WorldWideScience

Sample records for chemical dynamics studies

  1. Theoretical studies of chemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Schatz, G.C. [Argonne National Laboratory, IL (United States)

    1993-12-01

    This collaborative program with the Theoretical Chemistry Group at Argonne involves theoretical studies of gas phase chemical reactions and related energy transfer and photodissociation processes. Many of the reactions studied are of direct relevance to combustion; others are selected they provide important examples of special dynamical processes, or are of relevance to experimental measurements. Both classical trajectory and quantum reactive scattering methods are used for these studies, and the types of information determined range from thermal rate constants to state to state differential cross sections.

  2. NATO Advanced Study Institute on Advances in Chemical Reaction Dynamics

    CERN Document Server

    Capellos, Christos

    1986-01-01

    This book contains the formal lectures and contributed papers presented at the NATO Advanced Study Institute on. the Advances in Chemical Reaction Dynamics. The meeting convened at the city of Iraklion, Crete, Greece on 25 August 1985 and continued to 7 September 1985. The material presented describes the fundamental and recent advances in experimental and theoretical aspects of, reaction dynamics. A large section is devoted to electronically excited states, ionic species, and free radicals, relevant to chemical sys­ tems. In addition recent advances in gas phase polymerization, formation of clusters, and energy release processes in energetic materials were presented. Selected papers deal with topics such as the dynamics of electric field effects in low polar solutions, high electric field perturbations and relaxation of dipole equilibria, correlation in picosecond/laser pulse scattering, and applications to fast reaction dynamics. Picosecond transient Raman spectroscopy which has been used for the elucidati...

  3. Gas-Phase Molecular Dynamics: Theoretical Studies In Spectroscopy and Chemical Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Yu H. G.; Muckerman, J.T.

    2012-05-29

    The main goal of this program is the development and application of computational methods for studying chemical reaction dynamics and molecular spectroscopy in the gas phase. We are interested in developing rigorous quantum dynamics algorithms for small polyatomic systems and in implementing approximate approaches for complex ones. Particular focus is on the dynamics and kinetics of chemical reactions and on the rovibrational spectra of species involved in combustion processes. This research also explores the potential energy surfaces of these systems of interest using state-of-the-art quantum chemistry methods, and extends them to understand some important properties of materials in condensed phases and interstellar medium as well as in combustion environments.

  4. Crossed molecular beam studies of atmospheric chemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jingsong

    1993-04-01

    The dynamics of several elementary chemical reactions that are important in atmospheric chemistry are investigated. The reactive scattering of ground state chlorine or bromine atoms with ozone molecules and ground state chlorine atoms with nitrogen dioxide molecules is studied using a crossed molecular beams apparatus with a rotatable mass spectrometer detector. The Cl + O{sub 3} {yields} ClO + O{sub 2} reaction has been studied at four collision energies ranging from 6 kcal/mole to 32 kcal/mole. The derived product center-of-mass angular and translational energy distributions show that the reaction has a direct reaction mechanism and that there is a strong repulsion on the exit channel. The ClO product is sideways and forward scattered with respect to the Cl atom, and the translational energy release is large. The Cl atom is most likely to attack the terminal oxygen atom of the ozone molecule. The Br + O{sub 3} {yields} ClO + O{sub 2} reaction has been studied at five collision energies ranging from 5 kcal/mole to 26 kcal/mole. The derived product center-of-mass angular and translational energy distributions are quite similar to those in the Cl + O{sub 3} reaction. The Br + O{sub 3} reaction has a direct reaction mechanism similar to that of the Cl + O{sub 3} reaction. The electronic structure of the ozone molecule seems to play the central role in determining the reaction mechanism in atomic radical reactions with the ozone molecule. The Cl + NO{sub 2} {yields} ClO + NO reaction has been studied at three collision energies ranging from 10.6 kcal/mole to 22.4 kcal/mole. The center-of-mass angular distribution has some forward-backward symmetry, and the product translational energy release is quite large. The reaction proceeds through a short-lived complex whose lifetime is less than one rotational period. The experimental results seem to show that the Cl atom mainly attacks the oxygen atom instead of the nitrogen atom of the NO{sub 2} molecule.

  5. On the study of nonlinear dynamics of complex chemical reaction systems

    Institute of Scientific and Technical Information of China (English)

    XIN; Houwen; HOU; Zhonghuai

    2006-01-01

    With ever-increasing attentions being paid to complex systems such as the life system, soft matter, and nano-systems, theoretical studies of non-equilibrium nonlinear problems involved in chemical dynamics are now of general interest. In this mini-review, we mainly give a brief introduction to some frontier topics in this field, namely, nonlinear state-state dynamics, nonlinear chemical dynamics on complex networks, and nonlinear dynamics in mesoscopic chemical reaction systems. Deep study of these topics will make great contribution to discovering new laws of chemical dynamics, to exploring new control methods of complex chemical processes, to figuring out the very roles of chemical processes in the life system, and to crosslinking the scientific study of chemistry, physics and biology.

  6. Dynamic behavior of chemical reactivity indices in density functional theory: A Bohn-Oppenheimer quantum molecular dynamics study

    Indian Academy of Sciences (India)

    Shubin Liu

    2005-09-01

    Dynamic behaviors of chemical concepts in density functional theory such as frontier orbitals (HOMO/LUMO), chemical potential, hardness, and electrophilicity index have been investigated in this work in the context of Bohn-Oppenheimer quantum molecular dynamics in association with molecular conformation changes. Exemplary molecular systems like CH$^{+}_{5}$ , Cl- (H2O)30 and Ca2+ (H2O)15 are studied at 300 K in the gas phase, demonstrating that HOMO is more dynamic than LUMO, chemical potential and hardness often fluctuate concurrently. It is argued that DFT concepts and indices may serve as a good framework to understand molecular conformation changes as well as other dynamic phenomena.

  7. Theoretical studies of the dynamics of chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, A.F. [Argonne National Laboratory, IL (United States)

    1993-12-01

    Recent research effort has focussed on several reactions pertinent to combustion. The formation of the formyl radical from atomic hydrogen and carbon monoxide, recombination of alkyl radicals and halo-alkyl radicals with halogen atoms, and the thermal dissociation of hydrogen cyanide and acetylene have been studied by modeling. In addition, the inelastic collisions of NCO with helium have been investigated.

  8. Molecular dynamics study of phase separation in fluids with chemical reactions

    Science.gov (United States)

    Krishnan, Raishma; Puri, Sanjay

    2015-11-01

    We present results from the first d =3 molecular dynamics (MD) study of phase-separating fluid mixtures (AB) with simple chemical reactions (A ⇌B ). We focus on the case where the rates of forward and backward reactions are equal. The chemical reactions compete with segregation, and the coarsening system settles into a steady-state mesoscale morphology. However, hydrodynamic effects destroy the lamellar morphology which characterizes the diffusive case. This has important consequences for the phase-separating structure, which we study in detail. In particular, the equilibrium length scale (ℓeq) in the steady state suggests a power-law dependence on the reaction rate ɛ :ℓeq˜ɛ-θ with θ ≃1.0 .

  9. Crossed Molecular Beam Studies and Dynamics of Decomposition of Chemically Activated Radicals

    Science.gov (United States)

    Lee, Y. T.

    1973-09-01

    The power of the crossed molecular beams method in the investigation of the dynamics of chemical reactions lies mainly in the direct observation of the consequences of single collisions of well controlled reactant molecules. The primary experimental observations which provide information on reaction dynamics are the measurements of angular and velocity distributions of reaction products.

  10. Spectroscopic Studies of Azide compounds: Thermochemistry, Chemical Kinetics and Photodissociation Dynamics

    Science.gov (United States)

    Quinto Hernandez, Alfredo

    Some of the most difficult chemical systems, either to observe or produce in significant quantities, are polynitrogen molecules. One example of this type of molecules in the early stages of investigation is cyclic-N3, whose molecular geometry and promising technological applications have attracted our attention to define optimal experimental conditions for being photoproduced. High-resolution synchrotron-radiation-based Photoionization Mass Spectrometry (PIMS) was applied to study the dissociative photoionization of three azide precursors for cyclic-N3; chlorine azide (ClN3), hydrogen azide (HN3), and methyl azide (CH3N3). In our attempts to detect cyclic-N3, the thermochemistry derived in the PIMS studies stimulated our work to perform photodissociation dynamics experiments of CH3N3 at 193 nm using Photofragment Translational Spectroscopy (PTS) with electron impact (EI) detection under collision-free conditions, and chemical kinetic studies based on Infrared Spectroscopy (IR) in matrix-isolated ices formed from rare gases (Argon, Nitrogen and Xenon). PTS experiments lead us to derive the branching ratio between reactions CH 3+N3 (radical channel) vs CH3N+N2 (molecular channel), and to conclude that cyclic-N3 is the dominant product in the radical channel. In contrast, in the matrix isolation experiments we found no evidence of the radical channel, possibly due to barrier-less recombination. However, since no mechanistic reports of methyl azide dissociation exist at these conditions, these studies could have significant implications for future experiments addressed to detect cylic-N3 under matrix environments.

  11. Chemical crosslinking and mass spectrometry studies of the structure and dynamics of membrane proteins and receptors.

    Energy Technology Data Exchange (ETDEWEB)

    Haskins, William E.; Leavell, Michael D.; Lane, Pamela; Jacobsen, Richard B.; Hong, Joohee; Ayson, Marites J.; Wood, Nichole L.; Schoeniger, Joseph S.; Kruppa, Gary Hermann; Sale, Kenneth L.; Young, Malin M.; Novak, Petr

    2005-03-01

    Membrane proteins make up a diverse and important subset of proteins for which structural information is limited. In this study, chemical cross-linking and mass spectrometry were used to explore the structure of the G-protein-coupled photoreceptor bovine rhodopsin in the dark-state conformation. All experiments were performed in rod outer segment membranes using amino acid 'handles' in the native protein sequence and thus minimizing perturbations to the native protein structure. Cysteine and lysine residues were covalently cross-linked using commercially available reagents with a range of linker arm lengths. Following chemical digestion of cross-linked protein, cross-linked peptides were identified by accurate mass measurement using liquid chromatography-fourier transform mass spectrometry and an automated data analysis pipeline. Assignments were confirmed and, if necessary, resolved, by tandem MS. The relative reactivity of lysine residues participating in cross-links was evaluated by labeling with NHS-esters. A distinct pattern of cross-link formation within the C-terminal domain, and between loop I and the C-terminal domain, emerged. Theoretical distances based on cross-linking were compared to inter-atomic distances determined from the energy-minimized X-ray crystal structure and Monte Carlo conformational search procedures. In general, the observed cross-links can be explained by re-positioning participating side-chains without significantly altering backbone structure. One exception, between C3 16 and K325, requires backbone motion to bring the reactive atoms into sufficient proximity for cross-linking. Evidence from other studies suggests that residues around K325 for a region of high backbone mobility. These findings show that cross-linking studies can provide insight into the structural dynamics of membrane proteins in their native environment.

  12. Molecular Dynamics Study of Thermally Augmented Nanodroplet Motion on Chemical Energy Induced Wettability Gradient Surfaces.

    Science.gov (United States)

    Chakraborty, Monojit; Chowdhury, Anamika; Bhusan, Richa; DasGupta, Sunando

    2015-10-20

    Droplet motion on a surface with chemical energy induced wettability gradient has been simulated using molecular dynamics (MD) simulation to highlight the underlying physics of molecular movement near the solid-liquid interface including the contact line friction. The simulations mimic experiments in a comprehensive manner wherein microsized droplets are propelled by the surface wettability gradient against forces opposed to motion. The liquid-wall Lennard-Jones interaction parameter and the substrate temperature are varied to explore their effects on the three-phase contact line friction coefficient. The contact line friction is observed to be a strong function of temperature at atomistic scales, confirming their experimentally observed inverse functionality. Additionally, the MD simulation results are successfully compared with those from an analytical model for self-propelled droplet motion on gradient surfaces. PMID:26381847

  13. Chemical structure and dynamics: Annual report 1993

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.

    1994-07-01

    The Chemical Structure and Dynamics program responds to the need for a fundamental, molecular-level understanding of chemistry at the wide variety of environmentally-important interfaces. The research program is built around the established relationship between structure, thermodynamics, and kinetics. This research effort continues to evolve into a program of rigorous studies of fundamental molecular processes in model systems (e.g., well-characterized surfaces, single-component solutions, clusters, and biological molecules), and studies of complex systems found in the environment. Experimental studies of molecular and supramolecular structures and thermodynamics are key to understanding the nature of matter, and lead to direct comparison with computational results. Kinetic and mechanistic measurements, combined with real-time dynamics measurements of atomic and molecular motions during chemical reactions, provide for a molecular-level description of chemical reactions. The anticipated results of this work are the achievement of a quantitative understanding of chemical processes at complex interfaces, the development of new techniques for the detection and measurement of species at such interfaces, and the interpretation and extrapolation of the observations in terms of models of interfacial chemistry. The Chemical Structure and Dynamics research program includes five areas described in detail in this report: Reaction mechanisms at solid interfaces; Solution and solution interfaces; Structure and dynamics of biological systems; Analytical methods development; and atmospheric chemistry. Extended abstracts are presented for 23 studies.

  14. Hydration structure and dynamics of a hydroxide ion in water clusters of varying size and temperature: Quantum chemical and ab initio molecular dynamics studies

    International Nuclear Information System (INIS)

    Highlights: ► A theoretical study of hydroxide ion-water clusters is carried for varying cluster size and temperature. ► The structures of OH−(H2O)n are found out through quantum chemical calculations for n = 4, 8, 16 and 20. ► The finite temperature behavior of the clusters is studied through ab initio dynamical simulations. ► The spectral features of OH modes (deuterated) and their dependence on hydrogen bonding states of water are discussed. ► The mechanism and kinetics of proton transfer processes in these anionic clusters are also investigated. - Abstract: We have investigated the hydration structure and dynamics of OH−(H2O)n clusters (n = 4, 8, 16 and 20) by means of quantum chemical and ab initio molecular dynamics calculations. Quantum chemical calculations reveal that the solvation structure of the hydroxide ion transforms from three and four-coordinated surface states to five-coordinated interior state with increase in cluster size. Several other isomeric structures with energies not very different from the most stable isomer are also found. Ab initio simulations show that the most probable configurations at higher temperatures need not be the lowest energy isomeric structure. The rates of proton transfer in these clusters are found to be slower than that in bulk water. The vibrational spectral calculations reveal distinct features for free OH (deuterated) stretch modes of water in different hydrogen bonding states. Effects of temperature on the structural and dynamical properties are also investigated for the largest cluster considered here.

  15. Molecular beam studies of unimolecular and bimolecular chemical reaction dynamics using VUV synchrotron radiation as a product probe

    Energy Technology Data Exchange (ETDEWEB)

    Blank, D.A.

    1997-08-01

    This dissertation describes the use of a new molecular beam apparatus designed to use tunable VUV synchrotron radiation for photoionization of the products from scattering experiments. The apparatus was built at the recently constructed Advanced Light Source at Lawrence Berkeley National Laboratory, a third generation 1-2 GeV synchrotron radiation source. The new apparatus is applied to investigations of the dynamics of unimolecular reactions, photodissociation experiments, and bimolecular reactions, crossed molecular beam experiments. The first chapter describes the new apparatus and the VUV radiation used for photoionization. This is followed by a number of examples of the many advantages provided by using VUV photoionization in comparison with the traditional technique of electron bombardment ionization. At the end of the chapter there is a discussion of the data analysis employed in these scattering experiments. The remaining four chapters are complete investigations of the dynamics of four chemical systems using the new apparatus and provide numerous additional examples of the advantages provided by VUV photoionizaiton of the products. Chapters 2-4 are photofragment translational spectroscopy studies of the photodissociation dynamics of dimethyl sulfoxide, acrylonitrile, and vinyl chloride following absorption at 193 mn. All of these systems have multiple dissociation channels and provide good examples of the ability of the new apparatus to unravel the complex UV photodissociation dynamics that can arise in small polyatomic molecules.

  16. Chemical Reaction Dynamics in Nanoscle Environments

    Energy Technology Data Exchange (ETDEWEB)

    Evelyn M. Goldfield

    2006-09-26

    The major focus of the research in this program is the study of the behavior of molecular systems confined in nanoscale environments. The goal is to develop a theoretical framework for predicting how chemical reactions occur in nanoscale environments. To achieve this goal we have employed ab initio quantum chemistry, classical dynamics and quantum dynamics methods. Much of the research has focused on the behavior of molecules confined within single-walled carbon nanotubes (SWCNTs). We have also studied interactions of small molecules with the exterior surface of SWCNTs. Nonequilibrium molecular dynamics of interfaces of sliding surface interfaces have also been performed.

  17. 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.

  18. Chemical structure and dynamics: Annual report 1996

    International Nuclear Information System (INIS)

    The Chemical Structure and Dynamics (CS ampersand 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

  19. 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.

  20. Quantum Chemical and Molecular Dynamics Study of the Coordination of Th(IV) in Aqueous Solvent

    International Nuclear Information System (INIS)

    In this work, we investigate the solvation of tetravalent thorium Th(IV) in aqueous solution using classical molecular dynamics simulations at the 10 ns scale and based on polarizable force-field approaches, which treat explicitly the covalent character of the metal-water interaction (and its inherent cooperative character). We have carried out a thorough analysis of the accuracy of the ab initio data that we used to adjust the force-field parameters. In particular, we show that large atomic basis sets combined with wave function based methods (such as the MP2 level) have to be preferred to density functional theory when investigating Th(IV)/water aggregates in gas phase. The information extracted from trajectories in solution shows a well structured Th(IV) first hydration shell formed of 8.25 ± 0.2 water molecules and located at about 2.45 ± 0.02 Angstroms and a second shell of 17.5±0.5 water molecules at about 4.75 Angstroms. Concerning the first hydration sphere, our results correspond to the lower bounds of experimental estimates (which range from 8 to 12.7); however, they are in very good agreement with the average of existing experimental data, 2.45 ± 0.02 Angstroms. All our results demonstrate the predictable character of the proposed approach, as well as the need of accounting explicitly for the cooperative character of charge-transfer phenomena affecting the Th(IV)/water interaction to build up reliable and accurate force-field approaches devoted to such studies. (authors)

  1. Quantum chemical and molecular dynamics study of the coordination of Th(IV) in aqueous solvent.

    Science.gov (United States)

    Réal, Florent; Trumm, Michael; Vallet, Valérie; Schimmelpfennig, Bernd; Masella, Michel; Flament, Jean-Pierre

    2010-12-01

    In this work, we investigate the solvation of tetravalent thorium Th(IV) in aqueous solution using classical molecular dynamics simulations at the 10 ns scale and based on polarizable force-field approaches, which treat explicitly the covalent character of the metal-water interaction (and its inherent cooperative character). We have carried out a thorough analysis of the accuracy of the ab initio data that we used to adjust the force-field parameters. In particular, we show that large atomic basis sets combined with wave function-based methods (such as the MP2 level) have to be preferred to density functional theory when investigating Th(IV)/water aggregates in gas phase. The information extracted from trajectories in solution shows a well-structured Th(IV) first hydration shell formed of 8.25 ± 0.2 water molecules and located at about 2.45 ± 0.02 Å and a second shell of 17.5 ± 0.5 water molecules at about 4.75 Å. Concerning the first hydration sphere, our results correspond to the lower bounds of experimental estimates (which range from 8 to 12.7); however, they are in very good agreement with the average of existing experimental data, 2.45 ± 0.02 Å. All our results demonstrate the predictable character of the proposed approach, as well as the need of accounting explicitly for the cooperative character of charge-transfer phenomena affecting the Th(IV)/water interaction to build up reliable and accurate force-field approaches devoted to such studies. PMID:21070066

  2. Production of cold formaldehyde molecules for study and control of chemical reaction dynamics with hydroxyl radicals

    OpenAIRE

    Hudson, Eric R.; Ticknor, Christopher; Sawyer, Brian C.; Taatjes, Craig A.; Lewandowski, H. J.; Bochinski, J. R.; Bohn, John L.; Ye, Jun

    2005-01-01

    We propose a method for controlling a class of low temperature chemical reactions. Specifically, we show the hydrogen abstraction channel in the reaction of formaldehyde (H$_{2}$CO) and the hydroxyl radical (OH) can be controlled through either the molecular state or an external electric field. We also outline experiments for investigating and demonstrating control over this important reaction. To this end, we report the first Stark deceleration of the H$_{2}$CO molecule. We have decelerated ...

  3. Quantum Chemical and Molecular Dynamics Study of the Coordination of Th(IV) in Aqueous Solvent

    OpenAIRE

    Réal, Florent; Trumm, Michael; Vallet, Valérie; Schimmelpfennig, Bernd; Masella, Michel; Flament, Jean-Pierre

    2010-01-01

    In this work, we investigate the solvation of tetravalent thorium Th(IV) in aqueous solution using classical molecular dynamics simulations at the 10 ns scale and based on polarizable force-field approaches, which treat explicitly the covalent character of the metal−water interaction (and its inherent cooperative character). We have carried out a thorough analysis of the accuracy of the ab initio data that we used to adjust the force-field parameters. In particular, we show that large atomic ...

  4. Mechanism resulting in chemical imbalance due to cellular damage associated with mechanoporation: A molecular dynamics study

    Science.gov (United States)

    Sliozberg, Yelena R.; Chantawansri, Tanya L.

    2016-05-01

    To elucidate the mechanism of ion transport through a transmembrane pore, all-atom molecular dynamics simulations were employed. A model membrane where a pore connects the intra- and extra-cellular compartment was considered. Pores with radii of 1.5 nm or less exhibited resealing over the course of 135 ns simulations, and ionic disturbance is minimal. Ion transport through a larger pore (2 nm radius) leads to a substantial change in the intra- and extra-cellular ionic concentrations. The influx of Na+ and Cl- ions down their concentration gradients is greater than the efflux of K+ leading to an osmotic influx of water.

  5. Production of cold formaldehyde molecules for study and control of chemical reaction dynamics with hydroxyl radicals

    CERN Document Server

    Hudson, E R; Sawyer, B C; Taatjes, C A; Lewandowski, H J; Bochinski, J R; Bohn, J L; Ye, J; Hudson, Eric R.; Ticknor, Christopher; Sawyer, Brian C.; Taatjes, Craig A.; Bohn, John L.; Ye, Jun

    2005-01-01

    We propose a method for controlling a class of low temperature chemical reactions. Specifically, we show the hydrogen abstraction channel in the reaction of formaldehyde (H$_{2}$CO) and the hydroxyl radical (OH) can be controlled through either the molecular state or an external electric field. We also outline experiments for investigating and demonstrating control over this important reaction. To this end, we report the first Stark deceleration of the H$_{2}$CO molecule. We have decelerated a molecular beam of H$_{2}$CO essentially to rest, producing cold molecule packets at a temperature of 100 mK with a few million molecules in the packet at a density of $\\sim10^{6}$ cm$^{-3}$.

  6. 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.

  7. Electronic processes in fast thermite chemical reactions: A first-principles molecular dynamics study

    Science.gov (United States)

    Shimojo, Fuyuki; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya

    2008-06-01

    Rapid reaction of a molten metal with an oxide is the key to understanding recently discovered fast reactions in nanothermite composites. We have investigated the thermite reaction of Fe2O3 with aluminum by molecular dynamics simulations with interatomic forces calculated quantum mechanically in the framework of the density functional theory. A redox reaction to form iron metal and Al2O3 initiates with the rapid formation of Al-O bonds at the interface within 1 ps, followed by the propagation of the combustion front with a velocity of 70 m/s for at least 5 ps at 2000 K. The reaction time for an oxygen atom to change character from Fe2O3 type to Al2O3 type at the interface is estimated to be 1.7±0.9ps , and bond-overlap population analysis has been used to calculate reaction rates.

  8. Nonlinear Chemical Dynamics and Synchronization

    Science.gov (United States)

    Li, Ning

    Alan Turing's work on morphogenesis, more than half a century ago, continues to motivate and inspire theoretical and experimental biologists even today. That said, there are very few experimental systems for which Turing's theory is applicable. In this thesis we present an experimental reaction-diffusion system ideally suited for testing Turing's ideas in synthetic "cells" consisting of microfluidically produced surfactant-stabilized emulsions in which droplets containing the Belousov-Zhabotinsky (BZ) oscillatory chemical reactants are dispersed in oil. The BZ reaction has become the prototype of nonlinear dynamics in chemistry and a preferred system for exploring the behavior of coupled nonlinear oscillators. Our system consists of a surfactant stabilized monodisperse emulsion of drops of aqueous BZ solution dispersed in a continuous phase of oil. In contrast to biology, here the chemistry is understood, rate constants are measured and interdrop coupling is purely diffusive. We explore a large set of parameters through control of rate constants, drop size, spacing, and spatial arrangement of the drops in lines and rings in one-dimension (1D) and hexagonal arrays in two-dimensions (2D). The Turing model is regarded as a metaphor for morphogenesis in biology but not for prediction. Here, we develop a quantitative and falsifiable reaction-diffusion model that we experimentally test with synthetic cells. We quantitatively establish the extent to which the Turing model in 1D describes both stationary pattern formation and temporal synchronization of chemical oscillators via reaction-diffusion and in 2D demonstrate that chemical morphogenesis drives physical differentiation in synthetic cells.

  9. The Dart estuary, Devon, UK: a case study of chemical dynamics and pollutant mobility

    Science.gov (United States)

    Schuwerack, P.-M. M.; Neal, M.; Neal, C.

    2007-01-01

    Water, sediments and gill and digestive gland tissues of adult common shore crab (Carcinus maenas), collected at Noss Marina, Sandquay (Britannia Royal Naval College), the Dartmouth Pier, Warfleet Cove and Sugary Cove in the Dart estuary, Devon, UK, were analysed for major, minor and trace elements in spring 2004. Total acid-available measurements analysed included the truly dissolved component and acid-available sediments. Trace metal concentrations are associated largely with particulate and micro-particulate/colloidal phases, the latter being able to pass through standard filter papers. Wide ranges of chemical concentrations were found in the water, sediments and tissues at all the locations. In the water column, 48% of the variance is linked to the sea-salt component (Cl, Na, K, Ca, Mg, B, Li and Sr) and the sediment-associated acid-available fractions are linked to Fe-rich lithogenous materials (Ba, Co, Cu, Fe, Mn, V and Zn). In the sediments, trace elements of Cd, Co, Cr, Fe, Pb, Mn, Ni and V are correlated with the sea salts and associated with the fraction of fine sediments within the total sediment. In the gills and the digestive gland tissues of crabs, high concentrations of Al, Cu and Fe are found and there are correlations between acid-available trace metals of Cu, Cr, Fe, Mn, Ni, Sr and Zn. The relationships between trace metal contaminants, their site-specific concentrations, their temporal and spatial variability and the effects of human activities, such as moorland/agriculture with historic mining and recreational activities in the lower Dart estuary, are discussed.

  10. Molecular dynamics simulation of a chemical reaction

    International Nuclear Information System (INIS)

    Molecular dynamics is used to study the chemical reaction A+A→B+B. It is shown that the reaction rate constant follows the Arrhenius law both for Lennard-Jones and hard sphere interaction potentials between substrate particles. A. For the denser systems the reaction rate is proportional to the value of the radial distribution function at the contact point of two hard spheres. 10 refs, 4 figs

  11. Chemical Structure and Dynamics annual report 1997

    International Nuclear Information System (INIS)

    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

  12. 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.

  13. Molecular beams studies of the energetics and dynamics of elementary chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Hayden, C.C.

    1982-05-01

    Quantum mechanical effects on the angular distribution of HF products from the F + H/sub 2/ reaction were studied using crossed atomic and molecular beams with a rotatable mass spectrometer detector and time-of-flight velocity analysis. Measurement of the singlet-triplet splitting of CH/sub 2/ from the recoil velocities of fragments from ketene photodissociation in a molecular beam is also reported. Partial center-of-mass angular distributions, and velocity flux contour maps have been derived for individual vibrational states of the HF product from the F + H/sub 2/ reaction at collision energies of 2 and 3 kcal/mole. The center-of-mass distributions were obtained by analysis of laboratory angular and time-of-flight measurements of the reactive scattering. The results are consistent with recent three dimensional quantum mechanical scattering calculations, which predict that resonance effects should appear in the product angular distributions in this energy range. The photofragmentation of ketene in a molecular beam was used to measure the singlet-triplet splitting in CH/sub 2/. A rare gas halide excimer laser operating at 351 nm (XeF) and 308 nm (XeCl) dissociated the ketene. Time-of-flight measurements of the fragment velocities allowed determination of the energetics of the dissociation. The /sup 1/A/sub 1/ - /sup 3/B/sub 1/ splitting in CH/sub 2/ was found to be 8.5 +- 0.8 kcal/mole. This agrees with many experimental results, but not with the value of 19.5 kcal/mole derived from recent photodetachment experiments on CH/sub 2//sup -/.

  14. Chemical structure and dynamics. Annual report 1994

    Energy Technology Data Exchange (ETDEWEB)

    Colson, S.D.

    1995-07-01

    The Chemical Structure and Dynamics program was organized as a major component of Pacific Northwest Laboratory`s Environmental and Molecular Sciences Laboratory (EMSL), a state-of-the-art collaborative facility for studies of chemical structure and dynamics. Our program responds to the need for a fundamental, molecular-level understanding of chemistry at the 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, and (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. This research effort was initiated in 1989 and will continue to evolve over the next few years into a program of rigorous studies of fundamental molecular processes in model systems, such as well-characterized surfaces, single-component solutions, clusters, and biological molecules; and studies of complex systems found in the environment (multispecies, multiphase solutions; solid/liquid, liquid/liquid, and gas/surface interfaces; colloidal dispersions; ultrafine aerosols; and functioning biological systems). The success of this program will result in the achievement of a quantitative understanding of chemical reactions at interfaces, and more generally in condensed media, that is comparable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for predictions of macroscopic chemical behavior in condensed and heterogeneous media, adding significantly to the value of field-scale environmental models, the prediction of short- and long-term nuclear waste storage stabilities, and other problems related to the primary missions of the DOE.

  15. 1H NMR study of the solvent THF concerning their structural and dynamical properties in chemically Li-intercalated SWNT

    KAUST Repository

    Schmid, Marc R.

    2011-09-01

    Structural and dynamical properties of the THF solvent in single-walled carbon nanotubes intercalated with lithium are investigated by NMR. 1H NMR experiments reveal the existence of two types of inequivalent THF solvent molecules with different chemical environments and dynamical behavior. At low temperatures THF molecules perpendicularly arranged in between adjacent SWNT presumably exhibit a restricted rotation around their dipolar axis. At higher temperatures THF molecules are isotropically rotating and diffusing along the interstitial channels of the SWNT bundles. © 2011 Elsevier B.V. All rights reserved.

  16. A combined quantum chemical/molecular dynamics study of X-ray photoelectron spectra of polyvinyl alcohol using oligomer models

    International Nuclear Information System (INIS)

    X-ray photoelectron spectroscopy (XPS) is a powerful tool for probing the local chemical environment of atoms near surfaces. When applied to soft matter, such as polymers, XPS spectra are frequently shifted and broadened due to thermal atom motion and by interchain interactions. We present a combined quantum mechanical QM/molecular dynamics (MD) simulation of X-ray photoelectron spectra of polyvinyl alcohol (PVA) using oligomer models in order to account for and quantify these effects on the XPS (C1s) signal. In our study, molecular dynamics at finite temperature were performed with a classical forcefield and by ab initio MD (AIMD) using the Car–Parrinello method. Snapshots along the trajectories represent possible conformers and/or neighbouring environments, with different C1s ionization potentials for individual C atoms leading to broadened XPS peaks. The latter are determined by Δ-Kohn Sham calculations. We also examine the experimental practice of gauging XPS (C1s) signals of alkylic C-atoms in C-containing polymers to the C1s signal of polyethylene. We find that (i) the experimental XPS (C1s) spectra of PVA (position and width) can be roughly represented by single-strand models, (ii) interchain interactions lead to red-shifts of the XPS peaks by about 0.6 eV, and (iii) AIMD simulations match the findings from classical MD semi-quantitatively. Further, (iv) the gauging procedure of XPS (C1s) signals to the values of PE, introduces errors of about 0.5 eV

  17. Synchronization Dynamics of Coupled Chemical Oscillators

    Science.gov (United States)

    Tompkins, Nathan

    The synchronization dynamics of complex networks have been extensively studied over the past few decades due to their ubiquity in the natural world. Prominent examples include cardiac rhythms, circadian rhythms, the flashing of fireflies, predator/prey population dynamics, mammalian gait, human applause, pendulum clocks, the electrical grid, and of the course the brain. Detailed experiments have been done to map the topology of many of these systems and significant advances have been made to describe the mathematics of these networks. Compared to these bodies of work relatively little has been done to directly test the role of topology in the synchronization dynamics of coupled oscillators. This Dissertation develops technology to examine the dynamics due to topology within networks of discrete oscillatory components. The oscillatory system used here consists of the photo-inhibitable Belousov-Zhabotinsky (BZ) reaction water-in-oil emulsion where the oscillatory drops are diffusively coupled to one another and the topology is defined by the geometry of the diffusive connections. Ring networks are created from a close-packed 2D array of drops using the Programmable Illumination Microscope (PIM) in order to test Turing's theory of morphogenesis directly. Further technology is developed to create custom planar networks of BZ drops in more complicated topologies which can be individually perturbed using illumination from the PIM. The work presented here establishes the validity of using the BZ emulsion system with a PIM to study the topology induced effects on the synchronization dynamics of coupled chemical oscillators, tests the successes and limitations of Turing's theory of morphogenesis, and develops new technology to further probe the effects of network topology on a system of coupled oscillators. Finally, this Dissertation concludes by describing ongoing experiments which utilize this new technology to examine topology induced transitions of synchronization

  18. Annual Report 1998: Chemical Structure and Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    SD Colson; RS McDowell

    1999-05-10

    The Chemical Structure and Dynamics (CS&D) program is a major component of the William R. Wiley Environmental Molecular Sciences Labo- ratory (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 interracial chemical processes within which the new knowledge generated can be brought to bear on complex phenomena in envi- ronmental chemistry and in nuclear waste proc- essing and storage; and (3) developing state-of- the-art analytical methods for characterizing com- plex materials of the types found in stored wastes and contaminated soils, and for detecting and monitoring trace atmospheric species. Our program aims at achieving a quantitative understanding of chemical reactions at interfaces and, more generally, in condensed media, compa- rable to that currently available for gas-phase reactions. This understanding will form the basis for the development of a priori theories for pre- dicting macroscopic chemical behavior in con- densed and heterogeneous media, which will add significantly to the value of field-scale envi- ronmental models, predictions of short- and long- term nuclear waste storage stabilities, and other areas related to the primary missions of the U.S. Department of Energy (DOE).

  19. Chemical kinetics and reaction dynamics

    CERN Document Server

    Houston, Paul L

    2006-01-01

    This text teaches the principles underlying modern chemical kinetics in a clear, direct fashion, using several examples to enhance basic understanding. It features solutions to selected problems, with separate sections and appendices that cover more technical applications.Each chapter is self-contained and features an introduction that identifies its basic goals, their significance, and a general plan for their achievement. This text's important aims are to demonstrate that the basic kinetic principles are essential to the solution of modern chemical problems, and to show how the underlying qu

  20. Structure and dynamics of acrolein in 1,3(π,π *) excited electronic states: A quantum-chemical study

    Science.gov (United States)

    Bokareva, O. S.; Bataev, V. A.; Pupyshev, V. I.; Godunov, I. A.

    2009-08-01

    The geometrical structure, conformer energy differences, and conformational and vibrational dynamics of acrolein in 1,3(π,π *) electronic states were investigated using a number of single- and multi-reference quantum-chemical methods. Peculiarities of acrolein in the 1(π,π *) state were described with both conformers being significantly non-planar. A Valence Focal-Point Analysis of the conformer energy difference in the 3(π,π *) state was performed. The coupling of the internal rotation about C sbnd C and C dbnd C bonds with large amplitude molecular motions, such as non-planar distortions of carbonyl, methylene, and methyne fragments was also investigated. The corresponding two-dimensional PES sections were constructed.

  1. Chemical Imaging and Dynamical Studies of Reactivity and Emergent Behavior in Complex Interfacial Systems. Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Sibener, Steven J. [University of Chicago, IL (United States)

    2014-03-11

    This research program explored the efficacy of using molecular-level manipulation, imaging and scanning tunneling spectroscopy in conjunction with supersonic molecular beam gas-surface scattering to significantly enhance our understanding of chemical processes occurring on well-characterized interfaces. One program focus was on the spatially-resolved emergent behavior of complex reaction systems as a function of the local geometry and density of adsorbate-substrate systems under reaction conditions. Another focus was on elucidating the emergent electronic and related reactivity characteristics of intentionally constructed single and multicomponent atom- and nanoparticle-based materials. We also examined emergent chirality and self-organization in adsorbed molecular systems where collective interactions between adsorbates and the supporting interface lead to spatial symmetry breaking. In many of these studies we combined the advantages of scanning tunneling (STM) and atomic force (AFM) imaging, scanning tunneling local electronic spectroscopy (STS), and reactive supersonic molecular beams to elucidate precise details of interfacial reactivity that had not been observed by more traditional surface science methods. Using these methods, it was possible to examine, for example, the differential reactivity of molecules adsorbed at different bonding sites in conjunction with how reactivity is modified by the local configuration of nearby adsorbates. At the core of this effort was the goal of significantly extending our understanding of interfacial atomic-scale interactions to create, with intent, molecular assemblies and materials with advanced chemical and physical properties. This ambitious program addressed several key topics in DOE Grand Challenge Science, including emergent chemical and physical properties in condensed phase systems, novel uses of chemical imaging, and the development of advanced reactivity concepts in combustion and catalysis including carbon

  2. 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.

  3. Chiral recognition of Propranolol enantiomers by β-Cyclodextrin: Quantum chemical calculation and molecular dynamics simulation studies

    Energy Technology Data Exchange (ETDEWEB)

    Ghatee, Mohammad Hadi, E-mail: ghatee@susc.ac.ir; Sedghamiz, Tahereh

    2014-12-05

    Highlights: • Enantiomeric recognition of Propranolol studied by β-Cyclodextrin complexations. • Complexes characterized by PM3 and molecular dynamics (MD) simulation methods. • Results support more stability of R-enantiomer complex in gas and in aqueous solution phases. • Gas phase complexes are unlikely free-energy-wise, though solution phase’s are more likely. • Higher molecular diffusion in aqueous solution phase is inherent to S-enantiomer. - Abstract: Enantiomeric recognition of Propranolol by complexation with β-Cyclodextrin was studied by PM3 method and molecular dynamics (MD) simulation. Gas phase results show that the R-enantiomer complex is more stable than the S-enantiomer complex by 8.54 kJ/mol (Hartree–Fock energy). Using polarized continuum model, solution phase of R-enantiomer complex was found to be more stable than S-enantiomer complex by 25.95 kJ/mol. Both complexes hardly occur at room temperature free-energy-wise, though, complexation with R-enantiomer is more favorable than with S-enantiomer enthalpy-wise. Also, complexes were studied by molecular dynamics simulation in gas and solution phases. More stability of R-enantiomer complex in gas phase is confirmed by MD van der Waals energy (5.04 kJ/mol) and closely by the counterpart PM3 binding energy (8.54 kJ/mol). Simulation in solution phase indicates more stability of R-enantiomer complex. Finally, simulated transport property provides insight into the high anisotropic atoms motion according to which S-Propranolol found possessing significantly higher dynamics.

  4. Chiral recognition of Propranolol enantiomers by β-Cyclodextrin: Quantum chemical calculation and molecular dynamics simulation studies

    International Nuclear Information System (INIS)

    Highlights: • Enantiomeric recognition of Propranolol studied by β-Cyclodextrin complexations. • Complexes characterized by PM3 and molecular dynamics (MD) simulation methods. • Results support more stability of R-enantiomer complex in gas and in aqueous solution phases. • Gas phase complexes are unlikely free-energy-wise, though solution phase’s are more likely. • Higher molecular diffusion in aqueous solution phase is inherent to S-enantiomer. - Abstract: Enantiomeric recognition of Propranolol by complexation with β-Cyclodextrin was studied by PM3 method and molecular dynamics (MD) simulation. Gas phase results show that the R-enantiomer complex is more stable than the S-enantiomer complex by 8.54 kJ/mol (Hartree–Fock energy). Using polarized continuum model, solution phase of R-enantiomer complex was found to be more stable than S-enantiomer complex by 25.95 kJ/mol. Both complexes hardly occur at room temperature free-energy-wise, though, complexation with R-enantiomer is more favorable than with S-enantiomer enthalpy-wise. Also, complexes were studied by molecular dynamics simulation in gas and solution phases. More stability of R-enantiomer complex in gas phase is confirmed by MD van der Waals energy (5.04 kJ/mol) and closely by the counterpart PM3 binding energy (8.54 kJ/mol). Simulation in solution phase indicates more stability of R-enantiomer complex. Finally, simulated transport property provides insight into the high anisotropic atoms motion according to which S-Propranolol found possessing significantly higher dynamics

  5. Dynamic Simulation of Chemical Kinetics in Microcontroller

    Directory of Open Access Journals (Sweden)

    Renato Dutra Pereira Filho

    2014-12-01

    Full Text Available Arduino boards are interesting computational tools due to low cost and power consumption, as well as I/O ports, both analogs and digitals. Yet, small memory and clock frequency with truncation errors may disrupt numerical processing. This study aimed to design and evaluate the performance of a dynamic simulation based on ODEs in the Arduino, with three evaluated microprocessors; ATMEGA 328P and 2560, both 8 bits, and SAM3X8E Atmel ARM CORTEX – 32 bits. The study case was a batch reactor dynamic simulation. The Runge-Kutta 4th order algorithm was written in C++ and compiled for EPROM utilization. The output was a 115000bit/s serial connection. Processing time was almost identical for 8 bits architectures, while 32 bits was 25% faster. Without the serial connection the 8 bits architectures were 16 times faster and the 32 bits was 42 times faster. Error truncation was similar, since the floating points are done through software. The Arduino platform, despite its modest hardware, allows simple chemical systems simulation

  6. Resonance Raman spectroscopy and ultrafast chemical dynamics

    OpenAIRE

    Biswas, Nandita; Umapathy, Siva

    1998-01-01

    Resonance Raman (RR) spectroscopy is normally used to study the excited state structure and dynamics of various photochemical and photophysical processes. In this article. we briefly discuss the various applications of RR spectroscopy and show how experimental RR intensities along with time-dependent wavepacket dynamical calculations can be used to study the excited state structure and ultrafast dynamics (\\sim 10(- 15) secs).

  7. Molecular dynamics and quantum chemical calculation studies on 4,4-dimethyl-3-thiosemicarbazide as corrosion inhibitor in 2.5 M H2SO4

    International Nuclear Information System (INIS)

    Highlights: → This work deals with a study of chemical additives for corrosion inhibition of mild steel in acidic conditions. → The effects of the additive 4,4-dimethyl-3-thiosemicarbazide (DTS) on mild steel were studied by means of electrochemical techniques. → Quantum chemical calculations and molecular dynamic model were performed to characterize the inhibition mechanism. → The calculations provided information that helps in the analysis/interpretation of the experimental work. - Abstract: The inhibition of mild steel corrosion in a 2.5 M H2SO4 solution by 4,4-dimethyl-3-thiosemicarbazide (DTS) was studied at 30 deg. C using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Quantum chemical parameters were calculated for DTS using PM3-SCF method. The molecular dynamic method was performed to simulate the adsorption of the DTS molecules on Fe surface. Results showed that DTS performed excellent as inhibitor for mild steel corrosion in a 2.5 M H2SO4 solution and indicated that the inhibition efficiencies increase with the concentration of inhibitor. Theoretical results indicated that DTS could adsorb on the mild steel surface firmly through heteroatoms.

  8. Nanomotor dynamics in a chemically oscillating medium.

    Science.gov (United States)

    Robertson, Bryan; Kapral, Raymond

    2015-04-21

    Synthetic nanomotors powered by chemical reactions have potential uses as cargo transport vehicles in both in vivo and in vitro applications. In many situations, motors will have to operate in out-of-equilibrium complex chemically reacting media, which supply fuel to the motors and remove the products they produce. Using molecular simulation and mean-field theory, this paper describes some of the new features that arise when a chemically powered nanomotor, operating through a diffusiophoretic mechanism, moves in an environment that supports an oscillatory chemical reaction network. It is shown how oscillations in the concentrations in chemical species in the environment give rise to oscillatory motor dynamics. More importantly, since the catalytic reactions on the motor that are responsible for its propulsion couple to the bulk phase reaction network, the motor can change its local environment. This process can give rise to distinctive spatiotemporal structures in reaction-diffusion media that occur as a result of active motor motion. Such locally induced nonequilibrium structure will play an important role in applications that involve motor dynamics in complex chemical media. PMID:25903905

  9. Nanomotor dynamics in a chemically oscillating medium

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Bryan, E-mail: bryan.robertson@mail.utoronto.ca; Kapral, Raymond, E-mail: rkapral@chem.utoronto.ca [Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)

    2015-04-21

    Synthetic nanomotors powered by chemical reactions have potential uses as cargo transport vehicles in both in vivo and in vitro applications. In many situations, motors will have to operate in out-of-equilibrium complex chemically reacting media, which supply fuel to the motors and remove the products they produce. Using molecular simulation and mean-field theory, this paper describes some of the new features that arise when a chemically powered nanomotor, operating through a diffusiophoretic mechanism, moves in an environment that supports an oscillatory chemical reaction network. It is shown how oscillations in the concentrations in chemical species in the environment give rise to oscillatory motor dynamics. More importantly, since the catalytic reactions on the motor that are responsible for its propulsion couple to the bulk phase reaction network, the motor can change its local environment. This process can give rise to distinctive spatiotemporal structures in reaction-diffusion media that occur as a result of active motor motion. Such locally induced nonequilibrium structure will play an important role in applications that involve motor dynamics in complex chemical media.

  10. Nanomotor dynamics in a chemically oscillating medium

    International Nuclear Information System (INIS)

    Synthetic nanomotors powered by chemical reactions have potential uses as cargo transport vehicles in both in vivo and in vitro applications. In many situations, motors will have to operate in out-of-equilibrium complex chemically reacting media, which supply fuel to the motors and remove the products they produce. Using molecular simulation and mean-field theory, this paper describes some of the new features that arise when a chemically powered nanomotor, operating through a diffusiophoretic mechanism, moves in an environment that supports an oscillatory chemical reaction network. It is shown how oscillations in the concentrations in chemical species in the environment give rise to oscillatory motor dynamics. More importantly, since the catalytic reactions on the motor that are responsible for its propulsion couple to the bulk phase reaction network, the motor can change its local environment. This process can give rise to distinctive spatiotemporal structures in reaction-diffusion media that occur as a result of active motor motion. Such locally induced nonequilibrium structure will play an important role in applications that involve motor dynamics in complex chemical media

  11. Hot spot formation and chemical reaction initiation in shocked HMX crystals with nanovoids: a large-scale reactive molecular dynamics study.

    Science.gov (United States)

    Zhou, Tingting; Lou, Jianfeng; Zhang, Yangeng; Song, Huajie; Huang, Fenglei

    2016-07-14

    We report million-atom reactive molecular dynamic simulations of shock initiation of β-cyclotetramethylene tetranitramine (β-HMX) single crystals containing nanometer-scale spherical voids. Shock induced void collapse and subsequent hot spot formation as well as chemical reaction initiation are observed which depend on the void size and impact strength. For an impact velocity of 1 km s(-1) and a void radius of 4 nm, the void collapse process includes three stages; the dominant mechanism is the convergence of upstream molecules toward the centerline and the downstream surface of the void forming flowing molecules. Hot spot formation also undergoes three stages, and the principal mechanism is kinetic energy transforming to thermal energy due to the collision of flowing molecules on the downstream surface. The high temperature of the hot spot initiates a local chemical reaction, and the breakage of the N-NO2 bond plays the key role in the initial reaction mechanism. The impact strength and void size have noticeable effects on the shock dynamical process, resulting in a variation of the predominant mechanisms leading to void collapse and hot spot formation. Larger voids or stronger shocks result in more intense hot spots and, thus, more violent chemical reactions, promoting more reaction channels and generating more reaction products in a shorter duration. The reaction products are mainly concentrated in the developed hot spot, indicating that the chemical reactivity of the hmx crystal is greatly enhanced by void collapse. The detailed information derived from this study can aid a thorough understanding of the role of void collapse in hot spot formation and the chemical reaction initiation of explosives. PMID:27307079

  12. Catalysis of Dynamical Chiral Symmetry Breaking by Chiral Chemical Potential

    CERN Document Server

    Braguta, V V

    2016-01-01

    In this paper we study the properties of media with chiral imbalance parameterized by chiral chemical potential. It is shown that depending on the strength of interaction between constituents in the media the chiral chemical potential either creates or enhances dynamical chiral symmetry breaking. Thus the chiral chemical potential plays a role of the catalyst of dynamical chiral symmetry breaking. Physically this effect results from the appearance of the Fermi surface and additional fermion states on this surface which take part in dynamical chiral symmetry breaking. An interesting conclusion which can be drawn is that at sufficiently small temperature chiral plasma is unstable with respect to condensation of Cooper pairs and dynamical chiral symmetry breaking even for vanishingly small interactions between constituents.

  13. Reactive chemical dynamics through conical intersections

    Indian Academy of Sciences (India)

    S Ghosal; B Jayachander Rao; S Mahapatra

    2007-09-01

    Reaction dynamics of prototypical, D + H2 and Cl (2P) + H2, chemical reactions occurring through the conical intersections of the respective coupled multi-sheeted potential energy surfaces is examined here. In addition to the electronic coupling, nonadiabatic effects due to relativistic spin-orbit coupling are also considered for the latter reaction. A time-dependent wave packet propagation approach is undertaken and the quantum dynamical observables viz., energy resolved reaction probabilities, integral reaction cross-sections and thermal rate constants are reported.

  14. Neural Networks in Chemical Reaction Dynamics

    CERN Document Server

    Raff, Lionel; Hagan, Martin

    2011-01-01

    This monograph presents recent advances in neural network (NN) approaches and applications to chemical reaction dynamics. Topics covered include: (i) the development of ab initio potential-energy surfaces (PES) for complex multichannel systems using modified novelty sampling and feedforward NNs; (ii) methods for sampling the configuration space of critical importance, such as trajectory and novelty sampling methods and gradient fitting methods; (iii) parametrization of interatomic potential functions using a genetic algorithm accelerated with a NN; (iv) parametrization of analytic interatomic

  15. Cell patterns emerge from coupled chemical and physical fields with cell proliferation dynamics: the Arabidopsis thaliana root as a study system.

    Directory of Open Access Journals (Sweden)

    Rafael A Barrio

    Full Text Available A central issue in developmental biology is to uncover the mechanisms by which stem cells maintain their capacity to regenerate, yet at the same time produce daughter cells that differentiate and attain their ultimate fate as a functional part of a tissue or an organ. In this paper we propose that, during development, cells within growing organs obtain positional information from a macroscopic physical field that is produced in space while cells are proliferating. This dynamical interaction triggers and responds to chemical and genetic processes that are specific to each biological system. We chose the root apical meristem of Arabidopsis thaliana to develop our dynamical model because this system is well studied at the molecular, genetic and cellular levels and has the key traits of multicellular stem-cell niches. We built a dynamical model that couples fundamental molecular mechanisms of the cell cycle to a tension physical field and to auxin dynamics, both of which are known to play a role in root development. We perform extensive numerical calculations that allow for quantitative comparison with experimental measurements that consider the cellular patterns at the root tip. Our model recovers, as an emergent pattern, the transition from proliferative to transition and elongation domains, characteristic of stem-cell niches in multicellular organisms. In addition, we successfully predict altered cellular patterns that are expected under various applied auxin treatments or modified physical growth conditions. Our modeling platform may be extended to explicitly consider gene regulatory networks or to treat other developmental systems.

  16. Adsorption and dissociation of molecular hydrogen on Pt/CeO2 catalyst in the hydrogen spillover process: A quantum chemical molecular dynamics study

    International Nuclear Information System (INIS)

    Ultra accelerated quantum chemical molecular dynamics method (UA-QCMD) was used to study the dynamics of the hydrogen spillover process on Pt/CeO2 catalyst surface for the first time. The direct observation of dissociative adsorption of hydrogen on Pt/CeO2 catalyst surface as well as the diffusion of dissociative hydrogen from the Pt/CeO2 catalyst surface was simulated. The diffusion of the hydrogen atom in the gas phase explains the high reactivity observed in the hydrogen spillover process. Chemical changes, change of adsorption states and structural changes were investigated. It was observed that parallel adsorption of hydrogen facilitates the dissociative adsorption leading to hydrogen desorption. Impact with perpendicular adsorption of hydrogen causes the molecular adsorption on the surface, which decelerates the hydrogen spillover. The present study also indicates that the CeO2 support has strong interaction with Pt catalyst, which may cause an increase in Pt activity as well as enhancement of the metal catalyst dispersions and hence increasing the rate of hydrogen spillover reaction.

  17. Complex chemical dynamics through engineering-like methods

    OpenAIRE

    Moro, Lorenzo

    2014-01-01

    Most of the problems in modern structural design can be described with a set of equation; solutions of these mathematical models can lead the engineer and designer to get info during the design stage. The same holds true for physical-chemistry; this branch of chemistry uses mathematics and physics in order to explain real chemical phenomena. In this work two extremely different chemical processes will be studied; the dynamic of an artificial molecular motor and the generation and propagation ...

  18. Insight into the effect of inhibitor resistant S130G mutant on physico-chemical properties of SHV type beta-lactamase: a molecular dynamics study.

    Directory of Open Access Journals (Sweden)

    Mohd Hassan Baig

    Full Text Available Bacterial resistance is a serious threat to human health. The production of β-lactamase, which inactivates β-lactams is most common cause of resistance to the β-lactam antibiotics. The Class A enzymes are most frequently encountered among the four β-lactamases in the clinic isolates. Mutations in class A β-lactamases play a crucial role in substrate and inhibitor specificity. SHV and TEM type are known to be most common class A β-lactamases. In the present study, we have analyzed the effect of inhibitor resistant S130G point mutation of SHV type Class-A β-lactamase using molecular dynamics and other in silico approaches. Our study involved the use of different in silico methods to investigate the affect of S130G point mutation on the major physico-chemical properties of SHV type class A β-lactamase. We have used molecular dynamics approach to compare the dynamic behaviour of native and S130G mutant form of SHV β-lactamase by analyzing different properties like root mean square deviation (RMSD, H-bond, Radius of gyration (Rg and RMS fluctuation of mutation. The results clearly suggest notable loss in the stability of S130G mutant that may further lead to decrease in substrate specificity of SHV. Molecular docking further indicates that S130G mutation decreases the binding affinity of all the three inhibitors in clinical practice.

  19. The Chemical Evolution of Dynamically Hot Galaxies

    Directory of Open Access Journals (Sweden)

    Michael G. Richer

    2001-01-01

    Full Text Available We investigate the chemical properties of M32, the bulges of M31 and the Milky Way, and the dwarf spheroidal galaxies NGC 205, NGC 185, Sagittarius, and Fornax using oxygen abundances for their planetary nebulae. Our principal result is that the mean stellar oxygen abundances correlate very well with thei r mean velocity dispersions, implying that the balance between energy input from type II supernovae and the gravitational potential controls chemical evolution in bulges, ellipticals, and dwarf spheroidals. It appears that chemical evolution ceases once supernovae have injected sufficient energy that a galacti c wind develops. All of the galaxies follow a single relation between oxygen abundance and luminosity, but the dwarf spheroidals have systematically higher [O/Fe] ratios than the other galaxies. Consequently, dynamically hot galaxies do not share a common star formation history nor need to a common chemical evolution, despite attaining similar mean stellar oxygen abundances when formin g similar masses. The oxygen abundances support previous indications that stars in higher luminosity ellipticals and bulges were formed on a shorter time scale than their counterparts in less luminous systems.

  20. The chemical bond structure and dynamics

    CERN Document Server

    Zewail, Ahmed

    1992-01-01

    This inspired book by some of the most influential scientists of our time--including six Nobel laureates--chronicles our emerging understanding of the chemical bond through the last nine decades and into the future. From Pauling's early structural work using x-ray and electron diffraction to Zewail's femtosecond lasers that probe molecular dynamics in real time; from Crick's molecular biology to Rich's molecular recognition, this book explores a rich tradition of scientific heritage and accomplishment. The perspectives given by Pauling, Perutz, Rich, Crick, Porter, Polanyi, Herschbach, Zewail,

  1. Application of synchrotron radiation in chemical dynamics

    International Nuclear Information System (INIS)

    In October 1992, funding was approved to begin construction of a beamline and two end stations to support chemical dynamics experiments at LBL's Advanced Light Source (ALS). This workshop was organized to develop specifications and plans and to select a working team to design and supervise the construction project. Target date for starting the experiments is January 1995. Conclusions of the workshop and representative experiments proposed in earlier workshops to form the basis for beamline plans and end-station designs are summarized in this report. 6 figs

  2. Molecular dynamics study of the elastic response of crystalline, amorphous and chemically disordered NiZr2

    International Nuclear Information System (INIS)

    In this paper the authors calculate the shear elastic constants of the alloy NiZr2 by molecular dynamics simulations in the crystalline and amorphous phases as well as upon introduction of antisite defects in the crystal at T = 300K. For s (long range order parameter) equal to 0.5, the system is amorphous and C' is larger than the same quantity relative to the crystal whereas C44 and C66 are smaller

  3. Experimental studies on the dynamics of radionuclide transport in soils and plants: an investigation of the effects of soil type and chemical form

    International Nuclear Information System (INIS)

    The dynamics and distribution of radioisotopes of Ce, Ru, I, Sr and Cs have been studied in soils and grass in greenhouse conditions. Two soil types, representative of localities close to existing nuclear installations, have been investigated in combination with two chemical forms of Ce, Ru, Sr and Cs. The effect of administration of iodine at two different periods of growth has been investigated using I-125 and I-131. The time-dependent behaviour of the radionuclides has also been investigated by means of four harvests at various times after administration of the radionuclides. Parameter values for sorption of radionuclides to soil inorganic and organic fractions were determined by means of serial chemical extraction of soils at each harvest, and for transport from soil to root and from root to shoot by means of assay of derived plant material. In addition, the vertical distribution of radionuclides in the soil profile was determined by means of external scanning of undisturbed pots. The data from these scans have been used to calculate transfer coefficients for loss of radionuclides from surface soil for comparison with soil solution and mass transport parameters used in the model. The results are discussed. (author)

  4. Structure and dynamics of poly(ethylene- co-1,5-hexadiene) as studied by solid state 13C NMR and quantum chemical calculations

    Science.gov (United States)

    Kurosu, Hiromichi; Yamamoto, Yuuri; Fujikawa, Aki; Kawabata, Emika; Sone, Masato; Naga, Naofumi

    2009-03-01

    Poly(ethylene- co-1,5-hexadiene) with 1,5-hexadiene (HD) contents of 1.8, 8.1, 9.7 and 20.3% was prepared by copolymerization of ethylene and HD involving intermolecular cyclization. Higher-order structures and dynamics of these samples were studied by solid state NMR and quantum chemistry. The 13C solid state NMR spectra and 13C spin-lattice relaxation time ( T1) of the samples were measured. The observed 13C CP/MAS and PST/MAS NMR spectra for all samples were decomposed into six peaks. The cyclopentane units incorporated in the main chain of polyethylene affected not only the crystalline structure but also the noncrystalline structure. This causes a trans-rich conformation in the noncrystalline region. Even in the melt-quenched samples, incorporation of the cyclopentane structure into the polyethylene chain suppresses the increase in the gauche structure in the noncrystalline region. Based on the 13C chemical shift of the methylene carbon, the low cyclopentane content sample assumes an orthorhombic crystal structure, and the high cyclopentane content samples assume a hexagonal-type chain packing. 13C spin-lattice relaxation times show that the crystalline region of the low cyclopentane content sample has two regions with different mobility, although the high cyclopentane content samples have only one region with a high mobility for each peak. Furthermore, quantum chemical calculations for the 13C NMR shieldings were carried out for precise assignment of the peaks.

