WorldWideScience

Sample records for chemical state

  1. Chemical Implementation of Finite-State Machines

    Science.gov (United States)

    Hjelmfelt, Allen; Weinberger, Edward D.; Ross, John

    1992-01-01

    With methods developed in a prior article on the chemical kinetic implementation of a McCulloch-Pitts neuron, connections among neurons, logic gates, and a clocking mechanism, we construct examples of clocked finite-state machines. These machines include a binary decoder, a binary adder, and a stack memory. An example of the operation of the binary adder is given, and the chemical concentrations corresponding to the state of each chemical neuron are followed in time. Using these methods, we can, in principle, construct a universal Turing machine, and these chemical networks inherit the halting problem

  2. Chemical state speciation by resonant Raman scattering

    CERN Document Server

    Karydas, A G; Zarkadas, C; Paradelis, T; Kallithrakas-Kontos, N

    2002-01-01

    In the resonant Raman scattering (RRS) process the emitted photon exhibits a continuous energy distribution with a high energy cutoff limit. This cutoff energy depends on the chemical state of the element under examination. In the present work, the possibility of identifying the chemical state of V atoms by employing RRS spectroscopy with a semiconductor Si(Li) detector is investigated. A proton induced Cr K alpha x-ray beam was used as the incident radiation, having a fixed energy lower than the V K-absorption edge. The net RRS distributions extracted from the energy dispersive spectra of metallic V and its compound targets were simulated by an appropriate theoretical model. The results showed the possibility of employing RRS spectroscopy with a semiconductor detector for chemical speciation studies.

  3. Quantum-State Controlled Chemical Reactions of Ultracold KRb Molecules

    CERN Document Server

    Ospelkaus, S; Wang, D; de Miranda, M H G; Neyenhuis, B; Quéméner, G; Julienne, P S; Bohn, J L; Jin, D S; Ye, J

    2009-01-01

    How does a chemical reaction proceed at ultralow temperatures? Can simple quantum mechanical rules such as quantum statistics, single scattering partial waves, and quantum threshold laws provide a clear understanding for the molecular reactivity under a vanishing collision energy? Starting with an optically trapped near quantum degenerate gas of polar $^{40}$K$^{87}$Rb molecules prepared in their absolute ground state, we report experimental evidence for exothermic atom-exchange chemical reactions. When these fermionic molecules are prepared in a single quantum state at a temperature of a few hundreds of nanoKelvins, we observe p-wave-dominated quantum threshold collisions arising from tunneling through an angular momentum barrier followed by a near-unity probability short-range chemical reaction. When these molecules are prepared in two different internal states or when molecules and atoms are brought together, the reaction rates are enhanced by a factor of 10 to 100 due to s-wave scattering, which does not ...

  4. Reaction diffusion and solid state chemical kinetics handbook

    CERN Document Server

    Dybkov, V I

    2010-01-01

    This monograph deals with a physico-chemical approach to the problem of the solid-state growth of chemical compound layers and reaction-diffusion in binary heterogeneous systems formed by two solids; as well as a solid with a liquid or a gas. It is explained why the number of compound layers growing at the interface between the original phases is usually much lower than the number of chemical compounds in the phase diagram of a given binary system. For example, of the eight intermetallic compounds which exist in the aluminium-zirconium binary system, only ZrAl3 was found to grow as a separate

  5. Chemical state of fission products in irradiated uranium carbide fuel

    Science.gov (United States)

    Arai, Yasuo; Iwai, Takashi; Ohmichi, Toshihiko

    1987-12-01

    The chemical state of fission products in irradiated uranium carbide fuel has been estimated by equilibrium calculation using the SOLGASMIX-PV program. Solid state fission products are distributed to the fuel matrix, ternary compounds, carbides of fission products and intermetallic compounds among the condensed phases appearing in the irradiated uranium carbide fuel. The chemical forms are influenced by burnup as well as stoichiometry of the fuel. The results of the present study almost agree with the experimental ones reported for burnup simulated carbides.

  6. Topological engineering of glass for modulating chemical state of dopants.

    Science.gov (United States)

    Zhou, Shifeng; Guo, Qiangbing; Inoue, Hiroyuki; Ye, Qun; Masuno, Atsunobu; Zheng, Binbin; Yu, Yongze; Qiu, Jianrong

    2014-12-17

    A novel approach to modulating the chemical state of dopants by engineering the topological features of a glass matrix is presented. The method allows selective stabilization of dopants on a wide range of length scales, from dispersed ions to aggregated clusters to nanoparticles, leading to various intriguing optical phenomena, such as great emission enhancement and ultra-broadband optical amplification.

  7. Chemical state of fission products in irradiated UO 2

    Science.gov (United States)

    Imoto, S.

    1986-08-01

    The chemical state of fission products in irradiated UO 2 fuel has been estimated for FBR as well as LWR on the basis of equilibrium calculation with the SOLGASMIX-PV code. The system considered for the calculation is composed of a gas phase, a CaF 2 type oxide phase, three grey phases, a noble metal alloy, a mixed telluride phase and several other phases each consisting of single compound. The distribution of elements into these phases and the amount of chemical species in each phase at different temperatures are obtained as a function of oxygen potential for LWR and FBR. Changes of the chemical potential of the fuel-fission products system during burnup are also evaluated with particular attention to the difference between LWR and FBR. Some informations obtained by the calculation are compared with the results of post irradiation examination of UO 2 fuels.

  8. State estimation of chemical engineering systems tending to multiple solutions

    Directory of Open Access Journals (Sweden)

    N. P. G. Salau

    2014-09-01

    Full Text Available A well-evaluated state covariance matrix avoids error propagation due to divergence issues and, thereby, it is crucial for a successful state estimator design. In this paper we investigate the performance of the state covariance matrices used in three unconstrained Extended Kalman Filter (EKF formulations and one constrained EKF formulation (CEKF. As benchmark case studies we have chosen: a a batch chemical reactor with reversible reactions whose system model and measurement are such that multiple states satisfy the equilibrium condition and b a CSTR with exothermic irreversible reactions and cooling jacket energy balance whose nonlinear behavior includes multiple steady-states and limit cycles. The results have shown that CEKF is in general the best choice of EKF formulations (even if they are constrained with an ad hoc clipping strategy which avoids undesired states for such case studies. Contrary to a clipped EKF formulation, CEKF incorporates constraints into an optimization problem, which minimizes the noise in a least square sense preventing a bad noise distribution. It is also shown that, although the Moving Horizon Estimation (MHE provides greater robustness to a poor guess of the initial state, converging in less steps to the actual states, it is not justified for our examples due to the high additional computational effort.

  9. State waste discharge permit application, 200-E chemical drain field

    Energy Technology Data Exchange (ETDEWEB)

    1994-06-01

    As part of the Hanford Federal Facility Agreement and Consent Order negotiations (Ecology et al. 1994), the US Department of Energy, Richland Operations Office, the US Environmental Protection Agency, and the Washington State Department of Ecology agreed that liquid effluent discharges to the ground on the Hanford Site which affect groundwater or have the potential to affect ground would be subject to permitting under the structure of Chapter 173-216 (or 173-218 where applicable) of the Washington Administrative Code, the State Waste Discharge Permit Program. As a result of this decision, the Washington State Department of Ecology and the US Department of Energy, Richland Operations Office entered into Consent Order No. DE 91NM-177, (Ecology and DOE-RL 1991). The Consent Order No. DE 91NM-177 requires a series of permitting activities for liquid effluent discharges. This document presents the State Waste Discharge Permit (SWDP) application for the 200-E Chemical Drain Field. Waste water from the 272-E Building enters the process sewer line directly through a floor drain, while waste water from the 2703-E Building is collected in two floor drains, (north and south) that act as sumps and are discharged periodically. The 272-E and 2703-E Buildings constitute the only discharges to the process sewer line and the 200-E Chemical Drain Field.

  10. Linear complexions: Confined chemical and structural states at dislocations.

    Science.gov (United States)

    Kuzmina, M; Herbig, M; Ponge, D; Sandlöbes, S; Raabe, D

    2015-09-04

    For 5000 years, metals have been mankind's most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe-9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states.

  11. Structural simplification of chemical reaction networks in partial steady states.

    Science.gov (United States)

    Madelaine, Guillaume; Lhoussaine, Cédric; Niehren, Joachim; Tonello, Elisa

    2016-11-01

    We study the structural simplification of chemical reaction networks with partial steady state semantics assuming that the concentrations of some but not all species are constant. We present a simplification rule that can eliminate intermediate species that are in partial steady state, while preserving the dynamics of all other species. Our simplification rule can be applied to general reaction networks with some but few restrictions on the possible kinetic laws. We can also simplify reaction networks subject to conservation laws. We prove that our simplification rule is correct when applied to a module of a reaction network, as long as the partial steady state is assumed with respect to the complete network. Michaelis-Menten's simplification rule for enzymatic reactions falls out as a special case. We have implemented an algorithm that applies our simplification rules repeatedly and applied it to reaction networks from systems biology.

  12. Solid-State NMR Studies of Chemically Lithiated CFx

    Science.gov (United States)

    Leifer, N. D.; Johnson, V. S.; Ben-Ari, R.; Gan, H.; Lehnes, J. M.; Guo, R.; Lu, W.; Muffoletto, B. C.; Reddy, T.; Stallworth, P. E.; Greenbaum, S. G.

    2010-01-01

    Three types of fluorinated carbon, all in their original form and upon sequential chemical lithiations via n-butyllithium, were investigated by 13C and 19F solid-state NMR methods. The three starting CFx materials [where x = 1 (nominally)] were fiber based, graphite based, and petroleum coke based. The aim of the current study was to identify, at the atomic/molecular structural level, factors that might account for differences in electrochemical performance among the different kinds of CFx. Differences were noted in the covalent F character among the starting compounds and in the details of LiF production among the lithiated samples. PMID:20676233

  13. State-to-state dynamics of elementary chemical reactions using Rydberg H-atom translational spectroscopy

    Science.gov (United States)

    Yang, Xueming

    In this review, a few examples of state-to-state dynamics studies of both unimolecular and bimolecular reactions using the H-atom Rydberg tagging TOF technique were presented. From the H2O photodissociation at 157 nm, a direction dissociation example is provided, while photodissociation of H2O at 121.6 has provided an excellent dynamical case of complicated, yet direct dissociation process through conical intersections. The studies of the O(1D) + H2 → OH + H reaction has also been reviewed here. A prototype example of state-to-state dynamics of pure insertion chemical reaction is provided. Effect of the reagent rotational excitation and the isotope effect on the dynamics of this reaction have also been investigated. The detailed mechanism for abstraction channel in this reaction has also been closely studied. The experimental investigations of the simplest chemical reaction, the H3 system, have also been described here. Through extensive collaborations between theory and experiment, the mechanism for forward scattering product at high collision energies for the H + HD reaction was clarified, which is attributed to a slow down mechanism on the top of a quantized barrier transition state. Oscillations in the product quantum state resolved different cross sections have also been observed in the H + D2 reaction, and were attributed to the interference of adiabatic transition state pathways from detailed theoretical analysis. The results reviewed here clearly show the significant advances we have made in the studies of the state-to-state molecular reaction dynamics.

  14. Protein's native state stability in a chemically induced denaturation mechanism.

    Science.gov (United States)

    Olivares-Quiroz, L; Garcia-Colin, L S

    2007-05-21

    In this work, we present a generalization of Zwanzig's protein unfolding analysis [Zwanzig, R., 1997. Two-state models of protein folding kinetics. Proc. Natl Acad. Sci. USA 94, 148-150; Zwanzig, R., 1995. Simple model of protein folding kinetics. Proc. Natl Acad. Sci. USA 92, 9801], in order to calculate the free energy change Delta(N)(D)F between the protein's native state N and its unfolded state D in a chemically induced denaturation. This Extended Zwanzig Model (EZM) is both based on an equilibrium statistical mechanics approach and the inclusion of experimental denaturation curves. It enables us to construct a suitable partition function Z and to derive an analytical formula for Delta(N)(D)F in terms of the number K of residues of the macromolecule, the average number nu of accessible states for each single amino acid and the concentration C(1/2) where the midpoint of the ND transition occurs. The results of the EZM for proteins where chemical denaturation follows a sigmoidal-type profile, as it occurs for the case of the T70N human variant of lysozyme (PDB code: T70N) [Esposito, G., et al., 2003. J. Biol. Chem. 278, 25910-25918], can be splitted into two lines. First, EZM shows that for sigmoidal denaturation profiles, the internal degrees of freedom of the chain play an outstanding role in the stability of the native state. On the other hand, that under certain conditions DeltaF can be written as a quadratic polynomial on concentration C(1/2), i.e., DeltaF approximately aC(1/2)(2)+bC(1/2)+c, where a,b,c are constant coefficients directly linked to protein's size K and the averaged number of non-native conformations nu. Such functional form for DeltaF has been widely known to fit experimental measures in chemically induced protein denaturation [Yagi, M., et al., 2003. J. Biol. Chem. 278, 47009-47015; Asgeirsson, B., Guojonsdottir, K., 2006. Biochim. Biophys. Acta 1764, 190-198; Sharma, S., et al., 2006. Protein Pept. Lett. 13(4), 323-329; Salem, M., et al

  15. Reacting gas mixtures in the state-to-state approach: The chemical reaction rates

    Energy Technology Data Exchange (ETDEWEB)

    Kustova, Elena V. [Department of Mathematics and Mechanics, Saint Petersburg State University, 198504 Universitetskiy pr., 28, Saint Petersburg (Russian Federation); Kremer, Gilberto M. [Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba (Brazil)

    2014-12-09

    In this work chemically reacting mixtures of viscous flows are analyzed within the framework of Boltzmann equation. By applying a modified Chapman-Enskog method to the system of Boltzmann equations general expressions for the rates of chemical reactions and vibrational energy transitions are determined as functions of two thermodynamic forces: the velocity divergence and the affinity. As an application chemically reacting mixtures of N{sub 2} across a shock wave are studied, where the first lowest vibrational states are taken into account. Here we consider only the contributions from the first four single quantum vibrational-translational energy transitions. It is shown that the contribution to the chemical reaction rate related to the affinity is much larger than that of the velocity divergence.

  16. Reacting gas mixtures in the state-to-state approach: The chemical reaction rates

    Science.gov (United States)

    Kustova, Elena V.; Kremer, Gilberto M.

    2014-12-01

    In this work chemically reacting mixtures of viscous flows are analyzed within the framework of Boltzmann equation. By applying a modified Chapman-Enskog method to the system of Boltzmann equations general expressions for the rates of chemical reactions and vibrational energy transitions are determined as functions of two thermodynamic forces: the velocity divergence and the affinity. As an application chemically reacting mixtures of N2 across a shock wave are studied, where the first lowest vibrational states are taken into account. Here we consider only the contributions from the first four single quantum vibrational-translational energy transitions. It is shown that the contribution to the chemical reaction rate related to the affinity is much larger than that of the velocity divergence.

  17. Chemical state of tellurium in a degraded LWR core

    Science.gov (United States)

    Imoto, S.; Tanabe, T.

    1988-06-01

    Changes of the chemical state of tellurium in the heatup stage of a severe fuel damage accident are estimated thermodynamically. According to equilibrium calculations with the SOLGASMIX-PV code, tellurium exists as cesium telluride, as the element or possibly as PdTe during normal operation. In the heatup stage of an accident, elemental tellurium is absorbed in the Zircaloy cladding by formation of ZrTe x ( x = 1-2). Cesium telluride does not react with Zr even under the low oxygen potentials favoring the {Zr}/{UO 2} reaction. Tellurium is also absorbed in oxygen-stabilized alpha-zirconium. The stability of Cs 2Te in the steam/hydrogen atmosphere is discussed.

  18. Zirconia-based solid state chemical gas sensors

    CERN Document Server

    Zhuiykov, S

    2000-01-01

    This paper presents an overview of chemical gas sensors, based on solid state technology, that are sensitive to environmental gases, such as O sub 2 , SO sub x , NO sub x , CO sub 2 and hydrocarbons. The paper is focussed on performance of electrochemical gas sensors that are based on zirconia as a solid electrolyte. The paper considers sensor structures and selection of electrode materials. Impact of interfaces on sensor performance is discussed. This paper also provides a brief overview of electrochemical properties of zirconia and their effect on sensor performance. Impact of auxiliary materials on sensors performance characteristics, such as sensitivity, selectivity, response time and recovery time, is also discussed. Dual gas sensors that can be applied for simultaneous monitoring of the concentration of both oxygen and other gas phase components, are briefly considered

  19. Chemically modified solid state nanopores for high throughput nanoparticle separation

    Energy Technology Data Exchange (ETDEWEB)

    Prabhu, Anmiv S; Kim, Min Jun [School of Biomedical Engineering and Health Science, Drexel University, Philadelphia, PA 19104 (United States); Jubery, Talukder Zaki N; Dutta, Prashanta [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 (United States); Freedman, Kevin J; Mulero, Rafael, E-mail: mkim@coe.drexel.ed [Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104 (United States)

    2010-11-17

    The separation of biomolecules and other nanoparticles is a vital step in several analytical and diagnostic techniques. Towards this end we present a solid state nanopore-based set-up as an efficient separation platform. The translocation of charged particles through a nanopore was first modeled mathematically using the multi-ion model and the surface charge density of the nanopore membrane was identified as a critical parameter that determines the selectivity of the membrane and the throughput of the separation process. Drawing from these simulations a single 150 nm pore was fabricated in a 50 nm thick free-standing silicon nitride membrane by focused-ion-beam milling and was chemically modified with (3-aminopropyl)triethoxysilane to change its surface charge density. This chemically modified membrane was then used to separate 22 and 58 nm polystyrene nanoparticles in solution. Once optimized, this approach can readily be scaled up to nanopore arrays which would function as a key component of next-generation nanosieving systems.

  20. Testing fundamentals: The chemical state of geochemical tracers in biominerals.

    Science.gov (United States)

    Branson, O.; Redfern, S. A. T.; Read, E.; Elderfield, H.

    2015-12-01

    The use of many carbonate-derived geochemical proxies is underpinned by the assumption that tracer elements are incorporated 'ideally' as impurities the mineral lattice, following relatively straightforward kinetic and thermodynamic drives. This allows comparison to inorganic precipitation experiments, and provides a systematic starting point from which to translate geochemical tracers to environmental records. Biomineral carbonates are a prominent source of geochemical proxy material, and are far from an ideal inorganic system. They are structurally and compositionally heterogeneous mineral-organic composites, produced in tightly controlled biological environments, possibly via non-classical crystal growth mechanisms. Biominerals offer numerous opportunities for tracers to be incorporated in a 'non-ideal' state. For instance, tracers could be hosted within the organic component of the structure, in interstitial micro-domains of a separate mineral phase, or in localized high-impurity clusters. If a proxy element is hosted in a non-ideal state, our understanding of its incorporation and preservation is flawed, and the theoretical basis behind the proxies derived from it must be reevaluated. Thus far, the assumption of ideal tracer incorporation has remained largely untested, owing to the spatial resolution and sensitivity limits of available techniques. Developments in high-resolution, high-sensitivity X-ray spectroscopy at Scanning Transmission X-Ray Microscopes (STXMs) have allowed us to measure trace element coordination in foraminiferal calcite, at length-scales relevant to biomineralisation processes and tracer incorporation. This instrument has allowed us to test the fundamental assumptions behind several geochemical proxy elements. We present a summary of four STXM studies, assessing the chemical state and distribution of Mg (Branson et al, 2014), B (Branson et al, 2015), S and Na (unpub.), and highlight the implications of these data for the use of these

  1. Accumulation and chemical states of radiocesium by fungus Saccharomyces cerevisiae

    Science.gov (United States)

    Ohnuki, Toshihiko; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya; Yu, Qianqian

    2014-05-01

    After accident of Fukushima Daiichi Nuclear Power Plant, the fall-out radiocesium was deposited on the ground. Filamentous fungus is known to accumulate radiocesium in environment, even though many minerals are involved in soil. These facts suggest that fungus affect the migration behavior of radiocesium in the environment. However, accumulation mechanism of radiocesium by fungus is not understood. In the present study, accumulation and chemical states change of Cs by unicellular fungus of Saccharomyces cerevisiae have been studied to elucidate the role of microorganisms in the migration of radiocesium in the environment. Two different experimental conditions were employed; one is the accumulation experiments of radiocesium by S. cerevisiae from the agar medium containing 137Cs and a mineral of zeolite, vermiculite, smectite, mica, or illite. The other is the experiments using stable cesium to examine the chemical states change of Cs. In the former experiment, the cells were grown on membrane filter of 0.45 μm installed on the agar medium. After the grown cells were weighed, radioactivity in the cells was measured by an autoradiography technique. The mineral weight contents were changed from 0.1% to 1% of the medium. In the latter experiment, the cells were grown in the medium containing stable Cs between 1 mM and 10mM. The Cs accumulated cells were analyzed by SEM-EDS and EXAFS. The adsorption experiments of cesium by the cells under resting condition were also conducted to test the effect of cells metabolic activity. Without mineral in the medium, cells of S. cerevisiae accumulated 1.5x103 Bq/g from the medium containing 137Cs of 2.6x102 Bq/g. When mineral was added in the medium, concentration of 137Cs in the cells decreased. The concentration of 137Cs in the cells from the medium containing different minerals were in the following order; smectite, illite, mica > vermiculite > zeolite. This order was nearly the same as the inverse of distribution coefficient of

  2. Fourth-Order Vibrational Transition State Theory and Chemical Kinetics

    Science.gov (United States)

    Stanton, John F.; Matthews, Devin A.; Gong, Justin Z.

    2015-06-01

    Second-order vibrational perturbation theory (VPT2) is an enormously successful and well-established theory for treating anharmonic effects on the vibrational levels of semi-rigid molecules. Partially as a consequence of the fact that the theory is exact for the Morse potential (which provides an appropriate qualitative model for stretching anharmonicity), VPT2 calculations for such systems with appropriate ab initio potential functions tend to give fundamental and overtone levels that fall within a handful of wavenumbers of experimentally measured positions. As a consequence, the next non-vanishing level of perturbation theory -- VPT4 -- offers only slight improvements over VPT2 and is not practical for most calculations since it requires information about force constants up through sextic. However, VPT4 (as well as VPT2) can be used for other applications such as the next vibrational correction to rotational constants (the ``gammas'') and other spectroscopic parameters. In addition, the marriage of VPT with the semi-classical transition state theory of Miller (SCTST) has recently proven to be a powerful and accurate treatment for chemical kinetics. In this talk, VPT4-based SCTST tunneling probabilities and cumulative reaction probabilities are give for the first time for selected low-dimensional model systems. The prospects for VPT4, both practical and intrinsic, will also be discussed.

  3. Some Chemical and Electronic Considerations of Solid State Semiconductor Crystals.

    Science.gov (United States)

    Hinitz, Herman J.

    1986-01-01

    Describes the trend toward the use of electronic instrumentation to monitor and measure various parameters in chemical reactions. Stresses that a knowledge of the operational relationships involved in such instruments is essential for students beginning in science. Discusses electrostatic charges, semiconductor crystals, electronic conductors,…

  4. Chemical reaction rates and non-equilibrium pressure of reacting gas mixtures in the state-to-state approach

    Energy Technology Data Exchange (ETDEWEB)

    Kustova, Elena V., E-mail: e.kustova@spbu.ru [Department of Mathematics and Mechanics, Saint Petersburg State University, 198504 Universitetskiy pr. 28, Saint Petersburg (Russian Federation); Kremer, Gilberto M., E-mail: kremer@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba (Brazil)

    2014-12-05

    Highlights: • State-to-state approach for coupled vibrational relaxation and chemical reactions. • Self-consistent model for rates of non-equilibrium reactions and energy transitions. • In viscous flows mass action law is violated. • Cross coupling between reaction rates and non-equilibrium pressure in viscous flow. • Results allow implementing the state-to-state approach for viscous flow simulations. - Abstract: Viscous gas flows with vibrational relaxation and chemical reactions in the state-to-state approach are analyzed. A modified Chapman–Enskog method is used for the determination of chemical reaction and vibrational transition rates and non-equilibrium pressure. Constitutive equations depend on the thermodynamic forces: velocity divergence and chemical reaction/transition affinity. As an application, N{sub 2} flow with vibrational relaxation across a shock wave is investigated. Two distinct processes occur behind the shock: for small values of the distance the affinity is large and vibrational relaxation is in its initial stage; for large distances the affinity is small and the chemical reaction is in its final stage. The affinity contributes more to the transition rate than the velocity divergence and the effect of these two contributions are more important for small distances from the shock front. For the non-equilibrium pressure, the term associated with the bulk viscosity increases by a small amount the hydrostatic pressure.

  5. Occupational chemical exposures and congenital anomalies: state of the art

    Energy Technology Data Exchange (ETDEWEB)

    Cordier, S. (Centre de Lutte Contre le Cancer Gustave-Roussy, 94 - Villejuif (France)); Goujard, J. (Maternite Baudelocque, 75 - Paris (France))

    1994-01-01

    Several thousands of compounds with a potential reproductive toxicity have been identified in animals, some of them are teratogens. In humans, only a small number of chemicals, administered as drugs, present in the diet, or in the occupational environment are recognized human teratogens. In parallel, about 60% of congenital anomalies have no identified cause and most probably some compounds present in the environment may contribute to certain anomalies. This paper presents a review of published epidemiological studies on the association between occupational exposures and congenital anomalies, focusing more particularly on some groups of compounds or some occupations such as: anaesthetic gases, laboratory work, solvents, pesticides and lead. (authors).

  6. Chemical reaction rates and non-equilibrium pressure of reacting gas mixtures in the state-to-state approach

    Science.gov (United States)

    Kustova, Elena V.; Kremer, Gilberto M.

    2014-12-01

    Viscous gas flows with vibrational relaxation and chemical reactions in the state-to-state approach are analyzed. A modified Chapman-Enskog method is used for the determination of chemical reaction and vibrational transition rates and non-equilibrium pressure. Constitutive equations depend on the thermodynamic forces: velocity divergence and chemical reaction/transition affinity. As an application, N2 flow with vibrational relaxation across a shock wave is investigated. Two distinct processes occur behind the shock: for small values of the distance the affinity is large and vibrational relaxation is in its initial stage; for large distances the affinity is small and the chemical reaction is in its final stage. The affinity contributes more to the transition rate than the velocity divergence and the effect of these two contributions are more important for small distances from the shock front. For the non-equilibrium pressure, the term associated with the bulk viscosity increases by a small amount the hydrostatic pressure.

  7. Cyanobactins from Cyanobacteria: Current Genetic and Chemical State of Knowledge

    Directory of Open Access Journals (Sweden)

    Joana Martins

    2015-11-01

    Full Text Available Cyanobacteria are considered to be one of the most promising sources of new, natural products. Apart from non-ribosomal peptides and polyketides, ribosomally synthesized and post-translationally modified peptides (RiPPs are one of the leading groups of bioactive compounds produced by cyanobacteria. Among these, cyanobactins have sparked attention due to their interesting bioactivities and for their potential to be prospective candidates in the development of drugs. It is assumed that the primary source of cyanobactins is cyanobacteria, although these compounds have also been isolated from marine animals such as ascidians, sponges and mollusks. The aim of this review is to update the current knowledge of cyanobactins, recognized as being produced by cyanobacteria, and to emphasize their genetic clusters and chemical structures as well as their bioactivities, ecological roles and biotechnological potential.

  8. Cyanobactins from Cyanobacteria: Current Genetic and Chemical State of Knowledge.

    Science.gov (United States)

    Martins, Joana; Vasconcelos, Vitor

    2015-11-13

    Cyanobacteria are considered to be one of the most promising sources of new, natural products. Apart from non-ribosomal peptides and polyketides, ribosomally synthesized and post-translationally modified peptides (RiPPs) are one of the leading groups of bioactive compounds produced by cyanobacteria. Among these, cyanobactins have sparked attention due to their interesting bioactivities and for their potential to be prospective candidates in the development of drugs. It is assumed that the primary source of cyanobactins is cyanobacteria, although these compounds have also been isolated from marine animals such as ascidians, sponges and mollusks. The aim of this review is to update the current knowledge of cyanobactins, recognized as being produced by cyanobacteria, and to emphasize their genetic clusters and chemical structures as well as their bioactivities, ecological roles and biotechnological potential.

  9. Characterization of Chemical Suicides in the United States and Its Adverse Impact on Responders and Bystanders

    Directory of Open Access Journals (Sweden)

    Ayana R. Anderson

    2016-11-01

    Full Text Available Introduction: A suicide trend that involves mixing household chemicals to produce hydrogen sulfide or hydrogen cyanide, commonly referred to as a detergent, hydrogen sulfide, or chemical suicide is a continuing problem in the United States (U.S.. Because there is not one database responsible for tracking chemical suicides, the actual number of incidents in the U.S. is unknown. To prevent morbidity and mortality associated with chemical suicides, it is important to characterize the incidents that have occurred in the U.S. Methods: The author analyzed data from 2011-2013 from state health departments participating in the Agency for Toxic Substances and Disease Registry’s National Toxic Substance Incidents Program (NTSIP. NTSIP is a web-based chemical incident surveillance system that tracks the public health consequences (e.g., morbidity, mortality from acute chemical releases. Reporting sources for NTSIP incidents typically include first responders, hospitals, state environmental agencies, and media outlets. To find chemical suicide incidents in NTSIP’s database, the author queried open text fields in the comment, synopsis, and contributing factors variables for potential incidents. Results: Five of the nine states participating in NTSIP reported a total of 22 chemical suicide incidents or attempted suicides during 2011-2013. These states reported a total of 43 victims: 15 suicide victims who died, seven people who attempted suicide but survived, eight responders, and four employees working at a coroner’s office; the remainder were members of the general public. None of the injured responders reported receiving HazMat technician-level training, and none had documented appropriate personal protective equipment. Conclusion: Chemical suicides produce lethal gases that can pose a threat to responders and bystanders. Describing the characteristics of these incidents can help raise awareness among responders and the public about the dangers of

  10. Chemical climatology of the southeastern United States, 1999-2013

    Science.gov (United States)

    Hidy, G. M.; Blanchard, C. L.; Baumann, K.; Edgerton, E.; Tanenbaum, S.; Shaw, S.; Knipping, E.; Tombach, I.; Jansen, J.; Walters, J.

    2014-11-01

    A series of experiments (the Southern Oxidant and Aerosol Study - SOAS) took place in central Alabama in June-July, 2013 as part of the broader Southern Atmosphere Study (SAS). These projects were aimed at studying oxidant photochemistry and formation and impacts of aerosols at a detailed process level in a location where high biogenic organic vapor emissions interact with anthropogenic emissions, and the atmospheric chemistry occurs in a subtropical climate in North America. The majority of the ground-based experiments were located at the Southeastern Aerosol Research and Characterization (SEARCH) Centreville (CTR) site near Brent, Alabama, where extensive, unique aerometric measurements of trace gases and particles and meteorology were made beginning in the early 1990s through 2013. The SEARCH network data permits a characterization of the temporal and spatial context of the SOAS findings. Our earlier analyses of emissions and air quality trends are extended through 2013 to provide a perspective for continued decline in ambient concentrations, and the implications of these changes to regional sulfur oxide, nitrogen-ozone, and carbon chemistry. The narrative supports the SAS program in terms of long-term average chemistry (chemical climatology) and short-term comparisons of early summer average spatial variability across the southeastern US at high temporal (hourly) resolution. The long-term measurements show that the SOAS experiments took place during the second wettest and coolest year in the 2000-2013 period, with lower than average solar radiation. The pollution levels at CTR and other SEARCH sites were the lowest since full measurements began in 1999. Changes in anthropogenic gas and particle emissions between 1999 and 2013 account for the decline in pollutant concentrations at the monitoring sites in the region. The data provide an opportunity to contrast SOAS results with temporally and spatially variable conditions in support of the development of tests

  11. Chemical climatology of the southeastern United States, 1999–2013

    Directory of Open Access Journals (Sweden)

    G. M. Hidy

    2014-06-01

    Full Text Available A series of experiments (the Southern Oxidant and Aerosol Study-SOAS took place in central Alabama in June–July 2013 as part of the broader Southern Atmosphere Study (SAS. These projects were aimed at studying oxidant photochemistry and formation and impacts of aerosols at a detailed process level in a location where high biogenic organic vapor emissions interact with anthropogenic emissions, and the atmospheric chemistry occurs in a subtropical climate in North America. The majority of the ground-based experiments were located at the Southeastern Aerosol Research and Characterization (SEARCH Centreville (CTR site near Brent, Alabama, where extensive, unique aerometric measurements of meteorology, trace gases and particles have been made from the early 1990s through 2013. The SEARCH network data permits a characterization of temporal and spatial context of the SOAS findings. The long-term measurements show that the SOAS experiments took place during the second wettest and coolest year in the 2000–2013 period, with lower than average solar radiation. The pollution levels at CTR and other SEARCH sites were the lowest since full measurements began in 1999. This dataset provides a perspective for the SOAS program in terms of long-term average chemistry (chemical climatology and short-term comparisons of summer average spatial variability across the Southeast at high temporal (hourly resolution. Changes in anthropogenic gas and particle emissions between 1999 and 2013, account for the decline in pollutant concentrations at the monitoring sites in the region. The long-term and short-term data provide an opportunity to contrast SOAS results with temporally and spatially variable conditions in support for the development of tests for the robustness of SOAS findings.

  12. Steady-state properties of a finite system driven by a chemical-potential gradient

    DEFF Research Database (Denmark)

    Andersen, Jørgen Vitting; Mouritsen, Ole G.

    1990-01-01

    A two-dimensional lattice-gas model with repulsive interactions periodically infinite in one dimension and finite in the other is driven into a mass-transporting steady state by asymmetric chemical potentials applied at the open edges. By computer-simulation techniques the steady-state current...

  13. [Relationship among soil enzyme activities, vegetation state, and soil chemical properties of coal cinder yard].

    Science.gov (United States)

    Wang, Youbao; Zhang, Li; Liu, Dengyi

    2003-01-01

    From field investigation and laboratory analysis, the relationships among soil enzyme activities, vegetation state and soil chemical properties of coal cinder yard in thermal power station were studied. The results showed that vegetation on coal cinder yard was distributed in scattered patch mainly with single species of plant, and herbs were the dominant species. At the same time, the activity of three soil enzymes had a stronger relativity to environment conditions, such as vegetation state and soil chemical properties. The sensitivity of three soil enzymes to environmental stress was in order of urease > sucrase > catalase. The relativity of three soil enzymes to environmental factor was in order of sucrase > urease > catalase. Because of urease being the most susceptible enzyme to environmental conditions, and it was marked or utmost marked interrelated with vegetation state and soil chemical properties, urease activity could be used as an indicator for the reclamation of wasteland.

  14. Looking for chemical reaction networks exhibiting a drift along a manifold of marginally stable states.

    Science.gov (United States)

    Brogioli, Doriano

    2013-02-07

    I recently reported some examples of mass-action equations that have a continuous manifold of marginally stable stationary states [Brogioli, D., 2010. Marginally stable chemical systems as precursors of life. Phys. Rev. Lett. 105, 058102; Brogioli, D., 2011. Marginal stability in chemical systems and its relevance in the origin of life. Phys. Rev. E 84, 031931]. The corresponding chemical reaction networks show nonclassical effects, i.e. a violation of the mass-action equations, under the effect of the concentration fluctuations: the chemical system drifts along the marginally stable states. I proposed that this effect is potentially involved in abiogenesis. In the present paper, I analyze the mathematical properties of mass-action equations of marginally stable chemical reaction networks. The marginal stability implies that the mass-action equations obey some conservation law; I show that the mathematical properties of the conserved quantity characterize the motion along the marginally stable stationary state manifold, i.e. they allow to predict if the fluctuations give rise to a random walk or a drift under the effect of concentration fluctuations. Moreover, I show that the presence of the drift along the manifold of marginally stable stationary-states is a critical property, i.e. at least one of the reaction constants must be fine tuned in order to obtain the drift.

  15. Chemical imaging and solid state analysis at compact surfaces using UV imaging

    DEFF Research Database (Denmark)

    Wu, Jian X.; Rehder, Sönke; van den Berg, Frans;

    2014-01-01

    Fast non-destructive multi-wavelength UV imaging together with multivariate image analysis was utilized to visualize distribution of chemical components and their solid state form at compact surfaces. Amorphous and crystalline solid forms of the antidiabetic compound glibenclamide...... and excipients in a non-invasive way, as well as mapping the glibenclamide solid state form. An exploratory data analysis supported the critical evaluation of the mapping results and the selection of model parameters for the chemical mapping. The present study demonstrated that the multi-wavelength UV imaging...

  16. Chemical-state imaging of Li using scanning Auger electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, Nobuyuki, E-mail: ISHIDA.Nobuyuki@nims.go.jp [Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Fujita, Daisuke [Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Advanced Nanocharacterization Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2013-02-15

    Highlights: •Scanning Auger electron microscopy is used to image chemical states of Li. •The combined use of AES and EELS signals for the elemental mapping is powerful. •Distribution corresponding to metallic and oxidized states of Li can be imaged. -- Abstract: The demand for measurement tools to detect Li with high spatial resolution and precise chemical sensitivity is increasing with the spread of lithium-ion batteries (LIBs) for use in a wide range of applications. In this work, scanning Auger electron microscopy (SAM) is used to image chemical states of a partially oxidized Li surface on the basis of the Auger electron spectroscopy (AES) and electron energy loss spectroscopy (EELS) data obtained during an oxidation process of a metal Li. We show that distribution of metallic and oxidized states of Li is clearly imaged by mapping the intensity of the corresponding AES and EELS peaks. Furthermore, a tiny difference in the extent of oxidation can be distinguished by comparing the elemental map of an AES peak with that of an EELS peak owing to the different behaviors of those signals to the chemical states of Li.

  17. SURFACE AND LIGHTNING SOURCES OF NITROGEN OXIDES OVER THE UNITED STATES: MAGNITUDES, CHEMICAL EVOLUTION, AND OUTFLOW

    Science.gov (United States)

    We use observations from two aircraft during the ICARTT campaign over the eastern United States and North Atlantic during summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem) to test current understanding of regional sources, chemical evolution...

  18. Chemical Engineering Education in Japan and the United States: A Perspective (Part 2).

    Science.gov (United States)

    Floyd, Sigmund

    1988-01-01

    Compares graduate chemical engineering education practices of the U.S. and Japan. States that Japanese universities have set time limits on degrees due to industrial hiring practices. Concludes that Japanese graduates are highly trained and uniform. They tend to stay in the same job throughout their career. (MVL)

  19. The chemical state of arsenic in minerals of environmental interest--an XPS and an XAES study.

    Science.gov (United States)

    Atzei, Davide; Da Pelo, Stefania; Elsener, Bernhard; Fantauzzi, Marzia; Frau, Franco; Pierfranco, Lattanzi; Rossi, Antonella

    2003-01-01

    A systematic analytical study using X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) has been carried out to characterize the chemical state of arsenic in complex environmental samples. The conventional approach, which relies on the chemical shift of the core levels As3d, provides ambiguous results in determining the chemical environment of arsenic. A more accurate approach, based on the Auger parameter and on the Wagner (Chemical State) plot, which combines AsLMM kinetic energy and As3d binding energy, was adopted. This novel method for determining the chemical state of arsenic was employed to completely characterize arsenic in complex environmental samples.

  20. Inferring the unobserved chemical state of the atmosphere: idealized data assimilation experiments

    Science.gov (United States)

    Knote, C. J.; Barré, J.; Eckl, M.; Hornbrook, R. S.; Wiedinmyer, C.; Emmons, L. K.; Orlando, J. J.; Tyndall, G. S.; Arellano, A. F.

    2015-12-01

    Chemical data assimilation in numerical models of the atmosphere is a venture into uncharted territory, into a world populated by a vast zoo of chemical compounds with strongly non-linear interactions. Commonly assimilated observations exist for only a selected few of those key gas phase compounds (CO, O3, NO2), and assimilating those in models assuming linearity begs the question of: To what extent we can infer the remainder to create a new state of the atmosphere that is chemically sound and optimal? In our work we present the first systematic investigation of sensitivities that exist between chemical compounds under varying ambient conditions in order to inform scientists on the potential pitfalls when assimilating single/few chemical compounds into complex 3D chemistry transport models. In order to do this, we developed a box-modeling tool (BOXMOX) based on the Kinetic PreProcessor (KPP, http://people.cs.vt.edu/~asandu/Software/Kpp/) in which we can conduct simulations with a suite of 'mechanisms', sets of differential equations describing atmospheric photochemistry. The box modeling approach allows us to sample a large variety of atmospheric conditions (urban, rural, biogenically dominated, biomass burning plumes) to capture the range of chemical conditions that typically exist in the atmosphere. Included in our suite are 'lumped' mechanisms typically used in regional and global chemistry transport models (MOZART, RACM, RADM2, SAPRC99, CB05, CBMZ) as well as the Master Chemical Mechanism (MCM, U. Leeds). We will use an Observing System Simulation Experiment approach with the MCM prediction as 'nature' or 'true' state, assimilating idealized synthetic observations (from MCM) into the different ‚lumped' mechanisms under various environments. Two approaches to estimate the sensitivity of the chemical system will be compared: 1) adjoint: using Jacobians computed by KPP and 2) ensemble: by perturbing emissions, temperature, photolysis rates, entrainment, etc., in

  1. Application and state of development for remote chemical sensors in environmental monitoring: A literature review

    Energy Technology Data Exchange (ETDEWEB)

    Schabron, J.F.; Niss, N.D.; Hart, B.K.

    1991-09-01

    A study was performed on chemical sensor technology currently available and under development. The information was compiled into a format wherein information on the sensors is listed in a comparable manner. An introductory section is provided to illustrate the regulatory environment in which such sensor technology will be used. This information should allow corporations or federal agencies ready access to useful information for the potential licensing of sensor technology for commercial development or specific environmental monitoring operations. Although every attempt was made to identify as many chemical sensors as possible, we recognize that some may be missed inadvertently. The accuracy of the information provided by the various sources regarding the state of development for the various sensors was not verified. Judgments or opinions regarding the actual state of development or utility of these devices are not included in this report. However, we feel that this report accurately reflects the state of the art at the present time.

  2. Application and state of development for remote chemical sensors in environmental monitoring: A literature review

    Energy Technology Data Exchange (ETDEWEB)

    Schabron, J.F.; Niss, N.D.; Hart, B.K.

    1991-09-01

    A study was performed on chemical sensor technology currently available and under development. The information was compiled into a format wherein information on the sensors is listed in a comparable manner. As introductory section is provided to illustrate the regulatory environment in which such sensor technology will be used. This information should allow corporations or federal agencies ready access to useful information for the potential licensing of sensor technology for commercial development or specific environmental monitoring operations. Although every attempt was made to identify as many chemical sensors as possible, we recognize that some may be missed inadvertently. The accuracy of the information provided by the various sources regarding the state of development for the various sensors was not verified. Judgments or opinions regarding the actual state of development or utility of these devices are not included in this report. However, we feel that this report accurately reflects the state of the art at the present time.

  3. Hot QCD equation of state and quark-gluon plasma-- finite quark chemical potential

    CERN Document Server

    Chandra, Vinod

    2008-01-01

    We explore the relevance of a hot QCD equation of state of $O[g^6\\ln(1/g)]$, which has been obtained\\cite{avrn} for non-vanishing quark-chemical potentials to heavy ion collisions. Employing a method proposed in a recent paper \\cite{chandra1}, we use the EOS to determine a host of thermodynamic quantities, the energy density, specific heat, entropy dnesity, and the temperature dependence of screening lengths, with the behaviour of QGP at RHIC and LHC in mind. We also investigate the sensitivity of these observables to the quark chemical potential.

  4. Multi-GPU unsteady 2D flow simulation coupled with a state-to-state chemical kinetics

    Science.gov (United States)

    Tuttafesta, Michele; Pascazio, Giuseppe; Colonna, Gianpiero

    2016-10-01

    In this work we are presenting a GPU version of a CFD code for high enthalpy reacting flow, using the state-to-state approach. In supersonic and hypersonic flows, thermal and chemical non-equilibrium is one of the fundamental aspects that must be taken into account for the accurate characterization of the plasma and state-to-state kinetics is the most accurate approach used for this kind of problems. This model consists in writing a continuity equation for the population of each vibrational level of the molecules in the mixture, determining at the same time the species densities and the distribution of the population in internal levels. An explicit scheme is employed here to integrate the governing equations, so as to exploit the GPU structure and obtain an efficient algorithm. The best performances are obtained for reacting flows in state-to-state approach, reaching speedups of the order of 100, thanks to the use of an operator splitting scheme for the kinetics equations.

  5. Moisture-induced solid state instabilities in α-chymotrypsin and their reduction through chemical glycosylation

    Directory of Open Access Journals (Sweden)

    Solá Ricardo J

    2010-08-01

    Full Text Available Abstract Background Protein instability remains the main factor limiting the development of protein therapeutics. The fragile nature (structurally and chemically of proteins makes them susceptible to detrimental events during processing, storage, and delivery. To overcome this, proteins are often formulated in the solid-state which combines superior stability properties with reduced operational costs. Nevertheless, solid protein pharmaceuticals can also suffer from instability problems due to moisture sorption. Chemical protein glycosylation has evolved into an important tool to overcome several instability issues associated with proteins. Herein, we employed chemical glycosylation to stabilize a solid-state protein formulation against moisture-induced deterioration in the lyophilized state. Results First, we investigated the consequences of moisture sorption on the stability and structural conformation of the model enzyme α-chymotrypsin (α-CT under controlled humidity conditions. Results showed that α-CT aggregates and inactivates as a function of increased relative humidity (RH. Furthermore, α-CT loses its native secondary and tertiary structure rapidly at increasing RH. In addition, H/D exchange studies revealed that α-CT structural dynamics increased at increasing RH. The magnitude of the structural changes in tendency parallels the solid-state instability data (i.e., formation of buffer-insoluble aggregates, inactivation, and loss of native conformation upon reconstitution. To determine if these moisture-induced instability issues could be ameliorated by chemical glycosylation we proceeded to modify our model protein with chemically activated glycans of differing lengths (lactose and dextran (10 kDa. The various glycoconjugates showed a marked decrease in aggregation and an increase in residual activity after incubation. These stabilization effects were found to be independent of the glycan size. Conclusion Water sorption leads to

  6. Oxygen reduction reaction over silver particles with various morphologies and surface chemical states

    Science.gov (United States)

    Ohyama, Junya; Okata, Yui; Watabe, Noriyuki; Katagiri, Makoto; Nakamura, Ayaka; Arikawa, Hidekazu; Shimizu, Ken-ichi; Takeguchi, Tatsuya; Ueda, Wataru; Satsuma, Atsushi

    2014-01-01

    The oxygen reduction reaction (ORR) in an alkaline solution was carried out using Ag powders having various particle morphologies and surface chemical states (Size: ca. 40-110 nm in crystalline size. Shape: spherical, worm like, and angular. Surface: smooth with easily reduced AgOx, defective with AgOx, and Ag2CO3 surface layer). The various Ag powders were well characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and stripping voltammetry of underpotential-deposited lead. Defective and oxidized surfaces enhanced the Ag active surface area during the ORR. The ORR activity was affected by the morphology and surface chemical state: Ag particles with defective and angular surfaces showed smaller electron exchange number between three and four but showed higher specific activity compared to Ag particles with smooth surfaces.

  7. Chemical state analysis of conversion coatings by SR-XPS and TEY-XANES

    CERN Document Server

    Noro, H; Nagoshi, M

    2002-01-01

    Chromate coatings on galvanized steel have been studied by Synchrotron Radiation (SR) based techniques that include X-ray Photoelectron Spectroscopy (XPS) and Total-Electron-Yield X-ray Absorption Near Edge Structure (TEY-XANES). Non-destructive depth profiling of the coatings by SR-XPS reveals the enhancement of Cr sup 6 sup + in the outer surface. TEY-XANES spectroscopy based on simple specimen current measurement is demonstrated as an effective technique for analyzing chemical states of conversion coatings on general bulk substrates. The sampling depth of this technique, which exceeds several tens of nanometer, is determined by the penetration length of Auger electrons excited by X-ray and the inelastic mean free path of secondary electrons excited by inelastically scattered Auger electrons. The chemical states of phosphoric acid added chromate coatings are studied using this technique. The phosphoric acid is taken into the chromate coatings as partially changed into zinc and chromium phosphates, and the r...

  8. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  9. Application of Photocured Polymer Ion Selective Membranes for Solid-State Chemical Sensors

    Directory of Open Access Journals (Sweden)

    Natalia Abramova

    2015-06-01

    Full Text Available Application of conducting polymers with additional functional groups for a solid contact formation and photocurable membranes as sensitive elements of solid-state chemical sensors is discussed. Problems associated with application of UV-curable polymers for sensors are analyzed. A method of sensor fabrication using copolymerized conductive layer and sensitive membrane is presented and the proof of concept is confirmed by two examples of solid-contact electrodes for Ca ions and pH.

  10. Development of an Electrolyte CPA Equation of state for Applications in the Petroleum and Chemical Industries

    DEFF Research Database (Denmark)

    Maribo-Mogensen, Bjørn

    This thesis extends the Cubic Plus Association (CPA) equation of state (EoS) to handle mixtures containing ions from fully dissociated salts. The CPA EoS has during the past 18 years been applied to thermodynamic modeling of a wide range of industrially important chemicals, mainly in relation...... to provide sufficient driving forces for electrolytes towards the most polar phase. The static permittivity of the mixture was found to be the most important property; yet it was shown that the empirical models suggested by literature could lead to unphysical behavior of the equation of state. A new...

  11. Soft Sensor for Inputs and Parameters Using Nonlinear Singular State Observer in Chemical Processes

    Institute of Scientific and Technical Information of China (English)

    许锋; 汪晔晔; 罗雄麟

    2013-01-01

    Chemical processes are usually nonlinear singular systems. In this study, a soft sensor using nonlinear singular state observer is established for unknown inputs and uncertain model parameters in chemical processes, which are augmented as state variables. Based on the observability of the singular system, this paper presents a simplified observability criterion under certain conditions for unknown inputs and uncertain model parameters. When the observability is satisfied, the unknown inputs and the uncertain model parameters are estimated online by the soft sensor using augmented nonlinear singular state observer. The riser reactor of fluid catalytic cracking unit is used as an example for analysis and simulation. With the catalyst circulation rate as the only unknown input without model error, one temperature sensor at the riser reactor outlet will ensure the correct estimation for the catalyst cir-culation rate. However, when uncertain model parameters also exist, additional temperature sensors must be used to ensure correct estimation for unknown inputs and uncertain model parameters of chemical processes.

  12. Experiments on bifurcation of periodic states into tori for a periodically forced chemical oscillator

    Science.gov (United States)

    Vance, William; Ross, John

    1988-05-01

    We study experimentally continuous transitions from quasiperiodic to periodic states for a time-periodically forced chemical oscillator. The chemical reaction is the hydration of 2,3-epoxy-1-propanol, and is carried out in a continuous stirred tank reactor (CSTR). Periodic oscillatory states are observed to arise in the autonomous system through supercritical Hopf bifurcations as either the total flow rate or the cooling coil temperature is changed. Under conditions of oscillation for the autonomous system, small-amplitude periodic variation of the total flow rate generates an attracting two-torus from the stable limit cycle. From the experiments we determine the structure of the toroidal flow, stroboscopic phase portraits, and circle maps as a function of the forcing amplitude and period. A continuous transition from the quasiperiodic to a periodic state, in which the two-torus contracts to a closed curve (Neimark-Sacker torus bifurcation), is observed as the forcing amplitude is increased at a constant forcing period, or as the forcing period is changed at a constant moderate forcing amplitude. Qualitative theoretical predictions compare well with the experimental observations. This paper presents the first experimental observation of a Neimark-Sacker torus bifurcation in a forced chemical oscillator system, and relates the bifurcation diagram of the unforced system to that of the forced system.

  13. Emergence of a super-synchronized mobbing state in a large population of coupled chemical oscillators

    Science.gov (United States)

    Ghoshal, Gourab; Muñuzuri, Alberto P.; Pérez-Mercader, Juan

    2016-01-01

    Oscillatory phenomena are ubiquitous in Nature. The ability of a large population of coupled oscillators to synchronize constitutes an important mechanism to express information and establish communication among members. To understand such phenomena, models and experimental realizations of globally coupled oscillators have proven to be invaluable in settings as varied as chemical, biological and physical systems. A variety of rich dynamical behavior has been uncovered, although usually in the context of a single state of synchronization or lack thereof. Through the experimental and numerical study of a large population of discrete chemical oscillators, here we report on the unexpected discovery of a new phenomenon revealing the existence of dynamically distinct synchronized states reflecting different degrees of communication. Specifically, we discover a novel large-amplitude super-synchronized state separated from the conventionally reported synchronized and quiescent states through an unusual sharp jump transition when sampling the strong coupling limit. Our results assume significance for further elucidating globally coherent phenomena, such as in neuropathologies, bacterial cell colonies, social systems and semiconductor lasers.

  14. Chemical States of Lanthanum in Carbonized La2O3-Mo Thermionic Cathode Materials

    Institute of Scientific and Technical Information of China (English)

    王金淑; 周美玲; 王亦曼; 张久兴; 聂祚仁; 左铁镛

    2003-01-01

    The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in-situ X-ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La2O3 in the La2O3-Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG-DTA were taken. The experimental results show that the chemical state of lanthanum changes during heating. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.

  15. Quantum-chemical study of electronically excited states of protolytic forms of vanillic acid

    Science.gov (United States)

    Vusovich, O. V.; Tchaikovskaya, O. N.; Sokolova, I. V.; Vasil'eva, N. Y.

    2015-12-01

    The paper describes an analysis of possible ways of deactivation of electronically excited states of 4-hydroxy- 3-methoxy-benzoic acid (vanillic acid) and its protolytic forms with the use of quantum-chemical methods INDO/S (intermediate neglect of differential overlap with a spectroscopic parameterization) and MEP (molecular electrostatic potential). The ratio of radiative and non-radiative deactivation channels of the electronic excitation energy is established. The rate constants of photophysical processes (internal and intercombination conversions) occurring after the absorption of light in these forms are evaluated.

  16. Understanding the finite state projection and related methods for solving the chemical master equation

    Science.gov (United States)

    Dinh, Khanh N.; Sidje, Roger B.

    2016-06-01

    The finite state projection (FSP) method has enabled us to solve the chemical master equation of some biological models that were considered out of reach not long ago. Since the original FSP method, much effort has gone into transforming it into an adaptive time-stepping algorithm as well as studying its accuracy. Some of the improvements include the multiple time interval FSP, the sliding windows, and most notably the Krylov-FSP approach. Our goal in this tutorial is to give the reader an overview of the current methods that build on the FSP.

  17. Study of Cu-Inhibitor State for Post-Chemical Mechanical Polishing Cleaning

    Science.gov (United States)

    Harada, Ken; Ito, Atsushi; Kawase, Yasuhiro; Suzuki, Toshiyuki; Hara, Makoto; Sakae, Rina; Kimura, Chiharu; Aoki, Hidemitsu

    2011-05-01

    In order to reduce corrosion on the Cu surface in post-chemical mechanical polishing (CMP) cleaning, controlling the state of inhibitor layers is indispensable. In this study, to investigate the behavior of inhibitor layers in the cleaning process, Cu-benzotriazole (BTA) layers on CuOX were analyzed by electrochemical measurements and surface analysis. Electrochemical measurements revealed that Cu(I)-BTA can prevent corrosion more efficiently than Cu(II)-BTA, and surface analysis revealed that the Cu(I)-BTA layer is thin, whereas the Cu(II)-BTA layer is bulky. The Cu(I)-BTA layer is effective in preventing corrosion of the Cu surface.

  18. Ensemble velocity of non-processive molecular motors with multiple chemical states

    CERN Document Server

    Vilfan, Andrej

    2014-01-01

    We study the ensemble velocity of non-processive motor proteins, described with multiple chemical states. In particular, we discuss the velocity as a function of ATP concentration. Even a simple model which neglects the strain-dependence of transition rates, reverse transition rates and nonlinearities in the elasticity can show interesting functional dependencies, which deviate significantly from the frequently assumed Michaelis-Menten form. We discuss how the oder of events in the duty cycle can be inferred from the measured dependence. The model also predicts the possibility of velocity reversal at a certain ATP concentration if the duty cycle contains several conformational changes of opposite directionalities.

  19. Behaviors of optical and chemical state of Nb+ implanted sapphire after annealing

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The behavior of the radiation damage of sapphire crystal, produced by implantation with 380 keV Nb+ ion followed by annealing in a series of steps from 500 to 1100℃C at reducing atmosphere, was investigated in optical absorption and XPS measurements. It is found that the implanted niobium in sapphire is in different local environments with different chemical states after the annealing. The changes in optical density (OD) from the bands, based on the well known F-type centers, show that the annealing behavior of the radiation damage may be divided into different stages due to different mechanisms.

  20. Analytical solution of steady-state equations for chemical reaction networks with bilinear rate laws.

    Science.gov (United States)

    Halász, Adám M; Lai, Hong-Jian; McCabe Pryor, Meghan; Radhakrishnan, Krishnan; Edwards, Jeremy S

    2013-01-01

    True steady states are a rare occurrence in living organisms, yet their knowledge is essential for quasi-steady-state approximations, multistability analysis, and other important tools in the investigation of chemical reaction networks (CRN) used to describe molecular processes on the cellular level. Here, we present an approach that can provide closed form steady-state solutions to complex systems, resulting from CRN with binary reactions and mass-action rate laws. We map the nonlinear algebraic problem of finding steady states onto a linear problem in a higher-dimensional space. We show that the linearized version of the steady-state equations obeys the linear conservation laws of the original CRN. We identify two classes of problems for which complete, minimally parameterized solutions may be obtained using only the machinery of linear systems and a judicious choice of the variables used as free parameters. We exemplify our method, providing explicit formulae, on CRN describing signal initiation of two important types of RTK receptor-ligand systems, VEGF and EGF-ErbB1.

  1. THE IMPACT OF REDUCED AGRICULTURAL CHEMICAL USE ON FOOD: A REVIEW OF THE LITERATURE FOR THE UNITED STATES

    OpenAIRE

    Senauer, Benjamin

    1993-01-01

    Concerns about food safety and environmental quality have increased in recent years. Consumers are particularly concerned about the health risks posed by pesticide residues in food and the environmental impact of agricultural chemicals. These concerns have stimulated a considerable amount of recent research to assess the effects of reduced agricultural chemical use. This paper focuses on the research in the United States which has examined the impact of reduced agricultural chemical use on fo...

  2. Chemical composition of sage (Salvia officinalis L. essential oil from the Rio de Janeiro State (Brazil

    Directory of Open Access Journals (Sweden)

    A. Porte

    2013-01-01

    Full Text Available The purpose of this study was to investigate the chemical composition of the essential oil from fresh leaves of sage (Salvia officinalis L. from Petrópolis, Rio de Janeiro State, for international trade. The oil was isolated by hydrodistillation in a Clevenger-type apparatus and analyzed through a combination of GC-FID and GC-MS. The yield was 2.3 % on dry basis. Forty-seven constituents were identified according to their chromatographic retention indices and mass spectra, corresponding to 94.90 % of the compounds present. The major constituents of the oil were α-thujone (40.90 %, camphor (26.12 %, α-pinene (5.85 % and β-thujone (5.62 %. The essential oil studied was similar to those found in several European countries and can be a valuable product for the small farmers from the Petrópolis region in Rio de Janeiro State.

  3. What do molecules do when we are not looking? State sequence analysis for stochastic chemical systems.

    Science.gov (United States)

    Levin, Pavel; Lefebvre, Jérémie; Perkins, Theodore J

    2012-12-07

    Many biomolecular systems depend on orderly sequences of chemical transformations or reactions. Yet, the dynamics of single molecules or small-copy-number molecular systems are significantly stochastic. Here, we propose state sequence analysis--a new approach for predicting or visualizing the behaviour of stochastic molecular systems by computing maximum probability state sequences, based on initial conditions or boundary conditions. We demonstrate this approach by analysing the acquisition of drug-resistance mutations in the human immunodeficiency virus genome, which depends on rare events occurring on the time scale of years, and the stochastic opening and closing behaviour of a single sodium ion channel, which occurs on the time scale of milliseconds. In both cases, we find that our approach yields novel insights into the stochastic dynamical behaviour of these systems, including insights that are not correctly reproduced in standard time-discretization approaches to trajectory analysis.

  4. State Space Truncation with Quantified Errors for Accurate Solutions to Discrete Chemical Master Equation.

    Science.gov (United States)

    Cao, Youfang; Terebus, Anna; Liang, Jie

    2016-04-01

    The discrete chemical master equation (dCME) provides a general framework for studying stochasticity in mesoscopic reaction networks. Since its direct solution rapidly becomes intractable due to the increasing size of the state space, truncation of the state space is necessary for solving most dCMEs. It is therefore important to assess the consequences of state space truncations so errors can be quantified and minimized. Here we describe a novel method for state space truncation. By partitioning a reaction network into multiple molecular equivalence groups (MEGs), we truncate the state space by limiting the total molecular copy numbers in each MEG. We further describe a theoretical framework for analysis of the truncation error in the steady-state probability landscape using reflecting boundaries. By aggregating the state space based on the usage of a MEG and constructing an aggregated Markov process, we show that the truncation error of a MEG can be asymptotically bounded by the probability of states on the reflecting boundary of the MEG. Furthermore, truncating states of an arbitrary MEG will not undermine the estimated error of truncating any other MEGs. We then provide an overall error estimate for networks with multiple MEGs. To rapidly determine the appropriate size of an arbitrary MEG, we also introduce an a priori method to estimate the upper bound of its truncation error. This a priori estimate can be rapidly computed from reaction rates of the network, without the need of costly trial solutions of the dCME. As examples, we show results of applying our methods to the four stochastic networks of (1) the birth and death model, (2) the single gene expression model, (3) the genetic toggle switch model, and (4) the phage lambda bistable epigenetic switch model. We demonstrate how truncation errors and steady-state probability landscapes can be computed using different sizes of the MEG(s) and how the results validate our theories. Overall, the novel state space

  5. A Review of Equation of State Models, Chemical Equilibrium Calculations and CERV Code Requirements for SHS Detonation Modelling

    Science.gov (United States)

    2009-10-01

    Beattie - Bridgeman Virial expansion The above equations are suitable for moderate pressures and are usually based on either empirical constants...CR 2010-013 October 2009 A Review of Equation of State Models, Chemical Equilibrium Calculations and CERV Code Requirements for SHS Detonation...Defence R&D Canada. A Review of Equation of State Models, Chemical Equilibrium Calculations and CERV Code Requirements for SHS Detonation

  6. STUDIES ON THE CHEMICAL STRUCTURES OF ACTIVATED CARBON FIBERS BY SOLID STATE NMR

    Institute of Scientific and Technical Information of China (English)

    FURuowen; HuangWenqiang; 等

    1999-01-01

    The solid state C13-NMR spectra of different ACFs from various precursor fibers were recorded in this paper,The effects of activation conditions on chemical structures of ACFs,as well as the changes of chemical structures during carbonization and redox reaction were inverstigated by NMR technique,At same time,the soild state P31-NMR spectra of ACFS are studied.The C13-NMR spectra of ACFs can be divided into six bands that are assigned to methyl and methylene groups,hydroxyl and ether groups.acetal (or methylenedioxy) carbon,graphite-like aromatic carbon structure,phenol,and quinone groups,respectively.Only phosphorous pentoxide exists on ACFs and CFs.Moreover,most of them are stuck over the crystal face but not at the edge of graphite-like micro-crystal.The carbonization and activation conditions affect the C13-NMR spectra of ACFs.The experimental rsults indicate that the redox reaction of ACFs with oxidants greatly consumes C-H group.

