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Sample records for adjacent carbon atoms

  1. Submillimetre observations of atomic carbon

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.; Keene, J.

    1982-01-01

    Emission from the ground state fine structure transition of atomic carbon at 610 microns has been observed in Galactic sources. From comparison of the observations with CO emission, it can be deduced that the abundance of neutral carbon relative to CO is high (approximately 0.1-3). The spatial and velocity distribution of CI and CO are often very similar. If molecular clouds are older than 1 x 10 to the 6th power years, the observations necessitate a mechanism which can maintain a high abundance of neutral carbon in cloud material, either by hindering complete conversion of C into CO or by physically and chemically rejuvenating the material.

  2. Local Atomic Density of Microporous Carbons

    SciTech Connect

    Dmowski, Wojtek; Contescu, Cristian I.; Llobet, Anna; Gallego, Nidia C.; Egami, Takeskhi

    2012-07-12

    We investigated the structure of two disordered carbons: activated carbon fibers (ACF) and ultramicroporous carbon (UMC). These carbons have highly porous structure with large surface areas and consequently low macroscopic density that should enhance adsorption of hydrogen. We used the atomic pair distribution function to probe the local atomic arrangements. The results show that the carbons maintain an in-plane local atomic structure similar to regular graphite, but the stacking of graphitic layers is strongly disordered. Although the local atomic density of these carbons is lower than graphite, it is only {approx}20% lower and is much higher than the macroscopic density due to the porosity of the structure. For this reason, the density of graphene sheets that have optimum separation for hydrogen adsorption is lower than anticipated.

  3. Local atomic density of microporous carbons

    SciTech Connect

    Dmowski, Wojtek; Contescu, Cristian I; Llobet, Anna; Gallego, Nidia C; Egami, Takeshi

    2011-01-01

    We investigated the structure of two disordered carbons: activated carbon fibers (ACF) and ultramicroporous carbon (UMC). These carbons have highly porous structure with large surface areas and consequently low macroscopic density that should enhance adsorption of hydrogen. We used the atomic pair distribution function to probe the local atomic arrangements. The results show that the carbons maintain an in-plane local atomic structure similar to regular graphite, but the stacking of graphitic layers is strongly disordered. Although the local atomic density of these carbons is lower than graphite, it is only ~20% lower and is much higher than the macroscopic density due to the porosity of the structure. For this reason, the density of graphene sheets that have optimum separation for hydrogen adsorption is lower than anticipated.

  4. Atomic carbon in the atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Fox, J. L.

    1982-01-01

    The densities of atomic carbon in the Venusian thermosphere are computed for a model which includes both chemistry and transport. The maximum density of C is 2.8 x 10 to the 7th per cu cm near 150 km for an assumed O2 mixing ratio of 0.0001. Photoionization of atomic carbon is found to be the major source of C(+) above 200 km, and resonance scattering of sunlight by atomic carbon may be the major source of the C I emissions at 1561 A, 1657 A, and 1931 A. The computed C(+) densities are found to be in substantial agreement with those measured by Pioneer Venus.

  5. Comparison between soil and biomass carbon in adjacent hardwood and red pine forests

    SciTech Connect

    Perala, D.A.; Rollinger, J.L.; Wilson, D.M.

    1995-06-01

    The distribution of carbon in soil and biomass was studied across Minnesota, Wisconsin, and Michigan, USA, in 40 pole-sized red pine (Pinus resinosa Ait.) plantations paired with adjacent hardwood stands. Pine and hardwood stands shared a common boundary and soil. Hardwood stands were mixed species, naturally regenerated second growth following logging. Carbon in total, standing crop averaged the same in both hardwood and red pine forest types, although the hardwoods averaged 14 years older than red pine. Coarse woody debris, shrubs, and herbs contained little carbon. Only the forest floor carbon pool was significantly different between forest types. Forest floor had a greater mass beneath red pine than hardwoods. There was no difference in total ecosystem carbon between red pine and hardwood stands. Total mineral soil aggregated across the depth profile contained the same total amount of carbon in both pine and hardwood stands; however, the carbon was found in different vertical patterns. Amounts of carbon in the upper levels of soil (0--4 cm) were higher under hardwoods, and amounts were higher under red pine at the 8--16 cm and 16--32 cm soil depths. Where July air temperatures were relatively cool, red pine stored carbon more efficiently both in the forest floor and deep in the soil. Red pine also sequestered more carbon in mineral soil with increasing April--September precipitation.

  6. Carbon sources supporting benthic mineralization in mangrove and adjacent seagrass sediments (Gazi Bay, Kenya)

    NASA Astrophysics Data System (ADS)

    Bouillon, S.; Moens, T.; Dehairs, F.

    2004-08-01

    The origin of carbon substrates used by in situ sedimentary bacterial communities was investigated in an intertidal mangrove ecosystem and in adjacent seagrass beds in Gazi bay (Kenya) by δ13C analysis of bacteria-specific PLFA (phospholipid fatty acids) and bulk organic carbon. Export of mangrove-derived organic matter to the adjacent seagrass-covered bay was evident from sedimentary total organic carbon (TOC) and δ13CTOC data. PLFA δ13C data indicate that the substrate used by bacterial communities varied strongly and that exported mangrove carbon was a significant source for bacteria in the adjacent seagrass beds. Within the intertidal mangrove forest, bacterial PLFA at the surface layer (0-1 cm) typically showed more enriched δ13C values than deeper (up to 10 cm) sediment layers, suggesting a contribution from microphytobenthos and/or inwelled seagrass material. Under the assumption that seagrasses and mangroves are the dominant potential end-members, the estimated contribution of mangrove-derived carbon to benthic mineralization in the seagrass beds (16-74%) corresponds fairly well to the estimated contribution of mangrove C to the sedimentary organic matter pool (21-71%) across different seagrass sites. Based on these results and a compilation of literature data, we suggest that allochtonous carbon trapped in seagrass beds may often represent a significant fraction of the substrate for benthic mineralization - both in cases where seagrass C dominates the sediment TOC pool and in cases where external inputs are significant. Hence, it is likely that community respiration data systematically overestimate the role of mineralization in the overall seagrass C budget.

  7. The carbonate system of the amur estuary and the adjacent marine aquatic areas

    NASA Astrophysics Data System (ADS)

    Koltunov, A. M.; Tishchenko, P. Ya.; Zvalinskii, V. I.; Chichkin, R. V.; Lobanov, V. B.; Nekrasov, D. A.

    2009-10-01

    In July 2007, integrated studies of the Amur Estuary and the adjacent aquatic areas were performed on board R/V Professor Gagarinskii within the project of the Amur River basin exploration. On the basis of the data obtained during the cruise, the carbonate system of the Amur Estuary in the summer period was considered. It was shown that the distribution of the carbonate parameters in the Amur Estuary and the adjacent aquatic areas points to the high intensity of the bio-geochemical processes of production and mineralization of organic matter. It was found that the organic matter destruction is prevailing over the photosynthesis in the riverine part of the estuary. This aquatic area is a source of carbon dioxide for the atmosphere and rates as a heterotrophic basin. On the contrary, the surface waters at the outer boundaries of the estuary (the Gulf of Sakhalin and the Tatar Strait) act as a sink of the atmospheric carbon dioxide, which is caused by the intense photosynthesis in this area. This part of the estuary is treated as an autotrophic basin.

  8. Atomic resolution studies of carbonic anhydrase II

    SciTech Connect

    Behnke, Craig A.; Le Trong, Isolde; Godden, Jeff W.; Merritt, Ethan A.; Teller, David C.; Bajorath, Jürgen; Stenkamp, Ronald E.

    2010-05-01

    The structure of human carbonic anhydrase II has been solved with a sulfonamide inhibitor at 0.9 Å resolution. Structural variation and flexibility is seen on the surface of the protein and is consistent with the anisotropic ADPs obtained from refinement. Comparison with 13 other atomic resolution carbonic anhydrase structures shows that surface variation exists even in these highly ordered isomorphous crystals. Carbonic anhydrase has been well studied structurally and functionally owing to its importance in respiration. A large number of X-ray crystallographic structures of carbonic anhydrase and its inhibitor complexes have been determined, some at atomic resolution. Structure determination of a sulfonamide-containing inhibitor complex has been carried out and the structure was refined at 0.9 Å resolution with anisotropic atomic displacement parameters to an R value of 0.141. The structure is similar to those of other carbonic anhydrase complexes, with the inhibitor providing a fourth nonprotein ligand to the active-site zinc. Comparison of this structure with 13 other atomic resolution (higher than 1.25 Å) isomorphous carbonic anhydrase structures provides a view of the structural similarity and variability in a series of crystal structures. At the center of the protein the structures superpose very well. The metal complexes superpose (with only two exceptions) with standard deviations of 0.01 Å in some zinc–protein and zinc–ligand bond lengths. In contrast, regions of structural variability are found on the protein surface, possibly owing to flexibility and disorder in the individual structures, differences in the chemical and crystalline environments or the different approaches used by different investigators to model weak or complicated electron-density maps. These findings suggest that care must be taken in interpreting structural details on protein surfaces on the basis of individual X-ray structures, even if atomic resolution data are available.

  9. Detection of gas atoms with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Arash, B.; Wang, Q.

    2013-05-01

    Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.

  10. Detection of gas atoms with carbon nanotubes

    PubMed Central

    Arash, B.; Wang, Q.

    2013-01-01

    Owning to their unparalleled sensitivity resolution, nanomechanical resonators have excellent capabilities in design of nano-sensors for gas detection. The current challenge is to develop new designs of the resonators for differentiating distinct gas atoms with a recognizably high sensitivity. In this work, the characteristics of impulse wave propagation in carbon nanotube-based sensors are investigated using molecular dynamics simulations to provide a new method for detection of noble gases. A sensitivity index based on wave velocity shifts in a single-walled carbon nanotube, induced by surrounding gas atoms, is defined to explore the efficiency of the nano-sensor. The simulation results indicate that the nano-sensor is able to differentiate distinct noble gases at the same environmental temperature and pressure. The inertia and the strengthening effects by the gases on wave characteristics of carbon nanotubes are particularly discussed, and a continuum mechanics shell model is developed to interpret the effects.

  11. Oxygen atom loss coefficient of carbon nanowalls

    NASA Astrophysics Data System (ADS)

    Mozetic, Miran; Vesel, Alenka; Stoica, Silviu Daniel; Vizireanu, Sorin; Dinescu, Gheorghe; Zaplotnik, Rok

    2015-04-01

    Extremely high values of atomic oxygen loss coefficient on carbon nanowall (CNW) surface are reported. CNW layers consisting of interconnected individual nanostructures with average length of 1.1 μm, average thickness of 66 nm and surface density of 3 CNW/μm2 were prepared by plasma jet enhanced chemical-vapor deposition using C2H2/H2/Ar gas mixtures. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectrometry (RS) as well as X-ray photoelectron spectroscopy (XPS). The surface loss coefficient was measured at room temperature in a flowing afterglow at different densities of oxygen atoms supplied from inductively coupled radiofrequency O2 plasma. The RF generator operated at 13.56 MHz and different nominal powers up to 900 W corresponding to different O-atom density in the afterglow up to 1.3 × 1021 m-3. CNW and several different samples of known coefficients for heterogeneous surface recombination of neutral oxygen atoms have been placed separately in the afterglow chamber and the O-atom density in their vicinity was measured with calibrated catalytic probes. Comparison of measured results allowed for determination of the loss coefficient for CNWs and the obtained value of 0.59 ± 0.03 makes this material an extremely effective sink for O-atoms.

  12. Reaction studies of hot silicon, germanium and carbon atoms

    SciTech Connect

    Gaspar, P.P.

    1986-11-15

    Research has been continued on hot silicon, germanium and carbon atoms. Progress in the period November 16, 1985 to November 15, 1986 is reviewed in the following areas: (1) Recoil atom reaction studies. (2) Reactions of thermally generated free atoms.

  13. Soil Carbon Storage and Turnover in an Old-Growth Coastal Redwood Forest and Adjacent Prairie

    NASA Astrophysics Data System (ADS)

    McFarlane, K. J.; Torn, M. S.; Mambelli, S.; Dawson, T. E.

    2010-12-01

    Coastal redwood (Sequoia sempervirens) forests store lots of carbon in aboveground tree biomass because redwoods are very long-lived and can grow very large. Redwood is known for its high resistance to decay, a result of high levels of aromatic compounds (tannins) in the tree’s tissues. We tested the hypothesis that because coastal redwoods are highly productive and produce organic matter that is chemically resistant to decay, old-growth redwood forests should store large amounts of stabilized soil carbon. We measured soil C storage to 110 cm depth in an old-growth coastal redwood forest and used physical soil fractionation combined with radiocarbon measurements to determine soil organic matter turnover time. In addition, we measured soil C storage and turnover at an adjacent prairie experiencing the same climate and with soils derived from the same parent material. We found larger soil C stocks to 110 cm at the prairie (350 Mg C ha-1) than the redwood forest (277 Mg C ha-1) even with O-horizons included for the forest. Larger N stocks were also observed at the prairie than the redwood and these differences in stocks were driven by higher C and N concentrations in mineral soils at the prairie. Differences between ecosystems in soil C and N concentrations, C:N ratios, and C and N stocks were observed for the top 50 cm only, suggesting that the influence of the different litter types did not extend to deeper soils. Contrary to what was expected, bulk soil and heavy density-fraction Δ14C values were higher, indicating shorter turnover times, for the redwood forest than the prairie. In summary, we did not observe greater C storage or 14C-based turnover times in old-growth redwood forest compared to adjacent prairie, suggesting chemical recalcitrance of litter inputs does not drive soil C stabilization at these ecosystems.

  14. Carbon dynamics of two adjacent temperate forests under similar climatic conditions

    NASA Astrophysics Data System (ADS)

    Malla Thakuri, B.; Kim, J.

    2012-12-01

    The proximity (< 1.5 km) of the two KoFlux towers (i.e., Gwangneung coniferous forest site, GCK and deciduous forest site, GDK) provides an excellent opportunity to study carbon dynamics of the two different plant functional types under similar climate and environmental conditions. We have analyzed the CO2 flux data measured by eddy covariance from 2007 to 2010 at GCK and GDK sites. Our objectives were (1) to compare and contrast the seasonality and inter-annual variability in net ecosystem CO2 exchange (NEE) of the two adjacent forests and (2) to interpret their carbon dynamics in the framework of resilience concept. The multi-year measurements of CO2 fluxes at both sites showed contrasting inter-annual trends. Overall, both the annual gross primary productivity (GPP) and ecosystem respiration (RE) were higher for GCK site with an average NEE of -220 (±137) g C m-2 yr-1 while that of GDK was -67 (±58) g C m-2 yr-1. The GCK showed a continuous, threefold increase in NEE with lower water use efficiency whereas the GDK fluctuated between carbon source and weak to moderate carbon sink. Each year, both sites manifested a mid-season depression in GPP (and thus NEE), which was more pronounced at GCK. On a seasonal basis, summer was the most productive for GDK while spring for GCK. The results are interpreted in terms of phenology and different stages of adaptive cycles. Acknowledgment This work was funded by the Korea Meteorological Administration Research and Development Program under Grant CATER 2012-3030.

  15. Carbon nanotube atomic force microscopy probes

    NASA Astrophysics Data System (ADS)

    Yamanaka, Shigenobu; Okawa, Takashi; Akita, Seiji; Nakayama, Yoshikazu

    2005-05-01

    We have developed a carbon nanotube atomic force microscope probe. Because the carbon nanotube are well known to have high aspect ratios, small tip radii and high stiffness, carbon nanotube probes have a long lifetime and can be applied for the observation deep trenches. Carbon nanotubes were synthesized by a well-controlled DC arc discharge method, because this method can make nanotubes to have straight shape and high crystalline. The nanotubes were aligned on the knife-edge using an alternating current electrophoresis technique. A commercially available Si probe was used for the base of the nanotube probe. The nanotube probe was fabricated by the SEM manipulation method. The nanotube was then attached tightly to the Si probe by deposition of amorphous carbon. We demonstrate the measurement of a fine pith grating that has vertical walls. However, a carbon nanotube has a problem that is called "Sticking". The sticking is a chatter image on vertical like region in a sample. We solved this problem by applying 2 methods, 1. a large cantilever vibration amplitude in tapping mode, 2. an attractive mode measurement. We demonstrate the non-sticking images by these methods.

  16. Texturing Carbon-carbon Composite Radiator Surfaces Utilizing Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Raack, Taylor

    2004-01-01

    Future space nuclear power systems will require radiator technology to dissipate excess heat created by a nuclear reactor. Large radiator fins with circulating coolant are in development for this purpose and an investigation of how to make them most efficient is underway. Maximizing the surface area while minimizing the mass of such radiator fins is critical for obtaining the highest efficiency in dissipating heat. Processes to develop surface roughness are under investigation to maximize the effective surface area of a radiator fin. Surface roughness is created through several methods including oxidation and texturing. The effects of atomic oxygen impingement on carbon-carbon surfaces are currently being investigated for texturing a radiator surface. Early studies of atomic oxygen impingement in low Earth orbit indicate significant texturing due to ram atomic oxygen. The surface morphology of the affected surfaces shows many microscopic cones and valleys which have been experimentally shown to increase radiation emittance. Further study of this morphology proceeded in the Long Duration Exposure Facility (LDEF). Atomic oxygen experiments on the LDEF successfully duplicated the results obtained from materials in spaceflight by subjecting samples to 4.5 eV atomic oxygen from a fixed ram angle. These experiments replicated the conical valley morphology that was seen on samples subjected to low Earth orbit.

  17. A multiproxy analysis of sedimentary organic carbon in the Changjiang Estuary and adjacent shelf

    NASA Astrophysics Data System (ADS)

    Yao, Peng; Yu, Zhigang; Bianchi, Thomas S.; Guo, Zhigang; Zhao, Meixun; Knappy, Chris S.; Keely, Brendan J.; Zhao, Bin; Zhang, Tingting; Pan, Huihui; Wang, Jinpeng; Li, Dong

    2015-07-01

    Surface sediments from the Changjiang Estuary and adjacent shelf were analyzed using a variety of bulk and molecular techniques, including grain size composition, sediment surface area (SSA), elemental composition (C, N), stable carbon isotopic composition (δ13C), n-alkanes, lignin phenols, and glycerol dialkyl glycerol tetraether lipids to obtain a more comprehensive understanding of the sources and fate of sedimentary organic carbon (SOC) in this dynamic region. Bulk N/C ratios of 0.09 to 0.15, δ13C of -24.4‰ to -21.1‰, branched/isoprenoid tetraether index of 0 to 0.74, n-alkane content of 0.02 to 0.37 mg g-1 organic carbon (OC), and lignin content (Λ8) of 0.10 to 1.46 mg/100 mg OC and other related molecular indices in these samples indicate a mixed source of marine, soil, and terrestrial plant-derived OC in the study area. A three-end-member mixing model using principal component analysis (PCA) factors as source markers and based on Monte Carlo (MC) simulation was constructed to estimate the relative contributions of OC from different sources. Compared with traditional mixing models, commonly based on a few variables, this newly developed PCA-MC model supported bulk and biomarker data and yielded a higher-resolution OC inputs to different subregions of this system. In particular, the results showed that the average contributions of marine, soil, and terrestrial OC in the study area were 35.3%, 47.0%, and 17.6%, and the highest contribution from each OC source was mainly observed in the shelf, inner estuary, and coastal region, respectively.

  18. Ab initio study of semiconductor atoms impurities in zigzag edge (10,0) carbon nanotubes

    SciTech Connect

    Muttaqien, Fahdzi Suprijadi

    2015-04-16

    The substitutional impurities in zigzag edge (10,0) carbon nanotubes have been studied by using first principles calculations. Silicon (Si), gallium (Ga), and arsenic (As) atom have been chosen as semiconductor based-atom for replacing carbon atoms in CNT’s surface. The silicon atom changes the energy gap of pristine zigzag (10,0) CNT, it is 0.19 eV more narrow than that of pristine CNT. Geometrically, the silicon atom creates sp{sup 3} bond with three adjacent carbon atoms, where the tetrahedral form of its sp{sup 3} bond is consisted of free unoccupied state. The silicon atom does not induce magnetism to zigzag CNT. Due to gallium (Ga) and arsenic (As) atom substitution, the zigzag CNT becomes metallic and has magnetic moment of 1 µ{sub B}. The valance and conduction band are crossed each other, then the energy gap is vanished. The electronic properties of GaAs-doped CNT are dominantly affected by gallium atom and its magnetic properties are dominantly affected by arsenic atom. These results prove that the CNT with desired properties can be obtained with substitutional impurities without any giving structural defect.

  19. Functionalization of Carbon Nanotubes using Atomic Hydrogen

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Cassell, Alan M.; Nguyen, Cattien V.; Meyyappan, M.; Han, Jie; Arnold, Jim (Technical Monitor)

    2001-01-01

    We have investigated the irradiation of multi walled and single walled carbon nanotubes (SWNTs) with atomic hydrogen. After irradiating the SWNT sample, a band at 2940/cm (3.4 microns) that is characteristic of the C-H stretching mode is observed using Fourier transform infrared (FTIR) spectroscopy. Additional confirmation of SWNT functionalization is tested by irradiating with atomic deuterium. A weak band in the region 1940/cm (5.2 micron) to 2450/cm (4.1 micron) corresponding to C-D stretching mode is also observed in the FTIR spectrum. This technique provides a clean gas phase process for the functionalization of SWNTs, which could lead to further chemical manipulation and/or the tuning of the electronic properties of SWNTs for nanodevice applications.

  20. Exocyclic carbons adjacent to the N6 of adenine are targets for oxidation by the Escherichia coli adaptive response protein AlkB.

    PubMed

    Li, Deyu; Delaney, James C; Page, Charlotte M; Yang, Xuedong; Chen, Alvin S; Wong, Cintyu; Drennan, Catherine L; Essigmann, John M

    2012-05-30

    The DNA and RNA repair protein AlkB removes alkyl groups from nucleic acids by a unique iron- and α-ketoglutarate-dependent oxidation strategy. When alkylated adenines are used as AlkB targets, earlier work suggests that the initial target of oxidation can be the alkyl carbon adjacent to N1. Such may be the case with ethano-adenine (EA), a DNA adduct formed by an important anticancer drug, BCNU, whereby an initial oxidation would occur at the carbon adjacent to N1. In a previous study, several intermediates were observed suggesting a pathway involving adduct restructuring to a form that would not hinder replication, which would match biological data showing that AlkB almost completely reverses EA toxicity in vivo. The present study uses more sensitive spectroscopic methodology to reveal the complete conversion of EA to adenine; the nature of observed additional putative intermediates indicates that AlkB conducts a second oxidation event in order to release the two-carbon unit completely. The second oxidation event occurs at the exocyclic carbon adjacent to the N(6) atom of adenine. The observation of oxidation of a carbon at N(6) in EA prompted us to evaluate N(6)-methyladenine (m6A), an important epigenetic signal for DNA replication and many other cellular processes, as an AlkB substrate in DNA. Here we show that m6A is indeed a substrate for AlkB and that it is converted to adenine via its 6-hydroxymethyl derivative. The observation that AlkB can demethylate m6A in vitro suggests a role for AlkB in regulation of important cellular functions in vivo. PMID:22512456

  1. Impact of Quadrupolar Electrostatics on Atoms Adjacent to the Sigma-Hole in Condensed-Phase Simulations.

    PubMed

    El Hage, Krystel; Bereau, Tristan; Jakobsen, Sofie; Meuwly, Markus

    2016-07-12

    Halogenation is one of the cases for which advanced molecular simulation methods are mandatory for quantitative and predictive studies. The present work provides a systematic investigation of the importance of higher-order multipoles on specific sites of halobenzenes, other than the halogen, for static and dynamic properties in condensed-phase simulations. For that purpose, solute-solvent interactions using point charge (PC), multipole (MTP), and hybrid point charge/multipole (HYB) electrostatic models are analyzed in regions of halogen bonding and extended to regions of π orbitals of phenyl carbons. Using molecular dynamics simulations and quantum chemical methods, it is found that the sigma-hole does not only affect the halogen and the carbon bound to it but its effect extends to the carbons adjacent to the CX bond. This effect increases with the magnitude of the positive potential of the sigma-hole. With the MTP and HYB3 models, all hydration free energies of the PhX compounds are reproduced within 0.1 kcal/mol. Analysis of pair distribution functions and hydration free energies of halogenated benzenes provides a microscopic explanation why "point charge"-based representations with off-site charges fail in reproducing thermodynamic properties of the sigma-hole. Application of the hybrid models to study protein-ligand binding demonstrates both their accuracy and computational efficiency. PMID:27158892

  2. Reaction studies of hot silicon, germanium and carbon atoms

    SciTech Connect

    Gaspar, P.P.

    1989-02-01

    Research has been continued on hot silicon, germanium and carbon atoms. The results of experiments directed toward attaining the goals of this research program are briefly presented for the period September 1, 1987 to January 31, 1989 in sections entitled: (1) The mechanism of hydrogen acquisition by high energy silicon atoms. (2) The mechanism of disilene formation in the reactions of recoiling silicon atoms with silane. (3) The contribution of ionic processes to the primary reactions of recoiling silicon atoms. (4) The role of phosphine in hydrogen acquisition by recoiling silicon atoms. (5) Mechanism of reaction of recoiling carbon atoms with aromatic molecules.

  3. Atomic Carbon in the Southern Milky Way

    NASA Astrophysics Data System (ADS)

    Oka, Tomoharu; Kamegai, Kazuhisa; Hayashida, Masaaki; Nagai, Makoto; Ikeda, Masafumi; Kuboi, Nobuyuki; Tanaka, Kunihiko; Bronfman, Leonardo; Yamamoto, Satoshi

    2005-04-01

    We present a coarsely sampled longitude-velocity (l-V) map of the region l=300deg-354°, b=0deg in the 492 GHz fine-structure transition of neutral atomic carbon (C0 3P1-3P0 [C I]), observed with the Portable 18 cm Submillimeter-wave Telescope (POST18). The l-V distribution of the [C I] emission resembles closely that of the CO J=1-0 emission, showing a widespread distribution of atomic carbon on the Galactic scale. The ratio of the antenna temperatures, RCI/CO, concentrates on the narrow range from 0.05 to 0.3. A large velocity gradient (LVG) analysis shows that the [C I] emission from the Galactic disk is dominated by a population of neutral gas with high C0/CO abundance ratios and moderate column densities, which can be categorized as diffuse translucent clouds. The ratio of bulk emissivity, JCI/JCO, shows a systematic trend, suggesting the bulk C0/CO abundance ratio increasing with the Galactic radius. A mechanism related to kiloparsec-scale structure of the Galaxy may control the bulk C0/CO abundance ratio in the Galactic disk. Two groups of high-ratio (RCI/CO>0.3) areas reside in the l-V loci several degrees inside of tangential points of the Galactic spiral arms. These could be gas condensations just accumulated in the potential well of spiral arms and be in the early stages of molecular cloud formation.

  4. Structurally uniform and atomically precise carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Segawa, Yasutomo; Ito, Hideto; Itami, Kenichiro

    2016-01-01

    Nanometre-sized carbon materials consisting of benzene units oriented in unique geometric patterns, hereafter named nanocarbons, conduct electricity, absorb and emit light, and exhibit interesting magnetic properties. Spherical fullerene C60, cylindrical carbon nanotubes and sheet-like graphene are representative forms of nanocarbons, and theoretical simulations have predicted several exotic 3D nanocarbon structures. At present, synthetic routes to nanocarbons mainly lead to mixtures of molecules with a range of different structures and properties, which cannot be easily separated or refined into pure forms. Some researchers believe that it is impossible to synthesize these materials in a precise manner. Obtaining ‘pure’ nanocarbons is a great challenge in the field of nanocarbon science, and the construction of structurally uniform nanocarbons, ideally as single molecules, is crucial for the development of functional materials in nanotechnology, electronics, optics and biomedical applications. This Review highlights the organic chemistry approach — more specifically, bottom-up construction with atomic precision — that is currently the most promising strategy towards this end.

  5. Carbon based thirty six atom spheres

    DOEpatents

    Piskoti, Charles R.; Zettl, Alex K.; Cohen, Marvin L.; Cote, Michel; Grossman, Jeffrey C.; Louie, Steven G.

    2005-09-06

    A solid phase or form of carbon is based on fullerenes with thirty six carbon atoms (C.sub.36). The C.sub.36 structure with D.sub.6h symmetry is one of the two most energetically favorable, and is conducive to forming a periodic system. The lowest energy crystal is a highly bonded network of hexagonal planes of C.sub.36 subunits with AB stacking. The C.sub.36 solid is not a purely van der Waals solid, but has covalent-like bonding, leading to a solid with enhanced structural rigidity. The solid C.sub.36 material is made by synthesizing and selecting out C.sub.36 fullerenes in relatively large quantities. A C.sub.36 rich fullerene soot is produced in a helium environment arc discharge chamber by operating at an optimum helium pressure (400 torr). The C.sub.36 is separated from the soot by a two step process. The soot is first treated with a first solvent, e.g. toluene, to remove the higher order fullerenes but leave the C.sub.36. The soot is then treated with a second solvent, e.g. pyridine, which is more polarizable than the first solvent used for the larger fullerenes. The second solvent extracts the C.sub.36 from the soot. Thin films and powders can then be produced from the extracted C.sub.36. Other materials are based on C.sub.36 fullerenes, providing for different properties.

  6. Carbon nanotube-clamped metal atomic chain

    PubMed Central

    Tang, Dai-Ming; Yin, Li-Chang; Li, Feng; Liu, Chang; Yu, Wan-Jing; Hou, Peng-Xiang; Wu, Bo; Lee, Young-Hee; Ma, Xiu-Liang; Cheng, Hui-Ming

    2010-01-01

    Metal atomic chain (MAC) is an ultimate one-dimensional structure with unique physical properties, such as quantized conductance, colossal magnetic anisotropy, and quantized magnetoresistance. Therefore, MACs show great potential as possible components of nanoscale electronic and spintronic devices. However, MACs are usually suspended between two macroscale metallic electrodes; hence obvious technical barriers exist in the interconnection and integration of MACs. Here we report a carbon nanotube (CNT)-clamped MAC, where CNTs play the roles of both nanoconnector and electrodes. This nanostructure is prepared by in situ machining a metal-filled CNT, including peeling off carbon shells by spatially and elementally selective electron beam irradiation and further elongating the exposed metal nanorod. The microstructure and formation process of this CNT-clamped MAC are explored by both transmission electron microscopy observations and theoretical simulations. First-principles calculations indicate that strong covalent bonds are formed between the CNT and MAC. The electrical transport property of the CNT-clamped MAC was experimentally measured, and quantized conductance was observed. PMID:20427743

  7. Chains of carbon atoms: A vision or a new nanomaterial?

    PubMed

    Banhart, Florian

    2015-01-01

    Linear strings of sp(1)-hybridized carbon atoms are considered as a possible phase of carbon since decades. Whereas the debate about the stability of the corresponding bulk phase carbyne continues until today, the existence of isolated chains of carbon atoms has meanwhile been corroborated experimentally. Since graphene, as the two-dimensional sp(2)-bonded allotrope of carbon, has become a vast field, the question about the importance of one-dimensional carbon became of renewed interest. The present article gives an overview of the work that has been carried out on chains of carbon atoms in the past one or two decades. The review concentrates on isolated chains of carbon atoms and summarizes the experimental observations to date. While the experimental information is still very limited, many calculations of the physical and chemical properties have been published in the past years. Some of the most important theoretical studies and their importance in the present experimental situation are reviewed. PMID:25821697

  8. Chains of carbon atoms: A vision or a new nanomaterial?

    PubMed Central

    2015-01-01

    Summary Linear strings of sp1-hybridized carbon atoms are considered as a possible phase of carbon since decades. Whereas the debate about the stability of the corresponding bulk phase carbyne continues until today, the existence of isolated chains of carbon atoms has meanwhile been corroborated experimentally. Since graphene, as the two-dimensional sp2-bonded allotrope of carbon, has become a vast field, the question about the importance of one-dimensional carbon became of renewed interest. The present article gives an overview of the work that has been carried out on chains of carbon atoms in the past one or two decades. The review concentrates on isolated chains of carbon atoms and summarizes the experimental observations to date. While the experimental information is still very limited, many calculations of the physical and chemical properties have been published in the past years. Some of the most important theoretical studies and their importance in the present experimental situation are reviewed. PMID:25821697

  9. Iron-catalyzed N-alkylation of azoles via cleavage of an sp3 C-H bond adjacent to a nitrogen atom.

    PubMed

    Xia, Qinqin; Chen, Wanzhi

    2012-10-19

    Iron-catalyzed direct C-N bond formation between azoles and amides is described. The oxidative coupling reactions of sp(3) C-H bonds adjacent to a nitrogen atom in amides and sulfonamides with the N-H bond in azoles proceeded smoothly in the presence of FeCl(2) and di-tert-butyl peroxide (DTBP). PMID:23025235

  10. Reaction studies of hot silicon, germanium and carbon atoms

    SciTech Connect

    Gaspar, P.P.

    1990-11-01

    The goal of this project was to increase the authors understanding of the interplay between the kinetic and electronic energy of free atoms and their chemical reactivity by answering the following questions: (1) what is the chemistry of high-energy carbon silicon and germanium atoms recoiling from nuclear transformations; (2) how do the reactions of recoiling carbon, silicon and germanium atoms take place - what are the operative reaction mechanisms; (3) how does the reactivity of free carbon, silicon and germanium atoms vary with energy and electronic state, and what are the differences in the chemistry of these three isoelectronic atoms This research program consisted of a coordinated set of experiments capable of achieving these goals by defining the structures, the kinetic and internal energy, and the charge states of the intermediates formed in the gas-phase reactions of recoiling silicon and germanium atoms with silane, germane, and unsaturated organic molecules, and of recoiling carbon atoms with aromatic molecules. The reactions of high energy silicon, germanium, and carbon atoms created by nuclear recoil were studied with substrates chosen so that their products illuminated the mechanism of the recoil reactions. Information about the energy and electronic state of the recoiling atoms at reaction was obtained from the variation in end product yields and the extent of decomposition and rearrangement of primary products (usually reactive intermediates) as a function of total pressure and the concentration of inert moderator molecules that remove kinetic energy from the recoiling atoms and can induce transitions between electronic spin states. 29 refs.

  11. Nitrogenases-A Tale of Carbon Atom(s).

    PubMed

    Hu, Yilin; Ribbe, Markus W

    2016-07-11

    Named after its ability to catalyze the reduction of nitrogen to ammonia, nitrogenase has a surprising rapport with carbon-both through the interstitial carbide that resides in the central cavity of its cofactor and through its ability to catalyze the reductive carbon-carbon coupling of small carbon compounds into hydrocarbon products. Recently, a radical-SAM-dependent pathway was revealed for the insertion of carbide, which signifies a novel biosynthetic route to complex bridged metalloclusters. Moreover, a sulfur-displacement mechanism was proposed for the activation of carbon monoxide by nitrogenase, which suggests an essential role of the interstitial carbide in maintaining the stability while permitting a certain flexibility of the cofactor structure during substrate turnover. PMID:27206025

  12. ATOMIC CARBON IN THE UPPER ATMOSPHERE OF TITAN

    SciTech Connect

    Zhang, X.; Yung, Y. L.; Ajello, J. M.

    2010-01-01

    The atomic carbon emission C I line feature at 1657 A ({sup 3} P {sup 0} {sub J}-{sup 3} P{sub J} ) in the upper atmosphere of Titan is first identified from the airglow spectra obtained by the Cassini Ultra-violet Imaging Spectrograph. A one-dimensional photochemical model of Titan is used to study the photochemistry of atomic carbon on Titan. Reaction between CH and atomic hydrogen is the major source of atomic carbon, and reactions with hydrocarbons (C{sub 2}H{sub 2} and C{sub 2}H{sub 4}) are the most important loss processes. Resonance scattering of sunlight by atomic carbon is the dominant emission mechanism. The emission intensity calculations based on model results show good agreement with the observations.

  13. A modern analog for carbonate source-to-sink sedimentary systems: the Glorieuses archipelago and adjacent basin (SW Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Jorry, S.; Jouet, G.; Prat, S.; Courgeon, S.; Le Roy, P.; Camoin, G.; Caline, B.

    2014-12-01

    This study presents the geomorphological and sedimentological analysis of a modern carbonate source-to-sink system located north of Madagascar (SW Indian Ocean). The sedimentary system is composed of an isolated carbonate platform sited on top of a seamount rising steeply from the seabed located at 3000 m water depth. The slope of the seamount is incised by canyons, and meandering channels occur above lobbed sedimentary bodies at the foot of the slope. The dataset consists of dredges, sediment piston cores, swath bathymetry and seismic (sparker and 2D high-resolution) lines collected from inner platform (less than 5 m deep) to the adjacent deep sedimentary basin. Particle size analysis and composition of carbonate grains are used to characterize the distribution and heterogeneity of sands accumulated on the archipelago. Main results show that composition of carbonate sediments is dominated by segments of Halimeda, large benthic foraminifera, coral debris, molluscs, echinoderms, bryozoans and sponges. According to the shape and the position of sandwaves and intertidal sandbars developed in the back-barrier reef, the present organization of these well-sorted fine-sand accumulations appears to be strongly influenced by flood tidal currents. Seismic lines acquired from semi-enclosed to open lagoon demonstrate that most of the sediment is exported and accumulated along the leeward margin of the platform, which is connected to a canyon network incising the outer slope. Following the concept of highstand shedding of carbonate platforms (Schlager et al., 1994), excess sediment is exported by plumes and gravity flows to the adjacent deep sea where it feeds a carbonate deep-sea fan. Combined observations from platform to basin allow to explain how the Glorieuses carbonate source to sink system has evolved under the influence of climate and of relative sea-level changes since the last interglacial.

  14. Magnetism and spin-polarized transport in carbon atomic wires

    NASA Astrophysics Data System (ADS)

    Li, Z. Y.; Sheng, W.; Ning, Z. Y.; Zhang, Z. H.; Yang, Z. Q.; Guo, H.

    2009-09-01

    We report ab initio calculations of magnetic and spin-polarized quantum transport properties of pure and nitrogen-doped carbon atomic wires. For finite-sized wires with even number of carbon atoms, total magnetic moment of 2μB is found. On the other hand, wires with odd number atoms have no net magnetic moment. Doped with one or two nitrogen atom(s), the carbon atomic wires exhibit a spin-density-wave-like state. The magnetic properties can be rationalized through bonding patterns and unpaired states. When the wire is sandwiched between Au electrodes to form a transport junction, perfect spin filtering effect can be induced by slightly straining the wire.

  15. Carbon-atom wires: 1-D systems with tunable properties

    NASA Astrophysics Data System (ADS)

    Casari, C. S.; Tommasini, M.; Tykwinski, R. R.; Milani, A.

    2016-02-01

    This review provides a discussion of the current state of research on linear carbon structures and related materials based on sp-hybridization of carbon atoms (polyynes and cumulenes). We show that such systems have widely tunable properties and thus represent an intriguing and mostly unexplored field for both fundamental and applied sciences. We discuss the rich interplay between the structural, vibrational, and electronic properties focusing on recent advances and the future perspectives of carbon-atom wires and novel hybrid sp-sp2-carbon architectures.

  16. Carbon-atom wires: 1-D systems with tunable properties.

    PubMed

    Casari, C S; Tommasini, M; Tykwinski, R R; Milani, A

    2016-02-28

    This review provides a discussion of the current state of research on linear carbon structures and related materials based on sp-hybridization of carbon atoms (polyynes and cumulenes). We show that such systems have widely tunable properties and thus represent an intriguing and mostly unexplored field for both fundamental and applied sciences. We discuss the rich interplay between the structural, vibrational, and electronic properties focusing on recent advances and the future perspectives of carbon-atom wires and novel hybrid sp-sp(2)-carbon architectures. PMID:26847474

  17. Carbon Sequestration and Energy Balance of Turf in the Denver Urban Ecosystem and Adjacent Tallgrass Prairie

    NASA Astrophysics Data System (ADS)

    Thienelt, T.; Anderson, D. E.; Powell, K. M.

    2012-12-01

    Urban ecosystems are currently characterized by rapid growth and are expected to continually expand. They represent an important driver of land use change. A significant component of urban ecosystems is lawns, potentially the single largest irrigated "crop" in the U.S. Between March and October of 2011 and 2012, eddy covariance measurements of net carbon dioxide exchange and evapotranspiration along with energy balance fluxes were conducted for an irrigated, fertilized lawn (rye-bluegrass-mix) in metropolitan Denver and for a nearby tallgrass prairie (big bluestem, switchgrass, cheatgrass, blue grama). Due to the semi-arid climate conditions of the Denver region, differences in management (i.e., irrigation and fertilization) are expected to have a discernible impact on ecosystem productivity and thus on carbon sequestration rates, evapotranspiration, and the partitioning of sensible and latent heat. Data for the 2011 season showed that cumulative evapotranspiration was approximately 600 mm for the urban lawn and 305 mm for the tallgrass prairie; cumulative carbon sequestration was calculated to be 172 and 85 g C/m2, respectively. Also, patterns of carbon exchange differed between the grasslands. In 2011, both sites showed daily net uptake of carbon starting in late May, but the urban lawn displayed greater diurnal variability as well as greater uptake rates in general, especially following fertilization in mid-June. In contrast, the trend of carbon uptake at the prairie site was occasionally reversed following strong convective precipitation events, resulting in a temporary net release of carbon. Preliminary data for the 2012 season (up to early July) indicated an earlier start of net carbon uptake and higher cumulative evapotranspiration for both locations, likely due to a warm spring. The continuing acquisition of data and investigation of these relations will help assess the potential impact of urban growth on regional carbon sequestration.

  18. Atomic-Scale Investigations of Multiwall Carbon Nanotube Growth

    NASA Astrophysics Data System (ADS)

    Behr, Michael John

    ) rotations, twists, and bends along their axial length between adjacent locations. Distortions are most severe away from the base up into the nanotube where the number of walls is large. This suggests that the stresses generated by the surrounding nanotube distort the catalyst particle during growth. Fe 3C catalyst nanoparticles that are located inside the base of well-graphitized CNTs of similar structure and diameter do not exhibit a preferred orientation relative to the nanotube axis. Thus, it does not appear that the graphene nanotube walls of a CNT are necessarily produced in an epitaxial process directly from Fe3C faces. Chemical processes occurring at the catalyst-CNT interface during growth were inferred by measuring, ex situ, changes in atomic bonding at an atomic scale with a 0.15 nanometer electron probe. The observed variation in carbon concentration through the base of catalyst crystals reveals that carbon from the gas phase decomposes on Fe 3C, near where the CNT walls terminate at the catalyst base. An amorphous carbon-rich layer at the catalyst base provides the source for CNT growth. EELS measurements and Z-contrast STEM imaging provide evidence that carbon diffuses on the Fe3C catalyst surface, along its interface with both the iron oxide shell and CNT walls. Atomic-scale EELS measurements at the catalyst surface in locations of CNT wall formation revealed no change in the iron L23 edge compared to the bulk of the catalyst, indicating that Fe3C did not decompose to BCC iron and graphite during CNT wall formation. Hydrogen atoms also interact with the graphene walls of CNTs. When the flux of H atoms is high, the continuous cylindrical nanotube walls can be etched and amorphized. Etching is not uniform across the length of the CNT, but rather, small etch pits form at defective sites on the CNT walls along the entire nanotube length. Once an etch pit is formed, etching proceeds rapidly, and the remainder of the CNT is quickly etched away. By examining the H

  19. Angular distribution of photoelectrons from atomic oxygen, nitrogen, and carbon

    NASA Technical Reports Server (NTRS)

    Manson, S. T.; Kennedy, D. J.; Starace, A. F.; Dill, D.

    1974-01-01

    The angular distribution of photoelectrons from atomic oxygen is investigated using Hartree-Fock (HF) wave functions. The correct formulation is used to compare HS and HF results. Agreement between these results is good and the HS calculations have been extended to atomic nitrogen and carbon as well.

  20. Automated manipulation of carbon nanotubes using atomic force microscopy.

    PubMed

    Zhang, Chao; Wu, Sen; Fu, Xing

    2013-01-01

    The manipulation of carbon nanotubes is an important and essential step for carbon-based nanodevice or nanocircuit assembly. However, the conventional push-and-image approach of manipulating carbon nanotubes using atomic force microscopy has low efficiency on account of the reduplicated scanning process during manipulation. In this article, an automated manipulation system is designed and tested. This automated manipulation system, which includes an atomic force microscope platform and a self-developed computer program for one-dimensional manipulation, is capable of automatically moving any assigned individual carbon nanotube to a defined target location without any intermediate scanning procedure. To demonstrate the high-efficiency of this automated manipulation system and its potential applications in nanoassembly, two experiments were conducted. The first experiment used this system to manipulate a carbon nanotube to a defined target location. In the second experiment, this system was used to automatically manipulate several carbon nanotubes for generating and translating a defined pattern of nanotubes. PMID:23646781

  1. Atomic scale simulation of carbon nanotube nucleation from hydrocarbon precursors.

    PubMed

    Khalilov, Umedjon; Bogaerts, Annemie; Neyts, Erik C

    2015-01-01

    Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism. In spite of over twenty years of simulation efforts in this area, limited progress has so far been made on addressing the role of the hydrocarbon growth precursor. Here we report on atomic scale simulations of cap nucleation of single-walled carbon nanotubes from hydrocarbon precursors. The presented mechanism emphasizes the important role of hydrogen in the nucleation process, and is discussed in relation to previously presented mechanisms. In particular, the role of hydrogen in the appearance of unstable carbon structures during in situ experimental observations as well as the initial stage of multi-walled carbon nanotube growth is discussed. The results are in good agreement with available experimental and quantum-mechanical results, and provide a basic understanding of the incubation and nucleation stages of hydrocarbon-based CNT growth at the atomic level. PMID:26691537

  2. Atomic scale simulation of carbon nanotube nucleation from hydrocarbon precursors

    NASA Astrophysics Data System (ADS)

    Khalilov, Umedjon; Bogaerts, Annemie; Neyts, Erik C.

    2015-12-01

    Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism. In spite of over twenty years of simulation efforts in this area, limited progress has so far been made on addressing the role of the hydrocarbon growth precursor. Here we report on atomic scale simulations of cap nucleation of single-walled carbon nanotubes from hydrocarbon precursors. The presented mechanism emphasizes the important role of hydrogen in the nucleation process, and is discussed in relation to previously presented mechanisms. In particular, the role of hydrogen in the appearance of unstable carbon structures during in situ experimental observations as well as the initial stage of multi-walled carbon nanotube growth is discussed. The results are in good agreement with available experimental and quantum-mechanical results, and provide a basic understanding of the incubation and nucleation stages of hydrocarbon-based CNT growth at the atomic level.

  3. Atomic scale simulation of carbon nanotube nucleation from hydrocarbon precursors

    PubMed Central

    Khalilov, Umedjon; Bogaerts, Annemie; Neyts, Erik C.

    2015-01-01

    Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism. In spite of over twenty years of simulation efforts in this area, limited progress has so far been made on addressing the role of the hydrocarbon growth precursor. Here we report on atomic scale simulations of cap nucleation of single-walled carbon nanotubes from hydrocarbon precursors. The presented mechanism emphasizes the important role of hydrogen in the nucleation process, and is discussed in relation to previously presented mechanisms. In particular, the role of hydrogen in the appearance of unstable carbon structures during in situ experimental observations as well as the initial stage of multi-walled carbon nanotube growth is discussed. The results are in good agreement with available experimental and quantum-mechanical results, and provide a basic understanding of the incubation and nucleation stages of hydrocarbon-based CNT growth at the atomic level. PMID:26691537

  4. Organic carbon flux and particulate organic matter composition in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

    NASA Astrophysics Data System (ADS)

    Zhu, Zhuo-Yi; Wu, Ying; Liu, Su-Mei; Wenger, Fred; Hu, Jun; Zhang, Jing; Zhang, Rui-Feng

    2016-02-01

    In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier-fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 µM, respectively, in August, 2012. Amino acids (AAs) and phytoplankton carbon accounted for ˜ 10 % of the bulk POC in the Bayelva River, while AAs represented > 90 % of particulate nitrogen (PN) in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounted for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for PN were much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29 × 106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6 tons, 25 ± 5.6 tons, and 4.7 ± 0.75 tons, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02 × 106 tons year-1) and DOC (0.02 ± 0.01 × 106 tons year-1) fluxes of Svalbard glaciers are small in amount, its discharge-weighted flux of DOC was over twice higher than other pan-Arctic glacier systems, suggesting its important role as a terrestrial DOC source.

  5. Reactions of carbon atoms in pulsed molecular beams

    SciTech Connect

    Reisler, H.

    1993-12-01

    This research program consists of a broad scope of experiments designed to unravel the chemistry of atomic carbon in its two spin states, P and D, by using well-controlled initial conditions and state-resolved detection of products. Prerequisite to the proposed studies (and the reason why so little is known about carbon atom reactions), is the development of clean sources of carbon atoms. Therefore, in parallel with the studies of its chemistry and reaction dynamics, the authors continuously explore new, state-specific and efficient ways of producing atomic carbon. In the current program, C({sup 3}P) is produced via laser ablation of graphite, and three areas of study are being pursued: (i) exothermic reactions with small inorganic molecules (e.g., O{sub 2}, N{sub 2}O, NO{sub 2}) that can proceed via multiple pathways; (ii) the influence of vibrational and translational energy on endothermic reactions involving H-containing reactants that yield CH products (e.g., H{sub 2}O H{sub 2}CO); (iii) reactions of C({sup 3}P) with free radicals (e.g., HCO, CH{sub 3}O). In addition, the authors plan to develop a source of C({sup 1}D) atoms by exploiting the pyrolysis of diazotetrazole and its salts in the ablation source. Another important goal involves collaboration with theoreticians in order to obtain relevant potential energy surfaces, rationalize the experimental results and predict the roles of translational and vibrational energies.

  6. Influence of disturbance on carbon exchange in a permafrost collapse and adjacent burned forest

    USGS Publications Warehouse

    Myers-Smith, I. H.; McGuire, A.D.; Harden, J.W.; Chapin, F. S., III

    2007-01-01

    We measured CO2 and CH4 exchange from the center of a Sphagnum-dominated permafrost collapse, through an aquatic most, and into a recently burned black spruce forest on the Tanana River floodplain in interior Alaska. In the anomalously dry growing season of 2004, both the collapse and the surrounding burned area were net sink, s for CO2, with a mean daytime net ecosystem exchange of -1.4 ??mol CO2 m-2 s-1, while the moat was a CH4 source with a mean flux of 0.013 ??mol CH4 m-2 s-1. Regression analyses identified temperature as the dominant factor affecting intragrowing season variation in CO2 exchange and soil moisture as the primary control influencing CH4 emissions. CH4 emissions during the wettest portion of the growing season were four times higher than during the driest periods. If temperatures continue to warm, peatlahd vegetation will likely expand with permafrost degradation, resulting in greater carbon accumulation and methane emissions for the landscape as a whole. Copyright 2007 by the American Geophysical Union.

  7. Trapping cold atoms using surface-grown carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Petrov, P. G.; Machluf, S.; Younis, S.; Macaluso, R.; David, T.; Hadad, B.; Japha, Y.; Keil, M.; Joselevich, E.; Folman, R.

    2009-04-01

    We present a feasibility study for loading cold atomic clouds into magnetic traps created by single-wall carbon nanotubes grown directly onto dielectric surfaces. We show that atoms may be captured for experimentally sustainable nanotube currents, generating trapped clouds whose densities and lifetimes are sufficient to enable detection by simple imaging methods. This opens the way for a different type of conductor to be used in atomchips, enabling atom trapping at submicron distances, with implications for both fundamental studies and for technological applications.

  8. Localized stem chilling alters carbon processes in the adjacent stem and in source leaves.

    PubMed

    De Schepper, Veerle; Vanhaecke, Lynn; Steppe, Kathy

    2011-11-01

    Transport phloem is no longer associated with impermeable pipes, but is instead considered as a leaky system in which loss and retrieval mechanisms occur. Local stem chilling is often used to study these phenomena. In this study, 5-cm- lengths of stems of 3-year-old oak trees (Quercus robur L.) were locally chilled for 1 week to investigate whether observations at stem and leaf level can be explained by the leakage-retrieval mechanism. The chilling experiment was repeated three times across the growing season. Measurements were made of leaf photosynthesis, carbohydrate concentrations in leaves and bark, stem growth and maximum daily stem shrinkage. Across the growing season, a feedback inhibition in leaf photosynthesis was observed, causing increased dark respiration and starch concentration. This inhibition was attributed to the total phloem resistance which locally increased due to the cold temperatures. It is hypothesized that this higher phloem resistance increased the phloem pressure above the cold block up to the source leaves, inducing feedback inhibition. In addition, an increase in radial stem growth and carbohydrate concentration was observed above the cold block, while the opposite occurred below the block. These observations indicate that net lateral leakage of carbohydrates from the phloem was enhanced above the cold block and that translocation towards regions below the block decreased. This behaviour is probably also attributable to the higher phloem resistance. The chilling effects on radial stem growth and carbohydrate concentration were significant in the middle of the growing season, while they were not at the beginning and near the end of the growing season. Furthermore, maximum daily shrinkages were larger above the cold block during all chilling experiments, indicating an increased resistance in the xylem vessels, also generated by low temperatures. In conclusion, localized stem chilling altered multiple carbon processes in the source leaves

  9. Distribution of surficial sediment in Long Island Sound and adjacent waters: Texture and total organic carbon

    USGS Publications Warehouse

    Poppe, L.J.; Knebel, H. J.; Mlodzinska, Z.J.; Hastings, M.E.; Seekins, B.A.

    2000-01-01

    The surficial sediment distribution within Long Island Sound has been mapped and described using bottom samples, photography, and sidescan sonar, combined with information from the geologic literature. The distributions of sediment type and total organic carbon (TOC) reveal several broad trends that are largely related to the sea-floor geology, the bathymetry, and the effects of modern tidal- and wind-driven currents. Sediment types are most heterogeneous in bathymetrically complex and shallow nearshore areas; the heterogeneity diminishes and the texture fines with decreasing bottom-current energy. Lag deposits of gravel and gravelly sand dominate the surficial sediment texture in areas where bottom currents are the strongest (such as where tidal flow is constricted) and where glacial till crops out at the sea floor. Sand is the dominant sediment type in areas characterized by active sediment transport and in shallow areas affected by fine-grained winnowing. Silty sand and sand-silt-clay mark transitions within the basin from higher- to lower-energy environments, suggesting a diminished hydraulic ability to sort and transport sediment. Clayey silt and silty clay are the dominant sediment types accumulating in the central and western basins and in other areas characterized by long-term depositional environments. The amount of TOC in the sediments of Long Island Sound varies inversely with sediment grain size. Concentrations average more than 1.9% (dry weight) in clayey silt, but are less than 0.4% in sand. Generally, values for TOC increase both toward the west in the Sound and from the shallow margins to the deeper parts of the basin floor. Our data also suggest that TOC concentrations can vary seasonally.

  10. Neutral atomic carbon in dense molecular clouds

    NASA Technical Reports Server (NTRS)

    Zmuidzinas, J.; Betz, A. L.; Boreiko, R. T.; Goldhaber, D. M.

    1988-01-01

    The 370 micron 3P2-3P1 fine-structure line of neutral carbon was detected in seven sources: OMC 1, NGC 2024, S140, W3, DR 21, M17, and W51. Simultaneous analysis of J = 2-1 data and available observations of the J = 1-0 line make it possible to deduce optical depths and excitation temperatures for these lines. These data indicate that both C I lines are likely to be optically thin, and that the ratio of C I to CO column densities in these clouds is typically about 0.1.

  11. Organic carbon cycling in sediments of the Changjiang Estuary and adjacent shelf: Implication for the influence of Three Gorges Dam

    NASA Astrophysics Data System (ADS)

    Li, Dong; Yao, Peng; Bianchi, Thomas S.; Zhang, Tingting; Zhao, Bin; Pan, Huihui; Wang, Jinpeng; Yu, Zhigang

    2014-11-01

    Surface sediments collected from the Changjiang Estuary and adjacent shelf were analyzed for elemental and stable carbon isotopic composition, and lignin-phenols to investigate spatial variability of the sources, transport and decay of sedimentary organic carbon (OC). Bulk and molecular proxy data indicated a mixed marine/terrestrial OC sources in the study area. A three end-member mixing model using Monte-Carlo simulation showed that marine OC was the predominant OC source, accounting for an increasing fraction along the coast and seaward, while soil-derived OC and C3 vascular plant detrital OC decreased seaward and southward. Large fragments of lignin-rich C3 vascular plant OC were deposited mainly near the river mouth, whereas fine-grained lignin-poor soil-derived OC was delivered further south alongshore. Higher values of lignin decay indices, seaward and southward, were attributed to selective transport of terrestrial OC on fine-grained particles and efficient remineralization in mobile muds. Λ8 of OC in Changjiang Estuary sediments has slightly decreased in recent years, which could in part be due to the trapping of terrestrial coarse particles by the Three Gorges Dam (TGD). Also, we propose that there has been an increasing input of phytodetritus derived from freshwater phytoplankton to coastal sediments after the construction of the TGD.

  12. Rhenium-catalysed dehydrogenative borylation of primary and secondary C(sp3)-H bonds adjacent to a nitrogen atom.

    PubMed

    Murai, Masahito; Omura, Tetsuya; Kuninobu, Yoichiro; Takai, Kazuhiko

    2015-03-18

    Rhenium-catalysed C(sp(3))-H bond borylation in the absence of any oxidant, hydrogen acceptor, or external ligand, with the generation of H2 as the sole byproduct is described. The transformation, which represents a rare example of rhenium-catalysed C(sp(3))-H bond functionalisation, features high atom efficiency and simple reaction conditions. PMID:25688385

  13. The atomic carbon distribution in the coma of Comet Halley

    NASA Technical Reports Server (NTRS)

    Woods, T. N.; Feldman, P. D.; Dymond, K. F.

    1986-01-01

    The radial distribution of CO, OI, Ci, and CII emissions in the coma of comet Halley were measured by a long-slit far ultraviolet spectrograph aboard a sounding rocket on 26 Feb. and 13 Mar. 1986. While the CO profiles strongly suggest that CO is vaporized directly from the nucleus, the observed carbon distribution is not consistent with a radial outflow model of CO, suggesting an additional source of atomic carbon in the inner coma. Based on the in situ plasma measurements from the Vega and Giotto spacecraft, it is possible that this additional source of carbon could be the recombination of ionized CO in the inner coma.

  14. Dielectric barrier discharge carbon atomic emission spectrometer: universal GC detector for volatile carbon-containing compounds.

    PubMed

    Han, Bingjun; Jiang, Xiaoming; Hou, Xiandeng; Zheng, Chengbin

    2014-01-01

    It was found that carbon atomic emission can be excited in low temperature dielectric barrier discharge (DBD), and an atmospheric pressure, low power consumption, and compact microplasma carbon atomic emission spectrometer (AES) was constructed and used as a universal and sensitive gas chromatographic (GC) detector for detection of volatile carbon-containing compounds. A concentric DBD device was housed in a heating box to increase the plasma operation temperature to 300 °C to intensify carbon atomic emission at 193.0 nm. Carbon-containing compounds directly injected or eluted from GC can be decomposed, atomized, and excited in this heated DBD for carbon atomic emission. The performance of this new optical detector was first evaluated by determination of a series of volatile carbon-containing compounds including formaldehyde, ethyl acetate, methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol, and absolute limits of detection (LODs) were found at a range of 0.12-0.28 ng under the optimized conditions. Preliminary experimental results showed that it provided slightly higher LODs than those obtained by GC with a flame ionization detector (FID). Furthermore, it is a new universal GC detector for volatile carbon-containing compounds that even includes those compounds which are difficult to detect by FID, such as HCHO, CO, and CO2. Meanwhile, hydrogen gas used in conventional techniques was eliminated; and molecular optical emission detection can also be performed with this GC detector for multichannel analysis to improve resolution of overlapped chromatographic peaks of complex mixtures. PMID:24328147

  15. Particulate organic matter composition and organic carbon flux in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

    NASA Astrophysics Data System (ADS)

    Zhu, Z.-Y.; Wu, Y.; Liu, S.-M.; Wenger, F.; Hu, J.; Zhang, J.; Zhang, R.-F.

    2015-09-01

    In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier-fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 μM, respectively, in August 2012. Amino acids (AAs) and phytoplankton pigments accounted for ~ 10 % of the particulate organic matter (POM) in the Bayelva River, while AAs represented > 90 % of particulate nitrogen in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounts for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for particulate nitrogen (PN) are much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29 × 106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6, 25 ± 5.6, and 4.7 ± 0.75 t, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02 × 106 t yr-1) and DOC (0.02 ± 0.01 × 106 t yr-1) fluxes of Svalbard glaciers are small compared with those of the Greenland Ice Sheet, the area-weighted POC flux of Svalbard glaciers is twice that of the Greenland Ice Sheet, while the flux of DOC can be 4 to 7 times higher. Therefore, we propose that valley glaciers are efficient high-latitude sources of organic carbon.

  16. Chemical control of electrical contact to sp2 carbon atoms

    PubMed Central

    Frederiksen, Thomas; Foti, Giuseppe; Scheurer, Fabrice; Speisser, Virginie; Schull, Guillaume

    2014-01-01

    Carbon-based nanostructures are attracting tremendous interest as components in ultrafast electronics and optoelectronics. The electrical interfaces to these structures play a crucial role for the electron transport, but the lack of control at the atomic scale can hamper device functionality and integration into operating circuitry. Here we study a prototype carbon-based molecular junction consisting of a single C60 molecule and probe how the electric current through the junction depends on the chemical nature of the foremost electrode atom in contact with the molecule. We find that the efficiency of charge injection to a C60 molecule varies substantially for the considered metallic species, and demonstrate that the relative strength of the metal-C bond can be extracted from our transport measurements. Our study further suggests that a single-C60 junction is a basic model to explore the properties of electrical contacts to meso- and macroscopic sp2 carbon structures. PMID:24736561

  17. Abundance of atomic carbon /C I/ in dense interstellar clouds

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.; Huggins, P. J.

    1981-01-01

    The abundance of interstellar neutral atomic carbon is investigated by means of its ground state fine-structure line emission at 492 GHz using the 91.5 cm telescope of NASAs Kuiper Airborne Observatory. Atomic carbon is found to be very abundant in dense interstellar molecular clouds with column densities of about 10 to the 19th per sq cm. Because the observations have considerably greater column densities than current theories of carbon chemistry, it is suggested that the physical conditions of these clouds are not as simple as assumed in the models. Various situations are discussed which would lead to large C I abundances, including the possibility that the chemical lifetimes of the clouds are relatively short.

  18. Integrated atom detector based on field ionization near carbon nanotubes

    SciTech Connect

    Gruener, B.; Jag, M.; Stibor, A.; Visanescu, G.; Haeffner, M.; Kern, D.; Guenther, A.; Fortagh, J.

    2009-12-15

    We demonstrate an atom detector based on field ionization and subsequent ion counting. We make use of field enhancement near tips of carbon nanotubes to reach extreme electrostatic field values of up to 9x10{sup 9} V/m, which ionize ground-state rubidium atoms. The detector is based on a carpet of multiwall carbon nanotubes grown on a substrate and used for field ionization, and a channel electron multiplier used for ion counting. We measure the field enhancement at the tips of carbon nanotubes by field emission of electrons. We demonstrate the operation of the field ionization detector by counting atoms from a thermal beam of a rubidium dispenser source. By measuring the ionization rate of rubidium as a function of the applied detector voltage we identify the field ionization distance, which is below a few tens of nanometers in front of nanotube tips. We deduce from the experimental data that field ionization of rubidium near nanotube tips takes place on a time scale faster than 10{sup -10} s. This property is particularly interesting for the development of fast atom detectors suitable for measuring correlations in ultracold quantum gases. We also describe an application of the detector as partial pressure gauge.