  5. Molecular Dynamics Simulations of Solutions at Constant Chemical Potential

    CERN Document Server

    Perego, Claudio; Parrinello, Michele

    2015-01-01

    Molecular Dynamics studies of chemical processes in solution are of great value in a wide spectrum of applications, that range from nano-technology to pharmaceutical chemistry. However, these calculations are affected by severe finite-size effects, such as the solution being depleted as the chemical process proceeds, that influence the outcome of the simulations. To overcome these limitations, one must allow the system to exchange molecules with a macroscopic reservoir, thus sampling a Grand-Canonical ensemble. Despite the fact that different remedies have been proposed, this still represents a key challenge in molecular simulations. In the present work we propose the C$\\mu$MD method, which introduces an external force that controls the environment of the chemical process of interest. This external force, drawing molecules from a finite reservoir, maintains the chemical potential constant in the region where the process takes place. We have applied the C$\\mu$MD method to the paradigmatic case of urea crystall...

  6. Quantum dynamics of fast chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Light, J.C. [Univ. of Chicago, IL (United States)

    1993-12-01

    The aims of this research are to explore, develop, and apply theoretical methods for the evaluation of the dynamics of gas phase collision processes, primarily chemical reactions. The primary theoretical tools developed for this work have been quantum scattering theory, both in time dependent and time independent forms. Over the past several years, the authors have developed and applied methods for the direct quantum evaluation of thermal rate constants, applying these to the evaluation of the hydrogen isotopic exchange reactions, applied wave packet propagation techniques to the dissociation of Rydberg H{sub 3}, incorporated optical potentials into the evaluation of thermal rate constants, evaluated the use of optical potentials for state-to-state reaction probability evaluations, and, most recently, have developed quantum approaches for electronically non-adiabatic reactions which may be applied to simplify calculations of reactive, but electronically adiabatic systems. Evaluation of the thermal rate constants and the dissociation of H{sub 3} were reported last year, and have now been published.

  7. Dynamics of self-propelled nanomotors in chemically active media

    Science.gov (United States)

    Thakur, Snigdha; Kapral, Raymond

    2011-07-01

    Synthetic chemically powered nanomotors often rely on the environment for their fuel supply. The propulsion properties of such motors can be altered if the environment in which they move is chemically active. The dynamical properties of sphere dimer motors, composed of linked catalytic and noncatalytic monomers, are investigated in active media. Chemical reactions occur at the catalytic monomer and the reactant or product of this reaction is involved in cubic autocatalytic or linear reactions that take place in the bulk phase environment. For these reactions, as the bulk phase reaction rates increase, the motor propulsion velocity decreases. For the cubic autocatalytic reaction, this net effect arises from a competition between a reduction of the nonequilibrium concentration gradient that leads to smaller velocity and the generation of fuel in the environment that tends to increase the motor propulsion. The role played by detailed balance in determining the form of the concentration gradient in the motor vicinity in the active medium is studied. Simulations are carried out using reactive multiparticle collision dynamics and compared with theoretical models to obtain further insight into sphere dimer dynamics in active media.

  8. Model study of the impacts of emissions, chemical and dynamical processes on the CO variability in the tropical upper troposphere and lower stratosphere

    Directory of Open Access Journals (Sweden)

    Chunxiao Wang

    2015-07-01

    Full Text Available The Whole Atmosphere Community Climate Model (WACCM is used to investigate the relative importance of CO emissions, chemical and dynamical processes on temporal variations of CO in the tropical upper troposphere (UT and the lower stratosphere (LS. The semi-annual oscillation (SAO in the tropical UT and the annual oscillation (AO in the tropical LS detected in the MLS CO observations can be well captured by the model. The model simulations reveal that the CO surface emissions explain most of the SAO signals in the tropical UT, with the remainder being attributed to dynamical and chemical processes. The CO AO in the LS primarily results from combined effects of dynamical and chemical processes while the dynamical and chemical processes make opposite contributions to the CO AO signals, consistent with the previous findings. Our analysis further reveals that CO surface emissions tend to weaken the amplitude of the CO annual cycle in the tropical LS, while the annual variations in the meridional component of the Brewer–Dobson (BD circulation can amplify the annual variations of CO above 30 hPa. The model simulations also indicate that the CO annual cycle in the LS has a mixed behaviour with the annual variations of tropical upwelling reflected in CO between ~70 and ~50 hPa and a standard tape-recorder signal above 50 hPa. Moreover, the AO signals of CO exist up to 10 hPa when the chemical processes are switched off. The temporal and spatial variations of CO in the UT and near the tropopause are mainly driven by the upward transport of CO by tropical deep convection and the Asian summer monsoon circulation. In the early stage of the South Asian summer monsoon over the Bay of Bengal and the South China in the late spring and early summer, the transport of the CO surface emissions over Southeast Asia by the South Asian summer monsoon leads to an increase in the tropical CO, but the horizontal transport from the extratropics into the tropics (termed in

  9. Semiclassical methods in chemical reaction dynamics

    International Nuclear Information System (INIS)

    Semiclassical approximations, simple as well as rigorous, are formulated in order to be able to describe gas phase chemical reactions in large systems. We formulate a simple but accurate semiclassical model for incorporating multidimensional tunneling in classical trajectory simulations. This model is based on the existence of locally conserved actions around the saddle point region on a multidimensional potential energy surface. Using classical perturbation theory and monitoring the imaginary action as a function of time along a classical trajectory we calculate state-specific unimolecular decay rates for a model two dimensional potential with coupling. Results are in good comparison with exact quantum results for the potential over a wide range of coupling constants. We propose a new semiclassical hybrid method to calculate state-to-state S-matrix elements for bimolecular reactive scattering. The accuracy of the Van Vleck-Gutzwiller propagator and the short time dynamics of the system make this method self-consistent and accurate. We also go beyond the stationary phase approximation by doing the resulting integrals exactly (numerically). As a result, classically forbidden probabilties are calculated with purely real time classical trajectories within this approach. Application to the one dimensional Eckart barrier demonstrates the accuracy of this approach. Successful application of the semiclassical hybrid approach to collinear reactive scattering is prevented by the phenomenon of chaotic scattering. The modified Filinov approach to evaluating the integrals is discussed, but application to collinear systems requires a more careful analysis. In three and higher dimensional scattering systems, chaotic scattering is suppressed and hence the accuracy and usefulness of the semiclassical method should be tested for such systems

  10. Semiclassical methods in chemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Keshavamurthy, S.

    1994-12-01

    Semiclassical approximations, simple as well as rigorous, are formulated in order to be able to describe gas phase chemical reactions in large systems. We formulate a simple but accurate semiclassical model for incorporating multidimensional tunneling in classical trajectory simulations. This model is based on the existence of locally conserved actions around the saddle point region on a multidimensional potential energy surface. Using classical perturbation theory and monitoring the imaginary action as a function of time along a classical trajectory we calculate state-specific unimolecular decay rates for a model two dimensional potential with coupling. Results are in good comparison with exact quantum results for the potential over a wide range of coupling constants. We propose a new semiclassical hybrid method to calculate state-to-state S-matrix elements for bimolecular reactive scattering. The accuracy of the Van Vleck-Gutzwiller propagator and the short time dynamics of the system make this method self-consistent and accurate. We also go beyond the stationary phase approximation by doing the resulting integrals exactly (numerically). As a result, classically forbidden probabilties are calculated with purely real time classical trajectories within this approach. Application to the one dimensional Eckart barrier demonstrates the accuracy of this approach. Successful application of the semiclassical hybrid approach to collinear reactive scattering is prevented by the phenomenon of chaotic scattering. The modified Filinov approach to evaluating the integrals is discussed, but application to collinear systems requires a more careful analysis. In three and higher dimensional scattering systems, chaotic scattering is suppressed and hence the accuracy and usefulness of the semiclassical method should be tested for such systems.

  11. The study and applications of photochemical-dynamical gravity wave model Ⅱ-- The effects of stable gravity wave on chemical species distribution in mesosphere

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A nonlinear, compressible, non-isothermal gravity wave model that involves photochemistry is used to study the effects of gravity wave on atmospheric chemical species distributions in this paper. The changes in the distributions of oxygen compound and hydrogen compound density induced by gravity wave propagation are simulated. The results indicate that when a gravity wave propagates through a mesopause region, even if it does not break, it can influence the background distributions of chemical species. The effect of gravity wave on chemical species at night is larger than in daytime.

  12. A network dynamics approach to chemical reaction networks

    NARCIS (Netherlands)

    van der Schaft, Abraham; Rao, S.; Jayawardhana, B.

    2016-01-01

    A treatment of chemical reaction network theory is given from the perspective of nonlinear network dynamics, in particular of consensus dynamics. By starting from the complex-balanced assumption the reaction dynamics governed by mass action kinetics can be rewritten into a form which allows for a ve

  13. Probing the solvent shell with 195Pt chemical shifts: density functional theory molecular dynamics study of Pt(II) and Pt(IV) anionic complexes in aqueous solution.

    Science.gov (United States)

    Truflandier, Lionel A; Autschbach, Jochen

    2010-03-17

    Ab initio molecular dynamics (aiMD) simulations based on density functional theory (DFT) were performed on a set of five anionic platinum complexes in aqueous solution. (195)Pt nuclear magnetic shielding constants were computed with DFT as averages over the aiMD trajectories, using the two-component relativistic zeroth-order regular approximation (ZORA) in order to treat relativistic effects on the Pt shielding tensors. The chemical shifts obtained from the aiMD averages are in good agreement with experimental data. For Pt(II) and Pt(IV) halide complexes we found an intermediate solvent shell interacting with the complexes that causes pronounced solvent effects on the Pt chemical shifts. For these complexes, the magnitude of solvent effects on the Pt shielding constant can be correlated with the surface charge density. For square-planar Pt complexes the aiMD simulations also clearly demonstrate the influence of closely coordinated non-equatorial water molecules on the Pt chemical shift, relating the structure of the solution around the complex to the solvent effects on the metal NMR chemical shift. For the complex [Pt(CN)(4)](2-), the solvent effects on the Pt shielding constant are surprisingly small. PMID:20166712

  14. Chemical Dynamics, Molecular Energetics, and Kinetics at the Synchrotron

    Energy Technology Data Exchange (ETDEWEB)

    Leone, Stephen R.; Ahmed, Musahid; Wilson, Kevin R.

    2010-03-14

    Scientists at the Chemical Dynamics Beamline of the Advanced Light Source in Berkeley are continuously reinventing synchrotron investigations of physical chemistry and chemical physics with vacuum ultraviolet light. One of the unique aspects of a synchrotron for chemical physics research is the widely tunable vacuum ultraviolet light that permits threshold ionization of large molecules with minimal fragmentation. This provides novel opportunities to assess molecular energetics and reaction mechanisms, even beyond simple gas phase molecules. In this perspective, significant new directions utilizing the capabilities at the Chemical Dynamics Beamline are presented, along with an outlook for future synchrotron and free electron laser science in chemical dynamics. Among the established and emerging fields of investigations are cluster and biological molecule spectroscopy and structure, combustion flame chemistry mechanisms, radical kinetics and product isomer dynamics, aerosol heterogeneous chemistry, planetary and interstellar chemistry, and secondary neutral ion-beam desorption imaging of biological matter and materials chemistry.

  15. Experiences on dynamic simulation software in chemical engineering education

    DEFF Research Database (Denmark)

    Komulainen, Tiina M.; Enemark-rasmussen, Rasmus; Sin, Gürkan;

    2012-01-01

    Commercial process simulators are increasing interest in the chemical engineer education. In this paper, the use of commercial dynamic simulation software, D-SPICE® and K-Spice®, for three different chemical engineering courses is described and discussed. The courses cover the following topics......: basic chemical engineering, operability and safety analysis and process control. User experiences from both teachers and students are presented. The benefits of dynamic simulation as an additional teaching tool are discussed and summarized. The experiences confirm that commercial dynamic simulators...... provide realistic training and can be successfully integrated into undergraduate and graduate teaching, laboratory courses and research....

  16. Cluster dynamics transcending chemical dynamics toward nuclear fusion

    OpenAIRE

    Heidenreich, Andreas; Jortner, Joshua; Last, Isidore

    2006-01-01

    Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 1015–1020 W·cm−2). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C4+(D+)4)n and (D+I22+)n at IM = 1018 W·cm−2, that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. Th...

  17. Dynamic Reaction Figures: An Integrative Vehicle for Understanding Chemical Reactions

    Science.gov (United States)

    Schultz, Emeric

    2008-01-01

    A highly flexible learning tool, referred to as a dynamic reaction figure, is described. Application of these figures can (i) yield the correct chemical equation by simply following a set of menu driven directions; (ii) present the underlying "mechanism" in chemical reactions; and (iii) help to solve quantitative problems in a number of different…

  18. Origin of the Individual Basicity of Corrole NH-Tautomers: A Quantum Chemical Study on Molecular Structure and Dynamics, Kinetics, and Thermodynamics.

    Science.gov (United States)

    Beenken, Wichard; Maes, Wouter; Kruk, Mikalai; Martínez, Todd; Presselt, Martin

    2015-07-01

    Free-base corroles exist as individual NH-tautomers that may differ in their spectral and chemical properties. The present paper focuses on the origin of the basicity difference between two AB2-pyrimidinylcorrole NH-tautomers, which has been tentatively attributed to differences in the weak out-of-plane distortions of the pyrrolenic ring between two NH-tautomers. Using DFT-geometry optimizations, we show that the pyrroles involved in the NH-tautomerization process are approximately in-plane, whereas the other two pyrroles are tilted out-of-plane in opposite directions. Alternative out-of-plane distortion patterns play a minor role, as revealed by ab initio molecular dynamics simulations. Given that the protonated corrole is a unique species, the energy difference between the two NH-tautomers equals the difference in protonation driving force between them. This energy difference increases with improved theoretical level of accounting for intermolecular interactions and dielectric screening of surface charges. The different charge distributions of the two NH-tautomers result in electrostatic potential distributions that effect a larger proton attraction in the case of the T1 tautomer than in the case of the T2 tautomer. In summary, our quantum chemical results show clearly a higher basicity of the T1 tautomer as compared to the T2 tautomer: The previously assumed pronounced out-of-plane tilt of the T1-nonprotonated nitrogen is verified by ab initio molecular dynamics simulations. Together with analysis of the electrostatic potential distribution we show that the nonprotonated nitrogen is not only tilted stronger but also significantly more accessible for protons in the case of T1 as compared to T2. Additionally, the thermodynamic basicity is higher for T1 than for T2. PMID:26052732

  19. Chemical Dynamics, Molecular Energetics, and Kinetics at the Synchrotron

    OpenAIRE

    Leone, Stephen R.

    2010-01-01

    Scientists at the Chemical Dynamics Beamline of the Advanced Light Source in Berkeley are continuously reinventing synchrotron investigations of physical chemistry and chemical physics with vacuum ultraviolet light. One of the unique aspects of a synchrotron for chemical physics research is the widely tunable vacuum ultraviolet light that permits threshold ionization of large molecules with minimal fragmentation. This provides novel opportunities to assess molecular energetics and reaction me...

  20. Parametric and dynamic studies of an iron-based 25-kWth coal direct chemical looping unit using sub-bituminous coal

    International Nuclear Information System (INIS)

    Highlights: • Integrated, moving bed chemical looping reactor with iron-oxide based oxygen carrier. • Coal carbon conversion from 84.8% to 99.9%, thermal capacity 7.4 to 27.7 kWth, O2 demand less than 1.3%. • Dynamic temperature of moving bed reducer is established and tracked during coal injection. • CH4 and CO present at initial coal injection, eliminated after oxygen carrier activated. • Lower coal injection had higher volatiles residence time and conversion. - Abstract: The iron-based Coal-Direct Chemical Looping (CDCL) combustion process is an alternative to conventional oxy-combustion technologies, where the oxygen used for fuel conversion in the CDCL process is provided by an iron-oxide based oxygen carrier instead of an air separation unit. The iron oxide is reduced using coal in the reducer reactor, producing highly-pure CO2 in the flue gas, and the reduced iron oxide is regenerated in a separate combustor reactor using air. The CDCL process at Ohio State has been developed and demonstrated in a 25 kWth sub-pilot unit, and it is the first chemical looping demonstration unit with a circulating moving bed reactor for solid fuel conversion. To date, the CDCL sub-pilot unit at OSU has been operated for more than 680 h, with a 200-h continuous operation, providing important data on long term operability as well as parametric optimization. This paper discusses recent parametric operational experience with sub-bituminous coal as the fuel, where dynamic changes in variables were performed to observe the effects on the unit itself. Measurements included temperature, pressure, and gas concentrations from the reducer and combustor. Furthermore, effects of different variables, such as flue gas recycle ratios (enhancer gas flow rates), feed port injection, and temperature, were observed. Tests confirmed high coal conversions with high purity of CO2 achieved in the flue gas. Overall, the moving bed design of the reducer results in nearly full coal conversion

  1. A dynamical model of the chemical bond

    OpenAIRE

    Hofmann, Holger F.

    1996-01-01

    A new approach to chemical bonding is introduced in order to provide an improved understanding of the connection between basic quantum mechanics and the covalent pair bond. It's focus is on the fact that the energy of the bond is largely given by the kinetic energy of the electrons, while the Coulomb forces are only comparable to the kinetic energy terms close to the atomic nuclei, where they define the shape and the size of the atomic orbitals. If atomic orbitals are used as a starting point...

  2. Cluster dynamics transcending chemical dynamics toward nuclear fusion.

    Science.gov (United States)

    Heidenreich, Andreas; Jortner, Joshua; Last, Isidore

    2006-07-11

    Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 10(15)-10(20) W.cm(-2)). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C(4+)(D(+))(4))(n) and (D(+)I(22+))(n) at I(M) = 10(18) W.cm(-2), that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. The laser intensity and the cluster size dependence of the dynamics and energetics of CE of (D(2))(n), (HT)(n), (CD(4))(n), (DI)(n), (CD(3)I)(n), and (CH(3)I)(n) clusters were explored by electrostatic models and molecular dynamics simulations, quantifying energetic driving effects, and kinematic run-over effects. The optimization of table-top dd nuclear fusion driven by CE of deuterium containing heteroclusters is realized for light-heavy heteroclusters of the largest size, which allows for the prevalence of cluster vertical ionization at the highest intensity of the laser field. We demonstrate a 7-orders-of-magnitude enhancement of the yield of dd nuclear fusion driven by CE of light-heavy heteroclusters as compared with (D(2))(n) clusters of the same size. Prospective applications for the attainment of table-top nucleosynthesis reactions, e.g., (12)C(P,gamma)(13)N driven by CE of (CH(3)I)(n) clusters, were explored. PMID:16740666

  3. Correlation between dynamic wetting behavior and chemical components of thermally modified wood

    International Nuclear Information System (INIS)

    Highlights: • We studied the dynamic wetting behavior of thermally modified wood by wetting models. • We found lower wetting speed of water droplets on thermally modified wood surface. • Dynamic wetting behavior and surface chemical components show a strong correlation. - Abstract: In order to investigate the dynamic wetting behavior of thermally modified wood, Cathay poplar (Populus cathayana Rehd.) and Scots pine (Pinus sylvestris L.) samples were thermally modified in an oven at 160, 180, 200, 220 or 240 °C for 4 h in this study. The dynamic contact angles and droplet volumes of water droplets on modified and unmodified wood surfaces were measured by sessile drop method, and their changing rates (expression index: K value and wetting slope) calculated by wetting models were illustrated for mapping the dynamic wetting process. The surface chemical components were also measured by X-ray photoelectron spectroscopy analysis (XPS), thus the relationship between dynamic wetting behavior and chemical components of thermally modified wood were determined. The results indicated that thermal modification was capable of decreasing the dynamic wettability of wood, expressed in lowing spread and penetration speed of water droplets on wood surfaces. This change was more obvious with the increased heating temperature. The K values varied linearly with the chemical components parameter (mass loss, O/C ratio, and C1/C2 ratio), indicating a strong correlation between dynamic wetting behavior and chemical components of thermally modified wood

  4. Nonequilibrium dynamics in chemical systems A brief account

    Science.gov (United States)

    Nicolis, G.; Baras, F.

    1985-12-01

    During the period of September 3 to 7, 1984 a symposium on “Nonequilibrium Dynamics in Chemical Systems” was organized by the Centre de Recherche Paul Pascal in Bordeaux, France. It was supported, primarily, by the French Centre National de la Recherche Scientifique and attended by about 90 participants from Australia, Belgium, Canada, Denmark, France, Germany, Hungary, Israël, Italy, Japan, The Netherlands, Poland, Tchekoslovakia, Spain, United Kingdom, United States and Zimbabwe. A list of topics and speakers is found in the table below. Two highly successful conferences centered on nonlinear phenomena in chemical systems far from equilibrium had already been organized by the Bordeaux group in the past. The first of them [1], held in September 1978, was dominated by the theme that nonequilibrium can act as a source of order. Sustained oscillations and bistability were the two principal phenomena studied from this point of view. Thanks to the systematic utilization of the continuous stirred tank reactor (CSTR) the study of open systems could finally be realized. Reliable state diagrams were thus produced, notably by the Bordeaux group, in which one could identify the transition points to new states. The Belousov-Zhabotinskii (BZ) reaction and its variants were the main vehicle on which these new ideas could be illustrated. The second Bordeaux conference [2], held in September 1981, was largely dominated by the major progress that had just marked two vital areas of this field: the discovery of new classes of chemical oscillators; and the invasion of chaotic dynamics in chemistry. These themes also dominated the first Gordon Conference on Chemical Oscillations held in New Hampshire in July 1982. In contrast to its two predecessors, the third Bordeaux conference held in September 1984 was not dominated by a single central theme. New questions were raised in situations in which until very recently things were considered to be perfectly clear. Simple,

  5. Simulation of chemical reaction dynamics on an NMR quantum computer

    CERN Document Server

    Lu, Dawei; Xu, Ruixue; Chen, Hongwei; Gong, Jiangbin; Peng, Xinhua; Du, Jiangfeng

    2011-01-01

    Quantum simulation can beat current classical computers with minimally a few tens of qubits and will likely become the first practical use of a quantum computer. One promising application of quantum simulation is to attack challenging quantum chemistry problems. Here we report an experimental demonstration that a small nuclear-magnetic-resonance (NMR) quantum computer is already able to simulate the dynamics of a prototype chemical reaction. The experimental results agree well with classical simulations. We conclude that the quantum simulation of chemical reaction dynamics not computable on current classical computers is feasible in the near future.

  6. A network dynamics approach to chemical reaction networks

    Science.gov (United States)

    van der Schaft, A. J.; Rao, S.; Jayawardhana, B.

    2016-04-01

    A treatment of a chemical reaction network theory is given from the perspective of nonlinear network dynamics, in particular of consensus dynamics. By starting from the complex-balanced assumption, the reaction dynamics governed by mass action kinetics can be rewritten into a form which allows for a very simple derivation of a number of key results in the chemical reaction network theory, and which directly relates to the thermodynamics and port-Hamiltonian formulation of the system. Central in this formulation is the definition of a balanced Laplacian matrix on the graph of chemical complexes together with a resulting fundamental inequality. This immediately leads to the characterisation of the set of equilibria and their stability. Furthermore, the assumption of complex balancedness is revisited from the point of view of Kirchhoff's matrix tree theorem. Both the form of the dynamics and the deduced behaviour are very similar to consensus dynamics, and provide additional perspectives to the latter. Finally, using the classical idea of extending the graph of chemical complexes by a 'zero' complex, a complete steady-state stability analysis of mass action kinetics reaction networks with constant inflows and mass action kinetics outflows is given, and a unified framework is provided for structure-preserving model reduction of this important class of open reaction networks.

  7. 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.

  8. 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.

  9. Chemical dynamics in the gas phase: Time-dependent quantum mechanics of chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Gray, S.K. [Argonne National Laboratory, IL (United States)

    1993-12-01

    A major goal of this research is to obtain an understanding of the molecular reaction dynamics of three and four atom chemical reactions using numerically accurate quantum dynamics. This work involves: (i) the development and/or improvement of accurate quantum mechanical methods for the calculation and analysis of the properties of chemical reactions (e.g., rate constants and product distributions), and (ii) the determination of accurate dynamical results for selected chemical systems, which allow one to compare directly with experiment, determine the reliability of the underlying potential energy surfaces, and test the validity of approximate theories. This research emphasizes the use of recently developed time-dependent quantum mechanical methods, i.e. wave packet methods.

  10. Differential diagnosis of adrenal masses by chemical shift and dynamic gadolinium enhanced MR imaging

    International Nuclear Information System (INIS)

    Chemical shift MRI is widely used for identifying adenomas, but it is not a perfect method. We determined whether combined dynamic MRI methods can lead to improved diagnostic accuracy. Fifty-seven adrenal masses were examined by chemical shift and dynamic MR imaging using 2 MR systems. The masses included 38 adenomas and 19 non-adenomas. In chemical shift MRI studies, the signal intensity index (SI) was calculated, and the lesions classified into 5 types in the dynamic MRI studies. Of the 38 adenomas studied, 37 had an SI greater than 0. In the dynamic MRI, 34 of 38 adenomas showed a benign pattern (type 1). If the SI for the adenomas in the chemical shift MRI was considered to be greater than 0, the positive predictive value was 0.9, and the negative predictive value was 0.94 and κ=0.79. If type 1 was considered to indicate adenomas in the dynamic MRI, the corresponding values were 0.94, 0.81 and κ=0.77 respectively. The results obtained when the 2 methods were combined were 1, 0.95 and κ=0.96 respectively. The chemical shift MRI was found to be useful for identifying adenomas in most cases. If the adrenal mass had a low SI (0< SI<5), dynamic MRI was also found to be helpful for making a differential diagnosis. (author)

  11. Classical and semiclassical aspects of chemical dynamics

    International Nuclear Information System (INIS)

    Tunneling in the unimolecular reactions H2C2 → HC2H, HNC → HCN, and H2CO → H2 + CO is studied with a classical Hamiltonian that allows the reaction coordinate and transverse vibrational modes to be considered directly. A combination of classical perturbation theory and the semiclassical WKB method allows tunneling probabilities to be obtained, and a statistical theory (RRKM) is used to construct rate constants for these reactions in the tunneling regime. In this fashion, it is found that tunneling may be important, particularly for low excitation energies. Nonadiabatic charge transfer in the reaction Na + I → Na + + I- is treated with classical trajectories based on a classical Hamiltonian that is the analogue of a quantum matrix representation. The charge transfer cross section obtained is found to agree reasonably well with the exact quantum results. An approximate semiclassical formula, valid at high energies, is also obtained. The interaction of radiation and matter is treated from a classical viewpoint. The excitation of an HF molecule in a strong laser is described with classical trajectories. Quantum mechanical results are also obtained and compared to the classical results. Although the detailed structure of the pulse time averaged energy absorption cannot be reproduced classically, classical mechanics does predict the correct magnitude of energy absorption, as well as certain other qualitative features. The classical behavior of a nonrotating diatomic molecule in a strong laser field is considered further, by generating a period advance map that allows the solution over many periods of oscillation of the laser to be obtained with relative ease. Classical states are found to form beautiful spirals in phase space as time progresses. A simple pendulum model is found to describe the major qualitative features

  12. Chemical dynamics in time and energy space

    Energy Technology Data Exchange (ETDEWEB)

    Myers, J.D.

    1993-04-01

    The development of a versatile picosecond ultraviolet/vacuum ultraviolet temporal spectrometer and its potential use for measuring internal energy redistribution in isolated molecules are described in detail. A detailed description of the double-pass Nd:YAG amplifier and the dye amplifiers is given with the pulse energies achieved in the visible, ultraviolet, and vacuum ultraviolet. The amplified visible pulses are shown to be of sub-picosecond duration and near transform limited. The instrument`s temporal response ({le}10 ps) is derived from an instrument limited measurement of the dissociation lifetime of methyl iodide at 266 nm. The methyl iodide experiment is used to discuss the various sources of noise and background signals that are intrinsic to this type of experiment. Non-time-resolved experiments measuring the branching ratio and kinetic energy distributions of products from the 193 nm photodissociation of cyclopentadiene and thiophene are presented. These studies were done using the molecular beam Photofragment Translational Spectroscopy (PTS) technique. The results from the cyclopentadiene experiment confirm that H atom elimination to yield the cyclopentadienyl radical is the dominant dissociation channel. A barrier of {ge}5 kcal/mol can be understood in terms of the delocalization of the radical electron of the cyclopentadienyl fragment. A concerted elimination yielding cyclopropene and acetylene was also observed and is proposed to occur via a bicyclo-[2.1.0]pent-2-ene intermediate. Two other channels, yielding acetylene plus the CH{sub 2}CHCH triplet carbene, and CH{sub 2} plus 1-buten-3-yne, are postulated to occur via ring opening. The implications of the experimental results for bulk thermal oxidation and pyrolysis models are discussed. The thiophene experiment shows six competing dissociation channels. The postulated intermediates for the various thiophene dissociation channels include bicyclo, ring opened, and possibly ring contracted forms.

  13. Dynamic function studies

    International Nuclear Information System (INIS)

    Dynamic function studies can be defined as a measure of the variation of a quantity of a substance in an organ with time. Such studies are clinically useful only when the underlying physiological model is realistic. Usually the measurements are of three kinds: the uptake function, the transit function and the removal function. Sensitivity of these measurements can be enhanced in several clinical situations by intervention, such as exercise or drugs. It is possible to display a nuclear image in a variety of ways through computer manipulations which are justified only if based on a valid physiological model. The newer radiopharmaceuticals have also increased the range of functions that can be studied, especially in the case of the heart and the brain. Positron emission tomography (PET) images are fascinating but they are prohibitively expensive and routine clinical nuclear medicine will have to rely on information obtained with single photon emission computer tomography (SPECT). In the diagnosis of cancer, the instrument alone would not improve the diagnosis. It is necessary to have radiopharmaceuticals with a high degree of specificity of uptake. This can possibly be achieved with immunoscintigraphy. There also, the kinetics of uptake of the labelled antibody enable one to differentiate specific from non-specific uptake. The need for good reliable dynamic function studies is as great in the developing as in the developed countries, but a nuclear medicine specialist in a developing country would need more skills and experience because of the heavy odds against which one would be working. (author). 43 refs, 2 figs

  14. The hunt for the dynamical resonances in chemical reaction dynamics: a perspective on historical advances

    OpenAIRE

    Yu Angyang; Zhonghua Yang

    2015-01-01

    The theoretical background and basic definition of the resonances in chemical reaction dynamics have been introduced in this article. The historical breakthrough in the experimental search for the reaction resonances has been reviewed in this report, with an emphasis on the crossed molecular beam apparatus. The research of the chemical reaction resonances has attracted many scientists’ attention from 80s of last century. The chemical reaction resonances in the F+H2 reaction were firstly obser...

  15. Dynamical resonance in F+H2 chemical reaction and rotational excitation effect

    Institute of Scientific and Technical Information of China (English)

    YANG XueMing; XIE DaiQian; ZHANG DongHui

    2007-01-01

    Reaction resonance is a frontier topic in chemical dynamics research, and it is also essential to the understanding of mechanisms of elementary chemical reactions. This short article describes an important development in the frontier of research. Experimental evidence of reaction resonance has been detected in a full quantum state resolved reactive scattering study of the F+H2 reaction. Highly accurate full quantum scattering theoretical modeling shows that the reaction resonance is caused by two Feshbach resonance states. Further studies show that quantum interference is present between the two resonance states for the forward scattering product. This study is a significant step forward in our understanding of chemical reaction resonance in the benchmark F+H2 system. Further experimental studies on the effect of H2 rotational excitation on dynamical resonance have been carried out. Dynamical resonance in the F+H2 (j = 1) reaction has also been observed.

  16. Dynamic Adsorptive Removal of Toxic Chemicals for Purification of Water

    Directory of Open Access Journals (Sweden)

    Amit Saxena

    2005-04-01

    Full Text Available To determine the efficiency of carbon column for the removal of toxic chemicals from water, the adsorption of phenol in concentration range from 0.600 glt to 1.475 gll was studied on activecarbon of 80 CTC grade, 12 X 30 BSS particle size, 1280 m2/g surface area, and of coconut shell origin, under dynamic conditions at space velocity from 0.318 min-' to 4.24 min-' at 25 'C. The carbon column of 100 cm length and 2 cm diameter was found to be removing phenol from the aqueous solution of concentration 1.475 gll up to 84 min at 0.678 min-' space velocity at 5.0 ppm phenol breakthrough concentration. However, no phenol was observed in carbon-treated water after 80 min. The service life of carbon column (100 cm lengthX25 cm diameter was assessed through the water purification system developed at the Defence Laboratory, Jodhpur and was determined to be 4.095 days with twoas factor of safety for 10 ppm initial concentration of phenol at 0.678 min-' space velocity (corresponding to water flow rate. Effects of carbon bed length, water flow rate, and the phenol concentration were also studied.

  17. The hunt for the dynamical resonances in chemical reaction dynamics: a perspective on historical advances

    Directory of Open Access Journals (Sweden)

    Yu Angyang

    2015-06-01

    Full Text Available The theoretical background and basic definition of the resonances in chemical reaction dynamics have been introduced in this article. The historical breakthrough in the experimental search for the reaction resonances has been reviewed in this report, with an emphasis on the crossed molecular beam apparatus. The research of the chemical reaction resonances has attracted many scientists’ attention from 80s of last century. The chemical reaction resonances in the F+H2 reaction were firstly observed by the researchers of the Chinese Academy of Sciences in 2006. Besides, the partial wave resonances in the chemical reactions have been observed for the first time in 2010.

  18. Chemical organization theory: towards a theory of constructive dynamical systems

    OpenAIRE

    Dittrich, Peter; di Fenizio, Pietro Speroni

    2005-01-01

    Complex dynamical networks consisting of many components that interact and produce each other are difficult to understand, especially, when new components may appear. In this paper we outline a theory to deal with such systems. The theory consists of two parts. The first part introduces the concept of a chemical organization as a closed and mass-maintaining set of components. This concept allows to map a complex (reaction) network to the set of organizations, providing a new view on the syste...

  19. Simulation of chemical reaction dynamics on an NMR quantum computer

    OpenAIRE

    Lu, Dawei; Xu, Nanyang; Xu, Ruixue; Chen, Hongwei; Gong, Jiangbin; Peng, Xinhua; Du, Jiangfeng

    2011-01-01

    Quantum simulation can beat current classical computers with minimally a few tens of qubits and will likely become the first practical use of a quantum computer. One promising application of quantum simulation is to attack challenging quantum chemistry problems. Here we report an experimental demonstration that a small nuclear-magnetic-resonance (NMR) quantum computer is already able to simulate the dynamics of a prototype chemical reaction. The experimental results agree well with classical ...

  20. Dynamic processes of conceptual change: Analysis of constructing mental models of chemical equilibrium

    Science.gov (United States)

    Chiu, Mei-Hung; Chou, Chin-Cheng; Liu, Chia-Ju

    2002-10-01

    The purpose of this study was to investigate students' mental models of chemical equilibrium using dynamic science assessments. Research in chemical education has shown that students at various levels have misconceptions about chemical equilibrium. According to Chi's theory of conceptual change, the concept of chemical equilibrium has constraint-based features (e.g., random, simultaneous, uniform activities) that might prevent students from deeply understanding the nature of the concept of chemical equilibrium. In this study, we examined how students learned and constructed their mental models of chemical equilibrium in a cognitive apprenticeship context. Thirty 10th-grade students participated in the study: 10 in a control group and 20 in a treatment group. Both groups were presented with a series of hands-on chemical experiments. The students in the treatment group were instructed based on the main features of cognitive apprenticeship (CA), such as coaching, modeling, scaffolding, articulation, reflection, and exploration. However, the students in the control group (non-CA group) learned from the tutor without explicit CA support. The results revealed that the CA group significantly outperformed the non-CA group. The students in the CA group were capable of constructing the mental models of chemical equilibrium - including dynamic, random activities of molecules and interactions between molecules in the microworld - whereas the students in the non-CA group failed to construct similar correct mental models of chemical equilibrium. The study focuses on the process of constructing mental models, on dynamic changes, and on the actions of students (such as self-monitoring/self-correction) who are learning the concept of chemical equilibrium. Also, we discuss the implications for science education.

  1. Correlation of chemical shifts predicted by molecular dynamics simulations for partially disordered proteins

    International Nuclear Information System (INIS)

    There has been a longstanding interest in being able to accurately predict NMR chemical shifts from structural data. Recent studies have focused on using molecular dynamics (MD) simulation data as input for improved prediction. Here we examine the accuracy of chemical shift prediction for intein systems, which have regions of intrinsic disorder. We find that using MD simulation data as input for chemical shift prediction does not consistently improve prediction accuracy over use of a static X-ray crystal structure. This appears to result from the complex conformational ensemble of the disordered protein segments. We show that using accelerated molecular dynamics (aMD) simulations improves chemical shift prediction, suggesting that methods which better sample the conformational ensemble like aMD are more appropriate tools for use in chemical shift prediction for proteins with disordered regions. Moreover, our study suggests that data accurately reflecting protein dynamics must be used as input for chemical shift prediction in order to correctly predict chemical shifts in systems with disorder

  2. Probing cellular dynamics with a chemical signal generator.

    Directory of Open Access Journals (Sweden)

    Brandon Kuczenski

    Full Text Available Observations of material and cellular systems in response to time-varying chemical stimuli can aid the analysis of dynamic processes. We describe a microfluidic "chemical signal generator," a technique to apply continuously varying chemical concentration waveforms to arbitrary locations in a microfluidic channel through feedback control of the interface between parallel laminar (co-flowing streams. As the flow rates of the streams are adjusted, the channel walls are exposed to a chemical environment that shifts between the individual streams. This approach can be used to probe the dynamic behavior of objects or substances adherent to the interior of the channel. To demonstrate the technique, we exposed live fibroblast cells to ionomycin, a membrane-permeable calcium ionophore, while assaying cytosolic calcium concentration. Through the manipulation of the laminar flow interface, we exposed the cells' endogenous calcium handling machinery to spatially-contained discrete and oscillatory intracellular disturbances, which were observed to elicit a regulatory response. The spatiotemporal precision of the generated signals opens avenues to previously unapproachable areas for potential investigation of cell signaling and material behavior.

  3. Dynamics of prebiotic RNA reproduction illuminated by chemical game theory.

    Science.gov (United States)

    Yeates, Jessica A M; Hilbe, Christian; Zwick, Martin; Nowak, Martin A; Lehman, Niles

    2016-05-01

    Many origins-of-life scenarios depict a situation in which there are common and potentially scarce resources needed by molecules that compete for survival and reproduction. The dynamics of RNA assembly in a complex mixture of sequences is a frequency-dependent process and mimics such scenarios. By synthesizing Azoarcus ribozyme genotypes that differ in their single-nucleotide interactions with other genotypes, we can create molecules that interact among each other to reproduce. Pairwise interplays between RNAs involve both cooperation and selfishness, quantifiable in a 2 × 2 payoff matrix. We show that a simple model of differential equations based on chemical kinetics accurately predicts the outcomes of these molecular competitions using simple rate inputs into these matrices. In some cases, we find that mixtures of different RNAs reproduce much better than each RNA type alone, reflecting a molecular form of reciprocal cooperation. We also demonstrate that three RNA genotypes can stably coexist in a rock-paper-scissors analog. Our experiments suggest a new type of evolutionary game dynamics, called prelife game dynamics or chemical game dynamics. These operate without template-directed replication, illustrating how small networks of RNAs could have developed and evolved in an RNA world. PMID:27091972

  4. A comparative study of the chemical and integrated treatments impact against the defoliating insects on the structure and dynamics of the edaphic mesofauna in two oak forests from North-Eastern Romania

    Directory of Open Access Journals (Sweden)

    Adina Cãlugãr

    2009-11-01

    Full Text Available The author presents in this paper some aspects about the edaphicmicroarthropods from the organic horizon of two forest soils belonging to the Ciurea Forest District, Iasi County: ªanta (mixed stands mainly with oak, chemically treated against defoliating insects and Poieni - Tomesti (Quercus robur and Quercuspetraea stands with integrated treatments. The study of edaphic microarthropods was performed both from qualitative and quantitative point of view. It considered the average of the total density of the microarthropod populations and by each taxonomic group, according to stations and subhorizons, as well as the ratio between thetaxonomical and trophic groups. The investigations concerning edaphic mesofauna consist in inventory and analysis of the mites belonging to Oribatida, Gamasida, Actinedida and Acaridida orders, of the Collembola, as well as other insects; other groups of microarthropods were taken into consideration too (pseudoscorpiones,myriapods etc. The consequences of the treatments against the defoliators on theedaphic mesofauna were performed at four different moments. Generally, lower densities were observed in the case of the chemically treated stands. The communities of the edaphic mesofauna from the integrated management treated stands are more stableduring the time. In the chemically treated stands, the densities of the microartropods vary between large limits; this instability could be assigned to this kind of treatment. The vertical distribution of the mesofauna depends on the textural characteristics of the soil, being at the same time a dynamic parameter that is modifyed according to the variation of the climatic factors.

  5. Studies in combustion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Koszykowski, M.L. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    The goal of this program is to develop a fundamental understanding and a quantitative predictive capability in combustion modeling. A large part of the understanding of the chemistry of combustion processes comes from {open_quotes}chemical kinetic modeling.{close_quotes} However, successful modeling is not an isolated activity. It necessarily involves the integration of methods and results from several diverse disciplines and activities including theoretical chemistry, elementary reaction kinetics, fluid mechanics and computational science. Recently the authors have developed and utilized new tools for parallel processing to implement the first numerical model of a turbulent diffusion flame including a {open_quotes}full{close_quotes} chemical mechanism.

  6. Prevalence and Mechanisms of Dynamic Chemical Defenses in Tropical Sponges

    OpenAIRE

    Rohde, Sven; Nietzer, Samuel; Schupp, Peter J

    2015-01-01

    Sponges and other sessile invertebrates are lacking behavioural escape or defense mechanisms and rely therefore on morphological or chemical defenses. Studies from terrestrial systems and marine algae demonstrated facultative defenses like induction and activation to be common, suggesting that sessile marine organisms also evolved mechanisms to increase the efficiency of their chemical defense. However, inducible defenses in sponges have not been investigated so far and studies on activated d...

  7. Phase synchronization of bursting neural networks with electrical and delayed dynamic chemical couplings

    Science.gov (United States)

    Megam Ngouonkadi, Elie B.; Nono, Martial Kabong; Tamba, Victor Kamdoum; Fotsin, Hilaire B.

    2015-11-01

    Diffusive electrical connections in neuronal networks are instantaneous, while excitatory or inhibitory couplings through chemical synapses contain a transmission time-delay. Moreover, chemical synapses are nonlinear dynamical systems whose behavior can be described by nonlinear differential equations. In this work, neuronal networks with diffusive electrical couplings and time-delayed dynamic chemical couplings are considered. We investigate the effects of distributed time delays on phase synchronization of bursting neurons. We observe that in both excitatory and Inhibitory chemical connections, the phase synchronization might be enhanced when time-delay is taken into account. This distributed time delay can induce a variety of phase-coherent dynamical behaviors. We also study the collective dynamics of network of bursting neurons. The network model presents the so-called Small-World property, encompassing neurons whose dynamics have two time scales (fast and slow time scales). The neuron parameters in such Small-World network, are supposed to be slightly different such that, there may be synchronization of the bursting (slow) activity if the coupling strengths are large enough. Bounds for the critical coupling strengths to obtain burst synchronization in terms of the network structure are given. Our studies show that the network synchronizability is improved, as its heterogeneity is reduced. The roles of synaptic parameters, more precisely those of the coupling strengths and the network size are also investigated.

  8. Electron transfer modifies chemical properties of C70 fullerene surface: an ab initio molecular dynamics study of C70O3 molozonides doped with light atoms

    OpenAIRE

    Morrison, Carole; Bil, Andrzej; Hutter, Jurg

    2014-01-01

    Light metal atoms such as Li, K (electronic state 2S 1/2) or Ca (1S0) encapsulated in a C 70 cage considerably modifies the chemical properties of the fullerene surface due to metal-to-cage electron transfer. H-doped and anion ozonide systems were also considered to validate the electron transfer hypothesis. The relative stabilities of the eight isomers of the C 70O3 molozonide series at room temperature depend on the identity of the endohedral guest, as was the preferred channel for thermal ...

  9. The RAVE-on catalog of stellar atmospheric parameters and chemical abundances for chemo-dynamic studies in the Gaia era

    CERN Document Server

    Casey, Andrew R; Hogg, David W; Ness, Melissa; Walter-Rix, Hans; Kordopatis, Georges; Kunder, Andrea; Steinmetz, Matthias; Koposov, Sergey; Enke, Harry; Sanders, Jason; Gilmore, Gerry; Zwitter, Tomaž; Freeman, Kenneth C; Casagrande, Luca; Matijevič, Gal; Seabroke, George; Bienaymé, Olivier; Bland-Hawthorn, Joss; Gibson, Brad K; Grebel, Eva K; Helmi, Amina; Munari, Ulisse; Navarro, Julio F; Reid, Warren; Siebert, Arnaud; Wyse, Rosemary

    2016-01-01

    The orbits, atmospheric parameters, chemical abundances, and ages of individual stars in the Milky Way provide the most comprehensive illustration of galaxy formation available. The Tycho-Gaia Astrometric Solution (TGAS) will deliver astrometric parameters for the largest ever sample of Milky Way stars, though its full potential cannot be realized without the addition of complementary spectroscopy. Among existing spectroscopic surveys, the RAdial Velocity Experiment (RAVE) has the largest overlap with TGAS ($\\gtrsim$200,000 stars). We present a data-driven re-analysis of 520,781 RAVE spectra using The Cannon. For red giants, we build our model using high-fidelity APOGEE stellar parameters and abundances for stars that overlap with RAVE. For main-sequence and sub-giant stars, our model uses stellar parameters from the K2/EPIC. We derive and validate effective temperature $T_{\\rm eff}$, surface gravity $\\log{g}$, and chemical abundances of up to seven elements (O, Mg, Al, Si, Ca, Fe, Ni). We report a total of 1...

  10. Studying Dynamics in Business Networks

    DEFF Research Database (Denmark)

    Andersen, Poul Houman; Anderson, Helen; Havila, Virpi; Halinen-Havila, Aino

    1998-01-01

    This paper develops a theory on network dynamics using the concepts of role and position from sociological theory. Moreover, the theory is further tested using case studies from Denmark and Finland......This paper develops a theory on network dynamics using the concepts of role and position from sociological theory. Moreover, the theory is further tested using case studies from Denmark and Finland...

  11. Electron transfer modifies chemical properties of C70 fullerene surface: An ab initio molecular dynamics study of C70O3 molozonides doped with light atoms

    Science.gov (United States)

    Bil, Andrzej; Hutter, Jürg; Morrison, Carole A.

    2014-06-01

    Light metal atoms such as Li, K (electronic state 2S1/2) or Ca (1S0) encapsulated in a C70 cage considerably modifies the chemical properties of the fullerene surface due to metal-to-cage electron transfer. H-doped and anion ozonide systems were also considered to validate the electron transfer hypothesis. The relative stabilities of the eight isomers of the C70O3 molozonide series at room temperature depend on the identity of the endohedral guest, as was the preferred channel for thermal decomposition. No electron transfer was observed for the complex N@C70 where the fullerene acts as an inert container for the 4S3/2 radical.

  12. Chemical elements dynamic in the fermentation process of ethanol producing

    International Nuclear Information System (INIS)

    This paper provides useful information about the dynamics of chemical elements analysed by instrumental neutron activation analysis (INAA) and, found in the various segments of the fermentation process of producing ethanol from sugar cane. For this, a mass balance of Ce, Co, Cs, Eu, Fe, Hf, La, Sc, Sm, and Th, terrigenous elements, as well as Br, K, Rb, and Zn, sugar cane plant elements, has been demonstrated for the fermentation vats in industrial conditions of ethanol production. (author). 10 refs, 4 figs, 1 tab

  13. Quantum measurement corrections to chemically induced dynamic nuclear polarization

    CERN Document Server

    Kominis, I K

    2013-01-01

    Chemically induced dynamic nuclear polarization has emerged as a universal signature of spin order in photosynthetic reaction centers. Such polarization, significantly enhanced above thermal equilibrium, is known to result from the nuclear spin sorting inherent in the radical pair mechanism underlying long-lived charge-separated states in photosynthetic reaction centers. We will here show that the recently understood fundamental quantum dynamics of radical-ion-pair reactions open up a new and completely unexpected venue towards obtaining CIDNP signals. The fundamental decoherence mechanism inherent in the recombination process of radical pairs is shown to produce nuclear spin polarizations on the order of $10^4$ times or more higher than thermal equilibrium values at low fields relevant to natural photosynthesis in earth's magnetic field. This opens up the possibility of a fundamentally new exploration of the biological significance of high nuclear polarizations in photosynthesis.

  14. A Phenomenographic Study on Chemical Bonding

    Directory of Open Access Journals (Sweden)

    Şenol Şen

    2013-12-01

    Full Text Available This study aims to reveal how students perceive and identify the concept of chemical bonding, and to identify and explain the misconceptions of students on this subject through phenomenographic research method, as well. The present study included 17 2nd grade students who enrolled to Inorganic Chemistry course in the Faculty of Education. Concept maps and lotus blossom technique were used as data collection tools in order to determine the perceptions and definitions of students about chemical bonding. Data analysis results determined the misconceptions of students about chemical bonding classified misconceptions under seven categories, which are, according to the results of the study, physical changes and bonding, ionic bond, formation of chemical bonding, the existence of chemical bonding, covalent bonds, metallic bonds and intermolecular bonding.

  15. Studying chemical reactions in biological systems with MBN Explorer

    DEFF Research Database (Denmark)

    Sushko, Gennady B.; Solov'yov, Ilia A.; Verkhovtsev, Alexey V.;

    2016-01-01

    The concept of molecular mechanics force field has been widely accepted nowadays for studying various processes in biomolecular systems. In this paper, we suggest a modification for the standard CHARMM force field that permits simulations of systems with dynamically changing molecular topologies....... applied for studying processes where rupture of chemical bonds plays an essential role, e.g., in irradiation- or collision-induced damage, and also in transformation and fragmentation processes involving biomolecular systems....

  16. A Phenomenographic Study on Chemical Bonding

    OpenAIRE

    Şenol Şen; Ayhan Yılmaz

    2013-01-01

    This study aims to reveal how students perceive and identify the concept of chemical bonding, and to identify and explain the misconceptions of students on this subject through phenomenographic research method, as well. The present study included 17 2nd grade students who enrolled to Inorganic Chemistry course in the Faculty of Education. Concept maps and lotus blossom technique were used as data collection tools in order to determine the perceptions and definitions of students about chemical...

  17. Experimental studies on the dynamics of radionuclide transport in soils and plants: an investigation of the effects of soil type and chemical form. Appendix A, B, and C

    International Nuclear Information System (INIS)

    The main report (ANS 364) describes a greenhouse study on the distribution of added radioisotopes within pots containing soils and plants. The soils were sampled from two UK nuclear energy sites: (a) close to the CEGB installation at Sizewell, Suffolk; and (b) inside the perimeter of the BNFL establishment at Sellafield, Cumbria. Information on these soils is given in Appendices A and B. The time dependent behaviour of the radioisotopes has been investigated using I-125 and I-131 and by means of four harvests after administration of the radioisotopes. Relevant data are contained in Appendix C. Data for the watering of the pots, and temperature and humidity of the greenhouses, are given in Appendix D. (U.K.)

  18. Determination of Reference Chemical Potential Using Molecular Dynamics Simulations

    Directory of Open Access Journals (Sweden)

    Krishnadeo Jatkar

    2010-01-01

    Full Text Available A new method implementing molecular dynamics (MD simulations for calculating the reference properties of simple gas hydrates has been proposed. The guest molecules affect interaction between adjacent water molecules distorting the hydrate lattice, which requires diverse values of reference properties for different gas hydrates. We performed simulations to validate the experimental data for determining Δ0, the chemical potential difference between water and theoretical empty cavity at the reference state, for structure II type gas hydrates. Simulations have also been used to observe the variation of the hydrate unit cell volume with temperature. All simulations were performed using TIP4P water molecules at the reference temperature and pressure conditions. The values were close to the experimental values obtained by the Lee-Holder model, considering lattice distortion.

  19. Chemical "Double Slits": dynamical interference of photodissociation pathways in water

    Science.gov (United States)

    Dixon; Hwang; Yang; Harich; Lin; Yang

    1999-08-20

    Photodissociation of water at a wavelength of 121.6 nanometers has been investigated by using the H-atom Rydberg tagging technique. A striking even-odd intensity oscillation was observed in the OH(X) product rotational distribution. Model calculations attribute this oscillation to an unusual dynamical interference brought about by two dissociation pathways that pass through dissimilar conical intersections of potential energy surfaces, but result in the same products. The interference pattern and the OH product rotational distribution are sensitive to the positions and energies of the conical intersections, one with the atoms collinear as H-OH and the other as H-HO. An accurate simulation of the observations would provide a detailed test of global H(2)O potential energy surfaces for the three (&Xtilde;/A/&Btilde;) contributing states. The interference observed from the two conical intersection pathways provides a chemical analog of Young's well-known double-slit experiment. PMID:10455048

  20. Molecular beam studies of reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  1. Dynamic lung transmission studies

    International Nuclear Information System (INIS)

    The aim of this study was to develop a non-invasive method for determining regional lungvolumes, which could replace bronchospirometry in routine clinical use. Transmission through the thorax of sup(99m)Tc-gammarays is measured by means of a gamma camera on line with a computer. The technique of measurement and data analysis is described and tested in several series of phantom studies. The results proved to be good: the mean difference with the real volumes was -4%. The error varied between -10% and +1. Transmission studies and bronchospirometry are compared in a group of 11 patients and there proved to be a good correspondence between the results of these methods. It is concluded that transmission experiments can determine the vital capacity of both lungs as a whole as accurately as spirometry and allows the measurement of vital capacity for each lung separately with the same accuracy as bronchospirometry. (Auth.)

  2. Study of estuarine dynamics

    International Nuclear Information System (INIS)

    A case study of a shallow, well mixed fjord illustrates the use of radioactive and an activable tracer. An instantaneous injection of the rare earth lanthanum was used as an activable tracer to determine residence-time and internal recirculation in the fjord system. An instantaneous injection of bromine-82 was used to investigate tae bypass of water from a harbour area through a power plant cooling water system to a partly enclosed basin of the fjord. Instantaneous releases of bromine-82 were further used for short time studies of the primary spread and transport of river water discharged to the inner section of the fjord system. (Author)

  3. Small Open Chemical Systems Theory: Its Implications to Darwinian Evolution Dynamics, Complex Self-Organization and Beyond

    International Nuclear Information System (INIS)

    The study of biological cells in terms of mesoscopic, nonequilibrium, nonlinear, stochastic dynamics of open chemical systems provides a paradigm for other complex, self-organizing systems with ultra-fast stochastic fluctuations, short-time deterministic nonlinear dynamics, and long-time evolutionary behavior with exponentially distributed rare events, discrete jumps among punctuated equilibria, and catastrophe. (general)

  4. Small Open Chemical Systems Theory and Its Implications to Darwinian Evolutionary Dynamics, Complex Self-Organization and Beyond

    OpenAIRE

    Qian, Hong

    2012-01-01

    The study of biological cells in terms of mesoscopic, nonequilibrium, nonlinear, stochastic dynamics of open chemical systems provides a paradigm for other complex, self-organizing systems with ultra-fast stochastic fluctuations, short-time deterministic nonlinear dynamics, and long-time evolutionary behavior with exponentially distributed rare events, discrete jumps among punctuated equilibria, and catastrophe.

  5. Engineering studies on chemical uranium enrichment

    International Nuclear Information System (INIS)

    In multi-stage separation processes such as the Chemical Enrichment Process, back mixing phenomena are a matter of vital importance for understanding separation efficiency. Back mixing is composed of two parts, microscopic and macroscopic. The microscopic back mixing is known through molecular theory. The macroscopic back mixing effects are quantitatively determined using flow patterns obtained through computational calculations of the fluid dynamics, as well as experimental data. Judging from physical theory and experimental results, the sum of microscopic and the macroscopic back mixing terms is approximately 300μm in the Chemical Enrichment Process. This technology will also contribute to nuclear science in that it can be applied not only to the isotope separation of other elements and to other multi-stage separation processes, but also to the reprocessing of spent fuel. (author)

  6. Herbert P. Broida Prize Lecture: Probing chemical dynamics with negative ion photodetachment

    Science.gov (United States)

    Neumark, Daniel

    2013-03-01

    Photoelectron spectroscopy and its variants have been used in our laboratory to study diverse phenomena in chemical dynamics, including transition state spectroscopy, the electronic and vibrational spectroscopy of clusters, the photodissociation of reactive free radicals, hydrated electron dynamics in clusters and liquid jets, and the ultrafast dynamics of helium nanodroplets. This talk will focus on two examples of this type of work: slow electron velocity map imaging (SEVI) of trapped and cooled negative ions, and time-resolved photoelectron spectroscopy (TRPES) of negative ions. SEVI of cold ions represents a powerful means of performing high resolution photoelectron spectroscopy on complex species. Time-resolved radiation chemistry in nucleobases will be carried out with TRPES. In this work, starting with iodide-nucleobase complexes, we inject electrons into low-lying unoccupied orbitals of the nucleobase and follow the ensuing dynamics.

  7. Modelling of Mass Transfer Phenomena in Chemical and Biochemical Reactor Systems using Computational Fluid Dynamics

    DEFF Research Database (Denmark)

    Larsson, Hilde Kristina

    Computational fluid dynamics (CFD) is the application of numerical methods to solve systems of partial differential equations related to fluid dynamics. The continuity and the momentum equations are the most commonly applied equations within CFD, and together they can be used to calculate the...... velocity and pressure distributions in a fluid. CFD also enables the modelling of several fluids simultaneously, e.g. gas bubbles in a liquid, as well as the presence of turbulence and dissolved chemicals in a fluid, and many other phenomena. This makes CFD an appreciated tool for studying flow structures......, mixing, and other mass transfer phenomena in chemical and biochemical reactor systems. In this project, four selected case studies are investigated in order to explore the capabilities of CFD. The selected cases are a 1 ml stirred microbioreactor, an 8 ml magnetically stirred reactor, a Rushton impeller...

  8. Chemical spots and their dynamical evolution on HgMn stars

    OpenAIRE

    Korhonen, Heidi; Hubrig, Swetlana; Briquet, Maryline; González, Federico; Savanov, Igor

    2010-01-01

    Our recent studies of late B-type stars with HgMn peculiarity revealed for the first time the presence of fast dynamical evolution of chemical spots on their surfaces. These observations suggest a hitherto unknown physical process operating in the stars with radiative outer envelopes. Furthermore, we have also discovered existence of magnetic fields on these stars that have up to now been thought to be non-magnetic. Here we will discuss the dynamical spot evolution on HD 11753 and our new res...

  9. Chemical spots and their dynamical evolution on HgMn stars

    CERN Document Server

    Korhonen, Heidi; Briquet, Maryline; Gonzalez, Federico; Savanov, Igor

    2010-01-01

    Our recent studies of late B-type stars with HgMn peculiarity revealed for the first time the presence of fast dynamical evolution of chemical spots on their surfaces. These observations suggest a hitherto unknown physical process operating in the stars with radiative outer envelopes. Furthermore, we have also discovered existence of magnetic fields on these stars that have up to now been thought to be non-magnetic. Here we will discuss the dynamical spot evolution on HD 11753 and our new results on magnetic fields on AR Aur.

  10. Analysis of forward and inverse problems in chemical dynamics and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rabitz, H. [Princeton Univ., NJ (United States)

    1993-12-01

    The overall scope of this research concerns the development and application of forward and inverse analysis tools for problems in chemical dynamics and chemical kinetics. The chemical dynamics work is specifically associated with relating features in potential surfaces and resultant dynamical behavior. The analogous inverse research aims to provide stable algorithms for extracting potential surfaces from laboratory data. In the case of chemical kinetics, the focus is on the development of systematic means to reduce the complexity of chemical kinetic models. Recent progress in these directions is summarized below.

  11. Dynamical studies of nuclear multifragmentation

    International Nuclear Information System (INIS)

    We review some dynamical approaches developed by our group to study multifragmentation of nuclei. We first investigate the problem of disassembly of hot and compressed nuclei. We show that multifragmentation occurs at low density as a consequence of the fluctuations of the mean field. The magnitude of the fluctuations is evaluated using percolation methods (lattice percolation or restructured aggregation). The dynamical expansion of the nucleus is studied either using a self consistent Thomas Fermi approach or a simple extended liquid drop. Finally, introducing a preequilibrium model to describe the first phase of the collision between two heavy ions, we use the preceeding investigations to calculate multifragmentation excitation functions. (orig.)