  7. Chemical state of mercury and selenium in sewage sludge ash based P-fertilizers.

    Science.gov (United States)

    Vogel, Christian; Krüger, Oliver; Herzel, Hannes; Amidani, Lucia; Adam, Christian

    2016-08-05

    Phosphorus-fertilizers from secondary resources such as sewage sludge ash (SSA) will become more important in the future as they could substitute conventional fertilizers based on the nonrenewable resource phosphate rock. Thermochemical approaches were developed which remove heavy metals from SSA prior to its fertilizer application on farmlands. We analyzed the chemical state of mercury and selenium in SSA before and after thermochemical treatment under different conditions for P-fertilizer production by X-ray absorption near edge structure (XANES) spectroscopy. In some incineration plants the mercury loaded carbon adsorber from off-gas cleaning was collected together with the SSA for waste disposal. SSAs from those plants contained mercury mainly bound to carbon/organic material. The other SSAs contained inorganic mercury compounds which are most probably stabilized in the SSA matrix and were thus not evaporated during incineration. During thermochemical treatment, carbon-bound mercury was removed quantitatively. In contrast, a certain immobile fraction of inorganic mercury compounds remained in thermochemically treated SSA, which were not clearly identified. HgSe might be one of the inorganic compounds, which is supported by results of Se K-edge XANES spectroscopy. Furthermore, the chemical state of selenium in the SSAs was very sensitive to the conditions of the thermochemical treatment.

  8. Synthesis of high surface area nanometer magnesia by solid-state chemical reaction

    Institute of Scientific and Technical Information of China (English)

    GUAN Hongbo; WANG Pei; ZHAO Biying; ZHU Yuexiang; XIE Youchang

    2007-01-01

    Nanometer MgO samples with high surface area,small crystal size and mesoporous texture were synthesized tion process accelerated the sintering of MgO,and MgO with calcining its precursor in flowing dry nitrogen at 520℃ for 4 h.The samples were characterized by X-ray diffraction,N2 adsorption,transmission electron microscopy,thermogravimetry,and differential thermal analysis.The as-prepared MgO was composed of nanocrystals with a size of about 4-5 nm and formed a wormhole-like porous structure.The MgO also had good thermal stability,and its surface areas remained at 357 and 153 m2.g-1 after calcination at 600 and 800℃ for 2 h,respectively.Compared with the MgO sample prepared by the precipitation method,MgO prepared by solid-state chemical reaction has uniform pore size distribution,surface area,and crystal size.The solid-state chemical method has the advantages of low cost,low pollution,and high yield,therefore it appears to be a promising method in the industrial manufacture of nanometer MgO.

  9. Experimental and Quantum-Chemical Study of Electronically Excited States of Protolytic Isovanillin Species

    Science.gov (United States)

    Vusovich, O. V.; Tchaikovskaya, O. N.; Sokolova, I. V.; Vasil'eva, N. Yu.

    2014-05-01

    Methods of electronic spectroscopy and quantum chemistry are used to compare protolytic vanillin and isovanillin species. Three protolytic species: anion, cation, and neutral are distinguished in the ground state of the examined molecules. Vanillin and isovanillin in the ground state in water possess identical spectral characteristics: line positions and intensities in the absorption spectra coincide. Minima of the electrostatic potential demonstrate that the deepest isomer minimum is observed on the carbonyl oxygen atom. However, investigations of the fluorescence spectra show that the radiative properties of isomers differ. An analysis of results of quantum-chemical calculations demonstrate that the long-wavelength ππ* transition in the vanillin absorption spectra is formed due to electron charge transfer from the phenol part of the molecule to oxygen atoms of the methoxy and carbonyl groups, and in the isovanillin absorption spectra, it is formed only on the oxygen atom of the methoxy group. The presence of hydroxyl and carbonyl groups in the structure of the examined molecules leads to the fact that isovanillin in the ground S0 state, the same as vanillin, possesses acidic properties, whereas in the excited S1 state, they possess basic properties. A comparison of the рKа values of aqueous solutions demonstrates that vanillin possesses stronger acidic and basic properties in comparison with isovanillin.

  10. Chemically robust platform for optical solid-state conducting polymer sensor

    Science.gov (United States)

    Holt, A. L.; Bearinger, J. P.; Carter, S. A.

    2006-10-01

    Conjugated polymers are unique materials for use in the development of chemical and biological sensors because of their widely tunable optical and electrical properties that allow them dual functionality as both the sensing element and the signal transducer. Furthermore, as optical photoluminescence based sensors, electroactive polymers are found to exhibit high sensitivity due to the ability of the analyte of interest to quench the photoluminescence of the entire polymer chain. In order to produce a more chemically robust thin film for use as a "solid-state" optical sensor, we succeeded in grafting various poly (3-alkyl-thiophene)s to optically transparent substrates such as glass, quartz, and ITO coated glass. This was accomplished by first grafting a thiophene monomer to the surface then chemically growing the films via oxidative polymerization. XPS studies indicated that each chemical step was accurately understood. The polythiophene growth, unaltered by sonication and tape peeling tests, was uniform across the substrate and could be directed by selective silanization of the substrate. Film thicknesses range from 20 to 200 nm and exhibit varying degrees of surface roughness, depending on the polymerization process. The reaction times and solvents were varied in order to optimize the desired film properties. The absorption and photoluminescence properties of the thin films compared well with literature on spun-cast polythiophene films, as did the electrical conductivities of the doped and undoped material. The photoluminescence intensities of the films are found to be unaffected by paraquat in water but are sensitive to trace amounts of ferric chloride in acetonitrile with measurable Stern Volmer constants.

  11. Transmission coefficients for chemical reactions with multiple states: role of quantum decoherence.

    Science.gov (United States)

    de la Lande, Aurélien; Řezáč, Jan; Lévy, Bernard; Sanders, Barry C; Salahub, Dennis R

    2011-03-23

    Transition-state theory (TST) is a widely accepted paradigm for rationalizing the kinetics of chemical reactions involving one potential energy surface (PES). Multiple PES reaction rate constants can also be estimated within semiclassical approaches provided the hopping probability between the quantum states is taken into account when determining the transmission coefficient. In the Marcus theory of electron transfer, this hopping probability was historically calculated with models such as Landau-Zener theory. Although the hopping probability is intimately related to the question of the transition from the fully quantum to the semiclassical description, this issue is not adequately handled in physicochemical models commonly in use. In particular, quantum nuclear effects such as decoherence or dephasing are not present in the rate constant expressions. Retaining the convenient semiclassical picture, we include these effects through the introduction of a phenomenological quantum decoherence function. A simple modification to the usual TST rate constant expression is proposed: in addition to the electronic coupling, a characteristic decoherence time τ(dec) now also appears as a key parameter of the rate constant. This new parameter captures the idea that molecular systems, although intrinsically obeying quantum mechanical laws, behave semiclassically after a finite but nonzero amount of time (τ(dec)). This new degree of freedom allows a fresh look at the underlying physics of chemical reactions involving more than one quantum state. The ability of the proposed formula to describe the main physical lines of the phenomenon is confirmed by comparison with results obtained from density functional theory molecular dynamics simulations for a triplet to singlet transition within a copper dioxygen adduct relevant to the question of dioxygen activation by copper monooxygenases.

  12. Methods used to characterize the chemical composition and biological activity of environmental waters throughout the United States, 2012-14

    Science.gov (United States)

    Romanok, Kristin M.; Reilly, Timothy J.; Barber, Larry B.; Boone, J. Scott; Buxton, Herbert T.; Foreman, William T.; Furlong, Edward T.; Hladik, Michelle; Iwanowicz, Luke R.; Journey, Celeste; Kolpin, Dana W.; Kuivila, Kathryn; Loftin, Keith A.; Mills, Marc A.; Meyer, Michael T.; Orlando, James L.; Smalling, Kelly L.; Villeneuve, Daniel L.; Bradley, Paul M.

    2017-03-22

    A vast array of chemical compounds are in wide commercial use in the United States, and the potential ecological and human-health effect of exposure to chemical mixtures has been identified as a high priority in environment health science. Awareness of the potential effects of low-level chemical exposures is rising. The U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, conducted a study in which samples were collected from 38 streams in 25 States to provide an overview of contaminants found in stream water across the Nation. Additionally, biological screening assays were used to help determine any potential ecological and human-health effects of these chemical mixtures and to prioritize target chemicals for future toxicological studies. This report describes the site locations and the sampling and analytical methods and quality-assurance procedures used in the study.

  13. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR

    Science.gov (United States)

    Vacchi, Isabella A.; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-01

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO.Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by

  14. Matching Element Symbols with State Abbreviations: A Fun Activity for Browsing the Periodic Table of Chemical Elements

    Science.gov (United States)

    Woelk, Klaus

    2009-01-01

    A classroom activity is presented in which students are challenged to find matches between the United States two-letter postal abbreviations for states and chemical element symbols. The activity aims to lessen negative apprehensions students might have when the periodic table of the elements with its more than 100 combinations of letters is first…

  15. Research on the chemical adsorption precursor state of CaCl2-NH3 for adsorption refrigeration

    Institute of Scientific and Technical Information of China (English)

    WANG; Liwei; WANG; Ruzhu; WU; Jingyi; WANG; Kai

    2005-01-01

    As a type of chemical adsorption working pair, the physical adsorption occurs first for CaCl2-NH3 because the effective reaction distance for van der Waals force is longer than that for chemical reaction force, and this physical adsorption state is named the precursor state of chemical adsorption. In order to get the different precursor states of CaCl2-NH3, the different distances between NH3 gas and Ca2+ are realized by the control of different phenomena of swelling and agglomeration in the process of adsorption. When the serious swelling exists while the agglomeration does not exist in the process of adsorption, experimental results show that the activated energy consumed by adsorption reaction increases for the reason of longer distance between Ca2+ and NH3, and at the same time the performance attenuation occurs in the repeated adsorption cycles. When the agglomeration occurs in the process of adsorption, the activated energy for the transition from precursor state to chemical adsorption decreases because the distance between NH3 gas and Ca2+ is shortened by the limited expansion space of adsorbent, and at the same time the performance attenuation does not occur. The adsorption refrigeration isobars are researched by the precursor state of chemical adsorption; results also show that the precursor state is a key factor for isobaric adsorption performance while the distribution of Ca2+ does not influence the permeation of NH3 gas in adsorbent.

  16. Chemical fingerprinting of whitewares from Nanwa site of the Chinese Erlitou state

    Energy Technology Data Exchange (ETDEWEB)

    Li Baoping [Centre for Microscopy and Microanalysis, University of Queensland, QLD 4072 (Australia)], E-mail: b.li@uq.edu.au; Liu Li [Archaeology Program, La Trobe University, Melbourne, VIC 3086 (Australia); Zhao Jianxin [Centre for Microscopy and Microanalysis, University of Queensland, QLD 4072 (Australia); Chen Xingcan [Institute of Archaeology, Chinese Academy of Social Sciences, Beijing 100710 (China); Feng Yuexing [Centre for Microscopy and Microanalysis, University of Queensland, QLD 4072 (Australia); Han Guohe; Zhu Junxiao [Department of Archaeology, Zhengzhou University, Zhengzhou 450052 (China)

    2008-06-15

    Whitewares are among the most significant finds from Erlitou, China's earliest state (c. 1900-1500 BC). They were primarily discovered in small numbers from elite tombs of a few sites, leading to the hypothesis that they were made at only a few places and then circulated as prestige items. Recent archaeological work indicates Nanwa may be a whiteware production site. To facilitate determining provenances, we compare the ICP-MS trace elements and TIMS Sr isotopes of Nanwa whitewares with those from Tang dynasty (618-907 AD) Gongxian kilns and Song dynasty (960-1279 AD) Ding kilns. Although all were made of white-firing kaolinic clays, each of the three groups shows a different chemical composition. Furthermore, samples from Nanwa are chemically consistent and restricted in a way analogous to those from Gongxian and Ding, implying that Nanwa whiteware was probably produced in situ. In addition, Gongxian and Ding samples define two separate linear arrays in their {sup 87}Rb/{sup 86}Sr versus {sup 87}Sr/{sup 86}Sr ratios, demonstrating that the clays for these samples are respectively related geochemically. Nanwa samples fall out of the linear arrays of both Gongxian and Ding, indicating that Nanwa whiteware clays were not derived from the same source rock as Gongxian clays, although the two sites are only some 25.5 km apart. In sum, beyond the general similarity of kaolinic clays used at Nanwa, Gongxian and Ding and the geographical proximity of those sites, finer distinctions of elemental and Sr isotopic contents indicate relatively unique chemical characteristics for each group. These traits provide valuable criteria to source traded ceramics of uncertain origins.

  17. Effects of temperature and relative humidity on the solid-state chemical stability of ranitidine hydrochloride.

    Science.gov (United States)

    Teraoka, R; Otsuka, M; Matsuda, Y

    1993-06-01

    The chemical stability of ranitidine HCl in solution and in the solid state at various temperatures was investigated by high-performance liquid chromatography. Ranitidine HCl was unstable in lower pH buffer solutions, and the percent degradation after 72 h increased as the pH of the buffer solution was reduced. The percent degradation in the unbuffered solution increased dose dependently. The critical relative humidity (CRH) of the ranitidine HCl bulk powder was approximately 67% relative humidity (RH). The amount of water adsorbed onto the sample above the CRH was proportional to the RH level. The percent degradation of the powder below 50% RH was almost negligible because, at this level, it was a solid. The percent degradation at 60-70% RH was higher than that above 70% RH. Ranitidine HCl powder was unstable around the CRH.

  18. Interface chemical states of NiO/NiFe films and their effects on magnetic properties

    Institute of Scientific and Technical Information of China (English)

    于广华; 柴春林; 朱逢吾; 赖武彦

    2002-01-01

    Ta/NiOx/Ni81Fe19/Ta multilayers were prepared by rf reactive and dc magnetron sputtering.The exchange coupling field (Hex) and the coercivity (Hc) of NiOx/Ni81Fe19 as a function of the ratio of Ar to O2 during the deposition process were studied.The composition and chemical states at the interface region of NiOx/NiFe were also investigated using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique.The results show that the ratio of Ar to O2 has great effect on the nickel chemical states in NiOx film.When the ratio of Ar to O2 is equal to 7 and the argon sputtering pressure is 0.57 Pa,the x value is approximately 1 and the valence of nickel is +2.At this point,NiOx is antiferromagnetic NiO and the corresponding Hex is the largest.As the ratio of Ar/O2 deviates from 7,the exchange coupling field (Hex) will decrease due to the presence of magnetic impurities such as Ni+3 or metallic Ni at the interface region of NiOx/NiFe,while the coercivity (Hc) will increase due to the metallic Ni.XPS studies also show that there are two thermodynamically favorable reactions at the NiO/NiFe interface: NiO+Fe=Ni+FeO and 3NiO+2Fe=3Ni+Fe2O3.These interface reaction products are magnetic impurities at the interface region of NiO/NiFe.It is believed that these magnetic impurities would have effect on the exchange coupling field (Hex) and the coercivity (Hc) of NiO/NiFe.

  19. Pool chemical-associated health events in public and residential settings - United States, 2003-2012, and Minnesota, 2013.

    Science.gov (United States)

    Hlavsa, Michele C; Robinson, Trisha J; Collier, Sarah A; Beach, Michael J

    2014-05-16

    Pool chemicals are added to treated recreational water venues (e.g., pools, hot tubs/spas, and interactive fountains) primarily to protect public health by inactivating pathogens and maximizing the effectiveness of disinfection by controlling pH. However, pool chemicals also can cause injuries when handled or stored improperly. To estimate the number of emergency department (ED) visits for injuries associated with pool chemicals in the United States per year during 2003-2012, CDC analyzed data from the U.S. Consumer Product Safety Commission's National Electronic Injury Surveillance System (NEISS). This report summarizes the results of that analysis. In 2012 alone, an estimated 4,876 persons (95% confidence interval [CI] = 2,821-6,930) visited an ED for injuries associated with pool chemicals. Almost half of the patients were aged pool chemical-associated health event that occurred in Minnesota in 2013, which sent seven children and one adult to an ED. An investigation by the Minnesota Department of Health (MDH) determined the cause to be poor monitoring of or response to pool chemistry. Pool chemical-associated health events are preventable. CDC's Model Aquatic Health Code (MAHC) (1) is a resource that state and local agencies can use to optimize prevention of injuries and illnesses associated with public treated recreational water venues, including pool chemical-associated health events.

  20. Quantitative Chemical Analysis of Slag Ash of Novocherkassk State District Power Plant

    Directory of Open Access Journals (Sweden)

    Tatyana Germanovna Korotkova

    2017-02-01

    Full Text Available Quantitative chemical composition of ash and slag mix generated upon combustion of Donetsk culm is determined. It is established that ash and slag mix of Novocherkassk state district power plant (SDPP (Rostov region, Russia after coal combustion has the following composition: iron – 2.3%; mineral constituents – 75.8%; calcium oxide – 20.4%; aluminum oxide – 0.0118%; water – 1.3022%; manganese oxide – 0.18%; copper oxide – 0.0043%; plumbum – 0.0017%; it is qualified as hazard class IV for environment. Cadmium, mercury, arsenic, selenium, antimony, bismuth are contained in trace amounts < 0.1 mg/kg. In order to reduce dust emissions the cleaning stage I of gas scrubbing facility is equipped with group cyclone comprised of four cyclone units. Medium and coarse particles under the action of centrifugal force are deposited in the cyclone. This promoted decrease in dust load on bag filters, the cleaning stage II. Qualitative chemical composition of ash captured by group cyclone and that of ash captured by bag filter are determined. Cadmium, copper, plumbum, zinc, iron, manganese, and calcium are contained in coarse and fine particles captured by group cyclone and bag filter. Aluminum referred to light metals is completely captured by cyclone. The ash dust in its bulk is of dark gray color. The ash captured by cyclone contains coarse particles of black color and the ash captured bag filter contains fine particles of light colors (gray-yellow color producing silky gloss. This is characteristic for ash dust after combustion of Donetsk culm. The main component of the ash is silicon dioxide, its content in the ash captured by filter reaches 91%. These fine particles create light tone of this ash.

  1. Chemical and non-chemical s tressors affecting childhood obesity: a state-of-the-science-review

    Science.gov (United States)

    Childhood obesity has tripled in the last three decades and now affects 17% of children in the United States (US). In 2010, the percentage of obese children in the US was nearly 18% for both 6-11 and 12-19 years of age. Recent evidence in the literature suggests that exposure to ...

  2. Predicting the redox state and secondary structure of cysteine residues using multi-dimensional classification analysis of NMR chemical shifts.

    Science.gov (United States)

    Wang, Ching-Cheng; Lai, Wen-Chung; Chuang, Woei-Jer

    2016-09-01

    A tool for predicting the redox state and secondary structure of cysteine residues using multi-dimensional analyses of different combinations of nuclear magnetic resonance (NMR) chemical shifts has been developed. A data set of cysteine [Formula: see text], (13)C(α), (13)C(β), (1)H(α), (1)H(N), and (15)N(H) chemical shifts was created, classified according to redox state and secondary structure, using a library of 540 re-referenced BioMagResBank (BMRB) entries. Multi-dimensional analyses of three, four, five, and six chemical shifts were used to derive rules for predicting the structural states of cysteine residues. The results from 60 BMRB entries containing 122 cysteines showed that four-dimensional analysis of the C(α), C(β), H(α), and N(H) chemical shifts had the highest prediction accuracy of 100 and 95.9 % for the redox state and secondary structure, respectively. The prediction of secondary structure using 3D, 5D, and 6D analyses had the accuracy of ~90 %, suggesting that H(N) and [Formula: see text] chemical shifts may be noisy and made the discrimination worse. A web server (6DCSi) was established to enable users to submit NMR chemical shifts, either in BMRB or key-in formats, for prediction. 6DCSi displays predictions using sets of 3, 4, 5, and 6 chemical shifts, which shows their consistency and allows users to draw their own conclusions. This web-based tool can be used to rapidly obtain structural information regarding cysteine residues directly from experimental NMR data.

  3. Chemical Bonding States of TiC Films before and after Hydrogen Ion Irradiation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    TiC films deposited by rf magnetron sputtering followed by Ar+ ion bombardment were irradiated with a hydrogen ion beam. X-ray photoelectron spectroscopy (XPS) was used for characterization of the chemical bonding states of C and Ti elements of the TiC films before and after hydrogen ion irradiation, in order to understand the effect of hydrogen ion irradiation on the films and to study the mechanism of hydrogen resistance of TiC films. Conclusions can be drawn that ion bombardment at moderate energy can cause preferential physical sputtering of carbon atoms from the surface of low atomic number (Z) material. This means that ion beam bombardment leads to the formation of a non-stoichiometric composition of TiC on the surface.TiC films prepared by ion beam mixing have the more excellent characteristic of hydrogen resistance. One important cause, in addition to TiC itself, is that there are many vacant sites in TiC created by ion beam mixing.These defects can easily trap hydrogen and effectively enhance the effect of hydrogen resistance.

  4. Chemical Composition and Disruption of Quorum Sensing Signaling in Geographically Diverse United States Propolis

    Science.gov (United States)

    Savka, Michael A.; Dailey, Lucas; Popova, Milena; Mihaylova, Ralitsa; Merritt, Benjamin; Masek, Marissa; Le, Phuong; Nor, Sharifah Radziah Mat; Ahmad, Muhammad; Hudson, André O.; Bankova, Vassya

    2015-01-01

    Propolis or bee glue has been used for centuries for various purposes and is especially important in human health due to many of its biological and pharmacological properties. In this work we showed quorum sensing inhibitory (QSI) activity of ten geographically distinct propolis samples from the United States using the acyl-homoserine lactone- (AHL-) dependent Chromobacterium violaceum strain CV026. Based on GC-MS chemical profiling the propolis samples can be classified into several groups that are as follows: (1) rich in cinnamic acid derivatives, (2) rich in flavonoids, and (3) rich in triterpenes. An in-depth analysis of the propolis from North Carolina led to the isolation and identification of a triterpenic acid that was recently isolated from Hondurian propolis (Central America) and ethyl ether of p-coumaric alcohol not previously identified in bee propolis. QSI activity was also observed in the second group US propolis samples which contained the flavonoid pinocembrin in addition to other flavonoid compounds. The discovery of compounds that are involved in QSI activity has the potential to facilitate studies that may lead to the development of antivirulence therapies that can be complementary and/or alternative treatments against antibiotic resistant bacterial pathogens and/or emerging pathogens that have yet to be identified. PMID:25960752

  5. Rate constants of chemical reactions from semiclassical transition state theory in full and one dimension.

    Science.gov (United States)

    Greene, Samuel M; Shan, Xiao; Clary, David C

    2016-06-28

    Semiclassical Transition State Theory (SCTST), a method for calculating rate constants of chemical reactions, offers gains in computational efficiency relative to more accurate quantum scattering methods. In full-dimensional (FD) SCTST, reaction probabilities are calculated from third and fourth potential derivatives along all vibrational degrees of freedom. However, the computational cost of FD SCTST scales unfavorably with system size, which prohibits its application to larger systems. In this study, the accuracy and efficiency of 1-D SCTST, in which only third and fourth derivatives along the reaction mode are used, are investigated in comparison to those of FD SCTST. Potential derivatives are obtained from numerical ab initio Hessian matrix calculations at the MP2/cc-pVTZ level of theory, and Richardson extrapolation is applied to improve the accuracy of these derivatives. Reaction barriers are calculated at the CCSD(T)/cc-pVTZ level. Results from FD SCTST agree with results from previous theoretical and experimental studies when Richardson extrapolation is applied. Results from our implementation of 1-D SCTST, which uses only 4 single-point MP2/cc-pVTZ energy calculations in addition to those for conventional TST, agree with FD results to within a factor of 5 at 250 K. This degree of agreement and the efficiency of the 1-D method suggest its potential as a means of approximating rate constants for systems too large for existing quantum scattering methods.

  6. Finite state projection based bounds to compare chemical master equation models using single-cell data

    Science.gov (United States)

    Fox, Zachary; Neuert, Gregor; Munsky, Brian

    2016-08-01

    Emerging techniques now allow for precise quantification of distributions of biological molecules in single cells. These rapidly advancing experimental methods have created a need for more rigorous and efficient modeling tools. Here, we derive new bounds on the likelihood that observations of single-cell, single-molecule responses come from a discrete stochastic model, posed in the form of the chemical master equation. These strict upper and lower bounds are based on a finite state projection approach, and they converge monotonically to the exact likelihood value. These bounds allow one to discriminate rigorously between models and with a minimum level of computational effort. In practice, these bounds can be incorporated into stochastic model identification and parameter inference routines, which improve the accuracy and efficiency of endeavors to analyze and predict single-cell behavior. We demonstrate the applicability of our approach using simulated data for three example models as well as for experimental measurements of a time-varying stochastic transcriptional response in yeast.

  7. Octafluorodirhenate(III) Revisited: Solid-State Preparation, Characterization, and Multiconfigurational Quantum Chemical Calculations.

    Science.gov (United States)

    Mariappan Balasekaran, Samundeeswari; Todorova, Tanya K; Pham, Chien Thang; Hartmann, Thomas; Abram, Ulrich; Sattelberger, Alfred P; Poineau, Frederic

    2016-06-01

    A simple method for the high-yield preparation of (NH4)2[Re2F8]·2H2O has been developed that involves the reaction of (n-Bu4N)2[Re2Cl8] with molten ammonium bifluoride (NH4HF2). Using this method, the new salt [NH4]2[Re2F8]·2H2O was prepared in ∼90% yield. The product was characterized in solution by ultraviolet-visible light (UV-vis) and (19)F nuclear magnetic resonance ((19)F NMR) spectroscopies and in the solid-state by elemental analysis, powder X-ray diffraction (XRD), and infrared (IR) spectroscopy. Multiconfigurational CASSCF/CASPT2 quantum chemical calculations were performed to investigate the molecular and electronic structure, as well as the electronic absorption spectrum of the [Re2F8](2-) anion. The metal-metal bonding in the Re2(6+) unit was quantified in terms of effective bond order (EBO) and compared to that of its [Re2Cl8](2-) and [Re2Br8](2-) analogues.

  8. Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments.

    Science.gov (United States)

    Stoliker, Deborah L; Campbell, Kate M; Fox, Patricia M; Singer, David M; Kaviani, Nazila; Carey, Minna; Peck, Nicole E; Bargar, John R; Kent, Douglas B; Davis, James A

    2013-08-20

    Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).

  9. Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments

    Science.gov (United States)

    Stoliker, Deborah L.; Campbell, Kate M.; Fox, Patricia M.; Singer, David M.; Kaviani, Nazila; Carey, Minna; Peck, Nicole E.; Barger, John R.; Kent, Douglas B.; Davis, James A.

    2013-01-01

    Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).

  10. Chemical Composition and Disruption of Quorum Sensing Signaling in Geographically Diverse United States Propolis

    Directory of Open Access Journals (Sweden)

    Michael A. Savka

    2015-01-01

    Full Text Available Propolis or bee glue has been used for centuries for various purposes and is especially important in human health due to many of its biological and pharmacological properties. In this work we showed quorum sensing inhibitory (QSI activity of ten geographically distinct propolis samples from the United States using the acyl-homoserine lactone- (AHL- dependent Chromobacterium violaceum strain CV026. Based on GC-MS chemical profiling the propolis samples can be classified into several groups that are as follows: (1 rich in cinnamic acid derivatives, (2 rich in flavonoids, and (3 rich in triterpenes. An in-depth analysis of the propolis from North Carolina led to the isolation and identification of a triterpenic acid that was recently isolated from Hondurian propolis (Central America and ethyl ether of p-coumaric alcohol not previously identified in bee propolis. QSI activity was also observed in the second group US propolis samples which contained the flavonoid pinocembrin in addition to other flavonoid compounds. The discovery of compounds that are involved in QSI activity has the potential to facilitate studies that may lead to the development of antivirulence therapies that can be complementary and/or alternative treatments against antibiotic resistant bacterial pathogens and/or emerging pathogens that have yet to be identified.

  11. Computational analysis of the mechanism of chemical reactions in terms of reaction phases: hidden intermediates and hidden transition States.

    Science.gov (United States)

    Kraka, Elfi; Cremer, Dieter

    2010-05-18

    Computational approaches to understanding chemical reaction mechanisms generally begin by establishing the relative energies of the starting materials, transition state, and products, that is, the stationary points on the potential energy surface of the reaction complex. Examining the intervening species via the intrinsic reaction coordinate (IRC) offers further insight into the fate of the reactants by delineating, step-by-step, the energetics involved along the reaction path between the stationary states. For a detailed analysis of the mechanism and dynamics of a chemical reaction, the reaction path Hamiltonian (RPH) and the united reaction valley approach (URVA) are an efficient combination. The chemical conversion of the reaction complex is reflected by the changes in the reaction path direction t(s) and reaction path curvature k(s), both expressed as a function of the path length s. This information can be used to partition the reaction path, and by this the reaction mechanism, of a chemical reaction into reaction phases describing chemically relevant changes of the reaction complex: (i) a contact phase characterized by van der Waals interactions, (ii) a preparation phase, in which the reactants prepare for the chemical processes, (iii) one or more transition state phases, in which the chemical processes of bond cleavage and bond formation take place, (iv) a product adjustment phase, and (v) a separation phase. In this Account, we examine mechanistic analysis with URVA in detail, focusing on recent theoretical insights (with a variety of reaction types) from our laboratories. Through the utilization of the concept of localized adiabatic vibrational modes that are associated with the internal coordinates, q(n)(s), of the reaction complex, the chemical character of each reaction phase can be identified via the adiabatic curvature coupling coefficients, A(n,s)(s). These quantities reveal whether a local adiabatic vibrational mode supports (A(n,s) > 0) or resists

  12. Chemical-state analysis of organic semiconductors using soft X-ray absorption spectroscopy combined with first-principles calculation.

    Science.gov (United States)

    Natsume, Yutaka; Kohno, Teiichiro; Minakata, Takashi; Konishi, Tokuzo; Gullikson, Eric M; Muramatsu, Yasuji

    2012-02-16

    The chemical states of organic semiconductors were investigated by total-electron-yield soft X-ray absorption spectroscopy (TEY-XAS) and first-principles calculations. The organic semiconductors, pentacene (C(22)H(14)) and pentacenequinone (C(22)H(12)O(2)), were subjected to TEY-XAS and the experimental spectra obtained were compared with the 1s core-level excited spectra of C and O atoms, calculated by a first-principles planewave pseudopotential method. Excellent agreement between the measured and the calculated spectra were obtained for both materials. Using this methodology, we examined the chemical states of the aged pentacene, and confirmed that both C-OH and C═O chemical bonds are generated by exposure to air. This result implies that not only oxygen but also humidity causes pentacene oxidation.

  13. In situ chemical state analysis of buried polymer/metal adhesive interface by hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, Kenichi, E-mail: ozawa.k.ab@m.titech.ac.jp [Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Kakubo, Takashi; Shimizu, Katsunori; Amino, Naoya [The Yokohama Rubber Co., Ltd., Oiwake, Hiratsuka 254-8601 (Japan); Mase, Kazuhiko [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan); Ikenaga, Eiji; Nakamura, Tetsuya; Kinoshita, Toyohiko; Oji, Hiroshi [Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Hyogo 679-5198 (Japan)

    2014-11-30

    Highlights: • Chemical state analysis of the buried rubber/brass interface is conducted by HAXPES. • Ultrathin rubber films are prepared on the brass surface by two methods. • A high density of Cu{sub 2}S is found on the rubber side of the buried adhesive layer. • The chemical states of the buried and exposed interfaces are compared. - Abstract: Chemical state analysis of adhesive interfaces is important to understand an adhesion mechanism between two different materials. Although photoelectron spectroscopy (PES) is an ideal tool for such an analysis, the adhesive interfaces must be exposed to the surface because PES is essentially a surface sensitive technique. However, an in situ observation is possible by hard X-ray PES (HAXPES) owing to its large probing depth. In the present study, HAXPES is applied to investigate the adhesive interface between rubber and brass without exposing the interface. It is demonstrated that copper sulfides formed at the buried rubber/brass interface are distinguished from S-containing species in the rubber overlayer. The chemical state of the buried interface is compared with that of the “exposed” interface prepared by so-called a filter-paper method.

  14. Quantum chemical characterization of low-lying excited states of an aryl peroxycarbonate: mechanistic implications for photodissociation.

    Science.gov (United States)

    Olsen, Seth; Schwarzer, Dirk; Troe, Jürgen; Smith, Sean C

    2010-04-01

    Recent experiments have revealed the existence of an excited state dissociative mechanism for certain peroxycarbonates, with the demonstration that the lifetime of the excited state matches the picosecond time scale for appearance of nascent carbon dioxide product. The data infer that the photoreaction proceeds via an effectively concerted three-body dissociation within the lifetime of the singlet excited state. Many other arylperoxides decay sequentially via [(aryloxy)carbonyl]oxy radical intermediates on nanosecond-microsecond time scales. Uncertainty as to the lifetime of the excited state relates to the character and the relative energetic ordering of states of the parent molecule, since the spectra and photochemistry imply that low-lying states may exist on each of the aryl, carbonate, and peroxide chemical functionalities. We employ many-body electronic structure calculations to determine the energies and characters of the low-lying valence states of a minimal aryl peroxycarbonate model germane to the above-mentioned experiments, methyl phenyl peroxycarbonate (MPC). Our results indicate that the lowest-lying state is an intrinsically nondissociative aryl pipi* excited state. We identify additional low-lying states that are expected to be dissociative in nature and propose that the time scales observed for the dissociation reaction may correspond to the time scale for transfer of excited state population to these states.

  15. The influence of chemical composition and mixing state of Los Angeles urban aerosol on CCN number and cloud properties

    Directory of Open Access Journals (Sweden)

    M. J. Cubison

    2008-03-01

    Full Text Available The relationship between cloud condensation nuclei (CCN number and the physical and chemical properties of the atmospheric aerosol distribution is explored for a polluted urban data set from the Study of Organic Aerosols at Riverside I (SOAR-1 campaign conducted at Riverside, California, USA during summer 2005. The mixing state and, to a lesser degree, the average chemical composition are shown to be important parameters in determining the activation properties of those particles around the critical activation diameters for atmospherically-realistic supersaturation values. Closure between predictions and measurements of CCN number at several supersaturations is attempted by modeling a number of aerosol chemical composition and mixing state schemes of increasing complexity. It is shown that a realistic treatment of the state of mixing of the urban aerosol distribution is critical in order to eliminate model bias. Fresh emissions such as elemental carbon and small organic particles must be treated as non-activating and explicitly accounted for in the model scheme. The relative number concentration of these particles compared to inorganics and oxygenated organic compounds of limited hygroscopicity plays an important role in determining the CCN number. Furthermore, expanding the different composition/mixing state schemes to predictions of cloud droplet number concentration in a cloud parcel model highlights the dependence of cloud optical properties on the state of mixing and hygroscopic properties of the different aerosol modes, but shows that the relative differences between the different schemes are reduced compared to those from the CCN model.

  16. Calculation of Equation of State of QCD at Finite Chemical Potential and Temperature

    Institute of Scientific and Technical Information of China (English)

    QIAO Qing-Peng; ZONG Hong-Shi; TANG Jian; HOU Feng-Yao; LI Xue-Qian; SUN Wei-Min; L(U) Xiao-Fu

    2008-01-01

    In this paper, using path integral techniques we derive a model-independent formula for the pressure density (μ, T) (or equivalently the partition function) of Quantum Chromodynamics (QCD), which gives the equation of state (EOS) of QCD at finite chemical potential and temperature. In this formula the pressure density (μ, T) consists of two terms: the first term (μ,T) T=0) is a #-independent (but T-dependent) constant; the second term is totally determined by G[μ, T] (p ωn) (the dressed quark propagator at finite μ and finite T), which contains all the nontrivial μ-dependence. Then, in the framework of the rainbow-ladder approximation of the Dyson-Schwinger (DS) approach and under the approximation of neglecting the μ-dependence of the dressed gluon propagator, we show that G[μ, T] (p, ωn) can be obtained from G[T] (p, ωn) (the dressed quark propagator at μ = 0) by the substitution ωn →ωn + iμ. This result facilitates numerical calculations considerably. By this result, once G[T](p, ωn) is known, one can determine the EOS of QCD under the above approximations (up to the additive term (μ, T)[T=0). Finally, a comparison of the present EOS of QCD and the EOS obtained in the previous literatures in the framework of the rainbow-ladder approximation of the DS approach is given. It is found that the EOS given in the previous literatures does not satisfy the thermodynamic relation p(μ, T) = T.

  17. Octafluorodirhenate(III) Revisited: Solid-State Preparation, Characterization, and Multiconfigurational Quantum Chemical Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Mariappan Balasekaran, Samundeeswari; Todorova, Tanya K.; Pham, Chien Thang; Hartmann, Thomas; Abram, Ulrich; Sattelberger, Alfred P.; Poineau, Frederic

    2016-06-06

    A simple method for the high-yield preparation of (NH4)2[Re2F8]· 2H2O has been developed that involves the reaction of (n-Bu4N)2[Re2Cl8] with molten ammonium bifluoride (NH4HF2). Using this method, the new salt [NH4]2[Re2F8]·2H2O was prepared in ~90% yield. The product was characterized in solution by ultraviolet-visible light (UV-vis) and 19F nuclear magnetic resonance (19F NMR) spectroscopies and in the solid-state by elemental analysis, powder X-ray diffraction (XRD), and infrared (IR) spectroscopy. Multiconfigurational CASSCF/CASPT2 quantum chemical calculations were performed to investigate the molecular and electronic structure, as well as the electronic absorption spectrum of the [Re2F8] 2- anion. The metal-metal bonding in the Re2 6+ unit was quantified in terms of effective bond order (EBO) and compared to that of its [Re2Cl8] 2- and [Re2Br8] 2- analogues.

  18. Key study on the potential of hydrazine bisborane for solid- and liquid-state chemical hydrogen storage.

    Science.gov (United States)

    Pylypko, Sergii; Petit, Eddy; Yot, Pascal G; Salles, Fabrice; Cretin, Marc; Miele, Philippe; Demirci, Umit B

    2015-05-04

    Hydrazine bisborane N2H4(BH3)2 (HBB; 16.8 wt %) recently re-emerged as a potential hydrogen storage material. However, such potential is controversial: HBB was seen as a hazardous compound up to 2010, but now it would be suitable for hydrogen storage. In this context, we focused on fundamentals of HBB because they are missing in the literature and should help to shed light on its effective potential while taking into consideration any risk. Experimental/computational methods were used to get a complete characterization data sheet, including, e.g., XRD, NMR, FTIR, Raman, TGA, and DSC. From the reported results and discussion, it is concluded that HBB has potential in the field of chemical hydrogen storage given that both thermolytic and hydrolytic dehydrogenations were analyzed. In solid-state chemical hydrogen storage, it cannot be used in the pristine state (risk of explosion during dehydrogenation) but can be used for the synthesis of derivatives with improved dehydrogenation properties. In liquid-state chemical hydrogen storage, it can be studied for room-temperature dehydrogenation, but this requires the development of an active and selective metal-based catalyst. HBB is a thus a candidate for chemical hydrogen storage.

  19. Electronic Structure, Oxidation State of Sn, and Chemical Stability of Photovoltaic Perovskite Variant Cs2SnI6

    CERN Document Server

    Xiao, Zewen; Zhang, Xiao; Zhou, Yuanyuan; Hosono, Hideo; Kamiya, Toshio

    2015-01-01

    Cs2SnI6, a variant of perovskite CsSnI3, is expected for a photovoltaic material. Based on a simple ionic model, it is expected that Cs2SnI6 is composed of Cs+, I-, and Sn4+ ions and that the band gap is primarily made of occupied I- 5p6 valence band maximum (VBM) and unoccupied Sn4+ 5s conduction band minimum (CBM) similar to SnO2. In this work, we performed density functional theory (DFT) calculations and revealed that the real charge state of the Sn ion in this compound is +2 similar to CsSnI3. This is due to strong covalent nature between the I ion and the Sn ion, the VBM consists of I 5p - I 5p antibonding states, and the CBM of I 5p - Sn 5s antibonding states. The +2 oxidation state of Sn is realized by the apparent charge state of I-2/3, because the I 5p - Sn 5s antibonding states form the unoccupied CBM and apparently 1/18 of the I 5p orbitals are unoccupied. These results are further supported by comparing chemical bonding analyses with those of related compounds. The chemical stability of the Cs2SnI...

  20. Biopesticides: State of the Art and Future Opportunities by the American Chemical Society

    Science.gov (United States)

    This chapter from an American Chemical Society symposium reviews areas including how EPA views the benefits of biopesticides, related laws and legal requirements, biopesticide registration, and biopesticide data requirements.

  1. Reversible Diffusion-Limited Reactions: "Chemical Equilibrium" State and the Law of Mass Action Revisited

    OpenAIRE

    Voituriez, R.; Moreau, M.; Oshanin, G.

    2004-01-01

    The validity of two fundamental concepts of classical chemical kinetics - the notion of "Chemical Equilibrium" and the "Law of Mass Action" - are re-examined for reversible \\textit{diffusion-limited} reactions (DLR), as exemplified here by association/dissociation $A+A \\rightleftharpoons B$ reactions. We consider a general model of long-ranged reactions, such that any pair of $A$ particles, separated by distance $\\mu$, may react with probability $\\omega_+(\\mu)$, and any $B$ may dissociate wit...

  2. State of chemical modeling modules for the degradation of concrete and cements

    Energy Technology Data Exchange (ETDEWEB)

    Meike, A.

    1997-04-15

    This report describes the conceptual framework upon which modeling activities will be needed to predict the chemistry of water in contact with concrete and its degradation products cover a broad area, from developing databases for existing abiotic codes, to developing codes that can simulate the chemical impact of microbial activities at a level of sophistication equivalent to that of the abiotic modeling codes, and ultimately, to simulating drift-scale chemical systems in support of hydrological, geochemical,a nd engineering efforts.

  3. The multi-flavor Schwinger model with chemical potential - Overcoming the sign problem with Matrix Product States

    CERN Document Server

    Bañuls, Mari Carmen; Cirac, J Ignacio; Jansen, Karl; Kühn, Stefan; Saito, Hana

    2016-01-01

    During recent years there has been an increasing interest in the application of matrix product states, and more generally tensor networks, to lattice gauge theories. This non-perturbative method is sign problem free and has already been successfully used to compute mass spectra, thermal states and phase diagrams, as well as real-time dynamics for Abelian and non-Abelian gauge models. In previous work we showed the suitability of the method to explore the zero-temperature phase structure of the multi-flavor Schwinger model at non-zero chemical potential, a regime where the conventional Monte Carlo approach suffers from the sign problem. Here we extend our numerical study by looking at the spatially resolved chiral condensate in the massless case. We recover spatial oscillations, similar to the theoretical predictions for the single-flavor case, with a chemical potential dependent frequency and an amplitude approximately given by the homogeneous zero density condensate value.

  4. Excited state properties of the astaxanthin radical cation: A quantum chemical study

    Science.gov (United States)

    Dreuw, Andreas; Starcke, Jan Hendrik; Wachtveitl, Josef

    2010-07-01

    Using time-dependent density functional theory, the excited electronic states of the astaxanthin radical cation (AXT rad + ) are investigated. While the optically allowed excited D 1 and D 3 states are typical ππ∗ excited states, the D 2 and D 4 states are nπ∗ states. Special emphasis is put onto the influence of the carbonyl groups onto the excited states. For this objective, the excited states of four hypothetical carotenoids and zeaxanthin have been computed. Addition of a carbonyl group to a conjugated carbon double bond system does essentially not change the vertical excitation energies of the optically allowed ππ∗ states due to two counter-acting effects: the excitation energy should increase due to the -M-effect of the carbonyl group and at the same time decrease owing to the elongation of the conjugated double bond system by the carbonyl group itself.

  5. Excited state properties of the astaxanthin radical cation: A quantum chemical study

    Energy Technology Data Exchange (ETDEWEB)

    Dreuw, Andreas, E-mail: andreas.dreuw@theochem.uni-frankfurt.de [Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Max von Laue-Str. 7, 60438 Frankfurt am Main (Germany); Starcke, Jan Hendrik; Wachtveitl, Josef [Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Max von Laue-Str. 7, 60438 Frankfurt am Main (Germany)

    2010-07-19

    Using time-dependent density functional theory, the excited electronic states of the astaxanthin radical cation (AXT{sup {center_dot}+}) are investigated. While the optically allowed excited D{sub 1} and D{sub 3} states are typical {pi}{pi}* excited states, the D{sub 2} and D{sub 4} states are n{pi}* states. Special emphasis is put onto the influence of the carbonyl groups onto the excited states. For this objective, the excited states of four hypothetical carotenoids and zeaxanthin have been computed. Addition of a carbonyl group to a conjugated carbon double bond system does essentially not change the vertical excitation energies of the optically allowed {pi}{pi}* states due to two counter-acting effects: the excitation energy should increase due to the -M-effect of the carbonyl group and at the same time decrease owing to the elongation of the conjugated double bond system by the carbonyl group itself.

  6. Molecular perspectives on solid-state phase transformation and chemical reactivity of drugs: metoclopramide as an example.

    Science.gov (United States)

    Lin, Shan-Yang

    2015-02-01

    Here, I provide an overview of the solid-state characteristics, phase transformations and chemical reactions of metoclopramide hydrochloride monohydrate (MCP HCl H2O). Three unique techniques, including thermoanalytical methods, one-step simultaneous differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) microspectroscopy, and hot-stage microscopic (HSM) imaging, have been applied to study the solid-state phase transitions of MCP HCl H2O in continuous dehydration, amorphization and recrystallization processes. I also review the effects of grinding or heating on ion-exchange reactions, milling, compression or colyophilization on Maillard reactions, and γ-ray irradiation or electron beams on radiolysis in the solid state. I also report the exposure of MCP HCl H2O in solution to light, irradiation, oxidants or π-acceptors. This review will serve as a useful keynote for the evolving realm of solid-state chemistry research.

  7. Transition state trajectory stability determines barrier crossing rates in chemical reactions induced by time-dependent oscillating fields

    CERN Document Server

    Craven, Galen T; Hernandez, Rigoberto

    2015-01-01

    When a chemical reaction is driven by an external field, the transition state that the system must pass through as it changes from reactant to product -for example, an energy barrier- becomes time-dependent. We show that for periodic forcing the rate of barrier crossing can be determined through stability analysis of the non-autonomous transition state. Specifically, strong agreement is observed between the difference in the Floquet exponents describing stability of the transition state trajectory, which defines a recrossing-free dividing surface [G. T. Craven, T. Bartsch, and R. Hernandez, Phys. Rev. E 89, 040801(R) (2014)], and the rates calculated by simulation of ensembles of trajectories. This result opens the possibility to extract rates directly from the intrinsic stability of the transition state, even when it is time-dependent, without requiring a numerically-expensive simulation of the long-time dynamics of a large ensemble of trajectories.

  8. Prediction of the Chapman–Jouguet chemical equilibrium state in a detonation wave from first principles based reactive molecular dynamics

    OpenAIRE

    Guo, Dezhou; Zybin, Sergey V.; An, Qi; Goddard, William A.; Huang, Fenglei

    2016-01-01

    The combustion or detonation of reacting materials at high temperature and pressure can be characterized by the Chapman–Jouguet (CJ) state that describes the chemical equilibrium of the products at the end of the reaction zone of the detonation wave for sustained detonation. This provides the critical properties and product kinetics for input to macroscale continuum simulations of energetic materials. We propose the ReaxFF Reactive Dynamics to CJ point protocol (Rx2CJ) for predicting the CJ s...

  9. Mapping the chemical states of an element inside a sample using tomographic x-ray absorption spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Schroer, C G; Kuhlmann, M; Gunzler, T F; Lengeler, B; Richwin, M; Griesebock, B; Lutzenkirchen-Hect, D; Frahm, R; Ziegler, E; Mashayekhi, A; Haeffner, D R; Grunwaldt, J -D; Baiker, A; XFD,

    2003-05-12

    Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near-edge spectra of an elemental species at each location on an arbitrary virtual section through a sample. These spectra reveal the local concentrations of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state, the local atomic structure, and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses.

  10. Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR

    Science.gov (United States)

    Basse, Kristoffer; Shankar, Ravi; Bjerring, Morten; Vosegaard, Thomas; Nielsen, Niels Chr.; Nielsen, Anders B.

    2016-09-01

    We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization (RESPIRATIONCP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer. In this description, it becomes transparent that the main attribute leading to non-ideal performance is a fictitious field along the rf field axis, which is generated from second-order cross terms arising mainly between chemical shift tensors and themselves. This insight is useful for the development of improved recoupling experiments. We discuss the validity of this approach and present quaternion calculations to determine the effective resonance conditions in a combined rf field and chemical shift offset interaction frame transformation. Based on this, we derive a broad-banded version of the RESPIRATIONCP experiment. The new sequence is experimentally verified using SNNFGAILSS amyloid fibrils where simultaneous 15N → 13CO and 15N → 13Cα coherence transfer is demonstrated on high-field NMR instrumentation, requiring great offset stability.

  11. Chemical food safety issues in the United States: past, present, and future.

    Science.gov (United States)

    Jackson, Lauren S

    2009-09-23

    Considerable advances have been made over the past century in the understanding of the chemical hazards in food and ways for assessing and managing these risks. At the turn of the 20th century, many Americans were exposed to foods adulterated with toxic compounds. In the 1920s the increasing use of insecticides led to concerns of chronic ingestion of heavy metals such as lead and arsenic from residues remaining on crops. By the 1930s, a variety of agrochemicals were commonly used, and food additives were becoming common in processed foods. During the 1940s and 1950s advances were made in toxicology, and more systematic approaches were adopted for evaluating the safety of chemical contaminants in food. Modern gas chromatography and liquid chromatography, both invented in the 1950s and 1960s, were responsible for progress in detecting, quantifying, and assessing the risk of food contaminants and adulterants. In recent decades, chemical food safety issues that have been the center of media attention include the presence of natural toxins, processing-produced toxins (e.g., acrylamide, heterocyclic aromatic amines, and furan), food allergens, heavy metals (e.g., lead, arsenic, mercury, cadmium), industrial chemicals (e.g., benzene, perchlorate), contaminants from packaging materials, and unconventional contaminants (melamine) in food and feed. Due to the global nature of the food supply and advances in analytical capabilities, chemical contaminants will continue to be an area of concern for regulatory agencies, the food industry, and consumers in the future.

  12. A regional assessment of chemicals of concern in surface waters of four Midwestern United States national parks.

    Science.gov (United States)

    Elliott, Sarah M; VanderMeulen, David D

    2017-02-01

    Anthropogenic chemicals and their potential for adverse biological effects raise concern for aquatic ecosystem health in protected areas. During 2013-15, surface waters of four Midwestern United States national parks were sampled and analyzed for wastewater indicators, pharmaceuticals, personal care products, and pesticides. More chemicals and higher concentrations were detected at the two parks with greater urban influences (Mississippi National River and Recreation Area and Indiana Dunes National Lakeshore) than at the two more remote parks (Apostle Islands National Lakeshore and Isle Royale National Park). Atrazine (10-15ng/L) and N,N-diethyl-meta-toluamide (16-120ng/L) were the only chemicals detected in inland lakes of a remote island national park (Isle Royale National Park). Bisphenol A and organophosphate flame retardants were commonly detected at the other sampled parks. Gabapentin and simazine had the highest observed concentrations (>1000ng/L) in three and two samples, respectively. At the two parks with urban influences, metolachlor and simazine concentrations were similar to those reported for other major urban rivers in the United States. Environmental concentrations of detected chemicals were often orders of magnitude less than standards or reference values with three exceptions: (1) hydrochlorothiazide exceeded a human health-based screening value in seven samples, (2) estrone exceeded a predicted critical environmental concentration for fish pharmacological effects in one sample, and (3) simazine was approaching the 4000ng/L Maximum Contaminant Level in one sample even though this concentration is not expected to reflect peak pesticide use. Although few environmental concentrations were approaching or exceeded standards or reference values, concentrations were often in ranges reported to elicit effects in aquatic biota. Data from this study will assist in establishing a baseline for chemicals of concern in Midwestern national parks and highlight

  13. A regional assessment of chemicals of concern in surface waters of four Midwestern United States national parks

    Science.gov (United States)

    Elliott, Sarah M.; VanderMeulen, David

    2017-01-01

    Anthropogenic chemicals and their potential for adverse biological effects raise concern for aquatic ecosystem health in protected areas. During 2013–15, surface waters of four Midwestern United States national parks were sampled and analyzed for wastewater indicators, pharmaceuticals, personal care products, and pesticides. More chemicals and higher concentrations were detected at the two parks with greater urban influences (Mississippi National River and Recreation Area and Indiana Dunes National Lakeshore) than at the two more remote parks (Apostle Islands National Lakeshore and Isle Royale National Park). Atrazine (10–15 ng/L) and N,N-diethyl-meta-toluamide (16–120 ng/L) were the only chemicals detected in inland lakes of a remote island national park (Isle Royale National Park). Bisphenol A and organophosphate flame retardants were commonly detected at the other sampled parks. Gabapentin and simazine had the highest observed concentrations (> 1000 ng/L) in three and two samples, respectively. At the two parks with urban influences, metolachlor and simazine concentrations were similar to those reported for other major urban rivers in the United States. Environmental concentrations of detected chemicals were often orders of magnitude less than standards or reference values with three exceptions: (1) hydrochlorothiazide exceeded a human health-based screening value in seven samples, (2) estrone exceeded a predicted critical environmental concentration for fish pharmacological effects in one sample, and (3) simazine was approaching the 4000 ng/L Maximum Contaminant Level in one sample even though this concentration is not expected to reflect peak pesticide use. Although few environmental concentrations were approaching or exceeded standards or reference values, concentrations were often in ranges reported to elicit effects in aquatic biota. Data from this study will assist in establishing a baseline for chemicals of concern in Midwestern national parks and

  14. Chimera and chimera-like states in populations of nonlocally coupled homogeneous and heterogeneous chemical oscillators

    Science.gov (United States)

    Nkomo, Simbarashe; Tinsley, Mark R.; Showalter, Kenneth

    2016-09-01

    Chimera and chimera-like states are characterized in populations of photochemically coupled Belousov-Zhabotinsky (BZ) oscillators. Simple chimeras and chimera states with multiple and traveling phase clusters, phase-slip behavior, and chimera-like states with phase waves are described. Simulations with a realistic model of the discrete BZ system of populations of homogeneous and heterogeneous oscillators are compared with each other and with experimental behavior.

  15. Chemical Reactors.

    Science.gov (United States)

    Kenney, C. N.

    1980-01-01

    Describes a course, including content, reading list, and presentation on chemical reactors at Cambridge University, England. A brief comparison of chemical engineering education between the United States and England is also given. (JN)

  16. Solid-state nanoparticle coated emulsions for encapsulation and improving the chemical stability of all-trans-retinol.

    Science.gov (United States)

    Ghouchi-Eskandar, Nasrin; Simovic, Spomenka; Prestidge, Clive A

    2012-02-28

    Submicron oil-in-water (o/w) emulsions stabilised with conventional surfactants and silica nanoparticles were prepared and freeze-dried to obtain free-flowing powders with good redispersibility and a three-dimensional porous matrix structure. Solid-state emulsions were characterised for visual appearance, particle size distribution, zeta potential and reconstitution properties after freeze-drying with various sugars and at a range of sugar to oil ratios. Comparative degradation kinetics of all-trans-retinol from freeze-dried and liquid emulsions was investigated as a function of storage temperatures. Optimum stability was observed for silica-coated oleylamine emulsions at 4 °C in their wet state. The half-life of all-trans-retinol was 25.66 and 22.08 weeks for silica incorporation from the oil and water phases respectively. This was ∼4 times higher compared to the equivalent solid-state emulsions with drug half-life of 6.18 and 6.06 weeks at 4 °C. Exceptionally, at a storage temperature of 40 °C, the chemical stability of the drug was 3 times higher in the solid-state compared to the wet emulsions which confirmed that freeze-drying is a promising approach to improve the chemical stability of water-labile compounds provided that the storage conditions are optimised.

  17. Chemical imaging of ambient aerosol particles: Observational constraints on mixing state parameterization

    Science.gov (United States)

    O'Brien, Rachel E.; Wang, Bingbing; Laskin, Alexander; Riemer, Nicole; West, Matthew; Zhang, Qi; Sun, Yele; Yu, Xiao-Ying; Alpert, Peter; Knopf, Daniel A.; Gilles, Mary K.; Moffet, Ryan C.

    2015-09-01

    A new parameterization for quantifying the mixing state of aerosol populations has been applied for the first time to samples of ambient particles analyzed using spectro-microscopy techniques. Scanning transmission X-ray microscopy/near edge X-ray absorption fine structure (STXM/NEXAFS) and computer-controlled scanning electron microscopy/energy dispersive X-ray spectroscopy (CCSEM/EDX) were used to probe the composition of the organic and inorganic fraction of individual particles collected on 27 and 28 June during the 2010 Carbonaceous Aerosols and Radiative Effects study in the Central Valley, California. The first field site, T0, was located in downtown Sacramento, while T1 was located near the Sierra Nevada Mountains. Mass estimates of the aerosol particle components were used to calculate mixing state metrics, such as the particle-specific diversity, bulk population diversity, and mixing state index, for each sample. The STXM data showed evidence of changes in the mixing state associated with a buildup of organic matter confirmed by collocated measurements, and the largest impact on the mixing state was due to an increase in soot dominant particles during this buildup. The mixing state from STXM was similar between T0 and T1, indicating that the increased organic fraction at T1 had a small effect on the mixing state of the population. The CCSEM/EDX analysis showed the presence of two types of particle populations: the first was dominated by aged sea-salt particles and had a higher mixing state index (indicating a more homogeneous population); the second was dominated by carbonaceous particles and had a lower mixing state index.

  18. Electrostatic transition state stabilization rather than reactant destabilization provides the chemical basis for efficient chorismate mutase catalysis.

    Science.gov (United States)

    Burschowsky, Daniel; van Eerde, André; Ökvist, Mats; Kienhöfer, Alexander; Kast, Peter; Hilvert, Donald; Krengel, Ute

    2014-12-09

    For more than half a century, transition state theory has provided a useful framework for understanding the origins of enzyme catalysis. As proposed by Pauling, enzymes accelerate chemical reactions by binding transition states tighter than substrates, thereby lowering the activation energy compared with that of the corresponding uncatalyzed process. This paradigm has been challenged for chorismate mutase (CM), a well-characterized metabolic enzyme that catalyzes the rearrangement of chorismate to prephenate. Calculations have predicted the decisive factor in CM catalysis to be ground state destabilization rather than transition state stabilization. Using X-ray crystallography, we show, in contrast, that a sluggish variant of Bacillus subtilis CM, in which a cationic active-site arginine was replaced by a neutral citrulline, is a poor catalyst even though it effectively preorganizes chorismate for the reaction. A series of high-resolution molecular snapshots of the reaction coordinate, including the apo enzyme, and complexes with substrate, transition state analog and product, demonstrate that an active site, which is only complementary in shape to a reactive substrate conformer, is insufficient for effective catalysis. Instead, as with other enzymes, electrostatic stabilization of the CM transition state appears to be crucial for achieving high reaction rates.

  19. Step-Scan FTIR spectroscopy and quantum chemical calculations of xanthone in the triplet state

    Science.gov (United States)

    Buschhaus, L.; Kleinermanns, K.

    2014-10-01

    Step-Scan-FTIR spectroscopy has been used to measure the infrared spectrum of xanthone in the triplet state using chloroform as solvent. Xanthone is an important triplet sensitizer and therefore suitable as model system. Xanthone was excited at 266 nm and its IR triplet spectrum measured in the range 1000-1750 cm-1. The spectrum was analyzed by comparison with DFT/B3LYP/TZVP/COSMO calculations. Further on the results were compared to gas phase IR measurements of triplet xanthone and calculations of isolated xanthone. Mainly based on the calculations we tried to identify the geometry changes from the electronic ground state to the first triplet state.

  20. Physico-chemical characteristics of honey produced by Apis mellifera in the Picos region, state of Piauí, Brazil

    Directory of Open Access Journals (Sweden)

    Geni da Silva Sodré

    2011-08-01

    Full Text Available The objectives of this research were to determine physico-chemical characteristics of 1,758 Apis mellifera L. honey samples produced by in the productive pole of Picos, state of Piauí, to understand, based on these characteristics, how they are grouped and to determine the percentage of honey that fit the specifications determined by Brazilian legislation. Thirty-five honey samples were collected directly from beekeepers for determination of total sugars, reducing sugars, apparent sucrose, humidity, diastase activity, hydroxymethylfurfural (HMF, protein, ash, pH, acidity, formol index, electrical conductivity, viscosity and color. Mean values of each one of the analyzed physico-chemical parameters are within the limits established by the current Brazilian legislation, but it was verified for apparent sacarosis, diastase activity and HMF, values different from the established ones. Protein and HMF were the traits that contributed most for group formation.

  1. Chemical composition of lipids from native and exotic fish in reservoirs of the state of Ceará, Brazil

    Directory of Open Access Journals (Sweden)

    Selene Maia de Morais

    2016-08-01

    Full Text Available Current study analyzes the chemical composition of lipids in fish commonly found in the dams of the state of Ceará, Brazil, namely Pterygoplichthys pardalis (bodó, Hoplias malabaricus (traira, Cichla ocellaris (tucunaré, Prochilodus brevis (curimatã and Oreochomis niloticus (tilapia. The animals were collected during the summer and Folch extraction procedure was used for the extraction of lipids, whilst Iupac methodology (International Union of Pure and Applied Chemistry [Iupac], 1987 was used to methylate the fatty acids. Methyl esters were analyzed by GC/MS and the different components in fish oil were identified. Palmitic acid, C16:0 (35.71-45.02%, was the saturated fatty acid with the highest percentage, while oleic acid, C18:1Δ9 (10.62-25.29% had the highest percentage among the unsaturated fatty acids. The chemical composition of analyzed freshwater fish lipids revealed low levels of polyunsaturated fatty acids.