  19. Electroanalytical performance of carbon films with near-atomic flatness.

    PubMed

    Ranganathan, S; McCreery, R L

    2001-03-01

    Physicochemical and electrochemical characterization of carbon films obtained by pyrolyzing a commercially available photoresist has been performed. Photoresist spin-coated on to a silicon wafer was pyrolyzed at 1,000 degrees C in a reducing atmosphere (95% nitrogen and 5% hydrogen) to produce conducting carbon films. The pyrolyzed photoresist films (PPF) show unusual surface properties compared to other carbon electrodes. The surfaces are nearly atomically smooth with a root-mean-square roughness of <0.5 nm. PPF have a very low background current and oxygen/carbon atomic ratio compared to conventional glassy carbon and show relatively weak adsorption of methylene blue and anthraquinone-2,6-disulfonate. The low oxygen/carbon ratio and the relative stability of PPF indicate that surfaces may be partially hydrogen terminated. The pyrolyzed films were compared to glassy carbon (GC) heat treated under the same conditions as pyrolysis to evaluate the electroanalytical utility of PPF. Heterogeneous electron-transfer kinetics of various redox systems were evaluated. For Ru(NH3)6(3+/2+), Fe(CN)6(3-/4-), and chlorpromazine, fresh PPF surfaces show electron-transfer rates similar to those on GC, but for redox systems such as Fe3+/2+, ascorbic acid, dopamine, and oxygen, the kinetics on PPF are slower. Very weak interactions between the PPF surface and these redox systems lead to their slow electron-transfer kinetics. Electrochemical anodization results in a simultaneous increase in background current, adsorption, and electron-transfer kinetics. The PPF surfaces can be chemically modified via diazonium ion reduction to yield a covalently attached monolayer. Such a modification could help in the preparation of low-cost, high-volume analyte-specific electrodes for diverse electroanalytical applications. Overall, pyrolysis of the photoresist yields an electrode surface with properties similar to a very smooth version of glassy carbon, with some important differences in surface

  20. Encapsulating "armchair" carbon nanotubes with "zigzag" chains of Fe atoms

    NASA Astrophysics Data System (ADS)

    Boutko, V. G.; Gusev, A. A.; Shevtsova, T. N.; Pashkevich, Yu. G.

    2016-05-01

    Ab initio calculations of structural, electron, and magnetic properties of "armchair" carbon nanotubes (NT) encapsulated by a "zigzag" chain of Fe atoms Fe2@(n,n)m (m = 1, 2; n = 4, 5, 6, 7, 8, 9), are performed within the framework of the density functional theory. It is shown that optimizing the structure along the NT axis can significantly impact the binding energy of the NT and the Fe atom chain. It follows from the calculations that Fe2@(5,5) is the most stable of all the investigated encapsulated nanotubes. A two-fold decrease in the concentration of Fe in an encapsulated NT converts the system from exothermic to endothermic (Fe2@(5,5)m) and vice versa (Fe2@(6,6)m)). For large radii of an encapsulated NT (>4.13 Å) the binding energy of the NT and the Fe atom chain goes to zero, and the magnetic moments of the Fe atoms and the deviation of the Fe atoms from the NT axis go toward analogous values of the free "zigzag" Fe atom chain.

  1. Carbon nanotube forests growth using catalysts from atomic layer deposition

    SciTech Connect

    Chen, Bingan; Zhang, Can; Esconjauregui, Santiago; Xie, Rongsi; Zhong, Guofang; Robertson, John; Bhardwaj, Sunil; Cepek, Cinzia

    2014-04-14

    We have grown carbon nanotubes using Fe and Ni catalyst films deposited by atomic layer deposition. Both metals lead to catalytically active nanoparticles for growing vertically aligned nanotube forests or carbon fibres, depending on the growth conditions and whether the substrate is alumina or silica. The resulting nanotubes have narrow diameter and wall number distributions that are as narrow as those grown from sputtered catalysts. The state of the catalyst is studied by in-situ and ex-situ X-ray photoemission spectroscopy. We demonstrate multi-directional nanotube growth on a porous alumina foam coated with Fe prepared by atomic layer deposition. This deposition technique can be useful for nanotube applications in microelectronics, filter technology, and energy storage.

  2. Interpretation of Hund's multiplicity rule for the carbon atom.

    PubMed

    Hongo, Kenta; Maezono, Ryo; Kawazoe, Yoshiyuki; Yasuhara, Hiroshi; Towler, M D; Needs, R J

    2004-10-15

    Hund's multiplicity rule is investigated for the carbon atom using quantum Monte Carlo methods. Our calculations give an accurate account of electronic correlation and obey the virial theorem to high accuracy. This allows us to obtain accurate values for each of the energy terms and therefore to give a convincing explanation of the mechanism by which Hund's rule operates in carbon. We find that the energy gain in the triplet with respect to the singlet state is due to the greater electron-nucleus attraction in the higher spin state, in accordance with Hartree-Fock calculations and studies including correlation. The method used here can easily be extended to heavier atoms. PMID:15473780

  3. Probing the improbable: imaging carbon atoms in alumina

    SciTech Connect

    Marquis, E A; Yahia, Noor; Larson, David J.; Miller, Michael K; Todd, Richard

    2010-01-01

    Atom-probe tomography has proven very powerful to analyze the detailed structure and chemistry of metallic alloys and semiconductor structures while ceramic materials have remained outside its standard purview. In the current work, we demonstrate that bulk alumina can be quantitatively analyzed and microstructural features observed. The analysis of grain boundary carbon segregation - barely achievable by electron microscopy - opens the possibility of understanding the mechanistic effects of dopants on mechanical properties, fracture and wear properties of bulk oxides.

  4. Stability of conductance oscillations in carbon atomic chains

    NASA Astrophysics Data System (ADS)

    Yu, Jing-Xin; Hou, Zhi-Wei; Liu, Xiu-Ying

    2015-06-01

    The conductance stabilities of carbon atomic chains (CACs) with different lengths are investigated by performing theoretical calculations using the nonequilibrium Green’s function method combined with density functional theory. Regular even-odd conductance oscillation is observed as a function of the wire length. This oscillation is influenced delicately by changes in the end carbon or sulfur atoms as well as variations in coupling strength between the chain and leads. The lowest unoccupied molecular orbital in odd-numbered chains is the main transmission channel, whereas the conductance remains relatively small for even-numbered chains and a significant drift in the highest occupied molecular orbital resonance toward higher energies is observed as the number of carbon atoms increases. The amplitude of the conductance oscillation is predicted to be relatively stable based on a thiol joint between the chain and leads. Results show that the current-voltage evolution of CACs can be affected by the chain length. The differential and second derivatives of the conductance are also provided. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304079, 11404094, and 51201059), the Priority Scientific and Technological Project of Henan Province, China (Grant No. 14A140027), the School Fund (Grant No. 2012BS055), and the Plan of Natural Science Fundamental Research of Henan University of Technology, China (Grant No. 2014JCYJ15).

  5. Atom-scale insights into carbonate organic-mineral interfaces

    NASA Astrophysics Data System (ADS)

    Branson, O.; Perea, D. E.; Spero, H. J.; Winters, M. A.; Gagnon, A.

    2015-12-01

    Biominerals are formed by the complex interaction between guiding biological structures and the kinetics of inorganic mineral growth. Inorganic crystal growth experiments have advanced our understanding of mineral precipitation in the context of biological systems, but the structure and chemistry of the mineralizing interface between these two systems has remained elusive. We have used laser-pulsed Atom Probe Tomography to reveal the first atom-scale 3D view of an organic-mineral interface in calcite produced by the planktic foraminifera Orbulina universa. We observe elevated Na and Mg throughout the organic, and a 9-fold increase in Na in the surface 2 nm of the organic layer, relative to the adjacent calcite. The surface-specificity of this Na maximum suggests that Na may play an integral role in conditioning the organic layer for calcite nucleation. Na could accomplish this by modifying surface hydration or structure, to modify organic-fluid and/or organic-calcite interfacial energies. Our data constitute the first evidence of the role of 'spectator' ions in facilitating biomineralisation, which could be an overlooked but crucial aspect of the initial steps of skeleton formation in calcifying organisms.

  6. Voronoi analysis of the short–range atomic structure in iron and iron–carbon melts

    SciTech Connect

    Sobolev, Andrey; Mirzoev, Alexander

    2015-08-17

    In this work, we simulated the atomic structure of liquid iron and iron–carbon alloys by means of ab initio molecular dynamics. Voronoi analysis was used to highlight changes in the close environments of Fe atoms as carbon concentration in the melt increases. We have found, that even high concentrations of carbon do not affect short–range atomic order of iron atoms — it remains effectively the same as in pure iron melts.

  7. Spring Database for the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

    USGS Publications Warehouse

    Pavelko, Michael T.

    2007-01-01

    A database containing nearly 3,400 springs was developed for the Basin and Range carbonate-rock aquifer system study area in White Pine County, Nevada, and adjacent areas in Nevada and Utah. The spring database provides a foundation for field verification of springs in the study area. Attributes in the database include location, geographic and general geologic settings, and available discharge and temperature data for each spring.

  8. Current-induced dynamics in carbon atomic contacts

    PubMed Central

    Gunst, Tue

    2011-01-01

    Summary Background: The effect of electric current on the motion of atoms still poses many questions, and several mechanisms are at play. Recently there has been focus on the importance of the current-induced nonconservative forces (NC) and Berry-phase derived forces (BP) with respect to the stability of molecular-scale contacts. Systems based on molecules bridging electrically gated graphene electrodes may offer an interesting test-bed for these effects. Results: We employ a semi-classical Langevin approach in combination with DFT calculations to study the current-induced vibrational dynamics of an atomic carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed. Molecular dynamics including current-induced forces enables an energy redistribution mechanism among the modes, mediated by anharmonic interactions, which is found to be vital in the description of the electrical heating. Conclusion: We have developed a semiclassical Langevin equation approach that can be used to explore current-induced dynamics and instabilities. We find instabilities at experimentally relevant bias and gate voltages for the carbon-chain system. PMID:22259765

  9. Theoretical two-atom thick semiconducting carbon sheet.

    PubMed

    Hu, Meng; Shu, Yu; Cui, Lin; Xu, Bo; Yu, Dongli; He, Julong

    2014-09-14

    A two-dimensional carbon allotrope, H-net, is proposed using first principle calculations. H-net incorporates C4 distorted squares, C6 hexagons, and C8 octagons. Unlike previously reported planar graphene and other theoretical carbon sheets, H-net is a two-atom thick polymorph with identical C6 + C4 + C6 components cross-facing and covalently buckled to feature a handshake-like model. The feasibility of H-net is evident from its dynamic stability as confirmed by phonon-mode analysis and its lower total energy. H-net is energetically more favorable than synthesized graphdiyne and theoretical graphyne, BPC, S-graphene, polycyclic net, α-squarographite, and lithographite. We explored a possible route for the synthesis of H-net from graphene nanoribbons. Electronic band structure calculations indicated that H-net is a semiconductor with an indirect band gap of 2.11 eV, whereas graphene and many other two-dimensional carbon sheets are metallic. We also explored the electronic structure of one-dimensional nanoribbons derived from H-net. The narrowest H-net nanoribbon showed metallic behavior, whereas the other nanoribbons are semiconductors with band gaps that increase as the nanoribbons widen. H-net and its tailored nanoribbons are expected to possess more electronic properties than graphene because of their exceptional crystal structure and different energy band gaps. PMID:25053451

  10. Space-time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay and adjacent part of the Laptev Sea

    NASA Astrophysics Data System (ADS)

    Semiletov, I. P.; Shakhova, N. E.; Pipko, I. I.; Pugach, S. P.; Charkin, A. N.; Dudarev, O. V.; Kosmach, D. A.; Nishino, S.

    2013-09-01

    This study aims to improve understanding of carbon cycling in the Buor-Khaya Bay (BKB) and adjacent part of the Laptev Sea by studying the inter-annual, seasonal, and meso-scale variability of carbon and related hydrological and biogeochemical parameters in the water, as well as factors controlling carbon dioxide (CO2) emission. Here we present data sets obtained on summer cruises and winter expeditions during 12 yr of investigation. Based on data analysis, we suggest that in the heterotrophic BKB area, input of terrestrially borne organic carbon (OC) varies seasonally and inter-annually and is largely determined by rates of coastal erosion and river discharge. Two different BKB sedimentation regimes were revealed: Type 1 (erosion accumulation) and Type 2 (accumulation). A Type 1 sedimentation regime occurs more often and is believed to be the quantitatively most important mechanism for suspended particular matter (SPM) and particulate organic carbon (POC) delivery to the BKB. The mean SPM concentration observed in the BKB under a Type 1 regime was one order of magnitude greater than the mean concentration of SPM (~ 20 mg L-1) observed along the Lena River stream in summer 2003. Loadings of the BKB water column with particulate material vary by more than a factor of two between the two regimes. Higher partial pressure of CO2 (pCO2), higher concentrations of nutrients, and lower levels of oxygen saturation were observed in the bottom water near the eroded coasts, implying that coastal erosion and subsequent oxidation of eroded organic matter (OM) rather than the Lena River serves as the predominant source of nutrients to the BKB. Atmospheric CO2 fluxes from the sea surface in the BKB vary from 1 to 95 mmol m-2 day-1 and are determined by specific features of hydrology and wind conditions, which change spatially, seasonally, and inter-annually. Mean values of CO2 emission from the shallow Laptev Sea were similar in September 1999 and 2005 (7.2 and 7.8 mmol m-2 day-1

  11. The Relativistic Effects on the Carbon-Carbon Coupling Constants Mediated by a Heavy Atom.

    PubMed

    Wodyński, Artur; Malkina, Olga L; Pecul, Magdalena

    2016-07-21

    The (2)JCC, (3)JCC, and (4)JCC spin-spin coupling constants in the systems with a heavy atom (Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Bi, and Po) in the coupling path have been calculated by means of density functional theory. The main goal was to estimate the relativistic effects on spin-spin coupling constants and to explore the factors which may influence them, including the nature of the heavy atom and carbon hybridization. The methods applied range, in order of reduced complexity, from the Dirac-Kohn-Sham (DKS) method (density functional theory with four-component Dirac-Coulomb Hamiltonian), through DFT with two- and one-component zeroth-order regular approximation (ZORA) Hamiltonians, to scalar effective core potentials (ECPs) with the nonrelativistic Hamiltonian. The use of DKS and ZORA methods leads to very similar results, and small-core ECPs of the MDF and MWB variety reproduce correctly the scalar relativistic effects. Scalar relativistic effects usually are larger than the spin-orbit coupling effects. The latter tend to influence the most the coupling constants of the sp(3)-hybridized carbon atoms and in compounds of the p-block heavy atoms. Large spin-orbit coupling contributions for the Po compounds are probably connected with the inverse of the lowest triplet excitation energy. PMID:27177252

  12. The initial flow dynamics of light atoms through carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cannon, James; Kim, Daejoong; Hess, Ortwin

    2011-04-01

    Carbon nanotubes are becoming increasingly viable as membranes for application in a wide variety of nano-fluidic applications, such as nano-scale nozzles. For potential applications that utilize switching on and off of flow through nanotube nozzles, it is important to understand the initial flow dynamics. Furthermore, when the nanotube interacts strongly with the fluid, the flow may be very different from conventional simulations, which consider atoms (such as argon, for example) that interact only weakly with the nanotube. Therefore, to better understand such flows and explore the potential manipulation of flow that can be achieved, we consider the initial flow dynamics of a light fluid through carbon nanotube nozzles, using non-equilibrium molecular dynamics simulations. Our studies show that if the conditions are controlled carefully, unusual phenomena can be generated, such as pulsed flow and very nonlinear increases in flow rate with nanotube diameter. We detail the physical reasons for such phenomena and describe how the pulsation can be controlled using temperature.

  13. Relationships between pesticides and organic carbon fractions in sediments of the Danshui River estuary and adjacent coastal areas of Taiwan.

    PubMed

    Hung, Chin-Chang; Gong, Gwo-Ching; Chen, Hung-Yu; Hsieh, Hwey-Lian; Santschi, Peter H; Wade, Terry L; Sericano, Jose L

    2007-07-01

    In order to understand the fate of pesticides in marine environments, concentrations of pesticides and different carbonaceous fractions were determined for surface sediments in the Danshui River and nearby coastal areas of Taiwan. The major compounds detected were tetrachlorobenzene, HCHs, chlordane, aldrin, DDDs, DDEs and DDTs. Total concentrations of pesticides in the sediments ranged from not detectable to 23 ng g(-1), with the maximum value detected near the discharge point of the marine outfall from the Pali sewage treatment plant. These results confirm that pesticides persist in estuarine and nearby coastal environments of the Danshui River well after their ban. Concentrations of total pesticides significantly correlate with concentrations of total organic carbon and black carbon in these sediments, suggesting that total organic carbon and black carbon regulate the distribution of trace organic pollutants in fluvial and coastal marine sediments. PMID:17395347

  14. Comparison of Carbon Sequestration Rates and Energy Balance of Turf in the Denver Urban Ecosystem and an Adjacent Native Grassland

    NASA Astrophysics Data System (ADS)

    Thienelt, T. S.; Anderson, D. E.; Powell, K. M.

    2011-12-01

    Urban ecosystems are currently characterized by rapid growth, are expected to continually expand and, thus, represent an important driver of land use change. A significant component of urban ecosystems is lawns, potentially the single largest irrigated "crop" in the U.S. Beginning in March of 2011 (ahead of the growing season), eddy covariance measurements of net carbon exchange and evapotranspiration along with energy balance fluxes were conducted for a well-watered, fertilized lawn (rye-bluegrass-mix) in metropolitan Denver and for a nearby tallgrass prairie (big bluestem, switchgrass, cheatgrass, blue grama). Due to the semi-arid climate conditions of the Denver region, differences in management (i.e., irrigation and fertilization) are expected to have a discernible impact on ecosystem productivity and thus on carbon sequestration rates, evapotranspiration, and the sensible and latent heat partitioning of the energy balance. By mid-July, preliminary data indicated that cumulative evapotranspiration was approximately 270 mm and 170 mm for urban and native grasslands, respectively, although cumulative carbon sequestration at that time was similar for both (approximately 40 mg/m2). However, the pattern of carbon exchange differed between the grasslands. Both sites showed daily net uptake of carbon starting in late May, but the urban lawn displayed greater diurnal variability as well as greater uptake rates in general, especially following fertilization in mid-June. In contrast, the trend of carbon uptake at the prairie site was occasionally reversed following strong convective precipitation events, resulting in a temporary net release of carbon. The continuing acquisition of data and investigation of these relations will help us assess the potential impact of urban growth on regional carbon sequestration.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  16. Biofunctionalization of carbon nanotubes for atomic force microscopy imaging.

    PubMed

    Woolley, Adam T

    2004-01-01

    The study of biological processes relies increasingly on methods for probing structure and function of biochemical machinery (proteins, nucleic acids, and so on) with submolecular resolution. Atomic force microscopy (AFM) has recently emerged as a promising approach for imaging biological structures with resolution approaching the nanometer scale. Two important limitations of AFM in biological imaging are (1) resolution is constrained by probe tip dimensions, and (2) typical probe tips lack chemical specificity to differentiate between functional groups in biological structures. Single-walled carbon nanotubes (SWNTs) offer an intriguing possibility for providing both high resolution and chemical selectivity in AFM imaging, thus overcoming the enumerated limitations. Procedures for generating SWNT tips for AFM will be described. Carboxylic acid functional groups at the SWNT ends can be functionalized using covalent coupling chemistry to attach biological moieties via primary amine groups. Herein, the focus will be on describing methods for attaching biotin to SWNT tips and probing streptavidin on surfaces; importantly, this same coupling chemistry can also be applied to other biomolecules possessing primary amine groups. Underivatized SWNT tips can also provide high-resolution AFM images of DNA. Biofunctionalization of SWNT AFM tips offers great potential to enable high-resolution, chemically selective imaging of biological structures. PMID:15197321

  17. Site specific atomic polarizabilities in endohedral fullerenes and carbon onions

    SciTech Connect

    Zope, Rajendra R. Baruah, Tunna; Bhusal, Shusil; Basurto, Luis; Jackson, Koblar

    2015-08-28

    We investigate the polarizability of trimetallic nitride endohedral fullerenes by partitioning the total polarizability into site specific components. This analysis indicates that the polarizability of the endohedral fullerene is essentially due to the outer fullerene cage and has insignificant contribution from the encapsulated unit. Thus, the outer fullerene cages effectively shield the encapsulated clusters and behave like Faraday cages. The polarizability of endohedral fullerenes is slightly smaller than the polarizability of the corresponding bare carbon fullerenes. The application of the site specific polarizabilities to C{sub 60}@C{sub 240} and C{sub 60}@C{sub 180} onions shows that, compared to the polarizability of isolated C{sub 60} fullerene, the encapsulation of the C{sub 60} in C{sub 240} and C{sub 180} fullerenes reduces its polarizability by 75% and 83%, respectively. The differences in the polarizability of C{sub 60} in the two onions is a result of differences in the bonding (intershell electron transfer), fullerene shell relaxations, and intershell separations. The site specific analysis further shows that the outer atoms in a fullerene shell contribute most to the fullerene polarizability.

  18. Site specific atomic polarizabilities in endohedral fullerenes and carbon onions

    NASA Astrophysics Data System (ADS)

    Zope, Rajendra R.; Bhusal, Shusil; Basurto, Luis; Baruah, Tunna; Jackson, Koblar

    2015-08-01

    We investigate the polarizability of trimetallic nitride endohedral fullerenes by partitioning the total polarizability into site specific components. This analysis indicates that the polarizability of the endohedral fullerene is essentially due to the outer fullerene cage and has insignificant contribution from the encapsulated unit. Thus, the outer fullerene cages effectively shield the encapsulated clusters and behave like Faraday cages. The polarizability of endohedral fullerenes is slightly smaller than the polarizability of the corresponding bare carbon fullerenes. The application of the site specific polarizabilities to C60@C240 and C60@C180 onions shows that, compared to the polarizability of isolated C60 fullerene, the encapsulation of the C60 in C240 and C180 fullerenes reduces its polarizability by 75% and 83%, respectively. The differences in the polarizability of C60 in the two onions is a result of differences in the bonding (intershell electron transfer), fullerene shell relaxations, and intershell separations. The site specific analysis further shows that the outer atoms in a fullerene shell contribute most to the fullerene polarizability.

  19. Site specific atomic polarizabilities in endohedral fullerenes and carbon onions.

    PubMed

    Zope, Rajendra R; Bhusal, Shusil; Basurto, Luis; Baruah, Tunna; Jackson, Koblar

    2015-08-28

    We investigate the polarizability of trimetallic nitride endohedral fullerenes by partitioning the total polarizability into site specific components. This analysis indicates that the polarizability of the endohedral fullerene is essentially due to the outer fullerene cage and has insignificant contribution from the encapsulated unit. Thus, the outer fullerene cages effectively shield the encapsulated clusters and behave like Faraday cages. The polarizability of endohedral fullerenes is slightly smaller than the polarizability of the corresponding bare carbon fullerenes. The application of the site specific polarizabilities to C60@C240 and C60@C180 onions shows that, compared to the polarizability of isolated C60 fullerene, the encapsulation of the C60 in C240 and C180 fullerenes reduces its polarizability by 75% and 83%, respectively. The differences in the polarizability of C60 in the two onions is a result of differences in the bonding (intershell electron transfer), fullerene shell relaxations, and intershell separations. The site specific analysis further shows that the outer atoms in a fullerene shell contribute most to the fullerene polarizability. PMID:26328842

  20. Changes in Terrestrial Organic Carbon Delivery to the Colville River Delta and Adjacent Simpson's Lagoon Over the Late Holocene

    NASA Astrophysics Data System (ADS)

    Schreiner, K. M.; Bianchi, T. S.; Allison, M. A.; Miller, A. J.; Marcantonio, F.

    2012-04-01

    The Colville River in Alaska is the largest river in North America that drains only continuously permafrosted tundra, and as such provides a unique signal of historical changes in one of the world's most vulnerable areas to climate changes. Additionally, the Colville flows into Simpson's Lagoon, a shallow area of the Alaskan Beaufort coast protected by a barrier island chain, lessening the impacts of Arctic storms and ice grounding on sediment mixing. Cores collected from the Colville river delta in August of 2010 were found to be composed of muddy, organic-rich, well-laminated sediments. The 2.5 to 3 meter length of each core spans about one to two thousand years of Holocene history, including the entire Anthropocene and much of the late Holocene. Three cores were sampled for this data set, arranged latitudinally from the mouth of the Colville River east into Simpson's Lagoon. Samples were taken every 2 cm for the entire length of all cores. Bulk analyses including percent organic carbon, percent nitrogen, and stable carbon isotopic analysis were performed, and compound specific analyses including lignin-phenol and algal pigment analyses were performed. These analyses showed significant changes in carbon storage over the past one to two thousand years. There were also significant spatial differences in organic carbon inputs across the ~20km distance between the Colville mouth and the easternmost core. Lignin-phenol concentrations in surface sediments nearest to the river mouth correlated positively with reconstructed Alaskan North Slope temperatures, suggesting more terrestrial organic matter was delivered during higher temperature regimes. Molar C:N ratios and plant pigments correlated negatively and positively, respectively, with reconstructed Alaskan North Slope moisture regime, indicating greater algal inputs during wetter time periods. These data may in part be consistent with observed woody shrub encroachment and increasing expanse of permafrost lakes on the

  1. Effects of Bromus tectorum invasion on microbial carbon and nitrogen cycling in two adjacent undisturbed arid grassland communities

    USGS Publications Warehouse

    Schaeffer, Sean M.; Ziegler, Susan E.; Belnap, Jayne; Evans, R.D.

    2012-01-01

    Soil nitrogen (N) is an important component in maintaining ecosystem stability, and the introduction of non-native plants can alter N cycling by changing litter quality and quantity, nutrient uptake patterns, and soil food webs. Our goal was to determine the effects of Bromus tectorum (C3) invasion on soil microbial N cycling in adjacent non-invaded and invaded C3 and C4 native arid grasslands. We monitored resin-extractable N, plant and soil δ13C and δ15N, gross rates of inorganic N mineralization and consumption, and the quantity and isotopic composition of microbial phospholipid biomarkers. In invaded C3 communities, labile soil organic N and gross and net rates of soil N transformations increased, indicating an increase in overall microbial N cycling. In invaded C4 communities labile soil N stayed constant, but gross N flux rates increased. The δ13C of phospholipid biomarkers in invaded C4 communities showed that some portion of the soil bacterial population preferentially decomposed invader C3-derived litter over that from the native C4 species. Invasion in C4 grasslands also significantly decreased the proportion of fungal to bacterial phospholipid biomarkers. Different processes are occurring in response to B. tectorum invasion in each of these two native grasslands that: 1) alter the size of soil N pools, and/or 2) the activity of the microbial community. Both processes provide mechanisms for altering long-term N dynamics in these ecosystems and highlight how multiple mechanisms can lead to similar effects on ecosystem function, which may be important for the construction of future biogeochemical process models.

  2. Carbon fiber CVD coating by carbon nanostructured for space materials protection against atomic oxygen

    NASA Astrophysics Data System (ADS)

    Pastore, Roberto; Bueno Morles, Ramon; Micheli, Davide

    2016-07-01

    , by the purpose to integrate the carbon nanostructures in the carbon fibers by means of chemical vapor deposition (CVD) method, in order to develop the basic substrate of advanced carbon-based nanocomposite for atomic oxygen protection. The nanostructures grown onto the carbon fibers can be used to create multiscale hybrid carbon nanotube/carbon fiber composites where individual carbon fibers, which are several microns in diameter, are surrounded by nanotubes. The present objective is the setting-up of the CVD parameters for a reliable growth of carbon nanostructures on carbon fiber surface; after that, the results of a preliminary characterization related to atomic oxygen effects testing by means of a ground LEO simulation facility are reported and discussed.

  3. Carbon Nanotube Atomic Force Microscopy for Proteomics and Biological Forensics

    SciTech Connect

    Noy, A; De Yoreo, J J; Malkin, A J

    2002-01-01

    The Human Genome Project was focused on mapping the complete genome. Yet, understanding the structure and function of the proteins expressed by the genome is the real end game. But there are approximately 100,000 proteins in the human body and the atomic structure has been determined for less than 1% of them. Given the current rate at which structures are being solved, it will take more than one hundred years to complete this task. The rate-limiting step in protein structure determination is the growth of high-quality single crystals for X-ray diffraction. Synthesis of the protein stock solution as well as X-ray diffraction and analysis can now often be done in a matter of weeks, but developing a recipe for crystallization can take years and, especially in the case of membrane proteins, is often completely unsuccessful. Consequently, techniques that can either help to elucidate the factors controlling macromolecular crystallization, increase the amount of structural information obtained from crystallized macromolecules or eliminate the need for crystallization altogether are of enormous importance. In addition, potential applications for those techniques extend well beyond the challenges of proteomics. The global spread of modern technology has brought with it an increasing threat from biological agents such as viruses. As a result, developing techniques for identifying and understanding the operation of such agents is becoming a major area of forensic research for DOE. Previous to this project, we have shown that we can use in situ atomic force microscopy (AFM) to image the surfaces of growing macromolecular crystals with molecular resolution (1-5) In addition to providing unprecedented information about macromolecular nucleation, growth and defect structure, these results allowed us to obtain low-resolution phase information for a number of macromolecules, providing structural information that was not obtainable from X-ray diffraction(3). For some virus systems

  4. Controls on suspended sediment, particulate and dissolved organic carbon export from two adjacent catchments with contrasting land-uses, Exmoor UK.

    NASA Astrophysics Data System (ADS)

    Glendell, M.; Brazier, R. E.

    2012-04-01

    The fluvial export of total organic carbon (particulate and dissolved) plays an important role in the transportation of organic carbon from terrestrial to aquatic ecosystems, with implications for the understanding of the global carbon cycle and calculations of regional carbon budgets. The terrestrial biosphere contains large amounts of stored carbon in the soil and vegetation, thus a small change in the terrestrial carbon pool may have significant implications for atmospheric CO2 concentrations. Since the onset of agriculture, human activities have accelerated soil erosion rates 10- to 100- fold above all estimated natural background levels, especially in the uplands and at lower latitudes, whilst increasing DOC concentrations over the past decades have been reported in rivers across Western Europe and North America, raising concerns about potential destabilisation of the terrestrial soil carbon pool. The increased input of fine sediment and organic carbon into aquatic environments is also an important factor in stream water quality, being responsible for direct ecological effects as well as transport of a range of contaminants. Many factors, such as topography, hydrological regime and vegetation are known to influence the fluvial export of carbon from catchments. However, most work to date has focused on DOC losses from either forested or peaty catchments, with only limited studies examining the controls and rates of TOC (dissolved and particulate) fluxes from agricultural catchments, particularly during flood events. This research aims to: • Quantify the fluxes of total suspended sediment, total dissolved and total particulate carbon in two adjacent catchments with contrasting land-uses and • Examine the controlling factors of total fluvial carbon fluxes in a semi-natural and agricultural catchment in order to assess the impact of agricultural land-use on fluvial carbon export. The two contrasting study catchments (the Aller and Horner), in south

  5. Carbon-14 terrestrial ages and weathering of 27 meteorites from the southern high plains and adjacent areas (USA)

    NASA Technical Reports Server (NTRS)

    Jull, A. J. T.; Donahue, D. J.; Cielaszyk, E.; Wlotzka, F.

    1993-01-01

    We report on a series of 27 C-14 terrestrial ages of meteorites from four states in the central and southwestern U.S. These results were compared to the earlier work of Boeckl (1972). Our results showed that the weathering rate for destruction of meteorites is lower than suggested by Boeckl. We estimate a 'half-life' for removal of meteorites of about 10 to 15 ka, similar to that derived for Roosevelt County meteorites. We also studied the weathering of these meteorites compared to terrestrial age. Only a weak correlation was observed, and for these meteorites the degree of weathering can only be taken as a weak indicator of terrestrial residence time. We also measured the delta-C-13 and C-14 and amount of weathering-product carbonates which show some interesting variations with the length of time the meteorites have been exposed to weathering.

  6. Dynamics of carbon-hydrogen and carbon-methyl exchanges in the collision of 3P atomic carbon with propene

    NASA Astrophysics Data System (ADS)

    Lee, Shih-Huang; Chen, Wei-Kan; Chin, Chih-Hao; Huang, Wen-Jian

    2013-11-01

    We investigated the dynamics of the reaction of 3P atomic carbon with propene (C3H6) at reactant collision energy 3.8 kcal mol-1 in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. Products C4H5, C4H4, C3H3, and CH3 were observed and attributed to exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3; their translational-energy distributions and angular distributions were derived from the measurements of product time-of-flight spectra. Following the addition of a 3P carbon atom to the C=C bond of propene, cyclic complex c-H2C(C)CHCH3 undergoes two separate stereoisomerization mechanisms to form intermediates E- and Z-H2CCCHCH3. Both the isomers of H2CCCHCH3 in turns decompose to C4H5 + H and C3H3 + CH3. A portion of C4H5 that has enough internal energy further decomposes to C4H4 + H. The three exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3 have average translational energy releases 13.5, 3.2, and 15.2 kcal mol-1, respectively, corresponding to fractions 0.26, 0.41, and 0.26 of available energy deposited to the translational degrees of freedom. The H-loss and 2H-loss channels have nearly isotropic angular distributions with a slight preference at the forward direction particularly for the 2H-loss channel. In contrast, the CH3-loss channel has a forward and backward peaked angular distribution with an enhancement at the forward direction. Comparisons with reactions of 3P carbon atoms with ethene, vinyl fluoride, and vinyl chloride are stated.

  7. Surface reactions of molecular and atomic oxygen with carbon phosphide films.

    PubMed

    Gorham, Justin; Torres, Jessica; Wolfe, Glenn; d'Agostino, Alfred; Fairbrother, D Howard

    2005-11-01

    The surface reactions of atomic and molecular oxygen with carbon phosphide films have been studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Carbon phosphide films were produced by ion implantation of trimethylphosphine into polyethylene. Atmospheric oxidation of carbon phosphide films was dominated by phosphorus oxidation and generated a carbon-containing phosphate surface film. This oxidized surface layer acted as an effective diffusion barrier, limiting the depth of phosphorus oxidation within the carbon phosphide film to < 3 nm. The effect of atomic oxygen (AO) exposure on this oxidized carbon phosphide layer was subsequently probed in situ using XPS. Initially AO exposure resulted in a loss of carbon atoms from the surface, but increased the surface concentration of phosphorus atoms as well as the degree of phosphorus oxidation. For more prolonged AO exposures, a highly oxidized phosphate surface layer formed that appeared to be inert toward further AO-mediated erosion. By utilizing phosphorus-containing hydrocarbon thin films, the phosphorus oxides produced during exposure to AO were found to desorb at temperatures >500 K under vacuum conditions. Results from this study suggest that carbon phosphide films can be used as AO-resistant surface coatings on polymers. PMID:16853637

  8. A simple and clean source of low-energy atomic carbon

    SciTech Connect

    Krasnokutski, S. A.; Huisken, F.

    2014-09-15

    A carbon source emitting low-energy carbon atoms from a thin-walled, sealed tantalum tube via thermal evaporation has been constructed. The tube is made from a 0.05 mm thick tantalum foil and filled with {sup 12}C or {sup 13}C carbon powder. After being sealed, it is heated by direct electric current. The solvated carbon atoms diffuse to the outer surface of the tube and, when the temperature rises over 2200 K, the evaporation of atomic carbon from the surface of the tantalum tube is observed. As the evaporated species have low energy they are well-suited for the incorporation into liquid helium droplets by the pick-up technique. Mass analysis of the incorporated species reveals the dominant presence of atomic carbon and very low abundances of C{sub 2} and C{sub 3} molecules (<1%). This is in striking contrast to the thermal evaporation of pure carbon, where C{sub 3} molecules are found to be the dominant species in the gas phase. Due to the thermal evaporation and the absence of high-energy application required for the dissociation of C{sub 2} and C{sub 3} molecules, the present source provides carbon atoms with rather low energy.

  9. Effects of Atomic-Scale Structure on the Fracture Properties of Amorphous Carbon - Carbon Nanotube Composites

    NASA Technical Reports Server (NTRS)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2015-01-01

    The fracture of carbon materials is a complex process, the understanding of which is critical to the development of next generation high performance materials. While quantum mechanical (QM) calculations are the most accurate way to model fracture, the fracture behavior of many carbon-based composite engineering materials, such as carbon nanotube (CNT) composites, is a multi-scale process that occurs on time and length scales beyond the practical limitations of QM methods. The Reax Force Field (ReaxFF) is capable of predicting mechanical properties involving strong deformation, bond breaking and bond formation in the classical molecular dynamics framework. This has been achieved by adding to the potential energy function a bond-order term that varies continuously with distance. The use of an empirical bond order potential, such as ReaxFF, enables the simulation of failure in molecular systems that are several orders of magnitude larger than would be possible in QM techniques. In this work, the fracture behavior of an amorphous carbon (AC) matrix reinforced with CNTs was modeled using molecular dynamics with the ReaxFF reactive forcefield. Care was taken to select the appropriate simulation parameters, which can be different from those required when using traditional fixed-bond force fields. The effect of CNT arrangement was investigated with three systems: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. For each arrangement, covalent bonds are added between the CNTs and AC, with crosslink fractions ranging from 0-25% of the interfacial CNT atoms. The SWNT and MWNT array systems represent ideal cases with evenly spaced CNTs; the SWNT bundle system represents a more realistic case because, in practice, van der Waals interactions lead to the agglomeration of CNTs into bundles. The simulation results will serve as guidance in setting experimental processing conditions to optimize the mechanical properties of CNT

  10. Structure and stability of a silicon cluster on sequential doping with carbon atoms

    NASA Astrophysics Data System (ADS)

    AzeezullaNazrulla, Mohammed; Joshi, Krati; Israel, S.; Krishnamurty, Sailaja

    2016-02-01

    SiC is a highly stable material in bulk. On the other hand, alloys of silicon and carbon at nanoscale length are interesting from both technological as well fundamental view point and are being currently synthesized by various experimental groups (Truong et. al., 2015 [26]). In the present work, we identify a well-known silicon cluster viz., Si10 and dope it sequentially with carbon atoms. The evolution of electronic structure (spin state and the structural properties) on doping, the charge redistribution and structural properties are analyzed. It is interesting to note that the ground state SiC clusters prefer to be in the lowest spin state. Further, it is seen that carbon atoms are the electron rich centres while silicon atoms are electron deficient in every SiC alloy cluster. The carbon-carbon bond lengths in alloy clusters are equivalent to those seen in fullerene molecules. Interestingly, the carbon atoms tend to aggregate together with silicon atoms surrounding them by donating the charge. As a consequence, very few Si-Si bonds are noted with increasing concentrations of C atoms in a SiC alloy. Physical and chemical stability of doped clusters is studied by carrying out finite temperature behaviour and adsorbing O2 molecule on Si9C and Si8C2 clusters, respectively.

  11. Carbon fiber CVD coating by carbon nanostructured for space materials protection against atomic oxygen

    NASA Astrophysics Data System (ADS)

    Pastore, Roberto; Bueno Morles, Ramon; Micheli, Davide

    2016-07-01

    In recent years, the emphasis in space research has been shifting from space exploration to commercialization of space. In order to utilize space for commercial purposes it is necessary to understand the low earth orbit (LEO) space environment where most of the activities will be carried out. The studies on the LEO environment are mainly focused towards understanding the effect of atomic oxygen (AO) on spacecraft materials. In the first few shuttle flights, materials looked frosty because they were actually being eroded and textured: AO reacts with organic materials on spacecraft exteriors, gradually damaging them. When a spacecraft travel in LEO (where crewed vehicles and the International Space Station fly), the AO formed from the residual atmosphere can react with the spacecraft surfaces, causing damage to the vehicle. Polymers are widely used in space vehicles and systems as structural materials, thermal blankets, thermal control coatings, conformal coatings, adhesives, lubricants, etc. Exposure of polymers and composites to the space environment may result in different detrimental effects via modification of their chemical, electrical, thermal, optical and mechanical properties as well as surface erosion. The major degradation effects in polymers are due to their exposure to atomic oxygen, vacuum ultraviolet and synergistic effects, which result in different damaging effects by modification of the polymer's chemical properties. In hydrocarbon containing polymers the main AO effect is the surface erosion via chemical reactions and the release of volatile reaction products associated with the mass loss. The application of a thin protective coating to the base materials is one of the most commonly used methods of preventing AO degradation. The purpose is to provide a barrier between base material and AO environment or, in some cases, to alter AO reactions to inhibit its diffusion. The effectiveness of a coating depends on its continuity, porosity, degree of

  12. Plasmon enhanced Raman scattering effect for an atom near a carbon nanotube.

    PubMed

    Bondarev, I V

    2015-02-23

    Quantum electrodynamics theory of the resonance Raman scattering is developed for an atom in a close proximity to a carbon nanotube. The theory predicts a dramatic enhancement of the Raman intensity in the strong atomic coupling regime to nanotube plasmon near-fields. This resonance scattering is a manifestation of the general electromagnetic surface enhanced Raman scattering effect, and can be used in designing efficient nanotube based optical sensing substrates for single atom detection, precision spontaneous emission control, and manipulation. PMID:25836436

  13. Ultralow nanoscale wear through atom-by-atom attrition in silicon-containing diamond-like carbon.

    PubMed

    Bhaskaran, Harish; Gotsmann, Bernd; Sebastian, Abu; Drechsler, Ute; Lantz, Mark A; Despont, Michel; Jaroenapibal, Papot; Carpick, Robert W; Chen, Yun; Sridharan, Kumar

    2010-03-01

    Understanding friction and wear at the nanoscale is important for many applications that involve nanoscale components sliding on a surface, such as nanolithography, nanometrology and nanomanufacturing. Defects, cracks and other phenomena that influence material strength and wear at macroscopic scales are less important at the nanoscale, which is why nanowires can, for example, show higher strengths than bulk samples. The contact area between the materials must also be described differently at the nanoscale. Diamond-like carbon is routinely used as a surface coating in applications that require low friction and wear because it is resistant to wear at the macroscale, but there has been considerable debate about the wear mechanisms of diamond-like carbon at the nanoscale because it is difficult to fabricate diamond-like carbon structures with nanoscale fidelity. Here, we demonstrate the batch fabrication of ultrasharp diamond-like carbon tips that contain significant amounts of silicon on silicon microcantilevers for use in atomic force microscopy. This material is known to possess low friction in humid conditions, and we find that, at the nanoscale, it is three orders of magnitude more wear-resistant than silicon under ambient conditions. A wear rate of one atom per micrometre of sliding on SiO(2) is demonstrated. We find that the classical wear law of Archard does not hold at the nanoscale; instead, atom-by-atom attrition dominates the wear mechanisms at these length scales. We estimate that the effective energy barrier for the removal of a single atom is approximately 1 eV, with an effective activation volume of approximately 1 x 10(-28) m. PMID:20118919

  14. STEM Imaging of Single Pd Atoms in Activated Carbon Fibers Considered for Hydrogen Storage

    SciTech Connect

    Van Benthem, Klaus; Bonifacio, Cecile S; Contescu, Cristian I; Pennycook, Stephen J; Gallego, Nidia C

    2011-01-01

    Aberration corrected scanning transmission electron microscopy was used to demonstrate the feasibility of imaging individual Pd atoms that are highly dispersed throughout the volume of activated carbon fibers. Simultaneous acquisition of high-angle annular dark-field and bright-field images allows correlation of the location of single Pd atoms with microstructural features of the carbon host material. Sub-Angstrom imaging conditions revealed that 18 wt% of the total Pd content is dispersed as single Pd atoms in three re-occurring local structural arrangements. The identified structural configurations may represent effective storage sites for molecular hydrogen through Kubas complex formation as discussed in detail in the preceding article.

  15. Atomic carbon emission from photodissociation of CO2. [planetary atmospheric chemistry

    NASA Technical Reports Server (NTRS)

    Wu, C. Y. R.; Phillips, E.; Lee, L. C.; Judge, D. L.

    1978-01-01

    Atomic carbon fluorescence, C I 1561, 1657, and 1931 A, has been observed from photodissociation of CO2, and the production cross sections have been measured. A line emission source provided the primary photons at wavelengths from threshold to 420 A. The present results suggest that the excited carbon atoms are produced by total dissociation of CO2 into three atoms. The cross sections for producing the O I 1304-A fluorescence through photodissociation of CO2 are found to be less than 0.01 Mb in the wavelength region from 420 to 835 A. The present data have implications with respect to photochemical processes in the atmospheres of Mars and Venus.

  16. Synthetic Strategies toward Natural Products Containing Contiguous Stereogenic Quaternary Carbon Atoms.

    PubMed

    Büschleb, Martin; Dorich, Stéphane; Hanessian, Stephen; Tao, Daniel; Schenthal, Kyle B; Overman, Larry E

    2016-03-18

    Strategies for the total synthesis of complex natural products that contain two or more contiguous stereogenic quaternary carbon atoms in their intricate structures are reviewed with 12 representative examples. Emphasis has been put on methods to create quaternary carbon stereocenters, including syntheses of the same natural product by different groups, thereby showcasing the diversity of thought and individual creativity. A compendium of selected natural products containing two or more contiguous stereogenic quaternary carbon atoms and key reactions in their total or partial syntheses is provided in the Supporting Information. PMID:26836448

  17. Atomic Layer Deposition on Carbon Nanotubes and their Assemblies

    NASA Astrophysics Data System (ADS)

    Stano, Kelly Lynn

    Global issues related to energy and the environment have motivated development of advanced material solutions outside of traditional metals ceramics, and polymers. Taking inspiration from composites, where the combination of two or more materials often yields superior properties, the field of organic-inorganic hybrids has recently emerged. Carbon nanotube (CNT)-inorganic hybrids have drawn widespread and increasing interest in recent years due to their multifunctionality and potential impact across several technologically important application areas. Before the impacts of CNT-inorganic hybrids can be realized however, processing techniques must be developed for their scalable production. Optimization in chemical vapor deposition (CVD) methods for synthesis of CNTs and vertically aligned CNT arrays has created production routes both high throughput and economically feasible. Additionally, control of CVD parameters has allowed for growth of CNT arrays that are able to be drawn into aligned sheets and further processed to form a variety of aligned 1, 2, and 3-dimensional bulk assemblies including ribbons, yarns, and foams. To date, there have only been a few studies on utilizing these bulk assemblies for the production of CNT-inorganic hybrids. Wet chemical methods traditionally used for fabricating CNT-inorganic hybrids are largely incompatible with CNT assemblies, since wetting and drying the delicate structures with solvents can destroy their structure. It is therefore necessary to investigate alternative processing strategies in order to advance the field of CNT-inorganic hybrids. In this dissertation, atomic layer deposition (ALD) is evaluated as a synthetic route for the production of large-scale CNT-metal oxide hybrids as well as pure metal oxide architectures utilizing CNT arrays, ribbons, and ultralow density foams as deposition templates. Nucleation and growth behavior of alumina was evaluated as a function of CNT surface chemistry. While highly graphitic

  18. Study on nitrogen doped carbon atom chains with negative differential resistance effect

    NASA Astrophysics Data System (ADS)

    Shen, Ji-Mei; Liu, Jing; Min, Yi; Zhou, Li-Ping

    2016-05-01

    Recent calculations (Mahmoud and Lugli, 2013, [21]) of gold leads sandwiching carbon chains which are separated by diphenyl-dimethyl demonstrated that the negative differential resistance (NDR) effect appears only for "odd" numbers of carbon atoms. In this paper, according to a first-principles study based on non-equilibrium Green's function combining density functional theory, we find that the NDR effect appears both for "odd" and for "even" numbers of carbon atoms when the chains are doped by nitrogen atom. Our calculations remove the restriction of "odd/even" chains for the NDR effect, which may promise the potential applications of carbon chains in the nano-scale or molecular devices in the future.

  19. A nine-atom rhodium–aluminum oxide cluster oxidizes five carbon monoxide molecules

    PubMed Central

    Li, Xiao-Na; Zhang, Hua-Min; Yuan, Zhen; He, Sheng-Gui

    2016-01-01

    Noble metals can promote the direct participation of lattice oxygen of very stable oxide materials such as aluminum oxide, to oxidize reactant molecules, while the fundamental mechanism of noble metal catalysis is elusive. Here we report that a single atom of rhodium, a powerful noble metal catalyst, can promote the transfer of five oxygen atoms to oxidize carbon monoxide from a nine-atom rhodium–aluminum oxide cluster. This is a sharp improvement in the field of cluster science where the transfer of at most two oxygen atoms from a doped cluster is more commonly observed. Rhodium functions not only as the preferred trapping site to anchor and oxidize carbon monoxide by the oxygen atoms in direct connection with rhodium but also the primarily oxidative centre to accumulate the large amounts of electrons and the polarity of rhodium is ultimately transformed from positive to negative. PMID:27094921

  20. Optically promoted bipartite atomic entanglement in hybrid metallic carbon nanotube systems

    SciTech Connect

    Gelin, M. F.; Bondarev, I. V.; Meliksetyan, A. V.

    2014-02-14

    We study theoretically a pair of spatially separated extrinsic atomic type species (extrinsic atoms, ions, molecules, or semiconductor quantum dots) near a metallic carbon nanotube, that are coupled both directly via the inter-atomic dipole-dipole interactions and indirectly by means of the virtual exchange by resonance plasmon excitations on the nanotube surface. We analyze how the optical preparation of the system by using strong laser pulses affects the formation and evolution of the bipartite atomic entanglement. Despite a large number of possible excitation regimes and evolution pathways, we find a few generic scenarios for the bipartite entanglement evolution and formulate practical recommendations on how to optimize and control the robust bipartite atomic entanglement in hybrid carbon nanotube systems.

  1. A nine-atom rhodium-aluminum oxide cluster oxidizes five carbon monoxide molecules.

    PubMed

    Li, Xiao-Na; Zhang, Hua-Min; Yuan, Zhen; He, Sheng-Gui

    2016-01-01

    Noble metals can promote the direct participation of lattice oxygen of very stable oxide materials such as aluminum oxide, to oxidize reactant molecules, while the fundamental mechanism of noble metal catalysis is elusive. Here we report that a single atom of rhodium, a powerful noble metal catalyst, can promote the transfer of five oxygen atoms to oxidize carbon monoxide from a nine-atom rhodium-aluminum oxide cluster. This is a sharp improvement in the field of cluster science where the transfer of at most two oxygen atoms from a doped cluster is more commonly observed. Rhodium functions not only as the preferred trapping site to anchor and oxidize carbon monoxide by the oxygen atoms in direct connection with rhodium but also the primarily oxidative centre to accumulate the large amounts of electrons and the polarity of rhodium is ultimately transformed from positive to negative. PMID:27094921

  2. Direct chemical conversion of graphene to boron- and nitrogen- and carbon-containing atomic layers

    NASA Astrophysics Data System (ADS)

    Gong, Yongji; Shi, Gang; Zhang, Zhuhua; Zhou, Wu; Jung, Jeil; Gao, Weilu; Ma, Lulu; Yang, Yang; Yang, Shubin; You, Ge; Vajtai, Robert; Xu, Qianfan; MacDonald, Allan H.; Yakobson, Boris I.; Lou, Jun; Liu, Zheng; Ajayan, Pulickel M.

    2014-01-01

    Graphene and hexagonal boron nitride are typical conductor and insulator, respectively, while their hybrids hexagonal boron carbonitride are promising as a semiconductor. Here we demonstrate a direct chemical conversion reaction, which systematically converts the hexagonal carbon lattice of graphene to boron nitride, making it possible to produce uniform boron nitride and boron carbonitride structures without disrupting the structural integrity of the original graphene templates. We synthesize high-quality atomic layer films with boron-, nitrogen- and carbon-containing atomic layers with full range of compositions. Using this approach, the electrical resistance, carrier mobilities and bandgaps of these atomic layers can be tuned from conductor to semiconductor to insulator. Combining this technique with lithography, local conversion could be realized at the nanometre scale, enabling the fabrication of in-plane atomic layer structures consisting of graphene, boron nitride and boron carbonitride. This is a step towards scalable synthesis of atomically thin two-dimensional integrated circuits.

  3. Diamond like carbon coatings: Categorization by atomic number density

    NASA Technical Reports Server (NTRS)

    Angus, John C.

    1986-01-01

    Dense diamond-like hydrocarbon films grown at the NASA Lewis Research Center by radio frequency self bias discharge and by direct ion beam deposition were studied. A new method for categorizing hydrocarbons based on their atomic number density and elemental composition was developed and applied to the diamond-like hydrocarbon films. It was shown that the diamond-like hydrocarbon films are an entirely new class of hydrocarbons with atomic number densities lying between those of single crystal diamond and adamantanes. In addition, a major review article on these new materials was completed in cooperation with NASA Lewis Research Center personnel.

  4. Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah - Draft Report

    USGS Publications Warehouse

    Welch, Alan H., (Edited By); Bright, Daniel J.

    2007-01-01

    Summary of Major Findings This report summarizes results of a water-resources study for White Pine County, Nevada, and adjacent areas in east-central Nevada and western Utah. The Basin and Range carbonate-rock aquifer system (BARCAS) study was initiated in December 2004 through Federal legislation (Section 131 of the Lincoln County Conservation, Recreation, and Development Act of 2004) directing the Secretary of the Interior to complete a water-resources study through the U.S. Geological Survey, Desert Research Institute, and State of Utah. The study was designed as a regional water-resource assessment, with particular emphasis on summarizing the hydrogeologic framework and hydrologic processes that influence ground-water resources. The study area includes 13 hydrographic areas that cover most of White Pine County; in this report however, results for the northern and central parts of Little Smoky Valley were combined and presented as one hydrographic area. Hydrographic areas are the basic geographic units used by the State of Nevada and Utah and local agencies for water-resource planning and management, and are commonly defined on the basis of surface-water drainage areas. Hydrographic areas were further divided into subbasins that are separated by areas where bedrock is at or near the land surface. Subbasins represent subdivisions used in this study for estimating recharge, discharge, and water budget. Hydrographic areas represent the subdivision used for reporting summed and tabulated subbasin estimates.

  5. Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

    USGS Publications Warehouse

    Welch, Alan H., (Edited By); Bright, Daniel J.; Knochenmus, Lari A.

    2008-01-01

    INTRODUCTION This report summarizes results of a water-resources study for White Pine County, Nevada, and adjacent areas in east-central Nevada and western Utah. The Basin and Range carbonate-rock aquifer system (BARCAS) study was initiated in December 2004 through Federal legislation (Section 301(e) of the Lincoln County Conservation, Recreation, and Development Act of 2004; PL108-424) directing the Secretary of the Interior to complete a water-resources study through the U.S. Geological Survey, Desert Research Institute, and State of Utah. The study was designed as a regional water-resource assessment, with particular emphasis on summarizing the hydrogeologic framework and hydrologic processes that influence ground-water resources. The study area includes 13 hydrographic areas that cover most of White Pine County; in this report however, results for the northern and central parts of Little Smoky Valley were combined and presented as one hydrographic area. Hydrographic areas are the basic geographic units used by the State of Nevada and Utah and local agencies for water-resource planning and management, and are commonly defined on the basis of surface-water drainage areas. Hydrographic areas were further divided into subbasins that are separated by areas where bedrock is at or near the land surface. Subbasins are the subdivisions used in this study for estimating recharge, discharge, and water budget. Hydrographic areas are the subdivision used for reporting summed and tabulated subbasin estimates.

  6. Strain-induced metal–semiconductor transition observed in atomic carbon chains

    PubMed Central

    La Torre, A.; Botello-Mendez, A.; Baaziz, W.; Charlier, J. -C.; Banhart, F.

    2015-01-01

    Carbyne, the sp1-hybridized phase of carbon, is still a missing link in the family of carbon allotropes. While the bulk phases of carbyne remain elusive, the elementary constituents, that is, linear chains of carbon atoms, have already been observed using the electron microscope. Isolated atomic chains are highly interesting one-dimensional conductors that have stimulated considerable theoretical work. Experimental information, however, is still very limited. Here we show electrical measurements and first-principles transport calculations on monoatomic carbon chains. When the 1D system is under strain, the chains are semiconducting corresponding to the polyyne structure with alternating bond lengths. Conversely, when the chain is unstrained, the ohmic behaviour of metallic cumulene with uniform bond lengths is observed. This confirms the recent prediction of a metal–insulator transition that is induced by strain. The key role of the contacting leads explains the rectifying behaviour measured in monoatomic carbon chains in a nonsymmetric contact configuration. PMID:25818506

  7. Design-atom approach for the QM/MM covalent boundary: A design-carbon atom with five valence electrons

    PubMed Central

    Xiao, Chuanyun; Zhang, Yingkai

    2009-01-01

    A critical issue underlying the accuracy and applicability of the combined quantum mechanical/molecular mechanical (QM/MM) methods is how to describe the QM/MM boundary across covalent bonds. Inspired by the ab initio pseudo-potential theory, here we introduce a novel design-atom approach for a more fundamental and transparent treatment of this QM/MM covalent boundary problem. The main idea is to replace the boundary atom of the active part with a design-atom, which has a different number of valence electrons but very similar atomic properties. By modifying the Troullier-Martins scheme, which has been widely employed to construct norm-conserving pseudo-potentials for density functional calculations, we have successfully developed a design-carbon atom with five valence electrons. Tests on a series of molecules yield very good structural and energetic results, and indicate its transferability in describing a variety of chemical bonds, including double and triple bonds. PMID:17902888

  8. Molecular dynamics simulation for arrangement of nickel atoms filled in carbon nanotubes

    SciTech Connect

    Bai, Liu Zhenyu, Zhao; Lirui, Liu

    2014-08-28

    Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Atomic arrangement of the metals has an important role in the function of the composites. The tips of CNTs were opened, and then nickel was filled by means of hydrothermal oxidation/ultrasonic vibration method. The tests of TEM, HREM, and EDX (energy-dispersive X-ray spectroscopy) analysis showed that Ni was filled in CNTs successfully. The atomic arrangement of nickel filled into single wall carbon nanotubes was investigated by molecular dynamics simulation. The radial distribution function and bond orientation order were established to analyze the atomic arrangement of nickel filled in carbon nanotubes during the cooling process. The results show that nickel atoms became in order gradually and preferably crystallized on the inner wall of carbon nanotubes when the temperature decreased from 1600 K. After it cooled to 100 K, the arrangement of nickel atoms in outermost circle was regular and dense, but there were many defects far from the wall of CNTs. According to the calculation of bond orientation order parameters Q{sub 6} and its visualization, the structure of nickel is Face-centered cube (f.c.c). (1,1,1){sub Ni} was close on the inner surface of carbon nanotubes. Radial direction of CNTs was [1,1,1] crystal orientation. Axial direction of CNTs, namely, filling direction, was [1{sup ¯}, 1{sup ¯},2] crystal orientation.

  9. Molecular dynamics simulation for arrangement of nickel atoms filled in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Bai, Liu; Lirui, Liu; Zhenyu, Zhao

    2014-08-01

    Carbon Nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Atomic arrangement of the metals has an important role in the function of the composites. The tips of CNTs were opened, and then nickel was filled by means of hydrothermal oxidation/ultrasonic vibration method. The tests of TEM, HREM, and EDX (energy-dispersive X-ray spectroscopy) analysis showed that Ni was filled in CNTs successfully. The atomic arrangement of nickel filled into single wall carbon nanotubes was investigated by molecular dynamics simulation. The radial distribution function and bond orientation order were established to analyze the atomic arrangement of nickel filled in carbon nanotubes during the cooling process. The results show that nickel atoms became in order gradually and preferably crystallized on the inner wall of carbon nanotubes when the temperature decreased from 1600 K. After it cooled to 100 K, the arrangement of nickel atoms in outermost circle was regular and dense, but there were many defects far from the wall of CNTs. According to the calculation of bond orientation order parameters Q6 and its visualization, the structure of nickel is Face-centered cube (f.c.c). (1,1,1)Ni was close on the inner surface of carbon nanotubes. Radial direction of CNTs was [1,1,1] crystal orientation. Axial direction of CNTs, namely, filling direction, was [1¯, 1¯,2] crystal orientation.

  10. Integrating Carbon Nanotubes For Atomic Force Microscopy Imaging Applications

    NASA Technical Reports Server (NTRS)

    Ye, Qi; Cassell, Alan M.; Liu, Hongbing; Han, Jie; Meyyappan, Meyya

    2004-01-01

    Carbon nanotube (CNT) related nanostructures possess remarkable electrical, mechanical, and thermal properties. To produce these nanostructures for real world applications, a large-scale controlled growth of carbon nanotubes is crucial for the integration and fabrication of nanodevices and nanosensors. We have taken the approach of integrating nanopatterning and nanomaterials synthesis with traditional silicon micro fabrication techniques. This integration requires a catalyst or nanomaterial protection scheme. In this paper, we report our recent work on fabricating wafer-scale carbon nanotube AFM cantilever probe tips. We will address the design and fabrication considerations in detail, and present the preliminary scanning probe test results. This work may serve as an example of rational design, fabrication, and integration of nanomaterials for advanced nanodevice and nanosensor applications.

  11. Atomic migration of carbon in hard turned layers of carburized bearing steel

    SciTech Connect

    Bedekar, Vikram; Poplawsky, Jonathan D.; Guo, Wei; Shivpuri, Rajiv; Scott Hyde, R.

    2016-01-01

    In grain finement and non-equilibrium there is carbon segregation within grain boundaries alters the mechanical performance of hard turning layers in carburized bearing steel. Moreover, an atom probe tomography (APT) study on the nanostructured hard turning layers reveals carbon migration to grain boundaries as a result of carbide decomposition during severe plastic deformation. In addition, samples exposed to different cutting speeds show that the carbon migration rate increases with the cutting speed. For these two effects lead to an ultrafine carbon network structure resulting in increased hardness and thermal stability in the severely deformed surface layer.

  12. Synthesis of novel amorphous calcium carbonate by sono atomization for reactive mixing.

    PubMed

    Kojima, Yoshiyuki; Kanai, Makoto; Nishimiya, Nobuyuki

    2012-03-01

    Droplets of several micrometers in size can be formed in aqueous solution by atomization under ultrasonic irradiation at 2 MHz. This phenomenon, known as atomization, is capable of forming fine droplets for use as a reaction field. This synthetic method is called SARM (sono atomization for reactive mixing). This paper reports on the synthesis of a novel amorphous calcium carbonate formed by SARM. The amorphous calcium carbonate, obtained at a solution concentration of 0.8 mol/dm(3), had a specific surface area of 65 m(2)/g and a composition of CaCO(3)•0.5H(2)O as determined using thermogravimetric/differential thermal analysis (TG-DTA). Because the ACC had a lower hydrate composition than conventional amorphous calcium carbonate (ACC), the ACC synthesized in this paper was very stable at room temperature. PMID:21788149

  13. Ultra-low-temperature Reactions of Carbon Atoms with Hydrogen Molecules

    NASA Astrophysics Data System (ADS)

    Krasnokutski, S. A.; Kuhn, M.; Renzler, M.; Jäger, C.; Henning, Th.; Scheier, P.

    2016-02-01

    The reactions of carbon atoms with dihydrogen have been investigated in liquid helium droplets at T = 0.37 K. A calorimetric technique was applied to monitor the energy released in the reaction. The barrierless reaction between a single carbon atom and a single dihydrogen molecule was detected. Reactions between dihydrogen clusters and carbon atoms have been studied by high-resolution mass spectrometry. The formation of hydrocarbon cations of the type {{{C}}}m{{{{H}}}n}+ with m = 1-4 and n = 1-15 was observed. With enhanced concentration of dihydrogen, the mass spectra demonstrated the main “magic” peak assigned to the {{{CH}}5}+ cation. A simple formation pathway and the high stability of this cation suggest its high abundance in the interstellar medium.

  14. Atomic structure and dynamic behaviour of truly one-dimensional ionic chains inside carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Senga, Ryosuke; Komsa, Hannu-Pekka; Liu, Zheng; Hirose-Takai, Kaori; Krasheninnikov, Arkady V.; Suenaga, Kazu

    2014-11-01

    Materials with reduced dimensionality have attracted much interest in various fields of fundamental and applied science. True one-dimensional (1D) crystals with single-atom thickness have been realized only for few elemental metals (Au, Ag) or carbon, all of which showed very short lifetimes under ambient conditions. We demonstrate here a successful synthesis of stable 1D ionic crystals in which two chemical elements, one being a cation and the other an anion, align alternately inside carbon nanotubes. Unusual dynamical behaviours for different atoms in the 1D lattice are experimentally corroborated and suggest substantial interactions of the atoms with the nanotube sheath. Our theoretical studies indicate that the 1D ionic crystals have optical properties distinct from those of their bulk counterparts and that the properties can be engineered by introducing atomic defects into the chains.