  12. Dynamical studies of nuclear multifragmentation

    International Nuclear Information System (INIS)

    We review some dynamical approaches developed by our group to study multifragmentation of nuclei. We first investigate the problem of disassembly of hot and compressed nuclei. We show that multifragmentation occurs at low density as a consequence of the fluctuations of the mean field. The magnitude of the fluctuations is evaluated using percolation methods (lattice percolation or restructured aggregation). The dynamical expansion of the nucleus is studied either using a self consistent Thomas Fermi approach or a simple extended liquid drop. Finally, introducing a preequilibrium model to describe the first phase of the collision between two heavy ions, we use the preceding investigations to calculate multifragmentation excitation functions

  13. Dynamical studies of nuclear multifragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, C.; Boisgard, R.; Cerruti, C.; Leray, S.; Spina, M.E.; Desbois, J.; Ngo, H.; Nemeth, J.; Barranco, M.

    1989-05-01

    We review some dynamical approaches developed by our group to study multifragmentation of nuclei. We first investigate the problem of disassembly of hot and compressed nuclei. We show that multifragmentation occurs at low density as a consequence of the fluctuations of the mean field. The magnitude of the fluctuations is evaluated using percolation methods (lattice percolation or restructured aggregation). The dynamical expansion of the nucleus is studied either using a self consistent Thomas Fermi approach or a simple extended liquid drop. Finally, introducing a preequilibrium model to describe the first phase of the collision between two heavy ions, we use the preceeding investigations to calculate multifragmentation excitation functions.

  14. The quantum dynamics of electronically nonadiabatic chemical reactions

    Science.gov (United States)

    Truhlar, Donald G.

    1993-01-01

    Considerable progress was achieved on the quantum mechanical treatment of electronically nonadiabatic collisions involving energy transfer and chemical reaction in the collision of an electronically excited atom with a molecule. In the first step, a new diabatic representation for the coupled potential energy surfaces was created. A two-state diabatic representation was developed which was designed to realistically reproduce the two lowest adiabatic states of the valence bond model and also to have the following three desirable features: (1) it is more economical to evaluate; (2) it is more portable; and (3) all spline fits are replaced by analytic functions. The new representation consists of a set of two coupled diabatic potential energy surfaces plus a coupling surface. It is suitable for dynamics calculations on both the electronic quenching and reaction processes in collisions of Na(3p2p) with H2. The new two-state representation was obtained by a three-step process from a modified eight-state diatomics-in-molecules (DIM) representation of Blais. The second step required the development of new dynamical methods. A formalism was developed for treating reactions with very general basis functions including electronically excited states. Our formalism is based on the generalized Newton, scattered wave, and outgoing wave variational principles that were used previously for reactive collisions on a single potential energy surface, and it incorporates three new features: (1) the basis functions include electronic degrees of freedom, as required to treat reactions involving electronic excitation and two or more coupled potential energy surfaces; (2) the primitive electronic basis is assumed to be diabatic, and it is not assumed that it diagonalizes the electronic Hamiltonian even asymptotically; and (3) contracted basis functions for vibrational-rotational-orbital degrees of freedom are included in a very general way, similar to previous prescriptions for locally

  15. The quantum dynamics of electronically nonadiabatic chemical reactions

    Science.gov (United States)

    Truhlar, Donald G.

    1993-04-01

    Considerable progress was achieved on the quantum mechanical treatment of electronically nonadiabatic collisions involving energy transfer and chemical reaction in the collision of an electronically excited atom with a molecule. In the first step, a new diabatic representation for the coupled potential energy surfaces was created. A two-state diabatic representation was developed which was designed to realistically reproduce the two lowest adiabatic states of the valence bond model and also to have the following three desirable features: (1) it is more economical to evaluate; (2) it is more portable; and (3) all spline fits are replaced by analytic functions. The new representation consists of a set of two coupled diabatic potential energy surfaces plus a coupling surface. It is suitable for dynamics calculations on both the electronic quenching and reaction processes in collisions of Na(3p2p) with H2. The new two-state representation was obtained by a three-step process from a modified eight-state diatomics-in-molecules (DIM) representation of Blais. The second step required the development of new dynamical methods. A formalism was developed for treating reactions with very general basis functions including electronically excited states. Our formalism is based on the generalized Newton, scattered wave, and outgoing wave variational principles that were used previously for reactive collisions on a single potential energy surface, and it incorporates three new features: (1) the basis functions include electronic degrees of freedom, as required to treat reactions involving electronic excitation and two or more coupled potential energy surfaces; (2) the primitive electronic basis is assumed to be diabatic, and it is not assumed that it diagonalizes the electronic Hamiltonian even asymptotically; and (3) contracted basis functions for vibrational-rotational-orbital degrees of freedom are included in a very general way, similar to previous prescriptions for locally

  16. Theoretical studies of combustion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, J.M. [Emory Univ., Atlanta, GA (United States)

    1993-12-01

    The basic objectives of this research program are to develop and apply theoretical techniques to fundamental dynamical processes of importance in gas-phase combustion. There are two major areas currently supported by this grant. One is reactive scattering of diatom-diatom systems, and the other is the dynamics of complex formation and decay based on L{sup 2} methods. In all of these studies, the authors focus on systems that are of interest experimentally, and for which potential energy surfaces based, at least in part, on ab initio calculations are available.

  17. Chaotic Temperatures vs Coefficients of Thermodynamic Activity The Advantage of the Method of Chemical Dynamics

    CERN Document Server

    Zilbergleyt, B

    2002-01-01

    The article compares traditional coefficients of thermodynamic activity as a parameter related to individual chemical species to newly introduced reduced chaotic temperatures as system characteristics, both regarding their usage in thermodynamic simulation of open chemical systems. Logical and mathematical backgrounds of both approaches are discussed. It is shown that usage of reduced chaotic temperatures and the Method of Chemical Dynamics to calculate chemical and phase composition in open chemical systems is much less costly, easier to perform and potentially leads to better precision.

  18. Complexity of gold nanoparticle formation disclosed by dynamics study

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Jensen, Palle Skovhus; Sørensen, Karsten;

    2013-01-01

    from redox potential, pH, conductivity, and turbidity of the solution enables distinct observation of reduction and nucleation/growth of AuNPs phases. The dynamics of the electrochemical potential shows that reduction of gold salt (HAuCl 4 and its hydrolyzed forms) occurs via intermediate [AuCl 2......Although chemically synthesized gold nanoparticles (AuNPs) from gold salt (HAuCl4) are among the most studied nanomaterials, understanding the formation mechanisms is a challenge mainly due to limited dynamics information. A range of in situ methods with down to millisecond (ms) time resolution...... have been employed in the present report to monitor time-dependent physical and chemical properties in aqueous solution during the chemical synthesis. Chemical synthesis of AuNPs is a reduction process accompanied by release of ions and protons, and formation of solid particles. Dynamic information...

  19. Dynamics of the chemical composition of rainwater throughout Hurricane Irene

    Directory of Open Access Journals (Sweden)

    K. M. Mullaugh

    2013-03-01

    Full Text Available Sequential sampling of rainwater from Hurricane Irene was carried out in Wilmington, NC, USA on 26 and 27 August 2011. Eleven samples were analyzed for pH, major ions (Cl−, NO3−, SO42−, Na+, K+, Mg2+, Ca2+, NH4+, dissolved organic carbon (DOC and hydrogen peroxide (H2O2. Hurricane Irene contributed 16% of the total rainwater and 18% of the total chloride wet deposition received in Wilmington NC during all of 2011. This work highlights the main physical factors influencing the chemical composition of tropical storm rainwater: wind speed, wind direction, back trajectory and vertical mixing, time of day and total rain volume. Samples collected early in the storm, when winds blew out of the east, contained dissolved components indicative of marine sources (salts from sea spray and low DOC. The sea-salt components in the samples had two maxima in concentration during the storm the first of which occurred before the volume of rain had sufficiently washed out sea salt from the atmosphere and the second when back trajectories showed large volumes of marine surface air were lifted. As the storm progressed and winds shifted to a westerly direction, the chemical composition of the rainwater became characteristic of terrestrial storms (high DOC and NH4+ and low sea salt. This work demonstrates that tropical storms are not only responsible for significant wet deposition of marine components to land, but terrestrial components can also become entrained in rainwater, which can then be delivered to coastal waters via wet deposition. This study also underscores why analysis of one composite sample can lead to an incomplete interpretation of the factors that influence the chemically divergent analytes in rainwater during extreme weather events.

  20. Molecular Dynamics Simulations of Chemical Reactions for Use in Education

    Science.gov (United States)

    Qian Xie; Tinker, Robert

    2006-01-01

    One of the simulation engines of an open-source program called the Molecular Workbench, which can simulate thermodynamics of chemical reactions, is described. This type of real-time, interactive simulation and visualization of chemical reactions at the atomic scale could help students understand the connections between chemical reaction equations…

  1. Conventional and dynamic safety analysis: Comparison on a chemical batch reactor

    International Nuclear Information System (INIS)

    Dynamic safety analysis methodologies are an attractive approach to tackle systems with complex dynamics (i.e. with behavior highly dependent on the values of the process parameters): this is often the case in various areas of the chemical industry. The present paper compares analyses with Probabilistic Safety Assessment (PSA)/Quantitative Risk Assessment (QRA) methods with those from a dynamic methodology (Monte Carlo simulation). The results of a case study for a chemical batch reactor from the literature, overall risk figure and main contributors, are examined. The comparison has shown that, provided that the event success criteria are appropriately defined, consistent results can be obtained; otherwise important accident scenarios, identifiable by the dynamic Monte Carlo simulation, are possibly missed in the application of conventional methods. Defining such criteria was quite resource-intensive: for the analysis of this small system, the success criteria definitions required many system simulation runs (about 1000). Such large numbers of runs may not be practical in industrial-scale applications. It is shown that success criteria obtained with fewer simulation runs could have led to different quantitative PSA results and to the omission of important accident scenario variants.

  2. Chemical and dynamical speciation of mobile ions in the glassy fast ionic conductor Ag2S+B2S3+SiS2: A 109Ag nuclear magnetic resonance study

    International Nuclear Information System (INIS)

    109Ag NMR in the highly conductive glass 0.525Ag2S+0.475(0.5B2S3+0.5SiS2) was investigated from 230 to 433 K. The 109Ag NMR spectra reveal for the first time three well resolved lines corresponding to three kinds of chemically speciated Ag ions in sites with different chemical shifts in a macroscopically homogeneous glass. This chemical speciation of Ag ions is discussed in relation to the microstructure of the glass. As the temperature is increased, the three lines that originate from three different species of ions are narrowed, but these lines exist independently up to 433 K, the highest temperature measured. Nuclear spin-lattice relaxation rates (NSLR's), 1/T1, were also measured. Two relaxation processes were found; one is associated with two of the chemically speciated Ag ions and the other is associated with the other Ag ions. The two different NSLR's gradually approach a common value as the temperature is increased, and finally exhibit a common relaxation rate at and above 373 K. From the results of the NMR spectra and of the NSLR's, which observe the ion dynamics on different time scales, it is concluded that the silver ions move fast within separate clusters of similar chemical environments (>>kHz), but exchange among the three different clusters at relatively slow rates (≤100 Hz) above 373 K. From the time the ions reside at any one site, the mean free path of the ions is estimated

  3. Studying chemical reactivity in a virtual environment.

    Science.gov (United States)

    Haag, Moritz P; Reiher, Markus

    2014-01-01

    Chemical reactivity of a set of reactants is determined by its potential (electronic) energy (hyper)surface. The high dimensionality of this surface renders it difficult to efficiently explore reactivity in a large reactive system. Exhaustive sampling techniques and search algorithms are not straightforward to employ as it is not clear which explored path will eventually produce the minimum energy path of a reaction passing through a transition structure. Here, the chemist's intuition would be of invaluable help, but it cannot be easily exploited because (1) no intuitive and direct tool for the scientist to manipulate molecular structures is currently available and because (2) quantum chemical calculations are inherently expensive in terms of computational effort. In this work, we elaborate on how the chemist can be reintroduced into the exploratory process within a virtual environment that provides immediate feedback and intuitive tools to manipulate a reactive system. We work out in detail how this immersion should take place. We provide an analysis of modern semi-empirical methods which already today are candidates for the interactive study of chemical reactivity. Implications of manual structure manipulations for their physical meaning and chemical relevance are carefully analysed in order to provide sound theoretical foundations for the interpretation of the interactive reactivity exploration. PMID:25340884

  4. Atomic dynamics of alumina melt: A molecular dynamics simulation study

    OpenAIRE

    Jahn, S.; P. A. Madden

    2008-01-01

    The atomic dynamics of Al2O3 melt are studied by molecular dynamics simulation. The particle interactions are described by an advanced ionic interaction model that includes polarization effects and ionic shape deformations. The model has been shown to reproduce accurately the static structure factors S(Q) from neutron and x-ray diffraction and the dynamic structure factor S(Q,ω) from inelastic x-ray scattering. Analysis of the partial dynamic structure factors shows inelastic features in the ...

  5. Study of chemical and radiation induced carcinogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Chmura, A.

    1995-11-01

    The study of chemical and radiation induced carcinogenesis has up to now based many of its results on the detection of genetic aberrations using the fluorescent in situ hybridization (FISH) technique. FISH is time consuming and this tends to hinder its use for looking at large numbers of samples. We are currently developing new technological advances which will increase the speed, clarity and functionality of the FISH technique. These advances include multi-labeled probes, amplification techniques, and separation techniques.

  6. Kinetic studies of elementary chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Durant, J.L. Jr. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    This program concerning kinetic studies of elementary chemical reactions is presently focussed on understanding reactions of NH{sub x} species. To reach this goal, the author is pursuing experimental studies of reaction rate coefficients and product branching fractions as well as using electronic structure calculations to calculate transition state properties and reaction rate calculations to relate these properties to predicted kinetic behavior. The synergy existing between the experimental and theoretical studies allow one to gain a deeper insight into more complex elementary reactions.

  7. Nuclear magnetic resonance in pulse radiolysis. Chemically induced dynamic nuclear polarization

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance and chemically induced dynamic nuclear polarization (CIDNP) were applied to the study of pulse radiolysis. Samples were irradiated with a 3-MeV electron beam from the Argonne Van de Graaff accelerator in an EPR magnet (approximately 4000 G) which had axial holes for beam access. A fast flow system transferred the irradiated solution to the rotating 5-mm NMR sample tube. The NMR spectra of mixtures of sodium acetate and methanol were presented to demonstrate the features of the CIDNP in pulse radiolysis

  8. I. Cognitive and instructional factors relating to students' development of personal models of chemical systems in the general chemistry laboratory II. Solvation in supercritical carbon dioxide/ethanol mixtures studied by molecular dynamics simulation

    Science.gov (United States)

    Anthony, Seth

    Part I. Students' participation in inquiry-based chemistry laboratory curricula, and, in particular, engagement with key thinking processes in conjunction with these experiences, is linked with success at the difficult task of "transfer"---applying their knowledge in new contexts to solve unfamiliar types of problems. We investigate factors related to classroom experiences, student metacognition, and instructor feedback that may affect students' engagement in key aspects of the Model-Observe-Reflect-Explain (MORE) laboratory curriculum - production of written molecular-level models of chemical systems, describing changes to those models, and supporting those changes with reference to experimental evidence---and related behaviors. Participation in introductory activities that emphasize reviewing and critiquing of sample models and peers' models are associated with improvement in several of these key aspects. When students' self-assessments of the quality of aspects of their models are solicited, students are generally overconfident in the quality of their models, but these self-ratings are also sensitive to the strictness of grades assigned by their instructor. Furthermore, students who produce higher-quality models are also more accurate in their self-assessments, suggesting the importance of self-evaluation as part of the model-writing process. While the written feedback delivered by instructors did not have significant impacts on student model quality or self-assessments, students' resubmissions of models were significantly improved when students received "reflective" feedback prompting them to self-evaluate the quality of their models. Analysis of several case studies indicates that the content and extent of molecular-level ideas expressed in students' models are linked with the depth of discussion and content of discussion that occurred during the laboratory period, with ideas developed or personally committed to by students during the laboratory period being

  9. Dynamical and chemical properties of the "starless" core L1014

    CERN Document Server

    Crapsi, A; De Vries, C H; Huard, T L; Jørgensen, J K; Kauffmann, J; Lee, C W; Lee, J E; Myers, P C; Ridge, N A; Shirley, Y L; Young, C H

    2005-01-01

    Spitzer Space Telescope observations of a point-like source, L1014-IRS, close to the dust peak of the low-mass dense core L1014 have questioned its starless nature. The presence of an object with colors expected for an embedded protostar makes L1014-IRS the lowest luminosity isolated protostar known, and an ideal target with which to test star formation theories at the low mass end. In order to study its molecular content and to search for the presence of a molecular outflow, we mapped L1014 in at least one transition of 12CO, N2H+, HCO+, CS and of their isotopologues 13CO, C18O, C17O, N2D+ and H13CO+, using the FCRAO, the IRAM 30 meter and the CSO. The data show physical and chemical properties in L1014 typical of the less evolved starless cores: i.e. H2 central density of a few 10^5 molecules cm^-3, estimated mass of ~2M_sun, CO integrated depletion factor less than 10, N(N2H+)~6*10^12 cm^-2, N(N2D+)/N(N2H+) equal to 10% and relatively broad N2H+(1--0) lines (0.35 km/s). Infall signatures and significant ve...

  10. Steady dynamics of exothermic chemical wave fronts in van der Waals fluids.

    Science.gov (United States)

    Dumazer, G; Antoine, C; Lemarchand, A; Nowakowski, B

    2009-12-01

    We study the steady dynamics of an exothermic Fisher-Kolmogorov-Petrovsky-Piskunov chemical wave front traveling in a one-dimensional van der Waals fluid. The propagating wave is initiated by a nonuniformity in reactant concentration contrary to usual combustion ignition processes. The heat release and activation energy of the reaction play the role of control parameters. We recently proved that the propagation of an exothermic chemical wave front in a perfect gas displays a forbidden interval of stationary wave front speeds [G. Dumazer, M. Leda, B. Nowakowski, and A. Lemarchand, Phys. Rev. E 78, 016309 (2008)]. We examine how this result is modified for nonideal fluids and determine the effect of the van der Waals parameters and fluid density on the bifurcation between diffusion flames and Chapman-Jouguet detonation waves as heat release increases. Analytical predictions are confirmed by the numerical solution of the hydrodynamic equations including reaction kinetics. PMID:20365269

  11. Dynamical Interpretation of Chemical Freeze-Out Parameters

    CERN Document Server

    Toneev, V D; Nikonov, E G; Redlich, Krzysztof

    1999-01-01

    It is shown that the condition for chemical freeze-out, average energy per hadron approximately 1 GeV, selects the softest point of the equation of state, namely the point where the pressure divided by the energy density has a minimum. The sensitivity to the equation of state used is discussed. The previously proposed mixed phase model, which is consistent with lattice QCD data naturally leads to the chemical freeze-out condition.

  12. RPMDrate: Bimolecular chemical reaction rates from ring polymer molecular dynamics

    OpenAIRE

    Allen, Joshua W.; Green, William H; Suleimanov, Yu. V.

    2013-01-01

    We present RPMDrate, a computer program for the calculation of gas phase bimolecular reaction rate coefficients using the ring polymer molecular dynamics (RPMD) method. The RPMD rate coefficient is calculated using the Bennett–Chandler method as a product of a static (centroid density quantum transition state theory (QTST) rate) and a dynamic (ring polymer transmission coefficient) factor. The computational procedure is general and can be used to treat bimolecular polyatomic reactions of any ...

  13. Brazilian oil spills chemical characterization : case studies

    International Nuclear Information System (INIS)

    The Petrobras Research Centre has been active in responding to some significant oil spills in Brazil in the past decade. The centre has characterized spilled oil, monitored the affected ecosystems and determined the fate of oil in the environment. This paper described the use of some advanced chemical analytical techniques used in Brazilian oil spill studies to determine fractions and individual petroleum hydrocarbons in water, groundwater, sediment, sand, fish and the spilled oil itself. Some of the most recent oil spill cases were discussed in terms of chemical characterization of the spilled oil and the environmental samples from different matrices of the affected ecosystems for determining the fate of the oil in the environment and to assess environmental damage. In particular, methods such as gas chromatography/flame ionization detector, P and T/GC/PID and gas chromatography/mass spectrometry have been used to examine crude and fuel oil spills in Guanabara Bay, Barigui and Iguassu Rivers, and the Sao Sebastiao Channel. The chemical analytical methods are used to determine total petroleum hydrocarbons, n-alkanes, isoprenoids, unresolved complex mixtures, volatile monoaromatic compounds such as BTEX (benzene, toluene, ethylbenzene and xylenes), as well as parent and alkylated homologues polycyclic aromatic hydrocarbons (PAH) and terpanes and steranes. Acute ecotoxicity data for water and sediment samples was also included. It was determined that with certain limitations, PAH ratios can help determine the origin of hydrocarbons as being either petrogenic or pyrolytic. However, alkylated PAH homologues and parent compounds such as dibenzothiophene and perylene give more precise interpretation of the data. 30 refs., 9 tabs., 11 figs

  14. A comparative study of the chemical and integrated treatments impact against the defoliating insects on the structure and dynamics of the edaphic mesofauna in two oak forests from North-Eastern Romania

    OpenAIRE

    Adina Cãlugãr

    2009-01-01

    The author presents in this paper some aspects about the edaphic microarthropods from the organic horizon of two forest soils belonging to the Ciurea Forest District, Iasi County: Santa (mixed stands mainly with oak, chemically treated against defoliating insects) and Poieni - Tomesti (Quercus robur and Quercus petraea stands with integrated treatments). The study of edaphic microarthropods was performed both from qualitative and quantitative point of view. It considered the average of the to...

  15. A comparative study of the chemical and integrated treatments impact against the defoliating insects on the structure and dynamics of the edaphic mesofauna in two oak forests from North-Eastern Romania

    OpenAIRE

    Adina Cãlugãr

    2009-01-01

    The author presents in this paper some aspects about the edaphicmicroarthropods from the organic horizon of two forest soils belonging to the Ciurea Forest District, Iasi County: ªanta (mixed stands mainly with oak, chemically treated against defoliating insects) and Poieni - Tomesti (Quercus robur and Quercuspetraea stands with integrated treatments). The study of edaphic microarthropods was performed both from qualitative and quantitative point of view. It considered the average of the tota...

  16. Chemical Kinetics, Heat Transfer, and Sensor Dynamics Revisited in a Simple Experiment

    Science.gov (United States)

    Sad, Maria E.; Sad, Mario R.; Castro, Alberto A.; Garetto, Teresita F.

    2008-01-01

    A simple experiment about thermal effects in chemical reactors is described, which can be used to illustrate chemical reactor models, the determination and validation of their parameters, and some simple principles of heat transfer and sensor dynamics. It is based in the exothermic reaction between aqueous solutions of sodium thiosulfate and…

  17. Surface chemical studies of chemical vapour deposited diamond thin films

    International Nuclear Information System (INIS)

    Polycrystalime diamond grown by low pressure chemical vapour deposition (CVD) techniques has emerged in recent years as a new material with applications in such areas as optics, electronics, radiation detectors, chemical sensors and electrochemistry. A main aim of this thesis has been to advance current knowledge of the surface chemical properties of CVD diamond to underpin the development of our understanding of the properties and potential applications of this material. Cl2 is found to adsorb dissociatively on the clean, hydrogen-free diamond surface up to sub-monolayer coverage with a sticking probability of ∼1.2x10-3. Adsorption is a non-activated process, and the sticking probability and extent of coverage decreased with increasing temperature. This was shown to contrast with the behaviour found for the interaction of chlorine with the hydrogenated diamond surface where increased sticking probabilities and saturation surface coverages were observed, and where the reactivity also increased with temperature. Thermal desorption of atomic Cl occurred over a broad temperature range m both chemisorption systems, indicating the presence of more than one binding state. Atomic hydrogen was successful in efficiently etching the bound Cl from the surface. XeF2 was found to adsorb dissociatively onto the clean diamond surface to give up to monolayer coverages of F, which formed two distinct binding states. The first state, populated at low coverage, was predominantly covalent in character, while the second state, occurring at high surface coverages, had more ionic bonding character. Pre-hydrogenation of the diamond surface increased the reactive sticking probability observed, but decreased the extent of coverage by blocking reactive sites. The semi-ionic F was readily etched by atomic hydrogen, and underwent thermal desorption at temperatures as low as 300 deg C. The covalent form was more stable, being seemingly resistant to etching and persistent to high temperatures

  18. Molecular dynamics studies of aromatic hydrocarbon liquids

    International Nuclear Information System (INIS)

    This project mainly involves a molecular dynamics and Monte Carlo study of the effect of molecular shape on thermophysical properties of bulk fluids with an emphasis on the aromatic hydrocarbon liquids. In this regard we have studied the modeling, simulation methodologies, and predictive and correlating methods for thermodynamic properties of fluids of nonspherical molecules. In connection with modeling we have studied the use of anisotropic site-site potentials, through a modification of the Gay-Berne Gaussian overlap potential, to successfully model the aromatic rings after adding the necessary electrostatic moments. We have also shown these interaction sites should be located at the geometric centers of the chemical groups. In connection with predictive methods, we have shown two perturbation type theories to work well for fluids modeled using one-center anisotropic potentials and the possibility exists for extending these to anisotropic site-site models. In connection with correlation methods, we have studied, through simulations, the effect of molecular shape on the attraction term in the generalized van der Waals equation of state for fluids of nonspherical molecules and proposed a possible form which is to be studied further. We have successfully studied the vector and parallel processing aspects of molecular simulations for fluids of nonspherical molecules

  19. Chemical warfare, past and future. Study project

    Energy Technology Data Exchange (ETDEWEB)

    Tzihor, A.

    1992-05-15

    World War I was arena for the first use of chemical warfare. The enormous tactical success brought about by this first time use of chemical weapons caused the continued development of more sophisticated tactics and weapons in this category of unconventional warfare. This phenomenon has carried through to today. However, at present, because of technological developments, the global economic situation, and political factors, coupled with the inability of the western world to control the proliferation of chemical weapons, a situation weapon of mass destruction. Recent use by Iraq against Kurdish civilian indicates that chemical warfare is no longer limited to the battlefield. The western nations have a need to understand the risk. This paper conducts an analysis of past lessons and the factors which will affect the use of chemical warfare in the future. From this analysis, the paper reaches conclusions concerning the significant threat chemical weapons pose for the entire world in the not too distant future.

  20. The Chemical and Dynamical Evolution of Isolated Dwarf Galaxies

    OpenAIRE

    Pilkington, K.; Gibson, B. K.; Calura, F; Stinson, G.S.; Brook, C. B.; Brooks, A.

    2011-01-01

    Using a suite of simulations (Governato et al. 2010) which successfully produce bulgeless (dwarf) disk galaxies, we provide an analysis of their associated cold interstellar media (ISM) and stellar chemical abundance patterns. A preliminary comparison with observations is undertaken, in order to assess whether the properties of the cold gas and chemistry of the stellar components are recovered successfully. To this end, we have extracted the radial and vertical gas density profiles, neutral h...

  1. RPMDrate: Bimolecular chemical reaction rates from ring polymer molecular dynamics

    KAUST Repository

    Suleimanov, Yu.V.

    2013-03-01

    We present RPMDrate, a computer program for the calculation of gas phase bimolecular reaction rate coefficients using the ring polymer molecular dynamics (RPMD) method. The RPMD rate coefficient is calculated using the Bennett-Chandler method as a product of a static (centroid density quantum transition state theory (QTST) rate) and a dynamic (ring polymer transmission coefficient) factor. The computational procedure is general and can be used to treat bimolecular polyatomic reactions of any complexity in their full dimensionality. The program has been tested for the H+H2, H+CH 4, OH+CH4 and H+C2H6 reactions. © 2012 Elsevier B.V. All rights reserved.

  2. Dynamic capillary wetting studied with dissipative particle dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cupelli, Claudio; Glatzel, Thomas; Zengerle, Roland; Santer, Mark [Laboratory for MEMS applications, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg (Germany); Henrich, Bjoern; Moseler, Michael [Freiburg Materials Research Center (FMF), Stefan-Meier-Strasse 21, 79104 Freiburg (Germany)], E-mail: cupelli@imtek.de

    2008-04-15

    We present a study on dynamic capillary wetting in the framework of dissipative particle dynamics (DPD) based on a novel wall model for wetting on solid boundaries. We consider capillary impregnation of a slit pore in two situations: (i) forced (piston-driven) steady state flow and (ii) capillarity driven imbibition out of a finite reservoir. The dynamic contact angle behavior under condition (i) is consistent with the hydrodynamic theories of Cox under partial wetting conditions and Eggers for complete wetting. The flow field near the contact line shows a region of apparent slip flow which provides a natural way of avoiding a stress singularity at the triple line. The dynamics of the capillary imbibition, i.e. condition (ii), is consistently described by the Lucas-Washburn equation augmented by expressions that account for inertia and the influence of the dynamic contact angle.

  3. Studies in Chaotic adiabatic dynamics

    International Nuclear Information System (INIS)

    Chaotic adiabatic dynamics refers to the study of systems exhibiting chaotic evolution under slowly time-dependent equations of motion. In this dissertation the author restricts his attention to Hamiltonian chaotic adiabatic systems. The results presented are organized around a central theme, namely, that the energies of such systems evolve diffusively. He begins with a general analysis, in which he motivates and derives a Fokker-Planck equation governing this process of energy diffusion. He applies this equation to study the open-quotes goodnessclose quotes of an adiabatic invariant associated with chaotic motion. This formalism is then applied to two specific examples. The first is that of a gas of noninteracting point particles inside a hard container that deforms slowly with time. Both the two- and three-dimensional cases are considered. The results are discussed in the context of the Wall Formula for one-body dissipation in nuclear physics, and it is shown that such a gas approaches, asymptotically with time, an exponential velocity distribution. The second example involves the Fermi mechanism for the acceleration of cosmic rays. Explicit evolution equations are obtained for the distribution of cosmic ray energies within this model, and the steady-state energy distribution that arises when this equation is modified to account for the injection and removal of cosmic rays is discussed. Finally, the author re-examines the multiple-time-scale approach as applied to the study of phase space evolution under a chaotic adiabatic Hamiltonian. This leads to a more rigorous derivation of the above-mentioned Fokker-Planck equation, and also to a new term which has relevance to the problem of chaotic adiabatic reaction forces (the forces acting on slow, heavy degrees of freedom due to their coupling to light, fast chaotic degrees)

  4. Quantum chemical studies of estrogenic compounds

    Science.gov (United States)

    Quantum chemical methods are potent tools to provide information on the chemical structure and electronic properties of organic molecules. Modern computational chemistry methods have provided a great deal of insight into the binding of estrogenic compounds to estrogenic receptors (ER), an important ...

  5. Programming chemical kinetics: engineering dynamic reaction networks with DNA strand displacement

    Science.gov (United States)

    Srinivas, Niranjan

    Over the last century, the silicon revolution has enabled us to build faster, smaller and more sophisticated computers. Today, these computers control phones, cars, satellites, assembly lines, and other electromechanical devices. Just as electrical wiring controls electromechanical devices, living organisms employ "chemical wiring" to make decisions about their environment and control physical processes. Currently, the big difference between these two substrates is that while we have the abstractions, design principles, verification and fabrication techniques in place for programming with silicon, we have no comparable understanding or expertise for programming chemistry. In this thesis we take a small step towards the goal of learning how to systematically engineer prescribed non-equilibrium dynamical behaviors in chemical systems. We use the formalism of chemical reaction networks (CRNs), combined with mass-action kinetics, as our programming language for specifying dynamical behaviors. Leveraging the tools of nucleic acid nanotechnology (introduced in Chapter 1), we employ synthetic DNA molecules as our molecular architecture and toehold-mediated DNA strand displacement as our reaction primitive. Abstraction, modular design and systematic fabrication can work only with well-understood and quantitatively characterized tools. Therefore, we embark on a detailed study of the "device physics" of DNA strand displacement (Chapter 2). We present a unified view of strand displacement biophysics and kinetics by studying the process at multiple levels of detail, using an intuitive model of a random walk on a 1-dimensional energy landscape, a secondary structure kinetics model with single base-pair steps, and a coarse-grained molecular model that incorporates three-dimensional geometric and steric effects. Further, we experimentally investigate the thermodynamics of three-way branch migration. Our findings are consistent with previously measured or inferred rates for

  6. An infrared free-electron laser for the Chemical Dynamics Research Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Vaughan, D. (comp.)

    1992-04-01

    This document describes a free-electron laser (FEL) proposed as part of the Chemical Dynamics Research Laboratory (CDRL), a user facility that also incorporates several advanced lasers of conventional design and two beamlines for the ALS. The FEL itself addresses the needs of the chemical sciences community for a high-brightness, tunable source covering a broad region of the infrared spectrum -- from 3 to 50 {mu}m. All of these sources, together with a variety of sophisticated experimental stations, will be housed in a new building to be located adjacent to the ALS. The radiation sources can be synchronized to permit powerful two-color, pump-probe experiments that will further our fundamental understanding of chemical dynamics at the molecular level, especially those aspects relevant to practical issues in combustion chemistry. The technical approach adopted in this design makes use of superconducting radiofrequency (SCRF) accelerating structures. The primary motivation for adopting this approach was to meet the user requirement for wavelength stability equal to one part in 10{sup 4}. Previous studies concluded that a wavelength stability of only one part in 10{sup 3} could be achieved with currently available room-temperature technology. In addition, the superconducting design operates in a continuous-wave (cw) mode and hence offers considerably higher average optical output power. It also allows for various pulse-gating configurations that will permit simultaneous multiuser operations. A summary of the comparative performance attainable with room-temperature and superconducting designs is given. The FEL described in this report provides a continuous train of 30-ps micropulses, with 100{mu}J of optical energy per micropulse, at a repetition rate of 6.1 MHz. The device can also deliver pulses at a cw repetition rate of 12.2 MHz, with a peak power of 50 {mu}J per micropulse. 70 ref.

  7. An infrared free-electron laser for the Chemical Dynamics Research Laboratory. Design report

    Energy Technology Data Exchange (ETDEWEB)

    Vaughan, D. [comp.

    1992-04-01

    This document describes a free-electron laser (FEL) proposed as part of the Chemical Dynamics Research Laboratory (CDRL), a user facility that also incorporates several advanced lasers of conventional design and two beamlines for the ALS. The FEL itself addresses the needs of the chemical sciences community for a high-brightness, tunable source covering a broad region of the infrared spectrum -- from 3 to 50 {mu}m. All of these sources, together with a variety of sophisticated experimental stations, will be housed in a new building to be located adjacent to the ALS. The radiation sources can be synchronized to permit powerful two-color, pump-probe experiments that will further our fundamental understanding of chemical dynamics at the molecular level, especially those aspects relevant to practical issues in combustion chemistry. The technical approach adopted in this design makes use of superconducting radiofrequency (SCRF) accelerating structures. The primary motivation for adopting this approach was to meet the user requirement for wavelength stability equal to one part in 10{sup 4}. Previous studies concluded that a wavelength stability of only one part in 10{sup 3} could be achieved with currently available room-temperature technology. In addition, the superconducting design operates in a continuous-wave (cw) mode and hence offers considerably higher average optical output power. It also allows for various pulse-gating configurations that will permit simultaneous multiuser operations. A summary of the comparative performance attainable with room-temperature and superconducting designs is given. The FEL described in this report provides a continuous train of 30-ps micropulses, with 100{mu}J of optical energy per micropulse, at a repetition rate of 6.1 MHz. The device can also deliver pulses at a cw repetition rate of 12.2 MHz, with a peak power of 50 {mu}J per micropulse. 70 ref.

  8. Amoeba-Inspired Heuristic Search Dynamics for Exploring Chemical Reaction Paths.

    Science.gov (United States)

    Aono, Masashi; Wakabayashi, Masamitsu

    2015-09-01

    We propose a nature-inspired model for simulating chemical reactions in a computationally resource-saving manner. The model was developed by extending our previously proposed heuristic search algorithm, called "AmoebaSAT [Aono et al. 2013]," which was inspired by the spatiotemporal dynamics of a single-celled amoeboid organism that exhibits sophisticated computing capabilities in adapting to its environment efficiently [Zhu et al. 2013]. AmoebaSAT is used for solving an NP-complete combinatorial optimization problem [Garey and Johnson 1979], "the satisfiability problem," and finds a constraint-satisfying solution at a speed that is dramatically faster than one of the conventionally known fastest stochastic local search methods [Iwama and Tamaki 2004] for a class of randomly generated problem instances [ http://www.cs.ubc.ca/~hoos/5/benchm.html ]. In cases where the problem has more than one solution, AmoebaSAT exhibits dynamic transition behavior among a variety of the solutions. Inheriting these features of AmoebaSAT, we formulate "AmoebaChem," which explores a variety of metastable molecules in which several constraints determined by input atoms are satisfied and generates dynamic transition processes among the metastable molecules. AmoebaChem and its developed forms will be applied to the study of the origins of life, to discover reaction paths for which expected or unexpected organic compounds may be formed via unknown unstable intermediates and to estimate the likelihood of each of the discovered paths. PMID:26129639

  9. Dynamic model for selective metabolic activation in chemical carcinogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Selkirk, J.K.; MacLeod, M.C.

    1980-01-01

    Theoretical calculations predict the relative ease of formation of carbonium ions from 7,8-dihydro-7,8-dihydroxybenzo(a)pyrene-9,10-oxide or from either of the 2 symmetrical bay regions of B(e)P, and suggest their attraction to cellular nucleophiles. When both isomers were metabolized by hamster embryo fibroblasts (HEF) and the products analyzed, the results showed that the probable reason for benzo(e)pyrene's lack of carcinogenicity was its metabolic preference to attack the molecule away from the bay-region area. Particularly striking was the absence of any evidence for the formation of a significant amount of B(e)P-9,10-dihydrodiol. This suggests a metabolic basis for the relative lack of carcinogenic and mutagenic activity of B(e)P. The reason for this is not clear but may be due to physical or chemical factors such as membrane solubility or stereochemical requirements of the active site of the enzyme. The bay-region theory of PAH carcinogenesis predicts that carbonium ion formation from 9,10-dihydro-9,10-dihydroxybenzo(e)pyrene-11, 12-oxide, if formed, would be energetically favorable. Thus, the inability of HEF and microcomes to form B(e)P-9,10-dihydrodiol, the precursor of its potentially highly reactive diol-epoxide, would explain the relative inertness of B(e)P in several biological systems. As the subtle biochemical interactions of the various carcinogen intermediates become clarified, it becomes apparent that susceptibility and resistance to malignant transformation are based on a complex set of both chemical and physical parameters. It is becoming clear that metabolism kinetics, membrane interaction, and the role of nuclear metabolism help dictate the passage of the carcinogen and its reactive intermediates into and through the metabolic machinery of the cell. (ERB)

  10. System chemical biology studies of endocrine disruptors

    DEFF Research Database (Denmark)

    Taboureau, Olivier; Oprea, Tudor I.

    Endocrine disrupting chemicals (EDCs) alter hormonal balance and other physiological systems through inappropriate developmental or adult exposure, perturbing the reproductive function of further generations. While disruption of key receptors (e.g., estrogen, androgen, and thyroid) at the ligand...

  11. Theoretical study of chemical reactions in solution

    International Nuclear Information System (INIS)

    Quantum chemical calculations in solution are becoming more and more important in chemistry. Reference interaction site model self-consistent field (RISM-SCF) is one of the powerful approaches to perform quantum chemical calculations in solution. In this work, we developed a new generation of RISM-SCF, where a robust fitting method was newly introduced. We applied the new method to tautomerization reaction of cytosine in aqueous phase. Our calculation reproduced experimentally obtained relative stabilities and relative free energies correctly

  12. Synchronization dynamics of chemically coupled cells with activator–inhibitor pathways

    Energy Technology Data Exchange (ETDEWEB)

    Guemkam Ghomsi, P. [Complex Systems and Theoretical Biology Group, Laboratory of Research on Advanced Materials and Nonlinear Science (LaRAMaNS), Department of Physics, Faculty of Science, University of Buea, P.O. Box 63, Buea (Cameroon); Laboratoire de Mécanique, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé (Cameroon); Moukam Kakmeni, F.M., E-mail: moukam.kakmeni@ubuea.cm [Complex Systems and Theoretical Biology Group, Laboratory of Research on Advanced Materials and Nonlinear Science (LaRAMaNS), Department of Physics, Faculty of Science, University of Buea, P.O. Box 63, Buea (Cameroon); Kofane, T.C.; Tchawoua, C. [Laboratoire de Mécanique, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé (Cameroon)

    2014-08-01

    Systems of interacting cells containing an activator–inhibitor pathway, regulating naturally in their inner parts their end-product concentrations through a sequence of biochemical reactions with feedback-loops: an end-product inhibition of the first substrate, and an autocatalytic activation of the end-product through an allosteric enzyme-mediated reaction are investigated. The individual cells are considered to be identical and are described by nonlinear differential equations recently proposed following the concerted transition model. The chemical and electrical coupling types, realized by exchange of metabolites across concentration of the cells are used in order to analyze the onset of phase and complete synchronization in the biochemical system. It is found that depending on the coupling nature and the range of coupling strength, cells enter into different synchronization regimes going from low-quality to high-quality synchronization. The synchronization manifold's stability is analyzed. The results are supported by numerical simulations using indicators such as the conditional Lyapunov exponents and the rate of change of the Lyapunov function. The results indicate that the system cannot completely synchronize under the single action of the chemical coupling. The combined effect of both chemical and electrical couplings is found to be of capital importance in the onset of complete synchronization and high quality synchronization. - Highlights: • We investigate the dynamics and synchronization of cells with activator–inhibitor pathways. • A complete study of fixed points' stability and bifurcations of the system is done. • It is found that chemically coupled cells only display phase synchronization. • Electrical coupling is important for complete synchronization in the coupled cells. • High quality synchronization is observed in the coupled cells.

  13. Synchronization dynamics of chemically coupled cells with activator–inhibitor pathways

    International Nuclear Information System (INIS)

    Systems of interacting cells containing an activator–inhibitor pathway, regulating naturally in their inner parts their end-product concentrations through a sequence of biochemical reactions with feedback-loops: an end-product inhibition of the first substrate, and an autocatalytic activation of the end-product through an allosteric enzyme-mediated reaction are investigated. The individual cells are considered to be identical and are described by nonlinear differential equations recently proposed following the concerted transition model. The chemical and electrical coupling types, realized by exchange of metabolites across concentration of the cells are used in order to analyze the onset of phase and complete synchronization in the biochemical system. It is found that depending on the coupling nature and the range of coupling strength, cells enter into different synchronization regimes going from low-quality to high-quality synchronization. The synchronization manifold's stability is analyzed. The results are supported by numerical simulations using indicators such as the conditional Lyapunov exponents and the rate of change of the Lyapunov function. The results indicate that the system cannot completely synchronize under the single action of the chemical coupling. The combined effect of both chemical and electrical couplings is found to be of capital importance in the onset of complete synchronization and high quality synchronization. - Highlights: • We investigate the dynamics and synchronization of cells with activator–inhibitor pathways. • A complete study of fixed points' stability and bifurcations of the system is done. • It is found that chemically coupled cells only display phase synchronization. • Electrical coupling is important for complete synchronization in the coupled cells. • High quality synchronization is observed in the coupled cells

  14. Chemical feedbacks in climate sensitivity studies

    Science.gov (United States)

    Dietmüller, Simone; Ponater, Michael; Sausen, Robert

    2013-04-01

    Interactively coupled climate chemistry models extend the number of feedback mechanisms in climate change simulations by allowing a variation of several radiatively actice chemical tracers that are prescribed in conventional climate models. Different perturbation experiments including chemical feedbacks were performed using the chemistry-climate model system EMAC coupled to the mixed layer ocean model MLO. The influence of the chemical feedbacks O3, CH4 and N2O on climate response and climate sensitivity is quantified for a series of CO2-perturbation simulations: Equilibrium climate sensitivity is dampened, if chemical feedbacks are included. In case of a CO2 doubling simulation chemical feedbacks decrease climate sensitivity by -3.6% and in case of a 4*CO2 simulation by -8.1%. Analysis of the chemical feedbacks reveals, that the negative feedback of ozone, mainly the feedback of stratospheric ozone, is responsible for this dampening. The radiative feedbacks of CH4 and N2O are negligible, mainly because the model system does not allow interactive emission feedbacks at the Earth's surface for these gases. The feedback of physical parameters is significantly modified by the presence of chemical feedbacks. In case of the CO2-perturbation experiments the negative stratospheric ozone feedback is accompanied by a negative stratospheric H2O feedback change of the same order of magnitude. So the dampening effect of the direct O3 radiative feedback is enhanced. A non-linearity in the damping is found with increasing CO2 concentrations. Reasons are the nonlinear feedbacks of ozone, temperature, and stratospheric water vapor. Additional 6*CO2 simulations with and without chemical feedbacks included show, that the presence of chemic feedbacks helps to prevent a runaway greenhouse effect, as the O3 distribution can react to the upward shift of the tropopause. Also experiments driven by anthropogenic NOx- and CO-emissions were performed, where chemically active trace gases act

  15. Molecular beam studies of reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.T.

    1987-03-01

    Purpose of this research project is two-fold: (1) to elucidate detailed dynamics of simple elementary reactions which are theoretically important and to unravel the mechanism of complex chemical reactions or photo chemical processes which play an important role in many macroscopic processes and (2) to determine the energetics of polyatomic free radicals using microscopic experimental methods. Most of the information is derived from measurement of the product fragment translational energy and angular distributions using unique molecular beam apparati designed for these purposes.

  16. Atomic dynamics of alumina melt: A molecular dynamics simulation study

    Directory of Open Access Journals (Sweden)

    S.Jahn

    2008-03-01

    Full Text Available The atomic dynamics of Al2O3 melt are studied by molecular dynamics simulation. The particle interactions are described by an advanced ionic interaction model that includes polarization effects and ionic shape deformations. The model has been shown to reproduce accurately the static structure factors S(Q from neutron and x-ray diffraction and the dynamic structure factor S(Q,ω from inelastic x-ray scattering. Analysis of the partial dynamic structure factors shows inelastic features in the spectra up to momentum transfers, Q, close to the principal peaks of partial static structure factors. The broadening of the Brillouin line widths is discussed in terms of a frequency dependent viscosity η(ω.

  17. Dynamical and chemical evolution of the thin disc

    CERN Document Server

    Just, Andreas

    2015-01-01

    Our detailed analytic local disc model (JJ-model) quantifies the interrelation between kinematic properties (e.g. velocity dispersions and asymmetric drift), spatial parameters (scale-lengths and vertical density profiles), and properties of stellar sub-populations (age and abundance distributions). Any consistent radial extension of the disc evolution model should predict specific features in the different distribution functions and in their correlations. Large spectroscopic surveys (SEGUE, RAVE, APOGEE, Gaia-ESO) allow significant constraints on the long-term evolution of the thin disc. We discuss the qualitative difference of correlations (like the alpha-enhancement as function of metallicity) and distribution functions (e.g. in [Mg/H] or [Fe/H]) for the construction of a disc model. In the framework of the JJ-model we build a local chemical enrichment model and show that significant vertical gradients for main sequence and red clump stars are expected in the thin disc. A Jeans analysis of the asymmetric d...

  18. Dynamical study of liquid aluminium

    International Nuclear Information System (INIS)

    Recent molecular dynamics data of Ebbsjoe et al. in liquid aluminium have been analysed through the memory function formalism. Two forms of the memory functions which have correct asymptotic limit at large wavenumbers but accounts for interatomic correlations in a different manner are considered. The results for ω2s(q, ω) obtained from both models are compared with experimental data. (author)

  19. Lattice dynamics and chemical bonding in Sb2Te3 from first-principles calculations

    International Nuclear Information System (INIS)

    Pressure effects on the lattice dynamics and the chemical bonding of the three-dimensional topological insulator, Sb2Te3, have been studied from a first-principles perspective in its rhombohedral phase. Where it is possible to compare, theory agrees with most of the measured phonon dispersions. We find that the inclusion of relativistic effects, in terms of the spin-orbit interaction, affects the vibrational features to some extend and creates large fluctuations on phonon density of state in high frequency zone. By investigations of structure and electronic structure, we analyze in detail the semiconductor to metal transition at ∼2 GPa followed by an electronic topological transition at a pressure of ∼4.25 GPa

  20. Molecular dynamics of immiscible fluids in chemically patterned nanochannels

    Science.gov (United States)

    Cieplak, Marek; Banavar, Jayanth R.

    2008-03-01

    Molecular dynamics simulations of chain molecules are used to elucidate physical phenomena involved in flows of dense immiscible fluids in nanochannels. We first consider a force driven flow in which the channel walls are homogeneous and wetting to one fluid and nonwetting to the other fluid. The coating of the walls by the wetting fluid provides a fluctuating surface that confines the flow of the nonwetting fluid. The resulting dissipation yields stationary Poiseuille-like flows in contrast to the accelerating nature of flow in the absence of the coating. We then consider walls consisting of patches whose wetting preferences to a fluid alternate along the walls. In the resulting flow, the immiscible components exhibit periodic structures in their velocity fields such that the crests are located at the wettability steps in contrast to the behavior of a single fluid for which the crest occurs in the wetting region. We demonstrate that for a single fluid, the modulated velocity field scales with the size of the chain molecules.

  1. Dissipative particle dynamics simulation of wettability alternation phenomena in the chemical flooding process

    Institute of Scientific and Technical Information of China (English)

    Xiaobo Li; Yuewu Liu; Jianfei Tang; Shujiao Li

    2009-01-01

    Wettability alternation phenomena is considered one of the most important enhanced oil recovery (EOR) mechanisms in the chemical flooding process and induced by the adsorption of surfactant on the rock surface. These phenomena are studied by a mesoscopic method named as dissipative particle dynamics (DPD). Both the alteration phenomena of water-wet to oil-wet and that of oil-wet to waterwet are simulated based on reasonable definition of interaction parameters between beads. The wetting hysteresis phenomenon and the process of oil-drops detachment from rock surfaces with different wettability are simulated by adding long-range external forces on the fluid particles. The simulation results show that, the oil drop is liable to spread on the oil-wetting surface and move in the form of liquid film flow, whereas it is likely to move as a whole on the waterwetting surface. There are the same phenomena occuring in wettability-alternated cases. The results also show that DPD method provides a feasible approach to the problems of seepage flow with physicochemical phenomena and can be used to study the mechanism of EOR of chemical flooding.

  2. A Chemical Genetic Approach To The Study Of Cellular Transport

    NARCIS (Netherlands)

    Nieland, T.J.F.

    2005-01-01

    The focus of this thesis is the use of chemical genetics to study two different aspects of membrane biology, (a) the mechanisms underlying cellular lipid transport and (b) the intersection between endocytic and exocytic traffic. The broad goals of chemical genetics are to find novel chemical tool

  3. Study of Endocrine Disrupting Chemicals in Environment

    Directory of Open Access Journals (Sweden)

    Zoltán Juvancz

    2008-06-01

    Full Text Available Endocrine disrupting chemicals (EDC cause more and more seriousenvironmental pollutions. The EDCs show only ng-μg/l concentration level in theenvironment, therefore their determinations require multistep sample preparationprocesses and highly sophisticated instrumentation. This paper discuss the EDC effects,and show examples for determination of such compounds.

  4. Experimental study of chemical concentration variation of ASP flooding

    Institute of Scientific and Technical Information of China (English)

    WANG JiaLu; YUAN ShiYi; SHI FaShun; JIA Xu

    2009-01-01

    A physical modeling system of long slim tube was established. Several pressure measuring and sampling points were laid out at different positions along the tube. Through real-time measurements of pressures and chemical concentrations at different points, the mass transfer and chemical concentration of ASP flooding in porous media are studied. The concentration of chemicals declines gradually during the fluid flow from the inlet to the outlet of the model. The concentration increases in the front edge of the slug faster than the concentration decreases in the rear edge of the slug. The concentration variation of the chemicals is an asymmetrical and offset process. The order of motion velocities of the chemicals from fast to slow is polymer, alkali and surfactant. The motion lag and comprehensive diffusion are strong in the vicinity of the inlet, the motion velocities of the chemicals are high, the difference of flow velocities among the three chemicals is significant and the chromatographic separation of the chemicals is obvious. In the area near the outlet, the comprehensive diffusion and motion lag become weak, the concentrations of the chemicals decrease, the motion velocities of the chemicals are slow,the difference among the motion velocities of the chemicals becomes small, the chromatographic separation is not obvious, the adsorption and retention of chemicals gradually increase as the chemical slug moves further along the tube, the adsorption and retention of polymer is the most serious.

  5. Experimental study of chemical concentration variation of ASP flooding

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A physical modeling system of long slim tube was established. Several pressure measuring and sampling points were laid out at different positions along the tube. Through real-time measurements of pressures and chemical concentrations at different points, the mass transfer and chemical concentration of ASP flooding in porous media are studied. The concentration of chemicals declines gradually during the fluid flow from the inlet to the outlet of the model. The concentration increases in the front edge of the slug faster than the concentration decreases in the rear edge of the slug. The concentration variation of the chemicals is an asymmetrical and offset process. The order of motion velocities of the chemicals from fast to slow is polymer, alkali and surfactant. The motion lag and comprehensive diffusion are strong in the vicinity of the inlet, the motion velocities of the chemicals are high, the difference of flow velocities among the three chemicals is significant and the chromatographic separation of the chemicals is obvious. In the area near the outlet, the comprehensive diffusion and motion lag become weak, the concentrations of the chemicals decrease, the motion velocities of the chemicals are slow, the difference among the motion velocities of the chemicals becomes small, the chromatographic separation is not obvious, the adsorption and retention of chemicals gradually increase as the chemical slug moves further along the tube, the adsorption and retention of polymer is the most serious.

  6. Chemical Control for Host-Parasitoid Model within the Parasitism Season and Its Complex Dynamics

    Directory of Open Access Journals (Sweden)

    Tao Wang

    2016-01-01

    Full Text Available In the present paper, we develop a host-parasitoid model with Holling type II functional response function and chemical control, which can be applied at any time of each parasitism season or pest generation, and focus on addressing the importance of the timing of application pesticide during the parasitism season or pest generation in successful pest control. Firstly, the existence and stability of both the host and parasitoid populations extinction equilibrium and parasitoid-free equilibrium have been investigated. Secondly, the effects of key parameters on the threshold conditions have been discussed in more detail, which shows the importance of pesticide application times on the pest control. Thirdly, the complex dynamics including multiple attractors coexistence, chaotic behavior, and initial sensitivity have been studied by using numerical bifurcation analyses. Finally, the uncertainty and sensitivity of all the parameters on the solutions of both the host and parasitoid populations are investigated, which can help us to determine the key parameters in designing the pest control strategy. The present research can help us to further understand the importance of timings of pesticide application in the pest control and to improve the classical chemical control and to make management decisions.

  7. Silver-mediated base pairings: towards dynamic DNA nanostructures with enhanced chemical and thermal stability

    Science.gov (United States)

    Swasey, Steven M.; Gwinn, Elisabeth G.

    2016-04-01

    The thermal and chemical fragility of DNA nanomaterials assembled by Watson–Crick (WC) pairing constrain the settings in which these materials can be used and how they can be functionalized. Here we investigate use of the silver cation, Ag+, as an agent for more robust, metal-mediated self-assembly, focusing on the simplest duplex building blocks that would be required for more elaborate Ag+–DNA nanostructures. Our studies of Ag+-induced assembly of non-complementary DNA oligomers employ strands of 2–24 bases, with varied base compositions, and use electrospray ionization mass spectrometry to determine product compositions. High yields of duplex products containing narrowly distributed numbers of Ag+ can be achieved by optimizing solution conditions. These Ag+-mediated duplexes are stable to at least 60 mM Mg2+, higher than is necessary for WC nanotechnology schemes such as tile assemblies and DNA origami, indicating that sequential stages of Ag+-mediated and WC-mediated assembly may be feasible. Circular dichroism spectroscopy suggests simple helical structures for Ag+-mediated duplexes with lengths to at least 20 base pairs, and further indicates that the structure of cytosine-rich duplexes is preserved at high urea concentrations. We therefore propose an approach towards dynamic DNA nanomaterials with enhanced thermal and chemical stability through designs that combine sturdy silver-mediated ‘frames’ with WC paired ‘pictures’.

  8. Theoretical studies of combustion dynamics

    International Nuclear Information System (INIS)

    The reactions of O(3P)+H2, D2, and HD are the focus of this research. Their approximate three-dimensional quantum calculations of the rate constant for both the ground and first excited vibrational states of the above reactions were completed last year. Comparisons of the calculated rate constants, isotope effects and branching ratios have been made with available experimental work and also with the variational transition state theory calculations. The main conclusion of that paper is that tunneling plays a major role in the reaction dynamics at room temperature and below

  9. Computational modelling of the complex dynamics of chemically blown polyurethane foam

    Science.gov (United States)

    Ireka, I. E.; Niedziela, D.; Schäfer, K.; Tröltzsch, J.; Steiner, K.; Helbig, F.; Chinyoka, T.; Kroll, L.

    2015-11-01

    This study presents computational analysis of the complex dynamics observed in chemically blown polyurethane foams during reaction injection molding process. The mathematical formulation introduces an experimentally motivated non-divergence free setup for the continuity equations which reflects the self expanding behaviour observed in the physical system. The foam growth phenomena which is normally initiated by adequate pre-mixing of necessary reactant polymers, leading to an exothermic polymerization reaction, bubble nucleation, and gas formation, is captured numerically. We assume the dependence of material viscosity on the degree of cure/polymerization, gas volume fraction, and temperature as well as non-dependence of mixture density on pressure. The set of unsteady nonlinear coupled partial differential equations describing the dynamics of the system are solved numerically for state variables using finite volume techniques such that the front of the flow is tracked with high resolution interface capturing schemes. Graphical representation of the foam volume fraction, evolution of foam heights, and temperature distributions is presented. Results from our simulations are validated with experimental data. These results show good quantitative agreement with observations from experiments.

  10. Chemical approaches to studying stem cell biology

    Institute of Scientific and Technical Information of China (English)

    Wenlin Li; Kai Jiang; Wanguo Wei; Yan Shi; Sheng Ding

    2013-01-01

    Stem cells,including both pluripotent stem cells and multipotent somatic stem cells,hold great potential for interrogating the mechanisms of tissue development,homeostasis and pathology,and for treating numerous devastating diseases.Establishment of in vitro platforms to faithfully maintain and precisely manipulate stem cell fates is essential to understand the basic mechanisms of stem cell biology,and to translate stem cells into regenerative medicine.Chemical approaches have recently provided a number of small molecules that can be used to control cell selfrenewal,lineage differentiation,reprogramming and regeneration.These chemical modulators have been proven to be versatile tools for probing stem cell biology and manipulating cell fates toward desired outcomes.Ultimately,this strategy is promising to be a new frontier for drug development aimed at endogenous stem cell modulation.

  11. Dynamics of chemical reactions of multiply-charged cations: Information from beam scattering experiments

    Czech Academy of Sciences Publication Activity Database

    Herman, Zdeněk

    2015-01-01

    Roč. 378, FEB 2015 (2015), s. 113-126. ISSN 1387-3806 Institutional support: RVO:61388955 Keywords : Multiply-charged ions * Dynamics of chemical reactions * Beam scattering Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.972, year: 2014

  12. Physico-chemical study on guar gum

    International Nuclear Information System (INIS)

    Guar plant is an annual summer plant and it can resist diseases, pests and drought. Guar gum is used in a lot of industries. The present study deals with some physical properties of two commercial grade samples of guar gum cyamopsis tetragonoloba which where produced in 1996 and 1997 seasons (S1 and S2 respectively). Our analytical data are compared with those of previous workers in this area and international quality. Guar gum (S2) is separated into water-insoluble components. Three fractions were obtained from the water-soluble components by fractional participation using acetone. Guar gum powder is yellowish white; the water-insoluble component is brownish white. Comparison study between gum samples (S1 and S2) and water-insoluble fraction (1) and water-soluble fractions are close to each other in their physico-properties. chemical All samples and fractions contain galactomannan polysaccharide as explained by infra-red spectra.Moisture contents for the gum samples were 5.2% and 7.8% and that for the water-insoluble fraction 4.7% while that for fraction samples were 5.2%-7.5% ash contents for the gum samples was 0.81% and 1.14% and for the water-insoluble component 0.88% while the contents in the fractions between 0.5%-0.66%. Nitrogen content determination showed that the gum samples had value of 0.678% and 0.732% and water -insoluble fraction had a value of 0.118%. The values decreased in the water-soluble fractions giving 0.049%, 0.053 and 0.056%. Water-soluble component and its fractions record the following results: pH measurements showed that the water-soluble component had pH 6.70 and 6.84 while its fractions had pH 5.90 and 7.00. Viscosity measurements showed that water-soluble fractions had intrinsic viscosity of 6.4 and 6.8 dL. g-1. The fractions derived from water-soluble fraction had intrinsic viscosity of 6.6, 7 and 7.5 dl. g-1. Using Mark-Howink equation, calculated average molecular weights for the water-soluble components were 7.01x105, and 7.62x

  13. Physico-Chemical Dynamics of Nanoparticle Formation during Laser Decontamination

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, M.D.

