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Sample records for carbon stabilized expanded

  1. Lattice expansion of carbon-stabilized expanded austenite

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

    2010-01-01

    The lattice parameter of expanded austenite was determined as a function of the content of interstitially dissolved carbon in homogeneous, carburized thin stainless steel foils. For the first time this expansion of the face-centered cubic lattice is determined on unstrained austenite. It is found...

  2. Extended X-Ray Absorption Fine Structure Investigation of Carbon Stabilized Expanded Austenite and Carbides in Stainless Steel AISI 316

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny;

    2011-01-01

    Low temperature carburized AISI 316 stainless steel - carbon expanded austenite - was investigated with EXAFS and synchrotron diffraction together with synthesized carbides of the type M3C2, M7C3 and M23C6. It was found that the chemical environment of carbon expanded austenite is not associated ...

  3. Stress and Composition of Carbon Stabilized Expanded Austenite on Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2009-01-01

    Low-temperature gaseous carburizing of stainless steel is associated with a colossal supersaturation of the fcc lattice with carbon, without the development of carbides. This article addresses the simultaneous determination of stress and composition profiles in layers of carbon xpanded austenite...

  4. Stability of stagnation via an expanding accretion shock wave

    CERN Document Server

    Velikovich, A L; Taylor, B D; Giuliani, J L; Zalesak, S T; Iwamoto, Y

    2016-01-01

    Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Y. Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [H. Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); M. Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic...

  5. Stability of stagnation via an expanding accretion shock wave

    Science.gov (United States)

    Velikovich, A. L.; Murakami, M.; Taylor, B. D.; Giuliani, J. L.; Zalesak, S. T.; Iwamoto, Y.

    2016-05-01

    Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.

  6. Stability of expanded granular sludge bed process for terylene artificial silk printing and dyeing wastewater treatment

    Institute of Scientific and Technical Information of China (English)

    GUAN Bao-hong

    2005-01-01

    Terylene artificial silk printing and dyeing wastewater(TPD wastewater), containing averaged 710 mg/L terephthalic acid(TA) as the main carbon source and the character pollutant, was subjected to expanded granular sludge bed(EGSB) process. The stability of theEGSB process was firstly conducted by laboratory experiment. TA ionization was the predominated factor influencing the acid-base balance of the system. High concentration of TA in wastewater resulted in sufficient buffering capacity to neutralize the volatile fatty acids(VFA)generated from substrate degradation and provided strong base for anaerobic system to resist the pH decrease below 6.5. VFA and UFA caused almost no inhibition on the anaerobic process and biogas production except that pH was below 6.35 and VFA was at its maximum value. Along with the granulating of the activated sludge, the efficiency of organic removal and production rate of biogas increased gradually and became more stable. After start-up, the efficiency of COD removal increased to 57%-64%, pH stabilized in a range of 7.99-8.04, and production rate of biogas was relatively high and stable. Sludge granulating, suitable influent of pH and loading were responsible for the EGSB stability. The variation of VFA concentration only resulted in neglectable rebound of pH, and the inhibition from VFA could be ignored in EGSB. The EGSB reactor was stable for TPD wastewater treatment.

  7. Effect of hydrogen and oxygen on stability of expanders and performance of lead/acid batteries

    Energy Technology Data Exchange (ETDEWEB)

    Pavlov, D. (Bulgarian Academy of Sciences, Sofia (Bulgaria). Central Lab. of Electrochemical Power Sources); Gancheva, S. (Bulgarian Academy of Sciences, Sofia (Bulgaria). Central Lab. of Electrochemical Power Sources); Andreev, P. (Bulgarian Academy of Sciences, Sofia (Bulgaria). Central Lab. of Electrochemical Power Sources)

    1993-10-15

    Expanders are organic additives to the negative active mass that increase plate capacity, especially at low temperatures. They operate under constant hydrogen and oxygen attack at strongly negative potentials as a result of which they undergo degradation. This leads to changes in plate capacity, which may limit the life of the battery. The aims of the present work are: (i) to suggest a method for determining the effect of hydrogen, oxygen and the potential on the stability of expanders; (ii) to identify some of the structural groups in organic compounds that exert an efficient expander action. The influence of Velex, Mimosa, Quebraco, Syntan NK (SNK) and EZE-Skitan on the electrochemical characteristics and the life of negative battery plates has been investigated. It is established that structural groups of the pyrocatechin type (Quebraco and EZE-Skitan) have effective expander action. Quebraco increases the plate capacity during the first cycles. EZE-Skitan increases the capacity of the plates after 50 to 60 charge/discharge cycles, when disintegration of its structure, probably to pyrocatechin groups, proceeds. By applying a new method for determining the expander stability, it is found that expanders containing pyrocatechin structural groups are more easily oxidized than hydrogenated. It is concluded that the most effective expander should be a combination of several compounds with different stabilities to oxidation and reduction. Appropriate expanders should be selected for each type of battery. (orig.)

  8. Dynamic characteristics and seismic stability of expanded polystyrene geofoam embankments

    Science.gov (United States)

    Amini, Zahra A.

    Expanded Polystyrene (EPS) geofoam has become a preferred material in various construction applications due to its light weight. Application of EPS accelerates the projects particularly on soft soils. The focus of this research is on the application of the EPS in embankments and its behavior mainly under harmonic vibration. The goal of this study was to investigate dynamic characteristics of freestanding vertical EPS geofoam embankment and address potential seismic issues that result from the distinguished dynamic behavior of such systems due to the layered and discrete block structure. A series of experimental studies on EPS 19 and a commercially available adhesive was conducted. Two-dimensional numerical analyses were performed to replicate the response of EPS geofoam embankment to horizontal and vertical harmonic motions. The results of the analyses have shown that for some acceleration amplitude levels interlayer sliding is expected to occur in EPS geofoam embankments almost immediately after the start of the base excitation; however, as a highly efficient energy dissipation mechanism sliding ceases rapidly. Shear keys and adhesive may be used to prevent interlayer sliding if they cover the proper extent of area of the embankment. EPS blocks placed in the corners of the embankment and at the edges of the segment prohibited from sliding may experience high stress concentrations. The embankment may show horizontal sway and rocking once sliding is prevented.

  9. Stability of a Bubble Expanding and Translating Through an Inviscid Liquid

    Indian Academy of Sciences (India)

    Dinesh Khattar; B B Chakraborty

    2002-05-01

    A bubble expands adiabatically and translates in an incompressible and inviscid liquid. We investigate the number of equilibrium points of the bubble and the nature of stability of the bubble at these points. We find that there is only one equilibrium point and the bubble is stable there.

  10. Extended X-ray absorption fine structure investigation of nitrogen stabilized expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny;

    2010-01-01

    As-delivered austenitic stainless steel and nitrogen stabilized expanded austenite, both fully nitrided and denitrided (in H2), were investigated with Cr, Fe and Ni extended X-ray absorption fine structure. The data shows pronounced short-range ordering of Cr and N. For the denitrided specimen...

  11. Fabrication of porous carbon composite material from leaves waste as lightweight expanded carbon aggregate (LECA)

    Science.gov (United States)

    Sulhadi, Rosita, N.; Susanto, Nisa', K.; Wiguna, P. A.; Marwoto, P.; Aji, M. P.

    2016-04-01

    Leaves waste has been used as Lightweight Expanded Carbon Aggregates (LECA) because of its high carbon material. LECA can be used as a water storage media. LECA is low in density so thatits massis very light. Due to its use as a water storage medium, it is important to find out the absorption which occurs in LECA.The LECA's absorption and evaporation rate is affected by the pores. The pores serves to increase water storage ability from LECA. LECA with PEG (pore-forming agent) mass percent variation of 5%, 10%, 15%, 20% and 25% is the focus of this study. LECA fabrication was conducted by mixing the carbon resulting from leaves waste pyrolysis and PEG and PVAc. The characterization of LECA was found out by calculating the porosity, the pore size distribution, absorption rate and evaporation rate. The result of the calculation shows that the higher PEG mass percentage, the higher LECA's porosity, the pore size distribution, absorption rate and evaporation rate. However, the porosity, the pore size distributionand absorption rate will be saturated by 25% PEG mass percent addition.

  12. Influence of Expanded Graphite Surface Ozonation on the Adhesion between Carbon Additive and Cement Matrix

    OpenAIRE

    2015-01-01

    Cement mortars modified with expanded graphite (EG) subjected to surface treatments in gaseous ozone were investigated. It was shown that the bonding between carbon additive and cement paste strongly depends on the surface modification of EG and the chemical composition of EG surface plays the important role in shaping the mechanical properties of cement composites. The expanded graphite subjected to ozone treatment showed the substantial increase of flexural toughness of cement composite. Th...

  13. Extended x-ray absorption fine structure investigation of annealed carbon expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas L.; Somers, Marcel A. J.;

    2012-01-01

    Carbon expanded austenite synthesized through carburizing of austenitic stainless steel powder at 380°C was annealed at 470°C and investigated with extended X-ray absorption fine structure (EXAFS) and synchrotron powder diffraction (SPD). SPD showed that the samples consisted of carbon expanded...... austenite and Hägg carbide, Ξ-M5C2. EXAFS showed that the Cr atoms were mainly present in environments similar to the carbides Hägg Ξ-M5C2 and M23C6. The environments of the Fe and Ni atoms were concluded to be largely metallic austenite. Light optical micrograph of stainless steel AISI 316 gas......-carburized in a temperature regime around 470°C. The surface zone is converted into carbon expanded austenite; the high interstitial content of carbon dissolved in the surface results in highly favorable materials properties. In the present article the local atomic environment of (annealed) carbon expanded austenite...

  14. Topological triple-vortex lattice stabilized by mixed frustration in expanded honeycomb Kitaev-Heisenberg model.

    Science.gov (United States)

    Yao, Xiaoyan; Dong, Shuai

    2016-05-27

    The expanded classical Kitaev-Heisenberg model on a honeycomb lattice is investigated with the next-nearest-neighboring Heisenberg interaction considered. The simulation shows a rich phase diagram with periodic behavior in a wide parameter range. Beside the double 120° ordered phase, an inhomogeneous phase is uncovered to exhibit a topological triple-vortex lattice, corresponding to the hexagonal domain structure of vector chirality, which is stabilized by the mixed frustration of two sources: the geometrical frustration arising from the lattice structure as well as the frustration from the Kitaev couplings.

  15. On the Carbon Solubility in Expanded Austenite and Formation of Hägg Carbide in AISI 316 Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Ståhl, Kenny; Brink, Bastian;

    2016-01-01

    –420 °C and 465–470 °C, respectively. Hägg carbide (x-M5C2)develops when the carbon content in the expanded austenite exceeds the metastable solubility limit; the transformation of carbon expanded austenite into Hägg carbide occurs irrespective of carburizing temperature in the investigated temperature...

  16. The influence of complex biological feedstock on the fluidization and bed stability in expanded bed adsorption

    Science.gov (United States)

    Fernandez-Lahore; Kleef; Kula; Thommes

    1999-08-20

    The stability of expanded bed adsorption systems (EBA) was studied in biomass containing culture broth by residence time distribution (RTD) experiments, using pulse inputs of fluorescent molecules as tracers. Different commercial adsorbents (Streamline DEAE, SP, Phenyl, Chelating, and AC) were tested at various biomass concentrations (2.5-12 %, wet weight) of whole (Saccharomyces cerevisiae) yeast, yeast cell homogenate, and Escherichia coli homogenate. Analyzing the RTD according to the PDE model (PDE: axially dispersed plug-flow exchanging mass with stagnant zones) allowed the calculation of three parameters: the number of transfer units for mass exchange between mobile and stagnant fraction (N), the Peclet number for overall axial dispersion (P), and the mobile fraction of the liquid in axially dispersed plug flow (varphi). When fluidization was performed in particle-free buffer the normalized response signal (after perfect input pulse) was symmetric (N:0; P: 50-100; varphi: 1), thus, demonstrating the formation of a homogeneous fluidized (expanded) bed. Upon application of suspended biomass the RTD was skewed, depending on the adsorbent used and the type and level of biomass present in the sample. This situation leads to three different characteristic pictures: the well-fluidized system (N: >/= 7-10; P: >/= 40; varphi: 0.80-0.90), the system exhibiting bottom channeling (N: /= 40; varphi: 0.5-0.7) and, the system where extensive agglomeration develops (N: 4-7; P: 20-40; varphi: < 0.5). These results demonstrate that changes in the hydrodynamics of EBA already take place in the presence of moderate concentrations of biomass. Furthermore, those changes can be quantitatively described mainly in terms of the fraction of stagnant zones in the system, which are formed due to the interaction of biomass and adsorbent. The technique described here can be used to evaluate a certain combination of adsorbent and biomass with regard to its suitability for expanded bed

  17. Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets

    CERN Document Server

    Yang, Jun; Abbot, Dorian S

    2013-01-01

    The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phen...

  18. Configuration Consideration for Expander in Transcritical Carbon Dioxide Two-Stage Compression Cycle

    Institute of Scientific and Technical Information of China (English)

    MA Yitai; YANG Junlan; GUAN Haiqing; LI Minxia

    2005-01-01

    To investigate the configuration consideration of expander in transcritical carbon dioxide two-stage compression cycle, the best place in the cycle should be searched for to reinvest the recovery work so as to improve the system efficiency. The expander and the compressor are connected to the same shaft and integrated into one unit, with the latter being driven by the former, thus the transfer loss and leakage loss can be decreased greatly. In these systems, the expander can be either connected with the first stage compressor (shortened as DCDL cycle) or the second stage compressor (shortened as DCDH cycle), but the two configuration ways can get different performances. By setting up theoretical model for two kinds of expander configuration ways in the transcritical carbon dioxide two-stage compression cycle, the first and the second laws of thermodynamics are used to analyze the coefficient of performance, exergy efficiency, inter-stage pressure, discharge temperature and exergy losses of each component for the two cycles. From the model results, the performance of DCDH cycle is better than that of DCDL cycle. The analysis results are indispensable to providing a theoretical basis for practical design and operating.

  19. STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS

    Energy Technology Data Exchange (ETDEWEB)

    Yang Jun; Abbot, Dorian S. [Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States); Cowan, Nicolas B., E-mail: abbot@uchicago.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States)

    2013-07-10

    The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phenomenon a stabilizing climate feedback. Substellar clouds also effectively block outgoing radiation from the surface, reducing or even completely reversing the thermal emission contrast between dayside and nightside. The presence of substellar water clouds and the resulting clement surface conditions will therefore be detectable with the James Webb Space Telescope.

  20. Earthworms facilitate carbon sequestration through unequal amplification of carbon stabilization compared with mineralization.

    Science.gov (United States)

    Zhang, Weixin; Hendrix, Paul F; Dame, Lauren E; Burke, Roger A; Wu, Jianping; Neher, Deborah A; Li, Jianxiong; Shao, Yuanhu; Fu, Shenglei

    2013-01-01

    A recent review concluded that earthworm presence increases CO₂ emissions by 33% but does not affect soil organic carbon stocks. However, the findings are controversial and raise new questions. Here we hypothesize that neither an increase in CO₂ emission nor in stabilized carbon would entirely reflect the earthworms' contribution to net carbon sequestration. We show how two widespread earthworm invaders affect net carbon sequestration through impacts on the balance of carbon mineralization and carbon stabilization. Earthworms accelerate carbon activation and induce unequal amplification of carbon stabilization compared with carbon mineralization, which generates an earthworm-mediated 'carbon trap'. We introduce the new concept of sequestration quotient to quantify the unequal processes. The patterns of CO₂ emission and net carbon sequestration are predictable by comparing sequestration quotient values between treatments with and without earthworms. This study clarifies an ecological mechanism by which earthworms may regulate the terrestrial carbon sink.

  1. The Fuzzy Logic Model for the Prediction of Marshall Stability of Lightweight Asphalt Concretes Fabricated using Expanded Clay Aggregate

    Directory of Open Access Journals (Sweden)

    Sercan SERİN

    2014-07-01

    Full Text Available In the study, predictability of Marshall Stability (MS of light asphalt concrete that fabricated using expanded clay and had varied mix properties with Fuzzy Logic (FL were researched. With this aim, asphalt concrete samples that added expanded clay aggregate (EC in accordance with gradation determined in Highway Technical Specification, had different percentage of bitumen (POB (4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5% and unit weight (UW (1,75–1,87 (gr/cm3 were prepared and determined Marshall stabilities with Marshall test

  2. Carbon Fiber Morphology. 2. Expanded Wide-Angle X-Ray Diffraction Studies of Carbon Fibers

    Science.gov (United States)

    1991-02-01

    X- Ray Diffraction," JPS. Polym. Phys. Ed., 16, 939 (1978). 17. Rosalind E. Franklin , "The Structure of Graphitic Carbons," Acta Cryst., 4, 253 (1951...18. Rosalind E. Franklin , "The Interpretation of Diffuse X-ray Diagrams of Carbon," Acta CrL, 3, 107 (1950). 19. K. Jain and A. S. Abhiraman...been generally mentioned much earlier by Franklin [17,18]. Jain and Abhiraman [19] demonstrated that these corrections can make significant differences

  3. Influence of Expanded Graphite Surface Ozonation on the Adhesion between Carbon Additive and Cement Matrix

    Directory of Open Access Journals (Sweden)

    Agnieszka Ślosarczyk

    2015-06-01

    Full Text Available 800x600 Cement mortars modified with expanded graphite (EG subjected to surface treatments in gaseous ozone were investigated. It was shown that the bonding between carbon additive and cement paste strongly depends on the surface modification of EG and the chemical composition of EG surface plays the important role in shaping the mechanical properties of cement composites. The expanded graphite subjected to ozone treatment showed the substantial increase of flexural toughness of cement composite. The above results were confirmed by XPS and SEM analysis. Normal 0 21 false false false PL X-NONE X-NONE MicrosoftInternetExplorer4 DOI: http://dx.doi.org/10.5755/j01.ms.21.2.5860

  4. Phase equilibria in carbon dioxide expanded solvents: Experiments and molecular simulations.

    Science.gov (United States)

    Houndonougbo, Yao; Jin, Hong; Rajagopalan, Bhuma; Wong, Kean; Kuczera, Krzysztof; Subramaniam, Bala; Laird, Brian

    2006-07-06

    We present complementary molecular simulations and experimental results of phase equilibria for carbon dioxide expanded acetonitrile, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. The volume expansion measurements were done using a high-pressure Jerguson view cell. Molecular simulations were performed using the Gibbs ensemble Monte Carlo method. Calculations in the canonical ensemble (NVT) were performed to determine the coexistence curve of the pure solvent systems. Binary mixtures were simulated in the isobaric-isothermal distribution (NPT). Predictions of vapor-liquid equilibria of the pure components agree well with experimental data. The simulations accurately reproduced experimental data on saturated liquid and vapor densities for carbon dioxide, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. In all carbon dioxide expanded liquids (CXL's) studied, the molecular simulation results for the volume expansion of these binary mixtures were found to be as good as, and in many cases superior to, predictions based on the Peng-Robinson equation of state, demonstrating the utility of molecular simulation in the prediction of CXL phase equilibria.

  5. Effect of an Internal Heat Exchanger on Performance of the Transcritical Carbon Dioxide Refrigeration Cycle with an Expander

    OpenAIRE

    Zhenying Zhang; Lili Tian; Yanhua Chen; Lirui Tong

    2014-01-01

    The effect of the internal heat exchanger (IHE) on the performance of the transcritical carbon dioxide refrigeration cycle with an expander is analyzed theoretically on the basis of the first and second laws of thermodynamics. The possible parameters affecting system efficiency such as heat rejection pressure, gas cooler outlet temperature, evaporating temperature, expander isentropic efficiency and IHE effectiveness are investigated. It is found that the IHE addition in the carbon dioxide re...

  6. Nanocasting Process to Pore-Expanded Ordered Mesoporous Carbons with 2D Hexagonal Mesostructure

    Directory of Open Access Journals (Sweden)

    Chongwen Jiang

    2014-01-01

    Full Text Available Pore-expanded ordered mesoporous carbons with 2D hexagonal mesostructure were synthesized by a simple nanocasting process. We adopted sucrose as carbon precursors, mesoporous silica materials SBA-15 as the hard templates, and hexane as micelle swelling agents. The pore size distribution of OMCs was narrow and centered at 5.4 nm, which is larger than the upper limit of pore diameters typically reported for CMK-3. The BET surface area and mesopore volume of PE-CMK-3 can reach to 1213.47 m2/g and 1.56 cm3/g, respectively, indicating that choosing large pore size materials as template is good for preparation of high performance of OMCs.

  7. Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

    2008-01-01

    Abstract. In the present paper various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this end thermogravimetric carburization was simulated for various experimental conditions and the evaluated...... composition dependent diffusivity of carbon derived from the simulated experiments was compared with the input data. The most promising procedure for an accurate determination is shown to be stepwise gaseous carburizing of thin foils in a gaseous atmosphere; the finer the stepsize, the more accurate...... the approximation of the diffusivity. Thermogravimetry was applied to continuously monitor the weight change of thin foils of AISI 316 during carburizing in CO-H2 gas mixtures for one of the simulated experimental procedures....

  8. Effect of an Internal Heat Exchanger on Performance of the Transcritical Carbon Dioxide Refrigeration Cycle with an Expander

    Directory of Open Access Journals (Sweden)

    Zhenying Zhang

    2014-11-01

    Full Text Available The effect of the internal heat exchanger (IHE on the performance of the transcritical carbon dioxide refrigeration cycle with an expander is analyzed theoretically on the basis of the first and second laws of thermodynamics. The possible parameters affecting system efficiency such as heat rejection pressure, gas cooler outlet temperature, evaporating temperature, expander isentropic efficiency and IHE effectiveness are investigated. It is found that the IHE addition in the carbon dioxide refrigeration cycle with an expander increases the specific cooling capacity and compression work, and decreases the optimum heat rejection pressure and the expander output power. An IHE addition does not always improve the system performance in the refrigeration cycle with an expander. The throttle valve cycle with IHE provides a 5.6% to 17% increase in maximum COP compared to that of the basic cycle. For the ideal expander cycle with IHE, the maximum COP is approximately 12.3% to 16.1% lower than the maximum COP of the cycle without IHE. Whether the energy efficiency of the cycle by IHE can be improved depends on the isentropic efficiency level of the expander. The use of IHE is only applicable in the cases of lower expander isentropic efficiencies or higher gas cooler exit temperatures for the refrigeration cycle with an expander from the view of energy efficiency.

  9. Structure Stability of Ⅰ-Type Carbon Nanotube Junctions

    Institute of Scientific and Technical Information of China (English)

    夏丹; 袁喆; 李家明

    2002-01-01

    Carbon nanotubes with junctions may play an important role in future ‘nanoelectronics' and future ‘nano devices'.In particular, junctions constructed with metal and semiconducting nanotubes have potential applications. Basedon the orthogonal tight-binding molecular dynamics method, we present our study of the structure stability ofI-type carbon nanotube junctions.

  10. Effect of hydrogen and oxygen on stability of expanders and performance of lead/acid batteries

    Science.gov (United States)

    Pavlov, D.; Gancheva, S.; Andreev, P.

    1993-10-01

    Expanders are organic additives to the negative active mass that increase plate capacity, especially at low temperatures. They operate under constant hydrogen and oxygen attack at strongly negative potentials as a result of which they undergo degradation. This leads to changes in plate capacity, which may limit the life of the battery. The influence of Velex, Mimosa, Quebraco, Syntan NK (SNK), and EZE-Skitan on the electrochemical characteristics and the life of negative battery plates has been investigated. It is established that structural groups of the pyrocatechin type have effective expander action.

  11. High performance asymmetric supercapacitor based on molybdenum disulphide/graphene foam and activated carbon from expanded graphite.

    Science.gov (United States)

    Masikhwa, Tshifhiwa M; Madito, Moshawe J; Bello, Abdulhakeem; Dangbegnon, Julien K; Manyala, Ncholu

    2017-02-15

    Molybdenum disulphide which has a graphene-like single layer structure has excellent mechanical and electrical properties and unique morphology, which might be used with graphene foam as composite in supercapacitor applications. In this work, Molybdenum disulphide (MoS2)/graphene foam (GF) composites with different graphene foam loading were synthesized by the hydrothermal process to improve on specific capacitance of the composites. Asymmetric supercapacitor device was fabricated using the best performing MoS2/GF composite and activated carbon derived from expanded graphite (AEG) as positive and negative electrodes, respectively, in 6M KOH electrolyte. The asymmetric MoS2/GF//AEG device exhibited a maximum specific capacitance of 59Fg(-1) at a current density of 1Ag(-1) with maximum energy and power densities of 16Whkg(-1) and 758Wkg(-1), respectively. The supercapacitor also exhibited a good cyclic stability with 95% capacitance retention over 2000 constant charge-discharge cycles. The results obtained demonstrate the potential of MoS2/GF//AEG as a promising material for electrochemical energy storage application.

  12. Temporary stabilization of air pollution control residues using carbonation.

    Science.gov (United States)

    Zhang, Hua; He, Pin-Jing; Shao, Li-Ming; Lee, Duu-Jong

    2008-01-01

    Carbonation presents a good prospect for stabilizing alkaline waste materials. The risk of metal leaching from carbonated waste was investigated in the present study; in particular, the effect of the carbonation process and leachate pH on the leaching toxicity of the alkaline air pollution control (APC) residues from municipal solid waste incinerator was evaluated. The pH varying test was conducted to characterize the leaching characteristics of the raw and carbonated residue over a broad range of pH. Partial least square modeling and thermodynamic modeling using Visual MINTEQ were applied to highlight the significant process parameters that controlled metal leaching from the carbonated residue. By lowering the pH to 8-11, the carbonation process reduced markedly the leaching toxicity of the alkaline APC residue; however, the treated APC residue showed similar potential risk of heavy metal release as the raw ash when subjected to an acid shock. The carbonated waste could, thereby, not be disposed of safely. Nonetheless, carbonation could be applied as a temporary stabilization process for heavy metals in APC residues in order to reduce the leaching risk during its transportation and storage before final disposal.

  13. Stability and instability of expanding solutions to the Lorentzian constant-positive-mean-curvature flow

    CERN Document Server

    Wong, Willie Wai-Yeung

    2014-01-01

    We study constant mean curvature Lorentzian hypersurfaces of $\\mathbb{R}^{1,d+1}$ from the point of view of its Cauchy problem. We completely classify the spherically symmetric solutions, which include among them a manifold isometric to the de Sitter space of general relativity. We show that the spherically symmetric solutions exhibit one of three (future) asymptotic behaviours: (i) finite time collapse (ii) convergence to a time-like cylinder isometric to some $\\mathbb{R}\\times\\mathbb{S}^d$ and (iii) infinite expansion to the future converging asymptotically to a time translation of the de Sitter solution. For class (iii) we examine the future stability properties of the solutions under arbitrary (not necessarily spherically symmetric) perturbations. We show that the usual notions of asymptotic stability and modulational stability cannot apply, and connect this to the presence of cosmological horizons in these class (iii) solutions. We can nevertheless show the global existence and future stability for small...

  14. Stability of peatland carbon to rising temperatures

    Science.gov (United States)

    Wilson, R. M.; Hopple, A. M.; Tfaily, M. M.; Sebestyen, S. D.; Schadt, C. W.; Pfeifer-Meister, L.; Medvedeff, C.; McFarlane, K. J.; Kostka, J. E.; Kolton, M.; Kolka, R. K.; Kluber, L. A.; Keller, J. K.; Guilderson, T. P.; Griffiths, N. A.; Chanton, J. P.; Bridgham, S. D.; Hanson, P. J.

    2016-12-01

    Peatlands contain one-third of soil carbon (C), mostly buried in deep, saturated anoxic zones (catotelm). The response of catotelm C to climate forcing is uncertain, because prior experiments have focused on surface warming. We show that deep peat heating of a 2 m-thick peat column results in an exponential increase in CH4 emissions. However, this response is due solely to surface processes and not degradation of catotelm peat. Incubations show that only the top 20-30 cm of peat from experimental plots have higher CH4 production rates at elevated temperatures. Radiocarbon analyses demonstrate that CH4 and CO2 are produced primarily from decomposition of surface-derived modern photosynthate, not catotelm C. There are no differences in microbial abundances, dissolved organic matter concentrations or degradative enzyme activities among treatments. These results suggest that although surface peat will respond to increasing temperature, the large reservoir of catotelm C is stable under current anoxic conditions.

  15. Stability of peatland carbon to rising temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, R. M.; Hopple, A. M.; Tfaily, M. M.; Sebestyen, S. D.; Schadt, C. W.; Pfeifer-Meister, L.; Medvedeff, C.; McFarlane, K. J.; Kostka, J. E.; Kolton, M.; Kolka, R. K.; Kluber, L. A.; Keller, J. K.; Guilderson, T. P.; Griffiths, N. A.; Chanton, J. P.; Bridgham, S. D.; Hanson, P. J.

    2016-12-13

    Peatlands contain one-third of the world’s soil carbon (C), mostly in the deep permanently saturated anoxic zone (i.e., catotelm)1 where C mineralization rates may be constrained, in part, by low temperatures; yet all soil warming experiments to date have focused on the response of peatland C degradation to surface warming2, 3. If the slow decomposition of deep peat C is due to kinetic constraints, then increasing temperatures at depth should cause parallel increases in carbon dioxide (CO2) and/or methane (CH4) production rates. Increasing CH4 emissions are of particular concern because CH4 has a sustained-flux global warming potential (SGWP) 45-times greater than CO2 over a 100- year timeframe4, creating a significant positive feedback to climate warming. Using a novel whole-ecosystem scale experiment in a regression-based design we show that ecosystem scale warming of deep peat exponentially increased CH4 emissions —but not ecosystem respiration of CO2— in the first year. Multiple lines of evidence, including laboratory incubations and in situ analyses of 14C, dissolved gases, and microbial community metabolic potential, indicate that CH4 emissions increased due to surface processes and not degradation of deep C. Our results indicate that rapid changes to the large bank of deep buried C in temperate peatlands may be minimal under future climatic warming.

  16. Earthworms facilitate carbon sequestration through unequal amplification of carbon stabilization compared with mineralization

    Science.gov (United States)

    A recent review concluded that earthworm presence increases CO2 emissions by 33% but does not affect soil organic carbon stocks. However, the findings are controversial and raise new questions. Here we hypothesize that neither an increase in CO2 emission nor in stabilized carbon...

  17. Stability of Carbon Incorpoated Semipolar GaN(1101) Surface

    Science.gov (United States)

    Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori

    2011-08-01

    The structural stability of carbon incorporated GaN(1101) surfaces is theoretically investigated by performing first-principles pseudopotential calculations. The calculated surface formation energies taking account of the metal organic vapor phase epitaxy conditions demonstrate that several carbon incorporated surfaces are stabilized depending on the growth conditions. Using surface phase diagrams, which are obtained by comparing the calculated adsorption energy with vapor-phase chemical potentials, we find that the semipolar surface forms NH2 and CH2 below ˜1660 K while the polar GaN(0001) surface with CH3 is stabilized below ˜1550 K. This difference could be one of possible explanations for p-type doping on the semipolar GaN(1101) surface.

  18. Stabilization of ultrafine metal nanocatalysts on thin carbon sheets

    Science.gov (United States)

    Liu, Xiaofang; Cui, Xinrui; Liu, Yiding; Yin, Yadong

    2015-10-01

    A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the catalytic efficiency. The advantages of this ultra-stable architecture together with the densely dispersed catalytic sites were demonstrated by their high stability and superior catalytic activity in reducing hydrophilic 4-nitrophenol and hydrophobic nitrobenzene.A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the

  19. Nitrogen-enriched carbon sheets derived from egg white by using expanded perlite template and its high-performance supercapacitors

    Science.gov (United States)

    Chen, Jiucun; Liu, Yinqin; Li, Wenjun; Xu, Liqun; Yang, Huan; Li, Chang Ming

    2015-08-01

    Nitrogen-enriched carbon sheets were synthesized using egg white as a unique carbon source and expanded perlite as a novel template. The as-prepared material was further used as an electrode material for supercapacitor applications, demonstrating excellent supercapacitance with a maximum gravimetric specific capacitance of 302 F g-1 at 0.5 A g-1 in a 3-electrode setup for a sample carbonized at 850 °C and activated for 6 h. Moreover, the carbon sheet-based capacitor with 2-symmetric electrodes showed an excellent cycle life (2% loss at 0.1 A g-1 after 10 000 cycles). The excellent performance may be attributed to the combination of the 3D carbon structure and the highly concentrated doped nitrogen component from the natural egg source for superior pseudocapacitance.

  20. Spinal and bulbar muscular atrophy (SBMA): somatic stability of an expanded CAG repeat in fetal tissues.

    Science.gov (United States)

    Jedele, K B; Wahl, D; Chahrokh-Zadeh, S; Wirtz, A; Murken, J; Holinski-Feder, E

    1998-08-01

    Spinal and bulbar muscular atrophy (SBMA) is a rare X-linked motor neuron degenerative disease caused by an expanded trinucleotide repeat. Unlike most other trinucleotide repeat diseases, SBMA shows limited meiotic instability, and evidence thus far indicates absence of somatic instability in adults. Data regarding the presence of fetal tissue somatic mosaicism is unavailable. We present a family in which a woman whose father had SBMA requested prenatal testing. After informed consent. molecular genetic evaluation showed the male fetus to carry the SBMA repeat elongation. Testing of fetal tissues after elective pregnancy termination showed no somatic mosaicism in the CAG repeat length. This is the first report of molecular genetic analysis of multiple tissues in an affected fetus, and only the second report of prenatal diagnosis in SBMA.

  1. Remarkable crystallization morphologies of poly(4-vinylpyridine on single-walled carbon nanotubes in CO2-expanded liquids

    Directory of Open Access Journals (Sweden)

    Y. N. Wei

    2011-12-01

    Full Text Available Poly(4-vinylpyridine (P4VP is a widely studied polymer for applications in catalysis, humidity sensitive and antimicrobial materials due to its pyridine group exhibiting coordinative reactivity with transition metals. In this work, the non-covalent functionalization of single-walled carbon nanotubes (SWCNTs with P4VP in CO2-expanded liquids (CXLs is reported. It is found that P4VP stabilized SWCNTs show good dispersion in both organic solvent and aqueous solution (pH = 2. The ability to manipulate the dispersion state of CNTs in water with P4VP will likely benefit many biological applications, such as drug delivery and optical sensors. Furthermore, the structure and morphology of P4VP/SWCNTs composite are examined, with the focus on molecular weight of P4VP (MW-P4VP, the pressure of CXLs and the concentration of P4VP. It is amazing that the P4VP15470 wrapping patterns undergo a notable morphological evolution from dotlike crystals to bottle brush-like, then to compact kebab-like, and then to widely-spaced dotted kebab patterns by facile pressure tuning in the higher polymer concentration series. In other words, the CXLs method enables superior control of the P4VP crystallization patterns on SWCNTs. Meanwhile, the CXL-assisted P4VP crystal growth mechanism on SWCNT is investigated, and the dominating growth mechanism is attributed to ‘size dependent soft epitaxy’ in P4VP15470/SWCNTs composites. We believe these studies would r

  2. Stability of Double-Walled Carbon Nanotubes Revisited

    Science.gov (United States)

    Semenyuk, N. P.

    2016-01-01

    An approach to the stability analysis of orthotropic two-layer shells with mechanical and electrical properties of carbon nanotubes is proposed. Van der Waals forces act between the layers. The parameters of the continuum between the layers are obtained using the Lennard-Jones potential. The governing system of equations is written for rates of sixteen variables. The loading and boundary conditions are specified for each layer separately. Numerical results are obtained using the discrete orthogonalization method. The stability of single- and double-walled nanotubes is analyzed. Numerical results are summarized in tables and analyzed

  3. Evaluating Stability of Aqueous Multiwalled Carbon Nanotube Nanofluids by Using Different Stabilizers

    Directory of Open Access Journals (Sweden)

    Tun-Ping Teng

    2014-01-01

    Full Text Available The 0.5 wt.% multiwalled carbon nanotubes/water nanofluids (MWNFs were produced by using a two-step synthetic method with different types and concentrations of stabilizers. The static position method, centrifugal sedimentation method, zeta potential measurements, and rheological experiments were used to assess the stability of the MWNFs and to determine the optimal type and fixed MWCNTs-stabilizer concentration of stabilizer. Finally, MWNFs with different concentrations of MWCNTs were produced using the optimal type and fixed concentration ratio of stabilizer, and their stability, thermal conductivity, and pH were measured to assess the feasibility of using them in heat transfer applications. MWNFs containing SDS and SDBS with MWCNTs-stabilizer concentration ratio were 5 : 2 and 5 : 4, respectively, showed excellent stability when they were evaluated by static position, centrifugal sedimentation, zeta potential, and rheological experiments at the same time. The thermal conductivity of the MWNFs indicated that the most suitable dispersing MWNF contained SDBS. MWNFs with MWCNTs concentrations of 0.25, 0.5, and 1.0 wt.% were fabricated using an aqueous SDBS solution. In addition, the thermal conductivity of the MWNFs was found to have increased, and the thermal conductivity values were greater than that of water at 25°C by 3.20%, 8.46%, and 12.49%.

  4. Expanded polytetrafluoroethylene reinforced polyvinylidenefluoride-hexafluoropropylene separator with high thermal stability for lithium-ion batteries

    Science.gov (United States)

    Xiong, Ming; Tang, Haolin; Wang, Yadong; Lin, Yu; Sun, Meiling; Yin, Zhuangfei; Pan, Mu

    2013-11-01

    PVDF-HFP/ePTFE composite separator with high thermal stability and low thermal shrinkage characteristic has been developed. The PVDF-HFP acts to absorb the electrolyte and shutdown at elevated temperature. The thermally stable ePTFE matrix is adopted to improve the mechanical strength and sustain the insulation after the shutdown. This novel separator presents good ion conductivity (up to 1.29 mS cm-1) and has a low thermal shrinkage of 8.8% at 162 °C. The composite separator shutdown at 162 °C and keep its integrity before 329 °C. Cells based on the composite separator show excellent capacities at high rate discharge and stable cycling performance.

  5. Biochar carbon stability and effect on greenhouse gas emissions

    DEFF Research Database (Denmark)

    Bruun, Esben Wilson; Cross, Andrew; Hammond, Jim;

    2016-01-01

    on the biochar quality is necessary in order to produce the most beneficial biochars for soil application. Beside carbon sequestration in soil biochar may improve the GHG balance by reducing N2O and CH4 soil emissions, although contrasting results are found in the literature. The mechanisms behind......As demonstrated by several scientific studies there is no doubt that biochar in general is very recalcitrant compared to other organic matter additions and soil organic matter fractions and also that it is possible to sequester carbon at a climate change relevant time scale (~100 years or more......) by soil application of biochar. However, the carbon stability of biochar in soil is strongly correlated with the degree of thermal alteration of the original feedstock (the lower the temperature, the larger the labile fraction) and in depth understanding of the technology used and its effect...

  6. Flexible all-carbon photovoltaics with improved thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Chun; Ishihara, Hidetaka; Sodhi, Jaskiranjeet; Chen, Yen-Chang; Siordia, Andrew; Martini, Ashlie; Tung, Vincent C., E-mail: ctung@ucmerced.edu

    2015-04-15

    The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C{sub 60}s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C{sub 60}s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that “lock up” the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C{sub 60}s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C{sub 60}s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current–voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C{sub 60}:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests. - Graphical abstract: The incorporation of solvent resistant, mechanically flexible and electrically addressable 2-D soft graphene nanoribbons facilitates the assembly of photoconductive carbon nano-p/n junctions for thermally stable and flexible photovoltaic cells.

  7. The distribution of secondary mineral phases along an eroding hillslope and its effect on carbon stabilization mechanisms and the fate of soil carbon fractions

    Science.gov (United States)

    Doetterl, Sebastian; Cornelis, Jean-Thomas; Opfergelt, Sophie; Boeckx, Pascal; Bodé, Samuel; Six, Johan; Van Oost, Kristof

    2014-05-01

    Soil redistribution processes can change soil carbon (C) dynamics drastically by moving carbon from high decomposition and re-sequestration environments at the eroding hillslope to low decomposition and burial at the depositional footslope and valley basin. This leads to not only spatially diverse soil carbon storage throughout the landscape, but also to qualitative changes of the transported carbon and the mineral phase. The interaction between those parameters and the effect on stabilization mechanisms for soil C are still a matter of debate. Here, we present an analysis that aims to clarify the bio/geo-chemical and mineralogical components involved in stabilizing C at various depths along an eroding cropped slope and how this affects the abundance of microbial derived carbon. We use the results of an incubation experiment combined with the abundance of amino sugars in different isolated soil C fractions as a tracer for the stability of the respective fraction. We applied further (i) a sequential extraction of the reactive soil phase using pyrophosphate, oxalate and dithionite-citrate-bicarbonate, and (ii) a qualitative analysis of the clay mineralogy, to analyze the changes in the mineral phase for the different isolated fractions along the slope transect. Our results emphasize the importance of physical protection within microaggregates to stabilize buried, chemically labile C. Our data further indicates that the stability of these aggregates is related to the presence of organo-mineral associations and poorly crystalline minerals. However, decreasing contents of these minerals with depth indicate a temporal limitation of this stabilization mechanism. Non-expandable clay minerals experience a relative enrichment at the depositional site while expandable clay minerals experience the same at the eroding site. These changes in clay mineralogy along the slope are partly responsible for the abundance of silt and clay associated C and the effectiveness of the clay

  8. Carbon stabilization mechanisms in soils in the Andes

    Science.gov (United States)

    Jansen, Boris; Cammeraat, Erik

    2015-04-01

    The volcanic ash soils of the Andes contain very large stocks of soil organic matter (SOM) per unit area. Consequently, they constitute significant potential sources or sinks of the greenhouse gas CO2. Climate and/or land use change potentially have a strong effect on these large SOM stocks. To clarify the role of chemical and physical stabilisation mechanisms in volcanic ash soils in the montane tropics, we investigated carbon stocks and stabilization mechanisms in the top- and subsoil along an altitudinal transect in the Ecuadorian Andes. The transect encompassed a sequence of paleosols under forest and grassland (páramo), including a site where vegetation cover changed in the last century. We applied selective extraction techniques, performed X-ray diffraction analyses of the clay fraction and estimated pore size distributions at various depths in the top- and subsoil along the transect. In addition, from several soils the molecular composition of SOM was further characterized with depth in the current soil as well as the entire first and the top of the second paleosol using GC/MS analyses of extractable lipids and Pyrolysis-GC/MS analyses of bulk organic matter. Our results show that organic carbon stocks in the mineral soil under forest a páramo vegetation were roughly twice as large as global averages for volcanic ash soils, regardless of whether the first 30cm, 100cm or 200cm were considered. We found the carbon stabilization mechanisms involved to be: i) direct stabilization of SOM in organo-metallic (Al-OM) complexes; ii) indirect protection of SOM through low soil pH and toxic levels of Al; and iii) physical protection of SOM due to a very high microporosity of the soil (Tonneijck et al., 2010; Jansen et al. 2011). When examining the organic carbon at a molecular level, interestingly we found extensive degradation of lignin in the topsoil while extractable lipids were preferentially preserved in the subsoil (Nierop and Jansen, 2009). Both vegetation

  9. Removal of dispersant-stabilized carbon nanotubes by regular coagulants

    Institute of Scientific and Technical Information of China (English)

    Ni Liu; Changli Liu; Jing Zhang; Daohui Lin

    2012-01-01

    Coagulation followed by sedimentation,as a conventional technique in the water treatment plant,can be the first line of defense against exposures of carbon nanotubes(CNTs)to aquatic organisms and human beings,which has been rarely documented.This study investigated the removal of dispersant-stabilized CNT suspensions by poly aluminum chloride(PAC1)and KAI(SO4)2·12H2O (alum),with a focus on the effects of dispersant type,coagulant type and dosage.PAC1 performed better than alum in the removal of tannic acid-,humic acid-,and sodium dodecyl benzenesulfonate-stabilized CNTs,but worse for polyethylene glycol octylphenyl ether(TX100)-stabilized CNTs.Neither coagulant could effectively precipitate cetyltrimethyl ammonium bromide-stabilized CNTs.The removal by PAC1 first increased up to a plateau and then decreased with the continued increase of coagulant dosage.However,the removal rates leveled off but did not decrease after achieving their highest level with the continued addition of alum.The coagulation and flocculation of the CNT suspensions by PAC1 could be regulated mainly by the mechanism of adsorption charge neutralization,whereas the coagulation by alum mainly involved electrical double-layer compression.

  10. Graphite Sheet Coating for Improved Thermal Oxidative Stability of Carbon Fiber Reinforced/PMR-15 Composites

    Science.gov (United States)

    Campbell, Sandi; Papadopoulos, Demetrios; Heimann, Paula; Inghram, Linda; McCorkle, Linda

    2005-01-01

    Expanded graphite was compressed into graphite sheets and used as a coating for carbon fiber reinforced PMR-15 composites. BET analysis of the graphite indicated an increase in graphite pore size on compression, however the material was proven to be an effective barrier to oxygen when prepegged with PMR-15 resin. Oxygen permeability of the PMR-15/graphite was an order of magnitude lower than the compressed graphite sheet. By providing a barrier to oxygen permeation, the rate of oxidative degradation of PMR-15 was decreased. As a result, the composite thermo-oxidative stability increased by up to 25%. The addition of a graphite sheet as a top ply on the composites yielded little change in the material's flexural strength or interlaminar shear strength.

  11. Flexible all-carbon photovoltaics with improved thermal stability

    Science.gov (United States)

    Tang, Chun; Ishihara, Hidetaka; Sodhi, Jaskiranjeet; Chen, Yen-Chang; Siordia, Andrew; Martini, Ashlie; Tung, Vincent C.

    2015-04-01

    The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C60s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C60s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that "lock up" the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C60s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C60s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current-voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C60:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests.

  12. Synthesis and CO{sub 2} adsorption study of modified MOF-5 with multi-wall carbon nanotubes and expandable graphite

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Sami, E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Bustam, M. A., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Shariff, A. M., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Elkhalifah, Ali E. I., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Murshid, G., E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com; Riaz, Nadia, E-mail: samichemist1@gmail.com, E-mail: azmibustam@petronas.com.my, E-mail: azmish@petronas.com.my, E-mail: lkhlfh@gmail.com, E-mail: hmurshid@gmail.com, E-mail: nadiariazz@gmail.com [Research Center for Carbon Dioxide Capture, Dept. of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Sri Iskandar, Tronoh 31750 Perak (Malaysia)

    2014-10-24

    MOF-5 was synthesized by solvothermal method and its reactivation under anhydrous conditions. This research is conducted to investigate the effect of MOF-5 and MOF-5 modified with multi-wall carbon nanotubes (MWCNTs) and expandable graphite (EG) on the performance of CO{sub 2} adsorption. The synthesized MOFs were characterized using Field emission scanning electron microscopy (FESEM) for surface morphology, Thermogravimetric analysis (TGA) for thermal stability, X-ray diffraction (XRD) for crystals plane, Brunauer-Emmet-Teller (BET) for surface area and CO{sub 2} adsorption. The result had showed that the modified MOF-5 enhanced the CO{sub 2} adsorption compared to the pure MOF-5. The increment in the CO{sub 2} uptake capacities of MOF materials was attributed to the decrease in the pore size and enhancement of micropore volume of MOF-5 by multi-walled carbon nanotube and EG incorporation. The BET surface area of the synthesized MOF-5@MWCNTs is more than MOF-5. The CO{sub 2} sorption capacities of MOF-5 and MOF-5@MWCNTs were observed to increase from 0.00008 to 0.00048 mol g-1 at 298 K and 1 bar. The modified MOF-5@MWCNTs resulted in the highest CO{sub 2} adsorption followed by the modified MOF-5@ EG and lastly, MOF-5.

  13. Stabilization of carbon in composts and biochars in relation to carbon sequestration and soil fertility.

    Science.gov (United States)

    Bolan, N S; Kunhikrishnan, A; Choppala, G K; Thangarajan, R; Chung, J W

    2012-05-01

    There have been increasing interests in the conversion of organic residues into biochars in order to reduce the rate of decomposition, thereby enhancing carbon (C) sequestration in soils. However energy is required to initiate the pyrolysis process during biochar production which can also lead to the release of greenhouse gasses. Alternative methods can be used to stabilize C in composts and other organic residues without impacting their quality. The objectives of this study include: (i) to compare the rate of decomposition among various organic amendments and (ii) to examine the effect of clay materials on the stabilization of C in organic amendments. The decomposition of a number of organic amendments (composts and biochars) was examined by monitoring the release of carbon-dioxide using respiration experiments. The results indicated that the rate of decomposition as measured by half life (t(1/2)) varied between the organic amendments and was higher in sandy soil than in clay soil. The half life value ranged from 139 days in the sandy soil and 187 days in the clay soil for poultry manure compost to 9989 days for green waste biochar. Addition of clay materials to compost decreased the rate of decomposition, thereby increasing the stabilization of C. The half life value for poultry manure compost increased from 139 days to 620, 806 and 474 days with the addition of goethite, gibbsite and allophane, respectively. The increase in the stabilization of C with the addition of clay materials may be attributed to the immobilization of C, thereby preventing it from microbial decomposition. Stabilization of C in compost using clay materials did not impact negatively the value of composts in improving soil quality as measured by potentially mineralizable nitrogen and microbial biomass carbon in soil.

  14. Lignin-based carbon fibers: Carbon nanotube decoration and superior thermal stability

    KAUST Repository

    Xu, Xuezhu

    2014-08-23

    Lignin-based carbon fibers (CFs) decorated with carbon nanotubes (CNTs) were synthesized and their structure, thermal stability and wettability were systematically studied. The carbon fiber precursors were produced by electrospinning lignin/polyacrylonitrile solutions. CFs were obtained by pyrolyzing the precursors and CNTs were subsequently grown on the CFs to eventually achieve a CF–CNT hybrid structure. The processes of pyrolysis and CNT growth were conducted in a tube furnace using different conditions and the properties of the resultant products were studied and compared. The CF–CNT hybrid structure produced at 850 °C using a palladium catalyst showed the highest thermal stability, i.e., 98.3% residual weight at 950 °C. A mechanism for such superior thermal stability was postulated based on the results from X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and electron energy loss spectroscopy analyses. The dense CNT decoration was found to increase the hydrophobicity of the CFs.

  15. Carbon coating stabilized Ti(3+)-doped TiO2 for photocatalytic hydrogen generation under visible light irradiation.

    Science.gov (United States)

    Fu, Gao; Zhou, Peng; Zhao, Meiming; Zhu, Weidong; Yan, Shicheng; Yu, Tao; Zou, Zhigang

    2015-07-28

    Self-doping by Ti(3+) is a useful method to expand the light response of TiO2 into the visible light region. However, to obtain a stable Ti(3+)-doped TiO2 seems to be a challenge due to the easy oxidation of Ti(3+) during the heterogeneous reaction. Here, we propose a simple carbon coating route to stabilize the Ti(3+)-doped TiO2, in which both the Ti(3+) and precursor of the carbon coating layer were in situ formed from the hydrothermal hydrolysis of titanium isopropoxide. The carbon coated Ti(3+)-doped TiO2 exhibited excellent stability for photocatalytic hydrogen production. Based on electron paramagnetic resonance (EPR) analysis, the proposed stabilizing mechanism is that the conductive carbon coating layer as a barrier layer prevents the H2O and O2 from diffusing into the surface of the photocatalyst, which can oxidize the surface O vacancies and Ti(3+) in TiO2. Our findings offer a simple route to prepare a highly stable TiO2-based photocatalyst with visible light response.

  16. Influence of different carbon nanostructures on the electrocatalytic activity and stability of Pt supported electrocatalysts

    DEFF Research Database (Denmark)

    Stamatin, Serban Nicolae; Borghei, Maryam; Andersen, Shuang Ma;

    2014-01-01

    Commercially available graphitized carbon nanofibers and multi-walled carbon nanotubes, two carbon materials with very different structure, have been functionalized in a nitric–sulfuric acid mixture. Further on, the materials have been platinized by a microwave assisted polyol method. The relative...... that the functionalization improves the stability for multi-walled carbon nanotubes, at the cost of decreased activity....

  17. Carbon sequestration in an expanded lake system during the Toarcian oceanic anoxic event

    Science.gov (United States)

    Xu, Weimu; Ruhl, Micha; Jenkyns, Hugh C.; Hesselbo, Stephen P.; Riding, James B.; Selby, David; Naafs, B. David A.; Weijers, Johan W. H.; Pancost, Richard D.; Tegelaar, Erik W.; Idiz, Erdem F.

    2017-01-01

    The Early Jurassic Toarcian oceanic anoxic event (~183 Ma) was marked by marine anoxia-euxinia and globally significant organic-matter burial, accompanied by a major global carbon-cycle perturbation probably linked to Karoo-Ferrar volcanism. Although the Toarcian oceanic anoxic event is well studied in the marine realm, accompanying climatic and environmental change on the continents is poorly understood. Here, utilizing radioisotopic, palynological and geochemical data from lacustrine black shales, we demonstrate that a large lake system developed contemporaneously with the Toarcian oceanic anoxic event in the Sichuan Basin, China, probably due to enhanced hydrological cycling under elevated atmospheric pCO 2. We attribute increased lacustrine organic productivity to elevated fluvial nutrient supply, which resulted in the burial of ~460 Gt of organic carbon in the Sichuan Basin alone, creating an important negative feedback in the global exogenic carbon cycle. We suggest that enhanced nutrient delivery to marine and large lacustrine systems was a key component in the global carbon cycle recovery during the Toarcian oceanic anoxic event and acted to shorten the duration of the recovery of global δ13C values.

  18. Photodissociation and stability of carbon clusters; Photodissociation et stabilite d`agregats de carbone

    Energy Technology Data Exchange (ETDEWEB)

    Bouyer, R.

    1995-04-01

    This work is devoted to the study of the dissociation of ionised carbon clusters (containing 16 to 36 atoms) after photoexcitation by a UV-visible laser pulse. It contributes to experimental studies on formation mechanisms of carbon clusters, and particularly fullerenes. Its first aim is the knowledge of the internal energy of the clusters before dissociation. In the first part, a general overview summarizes the theoretical and experimental studies devoted to energetics (structure, stability, dissociation) of carbon clusters containing less than 60 atoms. In the second part, two techniques for producing mass-selected carbon clusters are described. The particular characteristics for such a production in a direct vaporization source are compared to those in a collisional-cooled source. The question of stability of intermediate-size clusters is asked. We study the photoabsorption spectroscopy of carbon clusters in the third part. A model for sequential absorption of several photons is developed, and used to analyze cluster dissociation versus the photoexcitation laser fluence. The absolute photoabsorption cross sections, and the number of absorbed photons are deduced. For some cluster sizes, laser wavelength scanning leads to evidence for existence of several clusters structures (or so-called isomers). The last part deals with photo dissociation mechanisms. Dissociation is found to occur after single-photon absorption, or after vibrational heating of the clusters. In that latter case, a statistical model including restricted intramolecular vibrational energy redistribution is used to calculate dissociation energies from measured fragmentation times of well-defined internal energy states. These energies, which are characteristic of cyclic structures, are then used to a better understanding of carbon cluster formation in a direct vaporization source. (Author). 76 refs., 63 figs., 23 tabs.

  19. Dispersion of Carbon Nanotubes: Mixing, Sonication, Stabilization, and Composite Properties

    Directory of Open Access Journals (Sweden)

    Eugene M. Terentjev

    2012-01-01

    Full Text Available Advances in functionality and reliability of carbon nanotube (CNT composite materials require careful formulation of processing methods to ultimately realize the desired properties. To date, controlled dispersion of CNTs in a solution or a composite matrix remains a challenge, due to the strong van der Waals binding energies associated with the CNT aggregates. There is also insufficiently defined correlation between the microstructure and the physical properties of the composite. Here, we offer a review of the dispersion processes of pristine (non-covalently functionalized CNTs in a solvent or a polymer solution. We summarize and adapt relevant theoretical analysis to guide the dispersion design and selection, from the processes of mixing/sonication, to the application of surfactants for stabilization, to the final testing of composite properties. The same approaches are expected to be also applicable to the fabrication of other composite materials involving homogeneously dispersed nanoparticles.

  20. Carbon Dioxide Expanded Ethanol Extraction: Solubility and Extraction Kinetics of α-Pinene and cis-Verbenol.

    Science.gov (United States)

    Al-Hamimi, Said; Abellan Mayoral, Alícia; Cunico, Larissa P; Turner, Charlotta

    2016-04-19

    In general, diffusion rates in extractions are enhanced by increasing the temperature. In this study, we instead add compressed liquid carbon dioxide to the extraction phase to accomplish faster mass transfer. The feasibility of using carbon dioxide expanded ethanol (CXE) as the extraction phase was explored, targeting two medium-polar analytes, α-pinene and cis-verbenol in Boswellia sacra tree resin. Hansen solubility parameters (HSP) were first calculated for the analytes and the extraction phases investigated, ethanol, CXE, and supercritical carbon dioxide (scCO2) containing ethanol as a cosolvent. Second, an extraction method with CXE as the extraction phase was optimized using a Box Behnken design, giving optimal conditions of 40 °C, 9.3 MPa, and 0.31 molar fraction of CO2 in ethanol. Third, the developed method was compared with a supercritical fluid extraction (SFE) method and a conventional solid liquid extraction (SLE) method, showing that CXE enables faster and more efficient extraction than both SFE and SLE. In fact, calculations based on Peleg's equation showed that the initial extraction rate of the new method is up to 10 times faster than SFE when using the highest flow rate tested, 3 mL/min. It was also discovered that it is crucial to cool the makeup solvent in the collection system for efficient analyte collection, at least in modern SFE equipment where pressure is regulated by a backpressure regulator. The use of CXE and pertinently also other CO2-expanded liquids in sample preparation shows a great potential in terms of increasing the extraction rate without elevating the temperature.

  1. Towards a mechanistic understanding of carbon stabilization in manganese oxides

    Science.gov (United States)

    Johnson, Karen; Purvis, Graham; Lopez-Capel, Elisa; Peacock, Caroline; Gray, Neil; Wagner, Thomas; März, Christian; Bowen, Leon; Ojeda, Jesus; Finlay, Nina; Robertson, Steve; Worrall, Fred; Greenwell, Chris

    2015-01-01

    Minerals stabilize organic carbon (OC) in sediments, thereby directly affecting global climate at multiple scales, but how they do it is far from understood. Here we show that manganese oxide (Mn oxide) in a water treatment works filter bed traps dissolved OC as coatings build up in layers around clean sand grains at 3%w/wC. Using spectroscopic and thermogravimetric methods, we identify two main OC fractions. One is thermally refractory (>550 °C) and the other is thermally more labile (<550 °C). We postulate that the thermal stability of the trapped OC is due to carboxylate groups within it bonding to Mn oxide surfaces coupled with physical entrapment within the layers. We identify a significant difference in the nature of the surface-bound OC and bulk OC . We speculate that polymerization reactions may be occurring at depth within the layers. We also propose that these processes must be considered in future studies of OC in natural systems. PMID:26194625

  2. On the stabilization of the carbonate dianion by sulfur dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Grein, F.; Chan, J.K.; Liko, I. [New Brunswick Univ., Fredericton, NB (Canada). Dept. of Chemistry

    2010-11-15

    Dianions CO{sub 3}{sup 2}, SO{sub 4}{sup 2} and other multiply charged anions (MCA) such as PO{sub 4}{sup 3} are not electronically stable in the gas phase. As such, they decay to a lower charge anion by auto electron detachment. The stabilization of dianions and more highly charged anions by common gases was investigated in this study, with particular reference to the stabilization in the gas phase of the carbonate dianion by sulphur dioxide (SO{sub 2}) molecules. Geometries of clusters were optimized by density functional theory (DFT) methods. This paper presented the geometries of different isomers of (SO{sub 2})n and (SO{sub 2})n, for which n = 1-4. Single-point CCSD and CCSD(T) energies at the DFT-optimized geometries were also obtained for n = 1-3. For n = 1 and 2, the monoanionic clusters were adiabatically more stable than the dianionic ones. They became less stable starting at n = 3. The CCSD adiabatic electron detachment energy of the dianionic cluster changed from -0.39 eV for n = 2 to +0.20 eV for n = 3. The vertical electron detachment energy became positive at n = 2, with a CCSD value of 1.35 eV. Many of the less stable dianionic, and most of the monoionic clusters were characterized by the transfer of an oxygen atom from CO{sub 3} to SO{sub 2}. It was concluded that a minimum of 3 water molecules are needed for the stabilization of the sulfate dianion by stepwise hydration. 5 tabs., 1 fig.

  3. Changes in the Thermal and Dimensional Stability of the Structure of a Polymer Composite After Carbonization

    Science.gov (United States)

    Gaidachuk, V. E.; Kondratiev, A. V.; Chesnokov, A. V.

    2017-01-01

    Based on the theory of reinforcement of polymer composites, approximate relations for the physicomechanical and strength properties of a carbon-carbon composite material are synthesized, which are used to perform a finite-element analysis of the degree and character of changes in the thermal and dimensional stability of its structure after carbonization. Using approximate criteria of structural optimization of carbon-carbon composites ensuring their maximum dimensional stability, a [0/±45/90] package of thermally nonquilibrium layers is investigated and compared with an analogous carbon-fiber-reinforced plastic.

  4. Stability and aggregation of silver and titanium dioxide nanoparticles in seawater: role of salinity and dissolved organic carbon.

    Science.gov (United States)

    Wang, Huanhua; Burgess, Robert M; Cantwell, Mark G; Portis, Lisa M; Perron, Monique M; Wu, Fengchang; Ho, Kay T

    2014-05-01

    The behavior and fate of nanoparticles (NPs) in the marine environment are largely unknown and potentially have important environmental and human health implications. The aggregation and fate of NPs in the marine environment are greatly influenced by their interactions with seawater and dissolved organic carbon (DOC). In the present study, the stability and aggregation of 30-nm-diameter silver nanoparticles (AgNPs) capped with citrate and polyvinylpyrrolidone (PVP; AgNP-citrate and AgNP-PVP) and 21-nm-diameter titanium dioxide (TiO(2)) NPs as affected by seawater salinity and DOC were investigated by measuring hydrodynamic diameters and zeta potentials. The added DOC (in humic acid form) stabilized the 3 types of NPs when the seawater salinities were ≤5 parts per thousand (ppt), but the stabilizing effect of DOC was reduced by a higher salinity (e.g., 30 ppt). In addition, AgNP-PVP was more stable than AgNP-citrate in seawater, indicating that surface capping agents and stabilization mechanisms govern the stability and aggregation of NPs. Statistical analysis showed that salinity is the most dominant influence on the stability and aggregation of AgNPs and TiO(2) NPs, followed by DOC. These findings expand our knowledge on the behavior of AgNPs and TiO2 NPs in seawater and indicate that the fate of these NPs will be primarily to aggregate in the water column, precipitate, and accumulate in sediments following release into the marine environment.

  5. Biomass burning in boreal forests and peatlands: Effects on ecosystem carbon losses and soil carbon stabilization as black carbon

    Science.gov (United States)

    Turetsky, M. R.; Kane, E. S.; Benscoter, B.

    2011-12-01

    to burning during subsequent fire events. We also observed no correlations between black carbon stocks in soils and fire frequency, again suggesting that pyrogenic C is susceptible to re-burning, or decay in the post-burn environment. The majority of pyrogenic carbon in boreal soils appears to be derived from recent wildfire activity, as the age of the black carbon pool often is equivalent to stand age. Together these results show that landscape characteristics that control decomposition and the accumulation of peat also have strong controls on combustion processes and post-fire soil chemistry. Warmer temperatures and drier or more variable precipitation patterns are likely to result in more intense burning of organic soils in the future. Research linking the conditions of char formation with its stabilization mechanisms (either consumption in wildfire or microbial attack) will shed light on spatial patterns of black carbon formation and preservation in high latitude soils.

  6. Activity and stability studies of platinized multi-walled carbon nanotubes as fuel cell electrocatalysts

    DEFF Research Database (Denmark)

    Stamatin, Serban Nicolae; Borghei, Maryam; Dhiman, Rajnish;

    2015-01-01

    A non-covalent functionalization for multi-walled carbon nanotubes has been used as an alternative to the damaging acid treatment. Platinum nanoparticles with similar particle size distribution have been deposited on the surface modified multi-walled carbon nanotubes. The interaction between...... platinum nanoparticles and multi-walled carbon nanotubes functionalized with 1-pyrenecarboxylic acid is studied and its electrochemical stability investigated. This study reveals the existence of a platinum-support interaction and leads to three main conclusions. First, the addition of 1-pyrenecarboxylic......-term stability by as much as 20%. Third, post-mortem microscopy analysis showed a surprising effect. During the electrochemical stability investigations concerned with carbon corrosion it was found that the multi-walled carbon nanotubes were undergoing severe structural change, transforming finally into carbon...

  7. Stability of Soil Carbon Fractions - from molecules to aggregates

    Science.gov (United States)

    Mueller, C. W.; Mueller, K. E.; Freeman, K. H.; Eissenstat, D.; Kögel-Knabner, I.

    2009-12-01

    The turnover of soil organic matter (SOM) is controlled both by its chemical composition, its spatial bioavailability and the association with the mineral phase. Separation by physical fractionation of bulk soils and subsequent chemical analysis of these fractions should give insights to how compositional differences in SOM drive turnover rates of different size-defined carbon pools. The main objective of the study was to elucidate the relative abundance and recalcitrance of lignin and plant lipids (e.g. cutin and suberin) in the course of SOM decomposition within aggregated bulk soils and SOM fractions. By the parallel incubation of physically-separated size fractions and bulk soils of the Ah horizon from a forested soil (Picea abies L.Karst) over a period of 400 days, a unique set of samples was created to study SOM dynamics. We used solid-state 13C-CPMAS NMR spectroscopy and GC-MS (after copper oxide oxidation and solvent extraction) to analyze the composition of the incubated samples. The abundance and isotopic composition (including 13C and 14C) of respired CO2 further enabled us to monitor the dynamics of SOM mineralization. This approach allowed for differentiating between C stabilization of soil fractions due to accessibility/aggregation and to recalcitrance at different scales of resolution (GC-MS, NMR). A relative enrichment of alkyl C and decreasing lignin contents in the order of sand cutin, and suberin monomers measured by GC-MS before and after the incubation indicate selective degradation and preservation patterns at the molecular scale that are rarely observed and are unresolved by NMR analyses. We suggest that the monomer-specific patterns of lignin, cutin, and suberin decomposition facilitate better understanding and modelling of SOM dynamics by providing a tool to potentially separate the influence of input rates from selective preservation on the abundance of these bipolymers in soil.

  8. Stabilization of STEP electrolyses in lithium-free molten carbonates

    CERN Document Server

    Licht, Stuart

    2012-01-01

    This communication reports on effective electrolyses in lithium-free molten carbonates. Processes that utilize solar thermal energy to drive efficient electrolyses are termed Solar Thermal Electrochemical Processes (STEP). Lithium-free molten carbonates, such as a sodium-potassium carbonate eutectic using an iridium anode, or a calcium-sodium-potassium carbonate eutectic using a nickel anode, can provide an effective medium for STEP electrolyses. Such electrolyses are useful in STEP carbon capture, and the production of staples including STEP fuel, iron, and cement.

  9. Carbon Fibers from UV-Assisted Stabilization of Lignin-Based Precursors

    Directory of Open Access Journals (Sweden)

    Meng Zhang

    2015-06-01

    Full Text Available Production of high strength carbon fibers from bio-derived precursors is of topical interest. Recently, we reported on dry-spinning of a partially acetylated softwood kraft lignin to produce carbon fibers with superior properties, but the thermo-oxidative stabilization step required a long time due to a slow heating rate needed to prevent the fibers from being heated too rapidly and sticking to each other. Here we report a rapid strategy of dual UV-thermoxidative stabilization (crosslinking of dry-spun lignin fibers that significantly reduces the stabilization time. The fibers undergo reaction close to the surface such that they can be subsequently thermally stabilized at a rapid heating rate without fibers fusing together, which reduces the total stabilization time significantly from 40 to 4 h. Consequently, the glass transition temperature of UV irradiated fibers was about 15 °C higher than that of fibers without UV treatment. Stabilized fibers were successfully carbonized at 1000 °C and resulting carbon fibers displayed a tensile strength of 900 ± 100 MPa, which is amongst the highest reported for carbon fibers derived from softwood lignin-based precursors. These results establish that UV irradiation is a rapid step that can effectively shorten the total stabilization time for production of lignin-derived carbon fibers.

  10. Crystalline polymer decoration on multiwalled carbon nanotubes: MWCNT-induced P4VP periodic crystallization in CO2-expanded liquids

    Directory of Open Access Journals (Sweden)

    2011-01-01

    Full Text Available This work reports the functionalization of multi-walled carbon nanotubes (MWCNTs with crystalline poly(4- vinylpyridine (P4VP in CO2-expanded liquids (CXLs. The structure and morphology of MWCNT-induced polymer crystallization are examined, with the focus on molecular weight of P4VP (MW-P4VP, the pressure of CXLs and the concentration of P4VP. First, it is observed that the crystallization morphologies for the P4VP/MWCNTs composite with a low molecular weight P4VP (LMW-P4VP matrix could be finely controlled in CXLs, and it is surprising to find that the P4VP8700 wrapping patterns undergo a morphological evolution from dot crystals to dotted helical wrappings, and then to dense helical patterns by facile pressure tuning under lower polymer concentration. In other words, the CXLs method enables superior control of the P4VP crystallization patternings on MWCNTs, particularly efficient for LMW-P4VP at lower polymer concentration. Meanwhile, the CXL-assisted P4VP crystal growth mechanism on MWCNT is investigated, and the dominating growth mechanism is attributed to 'normal epitaxy' at lower P4VP concentration rather than 'soft epitaxy' at higher concentration. We believe that this work reports a new crystalline polymer wrapping approach in CXLs to noncovalent engineering of MWCNTs surfaces.