  2. Chemical Imaging of Ambient Aerosol Particles: Observational Constraints on Mixing State Parameterization

    Energy Technology Data Exchange (ETDEWEB)

    O' Brien, Rachel; Wang, Bingbing; Laskin, Alexander; Riemer, Nicole; West, Matthew; Zhang, Qi; Sun, Yele; Yu, Xiao-Ying; Alpert, Peter A.; Knopf, Daniel A.; Gilles, Mary K.; Moffet, Ryan

    2015-09-28

    A new parameterization for quantifying the mixing state of aerosol populations has been applied for the first time to samples of ambient particles analyzed using spectro-microscopy techniques. Scanning transmission x-ray microscopy/near edge x-ray absorption fine structure (STXM/NEXAFS) and computer controlled scanning electron microscopy/energy dispersive x-ray spectroscopy (CCSEM/EDX) were used to probe the composition of the organic and inorganic fraction of individual particles collected on June 27th and 28th during the 2010 Carbonaceous Aerosols and Radiative Effects (CARES) study in the Central Valley, California. The first field site, T0, was located in downtown Sacramento, while T1 was located near the Sierra Nevada Mountains. Mass estimates of the aerosol particle components were used to calculate mixing state metrics, such as the particle-specific diversity, bulk population diversity, and mixing state index, for each sample. Both microscopy imaging techniques showed more changes over these two days in the mixing state at the T0 site than at the T1 site. The STXM data showed evidence of changes in the mixing state associated with a build-up of organic matter confirmed by collocated measurements and the largest impact on the mixing state was due to an increase in soot dominant particles during this build-up. The CCSEM/EDX analysis showed the presence of two types of particle populations; the first was dominated by aged sea salt particles and had a higher mixing state index (indicating a more homogeneous population), the second was dominated by carbonaceous particles and had a lower mixing state index.

  3. A chemically modified [alpha]-amylase with a molten-globule state has entropically driven enhanced thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, Khawar Sohail; Poljak, Anne; De Francisci, Davide; Guerriero, Gea; Pilak, Oliver; Burg, Dominic; Raftery, Mark J.; Parkin, Don M.; Trewhella, Jill; Cavicchioli, Ricardo (Sydney); (New South)

    2010-11-15

    The thermostability properties of TAA were investigated by chemically modifying carboxyl groups on the surface of the enzyme with AMEs. The TAA{sub MOD} exhibited a 200% improvement in starch-hydrolyzing productivity at 60 C. By studying the kinetic, thermodynamic and biophysical properties, we found that TAA{sub MOD} had formed a thermostable, MG state, in which the unfolding of the tertiary structure preceded that of the secondary structure by at least 20 C. The X-ray crystal structure of TAA{sub MOD} revealed no new permanent interactions (electrostatic or other) resulting from the modification. By deriving thermodynamic activation parameters of TAA{sub MOD}, we rationalised that thermostabilisation have been caused by a decrease in the entropy of the transition state, rather than being enthalpically driven. Far-UV CD shows that the origin of decreased entropy may have arisen from a higher helical content of TAA{sub MOD}. This study provides new insight into the intriguing properties of an MG state resulting from the chemical modification of TAA.

  4. Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

    Science.gov (United States)

    Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

    2016-09-01

    Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η - γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment.

  5. Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

    Science.gov (United States)

    Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

    2016-01-01

    Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η − γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment. PMID:27682811

  6. Temporal variation of chemical and mechanical weathering in NE Iceland: Evaluation of a steady-state model of erosion

    Science.gov (United States)

    Eiriksdottir, E. S.; Louvat, P.; Gislason, S. R.; Óskarsson, N.; Hardardóttir, J.

    2008-07-01

    This study critically assesses the temporal sensitivity of the steady-state model of erosion that has been applied to chemical and mechanical weathering studies of volcanic islands and the continents, using only one sample from each catchment. The model assumes a geochemical mass balance between the initially unweathered rock of a drainage basin and the dissolved and solid loads of the river. Chemical composition of 178 samples of suspended and dissolved inorganic river constituents, collected in 1998-2002, were studied from five basaltic river catchments in NE Iceland. The Hydrological Service in Iceland has monitored the discharge and the total suspended inorganic matter concentration (SIM) of the glacial rivers for ~ four decades, making it possible to compare modelled and measured SIM fluxes. Concentration of SIM and grain size increased with discharge. As proportion of clay size particles in the SIM samples increased, concentrations of insoluble elements increased and of soluble decreased. The highest proportion of altered basaltic glass was in the clay size particles. The concentration ratio of insoluble elements in the SIM was used along with data on chemical composition of unweathered rocks (high-Mg basalts, tholeiites, rhyolites) to calculate the pristine composition of the original catchment rocks. The calculated rhyolite proportions compare nicely with area-weighted average proportions, from geological maps of these catchments. The calculated composition of the unweathered bedrock was used in the steady-state model, together with the chemical composition of the suspended and dissolved constituents of the river. Seasonal changes in dissolved constituent concentrations resulted in too low modelled concentrations of SIM mod at high discharge (and too high SIM mod at low discharge). Samples collected at annual average river dissolved load yielded SIM mod concentrations close to the measured ones. According to the model, the studied rivers had specific

  7. Sulfur and ash reduction potential and selected chemical and physical properties of United States coals. [Contains glossary

    Energy Technology Data Exchange (ETDEWEB)

    Cavallaro, J.A.; Deurbrouck, A.W.; Killmeyer, R.P.; Fuchs, W. (USDOE Pittsburgh Energy Technology Center, PA (USA). Coal Preparation Div.); Jacobsen, P.S. (Burns and Roe Services Corp., Pittsburgh, PA (USA))

    1991-02-01

    This report presents the washability and comprehensive characterization results of 184 raw coal channel samples, including anthracite, bituminous and lignite coals, collected from the Central Region of the United States. This is the second of a three volume report on the coals of the United States. All the data are presented in six appendices. Statistical techniques and definitions are presented in Appendix A, and a glossary of terms is presented in Appendix B. The complete washability data and an in-depth characterization of each sample are presented alphabetically by state in Appendix C. In Appendix D, a statistical evaluation is given for the composited washability data, selected chemical and physical properties and washability data interpolated at various levels of Btu recovery. This presentation is shown by state, section, and region where four or more samples were collected. Appendix E presents coalbed codes and names for the Central Region coals. Graphical summations are presented by state, section and region showing the effects of crushing on impurity reductions, and the distribution of raw and clean coal samples meeting various levels of SO{sub 2} emissions. 35 figs., 5 tabs.

  8. Sulfur and ash reduction potential and selected chemical and physical properties of United States coals. [Contains glossary

    Energy Technology Data Exchange (ETDEWEB)

    Cavallaro, J.A.; Deurbrouck, A.W.; Killmeyer, R.P.; Fuchs, W. (USDOE Pittsburgh Energy Technology Center, PA (USA)); Jacobsen, P.S. (Burns and Roe Services Corp., Pittsburgh, PA (USA))

    1990-01-01

    This report presents the washability and comprehensive characterization results of 543 raw coal samples collected from the Eastern Region of the United States. This is the first volume of a three-volume report on the coals of the United States. All the data are presented in six appendices. Statistical techniques and definitions are presented in Appendix A, and a glossary of terms is presented in Appendix B. The complete washability data and an in- depth characterization of each sample are presented alphbetically by state in Appendix C. In Appendix D, a statistical evaluation is given for the composited washability data, selected chemical and physical properties, and washability data interpolated at various levels of Btu recovery. This presentation is shown by state, section, and region where four or more samples were collected. Appendix E presents coalbed codes and names for the Eastern Region coals. Graphical summations are presented by state, section, and region showing the effects of crushing on impurity reductions, and the distribution of raw and clean coal samples meeting various levels of SO{sub 2} emissions. 14 refs., 27 figs., 3 tabs.

  9. Phytoestrogens in postmenopause: the state of the art from a chemical, pharmacological and regulatory perspective.

    Science.gov (United States)

    Poluzzi, Elisabetta; Piccinni, Carlo; Raschi, Emanuel; Rampa, Angela; Recanatini, Maurizio; De Ponti, Fabrizio

    2014-01-01

    Phytoestrogens represent a diverse group of non-steroidal natural products, which seem to have some oestrogenic effects and are often marketed as food supplements. Population exposed to phytoestrogens is potentially increasing, in part because an unfavourable risk-benefit profile of Hormone Replacement Therapy (HRT) for prolonged treatments (e.g., osteoporosis prevention) highlighted by the publication of the Women Health Initiative (WHI) trial in 2002, but also because many post-menopausal women often perceived phytoestrogens in food supplements as a safer alternative than HRT. Despite of increasing preclinical and clinical studies in the past decade, appealing evidence is still lacking to support the overall positive risk-benefit profile of phytoestrogens. Their status as food supplements seems to discourage studies to obtain new evidence, and the chance to buy them by user's initiative make it difficult to survey their prevalence and pattern of use. The aim of the present review is to: (a) outline the clinical scenario underlying the increased interest on phytoestrogens, by overviewing the evolution of the evidence on HRT and its main therapeutic goals (e.g., menopausal symptoms relief, chemoprevention, osteoporosis prevention); (b) address the chemical and pharmacological features (e.g. chemical structure, botanical sources, mechanism of action) of the main compounds (e.g., isoflavones, lignans, coumestans); (c) describe the clinical evidence on potential therapeutic applications; (d) put available evidence on their riskbenefit profile in a regulatory perspective, in light of the recent regulation on health claims of food supplements.

  10. On the binary helium star DY Centauri: chemical composition and evolutionary state

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Gajendra; Rao, N. Kameswara [Indian Institute of Astrophysics, Bangalore 560034 (India); Jeffery, C. Simon [Armagh Observatory, Collage Hill, Armagh BT61 9DG (United Kingdom); Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: nkrao@iiap.res.in, E-mail: csj@arm.ac.uk, E-mail: dll@astro.as.utexas.edu [The W. J. McDonald Observatory and Department of Astronomy, University of Texas at Austin, Austin, TX 78712-1083 (United States)

    2014-10-01

    DY Cen has shown a steady fading of its visual light by about one magnitude in the last 40 yr, suggesting a secular increase in its effective temperature. We have conducted non-local thermodynamic equilibrium (LTE) and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 yr. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of a He white dwarf with a C-O white dwarf. Thus DY Cen by chemical composition appears to also be a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.

  11. Chemical vapor transport and solid-state exchange synthesis of new copper selenite bromides

    Science.gov (United States)

    Charkin, Dmitri O.; Kayukov, Roman A.; Zagidullin, Karim A.; Siidra, Oleg I.

    2017-02-01

    A new dimorphic copper selenite bromide, Cu5(SeO3)4Br2 was obtained via chemical transport reactions. α-Cu5(SeO3)4Br2, monoclinic (1m) and β-Cu5(SeO3)4Br2, triclinic (1a) polymorphs were produced simultaneously upon reaction of amorphous, partially dehydrated copper selenite and copper bromide. 1m is similar to Cu5(SeO3)4Cl2, whereas 1a is distantly related to Ni5(SeO3)4Br2 and Co5(SeO3)4Br2. Attempts to reproduce synthesis of 1a via exchange reaction between Na2SeO3 and CuBr2 resulted in a new Na2[Cu7O2](SeO3)4Br4 (2). Current study demonstrates for the first time, that both chemical vapor and exchange reactions can be employed in preparation of new selenite halides.

  12. Microsolvated transition state models for improved insight into chemical properties and reaction mechanisms.

    Science.gov (United States)

    Sunoj, Raghavan B; Anand, Megha

    2012-10-05

    Over the years, several methods have been developed to effectively represent the chemical behavior of solutes in solvents. The environmental effects arising due to solvation can generally be achieved either through inclusion of discrete solvent molecules or by inscribing into a cavity in a homogeneous and continuum dielectric medium. In both these approaches of computational origin, the perturbations on the solute induced by the surrounding solvent are at the focus of the problem. While the rigor and method of inclusion of solvent effects vary, such solvation models have found widespread applications, as evident from modern chemical literature. A hybrid method, commonly referred to as cluster-continuum model (CCM), brings together the key advantages of discrete and continuum models. In this perspective, we intend to highlight the latent potential of CCM toward obtaining accurate estimates on a number of properties as well as reactions of contemporary significance. The objective has generally been achieved by choosing illustrative examples from the literature, besides expending efforts to bring out the complementary advantages of CCM as compared to continuum or discrete solvation models. The majority of examples emanate from the prevalent applications of CCM to organic reactions, although a handful of interesting organometallic reactions have also been discussed. In addition, increasingly accurate computations of properties like pK(a) and solvation of ions obtained using the CCM protocol are also presented.

  13. Hyaloperonospora camelinae on Camelina sativa (L.) in Washington State: Detection, seed transmission, and chemical control

    Science.gov (United States)

    Camelina (Camelina sativa [L.] Crantz) plants with symptoms of downy mildew were obtained from three different locations in Washington State. Based on PCR and sequencing of the ITS1-5.8S-ITS2 region, the causal pathogen was identified as Hyaloperonospora camelinae. The PCR primers consistently ampli...

  14. THE BACTERIOLOGICAL AND PHYSICO-CHEMICAL STUDIES ON OLUMIRIN WATERFALL ERIN- IJESHA, OSUN STATE, NIGERIA

    Directory of Open Access Journals (Sweden)

    Oluwakemi Akindolapo

    2011-10-01

    Full Text Available The potability and qualities of Olumirin waterfall, Erin-Ijesa were investigated by determining the total bacteria and coliform count with antibiotic susceptibility of the isolated bacteria and physico-chemical qualities of the water samples. Total bacteria and coliform enumeration were determined using pour plating and multiple tube techniques, the antibiotic susceptibility were carried out using disc diffusion method, while physico-chemical and mineral studies were also carried out using standard methods. The mean total viable count of the water samples ranged 14.8 x 102 CFU.ml-1 - 21.3 x 103 CFU.ml-1 while the coliform count ranged 13 -175 MPN/100ml. The identified bacteria isolates and their percentage distribution were E.coli (43.1%, Klebsiella spp (20.7%, Proteus spp (12.1%, Salmonella spp (6.99%, Pseudomonas spp (5.17%, Shigella spp (6.9%, and Enterococcus spp (5.17 %. Antibiotic resistance shown by bacteria isolates were exhibited as follow; Nalixidic acid (31%, Ampicilin (76%, Cotrimoxazole (60%, Gentamicin (19%, Nitrofurantoin (24%, Colitin (48%, Streptomycin (34% and tetracycline (52%. 82.8% of the isolate exhibited multiple antibiotic resistance. The physico-chemical analysis also revealed the presence of some mineral elements in the water samples. The mineral value of the water samples include; magnesium (84.8 - 93.4 mg.L-1, phosphate (12.6 - 17.1 mg.L-1, sodium (47.8 - 87.6 mg.L-1, potassium (76.6 - 104.5 mg.L-1, chloride (59.0 - 90.2 mg.L-1, zinc (0.75 - 1.82 mg.L-1, lead (0.12 - 0.33 mg.L-1, iron (0.52 - 0.60 mg.L-1, copper (0.12 - 0.27 mg.L-1 while nickel and arsenic were not detected in any of the water samples. Comparing the experimental results with the international water standard for natural water, the waterfall is not fit for consumption or for any domestic purpose unless being treated. Also, problems that may arise from the resistance bacteria strains can be tackled while the new antibiotics can also be developed.

  15. Estimates of agricultural-chemical use in counties in the conterminous United States as reported in the 1987 Census of Agriculture

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This coverage contains estimates of agricultural-chemical use in counties in the conterminous United States as reported in the 1987 Census of Agriculture (U.S....

  16. Chemical and biochemical properties of Araucaria angustifolia (Bert. Ktze. forest soils in the state of São Paulo

    Directory of Open Access Journals (Sweden)

    Fernanda de Carvalho

    2012-08-01

    Full Text Available Araucaria angustifolia, commonly named Araucaria, is a Brazilian native species that is intensively exploited due to its timber quality. Therefore, Araucaria is on the list of species threatened by extinction. Despite the importance of soil for forest production, little is known about the soil properties of the highly fragmented Araucaria forests. This study was designed to investigate the use of chemical and biological properties as indicators of conservation and anthropogenic disturbance of Araucaria forests in different sampling periods. The research was carried out in two State parks of São Paulo: Parque Estadual Turístico do Alto do Ribeira and Parque Estadual de Campos de Jordão. The biochemical properties carbon and nitrogen in microbial biomass (MB-C and MB-N, basal respiration (BR, the metabolic quotient (qCO2 and the following enzyme activities: β-glucosidase, urease, and fluorescein diacetate hydrolysis (FDA were evaluated. The sampling period (dry or rainy season influenced the results of mainly MB-C, MB-N, BR, and qCO2. The chemical and biochemical properties, except K content, were sensitive indicators of differences in the conservation and anthropogenic disturbance stages of Araucaria forests. Although these forests differ in biochemical and chemical properties, they are efficient in energy use and conservation, which is shown by their low qCO2, suggesting an advanced stage of succession.

  17. Determination of chemical elements in africanized Apis mellifera (Hymenoptera: Apidae honey samples from the State of Piauí, Brazil

    Directory of Open Access Journals (Sweden)

    Geni da Silva Sodré

    2007-08-01

    Full Text Available Honey is a food used since the most remote times, appreciated for its characteristic flavor, considerable nutritional value and medicinal properties; however, little information exists about the presence of chemical elements in it. The objectives of this work were to determine the chemical elements present in 38 honey samples, collected directly from beekeepers from the State of Piauí, Brazil and to verify whether they presented any contamination. The chemical elements were determined by means of Total Reflection X-ray Fluorescence. The means of three replicates were: K (109.671 ± 17.487, Ca (14.471 ± 3.8797, Ti (0.112 ± 0.07, Cr (0.196 ± 0.11, Mn (0.493 ± 0.103, Fe (1.722 ± 0.446, Co (0.038, Ni (0.728 ± 0.706, Cu (0.179 ± 0.0471, Zn (0.967 ± 0.653, Se (not detected, Br (not detected, Rb (0.371 ± 0.097, Sr (0.145 ± 0.45, Ba (11.681, Hg (not detected, and Pb (0.863 µg g-1.

  18. Small targeted cytotoxics: current state and promises from DNA-encoded chemical libraries.

    Science.gov (United States)

    Krall, Nikolaus; Scheuermann, Jörg; Neri, Dario

    2013-01-28

    The targeted delivery of potent cytotoxic agents has emerged as a promising strategy for the treatment of cancer and other serious conditions. Traditionally, antibodies against markers of disease have been used as drug-delivery vehicles. More recently, lower molecular weight ligands have been proposed for the generation of a novel class of targeted cytotoxics with improved properties. Advances in this field crucially rely on efficient methods for the identification and optimization of organic molecules capable of high-affinity binding and selective recognition of target proteins. The advent of DNA-encoded chemical libraries allows the construction and screening of compound collections of unprecedented size. In this Review, we survey developments in the field of small ligand-based targeted cytotoxics and show how innovative library technologies will help develop the drugs of the future.

  19. Changes in the chemical structure of polytetrafluoroethylene induced by electron beam irradiation in the molten state

    CERN Document Server

    Lappan, U; Lunkwitz, K

    2000-01-01

    Polytetrafluoroethylene (PTFE) was exposed to electron beam radiation at elevated temperature above the melting point under nitrogen atmosphere and in vacuum for comparison. Fourier-transform infrared (FTIR) spectroscopy was used to study the changes in the chemical structure. The irradiation under nitrogen atmosphere leads to the same structures as described recently for PTFE irradiated in vacuum. Trifluoromethyl branches and double bond structures were detected. The concentrations of terminal and internal double bonds are higher after irradiation under nitrogen than in vacuum. Annealing experiments have shown that the thermal oxidative stability of the radiation-modified PTFE is reduced compared to unirradiated PTFE. The reason are the formation of unstable structures such as double bonds.

  20. High sensitivity detection and characterization of the chemical state of trace element contamination on silicon wafers

    CERN Document Server

    Pianetta, Piero A; Baur, K; Brennan, S; Homma, T; Kubo, N

    2003-01-01

    Increasing the speed and complexity of semiconductor integrated circuits requires advanced processes that put extreme constraints on the level of metal contamination allowed on the surfaces of silicon wafers. Such contamination degrades the performance of the ultrathin SiO sub 2 gate dielectrics that form the heart of the individual transistors. Ultimately, reliability and yield are reduced to levels that must be improved before new processes can be put into production. It should be noted that much of this metal contamination occurs during the wet chemical etching and rinsing steps required for the manufacture of integrated circuits and industry is actively developing new processes that have already brought the metal contamination to levels beyond the measurement capabilities of conventional analytical techniques. The measurement of these extremely low contamination levels has required the use of synchrotron radiation total reflection X-ray fluorescence (SR-TXRF) where sensitivities 100 times better than conv...

  1. (31)P Solid-State NMR study of the chemical setting process of a dual-paste injectable brushite cements.

    Science.gov (United States)

    Legrand, A P; Sfihi, H; Lequeux, N; Lemaître, J

    2009-10-01

    The composition and evolution of a brushite-type calcium phosphate cement was investigated by Solid-State NMR and X-ray during the setting process. The cement is obtained by mixing beta-tricalcium phosphate [Ca(3)(PO(4))(2), beta-TCP] and monocalcium phosphate monohydrate [Ca(H(2)PO(4))(2).H(2)O, MCPM] in presence of water, with formation of dicalcium phosphate dihydrate or brushite [CaHPO(2).2H(2)O, DCPD]. Analysis of the initial beta-TCP paste has shown the presence of beta-calcium pyrophosphate [Ca(2)P(2)O(7), beta-CPy] and that of the initial MCPM a mixture of MCPM and dicalcium phosphate [CaHPO(4), DCP]. Follow-up of the chemical composition by (31)P Solid-State NMR enables to show that the chemical setting process appeared to reach an end after 20 min. The constant composition observed at the end of the process was similarly determined.

  2. Theory of NMR chemical shift in an electronic state with arbitrary degeneracy

    CERN Document Server

    Heuvel, Willem Van den

    2012-01-01

    We present a theory of nuclear magnetic resonance (NMR) shielding tensors for electronic states with arbitrary degeneracy. The shieldings are here expressed in terms of generalized Zeeman ($g^{(k)}$) and hyperfine ($A^{(k)}$) tensors, of all ranks $k$ allowed by the size of degeneracy. Contrary to recent proposals [T. O. Pennanen and J. Vaara, Phys. Rev. Lett. 100, 133002 (2008)], our theory is valid in the strong spin-orbit coupling limit. Ab initio calculations for the 4-fold degenerate $\\Gamma_8$ ground state of lanthanide-doped fluorite crystals CaF$_2$:Ln (Ln = Pr$^{2+}$, Nd$^{3+}$, Sm$^{3+}$, and Dy$^{3+}$) show that previously neglected contributions can account for more than 50% of the paramagnetic shift.

  3. Error sensitivity to environmental noise in quantum circuits for chemical state preparation

    CERN Document Server

    Sawaya, Nicolas P D; McClean, Jarrod R; Aspuru-Guzik, Alán

    2016-01-01

    Calculating molecular energies is likely to be one of the first useful applications to achieve quantum supremacy, performing faster on a quantum than a classical computer. However, if future quantum devices are to produce accurate calculations, errors due to environmental noise and algorithmic approximations need to be characterized and reduced. In this study, we use the high performance qHiPSTER software to investigate the effects of environmental noise on the preparation of quantum chemistry states. We simulate nineteen 16-qubit quantum circuits under environmental noise, each corresponding to a unitary coupled cluster state preparation of a different molecule or molecular configuration. Additionally, we analyze the nature of simple gate errors in noise-free circuits of up to 40 qubits. We find that the Jordan-Wigner (JW) encoding produces consistently smaller errors under a noisy environment as compared to the Bravyi-Kitaev (BK) encoding. For the JW encoding, pure-dephasing noise is shown to produce substa...

  4. Quantum physical states for describing photonic assisted chemical change: I. Torsional phenomenon at femtosecond time scale

    CERN Document Server

    Tapia, O

    2012-01-01

    Femtosecond torsional relaxation processes experimentally detected and recently reported by Clark et al. (Nature Phys. 8,225 (2012)) are theoretically dissected with a Hilbert/Fock quantum physical (QP) framework incorporating entanglement of photon/matter base states overcoming standard semi-classic vibrational descriptions. The quantum analysis of a generic Z/E (cis/trans) isomerization in abstract QP terms shed light to fundamental roles played by photonic spin and excited electronic singlet coupled to triplet states. It is shown that one photon activation cannot elicit femtosecond phenomenon, while a two-photon pulse would do. Estimated time scales for the two-photon case indicate the process to lie between a slower than electronic Franck-Condon-like transition yet faster than (semi-classic) vibration relaxation ones.

  5. State Key Laboratory of Catalysis Dalian Institute of Chemical Physics, China

    Institute of Scientific and Technical Information of China (English)

    Can Li

    2002-01-01

    @@ I. Introduction The State Key Laboratory of Catalysis (SKLC)was founded in 1987 as one of the first state key labo-ratories in China. The current director of the SKLC isProfessor Can Li (the previous directors were Profes-sor Xiexian Guo and Professor Yide Xu). ProfessorLiwu Lin chairs the Academic Committee, which iscomposed of 15 distinguished Chinese catalytic scien-tists. In addition, the SKLC appoints internationallyknown scientists in the field of catalysis to its Inter-national Advisory Committee. There are about 35permanent staff members including professors, tech-nicians, and administrators, over 80 Ph.D. and M.S.graduate students and 10 post-doctoral fellows.

  6. Excited State Properties of Fluorine-Substituted Hexabenzocoronene: A Quantum-Chemical Characterization

    Institute of Scientific and Technical Information of China (English)

    LI Yuan-Zuo; SUN Yu; LI Yong-Qing; MA Feng-Cai

    2006-01-01

    The first fluorine-substituted hexabenzocoronene has been synthesized and its electronic structure and optical properties have been reported [Q. Zhang, et al., Org. Lett.7 (2005) 5019]. In this letter, the electronic structure and excited state properties of the fluorine-substituted hexabenzocoronene are studied with quantum chemistry method as well as the transition and the charge difference densities. The transition densities show the orientations and strength of the dipole moments and the charge difference densities reveal the orientation and results of the intramolecular charge transfer. The calculated transition energies and oscillator strengths are consistent with the experimental data, and the theoretical results of transition and charge difference densities are valuable to understanding the excited state properties of the fluorine-substituted hexabenzocoronene.

  7. Survey of chemical disinfectants used by poultry farmers in Imo state, Nigeria.

    Directory of Open Access Journals (Sweden)

    I.U. Chima

    2011-09-01

    Full Text Available Pathogen contamination can be prevented with aid of proper health care products such as disinfectants. This study was designed to evaluate the efficacy of common disinfectants and disinfection practice of poultry farmers in Imo State, Nigeria, in order to generate information needed for the proper regulation of disinfectant use in the area. Primary data were generated from structured questionnaires distributed to animal health practitioners and poultry farmers in the State. Results showed that farmers choice of disinfectants were dependent on cost and availability. Z-germicide® 10 (22.27% and Izal® with 9 (20.45% are more widely distributed in the various animal health outfits. This was closely followed by Lysol® 6 (13.63% and Diskol® 6 (13.63%. Morigard® 3 (6.81%, Dettol® and Septol® 3 (6.81% appeared each in three outfits. Vox® 1 (2.27% CID 20® 1 (2.27% a Virkon® 1 (2.27% occurred once and that is at the Avian influenza desk officer’s store. Izal® 140 (58.82 was more widely used by farmers followed by Z-germicide®, both of which are phenolic products. Morigad® with 2 (2.94% and Lysol® with 91.47%0 are also phenolic products. Altogether 76.47% of disinfectants used in Imo State were of phenolic products. Most poultry farms in the State did not use disinfectant footbath. Those that used them did not insist on workers or visitors dipping their feet in them before entering the farm house. They also did not reconstitute the disinfectants according to the manufacturer’s instructions.

  8. Integration of Biological Specificity with Solid-State Devices for Selective Chemical Sensing

    Science.gov (United States)

    2016-01-29

    transferred from air into a liquid or hydrogel layer that passes over a bank of aptamer functionalized sensor arrays. Figure 5. A multi-tip nanoscale...see any limitations for the integration of solid-state aptamer sensors with liquid flow cells. We have also investigated the scaling of chemiresistors...complex 3D structure. However, we did not test the aptamer against the ATP target, because the latter requires a liquid solution environment and our

  9. Phase state of ambient aerosol linked with water uptake and chemical aging in the southeastern US

    Science.gov (United States)

    Pajunoja, Aki; Hu, Weiwei; Leong, Yu J.; Taylor, Nathan F.; Miettinen, Pasi; Palm, Brett B.; Mikkonen, Santtu; Collins, Don R.; Jimenez, Jose L.; Virtanen, Annele

    2016-09-01

    During the summer 2013 Southern Aerosol and Oxidant Study (SOAS) field campaign in a rural site in the southeastern United States, the effect of hygroscopicity and composition on the phase state of atmospheric aerosol particles dominated by the organic fraction was studied. The analysis is based on hygroscopicity measurements by a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA), physical phase state investigations by an Aerosol Bounce Instrument (ABI) and composition measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). To study the effect of atmospheric aging on these properties, an OH-radical oxidation flow reactor (OFR) was used to simulate longer atmospheric aging times of up to 3 weeks. Hygroscopicity and bounce behavior of the particles had a clear relationship showing higher bounce at elevated relative humidity (RH) values for less hygroscopic particles, which agrees well with earlier laboratory studies. Additional OH oxidation of the aerosol particles in the OFR increased the O : C and the hygroscopicity resulting in liquefying of the particles at lower RH values. At the highest OH exposures, the inorganic fraction starts to dominate the bounce process due to production of inorganics and concurrent loss of organics in the OFR. Our results indicate that at typical ambient RH and temperature, organic-dominated particles stay mostly liquid in the atmospheric conditions in the southeastern US, but they often turn semisolid when dried below ˜ 50 % RH in the sampling inlets. While the liquid phase state suggests solution behavior and equilibrium partitioning for the SOA particles in ambient air, the possible phase change in the drying process highlights the importance of thoroughly considered sampling techniques of SOA particles.

  10. Level crossing analysis of chemically induced dynamic nuclear polarization: Towards a common description of liquid-state and solid-state cases.

    Science.gov (United States)

    Sosnovsky, Denis V; Jeschke, Gunnar; Matysik, Jörg; Vieth, Hans-Martin; Ivanov, Konstantin L

    2016-04-14

    Chemically Induced Dynamic Nuclear Polarization (CIDNP) is an efficient method of creating non-equilibrium polarization of nuclear spins by using chemical reactions, which have radical pairs as intermediates. The CIDNP effect originates from (i) electron spin-selective recombination of radical pairs and (ii) the dependence of the inter-system crossing rate in radical pairs on the state of magnetic nuclei. The CIDNP effect can be investigated by using Nuclear Magnetic Resonance (NMR) methods. The gain from CIDNP is then two-fold: it allows one to obtain considerable amplification of NMR signals; in addition, it provides a very useful tool for investigating elusive radicals and radical pairs. While the mechanisms of the CIDNP effect in liquids are well established and understood, detailed analysis of solid-state CIDNP mechanisms still remains challenging; likewise a common theoretical frame for the description of CIDNP in both solids and liquids is missing. Difficulties in understanding the spin dynamics that lead to the CIDNP effect in the solid-state case are caused by the anisotropy of spin interactions, which increase the complexity of spin evolution. In this work, we propose to analyze CIDNP in terms of level crossing phenomena, namely, to attribute features in the CIDNP magnetic field dependence to Level Crossings (LCs) and Level Anti-Crossings (LACs) in a radical pair. This approach allows one to describe liquid-state CIDNP; the same holds for the solid-state case where anisotropic interactions play a significant role in CIDNP formation. In solids, features arise predominantly from LACs, since in most cases anisotropic couplings result in perturbations, which turn LCs into LACs. We have interpreted the CIDNP mechanisms in terms of the LC/LAC concept. This consideration allows one to find analytical expressions for a wide magnetic field range, where several different mechanisms are operative; furthermore, the LAC description gives a way to determine CIDNP sign

  11. Level crossing analysis of chemically induced dynamic nuclear polarization: Towards a common description of liquid-state and solid-state cases

    Science.gov (United States)

    Sosnovsky, Denis V.; Jeschke, Gunnar; Matysik, Jörg; Vieth, Hans-Martin; Ivanov, Konstantin L.

    2016-04-01

    Chemically Induced Dynamic Nuclear Polarization (CIDNP) is an efficient method of creating non-equilibrium polarization of nuclear spins by using chemical reactions, which have radical pairs as intermediates. The CIDNP effect originates from (i) electron spin-selective recombination of radical pairs and (ii) the dependence of the inter-system crossing rate in radical pairs on the state of magnetic nuclei. The CIDNP effect can be investigated by using Nuclear Magnetic Resonance (NMR) methods. The gain from CIDNP is then two-fold: it allows one to obtain considerable amplification of NMR signals; in addition, it provides a very useful tool for investigating elusive radicals and radical pairs. While the mechanisms of the CIDNP effect in liquids are well established and understood, detailed analysis of solid-state CIDNP mechanisms still remains challenging; likewise a common theoretical frame for the description of CIDNP in both solids and liquids is missing. Difficulties in understanding the spin dynamics that lead to the CIDNP effect in the solid-state case are caused by the anisotropy of spin interactions, which increase the complexity of spin evolution. In this work, we propose to analyze CIDNP in terms of level crossing phenomena, namely, to attribute features in the CIDNP magnetic field dependence to Level Crossings (LCs) and Level Anti-Crossings (LACs) in a radical pair. This approach allows one to describe liquid-state CIDNP; the same holds for the solid-state case where anisotropic interactions play a significant role in CIDNP formation. In solids, features arise predominantly from LACs, since in most cases anisotropic couplings result in perturbations, which turn LCs into LACs. We have interpreted the CIDNP mechanisms in terms of the LC/LAC concept. This consideration allows one to find analytical expressions for a wide magnetic field range, where several different mechanisms are operative; furthermore, the LAC description gives a way to determine CIDNP sign

  12. Generalized molybdenum oxide surface chemical state XPS determination via informed amorphous sample model

    Energy Technology Data Exchange (ETDEWEB)

    Baltrusaitis, Jonas, E-mail: job314@lehigh.edu [Department of Chemical Engineering, Lehigh University, B336 Iacocca Hall, 111 Research Drive, Bethlehem, PA 18015 (United States); PhotoCatalytic Synthesis group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Meander 229, P.O. Box 217, 7500 AE Enschede (Netherlands); Mendoza-Sanchez, Beatriz [CRANN, Chemistry School, Trinity College Dublin, Dublin (Ireland); Fernandez, Vincent [Institut des Matériaux Jean Rouxel, 2 rue de la Houssinière, BP 32229, F-44322 Nantes Cedex 3 (France); Veenstra, Rick [PhotoCatalytic Synthesis group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Meander 229, P.O. Box 217, 7500 AE Enschede (Netherlands); Dukstiene, Nijole [Department of Physical and Inorganic Chemistry, Kaunas University of Technology, Radvilenu pl. 19, LT-50254 Kaunas (Lithuania); Roberts, Adam [Kratos Analytical Ltd, Trafford Wharf Road, Wharfside, Manchester, M17 1GP (United Kingdom); Fairley, Neal [Casa Software Ltd, Bay House, 5 Grosvenor Terrace, Teignmouth, Devon TQ14 8NE (United Kingdom)

    2015-01-30

    Highlights: • We analyzed and modeled spectral envelopes of complex molybdenum oxides. • Molybdenum oxide films of varying valence and crystallinity were synthesized. • MoO{sub 3} and MoO{sub 2} line shapes from experimental data were created. • Informed amorphous sample model (IASM) developed. • Amorphous molybdenum oxide XPS envelopes were interpreted. - Abstract: Accurate elemental oxidation state determination for the outer surface of a complex material is of crucial importance in many science and engineering disciplines, including chemistry, fundamental and applied surface science, catalysis, semiconductors and many others. X-ray photoelectron spectroscopy (XPS) is the primary tool used for this purpose. The spectral data obtained, however, is often very complex and can be subject to incorrect interpretation. Unlike traditional XPS spectra fitting procedures using purely synthetic spectral components, here we develop and present an XPS data processing method based on vector analysis that allows creating XPS spectral components by incorporating key information, obtained experimentally. XPS spectral data, obtained from series of molybdenum oxide samples with varying oxidation states and degree of crystallinity, were processed using this method and the corresponding oxidation states present, as well as their relative distribution was elucidated. It was shown that monitoring the evolution of the chemistry and crystal structure of a molybdenum oxide sample due to an invasive X-ray probe could be used to infer solutions to complex spectral envelopes.

  13. Resonant impurity states in chemically disordered half-Heusler Dirac semimetals

    Science.gov (United States)

    Chadova, K.; Ködderitzsch, D.; Minár, J.; Ebert, H.; Kiss, J.; D'Souza, S. W.; Wollmann, L.; Felser, C.; Chadov, S.

    2016-05-01

    We address the electron transport characteristics in bulk half-Heusler alloys with their compositions tuned to the borderline between topologically nontrivial semimetallic and trivial semiconducting phases. Accurate first-principles calculations based on the coherent potential approximation (CPA) reveal that all the studied systems exhibit sets of dispersionless impurity-like resonant levels, with one of them being located at the Dirac point. By means of the Kubo-Bastin formalism we reveal that the residual conductivity of these alloys is strongly suppressed by impurity scattering, whereas the spin Hall conductivity exhibits a rather complex behavior induced by the resonant states. In particular for LaPt0.5Pd0.5Bi we find that the total spin Hall conductivity is strongly suppressed by two large and opposite contributions: the negative Fermi-surface contribution produced by the resonant impurity and the positive Fermi-sea term stemming from the occupied states. At the same time, we identify no conductivity contributions from the conical states.

  14. Generalized molybdenum oxide surface chemical state XPS determination via informed amorphous sample model

    Science.gov (United States)

    Baltrusaitis, Jonas; Mendoza-Sanchez, Beatriz; Fernandez, Vincent; Veenstra, Rick; Dukstiene, Nijole; Roberts, Adam; Fairley, Neal

    2015-01-01

    Accurate elemental oxidation state determination for the outer surface of a complex material is of crucial importance in many science and engineering disciplines, including chemistry, fundamental and applied surface science, catalysis, semiconductors and many others. X-ray photoelectron spectroscopy (XPS) is the primary tool used for this purpose. The spectral data obtained, however, is often very complex and can be subject to incorrect interpretation. Unlike traditional XPS spectra fitting procedures using purely synthetic spectral components, here we develop and present an XPS data processing method based on vector analysis that allows creating XPS spectral components by incorporating key information, obtained experimentally. XPS spectral data, obtained from series of molybdenum oxide samples with varying oxidation states and degree of crystallinity, were processed using this method and the corresponding oxidation states present, as well as their relative distribution was elucidated. It was shown that monitoring the evolution of the chemistry and crystal structure of a molybdenum oxide sample due to an invasive X-ray probe could be used to infer solutions to complex spectral envelopes.

  15. IGE Model: An Extension of the Ideal Gas Model to Include Chemical Composition as Part of the Equilibrium State

    Directory of Open Access Journals (Sweden)

    Christopher P. Paolini

    2012-01-01

    Full Text Available The ideal gas (IG model is probably the most well-known gas models in engineering thermodynamics. In this paper, we extend the IG model into an ideal gas equilibrium (IGE model mixture model by incorporating chemical equilibrium calculations as part of the state evaluation. Through a simple graphical interface, users can set the atomic composition of a gas mixture. We have integrated this model into a thermodynamic web portal TEST (http://thermofluids.sdsu.edu/ that contains Java applets for various models for properties of pure substances. In the state panel of the IGE model, the known thermodynamic properties are entered. For a given pressure and temperature, the mixture's Gibbs function is minimized subject to atomic constraints and the equilibrium composition along with thermodynamic properties of the mixture are calculated and displayed. What is unique about this approach is that equilibrium computations are performed in the background, without requiring any major change in the familiar user interface used in other state daemons. Properties calculated by this equilibrium state daemon are compared with results from other established applications such as NASA CEA and STANJAN. Also, two different algorithms, an iterative approach and a direct approach based on minimizing different thermodynamic functions in different situation, are compared.

  16. Surface chemical state of Ti powders and its alloys: Effect of storage conditions and alloy composition

    Science.gov (United States)

    Hryha, Eduard; Shvab, Ruslan; Bram, Martin; Bitzer, Martin; Nyborg, Lars

    2016-12-01

    High affinity of titanium to oxygen in combination with the high surface area of the powder results in tremendous powder reactivity and almost inevitable presence of passivation oxide film on the powder surface. Oxide film is formed during the short exposure of the powder to the environment at even a trace amount of oxygen. Hence, surface state of the powder determines its usefulness for powder metallurgy processing. Present study is focused on the evaluation of the surface oxide state of the Ti, NiTi and Ti6Al4V powders in as-atomized state and after storage under air or Ar for up to eight years. Powder surface oxide state was studied by X-ray photoelectron spectroscopy (XPS) and high resolution scanning electron microscopy (HR SEM). Results indicate that powder in as-atomized state is covered by homogeneous Ti-oxide layer with the thickness of ∼2.9 nm for Ti, ∼3.2 nm and ∼4.2 nm in case of Ti6Al4V and NiTi powders, respectively. Exposure to the air results in oxide growth of about 30% in case of Ti and only about 10% in case of NiTi and Ti6Al4V. After the storage under the dry air for two years oxide growth of only about 3-4% was detected in case of both, Ti and NiTi powders. NiTi powder, stored under the dry air for eight years, indicates oxide thickness of about 5.3 nm, which is about 30% thicker in comparison with the as-atomized powder. Oxide thickness increase of only ∼15% during the storage for eight years in comparison with the powder, shortly exposed to the air after manufacturing, was detected. Results indicate a high passivation of the Ti, Ti6Al4V and NiTi powder surface by homogeneous layer of Ti-oxide formed even during short exposure of the powder to the air.

  17. Size and functional tuning of solid state nanopores by chemical functionalization

    Science.gov (United States)

    Mussi, Valentina; Fanzio, Paola; Firpo, Giuseppe; Repetto, Luca; Valbusa, Ugo

    2012-11-01

    We demonstrate the possibility of using a simple functionalization procedure, based on an initial vapour-phase silanization, to control the size and functionality of solid state nanopores. The presented results show that, by varying the silanization time, it is possible to modify the efficiency of probe molecule attachment, thus shrinking the pore to the chosen size, while introducing a specific sensing selectivity. The proposed method allows us to tune the nanopore biosensor adapting it to the specific final application, and it can be efficiently applied when the pore initial diameter does not exceed a limit dimension related to the mean free path of the silane molecules at the working pressure.

  18. Chemical Dynamics of State-Selected Atomic and Diatomic Ions of Aerospace Relevance

    Science.gov (United States)

    2008-11-01

    modified the triple - quadrupole -double-octopole y<t&te Cy» LJMW • • Figure 1. Schematic diagram of the comprehensive VUV laser system, which...H. Xu, and C. Y. Ng, "The Study of State-Selected Ion-Molecule Reactions using the Pulsed-Field Ionization- Photoion Technique ", J. Chem. Phys...8217==0-4) + He collisions in the ET range of 0-3 eV have also been measured using the VUV-photoionization-guided-ion beam mass spectrometric technique

  19. Chemical composition of Thymus vulgaris L. (thyme essential oil from the Rio de Janeiro State (Brazil

    Directory of Open Access Journals (Sweden)

    ALEXANDRE PORTE

    2008-03-01

    Full Text Available The essential oil from fresh leaves of Thymus vulgaris L. from Rio de Janeiro State, Brazil, was isolated by hydrodistillation and analyzed through a combination of GC and GC/MS. Compounds representing 95.1 % of the oil were identified. Thirty-nine constituents were detected, of which twenty-eight were identified according to their chromatographic retention indices and mass spectra. The major constituents of the oil were thymol (44.7 %, p-cymene (18.6 % and g-terpinene (16.5 %.

  20. Spatially organized dynamical states in chemical oscillator networks: synchronization, dynamical differentiation, and chimera patterns.

    Directory of Open Access Journals (Sweden)

    Mahesh Wickramasinghe

    Full Text Available Dynamical processes in many engineered and living systems take place on complex networks of discrete dynamical units. We present laboratory experiments with a networked chemical system of nickel electrodissolution in which synchronization patterns are recorded in systems with smooth periodic, relaxation periodic, and chaotic oscillators organized in networks composed of up to twenty dynamical units and 140 connections. The reaction system formed domains of synchronization patterns that are strongly affected by the architecture of the network. Spatially organized partial synchronization could be observed either due to densely connected network nodes or through the 'chimera' symmetry breaking mechanism. Relaxation periodic and chaotic oscillators formed structures by dynamical differentiation. We have identified effects of network structure on pattern selection (through permutation symmetry and coupling directness and on formation of hierarchical and 'fuzzy' clusters. With chaotic oscillators we provide experimental evidence that critical coupling strengths at which transition to identical synchronization occurs can be interpreted by experiments with a pair of oscillators and analysis of the eigenvalues of the Laplacian connectivity matrix. The experiments thus provide an insight into the extent of the impact of the architecture of a network on self-organized synchronization patterns.

  1. Chemical degradation of proteins in the solid state with a focus on photochemical reactions.

    Science.gov (United States)

    Mozziconacci, Olivier; Schöneich, Christian

    2015-10-01

    Protein pharmaceuticals comprise an increasing fraction of marketed products but the limited solution stability of proteins requires considerable research effort to prepare stable formulations. An alternative is solid formulation, as proteins in the solid state are thermodynamically less susceptible to degradation. Nevertheless, within the time of storage a large panel of kinetically controlled degradation reactions can occur such as, e.g., hydrolysis reactions, the formation of diketopiperazine, condensation and aggregation reactions. These mechanisms of degradation in protein solids are relatively well covered by the literature. Considerably less is known about oxidative and photochemical reactions of solid proteins. This review will provide an overview over photolytic and non-photolytic degradation reactions, and specially emphasize mechanistic details on how solid structure may affect the interaction of protein solids with light.

  2. Positronium in a Liquid Phase: Formation, Bubble State and Chemical Reactions

    Directory of Open Access Journals (Sweden)

    Sergey V. Stepanov

    2012-01-01

    Full Text Available The present approach describes the e+ fate since its injection into a liquid until its annihilation. Several stages of the e+ evolution are discussed: (1 energy deposition and track structure of fast positrons: ionization slowing down, number of ion-electron pairs, typical sizes, thermalization, electrostatic interaction between e+ and the constituents of its blob, and effect of local heating; (2 positronium formation in condensed media: the Ore model, quasifree Ps state, intratrack mechanism of Ps formation; (3 fast intratrack diffusion-controlled reactions: Ps oxidation and ortho-paraconversion by radiolytic products, reaction rate constants, and interpretation of the PAL spectra in water at different temperatures; (4 Ps bubble models. Inner structure of positronium (wave function, energy contributions, relationship between the pick-off annihilation rate and the bubble radius.

  3. Measurements of the aerosol chemical composition and mixing state in the Po Valley using multiple spectroscopic techniques

    Science.gov (United States)

    Decesari, S.; Allan, J.; Plass-Duelmer, C.; Williams, B. J.; Paglione, M.; Facchini, M. C.; O'Dowd, C.; Harrison, R. M.; Gietl, J. K.; Coe, H.; Giulianelli, L.; Gobbi, G. P.; Lanconelli, C.; Carbone, C.; Worsnop, D.; Lambe, A. T.; Ahern, A. T.; Moretti, F.; Tagliavini, E.; Elste, T.; Gilge, S.; Zhang, Y.; Dall'Osto, M.

    2014-11-01

    The use of co-located multiple spectroscopic techniques can provide detailed information on the atmospheric processes regulating aerosol chemical composition and mixing state. So far, field campaigns heavily equipped with aerosol mass spectrometers have been carried out mainly in large conurbations and in areas directly affected by their outflow, whereas lesser efforts have been dedicated to continental areas characterised by a less dense urbanisation. We present here the results obtained at a background site in the Po Valley, Italy, in summer 2009. For the first time in Europe, six state-of-the-art spectrometric techniques were used in parallel: aerosol time-of-flight mass spectrometer (ATOFMS), two aerosol mass spectrometers (high-resolution time-of-flight aerosol mass spectrometer - HR-ToF-AMS and soot particle aerosol mass spectrometer - SP-AMS), thermal desorption aerosol gas chromatography (TAG), chemical ionisation mass spectrometry (CIMS) and (offline) proton nuclear magnetic resonance (1H-NMR) spectroscopy. The results indicate that, under high-pressure conditions, atmospheric stratification at night and early morning hours led to the accumulation of aerosols produced by anthropogenic sources distributed over the Po Valley plain. Such aerosols include primary components such as black carbon (BC), secondary semivolatile compounds such as ammonium nitrate and amines and a class of monocarboxylic acids which correspond to the AMS cooking organic aerosol (COA) already identified in urban areas. In daytime, the entrainment of aged air masses in the mixing layer is responsible for the accumulation of low-volatility oxygenated organic aerosol (LV-OOA) and also for the recycling of non-volatile primary species such as black carbon. According to organic aerosol source apportionment, anthropogenic aerosols accumulating in the lower layers overnight accounted for 38% of organic aerosol mass on average, another 21% was accounted for by aerosols recirculated in

  4. Prediction of the Chapman-Jouguet chemical equilibrium state in a detonation wave from first principles based reactive molecular dynamics.

    Science.gov (United States)

    Guo, Dezhou; Zybin, Sergey V; An, Qi; Goddard, William A; Huang, Fenglei

    2016-01-21

    The combustion or detonation of reacting materials at high temperature and pressure can be characterized by the Chapman-Jouguet (CJ) state that describes the chemical equilibrium of the products at the end of the reaction zone of the detonation wave for sustained detonation. This provides the critical properties and product kinetics for input to macroscale continuum simulations of energetic materials. We propose the ReaxFF Reactive Dynamics to CJ point protocol (Rx2CJ) for predicting the CJ state parameters, providing the means to predict the performance of new materials prior to synthesis and characterization, allowing the simulation based design to be done in silico. Our Rx2CJ method is based on atomistic reactive molecular dynamics (RMD) using the QM-derived ReaxFF force field. We validate this method here by predicting the CJ point and detonation products for three typical energetic materials. We find good agreement between the predicted and experimental detonation velocities, indicating that this method can reliably predict the CJ state using modest levels of computation.

  5. Chemical, colloidal and mechanical contributions to the state of water in wood cell walls

    Science.gov (United States)

    Bertinetti, L.; Fratzl, P.; Zemb, T.

    2016-08-01

    The properties of wood depend strongly on its water content, but the physicochemical basis for the interaction of water with cell wall components is poorly understood. Due to the importance of the problem both in the context of wood technology and the biological function of swelling and dehydration for growth stresses and seed dispersal, a wealth of descriptive data has been accumulated but a microscopic theory of water-biomolecular interactions is missing. We develop here, at a primitive level, a minimal parameter-free, coarse-grained, model of wood secondary cell walls to predict water absorption, in the form of an equation of state. It includes for the first time all three—mechanical, colloidal and chemical—contributions, taking into account the cell walls microstructure. The hydration force around the elongated cellulose crystals and entropy of mixing of the matrix polymers (hemicelluloses and lignin) are the dominant contributions driving the swelling. The elastic energy needed to swell the composite is the main term opposing water uptake. Hysteresis is not predicted but water uptake versus humidity, is reproduced in a large temperature range. Within this framework, the origin of wood dissolution and different effects of wood treatments on water sorption can be understood at the molecular level.

  6. New Patterns in Steady-State Chemical Kinetics: Intersections, Coincidences, Map of Events (Two-Step Mechanism

    Directory of Open Access Journals (Sweden)

    Daniel Branco Pinto

    2015-10-01

    Full Text Available New patterns of steady-state chemical kinetics for continuously stirred-tank reactors (CSTR have been found, i.e., intersections, maxima and coincidences, for two-step mechanism A↔B→C. There were found elegant analytical relationships for characteristics of these patterns (space times, values of concentrations and rates allowing kinetic parameters to be easily determined. It was demonstrated that for the pair of species involved into the irreversible reaction (B and C, the space time of their corresponding concentration dependence intersection is invariant and does not depend on the initial conditions of the system. Maps of patterns are presented for visualization of their combinations and ranking in space time, and values of concentration and rates.

  7. Unconditionally stable, second-order accurate schemes for solid state phase transformations driven by mechano-chemical spinodal decomposition

    CERN Document Server

    Sagiyama, Koki; Garikipati, Krishna

    2015-01-01

    We consider solid state phase transformations that are caused by free energy densities with domains of non-convexity in strain-composition space. We refer to the non-convex domains as mechano-chemical spinodals. The non-convexity with respect to composition causes segregation into phases with different crystal structures. If, for one of these crystal structures, the free energy density is also non-convex with respect to strain, there is potential for the corresponding phase to further separate into multiple variants. For mathematical well-posedness the free energy description must be enhanced by interface terms that penalize gradients with respect to strain and composition. A system of PDEs results that couples the classical Cahn-Hilliard equation with those of gradient elasticity. Since the materials systems of interest display finite strains, the appropriate description is Toupin's theory of gradient elasticity at finite strains. The presence of strain and composition gradients in the free energy density le...

  8. Some Physico-Chemical and Bacteriological Characteristics of Soil Samples around Calabar Metropolis, Cross River State, Nigeria

    Directory of Open Access Journals (Sweden)

    Okorafor, K. A

    2016-08-01

    Full Text Available Physico-chemical and bacteriological parameters of soil samples around Calabar Metropolis, Cross River State, Nigeria were examined to determine the pollution status of the soil quality. Results of the physico-chemical analysis showed that the soil samples had pH range of 4.4 – 5.2. Tinapa soil has the highest value of Copper (39.63mg/kg and Nickel (11.36mg/kg and Anantigha has the highest value of Zinc (14.59mg/kg, Iron Fe (78.19mg/kg and Manganese (47.42mg/kg. The results revealed a high total count of 23.5x106 cfu/g in Anantigha and 24.5x10-3 cfu/g in Tinapa for bacteria and fungi respectively. Some bacteria isolates found during the study includes, Escherichia coli, Bacillus subtilus, Clostridium sp, Arthrobacter sp, Streptomyces sp, Nocardia sp, Pseudomonas sp and Micrococcus sp., and Fungal isolates includes, Actinomycete sp, Verticullium sp, Aspergillus sp, Mucor sp, Nigospora sp and Paecilomyces sp. From the result, soil sample from Anantigha have comparatively the highest Total Bacterial Counts compared to the other two locations. The health implications of this work is that Anantigha and Tinapa areas being low lying were likely, because of the presence of Escherichia coli, to experience gastro-intestinal diseases such as dysentery and cholera than the Ediba environments.

  9. Quasi-solid state dye-sensitized solar cells based on pyridine or imidazole containing copolymer chemically crosslinked gel electrolytes

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Quasi-solid state dye-sensitized solar cells based on chemically crosslinking with backbone polymers of poly(vinylpyridine-co-acrylonitrile) (P(VP-co-AN)) or poly(vinylimidazole-co-acrylonitrile) (P(VIM-co- AN)) and diiodide compounds of I(CH2)6I or I(CH2CH2O)nCH2CH2I solidified EC/PC/KI/I2 gel electrolytes have been fabricated. The ionic conductivities and apparent diffusion coefficients of I3-Of the electrolytes and cell performances have been investigated. Providing chemically crosslinking points, pyridine or imidazole from the backbone polymers benefited the open circuit voltage and fill factor of the cells. Consequently, the overall energy conversion efficiencies of the quasi-solid DSSCs improved over 10% even near 20% from that of the liquid electrolyte before solidification. Besides, the employing of crosslinker I(CH2CH2O)nCH2CH2I showed higher electrolytic and cell characters than that of I(CH2)6I.

  10. The modelling of dynamic chemical state of paper machine unit operations; Dynaamisen kemiallisen tilan mallintaminen paperikoneen yksikkoeoperaatioissa - MPKT 04

    Energy Technology Data Exchange (ETDEWEB)

    Ylen, J.P.; Jutila, P. [Helsinki Univ. of Technology, Otaniemi (Finland)

    1998-12-31

    The chemical state of paper mass is considered to be a key factor to the smooth operation of the paper machine. There are simulators that have been developed either for dynamic energy and mass balances or for static chemical phenomena, but the combination of these is not a straight forward task. Control Engineering Laboratory of Helsinki University of Technology has studied the paper machine wet end phenomena with the emphasis on pH-modelling. VTT (Technical Research Centre of Finland) Process Physics has used thermodynamical modelling successfully in e.g. Bleaching processes. In this research the different approaches are combined in order to get reliable dynamical models and modelling procedures for various unit operations. A flexible pilot process will be constructed and different materials will be processed starting from simple inorganic substances (e.g. Calcium carbonate and distilled water) working towards more complex masses (thick pulp with process waters and various reagents). The pilot process is well instrumented with ion selective electrodes, total calcium analysator and all basic measurements. (orig.)

  11. In Situ Solid-State Reactions Monitored by X-ray Absorption Spectroscopy: Temperature-Induced Proton Transfer Leads to Chemical Shifts.

    Science.gov (United States)

    Stevens, Joanna S; Walczak, Monika; Jaye, Cherno; Fischer, Daniel A

    2016-10-24

    The dramatic colour and phase alteration with the solid-state, temperature-dependent reaction between squaric acid and 4,4'-bipyridine has been probed in situ with X-ray absorption spectroscopy. The electronic and chemical sensitivity to the local atomic environment through chemical shifts in the near-edge X-ray absorption fine structure (NEXAFS) revealed proton transfer from the acid to the bipyridine base through the change in nitrogen protonation state in the high-temperature form. Direct detection of proton transfer coupled with structural analysis elucidates the nature of the solid-state process, with intermolecular proton transfer occurring along an acid-base chain followed by a domino effect to the subsequent acid-base chains, leading to the rapid migration along the length of the crystal. NEXAFS thereby conveys the ability to monitor the nature of solid-state chemical reactions in situ, without the need for a priori information or long-range order.

  12. NON-EQUILIBRIUM STATIONARY STATE IN CHEMICAL REACTION OF SiO2/Fe AT INTERFACE OF SLAG/METAL AND ITS STABILITY DURING ARC WELDING

    Institute of Scientific and Technical Information of China (English)

    LI Xiaoquan; DU Zeyu; YANG Xuguang

    2007-01-01

    For characteristics of open and far from thermodynamic equilibrium in welding chemical reaction, a new kind of quantitative method, which is used to analyze direction and extent for chemical reaction of SiO2/Fe during quasi-steady state period, is introduced with the concept of non-equilibrium stationary state. The main idea is based on thermodynamic driving forces, which result in non-zero thermodynamic fluxes and lead to chemical reaction far away from thermodynamic equilibrium. There exists certain dynamic equilibrium relationship between rates of diffusion fluxes in liquid phase of reactants or products and the rate equation of chemical reaction when welding is in quasi-steady state. As result of this, a group of non-linear equations containing concentrations of all substances at interface of slag/liquid-metal may be established. Moreover the stability of this non-equilibrium stationary state is discussed using dissipative structure theory and it is concluded theoretically that this non-equilibrium stationary state for welding chemical reaction is of stability.

  13. Estimation and Prediction of Bioconcentration Factors of Nonionic Organic Chemicals in Fish by Electrotopological State Indices and Structural Parameter

    Institute of Scientific and Technical Information of China (English)

    FENG Chang-Jun; YANG Wei-Hua; MU Lai-Long

    2008-01-01

    Based on the characteristics of atom types, Hall's electrotopological state indices (En) are calculated for 165 nonionic organic compounds. On the basis of the characteristics of substituent and conjugated matrix, a novel molecular structure parameter (G) is defined and calcu- lated for 165 molecules in this paper. En and G show good structural selectivity for organic molecules. G, a satisfactory relationship between bioconcentration factor (BCF) and En, is expressed as: lgBCF = -0.283 + 1.246G + 0.079E42 + 0.351E9 - 0.063E17 (n' = 122, R = 0.967, F = 425.636, s = 0.394), which could provide estimation and prediction for the lgBCF of nonionic organic chemicals. Furthermore, the model is examined to validate overall robustness with Jackknife tests, and the independent variables in model do not exist cross correlation with VIF. All these regression results show that the new parameter G and electrotopological state index have good rationality and efficiency. It is concluded that the En and G will be used widely in quantitative structure-property/activity relationship (QSPR/QSAR) research.

  14. Acoustic Imaging of Microstructure and Evaluation of the Adhesive's Physical, Mechanical and Chemical Properties Changes at Different Cure States

    Science.gov (United States)

    Severina, I. A.; Fabre, A. J.; Maeva, E. Yu.

    Epoxy thermoset adhesives transform during cure from liquid state into the highly cross-linked solid. Cure state of the material depends on condition of the reaction (temperature, pressure, time etc.) and resin/hardener ratio. It is known that the cure degree of the adhesive correlates with adhesion strength, which is critical for structural adhesives used in automotive, aerospace and marine industries. In this work, characterization of cure process of the adhesive with acoustic methods is presented. Evolution of the acoustic and elastic properties (attenuation, sound velocity, density, elastic moduli) during cure reaction was monitored in relation to the substantial physical and chemical changes of the material. These macro parameters of the adhesive were compared with the material's microstructure obtained by high-resolution acoustic microscopy technique in frequencies range of 50-400 MHz. Development of the microstructure of the adhesive as it cures at different conditions has been investigated. Appearance and development of the granular structure on the adhesive interface during cure reaction has been demonstrated. Acoustic images were analyzed by mathematical method to quantitatively characterize distribution of the adhesive's components. Statistical analysis of such images provides an accurate quantitative measure of the degree of cure of such samples. Research results presented in this paper can be useful as a basis for non-destructive evaluation of the adhesive materials

  15. Probing physical and chemical changes in cortical bone due to osteoporosis and type 2 diabetes by solid-state NMR

    Science.gov (United States)

    Zhou, Donghua; Taylor, Amanda; Rendina, Beth; Smith, Brenda; Department of Physics Collaboration; Department of Nutritional Sciences Collaboration

    2013-03-01

    Approximately 1.5 million fractures occur each year in the U.S. due to osteoporosis, which is characterized by decreased bone mineral density and deterioration of bone micro-architecture. On the other hand, type 2 diabetes also significantly increases fracture risks, despite having a normal or even higher bone mineral density. Solid-state NMR has been applied to bone tissues from normal and disease-inflicted mouse models to study structural and chemical dynamics as the disease progresses. Proton relaxation experiments were performed to measure water populations in the bone matrix and pores. Collagen-bound water has strong influence on bone resilience, while water content in the pores reveals amount and size of pores from micro- to millimeter range. Other biochemical and atomic-scale structural alterations in the mineral and organic phases and their interface were investigated by proton, phosphorus, and carbon NMR spectroscopy. Experiments were designed to individually detect different types of phosphorus environments: near the mineral surface, similar to hydroxyapatite, and deficient of hydrogens due to substitution of the hydroxyl group by other ions. A new method was also developed for accurate quantification of each phosphorus species. The authors appreciate financial support for this project from the College of Human Sciences and the College of Arts and Sciences, Oklahoma State University.

  16. Chemical state analysis of trace-level alkali metals sorbed in micaceous oxide by total reflection X-ray photoelectron spectroscopy

    Science.gov (United States)

    Baba, Y.; Shimoyama, I.; Hirao, N.