    2005-06-01

    Laser-ablation based decontamination is a new and effective approach for simultaneous removal and characterization of contaminants from surfaces (e.g., building interior and exterior walls, ground floors, etc.). The scientific objectives of this research are to: (1) characterize particulate matter generated during the laser-ablation based decontamination, (2) develop a technique for simultaneous cleaning and spectroscopic verification, and (3) develop an empirical model for predicting particle generation for the size range from 10 nm to tens of micrometers. This research project provides fundamental data obtained through a systematic study on the particle generation mechanism, and also provides a working model for prediction of particle generation such that an effective operational strategy can be devised to facilitate worker protection.

  14. Nanoscale Chemical Imaging of a Dynamic Molecular Phase Boundary with Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy.

    Science.gov (United States)

    Jiang, Nan; Chiang, Naihao; Madison, Lindsey R; Pozzi, Eric A; Wasielewski, Michael R; Seideman, Tamar; Ratner, Mark A; Hersam, Mark C; Schatz, George C; Van Duyne, Richard P

    2016-06-01

    Nanoscale chemical imaging of a dynamic molecular phase boundary has broad implications for a range of problems in catalysis, surface science, and molecular electronics. While scanning probe microscopy (SPM) is commonly used to study molecular phase boundaries, its information content can be severely compromised by surface diffusion, irregular packing, or three-dimensional adsorbate geometry. Here, we demonstrate the simultaneous chemical and structural analysis of N-N'-bis(2,6-diisopropylphenyl)-1,7-(4'-t-butylphenoxy)perylene-3,4:9,10-bis(dicarboximide) (PPDI) molecules by UHV tip-enhanced Raman spectroscopy. Both condensed and diffusing domains of PPDI coexist on Ag(100) at room temperature. Through comparison with time-dependent density functional theory simulations, we unravel the orientation of PPDI molecules at the dynamic molecular domain boundary with unprecedented ∼4 nm spatial resolution. PMID:27183322

  15. Dynamic three-dimensional micropatterned cell co-cultures within photocurable and chemically degradable hydrogels.

    Science.gov (United States)

    Sugiura, Shinji; Cha, Jae Min; Yanagawa, Fumiki; Zorlutuna, Pinar; Bae, Hojae; Khademhosseini, Ali

    2016-08-01

    In this paper we report on the development of dynamically controlled three-dimensional (3D) micropatterned cellular co-cultures within photocurable and chemically degradable hydrogels. Specifically, we generated dynamic co-cultures of micropatterned murine embryonic stem (mES) cells with human hepatocellular carcinoma (HepG2) cells within 3D hydrogels. HepG2 cells were used due to their ability to direct the differentiation of mES cells through secreted paracrine factors. To generate dynamic co-cultures, mES cells were first encapsulated within micropatterned photocurable poly(ethylene glycol) (PEG) hydrogels. These micropatterned cell-laden PEG hydrogels were subsequently surrounded by calcium alginate (Ca-Alg) hydrogels containing HepG2 cells. After 4 days, the co-culture step was halted by exposing the system to sodium citrate solution, which removed the alginate gels and the encapsulated HepG2 cells. The encapsulated mES cells were then maintained in the resulting cultures for 16 days and cardiac differentiation was analysed. We observed that the mES cells that were exposed to HepG2 cells in the co-cultures generated cells with higher expression of cardiac genes and proteins, as well as increased spontaneous beating. Due to its ability to control the 3D microenvironment of cells in a spatially and temporally regulated manner, the method presented in this study is useful for a range of cell-culture applications related to tissue engineering and regenerative medicine. Copyright © 2013 John Wiley & Sons, Ltd. PMID:24170301

  16. Molecular dynamics studies of palladium

    International Nuclear Information System (INIS)

    Equilibrium bulk properties of Pd are examined using molecular dynamics technique based on the embedded atom potential. We calculate the total energy and the lattice parameter as a function of temperature. Melting temperature is determined from the discontinuous transition in the energy and lattice parameter. Specific heat and linear coefficient of thermal expansion are calculated from the energy and lattice parameters respectively and results show good agreement with experimental values. Finally the mean square displacements of thermal expansion are calculated form the energy and lattice parameters respectively and results show good agreement with the experimental values. Finally the mean square displacements of the atoms in bulk Pd are compared with the mean square displacements on the three low-index faces (100), (110) and (III). (author)

  17. STUDY OF CYANOETHYLATED ALFA FIBER REINFORCED COMPOSITES BY DYNAMIC MECHANICAL ANALYSIS

    OpenAIRE

    Moufida, Ben; Ridha, Ben

    2008-01-01

    Cyanoethylation of long alfa fibers was studied, and these chemically modified fibers were used to manufacture alfa-polyester composites. The dynamic mechanical thermal properties of an unsaturated polyester resin (cured) and of composites of unmodified and chemically modified alfa-polyester were studied using a dynamic mechanical analyzer over a wide temperature range. The data suggest that in spite of the fragility of the cyanoethylated alfa fibers compared to the unmodified ones, both unmo...

  18. Studies on Chemical Constituents From Artabotrys Hainanensis

    Institute of Scientific and Technical Information of China (English)

    CHEN Guangying; SONG Xiao-Ping; HAN Chang-ri

    2004-01-01

    Artabotrys Hainanensis R.E. Fries are plants of the Annonaccac family artabotrys genus,which includes an estimated 100 types of plants distributed mainly in the tropical zone and the subtropics areas. Four types of the plants are discovered in our country, two of which, A.Hongkongensis Hance and A. hexapetalus (Linn. F.) Bhandari, in Guangdong Province, and the other two, A. Pilosus and A. Hainanensis R.E. Fries, in Hainan Province. The latter are widely distributed in Hainan Island with very rich reserves. They have long been used among the ordinary people as medicinal plants with antipyretic, antidotal, antiphlogistic and analgesic effects and are often used for malaria. Scholars from home and abroad have paid much attention to the plants of the Annonaccac family for their containing anti-tumor activities, and after early or late research of the chemical constituents of the root, stem (derm), leaf and fruit of many types of plants of Artabotrys genus, more than 40 compounds including alkaloid, flavone and terpenoid have been isolated and obtained. Artabotrys Hainanensis R.E. Fries are Hainan endemic plants and there has been no report on the research of their chemical constituents and biological activities so far. In order to find new constituents of pharmacologic activity, we have researched the chemical constituents of the leaf and stem.The crude drugs were collected from Hainan Jianfeng Mountain and were identified as Artabotrys Hainanensis R.E. Fries of the Annonaccac family artabotrys genus. Its sample specimen is now kept in Chemistry Department of Hainan Normal University.After isolation and identification of constituent, six compounds were isolated from the leaf of Artabotrys Hainanensis R.E. Fries and elucidated as β -sitosterol (Ⅰ), catechin (Ⅱ), mangiferin (Ⅲ),(Ⅳ), (Ⅴ), (Ⅵ). All the compounds were obtained from this plant for the first time. Compounds Ⅱ, Ⅲ,Ⅳ, Ⅴ and Ⅵ were obtained from the genus of Artabotrys for the first time.

  19. [Studies on chemical constituents of Tinospora hainanesis].

    Science.gov (United States)

    Guo, Y; Lin, L; Shen, J

    1998-05-01

    Tinospora hainanesis is a new species of Menispermaceae plant. It is used as folk remedy for joint pain and physical injury. Five compounds were isolated from the vine stalk of Tinospora hainanesis. By spectral analysis and chemical methods, the structures of the compounds were identified as makisterone A (I), 2,3-dimethoxy-9,10-dihydroxy-N-methyltetrahydroproto-berberine quaternary salt (II), palmatine (III), beta-amyrin (IV) and docosyl ferulate (V). II is a new quaternary alkaloid named as haitinosporine. I, IV and V were isolated for the first time from the plants of Tinospora genus. PMID:12017002

  20. System chemical biology studies of endocrine disruptors

    DEFF Research Database (Denmark)

    Taboureau, Olivier; Oprea, Tudor I.

    Endocrine disrupting chemicals (EDCs) alter hormonal balance and other physiological systems through inappropriate developmental or adult exposure, perturbing the reproductive function of further generations. While disruption of key receptors (e.g., estrogen, androgen, and thyroid) at the ligand...... binding domain (LBD) has been associated with EDCs, a significant number of EDCs do not appear to influence the LBDs of these receptors. Therefore, we evaluated the potential biological effects of EDCs in humans with the aim to rationalize the etiology of certain disorders associated with the reproductive...

  1. Studies of dynamical processes affecting global climate

    Energy Technology Data Exchange (ETDEWEB)

    Keller, C.; Cooper, D.; Eichinger, W. [and others

    1998-12-31

    This is the final report of a three-year, Laboratory Directed Research and Development project at the Los Alamos National Laboratory (LANL). The main objective was, by a combined theoretical and observational approach, to develop improved models of dynamic processes in the oceans and atmosphere and to incorporate them into large climate codes, chiefly in four main areas: numerical physics, chemistry, water vapor, and ocean-atmosphere interactions. Main areas of investigation included studies of: cloud parameterizations for global climate codes, Lidar and the planetary boundary layer, chemistry, climate variability using coupled ocean-atmospheric models, and numerical physical methods. This project employed a unique approach that included participation of a number of University of California faculty, postdoctoral fellows and graduate students who collaborated with Los Alamos research staff on specific tasks, thus greatly enhancing the research output. Overall accomplishments during the sensing of the atmospheric planetary were: (1) first two- and three-dimensional remote sensing of the atmospheric planetary boundary layer using Lidars, (2) modeling of 20-year cycle in both pressure and sea surface temperatures in North Pacific, (3) modeling of low frequency internal variability, (4) addition of aerosols to stratosphere to simulate Pinatubo effect on ozone, (5) development of fast, comprehensive chemistry in the troposphere for urban pollution studies, (6) new prognostic cloud parameterization in global atmospheric code remedied problems with North Pacific atmospheric circulation and excessive equatorial precipitation, (7) development of a unique aerosol analysis technique, the aerosol time-of-flight mass spectrometer (ATOFMS), which allows real-time analysis of the size and chemical composition of individual aerosol particles, and (8) numerical physics applying Approximate Inertial Manifolds to ocean circulation. 14 refs., 6 figs.

  2. Liquid helium fluid dynamics studies

    International Nuclear Information System (INIS)

    The present report describes the work carried out under the sponsorship of the Division of High Energy Physics. The report is divided into sections according to the original grant proposal (hydrodynamic studies of single phase helium; two phase flow studies; component development studies; and new research areas). Following the text is a listing of publications which have resulted from work under the grant

  3. The Panel Study of Income Dynamics (PSID)

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Panel Study of Income Dynamics (PSID) began in 1968 with a nationally representative sample of over 18,000 individuals living in 5,000 families in the United...

  4. Chemical Equilibrium in Supramolecular Systems as Studied by NMR Spectrometry

    Science.gov (United States)

    Gonzalez-Gaitano, Gustavo; Tardajos, Gloria

    2004-01-01

    Undergraduate students are required to study the chemical balance in supramolecular assemblies constituting two or more interacting species, by using proton NMR spectrometry. A good knowledge of physical chemistry, fundamentals of chemical balance, and NMR are pre-requisites for conducting this study.

  5. Chemical Reaction Rates from Ring Polymer Molecular Dynamics: Theory and Practical Applications

    CERN Document Server

    Suleimanov, Yury V; Guo, Hua

    2016-01-01

    This Feature Article presents an overview of the current status of Ring Polymer Molecular Dynamics (RPMD) rate theory. We first analyze theory and its connection to quantum transition state theory. We then focus on its practical application to prototypical chemical reactions in the gas phase, which demonstrate how accurate and reliable RPMD is for calculating thermal chemical reaction rates in multifarious cases. This review serves as an important checkpoint in RPMD rate theory development, which shows that RPMD is shifting from being just one of recent novel ideas to a well-established and validated alternative to conventional techniques for calculating thermal chemical rates. We also hope it will motivate further applications of RPMD to various chemical reactions.

  6. Detailed balance method for chemical potential determination in Monte Carlo and molecular dynamics simulations

    International Nuclear Information System (INIS)

    We present a new, nondestructive, method for determining chemical potentials in Monte Carlo and molecular dynamics simulations. The method estimates a value for the chemical potential such that one has a balance between fictitious successful creation and destruction trials in which the Monte Carlo method is used to determine success or failure of the creation/destruction attempts; we thus call the method a detailed balance method. The method allows one to obtain estimates of the chemical potential for a given species in any closed ensemble simulation; the closed ensemble is paired with a ''natural'' open ensemble for the purpose of obtaining creation and destruction probabilities. We present results for the Lennard-Jones system and also for an embedded atom model of liquid palladium, and compare to previous results in the literature for these two systems. We are able to obtain an accurate estimate of the chemical potential for the Lennard-Jones system at higher densities than reported in the literature

  7. Computer Simulations of Mechano-Chemical Networks Choreographing Actin Dynamics in Cell Motility

    Science.gov (United States)

    Zhuravlev, Pavel I.; Hu, Longhua; Papoian, Garegin A.

    In eukaryotic cells, cell motility is largely driven by self-assembly and growth of filamentous networks comprised of actin. Numerous proteins regulate actin network dynamics either biochemically, or through mechanical interactions. This regulation is rather complex, intricately coordinated both spatially and temporally. Although experiments in vivo and in vitro have provided a trove of structural and biochemical information about actin-based cell motility processes, experimental data is not always easy to interpret unambiguously, sometimes various interpretations being in contradiction with each other. Hence, mathematical modeling approaches are necessary for providing a physical foundation for interpreting and guiding experiments. In particular, computer simulations based on physicochemical interactions provide a systems-level description of protrusion dynamics. In this contribution, we review recent progress in modeling actin-based cell motility using detailed computer simulations. We elaborate on the way actin network dynamics is determined by the interplay between chemical reactions, mechanical feedbacks, and transport bottlenecks. We also discuss the role of inherent randomness of elementary chemical reactions in determining the dynamical behavior of the mechano-chemical network controlling actin polymerization and growth.

  8. The multiscale simulation of metal organic chemical vapor deposition growth dynamics of GaInP thin film

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin film. By combining the computational fluid dynamics (CFD) and the kinetic Monte Carlo (KMC) methods with virtual reality (VR) technology, this paper presents a multiscale simulation of fluid dynamics, thermodynamics, and molecular dynamics to study the growth process of GaInP thin film in a vertical MOCVD reactor. The results of visualization truly and intuitively not only display the distributional properties of the gas’ thermal and flow fields in a MOCVD reactor but also display the process of GaInP thin film growth in a MOCVD reactor. The simulation thus provides us with a fundamental guideline for optimizing GaInP MOCVD growth.

  9. THE STUDY OF CHEMICAL COMPOSITION FOR ANIMAL FATS DURING STORAGE

    OpenAIRE

    Flavia Pop; Cornel Laslo

    2009-01-01

    In this article the chemical composition for 3 types of animal fats (pork fat, beef tallow and buffalo tallow), following the variation of saturated and unsaturated fatty acids proportion during freezing storage was studied. Determination of chemical composition of animal fats is important in establishing organoleptic and physico-chemical parameters, the variation of them in time, nature and proportion of fatty acids conferring specific characteristics to them. For pork fat was determined the...

  10. Reaction Ensemble Molecular Dynamics: Direct Simulation of the Dynamic Equilibrium Properties of Chemically Reacting Mixtures

    Czech Academy of Sciences Publication Activity Database

    Brennan, J.K.; Lísal, Martin; Gubbins, K.E.; Rice, B.M.

    2004-01-01

    Roč. 70, č. 6 (2004), 0611031-0611034. ISSN 1063-651X R&D Projects: GA ČR GA203/03/1588 Grant ostatní: NSF(US) CTS-0211792 Institutional research plan: CEZ:AV0Z4072921 Keywords : reacting systems * simulation * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.352, year: 2004

  11. Physico-chemical studies of industrial pollutants

    International Nuclear Information System (INIS)

    Pollution problem industrial estates in more acute in some areas and district Haripur is one of those places. Industrial wastewater generated form various industries is drained into the natural streams / nallahs, which ultimately join river Indus through river Haro. Effluent of different industries were collected periodically and analysed for pH, conductivity, hardness, alkalinity/ acidity, chemical oxygen demand (COD), suspended and dissolved solids, ammonia and chlorine. cations like calcium, magnesium and iron, anions like phosphate, chlorides, sulphates and sulphides were also checked, using standard analytical techniques. Trace metals like arsenic cadmium, chromium cobalt copper lead manganese, nickel, tin and zinc were also detected by atomic absorption spectroscopy in the effluent samples. These results were evaluated and compared with the National Environmental Quality Standards (NEQS). Effluent of the fertilizer industries in Haripur, (both phosphatic and nitrogenous) are producing pollution and causing damage to the flora and fauna in the area. Effluent of the phosphatic fertilizer is acidic, having pH 1.5-3.0 due to acid, while effluent of nitrogenous fertilizer is alkaline having pH 9.0 -10.5 due to ammonia. Suggestion for useful remedial measures and the effective control of the pollutants are discussed. (author)

  12. Introduction to dynamic spin chemistry magnetic field effects on chemical and biochemical reactions

    CERN Document Server

    Hayashi, Hisaharu

    2004-01-01

    This book presents a detailed account of one of the most mysterious problems in science - whether ordinary magnetic fields can exert an appreciable influence on chemical and biochemical reactions. The first aim of the book is to introduce this research, through theoretical and dynamic spin chemistry, to graduate students and researchers, by means of detailed theoretical and experimental descriptions. The second aim is to review typical recent investigations, which will stimulate new interest and applications in the 21st century. Because dynamic spin chemistry is based on established science, i

  13. The imprint of satellite accretion on the chemical and dynamical properties of disc galaxies

    CERN Document Server

    Ruiz-Lara, T; Gibson, B K; Pérez, I; Florido, E; Minchev, I; Sánchez-Blázquez, P

    2015-01-01

    Aims: We study the effects of the cosmological assembly history on the chemical and dynamical properties of the discs of spiral galaxies as a function of radius. Methods: We make use of the simulated Milky-Way mass, fully-cosmological discs, from {\\tt RaDES} (Ramses Disc Environment Study). We analyse their assembly history by examining the proximity of satellites to the galactic disc, instead of their merger trees, to better gauge which satellites impact the disc. We present stellar age and metallicity profiles, Age-Metallicity Relation (AMR), Age-Velocity dispersion Relation (AVR), and Stellar Age Distribution (SAD) in several radial bins for the simulated galaxies. Results: Assembly histories can be divided into three different stages: i) a merger dominated phase, when a large number of mergers with mass ratios of $\\sim$1:1 take place (lasting $\\sim$3.2$\\pm$0.4 Gyr on average); ii) a quieter phase, when $\\sim$1:10 mergers take place (lasting $\\sim$4.4$\\pm$2.0 Gyr) - these two phases are able to kinematical...

  14. Universal imaging: Dissociative ionization of polyatomic molecules, chemical dynamics beamline 9.0.2

    International Nuclear Information System (INIS)

    A third endstation was recently added to the Chemical Dynamics beamline, designed to exploit the high flux broadband undulator light for a range of studies of reactive scattering, photochemistry and photoionization processes using time-of-flight mass spectroscopy coupled with position-sensitive detection. Two molecular beam sources are fixed at right angles, with the undulator light, or laser beams, intersecting the molecular beams at 45 degrees. To date, beamline experiments have included a study of dissociative photoionization of a variety of molecules including N2O and SF6. In this mode, a single molecular beam source is used, with the tunable undulator light inducing, in SF6 for example, the process SF6 → SF6+ + e- → SF5+ + F + e-. The SF5+ ions are accelerated up the flight tube, mass selected and detected as a function of position on a phosphor screen viewed by a CCD camera. The position directly reveals the recoil speed (or translational energy release) and angular distribution for the dissociative ionization process. Furthermore, this measurement is obtained for all recoil speeds and angles simultaneously. Such detailed angular information has not previously been obtained for dissociative ionization processes; typically ion time-of-flight profiles are deconvoluted to yield rough insight into the angular distributions. The recorded image is actually a 2-dimensional projection of the nascent 3-dimensional velocity distribution, but established tomographic techniques enable the authors to reconstruct the 3-D distribution

  15. Cine CT technique for dynamic airway studies

    International Nuclear Information System (INIS)

    The advent of cine CT scanning with its 50-msec data acquisition time promises a much wider range of dynamic CT studies. The authors describe a method for dynamic evaluation of the extrathoracic airway, which they believe has considerable potential application in nonfixed upper-airway disease, such as sleep apnea and stridor of unknown cause. Conventional CT is limited in such studies by long data acquisition time and can be used to study only prolonged maneuvers such as phonation. Fluoroscopy and digital subtraction studies are limited by relatively high radiation dose and inability to image all wall motions simultaneously

  16. Contribution to chemical-mineralogical study of carbonatites

    International Nuclear Information System (INIS)

    A preliminary chemical-mineralogical study of carbonatites from Jacupiranga (SP,Brazil) and Alto Pinheiros (SC,Brazil) enabled not only to ratify hypotheses previously described by Brazilian researchers but also made clear certain aspects related to the geochemistry of carbonatites concerning their occurrence, the probable genesis of these species and their chemical and mineralogical characteristics.(Author)

  17. Recent achievements in chemical studies of heaviest elements

    Science.gov (United States)

    Gäggeler, H. W.

    2011-09-01

    Discovery of heavy elements up to atomic number 118 at FLNR in Dubna has paved the way to also extend chemical knowledge to heavier members of the periodic table. Recent studies on the chemical properties of Cn and element 114 are summarized that have been performed at FLNR in Dubna using the fusion reactions 48Ca + 242/244Pu.

  18. Recent achievements in chemical studies of heaviest elements

    International Nuclear Information System (INIS)

    Discovery of heavy elements up to atomic number 118 at FLNR in Dubna has paved the way to also extend chemical knowledge to heavier members of the periodic table. Recent studies on the chemical properties of Cn and element 114 are summarized that have been performed at FLNR in Dubna using the fusion reactions 48Ca + 242/244Pu.

  19. Dynamics, chemical properties and bioavailability of DOC in an early successional catchment

    Directory of Open Access Journals (Sweden)

    U. Risse-Buhl

    2013-07-01

    Full Text Available The dynamics of dissolved organic carbon (DOC have been intensively studied in mature ecosystems, but little is known about DOC dynamics and the significance of DOC as a substrate for microbial activity in early-successional catchments. We determined the concentration, chemical composition, source, radiocarbon age, and bioavailability of DOC along the hydrological flow path from soil solution to a downstream pond in a recently constructed catchment (Chicken Creek Catchment, Germany. Soil solution, upwelling ground water, stream water, subsurface water in an alluvial fan, and pond water all had high DOC concentrations (averages: 6.0–11.6 mg DOC L–1, despite small carbon stocks in both vegetation and soil of the catchment. Solid-state CPMAS 13C NMR of DOC in upwelling ground water revealed a higher proportion of aromatic compounds (32% and a lower proportion of carbohydrates (33% than in pond water (18% and 45%, respectively. The average 14C age of DOC in upwelling ground water was 2600 to 2900 yr, while organic matter of the Quaternary substrate of the catchment had a 14C age of 3000 to 16 000 yr. Both the 14C age data and 13C NMR spectra suggest that DOC partly derived from organic matter of the Quaternary substrate (about 40 to 90% of the C in the DOC, indicating that both recent and old C of the DOC can support microbial activity during early ecosystem succession. However, in a 70 day incubation experiment, only about 11% of the total DOC was found to be bioavailable. This proportion was irrespective of the water type. Origin of the microbial communities within the catchment (enriched from soil, stream sediment or pond water also had only a marginal effect on overall DOC utilization.

  20. Dynamics, chemical properties and bioavailability of DOC in an early successional catchment

    Directory of Open Access Journals (Sweden)

    U. Risse-Buhl

    2013-01-01

    Full Text Available The dynamics of dissolved organic carbon (DOC have been intensively studied in mature ecosystems, but little is known about DOC dynamics and the significance of DOC as a substrate for microbial activity in early-successional catchments. We determined the concentration, chemical composition, source, radiocarbon age, and bioavailability of DOC along the hydrological flow path from soil solution to a downstream pond in a recently constructed catchment (Chicken Creek Catchment, Germany. Soil solution, upwelling ground water, subsurface water in an alluvial fan, and pond water all had high DOC concentrations (averages of 6.0–11.6 mg DOC L−1, despite small carbon stocks in either vegetation or soil of the early-successional catchment. The mean 14C age of DOC in upwelling ground water was 2600 to 2800 yr. Solid-state CPMAS 13C NMR revealed a higher proportion of aromatic compounds (32% and a lower proportion of carbohydrates (33% in upwelling ground water than in pond water (18% and 45%, respectively. The 14C age and 13C NMR spectra suggest that DOC was partly mobilized from charred organic matter of the Quaternary substrate. In an experimental 70-days incubation experiment, 20% of the total DOC was found to be bioavailable, irrespective of the water type. Origin of microbial communities (enriched from soil, stream sediment or pond water had only marginal effects on overall DOC utilization. Overall, these data suggest that the old DOC can support microbial activity during early ecosystem succession to some extent, although the largest fraction is recalcitrant DOC that is exported from the catchment once it has been mobilized.

  1. Dynamics, chemical properties and bioavailability of DOC in an early successional catchment

    Science.gov (United States)

    Risse-Buhl, U.; Hagedorn, F.; Dümig, A.; Gessner, M. O.; Schaaf, W.; Nii-Annang, S.; Gerull, L.; Mutz, M.

    2013-07-01

    The dynamics of dissolved organic carbon (DOC) have been intensively studied in mature ecosystems, but little is known about DOC dynamics and the significance of DOC as a substrate for microbial activity in early-successional catchments. We determined the concentration, chemical composition, source, radiocarbon age, and bioavailability of DOC along the hydrological flow path from soil solution to a downstream pond in a recently constructed catchment (Chicken Creek Catchment, Germany). Soil solution, upwelling ground water, stream water, subsurface water in an alluvial fan, and pond water all had high DOC concentrations (averages: 6.0-11.6 mg DOC L-1), despite small carbon stocks in both vegetation and soil of the catchment. Solid-state CPMAS 13C NMR of DOC in upwelling ground water revealed a higher proportion of aromatic compounds (32%) and a lower proportion of carbohydrates (33%) than in pond water (18% and 45%, respectively). The average 14C age of DOC in upwelling ground water was 2600 to 2900 yr, while organic matter of the Quaternary substrate of the catchment had a 14C age of 3000 to 16 000 yr. Both the 14C age data and 13C NMR spectra suggest that DOC partly derived from organic matter of the Quaternary substrate (about 40 to 90% of the C in the DOC), indicating that both recent and old C of the DOC can support microbial activity during early ecosystem succession. However, in a 70 day incubation experiment, only about 11% of the total DOC was found to be bioavailable. This proportion was irrespective of the water type. Origin of the microbial communities within the catchment (enriched from soil, stream sediment or pond water) also had only a marginal effect on overall DOC utilization.

  2. Chiral dynamics and operator relations at non-zero chemical potential

    International Nuclear Information System (INIS)

    We discuss Taylor expansions of operator expectation values in QCD with respect to chemical potentials of quarks. Maxwell's relations between coefficients and Ward identities between series are used to relate the operators which give the Taylor coefficients of the series for the chiral condensate, the pseudoscalar susceptibility and the mass dependence of quark number susceptibilities. Through such relations the physics of chiral dynamics are explored. The renormalized expectation values of the chiral condensate and its Taylor coefficients are extracted from simulation

  3. Structural dynamics effects on the ultrafast chemical bond cleavage of a photodissociation reaction

    OpenAIRE

    Corrales, Maria E.; Loriot, Vincent; Balerdi, Garikoitz; González-Vázquez, Jesús; de Nalda, Rebeca; Bañares, Luis; Zewail, Ahmed H.

    2014-01-01

    The correlation between chemical structure and dynamics has been explored in a series of molecules with increasing structural complexity in order to investigate its influence on bond cleavage reaction times in a photodissociation event. Femtosecond time-resolved velocity map imaging spectroscopy reveals specificity of the ultrafast carbon–iodine (C–I) bond breakage for a series of linear (unbranched) and branched alkyl iodides, due to the interplay between the pure reaction coordinate and the...

  4. The Dynamics of fluid flow and associated chemical fluxes at active continental margins

    OpenAIRE

    Solomon, Evan Alan

    2007-01-01

    Active fluid flow plays an important role in the geochemical, thermal, and physical evolution of the Earth’s crust. This dissertation investigates the active fluid flow and associated chemical fluxes at two dynamic continental margins: The Costa Rica subduction zone and the northern Gulf of Mexico hydrocarbon province, using novel seafloor instrumentation for continuous monitoring of fluid flow rates and chemistry. Traditional pore fluid sampling methods and flow rate models only provide a ...

  5. Molecular Dynamics Studies of Initiation in Energetic Materials

    OpenAIRE

    Haskins, P.

    1995-01-01

    In this paper an overview of Molecular Dynamics simulations of chemically reacting systems is described. In particular, molecular dynamics simulations of shock initiation in a model energetic material are reported. The use of Molecular Dynamics to model thermal initiation and determine reactions rates in energetic materials is also discussed. Finally, the future potential of MD techniques for energetic materials applications is considered.

  6. Dynamics of chemical vapor sensing with MoS2 using 1T/2H phase contacts/channel

    Science.gov (United States)

    Friedman, Adam L.; Perkins, F. Keith; Hanbicki, Aubrey T.; Culbertson, James C.; Campbell, Paul M.

    2016-06-01

    Ultra-thin transition metal dichalcogenides (TMDs) films show remarkable potential for use in chemical vapor sensing devices. Electronic devices fabricated from TMD films are inexpensive, inherently flexible, low-power, amenable to industrial-scale processing because of emergent growth techniques, and have shown high sensitivity and selectivity to electron donor analyte molecules important for explosives and nerve gas detection. However, for devices reported to date, the conductance response to chemical vapors is dominated by Schottky contacts, to the detriment of the sensitivity, selectivity, recovery, and obscuring their intrinsic behavior. Here, we use contact engineering to transition the contacts in a MoS2 FET-based chemical vapor sensor to the 1T conducting phase, while leaving the channel in the 2H semiconducting state, and thus providing Ohmic contacts to the film. We demonstrate that the resultant sensors have much improved electrical characteristics, are more selective, and recover fully after chemical vapor exposure--all major enhancements to previously MoS2 sensor devices. We identify labile nitrogen-containing electron donors as the primary species that generate a response in MoS2, and we study the dynamics of the sensing reactions, identifying two possible qualitative models for the chemical sensing reaction.

  7. Chemical - Elwha River Dam Removal Study

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This study examines the ecosystem response of the Elwha River to the removal of the Elwha River dams. We will measure the following attributes of ecosystem...

  8. Dynamics, Miscibility, and Morphology in Polymer-Molecule Blends: The Impact of Chemical Functionality

    KAUST Repository

    Do, Khanh

    2015-10-22

    In the quest to improve the performance of organic bulk-heterojunction solar cells, many recent efforts have focused on developing molecular and polymer alternatives to commonly used fullerene acceptors. Here, molecular dynamics simulations are used to investigate polymer-molecule blends comprised of the polymer donor poly(3-hexylthiophene) (P3HT) with a series of acceptors based on trialkylsilylethynyl-substituted pentacene. A matrix of nine pentacene derivatives, consisting of systematic chemical variation both in the nature of the alkyl groups and electron-withdrawing moieties appended to the acene, is used to draw connections between the chemical structure of the acene acceptor and the nanoscale properties of the polymer-molecule blend. These connections include polymer and molecular diffusivity, donor-acceptor packing and interfacial (contact) area, and miscibility. The results point to the very significant role that seemingly modest changes in chemical structure play during the formation of polymer-molecule blend morphologies.

  9. Personal Chemical Exposure informatics

    Science.gov (United States)

    Chemical Exposure science is the study of human contact with chemicals (from manufacturing facilities, everyday products, waste) occurring in their environments and advances knowledge of the mechanisms and dynamics of events that cause or prevent adverse health outcomes. (adapted...

  10. Dynamics of chemical elements in the fermentation process of ethanol production

    International Nuclear Information System (INIS)

    Brazil has become the largest producer of biomass ethanol derived from sugar cane. The industrial production is based on the fermentation of sugar cane juice by yeast, inside of large volume vats, in a fed-batch process that recycles yeast cells. To study the dynamics of chemical elements in each operating cycle, five stages of the fermentation process were considered: must, yeast suspension, wine, non-yeast wine and yeast cream. For this, a mass balance of the terrigenous elements, Ce, Co, Cs, Eu, Fe, Hf, La, Na, Sc, Sm, and Th, and the sugar cane plant elements, Br, K, Rb, and Zn, were established in fermentation vats of an industrial scale unit, with sampling undertaken during different climatic conditions (dry and rainy periods). A similar distribution of the sugar cane characteristics elements was found for the stages analysed, while for the terrigenous elements a trend of accumulation in the yeast cream was observed. Preferential absorption of Br, K, Rb, and Zn by yeast cells was indicated by the smaller concentrations observed in yeast suspension than in yeast cream. (author)

  11. Structural and dynamical properties of water on chemically modified surfaces: The role of the instantaneous surface

    Science.gov (United States)

    Bekele, Selemon; Tsige, Mesfin

    Surfaces of polymers such as atactic polystyrene (aPS) represent very good model systems for amorphous material surfaces. Such polymer surfaces are usually modified either chemically or physically for a wide range of applications that include friction, lubrication and adhesion. It is thus quite important to understand the structural and dynamical properties of liquids that come in contact with them to achieve the desired functional properties. Using molecular dynamics (MD) simulations, we investigate the structural and dynamical properties of water molecules in a slab of water in contact with atactic polystyrene surfaces of varying polarity. We find that the density of water molecules and the number distribution of hydrogen bonds as a function of distance relative to an instantaneous surface exhibit a structure indicative of a layering of water molecules near the water/PS interface. For the dynamics, we use time correlation functions of hydrogen bonds and the incoherent structure function for the water molecules. Our results indicate that the polarity of the surface dramatically affects the dynamics of the interfacial water molecules with the dynamics slowing down with increasing polarity. This work was supported by NSF Grant DMR1410290.

  12. Studies on Semantic Systems Chemical Biology

    Science.gov (United States)

    Chen, Bin

    2012-01-01

    Current "one disease, one target and one drug" drug development paradigm is under question as relatively few drugs have reached the market in the last two decades. Increasingly research focus is being placed on the study of drug action against biological systems as a whole rather than against a single component (called "Systems…

  13. In vivo Dynamic Studies of Brain Metabolism

    Institute of Scientific and Technical Information of China (English)

    LUO Xuechun; JIANG Yufeng; ZHANG Riqing

    2005-01-01

    Nuclear magnetic resonance (NMR) can noninvasively monitor intracellular concentrations and kinetic properties of numerous inorganic and organic compounds. A 31P NMR surface coil was used in vivo to dynamically measure phosphocreatine (PCr), adenosine triphosphate (ATP), and intracellular inorganic phosphate (Pi) levels in mouse brain during ischemia-reperfusion to study the damage of cerebral tissues caused by ischemia and effects of herbs on cerebral energy metabolism during ischemia-reperfusion. The study provides dynamic brain energy metabolism data during different periods. The data show that some herbs more rapidly increase the PCr level during the recovery phase than in the control group.

  14. Contributions to the Study of Dynamic Absorbers, a Case Study

    Directory of Open Access Journals (Sweden)

    Monica Balcau

    2012-01-01

    Full Text Available Dynamic absorbers are used to reduce torsional vibrations. This paper studies the effect of a dynamic absorber attached to a mechanical system formed of three reduced masses which are acted on by one, two or three order x harmonics of a disruptive force.

  15. Tight-binding quantum chemical molecular dynamics simulations for the elucidation of chemical reaction dynamics in SiC etching with SF6/O2 plasma.

    Science.gov (United States)

    Ito, Hiroshi; Kuwahara, Takuya; Kawaguchi, Kentaro; Higuchi, Yuji; Ozawa, Nobuki; Kubo, Momoji

    2016-03-01

    We used our etching simulator [H. Ito et al., J. Phys. Chem. C, 2014, 118, 21580-21588] based on tight-binding quantum chemical molecular dynamics (TB-QCMD) to elucidate SiC etching mechanisms. First, the SiC surface is irradiated with SF5 radicals, which are the dominant etchant species in experiments, with the irradiation energy of 300 eV. After SF5 radicals bombard the SiC surface, Si-C bonds dissociate, generating Si-F, C-F, Si-S, and C-S bonds. Then, etching products, such as SiS, CS, SiFx, and CFx (x = 1-4) molecules, are generated and evaporated. In particular, SiFx is the main generated species, and Si atoms are more likely to vaporize than C atoms. The remaining C atoms on SiC generate C-C bonds that may decrease the etching rate. Interestingly, far fewer Si-Si bonds than C-C bonds are generated. We also simulated SiC etching with SF3 radicals. Although the chemical reaction dynamics are similar to etching with SF5 radicals, the etching rate is lower. Next, to clarify the effect of O atom addition on the etching mechanism, we also simulated SiC etching with SF5 and O radicals/atoms. After bombardment with SF5 radicals, Si-C bonds dissociate in a similar way to the etching without O atoms. In addition, O atoms generate many C-O bonds and COy (y = 1-2) molecules, inhibiting the generation of C-C bonds. This indicates that O atom addition improves the removal of C atoms from SiC. However, for a high O concentration, many C-C and Si-Si bonds are generated. When the O atoms dissociate the Si-C bonds and generate dangling bonds, the O atoms terminate only one or two dangling bonds. Moreover, at high O concentrations there are fewer S and F atoms to terminate the dangling bonds than at low O concentration. Therefore, few dangling bonds of dissociated Si and C atoms are terminated, and they form many Si-Si and C-C bonds. Furthermore, we propose that the optimal O concentration is 50-60% because both Si and C atoms generate many etching products producing fewer C

  16. Computer processing of dynamic scintigraphic studies

    International Nuclear Information System (INIS)

    The methods are discussed of the computer processing of dynamic scintigraphic studies which were developed, studied or implemented by the authors within research task no. 30-02-03 in nuclear medicine within the five year plan 1981 to 85. This was mainly the method of computer processing radionuclide angiography, phase radioventriculography, regional lung ventilation, dynamic sequential scintigraphy of kidneys and radionuclide uroflowmetry. The problems are discussed of the automatic definition of fields of interest, the methodology of absolute volumes of the heart chamber in radionuclide cardiology, the design and uses are described of the multipurpose dynamic phantom of heart activity for radionuclide angiocardiography and ventriculography developed within the said research task. All methods are documented with many figures showing typical clinical (normal and pathological) and phantom measurements. (V.U.)

  17. Structural dynamics in complex liquids studied with multidimensional vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tokmakoff, Andrei [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2013-08-31

    The development of new sustainable energy sources is linked to our understanding of the molecular properties of water and aqueous solutions. Energy conversion, storage, and transduction processes, particularly those that occur in biology, fuel cells, and batteries, make use of water for the purpose of moving energy in the form of charges and mediating the redox chemistry that allows this energy to be stored as and released from chemical bonds. To build our fundamental knowledge in this area, this project supports work in the Tokmakoff group to investigate the molecular dynamics of water’s hydrogen bond network, and how these dynamics influence its solutes and the mechanism of proton transport in water. To reach the goals of this grant, we developed experiments to observe molecular dynamics in water as directly as possible, using ultrafast multidimensional vibrational spectroscopy. We excite and probe broad vibrational resonances of water, molecular solutes, and protons in water. By correlating how molecules evolve from an initial excitation frequency to a final frequency, we can describe the underlying molecular dynamics. Theoretical modeling of the data with the help of computational spectroscopy coupled with molecular dynamics simulations provided the atomistic insight in these studies.

  18. Molecular Dynamics Simulation of Chemical Vapor Deposition of Amorphous Carbon: Dependence on H/C Ratio of Source Gas

    OpenAIRE

    Ito, Atsushi M.; Takayama, Arimichi; Saito, Seiki; Ohno, Noriyasu; Kajita, Shin; Nakamura, Hiroaki

    2010-01-01

    By molecular dynamics simulation, the chemical vapor deposition of amorphous carbon onto graphite and diamond surfaces was studied. In particular, we investigated the effect of source H/C ratio, which is the ratio of the number of hydrogen atoms to the number of carbon atoms in a source gas, on the deposition process. In the present simulation, the following two source gas conditions were tested: one was that the source gas was injected as isolated carbon and hydrogen atoms, and the other was...

  19. Chemical Arsenal for the Study of O-GlcNAc

    Directory of Open Access Journals (Sweden)

    Eun J. Kim

    2011-02-01

    Full Text Available The concepts of both protein glycosylation and cellular signaling have been influenced by O-linked-β-N-acetylglucosamine (O-GlcNAc modification (O-GlcNAcylation on the hydroxyl group of serine or threonine residues. Unlike conventional protein glycosylation, O-GlcNAcylation is localized in the nucleocytoplasm and its cycling is a dynamic process that operates in a highly regulated manner in response to various cellular stimuli. These characteristics render O-GlcNAcylation similar to phosphorylation, which has long been considered a major regulatory mechanism in cellular processes. Various efficient chemical approaches and novel mass spectrometric (MS techniques have uncovered numerous O-GlcNAcylated proteins that are involved in the regulation of many important cellular events. These discoveries imply that O-GlcNAcylation is another major regulator of cellular signaling. However, in contrast to phosphorylation, which is regulated by hundreds of kinases and phosphatases, dynamic O-GlcNAc cycling is catalyzed by only two enzymes: uridine diphospho-N-acetyl-glucosamine:polypeptide β-N-acetylglucosaminyl transferase (OGT and β-D-N-acetylglucosaminidase (OGA. Many useful chemical tools have recently been used to greatly expand our understanding of the extensive crosstalk between O-GlcNAcylation and phosphorylation and hence of cellular signaling. This review article describes the various useful chemical tools that have been developed and discusses the considerable advances made in the O-GlcNAc field.

  20. Geochemical and fluid dynamic investigations into the nature of chemical heterogeneity in the earth's mantle. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Hauri, E.H.

    1992-09-01

    Variations in the abundances of elements and radiogenic isotopes in mantle derived periodotites and volcanic rocks are chemical integrals over time, space, and process, which ultimately contain information about the role of convection in the earth's mantle in creating, maintaining, and destroying geochemical heterogeneities. Successful inversion of these integrals extensive of these integrals requires extensive knowledge of the geochemical behavior of elements, the length scales of chemical variability, the evolution with time of geologic systems, the physical properties of mantle rocks, and the driving forces of phenomena which govern heat and mass transport in a dynamic earth. This dissertation attempts to add to this knowledge by examining the trace element and isotope geochemistry of mantle periodotites and oceanic island basalts, and by studying aspects of the flow of viscous fluids driven by thermal buoyancy.

  1. Study on scattering properties of tissues with hyperosmotic chemical agents

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Optical properties of biological tissue are variable due to the changes of micro-structures and scattering constituents after hyperosmotic chemical agents permeates into tissue. The changes of optical properties of biological tissue are due to the refractive indices matching between the scatterers with high refractive index and the ground substances, which reduce scattering of tissue. The main reasons are that permeated semipermeable chemical agents with higher refractive index than the ground substances of tissuemakes the refractive index of ground substances of tissue higher by the enhancement of the permeated concentration. We studied on the collimated transmittance changes of light penetrating biological tissue after the hyperosmotic chemical agents administrates with different concentration.

  2. Chemical kinetics with electrical and gas dynamics modelization for NOx removal in an air corona discharge

    International Nuclear Information System (INIS)

    A non-stationary reactive gas dynamics model in a mono-dimensional geometry, including radial mass diffusion, gas temperature variation and chemical kinetics, is developed in this paper. The aim is to analyse the spatio-temporal evolution of the main neutral species involved in a corona discharge used for NO pollution control in polluted air at atmospheric pressure and ambient temperature. The present reactive gas dynamics model takes into account 16 neutral chemical species (including certain metastable species) reacting following 110 selected chemical reactions. The initial concentration of each neutral species is obtained from a 1.5D electrical discharge model. The gas temperature variations are due to direct Joule heating during the discharge phase, and also result from the delayed heating due to the relaxation of the vibrational energy into a random thermal energy during the post-discharge phase. The simulation conditions are those of an existing experimental setup (anode voltage of 10 kV in the case of a point to plane geometry with an interelectrode distance of 10 mm). The obtained results show that the diffusion phenomena and the gas temperature rise affect quite well the gas reactivity and the neutral species evolution. This allows us to better understand the different reaction processes and transport phenomena affecting the NO concentration magnitude inside the discharge channel. (author)

  3. Numerical studies on dynamic behaviour of pipelines

    International Nuclear Information System (INIS)

    Dynamic excitation due to a pipe break can cause pipe to abruptly displace and hit the components, instrumentation and equipment nearby. In order to minimize the extensive damage caused by such pipe whips in a nuclear power plant, different types of restraints and supports are designed for the pipelines. Here, structural dynamic behaviour of pipelines is studied with finite element method. A relatively short pipe line section with one bend and one restraint and rigidly fixed from its other end is chosen as a test case. The usability of different types of elements provided by Abaqus finite element code in modelling the pipe, restraint and adjacent civil structure is tested

  4. Effects of mixing energy and flow dynamics on chemical dispersion of crude oil. Volume 1

    International Nuclear Information System (INIS)

    Oil spills at sea can be treated with chemical dispersants to reduce the oil-water interfacial tension and facilitate entrainment of the oil into the water column as small droplets. Removing the floating oil protects surface-swelling organisms and sensitive shorelines. The environmental impacts can be further minimized if the dispersed oil droplets can be diluted into a sufficiently large volume of water by turbulent diffusion. Therefore, this study investigated the effects of mixing energy and mixing systems on dispersion effectiveness of Mars crude oil using 2 bench-scale experimental systems. Two dispersant HLB (hydrophile-lipofile balance) of 10 and 12 were tested for size distribution and dispersed oil droplets. Dispersion effectiveness was defined as the volume of mass fraction of floating oil that becomes entrained in the water column after mixing energy is introduced. The size distribution of the dispersed oil droplets provides another measure of dispersion effectiveness since smaller oil droplets have a stronger tendency to remain suspended in the water column. In this study, dispersion effectiveness was measured at 4 different energy dissipation rates in 2 different mixing systems, namely a baffled flask system and a paddle jar system. It was shown that even when the average energy dissipation rate was the same, the fluid flow dynamics were quite different in the two systems. The droplet-size distributions were multimodal, with 2 major modes occurring in dispersions produced in the baffled-flask system. The diameters of mean volume of the major modes were not found to be sensitive to changes in the energy dissipation rates. However, in the baffled-flask system, the distribution of oil among the modes was influenced by the energy dissipation rate. 25 refs., 5 figs

  5. Effects of mixing energy and flow dynamics on chemical dispersion of crude oil. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, B.; Wrenn, B.A. [Washington Univ., St. Louis, MO (United States). Dept. of Energy, Environment and Chemical Engineering

    2007-07-01

    Oil spills at sea can be treated with chemical dispersants to reduce the oil-water interfacial tension and facilitate entrainment of the oil into the water column as small droplets. Removing the floating oil protects surface-swelling organisms and sensitive shorelines. The environmental impacts can be further minimized if the dispersed oil droplets can be diluted into a sufficiently large volume of water by turbulent diffusion. Therefore, this study investigated the effects of mixing energy and mixing systems on dispersion effectiveness of Mars crude oil using 2 bench-scale experimental systems. Two dispersant HLB (hydrophile-lipofile balance) of 10 and 12 were tested for size distribution and dispersed oil droplets. Dispersion effectiveness was defined as the volume of mass fraction of floating oil that becomes entrained in the water column after mixing energy is introduced. The size distribution of the dispersed oil droplets provides another measure of dispersion effectiveness since smaller oil droplets have a stronger tendency to remain suspended in the water column. In this study, dispersion effectiveness was measured at 4 different energy dissipation rates in 2 different mixing systems, namely a baffled flask system and a paddle jar system. It was shown that even when the average energy dissipation rate was the same, the fluid flow dynamics were quite different in the two systems. The droplet-size distributions were multimodal, with 2 major modes occurring in dispersions produced in the baffled-flask system. The diameters of mean volume of the major modes were not found to be sensitive to changes in the energy dissipation rates. However, in the baffled-flask system, the distribution of oil among the modes was influenced by the energy dissipation rate. 25 refs., 5 figs.

  6. Effects of mixing energy and flow dynamics on chemical dispersion of crude oil

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, B.; Wrenn, B.A. [Washington Univ., St. Louis, MO (United States). Dept. of Energy, Environment and Chemical Engineering

    2007-07-01

    Oil spills at sea can be treated with chemical dispersants to reduce the oil-water interfacial tension and facilitate entrainment of the oil into the water column as small droplets. Removing the floating oil protects surface-swelling organisms and sensitive shorelines. The environmental impacts can be further minimized if the dispersed oil droplets can be diluted into a sufficiently large volume of water by turbulent diffusion. Therefore, this study investigated the effects of mixing energy and mixing systems on dispersion effectiveness of Mars crude oil using 2 bench-scale experimental systems. Two dispersant HLB (hydrophile-lipofile balance) of 10 and 12 were tested for size distribution and dispersed oil droplets. Dispersion effectiveness was defined as the volume of mass fraction of floating oil that becomes entrained in the water column after mixing energy is introduced. The size distribution of the dispersed oil droplets provides another measure of dispersion effectiveness since smaller oil droplets have a stronger tendency to remain suspended in the water column. In this study, dispersion effectiveness was measured at 4 different energy dissipation rates in 2 different mixing systems, namely a baffled flask system and a paddle jar system. It was shown that even when the average energy dissipation rate was the same, the fluid flow dynamics were quite different in the two systems. The droplet-size distributions were multimodal, with 2 major modes occurring in dispersions produced in the baffled-flask system. The diameters of mean volume of the major modes were not found to be sensitive to changes in the energy dissipation rates. However, in the baffled-flask system, the distribution of oil among the modes was influenced by the energy dissipation rate. 25 refs., 5 figs.

  7. Universal imaging: Dissociative ionization of polyatomic molecules, chemical dynamics beamline 9.0.2

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, M.; Chen, D.; Suits, A.G. [Ernest Orlando Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    A third endstation was recently added to the Chemical Dynamics beamline, designed to exploit the high flux broadband undulator light for a range of studies of reactive scattering, photochemistry and photoionization processes using time-of-flight mass spectroscopy coupled with position-sensitive detection. Two molecular beam sources are fixed at right angles, with the undulator light, or laser beams, intersecting the molecular beams at 45{degrees}. To date, beamline experiments have included a study of dissociative photoionization of a variety of molecules including N{sub 2}O and SF{sub 6}. In this mode, a single molecular beam source is used, with the tunable undulator light inducing, in SF{sub 6} for example, the process SF{sub 6} {r_arrow} SF{sub 6}{sup +} + e{sup {minus}} {r_arrow} SF{sub 5}{sup +} + F + e{sup {minus}}. The SF{sub 5}{sup +} ions are accelerated up the flight tube, mass selected and detected as a function of position on a phosphor screen viewed by a CCD camera. The position directly reveals the recoil speed (or translational energy release) and angular distribution for the dissociative ionization process. Furthermore, this measurement is obtained for all recoil speeds and angles simultaneously. Such detailed angular information has not previously been obtained for dissociative ionization processes; typically ion time-of-flight profiles are deconvoluted to yield rough insight into the angular distributions. The recorded image is actually a 2-dimensional projection of the nascent 3-dimensional velocity distribution, but established tomographic techniques enable the authors to reconstruct the 3-D distribution.

  8. Automatic differentiation tools in the dynamic simulation of chemical engineering processes

    Directory of Open Access Journals (Sweden)

    Castro M.C.

    2000-01-01

    Full Text Available Automatic Differentiation is a relatively recent technique developed for the differentiation of functions applicable directly to the source code to compute the function written in standard programming languages. That technique permits the automatization of the differentiation step, crucial for dynamic simulation and optimization of processes. The values for the derivatives obtained with AD are exact (to roundoff. The theoretical exactness of the AD comes from the fact that it uses the same rules of differentiation as in differential calculus, but these rules are applied to an algorithmic specification of the function rather than to a formula. The main purpose of this contribution is to discuss the impact of Automatic Differentiation in the field of dynamic simulation of chemical engineering processes. The influence of the differentiation technique on the behavior of the integration code, the performance of the generated code and the incorporation of AD tools in consistent initialization tools are discussed from the viewpoint of dynamic simulation of typical models in chemical engineering.

  9. Nonlinear Stochastic Dynamics of Complex Systems, I: A Chemical Reaction Kinetic Perspective with Mesoscopic Nonequilibrium Thermodynamics

    CERN Document Server

    Qian, Hong

    2016-01-01

    We distinguish a mechanical representation of the world in terms of point masses with positions and momenta and the chemical representation of the world in terms of populations of different individuals, each with intrinsic stochasticity, but population wise with statistical rate laws in their syntheses, degradations, spatial diffusion, individual state transitions, and interactions. Such a formal kinetic system in a small volume $V$, like a single cell, can be rigorously treated in terms of a Markov process describing its nonlinear kinetics as well as nonequilibrium thermodynamics at a mesoscopic scale. We introduce notions such as open, driven chemical systems, entropy production, free energy dissipation, etc. Then in the macroscopic limit, we illustrate how two new "laws", in terms of a generalized free energy of the mesoscopic stochastic dynamics, emerge. Detailed balance and complex balance are two special classes of "simple" nonlinear kinetics. Phase transition is intrinsically related to multi-stability...

  10. Method for the deconvolution of incompletely resolved CARS spectra in chemical dynamics experiments

    International Nuclear Information System (INIS)

    We describe a method for deconvoluting incompletely resolved CARS spectra to obtain quantum state population distributions. No particular form for the rotational and vibrational state distribution is assumed, the population of each quantum state is treated as an independent quantity. This method of analysis differs from previously developed approaches for the deconvolution of CARS spectra, all of which assume that the population distribution is Boltzmann, and thus are limited to the analysis of CARS spectra taken under conditions of thermal equilibrium. The method of analysis reported here has been developed to deconvolute CARS spectra of photofragments and chemical reaction products obtained in chemical dynamics experiments under nonequilibrium conditions. The deconvolution procedure has been incorporated into a computer code. The application of that code to the deconvolution of CARS spectra obtained for samples at thermal equilibrium and not at thermal equilibrium is reported. The method is accurate and computationally efficient

  11. Single-collision studies of hot atom energy transfer and chemical reaction

    International Nuclear Information System (INIS)

    This report discusses research in the collision dynamics of translationally hot atoms, with funding with DOE for the project ''Single-Collision Studies of Hot Atom Energy Transfer and Chemical Reaction,'' Grant Number DE-FG03-85ER13453. The work reported here was done during the period September 9, 1988 through October 31, 1991. During this period this DOE-funded work has been focused on several different efforts: (1) experimental studies of the state-to-state dynamics of the H + RH → H2 R reactions where RH is CH4, C2H6, or C3H8, (2) theoretical (quasiclassical trajectory) studies of hot hydrogen atom collision dynamics, (3) the development of photochemical sources of translationally hot molecular free radicals and characterization of the high resolution CARS spectroscopy of molecular free radicals, (4) the implementation of stimulated Raman excitation (SRE) techniques for the preparation of vibrationally state-selected molecular reactants

  12. A chemical EOR benchmark study of different reservoir simulators

    Science.gov (United States)

    Goudarzi, Ali; Delshad, Mojdeh; Sepehrnoori, Kamy

    2016-09-01

    chemical design for field-scale studies using commercial simulators. The benchmark tests illustrate the potential of commercial simulators for chemical flooding projects and provide a comprehensive table of strengths and limitations of each simulator for a given chemical EOR process. Mechanistic simulations of chemical EOR processes will provide predictive capability and can aid in optimization of the field injection projects. The objective of this paper is not to compare the computational efficiency and solution algorithms; it only focuses on the process modeling comparison.

  13. Dynamic optimization case studies in DYNOPT tool

    Science.gov (United States)

    Ozana, Stepan; Pies, Martin; Docekal, Tomas

    2016-06-01

    Dynamic programming is typically applied to optimization problems. As the analytical solutions are generally very difficult, chosen software tools are used widely. These software packages are often third-party products bound for standard simulation software tools on the market. As typical examples of such tools, TOMLAB and DYNOPT could be effectively applied for solution of problems of dynamic programming. DYNOPT will be presented in this paper due to its licensing policy (free product under GPL) and simplicity of use. DYNOPT is a set of MATLAB functions for determination of optimal control trajectory by given description of the process, the cost to be minimized, subject to equality and inequality constraints, using orthogonal collocation on finite elements method. The actual optimal control problem is solved by complete parameterization both the control and the state profile vector. It is assumed, that the optimized dynamic model may be described by a set of ordinary differential equations (ODEs) or differential-algebraic equations (DAEs). This collection of functions extends the capability of the MATLAB Optimization Tool-box. The paper will introduce use of DYNOPT in the field of dynamic optimization problems by means of case studies regarding chosen laboratory physical educational models.

  14. Dynamic study and applications of metamaterial systems

    Science.gov (United States)

    Jiang, Xun-Ya; Liu, Zheng; Liang, Zi-Xian; Yao, Pei-Jun; Lin, Xu-Lin

    2011-03-01

    We investigate the dynamic characteristics of metamaterial systems, such as the temporal coherence gain of the superlens, the causality limitation on the ideal cloaking systems, the relaxation process and essential elements in the dispersive cloaking systems, and the extending of the working frequency range of cloaking systems. The key point of our study is the physical dispersive properties of metamaterials, which are well-known to be intrinsically strongly dispersive. With physical dispersion, new physical pictures can be obtained for the waves propagating inside metamaterial, such as the "group retarded time" for waves inside the superlens and cloak, the causality limitation on real metamaterial systems, and the essential elements for design optimization. Therefore, we believe the dynamic study of metamaterials will be an important direction for further research. All theoretical derivations and conclusions are demonstrated by powerful finite-difference time-domain simulations.

