06% and 20.50%~22.39%, respectively, of the ecosystem carbon pool. However, the relative contribution (to the ecosystem pool) of FFC stocks increased 1.38 times and that of UC decreased 2.30 times in the SR versus FR stand. These carbon pool changes over successive rotations were attributed to intensive successive rotation regimes of eucalyptus plantations. Our eight year study suggests that for the sustainable development of short-rotation plantations, a sound silvicultural strategy is required to achieve the best combination of high wood yield and carbon stock potential.

  18. Effects of Successive Rotation Regimes on Carbon Stocks in Eucalyptus Plantations in Subtropical China Measured over a Full Rotation

    PubMed Central

    Li, Xiaoqiong; Ye, Duo; Liang, Hongwen; Zhu, Hongguang; Qin, Lin; Zhu, Yuling; Wen, Yuanguang

    2015-01-01

    Plantations play an important role in carbon sequestration and the global carbon cycle. However, there is a dilemma in that most plantations are managed on short rotations, and the carbon sequestration capacities of these short-rotation plantations remain understudied. Eucalyptus has been widely planted in the tropics and subtropics due to its rapid growth, high adaptability, and large economic return. Eucalyptus plantations are primarily planted in successive rotations with a short rotation length of 6~8 years. In order to estimate the carbon-stock potential of eucalyptus plantations over successive rotations, we chose a first rotation (FR) and a second rotation (SR) stand and monitored the carbon stock dynamics over a full rotation from 1998 to 2005. Our results showed that carbon stock in eucalyptus trees (TC) did not significantly differ between rotations, while understory vegetation (UC) and soil organic matter (SOC) stored less carbon in the SR (1.01 vs. 2.76 Mg.ha-1 and 70.68 vs. 81.08 Mg. ha-1, respectively) and forest floor carbon (FFC) conversely stored more (2.80 vs. 2.34 Mg. ha-1). The lower UC and SOC stocks in the SR stand resulted in 1.13 times lower overall ecosystem carbon stock. Mineral soils and overstory trees were the two dominant carbon pools in eucalyptus plantations, accounting for 73.77%~75.06% and 20.50%~22.39%, respectively, of the ecosystem carbon pool. However, the relative contribution (to the ecosystem pool) of FFC stocks increased 1.38 times and that of UC decreased 2.30 times in the SR versus FR stand. These carbon pool changes over successive rotations were attributed to intensive successive rotation regimes of eucalyptus plantations. Our eight year study suggests that for the sustainable development of short-rotation plantations, a sound silvicultural strategy is required to achieve the best combination of high wood yield and carbon stock potential. PMID:26186367

  19. Salix response to different flow regimes in controlled experiments: first results

    NASA Astrophysics Data System (ADS)

    Gorla, Lorenzo; Signarbieux, Constant; Buttler, Alexandre; Perona, Paolo

    2013-04-01

    Dams and water management for hydropower production, agriculture and other human activities alter the natural flow regime of rivers. The new river hydrograph components depend on the type of impoundment and the policy of regulation but such a different flow regime will likely affect the riparian environment. The main challenge in order to define sustainable flow releases is to quantify hydrological effects in terms of geomorphology and ecosystem response. A considerable lack of knowledge still affects the link hydrology-ecology and inadequate flow rules (e.g., minimal or residual flows) are consequently still widespread: further research in this direction is urgently required. We present an experiment, which aims to investigate the effects of different water stage regimes on riparian vegetation (salix Viminalis cuttings) development in a temperate region (Switzerland). This work describes the installation setup, together with the first results concerning the first of the two scheduled seasons of campaign. Sixty Salix cuttings were planted in non-cohesive sandy-gravel sediment within 1 meter tall plastic pots installed outside in the EPFL campus. After grouping them in three batteries, the water level within them has been varying following three river regimes simulated by adjusting the water level within the pots by means of an automatic hydraulic system. The three water level regimes reproduce a natural flow regime, a minimum residual flow policy, which only conserves peaks during flooding conditions, and an artificial regime conserving only low frequencies (e.g., seasonality) of the natural dynamic. The natural flow regime of the first battery has been applied for two months to the entire system; the three regimes above said started in June 2012. This triggered a plant response transitory regime, which we monitored by measuring plant growth, soil and atmospheric variables. Particularly, measures concern with branches development leaves photosynthesis and

  20. Dynamic regime marginal structural mean models for estimation of optimal dynamic treatment regimes, Part II: proofs of results.

    PubMed

    Orellana, Liliana; Rotnitzky, Andrea; Robins, James M

    2010-03-03

    In this companion article to "Dynamic Regime Marginal Structural Mean Models for Estimation of Optimal Dynamic Treatment Regimes, Part I: Main Content" [Orellana, Rotnitzky and Robins (2010), IJB, Vol. 6, Iss. 2, Art. 7] we present (i) proofs of the claims in that paper, (ii) a proposal for the computation of a confidence set for the optimal index when this lies in a finite set, and (iii) an example to aid the interpretation of the positivity assumption.

  1. Molecular systems under shock compression into the dense plasma regime: carbon dioxide and hydrocarbon polymers

    NASA Astrophysics Data System (ADS)

    Mattsson, Thomas R.; Cochrane, Kyle R.; Root, Seth; Carpenter, John H.

    2013-10-01

    Density Functional Theory (DFT) has proven remarkably accurate in predicting properties of matter under shock compression into the dense plasma regime. Materials where chemistry plays a role are of interest for many applications, including planetary science and inertial confinement fusion (ICF). As examples of systems where chemical reactions are important, and demonstration of the high fidelity possible for these both structurally and chemically complex systems, we will discuss shock- and re-shock of liquid carbon dioxide (CO2) in the range 100 to 800 GPa and shock compression of hydrocarbon polymers, including GDP (glow discharge polymer) which is used as an ablator in laser ICF experiments. Experimental results from Sandia's Z machine validate the DFT simulations at extreme conditions and the combination of experiment and DFT provide reliable data for evaluating existing and constructing future wide-range equations of state models for molecular compounds. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Improved biological phosphorus removal performance driven by the aerobic/extended-idle regime with propionate as the sole carbon source.

    PubMed

    Wang, Dongbo; Li, Xiaoming; Yang, Qi; Zheng, Wei; Wu, Yan; Zeng, Tianjing; Zeng, Guangming

    2012-08-01

    Our previous studies proved that biological phosphorus removal (BPR) could be achieved in an aerobic/extended-idle (AEI) process employing two typical substrates of glucose and acetate as the carbon sources. This paper further evaluated the feasibility of another important substrate, propionate, serving as the carbon source for BPR in the AEI process, and compared the BPR performance between the AEI and anaerobic/oxic (A/O) processes. Two sequencing batch reactors (SBRs) were operated, respectively, as the AEI and A/O regimes for BPR using propionate as the sole substrate. The results showed that the AEI-reactor removed 2.98 ± 0.04-4.06 ± 0.06 mg of phosphorus per g of total suspended solids during the course of the steady operational trial, and the phosphorus content of the dried sludge was reached 8.0 ± 0.4% after 56-day operation, demonstrating the good performance of phosphorus removal. Then, the efficiencies of BPR and the transformations of the intracellular storages were compared between two SBRs. It was observed that the phosphorus removal efficiency was maintained around 95% in the AEI-reactor, and about 83% in the A/O-reactor, although the latter showed much greater transformations of both polyhydroxyalkanoates and glycogen. The facts clearly showed that BPR could be enhanced by the AEI regime using propionate as the carbon source. Finally, the mechanisms for the propionate fed AEI-reactor improving BPR were investigated. It was found that the sludge cultured by the AEI regime had more polyphosphate containing cells than that by the A/O regime. Further investigation revealed that the residual nitrate generated in the last aerobic period was readily deteriorated BPR in the A/O-SBR, but a slight deterioration was observed in the AEI-SBR. Moreover, the lower glycogen transformation measured in the AEI-SBR indicated that the biomass cultured by the AEI regime contained less glycogen accumulating organisms activities than that by the A/O regime.

  3. [Effects of different straw-returning regimes on soil organic carbon and carbon pool management index in Guanzhong Plain, Northwest China].

    PubMed

    Li, Shuo; Li, You-bing; Wang, Shu-juan; Shi, Jiang-lan; Tian, Xiao-hong

    2015-04-01

    A four-year (2008-2012) field experiment was conducted to investigate the effects of different straw-returning regimes on soil total organic carbon (TOC), labile organic carbon (LOC) and the ratio of LOC to TOC (LOC/TOC) as well as TOC stock (SCS) and soil carbon pool management index (CPMI) in a farmland with maize-wheat double cropping system in Guanzhong Plain area, Shaanxi Province, China. The results indicated that soil TOC and LOC contents and SCS were significantly increased when wheat or maize straw was returned to field, and the increasing extent showed the rising order as follows: double straw-returning > single straw-returning > no straw-returning. Compared to no straw returning, a significant increase of TOC and LOC contents and SCS was found in the treatment of wheat straw chopping retention combined with maize straw chopping subsoiling retention (WC-MM), and CPMI of WC-MM was significantly higher than in the other treatments in 0-20 cm soil layer. Compared to no wheat straw returning, soil CPMIs in 0-10 cm and 10-20 cm soil layer increased by 19.1% and 67.9% for the wheat straw chopping returning treatment, and by 22.6% and 32.4% for the maize straw chopping subsoiling treatment, respectively. Correlation analysis showed that soil CPMI was a more effective index reflecting the sequestration of soil organic carbon in 0-30 cm soil layer than the ratio of LOC to TOC. This study thus suggested that WC-MM regime is the best straw-returning regime for soil organic carbon sequestration.

  4. Thermal regime of the deep carbonate reservoir of the Po Plain (Italy)

    NASA Astrophysics Data System (ADS)

    Pasquale, V.; Chiozzi, P.; Verdoya, M.

    2012-04-01

    Italy is one of the most important countries in the world with regard to high-medium enthalpy geothermal resources, a large part of which is already extracted at relatively low cost. High temperatures at shallow to medium depth occur within a wide belt, several hundred kilometre long, west of the Apennines mountain chain. This belt, affected by recent lithosphere extension, includes several geothermal fields, which are largely exploited for electricity generation. Between the Alps and Apennines ranges, the deeper aquifer, occurring in carbonate rocks of the Po Plain, can host medium enthalpy fluids, which are exploited for district heating. Such a general picture of the available geothermal resources has been well established through several geophysical investigations and drillings. Nevertheless, additional studies are necessary to evaluate future developments, especially with reference to the deep carbonate aquifer of the Po Plain. In this paper, we focus on the eastern sector of the plain and try to gain a better understanding of the thermal regime by using synergically geothermal methodologies and geological information. The analysis of the temperatures recorded to about 6 km depth in hydrocarbon wells supplies basic constraints to outline the thermal regime of the sedimentary basin and to investigate the occurrence and importance of hydrothermal processes in the carbonate layer. After correction for drilling disturbance, temperatures were analysed, together with geological information, through an inversion technique based on a laterally constant thermal gradient model. The inferred thermal gradient changes with depth; it is quite low within the carbonate layer, while is larger in the overlying, practically impermeable formations. As the thermal conductivity variation does not justify such a thermal gradient difference, the vertical change can be interpreted as due to convective processes occurring in the carbonate layer, acting as thermal reservoir. The

  5. Classifying organic materials by oxygen-to-carbon elemental ratio to predict the activation regime of Cloud Condensation Nuclei (CCN)

    NASA Astrophysics Data System (ADS)

    Kuwata, M.; Shao, W.; Lebouteiller, R.; Martin, S. T.

    2013-05-01

    The governing highly soluble, slightly soluble, or insoluble activation regime of organic compounds as cloud condensation nuclei (CCN) was examined as a function of oxygen-to-carbon elemental ratio (O : C). New data were collected for adipic, pimelic, suberic, azelaic, and pinonic acids. Secondary organic materials (SOMs) produced by α-pinene ozonolysis and isoprene photo-oxidation were also included in the analysis. The saturation concentrations C of the organic compounds in aqueous solutions served as the key parameter for delineating regimes of CCN activation, and the values of C were tightly correlated to the O : C ratios. The highly soluble, slightly soluble, and insoluble regimes of CCN activation were found to correspond to ranges of [O : C] > 0.6, 0.2 < [O : C] < 0.6, and [O : C] < 0.2, respectively. These classifications were evaluated against CCN activation data of isoprene-derived SOM (O : C = 0.69-0.72) and α-pinene-derived SOM (O : C = 0.38-0.48). Isoprene-derived SOM had highly soluble activation behavior, consistent with its high O : C ratio. For α-pinene-derived SOM, although CCN activation can be modeled as a highly soluble mechanism, this behavior was not predicted by the O : C ratio, for which a slightly soluble mechanism was anticipated. Complexity in chemical composition, resulting in continuous water uptake and the absence of a deliquescence transition that can thermodynamically limit CCN activation, might explain the difference in the behavior of α-pinene-derived SOM compared to that of pure organic compounds. The present results suggest that atmospheric particles dominated by hydrocarbon-like organic components do not activate (i.e., insoluble regime) whereas those dominated by oxygenated organic components activate (i.e., highly soluble regime) for typical atmospheric cloud life cycles.

  6. Importance of soil thermal regime in terrestrial ecosystem carbon dynamics in the circumpolar north

    NASA Astrophysics Data System (ADS)

    Jiang, Yueyang; Zhuang, Qianlai; Sitch, Stephen; O'Donnell, Jonathan A.; Kicklighter, David; Sokolov, Andrei; Melillo, Jerry

    2016-07-01

    In the circumpolar north (45-90°N), permafrost plays an important role in vegetation and carbon (C) dynamics. Permafrost thawing has been accelerated by the warming climate and exerts a positive feedback to climate through increasing soil C release to the atmosphere. To evaluate the influence of permafrost on C dynamics, changes in soil temperature profiles should be considered in global C models. This study incorporates a sophisticated soil thermal model (STM) into a dynamic global vegetation model (LPJ-DGVM) to improve simulations of changes in soil temperature profiles from the ground surface to 3 m depth, and its impacts on C pools and fluxes during the 20th and 21st centuries. With cooler simulated soil temperatures during the summer, LPJ-STM estimates ~ 0.4 Pg C yr- 1 lower present-day heterotrophic respiration but ~ 0.5 Pg C yr- 1 higher net primary production than the original LPJ model resulting in an additional 0.8 to 1.0 Pg C yr- 1 being sequestered in circumpolar ecosystems. Under a suite of projected warming scenarios, we show that the increasing active layer thickness results in the mobilization of permafrost C, which contributes to a more rapid increase in heterotrophic respiration in LPJ-STM compared to the stand-alone LPJ model. Except under the extreme warming conditions, increases in plant production due to warming and rising CO2, overwhelm the e nhanced ecosystem respiration so that both boreal forest and arctic tundra ecosystems remain a net C sink over the 21st century. This study highlights the importance of considering changes in the soil thermal regime when quantifying the C budget in the circumpolar north.

  7. A Novel Method for Analyzing and Interpreting GCM Results Using Clustered Climate Regimes

    NASA Astrophysics Data System (ADS)

    Hoffman, F. M.; Hargrove, W. W.; Erickson, D. J.; Oglesby, R. J.

    2003-12-01

    A high-performance parallel clustering algorithm has been developed for analyzing and comparing climate model results and long time series climate measurements. Designed to identify biases and detect trends in disparate climate change data sets, this tool combines and simplifies large temporally-varying data sets from atmospheric measurements to multi-century climate model output. Clustering is a statistical procedure which provides an objective method for grouping multivariate conditions into a set of states or regimes within a given level of statistical tolerance. The groups or clusters--statistically defined across space and through time--possess centroids which represent the synoptic conditions of observations or model results contained in each state no matter when or where they occurred. The clustering technique was applied to five business-as-usual (BAU) scenarios from the Parallel Climate Model (PCM). Three fields of significance (surface temperature, precipitation, and soil moisture) were clustered from 2000 through 2098. Our analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The same analysis subsequently applied to the ensemble as a whole demonstrates the consistency and variability of trends from each ensemble member. The patterns of cluster changes can be used to show predicted variability in climate on global and continental scales. Novel three-dimensional phase space representations of these climate regimes show the portion of this phase space occupied by the land surface at all points in space and time. Any single spot on the globe will exist in one of these climate regimes at any single point in time, and by incrementing time, that same spot will trace out a trajectory or orbit among these climate regimes in phase space. When a

  8. Carbon Dioxide Emissions Resulting from Space Tourism

    NASA Astrophysics Data System (ADS)

    Fawkes, S.

    An earlier paper by the author examined the links between space tourism and sustainable development. One important aspect of sustainable development is environmental impact and within that anthropogenic greenhouse gas emission is a key issue as it is linked to climate change. Space tourism operators need to consider the environmental impact of their operations and in particular measure their total carbon emissions (“carbon footprint”) and then put in place arrangements to reduce or offset them. This paper presents some initial calculations on the carbon dioxide emissions likely to result from both sub-orbital and orbital space tourism flights and discusses options and prices for carbon offsetting. The effect of scaling up the space tourism industry is also considered.

  9. Response of vegetation to carbon dioxide - effect of elevated levels of CO{sub 2} on winter wheat under two moisture regimes

    SciTech Connect

    Chaudhuri, U.N.; Burnett, R.B.; Kanemasu, E.T.; Kirkham, M.B.

    1987-12-31

    This report deals with the second-year (1985-86) findings of an on going experiment with winter wheat (Triticum aestivum L.) at different carbon dioxide (CO{sub 2}) levels and under two moisture regimes. The results for the first year are given in the U.S. Department of Energy, Carbon Dioxide Research Division Response of Vegetation to Carbon Dioxide. The purpose of the second year`s experiment was to verify the results of 1984-85. However, based on the performance and the results of 1984-85 experiments, a few modifications were made.

  10. The influence of climate cycles on the water regime and carbonate profile in chernozems of Central European Russia and adjacent territories

    NASA Astrophysics Data System (ADS)

    Bazykina, G. S.; Ovechkin, S. V.

    2016-04-01

    The influence of long-term "dry" and "wet" climatic cycles on the water regime, hydrological parameters, and carbonate profiles of chernozems in Central European Russia and adjacent territories was studied. The hydrological and carbonate profiles were found to change during the wet cycle. However, the upper part of the hydrological profile is basically unchanging, whereas in its lower part, the number of hydrological horizons and contrast in their moistening decrease in the forest-steppe chernozems and increase in the steppe chernozems. The frequency of through wetting of chernozems increases during the wet cycles. The vertical lithological heterogeneity of the parent material affects the soil moisture status. In the wet climatic cycle, the moisture content above the lithological contact increases resulting in the development of the features of soil hydromorphism. In the carbonate profile, the character of pedofeatures is changing: some carbonate neoformations disappear, while the other ones develop. Possible variations of the periodically percolative water regime were revealed in chernozems. The classification of water regime proposed by A.A. Rode may be updated based on the data obtained during the dry climatic cycle. Rode's hypothesis about cyclic variations in the soil water regime is confirmed.

  11. Impacts of shifting fire regime on ecosystem carbon storage capacity in the interior Alaskan forests

    NASA Astrophysics Data System (ADS)

    Li, D.; Kelly, R.; Hu, F.; Luo, Y.

    2012-12-01

    Fire is the primary disturbance in the boreal forest, and variations in fire regimes have important ecological, biogeochemical, and socioeconomic implications. Recent widespread burning throughout the biome has been convincingly linked to climatic warming, with expectations of increased burning with future climate change. However, fire-regime dynamics are scale-dependent, and it is unclear whether empirical climate-fire relationships derived from the short observational record are applicable to future projections. Paleo-fire reconstructions offer a valuable extension to historical fire records by providing a context for ongoing change and offering insights to the causes and consequences of fire regime shifts over decades to millennia. The main objectives of this study are to address 1) how fire regime shift impacts ecosystem C dynamics at a millennial time scale; and 2) which factor is more important in regulating the dynamics of ecosystem C storage capacity at decades to millennium scales among fire, CO2 and temperature. In this study, the REGIME model (Weng et al. JGR, 2012) has been modified to evaluate the dynamics of ecosystem C storage capacity (the theoretic capacity of an ecosystem to store C) since 3000 years BP for the black spruce forests in interior Alaska under the influence of changing fire regime, rising atmospheric CO2 concentration, and climate warming, all of which were derived from paleo-data. In addition, C storage capacity was also modeled through the 21 century using IPCC scenarios for CO2 and temperature, and fire regime scenario derived based on a paleo-fire dataset. Overall, fire frequency has been constant but fire severity has increased significantly since 3000 years BP for the studied area. Our results indicate that this fire regime shifting alone or in combination with temperature and/or CO2 always decrease ecosystem C storage capacity over the past 3000 years. Among the single factors, fire regime shifting results in the greatest

  12. Paleodata-model integration reveals uncertain boreal forest carbon balance due to rapid recent fire regime change

    NASA Astrophysics Data System (ADS)

    Kelly, R.; Genet, H.; McGuire, D.; Hu, F.

    2013-12-01

    Climate warming is expected to increase the frequency and severity of natural fires in the boreal forest biome. Boreal forests represent >30% of terrestrial carbon (C) stocks, and fire is a key component of the C cycle in these ecosystems. However, predictions of fire-regime change face substantial uncertainty, largely because complex fire-climate-vegetation interactions are poorly characterized in brief observational records. Furthermore, previous studies suggest that model projections of future C dynamics are sensitive to assumptions about the prehistoric fire regime. Paleofire reconstructions offer valuable insights to address these limitations. We collected 14 lake-sediment cores from the Yukon Flats, Alaska to elucidate patterns of long-term environmental change. We then converted fire-regime reconstructions from these data to input drivers for the Dynamic Organic Soils version of the Terrestrial Ecosystem Model (DOS-TEM). Combined with simulated paleoclimate from an Earth System Model and CO2 data from ice core analysis, these 'paleo-forcing' data allowed us to model past changes in ecosystem C storage in our study area to (1) assess the relative importance of climate, atmospheric CO2 concentration, and fire in driving C dynamics of the past millennium, and (2) evaluate the effect of assumptions about prehistoric fire regime on predictions of current and future boreal-forest C balance. Fire-regime variations were the dominant control on simulated C storage, producing fluctuations of ~3 kg C/m2 (~25% of total ecosystem C) on centennial timescales. By comparison, climate and CO2 concentration played minor roles. Fire frequency shifts were particularly influential, suggesting that the role of fire in dictating stand age distribution at the landscape scale is of paramount importance to net C dynamics. That shifts in fire-regime were responsible for large and rapid losses of C in the past emphasizes the importance of incorporating fire into methodologies that

  13. Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes

    NASA Astrophysics Data System (ADS)

    Portner, H.; Bugmann, H.; Wolf, A.

    2009-08-01

    Models of carbon cycling in terrestrial ecosystems contain formulations for the dependence of respiration on temperature, but the sensitivity of predicted carbon pools and fluxes to these formulations and their parameterization is not understood. Thus, we made an uncertainty analysis of soil organic matter decomposition with respect to its temperature dependency using the ecosystem model LPJ-GUESS. We used five temperature response functions (Exponential, Arrhenius, Lloyd-Taylor, Gaussian, Van't Hoff). We determined the parameter uncertainty ranges of the functions by nonlinear regression analysis based on eight experimental datasets from northern hemisphere ecosystems. We sampled over the uncertainty bounds of the parameters and run simulations for each pair of temperature response function and calibration site. The uncertainty in both long-term and short-term soil carbon dynamics was analyzed over an elevation gradient in southern Switzerland. The function of Lloyd-Taylor turned out to be adequate for modelling the temperature dependency of soil organic matter decomposition, whereas the other functions either resulted in poor fits (Exponential, Arrhenius) or were not applicable for all datasets (Gaussian, Van't Hoff). There were two main sources of uncertainty for model simulations: (1) the uncertainty in the parameter estimates of the response functions, which increased with increasing temperature and (2) the uncertainty in the simulated size of carbon pools, which increased with elevation, as slower turn-over times lead to higher carbon stocks and higher associated uncertainties. The higher uncertainty in carbon pools with slow turn-over rates has important implications for the uncertainty in the projection of the change of soil carbon stocks driven by climate change, which turned out to be more uncertain for higher elevations and hence higher latitudes, which are of key importance for the global terrestrial carbon budget.

  14. Sedimentary structures formed by upper-regime flows on a Pleistocene carbonate ramp (Favignana Calcarenite, Sicily, Italy)

    NASA Astrophysics Data System (ADS)

    Slootman, Arnoud; Moscariello, Andrea; Cartigny, Matthieu; de Boer, Poppe

    2015-04-01

    flow. Using published experimental Froude numbers for breaking antidune waves, average flow thickness and sediment flux is computed. The ratio of bed volume and sediment flux provides an estimate for the duration of the sediment gravity flows. We show that applying hydraulic equations to upper-regime sedimentary structures in coarse-grained carbonate sandstones reveal that about half of the ramp deposits, that formed over ca. 350 thousand years, were deposited in not more than tens of hours. Our results provide renewed insight into the evolution of the Favignana Calcarenite and other carbonate ramp deposits.

  15. Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes

    NASA Astrophysics Data System (ADS)

    Portner, H.; Bugmann, H.; Wolf, A.

    2010-11-01

    Models of carbon cycling in terrestrial ecosystems contain formulations for the dependence of respiration on temperature, but the sensitivity of predicted carbon pools and fluxes to these formulations and their parameterization is not well understood. Thus, we performed an uncertainty analysis of soil organic matter decomposition with respect to its temperature dependency using the ecosystem model LPJ-GUESS. We used five temperature response functions (Exponential, Arrhenius, Lloyd-Taylor, Gaussian, Van't Hoff). We determined the parameter confidence ranges of the formulations by nonlinear regression analysis based on eight experimental datasets from Northern Hemisphere ecosystems. We sampled over the confidence ranges of the parameters and ran simulations for each pair of temperature response function and calibration site. We analyzed both the long-term and the short-term heterotrophic soil carbon dynamics over a virtual elevation gradient in southern Switzerland. The temperature relationship of Lloyd-Taylor fitted the overall data set best as the other functions either resulted in poor fits (Exponential, Arrhenius) or were not applicable for all datasets (Gaussian, Van't Hoff). There were two main sources of uncertainty for model simulations: (1) the lack of confidence in the parameter estimates of the temperature response, which increased with increasing temperature, and (2) the size of the simulated soil carbon pools, which increased with elevation, as slower turn-over times lead to higher carbon stocks and higher associated uncertainties. Our results therefore indicate that such projections are more uncertain for higher elevations and hence also higher latitudes, which are of key importance for the global terrestrial carbon budget.

  16. Chaoticity threshold in magnetized plasmas: Numerical results in the weak coupling regime

    SciTech Connect

    Carati, A. Benfenati, F.; Maiocchi, A.; Galgani, L.; Zuin, M.

    2014-03-15

    The present paper is a numerical counterpart to the theoretical work [Carati et al., Chaos 22, 033124 (2012)]. We are concerned with the transition from order to chaos in a one-component plasma (a system of point electrons with mutual Coulomb interactions, in a uniform neutralizing background), the plasma being immersed in a uniform stationary magnetic field. In the paper [Carati et al., Chaos 22, 033124 (2012)], it was predicted that a transition should take place when the electron density is increased or the field decreased in such a way that the ratio ω{sub p}/ω{sub c} between plasma and cyclotron frequencies becomes of order 1, irrespective of the value of the so-called Coulomb coupling parameter Γ. Here, we perform numerical computations for a first principles model of N point electrons in a periodic box, with mutual Coulomb interactions, using as a probe for chaoticity the time-autocorrelation function of magnetization. We consider two values of Γ (0.04 and 0.016) in the weak coupling regime Γ ≪ 1, with N up to 512. A transition is found to occur for ω{sub p}/ω{sub c} in the range between 0.25 and 2, in fairly good agreement with the theoretical prediction. These results might be of interest for the problem of the breakdown of plasma confinement in fusion machines.

  17. Methane Pyrolysis and Disposing Off Resulting Carbon

    NASA Technical Reports Server (NTRS)

    Sharma, P. K.; Rapp, D.; Rahotgi, N. K.

    1999-01-01

    Sabatier/Electrolysis (S/E) is a leading process for producing methane and oxygen for application to Mars ISPP. One significant problem with this process is that it produces an excess of methane for combustion with the amount of oxygen that is produced. Therefore, one must discard roughly half of the methane to obtain the proper stoichiometric methane/oxygen mixture for ascent from Mars. This is a waste of hydrogen, which must be brought from Earth and is difficult to transport to Mars and store on Mars. To reduce the problem of transporting hydrogen to Mars, the S/E process can be augmented by another process which reduces overall hydrogen requirement. Three conceptual approaches for doing this are (i) recover hydrogen from the excess methane produced by the S/E process, (ii) convert the methane to a higher hydrocarbon or other organic with a lower H/C ratio than methane, and (iii) use a separate process (such as zirconia or reverse water gas shift reaction) to produce additional oxygen, thus utilizing all the methane produced by the Sabatier process. We report our results here on recovering hydrogen from the excess methane using pyrolysis of methane. Pyrolysis has the advantage that it produces almost pure hydrogen, and any unreacted methane can pass through the S/E process reactor. It has the disadvantage that disposing of the carbon produced by pyrolysis presents difficulties. The goals of a research program on recovery of hydrogen from methane are (in descending priority order): 1) Study the kinetics of pyrolysis to arrive at a pyrolysis reactor design that produces high yields in a confined volume at the lowest possible operating temperature; 2) Study the kinetics of carbon burnoff to determine whether high yields can be obtained in a confined volume at acceptable operating temperatures; and 3) Investigate catalytic techniques for depositing carbon as a fine soot which can be physically separated from the reactor. In the JPL program, we have made significant

  18. Methane Pyrolysis and Disposing Off Resulting Carbon

    NASA Technical Reports Server (NTRS)

    Sharma, P. K.; Rapp, D.; Rahotgi, N. K.

    1999-01-01

    Sabatier/Electrolysis (S/E) is a leading process for producing methane and oxygen for application to Mars ISPP. One significant problem with this process is that it produces an excess of methane for combustion with the amount of oxygen that is produced. Therefore, one must discard roughly half of the methane to obtain the proper stoichiometric methane/oxygen mixture for ascent from Mars. This is wasteful of hydrogen, which must be brought from Earth and is difficult to transport to Mars and store on Mars. To reduced the problem of transporting hydrogen to Mars, the S/E process can be augmented by another process which reduces overall hydrogen requirement. Three conceptual approaches for doing this are (1) recover hydrogen from the excess methane produced by the S/E process, (2) convert the methane to a higher hydrocarbon or other organic with a lower H/C ratio than methane, and (3) use a separate process (such as zirconia or reverse water gas shift reaction) to produce additional oxygen, thus utilizing all the methane produced by the Sabatier process. We report our results here on recovering hydrogen from the excess methane using pyrolysis of methane. Pyrolysis has the advantage that it produces almost pure hydrogen, and any unreacted methane can pass through the S/E process reactor. It has the disadvantage that disposing of the carbon produced by pyrolysis presents difficulties. Hydrogen may be obtained from methane by pyrolysis in the temperature range 10000-12000C. The main reaction products are hydrogen and carbon, though very small amounts of higher hydrocarbons, including aromatic hydrocarbons are formed. The conversion efficiency is about 95% at 12000C. One needs to distinguish between thermodynamic equilibrium conversion and conversion limited by kinetics in a finite reactor.

  19. Evaluation of the feasibility of alcohols serving as external carbon sources for biological phosphorus removal induced by the oxic/extended-idle regime.

    PubMed

    Wang, Dongbo; Zheng, Wei; Li, Xiaoming; Yang, Qi; Liao, Dexiang; Zeng, Guangming

    2013-03-01

    Recently, a novel operational regime (i.e., the oxic/extended-idle [OEI] regime) has been reported to successfully achieve enhanced biological phosphorus removal (EBPR) when employing glucose and volatile fatty acids as the sole substrate. In the OEI regime, polyphosphate accumulating organisms (PAOs) could get a selective advantage over other populations during the extended-idle period where polyphosphate released but polyhydroxyalkanoates and glycogen transformations were negligible/low, thus energy requirements for maintenance purposes in the period could be covered by polyphosphate release. This study further evaluated the feasibility of alcohols as external carbon sources for EBPR induced by the OEI regime, as the available substrate in the raw wastewater is often deficient. First, phosphorus removal in the OEI process was compared, respectively, with methanol and ethanol as the sole substrate. The results showed that the ethanol-reactor achieved 90.8 ± 2.3% of phosphorus removal, which was approximate twofold than the methanol-reactor. Further studies displayed that the cells in the ethanol-reactor contained more PAOs, and had higher activities of exopolyphosphatase and polyphosphate kinase than those in the methanol-reactor. Also, the aerobic transformations of polyhydroxyalkanoates and glycogen in the ethanol-reactor were, respectively, higher and lower than those in the methanol-reactor, which were consistent with the reactors performances. Then, the feasibility of using ethanol as external substrate to enhance EBPR in the OEI process was confirmed for a municipal wastewater. Finally, EBPR performance and metabolic transformation values between the OEI and the anaerobic/oxic (A/O) regimes with ethanol as the sole substrate were compared. The results showed that EBPR in the ethanol-OEI reactor was higher than that in the ethanol-A/O reactor. All the above results proved that ethanol was a favorable external substrate to the OEI regime for EBPR enhancement.

  20. Temperature regime and carbon dioxide enrichment alter cotton boll development and fiber properties

    SciTech Connect

    Reddy, K.R.; Davidonis, G.H.; Johnson, A.S.; Vinyard, B.T.

    1999-10-01

    Temperature and atmospheric carbon dioxide concentration [CO{sub 2}] affect cotton (Gossypium hirsutum L.) growth and development, but the interaction of these two factors on bill and fiber properties has not been studied. An experiment was conducted in naturally lit plant growth chambers to determine the influence of temperature and atmospheric [CO{sub 2}] on cotton (cv. DPL-51) boll and fiber growth parameters. Five temperature regimes were evaluated: the 1995 temperature at Mississippi State, MS; the 1995 temperature minus 2 C; and the 1995 temperature plus 2, 5, and 7 C. Daily and seasonal variation and amplitudes were maintained. Atmospheric [CO{sub 2}] treatments were 360 (ambient) and 720 {micro}L L{sup {minus}1}. Boll number, boll growth, and fiber properties were measured. Boll size and maturation periods decreased as temperature increased. Boll growth increased with temperature to 25 C and then declined at the highest temperature. Boll maturation period, size, and growth rates were not affected by atmospheric [CO{sub 2}]. The most temperature-sensitive aspect of cotton development is boll retention. Almost no bolls were retained to maturity at 1995 plus 5 or 7 C, but squares and bolls were continuously produced even at those high temperatures. Therefore, the upper limit for cotton boll survival is 32 C, or 5 C warmer than the 1995 US Mid-South ambient temperatures. The 720 {micro}L L{sup {minus}1} atmospheric [CO{sub 2}] had about 40% more squares and bolls across temperatures than the 360 {micro}L L{sup {minus}1} [CO{sub 2}]. Fibers were longer when bolls grew at less than optimal temperatures (25 C) for boll growth. As temperature increased, fiber length distributions were more uniform. Fiber fineness and maturity increased linearly with the increase in temperature up to 26 C, but decreased at 32 C. Short-fiber content declined linearly from 17 to 26 C, but was higher at higher temperature. As for boll growth and developmental parameters, elevated

  1. Impacts of climate change on fire regimes and carbon stocks of the U.S. Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Rogers, Brendan M.; Neilson, Ronald P.; Drapek, Ray; Lenihan, James M.; Wells, John R.; Bachelet, Dominique; Law, Beverly E.

    2011-09-01

    The diverse vegetation types and carbon pools of the U.S. Pacific Northwest (PNW) are tightly coupled to fire regimes that depend on climate and fire suppression. To realistically assess the effects of twenty-first-century climate change on PNW fire and carbon dynamics, we developed a new fire suppression rule for the MC1 dynamic general vegetation model that we ran under three climate change scenarios. Climate projections from the CSIRO Mk3, MIROC 3.2 medres, and Hadley CM3 general circulation models, forced by the A2 CO2 emissions scenario, were downscaled to a 30 arc-second (˜0.6 km2) grid. Future climates amplify the already strong seasonality of temperature and precipitation across the domain. Simulations displayed large increases in area burned (76%-310%) and burn severities (29%-41%) by the end of the twenty-first century. The relatively dry ecosystems east of the Cascades gain carbon in the future despite projections of more intense wildfires, while the mesic maritime forests lose up to 1.2 Pg C from increased burning. Simulated fire suppression causes overall carbon gains yet leaves ecosystems vulnerable to large future fires. Overall, our simulations suggest the Pacific Northwest has the potential to sequester ˜1 Pg C over the next century unless summer droughts severely intensify fire regimes.

  2. An ecological regime shift resulting from disrupted predator-prey interactions in Holocene Australia.

    PubMed

    Prowse, Thomas A A; Johnson, Christopher N; Bradshaw, Corey J A; Brook, Barry W

    2014-03-01

    The mass extinction events during human prehistory are striking examples of ecological regime shifts, the causes of which are still hotly debated. In Australia, human arrival approximately 50 thousand years ago was associated with the continental-scale extinction of numerous marsupial megafauna species and a permanent change in vegetation structure. An alternative stable state persisted until a second regime shift occurred during the late Holocene, when the largest two remaining marsupial carnivores, the thylacine and devil, disappeared from mainland Australia. These extinctions have been widely attributed to the human-assisted invasion of a competing predator, the dingo. In this unusual case, the simultaneous effects of human "intensification" (population growth and technological advances) and climate change (particularly increased ENSO variability) have been largely overlooked. We developed a dynamic model system capable of simulating the complex interactions between the main predators (humans, thylacines, devils, dingoes) and their marsupial prey (macropods), which we coupled with reconstructions of human population growth and climate change for late-Holocene Australia. Because the strength of important interspecific interactions cannot be estimated directly, we used detailed scenario testing and sensitivity analysis to identify robust model outcomes and investigate competing explanations for the Holocene regime shift. This approach identified human intensification as the most probable cause, while also demonstrating the potential importance of synergies with the effects of climate change. Our models indicate that the prehistoric impact of humans on Australian mammals was not limited to the late Pleistocene (i.e., the megafaunal extinctions) but extended into the late Holocene. PMID:24804453

  3. Impact of carbon to nitrogen ratio and aeration regime on mainstream deammonification.

    PubMed

    Han, M; De Clippeleir, H; Al-Omari, A; Wett, B; Vlaeminck, S E; Bott, C; Murthy, S

    2016-01-01

    While deammonification of high-strength wastewater in the sludge line of sewage treatment plants has become well established, the potential cost savings spur the development of this technology for mainstream applications. This study aimed at identifying the effect of aeration and organic carbon on the deammonification process. Two 10 L sequencing bath reactors with different aeration frequencies were operated at 25°C. Real wastewater effluents from chemically enhanced primary treatment and high-rate activated sludge process were fed into the reactors with biodegradable chemical oxygen demand/nitrogen (bCOD/N) of 2.0 and 0.6, respectively. It was found that shorter aerobic solids retention time (SRT) and higher aeration frequency gave more advantages for aerobic ammonium-oxidizing bacteria (AerAOB) than nitrite oxidizing bacteria (NOB) in the system. From the kinetics study, it is shown that the affinity for oxygen is higher for NOB than for AerAOB, and higher dissolved oxygen set-point could decrease the affinity of both AerAOB and NOB communities. After 514 days of operation, it was concluded that lower organic carbon levels enhanced the activity of anoxic ammonium-oxidizing bacteria (AnAOB) over denitrifiers. As a result, the contribution of AnAOB to nitrogen removal increased from 40 to 70%. Overall, a reasonably good total removal efficiency of 66% was reached under a low bCOD/N ratio of 2.0 after adaptation. PMID:27438242

  4. Response to multi-generational selection under elevated [CO2] in two temperature regimes suggests enhanced carbon assimilation and increased reproductive output in Brassica napus L.

    PubMed Central

    Frenck, Georg; van der Linden, Leon; Mikkelsen, Teis Nørgaard; Brix, Hans; Jørgensen, Rikke Bagger

    2013-01-01

    Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO2] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO2] and temperature conditions, a full-factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO2] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO2] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co-occur. PMID:23762504

  5. Impact of inter-annual climatic variability on ecosystem carbon exchange in two grazed temperate grasslands with contrasting drainage regimes

    NASA Astrophysics Data System (ADS)

    Choncubhair, Órlaith Ní; Humphreys, James; Lanigan, Gary

    2014-05-01

    Temperate grasslands constitute over 30% of the Earth's naturally-occurring biomes and make an important contribution towards the partial mitigation of anthropogenic greenhouse gas emissions by terrestrial ecosystems. Accumulation of carbon (C) in grassland systems predominantly takes place in below-ground repositories, enhanced by the presence of a stable soil environment with low carbon turnover rates, active rhizodeposition and high levels of residue and organic inputs. Predicted future warming is expected to increase productivity in temperate zones, thereby enhancing rates of terrestrial carbon sequestration. However, the susceptibility of many ecosystems, including grasslands, to extreme climatic events and inter-annual variability has been demonstrated previously. Temperature anomalies as well as modifications in the temporal pattern and quantity of precipitation alter the balance between carbon uptake and release processes and a mechanistic understanding of ecosystem response to such changes is still lacking. In the present study, the impact of extreme inter-annual variability in summer rainfall and temperature on carbon dynamics in two rotationally-grazed grasslands in Ireland was examined. The sites experience similar temperate climatic regimes but differ in soil drainage characteristics. Eddy covariance measurements of net ecosystem exchange of carbon were complemented by regular assessment of standing biomass, leaf cover, harvest exports and organic amendment inputs. The summers of 2012 and 2013 showed contrasting climatic conditions, with summer precipitation 93% higher and 25% lower respectively than long-term means. In addition, soil temperatures were 7% lower and 11% higher than expected. Cool, wet conditions in 2012 facilitated net carbon uptake for more than ten months of the year at the poorly-drained site, however the ecosystem switched to a net source of carbon in 2013 during months with significantly reduced rainfall. In contrast, net C

  6. A Numerical Study of the Effect of Periodic Nutrient Supply on Pathways of Carbon in a Coastal Upwelling Regime

    NASA Technical Reports Server (NTRS)

    Carr, Mary-Elena

    1998-01-01

    A size-based ecosystem model was modified to include periodic upwelling events and used to evaluate the effect of episodic nutrient supply on the standing stock, carbon uptake, and carbon flow into mesozooplankton grazing and sinking flux in a coastal upwelling regime. Two ecosystem configurations were compared: a single food chain made up of net phytoplankton and mesozooplankton (one autotroph and one heterotroph, A1H1), and three interconnected food chains plus bacteria (three autotrophs and four heterotrophs, A3H4). The carbon pathways in the A1H1 simulations were under stronger physical control than those of the A3H4 runs, where the small size classes are not affected by frequent upwelling events. In the more complex food web simulations, the microbial pathway determines the total carbon uptake and grazing rates, and regenerated nitrogen accounts for more than half of the total primary production for periods of 20 days or longer between events. By contrast, new production, export of carbon through sinking and mesozooplankton grazing are more important in the A1H1 simulations. In the A3H4 simulations, the turnover time scale of the autotroph biomass increases as the period between upwelling events increases, because of the larger contribution of slow-growing net phytoplankton. The upwelling period was characterized for three upwelling sites from the alongshore wind speed measured by the NASA Scatterometer (NSCAT) and the corresponding model output compared with literature data. This validation exercise for three upwelling sites and a downstream embayment suggests that standing stock, carbon uptake and size fractionation were best supported by the A3H4 simulations, while the simulated sinking fluxes are not distinguishable in the two configurations.

  7. Projected carbon stocks in the conterminous USA with land use and variable fire regimes.

    PubMed

    Bachelet, Dominique; Ferschweiler, Ken; Sheehan, Timothy J; Sleeter, Benjamin M; Zhu, Zhiliang

    2015-12-01

    The dynamic global vegetation model (DGVM) MC2 was run over the conterminous USA at 30 arc sec (~800 m) to simulate the impacts of nine climate futures generated by 3GCMs (CSIRO, MIROC and CGCM3) using 3 emission scenarios (A2, A1B and B1) in the context of the LandCarbon national carbon sequestration assessment. It first simulated potential vegetation dynamics from coast to coast assuming no human impacts and naturally occurring wildfires. A moderate effect of increased atmospheric CO2 on water use efficiency and growth enhanced carbon sequestration but did not greatly influence woody encroachment. The wildfires maintained prairie-forest ecotones in the Great Plains. With simulated fire suppression, the number and impacts of wildfires was reduced as only catastrophic fires were allowed to escape. This greatly increased the expansion of forests and woodlands across the western USA and some of the ecotones disappeared. However, when fires did occur, their impacts (both extent and biomass consumed) were very large. We also evaluated the relative influence of human land use including forest and crop harvest by running the DGVM with land use (and fire suppression) and simple land management rules. From 2041 through 2060, carbon stocks (live biomass, soil and dead biomass) of US terrestrial ecosystems varied between 155 and 162 Pg C across the three emission scenarios when potential natural vegetation was simulated. With land use, periodic harvest of croplands and timberlands as well as the prevention of woody expansion across the West reduced carbon stocks to a range of 122-126 Pg C, while effective fire suppression reduced fire emissions by about 50%. Despite the simplicity of our approach, the differences between the size of the carbon stocks confirm other reports of the importance of land use on the carbon cycle over climate change. PMID:26207729

  8. Projected carbon stocks in the conterminous USA with land use and variable fire regimes.

    PubMed

    Bachelet, Dominique; Ferschweiler, Ken; Sheehan, Timothy J; Sleeter, Benjamin M; Zhu, Zhiliang

    2015-12-01

    The dynamic global vegetation model (DGVM) MC2 was run over the conterminous USA at 30 arc sec (~800 m) to simulate the impacts of nine climate futures generated by 3GCMs (CSIRO, MIROC and CGCM3) using 3 emission scenarios (A2, A1B and B1) in the context of the LandCarbon national carbon sequestration assessment. It first simulated potential vegetation dynamics from coast to coast assuming no human impacts and naturally occurring wildfires. A moderate effect of increased atmospheric CO2 on water use efficiency and growth enhanced carbon sequestration but did not greatly influence woody encroachment. The wildfires maintained prairie-forest ecotones in the Great Plains. With simulated fire suppression, the number and impacts of wildfires was reduced as only catastrophic fires were allowed to escape. This greatly increased the expansion of forests and woodlands across the western USA and some of the ecotones disappeared. However, when fires did occur, their impacts (both extent and biomass consumed) were very large. We also evaluated the relative influence of human land use including forest and crop harvest by running the DGVM with land use (and fire suppression) and simple land management rules. From 2041 through 2060, carbon stocks (live biomass, soil and dead biomass) of US terrestrial ecosystems varied between 155 and 162 Pg C across the three emission scenarios when potential natural vegetation was simulated. With land use, periodic harvest of croplands and timberlands as well as the prevention of woody expansion across the West reduced carbon stocks to a range of 122-126 Pg C, while effective fire suppression reduced fire emissions by about 50%. Despite the simplicity of our approach, the differences between the size of the carbon stocks confirm other reports of the importance of land use on the carbon cycle over climate change.

  9. Anthropogenic perturbation of the global carbon cycle as a result of agricultural carbon erosion and burial

    NASA Astrophysics Data System (ADS)

    Wang, Zhengang; Govers, Gerard; Kaplan, Jed; Hoffmann, Thomas; Doetterl, Sebastian; Six, Johan; Van Oost, Kristof

    2016-04-01

    Changes in terrestrial carbon storage exert a strong control over atmospheric CO2 concentrations but the underlying mechanisms are not fully constrained. Anthropogenic land cover change is considered to represent an important carbon loss mechanism, but current assessments do not consider the associated acceleration of carbon erosion and burial in sediments. We evaluated the role of anthropogenic soil erosion and the resulting carbon fluxes between land and atmosphere from the onset of agriculture to the present day. We show, here, that agricultural erosion induced a significant cumulative net uptake of 198±57 Pg carbon on terrestrial ecosystems. This erosion-induced soil carbon sink is estimated to have offset 74±21% of carbon emissions. Since 1850, erosion fluxes have increased 3-fold. As a result, the erosion and lateral transfer of organic carbon in relation to human activities is an important driver of the global carbon cycle at millennial timescales.

  10. Analytical results for quasiparticle excitations in the Fractional Quantum Hall Effect regime

    NASA Astrophysics Data System (ADS)

    Bentalha, Z.

    2016-07-01

    In this work, quasiparticle energies for systems with N = 3 , 4 , 5 , 6 and 7 electrons are calculated analytically in both Laughlin and composite fermions (CF) theories by considering the electron-electron interaction potential. The exact results we have obtained for the first and the second excited states agree with previous numerical results. This study shows that at this level the CF-wave function has lower energy in comparison with Laughlin wave function energy.

  11. Widely Tunable Single-Photon Source from a Carbon Nanotube in the Purcell Regime

    NASA Astrophysics Data System (ADS)

    Jeantet, A.; Chassagneux, Y.; Raynaud, C.; Roussignol, Ph.; Lauret, J. S.; Besga, B.; Estève, J.; Reichel, J.; Voisin, C.

    2016-06-01

    The narrow emission of a single carbon nanotube at low temperature is coupled to the optical mode of a fiber microcavity using the built-in spatial and spectral matching brought by this flexible geometry. A thorough cw and time-resolved investigation of the very same emitter both in free space and in cavity shows an efficient funneling of the emission into the cavity mode together with a strong emission enhancement corresponding to a Purcell factor of up to 5. At the same time, the emitted photons retain a strong sub-Poissonian statistics. By exploiting the cavity feeding effect on the phonon wings, we locked the emission of the nanotube at the cavity resonance frequency, which allowed us to tune the frequency over a 4 THz band while keeping an almost perfect antibunching. By choosing the nanotube diameter appropriately, this study paves the way to the development of carbon-based tunable single-photon sources in the telecom bands.

  12. The carbonate profile and water regime of migrational-mycelial chernozems in different ecosystems of Kursk oblast

    NASA Astrophysics Data System (ADS)

    Ovechkin, S. V.; Bazykina, G. S.

    2011-12-01

    The carbonate profiles of migrational-mycelial (typical) chernozems under regularly mown and absolutely reserved steppes in the V.V. Alekhin Central Chernozemic State Biospheric Reserve and under cropland with cereals (Kursk oblast) were studied in 2007-2009. A comparison of the results of these studies with previous results obtained in the mid-1970s attests to certain changes in the carbonate profiles of the soils. They are conditioned by the activation of the migration of carbonates and the more pronounced manifestation of differently directed processes of the leaching and accumulation of carbonates. The reasons for the observed transformation of the carbonate profiles are related to the increased moistening of the upper 3-m-deep chernozemic layer in different ecosystems because of a general rise in the humidity of the local climate in the recent decades (1973-2006).

  13. The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed

    USGS Publications Warehouse

    Hernes, P.J.; Spencer, R.G.M.; Dyda, R.Y.; Pellerin, B.A.; Bachand, P.A.M.; Bergamaschi, B.A.

    2008-01-01

    Willow Slough, a seasonally irrigated agricultural watershed in the Sacramento River valley, California, was sampled weekly in 2006 in order to investigate seasonal concentrations and compositions of dissolved organic carbon (DOC). Average DOC concentrations nearly doubled from winter baseflow (2.75 mg L-1) to summer irrigation (5.14 mg L-1), while a concomitant increase in carbon-normalized vanillyl phenols (0.11 mg 100 mg OC-1 increasing to 0.31 mg 100 mg OC-1, on average) indicates that this additional carbon is likely vascular plant-derived. A strong linear relationship between lignin concentration and total suspended sediments (r2 = 0.79) demonstrates that agricultural management practices that mobilize sediments will likely have a direct and significant impact on DOC composition. The original source of vascular plant-derived DOC to Willow Slough appears to be the same throughout the year as evidenced by similar syringyl to vanillyl and cinnamyl to vanillyl ratios. However, differing diagenetic pathways during winter baseflow as compared to the rest of the year are evident in acid to aldehyde ratios of both vanillyl and syringyl phenols. The chromophoric dissolved organic matter (CDOM) absorption coefficient at 350 nm showed a strong correlation with lignin concentration (r2 = 0.83). Other CDOM measurements related to aromaticity and molecular weight also showed correlations with carbon-normalized yields (e.g. specific UV absorbance at 254 nm (r2 = 0.57) and spectral slope (r2 = 0.54)). Our overall findings suggest that irrigated agricultural watersheds like Willow Slough can potentially have a significant impact on mainstem DOC concentration and composition when scaled to the entire watershed of the main tributary. ?? 2008 Elsevier Ltd.

  14. The role of hydrologic regimes on dissolved organic carbon composition in an agricultural watershed

    NASA Astrophysics Data System (ADS)

    Hernes, Peter J.; Spencer, Robert G. M.; Dyda, Rachael Y.; Pellerin, Brian A.; Bachand, Philip A. M.; Bergamaschi, Brian A.

    2008-11-01

    Willow Slough, a seasonally irrigated agricultural watershed in the Sacramento River valley, California, was sampled weekly in 2006 in order to investigate seasonal concentrations and compositions of dissolved organic carbon (DOC). Average DOC concentrations nearly doubled from winter baseflow (2.75 mg L -1) to summer irrigation (5.14 mg L -1), while a concomitant increase in carbon-normalized vanillyl phenols (0.11 mg 100 mg OC -1 increasing to 0.31 mg 100 mg OC -1, on average) indicates that this additional carbon is likely vascular plant-derived. A strong linear relationship between lignin concentration and total suspended sediments ( r2 = 0.79) demonstrates that agricultural management practices that mobilize sediments will likely have a direct and significant impact on DOC composition. The original source of vascular plant-derived DOC to Willow Slough appears to be the same throughout the year as evidenced by similar syringyl to vanillyl and cinnamyl to vanillyl ratios. However, differing diagenetic pathways during winter baseflow as compared to the rest of the year are evident in acid to aldehyde ratios of both vanillyl and syringyl phenols. The chromophoric dissolved organic matter (CDOM) absorption coefficient at 350 nm showed a strong correlation with lignin concentration ( r2 = 0.83). Other CDOM measurements related to aromaticity and molecular weight also showed correlations with carbon-normalized yields (e.g. specific UV absorbance at 254 nm ( r2 = 0.57) and spectral slope ( r2 = 0.54)). Our overall findings suggest that irrigated agricultural watersheds like Willow Slough can potentially have a significant impact on mainstem DOC concentration and composition when scaled to the entire watershed of the main tributary.

  15. Gunshot wounds (resulting from execution) of exhumed victims of the communist regime in Poland.

    PubMed

    Szleszkowski, Łukasz; Thannhäuser, Agata; Szwagrzyk, Krzysztof; Kawecki, Jerzy; Jurek, Tomasz

    2014-07-01

    This study presents the results of the analysis of the remains of 23 executed male individuals aged between 21 and 63 years, recovered from Osobowicki Cemetery in Wroclaw (Poland), field 83B, in 2012. In 1948 and 1949, prisoners sentenced to death by firing squad--most of them associated with the post-war anti-communist underground independence movement in Poland--were buried there. The aim of the study was to analyse fatal wounds and the method of execution, and to compare the results to data from archival documents. The results were also compared with studies concerning executions during a later period, i.e. 1949-1954. The research on the method of execution during this period of history carried out during the exhumations in Osobowicki Cemetery was the first conducted on such a scale in Poland. Forensic analysis revealed a wide variety of gunshot wounds inflicted during executions, revealing both gunshots to the head, especially single shots to the back of the head, and cases corresponding to the use of a firing squad, probably equipped with machine guns. The results of the research indicate that capital punishment by shooting was carried out in ways both similar to those the specified in the regulations and completely different.

  16. Gunshot wounds (resulting from execution) of exhumed victims of the communist regime in Poland.

    PubMed

    Szleszkowski, Łukasz; Thannhäuser, Agata; Szwagrzyk, Krzysztof; Kawecki, Jerzy; Jurek, Tomasz

    2014-07-01

    This study presents the results of the analysis of the remains of 23 executed male individuals aged between 21 and 63 years, recovered from Osobowicki Cemetery in Wroclaw (Poland), field 83B, in 2012. In 1948 and 1949, prisoners sentenced to death by firing squad--most of them associated with the post-war anti-communist underground independence movement in Poland--were buried there. The aim of the study was to analyse fatal wounds and the method of execution, and to compare the results to data from archival documents. The results were also compared with studies concerning executions during a later period, i.e. 1949-1954. The research on the method of execution during this period of history carried out during the exhumations in Osobowicki Cemetery was the first conducted on such a scale in Poland. Forensic analysis revealed a wide variety of gunshot wounds inflicted during executions, revealing both gunshots to the head, especially single shots to the back of the head, and cases corresponding to the use of a firing squad, probably equipped with machine guns. The results of the research indicate that capital punishment by shooting was carried out in ways both similar to those the specified in the regulations and completely different. PMID:24767546

  17. Critical adsorption in the undersaturated regime: Scaling and exact results in Ising strips

    NASA Astrophysics Data System (ADS)

    Ciach, A.; Maciolek, A.; Stecki, J.

    1998-04-01

    Critical adsorption for weak surface field h1 is reconsidered. On the basis of physical heuristic arguments, approximate behavior of the scaling function is derived. New form of a scaling for weak h1 in finite systems is proposed and verified by testing against exact results obtained for this purpose in the 2D Ising strips. For weak h1 we find the approximate behavior of adsorption Γ˜τβ-Δ1 for the reduced temperatures h11/Δ1˜τ≪1. This behavior is consistent with experimental data [N. S. Desai, S. Peach, and C. Franck, Phys. Rev. E 52, 4129 (1995)] obtained for τ=10-5, and is in a very good agreement with exact results in the 2D Ising strip.

  18. Variations in the fire regime in the North American boreal forest between 1990 and 2004 and their potential impacts on terrestrial carbon storage

    NASA Astrophysics Data System (ADS)

    Kasischke, E. S.; Turetsky, M. R.; McGuire, A. D.; French, N. H.

    2004-12-01

    that organic layers common in boreal forests and peatlands burn deeper and release more carbon during large fire events and during late season fires. In this paper, we will present the results of a study on how recent changes in the North American boreal fire regime have influenced carbon storage in the ground-organic layer in this region based on different assumption regarding levels of consumption of organic layer burning.

  19. Widely Tunable Single-Photon Source from a Carbon Nanotube in the Purcell Regime.

    PubMed

    Jeantet, A; Chassagneux, Y; Raynaud, C; Roussignol, Ph; Lauret, J S; Besga, B; Estève, J; Reichel, J; Voisin, C

    2016-06-17

    The narrow emission of a single carbon nanotube at low temperature is coupled to the optical mode of a fiber microcavity using the built-in spatial and spectral matching brought by this flexible geometry. A thorough cw and time-resolved investigation of the very same emitter both in free space and in cavity shows an efficient funneling of the emission into the cavity mode together with a strong emission enhancement corresponding to a Purcell factor of up to 5. At the same time, the emitted photons retain a strong sub-Poissonian statistics. By exploiting the cavity feeding effect on the phonon wings, we locked the emission of the nanotube at the cavity resonance frequency, which allowed us to tune the frequency over a 4 THz band while keeping an almost perfect antibunching. By choosing the nanotube diameter appropriately, this study paves the way to the development of carbon-based tunable single-photon sources in the telecom bands. PMID:27367407

  20. Shifts in the hydrodynamic regime determine patterns of regional changes of the Arctic Ocean carbon cycle in future climate change projections

    NASA Astrophysics Data System (ADS)

    Ilyina, T.; Heinze, M.; Li, H.; Jungclaus, J. H.; Six, K. D.

    2015-12-01

    In future projections the Arctic Ocean carbon cycle is a hotspot for changes driven by rising CO2 emissions. Concomitantly, the Arctic Ocean hydrodynamic regime undergoes substantial shifts so the net effect on the carbon cycle is not intuitively clear. In the high CO2 scenario RCP8.5 extended until 2300 in projections of the Max Planck Institute's Earth System Model, the averaged Arctic Ocean surface temperature rises by 4°C in 2100 and by 10°C in 2300, respectively. The Arctic becomes free of summer sea ice in the second half of the 21st century, whereas winter sea ice disappears at the beginning of the 23rd century. Owing to increased sea ice melting and runoff, fresh water content increases gradually until the end of the 22nd century and then drops abruptly as a result of an intensification of the saline Atlantic water inflow. Accumulation of Atlantic water collapses the halocline in the central basin of the Arctic Ocean by the first half of the 23rd century. Ongoing warming enhances thermal stratification and the mixed layer shoales. In contrast, halocline erosion and the cooling of the ice free water act in concert to favor formation of convection cells in the central basin. Freshening in the Canada basin and transport of salty water into the Eurasian basin generate a dipole structure in the anomalies of surface salinity. Driven by the rising CO2, the averaged dissolved inorganic carbon (DIC) is growing. Changes in the averaged total alkalinity (TA) go along with the fresh water content evolution and decreasing carbonate ion concentration so that TA drops below preindustrial values. Yet, along with salinity, the Eurasian basin receives waters with higher DIC and TA from the Atlantic. As a result, the distributions of TA and DIC anomalies resemble the dipole pattern projected for salinity. We show that while future changes in the Arctic Ocean carbon cycle proceed at rates determined by atmospheric CO2 levels, the regional patterns are driven by shifts in the

  1. The Blazing Arctic? Linkages of Tundra Fire Regimes to Climatic Change and Implications for Carbon Cycling (Invited)

    NASA Astrophysics Data System (ADS)

    Hu, F.; Higuera, P. E.; Walsh, J. E.; Chapman, W.; Duffy, P.; Brubaker, L.; Chipman, M. L.

    2010-12-01

    burned in Alaska was moderately correlated with sea-ice extent from 1979-2009 (r = -0.43, p = 0.02), suggesting links among multiple components of the climate system. These patterns imply that climate warming over land areas of the Arctic, amplified by the loss of sea ice, has the potential to dramatically increase tundra burns. Increased tundra burning and associated releases of soil carbon may change the role of tundra ecosystems in the global carbon cycle, but existing data are inadequate for evaluating this possibility. Ongoing work focuses on further characterizing the climatic and vegetation/fuel conditions under which large, severe tundra fires occur and assessing the effects of tundra fires on carbon cycling. Improving our understanding of tundra fire-regime responses to sea-ice reduction and climatic warming is necessary for projecting Earth system dynamics, developing ecosystem management strategies, and preparing arctic residents for future changes.

  2. Tc-99 Adsorption on Selected Activated Carbons - Batch Testing Results

    SciTech Connect

    Mattigod, Shas V.; Wellman, Dawn M.; Golovich, Elizabeth C.; Cordova, Elsa A.; Smith, Ronald M.

    2010-12-01

    CH2M HILL Plateau Remediation Company (CHPRC) is currently developing a 200-West Area groundwater pump-and-treat system as the remedial action selected under the Comprehensive Environmental Response, Compensation, and Liability Act Record of Decision for Operable Unit (OU) 200-ZP-1. This report documents the results of treatability tests Pacific Northwest National Laboratory researchers conducted to quantify the ability of selected activated carbon products (or carbons) to adsorb technetium-99 (Tc-99) from 200-West Area groundwater. The Tc-99 adsorption performance of seven activated carbons (J177601 Calgon Fitrasorb 400, J177606 Siemens AC1230AWC, J177609 Carbon Resources CR-1240-AW, J177611 General Carbon GC20X50, J177612 Norit GAC830, J177613 Norit GAC830, and J177617 Nucon LW1230) were evaluated using water from well 299-W19-36. Four of the best performing carbons (J177606 Siemens AC1230AWC, J177609 Carbon Resources CR-1240-AW, J177611 General Carbon GC20X50, and J177613 Norit GAC830) were selected for batch isotherm testing. The batch isotherm tests on four of the selected carbons indicated that under lower nitrate concentration conditions (382 mg/L), Kd values ranged from 6,000 to 20,000 mL/g. In comparison. Under higher nitrate (750 mg/L) conditions, there was a measureable decrease in Tc-99 adsorption with Kd values ranging from 3,000 to 7,000 mL/g. The adsorption data fit both the Langmuir and the Freundlich equations. Supplemental tests were conducted using the two carbons that demonstrated the highest adsorption capacity to resolve the issue of the best fit isotherm. These tests indicated that Langmuir isotherms provided the best fit for Tc-99 adsorption under low nitrate concentration conditions. At the design basis concentration of Tc 0.865 µg/L(14,700 pCi/L), the predicted Kd values from using Langmuir isotherm constants were 5,980 mL/g and 6,870 mL/g for for the two carbons. These Kd values did not meet the target Kd value of 9,000 mL/g. Tests

  3. Economic impacts of carbon taxes: Detailed results. Final report

    SciTech Connect

    Montgomery, W.D.; Yanchar, J.; Hughes, W. |

    1994-11-01

    This report presents the detailed results of an examination of the economic costs of carbon taxes, including where and how the US economy would be impacted. The analysis is built around a base-line projection for energy markets and the US economy and three alternative carbon tax scenarios. The scenarios were selected to bracket the range of estimates for carbon taxes required to stabilize emissions at present levels. The alternative scenarios phase in carbon taxes to a level of $50, $100, and $200 per metric ton (tonne) of carbon, respectively, by 2010. These scenarios make it possible to analyze the effects of a range of taxes on energy markets. They also provide a basis for the detailed analysis of consumption, investment, trade, industry, and regional impacts on which much of the study focuses. Major findings include the result that holding emissions at 1990 levels through 2010 would require carbon taxes higher than $100 per tonne. At the $100 level, GDP would decline by 2.3 percent below base-line levels by 2010. Reduced consumption accounts for about half of the loss in GDP, and reduced business investment accounts for about one-third. The costs of reducing emissions through 2010 are high because there are limited possibilities for fuel switching in existing equipment, vehicles, and buildings. Turnover in capital stock can take several decades. In the interim, price-induced conservation, which reduces total energy demand, provides the bulk of emissions reductions.

  4. Recent Results from EO Studies on Indian Carbon Cycle Assessment

    NASA Astrophysics Data System (ADS)

    Dadhwal, V. K.; Kushwaha, S. P. S.; Singh, S.; Patel, N. R.; Nayak, R. K.; Patil, P.; Dutt, C. B. S.; Murthy, M. S. R.; Jha, C. S.; Rajsekhar, G.; Pujar, G. S.; Trivedi, S.; Sharma, N.; Ali, M. M.

    2011-08-01

    The monsoon based climate system, diverse land use and land cover distribution and cultural practices poses complex issues in monitoring, assessment and simulation of Indian carbon cycle. Several studies reported lack of spatially and temporally consistent databases, need for calibration and validation of models, and development of national frame work to maintain consistency and completeness in efforts and reduction of uncertainty. Considering the need, as part of ISRO Geosphere Biosphere Programme, National Carbon Project (NCP) initiative was taken up to understand and assess land, atmosphere and oceanic components of carbon cycle with a significant scope for integration of remote sensing, geospatial and process based models. The results from the initial studies are discussed in the paper. An increase of the country's forest carbon stocks from 6244.8 to 6621.6 Mt with an annual increment of 37.7 Mt of the carbon from 1995 to 2005 is reported. In the national scale, CASA model based average annual NPP is estimated to be 1.5 Pg C Yr-1 and is increasing at the rate of 0.005 Pg C Yr-2 during past 25 years from 1981-2006. Analysis of Mid tropospheric CO2 levels retrieved from AIRS data since 2002 till now revealed increasing rate of CO2 at 2.14 ppmv yr-1. It was also o found that biosphere uptake over India and oceanic uptake over the south Indian Ocean could play positive role on the control of seasonal variability of atmospheric carbon dioxide growth rate The paper presents further details on different sub components, recent results and challenges ahead of the project.

  5. Carbon pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes

    SciTech Connect

    Brandstätter, Christian Laner, David Fellner, Johann

    2015-06-15

    Graphical abstract: Display Omitted - Highlights: • 40 year old waste from an old MSW landfill was incubated in LSR experiments. • Carbon balances for anaerobic and aerobic waste degradation were established. • The transformation of carbon pools during waste degradation was investigated. • Waste aeration resulted in the formation of a new, stable organic carbon pool. • Water addition did not have a significant effect on aerobic waste degradation. - Abstract: Landfill aeration has been proven to accelerate the degradation of organic matter in landfills in comparison to anaerobic decomposition. The present study aims to evaluate pools of organic matter decomposing under aerobic and anaerobic conditions using landfill simulation reactors (LSR) filled with 40 year old waste from a former MSW landfill. The LSR were operated for 27 months, whereby the waste in one pair was kept under anaerobic conditions and the four other LSRs were aerated. Two of the aerated LSR were run with leachate recirculation and water addition and two without. The organic carbon in the solid waste was characterized at the beginning and at the end of the experiments and major carbon flows (e.g. TOC in leachate, gaseous CO{sub 2} and CH{sub 4}) were monitored during operation. After the termination of the experiments, the waste from the anaerobic LSRs exhibited a long-term gas production potential of more than 20 NL kg{sup −1} dry waste, which corresponded to the mineralization of around 12% of the initial TOC (67 g kg{sup −1} dry waste). Compared to that, aeration led to threefold decrease in TOC (32–36% of the initial TOC were mineralized), without apparent differences in carbon discharge between the aerobic set ups with and without water addition. Based on the investigation of the carbon pools it could be demonstrated that a bit more than 10% of the initially present organic carbon was transformed into more recalcitrant forms, presumably due to the formation of humic substances

  6. Modelling Late Cenozoic isostatic elevation changes in the Barents Sea and their implications for oceanic and climatic regimes: preliminary results

    NASA Astrophysics Data System (ADS)

    Butt, Faisal A.; Drange, Helge; Elverhøi, Anders; Otterå, Odd Helge; Solheim, Anders

    2002-08-01

    Late Cenozoic isostatic changes in the elevation of the Barents Sea are simulated using a numerical model. Isopach maps of the deposits off present-day Bear Island and Storfjorden troughs made earlier are used to calculate the thickness of sediment cover removed from the respective drainages basins at various time intervals during the last 2.3 Ma. Results indicate that Barents Sea was subaerially exposed at 2.3 Ma and major parts of it became submarine after 1 Ma. Barents Sea today receives around 40% of the warm and saline North Atlantic waters flowing into the Scotland-Greenland Ridge and about half of the Atlantic water entering the Arctic Ocean. It thus has an important role to play in the present-day ocean circulation pattern in the Polar North Atlantic region and water-mass transformations that take place in the Greenland-Iceland-Norwegian Sea and the Arctic Ocean. The effects of an uplifted Barents Sea on the oceanic regime and the Arctic sea-ice cover under the present-day forcings fields are studied using the Miami Isopycnic Coordinate Ocean Model. Preliminary results indicate that a subaerial Barents Sea causes an increased input of warm Atlantic waters into the Arctic Ocean through the Fram Strait which results in warming of the Atlantic water masses in the Arctic Ocean, followed by a reduction in the sea-ice cover. The obtained findings can be used to explain the apparent discrepancy in the late Cenozoic record of the sub-Arctic and Arctic regions whereby Fennoscandia, Iceland and Greenland are envisaged to have been covered by major ice sheets during late Pliocene whereas high Arctic areas such as Svalbard and NE Greenland were apparently free of any major ice.

