WorldWideScience

Sample records for chemical dynamics studies

  1. Studies in Chemical Dynamics

    International Nuclear Information System (INIS)

    Rabitz, Herschel; Ho, Tak-San

    2003-01-01

    This final report draws together the research carried from February, 1986 through January, 2003 concerning a series of topics in chemical dynamics. The specific areas of study include molecular collisions, chemical kinetics, data inversion to extract potential energy surfaces, and model reduction of complex kinetic systems

  2. Studies in chemical dynamics

    International Nuclear Information System (INIS)

    Kuppermann, A.

    1978-01-01

    Progress made in the following studies is reported: low-energy electron scattering; variable-angle photoelectron spectroscopy; laser photochemistry and spectroscopy; and collisions in crossed molecular beams

  3. 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.

  4. 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...

  5. 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.

  6. Gas-Phase Molecular Dynamics: Theoretical Studies in Spectroscopy and Chemical Dynamics

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-06-01

    The 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.

  7. Photocatalytic oxidation dynamics of acetone on TiO2: tight-binding quantum chemical molecular dynamics study

    International Nuclear Information System (INIS)

    Lv Chen; Wang Xiaojing; Agalya, Govindasamy; Koyama, Michihisa; Kubo, Momoji; Miyamoto, Akira

    2005-01-01

    The clarification of the excited states dynamics on TiO 2 surface is important subject for the design of the highly active photocatalysts. In the present study, we applied our novel tight-binding quantum chemical molecular dynamics method to the investigation on the photocatalytic oxidation dynamics of acetone by photogenerated OH radicals on the hydrated anatase TiO 2 surface. The elucidated photocatalytic reaction mechanism strongly supports the previous experimental proposal and finally the effectiveness of our new approach for the clarification of the photocatalytic reaction dynamics employing the large simulation model was confirmed

  8. Catalytic performances of chemically immobilized urease under static and dynamic conditions: A comparative study

    OpenAIRE

    Yürekli, Yılmaz; Alsoy Altınkaya, Sacide

    2011-01-01

    Immobilized urease has been used for direct removal of urea from aqueous solution and as biological sensing material in the preparation of urea biosensors. The former application is carried out under dynamic condition using ultrafiltration membrane either in tubular form or in flat sheet, while the latter is used in static condition. In this study, the performance of chemically immobilized urease on poly(acrylonitrile-co-sodium methallyl sulfonate) ultrafiltration membrane was determined unde...

  9. Initial Chemical Events in CL-20 Under Extreme Conditions: An Ab Initio Molecular Dynamics Study

    National Research Council Canada - National Science Library

    Isaev, Olexandr; Kholod, Yana; Gorb, Leonid; Qasim, Mohammad; Fredrickson, Herb; Leszczynski, Jerzy

    2006-01-01

    .... In the present study molecular structure, electrostatic potential, vibrational spectrum and dynamics of thermal decomposition of CL-20 have been investigated by static and dynamic methods of ab...

  10. 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.

  11. Vacuum ultraviolet beamline at the Swiss Light Source for chemical dynamics studies

    International Nuclear Information System (INIS)

    Johnson, Melanie; Bodi, Andras; Schulz, Lothar; Gerber, Thomas

    2009-01-01

    A bend-magnet vacuum ultraviolet (VUV) beamline, intended for chemical dynamics studies, was constructed and brought into operation at the Swiss Light Source (SLS) of the Paul Scherrer Institut. The beamline delivers synchrotron radiation in the 5-30 eV photon energy range with a photon flux of 10 11 photons/s at 10 eV and 10 12 photons/s at 20 eV with a resolving power of 2500. The resolving power increases to 10 4 at the cost of photon flux. An in-house designed rare gas filter is used to suppress higher harmonic radiation by a factor of >10 4 , yielding purely monochromatic light in the energy range of 5-21.6 eV. The filter is compact, easy to align, requires a total pumping power of less than 645 l/s and consumes only 3 normal l/h of filter gas. It is located at the end of the beamline, right in front of the experimental endstation. It is usually operated at a higher pressure than the endstation, which offers the additional benefit of protecting the beamline vacuum from sample contamination.

  12. Intra- und intermolecular hydrogen bonds. Spectroscopic, quantum chemical and molecular dynamics studies

    International Nuclear Information System (INIS)

    Simperler, A.

    1999-03-01

    Intra- and intermolecular H-bonds have been investigated with spectroscopic, quantum chemical, and molecular dynamics methods. The work is divided into the following three parts: 1. Intramolecular interactions in ortho-substituted phenols. Theoretical and experimental data that characterizes the intramolecular hydrogen bonds in 48 different o-substituted phenols are discussed. The study covers various kinds of O-H ... Y -type interactions (Y= N, O, S, F, Cl, Br, I, C=C, C=-C, and C-=N). The bond strength sequences for several series of systematically related compounds as obtained from IR spectroscopy data (i.e., v(OH) stretching frequencies) are discussed and reproduced with several theoretical methods (B3LYP/6-31G(d,p), B3LYP/6-311G(d,p), B3LYP/6-31++G(d,p), B3LYP/DZVP, MP2/6-31G(d,p), and MP2/6-31++G(d,p) levels of theory). The experimentally determined sequences are interpreted in terms of the intrinsic properties of the molecules: hydrogen bond distances, Mulliken partial charges, van der Waals radii, and electron densities of the Y-proton acceptors. 2. Competitive hydrogen bonds and conformational equilibria in 2,6-disubstituted phenols containing two different carbonyl substituents. The rotational isomers of ten unsymmetrical 2,6-disubstituted phenols as obtained by combinations of five different carbonyl substituents (COOH, COOCH 3 , CHO, COCH 3 , and CONH 2 ) have been theoretically investigated at the B3LYP/6-31G(d,p) level of theory. The relative stability of four to five conformers of each compound were determined by full geometry optimization for free molecules as well as for molecules in reaction fields with dielectric constants up to ε=37.5. A comparison with IR spectroscopic data of available compounds revealed excellent agreement with the theoretically predicted stability sequences and conformational equilibria. The stability of a conformer could be interpreted to be governed by the following two contributions: (i) an attractive hydrogen bond

  13. 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.

  14. Chemical Dynamics at the Advanced Light Source

    International Nuclear Information System (INIS)

    Baer, T.; Berrah, N.; Fadley, C.; Moore, C.B.; Neumark, D.M.; Ng, C.Y.; Ruscic, B.; Smith, N.V.; Suits, A.G.; Wodtke, A.M.

    1999-01-01

    A day-long retreat was held January 15, 1999 to chart the future directions for chemical dynamics studies at the Advanced Light Source. This represents an important period for the Chemical Dynamics Beamline, as the hardware is well-developed, most of the initial experimental objectives have been realized and the mission is now to identify the future scientific priorities for the beamline and attract users of the highest caliber. To this end, we have developed a detailed scientific program for the near term; identified and prioritized the long range scientific opportunities, identified essential new hardware, and outlined an aggressive outreach program to involve the chemical physics community

  15. Moessbauer spectroscopy-nuclear hyperfine technique for studying dynamic chemical states of iron complexes

    International Nuclear Information System (INIS)

    Maeda, Y.

    2005-01-01

    A brief introduction of Moessbauer spectroscopy will be presented, followed by a discussion of the Moessbauer parameters, isomer shifts, quadrupole splittings, and spectral shapes of complexes in the presence of relaxation of the electronic states of the iron atoms. The usefulness of Moessbauer spectroscopy to demonstrate the dynamic phenomena of electronic states will be discussed in this lecture. (1) The Moessbauer spectra of mixed valence dinuclear and trinuclear iron complexes will be discussed in connection with the chemical structure of the complexes: The values of the quadrupole splittings and isomer shifts of [Fe II Fe III (bpmp) (ppa) 2 ](BF 4 ) 2 increase on raising the temperature, where Hbpmp represents 2,6-bis[bis(2- pyridylmethyl)aminoethyl]-4-methylphenol and ppa is 3-n-phenylpropionic acid. The spectra can be accounted for by postulating intramolecular electron exchange between two energetically inequivalent vibronic states Fe A 2+ Fe B 3+ and Fe A 3+ Fe B 2+ : The apparent time averaged valence states of the iron atoms are 2.2 and 2.8 on the Moessbauer time scale at 293 K. (2) The Moessbauer spectra of iron(III) spin-crossover complexes will be discussed in connection with the spin-transition rate and chemical structure of the complexes. The Moessbauer spectra of spin-crossover iron(III) complexes with LIESST (Light Induced Electronic Spin-State Transition) and of metallomesogens will be discussed to illustrate the extension of this research area by the use of Moessbauer spectroscopy.

  16. 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.

  17. 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.

  18. Chemical structure and dynamics: Annual report 1996

    International Nuclear Information System (INIS)

    Colson, S.D.; McDowell, R.S.

    1997-03-01

    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 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.

  20. 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)

    Bankura, Arindam; Chandra, Amalendu

    2012-01-01

    Highlights: ► A theoretical study of hydroxide ion-water clusters is carried for varying cluster size and temperature. ► The structures of OH − (H 2 O) 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 − (H 2 O) 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.

  1. Ultrafast infrared studies of chemical reaction dynamics in room-temperature liquids

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Haw [Univ. of California, Berkeley, CA (United States)

    1999-11-01

    Femtosecond infrared spectroscopy provides sufficient spectral and temporal resolution to support a detailed investigation of the early events of a photochemical reaction. Previously unreported transient species that arise as intermediates during the course of a reaction may have lifetimes that are too short for conventional characterization. For these species, quantum-mechanical (density functional theoretical and ab initio) electronic structure calculations provide invaluable insight into chemical properties including molecular structure and energetic. With the combination of experimental and theoretical results, it is possible to assemble a comprehensive picture of the reaction dynamics of a system that is intricately influenced by the surrounding solvent molecules. The mechanisms of several important organometallic reactions, such as alkane C– H bond activation by η3-Tp*Rh(CO), silane Si–H bond activation by η5-CpMn(CO)2 and η5-CpRe(CO)2, as well as chlorinated methane C–Cl bond cleavage by the Re(CO)5 radical are elucidated. The results demonstrate the importance of molecular morphology change (C–H and Si–H act ivat ion), solvent rearrangement (Si–H activation), intersystem crossing (Si–H activation), and solvent caging (C–Cl cleavage) in understanding the reactivity of the organometallic species, The nature of the apparent free-energy barrier for C–H, Si–H, and C–Cl bond activation reaction is found to be- cleavage of an alkane C–H bond, rearrangement of a silane molecule HSiR3 (R = alkyl group) from a nonreactive alkyl site to the reactive Si–H bond, and Cl atom transfer from a chlorinated methane molecule to Re(CO)5, respectively. These results support previous d initio calculations for C–H and Si–H bond activation reaction profiles which suggest that cleavage of an alkane C–H bond by a transition metal center, unlike that of a silane

  2. Amorphization induced by chemical disorder in crystalline NiZr2: A molecular-dynamics study based on an n-body potential

    International Nuclear Information System (INIS)

    Massobrio, C.; Pontikis, V.; Martin, G.

    1989-01-01

    We present the first molecular-dynamics study of the amorphization of a crystalline alloy (NiZr 2 ) induced by chemical disorder. We used a n-body potential in conjunction with isobaric-isothermal molecular dynamics. The behavior of the pair distribution function suggests that the instability leading to the amorphous state is a first-order phase transformation

  3. Chemical Structure and Dynamics annual report 1997

    International Nuclear Information System (INIS)

    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

  4. 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.

  5. Molecular dynamics simulation of a chemical reaction

    International Nuclear Information System (INIS)

    Gorecki, J.; Gryko, J.

    1988-06-01

    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

  6. Quantum and classical studies of collisional excitation in H + CO and two other projects in theoretical chemical dynamics

    International Nuclear Information System (INIS)

    Geiger, L.C.

    1985-01-01

    This dissertation is a collection of four projects in theoretical chemical dynamics. In the first two projects collisional excitation in H + CO was studied using the quasiclassical trajectory method and the quantum infinite order sudden approximation (QIOS). Integral cross sections calculated using these methods were found to agree well with experimental and classical IOS results. The trajectory study was also used to examine the effects of potential energy surface features on the dynamics. Two surfaces were examined: a fitted surface based on ab initio points and a global ab initio surface. Next, the quasiclassical trajectory method was used to obtain cross sections and rate constants for O + H 2 → OH + H and analogous deuterium isotope reactions. The results using the Johnson and Winter surface agreed well with those of transition state theory (TST) and experiment, except for O + HD → OH + D. TST rate constants were calculated using an ab initio surface. These results were in poor agreement with calculations using the Johnson and Winter surface. A theory of action-angle variables for coupled oscillator systems was developed in the fourth project

  7. Dynamic Passive Dosing for Studying the Biotransformation of Hydrophobic Organic Chemicals: Microbial Degradation as an Example

    DEFF Research Database (Denmark)

    Smith, Kilian E. C.; Rein, Arno; Trapp, Stefan

    2012-01-01

    Biotransformation plays a key role in hydrophobic organic compound (HOC) fate, and understanding kinetics as a function of (bio)availability is critical for elucidating persistence, accumulation, and toxicity. Biotransformation mainly occurs in an aqueous environment, posing technical challenges...... for producing kinetic data because of low HOC solubilities and sorptive losses. To overcome these, a new experimental approach based on passive dosing is presented. This avoids using cosolvent for introducing the HOC substrate, buffers substrate depletion so biotransformation is measured within a narrow...... also similar for both PAHs, but decreased by around 2 orders of magnitude with increasing dissolved concentrations. Dynamic passive dosing is a useful tool for measuring biotransformation kinetics at realistically low and defined dissolved HOC concentrations....

  8. 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.

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

    Directory of Open Access Journals (Sweden)

    2007-01-01

    Full Text Available 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. 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).

  11. 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.

  12. 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.

  13. 1H NMR study of the solvent THF concerning their structural and dynamical properties in chemically Li-intercalated SWNT

    KAUST Repository

    Schmid, Marc R.; Goze-Bac, Christophe; Bouhrara, Mohamed; Saih, Youssef; Mehring, Michael; Abou-Hamad, Edy

    2011-01-01

    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.

  14. Dynamic chemical characteristics of soil solution after pig manure application: a column study.

    Science.gov (United States)

    Hao, Xiuzhen; Zhou, Dongmei; Sun, Lei; Li, Lianzhen; Zhang, Hailin

    2008-06-01

    When manures from intensive livestock operations are applied to agricultural or vegetable fields at a high rate, large amounts of salts and metals will be introduced into soils. Using a column leaching experiment, this study assessed the leaching potential of the downward movement of Cu and Zn as well as some salt ions after an intensive farm pig manure at rates of 0%, 5% and 10% (w/w) were applied to the top 20 cm of two different textured soils (G soil -sandy loam soil; H soil-silty clay loam soil), and investigated the growth of amaranth and Cu and Zn transfer from soil to amaranth (Amaranthus tricolor). Soil solutions were obtained at 20, 40 and 60 cm depth of the packed column and analyzed for pH, electrical conductivity (EC), dissolved organic matter (DOC) and Cu and Zn concentrations. The results indicated that application of pig manure containing Cu and Zn to sandy loam soil might cause higher leaching and uptake risk than silty clay loam soil, especially at high application rates. And manure amendment at 5% and 10% significantly decreased the biomass of amaranth, in which the salt impact rather than Cu and Zn toxicity from manures played more important role in amaranth growth. Thus the farmer should avoid application the high rate of pig manure containing metal and salt to soil at a time, especially in sandy soil.

  15. molecular dynamics simulations and quantum chemical calculations

    African Journals Online (AJOL)

    ABSTRACT. The molecular dynamic (MD) simulation and quantum chemical calculations for the adsorption of [2-(2-Henicos-10- .... electronic properties of molecule clusters, surfaces and ... The local reactivity was analyzed by determining the.

  16. 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

  17. Molecular-dynamics study of amorphization by introduction of chemical disorder in crystalline NiZr2

    International Nuclear Information System (INIS)

    Massobrio, C.; Pontikis, V.; Martin, G.

    1990-01-01

    By means of constant-temperature, constant-pressure molecular dynamics, we investigate the crystal-to-amorphous transformation of the intermetallic alloy NiZr 2 resulting from the introduction of antisite defects. We constructed an n-body potential in the framework of the second-moment approximation of the tight-binding description of the electronic density of states. This modeling of the interatomic forces is successful in reproducing both static and thermodynamic properties of the real material. The imposition of chemical disorder quantified by the appropriate value of the long-range-order parameter, S, engenders a volume expansion followed by relaxation to a stationary state characterized by lower density and higher potential energy. The behavior of the pair distribution functions, g(r), reveals that amorphization takes place for values of S≤0.6, the corresponding volume expansion being of the order of 2%. Moreover the thermodynamic states obtained by chemical destabilization and rapid quenching from the liquid state are nearly identical. On the time scale of our simulations (10 -10 s), no detectable long-range diffusion of either species follows the introduction of chemical disorder. Some relevant features of the pair distribution functions (first and second peak positions, number of nearest neighbors) are in good agreement with those obtained experimentally from amorphous NiZr 2 samples generated by rapid quenching

  18. 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.

  19. Chemical reaction dynamics using the Advanced Light Source

    International Nuclear Information System (INIS)

    Yang, X.; Blank, D.A.; Heimann, P.A.; Lee, Y.T.; Suits, A.G.; Lin, J.; Wodtke, A.M.

    1995-01-01

    The recently commissioned Advanced Light Source (ALS) at Berkeley provides a high brightness, tunable VUV light source for chemical dynamics studies. A dedicated chemical dynamics beamline has been built at the ALS for studies of fundamental chemical processes. High flux (10(sup 16) photon/s with 2% bandwidth) VUV synchrotron radiation from 5 to 30 eV can be obtained from the beamline, whose source is the U8/10 undulator. Three endstations will be in operation for studies ranging from crossed beam reaction dynamics and photodissociation to high resolution photoionization dynamics and spectroscopy. A rotatable source crossed molecular beam apparatus (endstation one) has been established for unimolecular and bimolecular reactive scattering studies. Photodissociation of methylamine and ozone were carried out using VUV synchrotron radiation as the ionization detection technique at this endstation. Results show the advantages of the new endstation using VUV ionization as the detection scheme over similar machines using electron bombardment as the ionization source

  20. Chemical reaction dynamics using the Advanced Light Source

    International Nuclear Information System (INIS)

    Yang, X.; Blank, D.A.; Heimann, P.A.; Lee, Y.T.; Suits, A.G.; Lin, J.; Wodtke, A.M.

    1995-09-01

    The recently commissioned Advanced Light Source (ALS) at Berkeley provides a high brightness, tunable VUV light source for chemical dynamics studies. A dedicated chemical dynamics beamline has been built at the ALS for studies of fundamental chemical processes. High flux (10 16 photon/s with 2% bandwidth) VUV synchrotron radiation from 5 to 30 eV can be obtained from the beamline, whose source is the U8/10 undulator. Three endstations will be in operation for studies ranging from crossed beam reaction dynamics and photodissociation to high resolution photoionization dynamics and spectroscopy. A rotatable source crossed molecular beam apparatus (endstation one) has been established for unimolecular and bimolecular reactive scattering studies. Photodissociation of methylamine and ozone were carried out using VUV synchrotron radiation as the ionization detection technique at this endstation. Results show the advantages of the new endstation using VUV ionization as the detection scheme over similar machines using electron bombardment as the ionization source

  1. DNA-Encoded Dynamic Combinatorial Chemical Libraries.

    Science.gov (United States)

    Reddavide, Francesco V; Lin, Weilin; Lehnert, Sarah; Zhang, Yixin

    2015-06-26

    Dynamic combinatorial chemistry (DCC) explores the thermodynamic equilibrium of reversible reactions. Its application in the discovery of protein binders is largely limited by difficulties in the analysis of complex reaction mixtures. DNA-encoded chemical library (DECL) technology allows the selection of binders from a mixture of up to billions of different compounds; however, experimental results often show low a signal-to-noise ratio and poor correlation between enrichment factor and binding affinity. Herein we describe the design and application of DNA-encoded dynamic combinatorial chemical libraries (EDCCLs). Our experiments have shown that the EDCCL approach can be used not only to convert monovalent binders into high-affinity bivalent binders, but also to cause remarkably enhanced enrichment of potent bivalent binders by driving their in situ synthesis. We also demonstrate the application of EDCCLs in DNA-templated chemical reactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Trajectory calculation of a trapped particle in electro-dynamic balance for study of chemical reaction of aerosol particles

    International Nuclear Information System (INIS)

    Okuma, Miho; Itou, Takahiro; Harano, Azuchi; Takarada, Takayuki; James, Davis E

    2013-01-01

    Electrodynamic balance (EDB) is a powerful tool for investigating the chemical reactions between a fine particle and gaseous species. But the EDB device alone is inadequate to match the rapid weight change of a fine particle caused by chemical reactions, because it takes a few seconds to set a fine particle at null point. The particle trajectory calculation for the trapped particle added to the EDB is thus a very useful tool for the measurement of the transient response of a particle weight change with no need to adjust the applied DC voltage to set the null point. The purpose of this study is to develop the trajectory calculation method to track the particle oscillation pattern in the EDB and examine the possibility for kinetic studies on the reaction of a single aerosol particle with gaseous species. The results demonstrated the feasibility of applying particle trajectory calculation to realize the research purpose.

  3. 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. [Univ. of Chicago, IL (United States). James Franck Inst. and Dept. of Chemistry

    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

  4. 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.

  5. Nanomotor dynamics in a chemically oscillating medium

    International Nuclear Information System (INIS)

    Robertson, Bryan; Kapral, Raymond

    2015-01-01

    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

  6. Advanced Chemical Propulsion Study

    Science.gov (United States)

    Woodcock, Gordon; Byers, Dave; Alexander, Leslie A.; Krebsbach, Al

    2004-01-01

    A study was performed of advanced chemical propulsion technology application to space science (Code S) missions. The purpose was to begin the process of selecting chemical propulsion technology advancement activities that would provide greatest benefits to Code S missions. Several missions were selected from Code S planning data, and a range of advanced chemical propulsion options was analyzed to assess capabilities and benefits re these missions. Selected beneficial applications were found for higher-performing bipropellants, gelled propellants, and cryogenic propellants. Technology advancement recommendations included cryocoolers and small turbopump engines for cryogenic propellants; space storable propellants such as LOX-hydrazine; and advanced monopropellants. It was noted that fluorine-bearing oxidizers offer performance gains over more benign oxidizers. Potential benefits were observed for gelled propellants that could be allowed to freeze, then thawed for use.

  7. 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.

  8. Energy price slump and policy response in the coal-chemical industry district : a case study of Ordos with a system dynamics model

    OpenAIRE

    Wang, Delu; Ma, Gang; Song, Xuefeng; Liu, Yun

    2017-01-01

    We employ system dynamics method towards a coal-chemical industry district economy evolution model, using coal industry, the coal-chemical industry, their downstream industries, and the manufacture-related service industry. Moreover, we construct energy price and policy response scenarios based on Ordos’ management experience. The results show that the energy price slump had a negative impact on the overall economic development of the coal-chemical industry district, despite promoting non-res...

  9. Application of synchrotron radiation in chemical dynamics

    International Nuclear Information System (INIS)

    Heimann, P.; Koike, M.; Kung, A.H.; Ng, C.Y.; White, M.G.; Wodtke, A.

    1993-05-01

    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

  10. 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.

  11. Molecular dynamics simulations of solutions at constant chemical potential

    Science.gov (United States)

    Perego, C.; Salvalaglio, M.; Parrinello, M.

    2015-04-01

    Molecular dynamics studies of chemical processes in solution are of great value in a wide spectrum of applications, which 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, which 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 Constant Chemical Potential Molecular Dynamics (CμMD) 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 CμMD method to the paradigmatic case of urea crystallization in aqueous solution. As a result, we have been able to study crystal growth dynamics under constant supersaturation conditions and to extract growth rates and free-energy barriers.

  12. An integrated ion trap and time-of-flight mass spectrometer for chemical and photo- reaction dynamics studies.

    Science.gov (United States)

    Schowalter, Steven J; Chen, Kuang; Rellergert, Wade G; Sullivan, Scott T; Hudson, Eric R

    2012-04-01

    We demonstrate the integration of a linear quadrupole trap with a simple time-of-flight mass spectrometer with medium-mass resolution (m/Δm ∼ 50) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from the linear quadrupole trap into the mass analyzer, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. This provides the ability to address trapped ions with laser light and facilitates interactions with neutral background gases prior to analyzing the trapped ions. Here, we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates. © 2012 American Institute of Physics

  13. An integrated ion trap and time-of-flight mass spectrometer for chemical and photo- reaction dynamics studies

    International Nuclear Information System (INIS)

    Schowalter, Steven J.; Chen Kuang; Rellergert, Wade G.; Sullivan, Scott T.; Hudson, Eric R.

    2012-01-01

    We demonstrate the integration of a linear quadrupole trap with a simple time-of-flight mass spectrometer with medium-mass resolution (m/Δm∼ 50) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from the linear quadrupole trap into the mass analyzer, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. This provides the ability to address trapped ions with laser light and facilitates interactions with neutral background gases prior to analyzing the trapped ions. Here, we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates.

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

    International Nuclear Information System (INIS)

    Willaime, F.; Rosato, V.