  15. Carbon nanotube synthesis: from large-scale production to atom-by-atom growth.

    PubMed

    Journet, Catherine; Picher, Matthieu; Jourdain, Vincent

    2012-04-13

    The extraordinary electronic, thermal and mechanical properties of carbon nanotubes (CNTs) closely relate to their structure. They can be seen as rolled-up graphene sheets with their electronic properties depending on how this rolling up is achieved. However, this is not the way they actually grow. Various methods are used to produce carbon nanotubes. They all have in common three ingredients: (i) a carbon source, (ii) catalyst nanoparticles and (iii) an energy input. In the case where the carbon source is provided in solid form, one speaks about 'high temperature methods' because they involve the sublimation of graphite which does not occur below 3200 °C. The first CNTs were synthesized by these techniques. For liquid or gaseous phases, the generic term of 'medium or low temperature methods' is used. CNTs are now commonly produced by these latter techniques at temperatures ranging between 350 and 1000 °C, using metal nanoparticles that catalyze the decomposition of the gaseous carbon precursor and make the growth of nanotubes possible. The aim of this review article is to give a general overview of all these methods and an understanding of the CNT growth process. PMID:22433510

  16. Carbon nanotube synthesis: from large-scale production to atom-by-atom growth

    NASA Astrophysics Data System (ADS)

    Journet, Catherine; Picher, Matthieu; Jourdain, Vincent

    2012-04-01

    The extraordinary electronic, thermal and mechanical properties of carbon nanotubes (CNTs) closely relate to their structure. They can be seen as rolled-up graphene sheets with their electronic properties depending on how this rolling up is achieved. However, this is not the way they actually grow. Various methods are used to produce carbon nanotubes. They all have in common three ingredients: (i) a carbon source, (ii) catalyst nanoparticles and (iii) an energy input. In the case where the carbon source is provided in solid form, one speaks about ‘high temperature methods’ because they involve the sublimation of graphite which does not occur below 3200 °C. The first CNTs were synthesized by these techniques. For liquid or gaseous phases, the generic term of ‘medium or low temperature methods’ is used. CNTs are now commonly produced by these latter techniques at temperatures ranging between 350 and 1000 °C, using metal nanoparticles that catalyze the decomposition of the gaseous carbon precursor and make the growth of nanotubes possible. The aim of this review article is to give a general overview of all these methods and an understanding of the CNT growth process.

  17. Determination of cadmium in the livers and kidneys of puffins by carbon furnace atomic absorption spectrometry.

    PubMed

    Ottaway, J M; Campbell, W C

    1976-01-01

    A carbon furnace atomic absorption procedure is described for the determination of cadmium in the livers and kidneys of puffins, fratercula arctica. Samples are dried and weighed and 2 to 100 mg are dissolved in sulphuric and nitric acids. These solutions are analysed directly in the carbon furnace against aqueous standards and provide accurate results in the range 0-1 to 100 micrograms/g dry weight. The method is simple and rapid and requires much less of the small total sample than would be required for flame atomic absorption. PMID:1030692

  18. Catalytic conversion of alcohols having at least three carbon atoms to hydrocarbon blendstock

    DOEpatents

    Narula, Chaitanya K.; Davison, Brian H.

    2015-11-13

    A method for producing a hydrocarbon blendstock, the method comprising contacting at least one saturated acyclic alcohol having at least three and up to ten carbon atoms with a metal-loaded zeolite catalyst at a temperature of at least 100°C and up to 550°C, wherein the metal is a positively-charged metal ion, and the metal-loaded zeolite catalyst is catalytically active for converting the alcohol to the hydrocarbon blendstock, wherein the method directly produces a hydrocarbon blendstock having less than 1 vol % ethylene and at least 35 vol % of hydrocarbon compounds containing at least eight carbon atoms.

  19. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis.

    PubMed

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-01-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel-carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm(-2) and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis. PMID:26861684

  20. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    NASA Astrophysics Data System (ADS)

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-02-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel-carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm-2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis.

  1. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    PubMed Central

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-01-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel–carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm−2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis. PMID:26861684

  2. Isotope geochemistry and fluxes of carbon and organic matter in tropical small mountainous river systems and adjacent coastal waters of the Caribbean

    USGS Publications Warehouse

    Moyer, Ryan; Bauer, James; Grottoli, Andrea

    2012-01-01

    Recent studies have shown that small mountainous rivers (SMRs) may act as sources of aged and/or refractory carbon (C) to the coastal ocean, which may increase organic C burial at sea and subsidize coastal food webs and heterotrophy. However, the characteristics and spatial and temporal variability of C and organic matter (OM) exported from tropical SMR systems remain poorly constrained. To address this, the abundance and isotopic character (δ13C and Δ14C) of the three major C pools were measured in two Puerto Rico SMRs with catchments dominated by different land uses (agricultural vs. non-agricultural recovering forest). The abundance and character of C pools in associated estuaries and adjacent coastal waters were also examined. Riverine dissolved and particulate organic C (DOC and POC, respectively) concentrations were highly variable with respect to land use and sampling month, while dissolved inorganic C (DIC) was significantly higher at all times in the agricultural catchment. In both systems, riverine DOC and POC ranged from modern to highly aged (2,340 years before present), while DIC was always modern. The agricultural river and irrigation canals contained very old DOC (1,184 and 2,340 years before present, respectively), which is consistent with findings in temperate SMRs and indicates that these tropical SMRs provide a source of aged DOC to the ocean. During months of high river discharge, OM in estuarine and coastal waters had C isotope signatures reflective of direct terrestrial input, indicating that relatively unaltered OM is transported to the coastal ocean at these times. This is also consistent with findings in temperate SMRs and indicates that C transported to the coastal ocean by SMRs may differ from that of larger rivers because it is exported from smaller catchments that have steeper terrains and fewer land-use types.

  3. Single Pd atoms in activated carbon fibers and their contribution to hydrogen storage

    SciTech Connect

    Contescu, Cristian I; van Benthem, Klaus; Li, Sa; Bonifacio, Cecile S; Pennycook, Stephen J; Jena, Puru; Gallego, Nidia C

    2011-01-01

    Palladium-modified activated carbon fibers (Pd-ACF) were synthesized by meltspinning, carbonization and activation of an isotropic pitch carbon precursor premixed with an organometallic Pd compound. The hydrogen uptake at 25 oC and 20 bar on Pd- ACF exceeded the expected capacity based solely on Pd hydride formation and hydrogen physisorption on the microporous carbon support. Aberration-corrected scanning transmission electron microscopy (STEM) with sub- ngstrom spatial resolution provided unambiguous identification of isolated Pd atoms occurring in the carbon matrix that coexist with larger Pd particles. First principles calculations revealed that each single Pd atom can form Kubas-type complexes by binding up to three H2 molecules in the pressure range of adsorption measurements. Based on Pd atom concentration determined from STEM images, the contribution of various mechanisms to the excess hydrogen uptake measured experimentally was evaluated. With consideration of Kubas binding as a viable mechanism (along with hydride formation and physisorption to carbon support) the role of hydrogen spillover in this system may be smaller than previously thought.

  4. Atomic data for opacity calculations. XI - The carbon isoelectronic sequence

    NASA Technical Reports Server (NTRS)

    Luo, D.; Pradhan, A. K.

    1989-01-01

    Close-coupling calculations are carried out for radiative processes in neutral carbon and a number of carbon-like ions; energy levels, oscillator strengths, and photoionization cross sections have been computed for all bound states of the type 2 s(j)2p(k)nl with n not above 10 and 1 not above 3. The R-matrix method is employed to solve the coupled equations with a ten-state eigenfunction expansion for the parent ion C II and an eight-state expansion for the other boron-like target ions. A number of selected results for oscillator strengths are presented and compared with earlier data, as well as for photoionization cross sections with autoionizing resonance structures. Isoelectronic trends are discussed. The present results for the oscillator strengths of C I and N II are found to differ significantly from some earlier theoretical works for a number of transitions. However, the present C I f values are in excellent agreement with recent calculations and experimental results.

  5. Atom Vacancies on a Carbon Nanotube: To What Extent Can We Simulate their Effects?

    PubMed

    Kroes, Jaap M H; Pietrucci, Fabio; van Duin, Adri C T; Andreoni, Wanda

    2015-07-14

    Atom vacancies are intrinsic defects of carbon nanotubes. Using a zigzag nanotube as reference, this paper focuses on the comparison of calculations performed within density functional theory and a number of classical force fields widely used for carbon systems. The results refer to single and double vacancies and, in particular, to the induced structural changes, the formation energies, and the energy barriers relative to elementary processes such as reconstruction, migration, and coalescence. Characterization of these processes is remarkably different in the different approaches. These findings are meant to contribute to the construction of DFT-based classical schemes for carbon nanostructures. PMID:26575773

  6. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    M.J. McKelvy; R. Sharma; A.V.G. Chizmeshya; H. Bearat; R.W. Carpenter

    2000-08-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation before and/or during carbonation may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (i) its structural and chemical simplicity, (ii) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (iii) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for cost optimization of any lamellar-hydroxide-based mineral carbonation sequestration process.

  7. Migration behaviour of carbon atoms on clean diamond (0 0 1) surface: A first principle study

    NASA Astrophysics Data System (ADS)

    Liu, Xuejie; Xia, Qing; Li, Wenjuan; Luo, Hao; Ren, Yuan; Tan, Xin; Sun, Shiyang

    2016-01-01

    The adsorption and migration energies of a single carbon atom and the configuration evolution energies of two carbon atoms on a clean diamond (0 0 1) surface were calculated using the first principle method based on density functional theory to investigate the formation of ultra-nanocrystalline diamond (UNCD) film. The activation energy of a single atom diffusing along a dimer row is 1.96 eV, which is almost the same as that of a CH2 migrating along a dimer row under hydrogen-rich conditions. However, the activation energy of a single atom diffusing along a dimer chain is 2.66 eV, which is approximately 1.55 times greater than that of a CH2 migrating along a dimer chain in a hydrogen-rich environment. The configuration evolution of the two carbon atoms is almost impossible at common diamond film deposition temperatures (700-900 °C) because the activation energies reach 4.46 or 5.90 eV. Therefore, the high-energy barrier could result in insufficient migration of adatoms, leading to the formation of amorphous in UNCD films in hydrogen-poor CVD environment.

  8. Atomic scale observation of oxygen delivery during silver–oxygen nanoparticle catalysed oxidation of carbon nanotubes

    PubMed Central

    Yue, Yonghai; Yuchi, Datong; Guan, Pengfei; Xu, Jia; Guo, Lin; Liu, Jingyue

    2016-01-01

    To probe the nature of metal-catalysed processes and to design better metal-based catalysts, atomic scale understanding of catalytic processes is highly desirable. Here we use aberration-corrected environmental transmission electron microscopy to investigate the atomic scale processes of silver-based nanoparticles, which catalyse the oxidation of multi-wall carbon nanotubes. A direct semi-quantitative estimate of the oxidized carbon atoms by silver-based nanoparticles is achieved. A mechanism similar to the Mars–van Krevelen process is invoked to explain the catalytic oxidation process. Theoretical calculations, together with the experimental data, suggest that the oxygen molecules dissociate on the surface of silver nanoparticles and diffuse through the silver nanoparticles to reach the silver/carbon interfaces and subsequently oxidize the carbon. The lattice distortion caused by oxygen concentration gradient within the silver nanoparticles provides the direct evidence for oxygen diffusion. Such direct observation of atomic scale dynamics provides an important general methodology for investigations of catalytic processes. PMID:27406595

  9. The Reception of J. H. van't Hoff's Theory of the Asymmetric Carbon Atom

    ERIC Educational Resources Information Center

    Snelders, H. A. M.

    1974-01-01

    Discusses Jacobus Henricus van't Hoff's revolutionary theory of the asymmetric carbon atom and its early reception among his contemporaries in the Netherlands. Indicates that the extension of the new idea to practical problems gives the impetus to the development of stereochemistry. (CC)

  10. Atomic scale observation of oxygen delivery during silver-oxygen nanoparticle catalysed oxidation of carbon nanotubes.

    PubMed

    Yue, Yonghai; Yuchi, Datong; Guan, Pengfei; Xu, Jia; Guo, Lin; Liu, Jingyue

    2016-01-01

    To probe the nature of metal-catalysed processes and to design better metal-based catalysts, atomic scale understanding of catalytic processes is highly desirable. Here we use aberration-corrected environmental transmission electron microscopy to investigate the atomic scale processes of silver-based nanoparticles, which catalyse the oxidation of multi-wall carbon nanotubes. A direct semi-quantitative estimate of the oxidized carbon atoms by silver-based nanoparticles is achieved. A mechanism similar to the Mars-van Krevelen process is invoked to explain the catalytic oxidation process. Theoretical calculations, together with the experimental data, suggest that the oxygen molecules dissociate on the surface of silver nanoparticles and diffuse through the silver nanoparticles to reach the silver/carbon interfaces and subsequently oxidize the carbon. The lattice distortion caused by oxygen concentration gradient within the silver nanoparticles provides the direct evidence for oxygen diffusion. Such direct observation of atomic scale dynamics provides an important general methodology for investigations of catalytic processes. PMID:27406595

  11. Atomic scale observation of oxygen delivery during silver-oxygen nanoparticle catalysed oxidation of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yue, Yonghai; Yuchi, Datong; Guan, Pengfei; Xu, Jia; Guo, Lin; Liu, Jingyue

    2016-07-01

    To probe the nature of metal-catalysed processes and to design better metal-based catalysts, atomic scale understanding of catalytic processes is highly desirable. Here we use aberration-corrected environmental transmission electron microscopy to investigate the atomic scale processes of silver-based nanoparticles, which catalyse the oxidation of multi-wall carbon nanotubes. A direct semi-quantitative estimate of the oxidized carbon atoms by silver-based nanoparticles is achieved. A mechanism similar to the Mars-van Krevelen process is invoked to explain the catalytic oxidation process. Theoretical calculations, together with the experimental data, suggest that the oxygen molecules dissociate on the surface of silver nanoparticles and diffuse through the silver nanoparticles to reach the silver/carbon interfaces and subsequently oxidize the carbon. The lattice distortion caused by oxygen concentration gradient within the silver nanoparticles provides the direct evidence for oxygen diffusion. Such direct observation of atomic scale dynamics provides an important general methodology for investigations of catalytic processes.

  12. Reactions of the inner surface of carbon nanotubes and nanoprotrusion processes imaged at the atomic scale

    NASA Astrophysics Data System (ADS)

    Chamberlain, Thomas W.; Meyer, Jannik C.; Biskupek, Johannes; Leschner, Jens; Santana, Adriano; Besley, Nicholas A.; Bichoutskaia, Elena; Kaiser, Ute; Khlobystov, Andrei N.

    2011-09-01

    Although the outer surface of single-walled carbon nanotubes (atomically thin cylinders of carbon) can be involved in a wide range of chemical reactions, it is generally thought that the interior surface of nanotubes is unreactive. In this study, we show that in the presence of catalytically active atoms of rhenium inserted into nanotubes, the nanotube sidewall can be engaged in chemical reactions from the inside. Aberration-corrected high-resolution transmission electron microscopy operated at 80 keV allows visualization of the formation of nanometre-sized hollow protrusions on the nanotube sidewall at the atomic level in real time at ambient temperature. Our direct observations and theoretical modelling demonstrate that the nanoprotrusions are formed in three stages: (i) metal-assisted deformation and rupture of the nanotube sidewall, (ii) the fast formation of a metastable asymmetric nanoprotrusion with an open edge and (iii) a slow symmetrization process that leads to a stable closed nanoprotrusion.

  13. Reactions of the inner surface of carbon nanotubes and nanoprotrusion processes imaged at the atomic scale.

    PubMed

    Chamberlain, Thomas W; Meyer, Jannik C; Biskupek, Johannes; Leschner, Jens; Santana, Adriano; Besley, Nicholas A; Bichoutskaia, Elena; Kaiser, Ute; Khlobystov, Andrei N

    2011-09-01

    Although the outer surface of single-walled carbon nanotubes (atomically thin cylinders of carbon) can be involved in a wide range of chemical reactions, it is generally thought that the interior surface of nanotubes is unreactive. In this study, we show that in the presence of catalytically active atoms of rhenium inserted into nanotubes, the nanotube sidewall can be engaged in chemical reactions from the inside. Aberration-corrected high-resolution transmission electron microscopy operated at 80 keV allows visualization of the formation of nanometre-sized hollow protrusions on the nanotube sidewall at the atomic level in real time at ambient temperature. Our direct observations and theoretical modelling demonstrate that the nanoprotrusions are formed in three stages: (i) metal-assisted deformation and rupture of the nanotube sidewall, (ii) the fast formation of a metastable asymmetric nanoprotrusion with an open edge and (iii) a slow symmetrization process that leads to a stable closed nanoprotrusion. PMID:21860464

  14. Atomic-scale imaging of albite feldspar, calcium carbonate, rectorite, and bentonite using atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Drake, Barney; Hellmann, Roland; Sikes, C. Steven; Occelli, Mario L.

    1992-05-01

    Atomic force microscopy (AFM) was used to investigate the (010) surface of Amelia albite, the basal and (001) planes of CaCO3 (calcite), and the basal planes of rectorite and bentonite. Atomic scale images of the albite surface show six sided, interconnected en-echelon rings. Fourier transforms of the surface scans reveal two primary nearest neighbor distances of 4.7 and 4.9 +/- 0.5 angstroms. Analysis of the images using a 6 angstroms thick projection of the bulk structure was performed. Close agreement between the projection and the images suggests the surface is very close to an ideal termination of the bulk structure. Images of the calcite basal plane show a hexagonal array of Ca atoms measured to within +/- 0.3 angstroms of the 4.99 angstroms predicted by x-ray diffraction data. Putative images of the (001) plane of carbonate ions, with hexagonal 5 angstroms spacing, are also presented and discussed. Basal plane images of rectorite show hexagonal symmetry with 9.1 +/- 2.5 angstroms spacing, while bentonite results reveal a 4.9 +/- 0.5 angstroms nearest neighbor spacing.

  15. Spatial Distributions of Metal Atoms During Carbon SWNTs Formation: Measurements and Modelling

    NASA Technical Reports Server (NTRS)

    Cau, M.; Dorval, N.; Attal-Tretout, B.; Cochon, J. L.; Loiseau, A.; Farhat, S.; Hinkov, I.; Scott, C. D.

    2004-01-01

    Experiments and modelling have been undertaken to clarify the role of metal catalysts during single-wall carbon nanotube formation. For instance, we wonder whether the metal catalyst is active as an atom, a cluster, a liquid or solid nanoparticle [1]. A reactor has been developed for synthesis by continuous CO2-laser vaporisation of a carbon-nickel-cobalt target in laminar helium flow. The laser induced fluorescence technique [2] is applied for local probing of gaseous Ni, Co and CZ species throughout the hot carbon flow of the target heated up to 3500 K. A rapid depletion of C2 in contrast to the spatial extent of metal atoms is observed in the plume (Fig. 1). This asserts that C2 condenses earlier than Ni and Co atoms.[3, 4]. The depletion is even faster when catalysts are present. It may indicate that an interaction between metal atoms and carbon dimers takes place in the gas as soon as they are expelled from the target surface. Two methods of modelling are used: a spatially I-D calculation developed originally for the arc process [5], and a zero-D time dependent calculation, solving the chemical kinetics along the streamlines [6]. The latter includes Ni cluster formation. The peak of C2 density is calculated close to the target surface where the temperature is the highest. In the hot region, C; is dominant. As the carbon products move away from the target and mix with the ambient helium, they recombine into larger clusters, as demonstrated by the peak of C5 density around 1 mm. The profile of Ni-atom density compares fairly well with the measured one (Fig. 2). The early increase is due to the drop of temperature, and the final decrease beyond 6 mm results from Ni cluster formation at the eutectic temperature (approx.1600 K).

  16. Bias in bonding behavior among boron, carbon, and nitrogen atoms in ion implanted a-BN, a-BC, and diamond like carbon films

    SciTech Connect

    Genisel, Mustafa Fatih; Uddin, Md. Nizam; Say, Zafer; Bengu, Erman; Kulakci, Mustafa; Turan, Rasit; Gulseren, Oguz

    2011-10-01

    In this study, we implanted N{sup +} and N{sub 2}{sup +} ions into sputter deposited amorphous boron carbide (a-BC) and diamond like carbon (DLC) thin films in an effort to understand the chemical bonding involved and investigate possible phase separation routes in boron carbon nitride (BCN) films. In addition, we investigated the effect of implanted C{sup +} ions in sputter deposited amorphous boron nitride (a-BN) films. Implanted ion energies for all ion species were set at 40 KeV. Implanted films were then analyzed using x-ray photoelectron spectroscopy (XPS). The changes in the chemical composition and bonding chemistry due to ion-implantation were examined at different depths of the films using sequential ion-beam etching and high resolution XPS analysis cycles. A comparative analysis has been made with the results from sputter deposited BCN films suggesting that implanted nitrogen and carbon atoms behaved very similar to nitrogen and carbon atoms in sputter deposited BCN films. We found that implanted nitrogen atoms would prefer bonding to carbon atoms in the films only if there is no boron atom in the vicinity or after all available boron atoms have been saturated with nitrogen. Implanted carbon atoms also preferred to either bond with available boron atoms or, more likely bonded with other implanted carbon atoms. These results were also supported by ab-initio density functional theory calculations which indicated that carbon-carbon bonds were energetically preferable to carbon-boron and carbon-nitrogen bonds.

  17. Reaction studies of hot silicon, germanium and carbon atoms: Progress report, February 1, 1985-July 31, 1987

    SciTech Connect

    Gaspar, P.P.

    1987-08-01

    The experimental approach toward attaining the goals of this research program is briefly outlined, and the progress made in the 1985 to 1987 period is reviewed in sections entitled: (1) reactions of recoiling silicon atoms; (2) reactions of recoiling carbon atoms; and (3) reactions of thermally evaporated germanium atoms.

  18. Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

    NASA Astrophysics Data System (ADS)

    Peterson, Eric J.; Delariva, Andrew T.; Lin, Sen; Johnson, Ryan S.; Guo, Hua; Miller, Jeffrey T.; Hun Kwak, Ja; Peden, Charles H. F.; Kiefer, Boris; Allard, Lawrence F.; Ribeiro, Fabio H.; Datye, Abhaya K.

    2014-09-01

    Catalysis by single isolated atoms of precious metals has attracted much recent interest, as it promises the ultimate in atom efficiency. Most previous reports are on reducible oxide supports. Here we show that isolated palladium atoms can be catalytically active on industrially relevant γ-alumina supports. The addition of lanthanum oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated palladium atoms. Aberration-corrected scanning transmission electron microscopy and operando X-ray absorption spectroscopy confirm the presence of intermingled palladium and lanthanum on the γ-alumina surface. Carbon monoxide oxidation reactivity measurements show onset of catalytic activity at 40 °C. The catalyst activity can be regenerated by oxidation at 700 °C in air. The high-temperature stability and regenerability of these ionic palladium species make this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

  19. Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina.

    PubMed

    Peterson, Eric J; DeLaRiva, Andrew T; Lin, Sen; Johnson, Ryan S; Guo, Hua; Miller, Jeffrey T; Hun Kwak, Ja; Peden, Charles H F; Kiefer, Boris; Allard, Lawrence F; Ribeiro, Fabio H; Datye, Abhaya K

    2014-01-01

    Catalysis by single isolated atoms of precious metals has attracted much recent interest, as it promises the ultimate in atom efficiency. Most previous reports are on reducible oxide supports. Here we show that isolated palladium atoms can be catalytically active on industrially relevant γ-alumina supports. The addition of lanthanum oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated palladium atoms. Aberration-corrected scanning transmission electron microscopy and operando X-ray absorption spectroscopy confirm the presence of intermingled palladium and lanthanum on the γ-alumina surface. Carbon monoxide oxidation reactivity measurements show onset of catalytic activity at 40 °C. The catalyst activity can be regenerated by oxidation at 700 °C in air. The high-temperature stability and regenerability of these ionic palladium species make this catalyst system of potential interest for low-temperature exhaust treatment catalysts. PMID:25222116

  20. Atoms in carbon cages as a source of interstellar diffuse lines

    NASA Technical Reports Server (NTRS)

    Ballester, J. L.; Antoniewicz, P. R.; Smoluchowski, R.

    1990-01-01

    A model to describe the resonance absorption lines of various atoms trapped in closed carbon cages is presented. These systems may be responsible for some of the as yet unexplained diffuse interstellar bands. Model potentials for possible atom-C60 systems are obtained and used to calculate the resonance lines. The trapped atoms considered are O, N, Si, Mg, Al, Na, and S, and in all cases the resonance lines are shifted toward the red as compared to the isolated atoms. The calculated wavelengths are compared to the range of wavelengths observed for the diffuse interstellar bands, and good agreement is found for Mg and Si resonance lines. Other lines may be caused by other than resonance transitions or by trapped molecules. The oscillator strengths and the abundances are evaluated and compared with observation. Mechanisms to explain the observed band width of the lines and the existence of certain correlated pairs of lines are discussed.

  1. First principles study of foreign interstitial atom (carbon, nitrogen) interactions with intrinsic defects in tungsten

    NASA Astrophysics Data System (ADS)

    Kong, Xiang-Shan; You, Yu-Wei; Song, Chi; Fang, Q. F.; Chen, Jun-Ling; Luo, G.-N.; Liu, C. S.

    2012-11-01

    We performed a series of first-principles calculations to investigate the foreign interstitial atom (FIA) interactions with intrinsic defects in tungsten. We found the following: (i) The introduction of the FIA reduces the vacancy formation energy, resulting in the increase of the equilibrium concentration of vacancies. (ii) The positive binding energy between two FIAs suggests that the FIA can attract other FIAs. (iii) The FIA is easily trapped by the vacancy, and a single vacancy can accommodate up to 4 and 6 atoms in a stable manner for carbon and nitrogen, respectively. (iv) There is an attraction interaction between the FIA and the self-interstitial atom (SIA), and the FIA can reduce the SIA jump frequency and enhance the formation of SIA clusters in tungsten. Moreover, the difference between carbon and nitrogen are also discussed with respect to the formation of FIA-FIA covalent bond and the accumulation around the saturated -, where d is the ith nearest-neighbor (inn) solute-tungsten distance before relaxation and ▵di=(di-d) is the change in distance due to relaxation. The calculated relaxations are presented in Table 3. The relaxations of 1nn of octahedral interstitial carbon and nitrogen atoms are 23.30% and 22.42%, respectively, which are greatly larger than the relaxations of other nearest-neighbor atoms (0.1-2%). These results indicate that the influence range of FIA is very local. The lattice distortions introduced by the octahedral interstitial carbon or nitrogen atom can be characterized by determining the dipolar tensor from Kanzaki forces. Here, to obtain the dipolar tensor, we adopt a similar calculation procedure as used in Ref. [14], where the dipolar tensor P is calculated from the Kanzaki forces on all the tungsten atoms. The detailed procedure could be found in Ref. [14]. Due to the symmetry of the configuration, the dipolar tensor has two independent values: P11 and P33, which are listed in Table 3. Similarly with Ref. [14], approximate

  2. Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

    NASA Astrophysics Data System (ADS)

    Glover, Simon C. O.; Clark, Paul C.

    2016-03-01

    Carbon monoxide (CO) is widely used as a tracer of molecular hydrogen (H2) in metal-rich galaxies, but is known to become ineffective in low-metallicity dwarf galaxies. Atomic carbon has been suggested as a superior tracer of H2 in these metal-poor systems, but its suitability remains unproven. To help us to assess how well atomic carbon traces H2 at low metallicity, we have performed a series of numerical simulations of turbulent molecular clouds that cover a wide range of different metallicities. Our simulations demonstrate that in star-forming clouds, the conversion factor between [C I] emission and H2 mass, XCI, scales approximately as XCI ∝ Z-1. We recover a similar scaling for the CO-to-H2 conversion factor, XCO, but find that at this point in the evolution of the clouds, XCO is consistently smaller than XCI, by a factor of a few or more. We have also examined how XCI and XCO evolve with time. We find that XCI does not vary strongly with time, demonstrating that atomic carbon remains a good tracer of H2 in metal-poor systems even at times significantly before the onset of star formation. On the other hand, XCO varies very strongly with time in metal-poor clouds, showing that CO does not trace H2 well in starless clouds at low metallicity.

  3. Combined ab initio molecular dynamics and experimental studies of carbon atom addition to benzene.

    PubMed

    McKee, Michael L; Reisenauer, Hans Peter; Schreiner, Peter R

    2014-04-17

    Car-Parrinello molecular dynamics was used to explore the reactions between triplet and singlet carbon atoms with benzene. The computations reveal that, in the singlet C atom reaction, products are very exothermic where nearly every collision yields a product that is determined by the initial encounter geometry. The singlet C atom reaction does not follow the minimum energy path because the bimolecular reaction is controlled by dynamics (i.e., initial orientation of encounter). On the other hand, in a 10 K solid Ar matrix, ground state C((3)P) atoms do tend to follow RRKM kinetics. Thus, ab initio molecular dynamics (AIMD) results indicate that a significant fraction of C-H insertion occurs to form phenylcarbene whereas, in marked contrast to previous theoretical and experimental conclusions, the Ar matrix isolation studies indicate a large fraction of direct cycloheptatetraene formation, without the intermediacy of phenylcarbene. The AIMD calculations are more consistent with vaporized carbon atom experiments where labeling studies indicate the initial formation of phenylcarbene. This underlines that the availability of thermodynamic sinks can completely alter the observed reaction dynamics. PMID:24661002

  4. Reactions of atomic carbon with oxygenated compounds and the investigation of fullerene chemistry

    SciTech Connect

    Chang, Tsongming.

    1993-01-01

    The reaction of atomic carbon with oxygenated organics produces CO and an energetic fragment. Reactions involving deoxygenation of carbonyl compounds to carbenes, epoxides to alkenes, and ethers to a pair of radicals have been investigated. Carbon atom deoxygenation of cyclopentanone and cylcopentene oxide give the cleavage products, ethylene and allene, along with cyclopentene. The use of 2,2,5,5-d[sub 4]-cyclopentanone as the substrate reveals the direct cleavage of cyclopentanylidene carbene is occurring. A calculation of the energetics of this reaction at the MP4/6-31G[sup *]//6-31G[sup *] level suggests a nonconcerted cleavage via a biradical intermediate. Carbon atoms deoxygenate cyclohexene. Inert gas deactivated energetic cyclohexene. The deoxygenation of other oxygenated compounds by atomic carbon, such as 7-oxabicyclo[2.2.1]heptane to cyclohexane-1,4-diyl biradical, 1,2-epoxy-5-hexane to energetic 1,S-hexadiene, allyl ether to allyl radicals, and [gamma]-butyrolactone to trimethylene-1,3-diyl biradical have also been carried out. Methylketene was deoxygenated to vinylidene carbene which rearranges to propyne via a 1,2-H shift. Dimethylketene was deoxygenated to dimethylethylidene carbene which gives 2-butyne via a 1,2-methyl shift and 1,3-butadiene via a vicinal C-H bond insertion. The addition of hydrogen donors to systems in which C[sub 60] is generated results in the formation of polycyclic aromatic hydrocarbons whose carbon skeleton might represent intermediates in fullerene formation. Based on this result, the author proposed a mechanism of fullerene formation. The use of various amounts of propene as a trap showed that the yield of fullerenes decreases as the amount of the trapped product increases. Attempts to trap intermediates in fullerene formation using halides and metals have been studied. The author has attempted metal encapsulation reactions and investigated some possible chemical reactions of fullerenes.

  5. Quantum Monte Carlo calculation of the properties of atomic carbon and diamond

    SciTech Connect

    Fahy, S.; Wang, X.W.; Louie, S.G.

    1988-06-01

    A new method of calculating total energies of solids using non-local pseudopotentials in conjunction with the variational quantum Monte Carlo approach is presented. By using pseudopotentials, the large fluctuations of the energies in the core region of the atoms which occur in quantum Monte Carlo all-electron schemes are avoided. The method is applied to calculate the cohesive energy and structural properties of diamond and the first ionization energy and electron affinity of the carbon atom. Results are in excellent agreement with experiment. 8 refs., 1 fig., 2 tabs.

  6. Angular distribution of photoelectrons from atomic oxygen, nitrogen and carbon. [in upper atmosphere

    NASA Technical Reports Server (NTRS)

    Manson, S. J.; Kennedy, D. J.; Starace, A. F.; Dill, D.

    1974-01-01

    The angular distributions of photoelectrons from atomic oxygen, nitrogen, and carbon are calculated. Both Hartree-Fock and Hartree-Slater (Herman-Skillman) wave functions are used for oxygen, and the agreement is excellent; thus only Hartree-Slater functions are used for carbon and nitrogen. The pitch-angle distribution of photoelectrons is discussed, and it is shown that previous approximations of energy-independent isotropic or sin squared theta distributions are at odds with the authors' results, which vary with energy. This variation with energy is discussed, as is the reliability of these calculations.

  7. Fabrication and Characterization of Oriented Carbon Atom Wires Assembled on Gold

    SciTech Connect

    Xue,K.H.; Wu,L.; Chen, S.-P.; Wanga, L.X.; Wei, R.-B.; Xu, S.-M.; Cui, L.; Mao, B.-W.; Tian, Z.-Q.; Zen, C.-H.; Sun, S.-G.; Zhu, Y.-M.

    2009-02-17

    Carbon atom wires (CAWs) are of the sp-hybridized allotrope of carbon. To augment the extraordinary features based on sp-hybridization, we developed an approach to make CAWs be self-assembled and orderly organized on Au substrate. The self-assembling process was investigated in situ by using scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM). The properties of the assembled film were characterized by voltammetry, Raman spectroscopy, electron energy loss spectroscopy (EELS), and the contact angle measurements. Experimental results indicated that the assembled CAW film was of the good structural integrity and well organized, with the sp-hybridized features enhanced.

  8. Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

    PubMed

    Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

    2012-12-21

    In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications. PMID:23171130

  9. The interaction between Boron-carbon-nitride heteronanotubes and lithium atoms: Role of composition proportion

    NASA Astrophysics Data System (ADS)

    Zhong, Rong-Lin; Xu, Hong-Liang; Su, Zhong-Min

    2016-08-01

    A series of Li@BCN models were systematically investigated to explore the physical origin of the interaction between lithium atoms and BCNs. Theoretical results show that the crucial electron population in the BCNs of Li@B-BCN and Li@N-BCN series is dramatically different. As results, the first hyperpolarizability of Li@B-BCN series increases with the increase of carbon proportion whereas that of Li@N-BCN series significantly decreases with the increase of carbon proportion. The results indicate that the physical properties of Li@BCN models are significantly dependent on the different chemical environment of the tube termination.

  10. The abundance of atomic carbon near the ionization fronts in M17 and S140

    NASA Technical Reports Server (NTRS)

    Keene, J.; Blake, G. A.; Phillips, T. G.; Huggins, P. J.; Beichman, C. A.

    1985-01-01

    The 492 GHz ground-state line of atomic carbon in the edge-on ionization fronts in M17 and S140 were observed. It was found that, contrary to expectation, the C I emission peaks farther into the molecular cloud from the ionization front than does the CO. In fact the peak C I abundance in M17 occurs more than 60 mag of visual extinction into the cloud from the ionization front. Calculations of the ratio of C I to CO column densities yield values of 0.1-0.2. These observations do not support chemical models which predict that neutral atomic carbon should be found only near the edges of molelcular clouds. Other models are discussed which may explain the observations.

  11. Determination of gold in geological materials by carbon slurry sampling graphite furnace atomic absorption spectrometry.

    PubMed

    Dobrowolski, Ryszard; Kuryło, Michał; Otto, Magdalena; Mróz, Agnieszka

    2012-09-15

    A simple and cost effective preconcentration method on modified activated carbons is described for the determination of traces of gold (Au) in geological samples by carbon slurry sampling graphite furnace atomic absorption spectrometry (GFAAS). The basic parameters affecting the adsorption capacity of Au(III) ions on modified activated carbons were studied in detail and the effect of activated carbons modification has been determined by studying the initial runs of adsorption isotherms. The influence of chlorides and nitrates on adsorption ability of Au(III) ions onto the modified activated carbons for diluted aqueous solution was also studied in detail in respect to the determination of gold in solid materials after digestion steps in the analytical procedure, which usually involves the application of aqua regia. SEM-EDX and XPS studies confirmed that the surface reduction of Au(III) ions to Au(0) is the main gold adsorption mechanism on the activated carbon. Determination of gold after its preconcentration on the modified activated carbon was validated by applying certified reference materials. The experimental results are in good agreement with the certified values. The proposed method has been successfully applied for the determination of Au in real samples using aqueous standards. PMID:22967620

  12. Adjacent segment disease.

    PubMed

    Virk, Sohrab S; Niedermeier, Steven; Yu, Elizabeth; Khan, Safdar N

    2014-08-01

    EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Understand the forces that predispose adjacent cervical segments to degeneration. 2. Understand the challenges of radiographic evaluation in the diagnosis of cervical and lumbar adjacent segment disease. 3. Describe the changes in biomechanical forces applied to adjacent segments of lumbar vertebrae with fusion. 4. Know the risk factors for adjacent segment disease in spinal fusion. Adjacent segment disease (ASD) is a broad term encompassing many complications of spinal fusion, including listhesis, instability, herniated nucleus pulposus, stenosis, hypertrophic facet arthritis, scoliosis, and vertebral compression fracture. The area of the cervical spine where most fusions occur (C3-C7) is adjacent to a highly mobile upper cervical region, and this contributes to the biomechanical stress put on the adjacent cervical segments postfusion. Studies have shown that after fusion surgery, there is increased load on adjacent segments. Definitive treatment of ASD is a topic of continuing research, but in general, treatment choices are dictated by patient age and degree of debilitation. Investigators have also studied the risk factors associated with spinal fusion that may predispose certain patients to ASD postfusion, and these data are invaluable for properly counseling patients considering spinal fusion surgery. Biomechanical studies have confirmed the added stress on adjacent segments in the cervical and lumbar spine. The diagnosis of cervical ASD is complicated given the imprecise correlation of radiographic and clinical findings. Although radiological and clinical diagnoses do not always correlate, radiographs and clinical examination dictate how a patient with prolonged pain is treated. Options for both cervical and lumbar spine ASD include fusion and/or decompression. Current studies are encouraging regarding the adoption of arthroplasty in spinal surgery, but more long

  13. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    M.J. McKelvy; R. Sharma; A.V.G. Chizmeshya; H. Bearat; R.W. Carpenter

    2002-11-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation, before and/or during carbonation, may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (1) its structural and chemical simplicity, (2) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (3) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for minimizing the cost of any lamellar-hydroxide-based mineral carbonation sequestration process. This final report covers the overall progress of this grant.

  14. ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    M.J. McKelvy; R. Sharma; A.V.G. Chizmeshya; H. Bearat; R.W. Carpenter

    2001-10-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar-hydroxide based minerals (e.g., brucite and serpentine) offer a class of widely available, low-cost materials, with intriguing mineral carbonation potential. Carbonation of such materials inherently involves dehydroxylation, which can disrupt the material down to the atomic level. As such, controlled dehydroxylation, before and/or during carbonation, may provide an important parameter for enhancing carbonation reaction processes. Mg(OH){sub 2} was chosen as the model material for investigating lamellar hydroxide mineral dehydroxylation/carbonation mechanisms due to (i) its structural and chemical simplicity, (ii) interest in Mg(OH){sub 2} gas-solid carbonation as a potentially cost-effective CO{sub 2} mineral sequestration process component, and (iii) its structural and chemical similarity to other lamellar-hydroxide-based minerals (e.g., serpentine-based minerals) whose carbonation reaction processes are being explored due to their low-cost CO{sub 2} sequestration potential. Fundamental understanding of the mechanisms that govern dehydroxylation/carbonation processes is essential for minimizing the cost of any lamellar-hydroxide-based mineral carbonation sequestration process. This report covers the third year progress of this grant, as well as providing an integrated overview of the progress in years 1-3, as we have been granted a one-year no-cost extension to wrap up a few studies and publications to optimize project impact.

  15. Detection of the 610 micron /492 GHz/ line of interstellar atomic carbon

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.; Huggins, P. J.; Kuiper, T. B. H.; Miller, R. E.

    1980-01-01

    The ground-state transition of neutral atomic carbon, 3P1-3P0, has been detected in the interstellar medium at the frequency of 492.162 GHz determined in the laboratory by Saykally and Evenson (1980). The observations were made from the NASA Kuiper Airborne Observatory using an InSb heterodyne bolometer receiver. The line was detected as strong emission from eight molecular clouds and apparently provides a widely useful probe of the interstellar medium.

  16. The atomic configuration of graphene/vanadium carbide interfaces in vanadium carbide-encapsulating carbon nanocapsules.

    PubMed

    Yazaki, Gaku; Matsuura, Daisuke; Kizuka, Tokushi

    2014-03-01

    Carbon nanocapsules (CNCs) encapsulating vanadium carbide (VC) nanocrystals with a NaCI structure were synthesized by a gas-evaporation method using arc-discharge heating. The CNCs were observed by high-resolution transmission electron microscopy. The VC nanocrystals within the nanospaces of CNCs were truncated by low-index facets and were coated with several graphene layers, forming graphene/VC interfaces. The atomic configuration and interlayer spacings at the interfaces were found. PMID:24745251

  17. Atomic layer deposition on suspended single-walled carbon nanotubes via gas-phase noncovalent functionalization.

    PubMed

    Farmer, Damon B; Gordon, Roy G

    2006-04-01

    Alternating exposures of nitrogen dioxide gas and trimethylaluminum vapor are shown to functionalize the surfaces of single-walled carbon nanotubes with a self-limited monolayer. Functionalized nanotube surfaces are susceptible to atomic layer deposition of continuous, radially isotropic material. This allows for the creation of coaxial nanotube structures of multiple materials with precisely controlled diameters. Functionalization involves only weak physical bonding, avoiding covalent modification, which should preserve the unique optical, electrical, and mechanical properties of the nanotubes. PMID:16608267

  18. Carbon atom, dimer and trimer chemistry on diamond surfaces from molecular dynamics simulations

    SciTech Connect

    Valone, S.M.

    1995-07-01

    Spectroscopic studies of various atmospheres appearing in diamond film synthesis suggest evidence for carbon atoms, dimers, or trimers. Molecular dynamics simulations with the Brenner hydrocarbon potential are being used to investigate the elementary reactions of these species on a hydrogen-terminated diamond (111) surface. In principle these types of simulations can be extended to simulations of growth morphologies, in the 1-2 monolayer regime presently.

  19. Electronic transport in large systems through a QUAMBO-NEGF approach: Application to atomic carbon chains

    NASA Astrophysics Data System (ADS)

    Fang, X. W.; Zhang, G. P.; Yao, Y. X.; Wang, C. Z.; Ding, Z. J.; Ho, K. M.

    2011-10-01

    The conductance of single-atom carbon chain (SACC) between two zigzag graphene nanoribbons (GNR) is studied by an efficient scheme utilizing tight-binding (TB) parameters generated via quasi-atomic minimal basis set orbitals (QUAMBOs) and non-equilibrium Green's function (NEGF). Large systems (SACC contains more than 50 atoms) are investigated and the electronic transport properties are found to correlate with SACC's parity. The SACCs provide a stable off or on state in broad energy region (0.1-1 eV) around Fermi energy. The off state is not sensitive to the length of SACC while the corresponding energy region decreases with the increase of the width of GNR.

  20. A Molecular Dynamics of Cold Neutral Atoms Captured by Carbon Nanotube Under Electric Field and Thermal Effect as a Selective Atoms Sensor.

    PubMed

    Santos, Elson C; Neto, Abel F G; Maneschy, Carlos E; Chen, James; Ramalho, Teodorico C; Neto, A M J C

    2015-05-01

    Here we analyzed several physical behaviors through computational simulation of systems consisting of a zig-zag type carbon nanotube and relaxed cold atoms (Rb, Au, Si and Ar). These atoms were chosen due to their different chemical properties. The atoms individually were relaxed on the outside of the nanotube during the simulations. Each system was found under the influence of a uniform electric field parallel to the carbon nanotube and under the thermal effect of the initial temperature at the simulations. Because of the electric field, the cold atoms orbited the carbon nanotube while increasing the initial temperature allowed the variation of the radius of the orbiting atoms. We calculated the following quantities: kinetic energy, potential energy and total energy and in situ temperature, molar entropy variation and average radius of the orbit of the atoms. Our data suggest that only the action of electric field is enough to generate the attractive potential and this system could be used as a selected atoms sensor. PMID:26504991

  1. Development of carbon electrodes for electrochemistry, solid-state electronics and multimodal atomic force microscopy imaging

    NASA Astrophysics Data System (ADS)

    Morton, Kirstin Claire

    Carbon is one of the most remarkable elements due to its wide abundance on Earth and its many allotropes, which include diamond and graphite. Many carbon allotropes are conductive and in recent decades scientists have discovered and synthesized many new forms of carbon, including graphene and carbon nanotubes. The work in this thesis specifically focuses on the fabrication and characterization of pyrolyzed parylene C (PPC), a conductive pyrocarbon, as an electrode material for diodes, as a conductive coating for atomic force microscopy (AFM) probes and as an ultramicroelectrode (UME) for the electrochemical interrogation of cellular systems in vitro. Herein, planar and three-dimensional (3D) PPC electrodes were microscopically, spectroscopically and electrochemically characterized. First, planar PPC films and PPC-coated nanopipettes were utilized to detect a model redox species, Ru(NH3) 6Cl3. Then, free-standing PPC thin films were chemically doped, with hydrazine and concentrated nitric acid, to yield p- and n-type carbon films. Doped PPC thin films were positioned in conjunction with doped silicon to create Schottky and p-n junction diodes for use in an alternating current half-wave rectifier circuit. Pyrolyzed parylene C has found particular merit as a 3D electrode coating of AFM probes. Current sensing-atomic force microscopy imaging in air of nanoscale metallic features was undertaken to demonstrate the electronic imaging applicability of PPC AFM probes. Upon further insulation with parylene C and modification with a focused ion beam, a PPC UME was microfabricated near the AFM probe apex and utilized for electrochemical imaging. Subsequently, scanning electrochemical microscopy-atomic force microscopy imaging was undertaken to electrochemically quantify and image the spatial location of dopamine exocytotic release, elicited mechanically via the AFM probe itself, from differentiated pheochromocytoma 12 cells in vitro.

  2. Investigation of the Interactions and Bonding between Carbon and Group VIII Metals at the Atomic Scale.

    PubMed

    Zoberbier, Thilo; Chamberlain, Thomas W; Biskupek, Johannes; Suyetin, Mikhail; Majouga, Alexander G; Besley, Elena; Kaiser, Ute; Khlobystov, Andrei N

    2016-03-01

    The nature and dynamics of bonding between Fe, Ru, Os, and single-walled carbon nanotubes (SWNTs) is studied by aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM). The metals catalyze a wide variety of different transformations ranging from ejection of carbon atoms from the nanotube sidewall to the formation of hollow carbon shells or metal carbide within the SWNT, depending on the nature of the metal. The electron beam of AC-HRTEM serves the dual purpose of providing energy to the specimen and simultaneously enabling imaging of chemical transformations. Careful control of the electron beam parameters, energy, flux, and dose allowed direct comparison between the metals, demonstrating that their chemical reactions with SWNTs are determined by a balance between the cohesive energy of the metal particles and the strength of the metal-carbon σ- or π-bonds. The pathways of transformations of a given metal can be drastically changed by applying different electron energies (80, 40, or 20 keV), thus demonstrating AC-HRTEM as a new tool to direct and study chemical reactions. The understanding of interactions and bonding between SWNT and metals revealed by AC-HRTEM at the atomic level has important implications for nanotube-based electronic devices and catalysis. PMID:26848826

  3. Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel

    SciTech Connect

    Clarke, Amy J.; Miller, Michael K.; Alexander, David J.; Field, Robert D.; Clarke, Kester D.

    2012-08-07

    Quenching and tempering produces a wide range of mechanical properties in medium carbon, low alloyed steels - Study fragmentation behavior as a function of heat-treatment. Subtle microstructural changes accompany the mechanical property changes that result from quenching and tempering - Characterize the location and distribution of carbon and alloying elements in the microstructure using atom probe tomography (APT). Perform complementary transmission electron microscopy (TEM). Tempering influences the mechanical properties and fragmentation of quenched 4340 (hemi-shaped samples). APT revealed carbon-enriched features that contain a maximum of {approx}12-14 at.% carbon after quenching to RT (the level of carbon is perhaps associated with the extent of autotempering). TEM confirmed the presence of twinned martensite and indicates {var_epsilon} ({eta}) transition carbides after oil quenching to RT. Tempering at 325 C resulted in carbon-enriched plates (> 25 at.% C) with no significant element partitioning (transition carbides?). Tempering at 450 C and 575 C resulted in cementite ({approx} 25 at.% C) during late stage tempering; Cr, Mn, Mo partitioned to cementite and Si partitioned to ferrite. Tempering at 575 C resulted in P segregation at cementite interfaces and the formation of Cottrell atmospheres.

  4. Artificial neural network approach for atomic coordinate prediction of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Acı, Mehmet; Avcı, Mutlu

    2016-07-01

    In this paper, four artificial neural network (ANN) models [i.e., feed-forward neural network (FFNN), function fitting neural network (FITNET), cascade-forward neural network (CFNN) and generalized regression neural network] have been developed for atomic coordinate prediction of carbon nanotubes (CNTs). The research reported in this study has two primary objectives: (1) to develop ANN prediction models that calculate atomic coordinates of CNTs instead of using any simulation software and (2) to use results of the ANN models as an initial value of atomic coordinates for reducing number of iterations in calculation process. The dataset consisting of 10,721 data samples was created by combining the atomic coordinates of elements and chiral vectors using BIOVIA Materials Studio CASTEP (CASTEP) software. All prediction models yield very low mean squared normalized error and mean absolute error rates. Multiple correlation coefficient (R) results of FITNET, FFNN and CFNN models are close to 1. Compared with CASTEP, calculation times decrease from days to minutes. It would seem possible to predict CNTs' atomic coordinates using ANN models can be successfully used instead of mathematical calculations.

  5. The Kinetics of Oxygen Atom Recombination in the Presence of Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Jamieson, C. S.; Garcia, R. M.; Pejakovic, D.; Kalogerakis, K.

    2009-12-01

    Understanding processes involving atomic oxygen is crucial for the study and modeling of composition, energy transfer, airglow, and transport dynamics in planetary atmospheres. Significant gaps and uncertainties exist in the understanding of these processes and often the relevant input from laboratory measurements is missing or outdated. We are conducting laboratory experiments to measure the rate coefficient for O + O + CO2 recombination and investigating the O2 excited states produced following the recombination. These measurements will provide key input for a quantitative understanding and reliable modeling of the atmospheres of the CO2 planets and their airglow. An excimer laser providing pulsed output at either 193 nm or 248 nm is employed to produce O atoms by dissociating carbon dioxide, nitrous oxide, or ozone. In an ambient-pressure background of CO2, O atoms recombine in a time scale of a few milliseconds. Detection of laser-induced fluorescence at 845 nm following two-photon excitation near 226 nm monitors the decay of the oxygen atom population. From the temporal evolution of the signal the recombination rate coefficient is extracted. Fluorescence spectroscopy is used to detect the products of O-atom recombination and subsequent relaxation in CO2. This work is supported by the US National Science Foundation’s (NSF) Planetary Astronomy Program. Rosanne Garcia’s participation was funded by the NSF Research Experiences for Undergraduates (REU) Program.

  6. Bridged single-walled carbon nanotube-based atomic-scale mass sensors

    NASA Astrophysics Data System (ADS)

    Ali-Akbari, H. R.; Shaat, M.; Abdelkefi, A.

    2016-08-01

    The potentials of carbon nanotubes (CNTs) as mechanical resonators for atomic-scale mass sensing are presented. To this aim, a nonlocal continuum-based model is proposed to study the dynamic behavior of bridged single-walled carbon nanotube-based mass nanosensors. The carbon nanotube (CNT) is considered as an elastic Euler-Bernoulli beam with von Kármán type geometric nonlinearity. Eringen's nonlocal elastic field theory is utilized to model the interatomic long-range interactions within the structure of the CNT. This developed model accounts for the arbitrary position of the deposited atomic-mass. The natural frequencies and associated mode shapes are determined based on an eigenvalue problem analysis. An atom of xenon (Xe) is first considered as a specific case where the results show that the natural frequencies and mode shapes of the CNT are strongly dependent on the location of the deposited Xe and the nonlocal parameter of the CNT. It is also indicated that the first vibrational mode is the most sensitive when the mass is deposited at the middle of a single-walled carbon nanotube. However, when deposited in other locations, it is demonstrated that the second or third vibrational modes may be more sensitive. To investigate the sensitivity of bridged single-walled CNTs as mass sensors, different noble gases are considered, namely Xe, argon (Ar), and helium (He). It is shown that the sensitivity of the single-walled CNT to the Ar and He gases is much lower than the Xe gas due to the significant decrease in their masses. The derived model and performed analysis are so needed for mass sensing applications and particularly when the detected mass is randomly deposited.

  7. First principles study of foreign interstitial atom (carbon, nitrogen) interactions with intrinsic defects in tungsten

    NASA Astrophysics Data System (ADS)

    Kong, Xiang-Shan; You, Yu-Wei; Song, Chi; Fang, Q. F.; Chen, Jun-Ling; Luo, G.-N.; Liu, C. S.

    2012-11-01

    We performed a series of first-principles calculations to investigate the foreign interstitial atom (FIA) interactions with intrinsic defects in tungsten. We found the following: (i) The introduction of the FIA reduces the vacancy formation energy, resulting in the increase of the equilibrium concentration of vacancies. (ii) The positive binding energy between two FIAs suggests that the FIA can attract other FIAs. (iii) The FIA is easily trapped by the vacancy, and a single vacancy can accommodate up to 4 and 6 atoms in a stable manner for carbon and nitrogen, respectively. (iv) There is an attraction interaction between the FIA and the self-interstitial atom (SIA), and the FIA can reduce the SIA jump frequency and enhance the formation of SIA clusters in tungsten. Moreover, the difference between carbon and nitrogen are also discussed with respect to the formation of FIA-FIA covalent bond and the accumulation around the saturated -, where d is the ith nearest-neighbor (inn) solute-tungsten distance before relaxation and ▵di=(di-d) is the change in distance due to relaxation. The calculated relaxations are presented in Table 3. The relaxations of 1nn of octahedral interstitial carbon and nitrogen atoms are 23.30% and 22.42%, respectively, which are greatly larger than the relaxations of other nearest-neighbor atoms (0.1-2%). These results indicate that the influence range of FIA is very local. The lattice distortions introduced by the octahedral interstitial carbon or nitrogen atom can be characterized by determining the dipolar tensor from Kanzaki forces. Here, to obtain the dipolar tensor, we adopt a similar calculation procedure as used in Ref. [14], where the dipolar tensor P is calculated from the Kanzaki forces on all the tungsten atoms. The detailed procedure could be found in Ref. [14]. Due to the symmetry of the configuration, the dipolar tensor has two independent values: P11 and P33, which are listed in Table 3. Similarly with Ref. [14], approximate

  8. Influence of atomic vacancies on the dynamic characteristics of nanoresonators based on double walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Patel, Ajay M.; Joshi, Anand Y.

    2015-06-01

    The dynamic analysis of double walled carbon nanotubes (DWCNTs) with different boundary conditions has been performed using atomistic finite element method. The double walled carbon nanotube is modeled considering it as a space frame structure similar to a three dimensional beam. The elastic properties of beam element are calculated by considering mechanical characteristics of covalent bonds between the carbon atoms in the hexagonal lattice. Spring elements are used to describe the interlayer interactions between the inner and outer tubes caused due to the van der Waals forces. The mass of each beam element is assumed as point mass at nodes coinciding with carbon atoms at inner and outer wall of DWCNT. It has been reported that atomic vacancies are formed during the manufacturing process in DWCNT which tend to migrate leading to a change in the mechanical characteristics of the same. Simulations have been carried out to visualize the behavior of such defective DWCNTs subjected to different boundary conditions and when used as mass sensing devices. The variation of such atomic vacancies in outer wall of Zigzag and Armchair DWCNT is performed along the length and the change in response is noted. Moreover, as CNTs have been used as mass sensors extensively, the present approach is focused to explore the use of zigzag and armchair DWCNT as sensing device with a mono-atomic vacancy in it. The results clearly state that the dynamic characteristics are greatly influenced by defects like vacancies in it. A higher frequency shift is observed when the vacancy is located away from the fixed end for both Armchair as well as zigzag type of CNTs. A higher frequency shift is reported for armchair CNT for a mass of 10-22 g which remains constant for 10-21 g and then decreases gradually. Comparison with the other experimental and theoretical studies exhibits good association which suggests that defective DWCNTs can further be explored for mass sensing. This investigation is helpful

  9. Atomic scale enhancement of the adhesion of beryllium films to carbon substrates

    SciTech Connect

    Musket, R.G.; Wirtenson, G.R.

    1995-12-01

    We have used 200 keV carbon ions to enhance the adhesion of 240-nm thick Be films to polished, vitreous carbon substrates. Adhesion of the as-deposited films was below that necessary to pass the scotch-tape test. Carbon ion fluences less than 1.6x10{sup 14} C/cm{sup 2} were sufficient to ensure the passage of the tape test without affecting the optical properties of the films. Adhesion failure of the as-deposited film was attributed to an inner oxide layer between the Be and the carbon. Because this oxide ({approximately}5 nm of BeO) was not measurably changed by the irradiation process, these results are consistent with adhesion enhancement occurring on the atomic scale at the interface between the inner oxide and the carbon substrate. This conclusion was supported by Rutherford backscattering (RBS) data, and potential adhesion mechanisms are discussed with consideration of relative contributions from electronic and nuclear stopping.

  10. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    SciTech Connect

    Erikat, I. A.; Hamad, B. A.

    2013-11-07

    We employ density functional theory to examine the adsorption and absorption of carbon atom as well as the dissociation of carbon monoxide on Ir(100) surface. We find that carbon atoms bind strongly with Ir(100) surface and prefer the high coordination hollow site for all coverages. In the case of 0.75 ML coverage of carbon, we obtain a bridging metal structure due to the balance between Ir–C and Ir–Ir interactions. In the subsurface region, the carbon atom prefers the octahedral site of Ir(100) surface. We find large diffusion barrier for carbon atom into Ir(100) surface (2.70 eV) due to the strong bonding between carbon atom and Ir(100) surface, whereas we find a very small segregation barrier (0.22 eV) from subsurface to the surface. The minimum energy path and energy barrier for the dissociation of CO on Ir(100) surface are obtained by using climbing image nudge elastic band. The energy barrier of CO dissociation on Ir(100) surface is found to be 3.01 eV, which is appreciably larger than the association energy (1.61 eV) of this molecule.

  11. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface.

    PubMed

    Erikat, I A; Hamad, B A

    2013-11-01

    We employ density functional theory to examine the adsorption and absorption of carbon atom as well as the dissociation of carbon monoxide on Ir(100) surface. We find that carbon atoms bind strongly with Ir(100) surface and prefer the high coordination hollow site for all coverages. In the case of 0.75 ML coverage of carbon, we obtain a bridging metal structure due to the balance between Ir-C and Ir-Ir interactions. In the subsurface region, the carbon atom prefers the octahedral site of Ir(100) surface. We find large diffusion barrier for carbon atom into Ir(100) surface (2.70 eV) due to the strong bonding between carbon atom and Ir(100) surface, whereas we find a very small segregation barrier (0.22 eV) from subsurface to the surface. The minimum energy path and energy barrier for the dissociation of CO on Ir(100) surface are obtained by using climbing image nudge elastic band. The energy barrier of CO dissociation on Ir(100) surface is found to be 3.01 eV, which is appreciably larger than the association energy (1.61 eV) of this molecule. PMID:24206318

  12. A first principle study for the adsorption and absorption of carbon atom and the CO dissociation on Ir(100) surface

    NASA Astrophysics Data System (ADS)

    Erikat, I. A.; Hamad, B. A.

    2013-11-01

    We employ density functional theory to examine the adsorption and absorption of carbon atom as well as the dissociation of carbon monoxide on Ir(100) surface. We find that carbon atoms bind strongly with Ir(100) surface and prefer the high coordination hollow site for all coverages. In the case of 0.75 ML coverage of carbon, we obtain a bridging metal structure due to the balance between Ir-C and Ir-Ir interactions. In the subsurface region, the carbon atom prefers the octahedral site of Ir(100) surface. We find large diffusion barrier for carbon atom into Ir(100) surface (2.70 eV) due to the strong bonding between carbon atom and Ir(100) surface, whereas we find a very small segregation barrier (0.22 eV) from subsurface to the surface. The minimum energy path and energy barrier for the dissociation of CO on Ir(100) surface are obtained by using climbing image nudge elastic band. The energy barrier of CO dissociation on Ir(100) surface is found to be 3.01 eV, which is appreciably larger than the association energy (1.61 eV) of this molecule.

  13. Tetragonality and the distribution of carbon atoms in the Fe-C martensite: Molecular-dynamics simulation

    NASA Astrophysics Data System (ADS)

    Chirkov, P. V.; Mirzoev, A. A.; Mirzaev, D. A.

    2016-01-01

    In the statistical theory of the ordering of carbon atoms in the z sublattice of martensite, the most important role is played by the parameter of the strain interaction of carbon atoms λ0, which determines the critical temperature of the bcc-bct transition. The values of this parameter (6-11 eV/atom) obtained in recent years by the methods of computer simulation differ significantly from the value λ0 = 2.73 eV/atom obtained by A. G. Khachaturyan. In this article, we calculated the value of λ0 by two methods based on the molecular-dynamics simulation of the ordering of carbon atoms in the lattice of martensite at temperatures of 500, 750, 900, and 1000 K in a wide range of carbon concentrations, which includes c crit. No tails of ordering below c crit have been revealed. It has been shown analytically that there is an inaccuracy in the Khachaturyan theory of ordering for the crystal in an elastic environment. After eliminating this inaccuracy, no tails of the order parameter appear; the tetragonality changes jumpwise from η = 0 to ηcrit = 0.75 at c crit = 2.9 kT/λ0 instead of ηcrit = 0.5 and c crit= 2.77 kT/λ0 for an isolated crystal. Upon the simulation, clustering of carbon atoms was revealed in the form of platelike pileups along {102} planes separated by flat regions where no carbon atoms were present. The influence of short-range order in the arrangement of neighboring carbon atoms on the thermodynamics of ordering is discussed.

  14. Inelastic and reactive scattering of hyperthermal atomic oxygen from amorphous carbon

    NASA Technical Reports Server (NTRS)

    Minton, Timothy K.; Nelson, Christine M.; Brinza, David E.; Liang, Ranty H.

    1991-01-01

    The reaction of hyperthermal oxygen atoms with an amorphous carbon-13 surface was studied using a modified universal crossed molecular beams apparatus. Time-of-flight distributions of inelastically scattered O-atoms and reactively scattered CO-13 and CO2-13 were measured with a rotatable mass spectrometer detector. Two inelastic scattering channels were observed, corresponding to a direct inelastic process in which the scattered O-atoms retain 20 to 30 percent of their initial kinetic energy and to a trapping desorption process whereby O-atoms emerge from the surface at thermal velocities. Reactive scattering data imply the formation of two kinds of CO products, slow products whose translational energies are determined by the surface temperature and hyperthermal (Approx. 3 eV) products with translational energies comprising roughly 30 percent of the total available energy (E sub avl), where E sub avl is the sum of the collision energy and the reaction exothermicity. Angular data show that the hyperthermal CO is scattered preferentially in the specular direction. CO2 product was also observed, but at much lower intensities than CO and with only thermal velocities.

  15. The influence of atomic nitrogen flux on the composition of carbon nitride thin films

    SciTech Connect

    Merel, P.; Chaker, M.; Tabbal, M.; Moisan, M.

    1997-12-01

    Carbon nitride (CN{sub x}) thin films have been deposited using a hybrid system combining pulsed laser deposition of graphite with the surface-wave discharge atomic nitrogen source (3{percent} N{sub 2} in Ar). Using this system, an experiment is designed to study the influence of the atomic nitrogen flux on the composition of the CN{sub x} thin films at various laser intensities. The nitrogen percentage in the thin films is positively correlated with the N atom flux impinging on the substrate surface but it is counter-productive to use excessively high values of laser intensities on the graphite target. For a laser intensity of 6{times}10{sup 8}W/cm{sup 2}, the nitrogen percentage increases with the N atom flux and saturates at only about 16 at.{percent}. On the other hand, a maximum nitrogen percentage of 30 at.{percent} is obtained at the much lower laser intensity of 5{times}10{sup 7}W/cm{sup 2}. {copyright} {ital 1997 American Institute of Physics.}

  16. Atomic force microscopy studies of carbon nanotubes synthesized in porous alumina film

    NASA Astrophysics Data System (ADS)

    Sui, Yucheng; Sellmyer, David J.