  7. In situ application of activated carbon and biochar to PCB-contaminated soil and the effects of mixing regime.

    PubMed

    Denyes, Mackenzie J; Rutter, Allison; Zeeb, Barbara A

    2013-11-01

    The in situ use of carbon amendments such as activated carbon (AC) and biochar to minimize the bioavailability of organic contaminants is gaining in popularity. In the first in situ experiment conducted at a Canadian PCB-contaminated Brownfield site, GAC and two types of biochar were statistically equal at reducing PCB uptake into plants. PCB concentrations in Cucurbita pepo root tissue were reduced by 74%, 72% and 64%, with the addition of 2.8% GAC, Burt's biochar and BlueLeaf biochar, respectively. A complementary greenhouse study which included a bioaccumulation study of Eisenia fetida (earthworm), found mechanically mixing carbon amendments with PCB-contaminated soil (i.e. 24 h at 30 rpm) resulted in shoot, root and worm PCB concentrations 66%, 59% and 39% lower than in the manually mixed treatments (i.e. with a spade and bucket). Therefore, studies which mechanically mix carbon amendments with contaminated soil may over-estimate the short-term potential to reduce PCB bioavailability.

  8. In situ application of activated carbon and biochar to PCB-contaminated soil and the effects of mixing regime.

    PubMed

    Denyes, Mackenzie J; Rutter, Allison; Zeeb, Barbara A

    2013-11-01

    The in situ use of carbon amendments such as activated carbon (AC) and biochar to minimize the bioavailability of organic contaminants is gaining in popularity. In the first in situ experiment conducted at a Canadian PCB-contaminated Brownfield site, GAC and two types of biochar were statistically equal at reducing PCB uptake into plants. PCB concentrations in Cucurbita pepo root tissue were reduced by 74%, 72% and 64%, with the addition of 2.8% GAC, Burt's biochar and BlueLeaf biochar, respectively. A complementary greenhouse study which included a bioaccumulation study of Eisenia fetida (earthworm), found mechanically mixing carbon amendments with PCB-contaminated soil (i.e. 24 h at 30 rpm) resulted in shoot, root and worm PCB concentrations 66%, 59% and 39% lower than in the manually mixed treatments (i.e. with a spade and bucket). Therefore, studies which mechanically mix carbon amendments with contaminated soil may over-estimate the short-term potential to reduce PCB bioavailability. PMID:23933124

  9. THERMAL ESCAPE IN THE HYDRODYNAMIC REGIME: RECONSIDERATION OF PARKER's ISENTROPIC THEORY BASED ON RESULTS OF KINETIC SIMULATIONS

    SciTech Connect

    Volkov, Alexey N.; Johnson, Robert E.

    2013-03-10

    The one-dimensional steady-state problem of thermal escape from a single-component atmosphere of mon- and diatomic gases is studied in the hydrodynamic (blow-off) regime using the direct simulation Monte Carlo method for an evaporative-type condition at the lower boundary. The simulations are performed for various depths into an atmosphere, indicated by a Knudsen number, Kn{sub 0}, equal to the ratio of the mean free path of molecules to the radial position of the source surface, ranging from 10 to 10{sup -5}, and for the range of the source Jeans parameter, {lambda}{sub 0}, equal to the ratio of gravitational and thermal energies, specific to blow-off. The results of kinetic simulations are compared with the isentropic model (IM) and the Navier-Stokes model. It is shown that the IM can be simplified if formulated in terms of the local Mach number and Jeans parameter. The simulations predict that at Kn{sub 0} < {approx} 10{sup -3} the flow includes a near-surface non-equilibrium Knudsen layer, a zone where the flow can be well approximated by the IM, and a rarefied far field. The corresponding IM solutions, however, only approach Parker's critical solution as {lambda}{sub 0} approaches the upper limit for blow-off. The IM alone is not capable for predicting the flow and requires boundary conditions at the top of the Knudsen layer. For small Kn{sub 0}, the scaled escape rate and energy loss rate are found to be independent of {lambda}{sub 0}. The simulation results can be scaled to any single-component atmosphere exhibiting blow-off if the external heating above the lower boundary is negligible, in particular, to sublimation-driven atmospheres of Kuiper belt objects.

  10. Air filtration in the free molecular flow regime: a review of high-efficiency particulate air filters based on carbon nanotubes.

    PubMed

    Li, Peng; Wang, Chunya; Zhang, Yingying; Wei, Fei

    2014-11-01

    Air filtration in the free molecular flow (FMF) regime is important and challenging because a higher filtration efficiency and lower pressure drop are obtained when the fiber diameter is smaller than the gas mean free path in the FMF regime. In previous studies, FMF conditions have been obtained by increasing the gas mean free path through reducing the pressure and increasing the temperature. In the case of carbon nanotubes (CNTs) with nanoscale diameters, it is possible to filtrate in the FMF regime under normal conditions. This paper reviews recent progress in theoretical and experimental studies of air filtration in the FMF regime. Typical structure models of high-efficiency particulate (HEPA) air filters based on CNTs are introduced. The pressure drop in air filters operated in the FMF regime is less than that predicted by the conventional air filtration theory. The thinnest HEPA filters fabricated from single-walled CNT films have an extremely low pressure drop. CNT air filters with a gradient nanostructure are shown to give a much better filtration performance in dynamic filtration. CNT air filters with a hierarchical structure and an agglomerated CNT fluidized bed air filter are also introduced. Finally, the challenges and opportunities for the application of CNTs in air filtration are discussed.

  11. Air filtration in the free molecular flow regime: a review of high-efficiency particulate air filters based on carbon nanotubes.

    PubMed

    Li, Peng; Wang, Chunya; Zhang, Yingying; Wei, Fei

    2014-11-01

    Air filtration in the free molecular flow (FMF) regime is important and challenging because a higher filtration efficiency and lower pressure drop are obtained when the fiber diameter is smaller than the gas mean free path in the FMF regime. In previous studies, FMF conditions have been obtained by increasing the gas mean free path through reducing the pressure and increasing the temperature. In the case of carbon nanotubes (CNTs) with nanoscale diameters, it is possible to filtrate in the FMF regime under normal conditions. This paper reviews recent progress in theoretical and experimental studies of air filtration in the FMF regime. Typical structure models of high-efficiency particulate (HEPA) air filters based on CNTs are introduced. The pressure drop in air filters operated in the FMF regime is less than that predicted by the conventional air filtration theory. The thinnest HEPA filters fabricated from single-walled CNT films have an extremely low pressure drop. CNT air filters with a gradient nanostructure are shown to give a much better filtration performance in dynamic filtration. CNT air filters with a hierarchical structure and an agglomerated CNT fluidized bed air filter are also introduced. Finally, the challenges and opportunities for the application of CNTs in air filtration are discussed. PMID:25288476

  12. Preliminary Results from IODP Expedition 307, Porcupine Basin Carbonate Mounds

    NASA Astrophysics Data System (ADS)

    Williams, T.; Kano, A.; Ferdelman, T.; Henriet, J.; Shipboard Scientific Party, I.

    2005-12-01

    IODP Expedition 307 (April 26 - May 16, 2005) drilled three sites at Challenger Mound in the Porcupine Seabight, west of Ireland. Deep-water carbonate mounds up to 2 km wide and 200 m high have been found in typical water depths of 500-1000 m along the continental slope of NW Europe from Morocco to Norway. During the last ten years they have been studied using seismics, shallow coring, high resolution bathymetry, and remotely operated vehicles. The partly-buried Challenger Mound is the first to be completely cored to the mound base, with the aim of answering basic questions such as: What is the sedimentology and structure of the mound? What triggered mound initiation? How does the ecosystem interact with sedimentary fluxes to make the mound grow? How are mound growth phases related to glacial-interglacial cycles? What role do microbial communities and geochemical reaction play in the mound? Analytical work is at an early stage, but already shipboard results reveal some of the mound's secrets. The mound body consists of a 155-m-thick sequence of cold-water coral-bearing Pleistocene sediments (floatstone, rudstone, and wackestone), characterized by 10-meter-scale alternation of light gray and dark green intervals. The carbonate-rich and light-colored layers are partially lithified and feature poor coral preservation or even dissolution. The mound base, virtually identical in the on-mound and off-mound holes, is a sharp Pliocene erosional unconformity, separating coral-bearing sediments from a glauconitic and partly sandy siltstone. No evidence was found for a relation between mound development and hydrocarbon seepage. The results from Challenger Mound will help provide a depositional model with which to interpret deep water carbonate mounds in the geological rock record, and we look forward to future drilling of contrasting carbonate mounds.

  13. Thermal regime and potential bedrock weathering in alpine rockwalls of Austria: Results from eight years of monitoring (2006-2014)

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas; Wecht, Matthias

    2015-04-01

    Bedrock temperature at sites with a minor winter snow cover gives a good indication for the effects of air temperature anomalies on ground thermal conditions as well as for the intensity of near-surface physical weathering in bedrock. In this study we present results from an ongoing bedrock temperature monitoring program initiated in 2006. Within the framework of this program nine surface boreholes in rockwalls with different slope orientations and two additional boreholes at flat bedrock sites were drilled between August and September 2006 and subsequently instrumented. The altogether eleven rock temperature sites (RTS) are located in the alpine periglacial zone of the Austrian Alps at latitude 46°55' to 47°22' and longitude 12°44' to 14°41'. All RTS have been installed in metamorphic rock (5 x mica schist; 6 x gneiss) at elevations between 1960 and 2725 m asl (mean 2491 m asl.). Three temperature sensors (PT1000) have been inserted at each borehole site at vertical depths of 3, 10 and 30-40 cm. At each RTS the three sensors are connected to a 3-channel miniature temperature datalogger (MTD) manufactured by GeoPrecision, Germany. Our analysis focussed on (a) the variation of mean and extreme daily temperatures at the rock surface and at depth, (b) the variation of the daily temperature range, (c) the number of freeze-thaw-cycles (FTC) and (d) effective freeze-thaw cycles for frost shattering (eFTC), (e) the duration and intensity of freeze-thaw-cycles (DI-FTC), (f) the number of hours and days within the so-called frost-cracking-window (FCW), and effects of (g) aspect and (h) snow cover on the thermal regimes in the bedrock. Results show for instance that the number of FTC and eFTC varied substantially during the observation period at all eleven RTS and at all sensor depths. However, this variation differs from site to site related to snow cover condition, elevation and aspect. For instance, at one lower-elevated (2255 m asl) north exposed RTS the number of

  14. Carbon Dioxide Sequestration by Direct Mineral Carbonation: Results from Recent Studies and Current Status

    SciTech Connect

    O'Connor, William K.; Dahlin, David C.; Nilsen, David N.; Rush, G.E.; Walters, Richard P.; Turner, Paul C.

    2001-01-01

    Direct mineral carbonation has been investigated as a process to convert gaseous CO2 into a geologically stable, solid final form. The process utilizes a solution of sodium bicarbonate (NaHCO3), sodium chloride (NaCl), and water, mixed with a mineral reactant, such as olivine (Mg2SiO4) or serpentine [Mg3Si2O5(OH)4]. Carbon dioxide is dissolved into this slurry, by diffusion through the surface and gas dispersion within the aqueous phase. The process includes dissolution of the mineral and precipitation of magnesium carbonate (MgCO3) in a single unit operation. Optimum results have been achieved using heat pretreated serpentine feed material, with a surface area of roughly 19 m2 per gram, and high partial pressure of CO2 (PCO2). Specific conditions include: 155?C; PCO2=185 atm; 15% solids. Under these conditions, 78% stoichiometric conversion of the silicate to the carbonate was achieved in 30 minutes. Studies suggest that the mineral dissolution rate is primarily surface controlled, while the carbonate precipitation rate is primarily dependent on the bicarbonate concentration of the slurry. Current studies include further examination of the reaction pathways, and an evaluation of the resource potential for the magnesium silicate reactant, particularly olivine. Additional studies include the examination of various pretreatment options, the development of a continuous flow reactor, and an evaluation of the economic feasibility of the process.

  15. Carbon dioxide fluxes from Tifway bermudagrass: early results

    NASA Astrophysics Data System (ADS)

    Cotten, David L.; Zhang, G.; Leclerc, M. Y.; Raymer, P.; Steketee, C. J.

    2016-06-01

    This paper reports for the first time preliminary data on carbon uptake of warm-season turfgrass at a well-managed sod farm in south central Georgia. It examines the changes in carbon uptake from one of the most widely used warm-season turfgrass cultivars in the world, Tifway Bermudagrass. It elucidates the role of canopy density and light avalaibility on the net carbon uptake using the eddy-covariance technique. Preliminary evidence suggests that turfgrass is effective at sequestering carbon dioxide during the summer months even when the canopy is being reestablished following a grass harvest.

  16. Variation of organic carbon and nitrate with river flow within an oceanic regime in a rural area and potential impacts for drinking water production

    NASA Astrophysics Data System (ADS)

    Baurès, E.; Delpla, I.; Merel, S.; Thomas, M.-F.; Jung, A.-V.; Thomas, O.

    2013-01-01

    SummaryOver the last two decades, climate change has become a major environmental and public health concern due to the increase of the mean temperature on the Earth and its consequences on extreme meteorological events such as floods and droughts. These events induce very low or very high river flows that may impair surface water quality, and therefore result in potential health impacts when used for drinking water production. The present study aims at assessing the impact of hydrologic regime on surface water quality with a particular emphasis on total organic carbon (TOC) and nitrate. Water quality data from three French rivers acquired over a 27 years period, from January 1983 to December 2009, show the influence of extreme flows. Variation in TOC and nitrate concentrations showed opposite patterns for the whole range of flow rate (from less than 10% up to more than 100% of the mean flow). Regarding fluxes, TOC increased continuously with flow rate while nitrate was stable for very high discharges. The C/N ratio expressed from TOC and nitrate concentrations showed high values for extreme flows and particularly for very low flow rates, generally in summer, where nitrate is assimilated by biomass. Considering TOC and nitrate fluxes, it is confirmed that the worst situations were encountered for very high flow rates, namely for TOC exportation during surface runoff which was related to heavy rains or floods. These findings are of great importance with regard to the adaptation for drinking water treatment in facing extreme hydrological conditions, of which the frequency is increasing with climate change.

  17. Collective electronic excitations in the ultra violet regime in 2-D and 1-D carbon nanostructures achieved by the addition of foreign atoms

    PubMed Central

    Bangert, U.; Pierce, W.; Boothroyd, C.; Pan, C.-T.; Gwilliam, R.

    2016-01-01

    Plasmons in the visible/UV energy regime have attracted great attention, especially in nano-materials, with regards to applications in opto-electronics and light harvesting; tailored enhancement of such plasmons is of particular interest for prospects in nano-plasmonics. This work demonstrates that it is possible, by adequate doping, to create excitations in the visible/UV regime in nano-carbon materials, i.e., carbon nanotubes and graphene, with choice of suitable ad-atoms and dopants, which are introduced directly into the lattice by low energy ion implantation or added via deposition by evaporation. Investigations as to whether these excitations are of collective nature, i.e., have plasmonic character, are carried out via DFT calculations and experiment-based extraction of the dielectric function. They give evidence of collective excitation behaviour for a number of the introduced impurity species, including K, Ag, B, N, and Pd. It is furthermore demonstrated that such excitations can be concentrated at nano-features, e.g., along nano-holes in graphene through metal atoms adhering to the edges of these holes. PMID:27271352

  18. Collective electronic excitations in the ultra violet regime in 2-D and 1-D carbon nanostructures achieved by the addition of foreign atoms

    NASA Astrophysics Data System (ADS)

    Bangert, U.; Pierce, W.; Boothroyd, C.; Pan, C.-T.; Gwilliam, R.

    2016-06-01

    Plasmons in the visible/UV energy regime have attracted great attention, especially in nano-materials, with regards to applications in opto-electronics and light harvesting; tailored enhancement of such plasmons is of particular interest for prospects in nano-plasmonics. This work demonstrates that it is possible, by adequate doping, to create excitations in the visible/UV regime in nano-carbon materials, i.e., carbon nanotubes and graphene, with choice of suitable ad-atoms and dopants, which are introduced directly into the lattice by low energy ion implantation or added via deposition by evaporation. Investigations as to whether these excitations are of collective nature, i.e., have plasmonic character, are carried out via DFT calculations and experiment-based extraction of the dielectric function. They give evidence of collective excitation behaviour for a number of the introduced impurity species, including K, Ag, B, N, and Pd. It is furthermore demonstrated that such excitations can be concentrated at nano-features, e.g., along nano-holes in graphene through metal atoms adhering to the edges of these holes.

  19. Carbon dynamics of forests in Washington, U.S.A.: 21st century projections based on climate-driven changes in fire regimes.

    PubMed

    Raymond, Crystal L; McKenzie, Donald

    2012-07-01

    During the 21st century, climate-driven changes in fire regimes will be a key agent of change in forests of the U.S. Pacific Northwest (PNW). Understanding the response of forest carbon (C) dynamics to increases in fire will help quantify limits on the contribution of forest C storage to climate change mitigation and prioritize forest types for monitoring C storage and fire management to minimize C loss. In this study, we used projections of 21st century area burned to explore the consequences of changes in fire regimes on C dynamics in forests of Washington State. We used a novel empirical approach that takes advantage of chronosequences of C pools and fluxes and statistical properties of fire regimes to explore the effects of shifting age class distributions on C dynamics. Forests of the western Cascades are projected to be more sensitive to climate-driven increases in fire, and thus projected changes in C dynamics, than forests of the eastern Cascades. In the western Cascades, mean live biomass C is projected to decrease by 24-37%, and coarse woody debris (CWD) biomass C by 15-25% for the 2040s. Loss of live biomass C is projected to be lower for forests of the eastern Cascades and Okanogan Highlands (17-26%), and CWD biomass is projected to increase. Landscape mean net primary productivity is projected to increase in wet low-elevation forests of the western Cascades, but decrease elsewhere. These forests, and moist forests of the Okanogan Highlands, are projected to have the greatest percentage increases in consumption of live biomass. Percentage increases in consumption of CWD biomass are greater than 50% for all regions and up to four times greater than increases in consumption of live biomass. Carbon sequestration in PNW forests will be highly sensitive to increases in fire, suggesting a cautious approach to managing these forests for C sequestration to mitigate anthropogenic CO2 emissions.

  20. Snowpack regimes of the Western United States

    NASA Astrophysics Data System (ADS)

    Trujillo, Ernesto; Molotch, Noah P.

    2014-07-01

    Snow accumulation and melt patterns play a significant role in the water, energy, carbon, and nutrient cycles in the montane environments of the Western United States. Recent studies have illustrated that changes in the snow/rainfall apportionments and snow accumulation and melt patterns may occur as a consequence of changes in climate in the region. In order to understand how these changes may affect the snow regimes of the region, the current characteristics of the snow accumulation and melt patterns must be identified. Here we characterize the snow water equivalent (SWE) curve formed by the daily SWE values at 766 snow pillow stations in the Western United States, focusing on several metrics of the yearly SWE curves and the relationships between the different metrics. The metrics are the initial snow accumulation and snow disappearance dates, the peak snow accumulation and date of peak, the length of the snow accumulation season, the length of the snowmelt season, and the snow accumulation and snowmelt slopes. Three snow regimes emerge from these results: a maritime, an intermountain, and a continental regime. The maritime regime is characterized by higher maximum snow accumulations reaching 300 cm and shorter accumulation periods of less than 220 days. Conversely, the continental regime is characterized by lower maximum accumulations below 200 cm and longer accumulation periods reaching over 260 days. The intermountain regime lies in between. The regions that show the characteristics of the maritime regime include the Cascade Mountains, the Klamath Mountains, and the Sierra Nevada Mountains. The intermountain regime includes the Eastern Cascades slopes and foothills, the Blue Mountains, Northern and Central basins and ranges, the Columbia Mountains/Northern Rockies, the Idaho Batholith, and the Canadian Rockies. Lastly, the continental regime includes the Middle and Southern Rockies, and the Wasatch and Uinta Mountains. The implications of snow regime

  1. Relationship between starch degradation and carbon demand for maintenance and growth in Arabidopsis thaliana in different irradiance and temperature regimes.

    PubMed

    Pilkington, Sarah M; Encke, Beatrice; Krohn, Nicole; Höhne, Melanie; Stitt, Mark; Pyl, Eva-Theresa

    2015-01-01

    Experiments were designed to compare the relationship between starch degradation and the use of carbon for maintenance and growth in Arabidopsis in source-limited and sink-limited conditions. It is known that starch degradation is regulated by the clock in source-limited plants, which degrade their starch in a linear manner such that it is almost but not completely exhausted at dawn. We asked whether this response is maintained under an extreme carbon deficit. Arabidopsis was subjected to a sudden combination of a day of low irradiance, to decrease starch at dusk, and a warm night. Starch was degraded in a linear manner through the night, even though the plants became acutely carbon starved. We conclude that starch degradation is not increased to meet demand in carbon-limited plants. This network property will allow stringent control of starch turnover in a fluctuating environment. In contrast, in sink-limited plants, which do not completely mobilize their starch during the night, starch degradation was accelerated in warm nights to meet the increased demand for maintenance and growth. Across all conditions, the rate of growth at night depends on the rate of starch degradation, whereas the rate of maintenance respiration decreases only when starch degradation is very slow.

  2. Carbon pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes.

    PubMed

    Brandstätter, Christian; Laner, David; Fellner, Johann

    2015-06-01

    Landfill aeration has been proven to accelerate the degradation of organic matter in landfills in comparison to anaerobic decomposition. The present study aims to evaluate pools of organic matter decomposing under aerobic and anaerobic conditions using landfill simulation reactors (LSR) filled with 40 year old waste from a former MSW landfill. The LSR were operated for 27 months, whereby the waste in one pair was kept under anaerobic conditions and the four other LSRs were aerated. Two of the aerated LSR were run with leachate recirculation and water addition and two without. The organic carbon in the solid waste was characterized at the beginning and at the end of the experiments and major carbon flows (e.g. TOC in leachate, gaseous CO2 and CH4) were monitored during operation. After the termination of the experiments, the waste from the anaerobic LSRs exhibited a long-term gas production potential of more than 20 NL kg(-1) dry waste, which corresponded to the mineralization of around 12% of the initial TOC (67 g kg(-1) dry waste). Compared to that, aeration led to threefold decrease in TOC (32-36% of the initial TOC were mineralized), without apparent differences in carbon discharge between the aerobic set ups with and without water addition. Based on the investigation of the carbon pools it could be demonstrated that a bit more than 10% of the initially present organic carbon was transformed into more recalcitrant forms, presumably due to the formation of humic substances. The source of anaerobic degradation could be identified mainly as cellulose which played a minor role during aerobic degradation in the experiment.

  3. Compilation of reinforced carbon-carbon transatlantic abort landing arc jet test results

    NASA Technical Reports Server (NTRS)

    Milhoan, James D.; Pham, Vuong T.; Yuen, Eric H.

    1993-01-01

    This document consists of the entire test database generated to support the Reinforced Carbon-Carbon Transatlantic Abort Landing Study. RCC components used for orbiter nose cap and wing leading edge thermal protection were originally designed to have a multi-mission entry capability of 2800 F. Increased orbiter range capability required a predicted increase in excess of 3300 F. Three test series were conducted. Test series #1 used ENKA-based RCC specimens coated with silicon carbide, treated with tetraethyl orthosilicate, sealed with Type A surface enhancement, and tested at 3000-3400 F with surface pressure of 60-101 psf. Series #2 used ENKA- or AVTEX-based RCC, with and without silicon carbide, Type A or double Type AA surface enhancement, all impregnated with TEOS, and at temperatures from 1440-3350 F with pressures from 100-350 psf. Series #3 tested ENKA-based RCC, with and without silicon carbide coating. No specimens were treated with TEOS or sealed with Type A. Surface temperatures ranged from 2690-3440 F and pressures ranged from 313-400 psf. These combined test results provided the database for establishing RCC material single-mission-limit temperature and developing surface recession correlations used to predict mass loss for abort conditions.

  4. Hydrogen storage in carbon materials—preliminary results

    NASA Astrophysics Data System (ADS)

    Jörissen, Ludwig; Klos, Holger; Lamp, Peter; Reichenauer, Gudrun; Trapp, Victor

    1998-08-01

    Recent developments aiming at the accelerated commercialization of fuel cells for automotive applications have triggered an intensive research on fuel storage concepts for fuel cell cars. The fuel cell technology currently lacks technically and economically viable hydrogen storage technologies. On-board reforming of gasoline or methanol into hydrogen can only be regarded as an intermediate solution due to the inherently poor energy efficiency of such processes. Hydrogen storage in carbon nanofibers may lead to an efficient solution to the above described problems.

  5. Regime change?

    SciTech Connect

    Pilat, Joseph F.; Budlong-Sylvester, K. W.

    2004-01-01

    Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?

  6. Compressible magnetic Rayleigh-Taylor instability in stratified plasmas: Comparison of analytical and numerical results in the linear regime

    SciTech Connect

    Liberatore, S.; Jaouen, S.; Tabakhoff, E.; Canaud, B.

    2009-04-15

    Magnetic Rayleigh-Taylor instability is addressed in compressible hydrostatic media. A full model is presented and compared to numerical results from a linear perturbation code. A perfect agreement between both approaches is obtained in a wide range of parameters. Compressibility effects are examined and substantial deviations from classical Chandrasekhar growth rates are obtained and confirmed by the model and the numerical calculations.

  7. Brown Carbon: Results From Ground and Airborne Studies

    NASA Astrophysics Data System (ADS)

    Weber, R. J.; Forrister, H.; Liu, J.; Nenes, A.

    2015-12-01

    Brown carbon (BrC) is directly measured with high sensitivity by isolating it from black carbon in aerosol extracts and using long path wave-guide spectrophotometry. Ambient measurements by this approach show that BrC is pervasive and can be found in almost all locations, ranging from urban environments to remote continental sites and upper reaches of the free troposphere. Biomass burning appears to be the major source in many urban and rural locations, but other sources of incomplete combustion, such as vehicle emissions in urban environments also play a role. Secondary aerosols not associated with combustion sources may also contribute, but are likely of lesser importance. Studies of ambient wildfire smoke plumes show that BrC levels decrease as it ages, with a half-life of approximately 10 hours. However, a small fraction of the emitted BrC is stable and may account for much of the BrC observed throughout the atmosphere due to widely dispersed and ubiquitous smoke. A radiative transfer model indicates that this background BrC reduced US continental TOA forcing by 20 percent. Human health studies point to similar chemical components linked to BrC (i.e., HULIS), of this same ubiquitous smoke, as a significant source of adverse cardiorespiratory effects. This talk will summarize findings on BrC sources, transformations and estimates of environmental effects based on bulk measurements.

  8. Results of the "carbon conference" international aerosol carbon round robin test stage I

    NASA Astrophysics Data System (ADS)

    Schmid, Heidrun; Laskus, Lothar; Jürgen Abraham, Hans; Baltensperger, Urs; Lavanchy, Vincent; Bizjak, Mirko; Burba, Peter; Cachier, Helene; Crow, Dale; Chow, Judith; Gnauk, Thomas; Even, Arja; ten Brink, H. M.; Giesen, Klaus-Peter; Hitzenberger, Regina; Hueglin, Christoph; Maenhaut, Willy; Pio, Casimiro; Carvalho, Abel; Putaud, Jean-Philippe; Toom-Sauntry, Desiree; Puxbaum, Hans

    An international round robin test on the analysis of carbonaceous aerosols on quartz fiber filters sampled at an urban site was organized by the Vienna University of Technology. Seventeen laboratories participated using nine different thermal and optical methods. For the analysis of total carbon (TC), a good agreement of the values obtained by all laboratories was found (7 and 9% r.s.d.) with only two outliers in the complete data set. In contrast the results of the determination of elemental carbon (EC) in two not pre-extracted samples were highly variable ranging over more than one order of magnitude and the relative standard deviations (r.s.d.) of the means were 36.6 and 45.5%. The laboratories that obtained similar results by using methods which reduce the charring artifact were put together to a new data set in order to approach a "real EC" value. The new data set consisting of the results of 10 laboratories using seven different methods showed 16 and 24% lower averages and r.s.d. of 14 and 24% for the two not pre-extracted samples. Taking the current filters as "equivalents" for urban aerosol samples we conclude that the following methods can be used for the analysis of EC in carbonaceous aerosols: thermal methods with an optical feature to correct for charring during pyrolysis, two-step thermal procedures reducing charring during pyrolysis, the VDI 2465/1 method (removal of OC by solvent extraction and thermodesorption in nitrogen) and the VDI 2465/2 method (combustion of OC and EC at different temperatures) with an additional pre-extraction with a dimethyl formamide (DMF)/toluene mixture. Only thermal methods without any correction for charring during pyrolysis and the VDI 2465/2 method were outside the range of twice the standard deviation of the new data set. For a filter sample pre-extracted with the DMF/toluene mixture the average and r.s.d. from all laboratories (20.7 μgC; 24.4% r.s.d.) was very similar as for the laboratory set reduced to 10

  9. Self-aligned T-gate high-purity semiconducting carbon nanotube RF transistors operated in quasi-ballistic transport and quantum capacitance regime.

    PubMed

    Che, Yuchi; Badmaev, Alexander; Jooyaie, Alborz; Wu, Tao; Zhang, Jialu; Wang, Chuan; Galatsis, Kosmas; Enaya, Hani A; Zhou, Chongwu

    2012-08-28

    Carbon nanotube RF transistors are predicted to offer good performance and high linearity when operated in the ballistic transport and quantum capacitance regime; however, realization of such transistors has been very challenging. In this paper, we introduce a self-aligned fabrication method for carbon nanotube RF transistors, which incorporate a T-shaped (mushroom-shaped) aluminum gate, with oxidized aluminum as the gate dielectric. In this way, the channel length can be scaled down to 140 nm, which enables quasi-ballistic transport, and the gate dielectric is reduced to 2-3 nm aluminum oxide, leading to quasi-quantum capacitance operation. A current-gain cutoff frequency (f(t)) up to 23 GHz and a maximum oscillation frequency (f(max)) of 10 GHz are demonstrated. Furthermore, the linearity properties of nanotube transistors are characterized by using the 1 dB compression point measurement with positive power gain for the first time, to our knowledge. Our work reveals the importance and potential of separated semiconducting nanotubes for various RF applications.

  10. Free-carrier generation in aggregates of single-wall carbon nanotubes by photoexcitation in the ultraviolet regime.

    PubMed

    Crochet, Jared J; Hoseinkhani, Sajjad; Lüer, Larry; Hertel, Tobias; Doorn, Stephen K; Lanzani, Guglielmo

    2011-12-16

    We present evidence for the generation of free carriers in aggregated single-wall carbon nanotubes by photoexcitation in the energetic range of the π→π(*) transition associated with the M saddle point of the graphene lattice. The underlying broad absorption culminating at 4.3 eV can be fit well with a Fano line shape that describes strong coupling of a saddle-point exciton to an underlying free electron-hole pair continuum. Moreover, it is demonstrated that transitions in this energetic region autoionize into the continuum by detecting features unique to the presence of free charges in the transient transmission spectra of the continuum-embedded second sub-band exciton, S(2).

  11. 78 FR 21107 - Circular Welded Carbon Steel Pipes and Tubes from Turkey: Preliminary Results of Countervailing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-09

    ... International Trade Administration Circular Welded Carbon Steel Pipes and Tubes from Turkey: Preliminary Results... carbon steel pipes and tubes from Turkey (pipes and tubes from Turkey) for the period of review (POR) of... welded carbon steel pipe and tube with an outside diameter of 0.375 inch or more, but not over 16...

  12. Increase of Carbon Cycle Feedback with Climate Sensitivity: Results from a coupled Climate and Carbon Cycle Model

    SciTech Connect

    Govindasamy, B; Thompson, S; Mirin, A; Wickett, M; Caldeira, K; Delire, C

    2004-04-01

    Coupled climate and carbon cycle modeling studies have shown that the feedback between global warming and the carbon cycle, in particular the terrestrial carbon cycle, could accelerate climate change and result in larger warming. In this paper, we investigate the sensitivity of this feedback for year-2100 global warming in the range of 0 K to 8 K. Differing climate sensitivities to increased CO{sub 2} content are imposed on the carbon cycle models for the same emissions. Emissions from the SRES A2 scenario are used. We use a fully-coupled climate and carbon cycle model, the INtegrated Climate and CArbon model (INCCA) the NCAR/DOE Parallel Coupled Model coupled to the IBIS terrestrial biosphere model and a modified-OCMIP ocean biogeochemistry model. In our model, for scenarios with year-2100 global warming increasing from 0 to 8 K, land uptake decreases from 47% to 29% of total CO{sub 2} emissions. Due to competing effects, ocean uptake (16%) shows almost no change at all. Atmospheric CO{sub 2} concentration increases were 48% higher in the run with 8 K global climate warming than in the case with no warming. Our results indicate that carbon cycle amplification of climate warming will be greater if there is higher climate sensitivity to increased atmospheric CO{sub 2} content; the carbon cycle feedback factor increases from 1.13 to 1.48 when global warming increases from 3.2 to 8 K.

  13. National assessment of geologic carbon dioxide storage resources: results

    USGS Publications Warehouse

    ,

    2013-01-01

    In 2012, the U.S. Geological Survey (USGS) completed an assessment of the technically accessible storage resources (TASR) for carbon dioxide (CO2) in geologic formations underlying the onshore and State waters area of the United States. The formations assessed are at least 3,000 feet (914 meters) below the ground surface. The TASR is an estimate of the CO2 storage resource that may be available for CO2 injection and storage that is based on present-day geologic and hydrologic knowledge of the subsurface and current engineering practices. Individual storage assessment units (SAUs) for 36 basins were defined on the basis of geologic and hydrologic characteristics outlined in the assessment methodology of Brennan and others (2010, USGS Open-File Report 2010–1127) and the subsequent methodology modification and implementation documentation of Blondes, Brennan, and others (2013, USGS Open-File Report 2013–1055). The mean national TASR is approximately 3,000 metric gigatons (Gt). The estimate of the TASR includes buoyant trapping storage resources (BSR), where CO2 can be trapped in structural or stratigraphic closures, and residual trapping storage resources, where CO2 can be held in place by capillary pore pressures in areas outside of buoyant traps. The mean total national BSR is 44 Gt. The residual storage resource consists of three injectivity classes based on reservoir permeability: residual trapping class 1 storage resource (R1SR) represents storage in rocks with permeability greater than 1 darcy (D); residual trapping class 2 storage resource (R2SR) represents storage in rocks with moderate permeability, defined as permeability between 1 millidarcy (mD) and 1 D; and residual trapping class 3 storage resource (R3SR) represents storage in rocks with low permeability, defined as permeability less than 1 mD. The mean national storage resources for rocks in residual trapping classes 1, 2, and 3 are 140 Gt, 2,700 Gt, and 130 Gt, respectively. The known recovery

  14. Snowpack Regimes of the Western United States

    NASA Astrophysics Data System (ADS)

    Trujillo, E.; Molotch, N. P.

    2011-12-01

    Snow accumulation and melt patterns play a significant role in the water, energy, carbon and nutrient cycles in the montane environments of the Western United States. Recent studies have illustrated that changes in the snow/rainfall apportionments, and snow accumulation and melt patterns may occur as a consequence of changes in climate in the region. In order to understand how these changes may affect the snow regimes of the region, the current characteristics of the snow accumulation and melt patterns must be identified. Here, we characterize the snow water equivalent (SWE) curve formed by the daily SWE values at over seven hundred snow pillow stations in the Western U.S., focusing on several metrics of the yearly SWE curves and the cross relationships between the different metrics. The metrics include the initial snow accumulation and meltout dates, the peak accumulation and date of peak, the time from initial accumulation to peak, the time from peak to meltout, the accumulation and melt slopes, and the daily rates of accumulation and melt. Three distinct regimes emerge from these results: a maritime, an intermediate (intercontinental), and a continental regime. The maritime regime is characterized by higher maximum snow accumulations reaching 300 cm and shorter accumulation periods of less than 220 days, while on the other hand; the continental regime is characterized by lower maximum accumulations below 200 cm and longer accumulation periods reaching over 260 days. The intercontinental regime lies in between. Several other differences are identified between the metrics of the SWE curve in these regimes. The regions that show the characteristics of the maritime regime include the Cascade Mountains, the Klamath Mountains, and the Sierra Nevada Mountains. The intercontinental regime includes the Northern and Central basins and ranges, the Idaho Batholith, the Northern Rockies and the Blue Mountains. Lastly, the Continental regime includes the Middle and Southern

  15. Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an atmosphere-ocean general circulation model

    SciTech Connect

    Thornton, Peter E; Doney, Scott C.; Lindsay, Keith; Moore, Jefferson Keith; Mahowald, Natalie; Randerson, James T; Fung, Inez; Lamarque, Jean-Francois H; Feddema, Johan J.

    2009-01-01

    Inclusion of fundamental ecological interactions between carbon and nitrogen cycles in the land component of an atmosphere-ocean general circulation model (AOGCM) leads to decreased carbon uptake associated with CO{sub 2} fertilization, and increased carbon uptake associated with warming of the climate system. The balance of these two opposing effects is to reduce the fraction of anthropogenic CO{sub 2} predicted to be sequestered in land ecosystems. The primary mechanism responsible for increased land carbon storage under radiatively forced climate change is shown to be fertilization of plant growth by increased mineralization of nitrogen directly associated with increased decomposition of soil organic matter under a warming climate, which in this particular model results in a negative gain for the climate-carbon feedback. Estimates for the land and ocean sink fractions of recent anthropogenic emissions are individually within the range of observational estimates, but the combined land plus ocean sink fractions produce an airborne fraction which is too high compared to observations. This bias is likely due in part to an underestimation of the ocean sink fraction. Our results show a significant growth in the airborne fraction of anthropogenic CO{sub 2} emissions over the coming century, attributable in part to a steady decline in the ocean sink fraction. Comparison to experimental studies on the fate of radio-labeled nitrogen tracers in temperate forests indicates that the model representation of competition between plants and microbes for new mineral nitrogen resources is reasonable. Our results suggest a weaker dependence of net land carbon flux on soil moisture changes in tropical regions, and a stronger positive growth response to warming in those regions, than predicted by a similar AOGCM implemented without land carbon-nitrogen interactions. We expect that the between-model uncertainty in predictions of future atmospheric CO{sub 2} concentration and

  16. An Integrated Spatially Dynamic Disturbance and Forest Soil Carbon Model: Preliminary Results from Willow Creek Experimental Forest

    NASA Astrophysics Data System (ADS)

    Scheller, R. M.; Hua, D.; Bolstad, P. V.

    2008-12-01

    Total forest carbon (C) storage is determined by forest succession, multiple interacting disturbances, climate and the edaphic properties of a site or region, including soil texture and depth. How these complex processes interact will determine forest carbon dynamics at landscape and regional scales. We have developed a new succession extension for the LANDIS-II forest landscape simulation model that incorporates the belowground soil C dynamics of the Century soil model. This extension simulates three primary soil organic matter (SOM) pools (fast, slow, passive), litter dynamics, and nitrogen (N) feedbacks to overstory production. The extension was validated against data from the Willow Creek experimental forest in Wisconsin, USA. We subsequently initialized the full model to simulate forest dynamics of 10,000 ha of the surrounding forest landscape. We simulated a representative harvest regime and a historic wind throw regime (50 year wind rotation period, including light, moderate, and extreme events), two common disturbances in mesic forests of the Lake States. We also simulated forest change and total C storage assuming no atmospheric N deposition and N deposition equivalent to 2008 rates. Our results indicate a strong feedback from harvesting to litter C and the fast and slow SOM pools. The passive SOM pool was not significantly altered. Wind disturbance had a negligible effect on all pools. Simulations without N deposition significantly underestimated contemporary forest productivity and the system was more sensitive to disturbances when N deposition was excluded. In conclusion, we have developed a robust model of above and belowground C and N cycling that can readily plug into an existing forest modeling framework to simulate landscape and regional scale forest dynamics and the interactions among forest disturbances, climate change, and soil processes.

  17. On the heat capacity of elements in WMD regime

    NASA Astrophysics Data System (ADS)

    Hamel, Sebatien

    2014-03-01

    Once thought to get simpler with increasing pressure, elemental systems have been discovered to exhibit complex structures and multiple phases at high pressure. For carbon, QMD/PIMC simulations have been performed and the results are guiding alternative modelling methodologies for constructing a carbon equation-of-state covering the warm dense matter regime. One of the main results of our new QMD/PIMC carbon equation of state is that the decay of the ion-thermal specific heat with temperature is much faster than previously expected. An important question is whether this is only found in carbon and not other element. In this presentation, based on QMD calculations for several elements, we explore trends in the transition from condensed matter to warm dense matter regime.

  18. Carbon fluxes resulting from land-use changes in the Tamaulipan thornscrub of northeastern Mexico

    PubMed Central

    Návar-Chaidez, Jose de Jesus

    2008-01-01

    Information on carbon stock and flux resulting from land-use changes in subtropical, semi-arid ecosystems are important to understand global carbon flux, yet little data is available. In the Tamaulipan thornscrub forests of northeastern Mexico, biomass components of standing vegetation were estimated from 56 quadrats (200 m2 each). Regional land-use changes and present forest cover, as well as estimates of soil organic carbon from chronosequences, were used to predict carbon stocks and fluxes in this ecosystem. For the period of 1980–1996, the Tamaulipan thornscrub is presenting an annual deforestation rate of 2.27% indicating that approximately 600 km2 of this plant community are lost every year and that 60% of the original Mexican Tamaulipan thornscrub vegetation has been lost since the 1950's. On the other hand, intensive agriculture, including introduced grasslands increased (4,000 km2) from 32 to 42% of the total studied area, largely at the expense of the Tamaulipan thornscrub forests. Land-use changes from Tamaulipan thornscrub forest to agriculture contribute 2.2 Tg to current annual carbon emissions and standing biomass averages 0.24 ± 0.06 Tg, root biomass averages 0.17 ± 0.03 Tg, and soil organic carbon averages 1.80 ± 0.27 Tg. Land-use changes from 1950 to 2000 accounted for Carbon emissions of the order of 180.1 Tg. Projected land-use changes will likely contribute to an additional carbon flux of 98.0 Tg by the year 2100. Practices to conserve sequester, and transfer carbon stocks in semi-arid ecosystems are discussed as a means to reduce carbon flux from deforestation practices. PMID:18826617

  19. Targeting carbonic anhydrase to treat diabetic retinopathy: Emerging evidences and encouraging results

    SciTech Connect

    Weiwei, Zhang; Hu, Renming

    2009-12-18

    Diabetic retinopathy (DR) is the leading cause of vision loss among working-age populations in developed countries. Current treatment options are limited to tight glycemic, blood pressure control and destructive laser surgery. Carbonic anhydrases (CAs) are a group of enzymes involving in the rapid conversion of carbon dioxide to bicarbonate and protons. Emerging evidences reveal CA inhibitors hold the promise for the treatment of DR. This article summarizes encouraging results from clinical and animal studies, and reviews the possible mechanisms.

  20. [Carbon-fiber implants for knee ligament reconstruction. 10-year results].

    PubMed

    Hehl, G; Kinzl, L; Reichel, R

    1997-11-01

    The retrospective results of carbon prostheses for knee ligament reconstruction in 120 patients, as established by questionnaire, are reported at 10 +/- 2 years follow-up. Eighty patients could also be reviewed clinically. Some 60% of the patients showed good subjective function at reduced activity level. Complications were seen in 72.5% of the patients with rupture of the carbon prosthesis and in 68% of those with synovitis. X-ray showed osteoarthritis in up to 59% of the patients. Carbon prostheses for collateral ligament reconstruction (85% medial, 5.8% lateral) were successful in 75% of cases. Activity and time seem to be less responsible for failure of the carbon prostheses than the features of growing in. Destruction of the knee joint over time is due to reactive synovitis and catabolic enzyme reaction and correlates with joint effusion and pain. If these problems appear, (arthroscopic) resection of the synovia is indicated to interrupt the circulus vitiosus.

  1. The carbonate ion in hydroxyapatite: recent X-ray and infrared results.

    PubMed

    Fleet, Michael E

    2013-01-01

    The location and orientation of the carbonate ion in the channel (A) and phosphate (B) positions of hydroxyapatite (CHAP) have been investigated by single-crystal X-ray structure and Fourier transform infrared (FTIR) spectroscopy, using crystals synthesized at high pressure. The type A carbonate ion is oriented in the apatite channel with two oxygen atoms close to the c-axis and the B carbonate ion is located near a sloping face of the substituted phosphate tetrahedron. Close comparison of FTIR and X-ray structure results shows that a Na-bearing CHAP containing approximately equal amounts of A and B carbonate ions is a realistic model for the overall crystal structure of biological apatite. However, the absence of distinct OH stretch and OH libration bands indicates that the hydroxyl content of biological apatite is disordered in respect to its orientation and precise location both in the channel and elsewhere in the structure.

  2. Evaluating Carbon Sequestration and Solar Forcing Feedbacks Resulting from North American Afforestation

    NASA Astrophysics Data System (ADS)

    Mykleby, P.; Snyder, P. K.; Twine, T. E.

    2013-12-01

    The planting of trees and forests has long been accepted as a practical and efficient method to sequester carbon dioxide from the atmosphere. Assertive measures are now needed to ensure that atmospheric levels of carbon dioxide (CO2) do not continue to rise and cause additional planetary warming. However, recent studies have detected inadvertent biophysical feedbacks associated with land cover changes, especially in higher northern latitudes. The changes in surface reflectivity that occur when converting a lighter, more reflective surface, such as a grassland or bare soil, into a darker conifer forest, can result in surface warming due to the forest absorbing more shortwave radiation. This warming counteracts the cooling effect resulting from a reduction in atmospheric CO2 with increased vegetation productivity. This effect is further intensified in the higher northern latitudes where snow cover is prevalent during the long winter; the planting of trees can significantly decrease the reflectivity compared with white snow. The goal of this study is to determine whether the amount of carbon sequestered exceeds the carbon equivalent of the radiative forcing due to the change in surface reflectivity. This study uses the IBIS dynamic vegetation model with modified carbon dynamics for conifer forests validated with numerous Ameriflux and Fluxnet Canada field sites with varying stand ages and species compositions. We present results of model performance based on validation of net ecosystem exchange (NEE) and net radiation observations. Results from this study will be used to assess not only the net effect of conifer forest establishment on the long term carbon storage, but also the duration of time that a given location would remain a carbon sink during the lifetime of the forest. Only then, can policymakers begin to discuss the efficacy of afforestation as a sound climate mitigation strategy.

  3. REgional Carbon Cycle Assessment and Processes: Results and Data Legacy (Invited)

    NASA Astrophysics Data System (ADS)

    Canadell, J.; Ciais, P.

    2013-12-01

    The Global Carbon Project with the involvement of over 150 contributing scientists has finalized the largest and most comprehensive assessment of regional carbon budgets, land and oceans, ever undertaken: the REgional Carbon Cycle Assessment and Processes (RECCAP; http:// www.globalcarbonproject.org/reccap). The objective of RECCAP was to establish the mean carbon balance of 10 land regions (Africa, the Arctic tundra, Australia, Europe, Russia, East Asia, South Asia, Southeast Asia, Central and South America, and North America) and 4 major ocean basins (Atlantic and Arctic, Indian, Pacific, and Southern oceans) for the period 1990-2009. The fundamental tenet of RECCAP was to establish carbon budgets in each region by comparing and reconciling multiple bottom-up flux estimates with top-down estimates. Bottom-up flux approaches include estimates from ensembles of process-based land and ocean models, surface partial pressure of CO2 (pCO2), forest inventories, eddy covariance measurements, fire modeling, riverine export, and wood harvest among others, while top-down estimates relied on model ensembles of atmospheric CO2 and CH4 inversions. In this talk we'll present an overview of results of the various regions, compare with the independently developed global carbon budget, and emphasize major regional differences and data gaps. An important legacy of RECCAP are a number of updated and new databases including an ensemble of 9 Global Dynamic Vegetation Models (TRENDY), 4 Ocean biogeochemical models, and 10 atmospheric CO2 inversions for the period 1990-2009.

  4. The effects of a variable temperature regime on the physiology of the reef-building coral Seriatopora hystrix: results from a laboratory-based reciprocal transplant.

    PubMed

    Mayfield, Anderson B; Chan, Pei-Hsun; Putnam, Hollie M; Chen, Chii-Shiarng; Fan, Tung-Yung

    2012-12-01

    To understand the effects of global climate change on reef-building corals, a thorough investigation of their physiological mechanisms of acclimatization is warranted. However, static temperature manipulations may underestimate the thermal complexity of the reefs in which many corals live. For instance, corals of Houbihu, Taiwan, experience changes in temperature of up to 10°C over the course of a day during spring-tide upwelling events. To better understand the phenotypic plasticity of these corals, a laboratory-based experiment was conducted whereby specimens of Seriatopora hystrix from an upwelling reef (Houbihu) and conspecifics from a non-upwelling reef (Houwan) were exposed to both a stable seawater temperature (26°C) regime and a regime characterized by a 6°C fluctuation (23-29°C) over a 12 h period for 7 days. A suite of physiological and molecular parameters was measured in samples of both treatments, as well as in experimental controls, to determine site of origin (SO) and temperature treatment (TT) responses. Only chlorophyll a (chl a) concentration and growth demonstrated the hypothesized trend of higher levels when exposed to a TT that mimicked SO conditions. In contrast, chl a, maximum dark-adapted quantum yield of photosystem II (F(v)/F(m)), and Symbiodinium ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL), photosystem I (psI, subunit III) and phosphoglycolate phosphatase (pgpase) mRNA expression demonstrated significant TT effects. Specifically, levels of these response variables were higher in samples exposed to a variable temperature regime, suggesting that S. hystrix may acclimate to fluctuating temperatures by increasing its capacity for photosynthesis.

  5. Monitoring changes in soil carbon resulting from intensive production, a non-traditional agricultural methodology.

    SciTech Connect

    Dwyer, Brian P.

    2013-03-01

    New Mexico State University and a group of New Mexico farmers are evaluating an innovative agricultural technique they call Intensive Production (IP). In contrast to conventional agricultural practice, IP uses intercropping, green fallowing, application of soil amendments and soil microbial inocula to sequester carbon as plant biomass, resulting in improved soil quality. Sandia National Laboratories role was to identify a non-invasive, cost effective technology to monitor soil carbon changes. A technological review indicated that Laser Induced Breakdown Spectroscopy (LIBS) best met the farmers objectives. Sandia partnered with Los Alamos National Laboratory (LANL) to analyze farmers test plots using a portable LIBS developed at LANL. Real-time LIBS field sample analysis was conducted and grab samples were collected for laboratory comparison. The field and laboratory results correlated well implying the strong potential for LIBS as an economical field scale analytical tool for analysis of elements such as carbon, nitrogen, and phosphate.

  6. 75 FR 44766 - Certain Welded Carbon Steel Standard Pipe from Turkey: Final Results of Countervailing Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-29

    ...: Preliminary Results of Countervailing Duty Administrative Review, 75 FR 16439 (April 1, 2010) (Preliminary... Countervailing Duty Administrative Review, In Part, 74 FR 47921(September 18, 2009). This administrative review...: Certain Welded Carbon Steel Pipe and Tube Products From Turkey, 51 FR 7984 (March 7, 1986). On April...

  7. 78 FR 21105 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Preliminary Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-09

    ..., available in Antidumping Duty Order: Circular Welded Carbon Steel Pipes and Tubes from Thailand, 51 FR 8341... Duty Administrative Review, 75 FR 26922, 26923 (May 13, 2010), unchanged in Magnesium Metal From the Russian Federation: Final Results of Antidumping Duty Administrative Review, 75 FR 56989 (September...

  8. Carbon sequestration via reaction with basaltic rocks: geochemical modeling and experimental results

    USGS Publications Warehouse

    Rosenbauer, Robert J.; Thomas, Burt; Bischoff, James L.; Palandri, James

    2012-01-01

    Basaltic rocks are potential repositories for sequestering carbon dioxide (CO2) because of their capacity for trapping CO2 in carbonate minerals. We carried out a series of thermodynamic equilibrium models and high pressure experiments, reacting basalt with CO2-charged fluids over a range of conditions from 50 to 200 °C at 300 bar. Results indicate basalt has a high reactivity to CO2 acidified brine. Carbon dioxide is taken up from solution at all temperatures from 50 to 200 °C, 300 bar, but the maximum extent and rate of reaction occurs at 100 °C, 300 bar. Reaction path simulations utilizing the geochemical modeling program CHILLER predicted an equilibrium carbonate alteration assemblage of calcite, magnesite, and siderite, but the only secondary carbonate identified in the experiments was a ferroan magnesite. The amount of uptake at 100 °C, 300 bar ranged from 8% by weight for a typical tholeite to 26% for a picrite. The actual amount of CO2 uptake and extent of rock alteration coincides directly with the magnesium content of the rock suggesting that overall reaction extent is controlled by bulk basalt Mg content. In terms of sequestering CO2, an average basaltic MgO content of 8% is equivalent to 2.6 × 108 metric ton CO2/km3 basalt.

  9. Reconstruction of the anterior cruciate ligament with carbon fibres: unsatisfactory results after 8 years.

    PubMed

    Mäkisalo, S E; Visuri, T; Viljanen, A; Jokio, P

    1996-01-01

    A total of 37 patients were operated on for anterior cruciate ligament (ACL) insufficiency between 1980 and 1989 using two types of carbon fibre ligament substitutes. The average age of the population was 23.6 years. The carbon fibre prostheses were covered with either a strip of medial joint capsule or lyophilized dura. Follow-up averaged 8.1 years (range 4-13 years), most of the operations being done from 1983 to 1985. Evaluation included a questionnaire, physical examination, Lysholm scoring, radiographs and cruciometer testing. The operated ACLs were looser than those in the contralateral healthy knees. The Lysholm scoring system gave acceptable results (excellent and good) in 43.5%, fair in 31.4% and poor in 24.1% of cases. Acceptable results provided better stability and muscle strength. During the follow-up there was an evident deterioration in stability as well as in Lysholm score. The results between the two types of ligaments did not become statistically different. Osteoarthrosis increased in all the knees examined radiographically (28/37). The results indicate that the ACL reconstructions using these types of carbon fibre prostheses lead to unacceptable results in the long-term follow-up.

  10. Redox freezing and melting in the Earth's deep mantle resulting from carbon-iron redox coupling.

    PubMed

    Rohrbach, Arno; Schmidt, Max W

    2011-04-14

    Very low seismic velocity anomalies in the Earth's mantle may reflect small amounts of melt present in the peridotite matrix, and the onset of melting in the Earth's upper mantle is likely to be triggered by the presence of small amounts of carbonate. Such carbonates stem from subducted oceanic lithosphere in part buried to depths below the 660-kilometre discontinuity and remixed into the mantle. Here we demonstrate that carbonate-induced melting may occur in deeply subducted lithosphere at near-adiabatic temperatures in the Earth's transition zone and lower mantle. We show experimentally that these carbonatite melts are unstable when infiltrating ambient mantle and are reduced to immobile diamond when recycled at depths greater than ∼250 kilometres, where mantle redox conditions are determined by the presence of an (Fe,Ni) metal phase. This 'redox freezing' process leads to diamond-enriched mantle domains in which the Fe(0), resulting from Fe(2+) disproportionation in perovskites and garnet, is consumed but the Fe(3+) preserved. When such carbon-enriched mantle heterogeneities become part of the upwelling mantle, diamond will inevitably react with the Fe(3+) leading to true carbonatite redox melting at ∼660 and ∼250 kilometres depth to form deep-seated melts in the Earth's mantle. PMID:21441908

  11. Physiological changes of the lichen Parmotrema tinctorum as result of carbon nanotubes exposition.

    PubMed

    Viana, Camila de O; Vaz, Raissa P; Cano, Abraham; Santos, Adelina P; Cançado, Luiz G; Ladeira, Luiz O; Junior, Ary Corrêa

    2015-10-01

    Carbon nanotubes (CNT) is one of the more abundant nanomaterial produced in the world. Therefore, it is desirable to access its effects in all environment compartments, in order to mitigate environmental distress. This study aims to verify the potential use of lichens - classical atmospheric pollution indicators - as biomonitors of carbon nanotubes aerosols. To examine cause-effect relationships, preserving environmental microclimatic parameters, the lichen Parmotrema tinctorum (Nyl.) Hale was transplanted to open top chambers where aerosols of CNT were daily added. Physiological parameters such as cell viability, photosynthetic efficiency, cell permeability as well as nanoparticle internalization were assessed. Carbon nanotubes exposure led to reduction on the cell viability of P. tinctorum. The treatment with 100µg/mL of MWCNT-COOH resulted in intracellular ion leakage, probably due to changes in membrane permeability. No alterations on photosynthetic efficiency were detected. Carbon nanotubes entrapment and internalization into the lichen thallus were observed. Short term exposition of CNT produced measurable physiological changes in P. tinctorum lichen. This suggests the possibility of use of lichens as models to assess the environmental impact (air related) of engineered nanomaterials.

  12. Redox freezing and melting in the Earth's deep mantle resulting from carbon-iron redox coupling.

    PubMed

    Rohrbach, Arno; Schmidt, Max W

    2011-04-14

    Very low seismic velocity anomalies in the Earth's mantle may reflect small amounts of melt present in the peridotite matrix, and the onset of melting in the Earth's upper mantle is likely to be triggered by the presence of small amounts of carbonate. Such carbonates stem from subducted oceanic lithosphere in part buried to depths below the 660-kilometre discontinuity and remixed into the mantle. Here we demonstrate that carbonate-induced melting may occur in deeply subducted lithosphere at near-adiabatic temperatures in the Earth's transition zone and lower mantle. We show experimentally that these carbonatite melts are unstable when infiltrating ambient mantle and are reduced to immobile diamond when recycled at depths greater than ∼250 kilometres, where mantle redox conditions are determined by the presence of an (Fe,Ni) metal phase. This 'redox freezing' process leads to diamond-enriched mantle domains in which the Fe(0), resulting from Fe(2+) disproportionation in perovskites and garnet, is consumed but the Fe(3+) preserved. When such carbon-enriched mantle heterogeneities become part of the upwelling mantle, diamond will inevitably react with the Fe(3+) leading to true carbonatite redox melting at ∼660 and ∼250 kilometres depth to form deep-seated melts in the Earth's mantle.

  13. Basal insulin regime change from Lantus to Toujeo resulted in fewer hypoglycaemic episodes in a 28-year-old man with diabetes mellitus.

    PubMed

    Shields, Alexandra; Sankaranarayanan, Sailesh

    2016-01-01

    An active 28-year-old man with type 1 diabetes mellitus reported a reduced number of hypoglycaemic episodes following change in basal regime insulin glargine from U100 Lantus to U300 Toujeo. Consequently, an improved quality of life was also reported. Flash-based glucose monitoring was utilised to record 24-hour continuous glucose levels throughout two comparable 60-day periods before and after the change in regimen. Low blood glucose was most likely between 03:00 and 08:00. Nocturnal hypoglycaemic episodes (≤3.9 mmol/L) reduced by an average of 2.5 episodes per week. Severe hypoglycaemic episodes (≤2.9 mmol/L) reduced to an average of 0.4 per week, down from 1.5 per week. Nocturnal hypoglycaemic episodes reduced in frequency and severity. Furthermore, nocturnal hypoglycaemia episodes occurred in a more predictable time window. This was especially important in the reported reduction of impact on the patient's quality of life, as the episodes tended to be associated with anxiety and low mood. Patient education needed to facilitate this change was minimal, and benefits to the patient were great, including decreased sleep disturbances and reduced risk of associated anxiety symptoms. PMID:27307429

  14. Airborne Carbon Dioxide Laser Absorption Spectrometer for IPDA Measurements of Tropospheric CO2: Recent Results

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.; Menzies, Robert T.

    2008-01-01

    The National Research Council's decadal survey on Earth Science and Applications from Space[1] recommended the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission for launch in 2013-2016 as a logical follow-on to the Orbiting Carbon Observatory (OCO) which is scheduled for launch in late 2008 [2]. The use of a laser absorption measurement technique provides the required ability to make day and night measurements of CO2 over all latitudes and seasons. As a demonstrator for an approach to meeting the instrument needs for the ASCENDS mission we have developed the airborne Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) which uses the Integrated Path Differential Absorption (IPDA) Spectrometer [3] technique operating in the 2 micron wavelength region.. During 2006 a short engineering checkout flight of the CO2LAS was conducted and the results presented previously [4]. Several short flight campaigns were conducted during 2007 and we report results from these campaigns.

  15. Global Carbon Cycle Inside GISS ModelE GCM: Results of Equilibrium and Transient Simulations.

    NASA Astrophysics Data System (ADS)

    Aleinov, I.; Kiang, N. Y.; Romanou, A.; Puma, M. J.; Kharecha, P.; Moorcroft, P. R.; Kim, Y.

    2008-12-01

    We present simulation results for a fully coupled carbon cycle inside the ModelE General Circulation Model (GCM) developed at the NASA Goddard Institute for Space Studies (GISS). The current implementation utilizes the GISS dynamical atmospheric core coupled to the HYCOM ocean model. The atmospheric core uses a Quadratic Upstream Scheme (QUS) for advection of gas tracers, while HYCOM has its own built-in algorithm for advection of ocean tracers. The land surface part of the model consists of the GISS ground hydrology model coupled to the Ent dynamic global terrestrial ecosystem model. The ocean biogeochemistry model based on Watson Gregg's model was implemented inside the HYCOM ocean model. Together with ocean tracer transport, it describes all aspects of the carbon cycle inside the ocean and provides CO2 fluxes for exchange with the atmosphere. CO2 fluxes from land vegetation are provided by the Ent model, which employs well-known photosynthesis relationships of Farquhar, von Caemmerer, and Berry and stomatal conductance of Ball and Berry. Soil CO2 fluxes are also computed by the Ent model according to the CASA soil biogeochemistry model. We present results of fully coupled GCM simulations as well as off-line tests for different components. For GCM simulations, we present results of both equilibrium and transient runs and discuss implications of biases in GCM-predicted climate for accurate modeling of the carbon cycle.

  16. The anaerobic corrosion of carbon steel in alkaline media - Phase 2 results

    NASA Astrophysics Data System (ADS)

    Smart, N. R.; Rance, A. P.; Fennell, P. A. H.; Kursten, B.

    2013-07-01

    In the Belgian Supercontainer concept a carbon steel overpack will surround high-level waste and spent fuel containers and be encased in a cementitious buffer material. A programme of research was carried out to investigate and measure the rate of anaerobic corrosion of carbon steel in an artificial alkaline porewater that simulates the aqueous phase in the cementitious buffer material. The corrosion rates were measured by monitoring hydrogen evolution using a manometric gas cell technique and by applying electrochemical methods. Phase 2 of the programme has repeated and extended previous Phase 1 measurements of the effects of radiation, temperature and chloride concentration of the anaerobic corrosion rate. This paper provides an update on the results from Phase 2 of the programme. The results confirm previous conclusions that the long-term corrosion rate of carbon steel in alkaline simulated porewater is determined by the formation of a thin barrier layer and a thicker outer layer composed of magnetite. Anaerobic corrosion of steel in cement requires an external supply of water.

  17. OFF-GAS MERCURY CONTROL USING SULFUR-IMPREGNATED ACTIVATED CARBON – TEST RESULTS

    SciTech Connect

    Nick Soelberg

    2007-05-01

    Several laboratory and pilot-scale tests since the year 2000 have included demonstrations of off-gas mercury control using fixed bed, sulfur-impregnated activated carbon. These demonstrations have included operation of carbon beds with gas streams containing a wide range of mercury and other gas species concentrations representing off-gas from several U.S. Department of Energy (DOE) mixed waste treatment processes including electrical resistance heated (joule-heated) glass melters, fluidized bed calciners, and fluidized bed steam reformers. Surrogates of various DOE mixed waste streams (or surrogates of offgas from DOE mixed waste streams) including INL “sodium bearing waste” (SBW), liquid “low activity waste” (LAW) from the Pacific Northwest National Laboratory, and liquid waste from Savannah River National Laboratory (“Tank 48H waste”) have been tested. Test results demonstrate mercury control efficiencies up to 99.999%, high enough to comply with the Hazardous Waste (HWC) Combustor Maximum Achievable Control Technology (MACT) standards even when the uncontrolled off-gas mercury concentrations exceed 400,000 ug/dscm (at 7% O2), and confirm carbon bed design parameters for such high efficiencies. Results of several different pilot-scale and engineering-scale test programs performed over several years are presented and compared.

  18. Influence of gross versus net land-use transitions on the carbon cycle, land use emissions and fire regime in the Max-Planck-Institute Earth System Model

    NASA Astrophysics Data System (ADS)

    Wilkenskjeld, Stiig; Kloster, Silvia; Pongratz, Julia; Reick, Christian

    2013-04-01

    Since thousands of years mankind has altered the surface of the Earth by clearing forests for agricultural purposes and logging of wood for fuel and construction works. In total about half of the global land surface have at some point in history been altered by humans. Land use and land use changes (LULCC) have not only changed the physical surface properties of the Earth (albedo, roughness length) but also results in a release of carbon to the atmosphere (land use emissions, LUE). These fluxes have exceeded those from fossil fuel well into the 20th century and still amount to more than 10% of present day fossil fuel emissions. Thus quantification of the LUE is important for understanding the past and the prediction of the future climate. Therefore the last generation of Earth System Models (ESMs) used for the model intercomparison studies for the IPCC 5th assessment report include LULCC and LUE, but the implementation details and thus results are diverse. One important difference is whether sub-grid scale LULCC practices such as shifting cultivation (that is: clearing land, cultivating it for a few years then abandoning it again while clearing a new land piece), which is very important in certain regions of the world, is accounted for (gross transitions) or not (net transitions). The difference between the two approaches has been quantified using the ESM of the Max-Planck-Institute (MPI-ESM) by reducing the LULCC information which include shifting cultivation (gross transitions) to include net transitions only. Accumulated over the period 1850-2005 the LUE were about 85GtC (almost 40%) lower when accounting for net transitions only. Through differences in fuel availability also fire occurrence was changed, though only regionally important. Using the RCP-senarios, the results were projected until year 2100. The differences between the two transition implementations diminishes at different speed in the different RCPs but has (almost) vanished in 2100 in all

  19. Multi-century Changes to Global Climate and Carbon Cycle: Results from a Coupled Climate and Carbon Cycle Model

    SciTech Connect

    Bala, G; Caldeira, K; Mirin, A; Wickett, M; Delire, C

    2005-06-13

    In this paper, we use a coupled climate and carbon cycle model to investigate the global climate and carbon cycle changes out to year 2300 that would occur if CO2 emissions from all the currently estimated fossil fuel resources were released to the atmosphere. By year 2300, the global climate warms by about 8 K and atmospheric CO2 reaches 1423 ppmv. In our simulation, the prescribed cumulative emission since pre-industrial period is about 5400 Gt-C by the end of 23rd century. At year 2300, nearly 45 % of cumulative emissions remain in the atmosphere. In our simulations both soils and living biomass are net carbon sinks throughout the simulation. Despite having relatively low climate sensitivity and strong carbon uptake by the land biosphere, our model projections suggest severe long-term consequences for global climate if all the fossil-fuel carbon is ultimately released to the atmosphere.

  20. The impact of subgrid-scale vegetation distribution on the results of terrestrial carbon cycle modeling

    NASA Astrophysics Data System (ADS)

    Sergeev, Dennis; Eliseev, Alexey

    2013-04-01

    To understand the behavior of the terrestrial carbon cycle under changing atmospheric carbon dioxide levels and climate it is essential to integrate and improve an interactive carbon cycle in all climate models, including Earth system models of intermediate complexity (EMICs). Vegetation distribution and dynamics in each grid cell of these models due to their coarse resolution remains the key area of uncertainty. The present paper focuses on the impact of different mosaic approaches implemented in climate model on the main carbon cycle parameters, such as primary production and carbon stocks. In this study we use the new version of the A. M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS) climate model (CM) [1], which terrestrial carbon cycle module was improved by implementing subgrid-scale heterogeneity of plant functional types (PFT). Moreover, two additional PFTs were added: natural wetlands and bare land/deserts. The model was also extended by including the nitrogen limitation for plant photosynthesis. Different scenarios of natural and anthropogenic climate forcing described in the EMIC AR5 protocol [http://climate.uvic.ca/EMICAR5], were considered in simulations for the period of time from 850 to 2300 yr. In the 21st-23rd centuries simulations external forcing was prescribed according to the RCP (Representative Concentration Pathways) scenarios [2]. Natural vegetation in each 4.5°×6° grid cell was arranged in two different ways: 1) with a dominant PFT, spread on the whole grid cell space (mosaic-1), and 2) with all PFTs that are may be present in a grid cell (mosaic-2). In addition to natural vegetation, changes in agricultural area prescribed by CMIP5 scenarios were taken into account. Numerical experiments show that consideration of subgrid-scale PFT inhomogeneities results in 3 PgC yr-1 increase in global gross primary production (GPP) during the preindustrial period and the early 20th century. This growth is more

  1. Ecosystem Model Performance at Wetlands: Results from the North American Carbon Program Site Synthesis

    NASA Astrophysics Data System (ADS)

    Sulman, B. N.; Desai, A. R.; Schroeder, N. M.; NACP Site Synthesis Participants

    2011-12-01

    Northern peatlands contain a significant fraction of the global carbon pool, and their responses to hydrological change are likely to be important factors in future carbon cycle-climate feedbacks. Global-scale carbon cycle modeling studies typically use general ecosystem models with coarse spatial resolution, often without peatland-specific processes. Here, seven ecosystem models were used to simulate CO2 fluxes at three field sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor, sphagnum-dominated bog, from 2002-2006. Flux residuals (simulated - observed) were positively correlated with measured water table for both gross ecosystem productivity (GEP) and ecosystem respiration (ER) at the two fen sites for all models, and were positively correlated with water table at the bog site for the majority of models. Modeled diurnal cycles at fen sites agreed well with eddy covariance measurements overall. Eddy covariance GEP and ER were higher during dry periods than during wet periods, while model results predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP had no significant dependence on water table, while models predicted higher GEP during wet periods. All models significantly over-estimated GEP at the bog site, and all but one over-estimated ER at the bog site. Carbon cycle models in peatland-rich regions could be improved by incorporating better models or measurements of hydrology and by inhibiting GEP and ER rates under saturated conditions. Bogs and fens likely require distinct treatments in ecosystem models due to differences in nutrients, peat properties, and plant communities.

  2. 76 FR 63902 - Circular Welded Carbon Steel Pipes and Tubes From Taiwan: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-14

    ... Welded Carbon Steel Pipes and Tubes From Taiwan, 76 FR 33210 (June 8, 2011) (Preliminary Results). This... Circular Welded Carbon Steel Pipes and Tubes From Taiwan: Antidumping Duty Order, 49 FR 19369 (May 7, 1984... section 773(b) of the Tariff Act of 1930, as amended (the Act). See Preliminary Results, 76 FR at...

  3. Advancements for Active Remote Sensing of Carbon Dioxide from Space using the ASCENDS CarbonHawk Experiment Simulator: First Results

    NASA Astrophysics Data System (ADS)

    Obland, M. D.; Nehrir, A. R.; Lin, B.; Harrison, F. W.; Kooi, S. A.; Choi, Y.; Plant, J.; Yang, M. M.; Antill, C.; Campbell, J. F.; Ismail, S.; Browell, E. V.; Meadows, B.; Dobler, J. T.; Zaccheo, T. S.; Moore, B., III; Crowell, S.