  11. Phase stability of iron-carbon nanocarbides and implications for the growth of carbon nanotubes

    Science.gov (United States)

    Awasthi, Neha

    Catalyst nanoparticles play a crucial role in the synthesis of single-walled carbon nanotubes by chemical vapor deposition technique. Understanding the thermal behavior of the nano-catalysts, their interaction with Carbon and stability of nanocarbides can give better insight into the growth mechanism and control over selective, yield of nanotubes. In this work, we present results using first-principle calculations and classical molecular dynamics simulations to understand the thermodynamics of free and Al2O3 supported Fe-C nanoparticles. We observe that the substrate plays an important role during the growth reaction by increasing the melting temperatures of small and medium size Fe nanoparticles. We investigate Fe-C phase diagrams for small Fe nanoparticles (d˜2nm) and discover that as the size of the Fe nanoparticle is reduced, the eutectic point shifted significantly toward lower temperatures, as expected from the Gibbs-Thomson law, and also toward lower concentrations of C. We devise a simple model based on the Young-Laplace pressure-radius relation, to predict the behavior of the phases competing for stability in Fe-C nanoclusters at low temperature. We identify ranges of nanoparticle sizes which are compatible for steady state-, limited- and no-growth of SWCNTs corresponding to unaffected, reduced and no solubility of C in the Fe nanoparticles. We also calculate Fe-Mo-C ternary phase diagrams to investigate the behavior of bimetallic Fe:Mo catalyst nanoparticles. Our results show that addition of Mo (upto small concentrations) lowers the minimum radius when stable carbides nucleate and poison the catalyst, which enables a larger range of catalyst nanoparticles sizes to nucleate nanotubes. We also find that pure Fe has the highest surface concentration in Fe:Mo nanoparticles and is likely to be the active nucleation site for nanotubes.

  12. Expanding the potential for saline formations : modeling carbon dioxide storage, water extraction and treatment for power plant cooling.

    Energy Technology Data Exchange (ETDEWEB)

    2011-04-01

    The National Water, Energy and Carbon Sequestration simulation model (WECSsim) is being developed to address the question, 'Where in the current and future U.S. fossil fuel based electricity generation fleet are there opportunities to couple CO{sub 2} storage and extracted water use, and what are the economic and water demand-related impacts of these systems compared to traditional power systems?' The WECSsim collaborative team initially applied this framework to a test case region in the San Juan Basin, New Mexico. Recently, the model has been expanded to incorporate the lower 48 states of the U.S. Significant effort has been spent characterizing locations throughout the U.S. where CO{sub 2} might be stored in saline formations including substantial data collection and analysis efforts to supplement the incomplete brine data offered in the NatCarb database. WECSsim calculates costs associated with CO{sub 2} capture and storage (CCS) for the power plant to saline formation combinations including parasitic energy costs of CO{sub 2} capture, CO{sub 2} pipelines, water treatment options, and the net benefit of water treatment for power plant cooling. Currently, the model can identify the least-cost deep saline formation CO{sub 2} storage option for any current or proposed coal or natural gas-fired power plant in the lower 48 states. Initial results suggest that additional, cumulative water withdrawals resulting from national scale CCS may range from 676 million gallons per day (MGD) to 30,155 MGD depending on the makeup power and cooling technologies being utilized. These demands represent 0.20% to 8.7% of the U.S. total fresh water withdrawals in the year 2000, respectively. These regional and ultimately nation-wide, bottom-up scenarios coupling power plants and saline formations throughout the U.S. can be used to support state or national energy development plans and strategies.

  13. Synthesis, model and stability of helically coiled carbon nanotubes

    DEFF Research Database (Denmark)

    Fejes, Dora; Raffai, Manuella; Hernadi, Klara

    2013-01-01

    Structural model of helically coiled carbon nanotubes is proposed. It is constructed by means of topological coordinate method. Relaxation and cohesive energy calculation are performed by molecular mechanics, using second-generation bond order potential for hydrocarbons introduced by D. W. Brenner....... Our experiments focused on the production and development of catalysts for the synthesis of helically coiled CNTs (carbon nanotubes). The catalysts were tested in the decomposition of acetylene by CCVD (Catalytic Chemical Vapor Deposition) method. The carbon deposit was imaged by TEM (Transmission...

  14. Chronic in vivo stability assessment of carbon fiber microelectrode arrays

    Science.gov (United States)

    Patel, Paras R.; Zhang, Huanan; Robbins, Matthew T.; Nofar, Justin B.; Marshall, Shaun P.; Kobylarek, Michael J.; Kozai, Takashi D. Y.; Kotov, Nicholas A.; Chestek, Cynthia A.

    2016-12-01

    Objective. Individual carbon fiber microelectrodes can record unit activity in both acute and semi-chronic (∼1 month) implants. Additionally, new methods have been developed to insert a 16 channel array of carbon fiber microelectrodes. Before assessing the in vivo long-term viability of these arrays, accelerated soak tests were carried out to determine the most stable site coating material. Next, a multi-animal, multi-month, chronic implantation study was carried out with carbon fiber microelectrode arrays and silicon electrodes. Approach. Carbon fibers were first functionalized with one of two different formulations of PEDOT and subjected to accelerated aging in a heated water bath. After determining the best PEDOT formula to use, carbon fiber arrays were chronically implanted in rat motor cortex. Some rodents were also implanted with a single silicon electrode, while others received both. At the end of the study a subset of animals were perfused and the brain tissue sliced. Tissue sections were stained for astrocytes, microglia, and neurons. The local reactive responses were assessed using qualitative and quantitative methods. Main results. Electrophysiology recordings showed the carbon fibers detecting unit activity for at least 3 months with average amplitudes of ∼200 μV. Histology analysis showed the carbon fiber arrays with a minimal to non-existent glial scarring response with no adverse effects on neuronal density. Silicon electrodes showed large glial scarring that impacted neuronal counts. Significance. This study has validated the use of carbon fiber microelectrode arrays as a chronic neural recording technology. These electrodes have demonstrated the ability to detect single units with high amplitude over 3 months, and show the potential to record for even longer periods. In addition, the minimal reactive response should hold stable indefinitely, as any response by the immune system may reach a steady state after 12 weeks.

  15. Novel pentagonal silicon rings and nanowheels stabilized by flat pentacoordinate carbon(s).

    Science.gov (United States)

    Zdetsis, Aristides D

    2011-03-07

    It is predicted by accurate density functional and coupled-cluster theory that planar [Si(5)C](2-) and [Si(5)C](1-) rings can be stabilized by flat pentacoordinate carbon-silicon bonds. The energy difference of the [Si(5)C](2-) dianion from the lowest energy three-dimensional isomer is about 12.2 kcal∕mol at the level of the density functional theory using the Becke 3-parameter (exchange), Lee, Yang and Parr functional, and the triple-ζ doubly polarized basis sets. Stable composite [Si(5)C](2) structures are formed either as nanowheels with axial C-C bonds of 1.51 Å or as isoenergetic pentagonal graphiticlike layers with double C-C distance (3.02 Å) and almost double aromaticity index, based on nucleus independent chemical shifts. Both of these structures are at least 12 kcal∕mol lower in energy than the lowest energy Si(10)C(2) structure reported in the literature, but about 5 kcal∕mol higher than the lowest energy structure found here.

  16. Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Hu, C.X.; Zhou, J.S.; Luo, Z.Y.; He, S.; Wang, G.K.; Cen, K.F. [Zhejiang University, Hangzhou (China)

    2006-07-01

    Oxidation treatment on the adsorption and the stability of Hg on activated carbon (AC) was investigated. Both MnO{sub 2}-AC and FeCl{sub 3}-AC were produced during oxidation treatment. The measurement of modified AC's mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO{sub 4}{sup -}, Mn{sup 4+}, NO{sub 3}{sup -}, Fe{sup 3+} Cl{sup -}, etc. The Hg sorption capacity on MnO{sub 2}-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied. It was found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could be concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

  17. Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

    Institute of Scientific and Technical Information of China (English)

    HU Chang-xing; ZHOU Jin-song; LUO Zhong-yang; HE Sheng; WANG Guang-kai; CEN Ke-fa

    2006-01-01

    Oxidation treatment on the adsorption and the stability of Hg on activated carbon (AC) was inrestigated. Both MnO2-AC and FeCl3-AC were produced during oxidation treatment. The measurement of modified AC's mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO4-, Mn4+, O, NO3-, Fe3+, Cl-, etc. The Hg sorption capacity on MnO2-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied, it found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

  18. Factors controlling soil organic carbon stability along a temperate forest altitudinal gradient.

    Science.gov (United States)

    Tian, Qiuxiang; He, Hongbo; Cheng, Weixin; Bai, Zhen; Wang, Yang; Zhang, Xudong

    2016-01-06

    Changes in soil organic carbon (SOC) stability may alter carbon release from the soil and, consequently, atmospheric CO2 concentration. The mean annual temperature (MAT) can change the soil physico-chemical characteristics and alter the quality and quantity of litter input into the soil that regulate SOC stability. However, the relationship between climate and SOC stability remains unclear. A 500-day incubation experiment was carried out on soils from an 11 °C-gradient mountainous system on Changbai Mountain in northeast China. Soil respiration during the incubation fitted well to a three-pool (labile, intermediate and stable) SOC decomposition model. A correlation analysis revealed that the MAT only influenced the labile carbon pool size and not the SOC stability. The intermediate carbon pool contributed dominantly to cumulative carbon release. The size of the intermediate pool was strongly related to the percentage of sand particle. The decomposition rate of the intermediate pool was negatively related to soil nitrogen availability. Because both soil texture and nitrogen availability are temperature independent, the stability of SOC was not associated with the MAT, but was heavily influenced by the intrinsic processes of SOC formation and the nutrient status.

  19. Synergistic effects of expandable graphite and dimethyl methyl phosphonate on the mechanical properties, fire behavior, and thermal stability of a polyisocyanurate-polyurethane foam

    Institute of Scientific and Technical Information of China (English)

    Hu Xiangming; Wang Deming; Wang Shuailing

    2013-01-01

    In this study,a series of flame-retardant polyisocyanurate-polyurethane (PIR-PUR) foams were prepared using various concentrations (0-25% by weight) of expandable graphite (EG) and dimethyl methyl phosphonate (DMMP) (0-7% by weight).The effect of these additives on the properties of the PIR-PUR foams,including physico-mechanical,morphological,flame retardancy,and thermal stability,was studied.Increasing amounts of EG in the PIR-PUR foam caused a significant drop in the compression strength.However,DMMP caused the mechanical properties of PIR-PUR foam to improve compared to foam filled with EG alone.The flame retardancy of PIR-PUR foams containing both EG and DMMP was enhanced significantly compared to EG filled foams.Thermogravimetric analysis (TGA) indicated that EG enhances the thermal stability of PIR-PUR foams but that DMMP decreased it.The morphology of the residual char provided conclusive evidence for the weak thermal stability of foams filled with DMMP.

  20. Stability of singlet and triplet trions in carbon nanotubes

    DEFF Research Database (Denmark)

    Rønnow, Troels Frimodt; Pedersen, Thomas Garm; Cornean, Horia

    2009-01-01

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.5% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band ...

  1. Flame retardancy and thermal stability of polyurethane foam composites containing carbon additives

    Science.gov (United States)

    Lee, Pyoung-Chan; Kim, Bo-Ram; Jeoung, Sun Kyoung; Lee, Geesoo; Han, San Wook; Kim, Hyunchul; Lee, Ki-Dong; Han, Joo-Kwon

    2016-03-01

    Polyurethane (PU) is an important class of polymers that have wide application in a number of different industrial sectors. The goal of this work was the synthesis of flame-retarded PU foam with expandable graphite (EG) or commercial graphene. The flame retardancy and thermal stability of the foams has been studied through cone calorimeter analysis, the limited oxygen index and thermal conductivity. The presence of expandable graphite brings an improvement in fire behavior. In particular, the limited oxygen index increases in a linear way and the highest limited oxygen index values are obtained for EG-PU foams. The results from the cone calorimeter are in agreement with those of oxygen index; EG filled foams show a considerable decrease of maximum-heat release rate (M-HRR) with respect to unfilled foams. The results of thermal conductivity show that an increase in expandable graphite amount in PU foams lead to an increased conductivity.

  2. Sequestering CO(2) by mineral carbonation: stability against acid rain exposure.

    Science.gov (United States)

    Allen, Daniel J; Brent, Geoff F

    2010-04-01

    Mineral carbonation is a potentially attractive alternative to storage of compressed CO(2) in underground repositories, known as geosequestration. Processes for the conversion of basic ores, such as magnesium silicates, to carbonates have been proposed by various researchers, with storage of the carbonate as backfill in the original mine representing a solid carbon sink. The stability of such carbon sinks against acid rain and other sources of strong acids is examined here. It is acknowledged that in the presence of strong acid, carbonates will dissolve and release carbon dioxide. A sensitivity analysis covering annual average rainfall and pH that may be encountered in industrialized areas of the United States, China, Europe, and Australia was conducted to determine maximum CO(2) rerelease rates from mineral carbonation carbon sinks. This analysis is based on a worst-case premise that is equivalent to assuming infinitely rapid kinetics of dissolution of the carbonate. The analysis shows that under any likely conditions of pH and rainfall, leakage rates of stored CO(2) are negligible. This is illustrated in a hypothetical case study under Australian conditions. It is thus proposed that sequestration by mineral carbonation can be considered to be permanent on practical human time scales. Other possible sources of acid have also been considered.

  3. Annealing effect and stability of carbon nanotubes in hydrogen flame

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Annealing of carbon nanotubes (CNTs) by the hydrogen flame in air was investigated in this study. Raman spectroscopy and scanning electron microscopy were used to characterize the products. The peak width of Raman spectra decreased with the increase in the annealing time. The CNTs were not stable in the hydrogen flame and the etching rate of the CNTs by hydrogen flame was very high. The hydrogen flame annealing had some effects on improving the crystallinity of CNTs.

  4. Phosphorus-assisted biomass thermal conversion: reducing carbon loss and improving biochar stability.

    Directory of Open Access Journals (Sweden)

    Ling Zhao

    Full Text Available There is often over 50% carbon loss during the thermal conversion of biomass into biochar, leading to it controversy for the biochar formation as a carbon sequestration strategy. Sometimes the biochar also seems not to be stable enough due to physical, chemical, and biological reactions in soils. In this study, three phosphorus-bearing materials, H3PO4, phosphate rock tailing (PRT, and triple superphosphate (TSP, were used as additives to wheat straw with a ratio of 1: 0.4-0.8 for biochar production at 500°C, aiming to alleviate carbon loss during pyrolysis and to increase biochar-C stabilization. All these additives remarkably increased the biochar yield from 31.7% (unmodified biochar to 46.9%-56.9% (modified biochars. Carbon loss during pyrolysis was reduced from 51.7% to 35.5%-47.7%. Thermogravimetric analysis curves showed that the additives had no effect on thermal stability of biochar but did enhance its oxidative stability. Microbial mineralization was obviously reduced in the modified biochar, especially in the TSP-BC, in which the total CO2 emission during 60-d incubation was reduced by 67.8%, compared to the unmodified biochar. Enhancement of carbon retention and biochar stability was probably due to the formation of meta-phosphate or C-O-PO3, which could either form a physical layer to hinder the contact of C with O2 and bacteria, or occupy the active sites of the C band. Our results indicate that pre-treating biomass with phosphors-bearing materials is effective for reducing carbon loss during pyrolysis and for increasing biochar stabilization, which provides a novel method by which biochar can be designed to improve the carbon sequestration capacity.

  5. Polyethylene-Based Carbon Fibers by the Use of Sulphonation for Stabilization

    Directory of Open Access Journals (Sweden)

    Gisa Wortberg

    2015-09-01

    Full Text Available Polyethylene has great potential as an alternative material for carbon fiber production. Polyethylene can be processed in the economic melt spinning process. These precursors are prepared for the subsequent process step of carbonization by using chemical stabilization (sulphonation. The strategy is to adjust these precursor properties by the melt spinning process, thus resulting in a precursor, which can be stabilized sufficiently by sulphonation. The objective is to find the correlation between precursor properties and the results of the sulphonation. In this paper, the chemical stabilization is described and the results of the chemical stabilization are discussed. The novelty in this paper is that the results of the sulphonation are brought in correlation with the precursor properties. It can be shown that the filament diameter and the polymer structure (e.g., the crystallinity of the precursor have an influence on the sulphonation process.

  6. Stability and signatures of biexcitons in carbon nanotubes

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Pedersen, Kjeld; Cornean, Horia Decebal;

    2005-01-01

    The linear optical properties of semiconducting carbon nanotubes are dominated by quasi-one-dimensional excitons formed by single electron-hole pairs. Hence, the nonlinear response at high pump levels most likely leads to the formation of exciton complexes involving several electron-hole pairs....... Such complexes would threfore play an important role in e.g. lasing applications. We demonstrate here that the biexciton complex is surprisingly stable for nanotubes in a wide diameter range. Theoretical predictions for the signature of such states in pump-probe spectroscopy are presented....

  7. Thermodynamic stabilities of carbon-and nitrogen-centered radicals

    Institute of Scientific and Technical Information of China (English)

    程津培; 赵永昱; 还振威

    1995-01-01

    The gas-phase homolytic C-H and N-H bond dissociation energies(BDE)of the substi-tuted phenoacetonitrile families,aromatic amines,and semicarbazone derivatives were systematically investigatedor reinvestigated based on a cycle utilizing the thermodynamic quantities determined in DMSO solution.Theexperimental evidence collected in.this work dearly indicates that the radicals derived from the above familiesare of the‘Class O’type,i.e.to be stabilized by a remote electron-donating substituent but destabilized by anelectron-withdrawing substituent.

  8. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

    KAUST Repository

    Stoltz, Brian

    2010-06-14

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

  9. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates.

    Science.gov (United States)

    McDougal, Nolan T; Virgil, Scott C; Stoltz, Brian M

    2010-01-01

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

  10. Thermal Stability of Zirconia-coated Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    R. Manivannan

    2010-04-01

    Full Text Available Sol-gel method has been used to coat multiwalled carbon nanotubes (MWCNTs with zirconia at room temperature and the coated tubes were sintered at high temperature. The samples were characterised by Raman spectroscopy, x-ray diffraction, environmental scanning electron microscope, transmission electron microscopy, and energy-dispersive x-ray analyses. The performance of the coated-MWCNTs was investigated as a function of temperature. The TGA studies indicated that sintering of coated-MWCNTs has improved its oxidation resistance and this improvement is related to the proper selection of sintering temperature.Defence Science Journal, 2010, 60(3, pp.337-342, DOI:http://dx.doi.org/10.14429/dsj.60.362

  11. Recycling of graphite during Himalayan erosion: a geological stabilization of carbon in the crust.

    Science.gov (United States)

    Galy, Valier; Beyssac, Olivier; France-Lanord, Christian; Eglinton, Timothy

    2008-11-07

    At geological time scales, the role of continental erosion in the organic carbon (OC) cycle is determined by the balance between recent OC burial and petrogenic OC oxidation. Evaluating its net effect on the concentration of carbon dioxide and dioxygen in the atmosphere requires the fate of petrogenic OC to be assessed. Here, we report a multiscale (nanometer to micrometer) structural characterization of petrogenic OC in the Himalayan system. We show that graphitic carbon is preserved and buried in marine sediments, while the less graphitized forms are oxidized during fluvial transport. Radiocarbon dating indicates that 30 to 50% of the carbon initially present in the Himalayan rocks is conserved during the erosion cycle. Graphitization during metamorphism thus stabilizes carbon in the crust over geological time scales.

  12. Electrochemical stability of carbon nanofibers in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, Garbine [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Alcaide, Francisco, E-mail: falcaide@cidetec.es [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Miguel, Oscar [Energy Department, CIDETEC-IK4, Po Miramon, 196, 20009 San Sebastian (Spain); Cabot, Pere L. [Laboratori d' Electroquimica de Materials i del Medi Ambient, Dept. Quimica Fisica, Universitat de Barcelona, Marti i Franques, 1-11, 08028 Barcelona (Spain); Martinez-Huerta, M.V.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica (CSIC), Marie Curie 2, Cantoblanco, 28049 Madrid (Spain)

    2011-10-30

    This fundamental study deals with the electrochemical stability of several non-conventional carbon based catalyst supports, intended for low temperature proton exchange membrane fuel cell (PEMFC) cathodes. Electrochemical surface oxidation of raw and functionalized carbon nanofibers, and carbon black for comparison, was studied following a potential step treatment at 25.0 deg. C in acid electrolyte, which mimics the operating conditions of low temperature PEMFCs. Surface oxidation was characterized using cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Cyclic voltammograms clearly showed the presence of the hydroquinone/quinone couple. Furthermore, identification of carbonyl, ether, hydroxyl and carboxyl surface functional groups were made by deconvolution of the XPS spectra. The relative increase in surface oxides on carbon nanofibers during the electrochemical oxidation treatment is significantly smaller than that on carbon black. This suggests that carbon nanofibers are more resistant to the electrochemical corrosion than carbon black under the experimental conditions used in this work. This behaviour could be attributed to the differences found in the microstructure of both kinds of carbons. According to these results, carbon nanofibers possess a high potential as catalyst support to increase the durability of catalysts used in low temperature PEMFC applications.

  13. Thermal stability of catalytically grown multi-walled carbon nanotubes observed in transmission electron microscopy

    DEFF Research Database (Denmark)

    Wang, Cheng-Yu; Liu, Chuan-Pu; Boothroyd, Chris

    2009-01-01

    The thermal stability of multi-walled carbon nanotubes (MWCNTs) was assessed in situ by transmission electron microscopy. Upon heating, Ni catalysts in MWC-NTs containing bamboo structures shrank from the tail due to evaporation, leading to additional bamboo formation and tube elongation at 800...

  14. Soil and plant responses to pyrogenic organic matter: carbon stability and symbiotic patterns

    NARCIS (Netherlands)

    Sagrilo, E.

    2014-01-01

    Soil and plant responses to pyrogenic organic matter: carbon stability and symbiotic patterns Edvaldo Sagrilo Summary Pyrogenic organic matter (PyOM), also known as biochar, is the product of biomass combustion under low oxygen concentration. There

  15. Carbon Stabilization by Clays in the Environment: Process and Characterization Methods

    Science.gov (United States)

    Organic matter (OM) in soil plays vital roles with respect to global climate change, as the largest terrestrial reservoir of organic carbon, and with respect to soil quality through the stabilization of soil structure and the retention and cycling of plant nutrients. The interactions between clay mi...

  16. Citrate effects on amorphous calcium carbonate (ACC) structure, stability, and crystallization

    DEFF Research Database (Denmark)

    Tobler, Dominique Jeanette; Rodriguez Blanco, Juan Diego; Dideriksen, Knud;

    2015-01-01

    Understanding the role of citrate in the crystallization kinetics of amorphous calcium carbonate (ACC) is essential to explain the formation mechanisms, stabilities, surface properties, and morphologies of CaCO3 biominerals. It also contributes to deeper insight into fluid-mineral inte...

  17. Dispersion and film-forming properties of poly(acrylic acid)-stabilized carbon nanotubes.

    Science.gov (United States)

    Saint-Aubin, Karell; Poulin, Philippe; Saadaoui, Hassan; Maugey, Maryse; Zakri, Cécile

    2009-11-17

    We present a detailed study of the influence of pH on the dispersion and film-forming properties of poly(acrylic acid)-stabilized carbon nanotubes. Poly(acrylic acid) (PAA) is a weak polyelectrolyte, with a pH-responsive behavior in aqueous solution. We obtain quantitative UV-visible measurements to show that the amount of polyelectrolyte in optimal pH conditions is weak, showing a good efficiency of the polymer as a carbon nanotube dispersing agent. The best dispersion conditions are achieved at pH 5, a value close to the pK(a) of PAA. Apart from this tenuous pH value, the PAA is not efficient at stabilizing nanotubes and atomic force microscopy allows us to explain the delicate balance between the PAA adsorption and the suspension stability. This study finally permits optimal conditions for making homogeneous and conductive composite films to be determined.

  18. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    Science.gov (United States)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  19. Nucleation and stabilization of carbon-rich structures in interstellar media

    CERN Document Server

    Patra, N; Sadeghpour, H R

    2014-01-01

    We study conditions under which carbon clusters of different sizes form and stabilize. {We describe an approach to equilibrium by simulating tenuous carbon gas dynamics to long times.} First, we use reactive molecular dynamics simulations to describe the nucleation of long chains, large clusters, and complex cage structures in carbon and hydrogen rich interstellar gas phases. We study how temperature, particle density, presence of hydrogen, and carbon inflow affect the nucleation of molecular moieties with different characteristics, in accordance with astrophysical conditions. We extend the simulations to densities which are orders of magnitude lower than current laboratory densities, to temperatures relevant to circumstellar environments of planetary nebulae, and to longtime (microsecond) formation timescales. We correlate cluster size distributions from dynamical simulations with thermodynamic equilibrium intuitions, where at low temperatures and gas densities, entropy plays a significant role.

  20. Expanding earth

    Energy Technology Data Exchange (ETDEWEB)

    Carey, S.W.

    1976-01-01

    Arguments in favor of an expanding earth are presented. The author believes that the theory of plate tectonics is a classic error in the history of geology. The case for the expanding earth is organized in the following way: introductory review - face of the earth, development of expanding earth concept, necessity for expansion, the subduction myth, and definitions; some principles - scale of tectonic phenomena, non-uniformitarianism, tectonic profile, paleomagnetism, asymmetry of the earth, rotation of the earth, and modes of crustal extension; regional studies - western North America, Central America, South-East Asia, and the rift oceans; tests and cause of expansion. 824 references, 197 figures, 11 tables. (RWR)

  1. Organic Carbon Stabilization of Soils Formed on Acidic and Calcareous Bedrocks in Neotropical Alpine Grassland, Peru

    Science.gov (United States)

    Yang, Songyu; Cammeraat, Erik; Jansen, Boris; Cerli, Chiara; Kalbitz, Karsten

    2016-04-01

    Increasing evidence shows that Neotropical alpine ecosystems are vulnerable to global change. Since soils in the alpine grasslands of the Peruvian Andean region have large soil organic carbon (SOC) stocks, profound understanding of soil organic matter (OM) stabilization mechanisms will improve the prediction of the feedback between SOC stocks and global change. It is well documented that poor-crystalline minerals and organo-metallic complexes significantly contribute to the OM stabilization in volcanic ash soils, including those in the Andean region. However, limited research has focused on non-ash soils that also express significant SOC accumulation. A pilot study of Peruvian Andean grassland soils suggests that lithology is a prominent factor for such carbon accumulation. As a consequence of contrasting mineral composition and pedogenic processes in soils formed on different non-volcanic parent materials, differences in OM stabilization mechanisms may be profound and consequently may respond differently to global change. Therefore, our study aims at a further understanding of carbon stocks and OM stabilization mechanisms in soils formed on contrasting bedrocks in the Peruvian Andes. The main objective is to identify and compare the roles that organo-mineral associations and aggregations play in OM stabilization, by a combination of selective extraction methods and fractionations based on density, particle size and aggregates size. Soil samples were collected from igneous acidic and calcareous sedimentary bedrocks in alpine grassland near Cajamarca, Peru (7.17°S, 78.63°W), at around 3700m altitude. Samples were taken from 3 plots per bedrock type by sampling distinguishable horizons until the C horizons were reached. Outcomes confirmed that both types of soil accumulate large amounts of carbon: 405.3±41.7 t/ha of calcareous bedrock soil and 226.0±5.6 t/ha of acidic bedrock soil respectively. In addition, extremely high carbon contents exceeding 90g carbon per

  2. Mechanical synthesis of copper-carbon nanocomposites: Structural changes, strengthening and thermal stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, D., E-mail: daniela.nunes@ist.utl.pt [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Livramento, V. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Mateus, R. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Correia, J.B. [LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Alves, L.C. [ITN, Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Vilarigues, M. [Departamento de Conservacao e Restauro e R and D Unit Vidro e da Ceramica Para as Artes, FCT-UNL, Quinta da Torre, 2829-516 Caparica (Portugal); Carvalho, P.A. [ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Departamento de Bioengenharia, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2011-11-15

    Highlights: {yields} The study characterized Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites. {yields} Preservation of nD crystalline structure during high-energy milling was demonstrated. {yields} Higher refinement of matrix in Cu-nD comparing to Cu-G is due to a milling mechanism. {yields} Remarkable thermal stability and microhardness have been achieved in Cu-nD and Cu-G. {yields} Strengthening resulted mainly from grain refinement and second-phase reinforcement. - Abstract: Processing of copper-carbon nanocomposites by mechanical synthesis poses specific challenges as carbon phases are prone to amorphization and exhibit an intrinsically difficult bonding with copper. The present work investigates Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites produced by mechanical synthesis and subsequent heat treatments. Transmission electron microscopy observations showed homogeneous particle distributions and intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained essentially unaffected by the mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. Particle-induced X-ray emission spectroscopy showed that the total contamination originating from the milling media remained below 0.7 wt.%. The Cu-nanodiamond composite exhibited remarkable microhardness and microstructural thermal stability when compared with pure nanostructured copper.

  3. Expanding subjectivities

    DEFF Research Database (Denmark)

    Lundgaard Andersen, Linda; Soldz, Stephen

    2012-01-01

    A major theme in recent psychoanalytic thinking concerns the use of therapist subjectivity, especially “countertransference,” in understanding patients. This thinking converges with and expands developments in qualitative research regarding the use of researcher subjectivity as a tool to understa......-Saxon and continental traditions, this special issue provides examples of the use of researcher subjectivity, informed by psychoanalytic thinking, in expanding research understanding....

  4. Adsorption behavior of perfluorinated sulfonic acid ionomer on highly graphitized carbon nanofibers and their thermal stabilities

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma; Borghei, Maryam; Dhiman, Rajnish

    2014-01-01

    of decreasing hydrophobicity. This is indicated by the initial decrease and then increase in the value of Keq. with the increasing strength of the acid treatment. The corresponding carbon - ionomer composite also showed varying thermal stability depending on Nafion orientation. The specific maximum surface...... isotherm), the ionomer has varying affinities for CNFs (Keq. = between 5 and 22) as compared to Vulcan (Keq. = 18), depending on surface treatments. However, the interactions are most likely governed by different adsorption mechanisms depending on hydrophilicity / hydrophobicity of the adsorbent carbon...

  5. Soil carbon sequestration is a climate stabilization wedge: comments on Sommer and Bossio (2014).

    Science.gov (United States)

    Lassaletta, Luis; Aguilera, Eduardo

    2015-04-15

    Sommer and Bossio (2014) model the potential soil organic carbon (SOC) sequestration in agricultural soils (croplands and grasslands) during the next 87 years, concluding that this process cannot be considered as a climate stabilization wedge. We argue, however, that the amounts of SOC potentially sequestered in both scenarios (pessimistic and optimistic) fulfil the requirements for being considered as wedge because in both cases at least 25 GtC would be sequestered during the next 50 years. We consider that it is precisely in the near future, and meanwhile other solutions are developed, when this stabilization effort is most urgent even if after some decades the sequestration rate is significantly reduced. Indirect effects of SOC sequestration on mitigation could reinforce the potential of this solution. We conclude that the sequestration of organic carbon in agricultural soils as a climate change mitigation tool still deserves important attention for scientists, managers and policy makers.

  6. Surface morphology stabilization by chemical sputtering in carbon nitride film growth

    Energy Technology Data Exchange (ETDEWEB)

    Buijnsters, J G [Institute for Molecules and Materials (IMM), Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen (Netherlands); Vazquez, L [Instituto de Ciencia de Materiales de Madrid (CSIC), C/Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2008-01-07

    We have studied the influence of chemical sputtering effects on the morphology of carbon nitride films grown on silicon substrates by electron cyclotron resonance chemical vapour deposition. This study has been performed by comparing the evolution of their morphology with that of hydrogenated amorphous carbon films grown under similar conditions, where these effects are not present. When chemical sputtering effects operate we observe a film surface stabilization for length scales in the 60-750 nm range after a threshold roughness of about 3-4 nm has been developed. This stabilization is explained on the basis of the re-emission of nitrogen etching species, which is confirmed by growth experiments on microstructured substrates. (fast track communication)

  7. Integrating plant-microbe interactions to understand soil C stabilization with the MIcrobial-MIneral Carbon Stabilization model (MIMICS)

    Science.gov (United States)

    Grandy, Stuart; Wieder, Will; Kallenbach, Cynthia; Tiemann, Lisa

    2014-05-01

    If soil organic matter is predominantly microbial biomass, plant inputs that build biomass should also increase SOM. This seems obvious, but the implications fundamentally change how we think about the relationships between plants, microbes and SOM. Plant residues that build microbial biomass are typically characterized by low C/N ratios and high lignin contents. However, plants with high lignin contents and high C/N ratios are believed to increase SOM, an entrenched idea that still strongly motivates agricultural soil management practices. Here we use a combination of meta-analysis with a new microbial-explicit soil biogeochemistry model to explore the relationships between plant litter chemistry, microbial communities, and SOM stabilization in different soil types. We use the MIcrobial-MIneral Carbon Stabilization (MIMICS) model, newly built upon the Community Land Model (CLM) platform, to enhance our understanding of biology in earth system processes. The turnover of litter and SOM in MIMICS are governed by the activity of r- and k-selected microbial groups and temperature sensitive Michaelis-Menten kinetics. Plant and microbial residues are stabilized short-term by chemical recalcitrance or long-term by physical protection. Fast-turnover litter inputs increase SOM by >10% depending on temperature in clay soils, and it's only in sandy soils devoid of physical protection mechanisms that recalcitrant inputs build SOM. These results challenge centuries of lay knowledge as well as conventional ideas of SOM formation, but are they realistic? To test this, we conducted a meta-analysis of the relationships between the chemistry of plant liter inputs and SOM concentrations. We find globally that the highest SOM concentrations are associated with plant inputs containing low C/N ratios. These results are confirmed by individual tracer studies pointing to greater stabilization of low C/N ratio inputs, particularly in clay soils. Our model and meta-analysis results suggest

  8. Improvement of luminescent stability from carbon nanotube field emission display based on printed CNT film

    Institute of Scientific and Technical Information of China (English)

    ZENG; Fanguang; ZHU; Changchun; LIU; Xinghui

    2006-01-01

    Aiming at the influences of poor contact at carbon nanotube (CNT)/electrode interface on luminescence stability in printed CNT film, a new co-sintering process for cathode fabrication was presented to improve the luminescent stability of fully printed CNT-FED. By co-sintering the printed silver and CNT layers, CNTs geometrically matched with Ag surface and/or embedded into Ag layer at the bottom of the co-sintered film, large CNTs block and bulk silver nested each other at the top of the co-sintered film. All these structures increased the contact area at CNT/Ag interface, which could increase the probability of forming ohmic contact at CNT/Ag interface. The luminescent stability of printed CNT-FED with co-sintered cathode could be improved as 5.6 times high as that of common devices.

  9. Co-composting solid biowastes with alkaline materials to enhance carbon stabilization and revegetation potential.

    Science.gov (United States)

    Chowdhury, Saikat; Bolan, Nanthi S; Seshadri, Balaji; Kunhikrishnan, Anitha; Wijesekara, Hasintha; Xu, Yilu; Yang, Jianjun; Kim, Geon-Ha; Sparks, Donald; Rumpel, Cornelia

    2016-04-01

    Co-composting biowastes such as manures and biosolids can be used to stabilize carbon (C) without impacting the quality of these biowastes. This study investigated the effect of co-composting biowastes with alkaline materials on C stabilization and monitored the fertilization and revegetation values of these co-composts. The stabilization of C in biowastes (poultry manure and biosolids) was examined by their composting in the presence of various alkaline amendments (lime, fluidized bed boiler ash, flue gas desulphurization gypsum, and red mud) for 6 months in a controlled environment. The effects of co-composting on the biowastes' properties were assessed for different physical C fractions, microbial biomass C, priming effect, potentially mineralizable nitrogen, bioavailable phosphorus, and revegetation of an urban landfill soil. Co-composting biowastes with alkaline materials increased C stabilization, attributed to interaction with alkaline materials, thereby protecting it from microbial decomposition. The co-composted biowastes also increased the fertility of the landfill soil, thereby enhancing its revegetation potential. Stabilization of biowastes using alkaline materials through co-composting maintains their fertilization value in terms of improving plant growth. The co-composted biowastes also contribute to long-term soil C sequestration and reduction of bioavailability of heavy metals.

  10. Laccase immobilization over multi-walled carbon nanotubes: Kinetic, thermodynamic and stability studies.

    Science.gov (United States)

    Tavares, Ana P M; Silva, Cláudia G; Dražić, Goran; Silva, Adrián M T; Loureiro, José M; Faria, Joaquim L

    2015-09-15

    The biocatalytic performance of immobilized enzyme systems depends mostly on the intrinsic properties of both biomolecule and support, immobilization technique and immobilization conditions. Multi-walled carbon nanotubes (MWCNTs) possess unique features for enzyme immobilization by adsorption. Enhanced catalytic activity and stability can be achieved by optimization of the immobilization conditions and by investigating the effect of operational parameters. Laccase was immobilized over MWCNTs by adsorption. The hybrid material was characterized by Fourier transformed infrared (FTIR) spectroscopy, scanning and transmission electron microscopy (SEM and TEM, respectively). The effect of different operational conditions (contact time, enzyme concentration and pH) on laccase immobilization was investigated. Optimized conditions were used for thermal stability, kinetic, and storage and operational stability studies. The optimal immobilization conditions for a laccase concentration of 3.75μL/mL were a pH of 9.0 and a contact time of 30min (522 Ulac/gcarrier). A decrease in the thermal stability of laccase was observed after immobilization. Changes in ΔS and ΔH of deactivation were found for the immobilized enzyme. The Michaelis-Menten kinetic constant was higher for laccase/MWCNT system than for free laccase. Immobilized laccase maintained (or even increased) its catalytic performance up to nine cycles of utilization and revealed long-term storage stability.

  11. Nucleating Effect of Carbon Nanoparticles and Their Influence on the Thermal and Chemical Stability of Polypropylene

    Directory of Open Access Journals (Sweden)

    F. Avalos-Belmontes

    2012-01-01

    Full Text Available The effect of carbon nanofibers (CNFs and carbon nanotubes (CNTs on the thermal and chemical stability of polypropylene (PP when subjected to oxidation in a strong acid medium was studied. The effect of CNFs and CNTs on the crystalline morphology and the melting and crystallization temperatures was also studied. The thermal stability increased markedly; the decomposition temperature, for example, increased from 293∘C for pure PP to 312 and 320∘C for PP with CNFs and CNTs, respectively. The crystallization temperature increased perceptibly with the addition of CNTs or CNFs, from 107∘C for pure PP to 112 and 114∘C for PP with CNFs and CNTs, respectively. The oxidative degradation with nitric acid produced a reduction in molecular weight; however, this negative effect was less pronounced in the PP compositions with carbon nanoparticles. After 8 hours in nitric acid, this reduction was from 141,000 to 68,000 (for pure PP, to 75,000 (for PP-CNFs, and 79,500 (for PP-CNTs. X-ray diffraction showed that the alpha type crystallinity remains, irrespective of the nucleating agent. Finally, the intensity ratio between the (040 (at 16.7∘ and the (110 (at 13.9∘ reflections increased, which was taken as an indication of an increasing nucleating efficiency.

  12. Molecular dynamics study of the stability of a carbon nanotube atop a catalytic nanoparticle

    CERN Document Server

    Verkhovtsev, Alexey V; Solov'yov, Andrey V

    2014-01-01

    The stability of a single-walled carbon nanotube placed on top of a catalytic nickel nanoparticle is investigated by means of molecular dynamics simulations. As a case study, we consider the $(12,0)$ nanotube consisting of 720 carbon atoms and the icosahedral Ni$_{309}$ cluster. An explicit set of constant-temperature simulations is performed in order to cover a broad temperature range from 400 to 1200 K, at which a successful growth of carbon nanotubes has been achieved experimentally by means of chemical vapor deposition. The stability of the system depending on parameters of the involved interatomic interactions is analyzed. It is demonstrated that different scenarios of the nanotube dynamics atop the nanoparticle are possible depending on the parameters of the Ni-C potential. When the interaction is weak the nanotube is stable and resembles its highly symmetric structure, while an increase of the interaction energy leads to the abrupt collapse of the nanotube in the initial stage of simulation. In order t...

  13. Porous Carbon Paper as Interlayer to Stabilize the Lithium Anode for Lithium-Sulfur Battery.

    Science.gov (United States)

    Kong, Ling-Long; Zhang, Ze; Zhang, Ye-Zheng; Liu, Sheng; Li, Guo-Ran; Gao, Xue-Ping

    2016-11-23

    The lithium-sulfur (Li-S) battery is expected to be the high-energy battery system for the next generation. Nevertheless, the degradation of lithium anode in Li-S battery is the crucial obstacle for practical application. In this work, a porous carbon paper obtained from corn stalks via simple treating procedures is used as interlayer to stabilize the surface morphology of Li anode in the environment of Li-S battery. A smooth surface morphology of Li is obtained during cycling by introducing the porous carbon paper into Li-S battery. Meanwhile, the electrochemical performance of sulfur cathode is partially enhanced by alleviating the loss of soluble intermediates (polysulfides) into the electrolyte, as well as the side reaction of polysulfides with metallic lithium. The Li-S battery assembled with the interlayer exhibits a large capacity and excellent capacity retention. Therefore, the porous carbon paper as interlayer plays a bifunctional role in stabilizing the Li anode and enhancing the electrochemical performance of the sulfur cathode for constructing a stable Li-S battery.

  14. Mechanochemically Activated, Calcium Oxide-Based, Magnesium Oxide-Stabilized Carbon Dioxide Sorbents.

    Science.gov (United States)

    Kurlov, Alexey; Broda, Marcin; Hosseini, Davood; Mitchell, Sharon J; Pérez-Ramírez, Javier; Müller, Christoph R

    2016-09-01

    Carbon dioxide capture and storage (CCS) is a promising approach to reduce anthropogenic CO2 emissions and mitigate climate change. However, the costs associated with the capture of CO2 using the currently available technology, that is, amine scrubbing, are considered prohibitive. In this context, the so-called calcium looping process, which relies on the reversible carbonation of CaO, is an attractive alternative. The main disadvantage of naturally occurring CaO-based CO2 sorbents, such as limestone, is their rapid deactivation caused by thermal sintering. Here, we report a scalable route based on wet mechanochemical activation to prepare MgO-stabilized, CaO-based CO2 sorbents. We optimized the synthesis conditions through a fundamental understanding of the underlying stabilization mechanism, and the quantity of MgO required to stabilize CaO could be reduced to as little as 15 wt %. This allowed the preparation of CO2 sorbents that exceed the CO2 uptake of the reference limestone by 200 %.

  15. Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

    Directory of Open Access Journals (Sweden)

    Phei Li Lau

    2013-12-01

    Full Text Available The palladium metal catalysed Heck reaction of 4-iodoanisole with styrene or methyl acrylate has been studied in a continuous plug flow reactor (PFR using supercritical carbon dioxide (scCO2 as the solvent, with THF and methanol as modifiers. The catalyst was 2% palladium on silica and the base was diisopropylethylamine due to its solubility in the reaction solvent. No phosphine co-catalysts were used so the work-up procedure was simplified and the green credentials of the reaction were enhanced. The reactions were studied as a function of temperature, pressure and flow rate and in the case of the reaction with styrene compared against a standard, stirred autoclave reaction. Conversion was determined and, in the case of the reaction with styrene, the isomeric product distribution was monitored by GC. In the case of the reaction with methyl acrylate the reactor was scaled from a 1.0 mm to 3.9 mm internal diameter and the conversion and turnover frequency determined. The results show that the Heck reaction can be effectively performed in scCO2 under continuous flow conditions with a palladium metal, phosphine-free catalyst, but care must be taken when selecting the reaction temperature in order to ensure the appropriate isomer distribution is achieved. Higher reaction temperatures were found to enhance formation of the branched terminal alkene isomer as opposed to the linear trans-isomer.

  16. [Impact of land use type on stability and organic carbon of soil aggregates in Jinyun Mountain].

    Science.gov (United States)

    Li, Jian-Lin; Jiang, Chang-Sheng; Hao, Qing-Ju

    2014-12-01

    Soil aggregates have the important effect on soil fertility, soil quality and the sustainable utilization of soil, and they are the mass bases of water and fertilizer retention ability of soil and the supply or release of soil nutrients. In this paper, in order to study the impact of land use type on stability and organic carbon of soil aggregates in Jinyun Mountain, we separated four land use types of soil, which are woodland, abandoned land, orchard and sloping farmland by wet sieving method, then we got the proportion of large macroaggregates (> 2 mm), small macroaggregates (0.25-2 mm), microaggregates (53 μm-0.25 mm) and silt + clay (organic carbon in each aggregate fraction in soil depth of 0-60 cm and calculated the total content of organic carbon of all aggregates fraction in each soil. The results showed that reclamation of woodland will lead to fragmentation of macroaggregates and deterioration of soil structure, and the proportion of macroaggrgates (> 0.25 mm) were 44.62% and 32.28% respectively in the soils of orchard and sloping farmland, which reduced 38.58% (P soil fraction from silt + clay to large macroaggregates and small macroaggregates, so it will improve the soil structure. MWD (mean weight diameter) and GMD (geometric mean diameter) are important indicators of evaluating the stability of soil aggregates. We found the MWD and GWD in soil depth of 0-60 cm in orchards and sloping farmland were significantly lower than those in woodland (P soil aggregates, and they will be separated more easily by water. However, after changing the sloping farmland to abandoned land will enhance the stability of soil aggregates, and improve the ability of soil to resist external damage. The organic carbon content in each soil aggregate of four land use types decreased with the increase of soil depth. In soil depth of 0-60 cm, the storage of organic carbon of large macroaggregates in each soil are in orders of woodland (14.98 Mg x hm(-2)) > abandoned land (8.71 Mg

  17. Increase in Recalcitrant Carbon: a Positive Balance between Stabilization and Priming Effect

    Science.gov (United States)

    Liang, J.; Huo, C.; Shi, Z.; Xia, J.; Luo, Y.

    2014-12-01

    Recalcitrant carbon (C) stored in soils plays a critical role in regulating climate change because of its huge amount and relatively low turnover rate. Positive priming effect by increased labile C inputs could lead to more recalcitrant C release to the atmosphere. However, the stabilization of the newly added labile C has received much less attention. As a result, the quantitative balance between the stabilization and priming and consequently changes in recalcitrant C are still unclear. In this study, incubation data of different soils (i.e., forest, grassland, cropland, and vertisol) with isotope-labeled labile substrate additions were collected. An alternative version of the Introductory Carbon Balance Model (ICBM) with stabilization and positive priming effect was used to simulate the C dynamics during the incubation and then run forward for ten years. The results showed that at the end of incubation, an equivalent of 5.45 - 26.1% of added C was primed from the original SOM for the four soils. Meanwhile, 40.9 - 70.7% of added C was stabilized, leading to a net increase in recalcitrant C by an equivalent of 18.0 - 50.0% of added C. After running model for ten years, the recalcitrant C was greater with than without initial labile C addition by an equivalent of 33.0, 2.01, 21.6, and 0.62% of added C for the forest, grassland, cropland and vertisol, respectively. Our results suggest that stabilization overcompensates the C loss induced by positive priming effect, indicating that stimulated labile C input under CO2 enrichment may increase the recalcitrant C storage in soils, and consequently dampen the further increase in atmospheric CO2 concentrations and climate change. The results also suggest that both stabilization and positive priming effect may vary among ecosystems and with the type and amount of added substrates. To better quantify the net change in recalcitrant C and thus long-term soil C storage, comprehensive studies on the effects of soil type, added

  18. Short-Range-Order Mineral Physical Protection On Black Carbon Stabilization

    Science.gov (United States)

    Liang, B.; Weng, Y. T.; Wang, C. C.; Song, Y. F.; Lehmann, J.; Wang, C. H.

    2015-12-01

    Soil organic matter is one of the largest reservoirs in global carbon cycle, and black carbon (BC) represents a chemical resistant component. Black C plays an important role in global climate change. Generally considered recalcitrant due to high aromaticity, the reactive surface and functional groups of BC are crucial for carbon sequestration in soils. Mineral sorption and physical protection is an important mechanism for BC long term stabilization and sequestration in environments. Previous studies on mineral protection of BC were limited to analysis techniques in two-dimensions, for example, by SEM, TEM, and NanoSIMS. Little is known about the scope of organo-mineral association, the in-situ distribution and forms of minerals, and the ultimate interplay of BC and minerals. The aim of this study is to investigate the three-dimensional interaction of organic C and minerals in submicron scale using synchrotron-based Transmission X-ray Microcopy (TXM) and Fourier-Transform Infrared Spectroscopy (FTIR). Abundant poorly-crystallined nano-minerals particles were observed. These short-range-order (SRO) minerals also aggregate into clusters and sheets, and form envelops-like structures on the surface of BC. On top of large surface contact area, the intimate interplay between BC and minerals reinforces the stability of both organic C and minerals, resulting from chemical bonding through cation bridging and ligand exchange. The mineral protection enhances BC stabilization and sequestration and lowers its bioavailability in environment. The results suggest that mineral physical protection for BC sequestration may be more important than previous understanding.

  19. Fluoride enhances transfection activity of carbonate apatite by increasing cytoplasmic stability of plasmid DNA

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, E.H., E-mail: md.ezharul.hoque@med.monash.edu.my [Jeffrey Cheah School of Medicine and Health Sciences, Monash University Sunway Campus, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan (Malaysia)

    2011-06-17

    Highlights: {yields} Cytoplasmic stability of plasmid DNA is enhanced by fluoride incorporation into carbonate apatite carrier. {yields} Fluoridated carbonate apatite promotes a robust increase in transgene expression. {yields} Controlled dissolution of fluoridated carbonate apatite in endosomal acidic environment might buffer the endosomes and prevent degradation of the released DNA. -- Abstract: Intracellular delivery of a functional gene or a nucleic acid sequence to specifically knockdown a harmful gene is a potential approach to precisely treat a critical human disease. The intensive efforts in the last few decades led to the development of a number of viral and non-viral synthetic vectors. However, an ideal delivery tool in terms of the safety and efficacy has yet to be established. Recently, we have developed pH-sensing inorganic nanocrystals of carbonate apatite for efficient and cell-targeted delivery of gene and gene-silencing RNA. Here we show that addition of very low level of fluoride to the particle-forming medium facilitates a robust increase in transgene expression following post-incubation of the particles with HeLa cells. Confocal microscopic observation and Southern blotting prove the cytoplasmic existence of plasmid DNA delivered by likely formed fluoridated carbonate apatite particles while degradation of plasmid DNA presumably by cytoplasmic nucleases was noticed following delivery with apatite particles alone. The beneficial role of fluoride in enhancing carbonate apatite-mediated gene expression might be due to the buffering potential of generated fluoridated apatite in endosomal acidic environment, thereby increasing the half-life of delivered plasmid DNA.

  20. Ultrahigh volumetric capacitance and cyclic stability of fluorine and nitrogen co-doped carbon microspheres

    Science.gov (United States)

    Zhou, Junshuang; Lian, Jie; Hou, Li; Zhang, Junchuan; Gou, Huiyang; Xia, Meirong; Zhao, Yufeng; Strobel, Timothy A.; Tao, Lu; Gao, Faming

    2015-09-01

    Highly porous nanostructures with large surface areas are typically employed for electrical double-layer capacitors to improve gravimetric energy storage capacity; however, high surface area carbon-based electrodes result in poor volumetric capacitance because of the low packing density of porous materials. Here, we demonstrate ultrahigh volumetric capacitance of 521 F cm-3 in aqueous electrolytes for non-porous carbon microsphere electrodes co-doped with fluorine and nitrogen synthesized by low-temperature solvothermal route, rivaling expensive RuO2 or MnO2 pseudo-capacitors. The new electrodes also exhibit excellent cyclic stability without capacitance loss after 10,000 cycles in both acidic and basic electrolytes at a high charge current of 5 A g-1. This work provides a new approach for designing high-performance electrodes with exceptional volumetric capacitance with high mass loadings and charge rates for long-lived electrochemical energy storage systems.

  1. Influence of Carbon Nanotubes on Thermal Stability of Water-Dispersible Nanofibrillar Polyaniline/Nanotube Composite

    Directory of Open Access Journals (Sweden)

    Zhi-Bin Zhang

    2012-02-01

    Full Text Available Significant influence on the thermal stability of polyaniline (PANI in the presence of multi-walled carbon nanotubes (MWCNTs is reported. By means of in-situ rapid mixing approach, water-dispersible nanofibrillar PANI and composites, consisting of MWCNTs uniformly coated with PANI in the state of emeraldine salt, with a well-defined core-shell heterogeneous structure, were prepared. The de-protonation process in PANI occurs at a lower temperature under the presence of MWCNTs on the polyaniline composite upon thermal treatment. However, it is found that the presence of MWCNTs significantly enhances the thermal stability of PANI’s backbone upon exposure to laser irradiation, which can be ascribed to the core-shell heterogeneous structure of the composite of MWCNTs and PANI, and the high thermal conductivity of MWCNTs.

  2. Dynamics of Soil Organic Carbon and Aggregate Stability with Grazing Exclusion in the Inner Mongolian Grasslands.

    Science.gov (United States)

    Wen, Ding; He, Nianpeng; Zhang, Jinjing

    2016-01-01

    Grazing exclusion (GE) has been deemed as an important approach to enhance the soil carbon storage of semiarid grasslands in China; however, it remains unclear how different organic carbon (OC) components in soils vary with the duration of GE. Here, we observed the changing trends of different OC components in soils with increased GE duration in five grassland succession series plots, ranging from free grazing to 31-year GE. Specifically, we measured microbial biomass carbon (MBC), easily oxidizable OC (EOC), water-soluble OC (WSOC), and OC in water stable aggregates (macroaggregates [250-2000 μm], microaggregates [53-250 μm], and mineral fraction [soil depths. The results showed that GE significantly enhanced EOC and WSOC contents in soils, but caused a decline of MBC at the three decade scale. Macroaggregate content (F = 425.8, P soil aggregates (F = 371.3, P soil increases under three-decade GE with soil organic matter (SOM) stability improving to some extent. Long-term GE practices enhance the formation of soil aggregates through higher SOM input and an exclusion of animal trampling. Therefore, the practice of GE may be further encouraged to realize the soil carbon sequestration potential of semi-arid grasslands, China.

  3. Radial stability and configuration transition of carbon nanotubes regulated by enclosed cores

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Yonggang; He, Haitang; Ye, Hongfei, E-mail: yehf@dlut.edu.cn [State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024 (China)

    2015-05-15

    The radial stability and configuration transition of carbon nanotubes (CNTs) with enclosed cores have been studied in this paper by using atomistic simulations. We found that an abnormal transition of CNTs from open to collapse can be regulated by enclosing deformable and rigid cores. The energy barrier for the configuration transition can be reduced by nearly one order of magnitude due to the presence of these cores, i.e., from ∼0.3 eV/Å to ∼0.03 eV/Å. These findings may provide guidance for the design of controllable CNT-based carrier systems for the delivery of drug, gene and fluid.

  4. Temporal stability of multiple response systems to 7.5% carbon dioxide challenge.

    Science.gov (United States)

    Roberson-Nay, Roxann; Gorlin, Eugenia I; Beadel, Jessica R; Cash, Therese; Vrana, Scott; Teachman, Bethany A

    2017-03-01

    Self-reported anxiety, and potentially physiological response, to maintained inhalation of carbon dioxide (CO2) enriched air shows promise as a putative marker of panic reactivity and vulnerability. Temporal stability of response systems during low-dose, steady-state CO2 breathing challenge is lacking. Outcomes on multiple levels were measured two times, one week apart, in 93 individuals. Stability was highest during the CO2 breathing phase compared to pre-CO2 and recovery phases, with anxiety ratings, respiratory rate, skin conductance level, and heart rate demonstrating good to excellent temporal stability (ICCs≥0.71). Cognitive symptoms tied to panic were somewhat less stable (ICC=0.58) than physical symptoms (ICC=0.74) during CO2 breathing. Escape/avoidance behaviors and DSM-5 panic attacks were not stable. Large effect sizes between task phases also were observed. Overall, results suggest good-excellent levels of temporal stability for multiple outcomes during respiratory stimulation via 7.5% CO2.

  5. Biochar carbon stability in a clayey soil as a function of feedstock and pyrolysis temperature.

    Science.gov (United States)

    Singh, Bhupinder Pal; Cowie, Annette L; Smernik, Ronald J

    2012-11-06

    The stability of biochar carbon (C) is the major determinant of its value for long-term C sequestration in soil. A long-term (5 year) laboratory experiment was conducted under controlled conditions using 11 biochars made from five C3 biomass feedstocks (Eucalyptus saligna wood and leaves, papermill sludge, poultry litter, cow manure) at 400 and/or 550 °C. The biochars were incubated in a vertisol containing organic C from a predominantly C4-vegetation source, and total CO(2)-C and associated δ(13)C were periodically measured. Between 0.5% and 8.9% of the biochar C was mineralized over 5 years. The C in manure-based biochars mineralized faster than that in plant-based biochars, and C in 400 °C biochars mineralized faster than that in corresponding 550 °C biochars. The estimated mean residence time (MRT) of C in biochars varied between 90 and 1600 years. These are conservative estimates because they represent MRT of relatively labile and intermediate-stability biochar C components. Furthermore, biochar C MRT is likely to be higher under field conditions of lower moisture, lower temperatures or nutrient availability constraints. Strong relationships of biochar C stability with the initial proportion of nonaromatic C and degree of aromatic C condensation in biochar support the use of these properties to predict biochar C stability in soil.

  6. Quantitative stability analyses of multiwall carbon nanotube nanofluids following water/ice phase change cycling

    Science.gov (United States)

    Ivall, Jason; Langlois-Rahme, Gabriel; Coulombe, Sylvain; Servio, Phillip

    2017-02-01

    Multiwall carbon nanotube nanofluids are regularly investigated for phase change enhancement between liquid and solid states owing to their improved heat transfer properties. The potential applications are numerous, the most notable being latent heat thermal energy storage, but the success of all nanofluid-assisted technologies hinges greatly on the ability of nanoparticles to remain stably dispersed after repeated phase change cycles. In this report, the stability of aqueous nanofluids made from oxygen-functionalized multiwall carbon nanotubes (f-MWCNTs) was profiled over the course of 20 freeze/thaw cycles. Sonication was used after each cycle to re-disperse clusters formed from the crystallization process. This study offers a quantitative evaluation of f-MWCNT-nanofluid stability as a result of phase change through optical characterization of concentration and particle size. It also provides insight into the integrity of the surface functionalities through zeta potential and XPS analyses. Concentration and particle size measurements showed moderate and consistent recoverability of f-MWCNT dispersion following ultrasonication. XPS measurements of solid-state MWCNTs exposed to freeze/thaw cycling in water, and zeta potential analyses of the nanofluids indicate that the surface oxygen content is preserved throughout phase change and over repeated cycles. These results suggest a resilience of oxygen-functionalized MWCNTs to the freezing and thawing of water, which is ideal for their utilization as phase change enhancers.

  7. Stability, defect and electronic properties of graphane-like carbon-halogen compounds

    Institute of Scientific and Technical Information of China (English)

    Lu Di; Yang Yu-Rong; Xiao Yang; Zhang Xiao-Yu

    2011-01-01

    We perform first-principles total energy calculations to investigate the stabilities and the electronic structures of graphane-like structures of carbon-halogen compounds,where the hydrogen atoms in the graphane are substituted by halogen atoms.Three halogen elements,fluorine (F),chlorine (Cl) and bromine (Br),are considered,and the graphanelike structures are named as CF,CCl and CBr,respectively.It is found that for the single-atom adsorption,only the F adatom can be chemically adsorbed on the graphene.However,the stable graphane-like structures of CF,CCl and CBr can form due to the interaction between the halogen atoms.The carbon atoms in the stable CF,CCl and CBr compounds are in the sp3 hybridization,forming a hexagonal network similar to the graphane.The electronic band calculations show that CF and CCl are semiconductors with band gaps of 3.28 eV and 1.66 eV,respectively,while CBr is a metal.Moreover,the molecular dynamics simulation is employed to clarify the stabilities of CF and CCl.Those two compounds are stable at room temperature.A high temperature (≥ 1200 K) is needed to damage CF,while CCl is destroyed at 700 K.Furthermore,the effects of a vacancy on the structure and the electronic property of CF are discussed.

  8. Molecular dynamics study on core-shell structure stability of aluminum encapsulated by nano-carbon materials

    Science.gov (United States)

    Yi, Qingwen; Xu, Jingcheng; Liu, Yi; Zhai, Dong; Zhou, Kai; Pan, Deng

    2017-02-01

    A ReaxFF reactive forcefield for aluminum-carbon composite system has been developed to investigate structural stability and thermal decomposition mechanism of nano-carbon materials coating aluminum particles. Research results indicated the Al@C particles were structurally stable in a broad temperature range from room temperature up to 2735 K. In particular, the broken carbon cage self-healed to reconstruct a more stable Al@C core-shell structure after Al atoms sequentially departing from carbon cage during thermal decomposition, proffering an effective protection for aluminum surface-activeness.

  9. Polypropylene/Expanded Graphite/Carbon Fiber Thermal Conductive Composite%聚丙烯/膨胀石墨/碳纤维导热复合材料

    Institute of Scientific and Technical Information of China (English)

    徐睿杰; 雷彩红; 杨志广; 廖敦锃; 刘舜莉

    2012-01-01

    The thermal conductivity, mechanical properties and processing property of polypropylene ( PP)/expanded graphite (EG)/carbon fiber(CF) composite were studied. The results showed that the thermal conductivity of the composite with 20 % content of EC was 2 times that of pure PP,but its melt flow rate was decreased. The PE wax at the weight fraction of 1 % could improve the melt flow rate. When the content of carbon fiber was 5 % , the thermal conductivity reached 0.91 W ? M-1K-1 and was five times of pure PP. The melt flow rate was 1.72 g/10 min and the mechanical properties were good.%研究了聚丙烯(PP)/膨胀石墨(EG)/碳纤维(CF)复合材料的导热、力学以及加工性能.研究发现:当膨胀石墨的质量含量达到20%时,热导率是纯聚丙烯的2倍,但熔体流动性能有所下降;添加1%的聚乙烯蜡可以明显改善体系的熔体流动性能;将膨胀石墨与5%的碳纤维杂化使用,热导率达0.91 W·m-1K-1,是纯聚丙烯的5倍,熔体指数达到1.72 g/10 min,同时该复合材料具有较好的力学性能.

  10. Carbon doped PDMS: conductance stability over time and implications for additive manufacturing of stretchable electronics

    Science.gov (United States)

    Tavakoli, Mahmoud; Rocha, Rui; Osorio, Luis; Almeida, Miguel; de Almeida, Anibal; Ramachandran, Vivek; Tabatabai, Arya; Lu, Tong; Majidi, Carmel

    2017-03-01

    Carbon doped PDMS (cPDMS), has been used as a conductive polymer for stretchable electronics. Compared to liquid metals, cPDMS is low cost and is easier to process or to print with an additive manufacturing process. However, changes on the conductance of the carbon based conductive PDMS (cPDMS) were observed over time, in particular after integration of cPDMS and the insulating polymer. In this article we investigate the process parameters that lead to improved stability over conductance of the cPDMS over time. Slight modifications to the fabrication process parameters were conducted and changes on the conductance of the samples for each method were monitored. Results suggested that change of the conductance happens mostly after integration of a pre-polymer over a cured cPDMS, and not after integration of the cPDMS over a cured insulating polymer. We show that such changes can be eliminated by adjusting the integration priority between the conductive and insulating polymers, by selecting the right curing temperature, changing the concentration of the carbon particles and the thickness of the conductive traces, and when possible by changing the insulating polymer material. In this way, we obtained important conclusions regarding the effect of these parameters on the change of the conductance over time, that should be considered for additive manufacturing of soft electronics. Also, we show that these changes can be possibly due to the diffusion from PDMS into cPDMS.

  11. Enhancement of Electrochemical Stability about Silicon/Carbon Composite Anode Materials for Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Wei Xiao

    2015-01-01

    Full Text Available Silicon/carbon (Si/C composite anode materials are successfully synthesized by mechanical ball milling followed by pyrolysis method. The structure and morphology of the composite are characterized by X-ray diffraction and scanning electron microscopy and transmission electron microscope, respectively. The results show that the composite is composed of Si, flake graphite, and phenolic resin-pyrolyzed carbon, and Si and flake graphite are enwrapped by phenolic resin-pyrolyzed carbon, which can provide not only a good buffering matrix but also a conductive network. The Si/C composite also shows good electrochemical stability, in which the composite anode material exhibits a high initial charge capacity of 805.3 mAh g−1 at 100 mA g−1 and it can still deliver a high charge capacity of 791.7 mAh g−1 when the current density increases to 500 mA g−1. The results indicate that it could be used as a promising anode material for lithium ion batteries.

  12. Colloidal stability of carbonate-coated silver nanoparticles in synthetic and natural freshwater.

    Science.gov (United States)

    Piccapietra, Flavio; Sigg, Laura; Behra, Renata

    2012-01-17

    To gain important information on fate, mobility, and bioavailability of silver nanoparticles (AgNP) in aquatic systems, the influence of pH, ionic strength, and humic substances on the stability of carbonate-coated AgNP (average diameter 29 nm) was systematically investigated in 10 mM carbonate and 10 mM MOPS buffer, and in filtered natural freshwater. Changes in the physicochemical properties of AgNP were measured using nanoparticle tracking analysis, dynamic light scattering, and ultraviolet-visible spectroscopy. According to the pH-dependent carbonate speciation, below pH 4 the negatively charged surface of AgNP became positive and increased agglomeration was observed. Electrolyte concentrations above 2 mM Ca(2+) and 100 mM Na(+) enhanced AgNP agglomeration in the synthetic media. In the considered concentration range of humic substances, no relevant changes in the AgNP agglomeration state were measured. Agglomeration of AgNP exposed in filtered natural freshwater was observed to be primarily controlled by the electrolyte type and concentration. Moreover, agglomerated AgNP were still detected after 7 days of exposure. Consequently, slow sedimentation and high mobility of agglomerated AgNP could be expected under the considered natural conditions. A critical evaluation of the different methods used is presented as well.

  13. On the thermal stability of vacancy-carbon complexes in alpha iron.

    Science.gov (United States)

    Terentyev, D; Bonny, G; Bakaev, A; Van Neck, D

    2012-09-26

    In this work we have summarized the available ab initio data addressing the interaction of carbon with vacancy defects in bcc Fe and performed additional calculations to extend the available dataset. Using an ab initio based parameterization, we apply object kinetic Monte Carlo (OKMC) simulations to model the process of isochronal annealing in bcc Fe doped with carbon to compare with experimental data. As a result of this work, we clarify that a binding energy of ~0.65 eV for a vacancy-carbon (V-C) pair fits the available experimental data best. It is found that the V (2)-C complex is less stable than the V-C pair and its dissociation with activation energy of 0.55 + 0.49 eV also rationalizes a number of experimental data where the breakup of V-C complexes was assumed instead. From the summarized ab initio data, the subsequently obtained OKMC results and critical discussion, provided here, we suggest that the twofold interpretation of the V-C binding energy, which is believed to vary between 0.47 and 0.65 eV, depending on the ab initio approximation, should be removed. The stability and mobility of small and presumably immobile SIA clusters formed at stage II is also discussed in the view of experimental data.

  14. CONSIDERATIONS REGARDING THE INFLUENCE OF METALIC IONS OF THE STABILITY OF CARBONATES FROM SOILS

    Directory of Open Access Journals (Sweden)

    D. Bulgariu

    2005-10-01

    Full Text Available The distribution of minor elements in heterogeneous mineral / aqueous solutions systems represent one of important problem, with many applications in environmental geochemistry field. Ours studies was focus on the metal ions distribution in carbonate (CaCO3 / solution systems, from applicability point of view to the estimation of formation conditions and of carbonates stability from soils. On the base of our results obtained by sequential solid / liquid extraction for 17 soil samples and theoretical modeling of CaCO3 / solution systems, and the results from literature we try to develop the McIntire prognosis models and the free Gibbs enthalpy linear correlation model, by the inclusion in calculus relations of distribution coefficients a higher number of factors which effective influenced the thermodynamics and kinetics of interphase distribution processes of metal ions. The established correlations has been used to the estimation of time evolution of carbonate / solution equilibrium under the influence of some metal ions (Cd, Zn, Cu, Pb, Bi, which appear usual as pollutants in soils. The prognosis realized on the base of the established correlations are in agreement with the theoretical modelling results and studies of case for different types of polluted soils with heavy metals.

  15. Carbon Fibers: Reexamination of the Critical Low-Temperature (200-300C) Stabilization of Polyacrylonitrile,

    Science.gov (United States)

    CARBON FIBERS , SYNTHESIS(CHEMISTRY)), (*ACRYLONITRILE POLYMERS, CARBON FIBERS ), SHEETS, CARBON, FILMS, OXIDATION, THERMAL ANALYSIS, CHEMICAL BONDS, INFRARED SPECTRA, MOLECULAR STRUCTURE, HEAT TREATMENT

  16. Stability of Strength and Deformation Characteristics of Expanded Polystyrene (EPS within the Time of Long-Term Investigation of Creep Strain under Permanent Compressive Loading

    Directory of Open Access Journals (Sweden)

    Saulius VAITKUS

    2013-05-01

    Full Text Available The results of investigation of strength (s10 %, scr and deformability (E characteristics of expanded polystyrene specimens are presented. The results are based on the short-term compression in the organization of long-term creep study. For the experiments identical specimens stored 5 years at ambient temperature (23 ±2 °C and relative humidity (50 ±5 % as well specimens after removal long-term loading were used. There were established, that difference between experimental values of stress and initial modulus of tested expanded polystyrene specimens with confidence probability P = 90 % (on-sided test is negligible (random.DOI: http://dx.doi.org/10.5755/j01.ms.19.2.4442

  17. Grazing incidence beam expander

    Energy Technology Data Exchange (ETDEWEB)

    Akkapeddi, P.R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V.K.

    1985-01-01

    A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

  18. The stability of chalk during flooding of carbonated sea water at reservoir in-situ conditions

    Science.gov (United States)

    Nermoen, Anders; Korsnes, Reidar I.; Madland, Merete V.