    1990-01-01

    We calculate the shear elastic constants of the alloy NiZr 2 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 C 44 and C 66 are smaller

  15. Role of aromatic amino acids in carbohydrate binding of plant lectins : Laser photo chemically induced dynamic nuclear polarization study of hevein domain-containing lectins

    NARCIS (Netherlands)

    Siebert, HC; vonderLieth, CW; Kaptein, R; Beintema, JJ; Dijkstra, K; vanNuland, N; Soedjanaatmadja, UMS; Rice, A; Vliegenthart, JFG; Wright, CS; Gabius, HJ

    Carbohydrate recognition by lectins often involves the side chains of tyrosine, tryptophan, and histidine residues. These moieties are able to produce chemically induced dynamic nuclear polarization (CIDNP) signals after laser irradiation in the presence of a suitable radical pair-generating dye.

  16. Comparison of reactivity on step and terrace sites of Pd (3 3 2) surface for the dissociative adsorption of hydrogen: A quantum chemical molecular dynamics study

    International Nuclear Information System (INIS)

    Ahmed, Farouq; Nagumo, Ryo; Miura, Ryuji; Ai, Suzuki; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Miyamoto, Akira

    2011-01-01

    The notion of 'active sites' is fundamental to heterogeneous catalysis. However, the exact nature of the active sites, and hence the mechanism by which they act, are still largely a matter of speculation. In this study, we have presented a systematic quantum chemical molecular dynamics (QCMD) calculations for the interaction of hydrogen on different step and terrace sites of the Pd (3 3 2) surface. Finally the dissociative adsorption of hydrogen on step and terrace as well as the influence of surface hydrogen vacancy for the dissociative adsorption of hydrogen has been investigated through QCMD. This is a state-of-the-art method for calculating the interaction of atoms and molecules with metal surfaces. It is found that fully hydrogen covered (saturated) step sites can dissociate hydrogen moderately and that a monovacancy surface is suitable for significant dissociative adsorption of hydrogen. However in terrace site of the surface we have found that dissociation of hydrogen takes place only on Pd sites where the metal atom is not bound to any pre-adsorbed hydrogen atoms. Furthermore, from the molecular dynamics and electronic structure calculations, we identify a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage and directional dependence of atomic hydrogen diffusion on stepped palladium surface.

  17. 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.

  18. Semiclassical methods in chemical reaction dynamics

    International Nuclear Information System (INIS)

    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

  19. Semiclassical methods in chemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Keshavamurthy, Srihari [Univ. of California, Berkeley, CA (United States)

    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.

  20. 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

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

    International Nuclear Information System (INIS)

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

  2. Chemical memory reactions induced bursting dynamics in gene expression.

    Science.gov (United States)

    Tian, Tianhai

    2013-01-01

    Memory is a ubiquitous phenomenon in biological systems in which the present system state is not entirely determined by the current conditions but also depends on the time evolutionary path of the system. Specifically, many memorial phenomena are characterized by chemical memory reactions that may fire under particular system conditions. These conditional chemical reactions contradict to the extant stochastic approaches for modeling chemical kinetics and have increasingly posed significant challenges to mathematical modeling and computer simulation. To tackle the challenge, I proposed a novel theory consisting of the memory chemical master equations and memory stochastic simulation algorithm. A stochastic model for single-gene expression was proposed to illustrate the key function of memory reactions in inducing bursting dynamics of gene expression that has been observed in experiments recently. The importance of memory reactions has been further validated by the stochastic model of the p53-MDM2 core module. Simulations showed that memory reactions is a major mechanism for realizing both sustained oscillations of p53 protein numbers in single cells and damped oscillations over a population of cells. These successful applications of the memory modeling framework suggested that this innovative theory is an effective and powerful tool to study memory process and conditional chemical reactions in a wide range of complex biological systems.

  3. 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

    2002-01-01

    Investigates students' mental models of chemical equilibrium using dynamic science assessments. Reports that students at various levels have misconceptions about chemical equilibrium. Involves 10th grade students (n=30) in the study doing a series of hands-on chemical experiments. Focuses on the process of constructing mental models, dynamic…

  4. Energy price slump and policy response in the coal-chemical industry district: A case study of Ordos with a system dynamics model

    International Nuclear Information System (INIS)

    Wang, Delu; Ma, Gang; Song, Xuefeng; Liu, Yun

    2017-01-01

    We employ system dynamics method towards a coal-chemical industry district economy evolution model, using coal industry, the coal-chemical industry, their downstream industries, and the manufacture-related service industry. Moreover, we construct energy price and policy response scenarios based on Ordos’ management experience. The results show that the energy price slump had a negative impact on the overall economic development of the coal-chemical industry district, despite promoting non-resource industries. Furthermore, policies had different effects on the industry's output value and profit. In the long-term, developing alternative industries (AI) helps increase the industrial output value and profit. Decreasing value added tax (VAT) has immediate results and a distinctive effect on industrial short-term production value and profit, its long-term effect being limited. The effect of production limit (PL) on industrial profit is stronger than output value, and financial support (FS) is more conducive to improve the latter. However, coal mining and coal-chemical loan increases decrease the gross industrial profit level. Technology innovation (TI) has the best individual policy overall effect on production value and profits. Furthermore, the simultaneous implementation of PL, TI and AI can generate the synergy effect for each of them. And the simultaneous implementation of VAT and one or couple of other policies will generate the crowding-out effect both for VAT and other policies. - Highlights: • A system dynamics model of the coal-chemical industry district economy evolution in Ordos is constructed. • The impact of coal and oil prices slump on the output value and profit of each industry is revealed. • The differences in the effects especially cumulative effects of different response policies are clarified. • The crowding-out and synergy effects of policy implementation are analyzed.

  5. 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

  6. Development of a quantum chemical molecular dynamics tribochemical simulator and its application to tribochemical reaction dynamics of lubricant additives

    International Nuclear Information System (INIS)

    Onodera, T; Tsuboi, H; Hatakeyama, N; Endou, A; Miyamoto, A; Miura, R; Takaba, H; Suzuki, A; Kubo, M

    2010-01-01

    Tribology at the atomistic and molecular levels has been theoretically studied by a classical molecular dynamics (MD) method. However, this method inherently cannot simulate the tribochemical reaction dynamics because it does not consider the electrons in nature. Although the first-principles based MD method has recently been used for understanding the chemical reaction dynamics of several molecules in the tribology field, the method cannot simulate the tribochemical reaction dynamics of a large complex system including solid surfaces and interfaces due to its huge computation costs. On the other hand, we have developed a quantum chemical MD tribochemical simulator on the basis of a hybrid tight-binding quantum chemical/classical MD method. In the simulator, the central part of the chemical reaction dynamics is calculated by the tight-binding quantum chemical MD method, and the remaining part is calculated by the classical MD method. Therefore, the developed tribochemical simulator realizes the study on tribochemical reaction dynamics of a large complex system, which cannot be treated by using the conventional classical MD or the first-principles MD methods. In this paper, we review our developed quantum chemical MD tribochemical simulator and its application to the tribochemical reaction dynamics of a few lubricant additives

  7. Special Issue on Theoretical Chemistry/Chemical Dynamics

    Indian Academy of Sciences (India)

    2017-07-02

    Jul 2, 2017 ... This month's issue of the Journal of Chemical Sciences honours Professor Charusita Chakravarty, who has made immeasurable contributions to theoretical chemistry and chemical dynamics. The editors Biman Bagchi (FASc, FNA, FTWAS; Indian Institute of Science, Bangalore, India), David Clary (FRS; ...

  8. 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...

  9. Molecular dynamics simulations and quantum chemical calculations ...

    African Journals Online (AJOL)

    Molecular dynamic simulation results indicate that the imidazoline derivative molecules uses the imidazoline ring to effectively adsorb on the surface of iron, with the alkyl hydrophobic tail forming an n shape (canopy like covering) at geometry optimization and at 353 K. The n shape canopy like covering to a large extent may ...

  10. 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.

  11. Partial chemical equilibrium in fluid dynamics

    International Nuclear Information System (INIS)

    Ramshaw, J.D.

    1980-01-01

    An analysis is given for the flow of a multicomponent fluid in which an arbitrary number of chemical reactions may occur, some of which are in equilibrium while the others proceed kinetically. The primitive equations describing this situation are inconvenient to use because the progress rates omega-dot/sub s/ for the equilibrium reactions are determined implicitly by the associated equilibrium constraint conditions. Two alternative equivalent equation systems that are more pleasant to deal with are derived. In the first system, the omega-dot/sub s/ are eliminated by replacing the transport equations for the chemical species involved in the equilibrium reactions with transport equations for the basic components of which these species are composed. The second system retains the usual species transport equations, but eliminates the nonlinear algebraic equilibrium constraint conditions by deriving an explicit expression for the omega-dot/sub s/. Both systems are specialized to the case of an ideal gas mixture. Considerations involved in solving these equation systems numerically are discussed briefly

  12. The RAVE-on Catalog of Stellar Atmospheric Parameters and Chemical Abundances for Chemo-dynamic Studies in the Gaia Era

    Energy Technology Data Exchange (ETDEWEB)

    Casey, Andrew R.; Hawkins, Keith; Koposov, Sergey; Sanders, Jason; Gilmore, Gerry [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Hogg, David W. [Simons Center for Data Analysis, 160 Fifth Avenue, 7th Floor, New York, NY 10010 (United States); Ness, Melissa; Rix, Hans-Walter [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Kordopatis, Georges; Kunder, Andrea; Steinmetz, Matthias; Enke, Harry [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Zwitter, Tomaž; Matijevič, Gal [University of Ljubljana, Faculty of Mathematics and Physics, Jadranska 19, 1000 Ljubljana (Slovenia); Freeman, Kenneth C.; Casagrande, Luca [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, The Australian National University, ACT 2611 (Australia); Seabroke, George [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, RH5 6NT (United Kingdom); Bienaymé, Olivier [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, F-67000 Strasbourg (France); Bland-Hawthorn, Joss [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Gibson, Brad K. [E.A. Milne Centre for Astrophysics, University of Hull, Hull, HU6 7RX (United Kingdom); and others

    2017-05-01

    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 (≳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 {sub eff}, surface gravity log g , and chemical abundances of up to seven elements (O, Mg, Al, Si, Ca, Fe, and Ni). We report a total of 1,685,851 elemental abundances with a typical precision of 0.07 dex, a substantial improvement over previous RAVE data releases. The synthesis of RAVE-on and TGAS is the most powerful data set for chemo-dynamic analyses of the Milky Way ever produced.

  13. Annual Report 2000. Chemical Structure and Dynamics; FINAL

    International Nuclear Information System (INIS)

    Colson, Steve D; McDowell, Rod S

    2001-01-01

    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 and 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

  14. Dynamics of chemical equilibrium of hadronic matter close to Tc

    International Nuclear Information System (INIS)

    Noronha-Hostler, J.; Beitel, M.; Greiner, C.; Shovkovy, I.

    2010-01-01

    Quick chemical equilibration times of hadrons (specifically, pp-bar, KK-bar, ΛΛ-bar, and ΩΩ-bar pairs) within a hadron gas are explained dynamically using Hagedorn states, which drive particles into equilibrium close to the critical temperature. Within this scheme, we use master equations and derive various analytical estimates for the chemical equilibration times. We compare our model to recent lattice results and find that for both T c =176 MeV and T c =196 MeV, the hadrons can reach chemical equilibrium almost immediately, well before the chemical freeze-out temperatures found in thermal fits for a hadron gas without Hagedorn states. Furthermore, the ratios p/π, K/π, Λ/π, and Ω/π match experimental values well in our dynamical scenario.

  15. 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.

  16. Molecular dynamics simulation studies of transmembrane transport of chemical components in Chinese herbs and the function of platycodin D in a biological membrane

    Directory of Open Access Journals (Sweden)

    Shufang Yang

    2017-04-01

    Conclusion: The Martini force field was successfully applied to the study of the interaction between herbal compounds and a biological membrane. By combining the dynamics equilibrium morphology, the distribution of drugs inside and outside the biomembrane, and the interaction sites of drugs on the DPPC bilayer, factors influencing transmembrane transport of drugs were elucidated and the function of platycodin D in a biological membrane was reproduced.

  17. Investigation of Spark Ignition and Autoignition in Methane and Air Using Computational Fluid Dynamics and Chemical Reaction Kinetics. A numerical Study of Ignition Processes in Internal Combustion Engines

    Energy Technology Data Exchange (ETDEWEB)

    Nordrik, R.

    1993-12-01

    The processes in the combustion chamber of internal combustion engines have received increased attention in recent years because their efficiencies are important both economically and environmentally. This doctoral thesis studies the ignition phenomena by means of numerical simulation methods. The fundamental physical relations include flow field conservation equations, thermodynamics, chemical reaction kinetics, transport properties and spark modelling. Special attention is given to the inclusion of chemical kinetics in the flow field equations. Using his No Transport of Radicals Concept method, the author reduces the computational efforts by neglecting the transport of selected intermediate species. The method is validated by comparison with flame propagation data. A computational method is described and used to simulate spark ignition in laminar premixed methane-air mixtures and the autoignition process of a methane bubble surrounded by hot air. The spark ignition simulation agrees well with experimental results from the literature. The autoignition simulation identifies the importance of diffusive and chemical processes acting together. The ignition delay times exceed the experimental values found in the literature for premixed ignition delay, presumably because of the mixing process and lack of information on low temperature reactions in the skeletal kinetic mechanism. Transient turbulent methane jet autoignition is simulated by means of the KIVA-II code. Turbulent combustion is modelled by the Eddy Dissipation Concept. 90 refs., 81 figs., 3 tabs.

  18. Fractal sets generated by chemical reactions discrete chaotic dynamics

    International Nuclear Information System (INIS)

    Gontar, V.; Grechko, O.

    2007-01-01

    Fractal sets composed by the parameters values of difference equations derived from chemical reactions discrete chaotic dynamics (DCD) and corresponding to the sequences of symmetrical patterns were obtained in this work. Examples of fractal sets with the corresponding symmetrical patterns have been presented

  19. Control of chemical dynamics by lasers: theoretical considerations.

    Science.gov (United States)

    Kondorskiy, Alexey; Nanbu, Shinkoh; Teranishi, Yoshiaki; Nakamura, Hiroki

    2010-06-03

    Theoretical ideas are proposed for laser control of chemical dynamics. There are the following three elementary processes in chemical dynamics: (i) motion of the wave packet on a single adiabatic potential energy surface, (ii) excitation/de-excitation or pump/dump of wave packet, and (iii) nonadiabatic transitions at conical intersections of potential energy surfaces. A variety of chemical dynamics can be controlled, if we can control these three elementary processes as we desire. For (i) we have formulated the semiclassical guided optimal control theory, which can be applied to multidimensional real systems. The quadratic or periodic frequency chirping method can achieve process (ii) with high efficiency close to 100%. Concerning process (iii) mentioned above, the directed momentum method, in which a predetermined momentum vector is given to the initial wave packet, makes it possible to enhance the desired transitions at conical intersections. In addition to these three processes, the intriguing phenomenon of complete reflection in the nonadiabatic-tunneling-type of potential curve crossing can also be used to control a certain class of chemical dynamics. The basic ideas and theoretical formulations are provided for the above-mentioned processes. To demonstrate the effectiveness of these controlling methods, numerical examples are shown by taking the following processes: (a) vibrational photoisomerization of HCN, (b) selective and complete excitation of the fine structure levels of K and Cs atoms, (c) photoconversion of cyclohexadiene to hexatriene, and (d) photodissociation of OHCl to O + HCl.

  20. 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.

  1. DYNSIR; A dynamic simulator for the chemical process

    International Nuclear Information System (INIS)

    Park, Hyun Soo; Yoo, Jae Hyung; Byeon, Kee Hoh; Park, Jeong Hwa; Park, Seong Won

    1990-03-01

    A program code for dynamic simulation of arbitrary chemical process, called DYNSIR, is developed. The code can simulate rather arbitrary arrangements of individual chemical processing units whose models are described by ordinary differential equations. The code structure to handle input/output, memory and data management, numerical interactive or predetermined changes in parameter values during the simulation. Individual model is easy to maintain since the modular approach is used. The integration routine is highly effective because of the development of algorithm for modular integration method using the cubic spline. DYNSIR's data structures are not the index but the pointer structure. This pointer structure allows the dynamic memory allocation for the memory management. The dynamic memory allocation methods is to minimize the amount of memories and to overcome the limitation of the number of variables to be used. Finally, it includes various functions, such as the input preprocessor, the effective error processing, and plotting and reporting routines. (author)

  2. Chronic nitrogen deposition influences the chemical dynamics ...

    Science.gov (United States)

    Atmospheric nitrogen deposition induces a forest carbon sink across broad parts of the Northern Hemisphere; this carbon sink may partly result from slower litter decomposition. Although microbial responses to experimental nitrogen deposition have been well-studied, evidence linking these microbial responses to changes in the degradation of specific compounds in decaying litter is sparse. We used wet chemistry and Fourier transform infrared spectroscopy (FTIR) methodologies to study the effects of chronic simulated nitrogen deposition on leaf litter and fine root chemistry during a three-year decomposition experiment at four northern hardwood forests in the north-central USA. Leaf litter and fine roots were highly different in initial chemistry such as concentrations of acid-insoluble fraction (AIF, or Klason lignin) and condensed tannins (CTs). These initial differences persisted over the course of decomposition. Results from gravimetrically-defined AIF and lignin/carbohydrate reference IR peak ratios both provide evidence that lignin in fine roots was selectively preserved under simulated nitrogen deposition. Lignin/carbohydrate peak ratios were strongly correlated with AIF, suggesting that AIF is a good predictor of lignin. Because AIF is abundant in fine roots, slower AIF degradation was the major driver of the slower fine root decomposition under nitrogen enrichment, explaining 73.9 % of the additional root mass retention. Nitrogen enrichment also slowed the

  3. Development of tight-binding, chemical-reaction-dynamics simulator for combinatorial computational chemistry

    International Nuclear Information System (INIS)

    Kubo, Momoji; Ando, Minako; Sakahara, Satoshi; Jung, Changho; Seki, Kotaro; Kusagaya, Tomonori; Endou, Akira; Takami, Seiichi; Imamura, Akira; Miyamoto, Akira

    2004-01-01

    Recently, we have proposed a new concept called 'combinatorial computational chemistry' to realize a theoretical, high-throughput screening of catalysts and materials. We have already applied our combinatorial, computational-chemistry approach, mainly based on static first-principles calculations, to various catalysts and materials systems and its applicability to the catalysts and materials design was strongly confirmed. In order to realize more effective and efficient combinatorial, computational-chemistry screening, a high-speed, chemical-reaction-dynamics simulator based on quantum-chemical, molecular-dynamics method is essential. However, to the best of our knowledge, there is no chemical-reaction-dynamics simulator, which has an enough high-speed ability to perform a high-throughput screening. In the present study, we have succeeded in the development of a chemical-reaction-dynamics simulator based on our original, tight-binding, quantum-chemical, molecular-dynamics method, which is more than 5000 times faster than the regular first-principles, molecular-dynamics method. Moreover, its applicability and effectiveness to the atomistic clarification of the methanol-synthesis dynamics at reaction temperature were demonstrated

  4. Molecular dynamics and quantum chemical calculation studies on 4,4-dimethyl-3-thiosemicarbazide as corrosion inhibitor in 2.5 M H{sub 2}SO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Musa, Ahmed Y., E-mail: ahmed.musa@ymail.com [Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor (Malaysia); Kadhum, Abdul Amir H.; Mohamad, Abu Bakar; Takriff, Mohd Sobri [Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor (Malaysia)

    2011-09-15

    Highlights: {yields} This work deals with a study of chemical additives for corrosion inhibition of mild steel in acidic conditions. {yields} The effects of the additive 4,4-dimethyl-3-thiosemicarbazide (DTS) on mild steel were studied by means of electrochemical techniques. {yields} Quantum chemical calculations and molecular dynamic model were performed to characterize the inhibition mechanism. {yields} 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 H{sub 2}SO{sub 4} 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 H{sub 2}SO{sub 4} 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.

  5. Classical and semiclassical aspects of chemical dynamics

    International Nuclear Information System (INIS)

    Gray, S.K.

    1982-08-01

    Tunneling in the unimolecular reactions H 2 C 2 → HC 2 H, HNC → HCN, and H 2 CO → H 2 + 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

  6. 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

    2016-05-03

    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.

  7. 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

    2016-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Karp, Jerome M.; Erylimaz, Ertan; Cowburn, David, E-mail: cowburn@cowburnlab.org, E-mail: David.cowburn@einstein.yu.edu [Albert Einstein College of Medicine of Yeshiva University, Department of Biochemistry (United States)

    2015-01-15

    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.

  9. Dynamics and Control of Chemical Reactors-Selectively Surveyed

    DEFF Research Database (Denmark)

    Jørgensen, S. B.; Jensen, N.

    1989-01-01

    The chemical reactor or bioreactor is physically at a central position in a process, and often with a decisive role on the overall technical and economical performance. Even though application of feedback control on reactors is gaining momentum and on-line optimization has been implemented....... For bioreactors the theory and practice of reactor design, dynamics and control have to be adapted to the peculiarities of the biological catalysts. Enzymes, the protein catalysts, are the simplest ones, which have many common features with chemical catalysts. The living cells are much more complex, these growing...... in industry, many reactor control problems are still left unsolved or only partly solved using open loop strategies where disturbance rejection and model inaccuracies have to be handled through manual reactor control and feedback control of raw material preprocessing and product purification operations...

  10. 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.

  11. Modeling dynamics of biological and chemical components of aquatic ecosystems

    International Nuclear Information System (INIS)

    Lassiter, R.R.

    1975-05-01

    To provide capability to model aquatic ecosystems or their subsystems as needed for particular research goals, a modeling strategy was developed. Submodels of several processes common to aquatic ecosystems were developed or adapted from previously existing ones. Included are submodels for photosynthesis as a function of light and depth, biological growth rates as a function of temperature, dynamic chemical equilibrium, feeding and growth, and various types of losses to biological populations. These submodels may be used as modules in the construction of models of subsystems or ecosystems. A preliminary model for the nitrogen cycle subsystem was developed using the modeling strategy and applicable submodels. (U.S.)

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

    International Nuclear Information System (INIS)

    Nepomuceno, N.; Nadai Fernandes, E.A. de; Bacchi, M.A.

    1994-01-01

    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. DYNSYL: a general-purpose dynamic simulator for chemical processes

    International Nuclear Information System (INIS)

    Patterson, G.K.; Rozsa, R.B.

    1978-01-01

    Lawrence Livermore Laboratory is conducting a safeguards program for the Nuclear Regulatory Commission. The goal of the Material Control Project of this program is to evaluate material control and accounting (MCA) methods in plants that handle special nuclear material (SNM). To this end we designed and implemented the dynamic chemical plant simulation program DYNSYL. This program can be used to generate process data or to provide estimates of process performance; it simulates both steady-state and dynamic behavior. The MCA methods that may have to be evaluated range from sophisticated on-line material trackers such as Kalman filter estimators, to relatively simple material balance procedures. This report describes the overall structure of DYNSYL and includes some example problems. The code is still in the experimental stage and revision is continuing

  14. Theoretical and experimental studies of atmospheric structure and dynamics, using high altitude chemical release, Radio meteor, and meteorological rocket network and other data

    Science.gov (United States)

    Edwards, H. D.

    1976-01-01

    Data collected by the Georgia Tech Radio Meteor Wind Facility during the fall and winter of 1975 are analyzed indicating a relationship between lower thermospheric circulation at mid latitudes and polar stratospheric dynamics. Techniques of measurement of mixing processes in the upper atmosphere and the interpretation of those measurements are described along with a diffusion simulation program based on the Global Reference Atmosphere program.

  15. Advanced Chemical Propulsion System Study

    Science.gov (United States)

    Portz, Ron; Alexander, Leslie; Chapman, Jack; England, Chris; Henderson, Scott; Krismer, David; Lu, Frank; Wilson, Kim; Miller, Scott

    2007-01-01

    A detailed; mission-level systems study has been performed to show the benefit resulting from engine performance gains that will result from NASA's In-Space Propulsion ROSS Cycle 3A NRA, Advanced Chemical Technology sub-topic. The technology development roadmap to accomplish the NRA goals are also detailed in this paper. NASA-Marshall and NASA-JPL have conducted mission-level studies to define engine requirements, operating conditions, and interfaces. Five reference missions have been chosen for this analysis based on scientific interest, current launch vehicle capability and trends in space craft size: a) GTO to GEO, 4800 kg, delta-V for GEO insertion only approx.1830 m/s; b) Titan Orbiter with aerocapture, 6620 kg, total delta V approx.210 m/s, mostly for periapsis raise after aerocapture; c) Enceladus Orbiter (Titan aerocapture) 6620 kg, delta V approx.2400 m/s; d) Europa Orbiter, 2170 kg, total delta V approx.2600 m/s; and e) Mars Orbiter, 2250 kg, total delta V approx.1860 m/s. The figures of merit used to define the benefit of increased propulsion efficiency at the spacecraft level include propulsion subsystem wet mass, volume and overall cost. The objective of the NRA is to increase the specific impulse of pressure-fed earth storable bipropellant rocket engines to greater than 330 seconds with nitrogen tetroxide and monomothylhydrazine propellants and greater than 335 , seconds with nitrogen tetroxide and hydrazine. Achievement of the NRA goals will significantly benefit NASA interplanetary missions and other government and commercial opportunities by enabling reduced launch weight and/or increased payload. The study also constitutes a crucial stepping stone to future development, such as pump-fed storable engines.