    2014-12-01

    The ASCENDS CarbonHawk Experiment Simulator (ACES) is an Intensity-Modulated Continuous-Wave lidar system recently developed at NASA Langley Research Center that seeks to advance technologies and techniques critical to measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. These advancements include: (1) increasing the power-aperture product to approach ASCENDS mission requirements by implementing multi-aperture telescopes and multiple co-aligned laser transmitters; (2) incorporating high-efficiency, high-power Erbium-Doped Fiber Amplifiers (EDFAs); (3) developing and incorporating a high-bandwidth, low-noise HgCdTe detector and transimpedence amplifier (TIA) subsystem capable of long-duration operation on Global Hawk aircraft, and (4) advancing algorithms for cloud and aerosol discrimination. The ACES instrument architecture is being developed for operation on high-altitude aircraft and will be directly scalable to meet the ASCENDS mission requirements. ACES simultaneously transmits five laser beams: three from commercial EDFAs operating near 1571 nm, and two from the Exelis oxygen (O2) Raman fiber laser amplifier system operating near 1260 nm. The Integrated-Path Differential Absorption (IPDA) lidar approach is used at both wavelengths to independently measure the CO2 and O2 column number densities and retrieve the average column CO2 mixing ratio. The outgoing laser beams are aligned to the field of view of ACES' three fiber-coupled 17.8-cm diameter athermal telescopes. The backscattered light collected by the three telescopes is sent to the detector/TIA subsystem, which has a bandwidth of 4.7 MHz and operates service-free using a tactical dewar and cryocooler. Two key laser modulation approaches are being tested to significantly mitigate the effects of thin clouds on the retrieved CO2 column amounts. Full instrument development concluded in the

  4. Distribution of organic carbon and petroleum source rock potential of Cretaceous and lower Tertiary carbonates, South Florida Basin: preliminary results

    USGS Publications Warehouse

    Palacas, James George

    1978-01-01

    Analyses of 134 core samples from the South Florida Basin show that the carbonates of Comanchean age are relatively richer in average organic carbon (0.41 percent) than those of Coahuilan age (0.28 percent), Gulfian age (0.18 percent) and Paleocene age (0.20 percent). They are also nearly twice as rich as the average world, wide carbonate (average 0.24 percent). The majority of carbonates have organic carbons less than 0.30 percent but the presence of many relatively organic rich beds composed of highly bituminous, argillaceous, highly stylolitic, and algal-bearing limestones and dolomites accounts for the higher percentage of organic carbon in some of the stratigraphic units. Carbonate rocks that contain greater than 0.4 percent organic carbon and that might be considered as possible petroleum sources were noted in almost each subdivision of the Coahuilan and Comanchean Series but particularly the units of Fredericksburg 'B', Trinity 'A', Trinity 'F', and Upper Sunniland. Possible source rocks have been ascribed by others to the Lower Sunniland, but lack of sufficient samples precluded any firm assessment in this initial report. In the shallower section of the basin, organic-rich carbonates containing as much as 3.2 percent organic carbon were observed in the lowermost part of the Gulfian Series and carbonate rocks with oil staining or 'dead' and 'live oil' were noted by others in the uppermost Gulfian and upper Cedar Keys Formation. It is questionable whether these shallower rocks are of sufficient thermal maturity to have generated commercial oil. The South Florida basin is still sparsely drilled and produces only from the Sunniland Limestone at an average depth of 11,500 feet (3500 m). Because the Sunniland contains good reservoir rocks and apparently adequate source rocks, and because the success rate of new oil field discoveries has increased in recent years, the chances of finding additional oil reserves in the Sunniland are promising. Furthermore, the

  5. Carbon cycling in the Mesopelagic Zone of the central Arabian Sea: Results from a simple model

    NASA Astrophysics Data System (ADS)

    Anderson, Thomas R.; Ryabchenko, Vladimir A.

    Using a 3-D hydrodynamic-ecosystem model, Anderson et al. (2007) investigated the carbon budget of the mesopelagic zone of the central Arabian Sea and concluded that the vertical supply of sinking particles from the euphotic zone is sufficient to meet the carbon demand of the mesopelagic biota. Justifying this conclusion, they argued that the predicted rates of bacterial production (BP) and particle export, 1.92 and 6.97 mmol C m-2 d-1, respectively, were consistent with field estimates. Bacteria were, however, assumed to be the sole agents of detritus turnover (DT) in the mesopelagic, their production being calculated from the product of a fixed bacterial growth efficiency (BGE) of 0.27 and DT. A new model of the mesopelagic food web in the central Arabian Sea is presented in which both bacteria and zooplankton act as consumers of detritus and in which BGE is ⩽0.135. The predicted ratio of BP:DT in the mesopelagic zone was 0.10, with bacteria accounting for 82% of total respiration (zooplankton are responsible for the remainder). If the carbon budget of Anderson et al. (2007) is recalculated assuming BP:DT of 0.10 (rather than 0.27), the resulting BP is then only 1.07 mmol C m-2 d-1, less than half the observational estimate of 2.38 mmol C m-2 d-1. The results presented herein therefore reopen the debate as to whether BP in the central Arabian Sea is, at least in part, fueled by external sources of organic matter such as lateral advection from the western basin.

  6. Cellphone Monitoring of Multi-Qubit Emission Enhancements from Pd-Carbon Plasmonic Nanocavities in Tunable Coupling Regimes with Attomolar Sensitivity.

    PubMed

    Srinivasan, Venkatesh; Manne, Anupam Kumar; Patnaik, Sai Gourang; Ramamurthy, Sai Sathish

    2016-09-01

    We demonstrate for the first time the tuning of qubit emission based on cavity engineering on plasmonic silver thin films. This tunable transition from weak to strong coupling regime in plasmon-coupled fluorescence platform was achieved with the use of palladium nanocomposites. In addition to our recently established correlation between Purcell factor and surface plasmon-coupled emission enhancements, we now show that the qubit-cavity environment experiences the Purcell effect, Casimir force, internal fano resonance, and Rabi splitting. Finite-difference time-domain simulations and time correlated single photon counting studies helped probe the molecular structure of the radiating dipole, rhodamine-6G, in palladium-based nanocavities. The sensitivity of the qubit-cavity mode helped attain a DNA detection limit of 1 aM (attomolar) and multianalyte sensing at picomolar concentration with the use of a smartphone camera and CIE color space. We believe that this low-cost technology will lay the groundwork for mobile phone-based next-gen plasmonic sensing devices. PMID:27529116

  7. Multi-century Changes to Global Climate and Carbon Cycle: Results from a Coupled Climate and Carbon Cycle Model

    SciTech Connect

    Bala, G; Caldeira, K; Mirin, A; Wickett, M; Delire, C

    2005-02-17

    In this paper, we use a coupled climate and carbon cycle model to investigate the global climate and carbon cycle changes out to year 2300 that would occur if CO{sub 2} emissions from all the currently estimated fossil fuel resources were released to the atmosphere. By year 2300, the global climate warms by about 8 K and atmospheric CO{sub 2} reaches 1423 ppmv. The warming is higher than anticipated because the sensitivity to radiative forcing increases as the simulation progresses. In our simulation, the rate of emissions peak at over 30 PgC yr{sup -1} early in the 22nd century. Even at year 2300, nearly 50% of cumulative emissions remain in the atmosphere. In our simulations both soils and living biomass are net carbon sinks throughout the simulation. Despite having relatively low climate sensitivity and strong carbon uptake by the land biosphere, our model projections suggest severe long-term consequences for global climate if all the fossil-fuel carbon is ultimately released to the atmosphere.

  8. Carbonated Eclogite Solidus Between 14 and 20 GPa: Results from the Model CMAS-CO2 System and Contrasting Solidus Behavior to Carbonated Peridotite

    NASA Astrophysics Data System (ADS)

    Keshav, S.; Gudfinnsson, G. H.

    2007-12-01

    , and magnesite. From average calculated melting reactions along these isobarically univariant curves, stishovite is produced upon melting at all pressures investigated. Significantly, cpx at 14 and 16 GPa and capv at 20 GPa are the dominant contributors toward melt production/composition, in contrast to lower pressures (3-8 GPa) where carbonate dominantly contributes toward melt generation/composition at the solidus. The solidus of model carbonated eclogite at 14, 16, and 20 GPa, lies at 1350, 1450, and 1600 degrees C, respectively, and is nearly linear in P-T space. Melts in equilibrium with all the crystalline phases are highly calcic (Ca no.-0.70), resembling calcio-carbonatites. When magnesite is exhausted from the crystalline assemblage, the melts become slightly less calcic (Ca no.-65). The model carbonated eclogite solidus is always lower than the model carbonated peridotite solidus in the same pressure range. The most remarkable feature of this work is the absence of a drop in the solidus of model carbonated eclogite between 14 and 16 GPa, a result that is in stark contrast to that observed for the model carbonated peridotite at identical pressures. Therefore, even though the solidus temperatures in both carbonated peridotite and eclogite are strongly influenced by the presence of crystalline carbonate, melt compositions and the shape of the solidus in the pressure range investigated seem to be dominantly controlled by the silicate component of the rock in question. Given these results, it is fair to say that a wide range of petrological and geochemical processes operate at these depths in the mantle, and that we have barely scratched the surface in our investigation.

  9. Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry.

    PubMed

    Monteith, Donald T; Stoddard, John L; Evans, Christopher D; de Wit, Heleen A; Forsius, Martin; Høgåsen, Tore; Wilander, Anders; Skjelkvåle, Brit Lisa; Jeffries, Dean S; Vuorenmaa, Jussi; Keller, Bill; Kopácek, Jiri; Vesely, Josef

    2007-11-22

    Several hypotheses have been proposed to explain recent, widespread increases in concentrations of dissolved organic carbon (DOC) in the surface waters of glaciated landscapes across eastern North America and northern and central Europe. Some invoke anthropogenic forcing through mechanisms related to climate change, nitrogen deposition or changes in land use, and by implication suggest that current concentrations and fluxes are without precedent. All of these hypotheses imply that DOC levels will continue to rise, with unpredictable consequences for the global carbon cycle. Alternatively, it has been proposed that DOC concentrations are returning toward pre-industrial levels as a result of a gradual decline in the sulphate content of atmospheric deposition. Here we show, through the assessment of time series data from 522 remote lakes and streams in North America and northern Europe, that rising trends in DOC between 1990 and 2004 can be concisely explained by a simple model based solely on changes in deposition chemistry and catchment acid-sensitivity. We demonstrate that DOC concentrations have increased in proportion to the rates at which atmospherically deposited anthropogenic sulphur and sea salt have declined. We conclude that acid deposition to these ecosystems has been partially buffered by changes in organic acidity and that the rise in DOC is integral to recovery from acidification. Over recent decades, deposition-driven increases in organic matter solubility may have increased the export of DOC to the oceans, a potentially important component of regional carbon balances. The increase in DOC concentrations in these regions appears unrelated to other climatic factors. PMID:18033294

  10. Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes

    NASA Astrophysics Data System (ADS)

    Rotevatn, Atle; Thorsheim, Elin; Bastesen, Eivind; Fossmark, Heidi S. S.; Torabi, Anita; Sælen, Gunnar

    2016-09-01

    Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) bed-parallel pure compaction bands (PCB); (ii) pressure solution-dominated compactive shear bands (SCSB) and iii) cataclasis-dominated compactive shear bands (CCSB). Geometric and kinematic analyses show that the bands formed sequentially in the hangingwall of the evolving Maghlaq growth fault. PCBs formed first due to fault-controlled subsidence and vertical loading; a (semi-)tectonic control on PCB formation is thus documented for the first time in an extensional setting. Pressure solution (dominating SCSBs) and cataclasis (dominating CCSBs) appear to have operated separately, and not in concert. Our findings therefore suggest that, in some carbonate rocks, cataclasis within deformation bands may develop irrespective of whether pressure solution processes are involved. We suggest this may be related to stress state, and that whereas pressure solution is a significant facilitator of grain size reduction in contractional settings, grain size reduction within deformation bands in extensional settings is less dependent on pressure solution processes.

  11. 76 FR 77775 - Certain Hot-Rolled Carbon Steel Flat Products From India: Amended Final Results of Countervailing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-14

    ..., 75 FR 43448 (July 26, 2010) (Final Results), and accompanying Issues and Decision Memorandum. Tata... International Trade Administration Certain Hot-Rolled Carbon Steel Flat Products From India: Amended Final... administrative review of the countervailing duty order on certain ] hot-rolled carbon steel flat products...

  12. 75 FR 80455 - Certain Hot-Rolled Carbon Steel Flat Products From India: Amended Final Results of Countervailing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-22

    ..., 73 FR 40295 (July 14, 2008) (Final Results), and accompanying Issues and Decision Memorandum (``I&D... International Trade Administration Certain Hot-Rolled Carbon Steel Flat Products From India: Amended Final... administrative review of the countervailing duty order on certain hot-rolled carbon steel flat products...

  13. Whole-canopy carbon gain as a result of selection on individual performance of ten genotypes of a clonal plant.

    PubMed

    Vermeulen, Peter J; Anten, Niels P R; Stuefer, Josef F; During, Heinjo J

    2013-06-01

    Game theoretical models predict that plant competition for light leads to reduced productivity of vegetation stands through selection for traits that maximize carbon gains of individuals. Using empirical results from a 5-year competition experiment with 10 genotypes of the clonal plant Potentilla reptans, we tested this prediction by analyzing the effects of the existing leaf area values on the carbon gain of the different genotypes and the consequent whole canopy carbon gain. We focused on specific leaf area (SLA) due to its role in the trade-off between light capture area and photosynthetic capacity per unit area. By combining a canopy model based on measured leaf area and light profiles with a game theoretical approach, we analyzed how changes in the SLA affected genotypic and whole-stand carbon gain. This showed that all genotypes contributed to reduced stand productivity. The dominant genotype maximized its share of total carbon gain, resulting in lower than maximal absolute gain. Other genotypes did not maximize their share. Hypothetical mutants of the dominant genotype were not able to achieve a higher carbon gain. Conversely, in other genotypes, some mutations did result in increased carbon gain. Hence, genotypic differences in the ability to maximize performance may determine genotype frequency. It shows how genotypic selection may result in lower carbon gains of the whole vegetation, and of the individual genotypes it consists of, through similar mechanisms as those that lead to the tragedy of the commons. PMID:23114427

  14. 75 FR 63439 - Certain Welded Carbon Steel Standard Pipes and Tubes From India: Extension of the Final Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-15

    ... and tubes from India. See Certain Welded Carbon Steel Standard Pipes and Tubes from India: Preliminary Results of Antidumping Duty Administrative Review, 75 FR 33578 (June 14, 2010). The review covers the... International Trade Administration Certain Welded Carbon Steel Standard Pipes and Tubes From India: Extension...

  15. Granular Activated Carbon Treatment May Result in Higher Predicted Genotoxicity in the Presence of Bromide.

    PubMed

    Krasner, Stuart W; Lee, Tiffany Chih Fen; Westerhoff, Paul; Fischer, Natalia; Hanigan, David; Karanfil, Tanju; Beita-Sandí, Wilson; Taylor-Edmonds, Liz; Andrews, Robert C

    2016-09-01

    Certain unregulated disinfection byproducts (DBPs) are more of a health concern than regulated DBPs. Brominated species are typically more cytotoxic and genotoxic than their chlorinated analogs. The impact of granular activated carbon (GAC) on controlling the formation of regulated and selected unregulated DBPs following chlorine disinfection was evaluated. The predicted cyto- and genotoxicity of DBPs was calculated using published potencies based on the comet assay for Chinese hamster ovary cells (assesses the level of DNA strand breaks). Additionally, genotoxicity was measured using the SOS-Chromotest (detects DNA-damaging agents). The class sum concentrations of trihalomethanes, haloacetic acids, and unregulated DBPs, and the SOS genotoxicity followed the breakthrough of dissolved organic carbon (DOC), however the formation of brominated species did not. The bromide/DOC ratio was higher than the influent through much of the breakthrough curve (GAC does not remove bromide), which resulted in elevated brominated DBP concentrations in the effluent. Based on the potency of the haloacetonitriles and halonitromethanes, these nitrogen-containing DBPs were the driving agents of the predicted genotoxicity. GAC treatment of drinking or reclaimed waters with appreciable levels of bromide and dissolved organic nitrogen may not control the formation of unregulated DBPs with higher genotoxicity potencies. PMID:27467860

  16. [Tribological properties of carbon fiber-reinforced plastic. Experimental and clinical results].

    PubMed

    Früh, H J; Ascherl, R; Hipp, E

    1997-02-01

    Wear of the articulating components (especially PE-UHMW) of total hip endoprostheses is the most important technical factor limiting the functional lifetime. To minimize wear debris, ceramic heads, according to ISO 6474 (Al2O3), have been used, from 1969 paired with Al2O3 and since 1975 paired with PE-UHMW. Al2O3 balls articulating with cups made from CFRP have been in clinical use since 1988. Laboratory experiments and in-vivo testing showed minimized wear debris and mild biological response to wear products using CFRP (carbon fiber reinforced plastic) instead of PE-UHMW as the cup material. The articulating surfaces of retrieved ceramic heads (Al2O3-Biolox) and cementless CFRP cups (carbon fiber reinforced plastic, Caproman) were compared using sphericity measurement techniques, scanning electron microscopy (SEM) and roughness measurements (including advanced roughness parameters Rvk or Rpk according to ISO 4287). Altogether, the first results of the clinical study showed that the combination Al2O3-ball/CFRP-cup came up to the expected lower wear rates compared with the conventional combinations. The wear rates are comparable with the combination Al2O3/Al2O3 without the material-related problems of ceramic components in all ceramic combinations.

  17. Carbon, Water, and Energy Dynamics in a Savanna Mosaic: Results From an African Field Campaign

    NASA Astrophysics Data System (ADS)

    Williams, C. A.; Albertson, J. D.

    2002-12-01

    Savanna ecosystems cover a large fraction of the terrestrial landscape with a shifting mosaic of vegetation that is poorly understood. Vegetation dynamics in savannas are believed to be triggered by variation in climate forcing with potential local and regional scale feedbacks on climate and with nonlinear behavior, such as self-organization. Recent debate has brought attention to uncertainty regarding the role of savannas in global carbon and water cycles, identifying the need for data that can address the coupled water and carbon dynamics of these sensitive ecosystems. We report results from a 30-day field campaign conducted in southern Africa near Ghanzi, Botswana along the Kalahari Transect. This water-limited site is ideal for studies of soil and plant water relations because high spatial and temporal variability in rainfall has direct effects on vegetation function, extent, and composition. We characterized the functional response of tree/grass/bare soil mosaics during a prolonged drydown following a large rain event (85 mm) at the end of the 2002 wet season. Net radiation, sensible, latent and soil heat fluxes, carbon dioxide exchange, soil moisture, soil temperature, and vegetation temperatures were measured at two sites, one dominated by woody vegetation (Acacia and Terminalia) and the other composed of native grasses, shrubs, and bare soil. We characterized the vegetation structure within the footprints of both towers with measurements of leaf area, fractional vegetation cover, and profiles of aboveground and belowground biomass. Additionally, leaf-level gas exchange measurements were conducted on dominant species. Soil moisture decayed from a peak of 0.28 after the storm to 0.05, measured 5 cm below the soil surface. The drydown resulted in a continual increase in the daytime Bowen ratio, a decrease of leaf-level evapotranspiration, and reduced net ecosystem exchange of CO2. Biophysical differences between C3 trees and C4 grasses were evident from vapor

  18. Radiative Forcing associated with Particulate Carbon Emissions resulting from the Use of Mercury Control Technology

    NASA Astrophysics Data System (ADS)

    Clack, H.; Penner, J. E.; Lin, G.

    2013-12-01

    Mercury is a persistent, toxic metal that bio-accumulates within the food web and causes neurological damage and fetal defects in humans. The U.S. was the first country to regulate the leading anthropogenic source of mercury into the atmosphere: coal combustion for electric power generation. The U.S. EPA's 2005 Clean Air Mercury Rule (CAMR) was replaced and further tightened in 2012 by the Mercury and Air Toxics Standard (MATS), which required existing coal-fired utilities to reduce their mercury emissions by approximately 90% by 2015. Outside the U.S., the Governing Council of the United Nations Environment Programme (UNEP) has passed the legally binding Minamata global mercury treaty that compels its signatory countries to prevent and reduce the emission and release of mercury. The most mature technology for controlling mercury emissions from coal combustion is the injection into the flue gas of powdered activated carbon (PAC) adsorbents having chemically treated surfaces designed to rapidly oxidize and adsorb mercury. However, such PAC is known to have electrical properties that make it difficult to remove from flue gas via electrostatic precipitation, by far the most common particulate control technology used in countries such as the U.S., India, and China which rely heavily on coal for power generation. As a result, PAC used to control mercury emissions can be emitted into the atmosphere, the sub-micron fraction of which may result in unintended radiative forcing similar to black carbon (BC). Here, we estimate the potential increases in secondary BC emissions, those not produced from combustion but arising instead from the use of injected PAC for mercury emission reduction. We also calculate the radiative forcing associated with these secondary BC emissions by using a global atmospheric chemical transport model coupled with a radiative transfer model.

  19. Hydrothermal regime of the Iheya-North hydrothermal field inferred from surface heat flow data and, IODP Expedition 331 drilling results

    NASA Astrophysics Data System (ADS)

    Masaki, Y.; Takai, K.; Mottl, M. J.; Hartnett, H. E.; Kinoshita, M.; IODP Expedition 331 scientists

    2011-12-01

    hole at HHZ recorded around 300 °C, which is consistent with temperatures of black smokers. Hemipelagic sediment including pumiceous layer were found in the LHZ. The temperature at 37 m below seafloor (mbsf), was 6 °C. Between 70 and 90 mbsf, the coarser sediments were cored, and temperature increases from 25 °C to 40 °C. At the maximum drilled depth of 151 mbsf, the temperature was 90±5 °C, which was measured with thermoseal strips. Low thermal gradient in the upper 40 m supports the downward fluid flow. Seismic reflection data indicate a couple of horizontal layers continuously below MHZ. these layers could inhibit vertical fluid flux. Thus we assume that vertically-impermeable surface layers serve to generate kilometer scale hydrothermal circulation. In order to estimate permeability structure below HHZ through LHZ, we conducted a 2-dimensional numerical simulation, and the results will be shown.

  20. Woody plant encroachment effect on soil organic carbon dynamics: results from a latitudinal gradient in Italy

    NASA Astrophysics Data System (ADS)

    Pellis, Guido; Chiti, Tommaso; Moscatelli, Maria Cristina; Marinari, Sara; Papale, Dario

    2016-04-01

    Woody plant encroachment into pastures and grasslands represents a significant land cover change phenomenon, with a considerable impact on carbon dynamics at an ecosystem level. It was estimated that 7.64% of the Southern Europe land was subject to that process between 1950 to 2010. As a result of woody encroachment, changes in vegetation composition can produce substantial changes to the soil organic carbon (SOC) cycle. Despite the numerous papers published on land-use change, an evaluation of the IPCC terrestrial carbon pools changes occurring during woody encroachment on abandoned pastures and grasslands is still lacking, particularly for the Italian territory. Therefore, the aim of this study was to investigate the role of woody encroachment on carbon sequestration over abandoned pastures and grasslands in Alpine and Apennine ecosystems, with a particular focus on the SOC. We applied a chronosequence approach to seven selected sites located along a latitudinal gradient in Italy. Each chronosequence consisted of a pasture currently managed, three sites abandoned at different times in the past and, finally, a mature forest stand representing the last phase of the succession. The European Commission sampling protocols to certify SOC changes was adopted to estimate the variations following woody encroachment. Soil samples were collected at different depths in the topsoil (0-30 cm) and subsoil (30-70 cm), despite the original protocol formulation being limited to the topsoil only. In addition, aboveground living biomass (AGB), dead wood and litter were also measured following international protocols. Considering all C pools together, woody plant encroachment leads to a progressive C stock accumulation in all the chronosequences. The total C stock of mature forest stands ranges from 1.78±0.11 times (Eastern Alps) to 2.48±0.31 times (central Apennine) the initial value on pastures. Unsurprisingly, the C stocks of AGB, dead wood and litter all increase during the

  1. 75 FR 62366 - Circular Welded Carbon Steel Pipes and Tubes From Taiwan: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-08

    ... Welded Carbon Steel ] Pipes and Tubes From Taiwan, 75 FR 32911 (June 10, 2010) (Preliminary Results...) of the Act. See Preliminary Results, 75 FR at 32913. Those results apply to these final results... accordance with section 773(a)(4) of the Act. See Preliminary Results, 75 FR 32913. Analysis of...

  2. 76 FR 45509 - Final Results of Antidumping Duty Changed Circumstances Review: Carbon and Certain Alloy Steel...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-29

    ... Circumstances Review: Carbon and Certain Alloy Steel Wire Rod from Mexico, 75 FR 67685 (November 3, 2010... of the Antidumping Duty and Countervailing Duty Orders, and Intent To Revoke Orders in Part, 68 FR...: Carbon and Certain Alloy Steel Wire Rod From Mexico, 71 FR 27989 (May 15, 2006). Notification This...

  3. Divergent trajectories in tropical rainforest carbon-climate relationships: results from a new tropical forest carbon inventory database

    NASA Astrophysics Data System (ADS)

    Taylor, P.; Wieder, W.; Townsend, A.; Asner, G. P.; Cleveland, C.; Loarie, S.

    2010-12-01

    Intact tropical rainforests play a disproportionate role in the terrestrial carbon (C) cycle because they exchange more CO2 with the atmosphere than any other biome. As with any ecosystem, climate controls rates of C uptake and storage; however, the specific nature of climate-carbon relationships in the tropics remains poorly understood and oft-debated. Consequently, there are major uncertainties in how human-driven climate change may alter tropical C storage. One way to investigate climate - forest C interactions is via meta-analyses that examine shifts in forest C dynamics along climatic gradients. Past such analyses for the role of precipitation suggest tropical aboveground net primary production (ANPP) peaks near 2500 mm/yr, and then sharply declines in wetter regions. However, the downturn in ANPP is driven by a bias in early databases toward montane forests, which may exhibit temperature-driven biogeochemical feedbacks not present in wet lowland forests. To address this possibility, we assembled a tropical forest carbon dynamics database that includes nearly 900 different sites. We found substantial divergence in montane versus lowland forest ANPP responses to shifts in rainfall. As previous analyses imply, montane forest ANPP shows a distinct “hump-shaped” pattern, with a downturn in wetter sites. However, in contrast to prevailing assumptions, we find that lowland forest ANPP and biomass remain steady or increase with increasing rainfall. The data suggest that temperature plays a key role in determining the shape of rainfall - forest C interactions by regulating plant-soil nutrient feedbacks that underlie trends in ANPP. In montane systems, lower temperatures under wet conditions allow the development of organic horizons and the persistence of low redox conditions that reduce fertility, but in lowland systems, higher temperatures prevent organic matter accumulation, and high precipitation appears to drive rapid exchanges of nutrients between litter and

  4. CO2-brine-mineral Reactions in Geological Carbon Storage: Results from an EOR Experiment

    NASA Astrophysics Data System (ADS)

    Chapman, H.; Wigley, M.; Bickle, M.; Kampman, N.; Dubacq, B.; Galy, A.; Ballentine, C.; Zhou, Z.

    2012-04-01

    Dissolution of CO2 in brines and reactions of the acid brines ultimately dissolving silicate minerals and precipitating carbonate minerals are the prime long-term mechanisms for stabilising the light supercritical CO2 in geological carbon storage. However the rates of dissolution are very uncertain as they are likely to depend on the heterogeneity of the flow of CO2, the possibility of convective instability of the denser CO2-saturated brines and on fluid-mineral reactions which buffer brine acidity. We report the results of sampling brines and gases during a phase of CO2 injection for enhanced oil recovery in a small oil field. Brines and gases were sampled at production wells daily for 3 months after initiation of CO2 injection and again for two weeks after 5 months. Noble gas isotopic spikes were detected at producing wells within days of initial CO2 injection but signals continued for weeks, and at some producers for the duration of the sampling period, attesting to the complexity of gas-species pathways. Interpretations are complicated by the previous history of the oil field and re-injection of produced water prior to injection of CO2. However water sampled from some producing wells during the phase of CO2 injection showed monotonic increases in alkalinity and in concentrations of major cations to levels in excess of those in the injected water. The marked increase in Na, and smaller increases in Ca, Mg, Si, K and Sr are interpreted primarily to result from silicate dissolution as the lack of increase in S and Cl concentrations preclude additions of more saline waters. Early calcite dissolution was followed by re-precipitation. 87Sr/86Sr ratios in the waters apparently exceed the 87Sr/86Sr ratios of acetic and hydrochloric acid leaches of carbonate fractions of the reservoir rocks and the silicate residues from the leaching. This may indicate incongruent dissolution of Sr or larger scale isotopic heterogeneity of the reservoir. This is being investigated

  5. From carbon numbers to ecosystem services: usable results comparing natural versus managed lands

    NASA Astrophysics Data System (ADS)

    Bachelet, D. M.; Ferschweiler, K.; Sheehan, T.; Sleeter, B. M.; Zhu, Z.

    2015-12-01

    We ran the MC2 dynamic vegetation model for the conterminous US at 30 arc sec with and without land use and fire suppression for several climate change scenarios. We translated model results into key ecosystem services (ES) such as climate regulation through carbon uptake and sequestration (global climate) or through transpiration (regional climate) as well as water provision through runoff and throughflow. We also projected timber production and gauged the risk of production lost to fire and/or drought by simulating fuel loads and forest vigor annually through the 21st century. We calculated the rising irrigation demand for agricultural land which, coupled with available information on groundwater resources, could help plan for future cropping systems. By combining these results we can evaluate land cover value across the country in terms of quantity and quality of services rendered. By comparing projections with and without landuse and fire suppression we can illustrate differences in regulating and provisioning services between managed and natural lands.

  6. Incorporation of inorganic carbon by Antarctic cryptoendolithic fungi

    NASA Technical Reports Server (NTRS)

    Palmer, R. J. Jr; Friedmann, E. I.

    1988-01-01

    Fungi isolated from the cryptoendolithic community of the Ross Desert are capable of fixing inorganic carbon. Results suggest that lichen mycobionts and parasymbionts are adapted to different water regimes in the cryptoendolithic environment.

  7. SO{sub 2} removal and CO{sub 2} capture by limestone resulting from calcination/sulfation/carbonation cycles

    SciTech Connect

    Yan Li; Steve Buchi; John R. Grace; C. Jim Lim

    2005-10-01

    Experiments were conducted in a dual-environment thermogravimetric reactor to investigate the interaction between calcination, sulfation, and carbonation for a limestone that had previously been shown to sulfate primarily in an unreacted core manner. The results indicate that carbon dioxide (CO{sub 2}) can reactivate partially sulfated sorbent particles, contributing to an increase in overall calcium utilization efficiency. The ability of sorbents to recapture CO{sub 2} decreases when cycles of calcination and carbonation are performed, following a pattern similar to sulfation/hydration cycling. 16 refs., 10 figs., 3 tabs.

  8. Does Iron Fertilization Lead to Enhanced Carbon Sequestration? A Synthesis of Polar Star Results.

    SciTech Connect

    Buesseler, K.O.

    2002-12-01

    This research synthesized activities related to work conducted as part of the Southern Ocean Iron Experiment (SOFeX) which investigated the effects of iron fertilization on enhanced carbon sequestration. The primary interest was in the fate of sinking particles which carry carbon to the deep ocean, where it can be sequestered from the atmosphere for >100-1000 year time scales. This was accomplished through direct measurements of thorium-234, a naturally occurring particle reactive radionuclide that traces shallow particle export; SF6 measurements to track the position of the Fe fertilized region; and the collection of ancillary data and samples to augment the study of major C, nutrient and elemental budgets as well as appropriate samples for biological study. Results of this work show a small, but progressively increasing flux of particulate organic C to depth as a consequence of Fe fertilization. This is the first data set to show any effect of Fe fertilization on C sequestration in the Southern Ocean. The changes in particle export during SOFeX are significant, but only possible to detect given what is arguably the largest 234Th data set ever collected as part of an oceanographic experiment. Most prior 234Th studies, simply use a steady-state approximation and ignore advective and diffusive fluxes in the calculation of 234Th fluxes. High resolution time-series of average 0-50m 234Th activities in and out of the Southern patch find a clear steady decrease in 234Th flux that is slightly larger in vs. out of the Fe fertilized patch. This decrease must be included in the full 234Th flux calculation and the deliberate tagging of this water mass with SF6 combined with time-series sampling allowed for a careful evaluation of this non-steady state (NSS) term. Likewise, the addition of SF6 allows for the evaluation of vertical exchange (via the gradient of SF6 below the patch) and dilution effects (after correction for atmospheric losses). In most set tings these physical

  9. A dense Black Carbon network in the region of Paris, France: Implementation, objectives, and first results

    NASA Astrophysics Data System (ADS)

    Sciare, Jean; Petit, Jean-Eudes; Sarda-Esteve, Roland; Bonnaire, Nicolas; Gros, Valérie; Pernot, Pierre; Ghersi, Véronique; Ampe, Christophe; Songeur, Charlotte; Brugge, Benjamin; Debert, Christophe; Favez, Olivier; Le Priol, Tiphaine; Mocnik, Grisa

    2013-04-01

    Motivations. Road traffic and domestic wood burning emissions are two major contributors of particulate pollution in our cities. These two sources emit ultra-fine, soot containing, particles in the atmosphere, affecting health adversely, increasing morbidity and mortality from cardiovascular and respiratory conditions and casing lung cancer. A better characterization of soot containing aerosol sources in our major cities provides useful information for policy makers for assessment, implementation and monitoring of strategies to tackle air pollution issues affecting human health with additional benefits for climate change. Objectives. This study on local sources of primary Particulate Matter (PM) in the megacity of Paris is a follow-up of several programs (incl. EU-FP7-MEGAPOLI) that have shown that fine PM - in the Paris background atmosphere - is mostly secondary and imported. A network of 14 stations of Black Carbon has been implemented in the larger region of Paris to provide highly spatially resolved long term survey of local combustion aerosols. To our best knowledge, this is the first time that such densely BC network is operating over a large urban area, providing novel information on the spatial/temporal distribution of combustion aerosols within a post-industrialized megacity. Experimental. As part of the PRIMEQUAL "PREQUALIF" project, a dense Black Carbon network (of 14 stations) has been installed over the city of Paris beginning of 2012 in order to produce spatially resolved Equivalent Black Carbon (EBC) concentration maps with high time resolution through modeling and data assimilation. This network is composed of various real-time instruments (Multi-Angle Absorption Photometer, MAAP by THERMO; Multi-wavelength Aethalometers by MAGEE Scientific) implemented in contrasted sites (rural background, urban background, traffic) complementing the regulated measurements (PM, NOx) in the local air quality network AIRPARIF (http

  10. DISSOLVED ORGANIC CARBON TRENDS RESULTING FROM CHANGES IN ATMOSPHERIC DEPOSITION CHEMISTRY

    EPA Science Inventory

    Several hypotheses have been proposed to explain recent, widespread increases in concentrations of dissolved organic carbon (DOC) in the surface waters of glaciated landscapes across eastern North America and northern and central Europe. Some invoke anthropogenic forcing through ...

  11. Analysis of results of biomass forest inventory in northeastern Amazon for development of REDD+ carbon project.

    PubMed

    Mello, Leonel N C; Sales, Marcio H R; Rosa, Luiz P

    2016-03-01

    In Brazil, a significant reduction in deforestation rates occurred during the last decade. In spite of that fact, the average annual rates are still too high, approximately 400.000 ha/year (INPE/Prodes). The projects of emissions reduction through avoided deforestation (REED+) are an important tool to reduce deforestation rates in Brazil. Understanding the amazon forest structure, in terms of biomass stock is key to design avoided deforestation strategies. In this work, we analyze data results from aboveground biomass of 1,019.346,27 hectares in the state of Pará. It was collected data from 16,722 trees in 83 random independent plots. It was tested 4 allometric equations, for DBH > 10cm: Brown et al. (1989), Brown and Lugo (1999), Chambers et al. (2000), Higuchi et al. (1998). It revealed that the biggest carbon stock of above ground biomass is stocked on the interval at DBH between 30cm and 80cm. This biomass compartment stocks 75.70% of total biomass in Higuchi et al. (1998) equation, 75.56% of total biomass in Brown et al. (1989) equation, 78.83% of total biomass in Chambers et al. (2000) equation, and 73.22% in Brown and Lugo (1999) equation.

  12. An Experimental Evaluation of HVAC-Grade Carbon-Dioxide Sensors: Part 2, Performance Test Results

    SciTech Connect

    Shrestha, Som S; Maxwell, Dr. Gregory

    2010-01-01

    This is the second paper in a four-part series reporting on the test and evaluation of typical carbon-dioxide sensors used in building HVAC applications. Fifteen models of NDIR HVAC-grade CO2 sensors were tested and evaluated to determine the accuracy, linearity, repeatability, and hysteresis of each sensor. This paper describes the performance of the sensors and provides a comparison with the manufacturers specifications. The sensors were tested at 40% relative humidity, 73oF (22.8oC) temperature, 14.70 psia (101.35 kPa) pressure, and at five different CO2 concentrations (400 ppm, 750 ppm, 1100 ppm, 1450 ppm, and 1800 ppm). The test results showed a wide variation in sensor performance among the various manufacturers and in some cases a wide variation among sensors of the same model. In all, 45 sensors were evaluated: three from each of the 15 models. Among the 15 models tested, eight models have a single-lamp, single-wavelength configuration, four models have a dual-lamp, single-wavelength configuration, and three models have a single-lamp, dual-wavelength configuration.

  13. Analysis of results of biomass forest inventory in northeastern Amazon for development of REDD+ carbon project.

    PubMed

    Mello, Leonel N C; Sales, Marcio H R; Rosa, Luiz P

    2016-03-01

    In Brazil, a significant reduction in deforestation rates occurred during the last decade. In spite of that fact, the average annual rates are still too high, approximately 400.000 ha/year (INPE/Prodes). The projects of emissions reduction through avoided deforestation (REED+) are an important tool to reduce deforestation rates in Brazil. Understanding the amazon forest structure, in terms of biomass stock is key to design avoided deforestation strategies. In this work, we analyze data results from aboveground biomass of 1,019.346,27 hectares in the state of Pará. It was collected data from 16,722 trees in 83 random independent plots. It was tested 4 allometric equations, for DBH > 10cm: Brown et al. (1989), Brown and Lugo (1999), Chambers et al. (2000), Higuchi et al. (1998). It revealed that the biggest carbon stock of above ground biomass is stocked on the interval at DBH between 30cm and 80cm. This biomass compartment stocks 75.70% of total biomass in Higuchi et al. (1998) equation, 75.56% of total biomass in Brown et al. (1989) equation, 78.83% of total biomass in Chambers et al. (2000) equation, and 73.22% in Brown and Lugo (1999) equation. PMID:26959317

  14. Quantifying Fine Root Carbon Inputs To Soil: Results From Combining Radiocarbon And Traditional Methodologies.

    NASA Astrophysics Data System (ADS)

    Gaudinski, J. B.; Trumbore, S. E.; Dawson, T.; Torn, M.; Pregitzer, K.; Joslin, J. D.

    2002-12-01

    Estimates of high belowground net primary productivity (50% or more) in forest ecosystems are often based on assumptions that almost all fine roots (< 2 mm in diameter) live and die within one year. Recent radiocarbon (14C) measurements of fine root cellulose in three eastern temperate forests of the United States show that at least a portion of fine roots are living for more than 8 years (Gaudinski et al. 2001) and that fine root lifespans likely vary as a function of both diameter and position on the root branch system. New data from investigations under way in several different temperate forests further support the idea of large variations in root lifespans with radiocarbon-derived ages ranging from approximately one year to several years. In forests where both mini-rhizotron and 14C lifespan estimates have been made, the two techniques agree well when the 14C sampling is made on the same types of roots viewed by mini-rhizotron cameras (i.e. first and second order roots; the most distal and newest roots on the root branching system), and the 14C signature of new root growth is known. We have quantified the signature of new tree roots by taking advantage of locally-elevated 14C at Oak Ridge Tennessee, which shows that carbon making up new roots was photosynthesized approximately 1.5 years prior to new root growth. Position on the root branching system shows a correlation with age, with ages up to 7 years for 4th order roots of red maple. The method by which roots are sampled also affects the 14C-estimated age, with total fine root population, sampled via soil cores, showing longer lifespans relative to roots sampled by position on the root branch system (when similar diameter classes are compared). Overall, the implication of our studies is that assumptions of turnover times of 1 year result in underestimates of the true lifespan of a large portion of fine root biomass in temperate forests. This suggests that future calculations of belowground net primary

  15. The mechanism of production enhancement in coral reef carbonate systems: model and empirical results

    NASA Astrophysics Data System (ADS)

    Suzuki, A.; Nakamori, T.; Kayanne, H.

    1995-11-01

    Coral reefs are characterized by enormous carbonate production of the organisms. It is known that rapid calcification is linked to photosynthesis under control of the carbonate equilibrium in seawater. We have established a model simulating the coexisting states of photosynthesis and calcification in order to examine the effects of photosynthesis and calcification on the carbonate system in seawater. Supposing that the rates of photosynthesis and calcification are proportional to concentrations of their inorganic carbon source, the model calculations indicate that three kinds of unique interactions of the organic and inorganic carbon productions are expected. These are photosynthetic enhancement of calcification, calcification which benefits photosynthesis and carbonate dissolution induced by respiration. The first effect appears when the photosynthetic rate is more than approximately 1.2 larger than that of calcification. This effect is caused by the increase of CO32- content and carbonate saturation degree in seawater. If photosynthesis use molecular carbon dioxide, the second effect occurs when the calcification rate is more than approximately 1.6 times larger than that of photosynthesis. Time series model experiments indicate that photosynthesis and calcification potentially enhance each other and that organic and inorganic carbon is produced more efficiently in the coexisting system than in the isolated reactions. These coexisting effects on production enhancement of photosynthesis and calcification are expected to appear not only in the internal pool of organisms but also in a reef environment which is isolated from the outer ocean during low tide. According to the measurements on the fringing type Shiraho Reef in the Ryukyu Islands, the diurnal change of water properties (pH, total alkalinity, total carbon dioxide and carbonate saturation degree) were conspicuous. This environment offers an appropriate condition for the appearance of these coexisting effects

  16. 75 FR 64696 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-20

    ... Carbon Steel Pipes and Tubes from Thailand: Final Determination of Sales at Less Than Fair Value, 51 FR... Administrative Review, 75 FR 18788 (April 13, 2010) (Preliminary Results). In the Preliminary Results, the...: Extension of Time Limit for Final Results of Antidumping Duty Administrative Review, 75 FR 28557 (May...

  17. Arctic circulation regimes.

    PubMed

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  18. Arctic circulation regimes

    PubMed Central

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L.

    2015-01-01

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  19. Differences in chemical composition of soil organic carbon resulting from long-term fertilization strategies.

    PubMed

    Li, Zengqiang; Zhao, Bingzi; Wang, Qingyun; Cao, Xiaoyan; Zhang, Jiabao

    2015-01-01

    Chemical composition of soil organic carbon (SOC) is central to soil fertility. We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure. This study examined the effect of fertilization strategies along with the time of fertilizer application on the SOC composition by 13C nuclear magnetic resonance (NMR) spectroscopy. The soils (Aquic Inceptisol) subjected to seven fertilizer treatments were collected in 1989, 1999 and 2009, representing 0, 10 and 20 years of fertilization, respectively. The seven fertilizer treatments were (1-3) balanced fertilization with application of nitrogen (N), phosphorus (P) and potassium (K) including organic compost (OM), half organic compost plus half chemical fertilizer (1/2OM), and pure chemical NPK fertilizer (NPK); (4-6) unbalanced chemical fertilization without application of one of the major elements including NP fertilizer (NP), PK fertilizer (PK), and NK fertilizer (NK); and (7) an unamended control (CK). The SOC content in the balanced fertilization treatments were 2.3-52.6% and 9.4-64.6% higher than in the unbalanced fertilization/CK treatments in 1999 and 2009, respectively, indicating significant differences in SOC content with time of fertilizer application between the two treatment groups. There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009. Principal component analysis further showed that the C functional groups from various fertilization strategies tended to become compositionally similar with time. The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration. PMID:25884713

  20. Testing and Results of Vacuum Swing Adsorption Units for Spacesuit Carbon Dioxide and Humidity Control

    NASA Technical Reports Server (NTRS)

    McMillin, Summer D.; Broerman, Craig D.; Swickrath, Michael; Anderson, Molly

    2011-01-01

    A principal concern for extravehicular activity (EVA) spacesuits is the capability to control carbon dioxide (CO2) and humidity (H2O) for the crewmember. The release of CO2 in a confined or unventilated area is dangerous for human health and leads to asphyxiation; therefore, CO2 and H2O control become leading factors in the design and development of the spacesuit. An amine-based CO2 and H2O vapor sorbent for use in pressure-swing regenerable beds has been developed by Hamilton Sundstrand. The application of solidamine materials with vacuum swing adsorption technology has shown the capacity to concurrently manage CO2 and H2O levels through a fully regenerative cycle eliminating mission constraints imposed with nonregenerative technologies. Two prototype solid amine-based systems, known as rapid cycle amine (RCA), were designed to continuously remove CO2 and H2O vapor from a flowing ventilation stream through the use of a two-bed amine based, vacuum-swing adsorption system. The Engineering and Science Contract Group (ESCG) RCA implements radial flow paths, whereas the Hamilton Sundstrand RCA was designed with linear flow paths. Testing was performed in a sea-level pressure environment and a reduced-pressure environment with simulated human metabolic loads in a closed-loop configuration. This paper presents the experimental results of laboratory testing for a full-size and a sub-scale test article. The testing described here characterized and evaluated the performance of each RCA unit at the required Portable Life Support Subsystem (PLSS) operating conditions. The test points simulated a range of crewmember metabolic rates. The experimental results demonstrated the ability of each RCA unit to sufficiently remove CO2 and H2O from a closed loop ambient or sub-ambient atmosphere.

  1. Testing and Results of Vacuum Swing Adsorption Units for Spacesuit Carbon Dioxide and Humidity Control

    NASA Technical Reports Server (NTRS)

    McMillin, Summer; Broerman, Craig; Swickrath, Mike; Anderson, Molly

    2010-01-01

    A principal concern for extravehicular activity (EVA) space suits is the capability to control carbon dioxide (CO2) and humidity (H2O) for the crewmember. The release of CO2 in a confined or unventilated area is dangerous for human health and leads to asphyxiation; therefore, CO2 and H2O become leading factors in the design and development of the spacesuit. An amine-based CO2 and H2O vapor sorbent for use in pressure-swing re-generable beds has been developed by Hamilton Sundstrand. The application of solid-amine materials with vacuum swing adsorption technology has shown the capacity to concurrently manage CO2 and H2O levels through a fully regenerative cycle eliminating mission constraints imposed with non-regenerative technologies. Two prototype solid amine-based systems, known as rapid cycle amine (RCA), were designed to continuously remove CO2 and H2O vapor from a flowing ventilation stream through the use of a two-bed amine based, vacuum-swing adsorption system. The Engineering and Science Contract Group (ESCG) RCA is the first RCA unit implementing radial flow paths, whereas the Hamilton Sundstrand RCA was designed with linear flow paths. Testing was performed in a sea-level pressure environment and a reduced-pressure environment with simulated human metabolic loads in a closed-loop configuration. This paper presents the experimental results of laboratory testing for a full-size and a sub-scale test article. The testing described here characterized and evaluated the performance of each RCA unit at the required Portable Life Support Subsystem (PLSS) operating conditions. The test points simulated a range of crewmember metabolic rates. The experimental results demonstrate the ability of each RCA unit to sufficiently remove CO2 and H2O from a closed loop ambient or subambient atmosphere.

  2. Differences in Chemical Composition of Soil Organic Carbon Resulting From Long-Term Fertilization Strategies

    PubMed Central

    Li, Zengqiang; Zhao, Bingzi; Wang, Qingyun; Cao, Xiaoyan; Zhang, Jiabao

    2015-01-01

    Chemical composition of soil organic carbon (SOC) is central to soil fertility. We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure. This study examined the effect of fertilization strategies along with the time of fertilizer application on the SOC composition by 13C nuclear magnetic resonance (NMR) spectroscopy. The soils (Aquic Inceptisol) subjected to seven fertilizer treatments were collected in 1989, 1999 and 2009, representing 0, 10 and 20 years of fertilization, respectively. The seven fertilizer treatments were (1–3) balanced fertilization with application of nitrogen (N), phosphorus (P) and potassium (K) including organic compost (OM), half organic compost plus half chemical fertilizer (1/2OM), and pure chemical NPK fertilizer (NPK); (4–6) unbalanced chemical fertilization without application of one of the major elements including NP fertilizer (NP), PK fertilizer (PK), and NK fertilizer (NK); and (7) an unamended control (CK). The SOC content in the balanced fertilization treatments were 2.3–52.6% and 9.4–64.6% higher than in the unbalanced fertilization/CK treatments in 1999 and 2009, respectively, indicating significant differences in SOC content with time of fertilizer application between the two treatment groups. There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009. Principal component analysis further showed that the C functional groups from various fertilization strategies tended to become compositionally similar with time. The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration. PMID:25884713

  3. Differences in chemical composition of soil organic carbon resulting from long-term fertilization strategies.

    PubMed

    Li, Zengqiang; Zhao, Bingzi; Wang, Qingyun; Cao, Xiaoyan; Zhang, Jiabao

    2015-01-01

    Chemical composition of soil organic carbon (SOC) is central to soil fertility. We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure. This study examined the effect of fertilization strategies along with the time of fertilizer application on the SOC composition by 13C nuclear magnetic resonance (NMR) spectroscopy. The soils (Aquic Inceptisol) subjected to seven fertilizer treatments were collected in 1989, 1999 and 2009, representing 0, 10 and 20 years of fertilization, respectively. The seven fertilizer treatments were (1-3) balanced fertilization with application of nitrogen (N), phosphorus (P) and potassium (K) including organic compost (OM), half organic compost plus half chemical fertilizer (1/2OM), and pure chemical NPK fertilizer (NPK); (4-6) unbalanced chemical fertilization without application of one of the major elements including NP fertilizer (NP), PK fertilizer (PK), and NK fertilizer (NK); and (7) an unamended control (CK). The SOC content in the balanced fertilization treatments were 2.3-52.6% and 9.4-64.6% higher than in the unbalanced fertilization/CK treatments in 1999 and 2009, respectively, indicating significant differences in SOC content with time of fertilizer application between the two treatment groups. There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009. Principal component analysis further showed that the C functional groups from various fertilization strategies tended to become compositionally similar with time. The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration.

  4. A Regime Diagram for Subduction

    NASA Astrophysics Data System (ADS)

    Stegman, D. R.; Farrington, R.; Capitanio, F. A.; Schellart, W. P.

    2009-12-01

    Regime diagrams and associated scaling relations have profoundly influenced our understanding of planetary dynamics. Previous regime diagrams characterized the regimes of stagnant-lid, small viscosity contrast, transitional, and no-convection for temperature-dependent (Moresi and Solomatov, 1995), and non-linear power law rheologies (Solomatov and Moresi, 1997) as well as stagnant-lid, sluggish-lid, and mobile-lid regimes once the finite strength of rock was considered (Moresi and Solomatov, 1998). Scalings derived from such models have been the cornerstone for parameterized models of thermal evolution of rocky planets and icy moons for the past decade. While such a theory can predict the tectonic state of a planetary body, it is still rather incomplete in regards to predicting tectonics. For example, the mobile-lid regime is unspecific as to how continuous lithospheric recycling should occur on a terrestrial planet. Towards this goal, Gerya et al., (2008) advanced a new regime diagram aiming to characterize when subduction would manifest itself as a one-sided or two-sided downwelling and either symmetric or asymmetric. Here, we present a regime diagram for the case of a single-sided, asymmetric type of subduction (most Earth-like type). Using a 3-D numerical model of a free subduction, we describe a total of 5 different styles of subduction that can possibly occur. Each style is distinguished by its upper mantle slab morphology resulting from the sinking kinematics. We provide movies to illustrate the different styles and their progressive time-evolution. In each regime, subduction is accommodated by a combination of plate advance and slab rollback, with associated motions of forward plate velocity and trench retreat, respectively. We demonstrate that the preferred subduction mode depends upon two essential controlling factors: 1) buoyancy of the downgoing plate and 2) strength of plate in resisting bending at the hinge. We propose that a variety of subduction

  5. Integrated Assessment Modeling of Carbon Sequestration and Land Use Emissions Using Detailed Model Results and Observations

    SciTech Connect

    Dr. Atul Jain

    2005-04-17

    This report outlines the progress on the development and application of Integrated Assessment Modeling of Carbon Sequestrations and Land Use Emissions supported by the DOE Office of Biological and Environmental Research (OBER), U.S. Department of Energy, Grant No. DOE-DE-FG02-01ER63069. The overall objective of this collaborative project between the University of Illinois at Urbana-Champaign (UIUC), Oak Ridge National Laboratory (ORNL), Lawrence Livermore National Laboratory (LLNL), and Pacific Northwest National Laboratory (PNNL) was to unite the latest advances in carbon cycle research with scientifically based models and policy-related integrated assessment tools that incorporate computationally efficient representations of the latest knowledge concerning science and emission trajectories, and their policy implications. As part of this research we accomplished the following tasks that we originally proposed: (1) In coordination with LLNL and ORNL, we enhanced the Integrated Science Assessment Model's (ISAM) parametric representation of the ocean and terrestrial carbon cycles that better represent spatial and seasonal variations, which are important to study the mechanisms that influence carbon sequestration in the ocean and terrestrial ecosystems; (2) Using the MiniCAM modeling capability, we revised the SRES (IPCC Special Report on Emission Scenarios; IPCC, 2000) land use emission scenarios; and (3) On the application front, the enhanced version of ISAM modeling capability is applied to understand how short- and long-term natural carbon fluxes, carbon sequestration, and human emissions contribute to the net global emissions (concentrations) trajectories required to reach various concentration (emission) targets. Under this grant, 21 research publications were produced. In addition, this grant supported a number of graduate and undergraduate students whose fundamental research was to learn a disciplinary field in climate change (e.g., ecological dynamics and

  6. Stable Isotopic Variability in the Carbon Cycle: Reconciling Ocean Model Results with Atmospheric Observations

    NASA Astrophysics Data System (ADS)

    Alden, C. B.; White, J. W.; Miller, J. B.

    2009-12-01

    In the face of rising sea levels, species extinction, unpredictable precipitation changes, and other potential impacts of anthropogenic climate change, there is a push for the scientific community to expand our current understanding of the major sources and sinks of global warming’s most implicated culprit, CO2. Knowing the mechanisms controlling CO2 sinks and sources will be vital for policy-makers to make informed decisions regarding its mitigation. The stable carbon isotope, 13C, can be used to partition CO2 fluxes into land and ocean components. The major fluxes of this gas (fossil fuel, ocean and land) impose distinctive and predictable fractionation patterns upon the stable isotope ratio, making it an ideal tool for distinguishing between them. One drawback to this method is that photosynthesis and respiration are not contemporaneous, and because the 13C of atmospheric CO2 is being continuously depleted through the burning of 12C-rich fossil fuels (the Suess effect), there is an isotopic “disequilibrium flux” between CO2 moving into and out of the ocean and land reservoirs. In this study, we take a new approach and seek to reconcile independent estimates of time histories of ocean fluxes with atmospheric observations. We use a combination of atmospheric CO2 and 13CO2 data, fossil fuel emission estimates, and recent ocean model results (from two different approaches) for the ocean CO2 flux, within a box-inverse model as well as a 2D transport model. We calculate time series of land flux, disequilibrium flux and photosynthetic fractionation from 1991 through 2008. Our findings reveal that if ocean variability is as small as is suggested by the ocean model, and the isotopic variability is forced into the disequilibrium flux, then the resulting disequilibrium flux has very large interannual variability (~35 PgC‰/yr). While large interannual variability in DIS seems incompatible with the Suess effect alone, it could be explained by interannual variations

  7. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N2 and CO2 adsorption isotherms? Simulation results for a realistic carbon model

    NASA Astrophysics Data System (ADS)

    Furmaniak, Sylwester; Terzyk, Artur P.; Gauden, Piotr A.; Harris, Peter J. F.; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N2 and CO2 isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO2, and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions.

  8. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N(2) and CO(2) adsorption isotherms? Simulation results for a realistic carbon model.

    PubMed

    Furmaniak, Sylwester; Terzyk, Artur P; Gauden, Piotr A; Harris, Peter J F; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N(2) and CO(2) isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO(2), and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions. PMID:21828590

  9. Fire regime zonation under current and future climate over eastern Canada.

    PubMed

    Boulanger, Yan; Gauthier, Sylvie; Gray, David R; Le Goff, Héloïse; Lefort, Patrick; Morissette, Jacques

    2013-06-01

    Fire is a major disturbance in Canadian forests. Along with fuel and ignition characteristics, climatic conditions are seen as one of the main drivers of fire regimes. Projected changes in climate are expected to significantly influence fire regimes in Canada. As fire regime greatly shapes large-scale patterns in biodiversity, carbon, and vegetation, as well as forest and fire management strategies, it becomes necessary to define regions where current and future fire regimes are homogeneous. Random Forests (RF) modeling was used to relate fire regime attributes prevailing between 1961 and 1990 in eastern Canada with climatic/fire-weather and environmental variables. Using climatic normals outputs from the Canadian Regional Climate Model (CRCM), we delineated current (1961-1990) and future (2011-2040, 2040-2070, 2071 2100) homogeneous fire regime (HFR) zones. Heterogeneous response of fire regime to climate changes is projected for eastern Canada with some areas (e.g., western Quebec) experiencing very small alterations while others (e.g., southeastern Ontario) are facing great shifts. Overall, models predicted a 2.2- and 2.4-fold increase in the number of fires and the annual area burned respectively mostly as a result of an increase in extreme fire-weather normals and mean drought code. As extreme fire danger would occur later in the fire season on average, the fire season would shift slightly later (5-20 days) in the summer for much of the study area while remaining relatively stable elsewhere. Although fire regime values would change significantly over time, most zone boundaries would remain relatively stable. The information resulting from HFR zonations is clearly of interest for forest and fire management agencies as it reveals zones with peculiar fire regimes that would have been hidden otherwise using predefined administrative or ecological stratifications.

  10. Soil carbon sequestration resulting from long-term application of biosolids for land reclamation.

    PubMed

    Tian, G; Granato, T C; Cox, A E; Pietz, R I; Carlson, C R; Abedin, Z

    2009-01-01

    Investigations on the impact of application of biosolids for land reclamation on C sequestration in soil were conducted at Fulton County, Illinois, where 41 fields (3.6-66 ha) received biosolids at a cumulative loading rate from 455 to 1654 dry Mg ha(-1) for 8 to 23 yr in rotation from 1972 to 2004. The fields were cropped with corn, wheat, and sorghum and also with soybean and grass or fallowed. Soil organic carbon (SOC) increased rapidly with the application of biosolids, whereas it fluctuated slightly in fertilizer controls. The peak SOC in the 0- to 15-cm depth of biosolids-amended fields ranged from 4 to 7% and was greater at higher rates of biosolids. In fields where biosolids application ceased for 22 yr, SOC was still much higher than the initial levels. Over the 34-yr reclamation, the mean net soil C sequestration was 1.73 (0.54-3.05) Mg C ha(-1) yr(-1) in biosolids-amended fields as compared with -0.07 to 0.17 Mg C ha(-1) yr(-1) in fertilizer controls, demonstrating a high potential of soil C sequestration by the land application of biosolids. Soil C sequestration was significantly correlated with the biosolids application rate, and the equation can be expressed as y = 0.064x - 0.11, in which y is the annual net soil C sequestration (Mg C ha(-1) yr(-1)), and x is annual biosolids application in dry weight (Mg ha(-1) yr(-1)). Our results indicate that biosolids applications can turn Midwest Corn Belt soils from current C-neutral to C-sink. A method for calculating SOC stock under conditions in which surface soil layer depth and mass changes is also described.

  11. Thermostructural Analysis of Carbon Cloth Phenolics "Ply Lifting" and Correlation to LHMEL Test Results

    NASA Technical Reports Server (NTRS)

    Clayton, Louie

    2004-01-01

    This paper provides a discussion of the history of Carbon Cloth Phenolic (CCP) ply lifting in the Redesigned Solid Rocket Motor (RSRM) Program, a brief presentation of theoretical methods used for analytical evaluation, and results of parametric analyses of CCP material subject to test conditions of the Laser Hardened Material Evaluation Laboratory. CCP ply lift can occur in regions of the RSRM nozzle where ply angle to flame surface is generally less than about 20 degrees. There is a heat rate dependence on likelihood and severity of the condition with the higher heating rates generally producing more ply lift. The event occurs in-depth, near the heated surface, where the load necessary to mechanically separate the CCP plies is produced by the initial stages of pyrolysis gas generation due to the thermal decomposition of the phenolic resin matrix. Due to the shallow lay-up angle of the composite, normal components of the indepth mechanical load, due to "pore pressure", are imparted primarily as a cross-ply tensile force on the interlaminar ply boundaries. Tensile capability in the cross-ply (out of plane) direction is solely determined by the matrix material capability. The elevated temperature matrix material capabilities are overcome by pressure induced mechanical normal stress and ply-lift occurs. A theoretical model used for CCP in-depth temperature, pressure, and normal stress prediction, based on first principles, is briefly discussed followed by a parametric evaluation of response variables subject to boundary conditions typical of on-going test programs at the LHMEL facility. Model response demonstrates general trends observed in test and provides insight into the interactivity of material properties and constitutive relationships.

  12. Development of bond-length alternation in very large carbon rings: LDA pseudopotential results

    NASA Astrophysics Data System (ADS)

    Bylaska, Eric J.; Weare, John H.; Kawai, Ryoichi

    1998-09-01

    Carbon rings Cn and infinite chains C∞ are investigated by molecular-orbital and band-structure calculations within the local-density approximation. Carbon rings C4N (N<=8) exhibit a substantial first-order Jahn-Teller distortion that leads to long/short (single/triple) bond alternation decreasing with increasing N. Rings C4N+2 show no alternation (i.e., aromatic behavior is retained) until very large sizes (N>=20). For the infinite carbon chain uniform Brillouin-zone sampling with an even number of points Ns gives bond alternation. An odd number of sampling points gives no bond alternation for less than Ns=41. In the large Ns limit even and odd sampling lead to an upper and lower bound of 0.070a0 and 0.065a0 for bond alternation and 0.021-0.090 millihartrees/atom for condensation energy.

  13. Is polyphenol induction simply a result of altered carbon and nitrogen accumulation?

    PubMed

    Arnold, Thomas M; Appel, Heidi M; Schultz, Jack C

    2012-11-01

    Carbon translocation in plants is shaped by phyllotaxis and regulated by source/sink interactions that respond to the demands of growth and defense. We have studied this extensively in poplar saplings, and recently showed that unlike carbon import, nitrogen is not translocated to sink leaves in response to application of jasmonic acid. Here we report that this is also true for young trees in the field. We discuss the importance of transport processes in establishing local C:N ratios, and suggest that the JA-induced flow of C but not N to sink tissues, and their corresponding increases in C-based defenses, may simply reflect a plant adaptation to handle excess reduced carbon and energy.

  14. Is polyphenol induction simply a result of altered carbon and nitrogen accumulation?

    PubMed Central

    Arnold, Thomas M.; Appel, Heidi M.; Schultz, Jack C.

    2012-01-01

    Carbon translocation in plants is shaped by phyllotaxis and regulated by source/sink interactions that respond to the demands of growth and defense. We have studied this extensively in poplar saplings, and recently showed that unlike carbon import, nitrogen is not translocated to sink leaves in response to application of jasmonic acid. Here we report that this is also true for young trees in the field. We discuss the importance of transport processes in establishing local C:N ratios, and suggest that the JA-induced flow of C but not N to sink tissues, and their corresponding increases in C-based defenses, may simply reflect a plant adaptation to handle excess reduced carbon and energy. PMID:22960757

  15. 78 FR 70533 - Certain Activated Carbon From the People's Republic of China: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-26

    ...; 2011-2012, 78 FR 26748 (May 8, 2013) (``Preliminary Results''). DATES: Effective Date: November 26....\\12\\ \\2\\ See id. \\3\\ See id., 78 FR at 26749. \\4\\ See Memorandum to Christian Marsh, Deputy Assistant... Results, 78 FR at 26749; see also Notice of Antidumping Duty Order: Certain Activated Carbon from...

  16. 77 FR 67337 - Certain Activated Carbon From the People's Republic of China; 2010-2011; Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-09

    ... Fourth Antidumping Duty Administrative Review, and Intent To Rescind in Part, 77 FR 26496 (May 4, 2012... of Antidumping Duty Order: Certain Activated Carbon from the People's Republic of China, 72 FR 20988... Preliminary Results, 77 FR at 26498. Changes Since the Preliminary Results Based on a review of the record...

  17. 75 FR 69626 - Certain Welded Carbon Steel Standard Pipes and Tubes From India: Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-15

    ... Carbon Steel Standard Pipes and Tubes from India, 51 FR 17384 (May 12, 1986). These deposit requirements... Antidumping Duty Administrative Review, 75 FR 33578 (June 14, 2010) (Preliminary Results). The administrative... Final Results of Antidumping Duty Administrative Review, 75 FR 63439 (October 15, 2010). We...

  18. Regime Shifts in the Anthropocene: Drivers, Risks, and Resilience

    PubMed Central

    Rocha, Juan Carlos; Peterson, Garry D.; Biggs, Reinette

    2015-01-01

    Many ecosystems can experience regime shifts: surprising, large and persistent changes in the function and structure of ecosystems. Assessing whether continued global change will lead to further regime shifts, or has the potential to trigger cascading regime shifts has been a central question in global change policy. Addressing this issue has, however, been hampered by the focus of regime shift research on specific cases and types of regime shifts. To systematically assess the global risk of regime shifts we conducted a comparative analysis of 25 generic types of regime shifts across marine, terrestrial and polar systems; identifying their drivers, and impacts on ecosystem services. Our results show that the drivers of regime shifts are diverse and co-occur strongly, which suggests that continued global change can be expected to synchronously increase the risk of multiple regime shifts. Furthermore, many regime shift drivers are related to climate change and food production, whose links to the continued expansion of human activities makes them difficult to limit. Because many regime shifts can amplify the drivers of other regime shifts, continued global change can also be expected to increase the risk of cascading regime shifts. Nevertheless, the variety of scales at which regime shift drivers operate provides opportunities for reducing the risk of many types of regime shifts by addressing local or regional drivers, even in the absence of rapid reduction of global drivers. PMID:26267896

  19. Regime shifts in the anthropocene: drivers, risks, and resilience.

    PubMed

    Rocha, Juan Carlos; Peterson, Garry D; Biggs, Reinette

    2015-01-01

    Many ecosystems can experience regime shifts: surprising, large and persistent changes in the function and structure of ecosystems. Assessing whether continued global change will lead to further regime shifts, or has the potential to trigger cascading regime shifts has been a central question in global change policy. Addressing this issue has, however, been hampered by the focus of regime shift research on specific cases and types of regime shifts. To systematically assess the global risk of regime shifts we conducted a comparative analysis of 25 generic types of regime shifts across marine, terrestrial and polar systems; identifying their drivers, and impacts on ecosystem services. Our results show that the drivers of regime shifts are diverse and co-occur strongly, which suggests that continued global change can be expected to synchronously increase the risk of multiple regime shifts. Furthermore, many regime shift drivers are related to climate change and food production, whose links to the continued expansion of human activities makes them difficult to limit. Because many regime shifts can amplify the drivers of other regime shifts, continued global change can also be expected to increase the risk of cascading regime shifts. Nevertheless, the variety of scales at which regime shift drivers operate provides opportunities for reducing the risk of many types of regime shifts by addressing local or regional drivers, even in the absence of rapid reduction of global drivers.

  20. Regime shifts in the anthropocene: drivers, risks, and resilience.

    PubMed

    Rocha, Juan Carlos; Peterson, Garry D; Biggs, Reinette

    2015-01-01

    Many ecosystems can experience regime shifts: surprising, large and persistent changes in the function and structure of ecosystems. Assessing whether continued global change will lead to further regime shifts, or has the potential to trigger cascading regime shifts has been a central question in global change policy. Addressing this issue has, however, been hampered by the focus of regime shift research on specific cases and types of regime shifts. To systematically assess the global risk of regime shifts we conducted a comparative analysis of 25 generic types of regime shifts across marine, terrestrial and polar systems; identifying their drivers, and impacts on ecosystem services. Our results show that the drivers of regime shifts are diverse and co-occur strongly, which suggests that continued global change can be expected to synchronously increase the risk of multiple regime shifts. Furthermore, many regime shift drivers are related to climate change and food production, whose links to the continued expansion of human activities makes them difficult to limit. Because many regime shifts can amplify the drivers of other regime shifts, continued global change can also be expected to increase the risk of cascading regime shifts. Nevertheless, the variety of scales at which regime shift drivers operate provides opportunities for reducing the risk of many types of regime shifts by addressing local or regional drivers, even in the absence of rapid reduction of global drivers. PMID:26267896

  1. 78 FR 26748 - Certain Activated Carbon From the People's Republic of China: Preliminary Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-08

    ... Notice of Antidumping Duty Order: Certain Activated Carbon from the People's Republic of China, 72 FR... of Antidumping and Countervailing Duty Orders, 77 FR 29875 (May 21, 2012). Reference to 19 CFR 351... Administrative Review, 75 FR 70208, 70211 (November 17, 2010). \\6\\ In the third administrative review,...

  2. 78 FR 34340 - Welded Carbon Steel Standard Pipe and Tube Products From Turkey: Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-07

    ... for Revocation in Part, 77 FR 40565 (July 10, 2012). \\3\\ The Department initiated a review on the... Order; Welded Carbon Steel Standard Pipe and Tube Products from Turkey, 51 FR 17784 (May 15, 1986). The... clarification, see Antidumping and Countervailing Duty Proceedings: Assessment of Antidumping Duties, 68...

  3. 75 FR 70208 - Certain Activated Carbon From the People's Republic of China: Final Results and Partial...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-17

    ... Second Antidumping Duty Administrative Review, and Preliminary Rescission in Part, 75 FR 26927 (May 13... review was requested. See Initiation of Antidumping and Countervailing Duty Administrative Reviews, 74 FR... Administrative Review, 74 FR 31690 (July 2, 2009). \\3\\ See Certain Activated Carbon From the People's Republic...

  4. 75 FR 18788 - Circular Welded Carbon Steel Pipes and Tubes from Thailand: Preliminary Results and Rescission...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-13

    ...: Circular Welded Carbon Steel Pipes and Tubes from Thailand, 51 FR 8341 (March 11, 1986). On March 2, 2009..., Finding or Suspended Investigation; Opportunity to Request Administrative Review, 74 FR 9077 (March 2... Reviews and Request for Revocation in Part, 74 FR 19042 (April 27, 2009). On May 5, 2009, Pacific...

  5. 78 FR 34335 - Certain Circular Welded Carbon Steel Pipes and Tubes From Taiwan: Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-07

    ... Steel Pipes and Tubes From Taiwan: Antidumping Duty Order, 49 FR 19369 (May 7, 1984). These cash deposit... of Antidumping Duties, 68 FR 23954 (May 6, 2003). Cash Deposit Requirements The following cash... International Trade Administration Certain Circular Welded Carbon Steel Pipes and Tubes From Taiwan:...

  6. 77 FR 20782 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Preliminary Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-06

    ... Pipes and Tubes from Thailand, 51 FR 8341 (March 11, 1986). On March 1, 2011, the Department published a... investigation. See Antidumping Duty Order: Circular Welded Carbon Steel Pipes and Tubes From Thailand, 51 FR... Duty Order, Finding, or Suspended Investigation; Opportunity to Request Administrative Review, 76...