    2014-05-01

    Injection of CO2 into carbonate oil reservoirs has been proposed as a possible utilization of the captured CO2 due to its capability to enhance the oil recovery. For offshore reservoirs such as Ekofisk and Valhall it has been discussed to alternate the CO2 and sea water injection (WAG) to reduce costs and keep the beneficial effects of both sea water (SSW) and gas injection. Water and CO2 mix to form carbonic acids that enhance the solubility of carbonates, thus a serious concern has been raised upon the potential de-stabilization of the reservoirs during CO2 injection. In this study we focus on how carbonated sea water alters the mechanical integrity of carbonate rocks both to evaluate safety of carbon storage sites and in the planning of production strategies in producing oil fields since enhanced compaction may have both detrimental and beneficial effects. Here we will present results from long term experiments (approx. half year each) performed on Kansas outcrop chalk (38-41% porosity), which serves as model material to understand the physical and chemical interplaying processes taking place in chalk reservoirs. All tests are performed at uni-axial strain conditions, meaning that the confining radial stresses are automatically adjusted to ensure zero radial strain. The tests are performed at in-situ conditions and run through a series of stages that mimic the reservoir history at both Ekofisk and Valhall fields. We observe the strain response caused by the injected brine. The experimental stages are: (a) axial stress build-up by pore pressure depletion to stresses above yield with NaCl-brine which is inert to the chalk; (b) uni-axial creep at constant axial stresses with NaCl-brine; (c) sea water injection; and (d) injection of carbonated water (SSW+CO2) at various mixture concentrations. Two test series were performed in which the pore pressure was increased (re-pressurized) before stage (c) to explore the stress dependency of the fluid induced strain

  19. Radial stability and configuration transition of carbon nanotubes regulated by enclosed cores

    Directory of Open Access Journals (Sweden)

    Yonggang Zheng

    2015-05-01

    Full Text Available The radial stability and configuration transition of carbon nanotubes (CNTs with enclosed cores have been studied in this paper by using atomistic simulations. We found that an abnormal transition of CNTs from open to collapse can be regulated by enclosing deformable and rigid cores. The energy barrier for the configuration transition can be reduced by nearly one order of magnitude due to the presence of these cores, i.e., from ∼0.3 eV/Å to ∼0.03 eV/Å. These findings may provide guidance for the design of controllable CNT-based carrier systems for the delivery of drug, gene and fluid.

  20. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties

    Science.gov (United States)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-05-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ~4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (~60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications.Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability

  1. Mechanical stability of the diamond-like carbon film on nitinol vascular stents under cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun-Jong [Department of Materials Science and Engineering, Seoul National University, Kwan-ak, Seoul 151-744 (Korea, Republic of); Advanced Functional Materials Research Center, Korea Institute of Science and Technology, Seung-buk, Seoul 136-791 (Korea, Republic of); Moon, Myoung-Woon [Future Fusion Technology Laboratory, Korea Institute of Science and Technology, Seung-buk, Seoul 136-791 (Korea, Republic of)], E-mail: mwmoon@kist.re.kr; Lee, Kwang-Ryeol [Future Fusion Technology Laboratory, Korea Institute of Science and Technology, Seung-buk, Seoul 136-791 (Korea, Republic of); Seok, Hyun-Kwang; Han, Seung-Hee [Advanced Functional Materials Research Center, Korea Institute of Science and Technology, Seung-buk, Seoul 136-791 (Korea, Republic of); Ryu, Jae-Woo; Shin, Kyong-Min [Taewoong Medical Inc. Ltd, Gimpo, Gyeonggi 415-873 (Korea, Republic of); Oh, Kyu Hwan [Department of Materials Science and Engineering, Seoul National University, Kwan-ak, Seoul 151-744 (Korea, Republic of)

    2008-12-01

    The mechanical stability of diamond-like carbon (DLC) films coated on nitinol vascular stents was investigated under cyclic loading condition by employing a stent crimping system. DLC films were coated on the vascular stent of a three dimensional structure by using a hybrid ion beam system with rotating jig. The cracking or delamination of the DLC coating occurred dominantly near the hinge connecting the V-shaped segments of the stent where the maximum strain was induced by a cyclic loading of contraction and extension. However the failures were significantly suppressed as the amorphous Si (a-Si) buffer layer thickness increased. Interfacial adhesion strength was estimated from the spalled crack size in the DLC coating for various values of the a-Si buffer layer thickness.

  2. Enhancement of thermal stability of multiwalled carbon nanotubes via different silanization routes

    Energy Technology Data Exchange (ETDEWEB)

    Scheibe, B., E-mail: bscheibe@zut.edu.p [Centre of Knowledge Based Nanomaterials and Technologies, Institute of Chemical and Enviroment Engineering, West Pomeranian University of Technology, Szczecin (Poland); Borowiak-Palen, E.; Kalenczuk, R.J. [Centre of Knowledge Based Nanomaterials and Technologies, Institute of Chemical and Enviroment Engineering, West Pomeranian University of Technology, Szczecin (Poland)

    2010-06-18

    This work presents an effect of two different silanization procedures on thermal and structural properties of oxidized and oxidized followed by sodium borohydrate (NaBH{sub 4}) reduction of multiwalled carbon nanotubes (MWCNTs). Purified sample was oxidized in a mixture of nitric and sulfuric acids in a reflux. An oxidized material was divided into two batches. The first batch underwent a silanization procedure directly, while the second batch was reduced by NaBH{sub 4} treatment prior to the silanization. The silanization experiments were performed: (A) with {gamma}-aminopropyltriethoxysilane (APTES) at room temperature in acetone (pH {approx}7) and (B) with condensated {gamma}-aminopropyltriethoxysilane at 40 {sup o}C in water (pH 4). The extent of the functionalization of the samples after each procedure was examined by Raman spectroscopy. The vibrational properties of the materials were studied via Fourier transform infrared spectroscopy. Boehms titration technique was applied to quantify the amount of the functional groups on MWCNTs. The morphology of the pristine and functionalized carbon nanotubes was exposed to high-resolution transmission electron microscopy analysis. The energy dispersive X-ray (EDX) analysis was used to characterize the elemental composition of each sample. The effect of the silanization process on the thermal properties of MWCNTs was investigated by thermogravimetry analysis. Interestingly, the significant increase of the thermal stability of silanized MWCNTs samples in respect to the pristine MWCNTs was observed.

  3. Longitudinal vibration and stability analysis of carbon nanotubes conveying viscous fluid

    Science.gov (United States)

    Oveissi, Soheil; Toghraie, Davood; Eftekhari, Seyyed Ali

    2016-09-01

    Nowadays, carbon nanotubes (CNT) play an important role in practical applications in fluidic devices. To this end, researchers have studied various aspects of vibration analysis of a behavior of CNT conveying fluid. In this paper, based on nonlocal elasticity theory, single-walled carbon nanotube (SWCNT) is simulated. To investigate and analyze the effect of internal fluid flow on the longitudinal vibration and stability of SWCNT, the equation of motion for longitudinal vibration is obtained by using Navier-Stokes equations. In the governing equation of motion, the interaction of fluid-structure, dynamic and fluid flow velocity along the axial coordinate of the nanotube and the nano-scale effect of the structure are considered. To solve the nonlocal longitudinal vibration equation, the approximate Galerkin method is employed and appropriate simply supported boundary conditions are applied. The results show that the axial vibrations of the nanotubesstrongly depend on the small-size effect. In addition, the fluid flowing in nanotube causes a decrease in the natural frequency of the system. It is obvious that the system natural frequencies reach zero at lower critical flow velocities as the wave number increases. Moreover, the critical flow velocity decreases as the nonlocal parameter increases.

  4. Structure, stability, and motion of dislocations in double-wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    Zhang Kai-Wang; Li Zhong-Qiu; Wu Jian; Peng Xiang-Yang; Tan Xin-Jun; Sun Li-Zhong; Zhong Jian-Xin

    2012-01-01

    In this paper,a novel double-wall carbon nanotube (DWCNT) with both edge and screw dislocations is studied by using the molecular dynamics (MD) method. The differences between two adjacent tubule indexes of armchair and zigzag nanotubes are determined to be 5 and 9,respectively,by taking into account the symmetry,integrality,and thermal stability of the composite structures. It is found that melting first occurs near the dislocations,and the melting temperatures of the dislocated armchair and zigzag DWCNTs are around 2600 K-2700 K.At the premelting temperatures,the shrink of the dislocation loop,which is comprised of edge and screw dislocations,implies that the composite dislocation in DWCNTs has self-healing ability.The dislocated DWCNTs first fracture at the edge dislocations,which induces the entire break in axial tensile test. The dislocated DWCNTs have a smaller fracture strength compared to the perfect DWCNTs.Our results not only match with the dislocation glide of carbon nanotubes (CNTs) in experiments,but also can free from the electron beam radiation under experimental conditions observed by the high resolution transmission electron microscope (HRTEM),which is deemed to cause the motion of dislocation loop.

  5. Structure, stability, and motion of dislocations in double-wall carbon nanotubes

    Science.gov (United States)

    Zhang, Kai-Wang; Li, Zhong-Qiu; Wu, Jian; Peng, Xiang-Yang; Tan, Xin-Jun; Sun, Li-Zhong; Zhong, Jian-Xin

    2012-10-01

    In this paper, a novel double-wall carbon nanotube (DWCNT) with both edge and screw dislocations is studied by using the molecular dynamics (MD) method. The differences between two adjacent tubule indexes of armchair and zigzag nanotubes are determined to be 5 and 9, respectively, by taking into account the symmetry, integrality, and thermal stability of the composite structures. It is found that melting first occurs near the dislocations, and the melting temperatures of the dislocated armchair and zigzag DWCNTs are around 2600 K—2700 K. At the pre-melting temperatures, the shrink of the dislocation loop, which is comprised of edge and screw dislocations, implies that the composite dislocation in DWCNTs has self-healing ability. The dislocated DWCNTs first fracture at the edge dislocations, which induces the entire break in axial tensile test. The dislocated DWCNTs have a smaller fracture strength compared to the perfect DWCNTs. Our results not only match with the dislocation glide of carbon nanotubes (CNTs) in experiments, but also can free from the electron beam radiation under experimental conditions observed by the high resolution transmission electron microscope (HRTEM), which is deemed to cause the motion of dislocation loop.

  6. Iron oxide-decorated carbon for supercapacitor anodes with ultrahigh energy density and outstanding cycling stability.

    Science.gov (United States)

    Guan, Cao; Liu, Jilei; Wang, Yadong; Mao, Lu; Fan, Zhanxi; Shen, Zexiang; Zhang, Hua; Wang, John

    2015-05-26

    Supercapacitor with ultrahigh energy density (e.g., comparable with those of rechargeable batteries) and long cycling ability (>50000 cycles) is attractive for the next-generation energy storage devices. The energy density of carbonaceous material electrodes can be effectively improved by combining with certain metal oxides/hydroxides, but many at the expenses of power density and long-time cycling stability. To achieve an optimized overall electrochemical performance, rationally designed electrode structures with proper control in metal oxide/carbon are highly desirable. Here we have successfully realized an ultrahigh-energy and long-life supercapacitor anode by developing a hierarchical graphite foam-carbon nanotube framework and coating the surface with a thin layer of iron oxide (GF-CNT@Fe2O3). The full cell of anode based on this structure gives rise to a high energy of ∼74.7 Wh/kg at a power of ∼1400 W/kg, and ∼95.4% of the capacitance can be retained after 50000 cycles of charge-discharge. These performance features are superior among those reported for metal oxide based supercapacitors, making it a promising candidate for the next generation of high-performance electrochemical energy storage.

  7. Stabilization of electrical sensing properties of carbon fiber sensors using pre-tensioning approach

    Science.gov (United States)

    Saifeldeen, M. A.; Fouad, N.; Huang, H.; Wu, Z. S.

    2017-01-01

    Owing to fabrication defects in carbon fiber (CF) tows, the unevenness of fiber roves, such as local bends, misalignments, and skewness, results in irregular distribution of the electrical resistance in the transverse direction along the gauge length of a sensor, which affects its performance. In this study, a pre-tension approach was developed according to the creep mechanism of composites to straighten the CFs. In addition, the resin relaxation was controlled by tensioning the fibers during and after hardening of the epoxy resin using a double-tension method to enhance the electrical sensing properties of long gauge carbon fiber line (CFL) strain sensors. Different levels of sustained tensile stresses were studied to obtain the optimal tensile stress level both during and after hardening to be applied in the double-tension method. The results of static and dynamic tests showed that the double-tension technique could significantly straighten the fibers, and stabilize the transverse connections of CFL sensors in the case of tensioning the fibers during and after hardening under a sustained stress of 60% of the ultimate tensile stress of the CFs. The proposed double-tension method was utilized to improve the response of the CFL sensors with short gauge lengths.

  8. Density and stability of soil organic carbon beneath impervious surfaces in urban areas.

    Science.gov (United States)

    Wei, Zongqiang; Wu, Shaohua; Yan, Xiao; Zhou, Shenglu

    2014-01-01

    Installation of impervious surfaces in urban areas has attracted increasing attention due to its potential hazard to urban ecosystems. Urban soils are suggested to have robust carbon (C) sequestration capacity; however, the C stocks and dynamics in the soils covered by impervious surfaces that dominate urban areas are still not well characterized. We compared soil organic C (SOC) densities and their stabilities under impervious surface, determined by a 28-d incubation experiment, with those in open areas in Yixing City, China. The SOC density (0-20 cm) under impervious surfaces was, on average, 68% lower than that in open areas. Furthermore, there was a significantly (Psoils, whereas the correlation was not apparent for the impervious-covered soils, suggesting that the artificial soil sealing in urban areas decoupled the cycle of C and N. Cumulative CO2-C evolved during the 28-d incubation was lower from the impervious-covered soils than from the open soils, and agreed well with a first-order decay model (Ct = C1+C0(1-e-kt)). The model results indicated that the SOC underlying capped surfaces had weaker decomposability and lower turnover rate. Our results confirm the unique character of urban SOC, especially that beneath impervious surface, and suggest that scientific and management views on regional SOC assessment may need to consider the role of urban carbon stocks.

  9. Plant stimulation of soil microbial community succession: how sequential expression mediates soil carbon stabilization and turnover

    Energy Technology Data Exchange (ETDEWEB)

    Firestone, Mary [Univ. of California, Berkeley, CA (United States)

    2015-03-31

    It is now understood that most plant C is utilized or transformed by soil microorganisms en route to stabilization. Hence the composition of microbial communities that mediate decomposition and transformation of root C is critical, as are the metabolic capabilities of these communities. The change in composition and function of the C-transforming microbial communities over time in effect defines the biological component of soil C stabilization. Our research was designed to test 2 general hypotheses; the first two hypotheses are discussed first; H1: Root-exudate interactions with soil microbial populations results in the expression of enzymatic capacities for macromolecular, complex carbon decomposition; and H2: Microbial communities surrounding roots undergo taxonomic succession linked to functional gene activities as roots grow, mature, and decompose in soil. Over the term of the project we made significant progress in 1) quantifying the temporal pattern of root interactions with the soil decomposing community and 2) characterizing the role of root exudates in mediating these interactions.

  10. Surfactant-assisted dispersion of carbon nanotubes: mechanism of stabilization and biocompatibility of the surfactant

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Raman Preet, E-mail: ramanpreetsingh@hotmail.com [Evalueserve SEZ (Gurgaon) Pvt. Ltd. (India); Jain, Sanyog [National Institute of Pharmaceutical Education and Research, Centre for Pharmaceutical Nanotechnology, Department of Pharmaceutics (India); Ramarao, Poduri, E-mail: ramaraop@yahoo.com [Central University of Punjab, School of Basic and Applied Sciences (India)

    2013-10-15

    Nanoparticles (NPs) are thermodynamically unstable system and tend to aggregate to reduce free energy. The aggregation property of NPs results in inhomogeneous exposure of cells to NPs resulting in variable cellular responses. Several types of surfactants are used to stabilize NP dispersions and obtain homogenous dispersions. However, the effects of these surfactants, per se, on cellular responses are not completely known. The present study investigated the application of Pluronic F68 (PF68) for obtaining stable dispersion of NPs using carbon nanotubes as model NPs. PF68-stabilized NP suspensions are stable for long durations and do not show signs of aggregation or settling during storage or after autoclaving. The polyethylene oxide blocks in PF68 provide steric hindrance between adjacent NPs leading to stable NP dispersions. Further, PF68 is biocompatible in nature and does not affect integrity of mitochondria, lysosomes, DNA, and nuclei. Also, PF68 neither induce free radical or cytokine production nor does it interfere with cellular uptake mechanisms. The results of the present study suggest that PF68-assisted dispersion of NPs produced suspensions, which are stable after autoclaving. Further, PF68 does not interfere with normal physiological functions suggesting its application in nanomedicine and nanotoxicity evaluation.

  11. Binding energy and mechanical stability of single- and multi-walled carbon nanotube serpentines

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Junhua, E-mail: junhua.zhao@163.com, E-mail: timon.rabczuk@uni-weimar.de [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, 214122 Wuxi (China); Institute of Structural Mechanics, Bauhaus University, 99423 Weimar (Germany); Lu, Lixin [Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment and Technology, Jiangnan University, 214122 Wuxi (China); Rabczuk, Timon, E-mail: junhua.zhao@163.com, E-mail: timon.rabczuk@uni-weimar.de [Institute of Structural Mechanics, Bauhaus University, 99423 Weimar (Germany)

    2014-05-28

    Recently, Geblinger et al. [Nat. Nanotechnol. 3, 195 (2008)] and Machado et al. [Phys. Rev. Lett. 110, 105502 (2013)] reported the experimental and molecular dynamics realization of S-like shaped single-walled carbon nanotubes (CNTs), the so-called CNT serpentines. We reported here results from continuum modeling of the binding energy γ between different single- and multi-walled CNT serpentines and substrates as well as the mechanical stability of the CNT serpentine formation. The critical length for the mechanical stability and adhesion of different CNT serpentines are determined in dependence of E{sub i}I{sub i}, d, and γ, where E{sub i}I{sub i} and d are the CNT bending stiffness and distance of the CNT translation period. Our continuum model is validated by comparing its solution to full-atom molecular dynamics calculations. The derived analytical solutions are of great importance for understanding the interaction mechanism between different single- and multi-walled CNT serpentines and substrates.

  12. Unveiling Stability Criteria of DNA-Carbon Nanotubes Constructs by Scanning Tunneling Microscopy and Computational Modeling

    Directory of Open Access Journals (Sweden)

    Svetlana Kilina

    2011-01-01

    Full Text Available We present a combined approach that relies on computational simulations and scanning tunneling microscopy (STM measurements to reveal morphological properties and stability criteria of carbon nanotube-DNA (CNT-DNA constructs. Application of STM allows direct observation of very stable CNT-DNA hybrid structures with the well-defined DNA wrapping angle of 63.4° and a coiling period of 3.3 nm. Using force field simulations, we determine how the DNA-CNT binding energy depends on the sequence and binding geometry of a single strand DNA. This dependence allows us to quantitatively characterize the stability of a hybrid structure with an optimal π-stacking between DNA nucleotides and the tube surface and better interpret STM data. Our simulations clearly demonstrate the existence of a very stable DNA binding geometry for (6,5 CNT as evidenced by the presence of a well-defined minimum in the binding energy as a function of an angle between DNA strand and the nanotube chiral vector. This novel approach demonstrates the feasibility of CNT-DNA geometry studies with subnanometer resolution and paves the way towards complete characterization of the structural and electronic properties of drug-delivering systems based on DNA-CNT hybrids as a function of DNA sequence and a nanotube chirality.

  13. Synthesis of length-controlled aerosol carbon nanotubes and their dispersion stability in aqueous solution.

    Science.gov (United States)

    Moon, Young Kyun; Lee, Jaebeom; Lee, Jae Keun; Kim, Tae Kyu; Kim, Soo H

    2009-02-03

    A one-step method combining spray pyrolysis and thermal chemical vapor deposition (CVD) processes was developed to grow hybrid carbon nanotube (CNT)-bimetallic composite particles. Nickel, aluminum, and acetylene were used as the catalytic site, noncatalytic matrix, and hydrocarbon source, respectively. The bimetallic particles (i.e., Al-Ni) were spray pyrolized and subsequently passed through thermal CVD. During the thermal CVD, the catalytic decomposition of acetylene occurred on the free-floating bimetallic particles so that sea urchin-like CNTs were radially grown. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed the CNTs to have a uniform diameter of approximately 10 +/- 2 nm. The length of the CNTs was controlled by varying the residence time of the bimetallic nanoparticles with a length of 200-1000 nm. After nitric acid treatment, the CNTs were released by melting the bimetallic particles. The resulting CNTs were then dispersed in an aqueous solution to examine the effect of the length of CNTs on their dispersion stability, which is a critical issue for the stability and repeatability of the heat transfer performance in nanofluids. Ultraviolet-visible (UV-vis) spectrometer analysis showed that shorter CNTs were less stable than the longer CNTs due to the higher mobility-induced agglomeration of the shorter CNTs.

  14. Comparison of properties of traditional and accelerated carbonated solidified/stabilized contaminated soils

    Institute of Scientific and Technical Information of China (English)

    LIU Jiangying; XU Dimin; XIONG Lan; Colin HILLS; Paula CAREY; Kevin GARDNER

    2008-01-01

    The investigation of the long-term performance of solidified/stabilized (S/S) contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties (e. g. , degree of carbonation (DOC), pH, electrical conductivity (EC)) and physical properties (e. g. , moisture content (MC), liquid limit (LL), plastic limit (PL), plasticity index (PI)) of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology (ACT), and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e. g. , treatment with ordinary portland cement (OPC) or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order: the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order.

  15. Stability of organic carbon accumulating in Spartina alterniflora-dominated salt marshes of the Mid-Atlantic U.S.

    Science.gov (United States)

    Unger, Viktoria; Elsey-Quirk, Tracy; Sommerfield, Christopher; Velinsky, David

    2016-12-01

    Organic carbon sequestration in salt marsh soils is a function of factors that influence both spatial variability and chemical stability of accumulating carbon. Refractory carbon (slowly decomposed) may be the most important in terms of long-term sequestration and is widely referred to in models of carbon storage; however, little information exists about the quantity and variability of refractory carbon accumulation in marshes. In this study, total (CT), labile (CL) and refractory (CR) organic carbon accumulation rates were measured for Spartina alterniflora-dominated marshes representing different geomorphological settings with a range of vertical accretion rates. Three 50-cm long cores were collected in each of three marshes in Barnegat Bay and three marshes in Delaware Estuary, USA. Rates of C accumulation were calculated using Cesium-137 dating and the relative stability of soil organic carbon was quantified using acid-hydrolysis. CT accumulation ranged over fourfold among marshes from 72 to 346 g m-2 yr-1. CT and CL accumulation increased with increasing mineral sediment accumulation, while CR accumulation was uniform across cores averaging 78 ± 5 g m-2 yr-1. Similar rates of CR accumulation across marsh areas with different accretion and mineral sediment accumulation rates was associated with a decline in the CR:CL density ratio as mineral volume increased. Our results suggest that carbon accumulation is higher in salt marshes with higher mineral sedimentation due, primarily, to the burial of labile carbon, and that there is a limit on the rate of chemically recalcitrant carbon accumulation in marsh soils.

  16. Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

    NARCIS (Netherlands)

    van Haasterecht, T.; Ludding, C.C.I.; de Jong, K.P.; Bitter, J.H.

    2013-01-01

    Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 ◦C, autogenous pressure, batch reactor). The initial surface-specific activities

  17. Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol

    NARCIS (Netherlands)

    Haasterecht, van T.; Ludding, C.C.I.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 ¿, autogenous pressure, batch reactor). The initial surface-specific activities

  18. Stability of retained austenite in high carbon steel under compressive stress: an investigation from macro to nano scale

    Science.gov (United States)

    Hossain, R.; Pahlevani, F.; Quadir, M. Z.; Sahajwalla, V.

    2016-10-01

    Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels’ performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.

  19. Stability of retained austenite in high carbon steel under compressive stress: an investigation from macro to nano scale.

    Science.gov (United States)

    Hossain, R; Pahlevani, F; Quadir, M Z; Sahajwalla, V

    2016-10-11

    Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels' performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.

  20. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  1. XPS Study on the Stability and Transformation of Hydrate and Carbonate Phases within MgO Systems

    Directory of Open Access Journals (Sweden)

    Vanessa Rheinheimer

    2017-01-01

    Full Text Available MgO cements have great potential for carbon sequestration as they have the ability to carbonate and gain strength over time. The hydration of reactive MgO occurs at a similar rate as ordinary Portland cement (PC and forms brucite (Mg(OH2, magnesium hydroxide, which reacts with CO2 to form a range of hydrated magnesium carbonates (HMCs. However, the formation of HMCs within the MgO–CO2–H2O system depends on many factors, such as the temperature and CO2 concentration, among others, which play an important role in determining the rate and degree of carbonation, the type and stability of the produced HMCs and the associated strength development. It is critical to understand the stability and transformation pathway of HMCs, which are assessed here through the use of X-ray photoelectron spectroscopy (XPS. The effects of the CO2 concentration (in air or 10% CO2, exposure to high temperatures (up to 300 °C and curing period (one or seven days are reported. Observed changes in the binding energy (BE indicate the formation of different components and the transformation of the hydrated carbonates from one form to another, which will influence the final performance of the carbonated blends.

  2. Enhanced cycle stability of micro-sized Si/C anode material with low carbon content fabricated via spray drying and in situ carbonization

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dingsheng; Gao, Mingxia, E-mail: gaomx@zju.edu.cn; Pan, Hongge; Liu, Yongfeng; Wang, Junhua; Li, Shouquan; Ge, Hongwei

    2014-08-01

    Highlights: • Micro-sized Si/C composites were fabricated via. spray drying and carbonization. • Multi-morphology carbon was formed in the Si/C composites. • Si/C composite with 5.6 wt.% C provides significant improved cycling stability. • Multi-morphology carbon plays effective role in improving the electrochemical property. • The method provides potential for mass production of superior Si-based anode materials. - Abstract: Micro-sized Si/C composites with in situ introduced carbon of multi-morphology were fabricated via spray drying a suspension of commercial micro-sized Si and citric acid followed by a carbonization. Different ratios of Si to citric acid were used to optimize the composition and structure of the composites and thus the electrochemical performance. Carbon flakes including crooked and flat ones were well dispersed in between the Si particles, forming Si/C composites. Floc-like carbon layers and carbon fragments were also found to cover partially the Si particles. The Si/C composite with a low carbon content of 5.6 wt.% provides an initial reversible capacity of 2700 mA h/g and a capacity of 1860 mA h/g after 60 cycles at a current density of 100 mA/g as anode material for lithium-ion batteries (LIBs), which are much higher than those of pristine Si and the Si/C composites with higher carbon content. The mechanism of the enhancement of electrochemical performance of the micro-sized Si/C composite is discussed. The fabrication method and the structure design of the composites offer valuable potential in developing adaptable Si-based anode materials for industrial applications.

  3. Stabilization of carbon-fiber cold field-emission cathodes with a dielectric coating.

    Science.gov (United States)

    Mousa, M S; Kelly, T F

    2003-01-01

    A comprehensive investigation has been carried out to determine the source of an inherent temporal instability in the spatial distribution and the electron emission current obtained from field-emitting carbon fiber tips. These instability effects were successfully overcome by coating the tip with a sub-micron layer of dielectric epoxy resin coating. The influence of the coating thickness was studied and an optimum thickness of 0.2-0.3 microm that produced high emission stability was found. A large reduction in the intensity fluctuations of the emission image, at this coating thickness is demonstrated by using chart recorder traces in addition to slow scans of an optically monitored screen signal. The current-voltage (I-V) characteristics were obtained at a threshold field that is a few times lower than that of the uncoated tip. At low emission current levels linear F-N plots were obtained with a slope value lower than that of the uncoated emitter. The spatial distribution consisted of a very bright spot without any internal structure. The total energy distribution of the emitted electrons demonstrated a non-metallic behavior. The spectra obtained consisted of a single peak for low currents and a double peak for higher currents. The electron energy was measured relative to the Fermi level of tungsten and a spectral shift was shown to be a function of the current. Experiments have shown that the coated tips are not affected by the variations of pressure conditions down to 10(-6) mbar. These results suggest that a resin coated fiber tip offers superior performance to tungsten as a cold field emission electron source. Numerous improvements in the performance are underway. This includes a variety of polymeric coatings and more emissive carbon fibers.

  4. High temperature ultralow water content carbon dioxide-in-water foam stabilized with viscoelastic zwitterionic surfactants.

    Science.gov (United States)

    Alzobaidi, Shehab; Da, Chang; Tran, Vu; Prodanović, Maša; Johnston, Keith P

    2017-02-15

    Ultralow water content carbon dioxide-in-water (C/W) foams with gas phase volume fractions (ϕ) above 0.95 (that is foams may be stabilized with viscoelastic aqueous phases formed with a single zwitterionic surfactant at a concentration of only 1% (w/v) in DI water and over a wide range of salinity. Moreover, they are stable with a foam quality ϕ up to 0.98 even for temperatures up to 120°C. The properties of aqueous viscoelastic solutions and foams containing these solutions are examined for a series of zwitterionic amidopropylcarbobetaines, R-ONHC3H6N(CH3)2CH2CO2, where R is varied from C12-14 (coco) to C18 (oleyl) to C22 (erucyl). For the surfactants with long C18 and C22 tails, the relaxation times from complex rheology indicate the presence of viscoelastic wormlike micelles over a wide range in salinity and pH, given the high surfactant packing fraction. The apparent viscosities of these ultralow water content foams reached more than 120cP with stabilities more than 30-fold over those for foams formed with the non-viscoelastic C12-14 surfactant. At 90°C, the foam morphology was composed of ∼35μm diameter bubbles with a polyhedral texture. The apparent foam viscosity typically increased with ϕ and then dropped at ϕ values higher than 0.95-0.98. The Ostwald ripening rate was slower for foams with viscoelastic versus non-viscoelastic lamellae as shown by optical microscopy, as a consequence of slower lamellar drainage rates. The ability to achieve high stabilities for ultralow water content C/W foams over a wide temperature range is of interest in various technologies including polymer and materials science, CO2 enhanced oil recovery, CO2 sequestration (by greater control of the CO2 flow patterns), and possibly even hydraulic fracturing with minimal use of water to reduce the requirements for wastewater disposal.

  5. Metal organic frameworks/macroporous carbon composites with enhanced stability properties and good electrocatalytic ability for ascorbic acid and hemoglobin.

    Science.gov (United States)

    Zhang, Yufan; Nsabimana, Anaclet; Zhu, Liande; Bo, Xiangjie; Han, Ce; Li, Mian; Guo, Liping

    2014-11-01

    The thermal, water and electrochemical stability of Cu-based metal organic frameworks (Cu-MOFs) confined in macroporous carbon (MPC) hybrids has been investigated. Thermogravimetric analyses, X-Ray diffraction, scanning electron microscopy, and cyclic voltammetry were employed to confirm the stability of pure Cu-MOFs, MPC, and Cu-MOFs-MPC. As compared to pure Cu-MOFs, the porous composite materials of MPC and Cu-MOFs interact and seem to form new materials having homogenous structure and chemistry, which show structural stability in aqueous media and electrochemical stability in phosphate buffer solution (PBS pH 7.4). The detection of ascorbic acid and hemoglobin is performed as an electrochemical probe, indicating Cu-MOFs-MPC holds great promise for the design of electrochemical sensors.

  6. Performance and Stability of Supercapacitor Modules based on Porous Carbon Electrodes in Hybrid Powertrain

    Institute of Scientific and Technical Information of China (English)

    GONG Xuan; XIE Changjun; ZOU Yaohui; QUAN Shuhai; PIOTR Bujlo; SHEN Di

    2014-01-01

    Hybrid power sources have attracted much attention in the electric vehicle area. Particularly, electric-electric hybrid powertrain system consisting of supercapacitor modules and lithium-ion batteries has been widely applied because of the high power density of supercapacitors. In this study, we design a hybrid powertrain system containing two porous carbon electrode-based supercapacitor modules in parallel and one lithium ion battery pack. With the construction of the testing station, the performance and stability of the used supercapacitor modules are investigated in correlation with the structure of the supercapacitor and the nature of the electrode materials applied. It has been shown that the responding time for voltage vibration from 20 V to 48.5 V during charging or discharging process decreases from about 490 s to 94 s with the increase in applied current from 20 A to 100 A. The capacitance of the capacitor modules is nearly independent on the applied current. With the designed setup, the energy efficiency can reach as high as 0.99. The results described here provide a guidance for material selection of supercapacitors and optimized controlling strategy for hybrid power system applied in electric vehicles.

  7. Long term stabilization of reaction center protein photochemistry by carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Magyar, Melinda; Hajdu, Kata; Szabo, Tibor; Nagy, Laszlo [Department of Medical Physics and Informatics, University of Szeged, 6720 Szeged (Hungary); Hernadi, Klara [Department of Applied and Environmental Chemistry, University of Szeged, 6720 Szeged (Hungary); Dombi, Andras [Institute of Material Sciences and Engineering, University of Szeged, 6701 Szeged (Hungary); Horvath, Endre; Magrez, Arnaud; Forro, Laszlo [Institute of Physics of Complex Matter, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)

    2011-11-15

    The long term stability and the redox interaction between single walled carbon nanotubes (SWNTs) and photosynthetic reaction center proteins (RCs) purified from purple bacterium Rhodobacter sphaeroides R-26 in the SWNT/RC complex has been investigated. The binding of SWNT to RC results in an accumulation of positive (the oxidized primary electron donor, P{sup +}) and negative (semiquinone forms, Q{sup -}{sub A} and Q{sup -}{sub B}, the reduced primary and secondary quinones, respectively) charges followed by slow reorganization of the protein structure after excitation. The photochemical activity of the SWNT/RC complexes remains stable for several weeks even in dried form. In the absence of SWNT the secondary quinone activity decays quickly as a function of time after drying the RC onto a glass surface. Polarography measurements substantiate the idea that there is an electronic interaction between the RCs and SWNTs after light excitation, which was suggested earlier by optical measurements. The special electronic properties of the SWNT/protein complexes open the possibility for several applications, e.g., in microelectronics, analytics, or energy conversion and storage. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Shear instabilities in metallic nanoparticles: hydrogen-stabilized structure of Pt37 on carbon.

    Science.gov (United States)

    Wang, Lin-Lin; Johnson, D D

    2007-03-28

    Using density functional theory calculations, we have studied the morphology of a Pt37 nanoparticle supported on carbon with and without hydrogen (H) passivation that arises with postprocessing of nanoparticles before characterization. Upon heating in an anneal cycle, we find that without H (e.g., in a helium atmosphere or evacuation at high temperature), the morphology change of a truncated cuboctahedral Pt37 is driven by the shearing of (100) to (111) facets to lower the surface energy, a remnant shear instability that drives surface reconstruction in semi-infinite Pt(100). With H passivation from a postprocessing anneal, we show that the sheared structure automatically reverts to the observed truncated cuboctahedral structure and the average first nearest-neighbor Pt-Pt bond length increases by 3%, agreeing well with experiment. We explain the stabilization of the truncated cuboctahedral structure due to H passivation via adsorption energetics of hydrogen on Pt(100) and (111) facets, specifically, the preference for H adsorption at bridge sites on (100) facets, which should be considered in a realistic model for H adsorption on Pt nanoparticles. We find that dramatic morphological change of a nanoparticle can occur even with small changes to first-shell Pt-Pt coordination number. The implications of our findings when comparing to experimental data are discussed.

  9. Biochar affects carbon composition and stability in soil: a combined spectroscopy-microscopy study

    Science.gov (United States)

    Hernandez-Soriano, Maria C.; Kerré, Bart; Kopittke, Peter M.; Horemans, Benjamin; Smolders, Erik

    2016-04-01

    The use of biochar can contribute to carbon (C) storage in soil. Upon addition of biochar, there is a spatial reorganization of C within soil particles, but the mechanisms remain unclear. Here, we used Fourier transformed infrared-microscopy and confocal laser scanning microscopy to examine this reorganization. A silty-loam soil was amended with three different organic residues and with the biochar produced from these residues and incubated for 237 d. Soil respiration was lower in biochar-amended soils than in residue-amended soils. Fluorescence analysis of the dissolved organic matter revealed that biochar application increased a humic-like fluorescent component, likely associated with biochar-C in solution. The combined spectroscopy-microscopy approach revealed the accumulation of aromatic-C in discrete spots in the solid-phase of microaggregates and its co-localization with clay minerals for soil amended with raw residue or biochar.The co-localization of aromatic-C:polysaccharides-C was consistently reduced upon biochar application. We conclude that reduced C metabolism is an important mechanism for C stabilization in biochar-amended soils.

  10. Economic Stability to Papua New Guinea by Contribution in Reducing Carbon Emissions through Support of DC

    Directory of Open Access Journals (Sweden)

    Eshan Ahuja,

    2014-07-01

    Full Text Available Papua New Guinea is said to be PNG which is one of the most adversely affected small country by the impacts of climate change. Climate Change is one of the biggest challenges facing by them today, its devastation is widespread and intense. This issue has been discussed to evolve a method to support the nation in achieving the goal of emission reduction. The affects include those on Agriculture, Fisheries, Forestry and Tourism which have major contribution towards GDP of the PNG. PNG has a very low economic growth rate according to several economic and social indicators, the performance of the PNG economy since independence has been disappointing. Thus, there is need of taking special attention & responsibilities by giving cooperation by the nations. This is to be done by especially developed ones so as to support the small island nations in adaptation to the impacts of climate change through financial support. Through this act, the Least Developed Countries will achieve economic stability as well as imparting in reduction of carbon emissions. This paper discusses to find a path and sort out the issue. The paper also discusses various negotiating points so as to achieve the said goal mutually and amicably.

  11. Activity and stability of immobilized carbonic anhydrase for promoting CO2 absorption into a carbonate solution for post-combustion CO2 capture

    Science.gov (United States)

    Zhang, S.; Zhang, Z.; Lu, Y.; Rostam-Abadi, M.; Jones, A.

    2011-01-01

    An Integrated Vacuum Carbonate Absorption Process (IVCAP) currently under development could significantly reduce the energy consumed when capturing CO2 from the flue gases of coal-fired power plants. The biocatalyst carbonic anhydrase (CA) has been found to effectively promote the absorption of CO2 into the potassium carbonate solution that would be used in the IVCAP. Two CA enzymes were immobilized onto three selected support materials having different pore structures. The thermal stability of the immobilized CA enzymes was significantly greater than their free counterparts. For example, the immobilized enzymes retained at least 60% of their initial activities after 90days at 50??C compared to about 30% for their free counterparts under the same conditions. The immobilized CA also had significantly improved resistance to concentrations of sulfate (0.4M), nitrate (0.05M) and chloride (0.3M) typically found in flue gas scrubbing liquids than their free counterparts. ?? 2011 Elsevier Ltd.

  12. Dynamic Relationship Between Biologically Active Soil Organic Carbon and Aggregate Stability in Long-Term Organically Fertilized Soils

    Institute of Scientific and Technical Information of China (English)

    LI Cheng-Liang; XU Jiang-Bing; HE Yuan-Qiu; LIU Yan-Li; FAN Jian-Bo

    2012-01-01

    Biologically active soil organic carbon (BASOC) is an important fraction of soil organic carbon (SOC),but our understanding of the correlation between BASOC and soil aggregate stability is limited.At an ecological experimental station (28° 04′-28° 37′ N,116°41′-117° 09′ E) in Yujiang County,Jiangxi Province,China,we analyzed the dynamic relationship between soil aggregate stability and BASOC content over time in the red soil (Udic Ferrosols) fertilized with a nitrogen-phosphorus-potassium chemical fertilizer (NPK)without manure or with NPK plus livestock manure or green manure.The dynamics of BASOC was evaluated using CO2 efflux,and soil aggregates were separated according to size using a wet-sieving technique.The soils fertilized with NPK plus livestock manure had a significantly higher content of BASOC and an improved aggregate stability compared to the soils fertilized with NPK plus green manure or NPK alone The BASOC contents in all fertilized soils decreased over time The contents of large aggregates (800-2000μm) dramatically decreased over the first 7 d of incubation,but the contents of small aggregates (< 800.μm) either remained the same or increased,depending on the incubation time and specific aggregate sizes.The aggregate stability did not differ significantly at the beginning and end of incubation,but the lowest stability inall fertilized soils occurred in the middle of the incubation,which implied that the soils had a strong resilience for aggregate stability.The change in BASOC content was only correlated with aggregate stability during the first 27 d of incubation.

  13. Development and validation of a stability-indicating LC method for the assay of lodenafil carbonate in tablets.

    Science.gov (United States)

    Codevilla, Cristiane Franco; Lemos, Alice Machado; Delgado, Leila Schreiner; Rolim, Clarice Madalena Bueno; Adams, Andréa Inês Horn; Bergold, Ana Maria

    2011-08-01

    A stability-indicating liquid chromatographic method has been developed for the quantitative determination of lodenafil carbonate in tablets. The method employs a Synergi Fusion C18 column (250 × 4.6 mm, i.d., 4 μm particle size), with mobile phase consisting of a mixture of methanol-acetic acid 0.1% pH 4.0 (65:35, v/v) and UV detection at 290 nm, using a photodiode array detector. A linear response (r = 0.9999) was observed in the range of 10-80 μg/mL. The method showed good recoveries (average 100.3%) and also intra and inter-day precision (RSD method was found to be stability-indicating and due to its simplicity and accuracy can be applied for routine quality control analysis of lodenafil carbonate in tablets.

  14. Chapter 1. Bending the Curve: Ten Scalable Solutions for Carbon Neutrality and Climate Stability

    Directory of Open Access Journals (Sweden)

    V. Ramanathan

    2016-12-01

    Full Text Available We are living in a world of over seven billion people, with annual greenhouse gas emissions of approximately 50 billion tons a year and rising steadily. If continued unabated, the world is on target to warm by about 2 °C in less than 40 years, pushing the climate to a regime unlike any that has been witnessed in the last million years. Nonetheless, we still have time to avert such a catastrophic scenario, or delay its occurrence by several decades to provide human societies and the ecosystem with the time to adjust. In order to mitigate the possibility of climate disruption, we need to recognize that fossil fuel based technologies have become outdated and transform the energy system to that of low-carbon, sustainable and secure energy systems. In addition, we have to mitigate emissions of the four short-lived climate pollutants to bring immediate relief from climate change and protect vulnerable societies. Stability of the climate system involves not only the centrality of scientific and technological advancements and investments, but also necessary shifts in social structure and behavior by individuals, communities and societies worldwide as well as market based instruments, sub-national collaborations and governance structure. Fortunately, living laboratories—such as the State of California and the University of California system, which has pledged to become carbon neutral by 2025—provide demonstrable solutions which hold promise in alleviating the climate warming in the next generation. These jurisdictions are tiny emitters in the global picture, but they offer the potential for leverage through demonstrating (Figure 1 new technologies as well as workable institutions that cut emissions. We outline 10 pragmatic solutions—a “kit of parts” rooted in California but scalable to the world—that taken together, can “bend the curve” of the upward trajectory of human-caused warming trends. Wholesale transformation of our current

  15. Soil Organic Matter Stability and Soil Carbon Storage with Changes in Land Use Intensity in Uganda

    Science.gov (United States)

    Tiemann, L. K.; Grandy, S.; Hartter, J.

    2014-12-01

    As the foundation of soil fertility, soil organic matter (SOM) formation and break-down is a critical factor of agroecosystem sustainability. In tropical systems where soils are quickly weathered, the link between SOM and soil fertility is particularly strong; however, the mechanisms controlling the stabilization and destabilization of SOM are not well characterized in tropical soils. In western Uganda, we collected soil samples under different levels of land use intensity including maize fields, banana plantations and inside an un-cultivated native tropical forest, Kibale National Park (KNP). To better understand the link between land use intensity and SOM stability we measured total soil C and N, and respiration rates during a 369 d soil incubation. In addition, we separated soils into particle size fractions, and mineral adsorbed SOM in the silt (2-50 μm ) and clay (characterized via pyrolysis-GC/MS. Cultivated soil C and N have declined by 22 and 48%, respectively, in comparison to uncultivated KNP soils. Incubation data indicate that over the last decade, relatively accessible and labile soil organic carbon (SOC) pools have been depleted by 55-59% in cultivated soils. As a result of this depletion, the chemical composition of SOM has been altered such that clay and silt associated SOM differed significantly between agricultural fields and KNP. In particular, nitrogen containing compounds were in lower abundance in agricultural compared to KNP soils. This suggests that N depletion due to agriculture has advanced to pools of mineral associated organic N that are typically protected from break-down. In areas where land use intensity is relatively greater, increases in polysaccharides and lipids in maize fields compared to KNP indicate increases in microbial residues and decomposition by-products as microbes mine SOM for organic N. Chemical characterization of post-incubation SOM will help us better understand how microbes preferentially break-down SOM

  16. Pronounced Hysteresis and High Charge Storage Stability of Single-Walled Carbon Nanotube-Based Field-Effect Transistors

    OpenAIRE

    Wang, S.G.; Sellin, P.

    2005-01-01

    In this letter, pronounced hysteresis loops were observed in single-walled carbon nanotube-based field-effect transistors (CNTFETs). The shift in threshold voltage was found to increase with increasing gate voltage sweep ranges. A significant enhancement in the charge storage stability over 14 days was obtained at room temperature after a two-stage hydrogen and air annealing process was applied to the CNTFETs. The passivation of interface traps by annealing in hydrogen and the removal of phys...

  17. Degradation of lindane and hexachlorobenzene in supercritical carbon dioxide using palladium nanoparticles stabilized in microcellular high-density polyethylene.

    Science.gov (United States)

    Wu, Bei-Zen; Chen, GuanYu; Yak, HwaKwang; Liao, Weisheng; Chiu, KongHwa; Peng, Shie-Ming

    2016-06-01

    Palladium nanoparticles stabilized in microcellular high-density polyethylene prepared through supercritical foaming, supercritical impregnation, and H2 reduction are used for the hydrodechlorination of lindane and hexachlorobenzene in supercritical carbon dioxide below 100 °C. Both lindane and hexachlorobenzene can be almost 100% transformed to cyclohexane in 1 h. Reaction intermediates, such as lower chlorinated products or benzene, are not observed or exist in trace amount indicating that most of them may undergo reactions without leaving the metal surface.

  18. Radial deformation and stability of single-wall carbon nanotubes under hydrostatic pressure

    Science.gov (United States)

    Hasegawa, Masayuki; Nishidate, Kazume

    2006-09-01

    In this paper we have developed a theory of energetics for isolated single-wall carbon nanotubes (SWNTs) deformed in the radial direction, and applied this theory to investigate their deformation characteristics and stability under hydrostatic pressure. The starting point of the theory is the strain energy of SWNTs predicted by ab initio calculations based on the density functional theory (DFT), which shows the same behavior as that obtained for the continuum elastic shell model. We extend this result for inflated SWNTs with circular cross section to calculate the deformation energy of a deformed SWNT without performing further DFT calculations. This extension is then complemented by a van der Waals interaction, which is not fully taken into account in the DFT approximations currently in use but becomes important in highly deformed tubes. We find that the minimum pressure, P1 , for the radial deformation to occur is proportional to the inverse cube of tube diameter, D , in agreement with the recent theoretical predictions as well as the classical theory of buckling. The radial deformation of SWNTs with Dpressure and they hardly collapse. On the other hand, SWNTs with D>2.5nm show a plastic deformation and collapse if the applied hydrostatic pressure exceeds a critical value, which is about 30 40% higher than P1 and also varies as D-3 though approximately. These SWNTs with large D collapse when the cross-sectional area is about 60% reduced with respect to the circular one. It is also found that for SWNTs with D>7.0nm , the plastically deformed (collapsed) state is more stable than the inflated one. This critical value of D is somewhat larger than previously predicted.

  19. Electrochemical behaviour of ceramic yttria stabilized zirconia on carbon steel synthesized via sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Crespo, M.A. Dominguez, E-mail: mdominguezc@ipn.m [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Murillo, A. Garcia; Torres-Huerta, A.M. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Yanez-Zamora, C. [Estudiante del postgrado en Tecnologia Avanzada del CICATA-IPN, Unidad Altamira, km 14.5, Carr. Tampico-Puerto Industrial. C.P. 89600, Altamira, Tamaulipas (Mexico); Carrillo-Romo, F. de J [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico)

    2009-08-26

    Chromate conversion coatings have been widely applied for the corrosion of different metallic substrates. However, the waste containing Cr{sup 6+} has many limitations due to the environmental consideration and health hazards. An interesting alternative seems to be the deposition on metallic surface of thin layers of yttria or zirconia or both by the sol-gel process. In this study, Ytttria and Yttria stabilized zirconia (YSZ, 8% Y{sub 2}O{sub 3}) thin films were used for coating commercial carbon steel substrates by sol-gel method and the dip-coating process. The evolution of organic compounds up to crystallization process as a function of heat treatments was study by FT-IR spectroscopy. The structure and morphology of the coatings were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The anticorrosion performance of the coatings has been evaluated by using electrochemical techniques in an aggressive media (3.5 wt.% NaCl). The corrosion behaviour of sol-gel method was compared with traditional chromate conversion coatings. Differences in the electrochemical behaviour of YSZ coatings are related to the development of microcracks during the sintering process and to the presence of organic compounds during growth film. Electrochemical results showed that sol-gel YSZ and Y{sub 2}O{sub 3} coatings can act as protective barriers against wet corrosion; however yttria films displayed low adhesion to substrate. The corrosion parameters provide an explanation of the role of each film and show a considerable increase in the corrosion resistance for coated samples in comparison to the bare steel samples.

  20. Dissolution and storage stability of nanostructured calcium carbonates and phosphates for nutrition

    Science.gov (United States)

    Posavec, Lidija; Knijnenburg, Jesper T. N.; Hilty, Florentine M.; Krumeich, Frank; Pratsinis, Sotiris E.; Zimmermann, Michael B.

    2016-10-01

    Rapid calcium (Ca) dissolution from nanostructured Ca phosphate and carbonate (CaCO3) powders may allow them to be absorbed in much higher fraction in humans. Nanosized Ca phosphate and CaCO3 made by flame-assisted spray pyrolysis were characterized by nitrogen adsorption, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. As-prepared nanopowders contained both CaCO3 and CaO, but storing them under ambient conditions over 130 days resulted in a complete transformation into CaCO3, with an increase in both crystal and particle sizes. The small particle size could be stabilized against such aging by cation (Mg, Zn, Sr) and anion (P) doping, with P and Mg being most effective. Calcium phosphate nanopowders made at Ca:P ≤ 1.5 were XRD amorphous and contained γ-Ca2P2O7 with increasing hydroxyapatite content at higher Ca:P. Aging of powders with Ca:P = 1.0 and 1.5 for over 500 days gradually increased particle size (but less than for CaCO3) without a change in phase composition or crystallinity. In 0.01 M H3PO4 calcium phosphate nanopowders dissolved ≈4 times more Ca than micronsized compounds and about twice more Ca than CaCO3 nanopowders, confirming that nanosizing and/or amorphous structuring sharply increases Ca powder dissolution. Because higher Ca solubility in vitro generally leads to greater absorption in vivo, these novel FASP-made Ca nanostructured compounds may prove useful for nutrition applications, including supplementation and/or food fortification.

  1. Population Evolution of Oxide Inclusions in Ti-stabilized Ultra-low Carbon Steels after Deoxidation

    Institute of Scientific and Technical Information of China (English)

    Wen YANG; Ying ZHANG; Li-feng ZHANG; Hao-jian DUAN; Li WANG

    2015-01-01

    Population density function (PDF),which can eliminate the arbitrariness caused by the choice of the num-ber and the size of bins compared to the well-used histograms,was introduced to analyze the amount of inclusions. The population evolution of oxide inclusions in forms of PDF in Ti-stabilized ultra-low carbon steels after deoxidation during industrial RH refining and continuous casting processes was analyzed using an automated SEM-EDS system. It was found that after deoxidation till the early stage of casting,the alumina inclusions exhibited a lognormal PDF distribution,and three factors including the existence of a large amount of alumina clusters,the generation of alumi-na from the reduction of Al-Ti-O inclusions and the reoxidation of molten steel were estimated as the reasons.The shape parameterσwas high after deoxidation and then decreased after Ti treatment,indicating that in a short period after deoxidation,the size of alumina inclusions was widely distributed.After Ti treatment,the distribution of inclu-sion size was more concentrated.The scale parameter m decreased with time during the whole refining process,indi-cating that the proportion of large inclusions decreased during refining.Contrarily,the Al-Ti-O inclusions presented a fractal PDF distribution except at the end of casting with fractal dimension D of 4.3,and the constant of propor-tionality C decreased with time during RH refining and increased during casting process.The reoxidation of steel by slag entrapped from ladle was considered as the reason for the lognormal PDF behavior of Al-Ti-O inclusions at the end of casting.

  2. Light stability tests of CH3NH3PbI3 perovskite solar cells using porous carbon counter electrodes.

    Science.gov (United States)

    Ito, Seigo; Mizuta, Gai; Kanaya, Shusaku; Kanda, Hiroyuki; Nishina, Tomoya; Nakashima, Seiji; Fujisawa, Hironori; Shimizu, Masaru; Haruyama, Yuichi; Nishino, Hitoshi

    2016-10-21

    The CH3NH3PbI3 perovskite solar cells have been fabricated using three-porous-layered electrodes as, 〈glass/F-doped tin oxide (FTO)/dense TiO2/porous TiO2-perovskite/porous ZrO2-perovskite/porous carbon-perovskite〉 for light stability tests. Without encapsulation in air, the CH3NH3PbI3 perovskite solar cells maintained 80% of photoenergy conversion efficiency from the initial value up to 100 h under light irradiation (AM 1.5, 100 mW cm(-2)). Considering the color variation of the CH3NH3PbI3 perovskite layer, the significant improvement of light stability is due to the moisture-blocking effect of the porous carbon back electrodes. The strong interaction between carbon and CH3NH3PbI3 perovskite was proposed by the measurements of X-ray photoelectron spectroscopy and X-ray diffraction of the porous carbon-perovskite layers.

  3. The formation and stability of Si1-xCx alloys in Si implanted with carbon ions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Si1-xCx alloys of carbon (C) concentration between 0.6%-1.0% were grown in Si by ion implantation and high temperature annealing. The formation of Si1-xCx alloys under different ion doses and their stability during annealing were studied. If the implanted dose was less than that for amorphizing Si crystals, the implanted C atoms would like to combine with defects produced during implan-tation and it was difficult to form Si1-xCx alloys after being annealed at 850℃. With the increment of implanted C ion doses, the lattice damage increased and it was easier to form Si1-xCx alloys. But the lattice strain would become saturate and only part of implanted carbon atoms would occupy the substitutional positions to form Si1-xCx alloys as the implant-ed carbon dose increased to a certain degree. Once Si1-xCx alloys were formed, they were stable at 950℃, but part of their strain would release as the annealing temperature increased to 1 000℃. Stability of the alloys became worse with the increment of carbon concentration in the alloys.

  4. Evaluation of carbon monoxide treatment in modified atmosphere packaging or vacuum packaging to increase color stability of fresh beef.

    Science.gov (United States)

    Jayasingh, P; Cornforth, D P; Carpenter, C E; Whittier, D

    2001-11-01

    Our goal was to obtain > 21 days red color stability for carbon monoxide (CO)-treated beef steaks in vacuum packaging (VP). In preliminary tests, pretreatment for 24 h in a 5% CO modified atmosphere package (MAP) was needed to maintain redness after re-packaging in VP. Pressure pretreatment with 5% CO for 2 h developed redness, but was impractical for large-scale application. Color stability and microbial load were then compared after treatment of steaks in 5% CO-MAP for 24 h, then VP; 100% CO-MAP for 1 h, then VP; steaks and ground beef in 0.5% CO-MAP; and steaks and ground beef in polyvinyl chloride (PVC) wrap. Steaks remained red for 5, 6, 8 and 10(6)cfu/cm(2)) at 5, 6, 7 and <2-weeks, respectively. Thus, extended color stability in VP was achieved by pretreatment with 5% CO for 24 h or 100% CO for 1 h.

  5. Design of Modern Reactors for Synthesis of Thermally Expanded Graphite

    Science.gov (United States)

    Strativnov, Eugene V.

    2015-05-01

    One of the most progressive trends in the development of modern science and technology is the creation of energy-efficient technologies for the synthesis of nanomaterials. Nanolayered graphite (thermally exfoliated graphite) is one of the key important nanomaterials of carbon origin. Due to its unique properties (chemical and thermal stability, ability to form without a binder, elasticity, etc.), it can be used as an effective absorber of organic substances and a material for seal manufacturing for such important industries as gas transportation and automobile. Thermally expanded graphite is a promising material for the hydrogen and nuclear energy industries. The development of thermally expanded graphite production is resisted by high specific energy consumption during its manufacturing and by some technological difficulties. Therefore, the creation of energy-efficient technology for its production is very promising.

  6. Suzuki cross-coupling reactions on the surface of carbon-coated cobalt: expanding the applicability of core-shell nano-magnets.

    Science.gov (United States)

    Tan, Chun Ghee; Grass, Robert N

    2008-09-28

    To develop magnetic nanomaterials applicable to organic synthesis, the Suzuki cross-coupling method was adapted to attach a range of functional groups to carbon-coated core-shell materials via commercially-available substituted arylboronic acids.

  7. Effect of biochar and compost application on quantity, quality and stability of organic carbon in sandy soil

    Science.gov (United States)

    Holes, Annamaria; Szegi, Tamas; Fuchs, Marta; Micheli, Erika; Aleksza, Laszlo

    2014-05-01

    Nowadays the amount of waste is increasing as a consequence of civilization development. Significant proportion of municipal waste is biodegradable. For the treatment of these wastes composting and pyrolysis can be one solution. Many studies were published on the effects of composts in soils, but on combined application of biochars and composts only a limited number of articles are available. Total carbon content, water soluble organic carbon content and organic matter quality have decisive role in the utilization of soils. In our study the effects of combined application of biochars and compost on organic carbon quality, quantity and stability were measured in sandy soil. The sandy soil was mixed with different proportions (1w/w%, 2,5w/w%, 5w/w%, 10w/w%) of biochars. Two types of biochars produced by pyrolization were used: plant origin biochar (POB) and animal origin biochar (AOB). 20w/w% urban green compost was mixed into each sample in addition to biochars. After the 30 days of wet incubation soil organic carbon (SOC) content was determined by Walkley-Black method, while for the SOC quality measurements E4/E6 method was used. The dissolved organic carbon (DOC) was extracted from the soil samples by cold water, and determined by titrimetric method. The future purpose of our study is to find the optimal compost-biochar treatment in order to improve soil fertility and maximize crop yield.

  8. 100 °C Thermal Stability of Printable Perovskite Solar Cells Using Porous Carbon Counter Electrodes.

    Science.gov (United States)

    Baranwal, Ajay K; Kanaya, Shusaku; Peiris, T A Nirmal; Mizuta, Gai; Nishina, Tomoya; Kanda, Hiroyuki; Miyasaka, Tsutomu; Segawa, Hiroshi; Ito, Seigo

    2016-09-22

    Many efforts have been made towards improving perovskite (PVK) solar cell stability, but their thermal stability, particularly at 85 °C (IEC 61646 climate chamber tests), remains a challenge. Outdoors, the installed solar cell temperature can reach up to 85 °C, especially in desert regions, providing sufficient motivation to study the effect of temperature stress at or above this temperature (e.g., 100 °C) to confirm the commercial viability of PVK solar cells for industrial companies. In this work, a three-layer printable HTM-free CH3 NH3 PbI3 PVK solar cell with a mesoporous carbon back contact and UV-curable sealant was fabricated and tested for thermal stability over 1500 h at 100 °C. Interestingly, the position of the UV-curing glue was found to drastically affect the device stability. The side-sealed cells show high PCE stability and represent a large step toward commercialization of next generation organic-inorganic lead halide PVK solar cells.

  9. Stability and effects of carbon-induced surface reconstructions in cobalt Fischer-Tropsch synthesis

    Science.gov (United States)

    Ciobîcă, I. M.; van Helden, P.; van Santen, R. A.

    2016-11-01

    This computational study of carbon induced reconstruction of Co surfaces demonstrates that surface reconstruction is stable in the presence of a hydrogen at low coverage. These reconstructions can create new sites that allow for low activation energy CO dissociation. Carbon induced surface reconstruction of the edge of the FCC-Co(221) step surface will result in highly reactive step-edge sites. Such sites also provide a low activation energy for carbon to diffuse into the subsurface layer of cobalt.

  10. Comparing measured and modelled soil carbon: which site-specific variables are linked to high stability?

    Science.gov (United States)

    Robertson, Andy; Schipanski, Meagan; Ma, Liwang; Ahuja, Lajpat; McNamara, Niall; Smith, Pete; Davies, Christian

    2016-04-01

    Changes in soil carbon (C) stocks have been studied in depth over the last two decades, as net greenhouse gas (GHG) sinks are highlighted to be a partial solution to the causes of climate change. However, the stability of this soil C is often overlooked when measuring these changes. Ultimately a net sequestration in soils is far less beneficial if labile C is replacing more stable forms. To date there is no accepted framework for measuring soil C stability, and as a result there is considerable uncertainty associated with the simulated impacts of land management and land use change when using process-based systems models. However, a recent effort to equate measurable soil C fractions to model pools has generated data that help to assess the impacts of land management, and can ultimately help to reduce the uncertainty of model predictions. Our research compiles this existing fractionation data along with site metadata to create a simplistic statistical model able to quantify the relative importance of different site-specific conditions. Data was mined from 23 published studies and combined with original data to generate a dataset of 100+ land use change sites across Europe. For sites to be included they required soil C fractions isolated using the Zimmermann et al. (2007) method and specific site metadata (mean annual precipitation, MAP; mean annual temperature, MAT; soil pH; land use; altitude). Of the sites, 75% were used to develop a generalized linear mixed model (GLMM) to create coefficients where site parameters can be used to predict influence on the measured soil fraction C stocks. The remaining 25% of sites were used to evaluate uncertainty and validate this empirical model. Further, four of the aforementioned sites were used to simulate soil C dynamics using the RothC, DayCent and RZWQM2 models. A sensitivity analysis (4096 model runs for each variable applying Latin hypercube random sampling techniques) was then used to observe whether these models place

  11. Structure-property relationships in carbon nanotube-polymer systems: Influence of noncovalent stabilization techniques

    Science.gov (United States)

    Liu, Lei

    A variety of experiments were carried out to study the dispersion and microstructure of carbon nanotubes in aqueous suspensions and polymer composites with the goal to improve the electrical conductivity of the composites containing nanotubes. Epoxy composites containing covalently and noncovalently functionalized nanotubes were compared in terms of electrical and mechanical behavior. Covalent functionalization of nanotubes is based on chemical attachments of polyethylenimine (PEI) whereas noncovalent functionalization takes place through physical mixing of nanotubes and PEI. The electrical conductivity is reduced in composites containing covalently functionalized nanotubes due to damage of the tube's conjugated surface that reduces intrinsic conductivity. Conversely, the mechanical properties are always better for epoxy composites containing covalently functionalized nanotubes. Clay particles were used as a rigid dispersing aid for nanotubes in aqueous suspensions and epoxy composites. When both nanotubes and clay were introduced into water by sonication, the suspension is stable for weeks, whereas the nanotubes precipitate almost instantly for the suspension without clay. In epoxy composites, nanotubes form separated clusters of aggregation, whereas a continuous three-dimensional nanotube network is achieved when clay is introduced. Electrical conductivity of the epoxy composite is shown to significantly improve with a small addition of clay and the percolation threshold is simultaneously decreased (from 0.05 wt% nanotubes, when there is no clay, to 0.01 wt% when 2 wt% clay is introduced). The addition of clay can also improve the mechanical properties of the composites, especially at higher clay concentration. Weak polyelectrolytes (i.e., pH-responsive polymers) were also studied for their interaction with nanotubes and the electrical properties of the dried composite films. When dispersed by sonication, Nanotubes show pH-dependent dispersion and stability in

  12. The effect of intertube van der Waals interaction on the stability of pristine and functionalized carbon nanotubes under compression.

    Science.gov (United States)

    Kuang, Y D; Shi, S Q; Chan, P K L; Chen, C Y

    2010-03-26

    This paper investigates the effect of intertube van der Waals interaction on the stability of pristine and covalently functionalized carbon nanotubes under axial compression, using molecular mechanics simulations. After regulating the number of inner layers of the armchair four-walled (5, 5)@(10, 10)@(15, 15)@(20, 20) and zigzag four-walled (6, 0)@(15, 0)@(24, 0)@(33, 0) carbon nanotubes, the critical buckling strains of the corresponding tubes are calculated. The results show that each of the three inner layers in the functionalized armchair nanotube noticeably contributes to the stability of the outermost tube, and together increase the critical strain amplitude by 155%. However, the three inner layers in the corresponding pristine nanotube, taken together, increase the critical strain of the outermost tube by only 23%. In addition, for both the pristine and functionalized zigzag nanotubes, only the (24, 0) layer, among the three inner layers, contributes to the critical strain of the corresponding outermost tube, by 11% and 29%, respectively. The underlying mechanism of the enhanced stability related to nanotube chirality and functionalization is analyzed in detail.

  13. Effects of straw and biochar amendments on aggregate stability, soil organic carbon, and enzyme activities in the Loess Plateau, China.

    Science.gov (United States)

    Zhang, Man; Cheng, Gong; Feng, Hao; Sun, Benhua; Zhao, Ying; Chen, Haixin; Chen, Jing; Dyck, Miles; Wang, Xudong; Zhang, Jianguo; Zhang, Afeng

    2017-02-23

    Soil from the Loess Plateau of China is typically low in organic carbon and generally has poor aggregate stability. Application of organic amendments to these soils could help to increase and sustain soil organic matter levels and thus to enhance soil aggregate stability. A field experiment was carried out to evaluate the effect of the application of wheat straw and wheat straw-derived biochar (pyrolyzed at 350-550 °C) amendments on soil aggregate stability, soil organic carbon (SOC), and enzyme activities in a representative Chinese Loess soil during summer maize and winter wheat growing season from 2013 to 2015. Five treatments were set up as follows: no fertilization (CK), application of inorganic fertilizer (N), wheat straw applied at 8 t ha(-1) with inorganic fertilizer (S8), and wheat straw-derived biochar applied at 8 t ha(-1) (B8) and 16 t ha(-1) (B16) with inorganic fertilizer, respectively. Compared to the N treatment, straw and straw-derived biochar amendments significantly increased SOC (by 33.7-79.6%), microbial biomass carbon (by 18.9-46.5%), and microbial biomass nitrogen (by 8.3-38.2%), while total nitrogen (TN) only increased significantly in the B16 plot (by 24.1%). The 8 t ha(-1) straw and biochar applications had no significant effects on soil aggregation, but a significant increase in soil macro-aggregates (>2 mm) (by 105.8%) was observed in the B16 treatment. The concentrations of aggregate-associated SOC increased by 40.4-105.8% in macro-aggregates (>2 mm) under straw and biochar amendments relative to the N treatment. No significant differences in invertase and alkaline phosphatase activity were detected among different treatments. However, urease activity was greater in the biochar treatment than the straw treatment, indicating that biochar amendment improved the transformation of nitrogen in the soil. The carbon pool index and carbon management index were increased with straw and biochar amendments, especially in the B16

  14. Thermodynamic Stability of LiFeO2 in Molten Carbonate Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    LiFeO2, as one of candidate cathode materials or additive for molten carbonate fuel cell, has been found to be thermodynamically unstable in CO2 atmosphere at 650℃ (the condition of molten carbonate fuel cell) both by computation and experimental confirmation.

  15. Interannual stability of organic to inorganic carbon production on a coral atoll

    Science.gov (United States)

    Kwiatkowski, Lester; Albright, Rebecca; Hosfelt, Jessica; Nebuchina, Yana; Ninokawa, Aaron; Rivlin, Tanya; Sesboüé, Marine; Wolfe, Kennedy; Caldeira, Ken

    2016-04-01

    Ocean acidification has the potential to adversely affect marine calcifying organisms, with substantial ocean ecosystem impacts projected over the 21st century. Characterizing the in situ sensitivity of calcifying ecosystems to natural variability in carbonate chemistry may improve our understanding of the long-term impacts of ocean acidification. We explore the potential for intensive temporal sampling to isolate the influence of carbonate chemistry on community calcification rates of a coral reef and compare the ratio of organic to inorganic carbon production to previous studies at the same location. Even with intensive temporal sampling, community calcification displays only a weak dependence on carbonate chemistry variability. However, across three years of sampling, the ratio of organic to inorganic carbon production is highly consistent. Although further work is required to quantify the spatial variability associated with such ratios, this suggests that these measurements have the potential to indicate the response of coral reefs to ongoing disturbance, ocean acidification, and climate change.

  16. Soil carbon stabilization and turnover at alley-cropping systems, Eastern Germany

    Science.gov (United States)

    Medinski, T.; Freese, D.

    2012-04-01

    Alley-cropping system is seen as a viable land-use practice for mitigation of greenhouse gas CO2, energy-wood production and soil carbon sequestration. The extent to which carbon is stored in soil varies between ecosystems, and depends on tree species, soil types and on the extent of physical protection of carbon within soil aggregates. This study investigates soil carbon sequestration at alley-cropping systems presented by alleys of fast growing tree species (black locust and poplar) and maize, in Brandenburg, Eastern Germany. Carbon accumulation and turnover are assessed by measuring carbon fractions differing in decomposition rates. For this purpose soil samples were fractionated into labile and recalcitrant soil-size fractions by wet-sieving: macro (>250 µm), micro (53-250 µm) and clay + silt (water extractable OC, and microbial C. Litter decomposition was evaluated by litter bags experiment. Soil CO2 flux was measured by LiCor automated device LI-8100A. No differences for the total and stable (clay+silt, treatment. While cold water-extractable carbon was significantly higher at maize alley compared to black locust alley. This may indicate faster turnover of organic matter at maize alley due to tillage, which influenced greater incorporation of plant residues into the soil, greater soil respiration and microbial activity.

  17. Restoring forest structure and process stabilizes forest carbon in wildfire-prone southwestern ponderosa pine forests.