    2002-03-01

    Mechanical properties of carbon nanotubes (CNTs) have been investigated with atomic force microscopy (AFM) [1]. Tubes used in the corresponding investigations are CNTs consisting of long and straight coaxial cylindrical units. But CNTs made by chemical vapor deposition (CVD) in porous anodic alumina film have a different tube wall structure, which consist of numerous stacked flakes or chips of carbon atomic layers [2]. It should be especially noted that these nanotubes also possess interesting electronic properties. For example, they exhibit intrinsically nonlinear transport and reproducible rectifying behavior at room temperature [3]. In this study, non contact-mode (NC), intermittent contact-mode (IC mode) and contact-mode (C mode) of atomic force microscopy were adopted to investigate the axial deformation and cutting of carbon nanotubes. It was found that IC mode and NC mode exert similar force on the tube under the same scanning height, while contact mode deformed the CNTs more completely than the former two testing modes. No irreversible deformation can be found after repeated scanning under contact mode. No deformation was found by NC and IC mode for CNTs with larger wall thickness. Tube cutting was observed by both contact and non contact mode. Research was supported by AFOSR, NSF, NRI and CMRA. References: 1. M.F. Yu, T. Kowalewski, R.S. Ruoff, Phys. Rev. Lett. 85, 1456 (2000). 2. Y. C. Sui, D. R. Acosta, J. A. Gonz¨¢lez-Le¨®n, A. Berm¨2dez, J. Feuchtwanger, B. Z. Cui, J. O. Flores, and J. M. Saniger, J. Phys. Chem. B. 105 1523 (2001) 3. C. Papadopoulos, A. Rakitin, J. Li, A.S. Vedeneev, J.M. Xu, Phys. Rev. Lett. 85, 3476 (2000).

  17. Synthesis and characterization of carbon fibers functionalized with poly (glycidyl methacrylate) via atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Wu, Yongwei; Xiong, Lei; Qin, Xiaokang; Wang, Zhengyue; Ding, Bei; Ren, Huan; Pi, Xiaolong

    2015-07-01

    In this work, polyacrylonitrile (PAN)-based carbon fibers (CF) were chemically modified with poly (glycidyl methacrylate) (PGMA) via atom transfer radical polymerization (ATRP) to improve the interaction between the CF and polymer matrix. The FT-IR, TGA, and XPS were used to determine the chemical structure of the resulting products and the quantities of PGMA chains grafted from the CF surface. The experimental results confirm that the CF surface was functionalized and glycidyl methacrylate was graft-polymerized onto the CF, and the grafting content of polymer could reach 10.2%.

  18. Fabrication process of carbon nanotube field effect transistors using atomic layer deposition passivation for biosensors.

    PubMed

    Nakashima, Yasuhiro; Ohno, Yutaka; Kishimoto, Shigeru; Okochi, Mina; Honda, Hiroyuki; Mizutani, Takashi

    2010-06-01

    Fabrication process of the carbon nanotube (CNT) field effect transistors (FETs) for biosensors was studied. Atomic layer deposition (ALD) of HfO2 was applied to the deposition of the passivation/gate insulator film. The CNT-FETs did not show the drain current degradation after ALD passivation even though the passivation by Si3N4 deposited by plasma-enhanced chemical vapor deposition (PECVD) resulted in a significant drain current decrease. This indicates the advantage of the present ALD technique in terms of the damage suppression. The biosensing operation was confirmed using thus fabricated CNT-FETs. PMID:20355371

  19. Sc3CH@C80: selective (13)C enrichment of the central carbon atom.

    PubMed

    Junghans, Katrin; Rosenkranz, Marco; Popov, Alexey A

    2016-05-01

    Sc3CH@C80 is synthesized and characterized by (1)H, (13)C, and (45)Sc NMR. A large negative chemical shift of the proton, -11.73 ppm in the Ih and -8.79 ppm in the D5h C80 cage isomers, is found. (13)C satellites in the (1)H NMR spectrum enabled indirect determination of the (13)C chemical shift for the central carbon at 173 ± 1 ppm. Intensity of the satellites allowed determination of the (13)C content for the central carbon atom. This unique possibility is applied to analyze the cluster/cage (13)C distribution in mechanistic studies employing either (13)CH4 or (13)C powder to enrich Sc3CH@C80 with (13)C. PMID:27109443

  20. Redistribution of carbon atoms in Pt substrate for high quality monolayer graphene synthesis

    NASA Astrophysics Data System (ADS)

    Yinying, Li; Xiaoming, Wu; Huaqiang, Wu; He, Qian

    2015-01-01

    The two-dimensional material graphene shows its extraordinary potential in many application fields. As the most effective method to synthesize large-area monolayer graphene, chemical vapor deposition has been well developed; however, it still faces the challenge of a high occurrence of multilayer graphene, which causes the small effective area of monolayer graphene. This phenomenon limits its applications in which only a big size of monolayer graphene is needed. In this paper, by introducing a redistribution stage after the decomposition of carbon source gas to redistribute the carbon atoms dissolved in Pt foils, the number of multilayer flakes on the monolayer graphene decreases. The mean area of monolayer graphene can be extended to about 16 000 μm2, which is eight times larger than that of the graphene grown without the redistribution stage. A Raman spectrograph is used to demonstrate the high quality of the monolayer graphene grown by the improved process.

  1. Branched aliphatic alkanes with quaternary substituted carbon atoms in modern and ancient geologic samples

    PubMed Central

    Kenig, Fabien; Simons, Dirk-Jan H.; Crich, David; Cowen, James P.; Ventura, Gregory T.; Rehbein-Khalily, Tatiana; Brown, Todd C.; Anderson, Ken B.

    2003-01-01

    A pseudohomologous series of branched aliphatic alkanes with a quaternary substituted carbon atom (BAQCs, specifically 2,2-dimethylalkanes and 3,3- and 5,5-diethylalkanes) were identified in warm (65°C) deep-sea hydrothermal waters and Late Cretaceous black shales. 5,5-Diethylalkanes were also observed in modern and Holocene marine shelf sediments and in shales spanning the last 800 million years of the geological record. The carbon number distribution of BAQCs indicates a biological origin. These compounds were observed but not identified in previous studies of 2.0 billion- to 2.2 billion-year-old metasediments and were commonly misidentified in other sediment samples, indicating that BAQCs are widespread in the geological record. The source organisms of BAQCs are unknown, but their paleobiogeographic distribution suggests that they have an affinity for sulfides and might be nonphotosynthetic sulfide oxidizers. PMID:14551322

  2. Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires

    PubMed Central

    Milani, Alberto; Tommasini, Matteo; Russo, Valeria; Li Bassi, Andrea; Lucotti, Andrea; Cataldo, Franco

    2015-01-01

    Summary Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs) can be arranged in two possible structures: a sequence of double bonds (cumulenes), resulting in a 1D metal, or an alternating sequence of single–triple bonds (polyynes), expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms) and the type of termination (e.g., atom, molecular group or nanostructure). Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length). Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds. PMID:25821689

  3. Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires.

    PubMed

    Milani, Alberto; Tommasini, Matteo; Russo, Valeria; Li Bassi, Andrea; Lucotti, Andrea; Cataldo, Franco; Casari, Carlo S

    2015-01-01

    Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs) can be arranged in two possible structures: a sequence of double bonds (cumulenes), resulting in a 1D metal, or an alternating sequence of single-triple bonds (polyynes), expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms) and the type of termination (e.g., atom, molecular group or nanostructure). Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length). Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds. PMID:25821689

  4. Distribution of carbonate-rock aquifers and the potential for their development, southern Nevada and adjacent parts of California, Arizona, and Utah

    USGS Publications Warehouse

    Dettinger, M.D.; Harrill, J.R.; Schmidt, D.L.; Hess, J.W.

    1995-01-01

    In 1985, the State of Nevada entered into a cooperative effort with the U.S. Department of the Interior to study and test the State's carbonate- rock aquifers. The studies were focused on southern Nevada and were intended to address the following concerns: Where is water potentially available in the aquifers?; How much water potentially can bewithdrawn from aquifers?; and What effects might result from development of the aquifers? The studies included basic-data collection, geologic mapping, geophysical and geochemical analyses, well drilling, and aquifer testing. The studies showed that the carbonate rocks are continuous and extensive enough to form regional aquifer systems only beneath thecentral third of the region. About 130,000 acre-feet per year of ground water flows through all the aquifers in this corridor (carbonate and noncarbonate), and about 77,000 acre-feet per year discharges directly from the carbonate-rock aquifers at regional springs in southern Nevada or at discharge areas in Death Valley, California. A larger volume of water -as much as 6 million acre-feet in the upper 100 feet alone-is stored in the rocks. Once depleted, however, that resource would be replenished by natural processes only very slowly. Ultimately, long-term development of the carbonate-rock aquifers would result in depletion of stored water, or in the capture of water that otherwise would discharge from the aquifers of southern Nevada and vicinity, or both. In manyplaces, development might extract water from both carbonate-rock and basin-fill aquifers. Possible effects of developing the carbonate-rock aquifers include declining water levels, decreasing springflow rates, drying up of some streams, playas, and meadows, and changing water quality. Specific impacts would depend upon the magnitude and length of development and site-specific conditions around the areas where the water is withdrawn. Confidence in predictions of the potential effects ofdevelopment of the carbonate

  5. Conceptual evaluation of regional ground-water flow in the carbonate-rock province of the Great Basin, Nevada, Utah, and adjacent states

    USGS Publications Warehouse

    Prudic, D.E.; Harrill, J.R.; Burbey, T.J.

    1993-01-01

    The regional groundwater flow system in the carbonate rocks of Nevada and Utah is conceptualized as shallow systems superimposed on deeper systems, which transmit water primarily through carbonate rocks. A computer model was used to simulate the two systems. The regional model includes simplifying assumptions that are probably valid for parts of the province; however, the validity of each assumption is unknown for the province as a whole. Therefore, simulation results do not perfectly replicate actual groundwater flow; instead they provide a conceptual evaluation of regional groundwater flow. The model was calibrated by adjusting transmissivity and vertical leakance until simulated water levels and simulated discharge generally agreed with known water levels, mapped areas of discharge, and estimates of discharge. Simulated flow is about 1.5 million acre-ft/yr. Most groundwater flow is simulated in the upper model layer where about 45 shallow flow regions were identified. In the lower layer, 17 deep-flow subregions were identified and grouped into 5 large regions on the basis of water-flow patterns. Simulated flow in this layer is about 28 percent of the total inflow and about half is discharged as springflow. Interbasin flow to several large springs is through thick, continuous, permeable carbonate rocks; elsewhere deep consolidated rocks are not highly transmissive, suggesting that carbonate rocks are not highly permeable everywhere or are not present everywhere. (USGS)

  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

    NASA Astrophysics Data System (ADS)

    Kayler, Z. E.; Kaiser, M.; Gessler, A.; Ellerbrock, R. H.; Sommer, M.

    2011-03-01

    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 amount while

  7. Contribution of allochthonous organic carbon across the Serrano River Basin and the adjacent fjord system in Southern Chilean Patagonia: Insights from the combined use of stable isotope and fatty acid biomarkers

    NASA Astrophysics Data System (ADS)

    Lafon, Alejandra; Silva, Nelson; Vargas, Cristian A.

    2014-12-01

    Chilean Patagonia is characterized by an irregular geography involving many islands, peninsulas, channels, sounds and fjords, that prevent direct interaction between oceanic water masses and freshwater river discharges at the head of the continental fjords. In this paper, we evaluate the potential sources and composition of organic matter along the Serrano River basin and the adjacent channels and fjords in Southern Chilean Patagonia (51-52°S), as well as their importance for marine planktonic organisms. In spring of 2009, evidence of C:N ratio, δ13C, δ15N and fatty acids composition in particulate organic carbon (POC), surface sediment, soil, plankton, and vegetal tissue, as well some physical and chemical characteristics (i.e. salinity, dissolved oxygen, NO3-, NH4+, PO4-3, Si(OH)4), were measured in samples collected during the CIMAR 14 Fiordos oceanographic cruise. Significant differences in δ13C-POC were found between the terrestrial and marine environments but not within fjord stations. Along the fjord region, the high C:N ratio and depleted δ13C values in POC samples suggest that particulate organic matter (POM) in the upper level of the water column (0-10 m depth) is supported by different sources. Terrestrial organic carbon exported by rivers may constitute a significant subsidy, up to 70% based on two end-member mixing model, to the fjord ecosystem. Furthermore, terrestrial carbon might account for a significant percentage of the zooplankton body carbon, estimated both by using isotopic (∼24-61%) and fatty acid analysis (∼14-61%). Isotopic analyses in marine sediment samples suggest that POC seems to be decoupled from terrestrial-influenced surface sources at the fjord stations, and the contribution of surrounding vegetation seemingly unimportant for carbon export to the benthos. Local hydrographic and geomorphological characteristics might determine the presence of oceanographic frontal zones, which in turn might explain differences in carbon

  8. Carbon-, sulfur-, and phosphorus-based charge transfer reactions in inductively coupled plasma-atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Grindlay, Guillermo; Gras, Luis; Mora, Juan; de Loos-Vollebregt, Margaretha T. C.

    2016-01-01

    In this work, the influence of carbon-, sulfur-, and phosphorus-based charge transfer reactions on the emission signal of 34 elements (Ag, Al, As, Au, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, I, In, Ir, K, Li, Mg, Mn, Na, Ni, P, Pb, Pd, Pt, S, Sb, Se, Sr, Te, and Zn) in axially viewed inductively coupled plasma-atomic emission spectrometry has been investigated. To this end, atomic and ionic emission signals for diluted glycerol, sulfuric acid, and phosphoric acid solutions were registered and results were compared to those obtained for a 1% w w- 1 nitric acid solution. Experimental results show that the emission intensities of As, Se, and Te atomic lines are enhanced by charge transfer from carbon, sulfur, and phosphorus ions. Iodine and P atomic emission is enhanced by carbon- and sulfur-based charge transfer whereas the Hg atomic emission signal is enhanced only by carbon. Though signal enhancement due to charge transfer reactions is also expected for ionic emission lines of the above-mentioned elements, no experimental evidence has been found with the exception of Hg ionic lines operating carbon solutions. The effect of carbon, sulfur, and phosphorus charge transfer reactions on atomic emission depends on (i) wavelength characteristics. In general, signal enhancement is more pronounced for electronic transitions involving the highest upper energy levels; (ii) plasma experimental conditions. The use of robust conditions (i.e. high r.f. power and lower nebulizer gas flow rates) improves carbon, sulfur, and phosphorus ionization in the plasma and, hence, signal enhancement; and (iii) the presence of other concomitants (e.g. K or Ca). Easily ionizable elements reduce ionization in the plasma and consequently reduce signal enhancement due to charge transfer reactions.

  9. Electronic and magnetic properties of a carbon atom chemisorbed on model clusters simulating the (100) surface of nickel

    NASA Astrophysics Data System (ADS)

    Fournier, R.; Andzelm, J.; Goursot, A.; Russo, N.; Salahub, D. R.

    1990-08-01

    Both spin-polarized and unpolarized linear combinations of Gaussian-type orbitals-model core potential-local spin density (LCGTO-MCP-LSD) calculations have been performed for clusters representing the three possible high symmetry chemisorption sites for carbon on the (100) surface of nickel. We found that the most stable chemisorption site is the fourfold hollow, in agreement with the experimental evidence. For this site, the computed equilibrium NiC distances are 1.79 and 1.77 Å at the spin-polarized and unpolarized levels, very close to the most recent experimental measurements. The calculated spin-polarized vibrational frequency perpendicular to the surface is found to be 407 cm-1 (410 cm-1 expt). The values of the binding energy are 11.5 and 11.8 eV at polarized and unpolarized levels, respectively (˜7 eV, expt); the carbon atom is strongly bound, essentially by a triple bond formed by interaction of the px, py, and pz orbitals of carbon with, primarily, the d orbitals of the four nearby surface nickel atoms. The effect of carbon chemisorption on the nickel magnetism has also been studied. The addition of the carbon atom reduces the spin magnetic moment of pure nickel by 2 or 4 μB depending on which of the two nearly degenerate nickel cluster states is taken as reference. The reduction of atomic spin magnetic moments is clearly larger on the 4 nickel atoms nearest to the carbon. The global and local (atomic) reduction in spin magnetic moments originate from some up-spin d density of states being pushed above EF, through antibonding interactions with the carbon 2p orbitals, and hence emptied.

  10. Thermodynamics and Structure of One Monolayer of Simple Atoms Absorbed on Carbon Nanotube Bundles

    NASA Astrophysics Data System (ADS)

    Vilches, Oscar

    2007-05-01

    Following the discovery and production of carbon nanotube bundles more than fifteen years ago, ideas about the properties of one-dimensional (1d) lines of atoms which could be formed in or on interstitials or grooves in the bundles were either revisited or generated for the first time. It is well known that in an infinite ideal 1d system there is no long range order and no phase coexistence, an argument first put out by Peierls and discussed in Landau and Lifschitz text. Nevertheless, the possibility of forming finite length 1d chains of atoms with gaseous, fluid, or solid properties, and no phase transitions, was intriguing. The fact that the outside surface of the bundles is a curved basal plane of graphite (graphene) is also interesting, because if films could be grown starting on grooves on the outside of the bundles those lines will grow, eventually, onto the graphene to form long and narrow quasi 2d systems to be compared to those adsorbed on flat basal plane graphite. In this experimental talk I will introduce the subject and some of the techniques used, emphasizing results on two of the simplest physisorbed atoms, ^4He and Ne. The He atom has been studied with DC and AC calorimetry, adsorption isotherms, and neutron diffraction, while Ne is currently being studied with thermodynamic measurements. Ideas from current and future experiments will conclude the presentation. The current work is being done in collaboration with Subramanian Ramachandran, Zenghui Wang and David Cobden. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NWS07.A1.2

  11. Determining littoral sediment transport paths adjacent to an eroding carbonate beach through net sediment grain-size trend analysis: Lanikai Beach, Hawaii.

    NASA Astrophysics Data System (ADS)

    Bochicchio, C. J.; Fletcher, C.; Vitousek, S.; Romine, B.; Smith, T.

    2007-12-01

    Identifying long-term trends of sediment transport in coastal environments is a fundamental goal shared by coastal scientists, engineers, and resource managers. Historical photographic analysis and predictive computer models have served as the primary approaches to charactering long-term trends in sediment flux. Net sediment grain-size trend analysis is an empirical, sedimentologically based technique that uses physical sediment samples to identify long-term sediment transport pathways. Originally developed by McLaren and Bowles (1985), net sediment grain-size trend analysis identifies progressive trends in grain-size parameters (mean size, sorting, and skewness) in sediment samples. Ultimately, the results give an indication of long-shore sediment transport, a visualization of individual littoral cells, and a better understanding of sediment processes in the near- shore region. We applied two methodologies put forth by Gao and Collins (1992) and Roux (1994) to 214 samples collected off Lanikai Beach, Hawaii; an excellent example of a coastal environment with chronic beach erosion. The Gao methodology searches point-to-point search for the two trend types used by McLaren. The Roux methodology simultaneously searches between five adjacent points for four trend types. Despite significant differences, similar trends dominate in both sets of results. The Gao methodology produces generalized trends while the Roux methodology shows finer details of sediment transport. Long-shore transport direction is shown to be northward for the majority of the study area, implying a sediment supply to the south. Therefore erosion is instigated if the sediment supply south of Lanikai Beach is cut off. A strong onshore sediment transport trend fails to accrete a beach in an armored section of the southern Lanikai coastline, demonstrating the erosive effect of increased wave refraction from coastal armoring. Results of the sediment trend analyses agree well with tidal current models

  12. Mineral sequestration of carbon dioxide in San Carlos olivine: An atomic level reaction study

    NASA Astrophysics Data System (ADS)

    Nunez, Ryan

    Since the late 19th century, atmospheric carbon dioxide (CO2) levels have been steadily on the rise. Approximately one third of all human emissions come from fossil fuel power plants. As countries become more dependent on electrical energy and bring on line new power plants, these atmospheric CO2 levels will continue to rise, generating strong environmental concern. Potential avenues to address this problem convert the CO2 from the gaseous phase to a liquid, supercritical fluid, or solid state and store it. Oceans, subsurface reservoirs such as depleted oil fields, and terrestrial carbon pools have all been suggested. The essential problem with all of these possible solutions is the issue of permanency. Mineral sequestration of CO2 is a candidate technology for reducing the amount of anthropogenic CO2 that is being released into the atmosphere. Olivine (e.g. forsterite, Mg2SiO4) is a widely available mineral that reacts with CO2 to form magnesite (MgCO3) and silica (SiO2). Magnesite is capable of immobilizing CO2 over geological time periods. Thus the issue of permanency has been addressed. The most promising mineral sequestration process developed to date is aqueous solution mineral carbonation. The solid/aqueous solution reaction interface provides insight to the mechanisms that govern the carbonation reactivity of olivine. Study of these mechanisms at the atomic level is critically important to facilitate engineering new processes that will enhance the reactivity of olivine with CO2 bearing media and to lower process costs. The study of the olivine carbonation reaction herein can be divided into three separate areas of research. The first area is a comprehensive study of olivine under conditions of electron irradiation. Analyzing radiation damage is critical to the verification and reliability of data collected from the samples using electron beam techniques. The next area of research is the analysis of the reaction layer composition and structure using High

  13. Effects of ions and atomic hydrogen in plasma-assisted growth of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Denysenko, I.; Ostrikov, K.; Yu, M. Y.; Azarenkov, N. A.

    2007-10-01

    The growth of single-walled carbon nanotubes (SWCNTs) in plasma-enhanced chemical vapor deposition (PECVD) is studied using a surface diffusion model. It is shown that at low substrate temperatures (⩽1000K), the atomic hydrogen and ion fluxes from the plasma can strongly affect nanotube growth. The ion-induced hydrocarbon dissociation can be the main process that supplies carbon atoms for SWCNT growth and is responsible for the frequently reported higher (compared to thermal chemical vapor deposition) nanotube growth rates in plasma-based processes. On the other hand, excessive deposition of plasma ions and atomic hydrogen can reduce the diffusion length of the carbon-bearing species and their residence time on the nanotube lateral surfaces. This reduction can adversely affect the nanotube growth rates. The results here are in good agreement with the available experimental data and can be used for optimizing SWCNT growth in PECVD.

  14. DFT study of Fe-Ni core-shell nanoparticles: Stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth

    NASA Astrophysics Data System (ADS)

    Yang, Zhimin; Wang, Qiang; Shan, Xiaoye; Li, Wei-qi; Chen, Guang-hui; Zhu, Hongjun

    2015-02-01

    Metal catalysts play an important role in the nucleation and growth of single-walled carbon nanotubes (SWCNTs). It is essential for probing the nucleation and growth mechanism of SWCNTs to fundamentally understand the properties of the metal catalysts and their interaction with carbon species. In this study, we systematically studied the stability of 13- and 55-atom Fe and Fe-Ni core-shell particles as well as these particles interaction with the carbon atoms using the density functional theory calculations. Icosahedral 13- and 55-atom Fe-Ni core-shell bimetallic particles have higher stability than the corresponding monometallic Fe and Ni particles. Opposite charge transfer (or distribution) in these particles leads to the Fe surface-shell displays a positive charge, while the Ni surface-shell exhibits a negative charge. The opposite charge transfer would induce different chemical activities. Compared with the monometallic Fe and Ni particles, the core-shell bimetallic particles have weaker interaction with C atoms. More importantly, C atoms only prefer staying on the surface of the bimetallic particles. In contrast, C atoms prefer locating into the subsurface of the monometallic particles, which is more likely to form stable metal carbides. The difference of the mono- and bimetallic particles on this issue may result in different nucleation and growth mechanism of SWCNTs. Our findings provide useful insights for the design of bimetallic catalysts and a better understanding nucleation and growth mechanism of SWCNTs.

  15. DFT study of Fe-Ni core-shell nanoparticles: Stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth

    SciTech Connect

    Yang, Zhimin; Wang, Qiang Shan, Xiaoye; Zhu, Hongjun; Li, Wei-qi; Chen, Guang-hui

    2015-02-21

    Metal catalysts play an important role in the nucleation and growth of single-walled carbon nanotubes (SWCNTs). It is essential for probing the nucleation and growth mechanism of SWCNTs to fundamentally understand the properties of the metal catalysts and their interaction with carbon species. In this study, we systematically studied the stability of 13- and 55-atom Fe and Fe-Ni core-shell particles as well as these particles interaction with the carbon atoms using the density functional theory calculations. Icosahedral 13- and 55-atom Fe-Ni core-shell bimetallic particles have higher stability than the corresponding monometallic Fe and Ni particles. Opposite charge transfer (or distribution) in these particles leads to the Fe surface-shell displays a positive charge, while the Ni surface-shell exhibits a negative charge. The opposite charge transfer would induce different chemical activities. Compared with the monometallic Fe and Ni particles, the core-shell bimetallic particles have weaker interaction with C atoms. More importantly, C atoms only prefer staying on the surface of the bimetallic particles. In contrast, C atoms prefer locating into the subsurface of the monometallic particles, which is more likely to form stable metal carbides. The difference of the mono- and bimetallic particles on this issue may result in different nucleation and growth mechanism of SWCNTs. Our findings provide useful insights for the design of bimetallic catalysts and a better understanding nucleation and growth mechanism of SWCNTs.

  16. Selective determination of antimony(III) and antimony(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone by atomic-absorption spectrometry with a carbon-tube atomizer.

    PubMed

    Kamada, T; Yamamoto, Y

    1977-05-01

    The extraction behaviour of antimony(III) and antimony(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone in organic solvents has been investigated by means of frameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of antimony(III) and differential determination of antimony(III) and antimony(V) have been developed. With ammonium pyrrolidinedithiocarbamate and methyl isobutyl ketone, when the aqueous phase/solvent volume ratio is 50 ml/10 ml and the injection volume in the carbon tube is 20 mul, the sensitivity for antimony is 0.2 ng/ml for 1% absorption. The relative standard deviations are ca. 2%. Interferences by many metal ions can be prevented by masking with EDTA. The proposed methods have been applied satisfactorily to determination of antimony(III) and antimony(V) in various types of water. PMID:18962096

  17. Atomic force microscopy of silica nanoparticles and carbon nanohorns in macrophages and red blood cells

    SciTech Connect

    Tetard, Laurene; Passian, Ali; Farahi, R H; Thundat, Thomas George

    2010-01-01

    The emerging interest in understanding the interactions of nanomaterial with biological systems necessitates imaging tools that capture the spatial and temporal distributions and attributes of the resulting nano-bil amalgam. Studies targeting organ specific response and/ot nanoparticle-specific system toxicity would be profoundly benefited from tools that would allow imaging and tracking of in-vivo or in-vitro processes and particle-fate studies. Recently we demonstrated that mode systhesizing atomic force microscopy (MSAFM) can provide subsurface nanoscale informations on the mechanical properties of materials at the nanoscale. However, the underlying mechanism of this imaging methodology is currently subject to theoretical and experimental investigation. In this paper we present further analysis by investigating tip-sample excitation forces associated with nanomechanical image formation. Images and force curves acquired under various operational frequencies and amplitudes are presented. We examine samples of mouse cells, where buried distributions of single-walled carbon nanohorns and silica nanoparticles are visualized.

  18. Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes.

    PubMed

    Yazdani, Nuri; Chawla, Vipin; Edwards, Eve; Wood, Vanessa; Park, Hyung Gyu; Utke, Ivo

    2014-01-01

    Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT) arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD). Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays. PMID:24778944

  19. Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes

    PubMed Central

    Yazdani, Nuri; Chawla, Vipin; Edwards, Eve; Wood, Vanessa

    2014-01-01

    Summary Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT) arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD). Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays. PMID:24778944

  20. 4D electron microscopy visualization of anisotropic atomic motions in carbon nanotubes.

    PubMed

    Park, Sang Tae; Flannigan, David J; Zewail, Ahmed H

    2012-06-01

    We report the anisotropic atomic expansion dynamics of multi-walled carbon nanotubes, using 4D electron microscopy. From time-resolved diffraction on the picosecond to millisecond scale, following ultrafast heating at the rate of 10(13) K/s, it is shown that nanotubes expand only in the radial (intertubule) direction, whereas no significant change is observed in the intratubular axial or equatorial dimensions. The non-equilibrium heating occurs on an ultrafast time scale, indicating that the anisotropy is the result of an efficient electron-lattice coupling and is maintained up to equilibration. The recovery time, which measures the heat dissipation rate for equilibration, was found to be on the order of ∼100 μs. This recovery is reproduced theoretically by considering the composite specimen-substrate heat exchange. PMID:22591381

  1. Carbon kinetic isotope effect in the reaction of CH4 with Cl atoms

    NASA Astrophysics Data System (ADS)

    Saueressig, G.; Bergamaschi, P.; Crowley, J. N.; Fischer, H.; Harris, G. W.

    1995-05-01

    The carbon kinetic isotope effect in the reaction between Cl and CH4 (KIE(sub Cl)) has been measured using tunable diode laser absorption spectroscopy to determine (13)CH4/(12)CH4 ratios. Cl atoms were generated by the irradition of Cl2 in static mixtures of Cl2/CH4/N2 or Cl2/CH4/N2/O2. Both methods resulted in a (KIE(sub Cl)) of 1.066 +/- 0.002 at 297 K. The KIE(sub Cl) displayed a slight temperature dependence, increasing to 1.075 +/- 0.005 at 223 K. This result suggests a significant influence of the title reaction on the stratospheric CH4 isotopic composition and may help to resolve discrepancies between measurements of stratospheric (13)CH4/(12)CH4 profiles and laboratory measurements of KIE(sub OH).

  2. Observation of Suspended Carbon Nanotube Configurations Using an Atomic Force Microscopy Tip

    NASA Astrophysics Data System (ADS)

    Ono, Yuki; Ogino, Toshio

    2009-08-01

    Mechanical behaviors of suspended carbon nanotubes (CNTs) or their bundles over a trench fabricated on a Si substrate were investigated by monitoring the oscillation amplitude of an atomic force microscopy (AFM) tip that interacts with the CNTs. The amplitude was considered as a function of the vertical distance between the center of the oscillating tip and the equilibrium position of the CNTs. The amplitude-distance curve (AD curve) obtained in air is interpreted as a simple model that includes the mechanical response of the suspended CNTs to the oscillating tip, the attachment/detachment of the CNTs onto the tip surface, and the oscillation of the CNTs attached to the tip. Dependences of AD curves on CNT length, bundle configuration, and the type of environment during the oscillation were investigated, and it has been found that this technique can be applied to the in situ monitoring of CNT arrangements during the manipulation of CNT networks.

  3. Discovery of a shell of neutral atomic hydrogen surrounding the carbon star IRC+10216

    NASA Astrophysics Data System (ADS)

    Matthews, L. D.; Gérard, E.; Le Bertre, T.

    2015-05-01

    We have used the Robert C. Byrd Green Bank Telescope to perform the most sensitive search to date for neutral atomic hydrogen (H I) in the circumstellar envelope (CSE) of the carbon star IRC+10216. Our observations have uncovered a low surface brightness H I shell of diameter ˜1300 arcsec (˜0.8 pc), centred on IRC+10216. The H I shell has an angular extent comparable to the far ultraviolet-emitting astrosphere of IRC+10216 previously detected with the GALEX satellite, and its kinematics are consistent with circumstellar matter that has been decelerated by the local interstellar medium. The shell appears to completely surround the star, but the highest H I column densities are measured along the leading edge of the shell, near the location of a previously identified bow shock. We estimate a total mass of atomic hydrogen associated with the IRC+10216 CSE of M_{H I} ˜ 3× 10^{-3} M_{⊙}. This is only a small fraction of the expected total mass of the CSE (<1 per cent) and is consistent with the bulk of the stellar wind originating in molecular rather than atomic form, as expected for a cool star with an effective temperature Teff ≲ 2200 K. H I mapping of a 2° × 2° region surrounding IRC+10216 has also allowed us to characterize the line-of-sight interstellar emission in the region and has uncovered a link between diffuse FUV emission south-west of IRC+10216 and the Local Leo Cold Cloud.

  4. Self-trapping of carbon atoms in α'-Fe during the martensitic transformation: A qualitative picture from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Ruban, A. V.

    2014-10-01

    Strain-induced and chemical interactions of interstitial carbon atoms in bcc or α-Fe are obtained in first-principles calculations. Subsequent Monte Carlo simulations show that at low temperatures, carbon atoms prefer to occupy at least two different octahedral sublattices, which is due to quite strong attractive interactions of carbon atoms at the corresponding coordination shells. The direct total-energy calculations of one of the obtained ordered structures with composition Fe16C2, show that it is more stable than the predicted earlier structure with the same composition but carbon atoms occupying only one octahedral sublattice. This indicates that the long-existing thermodynamic mean-field theory of ordering of carbon in α-Fe assuming strong preference of carbon atoms to occupy only one octahedral sublattice is deficient. It is shown that the presence of carbon atoms only at one octahedral sublattice in the experimentally observed martensitic phase, α'-Fe, is a self-trapping effect. It occurs during a displacive martensitic transformation from γ- to α-Fe, which kinematically transfers the carbon atoms from a single fcc octahedral sublattice to one of three octahedral sublattices, where they appear to be locked by a consequent tetragonal distortion minimizing elastic energy of the phase. The latter creates a strong preference for carbon atoms to be only at one already occupied octahedral sublattice preventing them from further distribution over the other sublattices.

  5. In situ study of erosion and deposition of amorphous hydrogenated carbon films by exposure to a hydrogen atom beam

    SciTech Connect

    Markelj, Sabina; Pelicon, Primoz; Cadez, Iztok; Schwarz-Selinger, Thomas; Jacob, Wolfgang

    2012-07-15

    This paper reports on the first dual-beam experiment employing a hydrogen atom beam for sample exposure and an ion beam for analysis, enabling in situ and real-time studies of hydrogen atom interaction with materials. The erosion of an amorphous hydrogenated carbon (a-C:H) layer by deuterium atoms at 580 K sample temperature was studied and the uptake of deuterium during the erosion process was measured in real time. The deuterium areal density increased at the beginning to 7.3 Multiplication-Sign 10{sup 15} D cm{sup -2}, but then stabilized at a constant value of 5.5 Multiplication-Sign 10{sup 15} D cm{sup -2}. Formation of a polymer-like deposit on an a-C:H layer held at room temperature and subjected to the deuterium atom beam was observed and also studied in situ. For both erosion and deposition studies an a-{sup 13}C:H layer on top of an Si substrate was used as a sample, making the experiments isotopically fully specified and thereby differentiating the deposited from the original layer and the interacting D atoms from H atoms present in the layer and in the residual vacuum. From the deposition study it was shown that carbon in the deposited layer originates from carbon-carrying species in the background vacuum that interact with hydrogen atoms. The areal density of the carbon at the surface was determined from the energy shift of the Si edge in the Rutherford backscattering spectrum. The cross section for {sup 7}Li on D at 4.3 MeV Li ion energy and at a recoil angle of 30 Degree-Sign was also determined to be (236 {+-} 16) Multiplication-Sign 10{sup -27} cm{sup 2}/sr. This is a factor of 3 {+-} 0.2 times higher than the Rutherford elastic cross section.

  6. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes

    PubMed Central

    Lorenzoni, Matteo; Matsui, Soichiro; Tanemura, Masaki; Perez-Murano, Francesc

    2015-01-01

    Summary Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO) is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM) has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT)-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF) as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency. PMID:25671165

  7. Aligned Carbon Nanotube Array Functionalization for Enhanced Atomic Layer Deposition of Platinum Electrocatalysts

    SciTech Connect

    Dameron, A. A.; Pylypenko, S.; Bult, J. B.; Neyerlin, K. C.; Engtrakul, C.; Bochert, C.; Leong, G. J.; Frisco, S. L.; Simpson, L.; Dinh, H. N.; Pivovar, B.

    2012-04-15

    Uniform metal deposition onto high surface area supports is a key challenge of developing successful efficient catalyst materials. Atomic layer deposition (ALD) circumvents permeation difficulties, but relies on gas-surface reactions to initiate growth. Our work demonstrates that modified surfaces within vertically aligned carbon nanotube (CNT) arrays, from plasma and molecular precursor treatments, can lead to improved catalyst deposition. Gas phase functionalization influences the number of ALD nucleation sites and the onset of ALD growth and, in turn, affects the uniformity of the coating along the length of the CNTs within the aligned arrays. The induced chemical changes for each functionalization route are identified by X-ray photoelectron and Raman spectroscopies. The most effective functionalization routes increase the prevalence of oxygen moieties at defect sites on the carbon surfaces. The striking effects of the functionalization are demonstrated with ALD Pt growth as a function of surface treatment and ALD cycles examined by electron microscopy of the arrays and the individual CNTs. Finally, we demonstrate applicability of these materials as fuel cell electrocatalysts and show that surface functionalization affects their performance towards oxygen reduction reaction.

  8. Studies of single walled carbon nanotubes for biomedical, mechanical and electrical applications using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Lahiji, Roya Roientan

    The promise of carbon nanotubes to provide high-strength composites implies that carbon nanotubes might find widespread use throughout the world, implying that humans everywhere will be exposed to carbon nanotube-containing materials. In order to study what effects if any carbon nanotubes might have on the function of living cells, we have studied the association of single stranded DNA (ssDNA) with single wall carbon nanotubes (SWCNTs) as a first step toward understanding the interaction of SWCNTs with living matter. Studies have been performed on both as-received and chemically oxidized SWCNTs to better understand the preferential association of ssDNA with SWCNTs. Samples of T30 ssDNA:SWCNT were examined under ambient conditions using non-contact Atomic Force Microscopy (AFM)) techniques. AFM images of well-dispersed, as-received SWCNTs revealed isolated features on the SWCNT that are 1.4 to 2.8 nm higher than the bare SWCNT itself. X-ray Photoemission Spectroscopy (XPS) confirmed these features to be T30 ssDNA in nature. Chemically oxidizing SWCNTs before dispersion by sonication is found to be an effective way to increase the number of T30 ssDNA features. A series of experiments showed that free radical scavengers such as ascorbic acid and trolox can effectively prevent the conjugation of ssDNA to SWCNTs, suggesting a significant role of free radicals in this association. Also hybridization of the complimentary ssDNA sequences showed the covalent nature of this association. These results are important to understanding the precise mechanism of ssDNA:SWCNT association and provide valuable information for future use in electronics, biosensors and as a possible drug carrier into individual cells. If SWCNTs are used in biosensor or circuit design applications then it is important to note how much energy can be stored in a SWCNT based on its shape and configuration before a permanent damage is introduced to it. Therefore a study has been done on bending SWCNTs into

  9. Dynamics of carbon-hydrogen and carbon-methyl exchanges in the collision of {sup 3}P atomic carbon with propene

    SciTech Connect

    Lee, Shih-Huang Chen, Wei-Kan; Chin, Chih-Hao; Huang, Wen-Jian

    2013-11-07

    We investigated the dynamics of the reaction of {sup 3}P atomic carbon with propene (C{sub 3}H{sub 6}) at reactant collision energy 3.8 kcal mol{sup −1} in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. Products C{sub 4}H{sub 5}, C{sub 4}H{sub 4}, C{sub 3}H{sub 3}, and CH{sub 3} were observed and attributed to exit channels C{sub 4}H{sub 5} + H, C{sub 4}H{sub 4} + 2H, and C{sub 3}H{sub 3} + CH{sub 3}; their translational-energy distributions and angular distributions were derived from the measurements of product time-of-flight spectra. Following the addition of a {sup 3}P carbon atom to the C=C bond of propene, cyclic complex c-H{sub 2}C(C)CHCH{sub 3} undergoes two separate stereoisomerization mechanisms to form intermediates E- and Z-H{sub 2}CCCHCH{sub 3}. Both the isomers of H{sub 2}CCCHCH{sub 3} in turns decompose to C{sub 4}H{sub 5} + H and C{sub 3}H{sub 3} + CH{sub 3}. A portion of C{sub 4}H{sub 5} that has enough internal energy further decomposes to C{sub 4}H{sub 4} + H. The three exit channels C{sub 4}H{sub 5} + H, C{sub 4}H{sub 4} + 2H, and C{sub 3}H{sub 3} + CH{sub 3} have average translational energy releases 13.5, 3.2, and 15.2 kcal mol{sup −1}, respectively, corresponding to fractions 0.26, 0.41, and 0.26 of available energy deposited to the translational degrees of freedom. The H-loss and 2H-loss channels have nearly isotropic angular distributions with a slight preference at the forward direction particularly for the 2H-loss channel. In contrast, the CH{sub 3}-loss channel has a forward and backward peaked angular distribution with an enhancement at the forward direction. Comparisons with reactions of {sup 3}P carbon atoms with ethene, vinyl fluoride, and vinyl chloride are stated.

  10. Surface modification of nitrogen-doped carbon nanotubes by ozone via atomic layer deposition

    SciTech Connect

    Lushington, Andrew; Liu, Jian; Tang, Yongji; Li, Ruying; Sun, Xueliang

    2014-01-15

    The use of ozone as an oxidizing agent for atomic layer deposition (ALD) processes is rapidly growing due to its strong oxidizing capabilities. However, the effect of ozone on nanostructured substrates such as nitrogen-doped multiwalled carbon nanotubes (NCNTs) and pristine multiwalled carbon nanotubes (PCNTs) are not very well understood and may provide an avenue toward functionalizing the carbon nanotube surface prior to deposition. The effects of ALD ozone treatment on NCNTs and PCNTs using 10 wt. % ozone at temperatures of 150, 250, and 300 °C are studied. The effect of ozone pulse time and ALD cycle number on NCNTs and PCNTs was also investigated. Morphological changes to the substrate were observed by scanning electron microscopy and high resolution transmission electron microscopy. Brunauer-Emmett-Teller measurements were also conducted to determine surface area, pore size, and pore size distribution following ozone treatment. The graphitic nature of both NCNTs and PCNTs was determined using Raman analysis while x-ray photoelectron spectroscopy (XPS) was employed to probe the chemical nature of NCNTs. It was found that O{sub 3} attack occurs preferentially to the outermost geometric surface of NCNTs. Our research also revealed that the deleterious effects of ozone are found only on NCNTs while little or no damage occurs on PCNTs. Furthermore, XPS analysis indicated that ALD ozone treatment on NCNTs, at elevated temperatures, results in loss of nitrogen content. Our studies demonstrate that ALD ozone treatment is an effective avenue toward creating low nitrogen content, defect rich substrates for use in electrochemical applications and ALD of various metal/metal oxides.

  11. One-pot atom-efficient synthesis of bio-renewable polyesters and cyclic carbonates through tandem catalysis.

    PubMed

    Jia, Fan; Chen, Xiaoyu; Zheng, Yan; Qin, Yusheng; Tao, Youhua; Wang, Xianhong

    2015-05-18

    One-pot synthesis of well-defined bio-renewable polyesters and cyclic carbonates in high yields was successfully realized for the first time by way of a tandem reaction using metal salen complexes as catalysts. This tandem process offered unprecedented opportunities for the atom-efficient production of two relevant compounds. PMID:25892206

  12. Selective visualization of point defects in carbon nanotubes at the atomic scale by an electron-donating molecular tip.

    PubMed

    Nishino, Tomoaki; Kanata, Satoshi; Umezawa, Yoshio

    2011-07-14

    Electron-donating molecular tips were used for the observation of single-walled carbon nanotubes (SWNTs). Defects in SWNTs were selectively visualized at the atomic scale on the basis of charge-transfer interaction with the molecular tip. PMID:21629907

  13. Activation of extended red emission photoluminescence in carbon solids by exposure to atomic hydrogen and UV radiation

    NASA Technical Reports Server (NTRS)

    Furton, Douglas G.; Witt, Adolf N.

    1993-01-01

    We report on new laboratory results which relate directly to the observation of strongly enhanced extended red emission (ERE) by interstellar dust in H2 photodissociation zones. The ERE has been attributed to photoluminescence by hydrogenated amorphous carbon (HAC). We are demonstrating that exposure to thermally dissociated atomic hydrogen will restore the photoluminescence efficiency of previously annealed HAC. Also, pure amorphous carbon (AC), not previously photoluminescent, can be induced to photoluminesce by exposure to atomic hydrogen. This conversion of AC into HAC is greatly enhanced by the presence of UV irradiation. The presence of dense, warm atomic hydrogen and a strong UV radiation field are characteristic environmental properties of H2 dissociation zones. Our results lend strong support to the HAC photoluminescence explanation for ERE.

  14. Engineering the atomic structure of carbon nanotubes by a focused electron beam: new morphologies at the sub-nanometer scale.

    PubMed

    Rodríguez-Manzo, Julio A; Krasheninnikov, Arkady V; Banhart, Florian

    2012-07-16

    Carbon atoms are displaced in pre-selected locations of carbon nanotubes by using a focused electron beam in a scanning transmission electron microscope. Sub-nanometer-sized holes are created that change the morphology of double and triple-walled carbon nanotubes and connect the shells in a unique way. By combining in situ transmission electron microscopy experiments with atomistic simulations, we study the bonding between defective shells in the new structures which are reminiscent of the shape of a flute. We demonstrate that in double-walled nanotubes the shells locally merge by forming nanoarches while atoms with dangling bonds can be preserved in triple-walled carbon nanotubes. In the latter system, nanoarches are formed between the inner- and outermost shells, shielding small graphenic islands with open edges between the neighboring shells. Our results indicate that arrays of quantum dots may be produced in carbon nanotubes by spatially localized electron irradiation, generating atoms with dangling bonds that may give rise to localized magnetic moments. PMID:22407751

  15. The atomic scale structure of CXV carbon: wide-angle x-ray scattering and modeling studies.

    PubMed

    Hawelek, L; Brodka, A; Dore, J C; Honkimaki, V; Burian, A

    2013-11-13

    The disordered structure of commercially available CXV activated carbon produced from finely powdered wood-based carbon has been studied using the wide-angle x-ray scattering technique, molecular dynamics and density functional theory simulations. The x-ray scattering data has been converted to the real space representation in the form of the pair correlation function via the Fourier transform. Geometry optimizations using classical molecular dynamics based on the reactive empirical bond order potential and density functional theory at the B3LYP/6-31g* level have been performed to generate nanoscale models of CXV carbon consistent with the experimental data. The final model of the structure comprises four chain-like and buckled graphitic layers containing a small percentage of four-fold coordinated atoms (sp(3) defects) in each layer. The presence of non-hexagonal rings in the atomic arrangement has been also considered. PMID:24140935

  16. The atomic scale structure of CXV carbon: wide-angle x-ray scattering and modeling studies

    NASA Astrophysics Data System (ADS)

    Hawelek, L.; Brodka, A.; Dore, J. C.; Honkimaki, V.; Burian, A.

    2013-11-01

    The disordered structure of commercially available CXV activated carbon produced from finely powdered wood-based carbon has been studied using the wide-angle x-ray scattering technique, molecular dynamics and density functional theory simulations. The x-ray scattering data has been converted to the real space representation in the form of the pair correlation function via the Fourier transform. Geometry optimizations using classical molecular dynamics based on the reactive empirical bond order potential and density functional theory at the B3LYP/6-31g* level have been performed to generate nanoscale models of CXV carbon consistent with the experimental data. The final model of the structure comprises four chain-like and buckled graphitic layers containing a small percentage of four-fold coordinated atoms (sp3 defects) in each layer. The presence of non-hexagonal rings in the atomic arrangement has been also considered.

  17. 1. A BRICK AND CONCRETE FAN HOUSING ADJACENT TO ONE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. A BRICK AND CONCRETE FAN HOUSING ADJACENT TO ONE OF THE ADIT OPENINGS (VIEW TO THE NORTH). - Foster Gulch Mine, Fan Housing, Bear Creek 1 mile Southwest of Town of Bear Creek, Red Lodge, Carbon County, MT

  18. Carbon abundances of reference late-type stars from 1D analysis of atomic C I and molecular CH lines

    NASA Astrophysics Data System (ADS)

    Alexeeva, S. A.; Mashonkina, L. I.

    2015-10-01

    A comprehensive model atom was constructed for C I using the most up-to-date atomic data. We evaluated non-local thermodynamical equilibrium (NLTE) line formation for neutral carbon in classical one-dimensional (1D) models representing atmospheres of late-type stars, where carbon abundance varies from the solar value down to [C/H] = -3. NLTE leads to stronger C I lines compared with their local thermodynamical equilibrium (LTE) strength and negative NLTE abundance corrections, ΔNLTE. The deviations from LTE are large for the strong lines in the infrared (IR), with ΔNLTE = -0.10 to -0.45 dex, depending on stellar parameters, and minor for the weak lines in the visible spectral range, with |ΔNLTE| ≤ 0.03 dex. The NLTE abundance corrections were found to be dependent on the carbon abundance in the model. As the first application of the treated model atom, carbon NLTE abundances were determined for the Sun and eight late-type stars with well-determined stellar parameters that cover the -2.56 ≤ [Fe/H] ≤ -1.02 metallicity range. Consistent abundances from the visible and IR lines were found for the Sun and the most metal-rich star of our sample, when applying a scaling factor of SH = 0.3 to the Drawinian rates of C+H collisions. Carbon abundances were also derived from the molecular CH lines and agree with those from the atomic C I lines for each star. We present the NLTE abundance corrections for lines of C I in the grid of model atmospheres applicable to carbon-enhanced (CEMP) stars.

  19. C-atom-induced bandgap modulation in two-dimensional (100) silicon carbon alloys

    NASA Astrophysics Data System (ADS)

    Mizuno, Tomohisa; Nagamine, Yoshiki; Omata, Yuhsuke; Suzuki, Yuhya; Urayama, Wako; Aoki, Takashi; Sameshima, Toshiyuki

    2016-04-01

    We experimentally studied the effects of the C atom on bandgap E G modulation in two-dimensional (2D) silicon carbon alloys, Si1- Y C Y , fabricated by hot C+ ion implantation into the (100) SOI substrate in a wide range of Y (4 × 10-5 ≤ Y ≤ 0.13), in comparison with the characteristics of 3D silicon carbide (SiC). X-ray photoelectron spectroscopy (XPS) and UV-Raman analysis confirm the Si-C, C-C, and Si-Si bonds in the 2D-Si1- Y C Y layer. The photoluminescence (PL) method shows that the E G and PL intensity I PL of 2D-Si1- Y C Y drastically increase with increasing Y for high Y (≥0.005), and thus we demonstrated a high E G of 2.5 eV and a visible wavelength λPL less than 500 nm. Even for low Y (<10-3), I PL of 2D-Si1- Y C Y also increases with increasing Y, owing to the compressive strain of the 2D-Si1- Y C Y layer caused by the C atoms, but the Y dependence of E G is very small. E G of 2D-Si1- Y C Y can be controlled by changing Y. Thus, the 2D-Si1- Y C Y technique is very promising for new E G engineering of future high-performance CMOS and Si photonics.

  20. Excited-state intramolecular proton transfer to carbon atoms: nonadiabatic surface-hopping dynamics simulations.

    PubMed

    Xia, Shu-Hua; Xie, Bin-Bin; Fang, Qiu; Cui, Ganglong; Thiel, Walter

    2015-04-21

    Excited-state intramolecular proton transfer (ESIPT) between two highly electronegative atoms, for example, oxygen and nitrogen, has been intensely studied experimentally and computationally, whereas there has been much less theoretical work on ESIPT to other atoms such as carbon. We have employed CASSCF, MS-CASPT2, RI-ADC(2), OM2/MRCI, DFT, and TDDFT methods to study the mechanistic photochemistry of 2-phenylphenol, for which such an ESIPT has been observed experimentally. According to static electronic structure calculations, irradiation of 2-phenylphenol populates the bright S1 state, which has a rather flat potential in the Franck-Condon region (with a shallow enol minimum at the CASSCF level) and may undergo an essentially barrierless ESIPT to the more stable S1 keto species. There are two S1/S0 conical intersections that mediate relaxation to the ground state, one in the enol region and one in the keto region, with the latter one substantially lower in energy. After S1 → S0 internal conversion, the transient keto species can return back to the S0 enol structure via reverse ground-state hydrogen transfer in a facile tautomerization. This mechanistic scenario is verified by OM2/MRCI-based fewest-switches surface-hopping simulations that provide detailed dynamic information. In these trajectories, ESIPT is complete within 118 fs; the corresponding S1 excited-state lifetime is computed to be 373 fs in vacuum. Most of the trajectories decay to the ground state via the S1/S0 conical intersection in the keto region (67%), and the remaining ones via the enol region (33%). The combination of static electronic structure computations and nonadiabatic dynamics simulations is expected to be generally useful for understanding the mechanistic photophysics and photochemistry of molecules with intramolecular hydrogen bonds. PMID:25711992

  1. Density functional theory investigation of the VIIIB transition metal atoms deposited on (5,5) single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tabtimsai, Chanukorn; Ruangpornvisuti, Vithaya; Wanno, Banchob

    2013-03-01

    The binding of VIIIB transition metals i.e. Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, and Pt single atoms to single-walled carbon nanotube (SWCNT) was investigated using the density functional theory method. The B3LYP/LanL2DZ calculation shows that all these transition metal atoms have strong binding abilities to SWCNT. The binding abilities of these transition metals onto SWCNT are in following order: Os>Ru>Ir>Fe>Rh>Pt>Ni>Co>Pd. The Os single atom binding on SWCNT is the strongest binding of which the binding energy is -240.66 kcal/mol. The partial charge transfers from transition metal to SWCNT, density of states and energy gaps of metal atoms deposited on SWCNTs were analyzed and reported.

  2. Evaporation of carbon atoms from the open surface of silicon carbide and through graphene cells: Semiempirical quantum-chemical modeling

    NASA Astrophysics Data System (ADS)

    Alekseev, N. I.; Luchinin, V. V.; Charykov, N. A.

    2013-11-01

    The evaporation of silicon atoms during the epitaxial growth of graphene on the singular carbon and silicon faces of silicon carbide SiC was modeled by the semiempirical AM1 and PM3 methods. The analysis was performed for evaporation of atoms both from the open surface of SiC and through the surface of the formed graphene monolayers. The total activation barrier of the evaporation of the silicon atoms, their passage from the graphene cell, and further evaporation from graphene was shown to be lower than the barrier to evaporation of the silicon atom on a free surface of SiC. Passage through graphene is thus not the limiting stage of the process, but contributes significantly to the effective evaporation time.

  3. Merging Single-Atom-Dispersed Silver and Carbon Nitride to a Joint Electronic System via Copolymerization with Silver Tricyanomethanide.

    PubMed

    Chen, Zupeng; Pronkin, Sergey; Fellinger, Tim-Patrick; Kailasam, Kamalakannan; Vilé, Gianvito; Albani, Davide; Krumeich, Frank; Leary, Rowan; Barnard, Jon; Thomas, John Meurig; Pérez-Ramírez, Javier; Antonietti, Markus; Dontsova, Dariya

    2016-03-22

    Herein, we present an approach to create a hybrid between single-atom-dispersed silver and a carbon nitride polymer. Silver tricyanomethanide (AgTCM) is used as a reactive comonomer during templated carbon nitride synthesis to introduce both negative charges and silver atoms/ions to the system. The successful introduction of the extra electron density under the formation of a delocalized joint electronic system is proven by photoluminescence measurements, X-ray photoelectron spectroscopy investigations, and measurements of surface ζ-potential. At the same time, the principal structure of the carbon nitride network is not disturbed, as shown by solid-state nuclear magnetic resonance spectroscopy and electrochemical impedance spectroscopy analysis. The synthesis also results in an improvement of the visible light absorption and the development of higher surface area in the final products. The atom-dispersed AgTCM-doped carbon nitride shows an enhanced performance in the selective hydrogenation of alkynes in comparison with the performance of other conventional Ag-based materials prepared by spray deposition and impregnation-reduction methods, here exemplified with 1-hexyne. PMID:26863408

  4. Direct determination and speciation of mercury compounds in environmental and biological samples by carbon bed atomic absorption spectroscopy

    SciTech Connect

    Skelly, E.M.

    1982-01-01

    A method was developed for the direct determination of mercury in water and biological samples using a unique carbon bed atomizer for atomic absorption spectroscopy. The method avoided sources of error such as loss of volatile mercury during sample digestion and contamination of samples through added reagents by eliminating sample pretreatment steps. The design of the atomizer allowed use of the 184.9 nm mercury resonance line in the vacuum ultraviolet region, which increased sensitivity over the commonly used spin-forbidden 253.7 nm line. The carbon bed atomizer method was applied to a study of mercury concentrations in water, hair, sweat, urine, blood, breath and saliva samples from a non-occupationally exposed population. Data were collected on the average concentration, the range and distribution of mercury in the samples. Data were also collected illustrating individual variations in mercury concentrations with time. Concentrations of mercury found were significantly higher than values reported in the literature for a ''normal'' population. This is attributed to the increased accuracy gained by eliminating pretreatment steps and increasing atomization efficiency. Absorption traces were obtained for various solutions of pure and complexed mercury compounds. Absorption traces of biological fluids were also obtained. Differences were observed in the absorption-temperatures traces of various compounds. The utility of this technique for studying complexation was demonstrated.

  5. Geometric Characterization of Carbon Nanotubes by Atomic Force Microscopy in Conjunction with a Tip Characterizer

    NASA Astrophysics Data System (ADS)

    Wang, Chunmei; Itoh, Hiroshi; Homma, Yoshikazu; Sun, Jielin; Hu, Jun; Ichimura, Shingo

    2008-07-01

    An atomic force microscopy (AFM) probe tip characterizer with 14 line and space structures and two knife edges was fabricated by means of a superlattice technique. The shape of a probe tip both before and after AFM imaging was acquired by this tip characterizer with general variations <1.5 nm; depending on imaging conditions. The geometric structures of carbon nanotubes (CNTs) on a SiO2 substrate were studied by dynamic mode AFM in conjunction with this tip characterizer. Contact points between the tip and the CNTs were detected by observing changes in the AFM phase images. A modified CNT width correction model was established to calculate the estimated and upper-limit widths of two CNTs. The experimental results showed that imaging under a weak attractive force was suitable for obtaining accurate CNT height measurements, whereas a weak repulsive force provided the most accurate widths. Differing heights and widths between the two CNTs suggested that one CNT was double-walled, whereas the other had more than two walls; these results agree with transmission electron microscopy (TEM) measurements of the CNTs.

  6. Sub-5 nm nanostructures fabricated by atomic layer deposition using a carbon nanotube template.

    PubMed

    Woo, Ju Yeon; Han, Hyo; Kim, Ji Weon; Lee, Seung-Mo; Ha, Jeong Sook; Shim, Joon Hyung; Han, Chang-Soo

    2016-07-01

    The fabrication of nanostructures having diameters of sub-5 nm is very a important issue for bottom-up nanofabrication of nanoscale devices. In this work, we report a highly controllable method to create sub-5 nm nano-trenches and nanowires by combining area-selective atomic layer deposition (ALD) with single-walled carbon nanotubes (SWNTs) as templates. Alumina nano-trenches having a depth of 2.6 ∼ 3.0 nm and SiO2 nano-trenches having a depth of 1.9 ∼ 2.2 nm fully guided by the SWNTs have been formed on SiO2/Si substrate. Through infilling ZnO material by ALD in alumina nano-trenches, well-defined ZnO nanowires having a thickness of 3.1 ∼ 3.3 nm have been fabricated. In order to improve the electrical properties of ZnO nanowires, as-fabricated ZnO nanowires by ALD were annealed at 350 °C in air for 60 min. As a result, we successfully demonstrated that as-synthesized ZnO nanowire using a specific template can be made for various high-density resistive components in the nanoelectronics industry. PMID:27188268

  7. Atomic Force Microscopy of DNA-wrapped Single-walled Carbon Nanotubes in Aqueous Solution.

    PubMed

    Hayashida, Takuya; Umemura, Kazuo

    2016-07-01

    We evaluated hybrids of DNA and single-walled carbon nanotubes (SWNTs) in aqueous solution and in air using atomic force microscopy (AFM). Although intensive AFM observations of these hybrids were previously carried out for samples in air, this is the first report on AFM observations of these hybrids in solution. As expected, diameters of DNA-SWNT hybrids dramatically increased in tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid (TE) buffer solution. The data suggest that DNA molecules maintain their structures even on the SWNT surfaces. Furthermore, we simultaneously observed single DNA-SWNT hybrids using three different AFM modes in air and in the TE buffer solution. Height value of the hybrids was largest in the solution, and lowest for the mode that repulsive force is expected in air. For the bare SWNT molecules, height differences among the three AFM modes were much lower than those of the DNA-SWNT hybrids. DNA molecules adsorbed on SWNT surfaces flexibly changed their morphology as well as DNA molecules on flat surfaces such as mica. This is hopeful results for biological applications of DNA-SWNT hybrids. In addition, our results revealed the importance of the single-molecule approach to evaluate DNA structures on SWNT surfaces. PMID:27045980

  8. Contribution of Chirality to the Adsorption of a Kr Atom on a Single Wall Carbon Nanotube

    NASA Astrophysics Data System (ADS)

    Kim, Hye-Young; Booth, Eric C.; Mbaye, Mamadou T.; Gatica, Silvina M.

    2014-05-01

    Recent theoretical and simulation studies (Lueking et al. Phys Rev B 75:195425, 2007; Kim et al. J Phys Chem 115:7249-7257, 2011) on the adsorption of Kr on suspended nanotubes yielded different commensurate phases at submonolayer coverage than those found in a pioneering experiment (Wang et al. Science 327:552-555, 2010). This controversy between calculations and experiments is yet to be resolved. One of the tentative explanations of the apparent discrepancy is the possibly different chirality as the chirality of the nanotubes used in the experiment is not known. To address the question on chirality, we calculated the adsorption potential of krypton atoms on two sets of single wall carbon nanotubes of same radii with distinct chiralities. We found novel symmetries of the adsorption sites on a nanotube, which systematically vary depending on its chirality with an unexpected, yet intuitive delicacy. The same approach is equally feasible for other gases (Ar, Xe, CH, etc.). The results of classical grand canonical Monte Carlo simulations confirm the predicted behavior of adsorption phases.

  9. A vortex line for K-shell ionization of a carbon atom by electron impact

    NASA Astrophysics Data System (ADS)

    Ward, S. J.; Macek, J. H.

    2014-10-01

    We obtained using the Coulomb-Born approximation a deep minimum in the TDCS for K-shell ionization of a carbon atom by electron impact for the electron ejected in the scattering plane. The minimum is obtained for the kinematics of the energy of incident electron Ei = 1801.2 eV, the scattering angle θf = 4°, the energy of the ejected electron Ek = 5 . 5 eV, and the angle for the ejected electron θk = 239°. This minimum is due to a vortex in the velocity field. At the position of the vortex, the nodal lines of Re [ T ] and Im [ T ] intersect. We decomposed the CB1 T-matrix into its multipole components for the kinematics of a vortex, taking the z'-axis parallel to the direction of the momentum transfer vector. The m = +/- 1 dipole components are necessary to obtain a vortex. We also considered the electron to be ejected out of the scattering plane and obtained the positions of the vortex for different values of the y-component of momentum of the ejected electron, ky. We constructed the vortex line for the kinematics of Ei = 1801.2 eV and θf = 4°. S.J.W. and J.H.M. acknowledge support from NSF under Grant No. PHYS- 0968638 and from D.O.E. under Grant Number DE-FG02-02ER15283, respectively.

  10. Sub-5 nm nanostructures fabricated by atomic layer deposition using a carbon nanotube template

    NASA Astrophysics Data System (ADS)

    Woo, Ju Yeon; Han, Hyo; Kim, Ji Weon; Lee, Seung-Mo; Ha, Jeong Sook; Shim, Joon Hyung; Han, Chang-Soo

    2016-07-01

    The fabrication of nanostructures having diameters of sub-5 nm is very a important issue for bottom-up nanofabrication of nanoscale devices. In this work, we report a highly controllable method to create sub-5 nm nano-trenches and nanowires by combining area-selective atomic layer deposition (ALD) with single-walled carbon nanotubes (SWNTs) as templates. Alumina nano-trenches having a depth of 2.6 ∼ 3.0 nm and SiO2 nano-trenches having a depth of 1.9 ∼ 2.2 nm fully guided by the SWNTs have been formed on SiO2/Si substrate. Through infilling ZnO material by ALD in alumina nano-trenches, well-defined ZnO nanowires having a thickness of 3.1 ∼ 3.3 nm have been fabricated. In order to improve the electrical properties of ZnO nanowires, as-fabricated ZnO nanowires by ALD were annealed at 350 °C in air for 60 min. As a result, we successfully demonstrated that as-synthesized ZnO nanowire using a specific template can be made for various high-density resistive components in the nanoelectronics industry.