  16. A Grid-Based Cyber Infrastructure for High Performance Chemical Dynamics Simulations

    Directory of Open Access Journals (Sweden)

    Khadka Prashant

    2008-10-01

    Full Text Available Chemical dynamics simulation is an effective means to study atomic level motions of molecules, collections of molecules, liquids, surfaces, interfaces of materials, and chemical reactions. To make chemical dynamics simulations globally accessible to a broad range of users, recently a cyber infrastructure was developed that provides an online portal to VENUS, a popular chemical dynamics simulation program package, to allow people to submit simulation jobs that will be executed on the web server machine. In this paper, we report new developments of the cyber infrastructure for the improvement of its quality of service by dispatching the submitted simulations jobs from the web server machine onto a cluster of workstations for execution, and by adding an animation tool, which is optimized for animating the simulation results. The separation of the server machine from the simulation-running machine improves the service quality by increasing the capacity to serve more requests simultaneously with even reduced web response time, and allows the execution of large scale, time-consuming simulation jobs on the powerful workstation cluster. With the addition of an animation tool, the cyber infrastructure automatically converts, upon the selection of the user, some simulation results into an animation file that can be viewed on usual web browsers without requiring installation of any special software on the user computer. Since animation is essential for understanding the results of chemical dynamics simulations, this animation capacity provides a better way for understanding simulation details of the chemical dynamics. By combining computing resources at locations under different administrative controls, this cyber infrastructure constitutes a grid environment providing physically and administratively distributed functionalities through a single easy-to-use online portal

  17. 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.

  18. Material Cycles and Chemicals: Dynamic Material Flow Analysis of Contaminants in Paper Recycling

    DEFF Research Database (Denmark)

    Pivnenko, Kostyantyn; Laner, David; Astrup, Thomas Fruergaard

    2016-01-01

    material source-segregation and collection was the least effective strategy for reducing chemical contamination, if the overall recycling rates should be maintained at the current level (approximately 70% for Europe). The study provides a consistent approach for evaluating contaminant levels in material......This study provides a systematic approach for assessment of contaminants in materials for recycling. Paper recycling is used as an illustrative example. Three selected chemicals, bisphenol A (BPA), diethylhexyl phthalate (DEHP) and mineral oil hydrocarbons (MOHs), are evaluated within the paper...... cycle. The approach combines static material flow analysis (MFA) with dynamic material and substance flow modeling. The results indicate that phasing out of chemicals is the most effective measure for reducing chemical contamination. However, this scenario was also associated with a considerable lag...

  19. Photoconduction efficiencies and dynamics in GaN nanowires grown by chemical vapor deposition and molecular beam epitaxy: A comparison study

    International Nuclear Information System (INIS)

    Chen, R. S.; Tsai, H. Y.; Huang, Y. S.; Chen, Y. T.; Chen, L. C.; Chen, K. H.

    2012-01-01

    The normalized gains, which determines the intrinsic photoconduction (PC) efficiencies, have been defined and compared for the gallium nitride (GaN) nanowires (NWs) grown by chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). By excluding the contributions of experimental parameters and under the same light intensity, the CVD-grown GaN NWs exhibit the normalized gain which is near two orders of magnitude higher than that of the MBE-ones. The temperature-dependent time-resolved photocurrent measurement further indicates that the higher photoconduction efficiency in the CVD-GaN NWs is originated from the longer carrier lifetime induced by the higher barrier height (φ B = 160 ± 30 mV) of surface band bending. In addition, the experimentally estimated barrier height at 20 ± 2 mV for the MBE-GaN NWs, which is much lower than the theoretical value, is inferred to be resulted from the lower density of charged surface states on the non-polar side walls.

  20. Studying Dynamics in Business Networks

    DEFF Research Database (Denmark)

    Andersen, Poul Houman; Anderson, Helen; Havila, Virpi

    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...

  1. Direct single-molecule dynamic detection of chemical reactions.

    Science.gov (United States)

    Guan, Jianxin; Jia, Chuancheng; Li, Yanwei; Liu, Zitong; Wang, Jinying; Yang, Zhongyue; Gu, Chunhui; Su, Dingkai; Houk, Kendall N; Zhang, Deqing; Guo, Xuefeng

    2018-02-01

    Single-molecule detection can reveal time trajectories and reaction pathways of individual intermediates/transition states in chemical reactions and biological processes, which is of fundamental importance to elucidate their intrinsic mechanisms. We present a reliable, label-free single-molecule approach that allows us to directly explore the dynamic process of basic chemical reactions at the single-event level by using stable graphene-molecule single-molecule junctions. These junctions are constructed by covalently connecting a single molecule with a 9-fluorenone center to nanogapped graphene electrodes. For the first time, real-time single-molecule electrical measurements unambiguously show reproducible large-amplitude two-level fluctuations that are highly dependent on solvent environments in a nucleophilic addition reaction of hydroxylamine to a carbonyl group. Both theoretical simulations and ensemble experiments prove that this observation originates from the reversible transition between the reactant and a new intermediate state within a time scale of a few microseconds. These investigations open up a new route that is able to be immediately applied to probe fast single-molecule physics or biophysics with high time resolution, making an important contribution to broad fields beyond reaction chemistry.

  2. Molecular activation analysis for chemical speciation studies

    International Nuclear Information System (INIS)

    Chai-Chifang

    1998-01-01

    The term of Molecular Activation Analysis (MAA) refers to an activation analysis method that is able to provide information about the chemical species of elements in system of interests, though its definition has remained to be assigned. Its development is strongly stimulated by the urgent need to know the chemical species of elements, because the total concentrations are often without any meaning when assessing health or environmental risks of trace elements.In practice, the MAA is a combination of conventional instrumental or radiochemical activation analysis and physical, chemical or biochemical separation techniques. The MAA is able to play a particular role in speciation studies. However, the critical point in the MAA is that it is not permitted to change the primitive chemical species of elements in systems, or the change has to be under control; in the meantime it is not allowed to form the 'new artifact' originally not present in systems. Some practical examples of MAA for chemical species research performed recently in our laboratory will be presented as follows: Chemical species of platinum group elements in sediment; Chemical species of iodine in marine algae; Chemical species of mercury in human tissues; Chemical species of selenium in corn; Chemical species of rare earth elements in natural plant, etc. The merits and limitations of MAA will be described as well. (author)

  3. 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.

  4. Dynamics of Chemical and Charge Transfer Reactions of Molecular Dications: Part V. An Experimental and Theoretical Study of Reactions between CHCl2+ and Ar, Kr and Xe

    Czech Academy of Sciences Publication Activity Database

    Roithová, Jana; Žabka, Ján; Thissen, R.; Herman, Zdeněk

    2003-01-01

    Roč. 5, - (2003), s. 2988-2995 ISSN 1463-9076 R&D Projects: GA ČR GA203/00/0632; GA AV ČR KJB4040302 Grant - others:Konktakt Barrande(XE) 2002-013-1 Institutional research plan: CEZ:AV0Z4040901 Keywords : charge-transfer * experimental and theoretical study * molecular dications Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.959, year: 2003

  5. EXAFS characterization of supported metal catalysts in chemically dynamic environments

    International Nuclear Information System (INIS)

    Robota, H.J.

    1991-01-01

    Characterization of catalysts focuses on the identification of an active site responsible for accelerating desirable chemical reactions. The identification, characterization, and selective modification of such sites is fundamental to the development of structure-function relationships. Unfortunately, this goal is far from realized in nearly all catalysts, and particularly in catalysts comprised of small supported metal particles. X-ray absorption spectroscopy (XAS) has had a dramatic effect on our understanding of supported metal particles in their resting state. However, the performance of a catalyst can not be assessed from such simple resting state measurements. Among the factors which influence catalyst performance are the exact catalyst composition, including the support and any modifiers; particle size; catalyst finishing and pretreatment conditions; pressure, composition, and temperature of the operating environment; time. Gaining an understanding of how the structure of a catalytic site can change with such an array of variables requires that we begin to develop measurement methods which are effective under chemically dynamic conditions. Ideally, it should be possible to obtain a full X-ray absorption spectrum of each element thought to have a causal relationship with observed catalyst properties. From these spectra, we can optimally extract only a relatively limited amount of information which we must then piece together with information derived from other characterization methods and intuition to arrive at a hypothetical structure of the operating catalyst. Information about crystallinity, homogeneity, and general disorder can be obtained from the Debye-Waller factor. Finally, through analogy with known compounds, the electronic structure of the active atoms can be inferred from near edge absorption features

  6. 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

  7. Molecular beam studies of reaction dynamics

    International Nuclear Information System (INIS)

    Lee, Yuan T.

    1991-03-01

    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

  8. 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.

  9. Chemical Dynamics Studies of Reactions in Solids

    National Research Council Canada - National Science Library

    Thompson, Donald O

    1998-01-01

    ... the properties inherent in high-energy high-density materials. This research lays the groundwork for that by providing the theoretical and computational methods as well as accurate molecular and crystal models for important types of energetic systems...

  10. The Dynamics of Chemical Reactions: Atomistic Visualizations of Organic Reactions, and Homage to van 't Hoff.

    Science.gov (United States)

    Yang, Zhongyue; Houk, K N

    2018-03-15

    Jacobus Henricus van 't Hoff was the first Nobel Laureate in Chemistry. He pioneered in the study of chemical dynamics, which referred at that time to chemical kinetics and thermodynamics. The term has evolved in modern times to refer to the exploration of chemical transformations in a time-resolved fashion. Chemical dynamics has been driven by the development of molecular dynamics trajectory simulations, which provide atomic visualization of chemical processes and illuminate how dynamic effects influence chemical reactivity and selectivity. In homage to the legend of van 't Hoff, we review the development of the chemical dynamics of organic reactions, our area of research. We then discuss our trajectory simulations of pericyclic reactions, and our development of dynamic criteria for concerted and stepwise reaction mechanisms. We also describe a method that we call environment-perturbed transition state sampling, which enables trajectory simulations in condensed-media using quantum mechanics and molecular mechanics (QM/MM). We apply the method to reactions in solvent and in enzyme. Jacobus Henricus van 't Hoff (1852, Rotterdam-1911, Berlin) received the Nobel Prize for Chemistry in 1901 "in recognition of the extraordinary services he has rendered by the discovery of the laws of chemical dynamics and osmotic pressure in solutions". van 't Hoff was born the Netherlands, and earned his doctorate in Utrecht in 1874. In 1896 he moved to Berlin, where he was offered a position with more research and less teaching. van 't Hoff is considered one of the founders of physical chemistry. A key step in establishing this new field was the start of Zeitschrift für Physikalische Chemie in 1887. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Study of estuarine dynamics

    International Nuclear Information System (INIS)

    Genders, S.

    1979-01-01

    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) [pt

  12. Oral dosing of chemical indicators for in vivo monitoring of Ca2+ dynamics in insect muscle.

    Directory of Open Access Journals (Sweden)

    Ferdinandus

    Full Text Available 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 Insect. In order for Cyborg Insects to be of practical use, electrical stimulation parameters need to be optimized to induce desired muscle response (motor action and minimize the damage in the muscle due to the electrical stimuli. Staining tissues and organs as well as measuring the dynamics of chemicals of interest in muscle should be conducted to quantitatively and systematically evaluate the effect of various stimulation parameters on the muscle response. However, existing staining processes require invasive surgery and/or arduous procedures using genetically encoded sensors. In this study, we developed a non-invasive and remarkably facile method for staining, in which chemical indicators can be orally administered (oral dosing. A chemical Ca2+ indicator was orally introduced into an insect of interest via food containing the chemical indicator and the indicator diffused from the insect digestion system to the target muscle tissue. We found that there was a positive relationship between the fluorescence intensity of the indicator and the frequency of electrical stimulation which indicates the orally dosed indicator successfully monitored Ca2+ dynamics in the muscle tissue. This oral dosing method has a potential to globally stain tissues including neurons, and investigating various physiological events in insects.

  13. Oral dosing of chemical indicators for in vivo monitoring of Ca2+ dynamics in insect muscle.

    Science.gov (United States)

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

    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 Insect. In order for Cyborg Insects to be of practical use, electrical stimulation parameters need to be optimized to induce desired muscle response (motor action) and minimize the damage in the muscle due to the electrical stimuli. Staining tissues and organs as well as measuring the dynamics of chemicals of interest in muscle should be conducted to quantitatively and systematically evaluate the effect of various stimulation parameters on the muscle response. However, existing staining processes require invasive surgery and/or arduous procedures using genetically encoded sensors. In this study, we developed a non-invasive and remarkably facile method for staining, in which chemical indicators can be orally administered (oral dosing). A chemical Ca2+ indicator was orally introduced into an insect of interest via food containing the chemical indicator and the indicator diffused from the insect digestion system to the target muscle tissue. We found that there was a positive relationship between the fluorescence intensity of the indicator and the frequency of electrical stimulation which indicates the orally dosed indicator successfully monitored Ca2+ dynamics in the muscle tissue. This oral dosing method has a potential to globally stain tissues including neurons, and investigating various physiological events in insects.

  14. Chemical industrial areas and their dynamic danger behaviour

    NARCIS (Netherlands)

    Reniers, Genserik L L; Audenaert, Amaryllis; Dullaert, W.; Soudan, K.

    2007-01-01

    Chemical industrial areas or so-called chemical clusters consist of various companies situated next to each other. Such areas are composed of hundreds of chemical installations exhibiting danger to a certain degree for initiating or continuing knock-on effects. In this paper, a methodology to model

  15. 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.

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

    DEFF Research Database (Denmark)

    Larsson, Hilde Kristina

    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...... and an ion-exchange reaction are also modelled and compared to experimental data. The thesis includes a comprehensive overview of the fundamentals behind a CFD software, as well as a more detailed review of the fluid dynamic phenomena investigated in this project. The momentum and continuity equations...

  18. Dynamic Chemically Driven Dewetting, Spreading, and Self-Running of Sessile Droplets on Crystalline Silicon.

    Science.gov (United States)

    Arscott, Steve

    2016-12-06

    A chemically driven dewetting effect is demonstrated using sessile droplets of dilute hydrofluoric acid on chemically oxidized silicon wafers. The dewetting occurs as the thin oxide is slowly etched by the droplet and replaced by a hydrogen-terminated surface; the result of this is a gradual increase in the contact angle of the droplet with time. The time-varying work of adhesion is calculated from the time-varying contact angle; this corresponds to the changing chemical nature of the surface during dewetting and can be modeled by the well-known logistic (sigmoid) function often used for the modeling of restricted growth, in this case, the transition from an oxidized surface to a hydrogen-terminated silicon surface. The observation of the time-varying contact angle allows one to both measure the etch rate of the silicon oxide and estimate the hydrogenation rate as a function of HF concentration and wafer type. In addition to this, at a certain HF concentration, a self-running droplet effect is observed. In contrast, on hydrogen-terminated silicon wafers, a chemically induced spreading effect is observed using sessile droplets of nitric acid. The droplet spreading can also be modeled using a logistical function, where the restricted growth is the transition from hydrogen-terminated to a chemically induced oxidized silicon surface. The chemically driven dewetting and spreading observed here add to the methods available to study dynamic wetting (e.g., the moving three-phase contact line) of sessile droplets on surfaces. By slowing down chemical kinetics of the wetting, one is able to record the changing profile of the sessile droplet with time and gather information concerning the time-varying surface chemistry. The data also indicates a chemical interface hysteresis (CIH) that is compared to contact angle hysteresis (CAH). The approach can also be used to study the chemical etching and deposition behavior of thin films using liquids by monitoring the macroscopic

  19. The use of dynamic capabilities to boost innovation in a Brazilian Chemical Company

    Directory of Open Access Journals (Sweden)

    Cristiane Froehlich

    Full Text Available Abstract Dynamic capabilities seek to explain how competitive advantages can be built in rapidly changing environments. This study aims to assess how the application of dynamic capabilities can contribute to the expansion of innovation capabilities. Data was collected on ten semi-structured interviews with executives from a chemical company, and analyzed using qualitative content analysis. Results indicate that the application of dynamic capabilities contributes to the development of innovation capabilities through the consolidation of the first dynamic capability (sensing, which fosters innovation. Sensing can be considered an organizational capability, resulting from the integration between organizational strategies and the innovation practices of the organization as a whole. This study brings the following contributions the need to include a new microfoundation in the sensing capability, which in this study is called ‘processes to manage innovation on a strategic level' and the need to adapt another microfoundation related to the sensing capability, called ‘processes oriented toward collaboration with suppliers to complement and stimulate innovations within the company'. It is suggested that these processes should be reassessed in terms of their potential to generate and complement organizational innovation.

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

    International Nuclear Information System (INIS)

    Trifunac, A.D.; Johnson, K.W.; Lowers, R.H.

    1976-01-01

    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

  1. Evidence for Dynamic Chemical Kinetics at Individual Molecular Ruthenium Catalysts.

    Science.gov (United States)

    Easter, Quinn T; Blum, Suzanne A

    2018-02-05

    Catalytic cycles are typically depicted as possessing time-invariant steps with fixed rates. Yet the true behavior of individual catalysts with respect to time is unknown, hidden by the ensemble averaging inherent to bulk measurements. Evidence is presented for variable chemical kinetics at individual catalysts, with a focus on ring-opening metathesis polymerization catalyzed by the second-generation Grubbs' ruthenium catalyst. Fluorescence microscopy is used to probe the chemical kinetics of the reaction because the technique possesses sufficient sensitivity for the detection of single chemical reactions. Insertion reactions in submicron regions likely occur at groups of many (not single) catalysts, yet not so many that their unique kinetic behavior is ensemble averaged. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. 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…

  3. CHEMICAL PROPERTIES STUDYS OF PEATLANDON VARIOUS LANDUSE

    Directory of Open Access Journals (Sweden)

    Yondra Yondra

    2017-12-01

    Full Text Available Natural peat swamp forests converted can alter the soil chemical properties. This study aims to determine the extent to which changes in soil chemical properties that occur after the conversion of land from peat swamp forest to palm oil plantation, HTI Acacia crasicarpa, and sago plantation and to know which types of plants are sustainable on peatlands. The results showed that soil pH increased after the change of land function. While the water content decreased. Chemical properties such as C-organic, ash content, CEC, alkaline saturation, macro nutrients (NPK and bases can be changed also undergo changes after undergoing landuse changes, but no violations based on the law made by the government in pp No 25 of 2000 on the criteria of peatland damage and government regulation no. 150 of 2000 on the control of soil damage for biomass production. Sago is the most sustainable plant compared to others due to changes in soil chemical properties not too much different from other landuse although planted in the long term.

  4. Design of multi-phase dynamic chemical networks

    Science.gov (United States)

    Chen, Chenrui; Tan, Junjun; Hsieh, Ming-Chien; Pan, Ting; Goodwin, Jay T.; Mehta, Anil K.; Grover, Martha A.; Lynn, David G.

    2017-08-01

    Template-directed polymerization reactions enable the accurate storage and processing of nature's biopolymer information. This mutualistic relationship of nucleic acids and proteins, a network known as life's central dogma, is now marvellously complex, and the progressive steps necessary for creating the initial sequence and chain-length-specific polymer templates are lost to time. Here we design and construct dynamic polymerization networks that exploit metastable prion cross-β phases. Mixed-phase environments have been used for constructing synthetic polymers, but these dynamic phases emerge naturally from the growing peptide oligomers and create environments suitable both to nucleate assembly and select for ordered templates. The resulting templates direct the amplification of a phase containing only chain-length-specific peptide-like oligomers. Such multi-phase biopolymer dynamics reveal pathways for the emergence, self-selection and amplification of chain-length- and possibly sequence-specific biopolymers.

  5. 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.

  6. Molecular dynamics study of silver

    International Nuclear Information System (INIS)

    Akhter, J.I.; Yaldram, K.; Ahmad, W.; Khan, M.K.; Rehman, T.S.

    1995-03-01

    We present results of molecular dynamics study using the embedded atom potential to examine the equilibrium bulk properties of Ag. We calculate the total energy and the lattice parameters as a function of temperature. From these we determine the specific heat and linear coefficient of thermal expansion. The comparison with experimental results of these two quantities is found to be excellent. We have also calculated the mean square displacement of the atoms in the three directions. As expected because of symmetry the displacements in the three directions are comparable and increase with increasing temperature. (author) 5 figs

  7. 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.

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

    KAUST Repository

    Suleimanov, Yu.V.; Allen, J.W.; Green, W.H.

    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 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.

  9. Chemical Ligation and Isotope Labeling to Locate Dynamic Effects during Catalysis by Dihydrofolate Reductase.

    Science.gov (United States)

    Luk, Louis Y P; Ruiz-Pernía, J Javier; Adesina, Aduragbemi S; Loveridge, E Joel; Tuñón, Iñaki; Moliner, Vincent; Allemann, Rudolf K

    2015-07-27

    Chemical ligation has been used to alter motions in specific regions of dihydrofolate reductase from E. coli and to investigate the effects of localized motional changes on enzyme catalysis. Two isotopic hybrids were prepared; one with the mobile N-terminal segment containing heavy isotopes ((2) H, (13) C, (15) N) and the remainder of the protein with natural isotopic abundance, and the other one with only the C-terminal segment isotopically labeled. Kinetic investigations indicated that isotopic substitution of the N-terminal segment affected only a physical step of catalysis, whereas the enzyme chemistry was affected by protein motions from the C-terminal segment. QM/MM studies support the idea that dynamic effects on catalysis mostly originate from the C-terminal segment. The use of isotope hybrids provides insights into the microscopic mechanism of dynamic coupling, which is difficult to obtain with other studies, and helps define the dynamic networks of intramolecular interactions central to enzyme catalysis. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  10. 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

    Chemical reactions are manifestations of the dynamics of molecular valence electrons and their couplings to atomic motions. Emerging methods in attosecond science can probe purely electronic dynamics in atomic and molecular systems(1-6). By contrast, time-resolved structural-dynamics methods...... 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......,17): in both cases, this sensitivity derives from the ionization-matrix element(18,19). Here we demonstrate a time-resolved molecular-frame photoelectron-angular-distribution (TRMFPAD) method for imaging the purely valence-electron dynamics during a chemical reaction. Specifically, the TRMFPADs measured during...

  11. 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

  12. Computational Cellular Dynamics Based on the Chemical Master Equation: A Challenge for Understanding Complexity.

    Science.gov (United States)

    Liang, Jie; Qian, Hong

    2010-01-01

    Modern molecular biology has always been a great source of inspiration for computational science. Half a century ago, the challenge from understanding macromolecular dynamics has led the way for computations to be part of the tool set to study molecular biology. Twenty-five years ago, the demand from genome science has inspired an entire generation of computer scientists with an interest in discrete mathematics to join the field that is now called bioinformatics. In this paper, we shall lay out a new mathematical theory for dynamics of biochemical reaction systems in a small volume (i.e., mesoscopic) in terms of a stochastic, discrete-state continuous-time formulation, called the chemical master equation (CME). Similar to the wavefunction in quantum mechanics, the dynamically changing probability landscape associated with the state space provides a fundamental characterization of the biochemical reaction system. The stochastic trajectories of the dynamics are best known through the simulations using the Gillespie algorithm. In contrast to the Metropolis algorithm, this Monte Carlo sampling technique does not follow a process with detailed balance. We shall show several examples how CMEs are used to model cellular biochemical systems. We shall also illustrate the computational challenges involved: multiscale phenomena, the interplay between stochasticity and nonlinearity, and how macroscopic determinism arises from mesoscopic dynamics. We point out recent advances in computing solutions to the CME, including exact solution of the steady state landscape and stochastic differential equations that offer alternatives to the Gilespie algorithm. We argue that the CME is an ideal system from which one can learn to understand "complex behavior" and complexity theory, and from which important biological insight can be gained.

  13. Thermodiffusion as a means to manipulate liquid film dynamics on chemically patterned surfaces.

    Science.gov (United States)

    Kalpathy, Sreeram K; Shreyes, Amrita Ravi

    2017-06-07

    The model problem examined here is the stability of a thin liquid film consisting of two miscible components, resting on a chemically patterned solid substrate and heated from below. In addition to surface tension gradients, the temperature variations also induce gradients in the concentration of the film by virtue of thermodiffusion/Soret effects. We study the stability and dewetting behaviour due to the coupled interplay between thermal gradients, Soret effects, long-range van der Waals forces, and wettability gradient-driven flows. Linear stability analysis is first employed to predict growth rates and the critical Marangoni number for chemically homogeneous surfaces. Then, nonlinear simulations are performed to unravel the interfacial dynamics and possible locations of the film rupture on chemically patterned substrates. Results suggest that appropriate tuning of the Soret parameter and its direction, in conjunction with either heating or cooling, can help manipulate the location and time scales of the film rupture. The Soret effect can either potentially aid or oppose film instability depending on whether the thermal and solutal contributions to flow are cooperative or opposed to each other.

  14. 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.

  15. 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.

  16. Electro Thermal Chemical Gun Technology Study

    National Research Council Canada - National Science Library

    Diamond, P

    1999-01-01

    .... Michael Stroscio. Electro Thermal Chemical (ETC) gun technology refers to the use of plasma devices in place of traditional chemical ignitors to initiate the burning of high energy propellants in a controlled manner...

  17. Hydrophobic fluorine mediated switching of the hydrogen bonding site as well as orientation of water molecules in the aqueous mixture of monofluoroethanol: IR, molecular dynamics and quantum chemical studies.

    Science.gov (United States)

    Mondal, Saptarsi; Biswas, Biswajit; Nandy, Tonima; Singh, Prashant Chandra

    2017-09-20

    The local structures between water-water, alcohol-water and alcohol-alcohol have been investigated for aqueous mixtures of ethanol (ETH) and monofluoroethanol (MFE) by the deconvolution of IR bands in the OH stretching region, molecular dynamics simulation and quantum chemical calculations. It has been found that the addition of a small amount of ETH into the aqueous medium increases the strength of the hydrogen bonds between water molecules. In an aqueous mixture of MFE, the substitution of a single fluorine induces a change in the orientation as well as the hydrogen bonding site of water molecules from the oxygen to the fluorine terminal of MFE. The switching of the hydrogen bonding site of water in the aqueous mixture of MFE results in comparatively strong hydrogen bonds between MFE and water molecules as well as less clustering of water molecules, unlike the case of the aqueous mixture of ETH. These findings about the modification of a hydrogen bond network by the hydrophobic fluorine group probably make fluorinated molecules useful for pharmaceutical as well as biological applications.