    Science.gov (United States)

    Hurteau, Matthew D; Liang, Shuang; Martin, Katherine L; North, Malcolm P; Koch, George W; Hungate, Bruce A

    2016-03-01

    Changing climate and a legacy of fire-exclusion have increased the probability of high-severity wildfire, leading to an increased risk of forest carbon loss in ponderosa pine forests in the southwestern USA. Efforts to reduce high-severity fire risk through forest thinning and prescribed burning require both the removal and emission of carbon from these forests, and any potential carbon benefits from treatment may depend on the occurrence of wildfire. We sought to determine how forest treatments alter the effects of stochastic wildfire events on the forest carbon balance. We modeled three treatments (control, thin-only, and thin and burn) with and without the occurrence of wildfire. We evaluated how two different probabilities of wildfire occurrence, 1% and 2% per year, might alter the carbon balance of treatments. In the absence of wildfire, we found that thinning and burning treatments initially reduced total ecosystem carbon (TEC) and increased net ecosystem carbon balance (NECB). In the presence of wildfire, the thin and burn treatment TEC surpassed that of the control in year 40 at 2%/yr wildfire probability, and in year 51 at 1%/yr wildfire probability. NECB in the presence of wildfire showed a similar response to the no-wildfire scenarios: both thin-only and thin and burn treatments increased the C sink. Treatments increased TEC by reducing both mean wildfire severity and its variability. While the carbon balance of treatments may differ in more productive forest types, the carbon balance benefits from restoring forest structure and fire in southwestern ponderosa pine forests are clear.

  18. Sulfur loaded in micropore-rich carbon aerogel as cathode of lithium-sulfur battery with improved cyclic stability

    Science.gov (United States)

    Li, Zihao; Li, Xiaogang; Liao, Youhao; Li, Xiaoping; Li, Weishan

    2016-12-01

    We report a novel composite of sulfur loaded in micropore-rich carbon aerogel (CA-S), as cathode of lithium-sulfur battery. Carbon aerogel (CA) is synthesized through phenol-formaldehyde reaction with a low catalyst concentration and carbonization under high temperature, and loaded with sulfur via chemical deposition and heat treatment. The physical properties of the resulting CA and the electrochemical performances of the resulting CA-S are investigated by scanning electron microscopy, thermal gravimetric analysis, Brunauer-Emmett-Teller characterization, electrochemical impedance spectroscopy, and galvanostatic discharge/charge test, with a comparison of a common carbon material, acetylene black (AB), and sulfur loaded in AB (AB-S). It is found that the CA is micropore-rich with micropore volume over 66% of total pore volume, and the CA-S exhibits significantly improved cyclic stability compared with AB-S. The improved performance of CA-S is attributed to the confinement of the micropores in CA to small sulfur allotropes and corresponding lithium sulfides.

  19. Cycle stability of the electrochemical capacitors patterned with vertically aligned carbon nanotubes in an LiPF6-based electrolyte

    Science.gov (United States)

    Chiou, Yi-Deng; Tsai, Dah-Shyang; Lam, Hoa Hung; Chang, Chuan-Hua; Lee, Kuei-Yi; Huang, Ying-Sheng

    2013-08-01

    The miniature ultracapacitors, with interdigitated electrodes of vertically aligned carbon nanotubes (VACNTs) and an inter-electrode gap of 20 μm, have been prepared in the LiPF6 organic electrolyte with and without PVdF-HFP gel. PVdF-HFP between two opposing electrodes enhances the device reliability, but lessens its power performance because of the extra diffusion resistance. Also noteworthy are the gel influences on the cycle stability. When the applied voltage is 2.0 or 2.5 V, both the LiPF6 and the gel capacitors exhibit excellent stability, typified by a retention ratio of >=95% after 10 000 cycles. Their coulombic efficiencies quickly rise up, and hold steady at 100%. Nonetheless, when the applied voltage is 3.5 or 4.0 V, the cycle stability deteriorates, since the negative electrode potential descends below 0.9 V (vs. Li), leading to electrolyte decomposition and SEI formation. For the LiPF6 capacitor, its retention ratio could be around 60% after 10 000 cycles and the coulombic efficiency of 100% is difficult to reach throughout its cycle life. On the other hand, the gel capacitor cycles energy with a much higher retention ratio, >80% after 10 000 cycles, and a better coulombic efficiency, even though electrolyte decomposition still occurs. We attribute the superior stability of the gel capacitor to its extra diffusion resistance which slows down the performance deterioration.

  20. Structural stability of hydrogenated amorphous carbon overcoats used in heat-assisted magnetic recording investigated by rapid thermal annealing

    KAUST Repository

    Wang, N.

    2013-01-01

    Ultrathin amorphous carbon (a-C) films are extensively used as protective overcoats of magnetic recording media. Increasing demands for even higher storage densities have necessitated the development of new storage technologies, such as heat-assisted magnetic recording (HAMR), which uses laser-assisted heating to record data on high-stability media that can store single bits in extremely small areas (∼1 Tbit/in.2). Because HAMR relies on locally changing the coercivity of the magnetic medium by raising the temperature above the Curie temperature for data to be stored by the magnetic write field, it raises a concern about the structural stability of the ultrathin a-C film. In this study, rapid thermal annealing (RTA) experiments were performed to examine the thermal stability of ultrathin hydrogenated amorphous carbon (a-C:H) films deposited by plasma-enhanced chemical vapor deposition. Structural changes in the a-C:H films caused by RTA were investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray reflectivity, and conductive atomic force microscopy. The results show that the films exhibit thermal stability up to a maximum temperature in the range of 400-450 °C. Heating above this critical temperature leads to hydrogen depletion and sp 2 clustering. The critical temperature determined by the results of this study represents an upper bound of the temperature rise due to laser heating in HAMR hard-disk drives and the Curie temperature of magnetic materials used in HAMR hard disks. © 2013 American Institute of Physics.

  1. Influence of Preparation Conditions on Structural Stability of Ordered Mesoporous Carbons Synthesized by Evaporation-induced Triconstituent Co-assembly Method

    Institute of Scientific and Technical Information of China (English)

    Bo You; Jun Yang; Guo-ping Yong; Shao-min Liu; Wei Xie; Qing-de Su

    2011-01-01

    Various ordered mesoporous carbons (OMCs) have been prepared by evaporation-induced triconstituent co-assembly method. Their mesostructural stability under different carbon content, aging time and acidity were conveniently monitored by X-ray diffraction, transmission electron microscopy, and N2 sorption isotherms techniques. The results show mesostructural stability of OMCs is enhanced as the carbon content increases from 36% to 46%, further increasing carbon content deteriorates the mesostructural stability. Increasing aging time from 0.5 h to 5.0 h make themesostructural stability go through an optimum 2.0 h) and gradually reduce framework shrinkage of the OMCs. Highly OMCs can only be obtained in the acidity range of 0.2-1.2 mol/L HC1, when the acidity is near the isoelectric point of silica, the resulting OMCs have the best mesostructure stability. Under the optimum condition, the carbon content of 46%, aging time of 2.0 h, and 0.2 mol/L HC1, the resulting OMCs have the best mesostructure stability and the highest BET urface areas of 2281 m2/g.

  2. Climate, soil texture, and soil types affect the contributions of fine-fraction-stabilized carbon to total soil organic carbon in different land uses across China.

    Science.gov (United States)

    Cai, Andong; Feng, Wenting; Zhang, Wenju; Xu, Minggang

    2016-05-01

    Mineral-associated organic carbon (MOC), that is stabilized by fine soil particles (i.e., silt plus clay, soil organic carbon (SOC) persistence and sequestration, due to its large contribution to total SOC (TSOC) and long turnover time. Our objectives were to investigate how climate, soil type, soil texture, and agricultural managements affect MOC contributions to TSOC in China. We created a dataset from 103 published papers, including 1106 data points pairing MOC and TSOC across three major land use types: cropland, grassland, and forest. Overall, the MOC/TSOC ratio ranged from 0.27 to 0.80 and varied significantly among soil groups in cropland, grassland, and forest. Croplands and forest exhibited significantly higher median MOC/TSOC ratios than in grassland. Moreover, forest and grassland soils in temperate regions had higher MOC/TSOC ratios than in subtropical regions. Furthermore, the MOC/TSOC ratio was much higher in ultisol, compared with the other soil types. Both the MOC content and MOC/TSOC ratio were positively correlated with the amount of fine fraction (silt plus clay) in soil, highlighting the importance of soil texture in stabilizing organic carbon across various climate zones. In cropland, different fertilization practices and land uses (e.g., upland, paddy, and upland-paddy rotation) significantly altered MOC/TSOC ratios, but not in cropping systems (e.g., mono- and double-cropping) characterized by climatic differences. This study demonstrates that the MOC/TSOC ratio is mainly driven by soil texture, soil types, and related climate and land uses, and thus the variations in MOC/TSOC ratios should be taken into account when quantitatively estimating soil C sequestration potential of silt plus clay particles on a large scale.

  3. Drug loading, dispersion stability, and therapeutic efficacy in targeted drug delivery with carbon nanotubes

    OpenAIRE

    Heister, E; Neves, V.; Lamprecht, C.; Silva, SRP; Coley, HM; Mcfadden, J.

    2012-01-01

    We have designed a drug delivery system for the anti-cancer drugs doxorubicin and mitoxantrone based on carbon nanotubes, which is stable under biological conditions, allows for sustained release, and promotes selectivity through an active targeting scheme. Carbon nanotubes are particularly promising for this area of application due to their high surface area, allowing for high drug loading, and their unique interaction with cellular membranes. We have taken a systematic approach to PEG conju...

  4. Stability of Conductive Carbon Additives for High-voltage Li-ion Battery Cathodes

    OpenAIRE

    Nilssen, Benedicte Eikeland

    2014-01-01

    Conductive carbon additives are important constituents of the current state-of-the-art Li-ion battery cathodes, as the traditional active cathode materials are characterized by too low electronic conductivities. In high-voltage Li-ion batteries, these additives are subject for anion intercalation and electrolyte oxidation, which might cause changes in the conductive carbon network in the cathode, and hence the overall cycling performance of the electrode. This thesis has focused on study the ...

  5. Long-term rice cultivation stabilizes soil organic carbon and promotes soil microbial activity in a salt marsh derived soil chronosequence.

    Science.gov (United States)

    Wang, Ping; Liu, Yalong; Li, Lianqing; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Joseph, Stephen; Pan, Genxing

    2015-10-27

    Soil organic carbon (SOC) sequestration with enhanced stable carbon storage has been widely accepted as a very important ecosystem property. Yet, the link between carbon stability and bio-activity for ecosystem functioning with OC accumulation in field soils has not been characterized. We assessed the changes in microbial activity versus carbon stability along a paddy soil chronosequence shifting from salt marsh in East China. We used mean weight diameter, normalized enzyme activity (NEA) and carbon gain from straw amendment for addressing soil aggregation, microbial biochemical activity and potential C sequestration, respectively. In addition, a response ratio was employed to infer the changes in all analyzed parameters with prolonged rice cultivation. While stable carbon pools varied with total SOC accumulation, soil respiration and both bacterial and fungal diversity were relatively constant in the rice soils. Bacterial abundance and NEA were positively but highly correlated to total SOC accumulation, indicating an enhanced bio-activity with carbon stabilization. This could be linked to an enhancement of particulate organic carbon pool due to physical protection with enhanced soil aggregation in the rice soils under long-term rice cultivation. However, the mechanism underpinning these changes should be explored in future studies in rice soils where dynamic redox conditions exist.

  6. Stability of carbon electrodes for aqueous lithium-air secondary batteries

    Science.gov (United States)

    Ohkuma, Hirokazu; Uechi, Ichiro; Matsui, Masaki; Takeda, Yasuo; Yamamoto, Osamu; Imanishi, Nobuyuki

    2014-01-01

    The air electrode performance of various carbon materials, such as Ketjen black (KB), acetylene black (AB and AB-S), Vulcan XC-72R (VX), and vapor grown carbon fiber (VGCF) with and without La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) catalyst were examined in an aqueous solution of saturated LiOH with 10 M LiCl in the current density range 0.2-2.0 mA cm-2. The best performance for oxygen reduction and evolution reactions was observed for the KB electrode, which has the highest surface area among the carbon materials examined. A steady over-potential of 0.2 V was obtained for the oxygen reduction reaction using the KB electrode without the catalyst, while the over-potential was 0.15 V for KB with the LSCF catalyst at 2.0 mA cm-2. The over-potentials for the oxygen evolution reaction were slightly higher than those for the oxygen reduction reaction, and gradually increased with the polarization period. Analysis of the gas in the cell after polarization above 0.4 V revealed the evolution of a small amount of CO during the oxygen evolution reaction by the decomposition of carbon in the electrode. The amount of CO evolved was significantly decreased by the addition of LSCF to the carbon electrode.

  7. Controlled chemical stabilization of polyvinyl precursor fiber, and high strength carbon fiber produced therefrom

    Science.gov (United States)

    Naskar, Amit K.

    2016-12-27

    Method for the preparation of carbon fiber, which comprises: (i) immersing functionalized polyvinyl precursor fiber into a liquid solution having a boiling point of at least 60.degree. C.; (ii) heating the liquid solution to a first temperature of at least 25.degree. C. at which the functionalized precursor fiber engages in an elimination-addition equilibrium while a tension of at least 0.1 MPa is applied to the fiber; (iii) gradually raising the first temperature to a final temperature that is at least 20.degree. C. above the first temperature and up to the boiling point of the liquid solution for sufficient time to convert the functionalized precursor fiber to a pre-carbonized fiber; and (iv) subjecting the pre-carbonized fiber produced according to step (iii) to high temperature carbonization conditions to produce the final carbon fiber. Articles and devices containing the fibers, including woven and non-woven mats or paper forms of the fibers, are also described.

  8. [Effects of short-term fencing on organic carbon fractions and physical stability of sandy sierozem in desert steppe of Northwest China].

    Science.gov (United States)

    Yang, Xin-Guo; Song, Nai-Ping; Li, Xue-Bin; Liu, Bing-Ru

    2012-12-01

    In order to explore the change patterns of organic carbon fractions and physical stability of sandy sierozem in desert steppe at the early stage of fencing, 0-40 cm soil samples were collected from a 5-year fenced desert steppe (inside the fence) and a free grazing steppe (outside the fence) in Yanchi County of Ningxia, Northwest China, with the soil organic carbon, labile organic carbon, and particulate organic carbon contents and soil particle composition analyzed. No significant differences were observed in the soil organic carbon content and soil particle composition inside and outside the fence. The average soil organic carbon inside and outside the fences was 3.25 g x kg(-1), the percentages of sand, silt, and clay were averagely 72%, 16%, and 12%, respectively, and the soil physical stability index was 1.30% -1.31%. The soil active organic carbon showed a significant change in 10-20 cm layer. The soil labile organic carbon content was 0.80 g x kg(-1) inside the fence, which was significantly higher than that outside the fence (0.62 g x kg(-1)). The percentage of soil particulate organic carbon was 50.9% inside the fence, which was also significantly higher than that outside the fence (31.7%). The soil texture inside the fence changed from sandy to loam, and the soil labile organic carbon content increased gradually; while the soil texture outside the fence was sandy, and its vertical change was relatively smooth. The organic carbon of sandy si- erozem in the desert steppe under the conditions of short-term fencing was still in a balance between consumption and accumulation, the soil texture was relatively stable, and the soil physical stability changed little. It was suggested that the soil active organic carbon content and its relative percentage in 10-20 cm layer could be used as the indicators of early soil quality change of desert steppe.

  9. Utilize Cementitious High Carbon Fly Ash (CHCFA) to Stabilize Cold In-Place Recycled (CIR) Asphalt Pavement as Base Coarse

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Haifang; Li, Xiaojun; Edil, Tuncer; O' Donnell, Jonathan; Danda, Swapna

    2011-02-05

    The purpose of this study was to evaluate the performance of cementitious high carbon fly ash (CHCFA) stabilized recycled asphalt pavement as a base course material in a real world setting. Three test road cells were built at MnROAD facility in Minnesota. These cells have the same asphalt surface layers, subbases, and subgrades, but three different base courses: conventional crushed aggregates, untreated recycled pavement materials (RPM), and CHCFA stabilized RPM materials. During and after the construction of the three cells, laboratory and field tests were carried out to characterize the material properties. The test results were used in the mechanistic-empirical pavement design guide (MEPDG) to predict the pavement performance. Based on the performance prediction, the life cycle analyses of cost, energy consumption, and greenhouse gasses were performed. The leaching impacts of these three types of base materials were compared. The laboratory and field tests showed that fly ash stabilized RPM had higher modulus than crushed aggregate and RPM did. Based on the MEPDG performance prediction, the service life of the Cell 79 containing fly ash stabilized RPM, is 23.5 years, which is about twice the service life (11 years) of the Cell 77 with RPM base, and about three times the service life (7.5 years) of the Cell 78 with crushed aggregate base. The life cycle analysis indicated that the usage of the fly ash stabilized RPM as the base of the flexible pavement can significantly reduce the life cycle cost, the energy consumption, the greenhouse gases emission. Concentrations of many trace elements, particularly those with relatively low water quality standards, diminish over time as water flows through the pavement profile. For many elements, concentrations below US water drinking water quality standards are attained at the bottom of the pavement profile within 2-4 pore volumes of flow.

  10. Assessing the temporal stability of surface functional groups introduced by plasma treatments on the outer shells of carbon nanotubes

    Science.gov (United States)

    Merenda, Andrea; Ligneris, Elise Des; Sears, Kallista; Chaffraix, Thomas; Magniez, Kevin; Cornu, David; Schütz, Jürg A.; Dumée, Ludovic F.

    2016-08-01

    Plasma treatments are emerging as superior efficiency treatment for high surface to volume ratio materials to tune functional group densities and alter crystallinity due to their ability to interact with matter at the nanoscale. The purpose of this study is to assess for the first time the long term stability of surface functional groups introduced across the surface of carbon nanotube materials for a series of oxidative, reductive and neutral plasma treatment conditions. Both plasma duration dose matrix based exposures and time decay experiments, whereby the surface energy of the materials was evaluated periodically over a one-month period, were carried out. Although only few morphological changes across the graphitic planes of the carbon nanotubes were found under the uniform plasma treatment conditions, the time dependence of pertinent work functions, supported by Raman analysis, suggested that the density of polar groups decreased non-linearly over time prior to reaching saturation from 7 days post treatment. This work provides critical considerations on the understanding of the stability of functional groups introduced across high specific surface area nano-materials used for the design of nano-composites, adsorptive or separation systems, or sensing materials and where interfacial interactions are key to the final materials performance.

  11. Hard carbon nanoparticles as high-capacity, high-stability anodic materials for Na-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Lifen; Cao, Yuliang; Henderson, Wesley A.; Sushko, Maria L.; Shao, Yuyan; Xiao, Jie; Wang, Wei; Engelhard, Mark H.; Nie, Zimin; Liu, Jun

    2016-01-01

    Hard carbon nanoparticles (HCNP) were synthesized by the pyrolysis of a polyaniline precursor. The measured Na+ cation diffusion coefficient (10-13-10-15cm2s-1) in the HCNP obtained at 1150 °C is two orders of magnitude lower than that of Li+ in graphite (10-10-13-15cm2s-1), indicating that reducing the carbon particle size is very important for improving electrochemical performance. These measurements also enable a clear visualization of the stepwise reaction phases and rate changes which occur throughout the insertion/extraction processes in HCNP, The electrochemical measurements also show that the nano-sized HCNP obtained at 1150 °C exhibited higher practical capacity at voltages lower than 1.2 V (vs. Na/Na⁺), as well as a prolonged cycling stability, which is attributed to an optimum spacing of 0.366 nm between the graphitic layers and the nano particular size resulting in a low-barrier Na+ cation insertion. These results suggest that HCNP is a very promising high-capacity/stability anode for low cost sodium-ion batteries (SIBs).

  12. A MERGE model with endogenous technological change and the cost of carbon stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Kypreos, Socrates [Laboratory of Energy Systems Analysis, The Energy Departments, Energy Economics Group, Paul Scherrer Institute, CH-5232, Villigen PSI (Switzerland)

    2007-11-15

    Two stylized backstop systems with endogenous technological learning (ETL) are introduced in the ''model for evaluating regional and global effects'' (MERGE): one for the electric and the other for the non-electric markets. Then the model is applied to analyze the impacts of ETL on carbon-mitigation policy, contrasting the resulting impacts with the situation without ETL. We model research and development (R and D) spending and learning subsidies for the demonstration and deployment stage as control variables, and we investigate the ability of this extra spending to create path-dependent experience and knowledge to aid in the implementation of carbon-free technologies. Based on model estimations and sensitivity analyses, we conclude that increased commitments for the development of new technologies to advance along their learning curves has a potential for substantial reductions in the cost of mitigating climate change and thereby helping to reach safe concentrations of carbon in the atmosphere. (author)

  13. Stability and chirality effect on twist formation of collapsed double wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    XIAO Jian-liang; LIU Bin; HUANG Yong-gang; HWANG Ke-zhi; YU Min-feng

    2006-01-01

    This study is to reveal the effect of interlayer lattice registry on the formation of collapsed double wall carbon nanotubes (DWCNTs). It is found that collapsed carbon nanotubes can be energetically unstable,metastable or stable,depending mainly on the diameter of the CNT. A fully collapsed DWCNT can adopt different structural morphologies,such as a straight ribbon,a warping ribbon or a twisted ribbon,depending on the chirality of the CNT,which is similar to single wall carbon nanotubes (SWCNTs). Different from SWCNTs,this study also shows some unique phenomena in the formation of collapsed DWCNTs. A fully collapsed DWCNT can have different combinations of the interlayer lattice registry effect within the inner and outer tube,thus the outer tube can influence the formation of the collapsed CNT via lattice registry effect,sometimes even dominates the twist of the CNT.

  14. A high-porosity carbon molybdenum sulphide composite with enhanced electrochemical hydrogen evolution and stability

    DEFF Research Database (Denmark)

    Laursen, Anders B.; Vesborg, Peter C. K.; Chorkendorff, Ib

    2013-01-01

    This work describes a highly active and stable acid activated carbon fibre and amorphous MoSx composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show an impro......This work describes a highly active and stable acid activated carbon fibre and amorphous MoSx composite hydrogen evolution catalyst. The increased electrochemical-surface area is demonstrated to cause increased catalyst electrodeposition and activity. These composite electrodes also show...

  15. Carbon stabilization and microbial growth in acidic mine soils after addition of different amendments for soil reclamation

    Science.gov (United States)

    Zornoza, Raúl; Acosta, Jose; Ángeles Muñoz, María; Martínez-Martínez, Silvia; Faz, Ángel; Bååth, Erland

    2016-04-01

    The extreme soil conditions in metalliferous mine soils have a negative influence on soil biological activity and therefore on soil carbon estabilization. Therefore, amendments are used to increase organic carbon content and activate microbial communities. In order to elucidate some of the factors controlling soil organic carbon stabilization in reclaimed acidic mine soils and its interrelationship with microbial growth and community structure, we performed an incubation experiment with four amendments: pig slurry (PS), pig manure (PM) and biochar (BC), applied with and without marble waste (MW; CaCO3). Results showed that PM and BC (alone or together with MW) contributed to an important increment in recalcitrant organic C, C/N ratio and aggregate stability. Bacterial and fungal growths were highly dependent on pH and labile organic C. PS supported the highest microbial growth; applied alone it stimulated fungal growth, and applied with MW it stimulated bacterial growth. BC promoted the lowest microbial growth, especially for fungi, with no significant increase in fungal biomass. MW+BC increased bacterial growth up to values similar to PM and MW+PM, suggesting that part of the biochar was degraded, at least in short-term mainly by bacteria rather than fungi. PM, MW+PS and MW+PM supported the highest microbial biomass and a similar community structure, related with the presence of high organic C and high pH, with immobilization of metals and increased soil quality. BC contributed to improved soil structure, increased recalcitrant organic C, and decreased metal mobility, with low stimulation of microbial growth.

  16. Stability of soil organic carbon changes in successive rotations of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian; WANG Silong; FENG Zongwei; WANG Qingkui

    2009-01-01

    The importance of soil organic carbon (SOC) under forests in the global carbon cycle depends on the stability of the soil carbon and its availability to soil microbial biomass. We investigated the effects of successive rotations of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations on the stability of SOC and its availability to microbes by adopting the two-step hydrolysis with H2SO4 and density fractionation. The results showed that successive rotations of Chinese fir decreased the quantity of total SOC, recalcitrant fraction, and carbohydrates in Labile Pool I (LPI), and microbial properties evidently, especially at 0-10 cm horizon. However, cellulose included in Labile Pool II (LP II) and the cellulose/total carbohydrates ratio increased in successive rotations of Chinese fir. The non-cellulose of carbohydrates included in LPI maybe highly available to soil microbial biomass. Hence the availability of SOC to microbial biomass declined over the successive rotations. Although there was no significant change in recalcitrance of SOC over the successive rotations of Chinese fir, the percentage of heavy fraction to total SOC increased, suggesting that the degree of physical protection for SOC increased and SOC became more stable over the successive rotations. The degradation of SOC quality in successive rotation soils may be attributed to worse environmental conditions resulted from disturbance that related to "slash and burn" site preparation. Being highly correlated with soil microbial properties, the cellulose/total carbohydrates ratio as an effective indicator of changes in availability of SOC to microbial biomass brought by management practices in forest soils.

  17. Changes in Carbon Chemistry and Stability Along Deep Tropical Soil Profiles at the Luquillo Critical Zone Observatory

    Science.gov (United States)

    Stone, M.; Hockaday, W. C.; Plante, A. F.

    2014-12-01

    Tropical forests are the largest terrestrial carbon (C) sink, and tropical forest soils contribute disproportionately to the poorly-characterized deep soil C pool. The goal of this study was to evaluate how carbon chemistry and stability change with depth in tropical forest soils formed on two contrasting parent materials. We used soils from pits excavated to 140 cm depth that were stratified across two soil types (Oxisols and Inceptisols) at the Luquillo Critical Zone Observatory in northeast Puerto Rico. We used 13C nuclear magnetic resonance (NMR) spectroscopy to characterize soil C chemistry and differential scanning calorimetry (DSC) coupled with evolved gas analysis (CO2-EGA) to evaluate the thermal stability of soil C during ramped combustion. Thirty-four samples with an initial C concentration ≥1% were chosen from discrete depth intervals (0, 30, 60, 90 & 140 cm) for 13C NMR analysis, while DSC was performed on 122 samples that included the NMR sample set and additional samples at 20, 50, 80 and 110 cm depth. Preliminary 13C NMR results indicate higher alkyl : O-alkyl ratios and an enrichment of aliphatic and proteinaceous C with depth, compared with greater aromatic and carbohydrate signals in surface soils. The energy density of soil C (J mg-1 C) also declined significantly with depth. In Oxisols, most CO2 evolution from combustion occurred around 300ºC, while most CO2 evolution occurred at higher temperatures (400-500ºC) in Inceptisols. Our findings suggest soil C is derived primarily of plant biomolecules in surface soils and becomes increasingly microbial with depth. Soil matrix-mediated differences in C transport and preservation may result in differences in C chemistry between the two soil types and a more thermally labile C pool in the Oxisols. We suggest that energy-poor substrates, combined with potentially stronger organo-mineral interactions in subsoils, may explain the long-term stability of deep C in highly weathered tropical soils.

  18. Preformulation studies of novel 5'-O-carbonates of lamivudine with biological activity: solubility and stability assays.

    Science.gov (United States)

    Gualdesi, María S; Ravetti, Soledad; Raviolo, Mónica A; Briñón, Margarita C

    2014-09-01

    As a part of preformulation studies, the aim of this work was to examine the solubility and stability of a series of 5'-O-carbonates of lamivudine with proven antihuman immunodeficiency virus activity. Solubility studies were carried out using pure solvents (water, ethanol and polyethylene glycol 400 [PEG 400]), as well as cosolvents in binary mixture systems (water-ethanol and water-PEG 400). These ionizable compounds showed that their aqueous solubility is decreasing as the carbon length of the substituent moiety increases, but being enhanced as the pH was reduced from 7.4 to 1.2. Thus, 3TC-Metha an active compound of the series, with an intrinsic solubility at 25 °C of 17 mg/mL, was about 70 times more soluble than 3TC-Octa (0.24 mg/mL), and at pHs of 1.2, 5.8 and 7.4 had intrinsic solubilities of 36.48, 19.20 and 15.40 mg/mL, respectively. In addition, the solubility was enhanced significantly by using ethanol and PEG 400 as cosolvents. A stability study was conducted in buffer solutions at pH 1.2, 5.8, 7.4 and 13.0 and in human plasma at 37 °C. Stability-indicating high-performance liquid chromatography procedure was found to be selective, sensitive and accurate for these compounds and good recovery, linearity and precision were also observed.

  19. What Expands in an Expanding Universe?

    Directory of Open Access Journals (Sweden)

    JOSÉ A. DE FREITAS PACHECO

    2015-12-01

    Full Text Available ABSTRACT In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

  20. What Expands in an Expanding Universe?

    Science.gov (United States)

    Pacheco, José A De Freitas

    2015-01-01

    In the present investigation, the possible effects of the expansion of the Universe on systems bonded either by gravitational or electromagnetic forces, are reconsidered. It will be shown that the acceleration (positive or negative) of the expanding background, is the determinant factor affecting planetary orbits and atomic sizes. In the presently accepted cosmology (ΛCDM) all bonded systems are expanding at a decreasing rate that tends to be zero as the universe enters in a de Sitter phase. It is worth mentioning that the estimated expansion rates are rather small and they can be neglected for all practical purposes.

  1. Evaluation of metal oxide and carbonate nanoparticle stability in soybean oil: Implications for controlled release of alkalinity during subsurface remediation

    Science.gov (United States)

    Ramsburg, C. A.; Leach, O. I.; Sebik, J.; Muller, K.

    2011-12-01

    Traditional methods for adjusting groundwater pH rely on injection of aqueous solutes and therefore, amendment distribution is reliant upon aqueous phase flow and transport. This reliance can limit mixing and sustention of amendments within the treatment zone. Oil-in-water emulsions offer an alternative for amendment delivery - one that has potential to enhance control of the distribution and release of buffering agents within the subsurface. Focus here is placed on using metal oxide and carbonate nanoparticles to release alkalinity from soybean oil, a common dispersed phase within emulsions designed to support remediation activities. Batch reactor systems were employed to examine the influence of dispersed phase composition on particle stability and solubility. The stability of uncoated MgO and CaCO3 particles in unmodified soybean oil was explored in a series of sedimentation studies conducted at solid loadings of 0.05, 0.1, and 0.2% mass. Three nominal sizes of MgO particles were examined (20, 50, and 100 nm) and one CaCO3 particle size (60 nm). Results from sedimentation studies conducted over four hours suggest that the viscosity of the soybean oil imparts a kinetic stability, for all sizes of the uncoated MgO and CaCO3 nanoparticles, which is sufficient time for particle encapsulation within oil-in-water emulsions. Based upon these results, the sedimentation of the 50 nm and 100 nm MgO, and 60 nm CaCO3 particles was assessed over longer durations (≥72 hr). Results from these stability tests suggest that the 50 nm and 100 nm MgO particles have greater kinetic stability than the 60 nm CaCO3. Batch studies were also used to assess the influence of n-butanol, a co-solvent hypothesized to aid in controlling the rate of alkalinity release, on phase behavior and metal (Mg2+ and Ca2+) solubility. Phase behavior studies suggest that n-butanol has a limited region of miscibility within the soybean oil-water system. Use of n-butanol and water within this region of

  2. STRUCTURE, MECHANICAL PROPERTIES AND THERMAL STABILITY OF DIAMOND-LIKE CARBON FILMS PREPARED BY ARC ION PLATING

    Institute of Scientific and Technical Information of China (English)

    Y.S. Zou; J.D. Zheng; J. Gong; C. Sun; R.F. Huang; L.S. Wen

    2005-01-01

    Diamond-like Carbon (DLC) films have been prepared on Si(100) substrates by arc ion plating in conjunction with pulse bias voltage under H2 atmosphere. The deposited films have been characterized by scanning electron microscopy and atomic force microscopy. The results show that the surface of the film is smooth and dense without any cracks, and the surface roughness is low. The bonding characteristic of the films has been studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It shows the sp3 bond content of the film deposited at -200V is 26.7%. The hardness and elastic modulus of the film determined by nanoindentation technique are 30.8 and 250.1GPa, respectively. The tribological characteristic of the films reveals that they have low friction coefficient and good wear-resistance. After deposition, the films have been annealed in the range of 350-700℃ for 1h in vacuum to investigate the thermal stability. Raman spectra indicate that the ID/IG ratio and G peak position have few detectable changes below 500℃. Further increasing the annealing temperature, the hydrogen can be released, the structure rearranges, and the phase transition of sp3 configured carbon to sp2 configured carbon appears.

  3. Effect of Wrapped Carbon Nanotubes on Optical Properties, Morphology, and Thermal Stability of Electrospun Poly(vinyl alcohol Composite Nanofibers

    Directory of Open Access Journals (Sweden)

    Naoual Diouri

    2013-01-01

    Full Text Available Electrospinning was used to elaborate poly(vinyl alcohol (PVA nanofibers in the presence of embedded multiwall carbon nanotubes (MWCNTs in surfactant and polymer. MWCNTs were dispersed in aqueous solution using both sodium dodecyl sulfate (SDS as surfactant and Poly(vinyl pyrrolidone (PVP. Changing the surfactant and polymer concentration reveals that the maximum dispersion achievable is corresponding to the mass ratios MWCNTs : SDS—1 : 5 and MWCNTs : SDS : PVP—1 : 5 : 0.6 in the presence of the PVP. After the optimization of the dispersion process, the SEM image of the PVA/PVP/SDS/MWCNTs electrospun fibers presents high stability of the fibers with diameter around 224 nm. Infrared spectroscopy and thermal gravimetric analysis elucidate the type of interaction between the PVA and the coated carbon nanotube. The presence of PVP wrapped carbon nanotubes reduced slightly the onset of the degradation temperature of the electrospun nanofibers.

  4. Synthesis of core/shell spinel ferrite/carbon nanoparticles with enhanced cycling stability for lithium ion battery anodes.

    Science.gov (United States)

    Jin, Yun-Ho; Seo, Seung-Deok; Shim, Hyun-Woo; Park, Kyung-Soo; Kim, Dong-Wan

    2012-03-30

    Monodispersed core/shell spinel ferrite/carbon nanoparticles are formed by thermolysis of metal (Fe3+, Co2+) oleates followed by carbon coating. The phase and morphology of nanoparticles are characterized by x-ray diffraction and transmission electron microscopy. Pure Fe3O4 and CoFe2O4 nanoparticles are initially prepared through thermal decomposition of metal–oleate precursors at 310 degrees C and they are found to exhibit poor electrochemical performance because of the easy aggregation of nanoparticles and the resulting increase in the interparticle contact resistance. In contrast, uniform carbon coating of Fe3O4 and CoFe2O4 nanoparticles by low-temperature (180 degrees C) decomposition of malic acid allowed each nanoparticle to be electrically wired to a current collector through a conducting percolative path. Core/shell Fe3O4/C and CoFe2O4/C nanocomposite electrodes show a high specific capacity that can exceed 700 mAh g(-1) after 200 cycles, along with enhanced cycling stability.

  5. Probing the Interfacial Interaction in Layered-Carbon-Stabilized Iron Oxide Nanostructures: A Soft X-ray Spectroscopic Study.

    Science.gov (United States)

    Zhang, Hui; Liu, Jinyin; Zhao, Guanqi; Gao, Yongjun; Tyliszczak, Tolek; Glans, Per-Anders; Guo, Jinghua; Ma, Ding; Sun, Xu-Hui; Zhong, Jun

    2015-04-22

    We have stabilized the iron oxide nanoparticles (NPs) of various sizes on layered carbon materials (Fe-oxide/C) that show excellent catalytic performance. From the characterization of X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), scanning transmission X-ray microscopy (STXM) and X-ray magnetic circular dichroism spectroscopy (XMCD), a strong interfacial interaction in the Fe-oxide/C hybrids has been observed between the small iron oxide NPs and layered carbon in contrast to the weak interaction in the large iron oxide NPs. The interfacial interaction between the NPs and layered carbon is found to link with the improved catalytic performance. In addition, the Fe L-edge XMCD spectra show that the large iron oxide NPs are mainly γ-Fe2O3 with a strong ferromagnetic property, whereas the small iron oxide NPs with strong interfacial interaction are mainly α-Fe2O3 or amorphous Fe2O3 with a nonmagnetic property. The results strongly suggest that the interfacial interaction plays a key role for the catalytic performance, and the experimental findings may provide guidance toward rational design of high-performance catalysts.

  6. Effects of multiple polyaniline layers immobilized on carbon nanotube and glutaraldehyde on performance and stability of biofuel cell

    Science.gov (United States)

    Christwardana, Marcelinus; Kwon, Yongchai

    2015-12-01

    Enzymatic biofuel cell (EBC) employing new catalyst for anode electrode is fabricated. The new catalyst consists of glucose oxidase (GOx), polyaniline (PANI) and carbon nanotube (CNT) that are multiply stacked together and finally the stack layer is surrounded by glutaraldehyde (GA) (GA/[GOx/PANI/CNT]n). To evaluate how the GA/[GOx/PANI/CNT]n layer affects EBC performance and stability, electrochemical characterizations are implemented. Regarding optimization, GA/[GOx/PANI/CNT]3 is determined. For elucidating reaction mechanism between glucose and flavin adenine dinucleotide (FAD) of GA/[GOx/PANI/CNT]3, associated investigations are performed. In the evaluations, drop in reduction current peak of FAD is observed with provisions of glucose and O2, while glucose does not influence FAD reaction without O2, confirming O2 makes mediator role. When the GA/[GOx/PANI/CNT]3 layer is adopted, superior catalytic activity and EBC performance are gained (electron transfer rate constant of 5.1 s-1, glucose sensitivity of 150 ìA mM-1 cm-2, and EBC maximum power density (MPD) of 0.29 mW cm-2). Regarding EBC stability, MPD of EBC adopting GA/[GOx/PANI/CNT]3 maintains up to 93% of their initial value even after four weeks. Although GA is little effective for improving EBC performance, EBC stability is helped by GA due to its adhesion promotion capability with [GOx/PANI/CNT]n layer.

  7. Soil aggregation and the stabilization of organic carbon as affected by erosion and deposition

    NARCIS (Netherlands)

    Wang, X.; Cammeraat, E.L.H.; Cerli, C.; Kalbitz, K.

    2014-01-01

    The importance of soil aggregation in determining the dynamics of soil organic carbon (SOC) during erosion, transportation and deposition is poorly understood. Particularly, we do not know how aggregation contributes to the often-observed accumulation of SOC at depositional sites. Our objective was

  8. Effects of prenatal exposure to nanoparticles titanium dioxide and carbon black on female germline DNA stability

    DEFF Research Database (Denmark)

    Boisen, Anne Mette Zenner

    are actively dividing. The aim of this PhD study was to determine if two widely used nanoparticles titanium dioxide UV-Titan and carbon black Printex 90 induce ESTR mutations in the germ cells of prenatally exposed females. Pregnant generation P mice were exposed to ~42 mg UV-Titan/m3/1 h/d during gestation...

  9. 1D Ni-Co oxide and sulfide nanoarray/carbon aerogel hybrid nanostructures for asymmetric supercapacitors with high energy density and excellent cycling stability.

    Science.gov (United States)

    Hao, Pin; Tian, Jian; Sang, Yuanhua; Tuan, Chia-Chi; Cui, Guanwei; Shi, Xifeng; Wong, C P; Tang, Bo; Liu, Hong

    2016-09-15

    The fabrication of supercapacitor electrodes with high energy density and excellent cycling stability is still a great challenge. A carbon aerogel, possessing a hierarchical porous structure, high specific surface area and electrical conductivity, is an ideal backbone to support transition metal oxides and bring hope to prepare electrodes with high energy density and excellent cycling stability. Therefore, NiCo2S4 nanotube array/carbon aerogel and NiCo2O4 nanoneedle array/carbon aerogel hybrid supercapacitor electrode materials were synthesized by assembling Ni-Co precursor needle arrays on the surface of the channel walls of hierarchical porous carbon aerogels derived from chitosan in this study. The 1D nanostructures grow on the channel surface of the carbon aerogel vertically and tightly, contributing to the enhanced electrochemical performance with ultrahigh energy density. The energy density of NiCo2S4 nanotube array/carbon aerogel and NiCo2O4 nanoneedle array/carbon aerogel hybrid asymmetric supercapacitors can reach up to 55.3 Wh kg(-1) and 47.5 Wh kg(-1) at a power density of 400 W kg(-1), respectively. These asymmetric devices also displayed excellent cycling stability with a capacitance retention of about 96.6% and 92% over 5000 cycles.

  10. The Stability of Peatland Carbon Stores to Global Change: Evidence for Enhanced Methane and Carbon Dioxide Production

    Science.gov (United States)

    Chanton, J.; Wilson, R.; Tfaily, M. M.; Sebestyen, S. D.; Medvedeff, C.; McFarlane, K. J.; Kolka, R. K.; Kostka, J. E.; Keller, J.; Hanson, P. J.; Guilderson, T. P.; de La Cruz, F.; Cooper, W. T.; Bridgham, S. D.; Barlaz, M.

    2015-12-01

    Peatlands sequester large stores of carbon in sedimentary sequences that can be meters thick. Peatlands can be separated into two main layers: the acrotelm, which is exposed to the atmosphere and dominated by living plants, and the catotelm, which tends to be anoxic and is where the majority of organic matter is stored. In response to warming climate, to what extent will peatland organic matter be activated to form additional CH4 and CO2 relative to current production rates? To predict the answer to this question the SPRUCE (Spruce and Peatland Responses Under Climatic and Environmental Change) project is being conducted in a bog ecosystem in northern Minnesota. The study is designed to improve predictive skill in peat and wetland-methane models by defining quantitative relationships among decomposition indices, microbial communities, and CO2 and CH4 production rates. The manipulation is being conducted in a staged approach, and deep warming through the entire ~2 m peat profile was initiated in June of 2014 at +0, +2.2, +4.5, +6.8 and +9C. Starting in summer 2015, the project will enhance both above and belowground temperature and CO2 levels. Following months of temperature enhancement there is no evidence of an effect on catotelm peat. In bog pre-treatment, control and treatment plots, microbial respiration and CO2 and CH4 production in the deep peat is driven primarily by recent plant production and to date, this trend continues in the catolem following treatment. Methane d13C and fractionation factors are invariant across the treatments, as are gas concentrations at depth. Surface CH4 emission, however, has shown a positive correlation with peat temperature, and measurements of CH4 production in incubations across the depth profile suggest that surface peat is more responsive to increases in soil temperature, apparently driving the emission response. Shifts in the composition and metabolic potential of microbial communities are being examined using next

  11. Effect of charge on the stability of single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    LUO Ji; WU Jinlei

    2004-01-01

    By using density-functional-theory based DMol3 code, the structure optimizations are performed on a short charged single-walled carbon nanotube. Results show that the total energy of the nanotube exhibits a parabolic variation with respect to the amount of extra charge, and one negatively charged nanotube has the lowest total energy; thus the carbon nanotube has a positive electron affinity. When the charge is small, the variation of the atomic structure of the nanotube is also small, and neglecting the atomic structure variation leads to the qualitatively correct properties of the total energy and the energy of the highest occupied molecular orbital. When the extra charge is large, the end structure of the nanotube will be first affected and form into a trumpet shape. With the increasing of the extra charge, the nanotube end gradually becomes unstable, and this may lead to the ultimate destruction of the nanotube.

  12. Radial deformation and stability of single-wall carbon nanotubes under hydrostatic pressure

    OpenAIRE

    HASEGAWA, Masayuki; Nishidate, Kazume

    2006-01-01

    In this paper we have developed a theory of energetics for isolated single-wall carbon nanotubes SWNTsdeformed in the radial direction, and applied this theory to investigate their deformation characteristics andstability under hydrostatic pressure. The starting point of the theory is the strain energy of SWNTs predicted byab initio calculations based on the density functional theory DFT, which shows the same behavior as thatobtained for the continuum elastic shell model. We extend this resul...

  13. Conductivity and Ambient Stability of Halogen-Doped Carbon Nanotube Fibers

    Science.gov (United States)

    Gaier, J. R.; Chirino, C. M.; Chen, M.; Waters, D. L.; Tran, Mai Kim; Headrick, R.; Young, C. C.; Tsentalovich, D.; Whiting, B.; Pasquali, M.; Waarbeek, Ron ter; Otto, Marcin J.

    2014-01-01

    Carbon nanotube fibers were fabricated using a variety of spinning conditions and post-spinning processing with the goal of creating a high-conductivity yet environmentally stable fiber. These fiber variants were then doped with bromine, iodine, iodine chloride, or iodine bromide and their electrical and microstructural properties were characterized. Environmentally stable compounds were synthesized with electrical conductivity greater than 50,000 Scm.

  14. Stabilizing Acetylcholinesterase on Carbon Electrodes Using Peptide Nanotubes to Produce Effective Biosensors

    Science.gov (United States)

    2012-03-22

    2273 potentiostat connected to a notebook computer. Experiments were conducted in a Pine Research Instrumentation compact voltammetry cell. 2.3...and allowed to dry for 2 hours each. To measure stability, cyclic voltammetry measurements were taken in a testing solution of 0.1M KCl, 0.1M...and cyclic voltammetry measurements were taken every 10 days. The peak currents measured initially, io, and after storage, ii, were used to

  15. Flow induced vibration and stability analysis of multi wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Kyung Jae [Agency for Defense Development, Daejeon (Korea, Republic of); Choi, Jong Woon [Korean Intellectual Property Office, Daejeon (Korea, Republic of); Kim, Sung Kyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Song, Oh Seop [Chungnam National Univ., Daejeon (Korea, Republic of)

    2012-12-15

    The free vibration and flow induced flutter instability of cantilever multi wall carbon nanotubes conveying fluid are investigated and the nanotubes are modeled as thin-walled beams. The non-classical effects of the transverse shear, rotary inertia, warping inhibition, and van der Waals forces between two walls are incorporated into the structural model. The governing equations and associated boundary conditions are derived using Hamilton's principle. A numerical analysis is carried out by using the extended Galerkin method, which enables us to obtain more accurate solutions compared to the conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for a flow velocity below a certain critical value. However, beyond this critical flow velocity, flutter instability may occur. The variations in the critical flow velocity with respect to both the radius ratio and length of the carbon nanotubes are investigated and pertinent conclusions are outlined. The differences in the vibration and instability characteristics between the Timoshenko beam theory and Euler beam theory are revealed. A comparative analysis of the natural frequencies and flutter characteristics of MWCNTs and SWCNTs is also performed.

  16. Electrical resistance stability of high content carbon fiber reinforced cement composite

    Institute of Scientific and Technical Information of China (English)

    YANG Zai-fu; TANG Zu-quan; LI Zhuo-qiu; QIAN Jue-shi

    2005-01-01

    The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50℃C, increases relatively by 4% when ambient temperature decreases from 15℃ to-20℃, and decreases relatively by 13% with temperature increasing by 88℃. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

  17. Uniform Li2S precipitation on N,O-codoped porous hollow carbon fibers for high-energy-density lithium-sulfur batteries with superior stability.

    Science.gov (United States)

    Qie, Long; Manthiram, Arumugam

    2016-09-21

    A lithium-polysulfide cell with superior stability is reported with N,O-codoped carbon hollow fiber (NCHF) sheets as a current collector. Due to the highly effective chemisorption and physical adsorption of lithium polysulfides on doped NCHF and a uniform Li2S precipitation during cycling, the Li2S6-impregnated NCHF electrodes exhibit high sulfur utilization and superior cycling stability even with a high areal sulfur loading of 6.2 mg cm(-2).

  18. Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals

    Directory of Open Access Journals (Sweden)

    M. Schrumpf

    2013-03-01

    Full Text Available Conceptual models suggest that stability of organic carbon (OC in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Density fractionation is a useful tool to study the relevance of OC stabilization in aggregates and in association with minerals, but it has rarely been applied to full soil profiles. We aim to determine factors shaping the depth profiles of physically unprotected and mineral associated OC and test their relevance for OC stability across a range of European soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF were analysed for OC, total nitrogen (TN, δ14C, and Δ14C. Bulk samples were also incubated to determine CO2 evolution per g OC in the samples (specific mineralization rates as an indicator for OC stability. Depth profiles of OC in the light fraction (LF-OC matched those of roots for undisturbed grassland and forest sites, suggesting that roots are shaping the depth distribution of LF-OC. Organic C in the HF declined less with soil depth than LF-OC and roots, especially at grassland sites. The decrease in Δ14C (increase in age of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the Δ14C profiles. The LF at three sites were rather depleted in 14C, indicating the presence of fossil material such as coal and lignite, probably inherited from the parent material. At the other sites, modern Δ14C signatures and positive correlations between specific mineralization rates and fLF-OC indicate the fLF is a potentially available energy and

  19. Carbon doped molybdenum disulfide nanosheets stabilized on graphene for the hydrogen evolution reaction with high electrocatalytic ability

    Science.gov (United States)

    Li, Yong; Wang, Jiao; Tian, Xike; Ma, Longlong; Dai, Chu; Yang, Chao; Zhou, Zhaoxin

    2016-01-01

    Fabricating a cost effective hydrogen evolution reaction catalyst without using precious metal elements is in crucial demand for environmentally-benign energy production. In this work, the thin and edge-rich molybdenum disulfide nanosheets, with carbon doped in the interlayers and decorated on graphene, were developed by a facile solvothermal process. The as-synthesized nanohybrids exhibited high catalytic ability for the hydrogen evolution electrochemical reaction with an onset overpotential of 0.165 mV and a Tafel slope of 46 mV dec-1. Furthermore, the prepared nanohybrids also showed better durability and stability. Our work may lead to a potential method for in situ production of metal carbide-sulphur hybrid nanomaterials with promising applications for the hydrogen evolution reaction.Fabricating a cost effective hydrogen evolution reaction catalyst without using precious metal elements is in crucial demand for environmentally-benign energy production. In this work, the thin and edge-rich molybdenum disulfide nanosheets, with carbon doped in the interlayers and decorated on graphene, were developed by a facile solvothermal process. The as-synthesized nanohybrids exhibited high catalytic ability for the hydrogen evolution electrochemical reaction with an onset overpotential of 0.165 mV and a Tafel slope of 46 mV dec-1. Furthermore, the prepared nanohybrids also showed better durability and stability. Our work may lead to a potential method for in situ production of metal carbide-sulphur hybrid nanomaterials with promising applications for the hydrogen evolution reaction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07370g

  20. Functional Stability of a Mixed Microbial Consortium Producing PHA From Waste Carbon Sources

    Energy Technology Data Exchange (ETDEWEB)

    David N. Thompson; Erik R. Coats; William A. Smith; Frank J. Loge; Michael P. Wolcott

    2006-04-01

    Polyhydroxyalkanoates (PHAs) represent an environmentally-effective alternative to synthetic thermoplastics; however, current production practices are not sustainable. In this study, PHA production was accomplished in sequencing batch bioreactors utilizing real wastewaters and mixed microbial consortia from municipal activated sludge as inoculum. Polymer production reached 85%, 53%, and 10% of the cell dry weight from methanol-enriched pulp-and-paper mill foul condensate, fermented municipal primary solids, and biodiesel wastewater, respectively. Employing denaturing gradient gel electrophoresis of 16S-rDNA from PCR-amplified DNA extracts, distinctly different communities were observed between and within wastewaters following enrichment. Most importantly, functional stability was maintained despite differing and contrasting microbial populations.

  1. Structural stability of transparent conducting films assembled from length purified single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    J. M. Harris; G. R. S. Iyer; D. O. Simien; J. A. Fagan; J. Y. Huh; J. Y. Chung; S. D. Hudson; J. Obrzut; J. F. Douglas; C. M. Stafford; E. K. Hobbie

    2011-01-01

    Single-wall carbon nanotube (SWCNT) films show significant promise for transparent electronics applications that demand mechanical flexibility, but durability remains an outstanding issue. In this work, thin membranes of length purified single-wall carbon nanotubes (SWCNTs) are uniaxially and isotropically compressed by depositing them on prestrained polymer substrates. Upon release of the strain, the topography, microstructure, and conductivity of the films are characterized using a combination of optical/fluorescence microscopy, light scattering, force microscopy, electron microscopy, and impedance spectroscopy. Above a critical surface mass density, films assembled from nanotubes of well-defined length exhibit a strongly nonlinear mechanical response. The measured strain dependence reveals a dramatic softening that occurs through an alignment of the SWCNTs normal to the direction of prestrain, which at small strains is also apparent as an anisotropic increase in sheet resistance along the same direction. At higher strains, the membrane conductivities increase due to a compression-induced restoration of conductive pathways. Our measurements reveal the fundamental mode of elasto-plastic deformation in these films and suggest how it might be suppressed.

  2. Functional Stability Of A Mixed Microbial Consortia Producing PHA From Waste Carbon Sources

    Energy Technology Data Exchange (ETDEWEB)

    David N. Thompson; Erik R. Coats; William A. Smith; Frank J. Loge; Michael P. Wolcott

    2006-04-01

    Polyhydroxyalkanoates (PHAs), naturally-occurring biological polyesters that are microbially synthesized from a myriad of carbon sources, can be utilized as biodegradable substitutes for petroleum-derived thermoplastics. However, current PHA commercialization schemes are limited by high feedstock costs, the requirement for aseptic reactors, and high separation and purification costs. Bacteria indigenous to municipal waste streams can accumulate large quantities of PHA under environmentally controlled conditions; hence, a potentially more environmentally-effective method of production would utilize these consortia to produce PHAs from inexpensive waste carbon sources. In this study, PHA production was accomplished in sequencing batch bioreactors utilizing mixed microbial consortia from municipal activated sludge as inoculum, in cultures grown on real wastewaters. PHA production averaged 85%, 53%, and 10% of the cell dry weight from methanol-enriched pulp-and-paper mill foul condensate, fermented municipal primary solids, and biodiesel wastewater, respectively. The PHA-producing microbial consortia were examined to explore the microbial community changes that occurred during reactor operations, employing denaturing gradient gel electrophoresis (DGGE) of 16S-rDNA from PCR-amplified DNA extracts. Distinctly different communities were observed both between and within wastewaters following enrichment. More importantly, stable functions were maintained despite the differing and contrasting microbial populations.

  3. Soil organic carbon stabilization by iron in permafrost regions of the Qinghai-Tibet Plateau

    Science.gov (United States)

    Mu, C. C.; Zhang, T. J.; Zhao, Q.; Guo, H.; Zhong, W.; Su, H.; Wu, Q. B.

    2016-10-01

    A close relationship exists between soil organic carbon (SOC) and reactive iron; however, little is known about the role of iron in SOC preservation in permafrost regions. We determined the amount of SOC associated with reactive iron phases (OC-Fe) in the permafrost regions of the Qinghai-Tibetan Plateau (QTP). The results showed that the percentage of OC-Fe ranged between 0.9% and 59.5% in the upper 30 cm of soil and that the OC-Fe represented 19.5 ± 12.3% of the total SOC pool. No clear vertical distribution pattern in OC-Fe was present in the upper 1 m of soil. Throughout the year, the OC-Fe accounted for relatively stable proportions of the total SOC pool. This study suggests that approximately 20% of SOC is a potential rusty OC pool in the permafrost regions of the QTP. Biogeochemical processes related to the reaction of iron may play important roles in soil carbon cycles in permafrost regions.

  4. The Ferrocyanide/Stabilized Carbon System, a New Class of High Rate, Long Cycle Life, Aqueous Electrolyte Batteries

    KAUST Repository

    Huggins, R. A.

    2013-02-21

    Transient energy sources, such as wind and solar systems are getting increased attention. Their integration with the energy distribution grid requires methods for energy storage. The required characteristics of this type of storage are quite different from those for energy storage in portable devices. Size and weight are not so important. Instead, matters such as power, cost, calendar life, cycle life, and safety become paramount. A new family of hexacyanoferrate materials with the same open framework crystal structure as Prussian Blue has been recently developed with characteristics ideally suited for this type of application. Several monovalent cations can be rapidly and reversibly inserted into these materials, with very little crystallographic distortion, leading to high rates and long cycle lives. In addition, a new type of composite negative electrode material has been developed that has the rapid kinetics typical of carbon electrodes, but with a potential that varies little with the state of charge. The result is the development of a new battery system, the ferrocyanide/stabilized carbon, MHCF-SC, system. © 2013 The Electrochemical Society.

  5. Stability of carbon fiber surface chemistry under temperature and its influence on interfacial adhesion with polymer matrices

    Energy Technology Data Exchange (ETDEWEB)

    Vautard, Frederic [ORNL; Grappe, Hippolyte A [ORNL; Ozcan, Soydan [ORNL

    2013-01-01

    The thermal stability of the surface chemistry of a surface treated carbon fiber was investigated by X-ray Photoelectron Spectroscopy. Within a range of temperatures from room temperature to 400 C, the only surface functionalities that decomposed were carboxylic acids and dangling nitrogen containing functionalities like amines, amides or nitriles. Significant amounts of water were desorbed as well. This study enabled the testing of the coherence our the fitting of the C(1s), O(1s) and N(1s) peaks. Particularly, when considering the fitting of in the O(1s) peak, carboxylic acids were shown to be included in a single component peak centered at a binding energy of 532.1 eV. The reaction of the carbon fiber surface and an acrylate resin at high temperature, because of the decomposition of carboxylic acids, was highlighted by Differential Scanning Calorimetry. The thermal history of the composite material during its manufacture appeared to be a major influence on the nature of the interactions generated at the fiber-matrix interface and the resulting mechanical properties.

  6. Crystallization behavior and thermal stability of poly(butylene succinate)/poly(propylene carbonate) blends prepared by novel vane extruder

    Science.gov (United States)

    Chen, Rongyuan; Zou, Wei; Zhang, Haichen; Zhang, Guizhen; Qu, Jinping

    2016-03-01

    This work focused on the study of crystallization behavior and thermal stability of degradable poly(butylene succinate) (PBS) and poly(propylene carbonate) (PPC) blends prepared by vane extruder based on elongation force field, which is novel equipment for polymer processing. Dicumyl peroxide (DCP) was applied in this work as compatibilizer for PBS/PPC blend. Crystallization behavior and melting behavior of the blends were investigated by differential scanning calorimetry (DSC) testing. Thermal stability of the blends was studied by thermogravimetric (TG) testing. Furthermore, the melt flow indices (MFI) of the blends were examined by a MFI instrument. The results showed that the crystallization temperature of PBS decreased with the addition of PPC and DCP. The glass transition temperature of PPC increased and the melting temperature of the blend increased with the addition of PPC and DCP, which indicated that the entanglement between the molecular chains of PBS and PPC was enhanced. Thermogravimetric analysis showed that a two-step decomposition process of the blend occurred due to the different thermal resistance of PBS and PPC, and the addition of PBS reduced the decomposition rate of PPC. Moreover, the addition of PBS improved the melt flow property of PPC.

  7. Enhanced removal of Cd(II) and Pb(II) by composites of mesoporous carbon stabilized alumina

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Weichun [Department of Environmental Engineering, School of Metallurgy and Environment, Central South University, Lushan South Road 932, Changsha 410017 (China); Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Lushan South Road 932, Changsha 410017 (China); Tang, Qiongzhi; Wei, Jingmiao; Ran, Yajun [Department of Environmental Engineering, School of Metallurgy and Environment, Central South University, Lushan South Road 932, Changsha 410017 (China); Chai, Liyuan [Department of Environmental Engineering, School of Metallurgy and Environment, Central South University, Lushan South Road 932, Changsha 410017 (China); Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Lushan South Road 932, Changsha 410017 (China); Wang, Haiying, E-mail: haiyw25@163.com [Department of Environmental Engineering, School of Metallurgy and Environment, Central South University, Lushan South Road 932, Changsha 410017 (China); Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Lushan South Road 932, Changsha 410017 (China)

    2016-04-30

    Graphical abstract: - Highlights: • Mesoporous carbon stabilized alumina was prepared by one-pot hard-templating method. • MC/Al{sub 2}O{sub 3} showed excellent performance for Cd(II) and Pb(II) adsorption. • Enhanced adsorption was due to the high surface area and special functional groups. - Abstract: A novel adsorbent of mesoporous carbon stabilized alumina (MC/Al{sub 2}O{sub 3}) was synthesized through one-pot hard-templating method. The adsorption potential of MC/Al{sub 2}O{sub 3} for Cd(II) and Pb(II) from aqueous solution was investigated compared with the mesoporous carbon. The results indicated the MC/Al{sub 2}O{sub 3} showed excellent performance for Cd(II) and Pb(II) removal, the adsorption capacity reached 49.98 mg g{sup −1} for Cd(II) with initial concentration of 50 mg L{sup −1} and reached 235.57 mg g{sup −1} for Pb(II) with initial concentration of 250 mg L{sup −1}, respectively. The kinetics data of Cd(II) adsorption demonstrated that the Cd(II) adsorption rate was fast, and the removal efficiencies with initial concentration of 10 and 50 mg L{sup −1} can reach up 99% within 5 and 20 min, respectively. The pseudo-second-order kinetic model could describe the kinetics of Cd(II) adsorption well, indicating the chemical reaction was the rate-controlling step. The mechanism for Cd(II) and Pb(II) adsorption by MC/Al{sub 2}O{sub 3} was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR), and the results indicated that the excellent performance for Cd(II) and Pb(II) adsorption of MC/Al{sub 2}O{sub 3} was mainly attributed to its high surface area and the special functional groups of hydroxy-aluminum, hydroxyl, carboxylic through the formation of strong surface complexation or ion-exchange. It was concluded that MC/Al{sub 2}O{sub 3} can be recognized as an effective adsorbent for removal of Cd(II) and Pb(II) in aqueous solution.

  8. Field application of activated carbon amendment for in-situ stabilization of polychlorinated biphenyls in marine sediment.

    Science.gov (United States)

    Cho, Yeo-Myoung; Ghosh, Upal; Kennedy, Alan J; Grossman, Adam; Ray, Gary; Tomaszewski, Jeanne E; Smithenry, Dennis W; Bridges, Todd S; Luthy, Richard G

    2009-05-15

    We report results on the first field-scale application of activated carbon (AC) amendment to contaminated sediment for in-situ stabilization of polychlorinated biphenyls (PCBs). The test was performed on a tidal mud flat at South Basin, adjacent to the former Hunters Point Naval Shipyard, San Francisco Bay, CA. The major goals of the field study were to (1) assess scale up of the AC mixing technology using two available, large-scale devices, (2) validate the effectiveness of the AC amendment at the field scale, and (3) identify possible adverse effects of the remediation technology. Also, the test allowed comparison among monitoring tools, evaluation of longer-term effectiveness of AC amendment, and identification of field-related factors that confound the performance of in-situ biological assessments. Following background pretreatment measurements, we successfully incorporated AC into sediment to a nominal 30 cm depth during a single mixing event, as confirmed by total organic carbon and black carbon contents in the designated test plots. The measured AC dose averaged 2.0-3.2 wt% and varied depending on sampling locations and mixing equipment. AC amendment did not impact sediment resuspension or PCB release into the water column over the treatment plots, nor adversely impactthe existing macro benthic community composition, richness, or diversity. The PCB bioaccumulation in marine clams was reduced when exposed to sediment treated with 2% AC in comparison to the control plot Field-deployed semi permeable membrane devices and polyethylene devices showed about 50% reduction in PCB uptake in AC-treated sediment and similar reduction in estimated pore-water PCB concentration. This reduction was evident even after 13-month post-treatment with then 7 months of continuous exposure, indicating AC treatment efficacy was retained for an extended period. Aqueous equilibrium PCB concentrations and PCB desorption showed an AC-dose response. Field-exposed AC after 18 months

  9. Initial characterization of processes of soil carbon stabilization using forest stand-level radiocarbon enrichment

    Energy Technology Data Exchange (ETDEWEB)

    Swanston, C W; Torn, M S; Hanson, P J; Southon, J R; Garten, C T; Hanlon, E M; Ganio, L

    2004-01-15

    Although the rates and mechanisms of soil organic matter (SOM) stabilization are difficult to observe directly, radiocarbon has proven an effective tracer of soil C dynamics, particularly when coupled with practical fractionation schemes. To explore the rates of C cycling in temperate forest soils, we took advantage of a unique opportunity in the form of an inadvertent stand-level {sup 14}C-labeling originating from a local industrial release. A simple density fractionation scheme separated SOM into inter-aggregate particulate organic matter (free light fraction, free LF), particulate organic matter occluded within aggregates (occluded LF), and organic matter that is complexed with minerals to form a dense fraction (dense fraction, DF). Minimal agitation and density separation was used to isolate the free LF. The remaining dense sediment was subjected to physical disruption and sonication followed by density separation to separate it into occluded LF and DF. The occluded LF had higher C concentrations and C:N ratios than the free LF, and the C concentration in both light fractions was ten times that of the DF. As a result, the light fractions together accounted for less than 4% of the soil by weight, but contained 40% of the soil C in the 0-15 cm soil increment. Likewise, the light fractions were less than 1% weight of the 15-30 cm increment, but contained more than 35% of the soil C. The degree of SOM protection in the fractions, as indicated by {Delta}{sup 14}C, was different. In all cases the free LF had the shortest mean residence times. A significant depth by fraction interaction for {sup 14}C indicates that the relative importance of aggregation versus organo-mineral interactions for overall C stabilization changes with depth. The rapid incorporation of {sup 14}C label into the otherwise depleted DF shows that this organo-mineral fraction comprises highly stable material as well as more recent inputs.

  10. Organic carbon, water repellency and soil stability to slaking at aggregate and intra-aggregate scales

    Science.gov (United States)

    Jordán López, Antonio; García-Moreno, Jorge; Gordillo-Rivero, Ángel J.; Zavala, Lorena M.; Cerdà, Artemi; Alanís, Nancy; Jiménez-Compán, Elizabeth

    2015-04-01

    Water repellency (WR) is a property of some soils that inhibits or delays water infiltration between a few seconds and days or weeks. Inhibited or delayed infiltration contributes to ponding and increases runoff flow generation, often increasing soil erosion risk. In water-repellent soils, water infiltrates preferentially through cracks or macropores, causing irregular soil wetting patterns, the development of preferential flow paths and accelerated leaching of nutrients. Although low inputs of hydrophobic organic substances and high mineralization rates lead to low degrees of WR in cropped soils, it has been reported that conservative agricultural practices may induce soil WR. Although there are many studies at catchment, slope or plot scales very few studies have been carried out at particle or aggregate scale. Intra-aggregate heterogeneity of physical, biological and chemical properties conditions the transport of substances, microbial activity and biochemical processes, including changes in the amount, distribution and chemical properties of organic matter. Some authors have reported positive relationships between soil WR and aggregate stability, since it may delay the entry of water into aggregates, increase structural stability and contribute to reduce soil erosion risk. Organic C (OC) content, aggregate stability and WR are therefore strongly related parameters. In the case of agricultural soils, where both the type of management as crops can influence all these parameters, it is important to evaluate the interactions among them and their consequences. Studies focused on the intra-aggregate distribution of OC and WR are necessary to shed light on the soil processes at a detailed scale. It is extremely important to understand how the spatial distribution of OC in soil aggregates can protect against rapid water entry and help stabilize larger structural units or lead to preferential flow. The objectives of this research are to study [i] the OC content and the

  11. Forehead tissue expander.

    Science.gov (United States)

    Kisner, W H

    1991-02-01

    The use of the forehead flap for nasal reconstruction has long been used by reconstructive surgeons. A case is presented in which comprised forehead skin is utilized following expansion by a tissue expander.

  12. Reforestation with native mixed-species plantings in a temperate continental climate effectively sequesters and stabilizes carbon within decades.

    Science.gov (United States)

    Cunningham, Shaun C; Cavagnaro, Timothy R; Mac Nally, Ralph; Paul, Keryn I; Baker, Patrick J; Beringer, Jason; Thomson, James R; Thompson, Ross M

    2015-04-01

    Reforestation has large potential for mitigating climate change through carbon sequestration. Native mixed-species plantings have a higher potential to reverse biodiversity loss than do plantations of production species, but there are few data on their capacity to store carbon. A chronosequence (5-45 years) of 36 native mixed-species plantings, paired with adjacent pastures, was measured to investigate changes to stocks among C pools following reforestation of agricultural land in the medium rainfall zone (400-800 mm yr(-1)) of temperate Australia. These mixed-species plantings accumulated 3.09 ± 0.85 t C ha(-1) yr(-1) in aboveground biomass and 0.18 ± 0.05 t C ha(-1) yr(-1) in plant litter, reaching amounts comparable to those measured in remnant woodlands by 20 years and 36 years after reforestation respectively. Soil C was slower to increase, with increases seen only after 45 years, at which time stocks had not reached the amounts found in remnant woodlands. The amount of trees (tree density and basal area) was positively associated with the accumulation of carbon in aboveground biomass and litter. In contrast, changes to soil C were most strongly related to the productivity of the location (a forest productivity index and soil N content in the adjacent pasture). At 30 years, native mixed-species plantings had increased the stability of soil C stocks, with higher amounts of recalcitrant C and higher C:N ratios than their adjacent pastures. Reforestation with native mixed-species plantings did not significantly change the availability of macronutrients (N, K, Ca, Mg, P, and S) or micronutrients (Fe, B, Mn, Zn, and Cu), content of plant toxins (Al, Si), acidity, or salinity (Na, electrical conductivity) in the soil. In this medium rainfall area, native mixed-species plantings provided comparable rates of C sequestration to local production species, with the probable additional benefit of providing better quality habitat for native biota. These results

  13. The kinetic and thermodynamic sorption and stabilization of multiwalled carbon nanotubes in natural organic matter surrogate solutions: the effect of surrogate molecular weight.

    Science.gov (United States)

    Li, Tingting; Lin, Daohui; Li, Lu; Wang, Zhengyu; Wu, Fengchang

    2014-03-01

    Styrene sulfonate (SS) and polystyrene sulfonates (PSSs) were used as surrogates of natural organic matter to study the effect of molecular weight (from 206.2 to 70,000 Da) on their sorption by a multiwalled carbon nanotube (MWCNT) and an activated carbon (AC) and on their stabilization of MWCNT suspension. Results indicate that surface-diffusion through the liquid-sorbent boundary was the rate-controlling step of the kinetic sorption of both MWCNTs and AC, and surface-occupying and pore-filling mechanisms respectively dominated the thermodynamic sorption of MWCNTs and AC. Sorption rates and capacities of MWCNTs and AC in molecular concentration of SS and PSS decreased with increasing molecular weight. The PSSs but not SS facilitated the stabilization of MWCNT suspension because of the increased electrosteric repulsion. The PSSs with more monomers had greater capabilities to stabilize the MWCNT suspension, but the capabilities were comparable after being normalized by the total monomer number.