  15. 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

  16. The Dynamic Mechanism Analysis of Chemical Fiber Industry's Industrial Cluster in Zhejiang Province---A Case Study of Xiaoshan District%浙江省化纤产业集群动力机制分析--以萧山区为例

    Institute of Scientific and Technical Information of China (English)

    金平斌; 项凯旋

    2016-01-01

    Being an economic phenomenon, industrial cluster should be studied not only in the way of theoretical study, but also based on the microscopic actual fact to explore practical the-ory and local development distinctiveness. This article focuses on the dynamical study of industrial cluster. On the basis of teasing out former theoretical research, this work based on the typical cluster, the Xiaoshan chemical fiber industry cluster, to discuss the main dynamical factor through the way of entrepreneur inter-view, questionnaire designing and grading. The study reviews that, the government factor, entrepreneur spirit, marketing environment and enterprise's competition and cooperation mechanism are the major motive power. Entrepreneur spirit is the unique and core advantage of Xiaoshan's chemical fiber industry cluster, and is al-so the internal motivation of honest market atmosphere and smooth cooperation between enterprises. The government has made great contribution in this area by providing the hardware and software support and guiding the wave.%产业集群作为一种经济现象,在理论研究之外,亦要立足微观实际,探索理论实用性及地方发展特异性。本文聚焦于产业集群的动力研究,在梳理国内外理论研究的基础上,本文立足典型集群—萧山化纤产业集群,从微观企业主体的角度,通过企业家访谈和设计问卷、评分的方式,对萧山化纤集群能够形成的主要动力因素进行了探讨。研究揭示,政府因素、企业家精神、市场环境和企业竞合机制是主要的集群动力。企业家精神是萧山化纤产业集群形成的独有、核心优势,良好诚信的市场氛围和通畅的企业间竞合是集群的内在动力,政府在其中提供软硬件支持、以市场化手段引导,平抑波动,也起到了至关重要的作用。

  17. A Molecular Dynamics Study of the Structural and Dynamical Properties of Putative Arsenic Substituted Lipid Bilayers

    Directory of Open Access Journals (Sweden)

    Ratna Juwita

    2013-04-01

    Full Text Available Cell membranes are composed mainly of phospholipids which are in turn, composed of five major chemical elements: carbon, hydrogen, nitrogen, oxygen, and phosphorus. Recent studies have suggested the possibility of sustaining life if the phosphorus is substituted by arsenic. Although this issue is still controversial, it is of interest to investigate the properties of arsenated-lipid bilayers to evaluate this possibility. In this study, we simulated arsenated-lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-arsenocholine (POAC, lipid bilayers using all-atom molecular dynamics to understand basic structural and dynamical properties, in particular, the differences from analogous 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, (POPC lipid bilayers. Our simulations showed that POAC lipid bilayers have distinct structural and dynamical properties from those of native POPC lipid bilayers. Relative to POPC lipid bilayers, POAC lipid bilayers have a more compact structure with smaller lateral areas and greater order. The compact structure of POAC lipid bilayers is due to the fact that more inter-lipid salt bridges are formed with arsenate-choline compared to the phosphate-choline of POPC lipid bilayers. These inter-lipid salt bridges bind POAC lipids together and also slow down the head group rotation and lateral diffusion of POAC lipids. Thus, it would be anticipated that POAC and POPC lipid bilayers would have different biological implications.

  18. Simulation studies using multibody dynamics code DART

    Science.gov (United States)

    Keat, James E.

    1989-01-01

    DART is a multibody dynamics code developed by Photon Research Associates for the Air Force Astronautics Laboratory (AFAL). The code is intended primarily to simulate the dynamics of large space structures, particularly during the deployment phase of their missions. DART integrates nonlinear equations of motion numerically. The number of bodies in the system being simulated is arbitrary. The bodies' interconnection joints can have an arbitrary number of degrees of freedom between 0 and 6. Motions across the joints can be large. Provision for simulating on-board control systems is provided. Conservation of energy and momentum, when applicable, are used to evaluate DART's performance. After a brief description of DART, studies made to test the program prior to its delivery to AFAL are described. The first is a large angle reorientating of a flexible spacecraft consisting of a rigid central hub and four flexible booms. Reorientation was accomplished by a single-cycle sine wave shape torque input. In the second study, an appendage, mounted on a spacecraft, was slewed through a large angle. Four closed-loop control systems provided control of this appendage and of the spacecraft's attitude. The third study simulated the deployment of the rim of a bicycle wheel configuration large space structure. This system contained 18 bodies. An interesting and unexpected feature of the dynamics was a pulsing phenomena experienced by the stays whole playout was used to control the deployment. A short description of the current status of DART is given.

  19. 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.)

  20. The Dynamical and Chemical Evolution of Dwarf Spheroidal Galaxies with GEAR

    CERN Document Server

    Revaz, Yves

    2011-01-01

    We present a fully parallel chemo-dynamical Tree/SPH code, GEAR, which allows to perform high resolution simulations with detailed chemical diagnostics. Starting from the public version of Gadget-2, we included the complex treatment of the baryon physics: gas cooling, star formation law, chemical evolution and supernovae feedback. We qualified the performances of GEAR with the case of dSph galaxies. GEAR conserves the total energy budget of the systems to better than 5% over 14Gyr and proved excellent convergence of the results with numerical resolution. We showed that models of dSphs in a static Euclidean space, where the expansion of the universe is neglected are valid. In addition, we tackled some of the existing open questions in the field, like the stellar mass fraction of dSphs and its link with the predicted dark matter halo mass function, the effect of the supernova feedback, the spatial distribution of the stellar populations, and the origin of the diversity in star formation histories and chemical a...

  1. Solar dynamic power system definition study

    Science.gov (United States)

    Wallin, Wayne E.; Friefeld, Jerry M.

    1988-01-01

    The solar dynamic power system design and analysis study compared Brayton, alkali-metal Rankine, and free-piston Stirling cycles with silicon planar and GaAs concentrator photovoltaic power systems for application to missions beyond the Phase 2 Space Station level of technology for all power systems. Conceptual designs for Brayton and Stirling power systems were developed for 35 kWe and 7 kWe power levels. All power systems were designed for 7-year end-of-life conditions in low Earth orbit. LiF was selected for thermal energy storage for the solar dynamic systems. Results indicate that the Stirling cycle systems have the highest performance (lowest weight and area) followed by the Brayton cycle, with photovoltaic systems considerably lower in performance. For example, based on the performance assumptions used, the planar silicon power system weight was 55 to 75 percent higher than for the Stirling system. A technology program was developed to address areas wherein significant performance improvements could be realized relative to the current state-of-the-art as represented by Space Station. In addition, a preliminary evaluation of hardenability potential found that solar dynamic systems can be hardened beyond the hardness inherent in the conceptual designs of this study.

  2. Quantum chemical studies of epoxide-transforming enzymes

    OpenAIRE

    Hopmann, Kathrin H.

    2007-01-01

    Density functional theory is employed to study the reaction mechanisms of different epoxide-transforming enzymes. Calculations are based on quantum chemical active site models, which are build from X-ray crystal structures. The models are used to study conversion of various epoxides into their corresponding diols or substituted alcohols. Epoxide-transforming enzymes from three different families are studied. The human soluble epoxide hydrolase (sEH) belongs to the α/β-hydrolase fold family. s...

  3. [Scanning electron microscope study of chemically disinfected endodontic files].

    Science.gov (United States)

    Navarro, G; Mateos, M; Navarro, J L; Canalda, C

    1991-01-01

    Forty stainless steel endodontic files were observed at scanning electron microscopy after being subjected to ten disinfection cycles of 10 minutes each one, immersed in different chemical disinfectants. Corrosion was not observed on the surface of the files in circumstances that this study was made. PMID:1659857

  4. Health effects of chemical pollution: case-study in Algeria

    International Nuclear Information System (INIS)

    The analysis of some biological parameters of workers in a factory producing chemical fertilizers ASMIDAL (Algeria), and of residents a nearby city (El Bouni) who are exposed to the smell of chemical pollution, shows modifications of these parameters in terms of contamination due to nitric derivatives. The rat ingestion of infra-lethal dose of ammonium nitrate produced by ASMIDAL provokes modifications which are similar to those found in the subjects studied in this work. These modifications are of main concern to the levels of hemoglobin, methemoglobin, erythrocytes, seric and urinary nitrates. In addition, modifications in the activity of the spleen and of the liver have been observed in the rat. (author)

  5. Chemical and preclinical studies on Hedyotis diffusa with anticancer potential.

    Science.gov (United States)

    Niu, Yu; Meng, Qiu-Xia

    2013-01-01

    This paper presents the chemical and preclinical anticancer research on Hedyotis diffusa Willd. in detail, one of the most renowned herbs often prescribed in the polyherbal formulas for cancer treatment in traditional Chinese medicine. Anthraquinones, flavonoids, and terpenoids constitute the majority of the 69 compounds that have been isolated and identified from H. diffusa. The anticancer effects of the methanolic, ethanolic, and aqueous extracts in various preclinical cancer models have been described. This review also summarized the anticancer activity of constituents of the herb and the mechanisms of action. All the studies suggest that H. diffusa has enormous potential in the therapy of cancer and warrants further chemical and pharmacological investigation. PMID:23600735

  6. Chemical separation procedure proposed for studies of bohrium

    International Nuclear Information System (INIS)

    Off-line and on-line studies have been performed with radioactive tracers of various elements to develop a chemical separation procedure for bohrium (element 107). The proposed procedure is intended for use in the fast solvent extraction system SISAK. The homologs technetium and rhenium were used to model the chemical behavior of bohrium. The results show that high decontamination factors can be obtained for technetium and rhenium with respect to unwanted contaminants like trivalent actinides, polonium and the Group 5 elements. (author)

  7. Preliminary study of chemical compositional data from Amazon ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Toyota, Rosimeiri G.; Munita, Casimiro S.; Luz, Fabio A. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)]. E-mail: rosimeiritoy@yahoo.com.br; Neves, Eduardo G. [Museu de Arqueologia e Etnolgia, Sao Paulo, SP (Brazil)]. E-mail: egneves@usp.br; Oliveira, Paulo M.S. [Sao Paulo Univ., SP (Brazil). Escola Politecnica. Inst. de Matematica e Estatistica]. E-mail: poliver@usp.br

    2005-07-01

    Eighty seven ceramic samples from Acutuba, Lago Grande and Osvaldo archaeological sites located in the confluence of the rivers Negro and Solimoes were submitted to chemical analysis using instrumental neutron activation analysis to determine As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Rb, Na, Nd, Sb, Sc, Sm, Ta, Tb, Th, Yb, Zn, and U. The database were studied using the Mahalanobis distance, and discriminant analysis. The results showed that the ceramics of each site differ from each other in chemical composition and that they form three different groups. Chemical classification of the ceramics suggests that vessels were made locally, as only ceramics from the same area show homogeneity of data. (author)

  8. Preliminary study of chemical compositional data from Amazon ceramics

    International Nuclear Information System (INIS)

    Eighty seven ceramic samples from Acutuba, Lago Grande and Osvaldo archaeological sites located in the confluence of the rivers Negro and Solimoes were submitted to chemical analysis using instrumental neutron activation analysis to determine As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Rb, Na, Nd, Sb, Sc, Sm, Ta, Tb, Th, Yb, Zn, and U. The database were studied using the Mahalanobis distance, and discriminant analysis. The results showed that the ceramics of each site differ from each other in chemical composition and that they form three different groups. Chemical classification of the ceramics suggests that vessels were made locally, as only ceramics from the same area show homogeneity of data. (author)

  9. Characterization of electron-deficient chemical bonding of diborane with attosecond electron wavepacket dynamics and laser response

    Energy Technology Data Exchange (ETDEWEB)

    Yonehara, Takehiro, E-mail: yota@mns2.c.u-tokyo.ac.jp [Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba 153-8902, Tokyo (Japan); Takatsuka, Kazuo, E-mail: kaztak@mns2.c.u-tokyo.ac.jp [Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba 153-8902, Tokyo (Japan)

    2009-12-10

    We report a theoretical study of non-adiabatic electrons-nuclei coupled dynamics of diborane H{sub 2}BH{sub 2}BH{sub 2} under several types of short pulse lasers. This molecule is known to have particularly interesting geometrical and electronic structures, which originate from the electron-deficient chemical bondings. We revisit the chemical bonding of diborane from the view point of electron wavepacket dynamics coupled with nuclear motions, and attempt to probe the characteristics of it by examining its response to intense laser fields. We study in the following three aspects, (i) bond formation of diborane by collision between two monoboranes, (ii) attosecond electron wavepacket dynamics in the ground state and first excited state by circularly polarized laser pulse, and (iii) induced fragmentation back to monoborane molecules by linearly polarized laser. The wave lengths of two types of laser field employed are 200 nm (in UV range) and 800 nm (in IR range), and we track the dynamics from hundreds of attoseconds up to few tens of femtoseconds. To this end, we apply the ab initio semiclassical Ehrenfest theory, into which the classical vector potential of a laser field is introduced. Basic features of the non-adiabatic response of electrons to the laser fields is elucidated in this scheme. To analyze the electronic wavepackets thus obtained, we figure out bond order density that is a spatial distribution of the bond order and bond order flux density arising only from the bonding regions, and so on. Main findings in this work are: (i) dimerization of monoboranes to diborane is so efficient that even intense laser is hard to prevent it; (ii) collective motions of electron flux emerge in the central BHHB bonding area in response to the circularly polarized laser fields; (iii) laser polarization with the direction of central two BH bonding vector is efficient for the cleavage of BH{sub 3}-BH{sub 3}; and (iv) nuclear derivative coupling plays a critical role in the

  10. Do High School Chemistry Examinations Inhibit Deeper Level Understanding of Dynamic Reversible Chemical Reactions?

    Science.gov (United States)

    Wheeldon, R.; Atkinson, R.; Dawes, A.; Levinson, R.

    2012-01-01

    Background and purpose: Chemistry examinations can favour the deployment of algorithmic procedures like Le Chatelier's Principle (LCP) rather than reasoning using chemical principles. This study investigated the explanatory resources which high school students use to answer equilibrium problems and whether the marks given for examination answers…

  11. Study of the chemical sputtering in Tore-Supra

    International Nuclear Information System (INIS)

    The work presented in this thesis focuses on the interactions between energetic particles coming from thermonuclear plasma and the inner components of a fusion machine. This interaction induces two major problems: erosion of the wall, and tritium retention. This report treats the erosion of carbon based materials. The first part is devoted to chemical sputtering, that appears to be the principal erosion mechanism, compared to physical sputtering and radiation enhanced sublimation that both can be limited. Chemical sputtering has been studied in situ in the tokamak Tore-Supra for ohmic and lower hybrid (LH) heated discharges, by means of mass spectrometry and optical spectroscopy. We have shown that it is necessary to take into account both methane and heavier hydrocarbons (C2Dx and C3Dy) in the determination of the chemical sputtering yield. It is found that for the ohmic discharges, the sputtering yield of CD4 (YCD4) is highly flux (φ) dependent, showing a variation of the form: YCD4 ∝ φ-0.23. The experimental study also reveals that an increase of the surface temperature induces an augmentation of YCD4. The interpretation and the modelling of the experimental results have been performed with a Monte Carlo code (BBQ. In the second part of this work, we have developed and installed an infrared spectroscopy diagnostic in the 0.8-1.6, μm wavelength range dedicated to the measurement of surface temperature, and the identification of atomic and molecular lines emitted during plasma/wall interactions. In the third part, we present the feasibility study of an in situ tungsten deposition process at low temperature(<80 deg C) in order to suppress the chemical sputtering. This study shows that, with this method call Plasma Assisted Chemical Vapor Deposition (PACVD), we are able to coat the whole inner vessel of a tokamak with 1 μm of tungsten. (author)

  12. A study of suitability of some conventional chemical preservatives and natural antimicrobial compounds in allelopathic research

    Directory of Open Access Journals (Sweden)

    Plamen Marinov-Serafimov

    2015-12-01

    Full Text Available The impact of three conventional chemical preservatives (sodium benzoate, potassium sorbate and salicylic acid and a natural antimicrobial compound (thymol on germination, dynamics of growth and accumulation of fresh biomass (g per seedling of Lactuca sativa L., cultivar Great Lakes, was studied under laboratory conditions. The tested conventional chemical preservatives demonstrated strong inhibitory effects (GI 27.1-0.0% on germination and initial development of L. sativa, and they cannot be used in allelopathic studies in the laboratory. An addition of thymol at 0.5-1.0 ‰ concentration showed no inhibitory effect (GI varied 81.7-84.6% on germination and initial development of L. sativa. Thymol can therefore be used as a natural antimicrobial compound in allelopathic studies in the laboratory.

  13. NMR Dynamic Studies in Living Systems

    Institute of Scientific and Technical Information of China (English)

    闫永彬; 范明杰; 罗雪春; 张日清

    2002-01-01

    Nuclear magnetic resonance (NMR) can noninvasively monitor the intracellular concentrations and kinetic properties of numerous inorganic and organic compounds. These characteristics have made NMR a useful tool for dynamic studies of living systems. Applications of NMR to living systems have successfully extended to many areas, including studies of metabolic regulation, ion transport, and intracellular reaction rates in vivo. The major purpose of this review is to summarize the results that can be obtained by modern NMR techniques in living systems. With the advances of new techniques, NMR measurements of various nuclides have been performed for specific physiological purposes. Although some technical problems still remain and there are still discrepancies between NMR and traditional biochemical results, the abundant and unique information obtained from NMR spectra suggests that NMR will be more extensively applied in future studies of living systems. The fast development of these new techniques is providing many new NMR applications in living systems, as well as in structural biology.

  14. Studies on modelling of bubble driven flows in chemical reactors

    Energy Technology Data Exchange (ETDEWEB)

    Grevskott, Sverre

    1997-12-31

    Multiphase reactors are widely used in the process industry, especially in the petrochemical industry. They very often are characterized by very good thermal control and high heat transfer coefficients against heating and cooling surfaces. This thesis first reviews recent advances in bubble column modelling, focusing on the fundamental flow equations, drag forces, transversal forces and added mass forces. The mathematical equations for the bubble column reactor are developed, using an Eulerian description for the continuous and dispersed phase in tensor notation. Conservation equations for mass, momentum, energy and chemical species are given, and the k-{epsilon} and Rice-Geary models for turbulence are described. The different algebraic solvers used in the model are described, as are relaxation procedures. Simulation results are presented and compared with experimental values. Attention is focused on the modelling of void fractions and gas velocities in the column. The energy conservation equation has been included in the bubble column model in order to model temperature distributions in a heated reactor. The conservation equation of chemical species has been included to simulate absorption of CO{sub 2}. Simulated axial and radial mass fraction profiles for CO{sub 2} in the gas phase are compared with measured values. Simulations of the dynamic behaviour of the column are also presented. 189 refs., 124 figs., 1 tab.

  15. Integrated atomistic chemical imaging and reactive force field molecular dynamic simulations on silicon oxidation

    International Nuclear Information System (INIS)

    In this paper, we quantitatively investigate with atom probe tomography, the effect of temperature on the interfacial transition layer suboxide species due to the thermal oxidation of silicon. The chemistry at the interface was measured with atomic scale resolution, and the changes in chemistry and intermixing at the interface were identified on a nanometer scale. We find an increase of suboxide (SiOx) concentration relative to SiO2 and increased oxygen ingress with elevated temperatures. Our experimental findings are in agreement with reactive force field molecular dynamics simulations. This work demonstrates the direct comparison between atom probe derived chemical profiles and atomistic-scale simulations for transitional interfacial layer of suboxides as a function of temperature

  16. A "partitioned leaping" approach for multiscale modeling of chemical reaction dynamics

    CERN Document Server

    Harris, L A; Clancy, Paulette; Harris, Leonard A.

    2006-01-01

    We present a novel multiscale simulation approach for modeling stochasticity in chemical reaction networks. The approach seamlessly integrates exact-stochastic and "leaping" methodologies into a single *partitioned leaping* algorithmic framework. Distinguishing characteristics of the method include automatic, dynamic and theoretically justifiable time step determination and timescale separation procedures that utilize concepts underlying the tau-leap approach [D.T. Gillespie, J. Chem. Phys. 115, 1716 (2001); D.T. Gillespie and L.R. Petzold, J. Chem. Phys. 119, 8229 (2003)] and require the definition of only three model-independent parameters. Both procedures are based on an individual (but not independent) consideration of reactions, a subtle yet significant ideological concept used in the development of previous exact-stochastic simulation methods [D.T. Gillespie, J. Comput. Phys. 22, 403 (1976); M.A. Gibson and J. Bruck, J. Phys. Chem. A 104, 1876 (2000)]. The result is a method that correctly accounts for ...

  17. Integrated atomistic chemical imaging and reactive force field molecular dynamic simulations on silicon oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Dumpala, Santoshrupa; Broderick, Scott R.; Rajan, Krishna, E-mail: krajan@iastate.edu [Department of Materials Science and Engineering and Institute for Combinatorial Discovery, Iowa State University, 2220 Hoover Hall, Ames, Iowa 50011 (United States); Khalilov, Umedjon; Neyts, Erik C. [Department of Chemistry, PLASMANT Research Group, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp (Belgium); Duin, Adri C. T. van [Department of Mechanical and Nuclear Engineering, Penn State University, University Park, Pennsylvania 16801 (United States); Provine, J; Howe, Roger T. [Department of Electrical Engineering, Stanford University, 420 Via Palou Mall, Stanford, California 94305 (United States)

    2015-01-05

    In this paper, we quantitatively investigate with atom probe tomography, the effect of temperature on the interfacial transition layer suboxide species due to the thermal oxidation of silicon. The chemistry at the interface was measured with atomic scale resolution, and the changes in chemistry and intermixing at the interface were identified on a nanometer scale. We find an increase of suboxide (SiOx) concentration relative to SiO{sub 2} and increased oxygen ingress with elevated temperatures. Our experimental findings are in agreement with reactive force field molecular dynamics simulations. This work demonstrates the direct comparison between atom probe derived chemical profiles and atomistic-scale simulations for transitional interfacial layer of suboxides as a function of temperature.

  18. Chemical reactivity of the compressed noble gas atoms and their reactivity dynamics during collisions with protons

    Indian Academy of Sciences (India)

    P K Chattaraj; B Maiti; U Sarkar

    2003-06-01

    Attempts are made to gain insights into the effect of confinement of noble gas atoms on their various reactivity indices. Systems become harder, less polarizable and difficult to excite as the compression increases. Ionization also causes similar effects. A quantum fluid density functional technique is adopted in order to study the dynamics of reactivity parameters during a collision between protons and He atoms in different electronic states for various projectile velocities and impact parameters. Dynamical variants of the principles of maximum hardness, minimum polarizability and maximum entropy are found to be operative.

  19. Complex, dynamic combination of physical, chemical and nutritional variables controls spatio-temporal variation of sandy beach community structure.

    Directory of Open Access Journals (Sweden)

    Kelly Ortega Cisneros

    Full Text Available Sandy beach ecological theory states that physical features of the beach control macrobenthic community structure on all but the most dissipative beaches. However, few studies have simultaneously evaluated the relative importance of physical, chemical and biological factors as potential explanatory variables for meso-scale spatio-temporal patterns of intertidal community structure in these systems. Here, we investigate macroinfaunal community structure of a micro-tidal sandy beach that is located on an oligotrophic subtropical coast and is influenced by seasonal estuarine input. We repeatedly sampled biological and environmental variables at a series of beach transects arranged at increasing distances from the estuary mouth. Sampling took place over a period of five months, corresponding with the transition between the dry and wet season. This allowed assessment of biological-physical relationships across chemical and nutritional gradients associated with a range of estuarine inputs. Physical, chemical, and biological response variables, as well as measures of community structure, showed significant spatio-temporal patterns. In general, bivariate relationships between biological and environmental variables were rare and weak. However, multivariate correlation approaches identified a variety of environmental variables (i.e., sampling session, the C∶N ratio of particulate organic matter, dissolved inorganic nutrient concentrations, various size fractions of photopigment concentrations, salinity and, to a lesser extent, beach width and sediment kurtosis that either alone or combined provided significant explanatory power for spatio-temporal patterns of macroinfaunal community structure. Overall, these results showed that the macrobenthic community on Mtunzini Beach was not structured primarily by physical factors, but instead by a complex and dynamic blend of nutritional, chemical and physical drivers. This emphasises the need to recognise ocean

  20. Monitoring Ultrafast Chemical Dynamics by Time-Domain X-ray Photo- and Auger-Electron Spectroscopy.

    Science.gov (United States)

    Gessner, Oliver; Gühr, Markus

    2016-01-19

    The directed flow of charge and energy is at the heart of all chemical processes. Extraordinary efforts are underway to monitor and understand the concerted motion of electrons and nuclei with ever increasing spatial and temporal sensitivity. The element specificity, chemical sensitivity, and temporal resolution of ultrafast X-ray spectroscopy techniques hold great promise to provide new insight into the fundamental interactions underlying chemical dynamics in systems ranging from isolated molecules to application-like devices. Here, we focus on the potential of ultrafast X-ray spectroscopy techniques based on the detection of photo- and Auger electrons to provide new fundamental insight into photochemical processes of systems with various degrees of complexity. Isolated nucleobases provide an excellent testing ground for our most fundamental understanding of intramolecular coupling between electrons and nuclei beyond the traditionally applied Born-Oppenheimer approximation. Ultrafast electronic relaxation dynamics enabled by the breakdown of this approximation is the major component of the nucleobase photoprotection mechanisms. Transient X-ray induced Auger electron spectroscopy on photoexcited thymine molecules provides atomic-site specific details of the extremely efficient coupling that converts potentially bond changing ultraviolet photon energy into benign heat. In particular, the time-dependent spectral shift of a specific Auger band is sensitive to the length of a single bond within the molecule. The X-ray induced Auger transients show evidence for an electronic transition out of the initially excited state within only ∼200 fs in contrast to theoretically predicted picosecond population trapping behind a reaction barrier. Photoinduced charge transfer dynamics between transition metal complexes and semiconductor nanostructures are of central importance for many emerging energy and climate relevant technologies. Numerous demonstrations of photovoltaic and

  1. Search for new chemical elements and possibilities to synthesize transactinide isotopes for chemical studies

    International Nuclear Information System (INIS)

    Elements up to Z=112 as well as 114 and 116 are officially recognized as discovered and have been named. The current literature contains reports about the synthesis of all elements up to Z=118, meaning that more than 10% of all elements are members of the transactinide series with Z=104-118. Therefore, search experiments for the new elements with Z=119 and Z=120 have been performed. An important question for such experiments concerns the optimum choice of the nuclear reaction. While only one experiment has been conducted so far with the aim of discovering Z=119, already four experiments on the synthesis of Z=120 have been performed, all employing different reactions. Still, Z=119 and 120 are not yet announced as discovered. The situation using the TASCA experiments as an example and the perspectives for the discovery of new elements are studied. The optimum reactions leading to the relatively long-lived isotopes of the transactinides as they are frequently used in chemical studies of these elements, including elements which were not studied chemically to date are discussed

  2. A decontamination study of simulated chemical and biological agents

    International Nuclear Information System (INIS)

    A comprehensive decontamination scheme of the chemical and biological agents, including airborne agents and surface contaminating agents, is presented. When a chemical and biological attack occurs, it is critical to decontaminate facilities or equipments to an acceptable level in a very short time. The plasma flame presented here may provide a rapid and effective elimination of toxic substances in the interior air in isolated spaces. As an example, a reaction chamber, with the dimensions of a 22 cm diameter and 30 cm length, purifies air with an airflow rate of 5000 l/min contaminated with toluene, the simulated chemical agent, and soot from a diesel engine, the simulated aerosol for biological agents. Although the airborne agents in an isolated space are eliminated to an acceptable level by the plasma flame, the decontamination of the chemical and biological agents cannot be completed without cleaning surfaces of the facilities. A simulated sterilization study of micro-organisms was carried out using the electrolyzed ozone water. The electrolyzed ozone water very effectively kills endospores of Bacillus atrophaeus (ATCC 9372) within 3 min. The electrolyzed ozone water also kills the vegetative micro-organisms, fungi, and virus. The electrolyzed ozone water, after the decontamination process, disintegrates into ordinary water and oxygen without any trace of harmful materials to the environment

  3. The dynamical and chemical evolution of dwarf spheroidal galaxies with GEAR

    Science.gov (United States)

    Revaz, Y.; Jablonka, P.

    2012-02-01

    We present the fully parallel chemo-dynamical Tree/SPH code GEAR, which allows us to perform high resolution simulations with detailed chemical diagnostics. Starting from the public version of Gadget-2, we included the complex treatment of the baryon physics: gas cooling, star formation law, chemical evolution, and supernova feedback. We qualified the performances of GEAR in the case of dwarf spheroidal galaxies (dSphs) galaxies. Our code GEAR conserves the total energy budget of the systems to better than 5% over 14 Gyr and provides an excellent convergence of the results with numerical resolution. We showed that models of dSphs in a static Euclidean space, where the expansion of the universe is neglected are valid. In addition, we tackled some existing open questions in the field, such as the stellar mass fraction of dSphs and its link to the predicted dark matter halo mass function, the effect of supernova feedback, the spatial distribution of the stellar populations, and the origin of the diversity in star formation histories and chemical abundance patterns. Strong supernova-driven winds seem incompatible with the observed metallicities and luminosities. Despite newly formed stars being preferentially found in the galaxy central parts, turbulent motions in the gas can quickly erase any metallicity gradient. The diversity in properties of dSph are related to a range of total masses, as well as a range of dispersion in the central densities, which is also seen in the halos emerging from a ΛCDM cosmogony. Appendices A and B are available in electronic form at http://www.aanda.org

  4. Kinetically constrained ring-polymer molecular dynamics for non-adiabatic chemical reactions

    International Nuclear Information System (INIS)

    We extend ring-polymer molecular dynamics (RPMD) to allow for the direct simulation of general, electronically non-adiabatic chemical processes. The kinetically constrained (KC) RPMD method uses the imaginary-time path-integral representation in the set of nuclear coordinates and electronic states to provide continuous equations of motion that describe the quantized, electronically non-adiabatic dynamics of the system. KC-RPMD preserves the favorable properties of the usual RPMD formulation in the position representation, including rigorous detailed balance, time-reversal symmetry, and invariance of reaction rate calculations to the choice of dividing surface. However, the new method overcomes significant shortcomings of position-representation RPMD by enabling the description of non-adiabatic transitions between states associated with general, many-electron wavefunctions and by accurately describing deep-tunneling processes across asymmetric barriers. We demonstrate that KC-RPMD yields excellent numerical results for a range of model systems, including a simple avoided-crossing reaction and condensed-phase electron-transfer reactions across multiple regimes for the electronic coupling and thermodynamic driving force

  5. Kinetically constrained ring-polymer molecular dynamics for non-adiabatic chemical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Menzeleev, Artur R.; Bell, Franziska; Miller, Thomas F., E-mail: tfm@caltech.edu [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States)

    2014-02-14

    We extend ring-polymer molecular dynamics (RPMD) to allow for the direct simulation of general, electronically non-adiabatic chemical processes. The kinetically constrained (KC) RPMD method uses the imaginary-time path-integral representation in the set of nuclear coordinates and electronic states to provide continuous equations of motion that describe the quantized, electronically non-adiabatic dynamics of the system. KC-RPMD preserves the favorable properties of the usual RPMD formulation in the position representation, including rigorous detailed balance, time-reversal symmetry, and invariance of reaction rate calculations to the choice of dividing surface. However, the new method overcomes significant shortcomings of position-representation RPMD by enabling the description of non-adiabatic transitions between states associated with general, many-electron wavefunctions and by accurately describing deep-tunneling processes across asymmetric barriers. We demonstrate that KC-RPMD yields excellent numerical results for a range of model systems, including a simple avoided-crossing reaction and condensed-phase electron-transfer reactions across multiple regimes for the electronic coupling and thermodynamic driving force.

  6. Experimental studies of thermal and chemical interactions between molten aluminum and water

    Energy Technology Data Exchange (ETDEWEB)

    Farahani, A.A.; Corradini, M.L. [Univ. of Wisconsin, Madison, WI (United States)

    1995-09-01

    The possibility of rapid physical and chemical aluminum/water interactions during a core melt accident in a noncommercial reactor (e.g., HFIR, ATR) has resulted in extensive research to determine the mechanism by which these interactions occur and propagate on an explosive time scale. These events have been reported in nuclear testing facilities, i.e., during SPERT 1D experiment, and also in aluminum casting industries. Although rapid chemical reactions between molten aluminum and water have been subject of many studies, very few reliable measurements of the extent of the chemical reactions have thus far been made. We have modified an existing 1-D shock tube facility to perform experiments in order to determine the extent of the explosive thermal/chemical interactions between molton aluminum and water by measuring important physical quantities such as the maximum dynamic pressure and the amount of the generated hydrogen. Experimental results show that transient pressures greater than 69 MPa with a rise time of less than 125 {mu}sec can occur as the result of the chemical reaction of 4.2 grams of molton aluminum (approximately 15% of the total mass of the fuel of 28 grams) at 980 C with room temperature water.

  7. Feasibility study of chemical stabilization of dredged marine sediment

    OpenAIRE

    FURLAN, Ana Paola; RAZAKAMANANTSOA, Andry; Liang, Yingjie; Deneele, Dimitri

    2015-01-01

    Chemical stabilization is one of techniques which can improve mechanical and hydraulic properties of dredged sediments. This paper presents an experimental study focused on different techniques of stabilization of dredged sediment from La Baule-Le Pouliguen (France). Dredged sediments are stabilized with lime, Portland cement and fly ash. Three mixes were produced and submitted to uniaxial compression strength (UCS), indirect tensile strength (ITS) and shear tests at different curing ages. In...

  8. Chemical elements in invertebrate orders for environmental quality studies

    Energy Technology Data Exchange (ETDEWEB)

    Magalhaes, Marcelo R.L.; Franca, Elvis J.; Paiva, Jose D.S.; Hazin, Clovis A., E-mail: marcelo_rlm@hotmail.com, E-mail: ejfranca@cnen.gov.br, E-mail: dan-paiva@hotmail.com, E-mail: chazin@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Fonseca, Felipe Y.; Fernandes, Elisabete A. de Nadai; Bacchi, Marcio A., E-mail: felipe-yamada@hotmail.com, E-mail: lis@cena.usp.br, E-mail: mabacchi@cena.usp.br [Centro de Energia Nuclear na Agricultura (CENA/USP), Piracicaba, SP (Brazil)

    2013-07-01

    Among the biomonitors of environmental quality, there is a lack of studies on using invertebrates to evaluate quantitatively chemical elements in ecosystems. This group of animals is quite numerous, widely distributed and adaptable to the most diverse environmental conditions. These features are very useful for the environmental quality assessment, as well as the several occurring insect-plant interactions performing essential functions in ecosystems. The objective of this work is to study the variability of chemical composition of invertebrate orders for using in environmental quality monitoring studies. Instrumental neutron activation analysis - INAA was applied to determine some nutrients and trace elements in invertebrate samples. Sampling by pitfall traps was carried out in riverine ecosystems from the urban area from the Piracicaba Municipality, State of Sao Paulo, Brazil. Invertebrate and reference material samples were irradiated in the nuclear research reactor IEA-R1, Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN. Fragments of a Ni-Cr alloy were irradiated for monitoring the thermal neutron flux. Hymenoptera order was considered the most representative according to the total number of sampled species (about 60%). Significant amounts of Ba, Br, Fe and Sc were found in invertebrates of the order Opiliones. Potassium, rubidium and zinc were highly accumulated in species from Blattodea order, indicating a consistent pattern of accumulation for this invertebrate order. Taking into account the abundance of Hymenoptera order, the chemical composition of its species was significant different at the 95% confidence level for Br and Na in the sampled locals. (author)

  9. Chemical elements in invertebrate orders for environmental quality studies

    International Nuclear Information System (INIS)

    Among the biomonitors of environmental quality, there is a lack of studies on using invertebrates to evaluate quantitatively chemical elements in ecosystems. This group of animals is quite numerous, widely distributed and adaptable to the most diverse environmental conditions. These features are very useful for the environmental quality assessment, as well as the several occurring insect-plant interactions performing essential functions in ecosystems. The objective of this work is to study the variability of chemical composition of invertebrate orders for using in environmental quality monitoring studies. Instrumental neutron activation analysis - INAA was applied to determine some nutrients and trace elements in invertebrate samples. Sampling by pitfall traps was carried out in riverine ecosystems from the urban area from the Piracicaba Municipality, State of Sao Paulo, Brazil. Invertebrate and reference material samples were irradiated in the nuclear research reactor IEA-R1, Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN. Fragments of a Ni-Cr alloy were irradiated for monitoring the thermal neutron flux. Hymenoptera order was considered the most representative according to the total number of sampled species (about 60%). Significant amounts of Ba, Br, Fe and Sc were found in invertebrates of the order Opiliones. Potassium, rubidium and zinc were highly accumulated in species from Blattodea order, indicating a consistent pattern of accumulation for this invertebrate order. Taking into account the abundance of Hymenoptera order, the chemical composition of its species was significant different at the 95% confidence level for Br and Na in the sampled locals. (author)

  10. Study on Dynamic Alignment Technology of COIL Resonator

    International Nuclear Information System (INIS)

    The performance of great power chemical oxygen-iodine laser (COIL) beam is decided mostly by resonator mirror maladjustment and environment vibration. To improve the performance of light beam, an auto-alignment device is used in COIL resonator, the device can keep COIL resonator collimating by adjusting the optical components of resonator. So the coupling model of COIL resonator is present. The multivariable self study fuzzy uncoupling arithmetic and six-dimensional micro drive technology are used to design a six-input-three-output uncoupling controller, resulting in the realization of the high precision dynamic alignment. The experiments indicate that the collimating range of this system is 8 mrad, precision is 5 urad and frequency response is 20Hz, which meet the demand of resonator alignment system

  11. Ultrasonic Study of Dislocation Dynamics in Lithium -

    Science.gov (United States)

    Han, Myeong-Deok

    1987-09-01

    Experimental studies of dislocation dynamics in LiF single crystals, using ultrasonic techniques combined with dynamic loading, were performed to investigate the time evolution of the plastic deformation process under a short stress pulse at room temperature, and the temperature dependence of the dislocation damping mechanism in the temperature range 25 - 300(DEGREES)K. From the former, the time dependence of the ultrasonic attenuation was understood as resulting from dislocation multiplication followed by the evolution of mobile dislocations to immobile ones under large stress. From the latter, the temperature dependence of the ultrasonic attenuation was interpreted as due to the motion of the dislocation loops overcoming the periodic Peierls potential barrier in a manner analogous to the motion of a thermalized sine-Gordon chain under a small stress. The Peierls stress obtained from the experimental results by application of Seeger's relaxation model with exponential dislocation length distribution was 4.26MPa, which is consistent with the lowest stress for the linear relation between the dislocation velocity and stress observed by Flinn and Tinder.

  12. Contribution to the study of dynamic recrystallization

    International Nuclear Information System (INIS)

    An experimental and theoretical work on dynamic recrystallization is presented. The experimental study, sustained by creep deformation of NaCl single crystals, has shown that the structural evolution can occur in two distinct ways: rotation recrystallization, which consists in a progressive sub-boundary misorientation increase; migration recrystallization, which consists in the 'catastrophic' growth of some grains. Although rotation recrystallization is to be observed for all experimental used conditions, migration recrystallization occurs only in a well defined domain of the temperature-applied stress-impurity concentration space. The proposed interpretation emphasizes the generality of the observed behaviours: the sharp boundary of the migration recrystallization domain expresses the existence of a 'catastrophic' transition from a low velocity regime (boundaries migrate charged with segregate impurities) to a high velocity regime (boundaries migrate free from impurities). Owing to the importance of grain boundary migration in dynamic recrystallization, a detailed analysis of possible migration mechanisms is presented: we show how migration induced by applied stress or recrystallization force can be explained. Finally, an original kinetic model of grain growth is developed which throws a new insight in the abnormal grain growth process and, by analogy, in the migration recrystallization phenomenon. (author)

  13. Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics Lecture: Broadband Rotational Spectroscopy for Chemical Kinetics, Molecular Structure, and Analytical Chemistry

    Science.gov (United States)

    Pate, Brooks

    2013-03-01

    Advances in high-speed digital electronics have enabled a new generation of molecular rotational spectroscopy techniques that provide instantaneous broadband spectral coverage. These techniques use a chirped excitation pulse to coherently excite the molecular sample over a spectral bandwidth of 10 GHz or larger through rapid passage. The subsequent time-domain emission is recorded using high-speed digitizers (up to 100 Gigasample/s) and the frequency domain spectrum is produced by fast Fourier transformation. The chirped-pulse Fourier transform (CP-FT) method has been implemented in the microwave frequency range (2-40 GHz) for studies of cold samples in pulsed jet sources and in the mm-wave/terahertz (THz) frequency range for studies of samples at room-temperature. The method has opened new applications for molecular rotational spectroscopy in the area of chemical kinetics where dynamic rotational spectroscopy is used to measure the rates of unimolecular isomerization reactions in highly excited molecules prepared by pulsed infrared laser excitation. In these applications, the isomerization rate is obtained from an analysis of the overall line shapes which are modified by chemical exchange leading to coalescence behavior similar to the effect in NMR spectroscopy. The sensitivity of the method and the ability to extend it to low frequency (2-8 GHz) have significantly increased the size range of molecules and molecular clusters for structure determination using isotopic substitution to build up the 3D molecular structures atom-by-atom. Application to the structure of water clusters with up to 15 water molecules will be presented. When coupled with advances in solid-state mm-wave/THz devices, this method provides a direct digital technique for analytical chemistry of room-temperature gases based on molecular rotational spectroscopy. These high-throughput methods can analyze complex sample mixtures with unmatched chemical selectivity and short analysis times. Work

  14. Monte Carlo study of real time dynamics

    CERN Document Server

    Alexandru, Andrei; Bedaque, Paulo F; Vartak, Sohan; Warrington, Neill C

    2016-01-01

    Monte Carlo studies involving real time dynamics are severely restricted by the sign problem that emerges from highly oscillatory phase of the path integral. In this letter, we present a new method to compute real time quantities on the lattice using the Schwinger-Keldysh formalism via Monte Carlo simulations. The key idea is to deform the path integration domain to a complex manifold where the phase oscillations are mild and the sign problem is manageable. We use the previously introduced "contraction algorithm" to create a Markov chain on this alternative manifold. We substantiate our approach by analyzing the quantum mechanical anharmonic oscillator. Our results are in agreement with the exact ones obtained by diagonalization of the Hamiltonian. The method we introduce is generic and in principle applicable to quantum field theory albeit very slow. We discuss some possible improvements that should speed up the algorithm.

  15. Dynamic speckle study of microbial growth

    Science.gov (United States)

    Vincitorio, F. M.; Mulone, C.; Marcuzzi, P. A.; Budini, N.; Freyre, C.; Lopez, A. J.; Ramil, A.

    2015-08-01

    In this work we present a characterization of yeast dynamic speckle activity during growth in an isolated agar culture medium. We found that it is possible to detect the growth of the microorganisms even before they turn out to be visible. By observing the time evolution of the speckle activity at different regions of the culture medium we could extract a map of the growth process, which served to analyze how the yeast develops and spreads over the agar's medium. An interesting point of this study concerns with the influence of the laser light on the yeast growth rate. We have found that yeast finds hard to develop at regions with higher laser light illumination, although we used a synchronous system to capture the speckle pattern. The results obtained in this work would serve us as a starting point to fabricate a detector of growing microorganism colonies, with obvious interesting applications in diverse areas.

  16. Non Linear Beam Dynamics Studies at SPEAR

    International Nuclear Information System (INIS)

    The frequency map analysis of a Hamiltonian system recently introduced to accelerators physics in combination with turn-by-turn phase space measurements opens new experimental opportunities for studying non linear dynamic in storage rings. In this paper we report on the experimental program at SPEAR having the goal of measuring the frequency map of the machine. In this paper we discuss the accuracy of the instantaneous tune extraction from experimental data and demonstrate the possibility of the frequency map measurement. The instantaneous tune extraction technique can be applied to experimental tracking data with reasonable accuracy. Frequency map can be experimentally determined using the existing turn-by-turn phase space measurement techniques and NAFF instantaneous tune extraction.

  17. Molecular Dynamics Studies of Nanofluidic Devices

    DEFF Research Database (Denmark)

    Zambrano Rodriguez, Harvey Alexander

    of transport mechanism to drive fluids and solids at the nanoscale. Specifically, we present the results of three different research projects. Throughout the first part of this thesis, we include a comprenhensive introduction to computational nanofluidics and to molecular simulations, and describe...... the molecular dynamics methodology. In the second part of this thesis, we present the results of three different research projects. Fristly, we present a computational study of thermophoresis as a suitable mechanism to drive water droplets confined in different types of carbon nanotubes. We observe a...... motion of the water droplet in opposite direction to the imposed thermal gradient also we measure higher velocities as higher thermal gradients are imposed. Secondly, we present an atomistic analysis of a molecular linear motor fabricated of coaxial carbon nanotubes and powered by thermal gradients. The...

  18. Beam dynamics studies for photocathode RF gun

    International Nuclear Information System (INIS)

    Photocathode RF guns are very popular choice as injector for low emittance beams especially to light sources world wide. In demand for these gun is increasing steadily and efforts are on to make 2.6 cell RF Gun as SAMEER as proto type for future use at various laboratories. The base design of this 2.6 cell RF Gun is ready and fabrication is planned in near future. In this paper, we present beam dynamic study results of the gun and methodology to arrive at the operating point. Simulation results for Gaussian with nano-second pulse length will be discussed in detail and proposal for generation of few MeV beam will be presented. (author)

  19. Radionuclide renal dynamic and function study

    International Nuclear Information System (INIS)

    The radionuclide dynamic and function study, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were reported in 14 cases of renal and ureteral calculi patients before and after extracorporeal shock wave lithotripsy (ESWL). In 12 cases with normal renal blood flow, within 3 months after ESWL, the GFR of shock and non-shock side decreased with different extent, while the individual ERPF had little change. In 5 cases followed up 1 year after ESWL, the individual GFR and ERPF were normal. In 2 cases of severe renal function insufficiency, there was no improvement in renal function in shock side, after 5 months and 1 year, the renal function was still at low level. Thereby it is considered that ESWL is not suitable for the renal calculi patients with severe renal function insufficiency

  20. Stereophotogrammetry in studies of riparian vegetation dynamics

    Science.gov (United States)

    Hortobagyi, Borbala; Vautier, Franck; Corenblit, Dov; Steiger, Johannes

    2014-05-01

    Riparian vegetation responds to hydrogeomorphic disturbances and also controls sediment deposition and erosion. Spatio-temporal riparian vegetation dynamics within fluvial corridors have been quantified in many studies using aerial photographs and GIS. However, this approach does not allow the consideration of woody vegetation growth rates (i.e. vertical dimension) which are fundamental when studying feedbacks between the processes of fluvial landform construction and vegetation establishment and succession. We built 3D photogrammetric models of vegetation height based on aerial argentic and digital photographs from sites of the Allier and Garonne Rivers (France). The models were realized at two different spatial scales and with two different methods. The "large" scale corresponds to the reach of the river corridor on the Allier river (photograph taken in 2009) and the "small" scale to river bars of the Allier (photographs taken in 2002, 2009) and Garonne Rivers (photographs taken in 2000, 2002, 2006 and 2010). At the corridor scale, we generated vegetation height models using an automatic procedure. This method is fast but can only be used with digital photographs. At the bar scale, we constructed the models manually using a 3D visualization on the screen. This technique showed good results for digital and also argentic photographs but is very time-consuming. A diachronic study was performed in order to investigate vegetation succession by distinguishing three different classes according to the vegetation height: herbs (trees (>4 m). Both methods, i.e. automatic and manual, were employed to study the evolution of the three vegetation classes and the recruitment of new vegetation patches. A comparison was conducted between the vegetation height given by models (automatic and manual) and the vegetation height measured in the field. The manually produced models (small scale) were of a precision of 0.5-1 m, allowing the quantification of woody vegetation growth rates

  1. Models of disk chemical evolution focusing the pure dynamical radial mixing

    Directory of Open Access Journals (Sweden)

    Re Fiorentin P.

    2012-02-01

    Full Text Available We performed N-body simulations to study the dynamical evolution of a stellar disk inside a Dark Matter (DM halo. Our results evidence how a standard -radially decreasing- metallicity gradient produces a negative vϕ vs. [Fe/H] correlation, similar to that shown by the thin disk stars, while an inverse radial gradient generates a positive rotation-metallicity correlation, as that observed in the old thick population.

  2. Single-collision studies of energy transfer and chemical reaction

    Energy Technology Data Exchange (ETDEWEB)

    Valentini, J.J. [Columbia Univ., New York, NY (United States)

    1993-12-01

    The research focus in this group is state-to-state dynamics of reaction and energy transfer in collisions of free radicals such as H, OH, and CH{sub 3} with H{sub 2}, alkanes, alcohols and other hydrogen-containing molecules. The motivation for the work is the desire to provide a detailed understanding of the chemical dynamics of prototype reactions that are important in the production and utilization of energy sources, most importantly in combustion. The work is primarily experimental, but with an important and growing theoretical/computational component. The focus of this research program is now on reactions in which at least one of the reactants and one of the products is polyatomic. The objective is to determine how the high dimensionality of the reactants and products differentiates such reactions from atom + diatom reactions of the same kinematics and energetics. The experiments use highly time-resolved laser spectroscopic methods to prepare reactant states and analyze the states of the products on a single-collision time scale. The primary spectroscopic tool for product state analysis is coherent anti-Stokes Raman scattering (CARS) spectroscopy. CARS is used because of its generality and because the extraction of quantum state populations from CARS spectra is straightforward. The combination of the generality and easy analysis of CARS makes possible absolute cross section measurements (both state-to-state and total), a particularly valuable capability for characterizing reactive and inelastic collisions. Reactant free radicals are produced by laser photolysis of appropriate precursors. For reactant vibrational excitation stimulated Raman techniques are being developed and implemented.

  3. Rotational coherence spectroscopy at FLASH. Toward dynamic studies in nanosuperfluids

    International Nuclear Information System (INIS)

    The field of molecular physics, which is focusing on molecular motion in the transition states of physical, chemical, and biological changes, is a wide-spread research area. It strives to reveal the structural and functional properties of molecules, the chemical bonds between atoms and the time evolution. Many processes occurring in nature upon electronic excitation proceed on the ultrafast femtosecond timescale and can be triggered by modern ultrashort femtosecond-laser sources under laboratory conditions. In the present thesis pump-probe studies were performed to follow molecular motion using ultrashort light pulses in the nanometer wavelength range provided by an XUV freeelectron laser (FEL). In detail, alignment of molecular species in space under field-free conditions was investigated. In the specific case of rotational wave packets in molecules the rotational dynamics shows characteristic temporal features, which contain a wealth of information on molecular structure and give insight into molecular coupling mechanisms, i.e. rotational constants and transition frequencies. Within this thesis, Rotational Coherence Spectroscopy (RCS) reveals wave-packet motion observed by subsequent Coulomb explosion of Raman excited carbon monoxide, which results in a time-dependent asymmetry of spatial fragmentation patterns. With the method presented here, the time resolution to elucidate the fast dynamics of strong couplings can be pushed toward a single rotational period even for the fastest rotors. This is due to large pump-probe delays with small subpicosecond step size. This kind of spectroscopy can also be expanded to molecular species, which are not accessible by other powerful spectroscopic methods, such as Fourier-transform microwave spectroscopy (FTMW). Furthermore, it allows to measure weak molecular couplings on a long timescale (large pump-probe delays), e.g. couplings of molecules in a solution or molecules dissolved in quantum fluids. This is valuable to

  4. Rotational coherence spectroscopy at FLASH. Toward dynamic studies in nanosuperfluids

    Energy Technology Data Exchange (ETDEWEB)

    Kickermann, Andreas

    2013-07-15

    The field of molecular physics, which is focusing on molecular motion in the transition states of physical, chemical, and biological changes, is a wide-spread research area. It strives to reveal the structural and functional properties of molecules, the chemical bonds between atoms and the time evolution. Many processes occurring in nature upon electronic excitation proceed on the ultrafast femtosecond timescale and can be triggered by modern ultrashort femtosecond-laser sources under laboratory conditions. In the present thesis pump-probe studies were performed to follow molecular motion using ultrashort light pulses in the nanometer wavelength range provided by an XUV freeelectron laser (FEL). In detail, alignment of molecular species in space under field-free conditions was investigated. In the specific case of rotational wave packets in molecules the rotational dynamics shows characteristic temporal features, which contain a wealth of information on molecular structure and give insight into molecular coupling mechanisms, i.e. rotational constants and transition frequencies. Within this thesis, Rotational Coherence Spectroscopy (RCS) reveals wave-packet motion observed by subsequent Coulomb explosion of Raman excited carbon monoxide, which results in a time-dependent asymmetry of spatial fragmentation patterns. With the method presented here, the time resolution to elucidate the fast dynamics of strong couplings can be pushed toward a single rotational period even for the fastest rotors. This is due to large pump-probe delays with small subpicosecond step size. This kind of spectroscopy can also be expanded to molecular species, which are not accessible by other powerful spectroscopic methods, such as Fourier-transform microwave spectroscopy (FTMW). Furthermore, it allows to measure weak molecular couplings on a long timescale (large pump-probe delays), e.g. couplings of molecules in a solution or molecules dissolved in quantum fluids. This is valuable to

  5. Contents of chemical elements in stomach during prenatal development: different age-dependent dynamical changes and their significance

    Institute of Scientific and Technical Information of China (English)

    Shao-Fan Hou; Hai-Rong Li; Li-Zhen Wang; De-Zhu Li; Lin-Sheng Yang; Chong-Zheng Li

    2003-01-01

    AIM: To observe dynamic of different chemical elements in stomach tissue during fetal development.METHODS: To determine contents of the 21 chemical elements in each stomach samples from fetus aging four to ten months. The content values were compared to those from adult tissue samples, and the values for each month group were also analyzed for dynamic changes.RESULTS: Three representations were found regarding the relationship between contents of the elements and ages of the fetus, including the positive correlative (K), reversely correlative (Na, Ca, P, Al, Cu, Zn, Fe, Mn, Cr, Sr, Li, Cd, Ba,Se ) and irrelevant groups (Mg, Co, Ni, V, Pb, Ti).CONCLUSION: The chemical elements' contents in stomach tissues were found to change dynamically with the stomach weights. The age-dependent representations for different chemical elements during the prenatal development may be of some significance for assessing development of fetal stomach and some chemical elements. The data may be helpful for the nutritional balance of fetus and mothers during prenatal development and even the perinatal stages.

  6. Application of dynamic Bayesian network to risk analysis of domino effects in chemical infrastructures

    International Nuclear Information System (INIS)

    A domino effect is a low frequency high consequence chain of accidents where a primary accident (usually fire and explosion) in a unit triggers secondary accidents in adjacent units. High complexity and growing interdependencies of chemical infrastructures make them increasingly vulnerable to domino effects. Domino effects can be considered as time dependent processes. Thus, not only the identification of involved units but also their temporal entailment in the chain of accidents matter. More importantly, in the case of domino-induced fires which can generally last much longer compared to explosions, foreseeing the temporal evolution of domino effects and, in particular, predicting the most probable sequence of accidents (or involved units) in a domino effect can be of significance in the allocation of preventive and protective safety measures. Although many attempts have been made to identify the spatial evolution of domino effects, the temporal evolution of such accidents has been overlooked. We have proposed a methodology based on dynamic Bayesian network to model both the spatial and temporal evolutions of domino effects and also to quantify the most probable sequence of accidents in a potential domino effect. The application of the developed methodology has been demonstrated via a hypothetical fuel storage plant. - Highlights: • A Dynamic Bayesian Network methodology has been developed to model domino effects. • Considering time-dependencies, both spatial and temporal evolutions of domino effects have been modeled. • The concept of most probable sequence of accidents has been proposed instead of the most probable combination of accidents. • Using backward analysis, the most vulnerable units have been identified during a potential domino effect. • The proposed methodology does not need to identify a unique primary unit (accident) for domino effect modeling

  7. Use of radioisotopes as applied to the study of the metabolism of agricultural chemicals in plants, animals, and insects

    International Nuclear Information System (INIS)

    The use of radiolabeled compounds to study the fate of agricultural chemicals has found widespread acceptance during the last two decades. Radiochemicals provide the required sensitivity to study the dynamics of these biologically active molecules that are used in small concentrations in the agricultural environment. The metabolic interactions between climate, soil, air, water, plants, and animals present special problems. In this chapter, the authors will review the use of radiolabeled agricultural chemicals to study their metabolic fate in plants, animals, and insects. Specific references to the use of these radiochemicals include methods of dosing, isolation, and characterization of metabolic products

  8. Study of equilibrium using collision dynamics

    International Nuclear Information System (INIS)

    Full text: The heavy-ion collisions at low, intermediate and relativistic energies provide a unique possibility to investigate the different questions ranging from the fusion at low incident energies to the formation of quark-gluon-plasma at higher incident energies. The intermediate energy heavy-ion collisions are excellent tool to study the nuclear equation of state which depends on the temperature as well on the density of the matter. Another important question associated with heavy-ion collision is the degree of equilibrium reached in a reaction. The answer of this question is important as there are several models employed at intermediate energy that assume global (or local) equilibrium. We shall study this question with two different aims. First, we would like to see whether a equilibrium is reached in a heavy-ion collision or not. Secondly, one is interested to know the number of collisions one needs to thermalized the matter. This study is attempted within Quantum Molecular Dynamics (QMD) model [1]. The QMD model is based on molecular dynamics picture where nucleons propagate under the influence of two and three body interactions. Here nucleon-nucleon potential is represented by the Skyrme, Coulomb and Yukawa forces. The question of equilibrium is addressed with the help of rapidity distribution which is defined as: Yi = 1/2 Ln E(i) + pz (i) c / E(i) - pz (i) c Here E(i) and pz(i) denote, respectively, the total energy and longitudinal momentum of the with particle. For a complete equilibrium, one should get a single peak in the distribution at mid rapidity. We calculated the rapidity distribution of Sn-Xe reaction at incident of 50, 400 and 2000 MeV/nucleon. We find that central collisions lead to better global equilibrium whereas peripheral collisions lack equilibrium. Further, one needs 10 collisions for complete equilibrium i.e. for a single peak at mid rapidity distribution. Whereas, if the number of collisions is less than 10, one obtains two peaks

  9. Experimental Studies of Dynamics at Solid Surfaces

    Science.gov (United States)

    Germer, Thomas Avery

    1992-01-01

    Measurements of thermal and photoinduced processes on metal surfaces point to the importance of transient intermediate species in the understanding of dynamics. Experiments were performed using photoinduced desorption (PID), thermal desorption spectroscopy (TDS), high-resolution and time -resolved electron-energy-loss spectroscopy (HREELS and TREELS), and femtosecond multiphoton photoemission spectroscopy. The thermal and photoinduced reactions of Mo(CO)_6 adsorbed on Rh(100) were studied to better understand energy transfer between a photoexcited molecule and a metal surface. The Mo(CO)_6 partially dissociated upon adsorption, allowing a comparison to be made between Mo(CO)_6 adsorbed on the fragment-covered surface and a more ordered CO-covered surface. The energy transfer rate was found to be larger on the fragment-covered surface. The thermal reaction of hydrogen gas with oxygen adsorbed on Pt(111) was studied with TREELS between 130 and 160 K, observing the modes associated with hydroxyl adsorbed on the surface as a function of time while the sample, preadsorbed with atomic oxygen, was exposed to hydrogen gas. In coordination between Monte Carlo calculations and kinetic simulations, a model was developed whereby the reaction to form hydroxyl occurred between a molecular hydrogen precursor and oxygen at island boundaries. The photoinduced reaction of adsorbed atomic hydrogen and molecular oxygen to form hydroxyl and water on Pt(111) was studied in order to understand the reactivity of the hot oxygen atoms produced by photodissociation of molecular oxygen. The final products of the two oxygen -hydrogen reactions were the same. A measurement was made of the cross section for NO photodesorption from Pt(111) at 90 K. All of these experiments pointed to a need to make transient measurements on the ultrashort time scale in order to develop a more microscopic understanding of the dynamical processes that are occurring. As a result, a novel time-of-flight analyzer was

  10. Elucidating collision induced dissociation products and reaction mechanisms of protonated uracil by coupling chemical dynamics simulations with tandem mass spectrometry experiments.

    Science.gov (United States)

    Molina, Estefanía Rossich; Ortiz, Daniel; Salpin, Jean-Yves; Spezia, Riccardo

    2015-12-01

    In this study we have coupled mixed quantum-classical (quantum mechanics/molecular mechanics) direct chemical dynamics simulations with electrospray ionization/tandem mass spectrometry experiments in order to achieve a deeper understanding of the fragmentation mechanisms occurring during the collision induced dissociation of gaseous protonated uracil. Using this approach, we were able to successfully characterize the fragmentation pathways corresponding to ammonia loss (m/z 96), water loss (m/z 95) and cyanic or isocyanic acid loss (m/z 70). Furthermore, we also performed experiments with isotopic labeling completing the fragmentation picture. Remarkably, fragmentation mechanisms obtained from chemical dynamics simulations are consistent with those deduced from isotopic labeling. PMID:26634967

  11. Systems-Dynamic Analysis for Neighborhood Study

    Science.gov (United States)

    Systems-dynamic analysis (or system dynamics (SD)) helps planners identify interrelated impacts of transportation and land-use policies on neighborhood-scale economic outcomes for households and businesses, among other applications. This form of analysis can show benefits and tr...