  7. Regimes of DNA confined in a nanochannel

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Doyle, Patrick

    2014-03-01

    Scaling regimes for polymers confined to tubular channels are well established when the channel cross-sectional dimension is either very small (Odjik regime) or large (classic de Gennes regime) relative to the polymer Kuhn length. In the literature, there is no clear consensus regarding the intermediate region and if subregimes even exist to connect these two classic bounding regimes. The confluence of emerging single DNA mapping technologies and a resurged interest in the fundamental properties of confined polymers has led to extensive research in this area using DNA as a model system. Due to the DNA molecule's properties and limitations of nanofabrication, most experiments are performed in this intermediate regime with channel dimensions of a few Kuhn lengths. Here we use simulations and theory to reconcile conflicting theories and show that there are indeed extended de Gennes, partial alignment and hairpin regimes located between the two classic regimes. Simulations results for both chain extension and free energy support the existence of these regimes. This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's research program in BioSystems and Micromechanics, the National Science Foundation (CBET-1335938).

  8. Modeling of the Ablation of Fibrous Materials in the Knudsen Regime

    NASA Technical Reports Server (NTRS)

    Lachaud, J.; Mansour, N. N.

    2008-01-01

    During atmospheric entry of planetary probes, the thermal protection system (TPS) of the probe is exposed to high temperatures under low pressures. In these conditions, carbonous TPS materials undergo gasification in the Knudsen regime leading to mass loss and wall recession called ablation. This work aims to improve the understanding of materiaVenvironment interactions through a study of the coupling between carbon dioxide transport in the Knudsen regime, heterogeneous oxidation of carbon, and sutface recession. A 3D Monte-Carlo simulation tool is used for this study. The fibrous architecture of the materiils, consisting of high porosity random array of carbon fibers, is numerically reproduced on a 3D Cartesian grid. Mass transport in the Knudsen regime from the boundary layer to the surface, and inside this porous material is simulated by random walk. A reaction probability is used to simulate the heterogeneous oxidation reaction. The surface recession is followed by front tracking using a simplified marching cube approach. The output data of the simulations are ablation velocity and dynamic evolution of the material porosity. A parametric study is carried out to analyze the material behavior as a function of Knudsen number for the porous media (length of the mean free path compared to the mean pore diameter) and the intrinsic reactivity of the carbon fibers. The results enable extrapolation of laboratory experimental data to actual entry conditions.

  9. Net Carbon Emissions from Deforestation in Bolivia during 1990-2000 and 2000-2010: Results from a Carbon Bookkeeping Model.

    PubMed

    Andersen, Lykke E; Doyle, Anna Sophia; del Granado, Susana; Ledezma, Juan Carlos; Medinaceli, Agnes; Valdivia, Montserrat; Weinhold, Diana

    2016-01-01

    Accurate estimates of global carbon emissions are critical for understanding global warming. This paper estimates net carbon emissions from land use change in Bolivia during the periods 1990-2000 and 2000-2010 using a model that takes into account deforestation, forest degradation, forest regrowth, gradual carbon decomposition and accumulation, as well as heterogeneity in both above ground and below ground carbon contents at the 10 by 10 km grid level. The approach permits detailed maps of net emissions by region and type of land cover. We estimate that net CO2 emissions from land use change in Bolivia increased from about 65 million tons per year during 1990-2000 to about 93 million tons per year during 2000-2010, while CO2 emissions per capita and per unit of GDP have remained fairly stable over the sample period. If we allow for estimated biomass increases in mature forests, net CO2 emissions drop to close to zero. Finally, we find these results are robust to alternative methods of calculating emissions. PMID:26990865

  10. Net Carbon Emissions from Deforestation in Bolivia during 1990-2000 and 2000-2010: Results from a Carbon Bookkeeping Model

    PubMed Central

    Andersen, Lykke E.; Doyle, Anna Sophia; del Granado, Susana; Ledezma, Juan Carlos; Medinaceli, Agnes; Valdivia, Montserrat; Weinhold, Diana

    2016-01-01

    Accurate estimates of global carbon emissions are critical for understanding global warming. This paper estimates net carbon emissions from land use change in Bolivia during the periods 1990–2000 and 2000–2010 using a model that takes into account deforestation, forest degradation, forest regrowth, gradual carbon decomposition and accumulation, as well as heterogeneity in both above ground and below ground carbon contents at the 10 by 10 km grid level. The approach permits detailed maps of net emissions by region and type of land cover. We estimate that net CO2 emissions from land use change in Bolivia increased from about 65 million tons per year during 1990–2000 to about 93 million tons per year during 2000–2010, while CO2 emissions per capita and per unit of GDP have remained fairly stable over the sample period. If we allow for estimated biomass increases in mature forests, net CO2 emissions drop to close to zero. Finally, we find these results are robust to alternative methods of calculating emissions. PMID:26990865

  11. Net Carbon Emissions from Deforestation in Bolivia during 1990-2000 and 2000-2010: Results from a Carbon Bookkeeping Model.

    PubMed

    Andersen, Lykke E; Doyle, Anna Sophia; del Granado, Susana; Ledezma, Juan Carlos; Medinaceli, Agnes; Valdivia, Montserrat; Weinhold, Diana

    2016-01-01

    Accurate estimates of global carbon emissions are critical for understanding global warming. This paper estimates net carbon emissions from land use change in Bolivia during the periods 1990-2000 and 2000-2010 using a model that takes into account deforestation, forest degradation, forest regrowth, gradual carbon decomposition and accumulation, as well as heterogeneity in both above ground and below ground carbon contents at the 10 by 10 km grid level. The approach permits detailed maps of net emissions by region and type of land cover. We estimate that net CO2 emissions from land use change in Bolivia increased from about 65 million tons per year during 1990-2000 to about 93 million tons per year during 2000-2010, while CO2 emissions per capita and per unit of GDP have remained fairly stable over the sample period. If we allow for estimated biomass increases in mature forests, net CO2 emissions drop to close to zero. Finally, we find these results are robust to alternative methods of calculating emissions.

  12. JPL Carbon Dioxide Laser Absorption Spectrometer Data Processing Results for the 2010 Flight Campaign

    NASA Technical Reports Server (NTRS)

    Jacob, Joseph C.; Spiers, Gary D.; Menzie, Robert T.; Christensen, Lance E.

    2011-01-01

    As a precursor to and validation of the core technology necessary for NASA's Active Sensing of CO2 Emissions over Nights, Days,and Seasons (ASCENDS) mission, we flew JPL's Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) in a campaign of five flights onboard NASA's DC-8 Airborne Laboratory in July 2010. This is the latest in a series of annual flight campaigns that began in 2006, and our first on the DC-8 aircraft.

  13. Carbon isotope analysis of conodont organic material--Procedure and preliminary results

    SciTech Connect

    Over, D.J. . Dept. of Geological Sciences); Grossman, E.L. )

    1992-01-01

    Conodonts, the phosphatic microfossil remains of an extinct pelagic animal, are well suited for isotopic studies of Paleozoic marine organic carbon. The author report here what they believe are the first delta C-13 data for the organic matrix of conodont elements. Conodont delta C-13 values (PDB) for Upper Devonian Palmatolepis platform elements from a single interval of the Chappel Limestones in Texas range from [minus]24.5 to [minus]25.6 [per thousand] (n = 5). Lower Carboniferous Siphonodella platform elements from the same interval in the Chappel Limestone range from [minus]26.3 to [minus]27.3 [per thousand] (n = 2). Upper Carboniferous Streptognathodus elegantulus platform elements from four intervals in a 3.9 m section of the Necessity Shale in Texas range from [minus]23.0 to [minus]24.0 [per thousand] (n = 4). delta C-13 values also differ significantly between the three sample groups. Average values were [minus]4.7, [minus]7.1, and [minus]8.3 [per thousand] respectively, however, the relevance of these values is unclear. The conodont organic carbon isotopic values are within the range of delta C-13 values in sedimentary organic matter of late Paleozoic age. Although the data are limited, they show that significant isotopic differences occur between genera and between stratigraphically separate units. These isotopic differences in delta C-13 may be related to local changes in source of organic carbon, global changes in the carbon budget, or to dietary differences among conodont animals. Future study is directed toward evaluating the importance of each of these factors.

  14. Results.

    ERIC Educational Resources Information Center

    Zemsky, Robert; Shaman, Susan; Shapiro, Daniel B.

    2001-01-01

    Describes the Collegiate Results Instrument (CRI), which measures a range of collegiate outcomes for alumni 6 years after graduation. The CRI was designed to target alumni from institutions across market segments and assess their values, abilities, work skills, occupations, and pursuit of lifelong learning. (EV)

  15. CO2 release due to impact devolatilization of carbonate: Results of shock experiments

    NASA Astrophysics Data System (ADS)

    Bell, Mary Sue

    2016-04-01

    A study of pure, single crystal calcite shocked to pressures from 9.0 to 60.8 GPa was conducted to address contradictory data for carbonate shock behavior. The recovered materials were analyzed optically and by transmission electron microscopy (TEM), as well as by thermogravimetry (TGA), X-ray diffraction (XRD), and Raman-spectroscopy. In thin section, progressive comminution of calcite is observed although grains remain birefringent to at least 60.8 GPa. TGA analysis reveals a positive correlation between percent of mass loss due to shock and increasing shock pressure (R = 0.77) and suggests that shock loading leads to the modest removal of structural volatiles in this pressure range. XRD patterns of shocked Iceland spar samples produce peaks that are qualitatively and quantitatively less intense, more diffuse, and shift to lower o2θ. However, the regularity observed in these shocked powder patterns suggests that structures with very uniform unit cell separations persist to shock pressures as high as 60.8 GPa. Raman spectral analyses indicate no band asymmetry and no systematic peak shifting or broadening. TEM micrographs display progressively diminishing crystallite domain sizes. Selected area electron diffraction (SAED) patterns reveal no signatures of amorphous material. These data show that essentially intact calcite is recovered at shock pressures up to 60.8 GPa with only slight mass loss (~7%). This work suggests that the amount of CO2 gas derived from shock devolatilization of carbonate by large meteorite impacts into carbonate targets has been (substantially) overestimated.

  16. Radiative forcing associated with particulate carbon emissions resulting from the use of mercury control technology.

    PubMed

    Lin, Guangxing; Penner, Joyce E; Clack, Herek L

    2014-09-01

    Injection of powdered activated carbon (PAC) adsorbents into the flue gas of coal fired power plants with electrostatic precipitators (ESPs) is the most mature technology to control mercury emissions for coal combustion. However, the PAC itself can penetrate ESPs to emit into the atmosphere. These emitted PACs have similar size and optical properties to submicron black carbon (BC) and thus could increase BC radiative forcing unintentionally. The present paper estimates, for the first time, the potential emission of PAC together with their climate forcing. The global average maximum potential emissions of PAC is 98.4 Gg/yr for the year 2030, arising from the assumed adoption of the maximum potential PAC injection technology, the minimum collection efficiency, and the maximum PAC injection rate. These emissions cause a global warming of 2.10 mW m(-2) at the top of atmosphere and a cooling of -2.96 mW m(-2) at the surface. This warming represents about 2% of the warming that is caused by BC from direct fossil fuel burning and 0.86% of the warming associated with CO2 emissions from coal burning in power plants. Its warming is 8 times more efficient than the emitted CO2 as measured by the 20-year-integrated radiative forcing per unit of carbon input (the 20-year Global Warming Potential).

  17. Radiative forcing associated with particulate carbon emissions resulting from the use of mercury control technology.

    PubMed

    Lin, Guangxing; Penner, Joyce E; Clack, Herek L

    2014-09-01

    Injection of powdered activated carbon (PAC) adsorbents into the flue gas of coal fired power plants with electrostatic precipitators (ESPs) is the most mature technology to control mercury emissions for coal combustion. However, the PAC itself can penetrate ESPs to emit into the atmosphere. These emitted PACs have similar size and optical properties to submicron black carbon (BC) and thus could increase BC radiative forcing unintentionally. The present paper estimates, for the first time, the potential emission of PAC together with their climate forcing. The global average maximum potential emissions of PAC is 98.4 Gg/yr for the year 2030, arising from the assumed adoption of the maximum potential PAC injection technology, the minimum collection efficiency, and the maximum PAC injection rate. These emissions cause a global warming of 2.10 mW m(-2) at the top of atmosphere and a cooling of -2.96 mW m(-2) at the surface. This warming represents about 2% of the warming that is caused by BC from direct fossil fuel burning and 0.86% of the warming associated with CO2 emissions from coal burning in power plants. Its warming is 8 times more efficient than the emitted CO2 as measured by the 20-year-integrated radiative forcing per unit of carbon input (the 20-year Global Warming Potential). PMID:25093939

  18. 75 FR 43488 - Certain Hot-Rolled Carbon Steel Flat Products From India: Final Results of Countervailing Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-26

    ... Hot-Rolled Carbon Steel Flat Products from India, 66 FR 60198 (December 3, 2001). On February 2, 2009...; 75 FR 1495 (January 11, 2010) (Preliminary Results). We preliminarily found that Tata Steel Limited... Countervailing Duty Administrative Reviews and Requests for Revocation in Part, 74 FR 5821 (February 2,...

  19. 78 FR 60850 - Carbon and Certain Alloy Steel Wire Rod From Brazil: Final Results of the Expedited Second Sunset...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-02

    ... Alloy Steel Wire Rod from Brazil, 67 FR 55805 (August 30, 2002). \\2\\ See Initiation of Five-Year... Industries, Inc., DBA Cascade Steel Rolling Mills, Inc., Evraz Rocky Mountain Steel, Gerdau Ameristeel US Inc... International Trade Administration Carbon and Certain Alloy Steel Wire Rod From Brazil: Final Results of...

  20. 77 FR 13545 - Carbon and Certain Alloy Steel Wire Rod From Mexico: Notice of Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-07

    ... Antidumping Duty Administrative Review 76 FR 67407 (November 1, 2011) (Preliminary Results). \\2\\ We determined... Changed Circumstances Review: Carbon and Certain Alloy Steel Wire Rod from Mexico, 76 FR 45509 (July 29...) high nickel steel; (d) ball bearing steel; and (e) concrete reinforcing bars and rods. Also...

  1. 75 FR 64254 - Certain Hot-Rolled Flat-Rolled Carbon Quality Steel Products From Brazil; Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-19

    ... Antidumping Duty Administrative Review and Extension of Time Limit for the Final Results, 75 FR 19369 (April... Carbon-Quality Steel Products from the Russian Federation, 65 FR 5510, 5518 (February 4, 2000) (Russian...: Assessment of Antidumping Duties, 68 FR 23954 (May 6, 2003). This clarification will apply to entries...

  2. 75 FR 73033 - Circular Welded Carbon Steel Pipes and Tubes from Thailand: Amended Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-29

    ... Carbon Steel Pipes and Tubes From Thailand: Final Determination of Sales at Less Than Fair Value, 51 FR... Thailand: Final Results of Antidumping Duty Administrative Review, 75 FR 64696 (October 20, 2010). The... clarification, see Antidumping and Countervailing Duty Proceedings: Assessment of Antidumping Duties, 68...

  3. Fracture trace map and single-well aquifer test results in a carbonate aquifer in Berkeley County, West Virginia

    USGS Publications Warehouse

    McCoy, Kurt J.; Podwysocki, Melvin H.; Crider, E. Allen; Weary, David J.

    2005-01-01

    These data contain information on the results of single-well aquifer tests, lineament analysis, and a bedrock geologic map compilation for the low-lying carbonate and shale areas of eastern Berkeley County, West Virginia. Efforts have been initiated by management agencies of Berkeley County in cooperation with the U.S. Geological Survey to further the understanding of the spatial distribution of fractures in the carbonate regions and their correlation with aquifer properties. This report presents transmissivity values from about 200 single-well aquifer tests and a map of fracture-traces determined from aerial photos and field investigations. Transmissivity values were compared to geologic factors possibly affecting its magnitude.

  4. Carbon, oxygen and biological productivity in the Southern Ocean in and out the Kerguelen plume: CARIOCA drifter results

    NASA Astrophysics Data System (ADS)

    Merlivat, L.; Boutin, J.; d'Ovidio, F.

    2015-06-01

    The Kerguelen Plateau region in the Indian sector of the Southern Ocean supports annually a large-scale phytoplankton bloom which is naturally fertilized with iron. As part of the second Kerguelen Ocean and Plateau compared Study expedition (KEOPS2) in austral spring (October-November 2011), one CARbon Interface OCean Atmosphere (CARIOCA) buoy was deployed east of the Kerguelen Plateau. It drifted eastward downstream along the Kerguelen plume. Hourly surface measurements of pCO2, O2 and ancillary observations were collected between 1 November 2011 and 12 February 2012 with the aim of characterizing the spatial and temporal variability of the biological net community production, NCP, downstream the Kerguelen Plateau, assessing the impact of iron-induced productivity on the biological inorganic carbon consumption and consequently on the CO2 flux exchanged at the air-sea interface. The trajectory of the buoy up to mid-December was within the longitude range 72-83° E, close to the polar front and then in the polar frontal zone, PFZ, up to 97° E. From 17 November to 16 December, the buoy drifted within the Kerguelen plume following a filament carrying dissolved iron, DFe, for a total distance of 700 km. In the first part of the trajectory of the buoy, within the iron plume, the ocean surface waters were always a sink for CO2 and a source for O2, with fluxes of respective mean values equal to -8 mmol CO2 and +38 mmol O2 m-2 d-1. To the east, as the buoy escaped the iron-enriched filament, the fluxes were in the opposite direction, with respective mean values of +5 mmol CO2 and -48 mmol O2 m-2 d-1. These numbers clearly indicate the strong impact of biological processes on the biogeochemistry in the surface waters within the Kerguelen plume in November-mid-December, while it is undetectable to the east in the PFZ from mid- December to mid-February. While the buoy follows the Fe-enriched filament, simultaneous observations of dissolved inorganic carbon (DIC) and

  5. He-accreting white dwarfs: accretion regimes and final outcomes

    NASA Astrophysics Data System (ADS)

    Piersanti, L.; Tornambé, A.; Yungelson, L. R.

    2014-12-01

    The behaviour of carbon-oxygen (CO) white dwarfs (WDs) subject to direct helium accretion is extensively studied. We aim to analyse the thermal response of an accreting WD to mass deposition at different timescales. The analysis has been performed for initial WD masses and accretion rates in the range 0.60-1.02 M⊙ and 10-9-10-5 M⊙ yr-1, respectively. Thermal regimes in the parameter space MWD-dot{M}_He leading to formation of red-giant-like structures, steady burning of He, and mild, strong and dynamical flashes have been identified and the transition between these regimes has been studied in detail. In particular, the physical properties of WDs experiencing the He-flash accretion regime have been investigated to determine the mass retention efficiency as a function of the accretor total mass and accretion rate. We also discuss to what extent the building up of a He-rich layer via H burning could be described according to the behaviour of models accreting He-rich matter directly. Polynomial fits to the obtained results are provided for use in binary population synthesis computations. Several applications for close binary systems with He-rich donors and CO WD accretors are considered and the relevance of the results for interpreting He novae is discussed.

  6. Changes in mineralogical and leaching properties of converter steel slag resulting from accelerated carbonation at low CO2 pressure.

    PubMed

    van Zomeren, André; van der Laan, Sieger R; Kobesen, Hans B A; Huijgen, Wouter J J; Comans, Rob N J

    2011-11-01

    Steel slag can be applied as substitute for natural aggregates in construction applications. The material imposes a high pH (typically 12.5) and low redox potential (Eh), which may lead to environmental problems in specific application scenarios. The aim of this study is to investigate the potential of accelerated steel slag carbonation, at relatively low pCO2 pressure (0.2 bar), to improve the environmental pH and the leaching properties of steel slag, with specific focus on the leaching of vanadium. Carbonation experiments are performed in laboratory columns with steel slag under water-saturated and -unsaturated conditions and temperatures between 5 and 90 °C. Two types of steel slag are tested; free lime containing (K3) slag and K1 slag with a very low free lime content. The fresh and carbonated slag samples are investigated using a combination of leaching experiments, geochemical modelling of leaching mechanisms and microscopic/mineralogical analysis, in order to identify the major processes that control the slag pH and resulting V leaching. The major changes in the amount of sequestered CO2 and the resulting pH reduction occurred within 24h, the free lime containing slag (K3-slag) being more prone to carbonation than the slag with lower free lime content (K1-slag). While carbonation at these conditions was found to occur predominantly at the surface of the slag grains, the formation of cracks was observed in carbonated K3 slag, suggesting that free lime in the interior of slag grains had also reacted. The pH of the K3 slag (originally pH±12.5) was reduced by about 1.5 units, while the K1 slag showed a smaller decrease in pH from about 11.7 to 11.1. However, the pH reduction after carbonation of the K3 slag was observed to lead to an increased V-leaching. Vanadium leaching from the K1 slag resulted in levels above the limit values of the Dutch Soil Quality Decree, for both the untreated and carbonated slag. V-leaching from the carbonated K3 slag remained

  7. Dynamic Treatment Regimes

    PubMed Central

    Chakraborty, Bibhas; Murphy, Susan A.

    2014-01-01

    A dynamic treatment regime consists of a sequence of decision rules, one per stage of intervention, that dictate how to individualize treatments to patients based on evolving treatment and covariate history. These regimes are particularly useful for managing chronic disorders, and fit well into the larger paradigm of personalized medicine. They provide one way to operationalize a clinical decision support system. Statistics plays a key role in the construction of evidence-based dynamic treatment regimes – informing best study design as well as efficient estimation and valid inference. Due to the many novel methodological challenges it offers, this area has been growing in popularity among statisticians in recent years. In this article, we review the key developments in this exciting field of research. In particular, we discuss the sequential multiple assignment randomized trial designs, estimation techniques like Q-learning and marginal structural models, and several inference techniques designed to address the associated non-standard asymptotics. We reference software, whenever available. We also outline some important future directions. PMID:25401119

  8. The measurement results of carbon ion beam structure extracted by bent crystal from U-70 accelerator

    NASA Astrophysics Data System (ADS)

    Afonin, A. G.; Barnov, E. V.; Britvich, G. I.; Chesnokov, Yu A.; Chirkov, P. N.; Durum, A. A.; Kostin, M. Yu; Maisheev, V. A.; Pitalev, V. I.; Reshetnikov, S. F.; Yanovich, A. A.; Nazhmudinov, R. M.; Kubankin, A. S.; Shchagin, A. V.

    2016-07-01

    The carbon ion +6C beam with energy 25 GeV/nucleon was extracted by bent crystal from the U-70 ring. The bent angle of silicon crystal was 85 mrad. About 2×105 particles for 109 circulated ions in the ring were observed in beam line 4a after bent crystal. Geometrical parameters, time structure and ion beam structure were measured. The ability of the bent monocrystal to extract and generate ion beam with necessary parameters for regular usage in physical experiments is shown in the first time.

  9. Health effects of carbon-containing particulate matter: focus on sources and recent research program results.

    PubMed

    Rohr, Annette; McDonald, Jacob

    2016-02-01

    Air pollution is a complex mixture of gas-, vapor-, and particulate-phase materials comprised of inorganic and organic species. Many of these components have been associated with adverse health effects in epidemiological and toxicological studies, including a broad spectrum of carbonaceous atmospheric components. This paper reviews recent literature on the health impacts of organic aerosols, with a focus on specific sources of organic material; it is not intended to be a comprehensive review of all the available literature. Specific emission sources reviewed include engine emissions, wood/biomass combustion emissions, biogenic emissions and secondary organic aerosol (SOA), resuspended road dust, tire and brake wear, and cooking emissions. In addition, recent findings from large toxicological and epidemiological research programs are reviewed in the context of organic PM, including SPHERES, NPACT, NERC, ACES, and TERESA. A review of the extant literature suggests that there are clear health impacts from emissions containing carbon-containing PM, but difficulty remains in apportioning responses to certain groupings of carbonaceous materials, such as organic and elemental carbon, condensed and gas phases, and primary and secondary material. More focused epidemiological and toxicological studies, including increased characterization of organic materials, would increase understanding of this issue.

  10. Health effects of carbon-containing particulate matter: focus on sources and recent research program results.

    PubMed

    Rohr, Annette; McDonald, Jacob

    2016-02-01

    Air pollution is a complex mixture of gas-, vapor-, and particulate-phase materials comprised of inorganic and organic species. Many of these components have been associated with adverse health effects in epidemiological and toxicological studies, including a broad spectrum of carbonaceous atmospheric components. This paper reviews recent literature on the health impacts of organic aerosols, with a focus on specific sources of organic material; it is not intended to be a comprehensive review of all the available literature. Specific emission sources reviewed include engine emissions, wood/biomass combustion emissions, biogenic emissions and secondary organic aerosol (SOA), resuspended road dust, tire and brake wear, and cooking emissions. In addition, recent findings from large toxicological and epidemiological research programs are reviewed in the context of organic PM, including SPHERES, NPACT, NERC, ACES, and TERESA. A review of the extant literature suggests that there are clear health impacts from emissions containing carbon-containing PM, but difficulty remains in apportioning responses to certain groupings of carbonaceous materials, such as organic and elemental carbon, condensed and gas phases, and primary and secondary material. More focused epidemiological and toxicological studies, including increased characterization of organic materials, would increase understanding of this issue. PMID:26635181

  11. Results of a European interlaboratory comparison on CO2 sorption on activated carbon and coals

    NASA Astrophysics Data System (ADS)

    Gensterblum, Yves; Busch, Andreas; Krooss, Bernhard; de Weireld, Guy; Billemont, Pierre; van Hemert, Patrick; Wolf, Karl-Heinz

    2013-04-01

    For the assessment of CO2 storage in coal seams or enhanced coalbed methane production (ECBM), the sorption properties of natural coals are important parameters. Since more and more laboratories worldwide are concerned with measurements of gas sorption on coal it is indispensable to establish quality standards for such experiments. The first two interlaboratory studies on CO2 sorption on coal (Goodman et al. 2004, 2007) revealed a poor agreement of sorption isotherms among the participating laboratories, particularly in the high-pressure range. During the MOVECBM (http://www.movecbm.eu/) project funded by the European Commission (6th framework), an interlaboratory comparison of CO2 sorption on selected coals and activated carbon was initiated. Measurements were performed on dry samples at 45° C using the manometric and the gravimetric method. up to a final pressure of 15 MPa. The first set of high-pressure sorption measurements was performed on a Filtrasorb 400 activated carbon sample in order to minimise heterogeneity effects and to optimize the experimental procedures for the individual (manometric or gravimetric) methods (Gensterblum et al. 2009). Since comparability for the activated carbon was excellent, the measurements were continued using natural coals of various rank (anthracite, bituminous coal and lignite) to study the influence of heterogeneities and varying starting conditions on the CO2 sorption properties (Gensterblum et al. 2010). Compared to the poor reproducibility observed in previous interlaboratory studies (Goodman et al., 2004, 2007) this European study showed excellent agreement (<5 % deviation) among the participating laboratories with good repeatability. The sorption data and technical information on the different experimental setups have been used to investigate errors and potential pitfalls in the assessment of high-pressure CO2 sorption isotherms. References Gensterblum Y., P. van Hemert, P. Billemont, A. Busch, B.M. Krooss, G. de

  12. A quantitative comparison of Soil Development in four climatic regimes

    USGS Publications Warehouse

    Harden, J.W.; Taylor, E.M.

    1983-01-01

    A new quantitative Soil Development Index based on field data has been applied to chronosequences formed under different climatic regimes. The four soil chronosequences, developed primarily on sandy deposits, have some numeric age control and are located in xeric-inland (Merced, Calif.), xeric-coastal (Ventura, Calif.), aridic (Las Cruces, N. Mex.), and udic (Susquehanna Valley, Pa.) soil-moisture regimes. To quantify field properties, points are assigned for developmental increases in soil properties in comparison to the parent material. Currently ten soil-field properties are quantified and normalized for each horizon in a given chronosequence, including two new properties for carbonate-rich soils in addition to the eight properties previously defined. When individual properties or the combined indexes are plotted as a function of numeric age, rates of soil development can be compared in different climates. The results demonstrate that (1) the Soil Development Index can be applied to very different soil types, (2) many field properties develop systematically in different climatic regimes, (3) certain properties appear to have similar rates of development in different climates, and (4) the Profile Index that combines different field properties increases significantly with age and appears to develop at similar rates in different climates. The Soil Development Index can serve as a preliminary guide to soil age where other age control is lacking and can be used to correlate deposits of different geographical and climatic regions. ?? 1983.

  13. Preliminary Results from the NASA Orbiting Carbon Observatory-2 (OCO-2)

    NASA Astrophysics Data System (ADS)

    Crisp, D.; Eldering, A.; Gunson, M. R.

    2014-12-01

    The NASA Orbiting Carbon Observatory - 2 (OCO-2) was successfully launched from Vandenberg Air Force Base at 9:56:44 UTC on July 2, 2014. After a series of spacecraft checkout activities and orbit raising maneuvers, OCO-2 was inserted at the front of the 705-km Afternoon constellation (A-Train) on August 3rd. This presentation will summarize the science objectives, review the measurement approach, and introduce some preliminary data from the first few months of operation. OCO-2 was designed to return estimates of the column-averaged atmospheric carbon dioxide (CO2) dry air mole fraction (XCO2) with the precision, resolution, and coverage needed to quantify CO2 surface fluxes on regional scales. To meet these goals, it carries and points a 3-channel grating spectrometer that collects high resolution, co-bore-sighted spectra of reflected sunlight in the 765 nm O2 A-band and in the CO2 bands centered near 1610 and 2060 nm. Each channel records 24 spectra per second along a narrow (< 0.8-degree) track, returning about one million soundings each day. At least 10% of these soundings are expected to be sufficiently cloud free to yield full-column estimates of XCO2with single-sounding accuracies of 0.25 % on regional scales at monthly intervals. The instrument is calibrated using on-board sources and targets, the Moon, well-characterized surface sites (Pollock et al. this session), and comparisons with nearly-coincident observations from the Japanese Greenhouse gases Observing SATellite (GOSAT; Kuze et al. this session). Cloudy soundings are identified and screened out (Taylor et al. this session) and the remaining soundings are analyzed to yield spatially-resolved estimates of XCO2 and other geophysical products (c.f. Frankenberg et al. this session). OCO-2 XCO2 estimates are then validated against those from the Total Carbon Column Observing Network (TCCON) to assess their accuracy and precision (Wennberg et al. this session). Preliminary products from each step of this

  14. The relationship between void waves and flow regime transition

    SciTech Connect

    Lahey, R.T. Jr.; Drew, D.A.; Kalkach-Navarro, S.; Park, J.W.

    1992-12-31

    The results of an extensive experimental and analytical study on the relationship between void waves and flow regime transition are presented, in particular, the bubbly/slug flow regime transition. It is shown that void wave instability signals a flow regime transition.

  15. Climate change impacts on the vegetation carbon cycle of the Iberian Peninsula—Intercomparison of CMIP5 results

    NASA Astrophysics Data System (ADS)

    Aparício, Sara; Carvalhais, Nuno; Seixas, Júlia

    2015-04-01

    The vulnerability of a water-limited region like the Iberian Peninsula (IP) to climate changes drives a great concern and interest in understanding its impacts on the carbon cycle, namely, in terms of biomass production. This study assesses the effects of climate change and rising CO2 on forest growth, carbon sequestration, and water-use efficiency on the IP by late 21st century using 12 models from the CMIP5 project (Coupled Model Intercomparison Project Phase 5). We find a strong agreement among the models under representative concentration pathway 4.5 (RCP4.5) scenario, mostly regarding projected forest growth and increased primary production (13, 9% of gross primary production (GPP) increase projected by the models ensemble). Under RCP8.5 scenario, the results are less conclusive, as seven models project both GPP and net primary production to increase (up to 83% and 69%, respectively), while the remaining four models project the IP as a potential carbon source by late century. Divergences in carbon mass in wood predictions could be attributed to model structures, such as the N cycle, land model component, land cover data and parameterization, and distinct clusters of Earth System Models (ESMs). ESMs divergences in carbon feedbacks are likely being highly impacted by parameterization divergences and susceptibility to climate change and CO2 fertilization effect. Despite projected rainfall reductions, we observe a strong agreement between models regarding the increase of water-use efficiency (by 21% and 34%) under RCP4.5 and RCP8.5, respectively. Results suggest that rising CO2 has the potential to partially alleviate the adverse effects of drought.

  16. Microbial Growth and Air Pollutants in the Corrosion of Carbonate Rocks: Results from Laboratory and Outdoor Experimental Tests

    NASA Astrophysics Data System (ADS)

    Moroni, B.; Poli, G.; Pitzurra, L.

    2003-04-01

    Microorganisms and atmospheric pollution are primary causes of deterioration of materials exposed to open air. Due to the variety of chemical-mineralogical compositions and textures, stone represents a variegated substrate that interacts with environmental fluids and particulate, and is a selective environment for biological proliferation. Carbonate rocks, in particular, are highly exposed to environmental decay and extremely susceptible to acid attack caused by atmospheric pollutants and metabolic acid production. The aim of this work is to study the combined effect of microbial contamination and atmospheric pollutants in the weathering of carbonate rocks by means of laboratory and outdoor exposure tests. Laboratory experiments performed on carbonate rocks allowed evaluation of the influence of the gas mixture in the chemical modifications of the lithic substrate, and formulation of a kinetic model of sulphation. The obtained results suggest that nucleation alternates with growth as leading processes in the development of sulphation. In particular, nucleation of the reaction products is the leading process in the initial period of sulphation, which is characterized by a marked slowdown of the reaction progress, whereas growth of the products is the leading process in the subsequent period of resumption of sulphation. In situ experiments performed by exposing limestone specimens at two air monitoring stations in Perugia with different degrees of urban air pollution showed high levels of fungal colonization at early times and the presence of weathering products (i.e. gypsum) in the longer term. Results point to a combined effect of microbial colonization and atmospheric pollutants in promoting the weathering of stone through acid attack within the film of water present on the surface of the exposed material, and through the oxidation of metal sulphide particulate pollutant to sulphate. Laboratory tests assaying the extent of fungal colonization and/or chemical

  17. Cryogenic cave carbonates as an archive of Late Pleistocene permafrost in the Ural Mountains: preliminary results

    NASA Astrophysics Data System (ADS)

    Dublyansky, Yuri; Kadebskaya, Olga; Cheng, Hai; Luetscher, Mark; Spötl, Christoph

    2015-04-01

    A specific type of cave deposits, cryogenic cave carbonates (CCCs), was discovered in the late 1980s in several caves of Central Europe. Unlike 'common' speleothems that form primarily due to degassing of CO2 from Ca2+ and HCO3- -rich waters, CCCs form by freezing-induced segregation (Žák et al., 2004). The formation of CCCs, hence, requires the presence of both liquid water and freezing temperatures. The latter combination may occur in caves in two situations: (1) freezing-thawing cycles in cave entrance zones; and (2) degrading permafrost conditions, when the active layer reaches the cave ceiling, whilst the deeper parts of the cave remain frozen. The latter situation is associated with a particular type of CCCs, which can be used as a marker for permafrost conditions. Because cave carbonates can be accurately dated using the U/Th method, CCCs may be used to identify events of (degrading) palaeo-permafrost conditions. In this study, CCCs were identified and sampled in four caves, located along a 1000 km-long transect from the northern to the southern Ural Associating the CCCs to permafrost conditions was possible on the basis of field observations (locations deep inside the cave, far from entrance zones) and stable isotope properties (strongly depleted δ18O values, inverse correlation between δ18O and δ13C). Chaikovskiy et al. (2014) reported five U/Th analyses of CCC from three caves: 16.7 ka and 104.8 ka (Divja Cave, northern Ural); and 13.4 ka, 86.5 ka and 125.3 ka (Rossijskaya and Usvinskaya Caves, central Ural). In this study we report 25 additional U/Th ages from northern and central Ural, as well as the first CCC age from southern Ural (Shulgan-Tash Cave). Most of the younger ages (

  18. First results on stable isotopes in fluid inclusions in cryogenic carbonates from Ural Mountains (Russia)

    NASA Astrophysics Data System (ADS)

    Dublyansky, Yuri; Luetscher, Mark; Spötl, Christoph; Töchterle, Paul; Kadebskaya, Olga

    2015-04-01

    Cryogenic cave carbonates (CCC) were found in a number of caves in the Ural. In contrast to the CCC previously reported from Central Europe, the Uralian CCC have larger sizes (up to 4-5 cm), which allows for more detailed petrographic and geochemical studies. CCCs from Uralian caves commonly show spherulitic shapes due to crystal splitting, supporting the model of calcite precipitating in a freezing water pond. δ18O values of studied CCCs are lower by 1 to 14 o compared to noncryogenic speleothems of Pleistocene and Holocene age from the same caves. δ18O and δ13C values are inversely correlated and typically show a fractionation between the core and the rim of individual samples. These trends are similar to those reported for CCCs from European caves (Žák et al., 2004). Petrographic observations performed on doubly polished, 100-150 micron-thick sections revealed abundant fluid inclusions, trapped between fibres of the spherulites. Petrographic relationships suggest that these inclusions are primary. The isotopic composition of water trapped in fluid inclusions in CCCs from two caves was analyzed following mechanical crushing at 120 °C, cryo-trapping of released water, pyrolysis on glassy carbon at 1400 °C (TC/EA device; Thermo), and analysis of the evolved gases on an isotope ratio mass spectrometer (Delta V Advantage; Thermo Fisher). The lack of peaks on the m/z 2 trace during the heating of the loaded crushing cell attests for a good sealing of the fluid inclusions. The measured δD values range between -136 o and -145 o VSMOW. The values measured in CCCs are more negative than the typical values of fluid inclusion water measured in the Holocene stalagmites from central Ural (-99 to -108 ). This shift toward more negative values is attributed to the isotopic fractionation between ice and water during the freezing. Reference: Žák et al., 2004, Chemical Geology, 2006, 119-136.

  19. Gas flaring and resultant air pollution: A review focusing on black carbon.

    PubMed

    Fawole, Olusegun G; Cai, X-M; MacKenzie, A R

    2016-09-01

    Gas flaring is a prominent source of VOCs, CO, CO2, SO2, PAH, NOX and soot (black carbon), all of which are important pollutants which interact, directly and indirectly, in the Earth's climatic processes. Globally, over 130 billion cubic metres of gas are flared annually. We review the contribution of gas flaring to air pollution on local, regional and global scales, with special emphasis on black carbon (BC, "soot"). The temporal and spatial characteristics of gas flaring distinguishes it from mobile combustion sources (transport), while the open-flame nature of gas flaring distinguishes it from industrial point-sources; the high temperature, flame control, and spatial compactness distinguishes gas flaring from both biomass burning and domestic fuel-use. All of these distinguishing factors influence the quantity and characteristics of BC production from gas flaring, so that it is important to consider this source separately in emissions inventories and environmental field studies. Estimate of the yield of pollutants from gas flaring have, to date, paid little or no attention to the emission of BC with the assumption often being made that flaring produces a smokeless flame. In gas flares, soot yield is known to depend on a number of factors, and there is a need to develop emission estimates and modelling frameworks that take these factors into consideration. Hence, emission inventories, especially of the soot yield from gas flaring should give adequate consideration to the variation of fuel gas composition, and to combustion characteristics, which are strong determinants of the nature and quantity of pollutants emitted. The buoyant nature of gas flaring plume, often at temperatures in the range of 2000 K, coupled with the height of the stack enables some of the pollutants to escape further into the free troposphere aiding their long-range transport, which is often not well-captured by model studies.

  20. Gas flaring and resultant air pollution: A review focusing on black carbon.

    PubMed

    Fawole, Olusegun G; Cai, X-M; MacKenzie, A R

    2016-09-01

    Gas flaring is a prominent source of VOCs, CO, CO2, SO2, PAH, NOX and soot (black carbon), all of which are important pollutants which interact, directly and indirectly, in the Earth's climatic processes. Globally, over 130 billion cubic metres of gas are flared annually. We review the contribution of gas flaring to air pollution on local, regional and global scales, with special emphasis on black carbon (BC, "soot"). The temporal and spatial characteristics of gas flaring distinguishes it from mobile combustion sources (transport), while the open-flame nature of gas flaring distinguishes it from industrial point-sources; the high temperature, flame control, and spatial compactness distinguishes gas flaring from both biomass burning and domestic fuel-use. All of these distinguishing factors influence the quantity and characteristics of BC production from gas flaring, so that it is important to consider this source separately in emissions inventories and environmental field studies. Estimate of the yield of pollutants from gas flaring have, to date, paid little or no attention to the emission of BC with the assumption often being made that flaring produces a smokeless flame. In gas flares, soot yield is known to depend on a number of factors, and there is a need to develop emission estimates and modelling frameworks that take these factors into consideration. Hence, emission inventories, especially of the soot yield from gas flaring should give adequate consideration to the variation of fuel gas composition, and to combustion characteristics, which are strong determinants of the nature and quantity of pollutants emitted. The buoyant nature of gas flaring plume, often at temperatures in the range of 2000 K, coupled with the height of the stack enables some of the pollutants to escape further into the free troposphere aiding their long-range transport, which is often not well-captured by model studies. PMID:27262132

  1. Carbon, oxygen and biological productivity in the Southern Ocean in and out the Kerguelen plume: CARIOCA drifter results

    NASA Astrophysics Data System (ADS)

    Merlivat, L.; Boutin, J.; d'Ovidio, F.

    2014-12-01

    The Kerguelen Plateau region in the Indian sector of the Southern Ocean supports annually a large-scale phytoplankton bloom which is naturally fertilized with iron. As part of the second Kerguelen Ocean and Plateau compared Study expedition (KEOPS2) in austral spring (October-November 2011), one Carioca buoy was deployed east of the Kerguelen plateau. It drifted eastward downstream in the Kerguelen plume. Hourly surface measurements of pCO2, O2 and ancillary observations were collected between 1 November 2011 to 12 February 2012 with the aim of characterizing the spatial and temporal variability of the biological Net Community Production (NCP) downstream the Kerguelen plateau, assess the impact of iron-induced productivity on the biological carbon consumption and consequently on the CO2 flux exchanged at the air-sea interface. The trajectory of the buoy until mid-December was within the longitude range, 72-83° E, close to the polar front and then in the polar frontal zone, PFZ, until 97° E. From 17 November to 16 December, the buoy drifted within the Kerguelen plume following a filament carrying dissolved iron, DFe, for a total distance of 700 km. In the first part of the trajectory, the ocean surface waters are a sink for CO2 and a source for CO2, with fluxes of respective mean values equal to -8 and +38 mmol CO2 m-2 d-1. Eastward, as the buoy escapes the iron enriched filament, the fluxes are in opposite direction, with respective mean values of +5 and -48 mmol O2 m-2 d-1. These numbers clearly indicate the strong impact of biological processes on the biogeochemistry in the surface waters within the Kerguelen plume in November-mid-December, while it is undetectable eastward in the PFZ from mid-December to mid-February. While the buoy follows the Fe enriched filament, simultaneous observations of dissolved inorganic carbon, DIC, and dissolved oxygen, O2, highlight biological events lasting from 2 to 4 days. Stoichiometric ratios, O2/C, between 1.1 and 1.4 are

  2. [Factors influencing the spatial variability in soil respiration under different land use regimes].

    PubMed

    Chen, Shu-Tao; Liu, Qiao-Hui; Hu, Zheng-Hua; Liu, Yan; Ren, Jing-Quan; Xie, Wei

    2013-03-01

    In order to investigate the factors influencing the spatial variability in soil respiration under different land use regimes, field experiments were performed. Soil respiration and relevant environment, vegetation and soil factors were measured. The spatial variability in soil respiration and the relationship between soil respiration and these measured factors were investigated. Results indicated that land use regimes had significant effects on soil respiration. Soil respiration varied significantly (P < 0.001) among different land use regimes. Soil respiration rates ranged from 1.82 to 7.46 micromol x (m2 x s)(-1), with a difference of 5.62 micromol x (m2 x s)(-1) between the highest and lowest respiration rates. Soil organic carbon was a key factor controlling the spatial variability in soil respiration. In all, ecosystems studied, the relationship between soil respiration and soil organic carbon content can be described by a power function. Soil respiration increased with the increase of soil organic carbon. In forest ecosystem, the relationship between soil respiration and diameter at breast height (DBH) of trees can be explained by a natural logarithmic function. A model composed of soil organic carbon (C, %), available phosphorous (AP, g x kg(-1)) and diameter at breast height (DBH, cm) explained 92.8% spatial variability in soil respiration for forest ecosystems. PMID:23745410

  3. Plant interspecific differences in arbuscular mycorrhizal colonization as a result of soil carbon addition.

    PubMed

    Eschen, René; Müller-Schärer, Heinz; Schaffner, Urs

    2013-01-01

    Soil nutrient availability and colonization by arbuscular mycorrhizal fungi are important and potentially interacting factors shaping vegetation composition and succession. We investigated the effect of carbon (C) addition, aimed at reducing soil nutrient availability, on arbuscular mycorrhizal colonization. Seedlings of 27 plant species with different sets of life-history traits (functional group affiliation, life history strategy and nitrophilic status) were grown in pots filled with soil from a nutrient-rich set-aside field and amended with different amounts of C. Mycorrhizal colonization was progressively reduced along the gradient of increasing C addition in 17 out of 27 species, but not in the remaining species. Grasses had lower colonization levels than forbs and legumes and the decline in AM fungal colonization was more pronounced in legumes than in other forbs and grasses. Mycorrhizal colonization did not differ between annual and perennial species, but decreased more rapidly along the gradient of increasing C addition in plants with high Ellenberg N values than in plants with low Ellenberg N values. Soil C addition not only limits plant growth through a reduction in available nutrients, but also reduces mycorrhizal colonization of plant roots. The effect of C addition on mycorrhizal colonization varies among plant functional groups, with legumes experiencing an overproportional reduction in AM fungal colonization along the gradient of increasing C addition. We therefore propose that for a better understanding of vegetation succession on set-aside fields one may consider the interrelationship between plant growth, soil nutrient availability and mycorrhizal colonization of plant roots.

  4. Experimental Results in Support of Simulating Progressive Crush in Carbon-Fiber Textile Composites

    SciTech Connect

    DeTeresa, S J; Allison, L M; Cunningham, B J; Freeman, DC; Saculla, M D; Sanchez, R J; Winchester, S W

    2001-04-02

    This report summarizes the findings of an experimental program conducted to support the modeling of the crush behavior of triaxial braid carbon fiber composites. The matrix material as well as braided panels and tubes were characterized in order to determine material properties, to assess failure modes, and to provide a test bed for new analytical and numerical tools developed specifically for braided composites. The matrix material selected by the ACC was an epoxy vinyl ester (Ashland Hetron 922). Tensile tests were used to compare two formulations-one used by the ACC and one recommended by the resin supplier. The latter was a faster reacting system and gelled in one-third the time of the ACC formulation. Both formulations had an average elongation at failure that was only half of the resin supplier's reported value. Only one specimen of each type came close to the reported elongation value and it was shown that failure invariably initiated at both surface and internal defects. Overall, the tensile properties of the two formulations were nearly identical, but those of the ACC system were more consistent. The properties of the ACC matrix formulation were measured in tension, shear, and compression and the average properties obtained in these tests are summarized.

  5. Preliminary results on the effects of afforestation of maize soils with Populus alba L., on carbon metabolism

    NASA Astrophysics Data System (ADS)

    García-Campos, Elena; Zorita, Félix; Gil-Sotres, Fernando; Leirós, Mā Carmen; Trasar-Cepeda, Carmen

    2010-05-01

    Transformation of a natural soil to agricultural land is generally assumed to be accompanied by increased mineralization of the organic matter and increased CO2emissions; in contrast, afforestation of agricultural soil is thought to lead to sequestration of carbon and incorporation of atmospheric CO2 into the organic matter. In other words the type of management and land use determine whether soils act as carbon sinks or sources, so that transformation of agricultural land to forest land is generally considered to be accompanied by an increase in edaphic carbon, although it is not clear whether this effect is always produced or if it depends on the agricultural history of the land being afforested. In light of the recognised importance of forest land in sequestering C, and therefore in regulating climate change, in 1992 the EU established Regulation 2080 to promote the afforestation of marginal agricultural land. This had strong repercussions in regions such as Galicia (NW Spain) as the afforestation was mainly applied to good quality agricultural land rather than to marginal land. Although, as a result, large areas of agricultural land have been afforested in Galicia, the associated effects on edaphic carbon have not been widely investigated. The present study involves analysis of large number of afforested soils, planted with different trees and located in different areas throughout Galicia (NW Spain), with the aim of investigating the effects on carbon metabolism in agricultural soils transformed for forestry use. Here we report the preliminary results concerning the observed effects on carbon metabolism in six soils afforested with poplar, Populus alba L., of age between 4 and 8 years. In addition to the six soils planted with poplars, adjacent agricultural soils (x6) were analyzed. In each case the adjacent soil was the same as the original soil prior to afforestation, and all were maize soils. Samples of the soils were collected in autumn, after harvesting

  6. Effect of Carbon Ion Radiotherapy for Sacral Chordoma: Results of Phase I-II and Phase II Clinical Trials

    SciTech Connect

    Imai, Reiko; Kamada, Tadashi; Tsuji, Hiroshi; Sugawara, Shinji; Serizawa, Itsuko; Tsujii, Hirohiko; Tatezaki, Shin-ichiro

    2010-08-01

    Purpose: To summarize the results of treatment for sacral chordoma in Phase I-II and Phase II carbon ion radiotherapy trials for bone and soft-tissue sarcomas. Patients and Methods: We performed a retrospective analysis of 38 patients with medically unresectable sacral chordomas treated with the Heavy Ion Medical Accelerator in Chiba, Japan between 1996 and 2003. Of the 38 patients, 30 had not received previous treatment and 8 had locally recurrent tumor after previous resection. The applied carbon ion dose was 52.8-73.6 Gray equivalents (median, 70.4) in a total of 16 fixed fractions within 4 weeks. Results: The median patient age was 66 years. The cranial tumor extension was S2 or greater in 31 patients. The median clinical target volume was 523 cm{sup 3}. The median follow-up period was 80 months. The 5-year overall survival rate was 86%, and the 5-year local control rate was 89%. After treatment, 27 of 30 patients with primary tumor remained ambulatory with or without supportive devices. Two patients experienced severe skin or soft-tissue complications requiring skin grafts. Conclusion: Carbon ion radiotherapy appears effective and safe in the treatment of patients with sacral chordoma and offers a promising alternative to surgery.

  7. Sources of Respired Carbon in a Northern Minnesota Ombrotrophic Spruce Bog: Preliminary 14C Results from the SPRUCE Site.

    NASA Astrophysics Data System (ADS)

    Guilderson, T. P.; McNicol, G.; Machin, A.; Hanson, P. J.; McFarlane, K. J.; Osuna, J. L.; Pett-Ridge, J.; Singleton, M. J.

    2014-12-01

    A significant uncertainty in future land-surface carbon budgets is the response of wetlands to climate change. A corollary and related question is the future net climate (radiative) forcing impact from wetlands. Active wetlands emit both CO2 and CH4 to the atmosphere. CH4 is, over a few decades, a much more potent greenhouse gas than CO2. CO2 has a longer atmospheric lifetime and a longer 'tail' to its radiative influence. Whether wetlands are a net source or sink of atmospheric carbon under future climate change will depend on ecosystem response to rising temperatures and elevated CO2. The largest uncertainty in future wetland C-budgets, and their climate forcing is the stability of the large below-ground carbon stocks, often in the form of peat, and the partitioning of CO2 and CH4 released via ecosystem respiration. In advance of a long-term experimental warming and elevated CO2 manipulation at the DOE Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) site in the Marcell Experimental Forest, we have characterized the source of respired carbon used for both the production of CO2 and CH4. Samples were collected in early June, late July, and will be collected in early September from three large (~1.1 m2, ~0.5m3) chambers from the control plot, and two of the experimental plots selected for heating (+9°C, +4.5°C). Early June fluxes from the three chambers were ~5500 mgC-m-2-d-1 and ~16 mgC-m-2-d-1 for CO2 and CH4 respectively. Radiocarbon analysis of CO2 and CH4 indicate that the source for the respired carbon is for the most part recent, with most 14C values between 30 and 40‰ - i.e., carbon that was photosynthetically fixed in the last few years. In concert with rising air and ground temperatures fluxes in late July increased to ~6500 mgC-m-2-d-1 and ~86 mgC-m-2-d-1. Although deep-heating was initiated in mid to late June we hypothesize that the July respiration signal is dominated by the regular seasonal cycle of natural warming

  8. Option pricing with regime switching by trinomial tree method

    NASA Astrophysics Data System (ADS)

    Yuen, Fei Lung; Yang, Hailiang

    2010-02-01

    We present a fast and simple tree model to price simple and exotic options in Markov Regime Switching Model (MRSM) with multi-regime. We modify the trinomial tree model of Boyle (1986) [12] by controlling the risk neutral probability measure in different regime states to ensure that the tree model can accommodate the data of all different regimes at the same time preserving its combining tree structure. In MRSM, the market might not be complete, therefore we provide some ideas and discussions on managing the regime switching risk in support of our results.

  9. Effect of moisture regime on the redistribution of heavy metals in paddy soil.

    PubMed

    Zheng, Shunan; Zhang, Mingkui

    2011-01-01

    Sequential extraction procedure was applied to assess the dynamics of solid-phase transformation of added Cu, Pb, Cd, and Hg in a typical Chinese paddy soil incubated under three moisture regimes (75% field capacity, wetting-drying cycle, and flooding). The heavy metals spiked in the soil were time-dependently transferred from the easily extractable fraction (the exchangeable fraction) into less labile fractions (Fe-Mn oxide- and organic matter-bound fractions), and thus reduced lability of the metals. No significant changes were found for the carbonate-bound and residual fractions of the heavy metals in the soil during the whole incubation. Change rate of the mobility factor (MF), a proportion of weakly bound fractions (exchangeable and carbonate-bound) in the total metal of soil, reflected the transformation rate of metal speciation from the labile fractions toward stable fractions. It was found that soil moisture regime did not change the direction and pathways of transformation of metal speciation, but it significantly affected the transformation rate. In general, the paddy soil under flooding regime had higher metal reactivity compared with 75% field capacity and wetting-drying cycle regimes, resulting in the more complete movement of metals toward stable fractions. This might be related to the increased pH, precipitation of the metals with sulfides and higher concentration of amorphous Fe oxides under submerged condition.

  10. Acid rain and weathering damage to carbonate building stone: Results of material loss measurements

    SciTech Connect

    Reddy, M.; Youngdahl, C.A.

    1987-01-01

    Marble and limestone specimens were exposed to atmospheric conditions at four eastern U.S. sites. A number of methods were employed for damage assessment; this paper describes the results of chemical and physical measurements of material loss. Good agreement was observed among results obtained with different methods. A rate of surface recession near 15 ..mu..m/y was observed for skyward surfaces of marble tested in North Carolina, and comparable results were obtained at the other test sites. Response of the porous limestone was assessed with greater difficulty; a rate of loss similar to that of marble was inferred. Initial correlations of material loss with environmental factors are briefly discussed.

  11. Acid rain and weathering damage to carbonate building stone: Results of material loss measurements

    SciTech Connect

    Reddy, M.M.; Youngdahl, C.A.

    1986-11-01

    Marble and limestone specimens were exposed to atmospheric conditions at four eastern US sites. A number of methods were employed for damage assessment; this paper describes the results of chemical and physical measurements of material loss. Good agreement was observed among results obtained with different methods. A rate of surface recession near 15 ..mu..m/y was observed for skyward surfaces of marble tested in North Carolina, and comparable results were obtained at the other test sites. Response of the porous limestone was assessed with greater difficulty; a rate of loss similar to that of marble was inferred. Initial correlations of material loss with environmental factors are briefly discussed.

  12. Second Generation International Space Station (ISS) Total Organic Carbon Analyzer (TOCA) Verification Testing and On-Orbit Performance Results

    NASA Technical Reports Server (NTRS)

    Bentley, Nicole L.; Thomas, Evan A.; VanWie, Michael; Morrison, Chad; Stinson, Richard G.

    2010-01-01

    The Total Organic Carbon Analyzer (TOGA) is designed to autonomously determine recovered water quality as a function of TOC. The current TOGA has been on the International Space Station since November 2008. Functional checkout and operations revealed complex operating considerations. Specifically, failure of the hydrogen catalyst resulted in the development of an innovative oxidation analysis method. This method reduces the activation time and limits the hydrogen produced during analysis, while retaining the ability to indicate TOC concentrations within 25% accuracy. Subsequent testing and comparison to archived samples returned from the Station and tested on the ground yield high confidence in this method, and in the quality of the recovered water.

  13. Identifying natural flow regimes using fish communities

    NASA Astrophysics Data System (ADS)

    Chang, Fi-John; Tsai, Wen-Ping; Wu, Tzu-Ching; Chen, Hung-kwai; Herricks, Edwin E.

    2011-10-01

    SummaryModern water resources management has adopted natural flow regimes as reasonable targets for river restoration and conservation. The characterization of a natural flow regime begins with the development of hydrologic statistics from flow records. However, little guidance exists for defining the period of record needed for regime determination. In Taiwan, the Taiwan Eco-hydrological Indicator System (TEIS), a group of hydrologic statistics selected for fisheries relevance, is being used to evaluate ecological flows. The TEIS consists of a group of hydrologic statistics selected to characterize the relationships between flow and the life history of indigenous species. Using the TEIS and biosurvey data for Taiwan, this paper identifies the length of hydrologic record sufficient for natural flow regime characterization. To define the ecological hydrology of fish communities, this study connected hydrologic statistics to fish communities by using methods to define antecedent conditions that influence existing community composition. A moving average method was applied to TEIS statistics to reflect the effects of antecedent flow condition and a point-biserial correlation method was used to relate fisheries collections with TEIS statistics. The resulting fish species-TEIS (FISH-TEIS) hydrologic statistics matrix takes full advantage of historical flows and fisheries data. The analysis indicates that, in the watersheds analyzed, averaging TEIS statistics for the present year and 3 years prior to the sampling date, termed MA(4), is sufficient to develop a natural flow regime. This result suggests that flow regimes based on hydrologic statistics for the period of record can be replaced by regimes developed for sampled fish communities.

  14. Preliminary Results of the Permafrost Carbon Study in the Lower Kolyma Lowland (Eastern Siberia) Based on Drilling Record

    NASA Astrophysics Data System (ADS)

    Spektor, V. V.; Kholodov, A. L.; Bulygina, E. B.; Andreeva, V.; Broderick, D.; Spawn, S.; Natali, S.; Davydova, A.

    2012-12-01

    In 2012, the Polaris Project (thepolarisproject.org, Director R.M. Holmes) has conducted the permafrost drilling on the Kolyma Lowland for a complex study of permafrost carbon as a potential source for microbial decomposition. In July 2012, the first two boreholes, 15.1 and 13.4 m in depth, were drilled. The first borehole (BH 12/1) was drilled in the stratum of ice complex (yedoma) on the local watershed near the Schuch'e lake in the vicinity of the town Chersky (N68°44.7' E161°23'). The depth of active layer is 45 cm. The permafrost to the depth of 15.1 m represents grey and brown silts with predominant homogeneous structure. Silts contain numerous thread-like roots, scarce plant macrofossils, and in places are colored with unclear spots of ferrugination. Cryostructure is mainly pore ice or thin lense-like ice layers. Wedge ice is observed in the interval 12.5-12.9 m. The moisture volumetric percentage of silts varies along the stratum, mainly, between 40-50%. The organic content, defined in every 20 cm of the core as a loss on ignition, varies between 2-4%. The second borehole (BH 12/2), located in the Pleistocene Park (N68°30.8' E161°30') was drilled through modern floodplain sediments (0-0.6 m) of the Kolyma River with polygonal network at the surface, underlain by peat (0.6-1.3 m), silt deposits of thermokarst lake (1.3-12.0 m), and river grey sands (12.0-13.4 m). The active layer thickness is 65 cm. The cryostructure is predominantly lattice-like. Silts contain modern wedge ice at the depth of 2.5-2.7 m. Mollusk shells and large amount of plant macrofossils are observed in the interval 5.7-8.0 m. The organic content in the thermokarst deposits varies in average within 2-3 %, but is about 1% in the underlying river sands. To investigate permafrost carbon, samples for microbial and enzyme activities, as well as samples of trapped gases were collected from different horizons of frozen cores. Samples for palynological, diatom, and lithological analyses, as

  15. Nitrogen as a factor for enhanced carbon sequestration: Results from four NitroEurope-IP forest supersites

    NASA Astrophysics Data System (ADS)

    Ibrom, A.

    2012-04-01

    Nitrogen (N) fertilization, both intended and unintended, interacts with carbon cycling in terrestrial ecosystems, because the major processes of carbon (C) turnover depend on enzymes and thus on N availability. Comparisons between annual carbon dioxide flux (CO2) budgets and wet N deposition in forests showed a very strong linear increase of CO2 sequestration with increased N deposition. After considering total rather than only wet N deposition the ratios between increased carbon uptake and atmospheric N input were closer to C/N that can be found in wood. This suggested that the observed ecosystems responses to enhanced N inputs were mainly driven by plant responses. Finally, looking at changes in soil organic matter changes indicated even lower sensitivities of carbon sequestration to N addition. The objective of this study is to describe the mechanisms of the responses and the fate of the N in the ecosystem based on results from intensively investigated forest sites. Within the European NitroEuope-IP project the annual fluxes and pool sizes of C and N were estimated in four so-called forest supersites, including temperate coniferous forests in Southern Germany (Höglwald) and in the Netherlands (Speulderbos), one temperate beech forest close to Sorø on Zealand in Denmark and a boreal pine forest (Hyytiälä, Southern Finland). Due to differences in vegetation, bedrock and climate history, soils differed in acidity, organic matter content and biological activity; the levels of atmospheric N deposition varied from very low (Hyytiälä) to high (the other sites). Comparisons of N and C budgets of plants and soils confirmed a simple and stoichiometric effect dCuptake/dNdep = constant and in the order of magnitude of (C/N)wood for plants but not for soils and thus not for the forest ecosystems as a whole. Differences in soil processes as indicated by the differing C/N of SOM, differing amounts of N stored in the soil and considerable differences in N leaching rates

  16. Spin glasses in the nonextensive regime

    NASA Astrophysics Data System (ADS)

    Wittmann, Matthew; Young, A. P.

    2012-04-01

    Spin systems with long-range interactions are “nonextensive” if the strength of the interactions falls off sufficiently slowly with distance. It has been conjectured for ferromagnets and, more recently, for spin glasses that, everywhere in the nonextensive regime, the free energy is exactly equal to that for the infinite range model in which the characteristic strength of the interaction is independent of distance. In this paper we present the results of Monte Carlo simulations of the one-dimensional long-range spin glasses in the nonextensive regime. Using finite-size scaling, our results for the transition temperatures are consistent with this prediction. We also propose and provide numerical evidence for an analogous result for diluted long-range spin glasses in which the coordination number is finite, namely, that the transition temperature throughout the nonextensive regime is equal to that of the infinite-range model known as the Viana-Bray model.

  17. Biological and physical forcing of carbonate chemistry in an upwelling filament off northwest Africa: Results from a Lagrangian study

    NASA Astrophysics Data System (ADS)

    Loucaides, Socratis; Tyrrell, Toby; Achterberg, Eric P.; Torres, Ricardo; Nightingale, Philip D.; Kitidis, Vassilis; Serret, Pablo; Woodward, Malcolm; Robinson, Carol

    2012-09-01

    The Mauritanian upwelling system is one of the most biologically productive regions of the world's oceans. Coastal upwelling transfers nutrients to the sun-lit surface ocean, thereby stimulating phytoplankton growth. Upwelling of deep waters also supplies dissolved inorganic carbon (DIC), high levels of which lead to low calcium carbonate saturation states in surface waters, with potentially adverse effects on marine calcifiers. In this study an upwelled filament off the coast of northwest Africa was followed using drifting buoys and sulphur hexafluoride to determine how the carbonate chemistry changed over time as a result of biological, physical and chemical processes. The initial pHtot in the mixed layer of the upwelled plume was 7.94 and the saturation states of calcite and aragonite were 3.4 and 2.2, respectively. As the plume moved offshore over a period of 9 days, biological uptake of DIC (37 μmol kg-1) reduced pCO2 concentrations from 540 to 410 μatm, thereby increasing pHtot to 8.05 and calcite and aragonite saturation states to 4.0 and 2.7 respectively. The increase (25 μmol kg-1) in total alkalinity over the 9 day study period can be accounted for solely by the combined effects of nitrate uptake and processes that alter salinity (i.e., evaporation and mixing with other water masses). We found no evidence of significant alkalinity accumulation as a result of exudation of organic bases by primary producers. The ongoing expansion of oxygen minimum zones through global warming will likely further reduce the CaCO3 saturation of upwelled waters, amplifying any adverse consequences of ocean acidification on the ecosystem of the Mauritanian upwelling system.

  18. Dynamic regime marginal structural mean models for estimation of optimal dynamic treatment regimes, Part I: main content.

    PubMed

    Orellana, Liliana; Rotnitzky, Andrea; Robins, James M

    2010-01-01

    Dynamic treatment regimes are set rules for sequential decision making based on patient covariate history. Observational studies are well suited for the investigation of the effects of dynamic treatment regimes because of the variability in treatment decisions found in them. This variability exists because different physicians make different decisions in the face of similar patient histories. In this article we describe an approach to estimate the optimal dynamic treatment regime among a set of enforceable regimes. This set is comprised by regimes defined by simple rules based on a subset of past information. The regimes in the set are indexed by a Euclidean vector. The optimal regime is the one that maximizes the expected counterfactual utility over all regimes in the set. We discuss assumptions under which it is possible to identify the optimal regime from observational longitudinal data. Murphy et al. (2001) developed efficient augmented inverse probability weighted estimators of the expected utility of one fixed regime. Our methods are based on an extension of the marginal structural mean model of Robins (1998, 1999) which incorporate the estimation ideas of Murphy et al. (2001). Our models, which we call dynamic regime marginal structural mean models, are specially suitable for estimating the optimal treatment regime in a moderately small class of enforceable regimes of interest. We consider both parametric and semiparametric dynamic regime marginal structural models. We discuss locally efficient, double-robust estimation of the model parameters and of the index of the optimal treatment regime in the set. In a companion paper in this issue of the journal we provide proofs of the main results.

  19. Calcification of the planktonic foraminifera Globigerina bulloides and carbonate ion concentration: Results from the Santa Barbara Basin

    NASA Astrophysics Data System (ADS)

    Osborne, Emily B.; Thunell, Robert C.; Marshall, Brittney J.; Holm, Jessica A.; Tappa, Eric J.; Benitez-Nelson, Claudia; Cai, Wei-Jun; Chen, Baoshan

    2016-08-01

    Planktonic foraminiferal calcification intensity, reflected by shell wall thickness, has been hypothesized to covary with the carbonate chemistry of seawater. Here we use both sediment trap and box core samples from the Santa Barbara Basin to evaluate the relationship between the calcification intensity of the planktonic foraminifera species Globigerina bulloides, measured by area density (µg/µm2), and the carbonate ion concentration of seawater ([CO32-]). We also evaluate the influence of both temperature and nutrient concentration ([PO43-]) on foraminiferal calcification and growth. The presence of two G. bulloides morphospecies with systematically different calcification properties and offset stable isotopic compositions was identified within sampling populations using distinguishing morphometric characteristics. The calcification temperature and by extension calcification depth of the more abundant "normal" G. bulloides morphospecies was determined using δ18O temperature estimates. Calcification depths vary seasonally with upwelling and were used to select the appropriate [CO32-], temperature, and [PO43-] depth measurements for comparison with area density. Seasonal upwelling in the study region also results in collinearity between independent variables complicating a straightforward statistical analysis. To address this issue, we use additional statistical diagnostics and a down core record to disentangle the respective roles of each parameter on G. bulloides calcification. Our results indicate that [CO32-] is the primary variable controlling calcification intensity while temperature influences shell size. We report a modern calibration for the normal G. bulloides morphospecies that can be used in down core studies of well-preserved sediments to estimate past [CO32-].

  20. Results from Carbon Dioxide Washout Testing Using a Suited Manikin Test Apparatus with a Space Suit Ventilation Test Loop

    NASA Technical Reports Server (NTRS)

    Chullen, Cinda; Conger, Bruce; McMillin, Summer; Vonau, Walt; Kanne, Bryan; Korona, Adam; Swickrath, Mike

    2016-01-01

    NASA is developing an advanced portable life support system (PLSS) to meet the needs of a new NASA advanced space suit. The PLSS is one of the most critical aspects of the space suit providing the necessary oxygen, ventilation, and thermal protection for an astronaut performing a spacewalk. The ventilation subsystem in the PLSS must provide sufficient carbon dioxide (CO2) removal and ensure that the CO2 is washed away from the oronasal region of the astronaut. CO2 washout is a term used to describe the mechanism by which CO2 levels are controlled within the helmet to limit the concentration of CO2 inhaled by the astronaut. Accumulation of CO2 in the helmet or throughout the ventilation loop could cause the suited astronaut to experience hypercapnia (excessive carbon dioxide in the blood). A suited manikin test apparatus (SMTA) integrated with a space suit ventilation test loop was designed, developed, and assembled at NASA in order to experimentally validate adequate CO2 removal throughout the PLSS ventilation subsystem and to quantify CO2 washout performance under various conditions. The test results from this integrated system will be used to validate analytical models and augment human testing. This paper presents the system integration of the PLSS ventilation test loop with the SMTA including the newly developed regenerative Rapid Cycle Amine component used for CO2 removal and tidal breathing capability to emulate the human. The testing and analytical results of the integrated system are presented along with future work.

  1. Gradual regime shifts in fairy circles

    PubMed Central

    Zelnik, Yuval R.; Meron, Ehud; Bel, Golan

    2015-01-01

    Large responses of ecosystems to small changes in the conditions—regime shifts—are of great interest and importance. In spatially extended ecosystems, these shifts may be local or global. Using empirical data and mathematical modeling, we investigated the dynamics of the Namibian fairy circle ecosystem as a case study of regime shifts in a pattern-forming ecosystem. Our results provide new support, based on the dynamics of the ecosystem, for the view of fairy circles as a self-organization phenomenon driven by water–vegetation interactions. The study further suggests that fairy circle birth and death processes correspond to spatially confined transitions between alternative stable states. Cascades of such transitions, possible in various pattern-forming systems, result in gradual rather than abrupt regime shifts. PMID:26362787

  2. Gradual regime shifts in fairy circles.

    PubMed

    Zelnik, Yuval R; Meron, Ehud; Bel, Golan

    2015-10-01

    Large responses of ecosystems to small changes in the conditions--regime shifts--are of great interest and importance. In spatially extended ecosystems, these shifts may be local or global. Using empirical data and mathematical modeling, we investigated the dynamics of the Namibian fairy circle ecosystem as a case study of regime shifts in a pattern-forming ecosystem. Our results provide new support, based on the dynamics of the ecosystem, for the view of fairy circles as a self-organization phenomenon driven by water-vegetation interactions. The study further suggests that fairy circle birth and death processes correspond to spatially confined transitions between alternative stable states. Cascades of such transitions, possible in various pattern-forming systems, result in gradual rather than abrupt regime shifts. PMID:26362787

  3. Gradual regime shifts in fairy circles.

    PubMed

    Zelnik, Yuval R; Meron, Ehud; Bel, Golan

    2015-10-01

    Large responses of ecosystems to small changes in the conditions--regime shifts--are of great interest and importance. In spatially extended ecosystems, these shifts may be local or global. Using empirical data and mathematical modeling, we investigated the dynamics of the Namibian fairy circle ecosystem as a case study of regime shifts in a pattern-forming ecosystem. Our results provide new support, based on the dynamics of the ecosystem, for the view of fairy circles as a self-organization phenomenon driven by water-vegetation interactions. The study further suggests that fairy circle birth and death processes correspond to spatially confined transitions between alternative stable states. Cascades of such transitions, possible in various pattern-forming systems, result in gradual rather than abrupt regime shifts.