    2016-10-01

    In order to determine the chemical states of radioactive cesium (137Cs or 134Cs) sorbed in clay minerals, chemical states of cesium as well as the other alkali metals (sodium and rubidium) sorbed in micaceous oxides have been investigated by X-ray photoelectron spectroscopy (XPS). Since the number of atoms in radioactive cesium is extremely small, we specially focused on chemical states of trace-level alkali metals. For this purpose, we have measured XPS under X-ray total reflection (TR) condition. For cesium, it was shown that ultra-trace amount of cesium down to about 100 pg cm-2 can be detected by TR-XPS. This amount corresponds to about 200 Bq of 137Cs (t1/2 = 30.2 y). It was demonstrated that ultra-trace amount of cesium corresponding to radioactive cesium level can be measured by TR-XPS. As to the chemical states, it was found that core-level binding energy in TR-XPS for trace-level cesium shifted to lower-energy side compared with that for thicker layer. A reverse tendency is observed in sodium. Based on charge transfer within a simple point-charge model, it is concluded that chemical bond between alkali metal and micaceous oxide for ultra-thin layer is more polarized that for thick layer.

  17. Correlations between (51)V solid-state NMR parameters and chemical structure of vanadium (V) complexes as models for related metalloproteins and catalysts.

    Science.gov (United States)

    Fenn, Annika; Wächtler, Maria; Gutmann, Torsten; Breitzke, Hergen; Buchholz, Axel; Lippold, Ines; Plass, Winfried; Buntkowsky, Gerd

    2009-12-01

    The parameters describing the quadrupolar and CSA interactions of 51V solid-state MAS NMR investigations of model complexes mimicking vanadoenzymes as well as vanadium containing catalysts and enzyme complexes are interpreted with respect to the chemical structure. The interpretation is based on the data of 15 vanadium complexes including two new complexes with previously unpublished data and 13 complexes with data previously published by us. Correlations between the chemical structure and the 51V solid-state NMR data of this class of compounds have been established. Especially for the isotropic chemical shift delta(iso) and the chemical shift anisotropy delta(sigma), correlations with specific structural features like the coordination number of the vanadium atom, the number of coordinating nitrogens, the number of oxygen atoms and the chemical surrounding of the complex could be established for these compounds. Moreover, quantitative correlations between the solid-state NMR parameters and specific bond angles and bond lengths have been obtained. Our results can be of particular interest for future investigations concerning the structure and the mode of action of related vanadoenzymes and vanadate protein assemblies, including the use of vanadate adducts as transition state analogs for phosphate metabolizing systems.

  18. Measurements of the aerosol chemical composition and mixing state in the Po Valley using multiple spectroscopic techniques

    Directory of Open Access Journals (Sweden)

    S. Decesari

    2014-04-01

    Full Text Available The use of co-located multiple spectroscopic techniques can provide detailed information on the atmospheric processes regulating aerosol chemical composition and mixing state. So far, field campaigns heavily equipped with aerosol mass spectrometers have been carried out mainly in large conurbations and in areas directly affected by their outflow, whereas lesser efforts have been dedicated to continental areas characterized by a less dense urbanization. We present here the results obtained in San Pietro Capofiume, which is located in a sparsely inhabited sector of the Po Valley, Italy. The experiment was carried out in summer 2009 in the framework of the EUCAARI project ("European Integrated Project on Aerosol, Cloud Climate Aerosol Interaction". For the first time in Europe, six state-of-the-art techniques were used in parallel: (1 on-line TSI aerosol time-of-flight mass spectrometer (ATOFMS, (2 on-line Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS, (3 soot particle aerosol mass spectrometer (SP-AMS, (4 on-line high resolution time-of-flight mass spectrometer-thermal desorption aerosol gas chromatograph (HR-ToFMS-TAG, (5 off-line twelve-hour resolution proton nuclear magnetic resonance (H-NMR spectroscopy, and (6 chemical ionization mass spectrometry (CIMS for the analysis of gas-phase precursors of secondary aerosol. Data from each aerosol spectroscopic method were analysed individually following ad-hoc tools (i.e. PMF for AMS, Art-2a for ATOFMS. The results obtained from each techniques are herein presented and compared. This allows us to clearly link the modifications in aerosol chemical composition to transitions in air mass origin and meteorological regimes. Under stagnant conditions, atmospheric stratification at night and early morning hours led to the accumulation of aerosols produced by anthropogenic sources distributed over the Po Valley plain. Such aerosols include primary components such as black

  19. Microplastics as vectors for bioaccumulation of hydrophobic organic chemicals in the marine environment: A state-of-the-science review.

    Science.gov (United States)

    Ziccardi, Linda M; Edgington, Aaron; Hentz, Karyn; Kulacki, Konrad J; Kane Driscoll, Susan

    2016-07-01

    A state-of-the-science review was conducted to examine the potential for microplastics to sorb hydrophobic organic chemicals (HOCs) from the marine environment, for aquatic organisms to take up these HOCs from the microplastics, and for this exposure to result in adverse effects to ecological and human health. Despite concentrations of HOCs associated with microplastics that can be orders of magnitude greater than surrounding seawater, the relative importance of microplastics as a route of exposure is difficult to quantify because aquatic organisms are typically exposed to HOCs from various compartments, including water, sediment, and food. Results of laboratory experiments and modeling studies indicate that HOCs can partition from microplastics to organisms or from organisms to microplastics, depending on experimental conditions. Very little information is available to evaluate ecological or human health effects from this exposure. Most of the available studies measured biomarkers that are more indicative of exposure than effects, and no studies showed effects to ecologically relevant endpoints. Therefore, evidence is weak to support the occurrence of ecologically significant adverse effects on aquatic life as a result of exposure to HOCs sorbed to microplastics or to wildlife populations and humans from secondary exposure via the food chain. More data are needed to fully understand the relative importance of exposure to HOCs from microplastics compared with other exposure pathways. Environ Toxicol Chem 2016;35:1667-1676. © 2016 SETAC.

  20. Study of multi-site chemical exchange in solution state by NMR: 1D experiments with multiply selective excitation

    Indian Academy of Sciences (India)

    Samanwita Pal

    2010-07-01

    Chemical exchange in solution state has been investigated traditionally by both 1D and 2D NMR, permitting the extraction of kinetic parameters (e.g. the spin-lattice relaxation time 1, the exchange rate constant and the activation parameters). This work demonstrates a simple 1D NMR approach employing multiply selective excitation to study multi-site exchange processes in solution, applying it to systems that exhibit three-site exchange. This approach involves simultaneous excitation of all - or a chosen subset of - the exchanging sites by using an appropriately modulated shaped radiofrequency pulse. The pulse sequence, as well as analysis is summarized. Significant features of the experiment, which relies on sign labelling of the exchanging sites, include considerably shorter experiment time compared to standard 2D exchange work, clear definition of the exchange time window and uniform pulse non-ideality effects for all the exchanging sites. Complete kinetic information is reported in the study of dynamic processes in superacid solutions of two weak bases, studied by 1H NMR. An analytical solution, leading to the determination of four rate parameters, is presented for proton exchange studies on these systems, which involve a mixture of two weak bases in arbitrary concentration ratio, and stoichiometric excess of the superacid.

  1. Analysis of copper-rich precipitates in silicon: chemical state,gettering, and impact on multicrystalline silicon solar cellmaterial

    Energy Technology Data Exchange (ETDEWEB)

    Buonassisi, Tonio; Marcus, Matthew A.; Istratov, Andrei A.; Heuer, Matthias; Ciszek, Theodore F.; Lai, Barry; Cai, Zhonghou; Weber,Eicke R.

    2004-11-08

    In this study, synchrotron-based x-ray absorption microspectroscopy (mu-XAS) is applied to identifying the chemical states of copper-rich clusters within a variety of silicon materials, including as-grown cast multicrystalline silicon solar cell material with high oxygen concentration and other silicon materials with varying degrees of oxygen concentration and copper contamination pathways. In all samples, copper silicide (Cu3Si) is the only phase of copper identified. It is noted from thermodynamic considerations that unlike certain metal species, copper tends to form a silicide and not an oxidized compound because of the strong silicon-oxygen bonding energy; consequently the likelihood of encountering an oxidized copper particle in silicon is small, in agreement with experimental data. In light of these results, the effectiveness of aluminum gettering for the removal of copper from bulk silicon is quantified via x-ray fluorescence microscopy (mu-XRF),and a segregation coefficient is determined from experimental data to beat least (1-2)'103. Additionally, mu-XAS data directly demonstrates that the segregation mechanism of Cu in Al is the higher solubility of Cu in the liquid phase. In light of these results, possible limitations for the complete removal of Cu from bulk mc-Si are discussed.

  2. Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni

    Energy Technology Data Exchange (ETDEWEB)

    Biesinger, Mark C., E-mail: biesingr@uwo.ca [Surface Science Western, University of Western Ontario, University of Western Ontario Research Park, Room LL31, 999 Collip Circle, London, Ontario, N6G 0J3 (Canada); ACeSSS (Applied Centre for Structural and Synchrotron Studies), University of South Australia, Mawson Lakes, SA 5095 (Australia); Payne, Brad P. [Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Grosvenor, Andrew P. [Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C9 (Canada); Lau, Leo W.M. [Surface Science Western, University of Western Ontario, University of Western Ontario Research Park, Room LL31, 999 Collip Circle, London, Ontario, N6G 0J3 (Canada); Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Gerson, Andrea R.; Smart, Roger St.C. [ACeSSS (Applied Centre for Structural and Synchrotron Studies), University of South Australia, Mawson Lakes, SA 5095 (Australia)

    2011-01-15

    Chemical state X-ray photoelectron spectroscopic analysis of first row transition metals and their oxides and hydroxides is challenging due to the complexity of their 2p spectra resulting from peak asymmetries, complex multiplet splitting, shake-up and plasmon loss structure, and uncertain, overlapping binding energies. Our previous paper [M.C. Biesinger et al., Appl. Surf. Sci. 257 (2010) 887-898.] in which we examined Sc, Ti, V, Cu and Zn species, has shown that all the values of the spectral fitting parameters for each specific species, i.e. binding energy (eV), full wide at half maximum (FWHM) value (eV) for each pass energy, spin-orbit splitting values and asymmetric peak shape fitting parameters, are not all normally provided in the literature and data bases, and are necessary for reproducible, quantitative chemical state analysis. A more consistent, practical and effective approach to curve fitting was developed based on a combination of (1) standard spectra from quality reference samples, (2) a survey of appropriate literature databases and/or a compilation of literature references and (3) specific literature references where fitting procedures are available. This paper extends this approach to the chemical states of Cr, Mn, Fe, Co and Ni metals, and various oxides and hydroxides where intense, complex multiplet splitting in many of the chemical states of these elements poses unique difficulties for chemical state analysis. The curve fitting procedures proposed use the same criteria as proposed previously but with the additional complexity of fitting of multiplet split spectra which has been done based on spectra of numerous reference materials and theoretical XPS modeling of these transition metal species. Binding energies, FWHM values, asymmetric peak shape fitting parameters, multiplet peak separation and peak area percentages are presented. The procedures developed can be utilized to remove uncertainties in the analysis of surface states in nano

  3. The eruptive history and chemical stratigraphy of a post-caldera, steady-state volcano: Yasur, Vanuatu

    Science.gov (United States)

    Firth, Chris W.; Handley, Heather K.; Cronin, Shane J.; Turner, Simon P.

    2014-07-01

    The persistent activity of Yasur volcano, a post-caldera scoria cone in the southern Vanuatu Arc, along with the uniformity exhibited by its eruptive products, indicates that it is a "steady-state" volcano. This implies that rates of magma replenishment and tapping are in equilibrium. Examination of recently exposed tephra sequences suggests that Strombolian-style activity at Yasur has persisted in its current form for the last 630-850 years. Eruption of tephra with uniform grain size and texture throughout this period indicates invariant eruption magnitude and style. Based on tephra accumulation rates, a uniform, time-averaged eruption flux of ˜410-480 m3 days-1 is estimated. Major and trace element analyses of glass shards and mineral grains from these tephra deposits show limited variation in magma composition throughout that time, consistent with a chemically buffered magma reservoir and models for steady-state volcanism. Similarly, mineral crystallisation temperature estimates are within error, suggesting the magma reservoir has retained a constant temperature through this time, while pressure estimates suggest shallow crystallisation. Eruptions appear to be driven by gas release, with small fluctuations in magma chemistry and eruptive behaviour governed by perturbations in volatile flux. This period of steady-state activity was preceded by ˜600 years of higher-magnitude, lower-frequency eruptions during which less evolved compositions were erupted. Variation between these two styles of eruptive behaviour may be explained by a shift from a periodically closed to fully opened conduit, allowing more regular magma release and changes to degassing regimes. New radiocarbon ages suggest a period of irregular eruptive behaviour extending >1,400 year B.P. Overall, a transition from an irregular to a very steady magmatic system has occurred over the past ˜2 kyr. Previously determined tectonic indicators for caldera resurgence in the area suggest revived magma

  4. Chemical states of fission products in irradiated (U 0.3Pu 0.7)C 1+ x fuel at high burn-ups

    Science.gov (United States)

    Agarwal, Renu; Venugopal, V.

    2006-12-01

    The chemical states of fission products have been theoretically determined for the irradiated carbide fuel of Fast Breeder Test Reactor (FBTR) at Kalpakkam, India, at different burn-ups. The SOLGASMIX-PV computer code was used to determine the equilibrium chemical composition of the fuel. The system was assumed to be composed of a gaseous phase at one atmosphere pressure, and various solid phases. The distribution of elements in these phases and their chemical states at different temperatures were calculated as a function of burn-up. The FBTR fuel, (U 0.3Pu 0.7)C 1+ x, was loaded with C/M values in the range, 1.03-1.06. The present calculations indicated that even for the lowest starting C/M of 1.03 in the FBTR fuel, the liquid metal phase of (U, Pu), should not appear at a burn-up as high as 150 GWd/t.

  5. Investigation of electron density changes at the onset of a chemical reaction using the state-specific dual descriptor from conceptual density functional theory.

    Science.gov (United States)

    De Proft, Frank; Forquet, Valérian; Ourri, Benjamin; Chermette, Henry; Geerlings, Paul; Morell, Christophe

    2015-04-14

    The electron density changes from reactants towards the transition state of a chemical reaction is expressed as a linear combination of the state-specific dual descriptors (SSDD) of the corresponding reactant complexes. Consequently, the SSDD can be expected to bear important resemblance to the so-called natural orbitals for chemical valence (NOCV), introduced as the orbitals that diagonalize the deformation density matrix of interacting molecules. This agreement is shown for three case studies: the complexation of a Lewis acid with a Lewis base, a SN2 nucleophilic substitution reaction and a Diels-Alder cycloaddition reaction. As such, the SSDD computed for reactant complexes are shown to provide important information about charge transfer interactions during a chemical reaction.

  6. Current state and temporal evolution of the chemical composition of atmospheric depositions in forest areas of the CONECOFOR network

    Directory of Open Access Journals (Sweden)

    Marchetto A

    2014-04-01

    Full Text Available Current state and temporal evolution of the chemical composition of atmospheric depositions in forest areas of the CONECOFOR network. Since 1997, atmospheric deposition was sampled and analyzed in the permanent plots of the Italian network for the evaluation of forest health (CONECOFOR, under the coordination of the Italian Forest Service. This paper presents the results of the activity carried out in 2009, when the EU-funded LIFE+ “FutMon” project allowed to extend the sampling network to 22 sites. Long-term trends will also be evaluated for the sampling sites with the longest time series. The sampling of open field bulk deposition was performed in a clearance close to the CONECOFOR permanent plots, while throughfall deposition and stemflow (in beech stand, only were sampled in the plot. Deposition samples were collected weekly and sent to the laboratories, where they were analyzed for pH, conductivity, major ions, and total carbon and nitrogen. Most measured variables showed a strong geographical gradient. For example, nitrogen deposition was relatively high in the Po plain (where the emissions of nitrogen oxides and ammonia are the highest and surrounding hills, reaching 10-20 kgN ha-1 y-1 in the open field and 13-25 kgN ha-1 y-1 in the throughfall. Sulphate deposition also showed a marked geographical gradient. Deposition of marine aerosol also had an important impact on the chemical composition of atmospheric deposition in Italy, together with the episodic deposition of Saharan dust, which showed a marked gradient, with highest values in the southernmost plots. Trend analysis was carried out on 10 sites running since the beginning of the program. A general negative trend in sulphate concentration was detected, paralleled in most plots by a positive trend in deposition pH, in good agreement with the strong reduction in the emission of sulphur dioxide recorded in the last decades. Nitrogen concentration also showed a significant decrease

  7. Experimental Verification of the Chemical Sensitivity of Two-Site Double Core-Hole States Formed by an X-ray FEL

    CERN Document Server

    Salen, P; Schmidt, H T; Thomas, R D; Larsson, M; Feifel, R; Piancastelli, M N; Fang, L; Murphy, B; Osipov, T; Berrah, N; Kukk, E; Ueda, K; Bozek, J D; Bostedt, C; Wada, S; Richter, R; Feyer, V; Prince, K C

    2012-01-01

    We have performed X-ray two-photon photoelectron spectroscopy (XTPPS) using the Linac Coherent Light Source (LCLS) X-ray free-electron laser (FEL) in order to study double core-hole (DCH) states of CO2, N2O and N2. The experiment verifies the theory behind the chemical sensitivity of two-site (ts) DCH states by comparing a set of small molecules with respect to the energy shift of the tsDCH state and by extracting the relevant parameters from this shift.

  8. Reactions of 1-naphthyl radicals with ethylene. Single pulse shock tube experiments, quantum chemical, transition state theory, and multiwell calculations.

    Science.gov (United States)

    Lifshitz, Assa; Tamburu, Carmen; Dubnikova, Faina

    2008-02-07

    The reactions of 1-naphthyl radicals with ethylene were studied behind reflected shock waves in a single pulse shock tube, covering the temperature range 950-1200 K at overall densities behind the reflected shocks of approximately 2.5 x 10(-5) mol/cm3. 1-Iodonaphthalene served as the source for 1-naphthyl radicals as its C-I bond dissociation energy is relatively small. It is only approximately 65 kcal/mol as compared to the C-H bond strength in naphthalene which is approximately 112 kcal/mol and can thus produce naphthyl radicals at rather low reflected shock temperatures. The [ethylene]/[1-iodo-naphthalene] ratio in all of the experiments was approximately 100 in order to channel the free radicals into reactions with ethylene rather than iodonaphthalene. Four products resulting from the reactions of 1-naphthyl radicals with ethylene were found in the post shock samples. They were vinyl naphthalene, acenaphthene, acenaphthylene, and naphthalene. Some low molecular weight aliphatic products at rather low concentrations, resulting from the attack of various free radicals on ethylene were also found in the shocked samples. In view of the relatively low temperatures employed in the present experiments, the unimolecular decomposition rate of ethylene is negligible. Three potential energy surfaces describing the production of vinyl naphthalene, acenaphthene, and acenaphthylene were calculated using quantum chemical methods and rate constants for the elementary steps on the surfaces were calculated using transition state theory. Naphthalene is not part of the reactions on the surfaces. Acenaphthylene is obtained only from acenaphthene. A kinetics scheme containing 27 elementary steps most of which were obtained from the potential energy surfaces was constructed and computer modeling was performed. An excellent agreement between the experimental yields of the four major products and the calculated yields was obtained.

  9. Mining Available Data from the United States Environmental Protection Agency to Support Rapid Life Cycle Inventory Modeling of Chemical Manufacturing.

    Science.gov (United States)

    Cashman, Sarah A; Meyer, David E; Edelen, Ashley N; Ingwersen, Wesley W; Abraham, John P; Barrett, William M; Gonzalez, Michael A; Randall, Paul M; Ruiz-Mercado, Gerardo; Smith, Raymond L

    2016-09-06

    Demands for quick and accurate life cycle assessments create a need for methods to rapidly generate reliable life cycle inventories (LCI). Data mining is a suitable tool for this purpose, especially given the large amount of available governmental data. These data are typically applied to LCIs on a case-by-case basis. As linked open data becomes more prevalent, it may be possible to automate LCI using data mining by establishing a reproducible approach for identifying, extracting, and processing the data. This work proposes a method for standardizing and eventually automating the discovery and use of publicly available data at the United States Environmental Protection Agency for chemical-manufacturing LCI. The method is developed using a case study of acetic acid. The data quality and gap analyses for the generated inventory found that the selected data sources can provide information with equal or better reliability and representativeness on air, water, hazardous waste, on-site energy usage, and production volumes but with key data gaps including material inputs, water usage, purchased electricity, and transportation requirements. A comparison of the generated LCI with existing data revealed that the data mining inventory is in reasonable agreement with existing data and may provide a more-comprehensive inventory of air emissions and water discharges. The case study highlighted challenges for current data management practices that must be overcome to successfully automate the method using semantic technology. Benefits of the method are that the openly available data can be compiled in a standardized and transparent approach that supports potential automation with flexibility to incorporate new data sources as needed.

  10. Screening of antibiotics and chemical analysis of penicillin residue in fresh milk and traditional dairy products in Oyo state, Nigeria

    Science.gov (United States)

    Olatoye, Isaac Olufemi; Daniel, Oluwayemisi Folashade; Ishola, Sunday Ayobami

    2016-01-01

    Background and Aim: There are global public health and economic concerns on chemical residues in food of animal origin. The use of antibiotics in dairy cattle for the treatment of diseases such as mastitis has contributed to the presence of residues in dairy products. Penicillin residues as low as 1 ppb can lead to allergic reactions and shift of resistance patterns in microbial population as well as interfere with the processing of several dairy products. Antibiotic monitoring is an essential quality control measure in safe milk production. This study was aimed at determining antibiotic residue contamination and the level of penicillin in dairy products from Fulani cattle herds in Oyo State. Materials and Methods: The presence of antibiotic residues in 328 samples of fresh milk, 180 local cheese (wara), and 90 fermented milk (nono) from Southwest, Nigeria were determined using Premi® test kit (R-Biopharm AG, Germany) followed by high-performance liquid chromatography analysis of penicillin-G residue. Results: Antibiotic residues were obtained in 40.8%, 24.4% and 62.3% fresh milk, wara and nono, respectively. Penicillin-G residue was also detected in 41.1% fresh milk, 40.2% nono and 24.4% wara at mean concentrations of 15.22±0.61, 8.24±0.50 and 7.6±0.60 μg/L with 39.3%, 36.7% and 21.1%, respectively, containing penicillin residue above recommended Codex maximum residue limit (MRL) of 5 μg/L in dairy. There was no significant difference between the mean penicillin residues in all the dairy products in this study. Conclusion: The results are of food safety concern since the bulk of the samples and substantial quantities of dairy products in Oyo state contained violative levels of antibiotic residues including penicillin residues in concentrations above the MRL. This could be due to indiscriminate and unregulated administration of antibiotics to dairy cattle. Regulatory control of antibiotic use, rapid screening of milk and dairy farmers’ extension education

  11. Screening of antibiotics and chemical analysis of penicillin residue in fresh milk and traditional dairy products in Oyo state, Nigeria

    Directory of Open Access Journals (Sweden)

    Isaac Olufemi Olatoye

    2016-09-01

    Full Text Available Background and Aim: There are global public health and economic concerns on chemical residues in food of animal origin. The use of antibiotics in dairy cattle for the treatment of diseases such as mastitis has contributed to the presence of residues in dairy products. Penicillin residues as low as 1 ppb can lead to allergic reactions and shift of resistance patterns in microbial population as well as interfere with the processing of several dairy products. Antibiotic monitoring is an essential quality control measure in safe milk production. This study was aimed at determining antibiotic residue contamination and the level of penicillin in dairy products from Fulani cattle herds in Oyo State. Materials and Methods: The presence of antibiotic residues in 328 samples of fresh milk, 180 local cheese (wara, and 90 fermented milk (nono from Southwest, Nigeria were determined using Premi® test kit (R-Biopharm AG, Germany followed by high-performance liquid chromatography analysis of penicillin-G residue. Results: Antibiotic residues were obtained in 40.8%, 24.4% and 62.3% fresh milk, wara and nono, respectively. Penicillin-G residue was also detected in 41.1% fresh milk, 40.2% nono and 24.4% wara at mean concentrations of 15.22±0.61, 8.24±0.50 and 7.6±0.60 μg/L with 39.3%, 36.7% and 21.1%, respectively, containing penicillin residue above recommended Codex maximum residue limit (MRL of 5 μg/L in dairy. There was no significant difference between the mean penicillin residues in all the dairy products in this study. Conclusion: The results are of food safety concern since the bulk of the samples and substantial quantities of dairy products in Oyo state contained violative levels of antibiotic residues including penicillin residues in concentrations above the MRL. This could be due to indiscriminate and unregulated administration of antibiotics to dairy cattle. Regulatory control of antibiotic use, rapid screening of milk and dairy farmers

  12. State-selected chemical reaction dynamics at the S matrix level - Final-state specificities of near-threshold processes at low and high energies

    Science.gov (United States)

    Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

    1992-01-01

    State-to-state reaction probabilities are found to be highly final-state specific at state-selected threshold energies for the reactions O + H2 yield OH + H and H + H2 yield H2 + H. The study includes initial rotational states with quantum numbers 0-15, and the specificity is especially dramatic for the more highly rotationally excited reactants. The analysis is based on accurate quantum mechanical reactive scattering calculations. Final-state specificity is shown in general to increase with the rotational quantum number of the reactant diatom, and the trends are confirmed for both zero and nonzero values of the total angular momentum.

  13. Surface Ionization State and Nanoscale Chemical Composition of UV-Irradiated Poly(dimethylsiloxane) Probed by Chemical Force Microscopy, Force Titration, and Electrokinetic Measurements

    NARCIS (Netherlands)

    Song, Jing; Duval, Jerome F.L.; Cohen Stuart, Martien A.; Hillborg, Henrik; Gunst, Ullrich; Arlinghaus, Heinrich F.; Vancso, G. Julius

    2007-01-01

    The surface chemistry and ionization state of cross-linked poly(dimethylsiloxane) (PDMS) exposed to UV/ozone were studied as a function of treatment time. Various complementary and independent experimental techniques were utilized, which yielded information on the macroscopic as well as the nanometr

  14. Surface ionization state and nanoscale chemical composition of UV-irradiated poly(dimethylsiloxane) probed by chemical force microscopy, force titration, and electrokinetic measurements

    NARCIS (Netherlands)

    Song, J.; Duval, J.F.L.; Cohen Stuart, M.A.; Hillborg, H.; Gunst, U.; Arlinghaus, H.F.; Vancso, G.J.

    2007-01-01

    The surface chemistry and ionization state of cross-linked poly(dimethylsiloxane) (PDMS) exposed to UV/ozone were studied as a function of treatment time. Various complementary and independent experimental techniques were utilized, which yielded information on the macroscopic as well as the nanometr

  15. Physico-chemical and Bacteriological Quality of Water from Shallow Wells in Two Rural Communities in Benue State, Nigeria

    Directory of Open Access Journals (Sweden)

    Akaahan, Terngu J.

    2010-06-01

    Full Text Available Ground water abstraction from shallow wells is widely practiced in the Obi and in Oju rural areas of Benue State, Central Nigeria, as a means of fighting guinea worm infestation associated with the surface water sources (streams in these areas. To ascertain the physico-chemical and bacteriological quality of the water used by the population, water samples from 27 shallow wells in Obi and 19 Oju were taken and examined for key health-related quality parameters using routine methods. In Obi, the ground water colour ranged from 4.0-80.0 TCU, conductivity 55.2-1600.0 µS/cm, pH 6.1-8.6, TDS 38.6-1286 mg/L, turbidity 1.0-55.0 NTU, arsenic 0.001-0.210mg/L, copper 0.01-2.53mg/L, fluoride 0.08-1.82mg/L and nitrate 10.8-63.0mg/L, while in Oju, colour varied from 2.0-87.0 TCU, conductivity 107.4-1375 µS/cm, pH 6.4-8.53, TDS 75.2-1150 mg/L, turbidity 3.0-48.0 NTU, arsenic 0.001-0.023 mg/L, copper 0.01-2.10 mg/L, fluoride 0.01-1.54 mg/L and nitrate 10.2-59.7 mg/L. Some of these values in some instances exceed the WHO standard for drinking water. Alongside with the presence significant total coliform count in most of the wells (0-47/100 mL in Oju and 0-53/100 mL in Obi, the available water is considered largely unsafe for human consumption as obtained. It is concluded that, while ground water abstraction may be a safety measure against guinea worm infestation it, nevertheless presents other health challenges to the rural population in the area, as the quality of the ground water is generally low.

  16. Chemical State Mapping of Degraded B4C Control Rod Investigated with Soft X-ray Emission Spectrometer in Electron Probe Micro-analysis

    Science.gov (United States)

    Kasada, R.; Ha, Y.; Higuchi, T.; Sakamoto, K.

    2016-05-01

    B4C is widely used as control rods in light water reactors, such as the Fukushima Daiichi nuclear power plant, because it shows excellent neutron absorption and has a high melting point. However, B4C can melt at lower temperatures owing to eutectic interactions with stainless steel and can even evaporate by reacting with high-temperature steam under severe accident conditions. To reduce the risk of recriticality, a precise understanding of the location and chemical state of B in the melt core is necessary. Here we show that a novel soft X-ray emission spectrometer in electron probe microanalysis can help to obtain a chemical state map of B in a modeled control rod after a high-temperature steam oxidation test.

  17. Progress in spin dynamics solid-state nuclear magnetic resonance with the application of Floquet-Magnus expansion to chemical shift anisotropy.

    Science.gov (United States)

    Mananga, Eugene Stephane

    2013-01-01

    The purpose of this article is to present an historical overview of theoretical approaches used for describing spin dynamics under static or rotating experiments in solid state nuclear magnetic resonance. The article gives a brief historical overview for major theories in nuclear magnetic resonance and the promising theories. We present the first application of Floquet-Magnus expansion to chemical shift anisotropy when irradiated by BABA pulse sequence.

  18. Accurate Three States Model for Amino Acids with Two Chemically Coupled Titrating Sites in Explicit Solvent Atomistic Constant pH Simulations and pKa Calculations.

    Science.gov (United States)

    Dobrev, Plamen; Donnini, Serena; Groenhof, Gerrit; Grubmüller, Helmut

    2017-01-10

    Correct protonation of titratable groups in biomolecules is crucial for their accurate description by molecular dynamics simulations. In the context of constant pH simulations, an additional protonation degree of freedom is introduced for each titratable site, allowing the protonation state to change dynamically with changing structure or electrostatics. Here, we extend previous approaches for an accurate description of chemically coupled titrating sites. A second reaction coordinate is used to switch between two tautomeric states of an amino acid with chemically coupled titratable sites, such as aspartate (Asp), glutamate (Glu), and histidine (His). To this aim, we test a scheme involving three protonation states. To facilitate charge neutrality as required for periodic boundary conditions and Particle Mesh Ewald (PME) electrostatics, titration of each respective amino acid is coupled to a "water" molecule that is charged in the opposite direction. Additionally, a force field modification for Amber99sb is introduced and tested for the description of carboxyl group protonation. Our three states model is tested by titration simulations of Asp, Glu, and His, yielding a good agreement, reproducing the correct geometry of the groups in their different protonation forms. We further show that the ion concentration change due to the neutralizing "water" molecules does not significantly affect the protonation free energies of the titratable groups, suggesting that the three states model provides a good description of biomolecular dynamics at constant pH.

  19. Rationalizing structure, stability, and chemical bonding of pure and doped clusters, isolated and solvated multiply charged anions, and solid-state materials

    Science.gov (United States)

    Sergeeva, Alina P.

    Chemistry is the study of materials and the changes that materials undergo. One can tune the properties of the known materials and design the novel materials with desired properties knowing what is responsible for the chemical reactivity, structure, and stability of those materials. The unified chemical bonding theory could address all these questions, but we do not have one available yet. The most accepted general theory of chemical bonding was proposed by Lewis in 1916, though Lewis's theory fails to explain the bonding in materials with delocalized electron density such as sub-nano and nanoclusters, as well as aromatic organic and organometallic molecules. The dissertation presents a set of projects that can be considered the steps towards the development of the unified chemical bonding theory by extending the ideas of Lewis. The dissertation also presents the studies of the properties of multiply charged anions, which tend to undergo Coulomb explosion in the isolated state and release the excess energy stored in them. It is shown how the properties of multiply charged anions can be tuned upon changing the chemical identity of the species or interaction with solvent molecules. Our findings led to the discovery of a new long-lived triply charged anionic species, whose metastability was explained by the existence of a repulsive Coulomb barrier. We also proposed two ways to restore high symmetry of compounds by suppression of the pseudo Jahn-Teller effect, which could lead to the design of new materials with the restored symmetry and therefore the novel properties.

  20. Evidence for excited-state intramolecular proton transfer in 4-chlorosalicylic acid from combined experimental and computational studies: Quantum chemical treatment of the intramolecular hydrogen bonding interaction

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Bijan Kumar [Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Calcutta 700009 (India); Guchhait, Nikhil, E-mail: nikhil.guchhait@rediffmail.com [Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Calcutta 700009 (India)

    2012-07-25

    Highlights: Black-Right-Pointing-Pointer Experimental and computational studies on the photophysics of 4-chlorosalicylic acid. Black-Right-Pointing-Pointer Spectroscopically established ESIPT reaction substantiated by theoretical calculation. Black-Right-Pointing-Pointer Quantum chemical treatment of IMHB unveils strength, nature and directional nature. Black-Right-Pointing-Pointer Superiority of quantum chemical treatment of H-bond over geometric criteria. Black-Right-Pointing-Pointer Role of H-bond as a modulator of aromaticity. -- Abstract: The photophysical study of a pharmaceutically important chlorine substituted derivative of salicylic acid viz., 4-chlorosalicylic acid (4ClSA) has been carried out by steady-state absorption, emission and time-resolved emission spectroscopy. A large Stokes shifted emission band with negligible solvent polarity dependence marks the spectroscopic signature of excited-state intramolecular proton transfer (ESIPT) reaction in 4ClSA. Theoretical calculation by ab initio and Density Functional Theory methods yields results consistent with experimental findings. Theoretical potential energy surfaces predict the occurrence of proton transfer in S{sub 1}-state. Geometrical and energetic criteria, Atoms-In-Molecule topological parameters, Natural Bond Orbital population analysis have been exploited to evaluate the intramolecular hydrogen bond (IMHB) interaction and to explore its directional nature. The inter-correlation between aromaticity and resonance assisted H-bond is also discussed in this context. Our results unveil that the quantum chemical treatment is a more accurate tool to assess hydrogen bonding interaction in comparison to geometrical criteria.

  1. Chemical shift tensor determination using magnetically oriented microcrystal array (MOMA): 13C solid-state CP NMR without MAS

    Science.gov (United States)

    Kusumi, R.; Kimura, F.; Song, G.; Kimura, T.

    2012-10-01

    Chemical shift tensors for the carboxyl and methyl carbons of L-alanine crystals were determined using a magnetically oriented microcrystal array (MOMA) prepared from a microcrystalline powder sample of L-alanine. A MOMA is a single-crystal-like composite in which microcrystals are aligned three-dimensionally in a matrix resin. The single-crystal rotation method was applied to the MOMA to determine the principal values and axes of the chemical shift tensors. The result showed good agreement with the literature data for the single crystal of L-alanine. This demonstrates that the present technique is a powerful tool for determining the chemical shift tensor of a crystal from a microcrystal powder sample.

  2. Assessing exposure and health consequences of chemicals in drinking water : Current state of knowledge and research needs

    NARCIS (Netherlands)

    Villanueva, Cristina M.; Kogevinas, Manolis; Cordier, Sylvaine; Templeton, Michael R.; Vermeulen, Roel; Nuckols, John R.; Nieuwenhuijsen, Mark J.; Levallois, Patrick

    2014-01-01

    Background: Safe drinking water is essential for well-being. Although microbiological contamination remains the largest cause of water-related morbidity and mortality globally, chemicals in water supplies may also cause disease, and evidence of the human health consequences is limited or lacking for

  3. Multi-path variational transition state theory for chemical reaction rates of complex polyatomic species: ethanol + OH reactions.

    Science.gov (United States)

    Zheng, Jingjing; Truhlar, Donald G

    2012-01-01

    Complex molecules often have many structures (conformations) of the reactants and the transition states, and these structures may be connected by coupled-mode torsions and pseudorotations; some but not all structures may have hydrogen bonds in the transition state or reagents. A quantitative theory of the reaction rates of complex molecules must take account of these structures, their coupled-mode nature, their qualitatively different character, and the possibility of merging reaction paths at high temperature. We have recently developed a coupled-mode theory called multi-structural variational transition state theory (MS-VTST) and an extension, called multi-path variational transition state theory (MP-VTST), that includes a treatment of the differences in the multi-dimensional tunneling paths and their contributions to the reaction rate. The MP-VTST method was presented for unimolecular reactions in the original paper and has now been extended to bimolecular reactions. The MS-VTST and MP-VTST formulations of variational transition state theory include multi-faceted configuration-space dividing surfaces to define the variational transition state. They occupy an intermediate position between single-conformation variational transition state theory (VTST), which has been used successfully for small molecules, and ensemble-averaged variational transition state theory (EA-VTST), which has been used successfully for enzyme kinetics. The theories are illustrated and compared here by application to three thermal rate constants for reactions of ethanol with hydroxyl radical--reactions with 4, 6, and 14 saddle points.

  4. Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn

    Energy Technology Data Exchange (ETDEWEB)

    Biesinger, Mark C., E-mail: biesingr@uwo.ca [Surface Science Western, University of Western Ontario, University of Western Ontario Research Park, Room LL31, 999 Collip Circle, London, Ontario, N6G 0J3 (Canada); ACeSSS (Applied Centre for Structural and Synchrotron Studies), University of South Australia, Mawson Lakes, SA 5095 (Australia); Lau, Leo W.M. [Surface Science Western, University of Western Ontario, University of Western Ontario Research Park, Room LL31, 999 Collip Circle, London, Ontario, N6G 0J3 (Canada); Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Gerson, Andrea R.; Smart, Roger St.C. [ACeSSS (Applied Centre for Structural and Synchrotron Studies), University of South Australia, Mawson Lakes, SA 5095 (Australia)

    2010-11-15

    Chemical state X-ray photoelectron spectroscopic analysis of first row transition metals and their oxides and hydroxides is challenging due to the complexity of the 2p spectra resulting from peak asymmetries, complex multiplet splitting, shake-up and plasmon loss structure, and uncertain, overlapping binding energies. A review of current literature shows that all values necessary for reproducible, quantitative chemical state analysis are usually not provided. This paper reports a more consistent, practical and effective approach to curve-fitting the various chemical states in a variety of Sc, Ti, V, Cu and Zn metals, oxides and hydroxides. The curve-fitting procedures proposed are based on a combination of (1) standard spectra from quality reference samples, (2) a survey of appropriate literature databases and/or a compilation of the literature references, and (3) specific literature references where fitting procedures are available. Binding energies, full-width at half maximum (FWHM) values, spin-orbit splitting values, asymmetric peak-shape fitting parameters, and, for Cu and Zn, Auger parameters values are presented. The quantification procedure for Cu species details the use of the shake-up satellites for Cu(II)-containing compounds and the exact binding energies of the Cu(0) and Cu(I) peaks. The use of the modified Auger parameter for Cu and Zn species allows for corroborating evidence when there is uncertainty in the binding energy assignment. These procedures can remove uncertainties in analysis of surface states in nano-particles, corrosion, catalysis and surface-engineered materials.

  5. Incorporation of low energy activated nitrogen onto HOPG surface: Chemical states and thermal stability studies by in-situ XPS and Raman spectroscopy

    Science.gov (United States)

    Chandran, Maneesh; Shasha, Michal; Michaelson, Shaul; Hoffman, Alon

    2016-09-01

    In this paper we report the chemical states analysis of activated nitrogen incorporated highly oriented pyrolytic graphite (HOPG) surface under well-controlled conditions. Nitrogen incorporation is carried out by two different processes: an indirect RF nitrogen plasma and low energy (1 keV) N2+ implantation. Bonding configuration, concentration and thermal stability of the incorporated nitrogen species by aforesaid processes are systematically compared by in-situ X-ray photoelectron spectroscopy (XPS). Relatively large concentration of nitrogen is incorporated onto RF nitride HOPG surface (16.2 at.%), compared to N2+ implanted HOPG surface (7.7 at.%). The evolution of N 1s components (N1, N2, N3) with annealing temperature is comprehensively discussed, which indicates that the formation and reorganization of local chemical bonding states are determined by the process of nitridation and not by the prior chemical conditioning (i.e., amorphization or hydrogenation) of the HOPG surface. A combined XPS and Raman spectroscopy studies revealed that N2+ implantation process resulted in a high level of defects to the HOPG surface, which cannot be annealed-out by heat treatment up to 1000 °C. On the other hand, the RF nitrogen plasma process did not produce a high level of surface defects, while incorporating nearly the same amount of stable nitrogen species.

  6. Hydraulic Conductivity Functions in Relation to Some Chemical Properties in a Cultivated Oxisols of a Humid Region, Delta State, Nigeria

    Directory of Open Access Journals (Sweden)

    Egbuchua, C. N.

    2014-04-01

    Full Text Available The study was conducted to evaluate hydraulic conductivity functions in relation to some soil chemical properties in an oxisols of the tropics. Field and laboratory studies were carried out and data collected, subjected to statistical analytical procedure for computing coefficient of variability and correlation among soil properties. Results of the study showed that hydraulic conductivity functions varied spatially and temporarily across the experimental points with a moderate mean value of 0.0026 cm/h and a coefficient o variation of 31.45% soil chemical properties showed that the soils were acidic with a mean pH value of 5.12. Organic carbon, total nitrogen and available phosphorus were low with mean values of 1.29%, 0.68% and 4.43 mgkg-1. Coefficient of variability among soil properties indicated less to moderately variable. Soil pH had negative correlation with all the soil properties evaluated.

  7. Predicting paramagnetic 1H NMR chemical shifts and state-energy separations in spin-crossover host-guest systems.

    Science.gov (United States)

    Isley, William C; Zarra, Salvatore; Carlson, Rebecca K; Bilbeisi, Rana A; Ronson, Tanya K; Nitschke, Jonathan R; Gagliardi, Laura; Cramer, Christopher J

    2014-06-14

    The behaviour of metal-organic cages upon guest encapsulation can be difficult to elucidate in solution. Paramagnetic metal centres introduce additional dispersion of signals that is useful for characterisation of host-guest complexes in solution using nuclear magnetic resonance (NMR). However, paramagnetic centres also complicate spectral assignment due to line broadening, signal integration error, and large changes in chemical shifts, which can be difficult to assign even for known compounds. Quantum chemical predictions can provide information that greatly facilitates the assignment of NMR signals and identification of species present. Here we explore how the prediction of paramagnetic NMR spectra may be used to gain insight into the spin crossover (SCO) properties of iron(II)-based metal organic coordination cages, specifically examining how the structure of the local metal coordination environment affects SCO. To represent the tetrahedral metal-organic cage, a model system is generated by considering an isolated metal-ion vertex: fac-ML3(2+) (M = Fe(II), Co(II); L = N-phenyl-2-pyridinaldimine). The sensitivity of the (1)H paramagnetic chemical shifts to local coordination environments is assessed and utilised to shed light on spin crossover behaviour in iron complexes. Our data indicate that expansion of the metal coordination sphere must precede any thermal SCO. An attempt to correlate experimental enthalpies of SCO with static properties of bound guests shows that no simple relationship exists, and that effects are likely due to nuanced dynamic response to encapsulation.

  8. Interfacial chemical reaction and multiple gap state formation on three layer cathode in organic light-emitting diode: Ca/BaF2/Alq3

    Science.gov (United States)

    Kim, Tae Gun; Lee, Hyunbok; Yi, Yeonjin; Lee, Seung Mi; Kim, Jeong Won

    2015-07-01

    A three layer cathode is a promising stack structure for long lifetime and high efficiency in organic light-emitting diodes. The interfacial chemical reactions and their effects on electronic structures for alkaline-earth metal (Ca, Ba)/Alq3 [tris(8-hydroxyquinolinato)aluminum] and Ca/BaF2/Alq3 are investigated using in-situ X-ray and ultraviolet photoelectron spectroscopy, as well as molecular model calculation. The BaF2 interlayer initially prevents direct contact between Alq3 and the reactive Ca metal, but it is dissociated into Ba and CaF2 by the addition of Ca. As the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with the underlying Alq3. This series of chemical reactions takes place irrespective of the BaF2 buffer layer thickness as long as the Ca overlayer thickness is sufficient. The interface reaction between the alkaline-earth metal and Alq3 generates two energetically separated gap states in a sequential manner. This phenomenon is explained by step-by-step charge transfer from the alkaline-earth metal to the lowest unoccupied molecular orbital states of Alq3, forming new occupied states below the Fermi level.

  9. Interfacial chemical reaction and multiple gap state formation on three layer cathode in organic light-emitting diode: Ca/BaF{sub 2}/Alq{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Gun; Kim, Jeong Won, E-mail: jeongwonk@kriss.re.kr [Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Daejeon 305-340 (Korea, Republic of); Korea University of Science and Technology (UST), 206 Gajeong-ro, Daejeon 305-350 (Korea, Republic of); Lee, Hyunbok [Department of Physics, Kangwon National University, 1 Gangwondaehak-gil, Chuncheon-si, Gangwon-do 200-701 (Korea, Republic of); Yi, Yeonjin [Institute of Physics and Applied Physics, Yonsei University, 50 Yonsei-ro, Seodaemoon-Gu, Seoul 120-749 (Korea, Republic of); Lee, Seung Mi [Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Daejeon 305-340 (Korea, Republic of)

    2015-07-14

    A three layer cathode is a promising stack structure for long lifetime and high efficiency in organic light-emitting diodes. The interfacial chemical reactions and their effects on electronic structures for alkaline-earth metal (Ca, Ba)/Alq{sub 3} [tris(8-hydroxyquinolinato)aluminum] and Ca/BaF{sub 2}/Alq{sub 3} are investigated using in-situ X-ray and ultraviolet photoelectron spectroscopy, as well as molecular model calculation. The BaF{sub 2} interlayer initially prevents direct contact between Alq{sub 3} and the reactive Ca metal, but it is dissociated into Ba and CaF{sub 2} by the addition of Ca. As the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with the underlying Alq{sub 3}. This series of chemical reactions takes place irrespective of the BaF{sub 2} buffer layer thickness as long as the Ca overlayer thickness is sufficient. The interface reaction between the alkaline-earth metal and Alq{sub 3} generates two energetically separated gap states in a sequential manner. This phenomenon is explained by step-by-step charge transfer from the alkaline-earth metal to the lowest unoccupied molecular orbital states of Alq{sub 3}, forming new occupied states below the Fermi level.

  10. Balanced Steady-State Free Precession (bSSFP) from an effective field perspective: Application to the detection of chemical exchange (bSSFPX)

    Science.gov (United States)

    Zhang, Shu; Liu, Zheng; Grant, Aaron; Keupp, Jochen; Lenkinski, Robert E.; Vinogradov, Elena

    2017-02-01

    Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence. The bSSFP in itself is sensitive to the exchange processes; hence, no additional saturation or preparation is needed for CEST-like data acquisition. The bSSFP experiment can be regarded as observation during saturation, without separate saturation and acquisition modules as used in standard CEST and similar experiments. One of the differences from standard CEST methods is that the bSSFP spectrum is an XY-spectrum not a Z-spectrum. As the first proof-of-principle step, we have implemented the steady-state bSSFP sequence for chemical exchange detection (bSSFPX) and verified its feasibility in phantom studies. These studies have shown that bSSFPX can achieve exchange-mediated contrast comparable to the standard CEST experiment. Therefore, the bSSFPX method has a potential for fast and quantitative CEST data acquisition.

  11. Application of the cubic-plus-association equation of state to mixtures with polar chemicals and high pressures

    DEFF Research Database (Denmark)

    Folas, Georgios; Kontogeorgis, Georgios; Michelsen, Michael Locht

    2006-01-01

    was given to low pressures and liquid-liquid equilibria. In this work, CPA is applied to two classes of mixtures containing polar chemicals for which high-pressure data are available: acetone-containing systems and dimethyl ether mixtures. They are of both scientific and industrial importance. Moreover, CPA...... is applied to high-pressure solid-liquid equilibria (SLE) for alcohol-alkane mixtures. In the case of acetone-hydrocarbon mixtures, satisfactory results are achieved if acetone is allowed to self-associate. Satisfactory high-pressure acetone-water vapor-liquid equilibrium (VLE) is obtained, comparable...

  12. Nitrogen-Doped Chemical Vapour Deposited Diamond: a New Material for Room-Temperature Solid State Maser

    Institute of Scientific and Technical Information of China (English)

    N. A. Poklonski; N. M. Lapchuk; A. V. Khomich; LU Fan-Xiu; TANG Wei-Zhong; V. G. Ralchenko; I. I. Vlasov; M. V. Chukichev; Sambuu Munkhtsetseg

    2007-01-01

    Electron spin resonance (ESR) in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 1018 cm-3 are also characterized by Raman, cathodoluminescence and optical absorption spectra. The ESR signal from P1 centre with g-factor of 2.0024 (nitrogen impurity atom occupying C site in diamond lattice) is found to exhibit an inversion with increasing the microwave power in an H102 resonator. The spin inversion effect could be of interest for further consideration of N-doped diamonds as a medium for masers operated at room temperature.

  13. The chemical composition of smokeless tobacco: a survey of products sold in the United States in 2006 and 2007.

    Science.gov (United States)

    Borgerding, M F; Bodnar, J A; Curtin, G M; Swauger, J E

    2012-12-01

    Selected toxicant concentrations and other chemical measures have been determined for 43 U.S. smokeless tobacco products sold in 2006 and 2007. Products evaluated included moist snuff, dry snuff, loose leaf, plug, dissolvable and snus tobacco brands. Reference products available for scientific research purposes and eleven Swedish products were also evaluated and compared to the commercial products studied. Chemical endpoints determined included benzo[a]pyrene (B[a]P), N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-Nitrosodimethylamine (NDMA), nitrite, cadmium, lead, arsenic, nickel, chromium, chloride, water, pH and nicotine. Different toxicant profiles were observed for the products studied, with snus tobacco brands generally containing relatively low concentrations of B[a]P and tobacco specific nitrosamines (TSNAs) compared to other moist snuffs. Smokeless tobacco reference product toxicant profiles were similar to corresponding commercial products, with the exception of the TSNA content of the dry snuff reference material. TSNA concentrations observed for all commercial products were lower than historically reported values, likely reflecting changes in product shelf life, tobacco curing practices and, possibly, product blend formulations during the last 20-30 years. The survey results summarized provide a temporal point of comparison with future data anticipated from FDA "harmful and potentially harmful constituents in tobacco products" reporting.

  14. Growth control, structure, chemical state, and photoresponse of CuO-CdS core-shell heterostructure nanowires.

    Science.gov (United States)

    El Mel, A A; Buffière, M; Bouts, N; Gautron, E; Tessier, P Y; Henzler, K; Guttmann, P; Konstantinidis, S; Bittencourt, C; Snyders, R

    2013-07-05

    The growth of single-crystal CuO nanowires by thermal annealing of copper thin films in air is studied. We show that the density, length, and diameter of the nanowires can be controlled by tuning the morphology and structure of the copper thin films deposited by DC magnetron sputtering. After identifying the optimal conditions for the growth of CuO nanowires, chemical bath deposition is employed to coat the CuO nanowires with CdS in order to form p-n nanojunction arrays. As revealed by high-resolution TEM analysis, the thickness of the polycrystalline CdS shell increases when decreasing the diameter of the CuO core for a given time of CdS deposition. Near-edge x-ray absorption fine-structure spectroscopy combined with transmission x-ray microscopy allows the chemical analysis of isolated nanowires. The absence of modification in the spectra at the Cu L and O K edges after the deposition of CdS on the CuO nanowires indicates that neither Cd nor S diffuse into the CuO phase. We further demonstrate that the core-shell nanowires exhibit the I-V characteristic of a resistor instead of a diode. The electrical behavior of the device was found to be photosensitive, since increasing the incident light intensity induces an increase in the collected electrical current.

  15. Dynamics of phytoplankton in relation to physico-chemical factors of Almatti reservoir of Bijapur District, Karnataka State.

    Science.gov (United States)

    Hulyal, S B; Kaliwal, B B

    2009-06-01

    The present investigation deals with limnobiotic status of the Almatti reservoir from February, 2003 to January, 2005. The study revealed that there exists a fluctuations of the physical factors viz., rainfall, humidity, air and water temperature, pH and electrical conductivity (EC), and chemical factors viz., dissolved oxygen (DO), free carbon dioxide, total alkalinity, total hardness, calcium, magnesium, chloride, nitrate, phosphate, sulphate, bicarbonate and total dissolved solids (TDS). From the data it was also apparent that correlations between the physico-chemical factors and dynamics of phytoplankton could be seen. The simple correlation coefficient test revealed that the cyanophytes number was positively correlated with DO, nitrate, phosphate and negatively significant with total hardness, total alkalinity, EC, calcium, magnesium, sulphate, bicarbonate and TDS. They are inversely correlated with pH, chloride, rainfall and humidity. Bacillariphyceae are correlated with total alkalinity, bicarbonates, magnesium and TDS, whereas inverse correlation was found with rainfall, humidity, pH and phosphate. Desmids showed positive correlation with nitrates, while it was inversely correlated with chloride, rainfall and humidity. Dinophytes density was positively correlated with total alkalinity, EC, total hardness, calcium, bicarbonate, while it showed inverse correlation with rainfall, humidity and phosphate. However, it is obvious that the absence of significant difference between sampling stations for all these parameters in the Almatti reservoir indicated fairly homogeneous conditions and the water quality is also found to be homogeneous.

  16. An updated state of the science EQC model for evaluating chemical fate in the environment: application to D5 (decamethylcyclopentasiloxane).

    Science.gov (United States)

    Hughes, Lauren; Mackay, Don; Powell, David E; Kim, Jaeshin

    2012-04-01

    The EQuilibrium Criterion (EQC) model developed and published in 1996 has been widely used for screening level evaluations of the multimedia, fugacity-based environmental fate of organic chemicals for educational, industrial, and regulatory purposes. Advances in the science of chemical partitioning and reactivity and the need for more rigorous regulatory evaluations have resulted in a need to update the model. The New EQC model is described which includes an improved treatment of input partitioning and reactivity data, temperature dependence and an easier sensitivity and uncertainty analysis but uses the same multi-level approach, equations and environmental parameters as in the original version. A narrative output is also produced. The New EQC model, which uses a Microsoft Excel platform, is described and applied in detail to decamethylcyclopentasiloxane (D5; CAS No. 541-02-6). The implications of these results for the more detailed exposure and risk assessment of D5 are discussed. The need for rigorous evaluation and documentation of the input parameters is outlined.

  17. Topics in Chemical Instrumentation: Solid State Electrometer for pH and Specific Ion Electrode Potential Measurements.

    Science.gov (United States)

    Edstrom, Ronald D.; Ewing, Galen W., Ed.

    1979-01-01

    The design, construction, and operation of a solid state electrometer is described. The instrument used the case and meter movement from an obsolete commercial pH meter. The cost of materials, purchased in 1977 in unit quantities, was $60. (BB)

  18. Quantum state-resolved differential cross sections for complex-forming chemical reactions: Asymmetry is the rule, symmetry the exception

    Energy Technology Data Exchange (ETDEWEB)

    Larrégaray, Pascal, E-mail: pascal.larregaray@u-bordeaux.fr; Bonnet, Laurent, E-mail: laurent.bonnet@u-bordeaux.fr [ISM, UMR 5255, CNRS, F-33400 Talence (France); ISM, UMR 5255, Univ. Bordeaux, F-33400 Talence (France)

    2015-10-14

    We argue that statistical theories are generally unable to accurately predict state-resolved differential cross sections for triatomic bimolecular reactions studied in beam experiments, even in the idealized limit where the dynamics are fully chaotic. The basic reason is that quenching of interferences between partial waves is less efficient than intuitively expected, especially around the poles.

  19. A General Solid-State Synthesis of Chemically-Doped Fluorescent Graphene Quantum Dots for Bioimaging and Optoelectronic Applications

    KAUST Repository

    Ma, Chong-Bo

    2015-05-05

    Graphene quantum dots (GQDs) have attracted increasing interest because of their excellent properties such as strong photoluminescence, excellent biocompatibility and low cost. Herein, we develop a general method for the synthesis of doped and undoped GQDs, which relies on direct carbonization of organic precursors at solid state.

  20. Synthesis of Copper Oxalate Nanorods by a Simple One-step Solid-state Chemical Reaction Method

    Institute of Scientific and Technical Information of China (English)

    CAO Ya-li; JIA Dian-zeng; LIU Lang; XIAO Ding-quan; XIN Xin-quan

    2005-01-01

    Copper oxalate nanorods were successfully prepared by means of a simple one-step solid-state reaction method with the assistance of a suitable surfactant, polyethylene glycol 400. The product with uniform rodlike morphology was characterized by XRD, TEM and SEM. The formational mechanism of the rod-like structure was also preliminary discussed.

  1. Characterization of aerosol optical properties, chemical composition and mixing states in the winter season in Shanghai, China

    Institute of Scientific and Technical Information of China (English)

    Yong Tang; Yuanlong Huang; Ling Li; Hong Chen; Jianmin Chen; Xin Yang; Song Gao

    2014-01-01

    Physical and chemical properdes of ambient aerosols at the single particle level were studied in Shanghai from December 22 to 28,2009.A Cavity-Ring-Down Aerosol Extinction Spectrometer (CRD-AES) and a nephelometer were deployed to measure aerosol light extinction and scattering properties,respectively.An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS)was used to detect single particle sizes and chemical composition.Seven particle types were detected.Air parcels arrived at the sampling site from the vicinity of Shanghai until mid-day of December 25,when they started to originate from North China.The aerosol extinction,scattering,and absorption coefficients all dropped sharply when this cold,clean air arrived.Aerosol particles changed from a highly aged type before this meteorological shift to a relatively fresh type afterwards.The aerosol optical properties were dependent on the wind direction.Aerosols with high extinction coefficient and scattering Angstr(o)m exponent (SAE) were observed when the wind blew from the west and northwest,indicating that they were predominantly fine particles.Nitrate and ammonium correlated most strongly with the change in aerosol optical properties.In the elemental carbon/organic carbon (ECOC) particle type,the diurnal trends of single scattering albedo (SSA) and elemental carbon (EC) signal intensity had a negative correlation.We also found a negative correlation (r =-0.87) between high mass-OC particle number fraction and the SSA in a relatively clean period,suggesting that particulate aromatic components might play an important role in light absorption in urban areas.

  2. Integrating physical and chemical characteristics of lakes into the glacially influenced landscape of the Northern Cascade Mountains, Washington State, USA

    Science.gov (United States)

    Larson, Gary L.; Lomnicky, G.A.; Liss, W.J.; Deimling, E.

    1999-01-01

    A basic knowledge of the physical and chemical characteristics of lakes is needed by management to make informed decisions to protect water resources. In this study we investigated some of the physical and chemical characteristics of 58 lakes in alpine, subalpine, and forest vegetation zones in a natural area (North Cascades National Park Service Complex) between 1989 and 1993. The objectives of the study were to: (1) document the time of ice-out relative to lake elevation; (2) determine how a sharp climate gradient west and east of the hydrologic divide affected the time of ice-out for subalpine lakes; and (3) assess how lake water quality was associated with lake elevation, lake depth, and basin geology. As expected, lake ice-out times occurred earlier with decreasing elevation. East-slope subalpine lakes iced-out earlier than did west-slope subalpine lakes because the east slope of the study area was drier and warmer than the west slope. On average, the lakes were relatively cold, neutral in pH, and low in dissolved substances and concentrations of nitrogen and phosphorus. Although some shallow lakes (depth ,10 m) exhibited the highest alkalinities, conductivities, and concentrations of phosphorus and nitrogen, most shallow lakes exhibited low values for these variables that were comparable to values observed in deep lakes. Geology did not play a major role in segregating the lakes based on water quality. Overall, lake temperature, pH, alkalinity, conductivity, and concentrations of total phosphorus and total Kjeldahl N increased with decreasing elevation. These changes in water quality with decreasing elevation in this temperate mountainous region corresponded with warmer air temperatures and increased vegetation biomass, soil depth and maturity, and dissolved substances and nutrients.

  3. Morphology and chemical states of size-selected Pt(n) clusters on an aluminium oxide film on NiAl(110).

    Science.gov (United States)

    Beniya, Atsushi; Isomura, Noritake; Hirata, Hirohito; Watanabe, Yoshihide

    2014-12-28

    The adsorption states of size-selected Ptn clusters (7 ≤ n ≤ 20) soft-landed on an Al2O3/NiAl(110) substrate were investigated using scanning tunneling microscopy, infrared reflection absorption spectroscopy, and temperature programmed desorption. Ptn clusters lay flat on the surface with a planar structure (n ≤ 18), and three-dimensional two-layer clusters start to appear at n ≥ 19. By considering the Pt-Pt and Pt-oxide bonds in the cluster, the morphological transition could be reasonably explained. Using CO probe molecules, the chemical states of the Pt atoms inside the clusters were investigated. Two ontop CO species were observed inside the clusters, and were assigned as adsorbed CO on neutral and slightly cationic Pt atoms. Despite the first layer Pt atoms, the Ptn clusters are composed of two kinds of Pt atoms. The observed size dependence of the Pt atoms inside the clusters may contribute to the size-dependent chemical reactivity of Ptn clusters on the Al2O3 surface.

  4. Fractional enrichment of proteins using [2-{sup 13}C]-glycerol as the carbon source facilitates measurement of excited state {sup 13}Cα chemical shifts with improved sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Ahlner, Alexandra; Andresen, Cecilia; Khan, Shahid N. [Linköping University, Division of Chemistry, Department of Physics, Chemistry and Biology (Sweden); Kay, Lewis E. [The University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry, One King’s College Circle (Canada); Lundström, Patrik, E-mail: patlu@ifm.liu.se [Linköping University, Division of Chemistry, Department of Physics, Chemistry and Biology (Sweden)

    2015-07-15

    A selective isotope labeling scheme based on the utilization of [2-{sup 13}C]-glycerol as the carbon source during protein overexpression has been evaluated for the measurement of excited state {sup 13}Cα chemical shifts using Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion (RD) experiments. As expected, the fractional incorporation of label at the Cα positions is increased two-fold relative to labeling schemes based on [2-{sup 13}C]-glucose, effectively doubling the sensitivity of NMR experiments. Applications to a binding reaction involving an SH3 domain from the protein Abp1p and a peptide from the protein Ark1p establish that accurate excited state {sup 13}Cα chemical shifts can be obtained from RD experiments, with errors on the order of 0.06 ppm for exchange rates ranging from 100 to 1000 s{sup −1}, despite the small fraction of {sup 13}Cα–{sup 13}Cβ spin-pairs that are present for many residue types. The labeling approach described here should thus be attractive for studies of exchanging systems using {sup 13}Cα spin probes.