  14. Carotenoids, Fatty Acid Composition and Heat Stability of Supercritical Carbon Dioxide-Extracted-Oleoresins

    Directory of Open Access Journals (Sweden)

    Antonella Leone

    2012-03-01

    Full Text Available The risk of chronic diseases has been shown to be inversely related to tomato intake and the lycopene levels in serum and tissue. Cis-isomers represent approximately 50%–80% of serum lycopene, while dietary lycopene maintains the isomeric ratio present in the plant sources with about 95% of all-trans-lycopene. Supercritical CO2 extraction (S-CO2 has been extensively developed to extract lycopene from tomato and tomato processing wastes, for food or pharmaceutical industries, also by using additional plant sources as co-matrices. We compared two S-CO2-extracted oleoresins (from tomato and tomato/hazelnut matrices, which showed an oil-solid bi-phasic appearance, a higher cis-lycopene content, and enhanced antioxidant ability compared with the traditional solvent extracts. Heat-treating, in the range of 60–100 °C, led to changes in the lycopene isomeric composition and to enhanced antioxidant activity in both types of oleoresins. The greater stability has been related to peculiar lycopene isomer composition and to the lipid environment. The results indicate these oleoresins are a good source of potentially healthful lycopene.

  15. Mesoporous phenylalanine ammonia lyase microspheres with improved stability through calcium carbonate templating.

    Science.gov (United States)

    Cui, Jiandong; Zhao, Yamin; Tan, Zhilei; Zhong, Cheng; Han, Peipei; Jia, Shiru

    2017-05-01

    Cross-linked enzyme aggregates (CLEAs) have recently emerged as a promising method for enzyme immobilization due to its simplicity and low cost. However, a lack of good size and morphological control over the as-prepared CLEAs has limited their practical applications in some cases. Here, monodisperse spherical CLEAs of phenylalanine ammonia lyase (PAL microspheres) were prepared based on CaCO3 microtemplates. The preparation procedure involves filling porous CaCO3 microtemplates with the protein by salt precipitation, glutaraldehyde crosslinking, and dissolution of the microtemplates. The formulation of CaCO3 templates with controlled size was studied in detail. Characterization of the prepared PAL microspheres was investigated. The results showed that the PAL microspheres with high immobilization efficiency (79%) exhibited excellent stability, including increased tolerance to proteolysis, low pH, and denaturants, and excellent mechanical properties. For example, free PAL almost lost all activity after they were incubated in the presence of trypsin for 2min, whereas PAL microspheres still retained 95% of their initial activity. Moreover, scanning electron microscope, transmission electron microscope, and N2 adsorption-desorption isotherms revealed that the resultant PAL microspheres possessed good monodispersity and mesoporous structure instead of the amorphous clusters of conventional CLEAs with few pores. Compared with conventional CLEAs, the monodisperse PAL microspheres with mesoporous make them more potentially useful for biomedical and biotechnological applications.

  16. Carotenoids, fatty acid composition and heat stability of supercritical carbon dioxide-extracted-oleoresins.

    Science.gov (United States)

    Longo, Cristiano; Leo, Lucia; Leone, Antonella

    2012-01-01

    The risk of chronic diseases has been shown to be inversely related to tomato intake and the lycopene levels in serum and tissue. Cis-isomers represent approximately 50%-80% of serum lycopene, while dietary lycopene maintains the isomeric ratio present in the plant sources with about 95% of all-trans-lycopene. Supercritical CO(2) extraction (S-CO(2)) has been extensively developed to extract lycopene from tomato and tomato processing wastes, for food or pharmaceutical industries, also by using additional plant sources as co-matrices. We compared two S-CO(2)-extracted oleoresins (from tomato and tomato/hazelnut matrices), which showed an oil-solid bi-phasic appearance, a higher cis-lycopene content, and enhanced antioxidant ability compared with the traditional solvent extracts. Heat-treating, in the range of 60-100 °C, led to changes in the lycopene isomeric composition and to enhanced antioxidant activity in both types of oleoresins. The greater stability has been related to peculiar lycopene isomer composition and to the lipid environment. The results indicate these oleoresins are a good source of potentially healthful lycopene.

  17. Functionalization of Metal-Organic Frameworks for Enhanced Stability under Humid Carbon Dioxide Capture Conditions.

    Science.gov (United States)

    Andirova, Dinara; Lei, Yu; Zhao, Xiaodan; Choi, Sunho

    2015-10-26

    Metal-organic frameworks (MOFs) have been highlighted recently as promising materials for CO2 capture. However, in practical CO2 capture processes, such as capture from flue gas or ambient air, the adsorption properties of MOFs tend to be harmed by the presence of moisture possibly because of the hydrophilic nature of the coordinatively unsaturated sites (CUSs) within their framework. In this work, the CUSs of the MOF framework are functionalized with amine-containing molecules to prevent structural degradation in a humid environment. Specifically, the framework of the magnesium dioxybenzenedicarboxylate (Mg/DOBDC) MOF was functionalized with ethylenediamine (ED) molecules to make the overall structure less hydrophilic. Structural analysis after exposure to high-temperature steam showed that the ED-functionalized Mg/DOBDC (ED-Mg/DOBDC) is more stable under humid conditions, than Mg/DOBDC, which underwent drastic structural changes. ED-Mg/DOBDC recovered its CO2 adsorption capacity and initial adsorption rate quite well as opposed to the original Mg/DOBDC, which revealed a significant reduction in its capture capacity and kinetics. These results suggest that the amine-functionalization of the CUSs is an effective way to enhance the structural stability of MOFs as well as their capture of humid CO2 .

  18. Effect of sustainable land management practices on soil aggregation and stabilization of organic carbon in semiarid mediterranean ecosystems

    Science.gov (United States)

    Garcia-Franco, Noelia; Albaladejo, Juan; Almagro, María; Wiesmeier, Martin; Martínez-Mena, María

    2016-04-01

    Arid and semiarid regions represent about 47% of the total land area of the world (UNEP, 1992). At present, there is a priority interest for carbon (C) sequestration in drylands. These areas are considered as very fragile ecosystems with low organic carbon (OC) saturation, and potentially, high capacity for soil OC sequestration. In addition, the restoration of these areas is one of the major challenges for scientists, who will be able to identify and recommended the best land uses and sustainable land management (SLM) practices for soil conservation and mitigation of climate change in these environments. In this regard, in semiarid Mediterranean ecosystems there is an urgent need for the implementation of SLM practices regardless of land-use type (forest, agricultural and shrubland) to maintain acceptable levels of soil organic matter (SOM) and the physico-chemical protection of the OC. Long- and short-term effects of SLM practices on soil aggregation and SOC stabilization were studied in two land uses. The long-term experiment was conducted in a reforestation area with Pinus halepensis Mill., where two afforestation techniques were implemented 20 years ago: a) mechanical terracing with a single application of organic waste of urban soil refuse, and b) mechanical terracing without organic amendment. An adjacent shrubland was considered as the reference plot. The short-term experiment was conducted in a rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard where two SLM practices were introduced 4 years ago: a) reduced tillage plus green manure, and b) no tillage. Reduced tillage was considered as the reference plot given that it is the habitual management practice. Four aggregate size classes were differentiated by sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, different organic C fractions corresponding with active

  19. Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals

    Directory of Open Access Journals (Sweden)

    M. Schrumpf

    2012-09-01

    Full Text Available Conceptual models suggest that stability and age of organic carbon (OC in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Various tools like density fractionation, mineralization experiments, and radiocarbon analyses have been used to study the importance of these mechanisms. We systematically apply them to a range of European soils to test whether general controls emerge even for soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled in 10 cm depth intervals to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF were analysed for OC, total nitrogen (TN, δ13C, and Δ14C. Bulk samples were also incubated to determine mineralizable OC.

    Declining OC-normalized CO2 release and increasing age with soil depth confirm greater stability of OC in subsoils across sites. Depth profiles of LF-OC matched those of roots, which in turn reflect plant functional types in soil profiles not subject to ploughing. Modern Δ14C signatures and positive correlation between mineralizable C and fLF-OC indicate the fLF is an easily available energy and nutrient source for subsurface microbes. Fossil C derived from the geogenic parent material affected the age of OC especially in the LF at three study sites. The overall importance of OC stabilization by binding to minerals was demonstrated by declining OC-normalized CO2 release rates with increasing contributions of HF-OC to bulk soil OC and the low Δ14C values of HF-OC. The stability of HF-OC was greater in subsoils than in topsoils; nevertheless, a portion of HF-OC was active throughout the profile. The decrease in Δ14C (increase

  20. Structural and elastic properties and stability characteristics of oxygenated carbon nanotubes under physical adsorption of polymers

    Energy Technology Data Exchange (ETDEWEB)

    Ansari, R., E-mail: r_ansari@guilan.ac.ir [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Ajori, S. [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Rouhi, S. [Department of Mechanical Engineering, Langroud Branch, Islamic Azad University, Langroud (Iran, Islamic Republic of)

    2015-03-30

    Highlights: • Buckling of functionalized CNTs under physical adsorption of polymer is studied. • Molecular dynamics simulations are employed for the study. • Values of the critical buckling load and critical strain are shown to increase. • Values of Young's modulus and their variations are dependent on adsorbed polymer type. - Abstract: The importance of covalent and non-covalent functionalization approaches for modification the properties of carbon nanotubes is being more widely recognized. To this end, elastic properties and buckling behavior of oxygenated CNT with atomic oxygen and hydroxyl under physical adsorption of PE (Polyethylene) and PEO (Poly (ethylene oxide)) are determined through employing the molecular dynamics (MD) simulations. The results demonstrate that non-covalent bonding of polymer on the surface of oxygenated CNT causes reductions in the variations of critical buckling load and critical strain compared to oxygenated CNTs. Critical buckling load and critical strain of oxygenated CNT/polymer are higher than those of oxygenated CNT. Also, it is demonstrated that critical buckling load and critical strain values in the case of oxygenated CNT/polymer are independent of polymer type unlike the value of Young's modulus. It is shown that variations of Young's modulus decrease as PE adsorbed on the surface of oxygenated CNT. Moreover, the presence of oxygen atom on PEO chain leads to bigger variations of Young's modulus with weight percentage of chemisorbed component, i.e. atomic oxygen and hydroxyl. It is also demonstrated that Young's modulus reduces more considerably in the presence of PEO chain compared to PE one.

  1. Stabilization of Mass Absorption Cross Section of Elemental Carbon for Filter-Based Absorption Photometer by Heated Inlet

    Science.gov (United States)

    Kondo, Y.; Sahu, L.; Takegawa, N.; Miyazaki, Y.; Han, S.; Moteki, N.; Hu, M.; Kim Oanh, N.; Kim, Y.

    2008-12-01

    Accurate measurements of elemental carbon (EC) or black carbon on a long-term basis are important for the studies of impacts of EC on climate and human health. In principle, mass concentrations of EC (MEC) can be estimated by the measurement of light absorption coefficient by EC. Filter-based methods, which quantify the absorption coefficient (kabs) from the change in transmission through a filter loaded with particles, have been widely used to measure MEC because of the ease of the operation. However, in practice, reliable determination of MEC has been very difficult because of the large variability in the mass absorption cross sections (Cabs), which is a conversion factor from kabs to MEC. Coating of EC by volatile compounds and co-existence of light-scattering particles greatly contributes to the variability of Cabs. In order to overcome this difficulty, volatile aerosol components were removed before collection of EC particles on filters by heating an inlet section to 400°C. The heated inlet vaporized almost completely sulfate, nitrate, ammonium, and organics without any detectable loss of EC. Simultaneous measurements of kabs by two types photometers (Particle Soot Absorption Photometer (PSAP) and Continuous Soot Monitoring System (COSMOS)) together with MEC by the EC-OC analyzer were made to determine Cabs at 6 different locations in Asia (Japan, Korea, China, and Thailand) in different seasons. The Cabs was stable to be 10.5±0.7 m2 g-1 at the wavelength of 565 nm for EC strongly impacted by emissions from vehicles and biomass burning. The stability of the Cabs for different EC sources and under the different physical and chemical conditions provides a firm basis for its use in estimating MEC in fine mode with an accuracy of about 10%.

  2. Enhanced removal of Cd(II) and Pb(II) by composites of mesoporous carbon stabilized alumina

    Science.gov (United States)

    Yang, Weichun; Tang, Qiongzhi; Wei, Jingmiao; Ran, Yajun; Chai, Liyuan; Wang, Haiying

    2016-04-01

    A novel adsorbent of mesoporous carbon stabilized alumina (MC/Al2O3) was synthesized through one-pot hard-templating method. The adsorption potential of MC/Al2O3 for Cd(II) and Pb(II) from aqueous solution was investigated compared with the mesoporous carbon. The results indicated the MC/Al2O3 showed excellent performance for Cd(II) and Pb(II) removal, the adsorption capacity reached 49.98 mg g-1 for Cd(II) with initial concentration of 50 mg L-1 and reached 235.57 mg g-1 for Pb(II) with initial concentration of 250 mg L-1, respectively. The kinetics data of Cd(II) adsorption demonstrated that the Cd(II) adsorption rate was fast, and the removal efficiencies with initial concentration of 10 and 50 mg L-1 can reach up 99% within 5 and 20 min, respectively. The pseudo-second-order kinetic model could describe the kinetics of Cd(II) adsorption well, indicating the chemical reaction was the rate-controlling step. The mechanism for Cd(II) and Pb(II) adsorption by MC/Al2O3 was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR), and the results indicated that the excellent performance for Cd(II) and Pb(II) adsorption of MC/Al2O3 was mainly attributed to its high surface area and the special functional groups of hydroxy-aluminum, hydroxyl, carboxylic through the formation of strong surface complexation or ion-exchange. It was concluded that MC/Al2O3 can be recognized as an effective adsorbent for removal of Cd(II) and Pb(II) in aqueous solution.

  3. Soil Organic Carbon Storage and Stability in the Aspen-Conifer Ecotone in Montane Forests in Utah, USA

    Directory of Open Access Journals (Sweden)

    Mercedes Román Dobarco

    2014-04-01

    Full Text Available To assess the potential impact of conifer encroachment on soil organic carbon (SOC dynamics and storage in montane aspen-conifer forests from the interior western US, we sampled mineral soils (0–15 cm across the aspen-conifer ecotones in southern and northern Utah and quantified total SOC stocks, stable SOC (i.e., mineral-associated SOC (MoM, labile SOC (i.e., light fraction (LF, decomposable (CO2 release during long-term aerobic incubations and soluble SOC (hot water extractable organic carbon (HWEOC. Total SOC storage (47.0 ± 16.5 Mg C ha−1 and labile SOC as LF (14.0 ± 7.10 Mg C ha−1, SOC decomposability (cumulative released CO2-C of 5.6 ± 3.8 g C g−1 soil or HWEOC (0.6 ± 0.6 mg C g−1 soil did not differ substantially with vegetation type, although a slight increase in HWEOC was observed with increasing conifer in the overstory. There were statistically significant differences (p = 0.035 in stable MoM storage, which was higher under aspen (31.2 ± 15.1 Mg C ha−1 than under conifer (22.8 ± 9.0 Mg C ha−1, with intermediate values under mixed (25.7 ± 8.8 Mg C ha−1. Texture had the greatest impact on SOC distribution among labile and stable fractions, with increasing stabilization in MoM and decreasing bio-availability of SOC with increasing silt + clay content. Only at lower silt + clay contents (40%–70% could we discern the influence of vegetation on MoM content. This highlights the importance of chemical protection mechanisms for long-term C sequestration.

  4. Enhancement of electron emission and long-term stability of tip-type carbon nanotube field emitters via lithium coating

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong-Pil [Health and Medical Equipment R and D Team, Samsung Electronics, Suwon, Gyeonggi-do 443-742 (Korea, Republic of); Chang, Han-Beet; Kim, Bu-Jong [Dept. of Electronic Systems Engineering, Hanyang University, Ansan, Gyeonggi-do 426-791 (Korea, Republic of); Park, Jin-Seok, E-mail: jinsp@hanyang.ac.kr [Dept. of Electronic Systems Engineering, Hanyang University, Ansan, Gyeonggi-do 426-791 (Korea, Republic of)

    2013-01-01

    Carbon nanotubes (CNTs) were deposited on conical tip-type substrates via electrophoresis and coated with lithium (Li) thin films with diverse thicknesses via electroplating. For the as-deposited (i.e., without Li coating) CNT, the turn-on (or triggering) electric field was 0.92 V/μm, and the emission current, which was generated at an applied field of 1.2 V/μm was 56 μA. In the case of the 4.7 nm-thick Li-coated CNT, the turn-on field decreased to 0.65 V/μm and the emission current at the same applied field increased more than ten times to 618 μA. The analysis based on the Kelvin probe measurement and Fowler–Nordheim theory indicated that the coating of Li caused a loss in the structural-aspect-ratio of the CNTs and it reduced their effective work functions from 5.36 eV to 4.90 eV, which led to a great improvement of their electron emission characteristics. The results obtained in this study also showed that the long-term emission stability could be enhanced by the coating of thin Li films on CNTs. - Highlights: ► CNTs are deposited via electrophoretic deposition (EPD). ► Thin films of Li are coated on CNTs via electroplating, without plasma damage. ► Li coating enhanced field emission properties and emission stability of CNTs. ► The effective work functions and field enhancement factors of CNTs are evaluated.

  5. Stabilization by hydrophobic protection as a molecular mechanism for organic carbon sequestration in maize-amended rice paddy soils.

    Science.gov (United States)

    Song, X Y; Spaccini, R; Pan, G; Piccolo, A

    2013-08-01

    The hydrophobic components of soil organic matter (SOM) are reckoned to play an important role in the stabilization of soil organic carbon (SOC). The contribution of hydrophobic substances to SOC sequestration was evaluated in four different paddy soils in the South of China, following a 6-month incubation experiment with maize straw amendments. Soil samples included: a well developed paddy soil (TP) derived from clayey lacustrine deposits in the Tai Lake plain of Jiangsu; an acid clayey paddy soil (RP) derived from red earth in the rolling red soil area of Jiangxi; a weakly developed neutral paddy soil (PP) formed on Jurassic purple shale from Chongq; and a calcic Fluvisol (MS) derived from riverine sediments from a wetland along the Yangtze valley of Anhui, China. The SOC molecular composition after 30 and 180 days of incubation, was determined by off-line thermochemolysis followed by gas chromatography-mass spectrometry analysis. Lignin, lipids and carbohydrates were the predominant thermochemolysis products released from the treated soils. A selective preservation of hydrophobic OM, including lignin and lipids, was shown in maize amended soils with prolonged incubation. The decomposition of lignin and lipids was significantly slower in the TP and RP soils characterized by a larger content of extractable iron oxyhydrates (Fed) and lower pH. The overall increase in hydrophobic substances in maize incubated samples was correlated, positively, with total content of clay and Fed, and, negatively, with soil pH. Moreover, yields of both lignin and lipid components showed a significant relationship with SOC increase after incubation. These findings showed that the larger the lipid and lignin content of SOM, the greater was the stability of SOC, thereby suggesting that OM hydrophobic components may have an essential role in controlling the processes of OC sequestration in paddy soils of South China.

  6. Application of δ13C and δ15N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms

    Directory of Open Access Journals (Sweden)

    M. Sommer

    2011-10-01

    Full Text Available Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. Analysis of δ13C and δ15N isotopic signatures of stabilized OM fractions along with soil mineral characteristics may yield important information about OM-mineral associations and their processing history. We anlayzed the δ13C and δ15N isotopic signatures from two organic matter (OM fractions along with soil mineral proxies to identify the likely binding mechanisms involved. We analyzed OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1 OM separated chemically with sodium pyrophosphate (OM(PY and (2 OM occluded in micro-structures found in the chemical extraction residue (OM(ER. Because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established mineral and chemical proxies indicative for certain binding mechanisms. We found different mechanisms predominate in each land use type. For arable soils, the formation of OM(PY-Ca-mineral associations was identified as an important OM binding mechanism. Therefore, we hypothesize an increased stabilization of microbial processed OM(PY through Ca2+ interactions. In general, we found the forest soils to contain on average 10% more stabilized carbon relative to total carbon stocks, than the agricultural counter part. In forest soils, we found a positive relationship between isotopic signatures of OM(PY and the ratio of soil organic carbon content to soil surface area (SOC/SSA. This indicates that the OM(PY fractions of forest soils represent layers of slower exchange not directly attached to mineral surfaces. From the isotopic composition

  7. On Expanded Cyclic Codes

    CERN Document Server

    Wu, Yingquan

    2008-01-01

    The paper has a threefold purpose. The first purpose is to present an explicit description of expanded cyclic codes defined in $\\GF(q^m)$. The proposed explicit construction of expanded generator matrix and expanded parity check matrix maintains the symbol-wise algebraic structure and thus keeps many important original characteristics. The second purpose of this paper is to identify a class of constant-weight cyclic codes. Specifically, we show that a well-known class of $q$-ary BCH codes excluding the all-zero codeword are constant-weight cyclic codes. Moreover, we show this class of codes achieve the Plotkin bound. The last purpose of the paper is to characterize expanded cyclic codes utilizing the proposed expanded generator matrix and parity check matrix. We analyze the properties of component codewords of a codeword and particularly establish the precise conditions under which a codeword can be represented by a subbasis. With the new insights, we present an improved lower bound on the minimum distance of...

  8. Organo-mineral interactions promote greater soil organic carbon stability under aspen in semi-arid montane forests in Utah

    Science.gov (United States)

    Van Miegroet, H.; Roman Dobarco, M.

    2014-12-01

    Forest species influence soil organic carbon (SOC) storage through litter input, which in interaction with soil microclimate, texture and mineralogy, lead to different SOC stabilization and storage patterns. We sampled mineral soil (0-15 cm) across the ecotone between aspen (Populus tremuloides) and mixed conifers stands (Abies lasiocarpa and Pseudotsuga menziesii) in semi-arid montane forests from Utah, to investigate the influence of vegetation vs. site characteristics on SOC stabilization, storage and chemistry. SOC was divided into light fraction (LF), mineral-associated SOC in the silt and clay fraction (MoM), and a dense subfraction > 53 μm (SMoM) using wet sieving and electrostatic attraction. SOC decomposability and solubility was derived from long term laboratory incubations and hot water extractions (HWE). Fourier transform infrared spectroscopy (FTIR) was used to study differences in chemical functional groups in LF and MoM. Vegetation cover did not affect SOC storage (47.0 ± 16.5 Mg C ha-1), SOC decomposability (cumulative CO2-C release of 93.2 ± 65.4 g C g-1 C), or SOC solubility (9.8 ± 7.2 mg C g-1 C), but MoM content increased with presence of aspen [pure aspen (31.2 ± 15.1 Mg C ha-1) > mixed (25.7 ± 8.8 Mg C ha-1) > conifer (22.8 ± 9.0 Mg C ha-1)]. Organo-mineral complexes reduced biological availability of SOC, indicated by the negative correlation between silt+clay (%) and decomposable SOC per gram of C (r = -0.48, p = 0.001) or soluble SOC (r = -0.59, p < 0.0001). FTIR spectral analysis indicated that higher MoM content under aspen was not due to higher concentration of recalcitrant compounds (e.g., aliphatic and aromatic C), but rather to stabilization of simple molecules (e.g., polysaccharides) of plant or microbial origin. FTIR spectra clustered by sites with similar parent material rather than by vegetation cover. This suggests that initial differences in litter chemistry between aspen and conifers converged into similar MoM chemistry

  9. Foundations of Soil Organic Matter Stabilization: Tracing the Influence of Mineralogy on the Initial Sorption of Root-Derived Carbon

    Science.gov (United States)

    Neurath, R.; Nico, P. S.; Pett-Ridge, J.; Firestone, M.

    2014-12-01

    Soils are the largest terrestrial carbon (C) reservoir, storing 2,300 Gt C globally, with the largest C input allocated by plant roots. Many root-derived C inputs are low molecular weight compounds (exudates), although complex C compounds from sloughed off cells and decaying roots also contribute precursors to the soil organic matter (SOM) pool. Root-derived compounds are metabolized by microorganisms, using extracellular enzymes to degrade the more complex C compounds. Thus, products of microbial use of root C may be free in soil solution or occur as microbial cell material. Products of root decomposition are stabilized in soil when C compounds are protected from degradation by (i) chemical recalcitrance, (ii) physical protection by aggregation, or (iii) physical-chemical protection by sorption to mineral surfaces. Previous studies show that sorption of SOM to soil minerals can stabilize C compounds for up to thousands of years. We examined the influence of soil mineralogy on sorption of root-derived C. We hypothesized that differences in specific surface area (SSA) and chemical reactivity of four mineral types: goethite, kaolinite, quartz, as well as native minerals extracted from field soil, are significant controls on the rate, quantity, and composition of mineral-sorbed SOM. Soils were collected at the UC Hopland Research and Extension Center in Hopland, CA and planted in soil microcosms with the common annual grass A. barbata; seeds collected from the field site. Microcosms were incubated in a sealed chamber under 13CO2 (99 atom%) for 8 weeks. Plant photosynthesized-C is allocated to the soil via roots, and with the 13C label, allows us to trace the fate of plant-derived C in the soil. Minerals, which were isolated in 18 μm mesh to exclude roots but not microorganisms, were extracted and measured for total C and 13C atom% after a 12 week growing season of A. barbata. Preliminary FTIR and 13C-NMR analysis show differences in the chemical composition of

  10. Silicon microfabricated beam expander

    Energy Technology Data Exchange (ETDEWEB)

    Othman, A., E-mail: aliman@ppinang.uitm.edu.my; Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A. [Faculty of Electrical Engineering, Universiti Teknologi MARA Malaysia, 40450, Shah Alam, Selangor (Malaysia); Ain, M. F. [School of Electrical and Electronic Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300,Nibong Tebal, Pulau Pinang (Malaysia)

    2015-03-30

    The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed.

  11. Silicon microfabricated beam expander

    Science.gov (United States)

    Othman, A.; Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A.; Ain, M. F.

    2015-03-01

    The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed.

  12. Simultaneous Improvements of Thermal Stability and Mechanical Properties of Poly(propylene carbonate) via Incorporation of Environmental-friendly Polydopamine

    Institute of Scientific and Technical Information of China (English)

    Yu-han Li; Mi Zhou; Cheng-zhen Geng; Feng Chen; Qiang Fu

    2014-01-01

    Inspired by the photoprotection,radical scavenging of melanin together with versatile adhesive ability of mussel proteins,polydopamine (PDA) nanoparticles were successfully prepared and incorporated into environmentally friendly polymer,poly(propylene carbonate) (PPC) via solvent blending.The prepared composites exhibited excellent thermal stability in air and nitrogen atmosphere and extraordinary mechanical properties.The composites displayed eminent increase of temperature at 5% weight loss (T5%) by 30-100 K with 0.3 wt%-2.0 wt% loadings,meanwhile,the tensile strength and Young's modulus were significantly improved from 11.5 MPa and 553.7 MPa to 40.5 MPa and 2411.2 MPa,respectively.The kinetic calculation indicated that improvement of T5% is presumably derived from suppressing chain-end unzipping.The glass transition temperature (Tg) of the PPC/PDA composites increased by 8-10 K.This is probably due to hydrogen bonding interaction since the abundant proton donors along PDA chains would interact with proton acceptors like C =O and C-O-C in PPC which would cause restriction of segmental motion of PPC chains.

  13. Long-term leaching behavior of phenol in cement/activated-carbon solidified/stabilized hazardous waste.

    Science.gov (United States)

    Liu, Jianguo; Nie, Xiaoqin; Zeng, Xianwei; Su, Zhaoji

    2013-01-30

    The long-term leaching behavior of phenol in solidified/stabilized (S/S) hazardous wastes cured for 28 d with different amounts of activated carbon (AC) was investigated using synthetic inorganic acid (H(2)SO(4):HNO(3) = 2:1, pH = 3.2), acetic acid buffer (HAc/NaAc, pH = 4.93), and deionized water as leachants to simulate the leaching of phenol in three exposure scenarios: acid-precipitation, co-disposal, and neutral-precipitation. Phenol immobilization was enhanced by AC adsorption and impaired by the growth of micropores with increasing amount of AC; thus the optimal added amount of AC to be to added S/S wastes was 2%. The leaching behavior of phenol in co-disposal scenario was unpredictable due to inadequate ionization of HAc in the HAc-NaAc buffer solution. The findings indicated that S/S products should be disposed of in hazardous waste landfills rather than municipal solid waste landfills.

  14. Long-term stability of organic carbon-stimulated chromatereduction in contaminated soils, and its relation to manganese redoxstatus

    Energy Technology Data Exchange (ETDEWEB)

    Tokunaga, Tetsu K.; Wan, Jiamin; Lanzirotti, Antonio; Sutton,Steve R.; Newville, Matthew; Rao, William

    2007-03-13

    In-situ reduction of toxic Cr(V1) to less hazardous Cr(II1)is becoming a popular strategy for remediating contaminated soils.However, the long term stability of reduced Cr remains to be understood,especially given the common presence of MnfIIIJV) oxides that reoxidizeCr(II1). This 4.6 year laboratory study tracked Cr and Mn redoxtransformations in soils contaminated with Cr(V1) which were then treatedwith different amounts of organic carbon (OC). Changes in Cr and Mnoxidation states within soils were directly and nondestructively measuredusing micro X-ray absorption near edge structure spectroscopy. Chromatereduction was roughly lst-order, and the extent of reduction was enhancedwith higher OC additions. However, significant Cr(||1) reoxidationoccurred in soils exposed to the highest Cr(V1) concentrations (2,560 mgkg"'). Transient Cr(II1) reoxidation up to 420 mg kg1 was measured at 1.1years after OC treatment, followed by further reduction. Chromateconcentrations increased by 220 mg kgm1a t the end of the study (4.6years) in one soil. The causal role that Mn oxidation state had inreoxidizing Cr was supported by trends in Mn K-edge energies. Theseresults provide strong evidence for longterm dependence of soil Croxidation states on balances between OC availability and Mn redoxstatus.

  15. Changes in carbon stability and microbial activity in size fractions of micro-aggregates in a rice soil chronosequence under long term rice cultivation

    Science.gov (United States)

    Pan, Genxing; Liu, Yalong; Wang, Ping; Li, Lianqinfg; Cheng, Kun; Zheng, Jufeng; Zhang, Xuhui; Zheng, Jinwei; Bian, Rongjun; Ding, Yuanjun; Ma, Chong

    2016-04-01

    Recent studies have shown soil carbon sequestration through physical protection of relative labile carbon intra micro-aggregates with formation of large sized macro-aggregates under good management of soil and agricultural systems. While carbon stabilization had been increasingly concerned as ecosystem properties, the mechanisms underspin bioactivity of soil carbon with increased carbon stability has been still poorly understood. In this study, topsoil samples were collected from rice soils derived from salt marsh under different length of rice cultivation up to 700 years from eastern China. Particle size fractions (PSF) of soil aggregates were separated using a low energy dispersion protocol. Carbon fractions in the PSFs were analyzed either with FTIR spectroscopy. Soil microbial community of bacterial, fungal and archaeal were analyzed with molecular fingerprinting using specific gene primers. Soil respiration and carbon gain from amended maize as well as enzyme activities were measured using lab incubation protocols. While the PSFs were dominated by the fine sand (200-20μm) and silt fraction (20-2μm), the mass proportion both of sand (2000-200μm) and clay (content in the size fractions followed a similar trend to that of SOC. Bacterial and archaeal gene abundance was concentrated in both sand and clay fractions but that of fungi in sand fraction, and sharply decreased with the decreasing size of aggregate fraction. Gene abundance of archaeal followed a similar trend to that of bacterial but showing an increasing trend with prolonged rice cultivation in both sand and clay fractions. Change in community diversity with sizes of aggregate fractions was found of fungi and weakly of bacterial but not of archaeal. Soil respiration ratio (Respired CO2-C to SOC) was highest in silt fraction, followed by the fine sand fraction but lowest in sand and clay fractions in the rice soils cultivated over 100 years. Again, scaled by total gen concentration, respiration was

  16. Laboratory Investigations in Support of Carbon Dioxide-in-Water Emulsions Stabilized by Fine Particles for Ocean and Geologic Sequestration of Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Dan Golomb; Eugene Barry; David Ryan

    2006-07-08

    C/W emulsion, the total cost of preparing the emulsion on site is about $8.5 per ton of liquid CO{sub 2}, not including the cost of the emulsion mixer. Currently, the cost estimates of capturing and liquefying CO{sub 2} at a coal-fired power plant range from $15 to 75/t CO{sub 2}. Thus, the preparation of C/W emulsions stabilized by pulverized limestone particles would add about 10 to 50% to the capture cost of CO{sub 2}. At this juncture the primary research objectives of this Co-operative Agreement are shifting toward geologic sequestration of carbon dioxide. Experiments are underway to create micro-emulsions of CO{sub 2}-in-Water (C/W) and Water-in-CO{sub 2} (W/C) stabilized by ultrafine particles ranging from sub-micrometer to a few micrometer in size. Such microemulsions are expected to readily penetrate deep geologic formations, such as porous sedimentary layers, including saline aquifers and semi-depleted oil and gas fields. Injections of (C/W) and (W/C) type micro-emulsions may prove to be less prone to leakage from the formations compared to injections of neat liquid or supercritical CO{sub 2}.

  17. Expanding Student Assessment Opportunities.

    Science.gov (United States)

    Bartscher, Beth; Carter, Andrea; Lawlor, Anna; McKelvey, Barbara

    This paper describes an approach for expanding assessment opportunities for students to demonstrate their understanding of content. The targeted population consisted of elementary and junior high school students in two schools in a growing middle-class community in north central Illinois. The elementary school enrolled 467 students and the junior…

  18. Expanding mediation theory

    NARCIS (Netherlands)

    Verbeek, P.P.C.C.

    2012-01-01

    In his article In Between Us, Yoni van den Eede expands existing theories of mediation into the realm of the social and the political, focusing on the notions of opacity and transparency. His approach is rich and promising, but two pitfalls should be avoided. First, his concept of ‘in-between’ runs

  19. Tillage and crop residue management methods had minor effects on the stock and stabilization of topsoil carbon in a 30-year field experiment.

    Science.gov (United States)

    Singh, Pooja; Heikkinen, Jaakko; Ketoja, Elise; Nuutinen, Visa; Palojärvi, Ansa; Sheehy, Jatta; Esala, Martti; Mitra, Sudip; Alakukku, Laura; Regina, Kristiina

    2015-06-15

    We studied the effects of tillage and straw management on soil aggregation and soil carbon sequestration in a 30-year split-plot experiment on clay soil in southern Finland. The experimental plots were under conventional or reduced tillage with straw retained, removed or burnt. Wet sieving was done to study organic carbon and soil composition divided in four fractions: 1) large macroaggregates, 2) small macroaggregates, 3) microaggregates and 4) silt and clay. To further estimate the stability of carbon in the soil, coarse particulate organic matter, microaggregates and silt and clay were isolated from the macroaggregates. Total carbon stock in the topsoil (equivalent to 200 kg m(-2)) was slightly lower under reduced tillage (5.0 kg m(-2)) than under conventional tillage (5.2 kg m(-2)). Reduced tillage changed the soil composition by increasing the percentage of macroaggregates and decreasing the percentage of microaggregates. There was no evidence of differences in the composition of the macroaggregates or carbon content in the macroaggregate-occluded fractions. However, due to the higher total amount of macroaggregates in the soil, more carbon was bound to the macroaggregate-occluded microaggregates in reduced tillage. Compared with plowed soil, the density of deep burrowing earthworms (Lumbricus terrestris) was considerably higher under reduced tillage and positively associated with the percentage of large macroaggregates. The total amount of microbial biomass carbon did not differ between the treatments. Straw management did not have discernible effects either on soil aggregation or soil carbon stock. We conclude that although reduced tillage can improve clay soil structure, generally the chances to increase topsoil carbon sequestration by reduced tillage or straw management practices appear limited in cereal monoculture systems of the boreal region. This may be related to the already high C content of soils, the precipitation level favoring decomposition and

  20. Carbon-rich icosahedral boron carbides beyond B4C and their thermodynamic stabilities at high temperature and pressure from first principles

    Science.gov (United States)

    Ektarawong, A.; Simak, S. I.; Alling, B.

    2016-08-01

    We investigate the thermodynamic stability of carbon-rich icosahedral boron carbide at different compositions, ranging from B4C to B2C , using first-principles calculations. Apart from B4C , generally addressed in the literature, B2.5C , represented by B10C2p (C-C), where Cp and (C-C) denote a carbon atom occupying the polar site of the icosahedral cluster and a diatomic carbon chain, respectively, is predicted to be thermodynamically stable under high pressures with respect to B4C as well as pure boron and carbon phases. The thermodynamic stability of B2.5C is determined by the Gibbs free energy G as a function of pressure p and temperature T , in which the contributions from the lattice vibrations and the configurational disorder are obtained within the quasiharmonic and the mean-field approximations, respectively. The stability range of B2.5C is then illustrated through the p -T phase diagrams. Depending on the temperatures, the stability range of B2.5C is predicted to be within the range between 40 and 67 GPa. At T ≳ 500 K, the icosahedral Cp atoms in B2.5C configurationally disorder at the polar sites. By investigating the properties of B2.5C , e.g., elastic constants and phonon and electronic density of states, we demonstrate that B2.5C is both mechanically and dynamically stable at zero pressure, and is an electrical semiconductor. Furthermore, based on the sketched phase diagrams, a possible route for experimental synthesis of B2.5C as well as a fingerprint for its characterization from the simulations of x-ray powder diffraction pattern are suggested.

  1. Application of δ13C and δ15N isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms

    Directory of Open Access Journals (Sweden)

    M. Sommer

    2011-03-01

    Full Text Available Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. We used the δ13C and δ15N isotopic signatures from two organic matter (OM fractions from soil to identify the likely binding mechanisms involved. We used OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1 OM separated chemically with sodium pyrophosphate (OM(PY and (2 OM stabilized in microstructures found in the chemical extraction residue (OM(ER. Furthermore, because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms within these soils. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established proxies of different binding mechanisms. Parsing soil OM into different fractions is a systematic method of dissection, however, we are primarily interested in how OM is bound in soil as a whole, requiring a means of re-assembly. Thus, we implemented the recent zonal framework described by Kleber et al. (2007 to relate our findings to undisturbed soil. The δ15N signature of OM fractions served as a reliable indicator for microbial processed carbon in both arable and forest land use types. The δ13C signature of OM fractions in arable sites did not correlate well with proxies of soil mineral properties while a consistent pattern of enrichment was seen in the δ13C of OM fractions in the forest sites. We found a significant difference in δ13C of pooled OM fractions between the forest and arable land use type although it was relatively small (<1‰. We found different binding mechanisms predominate in each land use type. The isotopic signatures of OM fractions from arable soils were highly related to the clay and silt size particles

  2. Thermal stability and structural study of the poly(3-hexyl thiophene)/HiPCO single walled carbon nanotubes (P3HT/SWCNT) nanocomposites

    Science.gov (United States)

    Bakour, Anass; Baitoul, Mimouna; Faulques, Eric; Wery-Venturini, Jany

    2016-05-01

    In this work we present the effect of HiPCO single walled carbon nanotubes (SWCNT) introduction into the conjugated polymer matrix poly(3-hexyl thiophene) (P3HT) on the structural and thermal stability of these nanocomposites. The P3HT/SWCNT nanocomposite films were prepared using chloroform and chlorobenzene as solvents and optimised ultrasonication duration. The prepared samples were analyzed by thermogravimetric analysis (TGA), X-ray diffraction and transmission electron microscopy (TEM) to study the effect of carbon nanotubes on the thermal stability and structure of the polymer matrix. The measurements carried out for different SWCNT loadings show that the thermal stability was enhanced for a 0.5 wt.%, but exhibits a decrease with increasing the SWCNT content. Our results prove the structural enhancement which is in favor of a better organisation for both P3HT chains and carbon nanotubes due to their interaction. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  3. Expanding the HAWC Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Johanna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-17

    The High Altitude Water Cherenkov Gamma-Ray Observatory is expanding its current array of 300 water tanks to include 350 outrigger tanks to increase sensitivity to gamma rays above 10 TeV. This involves creating and testing hardware with which to build the new tanks, including photomultiplier tubes, high voltage supply units, and flash analog to digital converters. My responsibilities this summer included preparing, testing and calibrating that equipment.

  4. OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING

    Energy Technology Data Exchange (ETDEWEB)

    Hector Colonmer; Prabhu Ganesan; Nalini Subramanian; Dr. Bala Haran; Dr. Ralph E. White; Dr. Branko N. Popov

    2002-09-01

    This project focused on addressing the two main problems associated with state of art Molten Carbonate Fuel Cells, namely loss of cathode active material and stainless steel current collector deterioration due to corrosion. We followed a dual approach where in the first case we developed novel materials to replace the cathode and current collector currently used in molten carbonate fuel cells. In the second case we improved the performance of conventional cathode and current collectors through surface modification. States of art NiO cathode in MCFC undergo dissolution in the cathode melt thereby limiting the lifetime of the cell. To prevent this we deposited cobalt using an electroless deposition process. We also coated perovskite (La{sub 0.8}Sr{sub 0.2}CoO{sub 3}) in NiO thorough a sol-gel process. The electrochemical oxidation behavior of Co and perovskites coated electrodes is similar to that of the bare NiO cathode. Co and perovskite coatings on the surface decrease the dissolution of Ni into the melt and thereby stabilize the cathode. Both, cobalt and provskites coated nickel oxide, show a higher polarization compared to that of nickel oxide, which could be due to the reduced surface area. Cobalt substituted lithium nickel oxide (LiNi{sub 0.8}Co{sub 0.2}O{sub 2}) and lithium cobalt oxide were also studied. LiNi{sub x}Co{sub 1-x}O{sub 2} was synthesized by solid-state reaction procedure using lithium nitrate, nickel hydroxide and cobalt oxalate precursor. LiNi{sub x}Co{sub 1-x}O{sub 2} showed smaller dissolution of nickel than state of art nickel oxide cathode. The performance was comparable to that of nickel oxide. The corrosion of the current collector in the cathode side was also studied. The corrosion characteristics of both SS304 and SS304 coated with Co-Ni alloy were studied. This study confirms that surface modification of SS304 leads to the formation of complex scales with better barrier properties and better electronic conductivity at 650 C. A three

  5. In Situ Generation of Poly (Vinylene Carbonate) Based Solid Electrolyte with Interfacial Stability for LiCoO2 Lithium Batteries.

    Science.gov (United States)

    Chai, Jingchao; Liu, Zhihong; Ma, Jun; Wang, Jia; Liu, Xiaochen; Liu, Haisheng; Zhang, Jianjun; Cui, Guanglei; Chen, Liquan

    2017-02-01

    Nowadays it is extremely urgent to seek high performance solid polymer electrolyte that possesses both interfacial stability toward lithium/graphitic anodes and high voltage cathodes for high energy density solid state batteries. Inspired by the positive interfacial effect of vinylene carbonate additive on solid electrolyte interface, a novel poly (vinylene carbonate) based solid polymer electrolyte is presented via a facile in situ polymerization process in this paper. It is manifested that poly (vinylene carbonate) based solid polymer electrolyte possess a superior electrochemical stability window up to 4.5 V versus Li/Li(+) and considerable ionic conductivity of 9.82 × 10(-5) S cm(-1) at 50 °C. Moreover, it is demonstrated that high voltage LiCoO2/Li batteries using this solid polymer electrolyte display stable charge/discharge profiles, considerable rate capability, excellent cycling performance, and decent safety characteristic. It is believed that poly (vinylene carbonate) based electrolyte can be a very promising solid polymer electrolyte candidate for high energy density lithium batteries.

  6. Use of carbon and AlPO4 dual coating on H2Ti12O25 anode for high stability hybrid supercapacitor

    Science.gov (United States)

    Kim, Jin-Hyeon; Lee, Seung-Hwan

    2016-11-01

    We fabricated the cylindrical hybrid supercapacitors using the pristine H2Ti12O25, carbon coated H2Ti12O25, AlPO4 coated H2Ti12O25, AlPO4-carbon hybrid coated H2Ti12O25, and AlPO4-carbon dual coated H2Ti12O25 as anodes. The electrochemical performances and thermal stability of the hybrid supercapacitors with different surface-modified anodes were investigated. The uniform and ultrathin dual coated H2Ti12O25 maximizes the electrochemical performances with superior thermal stability. The dual coating layer acts as a bridge for the Li ion diffusion and electron conduction and as a barrier to suppress swelling phenomenon from HF attack. Moreover, the partially AlF3 areas at AlPO4 layer, due to the reaction with HF, have positive effects on electrochemical performances. Therefore, the novel design composed of carbon and AlPO4 can be regarded as an effective strategy for anode used in hybrid supercapacitors.

  7. Bank Directors’ Perceptions of Expanded Auditor's Reports

    DEFF Research Database (Denmark)

    Boolaky, Pran Krishansing; Quick, Reiner

    2016-01-01

    of expanded audit reports, namely information on the assurance level, materiality levels and key audit matters (KAM), on bank director perceptions of the quality of the financial statements, the audit and the audit report, as well as on their credit approval decisions. We conduct an experiment involving......Subsequent to the financial crisis, standard setters developed suggestions for enhancing the audit function, in order to increase financial stability. One related idea is to expand the audit report disclosed to the public, to ensure that it is fit for purpose. This study investigates the impact...... a sample of 105 bank directors and use ANCOVA to determine the predictors of bank director perceptions and decisions. Our findings suggest that disclosing the assurance level has a significantly positive impact. In contrast, we cannot demonstrate a material effect of expanding the audit report to include...

  8. Comprehensive study of pore evolution, mesostructural stability, and simultaneous surface functionalization of ordered mesoporous carbon (FDU-15) by wet oxidation as a promising adsorbent.

    Science.gov (United States)

    Wu, Zhangxiong; Webley, Paul A; Zhao, Dongyuan

    2010-06-15

    Fuctionalization of porous carbon materials through chemical methods orientates the development of new hybrid materials with specific functions. In this paper, a comprehensive study of pore evolution, mesostructural oxidation resistance, and simultaneous surface functionalization of ordered mesoporous carbon FDU-15 under various oxidation conditions is presented for the first time. The mesostructure and pore evolution with increasing oxidative strength are retrieved from XRD, TEM, and N(2) sorption techniques. The textural properties can be conveniently manipulated by changing the oxidation parameters, including different oxidative solution, temperature, and duration. It is revealed that the mesoporous carbon FDU-15 shows excellent structural stability under severe oxidation treatments by acidic (NH(4))(2)S(2)O(8), HNO(3), and H(2)O(2) solutions, much more stable than the mesostructural analogue CMK-3 carbon prepared by the nanocasting method. The surface area and porosity deteriorate to a large extent compared to the pristine carbon, with the micropores/small mesopores as the major contribution to the deterioration. The micropore/small mesopore can be blocked by the attached surface oxides under mild oxidation, while reopened with more carbon layer dissolution under more severe conditions. Simultaneously, high densities of surface oxygen complexes, especially carboxylic groups, can be generated. The contents and properties of the surface oxygen-containing groups are extensively studied by FTIR, TG, elemental analyses, and water and ammonia adsorption techniques. Such surface-functionalized mesoporous carbons can be used as a highly efficient adsorbent for immobilization of heavy metal ions as well as functional organic and biomolecules, with high capacities and excellent binding capabilities. Thus, we believe that the functionalized mesoporous carbon materials can be utilized as a promising solid and stable support for water treatment and organic

  9. Change in Chirality of Semiconducting Single-Walled Carbon Nanotubes Can Overcome Anionic Surfactant Stabilization: A Systematic Study of Aggregation Kinetics.

    Science.gov (United States)

    Khan, Iftheker A; Flora, Joseph R V; Nabiul Afrooz, A R M; Aich, Nirupam; Schierz, P Ariette; Ferguson, P Lee; Sabo-Attwood, Tara; Saleh, Navid B

    2015-05-20

    Single-walled carbon nanotubes' (SWNT) effectiveness in applications is enhanced by debundling or stabilization. Anionic surfactants are known to effectively stabilize SWNTs. However, the role of specific chirality on surfactant-stabilized SWNT aggregation has not been studied to date. The aggregation behavior of chirally enriched (6,5) and (7,6) semiconducting SWNTs, functionalized with three anionic surfactants-sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium deoxycholate (SDOCO)-was evaluated with time-resolved dynamic light scattering. A wide range of mono- (NaCl) and di-valent (CaCl2) electrolytes as well as a 2.5 mg TOC/L Suwannee River humic acid (SRHA) were used as background chemistry. Overall, SDBS showed the most effectiveness in SWNT stability, followed by SDOCO and SDS. However, the relatively larger diameter (7,6) chiral tubes compromised the surfactant stability, compared to (6,5) chiral enrichment, due to enhanced van der Waals interaction. The presence of di-valent electrolytes overshadowed the chirality effects and resulted in similar aggregation behavior for both the SWNT samples. Molecular modeling results enumerated key differences in surfactant conformation on SWNT surfaces and identified interaction energy changes between the two chiralities to delineate aggregation mechanisms. The stability of SWNTs increased in the presence of SRHA under 10 mM monovalent and mixed electrolyte conditions. The results suggest that change in chirality can overcome surfactant stabilization of semiconducting SWNTs. SWNT stability can also be strongly influenced by the anionic surfactant structure.

  10. The expanding universe

    CERN Document Server

    Lew, Kristi

    2011-01-01

    People have always been fascinated with the stars above and the universe that contains them. Over the years, astronomers have developed numerous theories to explain how the universe began, how it works, and what its ultimate fate will be. But all of the scientists' questions are far from answered. The Expanding Universe goes beyond the creation of the universe to explain how scientists think the universe works, grows, and changes, including what great thinkers Isaac Newton and Albert Einstein had to say about its fate. Readers will also learn about how researchers are slowly shedding light on

  11. Expanding Your Horizon 2015

    CERN Multimedia

    Kaltenhauser, Kristin

    2015-01-01

    Expanding your horizons is a bi-annual “Science Day” for girls aged 11 to 14, held at the University of Geneva on 14 November. The girls had the opportunity to take part in hands-on workshops held by local professional women in the field of science, mathematics, engineering and technology. For the fourth time, CERN was part of this event, offering three workshops as well as a booth at the Discovery Fair, including Higgnite, an interactive visualization of the Higgs Field.

  12. The Radical Stabilization Energy of a Substituted Carbon-centered Free Radical Depends both on the Functionality of the Substituent and the Ordinality of the Radical

    Energy Technology Data Exchange (ETDEWEB)

    Poutsma, Marvin L [ORNL

    2011-01-01

    Chemical intuition suggests that the stabilization of a carbon-centered free radical by a substituent X would be the greatest for a prim and least for a more stable tert radical because of saturation. However, analysis of a comprehensive recent set of bond dissociation energies computed by Coote and coworkers (Phys. Chem. Chem. Phys. 2010 12 9597) and transformed into radical stabilization energies (RSE) suggests that this supposition is often violated. The RSE for a given X depends not only on the nature of X but also on the ordinality (i.e., prim, sec, or tert) of the radical onto which it is substituted. For substituents that stabilize by electron delocalization but also contain electron-withdrawing centers, such as the carbonyl function, the stabilization of XCMe2 compared with HCMe2 is greater than for XCH2 compared with HCH2 . However, for substituents that stabilize by lone-pair electron donation, such as N or O centers, the order is strongly reversed. This contrast can be qualitatively rationalized by considering charge-separated VB contributors to the radical structure (R2C+ X- and R2C- X+ ) and the contrasting effects of methyl substituents on them. This conclusion is not dependent on the particular definition used for RSE.

  13. Changes in Marsh Vegetation, Stability and Dissolved Organic Carbon in Barataria Bay Marshes Following the Deepwater Horizon Oil Spill

    Science.gov (United States)

    Holloway, J. M.; Aiken, G.; Kokaly, R. F.; Heckman, D.; Butler, K.; Mills, C. T.; Hoefen, T. M.; Piazza, S.

    2010-12-01

    Coastal wetlands in Southern Louisiana were contaminated by the release of record volumes of oil between April and July 2010. Barataria Bay was extensively impacted, resulting in the oiling and dieback of marsh grasses along a discontinuous margin up to 30m into the marshes. Shoreline stability and biogeochemistry have been monitored over three site visits between between July 10 and August 25, 2010. Initial observations in early July were that grasses, dominantly shape Spartina alterniflora and shape Juncus roemerianus, were bent over under the weight of a thick oil coating. The bent-over grasses were broken off along some reaches, leaving a stubbled shoreline more susceptible to erosion. Repeated site visits in mid and late August found visible erosion along some of the effected shorelines. Water samples were collected from the shoreline marsh remnants and from visibly unaffected marshes to characterize dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). In spite of visible oil sheens in unfiltered water from contaminated shorelines and no visible sign of impact on vegetation in the “control” sites with no visible oil on vegetation, DOC concentrations were similar in impacted and visibly unimpacted sites in Barataria Bay. Subsequent samples in mid- and late-August had increased DOC concentrations relative to previous sample events regardless of whether the site was visibly impacted. There was a general increase in specific UV absorbance (SUVA), an index of aromaticity, with increasing DOC concentrations, either due to seasonal effects or continued dissolution of petroleum compounds. Further chemical characterization using fluorescence and gas chromatography will be used to confirm the presence of petroleum compounds. The ratio of DOC to TDN also increased over time, which may have implications for vegetation regrowth and plant community structure, including the shift of grass species dominating effected marshes. These initial findings suggest

  14. Frictional properties and slip stability of active faults within carbonate-evaporite sequences: The role of dolomite and anhydrite

    NARCIS (Netherlands)

    Scuderi, M.M.; Niemeijer, A.R.; Collettini, C.; Marone, C.

    2013-01-01

    Seismological observations show that many destructive earthquakes nucleate within, or propagate through, thick sequences of carbonates and evaporites. For example, along the Apennines range (Italy) carbonate and evaporite sequences are present at hypocentral depths for recent major earthquakes (5.0<

  15. Energetics, relative stabilities, and size-dependent properties of nanosized carbon clusters of different families: fullerenes, bucky-diamond, icosahedral, and bulk-truncated structures.

    Science.gov (United States)

    Yu, M; Chaudhuri, I; Leahy, C; Wu, S Y; Jayanthi, C S

    2009-05-14

    Structures and relative stabilities of carbon clusters belonging to different families have been investigated for diameters d simulation. Carbon clusters studied include fullerenes and fullerene-derived structures (e.g., cages and onions), icosahedral structures, bucky-diamond structures, and clusters cut from the bulk diamond with spherical and facetted truncations. The reason for using a semiempirical MD is partly due to the large number of different cases (or carbon allotropes) investigated and partly due to the size of the clusters investigated in this work. The particular flavor of the semiempirical MD scheme is based on a self-consistent and environment-dependent Hamiltonian developed in the framework of linear combination of atomic orbitals. We find that (i) among the families of carbon clusters investigated, fullerene structures have the lowest energy with the relative energy ordering being E(fullerene) structures is likely at d approximately 8 nm, (iii) the highest occupied molecular orbital-lowest unoccupied molecular orbital gap as a function of the diameter for the case of fullerenes shows an oscillatory behavior with the gap ranging from 2 eV to 6 meV, and the gap approaching that of gapless graphite for d > 3.5 nm, and (iv) there can be three types of phase transformations depending on the manner of heating and cooling in our simulated annealing studies: (a) a bucky-diamond structure --> an onionlike structure, (b) an onionlike --> a cage structure, and (c) a bucky-diamond --> a cage structure.

  16. Development of a cheap and accessible carbon fibers-in-poly(ether ether ketone) tube with high stability for online in-tube solid-phase microextraction.

    Science.gov (United States)

    Feng, Juanjuan; Sun, Min; Bu, Yanan; Luo, Chuannan

    2016-02-01

    Carbon fibers (CFs) are one kind of important industrial materials that can be obtained commercially at low price. Based on the high extraction efficiency of carbon sorbents, a cheap and accessible carbon fibers-in-poly(ether ether ketone) (PEEK) tube was developed for online in-tube solid-phase microextraction (SPME) method. Coupled to high performance liquid chromatography (HPLC), the CFs-in-tube SPME was applied to analyze eight polycyclic aromatic hydrocarbons (PAHs) in environmental aqueous samples. Extraction conditions (sampling rate, extraction time, methanol content) and desorption time were investigated for optimization of conditions. Under the optimum conditions, the CFs-in-tube SPME-HPLC method provided high extraction efficiency with enrichment factors up to 1748. Good linearity (0.05-50 μg L(-1), 0.5-50 μg L(-1)) and low detection limits (0.01-0.1 μg L(-1)) were also obtained. The online analysis method was finally applied to determine several model PAHs analytes in real environmental aqueous samples. Some target analytes were detected and relative recoveries were in the range of 92.3-111%. Due to natural chemical stability of carbon fibers and PEEK tube, the CFs-in-tube device exhibited high resistance to organic solvent, acid and alkaline conditions.

  17. Investigation of heavy metal (Cu, Pb, Cd, and Cr) stabilization in river sediment by nano-zero-valent iron/activated carbon composite.

    Science.gov (United States)

    Chen, Wei-fang; Zhang, Jinghui; Zhang, Xiaomao; Wang, Weiya; Li, Yuxiang

    2016-01-01

    Nano-zero-valent iron/activated carbon (nZVI/AC) composite was evaluated for its effectiveness in the stabilization of Cu, Pb, Cd, and Cr in dredged river sediment. Synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) were adopted to compare the effects of nZVI/AC dosage, particle size, time duration, and temperature on heavy metal leachability. The results show that leachability dropped considerably with the addition of nZVI/AC and powdered particles in the size of 0.075-0.18 mm was more effective in stabilization than granular ones. Stabilization effect was stable in long-term and robust against changes in temperature. Tessier sequential extraction revealed that heavy metals were associated with solid particle, inorganic or organic matters in sediment. The addition of nZVI/AC was able to convert relatively weakly bound heavy metals into more strongly bound species and thus reduce the bioavailability and toxicity. Also, the standard potential of heavy metals may decide the mechanism of stabilization process.

  18. The Artful Universe Expanded

    Energy Technology Data Exchange (ETDEWEB)

    Bassett, B A [Institute of Cosmology and Gravitation, University of Portsmouth (United Kingdom)

    2005-07-29

    The cosmos is an awfully big place and there is no better guide to its vast expanse and fascinating nooks and crannies than John Barrow. A professor of mathematical sciences at Cambridge University, Barrow embodies that rare combination of highly polished writer and expert scientist. His deft touch brings together the disparate threads of human knowledge and weaves them into a tapestry as rich and interesting for the expert as it is for the layperson. The Artful Universe Expanded is an updated edition of this popular book first published in 1995. It explores the deeply profound manner in which natural law and the nature of the cosmos have moulded and shaped us, our cultures and the very form of our arts and music-a new type of 'cosmic' anthropology. The main themes Barrow chooses for revealing this new anthropology are the subjects of evolution, the size of things, the heavens and the nature of music. The book is a large, eclectic repository of knowledge often unavailable to the layperson, hidden in esoteric libraries around the world. It rivals The Da Vinci Code for entertainment value and insights, but this time it is Nature's code that is revealed. It is rare indeed to find common threads drawn through topics as diverse as The Beetles, Bach and Beethoven or between Jackson Pollock, the Aztecs, Kant, Picasso, Byzantine mosaics, uranium-235 and the helix nebula. Barrow unerringly binds them together, presenting them in a stimulating, conversational style that belies the amount of time that must have gone into researching this book. Dip into it at random, or read it from cover to cover, but do read it. The Artful Universe Expanded is an entertaining antidote to the oft-lamented pressures to know more and more about less and less and the apparently inexorable march of specialization. On reading this book one can, for a short time at least, hold in one's mind a vision that unifies science, art and culture and glimpse a universal tapestry of great

  19. Influence of expander components on the processes at the negative plates of lead-acid cells on high-rate partial-state-of-charge cycling. Part II. Effect of carbon additives on the processes of charge and discharge of negative plates

    Energy Technology Data Exchange (ETDEWEB)

    Pavlov, D.; Nikolov, P.; Rogachev, T. [Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, Acad. Georgi Bonchev Street, bl. 10, Sofia 1113 (Bulgaria)

    2010-07-15

    Lead-acid batteries operated in the high-rate partial-state-of-charge (HRPSoC) duty rapidly lose capacity on cycling, because of sulfation of the negative plates. As the battery operates from a partially discharged state, the small PbSO{sub 4} crystals dissolve and precipitate onto the bigger crystals. The latter have low solubility and hence PbSO{sub 4} accumulates progressively in the negative plates causing capacity loss. In order to suppress this process, the rate of the charge process should be increased. In a previous publication of ours we have established that reduction of Pb{sup 2+} ions to Pb may proceed on the surface of both Pb and carbon black particles. Hence, the reversibility of the charge-discharge processes improves, which leads to improved cycle life performance of the batteries in the HRPSoC mode. However, not all carbon forms accelerate the charge processes. The present paper discusses the electrochemical properties of two groups of carbon blacks: Printex and active carbons. The influence of Vaniseprse A and BaSO{sub 4} (the other two components of the expander added to the negative plates) on the reversibility of the charge-discharge processes on the negative plates is also considered. It has been established that lignosulfonates are adsorbed onto the lead surface and retard charging of the battery. BaSO{sub 4} has the opposite effect, which improves the reversibility of the processes on cycling and hence prolongs battery life in the HRPSoC duty. It has been established that the cycle life of lead-acid cells depends on the type of carbon black or active carbon added to the negative plates. When the carbon particles are of nano-sizes (<180 nm), the HRPSoC cycle life is between 10,000 and 20,000 cycles. Lignosulfonates suppress this beneficial effect of carbon black and activated carbon additives to about 10,000 cycles. Cells with active carbons have the longest cycle life when they contain also BaSO{sub 4} but no lignosulfonate. A summary of

  20. Model study on the stability of carbon support materials under polymer electrolyte fuel cell cathode operation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Colmenares, L.C.; Jusys, Z.; Behm, R.J. [Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm (Germany); Wurth, A. [TS-IM-IM-CB Inorganic Materials, Evonik Degussa GmbH, D-50997 Cologne (Germany)

    2009-05-01

    The electrochemical oxidation and corrosion resistance of differently prepared and post-treated (graphitization, surface oxidation) carbon support materials, whose surface area and composition were characterized by adsorption measurements and X-ray photoelectron spectroscopy, were investigated in model studies performed under fuel cell cathode relevant potential conditions. These included also the abnormal cathode potentials (up to 1.5 V{sub RHE}) occurring during start-up and shut-down procedures. Reversible surface oxidation, leading, e.g., to the formation of quinones/hydroquinones, and irreversible oxidation to CO{sub 2} were discriminated by combining electrochemical and on-line mass spectrometry measurements. Oxygenated surface carbon species were found to affect the surface area normalized electrooxidation activity much more than the surface area and porosity of the material, with graphitized carbon with low porosity and low oxygen surface content being most resistant towards reversible oxidation and towards irreversible oxidation at high potentials. Trapped CO{sub 2}, formed upon carbon oxidation at high potentials, is proposed to be at least partly responsible for CO{sub 2} release at low potentials, below the standard potential for electrochemical carbon oxidation. (author)

  1. Thermal conductivity and stability of a three-phase blend of carbon nanotubes, conductive polymer, and silver nanoparticles incorporated into polycarbonate nanocomposites

    KAUST Repository

    Patole, Archana

    2015-04-16

    Metallic and non-metallic nanofillers can be used together in the design of polycarbonate (PC) nanocomposites with improved electrical properties. Here, the preparation of three-phase blend (carbon nanotubes (CNT), silver nanoparticles, and conductive polymer) in a two-step process before incorporation in the PC is reported. First, ethylene diamine functionalized multiwall carbon nanotubes (MWCNT-EDA) were decorated with Ag nanoparticles. Next, the Ag-decorated CNTs were coated with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Due to the high thermal conductivity instrinsic to both metallic and non-metallic phases, it is expected that the thermal properties of the resulting nanocomposite would largely differ from those of pristine PC. We thus investigated in detail how this hybrid conductive blend affected properties such as the glass transition temperature, the thermal stability, and the thermal conductivity of the nanocomposite. It was found that this strategy results in improved thermal conductivity and thermal stability of the material. © 2015 Wiley Periodicals, Inc.

  2. Carbothermal synthesis of ordered mesoporous carbon-supported nano zero-valent iron with enhanced stability and activity for hexavalent chromium reduction.

    Science.gov (United States)

    Dai, Ying; Hu, Yuchen; Jiang, Baojiang; Zou, Jinlong; Tian, Guohui; Fu, Honggang

    2016-05-15

    Composites of nano zero-valent iron (nZVI) and ordered mesoporous carbon (OMC) are prepared by using simultaneous carbothermal reduction methods. The reactivity and stability of nZVI are expected to be enhanced by embedding it in the ordered pore channels. The structure characteristics of nZVI/OMC and the removal pathway for hexavalent chromium (Cr(VI)) by nZVI/OMC are investigated. Results show that nZVI/OMC with a surface area of 715.16 m(2) g(-1) is obtained at 900 °C. nZVI with particle sizes of 20-30 nm is uniformly embedded in the OMC skeleton. The stability of nZVI is enhanced by surrounding it with a broad carbon layer and a little γ-Fe is derived from the passivation of α-Fe. Detection of ferric state (Fe 2p3/2, around 711.2eV) species confirms that part of the nZVI on the outer surface is inevitably oxidized by O2, even when unused. The removal efficiency of Cr(VI) (50 mg L(-1)) by nZVI/OMC is near 99% within 10 min through reduction (dominant mechanism) and adsorption. nZVI/OMC has the advantage in removal efficiency and reusability in comparison to nZVI/C, OMC and nZVI. This study suggests that nZVI/OMC has the potential for remediation of heavy metal pollution in water.

  3. The Artful Universe Expanded

    Science.gov (United States)

    Barrow, John D.

    2005-07-01

    Our love of art, writes John Barrow, is the end product of millions of years of evolution. How we react to a beautiful painting or symphony draws upon instincts laid down long before humans existed. Now, in this enhanced edition of the highly popular The Artful Universe , Barrow further explores the close ties between our aesthetic appreciation and the basic nature of the Universe. Barrow argues that the laws of the Universe have imprinted themselves upon our thoughts and actions in subtle and unexpected ways. Why do we like certain types of art or music? What games and puzzles do we find challenging? Why do so many myths and legends have common elements? In this eclectic and entertaining survey, Barrow answers these questions and more as he explains how the landscape of the Universe has influenced the development of philosophy and mythology, and how millions of years of evolutionary history have fashioned our attraction to certain patterns of sound and color. Barrow casts the story of human creativity and thought in a fascinating light, considering such diverse topics as our instinct for language, the origins and uses of color in nature, why we divide time into intervals as we do, the sources of our appreciation of landscape painting, and whether computer-generated fractal art is really art. Drawing on a wide variety of examples, from the theological questions raised by St. Augustine and C.S. Lewis to the relationship between the pure math of Pythagoras and the music of the Beatles, The Artful Universe Expanded covers new ground and enters a wide-ranging debate about the meaning and significance of the links between art and science.

  4. Understanding API-polymer proximities in amorphous stabilized composite drug products using fluorine-carbon 2D HETCOR solid-state NMR.

    Science.gov (United States)

    Abraham, Anuji; Crull, George

    2014-10-06

    A simple and robust method for obtaining fluorine-carbon proximities was established using a (19)F-(13)C heteronuclear correlation (HETCOR) two-dimensional (2D) solid-state nuclear magnetic resonance (ssNMR) experiment under magic-angle spinning (MAS). The method was applied to study a crystalline active pharmaceutical ingredient (API), avagacestat, containing two types of fluorine atoms and its API-polymer composite drug product. These results provide insight into the molecular structure, aid with assigning the carbon resonances, and probe API-polymer proximities in amorphous spray dried dispersions (SDD). This method has an advantage over the commonly used (1)H-(13)C HETCOR because of the large chemical shift dispersion in the fluorine dimension. In the present study, fluorine-carbon distances up to 8 Å were probed, giving insight into the API structure, crystal packing, and assignments. Most importantly, the study demonstrates a method for probing an intimate molecular level contact between an amorphous API and a polymer in an SDD, giving insights into molecular association and understanding of the role of the polymer in API stability (such as recrystallization, degradation, etc.) in such novel composite drug products.

  5. Ionic Liquid-Organic Carbonate Electrolyte Blends To Stabilize Silicon Electrodes for Extending Lithium Ion Battery Operability to 100 °C.

    Science.gov (United States)

    Ababtain, Khalid; Babu, Ganguli; Lin, Xinrong; Rodrigues, Marco-Tulio F; Gullapalli, Hemtej; Ajayan, Pulickel M; Grinstaff, Mark W; Arava, Leela Mohana Reddy

    2016-06-22

    Fabrication of lithium-ion batteries that operate from room temperature to elevated temperatures entails development and subsequent identification of electrolytes and electrodes. Room temperature ionic liquids (RTILs) can address the thermal stability issues, but their poor ionic conductivity at room temperature and compatibility with traditional graphite anodes limit their practical application. To address these challenges, we evaluated novel high energy density three-dimensional nano-silicon electrodes paired with 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide (Pip) ionic liquid/propylene carbonate (PC)/LiTFSI electrolytes. We observed that addition of PC had no detrimental effects on the thermal stability and flammability of the reported electrolytes, while largely improving the transport properties at lower temperatures. Detailed investigation of the electrochemical properties of silicon half-cells as a function of PC content, temperature, and current rates reveal that capacity increases with PC content and temperature and decreases with increased current rates. For example, addition of 20% PC led to a drastic improvement in capacity as observed for the Si electrodes at 25 °C, with stability over 100 charge/discharge cycles. At 100 °C, the capacity further increases by 3-4 times to 0.52 mA h cm(-2) (2230 mA h g(-1)) with minimal loss during cycling.