  4. Effect of carbon taxes and subsidies on optimal forest rotation age and supply of carbon services

    SciTech Connect

    Kooten, G.C. van; Binkley, C.S.; Delcourt, G.

    1995-05-01

    Carbon taxes and subsidies will affect the optimal forest rotation and, consequently, the carbon stored in forests. Unlike the Hartman rotation, where externality benefits are a function of the volume of timber growing on a site at any time, carbon benefits are a function of the change in biomass. Theoretical and empirical results (for coastal British Columbia and northern Alberta) indicate that, under some tax regimes, it may be socially optimal never to harvest the trees. In general, inclusion of the external benefits from carbon uptake results in rotation ages only a bit longer than the financial (Faustmann) rotation age. 27 refs., 2 figs., 2 tabs.

  5. An Assessment of Fire Regime Changes in the Northern Rocky Mountain Region Using Simulated Historical Fire Maps and Remotely Sensed Current Fires

    NASA Astrophysics Data System (ADS)

    Zhao, F.; Zhu, Z.; Huang, C.

    2011-12-01

    Wildland fire is a primary ecosystem process that shapes the landscape of Western United States. Changes in fire regime can therefore have profound impact on ecosystem functions and services, including carbon cycling, habitat conditions, and biodiversity. This poster presents a study on current fire regime and changes in the Northern Rocky Mountain region assessed using contemporary and historical fire regimes. Contemporary fire records from 1984 to 2008 were obtained from the Monitoring Trends in Burn Severity (MTBS) project. Historical (pre-EuroAmerican settlement) fire regimes and fire regime condition class (FRCC), produced by the LANDFIRE project, were simulated using a Landscape Succession Model (LANDSUM). We extracted historical fire frequency (Mean Fire Interval) and fire severity (percentage of severe fire) data from LANDFIRE, and calculated current fire frequency and severity using MTBS data by following the FRCC definition, to evaluate changes in fire regimes in Northern Rocky Mountain area. Preliminary results reveal that the current fire regime in Northern Rocky Mountains may exhibit a general pattern of longer return intervals and more severe fires. Biophysical Setting (BpS) map units from LANDFIRE are used as study units to describe environmental gradients and will be used to further examine whether the observed fire regime changes are controlled by land cover or biophysical settings. The findings of this study will help reveal contemporary fire dynamics in this region and serve for future fire studies and other forest management applications.

  6. Examination Regimes and Student Achievement

    ERIC Educational Resources Information Center

    Cosentino de Cohen, Clemencia

    2010-01-01

    Examination regimes at the end of secondary school vary greatly intra- and cross-nationally, and in recent years have undergone important reforms often geared towards increasing student achievement. This research presents a comparative analysis of the relationship between examination regimes and student achievement in the OECD. Using a micro…

  7. Experimental floods cause ecosystem regime shift in a regulated river.

    PubMed

    Robinson, Christopher T; Uehlinger, Urs

    2008-03-01

    Reservoirs have altered the flow regime of most rivers on the globe. To simulate the natural flow regime, experimental floods are being implemented on regulated rivers throughout the world to improve their ecological integrity. As a large-scale disturbance, the long-term sequential use of floods provides an excellent empirical approach to examine ecosystem regime shifts in rivers. This study evaluated the long-term effects of floods (15 floods over eight years) on a regulated river. We hypothesized that sequential floods over time would cause a regime shift in the ecosystem. The floods resulted in little change in the physicochemistry of the river, although particulate organic carbon and particulate phosphorus were lower after the floods. The floods eliminated moss cover on bed sediments within the first year of flooding and maintained low periphyton biomass and benthic organic matter after the third year of flooding. Organic matter in transport was reduced after the third year of flooding, although peaks were still observed during rain events due to tributary inputs and side slopes. The floods reduced macroinvertebrate richness and biomass after the first year of floods, but density was not reduced until the third year. The individual mass of invertebrates decreased by about one-half after the floods. Specific taxa displayed either a loss in abundance, or an increase in abundance, or an increase followed by a loss after the third year. The first three flood years were periods of nonequilibrium with coefficients of variation in all measured parameters increasing two to five times from those before the floods. Coefficients of variation decreased after the third year, although they were still higher than before the floods. Analysis of concordance using Kendall's W confirmed the temporal changes observed in macroinvertebrate assemblage structure. An assessment of individual flood effects showed that later floods had approximately 30% less effect on macroinvertebrates

  8. Spatiotemporal Trends in late-Holocene Fire Regimes in Arctic and Boreal Alaska

    NASA Astrophysics Data System (ADS)

    Hoecker, T. J.; Higuera, P. E.; Hu, F.; Kelly, R.

    2015-12-01

    Alaskan arctic and boreal ecosystems are of global importance owing to their sensitivity and feedbacks to directional climate change. Wildfires are a primary driver of boreal carbon balance, and altered fire regimes may significantly impact global climate through the release of stored carbon and changes to surface albedo. Paleoecological records provide a window to how these systems respond to change by revealing climatic and disturbance variability throughout the Holocene. These long-term records highlight the sensitivity of fire regimes to climate and vegetation change, including responses to the relatively warm Medieval Climate Anomaly (MCA), and the relatively cool Little Ice Age (LIA). Over millennial timescales, boreal forests and arctic tundra have been resilient to climate change, but continued directional climate change may result in novel vegetation compositions and fire regimes, with potentially significant implications for global climate. Here we present a spatiotemporal synthesis of 22 published sediment-charcoal records from three Alaskan ecoregions. We add to this network eight records collected in June 2015 from an additional ecoregion. Variability in fire return intervals (FRIs) was quantified within and among ecoregions and climatic periods spanning the past 2 millennia, based on a peak analysis representing local fire events. Preliminary results suggest that fire regimes were responsive to centennial-scale climatic shifts, including the MCA and LIA, but the degree of sensitivity varies by ecoregion. Over the past 2000 years, FRIs were shortest during the MCA, indicating the potential for climate warming to promote high rates of burning. FRIs in tundra regions of northwestern Alaska and in interior boreal forests were 20% shorter during the MCA than during the LIA, and 25% shorter in boreal forest in the south-central Brooks Range. Burning was likely promoted during the warmer, drier MCA through lower fuel moisture. Quantifying fire-regime

  9. Carbon dioxide sequestration by direct mineral carbonation with carbonic acid

    SciTech Connect

    O'Connor, W.K.; Dahlin, D.C.; Nilsen, D.N.; Walters, R.P.; Turner, P.C.

    2000-07-01

    The Albany Research Center (ARC) of the US Department of Energy (DOE) has been conducting a series of mineral carbonation tests at its Albany, Oregon, facility over the past 2 years as part of a Mineral Carbonation Study Program within the DOE. The ARC tests have focused on ex-situ mineral carbonation in an aqueous system. The process developed at ARC utilizes a slurry of water mixed with a magnesium silicate mineral, olivine [forsterite and member (mg{sub 2}SiO{sub 4})], or serpentine [Mg{sub 3}Si{sub 2}O{sub 5}(OH){sub 4}]. This slurry is reacted with supercritical carbon dioxide (CO{sub 2}) to produce magnesite (MgCO{sub 3}). The CO{sub 2} is dissolved in water to form carbonic acid (H{sub 2}CO{sub 3}), which dissociates to H{sup +} and HCO{sub 3}{sup {minus}}. The H{sup +} reacts with the mineral, liberating Mg{sup 2+} cations which react with the bicarbonate to form the solid carbonate. The process is designed to simulate the natural serpentinization reaction of ultramafic minerals, and for this reason, these results may also be applicable to in-situ geological sequestration regimes. Results of the baseline tests, conducted on ground products of the natural minerals, have been encouraging. Tests conducted at ambient temperature (22 C) and subcritical CO{sub 2} pressures (below 73 atm) resulted in very slow conversion to the carbonate. However, when elevated temperatures and pressures are utilized, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant reaction occurs within much shorter reaction times. Extent of reaction, as measured by the stoichiometric conversion of the silicate mineral (olivine) to the carbonate, is roughly 90% within 24 hours, using distilled water, and a reaction temperature of 185 C and a partial pressure of CO{sub 2} (P{sub CO{sub 2}}) of 115 atm. Recent tests using a bicarbonate solution, under identical reaction conditions, have achieved roughly 83% conversion of heat treated serpentine

  10. Carbon dioxide sequestration by direct mineral carbonation with carbonic acid

    SciTech Connect

    O'Connor, William K.; Dahlin, David C.; Nilsen, David N.; Walters, Richard P.; Turner, Paul C.

    2000-01-01

    The Albany Research Center (ARC) of the U.S. Dept. of Energy (DOE) has been conducting a series of mineral carbonation tests at its Albany, Oregon, facility over the past 2 years as part of a Mineral Carbonation Study Program within the DOE. Other participants in this Program include the Los Alamos National Laboratory, Arizona State University, Science Applications International Corporation, and the DOE National Energy Technology Laboratory. The ARC tests have focused on ex-situ mineral carbonation in an aqueous system. The process developed at ARC utilizes a slurry of water mixed with a magnesium silicate mineral, olivine [forsterite end member (Mg2SiO4)], or serpentine [Mg3Si2O5(OH)4]. This slurry is reacted with supercritical carbon dioxide (CO2) to produce magnesite (MgCO3). The CO2 is dissolved in water to form carbonic acid (H2CO3), which dissociates to H+ and HCO3 -. The H+ reacts with the mineral, liberating Mg2+ cations which react with the bicarbonate to form the solid carbonate. The process is designed to simulate the natural serpentinization reaction of ultramafic minerals, and for this reason, these results may also be applicable to in-situ geological sequestration regimes. Results of the baseline tests, conducted on ground products of the natural minerals, have been encouraging. Tests conducted at ambient temperature (22 C) and subcritical CO2 pressures (below 73 atm) resulted in very slow conversion to the carbonate. However, when elevated temperatures and pressures are utilized, coupled with continuous stirring of the slurry and gas dispersion within the water column, significant reaction occurs within much shorter reaction times. Extent of reaction, as measured by the stoichiometric conversion of the silicate mineral (olivine) to the carbonate, is roughly 90% within 24 hours, using distilled water, and a reaction temperature of 185?C and a partial pressure of CO2 (PCO2) of 115 atm. Recent tests using a bicarbonate solution, under identical reaction

  11. An analytical study of nitrogen oxides and carbon monoxide emissions in hydrocarbon combustion with added nitrogen - Preliminary results

    NASA Technical Reports Server (NTRS)

    Bittker, D. A.

    1980-01-01

    The influence of ground-based gas turbine combustor operating conditions and fuel-bound nitrogen (FBN) found in coal-derived liquid fuels on the formation of nitrogen oxides and carbon monoxide is investigated. Analytical predictions of NOx and CO concentrations are obtained for a two-stage, adiabatic, perfectly-stirred reactor operating on a propane-air mixture, with primary equivalence ratios from 0.5 to 1.7, secondary equivalence ratios of 0.5 or 0.7, primary stage residence times from 12 to 20 msec, secondary stage residence times of 1, 2 and 3 msec and fuel nitrogen contents of 0.5, 1.0 and 2.0 wt %. Minimum nitrogen oxide but maximum carbon monoxide formation is obtained at primary zone equivalence ratios between 1.4 and 1.5, with percentage conversion of FBN to NOx decreasing with increased fuel nitrogen content. Additional secondary dilution is observed to reduce final pollutant concentrations, with NOx concentration independent of secondary residence time and CO decreasing with secondary residence time; primary zone residence time is not observed to affect final NOx and CO concentrations significantly. Finally, comparison of computed results with experimental values shows a good semiquantitative agreement.

  12. Elevation of 20-carbon long chain bases due to a mutation in serine palmitoyltransferase small subunit b results in neurodegeneration.

    PubMed

    Zhao, Lihong; Spassieva, Stefka; Gable, Kenneth; Gupta, Sita D; Shi, Lan-Ying; Wang, Jieping; Bielawski, Jacek; Hicks, Wanda L; Krebs, Mark P; Naggert, Juergen; Hannun, Yusuf A; Dunn, Teresa M; Nishina, Patsy M

    2015-10-20

    Sphingolipids typically have an 18-carbon (C18) sphingoid long chain base (LCB) backbone. Although sphingolipids with LCBs of other chain lengths have been identified, the functional significance of these low-abundance sphingolipids is unknown. The LCB chain length is determined by serine palmitoyltransferase (SPT) isoenzymes, which are trimeric proteins composed of two large subunits (SPTLC1 and SPTLC2 or SPTLC3) and a small subunit (SPTssa or SPTssb). Here we report the identification of an Sptssb mutation, Stellar (Stl), which increased the SPT affinity toward the C18 fatty acyl-CoA substrate by twofold and significantly elevated 20-carbon (C20) LCB production in the mutant mouse brain and eye, resulting in surprising neurodegenerative effects including aberrant membrane structures, accumulation of ubiquitinated proteins on membranes, and axon degeneration. Our work demonstrates that SPT small subunits play a major role in controlling SPT activity and substrate affinity, and in specifying sphingolipid LCB chain length in vivo. Moreover, our studies also suggest that excessive C20 LCBs or C20 LCB-containing sphingolipids impair protein homeostasis and neural functions.

  13. Elevation of 20-carbon long chain bases due to a mutation in serine palmitoyltransferase small subunit b results in neurodegeneration.

    PubMed

    Zhao, Lihong; Spassieva, Stefka; Gable, Kenneth; Gupta, Sita D; Shi, Lan-Ying; Wang, Jieping; Bielawski, Jacek; Hicks, Wanda L; Krebs, Mark P; Naggert, Juergen; Hannun, Yusuf A; Dunn, Teresa M; Nishina, Patsy M

    2015-10-20

    Sphingolipids typically have an 18-carbon (C18) sphingoid long chain base (LCB) backbone. Although sphingolipids with LCBs of other chain lengths have been identified, the functional significance of these low-abundance sphingolipids is unknown. The LCB chain length is determined by serine palmitoyltransferase (SPT) isoenzymes, which are trimeric proteins composed of two large subunits (SPTLC1 and SPTLC2 or SPTLC3) and a small subunit (SPTssa or SPTssb). Here we report the identification of an Sptssb mutation, Stellar (Stl), which increased the SPT affinity toward the C18 fatty acyl-CoA substrate by twofold and significantly elevated 20-carbon (C20) LCB production in the mutant mouse brain and eye, resulting in surprising neurodegenerative effects including aberrant membrane structures, accumulation of ubiquitinated proteins on membranes, and axon degeneration. Our work demonstrates that SPT small subunits play a major role in controlling SPT activity and substrate affinity, and in specifying sphingolipid LCB chain length in vivo. Moreover, our studies also suggest that excessive C20 LCBs or C20 LCB-containing sphingolipids impair protein homeostasis and neural functions. PMID:26438849

  14. Elevation of 20-carbon long chain bases due to a mutation in serine palmitoyltransferase small subunit b results in neurodegeneration

    PubMed Central

    Zhao, Lihong; Spassieva, Stefka; Gable, Kenneth; Gupta, Sita D.; Shi, Lan-Ying; Wang, Jieping; Bielawski, Jacek; Hicks, Wanda L.; Krebs, Mark P.; Naggert, Juergen; Hannun, Yusuf A.; Dunn, Teresa M.; Nishina, Patsy M.

    2015-01-01

    Sphingolipids typically have an 18-carbon (C18) sphingoid long chain base (LCB) backbone. Although sphingolipids with LCBs of other chain lengths have been identified, the functional significance of these low-abundance sphingolipids is unknown. The LCB chain length is determined by serine palmitoyltransferase (SPT) isoenzymes, which are trimeric proteins composed of two large subunits (SPTLC1 and SPTLC2 or SPTLC3) and a small subunit (SPTssa or SPTssb). Here we report the identification of an Sptssb mutation, Stellar (Stl), which increased the SPT affinity toward the C18 fatty acyl-CoA substrate by twofold and significantly elevated 20-carbon (C20) LCB production in the mutant mouse brain and eye, resulting in surprising neurodegenerative effects including aberrant membrane structures, accumulation of ubiquitinated proteins on membranes, and axon degeneration. Our work demonstrates that SPT small subunits play a major role in controlling SPT activity and substrate affinity, and in specifying sphingolipid LCB chain length in vivo. Moreover, our studies also suggest that excessive C20 LCBs or C20 LCB-containing sphingolipids impair protein homeostasis and neural functions. PMID:26438849

  15. Synchronization regimes in conjugate coupled chaotic oscillators.

    PubMed

    Karnatak, Rajat; Ramaswamy, Ram; Prasad, Awadhesh

    2009-09-01

    Nonlinear oscillators that are mutually coupled via dissimilar (or conjugate) variables display distinct regimes of synchronous behavior. In identical chaotic oscillators diffusively coupled in this manner, complete synchronization occurs only by chaos suppression when the coupled subsystems drive each other into a regime of periodic dynamics. Furthermore, the coupling does not vanish but acts as an "internal" drive. When the oscillators are mismatched, phase synchronization occurs, while in a master slave configuration, generalized synchrony results. These effects are demonstrated in a system of coupled chaotic Rossler oscillators.

  16. Anomalous Hall effect in localization regime

    NASA Astrophysics Data System (ADS)

    Wu, Lin; Zhu, Kai; Yue, Di; Tian, Yuan; Jin, Xiaofeng

    2016-06-01

    The anomalous Hall effect in the ultrathin film regime is investigated in Fe(001)(1-3 nm) films epitaxial on MgO(001). The logarithmic localization correction to longitudinal resistivity and anomalous Hall resistivity are observed at low temperature. We identify that the coefficient of skew scattering has a reduction from metallic to localized regime, while the contribution of side jump has inconspicuous change except for a small drop below 10 K. Furthermore, we discover that the intrinsic anomalous Hall conductivity decreases with the reduction of thickness below 2 nm. Our results provide unambiguous experimental evidence to clarify the problem of localization correction to the anomalous Hall effect.

  17. Convective Regimes in Crystallizing Basaltic Magma Chambers

    NASA Astrophysics Data System (ADS)

    Gilbert, A. J.; Neufeld, J. A.; Holness, M. B.

    2015-12-01

    Cooling through the chamber walls drives crystallisation in crustal magma chambers, resulting in a cumulate pile on the floor and mushy regions at the walls and roof. The liquid in many magma chambers, either the bulk magma or the interstitial liquid in the mushy regions, may convect, driven either thermally, due to cooling, or compositionally, due to fractional crystallization. We have constructed a regime diagram of the possible convective modes in a system containing a basal mushy layer. These modes depend on the large-scale buoyancy forcing characterised by a global Rayleigh number and the proportion of the chamber height constituting the basal mushy region. We have tested this regime diagram using an analogue experimental system composed of a fluid layer overlying a pile of almost neutrally buoyant inert particles. Convection in this system is driven thermally, simulating magma convection above and within a porous cumulate pile. We observe a range of possible convective regimes, enabling us to produce a regime diagram. In addition to modes characterised by convection of the bulk and interstitial fluid, we also observe a series of regimes where the crystal pile is mobilised by fluid motions. These regimes feature saltation and scouring of the crystal pile by convection in the bulk fluid at moderate Rayleigh numbers, and large crystal-rich fountains at high Rayleigh numbers. For even larger Rayleigh numbers the entire crystal pile is mobilised in what we call the snowglobe regime. The observed mobilisation regimes may be applicable to basaltic magma chambers. Plagioclase in basal cumulates crystallised from a dense magma may be a result of crystal mobilisation from a plagioclase-rich roof mush. Compositional convection within such a mush could result in disaggregation, enabling the buoyant plagioclase to be entrained in relatively dense descending liquid plumes and brought to the floor. The phenocryst load in porphyritic lavas is often interpreted as a

  18. Carbon sink activity is stronger under grazing than under mowing: results from a paired eddy flux towers experiment

    NASA Astrophysics Data System (ADS)

    Pintér, Krisztina; Balogh, János; Koncz, Péter; Hidy, Dóra; Cserhalmi, Dóra; Papp, Marianna; Fóti, Szilvia; Nagy, Zoltán

    2014-05-01

    Effect of grazing vs. mowing on carbon balance of a grassland was investigated by a paired eddy towers (one of them measuring the grazed, the another the mowed treatment) experiment at the Bugacpuszta sandy grassland site (HU-Bug, 46.69° N, 19.6° E, 114m asl, 10.4 ° C annual mean temperature, 562 mm annual precipitation sum) located in the Hungarian Plain. Eddy covariance measurements started in July, 2002. The area of the mowed treatment is 1 ha, it is located within the grazed treatment (500 ha). Electric fence was set up around the selected area in spring of 2011. Study years include 2011, 2012 and 2013. The pasture is managed extensively (average grazing pressure of 0.5 cattle per hectare), the cattle herd regularly took several kilometres during a grazing day. Annual net ecosystem exchange (NEE) of the grassland is strongly limited by precipitation, there were 2 source years within the 11 years (2003-2013) of measurements, during which the average annual balance was -109 gCm-2year-1 with standard deviation of 106 gCm-2year-1. Carbon sink activity of the grassland was stronger in the grazed treatment than in the mowed treatment during the three year study period (paired t-test, P=0.058). In the grazed treatment the average sink strength was -142.8 ±40 gCm-2year-1, while in the mowed treatment the average sink strength was -61.5 ±46.5 gCm-2year-1. Differences of carbon balances between the treatments were positively correlated to the annual sum of evapotranspiration (ET), while ETs of the treatments were almost identical (differences within a 10mm year-1 range) in each study year. Water use efficiency in the mowed treatment was 44% of that in the grazed treatment (P=0.045) as a result of the differences in sink capacity. The higher sensitivity to drought by the mowed treatment manifested in decreased sink capacity during summer and in decreased regeneration capacity during autumn rains as shown by the cumulative NEE in the different years. Minor but

  19. An analytical study of nitrogen oxides and carbon monoxide emissions in hydrocarbon combustion with added nitrogen, preliminary results

    NASA Technical Reports Server (NTRS)

    Bittker, D. A.

    1979-01-01

    The effect of combustor operating conditions on the conversion of fuel-bound nitrogen (FBN) to nitrogen oxides NO sub x was analytically determined. The effect of FBN and of operating conditions on carbon monoxide (CO) formation was also studied. For these computations, the combustor was assumed to be a two stage, adiabatic, perfectly-stirred reactor. Propane-air was used as the combustible mixture and fuel-bound nitrogen was simulated by adding nitrogen atoms to the mixture. The oxidation of propane and formation of NO sub x and CO were modeled by a fifty-seven reaction chemical mechanism. The results for NO sub x and CO formation are given as functions of primary and secondary stage equivalence ratios and residence times.

  20. Optical and Thermo-optical Properties of Polyimide-Single-Walled Carbon Nanotube Films: Experimental Results and Empirical Equations

    NASA Technical Reports Server (NTRS)

    Smith, Joseph G., Jr.; Connell, John W.; Watson, Kent A.; Danehy, Paul M.

    2005-01-01

    The incorporation of single-walled carbon nanotubes (SWNTs) into the bulk of space environmentally durable polymers at loading levels greater than or equal to 0.05 wt % has afforded thin films with surface and volume resistivities sufficient for electrostatic charge mitigation. However, the optical transparency at 500 nm decreased and the thermo-optical properties (solar absorptivity and thermal emissivity) increased with increaed SWNT loading. These properties were also dependent on film thickness. The absorbance characteristics of the films as a function of SWNT loading and film thickness were measured and determined to follow the classical Beer-Lambert law. Based on these results, an empirical relationship was derived and molar absorptivities determined for both the SWNTs and polymer matrix to provide a predictive approximation of these properties. The molar absorptivity determined for SWNTs dispersed in the polymer was comparable to reported solution determined values for HiPco SWNTs.

  1. Guidance for evaluating and recommending temperature regimes to protect fish

    USGS Publications Warehouse

    Armour, Carl L.

    1991-01-01

    Procedures are presented for evaluating temperature regimes for fish. Although examples pertain to spring chinook salmon (Oncorhynchus tshawytscha), the principles apply to other species. Basic temperature tolerance relationships for fish are explained and three options are described for comparing alternative temperature regimes. The options are to base comparisons on experimental temperature tolerance results, suitability of a simulated temperature regime for key life stages, or population statistics and predicated responses to simulated temperatures.

  2. Carbon dioxide production in surface sediments of temporarily anoxic basins (Baltic Sea) and resulting sediment-water interface fluxes

    NASA Astrophysics Data System (ADS)

    Böttcher, M. E.; Al-Raei, A. M.; Winde, V.; Lenz, C.; Dellwig, O.; Leipe, T.; Segl, M.; Struck, U.

    2009-04-01

    Organic matter is mineralized in marine sediments by microbial activity using predominantly oxygen, sulfate, and metal oxides as electron acceptors. Modern euxinic basins as found in the Baltic Sea or the Black Sea are of particular importance because they may serve as type systems for anoxia in Earth's history. We present here results from biogeochemical investigations carried out in the Baltic deeps (Gotland Basin, Landsort Deep) during the first scientific cruise of RV M.S. MERIAN in 2006, additionally during RV Prof. Penck cruises in 2006 and 2007. Short sediment cores were obtained with a multi-corer and analyzed for particulate and dissolved main, minor and trace elements, pH, DIC, methane alkalinity, besides the stable carbon isotopes of dissolved inorganic carbon (DIC). Microsensors were applied to analyze steep gradients of oxygen, sulphide and sulphate. Pore water profiles are evaluated in terms of process rates and associated element fluxes using the PROFILE software (Berg et al., 1998, L&O). Gross and net anaerobic mineralization rates were additionally obtained from core incubations with 35S. Steep gradients in DIC are associated with a strong enrichment of the light stable isotope resulting in the Gotland basin from oxidized OM. Element fluxes across the sediment-water interface are compared with literature data and show for the Baltic Sea a dependence from bottom water redox conditions, and sediment compositions and formation conditions (e.g., accumulation rates). DIC in the anoxic part of the water column in the Landsort Deep and the Gotland Deep show relatively similar isotope values, close to the bottom water value, but steep gradients towards heavier values above the pelagic redoxcline. Acknowledgements: The research was supported by Leibniz IO Warnemünde, DFG (Cruise RV MSM MERIAN 01), and MPG. Thanks to B. Schneider and F. Pollehne stimulating discussions, and S. Lage and A. Schipper for technical support.

  3. Magnetostratigraphy of Mesozoic shallow-water carbonates: Preliminary results from the Middle Jurassic of the Paris basin

    SciTech Connect

    Aissaoui, D.M.; Kirschvink, J.L. )

    1991-03-01

    The use of sedimentary paleomagnetism has enhanced greatly our understanding of the timing of deposition and diagenesis of Cenozoic platform and reefal carbonates. Its application to similar but older deposits will have direct implications for economic exploration and development. The authors report here preliminary paleomagnetic results from the Middle Jurassic limestones of the Paris basin (France). The samples consist mainly of bioclastic and oolitic limestones deposited in ancient counterpart of the shallow-water environments of the Bahama platform. The Jurassic samples are stable to progressive, incremental demagnetization and exhibit magnetization patterns identical to Cenozoic rocks from the Bahama platform or Mururoa Atoll. The natural remanent magnetization of these limestones is weak and comprised between 7.7 x 10{sup {minus}9} to 1.8 x 10{sup {minus}8} AM{sup 2}/kg. Magnetic components of both normal and reversed polarity are observed. Paired isothermal remanent magnetization (IRM) and alternating field demagnetization experiments show that most of the remanence is lost between 20 and 45 mT, which is typical of single-domain biogenic magnetite or maghemite. The ratio of IRM at H{sub RG} to the saturation IRM ranges from 35 to 42% indicating a moderate to low interparticle interaction. This is confirmed by the anhysteretic remanent magnetization as compared with intact, freeze-dried cells of magnetotactic bacteria and chiton teeth. Magnetic minerals extracted from the Jurassic samples are examined to further confirm the occurrence of SD magnetite within the Middle Jurassic limestones of the Paris basin. The preliminary results suggest that the strata should be good for the paleomagnetic investigation of Mesozoic shallow-water carbonates.

  4. Barium in twilight zone suspended matter as a potential proxy for particulate organic carbon remineralization: Results for the North Pacific

    NASA Astrophysics Data System (ADS)

    Dehairs, F.; Jacquet, S.; Savoye, N.; Van Mooy, B. A. S.; Buesseler, K. O.; Bishop, J. K. B.; Lamborg, C. H.; Elskens, M.; Baeyens, W.; Boyd, P. W.; Casciotti, K. L.; Monnin, C.

    2008-07-01

    This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22°45'N, 158°W; Hawaii; studied during June-July 2004) and the mesotrophic Subarctic Pacific K2 site (47°N, 161°W; studied during July-August 2005). Earlier work has shown that non-lithogenic, excess particulate Ba (Ba xs) in the mesopelagic water column is a potential proxy of organic carbon remineralization. In general, Ba xs contents were significantly larger at K2 than at ALOHA. At ALOHA, the Ba xs profiles from repeated sampling (five casts) showed remarkable consistency over a period of three weeks, suggesting that the system was close to being at steady state. In contrast, more variability was observed at K2 (six casts sampled), reflecting the more dynamic physical and biological conditions prevailing in this environment. While for both sites Ba xs concentrations increased with depth, at K2 a clear maximum was present between the base of the mixed layer at around 50 and 500 m, reflecting production and release of Ba xs. Larger mesopelagic Ba xs contents and larger bacterial production in the twilight zone at the K2 site indicate that more material was exported from the upper mixed layer for bacterial degradation deeper, compared to the ALOHA site. Furthermore, application of a published transfer function [Dehairs, F., Shopova, D., Ober, S., Veth, C., Goeyens, L., 1997. Particulate barium stocks and oxygen consumption in the Southern Ocean mesopelagic water column during spring and early summer: relationship with export production. Deep-Sea Research II 44(1-2), 497-516] relating oxygen consumption to the observed Ba xs data indicated that the latter were in good agreement with bacterial respiration, calculated from bacterial production. These results corroborate earlier findings highlighting the potential of Ba xs as a proxy for organic carbon remineralization. The range of POC remineralization

  5. Barium in Twilight Zone suspended matter as a potential proxy for particulate organic carbon remineralization: Results for the North Pacific

    SciTech Connect

    Dehairs, F.; Jacquet, S.; Savoye, N.; Van Mooy, B.A.S.; Buesseler, K.; Bishop, J.K.B.; Lamborg, C.H.; Elskens, M.; Baeyens, W.; Boyd, P.W.; Casciotti, K.L.; Monnin, C.

    2008-04-10

    This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22 degrees 45 minutes N 158 degrees W; Hawaii; studied during June-July 2004) and the mesotrophic Subarctic Pacific K2 site (47 degrees N, 161 degrees W; studied during July-August 2005). Earlier work has shown that non-lithogenic, excess particulate Ba (Ba{sub xs}) in the mesopelagic water column is a potential proxy of organic carbon remineralization. In general Ba{sub xs} contents were significantly larger at K2 than at ALOHA. At ALOHA the Ba{sub xs} profiles from repeated sampling (5 casts) showed remarkable consistency over a period of three weeks, suggesting that the system was close to being at steady state. In contrast, more variability was observed at K2 (6 casts sampled) reflecting the more dynamic physical and biological conditions prevailing in this environment. While for both sites Ba{sub xs} concentrations increased with depth, at K2 a clear maximum was present between the base of the mixed layer at around 50m and 500m, reflecting production and release of Ba{sub xs}. Larger mesopelagic Ba{sub xs} contents and larger bacterial production in the twilight zone at the K2 site indicate that more material was exported from the upper mixed layer for bacterial degradation deeper, compared to the ALOHA site. Furthermore, application of a published transfer function (Dehairs et al., 1997) relating oxygen consumption to the observed Ba{sub xs} data indicated that the latter were in good agreement with bacterial respiration, calculated from bacterial production. These results corroborate earlier findings highlighting the potential of Ba{sub xs} as a proxy for organic carbon remineralization. The range of POC remineralization rates calculated from twilight zone excess particulate Ba contents did also compare well with the depth dependent POC flux decrease as recorded by neutrally buoyant sediment traps

  6. The First Eighteen Months of NASA's Orbiting Carbon Observatory-2 (OCO-2): Mission Status, Error Characterization, and Preliminary Results

    NASA Astrophysics Data System (ADS)

    O'Dell, Christopher

    2016-04-01

    OCO-2 began taking science data in September 2014 and continues to operate well, returning nearly 1 million observations per day. Approximately 10% of these are sufficiently free of cloud and aerosol contamination to allow for an accurate determination of the column mean carbon dioxide dry air mole fraction, XCO2. The measurements have relatively low noise, of order 0.5-1.0 ppm for most nadir soundings over land and sun-glint geometry soundings over water surfaces. A number of changes have been made to the observing strategy to maintain performance and enhance the science quality of the data: change in glint yaw angle in October 2014, change in nadir glint cycling in July 2015, change to nadir yaw and glint orbit optimization in late 2015, in addition to periodic instrument cyclings. In this presentation, we will summarize the data quality enabled via comparison to a number of validation metrics, discuss the current health and long-term prospects for the instrument, and give an overview of some early science results from the first 18 months of observations. While XCO2 and other products are still being validated to identify and correct biases, OCO-2's XCO2 observations are starting to reveal the most robust features of the atmospheric carbon cycle. At regional scales, fluxes from the eastern U.S. and China are most clear in the fall, when the north-south XCO2 gradient is small. Enhanced XCO2 coincident with biomass burning in the some parts of the tropics, in particular central Africa, is also obvious in the fall. The annual growth rate of CO2 was anomalously high in 2015 according to OCO-2, consistent with NOAA surface measurements and in accord with the warmer annual average surface temperature that year. This was also apparent in the decreased northern hemisphere summer uptake, likely due to anomalously warm boreal temperatures in the northern hemisphere summer of 2015.

  7. 78 FR 67334 - Suspension Agreement on Certain Cut-to-Length Carbon Steel Plate From Ukraine; Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-12

    ... Carbon Steel Plate From Ukraine; Administrative Review, 78 FR 46570 (August 1, 2013) and accompanying...: Certain Cut-to-Length Carbon Steel Plate from Ukraine, 73 FR 57602 (October 3, 2008) (Agreement). On... covering Metinvest Holding LLC (Metinvest) and its affiliated companies Azovstal Iron & Steel...

  8. Changes in constituent equilibrium leaching and pore water characteristics of a Portland cement mortar as a result of carbonation.

    PubMed

    Garrabrants, A C; Sanchez, F; Kosson, D S

    2004-01-01

    Two equilibrium-based characterization protocols were applied to ground samples of a cement-based material containing metal oxide powders in both noncarbonated and carbonated states. The effects of carbonation were shown through comparison of (i) material buffering capacity, (ii) constituent equilibrium as a function of leachate pH, and (iii) constituent solubility and release as a function of liquid-to-solid (LS) ratio. As expected, the material alkalinity was significantly neutralized during carbonation. In addition, carbonation of the cement material led to the formation of calcium carbonate and a corresponding increase in arsenic release across the entire pH range. The solubility as a function of pH for lead and copper was lower in the alkaline pH range (pH>9) for carbonated samples compared with the parent material. When solubility and release as a function of LS ratio was compared, carbonation was observed to decrease calcium solubility, sodium and potassium release, and ionic strength. In response to carbonate solid formation, chloride and sulfate release as a function of LS ratio was observed to increase. Trends in constituent concentration as a function of LS ratio were extrapolated to estimate pore water composition at a 0.06 mL/g LS ratio. Significant differences were observed upon comparison of estimated pore water composition to leachate concentrations extracted at LS ratio of 5 mL/g. These differences show that practical laboratory extractions cannot be assumed directly representative of pore water concentrations.

  9. The influence of temperature calibration on the OC–EC results from a dual-optics thermal carbon analyzer

    EPA Science Inventory

    The Sunset Laboratory Dual-Optical Carbonaceous Analyzer that simultaneously measures transmission and reflectance signals is widely used in thermal-optical analysis of particulate matter samples. Most often this instrument is used to measure total carbon (TC), organic carbon (O...

  10. Understanding the fate of black (pyrogenic) carbon in soil: Preliminary results from a long term field trial

    NASA Astrophysics Data System (ADS)

    Meredith, Will; Ascough, Philippa; Bird, Michael; Large, David; Shen, Licheng; Snape, Colin

    2014-05-01

    Black carbon (BC, also known as pyrogenic carbon) is an 'inert' form of carbon and has been proposed as a means of long-term carbon sequestration, particularly by amending soils and sediments with BC known as biochar. While there is abundant anecdotal evidence of biochar stability over extended timescales it is essential to gain a greater understanding of the degree and mechanisms of biochar degradation in the environment. This study aims to quantitatively assess the stability of biochar by investigating samples from field degradation trials first buried during 2009 in a tropical soil, and recovered after 12 and 36 month intervals. Catalytic hydropyrolysis (HyPy) is a novel analytical tool for the isolation of BC [1] in which high hydrogen pressure (150 bar) and a sulphided Mo catalyst reductively remove the non-BC fraction of the chars, and so isolate the most stable portion of the biochar, defined as BC(HyPy). This method also allows for the non-BC(HyPy) fraction of a sample, which from charcoal is known to include small ring PAHs (<7 rings) of pyrogenic origin to be recovered for molecular characterisation by GC-MS [2]. Biochars made from algae, sugarcane bagasse, and beech wood at 305, 414 and 512°C were emplaced under a variety of conditions allowing variables such as leaf cover, soil depth and pH to be investigated. Char stability (as measured by BC(HyPy) content) is dependent on both the feedstock and temperature of formation. HyPy is known to discriminate (in terms of BC isolation) against low temperature chars, composed of relatively small aromatic clusters [1], resulting in the low BC(HyPy) contents reported for the 305°C chars. Fresh charcoals, and those not subject to environmental degradation have display a similar distribution of aromatic clusters in the non-BC(HyPy) fraction, with 2 to 7 ring PAHs abundant [2]. However, environmentally degraded charcoals such as that from a Chinese river sediment, and an Australian river estuary [3] show a more

  11. Delinating Thermohaline Double-Diffusive Rayleigh Regimes

    NASA Astrophysics Data System (ADS)

    Graf, T.; Walther, M.; Kolditz, O.; Liedl, R.

    2013-12-01

    In natural systems, convective flow induced from density differences may occur in near-coastal aquifers, atmospheric boundary layers, oceanic streams or within the earth crust. Whether an initially stable, diffusive regime evolves into a convective (stable or chaotic) regime, or vice versa, depends on the system's framing boundary conditions. A conventional parameter to express the relation between diffusive and convective forces of such a density-driven regime is Rayleigh number (Ra). While most systems are mainly dominated by only a single significant driving force (i.e. only temperature or salinity), some systems need to consider two boundary processes (e.g. deep, thus warm, haline flow in porous media). In that case, a two-dimensional, 'double-diffusive' Rayleigh system can be defined. Nield (1998) postulated a boundary between diffusive and convective regime at RaT + RaC = 4pi^2 in the first quadrant (Q1), with Rayleigh numbers for temperature and concentration respectively. The boundary in the forth quadrant (Q4) could not exactly be determined, yet the approximate position estimated. Simulations with HydroGeoSphere (Therrien, 2010) using a vertical, quadratic, homogeneous, isotropic setup confirmed the existence of the 4pi^2-boundary and revealed additional regimes (diffusive, single-roll, double-roll, chaotic) in Q1. Also, non-chaotic, oscillating patterns could be identified in Q4. More detailed investigations with OpenGeoSys (Kolditz, 2012) confirmed the preceding HGS results, and, using a 1:10-scaled domain (height:length), uncovered even more distinctive regimes (diffusive, minimum ten roles, supposely up to 25 roles, and chaotic?) in Q1, while again, oscillating patterns were found in the transition zone between diffusive and chaotic regimes in Q4. Output of numerical simulations from Q1 and Q4 show the mentioned regimes (diffusive, stable-convective, stable-oscillatory, chaotic) while results are displayed in context of a possible delination between

  12. [Carbonization of heavy metal Cu implanted sewage sludge and stability of heavy metal in the resulting char].

    PubMed

    Dou, Xiao-Min; Chen, De-Zhen; Dai, Xiao-Hu

    2014-11-01

    In this research, a new method for sewage sludge (SS) disposal was introduced, by which heavy metals were implanted into sewage sludge before pyrolysis. Cu was adopted as the representative of heavy metals to test this process and was implanted in the form of CuCl2. Effects of Cu implanting concentration and reaction temperature on the residual ratio and immobilization of heavy metals in pyrolysis char were studied. Meanwhile, two leaching methods were employed with the purpose to determine the maximum capacity of heavy metal immobilization in the char. The primary research results showed that when the Cu implanting concentration was 0.5% (mass fraction), more than 90% of Cu remained in the char after carbonization, and the leachability of heavy metals in the char was related to pyrolysis temperature. Cu leaching from the char increased with increasing pyrolysis temperature. There was also a limitation for Cu implanting concentration in the sewage sludge, which was determined by the destination of the pyrolyzed char. If it went to sanitary landfill, the limitation would be 0.5%. The primary results showed that sewage sludge could be kneaded with other wastes containing heavy metals before pyrolysis to achieve co-processing. PMID:25639117

  13. Impact of land use change on the land atmosphere carbon flux of South and South East Asia: A Synthesis of Dynamic Vegetation Model Results

    NASA Astrophysics Data System (ADS)

    Cervarich, M.; Shu, S.; Jain, A. K.; Poulter, B.; Stocker, B.; Arneth, A.; Viovy, N.; Kato, E.; Wiltshire, A.; Koven, C.; Sitch, S.; Zeng, N.; Friedlingstein, P.

    2015-12-01

    Understanding our present day carbon cycle and possible solutions to recent increases in atmospheric carbon dioxide is dependent upon quantifying the terrestrial carbon budget. Currently, global land cover and land use change is estimated to emit 0.9 PgC yr-1 compared to emissions due to fossil fuel combustion and cement production of 8.4 PgC yr-1. South and Southeast Asia (India, Nepal, Bhutan, Bangladesh, Burma, Thailand, Laos, Vietnam, Cambodia, Malaysia, Philippines, Indonesia, Pakistan, Myanmar, and Singapore) is a region of rapid land cover and land use change due to the continuous development of agriculture, deforestation, reforestation, afforestation, and the increased demand of land for people to live. In this study, we synthesize outputs of nine models participated in Global Carbon Budget Project to identify the carbon budget of South and southeast Asia, diagnose the contribution of land cover and land use change to carbon emissions and assess areas of uncertainty in the suite of models. Uncertainty is determined using the standard deviation and the coefficient of variation of net ecosystem exchange and its component parts. Results show the region's terrestrial biosphere was a source of carbon emissions from the 1980 to the early 1990s. During the same time period, land cover and land use change increasingly contributed to carbon emission. In the most recent two decades, the region became a carbon sink since emission due to land cover land use changes. Spatially, the greatest total emissions occurred in the tropical forest of Southeast Asia. Additionally, this is the subregion with the greatest uncertainty and greatest biomass. Model uncertainty is shown to be proportional to total biomass. The atmospheric impacts of ENSO are shown to suppress the net biosphere productivity in South and Southeast Asia leading to years of increased carbon emissions.

  14. Technology Advancement for Active Remote Sensing of Carbon Dioxide from Space Using the ASCENDS CarbonHawk Experiment Simulator: First Results

    NASA Technical Reports Server (NTRS)

    Obland, Michael D.; Nehrir, Amin R.; Lin, Bing; Harrison, F. Wallace; Kooi, Susan; Choi, Yonghoon; Plant, James; Yang, Melissa; Antill, Charles; Campbell, Joel; Ismail, Syed; Browell, Edward V.; Meadows, Byron; Dobler, Jeremy; Zaccheo, T. Scott; Moore, Berrien; Crowell, Sean

    2015-01-01

    The ASCENDS CarbonHawk Experiment Simulator (ACES) is a newly developed lidar developed at NASA Langley Research Center and funded by NASA's Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP) that seeks to advance technologies critical to measuring atmospheric column carbon dioxide (CO2) mixing ratios in support of the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. The technology advancements targeted include: (1) increasing the power-aperture product to approach ASCENDS mission requirements by implementing multi-aperture telescopes and multiple co-aligned laser transmitters; (2) incorporating high-efficiency, high-power Erbium-Doped Fiber Amplifiers (EDFAs); (3) developing and incorporating a high-bandwidth, low-noise HgCdTe detector and transimpedence amplifier (TIA) subsystem capable of long-duration autonomous operation on Global Hawk aircraft, and (4) advancing algorithms for cloud and aerosol discrimination. The ACES instrument architecture is being developed for operation on high-altitude aircraft and will be directly scalable to meet the ASCENDS mission requirements. These technologies are critical towards developing not only spaceborne instruments but also their airborne simulators, with lower platform requirements for size, mass, and power, and with improved instrument performance for the ASCENDS mission. ACES transmits five laser beams: three from commercial EDFAs operating near 1.57 microns, and two from the Exelis oxygen (O2) Raman fiber laser amplifier system operating near 1.26 microns. The three EDFAs are capable of transmitting up to 10 watts average optical output power each and are seeded by compact, low noise, stable, narrow-linewidth laser sources stabilized with respect to a CO2 absorption line using a multi-pass gas absorption cell. The Integrated-Path Differential Absorption (IPDA) lidar approach is used at both wavelengths to independently measure the CO2 and O2 column number

  15. Size distribution characteristics of elemental carbon emitted from Chinese vehicles: results of a tunnel study and atmospheric implications.

    PubMed

    Huang, Xiao-Feng; Yu, Jian Zhen; He, Ling-Yan; Hu, Min

    2006-09-01

    The size distribution characteristics of elemental carbon (EC) emissions from Chinese vehicles have not been previously described. In this study, we collected size-segregated aerosol samples using a 10-stage MOUDI sampler (0.056-18 microm) in the Zhujiang tunnel, a roadway tunnel in the urban area of Guangzhou, China. The samples were analyzed for EC, organic carbon (OC), and inorganic ions. Fine particles had an OC/EC ratio of 0.57, indicating a dominant contribution of EC from diesel vehicles. Both EC and OC showed a dominant accumulation mode with a mass median aerodynamic diameter (MMAD) of 0.42 microm. In comparison, studies available in the literature typically reported a much lower MMAD for EC (approximately 0.1 microm) in vehicular emissions in North America. A theoretical analysis indicated that the larger EC particles observed in this study could not have resulted from after-emission growth processes (i.e., water accretion, coagulation, and vapor condensation). This leaves operating conditions such as high engine loads and low combustion efficiencies, which are more prevalent in diesel-fueled Chinese vehicles, as a more plausible inherent reason for producing the larger EC agglomerates. While fresh 0.1 microm EC particles are unlikely to act as cloud condensation nuclei (CCN), calculations showed that EC particles as large as 0.42 microm are effective CCN at atmospherically relevant critical supersaturation values of less than 1%. As a result, fresh EC particles from Chinese vehicle emissions could readily undergo cloud processing and form internal mixtures with sulfate in the residue droplet mode particles. This prediction is consistent with observations that EC frequently showed a dominant droplet mode in urban atmospheres in this region. The internal mixing of EC with highly hygroscopic sulfate would facilitate its removal by wet deposition and shorten its lifetime in the atmosphere. In addition, the light-absorbing capabilities of EC particles could

  16. Size distribution characteristics of elemental carbon emitted from Chinese vehicles: results of a tunnel study and atmospheric implications.

    PubMed

    Huang, Xiao-Feng; Yu, Jian Zhen; He, Ling-Yan; Hu, Min

    2006-09-01

    The size distribution characteristics of elemental carbon (EC) emissions from Chinese vehicles have not been previously described. In this study, we collected size-segregated aerosol samples using a 10-stage MOUDI sampler (0.056-18 microm) in the Zhujiang tunnel, a roadway tunnel in the urban area of Guangzhou, China. The samples were analyzed for EC, organic carbon (OC), and inorganic ions. Fine particles had an OC/EC ratio of 0.57, indicating a dominant contribution of EC from diesel vehicles. Both EC and OC showed a dominant accumulation mode with a mass median aerodynamic diameter (MMAD) of 0.42 microm. In comparison, studies available in the literature typically reported a much lower MMAD for EC (approximately 0.1 microm) in vehicular emissions in North America. A theoretical analysis indicated that the larger EC particles observed in this study could not have resulted from after-emission growth processes (i.e., water accretion, coagulation, and vapor condensation). This leaves operating conditions such as high engine loads and low combustion efficiencies, which are more prevalent in diesel-fueled Chinese vehicles, as a more plausible inherent reason for producing the larger EC agglomerates. While fresh 0.1 microm EC particles are unlikely to act as cloud condensation nuclei (CCN), calculations showed that EC particles as large as 0.42 microm are effective CCN at atmospherically relevant critical supersaturation values of less than 1%. As a result, fresh EC particles from Chinese vehicle emissions could readily undergo cloud processing and form internal mixtures with sulfate in the residue droplet mode particles. This prediction is consistent with observations that EC frequently showed a dominant droplet mode in urban atmospheres in this region. The internal mixing of EC with highly hygroscopic sulfate would facilitate its removal by wet deposition and shorten its lifetime in the atmosphere. In addition, the light-absorbing capabilities of EC particles could

  17. Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

    SciTech Connect

    Li, X.; Nilsson, D.; Danielsson, Ö.; Pedersen, H.; Janzén, E.; Forsberg, U.; Bergsten, J.; Rorsman, N.

    2015-12-28

    The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) epitaxial layer closest to the substrate and a lower doped layer (3 × 10{sup 16 }cm{sup −3}) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement shows a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.

  18. Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

    NASA Astrophysics Data System (ADS)

    Li, X.; Bergsten, J.; Nilsson, D.; Danielsson, Ö.; Pedersen, H.; Rorsman, N.; Janzén, E.; Forsberg, U.

    2015-12-01

    The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 1018 cm-3) epitaxial layer closest to the substrate and a lower doped layer (3 × 1016 cm-3) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement shows a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 1018 cm-3) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.

  19. Intermediate scaling regime for multilayer epitaxial growth

    NASA Astrophysics Data System (ADS)

    Ross, Richard S.; Gyure, Mark F.

    2000-04-01

    We explore the layer-by-layer (Frank-van der Merwe) growth regime within the context of a discrete solid-on-solid kinetic Monte Carlo model. Our results demonstrate a nontrivial scaling of the lattice step edge density, a quantity that oscillates about a nominally constant value prior to the onset of kinetic roughening. This value varies with the ratio of the surface diffusivity to the deposition flux, R≡D/F, as a nearly perfect power law over a wide range of R. This ``intermediate'' scaling regime extends in coverage from one to at least a few tens of monolayers, which is exactly the regime of most importance to the growth of device-quality semiconductor quantum heterostructures. Comparison with lowest-order linear theories for height fluctuations demonstrates the validity of the Wolf-Villain mean-field theory for the description of lattice step density and ``in-plane'' structure for all coverages down to the first monolayer of growth. However, the mean-field theory does not fully account for the surface width in this regime and consequently does not quantitatively predict the observed step density scaling.

  20. Two limiting regimes of interacting Bessel processes

    NASA Astrophysics Data System (ADS)

    Andraus, Sergio; Katori, Makoto; Miyashita, Seiji

    2014-06-01

    We consider the interacting Bessel processes, a family of multiple-particle systems in one dimension where particles evolve as individual Bessel processes and repel each other via a log-potential. We consider two limiting regimes for this family on its two main parameters: the inverse temperature β and the Bessel index ν. We obtain the time-scaled steady-state distributions of the processes for the cases where β or ν are large but finite. In particular, for large β we show that the steady-state distribution of the system corresponds to the eigenvalue distribution of the β-Laguerre ensembles of random matrices. We also estimate the relaxation time to the steady state in both cases. We find that in the freezing regime β → ∞, the scaled final positions of the particles are locked at the square root of the zeroes of the Laguerre polynomial of parameter ν - 1/2 for any initial configuration, while in the regime ν → ∞, we prove that the scaled final positions of the particles converge to a single point. In order to obtain our results, we use the theory of Dunkl operators, in particular the intertwining operator of type B. We derive a previously unknown expression for this operator and study its behaviour in both limiting regimes. By using these limiting forms of the intertwining operator, we derive the steady-state distributions, the estimations of the relaxation times and the limiting behaviour of the processes.

  1. Estimation of metabolic heat production and methane emission in Sahiwal and Karan Fries heifers under different feeding regimes

    PubMed Central

    Kumar, Sunil; Singh, S. V.; Pandey, Priyanka; Kumar, Narendra; Hooda, O. K.

    2016-01-01

    Aim: The objective of this study was designed to estimate the metabolic heat production and methane emission in Sahiwal and Karan Fries (Holstein-Friesian X Tharparkar) heifers under two different feeding regimes, i.e., feeding regime-1 as per the National Research Council (NRC) (2001) and feeding regime-2 having 15% higher energy (supplementation of molasses) than NRC (2001). Materials and Methods: Six (n = 6) healthy heifers of Sahiwal and Karan Fries with 18-24 months of age were selected from Indian Council of Agricultural Research-National Dairy Research Institute, Karnal. An initial 15 days was maintained under feeding regime-1 and feeding regime-2 as adaptation period; actual experiment was conducted from 16th day onward for next 15 days. At the end of feeding regimes (on day 15th and 16th), expired air and volume were collected in Douglas bag for two consecutive days (morning [6:00 am] and evening [4:00 pm]). The fraction of methane and expired air volume were measured by methane analyzer and wet test meter, respectively. The oxygen consumption and carbon dioxide production were measured by iWorx LabScribe2. Results: The heat production (kcal/day) was significantly (p<0.05) higher in feeding regime-2 as compared to feeding regimen-1 in both breeds. The heat production per unit metabolic body weight was numerically higher in feeding regime-1 than feeding regime-2; however, the values were found statistically non-significant (p>0.05). The energy loss as methane (%) from total heat production was significantly (p<0.05) higher in feeding regime-1. The body weight (kg), metabolic body weight (W0.75), and basal metabolic rate (kcal/kg0.75) were significantly (p<0.05) higher in feeding regime-2 in both breeds. Conclusions: This study indicates that higher energy diet by supplementing molasses may reduce energy loss as methane and enhance the growth of Sahiwal and Karan Fries heifers. PMID:27284226

  2. Great Lakes' regional climate regimes

    NASA Astrophysics Data System (ADS)

    Kravtsov, Sergey; Sugiyama, Noriyuki; Roebber, Paul

    2016-04-01

    We simulate the seasonal cycle of the Great Lakes' water temperature and lake ice using an idealized coupled lake-atmosphere-ice model. Under identical seasonally varying boundary conditions, this model exhibits more than one seasonally varying equilibrium solutions, which we associate with distinct regional climate regimes. Colder/warmer regimes are characterized by abundant/scarce amounts of wintertime ice and cooler/warmer summer temperatures, respectively. These regimes are also evident in the observations of the Great Lakes' climate variability over recent few decades, and are found to be most pronounced for Lake Superior, the deepest of the Great Lakes, consistent with model predictions. Multiple climate regimes of the Great Lakes also play a crucial role in the accelerated warming of the lakes relative to the surrounding land regions in response to larger-scale global warming. We discuss the physical origin and characteristics of multiple climate regimes over the lakes, as well as their implications for a longer-term regional climate variability.

  3. An Experimental Evaluation of HVAC-Grade Carbon-Dioxide Sensors: Part 3, Humidity, Temperature, and Pressure Sensitivity Test Results

    SciTech Connect

    Shrestha, Som S; Maxwell, Dr. Gregory

    2010-01-01

    This is the third paper in a four-part series reporting on the test and evaluation of typical carbon-dioxide sensors used in building HVAC applications. Fifteen models of NDIR HVAC-grade CO2 sensors were tested and evaluated to determine the humidity, temperature, and pressure sensitivity of the sensors. This paper reports the performance of the sensors at various relative humidity, temperature, and pressure levels common to building HVAC applications and provides a comparison with manufacturer specifications. Among the 15 models tested, eight models have a single-lamp, single-wavelength configuration, four models have a dual-lamp, single-wavelength configuration, and three models have a single-lamp, dual-wavelength configuration. The sensors were tested in a chamber specifically fabricated for this research. A description of the apparatus and the method of test are described in Part 1 (Shrestha and Maxwell 2009). The test result showed a wide variation in humidity, temperature, and pressure sensitivity of CO2 sensors among manufacturers. In some cases, significant variations in sensor performance exist between sensors of the same model. Even the natural variation in relative humidity could significantly vary readings of some CO2 sensor readings. The effects of temperature and pressure variation on NDIR CO2 sensors are unavoidable without an algorithm to compensate for the changes. For the range of temperature and pressure variation in an air-conditioned space, the effect of pressure variation is more significant compared to the effect of temperature variation.

  4. Cost-effective choices of marine fuels in a carbon-constrained world: results from a global energy model.

    PubMed

    Taljegard, Maria; Brynolf, Selma; Grahn, Maria; Andersson, Karin; Johnson, Hannes

    2014-11-01

    The regionalized Global Energy Transition model has been modified to include a more detailed shipping sector in order to assess what marine fuels and propulsion technologies might be cost-effective by 2050 when achieving an atmospheric CO2 concentration of 400 or 500 ppm by the year 2100. The robustness of the results was examined in a Monte Carlo analysis, varying uncertain parameters and technology options, including the amount of primary energy resources, the availability of carbon capture and storage (CCS) technologies, and costs of different technologies and fuels. The four main findings are (i) it is cost-effective to start the phase out of fuel oil from the shipping sector in the next decade; (ii) natural gas-based fuels (liquefied natural gas and methanol) are the most probable substitutes during the study period; (iii) availability of CCS, the CO2 target, the liquefied natural gas tank cost and potential oil resources affect marine fuel choices significantly; and (iv) biofuels rarely play a major role in the shipping sector, due to limited supply and competition for bioenergy from other energy sectors.

  5. Cost-effective choices of marine fuels in a carbon-constrained world: results from a global energy model.

    PubMed

    Taljegard, Maria; Brynolf, Selma; Grahn, Maria; Andersson, Karin; Johnson, Hannes

    2014-11-01

    The regionalized Global Energy Transition model has been modified to include a more detailed shipping sector in order to assess what marine fuels and propulsion technologies might be cost-effective by 2050 when achieving an atmospheric CO2 concentration of 400 or 500 ppm by the year 2100. The robustness of the results was examined in a Monte Carlo analysis, varying uncertain parameters and technology options, including the amount of primary energy resources, the availability of carbon capture and storage (CCS) technologies, and costs of different technologies and fuels. The four main findings are (i) it is cost-effective to start the phase out of fuel oil from the shipping sector in the next decade; (ii) natural gas-based fuels (liquefied natural gas and methanol) are the most probable substitutes during the study period; (iii) availability of CCS, the CO2 target, the liquefied natural gas tank cost and potential oil resources affect marine fuel choices significantly; and (iv) biofuels rarely play a major role in the shipping sector, due to limited supply and competition for bioenergy from other energy sectors. PMID:25286282

  6. Reactivity of Hontomín carbonate rocks to acidic solution injection: reactive "push-pull" tracer tests results

    NASA Astrophysics Data System (ADS)

    De Gaspari, Francesca; Cabeza, Yoar; Luquot, Linda; Rötting, Tobias; Saaltink, Maarten W.; Carrera, Jesus

    2014-05-01

    Several field tests will be carried out in order to characterize the reservoir for CO2 injection in Hontomín (Burgos, Spain) as part of the Compostilla project of "Fundación Ciudad de la Energía" (CIUDEN). Once injected, the dissolution of the CO2 in the resident brine will increase the acidity of the water and lead to the dissolution of the rocks, constituted mainly by carbonates. This mechanism will cause changes in the aquifer properties such as porosity and permeability. To reproduce the effect of the CO2 injection, a reactive solution with 2% of acetic acid is going to be injected in the reservoir and extracted from the same well (reactive "push-pull" tracer tests) to identify and quantify the geochemical reactions occurring into the aquifer. The reactivity of the rock will allow us also to evaluate the changes of its properties. Previously, theoretical calculations of Damkhöler numbers were done to determine the acid concentrations and injection flow rates needed to generate ramified-wormholes patterns, during theses "push-pull" experiments. The aim of this work is to present the results and a preliminary interpretation of the field tests.

  7. Dissolved organic carbon concentration controls benthic primary production: results from in situ chambers in north-temperate lakes

    USGS Publications Warehouse

    Godwin, Sean C.; Jones, Stuart E.; Weidel, Brian C.; Solomon, Christopher T.

    2014-01-01

    We evaluated several potential drivers of primary production by benthic algae (periphyton) in north-temperate lakes. We used continuous dissolved oxygen measurements from in situ benthic chambers to quantify primary production by periphyton at multiple depths across 11 lakes encompassing a broad range of dissolved organic carbon (DOC) and total phosphorous (TP) concentrations. Light-use efficiency (primary production per unit incident light) was inversely related to average light availability (% of surface light) in 7 of the 11 study lakes, indicating that benthic algal assemblages exhibit photoadaptation, likely through physiological or compositional changes. DOC alone explained 86% of the variability in log-transformed whole-lake benthic production rates. TP was not an important driver of benthic production via its effects on nutrient and light availability. This result is contrary to studies in other systems, but may be common in relatively pristine north-temperate lakes. Our simple empirical model may allow for the prediction of whole-lake benthic primary production from easily obtained measurements of DOC concentration.

  8. Modeling the spatiotemporal variability in subsurface thermal regimes across a low-relief polygonal tundra landscape

    NASA Astrophysics Data System (ADS)

    Kumar, Jitendra; Collier, Nathan; Bisht, Gautam; Mills, Richard T.; Thornton, Peter E.; Iversen, Colleen M.; Romanovsky, Vladimir

    2016-09-01

    Vast carbon stocks stored in permafrost soils of Arctic tundra are under risk of release to the atmosphere under warming climate scenarios. Ice-wedge polygons in the low-gradient polygonal tundra create a complex mosaic of microtopographic features. This microtopography plays a critical role in regulating the fine-scale variability in thermal and hydrological regimes in the polygonal tundra landscape underlain by continuous permafrost. Modeling of thermal regimes of this sensitive ecosystem is essential for understanding the landscape behavior under the current as well as changing climate. We present here an end-to-end effort for high-resolution numerical modeling of thermal hydrology at real-world field sites, utilizing the best available data to characterize and parameterize the models. We develop approaches to model the thermal hydrology of polygonal tundra and apply them at four study sites near Barrow, Alaska, spanning across low to transitional to high-centered polygons, representing a broad polygonal tundra landscape. A multiphase subsurface thermal hydrology model (PFLOTRAN) was developed and applied to study the thermal regimes at four sites. Using a high-resolution lidar digital elevation model (DEM), microtopographic features of the landscape were characterized and represented in the high-resolution model mesh. The best available soil data from field observations and literature were utilized to represent the complex heterogeneous subsurface in the numerical model. Simulation results demonstrate the ability of the developed modeling approach to capture - without recourse to model calibration - several aspects of the complex thermal regimes across the sites, and provide insights into the critical role of polygonal tundra microtopography in regulating the thermal dynamics of the carbon-rich permafrost soils. Areas of significant disagreement between model results and observations highlight the importance of field-based observations of soil thermal and

  9. Cloud regimes as phase transitions

    NASA Astrophysics Data System (ADS)

    Stechmann, Samuel N.; Hottovy, Scott

    2016-06-01

    Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes -- open versus closed cells -- fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. With this new conceptual viewpoint, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions.

  10. Simulation of Carbon-14 Migration Through a Thick Unsaturated Alluvial Basin Resulting from an Underground Nuclear Explosion

    NASA Astrophysics Data System (ADS)

    Martian, P.; Larentzos, J.

    2008-12-01

    Yucca Flat is one of several areas on the Nevada Test Site that was used for underground nuclear testing. Extensive testing performed in the unsaturated and saturated zones have resulted in groundwater contamination and surface subsidence craters in the vicinity of the underground test areas. Simulation of multiphase 14C transport through the thick Yucca Flat alluvial basin was performed to estimate the magnitude of radionuclide attenuation occurring within the unsaturated zone. Parameterization of the 14C transport in the multiphase flow and transport simulator (FEHM) was verified with experimental data collected from a large unsaturated soil column experiment. The experimental data included 14C as a radio-labeled bicarbonate solution, SF6 gas, and lithium bromide solution breakthroughs. Two representative simulation cases with working points located at shallow and deep depths relative to the water table were created to investigate the impact of subsidence crater-enhanced recharge, crater-playa areal extent, gas-phase partitioning, solid-phase partitioning, and a reduced permeability/porosity compressed zone created during the explosion on 14C transport. The representative shallow test had a detonation point located 175 m below land surface, and the deep test had a working point 435 m below land surface in a 500 m deep unsaturated zone. Carbon-14 transport is influenced by gas-phase diffusion and sorption within the alluvium. Gas-phase diffusion is an attenuation mechanism that transports 14C gas as 14CO2 throughout the unsaturated zone and exposes it to a large amount of soil moisture, resulting in dilute concentrations. The simulations indicated that the majority of the 14C inventory remains in the unsaturated zone over a 1,000-year time period after detonation because gas-phase diffusion moves the bulk of the 14C away from the higher recharge occurring in crater playas. Retardation also plays a role in slowing advective aqueous phase transport to the water

  11. Flow regimes in a single dimple on the channel surface

    NASA Astrophysics Data System (ADS)

    Kovalenko, G. V.; Terekhov, V. I.; Khalatov, A. A.

    2010-12-01

    The boundaries of the domains of existence of flow regimes past single dimples made as spherical segments on a flat plate are determined with the use of available experimental results. Regimes of a diffuser-confuser flow, a horseshoe vortex, and a tornado-like vortex in the dimple are considered. Neither a horseshoe vortex nor a tornado-like vortex is observed in dimples with the relative depth smaller than 0.1. Transformations from the diffuser-confuser flow regime to the horseshoe vortex regime and from the horseshoe vortex flow to the tornado-like vortex flow are found to depend not only on the Reynolds number, but also on the relative depth of the spherical segment. Dependences for determining the boundaries of the regime existence domains are proposed, and parameters at which the experimental results can be generalized are given.

  12. Density functional theory of the Seebeck coefficient in the Coulomb blockade regime

    NASA Astrophysics Data System (ADS)

    Yang, Kaike; Perfetto, Enrico; Kurth, Stefan; Stefanucci, Gianluca; D'Agosta, Roberto

    2016-08-01

    The Seebeck coefficient plays a fundamental role in identifying the efficiency of a thermoelectric device. Its theoretical evaluation for atomistic models is routinely based on density functional theory calculations combined with the Landauer-Büttiker approach to quantum transport. This combination, however, suffers from serious drawbacks for devices in the Coulomb blockade regime. We show how to cure the theory through a simple correction in terms of the temperature derivative of the exchange correlation potential. Our results compare well with both rate equations and experimental findings on carbon nanotubes.

  13. Carbon dioxide insufflation in routine colonoscopy is safe and more comfortable: results of a randomized controlled double-blinded trial.

    PubMed

    Geyer, M; Guller, U; Beglinger, C

    2011-01-01

    Many patients experience pain and discomfort after colonoscopy. Carbon dioxide (CO(2)) can reduce periprocedural pain although air insufflation remained the standard procedure. The objective of this double-blinded, randomized controlled trial was to evaluate whether CO(2) insufflation does decrease pain and bloating during and after colonoscopy compared to room air. Methods. 219 consecutive patients undergoing colonoscopy were randomized to either CO(2) or air insufflation. Propofol was used in all patients for sedation. Transcutaneous CO(2) was continuously measured with a capnograph as a safety parameter. Pain, bloating, and overall satisfaction were assessed at regular intervals before and after the procedure. Results(data are mean ±SD). 110 patients were randomized to CO(2) and 109 to room air. The baseline characteristics were similar in both groups. The mean propofol dose was not different between the treatments, as were the time to reach the ileum and the withdrawal time. pCO(2) at the end of the procedure was 35.2 ± 4.3 mmHg (CO(2) group) versus 35.6 ± 6.0 mmHg in the room air group (P > .05). No relevant complication occurred in either group. There was significantly less bloating for the CO(2) group during the postprocedural recovery period (P < .001) and over the 24-hour period (P < .001). Also, patients with CO(2) insufflation experienced significantly less pain (P = .014). Finally, a higher overall satisfaction (P = .04 ) was found in the CO(2) group. Conclusions. This trial provides compelling evidence that CO(2) insufflation significantly reduces bloating and pain after routine colonoscopy in propofol-sedated patients. The procedure is safe with no significant differences in CO(2) between the two groups. PMID:21747649

  14. Monitoring and diagnostics systems for nuclear power plant operating regimes

    SciTech Connect

    Abagyan, A.A.; Dmitriev, V.M.; Klebanov, L.A.; Kroshilin, A.E.; Larin, E.P.; Morozov, S.K.

    1988-05-01

    The development of new monitoring and diagnostics systems for Soviet reactors is discussed. An experimental test station is described where industrial operation of new experimental systems can be conducted for purposes of bringing their performance to the level of standard Soviet systems for monitoring reactor operation regimes and equipment resources. The requirements and parameters of the systems are described on a unit-by-unit basis, including the sensor reading monitoring unit, the vibroacoustic monitoring unit, the noise monitoring unit, the accident regime identification unit, and the nonstationary regime monitoring unit. Computer hardware and software requirements are discussed. The results of calculational and experimental research on two complex nonstationary regimes of reactor operation are given. The accident regimes identification unit for the VVER-1000 is analyzed in detail.

  15. Tracing Nitrate Contributions to Streams During Varying Flow Regimes at the Sleepers River Research Watershed, Vermont, USA

    NASA Astrophysics Data System (ADS)

    Sebestyen, S. D.; Shanley, J. B.; Boyer, E. W.; Ohte, N.; Doctor, D. H.; Kendall, C.

    2003-12-01

    Quantifying sources and transformations of nitrate in headwater catchments is fundamental to understanding the movement of nitrogen to streams. At the Sleepers River Research Watershed in northeastern Vermont (USA), we are using multiple chemical tracer and mixing model approaches to quantify sources and transport of nitrate to streams under varying flow regimes. We sampled streams, lysimeters, and wells at nested locations from the headwaters to the outlet of the 41 ha W-9 watershed under the entire range of flow regimes observed throughout 2002-2003, including baseflow and multiple events (stormflow and snowmelt). Our results suggest that nitrogen sources, and consequently stream nitrate concentrations, are rapidly regenerated during several weeks of baseflow and nitrogen is flushed from the watershed by stormflow events that follow baseflow periods. Both basic chemistry data (anions, cations, & dissolved organic carbon) and isotopic data (nitrate, dissolved organic carbon, and dissolved inorganic carbon) indicate that nitrogen source contributions vary depending upon the extent of saturation in the watershed, the initiation of shallow subsurface water inputs, and other hydrological processes. Stream nitrate concentrations typically peak with discharge and are higher on the falling than the rising limb of the hydrograph. Our data also indicate the importance of terrestrial and aquatic biogeochemical processes, in addition to hydrological connectivity in controlling how nitrate moves from the terrestrial landscape to streams. Our detailed sampling data from multiple flow regimes are helping to identify and quantify the "hot spots" and "hot moments" of biogeochemical and hydrological processes that control nitrogen fluxes in streams.