  5. Covellite CuS as a matrix for "invisible" gold: X-ray spectroscopic study of the chemical state of Cu and Au in synthetic minerals

    Science.gov (United States)

    Tagirov, Boris R.; Trigub, Alexander L.; Kvashnina, Kristina O.; Shiryaev, Andrey A.; Chareev, Dmitriy A.; Nickolsky, Maximilian S.; Abramova, Vera D.; Kovalchuk, Elena V.

    2016-10-01

    Geological processes leading to formation of sulfide ores often result in precipitation of gold-bearing sulfides which can contain high concentrations of this metal in "invisible" (or "refractory") state. Covellite (CuS) is ubiquitous mineral in many types of the ore deposits, and numerous studies of the natural ores show that covellite can contain high concentrations of Au. At the same time, Au-bearing covellite withstands cooling in contrast to other minerals of the Cu-Fe-S system (chalcocite, bornite, chalcopyrite), where Au exsolves at low temperatures. This makes covellite a convenient model system for investigation of the chemical state (local environment and valence) of the "invisible" Au in copper-sulfide ores (copper-porphyry, epithermal, volcanogenic massive sulfide, SEDEX deposits). Therefore, it is necessary to determine the location of Au in the covellite matrix as it will have important implications for the methods employed by mineral processing industry to extract Au from sulfide ores. Here we investigate the chemical state of Cu and Au in synthetic covellite containing up to 0.3 wt.% of Au in the "invisible" state. The covellite crystals were synthesized by hydrothermal and salt flux methods. Formation of the chemically bound Au is indicated by strong dependence of the concentration of Au in covellite on the sulfur fugacity in the experimental system (d(log C(Au))/d(log f(S2)) ∼ 0.65). The Au concentration of covellite grows with increasing temperature from 400 to 450 °C, whereas further temperature increase to 500 °C has only minor effect. The synthesized minerals were studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode. Ab initio simulations of Cu K edge XANES spectra show that the Cu oxidation state in two structural positions in covellite (tetrahedral and triangular coordination with S atoms) is identical: the total loss of electronic charge for the 3d shell is ∼0

  6. Legacy in the Sand: The United States Army Armament, Munitions and Chemical Command in Operations Desert Shield and Desert Storm

    Science.gov (United States)

    1992-12-21

    each inbound Scud. Yet at the time of deployment, the United States Army did not have a single Patriot missile capable of knocking down a Scud, or any...Yet the questions are moot. The Patriot missile did exist, and did have the capability of intercepting inbound missiles. That such capacities existed at... Logstics Assistance Division. And to ensure that the form was properly prepared and thus avoid any delays in processing, AMCCOM personnel devoted

  7. Chemical structural studies of natural lignin by dipolar dephasing solid-state 13C nuclear magnetic resonance

    Science.gov (United States)

    Hatcher, P.G.

    1987-01-01

    Two natural lignins, one from a gymnosperm wood the other from angiosperm wood, were examined by conventional solid-state and dipolar dephasing 13C nuclear magnetic resonance (NMR) techniques. The results obtained from both techniques show that the structure of natural lignins is consistent with models of softwood and hardwood lignin. The dipolar dephasing NMR data provide a measure of the degree of substitution on aromatic rings which is consistent with the models. ?? 1987.

  8. Estimation of ground and excited-state dipole moments of 1, 2-diazines by solvatochromic method and quantum-chemical calculation

    DEFF Research Database (Denmark)

    Manohara, S.R.; Kumar, V. Udaya; Shivakumaraiah;

    2013-01-01

    Using the theory of solvatochromism, the difference in the excited-state (μe) and ground-state (μg) dipole moments was determined from Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet, and McRae equations for three 1,2-diazines (pyrrolo-pyridazine derivatives). All of these equations are based...... on the variation of Stokes shift with solvent's relative permittivity and refractive index. Further, the change in dipole moment value (Δμ) was also calculated using the variation of Stokes shift with the molecular-microscopic empirical solvent polarity parameter. Theoretical μg values were evaluated by quantum...... chemical calculations using the DFT method by adopting B3LYP/6-31G* level of theory (Gaussian 03) and using the AM1 method (Chem3D Ultra 8.0). It was observed that, dipole moments of diazines in the excited-state (μe) were greater than the corresponding ground-state values (μg), indicating a substantial...

  9. A solid-state nuclear magnetic resonance study of post-plasma reactions in organosilicone microwave plasma-enhanced chemical vapor deposition (PECVD) coatings.

    Science.gov (United States)

    Hall, Colin J; Ponnusamy, Thirunavukkarasu; Murphy, Peter J; Lindberg, Mats; Antzutkin, Oleg N; Griesser, Hans J

    2014-06-11

    Plasma-polymerized organosilicone coatings can be used to impart abrasion resistance and barrier properties to plastic substrates such as polycarbonate. Coating rates suitable for industrial-scale deposition, up to 100 nm/s, can be achieved through the use of microwave plasma-enhanced chemical vapor deposition (PECVD), with optimal process vapors such as tetramethyldisiloxane (TMDSO) and oxygen. However, it has been found that under certain deposition conditions, such coatings are subject to post-plasma changes; crazing or cracking can occur anytime from days to months after deposition. To understand the cause of the crazing and its dependence on processing plasma parameters, the effects of post-plasma reactions on the chemical bonding structure of coatings deposited with varying TMDSO-to-O2 ratios was studied with (29)Si and (13)C solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) using both single-pulse and cross-polarization techniques. The coatings showed complex chemical compositions significantly altered from the parent monomer. (29)Si MAS NMR spectra revealed four main groups of resonance lines, which correspond to four siloxane moieties (i.e., mono (M), di (D), tri (T), and quaternary (Q)) and how they are bound to oxygen. Quantitative measurements showed that the ratio of TMDSO to oxygen could shift the chemical structure of the coating from 39% to 55% in Q-type bonds and from 28% to 16% for D-type bonds. Post-plasma reactions were found to produce changes in relative intensities of (29)Si resonance lines. The NMR data were complemented by Fourier transform infrared (FTIR) spectroscopy. Together, these techniques have shown that the bonding environment of Si is drastically altered by varying the TMDSO-to-O2 ratio during PECVD, and that post-plasma reactions increase the cross-link density of the silicon-oxygen network. It appears that Si-H and Si-OH chemical groups are the most susceptible to post-plasma reactions. Coatings produced at a

  10. Chemical contaminants, health indicators, and reproductive biomarker responses in fish from rivers in the Southeastern United States

    Science.gov (United States)

    Hinck, J.E.; Blazer, V.S.; Denslow, N.D.; Echols, K.R.; Gale, R.W.; Wieser, C.; May, T.W.; Ellersieck, M.; Coyle, J.J.; Tillitt, D.E.

    2008-01-01

    Largemouth bass (Micropterus salmoides) and common carp (Cyprinus carpio) were collected from 13 sites located in the Mobile (MRB), Apalachicola-Flint-Chattahoochee (ARB), Savannah (SRB), and Pee Dee (PRB) River Basins to document spatial trends in accumulative chemical contaminants, health indicators, and reproductive biomarkers. Organochlorine residues, 2,3,7,8-tetrachlorodibenzo-p-dioxin-like activity (TCDD-EQ), and elemental contaminants were measured in composite samples of whole fish, grouped by species and gender, from each site. Mercury (Hg) and polychlorinated biphenyls (PCBs) were the primary contaminants of concern. Concentrations of Hg in bass samples from all basins exceeded toxicity thresholds for piscivorous mammals (> 0.1????g/g ww), juvenile and adult fish (> 0.2????g/g ww), and piscivorous birds (> 0.3????g/g ww). Total PCB concentrations in samples from the MRB, ARB, and PRB were > 480??ng/g ww and may be a risk to piscivorous wildlife. Selenium concentrations also exceeded toxicity thresholds (> 0.75????g/g ww) in MRB and ARB fish. Concentrations of other formerly used (total chlordanes, dieldrin, endrin, aldrin, mirex, and hexachlorobenzene) and currently used (pentachlorobenzene, pentachloroanisole, dacthal, endosulfan, ??-hexachlorocyclohexane, and methoxychlor) organochlorine residues were generally low or did not exceed toxicity thresholds for fish and piscivorous wildlife. TCDD-EQs exceeded wildlife dietary guidelines (> 5??pg/g ww) in MRB and PRB fish. Hepatic ethoxyresorufin O-deethylase (EROD) activity was generally greatest in MRB bass and carp. Altered fish health indicators and reproductive biomarker were noted in individual fish, but mean responses were similar among basins. The field necropsy and histopathological examination determined that MRB fish were generally in poorer health than those from the other basins, primarily due to parasitic infestations. Tumors were found in few fish (n = 5; 0.01%); ovarian tumors of smooth muscle

  11. Application of the CPA equation of state to reservoir fluids in presence of water and polar chemicals

    DEFF Research Database (Denmark)

    Yan, Wei; Kontogeorgis, Georgios; Stenby, Erling Halfdan

    2009-01-01

    The complex phase equilibrium between reservoir fluids and associating compounds like water, methanol and glycols has become more and more important as the increasing global energy demand pushes the oil industry to target reservoirs with extreme or complicated conditions, such as deep or offshore...... reservoirs. Conventional equation of state (EoS) with classical mixing rules cannot satisfactorily predict or even correlate the phase equilibrium of those systems. A promising model for such systems is the Cubic-Plus-Association (CPA) EoS, which has been successfully applied to well-defined systems...

  12. Rapid Synthesis of Lead Oxide Nanorods by One-step Solid-state Chemical Reaction at Room Temperature

    Institute of Scientific and Technical Information of China (English)

    CAO, Ya-Li(曹亚丽); JIA, Dian-Zeng(贾殿赠); LIU, Lang(刘浪); LUO, Jian-Min(骆建敏)

    2004-01-01

    A simple and facile method was reported to synthesize lead oxide nanorods. Nanorods of lead oxide were obtained directly from grinding solid metal salt and sodium hydroxide in agate mortar with the assistance of a suitable nonionic surfactant in only one step, which is different from the result of hydroxide in solution. The product has been characterized by XRD, TEM and SEM. The formation mechanism of rod-like morphology is discussed and the surfactant plays an important soft-template role in modifying the interface of solid-state reaction and according process of rod-formation.

  13. Zn/O ratio and oxygen chemical state of nanocrystalline ZnO films grown at different temperatures

    Institute of Scientific and Technical Information of China (English)

    Fan Hai-Bo; Zheng Xin-Liang; Wu Si-Cheng; Liu Zhi-Gang; Yao He-Bao

    2012-01-01

    ZnO nanocrystalline films are prepared on Si substrates at different temperatures by using metal-organic chemical vapour deposition (MOCVD).It is observed that when the growth temperature is low,the stoichiometric ratio between Zn and O atoms has a large deviation from the ideal ratio of 1:1.The ZnO grains in the film have small sizes and are not well crystallized,resulting in a poor photoluminescence (PL) property.When the temperature is increased to an appropriate value,the Zn/O ratio becomes optimized,and most of Zn and O atoms are combined into Zn-O bonds.Then the film has good crystal quality and good PL property.If the temperature is fairly high,the interfacial mutual diffusion of atoms between the substrate and the epitaxial film appears,and the desorption process of the oxygen atoms is enhanced.However,it has no effect on the film property.The film still has the best crystal quality and PL property.

  14. Methyl rotor quantum states and the effect of chemical environment in organic crystals: γ -picoline and toluene

    Science.gov (United States)

    Khazaei, Somayeh; Sebastiani, Daniel

    2016-12-01

    Using a set of first-principles calculations, we have studied the methyl tunnel splitting for molecular crystals of γ-picoline and toluene. The effective rotational potential energy surface of the probe methyl rotor along the tunneling path is evaluated using first-principles electronic structure calculations combined with the nudged elastic band method. The tunnel splitting is calculated by an explicit diagonalization of the one-dimensional time-independent Hamiltonian matrix. The effects of chemical environment and rotor-rotor coupling on the rotational energy barriers were investigated. It is found that more dense packing of the molecules in toluene compared to that in γ-picoline gives rise to a larger rotational barrier which in turn yields a considerably smaller tunnel splitting. Moreover, it turned out that coupled motion of the face-to-face methyl groups in γ-picoline has a significant effect on the reduction of the rotational barrier. Our results are in good agreement with the experimentally observed tunnel splitting.

  15. On the chemical stability of post-lithiated garnet Al-stabilized Li7La3Zr2O12 solid state electrolyte thin films.

    Science.gov (United States)

    Rawlence, Michael; Garbayo, Inigo; Buecheler, Stephan; Rupp, J L M

    2016-08-21

    Garnet-based Al-doped Li7La3Zr2O12 has the potential to be used as a solid state electrolyte for future lithium microbattery architectures, due to its relatively high Li(+) conductivity and stability against Li. Through this work, a model experiment is presented in which the effect of post-lithiation on phase formation and chemical stability is studied for pulsed laser deposited Al-doped Li7La3Zr2O12 thin films on MgO substrates. We report the implications of the newly suggested post-lithiation route for films with thicknesses between 90 and 380 nm. The phase changes from cubic, to a mix of cubic and tetragonal Li7La3Zr2O12, to a cubic Li7La3Zr2O12 and La2Zr2O7 containing film is accompanied by a reduction in the degree of de-wetting as the thickness increases. This study reveals that the thicker, dense, and continuous films remain predominantly in a mixed phase containing cubic Li7La3Zr2O12 and the lithium free La2Zr2O7 phase whereas the thinner, de-wetted films exhibit improved lithium incorporation resulting in the absence of the lithium free phase. For tuning the electrical conductivity and effective use of these structures in future batteries, understanding this material system is of great importance as the chemical stability of the cubic Li7La3Zr2O12 phase in the thin film system will control its effective use. We report a conductivity of 1.2 × 10(-3) S cm(-1) at 325 °C for a 380 nm thick solid state electrolyte film on MgO for potential operation in future all solid state battery assemblies.

  16. Advances in simultaneous DSC-FTIR microspectroscopy for rapid solid-state chemical stability studies: some dipeptide drugs as examples.

    Science.gov (United States)

    Lin, Shan-Yang; Wang, Shun-Li

    2012-04-01

    The solid-state chemistry of drugs has seen growing importance in the pharmaceutical industry for the development of useful API (active pharmaceutical ingredients) of drugs and stable dosage forms. The stability of drugs in various solid dosage forms is an important issue because solid dosage forms are the most common pharmaceutical formulation in clinical use. In solid-state stability studies of drugs, an ideal accelerated method must not only be selected by different complicated methods, but must also detect the formation of degraded product. In this review article, an analytical technique combining differential scanning calorimetry and Fourier-transform infrared (DSC-FTIR) microspectroscopy simulates the accelerated stability test, and simultaneously detects the decomposed products in real time. The pharmaceutical dipeptides aspartame hemihydrate, lisinopril dihydrate, and enalapril maleate either with or without Eudragit E were used as testing examples. This one-step simultaneous DSC-FTIR technique for real-time detection of diketopiperazine (DKP) directly evidenced the dehydration process and DKP formation as an impurity common in pharmaceutical dipeptides. DKP formation in various dipeptides determined by different analytical methods had been collected and compiled. Although many analytical methods have been applied, the combined DSC-FTIR technique is an easy and fast analytical method which not only can simulate the accelerated drug stability testing but also at the same time enable to explore phase transformation as well as degradation due to thermal-related reactions. This technique offers quick and proper interpretations.

  17. Mixed-State Hall Effect in Chemically-Substituted YBa_2Cu_3O_7-δ Single Crystals

    Science.gov (United States)

    Han, S. H.; Herrmann, J.; Gajewski, D. A.; Paulius, L. M.; Almasan, C. C.; Maple, M. B.

    1996-03-01

    Longitudinal resistivity and Hall effect measurements on single crystals of Y_1-xPr_xBa_2Cu_3O_7-δ, YBa_2Cu_3O_7-y, and YBa_2Cu_3-zZn_zO_7-δ in the mixed-state reveal a ``negative Hall anomaly'' below T_c. The negative Hall signal decreases with decreasing CuO2 plane hole concentration and increasing disorder. The Hall conductivity has been analyzed using the expression σ_xy = C_1/B + C_2B + C_3, where C_1/B and C_2B are associated with the motion of the magnetic vortices and of the quasiparticles in the vortex cores, respectively. We extracted the scaling behavior of the parameters C1 and C2 with temperature in the form of A(1-T/T_c)^α and B_1(T_c/T)^β + B_2, respectively. We discovered a delayed onset of a finite transverse resistance with increasing applied magnetic fields, as compared to the longitudinal resistance. The results will be discussed in terms of a model involving quasiparticle density fluctuations in the vortex cores. This work was supported by the U. S. Department of Energy DE-FG03-86ER-45230. Financial support from LANL/INCOR (UC-91-6-A-110) (SHH) and DAAD (JH) is acknowledged. *Present Address: Department of Physics, Western Michigan University **Present Address: Department of Physics, Kent State University

  18. Comparative morphometric and chemical analyses of phenotypes of two invasive ambrosia beetles (Euwallacea spp.) in the United States of America.

    Science.gov (United States)

    Chen, Yigen; Dallara, Paul L; Nelson, Lori J; Coleman, Tom W; Hishinuma, Stacy M; Carrillo, Daniel; Seybold, Steven J

    2016-03-02

    The polyphagous shot hole borer (PSHB), Euwallacea sp., was first detected in 2003 in Los Angeles County, California, USA. Recently, this invasive species has become a major pest of many hardwood trees in urban and wildland forests throughout southern California. PSHB is nearly identical in morphology and life history to the tea shot hole borer (TSHB), Euwallacea fornicatus, an invasive pest of hardwoods in Florida, USA and many other parts of the world. However, molecular studies have suggested that the taxa are different species. We conducted morphometric and chemical analyses of the phenotypes of Euwallacea sp. collected in southern California (Los Angeles Co.) and E. fornicatus collected in Florida (Miami-Dade Co.). Our analyses indicated that PSHB has three larval instars. The third larval instar was separated from the first two instars by head capsule width with zero probability of misclassification. The body length, head width, and pronotal width of PSHB adult males were significantly less than those of females. Head width and pronotal width of female PSHB were significantly less than those of female TSHB. In contrast, body length, and ratio of body length to pronotal width of PSHB females were significantly greater than those of TSHB females. However, females of these two species could not be separated completely by these four measurements because of the overlapping ranges. Cuticular hydrocarbons detected in both species were exclusively alkanes (i.e., n-alkanes, monomethylalkanes, dimethylalkanes, and trimethylalkanes). Cuticular hydrocarbon profiles of PSHB males and females were similar, but they both differed from that of TSHB females. Cuticular hydrocarbons of PSHB were predominantly internally branched dimethylalkanes with backbones of 31 and 33 carbons, whereas cuticular hydrocarbons of TSHB females were dominated by internally branched monomethyl- and dimethylalkanes with backbones of 29 carbons. This article is protected by copyright. All rights

  19. Anisotropy of chemical transformation from In2Se3 to CuInSe2 nanowires through solid state reaction.

    Science.gov (United States)

    Schoen, David T; Peng, Hailin; Cui, Yi

    2009-06-17

    In(2)Se(3) nanowires synthesized by the VLS technique are transformed by solid-state reaction with copper into high-quality single-crystalline CuInSe(2) nanowires. The process is studied by in situ transmission electron microscopy. The transformation temperature exhibits a surprising anisotropy, with In(2)Se(3) nanowires grown along their [0001] direction transforming at a surprisingly low temperature of 225 degrees C, while nanowires in a [11(2)0] orientation require a much higher temperature of 585 degrees C. These results offer a route to the synthesis of CuInSe(2) nanowires at a relatively low temperature as well as insight into the details of a transformation commonly used in the fabrication of thin-film solar cells.

  20. Are safe results obtained when the PC-SAFT equation of state is applied to ordinary pure chemicals?

    DEFF Research Database (Denmark)

    Privat, Romain; Gani, Rafiqul; Jaubert, Jean-Noël

    2010-01-01

    The PC-SAFT equation of state is a very popular and promising model for fluids that employs a complicated pressure-explicit mathematical function (and can therefore not be solved analytically at a specified pressure and temperature, contrary to classical cubic equations). In this work, we...... demonstrate that in case of pure fluids, the PC-SAFT equation may exhibit up to five different volume-roots whereas cubic equations give at the most three volume-roots (and yet, only one or two volume roots have real significance). The consequence of this strongly atypical behaviour is the existence of two...... different fluid-fluid coexistence lines (the vapour pressure-curve and an additional liquid-liquid equilibrium curve) and two critical points for a same pure component, which is obviously physically inconsistent. In addition to n-alkanes, nearly sixty very common pure components (branched alkanes...

  1. Causes and Countermeasures of Brain Drain in State-owned Chemical Enterprises%国有化工企业人才流失原因及对策

    Institute of Scientific and Technical Information of China (English)

    王健

    2013-01-01

    In the era of knowledge economy, talents are the most valuable resource and core competitiveness of enterprises. In the fierce market competition, with the entry of foreign-funded enterprises, brain drain of China's state-owned enterprises becomes more and more serious. Based on current situation and characteristics of brain drain in state-owned chemical enterprises, the paper analyzes in-depth the causes of brain drain of the enterprises. It proposes the countermeasures for brain drain in state-owned enterprises from the as-pects of talents strategy, personnel security, human environment, pre-control of brain drain and turnover management.%在知识经济时代,人才资源是企业最宝贵的资源,是企业的核心竞争力。随着外资企业的进入,我国国有企业人才流失现象越来越严重。基于国有化工企业人才流失的特点,可以深入剖析企业人才流失的原因,从人才战略、人才保障、人文环境、人才流失预控与离职管理等方面提出国有企业人才流失的解决方案。

  2. Ab initio quantum-chemical computations of the electronic states in HgBr2 and IBr: Molecules of interest on the Earth's atmosphere

    Science.gov (United States)

    Sitkiewicz, Sebastian P.; Oliva, Josep M.; Dávalos, Juan Z.; Notario, Rafael; Saiz-Lopez, Alfonso; Alcoba, Diego R.; Oña, Ofelia B.; Roca-Sanjuán, Daniel

    2016-12-01

    The electronic states of atmospheric relevant molecules IBr and HgBr2 are reported, within the UV-Vis spectrum range (170 nm ≤λp h o t o n≤600 nm) by means of the complete-active-space self-consistent field/multi-state complete-active-space second-order perturbation theory/spin-orbit restricted-active-space state-interaction (CASSCF/MS-CASPT2/SO-RASSI) quantum-chemical approach and atomic-natural-orbital relativistic-correlation-consistent (ANO-RCC) basis sets. Several analyses of the methodology were carried out in order to reach converged results and therefore to establish a highly accurate level of theory. Good agreement is found with the experimental data with errors not higher than around 0.1 eV. The presented analyses shall allow upcoming studies aimed to accurately determine the absorption cross sections of interhalogen molecules and compounds with Hg that are relevant to better comprehend the photochemical processes taking place in the atmosphere.

  3. Determination of the Tautomeric Equilibria of Pyridoyl Benzoyl -Diketones in the Liquid and Solid State through the use of Deuterium Isotope Effects on 1H and 13C NMR Chemical Shifts and Spin Coupling Constants

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Borisov, Eugeny V.; Lindon, John C.

    2015-01-01

    The tautomeric equilibria for 2-pyridoyl-, 3-pyridoyl-, and 4-pyridoyl-benzoyl methane have been investigated using deuterium isotope effects on 1H and 13C chemical shifts both in the liquid and the solid state. Equilibria are established both in the liquid and the solid state. In addition, in th...

  4. Chemical Analysis of Suspected Unrecorded Alcoholic Beverages from the States of São Paulo and Minas Gerais, Brazil

    Directory of Open Access Journals (Sweden)

    Giuseppina Negri

    2015-01-01

    Full Text Available Our study analyzed 152 samples of alcoholic beverages collected from the states of São Paulo and Minas Gerais, Brazil, using gas chromatography with flame ionization detection (GC-FID and mass spectrometry (GC-MS, Fourier transform infrared spectroscopy (FT-IR, and inductively coupled plasma atomic emission spectrometry (ICP-AES. The methanol content varied from 20 to 180 ppm in 28 samples, and the limit of the accepted level of 200 ppm was exceeded in only one sample. High content of cyanide derivatives and ethyl carbamate, above the accepted level of 150 ppb, was observed in 109 samples. Carbonyl compounds were also observed in 111 samples, showing hydroxy 2-propanone, 4-methyl-4-hepten-3-one, furfural, and 2-hydroxyethylcarbamate as main constituents. Copper was found at concentrations above 5 ppm in 26 samples; the maximum value observed was 28 ppm. This work evaluated the human health risk associated with the poor quality of suspected unrecorded alcohols beverages.

  5. Potential of dispersion of Tecoma stans and chemical attributes of some soils of the Paraná state

    Directory of Open Access Journals (Sweden)

    Celina Wisniewski

    2009-03-01

    Full Text Available This work correlated invasiveness characteristic (potential dispersion of Tecoma stans (L. Jussieu ex. Kunth(BIGNONIACEAE known as a Yellow-Bell. Open field test was developed starting from stakes in vases with four different types soilsof the Paraná State, conduced to randomized block design with four treatments and five replications. The soils were analyzedregarding the pH, CTC, level of C, Al+³, macro and micronutrients, and content of sand, silt and clay. After 6 months the leaf area, dryweight of leaves and potential dispersion, calculated by given numeric values from 1 to 4 for phonological phases presented. Themacro and micronutrients content (except K and Fe were high in all the soils. The correlations between dispersion potential and pHand the V% were positive and significant and with effective CTC, the Fe and clay content were negative. It was not found significantcorrelations between the dispersion potential and biomass or leaf area. Positive and significant correlations of biomass and leaf areawith macro (except P and micronutrients (except Cu apparently indicate that if the evaluation had been accomplished at the end of theflowering period of the species, nutritional relationships with the dispersion potential would be clearer, although it can be concludedthat the species has a preference for less acid soils.

  6. A new chemical route to a hybrid nanostructure: room-temperature solid-state reaction synthesis of Ag@AgCl with efficient photocatalysis.

    Science.gov (United States)

    Hu, Pengfei; Cao, Yali

    2012-08-01

    The room-temperature solid-state chemical reaction technique has been used to synthesize the silver nanoparticle-loaded semiconductor silver@silver chloride for the first time. It has the advantages of convenient operation, lower cost, less pollution, and mass production. This simple technique created a wide array of nanosized silver particles which had a strong surface plasmon resonance effect in the visible region, and built up an excellent composite structure of silver@silver chloride hybrid which exhibited high photocatalytic activity and stability towards decomposition of organic methyl orange under visible-light illumination. Moreover, this work achieved the control of composition of the silver@silver chloride composite simply by adjusting the feed ratio of reactants. It offers an alternative method for synthesising metal@semiconductor composites.

  7. Degradation of chlorophenols and alkylphenol ethoxylates, two representative textile chemicals, in water by advanced oxidation processes: the state of the art on transformation products and toxicity.

    Science.gov (United States)

    Karci, Akin

    2014-03-01

    Advanced oxidation processes based on the generation of reactive species including hydroxyl radicals are viable options in eliminating a wide array of refractory organic contaminants in industrial effluents. The assessment of transformation products and toxicity should be, however, the critical point that would allow the overall efficiency of advanced oxidation processes to be better understood and evaluated since some transformation products could have an inhibitory effect on certain organisms. This article reviews the most recent studies on transformation products and toxicity for evaluating advanced oxidation processes in eliminating classes of compounds described as "textile chemicals" from aqueous matrices and poses questions in need of further investigation. The scope of this paper is limited to the scientific studies with two classes of textile chemicals, namely chlorophenols and alkylphenol ethoxylates, whose use in textile industry is a matter of debate due to health risks to humans and harm to the environment. The article also raises the critical question: What is the state of the art knowledge on relationships between transformation products and toxicity?

  8. Noise-induced modulation of the relaxation kinetics around a non-equilibrium steady state of non-linear chemical reaction networks.

    Science.gov (United States)

    Ramaswamy, Rajesh; Sbalzarini, Ivo F; González-Segredo, Nélido

    2011-01-28

    Stochastic effects from correlated noise non-trivially modulate the kinetics of non-linear chemical reaction networks. This is especially important in systems where reactions are confined to small volumes and reactants are delivered in bursts. We characterise how the two noise sources confinement and burst modulate the relaxation kinetics of a non-linear reaction network around a non-equilibrium steady state. We find that the lifetimes of species change with burst input and confinement. Confinement increases the lifetimes of all species that are involved in any non-linear reaction as a reactant. Burst monotonically increases or decreases lifetimes. Competition between burst-induced and confinement-induced modulation may hence lead to a non-monotonic modulation. We quantify lifetime as the integral of the time autocorrelation function (ACF) of concentration fluctuations around a non-equilibrium steady state of the reaction network. Furthermore, we look at the first and second derivatives of the ACF, each of which is affected in opposite ways by burst and confinement. This allows discriminating between these two noise sources. We analytically derive the ACF from the linear Fokker-Planck approximation of the chemical master equation in order to establish a baseline for the burst-induced modulation at low confinement. Effects of higher confinement are then studied using a partial-propensity stochastic simulation algorithm. The results presented here may help understand the mechanisms that deviate stochastic kinetics from its deterministic counterpart. In addition, they may be instrumental when using fluorescence-lifetime imaging microscopy (FLIM) or fluorescence-correlation spectroscopy (FCS) to measure confinement and burst in systems with known reaction rates, or, alternatively, to correct for the effects of confinement and burst when experimentally measuring reaction rates.

  9. Chemical Doping Induced Ferro- and Antiferro-magnetic States in non-Magnetic Insulating FeGa3

    Science.gov (United States)

    Haldolaarachchige, N.; Prestigiacomo, J.; Xiong, Y.; Phelan, A.; Chan, J.; Sheehy, D.; Adams, P.; Ditusa, J.; Stadler, S.; Young, D.

    2013-03-01

    A ferromagnetic quantum critical point (FM-QCP) in Ge-doped FeGa3 was reported very recently (Umeo et al. PRB 86 (14), 144421, 2012). We have simultaneously observed the FM-QCP in this system. Furthermore, we analyzed the magnetic properties of FeGa3 in the context of a unique structural feature, where the four Fe atoms in the unit cell exist as two Fe-Fe dimers (Yin and Picket, PRB 82 (15), 155202, 2010). We propose a phenomenological model where the extrinsic electrons from the Ge doping creates a mixed valence Fe-dimer with a net effective spin. Such a model provides a novel mechanism for the (FM-QCP) and is consistent with the system's magnetic and thermal properties. In addition to Ge doping, we have investigated effects of Ru/Mn substitution on the Fe site. Ru substitution produces an unexpected ferromagnetic (FM) insulating phase that develops immediately, and it disappears above an intermediate doping level. This behavior agrees well with our model of spin creation on the transition-metal dimers via conduction electrons, and the enhanced insulating behavior in the electrical resistivity suggests the Ru acquires a 2 + state. Interestingly, Mn-doped FeGa3 shows an apparent antiferromagnetic (AFM) insulating phase, where the magnetic data is consistent with the effective moment coming from Mn(3 +) . These results provide further evidence of the important role of the Fe-Fe dimer structure in FeGa3in determining its unique magnetic properties.

  10. Kinetics of Hydrogen Radical Reactions with Toluene Including Chemical Activation Theory Employing System-Specific Quantum RRK Theory Calibrated by Variational Transition State Theory.

    Science.gov (United States)

    Bao, Junwei Lucas; Zheng, Jingjing; Truhlar, Donald G

    2016-03-02

    Pressure-dependent reactions are ubiquitous in combustion and atmospheric chemistry. We employ a new calibration procedure for quantum Rice-Ramsperger-Kassel (QRRK) unimolecular rate theory within a chemical activation mechanism to calculate the pressure-falloff effect of a radical association with an aromatic ring. The new theoretical framework is applied to the reaction of H with toluene, which is a prototypical reaction in the combustion chemistry of aromatic hydrocarbons present in most fuels. Both the hydrogen abstraction reactions and the hydrogen addition reactions are calculated. Our system-specific (SS) QRRK approach is adjusted with SS parameters to agree with multistructural canonical variational transition state theory with multidimensional tunneling (MS-CVT/SCT) at the high-pressure limit. The new method avoids the need for the usual empirical estimations of the QRRK parameters, and it eliminates the need for variational transition state theory calculations as a function of energy, although in this first application we do validate the falloff curves by comparing SS-QRRK results without tunneling to multistructural microcanonical variational transition state theory (MS-μVT) rate constants without tunneling. At low temperatures, the two approaches agree well with each other, but at high temperatures, SS-QRRK tends to overestimate falloff slightly. We also show that the variational effect is important in computing the energy-resolved rate constants. Multiple-structure anharmonicity, torsional-potential anharmonicity, and high-frequency-mode vibrational anharmonicity are all included in the rate computations, and torsional anharmonicity effects on the density of states are investigated. Branching fractions, which are both temperature- and pressure-dependent (and for which only limited data is available from experiment), are predicted as a function of pressure.

  11. Comparison of Escherichia coli tRNAPhe in the free state, in the ternary complex and in the ribosomal A and P sites by chemical probing

    DEFF Research Database (Denmark)

    Douthwaite, S; Garrett, R A; Wagner, R

    1983-01-01

    with elongation factor EF-Tu and GTP and in the ribosomal A and P sites were compared. A special procedure was devised to monitor, exclusively, tRNA molecules in the aminoacylated state. In the free tRNA, the most reactive bases are confined to the A73-C-C-A sequence of the aminoacyl stem, the anticodon loop......tRNAPheE.coli was modified at accessible guanosine, cytidine, and adenosine residues using the chemical modification method described by Peattie and Gilbert [Proc. Natl Acad. Sci. USA, 77, 4679-4689 (1980)]. Modification characteristics of the tRNA in the free state, in the ternary complex......, the D-loop and the extra loop and the results correlate well with the three-dimensional structure of tRNAPheyeast determined by X-ray studies. The pattern of reactivity was not affected either by charging the tRNA with phenylalanine or by labelling the 3' terminus with pCp. In the ternary complex...

  12. Ground state lasing at 1.30 microm from InAs/GaAs quantum dot lasers grown by metal-organic chemical vapor deposition.

    Science.gov (United States)

    Guimard, Denis; Ishida, Mitsuru; Bordel, Damien; Li, Lin; Nishioka, Masao; Tanaka, Yu; Ekawa, Mitsuru; Sudo, Hisao; Yamamoto, Tsuyoshi; Kondo, Hayato; Sugawara, Mitsuru; Arakawa, Yasuhiko

    2010-03-12

    We investigated the effects of post-growth annealing on the photoluminescence (PL) characteristics of InAs/GaAs quantum dots (QDs) grown by metal-organic chemical vapor deposition (MOCVD). The onset temperature at which both the peak linewidth and the PL intensity degraded and the blueshift of the ground state emission wavelength occurred was found to depend on both the QD density and the In composition of the capping layer. This behavior is particularly important in view of QD integration in photonic devices. From the knowledge of the dependences of the PL characteristics after annealing on the QD and capping growth conditions, ground state lasing at 1.30 microm could be demonstrated from InAs/GaAs QDs grown by MOCVD. Finally, we compared the laser characteristics of InAs/GaAs QDs with those of InAs/Sb:GaAs QDs, grown according to the antimony-mediated growth technique, and showed that InAs/Sb:GaAs QDs are more appropriate for laser fabrication at 1.3 microm by MOCVD.

  13. Ground state lasing at 1.30 {mu}m from InAs/GaAs quantum dot lasers grown by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Guimard, Denis; Ishida, Mitsuru; Bordel, Damien; Li Lin; Nishioka, Masao; Arakawa, Yasuhiko [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Tanaka, Yu; Kondo, Hayato; Sugawara, Mitsuru [QD Laser Inc., 1-8-1 Ohtemachi, Chyoda-ku, Tokyo 100-0004 (Japan); Ekawa, Mitsuru; Sudo, Hisao; Yamamoto, Tsuyoshi, E-mail: dguimard@iis.u-tokyo.ac.jp [Fujitsu Laboratories Limited, 10-1 Morinosato-Wakamiya, Atsugi 243-0197 (Japan)

    2010-03-12

    We investigated the effects of post-growth annealing on the photoluminescence (PL) characteristics of InAs/GaAs quantum dots (QDs) grown by metal-organic chemical vapor deposition (MOCVD). The onset temperature at which both the peak linewidth and the PL intensity degraded and the blueshift of the ground state emission wavelength occurred was found to depend on both the QD density and the In composition of the capping layer. This behavior is particularly important in view of QD integration in photonic devices. From the knowledge of the dependences of the PL characteristics after annealing on the QD and capping growth conditions, ground state lasing at 1.30 {mu}m could be demonstrated from InAs/GaAs QDs grown by MOCVD. Finally, we compared the laser characteristics of InAs/GaAs QDs with those of InAs/Sb:GaAs QDs, grown according to the antimony-mediated growth technique, and showed that InAs/Sb:GaAs QDs are more appropriate for laser fabrication at 1.3 {mu}m by MOCVD.

  14. ¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations, Part I: Chemical shifts assignment.

    Science.gov (United States)

    Pisklak, Dariusz Maciej; Zielińska-Pisklak, Monika Agnieszka; Szeleszczuk, Łukasz; Wawer, Iwona

    2016-04-15

    Solid-state NMR is an excellent and useful method for analyzing solid-state forms of drugs. In the (13)C CP/MAS NMR spectra of the solid dosage forms many of the signals originate from the excipients and should be distinguished from those of active pharmaceutical ingredient (API). In this work the most common pharmaceutical excipients used in the solid drug formulations: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. Their (13)C CP/MAS NMR spectra were recorded and the signals were assigned, employing the results (R(2): 0.948-0.998) of GIPAW calculations and theoretical chemical shifts. The (13)C ssNMR spectra for some of the studied excipients have not been published before while for the other signals in the spectra they were not properly assigned or the assignments were not correct. The results summarize and complement the data on the (13)C ssNMR analysis of the most common pharmaceutical excipients and are essential for further NMR studies of API-excipient interactions in the pharmaceutical formulations.

  15. Relationships between microbial activity and soil physical and chemical properties in native and reforested Araucaria angustifolia forests in the state of São Paulo, Brazil

    Directory of Open Access Journals (Sweden)

    Jamil de Morais Pereira

    2013-06-01

    Full Text Available Araucaria angustifolia (Bert. O. Kuntze is the main component of the Mixed Ombrophilous forest and, in the State of São Paulo, it is associated with a high diversity of soil organisms, essential for the maintenance of soil quality, making the conservation of this ecosystem a major and pressing challenge. The objective of this study was to identify the physical and chemical properties that are most closely correlated with dehydrogenase enzyme activity, basal respiration and microbial biomass under native (NF and replanted (RF Araucaria angustifolia forests in three regions of the state of São Paulo, in winter and summer. The main differentiating factors between the areas were also determined. Each forest was represented by three true replications; at each site, from around the araucaria trees, 15 soil samples (0-20 cm were collected to evaluate the soil physical, chemical and microbiological properties. At the same points, forest litter was sampled to assess mass and chemical properties. The following microbiological properties were evaluated: microbial biomass carbon (MBC, basal respiration (CO2-C, metabolic quotient (Q: CO2, dehydrogenase enzyme activity (DHA as well as the physical properties (moisture, bulk density, macroporosity and total porosity, soil chemical properties [pH, organic carbon (org-C, P, Ca, K, Mg, Al, H+Al], litter dry mass, and C, N and S contents. The data were subjected to analysis of variance (TWO-WAY: ANOVA. A Canonical Discriminant Analysis (CDA and a Canonical Correlation Analysis (CCA were also performed. In the soil under NF, the values of K, P, soil macroporosity, and litter dry mass were higher and Q: CO2 and DHA lower, regardless of the sampling period, and DHA was lower in winter. In the RF areas, the levels of moisture, porosity and Q: CO2 were higher in both sampling periods, and DHA was higher in winter. The MBC was only higher under NF in the summer, while the litter contents of C, N and S were greater in

  16. Chemical Emergencies

    Science.gov (United States)

    When a hazardous chemical has been released, it may harm people's health. Chemical releases can be unintentional, as in the case of an ... the case of a terrorist attack with a chemical weapon. Some hazardous chemicals have been developed by ...

  17. Assessment Of Physico-Chemical Property Of Water Samples From Port Harcourt Bonny And Opobo Coastal Areas For Sustainable Coastal Tourism Development In Rivers State Nigeria.

    Directory of Open Access Journals (Sweden)

    Obinwanne

    2015-08-01

    Full Text Available Abstract The study evaluated some physico-chemical properties of water samples from Port Harcourt Bonny and Opobo to determine the safety of water from the areas for sustainable coastal tourism development in Rivers State Nigeria. Three water samples were collected with three sterilized plastic containers with a capacity of 25cl which were subjected to laboratory tests to know their constituents. The parameters tested were appearance temperature colour turbidity conductivity PH alkalinity lead Pb Chromium Cr Cadmium Cd Ammonia BODs and Dissolved Oxygen. The results of the water samples were compared with World Health Organization WHO water quality standard and the Nigeria National Water Quality standard to determine the safety of the water for human consumption and tourism development. The study revealed that Port Harcourt site has more prospects for tourism development more than Opobo study site because the Ph alkalinity and BODs levels were lower than that of Opobo making the water safer except that the amount of dissolved oxygen was a little high in Opobo and turbidity was not detected in Opobo. The study revealed that Bonny water was very dense in appearance dark brown in colour highly turbid basic and with mean concentration of the heavy metals Lead chromium and cadmium higher than the recommended World Health Organization WHO water quality standard and the Nigeria National Water Quality standard and therefore not safe for drinking and swimming. Treated portable water should be provided for the people of Port Harcourt Opobo and Bonny especially people from Bonny area and development of tourism in the state to save the people and tourists from imminent danger of fecal contaminants and toxic substances.

  18. The effects of ionic strength on the toxicity of aluminium to Atlantic salmon (Salmo salar under non-steady state chemical conditions

    Directory of Open Access Journals (Sweden)

    Antonio B.S. POLÉO

    2002-02-01

    Full Text Available We have tested the influence of water ionic strength on the toxicity of aluminium in fish by comparing the mortality of Atlantic salmon (Salmo salar parr exposed to Al-rich water with additions of Ca2+ or Na+. The fish were exposed in parallel to Al-rich water (Al 500 μg l-1, pH 5.8 under non-steady state conditions, with and without the addition of one of the two base cations. The amount of Na+ and Ca2+ added to the water was calculated in order to obtain an identical increase in water ionic strength. Fish mortality was dependent on water residence time and whether or not base cations were added to the Al-rich water. In all Al-exposures, the highest mortality was always observed in fish exposed to water with the shortest residence time. Mortality decreased systematically with increasing water residence time through the exposure set-up. The addition of a base cation, Ca2+ or Na+, to the Al-rich water reduced fish mortality significantly compared to the Al-only exposures. Furthermore, increasing ionic strength with Na+ reduced mortality to a larger extent than the corresponding increase in ionic strength by the addition of Ca2+. The variation in mortality between the various aluminium and base cation treatments is discussed in terms of aluminium chemistry, specific mitigating effects of Ca2+ and Na+, and the general importance of water ionic strength. This study clearly demonstrates that Ca2+ does not play an unique role as an ameliorating cation for Al-toxicity in fish under non-steady state chemical conditions. Thus, ionic strength seems to be important, probably for the interaction between aluminium and the gill surface, reducing the possibility for positively charged aluminium species to bind to negatively charged sites.

  19. The FMOS-COSMOS survey of star-forming galaxies at z~1.6. IV: Excitation state and chemical enrichment of HII regions

    CERN Document Server

    Kashino, D; Sanders, D; Kartaltepe, J S; Daddi, E; Renzini, A; Valentino, F; Rodighiero, G; Juneau, S; Kewley, L J; Zahid, H J; Arimoto, N; Nagao, T; Chu, J; Sugiyama, N; Civano, F; Ilbert, O; Kajisawa, M; Fevre, O Le; Maier, C; Onodera, M; Puglisi, A; Taniguchi, Y; COSMOS,

    2016-01-01

    We present results on the physical conditions of the interstellar medium of star-forming galaxies at 1.410^11Msun being well sampled. The excitation state and chemical enrichment of the ionized gas are investigated using diagnostic diagrams based on the ratios of emission line strengths, including Alpha, [NII]6584, [SII]6717,6731, Hbeta, and [OIII]5007. Our data confirm an offset of the star-forming sequence on the BPT diagram ([OIII]/Hbeta vs. [NII]/Halpha), primarily towards higher [OIII]/Hbeta, compared with local star-forming galaxies. Based on the [SII] ratio, we measure an electron density (n_e=222^{+172}_{-128} cm^-3), higher than that of local galaxies. Overall, these changes in emission-line properties are due to a higher ionization parameter in high redshift galaxies as demonstrated by a lower than expected [SII]/Halpha ratio and a comparison to theoretical models. These results likely rule out an offset in the BPT diagram caused by a harder radiation field or AGN as assessed with Chandra. Finally, ...

  20. Recycling of CO2: Probing the Chemical State of the Ni(111) Surface during the Methanation Reaction with Ambient-Pressure X-Ray Photoelectron Spectroscopy.

    Science.gov (United States)

    Heine, Christian; Lechner, Barbara A J; Bluhm, Hendrik; Salmeron, Miquel

    2016-10-12

    Using ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), we studied the adsorption and reactions of CO2 and CO2 + H2 on the Ni(111) surface to identify the surface chemical state and the nature of the adsorbed species during the methanation reaction. In 200 mTorr CO2, we found that NiO is formed from CO2 dissociation into CO and atomic oxygen. Additionally, carbonate (CO3(2-)) is present on the surface from further reaction of CO2 with NiO. The addition of H2 into the reaction environment leads to reduction of NiO and the disappearance of CO3(2-). At temperatures >160 °C, CO adsorbed on hollow sites, and atomic carbon and OH species are present on the surface. We conclude that the methanation reaction proceeds via dissociation of CO2, followed by reduction of CO to atomic carbon and its hydrogenation to methane.

  1. Investigation of the superconducting and normal state properties of the filled-skutterudite system PrPt4Ge12 via chemical substitution

    Science.gov (United States)

    Jeon, Inho; Huang, Kevin; Yazici, Duygu; Kanchanavatee, Noravee; White, Benjamin D.; Jang, Sooyoung; Pouse, Naveen; Maple, M. Brian; Ho, Pei-Chun

    We report a systematic chemical substitution study on the unconventional superconductor system PrPt4Ge12, which Sb ions are substituted for Ge. Polycrystalline samples of PrPt4Ge12-x Sbx up to x = 5 were synthesized and investigated by means of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We observed a suppression of superconductivity with increasing Sb substitutions and evidence for a weak ``rattling'' mode associated with the Pr ions, characterized by a value of ΘE ~ 60 K. As part of a systematic study of the effect of various elemental substitutions on the properties of PrPt4Ge12, measurements of the superconducting and normal state properties of the Pr1-xEuxPt4Ge12 system are currently being performed. This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Grant No. DE-FG02-04-ER46105 (characterization and physical properties measurements), and the National Science Foundation under Grant No. DMR 1206553 (low-temperature measurements).

  2. Early diagenesis of mangrove leaves in a tropical estuary: Bulk chemical characterization using solid-state 13C NMR and elemental analyses

    Science.gov (United States)

    Benner, R.; Hatcher, P.G.; Hedges, J.I.

    1990-01-01

    Changes in the chemical composition of mangrove (Rhizophora mangle) leaves during decomposition in tropical estuarine waters were characterized using solid-state 13C nuclear magnetic resonance (NMR) and elemental (CHNO) analysis. Carbohydrates were the most abundant components of the leaves accounting for about 50 wt% of senescent tissues. Tannins were estimated to account for about 20 wt% of leaf tissues, and lipid components, cutin, and possibly other aliphatic biopolymers in leaf cuticles accounted for about 15 wt%. Carbohydrates were generally less resistant to decomposition than the other constituents and decreased in relative concentration during decomposition. Tannins were of intermediate resistance to decomposition and remained in fairly constant proportion during decomposition. Paraffinic components were very resistant to decomposition and increased in relative concentration as decomposition progressed. Lignin was a minor component of all leaf tissues. Standard methods for the colorimetric determination of tannins (Folin-Dennis reagent) and the gravimetric determination of lignin (Klason lignin) were highly inaccurate when applied to mangrove leaves. The N content of the leaves was particularly dynamic with values ranging from 1.27 wt% in green leaves to 0.65 wt% in senescent yellow leaves attached to trees. During decomposition in the water the N content initially decreased to 0.51 wt% due to leaching, but values steadily increased thereafter to 1.07 wt% in the most degraded leaf samples. The absolute mass of N in the leaves increased during decomposition indicating that N immobilization was occurring as decomposition progressed. ?? 1990.

  3. Solid-state chemical synthesis of rod-like fluorine-doped β-Bi2O3 and their enhanced photocatalytic property under visible light

    Science.gov (United States)

    Liang, Zhiting; Cao, Yali; Li, Yizhao; Xie, Jing; Guo, Nana; Jia, Dianzeng

    2016-12-01

    The pure β-Bi2O3 and fluorine-doped β-Bi2O3 rod-like microstructures were successfully prepared by a facile solid-state chemical reaction process. The composition, structure and morphology of the samples were determined by XRD, EDS, SEM, TEM, HRTEM, XPS and PL. Photocatalytic activities of all samples were investigated via the degradation of methyl orange (MO) under the irradiation of visible light. The fluorine-doped β-Bi2O3 rods exhibited higher photocatalytic activities than the pure β-Bi2O3 rod-like structures and commercial sample. The 82% MO can be degraded by the fluorine-doped β-Bi2O3 rods after irradiation for 2 h under visible light, which is 2-3 times higher than that of counterparts. The enhanced properties of the fluorine-doped samples attribute to their higher separation efficiency of electron-hole pairs and strong oxidation potential of valance band holes. The results show that the as-prepared rod-like fluorine-doped β-Bi2O3 materials are potential candidates for photocatalysts irradiated by visible light.

  4. Impact of post-deposition annealing on interfacial chemical bonding states between AlGaN and ZrO{sub 2} grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong [Novitas, Nanoelectronics Center of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wang, Hong, E-mail: ewanghong@ntu.edu.sg [Novitas, Nanoelectronics Center of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); CINTRA CNRS/NTU/Thales, UMI 3288, 50 Nanyang Drive (Singapore); Ng, Serene Lay Geok; Ji, Rong [Data Storage Institute, Agency for Science Technology and Research (A-STAR), 5 Engineering Drive 1, 117608 (Singapore); Liu, Zhi Hong [Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602 (Singapore)

    2015-03-02

    The effect of post-deposition annealing on chemical bonding states at interface between Al{sub 0.5}Ga{sub 0.5}N and ZrO{sub 2} grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2p and Ga-O/Ga 3d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to “clean up” effect of ALD-ZrO{sub 2} on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through “clean up” effect near the interface. However, degradation of ZrO{sub 2}/AlGaN interface quality due to re-oxidation at higher annealing temperature (>500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO{sub 2}/AlGaN interface are easier to get oxidized as compared with Ga atoms.

  5. Tier II Chemical Storage Facilities

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — Facilities that store hazardous chemicals above certain quantities must submit an annual emergency and hazardous chemical inventory on a Tier II form. This is a...

  6. Chemical Data Access Tool

    Data.gov (United States)

    U.S. Environmental Protection Agency — This tool is intended to aid individuals interested in learning more about chemicals that are manufactured or imported into the United States. Health and safety...

  7. Trees and Weathering: Using Soil Petrographic and Chemical Analyses to Compare the Relative Weathering Effects of Gymnosperms and Angiosperms in the Cascade Mountains of Washington State, USA

    Science.gov (United States)

    Andrews, M. Y.; Ague, J. J.; Berner, R. A.

    2006-12-01

    Knowledge of the long-term carbon cycle and its control on atmospheric carbon dioxide levels over the Phanerozoic is crucial to understanding the impending dynamics of contemporary anthropogenic carbon contributions to the atmosphere. One aspect of the long-term carbon cycle that is poorly understood is the role of large vascular plants (trees) in contributing to the chemical weathering of silicate minerals. In particular, little is known about the differences in weathering rates between gymnosperms and angiosperms and how these dissimilarities may have impacted the carbon cycle subsequent to the evolution of angiosperm trees in the Mesozoic. One approach to evaluating these potential differences in weathering is to examine and quantitatively compare the chemistry and petrology of the soil mineral constituents from beneath modern groves of each broad tree type, where the groves have been subject to nearly identical environmental and geological conditions. This particular study focuses on field samples collected along transects through adjacent groves of angiosperms and gymnosperms in the Cascade Mountains of Washington State. Preliminary data demonstrate a significant difference in the soil texture and composition beneath the two types of trees. While soil at each field site has been generated from a homogeneous parent material, and subjected to similar inorganic environmental phenomena, soil density, particle size, and organic content vary across the transects. Soils beneath the angiosperms are denser and have a more clay-like texture, while soils beneath the gymnosperms are more organic-rich and have a sandy texture. Additional macroscopic and microscopic differences in the chemistry and petrology of these soils will illuminate the varied impacts these trees have on the silicate minerals in their immediate environment, and therefore lend insight into the potential impact these groups of organisms have had on the long-term carbon cycle over the past five hundred

  8. Chemical structures of coal lithotypes before and after CO2 adsorption as investigated by advanced solid-state 13C nuclear magnetic resonance spectroscopy

    Science.gov (United States)

    Cao, X.; Mastalerz, Maria; Chappell, M.A.; Miller, L.F.; Li, Y.; Mao, J.

    2011-01-01

    Four lithotypes (vitrain, bright clarain, clarain, and fusain) of a high volatile bituminous Springfield Coal from the Illinois Basin were characterized using advanced solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The NMR techniques included quantitative direct polarization/magic angle spinning (DP/MAS), cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CHn selection, and recoupled C-H long-range dipolar dephasing techniques. The lithotypes that experienced high-pressure CO2 adsorption isotherm analysis were also analyzed to determine possible changes in coal structure as a result of CO2 saturation at high pressure and subsequent evacuation. The main carbon functionalities present in original vitrain, bright clarain, clarain and fusain were aromatic carbons (65.9%-86.1%), nonpolar alkyl groups (9.0%-28.9%), and aromatic C-O carbons (4.1%-9.5%). Among these lithotypes, aromaticity increased in the order of clarain, bright clarain, vitrain, and fusain, whereas the fraction of alkyl carbons decreased in the same order. Fusain was distinct from other three lithotypes in respect to its highest aromatic composition (86.1%) and remarkably small fraction of alkyl carbons (11.0%). The aromatic cluster size in fusain was larger than that in bright clarain. The lithotypes studied responded differently to high pressure CO2 saturation. After exposure to high pressure CO2, vitrain and fusain showed a decrease in aromaticity but an increase in the fraction of alkyl carbons, whereas bright clarain and clarain displayed an increase in aromaticity but a decrease in the fraction of alkyl carbons. Aromatic fused-rings were larger for bright clarain but smaller for fusain in the post-CO2 adsorption samples compared to the original lithotypes. These observations suggested chemical CO2-coal interactions at high pressure and the selectivity of lithotypes in response to CO2 adsorption. ?? 2011 Elsevier B.V.

  9. Chemical and physical characterization of mume fruit collected from different locations and at different maturity stages in São Paulo State

    Directory of Open Access Journals (Sweden)

    Ernesto Quast

    2013-09-01

    Full Text Available Prunus mume is widely studied due to its health benefits regarding increase of blood fluidity and consequent improvement of the cardiovascular system and the prevention or even the fight against different types of cancer. However, in Brazil this culture is found only among oriental descendants. The present study aimed to characterize mume fruit collected from three different locations in the State of São Paulo regarding general aspects such as pH, total titratable acidity (TTA, total soluble solids (TTS, pectin content and yield of pulp and chemical characteristics: total phenolic compounds (TPC and antioxidant capacity. Mume fruit were collected unripe and analyzed until maturation about 88 days after flowering. Fruit collected in Botucatu came from a commercial mume fruit producer and had average weight of 16.9 g, while in fruit from other locations weight varied from 5.7-6.9 g. TSS ranged from 9.5 to 10.0 Brix, total solids was 10.2-12.2% and pH showed values between 2.5 and 2.7 for all locations. TTA expressed in citric acid decreased from 4.0-5.7 g (100g- 1 at unripe stage to 2.0-3.8 g (100g- 1 in mature-stage fruit. Pectin content decreased from 11.2 to 10.8% during fruit maturation, TPC content was 147-226 mg catechin (g- 1 on a dry matter basis and the antioxidant capacity was 96-169 µMol Trolox (g- 1 on a dry matter basis or 21-34 µMol Trolox (g- 1 on a wet matter basis.

  10. Reconnaissance of chemical and biological quality in the Owyhee River from the Oregon State line to the Owyhee Reservoir, Oregon, 2001–02

    Science.gov (United States)

    Hardy, Mark A.; Maret, Terry R.; George, David L.

    2004-01-01

    The Owyhee River drains an extremely rugged and sparsely populated landscape in northern Nevada, southwestern Idaho, and eastern Oregon. Most of the segment between the Oregon State line and Lake Owyhee is part of the National Wild and Scenic Rivers System, and few water-quality data exist for evaluating environmental impacts. As a result, the U.S. Geological Survey, in cooperation with the Bureau of Land Management, assessed this river segment to characterize chemical and biological quality of the river, identify where designated beneficial uses are met and where changes in stream quality occur, and provide data needed to address activities related to environmental impact assessments and Total Maximum Daily Loads. Water-quality issues identified at one or more sites were water temperature, suspended sediment, dissolved oxygen, pH, nutrients, trace elements, fecal bacteria, benthic invertebrate communities, and periphyton communities. Generally, summer water temperatures routinely exceeded Oregon's maximum 7-day average criteria of 17.8 degrees Celsius. The presence of few coldwater taxa in benthic invertebrate communities supports this observation. Suspended-sediment concentrations during summer base flow were less than 10 milligrams per liter (mg/L). Dissolved solids concentrations ranged from 46 to 222 mg/L, were highest during base flow, and tended to increase in a downstream direction. Chemical compositions of water samples indicated that large proportions of upland-derived water extend to the lower reaches of the study area during spring runoff. Dissolved fluoride and arsenic concentrations were highest during base flow and may be a result of geothermal springs discharging to the river. No dissolved selenium was detected. Upstream from the Rome area, spring runoff concentrations of suspended sediment ranged from 0 to 52 mg/L, and all except at the Three Forks site were typically below 20 mg/L. Stream-bottom materials from the North Fork Owyhee River, an area

  11. Translated chemical reaction networks.

    Science.gov (United States)

    Johnston, Matthew D

    2014-05-01

    Many biochemical and industrial applications involve complicated networks of simultaneously occurring chemical reactions. Under the assumption of mass action kinetics, the dynamics of these chemical reaction networks are governed by systems of polynomial ordinary differential equations. The steady states of these mass action systems have been analyzed via a variety of techniques, including stoichiometric network analysis, deficiency theory, and algebraic techniques (e.g., Gröbner bases). In this paper, we present a novel method for characterizing the steady states of mass action systems. Our method explicitly links a network's capacity to permit a particular class of steady states, called toric steady states, to topological properties of a generalized network called a translated chemical reaction network. These networks share their reaction vectors with their source network but are permitted to have different complex stoichiometries and different network topologies. We apply the results to examples drawn from the biochemical literature.

  12. Chemical use

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This is a summary of research and activities related to chemical use on Neal Smith National Wildlife Refuge between 1992 and 2009. The chemicals used on the Refuge...

  13. The low-lying excited states of neutral polyacenes and their radical cations: a quantum chemical study employing the algebraic diagrammatic construction scheme of second order

    OpenAIRE

    Knippenberg, Stefan; Starcke, Jan-Hendrik; Wormit, Michael; Dreuw, Andreas

    2010-01-01

    Abstract The vertical excited electronic states of linearly fused neutral polyacenes and their radical cations have been investigated using the algebraic diagrammatic construction scheme of sec- ond order (ADC(2)). While strict ADC(2) (ADC(2)-s) correctly reproduces trends for mainly singly excited states, in extended ADC(2) (ADC(2)-x) the description of doubly excited states is critically improved. It is shown that a combined application of strict and extended ADC(2) nicely reveal...

  14. Regulatory acceptance and use of 3R models for pharmaceuticals and chemicals: Expert opinions on the state of affairs and the way forward

    NARCIS (Netherlands)

    Schiffelers, M.J.W.A.; Blaauboer, B.J.; Bakker, W.E.; Beken, S.; Hendriksen, C.F.M.; Koeter, H.; Krul, C.A.M.

    2014-01-01

    Pharmaceuticals and chemicals are subjected to regulatory safety testing accounting for approximately 25% of laboratory animal use in Europe. This testing meets various objections and has led to the development of a range of 3R models to Replace, Reduce or Refine the animal models. However, these mo

  15. Proton-detected 3D (15)N/(1)H/(1)H isotropic/anisotropic/isotropic chemical shift correlation solid-state NMR at 70kHz MAS.

    Science.gov (United States)

    Pandey, Manoj Kumar; Yarava, Jayasubba Reddy; Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2016-01-01

    Chemical shift anisotropy (CSA) tensors offer a wealth of information for structural and dynamics studies of a variety of chemical and biological systems. In particular, CSA of amide protons can provide piercing insights into hydrogen-bonding interactions that vary with the backbone conformation of a protein and dynamics. However, the narrow span of amide proton resonances makes it very difficult to measure (1)H CSAs of proteins even by using the recently proposed 2D (1)H/(1)H anisotropic/isotropic chemical shift (CSA/CS) correlation technique. Such difficulties due to overlapping proton resonances can in general be overcome by utilizing the broad span of isotropic chemical shifts of low-gamma nuclei like (15)N. In this context, we demonstrate a proton-detected 3D (15)N/(1)H/(1)H CS/CSA/CS correlation experiment at fast MAS frequency (70kHz) to measure (1)H CSA values of unresolved amide protons of N-acetyl-(15)N-l-valyl-(15)N-l-leucine (NAVL).

  16. Chemical states of fission products in irradiated (U{sub 0.3}Pu{sub 0.7})C{sub 1+x} fuel at high burn-ups

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Renu [Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)]. E-mail: arenu@barc.gov.in; Venugopal, V. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2006-12-01

    The chemical states of fission products have been theoretically determined for the irradiated carbide fuel of Fast Breeder Test Reactor (FBTR) at Kalpakkam, India, at different burn-ups. The SOLGASMIX-PV computer code was used to determine the equilibrium chemical composition of the fuel. The system was assumed to be composed of a gaseous phase at one atmosphere pressure, and various solid phases. The distribution of elements in these phases and their chemical states at different temperatures were calculated as a function of burn-up. The FBTR fuel (U{sub 0.3}Pu{sub 0.7})C{sub 1+x}, was loaded with C/M values in the range, 1.03-1.06. The present calculations indicated that even for the lowest starting C/M of 1.03 in the FBTR fuel, the liquid metal phase of (U, Pu), should not appear at a burn-up as high as 150 GWd/t.