  12. Thermogravimetric study of chemical compatibility of graphite with metal oxides

    International Nuclear Information System (INIS)

    Graphite and graphite mixtures with metal oxides are studied in conditions of nonisothermal heating to 1000 deg C using the methods of thermodynamic and gravimetric analyses. Chemical compatibility of graphite with Al2O3, CaO, SiO2, MgO, Fe2O3, TiO2, Na2O, K2O in the compositions considered is established. A decrease in the sample mass observed on the gravimetric curves in the presence of admixtures does not exceed the same value in pure graphite samples in specified conditions

  13. Studies on the Chemical Constituents and Bioactivities of Tripterygium Wilfordii

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Tripterygium wilfordii Hook (TW) is a medicinal plant distributed widely in southern china. This plant was recently found to possess anti-inflammatory, antitumor and immunosuppressive activities. Some preparation of the plant root has been used for the treatment of rheumatoid arthritis, systemic acne rosacea, nephritis and some skin diseases. Chemical studies on this plant and its preparation have shown they contain a large number of sesquiterpenoid, diterpenoids, triterpenoids and alkaloids in which some diterpene triepoxy lactones such as triptolide and triptonide etc are considered as mainly active compounds.

  14. Studies on the Chemical Constituents and Bioactivities of Tripterygium Wilfordii

    Institute of Scientific and Technical Information of China (English)

    LI; YuanChao

    2001-01-01

    Tripterygium wilfordii Hook (TW) is a medicinal plant distributed widely in southern china. This plant was recently found to possess anti-inflammatory, antitumor and immunosuppressive activities. Some preparation of the plant root has been used for the treatment of rheumatoid arthritis, systemic acne rosacea, nephritis and some skin diseases. Chemical studies on this plant and its preparation have shown they contain a large number of sesquiterpenoid, diterpenoids, triterpenoids and alkaloids in which some diterpene triepoxy lactones such as triptolide and triptonide etc are considered as mainly active compounds.  ……

  15. Molecular dynamics studies on nanoscale gas transport

    Science.gov (United States)

    Barisik, Murat

    Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall Molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress calculations are based on the Irving-Kirkwood method, which divides the stress tensor into its kinetic and virial parts. The kinetic component recovers pressure based on the ideal gas law. The particle-particle virial increases with increased density, while the surface-particle virial develops due to the surface force field effects. Normal stresses within nano-scale confinements show anisotropy induced primarily by the surface force-field and local variations in the fluid density near the surfaces. For dilute and dense gas cases, surface-force field that extends typically 1nm from each wall induces anisotropic normal stress. For liquid case, this effect is further amplified by the density fluctuations that extend beyond the three field penetration region. Outside the wall force-field penetration and density fluctuation regions the normal stress becomes isotropic and recovers the thermodynamic pressure, provided that sufficiently large force cut-off distances are utilized in the computations. Next, non-equilibrium SWMD is utilized to investigate the surface-gas interaction effects on nanoscale shear-driven gas flows in the transition and free molecular flow regimes. For the specified surface properties and gas-surface pair interactions, density and stress profiles exhibit a universal behavior inside the

  16. Planetary Nebulae as Probes of the Chemical Evolution of Dynamically Hot Systems

    OpenAIRE

    Michael G. Richer; McCall, Marshall L.

    2004-01-01

    The measurement of chemical abundances in planetary nebulae in nearby galaxies is now relatively straightforward. The challenge is to use these chemical abundances to infer the chemical evolution of their host galaxies. At this point, our understanding of chemical evolution based upon planetary nebulae in galaxies without star formation is strongly coupled to our understanding of the relationship between the chemical abundances in stars and planetary nebulae in the Milky Way bulge. Supposing ...

  17. Matrix isolation as a tool for studying interstellar chemical reactions

    Science.gov (United States)

    Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

  18. Ultrafast Nanocrystals Decorated Micromotors for On-Site Dynamic Chemical Processes.

    Science.gov (United States)

    Jurado-Sánchez, B; Wang, J; Escarpa, A

    2016-08-01

    CdS-polyaniline-Pt and ZnS-polyaniline-Pt micromotors have been synthesized and characterized. The nanocrystals are generated "in situ" during the template electrosynthesis of the micromotors while being simultaneously trapped in the polymeric network, generating a hybrid structure. The presence of nanocrystal "edges" in the inner polyaniline layer result in a rough Pt catalytic surface and enhanced electron transfer for highly efficient bubble propulsion at remarkable speeds of over 2500 μm/s. The incorporation of CdS and ZnS nanocrystals impart several attractive functions, including cation-exchange based chemical transformation capabilities and enhanced photocatalytic performance. The remarkable ion-exchange properties of ZnS-polyaniline (PANI)-Pt micromotors are illustrated for the cation exchange of heavy metals cations. The superior photocatalytic performance of CdS-PANI-Pt micromotors is used for the enhanced photocatalytic oxidation of bisphenol A. Such self-propelled micromotors act as highly efficient dynamic platforms that offer significantly shorter and more efficient processes as compared with common static operations. The attractive properties of these micromotors will pave the way for diverse sensing, decontamination, energy generation, or electronic applications. PMID:27387459

  19. Dihydrofolate reductase as a model for studies of enzyme dynamics and catalysis [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Amnon Kohen

    2015-12-01

    Full Text Available Dihydrofolate reductase from Escherichia coli (ecDHFR serves as a model system for investigating the role of protein dynamics in enzyme catalysis. We discuss calculations predicting a network of dynamic motions that is coupled to the chemical step catalyzed by this enzyme. Kinetic studies testing these predictions are presented, and their potential use in better understanding the role of these dynamics in enzyme catalysis is considered. The cumulative results implicate motions across the entire protein in catalysis.

  20. A Hybrid Improved Genetic Algorithm and Its Application in Dynamic Optimization Problems of Chemical Processes

    Institute of Scientific and Technical Information of China (English)

    SUN Fan; DU Wenli; QI Rongbin; QIAN Feng; ZHONG Weimin

    2013-01-01

    The solutions of dynamic optimization problems are usually very difficult due to their highly nonlinear and multidimensional nature.Genetic algorithm(GA)has been proved to be a feasible method when the gradient is difficult to calculate.Its advantage is that the control profiles at all time stages are optimized simultaneously,but its convergence is very slow in the later period of evolution and it is easily trapped in the local optimum.In this study,a hybrid improved genetic algorithm(HIGA)for solving dynamic optimization problems is proposed to overcome these defects.Simplex method(SM)is used to perform the local search in the neighborhood of the optimal solution.By using SM,the ideal searching direction of global optimal solution could be found as soon as possible and the convergence speed of the algorithm is improved.The hybrid algorithm presents some improvements,such as protecting the best individual,accepting immigrations,as well as employing adaptive crossover and Gaussian mutation operators.The efficiency of the proposed algorithm is demonstrated by solving several dynamic optimization problems.At last,HIGA is applied to the optimal production of secreted protein in a fed batch reactor and the optimal feed-rate found by HIGA is effective and relatively stable.

  1. Study of vacancy elimination in chemical diffusion and electromigration

    International Nuclear Information System (INIS)

    We have made an attempt to know the vacancy elimination mechanisms in diffusion phenomena where important non conservative vacancy fluxes are induced. Firstly, we have studied the validity of the phenomenological equations used to describe the diffusion and the associated Kirkendall effect in Gold-Silver System. We found a discrepancy between the results of theory and experiences, due to the presence of macroscopic cavities in the couples. We have shown that the physical description of the phenomenon remained correct under pressure but that the chemical diffusion could give rise to a 'lateral Kirkendall effect'. Secondly, we have made some Electron Microscopic observation in Au-Ag chemical diffusion zones and in pure metals were both an electric field and a temperature gradient where applied: we observed cavities and studied mainly the conditions for their formation. We measured super-saturations and found them to be very small (≅ 10-2). We conclude the observed cavities were due to a precipitation of gases instead of vacancies. When they are big enough (≅ 1000 A), these bubbles can act as nuclei for the cavities currently observed by optical microscopy. (author)

  2. Chemical reaction and dust formation studies in laboratory hydrocarbon plasmas.

    Science.gov (United States)

    Hippler, Rainer; Majumdar, Abhijit; Thejaswini, H. C.

    Plasma chemical reaction studies with relevance to, e.g., Titan's atmosphere have been per-formed in various laboratory plasmas [1,2]. Chemical reactions in a dielectric barrier discharge at medium pressure of 250-300 mbar have been studied in CH4 /N2 and CH4 /Ar gas mixtures by means of mass spectrometry. The main reaction scheme is production of H2 by fragmenta-tion of CH4 , but also production of larger hydrocarbons like Cn Hm with n up to 10 including formation of different functional CN groups is observed. [1] A. Majumdar and R. Hippler, Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition, Rev. Sci. Instrum. 78, 075103 (2007) [2] H.T. Do, G. Thieme, M. Frühlich, H. Kersten, and R. Hippler, Ion Molecule and Dust Particle Formation in Ar/CH4 , Ar/C2 H2 and Ar/C3 H6 Radio-frequency Plasmas, Contrib. Plasma Phys. 45, No. 5-6, 378-384 (2005)

  3. Study of commercial chemical additives for cementation of radioactive waste

    International Nuclear Information System (INIS)

    In this research it has been studied the effects of chemical additives (admixtures) in the cementation process of radioactive wastes, which are used to improve the properties of waste cementation process, both of the paste and of the solidified product. However there are a large variety of these materials that are frequently changed or taken out of the market, then it is essential to know the commercially available materials and their effects. The tests were carried out with a solution simulating the evaporator concentrate waste coming from PWR nuclear reactors. It was cemented using two formulations, A and B, incorporating higher or lower amount of waste, respectively. It was added chemical admixtures from two manufacturers (S and H), which were: accelerators, set retarders and superplasticizers. The experiments were organized by a factorial design 23. The measured parameters were the viscosity, the setting time, the paste and product density and the compressive strength. In this study we performed comparative analyzes of the results of compressive strength at age of 28 and 90 days and between the densities of the samples at the same ages. The compressive strength test at age of 28 days is considered a parameter essential issues related to security handling, transport and storage of cemented waste product. The results showed that the addition of accelerators improved the compressive strength of the cemented product, but presented lower values density products. (authors)

  4. Dynamics of crowd disasters: An empirical study

    Science.gov (United States)

    Helbing, Dirk; Johansson, Anders; Al-Abideen, Habib Zein

    2007-04-01

    Many observations of the dynamics of pedestrian crowds, including various self-organization phenomena, have been successfully described by simple many-particle models. For ethical reasons, however, there is a serious lack of experimental data regarding crowd panic. Therefore, we have analyzed video recordings of the crowd disaster in Mina/Makkah during the Hajj in 1426H on 12 January 2006. They reveal two subsequent, sudden transitions from laminar to stop-and-go and “turbulent” flows, which question many previous simulation models. While the transition from laminar to stop-and-go flows supports a recent model of bottleneck flows [D. Helbing , Phys. Rev. Lett. 97, 168001 (2006)], the subsequent transition to turbulent flow is not yet well understood. It is responsible for sudden eruptions of pressure release comparable to earthquakes, which cause sudden displacements and the falling and trampling of people. The insights of this study into the reasons for critical crowd conditions are important for the organization of safer mass events. In particular, they allow one to understand where and when crowd accidents tend to occur. They have also led to organizational changes, which have ensured a safe Hajj in 1427H.

  5. Spatial dynamics chemical properties in a lowland soil under sugarcane crop

    Science.gov (United States)

    Pereira da Silva, Wellington; Duarte Guedes Cabral de Almeida, Ceres; Machado Siqueira, Glécio; Patrícia Prazeres Marques, Karina; Medeiros Bezerra, Joel; Gomes de Almeida, Brivaldo

    2013-04-01

    Lowland soils are very important to sugarcane crop in rainy coastal zone in Northeast of Brazil. This soil is flat, high yield potential and high natural soil fertility. However, soil salinity problems can be occurred due to incorrect management, poor drainage and seasonal flood. The objective of this study was to evaluate spatial variability of chemical soil properties in a Gley soil under sugarcane crop. The study area is located in Rio Formoso city, Pernambuco (Brazil), at latitude 08°38'91"S and longitude 35°16'08"W, 60.45 m above sea level and average annual rainfall of 2100 mm. The region is characterized by rainy tropical, with dry summer, rainy season between May and August and temperatures ranging from 24 to 29°C. Non-deformed soil samples were collected from the surface layer (0-20 cm) in 5 ha, total of 54 samples. The following chemical properties were studied: pH, electrical conductivity (EC), calcium, magnesium, potassium, sodium, aluminum, hydrogen + aluminum, sum of bases, cation exchange capacity (CEC), sodicity (ESP), aluminum saturation, bases saturation and total exchangeable bases. Descriptive statistics and geostatistical techniques were used to spatial modeling and construction of maps. Overall, the data appeared to be normally distributed, with the exception of Ca, Mg, K, Al and aluminum saturation. The highest coefficient of variation was found for percentage of aluminum saturation (113%) and the lowest was for Na (26.03%). The attributes that spatially dependent models were fitted to the Gaussian (pH and Ca), exponential (Mg) and spherical (base saturation and CEC), the other attributes denoted a pure nugget effect. The presence of nugget effect for most of the attributes is due of the high water table fluctuation and recharge that acts directly on the spatial distribution of them. The maps of spatial variability of chemical soil proprieties showed that EC have been influenced by different chemical elements, but sodium was the

  6. STUDY REGARDING THE CORELATION BETWEEN SOMATIC CELLS COUNT AND MAJOR CHEMICAL COMPOUNDS IN RAW MILK

    Directory of Open Access Journals (Sweden)

    S. ACATINCĂI

    2013-12-01

    Full Text Available This study approaches the dynamic of somatic cells number and chemical composition of milk during 13 months of control. The study also investigates the correlations between the number of somatic cells and some chemical parameters in milk. Studies were carried out on Romanian Black and White cows between March 2005 and March 2006 at the Didactical farm of the Banat University of Agricultural Sciences Timisoara. As quality indicator, the number of somatic cells has different values among the controls. Average values for the 13 months of control, with the exception of three controls, were below maximum limit admitted from 1th of January 2007 (600000 SCC/ml milk. There weren’t any significant differences for SCC between the two seasons. Chemical parameters in milk varied in close limits and the differences were not significant, with one exception for fat percent. Fat percent is higher (p<0.05 in the cold season 3.87% compared with 3.55% during the warm season. Somatic cells number is weak correlated with lactose and strong correlated with proteins.

  7. Studying chemical vapor deposition processes with theoretical chemistry

    OpenAIRE

    Pedersen, Henrik; Elliott, Simon D.

    2014-01-01

    In a chemical vapor deposition (CVD) process, a thin film of some material is deposited onto a surface via the chemical reactions of gaseous molecules that contain the atoms needed for the film material. These chemical reactions take place on the surface and in many cases also in the gas phase. To fully understand the chemistry in the process and thereby also have the best starting point for optimizing the process, theoretical chemical modeling is an invaluable tool for providing atomic-scale...

  8. Chemical dispersibility study of heavy bunker fuel oil

    Energy Technology Data Exchange (ETDEWEB)

    Fiocco, R. J. [R. J. Fiocco Associates, Summit, NJ (United States); Daling, P. S. [SINTEF, Trondheim, (Norway); DeMarco, G.; Lessard, R. R. [Exxon Research and Engineering Company, Florham Park, NJ (United States); Canevari, G. P. [G. P. Canevari and Associates, Cranford, NJ (United States)

    1999-08-01

    Chemical dispersibility of heavy bunker fuel oil, which historically has been characterized as not dispersible, was studied, using the well-known SINTEF methodology for evaluating the dispersibility of fresh and weathered oils. Several heavy fuel oils, specifically IFO-380 fuel oils, were involved in the study. Corexit 9500, which has been shown to be effective for viscous and weathered oils, was used as the dispersant. Results indicated that in many cases heavy fuel oils are dispersible, and that viscosity and dispersant dosage are particularly important factors. As a general rule, more viscous and weathered oils were found to require longer time for the dispersion process to occur. The standard SINTEF laboratory effectiveness test, particularly the 60-minute extended -time MNS tests, have been found to be very useful in characterizing heavy fuel oil dispersibility. 17 refs., 5 tabs., 1 fig.

  9. Chemical dispersibility study of heavy bunker fuel oil

    Energy Technology Data Exchange (ETDEWEB)

    Fiocco, R. J. [R. J. Fiocco Associates, Summit, NJ (United States); Daling, P. S. [SINTEF, Trondheim, (Norway); DeMarco, G.; Lessard, R. R. [Exxon Research and Engineering Company, Florham Park, NJ (United States); Canevari, G. P. [G. P. Canevari and Associates, Cranford, NJ (United States)

    1999-07-01

    Chemical dispersibility of heavy bunker fuel oil, which historically has been characterized as not dispersible, was studied, using the well-known SINTEF methodology for evaluating the dispersibility of fresh and weathered oils. Several heavy fuel oils, specifically IFO-380 fuel oils, were involved in the study. Corexit 9500, which has been shown to be effective for viscous and weathered oils, was used as the dispersant. Results indicated that in many cases heavy fuel oils are dispersible, and that viscosity and dispersant dosage are particularly important factors. As a general rule, more viscous and weathered oils were found to require longer time for the dispersion process to occur. The standard SINTEF laboratory effectiveness test, particularly the 60-minute extended -time MNS tests, have been found to be very useful in characterizing heavy fuel oil dispersibility. 17 refs., 5 tabs., 1 fig.

  10. Chemical dispersibility study of heavy bunker fuel oil

    Energy Technology Data Exchange (ETDEWEB)

    Fiocco, R. J. (R. J. Fiocco Associates, Summit, NJ (United States)); Daling, P. S. (SINTEF, Trondheim, (Norway)); DeMarco, G.; Lessard, R. R. (Exxon Research and Engineering Company, Florham Park, NJ (United States)); Canevari, G. P. (G. P. Canevari and Associates, Cranford, NJ (United States))

    1999-01-01

    Chemical dispersibility of heavy bunker fuel oil, which historically has been characterized as not dispersible, was studied, using the well-known SINTEF methodology for evaluating the dispersibility of fresh and weathered oils. Several heavy fuel oils, specifically IFO-380 fuel oils, were involved in the study. Corexit 9500, which has been shown to be effective for viscous and weathered oils, was used as the dispersant. Results indicated that in many cases heavy fuel oils are dispersible, and that viscosity and dispersant dosage are particularly important factors. As a general rule, more viscous and weathered oils were found to require longer time for the dispersion process to occur. The standard SINTEF laboratory effectiveness test, particularly the 60-minute extended -time MNS tests, have been found to be very useful in characterizing heavy fuel oil dispersibility. 17 refs., 5 tabs., 1 fig.

  11. Femtosecond fluorescence up-conversion: a time-gated frequency mixing technique for ultrafast chemical dynamics

    International Nuclear Information System (INIS)

    investigate the dynamics and mechanism of various ultrafast processes of having contemporary research interests in chemical sciences. (author)

  12. 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

  13. Attribution of ozone changes to dynamical and chemical processes in CCMs and CTMs

    Directory of Open Access Journals (Sweden)

    H. Garny

    2011-04-01

    Full Text Available Chemistry-climate models (CCMs are commonly used to simulate the past and future development of Earth's ozone layer. The fully coupled chemistry schemes calculate the chemical production and destruction of ozone interactively and ozone is transported by the simulated atmospheric flow. Due to the complexity of the processes acting on ozone it is not straightforward to disentangle the influence of individual processes on the temporal development of ozone concentrations. A method is introduced here that quantifies the influence of chemistry and transport on ozone concentration changes and that is easily implemented in CCMs and chemistry-transport models (CTMs. In this method, ozone tendencies (i.e. the time rate of change of ozone are partitioned into a contribution from ozone production and destruction (chemistry and a contribution from transport of ozone (dynamics. The influence of transport on ozone in a specific region is further divided into export of ozone out of that region and import of ozone from elsewhere into that region. For this purpose, a diagnostic is used that disaggregates the ozone mixing ratio field into 9 separate fields according to in which of 9 predefined regions of the atmosphere the ozone originated. With this diagnostic the ozone mass fluxes between these regions are obtained. Furthermore, this method is used here to attribute long-term changes in ozone to chemistry and transport. The relative change in ozone from one period to another that is due to changes in production or destruction rates, or due to changes in import or export of ozone, are quantified. As such, the diagnostics introduced here can be used to attribute changes in ozone on monthly, interannual and long-term time-scales to the responsible mechanisms. Results from a CCM simulation are shown here as examples, with the main focus of the paper being on introducing the method.

  14. Attribution of ozone changes to dynamical and chemical processes in CCMs and CTMs

    Directory of Open Access Journals (Sweden)

    H. Garny

    2011-01-01

    Full Text Available Chemistry-climate models (CCMs are commonly used to simulate the past and future development of Earth's ozone layer. The fully coupled chemistry schemes calculate the chemical production and destruction of ozone interactively and ozone is transported by the simulated atmospheric flow. Due to the complexity of the processes acting on ozone it is not straightforward to disentangle the influence of individual processes on the temporal development of ozone concentrations. A method is introduced here that quantifies the influence of chemistry and transport on ozone concentration changes and that is easily implemented in CCMs and chemistry-transport models (CTMs. In this method, ozone tendencies (i.e. the time rate of change of ozone are partitioned into a contribution from ozone production and destruction (chemistry and a contribution from transport of ozone (dynamics. The influence of transport on ozone in a specific region is further divided into export of ozone out of that region and import of ozone from elsewhere into that region. For this purpose, a diagnostic is used that disaggregates the ozone mixing ratio field into 9 separate fields according to in which of 9 predefined regions of the atmosphere the ozone originated. With this diagnostic the ozone mass fluxes between these regions are obtained. Furthermore, this method is used here to attribute long-term changes in ozone to chemistry and transport. The relative change in ozone from one period to another that is due to changes in production or destruction rates, or due to changes in import or export of ozone, are quantified. As such, the diagnostics introduced here can be used to attribute changes in ozone on monthly, interannual and long-term time-scales to the responsible mechanisms. Results from a CCM simulation are shown here as examples, with the main focus of the paper being on introducing the method.

  15. A computational study of stress fiber-focal adhesion dynamics governing cell contractility

    OpenAIRE

    Maraldi, Mirko; Valero, Clara; Garikipati, Krishna

    2014-01-01

    We apply a recently developed model of cytoskeletal force generation to study a cell intrinsic contractility, as well as its response to external loading. The model is based on a non-equilibrium thermodynamic treatment of the mechano-chemistry governing force in the stress fiber-focal adhesion system. Our computational study suggests that the mechanical coupling between the stress fibers and focal adhesions leads to a complex, dynamic, mechano-chemical response. We collect the results in resp...

  16. Study on microwave assisted process in chemical extraction

    International Nuclear Information System (INIS)

    The microwave assisted process is a revolutionary method of extraction that reduces the extraction time to as little as a few seconds, with up to a ten-fold decrease in the use of solvents. The target material is immersed in solvent that is transparent to microwaves, so only the target material is heated, and because of the microwaves tend to heat the inside of the material quickly, the target chemical are expelled in a few seconds. benefits from this process include significant reductions in the amount of energy required and substantial reductions in the cost and dispose of hazardous solvents. A thorough review has been displayed on: using the microwave in extraction, applications of microwave in industry, process flow diagram, mechanism of the process and comparison between microwave process and other extraction techniques (soxhlet, steam distillation and supercritical fluid). This review attempts to summarize the studies about microwave assisted process as a very promising technique. (Author)

  17. Study of physical chemical characteristics of a shungite

    OpenAIRE

    Maira Kazankapova; A. Bekzhanova; Sergey Efremov; Mikhail Nauryzbayev

    2012-01-01

    The physico-chemical characteristics of shungite from the field of Kazakhstan ("Bakyrchik") and Russia ("Zazhegino") was studied by elemental analysis, IR- spectroscopy and electron microscopy. The content of carbon in the schungite field "Zazhegino" is 28,0-31,0 %,  in the field "Bakyrchik" - 15,0-19,0 %, in schungite concentrate  "Bakyrchik" is 40,0 ± 2,0 %.  IR-spectroscopic analysis have been shown that carboxyl groups appear in addition to the concentrate of polycyclic hydrocarbons conta...

  18. Chemical treatment of zinc surface and its corrosion inhibition studies

    Indian Academy of Sciences (India)

    S K Rajappa; T V Venkatesha; B M Praveen

    2008-02-01

    The surface treatment of zinc and its corrosion inhibition was studied using a product (BTSC) formed in the reaction between benzaldehyde and thiosemicarbozide. The corrosion behaviour of chemically treated zinc surface was investigated in aqueous chloride–sulphate medium using galvanostatic polarization technique. Zinc samples treated in BTSC solution exhibited good corrosion resistance. The measured electrochemical data indicated a basic modification of the cathode reaction during corrosion of treated zinc. The corrosion protection may be explained on the basis of adsorption and formation of BTSC film on zinc surface. The film was binding strongly to the metal surface through nitrogen and sulphur atoms of the product. The formation of film on the zinc surface was established by surface analysis techniques such as scanning electron microscopy (SEM–EDS) and Fourier transform infrared spectroscopy (FTIR).

  19. [Study of quantum-pharmacological chemical characteristics of quercetin].

    Science.gov (United States)

    Zahorodnyĭ, M I

    2007-01-01

    It was established in the previous studies that quercetin prevented the development and caused faster regression of ulcers, petechia and anabroses in rats, which were induced by diclofenac taking. In the group of patients taking diclofenac together with quercetin, the ulcers and dyspeptic events were less found. The application of quercetin normalizes the function and metabolism of cartilage tissue of rabbits with an experimental osteoarthrosis and in patients with osteoartrosis. Quantum-chemical properties of molecule quercetin were studied using the methods of molecular mechanics MM+ and ab initio 6-31G*, and also semiempirical method. The following indices were investigated: distance between atoms (A), the distribution of electronic density of only external valency electrons, distribution of electrostatic potential; common energy of the exertion of molecule (kkal/mmol); binding energy (kkal/mmol); electron energy (kkal/mmol); energy of nucleus-nucleus interaction (kkal/mmol); formation heat (kkal/mmol); atomic charge (eB); value of the dipole moment of molecule (D); localization and energy of highest occupied orbital (HOMO) and the lowest unoccupied (LUMO) molecular orbital (eB) of quercetin miolecule; the value of absolute rigidity of chemical structure of bioflavonoid. It was shown, that bioflavonoid quercetin belongs to mild reagents, has nucleophilic properties, can react with alkaline, unsaturated and aromatic compounds,. Polar substitutes in the quercetine molecule influence on the distribution of superficial valency electrons and localization of HOMO and LUMO. The energy value of quercetin LUMO enables us to refer quercetine to the reducing agent and it is illustrated by antioxidant properties of this medicine. PMID:18663944

  20. ALTERNATIVE AND ENHANCED CHEMICAL CLEANING: CORROSION STUDIES RESULTS: FY2010

    Energy Technology Data Exchange (ETDEWEB)

    Wiersma, B.

    2010-09-29

    Due to the need to close High Level Waste storage tanks, chemical cleaning methods are needed for the removal of sludge heel materials remaining at the completion of mechanical tank cleaning efforts. Oxalic acid is considered the preferred cleaning reagent for heel dissolution of iron-based sludge. However, the large quantity of chemical reagents added to the tank farm from oxalic acid based cleaning has significant downstream impacts. Optimization of the oxalic acid cleaning process can potentially reduce the downstream impacts from chemical cleaning. To optimize oxalic acid usage, a detailed understanding of the chemistry of oxalic acid based sludge dissolution is required. Additionally, other acidic systems may be required for specific waste components that have low solubility in oxalic acid, and as a means to reduce oxalic acid usage in general. Electrochemical corrosion studies were conducted with 1 wt. % oxalic acid at mineral acid concentrations above and below the optimal conditions for this oxalic acid concentration. Testing environments included pure reagents, pure iron and aluminum phases, and sludge simulants. Mineral acid concentrations greater than 0.2 M and temperatures greater than 50 C result in unacceptably high corrosion rates. Results showed that manageable corrosion rates of carbon steel can be achieved at dilute mineral acid concentrations (i.e. less than 0.2 M) and low temperatures based on the contact times involved. Therefore, it is recommended that future dissolution and corrosion testing be performed with a dilute mineral acid and a less concentrated oxalic acid (e.g., 0.5 wt.%) that still promotes optimal dissolution. This recommendation requires the processing of greater water volumes than those for the baseline process during heel dissolution, but allows for minimization of oxalic acid additions. The following conclusions can be drawn from the test results: (1) In both nitric and sulfuric acid based reagents, the low temperature and

  1. Some Sensitivity Studies of Chemical Transport Simulated in Models of the Soil-Plant-Litter System

    Energy Technology Data Exchange (ETDEWEB)

    Begovich, C.L.

    2002-10-28

    Fifteen parameters in a set of five coupled models describing carbon, water, and chemical dynamics in the soil-plant-litter system were varied in a sensitivity analysis of model response. Results are presented for chemical distribution in the components of soil, plants, and litter along with selected responses of biomass, internal chemical transport (xylem and phloem pathways), and chemical uptake. Response and sensitivity coefficients are presented for up to 102 model outputs in an appendix. Two soil properties (chemical distribution coefficient and chemical solubility) and three plant properties (leaf chemical permeability, cuticle thickness, and root chemical conductivity) had the greatest influence on chemical transport in the soil-plant-litter system under the conditions examined. Pollutant gas uptake (SO{sub 2}) increased with change in plant properties that increased plant growth. Heavy metal dynamics in litter responded to plant properties (phloem resistance, respiration characteristics) which induced changes in the chemical cycling to the litter system. Some of the SO{sub 2} and heavy metal responses were not expected but became apparent through the modeling analysis.

  2. Dynamic Particle Growth Testing - Phase I Studies

    Energy Technology Data Exchange (ETDEWEB)

    Hu, M.Z-C.

    2001-05-17

    , particle growth in the bulk would still affect scale formation by consuming a portion of the scale-forming precursor materials. In either case, solid-particle-formation data must be obtained to understand the problem. Previous and ongoing testing based on the measurement of [Al] and [Si] consumption kinetics have indicated that the format of aluminosilicate may be rapid under evaporator conditions. However, the kinetics of particle formation (both in bulk solution and on surfaces) has not been studied. Conditions that cause extremely rapid particle formation are of particular interest, because in that case the solids-formation reactions in the evaporator would be sensitively dependent on process conditions such as chemical composition, temperature, fluid flow, and heat transfer.

  3. Potential for ultrafast dynamic chemical imaging with few-cycle infrared lasers

    International Nuclear Information System (INIS)

    We studied the photoelectron spectra generated by an intense few-cycle infrared laser pulse. By focusing on the angular distributions of the back rescattered high energy photoelectrons, we show that accurate differential elastic scattering cross-sections of the target ion by free electrons can be extracted. Since the incident direction and the energy of the free electrons can be easily changed by manipulating the laser's polarization, intensity and wavelength, these extracted elastic scattering cross-sections, in combination with more advanced inversion algorithms, may be used to reconstruct the effective single-scattering potential of the molecule, thus opening up the possibility of using few-cycle infrared lasers as powerful table-top tools for imaging chemical and biological transformations, with the desired unprecedented temporal and spatial resolutions

  4. High-explosive properties from classical molecular dynamics simulations and quantum-chemical computations

    Energy Technology Data Exchange (ETDEWEB)

    Sewell, T. D. (Thomas D.); Gan, C. K. (Chee Kwan); Jaramillo, E. (Eugenio); Strachan, A. H. (Alejandro H.)

    2004-01-01

    We are using classical molecular dynamics and condensed phase electronic-structure methods to predict some of the thermophysical and mechanical properties that are needed as input to realistic mesoscale models for plastic-bonded explosives. The main materials studied to date are HMX, PETN, Estane copolymer, and bi(2,2-dinitropropyl) formal/acetal (BDNPF/A). Emphasis is placed on non-reactive properties and thermodynamic states relevant to cookoff and shock initiation phenomena. Both crystal and liquid-state properties are of interest. Typical simulation sizes and times are {approx}10{sup 2} molecules and 2-10 ns, respectively. The overarching goal is to develop internally consistent model thermodynamic and elastic mechanical descriptions for the materials. Prioritization among the set of properties amenable to atomistic simulation is made based on ongoing interactions with mesoscale modelers at Los Alamos and elsewhere. Recent work will be summarized and our view of profitable directions for future research will be discussed, including preliminary results for large-scale molecular dynamics simulations of shock response of crystalline HMX.

  5. Spectroscopy and dynamics of chemical reactions in van der Waals complexes

    International Nuclear Information System (INIS)

    Transition metal elements have d valence electrons and are characterized by a great variety of electronic configurations responsible for their specific reactivity. The elements of the second row in particular have 4d and 5s atomic orbitals of similar size and energy which can be both involved in chemical processes. We have been interested in the reactivity of a transition metal element, zirconium, combined with a simple organic functionalized molecule in a van der Waals complex formed in a supersonic molecular beam in the model reaction Zr + CH3F. In this context, one of the chemicals reactions that we are interested in leads to the formation of ZrF. The electronic spectroscopy of ZrF in the spectral domain 400 - 470 nm is extremely rich and surprising for a diatomic molecule. With this study, we have been able to identify the ground state of ZrF (X2Δ) by simulating the observed rotational structures and obtain essential information on the electronic structure. These experimental results are in agreement with ab initio calculations. The excited states of the complex Zr...F-CH3 have been studied with a depopulation method. The spectral domain 615 - 700 nm is particularly interesting because it reveals a group of diffuse bands red-shifted and broadened with respect to the transition a3F → z3F in the metal. This transition is forbidden from the ground state a3F2 of zirconium but allowed from the a3F4 state. Complexation of the metal atom with a CH3F molecule allows coupling of these two states to occur which ensures the optical transition from the ground state of the complex. (author)

  6. Study of the influence on radiation, chemical and thermic treatment in Cesium and Cobalt absorption in natural zeolites

    International Nuclear Information System (INIS)

    The influence of radiation and thermic treatment of zeolites from El Piojillo (Villa Clara), Orozco (Pinar del Rio) and Palmarito (Santiago de Cuba) deposits in the absorption of cesium-137 is studied. It was verified that as it generally occurs in zeolites, the thermic treatment influences negatively the absorption and the radiation treatment with dose up to 105 Gy does not affect it. Alternatives to chemical and chemical-thermic treatment for zeolite from El Piojillo are also applied. It was noted that previous treatment with NH4OH at 2000C in the vacuum stove and its contact in dynamic regime with NaNO3 improves its capacity of cobalt absorption

  7. A Coupled Dynamical Model of Redox Flow Battery Based on Chemical Reaction, Fluid Flow, and Electrical Circuit

    OpenAIRE

    Li, Minghua; Hikihara, Takashi

    2008-01-01

    The redox (Reduction-Oxidation) flow battery is one of the most promising rechargeable batteries due to its ability to average loads and output of power sources. The transient characteristics are well known as the remarkable feature of the battery. Then it can also compensate for a sudden voltage drop. The dynamics are governed by the chemical reactions, fluid flow, and electrical circuit of its structure. This causes the difficulty of the analysis at transient state. This paper discusses the...

  8. Microbiological and physico-chemical studies on irradiated dewatered sludge

    International Nuclear Information System (INIS)

    Microbiological and physico-chemical studies on irradiated dewatered sludge. Microbiological and physico-chemical dewatered have been carried out and non-irradiated dewatered sludge of Jakarta city, collected during the rainy and dry season. Total bacterial counts of non-irradiated dewatered sludge with water content of around 20%, were found to be about 7x108 per g during the rainy season and 7x106 up to 1.3x108 per g during the dry season, while coliform fecal Streptococcus and Pseudomonas were found to be 1.6x104 to 1.0x107, 3x105, and 5x103 per g, respectively. No Salmonella, Shigella and Vibrio were detected in all of the samples observed. About 10% of the total number of coliforms were found to be Escherichia coli. A dose of 6 kGy could eliminate the coliform, E. Coli, fecal Streptococcus and Pseudomonas from all of the dewatered sludge observed. The nutrient value of the sludge was sufficient, i.e. total nitrogen content ranged between 1 and 4,42%, phosphorus between 1.55 and 2.36%, and potassium between 0,1 and 0,2% of dry matter. Heavy metal contents were found a little bit high to be applied as animal feed, but it is still acceptable for soil conditioner. Combining 3 months storage at ambient environment and irradiation dose of 2.5 kGy were found to work synergistically to eliminate coliforms and E. Coli from sludge. (author). 8 figs, 17 refs

  9. Oceanographic studies using dissolved gases as chemical tracers

    International Nuclear Information System (INIS)

    This article reviews the author's hitherto progress on marine geochemical studies using the concentration, radioactivity, and stable isotope ratio of dissolved gases as chemical tracers in the ocean. Shipboard gas chromatography was developed for the simultaneous measurement of major dissolved gases (O2, N2, Ar and ΣCO2). A Carpenter-modified titration method was introduced for the improvement of the accuracy of O2 data, which played an important role in discovering and monitoring temporal variations in deep convection systems in the Japan Sea, an ideal miniature of global oceans. Radiocarbon (14C) measurements together with precise ΣCO2 and δ13C data enabled the author to clarify the timescale of the abyssal circulation of the Japan Sea, the characteristics of bottom waters in the Philippine Sea, and the invasion rate of bomb 14C from the atmosphere to the western Pacific seawater. Minor dissolved gases, 222Rn and CH4 in seawater, were also analyzed using the originally designed shipboard measurement systems. The activity of 222Rn (in excess over the 226Ra-supported portion) in bottom seawaters was applied for the estimation of CO2 flux from a submarine volcano in Kagoshima Bay, and for the mapping of vertical eddy diffusivity just above the bottom over a wide area of the northwestern Pacific Ocean, where the distribution and characteristics of benthic boundary layers were also researched. Data on CH4 in deep seawaters were accumulated at and around hydrothermally active sites or cold seepage zones associated with plate boundaries, to discover new active vents and elucidate the chemical characteristics of emanating fluids from the seafloor. (author)

  10. STUDYING THE CHEMICAL COMPOSITION OF ALCOHOLIC EXTRACT SCHROTH RAPE

    Directory of Open Access Journals (Sweden)

    Елена Эдуардовна Чигиринец

    2014-09-01

    Full Text Available As the authors found that a promising material for a volatile atmospheric corrosion inhibitor is the use of waste generated in obtaining oil from rapeseed (family Brassicaceae, namely rapeseed meal, appropriate research was qualitative and quantitative determination of its basic compounds. Also found that the inhibition efficiency is extreme character with a maximum protective capacity for 2 hours. Why was it necessary to study changes in the composition of the extract in the evaporation process, and identification of compounds that do not take part in the formation of the film, that is remaining in the non-volatile sludge. The subject of this study is to extract 2-proрanol rapeseed cake extract . The purpose of work - a study of its component composition, namely, volatile and non-volatile compounds. The volatile chemical composition of the rapeseed cake extract involves glycosides, nucleosides, ketone, aldehyde, fatty acids, sterol and alkaloids. The most important compounds in rapeseed cake are: Guanosine , Sucrose , Xanthosine, 3',5'-Dimethoxyacetophenone Benzaldehyde, 4-hydroxy-3,5-dimethoxy, Acetic, Oleic, Linoleic and Palmitic acid and Sterols.

  11. Molecular Dynamics for Low Temperature Plasma-Surface Interaction Studies

    OpenAIRE

    Graves, David B.; Brault, Pascal

    2009-01-01

    The mechanisms of physical and chemical interactions of low temperature plasmas with surfaces can be fruitfully explored using molecular dynamics (MD) simulations. MD simulations follow the detailed motion of sets of interacting atoms through integration of atomic equations of motion, using inter-atomic potentials that can account for bond breaking and formation that result when energetic species from the plasma impact surfaces. This article summarizes the current status of the technique for ...

  12. Decomposition Dynamics and Changes in Chemical Composition of Wheat Straw Residue under Anaerobic and Aerobic Conditions

    Science.gov (United States)

    Gao, Hongjian; Chen, Xi; Wei, Junling; Zhang, Yajie; Zhang, Ligan; Chang, Jiang; Thompson, Michael L.

    2016-01-01

    Soil aeration is a crucial factor that regulates crop residue decomposition, and the chemical composition of decomposing crop residues may change the forms and availability of soil nutrients, such as N and P. However, to date, differences in the chemical composition of crop straw residues after incorporation into soil and during its decomposition under anaerobic vs. aerobic conditions have not been well documented. The objective of the present study was to assess changes in the C-containing functional groups of wheat straw residue during its decomposition in anaerobic and aerobic environments. A 12-month incubation experiment was carried out to investigate the temporal variations of mass, carbon, and nitrogen loss, as well as changes in the chemical composition of wheat (Triticum aestivum L) straw residues under anaerobic and aerobic conditions by measuring C-containing functional groups using solid state nuclear magnetic resonance (NMR) spectroscopy. The residual mass, carbon content, and nitrogen content of the straw residue sharply declined during the initial 3 months, and then slowly decreased during the last incubation period from 3 to 12 months. The decomposition rate constant (k) for mass loss under aerobic conditions (0.022 d-1) was higher than that under anaerobic conditions (0.014 d-1). The residual mass percentage of cellulose and hemicellulose in the wheat straw gradually declined, whereas that of lignin gradually increased during the entire 12-month incubation period. The NMR spectra of C-containing functional groups in the decomposing straw under both aerobic and anaerobic conditions were similar at the beginning of the incubation as well as at 1 month, 6 months, and 12 months. The main alterations in C-containing functional groups during the decomposition of wheat straw were a decrease in the relative abundances of O-alkyl C and an increase in the relative abundances of alkyl C, aromatic C and COO/N-C = O functional groups. The NMR signals of alkyl C

  13. Molecular dynamics study of cyclohexane interconversion

    Science.gov (United States)

    Wilson, Michael A.; Chandler, David

    1990-12-01

    Classical molecular dynamics calculations are reported for one C 6H 12 molecule in a bath of 250 CS 2 molecules at roomtemperature and liquid densities of 1.0, 1.3, 1.4 and 1.5 g/cm 3. The solvent contribution to the free energy of activation for the chair-boat isomerization has been determined to high accuracy. The transmission coefficient and reactive flux correlation functions have also been computed. The results obtained agree with earlier conclusions drawn from RISM integral equation calculations and stochastic molecular dynamics calculations. Namely, the solvent effect on the rate manifests a qualitative breakdown of transition state theory and the RRKM picture of unimolecular kinetics. Analysis of the activated trajectories indicate a significant degree of quasiperiodicity.

  14. Dynamics of SDS Micelles: Neutron Scattering Study

    Science.gov (United States)

    Sharma, V. K.; Mitra, S.; Verma, G.; Hassan, P. A.; Sakai, V. Garcia; Mukhopadhyay, R.

    2011-07-01

    Here we report dynamics of Sodium Dodecyl Sulphate (SDS) micelles as investigated by high-resolution incoherent quasielastic neutron scattering technique. Data analysis clearly shows the presence of two distinct motions namely global diffusion of the micelles and faster internal motion of the SDS monomer. The global diffusion is found to be Fickian in nature and the corresponding diffusion coefficient is consistent with those obtained from dynamic light scattering measurements. Internal motion of the micelles is described by a localized translational motion in which hydrogen atoms closer to the head group move within smaller spheres with lower diffusion constant compared to the hydrogen atoms away from head group, suggesting more flexibility and faster movement of the chain away from the head group.

  15. Effects of chemical composition and test conditions on the dynamic tensile response of Zr-based metallic glasses

    Science.gov (United States)

    Wang, F.; Laws, K. J.; Trujillo, C. P.; Brown, A. D.; Cerreta, E. K.; Hazell, P. J.; Quadir, M. Z.; Ferry, M.; Escobedo, J. P.

    2015-06-01

    The effects of impact velocity and temperature on the dynamic mechanical behavior of two bulk metallic glasses (BMG) with slightly different elemental compositions (Zr55Cu30Ni5Al30 and Zr46Cu38Ag8Al38) have been investigated. Bullet-shaped samples were accelerated by a gas gun to speeds in the 400 ~ 600m/s range and tested at room temperature and 250 °C. The specimens impacted a steel extrusion die which subjected them to high strains at high strain-rates. The extruded samples were subsequently soft recovered by using low density foams. The deformed specimens were examined by optical and electron microscopy, x-ray diffraction and hardness measurements. The characterization results aided to assess the effect of chemical composition on the microstructural evolution, i.e. phase changes or crystallization, which might influence the ductility on the nominally brittle amorphous BMGs. The most significant results from this study will be presented. School of Engineering and Information Technology, UNSW Canberra.

  16. Sustainability Indicators for Chemical Processes: III. Biodiesel Case Study

    Science.gov (United States)

    The chemical industry is one of the most important business sectors, not only economically, but also societally; as it allows humanity to attain higher standards and quality of life. Simultaneously, chemical products and processes can be the origin of potential human health and ...

  17. Chemical grouting – laboratory study of chemical grouts and geocomposites properties

    Czech Academy of Sciences Publication Activity Database

    Souček, Kamil; Staš, Lubomír; Ščučka, Jiří; Martinec, Petr

    Bombay : Indian Institute of Technology Bombay, 2008 - (Singh, D.), s. 3567-3574 [International Conference of IACMAG /12./. Goa - Panjim (IN), 01.10.2008-06.10.2008] R&D Projects: GA ČR(CZ) GA105/07/1533 Institutional research plan: CEZ:AV0Z30860518 Keywords : chemical grouts * grouting, geocomposite properties Subject RIV: DB - Geology ; Mineralogy

  18. Excess water dynamics in hydrotalcite: QENS study

    Indian Academy of Sciences (India)

    S Mitra; A Pramanik; D Chakrabarty; R Mukhopadhyay

    2004-08-01

    Results of the quasi-elastic neutron scattering (QENS) measurements on the dynamics of excess water in hydrotalcite sample with varied content of excess water are reported. Translational motion of excess water can be best described by random translational jump diffusion model. The observed increase in translational diffusivity with increase in the amount of excess water is attributed to the change in binding of the water molecules to the host layer.

  19. Organic chemical degradation by remote study of the redox conditions

    Science.gov (United States)

    Fernandez, P. M.; Revil, A.; Binley, A. M.; Bloem, E.; French, H. K.

    2014-12-01

    Monitoring the natural (and enhanced) degradation of organic contaminants is essential for managing groundwater quality in many parts of the world. Contaminated sites often have limited access, hence non-intrusive methods for studying redox processes, which drive the degradation of organic compounds, are required. One example is the degradation of de-icing chemicals (glycols and organic salts) released to the soil near airport runways during winter. This issue has been broadly studied at Oslo airport, Gardermoen, Norway using intrusive and non-intrusive methods. Here, we report on laboratory experiments that aim to study the potential of using a self-potential, DCresistivity, and time-domain induced polarization for geochemical characterization of the degradation of Propylene Glycol (PG). PG is completely miscible in water, does not adsorb to soil particles and does not contribute to the electrical conductivity of the soil water. When the contaminant is in the unsaturated zone near the water table, the oxygen is quickly consumed and the gas exchange with the surface is insufficient to ensure aerobic degradation, which is faster than anaerobic degradation. Since biodegradation of PG is highly oxygen demanding, anaerobic pockets can exist causing iron and manganese reduction. It is hypothesised that nitrate would boost the degradation rate under such conditions. In our experiment, we study PG degradation in a sand tank. We provide the system with an electron highway to bridge zones with different redox potential. This geo-battery system is characterized by self-potential, resistivity and induced polarization anomalies. An example of preliminary results with self-potential at two different times of the experiment can be seen in the illustration. These will be supplemented with more direct information on the redox chemistry: in-situ water sampling, pH, redox potential and electrical conductivity measurements. In parallel, a series of batch experiments have been

  20. Chemical studies of single-walled carbon nanotubes

    CERN Document Server

    Xu, C

    2001-01-01

    WCl sub 6 has also been introduced into arc-vapourised SWNTs. Chapter 6 gives the details for all the experimental work of the thesis. of H sub 2 have also been studied. Chapter four describes the various processes used to purify arc-vapourised SWNTs on a laboratory scale. Two potentially scalable processes have also been studied. Both acid and gas oxidants have been used to purify SWNTs grown in the CVD method. The chemical resistance of CVD SWNTs (48 h of conc. HNO sub 3 treatment) has been shown for the first time. Various assembly behaviours of purified SWNTs, including loop and spiral structures, straight long bundles or somewhat aligned structures, are also described. Chapter five presents the filling of arc-vapourised SWNTs with LnX sub n (X = Cl, Br and I, n = 2 or 3) using the capallarity method at high temperature (570-910 deg C). The first example of a polycrystalline structure within SWNTs filled with a single material (SmCl sub 3) has been provided. Fullerenes within SWNTs in the SWNT samples ext...

  1. NATO Advanced Study Institute on Chemical Transport in Melasomatic Processes

    CERN Document Server

    1987-01-01

    As indicated on the title page, this book is an outgrowth of the NATO Advanced Study Institute (ASI) on Chemical Transport in Metasomatic Processes, which was held in Greece, June 3-16, 1985. The ASI consisted of five days of invited lectures, poster sessions, and discussion at the Club Poseidon near Loutraki, Corinthia, followed by a two-day field trip in Corinthia and Attica. The second week of the ASI consisted of an excursion aboard M/S Zeus, M/Y Dimitrios II, and the M/S Irini to four of the Cycladic Islands to visit, study, and sample outstanding exposures of metasomatic activity on Syros, Siphnos, Seriphos, and Naxos. Nine­ teen invited lectures and 10 session chairmen/discussion leaders participated in the ASI, which was attended by a total of 92 professional scientists and graduate stu­ dents from 15 countries. Seventeen of the invited lectures and the Field Excursion Guide are included in this volume, together with 10 papers and six abstracts representing contributed poster sessions. Although more...

  2. Alternative Enhanced Chemical Cleaning Basic Studies Results FY09

    International Nuclear Information System (INIS)

    Due to the need to close waste storage tanks, chemical cleaning methods are needed for the effective removal of the heels. Oxalic acid is the preferred cleaning reagent for sludge heel dissolution, particularly for iron-based sludge, due to the strong complexing strength of the oxalate. However, the large quantity of oxalate added to the tank farm from oxalic acid based chemical cleaning has significant downstream impacts. Optimization of the oxalic acid cleaning process can potentially reduce the downstream impacts from chemical cleaning. To optimize oxalic acid usage, a detailed understanding of the chemistry of oxalic acid based sludge dissolution is required. Additionally, other acid systems may be required for specific waste components with low solubility in oxalic acid and as a means to reduce oxalic acid usage in general. Solubility tests were conducted using non-radioactive, pure metal phases known to be the primary phases present in High Level Waste sludge. The metal phases studied included the aluminum phases gibbsite and boehmite and the iron phases magnetite and hematite. Hematite and boehmite are expected to be the most difficult iron and aluminum phases to dissolve. These mineral phases have been identified in both SRS and Hanford High Level Waste sludge. Acids evaluated for dissolution included oxalic, nitric, and sulfuric acids. The results of the solubility tests indicate that oxalic and sulfuric acids are more effective for the dissolution of the primary sludge phases. For boehmite, elevated temperature will be required to promote effective phase dissolution in the acids studied. Literature reviews, thermodynamic modeling, and experimental results have all confirmed that pH control using a supplemental proton source (additional acid) is critical for minimization of oxalic acid usage during the dissolution of hematite. These results emphasize the importance of pH control in optimizing hematite dissolution in oxalic acid and may explain the somewhat

  3. Alternative Enhanced Chemical Cleaning Basic Studies Results FY09

    Energy Technology Data Exchange (ETDEWEB)

    Hay, M.; King, W.

    2010-05-05

    Due to the need to close waste storage tanks, chemical cleaning methods are needed for the effective removal of the heels. Oxalic acid is the preferred cleaning reagent for sludge heel dissolution, particularly for iron-based sludge, due to the strong complexing strength of the oxalate. However, the large quantity of oxalate added to the tank farm from oxalic acid based chemical cleaning has significant downstream impacts. Optimization of the oxalic acid cleaning process can potentially reduce the downstream impacts from chemical cleaning. To optimize oxalic acid usage, a detailed understanding of the chemistry of oxalic acid based sludge dissolution is required. Additionally, other acid systems may be required for specific waste components with low solubility in oxalic acid and as a means to reduce oxalic acid usage in general. Solubility tests were conducted using non-radioactive, pure metal phases known to be the primary phases present in High Level Waste sludge. The metal phases studied included the aluminum phases gibbsite and boehmite and the iron phases magnetite and hematite. Hematite and boehmite are expected to be the most difficult iron and aluminum phases to dissolve. These mineral phases have been identified in both SRS and Hanford High Level Waste sludge. Acids evaluated for dissolution included oxalic, nitric, and sulfuric acids. The results of the solubility tests indicate that oxalic and sulfuric acids are more effective for the dissolution of the primary sludge phases. For boehmite, elevated temperature will be required to promote effective phase dissolution in the acids studied. Literature reviews, thermodynamic modeling, and experimental results have all confirmed that pH control using a supplemental proton source (additional acid) is critical for minimization of oxalic acid usage during the dissolution of hematite. These results emphasize the importance of pH control in optimizing hematite dissolution in oxalic acid and may explain the somewhat

  4. Aggregation of model asphaltenes: a molecular dynamics study.

    Science.gov (United States)

    Costa, J L L F S; Simionesie, D; Zhang, Z J; Mulheran, P A

    2016-10-01

    Natural asphaltenes are defined as polyaromatic compounds whose chemical composition and structure are dependent on their geological origin and production history, hence are regarded as complex molecules with aromatic cores and aliphatic tails that occur in the heaviest fraction of crude oil. The aggregation of asphaltenes presents a range of technical challenges to the production and processing of oil. In this work we study the behaviour of the model asphaltene-like molecule hexa-tert-butylhexa-peri-hexabenzocoronene (HTBHBC) using molecular dynamics simulation. It was found that the regular arrangement of the tert-butyl side chains prevents the formation of strongly-bound dimers by severely restricting the configurational space of the aggregation pathway. In contrast, a modified molecule with only 3 side chains is readily able to form dimers. This work therefore confirms the influence of the molecular structure of polyaromatic compounds on their aggregation mechanism, and reveals the unexpected design rules required for model systems that can mimic the behavior of asphaltenes. PMID:27465036

  5. The Dynamic Free Rider Problem: A Laboratory Study

    OpenAIRE

    Battaglini, Marco; Nunnari, Salvatore; Palfrey, Thomas R.

    2013-01-01

    Most public goods are durable and have a significant dynamic component. In this paper, we report the results from a laboratory experiment designed explicitly to study the dynamics of free riding behavior in the accumulation of a durable public good that provides a stream of discounted benefits over a potentially infinite horizon. This dynamic free-rider problem differs from static ones in fundamental ways and implies several economically important predictions that are absent in static framewo...

  6. Dynamics of Model Hydraulic Fracturing Liquid Studied by Two-Dimensional Infrared Spectroscopy

    Science.gov (United States)

    Daley, Kim; Kubarych, Kevin J.

    2014-06-01

    The technique of two-dimensional infrared (2DIR) spectroscopy is used to expose the chemical dynamics of various concentrations of polymers and their monomers in heterogeneous mixtures. An environmentally relevant heterogeneous mixture, which inspires this study, is hydraulic fracturing liquid (HFL). Hydraulic fracking is a technique used to extract natural gas from shale deposits. HFL consists of mostly water, proppant (sand), an emulsifier (guar), and other chemicals specific to the drilling site. Utilizing a metal carbonyl as a probe, we observe the spectral dynamics of the polymer, guar, and its monomer, mannose, and compare the results to see how hydration dynamics change with varying concentration. Another polymer, Ficoll, and its monomer, sucrose, are also compared to see how polymer size affects hydration dynamics. The two results are as follows: (1) Guar experiences collective hydration at high concentrations, where as mannose experiences independent hydration; (2) no collective hydration is observed for Ficoll in the same concentration range as guar, possibly due to polymer shape and size. HFL experiences extremely high pressure during natural gas removal, so future studies will focus on how increased pressure affects the hydration dynamics of polymers and monomers.

  7. Dynamic study of thin cylindrical vessels

    International Nuclear Information System (INIS)

    Fluids essential for the safety of a nuclear reactor (water, boron...) are contained in thin cylindrical vessels. An experimental investigation of the dynamic buckling of a thin cylindrical vessel filled with a fluid has been carried out on a shaking table. An investigation of the frequencies and mode shape of the vessel had also been done prior to the test. Calculations performed in order to predict these frequencies and modes have shown the importance of taking into account the stiffening effect of the fluid static pressure

  8. Chemical-Free Cosmetics May Be Safer for Teen Girls, Study Suggests

    Science.gov (United States)

    ... nlm.nih.gov/medlineplus/news/fullstory_157640.html Chemical-Free Cosmetics May Be Safer for Teen Girls, Study Suggests Lower levels of hormone-disrupting chemicals seen in adolescents after trying products without potentially ...

  9. Rodent-repellent studies. III. Advanced studies in the evaluation of chemical repellents

    Science.gov (United States)

    Bellack, E.; DeWitt, J.B.

    1949-01-01

    In order to bridge the gap between preliminary screening of chemicals for potential rodent repellency and the application ofthese compounds to paper cartons, more advanced studies in the evaluation ofpromising materials have been carried out. These studies have resulted in: (1) a modification of the food acceptance technique which eliminates doubtful compounds and also provides a closer analogy to the ultimate goal, and (2) a method for rapidly testing chemicals incorporated in paper. When the results of these latter tests are expressed as a function of time, it can be shown that a distinct correlation exists between the deterrency exhibited by treated paper and the repellency of treated food.

  10. Studies on residue-free decontaminants for chemical warfare agents.

    Science.gov (United States)

    Wagner, George W

    2015-03-17

    Residue-free decontaminants based on hydrogen peroxide, which decomposes to water and oxygen in the environment, are examined as decontaminants for chemical warfare agents (CWA). For the apparent special case of CWA on concrete, H2O2 alone, without any additives, effectively decontaminates S-2-(diisopropylamino)ethyl O-ethyl methylphosphonothioate (VX), pinacolyl methylphosphorofluoridate (GD), and bis(2-choroethyl) sulfide (HD) in a process thought to involve H2O2 activation by surface-bound carbonates/bicarbonates (known H2O2 activators for CWA decontamination). A plethora of products are formed during the H2O2 decontamination of HD on concrete, and these are characterized by comparison to synthesized authentic compounds. As a potential residue-free decontaminant for surfaces other than concrete (or those lacking adsorbed carbonate/bicarbonate) H2O2 activation for CWA decontamination is feasible using residue-free NH3 and CO2 as demonstrated by reaction studies for VX, GD, and HD in homogeneous solution. Although H2O2/NH3/CO2 ("HPAC") decontaminants are active for CWA decontamination in solution, they require testing on actual surfaces of interest to assess their true efficacy for surface decontamination. PMID:25710477

  11. Study of physical chemical characteristics of a shungite

    Directory of Open Access Journals (Sweden)

    Maira Kazankapova

    2012-05-01

    Full Text Available The physico-chemical characteristics of shungite from the field of Kazakhstan ("Bakyrchik" and Russia ("Zazhegino" was studied by elemental analysis, IR- spectroscopy and electron microscopy. The content of carbon in the schungite field "Zazhegino" is 28,0-31,0 %,  in the field "Bakyrchik" - 15,0-19,0 %, in schungite concentrate  "Bakyrchik" is 40,0 ± 2,0 %.  IR-spectroscopic analysis have been shown that carboxyl groups appear in addition to the concentrate of polycyclic hydrocarbons containing methylene groups. Analysis of electron microscopy have been shown that as a result of enrichment by carbon, shungite can get a more developed surface structure and porosity.

  12. Quantum-chemical study of CHCl3-SO2 association

    Science.gov (United States)

    Hippler, Michael

    2005-11-01

    CHCl3-SO2 association is studied by high-level quantum-chemical calculations of stationary points of the dimer electronic potential-energy hypersurface, including correlated second-order Møller-Plesset and CCSD(T) calculations with basis sets up to 6-311++G(d,p). During geometry optimization, frequency, and energy calculations, a self-written computer code embedding the GAMESS ab initio program suite applies counterpoise correction of the basis set superposition error. A CH ⋯O hydrogen-bonded complex (ΔE0=-8.73kJ/mol) with a 2.4Å intermolecular H ⋯O distance and two very weak van der Waals complexes (ΔE0=-3.78 and -2.94kJ /mol) are located on the counterpoise-corrected potential-energy surface. The intermolecular interactions are characterized by Kitaura-Morokuma interaction energy decompositions and Mulliken electron population analyses. The unusual hydrogen bond is distinguished by a CH-bond contraction, a pronounced enhancement of the IR intensity and a shift to higher frequency ("blueshift") of the CH-stretching vibration compared to the CHCl3 monomer. Spectroscopy and association in liquid solution is also discussed; our results provide an alternative explanation for features in the CH-stretching vibration spectrum of chloroform dissolved in liquid sulfur dioxide which have been attributed previously to an intermolecular Fermi resonance.