  16. Altered peat hydrophysical properties following drainage and wildfire increases peatland vulnerability to ecosystem regime shift

    NASA Astrophysics Data System (ADS)

    Waddington, James; Kettridge, Nick; Sherwood, James; Granath, Gustaf

    2015-04-01

    Northern peatlands represent a globally significant carbon reservoir, composed largely of legacy carbon which is no longer part of the active carbon cycle. However, it is unclear whether this legacy carbon is vulnerable as a result of enhanced peat smouldering and combustion under the moderate drying conditions predicted for northern peatlands as a result of climate change and/or disturbance from forestry, mining, and associated transport development. A significant loss in legacy carbon as a result of wildfire has already been observed in smaller tropical peatlands where deep peat soils have been destabilized due to severe drainage and a shift in vegetation. Capitalizing on a unique long-term experiment, we quantify the post-wildfire recovery of a northern peatland several decades post drainage. We show that the moderate drop in water table position predicted for most northern regions triggers a shift in vegetation composition, previously observed within only severely disturbed tropical peatlands, when accompanied by wildfire. The combined impact of moderate drainage followed by wildfire resulted in a shift of the peat surface down the peat profile, exposing denser peat at the surface. In undisturbed northern peatlands where depth of burn is typically low, low-density near-surface peats help regulate water-table position and near-surface moisture availability post-fire, both of which are favourable to Sphagnum recolonization. As a result of drainage and fire at the study site, the self-regulating properties of the low-density Sphagnum surface were lost. We demonstrate that changes in peat hydrophysical properties increased hydrological limitations to Sphagnum recovery leading to the conversion to a non-carbon accumulating shrub-grass ecosystem. This new ecosystem is likely to experience a low intensity, high frequency wildfire regime, which will further deplete the legacy carbon stored in the peat.

  17. Global regime shift dynamics of catastrophic sea urchin overgrazing

    PubMed Central

    Ling, S. D.; Scheibling, R. E.; Rassweiler, A.; Johnson, C. R.; Shears, N.; Connell, S. D.; Salomon, A. K.; Norderhaug, K. M.; Pérez-Matus, A.; Hernández, J. C.; Clemente, S.; Blamey, L. K.; Hereu, B.; Ballesteros, E.; Sala, E.; Garrabou, J.; Cebrian, E.; Zabala, M.; Fujita, D.; Johnson, L. E.

    2015-01-01

    A pronounced, widespread and persistent regime shift among marine ecosystems is observable on temperate rocky reefs as a result of sea urchin overgrazing. Here, we empirically define regime-shift dynamics for this grazing system which transitions between productive macroalgal beds and impoverished urchin barrens. Catastrophic in nature, urchin overgrazing in a well-studied Australian system demonstrates a discontinuous regime shift, which is of particular management concern as recovery of desirable macroalgal beds requires reducing grazers to well below the initial threshold of overgrazing. Generality of this regime-shift dynamic is explored across 13 rocky reef systems (spanning 11 different regions from both hemispheres) by compiling available survey data (totalling 10 901 quadrats surveyed in situ) plus experimental regime-shift responses (observed during a total of 57 in situ manipulations). The emergent and globally coherent pattern shows urchin grazing to cause a discontinuous ‘catastrophic’ regime shift, with hysteresis effect of approximately one order of magnitude in urchin biomass between critical thresholds of overgrazing and recovery. Different life-history traits appear to create asymmetry in the pace of overgrazing versus recovery. Once shifted, strong feedback mechanisms provide resilience for each alternative state thus defining the catastrophic nature of this regime shift. Importantly, human-derived stressors can act to erode resilience of desirable macroalgal beds while strengthening resilience of urchin barrens, thus exacerbating the risk, spatial extent and irreversibility of an unwanted regime shift for marine ecosystems.

  18. Dominant takeover regimes for genetic algorithms

    NASA Technical Reports Server (NTRS)

    Noever, David; Baskaran, Subbiah

    1995-01-01

    The genetic algorithm (GA) is a machine-based optimization routine which connects evolutionary learning to natural genetic laws. The present work addresses the problem of obtaining the dominant takeover regimes in the GA dynamics. Estimated GA run times are computed for slow and fast convergence in the limits of high and low fitness ratios. Using Euler's device for obtaining partial sums in closed forms, the result relaxes the previously held requirements for long time limits. Analytical solution reveal that appropriately accelerated regimes can mark the ascendancy of the most fit solution. In virtually all cases, the weak (logarithmic) dependence of convergence time on problem size demonstrates the potential for the GA to solve large N-P complete problems.

  19. Marginal Mean Models for Dynamic Regimes

    PubMed Central

    Murphy, S. A.; van der Laan, M. J.; Robins, J. M.

    2009-01-01

    A dynamic treatment regime is a list of rules for how the level of treatment will be tailored through time to an individual’s changing severity. In general, individuals who receive the highest level of treatment are the individuals with the greatest severity and need for treatment. Thus there is planned selection of the treatment dose. In addition to the planned selection mandated by the treatment rules, the use of staff judgment results in unplanned selection of the treatment level. Given observational longitudinal data or data in which there is unplanned selection, of the treatment level, the methodology proposed here allows the estimation of a mean response to a dynamic treatment regime under the assumption of sequential randomization. PMID:20019887

  20. The optomechanical instability in the quantum regime

    NASA Astrophysics Data System (ADS)

    Ludwig, Max; Kubala, Björn; Marquardt, Florian

    2008-09-01

    We consider a generic optomechanical system, consisting of a driven optical cavity and a movable mirror attached to a cantilever. Systems of this kind (and analogues) have been realized in many recent experiments. It is well known that these systems can exhibit an instability towards a regime where the cantilever settles into self-sustained oscillations. In this paper, we briefly review the classical theory of the optomechanical instability, and then discuss the features arising in the quantum regime. We solve numerically a full quantum master equation for the coupled system, and use it to analyze the photon number, the cantilever's mechanical energy, the phonon probability distribution and the mechanical Wigner density, as a function of experimentally accessible control parameters. When a suitable dimensionless 'quantum parameter' is sent to zero, the results of the quantum mechanical model converge towards the classical predictions. We discuss this quantum-to-classical transition in some detail.

  1. 76 FR 33204 - Certain Welded Carbon Steel Pipe and Tube From Turkey; Notice of Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-08

    ..., 75 FR 37759 (June 30, 2010) (``Review Initiation'').\\1\\ This review covers the Borusan Group \\2... Order; Welded Carbon Steel Standard Pipe and Tube Products From Turkey, 51 FR 17784 (May 15, 1986... Investigation; Opportunity to Request Administrative Review, 75 FR 23236 (May 3, 2010). On May 28, 2010,...

  2. 77 FR 32508 - Circular Welded Carbon Steel Pipes and Tubes From Turkey: Notice of Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-01

    ... Duty Administrative Reviews and Request for Revocation in Part, 76 FR 37781 (June 28, 2011) (``Review... Order; Welded Carbon Steel Standard Pipe and Tube Products From Turkey, 51 FR 17784 (May 15, 1986... Investigation; Opportunity to Request Administrative Review, 76 FR 24460 (May 2, 2011). \\6\\ See Letter...

  3. Using a Class to Conduct a Carbon Inventory: A Case Study with Practical Results at Macalester College

    ERIC Educational Resources Information Center

    Wells, Christopher W.; Savanick, Suzanne; Manning, Christie

    2009-01-01

    Purpose: The purpose of this paper is to discuss the practical realities of using a college seminar to fulfill the carbon audit requirement for signatories to the American College and University Presidents Climate Commitment (ACUPCC) and presents evidence of this approach's advantages as an educational and practical tool.…

  4. 78 FR 61335 - Circular Welded Carbon-Quality Steel Pipe From the People's Republic of China: Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-03

    ...: Circular Welded Carbon Quality Steel Pipe from the People's Republic of China, 73 FR 42547 (July 22, 2008). \\2\\ See Initiation of Five-Year (``Sunset'') Review, 78 FR 33063 (June 3, 2013). Scope of the Order... Quality Steel Pipe from the People's Republic of China, 73 FR 42547 (July 22, 2008); Correction to...

  5. 77 FR 33420 - Certain Activated Carbon From the People's Republic of China: Final Results of Expedited Sunset...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-06

    ... Initiation of Five-Year (``Sunset'') Review, 77 FR 12562 (March 1, 2012); see also Notice of Antidumping Duty Order: Certain Activated Carbon From the People's Republic of China, 72 FR 20988 (April 27, 2007... limited to coal (including bituminous, lignite, and anthracite), wood, coconut shells, olive stones,...

  6. 76 FR 54209 - Corrosion-Resistant Carbon Steel Flat Products From the Republic of Korea: Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-31

    ...The Department of Commerce (the Department) is conducting an administrative review of the countervailing duty (CVD) order on corrosion-resistant carbon steel flat products (CORE) from the Republic of Korea (Korea) for the period of review (POR) January 1, 2009, through December 31, 2009. For information on the net subsidy for Hyundai HYSCO Ltd. (HYSCO), the company reviewed, see the......

  7. 76 FR 23978 - Certain Activated Carbon From the People's Republic of China: Preliminary Results of the Third...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-29

    ... Countervailing Duty Administrative Reviews, 75 FR 29976 (May 28, 2010); see also Initiation of Antidumping and Countervailing Duty Administrative Reviews and Requests for Revocation in Part, 75 FR 37759 (June 30, 2010... Duty Administrative Review, 75 FR 48644 (August 11, 2010). \\4\\ See Certain Activated Carbon from...

  8. The influence of temperature calibration on the OC-EC results from a dual optics thermal carbon analyzer

    NASA Astrophysics Data System (ADS)

    Pavlovic, J.; Kinsey, J. S.; Hays, M. D.

    2014-04-01

    Thermal-optical analysis (TOA) is a widely used technique that fractionates carbonaceous aerosol particles into organic and elemental carbon (OC and EC), or carbonate. Thermal sub-fractions of evolved OC and EC are also used for source identification and apportionment; thus, oven temperature accuracy during TOA analysis is essential. Evidence now indicates that the "actual" sample (filter) temperature and the temperature measured by the built-in oven thermocouple (or set-point temperature) can differ by as much as 50 °C. This difference can affect the OC-EC split point selection and consequently the OC and EC fraction and sub-fraction concentrations being reported, depending on the sample composition and in-use TOA method and instrument. The present study systematically investigates the influence of an oven temperature calibration procedure for TOA. A dual-optical carbon analyzer that simultaneously measures transmission and reflectance (TOT and TOR) is used, functioning under the conditions of both the NIOSH 5040 and IMPROVE protocols. Application of the oven calibration procedure to our dual optics instrument significantly changed NIOSH 5040 carbon fractions (OC and EC) and the IMPROVE OC fraction. In addition, the well-known OC-EC split difference between NIOSH and IMPROVE methods is even further perturbed following the instrument calibration. Further study is needed to determine if the wide-spread application of this oven temperature calibration procedure will indeed improve accuracy and our ability to compare among carbonaceous aerosol studies that use TOA.

  9. Measurements of the corrosion of low-carbon steel drums under environmental conditions at Hanford: One-year test results

    SciTech Connect

    Duncan, D.R.; Bunnell, L.R.

    1995-05-01

    This report describes the methods used to expose low-carbon steel drums to atmospheric and soil corrosion and describes the methods used to examine specimens retrieved from both types of tests. These drums are being tested to meet requirements of radioactive waste storage for both low-level radioactive wastes and transuranic wastes.

  10. 75 FR 47777 - Certain Cut-to-Length Carbon-Quality Steel Plate Products From Italy: Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-09

    ... steels (i.e., USS AR 400, USS AR 500); (5) products made to ASTM A202, A225, A514 grade S, A517 grade S, or their proprietary equivalents; (6) ball bearing steels; (7) tool steels; and (8) silicon manganese... International Trade Administration Certain Cut-to-Length Carbon-Quality Steel Plate Products From Italy:...

  11. Calculated Dipole Moments and Resulting Column Densities of Long Carbon Chain Molecules in TAURUS-MOLECULAR-CLOUD-1

    NASA Astrophysics Data System (ADS)

    Snyder, L. E.; Dykstra, C. E.; Bernholdt, D.

    A number of long carbon chain molecules have been detected in TMC-1 and many of these have no measured or calculated dipole moment. To remedy this, ab initio self-consistent field calculations with small empirical adjustments and extrapolation were used to find the dipole moments of molecules which are of interest for current or future TMC-1 observations.

  12. 75 FR 19369 - Certain Hot-Rolled Flat-Rolled Carbon Quality Steel Products from Brazil: Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-14

    ... Carbon Quality Steel Products from Brazil, 67 FR 11093 (March 12, 2002) (Antidumping Order). ] On March 2... Investigation; Opportunity To Request Administrative Review, 74 FR 9077 (March 2, 2009). In response, on March... and Countervailing Duty Administrative Reviews and Request for Revocation in Part, 74 FR 5821...

  13. 75 FR 64700 - Certain Hot-Rolled Flat-Rolled Carbon-Quality Steel Products From Brazil: Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-20

    ... FR 56040 (September 17, 2004) (HRS Order). The order was issued five years after the completion of...-Quality Steel Products from Brazil, 64 FR 38797 (July 19, 1999); see also Final Affirmative Countervailing Duty Determination: Certain Hot-Rolled Flat-Rolled Carbon-Quality Steel Products from Brazil, 64...

  14. 77 FR 66954 - Carbon and Certain Alloy Steel Wire Rod From Mexico: Preliminary Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-08

    ... of Sales at Less Than Fair Value: Carbon and Certain Alloy Steel Wire Rod From Mexico, 67 FR 55800..., Trinidad and Tobago, and Ukraine, 67 FR 65945 (October 29, 2002), remains dispositive. On October 1, 2012... Rod from Mexico: Affirmative Final Determination of Circumvention of the Antidumping Duty Order, 77...

  15. 77 FR 61738 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-11

    ... Antidumping Duty Order: Circular Welded Carbon Steel Pipes and Tubes From Thailand, 51 FR 8341 (January 27... FR 20782 (April 6, 2012). DATES: Effective Date: October 11, 2012. FOR FURTHER INFORMATION CONTACT... Proceedings: Assessment of Antidumping Duties, 68 FR 23954 (May 6, 2003). Cash Deposit Requirements...

  16. Constructing an interdisciplinary flow regime recommendation

    USGS Publications Warehouse

    Bartholow, J.M.

    2010-01-01

    It is generally agreed that river rehabilitation most often relies on restoring a more natural flow regime, but credibly defining the desired regime can be problematic. I combined four distinct methods to develop and refine month-by-month and event-based flow recommendations to protect and partially restore the ecological integrity of the Cache la Poudre River through Fort Collins, Colorado. A statistical hydrologic approach was used to summarize the river's natural flow regime and set provisional monthly flow targets at levels that were historically exceeded 75% of the time. These preliminary monthly targets were supplemented using results from three Poudre-specific disciplinary studies. A substrate maintenance flow model was used to better define the high flows needed to flush accumulated sediment from the river's channel and help sustain the riparian zone in this snowmelt-dominated river. A hydraulic/habitat model and a water temperature model were both used to better define the minimum flows necessary to maintain a thriving cool water fishery. The result is a range of recommended monthly flows and daily flow guidance illustrating the advantage of combining a wide range of available disciplinary information, supplemented by judgment based on ecological principles and a general understanding of river ecosystems, in a highly altered, working river. ?? 2010 American Water Resources Association.

  17. Changes in mineralogical and leaching properties of converter steel slag resulting from accelerated carbonation at low CO{sub 2} pressure

    SciTech Connect

    Zomeren, Andre van; Laan, Sieger R. van der; Kobesen, Hans B.A.; Huijgen, Wouter J.J.; Comans, Rob N.J.

    2011-11-15

    Highlights: > Accelerated carbonation studied to improve environmental properties of steel slag. > Carbonation found to occur predominantly at surface of the steel slag grains. > Combined geochemical modelling and mineral analysis revealed controlling processes. > Enhanced V-leaching with di-Ca silicate (C2S) dissolution identified as major source. > Identified mineral transformations provide guidance for further quality improvement. - Abstract: Steel slag can be applied as substitute for natural aggregates in construction applications. The material imposes a high pH (typically 12.5) and low redox potential (Eh), which may lead to environmental problems in specific application scenarios. The aim of this study is to investigate the potential of accelerated steel slag carbonation, at relatively low pCO{sub 2} pressure (0.2 bar), to improve the environmental pH and the leaching properties of steel slag, with specific focus on the leaching of vanadium. Carbonation experiments are performed in laboratory columns with steel slag under water-saturated and -unsaturated conditions and temperatures between 5 and 90 {sup o}C. Two types of steel slag are tested; free lime containing (K3) slag and K1 slag with a very low free lime content. The fresh and carbonated slag samples are investigated using a combination of leaching experiments, geochemical modelling of leaching mechanisms and microscopic/mineralogical analysis, in order to identify the major processes that control the slag pH and resulting V leaching. The major changes in the amount of sequestered CO{sub 2} and the resulting pH reduction occurred within 24 h, the free lime containing slag (K3-slag) being more prone to carbonation than the slag with lower free lime content (K1-slag). While carbonation at these conditions was found to occur predominantly at the surface of the slag grains, the formation of cracks was observed in carbonated K3 slag, suggesting that free lime in the interior of slag grains had also reacted

  18. Towards Extreme Field Physics: Relativistic Optics and Particle Acceleration in the Transparent-Overdense Regime

    NASA Astrophysics Data System (ADS)

    Hegelich, B. Manuel

    2011-10-01

    A steady increase of on-target laser intensity with also increasing pulse contrast is leading to light-matter interactions of extreme laser fields with matter in new physics regimes which in turn enable a host of applications. A first example is the realization of interactions in the transperent-overdense regime (TOR), which is reached by interacting a highly relativistic (a0 >10), ultra high contrast laser pulse [1] with a solid density target, turning it transparent to the laser by the relativistic mass increase of the electrons. Thus, the interactions becomes volumetric, increasing the energy coupling from laser to plasma, facilitating a range of effects, including relativistic optics and pulse shaping, mono-energetic electron acceleration [3], highly efficient ion acceleration in the break-out afterburner regime [4], and the generation of relativistic and forward directed surface harmonics. Experiments at the LANL 130TW Trident laser facility successfully reached the TOR, and show relativistic pulse shaping beyond the Fourier limit, the acceleration of mono-energetic ~40 MeV electron bunches from solid targets, forward directed coherent relativistic high harmonic generation >1 keV Break-Out Afterburner (BOA) ion acceleration of Carbon to >1 GeV and Protons to >100 MeV. Carbon ions were accelerated with a conversion efficiency of >10% for ions >20 MeV and monoenergetic carbon ions with an energy spread of <20%, have been accelerated at up to ~500 MeV, demonstrating 3 out of 4 for key requirements for ion fast ignition. The shown results now approach or exceed the limits set by many applications from ICF diagnostics over ion fast ignition to medical physics. Furthermore, TOR targets traverse a wide range of HEDP parameter space during the interaction ranging from WDM conditions (e.g. brown dwarfs) to energy densities of ~1011 J/cm3 at peak, then dropping back to the underdense but extremely hot parameter range of gamma-ray bursts. Whereas today this regime can

  19. Vegetation management with fire modifies peatland soil thermal regime.

    PubMed

    Brown, Lee E; Palmer, Sheila M; Johnston, Kerrylyn; Holden, Joseph

    2015-05-01

    Vegetation removal with fire can alter the thermal regime of the land surface, leading to significant changes in biogeochemistry (e.g. carbon cycling) and soil hydrology. In the UK, large expanses of carbon-rich upland environments are managed to encourage increased abundance of red grouse (Lagopus lagopus scotica) by rotational burning of shrub vegetation. To date, though, there has not been any consideration of whether prescribed vegetation burning on peatlands modifies the thermal regime of the soil mass in the years after fire. In this study thermal regime was monitored across 12 burned peatland soil plots over an 18-month period, with the aim of (i) quantifying thermal dynamics between burned plots of different ages (from <2 to 15 + years post burning), and (ii) developing statistical models to determine the magnitude of thermal change caused by vegetation management. Compared to plots burned 15 + years previously, plots recently burned (<2-4 years) showed higher mean, maximum and range of soil temperatures, and lower minima. Statistical models (generalised least square regression) were developed to predict daily mean and maximum soil temperature in plots burned 15 + years prior to the study. These models were then applied to predict temperatures of plots burned 2, 4 and 7 years previously, with significant deviations from predicted temperatures illustrating the magnitude of burn management effects. Temperatures measured in soil plots burned <2 years previously showed significant statistical disturbances from model predictions, reaching +6.2 °C for daily mean temperatures and +19.6 °C for daily maxima. Soil temperatures in plots burnt 7 years previously were most similar to plots burned 15 + years ago indicating the potential for soil temperatures to recover as vegetation regrows. Our findings that prescribed peatland vegetation burning alters soil thermal regime should provide an impetus for further research to understand the consequences of thermal regime

  20. Anterior cervical corpectomy: review and comparison of results using titanium mesh cages and carbon fibre reinforced polymer cages.

    PubMed

    Kabir, Syed M R; Alabi, J; Rezajooi, Kia; Casey, Adrian T H

    2010-10-01

    Different types of cages have recently become available for reconstruction following anterior cervical corpectomy. We review the results using titanium mesh cages (TMC) and stackable CFRP (carbon fibre reinforced polymer) cages. Forty-two patients who underwent anterior cervical corpectomy between November 2001 and September 2008 were retrospectively reviewed. Pathologies included cervical spondylotic myelopathy (CSM), cervical radiculopathy, OPLL (ossified posterior longitudinal ligament), metastasis/primary bone tumour, rheumatoid arthritis and deformity correction. All patients were evaluated clinically and radiologically. Outcome was assessed on the basis of the Odom's criteria, neck disability index (NDI) and myelopathy disability index (MDI). Mean age was 60 years and mean follow-up was 1½ years. Majority of the patients had single-level corpectomy. Twenty-three patients had TMC cages while 19 patients had CFRP cages. The mean subsidence noted with TMC cage was 1.91 mm, while with the stackable CFRP cage it was 0.5 mm. This difference was statistically significant (p < 0.05). However, there was no statistically significant correlation noted between subsidence and clinical outcome (p > 0.05) or between subsidence and post-operative sagittal alignment (p > 0.05) in either of the groups. Three patients had significant subsidence (> 3 mm), one of whom was symptomatic. There were no hardware-related complications. On the basis of the Odom's criterion, 9 patients (21.4%) had an excellent outcome, 14 patients (33.3%) had a good outcome, 9 patients (21.4%) had a fair outcome and 5 patients (11.9%) had a poor outcome, i.e. symptoms and signs unchanged or exacerbated. Mean post-operative NDI was 26.27% and mean post-operative MDI was 19.31%. Fusion was noted in all 42 cases. Both TMC and stackable CFRP cages provide solid anterior column reconstruction with good outcome following anterior cervical corpectomy. However, more subsidence is noted with TMC cages though

  1. Pulse dynamics in carbon nanotube mode-locked fiber lasers near zero cavity dispersion.

    PubMed

    Wang, Jinzhang; Cai, Zhiping; Xu, Ping; Du, Geguo; Wang, Fengqiu; Ruan, Shuangchen; Sun, Zhipei; Hasan, Tawfique

    2015-04-20

    We numerically and experimentally analyze the output characteristics and pulse dynamics of carbon nanotube mode-locked fiber lasers near zero cavity dispersion (from 0.02 to ~-0.02 ps(2)). We focus on such near zero dispersion cavities to reveal the dispersion related transition between different mode-locking regimes (such as soliton-like, stretched-pulse and self-similar regimes). Using our proposed model, we develop a nanotube-mode-locked fiber laser setup generating ~97 fs pulse which operates in the stretched-pulse regime. The corresponding experimental results and pulse dynamics are in good agreement with the numerical results. Also, the experimental results from soliton-like and self-similar regimes exhibit the same trends with simulations. Our study will aid design of different mode-locking regimes based on other new saturable absorber materials to achieve ultra-short pulse duration.

  2. The influence of temperature calibration on the OC-EC results from a dual-optics thermal carbon analyzer

    NASA Astrophysics Data System (ADS)

    Pavlovic, J.; Kinsey, J. S.; Hays, M. D.

    2014-09-01

    Thermal-optical analysis (TOA) is a widely used technique that fractionates carbonaceous aerosol particles into organic and elemental carbon (OC and EC), or carbonate. Thermal sub-fractions of evolved OC and EC are also used for source identification and apportionment; thus, oven temperature accuracy during TOA analysis is essential. Evidence now indicates that the "actual" sample (filter) temperature and the temperature measured by the built-in oven thermocouple (or set-point temperature) can differ by as much as 50 °C. This difference can affect the OC-EC split point selection and consequently the OC and EC fraction and sub-fraction concentrations being reported, depending on the sample composition and in-use TOA method and instrument. The present study systematically investigates the influence of an oven temperature calibration procedure for TOA. A dual-optical carbon analyzer that simultaneously measures transmission and reflectance (TOT and TOR) is used, functioning under the conditions of both the National Institute of Occupational Safety and Health Method 5040 (NIOSH) and Interagency Monitoring of Protected Visual Environment (IMPROVE) protocols. The application of the oven calibration procedure to our dual-optics instrument significantly changed NIOSH 5040 carbon fractions (OC and EC) and the IMPROVE OC fraction. In addition, the well-known OC-EC split difference between NIOSH and IMPROVE methods is even further perturbed following the instrument calibration. Further study is needed to determine if the widespread application of this oven temperature calibration procedure will indeed improve accuracy and our ability to compare among carbonaceous aerosol studies that use TOA.

  3. Measurement of contemporary and fossil carbon contents of PM 2.5 aerosols: results from Turtleback Dome, Yosemite National Park

    SciTech Connect

    Bench, G

    2003-10-17

    The impact of aerosol particulate matter of mean mass aerodynamic diameter {le} 2.5 {proportional_to}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 {sup 14}C/C ratio of the PM 2.5 aerosols, the absence of {sup 14}C in fossil carbon materials and the known {sup 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 {sup 14}C/C ratios is presented and illustrated using PM 2.5 aerosols collected at Yosemite National Park.

  4. Merging of Rhine flow regimes

    NASA Astrophysics Data System (ADS)

    Boessenkool, Berry; Bronstert, Axel; Bürger, Gerd

    2016-04-01

    The Rhine flow regime is changing: (a) in the alpine nival regime, snow melt floods occur earlier in the year and (b) in the pluvial middle-Rhine regime, rainfall induced flood magnitudes rise. The seasonality of each is currently separated in time, but it is conceivable that this may shift due to climate change. If extremes of both flood types coincide, this would create a new type of hydrologic extreme with disastrous consequences. Quantifying the probability for a future overlap of pluvial and nival floods is therefore of high relevance to society and particularly to reinsurance companies. In order to investigate possible changes in magnitude and timing of flood types, we are developing a chain of physical models for spatio-temporal combination of flood probabilities. As input, we aim to use stochastically downscaled temperature and rainfall extremes from climate model weather projections. Preliminary research shows a six-week forward-shift of peak discharge at the nival gauge Maxau in the past century. The aim of presenting our early-stage work as a poster is to induce an exchange of ideas with fellow scientists in close research disciplines.

  5. River flow regimes and vegetation dynamics along a river transect

    NASA Astrophysics Data System (ADS)

    Doulatyari, Behnam; Basso, Stefano; Schirmer, Mario; Botter, Gianluca

    2014-11-01

    Ecohydrological processes occurring within fluvial landscapes are strongly affected by natural streamflow variability. In this work the patterns of vegetation biomass in two rivers characterized by contrasting flow regimes were investigated by means of a comprehensive stochastic model which explicitly couples catchment-scale hydroclimatic processes, morphologic attributes of the river transect and in-stream bio-ecological features. The hydrologic forcing is characterized by the probability distribution (pdf) of streamflows and stages resulting from stochastic precipitation dynamics, rainfall-runoff transformation and reach scale morphologic attributes. The model proved able to reproduce the observed pdf of river flows and stages, as well as the pattern of exposure/inundation along the river transect in both regimes. Our results suggest that in persistent regimes characterized by reduced streamflow variability, mean vegetation biomass is chiefly controlled by the pattern of groundwater availability along the transect, leading to a marked transition between aquatic and terrestrial environments. Conversely, erratic regimes ensure wider aquatic-terrestrial zones in which optimal elevation ranges for species with different sensitivity to flooding and access to groundwater are separated. Patterns of mean biomass in erratic regimes were found to be more sensitive to changes in the underlying hydroclimatic conditions, notwithstanding the reduced responsiveness of the corresponding flow regimes. The framework developed highlights the important role played by streamflow regimes in shaping riverine environments, and may eventually contribute to identifying the influence of landscape, climate and morphologic features on in-stream ecological dynamics.

  6. 75 FR 75455 - Certain Hot-Rolled Flat-Rolled Carbon-Quality Steel Products From Brazil: Final Results of Full...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-03

    ...: Certain Hot-Rolled Flat-Rolled Carbon-Quality Steel Products From Brazil, 64 FR 38741, 38744 (July 19... FR 16437 (April 1, 2010). The domestic interested parties timely filed a notice of intent to...-Quality Steel Products from Brazil: Preliminary Results of Full Sunset Review, 75 FR 43931 (July 27,...

  7. On chaotic flow regimes in a rotating spherical layer

    NASA Astrophysics Data System (ADS)

    Zhilenko, D. Yu.; Krivonosova, O. É.; Nikitin, N. V.

    2008-12-01

    We present results of an experimental investigation and numerical simulations of chaotic flow regimes in a layer of a viscous incompressible fluid confined between counter-rotating spherical boundaries. The turbulent flow velocity pulsation profiles obtained by straightforward calculations are qualitatively similar to the analogous profiles known for a flat mixing layer. At the boundaries of their formation, chaotic flow regimes are characterized by a continuous spectrum of velocity pulsations and a high correlation dimension ( D > 8), in contrast to the chaotic regimes observed in an analogous layer with one (inner) rotating boundary.

  8. Multiple planetary flow regimes in the Southern Hemisphere

    NASA Technical Reports Server (NTRS)

    Yoden, Shigeo; Shiotani, Masato; Hirota, Isamu

    1987-01-01

    Low-frequency variations in the general circulation of the Southern Hemisphere during 1983 were studied using daily geopotential height and temperature analyses for 12 pressure levels from 1000 mb up to 50 mb, performed by the National Meteorological Center of Japan. Results disclosed the presence, in the Southern Hemisphere troposphere, of an irregular fluctuation of two zonal mean geostrophic wind patterns (named single-jet and double-jet regimes) during wintertime. The fluctuation is characterized by the persistence of one geostrophic wind regime, with characteristic duration of a month, followed by a rather rapid transition to another regime.

  9. Impacts of altered precipitation regimes on soil communities and biogeochemistry in arid and semi-arid ecosystems.

    PubMed

    Nielsen, Uffe N; Ball, Becky A

    2015-04-01

    Altered precipitation patterns resulting from climate change will have particularly significant consequences in water-limited ecosystems, such as arid to semi-arid ecosystems, where discontinuous inputs of water control biological processes. Given that these ecosystems cover more than a third of Earth's terrestrial surface, it is important to understand how they respond to such alterations. Altered water availability may impact both aboveground and belowground communities and the interactions between these, with potential impacts on ecosystem functioning; however, most studies to date have focused exclusively on vegetation responses to altered precipitation regimes. To synthesize our understanding of potential climate change impacts on dryland ecosystems, we present here a review of current literature that reports the effects of precipitation events and altered precipitation regimes on belowground biota and biogeochemical cycling. Increased precipitation generally increases microbial biomass and fungal:bacterial ratio. Few studies report responses to reduced precipitation but the effects likely counter those of increased precipitation. Altered precipitation regimes have also been found to alter microbial community composition but broader generalizations are difficult to make. Changes in event size and frequency influences invertebrate activity and density with cascading impacts on the soil food web, which will likely impact carbon and nutrient pools. The long-term implications for biogeochemical cycling are inconclusive but several studies suggest that increased aridity may cause decoupling of carbon and nutrient cycling. We propose a new conceptual framework that incorporates hierarchical biotic responses to individual precipitation events more explicitly, including moderation of microbial activity and biomass by invertebrate grazing, and use this framework to make some predictions on impacts of altered precipitation regimes in terms of event size and frequency as

  10. Carbon dioxide on the satellites of Saturn: Results from the Cassini VIMS investigation and revisions to the VIMS wavelength scale

    USGS Publications Warehouse

    Cruikshank, D.P.; Meyer, A.W.; Brown, R.H.; Clark, R.N.; Jaumann, R.; Stephan, K.; Hibbitts, C.A.; Sandford, S.A.; Mastrapa, R.M.E.; Filacchione, G.; Ore, C.M.D.; Nicholson, P.D.; Buratti, B.J.; McCord, T.B.; Nelson, R.M.; Dalton, J.B.; Baines, K.H.; Matson, D.L.

    2010-01-01

    Several of the icy satellites of Saturn show the spectroscopic signature of the asymmetric stretching mode of C-O in carbon dioxide (CO2) at or near the nominal solid-phase laboratory wavelength of 4.2675 ??m (2343.3 cm-1), discovered with the Visible-Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft. We report here on an analysis of the variation in wavelength and width of the CO2 absorption band in the spectra of Phoebe, Iapetus, Hyperion, and Dione. Comparisons are made to laboratory spectra of pure CO2, CO2 clathrates, ternary mixtures of CO2 with other volatiles, implanted and adsorbed CO2 in non-volatile materials, and ab initio theoretical calculations of CO2 * nH2O. At the wavelength resolution of VIMS, the CO2 on Phoebe is indistinguishable from pure CO2 ice (each molecule's nearby neighbors are also CO2) or type II clathrate of CO2 in H2O. In contrast, the CO2 band on Iapetus, Hyperion, and Dione is shifted to shorter wavelengths (typically ???4.255 ??m (???2350.2 cm-1)) and broadened. These wavelengths are characteristic of complexes of CO2 with different near-neighbor molecules that are encountered in other volatile mixtures such as with H2O and CH3OH, and non-volatile host materials like silicates, some clays, and zeolites. We suggest that Phoebe's CO2 is native to the body as part of the initial inventory of condensates and now exposed on the surface, while CO2 on the other three satellites results at least in part from particle or UV irradiation of native H2O plus a source of C, implantation or accretion from external sources, or redistribution of native CO2 from the interior. The analysis presented here depends on an accurate VIMS wavelength scale. In preparation for this work, the baseline wavelength calibration for the Cassini VIMS was found to be distorted around 4.3 ??m, apparently as a consequence of telluric CO2 gas absorption in the pre-launch calibration. The effect can be reproduced by convolving a sequence of model detector

  11. Film thickness for different regimes of fluid-film lubrication. [elliptical contacts

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Dowson, D.

    1983-01-01

    Mathematical formulas are presented which express the dimensionless minimum film thickness for the four lubrication regimes found in elliptical contacts: isoviscous-rigid regime; piezoviscous-rigid regime; isoviscous-elastic regime; and piezoviscous-elastic regime. The relative importance of pressure on elastic distortion and lubricant viscosity is the factor that distinguishes these regimes for a given conjunction geometry. In addition, these equations were used to develop maps of the lubrication regimes by plotting film thickness contours on a log-log grid of the dimensionless viscosity and elasticity parameters for three values of the ellipticity parameter. These results present a complete theoretical film thickness parameter solution for elliptical constants in the four lubrication regimes. The results are particularly useful in initial investigations of many practical lubrication problems involving elliptical conjunctions.

  12. Impact of hydrological variations on modeling of peatland CO2 fluxes: Results from the North American Carbon Program site synthesis

    NASA Astrophysics Data System (ADS)

    Sulman, Benjamin N.; Desai, Ankur R.; Schroeder, Nicole M.; Ricciuto, Dan; Barr, Alan; Richardson, Andrew D.; Flanagan, Lawrence B.; Lafleur, Peter M.; Tian, Hanqin; Chen, Guangsheng; Grant, Robert F.; Poulter, Benjamin; Verbeeck, Hans; Ciais, Philippe; Ringeval, Bruno; Baker, Ian T.; Schaefer, Kevin; Luo, Yiqi; Weng, Ensheng

    2012-03-01

    Northern peatlands are likely to be important in future carbon cycle-climate feedbacks due to their large carbon pools and vulnerability to hydrological change. Use of non-peatland-specific models could lead to bias in modeling studies of peatland-rich regions. Here, seven ecosystem models were used to simulate CO2fluxes at three wetland sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor,sphagnum-dominated bog, over periods between 1999 and 2007. Models consistently overestimated mean annual gross ecosystem production (GEP) and ecosystem respiration (ER) at all three sites. Monthly flux residuals (simulated - observed) were correlated with measured water table for GEP and ER at the two fen sites, but were not consistently correlated with water table at the bog site. Models that inhibited soil respiration under saturated conditions had less mean bias than models that did not. Modeled diurnal cycles agreed well with eddy covariance measurements at fen sites, but overestimated fluxes at the bog site. Eddy covariance GEP and ER at fens were higher during dry periods than during wet periods, while models predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP did not depend on water table, while simulated GEP was higher during wet periods. Carbon cycle modeling in peatland-rich regions could be improved by incorporating wetland-specific hydrology and by inhibiting GEP and ER under saturated conditions. Bogs and fens likely require distinct plant and soil parameterizations in ecosystem models due to differences in nutrients, peat properties, and plant communities.

  13. An Examination of the Nature of Global MODIS Cloud Regimes

    NASA Technical Reports Server (NTRS)

    Oreopoulos, Lazaros; Cho, Nayeong; Lee, Dongmin; Kato, Seiji; Huffman, George J.

    2014-01-01

    We introduce global cloud regimes (previously also referred to as "weather states") derived from cloud retrievals that use measurements by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Aqua and Terra satellites. The regimes are obtained by applying clustering analysis on joint histograms of retrieved cloud top pressure and cloud optical thickness. By employing a compositing approach on data sets from satellites and other sources, we examine regime structural and thermodynamical characteristics. We establish that the MODIS cloud regimes tend to form in distinct dynamical and thermodynamical environments and have diverse profiles of cloud fraction and water content. When compositing radiative fluxes from the Clouds and the Earth's Radiant Energy System instrument and surface precipitation from the Global Precipitation Climatology Project, we find that regimes with a radiative warming effect on the atmosphere also produce the largest implied latent heat. Taken as a whole, the results of the study corroborate the usefulness of the cloud regime concept, reaffirm the fundamental nature of the regimes as appropriate building blocks for cloud system classification, clarify their association with standard cloud types, and underscore their distinct radiative and hydrological signatures.

  14. Toward a Physical Characterization of Raindrop Collision Outcome Regimes

    NASA Technical Reports Server (NTRS)

    Testik, F. Y.; Barros, Ana P.; Bilven, Francis L.

    2011-01-01

    A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.

  15. The effect of refrigerants in the mixed lubrication regime

    SciTech Connect

    Mizuhara, Kazuyuki; Tomimoto, Makoto

    1997-12-31

    Because of environmental concerns, CFC (chlorofluorocarbon) refrigerants must be replaced with HFCs (hydrofluorocarbons). As a result, many tribological problems are caused especially in rotary piston compressors. To solve the problem, the effects of refrigerants on friction and wear characteristics of the oil and refrigerant mixtures at the mixed lubrication regime are investigated. The difference in refrigerants are clearly observed not only in boundary but also in the mixed lubrication regime. The effects of operating conditions on sliding conditions and experimental results are also discussed. It is concluded that for practical application where long life is essential, experiments must be conducted under the mixed lubrication regime. Also, the importance of defining the lubrication regime in terms of film parameter is emphasized.

  16. Results of high temperature processing of high-carbon materials from the lower Cambrian period of the Earth's history

    NASA Astrophysics Data System (ADS)

    Maslov, O. D.

    2016-07-01

    The paper reports on the observation of spontaneous fission of nuclides, concentrated in fly ash during the combustion of high-carbon (graphite) material, chemogenic siliceous-carbonaceous rocks and carbonaceous shale in the mixture with brown coal. In the samples obtained, the spontaneous fission was measured by track method. The zones of precipitation of spontaneous fission of nuclides and their lighter homologues on thermochromatographic column were determined. A nuclide with a half-life of 62 days was detected in the alkaline trap. The chemical treatment procedure included co-precipitation with iron hydroxide, dissolution in NH4OH + H2O2 solution and distillation by heating up to 100°C followed by AgI co-precipitation. Based on the chemical behavior it can be concluded that the detected radionuclide belongs to the halides. The content of the parent nuclide in high-carbon (graphite) material and chemogenic siliceous-carbonaceous rock corresponds to 10-14 g/g.

  17. Water level changes affect carbon turnover and microbial community composition in lake sediments.

    PubMed

    Weise, Lukas; Ulrich, Andreas; Moreano, Matilde; Gessler, Arthur; Kayler, Zachary E; Steger, Kristin; Zeller, Bernd; Rudolph, Kristin; Knezevic-Jaric, Jelena; Premke, Katrin

    2016-05-01

    Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. (13)C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions. PMID:26902802

  18. Water level changes affect carbon turnover and microbial community composition in lake sediments

    PubMed Central

    Weise, Lukas; Ulrich, Andreas; Moreano, Matilde; Gessler, Arthur; E. Kayler, Zachary; Steger, Kristin; Zeller, Bernd; Rudolph, Kristin; Knezevic-Jaric, Jelena; Premke, Katrin

    2016-01-01

    Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. 13C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions. PMID:26902802

  19. The thermal regime of Venus

    SciTech Connect

    Solomatov, V.S.; Zharkov, V.N. )

    1990-04-01

    In the present numerical modeling study of the thermal evolution of Venus, the mantle is taken to be composed of independently convecting upper and lower mantles. A novel parameterization is used which takes into account recent numerical investigations in media with complex rheology. The parameters of the convecting planet in the asymptotic regime do not depend on initial conditions, and are ascertained analytically. Convection in the lower part of the crust is demonstrated to be involved in regions having specific crustal composition; heat transfer to the surface is primarily via advection by magmas that are produced by melting of the lower layers of the crust. 50 refs.

  20. Breddin's graph for tectonic regimes

    NASA Astrophysics Data System (ADS)

    Célérier, Bernard; Séranne, Michel

    2001-05-01

    A simple graphical method is proposed to infer the tectonic regime from a fault and slip data set. An abacus is overlaid on a plot of the rake versus strike of the data. This yields the horizontal principal stress directions and a constraint on the stress tensor aspect ratio, in a manner similar to Breddin's graph for two-dimensional strain analysis. The main requirement is that one of the principal stress directions is close to the vertical. This method is illustrated on monophase synthetic and natural data, but is also expected to help sort out multiphase data sets.

  1. Preliminary results of a multi-scale structural analisys in an analogue carbonate reservoir (Hyblean Plateau, Sicily, Italy)

    NASA Astrophysics Data System (ADS)

    Cilona, Antonino; Agosta, Fabrizio; Criscenti, Alessandro; Dipasquale, Mario; Giunta, Giuseppe; Napoli, Giuseppe; Occhipinti, Rosario; Renda, Pietro; Tondi, Emanuele

    2010-05-01

    With the aim of studying the multi-scale fault architecture and permeability in hydrocarbon-rich porous carbonate rocks, we are currently involved in a project focused on the structural analysis of fractured and faulted platform-to-ramp carbonates cropping out in the Hyblean Plateau (Sicily, Italy). The Hyblean Plateau is part of the Maghrebian foreland and forms the northern portion of the African plate. The plateau is a NE-oriented structural high crosscut by a large-scale N10°-20°E oriented strike-slip fault system, named Scicli-Ragusa, which was affected by right-lateral kinematics during the Upper Miocene-Lower Pliocene. Some authors documented a recent activity of the Scicli-Ragusa fault system, during the Quaternary, characterized by left-lateral kinematics. The portion of the Hyblean Plateau crosscut by this fault system represents an excellent example of an outcropping analogue of a fractured carbonate reservoir. By taking advantage of the several oil shows located along the Scicli-Ragusa fault system, we combine stratigraphic-structural analyses, both at outcrop and microscopic scales, to assess the structural control exerted by faults and fractures on hydrocarbon migration and storage. The field work focused on the geological mapping, at 1:10.000 scale, on detailed stratigraphic characterization of the outcropping layered carbonates (Ragusa Fm.) and on traditional faults and fractures analysis. Sample collection was also performed in order to conduct, in the laboratory, optical microscope and image analyses. The Oligo-Miocenic Ragusa Fm. is comprised of two main members: i) the lower Leonardo Member, which is characterised by well-cemented carbonate packstones intercalated with marl-rich levels; ii) the upper Irminio Member, characterised by an alternation of well-cemented and poorly-cemented grainstones/packstones. According to both orientations and kinematics, we grouped the fault segments of the Scicli-Ragusa fault system into three major sets: (i

  2. Bose Polarons in the Strongly Interacting Regime.

    PubMed

    Hu, Ming-Guang; Van de Graaff, Michael J; Kedar, Dhruv; Corson, John P; Cornell, Eric A; Jin, Deborah S

    2016-07-29

    When an impurity is immersed in a Bose-Einstein condensate, impurity-boson interactions are expected to dress the impurity into a quasiparticle, the Bose polaron. We superimpose an ultracold atomic gas of ^{87}Rb with a much lower density gas of fermionic ^{40}K impurities. Through the use of a Feshbach resonance and radio-frequency spectroscopy, we characterize the energy, spectral width, and lifetime of the resultant polaron on both the attractive and the repulsive branches in the strongly interacting regime. The width of the polaron in the attractive branch is narrow compared to its binding energy, even as the two-body scattering length diverges. PMID:27517776

  3. Bose Polarons in the Strongly Interacting Regime

    NASA Astrophysics Data System (ADS)

    Hu, Ming-Guang; Van de Graaff, Michael J.; Kedar, Dhruv; Corson, John P.; Cornell, Eric A.; Jin, Deborah S.

    2016-07-01

    When an impurity is immersed in a Bose-Einstein condensate, impurity-boson interactions are expected to dress the impurity into a quasiparticle, the Bose polaron. We superimpose an ultracold atomic gas of 87Rb with a much lower density gas of fermionic 40 impurities. Through the use of a Feshbach resonance and radio-frequency spectroscopy, we characterize the energy, spectral width, and lifetime of the resultant polaron on both the attractive and the repulsive branches in the strongly interacting regime. The width of the polaron in the attractive branch is narrow compared to its binding energy, even as the two-body scattering length diverges.

  4. The New English Quality Assurance Regime

    ERIC Educational Resources Information Center

    Brown, Roger

    2011-01-01

    England is developing a new quality assurance regime that will come into effect in October 2011. A new funding regime will operate from the following year, together with new rules to ease the participation of private higher education providers. This article describes and analyses the new quality and funding regimes. It argues that the greater…

  5. Summary of 1978 Southeastern Virginia Urban Plume study: Aircraft results for carbon monoxide, methane, nonmethane hydrocarbons, and ozone

    NASA Technical Reports Server (NTRS)

    Hill, G. F.; Sachse, G. W.; Cofer, W. R., III

    1981-01-01

    The characteristics of the Southeastern Virginia urban plume were defined with emphasis on the photon-oxidant species. The measurement area was a rectangle, approximately 150 km by 100 km centered around Cape Charles, Virginia. Included in this area are the cities of Norfolk, Virginia Beach, Chesapeake, Newport News, and Hampton. The area is bounded on the north by Wallops Island, Virginia, and on the south by the Hampton Roads area of Tidewater Virginia. The major axis of the rectangle is oriented in the southwest-northeast direction. The data set includes aircraft measurements for carbon monoxide, methane, nonmethane hydrocarbons, and ozone. The experiment shows that CO can be successfully measured as a tracer gas and used as an index for determining localized and urban plumes. The 1978 data base provided sufficient data to assess an automated chromatograph with flame ionization detection used for measuring methane and nonmethane hydrocarbons in flight.

  6. Structural benefits of bisphenol S and its analogs resulting in their high sorption on carbon nanotubes and graphite.

    PubMed

    Guo, Huiying; Li, Hao; Liang, Ni; Chen, Fangyuan; Liao, Shaohua; Zhang, Di; Wu, Min; Pan, Bo

    2016-05-01

    Bisphenol S (BPS), a new bisphenol analog, is considered to be a potential replacement for bisphenol A (BPA), which has gained concern because of its potentially adverse health impacts. Therefore, studies are needed to investigate the environmental fate and risks of this compound. In this study, the adsorption of BPS and four structural analogs on multi-walled carbon nanotubes (MWCNTs) and graphite (GP) were investigated. When solid-phase concentrations were normalized by the surface areas, oxygen-containing functional groups on the absorbents showed a positive impact on phenol sorption but inhibited the sorption of chemicals with two benzene rings. Among BPS analogs, diphenyl sulfone showed the lowest sorption when hydrophobic effects were ruled out. Chemicals with a butterfly structure, formed between the two benzene rings, showed consistently high sorption on MWCNTs, independent of the substituted electron-donating or accepting functional groups. This study emphasizes the importance of chemical conformation on organic, contaminant sorption on engineered, carbonaceous materials. PMID:26822215

  7. Structural benefits of bisphenol S and its analogs resulting in their high sorption on carbon nanotubes and graphite.

    PubMed

    Guo, Huiying; Li, Hao; Liang, Ni; Chen, Fangyuan; Liao, Shaohua; Zhang, Di; Wu, Min; Pan, Bo

    2016-05-01

    Bisphenol S (BPS), a new bisphenol analog, is considered to be a potential replacement for bisphenol A (BPA), which has gained concern because of its potentially adverse health impacts. Therefore, studies are needed to investigate the environmental fate and risks of this compound. In this study, the adsorption of BPS and four structural analogs on multi-walled carbon nanotubes (MWCNTs) and graphite (GP) were investigated. When solid-phase concentrations were normalized by the surface areas, oxygen-containing functional groups on the absorbents showed a positive impact on phenol sorption but inhibited the sorption of chemicals with two benzene rings. Among BPS analogs, diphenyl sulfone showed the lowest sorption when hydrophobic effects were ruled out. Chemicals with a butterfly structure, formed between the two benzene rings, showed consistently high sorption on MWCNTs, independent of the substituted electron-donating or accepting functional groups. This study emphasizes the importance of chemical conformation on organic, contaminant sorption on engineered, carbonaceous materials.

  8. Carbonic anhydrase related protein 8 mutation results in aberrant synaptic morphology and excitatory synaptic function in the cerebellum

    PubMed Central

    Hirasawa, Michiru; Xu, Xinjie; Trask, Robert B.; Maddatu, Terry P.; Johnson, Britt A; Naggert, Jürgen K.; Nishina, Patsy M.; Ikeda, Akihiro

    2007-01-01

    Carbonic anhydrase related protein 8 (Car8) is known to be abundantly expressed in Purkinje cells (PCs), and its genetic mutation causes a motor coordination defect. To determine the underlying mechanism, we analyzed the mouse cerebellum carrying a Car8 mutation. Electrophysiological analysis showed that spontaneous excitatory transmission was largely diminished while paired pulse ratio at parallel fiber-PC synapses was comparable to wild-type, suggesting functional synapses have normal release probability but the number of functional synapses may be lower in mutants. Light microscopic study revealed an abnormal extension of climbing fibers to the distal PC dendrites. At ultrastructural level, we found numerous PC spines not forming synapses primarily in distal dendrites and occasionally multiple spines contacting a single varicosity. These abnormalities of parallel fiber-PC synapses may underlie the functional defect in excitatory transmission. Thus, Car8 plays a critical role in synaptogenesis and/or maintenance of proper synaptic morphology and function in the cerebellum. PMID:17376701

  9. Historical and projected changes in carbon and nutrient exports to the Gulf of Mexico as resulted from climate change and land use: 1850-2099

    NASA Astrophysics Data System (ADS)

    Tao, B.; Tian, H.; Yang, Q.; Lu, C.; Ren, W.; Yang, J.; Pan, S.; Lohrenz, S. E.; Cai, W.

    2012-12-01

    The transport of nutrients from terrestrial ecosystems to the coastal ocean represents a globally significant carbon flux and a critical biogeochemical linkage between land and coastal ecosystems. As one of the most productive agricultural regions in the world, the Mississippi River basin has experienced profound changes in climate and land use over the past century, fueled by food demand and growing population, and is likely to undergo further rapid development in the coming decades. These changes have greatly influenced carbon and nitrogen exports from land to the Gulf of Mexico (GOM). However, most existing associated studies in this region focused on either terrestrial or aquatic ecosystems separately and overlooked linkage between them, therefore potentially hinder the sustainability of ecosystems and efforts to mitigate and adapt to future environmental change. In this study, we used an integrated ecosystem model (Dynamic Land Ecosystem Model, DLEM) and new-developed gridded climate and land use/cover data as well as other ancillary data to assess historical changes in nutrient exports from Mississippi River basin to the GOM in responses to climate change and land use change during 1850-2010 and predict future changes through 2099 by off-line coupling with general circulation models (GCMs). We specifically quantified spatial patterns and interannual variations of carbon and nutrient exports (TOC, DOC, DIC, DIN, TON and TN, etc.) in responses to climate change and land use. The results indicated that carbon exports exhibited a significant inter-annual variations and land use change, characterized by crop expansion, has substantially increased nutrient exports in the study area. Based on different simulation experiments, our results further demonstrated how management practices (irrigation, nitrogen fertilizer application), the distribution of croplands, and patterns of climate can influence the biogeochemical cycles of carbon and nutrient exports.

  10. Changes in Forest Production, Biomass and Carbon: Results From the 2015 UN FAO Global Forest Resource Assessment

    NASA Astrophysics Data System (ADS)

    Navar, J.

    2015-12-01

    Forests are important sources of livelihoods to millions of people and contribute to national economic development of many countries. In addition, they are vital sources and sinks of carbon and contribute to the rate of climate change. The UN Food and Agriculture Organization has been collecting and presenting data on global forest resources and forest cover since 1948. This paper builds on data from FAO's 2015 Global Forest Resource Assessment (FRA) and presents information on growing stock, biomass, carbon stock, wood removals, and changes of forest area primarily designated for production and multiple use of the world's forests. Between 1990 and 2015, the total growing stock volume has increased in East Asia, Caribbean, Western and Central Asia, North America, Europe (including the Russian Federation), and Oceania with the highest relative increase in East Asia and the Caribbean. In all other subregions the total growing stock volume decreased. North and Central America, Europe and Asia report forest C stock increases while South America and Africa report strong decreases and Oceania reports stable forest C stocks. The annual rate of decrease of forest C stock weakened between 1990 and 2015. The total volume of annual wood removals including wood fuel removals increased between 1990 and 2011, but shows a remarkable decline during the 2008-2009 economic crisis. Forest areas designated for production purposes differ considerably between subregions. The percentage of production area out of total forest area ranges between 16 percent in South America and 53 percent in Europe. Globally about one quarter of the forest area is designated to multiple use forestry. The balance between biomass growth and removals shows considerable sub-regional differences and related implications for the sustainable use of forests.

  11. Adaptation in Collaborative Governance Regimes

    NASA Astrophysics Data System (ADS)

    Emerson, Kirk; Gerlak, Andrea K.

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  12. Different regimes of dynamic wetting

    NASA Astrophysics Data System (ADS)

    Gustav, Amberg; Wang, Jiayu; Do-Quang, Minh; Shiomi, Junichiro; Physiochemical fluid mechanics Team; Maruyama-Chiashi Laboratory Team

    2014-11-01

    Dynamic wetting, as observed when a droplet contacts a dry solid surface, is important in various engineering processes, such as printing, coating, and lubrication. Our overall aim is to investigate if and how the detailed properties of the solid surface influence the dynamics of wetting. Here we discuss how surface roughness influences the initial dynamic spreading of a partially wetting droplet by studying the spreading on a solid substrate patterned with microstructures just a few micrometers in size. This is complemented by matching numerical simulations. We present a parameter map, based on the properties of the liquid and the solid surface, which identifies qualitatively different spreading regimes, where the spreading speed is limited by either the liquid viscosity, the surface properties, or the liquid inertia. The peculiarities of the different spreading regimes are studied by detailed numerical simulations, in conjuction with experiments. This work was financially supported in part by, the Japan Society for the Promotion of Science (J.W. and J.S) and Swedish Governmental Agency for Innovation Systems (M.D.-Q. and G.A).

  13. Adaptation in collaborative governance regimes.

    PubMed

    Emerson, Kirk; Gerlak, Andrea K

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  14. Regime shifts and resilience in China's coastal ecosystems.

    PubMed

    Zhang, Ke

    2016-02-01

    Regime shift often results in large, abrupt, and persistent changes in the provision of ecosystem services and can therefore have significant impacts on human wellbeing. Understanding regime shifts has profound implications for ecosystem recovery and management. China's coastal ecosystems have experienced substantial deterioration within the past decades, at a scale and speed the world has never seen before. Yet, information about this coastal ecosystem change from a dynamics perspective is quite limited. In this review, I synthesize existing information on coastal ecosystem regime shifts in China and discuss their interactions and cascading effects. The accumulation of regime shifts in China's coastal ecosystems suggests that the desired system resilience has been profoundly eroded, increasing the potential of abrupt shifts to undesirable states at a larger scale, especially given multiple escalating pressures. Policy and management strategies need to incorporate resilience approaches in order to cope with future challenges and avoid major losses in China's coastal ecosystem services.

  15. Fixed points, stable manifolds, weather regimes, and their predictability

    SciTech Connect

    Deremble, Bruno; D'Andrea, Fabio; Ghil, Michael

    2009-10-27

    In a simple, one-layer atmospheric model, we study the links between low-frequency variability and the model’s fixed points in phase space. The model dynamics is characterized by the coexistence of multiple ''weather regimes.'' To investigate the transitions from one regime to another, we focus on the identification of stable manifolds associated with fixed points. We show that these manifolds act as separatrices between regimes. We track each manifold by making use of two local predictability measures arising from the meteorological applications of nonlinear dynamics, namely, ''bred vectors'' and singular vectors. These results are then verified in the framework of ensemble forecasts issued from clouds (ensembles) of initial states. The divergence of the trajectories allows us to establish the connections between zones of low predictability, the geometry of the stable manifolds, and transitions between regimes.

  16. Fixed points, stable manifolds, weather regimes, and their predictability.

    PubMed

    Deremble, Bruno; D'Andrea, Fabio; Ghil, Michael

    2009-12-01

    In a simple, one-layer atmospheric model, we study the links between low-frequency variability and the model's fixed points in phase space. The model dynamics is characterized by the coexistence of multiple "weather regimes." To investigate the transitions from one regime to another, we focus on the identification of stable manifolds associated with fixed points. We show that these manifolds act as separatrices between regimes. We track each manifold by making use of two local predictability measures arising from the meteorological applications of nonlinear dynamics, namely, "bred vectors" and singular vectors. These results are then verified in the framework of ensemble forecasts issued from "clouds" (ensembles) of initial states. The divergence of the trajectories allows us to establish the connections between zones of low predictability, the geometry of the stable manifolds, and transitions between regimes.

  17. Regime shifts and resilience in China's coastal ecosystems.

    PubMed

    Zhang, Ke

    2016-02-01

    Regime shift often results in large, abrupt, and persistent changes in the provision of ecosystem services and can therefore have significant impacts on human wellbeing. Understanding regime shifts has profound implications for ecosystem recovery and management. China's coastal ecosystems have experienced substantial deterioration within the past decades, at a scale and speed the world has never seen before. Yet, information about this coastal ecosystem change from a dynamics perspective is quite limited. In this review, I synthesize existing information on coastal ecosystem regime shifts in China and discuss their interactions and cascading effects. The accumulation of regime shifts in China's coastal ecosystems suggests that the desired system resilience has been profoundly eroded, increasing the potential of abrupt shifts to undesirable states at a larger scale, especially given multiple escalating pressures. Policy and management strategies need to incorporate resilience approaches in order to cope with future challenges and avoid major losses in China's coastal ecosystem services. PMID:26286204

  18. Fixed points, stable manifolds, weather regimes, and their predictability

    DOE PAGES

    Deremble, Bruno; D'Andrea, Fabio; Ghil, Michael

    2009-10-27

    In a simple, one-layer atmospheric model, we study the links between low-frequency variability and the model’s fixed points in phase space. The model dynamics is characterized by the coexistence of multiple ''weather regimes.'' To investigate the transitions from one regime to another, we focus on the identification of stable manifolds associated with fixed points. We show that these manifolds act as separatrices between regimes. We track each manifold by making use of two local predictability measures arising from the meteorological applications of nonlinear dynamics, namely, ''bred vectors'' and singular vectors. These results are then verified in the framework of ensemblemore » forecasts issued from clouds (ensembles) of initial states. The divergence of the trajectories allows us to establish the connections between zones of low predictability, the geometry of the stable manifolds, and transitions between regimes.« less

  19. QUANTIFYING FOREST ABOVEGROUND CARBON POOLS AND FLUXES USING MULTI-TEMPORAL LIDAR A report on field monitoring, remote sensing MMV, GIS integration, and modeling results for forestry field validation test to quantify aboveground tree biomass and carbon

    SciTech Connect

    Lee Spangler; Lee A. Vierling; Eva K. Stand; Andrew T. Hudak; Jan U.H. Eitel; Sebastian Martinuzzi

    2012-04-01

    Sound policy recommendations relating to the role of forest management in mitigating atmospheric carbon dioxide (CO{sub 2}) depend upon establishing accurate methodologies for quantifying forest carbon pools for large tracts of land that can be dynamically updated over time. Light Detection and Ranging (LiDAR) remote sensing is a promising technology for achieving accurate estimates of aboveground biomass and thereby carbon pools; however, not much is known about the accuracy of estimating biomass change and carbon flux from repeat LiDAR acquisitions containing different data sampling characteristics. In this study, discrete return airborne LiDAR data was collected in 2003 and 2009 across {approx}20,000 hectares (ha) of an actively managed, mixed conifer forest landscape in northern Idaho, USA. Forest inventory plots, established via a random stratified sampling design, were established and sampled in 2003 and 2009. The Random Forest machine learning algorithm was used to establish statistical relationships between inventory data and forest structural metrics derived from the LiDAR acquisitions. Aboveground biomass maps were created for the study area based on statistical relationships developed at the plot level. Over this 6-year period, we found that the mean increase in biomass due to forest growth across the non-harvested portions of the study area was 4.8 metric ton/hectare (Mg/ha). In these non-harvested areas, we found a significant difference in biomass increase among forest successional stages, with a higher biomass increase in mature and old forest compared to stand initiation and young forest. Approximately 20% of the landscape had been disturbed by harvest activities during the six-year time period, representing a biomass loss of >70 Mg/ha in these areas. During the study period, these harvest activities outweighed growth at the landscape scale, resulting in an overall loss in aboveground carbon at this site. The 30-fold increase in sampling density

  20. Porous anodes with helical flow pathways in bioelectrochemical systems: The effects of fluid dynamics and operating regimes

    NASA Astrophysics Data System (ADS)

    Kim, Jung Rae; Boghani, Hitesh C.; Amini, Negar; Aguey-Zinsou, Kondo-François; Michie, Iain; Dinsdale, Richard M.; Guwy, Alan J.; Guo, Zheng Xiao; Premier, Giuliano C.

    2012-09-01

    Bioelectrochemical systems (BES) and/or microbial fuel cell (MFC) mass transport and associated over-potential limitations are affected by flow regimes, which may simultaneously increase the power and pollution treatment capacities. Two electrodes with helical flow channels were compared in the same tubular MFC reactor. 1). A machined monolithic microporous conductive carbon (MMCC). 2). A layered carbon veil with spoked ABS former (LVSF); both presented helical flow channel. Anode performances were compared when subject to temperature, substrate concentration and flow rate variations. The MMCC maximum power increased from 2.9 ± 0.3 to 7.6 ± 0.7 mW with influent acetate concentration, from 1 to 10 mM (with 2 mL min-1), but decreased power to 5.5 ± 0.5 mW at 40 mM, implicated localized pH/buffering. Flow rate (0.1 to 7.5 mL min-1) effects were relatively small but an increase was evident from batch to continuous operation at 0.1 mL min-1. The LVSF configuration showed improved performance in power as the flow rate increased, indicating that flow pattern affects BES performance. Computational fluid dynamics (CFD) modelling showed less uniform flow with the LVSF. Thus flow regime driven mass transfer improves the power output in continuously fed system operation. These results indicate that electrode configuration, flow regime and operating condition need consideration to optimize the bioelectrochemical reaction.

  1. Synchronous marine pelagic regime shifts in the Northern Hemisphere

    PubMed Central

    Beaugrand, G.; Conversi, A.; Chiba, S.; Edwards, M.; Fonda-Umani, S.; Greene, C.; Mantua, N.; Otto, S. A.; Reid, P. C.; Stachura, M. M.; Stemmann, L.; Sugisaki, H.

    2015-01-01

    Regime shifts are characterized by sudden, substantial and temporally persistent changes in the state of an ecosystem. They involve major biological modifications and often have important implications for exploited living resources. In this study, we examine whether regime shifts observed in 11 marine systems from two oceans and three regional seas in the Northern Hemisphere (NH) are synchronous, applying the same methodology to all. We primarily infer marine pelagic regime shifts from abrupt shifts in zooplankton assemblages, with the exception of the East Pacific where ecosystem changes are inferred from fish. Our analyses provide evidence for quasi-synchronicity of marine pelagic regime shifts both within and between ocean basins, although these shifts lie embedded within considerable regional variability at both year-to-year and lower-frequency time scales. In particular, a regime shift was detected in the late 1980s in many studied marine regions, although the exact year of the observed shift varied somewhat from one basin to another. Another regime shift was also identified in the mid- to late 1970s but concerned less marine regions. We subsequently analyse the main biological signals in relation to changes in NH temperature and pressure anomalies. The results suggest that the main factor synchronizing regime shifts on large scales is NH temperature; however, changes in atmospheric circulation also appear important. We propose that this quasi-synchronous shift could represent the variably lagged biological response in each ecosystem to a large-scale, NH change of the climatic system, involving both an increase in NH temperature and a strongly positive phase of the Arctic Oscillation. Further investigation is needed to determine the relative roles of changes in temperature and atmospheric pressure patterns and their resultant teleconnections in synchronizing regime shifts at large scales.

  2. Laboratory experiment on boundaries of upper stage plane bed regime

    NASA Astrophysics Data System (ADS)

    Zrostlík, Štěpán; Matoušek, Václav

    2016-04-01

    Results are discussed of laboratory experiments on criteria determining the transition between the regime of dunes and the upper stage plane bed (UPB) regime and the transition between the UPB regime and the regime of wavy flow. The experiments were carried for 3 fractions of plastic material and two fractions of glass beads in a broad range of flow conditions (different discharges of water and solids and longitudinal bed slopes) in a tilting flume. The experiments reveal that, contrary to expectations, a constant value of the Shields parameter is not an appropriate criterion for the transition between the dune regime and the UPB regime. Furthermore, the transition appears to be insensitive to the total discharge of solids and water. Instead, the criterion seems to be well represented by a constant value of the average transport concentration of sediment (the ratio of volumetric discharge of solids and volumetric discharge of mixture). The experimental results exhibit a very tight correlation between the transport concentration and the longitudinal bed slope. Hence, a constant value of the bed slope can be considered an appropriate criterion for the transition. The transition between the UPB regime and the wavy regime (significant waves develop but they are not always standing waves) is found at a constant value of Froude number, which is in agreement with literature, although it is found at a higher value than the literature usually suggests (Fr = 1.2 instead of 1.0). Hence, the transition occurs in the super-critical flow but it is not necessarily associated with the critical flow.

  3. Inter-species comparisons in Water use with Different water Irrigation Regimes in a Semi-arid area of Korea-Mongolia Greenbelt Plantation

    NASA Astrophysics Data System (ADS)

    Cho, S.; Ser-Oddamba, B.; Batkhuu, N. O.; Kim, H. S.

    2014-12-01

    As an effort to mitigate desertification and to restore desert areas in Mongolia, Korea-Mongolia Green Belt was established to develop a 3000 ha plantation in 2006. Two native tree species, Populus sibirica and Ulmus pumila L., have been planted under different irrigation regimes (control, control+2L, control +4L and control +8L) since 2008. To investigate the responses of different tree species to different treatment and the effect of plantation on water balance, intensive field experiments have been carried out in 2013-2014 in Mongolia. The objectives of our study are 1) to investigate whether different irrigation regimes changed the physiological characteristics of tree species, 2) to quantify transpirations and water balance under different irrigation regimes, and 3) to compare the water-use-efficiencies among species and irrigation regimes. We used Granier type thermal dissipation sensor, portable photosynthesis analyzer (Li-Cor 6400) and species and site specific allometric equations for transpiration, photosynthetic characteristics and net primary production, respectively. Our preliminary results show that the transpiration rates of P. sibirica increased with the increase of irrigation amount. For examples, the average water consumption of P. sibirica was 1.87kg/tree under control+2L irrigation and 2.97kg/tree at controal+4L irrigation. However, the transpiration rates of U. pumila were not different among different irrigation regimes; the average transpiration of U. pumila at control+2L was 1.1kg/tree compared to 0.89kg/tree at control+4L. But, photosynthetic characteristic showed similar results, which no apparent response under high irrigation regimes. The water use and carbon assimilation of P. sibirica responded to the water irrigation, however, U. pumila did not show any significant response to added water. Our results show different species respond differently to irrigation regimes, and this would lead to different effects on water balance. Therefore

  4. Preliminary Results from the First Year of Operations of the NASA Orbiting Carbon Observatory-2 (OCO-2)

    NASA Astrophysics Data System (ADS)

    Crisp, D.; Eldering, A.; O'Dell, C.; Fisher, B.; Wunch, D.; Wennberg, P. O.; Osterman, G. B.; Mandrake, L.; Payne, V.; Natraj, V.; Frankenberg, C.; Taylor, T.; Worden, J. R.; Bloom, A. A.; Nelson, R. R.; Schwandner, F. M.; Fu, D.; Braverman, A. J.; Chatterjee, A.; Baker, I. T.; Avis, C.; Livermore, T. R.