  17. Chemical signature study of tupiguarani ceramic tradition from Central region of the Rio Grande do Sul state, Brazil; Estudo de assinaturas quimicas em ceramica da tradicao tupiguarani da regiao central do estado do Rio Grande do Sul, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Bona, Irene Akemy Tomiyoshi

    2006-07-01

    In this work a model based on experimental results using chemical composition data of the pottery sherds applied to Spearmann's no parametric test, principal component analysis and discriminant analysis, was applied. The samples are soils and Tupiguarani Tradition pottery sherd from the central area of the Rio Grande do Sul State. The chemical elements , Al, Ba, Ca, Cr, Fe, K Mn, Pb, Rb, S, Si, Sr, Ti, V and Zn were determined by energy dispersive X-ray fluorescence (EDXFR) while Ce, Cu, Gd, La, Nd, Pr, Sm, Th and Y by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) techniques. Relationships among the pottery characteristics, studied sites and sherd dispersion in the several sites were proposed. Indications of chemical signature of the small pottery with function to go or not to the fire were observed. The largest dispersion is of small pottery with surface treatment no corrugated. The potteries chemical fingerprints from Ijui River, Ibicui-Vacacai Mirim River and Jacui River were verified. (author)

  18. Solid state NMR of proteins at high MAS frequencies: symmetry-based mixing and simultaneous acquisition of chemical shift correlation spectra

    Energy Technology Data Exchange (ETDEWEB)

    Bellstedt, Peter [Fritz Lipmann Institute, Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany); Herbst, Christian [Ubon Ratchathani University, Department of Physics, Faculty of Science (Thailand); Haefner, Sabine; Leppert, Joerg; Goerlach, Matthias; Ramachandran, Ramadurai, E-mail: raman@fli-leibniz.de [Fritz Lipmann Institute, Biomolecular NMR spectroscopy, Leibniz Institute for Age Research (Germany)

    2012-12-15

    We have carried out chemical shift correlation experiments with symmetry-based mixing sequences at high MAS frequencies and examined different strategies to simultaneously acquire 3D correlation spectra that are commonly required in the structural studies of proteins. The potential of numerically optimised symmetry-based mixing sequences and the simultaneous recording of chemical shift correlation spectra such as: 3D NCAC and 3D NHH with dual receivers, 3D NC Prime C and 3D C Prime NCA with sequential {sup 13}C acquisitions, 3D NHH and 3D NC Prime H with sequential {sup 1}H acquisitions and 3D CANH and 3D C'NH with broadband {sup 13}C-{sup 15}N mixing are demonstrated using microcrystalline samples of the {beta}1 immunoglobulin binding domain of protein G (GB1) and the chicken {alpha}-spectrin SH3 domain.

  19. Soft X-ray imaging and spectromicroscopy: new insights in chemical state and morphology of the key components in operating fuel-cells.

    Science.gov (United States)

    Bozzini, Benedetto; Abyaneh, Majid Kazemian; Amati, Matteo; Gianoncelli, Alessandra; Gregoratti, Luca; Kaulich, Burkhard; Kiskinova, Maya

    2012-08-13

    Fuel cells are one of the most appealing environmentally friendly devices for the effective conversion of chemical energy into electricity and heat, but still there are key barriers to their broad commercialization. In addition to efficiency, a major challenge of fuel-cell technology is the durability of the key components (interconnects, electrodes, and electrolytes) that can be subject to corrosion or undesired morphology and chemical changes occurring under operating conditions. The complementary capabilities of synchrotron-based soft X-ray microscopes in terms of imaging, spectroscopy, spatial and time resolution, and variable probing depths are opening unique opportunities to shed light on the multiple processes occurring in these complex systems at microscopic length scales. This type of information is prerequisite for understanding and controlling the performance and durability of such devices. This paper reviews the most recent efforts in the implementation of these methods for exploring the evolving structure and chemical composition of some key fuel cell components. Recent achievements are illustrated by selected results obtained with simplified versions of proton-exchange fuel-cells (PEFC) and solid-oxide fuel-cells (SOFC), which allow in situ monitoring of the redox reactions resulting in: 1) undesired deposits at interconnects and electrodes (PEFC); 2) material interactions at the electrode-electrolyte interface (PEFC); 3) release of corrosion products to the electrolyte phase (PEFC, and 4) mass-transport processes and structural changes occurring at the high operation temperatures of SOFC and promoted by the polarization.

  20. Comparison among chemical, mineralogical and physical analysis from alluvial clays from counties of Southwest of Minas Gerais state (Brazil); Comparacao entre as analises quimicas, mineralogicas e tecnologicas das argilas aluvionares de alguns municipios do sudoeste de Minas Gerais

    Energy Technology Data Exchange (ETDEWEB)

    Gaspar Junior, L.A., E-mail: lineo.gaspar@unifal-mg.edu.br [Universidade Federal de Alfenas (UNIALFENAS), MG (Brazil). Instituto de Ciencias da Natureza; Varajao, A.F.D.C. [Universidade Federal de Ouro Preto (UFOP), MG (Brazil). Escola de Minas; Souza, M.H.O. [Universidade Federal de Uberlandia (UFU), MG (Brazil). Departamento de Geografia; Moreno, M.M.T. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Rio Claro, SP (Brazil). Departamento de Petrologia e Metalogenia

    2011-07-01

    The studied area is located in the southwestern portion of Minas Gerais State, encompassing the counties of Alfenas, Areado, Machado, Poco Fundo, Campestre, Serrania, Monte Belo, Bandeira do Sul, Botelhos and Cabo Verde. This region is dominated by strongly weathered pre-cambrian rocks in association with colluvial-alluvial sediments. The present work consisted in a comparison among the mineralogical (X-Ray Diffraction), textural (Laser Granulometry), chemical (X-Ray Fluorescence) and technological (mechanical resistance, water absorption, etc, made in specimen tests) properties of the clays collected on potteries located in these counties. The mineralogical and chemical analysis displayed the kaolinitic nature of the clays from this region, showing also small amount of interlayered clays and large amount of quartz. The best results of physical analysis were obtained for clays from the counties of Cabo Verde and Monte Belo due to the presence of lower values of SiO{sub 2} (quartz) associated with a finer particle size distribution. (author)

  1. Review of the state of the art of human biomonitoring for chemical substances and its application to human exposure assessment for food safety

    DEFF Research Database (Denmark)

    Choi, Judy; Mørck, Thit Aarøe; Polcher, Alexandra

    2015-01-01

    Human biomonitoring (HBM) measures the levels of substances in body fluids and tissues. Many countries have conducted HBM studies, yet little is known about its application towards chemical risk assessment, particularly in relation to food safety. Therefore a literature search was performed...... safety areas (namely exposure assessment), and for the implementation of a systematic PMM approach. But further work needs to be done to improve usability. Major deficits are the lack of HBM guidance values on a considerable number of substance groups, for which health based guidance values (HBGVs) have...

  2. Chemical sensors

    Science.gov (United States)

    Lowell, J.R. Jr.; Edlund, D.J.; Friesen, D.T.; Rayfield, G.W.

    1991-07-02

    Sensors responsive to small changes in the concentration of chemical species are disclosed. The sensors comprise a mechanochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment. They are operatively coupled to a transducer capable of directly converting the expansion or contraction to a measurable electrical response. 9 figures.

  3. Regulatory acceptance and use of 3R models for pharmaceuticals and chemicals: expert opinions on the state of affairs and the way forward.

    Science.gov (United States)

    Schiffelers, Marie-Jeanne W A; Blaauboer, Bas J; Bakker, Wieger E; Beken, Sonja; Hendriksen, Coenraad F M; Koëter, Herman B W M; Krul, Cyrille

    2014-06-01

    Pharmaceuticals and chemicals are subjected to regulatory safety testing accounting for approximately 25% of laboratory animal use in Europe. This testing meets various objections and has led to the development of a range of 3R models to Replace, Reduce or Refine the animal models. However, these models must overcome many barriers before being accepted for regulatory risk management purposes. This paper describes the barriers and drivers and options to optimize this acceptance process as identified by two expert panels, one on pharmaceuticals and one on chemicals. To untangle the complex acceptance process, the multilevel perspective on technology transitions is applied. This perspective defines influences at the micro-, meso- and macro level which need alignment to induce regulatory acceptance of a 3R model. This paper displays that there are many similar mechanisms within both sectors that prevent 3R models from becoming accepted for regulatory risk assessment and management. Shared barriers include the uncertainty about the value of the new 3R models (micro level), the lack of harmonization of regulatory requirements and acceptance criteria (meso level) and the high levels of risk aversion (macro level). In optimizing the process commitment, communication, cooperation and coordination are identified as critical drivers.

  4. Chemical defences against herbivores

    DEFF Research Database (Denmark)

    Pavia, Henrik; Baumgartner, Finn; Cervin, Gunnar;

    2012-01-01

    of these theories, concluding with new chemical approaches to tackle the questions and suggestions for future research directions. It explains that aquatic primary producers are a taxonomically and functionally diverse group of organisms that includes macroalgae, microalgae, and vascular plants. It also states...

  5. Surface state modulation through wet chemical treatment as a route to controlling the electrical properties of ZnO nanowire arrays investigated with XPS

    Energy Technology Data Exchange (ETDEWEB)

    Lord, Alex M., E-mail: a.m.lord@swansea.ac.uk [Centre for Nanohealth, College of Engineering, University of Swansea, Singleton Park, SA2 8PP (United Kingdom); Maffeis, Thierry G. [Multidisciplinary Nanotechnology Centre, College of Engineering, University of Swansea, Singleton Park, SA2 8PP (United Kingdom); Allen, Martin W. [MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Private Bag 4800, Christchurch, 8014 (New Zealand); Morgan, David; Davies, Philip R. [Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Park Place, Cardiff, CF10 3AT (United Kingdom); Jones, Daniel R.; Evans, Jonathan E. [Multidisciplinary Nanotechnology Centre, College of Engineering, University of Swansea, Singleton Park, SA2 8PP (United Kingdom); Smith, Nathan A.; Wilks, Steve P. [Multidisciplinary Nanotechnology Centre, Department of Physics, College of Science, University of Swansea, Singleton Park, SA2 8PP (United Kingdom)

    2014-11-30

    Highlights: • Direct measurement of the surface band bending exhibited by ZnO nanowires using monochromatic XPS. • Modulation of the surface depletion region using wet chemical treatment (EtOH, H{sub 2}O{sub 2}). • The measured surface potential barrier agrees with electrical measurements of individual nanowires. • H{sub 2}O{sub 2} depletes the nanowire of charge carriers while EtOH donates electrons at the surface. • EtOH has the effect of restoring the surface potential barrier of oxidised nanowires. - Abstract: ZnO is a wide bandgap semiconductor that has many potential applications including solar cell electrodes, transparent thin film transistors and gas/biological sensors. Since the surfaces of ZnO materials have no amorphous or oxidised layers, they are very environmentally sensitive, making control of their semiconductor properties challenging. In particular, the electronic properties of ZnO nanostructures are dominated by surface effects while surface conduction layers have been observed in thin films and bulk crystals. Therefore, the ability to use the ZnO materials in a controlled way depends on the development of simple techniques to modulate their surface electronic properties. Here, we use monochromatic x-ray photoelectron spectroscopy (XPS) to investigate the use of different wet chemical treatments (EtOH, H{sub 2}O{sub 2}) to control the electronic properties of ZnO nanowires by modulating the surface depletion region. The valence band and core level XPS spectra are used to explore the relationship between the surface chemistry of the nanowires and the surface band bending.

  6. Chemical intolerance

    DEFF Research Database (Denmark)

    Dantoft, Thomas Meinertz; Andersson, Linus; Nordin, Steven;

    2015-01-01

    Chemical intolerance (CI) is a term used to describe a condition in which the sufferer experiences a complex array of recurrent unspecific symptoms attributed to low-level chemical exposure that most people regard as unproblematic. Severe CI constitutes the distinguishing feature of multiple...... chemical sensitivity (MCS). The symptoms reported by CI subjects are manifold, involving symptoms from multiple organs systems. In severe cases of CI, the condition can cause considerable life-style limitations with severe social, occupational and economic consequences. As no diagnostic tools for CI...

  7. Hazardous Chemicals

    Centers for Disease Control (CDC) Podcasts

    2007-04-10

    Chemicals are a part of our daily lives, providing many products and modern conveniences. With more than three decades of experience, The Centers for Disease Control and Prevention (CDC) has been in the forefront of efforts to protect and assess people's exposure to environmental and hazardous chemicals. This report provides information about hazardous chemicals and useful tips on how to protect you and your family from harmful exposure.  Created: 4/10/2007 by CDC National Center for Environmental Health.   Date Released: 4/13/2007.

  8. Quantum Chemical Study of the Low-Lying Electronic States of VSi3(-/0) Clusters and Interpretation of the Anion Photoelectron Spectrum.

    Science.gov (United States)

    Tran, Van Tan; Tran, Quoc Tri

    2016-07-28

    The geometrical and electronic structures of VSi3(-/0) clusters have been investigated with the DFT, CCSD(T), and CASSCF/CASPT2 methods. The results showed that the suitable functional to identify the ground states of VSi3(-/0) clusters is not the B3LYP but the BP86. At the BP86, CCSD(T), and CASPT2 levels, the ground state of the anionic cluster was the (1)A' ((1)A1) of tetrahedral η(3)-(Si3)V(-) isomer, while that of the neutral cluster was the 1(2)A' and 1(2)A″ (1(2)E) of the same isomer. The 1(2)A' and 1(2)A″ of the tetrahedral η(3)-(Si3)V isomer were the results of the Jahn-Teller distortions of the 1(2)E in C3v symmetry. All three bands in the photoelectron spectrum of the VSi3(-) cluster were interpreted by one-electron detachments from the (1)A' anionic ground state on the basis of the BP86, CCSD(T), and CASPT2 methods. The calculated adiabatic and vertical detachment energies were in agreement with the experimental values. The broad shape of the first band was explained by Franck-Condon factor simulations for the (1)A' → 1(2)A' and (1)A' → 1(2)A″ transitions within the tetrahedral η(3)-(Si3)V(-/0) isomers.

  9. Excited state intramolecular proton transfer (ESIPT) in 2-(2'-hydroxyphenyl)benzoxazole and its naphthalene-fused analogs: a TD-DFT quantum chemical study.

    Science.gov (United States)

    Roohi, Hossein; Hejazi, Fahimeh; Mohtamedifar, Nafiseh; Jahantab, Mahjobeh

    2014-01-24

    The intramolecular proton transfer reactions in 2-(2'-hydroxyphenyl)benzoxazole (HBO) and its naphthalene-fused analogs, (HNB1-3) in both S0 and S1 states at the PBE1PBE/6-311++G(2d,2p) level of theory in the gas phase and water have been investigated to find the effects of extension of aromaticity on the intramolecular proton transfer and photophysical properties. The results show that the ground state intramolecular proton transfer (GSIPT) in the studied species is impossible. Excited states potential energy surface calculations support the existence of ESIPT process. Structural parameters, relative energy of isomers, H-bonding energy, adsorption and emission bands, vertical excitation and emission energies, oscillator strength, fluorescence rate constant, dipole moment, atomic charges and electron density at critical points were calculated. Orbital analysis shows that vertical S0→S1 transition in the studied molecules corresponds essentially to the excitation from HOMO (π) to LUMO (π(*)). The potential of HNB2 molecule as an emissive and electron transport material in designing improved organic white light emitting diodes is predicted in this work. Our calculations are also supported by the experimental observations.

  10. Lowest triplet (n, π*) electronic state of acrolein: Determination of structural parameters by cavity ringdown spectroscopy and quantum-chemical methods

    Science.gov (United States)

    Hlavacek, Nikolaus C.; McAnally, Michael O.; Drucker, Stephen

    2013-02-01

    The cavity ringdown absorption spectrum of acrolein (propenal, CH2=CH—CH=O) was recorded near 412 nm, under bulk-gas conditions at room temperature and in a free-jet expansion. The measured spectral region includes the 0^0_0 band of the T1(n, π*) ← S0 system. We analyzed the 0^0_0 rotational contour by using the STROTA computer program [R. H. Judge et al., J. Chem. Phys. 103, 5343 (1995)], 10.1063/1.470569, which incorporates an asymmetric rotor Hamiltonian for simulating and fitting singlet-triplet spectra. We used the program to fit T1(n, π*) inertial constants to the room-temperature contour. The determined values (cm-1), with 2σ confidence intervals, are A = 1.662 ± 0.003, B = 0.1485 ± 0.0006, C = 0.1363 ± 0.0004. Linewidth analysis of the jet-cooled spectrum yielded a value of 14 ± 2 ps for the lifetime of isolated acrolein molecules in the T1(n, π*), v = 0 state. We discuss the observed lifetime in the context of previous computational work on acrolein photochemistry. The spectroscopically derived inertial constants for the T1(n, π*) state were used to benchmark a variety of computational methods. One focus was on complete active space methods, such as complete active space self-consistent field (CASSCF) and second-order perturbation theory with a CASSCF reference function (CASPT2), which are applicable to excited states. We also examined the equation-of-motion coupled-cluster and time-dependent density function theory excited-state methods, and finally unrestricted ground-state techniques, including unrestricted density functional theory and unrestricted coupled-cluster theory with single and double and perturbative triple excitations. For each of the above methods, we or others [O. S. Bokareva et al., Int. J. Quantum Chem. 108, 2719 (2008)], 10.1002/qua.21803 used a triple zeta-quality basis set to optimize the T1(n, π*) geometry of acrolein. We find that the multiconfigurational methods provide the best agreement with fitted inertial

  11. Chemical Data Reporting rule (CDR)

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset contains information on chemicals that company's produce domestically or import into the United States during the principal reporting year. For the...

  12. Teaching Chemical Engineers about Teaching

    Science.gov (United States)

    Heath, Daniel E.; Hoy, Mary; Rathman, James F.; Rohdieck, Stephanie

    2013-01-01

    The Chemical and Biomolecular Engineering Department at The Ohio State University in collaboration with the University Center for the Advancement of Teaching developed the Chemical Engineering Mentored Teaching Experience. The Mentored Teaching Experience is an elective for Ph.D. students interested in pursuing faculty careers. Participants are…

  13. Addressing the chemical sorcery of "GaI": benefits of solid-state analysis aiding in the synthesis of P→Ga coordination compounds.

    Science.gov (United States)

    Malbrecht, Brian J; Dube, Jonathan W; Willans, Mathew J; Ragogna, Paul J

    2014-09-15

    The differing structures and reactivities of "GaI" samples prepared with different reaction times have been investigated in detail. Analysis by FT-Raman spectroscopy, powder X-ray diffraction, (71)Ga solid-state NMR spectroscopy, and (127)I nuclear quadrupole resonance (NQR) provides concrete evidence for the structure of each "GaI" sample prepared. These techniques are widely accessible and can be implemented quickly and easily to identify the nature of the "GaI" in hand. The "GaI" prepared from exhaustive reaction times (100 min) is shown to possess Ga2I3 and an overall formula of [Ga(0)]2[Ga(+)]2[Ga2I6(2-)], while the "GaI" prepared with the shortest reaction time (40 min) contains GaI2 and has the overall formula [Ga(0)]2[Ga(+)][GaI4(-)]. Intermediate "GaI" samples were consistently shown to be fractionally composed of each of these two preceding formulations and no other distinguishable phases. These "GaI" phases were then shown to give unique products upon reactions with the anionic bis(phosphino)borate ligand class. The reaction of the early-phase "GaI" gives rise to a unique phosphine Ga(II) dimeric coordination compound (3), which was isolated reproducibly in 48% yield and convincingly characterized. A base-stabilized GaI→GaI3 fragment (4) was also isolated using the late-phase "GaI" and characterized by multinuclear NMR spectroscopy and X-ray crystallography. These compounds can be considered unique examples of low-oxidation-state P→Ga coordination compounds and possess relatively long Ga-P bond lengths in the solid-state structures. The anionic borate backbone therefore results in interesting architectures about gallium that have not been observed with neutral phosphines.

  14. Chemical physics behind formation of efficient charge-separated state for complexation between PC70BM and designed diporphyrin in solution.

    Science.gov (United States)

    Ray, Anamika; Banerjee, Shrabanti; Ghosh, Shalini; Bauri, Ajoy K; Bhattacharya, Sumanta

    2016-01-05

    The present work reports supramolecular interaction of [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) with two designed diporphyrin molecules having dithiophene (1) and carbazole (2) spacer in solvent having varying polarity. Studies on complex formation reveal relatively higher binding constant for PC70BM/2 complex in all the solvent studied. Solvent dependence of charge separation and charge recombination processes in PC70BM/diporphyrin non-covalent complexes has been well established in present work. Donor-acceptor geometry and stabilization of the singlet excited state of the diporphyrin during charge recombination are considered to be the possible reasons for this behavior.

  15. Dollar Summary of Prime Contract Awards by Contractor, State or Country, and Place, FY83, Part 1 (A&A Chemical Toilet Rentals-Gillespie Construction Co.)

    Science.gov (United States)

    1983-01-01

    1L 11w1. MICROCOPY RESOLUTION TESI CHARI NATION. (TUH AO’I NP PRIME-CONTRACTS BY CONTRACTOR, STATE, AND CITY - (OCT 82 - SEP 83) Itir$ ",’? (0(4I.L ARS...INC ORANGE CALIFORNIA 44 14 44 44 FORMA RAPID CONSTRUCTION CORP PONCE PUERTO RCO 224 224 7OPMA RAP10 CONSTRUCTION C00Sp RnOSEVELT ROAD3 PUERTO RCO 60...o R C CONTRACTING INC JACKSONVILLE FLORIDA 58 56 58 58 S R 0 CO WARMINSTER PA 1,084 1,084 1 084 1,084 o R G ENGINEERING INC FORT BUCHANAN PUERTO RCO

  16. Enhanced UVB emission and analysis of chemical states of Ca5(PO4)3OH:Gd3+,Pr3+ phosphor prepared by co-precipitation

    Science.gov (United States)

    Mokoena, P. P.; Nagpure, I. M.; Kumar, Vinay; Kroon, R. E.; Olivier, E. J.; Neethling, J. H.; Swart, H. C.; Ntwaeaborwa, O. M.

    2014-08-01

    Hydroxyapatite (Ca5(PO4)3OH) is a well-known bioceramic material used in medical applications because of its ability to form direct chemical bonds with living tissues. This mineral is currently used as a host for rare-earth ions (e.g. Gd3+, Pr3+, Tb3+, etc.) to prepare phosphors that can be used in light emitting devices of different types. In this study Ca5(PO4)3OH:Gd3+,Pr3+ phosphors were prepared by the co-precipitation method and were characterised by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive x-ray spectroscopy and photoluminescence spectroscopy. The x-ray diffraction pattern was consistent with the hexagonal phase of Ca5(PO4)3OH referenced in JCPDS card number 73-0293. The x-ray photoelectron spectroscopy data indicated that Ca2+ occupied two different lattice sites, referred to as Ca1 and Ca2. The photoluminescence data exhibited a narrowband emission located at 313 nm, which is associated with the 6P7/2→8S7/2 transition of the Gd3+ ion. This emission is classified as ultraviolet B and it is suitable for use in phototherapy lamps to treat various skin diseases. The photoluminescence intensity of the 313 nm emission was enhanced considerably by Pr3+ co-doping.

  17. The structure and chemical and acid-base state of the surface of solid solutions and binary components in the InSb-CdS system

    Science.gov (United States)

    Kirovskaya, I. A.; Filatova, T. N.

    2012-03-01

    The surface physicochemical properties, including microstructure, chemical composition, and acid-base surface properties, of solid solutions and binary components in the InSb-CdS system obtained for the first time were studied. Films of all the components had a polycrystalline structure with a nonuniform character of the distribution of crystallites, which associated into agglomerates. The chemistry of the surface was mainly determined by adsorbed H2O and CO2 molecules, OH- groups, and, to a lesser extent, oxygen and hydrogen carbon compounds. The strength, concentration, and nature of acid centers were determined. Coordination-unsaturated In and Cd atoms, adsorbed water molecules, and OH-groups were responsible for acid-basic centers. Changes in the acid-base properties of the surface of InSb-CdS system components caused by composition variations were studied. They correlated with the "specific conductivity-composition" dependence, reflected the special features of donor-acceptor interactions in solid solutions, and could be used to predict adsorption-catalytic properties.

  18. A PCP Pincer Ligand for Coordination Polymers with Versatile Chemical Reactivity: Selective Activation of CO2 Gas over CO Gas in the Solid State.

    Science.gov (United States)

    He, Junpeng; Waggoner, Nolan W; Dunning, Samuel G; Steiner, Alexander; Lynch, Vincent M; Humphrey, Simon M

    2016-09-26

    A tetra(carboxylated) PCP pincer ligand has been synthesized as a building block for porous coordination polymers (PCPs). The air- and moisture-stable PCP metalloligands are rigid tetratopic linkers that are geometrically akin to ligands used in the synthesis of robust metal-organic frameworks (MOFs). Here, the design principle is demonstrated by cyclometalation with Pd(II) Cl and subsequent use of the metalloligand to prepare a crystalline 3D MOF by direct reaction with Co(II) ions and structural resolution by single crystal X-ray diffraction. The Pd-Cl groups inside the pores are accessible to post-synthetic modifications that facilitate chemical reactions previously unobserved in MOFs: a Pd-CH3 activated material undergoes rapid insertion of CO2 gas to give Pd-OC(O)CH3 at 1 atm and 298 K. However, since the material is highly selective for the adsorption of CO2 over CO, a Pd-N3 modified version resists CO insertion under the same conditions.

  19. Surface morphology and chemical state of epitaxial Al sub 2 O sub 3 film on Cu-9%Al(111) single crystal

    CERN Document Server

    Yamauchi, Y; Song, W

    2003-01-01

    We investigated the surface morphology, natures of chemical bond and thickness of oxide film grew on the Cu-9%Al (111) single crystal by means of Auger electron spectroscopy (AES) and a scanning electron microscopy (SEM). By introducing 1300L oxygen at 725degC, aluminum was oxidized and copper was not, and the epitaxial alumina film grew on the Cu-9%Al surface. The alumina surface showed two morphologies in SEM image. One was a flat surface with a few small defects, and the other was a rough surface which had smooth and rough regions. The rough surface was remarkably seen in sputtered region to obtain clean surface. The alumina film whose thickness was about 3.5 nm uniformly grew on the flat surface, and the thickness was about 3.0-3.5 nm on rough surface. It is concluded that the surface roughness in alumina is related to the roughness of clean surface. Therefore, to grow the uniform alumina film over large area of Cu-9%Al surface, it is essential to obtain the flat clean surface prior to oxidation. (author)

  20. Effect of surface pretreatment on interfacial chemical bonding states of atomic layer deposited ZrO{sub 2} on AlGaN

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wang, Hong, E-mail: ewanghong@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore and CINTRA CNRS/NTU/Thales, UMI 3288, 50 Nanyang Drive, Singapore 637553 (Singapore); Ng, Serene Lay Geok; Ji, Rong [Data Storage Institute, Agency for Science Technology and Research (A-STAR), 5 Engineering Drive 1, Singapore 117608 (Singapore); Liu, Zhi Hong [Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602 (Singapore)

    2015-09-15

    Atomic layer deposition (ALD) of ZrO{sub 2} on native oxide covered (untreated) and buffered oxide etchant (BOE) treated AlGaN surface was analyzed by utilizing x-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy. Evidenced by Ga–O and Al–O chemical bonds by XPS, parasitic oxidation during deposition is largely enhanced on BOE treated AlGaN surface. Due to the high reactivity of Al atoms, more prominent oxidation of Al atoms is observed, which leads to thicker interfacial layer formed on BOE treated surface. The results suggest that native oxide on AlGaN surface may serve as a protecting layer to inhibit the surface from further parasitic oxidation during ALD. The findings provide important process guidelines for the use of ALD ZrO{sub 2} and its pre-ALD surface treatments for high-k AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors and other related device applications.

  1. New insight brought by density functional theory on the chemical state of alaninol on Cu(100): Energetics and interpretation of x-ray photoelectron spectroscopy data

    Science.gov (United States)

    Irrera, S.; Costa, D.

    2008-03-01

    In recent years, an increasing interest has been focused on the adsorption of molecules on surfaces due to the importance of technologies based on the interaction of organic systems with metals and oxides for biosensors, catalysis, and molecularly imprinted polymer technology. A particularly attractive area is the study of chiral surfaces, as these can act as heterogeneous catalysts and sensors in the stereochemical industrial processes. This work reports on an ab initio simulation of chemisorption of the D-alaninol on Cu (100). This system has been investigated systematically by using the Vienna ab initio simulation Package (VASP) which performs density functional theory (DFT) calculations in periodic boundary conditions. Molecular dynamics at 300K is performed to explore all the possible geometries, finally, optimized at 0K to obtain the adsorption modes. C 1s, O 1s, and N 1s, core level shift (CLS) calculations of those adsorption modes have been evaluated and compared with x-ray photoelectron spectroscopy experimental data. Energetic and CLS indicate that both chemical functions, the NH2 and the dehydrogenated hydroxyl, are involved in the bonding to the surface at low coverage. Atomic hydrogen coadsorbs in a fourfold hollow site. An atomistic thermodynamics approach suggests that at room temperature under UHV conditions, coadsorbed hydrogen has recombined as H2 and desorbed from the surface.

  2. Near-infrared excited state dynamics of melanins: the effects of iron content, photo-damage, chemical oxidation, and aggregate size.

    Science.gov (United States)

    Simpson, Mary Jane; Wilson, Jesse W; Robles, Francisco E; Dall, Christopher P; Glass, Keely; Simon, John D; Warren, Warren S

    2014-02-13

    Ultrafast pump-probe measurements can discriminate the two forms of melanin found in biological tissue (eumelanin and pheomelanin), which may be useful for diagnosing and grading melanoma. However, recent work has shown that bound iron content changes eumelanin's pump-probe response, making it more similar to that of pheomelanin. Here we record the pump-probe response of these melanins at a wider range of wavelengths than previous work and show that with shorter pump wavelengths the response crosses over from being dominated by ground-state bleaching to being dominated by excited-state absorption. The crossover wavelength is different for each type of melanin. In our analysis, we found that the mechanism by which iron modifies eumelanin's pump-probe response cannot be attributed to Raman resonances or differences in melanin aggregation and is more likely caused by iron acting to broaden the unit spectra of individual chromophores in the heterogeneous melanin aggregate. We analyze the dependence on optical intensity, finding that iron-loaded eumelanin undergoes irreversible changes to the pump-probe response after intense laser exposure. Simultaneously acquired fluorescence data suggest that the previously reported "activation" of eumelanin fluorescence may be caused in part by the dissociation of metal ions or the selective degradation of iron-containing melanin.

  3. The quantum chemical causality of pMHC-TCR biological avidity: Peptide atomic coordination data and the electronic state of agonist N termini

    Science.gov (United States)

    Antipas, Georgios S.E.; Germenis, Anastasios E.

    2015-01-01

    The quantum state of functional avidity of the synapse formed between a peptide-Major Histocompatibility Complex (pMHC) and a T cell receptor (TCR) is a subject not previously touched upon. Here we present atomic pair correlation meta-data based on crystalized tertiary structures of the Tax (HTLV-1) peptide along with three artificially altered variants, all of which were presented by the (Class I) HLA-A201 protein in complexation with the human (CD8+) A6TCR. The meta-data reveal the existence of a direct relationship between pMHC-TCR functional avidity (agonist/antagonist) and peptide pair distribution function (PDF). In this context, antagonist peptides are consistently under-coordinated in respect to Tax. Moreover, Density Functional Theory (DFT) datasets in the BLYP/TZ2P level of theory resulting from relaxation of the H species on peptide tertiary structures reveal that the coordination requirement of agonist peptides is also expressed as a physical observable of the protonation state of their N termini: agonistic peptides are always found to retain a stable ammonium (NH3+) terminal group while antagonist peptides are not. PMID:26217741

  4. Principles of chemical kinetics

    CERN Document Server

    House, James E

    2007-01-01

    James House's revised Principles of Chemical Kinetics provides a clear and logical description of chemical kinetics in a manner unlike any other book of its kind. Clearly written with detailed derivations, the text allows students to move rapidly from theoretical concepts of rates of reaction to concrete applications. Unlike other texts, House presents a balanced treatment of kinetic reactions in gas, solution, and solid states. The entire text has been revised and includes many new sections and an additional chapter on applications of kinetics. The topics covered include quantitative rela

  5. Environmental/chemical thesaurus

    Energy Technology Data Exchange (ETDEWEB)

    Shriner, C.R.; Dailey, N.S.; Jordan, A.C.; Miller, K.C.; Owens, E.T.; Rickert, L.W.

    1978-06-01

    The Environmental/Chemical Thesaurus approaches scientific language control problems from a multidisciplinary view. The Environmental/Biomedical Terminology Index (EBTI) was used as a base for the present thesaurus. The Environmental/Chemical Thesaurus, funded by the Environmental Protection Agency, used as its source of new terms those major terms found in 13 Environmental Protection Agency data bases. The scope of this thesaurus includes not only environmental and biomedical sciences, but also the physical sciences with emphasis placed on chemistry. Specific chemical compounds are not included; only classes of chemicals are given. To adhere to this level of classification, drugs and pesticides are identified by class rather than by specific chemical name. An attempt was also made to expand the areas of sociology and economics. Terminology dealing with law, demography, and geography was expanded. Proper names of languages and races were excluded. Geographic terms were expanded to include proper names for oceans, continents, major lakes, rivers, and islands. Political divisions were added to allow for proper names of countries and states. With such a broad scope, terminology for specific sciences does not provide for indexing to the lowest levels in plant, animal, or chemical classifications.

  6. Energy partitioning in polyatomic chemical reactions: Quantum state resolved studies of highly exothermic atom abstraction reactions from molecules in the gas phase and at the gas-liquid interface

    Science.gov (United States)

    Zolot, Alexander M.

    This thesis recounts a series of experiments that interrogate the dynamics of elementary chemical reactions using quantum state resolved measurements of gas-phase products. The gas-phase reactions F + HCl → HF + Cl and F + H2O → HF + OH are studied using crossed supersonic jets under single collision conditions. Infrared (IR) laser absorption probes HF product with near shot-noise limited sensitivity and high resolution, capable of resolving rovibrational states and Doppler lineshapes. Both reactions yield inverted vibrational populations. For the HCl reaction, strongly bimodal rotational distributions are observed, suggesting microscopic branching of the reaction mechanism. Alternatively, such structure may result from a quantum-resonance mediated reaction similar to those found in the well-characterized F + HD system. For the H2O reaction, a small, but significant, branching into v = 2 is particularly remarkable because this manifold is accessible only via the additional center of mass collision energy in the crossed jets. Rotationally hyperthermal HF is also observed. Ab initio calculations of the transition state geometry suggest mechanisms for both rotational and vibrational excitation. Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic jet of F atoms with liquid squalane (C30H62), a low vapor pressure hydrocarbon compatible with the high vacuum environment. IR spectroscopy provides absolute HF( v,J) product densities and Doppler resolved velocity component distributions perpendicular to the surface normal. Compared to analogous gas-phase F + hydrocarbon reactions, the liquid surface is a more effective "heat sink," yet vibrationally excited populations reveal incomplete thermal accommodation with the surface. Non-Boltzmann J-state populations and hot Doppler lineshapes that broaden with HF excitation indicate two competing scattering mechanisms: (i) a direct reactive scattering channel

  7. Complex vibrational analysis of an antiferroelectric liquid crystal based on solid-state oriented quantum chemical calculations and experimental molecular spectroscopy.

    Science.gov (United States)

    Drużbicki, Kacper; Mikuli, Edward; Kocot, Antoni; Ossowska-Chruściel, Mirosława Danuta; Chruściel, Janusz; Zalewski, Sławomir

    2012-08-02

    The experimental and theoretical vibrational spectroscopic study of one of a novel antiferroelectric liquid crystals (AFLC), known under the MHPSBO10 acronym, have been undertaken. The interpretation of both FT-IR and FT-Raman spectra was focused mainly on the solid-state data. To analyze the experimental results along with the molecular properties, density functional theory (DFT) computations were performed using several modern theoretical approaches. The presented calculations were performed within the isolated molecule model, probing the performance of modern exchange-correlations functionals, as well as going beyond, i.e., within hybrid (ONIOM) and periodic boundary conditions (PBC) methodologies. A detailed band assignment was supported by the normal-mode analysis with SQM ab initio force field scaling. The results are supplemented by the noncovalent interactions analysis (NCI). The relatively noticeable spectral differences observed upon Crystal to AFLC phase transition have also been reported. For the most prominent vibrational modes, the geometries of the transition dipole moments along with the main components of vibrational polarizability were analyzed in terms of the molecular frame. One of the goals of the paper was to optimize the procedure of solid-state calculations to obtain the results comparable with the all electron calculations, performed routinely for isolated molecules, and to test their performance. The presented study delivers a complex insight into the vibrational spectrum with a noticeable improvement of the theoretical results obtained for significantly attracting mesogens using modern molecular modeling approaches. The presented modeling conditions are very promising for further description of similar large molecular crystals.

  8. Analysis of chemical drugs registered by State Food and Drug Administration in 2009%2009年SFDA批准注册的国产化学药品统计分析

    Institute of Scientific and Technical Information of China (English)

    李文哲; 陈昊; 李金平; 付君英; 舒丽芯

    2011-01-01

    Objective To investigate and analyze the distribution of chemical drugs registered by State Food and Drug Administration ( SFDA) in 2009. Methods The data of registered chemical drugs in 2009 including names, approval numbers, medication classifications and whether it belongs to national essential drugs or not were collected from SFDA website. Statistical analysis was implemented by Excel. Results 1 583 chemical drugs were registered which involved 489 generic chemical drugs. The most registered drugs according approval numbers were antibacterial agents, central nervous system agents and digestive system agents in turn. Conclusion The situation of chemical drugs registration in 2009 was still unsatisfied. The distribution of registration categories couldn't meet the requirement of public. The same generic drug had too much approval numbers. The productions of Antibacterial agents were competitive. A new indication of small climax of essential drugs registration appears at the same time.%目的 了解和分析2009年我国新注册的化学药品分布情况.方法 全面检索国家食品药品监督管理局数据库和相关资源,登记2009年注册的国产化学药品的名称、批准文号、药物化学治疗分类、是否属国家基本药物等,然后运用Excel进行分类汇总分析.结果 2009年共注册国产化学药品1 583个,涉及通用名药物489个,药品批准文号数量排序前三位的依次为抗微生物药物、作用于中枢神经系统的药物和作用于消化系统的药物.结论 2009年国产化学药品注册依然存在药品注册与需求不完全一致、个别药品“一药多号”、抗微生物药物生产竞争激烈等问题,同时也出现基本药物注册小高峰等新迹象.

  9. The FMOS-COSMOS Survey of Star-forming Galaxies at z ≈ 1.6. IV. Excitation State and Chemical Enrichment of the Interstellar Medium

    Science.gov (United States)

    Kashino, D.; Silverman, J. D.; Sanders, D.; Kartaltepe, J. S.; Daddi, E.; Renzini, A.; Valentino, F.; Rodighiero, G.; Juneau, S.; Kewley, L. J.; Zahid, H. J.; Arimoto, N.; Nagao, T.; Chu, J.; Sugiyama, N.; Civano, F.; Ilbert, O.; Kajisawa, M.; Le Fèvre, O.; Maier, C.; Masters, D.; Miyaji, T.; Onodera, M.; Puglisi, A.; Taniguchi, Y.

    2017-01-01

    We investigate the physical conditions of ionized gas in high-z star-forming galaxies using diagnostic diagrams based on the rest-frame optical emission lines. The sample consists of 701 galaxies with an Hα detection at 1.4≲ z≲ 1.7, from the Fiber Multi-Object Spectrograph (FMOS)-COSMOS survey, that represent the normal star-forming population over the stellar mass range {10}9.6≲ {M}* /{M}ȯ ≲ {10}11.6, with those at {M}* > {10}11 {M}ȯ being well sampled. We confirm an offset of the average location of star-forming galaxies in the Baldwin–Phillips–Terlevich (BPT) diagram ({{[O}} {{III}}]/{{H}}β versus {{[N}} {{II}}]/{{H}}α ), primarily toward higher {{[O}} {{III}}]/{{H}}β , compared with local galaxies. Based on the [S ii] ratio, we measure an electron density ({n}{{e}}={220}-130+170 {{cm}}-3), which is higher than that of local galaxies. Based on comparisons to theoretical models, we argue that changes in emission-line ratios, including the offset in the BPT diagram, are caused by a higher ionization parameter both at fixed stellar mass and at fixed metallicity, with additional contributions from a higher gas density and possibly a hardening of the ionizing radiation field. Ionization due to active galactic nuclei is ruled out as assessed with Chandra. As a consequence, we revisit the mass–metallicity relation using {{[N}}{{II}}]/{{H}}α and a new calibration including {{[N}} {{II}}]/{{[S}} {{II}}] as recently introduced by Dopita et al. Consistent with our previous results, the most massive galaxies ({M}* ≳ {10}11 {M}ȯ ) are fully enriched, while those at lower masses have metallicities lower than local galaxies. Finally, we demonstrate that the stellar masses, metallicities, and star formation rates of the FMOS sample are well fit with a physically motivated model for the chemical evolution of star-forming galaxies.

  10. Seasonal characterization of submicron aerosol chemical composition and organic aerosol sources in the southeastern United States: Atlanta, Georgia,and Look Rock, Tennessee

    Science.gov (United States)

    Hapsari Budisulistiorini, Sri; Baumann, Karsten; Edgerton, Eric S.; Bairai, Solomon T.; Mueller, Stephen; Shaw, Stephanie L.; Knipping, Eladio M.; Gold, Avram; Surratt, Jason D.

    2016-04-01

    A year-long near-real-time characterization of non-refractory submicron aerosol (NR-PM1) was conducted at an urban (Atlanta, Georgia, in 2012) and rural (Look Rock, Tennessee, in 2013) site in the southeastern US using the Aerodyne Aerosol Chemical Speciation Monitor (ACSM) collocated with established air-monitoring network measurements. Seasonal variations in organic aerosol (OA) and inorganic aerosol species are attributed to meteorological conditions as well as anthropogenic and biogenic emissions in this region. The highest concentrations of NR-PM1 were observed during winter and fall seasons at the urban site and during spring and summer at the rural site. Across all seasons and at both sites, NR-PM1 was composed largely of OA (up to 76 %) and sulfate (up to 31 %). Six distinct OA sources were resolved by positive matrix factorization applied to the ACSM organic mass spectral data collected from the two sites over the 1 year of near-continuous measurements at each site: hydrocarbon-like OA (HOA), biomass burning OA (BBOA), semi-volatile oxygenated OA (SV-OOA), low-volatility oxygenated OA (LV-OOA), isoprene-derived epoxydiols (IEPOX) OA (IEPOX-OA) and 91Fac (a factor dominated by a distinct ion at m/z 91 fragment ion previously observed in biogenic influenced areas). LV-OOA was observed throughout the year at both sites and contributed up to 66 % of total OA mass. HOA was observed during the entire year only at the urban site (on average 21 % of OA mass). BBOA (15-33 % of OA mass) was observed during winter and fall, likely dominated by local residential wood burning emission. Although SV-OOA contributes quite significantly ( ˜ 27 %), it was observed only at the urban site during colder seasons. IEPOX-OA was a major component (27-41 %) of OA at both sites, particularly in spring and summer. An ion fragment at m/z 75 is well correlated with the m/z 82 ion associated with the aerosol mass spectrum of IEPOX-derived secondary organic aerosol (SOA). The

  11. Ab initio study of the chemical states of water on Cr 2O 3(0 0 0 1): From the isolated molecule to saturation coverage

    Science.gov (United States)

    Costa, Dominique; Sharkas, Kamal; Islam, Mazharul M.; Marcus, Philippe

    2009-08-01

    The reactivity of the (0 0 0 1)-Cr-Cr 2O 3 surface towards water was studied by means of periodic DFT + U. Several water coverages were studied, from 1.2H 2O/nm 2 to 14.1H 2O/nm 2, corresponding to ¼, 1, 2 and 3 water/Cr at the (0 0 0 1)-Cr 2O 3 surface, respectively. With increasing coverage, water gradually completes the coordination sphere of the surface Cr atoms from 3 (dry surface) to 4 (1.2 and 4.7H 2O/nm 2), 5 (9.4H 2O/nm 2) and 6 (14.1H 2O/nm 2). For all studied coverages, water replaces an O atom from the missing above plane. At coverages 1.2 and 4.7H 2O/nm 2, the Cr-O s (surface oxygen) acid-base character and bond directionality govern the water adsorption. The adsorption is molecular at the lowest coverage. At 4.7H 2O/nm 2, molecular and dissociative states are isoenergetic. The activation energy barrier between the two states being as low as 12 kJ/mol, allowing protons exchanges between the OH groups, as evidenced by ab inito molecular dynamics at room temperature. At coverages of 9.4 and 14.1H 2O/nm 2, 1D- (respectively, 2D-) water networks are formed. The resulting surface terminations are -Cr(OH) 2 and -Cr(OH) 3- like, respectively. The increased stability of those terminations as compared to the previous ones are due to the stabilization of the adsorbed phase through a H-bond network and to the increase in the Cr coordination number, stabilizing the Cr ( t2g) orbitals in the valence band. An atomistic thermodynamic approach allows us to specify the temperature and water pressure domains of prevalence for each surface termination. It is found that the -Cr(OH) 3-like, -Cr(OH) 2 and anhydrous surfaces may be stabilized depending on ( T, P) conditions. Calculated energies of adsorption and OH frequencies are in good agreement with published experimental data and support the full hydroxylation model, where the Cr achieves a 6-fold coordination, at saturation.

  12. Chemical Physics Electrons and Excitations

    CERN Document Server

    Larsson, Sven

    2012-01-01

    A full understanding of modern chemistry is impossible without quantum theory. Since the advent of quantum mechanics in 1925, a number of chemical phenomena have been explained, such as electron transfer, excitation energy transfer, and other phenomena in photochemistry and photo-physics. Chemical bonds can now be accurately calculated with the help of a personal computer. Addressing students of theoretical and quantum chemistry and their counterparts in physics, Chemical Physics: Electrons and Excitations introduces chemical physics as a gateway to fields such as photo physics, solid-state ph

  13. Indium-Carrier Minerals in Polymetallic Sulphide Ore Deposits: A Crystal Chemical Insight into an Indium Binding State Supported by X-ray Absorption Spectroscopy Data

    Directory of Open Access Journals (Sweden)

    Diogo Rosa

    2012-11-01

    Full Text Available Indium is a typical chalcophile element of the Earth’s crust, with a very low average content that seldom forms specific minerals, occurring mainly as dispersed in polymetallic sulphides. Indium recovery is based primarily on zinc extraction from sphalerite, the prototype of so-called tetrahedral sulphides, wherein metal ions fill half of the available tetrahedral sites within the cubic closest packing of sulphur anions, leaving interstices accessible for further in-filling. Ascertaining the tendency towards the establishment of In-In interactions through an x-ray absorption spectroscopy approach would efficiently contribute to understanding the behavior of indium in the carrier mineral. The successful results of applying such a near-edge absorption (XANES study at In L3-edge to samples collected at the Lagoa Salgada polymetallic orebody in the Iberian Pyrite Belt (IPB are described and the crystal chemistry of indium is re-evaluated, disclosing a potential clue for the metal binding state in polymetallic sulphides.

  14. Applied chemical engineering thermodynamics

    CERN Document Server

    Tassios, Dimitrios P

    1993-01-01

    Applied Chemical Engineering Thermodynamics provides the undergraduate and graduate student of chemical engineering with the basic knowledge, the methodology and the references he needs to apply it in industrial practice. Thus, in addition to the classical topics of the laws of thermodynamics,pure component and mixture thermodynamic properties as well as phase and chemical equilibria the reader will find: - history of thermodynamics - energy conservation - internmolecular forces and molecular thermodynamics - cubic equations of state - statistical mechanics. A great number of calculated problems with solutions and an appendix with numerous tables of numbers of practical importance are extremely helpful for applied calculations. The computer programs on the included disk help the student to become familiar with the typical methods used in industry for volumetric and vapor-liquid equilibria calculations.

  15. 植入式医学仪器化学电源:历史与现状简述%History and state of chemical power sources used for implantable biomedical devices

    Institute of Scientific and Technical Information of China (English)

    徐艳辉; 耿海龙; 王振伟; 孟良荣

    2014-01-01

    Over 60 years had passed since the first human cardiac pacemaker was successfully im_planted into a patient in Sweden.From Zn_HgO battery to plutonium nuclear battery,recently the main candidate is Li_based organic battery.In the article,the history and state of chemical power sources used for implantable biomedical devices has been briefly overviewed.%化学电源作为植入式医学仪器的能源使用的历史已经有60多年,经历了最初的 Zn_HgO 电池以及后来的钚核电池,目前主要以锂系列电池为主。本文扼要综述了植入式医学仪器所用化学电源的历史与现状。

  16. Seasonal characterization of submicron aerosol chemical composition and organic aerosol sources in the southeastern United States: Atlanta, Georgia and Look Rock, Tennessee

    Directory of Open Access Journals (Sweden)

    S. H. Budisulistiorini

    2015-08-01

    Full Text Available A yearlong near-real-time characterization of non-refractory submicron aerosol (NR-PM1 was conducted at an urban (Atlanta, Georgia and rural (Look Rock, Tennessee site in the southeastern US using the Aerodyne aerosol chemical speciation monitor (ACSM collocated with established air-monitoring network measurements. Seasonal variations in organic aerosol (OA and inorganic aerosol species are attributed to meteorological conditions as well as anthropogenic and biogenic emissions in this region. The highest concentrations of NR-PM1 were observed during winter and fall seasons at the urban site and during spring and summer at the rural site. Across all seasons and at both sites, NR-PM1 was composed largely of OA (50–76 % and inorganic sulfate (12–31 %. Six distinct OA sources were resolved by positive matrix factorization applied to the ACSM organic mass spectral data collected from the two sites over the one year of near-continuous measurements at each site: hydrocarbon-like OA (HOA, biomass burning OA (BBOA, semi-volatile oxygenated OA (SV-OOA, low-volatility oxygenated OA (OOA, isoprene-derived epoxydiol (IEPOX OA (IEPOX-OA, and 91Fac OA (a factor dominated by a distinct ion at m/z 91 fragment ion previously observed in biogenic influenced areas. LV-OOA was observed throughout the year at both sites and contributed 30–66 % of total OA mass. HOA was also observed during the entire year only at the urban site (15–24 % of OA mass. BBOA (15–33 % of OA mass was observed during winter and fall, likely dominated by local residential wood burning emission. Although SV-OOA contributes quite significantly (∼ 27 %, it was observed only at the urban site during colder seasons. IEPOX-OA was a major component (27–41 % of OA at both sites, particularly in spring and summer. An ion fragment at m/z 75 is proposed as an additional marker for IEPOX-OA, as it is shown to correlate well with the m/z 82 ion shown to be associated with the aerosol mass

  17. Chemical Mahjong

    Science.gov (United States)

    Cossairt, Travis J.; Grubbs, W. Tandy

    2011-01-01

    An open-access, Web-based mnemonic game is described whereby introductory chemistry knowledge is tested using mahjong solitaire game play. Several tile sets and board layouts are included that are themed upon different chemical topics. Introductory tile sets can be selected that prompt the player to match element names to symbols and metric…

  18. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  19. Nuclear gamma resonance absorption (Moessbauer) spectroscopy as an archaeometric technique to assess chemical states of iron in a Tupiguarani ceramic artifact from Corinto, Minas Gerais, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Floresta, D.L.; Ardisson, J.D., E-mail: denise.floresta@ifmg.edu.br, E-mail: jdr@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Fagundes, M.; Fabris, J.D., E-mail: marcelo.fagundes@ufvjm.edu.br, E-mail: jdfabris@ufmg.edu.br [Universidade Federal dos Vales do Jequitinhonha e Mucuri (LAEP/UFVJM), Diamantina, MG (Brazil). Lab. de Arqueologia e Estudos da Paisagem

    2013-07-01

    Archaeological ceramics of Tupiguarani Tradition are found in many parts throughout the Brazilian territory and have many similarities. Fragments of Tupiguarani pottery found in the archaeological site known as Beltrao, in the municipality of Corinto, state of Minas Gerais, were identified and collected by researchers of the LAEP/UFVJM, in Diamantina, also in Minas Gerais. A selected fragment of about 15 mm-thick, with a color gradation across the ceramic wall ranging from red, on one side, grayish in the middle and orange on the opposite side, was transversely cut and a series of subsamples of powdered materials were collected from different depths across the wall, in layer segments of ∼3 mm, from the orange side. These powdered subsamples were analyzed with X-ray fluorescence and diffraction spectroscopy and {sup 57}Fe Moessbauer spectroscopy at room temperature (298 K) and at 80 K. According to the XRF results, the elementary composition does not clearly vary with the depth in the sample. The powder XRD analysis revealed the occurrence mainly of quartz and muscovite. Results of {sup 57}Fe Moessbauer spectroscopy reveal that hematite is the magnetically ordered phase. An Fe{sup 2+} component appears for the grayish subsample. According to these results, the red subsample seems to be the external part of the pottery, representing the side that had direct contact with fire used to burn the precursor clay in air for this primitive ceramics preparation. The grayish middle layer is probably due to burning clay mixed with some ashes containing residual carbon, under milder temperature than on the external . (author)

  20. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Lu; Smith, Jeremy; Laskin, Alexander; Anastasio, Cort N.; Laskin, Julia; Zhang, Qi

    2014-01-01

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (•OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), desorption electrospray ionization mass spectrometry (DESIMS), and ion chromatography (IC). A large number of oxygenated molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O/C) ratios of phenolic aqSOA are in the range of 0.85-1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than •OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O/C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.

  1. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    Science.gov (United States)

    Yu, L.; Smith, J.; Laskin, A.; Anastasio, C.; Laskin, J.; Zhang, Q.

    2014-12-01

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol (compound with formula C6H5OH)), guaiacol (2-methoxyphenol), and syringol (2,6-dimethoxyphenol) with two major aqueous-phase oxidants - the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (· OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS), and ion chromatography (IC). A large number of oxygenated molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O / C) ratios of phenolic aqSOA are in the range of 0.85-1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than · OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenolic compound has reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O / C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-visible region, suggesting that aqueous-phase reactions of phenols may contribute to formation of secondary brown carbon in the atmosphere, especially in regions influenced by biomass burning.

  2. Roles of steady-state and dynamic models for regulation of hydrophobic chemicals in aquatic systems: A case study of decamethylcyclopentasiloxane (D5) and PCB-180 in three diverse ecosystems.

    Science.gov (United States)

    Kim, Jaeshin; Mackay, Donald; Powell, David E

    2017-02-12

    We seek to contribute to the improved regulatory use of mass balance models to complement environmental monitoring data by applying the steady-state Quantitative Water Air Sediment Interactive model (QWASI) and a novel unsteady-state QWASI model. A steady-state model can yield not only a useful simulation of chemical fate under near steady-state conditions, but it can provide insights into the likely influences of increasing or decreasing emission rates, temperature changes, and unexpectedly high sensitivities to model parameters that may require additional investigation. We compared the consistency of insights from both types of model, in the expectation that while the dynamic model provides a closer simulation of actual conditions, for many purposes a simple, less computationally demanding, more transparent and less expensive model may be adequate for many regulatory purposes. We investigated the response times of decamethylcyclopentasiloxane (D5) and PCB-180 concentrations in water and sediment under three emission scenarios in three different aquatic systems, namely Lake Ontario, Oslofjord, and Lake Pepin. D5 was predicted to be removed largely by hydrolysis and volatilization in Lake Ontario and Oslofjord whereas it is subject to removal by advective loss in Lake Pepin. The half-times of D5 water concentration to a stepwise reduction in emission were <60 days in all three water bodies. In contrast, the predicted half-times were 0.53, 1.4, and 2.9 years in Lake Pepin, Oslofjord, and Lake Ontario, respectively. We also explored how uncertainties in input parameters propagate into uncertainties of concentrations in water and sediments possibly necessitating more accurate values.

  3. Chemical mixtures: considering the evolution of toxicology and chemical assessment.

    Science.gov (United States)

    Monosson, Emily

    2005-04-01

    The assessment of chemical mixtures is a complex topic for toxicologists, regulators, and the public. In this article the linkage between the science of toxicology and the needs of governmental regulatory agencies in the United States is explored through an overview of environmental regulations enacted over the past century and a brief history of modern toxicology. One of the goals of this overview is to encourage both regulators and scientists to consider the benefits and limitations of this science-regulatory relationship as they tackle existing issues such as chemical mixtures. It is clear that a) over the past 100 years chemical regulation and toxicologic research, have in large part, shared a common emphasis on characterization and regulation of individual chemicals. But chemical mixtures have been, and continue to be, evaluated at hazardous waste sites around the United States. For this reason the current U.S. Environmental Protection Agency guidelines for chemical mixtures assessment are also reviewed. These guidelines highlight the current practice of mixtures assessment, which relies primarily on the existing single-chemical database. It is also clear that b) the science and assessment of chemical mixtures are moving forward through the combined efforts of regulatory agencies and scientists from a broad range of disciplines, including toxicology. Because toxicology is at this exciting crossroads, particular attention should be paid to the forces (e.g., public demands, regulatory needs, funding, academic interests) that both promote and limit the growth of this expanding discipline.

  4. The Second 50 Industrial Chemicals, Part 1.

    Science.gov (United States)

    Chenier, Philip J.; Artibee, Danette S.

    1988-01-01

    Provides an introduction to and summaries of the manufacturing methods and uses of chemicals 51-75 on the list of chemicals arranged in order of decreasing production in the United States. Gives production in pounds, annual growth, average price per pound, and organization according to the seven basic organic chemicals. (CW)

  5. Chemical carcinogenesis

    Directory of Open Access Journals (Sweden)

    Paula A. Oliveira

    2007-12-01

    Full Text Available The use of chemical compounds benefits society in a number of ways. Pesticides, for instance, enable foodstuffs to be produced in sufficient quantities to satisfy the needs of millions of people, a condition that has led to an increase in levels of life expectancy. Yet, at times, these benefits are offset by certain disadvantages, notably the toxic side effects of the chemical compounds used. Exposure to these compounds can have varying effects, ranging from instant death to a gradual process of chemical carcinogenesis. There are three stages involved in chemical carcinogenesis. These are defined as initiation, promotion and progression. Each of these stages is characterised by morphological and biochemical modifications and result from genetic and/or epigenetic alterations. These genetic modifications include: mutations in genes that control cell proliferation, cell death and DNA repair - i.e. mutations in proto-oncogenes and tumour suppressing genes. The epigenetic factors, also considered as being non-genetic in character, can also contribute to carcinogenesis via epigenetic mechanisms which silence gene expression. The control of responses to carcinogenesis through the application of several chemical, biochemical and biological techniques facilitates the identification of those basic mechanisms involved in neoplasic development. Experimental assays with laboratory animals, epidemiological studies and quick tests enable the identification of carcinogenic compounds, the dissection of many aspects of carcinogenesis, and the establishment of effective strategies to prevent the cancer which results from exposure to chemicals.A sociedade obtém numerosos benefícios da utilização de compostos químicos. A aplicação dos pesticidas, por exemplo, permitiu obter alimento em quantidade suficiente para satisfazer as necessidades alimentares de milhões de pessoas, condição relacionada com o aumento da esperança de vida. Os benefícios estão, por

  6. Limno-chemical and microbiology aspects in Uranium Pit Mine Lake (Osamu Utsumi), in Antas and Bortolan reservoirs under the influence of effluent Ore Treatment Unit, Caldas - Minas Gerais State, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Ronqui, Leilane B.; Nasciment, Marcos R.L. do; Roque, Claudio V.; Bruschi, Armando; Borba Junior, Palvo J.; Nascimento, Heliana A. F. do, E-mail: leilanebio@yahoo.com.br, E-mail: pmarcos@cnen.gov.br, E-mail: cvroque@cnen.gov.br, E-mail: abruschi@cnen.gov.br, E-mail: jouber_borba@hotmail.com, E-mail: hazevedo@cnen.gov.br [Comissao Nacional de Energia Nuclear (LAPOC/CNEN), Pocos de Caldas, MG (Brazil). Laboratorio de Pocos de Caldas; Almeida, Tito C.M. de, E-mail: titoalmeida2008@gmail.com [Universidade do Vale do Itajai (CTT-Mar/UNIVALI), SC (Brazil). Centro de Ciencias Tecnologicas da Terra e do Mar

    2013-07-01

    Due to high natural radioactivity there in Pocos de Caldas Plateau (Minas Gerais State, Brazil) and the existence of the first uranium mine in Brazil (Pit Mine Osamu Utsumi - Mineral Treatment Unit/Brazilian Nuclear Industries, MTU/BNI), which is characterized by an open-pit mine presents as increased environmental liability the formation of acid mine drainage, this study was conducted to evaluate the limno-chemicals and microbiology aspects (protozooplankton and bacterioplankton) belonging to uranium pit mine lake (PM) and evaluate the possible effects of acid effluents treated and discharged by MTU/BNI in Antas reservoir-AR and downstream of this, the Bortolan reservoir-BR. Besides the realization of abiotic and microbiology analysis of protozooplankton and bacterioplankton; was held standardization and deployment of the Fluorescence 'In Situ' Hybridization (FISH) technical using oligonucleotide probes for extremophile Archaea and Bacteria. According to the results, the PM showed the highest values for the chemical variables, lower pH values, lower protozooplankton density, however, protozooplanktonic high biomass showing the presence of tolerant species in this extreme environment. Antas and Bortolan reservoirs showed differences in the abiotic and biotic variables, AR showed suffer greater interference of acid effluents released at P41point and downstream of this at P14 point, lower protozooplankton biomass, lower bacterial density and pollution characteristics of inorganic sources. Using the FISH technique standard in this study to water bodies evaluated, it was possible to detect the presence of the extremophile bacteria of the Archaea domain in the three water bodies. The results of this study contribute to the knowledge of the pit mine lakes limnology which have become a major concern due to increased mining in the open. (author)

  7. Environmentally-safe process control and state diagnostic in chemical plants by neuronal network. Subproject 2. Final report; Umweltgerechte Prozessfuehrung und Zustandserkennung in Chemieanlagen mit neuronalen Netzen. Teilvorhaben 2: Konzipierung und Erprobung des Zustandserkennungsverfahrens. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Hessel, G.; Heidrich, J.; Hilpert, R.; Roth, M. [Degussa AG (Germany); Kryk, H.; Schmitt, W.; Seiler, T.; Weiss, F.P.