  18. Nonlinear Hamiltonian mechanics applied to molecular dynamics theory and computational methods for understanding molecular spectroscopy and chemical reactions

    CERN Document Server

    Farantos, Stavros C

    2014-01-01

    This brief presents numerical methods for describing and calculating invariant phase space structures, as well as solving the classical and quantum equations of motion for polyatomic molecules. Examples covered include simple model systems to realistic cases of molecules spectroscopically studied. Vibrationally excited and reacting molecules are nonlinear dynamical systems, and thus, nonlinear mechanics is the proper theory to elucidate molecular dynamics by investigating invariant structures in phase space. Intramolecular energy transfer, and the breaking and forming of a chemical bond have now found a rigorous explanation by studying phase space structures.

  19. Three-Dimensional Optical Trapping for Cell Isolation Using Tapered Fiber Probe by Dynamic Chemical Etching

    International Nuclear Information System (INIS)

    Taguchi, K; Okada, J; Nomura, Y; Tamura, K

    2012-01-01

    In this paper, chemically etched fiber probe was proposed for laser trapping and manipulation of cells. We fabricated tapered fiber probe by dynamic chemical etching technique. Three-Dimensional optical trap of a yeast cell dispersed in water solution could be formed by the fiber tip with 17deg tip. Optical forces were sufficient to move the yeast cell for trapping and manipulation. From these experimental results, it was found that our proposed tapered fiber tip was a promising tool for cell isolation.

  20. Dynamical constraints and adiabatic invariants in chemical reactions.

    Science.gov (United States)

    Lorquet, J C

    2007-08-23

    For long-range electrostatic potentials and, more generally, when the topography of the potential energy surface is locally simple, the reaction path coordinate is adiabatically separable from the perpendicular degrees of freedom. For the ion-permanent dipole and ion-quadrupole interactions, the Poisson bracket of the adiabatic invariant decreases with the interfragment distance more rapidly than the electrostatic potential. The smaller the translational momentum, the moment of inertia of the neutral fragment, and the dipole or quadrupole moments are, the more reliable the adiabatic approximation is, as expected from the usual argumentation. Closed-form expressions for an effective one-dimensional potential in an adiabatic Hamiltonian are given. Connection with a model where the decoupling is exact is obtained in the limit of an infinitely heavy dipole. The dynamics is also constrained by adiabatic invariance for a harmonic valley about a curved reaction path, as shown by the reaction path Hamiltonian method. The maximum entropy method reveals that, as a result of the invariance properties of the entropy, constraints whose validity has been demonstrated locally only subsist in all parts of phase space. However, their form varies continuously, and they are not necessarily expressed in simple terms as they are in the asymptotic region. Therefore, although the influence of adiabatic invariance has been demonstrated at asymptotically large values of the reaction coordinate only, it persists in more interesting ranges.

  1. The development and application of dynamic operational risk assessment in oil/gas and chemical process industry

    International Nuclear Information System (INIS)

    Yang Xiaole; Mannan, M. Sam

    2010-01-01

    A methodology of dynamic operational risk assessment (DORA) is proposed for operational risk analysis in oil/gas and chemical industries. The methodology is introduced comprehensively starting from the conceptual framework design to mathematical modeling and to decision making based on cost-benefit analysis. The probabilistic modeling part of DORA integrates stochastic modeling and process dynamics modeling to evaluate operational risk. The stochastic system-state trajectory is modeled according to the abnormal behavior or failure of each component. For each of the possible system-state trajectories, a process dynamics evaluation is carried out to check whether process variables, e.g., level, flow rate, temperature, pressure, or chemical concentration, remain in their desirable regions. Component testing/inspection intervals and repair times are critical parameters to define the system-state configuration, and play an important role for evaluating the probability of operational failure. This methodology not only provides a framework to evaluate the dynamic operational risk in oil/gas and chemical industries, but also guides the process design and further optimization. To illustrate the probabilistic study, we present a case-study of a level control in an oil/gas separator at an offshore plant.

  2. Statistical trend of radiation chemical studies

    International Nuclear Information System (INIS)

    Yoshida, Hiroshi

    1980-01-01

    In the field of radiation chemistry, over 1,000 reports are published year after year. Attempt has been made to review the trends in this field for more than five years, by looking through the lists of papers statistically. As for the period from 1974 to 1978, Annual Cumulation with Keyword and Author Indexes in the Biweekly List of Papers on Radiation Chemistry was referred to. For 1979, because of the unavailability of the Cumulation, Chemical Abstracts Search by Japan Information Center of Science and Technology was referred to. The contents are as follows: how far radiation chemistry is studied, what the trends of radiation chemistry is in recent years, who contributes to the advance of radiation chemistry, and where, the trend radiation chemistry takes in 1979. (J.P.N.)

  3. Proton magnetic resonance study of the influence of chemical modification, mutation, quaternary state, and ligation state on dynamic stability of the heme pocket in hemoglobin as reflected in the exchange of the proximal histidyl ring labile proton

    International Nuclear Information System (INIS)

    Han, K.H.; La Mar, G.N.; Nagai, K.

    1989-01-01

    Proton nuclear magnetic resonance spectroscopy has been utilized to investigate the rates of exchange with deuterium of the proximal histidyl ring protons in a series of chemically modified and mutated forms of Hb A. Differences in rates of exchange are related to differences in the stability of the deformed or partially unfolded intermediates from which exchange with bulk solvent takes place. Each modified/mutated Hb exhibited kinetic subunit heterogeneity in the reduced ferrous state, with the alpha subunit exhibiting faster exchange than the beta subunit. Modification or mutation resulted in significant increases in the His F8 ring NH exchange rates primarily for the affected subunit and only if the modification/mutation occurs at the allosterically important alpha 1 beta 2 subunit interface. Moreover, this enhancement in exchange rate is observed primarily in that quaternary state of the modified/mutated Hb in which the modified/substituted residue makes the intersubunit contact. This confirms the importance of allosteric constraints in determining the dynamic properties of the heme pocket. Using modified or mutated Hbs that can switch between the alternate quaternary states within a given ligation state or ligate within a given quaternary state, we show that the major portion of the enhanced exchange rate in R-state oxy Hb relative to T-state deoxy Hb originates from the quaternary switch rather than from ligation. However, solely ligation effects are not negligible. The exchange rates of the His F8 ring labile protons increase dramatically upon oxidizing the iron to the ferric state, and both the subunit kinetic heterogeneity and the allosteric sensitivity to the quaternary state are essentially abolished

  4. Studies in Chaotic adiabatic dynamics

    International Nuclear Information System (INIS)

    Jarzynski, C.

    1994-01-01

    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)

  5. 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: 2.183, year: 2015

  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

    International Nuclear Information System (INIS)

    Swasey, Steven M; Gwinn, Elisabeth G

    2016-01-01

    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 Mg 2+ , 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’. (paper)

  8. The Role of Electronic Excitations on Chemical Reaction Dynamics at Metal, Semiconductor and Nanoparticle Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tully, John C. [Yale Univ., New Haven, CT (United States)

    2017-06-10

    Chemical reactions are often facilitated and steered when carried out on solid surfaces, essential for applications such as heterogeneous catalysis, solar energy conversion, corrosion, materials processing, and many others. A critical factor that can determine the rates and pathways of chemical reactions at surfaces is the efficiency and specificity of energy transfer; how fast does energy move around and where does it go? For reactions on insulator surfaces energy transfer generally moves in and out of vibrations of the adsorbed molecule and the underlying substrate. By contrast, on metal surfaces, metallic nanoparticles and semiconductors, another pathway for energy flow opens up, excitation and de-excitation of electrons. This so-called “nonadiabatic” mechanism often dominates the transfer of energy and can directly impact the course of a chemical reaction. Conventional computational methods such as molecular dynamics simulation do not account for this nonadiabatic behavior. The current DOE-BES funded project has focused on developing the underlying theoretical foundation and the computational methodology for the prediction of nonadiabatic chemical reaction dynamics at surfaces. The research has successfully opened up new methodology and new applications for molecular simulation. In particular, over the last three years, the “Electronic Friction” theory, pioneered by the PI, has now been developed into a stable and accurate computational method that is sufficiently practical to allow first principles “on-the-fly” simulation of chemical reaction dynamics at metal surfaces.

  9. 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 ...

  10. The dynamic behavior of chemically "stiffened" red blood cells in microchannel flows.

    Science.gov (United States)

    Forsyth, Alison M; Wan, Jiandi; Ristenpart, William D; Stone, Howard A

    2010-07-01

    The rigidity of red blood cells (RBCs) plays an important role in whole blood viscosity and is correlated with several cardiovascular diseases. Two chemical agents that are commonly used to study cell deformation are diamide and glutaraldehyde. Despite diamide's common usage, there are discrepancies in the literature surrounding diamide's effect on the deformation of RBCs in shear and pressure-driven flows; in particular, shear flow experiments have shown that diamide stiffens cells, while pressure-driven flow in capillaries did not give this result. We performed pressure-driven flow experiments with RBCs in a microfluidic constriction and quantified the cell dynamics using high-speed imaging. Diamide, which affects RBCs by cross-linking spectrin skeletal membrane proteins, did not reduce deformation and showed an unchanged effective strain rate when compared to healthy cells. In contrast, glutaraldehyde, which is a non-specific fixative that acts on all components of the cell, did reduce deformation and showed increased instances of tumbling, both of which are characteristic features of stiffened, or rigidified, cells. Because glutaraldehyde increases the effective viscosity of the cytoplasm and lipid membrane while diamide does not, one possible explanation for our results is that viscous effects in the cytoplasm and/or lipid membrane are a dominant factor in dictating dynamic responses of RBCs in pressure-driven flows. Finally, literature on the use of diamide as a stiffening agent is summarized, and provides supporting evidence for our conclusions. Copyright 2010 Elsevier Inc. All rights reserved.

  11. Gaia: unravelling the chemical and dynamical history of our Galaxy

    Science.gov (United States)

    Pancino, E.

    The Gaia astrometric mission - the Hipparcos successor - is described in some detail, with its three instruments: the two (spectro)photometers (BP and RP) covering the range 330-1050 nm, the white light (G-band) imager dedicated to astrometry, and the radial velocity spectrometer (RVS) covering the range 847-874 nm at a resolution R≃11500. The whole sky will be scanned repeatedly providing data for ˜109 point-like objects, down to a magnitude of V≃20, aiming to the full 6D reconstruction of the Milky Way kinematical and dinamical structure with unprecendented precision. The horizon of scientific questions that can find an answer with such a set of data is vast, including besides the Galaxy: Solar system studies, stellar astrophysics, exoplanets, supernovae, Local group physics, unresolved galaxies, Quasars, and fundamental physics. The Italian involvement in the mission preparation is briefly outlined.

  12. 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...

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

    International Nuclear Information System (INIS)

    Fay, P.J.; Ray, J.R.; Wolf, R.J.

    1994-01-01

    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

  14. Dynamical study of liquid aluminium

    International Nuclear Information System (INIS)

    Dubey, G.S.; Chaturvedi, D.K.

    1979-09-01

    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 ω 2 s(q, ω) obtained from both models are compared with experimental data. (author)

  15. 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 - others: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

  16. Nonequilibrium Chemical Effects in Single-Molecule SERS Revealed by Ab Initio Molecular Dynamics Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Sean A.; Apra, Edoardo; Govind, Niranjan; Hess, Wayne P.; El-Khoury, Patrick Z.

    2017-02-03

    Recent developments in nanophotonics have paved the way for achieving significant advances in the realm of single molecule chemical detection, imaging, and dynamics. In particular, surface-enhanced Raman scattering (SERS) is a powerful analytical technique that is now routinely used to identify the chemical identity of single molecules. Understanding how nanoscale physical and chemical processes affect single molecule SERS spectra and selection rules is a challenging task, and is still actively debated. Herein, we explore underappreciated chemical phenomena in ultrasensitive SERS. We observe a fluctuating excited electronic state manifold, governed by the conformational dynamics of a molecule (4,4’-dimercaptostilbene, DMS) interacting with a metallic cluster (Ag20). This affects our simulated single molecule SERS spectra; the time trajectories of a molecule interacting with its unique local environment dictates the relative intensities of the observable Raman-active vibrational states. Ab initio molecular dynamics of a model Ag20-DMS system are used to illustrate both concepts in light of recent experimental results.

  17. Contact Angle and Adhesion Dynamics and Hysteresis on Molecularly Smooth Chemically Homogeneous Surfaces.

    Science.gov (United States)

    Chen, Szu-Ying; Kaufman, Yair; Schrader, Alex M; Seo, Dongjin; Lee, Dong Woog; Page, Steven H; Koenig, Peter H; Isaacs, Sandra; Gizaw, Yonas; Israelachvili, Jacob N

    2017-09-26

    Measuring truly equilibrium adhesion energies or contact angles to obtain the thermodynamic values is experimentally difficult because it requires loading/unloading or advancing/receding boundaries to be measured at rates that can be slower than 1 nm/s. We have measured advancing-receding contact angles and loading-unloading adhesion energies for various systems and geometries involving molecularly smooth and chemically homogeneous surfaces moving at different but steady velocities in both directions, ±V, focusing on the thermodynamic limit of ±V → 0. We have used the Bell Theory (1978) to derive expressions for the dynamic (velocity-dependent) adhesion energies and contact angles suitable for both (i) dynamic adhesion measurements using the classic Johnson-Kendall-Roberts (JKR, 1971) theory of "contact mechanics" and (ii) dynamic contact angle hysteresis measurements of both rolling droplets and syringe-controlled (sessile) droplets on various surfaces. We present our results for systems that exhibited both steady and varying velocities from V ≈ 10 mm/s to 1 nm/s, where in all cases but one, the advancing (V > 0) and receding (V contact angles converged toward the same theoretical (thermodynamic) values as V → 0. Our equations for the dynamic contact angles are similar to the classic equations of Blake & Haynes (1969) and fitted the experimental adhesion data equally well over the range of velocities studied, although with somewhat different fitting parameters for the characteristic molecular length/dimension or area and characteristic bond formation/rupture lifetime or velocity. Our theoretical and experimental methods and results unify previous kinetic theories of adhesion and contact angle hysteresis and offer new experimental methods for testing kinetic models in the thermodynamic, quasi-static, limit. Our analyses are limited to kinetic effects only, and we conclude that hydrodynamic, i.e., viscous, and inertial effects do not play a role at the

  18. Spatiotemporal chaos in the dynamics of buoyantly and diffusively unstable chemical fronts

    Science.gov (United States)

    Baroni, M. P. M. A.; Guéron, E.; De Wit, A.

    2012-03-01

    Nonlinear dynamics resulting from the interplay between diffusive and buoyancy-driven Rayleigh-Taylor (RT) instabilities of autocatalytic traveling fronts are analyzed numerically for various values of the relevant parameters. These are the Rayleigh numbers of the reactant A and autocatalytic product B solutions as well as the ratio D =DB/DA between the diffusion coefficients of the two key chemical species. The interplay between the coarsening dynamics characteristic of the RT instability and the constant short wavelength modulation of the diffusive instability can lead in some regimes to complex dynamics dominated by irregular succession of birth and death of fingers. By using spectral entropy measurements, we characterize the transition between order and spatial disorder in this system. The analysis of the power spectrum and autocorrelation function, moreover, identifies similarities between the various spatial patterns. The contribution of the diffusive instability to the complex dynamics is discussed.

  19. Recoil generated radiotracers in studies of molecular dynamics

    International Nuclear Information System (INIS)

    Spicer, L.D.

    1981-01-01

    This chapter summarizes many of the contributions that the recoil technique of generating excited radiotracer atoms in the presence of a thermal environment is making to the field of chemical dynamics. Specific topics discussed critically include characterization of the generation and behavior of excited molecules including fragmentation kinetics and energy transfer, measurement of thermal and hot kinetic parameters, and studies of reaction mechanisms and stereochemistry as a function of reaction energy. Distinctive features that provide unique approaches to dynamical problems are evaluated in detail and the complementarity with more conventional techniques is addressed. Prospects for future applications are also presented

  20. Molecular activation analysis for chemical species studies

    International Nuclear Information System (INIS)

    Chai Zhifang; Mao Xueying; Wang Yuqi; Sun Jingxin; Qian Qingfang; Hou Xiaolin; Zhang Peiqun; Chen Chunying; Feng Weiyu; Ding Wenjun; Li Xiaolin; Li Chunsheng; Dai Xiongxin

    2001-01-01

    The Molecular Activation Analysis (MAA) mainly refers to an activation analysis method that is able to provide information about the chemical species of elements in systems of interest, though its exact definition has remained to be assigned. Its development is strongly stimulated by the urgent need to know the chemical species of elements, because the bulk contents or concentrations are often insignificant for judging biological, environmental or geochemical effects of elements. In this paper, the features, methodology and limitation of MAA were outlined. Further, the up-to-date MAA progress made in our laboratory was introduced as well. (author)

  1. Chemical Reactivity and Spectroscopy Explored From QM/MM Molecular Dynamics Simulations Using the LIO Code

    Directory of Open Access Journals (Sweden)

    Juan P. Marcolongo

    2018-03-01

    Full Text Available In this work we present the current advances in the development and the applications of LIO, a lab-made code designed for density functional theory calculations in graphical processing units (GPU, that can be coupled with different classical molecular dynamics engines. This code has been thoroughly optimized to perform efficient molecular dynamics simulations at the QM/MM DFT level, allowing for an exhaustive sampling of the configurational space. Selected examples are presented for the description of chemical reactivity in terms of free energy profiles, and also for the computation of optical properties, such as vibrational and electronic spectra in solvent and protein environments.

  2. Chemical reactivity and spectroscopy explored from QM/MM molecular dynamics simulations using the LIO code

    Science.gov (United States)

    Marcolongo, Juan P.; Zeida, Ari; Semelak, Jonathan A.; Foglia, Nicolás O.; Morzan, Uriel N.; Estrin, Dario A.; González Lebrero, Mariano C.; Scherlis, Damián A.

    2018-03-01

    In this work we present the current advances in the development and the applications of LIO, a lab-made code designed for density functional theory calculations in graphical processing units (GPU), that can be coupled with different classical molecular dynamics engines. This code has been thoroughly optimized to perform efficient molecular dynamics simulations at the QM/MM DFT level, allowing for an exhaustive sampling of the configurational space. Selected examples are presented for the description of chemical reactivity in terms of free energy profiles, and also for the computation of optical properties, such as vibrational and electronic spectra in solvent and protein environments.

  3. A phenomenological approach to modeling chemical dynamics in nonlinear and two-dimensional spectroscopy.

    Science.gov (United States)

    Ramasesha, Krupa; De Marco, Luigi; Horning, Andrew D; Mandal, Aritra; Tokmakoff, Andrei

    2012-04-07

    We present an approach for calculating nonlinear spectroscopic observables, which overcomes the approximations inherent to current phenomenological models without requiring the computational cost of performing molecular dynamics simulations. The trajectory mapping method uses the semi-classical approximation to linear and nonlinear response functions, and calculates spectra from trajectories of the system's transition frequencies and transition dipole moments. It rests on identifying dynamical variables important to the problem, treating the dynamics of these variables stochastically, and then generating correlated trajectories of spectroscopic quantities by mapping from the dynamical variables. This approach allows one to describe non-Gaussian dynamics, correlated dynamics between variables of the system, and nonlinear relationships between spectroscopic variables of the system and the bath such as non-Condon effects. We illustrate the approach by applying it to three examples that are often not adequately treated by existing analytical models--the non-Condon effect in the nonlinear infrared spectra of water, non-Gaussian dynamics inherent to strongly hydrogen bonded systems, and chemical exchange processes in barrier crossing reactions. The methods described are generally applicable to nonlinear spectroscopy throughout the optical, infrared and terahertz regions.

  4. Chemical kinetic insights into the ignition dynamics of n-hexane

    KAUST Repository

    Tingas, Alexandros

    2017-10-13

    Normal alkanes constitute a significant fraction of transportation fuels, and are the primary drivers of ignition processes in gasoline and diesel fuels. Low temperature ignition of n-alkanes is driven by a complex sequence of oxidation reactions, for which detailed mechanisms are still being developed. The current study explores the dynamics of low-temperature ignition of n-hexane/air mixtures, and identifies chemical pathways that characterize the combustion process. Two chemical kinetic mechanisms were selected as a comparative study in order to better understand the role of specific reaction sequences in ignition dynamics: one mechanism including a new third sequential O2 addition reaction pathways (recently proposed by Wang et al. 2017), while the other without (Zhang et al. 2015). The analysis is conducted by applying tools generated from the computational singular perturbation (CSP) approach to two distinct ignition phenomena: constant volume and compression ignition. In both cases, the role of the third sequential O2 addition reactions proves to be significant, although it is found to be much more pronounced in the constant volume cases compared to the HCCI. In particular, in the constant volume ignition case, reactions present in the third sequential O2 addition reaction pathways (e.g., KDHP  →  products + OH) contribute significantly to the explosivity of the mixture; when accounted for along with reactions P(OOH)2 + O2  →  OOP(OOH)2 and OOP(OOH)2  →  KDHP + OH, they decrease ignition delay time of the mixture by up to 40%. Under HCCI conditions, in the first-stage ignition, the third-O2 addition reactions contribute to the process, although their role decays with time and becomes negligible at the end of the first stage. The second ignition stage is dominated almost exclusively by hydrogen-related chemistry.

  5. Theoretical studies of combustion dynamics

    International Nuclear Information System (INIS)

    Bowman, J.M.

    1986-01-01

    The reactions of O( 3 P)+H 2 , D 2 , 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

  6. Can hydroxylamine be a more potent nucleophile for the reactivation of tabun-inhibited AChE than prototype oxime drugs? An answer derived from quantum chemical and steered molecular dynamics studies.

    Science.gov (United States)

    Lo, Rabindranath; Ganguly, Bishwajit

    2014-07-29

    Organophosphorus nerve agents are highly toxic compounds which strongly inhibit acetylcholinesterase (AChE) in the blood and in the central nervous system (CNS). Tabun is one of the highly toxic organophosphorus (OP) compounds and is resistant to many oxime drugs formulated for the reactivation of AChE. The reactivation mechanism of tabun-conjugated AChE with various drugs has been examined with density functional theory and ab initio quantum chemical calculations. The presence of a lone-pair located on the amidic group resists the nucleophilic attack at the phosphorus center of the tabun-conjugated AChE. We have shown that the newly designed drug candidate N-(pyridin-2-yl)hydroxylamine, at the MP2/6-31+G*//M05-2X/6-31G* level in the aqueous phase with the polarizable continuum solvation model (PCM), is more effective in reactivating the tabun-conjugated AChE than typical oxime drugs. The rate determining activation barrier with N-(pyridin-2-yl)hydroxylamine was found to be ∼1.7 kcal mol(-1), which is 7.2 kcal mol(-1) lower than the charged oxime trimedoxime (one of the most efficient reactivators in tabun poisonings). The greater nucleophilicity index (ω(-)) and higher CHelpG charge of pyridinylhydroxylamine compared to TMB4 support this observation. Furthermore, we have also examined the reactivation process of tabun-inhibited AChE with some other bis-quaternary oxime drug candidates such as methoxime (MMB4) and obidoxime. The docking analysis suggests that charged bis-quaternary pyridinium oximes have greater binding affinity inside the active-site gorge of AChE compared to the neutral pyridinylhydroxylamine. The peripheral ligand attached to the neutral pyridinylhydroxylamine enhanced the binding with the aromatic residues in the active-site gorge of AChE through effective π-π interactions. Steered molecular dynamics (SMD) simulations have also been performed with the charged oxime (TMB4) and the neutral hydroxylamine. From protein-drug interaction

  7. Dynamics of the stochastic low concentration trimolecular oscillatory chemical system with jumps

    Science.gov (United States)

    Wei, Yongchang; Yang, Qigui

    2018-06-01

    This paper is devoted to discern long time dynamics through the stochastic low concentration trimolecular oscillatory chemical system with jumps. By Lyapunov technique, this system is proved to have a unique global positive solution, and the asymptotic stability in mean square of such model is further established. Moreover, the existence of random attractor and Lyapunov exponents are obtained for the stochastic homeomorphism flow generated by the corresponding global positive solution. And some numerical simulations are given to illustrate the presented results.

  8. Chemical and Microbial Dynamics during Composting of Herbal Pharmaceutical Industrial Waste

    Directory of Open Access Journals (Sweden)

    Farhan Zameer

    2010-01-01

    Full Text Available A study was performed to analyze the dynamics of chemical, biochemical and microbial parameters during composting of herbal pharmaceutical waste. All the parameters were analyzed at three different intervals of composting (1st, 15th and 60th days. Temperature of the compost pile was initially high (46.2 °C and on 60th day it dropped to 33.3 °C. The pH of the sample was initially acidic (2.39 and with the progress of decomposition gradually changed to neutrality (7.55. Electrical conductivity (EC value was high (3.8 mS during last day of composting compared to other stages. The activity of degradative enzymes namely amylase, invertase and urease were initially high (4.1, 4.79 mg of glucose/g/h and 0.19 mg of ammonia/g/h respectively while it decreased with composting. The beneficial microbial load was initially low and very high at the last stages of decomposition. The bioassay studies using compost extracts revealed that the 60th day old sample was not phytotoxic in nature.

  9. Frictional melting dynamics in the upper conduit: A chemical answer to a complex physical question

    Science.gov (United States)

    Henton De Angelis, S.; Lavallee, Y.; Kendrick, J. E.; Hornby, A.; von Aulock, F. W.; Clesham, S.; Hirose, T.; Perugini, D.