  11. Quantitative Conductive Atomic Force Microscopy on Single-Walled Carbon Nanotube-Based Polymer Composites.

    PubMed

    Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leendert G J; de With, Gijsbertus

    2016-08-01

    Conductive atomic force microscopy (C-AFM) is a valuable technique for correlating the electrical properties of a material with its topographic features and for identifying and characterizing conductive pathways in polymer composites. However, aspects such as compatibility between tip material and sample, contact force and area between the tip and the sample, tip degradation and environmental conditions render quantifying the results quite challenging. This study aims at finding the suitable conditions for C-AFM to generate reliable, reproducible, and quantitative current maps that can be used to calculate the resistance in each point of a single-walled carbon nanotube (SWCNT) network, nonimpregnated as well as impregnated with a polymer. The results obtained emphasize the technique's limitation at the macroscale as the resistance of these highly conductive samples cannot be distinguished from the tip-sample contact resistance. Quantitative C-AFM measurements on thin composite sections of 150-350 nm enable the separation of sample and tip-sample contact resistance, but also indicate that these sections are not representative for the overall SWCNT network. Nevertheless, the technique was successfully used to characterize the local electrical properties of the composite material, such as sample homogeneity and resistance range of individual SWCNT clusters, at the nano- and microscale. PMID:27404764

  12. Torsional behaviors of polymer-infiltrated carbon nanotube yarn muscles studied with atomic force microscopy.

    PubMed

    Kwon, Cheong Hoon; Chun, Kyoung-Yong; Kim, Shi Hyeong; Lee, Jae-Hyeok; Kim, Jae-Ho; Lima, Márcio D; Baughman, Ray H; Kim, Seon Jeong

    2015-02-14

    Torsional behaviors of polymer-infiltrated carbon nanotube (CNT) yarn muscles have been investigated in relation to molecular architecture by using atomic force microscopy (AFM). Two polymers with different stiffnesses, polystyrene (PS) and poly(styrene-b-isoprene-b-styrene) (SIS), were uniformly infiltrated into CNT yarns for electrothermal torsional actuation. The torsional behaviors of hybrid yarn muscles are completely explained by the volume change of each polymer, based on the height and full width at half maximum profiles from the AFM morphological images. The volume expansion of the PS yarn muscle (1.7 nm of vertical change and 22 nm of horizontal change) is much larger than that of the SIS yarn muscle (0.3 nm and 11 nm change in vertical and horizontal directions) at 80 °C, normalized by their values at 25 °C. We demonstrate that their maximum rotations are consequently 29.7 deg mm(-1) for the PS-infiltrated CNT yarn muscle (relatively larger rotation) and 14.4 deg mm(-1) for the SIS-infiltrated CNT yarn muscle (smaller rotation) at 0.75 V m(-1). These hybrid yarn muscles could be applied in resonant controllers or damping magnetoelectric sensors. PMID:25567113

  13. Study of adhesion of vertically aligned carbon nanotubes to a substrate by atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Ageev, O. A.; Blinov, Yu. F.; Il'ina, M. V.; Il'in, O. I.; Smirnov, V. A.; Tsukanova, O. G.

    2016-02-01

    The adhesion to a substrate of vertically aligned carbon nanotubes (VA CNT) produced by plasmaenhanced chemical vapor deposition has been experimentally studied by atomic-force microscopy in the current spectroscopy mode. The longitudinal deformation of VA CNT by applying an external electric field has been simulated. Based on the results, a technique of determining VA CNT adhesion to a substrate has been developed that is used to measure the adhesion strength of connecting VA CNT to a substrate. The adhesion to a substrate of VA CNT 70-120 nm in diameter varies from 0.55 to 1.19 mJ/m2, and the adhesion force from 92.5 to 226.1 nN. When applying a mechanical load, the adhesion strength of the connecting VA CNT to a substrate is 714.1 ± 138.4 MPa, and the corresponding detachment force increases from 1.93 to 10.33 μN with an increase in the VA CNT diameter. As an external electric field is applied, the adhesion strength is almost doubled and is 1.43 ± 0.29 GPa, and the corresponding detachment force is changed from 3.83 to 20.02 μN. The results can be used in the design of technological processes of formation of emission structures, VA CNT-based elements for vacuum microelectronics and micro- and nanosystem engineering, and also the methods of probe nanodiagnostics of VA CNT.

  14. Atomic layer deposition of Co3O4 on carbon nanotubes/carbon cloth for high-capacitance and ultrastable supercapacitor electrode.

    PubMed

    Guan, Cao; Qian, Xu; Wang, Xinghui; Cao, Yanqiang; Zhang, Qing; Li, Aidong; Wang, John

    2015-03-01

    Co3O4 nanolayers have been successfully deposited on a flexible carbon nanotubes/carbon cloth (CC) substrate by atomic layer deposition. Much improved capacitance and ultra-long cycling life are achieved when the CNTs@Co3O4/CC is tested as a supercapacitor electrode. The improvement can be from the mechanically robust CC/CNTs substrate, the uniform coated high capacitance materials of Co3O4 nanoparticles, and the unique hierarchical structure. The flexible electrode of CNTs@Co3O4/CC with high areal capacitance and excellent cycling ability promises great potential for developing high-performance flexible supercapacitors. PMID:25665549

  15. Atomic layer deposition of Co3O4 on carbon nanotubes/carbon cloth for high-capacitance and ultrastable supercapacitor electrode

    NASA Astrophysics Data System (ADS)

    Guan, Cao; Qian, Xu; Wang, Xinghui; Cao, Yanqiang; Zhang, Qing; Li, Aidong; Wang, John

    2015-03-01

    Co3O4 nanolayers have been successfully deposited on a flexible carbon nanotubes/carbon cloth (CC) substrate by atomic layer deposition. Much improved capacitance and ultra-long cycling life are achieved when the CNTs@Co3O4/CC is tested as a supercapacitor electrode. The improvement can be from the mechanically robust CC/CNTs substrate, the uniform coated high capacitance materials of Co3O4 nanoparticles, and the unique hierarchical structure. The flexible electrode of CNTs@Co3O4/CC with high areal capacitance and excellent cycling ability promises great potential for developing high-performance flexible supercapacitors.

  16. Diamond-like carbon charge state conversion surfaces for low-energy neutral atom imaging instruments on future space missions

    NASA Astrophysics Data System (ADS)

    Neuland, M. B.; Scheer, J. A.; Riedo, A.; Wurz, P.

    2014-04-01

    The technique of surface ionisation for mapping lowenergy neutral atoms in space plasmas was successfully applied in several instruments onboard space missions in the past. We investigated diamond-like carbon surfaces regarding their eligibility as a charge state conversion surface material for future space missions, where improved characteristics of the conversion surfaces are required. Measurements on CVD (chemical vapour deposition) diamond surfaces, which are from stock available, show that the material has high potential to be used in neutral atom imaging detectors on future space missions.

  17. A journey from order to disorder — Atom by atom transformation from graphene to a 2D carbon glass

    NASA Astrophysics Data System (ADS)

    Eder, Franz R.; Kotakoski, Jani; Kaiser, Ute; Meyer, Jannik C.

    2014-02-01

    One of the most interesting questions in solid state theory is the structure of glass, which has eluded researchers since the early 1900's. Since then, two competing models, the random network theory and the crystallite theory, have both gathered experimental support. Here, we present a direct, atomic-level structural analysis during a crystal-to-glass transformation, including all intermediate stages. We introduce disorder on a 2D crystal, graphene, gradually, utilizing the electron beam of a transmission electron microscope, which allows us to capture the atomic structure at each step. The change from a crystal to a glass happens suddenly, and at a surprisingly early stage. Right after the transition, the disorder manifests as a vitreous network separating individual crystallites, similar to the modern version of the crystallite theory. However, upon increasing disorder, the vitreous areas grow on the expense of the crystallites and the structure turns into a random network. Thereby, our results show that, at least in the case of a 2D structure, both of the models can be correct, and can even describe the same material at different degrees of disorder.

  18. Atomic Scale Interface Manipulation, Structural Engineering, and Their Impact on Ultrathin Carbon Films in Controlling Wear, Friction, and Corrosion.

    PubMed

    Dwivedi, Neeraj; Yeo, Reuben J; Yak, Leonard J K; Satyanarayana, Nalam; Dhand, Chetna; Bhat, Thirumaleshwara N; Zhang, Zheng; Tripathy, Sudhiranjan; Bhatia, Charanjit S

    2016-07-13

    Reducing friction, wear, and corrosion of diverse materials/devices using <2 nm thick protective carbon films remains challenging, which limits the developments of many technologies, such as magnetic data storage systems. Here, we present a novel approach based on atomic scale interface manipulation to engineer and control the friction, wear, corrosion, and structural characteristics of 0.7-1.7 nm carbon-based films on CoCrPt:oxide-based magnetic media. We demonstrate that when an atomically thin (∼0.5 nm) chromium nitride (CrNx) layer is sandwiched between the magnetic media and an ultrathin carbon overlayer (1.2 nm), it modifies the film-substrate interface, creates various types of interfacial bonding, increases the interfacial adhesion, and tunes the structure of carbon in terms of its sp(3) bonding. These contribute to its remarkable functional properties, such as stable and lowest coefficient of friction (∼0.15-0.2), highest wear resistance and better corrosion resistance despite being only ∼1.7 nm thick, surpassing those of ∼2.7 nm thick current commercial carbon overcoat (COC) and other overcoats in this work. While this approach has direct implications for advancing current magnetic storage technology with its ultralow thickness, it can also be applied to advance the protective and barrier capabilities of other ultrathin materials for associated technologies. PMID:27267790

  19. Patterned forest-assembly of single-wall carbon nanotubes and carbon nanotube atomic force microscopy nanoprobes

    NASA Astrophysics Data System (ADS)

    Wei, Haoyan

    Single-wall carbon nanotubes (SWNTs) are envisioned to greatly impact future science and technology particularly in the nanoscale range due to their unique one dimensional structure with tunable electrical conductivity. Thus they have received considerable attention in the development of nanodevices, field emitters and biosensors. The ability to place carbon nanotubes (CNTs) with controlled orientation at desired sites presents one major challenge in assembling these remarkable nanostructures into useful functional devices. In this dissertation a metal-assisted self-assembly technique was utilized in which dense rope-lattice-like SWNT forests with upright direction were obtained by immobilizing carboxylated nanotubes from dimethylformamide (DMF) nonaqueous media onto the underlying substrates with the linkage of FeO(OH)/FeOCl crystallites. In comparison with growing CNTs by chemical vapor deposition (CVD) on patterned catalyst pads, this self-assembly approach can take advantage of post-synthesis SWNT separation according to length and type (met allic versus semiconducting). Since FeO(OH)/FeOCl crystallites acted as linkers to bridge CNTs onto the substrates, the appropriate placement of these iron deposits was pivotal to realize the desired SWNT patterns. To assist in localizing these FeO(OH)/FeOCl crystallites, three approaches on diverse substrates including Nafion, Si/SiO x and Au were investigated with the aid of low-energy electron-beam direct writing (on Nafion and Si/SiOx) and photolithography (on Au) by creating preferential precipitation sites for FeO(OH)/FeOCl crystallites. Such differential deposition of FeO(OH)/FeOCl crystallites provided the basis for the patterned site-specific self-assembly of SWNT forests as demonstrated by atomic force microscopy (AFM) and resonance Raman spectroscopy. A second part of this dissertation resulted in CNT nanoprobes on conductive AFM probes fabricated with the help of a positive dielectrophoretic (DEP) process. Under

  20. Single Atom (Pd/Pt) Supported on Graphitic Carbon Nitride as an Efficient Photocatalyst for Visible-Light Reduction of Carbon Dioxide.

    PubMed

    Gao, Guoping; Jiao, Yan; Waclawik, Eric R; Du, Aijun

    2016-05-18

    Reducing carbon dioxide to hydrocarbon fuel with solar energy is significant for high-density solar energy storage and carbon balance. In this work, single atoms of palladium and platinum supported on graphitic carbon nitride (g-C3N4), i.e., Pd/g-C3N4 and Pt/g-C3N4, respectively, acting as photocatalysts for CO2 reduction were investigated by density functional theory calculations for the first time. During CO2 reduction, the individual metal atoms function as the active sites, while g-C3N4 provides the source of hydrogen (H*) from the hydrogen evolution reaction. The complete, as-designed photocatalysts exhibit excellent activity in CO2 reduction. HCOOH is the preferred product of CO2 reduction on the Pd/g-C3N4 catalyst with a rate-determining barrier of 0.66 eV, while the Pt/g-C3N4 catalyst prefers to reduce CO2 to CH4 with a rate-determining barrier of 1.16 eV. In addition, deposition of atom catalysts on g-C3N4 significantly enhances the visible-light absorption, rendering them ideal for visible-light reduction of CO2. Our findings open a new avenue of CO2 reduction for renewable energy supply. PMID:27116595

  1. Regioselective Dichlorination of a Non-Activated Aliphatic Carbon Atom and Phenolic Bismethylation by a Multifunctional Fungal Flavoenzyme.

    PubMed

    Chankhamjon, Pranatchareeya; Tsunematsu, Yuta; Ishida-Ito, Mie; Sasa, Yuzuka; Meyer, Florian; Boettger-Schmidt, Daniela; Urbansky, Barbara; Menzel, Klaus-Dieter; Scherlach, Kirstin; Watanabe, Kenji; Hertweck, Christian

    2016-09-19

    The regioselective functionalization of non-activated carbon atoms such as aliphatic halogenation is a major synthetic challenge. A novel multifunctional enzyme catalyzing the geminal dichlorination of a methyl group was discovered in Aspergillus oryzae (Koji mold), an important fungus that is widely used for Asian food fermentation. A biosynthetic pathway encoded on two different chromosomes yields mono- and dichlorinated polyketides (diaporthin derivatives), including the cytotoxic dichlorodiaporthin as the main product. Bioinformatic analyses and functional genetics revealed an unprecedented hybrid enzyme (AoiQ) with two functional domains, one for halogenation and one for O-methylation. AoiQ was successfully reconstituted in vivo and in vitro, unequivocally showing that this FADH2 -dependent enzyme is uniquely capable of the stepwise gem-dichlorination of a non-activated carbon atom on a freestanding substrate. Genome mining indicated that related hybrid enzymes are encoded in cryptic gene clusters in numerous ecologically relevant fungi. PMID:27559694

  2. Insights in the plasma-assisted growth of carbon nanotubes through atomic scale simulations: effect of electric field.

    PubMed

    Neyts, Erik C; van Duin, Adri C T; Bogaerts, Annemie

    2012-01-18

    Carbon nanotubes (CNTs) are nowadays routinely grown in a thermal CVD setup. State-of-the-art plasma-enhanced CVD (PECVD) growth, however, offers advantages over thermal CVD. A lower growth temperature and the growth of aligned freestanding single-walled CNTs (SWNTs) makes the technique very attractive. The atomic scale growth mechanisms of PECVD CNT growth, however, remain currently entirely unexplored. In this contribution, we employed molecular dynamics simulations to focus on the effect of applying an electric field on the SWNT growth process, as one of the effects coming into play in PECVD. Using sufficiently strong fields results in (a) alignment of the growing SWNTs, (b) a better ordering of the carbon network, and (c) a higher growth rate relative to thermal growth rate. We suggest that these effects are due to the small charge transfer occurring in the Ni/C system. These simulations constitute the first study of PECVD growth of SWNTs on the atomic level. PMID:22126536

  3. Spatial evolutions of Co and Ni atoms during single-walled carbon nanotubes formation: measurements and modeling.

    PubMed

    Cau, M; Dorval, N; Cao, B; Attal-Trétout, B; Cochon, J L; Loiseau, A; Farhat, S; Scott, C D

    2006-05-01

    Spatial investigations of nickel and cobalt atoms and of C2 and C3 radicals are performed by laser induced fluorescence (LIF) in a continuous CO2 laser-vaporization reactor during the synthesis of single-walled carbon nanotubes. The chemical composition of the gas vaporized from bimetallic Ni/Co catalysts-carbon targets is determined using a chemical kinetic model. In this model, the evolution of Ni and Co atoms is driven by kinetics of condensation/evaporation process of pure metal clusters. Metal-carbon clusters are assumed to form from soot particles (C80) and 128-atom metal clusters. Spatial profiles of Ni and Co atoms obtained by LIF are compared with the calculations to validate the modeling and to adjust the input data. The value of the initial molar fraction of carbon-metal mixture diluted in helium is determined through a parametric study. Good agreement is found between the measured and the calculated evolution of Ni for a molar fraction of the helium diluent ranging from 10 to 15%. To fit the spatial profile of Co, the activation energy is adjusted in the evaporation rate, changing the cobalt dimer bond energy. The latter is found to be largely uncertain; and three values are tested: 167, 208, and 230 kJ x mol(-1). From comparison, the activation energy is found to be 208 kJ x mol(-1). However, the C2 LIF profiles show that the depletion of C2 is accelerated when cobalt is present. The observed Co evolutions suggest that small Co-C clusters are easier and/or faster to form compared to Ni-C clusters. PMID:16792356

  4. Dynamic response of a carbon nanotube-based rotary nano device with different carbon-hydrogen bonding layout

    NASA Astrophysics Data System (ADS)

    Yin, Hang; Cai, Kun; Wan, Jing; Gao, Zhaoliang; Chen, Zhen

    2016-03-01

    In a nano rotational transmission system (RTS) which consists of a single walled carbon nanotube (SWCNT) as the motor and a coaxially arranged double walled carbon nanotube (DWCNT) as a bearing, the interaction between the motor and the rotor in bearing, which has great effects on the response of the RTS, is determined by their adjacent edges. Using molecular dynamics (MD) simulation, the interaction is analyzed when the adjacent edges have different carbon-hydrogen (Csbnd H) bonding layouts. In the computational models, the rotor in bearing and the motor with a specific input rotational speed are made from the same armchair SWCNT. Simulation results demonstrate that a perfect rotational transmission could happen when the motor and rotor have the same Csbnd H bonding layout on their adjacent ends. If only half or less of the carbon atoms on the adjacent ends are bonded with hydrogen atoms, the strong attraction between the lower speed (100 GHz) motor and rotor leads to a synchronous rotational transmission. If only the motor or the rotor has Csbnd H bonds on their adjacent ends, no rotational transmission happens due to weak interaction between the bonded hydrogen atoms on one end with the sp1 bonded carbon atoms on the other end.

  5. Permeation of low-Z atoms through carbon sheets: Density functional theory study on energy barriers and deformation effects

    SciTech Connect

    Huber, Stefan E. E-mail: Michael.probst@uibk.ac.at; Mauracher, Andreas; Probst, Michael E-mail: Michael.probst@uibk.ac.at

    2013-12-15

    Energetic and geometric aspects of the permeation of the atoms hydrogen to neon neutral atoms through graphene sheets are investigated by investigating the associated energy barriers and sheet deformations. Density functional theory calculations on cluster models, where graphene is modeled by planar polycyclic aromatic hydrocarbons (PAHs), provide the energies and geometries. Particularities of our systems, such as convergence of both energy barriers and deformation curves with increasing size of the PAHs, are discussed. Three different interaction regimes, adiabatic, planar and vertical, are investigated by enforcing different geometrical constraints. The adiabatic energy barriers range from 5 eV for hydrogen to 20 eV for neon. We find that the permeation of oxygen and carbon into graphene is facilitated by temporary chemical bonding while for other, in principle reactive atoms, it is not. We discuss implications of our results for modeling chemical sputtering of graphite.

  6. Protection of Diamond-like Carbon Films from Energetic Atomic Oxygen Degradation Through Si-doping Technology

    SciTech Connect

    Yokota, Kumiko; Tagawa, Masahito; Kitamura, Akira; Matsumoto, Koji; Yoshigoe, Akitaka; Teraoka, Yuden; Fontaine, Julien; Belin, Michel

    2009-01-05

    The effect of hyperthermal atomic oxygen (AO) exposure on the surface properties of Si-doped diamond-like carbon (DLC) was investigated. Two types of DLC were tested that contain approximately 10 at% and 20 at% of Si atoms. Surface analytical results of high-resolution x-ray photoelectron spectroscopy using synchrotron radiation (synchrotron radiation photoemission spectroscopy; SR-PES) as well as Rutherford backscattering spectroscopy (RBS) have been used for characterization of the AO-exposed Si-doped DLC. It was identified by SR-PES that a SiO{sub 2} layer was formed by the hyperthermal AO exposure at the Si-doped DLC surface. RBS data indicates that AO exposure leads to severe thickness loss on the undopedd DLC. In contrast, a SiO{sub 2} layer formed by the hyperthermal atomic oxygen reaction of Si-doped DLC protects the DLC underneath the SiO{sub 2} layer.

  7. Survivability of Silicon-Doped Diamond-Like Carbon Films in Energetic Atomic/Molecular Oxygen Beam Environments

    NASA Astrophysics Data System (ADS)

    Tagawa, Masahito; Kishida, Kazuhiro; Yokota, Kumiko; Matsumoto, Koji; Yoshigoe, Akitaka; Teraoka, Yuden; Zhang, Jianming; Minton, Timothy K.

    Volatile products were measured from two types of diamond-like carbon films under the hyperthermal atomic oxygen (AO) beam bombardment. It was clearly observed that CO and CO2 were formed at the conventional hydrogenated DLC surface when exposed to hyperthermal AO beam. Desorption rates of CO and CO2 are constant with AO fluence which reflects the constant erosion rate of the hydrogenated DLC. In contrast, Si-doped DLC shows decrease in amount of CO and CO2 with increasing AO fluence. Oxidation of Si atoms at the DLC surface was detected by X-ray photoelectron spectroscopy, confirming the formation of SiO2 film formed at the DLC surface that could prevent AO reaction with C atoms in DLC which leads to loss of DLC. Since a self-healing capability can be expected on Si-doped DLC, metal doping is a promising technology for space application of DLC.

  8. Torsional behaviors of polymer-infiltrated carbon nanotube yarn muscles studied with atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kwon, Cheong Hoon; Chun, Kyoung-Yong; Kim, Shi Hyeong; Lee, Jae-Hyeok; Kim, Jae-Ho; Lima, Márcio D.; Baughman, Ray H.; Kim, Seon Jeong

    2015-01-01

    Torsional behaviors of polymer-infiltrated carbon nanotube (CNT) yarn muscles have been investigated in relation to molecular architecture by using atomic force microscopy (AFM). Two polymers with different stiffnesses, polystyrene (PS) and poly(styrene-b-isoprene-b-styrene) (SIS), were uniformly infiltrated into CNT yarns for electrothermal torsional actuation. The torsional behaviors of hybrid yarn muscles are completely explained by the volume change of each polymer, based on the height and full width at half maximum profiles from the AFM morphological images. The volume expansion of the PS yarn muscle (1.7 nm of vertical change and 22 nm of horizontal change) is much larger than that of the SIS yarn muscle (0.3 nm and 11 nm change in vertical and horizontal directions) at 80 °C, normalized by their values at 25 °C. We demonstrate that their maximum rotations are consequently 29.7 deg mm-1 for the PS-infiltrated CNT yarn muscle (relatively larger rotation) and 14.4 deg mm-1 for the SIS-infiltrated CNT yarn muscle (smaller rotation) at 0.75 V m-1. These hybrid yarn muscles could be applied in resonant controllers or damping magnetoelectric sensors.Torsional behaviors of polymer-infiltrated carbon nanotube (CNT) yarn muscles have been investigated in relation to molecular architecture by using atomic force microscopy (AFM). Two polymers with different stiffnesses, polystyrene (PS) and poly(styrene-b-isoprene-b-styrene) (SIS), were uniformly infiltrated into CNT yarns for electrothermal torsional actuation. The torsional behaviors of hybrid yarn muscles are completely explained by the volume change of each polymer, based on the height and full width at half maximum profiles from the AFM morphological images. The volume expansion of the PS yarn muscle (1.7 nm of vertical change and 22 nm of horizontal change) is much larger than that of the SIS yarn muscle (0.3 nm and 11 nm change in vertical and horizontal directions) at 80 °C, normalized by their values at 25

  9. Computational insights into the effect of carbon structures at the atomic level for non-aqueous sodium-oxygen batteries

    NASA Astrophysics Data System (ADS)

    Jiang, H. R.; Wu, M. C.; Zhou, X. L.; Yan, X. H.; Zhao, T. S.

    2016-09-01

    Carbon materials have been widely used to form air cathodes for non-aqueous sodium-oxygen (Nasbnd O2) batteries due to their large specific surface area, high conductivity and low cost. However, the effect of carbon structures at the atomic level remains poorly understood. In this work, a first-principles study is conducted to investigate how representative carbon structures, including graphite (0001) surface, point defects and fractured edge, influence the discharge and charge processes of non-aqueous Nasbnd O2 batteries. It is found that the single vacancy (SV) defect has the largest adsorption energy (5.81 eV) to NaO2 molecule among the structures studied, even larger than that of the NaO2 molecule on NaO2 crystal (2.81 eV). Such high adsorption energy is attributed to two factors: the dangling atoms in SV defects decrease the distance from NaO2 molecules, and the attachment through oxygen atoms increases the electrons transfer. The findings suggest that SV defects can act as the nucleation sites for NaO2 in the discharge process, and increasing the number of SV defects can facilitate the uniform formation of small-sized particles. The uniformly distributed discharge products lower the possibility for pore clogging, leading to an increased discharge capacity and improved cyclability for non-aqueous Nasbnd O2 batteries.

  10. Structural modifications of graphyne layers consisting of carbon atoms in the sp- and sp{sup 2}-hybridized states

    SciTech Connect

    Belenkov, E. A.; Mavrinskii, V. V.; Belenkova, T. E.; Chernov, V. M.

    2015-05-15

    A model scheme is proposed for obtaining layered compounds consisting of carbon atoms in the sp- and (vnsp){sup 2}-hybridized states. This model is used to find the possibility of existing the following seven basic structural modifications of graphyne: α-, β1-, β2-, β3-, γ1-, γ2-, and γ3-graphyne. Polymorphic modifications β3 graphyne and γ3 graphyne are described. The basic structural modifications of graphyne contain diatomic polyyne chains and consist only of carbon atoms in two different crystallographically equivalent states. Other nonbasic structural modifications of graphyne can be formed via the elongation of the carbyne chains that connect three-coordinated carbon atoms and via the formation of graphyne layers with a mixed structure consisting of basic layer fragments, such as α-β-graphyne, α-γ-graphyne, and β-γ-graphyne. The semiempirical quantum-mechanical MNDO, AM1, and PM3 methods and ab initio STO6-31G basis calculations are used to find geometrically optimized structures of the basic graphyne layers, their structural parameters, and energies of their sublimation. The energy of sublimation is found to be maximal for γ2-graphyne, which should be the most stable structural modification of graphyne.

  11. Atomic-scale wear of amorphous hydrogenated carbon during intermittent contact: a combined study using experiment, simulation, and theory.

    PubMed

    Vahdat, Vahid; Ryan, Kathleen E; Keating, Pamela L; Jiang, Yijie; Adiga, Shashishekar P; Schall, J David; Turner, Kevin T; Harrison, Judith A; Carpick, Robert W

    2014-07-22

    In this study, we explore the wear behavior of amplitude modulation atomic force microscopy (AM-AFM, an intermittent-contact AFM mode) tips coated with a common type of diamond-like carbon, amorphous hydrogenated carbon (a-C:H), when scanned against an ultra-nanocrystalline diamond (UNCD) sample both experimentally and through molecular dynamics (MD) simulations. Finite element analysis is utilized in a unique way to create a representative geometry of the tip to be simulated in MD. To conduct consistent and quantitative experiments, we apply a protocol that involves determining the tip-sample interaction geometry, calculating the tip-sample force and normal contact stress over the course of the wear test, and precisely quantifying the wear volume using high-resolution transmission electron microscopy imaging. The results reveal gradual wear of a-C:H with no sign of fracture or plastic deformation. The wear rate of a-C:H is consistent with a reaction-rate-based wear theory, which predicts an exponential dependence of the rate of atom removal on the average normal contact stress. From this, kinetic parameters governing the wear process are estimated. MD simulations of an a-C:H tip, whose radius is comparable to the tip radii used in experiments, making contact with a UNCD sample multiple times exhibit an atomic-level removal process. The atomistic wear events observed in the simulations are correlated with under-coordinated atomic species at the contacting surfaces. PMID:24922087

  12. Probing the role of an atomically thin SiNx interlayer on the structure of ultrathin carbon films.

    PubMed

    Dwivedi, Neeraj; Rismani-Yazdi, Ehsan; Yeo, Reuben J; Goohpattader, Partho S; Satyanarayana, Nalam; Srinivasan, Narasimhan; Druz, Boris; Tripathy, S; Bhatia, C S

    2014-01-01

    Filtered cathodic vacuum arc (FCVA) processed carbon films are being considered as a promising protective media overcoat material for future hard disk drives (HDDs). However, at ultrathin film levels, FCVA-deposited carbon films show a dramatic change in their structure in terms of loss of sp3 bonding, density, wear resistance etc., compared to their bulk counterpart. We report for the first time how an atomically thin (0.4 nm) silicon nitride (SiNx) interlayer helps in maintaining/improving the sp3 carbon bonding, enhancing interfacial strength/bonding, improving oxidation/corrosion resistance, and strengthening the tribological properties of FCVA-deposited carbon films, even at ultrathin levels (1.2 nm). We propose the role of the SiNx interlayer in preventing the catalytic activity of Co and Pt in media, leading to enhanced sp3C bonding (relative enhancement~40%). These findings are extremely important in view of the atomic level understanding of structural modification and the development of high density HDDs. PMID:24846506

  13. Probing the Role of an Atomically Thin SiNx Interlayer on the Structure of Ultrathin Carbon Films

    PubMed Central

    Dwivedi, Neeraj; Rismani-Yazdi, Ehsan; Yeo, Reuben J.; Goohpattader, Partho S.; Satyanarayana, Nalam; Srinivasan, Narasimhan; Druz, Boris; Tripathy, S.; Bhatia, C. S.

    2014-01-01

    Filtered cathodic vacuum arc (FCVA) processed carbon films are being considered as a promising protective media overcoat material for future hard disk drives (HDDs). However, at ultrathin film levels, FCVA-deposited carbon films show a dramatic change in their structure in terms of loss of sp3 bonding, density, wear resistance etc., compared to their bulk counterpart. We report for the first time how an atomically thin (0.4 nm) silicon nitride (SiNx) interlayer helps in maintaining/improving the sp3 carbon bonding, enhancing interfacial strength/bonding, improving oxidation/corrosion resistance, and strengthening the tribological properties of FCVA-deposited carbon films, even at ultrathin levels (1.2 nm). We propose the role of the SiNx interlayer in preventing the catalytic activity of Co and Pt in media, leading to enhanced sp3C bonding (relative enhancement ~40%). These findings are extremely important in view of the atomic level understanding of structural modification and the development of high density HDDs. PMID:24846506

  14. ATOMIC-LEVEL MODELING OF CO2 DISPOSAL AS A CARBONATE MINERAL: A SYNERGETIC APPROACH TO OPTIMIZING REACTION PROCESS DESIGN

    SciTech Connect

    A.V.G. Chizmeshya; M.J. McKelvy; J.B. Adams

    2001-11-01

    Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg-rich lamellar hydroxide mineral carbonation is a leading process candidate, which generates the stable naturally occurring mineral magnesite (MgCO{sub 3}) and water. Key to process cost and viability are the carbonation reaction rate and its degree of completion. This process, which involves simultaneous dehydroxylation and carbonation is very promising, but far from optimized. In order to optimize the dehydroxylation/carbonation process, an atomic-level understanding of the mechanisms involved is needed. In this investigation Mg(OH){sub 2} was selected as a model Mg-rich lamellar hydrocide carbonation feedstock material due to its chemical and structural simplicity. Since Mg(OH){sub 2} dehydroxylation is intimately associated with the carbonation process, its mechanisms are also of direct interest in understanding and optimizing the process. The aim of the current innovative concepts project is to develop a specialized advanced computational methodology to complement the ongoing experimental inquiry of the atomic level processes involved in CO{sub 2} mineral sequestration. The ultimate goal is to integrate the insights provided by detailed predictive simulations with the data obtained from optical microscopy, FESEM, ion beam analysis, SIMS, TGA, Raman, XRD, and C and H elemental analysis. The modeling studies are specifically designed to enhance the synergism with, and complement the analysis of, existing mineral-CO{sub 2} reaction process studies being carried out under DOE UCR Grant DE-FG2698-FT40112. Direct contact between the simulations and the experimental

  15. Application of the Basin Characterization Model to Estimate In-Place Recharge and Runoff Potential in the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

    USGS Publications Warehouse

    Flint, Alan L.; Flint, Lorraine E.

    2007-01-01

    A regional-scale water-balance model was used to estimate recharge and runoff potential and support U.S. Geological Survey efforts to develop a better understanding of water availability for the Basin and Range carbonate-rock aquifer system (BARCAS) study in White Pine County, Nevada, and adjacent areas in Nevada and Utah. The water-balance model, or Basin Characterization Model (BCM), was used to estimate regional ground-water recharge for the 13 hydrographic areas in the study area. The BCM calculates recharge by using a distributed-parameter, water-balance method and monthly climatic boundary conditions. The BCM requires geographic information system coverages of soil, geology, and topographic information with monthly time-varying climatic conditions of air temperature and precipitation. Potential evapotranspiration, snow accumulation, and snowmelt are distributed spatially with process models. When combined with surface properties of soil-water storage and saturated hydraulic conductivity of bedrock and alluvium, the potential water available for in-place recharge and runoff is calculated using monthly time steps using a grid scale of 866 feet (270 meters). The BCM was used with monthly climatic inputs from 1970 to 2004, and results were averaged to provide an estimate of the average annual recharge for the BARCAS study area. The model estimates 526,000 acre-feet of potential in-place recharge and approximately 398,000 acre-feet of potential runoff. Assuming 15 percent of the runoff becomes recharge, the model estimates average annual ground-water recharge for the BARCAS area of about 586,000 acre-feet. When precipitation is extrapolated to the long-term climatic record (1895-2006), average annual recharge is estimated to be 530,000 acre-feet, or about 9 percent less than the recharge estimated for 1970-2004.

  16. In vitro comparison of the hemocompatibility of diamond-like carbon and carbon nitride coatings with different atomic percentages of N.

    PubMed

    Zhao, Mengli; Li, Dejun; Zhang, Yiteng; Guo, Meixian; Deng, Xiangyun; Gu, Hanqing; Wan, Rongxin

    2012-04-01

    Carbon nitride (CN( x )) and diamond-like carbon (DLC) coatings were prepared by dc magnetron sputtering at room temperature. Different partial pressures of N(2) were used to synthesize CN( x ) to evaluate the relationship between the atomic percentage of nitrogen and hemocompatibility. Auger electron spectroscopy and atomic force microscopy indicated atomic percentages of N of 0.12 and 0.22 and that the CN( x ) coatings were smooth. An in vitro study of the hemocompatibility of the coatings revealed that both CN( x ) coatings had better anticoagulant properties and lower platelet adhesion than DLC. Compared with CN(0.12), the CN(0.22) coating showed longer dynamic clotting time (about 42 min), static clotting time (23.6 min) and recalcification time (45.6 s), as well as lower platelet adhesion (102 cells μm(-2)), aggregation, and activation. The presence of nitrogen in the CN( x ) coatings induced their enhanced hemocompatibility compared with DLC. PMID:22566091

  17. Carbon nanotubes randomly decorated with gold clusters: from nano2hybrid atomic structures to gas sensing prototypes

    NASA Astrophysics Data System (ADS)

    Charlier, J.-C.; Arnaud, L.; Avilov, I. V.; Delgado, M.; Demoisson, F.; Espinosa, E. H.; Ewels, C. P.; Felten, A.; Guillot, J.; Ionescu, R.; Leghrib, R.; Llobet, E.; Mansour, A.; Migeon, H.-N.; Pireaux, J.-J.; Reniers, F.; Suarez-Martinez, I.; Watson, G. E.; Zanolli, Z.

    2009-09-01

    Carbon nanotube surfaces, activated and randomly decorated with metal nanoclusters, have been studied in uniquely combined theoretical and experimental approaches as prototypes for molecular recognition. The key concept is to shape metallic clusters that donate or accept a fractional charge upon adsorption of a target molecule, and modify the electron transport in the nanotube. The present work focuses on a simple system, carbon nanotubes with gold clusters. The nature of the gold-nanotube interaction is studied using first-principles techniques. The numerical simulations predict the binding and diffusion energies of gold atoms at the tube surface, including realistic atomic models for defects potentially present at the nanotube surface. The atomic structure of the gold nanoclusters and their effect on the intrinsic electronic quantum transport properties of the nanotube are also predicted. Experimentally, multi-wall CNTs are decorated with gold clusters using (1) vacuum evaporation, after activation with an RF oxygen plasma and (2) colloid solution injected into an RF atmospheric plasma; the hybrid systems are accurately characterized using XPS and TEM techniques. The response of gas sensors based on these nano2hybrids is quantified for the detection of toxic species like NO2, CO, C2H5OH and C2H4.

  18. Computational design of organometallic oligomers featuring 1,3-metal-carbon bonding and planar tetracoordinate carbon atoms.

    PubMed

    Zhao, Xue-Feng; Yuan, Cai-Xia; Wang, Xiang; Li, Jia-Jia; Wu, Yan-Bo; Wang, Xiaotai

    2016-01-15

    Density functional theory computations (B3LYP) have been used to explore the chemistry of titanium-aromatic carbon "edge complexes" with 1,3-metal-carbon (1,3-MC) bonding between Ti and planar tetracoordinate Cβ . The titanium-coordinated, end-capping chlorides are replaced with OH or SH groups to afford two series of difunctional monomers that can undergo condensation to form oxide- and sulfide-bridged oligomers. The sulfide-linked oligomers have less molecular strain and are more exergonic than the corresponding oxide-linked oligomers. The HOMO-LUMO gap of the oligomers varies with their composition and decreases with growing oligomer chain. This theoretical study is intended to enrich 1,3-MC bonding and planar tetracoordinate carbon chemistry and provide interesting ideas to experimentalists. Organometallic complexes with the TiE2 (E = OH and SH) decoration on the edge of aromatic hydrocarbons have been computationally designed, which feature 1,3-metal-carbon (1,3-MC) bonding between titanium and planar tetracoordinate β-carbon. Condensation of these difunctional monomers by eliminating small molecules (H2O and H2S) produce chain-like oligomers. The HOMO-LUMO gaps of the oligomers decreases with growing oligomer chain, a trend that suggests possible semiconductor properties for oligomers with longer chains. PMID:26399226

  19. A FP-LAPW Study of Atomic Carbon, Nitrogen, and Oxygen Chemisorption on the (100) Surface of δ-Pu

    NASA Astrophysics Data System (ADS)

    Atta-Fynn, Raymond; Ray, Asok

    2006-10-01

    Fully relativistic full potential density functional calculations have been performed to investigate atomic carbon, nitrogen, and oxygen chemisorption on the (100) surface of δ-Pu using the all-electron augmented plane waves plus local basis code WIEN2k. The surface was modeled by a three-layer periodic slab with two atoms per surface unit cell. The center adsorption site is found to be the most preferred site with chemisorption energies of 7.964 eV, 7.665 eV, and 8.335 eV for the C, N, and O adatoms, respectively. The corresponding optimized distances of the adatoms from the surface are found to be 0.26 å, 0.35 å, and 0.48 å. The work functions and the net magnet moments respectively increased and decreased in all cases compared with the bare δ-Pu (100) surface. Analysis of partial charges inside the atomic spheres, charge density distributions, and the local density of states have been performed to investigate the nature of the interaction between the surface Pu atoms and the adatoms.

  20. Three-dimensional bicomponent supramolecular nanoporous self-assembly on a hybrid all-carbon atomically flat and transparent platform.

    PubMed

    Li, Juan; Wieghold, Sarah; Öner, Murat Anil; Simon, Patrick; Hauf, Moritz V; Margapoti, Emanuela; Garrido, Jose A; Esch, Friedrich; Palma, Carlos-Andres; Barth, Johannes V

    2014-08-13

    Molecular self-assembly is a versatile nanofabrication technique with atomic precision en route to molecule-based electronic components and devices. Here, we demonstrate a three-dimensional, bicomponent supramolecular network architecture on an all-carbon sp(2)-sp(3) transparent platform. The substrate consists of hydrogenated diamond decorated with a monolayer graphene sheet. The pertaining bilayer assembly of a melamine-naphthalenetetracarboxylic diimide supramolecular network exhibiting a nanoporous honeycomb structure is explored via scanning tunneling microscopy initially at the solution-highly oriented pyrolytic graphite interface. On both graphene-terminated copper and an atomically flat graphene/diamond hybrid substrate, an assembly protocol is demonstrated yielding similar supramolecular networks with long-range order. Our results suggest that hybrid platforms, (supramolecular) chemistry and thermodynamic growth protocols can be merged for in situ molecular device fabrication. PMID:25115337

  1. 137Cs, 239+240Pu and 240Pu/239Pu atom ratios in the surface waters of the western North Pacific Ocean, eastern Indian Ocean and their adjacent seas.

    PubMed

    Yamada, Masatoshi; Zheng, Jian; Wang, Zhong-Liang

    2006-07-31

    Surface seawater samples were collected along the track of the R/V Hakuho-Maru cruise (KH-96-5) from Tokyo to the Southern Ocean. The (137)Cs activities were determined for the surface waters in the western North Pacific Ocean, the Sulu and Indonesian Seas, the eastern Indian Ocean, the Bay of Bengal, the Andaman Sea, and the South China Sea. The (137)Cs activities showed a wide variation with values ranging from 1.1 Bq m(-3) in the Antarctic Circumpolar Region of the Southern Ocean to 3 Bq m(-3) in the western North Pacific Ocean and the South China Sea. The latitudinal distributions of (137)Cs activity were not reflective of that of the integrated deposition density of atmospheric global fallout. The removal rates of (137)Cs from the surface waters were roughly estimated from the two data sets of Miyake et al. [Miyake Y, Saruhashi K, Sugimura Y, Kanazawa T, Hirose K. Contents of (137)Cs, plutonium and americium isotopes in the Southern Ocean waters. Pap Meteorol Geophys 1988;39:95-113] and this study to be 0.016 yr(-1) in the Sulu and Indonesian Seas, 0.033 yr(-1) in the Bay of Bengal and Andaman Sea, and 0.029 yr(-1) in the South China Sea. These values were much lower than that in the coastal surface water of the western Northwest Pacific Ocean. This was likely due to less horizontal and vertical mixing of water masses and less scavenging. (239+240)Pu activities and (240)Pu/(239)Pu atom ratios were also determined for the surface waters in the western North Pacific Ocean, the Sulu and Indonesian Seas and the South China Sea. The (240)Pu/(239)Pu atom ratios ranged from 0.199+/-0.026 to 0.248+/-0.027 on average, and were significantly higher than the global stratospheric fallout ratio of 0.18. The contributions of the North Pacific Proving Grounds close-in fallout Pu were estimated to be 20% for the western North Pacific Ocean, 39% for the Sulu and Indonesian Seas and 42% for the South China Sea by using the two end-member mixing model. The higher (240)Pu/(239)Pu

  2. Large-Scale Fabrication of Carbon Nanotube Probe Tips For Atomic Force Microscopy Critical Dimension Imaging Applications

    NASA Technical Reports Server (NTRS)

    Ye, Qi Laura; Cassell, Alan M.; Stevens, Ramsey M.; Meyyappan, Meyya; Li, Jun; Han, Jie; Liu, Hongbing; Chao, Gordon

    2004-01-01

    Carbon nanotube (CNT) probe tips for atomic force microscopy (AFM) offer several advantages over Si/Si3N4 probe tips, including improved resolution, shape, and mechanical properties. This viewgraph presentation discusses these advantages, and the drawbacks of existing methods for fabricating CNT probe tips for AFM. The presentation introduces a bottom up wafer scale fabrication method for CNT probe tips which integrates catalyst nanopatterning and nanomaterials synthesis with traditional silicon cantilever microfabrication technology. This method makes mass production of CNT AFM probe tips feasible, and can be applied to the fabrication of other nanodevices with CNT elements.

  3. Atomic force microscopy and electrochemical investigation on the corrosion behavior of carbon steel passivated by molybdate and chromate.

    PubMed

    Chen, Zhenyu; Zhang, Xiulan; Huang, Ling; Guo, Xingpeng

    2013-02-01

    The effects of CrO(4)(2-) and MoO(4)(2-) ions on the corrosion behavior of carbon steel in 0.5 M NaCl solution have been studied using electrochemical measurements and atomic force microscopy. The results suggest that both ions have good inhibition effects on the general and pitting corrosion of carbon steel. At the same concentration, the inhibition efficiency of CrO(4)(2-) is higher than that of MoO(4)(2-). The passive film formed by CrO(4)(2-) is also much harder than that formed by MoO(4)(2-). The passive films formed by both ions are nonconductive. PMID:23180386

  4. Operando atomic structure and active sites of TiO2(110)-supported gold nanoparticles during carbon monoxide oxidation.

    PubMed

    Saint-Lager, Marie-Claire; Laoufi, Issam; Bailly, Aude

    2013-01-01

    It is well known that gold nanoparticles supported on TiO2 act as a catalyst for CO oxidation, even below room temperature. Despite extensive studies, the origin of this catalytic activity remains under debate. Indeed, when the particle size decreases, many changes may occur; thus modifying the nanoparticles' electronic properties and consequently their catalytic performances. Thanks to a state-of-the-art home-developed setup, model catalysts can be prepared in ultra-high vacuum and their morphology then studied in operando conditions by Grazing Incidence Small Angle X-ray Scattering, as well as their atomic structure by Grazing Incidence X-ray Diffraction as a function of their catalytic activity. We previously reported on the existence of a catalytic activity maximum observed for three-dimensional gold nanoparticles with a diameter of 2-3 nm and a height of 6-7 atomic planes. In the present work we correlate this size dependence of the catalytic activity to the nanoparticles' atomic structure. We show that even when their size decreases below the optimum diameter, the gold nanoparticles keep the face-centered cubic structure characteristic of bulk gold. Nevertheless, for these smallest nanoparticles, the lattice parameter presents anisotropic strains with a larger contraction in the direction perpendicular to the surface. Moreover a careful analysis of the atomic-scale morphology around the catalytic activity maximum tends to evidence the role of sites with a specific geometry at the interface between the nanoparticles and the substrate. This argues for models where atoms at the interface periphery act as catalytically active sites for carbon monoxide oxidation. PMID:24015583

  5. Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

    SciTech Connect

    Peterson, Eric J.; DelaRiva, Andrew T.; Lin, Sen; Johnson, Ryan S.; Guo, Hua; Miller, Jeffrey T.; Kwak, Ja Hun; Peden, Charles H.F.; Kiefer, Boris; Allard, Lawrence F.; Ribeiro, Fabio H.; Datye, Abhaya K.

    2014-09-15

    Catalysis by single isolated atoms of precious metals has attracted much recent interest since it promises the ultimate economy in atom efficiency. Previous reports have been confined to reducible oxide supports such as FeOx, TiO₂ or CeO₂. Here we show that isolated Pd atoms can be stabilized on industrially relevant gamma-alumina supports. At low Pd loadings (≤0.5 wt%) these catalysts contain exclusively atomically dispersed Pd species. The addition of lanthanum-oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated Pd atoms. Aberration-corrected scanning transmission electron microscopy (AC-STEM) confirms the presence of intermingled Pd and La on the gamma-alumina surface. Operando X-ray absorption spectroscopy, performed on Pd/La-alumina and Pd/gamma-alumina (0.5 wt% Pd) demonstrates the presence of catalytically active atomically dispersed ionic Pd in the Pd/La-doped gamma-alumina system. CO oxidation reactivity measurements show onset of catalytic activity at 40 °C, indicating that the ionic Pd species are not poisoned by CO. The reaction order in CO and O₂ is positive, suggesting a reaction mechanism that is different from that on metallic Pd. The catalyst activity is lost if the Pd species are reduced to their metallic form, but the activity can be regenerated by oxidation at 700 °C in air. The high-temperature stability of these ionic Pd species on commercial alumina supports makes this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

  6. Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel

    NASA Astrophysics Data System (ADS)

    Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

    2016-01-01

    Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially ‘clean’ strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2•- radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO-) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems

  7. Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel.

    PubMed

    Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

    2016-01-01

    Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially 'clean' strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2(•-) radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO(-)) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems

  8. Carbon Dioxide Activation by Scandium Atoms and Scandium Monoxide Molecules: Formation and Spectroscopic Characterization of ScCO3 and OCScCO3 in Solid Neon.

    PubMed

    Zhang, Qingnan; Qu, Hui; Chen, Mohua; Zhou, Mingfei

    2016-01-28

    The reactions of carbon dioxide with scandium monoxide molecules and scandium atoms are investigated using matrix isolation infrared spectroscopy in solid neon. The species formed are identified by the effects of isotopic substitution on their infrared spectra as well as density functional calculations. The results show that the ground state ScO molecule reacts with carbon dioxide to form the carbonate complex ScCO3 spontaneously on annealing. The ground state Sc atom reacts with two carbon dioxide molecules to give the carbonate carbonyl complex OCScCO3 via the previously reported OScCO insertion intermediate on annealing. The observation of these spontaneous reactions is consistent with theoretical predictions that both the Sc + 2CO2 → OCScCO3 and ScO + CO2 → ScCO3 reactions are thermodynamically exothermic and are kinetically facile, requiring little or no activation energy. PMID:26738558

  9. A density functional study of atomic oxygen and carbon adsorptions on (100) surface of γ-Uranium

    NASA Astrophysics Data System (ADS)

    Dholabhai, Pratik P.; Ray, Asok K.

    2007-04-01

    Oxygen and carbon adsorptions on a γ-Uranium (U) (100) surface have been studied at both non-spin-polarized (NSP) and spin-polarized (SP) levels using the generalized gradient approximation of the density functional theory (GGA-DFT) with Perdew and Wang (PW) functionals. For oxygen adsorption, the bridge position of (100) surface is found to be the most favourable site with chemisorption energy (CE) of 7.887 eV for the NSP case, and 7.965 eV for the SP case. The distances of the oxygen adatom from the U surface are found to be 1.19Å and 1.22 Å for the NSP and SP cases, respectively. The magnetic moment for this most favourable site is found to be 0.167μB per atom. For carbon adsorption, the centre position of (100) surface is found to be most favourable site with CE of 7.816 eV for the NSP case, and 7.895 eV for the SP case. The distances of the carbon adatom from the U surface are found to be 0.62 and 0.52 Å for the NSP and SP cases, respectively. The magnetic moment for this most favourable site is found to be 0.084μB per atom. The hybridization between the O 2p orbitals and U 5f orbitals is found to be rather weak but the hybridization between the C 2p orbitals and U 5f orbitals is observed to be strong.

  10. Determination of nickel in water, food, and biological samples by electrothermal atomic absorption spectrometry after preconcentration on modified carbon nanotubes.

    PubMed

    Taher, Mohammad Ali; Mazaheri, Lida; Ashkenani, Hamid; Mohadesi, Alireza; Afzali, Daryoush

    2014-01-01

    A new and sensitive SPE method using modified carbon nanotubes for extraction and preconcentration, and electrothermal atomic absorption spectrometric determination of nickel (Ni) in real samples at ng/L levels was investigated. First, multiwalled carbon nanotubes were oxidized with concentrated HNO3, then modified with 2-(5-bormo-2-pyridylazo)-5-diethylaminophenol reagent. The adsorption was achieved quantitatively on a modified carbon nanotubes column in a pH range of 6.5 to 8.5; the adsorbed Ni(II) ions were then desorbed by passing 5.0 mL of 1 M HNO3. The effects of analytical parameters, including pH of the solution, eluent type and volume, sample volume, flow rate of the eluent, and matrix ions, were investigated for optimization of the presented procedure. The enrichment factor was 180, and the LOD for Ni was 4.9 ng/L. The method was applied to the determination of Ni in water, food, and biological samples, and reproducible results were obtained. PMID:24672882

  11. A high-pressure atomic force microscope for imaging in supercritical carbon dioxide

    SciTech Connect

    Lea, A. S.; Higgins, S. R.; Knauss, K. G.; Rosso, K. M.

    2011-01-01

    A high-pressure atomic force microscope(AFM) that enables in situ, atomic scale measurements of topography of solid surfaces in contact with supercritical CO2 (scCO2) fluids has been developed. This apparatus overcomes the pressure limitations of the hydrothermal AFM and is designed to handle pressures up to 100 atm at temperatures up to ~350 K. A standard optically-based cantilever deflection detection system was chosen. When imaging in compressible supercritical fluids such as scCO2, precise control of pressure and temperature in the fluid cell is the primary technical challenge. Noise levels and imaging resolution depend on minimization of fluid density fluctuations that change the fluidrefractive index and hence the laser path. We demonstrate with our apparatus in situ atomic scale imaging of a calcite (CaCO3) mineral surface in scCO2; both single, monatomic steps and dynamic processes occurring on the (101¯4) surface are presented. Finally, this new AFM provides unprecedented in situ access to interfacial phenomena at solid–fluid interfaces under pressure.

  12. A high-pressure atomic force microscope for imaging in supercritical carbon dioxide

    SciTech Connect

    Lea, Alan S.; Higgins, Steven R.; Knauss, Kevin G.; Rosso, Kevin M.

    2011-04-26

    A high-pressure atomic force microscope (AFM) that enables in-situ, atomic scale measurements of topography of solid surfaces in contact with supercritical CO2 (scCO2) fluids has been developed. This apparatus overcomes the pressure limitations of the hydrothermal AFM and is designed to handle pressures up to 100 atm at temperatures up to ~ 350 K. A standard optically-based cantilever deflection detection system was chosen. When imaging in compressible supercritical fluids such as scCO2, precise control of pressure and temperature in the fluid cell is the primary technical challenge. Noise levels and imaging resolution depend on minimization of fluid density fluctuations that change the fluid refractive index and hence the laser path. We demonstrate with our apparatus in-situ atomic scale imaging of a calcite (CaCO3) mineral surface in scCO2; both single, monatomic steps and dynamic processes occurring on the (10¯14) surface are presented. This new AFM provides unprecedented in-situ access to interfacial phenomena at solid-fluid interfaces under pressure.

  13. Kinetic and Mechanistic Studies of Carbon-to-Metal Hydrogen Atom Transfer Involving Os-Centered Radicals: Evidence for Tunneling

    SciTech Connect

    Lewandowska-Androlojc, Anna; Grills, David C.; Zhang, Jie; Bullock, R. Morris; Miyazawa, Akira; Kawanishi, Yuji; Fujita, Etsuko

    2014-03-05

    We have investigated the kinetics of novel carbon-to-metal hydrogen atom transfer reactions, in which homolytic cleavage of a C-H bond is accomplished by a single metal-centered radical. Studies by means of time-resolved IR spectroscopic measurements revealed efficient hydrogen atom transfer from xanthene, 9,10-dihydroanthracene and 1,4-cyclohexadiene to Cp(CO)2Os• and (n5-iPr4C5H)(CO)2Os• radicals, formed by photoinduced homolysis of the corresponding osmium dimers. The rate constants for hydrogen abstraction from these hydrocarbons were found to be in the range 1.54 × 105 M 1 s 1 -1.73 × 107 M 1 s-1 at 25 °C. For the first time, kinetic isotope effects for carbon-to-metal hydrogen atom transfer were determined. Large primary kinetic isotope effects of 13.4 ± 1.0 and 16.6 ± 1.4 were observed for the hydrogen abstraction from xanthene to form Cp(CO)2OsH and (n5-iPr4C5H)(CO)2OsH, respectively, at 25 °C. Temperature-dependent measurements of the kinetic isotope effects over a 60 -C temperature range were carried out to obtain the difference in activation energies and the pre-exponential factor ratio. For hydrogen atom transfer from xanthene to (n5-iPr4C5H)(CO)2Os•, the (ED - EH) = 3.25 ± 0.20 kcal/mol and AH/AD = 0.056 ± 0.018 values are greater than the semi-classical limits and thus suggest a quantum mechanical tunneling mechanism. The work at BNL was carried out under contract DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Geosciences & Biosciences, Office of Basic Energy Sciences. RMB also thanks the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences for support. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  14. Tributyl phosphate as a sensitivity-enhancing solvent for organotin in carbon furnace atomic absorption spectrometry.

    PubMed

    Li, H; Gong, B; Matsumoto, K

    1996-07-01

    Tributyl phosphate (TBP) has been found to be a sensitivity-enhancing solvent for organotin compounds in graphite furnace atomic absorption spectrometry; (C(4)H(9))(2)Sn(O(2)CCH(3))(2), (C(4)H(9))(2)Sn(O(2)CC(11)H(23))(2), (C(4)H(9))(3)SnCl, and (C(4)H(9))(4)Sn all give 1 order of magnitude higher sensitivities in TBP than in toluene or ethyl acetate. The sensitivities are enhanced further 1-2 orders of magnitude in TBP, when PdCl(2)(CH(3)CN)(2) is added as a matrix modifier in the organic solvent. Among the four organotin compounds, (C(4)H(9))(2)Sn(O(2)CCH(3))(2) and (C(4)H(9))(2)Sn(O(2)CC(11)H(23))(2) give better sensitivities than (C(4)H(9))(3)SnCl and (C(4)H(9))(4)Sn in the absence of palladium in any organic solvent, which suggests that the oxygen atom in the tin compound might form tin oxides that are resistant to volatilization loss during ashing. Scanning electron microscopic, electrothermal vaporization ICPMS, and powder X-ray diffraction studies show that the final products before atomization include phosphorus-containing compounds Sn(2)P(2)O(7), SnP(2)O(7), and Pd(9)P(2), besides tin-palladium alloys, PdSn, Pd(3)Sn, Pd(2)Sn, Pd(3)Sn(2), and PdSn(3). These phosphorus-containing compounds would more efficiently stabilize tin and suppress tin vaporization loss during ashing, to give higher sensitivity. PMID:21619315

  15. Adsorption of glycine on diamond (001): Role of bond angle of carbon atoms

    NASA Astrophysics Data System (ADS)

    Li, Lin; Xu, Jing; Xu, Li-Fang; Lian, Chao-Sheng; Li, Jun-Jie; Wang, Jian-Tao; Gu, Chang-Zhi

    2015-05-01

    The adsorption behaviors of glycine on diamond (001) are systematically investigated by first-principles calculations. We have considered all possible adsorption configurations without a surface dangling bond and give a quantitative analysis for the relationship between the deviation of carbon bond angle and adsorption energy. We found that a smaller distortion of carbon covalent bond angle results in a more stable adsorption structure, and the most stable adsorption has a benzene-ring-like structure with the highest adsorption energy of 5.11 eV per molecule and the minimum distortion of carbon covalent bond angle. Project supported by the National Natural Science Foundation of China (Grant Nos. 51272278, 91323304, 10774177, and 11374341), the National Basic Research Program of China (Grand No. 2009CB930502), the Knowledge Innovation Project of Chinese Academy of Sciences (Grand No. KJCX2-EW-W02), the Fundamental Research Funds for the Central Universities of Ministry of Education of China, and the Research Funds of Renmin University of China.

  16. CH/pi interaction between benzene and hydrocarbons having six carbon atoms in their binary liquid mixtures.

    PubMed

    Kasahara, Yasutoshi; Suzuki, Yuji; Kabasawa, Aino; Minami, Hideyuki; Matsuzawa, Hideyo; Iwahashi, Makio

    2010-01-01

    Molecular interactions between benzene and hydrocarbons having six carbon atoms, such as hexane, cyclohexane and 1-hexene in their binary liquid mixtures were studied through the measurements of density, viscosity, self-diffusion coefficient, (13)C NMR spin-lattice relaxation time and (1)H NMR chemical shift. CH/pi attraction between hexane and benzene in their binary mixture was observed in a relatively benzene rich region, whereas a special attractive interaction was not observed between cyclohexane and benzene. On the other hand, 1-hexene and benzene in their binary mixtures were characteristic in their self-diffusion coefficient behaviors: 1-hexene more strongly attract benzene not only by the CH/pi attraction but also probably by the p/p interaction between the double bond in 1-hexene and the p-electron in benzene ring. PMID:20032596

  17. Nanopatterning on silicon surface using atomic force microscopy with diamond-like carbon (DLC)-coated Si probe

    PubMed Central

    2011-01-01

    Atomic force microscope (AFM) equipped with diamond-like carbon (DLC)-coated Si probe has been used for scratch nanolithography on Si surfaces. The effect of scratch direction, applied tip force, scratch speed, and number of scratches on the size of the scratched geometry has been investigated. The size of the groove differs with scratch direction, which increases with the applied tip force and number of scratches but decreases slightly with scratch speed. Complex nanostructures of arrays of parallel lines and square arrays are further fabricated uniformly and precisely on Si substrates at relatively high scratch speed. DLC-coated Si probe has the potential to be an alternative in AFM-based scratch nanofabrication on hard surfaces. PMID:21888633

  18. FORMATION OF CARBON DIOXIDE, METHANOL, ETHANOL, AND FORMIC ACID ON AN ICY GRAIN ANALOG USING FAST OXYGEN ATOMS

    SciTech Connect

    Madzunkov, S. M.; MacAskill, J. A.; Chutjian, A.

    2010-03-20

    Carbon dioxide (CO{sub 2}), methanol (CH{sub 3}OH), ethanol (CH{sub 3}CH{sub 2}OH), and formic acid (HCOOH) have been formed in collisions of a superthermal, 9 eV beam of O({sup 3} P) atoms with CH{sub 4} molecules, with an over coat of CO molecules, adsorbed on a gold surface at 4.8 K. The products are detected using temperature programmed-desorption and quadrupole mass spectrometry. Identification of the species is carried out through use of the Metropolis random walk algorithm as constrained by the fractionation patterns of the detected species. Relative formation yields are reported and reaction sequences are given to account for possible formation routes.

  19. How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces.

    PubMed

    Töpfer, Kai; Tremblay, Jean Christophe

    2016-07-21

    In this contribution, we study using first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: (1) co-adsorption is weakly supported at F(0) and F(2+) defects but not at F(1+) sites, (2) electron redistribution from the F(0) vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, (3) a metastable carbonate intermediate can form on defects of the F(0) type, (4) only a small activation barrier exists for the highly favorable dissociation of CO2 from F(0), and (5) the moderate adsorption energy of the gold atom on the F(0) defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken in the first oxidation step. PMID:27345190

  20. Biosynthesis of the antibiotic maduramicin. Origin of the carbon and oxygen atoms as well as the 13C NMR assignments.

    PubMed

    Tsou, H; Rajan, S; Fiala, R; Mowery, P C; Bullock, M W; Borders, D B; James, J C; Martin, J H; Morton, G O

    1984-12-01

    The biosynthesis of maduramicin alpha and beta in a culture of Actinomadura yumaensis has been studied using 13C, 14C and 18O labeled precursors. The alpha component of this recently discovered polyether antibiotic, containing forty-seven carbon atoms in a seven-ring system, is derived from eight acetate, seven propionate and four methionine molecules. The beta component which is missing one methoxy group incorporates three methionine methyl groups. The carbohydrate moiety was enriched by methionine, but not significantly by acetate or propionate. Studies of the incorporation of 13C labeled precursors permit the 13C NMR assignment of maduramicin. The origin of oxygen atoms of maduramicin has been examined by feeding [1-13C, 18O2]acetate and [1-13C, 18O2]propionate separately in the fermentation culture and the resulting doubly labeled maduramicin samples were analyzed by the isotopic shifts in the 13C NMR spectra. These results are consistent with the initial formation of a triene, which is converted to maduramicin by cyclization of the triepoxide. PMID:6526733

  1. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    SciTech Connect

    Nandan, Ravi Nanda, Karuna Kar

    2015-06-24

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min{sup −1}. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell.

  2. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Nandan, Ravi; Nanda, Karuna Kar

    2015-06-01

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min-1. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell.

  3. Influence of Different Defects in Vertically Aligned Carbon Nanotubes on TiO2 Nanoparticle Formation through Atomic Layer Deposition.