    2015-12-01

    On September 6, 2014, OCO-2 began routinely returning almost 106 soundings over the sunlit hemisphere each day. Over 10% of these soundings are sufficiently cloud free to yield full-column estimates of the column-averaged CO2 dry air mole fraction, XCO2. Nadir soundings over land yield XCO2 estimates with single-sounding random errors of 0.5 - 1 ppm at solar zenith angles (SZA) < 60° while ocean glint soundings yield precisions near 0.5 ppm at SZA < 70°. Nadir soundings over the ocean and glint soundings over high-latitude land are less precise. Initially, OCO-2 recorded only nadir soundings or glint soundings on alternate, 16-day ground-track repeat cycles. This provided adequate coverage of the globe each month, but produced 16-day gaps in ocean coverage while observing nadir, and similar gaps over high-latitude land while observing glint. In July 2015, this strategy was modified to alternate between glint and nadir soundings on consecutive orbits to yield more continuous coverage each day. While XCO2 and other products are being validated to identify and correct biases, global XCO2 maps are starting to reveal the most robust features of the atmospheric carbon cycle. XCO2 enhancements co-located with intense fossil fuel emissions in eastern U.S. and eastern China are most obvious in the fall, when the north-south XCO2 gradient is small. Enhanced XCO2 coincident with biomass burning in the Amazon, central Africa, and Indonesian is also obvious in the fall. In mid spring, when the north-south XCO2 gradient was largest, these sources were less apparent in global maps. From late May to mid-July, OCO-2 maps show a 2-3% reduction in XCO2 across the northern hemisphere, as the land biosphere rapidly absorbs CO2. As the carbon cycle community continues to analyze these OCO-2 data, quantitative estimates of regional-scale emission sources and natural sinks are expected to emerge. This presentation will summarize the OCO-2 mission status, early products, and near

  5. The discrete regime of flame propagation

    NASA Astrophysics Data System (ADS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew

    The propagation of laminar dust flames in iron dust clouds was studied in a low-gravity envi-ronment on-board a parabolic flight aircraft. The elimination of buoyancy-induced convection and particle settling permitted measurements of fundamental combustion parameters such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. The discrete regime of flame propagation was observed by substitut-ing nitrogen present in air with xenon, an inert gas with a significantly lower heat conductivity. Flame propagation in the discrete regime is controlled by the heat transfer between neighbor-ing particles, rather than by the particle burning rate used by traditional continuum models of heterogeneous flames. The propagation mechanism of discrete flames depends on the spa-tial distribution of particles, and thus such flames are strongly influenced by local fluctuations in the fuel concentration. Constant pressure laminar dust flames were observed inside 70 cm long, 5 cm diameter Pyrex tubes. Equally-spaced plate assemblies forming rectangular chan-nels were placed inside each tube to determine the quenching distance defined as the minimum channel width through which a flame can successfully propagate. High-speed video cameras were used to measure the flame speed and a fiber optic spectrometer was used to measure the flame temperature. Experimental results were compared with predictions obtained from a numerical model of a three-dimensional flame developed to capture both the discrete nature and the random distribution of particles in the flame. Though good qualitative agreement was obtained between model predictions and experimental observations, residual g-jitters and the short reduced-gravity periods prevented further investigations of propagation limits in the dis-crete regime. The full exploration of the discrete flame phenomenon would require high-quality, long duration reduced gravity environment

  6. River Flow Regimes and Effective Discharge

    NASA Astrophysics Data System (ADS)

    Basso, S.; Sprocati, R.; Frascati, A.; Marani, M.; Schirmer, M.; Botter, G.

    2015-12-01

    The concept of effective discharge is widespread in geomorphology and river engineering and restoration. For example, it is used to design the most stable channel configuration, to estimate sedimentation rate and lifespan of reservoirs and to characterize the hydrologic forcing in models studying long-term evolution of rivers. Accordingly, the effective discharge has been the focus of countless empirical, theoretical and numerical studies, which found it to vary among catchments as a function of climate, landscape and river morphology, type of transport (dissolved, suspended or bedload), and of streamflow variability. The heterogeneity of the effective discharge values observed in different catchments challenges a thorough understanding of its pivotal drivers, and a consistent framework which explains observations carried out in different geographic areas is still lacking. In the present work, the observed diversity is explained in terms of the underlying heterogeneity of river flow regimes, by linking effective discharge to attributes of the sediment rating curve and to streamflow variability, as resulting from climatic and landscape drivers. An analytic expression of the effective ratio (i.e. the ratio between effective discharge and mean streamflow) is provided, which captures observed values of effective discharge for suspended sediment transport in a set of catchments of the continental United States. The framework disentangles hydrologic and landscape controls on effective discharge, and highlights distinct effective ratios of persistent and erratic hydrologic regimes (respectively characterized by low and high flow variability), attributable to intrinsically different streamflow dynamics. Clusters of river catchments characterized by similar streamflow dynamics can be identified. The framework provides an opportunity for first-order estimates of effective discharge in rivers belonging to different areas, based on the type of flow regime.

  7. Mitochondrial Carbonic Anhydrase VA Deficiency Resulting from CA5A Alterations Presents with Hyperammonemia in Early Childhood

    PubMed Central

    van Karnebeek, Clara D.; Sly, William S.; Ross, Colin J.; Salvarinova, Ramona; Yaplito-Lee, Joy; Santra, Saikat; Shyr, Casper; Horvath, Gabriella A.; Eydoux, Patrice; Lehman, Anna M.; Bernard, Virginie; Newlove, Theresa; Ukpeh, Henry; Chakrapani, Anupam; Preece, Mary Anne; Ball, Sarah; Pitt, James; Vallance, Hilary D.; Coulter-Mackie, Marion; Nguyen, Hien; Zhang, Lin-Hua; Bhavsar, Amit P.; Sinclair, Graham; Waheed, Abdul; Wasserman, Wyeth W.; Stockler-Ipsiroglu, Sylvia

    2014-01-01

    Four children in three unrelated families (one consanguineous) presented with lethargy, hyperlactatemia, and hyperammonemia of unexplained origin during the neonatal period and early childhood. We identified and validated three different CA5A alterations, including a homozygous missense mutation (c.697T>C) in two siblings, a homozygous splice site mutation (c.555G>A) leading to skipping of exon 4, and a homozygous 4 kb deletion of exon 6. The deleterious nature of the homozygous mutation c.697T>C (p.Ser233Pro) was demonstrated by reduced enzymatic activity and increased temperature sensitivity. Carbonic anhydrase VA (CA-VA) was absent in liver in the child with the homozygous exon 6 deletion. The metabolite profiles in the affected individuals fit CA-VA deficiency, showing evidence of impaired provision of bicarbonate to the four enzymes that participate in key pathways in intermediary metabolism: carbamoylphosphate synthetase 1 (urea cycle), pyruvate carboxylase (anaplerosis, gluconeogenesis), propionyl-CoA carboxylase, and 3-methylcrotonyl-CoA carboxylase (branched chain amino acids catabolism). In the three children who were administered carglumic acid, hyperammonemia resolved. CA-VA deficiency should therefore be added to urea cycle defects, organic acidurias, and pyruvate carboxylase deficiency as a treatable condition in the differential diagnosis of hyperammonemia in the neonate and young child. PMID:24530203

  8. Mitochondrial carbonic anhydrase VA deficiency resulting from CA5A alterations presents with hyperammonemia in early childhood.

    PubMed

    van Karnebeek, Clara D; Sly, William S; Ross, Colin J; Salvarinova, Ramona; Yaplito-Lee, Joy; Santra, Saikat; Shyr, Casper; Horvath, Gabriella A; Eydoux, Patrice; Lehman, Anna M; Bernard, Virginie; Newlove, Theresa; Ukpeh, Henry; Chakrapani, Anupam; Preece, Mary Anne; Ball, Sarah; Pitt, James; Vallance, Hilary D; Coulter-Mackie, Marion; Nguyen, Hien; Zhang, Lin-Hua; Bhavsar, Amit P; Sinclair, Graham; Waheed, Abdul; Wasserman, Wyeth W; Stockler-Ipsiroglu, Sylvia

    2014-03-01

    Four children in three unrelated families (one consanguineous) presented with lethargy, hyperlactatemia, and hyperammonemia of unexplained origin during the neonatal period and early childhood. We identified and validated three different CA5A alterations, including a homozygous missense mutation (c.697T>C) in two siblings, a homozygous splice site mutation (c.555G>A) leading to skipping of exon 4, and a homozygous 4 kb deletion of exon 6. The deleterious nature of the homozygous mutation c.697T>C (p.Ser233Pro) was demonstrated by reduced enzymatic activity and increased temperature sensitivity. Carbonic anhydrase VA (CA-VA) was absent in liver in the child with the homozygous exon 6 deletion. The metabolite profiles in the affected individuals fit CA-VA deficiency, showing evidence of impaired provision of bicarbonate to the four enzymes that participate in key pathways in intermediary metabolism: carbamoylphosphate synthetase 1 (urea cycle), pyruvate carboxylase (anaplerosis, gluconeogenesis), propionyl-CoA carboxylase, and 3-methylcrotonyl-CoA carboxylase (branched chain amino acids catabolism). In the three children who were administered carglumic acid, hyperammonemia resolved. CA-VA deficiency should therefore be added to urea cycle defects, organic acidurias, and pyruvate carboxylase deficiency as a treatable condition in the differential diagnosis of hyperammonemia in the neonate and young child. PMID:24530203

  9. Mitochondrial carbonic anhydrase VA deficiency resulting from CA5A alterations presents with hyperammonemia in early childhood.

    PubMed

    van Karnebeek, Clara D; Sly, William S; Ross, Colin J; Salvarinova, Ramona; Yaplito-Lee, Joy; Santra, Saikat; Shyr, Casper; Horvath, Gabriella A; Eydoux, Patrice; Lehman, Anna M; Bernard, Virginie; Newlove, Theresa; Ukpeh, Henry; Chakrapani, Anupam; Preece, Mary Anne; Ball, Sarah; Pitt, James; Vallance, Hilary D; Coulter-Mackie, Marion; Nguyen, Hien; Zhang, Lin-Hua; Bhavsar, Amit P; Sinclair, Graham; Waheed, Abdul; Wasserman, Wyeth W; Stockler-Ipsiroglu, Sylvia

    2014-03-01

    Four children in three unrelated families (one consanguineous) presented with lethargy, hyperlactatemia, and hyperammonemia of unexplained origin during the neonatal period and early childhood. We identified and validated three different CA5A alterations, including a homozygous missense mutation (c.697T>C) in two siblings, a homozygous splice site mutation (c.555G>A) leading to skipping of exon 4, and a homozygous 4 kb deletion of exon 6. The deleterious nature of the homozygous mutation c.697T>C (p.Ser233Pro) was demonstrated by reduced enzymatic activity and increased temperature sensitivity. Carbonic anhydrase VA (CA-VA) was absent in liver in the child with the homozygous exon 6 deletion. The metabolite profiles in the affected individuals fit CA-VA deficiency, showing evidence of impaired provision of bicarbonate to the four enzymes that participate in key pathways in intermediary metabolism: carbamoylphosphate synthetase 1 (urea cycle), pyruvate carboxylase (anaplerosis, gluconeogenesis), propionyl-CoA carboxylase, and 3-methylcrotonyl-CoA carboxylase (branched chain amino acids catabolism). In the three children who were administered carglumic acid, hyperammonemia resolved. CA-VA deficiency should therefore be added to urea cycle defects, organic acidurias, and pyruvate carboxylase deficiency as a treatable condition in the differential diagnosis of hyperammonemia in the neonate and young child.

  10. Methanol Droplet Extinction in Oxygen/Carbon-dioxide/Nitrogen Mixtures in Microgravity: Results from the International Space Station Experiments

    NASA Technical Reports Server (NTRS)

    Nayagam, Vedha; Dietrich, Daniel L.; Ferkul, Paul V.; Hicks, Michael C.; Williams, Forman A.

    2012-01-01

    Motivated by the need to understand the flammability limits of condensed-phase fuels in microgravity, isolated single droplet combustion experiments were carried out in the Combustion Integrated Rack Facility onboard the International Space Station. Experimental observations of methanol droplet combustion and extinction in oxygen/carbon-dioxide/nitrogen mixtures at 0.7 and 1 atmospheric pressure in quiescent microgravity environment are reported for initial droplet diameters varying between 2 mm to 4 mm in this study.The ambient oxygen concentration was systematically lowered from test to test so as to approach the limiting oxygen index (LOI) at fixed ambient pressure. At one atmosphere pressure, ignition and some burning were observed for an oxygen concentration of 13% with the rest being nitrogen. In addition, measured droplet burning rates, flame stand-off ratios, and extinction diameters are presented for varying concentrations of oxygen and diluents. Simplified theoretical models are presented to explain the observed variations in extinction diameter and flame stand-off ratios.

  11. 76 FR 65497 - Certain Hot-Rolled Carbon Steel Flat Products From India: Amended Final Results of Countervailing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-21

    ...: Final Results of Countervailing Duty Administrative Review, 73 FR 40295 (July 14, 2008) (Final Results... Final Results of Administrative Review, 75 FR 59689 (September 28, 2010). The Department's... Review and Notice of Amended final Results of Administrative Review Pursuant to Court Decision, 76...

  12. 78 FR 22235 - Certain Magnesia Carbon Bricks From the People's Republic of China: Final Results of and Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-15

    ... China: 2010 Countervailing Duty Administrative Review, 77 FR 61397 (October 9, 2012) (Preliminary Results). \\2\\ See Preliminary Results, 77 FR 61399. DATES: Effective Date: April 15, 2013. FOR FURTHER... RHI companies, and NCR for these final results. \\5\\ See Preliminary Results, 77 FR 61398....

  13. Permafrost and the geothermal regime

    NASA Astrophysics Data System (ADS)

    Lachenbruch, A. H.; Marshall, B. V.

    Permafrost is the region in the solid earth where the temperature is below 0 C summer and winter. Within this region, water usually occurs as ice, often in massive segregated forms, although capillary water, brines, and gas hydrates also occur. The frozen condition renders permafrost impermeable to water flow, subject to brittle fracture under seasonally induced thermal stress, and subject to mechanical failure and flow when thawed by natural processes or disturbed by man. Hence an understanding of the factors controlling the geothermal regime is necessary for an understanding of geomorphic processes and for successful design of engineering structures such as roadways, heated buildings, pipelines, and oil wells in permafrost terrains. Studies of these factors are greatly simplified by the general absence of heat transfer by flowing ground water; temperatures are estimated with confidence from heat-conduction theory if the ground surface temperature, regional heat flow, and thermal properties are known.

  14. The effect of carbon credits on savanna land management and priorities for biodiversity conservation.

    PubMed

    Douglass, Lucinda L; Possingham, Hugh P; Carwardine, Josie; Klein, Carissa J; Roxburgh, Stephen H; Russell-Smith, Jeremy; Wilson, Kerrie A

    2011-01-01

    Carbon finance offers the potential to change land management and conservation planning priorities. We develop a novel approach to planning for improved land management to conserve biodiversity while utilizing potential revenue from carbon biosequestration. We apply our approach in northern Australia's tropical savanna, a region of global significance for biodiversity and carbon storage, both of which are threatened by current fire and grazing regimes. Our approach aims to identify priority locations for protecting species and vegetation communities by retaining existing vegetation and managing fire and grazing regimes at a minimum cost. We explore the impact of accounting for potential carbon revenue (using a carbon price of US$14 per tonne of carbon dioxide equivalent) on priority areas for conservation and the impact of explicitly protecting carbon stocks in addition to biodiversity. Our results show that improved management can potentially raise approximately US$5 per hectare per year in carbon revenue and prevent the release of 1-2 billion tonnes of carbon dioxide equivalent over approximately 90 years. This revenue could be used to reduce the costs of improved land management by three quarters or double the number of biodiversity targets achieved and meet carbon storage targets for the same cost. These results are based on generalised cost and carbon data; more comprehensive applications will rely on fine scale, site-specific data and a supportive policy environment. Our research illustrates that the duel objective of conserving biodiversity and reducing the release of greenhouse gases offers important opportunities for cost-effective land management investments.

  15. Initial Results from the Los Angeles Megacity Carbon Project: Exploring Spatial and Temporal Variability of the In Situ CO2 Observations

    NASA Astrophysics Data System (ADS)

    Verhulst, K. R.; Feng, S.; Kim, J.; Salameh, P.; Sloop, C.; Rao, P.; Hopkins, F. M.; Yadav, V.; Keeling, R. F.; Weiss, R. F.; Miller, J. B.; Miller, C. E.; Duren, R. M.

    2015-12-01

    The Megacities Carbon Project (megacities.jpl.nasa.gov) is a multi-national, multi-institution project aimed at quantifying multi-year carbon emissions trends from large urban areas. The Los Angeles Megacity greenhouse gas observation network includes fifteen surface in situ sites and was designed to capture spatial and temporal variability in carbon emissions across the South Coast Air Basin. The surface sites include a combination of towers and rooftops equipped with laser absorption spectrometers measuring carbon dioxide (CO2), with methane and carbon monoxide measurement capability at a subset of the sites. In this study, we report intial results from January-April 2015 collected at four tower sites: two "urban" sites, which predominantly exhibit urban CO2 enhancements, and two "background" sites, which are primarily influenced by unpolluted maritime or continental air masses and reflect local background CO2 levels. During January-April 2015, hourly-averaged in situ measurements ranged from roughly 395-650 ppm CO2, with the urban sites reflecting systematically higher CO2 levels compared to the background sites. The average CO2 enhancement observed at midday (12-4pm PST) ranged from 15-23 ppm CO2 excess at the urban sites, Compton and Granada Hills. The tower measurements also show diurnal, day of week, and monthly variability. Overall, the results from the in situ network are consistent with prior studies that utilized ground-based and space-based remote sensing data to demonstrate that the "urban CO2 dome" hypothesis applies to Los Angeles. The continuous measurement capability provided by the in situ network also highlights the fact that atmospheric CO2 enhancements vary in both space and time and are not uniform throughout the South Coast Air Basin. Future work will involve sectoral attribution of the emissions sources contributing to the urban CO2 enhancements using the Hestia high-resolution fossil fuel carbon emissions inventory. A forward model

  16. Quantity and quality of black carbon molecular markers as obtained by two chromatographic methods (GC-FID and HPLC-DAD) - How do results compare?

    NASA Astrophysics Data System (ADS)

    Schneider, M. P. W.; Smittenberg, R. H.; Dittmar, T.; Schmidt, M. W. I.

    2009-04-01

    Chars produced by wildfires are an important source of black carbon (BC) in the environment. After their deposition on the soil surface they can be distributed into rivers, marine waters and sediments. The analysis of benzenepolycarboxylic acids (BPCAs) as a quantitative measure for black carbon (BC) in soil and sediment samples is a well-established method (Glaser et al., 1998; Brodowski et al., 2005). Briefly, the nitric acid oxidation of fused aromatic ring systems in BC forms eight molecular markers (BPCAs), which can be assigned to BC, and which subsequently can be quantified by GC-FID (gas chromatography with flame ionization detector). Recently, this method was modified for the quantification of BC in seawater samples using HPLC-DAD (High performance liquid chromatography with diode array detector) for the determination of individual BPCAs (Dittmar, 2008). A direct comparison of both analytical techniques is lacking but would be important for future data comparison aimed at the calculation of global BC budgets. Here we present a systematic comparison of the two BPCA quantification methods. We prepared chars under well-defined laboratory conditions. In order to cover a broad spectrum of char properties we used two sources of biomass and a wide range of pyrolysis temperatures. Chestnut hardwood chips (Castanea sativa) and rice straw (Oryza sativa) were pyrolysed at temperatures between 200 and 1000°C under a constant N2 stream. The maximum temperatures were held constant for 5 hours (Hammes et al., 2006). The BC contents of the chars have been analysed using the BPCA extraction method followed by either GC-FID or HPLC-DAD quantification. Preliminary results suggest that both methods yield similar total quantities of BPCA, and also the proportions of the individual markers are similar. Ongoing experiments will allow for a more detailed comparison of the two methods. The BPCA composition of chars formed at different temperatures and from different precursor

  17. Sensitivity of streamflows to hydroclimatic fluctuations: resilience and regime shifts

    NASA Astrophysics Data System (ADS)

    Botter, Gianluca; Basso, Stefano; Rodriguez-Iturbe, Ignacio; Rinaldo, Andrea

    2016-04-01

    Landscape and climate alterations foreshadow global-scale shifts of river flow regimes. However, a theory that identifies the range of foreseen impacts on streamflows resulting from inhomogeneous forcings and sensitivity gradients across diverse regimes is lacking. In this contribution, we use a dimensionless index embedding simple climate and landscape attributes (the ratio of the mean interarrival of streamflow-producing rainfall events and the mean catchment response time) to discriminate erratic regimes with enhanced intra-seasonal streamflow variability from persistent regimes endowed with regular flow patterns. The proposed classification is successfully applied to 110 seasonal streamflow distributions observed in 44 catchments of the Alps and the United States, allowing the identification of emerging patterns in space and time. In the same framework, the impact of multi-scale fluctuations of the underlying climatic drivers (temperature, precipitation) on the streamflow distributions can be analyzed. Theoretical and empirical data show that erratic regimes, typical of rivers with low mean discharges, are highly resilient in that they hold a reduced sensitivity to variations in the external forcing. Specific temporal trajectories of streamflow distributions and flow regime shifts driven by land-cover change and rainfall patterns can be also evidenced. The approach developed offers an objective basis for the analysis and prediction of the impact of climate/landscape change on water resources.

  18. O-regime dynamics and modeling in Tore Supra

    SciTech Connect

    Turco, F.; Giruzzi, G.; Imbeaux, F.; Udintsev, V. S.; Artaud, J. F.; Barana, O.; Dumont, R.; Mazon, D.; Segui, J.-L.

    2009-06-15

    The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Equipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r) and the electron temperature T{sub e}(r) where the equation coefficients are functions of j and T{sub e} themselves. Both the integrated modeling code CRONOS[V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.

  19. Wavelength Dependence of the Absorption of Black Carbon Particles: Predictions and Results from the TARFOX Experiment and Implications for the Aerosol Single Scattering Albedo

    NASA Technical Reports Server (NTRS)

    Bergstrom, Robert W.; Russell, Philip B.; Hignett, Phillip

    2002-01-01

    Measurements are presented of the wavelength dependence of the aerosol absorption coefficient taken during the Tropical Aerosol Radiative Forcing Observational Experiment (TARFOX) over the northern Atlantic. The data show an approximate lamda(exp -1) variation between 0.40 and 1.0 micrometers. The theoretical basis of the wavelength variation of the absorption of solar radiation by elemental carbon [or black carbon (BC)] is explored. For a wavelength independent refractive index the small particle absorption limit simplifies to a lambda(exp -1) variation in relatively good agreement with the data. This result implies that the refractive indices of BC were relatively constant in this wavelength region, in agreement with much of the data on refractive indices of BC. However, the result does not indicate the magnitude of the refractive indices. The implications of the wavelength dependence of BC absorption for the spectral behavior of the aerosol single scattering albedo are discussed. It is shown that the single scattering albedo for a mixture of BC and nonabsorbing material decreases with wavelength in the solar spectrum (i.e., the percentage amount of absorption increases). This decease in the single scattering albedo with wavelength for black carbon mixtures is different from the increase in single scattering allied for most mineral aerosols (dusts). This indicates that, if generally true, the spectral variation of the single- scattering albedo can be used to distinguish aerosol types. It also highlights the importance of measurements of the spectral variation of the aerosol absorption coefficient and single scattering albedo.

  20. Graphite grains studded with silver nanoparticles: description and application in promoting direct biocatalysis between heme protein and the resulting carbon paste electrode.

    PubMed

    ElKaoutit, Mohammed; Naggar, Ahmad H; Naranjo-Rodríguez, Ignacio; de Cisneros, José L Hidalgo-Hidalgo

    2012-04-01

    The impregnation of graphite grains with silver nanoparticles (AgNPs) is proposed for making a novel carbon paste electrode (CPE). The resulting material promotes direct electron transfer and direct biocatalysis of embedded heme protein. It is demonstrated that the impregnation of graphite grains with AgNPs of 16-25 nm, incorporated in a CPE, can promote measurable bio-electrochemical phenomena involving hemoglobin and myoglobin. Unlike other biosensors prepared with simple carbon, those based on carbon grains studded with AgNPs show well-defined and quasi-reversible voltammetric peak with heterogeneous electron transfer rate k(s) of approximately 0.037±0.007 and 0.013±0.005s(-1) for hemoglobin and myoglobin, respectively. The embedded proteins also retain their bio-catalytical activity for hydrogen peroxide and nitrite reduction with linear ranges of 0.5-3000 μM and 30-150 μM, sensitivities of 73.6±0.6nA μM(-1) and 5.72±0.11 nA μM(-1), and detection limits close to 0.08 μM and 5.80 μM, for these two analytes respectively. These results support the viability of this preliminary approach for the development of advanced third-generation biosensors. PMID:22154098

  1. Fourier-transform infrared spectroscopy for the assesment of soil organic carbon removal by superheated water: preliminary results

    NASA Astrophysics Data System (ADS)

    Ćirić, Vladimir; Švarc-Gajić, Jaroslava; Jović, Branislav; Kordić, Branko; Šodić, Bojana; Šeremešić, Srđan

    2016-04-01

    Soil organic carbon (SOC) is key determinant of soil quality and thus can considerably affect ecosystem services, environmental and global climate changes. Consequently, characterization of SOC and its fractions is of an increasing interest. No standard method for assessment of SOC fractions was adopted. Subcritical water extraction (SCWE) provides great flexibility and could be used for the extraction of different organic compounds from soil as well as for the removal of different SOC fractions from soil. The purpose of this study was to assess the potential of the treatment with subcritical water (SCW), or superheated water, in combination with different catalysts to affect different SOC fractions and thus its spectral bands. Subcritical water treatment of soil samples was performed at 180°C and pressure of 40 bars, whilst three different catalysts were separately applied: titanium dioxide (TiO2), cerium sulfate Ce (SO4)2 and zeolite. Fourier-transform infrared (FTIR) spectroscopy was used as known technique for SOC characterization. After the SCW treatment the efficiency of catalysts regarding the removal of SOC fractions was studied via spectral bands of treated soil samples. Soil treatment with SCW without catalyst caused most changes in the region of 3800-3000 nm (-OH) that corresponds to cellulose. The aromatic compounds (C=C groups) in the region of 1800-1550 nm that corresponds to stable SOC fractions (humic materials and lignin) was strongly affected by treatment with TiO2. Aliphatic compounds in the region of 1500-1350 nm (C-H and C-O groups) were mostly affected by SCW in combination with zeolite, while SCW in combination with Ce(SO4)2 besides aliphatic region altered aromatic groups in lesser extent. Zeolite in combination with SCW was proved to be good tool for aliphatic (labile) SOC removal, while TiO2 in combination with SCW was proved efficient for the removal of aromatic (stable) SOC fractions.

  2. Deposition of organic carbon-rich sediments in narrow marine basins and open-marine upwelling environments - New results from the ocean drilling program

    SciTech Connect

    Stein, R. )

    1988-08-01

    Detailed sedimentological and organic geochemical investigations have been performed on Neogene sediments from ODP site 645 (Baffin Bay), ODP site 658 (upwelling area of northwest Africa), and ODP site 679 (upwelling area off Peru). The study is mainly based on (1) data derived from total organic carbon and nitrogen analyses, Rock-Eval pyrolysis, and kerogen microscopy (2) sedimentation rates, and (3) x-ray diffraction analyses. The main objective of this study was to point out the most important factors controlling the accumulation of organic carbon in the different sedimentary environments, such as supply of terrigenous organic matter, productivity of marine organic matter, and preservation of organic matter. These new results from the investigation of ODP sediments are compared with DSDP data from the Mesozoic Atlantic Ocean to characterize the depositional environments of Mesozoic black shales.

  3. 77 FR 13093 - Corrosion-Resistant Carbon Steel Flat Products From the Republic of Korea: Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-05

    ...: Preliminary Results of Countervailing Duty Administrative Review, 76 FR 54209 (August 31, 2011) (``Preliminary... from Korea, 58 FR 43752 (August 17, 1993). \\4\\ See Preliminary Results, 76 FR 54209. In the Preliminary...: Extension of Time Limit for Final Results of Countervailing Duty Administrative Review, 76 FR...

  4. 78 FR 286 - Circular Welded Carbon Steel Pipes and Tubes From Turkey; Amended Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-03

    ..., 77 FR 72818 (December 6, 2012) (Final Results). \\2\\ The Borusan Group includes the following entities...., Borusan Ithicat ve Dagitim A.S., and Tubeco Pipe and Steel Corporation. See Final Results, 77 FR at 72818... and Tube From Turkey: Notice of Final Results of Antidumping Duty Administrative Review, 76 FR...

  5. 78 FR 79665 - Welded Carbon Steel Standard Pipe and Tube Products From Turkey: Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-31

    ... Administrative Review; 2011-2012, 78 FR 34340 (June 7, 2013) (Preliminary Results). \\2\\ The Department initiated... during the POR. See Preliminary Results, 78 FR at 34340 n. 4. Furthermore, as we stated in the draft cash... Results, 78 FR at 34341. The Department has conducted this administrative review in accordance...

  6. 78 FR 25701 - Certain Hot-Rolled Carbon Steel Flat Products From India: Notice of Second Amended Final Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-02

    ...: Final Results and Partial Rescission of Countervailing Duty Administrative Review, 74 FR 20,923 (May 6... Pursuant to Court Decision, 76 FR 7810 (February 11, 2011) (Amended Final Results). DATES: Effective Date... deposits for Essar at the cash deposit rate of 22.19 percent. \\17\\ Amended Final Results, 76 FR at...

  7. 76 FR 27987 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Amended Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-13

    ... Review, 73 FR 61019 (October 15, 2008) (Final Results). FOR FURTHER INFORMATION CONTACT: Jacqueline... Not in Harmony with Final Results of Administrative Review, 75 FR 2487 (January 15, 2010). On February... Tubes From Thailand: Amended Final Results of Antidumping Duty Administrative Review, 75 FR...

  8. 77 FR 46713 - Circular Welded Carbon Steel Pipes and Tubes From Turkey: Final Results of Countervailing Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-06

    ... Steel Pipe and Tube Products From Turkey, 51 FR 7984 (March 7, 1986). \\5\\ See Preliminary Results, 77 FR... Results of Countervailing Duty Administrative Review, 77 FR 19623 (April 2, 2012) (Preliminary Results... Administrative Review, In Part, 77 FR 6542 (February 8, 2012). \\3\\ See Issues and Decision Memorandum...

  9. Revealing the quantum regime in tunnelling plasmonics.

    PubMed

    Savage, Kevin J; Hawkeye, Matthew M; Esteban, Rubén; Borisov, Andrei G; Aizpurua, Javier; Baumberg, Jeremy J

    2012-11-22

    When two metal nanostructures are placed nanometres apart, their optically driven free electrons couple electrically across the gap. The resulting plasmons have enhanced optical fields of a specific colour tightly confined inside the gap. Many emerging nanophotonic technologies depend on the careful control of this plasmonic coupling, including optical nanoantennas for high-sensitivity chemical and biological sensors, nanoscale control of active devices, and improved photovoltaic devices. But for subnanometre gaps, coherent quantum tunnelling becomes possible and the system enters a regime of extreme non-locality in which previous classical treatments fail. Electron correlations across the gap that are driven by quantum tunnelling require a new description of non-local transport, which is crucial in nanoscale optoelectronics and single-molecule electronics. Here, by simultaneously measuring both the electrical and optical properties of two gold nanostructures with controllable subnanometre separation, we reveal the quantum regime of tunnelling plasmonics in unprecedented detail. All observed phenomena are in good agreement with recent quantum-based models of plasmonic systems, which eliminate the singularities predicted by classical theories. These findings imply that tunnelling establishes a quantum limit for plasmonic field confinement of about 10(-8)λ(3) for visible light (of wavelength λ). Our work thus prompts new theoretical and experimental investigations into quantum-domain plasmonic systems, and will affect the future of nanoplasmonic device engineering and nanoscale photochemistry.

  10. Environmental and Physiological Influences on the TEX86 Proxy: Results from Continuous Culture Studies and Stable Carbon Isotope Analyses

    NASA Astrophysics Data System (ADS)

    Pearson, A.; Hurley, S.; Elling, F. J.; Koenneke, M.; Santoro, A. E.; Buchwald, C.; Wankel, S. D.; Hinrichs, K. U.; Zhang, Y.; Shah Walter, S. R.

    2015-12-01

    Membrane lipids of marine Archaea - known as GDGTs - are the basis of the TEX86 sea surface temperature (SST) paleoproxy. GDGTs are ubiquitous in marine sediments, and their broad distribution and high preservation potential have led to an ever-increasing use of TEX86. The planktonic Thaumarchaeota that are believed to be the major sources of GDGTs to marine sediments are autotrophic nitrifiers, assimilating carbon directly from dissolved CO2. Therefore the δ13C values of GDGTs additionally provide information about the DIC system and paleoproductivity. However, as for all biological proxies, understanding the physiology and biochemistry of the responsible organisms is essential to understanding how the proxies work. From this perspective, the TEX86-SST proxy is uniquely perplexing: How is it possible that multiple approaches to calibration show a good correlation between TEX86 and SSTs, when maximum activity of Thaumarchaeota is near and below the base of the photic zone? Here we show data from two studies that help address this question. Analyses of GDGT δ13C values show that the dominant GDGT flux to sediments is not from the sea surface. The data are measured on intact GDGTs purified by orthogonal dimensions of HPLC, followed by measurement of δ13C values on a Spooling Wire Microcombustion (SWiM)-IRMS with 1σ precision of ±0.2‰ and accuracy of ±0.3‰. Using this approach, we confirm that GDGTs, generally around -19.0‰ to -18.5‰, are isotopically "heavy" compared to other marine lipids, and that crenarchaeol in particular is a good tracer of water column GDGT export. In parallel, we investigated the mechanistic underpinning of the TEX86 proxy using isothermal culture studies of the ammonia-oxidizing thaumarchaeon Nitrosopumilus maritimus SCM1 to explore the relationship between TEX86 and growth conditions. Evidence suggests that growth rate and electron donor supply are important controls on GDGT ratios and that TEX86 scales with the in-situ rate of

  11. Fate of organic carbon in paddy soils - results of Alisol and Andosol incubation with 13C marker

    NASA Astrophysics Data System (ADS)

    Winkler, Pauline; Cerli, Chiara; Fiedler, Sabine; Woche, Susanne; Rahayu Utami, Sri; Jahn, Reinhold; Kalbitz, Karsten; Kaiser, Klaus

    2016-04-01

    For a better understanding of organic carbon (OC) decomposition in paddy soils an incubation experiment was performed. Two soil types with contrasting mineralogy (Alisol and Andosol) were exposed to 8 anoxic‒oxic cycles over 1 year. Soils received rice straw marked with 13C (228 ‰) at the beginning of each cycle. A second set of samples without straw addition was used as control. Headspaces of the incubation vessels were regularly analysed for CO2 and CH4. In soil solutions, redox potential, pH, dissolved organic C (DOC), and Fe2+ were measured after each anoxic and each oxic phase. Soils were fractionated by density at the end of the experiment and the different fractions were isotopically analysed. Samples of genuine paddy soils that developed from the test soils were used as reference. During anoxic cycles, soils receiving rice straw released large amounts of CO2 and CH4, indicating strong microbial activity. Consequently, Eh values dropped and pH as well as Fe2+ concentrations increased. Concentrations of DOC were relatively small, indicating either strong consumption and/or strong retention of dissolved organic compounds. During oxic cycles, concentrations of dissolved Fe dropped in both soils while DOC concentrations remained constant in the Alisol and decreased in the Andosol. Density fractionation revealed increased contents of mineral associated OC for the Andosol incubated with straw addition as compared to the parent soil. No changes were found for the Alisol. However, the mineral-associated OC fraction of both soil types contained 13C of the added straw. Hence, fresh organic matter is incorporated while part of the older organic matter has been released or mineralized. The increase in the Andosol might be due to effective binding of fresh OC to minerals and/or stronger retention/preservation of older OC. Both could be explained by the more reactive mineralogy of the Andosol than of the Alisol. XPS analyses of the soils are currently performed and

  12. Preliminary Results from High Time-Resolution Measurements of Particulate Inorganic Ions and Black Carbon Downwind of Seoul, Korea

    NASA Astrophysics Data System (ADS)

    Ghim, Y.; Lee, Y.; Kim, C.; Choi, Y.; Lee, T.

    2011-12-01

    Concentrations of inorganic ions and black carbon (BC) in PM2.5 were measured using PILS (particle-into-liquid sampler, ADI 2081, Applikon) and MAAP (Multiangle Absorption Photometer, Model 5012, Thermo), respectively, at intervals of 20-30 minutes. The measurements were made at the Yongin campus of Hankuk University of Foreign Studies, about 35 km southeast of downtown Seoul, which is affected by prevailing northwesterlies. The site is considered as an ideal place for exploring transport of air pollutants and variations of secondary ion formation caused by photochemical reactions since there are no major emission sources nearby except a 4-lane road running about 1.4 km to the west. The concentration of BC has been continuously measured since July 2010. However, the concentrations of inorganic ions were measured intermittently since February 2011. In the measurements in February, nitrate accounted for about 39% of the total inorganic ion concentrations and showed the highest correlation coefficient of 0.93 with ammonium. The fraction of sulfate among inorganic ions was about 31%, and the correlation coefficient with ammonium was 0.85, lower than that of nitrate. As was in other rural areas in Korea, potassium was highly correlated with major secondary ions such as sulfate, nitrate and ammonium, whose correlation coefficients were 0.70-0.74. Total inorganic ion concentrations were highest at 09:30 local time (LT) on February 9 probably due to the effect of vehicle emissions during the morning rush hour, but the concentration of nitrate was the highest at 13:00 LT on February 17 because of secondary ion formation just before a full development of the convective boundary layer. BC concentrations during the measurement period in February were generally higher at midnight than in the daytime including rush hours. BC showed moderately higher correlations with secondary ions. The BC concentration from MAAP obtained by aerosol absorption coefficient divided by mass

  13. 77 FR 72818 - Circular Welded Carbon Steel Pipes and Tubes From Turkey; Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-06

    ... Turkey: Notice of Preliminary Results of Antidumping Duty Administrative Review, 77 FR 32508 (June 1...\\ \\3\\ See id., 77 FR at 32510. \\4\\ See id., 77 FR at 32512. On October 23, 2012, the Department issued...: Notice of Final Results of Antidumping Duty Administrative Review, 76 FR 76939 (December 9,...

  14. 75 FR 8301 - Certain Cut-to-Length Carbon Steel Plate From the People's Republic of China: Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... Administrative Review, 74 FR 39921 (August 10, 2009) (``Preliminary Results''). The period of review (``POR'') is... of Extension of Time Limit for Final Results of Administrative Review, 74 FR 60237 (November 20, 2009..., 64 FR 46343 (August 25, 1999). See also Continuation of Antidumping Duty Order on Certain...

  15. 78 FR 19210 - Corrosion-Resistant Carbon Steel Flat Products From the Republic of Korea: Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-29

    ... Countervailing Duty Administrative Review, 77 FR 58512 (September 21, 2012) (Preliminary Results). DATES...: Revocation of Antidumping and Countervailing Duty Orders, 78 FR 16832 (March 19, 2013) (Revocation Notice... Pohang Iron & Steel Co. Ltd. (POSCO), received subsidies that result in de minimis net subsidy rates....

  16. 77 FR 69790 - Certain Hot-Rolled Carbon Steel Flat Products From the People's Republic of China: Final Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-21

    ... Results of 2010-2011 Antidumping Duty Administrative Review and Intent To Rescind in Part, 77 FR 45576... Products from the People's Republic of China, 66 FR 59561 (November 29, 2001), remains dispositive. Final... & Trading Co., Ltd., and Baoshan Iron & Steel Co., Ltd. \\3\\ See Preliminary Results, 77 FR at 45577. \\4\\...

  17. 78 FR 22230 - Certain Magnesia Carbon Bricks From the People's Republic of China: Final Results and Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-15

    ...: Antidumping Duty Administrative Review; 2010- 2011, 77 FR 61394 (October 9, 2012) (``Preliminary Results... Republic of China: Antidumping Duty Orders, 75 FR 57257 (September 20, 2010). Changes Since the Preliminary... Preliminary Results, 77 FR 61394-61395. \\5\\ See, e.g., Certain Tissue Paper Products from the...

  18. 75 FR 1495 - Certain Hot-Rolled Carbon Steel Flat Products From India: Preliminary Results of Countervailing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-11

    ... FR 6530 (February 12, 2007) and accompanying Issues and Decision Memorandum (Final Results of 3rd PET... Strip from India, 71 FR 7534 (February 13, 2006) (Final Results of 2nd PET Film Review), and... Polyethylene Terephthalate (``PET'') Resin From India (Preliminary Determination of PET Resin), 69 FR...

  19. 78 FR 16247 - Corrosion-Resistant Carbon Steel Flat Products From the Republic of Korea; Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-14

    ..., and Partial Rescission, 77 FR 54891 (September 6, 2012) (Preliminary Results). DATES: Effective Date...'s Preliminary Results.\\5\\ \\2\\ See id., 77 FR at 54893. \\3\\ See id., 77 FR at 54896. \\4\\ See Dongbu's... Modification, 77 FR 8101 (February 14, 2012). For any individually examined respondents whose...

  20. Microstructure and mechanical behavior of UFG copper processed by ECAP following different processing regimes

    NASA Astrophysics Data System (ADS)

    Purcek, G.; Saray, O.; Nagimov, M. I.; Nazarov, A. A.; Safarov, I. M.; Danilenko, V. N.; Valiakhmetov, O. R.; Mulyukov, R. R.

    2012-02-01

    Commercially pure (99.9%) copper was severe plastically deformed by equal-channel angular pressing (ECAP) following route-Bc in three different processing regimes in order to obtain ultrafine-grained (UFG) microstructures leading to improved mechanical properties. In regime-1, the billets were processed at room temperature up to eight passes. The billets were processed at 200°C up to eight passes in regime-2. Regime-3 is a hybrid regime by which the billets were deformed at 200°C up to four passes first, and these billets were then processed at room temperature for one, two and four passes. In all regimes, the ECAP processing results in a refinement of the conventionally grained (CG) initial microstructure of copper down to sub-micron level leading to a great improvement in the strength as compared to CG copper. Among the regimes applied, regime-3 was found to be the best regime for improvement in strength along with adequate ductility. The samples showed more than eight times increases in yield strength after processing in regime-3 for 4 + 4 passes, from 47 MPa for CG copper to about 408 MPa for the UFG sample. Such improvement in strength was accompanied by a 16.9% total elongation and 6% uniform elongation. The processing in regime-2 resulted in the best elongation to failure of about 22% after eight passes, but it gave the lowest strength values among others.

  1. The effect of abrupt permafrost thaw on the water table, vegetation and carbon feedback: results from a sub-arctic peatland

    NASA Astrophysics Data System (ADS)

    Malhotra, A.; Roulet, N. T.

    2015-12-01

    Uncertainty in estimating the carbon loss from thawing ice-rich permafrost is attributed, in part, to the abrupt changes in ecosystem structure and function after thaw. In a thawing peat plateau in the discontinuous permafrost zone (Stordalen, Mire, Sweden; ST), we tested for the occurrence of abrupt changes in hydrology and the effects of these changes on the water table and vegetation feedback. Using a chronosequence approach along three transects that capture several transitional thaw stages, we found abrupt hydrological changes following thaw, wherein adjacent areas (1 m apart) had unrelated water table depth (WTD) fluctuations. Despite these abrupt changes, surprisingly, the same Gaussian model of plant abundance explained by WTD could be applied to data from both ST and an undisturbed ombrotrophic peatland (Mer Bleue Bog, Canada; MB). However, the Gaussian model fit was better at MB than at ST. Furthermore, explanatory power of the model at ST decreased with increasing permafrost thaw. While water table and vegetation feedback in a thawing landscape is similar to that of a peatland without transitional land cover types, the vegetation and carbon feedback is complicated by non-linear shifts in the partitioning of gaseous effluxes between CO2 and CH4. These results will be presented along with key implications for modeling carbon loss from thawing landscapes.

  2. Propagation Regime of Iron Dust Flames

    NASA Technical Reports Server (NTRS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew J.

    2012-01-01

    A flame propagating through an iron-dust mixture can propagate in two asymptotic regimes. When the characteristic time of heat transfer between particles is much smaller than the characteristic time of particle combustion, the flame propagates in the continuum regime where the heat released by reacting particles can be modelled as a space-averaged function. In contrast, when the characteristic time of heat transfer is much larger than the particle reaction time, the flame can no longer be treated as a continuum due to dominating effects associated with the discrete nature of the particle reaction. The discrete regime is characterized by weak dependence of the flame speed on the oxygen concentration compared to the continuum regime. The discrete regime is observed in flames propagating through an iron dust cloud within a gas mixture containing xenon, while the continuum regime is obtained when xenon is substituted with helium.

  3. Discriminatory Proofreading Regimes in Nonequilibrium Systems

    NASA Astrophysics Data System (ADS)

    Murugan, Arvind; Huse, David A.; Leibler, Stanislas

    2014-04-01

    We use ideas from kinetic proofreading, an error-correcting mechanism in biology, to identify new kinetic regimes in nonequilibrium systems. These regimes are defined by the sensitivity of the occupancy of a state of the system to a change in its energy. In biological contexts, higher sensitivity corresponds to stronger discrimination between molecular substrates with different energetics competing in the same reaction. We study this discriminatory ability in systems with discrete states that are connected by a general network of transitions. We find multiple regimes of different discriminatory ability when the energy of a given state of the network is varied. Interestingly, the occupancy of the state can even increase with its energy, corresponding to an "antiproofreading" regime. The number and properties of such discriminatory regimes are limited by the topology of the network. Finally, we find that discriminatory regimes can be changed without modifying any "hard-wired" structural aspects of the system but rather by simply changing external chemical potentials.

  4. Evolution of the water regime of Phobos

    SciTech Connect

    Fanale, F.P.; Salvail, J.R. )

    1990-12-01

    In the present model of Phobos water regime evolution, a time-dependent solar insolation is influenced by both decreasing solar output over geologic time and the Mars and Phobos cycles of eccentricity and obliquity, which vary over 100,000-1,000,000 year time scales. The results presented address model cases which assume (1) a homogeneous distribution of water ice, and (2) a driving of water ice toward the surface by the internal thermal gradient near the poles. A two-dimensional model is used to compute temperatures, heat and vapor fluxes, and ice removal/deposition rates, for the case of uniform ice distribution throughout Phobos. The results obtained indicate that a substantial amount of vapor is produced within 1 km of the surface. 15 refs.

  5. 76 FR 65179 - Certain Welded Carbon Steel Standard Pipe From Turkey: Extension of Time for Preliminary Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-20

    ... Administrative Reviews, 76 FR 23545 (April 27, 2011). The preliminary results are currently due no later than.... See Memorandum to Melissa G. Skinner, Director, AD/CVD Operations, Office 3, from Robert...

  6. Modeling the spatiotemporal variability in subsurface thermal regimes across a low-relief polygonal tundra landscape

    DOE PAGES

    Kumar, Jitendra; Collier, Nathan; Bisht, Gautam; Mills, Richard T.; Thornton, Peter E.; Iversen, Colleen M.; Romanovsky, Vladimir

    2016-09-27

    Vast carbon stocks stored in permafrost soils of Arctic tundra are under risk of release to the atmosphere under warming climate scenarios. Ice-wedge polygons in the low-gradient polygonal tundra create a complex mosaic of microtopographic features. This microtopography plays a critical role in regulating the fine-scale variability in thermal and hydrological regimes in the polygonal tundra landscape underlain by continuous permafrost. Modeling of thermal regimes of this sensitive ecosystem is essential for understanding the landscape behavior under the current as well as changing climate. Here, we present an end-to-end effort for high-resolution numerical modeling of thermal hydrology at real-world fieldmore » sites, utilizing the best available data to characterize and parameterize the models. We also develop approaches to model the thermal hydrology of polygonal tundra and apply them at four study sites near Barrow, Alaska, spanning across low to transitional to high-centered polygons, representing a broad polygonal tundra landscape. A multiphase subsurface thermal hydrology model (PFLOTRAN) was developed and applied to study the thermal regimes at four sites. Using a high-resolution lidar digital elevation model (DEM), microtopographic features of the landscape were characterized and represented in the high-resolution model mesh. The best available soil data from field observations and literature were utilized to represent the complex heterogeneous subsurface in the numerical model. Simulation results demonstrate the ability of the developed modeling approach to capture – without recourse to model calibration – several aspects of the complex thermal regimes across the sites, and provide insights into the critical role of polygonal tundra microtopography in regulating the thermal dynamics of the carbon-rich permafrost soils. Moreover, areas of significant disagreement between model results and observations highlight the importance of field

  7. Regimes of suprathermal electron transport

    SciTech Connect

    Glinsky, M.E.

    1995-07-01

    Regimes of the one-dimensional (1-D) transport of suprathermal electrons into a cold background plasma are delineated. A well ordered temporal progression is found through eras where {ital J}{center_dot}{ital E} heating, hot electron--cold electron collisional heating, and diffusive heat flow dominate the cold electron energy equation. Scaling relations for how important quantities such as the width and temperature of the heated layer of cold electrons evolve with time are presented. These scaling relations are extracted from a simple 1-D model of the transport which can be written in dimensionless form with one free parameter. The parameter is shown to be the suprathermal electron velocity divided by the drift velocity of cold electrons which balances the suprathermal current. Special attention is paid to the assumptions which allow the reduction from the collisional Vlasov equation, using a Fokker--Planck collision operator, to this simple model. These model equations are numerically solved and compared to both the scaling relations and a more complete multigroup electron diffusion transport. Implications of the scaling relations on fast ion generation, magnetic field generation, and electric field inhibition of electron transport are examined as they apply to laser heated plasmas. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  8. Multistability of synchronous regimes in rotator ensembles.

    PubMed

    Kryukov, A K; Petrov, V S; Osipov, G V; Kurths, J

    2015-12-01

    We study collective dynamics in rotator ensembles and focus on the multistability of synchronous regimes in a chain of coupled rotators. We provide a detailed analysis of the number of coexisting regimes and estimate in particular, the synchronization boundary for different types of individual frequency distribution. The number of wave-based regimes coexisting for the same parameters and its dependence on the chain length are estimated. We give an analytical estimation for the synchronization frequency of the in-phase regime for a uniform individual frequency distribution. PMID:26723160

  9. North Sea wind climate in changing weather regimes

    NASA Astrophysics Data System (ADS)

    Anders, Ivonne; Rockel, Burkhardt

    2015-04-01

    Results from regional climate models (RCMs) are getting more and more important in future wind climate assessment. From RCMs often only the daily wind speed is available, but no information on prevailing wind direction of each day. Weather regime classification can close this gap and models ability of simulating surface wind speed can be analysed in detail. Several objective regime classifications have been investigated to be a sufficient diagnostic tool to evaluate the present wind climate at the German and Dutch coastal area of the North Sea. The classification by Jenkinson and Collison (1977) uses values for mean sea level pressure at 16 locations centered over the North Sea. Beside the predefined 8 prevailed wind directions and the two possibilities on cyclonic or anticyclonic turbulence, 2x8 hybrid weather types can be defined. In this way 27 different regimes can be distinguished including a class of non-classifiable cases. The 27 regimes could be reduced to a number of 11 by allotting the hybrid types to the directional or the centered types. As the classification is carried out for the North Sea based on ERA40 mean sea level pressure the different regimes clearly reflect the mean wind characteristics at the stations. Comparing the wind roses for the individual observations leads to the assumption that the regime classification described before fits the requirements to carry out the regime dependent evaluation of the RCMs with a focus on the German and Dutch coast. Trends in the occurrence of the regimes in the winter period of 1961 to 2000 show an increase of the regimes with Western and Southwestern wind directions and a decrease of wind events from Eastern directions in the North Sea. The trend is dominated by the strong positive phase of the NAO especially in the months January to March starting in the beginning of the 1980s. Due to the applied method ERA40 and the RCMs do not necessarily show the same regime at each day. The agreement among the RCM

  10. UV-VIS regime band gap in a 3-d photonic system

    NASA Astrophysics Data System (ADS)

    Yin, Ming; Arammash, Fouzi; Datta, Timir; Tsu, Ray

    2013-03-01

    Synthetic opals are self-organized bulk, close packed systems that are three-dimensionally ordered with periodicity determined by the sphere diameter. These materials have been used as templates for nano devices with novel properties. For example, in carbon inverse opals show quantum hall effect and related magneto electric responses. Inverse are also reported to show photonic band gap. It is expected that devices based on these materials will be an alternative to electronic devices. These opal specimens were hexagonal or face centered cubic crystals with silica sphere diameter ranging between 220 nm and 270nm. Here we will present results of structural and imaging studies such as SEM, AFM and XRD. In addition results of the (UV-VIS) optical behavior will be provided. The optical response will be analyzed in terms of photonic band gaps in the sub-micrometer optical and UV regime.

  11. 76 FR 3613 - Corrosion-Resistant Carbon Steel Flat Products From the Republic of Korea: Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-20

    ... program and the Act on the Promotion of the Development of Alternative Energy program in these final... under the Act on the Promotion of the Development of Alternative Energy III. Programs Found Not To Have... Results and Partial Rescission of Countervailing Duty Administrative Review, 75 FR 55745 (September...

  12. 77 FR 26496 - Certain Activated Carbon From the People's Republic of China: Preliminary Results of the Fourth...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-04

    ... People's Republic of China, 59 FR 22585 (May 2, 1994) (``Silicon Carbide'') \\55\\ See, e.g., Final Results... decentralizing control of companies.\\72\\ \\71\\ See Sparklers, 56 FR at 20589. \\72\\ See, e.g., Guanghua Cherishmet...''). \\2\\ See Initiation of Antidumping and Countervailing Duty Administrative Reviews, 76 FR 30912 (May...

  13. 75 FR 8650 - Carbon and Certain Alloy Steel Wire Rod from Trinidad and Tobago; Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-25

    ... Antidumping Duty Administrative Review, 74 FR 57648 (November 9, 2009) (Preliminary Results). We gave... Duties, 68 FR 23954 (May 6, 2003) (Assessment of Antidumping Duties). This clarification will apply to... from Brazil, Indonesia, Mexico, Moldova, Trinidad and Tobago, and Ukraine, 67 FR 65945, 65947...

  14. 76 FR 42679 - Certain Hot-Rolled Carbon Steel Flat Products From India: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-19

    ... Preliminary Results of Antidumping Duty Administrative Review, 76 FR 2344 (January 13, 2011) (``Preliminary... Review, 76 FR 28419 (May 17, 2011). Period of Review The period covered by this review is December 1... date of entry. \\7\\ See Antidumping Duties; Countervailing Duties, 62 FR 27296, 27393 (May 19, 1997)....

  15. 76 FR 76939 - Certain Welded Carbon Steel Pipe and Tube From Turkey: Notice of Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-09

    ... of Antidumping Duty Administrative Review, 76 FR 33204 (June 8, 2011) (``Preliminary Results''). We...: Assessment of Antidumping Duties, 68 FR 23954 (May 6, 2003). Cash Deposit Requirements The following... Products From Turkey, 51 FR 17784 (May 15, 1986). Notification to Importers This notice serves as a...

  16. 78 FR 76279 - Certain Cut-to-Length Carbon Steel Plate From the People's Republic of China: Final Results and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-17

    ...; 2011-2012, 78 FR 44525 (July 24, 2013) (``Preliminary Results''). DATES: Effective Date: December 17... FR 65694 (October 24, 2011) (``Assessment Practice Refinement''); see also the ``Assessment'' section... PRC companies: Hunan Valin Xiangtan Iron & Steel Co., Ltd. (``Hunan Valin''), Shanghai Pudong Iron...

  17. 76 FR 62039 - Certain Hot-Rolled Carbon Steel Flat Products From India: Final Results of 2009-2010 Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-06

    ...: Notice of Preliminary Results of 2009-2010 Antidumping Duty Administrative Review, 76 FR 31938 (June 2... proceeding.\\4\\ \\3\\ See Antidumping Duties; Countervailing Duties: Final Rule, 62 FR 27296, 27393 (May 19, 1997). \\4\\ See Antidumping and Countervailing Duty Proceedings: Assessment of Antidumping Duties, 68...

  18. 78 FR 65272 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-31

    ... of Antidumping Duty Administrative Review; 2011-2012, 78 FR 21105 (April 9, 2013) (Preliminary... during the POR.\\5\\ \\5\\ See Preliminary Results, 78 FR at 21105. Analysis of Comments Received All issues... Assessment Rate in Certain Antidumping Proceedings: Final Modification, 77 FR 8101, 8102 (February 14,...

  19. 75 FR 27297 - Certain Hot-Rolled Carbon Steel Flat Products from India: Notice of Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-14

    ... listed above (including, e.g., American Society for Testing and Materials (``ASTM'') specifications A543, A387, A514, A517, A506). * Society of Automotive Engineers (``SAE'')/American Iron &Steel Institute... Results of Antidumping duty Administrative Review, and Intent to Rescind in Part, 75 FR 1031 (January...

  20. 75 FR 1031 - Certain Hot-Rolled Carbon Steel Flat Products from India: Notice of Preliminary Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-08

    ... listed above (including, e.g., American Society for Testing and Materials (``ASTM'') specifications A543, A387, A514, A517, A506)). Society of Automotive Engineers (``SAE'')/American Iron & Steel Institute... final results no later than 120 days from the date of publication of this notice, pursuant to...

  1. 76 FR 22868 - Certain Hot-Rolled Flat-Rolled Carbon-Quality Steel Products From Brazil: Final Results of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-25

    ...: Preliminary Results of Countervailing Duty Administrative Review, 75 FR 64700 (October 20, 2010) (Preliminary... Duty Administrative Review, 75 FR 77828 (December 14, 2010). On January 21, 2011, USS submitted..., Usinas Siderurgicas de Minas Gerais (USIMINAS) and its subsidiary, Companhia Siderurgica Paulista...

  2. 78 FR 28190 - Carbon and Certain Alloy Steel Wire Rod From Mexico: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-14

    ... Certain Alloy Steel Wire Rod From Mexico, 67 FR 55800 (August 30, 2002). Notification to Importers This... Antidumping Duty Administrative Review; 2010- 2011, 77 FR 66954 (November 8, 2012) (Preliminary Results... Ukraine, 67 FR 65945 (October 29, 2002), remains dispositive. On October 1, 2012, the Department...

  3. 78 FR 71563 - Certain Circular Welded Carbon Steel Pipes and Tubes From Taiwan: Final Results of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-29

    ...; 2011-2012, 78 FR 34335 (June 7, 2013) (Preliminary Results). DATES: Effective November 29, 2013. FOR... FR 19369 (May 7, 1984) (Order). \\5\\ See Memorandum from Christian Marsh, Deputy Assistant Secretary..., see Antidumping and Countervailing Duty Proceedings: Assessment of Antidumping Duties, 68 FR...

  4. 75 FR 4529 - Circular Welded Carbon Steel Pipes and Tubes From Thailand: Final Results of Antidumping Duty New...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-28

    ... Steel Pipes and Tubes from Thailand: Preliminary Results of Antidumping Duty New Shipper Review, 74 FR... New Shipper Review, 74 FR 59961 (November 19, 2009). Scope of the Order The products covered by this... Less Than Fair Value, 51 FR 3384 (January 27, 1986). These cash deposit requirements shall remain...

  5. Fire History from Life-History: Determining the Fire Regime that a Plant Community Is Adapted Using Life-Histories

    PubMed Central

    Armstrong, Graeme; Phillips, Ben

    2012-01-01

    Wildfire is a fundamental disturbance process in many ecological communities, and is critical in maintaining the structure of some plant communities. In the past century, changes in global land use practices have led to changes in fire regimes that have radically altered the composition of many plant communities. As the severe biodiversity impacts of inappropriate fire management regimes are recognized, attempts are being made to manage fires within a more ‘natural’ regime. In this aim, the focus has typically been on determining the fire regime to which the community has adapted. Here we take a subtly different approach and focus on the probability of a patch being burnt. We hypothesize that competing sympatric taxa from different plant functional groups are able to coexist due to the stochasticity of the fire regime, which creates opportunities in both time and space that are exploited differentially by each group. We exploit this situation to find the fire probability at which three sympatric grasses, from different functional groups, are able to co-exist. We do this by parameterizing a spatio-temporal simulation model with the life-history strategies of the three species and then search for the fire frequency and scale at which they are able to coexist when in competition. The simulation gives a clear result that these species only coexist across a very narrow range of fire probabilities centred at 0.2. Conversely, fire scale was found only to be important at very large scales. Our work demonstrates the efficacy of using competing sympatric species with different regeneration niches to determine the probability of fire in any given patch. Estimating this probability allows us to construct an expected historical distribution of fire return intervals for the community; a critical resource for managing fire-driven biodiversity in the face of a growing carbon economy and ongoing climate change. PMID:22363670

  6. Fire history from life-history: determining the fire regime that a plant community is adapted using life-histories.

    PubMed

    Armstrong, Graeme; Phillips, Ben

    2012-01-01

    Wildfire is a fundamental disturbance process in many ecological communities, and is critical in maintaining the structure of some plant communities. In the past century, changes in global land use practices have led to changes in fire regimes that have radically altered the composition of many plant communities. As the severe biodiversity impacts of inappropriate fire management regimes are recognized, attempts are being made to manage fires within a more 'natural' regime. In this aim, the focus has typically been on determining the fire regime to which the community has adapted. Here we take a subtly different approach and focus on the probability of a patch being burnt. We hypothesize that competing sympatric taxa from different plant functional groups are able to coexist due to the stochasticity of the fire regime, which creates opportunities in both time and space that are exploited differentially by each group. We exploit this situation to find the fire probability at which three sympatric grasses, from different functional groups, are able to co-exist. We do this by parameterizing a spatio-temporal simulation model with the life-history strategies of the three species and then search for the fire frequency and scale at which they are able to coexist when in competition. The simulation gives a clear result that these species only coexist across a very narrow range of fire probabilities centred at 0.2. Conversely, fire scale was found only to be important at very large scales. Our work demonstrates the efficacy of using competing sympatric species with different regeneration niches to determine the probability of fire in any given patch. Estimating this probability allows us to construct an expected historical distribution of fire return intervals for the community; a critical resource for managing fire-driven biodiversity in the face of a growing carbon economy and ongoing climate change.

  7. Acid neutralizing capacity and leachate results for igneous rocks, with associated carbon contents of derived soils, Animas River AML site, Silverton, Colorado

    USGS Publications Warehouse

    Yager, Douglas B.; Stanton, Mark R.; Choate, LaDonna M.; Burchell,

    2009-01-01

    Mine planning efforts have historically overlooked the possible acid neutralizing capacity (ANC) that local igneous rocks can provide to help neutralize acidmine drainage. As a result, limestone has been traditionally hauled to mine sites for use in neutralizing acid drainage. Local igneous rocks, when used as part of mine life-cycle planning and acid mitigation strategy, may reduce the need to transport limestone to mine sites because these rocks can contain acid neutralizing minerals. Igneous hydrothermal events often introduce moderately altered mineral assemblages peripheral to more intensely altered rocks that host metal-bearing veins and ore bodies. These less altered rocks can contain ANC minerals (calcite-chlorite-epidote) and are referred to as a propylitic assemblage. In addition, the carbon contents of soils in areas of new mining or those areas undergoing restoration have been historically unknown. Soil organic carbon is an important constituent to characterize as a soil recovery benchmark that can be referred to during mine cycle planning and restoration.
    This study addresses the mineralogy, ANC, and leachate chemistry of propylitic volcanic rocks that host polymetallic mineralization in the Animas River watershed near the historical Silverton, Colorado, mining area. Acid titration tests on volcanic rocks containing calcite (2 – 20 wt %) and chlorite (6 – 25 wt %), have ANC ranging from 4 – 146 kg/ton CaCO3 equivalence. Results from a 6-month duration, kinetic reaction vessel test containing layered pyritic mine waste and underlying ANC volcanic rock (saturated with deionized water) indicate that acid generating mine waste (pH 2.4) has not overwhelmed the ANC of propylitic volcanic rocks (pH 5.8). Sequential leachate laboratory experiments evaluated the concentration of metals liberated during leaching. Leachate concentrations of Cu-Zn-As-Pb for ANC volcanic rock are one-to-three orders of magnitude lower when compared to leached

  8. Experimental results with fuel cell start-up and shut-down. Impact of type of carbon for cathode catalyst support

    SciTech Connect

    Lottin, Olivier; Dillet, Jerome; Maranzana, Gael; Abbou, Sofyane; Didierjean, Sophie; Lamibrac, Adrien; Borup, Rodney L.; Mukundan, Rangachary; Spernjak, Dusan

    2015-09-14

    Separate testing protocols for fuel cell startups and shutdowns were developed to distinguish between their effects on reverse currents and CO2 evolution. The internal currents and the local potentials were measured with different membrane-electrode assemblies (MEAs): we examined the influence of the type of carbon for cathode catalyst support as well as the mitigating effect of low anode Pt loading. In conclusion, significant differences were observed and the experiments also confirmed previous results that the evolved CO2 accounts for less than 25% of the total exchanged charge.

  9. Experimental results with fuel cell start-up and shut-down. Impact of type of carbon for cathode catalyst support

    DOE PAGES

    Lottin, Olivier; Dillet, Jerome; Maranzana, Gael; Abbou, Sofyane; Didierjean, Sophie; Lamibrac, Adrien; Borup, Rodney L.; Mukundan, Rangachary; Spernjak, Dusan

    2015-09-14

    Separate testing protocols for fuel cell startups and shutdowns were developed to distinguish between their effects on reverse currents and CO2 evolution. The internal currents and the local potentials were measured with different membrane-electrode assemblies (MEAs): we examined the influence of the type of carbon for cathode catalyst support as well as the mitigating effect of low anode Pt loading. In conclusion, significant differences were observed and the experiments also confirmed previous results that the evolved CO2 accounts for less than 25% of the total exchanged charge.

  10. Regime Changes in California Temperature Trends

    NASA Astrophysics Data System (ADS)

    Cordero, E. C.; Kessomkiat, W.; Mauget, S.

    2008-12-01

    Annual and seasonal temperature trends are analyzed for California using surface data from the US Historical Climate Network and the larger COOP network. While trends in Tmax and Tmin both show warming over the last 50 years, the temporal and spatial structure of these trends is quite different. An analysis using Mann Whitney U statistics reveals that the patterns of warming and cooling from individual stations have a distinct temporal signature that differs between Tmax and Tmin. Significant cooling trends in Tmin are found between 1920-1958, while significant warming only starts after the 1970s. In contrast, Tmax trends show a more variable pattern of warming and cooling between 1920-1980, with California wide warming only occurring after 1980. These results suggest regime changes in California temperature trends that could only occur through large scale forcing. A discussion of the various forcing mechanisms contributing to California trends and their spatial and temporal variability will be presented.

  11. Alumina strength degradation in the elastic regime

    SciTech Connect

    Furnish, M.D.; Chhabildas, L.C.

    1997-08-01

    Measurements of Kanel et. al. [1991] have suggested that deviatoric stresses in glasses shocked to nearly the Hugoniot Elastic limit (HEL) relax over a time span of microseconds after initial loading. Failure (damage) waves have been inferred on the basis of these measurements using time-resolved manganin normal and transverse stress gauges. Additional experiments on glass by other researchers, using time-resolved gauges, high-speed photography and spall strength determinations have also lead to the same conclusions. In the present study the authors have conducted transmitted-wave experiments on high-quality Coors AD995 alumina shocked to roughly 5 and 7 GPa (just below or at the HEL). The material is subsequently reshocked to just above its elastic limit. Results of these experiments do show some evidence of strength degradation in the elastic regime.

  12. Different spreading regimes of spray-flames

    NASA Astrophysics Data System (ADS)

    Suard, Sylvain; Haldenwang, Pierre; Nicoli, Colette

    2004-05-01

    We present a minimal model of spray combustion to investigate a flame front propagating through a fuel-lean mixture of fuel vapor, droplets and air. The model relies on a main control parameter, Da, named the Damkoehler number, which allows us to take into account a large variety of fuel sprays. Numerical results reveal, as a function of Da, a wide range of spray-flame structures, including the classical gaseous premixed flame, a specific regime controlled by vaporisation, and a pulsating mode of propagation. The latter appears when the vaporisation is smaller than (or equal to) the reaction time, and it occurs even with a unit Lewis number. To cite this article: S. Suard et al., C. R. Mecanique 332 (2004).

  13. FISHER INFORMATION AND ECOSYSTEM REGIME CHANGES

    EPA Science Inventory

    Following Fisher’s work, we propose two different expressions for the Fisher Information along with Shannon Information as a means of detecting and assessing shifts between alternative ecosystem regimes. Regime shifts are a consequence of bifurcations in the dynamics of an ecosys...

  14. Capacitance densitometer for flow regime identification

    DOEpatents

    Shipp, Jr., Roy L.

    1978-01-01

    This invention relates to a capacitance densitometer for determining the flow regime of a two-phase flow system. A two-element capacitance densitometer is used in conjunction with a conventional single-beam gamma densitometer to unambiguously identify the prevailing flow regime and the average density of a flowing fluid.

  15. Scaling mechanisms of vapour/plasma shielding from laser-produced plasmas to magnetic fusion regimes

    NASA Astrophysics Data System (ADS)

    Sizyuk, Tatyana; Hassanein, Ahmed

    2014-02-01

    The plasma shielding effect is a well-known mechanism in laser-produced plasmas (LPPs) reducing laser photon transmission to the target and, as a result, significantly reducing target heating and erosion. The shielding effect is less pronounced at low laser intensities, when low evaporation rate together with vapour/plasma expansion processes prevent establishment of a dense plasma layer above the surface. Plasma shielding also loses its effectiveness at high laser intensities when the formed hot dense plasma plume causes extensive target erosion due to radiation fluxes back to the surface. The magnitude of emitted radiation fluxes from such a plasma is similar to or slightly higher than the laser photon flux in the low shielding regime. Thus, shielding efficiency in LPPs has a peak that depends on the laser beam parameters and the target material. A similar tendency is also expected in other plasma-operating devices such as tokamaks of magnetic fusion energy (MFE) reactors during transient plasma operation and disruptions on chamber walls when deposition of the high-energy transient plasma can cause severe erosion and damage to the plasma-facing and nearby components. A detailed analysis of these abnormal events and their consequences in future power reactors is limited in current tokamak reactors. Predictions for high-power future tokamaks are possible only through comprehensive, time-consuming and rigorous modelling. We developed scaling mechanisms, based on modelling of LPP devices with their typical temporal and spatial scales, to simulate tokamak abnormal operating regimes to study wall erosion, plasma shielding and radiation under MFE reactor conditions. We found an analogy in regimes and results of carbon and tungsten erosion of the divertor surface in ITER-like reactors with erosion due to laser irradiation. Such an approach will allow utilizing validated modelling combined with well-designed and well-diagnosed LPP experimental studies for predicting

  16. Discrete fluorescent saturation regimes in multilevel systems

    NASA Technical Reports Server (NTRS)

    Kastner, S. O.; Bhatia, A. K.

    1988-01-01

    Using models of multilevel atoms, the fluorescent process was examined for the ratio of the photooxidation rate, Pij, to the collisional oxidation rate, Cij, in the pumped resonance transition i-j. It is shown that, in the full range of the parameter Pij/Cij, there exist three distinct regimes (I, II, and III) which may be usefully exploited. These regimes are defined, respectively, by the following conditions: Pij/Cij smaller than about 1; Pij/Cij much greater than 1 and Pij much lower than Cki; and Pij/Cij much greater than 1 and Pij much higher than Cki, where Cki is the collisional rate populating the source level i. The only regime which is characterized by the sensitivity of fluorescent-fluorescent line intensity ratios to Pij is regime I. If regime III is reached, even fluorescent-nonfluorescent line ratios become independent of Pij. The analysis is applied to the resonant photoexcitation of a carbonlike ion.

  17. Experimental determination of heat transfer coefficient in the slip regime and its anomalously low value.

    PubMed

    Demsis, Anwar; Verma, Bhaskar; Prabhu, S V; Agrawal, Amit

    2009-07-01

    In this paper, the measurement of the heat transfer coefficient in rarefied gases is presented; these are among the first heat transfer measurements in the slip flow regime. The experimental setup is validated by comparing friction factor in the slip regime and heat transfer coefficient in the continuum regime. Experimental results suggest that the Nusselt number is a function of Reynolds and Knudsen numbers in the slip flow regime. The measured values for Nusselt numbers are smaller than that predicted by theoretical or simulation results, and can become a few orders of magnitude smaller than the theoretical values in the continuum regime. The results are repeatable and expected to be useful for further experimentation and modeling of flow in the slip and transition regimes.

  18. Hydrogen bonding induced distortion of CO3 units and kinetic stabilization of amorphous calcium carbonate: results from 2D (13)C NMR spectroscopy.