    2013-12-01

    During volcanic eruptions the generation of frictional heat along the walls of the shallow conduit leads to melting of the rocks along the slip interface. Frictional melting has previously been described as a process out of thermodynamic equilibrium, but upon slip and mingling of the melt batches, homogeneity can be achieved, and may have an h important rheological control on the dynamics of slip. To test melt homogenization in the frictional melt zones of volcanic conduits we performed constant-rate slip experiments under controlled stress conditions using a high-velocity rotary shear apparatus. Volcanic dome samples from three different volcanoes (Volcán De Colima, Soufrière Hills Volcano and Santiaguito Volcano) were investigated. Each sample was subjected to a stress of 1 MPa and slip rate of 1 m/s. For each sample set 5 experiments were conducted: 1) experiment stopped at the onset of melting; 2) experiment stopped on the formation of a full melt layer; 3) experiment stopped after 5m of slip at steady state conditions; 4) experiment stopped after 10m of slip at steady state conditions; 5) experiment stopped after 15m of slip at steady state conditions. We analyzed the resulting proto-melt zones using micron sized X-ray spectroscopy in the high-brightness synchrotron beamline I18 (at Diamond Light Source UK). Particular focus was given to the concentration variance analysis of Rare Earth Elements as their mobilities can be used to precisely quantify the degree and timescale of homogenisation involved during frictional melting. This study refines our understanding of the chemical process of melting and mixing which carry important consequences for the rheological control on the physical dynamics of slip.

  10. 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.

  11. 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.

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

    KAUST Repository

    Do, Khanh; Risko, Chad; Anthony, John E; Amassian, Aram; Bredas, Jean-Luc

    2015-01-01

    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.

  13. Automated chemical kinetic modeling via hybrid reactive molecular dynamics and quantum chemistry simulations.

    Science.gov (United States)

    Döntgen, Malte; Schmalz, Felix; Kopp, Wassja A; Kröger, Leif C; Leonhard, Kai

    2018-06-13

    An automated scheme for obtaining chemical kinetic models from scratch using reactive molecular dynamics and quantum chemistry simulations is presented. This methodology combines the phase space sampling of reactive molecular dynamics with the thermochemistry and kinetics prediction capabilities of quantum mechanics. This scheme provides the NASA polynomial and modified Arrhenius equation parameters for all species and reactions that are observed during the simulation and supplies them in the ChemKin format. The ab initio level of theory for predictions is easily exchangeable and the presently used G3MP2 level of theory is found to reliably reproduce hydrogen and methane oxidation thermochemistry and kinetics data. Chemical kinetic models obtained with this approach are ready-to-use for, e.g., ignition delay time simulations, as shown for hydrogen combustion. The presented extension of the ChemTraYzer approach can be used as a basis for methodologically advancing chemical kinetic modeling schemes and as a black-box approach to generate chemical kinetic models.

  14. Ab initio/GIAO-CCSD(T) study of structures, energies, and 13C NMR chemical shifts of C4H7(+) and C5H9(+) ions: relative stability and dynamic aspects of the cyclopropylcarbinyl vs bicyclobutonium ions.

    Science.gov (United States)

    Olah, George A; Surya Prakash, G K; Rasul, Golam

    2008-07-16

    The structures and energies of the carbocations C 4H 7 (+) and C 5H 9 (+) were calculated using the ab initio method. The (13)C NMR chemical shifts of the carbocations were calculated using the GIAO-CCSD(T) method. The pisigma-delocalized bisected cyclopropylcarbinyl cation, 1 and nonclassical bicyclobutonium ion, 2 were found to be the minima for C 4H 7 (+) at the MP2/cc-pVTZ level. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level the structure 2 is 0.4 kcal/mol more stable than the structure 1. The (13)C NMR chemical shifts of 1 and 2 were calculated by the GIAO-CCSD(T) method. Based on relative energies and (13)C NMR chemical shift calculations, an equilibrium involving the 1 and 2 in superacid solutions is most likely responsible for the experimentally observed (13)C NMR chemical shifts, with the latter as the predominant equilibrating species. The alpha-methylcyclopropylcarbinyl cation, 4, and nonclassical bicyclobutonium ion, 5, were found to be the minima for C 5H 9 (+) at the MP2/cc-pVTZ level. At the MP4(SDTQ)/cc-pVTZ//MP2/cc-pVTZ + ZPE level ion 5 is 5.9 kcal/mol more stable than the structure 4. The calculated (13)C NMR chemical shifts of 5 agree rather well with the experimental values of C 5H 9 (+).

  15. Studies on chemical protectors against radiation, 18

    International Nuclear Information System (INIS)

    Shinoda, Masato; Ohta, Setsuko; Hayase, Yukitoshi

    1978-01-01

    Radiation protective effect of S,2-aminomethylisothiuronium bromide hydrobromide and 2-mercaptoethylamine hydrochloride was tested on mice irradiated with soft x-ray of 70 kVp, using life-prolongation effect as an index. These compounds showed a marked effect on mice irradiated with 11000--13000 R, using a 10 mm acrylate filter. This method seemed to be usable as a potency testing for chemical radioprotectors. (auth.)

  16. High resolution time-of-flight spectrometer for crossed molecular beam study of elementary chemical reactions

    International Nuclear Information System (INIS)

    Qiu Minghui; Che Li; Ren Zefeng; Dai Dongxu; Wang Xiuyan; Yang Xueming

    2005-01-01

    In this article, we describe an apparatus in our laboratory for investigating elementary chemical reactions using the high resolution time-of-flight Rydberg tagging method. In this apparatus, we have adopted a rotating source design so that collision energy can be changed for crossed beam studies of chemical reactions. Preliminary results on the HI photodissociation and the F atom reaction with H 2 are reported here. These results suggest that the experimental apparatus is potentially a powerful tool for investigating state-to-state dynamics of elementary chemical reactions

  17. Empirical Force Fields for Mechanistic Studies of Chemical Reactions in Proteins.

    Science.gov (United States)

    Das, A K; Meuwly, M

    2016-01-01

    Following chemical reactions in atomistic detail is one of the most challenging aspects of current computational approaches to chemistry. In this chapter the application of adiabatic reactive MD (ARMD) and its multistate version (MS-ARMD) are discussed. Both methods allow to study bond-breaking and bond-forming processes in chemical and biological processes. Particular emphasis is put on practical aspects for applying the methods to investigate the dynamics of chemical reactions. The chapter closes with an outlook of possible generalizations of the methods discussed. © 2016 Elsevier Inc. All rights reserved.

  18. Decay correction methods in dynamic PET studies

    International Nuclear Information System (INIS)

    Chen, K.; Reiman, E.; Lawson, M.

    1995-01-01

    In order to reconstruct positron emission tomography (PET) images in quantitative dynamic studies, the data must be corrected for radioactive decay. One of the two commonly used methods ignores physiological processes including blood flow that occur at the same time as radioactive decay; the other makes incorrect use of time-accumulated PET counts. In simulated dynamic PET studies using 11 C-acetate and 18 F-fluorodeoxyglucose (FDG), these methods are shown to result in biased estimates of the time-activity curve (TAC) and model parameters. New methods described in this article provide significantly improved parameter estimates in dynamic PET studies

  19. Chemical and biological activity in open flows: A dynamical system approach

    International Nuclear Information System (INIS)

    Tel, Tamas; Moura, Alessandro de; Grebogi, Celso; Karolyi, Gyoergy

    2005-01-01

    Chemical and biological processes often take place in fluid flows. Many of them, like environmental or microfluidical ones, generate filamentary patterns which have a fractal structure, due to the presence of chaos in the underlying advection dynamics. In such cases, hydrodynamical stirring strongly couples to the reactivity of the advected species: the outcome of the reaction is then typically different from that of the same reaction taking place in a well-mixed environment. Here we review recent progress in this field, which became possible due to the application of methods taken from dynamical system theory. We place special emphasis on the derivation of effective rate equations which contain singular terms expressing the fact that the reaction takes place on a moving fractal catalyst, on the unstable foliation of the reaction free advection dynamics

  20. Radiation-Induced Chemical Dynamics in Ar Clusters Exposed to Strong X-Ray Pulses

    Science.gov (United States)

    Kumagai, Yoshiaki; Jurek, Zoltan; Xu, Weiqing; Fukuzawa, Hironobu; Motomura, Koji; Iablonskyi, Denys; Nagaya, Kiyonobu; Wada, Shin-ichi; Mondal, Subhendu; Tachibana, Tetsuya; Ito, Yuta; Sakai, Tsukasa; Matsunami, Kenji; Nishiyama, Toshiyuki; Umemoto, Takayuki; Nicolas, Christophe; Miron, Catalin; Togashi, Tadashi; Ogawa, Kanade; Owada, Shigeki; Tono, Kensuke; Yabashi, Makina; Son, Sang-Kil; Ziaja, Beata; Santra, Robin; Ueda, Kiyoshi

    2018-06-01

    We show that electron and ion spectroscopy reveals the details of the oligomer formation in Ar clusters exposed to an x-ray free electron laser (XFEL) pulse, i.e., chemical dynamics triggered by x rays. With guidance from a dedicated molecular dynamics simulation tool, we find that van der Waals bonding, the oligomer formation mechanism, and charge transfer among the cluster constituents significantly affect ionization dynamics induced by an XFEL pulse of moderate fluence. Our results clearly demonstrate that XFEL pulses can be used not only to "damage and destroy" molecular assemblies but also to modify and transform their molecular structure. The accuracy of the predictions obtained makes it possible to apply the cluster spectroscopy, in connection with the respective simulations, for estimation of the XFEL pulse fluence in the fluence regime below single-atom multiple-photon absorption, which is hardly accessible with other diagnostic tools.

  1. Water dynamics of Ser-His-Glu-Cys-Asn powder and effects of moisture absorption on its chemical properties.

    Science.gov (United States)

    Lin, Songyi; Xue, Peiyu; Yang, Shuailing; Li, Xingfang; Dong, Xiuping; Chen, Feng

    2017-08-01

    This study has elucidated moisture dynamics in the soybean peptide, Ser-His-Glu-Cys-Asn (SHECN) powder by using dynamic vapor sorption (DVS) and nuclear magnetic resonance (NMR). We also tried to investigate the effects of moisture absorption on the biological activity and chemical properties of SHECN with some effective methods such as mid-infrared (MIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). DVS results showed that the moisture absorption of SHECN could reach a maximum of 33%, and the SHECN powder after synthesis actually existed in a trihydrate state of SHECN.3H 2 O. Low-field NMR revealed that three water proportions including strong combined water, binding water and bulk water were involved in SHECN moisture absorption and absored water dominantly existed in the form of combined water. Magnetic resonance imaging (MRI) and MIR spectroscopy results indicated that moisture absorption could change the morphology and structure of SHECN. After moisture absorption at 50% and 75% relative humidity, 19 volatiles were identified by GC-MS analysis. Additionally, this study showed that a part of reductive groups in SHECN was oxidized and its antioxidant ability declined significantly (P moisture absorption. Water absorbed into SHECN powder can significantly change its microstructure and cause its activity to decrease. We must prevent SHECN from absorbing moisture during storage because the water can accelerate the oxidation of samples and promote microbial reactions. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  2. Physico-chemical study on guar gum

    International Nuclear Information System (INIS)

    Mahmoud, Nahla Mubarak

    2000-05-01

    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 (S 1 and S 2 respectively). Our analytical data are compared with those of previous workers in this area and international quality. Guar gum (S 2 ) 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 (S 1 and S 2 ) 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 7.01x10 5

  3. Biofiltration of airborne VOCs with green wall systems-Microbial and chemical dynamics.

    Science.gov (United States)

    Mikkonen, A; Li, T; Vesala, M; Saarenheimo, J; Ahonen, V; Kärenlampi, S; Blande, J D; Tiirola, M; Tervahauta, A

    2018-05-06

    Botanical air filtration is a promising technology for reducing indoor air contaminants, but the underlying mechanisms need better understanding. Here, we made a set of chamber fumigation experiments of up to 16 weeks of duration, to study the filtration efficiencies for seven volatile organic compounds (VOCs; decane, toluene, 2-ethylhexanol, α-pinene, octane, benzene, and xylene) and to monitor microbial dynamics in simulated green wall systems. Biofiltration functioned on sub-ppm VOC levels without concentration-dependence. Airflow through the growth medium was needed for efficient removal of chemically diverse VOCs, and the use of optimized commercial growth medium further improved the efficiency compared with soil and Leca granules. Experimental green wall simulations using these components were immediately effective, indicating that initial VOC removal was largely abiotic. Golden pothos plants had a small additional positive impact on VOC filtration and bacterial diversity in the green wall system. Proteobacteria dominated the microbiota of rhizosphere and irrigation water. Airborne VOCs shaped the microbial communities, enriching potential VOC-utilizing bacteria (especially Nevskiaceae and Patulibacteraceae) in the irrigation water, where much of the VOC degradation capacity of the biofiltration systems resided. These results clearly show the benefits of active air circulation and optimized growth media in modern green wall systems. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. An automated method to find transition states using chemical dynamics simulations.

    Science.gov (United States)

    Martínez-Núñez, Emilio

    2015-02-05

    A procedure to automatically find the transition states (TSs) of a molecular system (MS) is proposed. It has two components: high-energy chemical dynamics simulations (CDS), and an algorithm that analyzes the geometries along the trajectories to find reactive pathways. Two levels of electronic structure calculations are involved: a low level (LL) is used to integrate the trajectories and also to optimize the TSs, and a higher level (HL) is used to reoptimize the structures. The method has been tested in three MSs: formaldehyde, formic acid (FA), and vinyl cyanide (VC), using MOPAC2012 and Gaussian09 to run the LL and HL calculations, respectively. Both the efficacy and efficiency of the method are very good, with around 15 TS structures optimized every 10 trajectories, which gives a total of 7, 12, and 83 TSs for formaldehyde, FA, and VC, respectively. The use of CDS makes it a powerful tool to unveil possible nonstatistical behavior of the system under study. © 2014 Wiley Periodicals, Inc.

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

    International Nuclear Information System (INIS)

    Nepomuceno, N.; Fernandes, E.A.N.; Bacchi, M.A.

    1997-01-01

    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)

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

    International Nuclear Information System (INIS)

    Yonehara, Takehiro; Takatsuka, Kazuo

    2009-01-01

    We report a theoretical study of non-adiabatic electrons-nuclei coupled dynamics of diborane H 2 BH 2 BH 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 3 -BH 3 ; and (iv) nuclear derivative coupling plays a critical role in the field induced

  7. Effects of chemical modifications on photophysics and exciton dynamics on {pi}-conjugation attenuated and metal-chelated photoconducting polymers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, L. X.; Jager, W. J. H.; Gosztola, D. J.; Niemczyk, M. P.; Wasielewski, M. R.

    2000-03-11

    Effects of two types of chemical modifications on photoconducting polymers consisting of polyphenylenevinylene (PPV) derivatives are studied by static and ultrafast transient optical spectroscopy as well as semi-empirical ZINDO calculations. The first type of modification inserts 2,2{prime}-bipyridyl-5-vinylene units (bpy V) in the PPV backbone, and the second type involves metal-chelation with the bpy sites. Photoluminescence and exciton dynamics of polymers 1 and 2 with PV:bpyV ratios of 1 and 3 were examined in solution, and compared to those of the homopolymer, poly(2,5-bis(2{prime}-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV). Similar studies were carried out for several metal-chelated polymers. These results can be explained by changes in {pi}-conjugation throughout the polymer backbone. The attenuation in {pi}-conjugation by the chemical modifications transforms a conducting polymer from one-dimensional semiconductor to molecular aggregates.

  8. 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...

  9. ORIGIN OF CHEMICAL AND DYNAMICAL PROPERTIES OF THE GALACTIC THICK DISK

    International Nuclear Information System (INIS)

    Bekki, Kenji; Tsujimoto, Takuji

    2011-01-01

    We adopt a scenario in which the Galactic thick disk was formed by minor merging between the first generation of the Galactic thin disk (FGTD) and a dwarf galaxy about ∼9 Gyr ago and thereby investigate chemical and dynamical properties of the Galactic thick disk. In this scenario, the dynamical properties of the thick disk have long been influenced both by the mass growth of the second generation of the Galactic thin disk (i.e., the present thin disk) and by its non-axisymmetric structures. On the other hand, the early star formation history and chemical evolution of the thin disk was influenced by the remaining gas of the thick disk. Based on N-body simulations and chemical evolution models, we investigate the radial metallicity gradient, structural and kinematical properties, and detailed chemical abundance patterns of the thick disk. Our numerical simulations show that the ancient minor merger event can significantly flatten the original radial metallicity gradient of the FGTD, in particular, in the outer part, and also can be responsible for migration of inner metal-rich stars into the outer part (R > 10 kpc). The simulations show that the central region of the thick disk can develop a bar due to dynamical effects of a separate bar in the thin disk. Whether or not rotational velocities (V φ ) can correlate with metallicities ([Fe/H]) for the simulated thick disks depends on the initial metallicity gradients of the FGTDs. The simulated orbital eccentricity distributions in the thick disk for models with higher mass ratios (∼0.2) and lower orbital eccentricities (∼0.5) of minor mergers are in good agreement with the corresponding observations. The simulated V φ -|z| relation of the thick disk in models with low orbital inclination angles of mergers are also in good agreement with the latest observational results. The vertical metallicity gradient of the simulated thick disk is rather flat or very weakly negative in the solar neighborhood. Our Galactic

  10. 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.

  11. Structures in dynamics finite dimensional deterministic studies

    CERN Document Server

    Broer, HW; van Strien, SJ; Takens, F

    1991-01-01

    The study of non-linear dynamical systems nowadays is an intricate mixture of analysis, geometry, algebra and measure theory and this book takes all aspects into account. Presenting the contents of its authors' graduate courses in non-linear dynamical systems, this volume aims at researchers who wish to be acquainted with the more theoretical and fundamental subjects in non-linear dynamics and is designed to link the popular literature with research papers and monographs. All of the subjects covered in this book are extensively dealt with and presented in a pedagogic

  12. Combinatorial computational chemistry approach of tight-binding quantum chemical molecular dynamics method to the design of the automotive catalysts

    International Nuclear Information System (INIS)

    Ito, Yuki; Jung, Changho; Luo, Yi; Koyama, Michihisa; Endou, Akira; Kubo, Momoji; Imamura, Akira; Miyamoto, Akira

    2006-01-01

    Recently, we have developed a new tight-binding quantum chemical molecular dynamics program 'Colors' for combinatorial computational chemistry approach. This methodology is based on our original tight-binding approximation and realized over 5000 times acceleration compared to the conventional first-principles molecular dynamics method. In the present study, we applied our new program to the simulations on various realistic large-scale models of the automotive three-way catalysts, ultrafine Pt particle/CeO 2 (111) support. Significant electron transfer from the Pt particle to the CeO 2 (111) surface was observed and it was found to strongly depend on the size of the Pt particle. Furthermore, our simulation results suggest that the reduction of the Ce atom due to the electron transfer from the Pt particle to the CeO 2 surface is a main reason for the strong interaction of the Pt particle and CeO 2 (111) support

  13. 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.

  14. Disorder-induced amorphization of intermetallic compounds: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Massobrio, C. (Ecole Polytechnique Federale, Lausanne (Switzerland). Inst. de Physique Experimentale); Pontikis, V.; Doan, N.V.; Martin, G. (CEA Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Physique des Particules Elementaires)

    The reaction of the crystalline compound NiZr{sub 2} to imposed chemical disorder has been studied by molecular dynamics in the isobaric canonical ensemble. The cohesive energy used is inspired by the second moment apporoximation of the local density of states in the tight binding model. Imposed chemical disorder induced swelling (3% for full disorder, 1% for 10% disorder). Above 10% disorder, the crystalline structure athermally collapses to an amorphous state which retains much of the local chemical order. (orig.).

  15. Disorder-induced amorphization of intermetallic compounds: A molecular dynamics study

    International Nuclear Information System (INIS)

    Massobrio, C.; Pontikis, V.; Doan, N.V.; Martin, G.

    1991-01-01

    The reaction of the crystalline compound NiZr 2 to imposed chemical disorder has been studied by molecular dynamics in the isobaric canonical ensemble. The cohesive energy used is inspired by the second moment apporoximation of the local density of states in the tight binding model. Imposed chemical disorder induced swelling (3% for full disorder, 1% for 10% disorder). Above 10% disorder, the crystalline structure athermally collapses to an amorphous state which retains much of the local chemical order. (orig.)

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

    International Nuclear Information System (INIS)

    Anda, A.A.; Phillips, D.L.; Valentini, J.J.

    1986-01-01

    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

  17. Dynamics of shearing force and its correlations with chemical compositions and dry matter digestibility of stylo ( stem

    Directory of Open Access Journals (Sweden)

    Xuejuan Zi

    2017-12-01

    Full Text Available Objective The study explored the dynamics of shearing force and its correlation with chemical compositions and in vitro dry matter digestibility (IVDMD of stylo. Methods The shearing force, diameter, linear density, chemical composition, and IVDMD of different height stylo stem were investigated. Linear regression analysis was done to determine the relationships between the shearing force and cut height, diameter, chemical composition, or IVDMD. Results The results showed that shearing force of stylo stem increased with plant height increasing and the crude protein (CP content and IVDMD decreased but fiber content increased over time, resulting in decreased forage value. In addition, tall stem had greater shearing force than short stem. Moreover, shearing force is positively correlated with stem diameter, linear density and fiber fraction, but negatively correlated with CP content and IVDMD. Conclusion Overall, shearing force is an indicator more direct, easier and faster to measure than chemical composition and digestibility for evaluation of forage nutritive value related to animal performance. Therefore, it can be used to evaluate the nutritive value of stylo.

  18. Contribution to chemical-mineralogical study of carbonatites

    International Nuclear Information System (INIS)

    Costa, M.Q. da; Lima, W.N. de; Correa, S.L.A.

    1982-01-01

    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) [pt

  19. Inventory Control: A Small Electronic Device for Studying Chemical Kinetics.

    Science.gov (United States)

    Perez-Rodriguez, A. L.; Calvo-Aguilar, J. L.

    1984-01-01

    Shows how the rate of reaction can be studied using a simple electronic device that overcomes the difficulty students encounter in solving the differential equations describing chemical equilibrium. The device, used in conjunction with an oscilloscope, supplies the voltages that represent the chemical variables that take part in the equilibrium.…

  20. Multimegawatt dynamic NEP PMAD study

    International Nuclear Information System (INIS)

    Metcalf, K.J.

    1993-01-01

    The National Aeronautics and Space Administration Lewis Research Center (NASA LeRC) is developing a Fortran--based model of a complete nuclear electric propulsion (NEP) vehicle to be used for piloted or cargo missions to the Moon or Mars. The proposed vehicle will use either a Brayton or K-Rankine power conversion cycle, and either ion or magnetoplasmadynamic (MPD) thrusters. In support of this effort, Rocketdyne evaluated various power management and distribution (PMAD) approaches and selected a low-frequency design that is based on the direct use of the alternator voltage and frequency for power transmission. This approach was compared with dc and high-frequency ac designs, and selected on the basis of mass, efficiency, and qualitative assessments of power quality, reliability and development costs. This low-frequency architecture will be used as the reference in future NEP PMAD studies and for the subsequent Fortran model development

  1. All-in-one light-tunable borated phosphors with chemical and luminescence dynamical control resolution.

    Science.gov (United States)

    Lin, Chun Che; Liu, Yun-Ping; Xiao, Zhi Ren; Wang, Yin-Kuo; Cheng, Bing-Ming; Liu, Ru-Shi

    2014-06-25

    Single-composition white-emitting phosphors with superior intrinsic properties upon excitation by ultraviolet light-emitting diodes are important constituents of next-generation light sources. Borate-based phosphors, such as NaSrBO3:Ce(3+) and NaCaBO3:Ce(3+), have stronger absorptions in the near-ultraviolet region as well as better chemical/physical stability than oxides. Energy transfer effects from sensitizer to activator caused by rare-earth ions are mainly found in the obtained photoluminescence spectra and lifetime. The interactive mechanisms of multiple dopants are ambiguous in most cases. We adjust the doping concentration in NaSrBO3:RE (RE = Ce(3+), Tb(3+), Mn(2+)) to study the energy transfer effects of Ce(3+) to Tb(3+) and Mn(2+) by comparing the experimental data and theoretical calculation. The vacuum-ultraviolet experimental determination of the electronic energy levels for Ce(3+) and Tb(3+) in the borate host regarding the 4f-5d and 4f-4f configurations are described. Evaluation of the Ce(3+)/Mn(2+) intensity ratios as a function of Mn(2+) concentration is based on the analysis of the luminescence dynamical process and fluorescence lifetime measurements. The results closely agree with those directly obtained from the emission spectra. Density functional calculations are performed using the generalized gradient approximation plus an on-site Coulombic interaction correction scheme to investigate the forbidden mechanism of interatomic energy transfer between the NaSrBO3:Ce(3+) and NaSrBO3:Eu(2+) systems. Results indicate that the NaSrBO3:Ce(3+), Tb(3+), and Mn(2+) phosphors can be used as a novel white-emitting component of UV radiation-excited devices.

  2. Experimental research of the impact of the dosing of chemical reagents on the dynamic behavior of regulation system of cycle chemistry

    Science.gov (United States)

    Yegoshina, O. V.; Bolshakova, N. A.