    PubMed

    Acauan, Luiz; Dias, Anna C; Pereira, Marcelo B; Horowitz, Flavio; Bergmann, Carlos P

    2016-06-29

    The chemical inertness of carbon nanotubes (CNT) requires some degree of "defect engineering" for controlled deposition of metal oxides through atomic layer deposition (ALD). The type, quantity, and distribution of such defects rules the deposition rate and defines the growth behavior. In this work, we employed ALD to grow titanium oxide (TiO2) on vertically aligned carbon nanotubes (VACNT). The effects of nitrogen doping and oxygen plasma pretreatment of the CNT on the morphology and total amount of TiO2 were systematically studied using transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The induced chemical changes for each functionalization route were identified by X-ray photoelectron and Raman spectroscopies. The TiO2 mass fraction deposited with the same number of cycles for the pristine CNT, nitrogen-doped CNT, and plasma-treated CNT were 8, 47, and 80%, respectively. We demonstrate that TiO2 nucleation is dependent mainly on surface incorporation of heteroatoms and their distribution rather than structural defects that govern the growth behavior. Therefore, selecting the best way to functionalize CNT will allow us to tailor TiO2 distribution and hence fabricate complex heterostructures. PMID:27269125

  4. The Fe-V Cofactor of Vanadium Nitrogenase Contains an Interstitial Carbon Atom.

    PubMed

    Rees, Julian A; Bjornsson, Ragnar; Schlesier, Julia; Sippel, Daniel; Einsle, Oliver; DeBeer, Serena

    2015-11-01

    The first direct evidence is provided for the presence of an interstitial carbide in the Fe-V cofactor of Azotobacter vinelandii vanadium nitrogenase. As for our identification of the central carbide in the Fe-Mo cofactor, we employed Fe Kβ valence-to-core X-ray emission spectroscopy and density functional theory calculations, and herein report the highly similar spectra of both variants of the cofactor-containing protein. The identification of an analogous carbide, and thus an atomically homologous active site in vanadium nitrogenase, highlights the importance and influence of both the interstitial carbide and the identity of the heteroatom on the electronic structure and catalytic activity of the enzyme. PMID:26376620

  5. The Fe–V Cofactor of Vanadium Nitrogenase Contains an Interstitial Carbon Atom

    PubMed Central

    Rees, Julian A; Bjornsson, Ragnar; Schlesier, Julia; Sippel, Daniel; Einsle, Oliver; DeBeer, Serena

    2015-01-01

    The first direct evidence is provided for the presence of an interstitial carbide in the Fe–V cofactor of Azotobacter vinelandii vanadium nitrogenase. As for our identification of the central carbide in the Fe–Mo cofactor, we employed Fe Kβ valence-to-core X-ray emission spectroscopy and density functional theory calculations, and herein report the highly similar spectra of both variants of the cofactor-containing protein. The identification of an analogous carbide, and thus an atomically homologous active site in vanadium nitrogenase, highlights the importance and influence of both the interstitial carbide and the identity of the heteroatom on the electronic structure and catalytic activity of the enzyme. PMID:26376620

  6. Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy

    NASA Technical Reports Server (NTRS)

    deBoer, Gary; Scott, Carl

    2003-01-01

    Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal

  7. Role of defects in the process of graphene growth on hexagonal boron nitride from atomic carbon

    SciTech Connect

    Dabrowski, J. Lippert, G.; Schroeder, T.; Lupina, G.

    2014-11-10

    Hexagonal boron nitride (h-BN) is an attractive substrate for graphene, as the interaction between these materials is weak enough for high carrier mobility to be retained in graphene but strong enough to allow for some epitaxial relationship. We deposited graphene on exfoliated h-BN by molecular beam epitaxy (MBE), we analyzed the atomistic details of the process by ab initio density functional theory (DFT), and we linked the DFT and MBE results by random walk theory. Graphene appears to nucleate around defects in virgin h-BN. The DFT analysis reveals that sticking of carbon to perfect h-BN is strongly reduced by desorption, so that pre-existing seeds are needed for the nucleation. The dominant nucleation seeds are C{sub N}C{sub B} and O{sub N}C{sub N} pairs and B{sub 2}O{sub 3} inclusions in the virgin substrate.

  8. Graphene as an atomically thin interface for growth of vertically aligned carbon nanotubes

    PubMed Central

    Rao, Rahul; Chen, Gugang; Arava, Leela Mohana Reddy; Kalaga, Kaushik; Ishigami, Masahiro; Heinz, Tony F.; Ajayan, Pulickel M.; Harutyunyan, Avetik R.

    2013-01-01

    Growth of vertically aligned carbon nanotube (CNT) forests is highly sensitive to the nature of the substrate. This constraint narrows the range of available materials to just a few oxide-based dielectrics and presents a major obstacle for applications. Using a suspended monolayer, we show here that graphene is an excellent conductive substrate for CNT forest growth. Furthermore, graphene is shown to intermediate growth on key substrates, such as Cu, Pt, and diamond, which had not previously been compatible with nanotube forest growth. We find that growth depends on the degree of crystallinity of graphene and is best on mono- or few-layer graphene. The synergistic effects of graphene are revealed by its endurance after CNT growth and low contact resistances between the nanotubes and Cu. Our results establish graphene as a unique interface that extends the class of substrate materials for CNT growth and opens up important new prospects for applications. PMID:23712556

  9. TRACING H{sub 2} COLUMN DENSITY WITH ATOMIC CARBON (C I) AND CO ISOTOPOLOGS

    SciTech Connect

    Lo, N.; Bronfman, L.; Cunningham, M. R.; Jones, P. A.; Lowe, V.; Cortes, P. C.; Simon, R.; Fissel, L.; Novak, G.

    2014-12-20

    We present the first results of neutral carbon ([C I] {sup 3} P {sub 1}-{sup 3} P {sub 0} at 492 GHz) and carbon monoxide ({sup 13}CO, J = 1-0) mapping in the Vela Molecular Ridge cloud C (VMR-C) and the G333 giant molecular cloud complexes with the NANTEN2 and Mopra telescopes. For the four regions mapped in this work, we find that [C I] has very similar spectral emission profiles to {sup 13}CO, with comparable line widths. We find that [C I] has an opacity of 0.1-1.3 across the mapped region while the [C I]/{sup 13}CO peak brightness temperature ratio is between 0.2 and 0.8. The [C I] column density is an order of magnitude lower than that of {sup 13}CO. The H{sub 2} column density derived from [C I] is comparable to values obtained from {sup 12}CO. Our maps show that C I is preferentially detected in gas with low temperatures (below 20 K), which possibly explains the comparable H{sub 2} column density calculated from both tracers (both C I and {sup 12}CO underestimate column density), as a significant amount of the C I in the warmer gas is likely in the higher energy state transition ([C I] {sup 3} P {sub 2}-{sup 3} P {sub 1} at 810 GHz), and thus it is likely that observations of both the above [C I] transitions are needed in order to recover the total H{sub 2} column density.

  10. Atomic and Molecular Layer Deposition for Enhanced Lithium Ion Battery Electrodes and Development of Conductive Metal Oxide/Carbon Composites

    NASA Astrophysics Data System (ADS)

    Travis, Jonathan

    The performance and safety of lithium-ion batteries (LIBs) are dependent on interfacial processes at the positive and negative electrodes. For example, the surface layers that form on cathodes and anodes are known to affect the kinetics and capacity of LIBs. Interfacial reactions between the electrolyte and the electrodes are also known to initiate electrolyte combustion during thermal runaway events that compromise battery safety. Atomic layer deposition (ALD) and molecular layer deposition (MLD) are thin film deposition techniques based on sequential, self-limiting surface reactions. ALD and MLD can deposit ultrathin and conformal films on high aspect ratio and porous substrates such as composite particulate electrodes in lithium-ion batteries. The effects of electrode surface modification via ALD and MLD are studied using a variety of techniques. It was found that sub-nm thick coatings of Al2O 3 deposited via ALD have beneficial effects on the stability of LIB anodes and cathodes. These same Al2O3 ALD films were found to improve the safety of graphite based anodes through prevention of exothermic solid electrolyte interface (SEI) degradation at elevated temperatures. Ultrathin and conformal metal alkoxide polymer films known as "metalcones" were grown utilizing MLD techniques with trimethylaluminum (TMA) or titanium tetrachloride (TiCl4) and organic diols or triols, such as ethylene glycol (EG), glycerol (GL) or hydroquinone (HQ), as the reactants. Pyrolysis of these metalcone films under inert gas conditions led to the development of conductive metal oxide/carbon composites. The composites were found to contain sp2 carbon using micro-Raman spectroscopy in the pyrolyzed films with pyrolysis temperatures ≥ 600°C. Four point probe measurements demonstrated that the graphitic sp2 carbon domains in the metalcone films grown using GL and HQ led to significant conductivity. The pyrolysis of conformal MLD films to obtain conductive metal oxide/carbon composite films

  11. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  12. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  13. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  14. 46 CFR 148.445 - Adjacent spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by...

  15. Materials design for electrocatalytic carbon capture

    NASA Astrophysics Data System (ADS)

    Tan, Xin; Tahini, Hassan A.; Smith, Sean C.

    2016-05-01

    We discuss our philosophy for implementation of the Materials Genome Initiative through an integrated materials design strategy, exemplified here in the context of electrocatalytic capture and separation of CO2 gas. We identify for a group of 1:1 X-N graphene analogue materials that electro-responsive switchable CO2 binding behavior correlates with a change in the preferred binding site from N to the adjacent X atom as negative charge is introduced into the system. A reconsideration of conductive N-doped graphene yields the discovery that the N-dopant is able to induce electrocatalytic binding of multiple CO2 molecules at the adjacent carbon sites.

  16. How does the exchange of one oxygen atom with sulfur affect the catalytic cycle of carbonic anhydrase?

    PubMed

    Schenk, Stephan; Kesselmeier, Jürgen; Anders, Ernst

    2004-06-21

    We have extended our investigations of the carbonic anhydrase (CA) cycle with the model system [(H(3)N)(3)ZnOH](+) and CO(2) by studying further heterocumulenes and catalysts. We investigated the hydration of COS, an atmospheric trace gas. This reaction plays an important role in the global COS cycle since biological consumption, that is, uptake by higher plants, algae, lichens, and soil, represents the dominant terrestrial sink for this gas. In this context, CA has been identified by a member of our group as the key enzyme for the consumption of COS by conversion into CO(2) and H(2)S. We investigated the hydration mechanism of COS by using density functional theory to elucidate the details of the catalytic cycle. Calculations were first performed for the uncatalyzed gas phase reaction. The rate-determining step for direct reaction of COS with H(2)O has an energy barrier of deltaG=53.2 kcal mol(-1). We then employed the CA model system [(H(3)N)(3)ZnOH](+) (1) and studied the effect on the catalytic hydration mechanism of replacing an oxygen atom with sulfur. When COS enters the carbonic anhydrase cycle, the sulfur atom is incorporated into the catalyst to yield [(H(3)N)(3)ZnSH](+) (27) and CO(2). The activation energy of the nucleophilic attack on COS, which is the rate-determining step, is somewhat higher (20.1 kcal mol(-1) in the gas phase) than that previously reported for CO(2). The sulfur-containing model 27 is also capable of catalyzing the reaction of CO(2) to produce thiocarbonic acid. A larger barrier has to be overcome for the reaction of 27 with CO(2) compared to that for the reaction of 1 with CO(2). At a well-defined stage of this cycle, a different reaction path can emerge: a water molecule helps to regenerate the original catalyst 1 from 27, a process accompanied by the formation of thiocarbonic acid. We finally demonstrate that nature selected a surprisingly elegant and efficient group of reactants, the [L(3)ZnOH](+)/CO(2)/H(2)O system, that helps

  17. Restricted access carbon nanotubes for direct extraction of cadmium from human serum samples followed by atomic absorption spectrometry analysis.

    PubMed

    Barbosa, Adriano F; Barbosa, Valéria M P; Bettini, Jefferson; Luccas, Pedro O; Figueiredo, Eduardo C

    2015-01-01

    In this paper, we propose a new sorbent that is able to extract metal ions directly from untreated biological fluids, simultaneously excluding all proteins from these samples. The sorbent was obtained through the modification of carbon nanotubes (CNTs) with an external bovine serum albumin (BSA) layer, resulting in restricted access carbon nanotubes (RACNTs). The BSA layer was fixed through the interconnection between the amine groups of the BSA using glutaraldehyde as cross-linker. When a protein sample is percolated through a cartridge containing RACNTs and the sample pH is higher than the isoelectric point of the proteins, both proteins from the sample and the BSA layer are negatively ionized. Thus, an electrostatic repulsion prevents the interaction between the proteins from the sample on the RACNTs surface. At the same time, metal ions are adsorbed in the CNTs (core) after their passage through the chains of proteins. The Cd(2+) ion was selected for a proof-of-principle case to test the suitability of the RACNTs due to its toxicological relevance. RACNTs were able to extract Cd(2+) and exclude almost 100% of the proteins from the human serum samples in an online solid-phase extraction system coupled with thermospray flame furnace atomic absorption spectrometry. The limits of detection and quantification were 0.24 and 0.80 μg L(-1), respectively. The sampling frequency was 8.6h(-1), and the intra- and inter-day precisions at the 0.80, 15.0, and 30.0 μg L(-1) Cd(2+) levels were all lower than 10.1% (RSD). The recoveries obtained for human blood serum samples fortified with Cd(2+) ranged from 85.0% to 112.0%. The method was successfully applied to analyze Cd(2+) directly from six human blood serum samples without any pretreatment, and the observed concentrations ranged from

  18. Fibrous Containment for Improved Laboratory Handling and Uniform Nanocoating of Milligram Quantities of Carbon Nanotubes by Atomic Layer Deposition

    PubMed Central

    Devine, Christina K.; Oldham, Christopher J.; Jur, Jesse S.; Gong, Bo; Parsons, Gregory N.

    2011-01-01

    The presence of nanostructured materials in the work place is bringing attention to the importance of safe practices for nanomaterial handling. We explored novel fiber containment methods to improve the handling of carbon nanotube (CNT) powders in the laboratory, while simultaneously allowing highly uniform and controlled atomic layer deposition (ALD) coatings on the nanotubes, down to less than 4 nm on some CNT materials. Moreover, the procedure yields uniform coatings on milligram quantities of nanotubes using a conventional viscous flow reactor system, circumventing the need for specialized fluidized bed or rotary ALD reactors for lab-scale studies. We explored both fiber bundles and fiber baskets as possible containment methods and conclude that the baskets are more suitable for coating studies. An extended precursor and reactant dose and soak periods allowed the gases to diffuse through the fiber containment, and the ALD coating thickness scaled linearly with the number of ALD cycles. The extended dose period produced thicker coatings compared with typical doses onto CNT controls not encased in the fibers, suggesting some effects due to the extended reactant dose. Film growth was compared on a range of single wall NTs, double wall NTs, and acid functionalized multiwall NTs and we found that ultrathin coatings were most readily controlled on the multi-walled NTs. PMID:22070742

  19. Increasing sp3 hybridized carbon atoms in germanium carbide films by increasing the argon ion energy and germanium content

    NASA Astrophysics Data System (ADS)

    Hu, C. Q.; Zheng, B.; Zhu, J. Q.; Han, J. C.; Zheng, W. T.; Guo, L. F.

    2010-04-01

    We have prepared germanium carbide (Ge1-xCx) films on Si(0 0 1) by radio frequency (RF) reactive sputtering a pure Ge(1 1 1) target in a CH4/Ar mixture discharge, and found that the sp3 hybridized carbon atoms in the Ge1-xCx film can be significantly increased in two ways. One is by increasing the Ge content via increasing the RF power during the film deposition, which can lead to a transition from sp2 C-C to sp3 C-Ge bonding in the film. Another is by increasing the Ar ion energy in a discharge Ar/CH4 gas by applying the negative bias voltage, which plays an important role in inducing the compressive stress in film. We find that when the compressive stress increases above a critical value of 2.2 GPa, an abrupt transition from sp2 C-C to sp3 C-C bonding occurs in the Ge1-xCx film, which is a consequence of energy minimization.

  20. Fabrication and characterization of tunnel barriers in a multi-walled carbon nanotube formed by argon atom beam irradiation

    NASA Astrophysics Data System (ADS)

    Tomizawa, H.; Yamaguchi, T.; Akita, S.; Ishibashi, K.

    2015-07-01

    We have evaluated tunnel barriers formed in multi-walled carbon nanotubes (MWNTs) by an Ar atom beam irradiation method and applied the technique to fabricate coupled double quantum dots. The two-terminal resistance of the individual MWNTs was increased owing to local damage caused by the Ar beam irradiation. The temperature dependence of the current through a single barrier suggested two different contributions to its Arrhenius plot, i.e., formed by direct tunneling through the barrier and by thermal activation over the barrier. The height of the formed barriers was estimated. The fabrication technique was used to produce coupled double quantum dots with serially formed triple barriers on a MWNT. The current measured at 1.5 K as a function of two side-gate voltages resulted in a honeycomb-like charge stability diagram, which confirmed the formation of the double dots. The characteristic parameters of the double quantum dots were calculated, and the feasibility of the technique is discussed.

  1. Fabrication and characterization of tunnel barriers in a multi-walled carbon nanotube formed by argon atom beam irradiation

    SciTech Connect

    Tomizawa, H.; Yamaguchi, T.; Akita, S.; Ishibashi, K.

    2015-07-28

    We have evaluated tunnel barriers formed in multi-walled carbon nanotubes (MWNTs) by an Ar atom beam irradiation method and applied the technique to fabricate coupled double quantum dots. The two-terminal resistance of the individual MWNTs was increased owing to local damage caused by the Ar beam irradiation. The temperature dependence of the current through a single barrier suggested two different contributions to its Arrhenius plot, i.e., formed by direct tunneling through the barrier and by thermal activation over the barrier. The height of the formed barriers was estimated. The fabrication technique was used to produce coupled double quantum dots with serially formed triple barriers on a MWNT. The current measured at 1.5 K as a function of two side-gate voltages resulted in a honeycomb-like charge stability diagram, which confirmed the formation of the double dots. The characteristic parameters of the double quantum dots were calculated, and the feasibility of the technique is discussed.

  2. Direct formation of anatase TiO2 nanoparticles on carbon nanotubes by atomic layer deposition and their photocatalytic properties.

    PubMed

    Huang, Sheng-Hsin; Liao, Shih-Yun; Wang, Chih-Chieh; Kei, Chi-Chung; Gan, Jon-Yiew; Perng, Tsong-Pyng

    2016-10-01

    TiO2 with different morphology was deposited on acid-treated multi-walled carbon nanotubes (CNTs) by atomic layer deposition at 100 °C-300 °C to form a TiO2@CNT structure. The TiO2 fabricated at 100 °C was an amorphous film, but became crystalline anatase nanoparticles when fabricated at 200 °C and 300 °C. The saturation growth rates of TiO2 nanoparticles at 300 °C were about 1.5 and 0.4 Å/cycle for substrate-enhanced growth and linear growth processes, respectively. It was found that the rate constants for methylene blue degradation by the TiO2@CNT structure formed at 300 °C were more suitable to fit with second-order reaction. The size of 9 nm exhibited the best degradation efficiency, because of the high specific area and appropriate diffusion length for the electrons and holes. PMID:27576914

  3. Impact of the atomic layer deposition precursors diffusion on solid-state carbon nanotube based supercapacitors performances.

    PubMed

    Fiorentino, Giuseppe; Vollebregt, Sten; Tichelaar, F D; Ishihara, Ryoichi; Sarro, Pasqualina M

    2015-02-13

    A study on the impact of atomic layer deposition (ALD) precursors diffusion on the performance of solid-state miniaturized nanostructure capacitor array is presented. Three-dimensional nanostructured capacitor array based on double conformal coating of multiwalled carbon nanotubes (MWCNTs) bundles is realized using ALD to deposit Al2O3 as dielectric layer and TiN as high aspect-ratio conformal counter-electrode on 2 μm long MWCNT bundles. The devices have a small footprint (from 100 μm(2) to 2500 μm(2)) and are realized using an IC wafer-scale manufacturing process with high reproducibility (≤0.3E-12F deviation). To evaluate the enhancement of the electrode surface, the measured capacitance values are compared to a lumped circuital model. The observed discrepancies are explained with a partial coating of the CNT, that determine a limited use of the available electrode surface area. To analyze the CNT coating effectiveness, the ALD precursors diffusions inside the CNT bundle is studied using a Knudsen diffusion mechanism. PMID:25604841

  4. Fiber containment for improved laboratory handling and uniform nanocoating of milligram quantities of carbon nanotubes by atomic layer deposition.

    PubMed

    Devine, Christina K; Oldham, Christopher J; Jur, Jesse S; Gong, Bo; Parsons, Gregory N

    2011-12-01

    The presence of nanostructured materials in the workplace is bringing attention to the importance of safe practices for nanomaterial handling. We explored novel fiber containment methods to improve the handling of carbon nanotube (CNT) powders in the laboratory while simultaneously allowing highly uniform and controlled atomic layer deposition (ALD) coatings on the nanotubes, down to less than 4 nm on some CNT materials. Moreover, the procedure yields uniform coatings on milligram quantities of nanotubes using a conventional viscous flow reactor system, circumventing the need for specialized fluidized bed or rotary ALD reactors for laboratory-scale studies. We explored both fiber bundles and fiber baskets as possible containment methods and conclude that the baskets are more suitable for coating studies. An extended precursor and reactant dose and soak periods allowed the gases to diffuse through the fiber containment, and the ALD coating thickness scaled linearly with the number of ALD cycles. The extended dose period produced thicker coatings compared to typical doses on CNT controls not encased in the fibers, suggesting some effects due to the extended reactant dose. Film growth was compared on a range of single-walled NTs, double-walled NTs, and acid-functionalized multiwalled NTs, and we found that ultrathin coatings were most readily controlled on the multiwalled NTs. PMID:22070742

  5. Synthesis of carbon nanotube-nickel nanocomposites using atomic layer deposition for high-performance non-enzymatic glucose sensing.

    PubMed

    Choi, Taejin; Kim, Soo Hyeon; Lee, Chang Wan; Kim, Hangil; Choi, Sang-Kyung; Kim, Soo-Hyun; Kim, Eunkyoung; Park, Jusang; Kim, Hyungjun

    2015-01-15

    A useful strategy has been developed to fabricate carbon-nanotube-nickel (CNT-Ni) nanocomposites through atomic layer deposition (ALD) of Ni and chemical vapor deposition (CVD) of functionalized CNTs. Various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), were used to characterize the morphology and the structure of as-prepared samples. It was confirmed that the products possess uniform Ni nanoparticles that are constructed by finely controlled deposition of Ni onto oxygen or bromine functionalized CNT surface. Electrochemical studies indicate that the CNT-Ni nanocomposites exhibit high electrocatalytic activity for glucose oxidation in alkaline solutions, which enables the products to be used in enzyme-free electrochemical sensors for glucose determination. It was demonstrated that the CNT-Ni nanocomposite-based glucose biosensor offers a variety of merits, such as a wide linear response window for glucose concentrations of 5 μM-2 mM, short response time (3 s), a low detection limit (2 μM), high sensitivity (1384.1 μA mM(-1) cm(-2)), and good selectivity and repeatability. PMID:25113051

  6. Metal atom oxidation laser

    DOEpatents

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-10-28

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides.

  7. Metal atom oxidation laser

    DOEpatents

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-10-28

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides. (auth)

  8. Atoms in Action

    SciTech Connect

    2009-01-01

    This movie produced with Berkeley Lab's TEAM 0.5 microscope shows the growth of a hole and the atomic edge reconstruction in a graphene sheet. An electron beam focused to a spot on the sheet blows out the exposed carbon atoms to make the hole. The carbon atoms then reposition themselves to find a stable configuration. http://newscenter.lbl.gov/press-releases/2009/03/26/atoms-in-action/

  9. Adsorption configurations of two nitrogen atoms on graphene

    SciTech Connect

    Rani, Babita; Jindal, V. K.; Dharamvir, Keya

    2014-04-24

    We present calculations for different possible configurations of two nitrogen adatoms on graphene using the code VASP, based on Density Functional Theory (DFT). Two N atoms adsorbed on the graphene sheet can share a bond in two ways. They take positions either just above two adjacent carbon atoms or they form a bridge across opposite bonds of a hexagon in the graphene sheet. Both these configurations result into structural distortion of the sheet. Another stable configuration involving two N atoms consists of an N{sub 2} molecule which is physisorbed at a distance 3.69 Å on the graphene sheet. Two N atoms can also be adsorbed on alternate bridge sites of neighbouring hexagons of graphene. This configuration again leads to distortion of the sheet in perpendicular direction.

  10. Stabilizing a high-temperature electrochemical silver-carbonate CO2 capture membrane by atomic layer deposition of a ZrO2 overcoat.

    PubMed

    Zhang, Peng; Tong, Jingjing; Jee, Youngseok; Huang, Kevin

    2016-07-28

    A high-selectivity and high-flux electrochemical silver-carbonate dual-phase membrane was coated with a nanoscaled ZrO2 layer by atomic layer deposition (ALD) for stable CO2 capture at high-temperature (≥800 °C); the latter has an important implication for direct dry methane reforming with the captured CO2 and O2 for syngas production. PMID:27417536

  11. Atomic structure of PtCu nanoparticles in PtCu/C catalysts prepared by simultaneous and sequential deposition of components on carbon support

    NASA Astrophysics Data System (ADS)

    Bugaev, L. A.; Srabionyan, V. V.; Pryadchenko, V. V.; Bugaev, A. L.; Avakyan, L. A.; Belenov, S. V.; Guterman, V. E.

    2016-05-01

    Nanocatalysts PtCu/C with different distribution of components in bimetallic PtCu nanoparticles (NPs) were synthesized by simultaneous and sequential deposition of Cu and Pt on carbon support. Electrochemical stability of the obtained samples PtCu/C was studied using the cyclic voltammetry. Characterization of atomic structure of as prepared PtCu NPs and obtained after acid treatment was performed by Pt L 3- and Cu K-edge EXAFS using the technique for determining local structure parameters of the absorbing atom under strong correlations among them. EXAFS derived parameters were used for generation of structural models of PtCu NPs by the method of cluster simulations. Within this approach, the models of atomic structure of PtCu NPs obtained by the two methods of synthesis, before and after post treatment and after two months from their preparation were revealed.

  12. Gas-phase reactions of carbon dioxide with atomic transition-metal and main-group cations: room-temperature kinetics and periodicities in reactivity.

    PubMed

    Koyanagi, Gregory K; Bohme, Diethard K

    2006-02-01

    The chemistry of carbon dioxide has been surveyed systematically with 46 atomic cations at room temperature using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and allowed to cool radiatively and to thermalize by collisions with Ar and He atoms prior to reaction downstream in a flow tube in helium buffer gas at 0.35 +/- 0.01 Torr and 295 +/- 2 K. Rate coefficients and products were measured for the reactions of first-row atomic ions from K(+) to Se(+), of second-row atomic ions from Rb(+) to Te(+) (excluding Tc(+)), and of third-row atomic ions from Cs(+) to Bi(+). CO(2) was found to react in a bimolecular fashion by O atom transfer only with 9 early transition-metal cations: the group 3 cations Sc(+), Y(+), and La(+), the group 4 cations Ti(+), Zr(+), and Hf(+), the group 5 cations Nb(+) and Ta(+), and the group 6 cation W(+). Electron spin conservation was observed to control the kinetics of O atom transfer. Addition of CO(2) was observed for the remaining 37 cations. While the rate of addition was not measurable some insight was obtained into the standard free energy change, DeltaG(o), for CO(2) ligation from equilibrium constant measurements. A periodic variation in DeltaG(o) was observed for first row cations that is consistent with previous calculations of bond energies D(0)(M(+)-CO(2)). The observed trends in D(0) and DeltaG(o) are expected from the variation in electrostatic attraction between M(+) and CO(2) which follows the trend in atomic-ion size and the trend in repulsion between the orbitals of the atomic cations and the occupied orbitals of CO(2). Higher-order CO(2) cluster ions with up to four CO(2) ligands also were observed for 24 of the atomic cations while MO(2)(+) dioxide formation by sequential O atom transfer was seen only with Hf(+), Nb(+), Ta(+), and W(+). PMID:16435784

  13. Polarizabilities and van der Waals C6 coefficients of fullerenes from an atomistic electrodynamics model: Anomalous scaling with number of carbon atoms.

    PubMed

    Saidi, Wissam A; Norman, Patrick

    2016-07-14

    The van der Waals C6 coefficients of fullerenes are shown to exhibit an anomalous dependence on the number of carbon atoms N such that C6 ∝ N(2.2) as predicted using state-of-the-art quantum mechanical calculations based on fullerenes with small sizes, and N(2.75) as predicted using a classical-metallic spherical-shell approximation of the fullerenes. We use an atomistic electrodynamics model where each carbon atom is described by a polarizable object to extend the quantum mechanical calculations to larger fullerenes. The parameters of this model are optimized to describe accurately the static and complex polarizabilities of the fullerenes by fitting against accurate ab initio calculations. This model shows that C6 ∝ N(2.8), which is supportive of the classical-metallic spherical-shell approximation. Additionally, we show that the anomalous dependence of the polarizability on N is attributed to the electric charge term, while the dipole-dipole term scales almost linearly with the number of carbon atoms. PMID:27421409

  14. Polarizabilities and van der Waals C6 coefficients of fullerenes from an atomistic electrodynamics model: Anomalous scaling with number of carbon atoms

    NASA Astrophysics Data System (ADS)

    Saidi, Wissam A.; Norman, Patrick

    2016-07-01

    The van der Waals C6 coefficients of fullerenes are shown to exhibit an anomalous dependence on the number of carbon atoms N such that C6 ∝ N2.2 as predicted using state-of-the-art quantum mechanical calculations based on fullerenes with small sizes, and N2.75 as predicted using a classical-metallic spherical-shell approximation of the fullerenes. We use an atomistic electrodynamics model where each carbon atom is described by a polarizable object to extend the quantum mechanical calculations to larger fullerenes. The parameters of this model are optimized to describe accurately the static and complex polarizabilities of the fullerenes by fitting against accurate ab initio calculations. This model shows that C6 ∝ N2.8, which is supportive of the classical-metallic spherical-shell approximation. Additionally, we show that the anomalous dependence of the polarizability on N is attributed to the electric charge term, while the dipole-dipole term scales almost linearly with the number of carbon atoms.

  15. High-Resolution Imaging of Plasmid DNA in Liquids in Dynamic Mode Atomic Force Microscopy Using a Carbon Nanofiber Tip

    NASA Astrophysics Data System (ADS)

    Kitazawa, Masashi; Ito, Shuichi; Yagi, Akira; Sakai, Nobuaki; Uekusa, Yoshitugu; Ohta, Ryo; Inaba, Kazuhisa; Hayashi, Akari; Hayashi, Yasuhiko; Tanemura, Masaki

    2011-08-01

    To understand the motion of DNA and DNA complexes, the real-time visualization of living DNA in liquids is quite important. Here, we report the high-resolution imaging of plasmid DNA in water using a rapid-scan atomic force microscopy (AFM) system equipped with a carbon nanofiber (CNF) probe. To achieve a rapid high-resolution scan, small SiN cantilevers with dimensions of 2 (width) × 0.1 (thickness) × 9 µm (length) and a bent end (tip view structure) were employed as base cantilevers onto which single CNFs were grown. The resonant frequencies of the cantilever were 1.5 MHz in air and 500 kHz in water, and the spring constant was calculated to be 0.1 N/m. Single CNFs, typically 88 nm in length, were formed on an array of the cantilevers in a batch process by the ion-irradiation method. An AFM image of a plasmid DNA taken in water at 0.2 fps (5 s/image) using a batch-fabricated CNF-tipped cantilever clearly showed the helix turns of the double strand DNA. The average helical pitch measured 3.4 nm (σ: 0.5 nm), which was in good agreement with that determined by the X-ray diffraction method, 3.4 nm. Thus, it is presumed that the combined use of the rapid-scan AFM system with the ion-induced CNF probe is promising for the dynamic analysis of biomolecules.

  16. Atomic force microscopy and tribology study of the adsorption of alcohols on diamond-like carbon coatings and steel

    NASA Astrophysics Data System (ADS)

    Kalin, M.; Simič, R.

    2013-04-01

    Polar molecules are known to affect the friction and wear of steel contacts via adsorption onto the surface, which represents one of the fundamental boundary-lubrication mechanisms. Since the basic chemical and physical effects of polar molecules on diamond-like carbon (DLC) coatings have been investigated only very rarely, it is important to find out whether such molecules have a similar effect on DLC coatings as they do on steel. In our study the adsorption of hexadecanol in various concentrations (2-20 mmol/l) on DLC was studied under static conditions using an atomic force microscope (AFM). The amount of surface coverage, the size and the density of the adsorbed islands of alcohol molecules were analyzed. Tribological tests were also performed to correlate the wear and friction behaviours with the adsorption of molecules on the surface. In this case, steel surfaces served as a reference. The AFM was successfully used to analyze the adsorption ability of polar molecules onto the DLC surfaces and a good correlation between the AFM results and the tribological behaviour of the DLC and the steel was found. We confirmed that alcohols can adsorb physically and chemically onto the DLC surfaces and are, therefore, potential boundary-lubrication agents for the DLC coatings. The adsorption of alcohol onto the DLC surfaces reduces the wear of the coatings, but it is less effective in reducing the friction because of the already inherently low-friction properties of DLC. Tentative adsorption mechanisms that include the environmental species effect, the temperature effect and the tribological rubbing effect are proposed for DLC and steel surfaces.

  17. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  18. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  19. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of off-road vehicle use on Reclamation lands will...

  20. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR...-managing agencies on adjacent lands (both public and private)....

  1. 43 CFR 420.3 - Adjacent lands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Adjacent lands. 420.3 Section 420.3 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR OFF-ROAD VEHICLE USE § 420.3 Adjacent lands. When administratively feasible, the regulation of...

  2. Atom probe study of the carbon distribution in a hardened martensitic hot-work tool steel X38CrMoV5-1.

    PubMed

    Lerchbacher, Christoph; Zinner, Silvia; Leitner, Harald

    2012-07-01

    The microstructure of the hardened common hot-work tool steel X38CrMoV5-1 has been characterized by atom probe tomography with the focus on the carbon distribution. Samples quenched with technically relevant cooling parameters λ from 0.1 (30 K/s) to 12 (0.25 K/s) have been investigated. The parameter λ is an industrially commonly used exponential cooling parameter, representing the cooling time from 800 to 500 °C in seconds divided with hundred. In all samples pronounced carbon segregation to dislocations and cluster formation could be observed after quenching. Carbon enriched interlath films with peak carbon levels of 6-10 at.%, which have been identified to be retained austenite by TEM, show a thickness increase with increasing λ. Therefore, the fraction of total carbon staying in the austenite grows. This carbon is not available for the tempering induced precipitation of secondary carbides in the bulk. Through all samples no segregation of any substitutional elements takes place. Charpy impact testing and fracture surface analysis of the hardened samples reveal the cooling rate induced microstructural distinctions. PMID:22391101

  3. Atomic-layer-deposition alumina induced carbon on porous NixCo1 - xO nanonets for enhanced pseudocapacitive and Li-ion storage performance

    NASA Astrophysics Data System (ADS)

    Guan, Cao; Wang, Yadong; Zacharias, Margit; Wang, John; Fan, Hong Jin

    2015-01-01

    A unique composite nanonet of metal oxide@carbon interconnected sheets is obtained by atomic layer deposition (ALD)-assisted fabrication. In this nanonet structure, mesoporous metal oxide nanosheets are covered by a layer of amorphous carbon nanoflakes. Specifically, quasi-vertical aligned and mesoporous NixCo1 - xO nanosheets are first fabricated directly on nickel foam substrates by a hydrothermal method. Then, an ALD-enabled carbon coating method is applied for the growth of carbon nanoflakes on the surface of the nanosheets. The thus formed 3D hierarchical structure of NixCo1 - xO@carbon composite flakes have a higher surface area, better electrical conductivity and structure stability than the bare NixCo1 - xO. The application of such composite nanomaterials is demonstrated as electrodes for a supercapacitor and a lithium-ion battery. In both tests, the composite electrode shows enhancement in capacity and cycling stability. This effective composite nanostructure design of metal oxides@carbon flakes could provide a promising method to construct high-performance materials for energy and environment applications.

  4. Control of hydrogen and carbon impurity inclusion during the growth of GaAsN thin film by atomic layer epitaxy

    NASA Astrophysics Data System (ADS)

    Yokoyama, Yuki; Fukuyama, Atsuhiko; Haraguchi, Tomohiro; Yamauchi, Toshihiro; Ikari, Tetsuo; Suzuki, Hidetoshi

    2016-01-01

    The effects of growth temperature and nitrogen (N) source duration on N, carbon (C), and hydrogen (H) concentrations in GaAsN layers grown by atomic layer epitaxy (ALE) were investigated to understand the incorporation mechanisms of these atoms. In addition, the effects of the above growth conditions on the self-limiting mechanism (SLM) were investigated. The SLM was in effect at growth temperatures of 500 and 520 °C. The origin of the residual C was not N but other sources. With increasing N source duration, the N and H concentrations increased and saturated. The N incorporation mechanisms were discussed by a simple model considering the absorption and desorption of N atoms on the gallium (Ga)-covered surface. H atoms originating from the N source were incorporated in to the GaAsN layer. According to the ratio of the H concentration to the N concentration, the difference in the incorporation processes of N and H atoms in ALE-grown GaAsN layers was discussed.

  5. Warm ISM in the Sagittarius A Complex. I. Mid-J CO, atomic carbon, ionized atomic carbon, and ionized nitrogen sub-mm/FIR line observations with the Herschel-HIFI and NANTEN2/SMART telescopes

    NASA Astrophysics Data System (ADS)

    García, P.; Simon, R.; Stutzki, J.; Güsten, R.; Requena-Torres, M. A.; Higgins, R.

    2016-04-01

    Aims: We investigate the spatial and spectral distribution of the local standard of rest (LSR) velocity resolved submillimetre emission from the warm (25-90 K) gas in the Sgr A Complex, located in the Galactic centre. Methods: We present large-scale submillimetre heterodyne observations towards the Sgr A Complex covering ~300 arcmin2. These data were obtained in the frame of the Herschel EXtraGALactic guaranteed time key program (HEXGAL) with the Herschel-HIFI satellite and are complemented with submillimetre observations obtained with the NANTEN2/SMART telescope as part of the NANTEN2/SMART Central Nuclear Zone Survey. The observed species are CO(J = 4-3) at 461.0 GHz observed with the NANTEN2/SMART telescope, and [CI] 3P1-3P0 at 492.2 GHz, [CI] 3P2-3P1 at 809.3 GHz, [NII] 3P1-3P0 at 1461.1 GHz, and [CII] 2P3/2-2P1/2 at 1900.5 GHz observed with the Herschel-HIFI satellite. The observations are presented in a 1 km s-1 spectral resolution and a spatial resolution ranging from 46 arcsec to 28 arcsec. The spectral coverage of the three lower frequency lines is ±200 km s-1, while in the two high frequency lines, the upper LSR velocity limit is +94 km s-1 and +145 km s-1 for the [NII] and [CII] lines, respectively. Results: The spatial distribution of the emission in all lines is very widespread. The bulk of the carbon monoxide emission is found towards Galactic latitudes below the Galactic plane, and all the known molecular clouds are identified. Both neutral atomic carbon lines have their brightest emission associated with the +50 km s-1 cloud. Their spatial distribution at this LSR velocity describes a crescent-shape structure, which is probably the result of interaction with the energetic event (one or several supernovae explosions) that gave origin to the non-thermal Sgr A-East source. The [CII] and [NII] emissions have most of their flux associated with the thermal arched-filaments and the H region and bright spots in [CII] emission towards the central nuclear

  6. Petroleum basins of Sakhalin and adjacent shelf

    SciTech Connect

    Mavrinski, Y.; Koblov, E. )

    1993-09-01

    Sixty-seven oil and gas fields have been discovered on Sakhalin and the adjacent shelf but the distribution of fields is uneven in north Sakhalin, south Sakhalin, and the Tatar basins. The sedimentary cover is composed of sandy, clayey, and siliceous rocks, with volcanogenic and coal-bearing deposits of Upper Cretaceous, Paleogene, and Neogene 8-12 km thick. Marine clayey and siliceous oil source rocks are regionally developed in the section at different stratigraphic levels; the organic matter is of mixed type and the content varies from 0.5 to 1.5%. The upper Oligocene and middle-upper Miocene source rocks in the north Sakhalin basin are typical, and the organic carbon content ranges from 1 to 5%. The level of organic matter catagenesis and conversion into hydrocarbons is high because of the high differential geothermal gradient in the basins, 30-50[degrees]C per km. Porous sandstones in the Miocene form the reservoirs in all fields with the exception of Okruzhnoye, where the pay zone is a siliceous claystone. Growth-fault rollovers and anticlines form the main traps ranging in area from 5 to 300 km[sup 2], with amplitudes between 100 and 600 m. both stratigraphic and structural traps have been identified. Considerable volumes of reserves are associated with the Miocene deposits of north Sakhalin, which are characterized by an optimum combination of oil source rocks, focused migration paths, and thick sequences of reservoirs and cap rocks. Six large fields have been discovered in the past 15 yr. Oil and condensate reserves stand at over 300 million MT, and gas reserves are about 900 billion m[sup 3].

  7. Designing electronic anisotropy of three-dimensional carbon allotropes for the all-carbon device

    NASA Astrophysics Data System (ADS)

    Xu, Li-Chun; Song, Xian-Jiang; Wang, Ru-Zhi; Yang, Zhi; Li, Xiu-Yan; Yan, Hui

    2015-07-01

    Extending two-dimensional (2D) graphene nanosheets to a three-dimensional (3D) network can enhance the design of all-carbon electronic devices. Based on the great diversity of carbon atomic bonding, we have constructed four superlattice-type carbon allotrope candidates, containing sp2-bonding transport channels and sp3-bonding insulating layers, using density functional theory. It was demonstrated through systematic simulations that the ultra-thin insulating layer with only three-atom thickness can switch off the tunneling transport and isolate the electronic connection between the adjacent graphene strips, and these alternating perpendicular strips also extend the electron road from 2D to 3D. Designing electronic anisotropy originates from the mutually perpendicular π bonds and the rare partial charge density of the corresponding carriers in insulating layers. Our results indicate the possibility of producing custom-designed 3D all-carbon devices with building blocks of graphene and diamond.

  8. Designing electronic anisotropy of three-dimensional carbon allotropes for the all-carbon device

    SciTech Connect

    Xu, Li-Chun Song, Xian-Jiang; Yang, Zhi; Li, Xiu-Yan; Wang, Ru-Zhi; Yan, Hui

    2015-07-13

    Extending two-dimensional (2D) graphene nanosheets to a three-dimensional (3D) network can enhance the design of all-carbon electronic devices. Based on the great diversity of carbon atomic bonding, we have constructed four superlattice-type carbon allotrope candidates, containing sp{sup 2}-bonding transport channels and sp{sup 3}-bonding insulating layers, using density functional theory. It was demonstrated through systematic simulations that the ultra-thin insulating layer with only three-atom thickness can switch off the tunneling transport and isolate the electronic connection between the adjacent graphene strips, and these alternating perpendicular strips also extend the electron road from 2D to 3D. Designing electronic anisotropy originates from the mutually perpendicular π bonds and the rare partial charge density of the corresponding carriers in insulating layers. Our results indicate the possibility of producing custom-designed 3D all-carbon devices with building blocks of graphene and diamond.

  9. Investigation of diamond-like carbon samples as a charge state conversion surface for neutral atom imaging detectors in space applications

    NASA Astrophysics Data System (ADS)

    Brigitte Neuland, Maike; Riedo, Andreas; Scheer, Jürgen; Wurz, Peter

    2014-05-01

    The detection of energetic neutral atoms is a substantial requirement on every space mission mapping particle populations of a planetary magnetosphere or plasma of the interstellar medium. For imaging neutrals, these first have to be ionized. Regarding the constraints of weight, volume and power consumption, the technique of surface ionization complies with all specifications of a space mission. Particularly low energy neutral atoms, which cannot be ionized by passing through a foil, are ionized by scattering on a charge state conversion surface. Since more than 30 years intense research work is done to find suitable materials for use as charge state conversion surfaces. Crucial parameters are the ionisation efficiency of the surface material and the scattering properties. Against all expectations, insulators showed very promising characteristics for serving as conversion surfaces. Particularly diamond-like carbon was proven advantageously: While efficiently ionising incoming neutral atoms, diamond stands out by its durability and chemical inertness. In the IBEX-Lo sensor, a diamond-like carbon surface is used for ionisation of neutral atoms. Energy resolved maps of neutral atoms from the IBEX mission revealed phenomena of the interaction between heliosphere and local interstellar medium (LISM) that demand for new theory and explanations [McComas et al., 2011]. Building on the successes of the IBEX mission, a follow up mission concept to further explore the boundaries of the heliosphere already exists. The Interstellar MApping Probe (IMAP) is planned to map neutral atoms in a larger energy range and with a distinct better angular resolution and sensitivity than IBEX [McComas et al.]. The aspired performance of the IMAP sensors implies also for charge state conversion surfaces with improved characteristics. We investigated samples of diamond-like carbon, manufactured by the chemical vapour and pulsed laser deposition method, regarding their ionisation efficiency

  10. Evolution of the atomic order and valence state of rare-earth atoms and uranium in a new carbon-metal composite—diphthalocyanine pyrolysate C64H32N16 Me ( Me = Y, La, Ce, Eu, and U)

    NASA Astrophysics Data System (ADS)

    Sovestnov, A. E.; Kapustin, V. K.; Tikhonov, V. I.; Fomin, E. V.; Chernenkov, Yu. P.

    2014-08-01

    The structure of a metal-carbon composite formed by the pyrolysis of diphthalocyanine of some rare-earth elements (Y, La, Ce, Eu) and uranium in the temperature range T ann = 800-1700°C has been investigated for the first time by the methods of X-ray diffraction analysis and X-ray line shift. It has been shown that, in the general case, the studied pyrolysates consist of three phases. One phase corresponds to the structure of graphite. The second phase corresponds to nitrides, carbides, and oxides of basic metal elements with a crystallite size ranging from 5 to 100 nm. The third phase is amorphous or consisting of crystallites with a size of ˜1 nm. It has been found that all the basic elements (Y, La, Ce, Eu, U) and incorporated iodine atoms in the third phase are in a chemically bound state. The previously unobserved electronic configurations have been revealed for europium. The possibility of including not only atoms of elements forming diphthalocyanine but also other elements (for example, iodine) in the composite structure is of interest, in particular, for the creation of a thermally, chemically, and radiation resistant metal-carbon matrix for the radioactive waste storage.

  11. Proposal for Testing and Validation of Vacuum Ultra-Violet Atomic Laser-Induced Fluorescence as a Method to Analyze Carbon Grid Erosion in Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Stevens, Richard

    2003-01-01

    Previous investigation under award NAG3-25 10 sought to determine the best method of LIF to determine the carbon density in a thruster plume. Initial reports from other groups were ambiguous as to the number of carbon clusters that might be present in the plume of a thruster. Carbon clusters would certainly affect the ability to LIF; if they were the dominant species, then perhaps the LIF method should target clusters. The results of quadrupole mass spectroscopy on sputtered carbon determined that minimal numbers of clusters were sputtered from graphite under impact from keV Krypton. There were some investigations in the keV range by other groups that hinted at clusters, but at the time the proposal was presented to NASA, there was no data from low-energy sputtering available. Thus, the proposal sought to develop a method to characterize the population only of atoms sputtered from a graphite target in a test cell. Most of the ground work had been established by the previous two years of investigation. The proposal covering 2003 sought to develop an anti-Stokes Raman shifting cell to generate VUW light and test this cell on two different laser systems, ArF and YAG- pumped dye. The second goal was to measure the lowest detectable amounts of carbon atoms by 156.1 nm and 165.7 nm LIF. If equipment was functioning properly, it was expected that these goals would be met easily during the timeframe of the proposal, and that is the reason only modest funding was requested. The PI was only funded at half- time by Glenn during the summer months. All other work time was paid for by Whitworth College. The college also funded a student, Charles Shawley, who worked on the project during the spring.

  12. Molecular dynamics study of human carbonic anhydrase II in complex with Zn(2+) and acetazolamide on the basis of all-atom force field simulations.

    PubMed

    Wambo, Thierry O; Chen, Liao Y; McHardy, Stanton F; Tsin, Andrew T

    2016-01-01

    Human carbonic anhydrase II (hCAII) represents an ultimate example of the perfectly efficient metalloenzymes, which is capable of catalyzing the hydration of carbon dioxide with a rate approaching the diffusion controlled limit. Extensive experimental studies of this physiologically important metalloprotein have been done to elucidate the fundamentals of its enzymatic actions: what residues anchor the Zn(2+) (or another divalent cation) at the bottom of the binding pocket; how the relevant residues work concertedly with the divalent cation in the reversible conversions between CO2 and HCO3(-); what are the protonation states of the relevant residues and acetazolamide, an inhibitor complexed with hCAII, etc. In this article, we present a detailed computational study on the basis of the all-atom CHARMM force field where Zn(2+) is represented with a simple model of divalent cation using the transferrable parameters available from the current literature. We compute the hydration free energy of Zn(2+), the characteristics of hCAII-Zn(2+) complexation, and the absolute free energy of binding acetazolamide to the hCAII-Zn(2+) complex. In each of these three problems, our computed results agree with the experimental data within the known margin of error without making any case-by-case adjustments to the parameters. The quantitatively accurate insights we gain in this all-atom molecular dynamics study should be helpful in the search and design of more specific inhibitors of this and other carbonic anhydrases. PMID:27232456

  13. Structural and surface features of multiwall carbon nanotube

    NASA Astrophysics Data System (ADS)

    Hembram, K. P. S. S.; Rao, G. Mohan

    2011-04-01

    We present the direct evidence of defective and disorder places on the surface of multiwall carbon nanotube (MWCNT), visualizing the presence of amorphous carbon at those sites. These defective surfaces being higher in energy are the key features of functionalization with different materials. The interaction of the π orbital electrons of different carbon atoms of adjacent layers is more at the bent portion, than that of regular portion of the CNT. Hence the tubular structure of the bent portion of nanotubes is spaced more than that of regular portion of the nanotubes, minimizing the stress.

  14. H ATOM IRRADIATION OF CARBON GRAINS UNDER SIMULATED DENSE INTERSTELLAR MEDIUM CONDITIONS: THE EVOLUTION OF ORGANICS FROM DIFFUSE INTERSTELLAR CLOUDS TO THE SOLAR SYSTEM

    SciTech Connect

    Mennella, Vito

    2010-08-01

    We present the results of experiments aimed at studying the interaction of hydrogen atoms at 80 K with carbon grains covered with a water ice layer at 12 K. The effects of H processing have been analyzed, using IR spectroscopy, as a function of the water ice layer. The results confirm that exposure of the samples to H atoms induces the activation of the band at 3.47 {mu}m with no evidence for the formation of aromatic and aliphatic C-H bonds in the CH{sub 2} and CH{sub 3} functional groups. The formation cross section of the 3.47 {mu}m band has been estimated from the increase of its integrated optical depth as a function of the H atom fluence. The cross section decreases with increasing thickness of the water ice layer, indicating an increase of adsorption of H atoms in the water ice layer. A penetration depth of 100 nm has been estimated for H atoms in the porous water ice covering carbon grains. Sample warm-up at room temperature causes the activation of the IR features due to the vibrations of the CH{sub 2} and CH{sub 3} aliphatic functional groups. The evolution of the 3.47 {mu}m band carrier has been evaluated for dense and diffuse interstellar clouds, using the estimated formation cross section and assuming that the destruction cross section by energetic processing is the same as that derived for the 3.4 {mu}m band. In both environments, the presence of the 3.47 {mu}m band carrier is compatible with the evolutionary timescale limit imposed by fast cycling of materials between dense and diffuse regions of the interstellar medium. In diffuse regions the formation of the CH{sub 2} and CH{sub 3} aliphatic bands, inhibited in dense regions, takes place, masking the 3.47 {mu}m band. The activation of the CH{sub 2} and CH{sub 3} aliphatic vibrational modes at the end of H processing after sample warm-up represents the first experimental evidence supporting an evolutionary connection between the interstellar carbon grain population, which is responsible for the 3

  15. Multiple dispersed phases in a high-strength low-carbon steel: An atom-probe tomographic and synchrotron X-ray diffraction study

    SciTech Connect

    Mulholland, Michael D.; Seidman, David N.

    2009-06-12

    The co-precipitation of Cu, M{sub 2}C (where M is any combination of Cr, Mo or Ti) and austenite (face-centered cubic) is characterized for 5 h isochronal aging times by synchrotron X-ray diffraction and three-dimensional atom-probe tomography for a high-strength low-carbon steel, BlastAlloy 160. High number densities, {approx}10{sup 23} m{sup 03}, of co-located Cu and M{sub 2}C preciptates were observed. Only small austenite volume percentages (<2.1%) were measured after aging at temperatures up to 625 C for 5 h.

  16. Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C36H12 open geodesic polyarene

    PubMed Central

    Cho, Hee Yeon; Ansems, Ronald B M

    2014-01-01

    Summary Circumtrindene (6, C36H12), one of the largest open geodesic polyarenes ever reported, exhibits fullerene-like reactivity at its interior carbon atoms, whereas its edge carbons react like those of planar polycyclic aromatic hydrocarbons (PAHs). The Bingel–Hirsch and Prato reactions – two traditional methods for fullerene functionalization – afford derivatives of circumtrindene with one of the interior 6:6 C=C bonds modified. On the other hand, functionalization on the rim of circumtrindene can be achieved by normal electrophilic aromatic substitution, the most common reaction of planar PAHs. This peripheral functionalization has been used to extend the π-system of the polyarene by subsequent coupling reactions and to probe the magnetic environment of the concave/convex space around the hydrocarbon bowl. For both classes of functionalization, computational results are reported to complement the experimental observations. PMID:24991245

  17. Atomic Layer Deposition of ZnO on Multi-walled Carbon Nanotubes and Its Use for Synthesis of CNT-ZnO Heterostructures.

    PubMed

    Li, X L; Li, C; Zhang, Y; Chu, D P; Milne, W I; Fan, H J

    2010-01-01

    In this article, direct coating of ZnO on PECVD-grown multi-walled carbon nanotubes (MWCNTs) is achieved using atomic layer deposition (ALD). Transmission electron microscopy investigation shows that the deposited ZnO shell is continuous and uniform, in contrast to the previously reported particle morphology. The ZnO layer has a good crystalline quality as indicated by Raman and photoluminescence (PL) measurements. We also show that such ZnO layer can be used as seed layer for subsequent hydrothermal growth of ZnO nanorods, resulting in branched CNT-inorganic hybrid nanostructures. Potentially, this method can also apply to the fabrication of ZnO-based hybrid nanostructures on other carbon nanomaterials. PMID:21124621

  18. Atomic Layer Deposition of ZnO on Multi-walled Carbon Nanotubes and Its Use for Synthesis of CNT-ZnO Heterostructures

    NASA Astrophysics Data System (ADS)

    Li, X. L.; Li, C.; Zhang, Y.; Chu, D. P.; Milne, W. I.; Fan, H. J.

    2010-11-01

    In this article, direct coating of ZnO on PECVD-grown multi-walled carbon nanotubes (MWCNTs) is achieved using atomic layer deposition (ALD). Transmission electron microscopy investigation shows that the deposited ZnO shell is continuous and uniform, in contrast to the previously reported particle morphology. The ZnO layer has a good crystalline quality as indicated by Raman and photoluminescence (PL) measurements. We also show that such ZnO layer can be used as seed layer for subsequent hydrothermal growth of ZnO nanorods, resulting in branched CNT-inorganic hybrid nanostructures. Potentially, this method can also apply to the fabrication of ZnO-based hybrid nanostructures on other carbon nanomaterials.

  19. Pd nanoparticles on ZnO-passivated porous carbon by atomic layer deposition: an effective electrochemical catalyst for Li-O2 battery.

    PubMed

    Luo, Xiangyi; Piernavieja-Hermida, Mar; Lu, Jun; Wu, Tianpin; Wen, Jianguo; Ren, Yang; Miller, Dean; Zak Fang, Zhigang; Lei, Yu; Amine, Khalil

    2015-04-24

    Uniformly dispersed Pd nanoparticles on ZnO-passivated porous carbon were synthesized via an atomic layer deposition (ALD) technique, which was tested as a cathode material in a rechargeable Li-O2 battery, showing a highly active catalytic effect toward the electrochemical reactions-in particular, the oxygen evolution reaction. Transmission electron microscopy (TEM) showed discrete crystalline nanoparticles decorating the surface of the ZnO-passivated porous carbon support in which the size could be controlled in the range of 3-6 nm, depending on the number of Pd ALD cycles performed. X-ray absorption spectroscopy (XAS) at the Pd K-edge revealed that the carbon-supported Pd existed in a mixed phase of metallic palladium and palladium oxide. The ZnO-passivated layer effectively blocks the defect sites on the carbon surface, minimizing the electrolyte decomposition. Our results suggest that ALD is a promising technique for tailoring the surface composition and structure of nanoporous supports for Li-O2 batteries. PMID:25829367

  20. On the time-course of adjacent and non-adjacent transposed-letter priming

    PubMed Central

    Ktori, Maria; Kingma, Brechtsje; Hannagan, Thomas; Holcomb, Phillip J.; Grainger, Jonathan

    2014-01-01

    We compared effects of adjacent (e.g., atricle-ARTICLE) and non-adjacent (e.g., actirle-ARTICLE) transposed-letter (TL) primes in an ERP study using the sandwich priming technique. TL priming was measured relative to the standard double-substitution condition. We found significantly stronger priming effects for adjacent transpositions than non-adjacent transpositions (with 2 intervening letters) in behavioral responses (lexical decision latencies), and the adjacent priming effects emerged earlier in the ERP signal, at around 200 ms post-target onset. Non-adjacent priming effects emerged about 50 ms later and were short-lived, being significant only in the 250-300 ms time-window. Adjacent transpositions on the other hand continued to produce priming in the N400 time-window (300-500 ms post-target onset). This qualitatively different pattern of priming effects for adjacent and non-adjacent transpositions is discussed in the light of different accounts of letter transposition effects, and the utility of drawing a distinction between positional flexibility and positional noise. PMID:25364497

  1. A nano universal joint made from curved double-walled carbon nanotubes

    SciTech Connect

    Cai, Kun; Cai, Haifang; Shi, Jiao; Qin, Qing H.

    2015-06-15

    A nano universal joint is constructed from curved double-wall carbon nanotubes with a short outer tube as stator and a long inner tube as a rotor. When one end of the rotor is driven (by a rotary motor) to rotate, the same rotational speed but with different rotational direction will be induced at the other end of the rotor. This mechanism makes the joint useful for designing a flexible nanodevice with an adjustable output rotational signal. The motion transmission effect of the universal joint is analyzed using a molecular dynamics simulation approach. In particular, the effects of three factors are investigated. The first factor is the curvature of the stator, which produces a different rotational direction of the rotor at the output end. The second is the bonding conditions of carbon atoms on the adjacent tube ends of the motor and the rotor, sp{sup 1} or sp{sup 2} atoms, which create different attraction between the motor and the rotor. The third is the rotational speed of the motor, which can be considered as the input signal of the universal joint. It is noted that the rotor's rotational speed is usually the same as that of the motor when the carbon atoms on the adjacent ends of the motor and the rotor are sp{sup 1} carbon atoms. When they become the new sp{sup 2} atoms, the rotor experiences a jump in rotational speed from a lower value to that of the motor. The mechanism of drops in potential of the motor is revealed. If the carbon atoms on the adjacent ends are sp{sup 2} atoms, the rotor rotates more slowly than the motor, whereas the rotational speed is stable when driven by a higher speed motor.

  2. A nano universal joint made from curved double-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cai, Kun; Cai, Haifang; Shi, Jiao; Qin, Qing H.

    2015-06-01

    A nano universal joint is constructed from curved double-wall carbon nanotubes with a short outer tube as stator and a long inner tube as a rotor. When one end of the rotor is driven (by a rotary motor) to rotate, the same rotational speed but with different rotational direction will be induced at the other end of the rotor. This mechanism makes the joint useful for designing a flexible nanodevice with an adjustable output rotational signal. The motion transmission effect of the universal joint is analyzed using a molecular dynamics simulation approach. In particular, the effects of three factors are investigated. The first factor is the curvature of the stator, which produces a different rotational direction of the rotor at the output end. The second is the bonding conditions of carbon atoms on the adjacent tube ends of the motor and the rotor, sp1 or sp2 atoms, which create different attraction between the motor and the rotor. The third is the rotational speed of the motor, which can be considered as the input signal of the universal joint. It is noted that the rotor's rotational speed is usually the same as that of the motor when the carbon atoms on the adjacent ends of the motor and the rotor are sp1 carbon atoms. When they become the new sp2 atoms, the rotor experiences a jump in rotational speed from a lower value to that of the motor. The mechanism of drops in potential of the motor is revealed. If the carbon atoms on the adjacent ends are sp2 atoms, the rotor rotates more slowly than the motor, whereas the rotational speed is stable when driven by a higher speed motor.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  6. An Ab Initio Full Potential Fully Relativistic Study of Atomic Carbon, Nitrogen, and Oxygen Chemisorption on the (111) Surface of δ-Pu

    NASA Astrophysics Data System (ADS)

    Atta-Fynn, Raymond; Ray, Asok

    2006-10-01

    Fully-relativistic full potential density functional calculations have been performed to investigate atomic carbon, nitrogen, and oxygen chemisorption on the (111) surface of δ-Pu using the all-electron linearized augmented plane wave plus local orbitals code WIEN2k and the generalized gradient approximation to density functional theory. The surface was modeled by a three-layer periodic slab separated by 60 Bohr vacuum with two atoms per surface unit cell. The hollow fcc adsorption site was found to be the most preferred site with chemisorption energies of 6.539 eV, 6.714 eV, and 8.2 eV for the C, N, and O adatoms, respectively. The respective distances of the C, N, and O adatoms from the surface were found to be 1.16 å, 1.08 å, and 1.25 å. Analysis of the partial charges inside the atomic spheres, charge density distributions, and the local density of states indicate hybridizations between Pu 5f and the 2p states of the adatoms.

  7. Impact of carbon co-implantation on boron distribution and activation in silicon studied by atom probe tomography and spreading resistance measurements

    NASA Astrophysics Data System (ADS)

    Shimizu, Yasuo; Takamizawa, Hisashi; Inoue, Koji; Yano, Fumiko; Kudo, Shuichi; Nishida, Akio; Toyama, Takeshi; Nagai, Yasuyoshi

    2016-02-01

    The impact of carbon (C) co-implantation on boron (B) activation in crystalline silicon was investigated. The detailed distribution of B and C atoms and B activation ratios dependent on the C ion-implantation energies were examined based on three-dimensional spatial mappings of B and C obtained by atom probe tomography and from depth profiles of their concentrations from secondary ion mass spectrometry and depth profiles of carrier concentrations with spreading resistance measurements. At all C implantation energies (8, 15, and 30 keV), B out-diffusion during activation annealing was reduced, so that more B atoms were observed in the C co-implanted samples. The carrier concentration was decreased throughout the entire implanted region for C implantation energies of 15 and 30 keV, although it was only increased at greater depths for C co-implantation at 8 keV. Two different effects of C co-implantation, (I) reduction of B out-diffusion and (II) influence of B activation, were confirmed.

  8. Reactivity of atomic oxygen radical anions bound to titania and zirconia nanoparticles in the gas phase: low-temperature oxidation of carbon monoxide.

    PubMed

    Ma, Jia-Bi; Xu, Bo; Meng, Jing-Heng; Wu, Xiao-Nan; Ding, Xun-Lei; Li, Xiao-Na; He, Sheng-Gui

    2013-02-27

    Titanium and zirconium oxide cluster anions with dimensions up to nanosize are prepared by laser ablation and reacted with carbon monoxide in a fast low reactor. The cluster reactions are characterized by time-of-flight mass spectrometry and density functional theory calculations. The oxygen atom transfers from (TiO(2))(n)O(-) (n = 3-25) to CO and formations of (TiO(2))(n)(-) are observed, whereas the reactions of (ZrO(2))(n)O(-) (n = 3-25) with CO generate the CO addition products (ZrO(2))(n)OCO(-), which lose CO(2) upon the collisions (studied for n = 3-9) with a crossed helium beam. The computational study indicates that the (MO(2))(n)O(-) (M = Ti, Zr; n = 3-8) clusters are atomic radical anion (O(-)) bonded systems, and the energetics for CO oxidation by the O(-) radicals to form CO(2) is strongly dependent on the metals as well as the cluster size for the titanium system. Atomic oxygen radical anions are important reactive intermediates, while it is difficult to capture and characterize them for condensed phase systems. The reactivity pattern of the O(-)-bonded (TiO(2))(n)O(-) and (ZrO(2))(n)O(-) correlates very well with different behaviors of titania and zirconia supports in the low-temperature catalytic CO oxidation. PMID:23368886

  9. Adsorption of carbon monoxide on small aluminum oxide clusters: Role of the local atomic environment and charge state on the oxidation of the CO molecule

    NASA Astrophysics Data System (ADS)

    Ornelas-Lizcano, J. C.; Guirado-López, R. A.