  6. Endohedral confinement of a DNA dodecamer onto pristine carbon nanotubes and the stability of the canonical B form

    Science.gov (United States)

    Cruz, Fernando J. A. L.; de Pablo, Juan J.; Mota, José P. B.

    2014-06-01

    Although carbon nanotubes are potential candidates for DNA encapsulation and subsequent delivery of biological payloads to living cells, the thermodynamical spontaneity of DNA encapsulation under physiological conditions is still a matter of debate. Using enhanced sampling techniques, we show for the first time that, given a sufficiently large carbon nanotube, the confinement of a double-stranded DNA segment, 5'-D(*CP*GP*CP*GP*AP*AP*TP*TP*CP*GP*CP*G)-3', is thermodynamically favourable under physiological environments (134 mM, 310 K, 1 bar), leading to DNA-nanotube hybrids with lower free energy than the unconfined biomolecule. A diameter threshold of 3 nm is established below which encapsulation is inhibited. The confined DNA segment maintains its translational mobility and exhibits the main geometrical features of the canonical B form. To accommodate itself within the nanopore, the DNA's end-to-end length increases from 3.85 nm up to approximately 4.1 nm, due to a ˜0.3 nm elastic expansion of the strand termini. The canonical Watson-Crick H-bond network is essentially conserved throughout encapsulation, showing that the contact between the DNA segment and the hydrophobic carbon walls results in minor rearrangements of the nucleotides H-bonding. The results obtained here are paramount to the usage of carbon nanotubes as encapsulation media for next generation drug delivery technologies.

  7. Impact of short-lived non-CO2 mitigation on carbon budgets for stabilizing global warming

    NARCIS (Netherlands)

    Rogelj, Joeri; Meinshausen, M.; Schaeffer, M.; Knutti, R.; Riahi, Keywan

    2015-01-01

    Limiting global warming to any level requires limiting the total amount of CO2 emissions, or staying within a CO2 budget. Here we assess how emissions from short-lived non-CO2 species like methane, hydrofluorocarbons (HFCs), black-carbon, and sulphates influence these CO2 budgets. Our default case,

  8. Interseismic re-strengthening and stabilization of carbonate faults by "non-Dieterich" healing under hydrothermal conditions

    NARCIS (Netherlands)

    Chen, Jianye; Verberne, Berend A.; Spiers, Christopher J.

    2015-01-01

    Friction experiments, consisting of a "velocity stepping" stage, a "slide-hold-slide" (SHS) stage and a second "velocity stepping" stage, have been performed to study the frictional healing behavior of carbonate fault gouge, and the effects of healing on the velocity dependence of friction, at 20-14

  9. Mechanical stability model of progradational carbonate platform margins under tectonic loads: Deformation of Cretaceous carbonate platforms in the Sierra Madre Oriental fold-thrust belt (east central Mexico)

    Science.gov (United States)

    Contreras, Juan; Suter, Max

    2015-02-01

    Shortening in the Sierra Madre Oriental fold-thrust belt (east central Mexico) is localized along the margins of Cretaceous carbonate platforms and controlled by mechanical stratigraphy. The platform margins are deformed by imbricate series of thrust ramps, whereas the coeval basins and platform interiors are deformed by map-scale detachment folds. Here we present a finite element model to evaluate the influence of the boundary geometry and boundary conditions on the style of deformation observed at these basinward progradational platform margins. We calculate the stress distribution in a linearly elastic platform-basin transition zone under the action of horizontal tectonic stress, taking into account changes of rock mechanical properties across the platform margin, as well as their dependence on direction, and infer the resulting fracture patterns based on the Mohr-Coulomb failure criterion. Stress concentrations are predicted at the contacts between the massive rocks of the platform margin and the well-layered rocks of both, the platform interior and the adjacent basin. Brittle failure of the platform border can be mostly attributed to three effects: mechanical coupling between the carbonate platform and a substratum of moderate to low viscosity, variations in layering and texture that governed the mechanical properties of the involved carbonates as well as their dependence on direction, and the development of sharp domain boundary corners associated with progradational facies changes. In contrast, the dip of the basement and a possible taper of the overlying Upper Cretaceous shale toward the basin appear to have little influence on the mechanical failure of the platform margin.

  10. Effect of heat treatment on the activity and stability of carbon supported PtMo alloy electrocatalysts for hydrogen oxidation in proton exchange membrane fuel cells

    Science.gov (United States)

    Hassan, Ayaz; Carreras, Alejo; Trincavelli, Jorge; Ticianelli, Edson Antonio

    2014-02-01

    The effect of heat treatment on the activity, stability and CO tolerance of PtMo/C catalysts was studied, due to their applicability in the anode of proton exchange membrane fuel cells (PEMFCs). To this purpose, a carbon supported PtMo (60:40) alloy electrocatalyst was synthesized by the formic acid reduction method, and samples of this catalyst were heat-treated at various temperatures ranging between 400 and 700 °C. The samples were characterized by temperature programmed reduction (TPR), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), cyclic voltammetry (CV), scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDS). Cyclic voltammetry was used to study the stability, and polarization curves were used to investigate the performance of all materials as CO tolerant anode on a PEM single cell text fixture. The catalyst treated at 600 °C, for which the average crystallite size was 16.7 nm, showed the highest hydrogen oxidation activity in the presence of CO, giving an overpotential induced by CO contamination of 100 mV at 1 Acm-2. This catalyst also showed a better stability up to 5000 potential cycles of cyclic voltammetry, as compared to the untreated catalyst. CV, SEM and WDS results indicated that a partial dissolution of Mo and its migration/diffusion from the anode to the cathode occurs during the single cell cycling. Polarization results showed that the catalytic activity and the stability can be improved by a heat treatment, in spite of a growth of the catalyst particles.

  11. Enhanced dispersion stability and mobility of carboxyl-functionalized carbon nanotubes in aqueous solutions through strong hydrogen bonds

    Energy Technology Data Exchange (ETDEWEB)

    Bahk, Yeon Kyoung; He, Xu; Gitsis, Emmanouil; Kuo, Yu-Ying [ETH Zurich, Institute of Environmental Engineering (Switzerland); Kim, Nayoung [EMPA, Building Energy Materials and Components (Switzerland); Wang, Jing, E-mail: jing.wang@ifu.baug.ethz.ch [ETH Zurich, Institute of Environmental Engineering (Switzerland)

    2015-10-15

    Dispersion of carbon nanotubes has been heavily studied due to its importance for their technical applications, toxic effects, and environmental impacts. Common electrolytes, such as sodium chloride and potassium chloride, promote agglomeration of nanoparticles in aqueous solutions. On the contrary, we discovered that acetic electrolytes enhanced the dispersion of multi-walled carbon nanotubes (MWCNTs) with carboxyl functional group through the strong hydrogen bond, which was confirmed by UV–Vis spectrometry, dispersion observations and aerosolization-quantification method. When concentrations of acetate electrolytes such as ammonium acetate (CH{sub 3}CO{sub 2}NH{sub 4}) and sodium acetate (CH{sub 3}CO{sub 2}Na) were lower than 0.03 mol per liter, MWCNT suspensions showed better dispersion and had higher mobility in porous media. The effects by the acetic environment are also applicable to other nanoparticles with the carboxyl functional group, which was demonstrated with polystyrene latex particles as an example.

  12. Nanoscale stabilization of zintl compounds: 1D ionic Li-P double helix confined inside a carbon nanotube.

    Science.gov (United States)

    Ivanov, Alexander S; Kar, Tapas; Boldyrev, Alexander I

    2016-02-14

    One-dimensional (1D) ionic nanowires are extremely rare materials due to the difficulty in stabilizing 1D chains of ions under ambient conditions. We demonstrate here a theoretical prediction of a novel hybrid material, a nanotube encapsulated 1D ionic lithium monophosphide (LiP) chain, featuring a unique double-helix structure, which is very unusual in inorganic chemistry. This nanocomposite has been investigated with density functional theory, including molecular dynamics simulations and electronic structure calculations. We find that the formation of the LiP double-helical nanowire is facilitated by strong interactions between LiP and CNTs resulting in a charge transfer. This work suggests that nanostructured confinement may be used to stabilize other polyphosphide 1D chains, thus opening new ways to study the chemistry of zintl compounds at the nanoscale.

  13. Endohedral confinement of a DNA dodecamer onto pristine carbon nanotubes and the stability of the canonical B form

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, Fernando J. A. L., E-mail: fj.cruz@fct.unl.pt [Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica 2829-516 (Portugal); Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Pablo, Juan J. de [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Institute of Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Mota, José P. B. [Requimte/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica 2829-516 (Portugal)

    2014-06-14

    Although carbon nanotubes are potential candidates for DNA encapsulation and subsequent delivery of biological payloads to living cells, the thermodynamical spontaneity of DNA encapsulation under physiological conditions is still a matter of debate. Using enhanced sampling techniques, we show for the first time that, given a sufficiently large carbon nanotube, the confinement of a double-stranded DNA segment, 5′-D({sup *}CP{sup *}GP{sup *}CP{sup *}GP{sup *}AP{sup *}AP{sup *}TP{sup *}TP{sup *}CP{sup *}GP{sup *}CP{sup *}G)-3′, is thermodynamically favourable under physiological environments (134 mM, 310 K, 1 bar), leading to DNA-nanotube hybrids with lower free energy than the unconfined biomolecule. A diameter threshold of 3 nm is established below which encapsulation is inhibited. The confined DNA segment maintains its translational mobility and exhibits the main geometrical features of the canonical B form. To accommodate itself within the nanopore, the DNA's end-to-end length increases from 3.85 nm up to approximately 4.1 nm, due to a ∼0.3 nm elastic expansion of the strand termini. The canonical Watson-Crick H-bond network is essentially conserved throughout encapsulation, showing that the contact between the DNA segment and the hydrophobic carbon walls results in minor rearrangements of the nucleotides H-bonding. The results obtained here are paramount to the usage of carbon nanotubes as encapsulation media for next generation drug delivery technologies.

  14. Enhanced Stability of PtRu Supported on N-Doped Carbon for the Anode of a DMFC

    Science.gov (United States)

    2012-09-18

    Stability of PtRu Supported on N-Dop Block 13: Supplementary Note © 2012 . Published in Journal of the Electrochemical Society , Vol. Ed. 0 159, (11...sign up http://jes.ecsdl.org/subscriptions go to: Journal of The Electrochemical SocietyTo subscribe to © 2012 The Electrochemical Society F768...Journal of The Electrochemical Society , 159 (11) F768-F778 (2012) 0013-4651/2012/159(11)/F768/11/$28.00 © The Electrochemical Society Enhanced

  15. Effects of carbon on the stability and chemical performance of transition metal carbides: A density functional study

    Science.gov (United States)

    Liu, Ping; Rodriguez, José A.

    2004-03-01

    Density functional theory was employed to study the stabilities and chemical activities of transition metal carbides. Here we take the well-known Mo carbides and Ti carbides as an example. Different kinds of structures including the bulk surfaces [Mo2C(001), MoC(001), and TiC(001)] and metcars [Mo8C12 and Ti8C12] are taken into consideration. Systematic studies show that by raising the C coordination number of the metal atoms in the carbides, in general the stability of the carbides increases (metcars are an exception since they include both high-coordinated and low-coordinated metal atoms.); at the same time, the chemical activities of the carbides decrease due to a downshift of the metal d-band center (ligand effect). Considering the better catalysts those that combine high stability and moderate chemical activity, our results suggest that the catalytic potential of Mo carbide systems should decrease in the following sequence: Mo8C12>Mo2C(001) or MoC(001)>pure Mo(110). In spite of having the largest C/Mo ratio, the metcar appears as the most attractive system. Our studies also indicate that the "magic" behavior of metcars is not unique for Mo carbides. Similar behavior is also observed for Ti carbides. This implies that nanoparticles like metcar species could exhibit better performances than the corresponding bulk metal carbides as catalysts.

  16. Synergistic effects from graphene and carbon nanotubes endow ordered hierarchical structure foams with a combination of compressibility, super-elasticity and stability and potential application as pressure sensors

    Science.gov (United States)

    Kuang, Jun; Dai, Zhaohe; Liu, Luqi; Yang, Zhou; Jin, Ming; Zhang, Zhong

    2015-05-01

    Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and CNT. The resulting materials possess excellent properties of combined high specific strength, elasticity and mechanical stability, which cannot be achieved in neat CNT and graphene foams. The improved mechanical properties are attributed to the synergistic-effect-induced highly organized, multi-scaled hierarchical architectures. Moreover, with their excellent electrical conductivity, we demonstrated that the hybrid foams could be used as pressure sensors in the fields related to artificial skin.Nanostructured carbon material based three-dimensional porous architectures have been increasingly developed for various applications, e.g. sensors, elastomer conductors, and energy storage devices. Maintaining architectures with good mechanical performance, including elasticity, load-bearing capacity, fatigue resistance and mechanical stability, is prerequisite for realizing these functions. Though graphene and CNT offer opportunities as nanoscale building blocks, it still remains a great challenge to achieve good mechanical performance in their microarchitectures because of the need to precisely control the structure at different scales. Herein, we fabricate a hierarchical honeycomb-like structured hybrid foam based on both graphene and

  17. The Evolution of Multicomponent Systems at High Pressures: VI. The Thermodynamic Stability of the Hydrogen-Carbon System: The Genesis of Hydrocarbons and the Origin of Petroleum

    CERN Document Server

    Kenney, J F; Bendeliani, N A; Alekseev, V A; Kutcherov, Vladimir G.; Bendeliani, Nikolai A.; Alekseev, Vladimir A.

    2002-01-01

    The spontaneous genesis of hydrocarbons which comprise natural petroleum have been analyzed by chemical thermodynamic stability theory. The constraints imposed upon chemical evolution by the second law of thermodynamics are briefly reviewed; and the effective prohibition of transformation, in the regime of temperatures and pressures characteristic of the near-surface crust of the Earth, of biological molecules into hydrocarbon molecules heavier than methane is recognized. A general, first-principles equation of state has been developed by extending scaled particle theory (SPT) and by using the technique of the factored partition function of the Simplified Perturbed Hard Chain Theory (SPHCT). The chemical potentials, and the respective thermodynamic Affinity, have been calculated for typical components of the hydrogen-carbon (H-C) system over a range pressures between 1-100 kbar, and at temperatures consistent with those of the depths of the Earth at such pressures. The theoretical analyses establish that the ...

  18. Active packaged lamb with oxygen scavenger/carbon dioxide emitter sachet: physical-chemical and microbiological stability during refrigerated storage

    Directory of Open Access Journals (Sweden)

    Marco Antonio Trindade

    2013-09-01

    Full Text Available Lamb meat has been commercialized in Brazil almost exclusively as a frozen product due to the longer shelf life provided by freezing when compared to refrigeration. However, as a result of the current trend of increased demand for convenience products, a need has emerged for further studies to facilitate the marketing of refrigerated lamb cuts. The aim of the present study was to evaluate the contribution of active packaging technology in extending the shelf life of lamb loins (Longissimus lumborum stored under refrigeration (1±1 ° C when compared to the traditional vacuum packaging. For this purpose, two kinds of sachets were employed: oxygen scavenger sachet and oxygen scavenger/carbon dioxide emitter sachet. Experiments were conducted in three treatments: 1 Vacuum (Control, 2 Vacuum + oxygen scavenger sachet and 3 Vacuum + oxygen scavenger/carbon dioxide emitter sachet. Microbiological (counts of anaerobic psychrotrophs, coliform at 45 ° C, coagulase-positive staphylococci, Salmonella and lactic acid bacteria and physical-chemical (thiobarbituric acid reactive substances, objective color, pH value, water loss from cooking and shear force analyses were carried out weekly for a total storage period of 28 days. The experiment was performed three times for all treatments. Results showed that the lamb meat remained stable with respect to the majority of the evaluated physical and chemical indexes and remained within the standards established by Brazilian legislation for pathogenic microorganisms throughout the storage period in all three packaging systems. However, all treatments presented elevated counts of anaerobic psychrotrophic microorganisms and lactic acid bacteria, reaching values above 10(7 CFU/g at 28 days of storage. Thus, under the conditions tested, neither the oxygen scavenger sachet nor the dual function sachet (oxygen scavenger/carbon dioxide emitter were able to extend the shelf life of refrigerated lamb loin when added to this

  19. Stability of IRA-45 solid amine resin as a function of carbon dioxide absorption and steam desorption cycling

    Science.gov (United States)

    Wood, Peter C.; Wydeven, Theodore

    1987-01-01

    The removal of CO2 from the NASA Space Station's cabin atmosphere, which may be undertaken by a solid-amine water (steam)-desorbed system, is presently evaluated with a view to long-term amine resin stability and adsorption/desorption cycling by means of an automated laboratory flow-testing facility. While the CO2-adsorption capacity of the IRA-45 amine resin used gradually decreased over time, the rate of degradation significantly decreased after the first 10 cycles. Attention is given to the presence (and possible need for removal) of trimethylamine in the process air downstream of the resin bed.

  20. A fundamental investigation of the surfactant-stabilized single-walled carbon nanotube/epoxy resin suspensions by molecular dynamics simulation

    Science.gov (United States)

    Rahmani, Farzin; Nouranian, Sasan; Mahdavi, Mina; O’Haver, John H.

    2017-01-01

    The surfactant-assisted stabilization of single-walled carbon nanotubes (SWCNTs) in SWCNT/epoxy resin suspensions were investigated for different surfactant types, concentrations, and temperatures using molecular dynamics simulation. One cationic surfactant, i.e. cetyltrimethylammonium bromide (CTAB), and three anionic surfactants, i.e. sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (NaDDBS), and sodium cholate (SC), as well as a 1:1 mixture of CTAB and SDS were used. Potentials of mean force (PMFs) were generated between two fixed-size (6,6) SWCNTs for all neat (no surfactant) and surfactant-loaded SWCNT/epoxy resin systems at three different surfactant concentrations (0.25, 0.50, and 1.00 wt%) at room (298 K) and elevated temperature (398 K, only for low-surfactant-concentration systems). Overall, two distinct mechanisms of SWCNT stabilization by the surfactants were identified: (1) an increase in the SWCNT aggregation energy barrier due to the wrapping of the SWCNTs by the surfactant molecules, and (2) a constantly positive free energy (repulsion) for all SWCNT separation distances due to the encapsulation of the two approaching SWCNTs. With the second mechanism, there is a delay for the epoxy molecules to be pushed out from the space between the two SWCNTs. With an increase in the surfactant concentration, the first mechanism becomes more prevalent. With an increase in temperature to 398 K, all surfactants migrate to the suspending medium, thereby the second mechanism of SWCNT stabilization dominates. A drop in the SWCNT-surfactant binding energy is observed around 360–370 K, signifying the surfactant migration to the suspending medium. More or less, all surfactants stabilize the SWCNTs in an epoxy resin at one or more surfactant concentrations. However, NaDDBS exhibits a higher SWCNT aggregation barrier at high concentrations and both temperatures (298 K and 398 K), thereby providing a better SWCNT stabilization in the epoxy resin

  1. Endohedral confinement of a DNA dodecamer onto pristine carbon nanotubes and the stability of the canonical B form

    CERN Document Server

    Cruz, Fernando J A L; Mota, José P B

    2016-01-01

    Although carbon nanotubes are potential candidates for DNA encapsulation and subsequent delivery of biological payloads to living cells, the thermodynamical spontaneity of DNA encapsulation under physiological conditions is still a matter of debate. Using enhanced sampling techniques, we show for the first time that, given a sufficiently large carbon nanotube, the confinement of a double-stranded DNA segment, 5'-D(*CP*GP*CP*GP*AP*AP*TP*TP*CP*GP*CP*G)-3', is thermodynamically favourable under physiological environments (134 mM, 310 K, 1 bar), leading to DNA-nanotube hybrids with lower free energy than the unconfined biomolecule. A diameter threshold of 3 nm is established below which encapsulation is inhibited. The confined DNA segment maintains its translational mobility and exhibits the main geometrical features of the canonical B form. To accommodate itself within the nanopore, the DNA end-to-end length increases from 3.85 nm up to approximately 4.1 nm, due to a 0.3 nm elastic expansion of the strand termin...

  2. Behavior of Na+-Polystyrene Sulfonate at the Interface with Single-Walled Carbon Nanotubes (SWNTs and Its Implication to SWNT Suspension Stability

    Directory of Open Access Journals (Sweden)

    Yuri Lvov

    2011-06-01

    Full Text Available The assembly of sodium polystyrene sulfonate (Na+-PSS at the surface of single-walled carbon nanotubes (SWNTs in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na+-PSS adopts a spherically collapsed conformation believed to be the result of cation (either Na+ or H+ condensation onto the ionized polymer chain. It is well reported that cations (and also anions adsorb preferentially onto single-walled and multi-walled carbon nanotube surfaces leading to an increased ion concentration in the near surface regions relative to the bulk solution. This work provides experimental evidence for preferentially absorbed cation condensation onto PSS anions until those cations are spaced at distances corresponding to the Bjerrum length ( B, as defined by the Manning theory of ion condensation, at the SWNT surface. The resulting electrostearic repulsions allow the SWNTs to remain suspended for days. Furthermore , coulombic repulsion among SWNT bundles after cation adsorption alone is not sufficient to form stable suspensions—but rather the stearic repulsions associated with spherically collapsed PSS at the nanotube surface is responsible for suspension stability. It is believed that the ultrasonic agitation drives cations into the small spaces between SWNT bundles and coulombic potential attracts the PSS to those regions.

  3. Application of Stabilized Silver Nanoparticles as Thin Films as Corrosion Inhibitors for Carbon Steel Alloy in 1 M Hydrochloric Acid

    Directory of Open Access Journals (Sweden)

    Ayman M. Atta

    2013-01-01

    Full Text Available Nanometer scaled materials have attracted tremendous interest as corrosion protective films due to their high ability to form self-assembled films on the metal surfaces. It is well known that the silver nanoparticles have higher reactivity towards aqueous acidic solution. The present work aims to prepare coated silver nanoparticles to protect carbon steel alloys from aqueous acidic corrosive media. In this respect, Ag nanoparticles colloid solutions were produced through reducing AgNO3 separately with trisodium citrate in an aqueous solution or in the presence of stabilizer such as poly(ethylene glycol thiol and poly(vinyl pyrrolidone. The morphology of the modified silver nanoparticles was investigated by TEM and DLS. UV-Vis absorption spectrum was used to study the effect of HCl on the stability of the dispersed silver nanoparticles. The corrosion inhibition efficiency of the poly (ethylene glycolthiol, the self-assembled monolayers of Ag nanoparticles, was determined by polarization method and electrochemical impedance spectroscopy (EIS. Polarization curves indicated that the coated silver poly (ethylene glycolthiol acted as a mixed type inhibitor. The data of inhibition efficiencies obtained measured by polarization measurements are in good agreement with those obtained with electrochemical impedance.

  4. Trivalent expanders and hyperbolic surfaces

    CERN Document Server

    Ivrissimtzis, Ioannis; Vdovina, Alina

    2012-01-01

    We introduce a family of trivalent expanders which tessellate compact hyperbolic surfaces with large isometry groups. We compare this family with Platonic graphs and modifications of them and prove topological and spectral properties of these families.

  5. Significantly improved long-cycle stability in high-rate Li-S batteries enabled by coaxial graphene wrapping over sulfur-coated carbon nanofibers.

    Science.gov (United States)

    Lu, Songtao; Cheng, Yingwen; Wu, Xiaohong; Liu, Jie

    2013-06-12

    Long-term instability of Li-S batteries is one of their major disadvantages compare to other secondary batteries. The reasons for the instability include dissolution of polysulfide intermediates and mechanical instability of the electrode film caused by volume changes during charging/discharging cycles. In this paper, we report a novel graphene-sulfur-carbon nanofibers (G-S-CNFs) multilayer and coaxial nanocomposite for the cathode of Li-S batteries with increased capacity and significantly improved long-cycle stability. Electrodes made with such nanocomposites were able to deliver a reversible capacity of 694 mA h g(-1) at 0.1C and 313 mA h g(-1) at 2C, which are both substantially higher than electrodes assembled without graphene wrapping. More importantly, the long-cycle stability was significantly improved by graphene wrapping. The cathode made with G-S-CNFs with a initial capacity of 745 mA h g(-1) was able to maintain ~273 mA h g(-1) even after 1500 charge-discharge cycles at a high rate of 1C, representing an extremely low decay rate (0.043% per cycle after 1500 cycles). In contrast, the capacity of an electrode assembled without graphene wrapping decayed dramatically with a 10 times high rate (~0.40% per cycle after 200 cycles). These results demonstrate that the coaxial nanocomposites are of great potential as the cathode for high-rate rechargeable Li-S batteries. Such improved rate capability and cycle stability could be attributed to the unique coaxial architecture of the nanocomposite, in which the contributions from graphene and CNFs enable electrodes with improved electrical conductivity, better ability to trap soluble the polysulfides intermediate and accommodate volume expansion/shrinkage of sulfur during repeated charge/discharge cycles.

  6. Cyclic hydrogenation stability of γ-hydrides for Ti{sub 25}V{sub 35}Cr{sub 40} alloys doped with carbon

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chia-Chieh, E-mail: ccshen@saturn.yzu.edu.tw [Department of Mechanical Engineering, Yuan Ze University, Chungli 32003, Taiwan (China); Graduate School of Renewable Energy and Engineering, Yuan Ze University, Chungli 32003, Taiwan (China); Fuel Cell Center, Yuan Ze University, Chungli 32003, Taiwan (China); Li, Hsueh-Chih [Graduate School of Renewable Energy and Engineering, Yuan Ze University, Chungli 32003, Taiwan (China)

    2015-11-05

    An automatic Sievert's apparatus equipped with a temperature-programmed desorption spectrometer was constructed to study the stability of annealed Ti{sub 25}V{sub 35}Cr{sub 40}C{sub x} (x = 0 and 0.1) alloy under cyclic hydrogenation at 6 N H{sub 2}. The specimens were tested at 30 °C with a hydrogen loading of around 1.00 H/M, which enabled the phase transformation from β-to γ-hydrides. After 500 cycles, 83% and 90% of the initial hydrogen capacities were preserved for Ti{sub 25}V{sub 35}Cr{sub 40} and Ti{sub 25}V{sub 35}Cr{sub 40}C{sub 0.1}, respectively. Therefore, a small amount of C doping was effective in reducing the hydrogenation degradation of Ti{sub 25}V{sub 35}Cr{sub 40}. The hydrogenation degradation of Ti{sub 25}V{sub 35}Cr{sub 40} was examined by measuring the P–C isotherms, temperature-programmed desorption spectra, and X-ray diffraction patterns. The degradation was ascribed to intrinsic disproportionation, i.e., Ti{sub 0.25}V{sub 0.35}Cr{sub 0.40} + 0.88H{sub 2} → yTiH{sub 2} + Ti{sub 0.25−y}V{sub 0.35}Cr{sub 0.40}H{sub 1.76–2y}, where the coefficient y indicates the amount of Ti-rich precipitate. The better cyclic hydrogenation stability of Ti{sub 25}V{sub 35}Cr{sub 40}C{sub 0.1} was related to the suppression of intrinsic disproportionation by the presence of carbon atoms in the body-centered-cubic lattice. - Highlights: • The stability of γ-hydride for Ti{sub 25}V{sub 35}Cr{sub 40} alloys was examined for 500 cycles. • The γ-hydride of Ti{sub 25}V{sub 35}Cr{sub 40} alloy degraded by intrinsic disproportionation. • The disproportionation of γ-hydride can be suppressed through carbon inclusion.

  7. Dissolved Organic Matter as a Mechanism for Carbon Stabilization at Depth in Wet Tropical Forest Volcanic Soils

    Science.gov (United States)

    Marin-Spiotta, E.; Kramer, M. G.; Chadwick, O. A.

    2007-12-01

    Dissolved organic matter (DOM) plays an important role in many biological and chemical processes in soils. Our understanding of the types of plant and microbially-derived organic matter that accumulate in soils and the mechanisms responsible for their transformation and stabilization is still limited. In particular, we know very little about how microbial activity and water movement contribute to the production of DOM and the formation of stable C in soils. In well-drained soils under wet climates, DOM is potentially a primary pathway for the transport of C from the surface litter layers and the zones of highest microbial activity to deeper horizons in the soil profile where the potential for long-term storage increases. The mechanisms for long-term stabilization of organic C in deep mineral horizons include an accumulation of chemically recalcitrant C, strong sorption of soluble and otherwise labile C to mineral and/or metals making them inaccessible to decomposers, and microenvironmental conditions (low pH, low O2) which result in incomplete decomposition and persistence of labile C. Although most work to date has focused on the role of dissolved organic C and N (DOC and DON) in the C and N cycles of temperate forests, DOM fluxes may be even more important in forests in the wet tropics, where high rainfall and high primary productivity could lead to greater DOM production. In order to address the role of DOC in the transport and stabilization of C in mineral horizons, we are studying DOC production, transformation, and loss pathways in volcanic soils dominated by highly reactive, non-crystalline minerals (allophane). We are quantifying flux and solute concentrations (C, N, cations, anions) in rainwater, throughfall, and in soil water. We have installed tension and zero tension lysimeters throughout sequentially deeper organic and mineral horizons in an intermediate aged soil (ca. 350k years) under wet (ca. 3000 mm mean annual rainfall) native tropical forest

  8. Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost

    Science.gov (United States)

    Euskirchen, Eugenie S; Edgar, C.W.; Turetsky, M.R.; Waldrop, Mark P.; Harden, Jennifer W.

    2016-01-01

    Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2), water, and energy fluxes, associated environmental variables, and methane (CH4) fluxes at the collapse scar bog. The ecosystems all acted as net sinks of CO2 in 2011 and 2012, when air temperature and precipitation remained near long-term means. In 2013, under a late snowmelt and late leaf out followed by a hot, dry summer, the permafrost forest and collapse scar bog were sources of CO2. In this same year, CO2 uptake in the fen increased, largely because summer inundation from groundwater inputs suppressed ecosystem respiration. CO2 exchange in the permafrost forest and collapse scar bog was sensitive to warm air temperatures, with 0.5 g C m−2 lost each day when maximum air temperature was very warm (≥29°C). The bog lost 4981 ± 300 mg CH4 m−2 between April and September 2013, indicating that this ecosystem acted as a significant source of both CO2 and CH4 to the atmosphere in 2013. These results suggest that boreal peatland responses to warming and drying, both of which are expected to occur in a changing climate, will depend on permafrost regime.

  9. Spatial Prediction of Soil Aggregate Stability and Aggregate-Associated Organic Carbon Content at the Catchment Scale Using Geostatistical Techniques

    Institute of Scientific and Technical Information of China (English)

    J.MOHAMMADI; M.H.MOTAGHIAN

    2011-01-01

    The association of organic carbon with secondary parzicles (aggregates) results in its storage and retention in soil. A study was carried out at a catchment covering about 92 km2 to predict spatial variability of soil water-stable aggregates (WSA), mean weight diameter (MWD) of aggregates and organic carbon (OC) content in macro- (> 2 mm), meso- (1-2 mm), and micro-aggregate (< 1 mm) fractions, using geostatistical methods. One hundred and eleven soil samples were c(o)llected at the 0-10 cm depth and fractionated into macro-, meso-, and micro-aggregates by wet sieving. The OC content was determined for each fraction. A greater percentage of water-stable aggregates was found for micro-aggregates, followed by meso-aggregates. Aggregate OC content was greatest in meso-aggregates (9 g kg-1), followed by micro-aggregates (7 g kg-1), while the least OC content was found in macro-aggregates (3 g kg-1). Although a significart effect (P = 0.000) of aggregate size on aggregate OC content was found, however, our findings did not support the model of aggregate hierarchy.Land use had a significant effect (P = 0.073) on aggregate OC content. The coefficients of variation (CVs) for OC contents associated with each aggregate fraction indicated macro-aggregates as the most variable (CV = 71%). Among the aggregate fractions, the micro-aggregate fraction had a lower CV value of 27%. The mean content of WSA ranged from 15% for macro-aggregates to 84% for micro-aggregates. Geostatistical analysis showed that the measured soil variables exhibited differences in their spatial patterns in both magnitude and space at each aggregate size fraction. The relative nugget variance for most aggregate-associated properties was lower than 45%. The range value for the variogram of water-stable aggregates was almost similar (about 3 km) for the three studied aggregate size classes. The range value for the variogram of aggregate-associated OC contents ranged from about 3 km for macro

  10. Oxygen reduction at carbon supported ruthenium-selenium catalysts: Selenium as promoter and stabilizer of catalytic activity

    Science.gov (United States)

    Schulenburg, Hendrik; Hilgendorff, Marcus; Dorbandt, Iris; Radnik, Jörg; Bogdanoff, Peter; Fiechter, Sebastian; Bron, Michael; Tributsch, Helmut

    Carbon supported ruthenium-based catalysts (Ru/C) for the oxygen reduction in acid electrolytes were investigated. A treatment of Ru/C catalysts with selenious acid had a beneficial effect on catalytic activity but no influence on intrinsic kinetic properties, like Tafel slope and hydrogen peroxide generation. Reasons for the increased activity of RuSe x/C catalysts are discussed. Potential step measurements suggest that at potentials around 0.8 V (NHE) a selenium or selenium-oxygen species protects the catalyst from formation of inactive RuO 2-films. This protective effect leads to an enhanced activity of RuSe x/C compared to Ru/C. No evidence was found for a catalytically active stoichiometric selenium compound. The active phase may be described as a ruthenium suboxide RuO x (x RuSe y phase or RuSe yO v (y < 2, v < 2) layer at the particle surface.

  11. The effect of carbon monoxide pretreatment exposure time on the colour stability and quality attributes of vacuum packaged beef steaks.

    Science.gov (United States)

    Van Rooyen, Lauren Anne; Allen, Paul; Crawley, Sarah M; O'Connor, David I

    2017-02-24

    The effect of 5% CO pretreatments prior to vacuum packaging of beef striploin steaks (Longissimus thoracis et lumborum, LTL) on quality attributes, primarily colour stability was investigated. The aim was to determine the optimum pretreatment that would induce the desirable red colour, while allowing discoloration to occur by the end of a 28-day display period (2°C), so as to not mask spoilage. A range of pretreatment exposure times (1, 3, 5, 7, 9, 15 and 24h) were applied to steaks using a gas mixture of 5% CO, 60% CO2 and 35% N2. The 5h CO pretreatment exposure time achieved the desirable colour and discoloration reached unacceptable levels (a*=12, C*=16) by the use-by date (28days), thus ensuring consumers' of a reliable visual indication of freshness and addressing concerns about safety. The 5% CO pretreatment had no negative effect on microbiological safety, lipid oxidation, cooking loss and WBSF measurements at the end of storage (P>0.05).

  12. The relationship between the structures of polyacrylonitrile carbon fibers and the stabilized fiber precursors%预氧结构对聚丙烯腈基碳纤维致密结构的影响

    Institute of Scientific and Technical Information of China (English)

    赵震; 张琨; 史晓健; 徐樑华

    2013-01-01

    In the carbonization of polyacrylonitrile (PAN) fibers, the stabilized structure evolves into the compact structure of PAN-based carbonized fibers by pyrolysis and rearrangement. The compact structure of the carbon fiber is one of the factors affecting its performance. TG analysis, Raman spectroscopy, NMR spectroscopy, elemental a-nalysis and other methods have been used to explore the evolution of the stabilized structure during the carbonization process. The results show that the bulk density of the carbon fiber decreases with increasing bulk density of the stabilized fiber. Further studies reveal that the structure of the oxygen-containing material has an effect on the compact structure of the carbon fiber. The removal of oxygen has an effect on the degree of entanglement in the non-crystalline structure and thus affects the bulk density of the carbon fiber. The bulk density of the carbon fiber decreases with increasing oxygen content of the stabilization fiber. Preliminary details of the relationship between the compact structure of the stabilized structure and that of the carbon fiber have thus been established.%利用TG,Raman,EA,XRD,NMR等分析手段,研究了预氧纤维在碳化过程中的结构转变.研究结果表明:碳纤维体密度随预氧纤维体密度的升高呈下降趋势;预氧纤维中的含氧量会影响碳纤维的致密结构,氧元素的脱除影响碳纤维非晶区结构的交缠程度进而影响碳纤维体密度,碳纤维体密度随预氧纤维的含氧量增加而降低.通过碳纤维致密结构与预氧纤维结构的相关性分析,初步建立了两者之间的关联关系.

  13. Soil Aggregate Stability and Aggregate-Associated Carbon Under Different Tillage Systems in the North China Plain

    Institute of Scientific and Technical Information of China (English)

    DU Zhang-liu; REN Tu-sheng; HU Chun-sheng; ZHANG Qing-zhong; Humberto Blanco-Canqui

    2013-01-01

    The inlfuences of tillage systems on soil carbon (C) stocks have been studied extensively, but the distribution of soil C within aggregate fractions is not well understood. The objective of this study was to determine the inlfuences of various tillage systems on soil aggregation and aggregate-associated C under wheat (Triticum aestivum L.) and corn (Zea mays L.) double cropping systems in the North China Plain. The experiment was established in 2001, including four treatments:moldboard plow (MP) with residue (MP+R) and without residue (MP-R), rotary tillage with residue (RT), and no-till with residue (NT). In 2007 soil samples were collected from the 0-5, 5-10, and 10-20 cm depths, and were separated into four aggregate-size classes (>2 000, 250-2 000, 53-250, and2 000 and 250-2 000 µm) compared with the MP-R and MP+R treatments. Averaged across all depths, mean weight diameters of aggregates (MWD) in NT and RT were 47 and 20% higher than that in MP+R. The concentration of bulk soil organic C was positively correlated with MWD (r=0.98; P=0.024) and macroaggregate fraction (r=0.96; P=0.036) in the 0-5 cm depth. In the 0-20 cm depth, comparing with MP+R, total C occluded in the>2 000 µm fraction was increased by 9 and 6%under NT and RT, respectively. We conclude that adoption of conservation tillage system, especially no-till, can increase soil macro-aggregation and total C accumulation in macroaggregates, which may improve soil C sequestration in the intensive agricultural region of the North China Plain.

  14. Co-composting of distillery wastes with animal manures: carbon and nitrogen transformations in the evaluation of compost stability.

    Science.gov (United States)

    Bustamante, M A; Paredes, C; Marhuenda-Egea, F C; Pérez-Espinosa, A; Bernal, M P; Moral, R

    2008-06-01

    The aim of this work was to study the viability of recycling the solid wastes generated by the winery and distillery industry by means of co-composting with animal manures, as well as to evaluate the quality of the composts obtained. Two piles, using exhausted grape marc and cattle manure or poultry manure, respectively (at ratios, on a fresh weight basis, of 70:30), were composted by the Rutgers static pile composting system. Throughout the composting process, a number of parameters were monitored, such as pH, electrical conductivity, organic matter, water-soluble carbon, water-soluble polyphenols, different forms of nitrogen (organic nitrogen, ammonium and nitrate) and humification indices (humification ratio, humification index, percentage of humic acid-like C, polymerisation ratio and cation exchange capacity), as well as the germination index. Organic matter losses followed first-order kinetics equation in both piles, the highest organic matter mineralisation rate being observed with exhausted grape marc and cow manure. On the other hand, the mixture with the lowest C/N ratio, using exhausted grape marc and poultry manure, showed the highest initial ammonium contents, probably due to the higher and more labile N content of poultry manure. The increase in the cation exchange capacity revealed the organic matter humification during composting. In contrast, other humification parameters, such as the humification ratio and the humification index, did not show the expected evolution and, thus, could not be used to assess compost maturity. Composting produced a degradation of the phytotoxic compounds, such as polyphenols, to give composts without a phytotoxic character. Therefore, composting can be considered as an efficient treatment to recycle this type of wastes, due to composts presented a stable and humified organic matter and without phytotoxic effects, which makes them suitable for their agronomic use.

  15. Federal government expands compliance initiatives.

    Science.gov (United States)

    Dugan, J K

    1997-09-01

    In 1995, the Federal government initiated Operation Restore Trust to increase enforcement of fraud and abuse regulations in Medicare and Medicaid programs. With the success of the original initiative, the government is expanding the project to additional states and program areas. The initial scrutiny of home health agencies, nursing homes, hospice care, and durable medical equipment is being expanded to managed care plans and acute care hospitals with an eye toward DRG creep. To manage this increased enforcement activity, healthcare organizations should institute comprehensive corporate compliance programs. Such programs should provide a framework that delineates responsibilities and provides a systematic means to resolve issues in a timely manner.

  16. Single-walled carbon nanotubes dispersed in aqueous media via non-covalent functionalization: effect of dispersant on the stability, cytotoxicity, and epigenetic toxicity of nanotube suspensions.

    Science.gov (United States)

    Alpatova, Alla L; Shan, Wenqian; Babica, Pavel; Upham, Brad L; Rogensues, Adam R; Masten, Susan J; Drown, Edward; Mohanty, Amar K; Alocilja, Evangelyn C; Tarabara, Volodymyr V

    2010-01-01

    As the range of applications for carbon nanotubes (CNTs) rapidly expands, understanding the effect of CNTs on prokaryotic and eukaryotic cell systems has become an important research priority, especially in light of recent reports of the facile dispersion of CNTs in a variety of aqueous systems including natural water. In this study, single-walled carbon nanotubes (SWCNTs) were dispersed in water using a range of natural (gum arabic, amylose, Suwannee River natural organic matter) and synthetic (polyvinyl pyrrolidone, Triton X-100) dispersing agents (dispersants) that attach to the CNT surface non-covalently via different physiosorption mechanisms. The charge and the average effective hydrodynamic diameter of suspended SWCNTs as well as the concentration of exfoliated SWCNTs in the dispersion were found to remain relatively stable over a period of 4 weeks. The cytotoxicity of suspended SWCNTs was assessed as a function of dispersant type and exposure time (up to 48 h) using general viability bioassay with Escherichia coli and using neutral red dye uptake (NDU) bioassay with WB-F344 rat liver epithelia cells. In the E. coli viability bioassays, three types of growth media with different organic loadings and salt contents were evaluated. When the dispersant itself was non-toxic, no losses of E. coli and WB-F344 viability were observed. The cell viability was affected only by SWCNTs dispersed using Triton X-100, which was cytotoxic in SWCNT-free (control) solution. The epigenetic toxicity of dispersed CNTs was evaluated using gap junction intercellular communication (GJIC) bioassay applied to WB-F344 rat liver epithelial cells. With all SWCNT suspensions except those where SWCNTs were dispersed using Triton X-100 (wherein GJIC could not be measured because the sample was cytotoxic), no inhibition of GJIC in the presence of SWCNTs was observed. These results suggest a strong dependence of the toxicity of SWCNT suspensions on the toxicity of the dispersant and point to

  17. Changes in soil organic carbon and aggregate stability after conversion to conservation tillage for seven years in the Huang-Huai-Hai Plain of China

    Institute of Scientific and Technical Information of China (English)

    SHU Xin; ZHU An-ning; ZHANG Jia-bao; YANG Wen-liang; XIN Xiu-li; ZHANG Xian-feng

    2015-01-01

    Soil aggregate stability and organic carbon (OC) are regarded as effective indicators of soil structure and quality. A long-term ifeld experiment was established in 2006 to examine the inlfuence of til age systems on soil aggregation and OC in a sandy loam soil in the Huang-Huai-Hai Plain of China. The study involved eight treatments:plowing every year with (TS) and without residue (T), plowing every 2 years with (2TS) and without residue (2T), plowing every 4 years with (4TS) and without residue (4T), and no plowing with (NTS) and without residue (NT). In 2013, soil samples were col ected at depths of 0–5, 5–10 and 10–20 cm, and separated into three aggregate-size classes:macroaggregates (>250μm), microaggregates (53–250μm) and the silt+clay fraction (microaggregates>silt+clay fraction. In the 0–5 cm soil layer, concentrations of macroaggregate-associated OC in 2TS, 4TS and NTS were 14, 56 and 83%higher than for T, whereas T had the greatest concentration of OC associated with the silt+clay fraction in the 10–20 cm layer. Soil OC concentrations under 4TS and NTS were signiifcantly higher (P<0.05) than that of T in the 0–10 cm layer. Residue retention promoted formation of macroaggregates, increased macroaggregate-associated OC concentrations and thus increased total soil OC stock. The macroaggregate-associated OC was positively correlated (R2=0.96) with soil OC concentration, while the silt+clay fraction-associated OC was negatively correlated (R2=0.82) with soil OC concentration. The concentration of soil OC was positively correlated with MWD (R2=0.94) and GMD (R2=0.92). We concluded that increasing til age intensity led to a loss of carbon (C)-rich macroaggregates and an increase of C-depleted silt+clay fraction. The conservation til age system, especial y NTS and 4TS, increased soil aggregate stability and promoted OC accumulation in macroaggregates, provided the potential to improve soil C sequestration and soil structure in the Huang

  18. Surfactant-promoted Prussian Blue-modified carbon electrodes: enhancement of electro-deposition step, stabilization, electrochemical properties and application to lactate microbiosensors for the neurosciences.

    Science.gov (United States)

    Salazar, P; Martín, M; O'Neill, R D; Roche, R; González-Mora, J L

    2012-04-01

    We report here for the first time a comparison of the beneficial effects of different cationic surfactants - cetyl trimethyl ammonium bromide (CTAB), benzethonium chloride (BZT) and cetylpyridinium chloride (CPC) - for the electrochemical synthesis of Prussian Blue (PB) films, using cyclic voltammetry (CV), on screen-printed carbon electrodes (SPCEs). Their electrochemical properties were investigated, paying special attention to parameters such as the amount of PB deposited, film thickness, charge transfer rate, permeability, reversibility, stability and sensitivity to hydrogen peroxide detection. All surfactant-enhanced PB-modified SPCEs displayed a significant improvement in their electrochemical properties compared with PB-modified SPCEs formed in the absence of surfactants. Surfactant-modified electrodes displayed a consistently higher PB surface concentration value of 2.1±0.4×10(-8) mol cm(-2) (mean±SD, n=3) indicating that PB deposition efficiency was improved 2-3 fold. K(+) and Na(+) permeability properties of the films were also studied, as were kinetic parameters, such as the surface electron transfer rate constant (k(s)) and the transfer coefficient (α). The hydrogen peroxide sensitivity of surfactant-modified PB films generated by 10 electro-deposition CV cycles gave values of 0.63 A M(-1) cm(-2), which is higher than those reported previously for SPCEs by other authors. Finally, the first lactate microbiosensor described in the literature based on BZT-modified PB-coated carbon fiber electrodes is presented. Its very small cross-section (~10 μm diameter) makes it particularly suitable for neuroscience studies in vivo.

  19. A comparative study on the efficiency of ozonation and coagulation-flocculation as pretreatment to activated carbon adsorption of biologically stabilized landfill leachate.

    Science.gov (United States)

    Oloibiri, Violet; Ufomba, Innocent; Chys, Michael; Audenaert, Wim T M; Demeestere, Kristof; Van Hulle, Stijn W H

    2015-09-01

    The present work investigates the potential of coagulation-flocculation and ozonation to pretreat biologically stabilized landfill leachate before granular activated carbon (GAC) adsorption. Both iron (III) chloride (FeCl3) and polyaluminium chloride (PACl) are investigated as coagulants. Better organic matter removal is observed when leachate was treated with FeCl3. At a dose of 1mg FeCl3/mg CODo (CODo: initial COD content), the COD and α254 removal was 66% and 88%, respectively. Dosing 1mg PACl/mg CODo resulted in 44% COD and 72% α254 removal. The settle-ability of sludge generated by PACl leveled off at 252mL/g, while a better settle-ability of 154mL/g was obtained for FeCl3 after dosing 1mg coagulant/mg CODo. For ozonation, the percentage of COD and α254 removal increased as the initial COD concentration decreased. Respectively 44% COD and 77% α254 removal was observed at 112mg COD/L compared to 5% COD and 26% α254 removal at 1846mg COD/L. Subsequent activated carbon adsorption of ozonated, coagulated and untreated leachate resulted in 77%, 53% and 8% total COD removal after treatment of 6 bed volumes. Clearly showing the benefit of treating the leachate before GAC adsorption. Mathematical modeling of the experimental GAC adsorption data with Thomas and Yoon-Nelson models show that ozonation increases the adsorption capacity and breakthrough time of GAC by a factor of 2.5 compared to coagulation-flocculation.

  20. Phosphorylation of Arabidopsis ubiquitin ligase ATL31 is critical for plant carbon/nitrogen nutrient balance response and controls the stability of 14-3-3 proteins.

    Science.gov (United States)

    Yasuda, Shigetaka; Sato, Takeo; Maekawa, Shugo; Aoyama, Shoki; Fukao, Yoichiro; Yamaguchi, Junji

    2014-05-30

    Ubiquitin ligase plays a fundamental role in regulating multiple cellular events in eukaryotes by fine-tuning the stability and activity of specific target proteins. We have previously shown that ubiquitin ligase ATL31 regulates plant growth in response to nutrient balance between carbon and nitrogen (C/N) in Arabidopsis. Subsequent study demonstrated that ATL31 targets 14-3-3 proteins for ubiquitination and modulates the protein abundance in response to C/N-nutrient status. However, the underlying mechanism for the targeting of ATL31 to 14-3-3 proteins remains unclear. Here, we show that ATL31 interacts with 14-3-3 proteins in a phosphorylation-dependent manner. We identified Thr(209), Ser(247), Ser(270), and Ser(303) as putative 14-3-3 binding sites on ATL31 by motif analysis. Mutation of these Ser/Thr residues to Ala in ATL31 inhibited the interaction with 14-3-3 proteins, as demonstrated by yeast two-hybrid and co-immunoprecipitation analyses. Additionally, we identified in vivo phosphorylation of Thr(209) and Ser(247) on ATL31 by MS analysis. A peptide competition assay showed that the application of synthetic phospho-Thr(209) peptide, but not the corresponding unphosphorylated peptide, suppresses the interaction between ATL31 and 14-3-3 proteins. Moreover, Arabidopsis plants overexpressing mutated ATL31, which could not bind to 14-3-3 proteins, showed accumulation of 14-3-3 proteins and growth arrest in disrupted C/N-nutrient conditions similar to wild-type plants, although overexpression of intact ATL31 resulted in repression of 14-3-3 accumulation and tolerance to the conditions. Together, these results demonstrate that the physiological role of phosphorylation at 14-3-3 binding sites on ATL31 is to modulate the binding ability and stability of 14-3-3 proteins to control plant C/N-nutrient response.

  1. Heptaphyrins: Expanded porphyrins with seven heterocyclic rings

    Indian Academy of Sciences (India)

    Venkataramanarao G Anand; Simi K Pushpan; Sundararaman Venkatraman; Tavarekere K Chandrashekar

    2003-10-01

    Expanded porphyrins containing seven pyrrole/heterocyclic rings linked in a cyclic fashion are termed heptaphyrins. The number of -electrons in heptaphyrins depends on the number of meso carbon bridges used to link the heterocyclic rings, accordingly heptaphyrins with 28-electrons and 30 -electrons are reported to date. Both condensation reactions of the appropriate precursors and acid-catalysed oxidative coupling reactions have been utilized to synthesise the heptaphyrins. The 30 heptaphyrins exhibit rich structural diversity where some of the heterocyclic rings in the macrocycle undergo a 180° ring flipping. An overview of the synthetic methods employed for the synthesis of heptaphyrins, their spectroscopic properties, structural behaviour and aromatic properties are highlighted in this paper.

  2. Cosmic strings in an expanding spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Stein-Schabes, J.A.; Burd, A.B.

    1987-04-01

    We investigate the stability of a static, infinitely long and straight vacuum string solution under inhomogeneous axisymmetric time-dependent perturbations. We find it to be perturbatively stable. We further extend our work by finding a string solutions in an expanding Universe. The back reaction of the string on the gravitational field has been ignored. The background is assumed to be a Friedman-Robertson-Walker (FRW) cosmology. By numerically integrating the field equations in a radiation and matter dominated models, we discover oscillatory solutions. The possible damping of these oscillations is discussed. For late times the solution becomes identical to the static one studied in the first part of the paper. 19 refs., 8 figs.

  3. Carbon dioxide-expanded ethanol-assisted synthesis of carbon-based metal composites and their catalytic and electrochemical performance in lithium-ion batteries%二氧化碳膨胀乙醇体系中碳基金属复合物的合成及其催化和电化学性能

    Institute of Scientific and Technical Information of China (English)

    王凌燕; 禚林海; 赵凤玉

    2016-01-01

    Highly dispersed metals, metal oxides and their composites on substrates have received considera‐ble interest in catalysis and lithium‐ion batteries, because of their superior properties compared with their single‐component counterparts. In this review, we introduce the properties of super‐critical carbon dioxide (scCO2) expanded ethanol, such as low viscosity, near‐zero surface tension and high diffusivity. We discuss the deposition procedure and formation mechanism of car‐bon‐based composites in scCO2‐expanded ethanol. This method has been used to fabricate several carbon‐based composites, such as metal and metal oxide composites deposited on zero‐dimensional colloidal carbon, one‐dimensional carbon nanotubes, two‐dimensional graphene, and three‐dimensional hierarchical porous carbon. These materials and their performance as anodic materials for lithium‐ion batteries will also be reviewed.%与块体材料相比,功能复合材料表现了更加优异的性能,而且比其中任何单一组分的性能都好,因此在催化、锂离子电池等领域得以广泛研究。通常情况下,在复合材料的制备中金属或金属氧化物粒子要求能够以足够小的粒径在基底上均匀分散,并实现活性组分负载量的可控。据报道,很多方法可以将金属(或氧化物)活性组分引入到载体之中,比如水热/溶剂热、水解、热分解、化学气相沉积等,但这些方法均存在如下缺点。第一,为了获得满意的负载量和可控包覆,碳基底需要预氧化处理使其表面含有丰富的含氧官能团。例如,由于碳纳米管自身的相容性和加工性较差,需要硝酸预氧化处理;石墨烯也需要预处理为石墨烯氧化物然后再进行第二组分的负载。但是,剧烈的氧化处理条件不可避免地造成对碳sp2结构和电子特性的破坏,并且增加了繁杂的后续处理过程。第二,金属组分前驱体在基底上

  4. Expanding the eukaryotic genetic code

    Science.gov (United States)

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2013-01-22

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  5. Expanding the eukaryotic genetic code

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Jason W.; Cropp, T. Ashton; Anderson, J. Christopher; Schultz, Peter G.

    2017-02-28

    This invention provides compositions and methods for producing translational components that expand the number of genetically encoded amino acids in eukaryotic cells. The components include orthogonal tRNAs, orthogonal aminoacyl-tRNA synthetases, orthogonal pairs of tRNAs/synthetases and unnatural amino acids. Proteins and methods of producing proteins with unnatural amino acids in eukaryotic cells are also provided.

  6. ERBU, Expanding Rubber Band Universe

    CERN Document Server

    Soares, Domingos

    2015-01-01

    I put forward a simple unidimensional mechanical analogue of the three-dimensional universe models of modern relativistic cosmology. The main goal of the proposal is the appropriate appreciation of the intrinsic relationship between Hubble's law and the homogeneity of expanding relativistic models.

  7. Expandable Shelter/Container Report.

    Science.gov (United States)

    1973-06-01

    without removing whatever payload might be in the contai ner. Equ i pment located in the expanded porti on of the ES/C durin g norma l operat i ons is...and Supply BattalIon , Div isi on Support Coianand. In addition , divisional avIation battalions have an A Irc raft Maintenance Company. The TOE

  8. Applying a new procedure to assess the controls on aggregate stability - including soil parent material and soil organic carbon concentrations - at the landscape scale

    Science.gov (United States)

    Turner, Gren; Rawlins, Barry; Wragg, Joanna; Lark, Murray

    2014-05-01

    Aggregate stability is an important physical indicator of soil quality and influences the potential for erosive losses from the landscape, so methods are required to measure it rapidly and cost-effectively. Previously we demonstrated a novel method for quantifying the stability of soil aggregates using a laser granulometer (Rawlins et al., 2012). We have developed our method further to mimic field conditions more closely by incorporating a procedure for pre-wetting aggregates (for 30 minutes on a filter paper) prior to applying the test. The first measurement of particle-size distribution is made on the water stable aggregates after these have been added to circulating water (aggregate size range 1000 to 2000 µm). The second measurement is made on the disaggregated material after the circulating aggregates have been disrupted with ultrasound (sonication). We then compute the difference between the mean weight diameters (MWD) of these two size distributions; we refer to this value as the disaggregation reduction (DR; µm). Soils with more stable aggregates, which are resistant to both slaking and mechanical breakdown by the hydrodynamic forces during circulation, have larger values of DR. We made repeated analyses of DR using an aggregate reference material (RM; a paleosol with well-characterised disaggregation properties) and used this throughout our analyses to demonstrate our approach was reproducible. We applied our modified technique - and also the previous technique in which dry aggregates were used - to a set of 60 topsoil samples (depth 0-15 cm) from cultivated land across a large region (10 000 km2) of eastern England. We wished to investigate: (i) any differences in aggregate stability (DR measurements) using dry or pre-wet aggregates, and (ii) the dominant controls on the stability of aggregates in water using wet aggregates, including variations in mineralogy and soil organic carbon (SOC) content, and any interaction between them. The sixty soil

  9. Potential and barriers for biogas production in Denmark at widely expanded organic farming with focus on the soil carbon content; Potentiale og barrierer for biogasproduktion i Danmark ved omfattende oekologisk jordbrug med fokus paa dyrkningsjordens kulstofforhold

    Energy Technology Data Exchange (ETDEWEB)

    Buch Salomonsen, K.

    2000-06-01

    The Ph.D. thesis describes the influence from continued expansion of organic farming systems to the potential for energy production from biogas in Denmark. The project analyses the consequence from three categories of barriers: 1) Practical barriers, 2) The attitude of organic farmers, and 3) Agricultural biological problems. Economic and political barriers are not examined. When the barriers can be quantified, they are included in the calculation of the maximum biogas potential. When not, the implications of barriers are expressed qualitatively. It has been a particular goal to provide new information on whether agricultural biological problems are a barrier to biogas production in organic farming systems. One important question in this connection is whether biogas production has a negative influence on the soil carbon content compared to composting. This question is investigated by an experiment. The project is based on technical and natural science disciplines, with an interdisciplinary basis ranging over energy planning, agricultural science, microbiology, and crop, and animal operation. (au)

  10. On the stability of conventional and nano-structured carbon-based catalysts in the oxidative dehydrogenation of ethylbenzene under industrially relevant conditions

    NARCIS (Netherlands)

    Zarubina, Valeriya; Talebi, Hesamoddin; Nederlof, Christian; Kapteijn, Freek; Makkee, Michiel; Melian-Cabrera, Ignacio

    2014-01-01

    Relevant carbon-based materials, home-made carbon-silica hybrids, commercial activated carbon, and nanostructured multi-walled carbon nanotubes (MWCNT) were tested in the oxidative dehydrogenation of ethylbenzene (EB). Special attention was given to the reaction conditions, using a relatively concen

  11. Tribological properties and thermal stability of hydrogenated, silicon/nitrogen-coincorporated diamond-like carbon films prepared by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Nakazawa, Hideki; Okuno, Saori; Magara, Kohei; Nakamura, Kazuki; Miura, Soushi; Enta, Yoshiharu

    2016-12-01

    We have deposited hydrogenated, silicon/nitrogen-incorporated diamond-like carbon (Si-N-DLC) films by plasma-enhanced chemical vapor deposition using hexamethyldisilazane [((CH3)3Si)2NH; HMDS] as the Si and N source, and compared the tribological performance and thermal stability of the Si-N-DLC films with those of hydrogenated, Si-incorporated DLC (Si-DLC) films prepared using dimethylsilane [SiH2(CH3)2] as the Si source. The deposited films were annealed at 723-873 K in air atmosphere. The friction coefficients of hydrogenated DLC films after annealing significantly increased at the initial stages of friction tests. On the other hand, the friction coefficients of the Si-N-DLC films deposited at an HMDS flow ratio [HMDS/(HMDS+CH4)] of 2.27% remained low after the annealing even at 873 K. We found that the wear rate of the Si-N-DLC film deposited at 2.27% and -1000 V remained almost unchanged after the annealing at 873 K, whereas that of the Si-DLC film with a similar Si fraction deposited at -1000 V significantly increased after the annealing at 773 K.

  12. Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

    Science.gov (United States)

    Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S.

    2016-08-01

    A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g-1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g-1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

  13. Mesoporous carbon stabilized MgO nanoparticles synthesized by pyrolysis of MgCl2 preloaded waste biomass for highly efficient CO2 capture.

    Science.gov (United States)

    Liu, Wu-Jun; Jiang, Hong; Tian, Ke; Ding, Yan-Wei; Yu, Han-Qing

    2013-08-20

    Anthropogenic CO2 emission makes significant contribution to global climate change and CO2 capture and storage is a currently a preferred technology to change the trajectory toward irreversible global warming. In this work, we reported a new strategy that the inexhaustible MgCl2 in seawater and the abundantly available biomass waste can be utilized to prepare mesoporous carbon stabilized MgO nanoparticles (mPC-MgO) for CO2 capture. The mPC-MgO showed excellent performance in the CO2 capture process with the maximum capacity of 5.45 mol kg(-1), much higher than many other MgO based CO2 trappers. The CO2 capture capacity of the mPC-MgO material kept almost unchanged in 19-run cyclic reuse, and can be regenerated at low temperature. The mechanism for the CO2 capture by the mPC-MgO was investigated by FTIR and XPS, and the results indicated that the high CO2 capture capacity and the favorable selectivity of the as-prepared materials were mainly attributed to their special structure (i.e., surface area, functional groups, and the MgO NPs). This work would open up a new pathway to slow down global warming as well as resolve the pollution of waste biomass.

  14. Influence of electrolyte composition on the photovoltaic performance and stability of dye-sensitized solar cells with multiwalled carbon nanotube catalysts.

    Science.gov (United States)

    Seo, Seon Hee; Kim, Su Yeon; Koo, Bo-Kun; Cha, Seung-Il; Lee, Dong Yoon

    2010-06-15

    Efficient dye-sensitized solar cells (DSCs) were realized by using multiwalled carbon nanotubes (CNTs) as the counter-electrode catalyst. The catalytic layers were produced from an aqueous paste of mass-produced raw CNTs with carboxymethylcellulose polymer by low-temperature (70 degrees C) drying. We found that the highly disordered CNTs played the important role of increasing the fill factor of DSCs with electrolytes including large molecules and that the presence of Li(+) as the counter charges for I(3)(-)/I(-) redox couples reduced the chemical stability when using the CNT catalyst. Our experiments showed that by replacing the conventional Pt catalyst and Li(+)-based electrolyte with the proposed CNT catalyst and an electrolyte containing 1-butyl-3-methylimidazolium cations instead of Li(+), the energy conversion efficiency increased from 6.51% to 7.13%. This result suggests that highly defective CNT catalysts prepared by low-temperature drying are viable cost-effective alternatives for DSCs, as long as the electrolytes composition is optimized.

  15. Conceptual design and scaled experimental validation of an actively damped carbon tie rods support system for the stabilization of future particle collider superstructures.

    Science.gov (United States)

    Collette, C; Tshilumba, D; Fueyo-Rosa, L; Romanescu, I

    2013-02-01

    This paper presents a simple solution to increase the stability of the large superstructures supporting the final electromagnets of future linear particle collider. It consists of active carbon fiber tie rods, fixed at one end on the structure and at the other end to the detector through active tendons. In the first part of the paper, the solution has been tested on a finite element model of one half of the CLIC_ILD final focus structure. With a reasonable design, it is shown numerically that the compliance can be decreased by at least a factor 4, i.e., that the structure is 4 times more robust to technical noise at low frequency. Two additional features of the active rods are that they can also actively damp the structural resonances and realign the superstructures. The second part of the paper presents a successful experimental validation of the concept, applied to a scaled test bench, especially designed to contain the same modal characteristics as the full scale superstructure.

  16. Chemical reactions confined within carbon nanotubes.

    Science.gov (United States)

    Miners, Scott A; Rance, Graham A; Khlobystov, Andrei N

    2016-08-22

    In this critical review, we survey the wide range of chemical reactions that have been confined within carbon nanotubes, particularly emphasising how the pairwise interactions between the catalysts, reactants, transition states and products of a particular molecular transformation with the host nanotube can be used to control the yields and distributions of products of chemical reactions. We demonstrate that nanoscale confinement within carbon nanotubes enables the control of catalyst activity, morphology and stability, influences the local concentration of reactants and products thus affecting equilibria, rates and selectivity, pre-arranges the reactants for desired reactions and alters the relative stability of isomeric products. We critically evaluate the relative advantages and disadvantages of the confinement of chemical reactions inside carbon nanotubes from a chemical perspective and describe how further developments in the controlled synthesis of carbon nanotubes and the incorporation of multifunctionality are essential for the development of this ever-expanding field, ultimately leading to the effective control of the pathways of chemical reactions through the rational design of multi-functional carbon nanoreactors.

  17. 47 CFR 64.1401 - Expanded interconnection.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Expanded interconnection. 64.1401 Section 64...) MISCELLANEOUS RULES RELATING TO COMMON CARRIERS Expanded Interconnection § 64.1401 Expanded interconnection. (a... 69, subpart G of this chapter, shall offer expanded interconnection for interstate special...

  18. 氧化镁活性对碳化固化效果影响研究%Influence of MgO activity on stabilization efficiency of carbonated mixing method

    Institute of Scientific and Technical Information of China (English)

    刘松玉; 李晨

    2015-01-01

    The carbonated deep mixing method is an innovative CO2 consuming method for ground improvement, in which the MgO binder is firstly mixed with the soft soils and then CO2 is injected for carbonating in few hours. Using the carbonated mixing method, higher soil-MgO stabilized strength can be obtained in very short time. The influence of MgO activity on the stabilization efficiency and its mechanism were studied in this paper. A typical clay from Wuhan was used as the target soil and three different activities of MgO were selected as binders for laboratory tests. The results show that the carbonated degree with different active MgO binders can be predominantly completed in 3~6 hours and reaches stability after 24 hours. There are almost the same volume expansion of about 16% during carbonating process at all MgO binders. While the MgO activity has significant influences on the efficiency of the carbonated mixing method. With the higher activity MgO binder, the higher carbonated degree and more carbonated products forming denser texture are observed. Its unconfined compressive strength after carbonating 6 hours with higher activity MgO gets to the similar strength of 28 day-cured cement-stabilized soils. The final strength with higher activity MgO carbonated mixing soils can reach 2.5 MPa, while that with much lower activity MgO is only 0.5 MPa. The carbonated MgO-stabilized soils have considerable lower pH value (9.0~9.6) than the pH value (12) of the cement-stabilized soils.%碳化固化技术是近年来提出的一种低碳搅拌处理软弱土创新技术。该技术先采用MgO水泥与土进行搅拌,再利用CO2对之进行碳化,以达到快速提高强度的目的。针对MgO活性对碳化固化的影响规律进行了室内试验研究,并分析了其微观机理。结果表明:试样能在3~6 h内完成大部分碳化,碳化24 h后达到稳定,氧化镁活性对碳化固化效果有显著影响,具体表现为氧化镁活性越高,试样

  19. Expanding the Game Design Space

    DEFF Research Database (Denmark)

    Larsen, Lasse Juel; Majgaard, Gunver

    2016-01-01

    This article considers game design research in educational settings. Its focus is on how undergraduate students – particularly engineering students – learn computer game design. From observations conducted during our game design courses we have developed a model of expanded game design space....... It encapsulates the entire development process from the first ideas to the final game with emphasis on game design thinking. Our model of expanded game design space consists of four separate – yet interconnected – layers in the process of game development. The first layer addresses the importance of framing......, providing a clear game design assignment that involves the formulation of intended player experience and a description of game mechanics. The second layer focuses on game design thinking from six different aspects of game design chosen in relation to the framing of the game design assignment. The third...

  20. Effects of Land Use Practices on the Organic Carbon Content, Cation Exchange Capacity and Aggregate Stability of Soils in the Catchment Zones

    Directory of Open Access Journals (Sweden)

    Mosayeb Heshmati

    2011-01-01

    Full Text Available Problem statement: Land use practice leads to changes in the physico-chemical properties of soils, such as Soil Organic Carbon (SOC, Cation Exchange Capacity (CEC and Soil Aggregate Stability (SAS that cause soil erosion. Approach: Merek catchment, Iran suffers from land degradation due to poor land use practice. A study was carried out with the objectives: (i to determine soil nutrient status in different agro-ecological zones in Merek catchment; and (ii to evaluate the influence of land use practices on SOC, CEC and SAS. Results: It was found that soil texture was silty and clay, while soil reaction was alkaline (pH was 7.75. The respective amount of carbonates was 32 and 36% in the top-soil and sub-soil respectively, indicating high level of alkalinity in the soils of the study area. The mean SAS of the surface soil layer for agriculture, rangeland and forest was 53, 61 and 64%, respectively with its mean in the topsoil of agriculture is significantly lower (P≤0.05 than the other zones. SOC level in the agriculture, rangeland and forest were 1.35, 1.56, 2.14 % in the topsoil and 1.03, 1.33 and 1.45%, in the subsoil of the respective areas. The results of t-test and ANOVA analyses showed that SOC means are significantly different from each other within soil depth and among agro-ecological zones. The CEC in the agriculture, rangeland and forest areas were 25.8, 24.6 and 35.1 cmolckg-1 for the top-soil and 31.1, 26.8 and 26.9 cmolckg-1 in the sub-soil, respectively. All the above changes are due to the negative effects of agricultural activities. Conclusion: Improper tillage practice (up-down the slope, conversion of the rangeland and forest to rain-fed areas, crop residue burning, over grazing and forest clearance contribute to reduction in SOC and SAS in the Merek catchment, Iran.

  1. [Effect of Long-term Fertilizer Application on the Stability of Organic Carbon in Particle Size Fractions of a Paddy Soil in Zhejiang Province, China].