    2002-12-01

    In the frame of the sub-project, an on-line monitoring system for strongly exothermic reactions was developed to support the operational personnel in the optimal and environmentally compatible process control of complex or safety-difficult reactions in semibatch-mode in stirred tank reactors (batch reactor). The Monitoring System (MoSys) based on dimensionless mass and heat balances with adaptive functions has first to be trained using process data from normal and undesired courses of batches carried out in a miniplant under conditions of the industrial process. The adaptation of balance models to the target plant is done by two-layer perceptron networks. To ensure a complete scale-up, MoSys should be adapted and validated using process data of at least one normal batch course in the chemical plant. MoSys was designed for both a homogeneous exothermic esterification reaction and a heterogeneous exothermic hydrogenation process. Experimental tests were carried out in a pilot plant (esterification) and in an industrial plant (hydrogenation). For industrial testing, MoSys was integrated into a Batch-Information-Management System (BIMS) which was also developed and implemented in the Process Control System (PCS) of a multi-purpose reactor installation in the fine chemical factory at Radebeul (Degussa Inc.). As a result, the MoSys outputs can simultaneously be visualised with important process signals on the terminals of PCS. For example, the progress of hydrogenation, the predictive end of reaction and the concentration profiles of the educt, intermediate and product are displayed on the terminals of operator stations. Furthermore, when undesired operating states occur, the operational personnel is early alarmed and recommendation are given for countermeasures that are allowed to be only done by the operator. The efficiency of BIMS/MoSys could be proven during two industrial hydrogenation campaigns. (orig.)

  8. Chemical cosmology

    CERN Document Server

    Boeyens, Jan CA

    2010-01-01

    The composition of the most remote objects brought into view by the Hubble telescope can no longer be reconciled with the nucleogenesis of standard cosmology and the alternative explanation, in terms of the LAMBDA-Cold-Dark-Matter model, has no recognizable chemical basis. A more rational scheme, based on the chemistry and periodicity of atomic matter, opens up an exciting new interpretation of the cosmos in terms of projective geometry and general relativity. The response of atomic structure to environmental pressure predicts non-Doppler cosmical redshifts and equilibrium nucleogenesis by alp

  9. Ni的化学态对甲烷部分氧化反应机理的影响:能学分析%Influence of Ni Chemical States on the Partial Oxidation Mechanism of Methane: An Energetics Analysis

    Institute of Scientific and Technical Information of China (English)

    夏文生; 常刚; 侯玉慧; 翁维正; 万惠霖

    2011-01-01

    采用键指数归一-平方势(UBI-QEP)法对不同化学态Ni上甲烷部分氧化反应中各可能基元步骤进行了能学计算研究.结果表明,反应的速度控制步骤与金属Ni的化学态有关.还原态Ni上CO形成的反应速度控制步骤为表面上CH3与O物种间的缔合,而带部分正电荷的Ni上CO形成的反应速度控制步骤则为甲烷氧助解离形成表面CHxO物种.还原态和带部分正电荷的Ni中心在表面上共存时,反应的速度控制步骤将取决于表面CH3形成与表面CH3、O物种缔合两反应间的竞争,其竞争的强弱涉及Ni的化学态.此外,反应活性中心向正电荷的Ni转化时,会导致表面C和O及H和H物种缔合的活化能显著降低,有利于CO、H2的形成,而表面CHx物种解离则变得不容易,表面积炭受到明显的抑制.%An energetics analysis of the possible elementary steps involved in the partial oxidation of methane (POM) over different chemical states of Ni was carried out using the unity bond index-quadratic exponential potential (UBI-QEP) method. The results show that the rate determining step for the partial oxidation mechanism of methane is related to the chemical state of the Ni. Over reduced Ni the rate determining step for CO formation is the association of surface CH3 species with surface O species. Over apartial positive charged Ni surface the rate determining step is that methane dissociates into the CHxO species with the assistance of oxygen. Over the reduced and partial positive charged Ni sites in coexistence, however, the rate determining step depends on the competition between the formation of surface CH3 species and the recombination of surface CH3 species with surface O species. This competition is related to the chemical states of the Ni sites. If the partial positive charged Ni sites are predominant on the surface, the recombination of surface C species with surface O species and the recombination of surface H atom species favor CO and H

  10. Sistemas agroflorestais e seus efeitos sobre os atributos químicos em Argissolo Vermelho-Amarelo do Cerrado piauiense Agroforestry systems and its effects on chemical attributes of an Ultisol in the 'Cerrado' of Piaui state, Brazil

    Directory of Open Access Journals (Sweden)

    Bruna de F. Iwata

    2012-07-01

    Full Text Available Objetivou-se, com este trabalho, quantificar os efeitos dos Sistemas Agroflorestais com diferentes tempos de adoção e a agricultura de corte e queima sobre os atributos químicos de um Argissolo Vermelho-Amarelo em áreas de cerrado do estado do Piauí. Em duas épocas climáticas foram estudados quatro sistemas: sistemas agroflorestais com seis e treze anos de adoção, agricultura de corte e queima e uma floresta nativa do cerrado. As amostras de solo foram coletadas em quatro profundidades para determinação dos atributos químicos. No solo sob os Sistemas Agroflorestais foram observados, em todas as camadas avaliadas, redução dos teores de Al3+ e H++Al3+ e aumento do pH, dos teores dos nutrientes e do carbono orgânico total em relação aos demais sistemas. No solo sob agricultura de corte e queima, verificou-se que apenas nas camadas superficiais a cinza depositada sobre o solo promoveu aumento dos nutrientes, exceto para o P, que foi maior em todas as camadas. Nos demais sistemas houve diminuição dos teores dos nutrientes no período chuvoso. Os sistemas agroflorestais promoveram aumento dos teores de nutrientes do solo e garantiram melhoria da qualidade química do solo em áreas de cerrado no estado do Piauí.This study aimed to quantify the effects of agroforestry systems (AFS, with different periods of adoption, and slash and burn agriculture (SB on the chemical attributes of an Ultisol in the 'Cerrado' of Piaui State, Brazil. In two distinct climatic seasons (dry and rainy four systems were studied: AFS with six (AFS6 and thirteen years (AFS13 of adoption, an area under SB and a native forest (NF, as a reference. In the AFS, in all depths, higher reduction in the Al3+ and H+ + Al3+ contents were observed as well as an increase of pH value and contents of nutrients (N, P, Ca, Mg and K and organic carbon in soil. In the soil under SB, only in superficial layers, the ash deposited on the soil caused an increase in contents of

  11. The Chemical Production of Excited State Moleculea.

    Science.gov (United States)

    2014-09-26

    products may impart some particular stability to the exciplex as in 1. However, when acetone was the companion ketone product to the acetophenone (as in 4...expected when acetone (ET1 = 80 kcal/mol) is the companion carbonyl product . With a higher triplet energy, acetone destabilizes the exciplex...Yield Trapped k2 [ t2 (Z Yield Acetone )/(ZYield Trapped Products ) (4) kr[RH] [A2 kr (% Yield Acetone )[RH] k2 = (5) (% Yield Trapped Products ) Products

  12. Uncoated microcantilevers as chemical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Thundat, Thomas G. (Knoxville, TN)

    2001-01-01

    A method and device are provided for chemical sensing using cantilevers that do not use chemically deposited, chemically specific layers. This novel device utilizes the adsorption-induced variation in the surfaces states on a cantilever. The methodology involves exciting charge carriers into or out of the surface states with photons having increasing discrete levels of energy. The excitation energy is provided as discrete levels of photon energy by scanning the wavelength of an exciting source that is illuminating the cantilever surface. When the charge carriers are excited into or out of the surface states, the cantilever bending changes due to changes in surface stress. The amount of cantilever bending with respect to an identical cantilever as a function of excitation energy is used to determine the energy levels associated with adsorbates.

  13. Surface properties of palladium catalysts supported on ternary ZrO2-Al2O3-WOx oxides prepared by the sol-gel method: Study of the chemical state of the support

    Science.gov (United States)

    Barrera, A.; Montoya, J. A.; del Angel, P.; Navarrete, J.; Cano, M. E.; Tzompantzi, F.; López-Gaona, A.

    2012-08-01

    The surface properties of Pd and Pd-Pt catalysts supported on binary ZrO2-WOx and ternary ZrO2-Al2O3-WOx oxides prepared by the sol-gel method were studied. Special attention was paid to the study of the texture of the catalysts as well as the chemical state of tungstated zirconia and tungstated zirconia promoted with alumina in the palladium catalysts. The catalysts were tested in the isomerization of n-hexane and were characterized by N2 physisorption, XRD, TPR, Raman spectroscopy, XPS and FT-IR of adsorbed pyridine. The catalysts had bimodal pore size distributions with mesopores in the range 55-70 Å and macropores of 1000 Å in diameter. The catalysts had a surface WOx coverage (4.4-6.0 W nm-2) lower than that of the theoretical monolayer (7.0 W nm-2). A lower acidity of the ternary ZrO2-Al2O3-WOx oxide as compared to the binary ZrO2-WOx oxide was found. Higher activity in the isomerisation of n-hexane was obtained in the Pd-Pt catalysts supported on ternary ZrAlW oxides prepared by sol-gel that is correlated with the coexistence on the surface of W4+ (WO2) or W0 and W6+ (Al2(WO4)3) species, ZrO2 in the tetragonal phase and a high amount of ZrOx suboxides species in a low oxidation state (Zr3+ and Zr2+).

  14. Interactive Chemical Reactivity Exploration

    CERN Document Server

    Haag, Moritz P; Bosson, Mael; Redon, Stephane; Reiher, Markus

    2014-01-01

    Elucidating chemical reactivity in complex molecular assemblies of a few hundred atoms is, despite the remarkable progress in quantum chemistry, still a major challenge. Black-box search methods to find intermediates and transition-state structures might fail in such situations because of the high-dimensionality of the potential energy surface. Here, we propose the concept of interactive chemical reactivity exploration to effectively introduce the chemist's intuition into the search process. We employ a haptic pointer device with force-feedback to allow the operator the direct manipulation of structures in three dimensions along with simultaneous perception of the quantum mechanical response upon structure modification as forces. We elaborate on the details of how such an interactive exploration should proceed and which technical difficulties need to be overcome. All reactivity-exploration concepts developed for this purpose have been implemented in the Samson programming environment.

  15. Chemical Analyses

    Science.gov (United States)

    Bulluck, J. W.; Rushing, R. A.

    1994-01-01

    As a preliminary study on the effects of chemical aging of polymer materials MERL and TRI have examined two polymeric materials that are typically used for offshore umbilical applications. These two materials were Tefzel, a copolymer of ethylene and tetrafluoroethylene, and Coflon, polyvinylidene fluoride. The Coflon specimens were cut from pipe sections and exposed to H2S at various temperatures and pressures. One of these specimens was tested for methane permeation, and another for H2S permeation. The Tefzel specimens were cut from .05 mm sheet stock material and were exposed to methanol at elevated temperature and pressure. One of these specimens was exposed to methanol permeation for 2 days at 100 C and 2500 psi. An additional specimen was exposed to liquid methanol for 3 days at 150 C and 15 Bar. Virgin specimens of each material were similarly prepared and tested.

  16. 78 FR 55326 - Determinations Regarding Use of Chemical Weapons in Syria Under the Chemical and Biological...

    Science.gov (United States)

    2013-09-10

    ... Determinations Regarding Use of Chemical Weapons in Syria Under the Chemical and Biological Weapons Control and..., 22 U.S.C. 5604(a), that the Government of Syria has used chemical weapons in violation of... Under Secretary of State for Political Affairs: (1) Determined that the Government of Syria has...

  17. CHEMICAL EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Calvin, Melvin

    1965-06-01

    How did life come to be on the surface of the earth? Darwin himself recognized that his basic idea of evolution by variation and natural selection must be a continuous process extending backward in time through that period in which the first living things arose and into the period of 'Chemical Evolution' which preceded it. We are approaching the examination of these events by two routes. One is to seek for evidence in the ancient rocks of the earth which were laid down prior to that time in which organisms capable of leaving their skeletons in the rocks to be fossilized were in existence. This period is sometime prior to approximately 600 million years ago. The earth is believed to have taken its present form approximately 4700 million years ago. We have found in rocks whose age is about 1000 million years certain organic molecules which are closely related to the green pigment of plants, chlorophyll. This seems to establish that green plants were already fluorishing prior to that time. We have now found in rocks of still greater age, namely, 2500 million years, the same kinds of molecules mentioned above which can be attributed to the presence of living organisms. If these molecules are as old as the rocks, we have thus shortened the time available for the generation of the complex biosynthetic sequences which give rise to these specific hydrocarbons (polyisoprenoids) to less than 2000 million years.

  18. Chemical information science coverage in Chemical Abstracts.

    Science.gov (United States)

    Wiggins, G

    1987-02-01

    For many years Chemical Abstracts has included in its coverage publications on chemical documentation or chemical information science. Although the bulk of those publications can be found in section 20 of Chemical Abstracts, many relevant articles were found scattered among 39 other sections of CA in 1984-1985. In addition to the scattering of references in CA, the comprehensiveness of Chemical Abstracts as a secondary source for chemical information science is called into question. Data are provided on the journals that contributed the most references on chemical information science and on the languages of publication of relevant articles.

  19. Nature's chemicals and synthetic chemicals: comparative toxicology.

    OpenAIRE

    Ames, B N; Profet, M; Gold, L S

    1990-01-01

    The toxicology of synthetic chemicals is compared to that of natural chemicals, which represent the vast bulk of the chemicals to which humans are exposed. It is argued that animals have a broad array of inducible general defenses to combat the changing array of toxic chemicals in plant food (nature's pesticides) and that these defenses are effective against both natural and synthetic toxins. Synthetic toxins such as dioxin are compared to natural chemicals, such as indole carbinol (in brocco...

  20. Quantum Entanglement and Chemical Reactivity.

    Science.gov (United States)

    Molina-Espíritu, M; Esquivel, R O; López-Rosa, S; Dehesa, J S

    2015-11-10

    The water molecule and a hydrogenic abstraction reaction are used to explore in detail some quantum entanglement features of chemical interest. We illustrate that the energetic and quantum-information approaches are necessary for a full understanding of both the geometry of the quantum probability density of molecular systems and the evolution of a chemical reaction. The energy and entanglement hypersurfaces and contour maps of these two models show different phenomena. The energy ones reveal the well-known stable geometry of the models, whereas the entanglement ones grasp the chemical capability to transform from one state system to a new one. In the water molecule the chemical reactivity is witnessed through quantum entanglement as a local minimum indicating the bond cleavage in the dissociation process of the molecule. Finally, quantum entanglement is also useful as a chemical reactivity descriptor by detecting the transition state along the intrinsic reaction path in the hypersurface of the hydrogenic abstraction reaction corresponding to a maximally entangled state.

  1. Atributos químicos e estoques de carbono em Latossolo sob plantio direto no cerrado do Piauí Chemical attributes and carbon stocks in an Oxisol under no-tillage in savannah of Piauí state

    Directory of Open Access Journals (Sweden)

    Luiz F. C. Leite

    2010-12-01

    H, extractable P and exchangeable cations contents. Compared to conventional tillage, TOC and Cmic stocks increased 34 and 99% (NT2, 47 and 92% (NT4 and 61 and 108% (NT6, respectively, in the superficial layer (0-20 cm. No-tillage adoption improves chemical attributes and increases total organic carbon and microbial carbon and its continuous use contributes to soil quality in savannah soils of Piaui state.

  2. Chemical products injection in wells by using the gas-lift line: state-of-art; Injecao de produtos quimicos em poco atraves de linha de gas-lift: estado-da-arte

    Energy Technology Data Exchange (ETDEWEB)

    Ramalho, Joao Batista Vianey da Silva [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2000-07-01

    The subsurface injection of chemicals for control of scale, corrosion, emulsion, paraffin, and others problems, is a practice not very used in the petroleum production. The problem concern in how to transport these products. Recently, downhole injection into lift gas stream has been used in order to solve these problems, allowing to control the treatment for individual wells. The main conclusions reported are: is possible to inject chemicals into gas-lift; chemicals must be formulated for specific needs, having enough amount of solvent to prevent dropping out of active ingredient; the chemicals must be inject individually into gas-lift of each well. (author)

  3. Avaliação qualitativa de pulverizadores da região de Cascavel, Estado do Paraná = Sprayers qualitative evaluation in chemical application in Cascavel, State of Paraná

    Directory of Open Access Journals (Sweden)

    João Cleber Modernel da Silveira

    2006-10-01

    Full Text Available No processo de tratamento fitossanitário, o controle das características da pulverização deve ser realizado com o objetivo de garantir a eficiência dos tratamentos, evitando-se perdas de produtos sem causar danos ao meio e ao próprio homem. Dessa forma, é fundamental que os pulverizadores estejam em perfeito estado de conservação. O objetivo deste trabalho foi realizar na região de Cascavel, Estado do Paraná, uma avaliação qualitativa de pulverizadores agrícolas. Foram checados, no campo, o estado e presença dos principais componentes de 62 pulverizadores. Os pulverizadores avaliados foram divididos em três categorias: montado, arrasto e autopropelido. Observou-se que os equipamentos avaliadosestão com manutenção inadequada. Considerando a presença e o estado de alguns componentes (bicos, manômetros, filtros de linhas, entre outros, apenas 17% dos equipamentos estão em condições adequadas de uso.Spray quality control should be accomplished in the process of chemical treatment, aiming to guarantee the efficiency, avoiding loss of product and damages to the environment. It is fundamental, thus, sprayers optimum conservation. This work aimed to carry out a qualitative evaluation of the sprayers in farms in the municipality of Cascavel, State of Paraná, southern Brazil. The conditions and presence (or absence of main components in 62 sprayers were checked in the field. The appraised sprayers were divided in three categories: attached to tractors, PTO-driven trailed and self-propelled. The equipments showed inadequate maintenance. Considering the presence and the conditions of some components (nozzles, filters of lines, nozzles filters, among others, only 17% of the equipment evaluated was in good condition.

  4. Effect of pH, Temperature, and Chemicals on the Endoglucanases and β-Glucosidases from the Thermophilic Fungus Myceliophthora heterothallica F.2.1.4. Obtained by Solid-State and Submerged Cultivation

    Directory of Open Access Journals (Sweden)

    Vanessa de Cássia Teixeira da Silva

    2016-01-01

    Full Text Available This work reports endoglucanase and beta-glucosidase production by the thermophilic fungus Myceliophthora heterothallica in solid-state (SSC and submerged (SmC cultivation. Wheat bran and sugarcane bagasse were used for SSC and cardboard for SmC. Highest endoglucanase production in SSC occurred after 192 hours: 1,170.6 ± 0.8 U/g, and in SmC after 168 hours: 2,642 ± 561 U/g. The endoglucanases and beta-glucosidases produced by both cultivation systems showed slight differences concerning their optimal pH and temperature. The number of endoglucanases was also different: six isoforms in SSC and ten in SmC. Endoglucanase activity remained above 50% after incubation between pH 3.0 and 9.0 for 24 h for both cultivation systems. The effect of several chemicals displayed variation between SSC and SmC isoenzymes. Manganese activated the enzymes from SmC but inhibited those from SSC. For β-glucosidases, maximum production on SmC was 244 ± 48 U/g after 168 hours using cardboard as carbon source. In SSC maximum production reached 10.9 ± 0.3 U/g after 240 h with 1 : 1 wheat bran and sugarcane bagasse. Manganese exerted a significant activation on SSC β-glucosidases, and glucose inhibited the enzymes from both cultivation systems. FeCl3 exerted the strongest inhibition for endoglucanases and β-glucosidases.

  5. Frontiers in Chemical Physics

    Energy Technology Data Exchange (ETDEWEB)

    Bowlan, Pamela Renee [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-02

    These are slides dealing with frontiers in chemical physics. The following topics are covered: Time resolving chemistry with ultrashort pulses in the 0.1-40 THz spectral range; Example: Mid-infrared absorption spectrum of the intermediate state CH2OO; Tracking reaction dynamics through changes in the spectra; Single-shot measurement of the mid-IR absorption dynamics; Applying 2D coherent mid-IR spectroscopy to learn more about transition states; Time resolving chemical reactions at a catalysis using mid-IR and THz pulses; Studying topological insulators requires a surface sensitive probe; Nonlinear phonon dynamics in Bi2Se3; THz-pump, SHG-probe as a surface sensitive coherent 2D spectroscopy; Nanometer and femtosecond spatiotemporal resolution mid-IR spectroscopy; Coherent two-dimensional THz/mid-IR spectroscopy with 10nm spatial resolution; Pervoskite oxides as catalysts; Functionalized graphene for catalysis; Single-shot spatiotemporal measurements; Spatiotemporal pulse measurement; Intense, broad-band THz/mid-IR generation with organic crystals.

  6. Toxicological evaluation of chemical mixtures

    NARCIS (Netherlands)

    Feron, V.J.; Groten, J.P.

    2002-01-01

    This paper addresses major developments in the safety evaluation of chemical mixtures during the past 15 years, reviews today's state of the art of mixture toxicology, and discusses challenges ahead. Well-thought-out tailor-made mechanistic and empirical designs for studying the toxicity of mixtures

  7. Apparent tunneling in chemical reactions

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm; Hansen, Flemming Yssing; Billing, G. D.

    2000-01-01

    A necessary condition for tunneling in a chemical reaction is that the probability of crossing a barrier is non-zero, when the energy of the reactants is below the potential energy of the barrier. Due to the non-classical nature (i.e, momentum uncertainty) of vibrational states this is, however...

  8. Extended range chemical sensing apparatus

    Science.gov (United States)

    Hughes, Robert C.; Schubert, W. Kent

    1994-01-01

    An apparatus for sensing chemicals over extended range of concentrations. In particular, first and second sensors each having separate, but overlapping ranges for sensing concentrations of hydrogen are provided. Preferably, the first sensor is a MOS solid state device wherein the metal electrode or gate is a nickel alloy. The second sensor is a chemiresistor comprising a nickel alloy.

  9. Chemical properties of mendelevium

    Energy Technology Data Exchange (ETDEWEB)

    Hulet, E.K.

    1980-11-01

    Even with the most intense ion beams and the largest available quantities of target isotope, about 10/sup 6/ atoms at a time is all the Md that can be produced for chemical studies. This lack of sufficient sample size coupled with the very short lifetimes of the few atoms produced has severely restricted the gathering and the broadness of our knowledge concerning the properties of Md and the heavier elements. To illustrate, the literature contains a mere eleven references to the chemical studies of Md, and none of these deal with bulk properties associated with the element bound in solid phases. Some of these findings are: Md was found to be more volatile than other actinide metals which lead to the belief that it is divalent in the metallic state; separation of Md from the other actinides can be accomplished either by reduction of Md/sup 3 +/ to the divalent state or by chromatographic separations with Md remaining in the tripositive state; extraction of Md/sup 2 +/ with bis(2-ethylhexyl)phosphoric acid is much poorer than the extraction of the neighboring tripositive actinides; attempts to oxidize Md/sup 3 +/ with sodium bismuthate failed to show any evidence for Md/sup 4 +/; reduction potential of Md/sup 3 +/ was found to be close to -0.1 volt; Md/sup 3 +/ can be reduced to Md(Hg) by sodium amalgams and by electrolysis; the electrochemical behavior of Md is very similar to that of Fm and can be summarized in the equation, Md/sup 2 +/ + 2e/sup -/ = Md(Hg) and E/sup 0/ = -1.50 V.; and Md cannot be reduced to a monovalent ion with Sm/sup 2 +/.

  10. Resposta do arroz irrigado à adubação verde e química no Estado de Tocantins Response of irrigated rice to green manure and chemical fertilization in the State of Tocantins

    Directory of Open Access Journals (Sweden)

    Nand K. Fageria

    2007-08-01

    Full Text Available O arroz irrigado é uma cultura significativa para o País, do ponto de vista socioeconômico, em especial nas várzeas tropicais do Estado do Tocantins. Muitas vezes, devido ao uso de adubação inadequada, sua produtividade é limitada. Conduziram-se dois experimentos de campo, na Fazenda Xavante, município de Dueré, Estado do Tocantins, durante dois anos consecutivos, para se avaliar a resposta do arroz irrigado à adubação verde e química, cultivado em um Inceptissolo, cujos tratamentos consistiram de oito combinações de adubação: Adubo verde + N0P0K0; Adubo verde + N100P120K100; Adubo verde + N50P60K50; Adubo verde + N75P90K75; Adubo verde + N45P120K100 (aplicação de N, P e K no plantio; Adubo verde + N45P120K100 (aplicação de P e K no plantio e N em cobertura; Adubo verde + N100P120K100 + 4 Mg ha-1 calcário; e Sem adubo verde + N100P120K100. Obteve-se a produtividade máxima (kg ha-1 de grãos com o tratamento adubo verde + N45P120K100 (aplicação de P e K no plantio e N em cobertura. Entre os componentes da produtividade, o comprimento da panícula foi influenciado positiva e significativamente, pelos tratamentos de adubação. Com a prática da adubação verde, a quantidade de fertilizante nitrogenado a ser empregada pode ser reduzida e, em conseqüência, diminuir também o custo de produção do arroz irrigado.Lowland rice is an important crop in Brazil due to its socio-economic value. Often due to inadequate fertilization, production is limited. Two field experiments were conducted at Xavante Farm, Municipality of Dueré, State of Tocantins, Brazil, during two consecutive years to determine the response of irrigated rice to green manure and to chemical fertilization grown in an Inceptisol. The treatments consisted of green manure + N0P0K0; green manure + N100P120K100; green manure + N50P60K50; green manure + N75P90K75; green manure + N45P120K100 (application of N, P, and K at sowing; green manure + N45P120K100

  11. Optical MEMS for chemical analysis and biomedicine

    CERN Document Server

    Jiang, Hongrui

    2016-01-01

    This book describes the current state of optical MEMS in chemical and biomedical analysis and brings together current trends and highlights topics representing the most exciting progress in recent years in the field.

  12. Chemical implementation and thermodynamics of collective neural networks.

    Science.gov (United States)

    Hjelmfelt, A; Ross, J

    1992-01-01

    The chemical implementation of a neuron and connections among neurons described in prior work is used to construct collective neural networks. With stated approximations, these chemical networks are reduced to networks of the Hopfield type. Chemical networks approaching a stationary or equilibrium state provide a Liapunov function with the same extremal properties as Hopfield's energy function. Numerical comparisons of chemical and Hopfield networks with small numbers (2-16) of neurons show agreement on the results of given computations. PMID:1729709

  13. Valence-Bond Theory and Chemical Structure.

    Science.gov (United States)

    Klein, Douglas J.; Trinajstic, Nenad

    1990-01-01

    Discussed is the importance of valence bond theory on the quantum-mechanical theory of chemical structure and the nature of the chemical bond. Described briefly are early VB theory, development of VB theory, modern versions, solid-state applications, models, treatment in textbooks, and flaws in criticisms of valence bond theory. (KR)

  14. Better Tomorrow of China Rubber Chemicals Industry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    I. Development of China Rubber Chemicals Industry During the "11th Five-Year Plan" period, China rubber Chemicals industry fully implemented the development guideline of "Adhering to science and technology development, developing green chemistry with environmental protection, safety and energy conservation as the core, and building enterprise and world brands". With the great support of the state,

  15. Environmental and chemical carcinogenesis.

    Science.gov (United States)

    Wogan, Gerald N; Hecht, Stephen S; Felton, James S; Conney, Allan H; Loeb, Lawrence A

    2004-12-01

    People are continuously exposed exogenously to varying amounts of chemicals that have been shown to have carcinogenic or mutagenic properties in experimental systems. Exposure can occur exogenously when these agents are present in food, air or water, and also endogenously when they are products of metabolism or pathophysiologic states such as inflammation. It has been estimated that exposure to environmental chemical carcinogens may contribute significantly to the causation of a sizable fraction, perhaps a majority, of human cancers, when exposures are related to "life-style" factors such as diet, tobacco use, etc. This chapter summarizes several aspects of environmental chemical carcinogenesis that have been extensively studied and illustrates the power of mechanistic investigation combined with molecular epidemiologic approaches in establishing causative linkages between environmental exposures and increased cancer risks. A causative relationship between exposure to aflatoxin, a strongly carcinogenic mold-produced contaminant of dietary staples in Asia and Africa, and elevated risk for primary liver cancer has been demonstrated through the application of well-validated biomarkers in molecular epidemiology. These studies have also identified a striking synergistic interaction between aflatoxin and hepatitis B virus infection in elevating liver cancer risk. Use of tobacco products provides a clear example of cancer causation by a life-style factor involving carcinogen exposure. Tobacco carcinogens and their DNA adducts are central to cancer induction by tobacco products, and the contribution of specific tobacco carcinogens (e.g. PAH and NNK) to tobacco-induced lung cancer, can be evaluated by a weight of evidence approach. Factors considered include presence in tobacco products, carcinogenicity in laboratory animals, human uptake, metabolism and adduct formation, possible role in causing molecular changes in oncogenes or suppressor genes, and other relevant data

  16. Chemical Engineering in Space

    Science.gov (United States)

    Lobmeyer, Dennis A.; Meneghelli, Barry; Steinrock, Todd (Technical Monitor)

    2001-01-01

    The aerospace industry has long been perceived as the domain of both physicists and mechanical engineers. This perception has endured even though the primary method of providing the thrust necessary to launch a rocket into space is chemical in nature. The chemical engineering and chemistry personnel behind the systems that provide access to space have labored in the shadows of the physicists and mechanical engineers. As exploration into the cosmos moves farther away from Earth, there is a very distinct need for new chemical processes to help provide the means for advanced space exploration. The state of the art in launch systems uses chemical propulsion systems, primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit. As we move away from Earth, there are additional options for propulsion. Unfortunately, few of these options can compare to the speed or ease of use provided by the chemical propulsion agents. It is with great care and significant cost that gaseous compounds such as hydrogen and oxygen are liquefied and become dense enough to use for rocket fuel. These low-temperature liquids fall within a specialty area known as cryogenics. Cryogenics, the science and art of producing cold operating conditions for use on Earth, in orbit, or on some other nonterrestrial body, has become increasingly important to our ability to travel within our solar system. The production of cryogenic fuels and the long-term storage of these fluids are necessary for travel. As our explorations move farther away from Earth, we need to address how to produce the necessary fuels to make a round-trip. The cost and the size of these expeditions are extreme at best. If we take everything necessary for our survival for the round-trip, we invalidate any chance of travel in the near future. As with the early explorers on Earth, we need to harvest much of our energy and our life support from the celestial bodies. The in situ production of these energy

  17. Microfluidic chemical reaction circuits

    Science.gov (United States)

    Lee, Chung-cheng; Sui, Guodong; Elizarov, Arkadij; Kolb, Hartmuth C.; Huang, Jiang; Heath, James R.; Phelps, Michael E.; Quake, Stephen R.; Tseng, Hsian-rong; Wyatt, Paul; Daridon, Antoine

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  18. Geochemical evolution of groundwater in a basaltic aquifer based on chemical and stable isotopic data: Case study from the Northeastern portion of Serra Geral Aquifer, São Paulo state (Brazil)

    Science.gov (United States)

    Gastmans, Didier; Hutcheon, Ian; Menegário, Amauri Antônio; Chang, Hung Kiang

    2016-04-01

    Groundwater from the fractured basalt Serra Geral Aquifer (SGA) represents an important source for water supply in Northeastern São Paulo state (Brazil). Groundwater flow conditions in fractured aquifers hosted in basaltic rocks are difficult to define because flow occurs through rock discontinuities. The evaluation of hydrodynamic information associated with hydrochemical data has identified geochemical processes related to groundwater evolution, observed in regional flowpaths. SGA groundwaters are characterized by low TDS with pH varying from neutral to alkaline. Two main hydrochemical facies are recognized: Ca-Mg-HCO3, and Na-HCO3 types. Primarily, the geochemical evolution of SGA groundwater occurs under CO2 open conditions, and the continuous uptake of CO2 is responsible for mineral dissolution, producing bicarbonate as the main anion, and calcium and magnesium in groundwater. Ion exchange between smectites (Na and Ca-beidelites) seems to be responsible for the occurrence of Na-HCO3 groundwater. Toward the Rio Grande, in the northern portion of the study area, there is mixing between SGA groundwater and water from the sandstones of the Guarani Aquifer System, as evidenced by the chemical and isotopic composition of the groundwater. Inverse mass balance modeling performed using NETPATH XL produces results in agreement with the dissolution of minerals in basalt (feldspars and pyroxenes) associated with the uptake of atmospheric CO2, as well as the dissolution of clay minerals present in the soil. Kaolinite precipitation occurs due to the incongruent dissolution of feldspars, while Si remains almost constant due to the precipitation of silica. The continuous uptake of CO2 under open conditions leads to calcite precipitation, which in addition to ion exchange are responsible by Ca removal from groundwater and an increase in Na concentrations. Down the flow gradientCO2 is subject to closed conditions where the basalts are covered by the sediments of Bauru Group or

  19. Wood Chemical Modification: the State of the Art of Technologies and Commercialization%木材化学功能改良技术进展与产业现状

    Institute of Scientific and Technical Information of China (English)

    谢延军; 符启良; 王清文; 王海刚

    2012-01-01

    Wood modification is the technologies with which the properties of wood are permanently altered by heating at high temperatures or reacting with low molecular weight monomers or oligomers. The specific properties of wood are consequently improved and certain new characteristics imparted due to the modification. The modified woods can resultantly serve for a longer term compared to the non-modified ones. As a result, the tension due to the lack of wood resource can be reduced. In this paper, the development and the state of the art of wood modification are systematically reviewed. The typical modification technologies such as thermal treatment, acetylation, treatments with N-methylol compounds, furfurylation, and impregnation with thermoset resins are introduced. The effects of chemical modification on the properties of the resulting wood are analyzed and the commercialization status of modified products presented. Consequently, an outlook for the development trends and challenges of wood modification is given.%木材化学功能改良旨在通过物理或化学的方法(主要是利用热或具有反应活性官能团的低分子单体/低聚体),对木材细胞壁成分进行永久改变和/或对木材细胞腔进行物理填充,由此改善木材的各项物理力学性能,并赋予其特定的新功能,提高木材的附加值,延长木材的使用寿命,从而实现木材的高效节约利用,缓解木材资源紧张的局面.对国内、国际上木材功能改良技术的发展和现状进行系统回顾,介绍炭化处理、乙酰化、氮甲氧基树脂处理、糠醇处理、热固性树脂处理等典型改性技术的原理、产品性能的优缺点及其商业化现状,展望木材功能改良技术发展面临的机遇与挑战.

  20. Chemical Visualization of Boolean Functions: A Simple Chemical Computer

    Science.gov (United States)

    Blittersdorf, R.; Müller, J.; Schneider, F. W.

    1995-08-01

    We present a chemical realization of the Boolean functions AND, OR, NAND, and NOR with a neutralization reaction carried out in three coupled continuous flow stirred tank reactors (CSTR). Two of these CSTR's are used as input reactors, the third reactor marks the output. The chemical reaction is the neutralization of hydrochloric acid (HCl) with sodium hydroxide (NaOH) in the presence of phenolphtalein as an indicator, which is red in alkaline solutions and colorless in acidic solutions representing the two binary states 1 and 0, respectively. The time required for a "chemical computation" is determined by the flow rate of reactant solutions into the reactors since the neutralization reaction itself is very fast. While the acid flow to all reactors is equal and constant, the flow rate of NaOH solution controls the states of the input reactors. The connectivities between the input and output reactors determine the flow rate of NaOH solution into the output reactor, according to the chosen Boolean function. Thus the state of the output reactor depends on the states of the input reactors.

  1. Underway and profile, chemical and physical data collected aboard NOAA Ship Ronald H. Brown in the East Coast of the United States and Gulf of Mexico from 2007-05-11 to 2007-08-04 (NODC Accession 0083633)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0083633 includes chemical, discrete bottle, physical, profile, underway - surface data collected aboard NOAA Ship RONALD H. BROWN in East Coast -...

  2. Effort problem of chemical pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Okrajni, J.; Ciesla, M.; Mutwil, K. [Silesian Technical University, Katowice (Poland)

    1998-12-31

    The problem of the technical state assessment of the chemical pipelines working under mechanical and thermal loading has been shown in the paper. The pipelines effort after the long time operating period has been analysed. Material geometrical and loading conditions of the crack initiation and crack growth process in the chosen object has been discussed. Areas of the maximal effort have been determined. The material structure charges after the long time operating period have been described. Mechanisms of the crack initiation and crack growth in the pipeline elements have been analysed and mutual relations between the chemical and mechanical influences have been shown. (orig.) 16 refs.

  3. Chemical patterning in biointerface science

    Directory of Open Access Journals (Sweden)

    Ryosuke Ogaki

    2010-04-01

    Full Text Available Patterning of surfaces with different chemistries provides novel insights into how proteins, cells and tissues interact with materials. New materials, and the properties that their surfaces impart, are highly desirable for the next generation of implants, regenerative medicine and tissue engineering devices, and biosensors and drug delivery devices for disease diagnosis and treatment. Patterning is thus seen as a key technology driver for these materials. We provide an overview of state-of-the-art fabrication tools for creating chemical patterns over length scales ranging from millimeters to micrometers to nanometers. The importance of highly sensitive surface analytical tools in the development of new chemically patterned surfaces is highlighted.

  4. Chemical Security Analysis Center

    Data.gov (United States)

    Federal Laboratory Consortium — In 2006, by Presidential Directive, DHS established the Chemical Security Analysis Center (CSAC) to identify and assess chemical threats and vulnerabilities in the...

  5. Utilization of chemical looping strategy in coal gasification processes

    Institute of Scientific and Technical Information of China (English)

    Liangshih Fan; Fanxing Li; Shwetha Ramkumar

    2008-01-01

    Three chemical looping gasification processes, i. e. Syngas Chemical Looping (SCL) process, Coal Direct Chemical Looping (CDCL) process, and Calcium Looping process (CLP), are being developed at the Ohio State University (OSU). These processes utilize simple reaction schemes to convert carbonaceous fuels into products such as hydrogen, electricity, and synthetic fuels through the transformation of a highly reactive, highly recyclable chemical intermediate. In this paper, these novel chemical looping gasification processes are described and their advantages and potential challenges for commercialization are discussed.

  6. Quantum Matter-Photonics Framework: Analyses of Chemical Conversion Processes

    CERN Document Server

    Tapia, O

    2014-01-01

    A quantum Matter-Photonics framework is adapted to help scrutinize chemical reaction mechanisms and used to explore a process mapped from chemical tree topological model. The chemical concept of bond knitting/breaking is reformulated via partitioned base sets leading to an abstract and general quantum presentation. Pivotal roles are assigned to entanglement, coherence,de-coherence and Feshbach resonance quantum states that permit apprehend gating states in conversion processes. A view from above in the state energy eigenvalue ladder, belonging to full system spectra complement the standard view from ground state. A full quantum physical view supporting chemical change obtains.

  7. The chemical life(1).

    Science.gov (United States)

    Hodges, Nathan

    2015-01-01

    You write this narrative autoethnography to open up a conversation about our chemical lives. You go through your day with chemical mindfulness, questioning taken-for-granted ideas about natural and artificial, healthy and unhealthy, dependency and addiction, trying to understand the chemical messages we consume through the experiences of everyday life. You reflect on how messages about chemicals influence and structure our lives and why some chemicals are celebrated and some are condemned. Using a second-person narrative voice, you show how the personal is relational and the chemical is cultural. You write because you seek a connection, a chemical bond.

  8. The Glória quartz-monzodiorite: isotopic and chemical evidence of arc-related magmatism in the central part of the Paleoproterozoic Mineiro belt, Minas Gerais State, Brazil

    Directory of Open Access Journals (Sweden)

    Ciro A. Ávila

    2006-09-01

    Full Text Available The Glória quartz-monzodiorite, one of the mafic plutons of the Paleoproterozoic Mineiro belt, is intrusive into banded gneisses, amphibolites, schists and phyllites of the Rio das Mortes greenstone belt, in the southern portion of the São Francisco Craton, State of Minas Gerais, Brazil. The Glória quartz-monzodiorite yields a SHRIMP U-Pb zircon age of 2188 ± 29 Ma, suggesting a tectonic relationship with the pre-collisional phase of the Mineiro belt. According to the Nd isotopic evidence (epsilonNd(T = -3.4; T DM = 2.68 Ga the original magmas was formed by a mixture among Archean crustal material and Paleoproterozoic juvenile magma. The Glória quartz-monzodiorite shows metaluminous and calc-alkaline tendency with intermediate K content, comparable to that of volcanic-arc rocks. The primary mineralogical assemblage was partly modified by metamorphism, dated between 2131-2121 Ma in nearby coeval plutons. Such metamorphism is significantly older than the reported metamorphic episodes of the Mineiro belt in the Quadrilátero Ferrífero region (2059-2041 Ma in the eastern portion of the study area. This evidence, together with chemical and isotopic data from other mafic and felsic plutons coeval with the Glória quartz-monzodiorite, indicate a tectonic and magmatic migration within the Mineiro belt from west to east.O Quartzo Monzodiorito Glória é um corpo plutônicomáfico associado à evolução Paleoproterozóica do Cinturão Mineiro. Este é intrusivo em gnaisses bandados, anfibolitos, xistos e filitos do Greenstone Belt Rio das Mortes, na porção sudeste do Cráton São Francisco, Estado de Minas Gerais, Brasil. Este corpo possui idade de cristalização SHRIMP (em zircão de 2188 ± 29 Ma, enquanto os isótopos de Nd (épsilonNd(T = -3,4; T DM = 2,68 Ga apontam que sua fonte magmática envolveumaterial juvenil paleoproterozóico contaminada por protólitos arqueanos. As rochas do Quartzo Monzodiorito Glória são metaluminosas, c

  9. Origin of the Chemical Elements

    CERN Document Server

    Rauscher, T

    2010-01-01

    This review provides the necessary background from astrophysics, nuclear, and particle physics to understand the cosmic origin of the chemical elements. It reflects the year 2009 state of the art in this extremely quickly developing interdisciplinary research direction. The discussion summarizes the nucleosynthetic processes in the course of the evolution of the Universe and the galaxies contained within, including primordial nucleosynthesis, stellar evolution, and explosive nucleosynthesis in single and binary systems.

  10. New Thermodynamic Paradigm of Chemical Equilibria

    CERN Document Server

    Zilbergleyt, B

    2011-01-01

    The paper presents new thermodynamic paradigm of chemical equilibrium, setting forth comprehensive basics of Discrete Thermodynamics of Chemical Equilibria (DTd). Along with previous results by the author during the last decade, this work contains also some new developments of DTd. Based on the Onsager's constitutive equations, reformulated by the author thermodynamic affinity and reaction extent, and Le Chatelier's principle, DTd brings forward a notion of chemical equilibrium as a balance of internal and external thermodynamic forces (TdF), acting against a chemical system. Basic expression of DTd is the chemical system logistic map of thermodynamic states that ties together energetic characteristics of chemical reaction, occurring in the system, the system shift from "true" thermodynamic equilibrium (TdE), and causing that shift external thermodynamic forces. Solutions to the basic map are pitchfork bifurcation diagrams in coordinates "shift from TdE - growth factor (or TdF)"; points, corresponding to the ...

  11. Density Functionals of Chemical Bonding

    Directory of Open Access Journals (Sweden)

    Mihai V. Putz

    2008-06-01

    Full Text Available The behavior of electrons in general many-electronic systems throughout the density functionals of energy is reviewed. The basic physico-chemical concepts of density functional theory are employed to highlight the energy role in chemical structure while its extended influence in electronic localization function helps in chemical bonding understanding. In this context the energy functionals accompanied by electronic localization functions may provide a comprehensive description of the global-local levels electronic structures in general and of chemical bonds in special. Becke-Edgecombe and author’s Markovian electronic localization functions are discussed at atomic, molecular and solid state levels. Then, the analytical survey of the main workable kinetic, exchange, and correlation density functionals within local and gradient density approximations is undertaken. The hierarchy of various energy functionals is formulated by employing both the parabolic and statistical correlation degree of them with the electronegativity and chemical hardness indices by means of quantitative structure-property relationship (QSPR analysis for basic atomic and molecular systems.

  12. The problem of current toxic chemicals management.

    Science.gov (United States)

    Tickner, Joel; Geiser, Ken

    2004-01-01

    In this article, we explore the limitations of current chemicals management policies worldwide and the evolution of new European, International and U.S. policies to address the problem of toxic chemicals control. It is becoming increasingly apparent that current chemicals management policies in Europe and the United States are inadequate. There is a general lack of toxicity and exposure information on chemicals in commerce and the vast majority of chemicals were considered safe until proven guilty in legislation. Governments must then prove each chemical is dangerous through a slow and resource-intensive risk assessment process. For more than a decade, Nordic countries, such as Denmark and Sweden, have actively promoted integrated chemicals policies to address contamination of critical waterways. They have successfully used a variety of voluntary and mandatory policy tools, such as education, procurement, lists of chemicals of concern, eco-labeling, research and development on safer substitutes, and chemical phase-out requirements, to encourage companies using chemicals to reduce their reliance on harmful substances and to develop safer substitutes. While previously isolated to particular countries, innovative and exciting European-wide policies to promote sustainable chemicals management are now moving forward, including the recently published draft Registration, Evaluation and Authorization of CHemicals (REACH) policy of the European Union. A sweeping change in chemicals management policies in Europe is inevitable and it will ultimately affect manufacturers in the U.S. and globally. The European movement provides an opportunity to initiate a discussion on integrated chemicals policy in the U.S. where some innovative initiatives already are underway.

  13. Existing chemicals: international activities.

    Science.gov (United States)

    Purchase, J F

    1989-01-01

    The standards of care used in the protection of the health and safety of people exposed to chemicals has increased dramatically in the last decade. Standards imposed by regulation and those adopted by industry have required a greater level of knowledge about the hazards of chemicals. In the E.E.C., the 6th amendment of the dangerous substances directive imposed the requirement that al new chemicals should be tested according to prescribed programme before introduction on to the market. The development of a European inventory of existing chemicals was an integral part of the 6th amendment. It has now become clear that increased standards of care referred to above must be applied to the chemicals on the inventory list. There is, however, a considerable amount of activity already under way in various international agencies. The OECD Chemicals Programme has been involved in considering the problem of existing chemicals for some time, and is producing a priority list and action programme. The International Programme on Chemical Safety produces international chemical safety cards, health and safety guides and environmental health criteria documents. The international register of potentially toxic compounds (part of UNEP) has prepared chemical data profiles on 990 compounds. The International Agency for Research on Cancer prepared monographs on the carcinogenic risk of chemicals to man. So far 42 volumes have been prepared covering about 900 substances. IARC and IPCS also prepare periodic reports on ongoing research on carcinogenicity or toxicity (respectively) of chemicals. The chemical industry through ECETOC (the European Chemical Industry Ecology and Toxicology Centre) has mounted a major initiative on existing chemicals. Comprehensive reviews of the toxicity of selected chemicals are published (Joint Assessment of Commodity Chemicals). In its technical report no. 30 ECETOC lists reviews and evaluations by major national and international organisations, which provides

  14. THE USE OF CHEMICALS AS FERTILIZERS. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 1.

    Science.gov (United States)

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    THE PURPOSE OF THIS GUIDE IS TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS. ONE OF A SERIES OF EIGHT MODULES, IT WAS DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF DATA FROM STATE STUDIES. SUBJECT MATTER AREAS ARE (1) CHEMICAL NUTRITION OF PLANTS, (2) PLANT GROWTH, (3) TERMINOLOGY,…

  15. Advances in chemical physics

    CERN Document Server

    Rice, Stuart A

    2012-01-01

    The Advances in Chemical Physics series-the cutting edge of research in chemical physics The Advances in Chemical Physics series provides the chemical physics field with a forum for critical, authoritative evaluations of advances in every area of the discipline. Filled with cutting-edge research reported in a cohesive manner not found elsewhere in the literature, each volume of the Advances in Chemical Physics series serves as the perfect supplement to any advanced graduate class devoted to the study of chemical physics. This volume explores: Quantum Dynamical Resonances in Ch

  16. Chemical substances injection in wells through the gas-lift line: state of the art; Injecao de produtos quimicos em pocos atraves de linha de gas-lift: estado-da-arte

    Energy Technology Data Exchange (ETDEWEB)

    Ramalho, Joao Batista Vianey da Silva [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas. Setor de Tecnologia de Producao, Processamento e Transporte]. E-mail: jramalho@cenpes.petrobras.com.br

    2000-12-01

    Injecting chemical substances on the subsurface in order to control incrustation, corrosion, emulsion and waxes, among other problems caused by the production at the oil wells, has not been used much because of the way they are usually injected. Recently, these products have been injected in wells through the gas-lift line, thus allowing control over the individual treatment in each well. The main conclusions arrived at with the reports made are the following: it is possible to inject chemical substances through the gas-lift line. The formulations of such products must be specific and they must contain the proper amounts of solvent to prevent the segregation of active matter. These products must be injected individually in the gas-lift line at each well. (author)

  17. Capacitive chemical sensor

    Science.gov (United States)

    Manginell, Ronald P; Moorman, Matthew W; Wheeler, David R

    2014-05-27

    A microfabricated capacitive chemical sensor can be used as an autonomous chemical sensor or as an analyte-sensitive chemical preconcentrator in a larger microanalytical system. The capacitive chemical sensor detects changes in sensing film dielectric properties, such as the dielectric constant, conductivity, or dimensionality. These changes result from the interaction of a target analyte with the sensing film. This capability provides a low-power, self-heating chemical sensor suitable for remote and unattended sensing applications. The capacitive chemical sensor also enables a smart, analyte-sensitive chemical preconcentrator. After sorption of the sample by the sensing film, the film can be rapidly heated to release the sample for further analysis. Therefore, the capacitive chemical sensor can optimize the sample collection time prior to release to enable the rapid and accurate analysis of analytes by a microanalytical system.

  18. Tobacco and chemicals (image)

    Science.gov (United States)

    Some of the chemicals associated with tobacco smoke include ammonia, carbon dioxide, carbon monoxide, propane, methane, acetone, hydrogen cyanide and various carcinogens. Other chemicals that are associated with chewing ...

  19. Chemical Industry Bandwidth Study

    Energy Technology Data Exchange (ETDEWEB)

    none,

    2006-12-01

    The Chemical Bandwidth Study provides a snapshot of potentially recoverable energy losses during chemical manufacturing. The advantage of this study is the use of "exergy" analysis as a tool for pinpointing inefficiencies.

  20. Chemical Search Web Utility

    Data.gov (United States)

    U.S. Environmental Protection Agency — The Chemical Search Web Utility is an intuitive web application that allows the public to easily find the chemical that they are interested in using, and which...

  1. Chemicals Industry Vision

    Energy Technology Data Exchange (ETDEWEB)

    none,

    1996-12-01

    Chemical industry leaders articulated a long-term vision for the industry, its markets, and its technology in the groundbreaking 1996 document Technology Vision 2020 - The U.S. Chemical Industry. (PDF 310 KB).

  2. Chemical Physics Courses.

    Science.gov (United States)

    Lee, J.; Munn, R. W.

    1978-01-01

    This is a guide to the chemical physics major. The scope of chemical physics is presented, along with the general features of course contents and possible course structures. This information was derived from a survey of British universities and colleges offering undergraduate degree courses in chemical physics. (BB)

  3. Chemical Recycle of Plastics

    Directory of Open Access Journals (Sweden)

    Sara Fatima

    2014-11-01

    Full Text Available Various chemical processes currently prevalent in the chemical industry for plastics recycling have been discussed. Possible future scenarios in chemical recycling have also been discussed. Also analyzed are the effects on the environment, the risks, costs and benefits of PVC recycling. Also listed are the various types of plastics and which plastics are safe to use and which not after rcycle

  4. Chemicals for worldwide aquaculture

    Science.gov (United States)

    Schnick, R.A.

    1991-01-01

    Regulations and therapeutants or other safe chemicals that are approved or acceptable for use in the aquaculture industry in the US, Canada, Europe and Japan are presented, discussing also compounds that are unacceptable for aquaculture. Chemical use practices that could affect public health are considered and details given regarding efforts to increase the number of registered and acceptable chemicals.

  5. Chemical structure and dynamics. Annual report 1995

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.; McDowell, R.S.

    1996-05-01

    The Chemical Structure and Dynamics program is a major component of Pacific Northwest National Laboratory`s Environmental Molecular Sciences Laboratory (EMSL), providing a state-of-the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for the characterization of waste tanks and pollutant distributions, and for detection and monitoring of trace atmospheric species.

  6. Chemical structure and dynamics: Annual report 1996

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.; McDowell, R.S.

    1997-03-01

    The Chemical Structure and Dynamics (CS&D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. We respond to the need for a fundamental, molecular-level understanding of chemistry at a wide variety of environmentally important interfaces by (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing waste tanks and pollutant distributions, and for detecting and monitoring trace atmospheric species.

  7. Advances in chemical physics

    CERN Document Server

    Rice, Stuart A

    2012-01-01

    The Advances in Chemical Physics series-the cutting edge of research in chemical physics The Advances in Chemical Physics series provides the chemical physics and physical chemistry fields with a forum for critical, authoritative evaluations of advances in every area of the discipline. Filled with cutting-edge research reported in a cohesive manner not found elsewhere in the literature, each volume of the Advances in Chemical Physics series presents contributions from internationally renowned chemists and serves as the perfect supplement to any advanced graduate class devoted to the study o

  8. Advances in chemical Physics

    CERN Document Server

    Rice, Stuart A

    2011-01-01

    The Advances in Chemical Physics series-the cutting edge of research in chemical physics The Advances in Chemical Physics series provides the chemical physics and physical chemistry fields with a forum for critical, authoritative evaluations of advances in every area of the discipline. Filled with cutting-edge research reported in a cohesive manner not found elsewhere in the literature, each volume of the Advances in Chemical Physics series offers contributions from internationally renowned chemists and serves as the perfect supplement to any advanced graduate class devoted to the study of che

  9. Advances in chemical physics

    CERN Document Server

    Rice, Stuart A

    2014-01-01

    Advances in Chemical Physics is the only series of volumes available that explores the cutting edge of research in chemical physics. This is the only series of volumes available that presents the cutting edge of research in chemical physics.Includes contributions from experts in this field of research.Contains a representative cross-section of research that questions established thinking on chemical solutions.Structured with an editorial framework that makes the book an excellent supplement to an advanced graduate class in physical chemistry or chemical physics.

  10. Advances in chemical physics

    CERN Document Server

    Rice, Stuart A

    2011-01-01

    The Advances in Chemical Physics series-the cutting edge of research in chemical physics The Advances in Chemical Physics series provides the chemical physics and physical chemistry fields with a forum for critical, authoritative evaluations of advances in every area of the discipline. Filled with cutting-edge research reported in a cohesive manner not found elsewhere in the literature, each volume of the Advances in Chemical Physics series offers contributions from internationally renowned chemists and serves as the perfect supplement to any advanced graduate class devoted to the study of che

  11. Chemical Sciences Division: Annual report 1992

    Energy Technology Data Exchange (ETDEWEB)

    1993-10-01

    The Chemical Sciences Division (CSD) is one of twelve research Divisions of the Lawrence Berkeley Laboratory, a Department of Energy National Laboratory. The CSD is composed of individual groups and research programs that are organized into five scientific areas: Chemical Physics, Inorganic/Organometallic Chemistry, Actinide Chemistry, Atomic Physics, and Physical Chemistry. This report describes progress by the CSD for 1992. Also included are remarks by the Division Director, a description of work for others (United States Office of Naval Research), and appendices of the Division personnel and an index of investigators. Research reports are grouped as Fundamental Interactions (Photochemical and Radiation Sciences, Chemical Physics, Atomic Physics) or Processes and Techniques (Chemical Energy, Heavy-Element Chemistry, and Chemical Engineering Sciences).

  12. Atoms of multistationarity in chemical reaction networks

    CERN Document Server

    Joshi, Badal

    2011-01-01

    Chemical reaction networks taken with mass-action kinetics are dynamical systems that arise in chemical engineering and systems biology. Deciding whether a chemical reaction network admits multiple positive steady states is to determine existence of multiple positive solutions to a system of polynomials with unknown coefficients. In this work, we consider the question of whether the minimal (in a precise sense) networks, which we propose to call `atoms of multistationarity,' characterize the entire set of multistationary networks. We show that if a subnetwork admits multiple nondegenerate positive steady states, then these steady states can be extended to establish multistationarity of a larger network, provided that the two networks share the same stoichiometric subspace. Our result provides the mathematical foundation for a technique used by Siegal-Gaskins et al. of establishing bistability by way of `network ancestry.' Here, our main application is for enumerating small multistationary continuous-flow stir...

  13. Geometrical criteria versus quantum chemical criteria for assessment of intramolecular hydrogen bond (IMHB) interaction: A computational comparison into the effect of chlorine substitution on IMHB of salicylic acid in its lowest energy ground state conformer

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Bijan Kumar [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India); Guchhait, Nikhil, E-mail: nikhil.guchhait@rediffmail.com [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India)

    2013-02-01

    Highlights: ► Intramolecular hydrogen bonding (IMHB) in salicylic acid and its chloro derivatives. ► A complex effect of +R and −I effect of chlorine substituents on IMHB energy. ► Interplay between IMHB energy and aromaticity. ► Directional nature of IMHB from quantum chemical assessment. ► Quantum chemical treatment vs. geometrical criteria to assess weak interaction. - Abstract: Density functional theory based computational study has been performed to characterize intramolecular hydrogen bonding (IMHB) interaction in a series of salicylic acid derivatives varying in chlorine substitution on the benzene ring. The molecular systems studied are salicylic acid, 5-chlorosalicylic acid, 3,5-dichlorosalicylic acid and 3,5,6-tricholorosalicylic acid. Major emphasis is rendered on the analysis of IMHB interaction by calculation of electron density ρ(r) and Laplacian ∇{sup 2}ρ(r) at the bond critical point using atoms-in-molecule theory. Topological features, energy densities based on ρ(r) through perturbing the intramolecular H-bond distances suggest that at equilibrium geometry the IMHB interaction develops certain characteristics typical of covalent interaction. The interplay between aromaticity and resonance-assisted hydrogen bonding (RAHB) is discussed using both geometrical and magnetic criteria as the descriptors of aromaticity. The optimized geometry features, molecular electrostatic potential map analysis are also found to produce a consensus view in relation with the formation of RAHB in these systems.

  14. Diffusion approximations to the chemical master equation only have a consistent stochastic thermodynamics at chemical equilibrium

    Energy Technology Data Exchange (ETDEWEB)

    Horowitz, Jordan M., E-mail: jordan.horowitz@umb.edu [Department of Physics, University of Massachusetts at Boston, Boston, Massachusetts 02125 (United States)

    2015-07-28

    The stochastic thermodynamics of a dilute, well-stirred mixture of chemically reacting species is built on the stochastic trajectories of reaction events obtained from the chemical master equation. However, when the molecular populations are large, the discrete chemical master equation can be approximated with a continuous diffusion process, like the chemical Langevin equation or low noise approximation. In this paper, we investigate to what extent these diffusion approximations inherit the stochastic thermodynamics of the chemical master equation. We find that a stochastic-thermodynamic description is only valid at a detailed-balanced, equilibrium steady state. Away from equilibrium, where there is no consistent stochastic thermodynamics, we show that one can still use the diffusive solutions to approximate the underlying thermodynamics of the chemical master equation.

  15. Chemical bond fundamental aspects of chemical bonding

    CERN Document Server

    Frenking, Gernot

    2014-01-01

    This is the perfect complement to ""Chemical Bonding - Across the Periodic Table"" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemica

  16. Hand chemical burns.

    Science.gov (United States)

    Robinson, Elliot P; Chhabra, A Bobby

    2015-03-01

    There is a vast and ever-expanding variety of potentially harmful chemicals in the military, industrial, and domestic landscape. Chemical burns make up a small proportion of all skin burns, yet they can cause substantial morbidity and mortality. Additionally, the hand and upper extremity are the most frequently involved parts of the body in chemical burns, and therefore these injuries may lead to severe temporary or permanent loss of function. Despite this fact, discussion of the care of these injuries is sparse in the hand surgery literature. Although most chemical burns require only first response and wound care, some require the attention of a specialist for surgical debridement and, occasionally, skin coverage and reconstruction. Exposure to certain chemicals carries the risk of substantial systemic toxicity and even mortality. Understanding the difference between thermal and chemical burns, as well as special considerations for specific compounds, will improve patient treatment outcomes.

  17. A Numerical Analysis of the Transient Response of an Ablation System Including Effects of Thermal Nonequilibrium, Mass Transfer and Chemical Kinetics. Ph.D Thesis - Virginia Polytechnic Inst. and State Univ.

    Science.gov (United States)

    Clark, R. K.

    1972-01-01

    The differential equations governing the transient response of a one-dimensional ablative thermal protection system undergoing stagnation ablation are derived. These equations are for thermal nonequilibrium effects between the pyrolysis gases and the char layer and kinetically controlled chemical reactions and mass transfer between the pyrolysis gases and the char layer. The boundary conditions are written for the particular case of stagnation heating with surface removal by oxidation or sublimation and pyrolysis of the uncharred layer occurring in a plane. The governing equations and boundary conditions are solved numerically using the modified implicit method (Crank-Nicolson method). Numerical results are compared with exact solutions for a number of simplified cases. The comparison is favorable in each instance.

  18. Chemical Biology is.....

    OpenAIRE

    2007-01-01

    Chemical Biology is a relatively new field, and as such is not yet simply or succinctly defined. It includes such a wide range of fundamental problems that this commentary could only include just a few snapshots of potential areas of interest. Overarching themes and selected recent successes and ideas in chemical biology are described to illustrate broadly the scope of the field, but should not be taken as exhaustive. The Chemical Biology Section of Chemistry Central Journal is pleased to rec...

  19. Multivariate Quantitative Chemical Analysis

    Science.gov (United States)

    Kinchen, David G.; Capezza, Mary

    1995-01-01

    Technique of multivariate quantitative chemical analysis devised for use in determining relative proportions of two components mixed and sprayed together onto object to form thermally insulating foam. Potentially adaptable to other materials, especially in process-monitoring applications in which necessary to know and control critical properties of products via quantitative chemical analyses of products. In addition to chemical composition, also used to determine such physical properties as densities and strengths.

  20. Hagedorn States and Thermalization

    CERN Document Server

    Noronha-Hostler, Jacquelyn

    2010-01-01

    In recent years Hagedorn states have been used to explain the physics close to the critical temperature within a hadron gas. Because of their large decay widths these massive resonances lower $\\eta/s$ to near the AdS/CFT limit within the hadron gas phase. A comparison of the Hagedorn model to recent lattice results is made and it is found that for both Tc =176 MeV and Tc=196 MeV, the hadrons can reach chemical equilibrium almost immediately, well before the chemical freeze-out temperatures found in thermal fits for a hadron gas without Hagedorn states. In this paper we also observe the effects of Hagedorn States on the $K^+/\\pi^+$ horn seen at AGS, SPS, and RHIC.

  1. Introduction to chemical kinetics

    CERN Document Server

    Soustelle, Michel

    2013-01-01

    This book is a progressive presentation of kinetics of the chemical reactions. It provides complete coverage of the domain of chemical kinetics, which is necessary for the various future users in the fields of Chemistry, Physical Chemistry, Materials Science, Chemical Engineering, Macromolecular Chemistry and Combustion. It will help them to understand the most sophisticated knowledge of their future job area. Over 15 chapters, this book present the fundamentals of chemical kinetics, its relations with reaction mechanisms and kinetic properties. Two chapters are then devoted to experimental re

  2. Laboratory of Chemical Physics

    Data.gov (United States)

    Federal Laboratory Consortium — Current research in the Laboratory of Chemical Physics is primarily concerned with experimental, theoretical, and computational problems in the structure, dynamics,...