    2017-11-01

    Organization of reliable chemical control for maintaining cycle chemistry is one of the most important problems to be solved at the present time the design and operation of thermal power plants. To maintain optimal parameters of cycle chemistry are used automated chemical control system and regulation system of dosing chemical reagents. Reliability and stability analyzer readings largely determine the reliability of the water cycle chemistry. Now the most common reagents are ammonia, alkali and film-forming amines. In this paper are presented the results of studies of the impact of concentration and composition of chemical reagents for readings stability of automatic analyzers and transients time of control systems for cycles chemistry. Research of the impact of chemical reagents on the dynamic behavior of regulation system for cycle chemistry was conducted at the experimental facility of the Department of thermal power stations of the Moscow Engineering Institute. This experimental facility is model of the work of regulation system for cycle chemistry close to the actual conditions on the energy facilities CHP. Analysis of results of the impact of chemical reagent on the dynamic behavior of ammonia and film forming amines dosing systems showed that the film-forming amines dosing system is more inertia. This emphasizes the transition process of the system, in which a half times longer dosing of ammonia. Results of the study can be used to improve the monitoring systems of water chemical treatment.

  3. Nanomaterials under extreme environments: A study of structural and dynamic properties using reactive molecular dynamics simulations

    Science.gov (United States)

    Shekhar, Adarsh

    Nanotechnology is becoming increasingly important with the continuing advances in experimental techniques. As researchers around the world are trying to expand the current understanding of the behavior of materials at the atomistic scale, the limited resolution of equipment, both in terms of time and space, act as roadblocks to a comprehensive study. Numerical methods, in general and molecular dynamics, in particular act as able compliment to the experiments in our quest for understanding material behavior. In this research work, large scale molecular dynamics simulations to gain insight into the mechano-chemical behavior under extreme conditions of a variety of systems with many real world applications. The body of this work is divided into three parts, each covering a particular system: 1) Aggregates of aluminum nanoparticles are good solid fuel due to high flame propagation rates. Multi-million atom molecular dynamics simulations reveal the mechanism underlying higher reaction rate in a chain of aluminum nanoparticles as compared to an isolated nanoparticle. This is due to the penetration of hot atoms from reacting nanoparticles to an adjacent, unreacted nanoparticle, which brings in external heat and initiates exothermic oxidation reactions. 2) Cavitation bubbles readily occur in fluids subjected to rapid changes in pressure. We use billion-atom reactive molecular dynamics simulations on a 163,840-processor BlueGene/P supercomputer to investigate chemical and mechanical damages caused by shock-induced collapse of nanobubbles in water near amorphous silica. Collapse of an empty nanobubble generates high-speed nanojet, resulting in the formation of a pit on the surface. The pit contains a large number of silanol groups and its volume is found to be directly proportional to the volume of the nanobubble. The gas-filled bubbles undergo partial collapse and consequently the damage on the silica surface is mitigated. 3) The structure and dynamics of water confined in

  4. Assessing the chemical contamination dynamics in a mixed land use stream system.

    Science.gov (United States)

    Sonne, Anne Th; McKnight, Ursula S; Rønde, Vinni; Bjerg, Poul L

    2017-11-15

    Traditionally, the monitoring of streams for chemical and ecological status has been limited to surface water concentrations, where the dominant focus has been on general water quality and the risk for eutrophication. Mixed land use stream systems, comprising urban areas and agricultural production, are challenging to assess with multiple chemical stressors impacting stream corridors. New approaches are urgently needed for identifying relevant sources, pathways and potential impacts for implementation of suitable source management and remedial measures. We developed a method for risk assessing chemical stressors in these systems and applied the approach to a 16-km groundwater-fed stream corridor (Grindsted, Denmark). Three methods were combined: (i) in-stream contaminant mass discharge for source quantification, (ii) Toxic Units and (iii) environmental standards. An evaluation of the chemical quality of all three stream compartments - stream water, hyporheic zone, streambed sediment - made it possible to link chemical stressors to their respective sources and obtain new knowledge about source composition and origin. Moreover, toxic unit estimation and comparison to environmental standards revealed the stream water quality was substantially impaired by both geogenic and diffuse anthropogenic sources of metals along the entire corridor, while the streambed was less impacted. Quantification of the contaminant mass discharge originating from a former pharmaceutical factory revealed that several 100 kgs of chlorinated ethenes and pharmaceutical compounds discharge into the stream every year. The strongly reduced redox conditions in the plume result in high concentrations of dissolved iron and additionally release arsenic, generating the complex contaminant mixture found in the narrow discharge zone. The fingerprint of the plume was observed in the stream several km downgradient, while nutrients, inorganics and pesticides played a minor role for the stream health. The

  5. Emergency material allocation with time-varying supply-demand based on dynamic optimization method for river chemical spills.

    Science.gov (United States)

    Liu, Jie; Guo, Liang; Jiang, Jiping; Jiang, Dexun; Wang, Peng

    2018-04-13

    Aiming to minimize the damage caused by river chemical spills, efficient emergency material allocation is critical for an actual emergency rescue decision-making in a quick response. In this study, an emergency material allocation framework based on time-varying supply-demand constraint is developed to allocate emergency material, minimize the emergency response time, and satisfy the dynamic emergency material requirements in post-accident phases dealing with river chemical spills. In this study, the theoretically critical emergency response time is firstly obtained for the emergency material allocation system to select a series of appropriate emergency material warehouses as potential supportive centers. Then, an enumeration method is applied to identify the practically critical emergency response time, the optimum emergency material allocation and replenishment scheme. Finally, the developed framework is applied to a computational experiment based on south-to-north water transfer project in China. The results illustrate that the proposed methodology is a simple and flexible tool for appropriately allocating emergency material to satisfy time-dynamic demands during emergency decision-making. Therefore, the decision-makers can identify an appropriate emergency material allocation scheme in a balance between time-effective and cost-effective objectives under the different emergency pollution conditions.

  6. Study on flow characteristics of chemically reacting liquid jet

    International Nuclear Information System (INIS)

    Hong Seon Dae; Okamoto, Koji; Takata, Takashi; Yamaguchi, Akira

    2004-07-01

    Tube rupture accidents in steam generators of sodium-cooled fast breeder reactors are important for safety because the rupture may propagates to neighboring tubes due to sodium-water reaction. In order to clarify the thermal-hydraulic phenomena in the accidents, the flow pattern and the interface in multi-phase flow must be investigated. The JNC cooperative research scheme on the nuclear fuel cycle with the University of Tokyo has been carried to develop a simultaneous measurement system of concentration and velocity profiles and to evaluate influence of chemical reaction on mixing phenomena. In the experiments, aqueous liquor of acetic acid and ammonium hydroxide are selected as a simulant fluid instead of liquid sodium and water vapor. The following conclusions are obtained in this research. Laser Induced Fluorescence (LIF) technique was adopted to measure reacting zone and pH distribution in chemically reacting liquid round free jet. As a result, it was found that the chemical reaction, which took place at the interface between the jet and outer flow, suppressed the mixing phenomenon (in 2001 research). Dynamic Particle Image Velocimetry (PIV) method was developed to measure instantaneous velocity profile with high temporal resolution. In the Dynamic PIV, a high-speed video camera coupled with a high-speed laser pulse generator was implemented. A time-line trend of interfacial area in the free jet was investigated with the Dynamic PIV. This technique was also applied to a complicated geometry (in 2002 research). A new algorithms for image analysis was developed to evaluated the Dynamic PIV data in detail. The characteristics of the mixing phenomenon with reacting jet such as the turbulent kinetic energy and the Reynolds stress were estimated in a spatial and temporal spectrum (in 2003 research). (author)

  7. Resonance Ionization Mass Spectrometry (RIMS): applications in spectroscopy and chemical dynamics

    International Nuclear Information System (INIS)

    Naik, P.D.; Kumar, Awadhesh; Upadhyaya, Hari; Bajaj, P.N.

    2009-01-01

    Resonance ionization is a photophysical process wherein electromagnetic radiation is used to ionize atoms, molecules, transient species, etc., by exciting them through their quantum states. The number of photons required to ionize depends on the species being investigated and energy of the photon. Once a charged particle is produced, it is easy to detect it with high efficiency. With the advent of narrow band high power pulsed and cw tunable dye lasers, it has blossomed into a powerful spectroscopic and analytical technique, commonly known as resonance ionization spectroscopy (RIS)/resonance enhanced multiphoton ionization (REMPI). The alliance of resonance ionization with mass spectrometry has grown into a still more powerful technique, known as resonance ionization mass spectrometry (RIMS), which has made significant contributions in a variety of frontier areas of research and development, such as spectroscopy, chemical dynamics, analytical chemistry, cluster science, surface science, radiochemistry, nuclear physics, biology, environmental science, material science, etc. In this article, we shall describe the application of resonance ionization mass spectrometry to spectroscopy of uranium and chemical dynamics of polyatomic molecules

  8. Quantum chemical molecular dynamical investigation of alkyl nitrite photo-dissociated on copper surfaces

    International Nuclear Information System (INIS)

    Wang Xiaojing; Wang Wei; Han Peilin; Kubo, Momoji; Miyamoto, Akira

    2008-01-01

    An accelerated quantum chemical molecular dynamical code 'Colors-Excite' was used to investigate the photolysis of alkyl nitrites series, RONO (R=CH 3 and C(CH 3 ) 3 ) on copper surfaces. Our calculations showed that the photo-dissociated processes are associated with the alkyl substituents of RONO when adsorbed on copper surfaces. For R=CH 3 , a two-step photolysis reaction occurred, yielding diverse intermediate products including RO radical, NO, and HNO, consistent with those reported in gas phase. While for R=C(CH 3 ) 3 , only one-step photolysis reaction occurred and gave intermediate products of RO radical and NO. Consequently, pure RO species were achieved to adsorb on metal surfaces by removing the NO species in photolysis reaction. The detailed photo-dissociated behaviors of RONO on copper surfaces with different alkyl substituents which are uncovered by the present simulation can be extended to explain the diverse dissociative mechanism experimentally observed. The quantum chemical molecular dynamical code 'Colors-Excite' is proved to be highly applicable to the photo-dissociations on metal surfaces

  9. Dynamics-based selective 2D 1H/1H chemical shift correlation spectroscopy under ultrafast MAS conditions

    Science.gov (United States)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-05-01

    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 1H 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 1H/1H 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.

  10. Dynamics-based selective 2D 1H/1H chemical shift correlation spectroscopy under ultrafast MAS conditions

    International Nuclear Information System (INIS)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-01-01

    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 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 1 H/ 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

  11. Population dynamics of earthworms in relation to soil physico-chemical parameters in agroforestry systems of Mizoram, India.

    Science.gov (United States)

    Lalthanzara, H; Ramanujam, S N; Jha, L K

    2011-09-01

    Earthworm population dynamics was studied in two agroforestry systems in the tropical hilly terrain of Mizoram, north-east India, over a period of 24 months, from July 2002 to June 2004. Two sites of agroforestry situated at Sakawrtuichhun (SKT) and Pachhunga University College (PUC) campus, Aizawl, having pineapple as the main crop, were selected for detail studies on population dynamics. Five of the total twelve species of earthworm reported from the state were recorded in the study sites. The density of earthworm ranged from 6 to 243 ind.m(-2) and biomass from 3.2 - 677.64 g.m(-2) in SKT. Comparatively the density and biomass in PUC, which is at relatively higher altitude were lowerwith a range of 0 to 176 ind.m(-2) and biomass from 0 - 391.36 g.m(-2) respectively. Population dynamics of earthworm was significantly correlated with rainfall and physical characters of the soil. Earthworm biomass was significantly affected by rainfall and moisture content of the soil. The influence of chemical factors was relatively less.

  12. Molecular dynamics studies of superionic conductors

    International Nuclear Information System (INIS)

    Rahman, A.; Vashishta, P.

    1983-01-01

    Structural and dynamical properties of superionic conductors AgI and CuI are studied using molecular dynamics (MD) techniques. The model of these superionic conductors is based on the use of effective pair potentials. To determine the constants in these potentials, cohesive energy and bulk modulus are used as input: in addition one uses notions of ionic size based on the known crystal structure. Salient features of the MD technique are outlined. Methods of treating long range Coulomb forces are discussed in detail. This includes the manner of doing Ewald sum for MD cells of arbitrary shape. Features that can be incorporated to expedite the MD calculations are also discussed. A novel MD technique which allows for a dynamically controlled variation of the shape and size of the MD cell is described briefly. The development of this novel technique has made it possible to study structural phase transitions in superionic conductors. 68 references, 17 figures, 2 tables

  13. Computer processing of dynamic scintigraphic studies

    International Nuclear Information System (INIS)

    Ullmann, V.

    1985-01-01

    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.)

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

    Indian Academy of Sciences (India)

    WINTEC

    Department of PG Studies and Research in Chemistry, School of Chemical Sciences, Kuvempu University, ... cations and is mainly used for the corrosion protection of ... provide a greater resistance to corrosion, but when exposed to humid ...

  15. Dynamic absorption coefficients of chemically amplified resists and nonchemically amplified resists at extreme ultraviolet

    Science.gov (United States)

    Fallica, Roberto; Stowers, Jason K.; Grenville, Andrew; Frommhold, Andreas; Robinson, Alex P. G.; Ekinci, Yasin

    2016-07-01

    The dynamic absorption coefficients of several chemically amplified resists (CAR) and non-CAR extreme ultraviolet (EUV) photoresists are measured experimentally using a specifically developed setup in transmission mode at the x-ray interference lithography beamline of the Swiss Light Source. The absorption coefficient α and the Dill parameters ABC were measured with unprecedented accuracy. In general, the α of resists match very closely with the theoretical value calculated from elemental densities and absorption coefficients, whereas exceptions are observed. In addition, through the direct measurements of the absorption coefficients and dose-to-clear values, we introduce a new figure of merit called chemical sensitivity to account for all the postabsorption chemical reaction ongoing in the resist, which also predicts a quantitative clearing volume and clearing radius, due to the photon absorption in the resist. These parameters may help provide deeper insight into the underlying mechanisms of the EUV concepts of clearing volume and clearing radius, which are then defined and quantitatively calculated.

  16. Aldehyde-functionalized chitosan-montmorillonite films as dynamically-assembled, switchable-chemical release bioplastics.

    Science.gov (United States)

    Chabbi, Jamal; Jennah, Oumayma; Katir, Nadia; Lahcini, Mohamed; Bousmina, Mosto; El Kadib, Abdelkrim

    2018-03-01

    Temporal release of synergistic and/or complementary chemicals (e.g.: drugs) is recognized as extremely challenging because of their frequently intertwined kinetic delivery and presently, straightforward concepts enabling to circumvent this bottleneck are missing in the open literature. In this framework, we report herein on aldehyde-functionalized, transparent and flexible chitosan-montmorillonite hybrid films that act as a new generation of eco-friendly, controlled-chemical release bioplastics. These dynamically-assembled nanomaterials are designed by a ternary assembly from biowaste derived chitin biopolymer, aromatic aldehydes and layered clay nanoparticles. On the basis of their geometrical and conformational properties, the oxygenated groups on the grafted aromatics interact preferentially with either the base Schiff belonging to the carbohydrate (via intramolecular CNHO-Ar known as "imine clip") or with the hydroxyl groups belonging to the clay surface (via intermolecular Si-OHO-Ar). The exfoliated clay nanoparticles within the carbohydrate polymer enables either accelerating or slowing down of the imine (CN) hydrolysis depending on the interaction of the conjugated aromatics. This provides the driving force for fine tuning host-guest interactions at the molecular level and constitutes an entry toward subtle discrimination of different chemicals (e.g. complementary fertilizers, synergistic drugs) during their sequential release. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. 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

  18. Studies on chemical protectors against radiation, 26

    International Nuclear Information System (INIS)

    Sato, Yushi; Ohta, Setsuko; Sakurai, Nobuko; Shinoda, Masato

    1989-01-01

    The protective potency against skin injury on mice induced by X-irradiation was studied by use of 72 extracts of crude drugs. The protective potency was determined according to the degrees of skin injury after irradiation of 1100 R, 30 kVp soft X-ray. As a result of this study, 16 kinds of crude drugs such as Rosae Fructus, Aloe arboresces (Herba), Citri Leiocarpae Exocarpium, Schizonepetae Spica, Evodiae Fructus, Bupleuri Radix, Corni Fructus, Perillae Herba, Anemarrhenae Rhizoma, Menthae Herba, Trapae Fructus, Angelicae Dahuricae Radix, Sinomeni Caulis et Rhizoma, Ephedrae Herba. Acer nikoense (Cortex), Forsythiae Fructus, revealed protective potencies on skin injury. (author)

  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. Electrochemical, surface analytical and quantum chemical studies ...

    Indian Academy of Sciences (India)

    subject of numerous studies due to their high technological value and wide range .... Mulliken population analysis of atoms in triazole derivatives, depending on the ... 2102–0003) with an accelerating voltage of 20 kV, at a scan speed=slow 5 and ... the corrosion rate can also be determined by Tafel extra- polation of either ...

  1. Studies on the chemical composition and physicochemical ...

    African Journals Online (AJOL)

    Results obtained showed that the saponification value (SV), iodine value (IV), peroxide value (PV), acid value (AV), percentage free fatty acid (%FFA) and refractive index of the oil are 196 ± 0.05 mg/KOH, ... The storage property of the oil from baobab seeds studied over a period of four weeks under conditions of light

  2. 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)

    1999-12-31

    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.)

  3. 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.)

  4. 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.

  5. A study of the HEB longitudinal dynamics

    International Nuclear Information System (INIS)

    Larson, D.J.

    1993-12-01

    A study of the High Energy Booster (HEB) longitudinal dynamics is presented. Full derivations of ramp dependent longitudinal variables are given. The formulas assume that the input magnetic field and beam longitudinal emittance are known as a function of time, and that either the rf voltage or the rf bucket area are known as a function of time. Once these three inputs are specified, the formulas can be used to calculate values for all other longitudinal dynamics variables. The formulas have been incorporated into a single computer code named ELVIRA: Evaluation of Longitudinal Variables in Relativistic Accelerators. The ELVIRA code is documented here in detail. The ELVIRA code is used under two initial longitudinal emittance assumptions to plot ramp functions for the longitudinal dynamics design of the HEB as of May 5, 1992

  6. Study on dynamic performance of SOFC

    Science.gov (United States)

    Zhan, Haiyang; Liang, Qianchao; Wen, Qiang; Zhu, Runkai

    2017-05-01

    In order to solve the problem of real-time matching of load and fuel cell power, it is urgent to study the dynamic response process of SOFC in the case of load mutation. The mathematical model of SOFC is constructed, and its performance is simulated. The model consider the influence factors such as polarization effect, ohmic loss. It also takes the diffusion effect, thermal effect, energy exchange, mass conservation, momentum conservation. One dimensional dynamic mathematical model of SOFC is constructed by using distributed lumped parameter method. The simulation results show that the I-V characteristic curves are in good agreement with the experimental data, and the accuracy of the model is verified. The voltage response curve, power response curve and the efficiency curve are obtained by this way. It lays a solid foundation for the research of dynamic performance and optimal control in power generation system of high power fuel cell stack.

  7. Chemical analysis developments for fusion materials studies

    International Nuclear Information System (INIS)

    McCown, J.J.; Baldwin, D.L.; Keough, R.F.; Van der Cook, B.P.

    1985-04-01

    Several projects at Hanford under the management of the Westinghouse Hanford Company have involved research and development (R and D) on fusion materials. They include work on the Fusion Materials Irradiation Test Facility and its associated Experimental Lithium System; testing of irradiated lithium compounds as breeding materials; and testing of Li and Li-Pb alloy reactions with various atmospheres, concrete, and other reactor materials for fusion safety studies. In the course of these projects, a number of interesting and challenging analytical chemistry problems were encountered. They include sampling and analysis of lithium while adding and removing elements of interest; sampling, assaying and compound identification efforts on filters, aerosol particles and fire residues; development of dissolution and analysis techniques for measuring tritium and helium in lithium ceramics including oxides, aluminates, silicates and zirconates. An overview of the analytical chemistry development problems plus equipment and procedures used will be presented

  8. Studies on chemical protectors against radiation, 29

    International Nuclear Information System (INIS)

    Wang, Cheng-Ming; Ohta, Setsuko; Shinoda, Masato

    1990-01-01

    In order to investigate useful protective medicines for the relief of skin injury induced by irradiation, 60 methanol extracts of Chinese traditional medicines were used in the test of protective potency on skin injury. ICR male mice at 6 weeks of age were whole-body irradiated with 1100R by using a soft X-ray generator (30 kVp, 10 mA, 190 R/min). Each methanol extract of these medicines was injected intraperitoneally into mice before or after irradiation. The degrees of skin injury were determined by a score system of skin reaction within the observation period from 21st to 40th day after irradiation. Protective potency of each medicine on skin injury was calculated from the maximum mean scores of administrated group and un-administrated group. As a result of these studies, the protective potency was detected in Unsei-in, Kumibinro-to, Keisi-syakuyaku-chimo-to, Keigai-rengyo-to, Gosyuyu-to, Koso-san, Saiko-seikan-to, Syo-kankyo-to, Syo-saiko-to, Syoma-kakkon-to, Sen-kan-meimoku-to, Zokumei-to, Sokei-kakketu-to, Bokuryo-in, Mao-to and Rikkunsi-to by intraperitoneal injection before irradiation. Of these effective medicines, only Unsei-in and Mao-to are shown to have a significant protective effect by intraperitoneal injection after irradiation. (author)

  9. Dynamic Monte-Carlo modeling of hydrogen retention and chemical erosion from Tore Supra deposits

    International Nuclear Information System (INIS)

    Rai, A.; Schneider, R.; Warrier, M.; Roubin, P.; Martin, C.

    2009-01-01

    A multi-scale model has been developed to study the hydrogen retention [A. Rai, R. Schneider, M. Warrier, J. Nucl. Mater. 374 (2008) 304] and chemical erosion of porous graphite. To model the chemical erosion process due to thermal hydrogen ions, Kueppers cycle [J. Kueppers, Surf. Sci. Rep. 22 (1995) 249; M. Wittmann, J. Kueppers, J. Nucl. Mater. 227 (1996) 186] has been introduced. The model is applied to study hydrogen transport in deposits collected from the leading edge of neutralizers of Tore Supra. The effect of internal structure on chemical erosion is studied. The MD study [E. Salonen et al., J. Nucl. Mater. 290-293 (2001) 144] shows that the experimentally observed decrease of erosion yield at higher fluxes is due to the decrease of carbon collision cross-section at a surface due to shielding by hydrogen atom already present on the surface. Inspired by this study, a simple multi-scale model is developed to describe the flux dependence of chemical erosion. The idea is to use the local chemistry effect from the Kueppers model to calculate the hydrocarbon molecule formation process and then to find the release probability of the produced hydrocarbon based on the purely geometrical constraints. The model represents quite well the trends in experimental data.

  10. Dynamical, structural and chemical heterogeneities in a binary metallic glass-forming liquid

    Science.gov (United States)

    Puosi, F.; Jakse, N.; Pasturel, A.

    2018-04-01

    As it approaches the glass transition, particle motion in liquids becomes highly heterogeneous and regions with virtually no mobility coexist with liquid-like domains. This complex dynamic is believed to be responsible for different phenomena including non-exponential relaxation and the breakdown of the Stokes-Einstein relation. Understanding the relationships between dynamical heterogeneities and local structure in metallic liquids and glasses is a major scientific challenge. Here we use classical molecular dynamics simulations to study the atomic dynamics and microscopic structure of Cu50Zr50 alloy in the supercooling regime. Dynamical heterogeneities are identified via an isoconfigurational analysis. We demonstrate the transition from isolated to clustering low mobility with decreasing temperature. These slow clusters, whose sizes grow upon cooling, are also associated with concentration fluctuations, characterized by a Zr-enriched phase, with a composition CuZr2 . In addition, a structural analysis of slow clusters based on Voronoi tessellation evidences an increase with respect of the bulk system of the fraction of Cu atoms having a local icosahedral order. These results are in agreement with the consolidated scenario of the relevant role played by icosahedral order in the dynamic slowing-down in supercooled metal alloys.

  11. Chemical Reaction Rates from Ring Polymer Molecular Dynamics: Zero Point Energy Conservation in Mu + H2 → MuH + H.

    Science.gov (United States)

    Pérez de Tudela, Ricardo; Aoiz, F J; Suleimanov, Yury V; Manolopoulos, David E

    2012-02-16

    A fundamental issue in the field of reaction dynamics is the inclusion of the quantum mechanical (QM) effects such as zero point energy (ZPE) and tunneling in molecular dynamics simulations, and in particular in the calculation of chemical reaction rates. In this work we study the chemical reaction between a muonium atom and a hydrogen molecule. The recently developed ring polymer molecular dynamics (RPMD) technique is used, and the results are compared with those of other methods. For this reaction, the thermal rate coefficients calculated with RPMD are found to be in excellent agreement with the results of an accurate QM calculation. The very minor discrepancies are within the convergence error even at very low temperatures. This exceptionally good agreement can be attributed to the dominant role of ZPE in the reaction, which is accounted for extremely well by RPMD. Tunneling only plays a minor role in the reaction.

  12. 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…

  13. 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.

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

    International Nuclear Information System (INIS)

    Valentini, J.J.

    1991-01-01

    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 → H 2 R reactions where RH is CH 4 , C 2 H 6 , or C 3 H 8 , (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

  15. Chemically induced dynamic electron polarization. Pulse radiolysis of aqueous solutions of alcohols

    International Nuclear Information System (INIS)

    Trifunac, A.D.; Thurnauer, M.C.