    Science.gov (United States)

    Mao, Xia-li; Lu, Kou-ping; Sun, Tao; Zhang, Xiao-kai; He, Li-zhi; Wang, Hai-long

    2015-05-01

    Effects of chemical fertilizers and organic manure on the soil organic carbon (SOC) content in particle size fractions of paddy soil were investigated in a 17-year long-term fertilization field experiment in Zhejiang Province, China. The inherent chemical composition of silt- and clay-associated SOC was evaluated with solid-state 13C-NMR spectroscopy. Compared to CK (no fertilizer treatment), NPKRS (NPK fertilizers plus rice straw) , NPKOM (NPK fertilizers plus organic manure) , NPK (NPK fertilizers) and OM (organic manure alone) treatments significantly (P fertilizers alone, combined application of organic amendments and NPK fertilizers facilitated the storage of newly sequestered SOC in silt- and clay-sized fractions, which could be more conducive to the stability of SOC. Based on 13C-NMR spectra, both silt and clay fractions were composed of Alkyl-C, O-alkyl-C, Aromatic-C and carbonyl-C. Changes in the relative proportion of different C species were observed between silt and clay fractions: the clay fraction had relatively more Alkyl-C, carbonyl-C and less O-alkyl-C, Aromatic-C than those in the silt fraction. This might be ascribed to the fact that the organic matter complexed with clay was dominated by microbial products, whereas the silt appeared to be rich in aromatic residues derived from plants. The spectra also showed that the relative proportion of different C species was modified by fertilization practices. In comparison with organic amendments alone, the relative proportion of Alkyl-C was decreased by 9.1%-11.9% and 13.7%-19.9% under combined application of organic amendments and chemical fertilizers, for silt and clay, respectively, and that of O-alkyl-C was increased by 2.9%-6.3% and 13.4%-22.1%, respectively. These results indicated that NPKOM and NPKRS treatments reduced the decomposition rate of SOC. The aromaticity, hydrophobicity and, hence, chemical recalcitrance of silt- and clay-associated SOC in the NPK fertilizer treatments were lower than

  2. Studies of an expanded trinucleotide repeat in transgenic mice

    Energy Technology Data Exchange (ETDEWEB)

    Bingham, P.; Wang, S.; Merry, D. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    1994-09-01

    Spinal and bulbar muscular atrophy (SBMA) is a progressive motor neuron disease caused by expansion of a trinucleotide repeat in the androgen receptor gene (AR{sup exp}). AR{sup exp} repeats expand further or contract in approximately 25% of transmissions. Analogous {open_quotes}dynamic mutations{close_quotes} have been reported in other expanded trinucleotide repeat disorders. We have been developing a mouse model of this disease using a transgenic approach. Expression of the SBMA AR was documented in transgenic mice with an inducible promoter. No phenotypic effects of transgene expression were observed. We have extended our previous results on stability of the expanded trinucleotide repeat in transgenic mice in two lines carrying AR{sup exp}. Tail DNA was amplified by PCR using primers spanning the repeat on 60 AR{sup exp} transgenic mice from four different transgenic lines. Migration of the PCR product through an acrylamide gel showed no change of the 45 CAG repeat length in any progeny. Similarly, PCR products from 23 normal repeat transgenics showed no change from the repeat length of the original construct. Unlike the disease allele in humans, the expanded repeat AR cDNA in transgenic mice showed no change in repeat length with transmission. The relative stability of CAG repeats seen in the transgenic mice may indicate either differences in the fidelity of replicative enzymes, or differences in error identification and repair between mice and humans. Integration site or structural properties of the transgene itself might also play a role.

  3. DNA-stabilized silver nanoclusters and carbon nanoparticles oxide: A sensitive platform for label-free fluorescence turn-on detection of HIV-DNA sequences.

    Science.gov (United States)

    Ye, Yu-Dan; Xia, Li; Xu, Dang-Dang; Xing, Xiao-Jing; Pang, Dai-Wen; Tang, Hong-Wu

    2016-11-15

    Based on the remarkable difference between the interactions of carbon nanoparticles (CNPs) oxide with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), and the fact that fluorescence of DNA-stabilized silver nanoclusters (AgNCs) can be quenched by CNPs oxide, DNA-functionalized AgNCs were applied as label-free fluorescence probes and a novel fluorescence resonance energy transfer (FRET) sensor was successfully constructed for the detection of human immunodeficiency virus (HIV) DNA sequences. CNPs oxide were prepared with the oxidation of candle soot, hence it is simple, time-saving and low-cost. The strategy of dual AgNCs probes was applied to improve the detection sensitivity by using dual- probe capturing the same target DNA in a sandwich mode and as the fluorescence donor, and using CNPs oxide as the acceptor. In the presence of target DNA, a dsDNA hybrid forms, leading to the desorption of the ssDNA-AgNCs probes from CNPs oxide, and the recovering of fluorescence of the AgNCs in a HIV-DNA concentration-dependent manner. The results show that HIV-DNA can be detected in the range of 1-50nM with a detection limit of 0.40nM in aqueous buffer. The method is simple, rapid and sensitive with no need of labeled fluorescent probes, and moreover, the design of fluorescent dual-probe makes full use of the excellent fluorescence property of AgNCs and further improves the detection sensitivity.

  4. Stability tables for opencast mining of coal and sedimentary deposits in inclined seams. Abacos de estabilidad para mineria de carbon y sedimentaria a cielo abierto con capas inclinadas

    Energy Technology Data Exchange (ETDEWEB)

    Ayala, F.J.; Granda, J.R.; Sarti, A.

    1985-01-01

    The six chapters of the book cover the following aspects of strata control in surface mining: design of opencast coal sites; parameters for the geomechanical design of opencast sites; methods for calculating slope stability; calculating the stability of spoil tips with a fractured cement base; calculation of stripping ratios; and stability tables.

  5. Carbon substituting for oxygen in silicates: A novel mechanism for carbon incorporation in the deep Earth

    Science.gov (United States)

    Armentrout, M. M.; Tavakoli, A.; Ionescu, E.; Mera, G.; Riedel, R.; Navrotsky, A.

    2013-12-01

    Traditionally, carbon in the deep Earth has been thought of in terms of either carbonate at high oxygen fugacities or graphite or diamond under more reducing conditions. However, material science studies of amorphous Si-O-C polymer derived ceramics have demonstrated that carbon can be accommodated as an anion substituting for oxygen in mixed silica tetrahedra. Furthermore these structures are energetically favorable relative to a mixture of crystalline silica, silicon carbide, and graphite by ten or more kJ/g.atom. Thermodynamic stability suggests that these nano-structured composites are a potentially important storage mechanism for carbon under moderately reducing conditions. Here we expand the scope of the previous work by examining the compositional effect of geologically relevant cations (calcium and magnesium) on the thermodynamic stability, nanostructure, and ability to accommodate carbon of these composites. Silicon oxy-carbides doped with magnesium, magnesium and calcium or undoped resisted crystallization at 1100 C under inert atmosphere. 29Si NMR of the samples shows a similar distribution of silicon between end-member and mixed sites (Table 1). Results are presented from studies utilizing NMR, high temperature solution calorimetry, and microprobe. Table 1. Percentages of Si species in each material as determined by 29Si NMR.

  6. Expanded retroauricular skin and fascial flap in congenital microtia reconstruction.

    Science.gov (United States)

    Zhang, Qingguo; Quan, Yuzhu; Su, Yuanda; Shi, Lei; Xie, Yangchun; Liu, Xinhai

    2010-04-01

    The aim of this article is to report the application of expanding retroauricular skin fascia flap, and autogenous costal cartilage for congenital microtia reconstruction. Microtia reconstruction was generally completed in 3 surgical stages. In the first surgical stage, a 50 or 80 mL kidney-shaped tissue expander was inserted subcutaneously in the retroauricular mastoid region. Inflation of saline volume increased up to 60 to 80 mL, and skin flap was expanded for 2 to 3 months postoperatively. In the second surgical stage, removal of tissue expander, formation of retroauricular skin flap, elevation of retroauricular fascia flap, and pedicles of both flaps in remnant ear side were performed. Costal cartilage was harvested from ipsilateral side chest to the ear for reconstruction. The 3D ear framework was sculpted with stabilization of structure, contour and erection. Simultaneously, intermediate full thickness skin graft of 4 x 8 cm was obtained from previous incision site from where costal cartilage was harvested. Cartilage ear framework was anchored between skin flap and fascia flap, and fixed it symmetrically to the opposite normal ear, inferior portion of the ear framework was wrapped by remnant ear lobule, expanded skin flap covered the anterior portion of the framework, fascial flap was draped to the posterior side of framework and helical rim, then fascial flap was surfaced by intermediate full thickness skin graft. Suction drain was inserted and coated between skin flap and framework, drain was removed fifth postoperative day. Tragus construction and conchal excavation with skin graft was performed in the third stage of microtia reconstruction. Between October 2000 and October 2007, 426 cases were diagnosed as unilateral microtia patients and 22 cases were bilateral microtia patients. Therefore, 448 microtia ears were treated with tissue expander and autogenous costal cartilage. In 262 cases, structure of the helix, tragus, conchal excavation

  7. Black holes in an expanding universe.

    Science.gov (United States)

    Gibbons, Gary W; Maeda, Kei-ichi

    2010-04-02

    An exact solution representing black holes in an expanding universe is found. The black holes are maximally charged and the universe is expanding with arbitrary equation of state (P = w rho with -1 black hole temperature.

  8. Collapsible truss structure is automatically expandable

    Science.gov (United States)

    1965-01-01

    Coil springs wound with maximum initial tension in a three-truss, closed loop structure form a collapsible truss structure. The truss automatically expands and provides excellent rigidity and close dimensional tolerance when expanded.

  9. Low-temperature formation and stabilization of rare allotropes of cyclooctasulfur (β-S8 and γ-S8) in the presence of organic carbon at a sulfur-rich glacial site in the Canadian High Arctic

    Science.gov (United States)

    Lau, Graham E.; Cosmidis, Julie; Grasby, Stephen E.; Trivedi, Christopher B.; Spear, John R.; Templeton, Alexis S.

    2017-03-01

    Large-scale deposits of elemental sulfur form annually on a glacier's surface at Borup Fiord Pass in the Canadian High Arctic. However, the mechanisms of mineralization and stabilization of elemental sulfur at this site are currently unknown. Here we show that X-ray diffraction (XRD) data for fresh sulfur precipitates collected from the surface of a melt pool over sulfide-rich ice reveal the presence of three sulfur allotropes, α-S8, β-S8, and γ-S8 (the three solid forms of cyclooctasulfur (S8)). The detection of the β-S8 allotrope of elemental sulfur is notable, since β-S8 typically only forms in high temperature environments (>96 °C). The γ-S8 allotrope is also rare in natural settings and has previously been implicated as a signature of microbial sulfur cycling. Using combustion and infrared spectroscopy approaches, organic carbon is also detected within the sample bearing the three allotropes of elemental sulfur. Electron microscopy and scanning transmission X-ray microscopy (STXM) at the C K-edge show that the sulfur precipitates are intimately associated with the organic carbon at the submicron scale. The occurrence of β-S8 and γ-S8 in this low-temperature setting indicates that there are unknown pathways for the formation and stabilization of these rare allotropes of elemental sulfur. In particular, we infer that the occurrence of these allotropes is related to their association with organic carbon. The formation of carbon-associated sulfur globules may not be a direct by-product of microbial activity; however, a potential role of direct or indirect microbial mediation in the formation and stabilization of β-S8 and γ-S8 remains to be assessed.

  10. Shear Acceleration in Expanding Flows

    CERN Document Server

    Rieger, F M

    2016-01-01

    Shear flows are naturally expected to occur in astrophysical environments and potential sites of continuous non-thermal Fermi-type particle acceleration. Here we investigate the efficiency of expanding relativistic outflows to facilitate the acceleration of energetic charged particles to higher energies. To this end, the gradual shear acceleration coefficient is derived based on an analytical treatment. The results are applied to the context of the relativistic jets of active galactic nuclei. The inferred acceleration timescale is investigated for a variety of conical flow profiles (i.e., power law, Gaussian, Fermi-Dirac) and compared to the relevant radiative and non-radiative loss timescales. The results exemplify that relativistic shear flows are capable of boosting cosmic-rays to extreme energies. Efficient electron acceleration, on the other hand, requires weak magnetic fields and may thus be accompanied by a delayed onset of particle energization and affect the overall jet appearance (e.g., core, ridge ...

  11. OCT Expanded Clinical Data Analysis

    Science.gov (United States)

    Van Baalen, Mary; Tafreshi, Ali; Patel, Nimesh; Young, Millennia; Mason, Sara; Otto, Christian; Samuels, Brian; Koslovsky, Matthew; Schaefer, Caroline; Taiym, Wafa; Wear, Mary; Gibson, Charles; Tarver, William

    2017-01-01

    Vision changes identified in long duration space fliers has led to a more comprehensive clinical monitoring protocol. Optical Coherence Tomography (OCT) was recently implemented on board the International Space Station in 2013. NASA is collaborating with Heidelberg Engineering to expand our current OCT data analysis capability by implementing a volumetric approach. Volumetric maps will be created by combining the circle scan, the disc block scan, and the radial scan. This assessment may provide additional information about the optic nerve and further characterize changes related microgravity exposure. We will discuss challenges with collection and analysis of OCT data, present the results of this reanalysis and outline the potential benefits and limitations of the additional data.

  12. A computational study on structure, stability and bonding in Noble Gas bound metal Nitrates, Sulfates and Carbonates (Metal = Cu, Ag, Au)

    Indian Academy of Sciences (India)

    MANAS GHARA; SUDIP PAN; JYOTIRMOY DEB; ANAND KUMAR; UTPAL SARKAR; PRATIM KUMAR CHATTARAJ

    2016-10-01

    A density functional theory based study is performed to investigate the noble gas (Ng = Ar-Rn) binding ability of nitrates, sulfates and carbonates of noble metal (M). Their ability to bind Ng atoms is assessed through bond dissociation energy and thermochemical parameters like dissociation enthalpy and dissociation free energy change corresponding to the dissociation of Ng bound compound producing Ngand the respective salt. The zero-point energy corrected dissociation energy values per Ng atom for the dissociation process producing Ng atom(s) and the corresponding salts range within 6.0–13.1 kcal/mol in NgCuNO₃, 3.1–9.8 kcal/mol in NgAgNO₃, 6.0–13.2 kcal/mol in NgCuSO₄, 3.2–10.1 kcal/mol in NgAgSO₄, 5.1–11.7 kcal/mol in Ng₂Cu₂SO₄, 2.5–8.6 kcal/mol in Ng₂Ag₂SO₂, 8.1–19.9 kcal/mol in Ng₂Au2SO₂, 5.7–12.4 kcal/mol in NgCuCO₃, 2.3–8.0 kcal/mol in Ng₂Ag₂CO₃ and 7.3–18.2 kcal/mol in Ng₂Au₂CO₃, with a gradual increase in moving from Ar to Rn. For a given type of system, the stability of Ng bound analogues follows the order as Au > Cu > Ag. All dissociation processes are endothermic in nature whereas they become endergonic as well in most of the cases of Kr-Rn bound analogues at 298 K. Natural population analysis along with the computation of Wiberg bond indices, and electron density analyses provide insights into the nature of the Ng-M bonds. The Ng-M bonds can be represented as partial covalent bonds as supported by the different electron density descriptors.

  13. Preparation and characterization of shape-stabilized PCM of capric-stearic acid/expanded perlite for latent heat storage wallboard%储能墙板用癸酸-硬脂酸/膨胀珍珠岩定型复合相变材料的制备与表征

    Institute of Scientific and Technical Information of China (English)

    魏艳玲; 徐玲玲; 李文浩

    2012-01-01

    采用真空吸附法将液态的癸酸-硬脂酸(CA-SA)二元共晶相变材料封装入多孔膨胀珍珠岩(EP)中,制备颗粒定型复合相变材料CA-SA/EP,并以石膏为无机基体研制储能墙板.采用傅里叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)、差示扫描量热仪(DSC)、多路温度测试仪和热扩散系数测试仪表征材料的性能.结果表明:以质量比4:1的CA-SA二元共晶相变材料在EP复合相变材料中的最佳吸附质量分数为75%,且在EP的多孔网络结构中均匀分布,复合过程中CA-SA二元共晶相变材料与EP间不发生化学反应,没有新产物形成 ;CA-SA/EP颗粒定型复合相变材料的相变温度和相变潜热分别为20.7℃和120.4 J/g,500次热循环后,颗粒定型复合相变材料的热性能基本不变.%Binary capric acid-stearic acid (CA-SA) eutectic mixture was absorbed into expanded perlite ( EP) by vacuum impregnation to prepare granular shape-stabilized phase change material ( PCM) ,then it was added into inorganic substrate gypsum to develop PCM wallboard. PCM was characterized by Fourier transform infrared spectrometer (FT-IR) , scanning electron microscope (SEM) , differential scanning cal-orimetry (DSC) ,multiway temperature detector, and heat diffusion coefficient detector. The results indicated that the optimum absorption ratio of binary CA-SA eutectic mixture with the mass ratio of 4: 1 in the EP composite PCM was 75% (mass fraction). The CA-SA eutectic mixture was uniformly distributed in the porous network of EP, and there was no chemical reaction between binary CA-SA eutectic mixture and EP because no substance was produced in the composite PCM. Phase change temperature and latent heat of CA-SA/EP composite were 20. 7 ℃ and 120. 4 J/g, respectively. The thermal properties of the shape-stabilized PCM were stable after 500 thermal cycles.

  14. Effects of pyrolysis temperature on carbon retention and stability of biochar%热解温度对生物质炭碳保留量及稳定性的影响

    Institute of Scientific and Technical Information of China (English)

    李飞跃; 汪建飞; 谢越; 李贺; 李孝良; 李粉茹

    2015-01-01

    以核桃壳为生物质炭生产原料,研究热解温度(200~700℃)对生物质炭产率、元素组成、表面官能团分布及其稳定性的影响,以期探明生物质炭基本性质随热解温度变化的规律,为全面了解生物质炭固碳减排效果提供理论参考。结果表明,生物质炭的C含量随温度升高而增加,H和O元素含量却随温度升高而降低。此外,生物质炭的H/C和O/C随着温度增加而减少。生物质炭的产率及碳保留量随着温度的升高而降低。红外光谱分析结果表明,经过热解核桃壳原材料分子中所含的-C-O和O-CH3基团消失,随着热解温度升高,生物质炭中的烷烃基团-CH逐渐减少,芳香化程度逐渐升高。500℃制备生物质炭的K2Cr2O7和KMnO4氧化碳损失量均最低,分别为10.4%和1.66%。相关分析表明,生物质炭的产率、碳保留量及稳定性与热解温度之间均具有显著相关关系。%Turning biomass wastes into biochar under the conditions of low temperature and limited oxygen has recently proven to be a promising approach for long-term carbon sequestration. However, the ultimate carbon sequestration efficiency of biochar depends not only on the feedstock type and production condition, but also on the environmental conditions of soil. In order to reveal the effects of pyrolysis temperature which is main parameter of biochar production condition on carbon retention and biochar stability, and provide more information for further improvement of carbon sequestration potential by turning biomass into biochar, the characteristics of biochar derived from walnut shell under lab condition were analyzed. During a typical slow pyrolysis process, the biochar was heated at a speed of approximately 20℃/minin a Muffle Furnace under limited oxygen and held at 200-700℃ for 2 h; then, biochar yield, elemental composition, functional groups distribution using Fourier transform infrared spectroscopy (FTIR

  15. Compact Radiometers Expand Climate Knowledge

    Science.gov (United States)

    2010-01-01

    To gain a better understanding of Earth's water, energy, and carbon cycles, NASA plans to embark on the Soil Moisture Active and Passive mission in 2015. To prepare, Goddard Space Flight Center provided Small Business Innovation Research (SBIR) funding to ProSensing Inc., of Amherst, Massachusetts, to develop a compact ultrastable radiometer for sea surface salinity and soil moisture mapping. ProSensing incorporated small, low-cost, high-performance elements into just a few circuit boards and now offers two lightweight radiometers commercially. Government research agencies, university research groups, and large corporations around the world are using the devices for mapping soil moisture, ocean salinity, and wind speed.

  16. Discovery of Uniformly Expanding Universe

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2012-01-01

    Full Text Available Saul Perlmutter and the Brian Schmidt – Adam Riess teams reported that their Friedmann-model GR-based analysis of their supernovae magnitude-redshift data re- vealed a new phenomenon of “dark energy” which, it is claimed, forms 73% of the energy / matter density of the present-epoch universe, and which is linked to the further claim of an accelerating expansion of the universe. In 2011 Perlmutter, Schmidt and Riess received the Nobel Prize in Physics “for the discovery of the accelerating ex- pansion of the Universe through observations of distant supernovae”. Here it is shown that (i a generic model-independent analysis of this data reveals a uniformly expanding universe, (ii their analysis actually used Newtonian gravity, and finally (iii the data, as well as the CMB fluctuation data, does not require “dark energy” nor “dark matter”, but instead reveals the phenomenon of a dynamical space, which is absent from the Friedmann model.

  17. Cat Scratch Disease: Expanded Spectrum

    Science.gov (United States)

    Aziz, Hassan A.; Plesec, Thomas P.; Sabella, Camille; Udayasankar, Unni K.; Singh, Arun D.

    2016-01-01

    Background To expand the spectrum of ophthalmic manifestations in cat scratch disease. Methods Case report. Results A 7-year-old male was referred for evaluation of his left optic disc after failing vision screening test at school. His visual acuity was 20/20 OD and light perception OS. Fundus examination showed a left optic disc lesion associated with an exudative retinal detachment and vitreous seeding. Ultrasonography revealed a 7 × 7.5 × 3.8 mm lesion with a possible 6.3 mm of retrolaminar extension into the substance of the optic nerve. Brain MRI did not show evidence of optic nerve involvement but revealed a 6-mm nodule of the pineal gland suggestive of a pineoblastoma. Enucleation was performed and histopathology revealed a suppurative granulomatous inflammation suggestive of Bartonella infection. Upon further questioning, the patient had recent exposure to kittens with areas of cat scratches along both of his arms. He was subsequently referred to and treated with a 2-week course of trimethoprim-sulfamethoxazole and rifampin by the pediatric infectious disease specialist. Repeat brain MRI showed interval total resolution of enlarged pineal gland. Conclusion: Optic nerve granulomas are a rare presentation of cat scratch disease and could potentially masquerade as retinoblastoma. PMID:27843905

  18. Expanding mTOR signaling

    Institute of Scientific and Technical Information of China (English)

    Qian Yang; Kun-Liang Guan

    2007-01-01

    The mammalian target of rapamycin (mTOR) has drawn much attention recently because of its essential role in cell growth control and its involvement in human tumorigenesis. Great endeavors have been made to elucidate the functions and regulation of mTOR in the past decade. The current prevailing view is that mTOR regulates many fundamental biological processes, such as cell growth and survival, by integrating both intracellular and extracellular signals, including growth factors, nutrients, energy levels, and cellular stress. The significance of mTOR has been highlighted most recently by the identification of mTOR-associated proteins. Amazingly, when bound to different proteins, mTOR forms distinctive complexes with very different physiological functions. These findings not only expand the roles that mTOR plays in cells but also further complicate the regulation network. Thus, it is now even more critical that we precisely understand the underlying molecular mechanisms in order to directly guide the development and usage of anti-cancer drugs targeting the mTOR signaling pathway. In this review, we will discuss different mTOR-associated proteins, the regulation of mTOR complexes, and the consequences of mTOR dysregulation under pathophysiological conditions.

  19. Preparation and Optical Properties of N-doped Carbon Dots as Light Stabilizer%N掺杂碳量子点光稳定剂的制备及光学性能

    Institute of Scientific and Technical Information of China (English)

    王子儒; 张光华; 郭明媛

    2016-01-01

    Novel carbon dots were successfully synthesized by hydrothermal reaction with citric acid as carbon source, and 4-amino-2,2,6,6-tetramethylpiperidine was used to react with the oxygen-containing groups on carbon dots surface. This method would optimize the properties of carbon dots. The modified carbon dots are better than the unmodified carbon dots on the characteristics of ultravi-olet absorption and blue fluorescence-emission. The modified carbon dots exist in average particle size of 3. 16 nm, and have high fluorescence quantum yield of 21. 2% besides good water solubility and light color. The results show that the novel carbon dots can be used as light stabilizer in paper-making with high yield pulp and improved initial brightness of paper by 3 ISO% -4 ISO%. With the introducing of the radical scavenger groups, the novel carbon dots can effectively improve the light resistance of paper by capturing free radicals formed under lights.%利用水热反应,以柠檬酸为碳源制备碳量子点,再以2,2,6,6-四甲基哌啶胺为修饰剂,使碳量子点表面的含氧基团与2,2,6,6-四甲基哌啶胺反应,实现了碳量子点的功能化。实验结果表明,修饰后的碳量子点紫外吸收和蓝色荧光发射特性明显优于未修饰的碳量子点。修饰后的碳量子点平均粒径为3.16 nm,荧光量子产率为21.2%,水溶性好,颜色浅,可作为高得率浆纸张的光稳定剂使用,并能提高纸张初始白度3ISO%~4ISO%。随着自由基捕获剂基团的引入,碳量子点能有效捕获纸张因光照而产生的活性自由基,提高了纸张的耐光性。

  20. Effects of dominant material properties on the stability and transport of TiO2 nanoparticles and carbon nanotubes in aquatic environment: From synthesis to fate

    Science.gov (United States)

    Recently, increasing studies have focused on the environment stability, transport, and fate of the anthropogenic nanomaterials in the environment, which contributes to the understanding of the potential risks when released. However, applying nanomaterials from different manufactu...

  1. Understanding the Effects of Surface Chemistry and Microstructure on the Activity and Stability of Pt Electrocatalysts on Non-Carbon Supports

    Energy Technology Data Exchange (ETDEWEB)

    Mustain, William [Univ. of Conneticut, Storrs, CT (United States)

    2015-02-12

    The objective of this project is to elucidate the effects of the chemical composition and microstructure of the electrocatalyst support on the activity, stability and utilization of supported Pt clusters.

  2. Carbon Residence Times in Pedogenic Carbonate Pools

    Science.gov (United States)

    Monger, H.; Feng, Y.; Karnjanapiboonwang, A.

    2013-12-01

    Soil carbonate is a huge pool of terrestrial carbon that contains at least 930 to 940 Pg C and has influx rates on the order of 1 to 12 g CaCO3/m2/yr. Such large mass to flux ratios yield long mean residence times for carbon (e.g., 85,000 years)--assuming steady state. Like other global carbon pools, the soil carbonate pool has smaller sub-pools with higher influx rates and shorter mean residence times. For example, pedogenic carbonate in coppice dunes known to have formed since 1858 and carbonate formed on lithic artifacts in soils at archaeology sites suggests mean residence times can be as short as 120 years--again assuming steady state. Harder to assess are efflux rates as CO2 emissions or bicarbonate leaching. Some Bowen-ratio studies have nevertheless found evidence for CO2 emissions resulting from carbonate dissolution, and other studies have found evidence for bicarbonate leaching based on dissolution pipes through calcic horizons using soil morphology studies. Since an understanding of mean residence times are prerequisite for a better understanding of soil carbonate in the global carbon cycle, especially in a scenario of an expanding Aridosphere, more influx and efflux measurements are needed to evaluate the possibility of carbon sequestration by soil carbonate in hyperarid, arid, semiarid, or subhumid soils.

  3. Preparation of Silicon-Carbon-Based Dots@Dopamine and Its Application in Intracellular Ag(+) Detection and Cell Imaging.

    Science.gov (United States)

    Jiang, Yuliang; Wang, Zhaoyin; Dai, Zhihui

    2016-02-17

    A novel nanocomposite, silicon-carbon-based dots@dopamine (Si-CDs@DA) was prepared using (3-aminopropyl) triethoxysilane, glycerol, and dopamine as raw materials via a rapid microwave-assisted irradiation. This type of Si-CDs@DA exhibited ultrabright fluorescence emission (quantum yield of 12.4%) and could response to Ag(+) selectively and sensitively. Moreover, the obtained Si-CDs@DA can be further applied in sensing intracellular Ag(+) and cell imaging, because of its photostability, salt stability, and low cytotoxicity. This study provides a simple and efficient approach for preparing novel Ag(+) fluorescent probes, which could expand the application of carbon nanomaterials in designing related biosensors.

  4. Metabolic Engineering for Expanding the Substrate Range of Yarrowia lipolytica.

    Science.gov (United States)

    Ledesma-Amaro, Rodrigo; Nicaud, Jean-Marc

    2016-10-01

    Economically viable biotechnology processes must be characterized by a favorable ratio between the production costs and the product market price. In the bioproduction of bulk chemicals, costs must be minimized so that the process is competitive relative to petroleum-based production. The substrate costs must thus be reduced by employing inexpensive carbon sources, such as industrial wastes. Unfortunately, the most convenient microorganisms for a bioconversion are typically unable to degrade such substrates. Fortunately, the discovery of new enzymes together with advances in synthetic biology has moved metabolic engineering forward, expanding substrate ranges. Here we review the latest advances made using the industrial yeast Yarrowia lipolytica, which can exploit various carbon sources to produce biofuels and chemicals.

  5. Metagenome of a Versatile Chemolithoautotroph from Expanding Oceanic Dead Zones

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, David A.; Zaikova, Elena; Howes, Charles L.; Song, Young; Wright, Jody; Tringe, Susannah G.; Tortell, Philippe D.; Hallam, Steven J.

    2009-07-15

    Oxygen minimum zones (OMZs), also known as oceanic"dead zones", are widespread oceanographic features currently expanding due to global warming and coastal eutrophication. Although inhospitable to metazoan life, OMZs support a thriving but cryptic microbiota whose combined metabolic activity is intimately connected to nutrient and trace gas cycling within the global ocean. Here we report time-resolved metagenomic analyses of a ubiquitous and abundant but uncultivated OMZ microbe (SUP05) closely related to chemoautotrophic gill symbionts of deep-sea clams and mussels. The SUP05 metagenome harbors a versatile repertoire of genes mediating autotrophic carbon assimilation, sulfur-oxidation and nitrate respiration responsive to a wide range of water column redox states. Thus, SUP05 plays integral roles in shaping nutrient and energy flow within oxygen-deficient oceanic waters via carbon sequestration, sulfide detoxification and biological nitrogen loss with important implications for marine productivity and atmospheric greenhouse control.

  6. Effects of enhancing soil organic carbon sequestration in the topsoil by fertilization on crop productivity and stability: Evidence from long-term experiments with wheat-maize cropping systems in China.

    Science.gov (United States)

    Zhang, Xubo; Sun, Nan; Wu, Lianhai; Xu, Minggang; Bingham, Ian J; Li, Zhongfang

    2016-08-15

    Although organic carbon sequestration in agricultural soils has been recommended as a 'win-win strategy' for mitigating climate change and ensuring food security, great uncertainty still remains in identifying the relationships between soil organic carbon (SOC) sequestration and crop productivity. Using data from 17 long-term experiments in China we determined the effects of fertilization strategies on SOC stocks at 0-20cm depth in the North, North East, North West and South. The impacts of changes in topsoil SOC stocks on the yield and yield stability of winter wheat (Triticum aestivum L.) and maize (Zea mays L.) were determined. Results showed that application of inorganic fertilizers (NPK) plus animal manure over 20-30years significantly increased SOC stocks to 20-cm depth by 32-87% whilst NPK plus wheat/maize straw application increased it by 26-38% compared to controls. The efficiency of SOC sequestration differed between regions with 7.4-13.1% of annual C input into the topsoil being retained as SOC over the study periods. In the northern regions, application of manure had little additional effect on yield compared to NPK over a wide range of topsoil SOC stocks (18->50MgCha(-1)). In the South, average yield from manure applied treatments was 2.5 times greater than that from NPK treatments. Moreover, the yield with NPK plus manure increased until SOC stocks (20-cm depth) increased to ~35MgCha(-1). In the northern regions, yield stability was not increased by application of NPK plus manure compared to NPK, whereas in the South there was a significant improvement. We conclude that manure application and straw incorporation could potentially lead to SOC sequestration in topsoil in China, but beneficial effects of this increase in SOC stocks to 20-cm depth on crop yield and yield stability may only be achieved in the South.

  7. Prótesis de cuerpo vertebral JR: dispositivo modular, anatómico y expandible, con función de jaula y placa diseñada ad hoc para estabilizar la columna después de corpectomía Prótese do corpo vertebral JR: dispositivo modular, anatômico e expansível, com função de jaula e placa desenhada ad hoc para estabilizar a coluna depois da corpectomia JR vertebral body prosthesis: a modular, anatomical and expandable device, with cage function and plate dual designed ad hoc for spine stabilization after corpectomy

    Directory of Open Access Journals (Sweden)

    Juan José Ramírez Jiménez

    2009-06-01

    função de jaula e placa separadamente, uma vez que o desenho da prótese permite aplicar força axial e fixação lateral ao mesmo tempo, por meio de um só implante. Os resultados da colocação do implante no paciente foram satisfatórios.INTRODUCTION: due to the unsatisfactory results obtained with posterior instrumentations in cases of vertebral tumors and to the economical limitations of our patients for acquiring the systems available in the market, a vertebral body prosthesis to stabilize the spine after corpectomy was designed. OBJECTIVE: to describe the structural and functional characteristics of the JR prosthesis, the biomechanical assays in cadaver and the surgical technique on the patient. METHODS: firstly, it was performed a detailed anatomical study of the vertebral bodies. A design of a modular, anatomical and expandable device was obtained. Its components once assembled make an implant with expandable cage and plate dual function. Afterwards, a biomechanical assay was performed in a cadaver and the device was implanted in a patient with vertebral body metastasis. RESULTS: the radiographs extracted from the cadaver after implant location did not show loss of fixation. When the cadaver was raised, flexion moments were generated laterally with levers 80 cm long; therefore, the prosthesis was demanded in its most vulnerable point with a force of approximately 588 N. With rotation, flexion and extensions forced, stability was preserved and no movement was observed. The device was implanted in a 50-year-old woman with metastatic thyroid cancer affecting L3. Pain improved in the postoperative immediate, as well as its motor function, which allowed her to walk with a stable and painless spine for seven years. No implant failure was observed. CONCLUSION: the dual cage function and plate integrated in a single device offers a mechanical advantage, compared with the cages and plates used separately, since the prosthesis design permits to apply a distraction

  8. Microbial biomass, microbial diversity, soil carbon storage, and stability after incubation of soil from grass-clover pastures of different age

    DEFF Research Database (Denmark)

    Müller-Stöver, Dorette Sophie; Hauggaard-Nielsen, Henrik; Eriksen, Jørgen

    2012-01-01

    A laboratory incubation study with clover grass pasture soils of seven different ages (0, 1, 2, 3, 4, 5, and 16 production years) was carried out to determine initial soil carbon (C) and nitrogen (N) stocks and potentials for greenhouse gas emissions (N2O and CO2). Compared with the soil from...

  9. Synthesis of carbon materials via the cold compression of aromatic molecules and carbon nanostructures

    Science.gov (United States)

    Fitzgibbons, Thomas C.

    Carbon's ability for catenation makes it a remarkable element and allows for many interesting and surprising properties and structures. Carbon can exist in one of its two thermodynamically stable bulk crystals, graphite or diamond, one of its several nanostructures: fullerene, nanotube, or graphene, or as an amorphous material with a mixed bonding pattern. Carbon also has an ability to bond heteroatoms such as hydrogen which can increase its properties and structures even further. Pressure has been shown to be able to drastically change the bonding in and structure of carbon based materials. In this dissertation I will present how pressure can be used to synthesize new amorphous hydrogenated carbons and how a battery of analytical techniques can be used to elicit the microstructure of the carbon networks. This microstructure can then be related back to the reaction conditions and more importantly the starting small molecule. This work has been expanded to looking for a molecular analogue to the cold compressed graphite system by investigating the high pressure stability and reactivity of 2-D polycyclic aromatic hydrocarbons. This work was followed by discovering the failure of Single Walled Carbon Nanotubes at high static pressures. When the tubes fail they transform into nano-graphitic polyhedra. It has been found that metallic tubes preferentially collapse, leaving the semiconducting tubes intact for the most part. Finally, the most influential work performed in my dissertation has been related to the kinetically controlled solid state reaction of molecular benzene to form diamond nanothreads. These nanothreads pack into hexagonal bundles without axial order. A combination of Raman spectroscopy, x-ray and neutron scattering, transmission electron microscopy, and first principles calculations were performed to confirm their existence. The three data chapters in this dissertation are enhanced by an introduction to carbon based materials and high pressure chemistry

  10. Mechanism of Fume Suppression and Performance on Asphalt of Expanded Graphite for Pavement under High Temperature Condition

    Institute of Scientific and Technical Information of China (English)

    HUANG Gang; HE Zhaoyi; HUANG Yangcheng; ZHOU Chao; YUAN Xiaoya

    2014-01-01

    Fume suppression mechanisms and the effect of expanded graphite on the performance of asphalt were studied by applying infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and comprehensive thermal analysis (TG, DSC). The experimental results confirm that asphalt which is mixed with expandable graphite will expand in the process of hot mix, and the expanded graphite layer will swell by the light component in the asphalt. The light component in the asphalt and PAHs adsorption on expanded graphite surface or part of the plug in the expanded graphite layer between plates made nucleation crystallization growth. And the Van der Waals force and the bonding of the lattice can effectively restrain the asphalt fume release. Meanwhile, the expanding agent with oxidative can spread into the asphalt, leading to asphalt oxygenated and plastic abate, while the ductility decreases. Expanded graphite, SBS modifier and environment- friendly plasticizers are used to composite modified asphalt. According to asphalt fume release experiment, normal test of asphalt performance, Brookfield viscosity test, RTFOT test and asphalt mixture tests (high temperature stability, low temperature stability, water stability), it has been proven that the modified asphalt’s performance is better than that of matrix asphalt and equivalent to that of SBS modified asphalt. Furthermore, it has good fume suppression effect.

  11. Ideal Stabilization

    CERN Document Server

    Nesterenko, Mikhail

    2009-01-01

    We define and explore the concept of ideal stabilization. The program is ideally stabilizing if its every state is legitimate. Ideal stabilization allows the specification designer to prescribe with arbitrary degree of precision not only the fault-free program behavior but also its recovery operation. Specifications may or may not mention all possible states. We identify approaches to designing ideal stabilization to both kinds of specifications. For the first kind, we state the necessary condition for an ideally stabilizing solution. On the basis of this condition we prove that there is no ideally stabilizing solution to the leader election problem. We illustrate the utility of the concept by providing examples of well-known programs and proving them ideally stabilizing. Specifically, we prove ideal stabilization of the conflict manager, the alternator, the propagation of information with feedback and the alternating bit protocol.

  12. Stability Analysis in a Model of 1,2-dichloroethane Biodegradation by Klebsiella Oxytoca va 8391Immobilized on Granulated Activated Carbon

    Science.gov (United States)

    Borisov, M.; Dimitrova, N.

    2011-11-01

    We consider an ecological model for biodegradation of toxic substances in aquatic and atmospheric biotic systems. The model, which is described by a nonlinear system of four ordinary differential equations, is known to be experimentally validated. We compute the equilibrium points of the model and study their asymptotic stability. The Maple package BifTools is used to calculate one- and two-parameter bifurcations of the equilibrium points.

  13. The correlation between carbon structures and electrochemical properties of sulfur/carbon composites for Li-S batteries

    Science.gov (United States)

    Du, Zhenzhen; Xu, Jin; Jin, Song; Shi, Yuchen; Guo, Chengkun; Kong, Xianghua; Zhu, Yanwu; Ji, Hengxing

    2017-02-01

    The structures of carbon materials greatly affect the electrochemical properties of sulfur/carbon composites for lithium-sulfur (Li-S) batteries. Understanding the effect of carbon structure factors on the electrochemical properties of sulfur/carbon composites helps in rational designing of the cathode material for optimized battery performance. We prepare reduced graphene oxide (RGO), cysteine-modified RGO (RGO-CYS), microwave-expanded graphite oxide (MEGO) and activated-MEGO (aMEGO) with specific surface areas (SSA) of 58-3010 m2 g-1, C/O atomic ratios of 2.41-10.81, pore sizes of 0.9-5.6 nm and pore volumes of 0.14-2.03 cm3 g-1. The electrochemical performance researches S/RGO-CYS > S/RGO > S/MEGO > S/aMEGO when it is listed in the order of their specific capacity, rate capability and cyclic life. And the S/RGO-CYS delivers a high reversible capacity of 455 mA h g-1 at 8 C. The excellent performance of S/RGO-CYS composite is ascribed to the sulfur-containing functional groups of the RGO-CYS, which helps the sulfur dispersion and stabilizes the dissoluble lithium polysulfides. Our results demonstrate that the surface chemistry of carbon materials plays a more important role than the SSA, pore size and pore volume for the electrochemical properties of sulfur/carbon composites for Li-S batteries.

  14. Confining caesium in expanded natural Perlite

    OpenAIRE

    Rehspringer, Jean Luc; Balencie, J.; Vilminot, Serge; Burger, Didier; Boos, Anne; Estournès, Claude

    2007-01-01

    International audience; We present the potential use of expanded perlite, a metastable amorphous hydrated aluminum silicate, as a permanent medium for the long-term confinement of caesium. A simple loading by mixing an aqueous caesium nitrate solution and expanded perlite at 300K followed by thermal annealing leads to 96% sintering. The formation of pollucite, CsAlSi2O6, a naturally occurring mineral phase, appears as the crystalline phase embedded in a glassy phase. Leaching tests on the res...

  15. Voltammetric Detection of Urea on an Ag-Modified Zeolite- Expanded Graphite-Epoxy Composite Electrode

    NARCIS (Netherlands)

    Manea, F.; Pop, A.; Radovan, C.; Malchev, P.G.; Bebeselea, A.; Burtica, G.; Picken, S.J.; Schoonman, J.

    2008-01-01

    In this paper, a modified expanded graphite composite electrode based on natural zeolitic volcanic tuff modified with silver (EG-Ag-Z-Epoxy) was developed. Cyclic voltammetry measurements revealed a reasonably fast electron transfer and a good stability of the electrode in 0.1 M NaOH supporting elec

  16. TiO2@Carbon Photocatalysts: The Effect of Carbon Thickness on Catalysis.

    Science.gov (United States)

    Zhang, Jianming; Vasei, Mitra; Sang, Yuanhua; Liu, Hong; Claverie, Jerome P

    2016-01-27

    Nanocomposites composed of TiO2 and carbon materials (C) are widely popular photocatalysts because they combine the advantages of TiO2 (good UV photocatalytic activity, low cost, and stability) to the enhanced charge carrier separation and lower charge transfer resistance brought by carbon. However, the presence of carbon can also be detrimental to the photocatalytic performance as it can block the passage of light and prevent the reactant from accessing the TiO2 surface. Here using a novel interfacial in situ polymer encapsulation-graphitization method, where a glucose-containing polymer was grown directly on the surface of the TiO2, we have prepared uniform TiO2@C core-shell structures. The thickness of the carbon shell can be precisely and easily tuned between 0.5 and 8 nm by simply programming the polymer growth on TiO2. The resulting core@shell TiO2@C nanostructures are not black and they possess the highest activity for the photodegradation of organic compounds when the carbon shell thickness is 1-2 nm, corresponding to ∼3-5 graphene layers. Photoluminescence and photocurrent generation tests further confirm the crucial contribution of the carbon shell on charge carrier separation and transport. This in situ polymeric encapsulation approach allows for the careful tuning of the thickness of graphite-like carbon, and it potentially constitutes a general and efficient route to prepare other oxide@C catalysts, which can therefore largely expand the applications of nanomaterials in catalysis.

  17. Facile synthesis of CdS/C core–shell nanospheres with ultrathin carbon layer for enhanced photocatalytic properties and stability

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing [Department of Chemistry, Zhejiang Normal University, Jinhua 321004 (China); Zhang, Fu [Department of Medical Materials and Rehabilitation Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009 (China); Zhao, Yu-Ling, E-mail: yulingzhao@zjnu.cn [Department of Chemistry, Zhejiang Normal University, Jinhua 321004 (China); Guo, Yan-Chuan [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Gong, Peijun [Department of Chemistry, Zhejiang Normal University, Jinhua 321004 (China); Li, Zheng-Quan, E-mail: zqli@zjnu.cn [Department of Chemistry, Zhejiang Normal University, Jinhua 321004 (China); Qian, Hai-Sheng, E-mail: shqian@hfut.edu.cn [Department of Medical Materials and Rehabilitation Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009 (China)

    2016-01-30

    Graphical abstract: Uniform CdS/C core–shell nanospheres with several nanometers in thickness for carbon shell have been synthesized successfully; which show enhanced photocatalytic activities than single-component counterparts (CdS nanospheres). - Highlights: • The CdS/C nanospheres have been synthesized by a facile hydrothermal method. • The CdS/C nanospheres showed enhanced photocatalytic properties and photostability. • The as-prepared CdS/C core-shell nanospheres show better biocompatibility. - Abstract: In this work, we described a facile one-pot hydrothermal process developed to synthesize CdS/C core–shell nanospheres successfully. The as-prepared CdS/C core–shell nanospheres are with 100 nm in diameter and the amorphous carbon shell is with several nanometers in thickness. The phase, morphology and structures of the samples were investigated by X-ray power diffraction (XRD) analyses, field-emission scanning electron microscopy (FESEM, JEOL-6700F) and transmission electron microscopy (TEM, JEOL 3010); respectively. The as-prepared CdS/C core–shell nanospheres showed enhanced photocatalytic properties and photostability compared to the single counterpart of CdS nanospheres owing to the efficiently separation of photogenerated electrons (e{sup −}) and holes (h{sup +}) derived from the photocatalyst. In addition, the as-prepared CdS/C core–shell nanospheres might find wide application in wastewater treatment, solar cells, lithium ion batteries, etc.

  18. Expanded Schools: Developing Mindsets to Support Academic Success. Research Brief

    Science.gov (United States)

    ExpandED Schools, 2014

    2014-01-01

    The national demonstration of ExpandED Schools, The After-School Corporation's (TASC) expanded learning model, was launched in 2011-12 in New York City, Baltimore, and New Orleans. The ExpandED Schools demonstration is being evaluated by Policy Studies Associates (PSA) and is rolling out at a time when there is heightened awareness among…

  19. Co-precipitation Synthesis and Thermal Stability of Zircon Encapsulated Carbon Black%共沉淀法制备硅酸锆包裹炭黑及其高温稳定性

    Institute of Scientific and Technical Information of China (English)

    彭诚; 张楚鑫; 吕明; 李智鸿; 吴建青

    2013-01-01

    以正硅酸乙酯和氧氯化锆为原料,采用溶胶共沉淀法制备了硅酸锆包裹炭黑复合粉体.利用XRD、SEM、色度计和粒度分析仪等手段对样品进行了表征.采用正交试验考察了前驱体pH值、煅烧温度、矿化剂种类和用量等工艺条件对复合粉体高温稳定性的影响.结果表明,矿化剂和煅烧温度是最重要的影响因素.最佳的工艺条件是前驱溶液pH为5、矿化剂为5wt%LiF、煅烧温度为1 150℃.该工艺条件下形成的球形镶嵌结构能够有效防止炭黑被氧化.获得的硅酸锆包裹炭黑粉体具有较好的高温稳定性,粒度分布符合陶瓷色料的要求.该粉体用于熔块釉中,1000℃烧成仍然具有较好的发色效果.%Zircon encapsulated carbon black powders were synthesized by a co-precipitation method using TEOS and zirconium oxychloride as starting materials.X-ray diffraction (XRD),scanning electronic microscope (SEM),colorimeter and laser grain size analyzer were used to investigate the phase structure,morphology,thermal stability and size distribution of the prepared composite powders,respectively.The effect of experimental conditions including the pH of the precursor solution,the calcination temperature,the type and amount of mineralizers on their thermal stability was studied by orthogonal test.The optimal conditions were accordingly determined as follows:precursor solution pH=5,calcination temperature 1150℃ and 5% LiF mineralizer.Under these conditions,zircon encapsulated carbon black with embedded structures can be obtained.The composite powder has high thermal stability and adequate size distribution,and thus it is a good candidate material for black ceramic pigment.When calcined at 1000℃ in the frit glaze,the powder shows considerable tilting strength.

  20. Carbon Farming as a Carbon Negative Technology

    Science.gov (United States)

    Anderson, C.; Laird, D.; Hayes, D. J.

    2015-12-01

    Carbon farms have a pivotal role in national and international efforts to mitigate and adapt to climate change. A carbon farm in its broadest sense is one that reduces greenhouse gas (GHG) emissions or captures and holds carbon in vegetation and soils. Their capacity to remove carbon from the air and store it safely and permanently, while providing additional human and ecosystem benefits, means they could contribute significantly to national efforts to stabilize or reduce GHGs. We examine carbon farms in the context of corn and soybean production agriculture. We illustrate, using Iowa data but with relevance across United States corn and soybean production, the potential for carbon farms to reduce human GHG emissions and sequester carbon permanently at a rate that has meaningful impact on global greenhouse gas concentration. Carbon has been viewed as a next generation cash crop in Iowa for over a decade. The carbon farm perspective, however, goes beyond carbon as cash crop to make carbon the center of an entire farm enterprise. The transformation is possible through slight adjustment crop practices mixed with advances in technology to sequester carbon through biochar. We examine carbon balance of Iowa agriculture given only the combination of slight reduction in fertilizer and sequestration by biochar. We find the following. Iowa carbon farms could turn Iowa agriculture into a carbon sink. The estimated range of GHG reduction by statewide implementation of carbon farms is 19.46 to 90.27 MMt CO2-equivalent (CO2-e), while the current agricultural CO2-e emission estimate is 35.38 MMt CO2-e. Iowa carbon farm GHG reduction would exceed Iowa GHG reduction by wind energy (8.7 MMt CO2-e) and could exceed combined reductions from wind energy and corn grain ethanol (10.7 MMt CO2-e; 19.4 MMt CO2-e combined). In fact, Iowa carbon farms alone could exceed GHG reduction from national corn grain ethanol production (39.6 MMt CO2-e). A carbon price accessible to agricultural

  1. Stability and flexibility of the message carried by semiochemical stimuli, as revealed by devaluation of carbon disulfide followed by social transmission of food preference.

    Science.gov (United States)

    Maier, Joost X; Blankenship, Meredith L; Barry, Nicholas C; Richards, Sarah E; Katz, Donald B

    2014-08-01

    Semiochemicals are volatile compounds that communicate specific meaning between individuals and elicit specific behavioral and/or physiological responses mediated by highly sensitive and highly specific olfactory pathways. Recent work suggests that semiochemicals can activate multiple olfactory pathways at once, but the degree to which parallel pathways activated by the same semiochemical interact and what the behavioral consequences of such interactions are remains a topic of debate. Here, we approached this question behaviorally, investigating whether rats could be trained to avoid carbon disulfide (CS₂; conditional stimulus) via taste-potentiated odor aversion, and asking whether any such learning would have an impact on rats' subsequent use of CS₂ as a semiochemical cue (i.e., in a socially transmitted food preference paradigm). The results show that CS₂-mediated food preference learning is unimpaired by aversions conditioned to CS₂, a result indicating that canonical and semiochemical pathways for the processing of CS₂ function in a largely independent manner.

  2. Thermal stability and long term hydrogen/deuterium release from soft to hard amorphous carbon layers analyzed using in-situ Raman spectroscopy. Comparison with Tore Supra deposits

    CERN Document Server

    Pardanaud, C; Giacometti, G; Mellet, N; Pégourié, B; Roubin, P

    2015-01-01

    The thermal stability of 200 nm thick plasma enhanced chemical vapor deposited a-C:H and a-C:D layers ranging from soft to hard layers has been studied and compared to that of deposits collected on the Tore Supra tokamak plasma facing components by means of in-situ Raman spectroscopy. Linear ramp heating and long term isotherms (from several minutes to 21 days) have been performed and correlations between spectrometric parameters have been found. The information obtained on the sp 2 clustering has been investigated by comparing the G band shift and the 514 nm photon absorption evolution due to the thermal treatment of the layer. The effects of isotopic substitution have also been investigated.

  3. Electrical Properties of Expanded Graphite Intercalation Compounds

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The intercalation compounds of CuCl2 were synthesized with expanded graphite, whose magnitude of the electrical conductivity is about 103S.cm-1. Their electrical conductivity is 3~6 times as high as that of the expanded graphite, and about 10 times as high as that of GIC made of the non-expanded graphite. The microanalysis results of chemical compounds by X-ray energy spectrum scanning of TEM testified that the atomic ratio of chloride and cupric is nonstoichoimetric. The multivalence and exchange of electrovalence of the cupric ion was confirmed by the XPS-ESCA. Vacancy of chlorine anion increases the concentration of charge carrier.The special stage structure, made of graphite and chloride, produces a weak chemical bond belt and provides a carrier space in the direction of GIC layer. These factors develop the electrical properties.

  4. Analog model for an expanding universe

    CERN Document Server

    Weinfurtner, S E C

    2004-01-01

    Over the last few years numerous papers concerning analog models for gravity have been published. It was shown that the dynamical equation of several systems (e.g. Bose-Einstein condensates with a sink or a vortex) have the same wave equation as light in a curved-space (e.g. black holes). In the last few months several papers were released which deal with simulations of the universe. In this article the de-Sitter universe will be compared with a freely expanding three-dimensional spherical Bose-Einstein condensate. Initially the condensate is in a harmonic trap, which suddenly will be switched off. At the same time a small perturbation will be injected in the center of the condensate cloud. The motion of the perturbation in the expanding condensate will be discussed, and after some transformations the similarity to an expanding universe will be shown.

  5. From carbon nanotubes to carbon atomic chains

    Science.gov (United States)

    Casillas García, Gilberto; Zhang, Weijia; José-Yacamán, Miguel

    2010-10-01

    Carbyne is a linear allotrope of carbon. It is formed by a linear arrangement of carbon atoms with sp-hybridization. We present a reliable and reproducible experiment to obtain these carbon atomic chains using few-layer-graphene (FLG) sheets and a HRTEM. First the FLG sheets were synthesized from worm-like exfoliated graphite and then drop-casted on a lacey-carbon copper grid. Once in the TEM, two holes are opened near each other in a FLG sheet by focusing the electron beam into a small spot. Due to the radiation, the carbon atoms rearrange themselves between the two holes and form carbon fibers. The beam is concentrated on the carbon fibers in order excite the atoms and induce a tension until multi wall carbon nanotube (MWCNT) is formed. As the radiation continues the MWCNT breaks down until there is only a single wall carbon nanotube (SWCNT). Then, when the SWCNT breaks, an atomic carbon chain is formed, lasts for several seconds under the radiation and finally breaks. This demonstrates the stability of this carbon structure.

  6. Bound systems in an expanding universe

    CERN Document Server

    Baker, G A

    2000-01-01

    The Schwarzchild solution insertion in an expanding universe, the so-called "Swiss cheese model," is shown to possess an extrinsic curvature miss-match. One consequence is that some trajectories are discontinuous functions of their initial conditions. An alternate metric is proposed which goes smoothly between the Schwarzchild exterior solution and the Friedmann-Lemaitre, expanding universe metric. It is further shown that the effects of the expansion on planetary motions in the solar system are too small to be currently observed for this alternate metric.

  7. Radiation damping in closed expanding universes

    Science.gov (United States)

    Bernui, Armando

    The dynamics of a coupled model (harmonic oscillator-relativistic scalar field) in Conformal Robertson-Walker (k = +1) spacetimes is investigated. The exact radiation-reaction equation of the source-including the retarded radiation terms due to the closed space geometry - is obtained and analyzed. A suitable family of Lyapunov functions is constructed to show that, if the spacetime expands monotonely, then the source's energy damps. A numerical simulation of this equation for expanding Universes, with and without Future Event Horizon, is performed.

  8. Wankel engines as steam expanders: design considerations

    Energy Technology Data Exchange (ETDEWEB)

    Badr, O.; Naik, S.; O' Callaghan, P.W.; Probert, S.D. (Cranfield Inst. of Tech., Bedford (GB). Dept. of Applied Energy)

    1991-01-01

    Rotary Wankel engines offer several advantages compared with turbines and other positive-displacement machines as the expansion devices in low-power-output Rankine-cycle systems. So a Wankel expander was selected as the most appropriate device for a steam Rankine-engine, operating principally as a mini combined heat-and-power unit, providing a mechanical output of 5-20 kW. A computer-aided-design technique for selecting the optimal geometry and location of the ports of the expander is described: the computer programs are available from the authors. Lubrication and possible material combinations are also discussed. (author).

  9. Graphene for Expandable Space Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Graphene's tightly bonded impermeable single atomic layer of carbon offers unrivalled potential for lightweight flexible gas barrier applications. Graphene has been...

  10. Decay of the Weyl curvature in expanding black hole cosmologies

    CERN Document Server

    Schlue, Volker

    2016-01-01

    This paper presents a partial proof of the non-linear stability of the expanding region of Schwarzschild de Sitter cosmologies. We show that under dynamically realistic assumptions the conformal Weyl curvature decays towards null infinity. Our assumptions are consistent with the expectation that a dynamical solution to Einstein's equations with positive cosmological constant does not converge globally to a member of the Kerr de Sitter family. In particular in this problem the geometry of null infinity is a priori unknown. One expects this result to form an essential part of a global existence proof for the cosmological region, which - along with the precise asymptotics of these solutions - is the subject of a subsequent paper.

  11. Stabilization and Economic Growth Workshop

    Science.gov (United States)

    2009-03-25

    Haiti Gangs One Street at a Time.” 8 “Consolidating Stability in Haiti,” International Crisis Group, Latin America /Caribbean Report, N°21 (18 July...Crisis Group. Latin America /Caribbean Briefing No. 12, Port-au-Prince/Brussels, 30 October 2006. 11 “Social Resilience and State Fragility in Haiti...and agribusiness investments in dairy and other food products, fish farming, and bakeries. These grants helped them to start or expand their

  12. Stability Functions

    CERN Document Server

    Burns, Daniel; Wang, Zuoqin

    2008-01-01

    In this article we discuss the role of stability functions in geometric invariant theory and apply stability function techniques to problems in toric geometry. In particular we show how one can use these techniques to recover results of Burns-Guillemin-Uribe and Shiffman-Tate-Zelditch on asymptotic properties of sections of holomorphic line bundles over toric varieties.

  13. 碳纤维/氰酸酯复合材料尺寸稳定性能%Stability of Carbon Fiber Reinforced Cyanate Ester Composite

    Institute of Scientific and Technical Information of China (English)

    诸静; 郝旭峰; 叶周军

    2013-01-01

    对碳纤维/氰酸酯复合材料的吸湿、空间放气、吸湿变形性能进行了研究,并与传统碳纤维/环氧复合材料的性能进行对比.研究表明:氰酸酯基复合材料的吸湿性能优于碳纤维/环氧树脂复合材料,且其各项空间环境性能均与环氧树脂基复合材料相当.%In this paper,moisture absorption,outgas capacity in vacuum and deformation after moisture absorption of carbon fiber reinforced cyanate ester composite were studied,and were compared with corresponding capacity of epoxy resin composites.Result show that the moisture absorption of cyanate ester composite is lower than epoxy resin composites,and capacity in simulated space environment is compatible with epoxy resin composites.

  14. Low temperature and cost-effective growth of vertically aligned carbon nanofibers using spin-coated polymer-stabilized palladium nanocatalysts

    Science.gov (United States)

    Saleem, Amin M.; Shafiee, Sareh; Krasia-Christoforou, Theodora; Savva, Ioanna; Göransson, Gert; Desmaris, Vincent; Enoksson, Peter

    2015-02-01

    We describe a fast and cost-effective process for the growth of carbon nanofibers (CNFs) at a temperature compatible with complementary metal oxide semiconductor technology, using highly stable polymer-Pd nanohybrid colloidal solutions of palladium catalyst nanoparticles (NPs). Two polymer-Pd nanohybrids, namely poly(lauryl methacrylate)-block-poly((2-acetoacetoxy)ethyl methacrylate)/Pd (LauMAx-b-AEMAy/Pd) and polyvinylpyrrolidone/Pd were prepared in organic solvents and spin-coated onto silicon substrates. Subsequently, vertically aligned CNFs were grown on these NPs by plasma enhanced chemical vapor deposition at different temperatures. The electrical properties of the grown CNFs were evaluated using an electrochemical method, commonly used for the characterization of supercapacitors. The results show that the polymer-Pd nanohybrid solutions offer the optimum size range of palladium catalyst NPs enabling the growth of CNFs at temperatures as low as 350 °C. Furthermore, the CNFs grown at such a low temperature are vertically aligned similar to the CNFs grown at 550 °C. Finally the capacitive behavior of these CNFs was similar to that of the CNFs grown at high temperature assuring the same electrical properties thus enabling their usage in different applications such as on-chip capacitors, interconnects, thermal heat sink and energy storage solutions.

  15. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    Science.gov (United States)

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M.; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M.

    2016-06-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.

  16. Expanded austenite, crystallography and residual stress

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

    2010-01-01

    compositions and (b) unravelling of the contributions of stress-depth and composition-depth profiles in expanded austenite layers are summarised and discussed. It is shown through simulation of line profiles that the combined effects of composition gradients, stress gradients and stacking fault gradients can...

  17. Expanded austenite; crystallography and residual stress

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

    2009-01-01

    The identity of expanded austenite as developing during low temperature nitriding and/or carburizing of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article recent results obtained with i) homogeneous samples of various uniform...

  18. Properties of extruded expandable breadfruit products

    Science.gov (United States)

    Dried breadfruit was extruded with a twin screw extruder to develop a value-added expanded fruit product. This research studied the effects of barrel temperature (120-160°C), moisture content (13-25%), feeding rate (13-25 kg/h) and screw speed (115-175rpm) on physicochemical properties (bulk densit...

  19. Expanding the applicability of Heallth Technology Assessments

    DEFF Research Database (Denmark)

    Draborg, Eva; Hansen, Helle Ploug

    2012-01-01

    The objective of the presentation is to expand the foundations of input into policy decision making relying on health technology assessments (HTA). HTAs are primarily based on systematic reviews (SR) and thereby mostly on randomized controlled trials (RCT). RCTs can be distinguished on a continuu...

  20. Expanding the collaboration between CERN and Pakistan

    CERN Multimedia

    2002-01-01

    Parvez Butt, chairman of the Pakistan Atomic Energy Commission, and CERN Director General, Luciano Maiani, signed a letter of intent last week to expand collaboration. Through an agreement which should be formalized within a few months, Pakistan would make a substantial contribution to the LHC and its detectors, coordinated by the Pakistani National Centre of Physics.

  1. Expanding Your Horizons Conference in Geneva

    CERN Multimedia

    Chromek-Burckhart, Doris

    2011-01-01

    CERN and its experiments participated in Expanding Your Horizons (EYH) in Science and Mathematics conference in Geneva on 12th November. EYH nurture girls' interest in science and math courses to encourage them to consider careers in science, technology, engineering, and math.

  2. Responsible implementation of expanded carrier screening

    Science.gov (United States)

    Henneman, Lidewij; Borry, Pascal; Chokoshvili, Davit; Cornel, Martina C; van El, Carla G; Forzano, Francesca; Hall, Alison; Howard, Heidi C; Janssens, Sandra; Kayserili, Hülya; Lakeman, Phillis; Lucassen, Anneke; Metcalfe, Sylvia A; Vidmar, Lovro; de Wert, Guido; Dondorp, Wybo J; Peterlin, Borut

    2016-01-01

    This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines. PMID:26980105

  3. Expanding CTE Opportunities through Blended Learning

    Science.gov (United States)

    McKinstry, Elizabeth

    2012-01-01

    The global economy, 21st century skills, knowledge society, college and career readiness, digital and project-based learning are all common terms to educators who are expanding their learning environments beyond the classroom to meet the needs of all students. It is common knowledge that the rapid technological advances of this century have…

  4. Expanding the Focus of Career Assessment.

    Science.gov (United States)

    Lock, Jared D.; Hogan, Robert

    2000-01-01

    Issues affecting career assessment include change in the focus and definition of career, emphasis on quality of work life, expansion of career paths, increased amount of career information available on the Internet, and questionable quality of online assessment. An expanded model of career assessment now includes technical fit, personal fit,…

  5. Responsible implementation of expanded carrier screening.

    Science.gov (United States)

    Henneman, Lidewij; Borry, Pascal; Chokoshvili, Davit; Cornel, Martina C; van El, Carla G; Forzano, Francesca; Hall, Alison; Howard, Heidi C; Janssens, Sandra; Kayserili, Hülya; Lakeman, Phillis; Lucassen, Anneke; Metcalfe, Sylvia A; Vidmar, Lovro; de Wert, Guido; Dondorp, Wybo J; Peterlin, Borut

    2016-06-01

    This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines.

  6. Heat expanded starch-based compositions.

    Science.gov (United States)

    Glenn, Gregory M; Klamczynski, Artur K; Holtman, Kevin M; Shey, Justin; Chiou, Bor-Sen; Berrios, Jose; Wood, Delilah; Orts, William J; Imam, Syed H

    2007-05-16

    A heat expansion process similar to that used for expanded bead polystyrene was used to expand starch-based compositions. Foam beads made by solvent extraction had the appearance of polystyrene beads but did not expand when heated due to an open-cell structure. Nonporous beads, pellets, or particles were made by extrusion or by drying and milling cooked starch slurries. The samples expanded into a low-density foam by heating 190-210 degrees C for more than 20 s at ambient pressures. Formulations containing starch (50-85%), sorbitol (5-15%), glycerol (4-12%), ethylene vinyl alcohol (EVAL, 5-15%), and water (10-20%) were studied. The bulk density was negatively correlated to sorbitol, glycerol, and water content. Increasing the EVAL content increased the bulk density, especially at concentrations higher than 15%. Poly(vinyl alcohol) (PVAL) increased the bulk density more than EVAL. The bulk density was lowest in samples made of wheat and potato starch as compared to corn starch. The expansion temperature for the starch pellets decreased more than 20 degrees C as the moisture content was increased from 10 to 25%. The addition of EVAL in the formulations decreased the equilibrium moisture content of the foam and reduced the water absorption during a 1 h soaking period.

  7. Exponentially Expanded Grid Network Approach (EEGNA) : An Efficient Way for the Simulation of Stiff Electrochemical Problems

    Institute of Scientific and Technical Information of China (English)

    邓兆祥; 林祥钦; 童中华

    2003-01-01

    The exponentially expanded space grid was incorporated into the network approach to overcome the problem of low simulation efficiency during the simulations of electrochemical problems with stiff kinetics or wide dlsperslon of diffusion coefficients, resulting in an effective electrochemical simulation method: exponentially expanded grid network approach (EEG-NA). The stability and accuracy of the EEGNA for the simulation of various electrode processes .coupled with different types of homogeneous reactions were investigated.

  8. Interactive Effects of Climate Change and Decomposer Communities on the Stabilization of Wood-Derived Carbon Pools: Catalyst for a New Study

    Energy Technology Data Exchange (ETDEWEB)

    Resh, Sigrid C. [Michigan Technological University

    2014-11-17

    Globally, forest soils store ~two-thirds as much carbon (C) as the atmosphere. Although wood makes up the majority of forest biomass, the importance of wood contributions to soil C pools is unknown. Even with recent advances in the mechanistic understanding of soil processes, integrative studies tracing C input pathways and biological fluxes within and from soils are lacking. Therefore, our research objectives were to assess the impact of different fungal decay pathways (i.e., white-rot versus brown-rot)—in interaction with wood quality, soil temperature, wood location (i.e., soil surface and buried in mineral soil), and soil texture—on the transformation of woody material into soil CO2 efflux, dissolved organic carbon (DOC), and soil C pools. The use of 13C-depleted woody biomass harvested from the Rhinelander, WI free-air carbon dioxide enrichment (Aspen-FACE) experiment affords the unique opportunity to distinguish the wood-derived C from other soil C fluxes and pools. We established 168 treatment plots across six field sites (three sand and three loam textured soil). Treatment plots consisted of full-factorial design with the following treatments: 1. Wood chips from elevated CO2, elevated CO2 + O3, or ambient atmosphere AspenFACE treatments; 2. Inoculated with white rot (Bjerkandera adusta) or brown rot (Gloeophyllum sepiarium) pure fungal cultures, or the original suite of endemic microbial community on the logs; and 3. Buried (15cm in soil as a proxy for coarse roots) or surface applied wood chips. We also created a warming treatment using open-topped, passive warming chambers on a subset of the above treatments. Control plots with no added wood (“no chip control”) were incorporated into the research design. Soils were sampled for initial δ13C values, CN concentrations, and bulk density. A subset of plots were instrumented with lysimeters for sampling soil water and temperature data loggers for measuring soil temperatures. To determine the early

  9. Interactive Effects of Climate Change and Decomposer Communities on the Stabilization of Wood-Derived Carbon Pools: Catalyst for a New Study

    Energy Technology Data Exchange (ETDEWEB)

    Resh, Sigrid C. [Michigan Technological Univ., Houghton, MI (United States)

    2014-11-17

    Globally, forest soils store ~two-thirds as much carbon (C) as the atmosphere. Although wood makes up the majority of forest biomass, the importance of wood contributions to soil C pools is unknown. Even with recent advances in the mechanistic understanding of soil processes, integrative studies tracing C input pathways and biological fluxes within and from soils are lacking. Therefore, our research objectives were to assess the impact of different fungal decay pathways (i.e., white-rot versus brown-rot)—in interaction with wood quality, soil temperature, wood location (i.e., soil surface and buried in mineral soil), and soil texture—on the transformation of woody material into soil CO2 efflux, dissolved organic carbon (DOC), and soil C pools. The use of 13C-depleted woody biomass harvested from the Rhinelander, WI free-air carbon dioxide enrichment (Aspen-FACE) experiment affords the unique opportunity to distinguish the wood-derived C from other soil C fluxes and pools. We established 168 treatment plots across six field sites (three sand and three loam textured soil). Treatment plots consisted of full-factorial design with the following treatments: 1. Wood chips from elevated CO2, elevated CO2 + O3, or ambient atmosphere AspenFACE treatments; 2. Inoculated with white rot (Bjerkandera adusta) or brown rot (Gloeophyllum sepiarium) pure fungal cultures, or the original suite of endemic microbial community on the logs; and 3. Buried (15cm in soil as a proxy for coarse roots) or surface applied wood chips. We also created a warming treatment using open-topped, passive warming chambers on a subset of the above treatments. Control plots with no added wood (“no chip control”) were incorporated into the research design. Soils were sampled for initial δ13C values, CN concentrations, and bulk density. A subset of plots were instrumented with lysimeters for sampling soil water and temperature data

  10. Ensuring Stability

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    "Stable"will be a key word for China’s economy in 2012.That’s the beat set at the annual Central Economic Work Conference held in Beijing on December 12-14,which reviewed this year’s development and mapped out plans for the next year.Policymakers at the conference decided to keep macroeconomic policies stable,seek a stable and relatively fast economic growth,stabilize consumer prices and maintain social stability in 2012.On the basis of stability,the government will transform the development model,deepen reform and improve people’s livelihood.