  13. Chemical and environmental isotope study of precipitation in Syria

    International Nuclear Information System (INIS)

    The rain waters from a network covering 9 meteorological stations distributed mainly in the western part of Syria have been investigated using chemical and environmental isotope techniques during a period of 5 months from December 1989 to April 1990. The chemistry of rain waters falling over the mountainous stations shows a low solute concentration (16-55 mg/L) comparing with those falling over the coastal and anterior stations (36-150 mg/L). The study shows also that the rain water are generally characterized by a high deuterium excess (d = 19 per mille) comparing with that of the global meteoric waters (d = 10 per mille). Mean while, the estimated deuterium excess is found to be lower than that given for the eastern Mediterranean meteoric water (d = 22 per mille). The altitude effect is shown up by a depletion of heavy stable isotopes of about -0.23 per mille and -1.65 per mille per 100 meters for δoxygen-18 and δdeuterium, respectively. The spatial distribution pattern of tritium contents shows a gradual build up with the increasing distance from the Syrian coast. The weighted mean tritium content in rain waters falling over the country is estimated to be around 9.5 TU during the period of observation. (author). 22 refs, 9 figs, 2 tabs

  14. Coupling aerosol optics to the chemical transport model MATCH (v5.5.0) and aerosol dynamics module SALSA (v1)

    Science.gov (United States)

    Andersson, E.; Kahnert, M.

    2015-12-01

    Modelling aerosol optical properties is a notoriously difficult task due to the particles' complex morphologies and compositions. Yet aerosols and their optical properties are important for Earth system modelling and remote sensing applications. Operational optics models often make drastic and non realistic approximations regarding morphological properties, which can introduce errors. In this study a new aerosol optics model is implemented, in which more realistic morphologies and mixing states are assumed, especially for black carbon aerosols. The model includes both external and internal mixing of all chemical species, it treats externally mixed black carbon as fractal aggregates, and it accounts for inhomogeneous internal mixing of black carbon by use of a novel "core-grey shell" model. Simulated results of radiative fluxes, backscattering coefficients and the Ångström exponent from the new optics model are compared with results from another model simulating particles as externally mixed homogeneous spheres. To gauge the impact on the optical properties from the new optics model, the known and important effects from using aerosol dynamics serves as a reference. The results show that using a more detailed description of particle morphology and mixing states influences the optical properties to the same degree as aerosol dynamics. This is an important finding suggesting that over-simplified optics models coupled to a chemical transport model can introduce considerable errors; this can strongly effect simulations of radiative fluxes in Earth-system models, and it can compromise the use of remote sensing observations of aerosols in model evaluations and chemical data assimilation.

  15. Comparative Study of Chemical Methods for Fuel Removal

    International Nuclear Information System (INIS)

    Full text: To extend the availability of ITER, tritium stored in the vessel has to be removed on a regular basis. The research on the fuel removal at Forschungszentrum Juelich has been concentrated in recent years on chemical methods including thermo-chemical erosion (TCE) also known as baking in reactive gases, glow-discharge conditioning (GDC) and ion-cyclotron wall conditioning (ICWC). The studies were conducted in the tokamak TEXTOR and in laboratory devices using pre-characterized samples with deuterated carbon layers. GDC, in contrast to TCE and ICWC, is not applicable in the presence of the nominal magnetic field. Our investigations showed that GDC can be operated at a magnetic field of up to 10 mT and is therefore compatible with the ferritic inserts foreseen in ITER. The TCE using oxygen as the removal gas can effectively be employed at elevated temperatures of at least 300°C. Plasma-based GDC and ICWC can also be applied at lower wall temperatures. TCE is equally efficient in cleaning from the wall surface as from the remote areas such as gaps of castellations. GDC is homogeneous along the wall surface except for small recessed areas like gaps. ICWC is typically inhomogeneous along the poloidal circumference. Applying the radial magnetic field, we were able to control the poloidal position of the main IC plasma production. Thus, some wall regions, e.g., the divertor, can selectively be exposed to ICWC. Owing to higher ion fluxes to the wall, ICWC activates a larger amount of neutrals than GDC, which then penetrate in gaps and clean gap walls efficiently. Removal rates with oxygen were typically by a factor of 3 - 10 higher than with hydrogen and ammonia and 10 - 30 than with nitrogen. The estimates using the highest removal rate for ICWC show that about 2 hours are needed to remove the layer deposited within one ITER pulse. The application of ammonia in TCE led to the pealing-off of layers, which is a potential dust production mechanism. However, it

  16. USI/Chemplex/Quantum Chemical Co. Outfall Study, 1987

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Sediment samples collected in 1987 from the Quantum Chemical Corporation outfall on the Upper Mississippi River detected 14 polycyclic aromatic hydrocarbons...

  17. Chemical evolution in hierarchical scenarios

    OpenAIRE

    Tissera P.B.

    2012-01-01

    We studied the chemical properties of Milky-Way mass galaxies. We found common global chemical patterns with particularities which reflect their different assembly histories in a hierarchical scenario. We carried out a comprehensively analysis of the dynamical components (central spheroid, disc, inner and outer haloes) and their chemical properties.

  18. Study of critical dynamics in fluids via molecular dynamics in canonical ensemble.

    Science.gov (United States)

    Roy, Sutapa; Das, Subir K

    2015-12-01

    With the objective of understanding the usefulness of thermostats in the study of dynamic critical phenomena in fluids, we present results for transport properties in a binary Lennard-Jones fluid that exhibits liquid-liquid phase transition. Various collective transport properties, calculated from the molecular dynamics (MD) simulations in canonical ensemble, with different thermostats, are compared with those obtained from MD simulations in microcanonical ensemble. It is observed that the Nosé-Hoover and dissipative particle dynamics thermostats are useful for the calculations of mutual diffusivity and shear viscosity. The Nosé-Hoover thermostat, however, as opposed to the latter, appears inadequate for the study of bulk viscosity. PMID:26687057

  19. A study on chemical composition and detection of chemical adulteration in tetra pack milk samples commercially available in Multan.

    Science.gov (United States)

    Awan, Adeela; Naseer, Misbah; Iqbal, Aasfa; Ali, Muhammad; Iqbal, Rehana; Iqbal, Furhan

    2014-01-01

    The aim of this study was to analyze and compare the chemical composition of 8 tetra pack milk samples, Olpers (S1), Haleeb (S2), Good milk (S3), Everyday (S4), Milk Pack (S5), Dairy Queen (S6), Dairy Umang (S7), Nurpur (S8) available in local markets and to detect the presence of various chemical adulterants in tetra pack milk samples in Southern Punjab (Pakistan). Density, pH, solid not fat, total solids, lactometer reading, specific gravity and fat contents were analyzed to determine the chemical composition of milk samples. Our results revealed that all the studied parameters had statistically non significant differences (P>0.05) except total fat in milk samples which was significantly different (P=0.03) among the 8 studied milk samples. Presence of a number of chemical adulterants, formalin, cane sugar, starch, glucose, ammonium sulphate, salt, pulverized soap, detergents, skim milk powder, benzoic acid, salicylic acid, borax, boric acid and alkalinity were also detected in milk samples following standard procedures. Results indicated that formalin, cane sugar, glucose, alkalinity and benzoic acid were present in all samples while salt test was positive only for Olper milk. All other studied adulterants were not detected in 8 milk samples under study. % fat was the only significantly different feature among the studied milk quality parameters with S8 containing lowest while S5 having the maximum % fat. PMID:24374447

  20. Comparisons of classical and Wigner sampling of transition state energy levels for quasiclassical trajectory chemical dynamics simulations

    International Nuclear Information System (INIS)

    Quasiclassical trajectory calculations are compared, with classical and Wigner sampling of transition state (TS) energy levels, for C2H5F≠→HF+C2H4 product energy partitioning and [Cl···CH3···Cl]- central barrier dynamics. The calculations with Wigner sampling are reported here for comparison with the previously reported calculations with classical sampling [Y. J. Cho et al., J. Chem. Phys. 96, 8275 (1992); L. Sun and W. L. Hase, J. Chem. Phys. 121, 8831 (2004)]. The C2H5F≠ calculations were performed with direct dynamics at the MP2/6-31G* level of theory. Classical and Wigner sampling give post-transition state dynamics, for these two chemical systems, which are the same within statistical uncertainties. This is a result of important equivalences in these two sampling methods for selecting initial conditions at a TS. In contrast, classical and Wigner sampling often give different photodissociation dynamics [R. Schinke, J. Phys. Chem. 92, 3195 (1988)]. Here the sampling is performed for a vibrational state of the ground electronic state potential energy surface (PES), which is then projected onto the excited electronic state's PES. Differences between the ground and the excited PESs may give rise to substantially different excitations of the vibrational and dissociative coordinates on the excited state PES by classical and Wigner sampling, resulting in different photodissociation dynamics.

  1. Effects of chemical reactions on the performance of gas dynamic lasers

    Energy Technology Data Exchange (ETDEWEB)

    Rom, J.; Stricker, J.

    1974-01-01

    It is shown that chemical reactions in the stagnation region of a gasdynamic laser in the shock tube may not be completed during the available test time. Therefore, analysis of data obtained in the shock tube must account for the instantaneous composition which may be effected by chemical reactions. A CO/sub 2/--N/sub 2/ gasdynamic laser experimental program in the shock tube including addition of H/sub 2/ into the system is described. This experiment involves reasonably complicated chemical reactions. These chemical reactions result in H/sub 2/O production under certain conditions. The comparison of the experimental results with the calculated results shows that such measurements can also be used to evaluate the energy transfer rates. The small-signal gain measurements indicate that the hydrogen is much more effective in depopulating the ..nu.. sub 3 level to ..nu.. sub 2 than previously assumed.

  2. Quantitative chemical tagging, stellar ages and the chemo-dynamical evolution of the Galactic disc

    CERN Document Server

    Mitschang, A W; Zucker, D B; Anguiano, B; Bensby, T; Feltzing, S

    2013-01-01

    The early science results from the new generation of high-resolution stellar spectroscopic surveys, such as GALAH and the Gaia-ESO survey, will represent major milestones in the quest to chemically tag the Galaxy. Yet this technique to reconstruct dispersed coeval stellar groups has remained largely untested until recently. We build on previous work that developed an empirical chemical tagging probability function, which describes the likelihood that two field stars are conatal, that is, they were formed in the same cluster environment. In this work we perform the first ever blind chemical tagging experiment, i.e., tagging stars with no known or otherwise discernable associations, on a sample of 714 disc field stars with a number of high quality high resolution homogeneous metal abundance measurements. We present evidence that chemical tagging of field stars does identify coeval groups of stars, yet these groups may not represent distinct formation sites, e.g. as in dissolved open clusters, as previously thou...

  3. Study of chemical and physical properties of irradiated Guar Gum

    International Nuclear Information System (INIS)

    This study was carried out to evaluate the effect of different gamma radiation doses to decontamination of micro-organisms present in Guar Gum powder. As well as to study the effect of radiation on the chemical and physical properties of the carbohydrate components of the Gum's material. Two types of samples were used in this study (powder and liquid). All samples were collected from commercially available Guar Gum (G G), which were obtained from the company (Sudanese Guar Gum ltd). Samples putted in polyethylene tightly closed container, then irradiated by applying different doses (2.5, 5, 7.5, 10, 20,30,40,and 50 kGy) from Co-60 source at room temperature in air. And take zero kGy as control. Irradiated powder samples of (2.5, 5, 7.5, 10 kGy) were investigated for contamination by using growth media agar and the result showed that 2.5 kGy is appropriate dose to remove the contamination of the samples. And then analyzed using fourier transform infrared (FTTR) x-ray fluorescence (X RF) and spectroscopy. The FTIR spectroscopy results suggested that there were no major chemical functional group transformation during irradiation. No change occurs by using low dose as 2.5 kGy. Also evaluation impact of radiation on liquid Samples (Aqueous solutions prepared in tow concentration of 1% and 5% wv that is by exposing the samples to the same dose of gamma rays) the effect of irradiation on it were investigated by using ultra violet spectroscopy ( UV.Vis), results showed that low dose has steeply effect in solutions specially in low concentration, it was more pronoun than that in high concentration, high dose has made change similar to that it made in powder. Also for both concentrations of liquid samples and for solutions made of irradiated powder pH measured and viscosity which used in investigations of molecular weight of liquid and powder, comparing the results of impact in the form of powder with the results of effects in the solutions found that the effects of

  4. Systems approaches to study root architecture dynamics

    Directory of Open Access Journals (Sweden)

    Candela eCuesta

    2013-12-01

    Full Text Available The plant root system is essential for providing anchorage to the soil, supplying minerals and water, and synthesizing metabolites. It is a dynamic organ modulated by external cues such as environmental signals, water and nutrients availability, salinity and others. Lateral roots are initiated from the primary root post-embryonically, after which they progress through discrete developmental stages which can be independently controlled, providing a high level of plasticity during root system formation.Within this review, main contributions are presented, from the classical forward genetic screens to the more recent high-throughput approaches, combined with computer model predictions, dissecting how lateral roots and thereby root system architecture is established and developed.

  5. NMR studies of nucleic acid dynamics

    Science.gov (United States)

    Al-Hashimi, Hashim M.

    2013-12-01

    Nucleic acid structures have to satisfy two diametrically opposite requirements; on one hand they have to adopt well-defined 3D structures that can be specifically recognized by proteins; on the other hand, their structures must be sufficiently flexible to undergo very large conformational changes that are required during key biochemical processes, including replication, transcription, and translation. How do nucleic acids introduce flexibility into their 3D structure without losing biological specificity? Here, I describe the development and application of NMR spectroscopic techniques in my laboratory for characterizing the dynamic properties of nucleic acids that tightly integrate a broad set of NMR measurements, including residual dipolar couplings, spin relaxation, and relaxation dispersion with sample engineering and computational approaches. This approach allowed us to obtain fundamental new insights into directional flexibility in nucleic acids that enable their structures to change in a very specific functional manner.

  6. Determination of the Orientation and Dynamics of Ergosterol in Model Membranes Using Uniform 13C Labeling and Dynamically Averaged 13C Chemical Shift Anisotropies as Experimental Restraints

    Science.gov (United States)

    Soubias, O.; Jolibois, F.; Massou, S.; Milon, A.; Réat, V.

    2005-01-01

    A new strategy was established to determine the average orientation and dynamics of ergosterol in dimyristoylphosphatidylcholine model membranes. It is based on the analysis of chemical shift anisotropies (CSAs) averaged by the molecular dynamics. Static 13C CSA tensors were computed by quantum chemistry, using the gauge-including atomic-orbital approach within Hartree-Fock theory. Uniformly 13C-labeled ergosterol was purified from Pichia pastoris cells grown on labeled methanol. After reconstitution into dimyristoylphosphatidylcholine lipids, the complete 1H and 13C assignment of ergosterol's resonances was performed using a combination of magic-angle spinning two-dimensional experiments. Dynamically averaged CSAs were determined by standard side-band intensity analysis for isolated 13C resonances (C3 and ethylenic carbons) and by off-magic-angle spinning experiments for other carbons. A set of 18 constraints was thus obtained, from which the sterol's molecular order parameter and average orientation could be precisely defined. The validity of using computed CSAs in this strategy was verified on cholesterol model systems. This new method allowed us to quantify ergosterol's dynamics at three molar ratios: 16 mol % (Ld phase), 30 mol % (Lo phase), and 23 mol % (mixed phases). Contrary to cholesterol, ergosterol's molecular diffusion axis makes an important angle (14°) with the inertial axis of the rigid four-ring system. PMID:15923221

  7. Ab initio studies of equations of state and chemical reactions of reactive structural materials

    Science.gov (United States)

    Zaharieva, Roussislava

    subject of studies of the shock or thermally induced chemical reactions of the two solids comprising these reactive materials, from first principles, is a relatively new field of study. The published literature on ab initio techniques or quantum mechanics based approaches consists of the ab initio or ab initio-molecular dynamics studies in related fields that contain a solid and a gas. One such study in the literature involves a gas and a solid. This is an investigation of the adsorption of gasses such as carbon monoxide (CO) on Tungsten. The motivation for these studies is to synthesize alternate or synthetic fuel technology by Fischer-Tropsch process. In this thesis these studies are first to establish the procedure for solid-solid reaction and then to extend that to consider the effects of mechanical strain and temperature on the binding energy and chemisorptions of CO on tungsten. Then in this thesis, similar studies are also conducted on the effect of mechanical strain and temperature on the binding energies of Titanium and hydrogen. The motivations are again to understand the method and extend the method to such solid-solid reactions. A second motivation is to seek strained conditions that favor hydrogen storage and strain conditions that release hydrogen easily when needed. Following the establishment of ab initio and ab initio studies of chemical reactions between a solid and a gas, the next step of research is to study thermally induced chemical reaction between two solids (Ni+Al). Thus, specific new studies of the thesis are as follows: (1) Ab initio Studies of Binding energies associated with chemisorption of (a) CO on W surfaces (111, and 100) at elevated temperatures and strains and (b) adsorption of hydrogen in titanium base. (2) Equations of state of mixtures of reactive material structures from ab initio methods. (3) Ab initio studies of the reaction initiation, transition states and reaction products of intermetallic mixtures of (Ni+Al) at elevated

  8. Analysis of the chemical evolution of the Galactic disk via dynamical simulations of the open cluster system

    OpenAIRE

    Tecce, T. E.; Pellizza, L. J.; Piatti, A. E.

    2006-01-01

    For several decades now, open clusters have been used to study the structure and chemical evolution of the disk of our Galaxy. Due to the fact that their ages and metallicities can be determined with relatively good precision, and since they can be observed even at great distances, they are excellent tracers of the variations in the abundance of heavy chemical elements with age and position in the Galactic disk. In the present work we analyze the star formation history and the chemical evolut...

  9. Studies of coupled chemical and catalytic coal conversion methods

    Energy Technology Data Exchange (ETDEWEB)

    Stock, L.M.

    1988-01-01

    Liquefaction of coal by depolymerization in an organic solvent has been studied for several years. The liquefied coal extract which results from such a process is far more suitable for conversion into liquid fuel by hydrogenolysis than is the untreated coal. Investigations on the chemical structure and the reactive sites of coal can help to select useful reactions for the production of liquids from coal. Sternberg et al. demonstrated that the reductive alkylation method transforms bituminous coal into an enormously soluble substance, irrespective of the mild reaction conditions. The effectiveness of newly introduced alkyl groups for the disruption of intermolecular hydrogen bonds and pi-pi interactions between the aromatic sheets in coal macromolecules has been recognized. It has been reported by Ignasiak et al. that a C-alkylabon reaction using sodium or potassium amide in liquid ammonia can be used to introduce alkyl groups at acidic carbon sites. A method has been developed recently in this laboratory for the solubilization of high rank coals. In the previous reports it was shown that n-butyl lithium and potassium t-butoxide in refluxing heptane produced coal anions which could be alkylated with different alkyl halides. Such alkylated coals were soluble up to 92% in solvents like pyridine. Though the solubilization of coal depended very much on the length of the alkyl group, it also depended very much on the nature of the base used. Strong bases like n-butyl lithium (pKa=42) can cause proton abstraction from aromatic structures, if the more acidic benzylic protons are absent. The utility of this procedure, initially developed and used by Miyake and Stock, has now been tested with the high oxygen containing, low rank Illinois No. 6 and Wyodak coals.

  10. Molecular dynamics study of structural and dynamical properties of amorphous Si-Ge alloys

    International Nuclear Information System (INIS)

    Structural and dynamical properties of amorphous silicon-germanium (a-Si1-xGex) alloys have been examined by molecular dynamics simulations using the Tersoff interatomic potential. Amorphous networks were generated by rapid quenching from liquid Si1-xGex alloys. Good agreement was obtained between the simulated and experimentally measured radial distribution functions and phonon densities of states, suggesting that the Tersoff potential is useful for analyzing the atomic configurations and vibrational properties of a-Si1-xGex alloys. Local atomistic structures, such as topological and chemical short-range order states, were also examined in detail, and we compared them with experimental and theoretical results reported previously. On the basis of the results obtained here, we proposed that the bond length and bond angle around Ge atoms have more distortion than those around Si atoms in a-Si1-xGex networks

  11. Oral Dosing of Chemical Indicators for In Vivo Monitoring of Ca2+ Dynamics in Insect Muscle

    OpenAIRE

    Ferdinandus,; Satoshi Arai; Shin'ichi Ishiwata; Madoka Suzuki; Hirotaka Sato

    2015-01-01

    This paper proposes a remarkably facile staining protocol to visually investigate dynamic physiological events in insect tissues. We attempted to monitor Ca2+ dynamics during contraction of electrically stimulated living muscle. Advances in circuit miniaturization and insect neuromuscular physiology have enabled the hybridization of living insects and man-made electronic components, such as microcomputers, the result of which has been often referred as a Living Machine, Biohybrid, or Cyborg I...

  12. A Case Study of Search Engine on World Wide Web for Chemical Fiber Engineering

    Institute of Scientific and Technical Information of China (English)

    张利; 邵世煌; 曾献辉; 尹美华

    2001-01-01

    Search engine is an effective approach to promote the service quality of the World Wide Web. On terms of the analysis of search engines at home and abroad, the developing principle of search engines is given according to the requirement of Web information for chemical fiber engineering. The implementation method for the communication and dynamic refreshment of information on home page of the search engines are elaborated by using programming technology of Active Server Page 3.0 (ASP3.0). The query of chemical fiber information and automatic linking of chemical fiber Web sites can be easily realized by the developed search engine under Internet environment according to users' requirement.

  13. Study on New Approaches for extended chemical management and REACH

    DEFF Research Database (Denmark)

    Lee, Jihyun

    2014-01-01

    existing chemical regulations in view of protecting vulnerable populations from “excessive total risk” and to explore the possibilities for improvement. Firstly, the completeness of the REACH exposure scenario was reviewed with the finding that the current scenario does not take into account territorial...... without controlling the quality of recycled materials, increased recycling of resources in a circular economy might increase undesirable recycling of micro-pollutants. Finally, a systemic approach based on sustainable resource flows was proposed for extended chemical management and the role of REACH in a...

  14. EXPERIMENTAL STUDY OF CHEMICAL CHOLECYSTECTOMY: OBSERVATION OF PATHOLOGICAL CHANGES

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Objective: TO verify through animal experiment the validity of chemical cholecystectomy . Methods: The experimental objects seven healthy juvenile pigs,hardener was infused into the gallbladder,after infusion the samples were collected by pathoiogical examination , according to the different duration under anesthestize. Reslts:The mucous destructive and digestive process remained with one week, the inflammatory reacton in two weeks,the chronic inflatoy reaction compained a a great deal of granu lation tissue and scar formation occurred in 4th-8th week,10 weeks latter,the inflmmatory reaction reduced ,and scar tissue formed. Conclusion: Chemical cholecystectomy is safe and reliable in clinical.

  15. EXPERIMENTAL STUDY OF CHEMICAL CHOLECYSTECTOMY OF PATHOLOGIC OBSERVATION

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective:To verify through animal experiment the validity of chemical cholecystectomy.Mothods:The expermental objects seven healthy juvenile pigs,hardener was infused into the gallbladder,after infusion the sapmles were collected by pathological examination,according to the different duration under anesthestize.Results:The mucous destructive and digestive process remained with one week,the inflammatory reaction in two weeks,the chronic inflammatory reaction compained a great deal of granulation tissue and scar formation occurred in 4th-8th week,10 weeks latter,the inflammatory reaction reduced,and scar tissue formed.Conlusion:Chemical cholecystecomy is safe and reliable in clinic.

  16. Laser studies of chemical reaction and collision processes

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, G. [Columbia Univ., New York, NY (United States)

    1993-12-01

    This work has concentrated on several interrelated projects in the area of laser photochemistry and photophysics which impinge on a variety of questions in combustion chemistry and general chemical kinetics. Infrared diode laser probes of the quenching of molecules with {open_quotes}chemically significant{close_quotes} amounts of energy in which the energy transferred to the quencher has, for the first time, been separated into its vibrational, rotational, and translational components. Probes of quantum state distributions and velocity profiles for atomic fragments produced in photodissociation reactions have been explored for iodine chloride.

  17. Study about chemical and radiological toxicity of rare earths

    International Nuclear Information System (INIS)

    The maximum permissible concentration in workplace air for an admixture of rare earths is calculated to be 1.47 mg/m3 of air. This value takes into account the biological mean-life of those chemical elements in human body and acute toxicological data. A simplified mathematical models is done that describes the body content of this product as a time function, for cronic intoxication by air particulate inhalation. Under the radiological point of view the limit calculated for the air concentration is about 100 mg/m3, showing that the chemical toxity of these products is predominant. (Author)

  18. Ab Initio Studies of Shock-Induced Chemical Reactions of Inter-Metallics

    Science.gov (United States)

    Zaharieva, Roussislava; Hanagud, Sathya

    2009-06-01

    Shock-induced and shock assisted chemical reactions of intermetallic mixtures are studied by many researchers, using both experimental and theoretical techniques. The theoretical studies are primarily at continuum scales. The model frameworks include mixture theories and meso-scale models of grains of porous mixtures. The reaction models vary from equilibrium thermodynamic model to several non-equilibrium thermodynamic models. The shock-effects are primarily studied using appropriate conservation equations and numerical techniques to integrate the equations. All these models require material constants from experiments and estimates of transition states. Thus, the objective of this paper is to present studies based on ab initio techniques. The ab inito studies, to date, use ab inito molecular dynamics. This paper presents a study that uses shock pressures, and associated temperatures as starting variables. Then intermetallic mixtures are modeled as slabs. The required shock stresses are created by straining the lattice. Then, ab initio binding energy calculations are used to examine the stability of the reactions. Binding energies are obtained for different strain components super imposed on uniform compression and finite temperatures. Then, vibrational frequencies and nudge elastic band techniques are used to study reactivity and transition states. Examples include Ni and Al.

  19. Chemical Risk Evaluation: A Case Study in an Automotive Air Conditioner Production Facility

    OpenAIRE

    Tengku Hanidza T.I.

    2010-01-01

    There has been limited knowledge on worker’s exposure to chemicals used in the automotive industries. The purpose of this study is to assess chemical risk and to determine the adequacy of the existing control measures to reduce chemical exposure. A cross sectional survey was conducted in a factory involving installation and servicing of automotive air conditioner units. Qualitative exposure assessment was carried out following the Malaysian Chemical Health Risk Assessment Manual (CHRA). There...

  20. Systematic quantum chemical study of DNA-base tautomers.

    Science.gov (United States)

    Piacenza, M; Grimme, S

    2004-01-15

    The relative energies of the energetically low-lying tautomers of pyridone, cytosine, uracil, thymine, guanine, and iso-cytosine are studied by a variety of different quantum chemical methods. In particular, we employ density functional theory (DFT) using the six functionals HCTH407, PBE, BP86, B-LYP, B3-LYP, and BH-LYP, and the ab initio methods Hartree-Fock (HF), standard second-order Møller-Plesset perturbation theory (MP2), an improved version of it (SCS-MP2), and quadratic configuration interaction including single and double excitations (QCISD) and perturbative triple corrections [QCISD(T)]. A detailed basis set study is performed for the formamide/formamidic acid tautomeric pair. In general, large AO basis sets of at least valence triple-zeta quality including f-functions (TZV) are employed, which are found to be necessary for an accurate energetic description of the various structures. The performance of the more approximate methods is evaluated with QCISD(T)/TZV(2df,2dp) data taken as reference. In general it is found that DFT is not an appropriate method for the problem. For the tautomers of pyridone and cytosine, most density functionals, including the popular B3-LYP hybrid, predict a wrong energetic order, and only for guanine, the correct sequence of tautomers is obtained with all functionals. Out of the density functionals tested, BH-LYP, which includes a rather large fraction of HF exchange, performs best. A consistent description of the nonaromatic versus aromatic tautomers seems to be a general problem especially for pure, nonhybrid functionals. Tentatively, this could be assigned to the exchange potentials used while the functional itself, including the correlation part, seems to be appropriate. Out of the ab initio methods tested, the new SCS-MP2 approach seems to perform best because it effectively reduces some outliers obtained with standard MP2. It outperforms the much more costly QCISD method and seems to be a very good compromise between

  1. Adhesive capsulitis and dynamic splinting: a controlled, cohort study

    OpenAIRE

    Willis F Buck; Gaspar Paul D

    2009-01-01

    Abstract Background Adhesive Capsulitis (AC) affects patient of all ages, and stretching protocols are commonly prescribed for this condition. Dynamic splinting has been shown effective in contracture reduction from pathologies including Trismus to plantar fasciitis. The purpose of this study was to examine the efficacy of dynamic splinting on patients with AC. Methods This controlled, cohort study, was conducted at four physical therapy, sports medicine clinics in Texas and California. Sixty...

  2. NATO Advanced Research Workshop on The Theory of Chemical Reaction Dynamics

    CERN Document Server

    1986-01-01

    The calculation of cross sections and rate constants for chemical reactions in the gas phase has long been a major problem in theoretical chemistry. The need for reliable and applicable theories in this field is evident when one considers the significant recent advances that have been made in developing experimental techniques, such as lasers and molecular beams, to probe the microscopic details of chemical reactions. For example, it is now becoming possible to measure cross sections for chemical reactions state selected in the vibrational­ rotational states of both reactants and products. Furthermore, in areas such as atmospheric, combustion and interstellar chemistry, there is an urgent need for reliable reaction rate constant data over a range of temperatures, and this information is often difficult to obtain in experiments. The classical trajectory method can be applied routinely to simple reactions, but this approach neglects important quantum mechanical effects such as tunnelling and resonances. For al...

  3. Dynamics of the chemical master equation, a strip of chains of equations in d-dimensional space.

    Science.gov (United States)

    Galstyan, Vahe; Saakian, David B

    2012-07-01

    We investigate the multichain version of the chemical master equation, when there are transitions between different states inside the long chains, as well as transitions between (a few) different chains. In the discrete version, such a model can describe the connected diffusion processes with jumps between different types. We apply the Hamilton-Jacobi equation to solve some aspects of the model. We derive exact (in the limit of infinite number of particles) results for the dynamic of the maximum of the distribution and the variance of distribution. PMID:23005386

  4. Chemically induced dynamic electron polarization investigation of the triplet-radical system in the solution of the triplet quencher

    Institute of Scientific and Technical Information of China (English)

    LU, Tong-Xing; CUI, Zhi-Feng; XU, Xin-Sheng; ZHANG, Xian-Yi

    2000-01-01

    The chemically induced dynamic electron polariztiion (CIDEP) of the triplet molecule/triplet quencher/2,2,6,6-te tranethyl-1-piperidinyioxyl (TEMPO) systems were measured using the high time-resolved FESR spectrometer. The competi tion between the radical-triplet pair mechanism (RTPM) and triplet mechanism (TM) or radical pair mechanism (RPM) polarization in the solution of the triplet quencher was investi gated, and the relationship between reaction rate of the radi cal-triplet pair and quenching rate of triplet was deduced.

  5. High-power supersonic chemical lasers: gas-dynamic problems of operation of mobile systems with PRS

    Science.gov (United States)

    Boreysho, A. S.; Malkov, V. M.; Savin, A. V.

    2008-10-01

    Supersonic chemical lasers, such as HF /DF and COIL, have always been in the focus of special interest as the most powerful sources of continuous wave generation. Presently, autonomous mobile laser complexes (both air- and landbased) are being developed on the basis of SCL [1-3]. It is commonly accepted that SCL appeared, conditionally speaking, at the crossroads of a number of sciences: of physics - quantum electronics and physical kinetics; chemistry - combustion theory and chemical kinetics; classic optics - theory of resonators, aero-optics, and gas dynamics (there is a supersonic flow in the SCL channel). Due to this fact, all tasks and problems which could be resolved in the course of SCL development have complex character and could be considered as the next stage of complexity in comparison with the well known similar tasks which had been considered earlier. This is why they should be resolved anew with consideration of the specific aspects of the SCL processes. This is true for the gas-dynamic problems: new parameter areas, non-traditional channel geometry, consideration of new phenomena, etc.Supersonic chemical lasers, such as HF /DF and COIL, have always been in the focus of special interest as the most powerful sources of continuous wave generation. Presently, autonomous mobile laser complexes (both air- and landbased) are being developed on the basis of SCL [1-3]. It is commonly accepted that SCL appeared, conditionally speaking, at the crossroads of a number of sciences: of physics - quantum electronics and physical kinetics; chemistry - combustion theory and chemical kinetics; classic optics - theory of resonators, aero-optics, and gas dynamics (there is a supersonic flow in the SCL channel). Due to this fact, all tasks and problems which could be resolved in the course of SCL development have complex character and could be considered as the next stage of complexity in comparison with the well known similar tasks which had been considered earlier

  6. Concentration dynamics in lakes and reservoirs. Studies using radioactive tracers

    International Nuclear Information System (INIS)

    The use of radioactive tracers for the investigation of concentration dynamics of inert soluble matter in lakes and reservoirs is reviewed. Shallow and deep stratified lakes are considered. The mechanism of mixing in lakes, flow pattern and input - output response are discussed. The methodology of the use of radioactive tracers for concentration dynamic studies is described. Examples of various investigations are reviewed. The dynamics of shallow lakes can be found and expressed in terms of transfer functions, axial dispersion models, residence time distributions and sometimes only semiquantitative information about the flow pattern. The dynamics of deep, stratified lakes is more complex and difficult to investigate with tracers. Flow pattern, horizontal and vertical eddy diffusivities, mass transfer between the hypolimnion and epilimnion are tools used for describing this dynamics. (author)

  7. Study on dynamic lifting characteristics of control rod drive mechanism

    International Nuclear Information System (INIS)

    Based on the equations of the electric circuit and the magnetic circuit and analysis of the dynamic lifting process for the control rod drive mechanism (CRDM), coupled magnetic-electric-mechanical equations both for the static status and the dynamic status are derived. The analytical method is utilized to obtain the current and the time when the lift starts. The numerical simulation method of dynamic analysis recommended by ASME Code is utilized to simulate the dynamic lifting process of CRDM, and the dynamic features of the system with different design gaps are studied. Conclusions are drawn as: (1) the lifting-start time increases with the design gap, and the time for the lifting process is longer with larger gaps; (2) the lifting velocity increases with time; (3) the lifting acceleration increases with time, and with smaller gaps, the impact acceleration is larger. (author)

  8. Hybrid density functional study on lattice vibration, thermodynamic properties, and chemical bonding of plutonium monocarbide

    Science.gov (United States)

    Rong, Yang; Bin, Tang; Tao, Gao; BingYun, Ao

    2016-06-01

    Hybrid density functional theory is employed to systematically investigate the structural, magnetic, vibrational, thermodynamic properties of plutonium monocarbide (PuC and PuC0.75). For comparison, the results obtained by DFT, DFT + U are also given. For PuC and PuC0.75, Fock-0.25 hybrid functional gives the best lattice constants and predicts the correct ground states of antiferromagnetic (AFM) structure. The calculated phonon spectra suggest that PuC and PuC0.75 are dynamically stable. Values of the Helmholtz free energy ΔF, internal energy ΔE, entropy S, and constant-volume specific heat C v of PuC and PuC0.75 are given. The results are in good agreement with available experimental or theoretical data. As for the chemical bonding nature, the difference charge densities, the partial densities of states and the Bader charge analysis suggest that the Pu–C bonds of PuC and PuC0.75 have a mixture of covalent character and ionic character. The effect of carbon vacancy on the chemical bonding is also discussed in detail. We expect that our study can provide some useful reference for further experimental research on the phonon density of states, thermodynamic properties of the plutonium monocarbide. Project supported by the National Natural Science Foundation of China (Grant Nos. 21371160 and 21401173).

  9. Dynamical properties of liquid Al near melting. An orbital-free molecular dynamics study

    OpenAIRE

    Gonzalez, David J; Gonzalez, Luis Enrique; Lopez, Jose Manuel; Stott, Malcolm J.

    2001-01-01

    The static and dynamic structure of liquid Al is studied using the orbital free ab-initio molecular dynamics method. Two thermodynamic states along the coexistence line are considered, namely T = 943 K and 1323 K for which X-ray and neutron scattering data are available. A new kinetic energy functional, which fulfills a number of physically relevant conditions is employed, along with a local first principles pseudopotential. In addition to a comparison with experiment, we also compare our ab-...

  10. Collision induced dissociation of doubly-charged ions: Coulomb explosion vs. neutral loss in [Ca(urea)]2+ gas phase unimolecular reactivity via chemical dynamics simulations

    International Nuclear Information System (INIS)

    In this paper we report different theoretical approaches to study the gas-phase unimolecular dissociation of the doubly-charged cation [Ca(urea)]2+, in order to rationalize recent experimental findings. Quantum mechanical plus molecular mechanical (QM/MM) direct chemical dynamics simulations were used to investigate collision induced dissociation (CID) and rotational-vibrational energy transfer for Ar+ [Ca(urea)]2+ collisions. For the picosecond time-domain of the simulations, both neutral loss and Coulomb explosion reactions were found and the differences in their mechanisms elucidated. The loss of neutral urea subsequent to collision with Ar occurs via a shattering mechanism, while the formation of two singly-charged cations follows statistical (or almost statistical) dynamics. Vibrational-rotational energy transfer efficiencies obtained for trajectories that do not dissociate during the trajectory integration were used in conjunction with RRKM rate constants to approximate dissociation pathways assuming complete intramolecular vibrational energy redistribution (IVR) and statistical dynamics. This statistical limit predicts, as expected, that at long time the most stable species on the potential energy surface (PES) dominate. These results, coupled with experimental CID from which both neutral loss and Coulomb explosion products were obtained, show that the gas phase dissociation of this ion occurs by multiple mechanisms leading to different products and that reactivity on the complicated PES is dynamically complex. (authors)

  11. The VENUS/NWChem Software Package. Tight Coupling Between Chemical Dynamics Simulations and Electronic Structure Theory

    Energy Technology Data Exchange (ETDEWEB)

    Lourderaj, Upakarasamy; Sun, Rui; De Jong, Wibe A.; Windus, Theresa L.; Hase, William L.

    2014-03-01

    The interface for VENUS and NWChem, and the resulting software package for direct dynamics simulations are described. The coupling of the two codes is considered to be a tight coupling. The two codes are compiled and linked together and act as one executable with data being passed between the two codes through routine calls. The advantages of this type of coupling are discussed. The interface has been designed to have as little interference as possible with the core codes of both VENUS and NWChem. VENUS is the code that propagates the direct dynamics trajectories and, therefore, is the program that drives the overall execution of VENUS/NWChem. VENUS has remained an essentially sequential code, which uses the highly parallel structure of NWChem. Subroutines of the interface which accomplish the data transmission and communication between the two computer programs are described. Recent examples of the use of VENUS/NWChem for direct dynamics simulations are summarized.

  12. Theoretical Studies of Chemical Reactions following Electronic Excitation

    Science.gov (United States)

    Chaban, Galina M.

    2003-01-01

    The use of multi-configurational wave functions is demonstrated for several processes: tautomerization reactions in the ground and excited states of the DNA base adenine, dissociation of glycine molecule after electronic excitation, and decomposition/deformation of novel rare gas molecules HRgF. These processes involve bond brealung/formation and require multi-configurational approaches that include dynamic correlation.

  13. D44 - Multiple beam SANS for dynamic studies on small sample volumes

    International Nuclear Information System (INIS)

    Tracking of kinetics and dynamical processes on extremely low sample volumes is one of the most promising fields for new applications of neutron scattering complementing synchrotron X-ray research. The proposed SANS instrument using multiple beams focussed on the sample is designed for investigations of nano-scaled fluctuations and sub-millisecond dynamics in new materials obtained only in small quantities from complex and expensive syntheses, such as biological or isotope enriched materials. It allows kinetics of chemical processes to be studied in a large dynamic range in one shot when fast changes of external parameters (B, H, T, p, pH, etc) has to be applied on small sample volumes

  14. Dynamics-based selective 2D {sup 1}H/{sup 1}H chemical shift correlation spectroscopy under ultrafast MAS conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy, E-mail: ramamoor@umich.edu [Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055 (United States)

    2015-05-28

    Dynamics plays important roles in determining the physical, chemical, and functional properties of a variety of chemical and biological materials. However, a material (such as a polymer) generally has mobile and rigid regions in order to have high strength and toughness at the same time. Therefore, it is difficult to measure the role of mobile phase without being affected by the rigid components. Herein, we propose a highly sensitive solid-state NMR approach that utilizes a dipolar-coupling based filter (composed of 12 equally spaced 90° RF pulses) to selectively measure the correlation of {sup 1}H chemical shifts from the mobile regions of a material. It is interesting to find that the rotor-synchronized dipolar filter strength decreases with increasing inter-pulse delay between the 90° pulses, whereas the dipolar filter strength increases with increasing inter-pulse delay under static conditions. In this study, we also demonstrate the unique advantages of proton-detection under ultrafast magic-angle-spinning conditions to enhance the spectral resolution and sensitivity for studies on small molecules as well as multi-phase polymers. Our results further demonstrate the use of finite-pulse radio-frequency driven recoupling pulse sequence to efficiently recouple weak proton-proton dipolar couplings in the dynamic regions of a molecule and to facilitate the fast acquisition of {sup 1}H/{sup 1}H correlation spectrum compared to the traditional 2D NOESY (Nuclear Overhauser effect spectroscopy) experiment. We believe that the proposed approach is beneficial to study mobile components in multi-phase systems, such as block copolymers, polymer blends, nanocomposites, heterogeneous amyloid mixture of oligomers and fibers, and other materials.

  15. An Orbital-free Molecular Dynamics Study of Static and Dynamic Properties of Liquid Sn

    Directory of Open Access Journals (Sweden)

    González D.J.

    2011-05-01

    Full Text Available The static and dynamic properties of liquid Sn at two different thermodynamic states have been studied from the Orbital Free Ab-Initio Molecular Dynamics (OFAIMD simulation method. This method is based on the density functional theory (DFT of Hohenberg and Kohn. The exchange and correlation interaction is described here with the local density approximation (LDA. We, in this study, have developed a pseudopotential model to describe the external non-Coulombic interaction acting on an electron; this is an essential ingredient of the theory. We have studied several static and dynamic properties of the system. The calculated results are found to be good in agreement with the available experimental data. They are also found to be of similar accuracy as those of other ab-initio studies.

  16. Accelerating Wave Function Convergence in Interactive Quantum Chemical Reactivity Studies

    CERN Document Server

    Mühlbach, Adrian H; Reiher, Markus

    2015-01-01

    The inherently high computational cost of iterative self-consistent-field (SCF) methods proves to be a critical issue delaying visual and haptic feedback in real-time quantum chemistry. In this work, we introduce two schemes for SCF acceleration. They provide a guess for the initial density matrix of the SCF procedure generated by extrapolation techniques. SCF optimizations then converge in fewer iterations, which decreases the execution time of the SCF optimization procedure. To benchmark the proposed propagation schemes, we developed a test bed for performing quantum chemical calculations on sequences of molecular structures mimicking real-time quantum chemical explorations. Explorations of a set of six model reactions employing the semi-empirical methods PM6 and DFTB3 in this testing environment showed that the proposed propagation schemes achieved speedups of up to thirty percent as a consequence of a reduced number of SCF iterations.

  17. Accelerating Wave Function Convergence in Interactive Quantum Chemical Reactivity Studies.

    Science.gov (United States)

    Mühlbach, Adrian H; Vaucher, Alain C; Reiher, Markus

    2016-03-01

    The inherently high computational cost of iterative self-consistent field (SCF) methods proves to be a critical issue delaying visual and haptic feedback in real-time quantum chemistry. In this work, we introduce two schemes for SCF acceleration. They provide a guess for the initial density matrix of the SCF procedure generated by extrapolation techniques. SCF optimizations then converge in fewer iterations, which decreases the execution time of the SCF optimization procedure. To benchmark the proposed propagation schemes, we developed a test bed for performing quantum chemical calculations on sequences of molecular structures mimicking real-time quantum chemical explorations. Explorations of a set of six model reactions employing the semi-empirical methods PM6 and DFTB3 in this testing environment showed that the proposed propagation schemes achieved speedups of up to 30% as a consequence of a reduced number of SCF iterations. PMID:26788887

  18. Chemical and pharmacological studies of the plants from genus Celastrus.

    Science.gov (United States)

    Su, Xiao-Hui; Zhang, Man-Li; Zhan, Wen-Hong; Huo, Chang-Hong; Shi, Qing-Wen; Gu, Yu-Cheng; Kiyota, Hiromasa

    2009-02-01

    The plants of genus Celastrus, distributed in Asia, have been used as natural insecticides and folk medicines to treat fever, chill, joint pain, edema, rheumatoid arthritis, and bacterial infection in China for a long time. This contribution reviews the chemical constituents, isolated from the plants in genus Celastrus in the past few decades, and their biological activities. The compounds listed are sesquiterpenes (beta-agarofurans), diterpenes, triterpenes, alkaloids, and flavonoids. PMID:19235157

  19. Green strength sustainability: a case study of chemical engineering students

    OpenAIRE

    Avsec, Stanislav; Kaučič, Branko

    2015-01-01

    Green chemistry is a relatively new area of science and technology aimed at improving chemical processes and thereby avoiding negative impacts on human health, safety, and the environment (EHS). It is based on careful selection of raw materials for the production of various products, excluding the use of hazardous substances. The field of green chemistry has received much attention from the scientific and industrial communities in almost every highly industrialized nation. It i...

  20. Dynamics of antibody domains studied by solution NMR.

    Science.gov (United States)

    Vu, Bang K; Walsh, Joseph D; Dimitrov, Dimiter S; Ishima, Rieko

    2009-01-01

    Information on local dynamics of antibodies is important to evaluate stability, to rationally design variants, and to clarify conformational disorders at the epitope binding sites. Such information may also be useful for improved understanding of antigen recognition. NMR can be used for characterization of local protein dynamics at the atomic level through relaxation measurements. Due to the complexity of the NMR spectra, an extensive use of this method is limited to small protein molecules, for example, antibody domains and some scFv. Here, we describe a protocol that was used to study the dynamics of an antibody domain in solution using NMR. We describe protein preparation for NMR studies, NMR sample optimization, signal assignments, and dynamics experiments. PMID:19252840

  1. Time-resolved imaging of purely valence-electron dynamics during a chemical reaction

    DEFF Research Database (Denmark)

    Hockett, Paul; Bisgaard, Christer Z.; Clarkin, Owen J.;

    2011-01-01

    such as electron(7-10) or X-ray diffraction(11) and X-ray absorption(12) yield complementary information about the atomic motions. Time-resolved methods that are directly sensitive to both valence-electron dynamics and atomic motions include photoelectron spectroscopy(13-15) and high-harmonic generation(16...

  2. Conformational Sampling by Ab Initio Molecular Dynamics Simulations Improves NMR Chemical Shift Predictions

    Czech Academy of Sciences Publication Activity Database

    Dračínský, Martin; Möller, H. M.; Exner, T. E.

    2013-01-01

    Roč. 9, č. 8 (2013), s. 3806-3815. ISSN 1549-9618 R&D Projects: GA ČR GA13-24880S Institutional support: RVO:61388963 Keywords : ab initio molecular dynamics * NMR spectroscopy * DFT calculations * hydration Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.310, year: 2013

  3. Acceleration of the KINETICS Integrated Dynamical/Chemical Computational Model Using MPI

    Science.gov (United States)

    Grossman, Max; Willacy, Karen; Allen, Mark

    2011-01-01

    Understanding the evolution of a planet's atmosphere not only provides a better theoretical understanding of planetary physics and the formation of planets, but also grants useful insight into Earth's own atmosphere. One of the tools used at JPL for the modeling of planetary atmospheres and protostellar disks is KINETICS. KINETICS can simulate years of complex dynamics and chemistry.

  4. Protonation states and catalysis: Molecular dynamics studies of intermediates in tryptophan synthase.

    Science.gov (United States)

    Huang, Yu-Ming M; You, Wanli; Caulkins, Bethany G; Dunn, Michael F; Mueller, Leonard J; Chang, Chia-En A

    2016-01-01

    The importance of protonation states and proton transfer in pyridoxal 5'-phosphate (PLP)-chemistry can hardly be overstated. Although experimental approaches to investigate pKa values can provide general guidance for assigning proton locations, only static pictures of the chemical species are available. To obtain the overall protein dynamics for the interpretation of detailed enzyme catalysis in this study, guided by information from solid-state NMR, we performed molecular dynamics (MD) simulations for the PLP-dependent enzyme tryptophan synthase (TRPS), whose catalytic mechanism features multiple quasi-stable intermediates. The primary objective of this work is to elucidate how the position of a single proton on the reacting substrate affects local and global protein dynamics during the catalytic cycle. In general, proteins create a chemical environment and an ensemble of conformational motions to recognize different substrates with different protonations. The study of these interactions in TRPS shows that functional groups on the reacting substrate, such as the phosphoryl group, pyridine nitrogen, phenolic oxygen and carboxyl group, of each PLP-bound intermediate play a crucial role in constructing an appropriate molecular interface with TRPS. In particular, the protonation states of the ionizable groups on the PLP cofactor may enhance or weaken the attractions between the enzyme and substrate. In addition, remodulation of the charge distribution for the intermediates may help generate a suitable environment for chemical reactions. The results of our study enhance knowledge of protonation states for several PLP intermediates and help to elucidate their effects on protein dynamics in the function of TRPS and other PLP-dependent enzymes. PMID:26013176

  5. Studying the Complex Dynamics of Family Relationships: A Figurational Approach

    OpenAIRE

    Anna-Maija Castrén; Kaisa Ketokivi

    2015-01-01

    In this paper, we present a figurational approach to studying family relationships drawing from Norbert Elias’s notion of figuration that combines insider and outsider perspectives to complex relational dynamics. In recent discussions on intimacy and personal lives, the family has been viewed as a subset of any personal relationships despite the structural dynamics of, for example, gender and generation that are at play within families. On the other hand, it has been claimed that a family h...

  6. Studies on pressure suppression pool dynamic loads

    International Nuclear Information System (INIS)

    Several newly identified pressure suppression pool hydrodynamic loads associated with a loss-of-coolant accident, or actuation of the safety/relief valves, are attracting attention because of their potential influence on integrity of the BWR pressure suppression containment. This report provides a survey of the research works and experiences on performance of the pressure suppression system during abnormal and normal reactor operating conditions. Specific areas for future studies are also indicated. (author)

  7. Clinical application of cerebral dynamic perfusion studies

    International Nuclear Information System (INIS)

    Radionuclide cerebral perfusion studies are assuming a far greater importance in the detection and differential diagnosis of cerebral lesions. Perfusion studies not only contribute to the differential diagnosis of lesions but in certain cases are the preferred methods by which more accurate clinical interpretations can be made. The characteristic blood flow of arterio-venous malformations readily differentiates this lesion from neoplasms. The decreased perfusion or absent perfusion observed in cerebral infarctions is diagnostic without concurrent evidence from static images. Changes in rates and direction of blood flow contribute fundamental information to the status of stenosis and vascular occlusion and, in addition, offer valuable information on the competency and routes of collateral circulation. The degree of cerebral perfusion after cerebral vascular accidents appears to be directly related to patient recovery, particularly muscular function. Cerebral perfusion adds a new parameter in the diagnosis of subdural haematomas and concussion and in the differentiation of obscuring radioactivity from superficial trauma. Although pictorial displays of perfusion blood flow will offer information in most cerebral vascular problems, the addition of computer analysis better defines temporal relationships of regional blood flow, quantitative changes in flow and the detection of the more subtle increases or decreases in cerebral blood flow. The status of radionuclide cerebral perfusion studies has taken on an importance making it the primary modality for the diagnosis of cerebral lesions. (author)

  8. Physically and chemically stable ionic liquid-infused textured surfaces showing excellent dynamic omniphobicity

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, Daniel F.; Urata, Chihiro; Masheder, Benjamin; Dunderdale, Gary J.; Hozumi, Atsushi, E-mail: a.hozumi@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), 2266-98, Anagahora, Shimo-Shidami, Moriyama-ku, Nagoya, Aichi 463-8560 (Japan); Yagihashi, Makoto [Nagoya Municipal Industrial Research Institute, Rokuban, Atsuta-ku, Nagoya 456-0058 (Japan)

    2014-05-01

    A fluorinated and hydrophobic ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, effectively served as an advantageous lubricating liquid for the preparation of physically and chemically stable omniphobic surfaces based on slippery liquid-infused porous surfaces. Here, we used particulate microstructures as supports, prepared by the chemical vapor deposition of 1,3,5,7-tetramethylcyclotetrasiloxane and subsequent surface modification with (3-aminopropyl)triethoxysilane. Confirmed by SEM and contact angle measurements, the resulting IL-infused microtextured surfaces are smooth and not only water but also various low surface tension liquids can easily slide off at low substrate tilt angles of <5°, even after exposure to high temperature, vacuum, and UV irradiation.

  9. Dynamics of the chemical composition and productivity of composts for the cultivation of Agaricus bisporus strains

    Directory of Open Access Journals (Sweden)

    Meire Cristina Nogueira de Andrade

    2013-12-01

    Full Text Available Two compost formulations based on oat straw (Avena sativa and brachiaria (Brachiaria sp. were tested for the cultivation of three Agaricus bisporus strains (ABI-07/06, ABI-05/03, and PB-1. The experimental design was a 2 x 3 factorial scheme (composts x strains with 6 treatments and 8 repetitions (boxes containing 12 kg of compost. The chemical characterization of the compost (humidity, organic matter, carbon, nitrogen, pH, raw protein, ethereal extract, fibers, ash, cellulose, hemicellulose, and lignin before and after the cultivation of A. bisporus and the production (basidiomata mass, productivity, and biological efficiency were evaluated. Data were submitted to variance analysis, and averages were compared by means of the Tukey's test. According to the results obtained, the chemical and production characteristics showed that the best performances for the cultivation of A. bisporus were presented by the compost based on oat and the strain ABI-07/06.

  10. Attribution of ozone changes to dynamical and chemical processes in CCMs and CTMs

    OpenAIRE

    Garny, H.; Grewe, V.; Dameris, M.; Bodeker, G. E.; Stenke, A.

    2011-01-01

    Chemistry-climate models (CCMs) are commonly used to simulate the past and future development of Earth's ozone layer. The fully coupled chemistry schemes calculate the chemical production and destruction of ozone interactively and ozone is transported by the simulated atmospheric flow. Due to the complexity of the processes acting on ozone it is not straightforward to disentangle the influence of individual processes on the temporal development of ozone concentrations. A method is introduced ...

  11. Attribution of ozone changes to dynamical and chemical processes in CCMs and CTMs

    OpenAIRE

    Garny, Hella; Grewe, Volker; Dameris, Martin; Bodeker, Greg; Stenke, Andrea

    2011-01-01

    Chemistry-climate models (CCMs) are commonly used to simulate the past and future development of Earth’s ozone layer. The fully coupled chemistry schemes calculate the chemical production and destruction of ozone interactively and ozone is transported by the simulated atmospheric flow. Due to the complexity of the processes acting on ozone it is not straightforward to disentangle the influence of individual processes on the temporal development of ozone concentrations. A method is intro...

  12. Modelling chemical composition in electric systems ? implications to the dynamics of dye-sensitised solar cells

    OpenAIRE

    Kovanen, T.; Tarhasaari, T.; Kettunen, L.; Korppi-Tommola, J.

    2010-01-01

    Abstract Classical electromagnetism provides limited means to model electric generators. To extend the classical theory in this respect, additional information on microscopic processes is required. In semiconductor devices and electrochemical generators such information may be obtained by modelling chemical composition. Here we use this approach for the modelling of dye-sensitised solar cells. We simulate the steady-state current-voltage characteristics of such a cell, as well as i...

  13. Nonlinear Stochastic Dynamics of Complex Systems, I: A Chemical Reaction Kinetic Perspective with Mesoscopic Nonequilibrium Thermodynamics

    OpenAIRE

    Qian, Hong

    2016-01-01

    We distinguish a mechanical representation of the world in terms of point masses with positions and momenta and the chemical representation of the world in terms of populations of different individuals, each with intrinsic stochasticity, but population wise with statistical rate laws in their syntheses, degradations, spatial diffusion, individual state transitions, and interactions. Such a formal kinetic system in a small volume $V$, like a single cell, can be rigorously treated in terms of a...

  14. Dynamics of the chemical composition and productivity of composts for the cultivation of Agaricus bisporus strains

    OpenAIRE

    Meire Cristina Nogueira de Andrade; João Paulo Furlan de Jesus; Fabrício Rocha Vieira; Sthefany Rodrigues Fernandes Viana; Marta Helena Fillet Spoto; Marli Teixeira de Almeida Minhoni

    2014-01-01

    Two compost formulations based on oat straw (Avena sativa) and brachiaria (Brachiaria sp.) were tested for the cultivation of three Agaricus bisporus strains (ABI-07/06, ABI-05/03, and PB-1). The experimental design was a 2 x 3 factorial scheme (composts x strains) with 6 treatments and 8 repetitions (boxes containing 12 kg of compost). The chemical characterization of the compost (humidity, organic matter, carbon, nitrogen, pH, raw protein, ethereal extract, fibers, ash, cellulose, hemicellu...

  15. Dynamics of transient metastable states in mixtures under coupled phase ordering and chemical demixing

    OpenAIRE

    Soulé, Ezequiel R.; Rey, Alejandro D.

    2013-01-01

    We present theory and simulation of simultaneous chemical demixing and phase ordering in a polymer-liquid crystal mixture in conditions where isotropic-isotropic phase separation is metastable with respect to isotropic-nematic phase transition. In the case the mechanism is nucleation and growth, it is found that mesophase growth proceeds by a transient metastable phase that surround the ordered phase, and whose lifetime is a function of the ratio of diffusional to orientational mobilities. In...

  16. ALTERNATIVE AND ENHANCED CHEMICAL CLEANING: BASIC STUDIES RESULTS FY2010

    Energy Technology Data Exchange (ETDEWEB)

    King, W.; Hay, M.

    2011-01-24

    In an effort to develop and optimize chemical cleaning methods for the removal of sludge heels from High Level Waste tanks, solubility tests have been conducted using nonradioactive, pure metal phases. The metal phases studied included the aluminum phase gibbsite and the iron phases hematite, maghemite, goethite, lepidocrocite, magnetite, and wustite. Many of these mineral phases have been identified in radioactive, High Level Waste sludge at the Savannah River and Hanford Sites. Acids evaluated for dissolution included oxalic, nitric, and sulfuric acids and a variety of other complexing organic acids. The results of the solubility tests indicate that mixtures of oxalic acid with either nitric or sulfuric acid are the most effective cleaning solutions for the dissolution of the primary metal phases in sludge waste. Based on the results, optimized conditions for hematite dissolution in oxalic acid were selected using nitric or sulfuric acid as a supplemental proton source. Electrochemical corrosion studies were also conducted (reported separately; Wiersma, 2010) with oxalic/mineral acid mixtures to evaluate the effects of these solutions on waste tank integrity. The following specific conclusions can be drawn from the test results: (1) Oxalic acid was shown to be superior to all of the other organic acids evaluated in promoting the dissolution of the primary sludge phases. (2) All iron phases showed similar solubility trends in oxalic acid versus pH, with hematite exhibiting the lowest solubility and the slowest dissolution. (3) Greater than 90% hematite dissolution occurred in oxalic/nitric acid mixtures within one week for two hematite sources and within three weeks for a third hematite sample with a larger average particle size. This dissolution rate appears acceptable for waste tank cleaning applications. (4) Stoichiometric dissolution of iron phases in oxalic acid (based on the oxalate concentration) and the formation of the preferred 1:1 Fe to oxalate complex

  17. Dynamics of Peer Grading: An Empirical Study

    OpenAIRE

    Alfaro, L; Shavlovsky, M

    2016-01-01

    Peer grading is widely used in MOOCs and in standard university settings. The quality of grades obtained via peer grading is essential for the educational process. In this work, we study the factors that influence errors in peer grading. We analyze 288 assignments with 25,633 submissions and 113,169 reviews conducted with CrowdGrader, a web based peer grading tool. First, we found that large grading errors are generally more closely correlated with hard-to-grade submission, rather than ...