    1975-01-01

    The radical pair model of chemically induced dynamic electron polarization (CIDEP) is experimentally verified. Aqueous solutions of alcohols were irradiated with 3 MeV electrons and observed with time resolved electron paramagnetic resonance (EPR) spectroscopy. Relative line intensities of the polarized EPR spectra of radicals from methanol and especially ethylene glycol, alone and in the presence of radicals from compounds containing halogens, illustrates the polarization dependence on the g-factor differences between the radical pair components. The observation of the relative polarization enhancement in the various lines of the multiline EPR spectra illustrates the polarization dependence on the hyperfine terms. Intrinsic enhancements are calculated and are shown to be proportional to the observed enhancement, showing that the radical pair model of CIDEP is qualitatively correct

  16. Molecular dynamics simulation of chemical sputtering of hydrogen atom on layer structured graphite

    International Nuclear Information System (INIS)

    Ito, A.; Wang, Y.; Irle, S.; Morokuma, K.; Nakamura, H.

    2008-10-01

    Chemical sputtering of hydrogen atom on graphite was simulated using molecular dynamics. Especially, the layer structure of the graphite was maintained by interlayer intermolecular interaction. Three kinds of graphite surfaces, flat (0 0 0 1) surface, armchair (1 1 2-bar 0) surface and zigzag (1 0 1-bar 0) surface, are dealt with as targets of hydrogen atom bombardment. In the case of the flat surface, graphene layers were peeled off one by one and yielded molecules had chain structures. On the other hand, C 2 H 2 and H 2 are dominant yielded molecules on the armchair and zigzag surfaces, respectively. In addition, the interaction of a single hydrogen isotope on a single graphene is investigated. Adsorption, reflection and penetration rates are obtained as functions of incident energy and explain hydrogen retention on layered graphite. (author)

  17. A Molecular Dynamics Study of Lunasin | Singh | South African ...

    African Journals Online (AJOL)

    A Molecular Dynamics Study of Lunasin. ... profile of lunasin,using classical molecular dynamics (MD) simulations at the time scale of 300 ns. ... Keywords: Lunasin, molecular dynamics, amber, CLASICO, α-helix, β-turn, PTRAJ, RGD, RMSD ...

  18. Molecular Dynamics Studies of Nanofluidic Devices

    DEFF Research Database (Denmark)

    Zambrano Rodriguez, Harvey Alexander

    of such devices. Computational nanofluidics complements experimental studies by providing detailed spatial and temporal information of the nanosystem. In this thesis, we conduct molecular dynamics simulations to study basic nanoscale devices. We focus our studies on the understanding 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...... 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 MD simulation results indicate...

  19. PHYSICO-CHEMICAL STUDIES OF DISAZO DYES DERIVED ...

    African Journals Online (AJOL)

    DJFLEX

    with disazo disperse dyes on synthetic polymer-fibres. (Venkataraman, 1974; Otutu et al., 2008). In this present study, the physico-chemical studies of disazo dyes derived from p-aminophenol recently prepared by our research group is described. We also described the kinetics of the dyes on nylon 6 fibre. In another study.

  20. Study of Intelligent Secure Chemical Inventory Management System

    Science.gov (United States)

    Shukran, Mohd Afizi Mohd; Naim Abdullah, Muhammad; Nazri Ismail, Mohd; Maskat, Kamaruzaman; Isa, Mohd Rizal Mohd; Shahfee Ishak, Muhammad; Adib Khairuddin, Muhamad

    2017-08-01

    Chemical inventory management system has been experiencing a new revolution from traditional inventory system which is manual to an automated inventory management system. In this paper, some review of the classic and modern approaches to chemical inventory management system has been discussed. This paper also describe about both type of inventory management. After a comparative analysis of the traditional method and automated method, it can be said that both methods have some distinctive characteristics. Moreover, the automated inventory management method has higher accuracy of calculation because the calculations are handled by software, eliminating possible errors and saving time. The automated inventory system also allows users and administrators to track the availability, location and consumption of chemicals. The study of this paper can provide forceful review analysis support for the chemical inventory management related research.

  1. Chemical and Dynamical Impacts of Stratospheric Sudden Warmings on Arctic Ozone Variability

    Science.gov (United States)

    Strahan, S. E.; Douglass, A. R.; Steenrod, S. D.

    2016-01-01

    We use the Global Modeling Initiative (GMI) chemistry and transport model with Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields to quantify heterogeneous chemical ozone loss in Arctic winters 2005-2015. Comparisons to Aura Microwave Limb Sounder N2O and O3 observations show the GMI simulation credibly represents the transport processes and net heterogeneous chemical loss necessary to simulate Arctic ozone. We find that the maximum seasonal ozone depletion varies linearly with the number of cold days and with wave driving (eddy heat flux) calculated from MERRA fields. We use this relationship and MERRA temperatures to estimate seasonal ozone loss from 1993 to 2004 when inorganic chlorine levels were in the same range as during the Aura period. Using these loss estimates and the observed March mean 63-90N column O3, we quantify the sensitivity of the ozone dynamical resupply to wave driving, separating it from the sensitivity of ozone depletion to wave driving. The results show that about 2/3 of the deviation of the observed March Arctic O3 from an assumed climatological mean is due to variations in O3 resupply and 13 is due to depletion. Winters with a stratospheric sudden warming (SSW) before mid-February have about 1/3 the depletion of winters without one and export less depletion to the midlatitudes. However, a larger effect on the spring midlatitude ozone comes from dynamical differences between warm and cold Arctic winters, which can mask or add to the impact of exported depletion.

  2. Computational fluid dynamics simulation for chemical looping combustion of coal in a dual circulation fluidized bed

    International Nuclear Information System (INIS)

    Su, Mingze; Zhao, Haibo; Ma, Jinchen

    2015-01-01

    Highlights: • CFD simulation of a 5 kW_t_h CLC reactor of coal was conducted. • Gas leakage, flow pattern and combustion efficiency of the reactor was analyzed. • Optimal condition was achieved based on operation characteristics understanding. - Abstract: A dual circulation fluidized bed system is widely accepted for chemical looping combustion (CLC) for enriching CO_2 from the utilization of fossil fuels. Due to the limitations of the measurement, the details of multiphase reactive flows in the interconnected fluidized bed reactors are difficult to obtain. Computational Fluid Dynamics (CFD) simulation provides a promising method to understand the hydrodynamics, chemical reaction, and heat and mass transfers in CLC reactors, which are very important for the rational design, optimal operation, and scaling-up of the CLC system. In this work, a 5 kW_t_h coal-fired CLC dual circulation fluidized bed system, which was developed by our research group, was first simulated for understanding gas leakage, flow pattern and combustion efficiency. The simulation results achieved good agreement with the experimental measurements, which validates the simulation model. Subsequently, to improve the combustion efficiency, a new operation condition was simulated by increasing the reactor temperature and decreasing the coal feeding. An improvement in the combustion efficiency was attained, and the simulation results for the new operation condition were also validated by the experimental measurements in the same CLC combustor. All of the above processes demonstrated the validity and usefulness of the simulation results to improve the CLC reactor operation.

  3. Effects of ion-neutral chemical reactions on dynamics of lightning-induced electric field

    International Nuclear Information System (INIS)

    Hiraki, Yasutaka

    2009-01-01

    Secondary lightning phenomena in the upper atmosphere called sprites attract interest from the viewpoint of atomic-molecular and plasma physics. Lightning-induced electric field accelerates the ionospheric electrons up to tens of electron-volts, inducing electrical breakdown as well as strong optical emissions, through electron impact ionization of molecules. A large-scale structure of sprites is constructed by collective dynamics of filamentary streamer discharges in a rarified gas, which in turn is controlled by the distribution of the background electric field. In this paper, we firstly reanalyze the relationship between quasi-static field formation and local ion chemistry with first-order perturbation techniques. Secondly, we investigate with a full ion chemical model the effects of electron attachment to oxygen molecules on its density in moderate cases of undervoltage lightning electric fields rather than the cases of intense ionization in streamers. We estimate the minimum values that are provided by the chemical balance with electron detachment from negative ions. We also investigate the recovery timescale of the electron density and find that the scale (≥1 s) is occasionally much larger than the interval of each lightning stroke (∼10 ms). We suggest that the subsequent sprite event as well as the field formation could be well affected by the ghost of the primary event. We discuss further the negative ion chemistry triggered by electron attachment in the nighttime mesosphere.

  4. Crop rotations and poultry litter impact dynamic soil chemical properties and soil biota long-term

    Science.gov (United States)

    Dynamic soil physiochemical interactions with conservation agricultural practices and soil biota are largely unknown. Therefore, this study aims to quantify long-term (12-yr) impacts of cover crops, poultry litter, crop rotations, and conservation tillage and their interactions on soil physiochemica...

  5. Dynamic MRI study for breast tumors

    International Nuclear Information System (INIS)

    Seki, Tsuneaki

    1990-01-01

    Application of MRI for diagnosis of breast tumors was retrospectively examined in 103 consecutive cases. Contrast enhancement, mostly by dynamic study, was performed in 83 cases using Gd-DTPA and 0.5 T superconductive apparatus. Results were compared to those of mammography and sonography. On dynamic study, carcinoma showed abrupt rise of signal intensity with clear-cut peak formation in early phase, while benign fibroadenoma showed slow rise of signal intensity and prolonged enhancement without peak formation. In 12 of 33 carcinomas (33%), peripheral ring enhancement was noted reflecting vascular stroma of histologic sections. All fibroadenomas showed homogenous enhancement without peripheral ring. In MRI, sensitivity, specificity, and accuracy were 86%, 96%, 91%. In mammography 82%, 95%, 87% and in ultrasonography 91%, 95%, 93%. Although MRI should not be regarded as routine diagnostic procedure because of expense and limited availability, it may afford useful additional information when standard mammographic findings are not conclusive. (author)

  6. Experimental studies of nonlinear beam dynamics

    International Nuclear Information System (INIS)

    Caussyn, D.D.; Ball, M.; Brabson, B.; Collins, J.; Curtis, S.A.; Derenchuck, V.; DuPlantis, D.; East, G.; Ellison, M.; Ellison, T.; Friesel, D.; Hamilton, B.; Jones, W.P.; Lamble, W.; Lee, S.Y.; Li, D.; Minty, M.G.; Sloan, T.; Xu, G.; Chao, A.W.; Ng, K.Y.; Tepikian, S.

    1992-01-01

    The nonlinear beam dynamics of transverse betatron oscillations were studied experimentally at the Indiana University Cyclotron Facility cooler ring. Motion in one dimension was measured for betatron tunes near the third, fourth, fifth, and seventh integer resonances. This motion is described by coupling between the transverse modes of motion and nonlinear field errors. The Hamiltonian for nonlinear particle motion near the third- and fourth-integer-resonance conditions has been deduced

  7. Nonlinear longitudinal dynamics studies at the ALS

    International Nuclear Information System (INIS)

    Byrd, J.M.; Cheng, W.-H.; De Santis, S.; Li, D.; Stupakov, G.; Zimmermann, F.

    1999-01-01

    We present a summary of results for a variety of studies of nonlinear longitudinal dynamics in the Advanced Light Source, an electron storage ring. These include observation of decoherence at injection, decay of an injected beam, forced synchrotron oscillations and diffusion from one bunch to the next. All of the measurements were made using a dual-scan streak camera which allowed the real-time observation of the longitudinal distribution of the electron beam

  8. High-speed AFM for Studying Dynamic Biomolecular Processes

    Science.gov (United States)

    Ando, Toshio

    2008-03-01

    Biological molecules show their vital activities only in aqueous solutions. It had been one of dreams in biological sciences to directly observe biological macromolecules (protein, DNA) at work under a physiological condition because such observation is straightforward to understanding their dynamic behaviors and functional mechanisms. Optical microscopy has no sufficient spatial resolution and electron microscopy is not applicable to in-liquid samples. Atomic force microscopy (AFM) can visualize molecules in liquids at high resolution but its imaging rate was too low to capture dynamic biological processes. This slow imaging rate is because AFM employs mechanical probes (cantilevers) and mechanical scanners to detect the sample height at each pixel. It is quite difficult to quickly move a mechanical device of macroscopic size with sub-nanometer accuracy without producing unwanted vibrations. It is also difficult to maintain the delicate contact between a probe tip and fragile samples. Two key techniques are required to realize high-speed AFM for biological research; fast feedback control to maintain a weak tip-sample interaction force and a technique to suppress mechanical vibrations of the scanner. Various efforts have been carried out in the past decade to materialize high-speed AFM. The current high-speed AFM can capture images on video at 30-60 frames/s for a scan range of 250nm and 100 scan lines, without significantly disturbing week biomolecular interaction. Our recent studies demonstrated that this new microscope can reveal biomolecular processes such as myosin V walking along actin tracks and association/dissociation dynamics of chaperonin GroEL-GroES that occurs in a negatively cooperative manner. The capacity of nanometer-scale visualization of dynamic processes in liquids will innovate on biological research. In addition, it will open a new way to study dynamic chemical/physical processes of various phenomena that occur at the liquid-solid interfaces.

  9. Vibrational studies of Thyroxine hormone: Comparative study with quantum chemical calculations

    Science.gov (United States)

    Borah, Mukunda Madhab; Devi, Th. Gomti

    2017-11-01

    The FTIR and Raman techniques have been used to record spectra of Thyroxine. The stable geometrical parameters and vibrational wave numbers were calculated based on potential energy distribution (PED) using vibrational energy distribution analysis (VEDA) program. The vibrational energies are assigned to monomer, chain dimer and cyclic dimers of this molecule using the basis set B3LYP/LANL2DZ. The computational scaled frequencies are in good agreements with the experimental results. The study is extended to calculate the HOMO-LUMO energy gap, Molecular Electrostatic Potential (MEP) surface, hardness (η), chemical potential (μ), Global electrophilicity index (ω) and different thermo dynamical properties of Thyroxine in different states. The calculated HOMO-LUMO energies show the charge transfer occurs within the molecule. The calculated Natural bond orbital (NBO) analysis confirms the presence of intra-molecular charge transfer as well as the hydrogen bonding interaction.

  10. 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.

  11. Dynamic isotope studies in liver disease

    Energy Technology Data Exchange (ETDEWEB)

    Weits, J

    1978-01-01

    Much information in the field of liver research has been gained by dynamic isotope studies. Clinically, these studies can help to settle selection criteria for different types of surgical shunt, which relieve the complications of portal hypertension. By performing splenoportoscintigraphy, splenic and portal vein thrombosis can be easily and safely excluded. So-called hypoxaemia of cirrhosis can most easily be diagnosed. Suprahepatic caval vein obstruction in a patient with cryptogenic liver disease is easily excluded by a radionuclide cavogram after injection of pertechnetate into a foot vein.

  12. Study of phenol extraction from coke-chemical sources

    Energy Technology Data Exchange (ETDEWEB)

    Catana, E.; Mateescu, I.; Giurcaneanu, V.; Bota, T.

    1990-09-01

    The paper presents an experimental study of the phase equilibrium in the coke-chemical tarphenols-solvent system (NaOH) solution and (phenolate solution) implied in the extraction of the phenols from coke-chemical sources. The possibility of using the phenolate solution as an extraction agent, thus making possible the improvement of the specific consumption and also simplifying the problem of the corrosion and of the waste water at the same time is presented. The influence of the solvent tar mass ratio on the selectivity of the process is discussed, this criterion being considered for establishing the conditions of the extraction. 2 figs., 7 tabs., 13 refs.

  13. [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.

  14. Examples and Case Studies for the 2012 Chemical Data Reporting

    Science.gov (United States)

    This document presents examples and case studies to help you in reporting for 2012 Chemical Data Reporting (CDR), formerly known as Inventory Update Reporting (IUR).EPA designed these examples to illustrate the new reporting requirements, which were published as part of the CDR Rule (published August 16, 2011), and to address general reporting issues from the 2006 IUR.

  15. [Study on the chemical constituent from Buddleja purdomii].

    Science.gov (United States)

    Gao, Yan; Li, Chong; Zhang, Chengzhong; Xu, Yourui; Tao, Baoquan

    2004-05-01

    To study the chemical constituents from Buddleja purdomii W. W. Smith. The constituents were isolated and purified by various chromatographic methods and structurally identified by spectral analysis. 4 compounds were identified as vanillin (I), vanillic acid (II), acteoside (III), acteoside isomer (IV). All these compounds were obtained from this plant for the first time.

  16. [Study on the chemical constituents of Buddleja purdomii].

    Science.gov (United States)

    Zhang, Yinghua; Li, Chong; Zhang, Chengzhong; Tao, Baoquan

    2005-11-01

    To study the chemical constituents of Buddleja purdomii W. W Smith. The constituents were isolated and purified by various chromatographic methods and structurally identified by spectral analysis. 4 compounds were obtained as cryptomeridiol (I), aucubin (II), galactilol (III), daucosterol (IV). All these compounds are obtained from this plant for the first time.

  17. Comparative Studies of Physico-chemical Properties of Some ...

    African Journals Online (AJOL)

    The aim of this study was to evaluate some physico-chemical properties of four major general purpose cement (As, Br, De and Sk) sold in Nigerian market using standard methods; due to the persistent collapse of buildings. The results showed that Br cement recorded the least CaO content (56.17%) while De cement had ...

  18. Studies of radiation and chemical toxicity. Progress report

    International Nuclear Information System (INIS)

    1986-01-01

    Annual report for the Studies of Radiation and Chemical Toxicity Program at the University of Rochester is presented. Progress is reported on four projects: Neurobehavorial Toxicity of Organometallic Fuel Additives, Mechanisms of Permanent and Delayed Pathologic Effects of Ionizing Radiation, Solid State Radiation Chemistry of the DNA Backbone, and Pulmonary Biochemistry

  19. Researchers study decontamination of chemical, biological warfare agents

    OpenAIRE

    Trulove, Susan

    2007-01-01

    The U.S. Army Research Office has awarded Virginia Tech a $680,000 grant over two years to build an instrument that can be used to study the chemistry of gases that will decompose both chemical and biological warfare agents on surfaces.

  20. 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....... The implementation of the modified force field was carried out in the popular program MBN Explorer, and, to support the development, we provide several illustrative case studies where dynamical topology is necessary. In particular, it is shown that the modified molecular mechanics force field can be applied...

  1. Preliminary study of chemical compositional data from Amazon ceramics

    International Nuclear Information System (INIS)

    Toyota, Rosimeiri G.; Munita, Casimiro S.; Luz, Fabio A.; Neves, Eduardo G.; Oliveira, Paulo M.S.

    2005-01-01

    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)

  2. Effects of Graphene Oxide and Chemically-Reduced Graphene Oxide on the Dynamic Mechanical Properties of Epoxy Amine Composites

    Directory of Open Access Journals (Sweden)

    Cristina Monteserín

    2017-09-01

    Full Text Available Composites based on epoxy/graphene oxide (GO and epoxy/reduced graphene oxide (rGO were investigated for thermal-mechanical performance focusing on the effects of the chemical groups present on nanoadditive-enhanced surfaces. GO and rGO obtained in the present study have been characterized by Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS, and X-ray powder diffraction (XRD demonstrating that materials with different oxidation degrees have been obtained. Thereafter, GO/epoxy and rGO/epoxy nanocomposites were successfully prepared and thoroughly characterized by dynamic mechanical thermal analysis (DMTA and transmission electron microscopy (TEM. A significant increase in the glass transition temperature was found in comparison with the neat epoxy. The presence of functional groups on the graphene surface leads to chemical interactions between these functional groups on GO and rGO surfaces with the epoxy, contributing to the possible formation of covalent bonds between GO and rGO with the matrix. The presence of oxidation groups on GO also contributes to an improved exfoliation, intercalation, and distribution of the GO sheets in the composites with respect to the rGO based composites.

  3. Molecular dynamics simulation of chemical vapor deposition of amorphous carbon. Dependence on H/C ratio of source gas

    International Nuclear Information System (INIS)

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

    2011-01-01

    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 that the source gas was injected as hydrocarbon molecules. Under the former condition, we found that as the source H/C ratio increases, the deposition rate of carbon atoms decreases exponentially. This exponential decrease in the deposition rate with increasing source H/C ratio agrees with experimental data. However, under the latter molecular source condition, the deposition rate did not decrease exponentially because of a chemical reaction peculiar to the type of hydrocarbon in the source gas. (author)

  4. 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.

    2012-07-01

    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 require students to use approaches beyond direct application of LCP. Sample : The questionnaire was administered to 162 students studying their first year of advanced chemistry (age 16/17) in three high achieving London high schools. Design and methods : The students' explanations of reversible chemical systems were inductively coded to identify the explanatory approaches used and interviews with 13 students were used to check for consistency. AS level examination questions on reversible reactions were analysed to identify the types of explanations sought and the students' performance in these examinations was compared to questionnaire answers. Results : 19% of students used a holistic explanatory approach: when the rates of forward and reverse reactions are correctly described, recognising their simultaneous and mutually dependent nature. 36% used a mirrored reactions approach when the connected nature of the forward and reverse reactions is identified, but not their mutual dependency. 42% failed to recognize the interdependence of forward and reverse reactions (reactions not connected approach). Only 4% of marks for AS examination questions on reversible chemical systems asked for responses which went beyond either direct application of LCP or recall of equilibrium knowledge. 37% of students attained an A grade in their AS national examinations. Conclusions : Examinations favour the application of LCP making it possible to obtain the highest grade with little understanding of reversible chemical systems beyond a direct application of this algorithm. Therefore students' understanding may be attenuated so that they are

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

    International Nuclear Information System (INIS)

    Khakzad, Nima

    2015-01-01

    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

  6. 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.

  7. Toxicity studies of drugs and chemicals in animals: An overview

    Directory of Open Access Journals (Sweden)

    S. Saganuwan

    2017-12-01

    Full Text Available Toxicity study is the investigation of either short or long-term toxic effects of a drug or chemical on animals. The toxicity is dose-dependent as asserted by Paracelsus over 500 years ago. However, short-term toxic effect is determined using median lethal dose (LD50 first introduced by Trevan in 1927 and revised many times. Presently there is a growing preponderance of rejection of scientific papers on acute toxicity study, simply because of the belief that in the current hazard and safety as-sessment of drugs and chemicals, LD50 values are no longer used. In view of this, literature search was carried out with a view to investigating the relevance of LD50 in development and assessment of drugs and chemicals. The findings revealed that in the past, many animals had been used for LD50 determination. OECD has reduced the number of test animals to 5–15 and presently it is further re-duced to 2–6. Acute toxicity study is being carried out in medicinal plants research and in the study of patent medicine. Although the application of LD50 has been drastically reduced, it is still applied and accepted in some parts of the world. Moreover, animals on which LD50 tests are conducted, should be allowed to die to see the end effect of the test drug or chemical because euthanisia of test animals may mask some toxicity signs of the test agents. Therefore, toxicity study of drugs and chemicals is a sci-entific process necessary for discovery and development of drugs as well as identification of potential toxicants.

  8. Chemical dynamics of the first proton-coupled electron transfer of water oxidation on TiO2 anatase.

    Science.gov (United States)

    Chen, Jia; Li, Ye-Fei; Sit, Patrick; Selloni, Annabella

    2013-12-18

    Titanium dioxide (TiO2) is a prototype, water-splitting (photo)catalyst, but its performance is limited by the large overpotential for the oxygen evolution reaction (OER). We report here a first-principles density functional theory study of the chemical dynamics of the first proton-coupled electron transfer (PCET), which is considered responsible for the large OER overpotential on TiO2. We use a periodic model of the TiO2/water interface that includes a slab of anatase TiO2 and explicit water molecules, sample the solvent configurations by first principles molecular dynamics, and determine the energy profiles of the two electronic states involved in the electron transfer (ET) by hybrid functional calculations. Our results suggest that the first PCET is sequential, with the ET following the proton transfer. The ET occurs via an inner sphere process, which is facilitated by a state in which one electronic hole is shared by the two oxygen ions involved in the transfer.

  9. Molecular dynamics studies of actinide nitrides

    International Nuclear Information System (INIS)

    Kurosaki, Ken; Uno, Masayoshi; Yamanaka, Shinsuke; Minato, Kazuo

    2004-01-01

    The molecular dynamics (MD) calculation was performed for actinide nitrides (UN, NpN, and PuN) in the temperature range from 300 to 2800 K to evaluate the physical properties viz., the lattice parameter, thermal expansion coefficient, compressibility, and heat capacity. The Morse-type potential function added to the Busing-Ida type potential was employed for the ionic interactions. The interatomic potential parameters were determined by fitting to the experimental data of the lattice parameter. The usefulness and applicability of the MD method to evaluate the physical properties of actinide nitrides were studied. (author)

  10. Study of the chemical sputtering in Tore-Supra

    International Nuclear Information System (INIS)

    Cambe, A.

    2002-01-01

    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 (C 2 D x and C 3 D y ) in the determination of the chemical sputtering yield. It is found that for the ohmic discharges, the sputtering yield of CD 4 (Y CD4 ) is highly flux (φ) dependent, showing a variation of the form: Y CD4 ∝ φ -0.23 . The experimental study also reveals that an increase of the surface temperature induces an augmentation of Y CD4 . 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)

  11. 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.

  12. One- and two-dimensional chemical exchange nuclear magnetic resonance studies of the creatine kinase catalyzed reaction

    International Nuclear Information System (INIS)

    Gober, J.R.

    1988-01-01

    The equilibrium chemical exchange dynamics of the creatine kinase enzyme system were studied by one- and two-dimensional 31 P NMR techniques. Pseudo-first-order reaction rate constants were measured by the saturation transfer method under an array of experimental conditions of pH and temperature. Quantitative one-dimensional spectra were collected under the same conditions in order to calculate the forward and reverse reaction rates, the K eq , the hydrogen ion stoichiometry, and the standard thermodynamic functions. The pure absorption mode in four quadrant two-dimensional chemical exchange experiment was employed so that the complete kinetic matrix showing all of the chemical exchange process could be realized

  13. 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.