  11. 碳包裹软磁金属纳米粒子的绿色合成及热稳定性研究%"Green" Synthesis and Thermal Stability of Carbon-Coated Metallic Nanoparticles with Soft Magnetism

    Institute of Scientific and Technical Information of China (English)

    王鑫; 姬广斌; 张斌; 常晓峰

    2011-01-01

    本文报道了一种制备碳包裹软磁金属纳米粒子的绿色合成方法:将金属醋酸盐溶液与可溶性淀粉均匀混合,蒸发、烘干后在N2保护下热处理,得到金属纳米复合粒子(C@Ni,C@Co,C@Fe,C@CoNi,C@CoFe,C@FeNi).TEM结果表明金属粒子均匀分散在碳介质中,粒径为3~5 nm.样品在室温下具有良好的抗氧化性、热稳定性和软磁性能.%We present a route for the “green” synthesis of carbon-coated metallic nanoparticles with soft magnetism by using soluble starch, mentallic acetate as the raw materials.The final products can be obtained via evaporating the mixture of aqueous solutions then annealing under the nitrogen flow.X-ray diffraction (XRD) analysis showed the carbon-protected metallic nanoparticles (C@Ni, C@Co, C@Fe, C@CoNi, C@CoFe, C@FeNi) were successfully synthetized.Transmission electron microscopy (TEM) image indicated that the particles were well dispersed with the average particle diameter of 3~5 nm.The as-synthesized samples had good srability at room temperature in empty atmosphere, excellent stability and soft magnetic property too.

  12. Stabilizing Niger

    DEFF Research Database (Denmark)

    Hahonou, Eric Komlavi

    international intervention in Niger. Their main objective is to secure their own strategic, economic and political interests by strengthening the Nigerien authorities through direct intervention and capacity building activities. For western states reinforcing state security institutions and stabilizing elite...

  13. Expanding the product profile of a microbial alkane biosynthetic pathway.

    Science.gov (United States)

    Harger, Matthew; Zheng, Lei; Moon, Austin; Ager, Casey; An, Ju Hye; Choe, Chris; Lai, Yi-Ling; Mo, Benjamin; Zong, David; Smith, Matthew D; Egbert, Robert G; Mills, Jeremy H; Baker, David; Pultz, Ingrid Swanson; Siegel, Justin B

    2013-01-18

    Microbially produced alkanes are a new class of biofuels that closely match the chemical composition of petroleum-based fuels. Alkanes can be generated from the fatty acid biosynthetic pathway by the reduction of acyl-ACPs followed by decarbonylation of the resulting aldehydes. A current limitation of this pathway is the restricted product profile, which consists of n-alkanes of 13, 15, and 17 carbons in length. To expand the product profile, we incorporated a new part, FabH2 from Bacillus subtilis , an enzyme known to have a broader specificity profile for fatty acid initiation than the native FabH of Escherichia coli . When provided with the appropriate substrate, the addition of FabH2 resulted in an altered alkane product profile in which significant levels of n-alkanes of 14 and 16 carbons in length are produced. The production of even chain length alkanes represents initial steps toward the expansion of this recently discovered microbial alkane production pathway to synthesize complex fuels. This work was conceived and performed as part of the 2011 University of Washington international Genetically Engineered Machines (iGEM) project.

  14. Expanding advanced civilizations in the universe

    CERN Document Server

    Gros, C

    2005-01-01

    The 1950 lunch-table remark by Enrico Fermi `Where is everybody' has started intensive scientific and philosophical discussions about what we call nowadays the `Fermi paradox': If there had been ever a single advanced civilization in the cosmological history of our galaxy, dedicated to expansion, it would have had plenty of time to colonize the entire galaxy via exponential growth. No evidence of present or past alien visits to earth are known to us, leading to the standard conclusion that no advanced expanding civilization has ever existed in the milky-way \\cite{Webb}. This conclusion rest fundamentally on the ad-hoc assumption, that any alien civilizations dedicated to expansion at one time would remain dedicated to expansions forever. Considering our limited knowledge about alien civilizations we need however to relax this basic assumption. Here we show that a substantial and stable population of expanding advanced civilization might consequently exist in our galaxy.

  15. Parameter estimation for an expanding universe

    Directory of Open Access Journals (Sweden)

    Jieci Wang

    2015-03-01

    Full Text Available We study the parameter estimation for excitations of Dirac fields in the expanding Robertson–Walker universe. We employ quantum metrology techniques to demonstrate the possibility for high precision estimation for the volume rate of the expanding universe. We show that the optimal precision of the estimation depends sensitively on the dimensionless mass m˜ and dimensionless momentum k˜ of the Dirac particles. The optimal precision for the ratio estimation peaks at some finite dimensionless mass m˜ and momentum k˜. We find that the precision of the estimation can be improved by choosing the probe state as an eigenvector of the hamiltonian. This occurs because the largest quantum Fisher information is obtained by performing projective measurements implemented by the projectors onto the eigenvectors of specific probe states.

  16. Carbohydrate plasma expanders for passive tumor targeting

    DEFF Research Database (Denmark)

    Hoffmann, Stefan; Caysa, Henrike; Kuntsche, Judith

    2013-01-01

    The objective of this study was to investigate the suitability of carbohydrate plasma volume expanders as a novel polymer platform for tumor targeting. Many synthetic polymers have already been synthesized for targeted tumor therapy, but potential advantages of these carbohydrates include...... inexpensive synthesis, constant availability, a good safety profile, biodegradability and the long clinical use as plasma expanders. Three polymers have been tested for cytotoxicity and cytokine activation in cell cultures and conjugated with a near-infrared fluorescent dye: hydroxyethyl starches (HES 200 k......Da and HES 450 kDa) and dextran (DEX 500 kDa). Particle size and molecular weight distribution were determined by asymmetric flow field-flow fractionation (AF4). The biodistribution was investigated non-invasively in nude mice using multispectral optical imaging. The most promising polymer conjugate...

  17. Hubble, Hubble's law and the expanding universe

    OpenAIRE

    Bagla, J. S.

    2009-01-01

    Hubble's name is associated closely with the idea of an expanding universe as he discovered the relation between the recession velocity and distances of galaxies. Hubble also did a lot of pioneering work on the distribution of galaxies in the universe. In this article we take a look at Hubble's law and discuss how it relates with models of the universe. We also give a historical perspective of the discoveries that led to the Hubble's law.

  18. Inextendibility of expanding cosmological models with symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Dafermos, Mihalis [University of Cambridge, Department of Pure Mathematics and Mathematical Statistics, Wilberforce Road, Cambridge CB3 0WB (United Kingdom); Rendall, Alan D [Max Planck Institute for Gravitational Physics, Albert Einstein Institute, Am Muehlenberg 1, D-14476 Golm (Germany)

    2005-12-07

    A new criterion for inextendibility of expanding cosmological models with symmetry is presented. It is applied to derive a number of new results and to simplify the proofs of existing ones. In particular, it shows that the solutions of the Einstein-Vlasov system with T{sup 2} symmetry, including the vacuum solutions, are inextendible in the future. The technique introduced adds a qualitatively new element to the available tool-kit for studying strong cosmic censorship. (letter to the editor)

  19. Expander Graphs in Pure and Applied Mathematics

    OpenAIRE

    Lubotzky, Alexander

    2011-01-01

    Expander graphs are highly connected sparse finite graphs. They play an important role in computer science as basic building blocks for network constructions, error correcting codes, algorithms and more. In recent years they have started to play an increasing role also in pure mathematics: number theory, group theory, geometry and more. This expository article describes their constructions and various applications in pure and applied mathematics.

  20. GWDC Expands High-End Market Share

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ It is a decision of great significance for GWDC to expand high-end market share in order to realize its transformation of development strategy and improve its development quality. As an important step of GWDC to explore high-end market, Oman PDO Project marks the first time that the Chinese petroleum engineering service team cooperates with the transnational petroleum corporations ranking first three in the world.

  1. Cosmic strings in an expanding spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Stein-Schabes, J.A.; Burd, A.B.

    1988-03-15

    We study string solutions in an expanding Friedmann-Robertson-Walker (FRW) spacetime. The back reaction of the string on the spacetime has been ignored so that the background stays Friedmannian throughout the evolution. By numerically integrating the field equations in both radiation- and matter-dominated eras, we discover some new oscillatory solutions. The possible damping of these oscillations is discussed. For late times the solution becomes identical to the static one.

  2. Strings, Fivebranes and an Expanding Universe

    OpenAIRE

    2002-01-01

    It was recently shown that velocity-dependent forces between parallel fundamental strings moving apart in a $D-$dimensional spacetime implied an accelerating expanding universe in $D-1$-dimensional space-time. Exact solutions were obtained for the early time expansion in $D=5,6$. Here we show that this result also holds for fundamental strings in the background of a fivebrane, and argue that the feature of an accelerating universe would hold for more general $p$-brane-seeded models.

  3. Simultaneous determination of the isomers of Ponceau 4R and Amaranth using an expanded graphite paste electrode.

    Science.gov (United States)

    Zhang, Jing; Wang, Meiling; Shentu, Chao; Wang, Wenchang; Chen, Zhidong

    2014-10-01

    A sensitive and convenient electrochemical method was developed for the simultaneous determination of the isomers of Ponceau 4R and Amaranth by an expanded graphite paste electrode (EGPE). The EGPE was prepared by mixing EG with solid paraffin. Compared with flake graphite paste and carbon paste electrodes, the EGPE showed higher electrocatalytic activity towards the oxidization of Ponceau 4R and Amaranth. Under optimal experimental conditions, the EGPE exhibited wide linear responses to Ponceau 4R and Amaranth ranging from 6×10(-8) to 4×10(-6) mol/L and 8×10(-8) to 4×10(-6)mol/L, respectively, and the detection limits for Ponceau 4R and Amaranth were 2 and 36 nmol/L, respectively, at a signal-to-noise ratio of 3. The EGPE showed good reproducibility, stability and reusability. The proposed method was successfully applied in the detection of Ponceau 4R and Amaranth in grape juice samples.

  4. Measurements of an expanding surface flashover plasma

    Energy Technology Data Exchange (ETDEWEB)

    Harris, J. R., E-mail: john.harris@colostate.edu [Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States)

    2014-05-21

    A better understanding of vacuum surface flashover and the plasma produced by it is of importance for electron and ion sources, as well as advanced accelerators and other vacuum electronic devices. This article describes time-of-flight and biased-probe measurements made on the expanding plasma generated from a vacuum surface flashover discharge. The plasma expanded at velocities of 1.2–6.5 cm/μs, and had typical densities of 10{sup 10}–10{sup 12} cm{sup −3}. The expansion velocity of the plasma leading edge often exhibited a sharp increase at distances of about 50 mm from the discharge site. Comparison with biased-probe data suggests that, under most conditions, the plasma leading edge was dominated by negative ions, with the apparent increase in velocity being due to fast H{sup −} overtaking slower, heavier ions. In some cases, biased-probe data also showed abrupt discontinuities in the plasma energy distribution co-located with large changes in the intercepted plasma current, suggesting the presence of a shock in the leading edge of the expanding plasma.

  5. Optical cavity resonator in an expanding universe

    CERN Document Server

    Kopeikin, Sergei

    2014-01-01

    We study evolution of frequency of a standing electromagnetic (EM) wave in a resonant optical cavity placed to the expanding manifold described by the Robertson-Walker metric. One builds a local coordinate system in which spacetime is locally Minkowskian. However, due to the conformal nature of the Robertson-Walker metric the conventional transformation to the local inertial coordinates introduces ambiguity in the physical interpretation of the local time coordinate. Therefore, contrary to a common-sense expectation, a straightforward implementation of EEP alone does not allow us to decide whether atomic clocks ticks at the same rate as the clocks based on EM modes of a cavity. To resolve the ambiguity we analyzed the cavity rigidity and the oscillation of its EM modes in an expanding universe by employing the Maxwell equations. We found out that both the size of the cavity and the EM frequency experience an adiabatic drift in conformal coordinates as the universe expands. We set up the oscillation equation f...

  6. Lubricin in human breast tissue expander capsules.

    Science.gov (United States)

    Cheriyan, Thomas; Guo, Lifei; Orgill, Dennis P; Padera, Robert F; Schmid, Thomas M; Spector, Myron

    2012-10-01

    Capsular contraction is the most common complication of breast reconstruction surgery. While presence of the contractile protein alpha smooth muscle actin (α-SMA) is considered among the causes of capsular contraction, the exact etiology and pathophysiology is not fully understood. The objective of this study was to investigate the possible role of lubricin in capsular formation and contraction by determining the presence and distribution of the lubricating protein lubricin in human breast tissue expander capsules. Related aims were to evaluate select histopathologic features of the capsules, and the percentage of cells expressing α-SMA, which reflects the myofibroblast phenotype. Capsules from tissue expanders were obtained from eight patients. Lubricin, at the tissue-implant interface, in the extracellular matrix, and in cells, and α-SMA-containing cells were evaluated immunohistochemically. The notable finding was that lubricin was identified in all tissue expander capsules: as a discrete layer at the tissue-implant interface, extracellular, and intracellular. There was a greater amount of lubricin in the extracellular matrix in the intimal-subintimal zone when compared with the tissue away from the implant. Varying degrees of synovial metaplasia were seen at the tissue-implant interface. α-SMA-containing cells were also seen in all but one patient. The findings might help us better understand factors involved in capsule formation.

  7. Inverted porphyrins and expanded porphyrins: An overview

    Indian Academy of Sciences (India)

    S K Pushpan; S Venkatraman; V G Anand; J Sankar; H Rath; T K Chandrashekar

    2002-08-01

    Porphyrins and metallopophyrins have attracted the attention of chemists for the past 100 years or more owing to their widespread involvement in biology. More recently, synthetic porphyrins and porphyrin-like macrocycles have attracted the attention of researchers due to their diverse applications as sensitizers for photodynamic therapy, MRI contrasting agents, and complexing agents for larger metal ions and also for their anion binding abilities. The number of -electrons in the porphyrin ring can be increased either by increasing the number of conjugated double bonds between the pyrrole rings or by increasing the number of heterocyclic rings. Thus, 22 sapphyrins, 26 rubyrins, 30 heptaphyrins, 34 octaphyrins and higher cyclic polypyrrole analogues containing 40, 48, 64, 80 and 96 systems have recently been reported in the literature. These macrocycles show rich structural diversity where normal and different kinds of inverted structures have been identified. In this review, an attempt has been made to collect the literature of the inverted porphyrins and expanded porphyrins reported until December 2001. Since the meso aryl expanded porphyrins have tendency to form both inverted and non-inverted structures more emphasis has been given to meso aryl expanded porphyrins.

  8. Advanced oxidation (H₂O₂ and/or UV) of functionalized carbon nanotubes (CNT-OH and CNT-COOH) and its influence on the stabilization of CNTs in water and tannic acid solution.

    Science.gov (United States)

    Czech, Bożena; Oleszczuk, Patryk; Wiącek, Agnieszka

    2015-05-01

    The properties of carbon nanotubes (CNTs) functionalized with -OH and -COOH groups during simulated water treatment with H2O2 and/or UV were tested. There following properties of CNTs were investigated: specific surface area, elemental composition (CHN), dynamic light scattering, Raman spectroscopy, X-ray photoelectron spectroscopy and changes in the CNTs structure were observed using transmission electron microscopy. Treatment of CNTs with H2O2 and/or UV affected their properties. This effect, however, was different depending on the functionalization of CNTs and also on the factor used (UV and/or H2O2). H2O2 plays a key role as a factor modifying the surface of CNT-OHs, whereas the properties of CNT-COOHs were most affected by UV rays. A shortening of the nanotubes, exfoliation, the opening of their ends, and changes in the surface charge were observed as a result of the action of UV and/or H2O2. The changes in observed parameters may influence the stability of the aqueous suspensions of CNTs.

  9. ALD TiO2-Coated Flower-like MoS2 Nanosheets on Carbon Cloth as Sodium Ion Battery Anode with Enhanced Cycling Stability and Rate Capability.

    Science.gov (United States)

    Ren, Weina; Zhou, Weiwei; Zhang, Haifeng; Cheng, Chuanwei

    2017-01-11

    We report the fabrication of 3D flower-like MoS2 nanosheets arrays on carbon cloth as a binder-free anode for sodium ion battery. Ultrathin and conformal TiO2 layers are used to modify the surface of MoS2 by atomic layer deposition. The electrochemical performance measurements demonstrate that the ALD TiO2 layer can improve the cycling stability and rate capability of MoS2. The MoS2 nanosheets with 0.5-nm TiO2 coating electrode show the highest initial discharge capacity of 1392 mA h g(-1) at 200 mA g(-1), which is increased by 53% compared with that of bare MoS2. After 150 cycles, the capacity retention rate of the TiO2-coated MoS2 achieves 75.8% of its second cycle's capacity at 200 mA h g(-1) in contrast to that of 59% of pure MoS2. Furthermore, the mechanism behind the experimental results is revealed by ex situ scanning electron microscope (SEM), X-ray powder diffraction (XRD), and electrochemical impedance spectroscopy (EIS) characterizations, which confirms that the ultrathin TiO2 modifications can prevent the structural degradation and the formation of SEI film of MoS2 electrode.

  10. Stabilization of Branching Queueing Networks

    CERN Document Server

    Brázdil, Tomáš

    2011-01-01

    Queueing networks are gaining attraction for the performance analysis of parallel computer systems. A Jackson network is a set of interconnected servers, where the completion of a job at server i may result in the creation of a new job for server j. We propose to extend Jackson networks by "branching" and by "control" features. Both extensions are new and substantially expand the modelling power of Jackson networks. On the other hand, the extensions raise computational questions, particularly concerning the stability of the networks, i.e, the ergodicity of the underlying Markov chain. We show for our extended model that it is decidable in polynomial time if there exists a controller that achieves stability. Moreover, if such a controller exists, one can efficiently compute a static randomized controller which stabilizes the network in a very strong sense; in particular, all moments of the queue sizes are finite.

  11. Somatic instability of the expanded allele of IT-15 from patients with Huntington disease

    Energy Technology Data Exchange (ETDEWEB)

    Stine, O.C.; Pleasant, N.; Ross, C.A. [Johns Hopkins Univ., Baltimore, MD (United States)] [and others

    1994-09-01

    Huntington`s disease (HD) is an inherited neurodegenerative disorder caused by an expanded trinucleotide repeat in the gene IT-15. Although the expanded allele of IT-15 is unstable during gametogenesis, particularly, spermatogenesis, it is not clear if there is somatic stability. There are two reports of stability and one of instability. In order to test whether somatic instability occurs in the expansions found in HD, we have compared amplified genomic DNA isolated from either blood or distinct regions of autopsied brains of persons with Huntington disease. We find that somatic variation occurs in at least two ways. First, in cases with longer repeats (n > 47), the cerebellum often (8 of 9 cases) has a smaller number of repeats (2 to 10 less) than other tested regions of the brain. The larger the expanded allele, the larger the reduction in size of the repeat in the cerebellum (r=0.94, p<0.0001, df=12). Second, regardless of the repeat size, the number of amplification products from genomic DNA isolated from the cerebellum is smaller than that from genomic DNA from other forebrain regions such as the dorsal parietal cortex. As the length of the expanded allele increases, the number of amplification products increase in either tissue (r=0.86, p<0.001, df=12). Therefore our data demonstrates somatic instability especially for longer repeats.

  12. PARALLEL STABILIZATION

    Institute of Scientific and Technical Information of China (English)

    J.L.LIONS

    1999-01-01

    A new algorithm for the stabilization of (possibly turbulent, chaotic) distributed systems, governed by linear or non linear systems of equations is presented. The SPA (Stabilization Parallel Algorithm) is based on a systematic parallel decomposition of the problem (related to arbitrarily overlapping decomposition of domains) and on a penalty argument. SPA is presented here for the case of linear parabolic equations: with distrjbuted or boundary control. It extends to practically all linear and non linear evolution equations, as it will be presented in several other publications.

  13. Expanded mode lasers for telecommunications applications

    Science.gov (United States)

    Lealman, Ian F.

    This thesis describes the development of a long wavelength (1.55 μm) expanded mode semiconductor laser. The increased spot size of the laser improves both the coupling efficiency to cleaved fibre and fibre alignment tolerances and reduces packaging cost. In this type of device the strength of the waveguide is gradually reduced towards the front facet allowing the mode to adiabatically expand so that the laser mode is better matched in size to that of a cleaved fibre. This can be achieved by either reducing the refractive index of the guide or reducing the amount of material in the core. The structure chosen was a buried heterostructure laser that utilised a twin guide consisting of an upper higher refractive index guide (the active region of the laser) above a weak passive guide. The width of the active region was reduced along part of the device allowing the mode to expand into the weak underlying guide. The guide structure was optimised using a variable grid finite difference mode solver, and the taper length calculated by an approximation to Love's method. Detailed results are presented for the measured light-current characteristic, farfield and coupling loss to cleaved fibre. These coupling losses were compared to the calculated data thus allowing the waveguide design to be optimised. Several iterations in the design of the device were undertaken, with the aim of reducing the coupling loss to cleaved single mode fibre without significantly compromising the laser performance. The final device design had extremely low coupling losses as low as 1.2 dB to cleaved fibre. Finally, the positive impact this device had on passive alignment using a silicon motherboard is examined, and the application this technology to a range of other optoelectronic components is discussed.

  14. Expanding Slayer Statutes to Elder Abuse.

    Science.gov (United States)

    Piel, Jennifer

    2015-09-01

    Common law has a dictum that people must not benefit from their crimes. In years past, states have enacted slayer rules to prevent killers from inheriting from their victims. The specific criteria and applicability of slayer rules vary by jurisdiction. Recently, several states, including Washington, have expanded their slayer rules to disqualify persons from inheriting if they have been involved in abuse or financial exploitation of the deceased. Reviewed herein are the abuse disinheritance laws, the relationship of the laws to concepts of testamentary capacity and undue influence, and the relevance to forensic psychiatric evaluations.

  15. Sinopec Strives to Expand Domestic Market

    Institute of Scientific and Technical Information of China (English)

    Zhang Yan

    2001-01-01

    @@ China Petrochemical Corporation (Sinopec) strives to expand its domestic market share during the Tenth Five-Year Plan period (2001~2005). The assets of Sinopec totaled 536.3 billion yuan at the end of 2000 while the business income reached 375.4billion yuan. Sinopec produced 37.24 million tons of crude oil and 3.916 billion cubic meters of natural gas and processed 105.47million tons of crude and 2.165million tons of ethylene in 2000.

  16. Concurrent Manipulation of Expanded AVL Trees

    Institute of Scientific and Technical Information of China (English)

    章寅; 许卓群

    1998-01-01

    The concurrent manipulation of an expanded AVL tree(EAVL tree)s considered in this paper.The presented system can support any number of concurrent processes which perform searching,insertion and deletion on the tree.Simulation results indicate the high performance of the system.Elaborate techniques are used to achieve such a system unavailable based on any known algorithms.Methods developed in this paper may provide new insights into other problems in the area of concurrent search structure manipulation.

  17. Macroeconomic stability

    DEFF Research Database (Denmark)

    Jespersen, Jesper

    2004-01-01

    It is demonstrated that full employment and sustainable development not necessarily are conflicting goals. On the other hand macroeconomic stability cannot be obtained without a deliberate labour sharing policy and a shift in the composition of private consumption away from traditional material...

  18. The study of susceptibility to carbon tetrachloride and benzene in offspring of expanded simple tandem repeats mutation mice exposed to formaldehyde%甲醛致扩张性简单串联重复序列突变小鼠子代对四氯化碳和苯暴露易感性研究

    Institute of Scientific and Technical Information of China (English)

    王超; 刘云儒; 周印; 李爱萍; 周建伟

    2011-01-01

    为5.88‰±4.55‰,F10代为8.25‰±2.06‰;C组1000 mg/kg苯染毒组:F5代为7.50‰±6.99‰,F10代为10.67‰±1.16‰;H组500 mg/kg苯染毒组:F5代为7.88‰±3.09‰,F10代为9.20‰±1.30‰;H组1000 mg/kg苯染毒组:F5代为9.63‰±4.34‰,F10代为13.33‰±2.08‰)随苯剂量的增加而增加,与溶剂对照组(C组F5代为1.13‰±0.35‰,F10代为1.20‰±0.82‰;H组F5代为1.25‰±0.46‰,F10代为1.33‰±1.03‰)的差异均有统计学意义(P<0.05,P<0.01).结论 甲醛暴露引起的基因组ESTR突变可改变子代小鼠对CCl4和苯的易感性.ESTR突变可能是影响机体对化学物易感性的生物学标志,其分子机制有待进一步阐明.%Objective To investigate the susceptibility to carbon tetrachloride and benzene in offspring of expanded simple tandem repeats (ESTR) mutation mice exposed to formaldehyde (FA). Methods F5 and F10 offspring (200 mg/m3 ×2 hours) served as H group and ICR mice were used as control group(group C). The F5 and F10 offspring were exposed to 10 ml/kg carbon tetrachloride at the doses of 0.05%, 0.50% or 5.00% for 24 hours, respectively or 500 or 1000 mg/kg benzene for 24 hours, respectively by intraperitoneal injection. Serum alanine transaminase (ALT), aspartate transaminase (AST) and the hepatic superoxide dismutase (SOD) or malondialdehyde (MDA) were detected; also the hepatic pathological changes were observed under light microscope; the micronucleus in sternum bone marrow cells as the biomarker of benzene blood toxicity were measured. Results ALT and AST activities in group C of F5 mice exposed to 0.50% and 5.00% CCl4, ALT in groups C and H of F10 mice exposed to 0.05%, 0.50%, 5.00% CCl4, AST in groups C and H of F10 mice exposed to 0.50% and 5.00% CCl4 were significantly higher than those in controls, respectively (P<0.05); as compared to the control, hepatic SOD activities in group C of F5 and F10 mice exposed to 0.50% and 5.00% CCl4, in group H of F5 mice exposed to 0.50% and 5.00% CCl4, and

  19. Recuperative supercritical carbon dioxide cycle

    Science.gov (United States)

    Sonwane, Chandrashekhar; Sprouse, Kenneth M; Subbaraman, Ganesan; O'Connor, George M; Johnson, Gregory A

    2014-11-18

    A power plant includes a closed loop, supercritical carbon dioxide system (CLS-CO.sub.2 system). The CLS-CO.sub.2 system includes a turbine-generator and a high temperature recuperator (HTR) that is arranged to receive expanded carbon dioxide from the turbine-generator. The HTR includes a plurality of heat exchangers that define respective heat exchange areas. At least two of the heat exchangers have different heat exchange areas.

  20. Familiarity expands space and contracts time.

    Science.gov (United States)

    Jafarpour, Anna; Spiers, Hugo

    2017-01-01

    When humans draw maps, or make judgments about travel-time, their responses are rarely accurate and are often systematically distorted. Distortion effects on estimating time to arrival and the scale of sketch-maps reveal the nature of mental representation of time and space. Inspired by data from rodent entorhinal grid cells, we predicted that familiarity to an environment would distort representations of the space by expanding the size of it. We also hypothesized that travel-time estimation would be distorted in the same direction as space-size, if time and space rely on the same cognitive map. We asked international students, who had lived at a college in London for 9 months, to sketch a south-up map of their college district, estimate travel-time to destinations within the area, and mark their everyday walking routes. We found that while estimates for sketched space were expanded with familiarity, estimates of the time to travel through the space were contracted with familiarity. Thus, we found dissociable responses to familiarity in representations of time and space. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc.

  1. Historical Notes on the Expanding Universe

    Science.gov (United States)

    Way, Michael J.; Belenkyi, Ari; Nussbaumer, Harry; Peacock, John

    2014-01-01

    The article Measuring the Hubble constant by Mario Livio and Adam Riess (Physics Today, October 2013, page 41) reviewed studies of the expanding universe from the 1920s to the present. Although the history of the subject underwent considerable compression to fit the length of a magazine article, we think it may leave a misleading impression of some of the key steps to our current understanding. We therefore offer the following clarifications. Most significantly, papers by Arthur Eddington and by Willem de Sitter in 1930, who successfully promoted Georges Lematres 1927 article for the Scientific Society of Brussels, effected a paradigm shift in interpretation of extragalactic redshifts in 1930. Before then, the astronomical community was generally unaware of the existence of nonstatic cosmological solutions and did not broadly appreciate that redshifts could be thought of locally as Doppler shifts in an expanding matter distribution. Certainly, in 1929 Edwin Hubble referred only to the de Sitter solution of 1917. At the time, the relation between distance and redshift predicted in that model was generally seen purely as a manifestation of static spacetime curvature.

  2. Unintended Consequences of Expanding the Genetic Alphabet.

    Science.gov (United States)

    Pollum, Marvin; Ashwood, Brennan; Jockusch, Steffen; Lam, Minh; Crespo-Hernández, Carlos E

    2016-09-14

    The base pair d5SICS·dNaM was recently reported to incorporate and replicate in the DNA of a modified strain of Escherichia coli, thus making the world's first stable semisynthetic organism. This newly expanded genetic alphabet may allow organisms to store considerably more information in order to translate proteins with unprecedented enzymatic activities. Importantly, however, there is currently no knowledge of the photochemical properties of d5SICS or dNaM-properties that are central to the chemical integrity of cellular DNA. In this contribution, it is shown that excitation of d5SICS or dNaM with near-visible light leads to efficient trapping of population in the nucleoside's excited triplet state in high yield. Photoactivation of these long-lived, reactive states is shown to photosensitize cells, leading to the generation of reactive oxygen species and to a marked decrease in cell proliferation, thus warning scientists of the potential phototoxic side effects of expanding the genetic alphabet.

  3. Expanding ester biosynthesis in Escherichia coli.

    Science.gov (United States)

    Rodriguez, Gabriel M; Tashiro, Yohei; Atsumi, Shota

    2014-04-01

    To expand the capabilities of whole-cell biocatalysis, we have engineered Escherichia coli to produce various esters. The alcohol O-acyltransferase (ATF) class of enzyme uses acyl-CoA units for ester formation. The release of free CoA upon esterification with an alcohol provides the free energy to facilitate ester formation. The diversity of CoA molecules found in nature in combination with various alcohol biosynthetic pathways allows for the biosynthesis of a multitude of esters. Small to medium volatile esters have extensive applications in the flavor, fragrance, cosmetic, solvent, paint and coating industries. The present work enables the production of these compounds by designing several ester pathways in E. coli. The engineered pathways generated acetate esters of ethyl, propyl, isobutyl, 2-methyl-1-butyl, 3-methyl-1-butyl and 2-phenylethyl alcohols. In particular, we achieved high-level production of isobutyl acetate from glucose (17.2 g l(-1)). This strategy was expanded to realize pathways for tetradecyl acetate and several isobutyrate esters.

  4. "Phase freezeout" in isentropically expanding matter

    CERN Document Server

    Iosilevskiy, Igor

    2014-01-01

    Features of isentropic expansion of warm dense matter (WDM) created by intense energy fluxes (strong shock compression or instant isochoric heating by laser or heavy ions) are under discussion in situation when ($i$) -- thermodynamic trajectory of such expansion crosses binodal of liquid-gas phase transition, and ($ii$) -- expansion within the two-phase region is going along equilibrium branch (not metastable one) of the two-phase mixture isentrope. It is known in the plane case that because of break in the expansion isentrope at binodal point (in $P-V$ plane) i.e. jump of sound velocity in this point, there appears extended zone ("boiling layer") of uniformity in expanding material with constant thermodynamic and kinematic parameters. It corresponds just to the state on this binodal of boiling liquid. The point is that because of self-similarity of such expansion (in plane case) this boiling layer contains finite and fixed part of whole expanding material. This property makes it possible (at least formally) ...

  5. Nanotube Production Devices Expand Research Capabilities

    Science.gov (United States)

    2012-01-01

    In order for the Hubble Space Telescope to take incredible, never-seen-before shots of celestial bodies and then send them back to Earth, the spacecraft needs power. While in orbit, Hubble cannot plug into an electrical outlet or stop at a store for some batteries. One of the ways NASA supplies power aboard a spacecraft is by harnessing energy from the most powerful entity in the solar system: the Sun. Since the 1960s, photovoltaic technology, or technology that converts sunlight into electricity, has been instrumental in the exploration of space. To build upon existing photovoltaic technology, NASA s Glenn Research Center has worked on a variety of innovative designs and materials to incorporate into photovoltaic cells, the building blocks of solar power systems. One of these materials is the carbon nanotube - a tiny structure about 50,000 times finer than the average human hair, with notably high electrical and thermal conductivity and an extreme amount of mechanical strength. Such properties give carbon nanotubes great potential to enhance the reliability of power generation and storage devices in space and on Earth. Dennis J. Flood, the branch chief of the photovoltaic division at Glenn in the 1990s, was looking into using carbon nanotubes to improve the efficiency of solar cells when he ran into a major roadblock - high-quality carbon nanotubes were not readily available. To address this problem, one of the chemists in Flood s group came up with a process and system for growing them. A senior chemist at Glenn, Aloysius F. Hepp, devised an injection chemical vapor deposition process using a specific organometallic catalyst in a two-zone furnace. Hepp's group found the unique process produced high-quality carbon nanotubes with less than 5 percent metal impurity. In addition, the process was more efficient than existing techniques, as it eliminated pre-patterning of the substrate used for growing the nanotubes, a timely and cost-prohibitive step.

  6. The Role of Genetic Polymorphisms as Related to One-Carbon Metabolism, Vitamin B6, and Gene–Nutrient Interactions in Maintaining Genomic Stability and Cell Viability in Chinese Breast Cancer Patients

    Directory of Open Access Journals (Sweden)

    Xiayu Wu

    2016-06-01

    Full Text Available Folate-mediated one-carbon metabolism (FMOCM is linked to DNA synthesis, methylation, and cell proliferation. Vitamin B6 (B6 is a cofactor, and genetic polymorphisms of related key enzymes, such as serine hydroxymethyltransferase (SHMT, methionine synthase reductase (MTRR, and methionine synthase (MS, in FMOCM may govern the bioavailability of metabolites and play important roles in the maintenance of genomic stability and cell viability (GSACV. To evaluate the influences of B6, genetic polymorphisms of these enzymes, and gene–nutrient interactions on GSACV, we utilized the cytokinesis-block micronucleus assay (CBMN and PCR-restriction fragment length polymorphism (PCR-RFLP techniques in the lymphocytes from female breast cancer cases and controls. GSACV showed a significantly positive correlation with B6 concentration, and 48 nmol/L of B6 was the most suitable concentration for maintaining GSACV in vitro. The GSACV indexes showed significantly different sensitivity to B6 deficiency between cases and controls; the B6 effect on the GSACV variance contribution of each index was significantly higher than that of genetic polymorphisms and the sample state (tumor state. SHMT C1420T mutations may reduce breast cancer susceptibility, whereas MTRR A66G and MS A2756G mutations may increase breast cancer susceptibility. The role of SHMT, MS, and MTRR genotype polymorphisms in GSACV is reduced compared with that of B6. The results appear to suggest that the long-term lack of B6 under these conditions may increase genetic damage and cell injury and that individuals with various genotypes have different sensitivities to B6 deficiency. FMOCM metabolic enzyme gene polymorphism may be related to breast cancer susceptibility to a certain extent due to the effect of other factors such as stress, hormones, cancer therapies, psychological conditions, and diet. Adequate B6 intake may be good for maintaining genome health and preventing breast cancer.

  7. Hydrogen peroxide biosensor based on electrodeposition of zinc oxide nanoflowers onto carbon nanotubes film electrode

    Institute of Scientific and Technical Information of China (English)

    Hui Ping Bai; Xu Xiao Lu; Guang Ming Yang; Yun Hui Yang

    2008-01-01

    A new amperometric biosensor for hydrogen peroxide was developed based on adsorption of horseradish peroxidase at the glassy carbon electrode modified with zinc oxide nanoflowers produced by electrodeposition onto multi-walled carbon nanotubes (MWNTs) firm. The morphology of the MWNTs/nano-ZnO electrode has been investigated by scanning electron microscopy (SEM), and the electrochemical performance of the electrode has also been studied by amperometric method. The resulting electrode offered an excellent detection for hydrogen peroxide at -0.11 V with a linear response range of 9.9 × 10(-7) to 2.9 × 10(-3) mol/L with a correlation coefficient of 0.991, and response time <5 s. The biosensor displays rapid response and expanded linear response range, and excellent stability.

  8. Carbon Superatom Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Canning, A. [Cray Research, PSE, EPFL, 1015 Lausanne (Switzerland); Canning, A.; Galli, G. [Institut Romand de Recherche Numerique en Physique des Materiaux (IRRMA), IN-Ecublens, 1015 Lausanne (Switzerland); Kim, J. [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

    1997-06-01

    We report on quantum molecular dynamics simulations of C{sub 28} deposition on a semiconducting surface. Our results show that under certain deposition conditions C{sub 28} {close_quote}s act as building blocks on a nanometer scale to form a thin film of nearly defect-free molecules. The C{sub 28} {close_quote}s behave as carbon superatoms, with the majority of them being threefold or fourfold coordinated, similar to carbon atoms in amorphous systems. The microscopic structure of the deposited film supports recent suggestions about the stability of a new form of carbon, the hyperdiamond solid. {copyright} {ital 1997} {ital The American Physical Society}

  9. Optical cavity resonator in an expanding universe

    Science.gov (United States)

    Kopeikin, Sergei M.

    2015-02-01

    We study the cosmological evolution of frequency of a standing electromagnetic wave in a resonant optical cavity placed to the expanding manifold described by the Robertson-Walker metric. Because of the Einstein principle of equivalence (EEP), one can find a local coordinate system (a local freely falling frame), in which spacetime is locally Minkowskian. However, due to the conformal nature of the Robertson-Walker metric the conventional transformation to the local inertial coordinates introduces ambiguity in the physical interpretation of the local time coordinate, . Therefore, contrary to a common-sense expectation, a straightforward implementation of EEP alone does not allow us to unambiguously decide whether atomic clocks based on quantum transitions of atoms, ticks at the same rate as the clocks based on electromagnetic modes of a cavity. To resolve this ambiguity we have to analyse the cavity rigidity and the oscillation of its electromagnetic modes in an expanding universe by employing the full machinery of the Maxwell equations irrespectively of the underlying theory of gravity. We proceed in this way and found out that the size of the cavity and the electromagnetic frequency experience an adiabatic drift in conformal (unphysical) coordinates as the universe expands in accordance with the Hubble law. We set up the oscillation equation for the resonant electromagnetic modes, solve it by the WKB approximation, and reduce the coordinate-dependent quantities to their counterparts measured by a local observer who counts time with atomic clock. The solution shows that there is a perfect mutual cancellation of the adiabatic drift of cavity's frequency by space transformation to local coordinates and the time counted by the clocks based on electromagnetic modes of cavity has the same rate as that of atomic clocks. We conclude that if general relativity is correct and the local expansion of space is isotropic there should be no cosmological drift of frequency of a

  10. The Expanding Marketplace for Applied Geophysics

    Science.gov (United States)

    Carlson, N.; Sirles, P.

    2012-12-01

    While the image of geophysics for the proverbial "layman" often seems limited to volcanoes and earthquakes, and to the geoscientist this image enlarges to include oil or minerals exploration and whole earth studies, there has been a steady increase in the application of geophysics into the realm of "daily life", such as real estate deals, highway infrastructure, and flood protection. This expansion of applications can be attributed to the improved economics from advances in equipment and interpretation. Traditional geophysical methods that at one time often only fit within the budgets of oil, gas, and minerals exploration programs can now be economically applied to much smaller scale needs like contaminant mapping, landfill delineation, and levee investigations. A real-world, economic example of this expanding marketplace is our company, which began very small and was aimed almost exclusively at the minerals exploration market. Most of our growth has been in the last 10 years, when we have expanded to five offices and a staff with almost 40 geoscientist degrees (21 in geophysics); much of this growth has been in the non-oil, non-minerals arenas. While much of our work still includes minerals exploration, other projects this year include wind-farm foundation studies, cavity detection above underground nuclear tests, landfill studies, acid mine drainage problems, and leaks in evaporation ponds. A methodology example of this expanding market is the induced polarization (IP) survey, once primarily used for minerals exploration, particularly large porphyry copper deposits, but now efficient enough to also use in environmental studies. The IP method has been particularly useful in delineating and characterizing old, poorly documented landfills, and recent research suggests it may also be useful in monitoring the accelerated biodegradation processes used in some cases to rehabilitate the sites. Compared to temperature monitoring systems, IP may be more useful in providing

  11. Vibrational stability of graphene

    Directory of Open Access Journals (Sweden)

    Yangfan Hu

    2013-05-01

    Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.

  12. Yaglom law in the expanding solar wind

    CERN Document Server

    Gogoberidze, G; Carbone, V

    2013-01-01

    We study the Yaglom law, which relates the mixed third order structure function to the average dissipation rate of turbulence, in a uniformly expanding solar wind by using the two scales expansion model of magnetohydrodynamic (MHD) turbulence. We show that due to the expansion of the solar wind two new terms appear in the Yaglom law. The first term is related to the decay of the turbulent energy by nonlinear interactions, whereas the second term is related to the non-zero cross-correlation of the Els\\"asser fields. Using magnetic field and plasma data from WIND and Helios 2 spacecrafts, we show that at lower frequencies in the inertial range of MHD turbulence the new terms become comparable to Yaglom's third order mixed moment, and therefore they cannot be neglected in the evaluation of the energy cascade rate in the solar wind.

  13. Expanding Technological Frames Towards Mediated Collaboration

    DEFF Research Database (Denmark)

    Bjørn, Pernille; Scupola, Ada; Fitzgerald, Brian

    2006-01-01

    This paper provides an in-depth analysis of technological and social factors leading to the successful adoption of groupware in a virtual team in educational setting. Drawing on a theoretical framework based on the concept of technological frames, we conducted an action research study to analyze...... the chronological sequence of events leading to groupware adoption. We argue that groupware adoption can be conceptualized as a three-step process of expanding and aligning individual technological frames towards groupware: The first step comprises activities facilitating participants in articulation and evaluation...... of their work practices and use of technology. Finally the third step includes participants' commitment and practical enactment of groupware. One of the key findings is that in groupware adoption the alignment of the individual technological frames requires articulation and re-evaluation of experienced...

  14. Expanding forensic science through forensic intelligence.

    Science.gov (United States)

    Ribaux, Olivier; Talbot Wright, Benjamin

    2014-12-01

    Research and Development ('R&D') in forensic science currently focuses on innovative technologies improving the efficiency of existing forensic processes, from the detection of marks and traces at the scene, to their presentation in Court. R&D approached from this perspective provides no response to doubts raised by recent criminological studies, which question the effective contribution of forensic science to crime reduction, and to policing in general. Traces (i.e. forensic case data), as remnants of criminal activity are collected and used in various forms of crime monitoring and investigation. The aforementioned doubts therefore need to be addressed by expressing how information is conveyed by traces in these processes. Modelling from this standpoint expands the scope of forensic science and provides new R&D opportunities. Twelve propositions for R&D are stated in order to pave the way.

  15. Rubella Seroprevalence Before Expanded Vaccination Program

    Directory of Open Access Journals (Sweden)

    Kenan Sener

    2007-10-01

    Full Text Available Altough rubella is usually a mild childhood disease, but when it occurs early in pregnancy are severe. In this study, seroprevalence of rubella antibodies have been invastegated in various age groups especially chilbearing age’s women before Expanded Vaccination Programme. IgM and IgG antibodies against rubella were tested by ELISA kits. Seropositivity of rubella IgG was 89,5% in chlidbearing age’s women. In Turkey, the vaccine has been on the market since 1989 but rubella vaccination is currently included in the national immunization programme. Hence, our results are important for comparison of the seroprevalence rates after national vaccination program. [TAF Prev Med Bull 2007; 6(5.000: 371-374

  16. Rubella Seroprevalence Before Expanded Vaccination Program

    Directory of Open Access Journals (Sweden)

    Kenan Sener

    2007-10-01

    Full Text Available Altough rubella is usually a mild childhood disease, but when it occurs early in pregnancy are severe. In this study, seroprevalence of rubella antibodies have been invastegated in various age groups especially chilbearing age’s women before Expanded Vaccination Programme. IgM and IgG antibodies against rubella were tested by ELISA kits. Seropositivity of rubella IgG was 89,5% in chlidbearing age’s women. In Turkey, the vaccine has been on the market since 1989 but rubella vaccination is currently included in the national immunization programme. Hence, our results are important for comparison of the seroprevalence rates after national vaccination program. [TAF Prev Med Bull. 2007; 6(5: 371-374

  17. Particles formation in an expanding plasma

    Energy Technology Data Exchange (ETDEWEB)

    Lescoute, E.; Hallo, L.; Chimier, B.; Tikhonchuk, V.T.; Stenz, C. [Bordeaux-1 Univ., CELIA, CNRS-CEA, 33 - Talence (France); Hebert, D.; Chevalier, J.M.; Rullier, J.L.; Palmier, S. [CEA Centre d' Etudes Scientifiques et Techniques d' Aquitaine, 33 - Le Barp (France)

    2009-08-15

    Interaction of a laser beam with a target generates a high velocity expanding plasma plume, solid debris and liquid nano- and micro-particles. They are produced from plasma recombination and vapor condensation and can be deposited on optical elements located nearby the target. Two distinct kinds of particles were observed depending on the temperature achieved in the plasma plume: large micrometer-size fragments for temperatures lower than the critical temperature, and very small nanometer-size particles for higher temperatures. The paper presents experimental observations of fragments and nano-particles in plasma plumes and a comparison with models. A good agreement has been found for nano-particle sizes and distributions. This simple modeling can also be used for nuclei production in the nanosecond time scale. Our estimates show that particle size can be correlated to laser wavelength and fluences.

  18. Homogeneous cosmology with aggressively expanding civilizations

    CERN Document Server

    Olson, S Jay

    2014-01-01

    In the context of a homogeneous universe, we note that the appearance of aggressively expanding advanced life is geometrically similar to the process of nucleation and bubble growth in a first-order cosmological phase transition. We exploit this similarity to describe the dynamics of life saturating the universe on a cosmic scale, adapting the phase transition model to incorporate probability distributions of expansion and resource consumption strategies. Through a series of numerical solutions covering several orders of magnitude in the input assumption parameters, the resulting cosmological model is used to address basic questions related to the intergalactic spreading of life, dealing with issues such as timescales, observability, competition between strategies, and first-mover advantage. Finally, we examine physical effects on the universe itself, such as reheating and the backreaction on the evolution of the scale factor, if such life is able to control and convert a significant fraction of the available...

  19. Helical chirality induction of expanded porphyrin analogues

    Indian Academy of Sciences (India)

    Jun-Ichiro Setsune

    2012-11-01

    Expanded porphyrin analogues with unique figure-eight conformation were prepared by way of useful pyrrole intermediates such as bis(azafulvene)s and 2-borylpyrrole. Supramolecular chirogenesis of cyclooctapyrrole O1 with 32-cycloconjugation was successfully applied to determine absolute configuration of chiral carboxylic acids. Dinuclear CuII complex of cyclooctapyrrole O2 with interrupted -conjugation was resolved by HPLC into enantiomers and their helical handedness was determined by theoretical simulation of their CD spectral pattern. Enantioselective induction of helicity in the metal helicate formation in the presence of a chiral promoter was demonstrated by using ()-(+)-1-(1-phenyl)ethylamine that favoured , helicity. Dinuclear CoII complexes of cyclotetrapyrroletetrapyridine O3 were found to be substitution labile and pick up amino acid anions in water. Those amino acid complexes of O3Co2 were rendered to adopt a particular unidirectional helical conformation preferentially depending on the ligated amino acid anion.

  20. Trichorhinophalangeal syndrome II, expanding the clinical spectrum

    Directory of Open Access Journals (Sweden)

    Rabah M. Shawky

    2015-01-01

    Full Text Available We report a 4.5 year old Egyptian male child, fourth in the order of birth of healthy remote consanguineous parents. He has typical facial as well as skeletal features of Trichorhinophalangeal syndrome (TRPS II. The facial features included bilateral downward slanting palpebral fissures, bulbous nose, long filtrum, retromicrognathia, sparse hair in the scalp and thick eyebrows. The skeletal features included retarded bone age, cone shaped epiphyses of the phalanges and multiple exostoses. The patient has also growth retardation, moderate mental retardation and hyperlaxity of the right knee joint. However our patient has some features not reported in TRPS II patients. These included bilateral partial ptosis, long eye lashes, preauricular skin tag, short 2nd right finger, short metacarpals of both thumbs. So we have to expand the clinical spectrum. Karyotype demonstrated 46,XY,del 8(q23.3-q24.1.

  1. Expanding Greenland’s Glacial Record

    DEFF Research Database (Denmark)

    Bjørk, Anders Anker

    Mass loss from the Greenland Ice Sheet and adjecent glaciers and ice caps has accelerated within the last decades, and these changes are accurately observed using a variety of different data products. However, the observational era is relatively short offering little insight into past dynamics. O...... the entire 20th century show rapid and widespread responses to climate change. On a longer time-scale is the Holocene history of Helheim Glacier reconstructed using evidence of glacial presence accumulated in lake sediments....... On order to expand the glacial history of Greenland, this thesis explores physical and geological archives for evidence of the glaciers’ past response to climatic variations. Using aerial photographs, the dynamic history of the Greenland Ice Sheet is extended back to 1900 C.E. Glacier changes covering...

  2. Gravitational wave memory in an expanding universe

    Science.gov (United States)

    Tolish, Alexander; Wald, Robert

    2016-03-01

    We investigate the gravitational wave memory effect in an expanding FLRW spacetime. We find that if the gravitational field is decomposed into gauge-invariant scalar, vector, and tensor modes after the fashion of Bardeen, only the tensor mode gives rise to memory, and this memory can be calculated using the retarded Green's function associated with the tensor wave equation. If locally similar radiation source events occur on flat and FLRW backgrounds, we find that the resulting memories will differ only by a redshift factor, and we explore whether or not this factor depends on the expansion history of the FLRW universe. We compare our results to related work by Bieri, Garfinkle, and Yau.

  3. Expanding Policy Imagination in Political Economy

    DEFF Research Database (Denmark)

    Seabrooke, Leonard

    2006-01-01

    be implemented. Historical sociology provides a way to generate information about contextual constellations through two "tonics": intentional rationality and social mechanisms. With the assistance of these tonics, historical sociology widens political economy's policy imagination.......Much of the literature in political economy seeks to capture an essential insight into the evolution of political and economic systems to provide a foundation for policy advice. This article suggests that attempts to nut out the kernels of change often restrict rather than expand policy imagination...... capacity to see political, social, and economic changes that do not conform to conventional theories, as well as distorting our understanding of how the contemporary world works. What policymakers want, more than prediction or recitation of conventional theories, is context to understand how policy can...

  4. Henry Norris Russell and the Expanding Universe

    CERN Document Server

    DeVorkin, David H

    2013-01-01

    Henry Norris Russell, one of the most influential American astronomers of the first half of the 20th Century, had a special place in his heart for the Lowell Observatory. Although privately critical of the founder for his pronouncements about life on Mars and the superiority of the Mars Hill observing site, he always supported the Observatory in public and professional circles. He staunchly supported Tombaugh's detection of a planet as leading from Lowell's prediction, and always promoted V. M. Slipher's spectroscopic investigations of planetary and stellar phenomena. But how did he react to Slipher's puzzling detection of the extreme radial velocities of spiral nebulae starting in 1912, and how did he regard the extension and interpretation of those observations by Hubble and others in following decades? Here we describe the arc of Russell's reactions, dating from Slipher's first detection, as an indicator of how mainstream stellar astronomers reacted to the concept of an expanding universe.

  5. Carbon Carbon Composites: An Overview .

    Directory of Open Access Journals (Sweden)

    G. Rohini Devi

    1993-10-01

    Full Text Available Carbon carbon composites are a new class of engineering materials that are ceramic in nature but exhibit brittle to pseudoplastic behaviour. Carbon-carbon is a unique all-carbon composite with carbon fibre embeded in carbon matrix and is known as an inverse composite. Due to their excellent thermo-structural properties, carbon-carbon composites are used in specialised application like re-entry nose-tips, leading edges, rocket nozzles, and aircraft brake discs apart from several industrial and biomedical applications. The multidirectional carbon-carbon product technology is versatile and offers design flexibility. This paper describes the multidirectional preform and carbon-carbon process technology and research and development activities within the country. Carbon-carbon product experience at DRDL has also been discussed. Development of carbon-carbon brake discs process technology using the liquid impregnation process is described. Further the test results on material characterisation, thermal, mechanical and tribological properties are presented.

  6. Roots Air Management System with Integrated Expander

    Energy Technology Data Exchange (ETDEWEB)

    Stretch, Dale [Eaton Corporation, Menomonee Falls, WI (United States); Wright, Brad [Eaton Corporation, Menomonee Falls, WI (United States); Fortini, Matt [Eaton Corporation, Menomonee Falls, WI (United States); Fink, Neal [Ballard Power Systems, Burnaby, BC (Canada); Ramadan, Bassem [Kettering Univ., Flint, MI (United States); Eybergen, William [Eaton Corporation, Menomonee Falls, WI (United States)

    2016-07-06

    PEM fuel cells remain an emerging technology in the vehicle market with several cost and reliability challenges that must be overcome in order to increase market penetration and acceptance. The DOE has identified the lack of a cost effective, reliable, and efficient air supply system that meets the operational requirements of a pressurized PEM 80kW fuel cell as one of the major technological barriers that must be overcome. This project leveraged Roots positive displacement development advancements and demonstrated an efficient and low cost fuel cell air management system. Eaton built upon its P-Series Roots positive displacement design and shifted the peak efficiency making it ideal for use on an 80kW PEM stack. Advantages to this solution include: • Lower speed of the Roots device eliminates complex air bearings present on other systems. • Broad efficiency map of Roots based systems provides an overall higher drive cycle fuel economy. • Core Roots technology has been developed and validated for other transportation applications. Eaton modified their novel R340 Twin Vortices Series (TVS) Roots-type supercharger for this application. The TVS delivers more power and better fuel economy in a smaller package as compared to other supercharger technologies. By properly matching the helix angle with the rotor’s physical aspect ratio, the supercharger’s peak efficiency can be moved to the operating range where it is most beneficial for the application. The compressor was designed to meet the 90 g/s flow at a pressure ratio of 2.5, similar in design to the P-Series 340. A net shape plastic expander housing with integrated motor and compressor was developed to significantly reduce the cost of the system. This integrated design reduced part count by incorporating an overhung expander and motor rotors into the design such that only four bearings and two shafts were utilized.

  7. Correlations Between Structures of Expanded Graphite – Polymer Composites and Acoustic Emission Phenomena / Korelacje Pomiędzy Strukturą Kompozytów Grafit Ekspandowany-Polimer A Zjawiskami Emisji Akustycznej

    Directory of Open Access Journals (Sweden)

    Berdowska A.

    2015-12-01

    Full Text Available Compressed expanded graphite was applied as a base matrix to the preparation of microporous composites as products of impregnation, polymerization and carbonization of poly-furfuryl alcohol. During carbonization, the original polymeric structure is transformed into an amorphous turbostratic carbon structure with ultramicropores. The structure, porosity and many chemical and physical properties change after each stage of their technological treatment.

  8. 长期施肥下水稻土有机碳固持形态与特征%Characteristics of Organic Carbon Stabilization in Paddy Soil Under Long-term Different Fertilization

    Institute of Scientific and Technical Information of China (English)

    徐香茹; 蔡岸冬; 徐明岗; 汪景宽; 张文菊

    2015-01-01

    Understanding the mechanisms of soil organic carbon(SOC)stabilization would help improve soil carbon sequestration in paddy soil. In this paper, we obtained paddy soils from a 30 year experimental field under five different fertilization, including no fertilizer(con-trol), mineral nitrogen(N)-phosphorus(P)-potassium(K)fertilizers(NPK), 70%mineral N+30%organic N plus PK(NPKM7/3), 50%mineral N+50%organic N plus PK(NPKM5/5), and 30%mineral N+70%organic N plus PK(NPKM3/7). Organic N was provided from green manure and pig manure. The soils were subjected to separating unprotected, and physically, chemically, bio-chemically, physical-chemically, and physical-biochemically protected SOC fractions by a physical-chemical combined fractionation method. Except the unpro-tected light fraction and the occluded silt and clay-sized fraction, the mass proportion of all other SOC factions was significantly different be-tween the treatments. Compared with non-fertilization(CK)treatment, chemical fertilizers mixed with organic manure(NPKM7/3、NPKM5/5 and NPKM3/7)significantly increased the content of total SOC(19.1~25.0 g·kg-1), unprotected coarse particulate organic carbon(cPOM) (8.41~12.7 g·kg-1), and physically protected aggregate(μagg)organic carbon(6.41~6.62 g·kg-1)in red paddy soil(P﹤0.05). There were no significant differences for the chemically, biochemically, physical-chemically and physical-biochemically protected fractions between the five treatments. These results indicated that the unprotected cPOM and the physically protected μagg fractions were the most sensitive ones in long-term fertilization. There was a linear positive correlation between total SOC and tcPOM, physically protected μagg, and oc-cluded POM inside theμagg(iPOM)fraction(P﹤0.05), and their response efficiency to total SOC accumulation(the slope of the regression) was 0.5, 0.12, and 0.12 respectively. However, the response efficiency of non-hydrolysis clay and physic-chemically protected silt

  9. Carbon nanotubes for supercapacitor.

    Science.gov (United States)

    Pan, Hui; Li, Jianyi; Feng, Yuanping

    2010-01-05

    As an electrical energy storage device, supercapacitor finds attractive applications in consumer electronic products and alternative power source due to its higher energy density, fast discharge/charge time, low level of heating, safety, long-term operation stability, and no disposable parts. This work reviews the recent development of supercapacitor based on carbon nanotubes (CNTs) and their composites. The purpose is to give a comprehensive understanding of the advantages and disadvantages of carbon nanotubes-related supercapacitor materials and to find ways for the improvement in the performance of supercapacitor. We first discussed the effects of physical and chemical properties of pure carbon nanotubes, including size, purity, defect, shape, functionalization, and annealing, on the supercapacitance. The composites, including CNTs/oxide and CNTs/polymer, were further discussed to enhance the supercapacitance and keep the stability of the supercapacitor by optimally engineering the composition, particle size, and coverage.

  10. Carbon Nanotubes for Supercapacitor

    Directory of Open Access Journals (Sweden)

    Li Jianyi

    2010-01-01

    Full Text Available Abstract As an electrical energy storage device, supercapacitor finds attractive applications in consumer electronic products and alternative power source due to its higher energy density, fast discharge/charge time, low level of heating, safety, long-term operation stability, and no disposable parts. This work reviews the recent development of supercapacitor based on carbon nanotubes (CNTs and their composites. The purpose is to give a comprehensive understanding of the advantages and disadvantages of carbon nanotubes-related supercapacitor materials and to find ways for the improvement in the performance of supercapacitor. We first discussed the effects of physical and chemical properties of pure carbon nanotubes, including size, purity, defect, shape, functionalization, and annealing, on the supercapacitance. The composites, including CNTs/oxide and CNTs/polymer, were further discussed to enhance the supercapacitance and keep the stability of the supercapacitor by optimally engineering the composition, particle size, and coverage.

  11. High surface area silicon carbide-coated carbon aerogel

    Science.gov (United States)

    Worsley, Marcus A; Kuntz, Joshua D; Baumann, Theodore F; Satcher, Jr, Joe H

    2014-01-14

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust. Carbon aerogels can be coated with sol-gel silica and the silica can be converted to silicone carbide, improved the thermal stability of the carbon aerogel.

  12. Carbon sp chains in graphene nanoholes

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Ferri, Nicola; Onida, Giovanni

    2012-01-01

    Nowadays sp carbon chains terminated by graphene or graphitic-like carbon are synthesized routinely in several nanotech labs. We propose an ab initio study of such carbon-only materials, by computing their structure and stability, as well as their electronic, vibrational and magnetic properties. We...

  13. Neutralizing Carbonic Acid in Deep Carbonate Strata below the North Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Daniel P. Schrag

    2006-07-14

    Our research is aimed at investigating several technical issues associated with carbon dioxide sequestration in calcium carbonate sediments below the sea floor through laboratory experiments and chemical transport modeling. Our goal is to evaluate the basic feasibility of this approach, including an assessment of optimal depths, sediment types, and other issues related to site selection. The results of our modeling efforts were published this past summer in the Proceedings of the National Academy of Sciences. We are expanding on that work through a variety of laboratory and modeling efforts. In the laboratories at Columbia and at Harvard, we are studying the flow of liquid carbon dioxide and carbon dioxide-water mixtures through calcium carbonate sediments to better understand the geomechanical and structural stability of the sediments during and after injection. We are currently preparing the results of these findings for publication. In addition, we are investigating the kinetics of calcium carbonate dissolution in the presence of CO{sub 2}-water fluids, which is a critical feature of the system as it allows for increased permeability during injection. We are also investigating the possibility of carbon dioxide hydrate formation in the pore fluid, which might complicate the injection procedure by reducing sediment permeability but might also provide an upper seal in the sediment-pore fluid system, preventing release of CO{sub 2} into the deep ocean, particularly if depth and temperature at the injection point rule out immediate hydrate formation. This is done by injecting liquid CO{sub 2} into various types of porous media, and then monitoring the changes in permeability. Finally, we are performing an economic analysis to estimate costs of drilling and gas injection, site monitoring as well as the availability of potential disposal sites with particular emphasis on those sites that are within the 200-mile economic zone of the United States. We present some

  14. 2D quasi-ordered nitrogen-enriched porous carbon nanohybrids for high energy density supercapacitors

    Science.gov (United States)

    Kan, Kan; Wang, Lei; Yu, Peng; Jiang, Baojiang; Shi, Keying; Fu, Honggang

    2016-05-01

    Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are intercalated into the interlayers of the expanded EG with the assistance of a vacuum. Subsequently, the intercalated aniline monomers could assemble on the interlayer surface of the expanded EG, accompanied by the in situ polymerization from aniline monomers to polyaniline. Meanwhile, the expanded EG could be exfoliated to graphite nanosheets. By subsequent pyrolysis and activation processes, the QNPC nanohybrids could be prepared. As supercapacitor electrodes, a typical QNPC12-700 sample derived from the precursor containing an EG content of 12%, with a high level of nitrogen doping of 5.22 at%, offers a high specific capacitance of 305.7 F g-1 (1 A g-1), excellent rate-capability and long-term stability. Notably, an extremely high energy density of 95.7 Wh kg-1 at a power density of 449.7 W kg-1 in an ionic liquid electrolyte can be achieved. The unique structural features and moderate heteroatom doping of the QNPC nanohybrids combines electrochemical double layer and faradaic capacitance contributions, which make these nanohybrids ideal candidates as electrode materials for high-performance energy storage devices.Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are

  15. Expandable Purge Chambers Would Protect Cryogenic Fittings

    Science.gov (United States)

    Townsend, Ivan I., III

    2004-01-01

    Expandable ice-prevention and cleanliness-preservation (EIP-CP) chambers have been proposed to prevent the accumulation of ice or airborne particles on quick-disconnect (QD) fittings, or on ducts or tubes that contain cryogenic fluids. In the original application for which the EIP-CP chambers were conceived, there is a requirement to be able to disconnect and reconnect the QD fittings in rapid succession. If ice were to form on the fittings by condensation and freezing of airborne water vapor on the cold fitting surfaces, the ice could interfere with proper mating of the fittings, making it necessary to wait an unacceptably long time for the ice to thaw before attempting reconnection. By keeping water vapor away from the cold fitting surfaces, the EIP-CP chambers would prevent accumulation of ice, preserving the ability to reconnect as soon as required. Basically, the role of an EIP-CP chamber would be to serve as an enclosure for a flow of dry nitrogen gas that would keep ambient air away from QD cryogenic fittings. An EIP-CP chamber would be an inflatable device made of a fabriclike material. The chamber would be attached to an umbilical plate holding a cryogenic QD fitting.

  16. Helical Screw Expander Evaluation Project. Final report

    Energy Technology Data Exchange (ETDEWEB)

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing operation on two-phase geothermal fluids. The Project also produced a computer-equipped data system, an instrumentation and control van, and a 1000-kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  17. Expanded polylactide bead foaming - A new technology

    Science.gov (United States)

    Nofar, M.; Ameli, A.; Park, C. B.

    2015-05-01

    Bead foaming technology with double crystal melting peak structure has been recognized as a promising method to produce low-density foams with complex geometries. During the molding stage of the bead foams, the double peak structure generates a strong bead-to-bead sintering and maintains the overall foam structure. During recent years, polylactide (PLA) bead foaming has been of the great interest of researchers due to its origin from renewable resources and biodegradability. However, due to the PLA's low melt strength and slow crystallization kinetics, the attempts have been limited to the manufacturing methods used for expanded polystyrene. In this study, for the first time, we developed microcellular PLA bead foams with double crystal melting peak structure. Microcellular PLA bead foams were produced with expansion ratios and average cell sizes ranging from 3 to 30-times and 350 nm to 15 µm, respectively. The generated high melting temperature crystals during the saturation significantly affected the expansion ratio and cell density of the PLA bead foams by enhancing the PLA's poor melt strength and promoting heterogeneous cell nucleation around the crystals.

  18. The expanding fireball of Nova Delphini 2013.

    Science.gov (United States)

    Schaefer, G H; ten Brummelaar, T; Gies, D R; Farrington, C D; Kloppenborg, B; Chesneau, O; Monnier, J D; Ridgway, S T; Scott, N; Tallon-Bosc, I; McAlister, H A; Boyajian, T; Maestro, V; Mourard, D; Meilland, A; Nardetto, N; Stee, P; Sturmann, J; Vargas, N; Baron, F; Ireland, M; Baines, E K; Che, X; Jones, J; Richardson, N D; Roettenbacher, R M; Sturmann, L; Turner, N H; Tuthill, P; van Belle, G; von Braun, K; Zavala, R T; Banerjee, D P K; Ashok, N M; Joshi, V; Becker, J; Muirhead, P S

    2014-11-13

    A classical nova occurs when material accreting onto the surface of a white dwarf in a close binary system ignites in a thermonuclear runaway. Complex structures observed in the ejecta at late stages could result from interactions with the companion during the common-envelope phase. Alternatively, the explosion could be intrinsically bipolar, resulting from a localized ignition on the surface of the white dwarf or as a consequence of rotational distortion. Studying the structure of novae during the earliest phases is challenging because of the high spatial resolution needed to measure their small sizes. Here we report near-infrared interferometric measurements of the angular size of Nova Delphini 2013, starting one day after the explosion and continuing with extensive time coverage during the first 43 days. Changes in the apparent expansion rate can be explained by an explosion model consisting of an optically thick core surrounded by a diffuse envelope. The optical depth of the ejected material changes as it expands. We detect an ellipticity in the light distribution, suggesting a prolate or bipolar structure that develops as early as the second day. Combining the angular expansion rate with radial velocity measurements, we derive a geometric distance to the nova of 4.54 ± 0.59 kiloparsecs from the Sun.

  19. Expanding the role of internal facility assessments

    Energy Technology Data Exchange (ETDEWEB)

    Kolpa, R.L.; Levenson, J.B. [Argonne National Lab., IL (United States); Weaver, M.A. [Headquarters Air Force Materiel Command, Wright-Patterson AFB, OH (United States)

    1996-05-01

    The US Air Force (USAF) Environmental Compliance Assessment and Management Program (ECAMP) is an effective and comprehensive system to evaluate environmental compliance at individual USAF installations. The ECAMP assessment is typically performed by a team of experts from the installation`s Major Command (MAJCOM) Headquarters, and is often augmented with technical contractor support. As directed by Air Force policy, an external ECAMP assessment is required at a minimum of every three years for each installation. In the intervening years, each installation is required to perform an internal ECAMP assessment, with its own personnel and resources. Even though team composition differs, the internal and external ECAMP assessments are likely to be very similar in scope, objectives, and deliverables. For over nine years, Argonne National Laboratory (ANL) has supported several Air Force MAJCOMs in performing their external ECAMP assessments. More recently, ANL has also had the opportunity to provide technical support and training at individual installations during their preparation and conduct of internal ECAMP assessments. From that experience, the authors have learned that the quality and value of the internal assessment is enhanced by making it a vehicle for training, planning, and interaction among organizations. Various strategies and techniques have been successfully employed to derive maximum benefit and insight from the internal assessment process. Experiences that involve expanding the scope and objectives of internal assessments to meet specific goals are presented. The expansion of scope and objectives include preassessment training, planning, and evaluator interactions as part of the overall internal assessment process.

  20. Massive Fermi gas in the expanding universe

    Science.gov (United States)

    Trautner, Andreas

    2017-03-01

    The behavior of a decoupled ideal Fermi gas in a homogeneously expanding three-dimensional volume is investigated, starting from an equilibrium spectrum. In case the gas is massless and/or completely degenerate, the spectrum of the gas can be described by an effective temperature and/or an effective chemical potential, both of which scale down with the volume expansion. In contrast, the spectrum of a decoupled massive and non-degenerate gas can only be described by an effective temperature if there are strong enough self-interactions such as to maintain an equilibrium distribution. Assuming perpetual equilibration, we study a decoupled gas which is relativistic at decoupling and then is red-shifted until it becomes non-relativistic. We find expressions for the effective temperature and effective chemical potential which allow us to calculate the final spectrum for arbitrary initial conditions. This calculation is enabled by a new expansion of the Fermi-Dirac integral, which is for our purpose superior to the well-known Sommerfeld expansion. We also compute the behavior of the phase space density under expansion and compare it to the case of real temperature and real chemical potential. Using our results for the degenerate case, we also obtain the mean relic velocity of the recently proposed non-thermal cosmic neutrino background.