    2015-03-01

    We present extensive density functional theory (DFT) calculations dedicated to analyze the adsorption behavior of CO molecules on small AlxOy± clusters. Following the experimental results of Johnson et al. [J. Phys. Chem. A 112, 4732 (2008)], we consider structures having the bulk composition Al2O3, as well as smaller Al2O2 and Al2O units. Our electron affinity and total energy calculations are consistent with aluminum oxide clusters having two-dimensional rhombus-like structures. In addition, interconversion energy barriers between two- and one-dimensional atomic arrays are of the order of 1 eV, thus clearly defining the preferred isomers. Single CO adsorption on our charged AlxOy± clusters exhibits, in general, spontaneous oxygen transfer events leading to the production of CO2 in line with the experimental data. However, CO can also bind to both Al and O atoms of the clusters forming aluminum oxide complexes with a CO2 subunit. The vibrational spectra of AlxOy + CO2 provides well defined finger prints that may allow the identification of specific isomers. The AlxOy+ clusters are more reactive than the anionic species and the final Al2O+ + CO reaction can result in the production of atomic Al and carbon dioxide as observed from experiments. We underline the crucial role played by the local atomic environment, charge density distribution, and spin-multiplicity on the oxidation behavior of CO molecules. Finally, we analyze the importance of coadsorption and finite temperature effects by performing DFT Born-Oppenheimer molecular dynamics. Our calculations show that CO oxidation on AlxOy+ clusters can be also promoted by the binding of additional CO species at 300 K, revealing the existence of fragmentation processes in line with the ones experimentally inferred.

  10. Multielement determination of heavy metals in water samples by continuous powder introduction microwave-induced plasma atomic emission spectrometry after preconcentration on activated carbon

    NASA Astrophysics Data System (ADS)

    Jankowski, Krzysztof; Yao, Jun; Kasiura, Krzysztof; Jackowska, Adrianna; Sieradzka, Anna

    2005-03-01

    A novel continuous powder introduction microwave-induced plasma atomic emission spectrometry method (CPI-MIP-AES) has been developed for trace determination of metals in ground and tap water samples after preconcentration on activated carbon. The experimental setup consisted of integrated rectangular cavity TE 101 and vertically positioned plasma torch. The technical arrangement of the sample introduction system has been designed based on the fluidized bed concept. The satisfactory signal stability required for sequential analysis was attained owing to the vertical plasma configuration, as well as the plasma gas flow rate compatibility with sample introduction flow rate. The elements of interest (Cd, Cu, Cr, Fe, Mn, Pb, Zn) were preconcentrated in a batch procedure at pH 8-8.5 after addition of activated carbon and then, after filtering and drying of the activated carbon suspension, introduced to the MIP by the CPI system. An enrichment factor of about 1000-fold for a sample volume of 1 l was obtained. The detection limit values for the proposed method were 17-250 ng l -1. The proposed method was validated by analyzing the certified reference materials: SRW "Warta" Synthetic River Water and BCR CRM 399 major elements in freshwater. The method was successfully applied to the determination of the heavy metals in tap water samples.

  11. SOLIDS TRANSPORT BETWEEN ADJACENT CAFB FLUIDIZED BEDS

    EPA Science Inventory

    The report gives results of an experimental investigation of a pulsed, dense-phase pneumatic transport system for controlled circulation between adjacent fluidized beds. A model was developed to predict performance. The program provides technical support for EPA's program to demo...

  12. Border separation for adjacent orthogonal fields

    SciTech Connect

    Werner, B.L.; Khan, F.M.; Sharma, S.C.; Lee, C.K.; Kim, T.H. )

    1991-06-01

    Field border separations for adjacent orthogonal fields can be calculated geometrically, given the validity of some important assumptions such as beam alignment and field uniformity. Thermoluminescent dosimetry (TLD) measurements were used to investigate dose uniformity across field junctions as a function of field separation and, in particular, to review the CCSG recommendation for the treatment of medulloblastoma with separate head and spine fields.

  13. Atomic data and spectral analysis of carbon, nitrogen, oxygen and silicon ions observed with the International Ultraviolet Explorer

    NASA Technical Reports Server (NTRS)

    Pradhan, Anil K.

    1992-01-01

    According to the plan presented in the original proposal we have now completed most of the atomic calculations involving collision strengths and rate coefficients for electron impact excitation of C II, N III, and O IV ions. These have been reported in the first two publications appended with this report. We have now moved into the applications phase of the project with the new data being used to analyze the International Ultraviolet Explorer (IUE) observations of a variety of objects, as described in the third publication recently submitted (also appended). The analysis and interpretation of archival data will continue well into the next year with several collaborators that the PI and Co-PI are involved with. In addition, the atomic calculations on Si II have been started.

  14. Study of modification methods of probes for critical-dimension atomic-force microscopy by the deposition of carbon nanotubes

    SciTech Connect

    Ageev, O. A.; Bykov, Al. V.; Kolomiitsev, A. S.; Konoplev, B. G.; Rubashkina, M. V.; Smirnov, V. A.; Tsukanova, O. G.

    2015-12-15

    The results of an experimental study of the modification of probes for critical-dimension atomicforce microscopy (CD-AFM) by the deposition of carbon nanotubes (CNTs) to improve the accuracy with which the surface roughness of vertical walls is determined in submicrometer structures are presented. Methods of the deposition of an individual CNT onto the tip of an AFM probe via mechanical and electrostatic interaction between the probe and an array of vertically aligned carbon nanotubes (VACNTs) are studied. It is shown that, when the distance between the AFM tip and a VACNT array is 1 nm and the applied voltage is within the range 20–30 V, an individual carbon nanotube is deposited onto the tip. On the basis of the results obtained in the study, a probe with a carbon nanotube on its tip (CNT probe) with a radius of 7 nm and an aspect ratio of 1:15 is formed. Analysis of the CNT probe demonstrates that its use improves the resolution and accuracy of AFM measurements, compared with the commercial probe, and also makes it possible to determine the roughness of the vertical walls of high-aspect structures by CD-AFM. The results obtained can be used to develop technological processes for the fabrication and reconditioning of special AFM probes, including those for CD-AFM, and procedures for the interoperational express monitoring of technological process parameters in the manufacturing of elements for micro- and nanoelectronics and micro- and nanosystem engineering.

  15. Carbon Monoxide-Induced Stability and Atomic Segregation Phenomena in Shape-Selected Octahedral PtNi Nanoparticles.

    PubMed

    Ahmadi, Mahdi; Cui, Chunhua; Mistry, Hemma; Strasser, Peter; Cuenya, Beatriz Roldan

    2015-11-24

    The chemical and morphological stability of size- and shape-selected octahedral PtNi nanoparticles (NP) were investigated after different annealing treatments up to a maximum temperature of 700 °C in a vacuum and under 1 bar of CO. Atomic force microscopy was used to examine the mobility of the NPs and their stability against coarsening, and X-ray photoelectron spectroscopy to study the surface composition, chemical state of Pt and Ni in the NPs, and thermally and CO-induced atomic segregation trends. Exposing the samples to 1 bar of CO at room temperature before annealing in a vacuum was found to be effective at enhancing the stability of the NPs against coarsening. In contrast, significant coarsening was observed when the sample was annealed in 1 bar of CO, most likely as a result of Ni(CO)4 formation and their enhanced mobility on the support surface. Sample exposure to CO at room temperature prior to annealing led to the segregation of Pt to the NP surface. Nevertheless, oxidic PtOx and NiOx species still remained at the NP surface, and, irrespective of the initial sample pretreatment, Ni surface segregation was observed upon annealing in a vacuum at moderate temperature (T < 300 °C). Interestingly, a distinct atomic segregation trend was detected between 300 and 500 °C for the sample pre-exposed to CO; namely, Ni surface segregation was partially hindered. This might be attributed to the higher bonding energy of CO to Pt as compared to Ni. Annealing in the presence of 1 bar CO also resulted in the initial surface segregation of Ni (T < 400 °C) as long as PtOx and NiOx species were available on the surface as a result of the higher affinity of Ni for oxygen. Above 500 °C, and regardless of the sample pretreatment, the diffusion of Pt atoms to the NP surface and the formation of a Ni-Pt alloy are observed. PMID:26418831

  16. Two-dimensional Penning ionization electron spectroscopy of carbon disulfide: spectral assignments and anisotropic interactions with a He*(2 3S) metastable atom

    NASA Astrophysics Data System (ADS)

    Tian, Shan Xi; Kishimoto, Naoki; Ohno, Koichi

    2002-10-01

    Collision-energy-resolved Penning ionization electron spectra are measured for carbon disulfide (CS 2) by collision with a He*(2 3S) metastable atom. Assignments in Penning ionization electron spectrum are made on the basis of collision energy dependence of the partial ionization cross sections (CEDPICS). CEDPICS for the X2Π g, A2Π u, B2Σ u+ and C2Σ g+ states demonstrates that interactions for the He * access perpendicular to the molecular axis are more attractive than those for the collinear access, which is supported by the model calculations of the interaction potential energies. It is found that the perpendicular access plays an important role in a formation of the intermediate He ++CS 2- state.

  17. Inhomogeneous broadening of optically detected magnetic resonance of the ensembles of nitrogen-vacancy centers in diamond by interstitial carbon atoms

    SciTech Connect

    Levchenko, A. O. Vasil'ev, V. V.; Zibrov, S. A.; Zibrov, A. S.; Sivak, A. V.; Fedotov, I. V.

    2015-03-09

    We study the impact of the negatively charged nitrogen-vacancy (NV{sup –}) center density on the lattice strain resulting in the splitting of the optically detected magnetic resonance of HPHT diamond. A simple model, taking into account the presence of the interstitial carbon atoms, acting like a wedge force on the crystal lattice, explains the broadening and splitting of the optically detected magnetic resonance of the ensemble of NV{sup –} centers at densities within the range of 10{sup 13} ÷ 10{sup 14 }cm{sup −3}. This model uses a complete generalized spin Hamiltonian, takes into account the strain-effect of each center in the ensemble and gives good agreement with experimental data.

  18. The states of carbon and nitrogen atoms after photodissociation of CN, CH, CH(+), C2, C3, and CO in comets

    NASA Technical Reports Server (NTRS)

    Singh, P. D.; De Almeida, A. A.; Huebner, W. F.

    1991-01-01

    The photodissociation of carbon compounds by solar UV radiation at a heliocentric distance of 1 AU is examined, comparing published observational data with the predictions of theoretical models and results from laboratory experiments. It is shown that species other than CO, including CN, CH, CH(+), C2, and C3, can contribute to the observed brightness of the VUV lines of C I (156.1, 165.7, and 193.1 nm) and C II (133.5 nm) in comet comae. CN photodissociation is also found to produce metastable 2D0 and 2P0 N I atoms, possibly leading (at heliocentric distances less than 0.25 AU) to 143.9-nm emission via resonance fluorescence.

  19. Effect of surface finishing on early-stage corrosion of a carbon steel studied by electrochemical and atomic force microscope characterizations

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Cheng, Y. Frank

    2016-03-01

    In this work, the early-stage corrosion of a carbon steel with various surface roughness, which was created by different levels of surface finishing treatment, was characterized by an atomic force microscope and electrochemical measurements. It is found that the resulting surface roughness is at nano-meter scale. As the surface roughness increases, the corrosion activity of the steel is increased. The early-stage corrosion of the steel is featured with two stages of dissolution. While the first stage involves a rapid dissolution and increasing surface roughness of the steel, stage two is in an equilibrium state to have an approximately constant corrosion rate and surface roughness. Generally, the corrosion rate of the steel decreases when the surface finish of the specimen becomes finer. Local preferential corrosion occurs at surface irregularities, resulting in the deepening and widening of the features such as scratches with time.

  20. First principle study of magnetic and electronic properties of single X (X = Al, Si) atom added to small carbon clusters (C n X, n = 2-10)

    NASA Astrophysics Data System (ADS)

    Afshar, M.; Hoseini, S. S.; Sargolzaei, M.

    2016-07-01

    In this paper, the magnetic and electronic properties of single aluminum and silicon atom added to small carbon clusters (C n X; X = Al, Si; n = 2-10) are studied in the framework of generalized-gradient approximation using density functional theory. The calculations were performed for linear, two dimensional and three dimensional clusters based on full-potential local-orbital (FPLO) method. The total energies, HOMO-LUMO energy gap and total magnetic moments of the most stable structures are presented in this work. The calculations show that C n Si clusters have more stability compared to C n Al clusters. In addition, our magnetic calculations were shown that the C n Al isomers are magnetic objects whereas C n Si clusters are nonmagnetic objects.

  1. Adjacent Segment Pathology after Lumbar Spinal Fusion.

    PubMed

    Lee, Jae Chul; Choi, Sung-Woo

    2015-10-01

    One of the major clinical issues encountered after lumbar spinal fusion is the development of adjacent segment pathology (ASP) caused by increased mechanical stress at adjacent segments, and resulting in various radiographic changes and clinical symptoms. This condition may require surgical intervention. The incidence of ASP varies with both the definition and methodology adopted in individual studies; various risk factors for this condition have been identified, although a significant controversy still exists regarding their significance. Motion-preserving devices have been developed, and some studies have shown their efficacy of preventing ASP. Surgeons should be aware of the risk factors of ASP when planning a surgery, and accordingly counsel their patients preoperatively. PMID:26435804

  2. Impact of adjacent land use on coastal wetland sediments.

    PubMed

    Karstens, Svenja; Buczko, Uwe; Jurasinski, Gerald; Peticzka, Robert; Glatzel, Stephan

    2016-04-15

    Coastal wetlands link terrestrial with marine ecosystems and are influenced from both land and sea. Therefore, they are ecotones with strong biogeochemical gradients. We analyzed sediment characteristics including macronutrients (C, N, P, K, Mg, Ca, S) and heavy metals (Mn, Fe, Cu, Zn, Al, Co, Cr, Ni) of two coastal wetlands dominated by Phragmites australis at the Darss-Zingst Bodden Chain, a lagoon system at the Southern Baltic Sea, to identify the impact of adjacent land use and to distinguish between influences from land or sea. In the wetland directly adjacent to cropland (study site Dabitz) heavy metal concentrations were significantly elevated. Fertilizer application led to heavy metal accumulation in the sediments of the adjacent wetland zones. In contrast, at the other study site (Michaelsdorf), where the hinterland has been used as pasture, heavy metal concentrations were low. While the amount of macronutrients was also influenced by vegetation characteristics (e.g. carbon) or water chemistry (e.g. sulfate), the accumulation of heavy metals is regarded as purely anthropogenic influence. A principal component analysis (PCA) based on the sediment data showed that the wetland fringes of the two study sites are not distinguishable, neither in their macronutrient status nor in their concentrations of heavy metals, whereas the interior zones exhibit large differences in terms of heavy metal concentrations. This suggests that seaside influences are minor compared to influences from land. Altogether, heavy metal concentrations were still below national precautionary and action values. However, if we regard the macronutrient and heavy metal concentrations in the wetland fringes as the natural background values, an accumulation of trace elements from agricultural production in the hinterland is apparent. Thus, coastal wetlands bordering croplands may function as effective pollutant buffers today, but the future development has to be monitored closely to avoid

  3. Multiwalled carbon nanotubes as a sorbent material for the solid phase extraction of lead from urine and subsequent determination by electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Peña Crecente, Rosa M.; Lovera, Carlha Gutiérrez; García, Julia Barciela; Méndez, Jennifer Álvarez; Martín, Sagrario García; Latorre, Carlos Herrero

    2014-11-01

    The determination of lead in urine is a way of monitoring the chemical exposure to this metal. In the present paper, a new method for the Pb determination by electrothermal atomic absorption spectrometry (ETAAS) in urine at low levels has been developed. Lead was separated from the undesirable urine matrix by means of a solid phase extraction (SPE) procedure. Oxidized multiwalled carbon nanotubes have been used as a sorbent material. Lead from urine was retained at pH 4.0 and was quantitatively eluted using a 0.7 M nitric acid solution and was subsequently measured by ETAAS. The effects of parameters that influence the adsorption-elution process (such as pH, eluent volume and concentration, sampling and elution flow rates) and the atomic spectrometry conditions have been studied by means of different factorial design strategies. Under the optimized conditions, the detection and quantification limits obtained were 0.08 and 0.26 μg Pb L- 1, respectively. The results demonstrate the absence of a urine matrix effect and this is the consequence of the SPE process carried out. Therefore, the developed method is useful for the analysis of Pb at low levels in real samples without the influence of other urine components. The proposed method was applied to the determination of lead in urine samples of unexposed healthy people and satisfactory results were obtained (in the range 3.64-22.9 μg Pb L- 1).

  4. Precursor of N atoms of hydrogenated amorphous carbon nitride films formed from the microwave discharge of C2H2/N2 gas mixture

    NASA Astrophysics Data System (ADS)

    Ito, Haruhiko; Tsudome, Hiroki; Mogi, Nobuyoshi; Saitoh, Hidetoshi

    2016-01-01

    Hydrogenated amorphous carbon nitride films with the [N]/([N] + [C]) ratios of 0.29-0.44 were formed from the microwave discharge of the gas mixture of C2H2 with an excess amount of N2. The ratio of the fluxes, s = Φa-CN/ΦCN(X), was evaluated in this study, where Φa-CN was the flux of N atoms incorporated into the films and ΦCN(X) was that of CN radicals in the gas phase. ΦCN(X) was evaluated from the density of CN radicals using the A2Πi-X2Σ+ laser-induced fluorescence spectra and from the flow speed using the time-resolved emission, and Φa-CN from the film mass calibrated against atomic compositions. The s value was in the range of 0.22-0.78, being 1.2-1.7 times the sticking probability of CN radicals corrected in this study, 0.19-0.45. Then, the contribution of CN radicals was evaluated to be 60-80% of the N source of the films. The chemical structure and mechanical property of the films were analyzed in terms of Raman scattering, IR absorption, and nanoindentation measurements.

  5. Adjacent Segment Pathology after Anterior Cervical Fusion

    PubMed Central

    Chung, Jae Yoon; Park, Jong-Beom; Seo, Hyoung-Yeon

    2016-01-01

    Anterior cervical fusion has become a standard of care for numerous pathologic conditions of the cervical spine. However, subsequent development of clinically significant disc disease at levels adjacent to fused discs is a serious long-term complication of this procedure. As more patients live longer after surgery, it is foreseeable that adjacent segment pathology (ASP) will develop in increasing numbers of patients. Also, ASP has been studied more intensively with the recent popularity of motion preservation technologies like total disc arthroplasty. The true nature and scope of ASP remains poorly understood. The etiology of ASP is most likely multifactorial. Various factors including altered biomechanical stresses, surgical disruption of soft tissue and the natural history of cervical disc disease contribute to the development of ASP. General factors associated with disc degeneration including gender, age, smoking and sports may play a role in the development of ASP. Postoperative sagittal alignment and type of surgery are also considered potential causes of ASP. Therefore, a spine surgeon must be particularly careful to avoid unnecessary disruption of the musculoligamentous structures, reduced risk of direct injury to the disc during dissection and maintain a safe margin between the plate edge and adjacent vertebrae during anterior cervical fusion. PMID:27340541

  6. Adjacent Segment Pathology after Anterior Cervical Fusion.

    PubMed

    Chung, Jae Yoon; Park, Jong-Beom; Seo, Hyoung-Yeon; Kim, Sung Kyu

    2016-06-01

    Anterior cervical fusion has become a standard of care for numerous pathologic conditions of the cervical spine. However, subsequent development of clinically significant disc disease at levels adjacent to fused discs is a serious long-term complication of this procedure. As more patients live longer after surgery, it is foreseeable that adjacent segment pathology (ASP) will develop in increasing numbers of patients. Also, ASP has been studied more intensively with the recent popularity of motion preservation technologies like total disc arthroplasty. The true nature and scope of ASP remains poorly understood. The etiology of ASP is most likely multifactorial. Various factors including altered biomechanical stresses, surgical disruption of soft tissue and the natural history of cervical disc disease contribute to the development of ASP. General factors associated with disc degeneration including gender, age, smoking and sports may play a role in the development of ASP. Postoperative sagittal alignment and type of surgery are also considered potential causes of ASP. Therefore, a spine surgeon must be particularly careful to avoid unnecessary disruption of the musculoligamentous structures, reduced risk of direct injury to the disc during dissection and maintain a safe margin between the plate edge and adjacent vertebrae during anterior cervical fusion. PMID:27340541

  7. S-Ribosylhomocysteine analogues with the carbon-5 and sulfur atoms replaced by a vinyl or (fluoro)vinyl unit

    PubMed Central

    Wnuk, Stanislaw F.; Lalama, Jennifer; Garmendia, Craig A.; Robert, Jenay; Zhu, Jinge; Pei, Dehua

    2008-01-01

    Treatment of the protected ribose or xylose 5-aldehyde with sulfonyl-stabilized fluorophosphonate gave (fluoro)vinyl sulfones. Stannyldesulfonylation followed by iododestannylation afforded 5,6-dideoxy-6-fluoro-6-iodo-d-ribo or xylo-hex-5-enofuranoses. Coupling of the hexenofuranoses with alkylzinc bromides gave ten-carbon ribosyl- and xylosylhomocysteine analogues incorporating a fluoroalkene. The fluoroalkenyl and alkenyl analogues were evaluated for inhibition of Bacillus subtilis S-ribosylhomocysteinase (LuxS). One of the compounds, 3,5,6-trideoxy-6-fluoro-d-erythro-hex-5-enofuranose, acted as a competitive inhibitor of moderate potency (KI = 96 µM). PMID:18375129

  8. Theoretical study of the bonding of ammonia, carbon monoxide, and ethylene, to copper atom, dimer, and trimer

    NASA Astrophysics Data System (ADS)

    Fournier, René

    1995-04-01

    Kohn-Sham density functional theory (KS-DFT) calculations were performed for the association complexes Cun-L, with n=1, 2, 3 and L=NH3, CO, and C2H4. Two geometries for Cu2-L are considered; with the ligand bonded to a single copper atom (``atop,'' or A), and with the ligand bonded to both atoms (``bridge,'' or B). In addition to A and B, a third geometry was considered for Cu3-L, with the ligand bonded to all three copper atoms; in each case, no minimum was found for that third geometry. I report fully optimized equilibrium geometries and harmonic frequencies calculated within the local spin density (LSD) approximation for all the bound complexes and estimates of their binding energies obtained with a gradient-corrected exchange-correlation functional. Structure A is the most stable in all cases but, for Cu3CO and Cu3C2H4, structure B is only a few kcal/mol higher in energy. The energetic contribution from the geometrical relaxation of Cu3 ranges from essentially zero (Cu3NH3 B) to 3.4 kcal/mol (Cu3CO B). In agreement with previous calculations on Cun-C2H2 and with experiments, the calculated Cun-L binding energy is found to increase with n for all ligands. Although the bonding mechanism differs among the three ligands, repulsion of a filled ligand orbital with the half-filled 4s orbital of copper (or 4s-derived molecular orbitals of Cu2 and Cu3) always plays an important role and is responsible for the smaller binding energies in the CuL complexes. This repulsion decreases from Cu to Cu2 because of charge accumulation in Cu-Cu midbond region and of the greater polarizability of Cu2. The Cu3L binding energies are larger than those of Cu2L mostly because of the greater involvement of copper 4p orbitals in bonding to the ligand. The ligand vibrational frequency shifts relative to the free molecules are compared to experiment and discussed in relation to the nature of the metal-ligand interaction. In particular, an interesting correlation, between the frequency of

  9. [Carbon stable isotope composition (delta 13C) of lichen thalli in the forests in the vicinity of the Chernobyl atomic power station].

    PubMed

    Biazrov, L G; Gongal'skiĭ, K B; Pel'gunova, L A; Tiunov, A V

    2010-01-01

    The stable isotope abundance of carbon in the lichens Cladina mitis, Cladonia crispata Hypogymnia physodes, Parmelia sulcata has been investigated in a study relating these values with known levels of 106Ru, 134Cs, 137Cs and 144Ce defined activity in their thalli in the pine forests of region within a 30-km radius of the Chernobyl atomic power station and beyond it (37 km). All 63 samples of the lichens were obtained from 7 different sites. Small effects on delta 13C values in the lichens Cladina mitis, Hypogymnia physodes were found to be associated with distance from CNPP, activity level of radionuclides in them thalli whereas at Cladonia crispata is observed weighting of carbon with increase in values of 134Cs and 137Cs activity in thalli. Values of delta 13C the investigated lichen species more depends on habitat conditions rather than from levels of thalli radioactivity. In our study we didn't reveal the isotope specificity of any one species as it was not possible to establish a correlation between values of delta 13C and a particular species. PMID:20297687

  10. Non-destructive functionalisation for atomic layer deposition of metal oxides on carbon nanotubes: effect of linking agents and defects

    NASA Astrophysics Data System (ADS)

    Kemnade, N.; Shearer, C. J.; Dieterle, D. J.; Cherevan, A. S.; Gebhardt, P.; Wilde, G.; Eder, D.

    2015-02-01

    The hybridisation of metal oxides and nanocarbons has created a promising new class of functional materials for environmental and sustainable energy applications. The performance of such hybrids can be further improved by rationally designing interfaces and morphologies. Atomic layer deposition (ALD) is among the most powerful techniques for the controlled deposition of inorganic compounds, due to its ability to form conformal coatings on porous substrates at low temperatures with high surface sensitivity and atomic control of film thickness. The hydrophobic nature of the nanocarbon surface has so far limited the applicability of ALD on CNTs. Herein we investigate the role of structural defects in CNTs, both intrinsic and induced by acid treatment, on coverage, uniformity and crystallinity of ZnO coatings. Furthermore, we demonstrate the potential of small aromatic molecules, including benzyl alcohol (BA), naphthalene carboxylic acid (NA) and pyrene carboxylic acid (PCA), as active nucleation sites and linking agents. Importantly, only PCA exhibits sufficiently strong interactions with the pristine CNT surface to withstand desorption under reaction conditions. Thus, PCA enables a versatile and non-destructive alternative route for the deposition of highly uniform metal oxide coatings onto pristine CNTs via ALD over a wide temperature range and without the typical surface corrosion induced by covalent functionalisation. Importantly, preliminary tests demonstrated that the improved morphology obtained with PCA has indeed considerably increased the hybrid's photocatalytic activity towards hydrogen evolution via sacrificial water splitting. The concept demonstrated in this work is transferable to a wide range of other inorganic compounds including metal oxides, metal (oxy)nitrides and metal chalcogenides on a variety of nanocarbons.The hybridisation of metal oxides and nanocarbons has created a promising new class of functional materials for environmental and

  11. Atomic branching in molecules

    NASA Astrophysics Data System (ADS)

    Estrada, Ernesto; Rodríguez-Velázquez, Juan A.; Randić, Milan

    A graph theoretic measure of extended atomic branching is defined that accounts for the effects of all atoms in the molecule, giving higher weight to the nearest neighbors. It is based on the counting of all substructures in which an atom takes part in a molecule. We prove a theorem that permits the exact calculation of this measure based on the eigenvalues and eigenvectors of the adjacency matrix of the graph representing a molecule. The definition of this measure within the context of the Hückel molecular orbital (HMO) and its calculation for benzenoid hydrocarbons are also studied. We show that the extended atomic branching can be defined using any real symmetric matrix, as well as any Hermitian (self-adjoint) matrix, which permits its calculation in topological, geometrical, and quantum chemical contexts.

  12. High temperature shock tube and theoretical studies on the thermal decomposition of dimethyl carbonate and its bimolecular reactions with H and D-atoms.

    PubMed

    Peukert, S L; Sivaramakrishnan, R; Michael, J V

    2013-05-01

    The shock tube technique was used to study the high temperature thermal decomposition of dimethyl carbonate, CH3OC(O)OCH3 (DMC). The formation of H-atoms was measured behind reflected shock waves by using atomic resonance absorption spectrometry (ARAS). The experiments span a T-range of 1053-1157 K at pressures ∼0.5 atm. The H-atom profiles were simulated using a detailed chemical kinetic mechanism for DMC thermal decomposition. Simulations indicate that the formation of H-atoms is sensitive to the rate constants for the energetically lowest-lying bond fission channel, CH3OC(O)OCH3 → CH3 + CH3OC(O)O [A], where H-atoms form instantaneously at high temperatures from the sequence of radical β-scissions, CH3OC(O)O → CH3O + CO2 → H + CH2O + CO2. A master equation analysis was performed using CCSD(T)/cc-pv∞z//M06-2X/cc-pvtz energetics and molecular properties for all thermal decomposition processes in DMC. The theoretical predictions were found to be in good agreement with the present experimentally derived rate constants for the bond fission channel (A). The theoretically derived rate constants for this important bond-fission process in DMC can be represented by a modified Arrhenius expression at 0.5 atm over the T-range 1000-2000 K as, kA(T) = 6.85 × 10(98)T (-24.239) exp(-65250 K/T) s(-1). The H-atom temporal profiles at long times show only minor sensitivity to the abstraction reaction, H + CH3OC(O)OCH3 → H2 + CH3OC(O)OCH2 [B]. However, H + DMC is an important fuel destruction reaction at high temperatures. Consequently, measurements of D-atom profiles using D-ARAS allowed unambiguous rate constant measurements for the deuterated analog of reaction B, D + CH3OC(O)OCH3 → HD + CH3OC(O)OCH2 [C]. Reaction C is a surrogate for H + DMC since the theoretically predicted kinetic isotope effect at high temperatures (1000 - 2000K) is close to unity, kC ≈ 1.2 kB. TST calculations employing CCSD(T)/cc-pv∞z//M06-2X/cc-pvtz energetics and molecular properties

  13. A crossed beams study of the reaction of carbon atoms, C(3Pj), with vinyl cyanide, C2H3CN(X 1A')--investigating the formation of cyano propargyl radicals.

    PubMed

    Guo, Y; Gu, X; Zhang, F; Tang, M S; Sun, B J; H Chang, A H; Kaiser, R I

    2006-12-14

    The chemical dynamics of the reaction of ground state carbon atoms, C(3Pj), with vinyl cyanide, C2H3CN(X 1A'), were examined under single collision conditions at collision energies of 29.9 and 43.9 kJ mol(-1) using the crossed molecular beams approach. The experimental studies were combined with electronic structure calculations on the triplet C4H3N potential energy surface (H. F. Su, R. I. Kaiser, A. H. H. Chang, J. Chem. Phys., 2005, 122, 074320). Our investigations suggest that the reaction follows indirect scattering dynamics via addition of the carbon atom to the carbon-carbon double bond of the vinyl cyanide molecule yielding a cyano cyclopropylidene collision complex. The latter undergoes ring opening to form cis/trans triplet cyano allene which fragments predominantly to the 1-cyano propargyl radical via tight exit transition states; the 3-cyano propargyl isomer was inferred to be formed at least a factor of two less; also, no molecular hydrogen elimination channel was observed experimentally. These results are in agreement with the computational studies predicting solely the existence of a carbon versus hydrogen atom exchange pathway and the dominance of the 1-cyano propargyl radical product. The discovery of the cyano propargyl radical in the reaction of atomic carbon with vinyl cyanide under single collision conditions implies that this molecule can be an important reaction intermediate in combustion flames and also in extraterrestrial environments (cold molecular clouds, circumstellar envelopes of carbon stars) which could lead to the formation of cyano benzene (C6H5CN) upon reaction with a propargyl radical. PMID:17119654

  14. Adsorption of carbon monoxide on small aluminum oxide clusters: Role of the local atomic environment and charge state on the oxidation of the CO molecule

    SciTech Connect

    Ornelas-Lizcano, J. C.; Guirado-López, R. A.

    2015-03-28

    We present extensive density functional theory (DFT) calculations dedicated to analyze the adsorption behavior of CO molecules on small Al{sub x}O{sub y}{sup ±} clusters. Following the experimental results of Johnson et al. [J. Phys. Chem. A 112, 4732 (2008)], we consider structures having the bulk composition Al{sub 2}O{sub 3}, as well as smaller Al{sub 2}O{sub 2} and Al{sub 2}O units. Our electron affinity and total energy calculations are consistent with aluminum oxide clusters having two-dimensional rhombus-like structures. In addition, interconversion energy barriers between two- and one-dimensional atomic arrays are of the order of 1 eV, thus clearly defining the preferred isomers. Single CO adsorption on our charged Al{sub x}O{sub y}{sup ±} clusters exhibits, in general, spontaneous oxygen transfer events leading to the production of CO{sub 2} in line with the experimental data. However, CO can also bind to both Al and O atoms of the clusters forming aluminum oxide complexes with a CO{sub 2} subunit. The vibrational spectra of Al{sub x}O{sub y} + CO{sub 2} provides well defined finger prints that may allow the identification of specific isomers. The Al{sub x}O{sub y}{sup +} clusters are more reactive than the anionic species and the final Al{sub 2}O{sup +} + CO reaction can result in the production of atomic Al and carbon dioxide as observed from experiments. We underline the crucial role played by the local atomic environment, charge density distribution, and spin-multiplicity on the oxidation behavior of CO molecules. Finally, we analyze the importance of coadsorption and finite temperature effects by performing DFT Born-Oppenheimer molecular dynamics. Our calculations show that CO oxidation on Al{sub x}O{sub y}{sup +} clusters can be also promoted by the binding of additional CO species at 300 K, revealing the existence of fragmentation processes in line with the ones experimentally inferred.

  15. Reconstructing genome mixtures from partial adjacencies.

    PubMed

    Mahmoody, Ahmad; Kahn, Crystal L; Raphael, Benjamin J

    2012-01-01

    Many cancer genome sequencing efforts are underway with the goal of identifying the somatic mutations that drive cancer progression. A major difficulty in these studies is that tumors are typically heterogeneous, with individual cells in a tumor having different complements of somatic mutations. However, nearly all DNA sequencing technologies sequence DNA from multiple cells, thus resulting in measurement of mutations from a mixture of genomes. Genome rearrangements are a major class of somatic mutations in many tumors, and the novel adjacencies (i.e. breakpoints) resulting from these rearrangements are readily detected from DNA sequencing reads. However, the assignment of each rearrangement, or adjacency, to an individual cancer genome in the mixture is not known. Moreover, the quantity of DNA sequence reads may be insufficient to measure all rearrangements in all genomes in the tumor. Motivated by this application, we formulate the k-minimum completion problem (k-MCP). In this problem, we aim to reconstruct k genomes derived from a single reference genome, given partial information about the adjacencies present in the mixture of these genomes. We show that the 1-MCP is solvable in linear time in the cases where: (i) the measured, incomplete genome has a single circular or linear chromosome; (ii) there are no restrictions on the chromosomal content of the measured, incomplete genome. We also show that the k-MCP problem, for k ≥ 3 in general, and the 2-MCP problem with the double-cut-and-join (DCJ) distance are NP-complete, when there are no restriction on the chromosomal structure of the measured, incomplete genome. These results lay the foundation for future algorithmic studies of the k-MCP and the application of these algorithms to real cancer sequencing data. PMID:23282028

  16. Preparation and bioactive properties of nanocrystalline hydroxyapatite thin films obtained by conversion of atomic layer deposited calcium carbonate.

    PubMed

    Holopainen, Jani; Kauppinen, Kyösti; Mizohata, Kenichiro; Santala, Eero; Mikkola, Esa; Heikkilä, Mikko; Kokkonen, Hanna; Leskelä, Markku; Lehenkari, Petri; Tuukkanen, Juha; Ritala, Mikko

    2014-09-01

    Nanocrystalline hydroxyapatite thin films were fabricated on silicon and titanium by atomic layer deposition (ALD) of CaCO3 and its subsequent conversion to hydroxyapatite by diammonium hydrogen phosphate (DAP) solution. The effects of conversion process parameters to crystallinity and morphology of the films were examined. DAP concentration was found to be critical in controlling the crystal size and homogeneity of the films. The hydroxyapatite phase was identified by XRD. ToF-elastic recoil detection analysis studies revealed that the films are calcium deficient in relation to hydroxyapatite with a Ca/P ratio of 1.39 for films converted with 0.2 M DAP at 95 °C. The coatings prepared on titanium conformally follow the rough surface topography of the substrate, verifying that the good step coverage of the ALD method was maintained in the conversion process. The dissolution tests revealed that the coating was nondissolvable in the cell culture medium. Annealing the coated sample at 700 °C for 1 h seemed to enhance its bonding properties to the substrate. Also, the biocompatibility of the coatings was confirmed by human bone marrow derived cells in vitro. The developed method provides a new possibility to produce thin film coatings on titanium implants with bone-type hydroxyapatite that is biocompatible with human osteoblasts and osteoclasts. PMID:25280849

  17. Influence of krypton atoms on the structure of hydrogenated amorphous carbon deposited by plasma enhanced chemical vapor deposition

    SciTech Connect

    Oliveira, M. H. Jr.; Viana, G. A.; Marques, F. C.; Lima, M. M. Jr. de; Cros, A.; Cantarero, A.

    2010-12-15

    Hydrogenated amorphous carbon (a-C:H) films were prepared by plasma enhanced chemical vapor deposition using methane (CH{sub 4}) plus krypton (Kr) mixed atmosphere. The depositions were performed as function of the bias voltage and krypton partial pressure. The goal of this work was to study the influence of krypton gas on the physical properties of a-C:H films deposited on the cathode electrode. Krypton concentration up to 1.6 at. %, determined by Rutherford Back-Scattering, was obtained at high Kr partial pressure and bias of -120 V. The structure of the films was analyzed by means of optical transmission spectroscopy, multi-wavelength Raman scattering and Fourier Transform Infrared spectroscopy. It was verified that the structure of the films remains unchanged up to a concentration of Kr of about 1.0 at. %. A slight graphitization of the films occurs for higher concentration. The observed variation in the film structure, optical band gap, stress, and hydrogen concentration were associated mainly with the subplantation process of hydrocarbons radicals, rather than the krypton ion energy.

  18. The transport properties of silicon and carbon nanotubes at the atomic scale: a first-principles study.

    PubMed

    Ma, Tengying; Wen, Shizheng; Yan, Likai; Wu, Caixia; Zhang, Chunmei; Zhang, Min; Su, Zhongmin

    2016-08-24

    Nanotubes are one of the most promising functional materials in nanotechnology. Silicon nanotubes (SiNTs) have been experimentally validated; they are unique puckered nanotubular structures unlike carbon nanotubes (CNTs). Although the electronic and optical properties of SiNTs have been previously studied, their structure-related capability for electron transport has not been investigated. Here we report a comparative study of the intrinsic electronic and transport properties of four pairs of SiNTs and CNTs (one armchair nanotubes (3,3) and three zigzag nanotubes (5,0), (6,0) and (7,0)) using density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) method. All our investigated systems of SiNTs and CNTs are conductors. Both the armchair SiNTs and CNTs possess superior electron transport performance to their zigzag counterparts. Compared with CNTs, SiNTs have more advantages in the high bias voltage region. Especially, Si(3,3) possesses around double the potential charge capacity of C(3,3) under the bias voltage of 2.0 V. In particular, the CNT(6,0) exhibits distinct negative differential resistance (NDR) behavior and the peak-valley ratio (PVR) for C(6,0) is about 1.2. PMID:27510551

  19. Hydrogen-Atom Transfer Reactions.

    PubMed

    Wang, Liang; Xiao, Jian

    2016-04-01

    The cascade [1,n]-hydrogen transfer/cyclization, recognized as the tert-amino effect one century ago, has received considerable interest in recent decades, and great achievements have been made. With the aid of this strategy, the inert C(sp(3))-H bonds can be directly functionalized into C-C, C-N, C-O bonds under catalysis of Lewis acids, Brønsted acids, as well as organocatalysts, and even merely under thermal conditions. Hydrogen can be transferred intramolecularly from hydrogen donor to acceptor in the form of hydride, or proton, followed by cyclization to furnish the cyclic products in processes featuring high atom economy. Methylene/methine adjacent to heteroatoms, e.g., nitrogen, oxygen, sulfur, can be exploited as hydride donor as well as methylene/methine without heteroatom assistance. Miscellaneous electrophilic subunits or intermediates, e.g., alkylidene malonate, carbophilic metal activated alkyne or allene, α,β-unsaturated aldehydes/ketone, saturated aldehydes/iminium, ketenimine/carbodiimide, metal carbenoid, electron-withdrawing groups activated allene/alkyne, in situ generated carbocation, can serve as hydride acceptors. This methodology has shown preeminent power to construct 5-, 6-, or 7-membered heterocyclic as well as carbon rings. In this chapter, various hydrogen donors and acceptors are adequately discussed. PMID:27573142

  20. Morphology and crystallinity control of ultrathin TiO2 layers deposited on carbon nanotubes by temperature-step atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Guerra-Nuñez, Carlos; Zhang, Yucheng; Li, Meng; Chawla, Vipin; Erni, Rolf; Michler, Johann; Park, Hyung Gyu; Utke, Ivo

    2015-06-01

    Carbon nanotubes (CNTs) coated with titanium oxide (TiO2) have generated considerable interest over the last decade and become a promising nanomaterial for a wide range of energy applications. The efficient use of the outstanding electrical properties of this nanostructure relies heavily on the quality of the interface and the thickness and morphology of the TiO2 layer. However, complete surface coverage of the chemically inert CNTs and appropriate control of the morphology of the TiO2 layer have not been achieved so far. Here, we report a new strategy to obtain ultrathin TiO2 coatings deposited by ``Temperature-step'' Atomic Layer Deposition (TS-ALD) with complete surface coverage of non-functionalized multiwall carbon nanotubes (MWCNTs) and controlled morphology and crystallinity of the TiO2 film. This strategy consists of adjusting the temperature during the ALD deposition to obtain the desired morphology. Complete coverage of long non-functionalized MWCNTs with conformal anatase layers was obtained by using a low temperature of 60 °C during the nucleation stage followed by an increase to 220 °C during the growth stage. This resulted in a continuous and amorphous TiO2 layer, covered with a conformal anatase coating. Starting with the deposition at 220 °C and reducing to 60 °C resulted in sporadic crystal grains at the CNT/TiO2 interface covered with an amorphous TiO2 layer. The results were accomplished through an extensive study of nucleation and growth of titanium oxide films on MWCNTs, of which a detailed characterization is presented in this work.Carbon nanotubes (CNTs) coated with titanium oxide (TiO2) have generated considerable interest over the last decade and become a promising nanomaterial for a wide range of energy applications. The efficient use of the outstanding electrical properties of this nanostructure relies heavily on the quality of the interface and the thickness and morphology of the TiO2 layer. However, complete surface coverage of the

  1. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    PubMed Central

    Wang, Yang-Gang; Mei, Donghai; Glezakou, Vassiliki-Alexandra; Li, Jun; Rousseau, Roger

    2015-01-01

    Catalysis by gold supported on reducible oxides has been extensively studied, yet issues such as the nature of the catalytic site and the role of the reducible support remain fiercely debated topics. Here we present ab initio molecular dynamics simulations of an unprecedented dynamic single-atom catalytic mechanism for the oxidation of carbon monoxide by ceria-supported gold clusters. The reported dynamic single-atom catalytic mechanism results from the ability of the gold cation to strongly couple with the redox properties of the ceria in a synergistic manner, thereby lowering the energy of redox reactions. The gold cation can break away from the gold nanoparticle to catalyse carbon monoxide oxidation, adjacent to the metal/oxide interface and subsequently reintegrate back into the nanoparticle after the reaction is completed. Our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in catalysis. PMID:25735407

  2. Morphology and crystallinity control of ultrathin TiO2 layers deposited on carbon nanotubes by temperature-step atomic layer deposition.

    PubMed

    Guerra-Nuñez, Carlos; Zhang, Yucheng; Li, Meng; Chawla, Vipin; Erni, Rolf; Michler, Johann; Park, Hyung Gyu; Utke, Ivo

    2015-06-28

    Carbon nanotubes (CNTs) coated with titanium oxide (TiO2) have generated considerable interest over the last decade and become a promising nanomaterial for a wide range of energy applications. The efficient use of the outstanding electrical properties of this nanostructure relies heavily on the quality of the interface and the thickness and morphology of the TiO2 layer. However, complete surface coverage of the chemically inert CNTs and appropriate control of the morphology of the TiO2 layer have not been achieved so far. Here, we report a new strategy to obtain ultrathin TiO2 coatings deposited by "Temperature-step" Atomic Layer Deposition (TS-ALD) with complete surface coverage of non-functionalized multiwall carbon nanotubes (MWCNTs) and controlled morphology and crystallinity of the TiO2 film. This strategy consists of adjusting the temperature during the ALD deposition to obtain the desired morphology. Complete coverage of long non-functionalized MWCNTs with conformal anatase layers was obtained by using a low temperature of 60 °C during the nucleation stage followed by an increase to 220 °C during the growth stage. This resulted in a continuous and amorphous TiO2 layer, covered with a conformal anatase coating. Starting with the deposition at 220 °C and reducing to 60 °C resulted in sporadic crystal grains at the CNT/TiO2 interface covered with an amorphous TiO2 layer. The results were accomplished through an extensive study of nucleation and growth of titanium oxide films on MWCNTs, of which a detailed characterization is presented in this work. PMID:26018433

  3. Adjacent Lone Pair (ALP) Effect: A Computational Approach for Its Origin.

    PubMed

    Zhang, Huaiyu; Wu, Wei; Ahmed, Basil M; Mezei, Gellert; Mo, Yirong

    2016-05-23

    The adjacent lone pair (ALP) effect is an experimental phenomenon in certain nitrogenous heterocyclic systems exhibiting the preference of the products with lone pairs separated over other isomers with lone pairs adjacent. A theoretical elucidation of the ALP effect requires the decomposition of intramolecular energy terms and the isolation of lone pair-lone pair interactions. Here we used the block-localized wavefunction (BLW) method within the ab initio valence bond (VB) theory to derive the strictly localized orbitals which are used to accommodate one-atom centered lone pairs and two-atom centered σ or π bonds. As such, interactions among electron pairs can be directly derived. Two-electron integrals between adjacent lone pairs do not support the view that the lone pair-lone pair repulsion is responsible for the ALP effect. Instead, the disabling of π conjugation greatly diminishes the ALP effect, indicating that the reduction of π conjugation in deprotonated forms with two σ lone pairs adjacent is one of the major causes for the ALP effect. Further electrostatic potential analysis and intramolecular energy decomposition confirm that the other key factor is the favorable electrostatic attraction within the isomers with lone pairs separated. PMID:27139318

  4. Exchange coupling between laterally adjacent nanomagnets.

    PubMed

    Dey, H; Csaba, G; Bernstein, G H; Porod, W

    2016-09-30

    We experimentally demonstrate exchange-coupling between laterally adjacent nanomagnets. Our results show that two neighboring nanomagnets that are each antiferromagnetically exchange-coupled to a common ferromagnetic bottom layer can be brought into strong ferromagnetic interaction. Simulations show that interlayer exchange coupling effectively promotes ferromagnetic alignment between the two nanomagnets, as opposed to antiferromagnetic alignment due to dipole-coupling. In order to experimentally demonstrate the proposed scheme, we fabricated arrays of pairs of elongated, single-domain nanomagnets. Magnetic force microscopy measurements show that most of the pairs are ferromagnetically ordered. The results are in agreement with micromagnetic simulations. The presented scheme can achieve coupling strengths that are significantly stronger than dipole coupling, potentially enabling far-reaching applications in Nanomagnet Logic, spin-wave devices and three-dimensional storage and computing. PMID:27535227

  5. Seismicity in Azerbaijan and Adjacent Caspian Sea

    SciTech Connect

    Panahi, Behrouz M.

    2006-03-23

    So far no general view on the geodynamic evolution of the Black Sea to the Caspian Sea region is elaborated. This is associated with the geological and structural complexities of the region revealed by geophysical, geochemical, petrologic, structural, and other studies. A clash of opinions on geodynamic conditions of the Caucasus region, sometimes mutually exclusive, can be explained by a simplified interpretation of the seismic data. In this paper I analyze available data on earthquake occurrences in Azerbaijan and the adjacent Caspian Sea region. The results of the analysis of macroseismic and instrumental data, seismic regime, and earthquake reoccurrence indicate that a level of seismicity in the region is moderate, and seismic event are concentrated in the shallow part of the lithosphere. Seismicity is mostly intra-plate, and spatial distribution of earthquake epicenters does not correlate with the plate boundaries.

  6. Boundary Layers of Air Adjacent to Cylinders

    PubMed Central

    Nobel, Park S.

    1974-01-01

    Using existing heat transfer data, a relatively simple expression was developed for estimating the effective thickness of the boundary layer of air surrounding cylinders. For wind velocities from 10 to 1000 cm/second, the calculated boundary-layer thickness agreed with that determined for water vapor diffusion from a moistened cylindrical surface 2 cm in diameter. It correctly predicted the resistance for water vapor movement across the boundary layers adjacent to the (cylindrical) inflorescence stems of Xanthorrhoea australis R. Br. and Scirpus validus Vahl and the leaves of Allium cepa L. The boundary-layer thickness decreased as the turbulence intensity increased. For a turbulence intensity representative of field conditions (0.5) and for νwindd between 200 and 30,000 cm2/second (where νwind is the mean wind velocity and d is the cylinder diameter), the effective boundary-layer thickness in centimeters was equal to [Formula: see text]. PMID:16658855

  7. Quantitative analysis of mechanical and electrostatic properties of poly(lactic) acid fibers and poly(lactic) acid-carbon nanotube composites using atomic force microscopy.

    PubMed

    Iqbal, Qais; Bernstein, Peter; Zhu, Yazhe; Rahamim, Joseph; Cebe, Peggy; Staii, Cristian

    2015-03-13

    We use atomic force microscopy (AFM) to perform a systematic quantitative characterization of the elastic modulus and dielectric constant of poly(L-lactic acid) electrospun nanofibers (PLLA), as well as composites of PLLA fibers with 1.0 wt% embedded multiwall carbon nanotubes (MWCNTs-PLLA). The elastic moduli are measured in the fiber skin region via AFM nanoindentation, and the dielectric constants are determined by measuring the phase shifts obtained via electrostatic force microscopy (EFM). We find that the average value for the elastic modulus for PLLA fibers is (9.8 ± 0.9) GPa, which is a factor of 2 larger than the measured average elastic modulus for MWCNT-PLLA composites (4.1 ± 0.7) GPa. We also use EFM to measure dielectric constants for both types of fibers. These measurements show that the dielectric constants of the MWCNT-PLLA fibers are significantly larger than the corresponding values obtained for PLLA fiber. This result is consistent with the higher polarizability of the MWCNT-PLLA composites. The measurement methods presented are general, and can be applied to determine the mechanical and electrical properties of other polymers and polymer nanocomposites. PMID:25683087

  8. Quantitative analysis of mechanical and electrostatic properties of poly(lactic) acid fibers and poly(lactic) acid—carbon nanotube composites using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Iqbal, Qais; Bernstein, Peter; Zhu, Yazhe; Rahamim, Joseph; Cebe, Peggy; Staii, Cristian

    2015-03-01

    We use atomic force microscopy (AFM) to perform a systematic quantitative characterization of the elastic modulus and dielectric constant of poly(L-lactic acid) electrospun nanofibers (PLLA), as well as composites of PLLA fibers with 1.0 wt% embedded multiwall carbon nanotubes (MWCNTs-PLLA). The elastic moduli are measured in the fiber skin region via AFM nanoindentation, and the dielectric constants are determined by measuring the phase shifts obtained via electrostatic force microscopy (EFM). We find that the average value for the elastic modulus for PLLA fibers is (9.8 ± 0.9) GPa, which is a factor of 2 larger than the measured average elastic modulus for MWCNT-PLLA composites (4.1 ± 0.7) GPa. We also use EFM to measure dielectric constants for both types of fibers. These measurements show that the dielectric constants of the MWCNT-PLLA fibers are significantly larger than the corresponding values obtained for PLLA fiber. This result is consistent with the higher polarizability of the MWCNT-PLLA composites. The measurement methods presented are general, and can be applied to determine the mechanical and electrical properties of other polymers and polymer nanocomposites.

  9. Separation and Enrichment of Gold in Water, Geological and Environmental Samples by Solid Phase Extraction on Multiwalled Carbon Nanotubes Prior to its Determination by Flame Atomic Absorption Spectrometry.

    PubMed

    Duran, Ali; Tuzen, Mustafa; Soylak, Mustafa

    2015-01-01

    This study proposes the application of multi-walled carbon nanotubes as a solid sorbent for the preconcentration of gold prior to its flame atomic absorption spectrometry determination. Extraction was achieved by using a glass column (15.0 cm in length and 1.0 cm in diameter). Quantitative recoveries were obtained in the pH range of 2.5-4.0; the elution step was carried out with 5.0 ml of 1.0 mol/L HNO3 in acetone. In the ligand-free study, variables such as pH, eluent type, sample volume, flow rates, and matrix effect were examined for the optimum recovery of gold ions. The gold ions were able to be pre-concentrated by a factor of 150 and their LOD was determined to be 1.71 μg/L. In order to evaluate the accuracy of the developed method, addition-recovery tests were applied for the tap water, mineral water, and sea water samples. Gold recovery studies were implemented using a wet digestion technique for mine and soil samples taken from various media, and this method was also applied for anodic slime samples taken from the factories located in the Kayseri Industrial Zone of Turkey. PMID:26651587

  10. 30 CFR 56.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Clearance on adjacent tracks. 56.9103 Section..., Hauling, and Dumping Traffic Safety § 56.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  11. 30 CFR 57.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Clearance on adjacent tracks. 57.9103 Section..., Hauling, and Dumping Traffic Safety § 57.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  12. 30 CFR 56.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Clearance on adjacent tracks. 56.9103 Section..., Hauling, and Dumping Traffic Safety § 56.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  13. 30 CFR 57.9103 - Clearance on adjacent tracks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Clearance on adjacent tracks. 57.9103 Section..., Hauling, and Dumping Traffic Safety § 57.9103 Clearance on adjacent tracks. Railcars shall not be left on side tracks unless clearance is provided for traffic on adjacent tracks....

  14. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  15. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  16. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  17. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  18. 33 CFR 80.1395 - Puget Sound and adjacent waters.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake...

  19. Entanglement of remote atomic qubits.

    PubMed

    Matsukevich, D N; Chanelière, T; Jenkins, S D; Lan, S-Y; Kennedy, T A B; Kuzmich, A

    2006-01-27

    We report observations of entanglement of two remote atomic qubits, achieved by generating an entangled state of an atomic qubit and a single photon at site , transmitting the photon to site in an adjacent laboratory through an optical fiber, and converting the photon into an atomic qubit. Entanglement of the two remote atomic qubits is inferred by performing, locally, quantum state transfer of each of the atomic qubits onto a photonic qubit and subsequent measurement of polarization correlations in violation of the Bell inequality [EQUATION: SEE TEXT]. We experimentally determine [EQUATION: SEE TEXT]. Entanglement of two remote atomic qubits, each qubit consisting of two independent spin wave excitations, and reversible, coherent transfer of entanglement between matter and light represent important advances in quantum information science. PMID:16486672

  20. Electrocatalytic oxygen evolution at surface-oxidized multiwall carbon nanotubes.

    PubMed

    Lu, Xunyu; Yim, Wai-Leung; Suryanto, Bryan H R; Zhao, Chuan

    2015-03-01

    Large-scale storage of renewable energy in the form of hydrogen (H2) fuel via electrolytic water splitting requires the development of water oxidation catalysts that are efficient and abundant. Carbon-based nanomaterials such as carbon nanotubes have attracted significant applications for use as substrates for anchoring metal-based nanoparticles. We show that, upon mild surface oxidation, hydrothermal annealing and electrochemical activation, multiwall carbon nanotubes (MWCNTs) themselves are effective water oxidation catalysts, which can initiate the oxygen evolution reaction (OER) at overpotentials of 0.3 V in alkaline media. Oxygen-containing functional groups such as ketonic C═O generated on the outer wall of MWCNTs are found to play crucial roles in catalyzing OER by altering the electronic structures of the adjacent carbon atoms and facilitates the adsorption of OER intermediates. The well-preserved microscopic structures and highly conductive inner walls of MWCNTs enable efficient transport of the electrons generated during OER. PMID:25658670

  1. Interaction between adjacent lightning discharges in clouds

    NASA Astrophysics Data System (ADS)

    Wang, Yanhui; Zhang, Guangshu; Zhang, Tong; Li, Yajun; Wu, Bin; Zhang, Tinglong

    2013-07-01

    Using a 3D lightning radiation source locating system (LLS), three pairs of associated lightning discharges (two or more adjacent lightning discharges following an arbitrary rule that their space-gap was less than 10 km and their time-gap was less than 800 ms) were observed, and the interaction between associated lightning discharges was analyzed. All these three pairs of associated lightning discharges were found to involve three or more charge regions (the ground was considered as a special charge region). Moreover, at least one charge region involved two lightning discharges per pair of associated lightning discharges. Identified from electric field changes, the subsequent lightning discharges were suppressed by the prior lightning discharges. However, it is possible that the prior lightning discharge provided a remaining discharge channel to facilitate the subsequent lightning discharge. The third case provided evidence of this possibility. Together, the results suggested that, if the charges in the main negative charge region can be consumed using artificial lightning above the main negative charge regions, lightning accidents on the ground could be greatly reduced, on the condition that the height of the main negative charge region and the charge intensity of the lower positive charge region are suitable.

  2. Atomic and molecular supernovae

    SciTech Connect

    Liu, W.

    1997-12-01

    Atomic and molecular physics of supernovae is discussed with an emphasis on the importance of detailed treatments of the critical atomic and molecular processes with the best available atomic and molecular data. The observations of molecules in SN 1987A are interpreted through a combination of spectral and chemical modelings, leading to strong constraints on the mixing and nucleosynthesis of the supernova. The non-equilibrium chemistry is used to argue that carbon dust can form in the oxygen-rich clumps where the efficient molecular cooling makes the nucleation of dust grains possible. For Type Ia supernovae, the analyses of their nebular spectra lead to strong constraints on the supernova explosion models.

  3. Atomic and molecular supernovae

    NASA Technical Reports Server (NTRS)

    Liu, Weihong

    1997-01-01

    Atomic and molecular physics of supernovae is discussed with an emphasis on the importance of detailed treatments of the critical atomic and molecular processes with the best available atomic and molecular data. The observations of molecules in SN 1987A are interpreted through a combination of spectral and chemical modelings, leading to strong constraints on the mixing and nucleosynthesis of the supernova. The non-equilibrium chemistry is used to argue that carbon dust can form in the oxygen-rich clumps where the efficient molecular cooling makes the nucleation of dust grains possible. For Type Ia supernovae, the analyses of their nebular spectra lead to strong constraints on the supernova explosion models.

  4. Application of multiwall carbon nanotubes impregnated with 5-dodecylsalicylaldoxime for on-line copper preconcentration and determination in water samples by flame atomic absorption spectrometry.

    PubMed

    Tobiasz, Anna; Walas, Stanisław; Soto Hernández, Arlene; Mrowiec, Halina

    2012-07-15

    The paper presents application of multiwall carbon nanotubes (MWCNTs) modified with 5-dodecylsalicylaldoxime to copper(II) flow-injection on-line preconcentration and flame atomic absorption spectrometric (FAAS) determination. Two new sorbents were obtained by impregnation of MWCNTs with Cu(II)-LIX 622(®) complex, however in the first case modification was preceded by carbon wall activation via oxidization (Cu-LIX-CNT-A sorbent), and in the second one no surface activation was performed (Cu-LIX-CNT sorbent). It was found that effective leaching of initially introduced copper and Cu(II) retained in preconcentration process could be realized with the use 7% and 5% (v/v) nitric acid, for particular sorbents. Testing the influence of loading solution pH and rate of loading on sorption it was found out that optimal range of loading solution pH was about 4.5-6.3 for activated and 6.15-6.25 for non-activated CNT. Investigation of sorption kinetics showed that the process can be described by pseudo-second order reaction model. Sorption equilibrium conditions (90% sorption) for LIX-CNT-A and LIX-CNT were obtained after 8-15min, respectively and maximum sorption capacity for the new sorbents amounted to 18.1mgg(-1) and 31.6mgg(-1), respectively. For the examined sorbents enrichment factors increased with extension of loading time up to 180s: linearly for activated and non-linearly for non-activated MWCNTs. Influence of potential interferents such as Cd(II), Zn(II), Fe(III), Mg(II) and Ca(II) ions on copper(II) sorption on the new CNT materials was examined individually and with the use of 2(5-2) factorial design. The study revealed significant interference from iron, magnesium and calcium ions at relatively high concentrations. Applicability of the proposed sorbents was tested for Cu(II) determination in various kinds of water samples and the results were compared with those obtained with the use of ICP MS as a reference technique. Copper(II) determination in two certified

  5. Theoretical model for electrophilic oxygen atom insertion into hydrocarbons

    SciTech Connect

    Bach, R.D.; Su, M.D. ); Andres, J.L. Wayne State Univ., Detroit, MI ); McDouall, J.J.W. )

    1993-06-30

    A theoretical model suggesting the mechanistic pathway for the oxidation of saturated-alkanes to their corresponding alcohols and ketones is described. Water oxide (H[sub 2]O-O) is employed as a model singlet oxygen atom donor. Molecular orbital calculations with the 6-31G basis set at the MP2, QCISD, QCISD(T), CASSCF, and MRCI levels of theory suggest that oxygen insertion by water oxide occurs by the interaction of an electrophilic oxygen atom with a doubly occupied hydrocarbon fragment orbital. The electrophilic oxygen approaches the hydrocarbon along the axis of the atomic carbon p orbital comprising a [pi]-[sub CH(2)] or [pi]-[sub CHCH(3)] fragment orbital to form a carbon-oxygen [sigma] bond. A concerted hydrogen migration to an adjacent oxygen lone pair of electrons affords the alcohol insertion product in a stereoselective fashion with predictable stereochemistry. Subsequent oxidation of the alcohol to a ketone (or aldehyde) occurs in a similar fashion and has a lower activation barrier. The calculated (MP4/6-31G*//MP2/6-31G*) activation barriers for oxygen atom insertion into the C-H bonds of methane, ethane, propane, butane, isobutane, and methanol are 10.7, 8.2, 3.9, 4.8, 4.5, and 3.3 kcal/mol, respectively. We use ab initio molecular orbital calculations in support of a frontier MO theory that provides a unique rationale for both the stereospecificity and the stereoselectivity of insertion of electrophilic oxygen and related electrophiles into the carbon-hydrogen bond. 13 refs., 7 figs., 2 tabs.

  6. Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all-atom molecular dynamics simulations.

    PubMed

    Ou, Shu-Ching; Cui, Di; Wezowicz, Matthew; Taufer, Michela; Patel, Sandeep

    2015-06-15

    In this study, we examine the temperature dependence of free energetics of nanotube association using graphical processing unit-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion, and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intratube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and

  7. Free Energetics of Carbon Nanotube Association in Aqueous Inorganic NaI Salt Solutions: Temperature Effects using All-Atom Molecular Dynamics Simulations

    PubMed Central

    Ou, Shu-Ching; Cui, Di; Wezowicz, Matthew; Taufer, Michela; Patel, Sandeep

    2015-01-01

    In this study we examine the temperature dependence of free energetics of nanotube association by using GPU-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intra-tube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation also shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and interpretations of

  8. Activated carbon-modified knotted reactor coupled to electrothermal atomic absorption spectrometry for sensitive determination of arsenic species in medicinal herbs and tea infusions

    NASA Astrophysics Data System (ADS)

    Grijalba, Alexander Castro; Martinis, Estefanía M.; Lascalea, Gustavo E.; Wuilloud, Rodolfo G.

    2015-01-01

    A flow injection system based on a modified polytetrafluoroethylene (PTFE) knotted reactor (KR) was developed for arsenite [As(III)] and arsenate [As(V)] species preconcentration and determination by electrothermal atomic absorption spectrometry (ETAAS). Activated carbon (AC) was immobilized on the inner walls of a PTFE KR by a thermal treatment. A significant increase in analyte retention was obtained with the AC-modified KR (100%) as compared to the regular PTFE KR (25%). The preconcentration method involved the on-line formation of As(III)-ammonium pyrrolidinedithiocarbamate (As-APDC) complex, followed by its adsorption onto the inner walls of the AC-modified KR. After analyte retention, the complex was eluted with acetone directly into the graphite furnace of ETAAS. The parameters affecting the flow injection system were evaluated with a full central composite face centered design with three center points. Under optimum conditions, a preconcentration factor of 200 was obtained with 10 ml of sample. The detection limit was 4 ng L- 1 and the relative standard deviation (RSD) for six replicate measurements at 0.2 μg L- 1 of As were 4.3% and 4.7% for As(III) and As(V), respectively. The developed methodology was highly selective towards As(III), while As(V), monomethylarsonic acid [MMA(V)] and dimethylarsinic [DMA(V)] were not retained in the AC-modified KR. The proposed method was successfully applied for As speciation analysis in infusions originated from medicinal herbs and tea.