    PubMed

    Sen, Sabyasachi; Kaseman, Derrick C; Colas, Bruno; Jacob, Dorrit E; Clark, Simon M

    2016-07-27

    Systematic correlation in alkaline-earth carbonate compounds between the deviation of the CO3 units from the perfect D3h symmetry and their (13)C nuclear magnetic resonance (NMR) chemical shift anisotropy (CSA) parameters is established. The (13)C NMR CSA parameters of amorphous calcium carbonate (ACC) are measured using two-dimensional (13)C phase adjusted spinning sidebands (PASS) NMR spectroscopy and are analyzed on the basis of this correlation. The results indicate a distortion of the CO3 units in ACC in the form of an in-plane displacement of the C atom away from the centroid of the O3 triangle, resulting from hydrogen bonding with the surrounding H2O molecules, without significant out-of-plane displacement. Similar distortion for all C atoms in the structure of ACC suggests a uniform spatial disposition of H2O molecules around the CO3 units forming a hydrogen-bonded amorphous network. This amorphous network is stabilized against crystallization by steric frustration, while additives such as Mg presumably provide further stabilization by increasing the energy of dehydration. PMID:27276013

  19. Regime switching model for financial data: Empirical risk analysis

    NASA Astrophysics Data System (ADS)

    Salhi, Khaled; Deaconu, Madalina; Lejay, Antoine; Champagnat, Nicolas; Navet, Nicolas

    2016-11-01

    This paper constructs a regime switching model for the univariate Value-at-Risk estimation. Extreme value theory (EVT) and hidden Markov models (HMM) are combined to estimate a hybrid model that takes volatility clustering into account. In the first stage, HMM is used to classify data in crisis and steady periods, while in the second stage, EVT is applied to the previously classified data to rub out the delay between regime switching and their detection. This new model is applied to prices of numerous stocks exchanged on NYSE Euronext Paris over the period 2001-2011. We focus on daily returns for which calibration has to be done on a small dataset. The relative performance of the regime switching model is benchmarked against other well-known modeling techniques, such as stable, power laws and GARCH models. The empirical results show that the regime switching model increases predictive performance of financial forecasting according to the number of violations and tail-loss tests. This suggests that the regime switching model is a robust forecasting variant of power laws model while remaining practical to implement the VaR measurement.

  20. Early regimes of water capillary flow in slit silica nanochannels.

    PubMed

    Oyarzua, Elton; Walther, Jens H; Mejía, Andrés; Zambrano, Harvey A

    2015-06-14

    Molecular dynamics simulations are conducted to investigate the initial stages of spontaneous imbibition of water in slit silica nanochannels surrounded by air. An analysis is performed for the effects of nanoscopic confinement, initial conditions of liquid uptake and air pressurization on the dynamics of capillary filling. The results indicate that the nanoscale imbibition process is divided into three main flow regimes: an initial regime where the capillary force is balanced only by the inertial drag and characterized by a constant velocity and a plug flow profile. In this regime, the meniscus formation process plays a central role in the imbibition rate. Thereafter, a transitional regime takes place, in which, the force balance has significant contributions from both inertia and viscous friction. Subsequently, a regime wherein viscous forces dominate the capillary force balance is attained. Flow velocity profiles identify the passage from an inviscid flow to a developing Poiseuille flow. Gas density profiles ahead of the capillary front indicate a transient accumulation of air on the advancing meniscus. Furthermore, slower capillary filling rates computed for higher air pressures reveal a significant retarding effect of the gas displaced by the advancing meniscus.

  1. THE IMPACT OF THE GLOBAL NUCLEAR SAFETY REGIME IN BRAZIL

    SciTech Connect

    Almeida, C.

    2004-10-06

    A turning point of the world nuclear industry with respect to safety occurred due to the accident at Chernobyl, in 1986. A side from the tragic personal losses and the enormous financial damage, the Chernobyl accident has literally demonstrated that ''a nuclear accident anywhere is an accident everywhere''. The impact was felt immediately by the nuclear industry, with plant cancellations (e.g. Austria), elimination of national programs (e.g. Italy) and general construction delays. However, the reaction of the nuclear industry was equally immediate, which led to the proposal and establishment of a Global Nuclear Safety Regime. This regime is composed of biding international safety conventions, globally accepted safety standard, and a voluntary peer review system. In a previous work, the author has presented in detail the components of this Regime, and briefly discussed its impact in the Brazilian nuclear power organizations, including the Regulatory Body. This work, on the opposite, briefly reviews the Global Nuclear Safety Regime, and concentrates in detail in the discussion of its impact in Brazil, showing how it has produced some changes, and where the peer pressure regime has failed to produce real results.

  2. Regional Assesssment and Monitoring of Teh Carbon Balance Within Europe (recab): Experimental Strategy and Mesoscale Modeling Preliminary Results

    NASA Astrophysics Data System (ADS)

    Dolman, H.; de Martino, B.; Gioli, B.; Hutjes, R. W. A.; Lindroth, A.; Miglietta, F.; Millan, M. M.; Sanz, M. J.; Schumacher, M.

    . Experimental deployments and preliminary experimental an modelling results show- ing different synoptic weather conditions are available, including CO2 vertical profiles (isotopes and concentration), horizontal flux transects and other relevant parameters. Also measurements from eddy flux towers in the measurement areas. are available, and in addition various ABL probes (RASS, SODAR, tethered balloons). 2

  3. Atlantic Ocean Carbon Experiment (acex): Implementation of Eddy Covariance Implementation of Eddy Covariance CO2 Flux Measurements on the SW Atlantic Ocean and Results from the Second Cruise

    NASA Astrophysics Data System (ADS)

    Schultz, C.; Pezzi, L. P.; Miller, S. D.; Martins, L. G.; Araujo, R. G.; Acevedo, O. C.; Moller, O.; Souza, R.; Tavano, V. M.; Farias, P.; Casagrande, F.

    2013-05-01

    The project observational and numerical study of heat, momentum and CO2 fluxes at the ocean-atmosphere interface in the South Atlantic Ocean - Atlantic Ocean Carbon Experiment (ACEx) combines observational and modeling approaches to characterize heat, momentum and CO2 fluxes at the ocean-atmosphere interface in the South Atlantic Ocean. This project is part of an innovative initiative aimed at providing a better understanding of the chemical, physical and dynamic processes of ocean-atmosphere interaction in micro and meso-scales at the South Atlantic Ocean, as well as fluxes across this interface. The ACEx project has performed three cruises so far, collecting measurements with CTDs and XBTs, launching radiosondes, and deploying a micro-meteorological tower to make in situ measurements of heat, momentum and CO2 fluxes. Our successful deployment of this tower represents the first use of a CO2 flux measurement system using eddy covariance technique in the Southwestern Atlantic Ocean. In this work, we present results from the second ACEx cruise, in which the crew onboard the Hydro-oceanographic Vessel Cruzeiro do Sul took measurements at 31 stations between Paranaguá (PR) and Chuí (RS). In addition to physical data, this cruise collected phytoplankton and nutrient data, allowing carbonic gas fluxes to be analyzed and compared with both physical and biological forcings. The highest chlorophyll concentrations were found in water derived from the La Plata River, which showed low salinity waters close to the surface. The influence of these waters was observed mainly at the southernmost stations of the cruise, coincident with increases on the CO2 fluxes that had remained slightly negative until then. This suggests that the biological forcings might have a significant impact on the gas fluxes in this area, through both respiration and the consumption of organic matter. We are currently working to apply circulation and biogeochemical models to evaluate the importance of

  4. Effects of acidic deposition on the erosion of carbonate stone - experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

    USGS Publications Warehouse

    Baedecker, P.A.; Reddy, M.M.; Reimann, K.J.; Sciammarella, C.A.

    1992-01-01

    One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30?? to horizontal at the five NAPAP materials exposure sites range from ~15 to ~30?? ??m yr-1 for marble, and from ~25 to ~45 ??m yr -1 for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ~30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ~70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide ('clean rain'). These results are for marble and limestone slabs exposed at an angle of 30?? from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60?? or 85??. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC

  5. Identification of absorbing organic (brown carbon) aerosols through Sun Photometry: results from AEROCAN / AERONET stations in high Arctic and urban Locations

    NASA Astrophysics Data System (ADS)

    Kerr, G. H.; Chaubey, J. P.; O'Neill, N. T.; Hayes, P.; Atkinson, D. B.

    2014-12-01

    Light absorbing organic aerosols or brown carbon (BrC) aerosols are prominent species influencing the absorbing aerosol optical depth (AAOD) of the total aerosol optical depth (AOD) in the UV wavelength region. They, along with dust, play an important role in modifying the spectral AAOD and the spectral AOD in the UV region: this property can be used to discriminate BrC aerosols from both weakly absorbing aerosols such as sulfates as well as strongly absorbing aerosols such as black carbon (BC). In this study we use available AERONET inversions (level 1.5) retrieved for the measuring period from 2009 to 2013, for the Arctic region (Eureka, Barrow and Hornsund), Urban/ Industrial regions (Kanpur, Beijing), and the forest regions (Alta Foresta and Mongu), to identify BrC aerosols. Using Dubovik's inversion algorithm results, we analyzed parameters that were sensitive to BrC presence, notably AAOD, AAODBrC estimated using the approach of Arola et al. [2011], the fine-mode-aerosol absorption derivative (αf, abs) and the fine-mode-aerosol absorption 2nd derivative (αf, abs'), all computed at a near UV wavelength (440 nm). Temporal trends of these parameters were investigated for all test stations and compared to available volume sampling surface data as a means of validating / evaluating the sensitivity of ostensible sunphotometer indicators of BrC aerosols to the presence of BrC as measured using independent indicators. Reference: Arola, A., Schuster, G., Myhre, G., Kazadzis, S., Dey, S., and Tripathi, S. N.: Inferring absorbing organic carbon content from AERONET data, Atmos. Chem. Phys., 11, 215-225, doi:10.5194/acp-11-215-2011, 2011

  6. Effects of atmospheric carbon dioxide on insect herbivores and their host plants. Technical progress report

    SciTech Connect

    Lincoln, D.E.

    1984-01-01

    The goal was to examine and confirm the observation that leaf eting insects feed at higher rates on plants grown under elevated carbon dioxide regimes. Results confirm and refine the preliminary observation. Subsequent experiments are designd to examine the basis for the increased feeding and examine the generality by testing another plant/herbivore system. (ACR)

  7. Fatigue of Austempered Ductile Iron with Two Strength Grades in Very High Cycle Regime

    NASA Astrophysics Data System (ADS)

    Zhang, Jiwang; Li, Wei; Song, Qingpeng; Zhang, Ning; Lu, Liantao

    2016-03-01

    In this study, Austempered ductile irons (ADIs) with two different strength grades were produced and the fatigue properties were measured at 109 cycles. The results show that the S-N curves give a typical step-wise shape and there is no fatigue limit in the very high cycle fatigue regime. The two grades ADI have the similar fracture behaviors and fatigue failure can initiate from defects at specimen surface and subsurface zone. On the fracture surfaces of some specimens, the `granular-bright-facet' area with rich carbon distribution is observed in the vicinity of the defect. The microstructure affects the crack behaviors at the early propagation stage. The ADI with upper and lower bainite shows higher fatigue strength compared with the ADI with coarse upper bainite.

  8. Collimated proton acceleration in light sail regime with a tailored pinhole target

    NASA Astrophysics Data System (ADS)

    Wang, H. Y.; Yan, X. Q.; Zepf, M.

    2014-06-01

    A scheme for producing collimated protons from laser interactions with a diamond-like-carbon + pinhole target is proposed. The process is based on radiation pressure acceleration in the multi-species light-sail regime [B. Qiao et al., Phys. Rev. Lett. 105, 155002 (2010); T. P. Yu et al., Phys. Rev. Lett. 105, 065002 (2010)]. Particle-in-cell simulations demonstrate that transverse quasistatic electric field at TV/m level can be generated in the pinhole. The transverse electric field suppresses the transverse expansion of protons effectively, resulting in a higher density and more collimated proton beam compared with a single foil target. The dependence of the proton beam divergence on the parameters of the pinhole is also investigated.

  9. Inhomogeneous stationary and oscillatory regimes in coupled chaotic oscillators.

    PubMed

    Liu, Weiqing; Volkov, Evgeny; Xiao, Jinghua; Zou, Wei; Zhan, Meng; Yang, Junzhong

    2012-09-01

    The dynamics of linearly coupled identical Lorenz and Pikovsky-Rabinovich oscillators are explored numerically and theoretically. We concentrate on the study of inhomogeneous stable steady states ("oscillation death (OD)" phenomenon) and accompanying periodic and chaotic regimes that emerge at an appropriate choice of the coupling matrix. The parameters, for which OD occurs, are determined by stability analysis of the chosen steady state. Three model-specific types of transitions to and from OD are observed: (1) a sharp transition to OD from a nonsymmetric chaotic attractor containing random intervals of synchronous chaos; (2) transition to OD from the symmetry-breaking chaotic regime created by negative coupling; (3) supercritical bifurcation of OD into inhomogeneous limit cycles and further evolution of the system to inhomogeneous chaotic regimes that coexist with complete synchronous chaos. These results may fill a gap in the understanding of the mechanism of OD in coupled chaotic systems.

  10. The transition between the niche and neutral regimes in ecology

    PubMed Central

    Fisher, Charles K.; Mehta, Pankaj

    2014-01-01

    An ongoing debate in ecology concerns the impacts of ecological drift and selection on community assembly. Here, we show that there is a transition in diverse ecological communities between a selection-dominated regime (the niche phase) and a drift-dominated regime (the neutral phase). Simulations and analytic arguments show that the niche phase is favored in communities with large population sizes and relatively constant environments, whereas the neutral phase is favored in communities with small population sizes and fluctuating environments. Our results demonstrate how apparently neutral populations may arise even in communities inhabited by species with varying traits. PMID:25157131

  11. Primary Thermometry in the Intermediate Coulomb Blockade Regime

    NASA Astrophysics Data System (ADS)

    Feshchenko, A. V.; Meschke, M.; Gunnarsson, D.; Prunnila, M.; Roschier, L.; Penttilä, J. S.; Pekola, J. P.

    2013-10-01

    We investigate Coulomb blockade thermometers (CBT) in an intermediate temperature regime, where measurements with enhanced accuracy are possible due to the increased magnitude of the differential conductance dip. Previous theoretical results show that corrections to the half width and to the depth of the measured conductance dip of a sensor are needed, when leaving the regime of weak Coulomb blockade towards lower temperatures. In the present work, we demonstrate experimentally that the temperature range of a CBT sensor can be extended by employing these corrections without compromising the primary nature or the accuracy of the thermometer.

  12. Geothermal regimes at Clearlake California: A preliminary review

    SciTech Connect

    Burns, K.L.; Potter, R.M.; Zyvoloski, G.

    1992-01-01

    Three distinct geothermal regimes are inferred in the vicinity of the city of Clearlake, California. The first is a conductive heat flow regime, the second is a fault-controlled hot spring flow of magmatic'' fluids, and the third is a resurgent flow of meteoric warm water. The conductive heat flow results in flat, horizontal isotherms. The hot spring generates a localized spike in the isotherms. The advective disturbance carries heat laterally to a fault-line resurgence, lowering the apparent heat flow at the surface.

  13. Geothermal regimes at Clearlake California: A preliminary review

    SciTech Connect

    Burns, K.L.; Potter, R.M.; Zyvoloski, G.

    1992-08-01

    Three distinct geothermal regimes are inferred in the vicinity of the city of Clearlake, California. The first is a conductive heat flow regime, the second is a fault-controlled hot spring flow of ``magmatic`` fluids, and the third is a resurgent flow of meteoric warm water. The conductive heat flow results in flat, horizontal isotherms. The hot spring generates a localized spike in the isotherms. The advective disturbance carries heat laterally to a fault-line resurgence, lowering the apparent heat flow at the surface.

  14. Is Thawing Permafrost as a Result of Global Warming a Possible Significant Source of Degradable Carbon for Microbiota Residing In Situ and in Arctic Rivers?

    NASA Astrophysics Data System (ADS)

    Zhu, E. Y.; Coolen, M. J.

    2008-12-01

    Northern high-latitude ecosystems contain about half of the world's soil carbon, most of which is stored in permanently frozen soil (permafrost). Global warming through the 21st century is expected to induce permafrost thaw, which will increase microbial organic matter (OM) decomposition and release large amounts of the greenhouse gasses methane and carbon dioxide into the atmosphere. In addition, Arctic rivers are a globally important source of terrestrial organic carbon to the ocean and further permafrost melting will impact surface runoff, directly affecting groundwater storage and river discharge. Up to now, it remains largely unknown to what extent the ancient OM stored in newly thawing permafrost can be consumed by microbes in situ or by microbes residing in Arctic rivers which become exposed to newly discharged permafrost OM. In addition, we know little about which microbes are capable of degrading permafrost OM. During a field trip to the Toolik Lake Arctic Long Term Ecological Research (LTER) field station in northern Alaska in August 2008, we cored permafrost located near the Kuparuk River down to 110 cm below the active layer (i.e. the top layer which melts each summer) and analyzed the initial microbial enzymatic cleavage of particulate OM (POM) stored in permafrost. Alkaline phosphatase activity remained fairly constant throughout the permafrost and was only one order of magnitude lower than in the active layer. The latter enzyme cleaves organic phosphoesters into phosphate, which could cause eutrophication of lakes and rivers via ground water discharge. Similar results were found for β-glucosidase, which cleaves cellobiose into glucose. This process could fuel heterotrophic bacteria to produce carbon dioxide which, in return, could be converted to the stronger greenhouse gas methane by methanogenic archaea. Leucine aminopeptidase activities, on the other hand, were highest in the top Sphagnum root layer and quickly dropped to below detection limit

  15. Varying results using the shell weights of different planktonic foraminiferal species as a proxy for changing carbonate ion concentrations in the Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Marshall, B. J.; McConnell, M. C.; Thunell, R.; Astor, Y.

    2011-12-01

    Ocean acidification, due in part to increased atmospheric CO2, is thought to reduce calcification rates of planktonic foraminifera. A positive linear relationship has been found between foraminiferal shell weight and the carbonate ion concentrations [CO32-] of the waters in which they calcify (Barker and Elderfield, 2002). Such a relationship provides a useful proxy for determining past changes in ocean carbonate chemistry. The Cariaco Basin, Venezuela (10°30' N, 65°31 W) is an ideal study area to determine the relationship between seawater [CO32-] and planktonic foraminiferal shell weight as the region is characterized by the seasonal upwelling of low pH, low temperature, and low carbonate ion concentrated waters. In this study we use biweekly sediment trap samples and concurrent hydrographic measurements collected between January 2005 and May 2010 in the Cariaco Basin to assess the relationship between [CO32-] and shell weight of three planktonic foraminiferal species, Globigerinoides ruber, Orbulina universa and Globigerinoides sacculifer. Measured salinity, pH, sea surface temperature (SST) and total alkalinity (TA) were used to estimate pCO2 and [CO32-]. Size-normalized shells of G. ruber, O. universa and G. sacculifer were picked (> 10 per sample), photographed for size analysis and weighed. Globigerinoides ruber shell weights varied from 10.4 μg to 17.7 μg, with an average weight of 14.62 μg from 2005 to 2007, with concurrent surface water [CO32-] ranging from ~220-280 μmol/kg. Orbulina universa shell weights ranged from 35.4 μg to 67.8 μg with an average shell weight of 50.1 μg. Preliminary data reveal a strong positive linear relationship between foraminiferal shell weight and [CO32-] for G. ruber (R2 = 0.52, 99% confidence level; p = 0.007) but no significant relationship for O. universa (R2 = 0.05, ; p = 0.4). The initial results suggest that the foraminiferal shell weight changes of certain planktonic foraminiferal species may reflect changes

  16. Testing new approaches to carbonate system simulation at the reef scale: the ReefSam model first results, application to a question in reef morphology and future challenges.

    NASA Astrophysics Data System (ADS)

    Barrett, Samuel; Webster, Jody

    2016-04-01

    Numerical simulation of the stratigraphy and sedimentology of carbonate systems (carbonate forward stratigraphic modelling - CFSM) provides significant insight into the understanding of both the physical nature of these systems and the processes which control their development. It also provides the opportunity to quantitatively test conceptual models concerning stratigraphy, sedimentology or geomorphology, and allows us to extend our knowledge either spatially (e.g. between bore holes) or temporally (forwards or backwards in time). The later is especially important in determining the likely future development of carbonate systems, particularly regarding the effects of climate change. This application, by its nature, requires successful simulation of carbonate systems on short time scales and at high spatial resolutions. Previous modelling attempts have typically focused on the scales of kilometers and kilo-years or greater (the scale of entire carbonate platforms), rather than at the scale of centuries or decades, and tens to hundreds of meters (the scale of individual reefs). Previous work has identified limitations in common approaches to simulating important reef processes. We present a new CFSM, Reef Sedimentary Accretion Model (ReefSAM), which is designed to test new approaches to simulating reef-scale processes, with the aim of being able to better simulate the past and future development of coral reefs. Four major features have been tested: 1. A simulation of wave based hydrodynamic energy with multiple simultaneous directions and intensities including wave refraction, interaction, and lateral sheltering. 2. Sediment transport simulated as sediment being moved from cell to cell in an iterative fashion until complete deposition. 3. A coral growth model including consideration of local wave energy and composition of the basement substrate (as well as depth). 4. A highly quantitative model testing approach where dozens of output parameters describing the reef

  17. An assessment of biodegradability of quaternary carbon-containing fragrance compounds: comparison of experimental OECD screening test results and in silico prediction data.

    PubMed

    Seyfried, Markus; Boschung, Alain

    2014-05-01

    An assessment of biodegradability was carried out for fragrance substances containing quaternary carbons by using data obtained from Organisation for Economic Co-operation and Development (OECD) 301F screening tests for ready biodegradation and from Biowin and Catalogic prediction models. Despite an expected challenging profile, a relatively high percentage of common-use fragrance substances showed significant biodegradation under the stringent conditions applied in the OECD 301F test. Among 27 test compounds, 37% met the pass level criteria after 28 d, while another 26% indicated partial breakdown (≥20% biodegradation). For several compounds for which structural analogs were available, the authors found that structures that were rendered less water soluble by either the presence of an acetate ester or the absence of oxygen tended to degrade to a lesser extent compared to the primary alcohols or oxygenated counterparts under the test conditions applied. Difficulties were encountered when attempting to correlate experimental with in silico data. Whereas the Biowin model combinations currently recommended by regulatory agencies did not allow for a reliable discrimination between readily and nonbiodegradable compounds, only a comparably small proportion of the chemicals studied (30% and 63% depending on the model) fell within the applicability domain of Catalogic, a factor that critically reduced its predictive power. According to these results, currently neither Biowin nor Catalogic accurately reflects the potential for biodegradation of fragrance compounds containing quaternary carbons.

  18. Risk of lung cancer following exposure to carbon black, titanium dioxide and talc: results from two case-control studies in Montreal.

    PubMed

    Ramanakumar, Agnihotram V; Parent, Marie-Elise; Latreille, Benoit; Siemiatycki, Jack

    2008-01-01

    The International Agency for Research on Cancer (IARC) recently evaluated the carcinogenicity of three poorly soluble weakly-toxic substances: carbon black, titanium dioxide and talc. Though there is evidence of carcinogenity in experimental animals for these substances, the evidence in humans is sparse and equivocal. In the context of two large population based case-control studies of lung cancer carried out in Montreal, we were able to study the possible relationships between the exposure to each of these substances and subsequent risk of lung cancer. We were able to distinguish talc used for industrial purposes from that used for cosmetic purposes. Interviews for Study I were conducted in 1979-1986 (857 cases, 533 population controls, 1,349 cancer controls) and interviews for Study II were conducted in 1996-2001 (1,236 cases and 1,512 controls). Detailed lifetime job histories were elicited, and a team of hygienists and chemists evaluated the evidence of exposure to a host of occupational substances. Lung cancer risk was analysed in relation to each exposure, adjusting for several potential confounders, including smoking. Subjects with occupational exposure to carbon black, titanium dioxide, industrial talc and cosmetic talc did not experience any detectable excess risk of lung cancer. The results are consistent with the recent evaluations of the IARC Monographs.

  19. Evaluation of terrestrial carbon cycle models with atmospheric CO2 measurements: Results from transient simulations considering increasing CO2, climate, and land-use effects

    USGS Publications Warehouse

    Dargaville, R.J.; Heimann, Martin; McGuire, A.D.; Prentice, I.C.; Kicklighter, D.W.; Joos, F.; Clein, J.S.; Esser, G.; Foley, J.; Kaplan, J.; Meier, R.A.; Melillo, J.M.; Moore, B.; Ramankutty, N.; Reichenau, T.; Schloss, A.; Sitch, S.; Tian, H.; Williams, L.J.; Wittenberg, U.

    2002-01-01

    An atmospheric transport model and observations of atmospheric CO2 are used to evaluate the performance of four Terrestrial Carbon Models (TCMs) in simulating the seasonal dynamics and interannual variability of atmospheric CO2 between 1980 and 1991. The TCMs were forced with time varying atmospheric CO2 concentrations, climate, and land use to simulate the net exchange of carbon between the terrestrial biosphere and the atmosphere. The monthly surface CO2 fluxes from the TCMs were used to drive the Model of Atmospheric Transport and Chemistry and the simulated seasonal cycles and concentration anomalies are compared with observations from several stations in the CMDL network. The TCMs underestimate the amplitude of the seasonal cycle and tend to simulate too early an uptake of CO2 during the spring by approximately one to two months. The model fluxes show an increase in amplitude as a result of land-use change, but that pattern is not so evident in the simulated atmospheric amplitudes, and the different models suggest different causes for the amplitude increase (i.e., CO2 fertilization, climate variability or land use change). The comparison of the modeled concentration anomalies with the observed anomalies indicates that either the TCMs underestimate interannual variability in the exchange of CO2 between the terrestrial biosphere and the atmosphere, or that either the variability in the ocean fluxes or the atmospheric transport may be key factors in the atmospheric interannual variability.

  20. Carbon dioxide emissions and the overshoot ratio change resulting from the implementation of 2nd Energy Master Plan in South Korea

    NASA Astrophysics Data System (ADS)

    Yeo, M. J.; Kim, Y. P.

    2015-12-01

    The direction of the energy policies of the country is important in the projection of environmental impacts of the country. The greenhouse gases (GHGs) emission of the energy sector in South Korea is very huge, about 600 MtCO2e in 2011. Also the carbon footprint due to the energy consumption contributes to the ecological footprint is also large, more than 60%. Based on the official plans (the national greenhouse gases emission reduction target for 2030 (GHG target for 2030) and the 2nd Energy Master Plan (2nd EMP)), several scenarios were proposed and the sensitivity of the GHG emission amount and 'overshoot ratio' which is the ratio of ecological footprint to biocapacity were estimated. It was found that to meet the GHG target for 2030 the ratio of non-emission energy for power generation should be over 71% which would be very difficult. We also found that the overshoot ratio would increase from 5.9 in 2009 to 7.6 in 2035. Thus, additional efforts are required to reduce the environmental burdens in addition to optimize the power mix configuration. One example is the conversion efficiency in power generation. If the conversion efficiency in power generation rises up 50% from the current level, 40%, the energy demand and resultant carbon dioxide emissions would decrease about 10%. Also the influence on the environment through changes in consumption behavior, for example, the diet choice is expected to be meaningful.

  1. Quantifying stomatal and non-stomatal limitations to carbon assimilation resulting from leaf aging and drought in mature deciduous tree species.

    PubMed

    Wilson, Kell B.; Baldocchi, Dennis D.; Hanson, Paul J.

    2000-06-01

    Gas exchange techniques were used to investigate light-saturated carbon assimilation and its stomatal and non-stomatal limitations over two seasons in mature trees of five species in a closed deciduous forest. Stomatal and non-stomatal contributions to decreases in assimilation resulting from leaf age and drought were quantified relative to the maximum rates obtained early in the season at optimal soil water contents. Although carbon assimilation, stomatal conductance and photosynthetic capacity (V(cmax)) decreased with leaf age, decreases in V(cmax) accounted for about 75% of the leaf-age related reduction in light-saturated assimilation rates, with a secondary role for stomatal conductance (around 25%). However, when considered independently from leaf age, the drought response was dominated by stomatal limitations, accounting for about 75% of the total limitation. Some of the analytical difficulties associated with computing limitation partitioning are discussed, including path dependence, patchy stomatal closure and diffusion in the mesophyll. Although these considerations may introduce errors in our estimates, our analysis establishes some reasonable boundaries on relative limitations and shows differences between drought and non-drought years. Estimating seasonal limitations under natural conditions, as shown in this study, provides a useful basis for comparing limitation processes between years and species.

  2. Analysis of the linkage between rain and flood regime and its application to regional flood frequency estimation

    NASA Astrophysics Data System (ADS)

    Cunderlik, Juraj M.; Burn, Donald H.

    2002-04-01

    Improving techniques of flood frequency estimation at ungauged sites is one of the foremost goals of contemporary hydrology. River flood regime is a resultant reflection of a composite catchment hydrologic response to flood producing processes. In this sense the process of identifying homogeneous pooling groups can be plausibly based on catchment similarity in flood regime. Unfortunately the application of any pooling approach that is based on flood regime is restricted to gauged sites. Because flood regime can be markedly determined by rainfall regime, catchment similarity in rainfall regime can be an alternative option for identifying flood frequency pooling groups. An advantage of such a pooling approach is that rainfall data are usually spatially and temporary more abundant than flood data and the approach can also be applied at ungauged sites. Therefore in this study we have quantified the linkage between rainfall and flood regime and explored the appropriateness of substituting rainfall regime for flood regime in regional pooling schemes. Two different approaches to describing rainfall regime similarity using tools of directional statistics have been tested and used for evaluation of the potential of rainfall regime for identification of hydrologically homogeneous pooling groups. The outputs were compared to an existing pooling framework adopted in the Flood Estimation Handbook. The results demonstrate that regional pooling based on rainfall regime information leads to a high number of initially homogeneous groups and seems to be a sound pooling alternative for catchments with a close linkage between rain and flood regimes.

  3. Effect of rainfall regime and slope on runoff in a gullied loess region on the Loess Plateau in China.

    PubMed

    Fang, H Y; Cai, Q G; Chen, H; Li, Q Y

    2008-09-01

    Runoff was measured from seven plots with different slopes nested in Tuanshangou catchment on the Loess Plateau to study effect of slopes on runoff in relation to rainfall regimes. Based on nine years of field observation and K-mean clusters, 84 rainfall events were grouped into three rainfall regimes. Rainfall regime A is the group of events with strong rainfall intensity, high frequency, and short duration. Rainfall regime C consists of events with low intensity, long duration, and infrequent occurrence. Rainfall regime B is the aggregation of events of medium intensity and medium duration, and less frequent occurrence. The following results were found: (1) Different from traditional studies, runoff coefficient neither decreased nor increased, but presented peak value on the slope surfaces; (2) For individual plot, runoff coefficients induced by rainfall regime A were the highest, and those induced by rainfall regime C were the lowest; Downslope, the runoff coefficients induced by three rainfall regimes presented the same changing trend, although the peak value induced by regime A occurred on a shorter slope length compared to those by regime B and C; (3) Scale effect on runoff induced by rainfall regime A was the least, and that induced by rainfall regime C was the largest. These results can be explained by the interactions of crusting, soil moisture content, slope length and gradient, and erosion units, etc., in the context of different rainfall regimes.

  4. Abrupt climate-independent fire regime changes

    USGS Publications Warehouse

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  5. Generation of stretched pulses and dissipative solitons at 2  μm from an all-fiber mode-locked laser using carbon nanotube saturable absorbers.

    PubMed

    Wang, Yu; Alam, Shaif-Ul; Obraztsova, Elena D; Pozharov, Anatoly S; Set, Sze Y; Yamashita, Shinji

    2016-08-15

    We demonstrate for the first time, to the best of our knowledge, a thulium-doped, all-fiber, mode-locked laser using a carbon nanotube saturable absorber, operating in the dissipative-soliton regime and the stretched-pulse-soliton regime. The net dispersion of the laser cavity is adjusted by inserting different lengths of normal dispersion fiber, resulting in different mode-locking regimes. These results could serve as a foundation for the optimization of mode-locked fiber-laser cavity design at the 2 μm wavelength region. PMID:27519109

  6. Generation of stretched pulses and dissipative solitons at 2  μm from an all-fiber mode-locked laser using carbon nanotube saturable absorbers.

    PubMed

    Wang, Yu; Alam, Shaif-Ul; Obraztsova, Elena D; Pozharov, Anatoly S; Set, Sze Y; Yamashita, Shinji

    2016-08-15

    We demonstrate for the first time, to the best of our knowledge, a thulium-doped, all-fiber, mode-locked laser using a carbon nanotube saturable absorber, operating in the dissipative-soliton regime and the stretched-pulse-soliton regime. The net dispersion of the laser cavity is adjusted by inserting different lengths of normal dispersion fiber, resulting in different mode-locking regimes. These results could serve as a foundation for the optimization of mode-locked fiber-laser cavity design at the 2 μm wavelength region.

  7. Welfare state regimes, health and health inequalities in adolescence: a multilevel study in 32 countries.

    PubMed

    Richter, Matthias; Rathman, Katharina; Nic Gabhainn, Saoirse; Zambon, Alessio; Boyce, William; Hurrelmann, Klaus

    2012-07-01

    Comparative research on health and health inequalities has recently started to establish a welfare regime perspective. The objective of this study was to determine whether different welfare regimes are associated with health and health inequalities among adolescents. Data were collected from the 'Health Behaviour in School-aged Children' study in 2006, including 11- to 15-year-old students from 32 countries (N = 141,091). Prevalence rates and multilevel logistic regression models were calculated for self-rated health (SRH) and health complaints. The results show that between 4 per cent and 7 per cent of the variation in both health outcomes is attributable to differences between countries. Compared to the Scandinavian regime, the Southern regime had lower odds ratios for SRH, while for health complaints the Southern and Eastern regime showed high odds ratios. The association between subjective health and welfare regime was largely unaffected by adjusting for individual socioeconomic position. After adjustment for the welfare regime typology, the country-level variations were reduced to 4.6 per cent for SRH and to 2.9 per cent for health complaints. Regarding cross-level interaction effects between welfare regimes and socioeconomic position, no clear regime-specific pattern was found. Consistent with research on adults this study shows that welfare regimes are important in explaining variations in adolescent health across countries.

  8. Impacts of Arctic Climate Change on Tundra Fire Regimes at Interannual to Millennial Timescales

    NASA Astrophysics Data System (ADS)

    Hu, F.; Young, A. M.; Chipman, M. L.; Duffy, P.; Higuera, P. E.

    2014-12-01

    Tundra burning is emerging as a key process in the rapidly changing Arctic, and knowledge of tundra fire-regime responses to climate change is essential for projecting Earth system dynamics. This presentation will focus on climate-fire relationships in the Arctic, spatiotemporal patterns of Holocene tundra burning, and the effects of tundra burning on carbon cycling. Analysis of historical records reveals that across the Arctic, tundra burning occurred primarily in areas where mean summer temperature exceeded 9 °C and total summer precipitation was below 115 mm. In Alaska, summer temperature and precipitation explain >90% of the interannual variability in tundra area burned from AD 1950-2009, with thresholds of 10.5 °C and 140 mm. These patterns imply tipping points in tundra fire-regime responses to climate change. The frequency of tundra fires has varied greatly across space and through time. Approximately 1.0% of the circum-Arctic tundra burned from AD 2002-2013, and 4.5% of the Alaskan tundra burned from AD 1950-2009. The latter encompassed ecoregions with fire rotation periods ranging from ~400 to 13,640 years. Charcoal analysis of lake sediments also shows that Arctic tundra can sustain a wide range of fire regimes. Fires were rare on the Alaskan North Slope throughout the Holocene, implying that the climate thresholds evident in the historical records have seldom been crossed. In contrast, in areas of NW Alaska, tundra has burned regularly at 100-250 year intervals during the late Holocene. Tundra burning may cause sudden releases of the enormous amount of Arctic soil C. Charcoal particles from recent burns yielded 14C ages of AD 1952-2006. Thus the C consumed in recent fires may recover through vegetation succession. However, our results suggest that in areas that have burned multiple times in recent decades, old soil C is vulnerable to future fires.

  9. Safe Fast Reactor Based on Nuclear Burning Wave Regime

    SciTech Connect

    Fomin, S.; Mel'nik, Yu.; Pilipenko, V.; Shul'ga, N.

    2006-07-01

    The deterministic approach for describing the phenomenon of self-sustained regime of nuclear burning wave in a fast critical reactor is developed. The results of calculations of the space-time evolution of neutron flux and the fuel burn-up in such a system are presented. (authors)

  10. Magnetised Kelvin-Helmholtz instability in the intermediate regime between subsonic and supersonic regimes

    SciTech Connect

    Henri, P.; Califano, F.; Pegoraro, F.; Faganello, M.

    2012-07-15

    The understanding of the dynamics at play at the Earth's Magnetopause, the boundary separating the Earth's magnetosphere and the solar wind plasmas, is of primary importance for space plasma modeling. We focus our attention on the low latitude flank of the magnetosphere where the velocity shear between the magnetosheath and the magnetospheric plasmas is the energetic source of Kelvin-Helmholtz instability. On the shoulder of the resulting vortex chain, different secondary instabilities are at play depending on the local plasma parameters and compete with the vortex pairing process. Most important, secondary instabilities, among other magnetic reconnection, control the plasma mixing as well as the entry of solar wind plasma in the magnetosphere. We make use of a two-fluid model, including the Hall term and the electron mass in the generalized Ohm's law, to study the 2D non-linear evolution of the Kelvin-Helmholtz instability at the magnetosheath-magnetosphere interface, in the intermediate regime between subsonic and supersonic regimes. We study the saturation mechanisms, depending on the density jump across the shear layer and the magnetic field strength in the plane. In the presence of a weak in-plane magnetic field, the dynamics of the Kelvin-Helmholtz rolled-up vortices self-consistently generates thin current sheets where reconnection instability eventually enables fast reconnection to develop. Such a system enables to study guide field multiple-island collisionless magnetic reconnection as embedded in a large-scale dynamic system, unlike the classical static, ad hoc reconnection setups. In this regime, reconnection is shown to inhibit the vortex pairing process. This study provides a clear example of nonlinear, cross-scale, collisionless plasma dynamics.

  11. L-[METHYL-{sup 11}C] Methionine Positron Emission Tomography for Target Delineation in Malignant Gliomas: Impact on Results of Carbon Ion Radiotherapy

    SciTech Connect

    Mahasittiwat, Pawinee; Mizoe, Jun-etsu Hasegawa, Azusa; Ishikawa, Hiroyuki; Yoshikawa, Kyosan; Mizuno, Hideyuki; Yanagi, Takeshi; Takagi, Ryou D.D.S.; Pattaranutaporn, Pittayapoom; Tsujii, Hirohiko

    2008-02-01

    Purpose: To assess the importance of {sup 11}C-methionine (MET)-positron emission tomography (PET) for clinical target volume (CTV) delineation. Methods and Materials: This retrospective study analyzed 16 patients with malignant glioma (4 patients, anaplastic astrocytoma; 12 patients, glioblastoma multiforme) treated with surgery and carbon ion radiotherapy from April 2002 to Nov 2005. The MET-PET target volume was compared with gross tumor volume and CTV, defined by using computed tomography/magnetic resonance imaging (MRI). Correlations with treatment results were evaluated between positive and negative extended volumes (EVs) of the MET-PET target for CTV. Results: Mean volumes of the MET-PET targets, CTV1 (defined by means of high-intensity volume on T2-weighted MRI), and CTV2 (defined by means of contrast-enhancement volume on T1-weighted MRI) were 6.35, 264.7, and 117.7 cm{sup 3}, respectively. Mean EVs of MET-PET targets for CTV1 and CTV2 were 0.6 and 2.2 cm{sup 3}, respectively. The MET-PET target volumes were included in CTV1 and CTV2 in 13 (81.3%) and 11 patients (68.8%), respectively. Patients with a negative EV for CTV1 had significantly greater survival rate (p = 0.0069), regional control (p = 0.0047), and distant control time (p = 0.0267) than those with a positive EV. Distant control time also was better in patients with a negative EV for CTV2 than those with a positive EV (p = 0.0401). Conclusions: For patients with malignant gliomas, MET-PET has a possibility to be a predictor of outcome in carbon ion radiotherapy. Direct use of MET-PET fused to planning computed tomography will be useful and yield favorable results for the therapy.

  12. A Laminated Carbonate Record of Late Holocene Mid-Continental Hydroclimate: Geochemical and Sedimentological Results from Martin Lake, LaGrange County, Indiana

    NASA Astrophysics Data System (ADS)

    Stamps, L. G.; Bird, B. W.; Gilhooly, W., III

    2014-12-01

    Paleoclimate records from the mid-continental United States that span the Holocene with sub-decadal resolution are rare. This is especially true for geochemical records that capture the isotopic composition of precipitation or local precipitation/evaporation balances. As a result, many questions remain about the hydrologic expression of abrupt climate events in this region that today is one of the world's largest agricultural centers. Here, we present sedimentological, geochemical, and chronological data spanning the last 3,000 years from a set of sediment cores from Martin Lake in northeastern Indiana. Today, this kettle lake is hydrologically open with persistent water column stratification and bottom water anoxia. Radiometric dating shows that the lake formed at approximately 16,000 cal yr BP and continuously accumulated sediment thereafter. We focus here on developing a stable isotope record of the late Holocene at decadal resolution to provide a detailed view of precipitation isotopic variability during this time. The Midwest has been influenced by changes in atmospheric circulation patterns throughout the late Holocene, leading to climate events like the Little Ice Age and Medieval Climate Anomaly, which significantly changed temperature and precipitation regimes. The isotopic composition of precipitation in the Midwest has been shown to be heavily influenced by the source of atmospheric moisture as mediated by the Pacific North American mode of atmospheric variability that in turn affects the position of the Polar Front Jetstream. Using high-resolution stable isotope measurements and ultimately climate modeling, we seek to reconstruct the isotopic expression of late Holocene climate events in the mid continental United States and assess the possible relationship with these dominant modes of atmospheric variability. Future work includes extending this reconstruction through the Holocene and increasing the temporal resolution of the data.

  13. Temporal evolution of flow regimes in urbanizing basins

    NASA Astrophysics Data System (ADS)

    Mejia, A.; Rossel, F.; Gironas, J. A.; Jovanovic, T.

    2014-12-01

    We characterize the temporal evolution of the flow regime of urbanizing basins. By urbanizing basins, we mean basins that have experienced urban growth during their observation period. To represent the flow regime, we use flow duration curves (FDCs). We compute the FDCs using a stochastic model of daily streamflow for urban basins. In this case, the model aids in discerning the influence of key factors (e.g., climate, land use change, stormwater managenment conditions, and the slow and fast properties of the hydrologic response) on streamflow. To implement the model, we first divide the complete observation period of a given urban basin into intervals of equal duration, e.g. 5 years. Subsequently, we apply the model to each interval and this is how we capture the influence of land use changes and climatic fluctuations on the flow regime. We apply this modeling framework to 14 urbanizing basins in the Baltimore-Washington DC region. Results from this application indicate consistent changes in the temporal evolution of the altered flow regimes, which can largely be explained by the progressive redistribution with urban growth of water from slow subsurface runoff and evapotranspiration to fast urban runoff. We also use the modeling framework to determine indicators of ecohydrological alteration for urbanizing basins. The application of these indicators to our study area suggests that the flow regime is sensitive to alterations up to a certain level of urbanization after which sensitivity seems to level off. The flow regime also seems to be relatively more resistant to alterations for both the smaller and larger levels of urbanization considered. In the future, we would like to extend the application of the proposed modeling framework to other metropolitan areas.

  14. Properties and regimes of vertisols with gilgai microtopography (a review)

    NASA Astrophysics Data System (ADS)

    Khitrov, N. B.

    2016-03-01

    Data on the morphology and spatial distribution of slickensides and cracks, particle-size distribution, the organic carbon content, the content and forms of carbonate concentrations, and physical and physicochemical properties of Vertisols with the gilgai microtopography are systematized. Relatively scarce information on the functioning regimes of gilgai soil complexes (their temperature and moisture conditions, redox potential, vertical and horizontal deformations, and soil density changes) is discussed. Common properties of gilgai soils are the clayey texture of their profiles and the high portion of smectitic minerals specifying the high shrink-swell capacity of the soil material. The most important specificity of soils with the gilgai microtopography is a significant horizontal differentiation of the soil profiles with alternation of bowl-shaped morphostructures with a thick dark layer without carbonates in microlows and diapiric morphostructures composed of the rising material of the lower layers with diverse carbonate concentrations on microhighs. Data on the spatial distribution of soil properties within the gilgai microcatenas can be applied in the studies of the genesis and evolution stages of the gilgai soil complexes.

  15. Nonlinear transport processes in tokamak plasmas. I. The collisional regimes

    SciTech Connect

    Sonnino, Giorgio; Peeters, Philippe

    2008-06-15

    An application of the thermodynamic field theory (TFT) to transport processes in L-mode tokamak plasmas is presented. The nonlinear corrections to the linear ('Onsager') transport coefficients in the collisional regimes are derived. A quite encouraging result is the appearance of an asymmetry between the Pfirsch-Schlueter (P-S) ion and electron transport coefficients: the latter presents a nonlinear correction, which is absent for the ions, and makes the radial electron coefficients much larger than the former. Explicit calculations and comparisons between the neoclassical results and the TFT predictions for Joint European Torus (JET) plasmas are also reported. It is found that the nonlinear electron P-S transport coefficients exceed the values provided by neoclassical theory by a factor that may be of the order 10{sup 2}. The nonlinear classical coefficients exceed the neoclassical ones by a factor that may be of order 2. For JET, the discrepancy between experimental and theoretical results for the electron losses is therefore significantly reduced by a factor 10{sup 2} when the nonlinear contributions are duly taken into account but, there is still a factor of 10{sup 2} to be explained. This is most likely due to turbulence. The expressions of the ion transport coefficients, determined by the neoclassical theory in these two regimes, remain unaltered. The low-collisional regimes, i.e., the plateau and the banana regimes, are analyzed in the second part of this work.

  16. Decomposing uncertainties in the future terrestrial carbon budget associated with emission scenarios, climate projections, and ecosystem simulations using the ISI-MIP results

    NASA Astrophysics Data System (ADS)

    Nishina, K.; Ito, A.; Falloon, P.; Friend, A. D.; Beerling, D. J.; Ciais, P.; Clark, D. B.; Kahana, R.; Kato, E.; Lucht, W.; Lomas, M.; Pavlick, R.; Schaphoff, S.; Warszawaski, L.; Yokohata, T.

    2015-07-01

    We examined the changes to global net primary production (NPP), vegetation biomass carbon (VegC), and soil organic carbon (SOC) estimated by six global vegetation models (GVMs) obtained from the Inter-Sectoral Impact Model Intercomparison Project. Simulation results were obtained using five global climate models (GCMs) forced with four representative concentration pathway (RCP) scenarios. To clarify which component (i.e., emission scenarios, climate projections, or global vegetation models) contributes the most to uncertainties in projected global terrestrial C cycling by 2100, analysis of variance (ANOVA) and wavelet clustering were applied to 70 projected simulation sets. At the end of the simulation period, changes from the year 2000 in all three variables varied considerably from net negative to positive values. ANOVA revealed that the main sources of uncertainty are different among variables and depend on the projection period. We determined that in the global VegC and SOC projections, GVMs are the main influence on uncertainties (60 % and 90 %, respectively) rather than climate-driving scenarios (RCPs and GCMs). Moreover, the divergence of changes in vegetation carbon residence times is dominated by GVM uncertainty, particularly in the latter half of the 21st century. In addition, we found that the contribution of each uncertainty source is spatiotemporally heterogeneous and it differs among the GVM variables. The dominant uncertainty source for changes in NPP and VegC varies along the climatic gradient. The contribution of GVM to the uncertainty decreases as the climate division becomes cooler (from ca. 80 % in the equatorial division to 40 % in the snow division). Our results suggest that to assess climate change impacts on global ecosystem C cycling among each RCP scenario, the long-term C dynamics within the ecosystems (i.e., vegetation turnover and soil decomposition) are more critical factors than photosynthetic processes. The different trends in the

  17. The Widespread Occurrence of Water Vapor in the Circumstellar Envelopes of Carbon-rich Asymptotic Giant Branch Stars: First Results from a Survey with Herschel/HIFI

    NASA Astrophysics Data System (ADS)

    Neufeld, D. A.; González-Alfonso, E.; Melnick, G.; Szczerba, R.; Schmidt, M.; Decin, L.; Alcolea, J.; de Koter, A.; Schöier, F. L.; Bujarrabal, V.; Cernicharo, J.; Dominik, C.; Justtanont, K.; Marston, A. P.; Menten, K.; Olofsson, H.; Planesas, P.; Teyssier, D.; Waters, L. B. F. M.

    2011-02-01

    We report the preliminary results of a survey for water vapor in a sample of eight C stars with large mid-IR continuum fluxes: V384 Per, CIT 6, V Hya, Y CVn, IRAS 15194-5115, V Cyg, S Cep, and IRC+40540. This survey, performed using the HIFI instrument on board the Herschel Space Observatory, entailed observations of the lowest transitions of both ortho- and para-water: the 556.936 GHz 110-101 and 1113.343 GHz 111-000 transitions, respectively. Water vapor was unequivocally detected in all eight of the target stars. Prior to this survey, IRC+10216 was the only carbon-rich asymptotic giant branch (AGB) star from which thermal water emissions had been discovered, in that case with the use of the Submillimeter Wave Astronomy Satellite (SWAS). Our results indicate that IRC+10216 is not unusual, except insofar as its proximity to Earth leads to a large line flux that was detectable with SWAS. The water spectral line widths are typically similar to those of CO rotational lines, arguing against the vaporization of a Kuiper Belt analog being the general explanation for water vapor in carbon-rich AGB stars. There is no apparent correlation between the ratio of the integrated water line fluxes to the 6.3 μm continuum flux—a ratio which measures the water outflow rate—and the total mass-loss rate for the stars in our sample. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  18. THE WIDESPREAD OCCURRENCE OF WATER VAPOR IN THE CIRCUMSTELLAR ENVELOPES OF CARBON-RICH ASYMPTOTIC GIANT BRANCH STARS: FIRST RESULTS FROM A SURVEY WITH HERSCHEL /HIFI

    SciTech Connect

    Neufeld, D. A.; Gonzalez-Alfonso, E.; Melnick, G.; Szczerba, R.; Schmidt, M.; Decin, L.; Alcolea, J.; De Koter, A.; Dominik, C.; Waters, L. B. F. M.; Schoeier, F. L.; Justtanont, K.; Olofsson, H.; Bujarrabal, V.; Planesas, P.; Cernicharo, J.; Teyssier, D.; Marston, A. P.; Menten, K.

    2011-02-01

    We report the preliminary results of a survey for water vapor in a sample of eight C stars with large mid-IR continuum fluxes: V384 Per, CIT 6, V Hya, Y CVn, IRAS 15194-5115, V Cyg, S Cep, and IRC+40540. This survey, performed using the HIFI instrument on board the Herschel Space Observatory, entailed observations of the lowest transitions of both ortho- and para-water: the 556.936 GHz 1{sub 10}-1{sub 01} and 1113.343 GHz 1{sub 11}-0{sub 00} transitions, respectively. Water vapor was unequivocally detected in all eight of the target stars. Prior to this survey, IRC+10216 was the only carbon-rich asymptotic giant branch (AGB) star from which thermal water emissions had been discovered, in that case with the use of the Submillimeter Wave Astronomy Satellite (SWAS). Our results indicate that IRC+10216 is not unusual, except insofar as its proximity to Earth leads to a large line flux that was detectable with SWAS. The water spectral line widths are typically similar to those of CO rotational lines, arguing against the vaporization of a Kuiper Belt analog being the general explanation for water vapor in carbon-rich AGB stars. There is no apparent correlation between the ratio of the integrated water line fluxes to the 6.3 {mu}m continuum flux-a ratio which measures the water outflow rate-and the total mass-loss rate for the stars in our sample.

  19. Decomposing uncertainties in the future terrestrial carbon budget associated with emission scenario, climate projection, and ecosystem simulation using the ISI-MIP result

    NASA Astrophysics Data System (ADS)

    Nishina, K.; Ito, A.; Falloon, P.; Friend, A. D.; Beerling, D. J.; Ciais, P.; Clark, D. B.; Kahana, R.; Kato, E.; Lucht, W.; Lomas, M.; Pavlick, R.; Schaphoff, S.; Warszawaski, L.; Yokohata, T.

    2014-10-01

    Changes to global net primary production (NPP), vegetation biomass carbon (VegC), and soil organic carbon (SOC) estimated by six global vegetation models (GVM) obtained from an Inter-Sectoral Impact Model Intercomparison Project study were examined. Simulation results were obtained using five global climate models (GCM) forced with four representative concentration pathway (RCP) scenarios. To clarify which component (emission scenarios, climate projections, or global vegetation models) contributes the most to uncertainties in projected global terrestrial C cycling by 2100, analysis of variance (ANOVA) and wavelet clustering were applied to 70 projected simulation sets. In the end of simulation period, the changes from the year of 2000 in all three variables considerably varied from net negative to positive values. ANOVA revealed that the main sources of uncertainty are different among variables and depend on the projection period. We determined that in the global VegC, and SOC projections, GVMs dominate uncertainties (60 and 90%, respectively) rather than climate driving scenarios, i.e., RCPs and GCMs. These results suggested that we don't have still enough resolution among each RCP scenario to evaluate climate change impacts on ecosystem conditions in global terrestrial C cycling. In addition, we found that the contributions of each uncertainty source were spatio-temporally heterogeneous and differed among the GVM variables. The dominant uncertainty source for changes in NPP and VegC varies along the climatic gradient. The contribution of GVM to the uncertainty decreases as the climate division gets cooler (from ca. 80% in the equatorial division to 40% in the snow climatic division). To evaluate the effects of climate change on ecosystems with practical resolution in RCP scenarios, GVMs require further improvement to reduce the uncertainties in global C cycling as much as, if not more than, GCMs. Our study suggests that the improvement of GVMs is a priority for

  20. Regimes of validity for balanced models

    NASA Astrophysics Data System (ADS)

    Gent, Peter R.; McWilliams, James C.

    1983-07-01

    Scaling analyses are presented which delineate the atmospheric and oceanic regimes of validity for the family of balanced models described in Gent and McWilliams (1983a). The analyses follow and extend the classical work of Charney (1948) and others. The analyses use three non-dimensional parameters which represent the flow scale relative to the Earth's radius, the dominance of turbulent or wave-like processes, and the dominant component of the potential vorticity. For each regime, the models that are accurate both at leading order and through at least one higher order of accuracy in the appropriate small parameter are then identified. In particular, it is found that members of the balanced family are the appropriate models of higher-order accuracy over a broad range of parameter regimes. Examples are also given of particular atmospheric and oceanic phenomena which are in the regimes of validity for the different balanced models.

  1. Earth Regime Network Evolution Study (ERNESt)

    NASA Technical Reports Server (NTRS)

    Menrad, Bob

    2016-01-01

    Speaker and Presenter at the Lincoln Laboratory Communications Workshop on April 5, 2016 at the Massachusetts Institute of Technology Lincoln Laboratory in Lexington, MA. A visual presentation titled Earth Regimes Network Evolution Study (ERNESt).

  2. Historical fire regime in southern California

    USGS Publications Warehouse

    Keeley, Jon E.; Fotheringham, Connie J.

    2003-01-01

    The historical variability in fire regime is a conservative indicator of ecosystem sustainability. Understanding the natural role of fire in chaparral ecosystems is therefore necessary for effective fire management.

  3. Initial results of comparing cold-seep carbonates from mussel- and tubeworm-associated environments at Atwater Valley lease block 340, northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Feng, Dong; Roberts, Harry H.

    2010-11-01

    Chemosymbiotic macrofauna (such as mussels and tubeworms) and authigenic carbonates are typical of many hydrocarbon seeps. To address whether mussels and tubeworms could impact the sediment geochemistry of their habitat where authigenic carbonates are precipitated, a comparative study of petrographic and geochemical features of the authigenic carbonates from mussel- and tubeworm-associated environments at hydrocarbon seeps in Atwater Valley lease area block 340 (AT340) of the Gulf of Mexico was undertaken. Both mussel- and tubeworm-associated carbonates are dominated by high-magnesium calcite (HMC) and aragonite, and two tubeworm-associated carbonate samples have minor amounts of dolomite. The δ13C values of all carbonates are low, ranging from -60.8‰ to -35.5‰ PDB. Although there is much overlap, surprisingly the δ13C values of mussel-associated carbonates are generally higher than those of tubeworm-associated carbonates (-51.8‰ vs. -54.8‰ for an average of over 60 subsamples). It is suggested that (1) carbon isotopic vital effect of seep mussels and tubeworms, (2) fluid physical pumping of mussels, and (3) release of sulfate by tubeworm roots may be responsible for the relatively lower δ13C values of tubeworm-associated carbonates. It has been suggested that the heterogeneities in mineralogy and stable carbon isotope geochemistry of the seep carbonates may be attributed to the activity of macrofauna (mussels and tubeworms) and associated microbes. Our observations also suggest that at AT340 the geochemical evolution of seep macrofauna is from a mussel-dominated environment to a mixed mussel-tubeworm environment, and finally to a mostly tubeworm-dominated environment. This evolution is controlled mainly by the habitat, e.g., hydrocarbon seep flux.

  4. Electron transport fluxes in potato plateau regime

    SciTech Connect

    Shaing, K.C.; Hazeltine, R.D.

    1997-12-01

    Electron transport fluxes in the potato plateau regime are calculated from the solutions of the drift kinetic equation and fluid equations. It is found that the bootstrap current density remains finite in the region close to the magnetic axis, although it decreases with increasing collision frequency. This finite amount of the bootstrap current in the relatively collisional regime is important in modeling tokamak startup with 100{percent} bootstrap current. {copyright} {ital 1997 American Institute of Physics.}

  5. Using Clustering to Establish Climate Regimes from PCM Output

    NASA Technical Reports Server (NTRS)

    Oglesby, Robert; Arnold, James E. (Technical Monitor); Hoffman, Forrest; Hargrove, W. W.; Erickson, D.

    2002-01-01

    A multivariate statistical clustering technique--based on the k-means algorithm of Hartigan has been used to extract patterns of climatological significance from 200 years of general circulation model (GCM) output. Originally developed and implemented on a Beowulf-style parallel computer constructed by Hoffman and Hargrove from surplus commodity desktop PCs, the high performance parallel clustering algorithm was previously applied to the derivation of ecoregions from map stacks of 9 and 25 geophysical conditions or variables for the conterminous U.S. at a resolution of 1 sq km. Now applied both across space and through time, the clustering technique yields temporally-varying climate regimes predicted by transient runs of the Parallel Climate Model (PCM). Using a business-as-usual (BAU) scenario and clustering four fields of significance to the global water cycle (surface temperature, precipitation, soil moisture, and snow depth) from 1871 through 2098, the authors' analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The patterns of cluster changes have been analyzed to understand the predicted variability in the water cycle on global and continental scales. In addition, representative climate regimes were determined by taking three 10-year averages of the fields 100 years apart for northern hemisphere winter (December, January, and February) and summer (June, July, and August). The result is global maps of typical seasonal climate regimes for 100 years in the past, for the present, and for 100 years into the future. Using three-dimensional data or phase space representations of these climate regimes (i.e., the cluster centroids), the authors demonstrate the portion of this phase space occupied by the land surface at all points in space and time

  6. Using Clustering to Establish Climate Regimes from PCM Output

    NASA Astrophysics Data System (ADS)

    Hoffman, F.; Oglesby, R.; Hargrove, W. W.; Erickson, D.

    2002-12-01

    A multivariate statistical clustering technique--based on the k-means algorithm of Hartigan--has been used to extract patterns of climatological significance from 200 years of general circulation model (GCM) output. Originally developed and implemented on a Beowulf-style parallel computer constructed by Hoffman and Hargrove from surplus commodity desktop PCs, the high performance parallel clustering algorithm was previously applied to the derivation of ecoregions from map stacks of 9 and 25 geophysical conditions or variables for the conterminous U.S. at a resolution of 1 sq km. Now applied both across space and through time, the clustering technique yields temporally-varying climate regimes predicted by transient runs of the Parallel Climate Model (PCM). Using a business-as-usual (BAU) scenario and clustering four fields of significance to the global water cycle (surface temperature, precipitation, soil moisture, and snow depth) from 1871 through 2098, the authors' analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The patterns of cluster changes have been analyzed to understand the predicted variability in the water cycle on global and continental scales. In addition, representative climate regimes were determined by taking three 10-year averages of the fields 100 years apart for northern hemisphere winter (December, January, and February) and summer (June, July, and August). The result is global maps of typical seasonal climate regimes for 100 years in the past, for the present, and for 100 years into the future. Using three-dimensional data or phase space representations of these climate regimes (i.e., the cluster centroids), the authors demonstrate the portion of this phase space occupied by the land surface at all points in space and

  7. Flow regimes in a trapped vortex cell

    NASA Astrophysics Data System (ADS)

    Lasagna, D.; Iuso, G.

    2016-03-01

    This paper presents results of an experimental investigation on the flow in a trapped vortex cell, embedded into a flat plate, and interacting with a zero-pressure-gradient boundary layer. The objective of the work is to describe the flow features and elucidate some of the governing physical mechanisms, in the light of recent investigations on flow separation control using vortex cells. Hot-wire velocity measurements of the shear layer bounding the cell and of the boundary layers upstream and downstream are reported, together with spectral and correlation analyses of wall-pressure fluctuation measurements. Smoke flow visualisations provide qualitative insight into some relevant features of the internal flow, namely a large-scale flow unsteadiness and possible mechanisms driving the rotation of the vortex core. Results are presented for two very different regimes: a low-Reynolds-number case where the incoming boundary layer is laminar and its momentum thickness is small compared to the cell opening, and a moderately high-Reynolds-number case, where the incoming boundary layer is turbulent and the ratio between the momentum thickness and the opening length is significantly larger than in the first case. Implications of the present findings to flow control applications of trapped vortex cells are also discussed.

  8. Initiation of detonation regimes in hybrid two-phase mixtures

    NASA Astrophysics Data System (ADS)

    Khasainov, B. A.; Veyssiere, B.

    1996-06-01

    The problem of detonation initiation is studied in the case of hybrid two-phase mixtures consisting of a hydrogen-air gaseous mixture with suspended fine aluminium particles. In preceding works on this subject, investigation of the steady propagation regimes has shown that three main propagation regimes could exist: the Pseudo-Gas Detonation (PGD), the Single-Front Detonation (SFD), and the Double-Front Detonation (DFD). In the present study, a one-dimensional unsteady numerical code has been improved to study the build-up of the detonation in a heterogeneous solid particle gas mixture contained in a tube. The initiation is simulated by the deposition of a given energy in a point source explosion, and the formation of the detonation is observed over distances of 15 m to 30 m. As the code has been designed to run on a micro-computer, memory limitations preclude sufficient accuracy for quantitative results, however, good qualitative agreement has been found with the results of the steady analysis. In addition, it has been demonstrated that when both PGD and SFD could exist at the same particle concentration, the PGD regime was unstable and was able to exist only over a limited distance (a few meters): after some time, the reaction of aluminium particles in the unsteady flow perturbs the leading wave and accelerates it to the SFD regime. Influence of particle diameter and of initiation energy are examined.

  9. Dynamic Financial Constraints: Distinguishing Mechanism Design from Exogenously Incomplete Regimes.

    PubMed

    Karaivanov, Alexander; Townsend, Robert M

    2014-05-01

    We formulate and solve a range of dynamic models of constrained credit/insurance that allow for moral hazard and limited commitment. We compare them to full insurance and exogenously incomplete financial regimes (autarky, saving only, borrowing and lending in a single asset). We develop computational methods based on mechanism design, linear programming, and maximum likelihood to estimate, compare, and statistically test these alternative dynamic models with financial/information constraints. Our methods can use both cross-sectional and panel data and allow for measurement error and unobserved heterogeneity. We estimate the models using data on Thai households running small businesses from two separate samples. We find that in the rural sample, the exogenously incomplete saving only and borrowing regimes provide the best fit using data on consumption, business assets, investment, and income. Family and other networks help consumption smoothing there, as in a moral hazard constrained regime. In contrast, in urban areas, we find mechanism design financial/information regimes that are decidedly less constrained, with the moral hazard model fitting best combined business and consumption data. We perform numerous robustness checks in both the Thai data and in Monte Carlo simulations and compare our maximum likelihood criterion with results from other metrics and data not used in the estimation. A prototypical counterfactual policy evaluation exercise using the estimation results is also featured.

  10. Dynamic Financial Constraints: Distinguishing Mechanism Design from Exogenously Incomplete Regimes.

    PubMed

    Karaivanov, Alexander; Townsend, Robert M

    2014-05-01

    We formulate and solve a range of dynamic models of constrained credit/insurance that allow for moral hazard and limited commitment. We compare them to full insurance and exogenously incomplete financial regimes (autarky, saving only, borrowing and lending in a single asset). We develop computational methods based on mechanism design, linear programming, and maximum likelihood to estimate, compare, and statistically test these alternative dynamic models with financial/information constraints. Our methods can use both cross-sectional and panel data and allow for measurement error and unobserved heterogeneity. We estimate the models using data on Thai households running small businesses from two separate samples. We find that in the rural sample, the exogenously incomplete saving only and borrowing regimes provide the best fit using data on consumption, business assets, investment, and income. Family and other networks help consumption smoothing there, as in a moral hazard constrained regime. In contrast, in urban areas, we find mechanism design financial/information regimes that are decidedly less constrained, with the moral hazard model fitting best combined business and consumption data. We perform numerous robustness checks in both the Thai data and in Monte Carlo simulations and compare our maximum likelihood criterion with results from other metrics and data not used in the estimation. A prototypical counterfactual policy evaluation exercise using the estimation results is also featured. PMID:25246710

  11. Transport processes in magnetically confined plasmas in the nonlinear regime

    SciTech Connect

    Sonnino, Giorgio

    2006-06-15

    A field theory approach to transport phenomena in magnetically confined plasmas is presented. The thermodynamic field theory (TFT), previously developed for treating the generic thermodynamic system out of equilibrium, is applied to plasmas physics. Transport phenomena are treated here as the effect of the field linking the thermodynamic forces with their conjugate flows combined with statistical mechanics. In particular, the Classical and the Pfirsch-Schlueter regimes are analyzed by solving the thermodynamic field equations of the TFT in the weak-field approximation. We found that, the TFT does not correct the expressions of the ionic heat fluxes evaluated by the neoclassical theory in these two regimes. On the other hand, the fluxes of matter and electronic energy (heat flow) is further enhanced in the nonlinear Classical and Pfirsch-Schlueter regimes. These results seem to be in line with the experimental observations. The complete set of the electronic and ionic transport equations in the nonlinear Banana regime, is also reported. A paper showing the comparison between our theoretic results and the experimental observations in the JET machine is currently in preparation.

  12. Dynamics of liquid drops coalescing in the inertial regime.

    PubMed

    Sprittles, James E; Shikhmurzaev, Yulii D

    2014-06-01

    We examine the dynamics of two coalescing liquid drops in the "inertial regime," where the effects of viscosity are negligible and the propagation of the front of the bridge connecting the drops can be considered as "local." The solution fully computed in the framework of classical fluid mechanics allows this regime to be identified, and the accuracy of the approximating scaling laws proposed to describe the propagation of the bridge to be established. It is shown that the scaling law known for this regime has a very limited region of accuracy, and, as a result, in describing experimental data it has frequently been applied outside its limits of applicability. The origin of the scaling law's shortcoming appears to be the fact that it accounts for the capillary pressure due only to the longitudinal curvature of the free surface as the driving force for the process. To address this deficiency, the scaling law is extended to account for both the longitudinal and azimuthal curvatures at the bridge front, which, fortuitously, still results in an explicit analytic expression for the front's propagation speed. This expression is shown to offer an excellent approximation for both the fully computed solution and for experimental data from a range of flow configurations for a remarkably large proportion of the coalescence process. The derived formula allows one to predict the speed at which drops coalesce for the duration of the inertial regime, which should be useful for the analysis of experimental data. PMID:25019880

  13. Dynamic Financial Constraints: Distinguishing Mechanism Design from Exogenously Incomplete Regimes*

    PubMed Central

    Karaivanov, Alexander; Townsend, Robert M.

    2014-01-01

    We formulate and solve a range of dynamic models of constrained credit/insurance that allow for moral hazard and limited commitment. We compare them to full insurance and exogenously incomplete financial regimes (autarky, saving only, borrowing and lending in a single asset). We develop computational methods based on mechanism design, linear programming, and maximum likelihood to estimate, compare, and statistically test these alternative dynamic models with financial/information constraints. Our methods can use both cross-sectional and panel data and allow for measurement error and unobserved heterogeneity. We estimate the models using data on Thai households running small businesses from two separate samples. We find that in the rural sample, the exogenously incomplete saving only and borrowing regimes provide the best fit using data on consumption, business assets, investment, and income. Family and other networks help consumption smoothing there, as in a moral hazard constrained regime. In contrast, in urban areas, we find mechanism design financial/information regimes that are decidedly less constrained, with the moral hazard model fitting best combined business and consumption data. We perform numerous robustness checks in both the Thai data and in Monte Carlo simulations and compare our maximum likelihood criterion with results from other metrics and data not used in the estimation. A prototypical counterfactual policy evaluation exercise using the estimation results is also featured. PMID:25246710

  14. Ten Years of Near-Surface-Sensitive Satellite Observations of Carbon Dioxide and Methane: Selected Results Related to Natural and Anthropogenic Sources and Sinks

    NASA Astrophysics Data System (ADS)

    Buchwitz, M. A.; Reuter, M.; Schneising, O.; Bovensmann, H.; Burrows, J. P.

    2014-12-01

    Prior to the recently successfully launched OCO-2 mission, global near-surface-sensitive satellite observations of carbon dioxide (CO2) have been made with SCIAMACHY/ENVISAT during 2002-2012 and are still being made since 2009 with TANSO-FTS/GOSAT, which also deliver atmospheric methane (CH4). The SCIAMACHY and GOSAT overlapping time series of atmospheric column-averaged mole fractions, i.e., XCO2 and XCH4, now cover more than 10 years. During the last years significant progress has been made in improving the quality of the XCO2 and XCH4 data products retrieved from SCIAMACHY and GOSAT and in extending the time series so that more and more applications can be addressed. In this presentation we present some recent results related to CO2 and CH4 sources and sinks. The SCIAMACHY products have been generated using retrieval algorithms developed at University of Bremen. For XCO2 we use an ensemble of data products generated using GOSAT retrieval algorithms developed in Japan (at NIES), in the US (at NASA/JPL and collaborating institutes) and at European institutions (University of Leicester, UK, and SRON, Netherlands, in collaboration with KIT, Germany). Focus will be on three applications: (i) An assessment of the strength of the European terrestrial carbon sink during 2003-2010 based on an ensemble of SCIAMACHY (2003-2010) and GOSAT (2010) XCO2 data products, (ii) an assessment of CO2 and NO2 anthropogenic emission and emission ratio trends using co-located SCIAMACHY XCO2 and NO2 observations over Europe, North America and East Asia, and (iii) an analysis of SCIAMACHY XCH4 retrievals during 2006-2011 over North America focusing on fugitive methane emissions from oil and gas production using tight geological formations ("fracking"). It will be shown that (i) the European terrestrial carbon sink appears to be stronger than expected, (ii) that recent Chinese CO2 and NO2 emissions are increasin