  18. Atomistic Mechanisms of Chemical Mechanical Polishing of a Cu Surface in Aqueous H2O2: Tight-Binding Quantum Chemical Molecular Dynamics Simulations.

    Science.gov (United States)

    Kawaguchi, Kentaro; Ito, Hiroshi; Kuwahara, Takuya; Higuchi, Yuji; Ozawa, Nobuki; Kubo, Momoji

    2016-05-11

    We applied our original chemical mechanical polishing (CMP) simulator based on the tight-binding quantum chemical molecular dynamics (TB-QCMD) method to clarify the atomistic mechanism of CMP processes on a Cu(111) surface polished with a SiO2 abrasive grain in aqueous H2O2. We reveal that the oxidation of the Cu(111) surface mechanically induced at the friction interface is a key process in CMP. In aqueous H2O2, in the first step, OH groups and O atoms adsorbed on a nascent Cu surface are generated by the chemical reactions of H2O2 molecules. In the second step, at the friction interface between the Cu surface and the abrasive grain, the surface-adsorbed O atom intrudes into the Cu bulk and dissociates the Cu-Cu bonds. The dissociation of the Cu-Cu back-bonds raises a Cu atom from the surface that is mechanically sheared by the abrasive grain. In the third step, the raised Cu atom bound to the surface-adsorbed OH groups is removed from the surface by the generation and desorption of a Cu(OH)2 molecule. In contrast, in pure water, there are no geometrical changes in the Cu surface because the H2O molecules do not react with the Cu surface, and the abrasive grain slides smoothly on the planar Cu surface. The comparison between the CMP simulations in aqueous H2O2 and pure water indicates that the intrusion of a surface-adsorbed O atom into the Cu bulk is the most important process for the efficient polishing of the Cu surface because it induces the dissociation of the Cu-Cu bonds and generates raised Cu atoms that are sheared off by the abrasive grain. Furthermore, density functional theory calculations show that the intrusion of the surface-adsorbed O atoms into the Cu bulk has a high activation energy of 28.2 kcal/mol, which is difficult to overcome at 300 K. Thus, we suggest that the intrusion of surface-adsorbed O atoms into the Cu bulk induced by abrasive grains at the friction interface is a rate-determining step in the Cu CMP process. PMID:27092706

  19. Bandwidth Study on Energy Use and Potential Energy Saving Opportunities in U.S. Chemical Manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Sabine Brueske, Caroline Kramer, Aaron Fisher

    2015-06-01

    Energy bandwidth studies of U.S. manufacturing sectors can serve as foundational references in framing the range (or bandwidth) of potential energy savings opportunities. This bandwidth study examines energy consumption and potential energy savings opportunities in U.S. chemical manufacturing. The study relies on multiple sources to estimate the energy used in the production of 74 individual chemicals, representing 57% of sector-wide energy consumption. Energy savings opportunities for individual chemicals and for 15 subsectors of chemicals manufacturing are based on technologies currently in use or under development; these potential savings are then extrapolated to estimate sector-wide energy savings opportunity.

  20. Tracking chemicals in products around the world: introduction of a dynamic substance flow analysis model and application to PCBs.

    Science.gov (United States)

    Li, Li; Wania, Frank

    2016-09-01

    Dynamically tracking flows and stocks of problematic chemicals in products (CiPs) in the global anthroposphere is essential to understanding their environmental fates and risks. The complex behavior of CiPs during production, use and waste disposal makes this a challenging task. Here we introduce and describe a dynamic substance flow model, named Chemicals in Products - Comprehensive Anthropospheric Fate Estimation (CiP-CAFE), which facilitates the quantification of time-variant flows and stocks of CiPs within and between seven interconnected world regions and the generation of global scale emission estimates. We applied CiP-CAFE to polychlorinated biphenyls (PCBs), first to evaluate its ability to reproduce previously reported global-scale atmospheric emission inventories and second to illustrate its potential applications and merits. CiP-CAFE quantifies the pathways of PCBs during production, use and waste disposal stages, thereby deducing the temporal evolution of in-use and waste stocks and identifying their long-term final sinks. Time-variant estimates of PCB emissions into air, water and soil can be attributed to different processes and be fed directly into a global fate and transport model. By capturing the international movement of PCBs as technical chemicals, and in products and waste, CiP-CAFE reveals that the extent of global dispersal caused by humans is larger than that occurring in the natural environment. Sensitivity analysis indicates that the model output is most sensitive to the PCB production volume and the lifetime of PCB-containing products, suggesting that a shortening of that lifetime is key to reducing future PCB emissions. PMID:27431909

  1. Shear viscosity, bulk viscosity, and relaxation times of causal dissipative relativistic fluid-dynamics at finite temperature and chemical potential

    Science.gov (United States)

    Huang, Xu-Guang; Koide, Tomoi

    2012-09-01

    The microscopic formulas for the shear viscosity η, the bulk viscosity ζ, and the corresponding relaxation times τπ and τΠ of causal dissipative relativistic fluid-dynamics are obtained at finite temperature and chemical potential by using the projection operator method. The non-triviality of the finite chemical potential calculation is attributed to the arbitrariness of the operator definition for the bulk viscous pressure. We show that, when the operator definition for the bulk viscous pressure Π is appropriately chosen, the leading-order result of the ratio, ζ over τΠ, coincides with the same ratio obtained at vanishing chemical potential. We further discuss the physical meaning of the time-convolutionless (TCL) approximation to the memory function, which is adopted to derive the main formulas. We show that the TCL approximation violates the time reversal symmetry appropriately and leads results consistent with the quantum master equation obtained by van Hove. Furthermore, this approximation can reproduce an exact relation for transport coefficients obtained by using the f-sum rule derived by Kadanoff and Martin. Our approach can reproduce also the result in Baier et al. (2008) [8] by taking into account the next-order correction to the TCL approximation, although this correction causes several problems.

  2. Studies on magnetic dynamics in RFX

    International Nuclear Information System (INIS)

    The RFP configuration is maintained by an intrinsic dynamo mechanism associated to resistive MHD tearing modes. These dynamo modes are responsible for field line stochasticity and have a strong influence on plasma confinement. RFX results relevant to the subject are discussed both in terms of the influence of the magnetic boundary and of the characteristics of the RFP enhanced confinement regimes. The dynamo modes are often locked in phase and to the wall, which spoils the stabilising effect of the conducting shell and leads to severe plasma-wall interactions. The driven rotation of the locked dynamo modes has been studied in RFX by means of a new Toroidal Field Modulation System. A rotating toroidally localised perturbation of the toroidal magnetic field couples to the modes and induces their rotation. (author)

  3. Temperature dependent dynamics of DegP-trimer: A molecular dynamics study

    Directory of Open Access Journals (Sweden)

    Nivedita Rai

    2015-01-01

    Full Text Available DegP is a heat shock protein from high temperature requirement protease A family, which reacts to the environmental stress conditions in an ATP independent way. The objective of the present analysis emerged from the temperature dependent functional diversity of DegP between chaperonic and protease activities at temperatures below and above 28 °C, respectively. DegP is a multimeric protein and the minimal functional unit, DegP-trimer, is of great importance in understanding the DegP pathway. The structural aspects of DegP-trimer with respect to temperature variation have been studied using molecular dynamics simulations (for 100 ns and principal component analysis to highlight the temperature dependent dynamics facilitating its functional diversity. The DegP-trimer revealed a pronounced dynamics at both 280 and 320 K, when compared to the dynamics observed at 300 K. The LA loop is identified as the highly flexible region during dynamics and at extreme temperatures, the residues 46–80 of LA loop express a flip towards right (at 280 and left ( at 320 K with respect to the fixed β-sheet connecting the LA loop of protease for which Phe46 acts as one of the key residues. Such dynamics of LA loop facilitates inter-monomeric interaction with the PDZ1 domain of the neighbouring monomer and explains its active participation when DegP exists as trimer. Hence, the LA loop mediated dynamics of DegP-trimer is expected to provide further insight into the temperature dependent dynamics of DegP towards the understanding of its assembly and functional diversity in the presence of substrate.

  4. Equilibration in Heavy Ion Collisions Studied via Dynamical Fluctuations

    International Nuclear Information System (INIS)

    A novel method to study fluctuations in distributions of reaction products has been applied to investigate the process of chemical and thermal equilibration of nuclear matter in Ru+Ru reaction at 1.69 A GeV. The analysed data were obtained with the FOPI detector. Nontrivial fluctuations of the chemical composition and of transverse momenta, and their dependence on centrality were studied. Fluctuations of pion multiplicity were found to decrease with increasing centrality. This kind of dependence is less evident in the case of proton transversal momentum fluctuations. (author)

  5. Multi-Bunch Beam Dynamics Studies for the European XFEL

    CERN Document Server

    Baboi, N

    2004-01-01

    In the X-ray free electron laser planned to be built at DESY (TESLA XFEL) the acceleration of the electron bunches will be made with 9-cell superconducting cavities. These cavities have been initially developed within the TESLA linear collider study. The impact of the higher order modes (HOM) has been shown to be within the acceptable beam dynamics limits for the collider. For the XFEL the dynamics is relaxed from point of view of multi-bunch effects (e.g. shorter length, higher emittance). However the lower energy and different time structure of the beam make the study of the HOM effects in the XFEL linac necessary. Multi-bunch beam dynamics studies are ongoing. The results of the HOM measurements at the TESLA Test Facility are used. Several options for the beam structure, as necessary for various applications, are studied. The results will be discussed.

  6. An Exploratory Study of The Malaysian Chemical Industry

    OpenAIRE

    Lee, Chun Hooi

    2008-01-01

    With the force of globalization and huge product commoditization pressure in the Business-To-Business (B2B) markets, the B2B marketers have turn their attention to branding in order to tap the brand potential from their product and corporate name. The main objective of this dissertation is to explore the industrial brand value and B2B brand equity in the context of the Malaysian chemical industry. The industrial brand value is explored by using the pinwheel model proposed by Mudambi et al (19...

  7. Fundamental studies of chemical vapor deposition diamond growth processes

    International Nuclear Information System (INIS)

    We are developing laser spectroscopic techniques to foster a fundamental understanding of diamond film growth by hot filament chemical vapor deposition (CVD). Several spectroscopic techniques are under investigation to identify intermediate species present in the bulk reactor volume, the thin active volume immediately above the growing film, and the actual growing surface. Such a comprehensive examination of the overall deposition process is necessary because a combination of gas phase and surface chemistry is probably operating. Resonantly enhanced multiphoton ionization (REMPI) techniques have been emphasized. A growth rector that permits through-the-substrate gas sampling for REMPI/time-of-flight mass spectroscopy has been developed. 7 refs., 2 figs

  8. [Study on chemical constituents of Drosera peltata var. multisepala].

    Science.gov (United States)

    Li, Lin; Huang, Jin; Xu, Xianghua; Zhang, Yao; Cheng, Kejun; Yu, Peizhong

    2012-01-01

    Chemical investigatation of Drosera peltata var. multisepala led to the isolation of eleven compounds using various chromatographic techniques. The structures of these compounds were elucidated as isoshinanolone-4-O-beta-D-glucoside (1), isoshinanolone (2), epi-isoshinanolone (3), plumbagin (4), droserone (5), droserone-5-O-glucoside (6), quercetin (7), kaempferol (8) , gossypetin-8-O-glucoside (9), 3,3'-dimethoxy ellagic acid (10), and ellagic acid (11) by their physicochemical properties and spectral data analysis. Compound 1 was a new compound. Compounds 3, 8, 10, and 11 were isolated from this plant for the first time. PMID:22737855

  9. Physico-chemical studies on samarium soaps in solid state

    International Nuclear Information System (INIS)

    The physico-chemical characteristics of samarium soaps (caproate and caprate) in solid state were investigated by IR, X-ray diffraction and TGA measurements. The IR results revealed that the fatty acids exist in dimeric state through hydrogen bonding and samarium soaps possess partial ionic character. The X-ray diffraction measurements were used to calculate the long spacings and the results confirmed the double layer structure of samarium soaps. The decomposition reaction was found kinetically of zero order and the values of energy of activation for the decomposition process for caproate and caprate were found to be 8,0 and 7,8 kcal mol-1, respectively. (Authors)

  10. Collagen-curcumin interaction - A physico-chemical study

    Indian Academy of Sciences (India)

    N Nishad Fathima; R Saranya Devi; K B Rekha; Aruna Dhathathreyan

    2009-07-01

    Curcumin is a widely used therapeutic agent with a wide spectrum of biological and physiological applications like wound healing and interacts with the skin protein, collagen. This work reports the effect of curcumin on various physico-chemical properties of collagen. The results suggest that significant changes in viscosity and surface tension occur on collagen interacting with curcumin. Secondary structure analysis using circular dichroism shows that curcumin does not alter the triple helical structure of collagen. Increasing concentration of curcumin resulted in aggregation of the protein. Further, curcumin imparts high level of thermal stability to collagen with shrinkage temperature of collagen increasing from 60 to 90°C.

  11. [Studies on the chemical constitutens of Vicia amoena Fisch].

    Science.gov (United States)

    Wei, F; Yan, W M

    1997-10-01

    One new flavonoide was isolated from Vicia amoena Fisch. On the basis of spectral (UV, MS, NMR) and chemical reactions, it was elucidated to be kaempferol-3-O-beta-D-mannoside, named amoenin(A3). Moreover, five known compounds have been isolated and identified as quercetin, kaempferol, quercetin-3-O-alpha-L-rhamoside, quercetin-3-O-beta-D-glucoside, kaempferol-3, 7-O-alpha-L-dirhamoside. The total flavonoides showed significant effects on inducing hyperlipidemia and increasing micro-blood vessel elasticity. PMID:11596220

  12. Molecular dynamics and quantum mechanics of RNA: Conformational and chemical change we can believe in

    Czech Academy of Sciences Publication Activity Database

    Ditzler, M.A.; Otyepka, M.; Šponer, Jiří; Walter, N.G.

    2010-01-01

    Roč. 43, č. 1 (2010), s. 40-47. ISSN 0001-4842 R&D Projects: GA AV ČR(CZ) IAA400040802; GA MŠk(CZ) LC06030; GA ČR(CZ) GA203/09/1476 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : molecular dynamics * quantum chemistry * RNA Subject RIV: BO - Biophysics Impact factor: 21.840, year: 2010

  13. Experimental Study of Gas Hydrate Dynamics

    Science.gov (United States)

    Fandino, O.; Ruffine, L.

    2011-12-01

    Important quantities of methane and other gases are trapped below the seafloor and in the permafrost by an ice-like solid, called gas hydrates or clathrate hydrates. The latter is formed when water is mixing with different gases at high pressures and low temperatures. Due to a their possible use as a source of energy [1] or the problematic related to flow assurance failure in pipelines [2] the understanding of their processes of formation/destabilisation of these structures becomes a goal for many laboratories research as well as industries. In this work we present an experimental study on the stochastic behaviour of hydrate formation from a bulk phase. The method used here for the experiments was to repeat several time the same hydrate formation procedure and to notice the different from one experiment to another. A variable-volume type high-pressure apparatus with two sapphire windows was used. This device, already presented by Ruffine et al.[3], allows us to perform both kinetics and phase equilibrium measurements. Three initial pressure conditions were considered here, 5.0 MPa, 7.5 MPa and 10.0 MPa. Hydrates have been formed, then allowed to dissociate by stepwise heating. The memory effect has also been investigated after complete dissociation. It turned out that, although the thermodynamics conditions of formation and/or destabilization were reproducible. An attempt to determine the influence of pressure on the nucleation induction time will be discussed. References 1. Sum, A. K.; Koh, C. A.; Sloan, E. D., Clathrate Hydrates: From Laboratory Science to Engineering Practice. Industrial & Engineering Chemistry Research 2009, 48, 7457-7465. 2. Sloan, E. D., A changing hydrate paradigm-from apprehension to avoidance to risk management. Fluid Phase Equilibria 2005, 228, 67-74. 3. Ruffine, L.; Donval, J. P.; Charlou, J. L.; Cremière, A.; Zehnder, B. H., Experimental study of gas hydrate formation and destabilisation using a novel high-pressure apparatus. Marine

  14. Studying Human Dynamics Through Web Analytics

    Science.gov (United States)

    Ramasco, Jose; Goncalves, Bruno

    2008-03-01

    When Tim Berners Lee, a physicist at the European Center for Nuclear Research (CERN) first conceived the World Wide Web (WWW) in 1990 as a way to facilitate the sharing of scientific information and results among the centers different researchers and groups, even the most ingenious of science fiction writers could not have imagined the role it would come to play in the following decades. The increasing ubiquitousness of Internet access and the frequency with which people interact with it raise the possibility of using it to better observe, understand, and even monitor several aspects of human social behavior. Websites with large numbers of frequently returning users, such as search engines, company or university websites, are ideal for this task. The properly anonymized logs detailing the access history to Emory University's website is studied. We find that a small number of users is responsible for a finite fraction of the total activity. A saturation phenomenon is observed where, certain connections age, becoming less attractive to new activity over time. Finally, by measuring the average activity as a function of the day of the week, we find that productivity seems to be higher on Tuesdays and Wednesdays, with Sundays being the least active day.

  15. Effects of chemical structure on the dynamic and static surface tensions of short-chain, multi-arm nonionic fluorosurfactants.

    Science.gov (United States)

    Schuster, Thomas; Krumpfer, Joseph W; Schellenberger, Steffen; Friedrich, Reiner; Klapper, Markus; Müllen, Klaus

    2014-08-15

    Fluorinated surfactants with short perfluoroalkyl chains (R(F)) as potential substitutes for the environmentally questionable, long R(F) systems are presented. Three types of nonionic hydrophilic-fluorophilic amphiphiles are synthesized and evaluated based on surface activity in equilibrated (static) and non-equilibrated (dynamic) states. Furthermore, several mono- and disaccharide-based fluorosurfactants are also examined as potential non-bioaccumulative alternatives. A correlation between the chemical structure and resulting surface properties is made by comparing R(F) length, number and size, alkyl-spacer, and hydrophilic moieties. Based on dynamic and static surface tension experiments, the effects of surfactant structure are summarized to provide a basis for the future design of fluorosurfactants. We have found that surfactants with more perfluorinated chains tend to have a higher surface tension reduction, but typically result in slower dynamic behaviors. Using the presented structural characteristics, surfactants with R(F)<4 can be prepared with static surface tensions as low as 18.1 mN/m or reduce surface tension within milliseconds. PMID:24910063

  16. A Rapid Compression Expansion Machine (RCEM) for studying chemical kinetics: Experimental principle and first applications

    CERN Document Server

    Werler, Marc; Maas, Ulrich

    2016-01-01

    A novel extension of a rapid compression machine (RCM), namely a Rapid Compression Expansion Machine (RCEM), is described and its use for studying chemical kinetics is demonstrated. Like conventional RCMs, the RCEM quickly compresses a fuel/air mixture by pushing a piston into a cylinder; the resulting high temperatures and pressures initiate chemical reactions. In addition, the machine can rapidly expand the compressed gas in a controlled way by pulling the piston outwards again. This freezes chemical activity after a pre-defined reaction duration, and therefore allows a convenient probe sampling and ex-situ gas analysis of stable species. The RCEM therefore is a promising instrument for studying chemical kinetics, including also partially reacted fuel/air mixtures. The setup of the RCEM, its experimental characteristics and its use for studying chemical reactions are outlined in detail. To allow comparisons of RCEM results with predictions of chemical reaction mechanisms, a simple numerical model of the RCE...

  17. A microwave and quantum chemical study of allyltrifluorosilane

    Science.gov (United States)

    Møllendal, H.; Guirgis, G. A.

    2003-04-01

    The structural and conformational properties of allytrifluorsilane, H 2CCH-CH 2-SiF 3, have been explored by microwave (MW) spectroscopy and high-level ab initio and density functional theory quantum chemical calculations. The microwave spectrum was investigated in the 18-62 GHz spectral regions. The a-type R-branch transitions of one conformer were assigned for the ground as well as for 10 vibrationally excited states. The CC-C-Si chain of atoms in this rotamer takes an anti-clinal ('skew') conformation, with a dihedral angle calculated to be 111.6° from the syn-periplanar (0°) conformation. The question whether a CC-C-Si syn-periplanar conformer exists as a high-energy form in the gas phase remains open. In most of the quantum chemical calculations this conformation is predicted to be a transition state. However, in the most advanced calculations (B3LYP/aug-cc-pVTZ level of theory) the syn-periplanar conformer is predicted to be a stable rotamer that is calculated to be 6.5 kJ/mol higher in energy than the anti-clinal form. Since there is no indication in the MW spectrum for the presence of high-energy form(s), it is concluded that the anti-clinal conformer is at least 4 kJ/mol more stable than any other hypothetical rotamer.

  18. Quantum Chemical Study of the Thermochemical Properties of Organophosphorous Compounds.

    Science.gov (United States)

    Khalfa, A; Ferrari, M; Fournet, R; Sirjean, B; Verdier, L; Glaude, P A

    2015-10-22

    Organophosphorous compounds are involved in many toxic compounds such as fungicides, pesticides, or chemical warfare nerve agents. The understanding of the decomposition chemistry of these compounds in the environment is largely limited by the scarcity of thermochemical data. Because of the high toxicity of many of these molecules, experimental determination of their thermochemical properties is very difficult. In this work, standard gas-phase thermodynamic data, i.e., enthalpies of formation (ΔfH298°), standard entropies (S298°), and heat capacities (Cp°(T)), were determined using quantum chemical calculations and more specifically the CBS-QB3 composite method, which was found to be the best compromise between precision and calculation time among high accuracy composite methods. A large number of molecules was theoretically investigated, involving trivalent and pentavalent phosphorus atoms, and C, H, O, N, S, and F atoms. These data were used to propose 83 original groups, used in the semiempirical group contribution method proposed by Benson. Thanks to these latter group values, thermochemical properties of several nerve agents, common pesticides and herbicides have been evaluated. Bond dissociations energies (BDE), useful for the analysis the thermal stability of the compounds, were also determined in several molecules of interest. PMID:26434606

  19. Flow around fishlike shapes studied using multiparticle collision dynamics

    NARCIS (Netherlands)

    Reid, Daniel A.P.; Hildenbrandt, H.; Padding, J.T.; Hemelrijk, C.K.

    2009-01-01

    Empirical measurements of hydrodynamics of swimming fish are very difficult. Therefore, modeling studies may be of great benefit. Here, we investigate the suitability for such a study of a recently developed mesoscale method, namely, multiparticle collision dynamics. As a first step, we confine ours

  20. Building Dynamic Learning Communities: Ten Regional Case Studies.

    Science.gov (United States)

    Tasmania Univ., Launceston (Australia). Centre for Research and Learning in Regional Australia.

    This report presents the second phase of a 4-year study commissioned by the Australian National Training Authority (ANTA) to examine the dynamics of Vocational Education and Training (VET). Ten case studies, most involving rural or indigenous communities, are presented, each illustrating an aspect of VET. Twenty-six findings and implications for…

  1. Interactive computer system for analysis of dynamic renal studies

    International Nuclear Information System (INIS)

    An interactive computer system is described for a small minicomputer to be used in the evaluation of radionuclide scintiscanning studies of renal transplants and other dynamic kidney function studies. The package consists of programs for data acquisition, analysis, and report generation. As an added feature, the program dissociates the kidney view into total kidney, cortical, and medullar components

  2. Impact dynamics of water droplets on chemically modified WOx nanowire arrays

    Science.gov (United States)

    Kwak, Geunjae; Lee, Mikyung; Senthil, Karuppanan; Yong, Kijung

    2009-10-01

    The effects of surface energy on the wetting transition for impinging water droplets were investigated on the chemically modified WOx nanowire surfaces. We could modify the surface energy of the nanowires through chemisorption of alkyltrichlorosilanes with various carbon chain lengths and also by the ultraviolet-enhanced decomposition of self assembled monolayer molecules. Three surface wetting states could be identified through the balance between antiwetting and wetting pressures. This approach establishes a simple strategy for design of the water-repellent surface to impinging droplets.

  3. A ``partitioned leaping'' approach for multiscale modeling of chemical reaction dynamics

    Science.gov (United States)

    Harris, Leonard A.; Clancy, Paulette

    2006-10-01

    We present a novel multiscale simulation approach for modeling stochasticity in chemical reaction networks. The approach seamlessly integrates exact-stochastic and "leaping" methodologies into a single partitioned leaping algorithmic framework. The technique correctly accounts for stochastic noise at significantly reduced computational cost, requires the definition of only three model-independent parameters, and is particularly well suited for simulating systems containing widely disparate species populations. We present the theoretical foundations of partitioned leaping, discuss various options for its practical implementation, and demonstrate the utility of the method via illustrative examples.

  4. Use of the LITEE Lorn Manufacturing Case Study in a Senior Chemical Engineering Unit Operations Laboratory

    Science.gov (United States)

    Abraham, Nithin Susan; Abulencia, James Patrick

    2011-01-01

    This study focuses on the effectiveness of incorporating the Laboratory for Innovative Technology and Engineering Education (LITEE) Lorn Manufacturing case into a senior level chemical engineering unit operations course at Manhattan College. The purpose of using the case study is to demonstrate the relevance of ethics to chemical engineering…

  5. Study on Physical Properties and Chemical Composition of Some Myanmar Gems

    International Nuclear Information System (INIS)

    Physical properties of some Myanmar gems were studied by using refractometer, dichroscope, polariscope, SG test, UV test and microscope. Then, chemical composition were investigated by XRF-technique. After that, gem identification, evaluation, colour improvement were studied according to these physical properties and chemical composition

  6. Cluster fragmentation and cluster beam steering studied by dynamic reaction coordinate and molecular dynamics calculations

    International Nuclear Information System (INIS)

    In this study either cluster fragmentation, using a time-dependent Hartree-Fock formulation, or cluster deposition, based on classical molecular dynamics, have been studied. An exhaustive analysis has been performed on the many parameters acting on the two processes. Fragmentation calculations show a primary dependence on the input energy whereas the interatomic forces play a primary role in deposition. However the central result of this study is the essential agreement between the classical and quantum mechanical calculation

  7. CORRELATION STUDIES BETWEEN PHYSICO-CHEMICAL, CHEMICAL AND NUTRIENT UPTAKES OF PADDY IN PHOSPHORUS RICH VERTISOLS

    OpenAIRE

    V Siva Jyothi; T Giridhara Krishna; P.KAVITHA; Srinivasa Reddy, M.

    2014-01-01

    A field experiment was conducted in paddy having high soil available P vertisols under K.C. Canal ayacut at Regional Agricultural Research Station, Nandyal, Andhra Pradesh. The correlation studies revealed that there exist a positive strong correlation between agronomic characters at different stages with the yield. pH and EC was positively correlate with yield except pH at panicle initiation stage is non significantly correlate with yield. The available nitrogen at tillering (r= 0.446), pani...

  8. Nanoparticle dynamics in the presence and absence of a cellular uptake altering chemical

    International Nuclear Information System (INIS)

    The far-reaching applications of nanoparticles (NPs) in drug delivery, medical imaging, diagnostics, and therapeutics have led to an increased potential for interfacing with a diverse range of biological environments. While metallic NPs such as copper NPs have been explored for their antimicrobial and catalytic properties, they have been shown to induce undesirable toxic effects. Nonetheless, bio modulators may be employed to control this cytotoxicity. Dynasore is a dynamin GTPase inhibitor that has been shown to rapidly and reversibly block clathrin dependent endocytic traffic within minutes of application. Here, we demonstrate that Dynasore can chemically bio-modulate the toxic effects of copper nanoparticles (Cu NPs), but not through reducing Cu NP internalization. In fact, Dynasore seems to possess secondary effects that have been unreported to date. We propose and test three potential mechanisms of cytotoxicity modulation: 1) through changes in agglomeration pattern, 2) through potential quenching of reactive oxygen species (ROS), and 3) through Cu+2 ion chelation. These results have far-reaching implications for understanding the complex interactions that occur at the interface of NPs in biological environments, especially during mechanistic chemical modification strategies.

  9. 3D dynamics of hydrous thermal-chemical plumes in subduction zones

    Science.gov (United States)

    Zhu, G.; Gerya, T.; Yuen, D.; Connolly, J. A. D.

    2009-04-01

    Mantle wedges are identified as sites of intense thermal convection and thermal-chemical Rayleigh-Taylor instabilities ("cold plumes") controlling distribution and intensity of magmatic activity in subduction zones. To investigate 3D hydrous partially molten cold plumes forming in the mantle wedge in response to slab dehydration, we perform 3D petrological-thermomechanical numerical simulations of the intraoceanic one-sided subduction with spontaneously bending retreating slab characterized by weak hydrated upper interface. I3ELVIS code is used which is developed based on multigrid approach combined with marker-in-cell method with conservative finite-difference schemes. We investigated regional 800 km wide and 200 km deep 3D subduction models with variable 200 to 800 km lateral dimension along the trench using uniform numerical staggered grid with 405x101x101 nodal points and up to 50 million markers. Our results show three patterns (roll(sheet)-, zig-zag- and finger-like) of Rayleigh-Taylor instabilities can develop above the subducting slab, which are controlled by effective viscosity of partially molten rocks. Spatial and temporal periodicity of plumes correlate well with that of volcanic activity in natural intraoceanic arcs such as Japan. High laterally variable surface heat flow predicted in the arc region in response to thermal-chemical plumes activity is also consistent with natural observations.

  10. Ozone decay in chemical reactor for ozone-dynamical disintegration of used tyres

    International Nuclear Information System (INIS)

    The ozone decay kinetics in the chemical reactor intended for used tyres disintegration is investigated experimentally and theoretically. Ozone was synthesized in barrierless ozonizers based on the streamer discharge. The chemical reactor for tyres disintegration in the ozone-air environment represents the cylindrical chamber, which feeds from the ozonizer by ozone-air mixture with the specified rate of volume flow, and with known ozone concentration. The output of the used mixture, which rate of volume flow is also known, is carried out through the ozone destructor. As a result of ozone decay in the volume and on the reactor walls, and output of the used mixture from the reactor, the ozone concentration in the reactor depends from time. In the paper, the analytical expression for dependence of ozone concentration in the reactor from time and from the parameters of a problem such as the volumetric feed rate, ozone concentration on the input in the reactor, volume flow rate of the used mixture, the volume of the reactor and the area of its internal surface is obtained. It is shown that experimental results coincide with good accuracy with analytical ones.

  11. TREATMENT TANK CORROSION STUDIES FOR THE ENHANCED CHEMICAL CLEANING PROCESS

    Energy Technology Data Exchange (ETDEWEB)

    Wiersma, B.

    2011-08-24

    Radioactive waste is stored in high level waste tanks on the Savannah River Site (SRS). Savannah River Remediation (SRR) is aggressively seeking to close the non-compliant Type I and II waste tanks. The removal of sludge (i.e., metal oxide) heels from the tank is the final stage in the waste removal process. The Enhanced Chemical Cleaning (ECC) process is being developed and investigated by SRR to aid in Savannah River Site (SRS) High-Level Waste (HLW) as an option for sludge heel removal. Corrosion rate data for carbon steel exposed to the ECC treatment tank environment was obtained to evaluate the degree of corrosion that occurs. These tests were also designed to determine the effect of various environmental variables such as temperature, agitation and sludge slurry type on the corrosion behavior of carbon steel. Coupon tests were performed to estimate the corrosion rate during the ECC process, as well as determine any susceptibility to localized corrosion. Electrochemical studies were performed to develop a better understanding of the corrosion mechanism. The tests were performed in 1 wt.% and 2.5 wt.% oxalic acid with HM and PUREX sludge simulants. The following results and conclusions were made based on this testing: (1) In 1 wt.% oxalic acid with a sludge simulant, carbon steel corroded at a rate of less than 25 mpy within the temperature and agitation levels of the test. No susceptibility to localized corrosion was observed. (2) In 2.5 wt.% oxalic acid with a sludge simulant, the carbon steel corrosion rates ranged between 15 and 88 mpy. The most severe corrosion was observed at 75 C in the HM/2.5 wt.% oxalic acid simulant. Pitting and general corrosion increased with the agitation level at this condition. No pitting and lower general corrosion rates were observed with the PUREX/2.5 wt.% oxalic acid simulant. The electrochemical and coupon tests both indicated that carbon steel is more susceptible to localized corrosion in the HM/oxalic acid environment than

  12. A-minor tertiary interactions in RNA kink-turns. Molecular dynamics and quantum chemical analysis

    Czech Academy of Sciences Publication Activity Database

    Réblová, Kamila; Šponer, Judit E.; Špačková, Naďa; Beššeová, Ivana; Šponer, Jiří

    2011-01-01

    Roč. 115, č. 47 (2011), s. 13897-13910. ISSN 1520-6106 R&D Projects: GA AV ČR(CZ) KJB400040901; GA AV ČR(CZ) IAA400040802; GA ČR(CZ) GD203/09/H046; GA ČR(CZ) GA203/09/1476; GA ČR(CZ) GAP208/10/2302; GA MŠk(CZ) LC06030 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : molecular dynamics * RNA * kink turn Subject RIV: BO - Biophysics Impact factor: 3.696, year: 2011

  13. Adsorption study of copper (II) by chemically modified orange peel

    International Nuclear Information System (INIS)

    An adsorbent, the chemically modified orange peel, was prepared from hydrolysis of the grafted copolymer, which was synthesized by interaction of methyl acrylate with cross-linking orange peel. The presence of poly (acrylic acid) on the biomass surface was verified by infrared spectroscopy (IR), scanning electron microscopy (SEM) and thermogravimetry (TG). Total negative charge in the biomass surface and the zeta potentials were determined. The modified biomass was found to present high adsorption capacity and fast adsorption rate for Cu (II). From Langmuir isotherm, the adsorption capacity for Cu (II) was 289.0 mg g-1, which is about 6.5 times higher than that of the unmodified biomass. The kinetics for Cu (II) adsorption followed the pseudo-second-order kinetics. The adsorbent was used to remove Cu (II) from electroplating wastewater and was suitable for repeated use for more than four cycles.

  14. Groundwater hydrology study of the Ames Chemical Disposal Site

    International Nuclear Information System (INIS)

    The Ames Laboratory Chemical Disposal Site is located in northwestern Ames, Iowa west of Squaw Creek. From 1957 to 1966, Ames Laboratory conducted research to develop processes to separate uranium and thorium from nuclear power fuel and to separate yttrium from neutron shielding sources. The wastes from these processes, which contained both hazardous and radiological components, were placed into nine burial pits. Metal drums, plywood boxes, and steel pails were used to store the wastes. Uranium was also burned on the ground surface of the site. Monitoring wells were placed around the waste burial pits. Groundwater testing in 1993 revealed elevated levels of Uranium 234, Uranium 238, beta and alpha radiation. The north side of the burial pit had elevated levels of volatile organic compounds. Samples in the East Ravine showed no volatile organics; however, they did contain elevated levels of radionuclides. These analytical results seem to indicate that the groundwater from the burial pit is flowing down hill and causing contamination in the East Ravine. Although there are many avenues for the contamination to spread, the focus of this project is to understand the hydrogeology of the East Ravine and to determine the path of groundwater flow down the East Ravine. The groundwater flow data along with other existing information will be used to assess the threat of chemical migration down the East Ravine and eventually off-site. The primary objectives of the project were as follows: define the geology of the East Ravine; conduct slug tests to determine the hydraulic conductivity of both oxidized and unoxidized till; develop a three-dimensional mathematical model using ModIME and MODFLOW to simulate groundwater flow in the East Ravine

  15. Dynamics of IGBT based PWM Converter A Case Study

    Directory of Open Access Journals (Sweden)

    Vijay Shukla

    2012-04-01

    Full Text Available Optimizing the efficiency and dynamics of power converters is a critical tradeoff in power electronics. The increase of switching frequency can improve the dynamics of power converters, but theefficiency may be degraded as well as the switching losses. As power semiconductor devices like diodes, MOSFETS, IGBTs, Thyristors, BJTs have their own characterstics and dynamic responses. It is desired toanalyze and observe the dynamics of different semiconductor devices before they actually employed in the model. Inclusion of different PWM techniques help in the removal of power line interferences like harmonic losses, unwanted ripples, chopped frequencies, spikes. In this paper, we have studied and analyzed the dynamics of IGBT based PWM converter with subjected to different conditions like transient state, steady state feeding the RLC load. Snubber circuits are used to reduce the switching losses. The IGBT based PWM converter reflects the better dynamics with improved efficiency and reduced harmonics as compared to some other power semiconductor devices when FFT is performed and subjected to standard parameterized RLC load understeady state and transient analysis.

  16. Study of beam dynamics at cooler synchrotron TARN-II

    International Nuclear Information System (INIS)

    Several kinds of beam diagnostic instruments, have been developed at cooler-synchrotron TARN-II. These are intended to study beam dynamics at low beam current of several microamperes and then have high sensitivity of good S/N ratio. In addition, the acceleration system, especially low level RF system, has been improved to attain the maximum beam energy. With the successful performance of these instrumentations, the study of beam dynamics are presently being carried out. For example, the synchrotron acceleration of the light ions was achieved up to 220 MeV/u without any beam loss. (author)

  17. Study of dynamics of level of physical preparedness of students.

    Directory of Open Access Journals (Sweden)

    Коvalenko Y.A.

    2010-12-01

    Full Text Available The dynamics of level of physical preparedness of students is studied in the article. A tendency is marked to the decline of level of physical preparedness of students of 1-3 courses. Methodical recommendations are presented on the improvement of the system of organization of physical education of students of the Zaporizhzhya national university. The dynamics of indexes of physical preparedness of students 1, 2, 3 courses of different years of teaching is studied. Principal reasons of decline of level of physical preparedness of students are certain. There are recommendations the department of physical education in relation to physical preparedness of students.

  18. Imaging the impact of chemically inducible proteins on cellular dynamics in vivo.

    Directory of Open Access Journals (Sweden)

    Hon S Leong

    Full Text Available The analysis of dynamic events in the tumor microenvironment during cancer progression is limited by the complexity of current in vivo imaging models. This is coupled with an inability to rapidly modulate and visualize protein activity in real time and to understand the consequence of these perturbations in vivo. We developed an intravital imaging approach that allows the rapid induction and subsequent depletion of target protein levels within human cancer xenografts while assessing the impact on cell behavior and morphology in real time. A conditionally stabilized fluorescent E-cadherin chimera was expressed in metastatic breast cancer cells, and the impact of E-cadherin induction and depletion was visualized using real-time confocal microscopy in a xenograft avian embryo model. We demonstrate the assessment of protein localization, cell morphology and migration in cells undergoing epithelial-mesenchymal and mesenchymal-epithelial transitions in breast tumors. This technique allows for precise control over protein activity in vivo while permitting the temporal analysis of dynamic biophysical parameters.

  19. The chemical dynamics of nanosensors capable of single-molecule detection.

    Science.gov (United States)

    Boghossian, Ardemis A; Zhang, Jingqing; Le Floch-Yin, François T; Ulissi, Zachary W; Bojo, Peter; Han, Jae-Hee; Kim, Jong-Ho; Arkalgud, Jyoti R; Reuel, Nigel F; Braatz, Richard D; Strano, Michael S

    2011-08-28

    Recent advances in nanotechnology have produced the first sensor transducers capable of resolving the adsorption and desorption of single molecules. Examples include near infrared fluorescent single-walled carbon nanotubes that report single-molecule binding via stochastic quenching. A central question for the theory of such sensors is how to analyze stochastic adsorption events and extract the local concentration or flux of the analyte near the sensor. In this work, we compare algorithms of varying complexity for accomplishing this by first constructing a kinetic Monte Carlo model of molecular binding and unbinding to the sensor substrate and simulating the dynamics over wide ranges of forward and reverse rate constants. Methods involving single-site probability calculations, first and second moment analysis, and birth-and-death population modeling are compared for their accuracy in reconstructing model parameters in the presence and absence of noise over a large dynamic range. Overall, birth-and-death population modeling was the most robust in recovering the forward rate constants, with the first and second order moment analysis very efficient when the forward rate is large (>10(-3) s(-1)). The precision decreases with increasing noise, which we show masks the existence of underlying states. Precision is also diminished with very large forward rate constants, since the sensor surface quickly and persistently saturates. PMID:21895176

  20. Risk management and governance of chemicals in articles. Case study textiles

    OpenAIRE

    Assmuth, Timo; HÀkkinen, Piia; Heiskanen, Jaana; Kautto, Petrus; Lindh, PÀivi; Mattila, Tuomas; Mehtonen, Jukka; Saarinen, Kristiina

    2011-01-01

    Chemicals and textiles both arouse great interest and emotions. The risks from chemicals in textiles however have been paid little attention, both from the perspective of human health and even more with regard to the environment. The present case study analyzes risks as well as benefits and other impacts from chemicals associated with consumer textiles, as well as management and governance approaches to deal with the multi-faceted problems involved, in the broader context of product and chemi...

  1. Relativistic second-order dissipative fluid dynamics at finite chemical potential

    Science.gov (United States)

    Jaiswal, Amaresh; Friman, Bengt; Redlich, Krzysztof

    2016-07-01

    We employ a Chapman-Enskog like expansion for the distribution function close to equilibrium to solve the Boltzmann equation in the relaxation time approximation and subsequently derive second-order evolution equations for dissipative charge currentand shear stress tensor for a system of massless quarks and gluons. We use quantum statistics for the phase space distribution functions to calculate the transport coefficients. We show that, the second-order evolution equations for the dissipative charge current and the shear stress tensor can be decoupled. We find that, for large chemical potential, the charge conductivity is small compared to the shear viscosity. Moreover, we demonstrate that the limiting behaviour of the ratio of heat conductivity to shear viscosity is identicalto that obtained for a strongly coupled conformal plasma.

  2. Photo-induced isomerization and chemical reaction dynamics in superfluid helium droplets

    Science.gov (United States)

    Merritt, Jeremy; Douberly, Gary; Miller, Roger

    2008-03-01

    Near threshold photo-induced isomerization and photo-induced chemical reactions have long been sough after as sensitive probes of the underlying potential energy surface. One of the most important questions asked is how the initially bright quantum state couples to the reaction coordinate, and thus relates to energy transfer in general. Helium droplets have now allowed us to stabilize entrance channel clusters behind very small reaction barriers such that vibrational excitation may result in reaction. Through two examples, namely the isomerization of the 2 binary complexes of HF-HCN Douberly et al. PCCP 2005, 7,463, and the induced reaction of the gallium-HCN complex Merritt et al. JPCA 2007, DOI:10.1021/jp074981e we will show how the branching ratios for reaction and predissociation can determined and the influence of the superfluid He solvent.

  3. Inelastic neutron scattering and lattice dynamics studies in complex solids

    Indian Academy of Sciences (India)

    Mala N Rao; R Mittal; Narayani Choudhury; S L Chaplot

    2004-07-01

    At Trombay, lattice dynamics studies employing coherent inelastic neutron scattering (INS) experiments have been carried out at the two research reactors, CIRUS and Dhruva. While the early work at CIRUS involved many elemental solids and ionic molecular solids, recent experiments at Dhruva have focussed on certain superconductors (cuprates and intermetallics), geophysically important minerals (Al2SiO5, ZrSiO4, MnCO3) and layered halides (BaFCl, ZnCl2). In most of the studies, theoretical modelling of lattice dynamics has played a significant role in the interpretation and analysis of the results from experiments. This talk summarises the developments and current activities in the field of inelastic neutron scattering and lattice dynamics at Trombay.

  4. Physiological enhancement of factors in factor analysis of dynamic studies

    International Nuclear Information System (INIS)

    Factor analysis of dynamic radionuclide studies provides their decomposition into the images and time-activity curves corresponding to the underlying dynamic structures. The method is based on the analysis of study variance and on the subsequent differential imaging of its principal components into a simplified factor space. By changing the amount and the composition of the variance processed in the analysis it is possible to enhance the factors that are important for diagnosis while the less important factors can be suppressed. In our report, a short theoretical review of the problem is given and illustrated by the analysis of dynamic cholescintigraphy. It is shown that a suitable choice of region and/or the temporal interval of interest enables the differential evaluation of such intrahepatic compartments, which could not be observed without enhancement. (orig.)

  5. Chemical evolution of the Salton Sea, California: Nutrient and selenium dynamics

    Science.gov (United States)

    Schroeder, R.A.; Orem, W.H.; Kharaka, Y.K.

    2002-01-01

    The Salton Sea is a 1000-km2 terminal lake located in the desert area of southeastern California. This saline (???44 000 mg l-1 dissolved solids) lake started as fresh water in 1905-07 by accidental flooding of the Colorado River, and it is maintained by agricultural runoff of irrigation water diverted from the Colorado River. The Salton Sea and surrounding wetlands have recently acquired substantial ecological importance because of the death of large numbers of birds and fish, and the establishment of a program to restore the health of the Sea. In this report, we present new data on the salinity and concentration of selected chemicals in the Salton Sea water, porewater and sediments, emphasizing the constituents of concern: nutrients (N and P), Se and salinity. Chemical profiles from a Salton Sea core estimated to have a sedimentation rate of 2.3 mm yr-1 show increasing concentrations of OC, N, and P in younger sediment that are believed to reflect increasing eutrophication of the lake. Porewater profiles from two locations in the Sea show that diffusion from bottom sediment is only a minor source of nutrients to the overlying water as compared to irrigation water inputs. Although loss of N and Se by microbial-mediated volatilization is possible, comparison of selected element concentrations in river inputs and water and sediments from the Salton Sea indicates that most of the N (from fertilizer) and virtually all of the Se (delivered in irrigation water from the Colorado River) discharged to the Sea still reside within its bottom sediment. Laboratory simulation on mixtures of sediment and water from the Salton Sea suggest that sediment is a potential source of N and Se to the water column under aerobic conditions. Hence, it is important that any engineered changes made to the Salton Sea for remediation or for transfer of water out of the basin do not result in remobilization of nutrients and Se from the bottom sediment into the overlying water.

  6. Modeling studies of the chemical vapor deposition of boron films from B 2H 6

    Science.gov (United States)

    Lamborn, Daniel R.; Snyder, David W.; Xi, X. X.; Redwing, Joan M.

    2007-02-01

    The effect of growth conditions on the chemical vapor deposition of boron thin films from diborane (B 2H 6) was investigated using a combination of experimental studies and computational fluid dynamics-based reactor modeling. A multi-physics computational model was developed to simulate the thermal-fluid environment in the reactor. The proposed chemistry model incorporated into the simulations includes gas-phase decomposition and formation of B 2H 6 and surface adsorption and reaction of borane (BH 3). The model accurately predicts the experimentally measured temperature and partial pressure dependence of the boron growth rate using the sticking coefficient of BH 3 on the growth surface as the only adjustable parameter in the calculations. The results indicate that at lower growth temperatures (500 °C) the growth rate is limited by mass transfer of BH 3 to the substrate surface. The studies of boron thin film growth are relevant to the deposition of superconducting MgB 2 thin films, in which B 2H 6 is used as the boron precursor.

  7. The interplay between dynamic heterogeneities and structure of bulk liquid water: A molecular dynamics simulation study

    International Nuclear Information System (INIS)

    In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130–350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational relaxation constants, the atomic mean-square displacements, the relaxation of the cross correlation functions between the linear and squared displacements of H and O atoms of each molecule, the tetrahedral order parameter q and, finally, the number of nearest neighbors (NNs) and of hydrogen bonds (HBs) per molecule. Two different potentials are considered: TIP4P-Ew and a model developed in this laboratory for the study of nanoconfined water. The results are similar for the dynamical properties, but are markedly different for the structural characteristics. In particular, for temperatures higher than that of the dynamic crossover between “fragile” (at higher temperatures) and “strong” (at lower temperatures) liquid behaviors detected around 207 K, the rotational relaxation of supercooled water appears to be remarkably homogeneous. However, the structural parameters (number of NNs and of HBs, as well as q) do not show homogeneous distributions, and these distributions are different for the two water models. Another dynamic crossover between “fragile” (at lower temperatures) and “strong” (at higher temperatures) liquid behaviors, corresponding to the one found experimentally at T∗ ∼ 315 ± 5 K, was spotted at T∗ ∼ 283 K and T∗ ∼ 276 K for the TIP4P-Ew and the model developed in this laboratory, respectively. It was detected from the trend of Arrhenius plots of dynamic quantities and from the onset of a further heterogeneity in the rotational relaxation. To our best knowledge, it is the first time that this dynamical crossover is detected in computer simulations of bulk water. On the basis of the simulation results, the possible mechanisms of the

  8. Femtosecond photodissociation dynamics of I studied by ion imaging

    DEFF Research Database (Denmark)

    Larsen, J.J.; Bjerre, N.; Mørkbak, N.J.;

    1998-01-01

    on imaging is employed to analyze the fragments from timed Coulomb explosion studies of femtosecond (fs) molecular dynamics. The technique provides high detection efficiency and direct recording of the two-dimensional velocity of all ionized fragments. We illustrate the approach by studying...... agreement with quantum mechanical wave packet simulations. We discuss the perspectives for extending the studies to photochemical reactions of small polyatomic molecules...

  9. Chemical modification studies of the streptokinase-plasminogen interaction

    International Nuclear Information System (INIS)

    The streptokinase (SK) interaction with human plasminogen (Pg) was investigated by differential chemical modification. In separate experiments, available lysine residues in both free streptokinase and streptokinase in complex with Pg were trace labeled by reaction with high specific activity [3H]-acetic anhydride at a reagent-to-lysine molar ratio of 0.5%. The [3H]-acetyl-SK from the complex was reisolated. Both the free and complex forms of 3H-acetyl-SK were then each mixed with uniformly and quantitatively modified [14C]-acetyl-SK in a 3H/14C isotopic ratio of ten-to-one. Each of the SK forms was fragmented by reaction with CNBr. These CNBr fragments, which were purified by Sephadex G-75 chromatography, were further cleaved by proteases to produce peptides containing a minimum number of lysines. After the isolation of peptides by reversed-phase HPLC, the 3H/14C ratios of lysines were individually determined. By comparison of the 3H/14C ratio's in the free-SK and complex-SK it was found that the majority of lysines did not change its reactivities in free or complex forms. However, several lysines were relatively unreactive in the SK complexed with Pg as compared to that in free SK. This suggests that these residues are either in the complex binding interface or they were less reactive as a result of conformational change induced by complex formation

  10. Study of Chemical Decontamination Process for CRUD Removal

    International Nuclear Information System (INIS)

    Chalk River Unidentified Deposit (CRUD) is a technical term in nuclear engineering which is an accumulated material on external fuel rod cladding surfaces in nuclear power plants. It is a corrosion product which is composed of either dissolved ions or solid particles such as Ni, Fe and Co. It consists mainly of NiO and NiFe2O4. It can affect to reduce fuel lifetime, degrade heat transfer to the coolant, and threaten human health and environment. Therefore, decontamination process is essential for reducing occupational exposures, limiting potential releases and uptakes of radioactive materials, allowing the reuse of components, and facilitating waste management process. In this paper, we have conducted the synthesis of Cobalt ferrite as power foam to use for decontamination process. In dissolution test of Co ferrite and Ni ferrite, oxalic acid shows the most effective chemical decontamination reagent to remove the contaminants. Generally, the dissolved amount of cobalt and nickel increases at low pH condition and as the temperature goes higher, dissolved amount of cobalt and iron are much higher

  11. Study of Chemical Decontamination Process for CRUD Removal

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Seongsik; Kim, Won-Seok; Kim, Jungjin; Um, Wooyong [POSTECH, Pohang (Korea, Republic of)

    2015-05-15

    Chalk River Unidentified Deposit (CRUD) is a technical term in nuclear engineering which is an accumulated material on external fuel rod cladding surfaces in nuclear power plants. It is a corrosion product which is composed of either dissolved ions or solid particles such as Ni, Fe and Co. It consists mainly of NiO and NiFe{sub 2}O{sub 4}. It can affect to reduce fuel lifetime, degrade heat transfer to the coolant, and threaten human health and environment. Therefore, decontamination process is essential for reducing occupational exposures, limiting potential releases and uptakes of radioactive materials, allowing the reuse of components, and facilitating waste management process. In this paper, we have conducted the synthesis of Cobalt ferrite as power foam to use for decontamination process. In dissolution test of Co ferrite and Ni ferrite, oxalic acid shows the most effective chemical decontamination reagent to remove the contaminants. Generally, the dissolved amount of cobalt and nickel increases at low pH condition and as the temperature goes higher, dissolved amount of cobalt and iron are much higher.

  12. Chemical and environmental isotope study of precipitation in Syria

    International Nuclear Information System (INIS)

    Waters from a network of rainfall collection covering mine meteorological stations distributed mainly in the western part of Syria have been assayed using chemical and environmental isotope techniques for a period of 5 months from Dec. 1989 to Apr. 1990. The chemistry of rain waters falling over the mountainous stations shows a low solute concentration (20-105 mg 1-1) compared with those falling over the coastal and anterior stations (50-210 mg 1-1). The rain waters was generally characterized by a high deuterium excess (d=19%) compared with that of typical global meteoric waters (d=10%). The estimated deuterium excess is lower than that for the eastern Mediterranean meteoric waters (d=22%). The altitude effect is shown up by a depletion of heavy stable isotopes of about - 0.23% and -1.65% per 100 m elevation of δ 18O and δD, respectively. The spatial distribution pattern of tritium contents shows a gradual build up with increasing distance from the Syrian coast. The weighted mean tritium content in rain waters falling over the country is estimated to amount to 9.5 tritium units (TU) during the period of observation. (author)

  13. COOEE bitumen: chemical aging

    CERN Document Server

    Lemarchand, Claire A; Dyre, Jeppe C; Hansen, Jesper S

    2013-01-01

    We study chemical aging in "COOEE bitumen" using molecular dynamic simulations. The model bitumen is composed of four realistic molecule types: saturated hydrocarbon, resinous oil, resin, and asphaltene. The aging reaction is modelled by the chemical reaction: "2 resins $\\rightarrow$ 1 asphaltene". Molecular dynamic simulations of four bitumen compositions, obtained by a repeated application of the aging reaction, are performed. The stress autocorrelation function, the fluid structure, the rotational dynamics of the plane aromatic molecules, and the diffusivity of each molecule, are determined for the four different compositions. The aging reaction causes a significant dynamics slowdown, which is correlated to the aggregation of asphaltene molecules in larger and dynamically slower nanoaggregates. Finally, a detailed description of the role of each molecule types in the aggregation and aging processes is given.

  14. Elastic properties of amorphous boron suboxide based solids studied using ab initio molecular dynamics

    International Nuclear Information System (INIS)

    We have studied the correlation between chemical composition, structure, chemical bonding and elastic properties of amorphous B6O based solids using ab initio molecular dynamics. These solids are of different chemical compositions, but the elasticity data appear to be a function of density. This is in agreement with previous experimental observations. As the density increases from 1.64 to 2.38 g cm-3, the elastic modulus increases from 74 to 253 GPa. This may be understood by analyzing the cohesive energy and the chemical bonding of these compounds. The cohesive energy decreases from -7.051 to -7.584 eV/atom in the elastic modulus range studied. On the basis of the electron density distributions, Mulliken analysis and radial distribution functions, icosahedral bonding is the dominating bonding type. C and N promote cross-linking of icosahedra and thus increase the density, while H hinders the cross-linking by forming OH groups. The presence of icosahedral bonding is independent of the density

  15. Molecular Dynamics for Low Temperature Plasma-Surface Interaction Studies

    CERN Document Server

    Graves, David B

    2009-01-01

    The mechanisms of physical and chemical interactions of low temperature plasmas with surfaces can be fruitfully explored using molecular dynamics (MD) simulations. MD simulations follow the detailed motion of sets of interacting atoms through integration of atomic equations of motion, using inter-atomic potentials that can account for bond breaking and formation that result when energetic species from the plasma impact surfaces. This article summarizes the current status of the technique for various applications of low temperature plasmas to material processing technologies. The method is reviewed, and commonly used inter-atomic potentials are described. Special attention is paid to the use of MD in understanding various representative applications, including tetrahedral amorphous carbon film deposition from energetic carbon ions; the interactions of radical species with amorphous hydrogenated silicon films; silicon nano-particles in plasmas; and plasma etching.

  16. C60 molecular dynamics studied by muon spin relaxation

    International Nuclear Information System (INIS)

    In muonium-substituted organic radicals, the muon spin can serve as a probe of molecular dynamics. The motional perturbation induces transitions between the coupled spin states of muon and unpaired electron. Studies of the resultant muon spin relaxation in C60Mu, the species formed by muon implantation in solid C60, yield the correlation time characteristic of the reorientational motion

  17. Dynamic study of the larynx with spiral CT

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Yeon; Choi, Chang Ho; Yoon, Chi Soon; Kim, Yoon Gyoo; Nam, Sang Hwa; Kim, Kun Il; Kim, Byung Soo; Wang, Soo Guen [College of Medicine, Pusan National University, Busan (Korea, Republic of)

    1994-03-15

    It is essential to know the functional and morphologic changes of the larynx in the evaluation of laryngeal lesions. Conventional CT which has relatively long examination time is not suitable for this aim. The purposes of this study are to evaluate the capability of spiral CT in the dynamic study of the larynx and to know whether this new technique can replace conventional laryngography or not. Five healthy volunteers and 20 patients with laryngeal lesions underwent spiral dynamic CT scans with 3-dimensional reconstruction of the mucosal surface. A series of spiral CT scans were done while the volunteers performed various laryngeal positions to obtain the functional and morphologic information. The maneuvers used were: quite breathing, 'E' phonation, Valsalva maneuver, modified Valsalva maneuver, and a new method of our own, 'modified breath holding' technique. The patients were scanned when in quite breathing. Additional scans were obtained by using the 'modified breath holding' technique. The dynamic study with spiral CT could provide high resolutional images which nicely depicted the mobility of vocal cords and the mucosal changes of the laryngeal cavity in both healthy volunteer and patient groups. In patient group, the new 'modified breath holding' technique was easier and more reproducible than other maneuvers. Spiral CT allows a dynamic study of the larynx and can be a new alternative of laryngography.

  18. COMPARISON OF SAMPLING TECHNIQUES USED IN STUDYING LEPIDOPTERA POPULATION DYNAMICS

    Science.gov (United States)

    Four methods (light traps, foliage samples, canvas bands, and gypsy moth egg mass surveys) that are used to study the population dynamics of foliage-feeding Lepidoptera were compared for 10 species, including gypsy moth, Lymantria dispar L. Samples were collected weekly at 12 sit...

  19. Quasi-elastic neutron scattering studies of protein dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Rorschach, H.E.

    1991-03-20

    The techniques of X-ray and neutron scattering that have been so successfully applied to the study of the structure of biological macromolecules have in recent years been also used for the study of the thermal motion of these molecules. The diffraction of X-rays has been widely used to investigate the high-frequency motion of the heavy-atom residues of proteins. In these studies, the mean-square thermal amplitudes can be determined from the intensities of the sharp structural lines obtained from single crystals of the hydrated proteins. Similar information can be obtained on lighter atoms from the study of the neutron scattering from single crystals. The results of these measurements are coupled closely to the rapidly developing field of theoretical molecular dynamics which is now being applied to study the dynamics of large biological molecules. This report discusses research in this area.

  20. Experimental study of chemical embolus therapy combined with radiotherapy for VX2 bone tumors

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Hiroshi; Mochizuki, Kazuo; Ishii, Yoshiaki [Kyorin Univ., Mitaka, Tokyo (Japan). School of Medicine

    2000-12-01

    We conducted an experimental study, using a combination of coarse crystal cisplatin and radiotherapy for bone tumors, to evaluate the possibility of the clinical application of chemical embolus therapy in the field of orthopedic surgery. Experimental femoral bone tumors were produced, in rabbits, using VX2 carcinoma. The rabbits were allocated to five groups: untreated control, embolus, chemical embolus, irradiation alone, and chemical embolus and irradiation combination. These therapies were evaluated comparatively, in terms of local antitumor effects (including body weight, X-ray findings, angiography, and histopathology) and in terms of inhibition of pulmonary metastasis. Local antitumor effects, as evaluated by all parameters, except for body weight, were significantly greater for the chemical and irradiation combination group than for the chemical embolus, irradiation alone, untreated control, and embolus groups. There was no significant difference in the inhibition of pulmonary metastasis among the chemical embolus and irradiation combination, chemical embolus, and irradiation alone groups. These findings demonstrated the synergistic effect of the combination of chemical embolus therapy and radiotherapy. In this study, however, no significant difference was found between the chemical embolus therapy alone and the combination therapy groups in the inhibitory effect on pulmonary tumor metastasis, suggesting the need to conduct combination therapy repeatedly in the clinical setting. (author)