  3. Chemical Processing Manual

    Science.gov (United States)

    Beyerle, F. J.

    1972-01-01

    Chemical processes presented in this document include cleaning, pickling, surface finishes, chemical milling, plating, dry film lubricants, and polishing. All types of chemical processes applicable to aluminum, for example, are to be found in the aluminum alloy section. There is a separate section for each category of metallic alloy plus a section for non-metals, such as plastics. The refractories, super-alloys and titanium, are prime candidates for the space shuttle, therefore, the chemical processes applicable to these alloys are contained in individual sections of this manual.

  4. Pattern formation in arrays of chemical oscillators

    Indian Academy of Sciences (India)

    Neeraj Kumar Kamal

    2012-05-01

    We describe a simple model mimicking diffusively coupled chemical micro-oscillators. We characterize the rich variety of dynamical states emerging from the model under variation of time delay in coupling, coupling strength and boundary conditions. The spatiotemporal patterns obtained include clustering, mixed dynamics, inhomogeneous steady states and amplitude death. Further, under delay in coupling, the model yields transitions from phase to antiphase oscillations, reminiscent of that observed in experiments [M Toiya et al, J. Chem. Lett. 1, 1241 (2010)].

  5. Multiple chemical sensitivity

    DEFF Research Database (Denmark)

    Tran, Marie Thi Dao; Arendt-Nielsen, Lars; Kupers, Ron;

    2013-01-01

    BACKGROUND: Multiple Chemical Sensitivity (MCS) is a chronic condition characterized by recurrent, non-specific symptoms in response to chemically unrelated exposures in non-toxic concentrations. Although the pathophysiology of MCS remains unknown, central sensitization may be an important factor...

  6. Chemical burn or reaction

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/000059.htm Chemical burn or reaction To use the sharing features on this page, please enable JavaScript. Chemicals that touch skin can lead to a reaction on the skin, throughout the body, or both. ...

  7. Chemical warfare in freshwater

    NARCIS (Netherlands)

    Mulderij, Gabi

    2006-01-01

    Aquatic macrophytes can excrete chemical substances into their enviroment and these compounds may inhibit the growth of phytoplankton. This process is defined as allelopathy: one organism has effects on another via the excretion of a (mixture of) chemical substance(s). With laboratory and field expe

  8. Chemical Reactivity Test (CRT)

    Energy Technology Data Exchange (ETDEWEB)

    Zaka, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-12-13

    The Chemical Reactivity Test (CRT) is used to determine the thermal stability of High Explosives (HEs) and chemical compatibility between (HEs) and alien materials. The CRT is one of the small-scale safety tests performed on HE at the High Explosives Applications Facility (HEAF).

  9. Biobased chemicals from polyhydroxybutyrate

    NARCIS (Netherlands)

    Spekreijse, Jurjen

    2016-01-01

    Currently, most chemicals and materials are obtained from fossil resources. After use, these chemicals and materials are converted to CO2. As discussed in chapter 1, this causes a build-up of CO2 in the atmosphere, the main driving force of global warming. In order to reach a sustai

  10. Chemical recognition software

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, J.S.; Trahan, M.W.; Nelson, W.E.; Hargis, P.H. Jr.; Tisone, G.C.

    1994-06-01

    We have developed a capability to make real time concentration measurements of individual chemicals in a complex mixture using a multispectral laser remote sensing system. Our chemical recognition and analysis software consists of three parts: (1) a rigorous multivariate analysis package for quantitative concentration and uncertainty estimates, (2) a genetic optimizer which customizes and tailors the multivariate algorithm for a particular application, and (3) an intelligent neural net chemical filter which pre-selects from the chemical database to find the appropriate candidate chemicals for quantitative analyses by the multivariate algorithms, as well as providing a quick-look concentration estimate and consistency check. Detailed simulations using both laboratory fluorescence data and computer synthesized spectra indicate that our software can make accurate concentration estimates from complex multicomponent mixtures, even when the mixture is noisy and contaminated with unknowns.

  11. Chemical recognition software

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, J.S.; Trahan, M.W.; Nelson, W.E.; Hargis, P.J. Jr.; Tisone, G.C.

    1994-12-01

    We have developed a capability to make real time concentration measurements of individual chemicals in a complex mixture using a multispectral laser remote sensing system. Our chemical recognition and analysis software consists of three parts: (1) a rigorous multivariate analysis package for quantitative concentration and uncertainty estimates, (2) a genetic optimizer which customizes and tailors the multivariate algorithm for a particular application, and (3) an intelligent neural net chemical filter which pre-selects from the chemical database to find the appropriate candidate chemicals for quantitative analyses by the multivariate algorithms, as well as providing a quick-look concentration estimate and consistency check. Detailed simulations using both laboratory fluorescence data and computer synthesized spectra indicate that our software can make accurate concentration estimates from complex multicomponent mixtures. even when the mixture is noisy and contaminated with unknowns.

  12. Tortuous path chemical preconcentrator

    Science.gov (United States)

    Manginell, Ronald P.; Lewis, Patrick R.; Adkins, Douglas R.; Wheeler, David R.; Simonson, Robert J.

    2010-09-21

    A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.

  13. Contribution to research on the metabolism of fission product. Studies on the physico-chemical state and the metabolic fate of radio-cerium solution; Contribution a l'etude du metabolisme des produits de fission. Recherches sur l'etat physico-chimique et le devenir metabolique des solutions de radiocerium

    Energy Technology Data Exchange (ETDEWEB)

    Aeberhardt, A. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    This paper describes a study of the physico-chemical state of radio-cerium in dilute solutions on the tracer scale, as a function of the pH of the solution. The way in which this radioelement is transported in the blood is studied in vitro and in vivo, with reference to the ionic or colloidal state of the radio-cerium used. The distribution of cerium amongst the various components of the blood is studied by a new method of blood fractionation and by paper electrophoresis. Evidence of a cerium globulin connection is shown in the case of ionic cerium. A study of the initial distribution of radio-cerium in rats, after intravenous administration of ionic or colloidal solutions, shows considerable differences according to the physico-chemical state of the cerium injected. (author) [French] Ce travail presente une etude de l'etat physico-chimique du radiocerium en solutions diluees a l'echelle des indicateurs, en fonction du pH de la solution. En fonction de l'etat ionique ou colloidal du radiocerium utilise, le mode de transport de ce radioelement dans le sang est etudie in vitro et in vivo. La distribution du cerium entre les differents constituants du sang est etudiee par une methode nouvelle de fractionnement du sang et par electrophorese sur papier. L'existence d'une liaison cerium-globuline est mise en evidence dans le cas du cerium ionique. L'etude de la distribution initiale du radiocerium, chez le rat apres administration par voie veineuse de solutions ionique ou colloidale, montre des differences importantes en fonction de l'etat physico-chimique du cerium injecte. (auteur)

  14. Development of Oilfield Chemicals Based on Advantages in Petrochemical Feedstocks

    Institute of Scientific and Technical Information of China (English)

    Wang Xieqing; Peng Pu

    2002-01-01

    This article focuses on the routes for development of oilfield chemicals by making use of the feedstock advantages of the petrochemical industry. The diversification of oilfield chemicals has re sulted in thousand product grades. Because there are hundred domestic producers of oilfield chemicals,mostly medium and small producers, the fluctuations of feedstock prices and product quality cannot be conducive to the application and development of oilfield chemicals. This article illustrates the feasibility of oilfield chemical production by state-run medium and large petrochemical enterprises by allowing full play to their own advantages in petrochemical feedstocks.

  15. Toxicology of chemical mixtures: International perspective

    NARCIS (Netherlands)

    Feron, V.J.; Cassee, F.R.; Groten, J.P.

    1998-01-01

    This paper reviews major activities outside the United States on human health issues related to chemical mixtures. In Europe an international study group on combination effects has been formed and has started by defining synergism and antagonism. Successful research programs in Europe include the de

  16. Theory and Experiments on Chemical Instabilities.

    Science.gov (United States)

    1983-12-31

    following institutions and conferences: 1981 Jan. 8 X Reunion de Fisica Estadistica , Cocoyoc, Mexico, Resonances and Control Features Feb. 13 Michigan State...Aeronautics and Astronautics, Invited Remarks, Palo Alto, CA 1982 Feb. 25,26 Industrial Affiliates Program ": .’ Hydrodynamic and Chemical Instabilities

  17. Annual Report 2000. Chemical Structure and Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Colson, Steven D.; McDowell, Robin S.

    2001-04-15

    This annual report describes the research and accomplishments of the Chemical Structure and Dynamics Program in the year 2000, one of six research programs at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) - a multidisciplinary, national scientific user facility and research organization. The Chemical Structure and Dynamics (CS&D) program is meeting the need for a fundamental, molecular-level understanding by 1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; 2) developing a multidisciplinary capability for describing interfacial chemical processes relevant to environmental chemistry; and 3) developing state-of-the-art research and analytical methods for characterizing complex materials of the types found in natural and contaminated systems.

  18. Complete mapping of crystallization pathways during cholesterol precipitation from model bile: influence of physical-chemical variables of pathophysiologic relevance and identification of a stable liquid crystalline state in cold, dilute and hydrophilic bile salt-containing systems.

    Science.gov (United States)

    Wang, D Q; Carey, M C

    1996-03-01

    Using complementary physical-chemical techniques we defined five different crystallization pathways as functions of time (30 days) and increasing lecithin (egg yolk) content in pathophysiologically relevant model biles super-saturated (cholesterol saturation indices, 1.2 - 2.7) by dilution of approximately equal to 29 g/dl bile salt-lecithin-cholesterol micellar solutions. As evidenced by quasi-elastic light-scattering spectroscopy, supersaturation was heralded by the appearance of unilamellar vesicles. With the lowest lecithin contents, arc-like crystals with habit and density (d 1.030 g/mL) consistent with anhydrous cholesterol appeared first and evolved via helical and tubular crystals to form plate-like cholesterol monohydrate crystals (d 1.045 g/mL). With higher lecithin fractions, cholesterol monohydrate crystals appeared earlier than arc and other transitional crystals. With typical physiological lecithin contents, early liquid crystals (d 1.020 g/mL) were followed by cholesterol monohydrate crystals and subsequent appearances of arc and other intermediate crystals. With higher lecithin contents, liquid crystals were followed by cholesterol monohydrate crystals only, and at the highest lecithin mole fractions, liquid crystals appeared that did not generate solid crystals. Added calcium increased solid crystal number in proportion to its concentration (5 - 20 mM) but did not influence appearance times, crystallization pathways, or micellar cholesterol solubilities. Decreases in temperature (37 degrees --> 4 degrees C), total lipid concentration (7.3 --> 2.4 g/dL), and bile salt hydrophobicity (3 alpha, 12 alpha --> 3 alpha, 7 alpha, 12 alpha --> 3 alpha, 7 beta hydroxylated taurine conjugates) progressively shifted all crystallization pathways to lower lecithin contents, retarded crystallization, and decreased micellar cholesterol solubilities. The lecithin content of mother biles decreased markedly during crystallization especially where liquid crystals were

  19. China Oilfield Chemical Company--A Unified Company for Development,Production and Selling of Oilfield Chemicals

    Institute of Scientific and Technical Information of China (English)

    Li Guozhang

    1994-01-01

    @@ China Oilfield Chemical Company (COCC) is a subsidiary company of China National Petroleum Corporation (CNPC), approved by the former Production Office of the State Council for its establishment. It is an enterprise with state ownership and having qualification of a legal person registered in the State Industry and Commerce Administration. The Company's headquarters is located in Beijing.

  20. Chemical ecology of fungi.

    Science.gov (United States)

    Spiteller, Peter

    2015-07-01

    Fungi are widespread in nature and have conquered nearly every ecological niche. Fungi occur not only in terrestrial but also in freshwater and marine environments. Moreover, fungi are known as a rich source of secondary metabolites. Despite these facts, the ecological role of many of these metabolites is still unknown and the chemical ecology of fungi has not been investigated systematically so far. This review intends to present examples of the various chemical interactions of fungi with other fungi, plants, bacteria and animals and to give an overview of the current knowledge of fungal chemical ecology.

  1. CHEMICALS AND REPRODUCTIVE HEALTH

    Directory of Open Access Journals (Sweden)

    Omer Faruk TEKBAS

    2006-02-01

    Full Text Available However a lot of chemicals had been used in our daily life, we have enough knowledge about the effects of only for a small portion of them on reproductive health. Our knowledge had been arisen from epidemiologic and experimental studies. In order to protect ourselves from chemicals in the environment it should be concentrate on experimental studies and the results of them should be carefully studied during epidemiological researches. It would be tried to tell about the main chemicals which had been known as effective on reproductive health on the following review. [TAF Prev Med Bull 2006; 5(1.000: 50-59

  2. State Fairgrounds

    Data.gov (United States)

    Department of Homeland Security — This shapefile is a point shapefile that displays the locations of the major state/regional agricultural fairs held throughout the United States. Some states (e.g.,...

  3. Creating and maintaining chemical artificial life by robotic symbiosis.

    Science.gov (United States)

    Hanczyc, Martin M; Parrilla, Juan M; Nicholson, Arwen; Yanev, Kliment; Stoy, Kasper

    2015-01-01

    We present a robotic platform based on the open source RepRap 3D printer that can print and maintain chemical artificial life in the form of a dynamic, chemical droplet. The robot uses computer vision, a self-organizing map, and a learning program to automatically categorize the behavior of the droplet that it creates. The robot can then use this categorization to autonomously detect the current state of the droplet and respond. The robot is programmed to visually track the droplet and either inject more chemical fuel to sustain a motile state or introduce a new chemical component that results in a state change (e.g., division). Coupling inexpensive open source hardware with sensing and feedback allows for replicable real-time manipulation and monitoring of nonequilibrium systems that would be otherwise tedious, expensive, and error-prone. This system is a first step towards the practical confluence of chemical, artificial intelligence, and robotic approaches to artificial life.

  4. State space consistency and differentiability

    CERN Document Server

    Serakos, Demetrios

    2014-01-01

    By investigating the properties of the natural state, this book presents an analysis of input-output systems with regard to the mathematical concept of state. The state of a system condenses the effects of past inputs to the system in a useful manner. This monograph emphasizes two main properties of the natural state; the first has to do with the possibility of determining the input-output system from its natural state set and the second deals with differentiability properties involving the natural state inherited from the input-output system, including differentiability of the natural state and natural state trajectories. The results presented in this title aid in modeling physical systems since system identification from a state set holds in most models. Researchers and engineers working in electrical, aerospace, mechanical, and chemical fields along with applied mathematicians working in systems or differential equations will find this title useful due to its rigorous mathematics.  

  5. Study on the association between environmental chemical elements and fluorosis caused by coal-fire pollution

    Institute of Scientific and Technical Information of China (English)

    焦永卓

    2013-01-01

    Objective To understand the distribution of chemical elements in soil,to investigate the differences between patients under different state of fluorosis and normal population after preventive measurement was implemented to get rid of some chemical elements and to lower

  6. 75 FR 33824 - Pharmaceutical Products and Chemical Intermediates, Fourth Review: Advice Concerning the Addition...

    Science.gov (United States)

    2010-06-15

    ... COMMISSION Pharmaceutical Products and Chemical Intermediates, Fourth Review: Advice Concerning the Addition of Certain Products to the Pharmaceutical Appendix to the HTS AGENCY: United States International... (Commission) instituted investigation No. 332-520, Pharmaceutical Products and Chemical Intermediates,...

  7. Elements of chemical thermodynamics

    CERN Document Server

    Nash, Leonard K

    2005-01-01

    This survey of purely thermal data in calculating the position of equilibrium in a chemical reaction highlights the physical content of thermodynamics, as distinct from purely mathematical aspects. 1970 edition.

  8. Chemical Physics Summer School

    Energy Technology Data Exchange (ETDEWEB)

    None

    2002-06-28

    The Gordon Research Conference (GRC) on Chemical Physics Summer School was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  9. Biotechnology for renewable chemicals

    DEFF Research Database (Denmark)

    Borodina, Irina; Kildegaard, Kanchana Rueksomtawin; Jensen, Niels Bjerg

    2014-01-01

    The majority of the industrial organic chemicals are derived from fossil sources. With the oil and gas resources becoming limiting, biotechnology offers a sustainable alternative for production ofchemicals from renewable feedstocks. Yeast is an attractive cell factory forsustainable production...

  10. Chemical Engineering at NASA

    Science.gov (United States)

    Collins, Jacob

    2008-01-01

    This viewgraph presentation is a review of the career paths for chemicals engineer at NASA (specifically NASA Johnson Space Center.) The author uses his personal experience and history as an example of the possible career options.

  11. Legendary Chemical Aphrodisiacs.

    Science.gov (United States)

    Waddell, Thomas G.; And Others

    1980-01-01

    Presents a survey of the literature and a summary of information regarding aphrodisiacs. Chemical compounds are discussed as groups of plant natural products, animal natural products, and synthetic products. (CS)

  12. Chemical evolution and life

    Directory of Open Access Journals (Sweden)

    Malaterre Christophe

    2015-01-01

    Full Text Available In research on the origins of life, the concept of “chemical evolution” aims at explaining the transition from non-living matter to living matter. There is however strong disagreement when it comes to defining this concept more precisely, and in particular with reference to a chemical form of Darwinian evolution: for some, chemical evolution is nothing but Darwinian evolution applied to chemical systems before life appeared; yet, for others, it is the type of evolution that happened before natural selection took place, the latter being the birthmark of living systems. In this contribution, I review the arguments defended by each side and show how both views presuppose a dichotomous definition of “life”.

  13. Chemical agent recoveries

    Data.gov (United States)

    U.S. Environmental Protection Agency — Dataset shows the calculation of reported decontamination efficacies from the raw data (i.e., measured amount of chemical recovered from test coupons and positive...

  14. 219-S chemical compatibility

    Energy Technology Data Exchange (ETDEWEB)

    GOODWIN, L.D.

    1999-08-31

    This document consists of tables of the materials that make up the ''wetted'' parts of the 219-S waste handling facility and a combination of manufacturer lists of chemicals that are not recommended.

  15. Chemicals from coal

    Energy Technology Data Exchange (ETDEWEB)

    Harold A. Wittcoff; Bryan G. Reuben; Jeffrey S. Plotkin

    2004-12-01

    This chapter contains sections titled: Chemicals from Coke Oven Distillate; The Fischer-Tropsch Reaction; Coal Hydrogenation; Substitute Natural Gas (SNG); Synthesis Gas Technology; Calcium Carbide; Coal and the Environment; and Notes and References

  16. A bionics chemical synapse.

    Science.gov (United States)

    Thanapitak, Surachoke; Toumazou, Christofer

    2013-06-01

    Implementation of the current mode CMOS circuit for chemical synapses (AMPA and NMDA receptors) with dynamic change of glutamate as the neurotransmitter input is presented in this paper. Additionally, circuit realisation for receptor GABA(A) and GABA(B) with an electrical signal which symbolises γ-Aminobutyric Acid (GABA) perturbation is introduced. The chemical sensor for glutamate sensing is the modified ISFET with enzyme (glutamate oxidase) immobilisation. The measured results from these biomimetics chemical synapse circuits closely match with the simulation result from the mathematical model. The total power consumption of the whole chip (four chemical synapse circuits and all auxiliary circuits) is 168.3 μW. The total chip area is 3 mm(2) in 0.35-μm AMS CMOS technology.

  17. Sensitive chemical compass assisted by quantum criticality

    Science.gov (United States)

    Cai, C. Y.; Ai, Qing; Quan, H. T.; Sun, C. P.

    2012-02-01

    A radical-pair-based chemical reaction might be used by birds for navigation via the geomagnetic direction. The inherent physical mechanism is that the quantum coherent transition from a singlet state to triplet states of the radical pair could respond to a weak magnetic field and be sensitive to the direction of such a field; this then results in different photopigments to be sensed by the avian eyes. Here, we propose a quantum bionic setup, inspired by the avian compass, as an ultrasensitive probe of a weak magnetic field based on the quantum phase transition of the environments of the two electrons in the radical pair. We prove that the yield of the chemical products via recombination from the singlet state is determined by the Loschmidt echo of the environments with interacting nuclear spins. Thus quantum criticality of environments could enhance the sensitivity of detection of weak magnetic fields.

  18. Sensitive Chemical Compass Assisted by Quantum Criticality

    CERN Document Server

    Cai, C Y; Quan, H T; Sun, C P

    2011-01-01

    The radical-pair-based chemical reaction could be used by birds for the navigation via the geomagnetic direction. An inherent physical mechanism is that the quantum coherent transition from a singlet state to triplet states of the radical pair could response to the weak magnetic field and be sensitive to the direction of such a field and then results in different photopigments in the avian eyes to be sensed. Here, we propose a quantum bionic setup for the ultra-sensitive probe of a weak magnetic field based on the quantum phase transition of the environments of the two electrons in the radical pair. We prove that the yield of the chemical products via the recombination from the singlet state is determined by the Loschmidt echo of the environments with interacting nuclear spins. Thus quantum criticality of environments could enhance the sensitivity of the detection of the weak magnetic field.

  19. Countermeasures to Hazardous Chemicals,

    Science.gov (United States)

    1989-04-01

    of any effective community awareness and emergency response program is an informed public familiar with the operations of local chemical plants. Such a...protection systems. 2. Booklel, ’Protecting People and the Environment.’ - A concise booklet developed to familiarize the public with chemical operations and...Jefe, Seccion de Estudios y Planificacion 102. Civil Defense Administation c/Evaristo San Miguel, 8 Ministry of Interior Madrid-8 Ankara ESPANA

  20. Computational Systems Chemical Biology

    OpenAIRE

    Oprea, Tudor I.; Elebeoba E. May; Leitão, Andrei; Tropsha, Alexander

    2011-01-01

    There is a critical need for improving the level of chemistry awareness in systems biology. The data and information related to modulation of genes and proteins by small molecules continue to accumulate at the same time as simulation tools in systems biology and whole body physiologically-based pharmacokinetics (PBPK) continue to evolve. We called this emerging area at the interface between chemical biology and systems biology systems chemical biology, SCB (Oprea et al., 2007).

  1. Sawmill chemicals and carcinogenesis.

    OpenAIRE

    Huff, J

    2001-01-01

    Workers in wood industries are exposed to variable medleys of chemicals, both natural and synthetic. Additional exposures include fungi, bacteria, bark and wood dusts, solvents, paints, and various other wood coatings. These individual and conglomerate exposures have been associated with diverse occupational illnesses and hazards, including cancers. In this commentary, I summarize both experimental and epidemiologic carcinogenesis results for several chemicals used in the wood industry, as we...

  2. Chemical Ionization Mass Spectrometry.

    Science.gov (United States)

    1980-01-30

    mass spectrometer. Also discussed were Corporation, St. Louis , Mo. unique analytical applications of several negative ion chemical Synthesis of the...were purchsed from obtained at a probe temperature of 180-200 °C and displays Sigma Chemical Co.. St. Louis , Mo. Arginine hydrochloride (4) a M4...13) Rosenstock. H, M.: Drax . K.: Stener. B. W: Hernon J. T. J. Phys. Chem, Ref. Data 1977, 6, Supl. 1. 774-783,167 occur in the ratio of 10/ 1

  3. A Corpuscular Picture of Electrons in Chemical Bond

    CERN Document Server

    Ando, Koji

    2015-01-01

    We introduce a theory of chemical bond with a corpuscular picture of electrons. It employs a minimal set of localized electron wave packets with 'floating and breathing' degrees of freedom and the spin-coupling of non-orthogonal valence-bond theory. It accurately describes chemical bonds in ground and excited states of spin singlet and triplet, in a distinct manner from conventional theories, indicating potential for establishing a dynamical theory of electrons in chemical bonds.

  4. Computational systems chemical biology.

    Science.gov (United States)

    Oprea, Tudor I; May, Elebeoba E; Leitão, Andrei; Tropsha, Alexander

    2011-01-01

    There is a critical need for improving the level of chemistry awareness in systems biology. The data and information related to modulation of genes and proteins by small molecules continue to accumulate at the same time as simulation tools in systems biology and whole body physiologically based pharmacokinetics (PBPK) continue to evolve. We called this emerging area at the interface between chemical biology and systems biology systems chemical biology (SCB) (Nat Chem Biol 3: 447-450, 2007).The overarching goal of computational SCB is to develop tools for integrated chemical-biological data acquisition, filtering and processing, by taking into account relevant information related to interactions between proteins and small molecules, possible metabolic transformations of small molecules, as well as associated information related to genes, networks, small molecules, and, where applicable, mutants and variants of those proteins. There is yet an unmet need to develop an integrated in silico pharmacology/systems biology continuum that embeds drug-target-clinical outcome (DTCO) triplets, a capability that is vital to the future of chemical biology, pharmacology, and systems biology. Through the development of the SCB approach, scientists will be able to start addressing, in an integrated simulation environment, questions that make the best use of our ever-growing chemical and biological data repositories at the system-wide level. This chapter reviews some of the major research concepts and describes key components that constitute the emerging area of computational systems chemical biology.

  5. The Chemical Revolution revisited.

    Science.gov (United States)

    Chang, Hasok

    2015-02-01

    I respond to the critical comments by Martin Kusch and Ursula Klein on my account of the Chemical Revolution. I comment along three different lines: descriptive, explanatory, and normative. (1) I agree with Klein that Lavoisier did not introduce drastic changes in chemical ontology, but maintain that there was methodological incommensurability in the Chemical Revolution; in response to Kusch's view, I maintain that Lavoisier's victory was slow and incomplete. (2) Admitting that there were many causes shaping the outcome of the Chemical Revolution, including the convenience of Lavoisier's theoretical scheme and various complicated social factors, I still think that the general rise of compositionism was an important factor. (3) I defend my normative pluralist view on the Chemical Revolution, denying Kusch's argument that chemists had overwhelmingly good reasons to trust Lavoisier and his allies over the phlogistonists. Overall, I agree with Kusch that it would be desirable to have a good descriptive-normative sociological account of the Chemical Revolution, but I also think that it should be an account that allows for divergence in individuals' and sub-communities' self-determination.

  6. Chemical Structure and Dynamics annual report 1997

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.; McDowell, R.S.

    1998-03-01

    The Chemical Structure and Dynamics (CS and D) program is a major component of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), developed by Pacific Northwest National Laboratory (PNNL) to provide a state-of-the-art collaborative facility for studies of chemical structure and dynamics. The authors respond to the need for a fundamental, molecular level understanding of chemistry at a wide variety of environmentally important interfaces by: (1) extending the experimental characterization and theoretical description of chemical reactions to encompass the effects of condensed media and interfaces; (2) developing a multidisciplinary capability for describing interfacial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in environmental chemistry and in nuclear waste processing and storage; and (3) developing state-of-the-art analytical methods for characterizing complex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. The focus of the research is defined primarily by DOE`s environmental problems: fate and transport of contaminants in the subsurface environment, processing and storage of waste materials, cellular effects of chemical and radiological insult, and atmospheric chemistry as it relates to air quality and global change. Twenty-seven projects are described under the following topical sections: Reaction mechanisms at interfaces; High-energy processes at environmental interfaces; Cluster models of the condensed phase; and Miscellaneous.

  7. Results of the 2010 Survey on Teaching Chemical Reaction Engineering

    Science.gov (United States)

    Silverstein, David L.; Vigeant, Margot A. S.

    2012-01-01

    A survey of faculty teaching the chemical reaction engineering course or sequence during the 2009-2010 academic year at chemical engineering programs in the United States and Canada reveals change in terms of content, timing, and approaches to teaching. The report consists of two parts: first, a statistical and demographic characterization of the…

  8. Revisiting the definition of the electronic chemical potential, chemical hardness, and softness at finite temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Franco-Pérez, Marco, E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México D. F. 09340 (Mexico); Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Gázquez, José L., E-mail: qimfranco@hotmail.com, E-mail: jlgm@xanum.uam.mx [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, México D. F. 09340 (Mexico); Ayers, Paul W. [Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Vela, Alberto [Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), Av. Instituto Politécnico Nacional 2508, México D. F. 07360 (Mexico)

    2015-10-21

    We extend the definition of the electronic chemical potential (μ{sub e}) and chemical hardness (η{sub e}) to finite temperatures by considering a reactive chemical species as a true open system to the exchange of electrons, working exclusively within the framework of the grand canonical ensemble. As in the zero temperature derivation of these descriptors, the response of a chemical reagent to electron-transfer is determined by the response of the (average) electronic energy of the system, and not by intrinsic thermodynamic properties like the chemical potential of the electron-reservoir which is, in general, different from the electronic chemical potential, μ{sub e}. Although the dependence of the electronic energy on electron number qualitatively resembles the piecewise-continuous straight-line profile for low electronic temperatures (up to ca. 5000 K), the introduction of the temperature as a free variable smoothens this profile, so that derivatives (of all orders) of the average electronic energy with respect to the average electron number exist and can be evaluated analytically. Assuming a three-state ensemble, well-known results for the electronic chemical potential at negative (−I), positive (−A), and zero values of the fractional charge (−(I + A)/2) are recovered. Similarly, in the zero temperature limit, the chemical hardness is formally expressed as a Dirac delta function in the particle number and satisfies the well-known reciprocity relation with the global softness.

  9. Indices chimiques pour l'évaluation de l'état diagénétique des huiles et des roches sapropéliques Chemical Evidence for Evaluating the Diagenetic State of Sapropelic Oils and Rocks

    Directory of Open Access Journals (Sweden)

    Du Rouchet J.

    2006-11-01

    Full Text Available Les analyses chromatographiques des vapeurs produites par le chauffage à 220 °C d'huiles brutes et de roches mettent en évidence une augmentation avec la diagenèse des teneurs en n-alcanes relativement aux teneurs en cyclones et en iso-alcanes. Une étude statistique permet de préciser la regularite de l'evolution des rapports des teneurs en n-C 6 et en méthylcyclopentane etdes teneurs en n-C 7 et en I-trans-2-diméthylcyclopentane et met en évidence pour les roches une corrélation significative entre ces rapports et les réflectances de la vitrinite. Ces rapports peuvent donc être considérés comme des indicateurs diagénétiques; ils paraissent être moins dépendants des caractéristiques particulières de la matière organique originelle que les couples pristane-n-C 17 et phytane-n-C 18 habituellement utilisés pour repérer l'état d'évolution des huiles et des extraits de roche. Une calibration en termes de réflectance de la vitrinite est proposée. Chromatographic analyses of the vapors produced by crude cils and rocks heated to 220°C reveal, with diagenesis, an increase in the n-alkane contents with respect to the cyclone and isoalkane contents. A statistical survey shows the regularity of the variation in the ratios of the n-C 6 and methylcyclopentane contents and the n-C7 and I-trans-2-dimethylcyclopentane contents and reveals a meaningful corrélation for rocks between these ratios and the vitrinite reflectances. Therefore, these ratios may be considered as diagenetic indicators. They appear to depend less on the particular properties of the original organic motter thon on the pristane/n-C 17 and phytane/n-C 18 pairs normally used to determine the state of evolution of ails and of rock extracts. A calibration in terms of vitrinite reflectance is proposed.

  10. Chemical kinetics of gas reactions

    CERN Document Server

    Kondrat'Ev, V N

    2013-01-01

    Chemical Kinetics of Gas Reactions explores the advances in gas kinetics and thermal, photochemical, electrical discharge, and radiation chemical reactions. This book is composed of 10 chapters, and begins with the presentation of general kinetic rules for simple and complex chemical reactions. The next chapters deal with the experimental methods for evaluating chemical reaction mechanisms and some theories of elementary chemical processes. These topics are followed by discussions on certain class of chemical reactions, including unimolecular, bimolecular, and termolecular reactions. The rema

  11. THE USE OF CHEMICALS IN THE FIELD OF FARM ANIMAL HEALTH (NUTRITION, ENTOMOLOGY, PATHOLOGY). AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 7.

    Science.gov (United States)

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF STATE STUDIES, THIS MODULE IS ONE OF A SERIES DESIGNED TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS. THE SPECIFIC OBJECTIVE OF THIS MODULE IS TO PREPARE TECHNICIANS IN THE FIELD OF THE USE OF CHEMICALS FOR ANIMAL HEALTH. SECTIONS INCLUDE -- (1)…

  12. Mini-projects in Chemical Engineering Laboratory

    Directory of Open Access Journals (Sweden)

    Angeles Cancela

    2013-03-01

    Full Text Available Chemical engineering laboratory practices based in mini-projects were design and applied the students of forestry engineering in chemical subject. This way of practice reveals a more cooperative learning and a different style of experimentation. The stated goal was to design practices that motivate students and to enable them to develop different skills, including cross teamwork and communication. This paper describes how these practices were developed and the advantages and disadvantages of using this methodology of teaching.

  13. Fundamental aspects of plasma chemical physics kinetics

    CERN Document Server

    Capitelli, Mario; Colonna, Gianpiero; Esposito, Fabrizio; Gorse, Claudine; Hassouni, Khaled; Laricchiuta, Annarita; Longo, Savino

    2016-01-01

    Describing non-equilibrium "cold" plasmas through a chemical physics approach, this book uses the state-to-state plasma kinetics, which considers each internal state as a new species with its own cross sections. Extended atomic and molecular master equations are coupled with Boltzmann and Monte Carlo methods to solve the electron energy distribution function. Selected examples in different applied fields, such as microelectronics, fusion, and aerospace, are presented and discussed including the self-consistent kinetics in RF parallel plate reactors, the optimization of negative ion sources and the expansion of high enthalpy flows through nozzles of different geometries. The book will cover the main aspects of the state-to-state kinetic approach for the description of nonequilibrium cold plasmas, illustrating the more recent achievements in the development of kinetic models including the self-consistent coupling of master equations and Boltzmann equation for electron dynamics. To give a complete portrayal, the...

  14. Glucans monomer-exchange dynamics as an open chemical network

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Riccardo, E-mail: riccardo.rao@uni.lu; Esposito, Massimiliano, E-mail: massimiliano.esposito@uni.lu [Complex Systems and Statistical Mechanics, Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg (Luxembourg); Lacoste, David [Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI - 10 rue Vauquelin, F-75231 Paris (France)

    2015-12-28

    We describe the oligosaccharides-exchange dynamics performed by the so-called D-enzymes on polysaccharides. To mimic physiological conditions, we treat this process as an open chemical network by assuming some of the polymer concentrations fixed (chemostatting). We show that three different long-time behaviors may ensue: equilibrium states, nonequilibrium steady states, and continuous growth states. We dynamically and thermodynamically characterize these states and emphasize the crucial role of conservation laws in identifying the chemostatting conditions inducing them.

  15. Glucans monomer-exchange dynamics as an open chemical network

    CERN Document Server

    Rao, Riccardo; Esposito, Massimiliano

    2015-01-01

    We describe the oligosaccharides-exchange dynamics performed by so-called D-enzymes on polysaccharides. To mimic physiological conditions, we treat this process as an open chemical network by assuming some of the polymer concentrations fixed (chemostatting). We show that three different long-time behaviors may ensue: equilibrium states, nonequilibrium steady states, and continuous growth states. We dynamically and thermodynamically characterize these states and emphasize the crucial role of conservation laws in identifying the chemostatting conditions inducing them.

  16. Current Chemical Risk Reduction Activities

    Science.gov (United States)

    EPA's existing chemicals programs address pollution prevention, risk assessment, hazard and exposure assessment and/or characterization, and risk management for chemicals substances in commercial use.

  17. Accessing and using chemical databases

    DEFF Research Database (Denmark)

    Nikolov, Nikolai Georgiev; Pavlov, Todor; Niemelä, Jay Russell

    2013-01-01

    , and dissemination. Structure and functionality of chemical databases are considered. The typical kinds of information found in a chemical database are considered-identification, structural, and associated data. Functionality of chemical databases is presented, with examples of search and access types. More details...... are included about the OASIS database and platform and the Danish (Q)SAR Database online. Various types of chemical database resources are discussed, together with a list of examples.......Computer-based representation of chemicals makes it possible to organize data in chemical databases-collections of chemical structures and associated properties. Databases are widely used wherever efficient processing of chemical information is needed, including search, storage, retrieval...

  18. Biological and Chemical Security

    Energy Technology Data Exchange (ETDEWEB)

    Fitch, P J

    2002-12-19

    The LLNL Chemical & Biological National Security Program (CBNP) provides science, technology and integrated systems for chemical and biological security. Our approach is to develop and field advanced strategies that dramatically improve the nation's capabilities to prevent, prepare for, detect, and respond to terrorist use of chemical or biological weapons. Recent events show the importance of civilian defense against terrorism. The 1995 nerve gas attack in Tokyo's subway served to catalyze and focus the early LLNL program on civilian counter terrorism. In the same year, LLNL began CBNP using Laboratory-Directed R&D investments and a focus on biodetection. The Nunn-Lugar-Domenici Defense Against Weapons of Mass Destruction Act, passed in 1996, initiated a number of U.S. nonproliferation and counter-terrorism programs including the DOE (now NNSA) Chemical and Biological Nonproliferation Program (also known as CBNP). In 2002, the Department of Homeland Security was formed. The NNSA CBNP and many of the LLNL CBNP activities are being transferred as the new Department becomes operational. LLNL has a long history in national security including nonproliferation of weapons of mass destruction. In biology, LLNL had a key role in starting and implementing the Human Genome Project and, more recently, the Microbial Genome Program. LLNL has over 1,000 scientists and engineers with relevant expertise in biology, chemistry, decontamination, instrumentation, microtechnologies, atmospheric modeling, and field experimentation. Over 150 LLNL scientists and engineers work full time on chemical and biological national security projects.

  19. Protein Chemical Shift Prediction

    CERN Document Server

    Larsen, Anders S

    2014-01-01

    The protein chemical shifts holds a large amount of information about the 3-dimensional structure of the protein. A number of chemical shift predictors based on the relationship between structures resolved with X-ray crystallography and the corresponding experimental chemical shifts have been developed. These empirical predictors are very accurate on X-ray structures but tends to be insensitive to small structural changes. To overcome this limitation it has been suggested to make chemical shift predictors based on quantum mechanical(QM) calculations. In this thesis the development of the QM derived chemical shift predictor Procs14 is presented. Procs14 is based on 2.35 million density functional theory(DFT) calculations on tripeptides and contains corrections for hydrogen bonding, ring current and the effect of the previous and following residue. Procs14 is capable at performing predictions for the 13CA, 13CB, 13CO, 15NH, 1HN and 1HA backbone atoms. In order to benchmark Procs14, a number of QM NMR calculatio...

  20. Chemically Powered Nanomotors

    Science.gov (United States)

    Kapral, Raymond

    2007-03-01

    Molecular motors play important roles in transport in biological systems. These molecular machines are powered by chemical energy and operate in the regime of low Reynolds number hydrodynamics. Recently a class of simple inorganic molecular motors has been constructed and studied experimentally [1,2]. These motors are bimetallic rods, one end of which is chemically active. The talk will describe simple mesoscopic models for the motion of such nanomotors. The motor consists of two linked spheres, one of which catalyzes the conversion between two chemical species. The chemical species interact differently with the the two spheres in the dimer. The nano-dimer motor is solvated by a molecules treated at a mesoscopic level whose evolution is governed by multi-particle collision dynamics. The dynamics conserves mass, momentum and energy so that coupling between the nanomotor and the hydrodynamic modes of the solvent is treated correctly. The simulations allow one to explore the mechanisms of the chemically powered motion and the effects of fluctuations on the motor dynamics. [1] W. F. Paxton, et al., ``Catalytic Nanomotors: Autonomous Movement of Striped Nanorods,'' J. Am. Chem. Soc. (JACS), 126 (41), 13424 (2004). [2] S. Fournier-Bidoz, et al. ``Synthetic Self-Propelled Nanorotors,'' Chem. Commun., (4), 441 (2005).

  1. Tungsten chemical vapor deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, Kiichi; Takeda, Nobuo.

    1993-07-13

    A tungsten chemical vapor deposition method is described, comprising: a first step of selectively growing a first thin tungsten film of a predetermined thickness in a desired region on the surface of a silicon substrate by reduction of a WF[sub 6] gas introduced into an atmosphere of a predetermined temperature containing said silicon substrate; and a second step of selectively growing a second tungsten film of a predetermined thickness on said first thin tungsten film by reduction of said WF[sub 6] with a silane gas further introduced into said atmosphere, wherein the surface state of said substrate is monitored by a pyrometer and the switching from said first step to said second step is performed when the emissivity of infrared light from the substrate surfaces reaches a predetermined value.

  2. Nanotechnology for chemical engineers

    CERN Document Server

    Salaheldeen Elnashaie, Said; Hashemipour Rafsanjani, Hassan

    2015-01-01

    The book describes the basic principles of transforming nano-technology into nano-engineering with a particular focus on chemical engineering fundamentals. This book provides vital information about differences between descriptive technology and quantitative engineering for students as well as working professionals in various fields of nanotechnology. Besides chemical engineering principles, the fundamentals of nanotechnology are also covered along with detailed explanation of several specific nanoscale processes from chemical engineering point of view. This information is presented in form of practical examples and case studies that help the engineers and researchers to integrate the processes which can meet the commercial production. It is worth mentioning here that, the main challenge in nanostructure and nanodevices production is nowadays related to the economic point of view. The uniqueness of this book is a balance between important insights into the synthetic methods of nano-structures and nanomaterial...

  3. Rapid chemical separations

    CERN Document Server

    Trautmann, N

    1976-01-01

    A survey is given on the progress of fast chemical separation procedures during the last few years. Fast, discontinuous separation techniques are illustrated by a procedure for niobium. The use of such techniques for the chemical characterization of the heaviest known elements is described. Other rapid separation methods from aqueous solutions are summarized. The application of the high speed liquid chromatography to the separation of chemically similar elements is outlined. The use of the gas jet recoil transport method for nuclear reaction products and its combination with a continuous solvent extraction technique and with a thermochromatographic separation is presented. Different separation methods in the gas phase are briefly discussed and the attachment of a thermochromatographic technique to an on-line mass separator is shown. (45 refs).

  4. Precision Chemical Abundance Measurements

    DEFF Research Database (Denmark)

    Yong, David; Grundahl, Frank; Meléndez, Jorge;

    2012-01-01

    This talk covers preliminary work in which we apply a strictly differential line-by-line chemical abundance analysis to high quality UVES spectra of the globular cluster NGC 6752. We achieve extremely high precision in the measurement of relative abundance ratios. Our results indicate that the ob......This talk covers preliminary work in which we apply a strictly differential line-by-line chemical abundance analysis to high quality UVES spectra of the globular cluster NGC 6752. We achieve extremely high precision in the measurement of relative abundance ratios. Our results indicate...... that the observed abundance dispersion exceeds the measurement uncertainties and that many pairs of elements show significant correlations when plotting [X1/H] vs. [X2/H]. Our tentative conclusions are that either NGC 6752 is not chemically homogeneous at the ~=0.03 dex level or the abundance variations...

  5. Chemical Inhibition of Autophagy

    DEFF Research Database (Denmark)

    Baek, Eric; Lin Kim, Che; Gyeom Kim, Mi;

    2016-01-01

    Chinese hamster ovary (CHO) cells activate and undergo apoptosis and autophagy for various environmental stresses. Unlike apoptosis, studies on increasing the production of therapeutic proteins in CHO cells by targeting the autophagy pathway are limited. In order to identify the effects of chemical...... autophagy inhibitors on the specific productivity (qp), nine chemical inhibitors that had been reported to target three different phases of autophagy (metformin, dorsomorphin, resveratrol, and SP600125 against initiation and nucleation; 3-MA, wortmannin, and LY294002 against elongation, and chloroquine...... and bafilomycin A1 against autophagosome fusion) were used to treat three recombinant CHO (rCHO) cell lines: the Fc-fusion protein-producing DG44 (DG44-Fc) and DUKX-B11 (DUKX-Fc) and antibody-producing DG44 (DG44-Ab) cell lines. Among the nine chemical inhibitors tested, 3-MA, dorsomorphin, and SP600125...

  6. Chemical inhomogeneities and pulsation

    CERN Document Server

    Turcotte, S

    2001-01-01

    Major improvements in models of chemically peculiar stars have been achieved in the past few years. With these new models it has been possible to test quantitatively some of the processes involved in the formation of abundance anomalies and their effect on stellar structure. The models of metallic A (Am) stars have shown that a much deeper mixing has to be present to account for observed abundance anomalies. This has implications on their variability, which these models also reproduce qualitatively. These models also have implications for other chemically inhomogeneous stars such as HgMn B stars which are not known to be variable and lambda Bootis stars which can be. The study of the variability of chemically inhomogeneous stars can provide unique information on the dynamic processes occurring in many types of stars in addition to modeling of the evolution of their surface composition.

  7. Chemical Kinetics Database

    Science.gov (United States)

    SRD 17 NIST Chemical Kinetics Database (Web, free access)   The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these. In addition, the bibliography can be searched by author name or combination of names. The database contains in excess of 38,000 separate reaction records for over 11,700 distinct reactant pairs. These data have been abstracted from over 12,000 papers with literature coverage through early 2000.

  8. Chemicals in material cycles

    DEFF Research Database (Denmark)

    Pivnenko, Kostyantyn; Eriksson, Eva; Astrup, Thomas Fruergaard

    2015-01-01

    Material recycling has been found beneficial in terms of resource and energy performance and is greatly promoted throughout the world. A variety of chemicals is used in materials as additives and data on their presence is sparse. The present work dealt with paper as recyclable material and diisob......Material recycling has been found beneficial in terms of resource and energy performance and is greatly promoted throughout the world. A variety of chemicals is used in materials as additives and data on their presence is sparse. The present work dealt with paper as recyclable material...... and diisobutyl phthalate (DiBP) as chemical in focus. The results showed variations, between 0.83 and 32 μg/g, in the presence of DiBP in Danish waste paper and board and potential accumulation due to recycling....

  9. Endocrine disrupting chemicals

    DEFF Research Database (Denmark)

    Mandrup, Karen

    BACKGROUND: Endocrine disrupting chemicals (EDCs) may contribute to reproductive changes in boys in the Western world, however, less is known about influence of EDCs in women. The incidence of precocious breast development is increasing in USA and Europe and mammary gland development has been...... suggested as particularly sensitive to endocrine disruption. Mammary gland examination in toxicological studies may be useful for improving knowledge on possible influences of EDCs on human mammary glands and also be useful for detection of endocrine disrupting effects of chemicals as part of safety testing...... and genistein, a mixture of phytoestrogens, and a mixture of environmentally relevant estrogenic EDCs of various origins. Moreover, mixtures of antiandrogenic chemicals were investigated. These include a mixture of pesticides and a mixture of environmentally relevant anti-androgenic EDCs of various origins...

  10. Chemical profiling of chemical warfare agents for forensic purposes

    NARCIS (Netherlands)

    Noort, D.; Reuver, L.P.J. de; Fidder, A.; Tromp, M.; Verschraagen, M.

    2010-01-01

    A program has been initiated towards the chemical profiling of chemical warfare agents, in order to support forensic investigations towards synthesis routes, production sites and suspect chemical suppliers. Within the first stage of the project various chemical warfare agents (VX, sulfur mustard, sa

  11. Idaho Chemical Processing Plant safety document ICPP hazardous chemical evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Harwood, B.J.

    1993-01-01

    This report presents the results of a hazardous chemical evaluation performed for the Idaho Chemical Processing Plant (ICPP). ICPP tracks chemicals on a computerized database, Haz Track, that contains roughly 2000 individual chemicals. The database contains information about each chemical, such as its form (solid, liquid, or gas); quantity, either in weight or volume; and its location. The Haz Track database was used as the primary starting point for the chemical evaluation presented in this report. The chemical data and results presented here are not intended to provide limits, but to provide a starting point for nonradiological hazards analysis.

  12. Chemical allergy in humans

    DEFF Research Database (Denmark)

    Kimber, Ian; Basketter, David A; Thyssen, Jacob P

    2014-01-01

    functional sub-populations of CD4(+) and CD8(+) T-lymphocytes. Evidence for a similar association of chemical allergy in humans with discrete T-lymphocyte populations is, however, limited. It is of some interest, therefore, that two recent articles from different teams of investigators have shed new light...... on the role of polarized T-lymphocyte responses in the development of allergic contact dermatitis and occupational asthma in humans. The implications for understanding of chemical allergy in humans are explored in this Commentary....

  13. Chemical space and biology.

    Science.gov (United States)

    Dobson, Christopher M

    2004-12-16

    Chemical space--which encompasses all possible small organic molecules, including those present in biological systems--is vast. So vast, in fact, that so far only a tiny fraction of it has been explored. Nevertheless, these explorations have greatly enhanced our understanding of biology, and have led to the development of many of today's drugs. The discovery of new bioactive molecules, facilitated by a deeper understanding of the nature of the regions of chemical space that are relevant to biology, will advance our knowledge of biological processes and lead to new strategies to treat disease.

  14. CHEMICAL TOXICITY OF URANIUM

    Directory of Open Access Journals (Sweden)

    Sermin Cam

    2007-06-01

    Full Text Available Uranium, occurs naturally in the earth’s crust, is an alpha emitter radioactive element from the actinide group. For this reason, U-235 and U-238, are uranium isotopes with long half lives, have got radiological toxicity. But, for natural-isotopic-composition uranium (NatU, there is greater risk from chemical toxicity than radiological toxicity. When uranium is get into the body with anyway, also its chemical toxicity must be thought. [TAF Prev Med Bull 2007; 6(3.000: 215-220

  15. Magnetic chemically peculiar stars

    CERN Document Server

    Schöller, Markus

    2015-01-01

    Chemically peculiar (CP) stars are main-sequence A and B stars with abnormally strong or weak lines for certain elements. They generally have magnetic fields and all observables tend to vary with the same period. Chemically peculiar stars provide a wealth of information; they are natural atomic and magnetic laboratories. After a brief historical overview, we discuss the general properties of the magnetic fields in CP stars, describe the oblique rotator model, explain the dependence of the magnetic field strength on the rotation, and concentrate at the end on HgMn stars.

  16. Improved chemical shift prediction by Rosetta conformational sampling

    Energy Technology Data Exchange (ETDEWEB)

    Tian Ye [Sanford Burnham Medical Research Institute (United States); Opella, Stanley J. [University of California San Diego, Department of Chemistry and Biochemistry (United States); Marassi, Francesca M., E-mail: fmarassi@sbmri.org [Sanford Burnham Medical Research Institute (United States)

    2012-11-15

    Chemical shift frequencies represent a time-average of all the conformational states populated by a protein. Thus, chemical shift prediction programs based on sequence and database analysis yield higher accuracy for rigid rather than flexible protein segments. Here we show that the prediction accuracy can be significantly improved by averaging over an ensemble of structures, predicted solely from amino acid sequence with the Rosetta program. This approach to chemical shift and structure prediction has the potential to be useful for guiding resonance assignments, especially in solid-state NMR structural studies of membrane proteins in proteoliposomes.

  17. How accurate are the nonlinear chemical Fokker-Planck and chemical Langevin equations?

    Science.gov (United States)

    Grima, Ramon; Thomas, Philipp; Straube, Arthur V

    2011-08-28

    The chemical Fokker-Planck equation and the corresponding chemical Langevin equation are commonly used approximations of the chemical master equation. These equations are derived from an uncontrolled, second-order truncation of the Kramers-Moyal expansion of the chemical master equation and hence their accuracy remains to be clarified. We use the system-size expansion to show that chemical Fokker-Planck estimates of the mean concentrations and of the variance of the concentration fluctuations about the mean are accurate to order Ω(-3∕2) for reaction systems which do not obey detailed balance and at least accurate to order Ω(-2) for systems obeying detailed balance, where Ω is the characteristic size of the system. Hence, the chemical Fokker-Planck equation turns out to be more accurate than the linear-noise approximation of the chemical master equation (the linear Fokker-Planck equation) which leads to mean concentration estimates accurate to order Ω(-1∕2) and variance estimates accurate to order Ω(-3∕2). This higher accuracy is particularly conspicuous for chemical systems realized in small volumes such as biochemical reactions inside cells. A formula is also obtained for the approximate size of the relative errors in the concentration and variance predictions of the chemical Fokker-Planck equation, where the relative error is defined as the difference between the predictions of the chemical Fokker-Planck equation and the master equation divided by the prediction of the master equation. For dimerization and enzyme-catalyzed reactions, the errors are typically less than few percent even when the steady-state is characterized by merely few tens of molecules.

  18. Chemical Potential of Vacancies in Metal Crystals

    Institute of Scientific and Technical Information of China (English)

    SUN Jun; W.R.Tyson

    2000-01-01

    In this paper, a concept, the chemical potential of vacancies in metal crystals, has been derived from the partial mole free energy of vacancies based on a model of an atom-vacancy binary solution.For a pure metal crystal containing the mole concentration of vacancies, Cv and it's value in thermal equilibrium,C0, at temperature T the chemical potential can be expressed respectively as: μ v(Cv)=RT[1+1n(C√Co)]and μ v (Co)=RT The second term in μ v(Cv) is the chemical potential of the vacancies referred to the standardstate concentration given by J. P. Hirth [1] and first term is the standard-state one presented in this paper.

  19. Controlling chemical reactions of a single particle

    CERN Document Server

    Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2012-01-01

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achi...

  20. Rayleigh-type parametric chemical oscillation.

    Science.gov (United States)

    Ghosh, Shyamolina; Ray, Deb Shankar

    2015-09-28

    We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

  1. Rayleigh-type parametric chemical oscillation

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Shyamolina; Ray, Deb Shankar, E-mail: pcdsr@iacs.res.in [Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2015-09-28

    We consider a nonlinear chemical dynamical system of two phase space variables in a stable steady state. When the system is driven by a time-dependent sinusoidal forcing of a suitable scaling parameter at a frequency twice the output frequency and the strength of perturbation exceeds a threshold, the system undergoes sustained Rayleigh-type periodic oscillation, wellknown for parametric oscillation in pipe organs and distinct from the usual forced quasiperiodic oscillation of a damped nonlinear system where the system is oscillatory even in absence of any external forcing. Our theoretical analysis of the parametric chemical oscillation is corroborated by full numerical simulation of two well known models of chemical dynamics, chlorite-iodine-malonic acid and iodine-clock reactions.

  2. THE USE OF CHEMICALS AS INSECTICIDES--PLANTS. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 2.

    Science.gov (United States)

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    THIS GUIDE IS ONE OF A SERIES DESIGNED TO PROVIDE GROUP INSTRUCTION AND INDIVIDUAL OCCUPATIONAL EXPERIENCE FOR POST-SECONDARY STUDENTS PREPARING FOR EMPLOYMENT AS AGRICULTURAL CHEMICAL TECHNICIANS. IT WAS DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF STATE STUDY DATA. THE OBJECTIVES ARE TO DEVELOP (1) INTEREST, APPRECIATION, AND UNDERSTANDING…

  3. 77 FR 41300 - Hazardous Chemical Reporting: Revisions to the Emergency and Hazardous Chemical Inventory Forms...

    Science.gov (United States)

    2012-07-13

    ... for most of the data elements from various organizations. While some commenters from industry opposed... new data elements and revising some existing data elements on the Emergency and Hazardous Chemical... Act (EPCRA). State and local implementing agencies requested that EPA add the new data elements...

  4. State Snapshots

    Data.gov (United States)

    U.S. Department of Health & Human Services — The State Snapshots provide graphical representations of State-specific health care quality information, including strengths, weaknesses, and opportunities for...

  5. Complications - State

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Complications measures - state data. This data set includes state-level data for the hip/knee complication measure, and the Agency for Healthcare Research and...

  6. ILO activities in the area of chemical safety.

    Science.gov (United States)

    Obadia, Isaac

    2003-08-21

    The ILO has been active in the area of safety in the use of chemicals at work since the year of its creation in 1919, including the development of international treaties and other technical instruments, the provision of technical assistance to its member States, and the development of chemical safety information systems. The two key ILO standards in this area are the Conventions on safety in the use of chemicals at work (No. 170, 1990), and the Prevention of Major Industrial Accidents (No. 174, 1993). The ILO Programme on occupational safety, health and environment (Safe Work) is currently responsible for ILO chemical safety activities. In the past two decades, most of ILO work in this area has been carried out within the context of inter-agency collaboration frameworks linking the ILO, WHO, UNEP, FAO, UNIDO, UNITAR, and the OECD, including the International Programme on Chemical Safety (IPCS), the Inter-Organisation Programme for the Sound Management of Chemicals (IOMC), and the Intergovernmental Forum on Chemical Safety (IFCS). Apart from the regular development, updating and dissemination of chemical safety information data bases such as the IPCS International Chemical Cards, the elaboration of a Globally harmonized system for the classification and labelling of Chemicals (GHS) has been the most outstanding achievement of this international collaboration on chemical safety.

  7. Mesoscale simulations of shockwave energy dissipation via chemical reactions.

    Science.gov (United States)

    Antillon, Edwin; Strachan, Alejandro

    2015-02-28

    We use a particle-based mesoscale model that incorporates chemical reactions at a coarse-grained level to study the response of materials that undergo volume-reducing chemical reactions under shockwave-loading conditions. We find that such chemical reactions can attenuate the shockwave and characterize how the parameters of the chemical model affect this behavior. The simulations show that the magnitude of the volume collapse and velocity at which the chemistry propagates are critical to weaken the shock, whereas the energetics in the reactions play only a minor role. Shock loading results in transient states where the material is away from local equilibrium and, interestingly, chemical reactions can nucleate under such non-equilibrium states. Thus, the timescales for equilibration between the various degrees of freedom in the material affect the shock-induced chemistry and its ability to attenuate the propagating shock.

  8. Environmental Chemicals in Breast Milk

    Science.gov (United States)

    Most of the information available on environmental chemicals in breast milk is focused on persistent, lipophilic chemicals; the database on levels of these chemicals has expanded substantially since the 1950s. Currently, various types of chemicals are measured in breast milk and ...

  9. Chemical Analysis Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Uses state-of-the-art instrumentation for qualitative and quantitative analysis of organic and inorganic compounds, and biomolecules from gas, liquid, and...

  10. USE OF CHEMICAL INVENTORY ACCURACY MEASUREMENTS AS LEADING INDICATORS

    Energy Technology Data Exchange (ETDEWEB)

    Kuntamukkula, M.

    2011-02-10

    Chemical safety and lifecycle management (CSLM) is a process that involves managing chemicals and chemical information from the moment someone begins to order a chemical and lasts through final disposition(1). Central to CSLM is tracking data associated with chemicals which, for the purposes of this paper, is termed the chemical inventory. Examples of data that could be tracked include chemical identity, location, quantity, date procured, container type, and physical state. The reason why so much data is tracked is that the chemical inventory supports many functions. These functions include emergency management, which depends upon the data to more effectively plan for, and respond to, chemical accidents; environmental management that uses inventory information to aid in the generation of various federally-mandated and other regulatory reports; and chemical management that uses the information to increase the efficiency and safety with which chemicals are stored and utilized. All of the benefits of having an inventory are predicated upon having an inventory that is reasonably accurate. Because of the importance of ensuring one's chemical inventory is accurate, many have become concerned about measuring inventory accuracy. But beyond providing a measure of confidence in information gleaned from the inventory, does the inventory accuracy measurement provide any additional function? The answer is 'Yes'. It provides valuable information that can be used as a leading indicator to gauge the health of a chemical management system. In this paper, we will discuss: what properties make leading indicators effective, how chemical inventories can be used as a leading indicator, how chemical inventory accuracy can be measured, what levels of accuracies should realistically be expected in a healthy system, and what a subpar inventory accuracy measurement portends.

  11. Chemical hygiene plan

    Energy Technology Data Exchange (ETDEWEB)

    1994-09-01

    This plan was written to administer and monitor safety measures and chemical hygiene principles in the TAC Uranium Mill Tailing Remedial Action Project sample preparation facility in Albuquerque, New Mexico. It applies to toxic and/or hazardous materials to radioactive materials.

  12. Chemical Product Design

    DEFF Research Database (Denmark)

    Gani, Rafiqul

    2004-01-01

    This paper highlights for a class of chemical products, the design process, their design with respect to the important issues, the need for appropriate tools and finally, lists some of the challenges and opportunities for the process systems engineering (PSE)/computer-aided process engineering...

  13. Chemical and Petrochemical Sector

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    This publication is a background document on the global chemical and petrochemical sector for the IEA publication Energy Technology Transitions in Industry (IEA, 2009). It provides further, more detailed information on the methodology and data issues for energy efficiency indicators for the sector. The indicators discussed offer insight regarding the energy efficiency improvement potential in the short- to medium-term (by proven technologies).

  14. The renewable chemicals industry

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Rass-Hansen, J.; Marsden, Charlotte Clare;

    2008-01-01

    The possibilities for establishing a renewable chemicals industry featuring renewable resources as the dominant feedstock rather than fossil resources are discussed in this Concept. Such use of biomass can potentially be interesting from both an economical and ecological perspective. Simple and e...

  15. Chemically Reacting Turbulent Flow.

    Science.gov (United States)

    1987-04-14

    two stages of gen I tubes equipped with P-47 phosphor screens The detector chosen for the camera was a Reticon RL128S* line detectoI- .,hich consists...the Stud’, of Turbulent Mixing," William M. Pitts, Nuclear Engineering Seminar of the Department of Chemical and Nuclear Engineering, University of

  16. Chemical Absorption Materials

    DEFF Research Database (Denmark)

    Thomsen, Kaj

    2011-01-01

    Chemical absorption materials that potentially can be used for post combustion carbon dioxide capture are discussed. They fall into five groups, alkanolamines, alkali carbonates, ammonia, amino acid salts, and ionic liquids. The chemistry of the materials is discussed and advantages and drawbacks...

  17. Chemical Safety – Introduction

    CERN Multimedia

    DG Unit

    2009-01-01

    A course of "Chemical Safety – Introduction" will be held in English on 29 May 2009, 9:30-12:00. There are some places left. If you are interested in participating, please register on the Training Catalogue. You will then receive an invitation by email.

  18. Multiple Chemical Sensitivity

    DEFF Research Database (Denmark)

    Junge, Anne Gram

    Et voksende antal mennesker i Danmark oplever at være overfølsomme over for dufte og kemikalier. Imidlertid er den tilskrevne diagnose Multiple Chemical Sensitivity (MCS) ikke medicinsk anerkendt i Danmark pga. mangel på organiske og patofysiologisk basis for symptomerne. Dette speciale bygger på...

  19. Hydroxyl Radical Chemical Laser

    Science.gov (United States)

    1977-11-01

    Stone (I) 1 Atlantic Research Corporation, Alexandria, VA (Robert Naismith ) I Battelle Columbus laboratories, Columbus, OH (Fred Tietzel) 1...Corporation, Santa Monica, CA (Dr. Claude R. Culp) 1 Thiokol Chemical Corporation, Wasatch Division, Brigham City, UT ( James E. Hansen) 4 United

  20. Chemical Aspects of Dentistry.

    Science.gov (United States)

    Helfman, Murry

    1982-01-01

    Dental caries (tooth decay) and periodontal (gum) disease are treated/prevented by procedures utilizing chemical expertise. Procedures and suggestions on how they might be incorporated into the high school chemistry curriculum are described. Specific topics discussed include dental caries, fluoride, diet, tooth decay prevention, silver amalgan,…