  9. Synthesis of ZnTe dendrites on multi-walled carbon nanotubes/polyimide nanocomposite membrane by electrochemical atomic layer deposition and photoelectrical property research

    SciTech Connect

    Jiang, Yimin; Kou, Huanhuan; Li, Jiajia; Yu, Shengjiao; Du, Yongling; Ye, Weichun; Wang, Chunming

    2012-10-15

    We report on the electrochemical atomic layer deposition (EC-ALD) of ZnTe dendrites on the carboxyl-functionalized multi-walled carbon nanotubes/polyimide (COOH-MWCNTs/PI) membrane. Electrochemical characteristics were studied by cyclic voltammetry (CV) and the deposition of ZnTe dendrites was completed using amperometric method (I-t). The prepared ZnTe dendrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The growth mechanism of ZnTe dendrites was elucidated to give a deep understanding of crystal growth. The concentration of reagents and deposition cycle had a significant effect on the morphology and structure of deposits. UV-vis transmission study indicated a direct band gap of 2.26 eV. Photoelectrical measurement confirmed the p-type conductivity of ZnTe dendrites, which indicated that the dendritic ZnTe crystals may have potential practical application in optoelectronic devices. - Graphical abstract: Representative SEM images of ZnTe dendrites. (a) Panorama of ZnTe dendrites; (b) a single dendrite. The regular branches appeared like leaves and showed a parallel arrangement layer upon layer between each other. Highlights: Black-Right-Pointing-Pointer ZnTe dendrites were successfully synthesized on CNTs/PI membrane by electrodeposition. Black-Right-Pointing-Pointer The growth mechanism of ZnTe dendritic structures was investigated in detail. Black-Right-Pointing-Pointer The concentration and deposition cycle greatly affected the morphology of ZnTe. Black-Right-Pointing-Pointer OCP and I-t studies showed that ZnTe can be beneficial to photoelectric applications.

  10. L-tyrosine immobilized on multiwalled carbon nanotubes: a new substrate for thallium separation and speciation using stabilized temperature platform furnace-electrothermal atomic absorption spectrometry.

    PubMed

    Pacheco, Pablo H; Gil, Raúl A; Smichowski, Patricia; Polla, Griselda; Martinez, Luis D

    2009-12-10

    An approach for the separation and determination of inorganic thallium species is described. A new sorbent, L-tyrosine-carbon nanotubes (L-tyr-CNTs), was used and applied to the analysis of tap water samples. At pH 5.0, L-tyr was selective only towards Tl(III), while total thallium was determined directly by stabilized temperature platform furnace-electrothermal atomic absorption spectrometry (STPF-ETAAS). The Tl(III) specie, which was retained by L-tyrosine, was quantitatively eluted from the column with 10% of nitric acid. An on-line breakthrough curve was used to determine the column capacity, which resulted to be 9.00 micromol of Tl(III) g(-1) of L-tyr-CNTs with a molar ratio of 0.14 (moles of Tl bound to moles of L-tyr at pH 5). Transient peak areas revealed that Tl stripping from the column occurred instantaneously. Effects of sample flow rate, concentration and flow rate of the eluent, and interfering ions on the recovery of the analyte were systematically investigated. The detection limit for the determination of total thallium (3sigma) by STPF-ETAAS was 150 ng L(-1). The detection limit (3sigma) for Tl(III) employing the separation system was 3 ng L(-1), with an enrichment factor of 40. The precision of the method expressed as the relative standard deviation (RSD) resulted to be 3.4%. The proposed method was applied to the speciation and determination of inorganic thallium in tap water samples. The found concentrations were in the range of 0.88-0.91 microg L(-1) of Tl(III), and 3.69-3.91 microg L(-1) of total thallium. PMID:19932812

  11. Hydrocarbon provinces and productive trends in Libya and adjacent areas

    SciTech Connect

    Missallati, A.A. Ltd., Tripoli )

    1988-08-01

    According to the age of major reservoirs, hydrocarbon occurrences in Libya and adjacent areas can be grouped into six major systems which, according to their geographic locations, can be classified into two major hydrocarbon provinces: (1) Sirte-Pelagian basins province, with major reservoirs ranging from middle-late Mesozoic to early Tertiary, and (2) Murzog-Ghadames basins province, with major reservoirs ranging from early Paleozoic to early Mesozoic. In the Sirte-Pelagian basins province, hydrocarbons have been trapped in structural highs or in stratigraphic wedge-out against structural highs and in carbonate buildups. Here, hydrocarbon generation is characterized by the combined effect of abundant structural relief and reservoir development in the same hydrocarbon systems of the same age, providing an excellent example of hydrocarbon traps in sedimentary basins that have undergone extensive tensional fracturing in a shallow marine environment. In the Murzog-Ghadames basins province, hydrocarbons have been trapped mainly in structural highs controlled by paleostructural trends as basement arches which acted as focal points for oil migration and accumulation.

  12. Liquid atomization

    NASA Astrophysics Data System (ADS)

    Bayvel, L.; Orzechowski, Z.

    The present text defines the physical processes of liquid atomization, the primary types of atomizers and their design, and ways of measuring spray characteristics; it also presents experimental investigation results on atomizers and illustrative applications for them. Attention is given to the macrostructural and microstructural parameters of atomized liquids; swirl, pneumatic, and rotary atomizers; and optical drop sizing methods, with emphasis on nonintrusive optical methods.

  13. Results of apparent atomic oxygen reactions on Ag, C, and Os exposed during the Shuttle STS-4 orbits

    NASA Technical Reports Server (NTRS)

    Peters, P. N.; Linton, R. C.; Miller, E. R.

    1983-01-01

    Films selected for anticipated reaction with atomic oxygen, namely carbon, silver, and osmium, were exposed during the Shuttle STS-4 mission. A silver film within 5 nm of 225 nm thick was converted to a transparent blue-green interference film within 5 nm of 355 nm thick. Both carbon and osmium films 10-30 nm thick apparently formed volatile oxides and disappeared, except where well shielded. A calculated total of approximately 7 x 10 to the 19th oxygen atoms per sq cm struck the surfaces, which could have removed on the order of 3 microns of material if only 10 percent reacted. The absence of apparent effects on adjacent thin and thick gold films is offered as evidence that sputtering is not responsible.

  14. Ius Chasma Tributary Valleys and Adjacent Plains

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image covers valley tributaries of Ius Chasma, as well as the plains adjacent to the valleys. Ius Chasma is one of several canyons that make up the Valles Marineris canyon system. Valles Marineris likely formed by extension associated with the growth of the large volcanoes and topographic high of Tharsis to the northwest. As the ground was pulled apart, large and deep gaps resulted in the valleys seen in the top and bottom of this HiRISE image. Ice that was once in the ground could have also melted to create additional removal of material in the formation of the valleys. HiRISE is able to see the rocks along the walls of both these valleys and also impact craters in the image. Rock layers that appear lower down in elevation appear rougher and are shedding boulders. Near the top of the walls and also seen in patches along the smooth plains are brighter layers. These brighter layers are not shedding boulders so they must represent a different kind of rock formed in a different kind of environment than those further down the walls. Because they are highest in elevation, the bright layers are youngest in age. HiRISE is able to see dozens of the bright layers, which are perhaps only a meter in thickness. Darker sand dunes and ripples cover most of the plains and fill the floors of impact craters.

    Image PSP_001351_1715 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 9, 2006. The complete image is centered at -8.3 degrees latitude, 275.4 degrees East longitude. The range to the target site was 254.3 km (158.9 miles). At this distance the image scale ranges from 25.4 cm/pixel (with 1 x 1 binning) to 101.8 cm/pixel (with 4 x 4 binning). The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 3:32 PM and the scene is illuminated from the west with a solar incidence angle of 59 degrees, thus the sun was about

  15. A molecular dynamics study of the effect of thermal boundary conductance on thermal transport of ideal crystal of n-alkanes with different number of carbon atoms

    NASA Astrophysics Data System (ADS)

    Rastgarkafshgarkolaei, Rouzbeh; Zeng, Yi; Khodadadi, J. M.

    2016-05-01

    Phase change materials such as n-alkanes that exhibit desirable characteristics such as high latent heat, chemical stability, and negligible supercooling are widely used in thermal energy storage applications. However, n-alkanes have the drawback of low thermal conductivity values. The low thermal conductivity of n-alkanes is linked to formation of randomly oriented nano-domains of molecules in their solid structure that is responsible for excessive phonon scattering at the grain boundaries. Thus, understanding the thermal boundary conductance at the grain boundaries can be crucial for improving the effectiveness of thermal storage systems. The concept of the ideal crystal is proposed in this paper, which describes a simplified model such that all the nano-domains of long-chain n-alkanes are artificially aligned perfectly in one direction. In order to study thermal transport of the ideal crystal of long-chain n-alkanes, four (4) systems (C20H42, C24H50, C26H54, and C30H62) are investigated by the molecular dynamics simulations. Thermal boundary conductance between the layers of ideal crystals is determined using both non-equilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) simulations. Both NEMD and EMD simulations exhibit no significant change in thermal conductance with the molecular length. However, the values obtained from the EMD simulations are less than the values from NEMD simulations with the ratio being nearly three (3) in most cases. This difference is due to the nature of EMD simulations where all the phonons are assumed to be in equilibrium at the interface. Thermal conductivity of the n-alkanes in three structures including liquid, solid, and ideal crystal is investigated utilizing NEMD simulations. Our results exhibit a very slight rise in thermal conductivity values as the number of carbon atoms of the chain increases. The key understanding is that thermal transport can be significantly altered by how the molecules and the

  16. View of north side from exterior stairs of adjacent building, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of north side from exterior stairs of adjacent building, bottom cut off by fringed buildings, view facing south-southwest - U.S. Naval Base, Pearl Harbor, Industrial X-Ray Building, Off Sixth Street, adjacent to and south of Facility No. 11, Pearl City, Honolulu County, HI

  17. Learning Non-Adjacent Regularities at Age 0 ; 7

    ERIC Educational Resources Information Center

    Gervain, Judit; Werker, Janet F.

    2013-01-01

    One important mechanism suggested to underlie the acquisition of grammar is rule learning. Indeed, infants aged 0 ; 7 are able to learn rules based on simple identity relations (adjacent repetitions, ABB: "wo fe fe" and non-adjacent repetitions, ABA: "wo fe wo", respectively; Marcus et al., 1999). One unexplored issue is…

  18. Delayed Acquisition of Non-Adjacent Vocalic Distributional Regularities

    ERIC Educational Resources Information Center

    Gonzalez-Gomez, Nayeli; Nazzi, Thierry

    2016-01-01

    The ability to compute non-adjacent regularities is key in the acquisition of a new language. In the domain of phonology/phonotactics, sensitivity to non-adjacent regularities between consonants has been found to appear between 7 and 10 months. The present study focuses on the emergence of a posterior-anterior (PA) bias, a regularity involving two…

  19. Atomic-absorption determination of mercury in geological materials by flame and carbon-rod atomisation after solvent extraction and using co-extracted silver as a matrix modifier

    USGS Publications Warehouse

    Sanzolone, R.F.; Chao, T.T.

    1983-01-01

    Based on modifications and expansion of the original Tindall's solvent extraction flame atomic-absorption procedure, an atomic-absorption spectrophotometric method has been developed for the determination of mercury in geological materials. The sample is digested with nitric and hydrochloric acids in a boiling water-bath. The solution is made ammoniacal and potassium iodide and silver nitrate are added. The mercury is extracted into isobutyl methyl ketone as the tetraiodomercurate(ll). Added silver is co-extracted with mercury and serves as a matrix modifier in the carbon-rod atomiser. The mercury in the isobutyl methyl ketone extract may be determined by either the flame- or the carbon-rod atomisation method, depending on the concentration level. The limits of determination are 0.05-10 p.p.m. of mercury for the carbon-rod atomisation and 1 -200 p.p.m. of mercury for the flame atomisation. Mercury values for reference samples obtained by replicate analyses are in good agreement with those reported by other workers, with relative standard deviations ranging from 2.3 to 0.9%. Recoveries of mercury spiked at two levels were 93-106%. Major and trace elements commonly found in geological materials do not interfere.

  20. Atomic polarizabilities

    SciTech Connect

    Safronova, M. S.; Mitroy, J.; Clark, Charles W.; Kozlov, M. G.

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  1. Thermoelastic response of thin metal films and their adjacent materials

    SciTech Connect

    Kang, S.; Yoon, Y.; Kim, J.; Kim, W.

    2013-01-14

    A pulsed laser beam applied to a thin metal film is capable of launching an acoustic wave due to thermal expansion. Heat transfer from the thin metal film to adjacent materials can also induce thermal expansion; thus, the properties of these adjacent materials (as well as the thin metal film) should be considered for a complete description of the thermoelastic response. Here, we show that adjacent materials with a small specific heat and large thermal expansion coefficient can generate an enhanced acoustic wave and we demonstrate a three-fold increase in the peak pressure of the generated acoustic wave on substitution of parylene for polydimethylsiloxane.

  2. 73. PASSAGE ADJACENT TO ROOM 232, EAST WING, SECOND FLOOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    73. PASSAGE ADJACENT TO ROOM 232, EAST WING, SECOND FLOOR, LOOKING WEST BY NORTHWEST, SHOWING EASTERNMOST ARCH OF FORMER GREAT HALL NORTH ARCADE - Smithsonian Institution Building, 1000 Jefferson Drive, between Ninth & Twelfth Streets, Southwest, Washington, District of Columbia, DC

  3. View of viaduct, looking SE from roof of adjacent parking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of viaduct, looking SE from roof of adjacent parking garage. - Mulberry Street Viaduct, Spanning Paxton Creek & Cameron Street (State Route 230) at Mulberry Street (State Route 3012), Harrisburg, Dauphin County, PA

  4. Cement Leakage into Adjacent Vertebral Body Following Percutaneous Vertebroplasty

    PubMed Central

    Park, Jae Hoo; Kim, Hyeun Sung

    2016-01-01

    Percutaneous vertebroplasty (PV) is a minimally invasive procedure for osteoporotic vertebral compression fractures that fail to respond to conventional conservative treatment. It significantly improves intolerable back pain within hours, and has a low complication rate. Although rare, PV is not free of complications, most of which are directly related to cement leakage. Because of its association with new adjacent fracture, the importance of cement leakage into the adjacent disc space is paramount. Here, we report an interesting case of cement leakage into the adjacent upper vertebral body as well as disc space following PV. To the best of our knowledge, there has been no report of cement leakage into the adjacent vertebral body following PV. This rare case is presented along with a review of the literature. PMID:27437018

  5. 1. HEBRONVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR. HEBRONVILLE, BRISTOL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. HEBRONVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR. HEBRONVILLE, BRISTOL CO., MA. Sec. 4116, MP 193.75. - Northeast Railroad Corridor, Amtrak Route between RI/MA State Line & South Station, Boston, Suffolk County, MA

  6. 3. DODGEVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR DODGEVILLE, BRISTOL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. DODGEVILLE MILL COMPLEX ADJACENT TO NORTHEAST CORRIDOR DODGEVILLE, BRISTOL CO., MA. Sec. 4116, MP 195.55. - Northeast Railroad Corridor, Amtrak Route between RI/MA State Line & South Station, Boston, Suffolk County, MA

  7. 33. HISTORIC PLAQUE MARKING WHERE JOHNSTON DIED, ADJACENT TO PATHWAY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    33. HISTORIC PLAQUE MARKING WHERE JOHNSTON DIED, ADJACENT TO PATHWAY WITH CONCRETE CULVERT LEADING NORTH OUT OF RAVINE TOWARD JOHNSTON MEMORIAL SITE. VIEW NW. - Shiloh National Military Park Tour Roads, Shiloh, Hardin County, TN

  8. Lock 4 View east of lock wall and adjacent ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Lock 4 - View east of lock wall and adjacent roadway built atop tow path. The gate pocket can be seen at center. - Savannah & Ogeechee Barge Canal, Between Ogeechee & Savannah Rivers, Savannah, Chatham County, GA

  9. 1. Ninth Street (west) facade. Adjacent on the north is ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Ninth Street (west) facade. Adjacent on the north is the 9th Street facade of 816 E Street. Both buildings were originally one property. - Riley Building, Rendezvous Adult Magazines & Films, 437 Ninth Street, Northwest, Washington, District of Columbia, DC

  10. 2. THREEQUARTER VIEW FROM ADJACENT ACCESS ROAD SHOWING THREE SPANS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. THREE-QUARTER VIEW FROM ADJACENT ACCESS ROAD SHOWING THREE SPANS AND NORTHWEST APPROACH SPANS, LOOKING SOUTHEAST - Red River Bridge, Spanning Red River at U.S. Highway 82, Garland, Miller County, AR

  11. 1. VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD HOMES, LOOKING SOUTH. GARAGE TO EXTREME LEFT, BUILDING 1 TO EXTREME RIGHT. - Techwood Homes (Public Housing), Bounded by North Avenue, Parker Street, William Street & Lovejoy Street, Atlanta, Fulton County, GA

  12. 3. View of north side of house facing from adjacent ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. View of north side of house facing from adjacent vacant property. Original wood lap siding and trim is covered by aluminum siding. Recessed side porch is in middle. - 645 South Eighteenth Street (House), Louisville, Jefferson County, KY

  13. 7. August, 1970 9 ORANGE STREET, ADJACENT TO UNITARIAN CHURCH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. August, 1970 9 ORANGE STREET, ADJACENT TO UNITARIAN CHURCH (NOT IN STUDY AREA) - Orange & Union Streets Neighborhood Study, 8-31 Orange Street, 9-21 Union Street & Stone Alley, Nantucket, Nantucket County, MA

  14. OBLIQUE OF SOUTHWEST END AND SOUTHEAST SIDE, WITH ADJACENT FACILITY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OBLIQUE OF SOUTHWEST END AND SOUTHEAST SIDE, WITH ADJACENT FACILITY 391 IN THE FOREGROUND. - U.S. Naval Base, Pearl Harbor, Joint Intelligence Center, Makalapa Drive in Makalapa Administration Area, Pearl City, Honolulu County, HI

  15. Complications in exodontia--accidental dislodgment to adjacent anatomical areas.

    PubMed

    Grandini, S A; Barros, V M; Salata, L A; Rosa, A L; Soares, U N

    1993-01-01

    The authors report 4 cases of accidental dislodgement of teeth to adjacent anatomical areas during extraction. The causes and their prevention are discussed and solutions for the problem are suggested. PMID:8241759

  16. 6. Detail, vertical guides adjacent to east portal of Tunnel ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. Detail, vertical guides adjacent to east portal of Tunnel 28, view to southwest, 135mm lens with electronic flash fill. - Central Pacific Transcontinental Railroad, Tunnel No. 28, Milepost 134.75, Applegate, Placer County, CA

  17. VIEW OF CONSTRUCTION CAMP ROCK FEATURE WITH OVER, ADJACENT TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF CONSTRUCTION CAMP ROCK FEATURE WITH OVER, ADJACENT TO THE COLUMBIA SOUTHERN CANAL. LOOKING NORTHWEST - Tumalo Irrigation District, Tumalo Project, West of Deschutes River, Tumalo, Deschutes County, OR

  18. Pump house adjacent to the superintendent's house at the west ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Pump house adjacent to the superintendent's house at the west end of the complex near Highway 101. Detail of Holloshaft pump. View to the south. - Prairie Creek Fish Hatchery, Hwy. 101, Orick, Humboldt County, CA

  19. VIEW OF NORTHERN AND EASTERN SIDES FROM PARKING LOT ADJACENT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF NORTHERN AND EASTERN SIDES FROM PARKING LOT ADJACENT TO BUILDING 199 (POLICE STATION) - U.S. Naval Base, Pearl Harbor, Post Office, Avenue A near Eleventh Avenue, Pearl City, Honolulu County, HI

  20. 24. INTERIOR VIEW, WILLIAM GRAY AT SIZING GUAGE ADJACENT TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    24. INTERIOR VIEW, WILLIAM GRAY AT SIZING GUAGE ADJACENT TO BRADLEY HAMMER; NOTE THIS IS THE SAME TOOL AS BEING FORGED ABOVE - Warwood Tool Company, Foot of Nineteenth Street, Wheeling, Ohio County, WV

  1. Detail exterior view looking north showing piping system adjacent to ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail exterior view looking north showing piping system adjacent to engine house. Gas cooling system is on far right. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV

  2. VIEW OF LAMP FIXTURE (EXTERIOR) ADJACENT TO ENTRANCE AT SOUTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF LAMP FIXTURE (EXTERIOR) ADJACENT TO ENTRANCE AT SOUTHWEST CORNER OF BUILDING 23, FACING NORTH - Roosevelt Base, Auditorium-Gymnasium, West Virginia Street between Richardson & Reeves Avenues, Long Beach, Los Angeles County, CA

  3. 14. Charles Acey Cobb standing adjacent to the fish screen ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Charles Acey Cobb standing adjacent to the fish screen he designed and installed in the Congdon Canal, facing southeast. Photo dates ca. late 1920's. - Congdon Canal, Fish Screen, Naches River, Yakima, Yakima County, WA

  4. 52. EASTSIDE PLANT: GENERAL VIEW OF GOVERNOR ADJACENT TO GENERATOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. EASTSIDE PLANT: GENERAL VIEW OF GOVERNOR ADJACENT TO GENERATOR - American Falls Water, Power & Light Company, Island Power Plant, Snake River, below American Falls Dam, American Falls, Power County, ID

  5. Interior building details of Building A, dungeon cell adjacent to ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Interior building details of Building A, dungeon cell adjacent to northwest cell: granite and brick threshold, poured concrete floors, plastered finished walls, vaulted veiling; northwesterly view - San Quentin State Prison, Building 22, Point San Quentin, San Quentin, Marin County, CA

  6. VIEW OF CONCRETE CHANNEL ADJACENT TO TUMALO FEED CANAL INTAKE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF CONCRETE CHANNEL ADJACENT TO TUMALO FEED CANAL INTAKE STRUCTURE (DOWNSTREAM SIDE). LOOKING EAST/NORTHEAST - Tumalo Irrigation District, Tumalo Project, West of Deschutes River, Tumalo, Deschutes County, OR

  7. A Comparison of Atomic Oxygen Erosion Yields of Carbon and Selected Polymers Exposed in Ground Based Facilities and in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Rutledge, Sharon K.; Banks, Bruce A.; Cales, Michael

    1994-01-01

    A comparison of the relative erosion yields (volume of material removed per oxygen atom arriving) for FEP Teflon, polyethylene, and pyrolytic graphite with respect to Kapton HN was performed in an atomic oxygen directed beam system, in a plasma asher, and in space on the EOIM-III (Evaluation of Oxygen Interaction with Materials-III) flight experiment. This comparison was performed to determine the sensitivity of material reaction to atomic oxygen flux, atomic oxygen fluence, and vacuum ultraviolet radiation for enabling accurate estimates of durability in ground based facilities. The relative erosion yield of pyrolytic graphite was found not to be sensitive to these factors, that for FEP was sensitive slightly to fluence and possibly ions, and that for polyethylene was found to be partially VUV and flux sensitive but more sensitive to an unknown factor. Results indicate that the ability to use these facilities for material relative durability prediction is great as long as the sensitivity of particular materials to conditions such as VUV, and atomic oxygen flux and fluence are taken into account. When testing materials of a particular group such as teflon, it may be best to use a witness sample made of a similar material that has some available space data on it. This would enable one to predict an equivalent exposure in the ground based facility.

  8. Adjacent Segment Disease Perspective and Review of the Literature

    PubMed Central

    Saavedra-Pozo, Fanor M.; Deusdara, Renato A. M.; Benzel, Edward C.

    2014-01-01

    Background Adjacent segment disease has become a common topic in spine surgery circles because of the significant increase in fusion surgery in recent years and the development of motion preservation technologies that theoretically should lead to a decrease in this pathology. The purpose of this review is to organize the evidence available in the current literature on this subject. Methods For this literature review, a search was conducted in PubMed with the following keywords: adjacent segment degeneration and disease. Selection, review, and analysis of the literature were completed according to level of evidence. Results The PubMed search identified 850 articles, from which 41 articles were selected and reviewed. The incidence of adjacent segment disease in the cervical spine is close to 3% without a significant statistical difference between surgical techniques (fusion vs arthroplasty). Authors report the incidence of adjacent segment disease in the lumbar spine to range from 2% to 14%. Damage to the posterior ligamentous complex and sagittal imbalances are important risk factors for both degeneration and disease. Conclusion Insufficient evidence exists at this point to support the idea that total disc arthroplasty is superior to fusion procedures in minimizing the incidence of adjacent segment disease. The etiology is most likely multifactorial but it is becoming abundantly clear that adjacent segment disease is not caused by motion segment fusion alone. Fusion plus the presence of abnormal end-fusion alignment appears to be a major factor in creating end-fusion stresses that result in adjacent segment degeneration and subsequent disease. The data presented cast further doubt on previously established rationales for total disc arthroplasty, at least with regard to the effect of total disc arthroplasty on adjacent segment degeneration pathology. PMID:24688337

  9. Approximating the largest eigenvalue of network adjacency matrices

    NASA Astrophysics Data System (ADS)

    Restrepo, Juan G.; Ott, Edward; Hunt, Brian R.

    2007-11-01

    The largest eigenvalue of the adjacency matrix of a network plays an important role in several network processes (e.g., synchronization of oscillators, percolation on directed networks, and linear stability of equilibria of network coupled systems). In this paper we develop approximations to the largest eigenvalue of adjacency matrices and discuss the relationships between these approximations. Numerical experiments on simulated networks are used to test our results.

  10. Carbon fuel cells with carbon corrosion suppression

    DOEpatents

    Cooper, John F.

    2012-04-10

    An electrochemical cell apparatus that can operate as either a fuel cell or a battery includes a cathode compartment, an anode compartment operatively connected to the cathode compartment, and a carbon fuel cell section connected to the anode compartment and the cathode compartment. An effusion plate is operatively positioned adjacent the anode compartment or the cathode compartment. The effusion plate allows passage of carbon dioxide. Carbon dioxide exhaust channels are operatively positioned in the electrochemical cell to direct the carbon dioxide from the electrochemical cell.

  11. Atomic supersymmetry

    NASA Technical Reports Server (NTRS)

    Kostelecky, V. Alan

    1993-01-01

    Atomic supersymmetry is a quantum-mechanical supersymmetry connecting the properties of different atoms and ions. A short description of some established results in the subject are provided and a few recent developments are discussed including the extension to parabolic coordinates and the calculation of Stark maps using supersymmetry-based models.

  12. Atomic Calligraphy

    NASA Astrophysics Data System (ADS)

    Imboden, Matthias; Pardo, Flavio; Bolle, Cristian; Han, Han; Tareen, Ammar; Chang, Jackson; Christopher, Jason; Corman, Benjamin; Bishop, David

    2013-03-01

    Here we present a MEMS based method to fabricate devices with a small number of atoms. In standard semiconductor fabrication, a large amount of material is deposited, after which etching removes what is not wanted. This technique breaks down for structures that approach the single atom limit, as it is inconceivable to etch away all but one atom. What is needed is a bottom up method with single or near single atom precision. We demonstrate a MEMS device that enables nanometer position controlled deposition of gold atoms. A digitally driven plate is swept as a flux of gold atoms passes through an aperture. Appling voltages on four comb capacitors connected to the central plate by tethers enable nanometer lateral precision in the xy plane over 15x15 sq. microns. Typical MEMS structures have manufacturing resolutions on the order of a micron. Using a FIB it is possible to mill apertures as small as 10 nm in diameter. Assuming a low incident atomic flux, as well as an integrated MEMS based shutter with microsecond response time, it becomes possible to deposit single atoms. Due to their small size and low power consumption, such nano-printers can be mounted directly in a cryogenic system at ultrahigh vacuum to deposit clean quench condensed metallic structures.

  13. Liquid atomization

    SciTech Connect

    Walzel, P. )

    1993-01-01

    A systematic review of different liquid atomizers is presented, accompanied by a discussion of various mechanisms of droplet formation in a gas atmosphere as a function of the liquid flow-regime and the geometry of the atomizer. Equations are presented for the calculation of the mean droplet-diameter. In many applications, details of the droplet size distribution are, also, important, e.g., approximate values of the breadth of the droplet formation are given. The efficiency of utilization of mechanical energy in droplet formation is indicated for the different types of atomizers. Atomization is used, in particular, for the following purposes: (1) atomization of fuels; (2) making granular products; (3) carrying out mass-transfer operations; and (4) coating of surfaces.

  14. A full-potential linearized augmented plane wave (FP-LAPW) study of atomic carbon, nitrogen, and oxygen chemisorption on the (1 0 0) surface of δ-Pu

    NASA Astrophysics Data System (ADS)

    Atta-Fynn, Raymond; Ray, Asok K.

    2007-04-01

    Fully relativistic full-potential density functional calculations with an all-electron linearized augmented plane wave plus local orbitals method have been performed to investigate the electronic and geometric structures of atomic carbon, nitrogen, and oxygen chemisorption on the (1 0 0) surface of δ-Pu. For all chemisorption processes, the center adsorption site is found to be the most preferred site with chemisorption energies of 7.964, 7.665, and 8.335 eV for the C, N, and O adatoms, respectively. The respective optimized distances of the C, N, and O adatoms from the surface were found to be 0.26, 0.35, and 0.48 Å. The work functions and the net magnet moments, respectively, increased and decreased in all cases compared with the bare δ-Pu (1 0 0) surface. In particular, the work function shift is largest for the least preferred top site and lowest for the most preferred center site. A detailed analysis of partial charges inside the atomic spheres, charge density distributions, and the local density of states have been performed to investigate the nature of the interaction between the surface Pu atoms and the adatoms.

  15. Se atoms and Se6 molecules as guests in Se-carbons - prepared by reduction of a SeCl4-graphite precursor

    NASA Astrophysics Data System (ADS)

    Walter, J.; Shioyama, H.

    2000-01-01

    A SeCl4 -graphite intercalation compound precursor was reduced by a solution of lithium diphenylide in tetrahydrofuran at room temperature. X-ray diffraction measurements gave two distinguishable stages. One stage represented a Se-atom intercalation the other represented an intercalation of Se6 molecules. The in-plane diffraction patterns were estimated by selected-area electron diffraction, the existence of two different guest species (atoms and molecules) could be proved. The Se6 -molecule phase shows an incommensurate lattice with regard to the host lattice, but they are in the same orientation. The lattice parameter of intercalated Se6 is a Se 6-guest = 1158+/-36 pm, c Se 6-guest = 483+/-38 pm, which fits with the lattice parameter of non-intercalated Se6 molecules. Se atom domains show a 2 × agraphite superlattice with respect to the host lattice, which is a commensurate superstructure. Raman scattering data showed the occurrence of an acceptor-type graphite intercalation compound. Three different types of spectra could be obtained, two kinds of spectra consists of doublets at 1588 cm-1 and 1608 cm-1 , with different intensity ratios. These two kinds of spectra are certainly attributed to Se-atom domains, with different stages. A third type of spectrum show bands at higher wavenumbers (1646 cm-1 and 1653 cm-1 ). These bands are probably correlated to Se6 -molecule domains. They represent maybe very early stages of nanoparticle formation.

  16. High temperature shock tube studies on the thermal decomposition of O3 and the reaction of dimethyl carbonate with O-atoms.

    PubMed

    Peukert, S L; Sivaramakrishnan, R; Michael, J V

    2013-05-01

    The shock tube technique was used to study the thermal decomposition of ozone, O3, with a view to using this as a thermal precursor of O-atoms at high temperatures. The formation of O-atoms was measured behind reflected shock waves by using atomic resonance absorption spectrometry (ARAS). The experiments span a T-range, 819 K ≤ T ≤ 1166 K, at pressures 0.13 bar ≤ P ≤ 0.6 bar. Unimolecular rate theory provides an excellent representation of the falloff characteristics from the present and literature data on ozone decomposition at high temperatures. The present decomposition study on ozone permits its usage as a thermal source for O-atoms allowing measurements for, O + CH3OC(O)OCH3 → OH + CH3OC(O)OCH2 [A]. Reflected shock tube experiments monitoring the formation and decay of O-atoms were performed on reaction A using mixtures of O3 and CH3OC(O)OCH3, (DMC), in Kr bath gas over the T-range, 862 K ≤ T ≤ 1167 K, and pressure range, 0.15 bar ≤ P ≤ 0.33 bar. A detailed model was used to fit the O-atom temporal profile to obtain experimental rate constants for reaction A. Rate constants from the present experiments for O + DMC can be represented by the Arrhenius expression: kA(T) = 2.70 × 10(-11) exp(-2725 K/T) cm(3) molecule(-1) s(-1) (862-1167 K). Transition state theory calculations employing CCSD(T)/cc-pv∞z//M06-2X/cc-pvtz energetics and molecular properties for reaction A are in good agreement with the experimental rate constants. The theoretical rate constants can be well represented (to within ±10%) over the 500-2000 K temperature range by: kA(T) = 1.87 × 10(-20)T(2.924) exp(-2338 K/T) cm(3) molecule(-1) s(-1). The present study represents the first experimental measurement and theoretical study on this bimolecular reaction which is of relevance to the high temperature oxidation of DMC. PMID:23510082

  17. High-energy X-ray powder diffraction and atomic-pair distribution-function studies of charged/discharged structures in carbon-hybridized Li2MnSiO4 nanoparticles as a cathode material for lithiumion batteries

    SciTech Connect

    Moriya, Maki; Miyahara, Masahiko; Hokazono, Mana; Sasaki, Hirokazu; Nemoto, Atsushi; Katayama, Shingo; Akimoto, Yuji; Hirano, Shin-ichi; Ren, Yang

    2014-10-01

    The stable cycling performance with a high discharge capacity of similar to 190 mAh g(-1) in a carbon-hybridized Li2MnSiO4 nanostructured powder has prompted an experimental investigation of the charged/discharged structures using synchrotron-based and laboratory-based X-rays and atomic-pair distributionfunction (PDF) analyses. A novel method of in-situ spray pyrolysis of a precursor solution with glucose as a carbon source enabled the successful synthesis of the carbon-hybridized Li2(M)nSiO(4) nanoparticles. The XRD patters of the discharged (lithiated) samples exhibit a long-range ordered structure characteristic of the (beta) Li2MnSiO4 crystalline phase (space group Pmn2(1)) which dissipates in the charged (delithiated) samples. However, upon discharging the long-range ordered structure recovers in each cycle. The disordered structure, according to the PDF analysis, is mainly due to local distortions of the MnO4 tetrahedra which show a mean Mn-O nearest neighbor distance shorter than that of the long-range ordered phase. These results corroborate the notion of the smaller Mn3+/Mn4+ ionic radii in the Li extracted phase versus the larger Mn2+ ionic radius in Li inserted phase. Thus Li extraction/insertion drives the fluctuation between the disordered and the long-range ordered structures. (C) 2014 Elsevier B.V. All rights reserved.

  18. Gene promoter methylation in colorectal cancer and healthy adjacent mucosa specimens

    PubMed Central

    Coppedè, Fabio; Migheli, Francesca; Lopomo, Angela; Failli, Alessandra; Legitimo, Annalisa; Consolini, Rita; Fontanini, Gabriella; Sensi, Elisa; Servadio, Adele; Seccia, Massimo; Zocco, Giuseppe; Chiarugi, Massimo; Spisni, Roberto; Migliore, Lucia

    2014-01-01

    We evaluated the promoter methylation levels of the APC, MGMT, hMLH1, RASSF1A and CDKN2A genes in 107 colorectal cancer (CRC) samples and 80 healthy adjacent tissues. We searched for correlation with both physical and pathological features, polymorphisms of folate metabolism pathway genes (MTHFR, MTRR, MTR, RFC1, TYMS, and DNMT3B), and data on circulating folate, vitamin B12 and homocysteine, which were available in a subgroup of the CRC patients. An increased number of methylated samples were found in CRC respect to adjacent healthy tissues, with the exception of APC, which was also frequently methylated in healthy colonic mucosa. Statistically significant associations were found between RASSF1A promoter methylation and tumor stage, and between hMLH1 promoter methylation and tumor location. Increasing age positively correlated with both hMLH1 and MGMT methylation levels in CRC tissues, and with APC methylation levels in the adjacent healthy mucosa. Concerning gender, females showed higher hMLH1 promoter methylation levels with respect to males. In CRC samples, the MTR 2756AG genotype correlated with higher methylation levels of RASSF1A, and the TYMS 1494 6bp ins/del polymorphism correlated with the methylation levels of both APC and hMLH1. In adjacent healthy tissues, MTR 2756AG and TYMS 1494 6bp del/del genotypes correlated with APC and MGMT promoter methylation, respectively. Low folate levels were associated with hMLH1 hypermethylation. Present results support the hypothesis that DNA methylation in CRC depends from both physiological and environmental factors, with one-carbon metabolism largely involved in this process. PMID:24500500

  19. Acting Atoms.

    ERIC Educational Resources Information Center

    Farin, Susan Archie

    1997-01-01

    Describes a fun game in which students act as electrons, protons, and neutrons. This activity is designed to help students develop a concrete understanding of the abstract concept of atomic structure. (DKM)

  20. Kinetic Atom.

    ERIC Educational Resources Information Center

    Wilson, David B.

    1981-01-01

    Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

  1. Newton's Atom

    NASA Astrophysics Data System (ADS)

    Chaney, Andrea; Espinosa, James; Espinosa, James

    2006-10-01

    At the turn of the twentieth century, physicists and chemists were developing atomic models. Some of the phenomena that they had to explain were the periodic table, the stability of the atom, and the emission spectra. Niels Bohr is known as making the first modern picture that accounted for these. Unknown to much of the physics community is the work of Walter Ritz. His model explained more emission spectra and predates Bohr's work. We will fit several spectra using Ritz's magnetic model for the atom. The problems of stability and chemical periodicity will be shown to be challenges that this model has difficulty solving, but we will present some potentially useful adaptations to the Ritzian atom that can account for them.

  2. Methane carbon isotope effects caused by atomic chlorine in the marine boundary layer: Global model results compared with Southern Hemisphere measurements

    NASA Astrophysics Data System (ADS)

    Allan, W.; Struthers, H.; Lowe, D. C.

    2007-02-01

    Recent measurements of the apparent kinetic isotope effect (KIE) of the methane (CH4) atmospheric sink in the extratropical Southern Hemisphere (ETSH) have shown the apparent KIE to be larger in magnitude than expected if the sink were the hydroxyl radical (OH•) alone. We present results from simulations using the U.K. Met Office's Unified Model (UM) to evaluate whether atomic chlorine (Cl•) in the marine boundary layer (MBL) could give this effect. We modify the UM to include sources of 12CH4 and 13CH4, soil and stratospheric sinks, and a tropospheric OH• sink. Also included is a Cl• sink in the MBL with a large seasonal cycle and a constant mean value (Cl•mean) in latitude. We show that analysis of the simulated seasonal cycles in CH4 mixing ratio and δ13C give an accurate estimate of the OH• KIE at ETSH midlatitudes. The apparent KIE of the combined OH• and Cl• sink increases in magnitude as Cl•mean increases. The experimentally measured values of apparent KIE in the ETSH midlatitudes of -15‰ in 1994-1996 and -7‰ in 1998-2000 are attained with MBL Cl•mean values of 28 × 103 atoms cm-3 and 9×103 atoms cm-3, respectively (although we consider the latter to be a lower bound). We suggest that 18×103 atoms cm-3 is a reasonable midrange estimate of Cl•mean in the MBL. This value results in a Cl• sink strength of 25 Tg y-1 (range 13-37 Tg y-1) and an enrichment in δ13C of atmospheric CH4 by 2.6‰ (range 1.4-3.8‰). This sink strength is significant but has not yet been included in global CH4 budgets.

  3. Nanoamorphous carbon-based photonic crystal infrared emitters

    DOEpatents

    Norwood, Robert A.; Skotheim, Terje

    2011-12-13

    Provided is a tunable radiation emitting structure comprising: a nanoamorphous carbon structure having a plurality of relief features provided in a periodic spatial configuration, wherein the relief features are separated from each other by adjacent recessed features, and wherein the nanoamorphous carbon comprises a total of from 0 to 60 atomic percent of one or more dopants of the dopant group consisting of: transition metals, lanthanoids, electro-conductive carbides, silicides and nitrides. In one embodiment, a dopant is selected from the group consisting of: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La and other lanthanides, Hf, Ta, W, Rh, Os, Ir, Pt, Au, and Hg. In one embodiment, a dopant is selected from the group consisting of: electro-conductive carbides (like Mo.sub.2C), silicides (like MoSi.sub.2) and nitrides (like TiN).

  4. Laplacian versus adjacency matrix in quantum walk search

    NASA Astrophysics Data System (ADS)

    Wong, Thomas G.; Tarrataca, Luís; Nahimov, Nikolay

    2016-06-01

    A quantum particle evolving by Schrödinger's equation contains, from the kinetic energy of the particle, a term in its Hamiltonian proportional to Laplace's operator. In discrete space, this is replaced by the discrete or graph Laplacian, which gives rise to a continuous-time quantum walk. Besides this natural definition, some quantum walk algorithms instead use the adjacency matrix to effect the walk. While this is equivalent to the Laplacian for regular graphs, it is different for non-regular graphs and is thus an inequivalent quantum walk. We algorithmically explore this distinction by analyzing search on the complete bipartite graph with multiple marked vertices, using both the Laplacian and adjacency matrix. The two walks differ qualitatively and quantitatively in their required jumping rate, runtime, sampling of marked vertices, and in what constitutes a natural initial state. Thus the choice of the Laplacian or adjacency matrix to effect the walk has important algorithmic consequences.

  5. Cold Atoms

    NASA Astrophysics Data System (ADS)

    Bellac, Michel Le

    2014-11-01

    This chapter and the following one address collective effects of quantum particles, that is, the effects which are observed when we put together a large number of identical particles, for example, electrons, helium-4 or rubidium-85 atoms. We shall see that quantum particles can be classified into two categories, bosons and fermions, whose collective behavior is radically different. Bosons have a tendency to pile up in the same quantum state, while fermions have a tendency to avoid each other. We say that bosons and fermions obey two different quantum statistics, the Bose-Einstein and the Fermi-Dirac statistics, respectively. Temperature is a collective effect, and in Section 5.1 we shall explain the concept of absolute temperature and its relation to the average kinetic energy of molecules. We shall describe in Section 5.2 how we can cool atoms down thanks to the Doppler effect, and explain how cold atoms can be used to improve the accuracy of atomic clocks by a factor of about 100. The effects of quantum statistics are prominent at low temperatures, and atom cooling will be used to obtain Bose-Einstein condensates at low enough temperatures, when the atoms are bosons.

  6. On the Adjacent Eccentric Distance Sum Index of Graphs

    PubMed Central

    Qu, Hui; Cao, Shujuan

    2015-01-01

    For a given graph G, ε(v) and deg(v) denote the eccentricity and the degree of the vertex v in G, respectively. The adjacent eccentric distance sum index of a graph G is defined as ξsv(G)=∑v∈V(G)ε(v)D(v)deg(v), where D(v)=∑u∈V(G)d(u,v) is the sum of all distances from the vertex v. In this paper we derive some bounds for the adjacent eccentric distance sum index in terms of some graph parameters, such as independence number, covering number, vertex connectivity, chromatic number, diameter and some other graph topological indices. PMID:26091095

  7. Nonlinear spin wave coupling in adjacent magnonic crystals

    NASA Astrophysics Data System (ADS)

    Sadovnikov, A. V.; Beginin, E. N.; Morozova, M. A.; Sharaevskii, Yu. P.; Grishin, S. V.; Sheshukova, S. E.; Nikitov, S. A.

    2016-07-01

    We have experimentally studied the coupling of spin waves in the adjacent magnonic crystals. Space- and time-resolved Brillouin light-scattering spectroscopy is used to demonstrate the frequency and intensity dependent spin-wave energy exchange between the side-coupled magnonic crystals. The experiments and the numerical simulation of spin wave propagation in the coupled periodic structures show that the nonlinear phase shift of spin wave in the adjacent magnonic crystals leads to the nonlinear switching regime at the frequencies near the forbidden magnonic gap. The proposed side-coupled magnonic crystals represent a significant advance towards the all-magnonic signal processing in the integrated magnonic circuits.

  8. Molecular disorganization of axons adjacent to human lacunar infarcts

    PubMed Central

    Lee, Monica D.; Tung, Spencer; Vinters, Harry V.; Carmichael, S. Thomas

    2015-01-01

    Cerebral microvascular disease predominantly affects brain white matter and deep grey matter, resulting in ischaemic damage that ranges from lacunar infarcts to white matter hyperintensities seen on magnetic resonance imaging. These lesions are common and result in both clinical stroke syndromes and accumulate over time, resulting in cognitive deficits and dementia. Magnetic resonance imaging studies suggest that these lesions progress over time, accumulate adjacent to prior lesions and have a penumbral region susceptible to further injury. The pathological correlates of this adjacent injury in surviving myelinated axons have not been previously defined. In this study, we sought to determine the molecular organization of axons in tissue adjacent to lacunar infarcts and in the regions surrounding microinfarcts, by determining critical elements in axonal function: the morphology and length of node of Ranvier segments and adjacent paranodal segments. We examined post-mortem brain tissue from six patients with lacunar infarcts and tissue from two patients with autosomal dominant retinal vasculopathy and cerebral leukoencephalopathy (previously known as hereditary endotheliopathy with retinopathy, nephropathy and stroke) who accumulate progressive white matter ischaemic lesions in the form of lacunar and microinfarcts. In axons adjacent to lacunar infarcts yet extending up to 150% of the infarct diameter away, both nodal and paranodal length increase by ∼20% and 80%, respectively, reflecting a loss of normal cell-cell adhesion and signalling between axons and oligodendrocytes. Using premorbid magnetic resonance images, brain regions from patients with retinal vasculopathy and cerebral leukoencephalopathy that harboured periventricular white matter hyperintensities were selected and the molecular organization of axons was determined within these regions. As in regions adjacent to lacunar infarcts, nodal and paranodal length in white matter of these patients is

  9. Simultaneous determination of mercury and organic carbon in sediment and soils using a direct mercury analyzer based on thermal decomposition-atomic absorption spectrophotometry.

    PubMed

    Chen, Jingjing; Chakravarty, Pragya; Davidson, Gregg R; Wren, Daniel G; Locke, Martin A; Zhou, Ying; Brown, Garry; Cizdziel, James V

    2015-04-29

    The purpose of this work was to study the feasibility of using a direct mercury analyzer (DMA) to simultaneously determine mercury (Hg) and organic matter content in sediment and soils. Organic carbon was estimated by re-weighing the sample boats post analysis to obtain loss-on-ignition (LOI) data. The DMA-LOI results were statistically similar (p<0.05) to the conventional muffle furnace approach. A regression equation was developed to convert DMA-LOI data to total organic carbon (TOC), which varied between 0.2% and 13.0%. Thus, mercury analyzers based on combustion can provide accurate estimates of organic carbon content in non-calcareous sediment and soils; however, weight gain from moisture (post-analysis), measurement uncertainty, and sample representativeness should all be taken into account. Sediment cores from seasonal wetland and open water areas from six oxbow lakes in the Mississippi River alluvial flood plain were analyzed. Wetland sediments generally had higher levels of Hg than open water areas owing to a greater fraction of fine particles and higher levels of organic matter. Annual loading of Hg in open water areas was estimated at 4.3, 13.4, 19.2, 20.7, 129, and 135 ng cm(-2) yr(-1) for Beasley, Roundaway, Hampton, Washington, Wolf and Sky Lakes, respectively. Generally, the interval with the highest Hg flux was dated to the 1960s and 1970s. PMID:25847156

  10. Atomic research

    NASA Technical Reports Server (NTRS)

    Hadaway, James B.; Connatser, Robert; Cothren, Bobby; Johnson, R. B.

    1993-01-01

    Work performed by the University of Alabama in Huntsville's (UAH) Center for Applied Optics (CAO) entitled Atomic Research is documented. Atomic oxygen (AO) effects on materials have long been a critical concern in designing spacecraft to withstand exposure to the Low Earth Orbit (LEO) environment. The objective of this research effort was to provide technical expertise in the design of instrumentation and experimental techniques for analyzing materials exposed to atomic oxygen in accelerated testing at NASA/MSFC. Such testing was required to answer fundamental questions concerning Space Station Freedom (SSF) candidate materials and materials exposed to atomic oxygen aboard the Long-Duration Exposure Facility (LDEF). The primary UAH task was to provide technical design, review, and analysis to MSFC in the development of a state-of-the-art 5eV atomic oxygen beam facility required to simulate the RAM-induced low earth orbit (LEO) AO environment. This development was to be accomplished primarily at NASA/MSFC. In support of this task, contamination effects and ultraviolet (UV) simulation testing was also to be carried out using NASA/MSFC facilities. Any materials analysis of LDEF samples was to be accomplished at UAH.

  11. Actuated atomizer

    NASA Technical Reports Server (NTRS)

    Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

    2008-01-01

    An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

  12. 7. VIEW OF WATER TREATMENT PLANT, ADJACENT TO THE COAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. VIEW OF WATER TREATMENT PLANT, ADJACENT TO THE COAL CONVEYOR; IN THE DISTANCE IS THE FREQUENCY CHANGER HOUSE, WHICH IS ATTACHED TO SWITCH HOUSE NO. 1; LOOKING WEST. - Commonwealth Electric Company, Fisk Street Electrical Generating Station, 1111 West Cermak Avenue, Chicago, Cook County, IL

  13. Colposcopy of vaginal and vulvar human papillomavirus and adjacent sites.

    PubMed

    Hatch, K

    1993-03-01

    Human papillomaviral infections can affect the entire lower female genital tract as multifocal or multicentric disease as well as the surrounding anatomic and adjacent sites. The traditional colposcopic methods are necessary to assist in the diagnosis and help differentiate these infections from other disease mimics. PMID:8392676

  14. Biogeochemistry of hydrothermally and adjacent non-altered soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a field/lab project, students in the Soil Biogeochemistry class of the University of Nevada, Reno described and characterized seven pedons, developed in hydrothermally and adjacent non-hydrothermally altered andesitic parent material near Reno, NV. Hydrothermally altered soils had considerably lo...

  15. 22. Float located adjacent to entry stair in filtration bed. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. Float located adjacent to entry stair in filtration bed. The float actuates a valve that maintains water level over the bed. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

  16. 2. VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. VIEW FROM ROOFTOP OF BUILDING (MOTEL) ADJACENT TO TECHWOOD HOMES, LOOKING WEST. GEORGIA TECH DORMITORY BUILDING, 581-587 TECHWOOD DRIVE, IN FOREGROUND. - Techwood Homes (Public Housing), Bounded by North Avenue, Parker Street, William Street & Lovejoy Street, Atlanta, Fulton County, GA

  17. 10. Detail and contextual view of bridge and adjacent farmstead ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Detail and contextual view of bridge and adjacent farmstead setting. Note laced vertical compression members, latticed portal strut, decorative strut bracing, and lightness of diagonal and lateral tension members. View to southeast through southeast portal from truss mid-span. - Red Bank Creek Bridge, Spanning Red Bank Creek at Rawson Road, Red Bluff, Tehama County, CA

  18. LEHR NO. 2 AND LEHR NO. 3 ADJACENT TO FURNACE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LEHR NO. 2 AND LEHR NO. 3 ADJACENT TO FURNACE ROOM; THE PIPES AT THE BOTTOM ARE PART OF THE RADIANT HEATING SYSTEM USED FOR HEATING THE FACTORY DURING COLD WEATHER. - Westmoreland Glass Company, Seventh & Kier Streets, Grapeville, Westmoreland County, PA

  19. Effects on stink bugs of field edges adjacent to woodland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Producers face significant crop losses from stink bug species in the southeastern USA, but the high mobility and polyphagy of the bugs make predictions of their presence in crops difficult. While there is some evidence that they colonize crops from adjacent crops, there are no studies of their colo...

  20. VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING INTERSECTION OF ACACIA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING INTERSECTION OF ACACIA ROAD WITH BIRCH CIRCLE. VIEW FACING NORTHEAST - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, Intersection of Acacia Road and Brich Circle, Pearl City, Honolulu County, HI

  1. VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING RECREATION AREA AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING RECREATION AREA AND ENTRY TO NEIGHBORHOOD. VIEW FACING SOUTHEAST - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, Intersection of Acacia Road and Brich Circle, Pearl City, Honolulu County, HI

  2. VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING WESTERN SIDE OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING WESTERN SIDE OF NEIGHBORHOOD. VIEW FACING NORTHWEST - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, Intersection of Acacia Road and Brich Circle, Pearl City, Honolulu County, HI

  3. VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING RECREATION AREA ON ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW FROM ATOP ADJACENT RESIDENTIAL TOWER, SHOWING RECREATION AREA ON RIGHT, AND HOUSING AREA ON LEFT. VIEW FACING EAST/NORTHEAST - Camp H.M. Smith and Navy Public Works Center Manana Title VII (Capehart) Housing, Intersection of Acacia Road and Brich Circle, Pearl City, Honolulu County, HI

  4. How subaerial salt extrusions influence water quality in adjacent aquifers

    NASA Astrophysics Data System (ADS)

    Mehdizadeh, Razieh; Zarei, Mehdi; Raeisi, Ezzat

    2015-12-01

    Brines supplied from salt extrusions cause significant groundwater salinization in arid and semi-arid regions where salt rock is exposed to dissolution by episodic rainfalls. Here we focus on 62 of the 122 diapirs of Hormuz salt emergent in the southern Iran. To consider managing the degradation effect that salt extrusions have on the quality of adjoining aquifers, it is first necessary to understand how they influence adjacent water resources. We evaluate here the impacts that these diapirs have on adjacent aquifers based on investigating their geomorphologies, geologies, hydrologies and hydrogeologies. The results indicate that 28/62 (45%) of our sample of salt diapirs have no significant impact on the quality of groundwater in adjoining aquifers (namely Type N), while the remaining 34/62 (55%) degrade nearby groundwater quality. We offer simple conceptual models that account for how brines flowing from each of these types of salt extrusions contaminate adjacent aquifers. We identify three main mechanisms that lead to contamination: surface impact (Type A), subsurface intrusion (Type B) and indirect infiltration (Type C). A combination of all these mechanisms degrades the water quality in nearby aquifers in 19/62 (31%) of the salt diapirs studied. Having characterized the mechanism(s) by which each diapir affects the adjacent aquifer, we suggest a few possible remediation strategies to be considered. For instance, engineering the surface runoff of diapirs Types A and C into nearby evaporation basins would improve groundwater quality.

  5. 45. 1915 CLOTH ROOM ADJACENT TO PICKER ROOM, SECOND FLOOR, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    45. 1915 CLOTH ROOM ADJACENT TO PICKER ROOM, SECOND FLOOR, NORTH END OF MILL NO. 2, WALL ON LEFT DIVIDING CLOTH ROOM ADDED LATER (PROBABLY C. 1970s). - Prattville Manufacturing Company, Number One, 242 South Court Street, Prattville, Autauga County, AL

  6. Detail of north intermediate abutment pylon showing proximity of adjacent ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of north intermediate abutment pylon showing proximity of adjacent 1001-1007 East First Street (James K. Hill and Sons Pickle Works Building), facing east - First Street Bridge, Spanning Los Angeles River at First Street, Los Angeles, Los Angeles County, CA

  7. 8. Exterior view, showing tank and associated piping adjacent to ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Exterior view, showing tank and associated piping adjacent to Test Cell 6, Systems Integration Laboratory Building (T-28), looking south. - Air Force Plant PJKS, Systems Integration Laboratory, Systems Integration Laboratory Building, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  8. 4. REAR ELEVATION, DETAIL OF CONSTRUCTION, ADJACENT CORNER POSTS BETWEEN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. REAR ELEVATION, DETAIL OF CONSTRUCTION, ADJACENT CORNER POSTS BETWEEN BUILDING PERIODS 1 AND 3. NOTE REUSED WOOD STRIP NAILED TO BUILDING PERIOD 1 POST INSCRIBED 'ST. LEONARD'. THERE ARE NO NAIL HOLES IN THE PERIOD 3 POST, THE FARRING STRIPS ADJUST FOR CLADDING - Charles' Gift, State Routes 2 & 4, Lusby, Calvert County, MD

  9. 1. OVERVIEW SHOWING FIRING CONTROL BLOCKHOUSE 0502 AND ADJACENT OBSERVATION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. OVERVIEW SHOWING FIRING CONTROL BLOCKHOUSE 0502 AND ADJACENT OBSERVATION TOWER. WATER BRAKE TROUGH SEGMENT AT LOWER RIGHT. Looking north northeast. - Edwards Air Force Base, South Base Sled Track, Firing & Control Blockhouse for 10,000-foot Track, South of Sled Track at midpoint of 20,000-foot track, Lancaster, Los Angeles County, CA

  10. 4. Elevation looking southwest from adjacent hills on northeast side ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Elevation looking southwest from adjacent hills on northeast side of bridge, taken from river level. Note entire east side and substructure. - Presumpscot Falls Bridge, Spanning Presumptscot River at Allen Avenue extension, 0.75 mile west of U.S. Interstate 95, Falmouth, Cumberland County, ME

  11. 49 CFR 236.404 - Signals at adjacent control points.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Signals at adjacent control points. 236.404 Section 236.404 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR...

  12. 12. LOG FOUNDATION ELEMENTS OF THE SAWMILL ADJACENT TO THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. LOG FOUNDATION ELEMENTS OF THE SAWMILL ADJACENT TO THE CANAL, LOOKING EAST. BARREN AREA IN FOREGROUND IS DECOMPOSING SAWDUST. DIRT PILE IN BACKGROUND IS THE EDGE OF THE SUMMIT COUNTY LANDFILL. - Snake River Ditch, Headgate on north bank of Snake River, Dillon, Summit County, CO

  13. Atom Interferometry

    SciTech Connect

    Kasevich, Mark

    2008-05-08

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton's constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gyroscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be used to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  14. Atom Interferometry

    SciTech Connect

    Mark Kasevich

    2008-05-07

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  15. Atom Interferometry

    ScienceCinema

    Mark Kasevich

    2010-01-08

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton?s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  16. Ionic liquid-assisted multiwalled carbon nanotube-dispersive micro-solid phase extraction for sensitive determination of inorganic As species in garlic samples by electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Grijalba, Alexander Castro; Escudero, Leticia B.; Wuilloud, Rodolfo G.

    2015-08-01

    A highly sensitive dispersive micro-solid phase extraction (D-μ-SPE) method combining an ionic liquid (IL) and multi-walled carbon nanotubes (MWCNTs) for inorganic As species (As(III) and As(V)) species separation and determination in garlic samples by electrothermal atomic absorption spectrometry (ETAAS) was developed. Trihexyl(tetradecil)phosphonium chloride IL was used to form an ion pair with the arsenomolybdate complex obtained by reaction of As(V) with molybdate ion. Afterwards, 1.0 mg of MWCNTs was dispersed for As(V) extraction and the supernatant was separated by centrifugation. MWCNTs were re-dispersed with tetradecyltrimethylammonium bromide surfactant and ultrasound followed by direct injection into the graphite furnace of ETAAS for As determination. Pyrolysis and atomization conditions were carefully studied for complete decomposition of MWCNTs and IL matrices. Under optimum conditions, an extraction efficiency of 100% and a preconcentration factor of 70 were obtained with 5 mL of garlic extract. The detection limit was 7.1 ng L- 1 and the relative standard deviations (RSDs) for six replicate measurements at 5 μg L- 1 of As were 5.4% and 4.8% for As(III) and As(V), respectively. The proposed D-μ-SPE method allowed the efficient separation and determination of inorganic As species in a complex matrix such as garlic extract.

  17. Is there a Difference in Van Der Waals Interactions between Rare Gas Atoms Adsorbed on Metallic and Semiconducting Single-Walled Carbon Nanotubes?

    SciTech Connect

    Chen, De-Li; Mandeltort, Lynn; Saidi, Wissam A.; Yates, John T.; Cole, Milton W.; Johnson, J. Karl

    2013-03-01

    Differences in polarizabilities of metallic (M) and semiconducting (S) single-walled carbon nanotubes (SWNTs) might give rise to differences in adsorption potentials. We show from experiments and van der Waals-corrected density functional theory (DFT) that binding energies of Xe adsorbed on M- and S-SWNTs are nearly identical. Temperature programmed desorption of Xe on purified M- and S-SWNTs give similar peak temperatures, indicating that desorption kinetics and binding energies are independent of the type of SWNT. Binding energies computed from vdW-corrected DFT are in good agreement with experiments.

  18. Microwave ionization of Rydberg atoms

    SciTech Connect

    Gallagher, T.F.

    1996-12-31

    An atom can be ionized by a static field if the field depresses the potential below the binding energy W, leading to the requirement E = W{sup 2}/4 in atomic units. The atomic units of field and energy are 5.14 {times} 10{sup 9} V/cm and 27.2 eV. The ionization field is often expressed in terms of the principal quantum number n of the state in question as E = 1/16n{sup 4}. In a microwave field with frequency far less than the separation {Delta}W = 1/n{sup 3} between adjacent n states, atoms other than H ionize at the much lower microwave field amplitude of E = 1/3n{sup 5}. This field corresponds to the Inglis-Teller limit, where it is impossible to resolve spectrally adjacent n states due to Stark broadening in a plasma. In H ionization occurs as it does in a static field. The difference exists because the finite sized ionic core of a non hydrogenic atom breaks one of the symmetries found in H. In non hydrogenic atoms the microwave field drives a series of transitions through successively higher n states culminating in ionization. These transitions can be understood in terms of a Landau-Zener picture based on the variation of the energies of the atoms produced by the time varying field or as the resonant multiphoton absorption of the microwave photons. In either case, the atoms make transitions through real intermediate states en route to ionization. With short, four cycle, microwave pulses complete ionization does not occur with fields of E = 1/3n{sup 5}, and population is left in intermediate states. The transition from ionization at fields near E = 1/3n{sup 5} to fields of E = 1/16n{sup 4} occurs when the frequency becomes low enough that the energies of the states vary adiabatically in the temporally varying field.

  19. Reactivity of boron- and nitrogen-doped carbon nanotubes functionalized by (Pt, Eu) atoms toward O2 and CO: A density functional study

    NASA Astrophysics Data System (ADS)

    Abdel Aal, S.

    2016-01-01

    The adsorption behavior and electronic properties of CO and O2 molecules at the supported Pt and Eu atoms on (5,5) armchair SWCNT have been systematically investigated within density functional theory (DFT). Fundamental aspects such as adsorption energy, natural bond orbital (NBO), charge transfer, frontier orbitals and the projected density of states (PDOS) are elucidated to analyze the adsorption properties of CO and O2 molecules. The results reveal that B- and N-doping CNTs can enhance the binding strength and catalytic activity of Pt (Eu) anchored on the doped-CNT, where boron-doping is more effective. The electronic structures of supported metal are strongly influenced by the presence of gases. After adsorption of CO and O2, the changes in binding energy, charge transfer and conductance may lead to the different response in the metal-doped CNT-based sensors. It is expected that these results could provide helpful information for the design and fabrication of the CO and O2 sensing devices. The high catalytic activity of Pt supported at doped-CNT toward the interaction with CO and O2 may be attributed to the electronic resonance particularly among Pt-5d, CO-2π* and O2-2π* antibonding orbitals. In contrast to the supported Eu at doped-CNT, the Eu atom becomes more positively charged, which leads to weaken the CO adsorption and promote the O2 adsorption, consequently enhancing the activity for CO oxidation and alleviating the CO poisoning of the europium catalysts. A notable orbital hybridization and electrostatic interaction between these two species in adsorption process being an evidence of strong interaction. The electronic structure of O2 adsorbed on Eu-doped CNT resembles that of O2‑, therefore the transferred charge weakens the O-O bonds and facilitates the dissociation process, which is the precondition for the oxygen reduction reaction (ORR).

  20. Study on the dynamics responses of a transmission system made from carbon nanotubes

    SciTech Connect

    Yin, Hang; Cai, Kun Wei, Ning; Qin, Qing-Hua; Shi, Jiao

    2015-06-21

    A rotational transmission system from coaxial carbon nanotubes (CNTs) is investigated using a computational molecular dynamics approach. The system consists of a motor from a single-walled carbon nanotube and a bearing from a double-walled carbon nanotube. The motor has a high fixed rotational frequency and the two ends of the outer tube in the bearing are fixed. The inner tube in the bearing works as a rotor. Because of the interlayer friction in the bearing, configurations of the joint between the adjacent ends of motor and rotor have significant effects on rotational transmission properties. Four factors are considered in simulation, i.e., the bonding types of atoms (sp{sup 1} and sp{sup 2}) on the ends of motor and rotor, the difference between motor and rotor radii, the rotational speed of motor, and the environmental temperature. It is found that the synchronous transmission happens if the sp{sup 1} atoms on the jointed ends of motor and rotor are bonded each other and become new sp{sup 2} atoms. Therefore, the lower difference between radii of motor and rotor, higher temperature of environment leads to synchronous rotational transmission easily. If the environmental temperature is too low (e.g., <150 K), the end of motor adjacent to rotor is easily under buckling and new sp{sup 2} atoms appear, too. With capped CNTs or higher radii difference between rotor and motor at an appropriate temperature, a stable asynchronous rotation of rotor can be generated, and the rotor's frequency varying linearly with motor's frequency between 230 and 270 GHz. A multi-signal transmission device combined with oscillating and rotational motion is proposed for motor and stator shares a same size in radius.