  14. Study on Dynamic Alignment Technology of COIL Resonator

    International Nuclear Information System (INIS)

    Xiong, M D; Zou, X J; Guo, J H; Jia, S N; Zhang, Z B

    2006-01-01

    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

  15. Correlation study of chemical elements in phosphate ores

    International Nuclear Information System (INIS)

    Braganca, Maura Julia Camara da Silva

    1999-07-01

    Geological phenomena, 1) endogenous (volcanism, magmatic flow, metasomatism); 2) metamorphic (resultant of action of high temperature and pressure) and; 3) exogenous (intemperism, contamination) can modify the chemical composition of rocks soils. Thus, chemical elements with little mobility can be used as indicators of the previous geological situation before the occurrence of these phenomena and can sign the chemical composition of the initial formation. The elements with great mobility can already be used as indicators of the characteristic and intensity of the changes, can point out the influence factors and its space and time conditions. In this work the results of the study of phosphated samples ores coming from two alkaline-carbonatitic chimneys (Araxa and Catalao) and from a meta sedimentary rock (Patos de Minas), located phosphate rock deposit, are presented. The results were obtained using the instrumental neutron activation analysis, inductively coupled plasma-mass spectrometry (ICP-MS) and ICP-AES techniques. A comparison of the three types of samples ores, using chemical, crystallographic and statistical methods, shows that the Araxa and Catalao present some geochemical similarities and they are distinguished of Patos de Minas, despite its geographic proximity. (author)

  16. A dynamic approach to dependability studies

    International Nuclear Information System (INIS)

    Labeau, P.E.

    2008-01-01

    Dependability studies have now become an important part of the performance management of industrial plants. These last decades, several methods have been proposed and widely used for the analysis of systems of components subject to degradation and failure. These methods are based either on Boolean representations (for example, event trees/fault trees), or on discrete-state models (Markovian reliability, Petri nets, Bayesian networks...). However, the underlying, inherently continuous, physical processes have scarcely been accounted for, at least in an integrated fashion, in dependability studies. This paper first describes, through simple cases, the limitations of discrete approaches and the need of hybrid, discrete-continuous methods. It then summarizes the main concepts of dynamic reliability. Finally, some possible application domains are presented, as well as challenges that still need to be tackled to favour the diffusion of this approach among industrial circles. (author)

  17. Contribution to the study of dynamic recrystallization

    International Nuclear Information System (INIS)

    Guillope, Michel

    1981-01-01

    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) [fr

  18. 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.

  19. Experimental study of vapor bubble dynamics

    International Nuclear Information System (INIS)

    Pasquini, Maria-Elena

    2015-01-01

    The object of this thesis is an experimental study of vapor bubble dynamics in sub-cooled nucleate boiling. The test section is locally heated by focusing a laser beam: heat fluxes from 1 e4 to 1.5 e6 W/m 2 and water temperature between 100 and 88 C have been considered. Three boiling regimes have been observed. Under saturated conditions and with low heat fluxes a developed nucleate boiling regime has been observed. Under higher sub-cooling and still with low heat fluxes an equilibrium regime has been observed in which the liquid flowrate evaporating at the bubble base is compensated by the vapor condensing flowrate at bubble top. A third regime have been observed at high heat fluxes for all water conditions: it is characterized by the formation of a large dry spot on the heated surface that keeps the nucleation site dry after bubble detachment. The condensation phase starts after bubble detachment. Bubble equivalent radius at detachment varies between 1 and 2.5 mm. Bubble properties have been measured and non-dimensional groups have been used to characterize bubble dynamics. Capillary waves have been observed on the bubble surface thanks to high-speed images acquisition. Two main phenomena have been proposed to explain capillary waves effects on bubble condensation: increasing of the phases interface area and decreasing of vapor bubble translation velocity, because of the increased drag force on the deformed bubble. (author) [fr

  20. Chemical freeze-out study in proton-proton collisions at RHIC and LHC energies

    International Nuclear Information System (INIS)

    Das, Sabita; Mishra, Debadeepti; Mohanty, Bedangadas; Chatterjee, Sandeep

    2016-01-01

    Particle multiplicities measured at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) facilities can be used to understand the chemical freeze-out dynamics. At chemical freeze-out (CFO), inelastic collisions cease and the freeze-out parameters can be determined using measured particle multiplicities within the framework of a statistical model. The statistical model has proven to be quite successful in describing the particle production from elementary p-p and e"+e"- collisions up to heavy-ion collisions. It helps to do a systematic study of the centrality and energy dependence of freeze-out parameters in heavy-ion collisions from lower SPS to higher LHC energies. The new data at LHC along with the RHIC data can be used to do such a systematic study in proton-proton collisions

  1. Can disorder act as a chemical pressure? An optical study of the Hubbard model

    Science.gov (United States)

    Barman, H.; Laad, M. S.; Hassan, S. R.

    2018-05-01

    The optical properties have been studied using the dynamical mean-field theory on a disordered Hubbard model. Despite the fact that disorder turns a metal to an insulator in high dimensional correlated materials, we notice that it can enhance certain metallic behavior as if a chemical pressure is applied to the system resulting in an increase of the effective lattice bandwidth (BW). We study optical properties in such a scenario and compare results with experiments where the BW is changed through isovalent chemical substitution (keeping electron filling unaltered) and obtain remarkable similarities vindicating our claim. We also make the point that these similarities differ from some other forms of BW tuned optical effects.

  2. Effect of chemical composition on the flocculation dynamics of latex-based synthetic activated sludge

    International Nuclear Information System (INIS)

    Tan Phong Nguyen; Hankins, Nicholas P.; Hilal, Nidal

    2007-01-01

    This study investigates the effect of calcium, alginate, fibrous cellulose, and pH on the flocculation dynamics and final properties of synthetic activated sludges. A laboratory-scale batch reactor, fed with standard synthetic sludges was used. The effects of varying calcium concentration (5-25 mM), alginate concentration (25-125 mg/L), fibrous cellulose concentration (0.2-0.8 g/L) and pH (3-9) on the sludge characteristics were studied by varying one parameter whilst keeping the others constant. The results from experiments indicated that the calcium, alginate, fibrous cellulose, and pH had the critical effect on the aggregation rate, flocs size, and made the improvement of the final properties of sludge. Dynamic measurements have established the optimum conditions for floc formation and can accurately reflect the state of formation of the synthetic activated sludge flocs. These correlate well with measurements of settleability and turbidity of the synthetic activated sludge. The results of this study support the bonding theory and indicate that formation of cations-polymer complexes and polymer gelation are important means of flocculation. The development of synthetic activated sludges is suggested also to be a possible surrogate for studying the final properties of activated sludge

  3. Using chemical imaging to study bonding of dissimilar alloys

    International Nuclear Information System (INIS)

    Wuhrer, R.; Phillips, M.R.; Huggett, P.

    2002-01-01

    Full text: New welding techniques are currently being developed to bond very dissimilar materials such as cast irons or wear resistant steels welded to mild steel. X-ray mapping and chemical phase imaging provides useful information on the mass transport across the interface as well as phase segregation within the weld joint. Cast iron / steel and wear resistant steel / mild steel weld joints were mounted in a bakelite mount, cross-sectioned with a diamond wafering blade and polished to an optical finish using diamond abrasives. X-ray maps were collected at over a range of accelerating voltages using a Moran Scientific energy dispersive x-ray analysis and mapping system. These elemental x-ray maps were used to generate scatter plots, where pixel frequency versus element concentration profiles are plotted against each other in two or three dimensions for selected elements within the sample. The clusters observed in these plots correspond to different phases within the weld seam. The contributing pixels to each cluster can be used to reconstruct the spatial distribution of its associated phase in a chemical image of the specimen. Of particular interest to this study were the branches and links between clusters in each scatter plot and how these features correlate the chemical distribution of elements both in and around the bond region. Preliminary analysis indicated that these links and branches in the scatter plot correspond to solid solutions between chemical phases and diffusion gradients. Proper interpretation of these scatter plots will provide a better understanding of the chemical processes involved in welding dissimilar materials. Copyright (2002) Australian Society for Electron Microscopy Inc

  4. [Studies on the chemical constituents of Buddleja albiflora (II)].

    Science.gov (United States)

    Zhang, Hai-Ping; Tao, Liang

    2010-06-01

    To study the chemical constituents of Buddleja albiflora. The constituents were isolated by column chromatography and their structures were elucidated by spectroscopic analyses. seven compounds were isolated and identified as aucubin (1), catalpol (2), acteoside (3), martynoside (4), ursolicacid (5), daucosterol (6), beta-sitosterol-3-0-beta-D-(6'-0-palmitate) glucopyranosisde (7). All these compounds are obtained from Buddleja albiflora for the first time.

  5. [Studies on chemical constituents from Buddleja lindleyana Fert].

    Science.gov (United States)

    Lu, J H; Zhao, Y Y; Qiao, L; Fang, Y O; Huang, Q A

    2001-01-01

    To study the chemical constituents of Buddleja lindleyana. Separation by chromatographic methods and identification by spectral analysis. Seven compounds vanillic acid, daidzein octacosanoic acid, beta-sitosterol-3-O-beta-D-glucopyranoside, stigmasterol-3-O-beta-D-glucopyranoside, alpha-spinasterol-3-O-beta-D-glucopyranoside, betulin acid were isolated. All the compounds were obtained from this plant for the first time.

  6. [Studies on the chemical constituents of Portulaca oleracea].

    Science.gov (United States)

    Liu, Ce-jia; Liu, Dian-yu; Xiang, Lan; Zhou, Wen; Shao, Ning-ning

    2009-11-01

    To study the chemical constituents of Portulaca oleracea. The constituents were isolated by column chromatography and identified on the basis of physicochemical and spectral data. Five compounds were isolated from 70% ethanol extract of this plant and their structures were elucidated as cyclo (Phe-Ile) (1), cycle (Tyr-Ala) (2), adenine (3), friedelin (4) and isoselachoceric acid (5). Compounds 1-5 are isolated from Portulaca oleracea for the first time.

  7. Analysing chemical equilibrium conditions when studying butyl acetate synthesis

    OpenAIRE

    Álvaro Orjuela Londoño; Fernando Leiva Lenis; Luis Alejandro Boyacá Mendivelso; Gerardo Rodríguez Niño; Luis María Carballo Suárez

    2010-01-01

    This work studied the liquid phase of acetic acid and butyl alcohol esterification reaction (P atm = 560 mmHg),using an ion exchange resin (Lewatit K-2431) as catalyst. A set of assays were carried out for determining the effect of catalyst load, temperature and molar ratio (acid/alcohol) on chemical equilibrium constant. Components’ selective sorption on the resin matrix was noticed; its effect on equilibrium conditions was verified, by using different acid/alcohol starting ratios. A non-ide...

  8. Study of interfacial phenomena for bio/chemical sensing applications

    Science.gov (United States)

    Min, Hwall

    This work presents the fundamental study of biological and chemical interfacial phenomena and (bio)chemical sensing applications using high frequency resonator arrays. To realize a versatile (bio)chemical sensing system for the fundamental study as well as their practical applications, the following three distinct components were studied and developed: i) detection platforms with high sensitivity, ii) novel innovative sensing materials with high selectivity, iii) analytical model for data interpretation. 8-pixel micromachined quartz crystal resonator (muQCR) arrays with a fundamental resonance frequency of 60 ¡V 90 MHz have been used to provide a reliable detection platform with high sensitivity. Room temperature ionic liquid (RTIL) has been explored and integrated into the sensing system as a smart chemical sensing material. The use of nanoporous gold (np-Au) enables the combination of the resonator and surface-enhanced Raman spectroscopy for both quantitative and qualitative measurement. A statistical model for the characterization of resonator behavior to study the protein adsorption kinetics is developed by random sequential adsorption (RSA) approach with the integration of an effective surface depletion theory. The investigation of the adsorption kinetics of blood proteins is reported as the fundamental study of biological phenomena using the proposed sensing system. The aim of this work is to study different aspects of protein adsorption and kinetics of adsorption process with blood proteins on different surfaces. We specifically focus on surface depletion effect in conjunction with the RSA model to explain the observed adsorption isotherm characteristics. A number of case studies on protein adsorption conducted using the proposed sensing system has been discussed. Effort is specifically made to understand adsorption kinetics, and the effect of surface on the adsorption process as well as the properties of the adsorbed protein layer. The second half of the

  9. Study on chemical reactivity control of liquid sodium. Research program

    International Nuclear Information System (INIS)

    Saito, Jun-ichi; Ara, Kuniaki; Sugiyama, Ken-ichiro; Kitagawa, Hiroshi; Oka, Nobuki; Yoshioka, Naoki

    2007-01-01

    Liquid sodium has the excellent properties as coolant of the fast breeder reactor (FBR). On the other hand, it reacts high with water and oxygen. So an innovative technology to suppress the reactivity is desired. The purpose of this study is to control the chemical reactivity of liquid sodium by dispersing the nanometer-size metallic particles (we call them Nano-particles) into liquid sodium. We focus on the atomic interaction between Nano-particles and sodium atoms. And we try to apply it to suppress the chemical reactivity of liquid sodium. Liquid sodium dispersing Nano-particles is named 'Nano-fluid'. Research programs of this study are the Nano-particles production, the evaluation of reactivity suppression of liquid sodium and the feasibility study to FBR plant. In this paper, the research programs and status are described. The important factors for particle production were understood. In order to evaluate the chemical reactivity of Nano-fluid the research programs were planned. The feasibility of the application of Nano-fluid to the coolant of FBR plant was evaluated preliminarily from the viewpoint of design and operation. (author)

  10. Chemical elements in invertebrate orders for environmental quality studies

    International Nuclear Information System (INIS)

    Magalhaes, Marcelo R.L.; Franca, Elvis J.; Paiva, Jose D.S.; Hazin, Clovis A.; Fonseca, Felipe Y.; Fernandes, Elisabete A. de Nadai; Bacchi, Marcio A.

    2013-01-01

    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)

  11. 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)

  12. Molecular dynamic simulation study of molten cesium

    Directory of Open Access Journals (Sweden)

    Yeganegi Saeid

    2017-01-01

    Full Text Available Molecular dynamics simulations were performed to study thermodynamics and structural properties of expanded caesium fluid. Internal pressure, radial distribution functions (RDFs, coordination numbers and diffusion coefficients have been calculated at temperature range 700–1600 K and pressure range 100–800 bar. We used the internal pressure to predict the metal–non-metal transition occurrence region. RDFs were calculated at wide ranges of temperature and pressure. The coordination numbers decrease and positions of the first peak of RDFs slightly increase as the temperature increases and pressure decreases. The calculated self-diffusion coefficients at various temperatures and pressures show no distinct boundary between Cs metallic fluid and its expanded fluid where it continuously increases with temperature.

  13. Non Linear Beam Dynamics Studies at SPEAR

    International Nuclear Information System (INIS)

    Terebilo, A.; Pellegrini, C.; Cornacchia, M.; Corbett, J.; Martin, D.

    2011-01-01

    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.

  14. Theoretical study of fission dynamics with muons

    International Nuclear Information System (INIS)

    Oberacker, V.E.; Umar, A.S.; Bottcher, C.; Strayer, M.R.; Maruhn, J.A.; Frankfurt Univ.

    1992-01-01

    Following muon capture by actinide atoms, some of the inner shell muonic transitions proceed by inverse internal conversion, i.e. the excitation energy of the muonic atom is transferred to the nucleus. In particular, the muonic E2:(3d→1s) transition energy is close to the peak of the isoscalar giant quadrupole resonance in actinide nuclei which exhibits a large fission width. Prompt fission in the presence of a bound muon allows us to study the dynamics of large-amplitude collective motion. We solve the time-dependent Dirac equation for the muonic spinor wave function in the Coulomb field of the fissioning nucleus on a 3-dimensional lattice and demonstrate that the muon attachment probability to the light fission fragment is a measure of the nuclear energy dissipation between the outer fission barrier and the scission point

  15. Radionuclide renal dynamic and function study

    International Nuclear Information System (INIS)

    Guan Liang

    1991-01-01

    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

  16. STUDY ON HEAT DYNAMIC LOADING OF RUBBER

    Directory of Open Access Journals (Sweden)

    T. I. Igumenova

    2015-01-01

    Full Text Available A number of studies on heat buildup in tire rubber surface scan method samples using a thermal imaging camera. Investigated the exothermic chemical reaction mechanical destruction rubber when loading designs permanent cyclic stretching with deformation of the working zone 50%. Percentage of deformation of the working zone was chosen on the basis of the actual data on the stretch-compression zone "Rusk" tires, which is the maximum level difference of deformation during run-in. Experiment plan provided for periodic relaxation samples of at least 72 hours for more accurate simulation of operation process of structural products. Created and processed data on temperature changes in samples for bar and line profile for rubber compounds with the introduction of nanomodifiers (fulleren technical carbon in comparison with the control sample without him. The data obtained reflect the nature of heat depending on the composition of the compound. Identified common patterns of thermal nature of physico-chemical process mechanical destruction rubbers. For rubber with nanomodifikatorom there has been an increase in the temperature interval reaction from a minimum to a maximum 2 degrees that is also linked to the rise in the average temperature of the reaction on the histogram also at 2-3 degrees of deformation under the same conditions and the level of cyclic loading. However, the temperature in the control sample that is associated with the beginning of the formation of hardened rubber structures, economies of Mallinz-Petrikeev, occurs with delay twice compared with modified Fullerenes. Measurement of physic-mechanical indicators selected in the course of testing of samples showed the beginning of formation of structure with increased strength of samples in the sample temperature zone that corresponds to the thermal effect of èndotermičeskomu recombination reactions of macromolecules.

  17. 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

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

    International Nuclear Information System (INIS)

    Kickermann, Andreas

    2013-07-01

    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

  19. 1H chemically induced dynamic nuclear polarization in the photodecomposition of uranyl carboxylates

    International Nuclear Information System (INIS)

    Rykov, S.V.; Khudyakov, I.V.; Skakovsky, E.D.; Burrows, H.D.; Formosinho, S.J.; Miguel, M. da G.M.

    1991-01-01

    Chemically induced dynamic nuclear polarization ( 1 H CIDNP) has been observed during photolysis of uranyl salts of pivalic, propionic, and acetic acids in D 2 O solution, [ 2 H 6 ]acetone, [ 2 H 4 ]methanol, or in some other solvent. The multiplet polarization of isobutene and isobutane protons has been found under photolysis of deoxygenated pivalate solution. The polarized compounds are formed in the triplet pairs of tert-butyl free radicals. 1 H Emission of the tert-butylperoxyl group and emission of 1 H from isobutene have been recorded under photolysis of air-saturated pivalate solutions. The CIDNP of butane protons stays as a multiplet. Such changes in the presence of air/oxygen have arisen apparently because of the formation of tert-butylperoxyl free radical and its reaction with tert-butyl radical products, i.e. hydroperoxide (peroxide) and isobutene. Isobutene probably forms a complex with molecular oxygen which has a very short proton relaxation time. During the photolysis of uranyl pivalate in the presence of p-benzoquinone (5 x 10 -2 -0.1 mol dm -3 ) we have not observed any CIDNP, whereas under p-benzoquinone concentrations of 10 -3 -10 -2 mol dm -3 the CIDNP from both hydroquinone and p-benzoquinone has been followed. Photolysis of uranyl propionate has led to CIDNP from butane protons. An emission from methyl group protons of a compound with an ethylperoxyl fragment in the presence of air/oxygen has been observed. The same polarization picture has arisen under interaction of photoexcited uranyl with propionic acid. During the photolysis of uranyl acetate at relatively low concentrations (10 -2 mol dm -3 ) a CIDNP very similar to that registered for uranyl propionate was recorded. The ethyl fragment is probably obtained in reactions for two methyl radicals formed from acetate with the parent uranyl acetate, namely hydrogen-atom abstraction and addition reactions. (author)

  20. 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.

  1. Potential of an ensemble Kalman smoother for stratospheric chemical-dynamical data assimilation

    Directory of Open Access Journals (Sweden)

    Thomas Milewski

    2013-02-01

    Full Text Available A new stratospheric ensemble Kalman smoother (EnKS system is introduced, and the potential of assimilating posterior stratospheric observations to better constrain the whole model state at analysis time is investigated. A set of idealised perfect-model Observation System Simulation Experiments (OSSE assimilating synthetic limb-sounding temperature or ozone retrievals are performed with a chemistry–climate model. The impact during the analysis step is characterised in terms of the root mean square error reduction between the forecast state and the analysis state. The performances of (1 a fixed-lag EnKS assimilating observations spread over 48 hours and (2 an ensemble Kalman Filter (EnKF assimilating a denser network of observations are compared with a reference EnKF. The ozone assimilation with EnKS shows a significant additional reduction of analysis error of the order of 10% for dynamical and chemical variables in the extratropical upper troposphere lower stratosphere (UTLS and Polar Vortex regions when compared to the reference EnKF. This reduction has similar magnitude to the one achieved by the denser-network EnKF assimilation. Similarly, the temperature assimilation with EnKS significantly decreases the error in the UTLS for the wind variables like the denser-network EnKF assimilation. However, the temperature assimilation with EnKS has little or no significant impact on the temperature and ozone analyses, whereas the denser-network EnKF shows improvement with respect to the reference EnKF. The different analysis impacts from the assimilation of current and posterior ozone observations indicate the capacity of time-lagged background-error covariances to represent temporal interactions up to 48 hours between variables during the ensemble data assimilation analysis step, and the possibility to use posterior observations whenever additional current observations are unavailable. The possible application of the EnKS for reanalyses is

  2. Molecular dynamic and quantum chemical calculations for phthalazine derivatives as corrosion inhibitors of mild steel in 1 M HCl

    Energy Technology Data Exchange (ETDEWEB)

    Musa, Ahmed Y., E-mail: AMUSA6@UWO.CA [Department of Chemistry, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 5B7 (Canada); Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, Bangi, 43600 Selangor (Malaysia); Jalgham, Ramzi T.T.; Mohamad, Abu Bakar [Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, Bangi, 43600 Selangor (Malaysia)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer The inhibition of three phthalazine derivatives was studied. Black-Right-Pointing-Pointer The inhibition efficiency increased in the following order: PTD < PT < PTO. Black-Right-Pointing-Pointer The adsorption energies were calculated using molecular dynamics simulations. Black-Right-Pointing-Pointer Quantum chemical parameters were calculated using the AM1, MNDO and PM3 methods. Black-Right-Pointing-Pointer The adsorption of phthalazine derivatives obeys the Langmuir adsorption isotherm. - Abstract: The abilities of phthalazine derivatives, including phthalazine (PT), phthalazone (PTO) and phthalhydrazide (PTD), to inhibit the corrosion of mild steel in 1 M HCl at 30 Degree-Sign C were studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Theoretical calculations were performed to investigate the electronic structures of the PT derivatives. Our results showed that the inhibition efficiencies of these derivatives improved with increases in concentration. The data also showed that PTD < PT < PTO in terms of the inhibiting efficiency. Theoretical calculations also revealed that PTO is expected to be the best inhibitor among the studied phthalazine derivatives.

  3. Chemical study of some ceramics from Brazilian Northeast

    International Nuclear Information System (INIS)

    Munita, C.S.; Schreiber, S.B.; Nascimento, A.; Luna, S.; Oliveira, P.M.S.

    2004-01-01

    80 ceramic fragments from six archaeological sites were studied by considering two main aspects: (1) mineralogical/petrographic examination to identify the compounds and minerals present, and (2) elemental analysis via INAA to determine the concentration of As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn. Petrographic analysis showed that the samples from all sites are quite similar in general paste characteristics. The paste is rich in sand, mica and opaque minerals, especially iron and titanium oxides. Principal component analysis was carried out using the log transformed concentrations of determined elemental concentrations. Three components with eigenvalues greater than 1 had been extracted from the variance-covariance matrix that explained 74% of the total variation. Bivariate plot of the first two principal components showed a high degree chemically homogeneous group, providing a high degree of chemical similarity between the samples. (author)

  4. Chemical Tools for the Study of Intramembrane Proteases.

    Science.gov (United States)

    Nguyen, Minh T N; Van Kersavond, Tim; Verhelst, Steven H L

    2015-11-20

    Intramembrane proteases (IMPs) reside inside lipid bilayers and perform peptide hydrolysis in transmembrane or juxtamembrane regions of their substrates. Many IMPs are involved in crucial regulatory pathways and human diseases, including Alzheimer's disease, Parkinson's disease, and diabetes. In the past, chemical tools have been instrumental in the study of soluble proteases, enabling biochemical and biomedical research in complex environments such as tissue lysates or living cells. However, IMPs place special challenges on probe design and applications, and progress has been much slower than for soluble proteases. In this review, we will give an overview of the available chemical tools for IMPs, including activity-based probes, affinity-based probes, and synthetic substrates. We will discuss how these have been used to increase our structural and functional understanding of this fascinating group of enzymes, and how they might be applied to address future questions and challenges.

  5. Chemistry and Chemical Equilibrium Dynamics of BMAA and Its Carbamate Adducts.

    Science.gov (United States)

    Diaz-Parga, Pedro; Goto, Joy J; Krishnan, V V

    2018-01-01

    Beta-N-methylamino-L-alanine (BMAA) has been demonstrated to contribute to the onset of the ALS/Parkinsonism-dementia complex (ALS/PDC) and is implicated in the progression of other neurodegenerative diseases. While the role of BMAA in these diseases is still debated, one of the suggested mechanisms involves the activation of excitatory glutamate receptors. In particular, the excitatory effects of BMAA are shown to be dependent on the presence of bicarbonate ions, which in turn forms carbamate adducts in physiological conditions. The formation of carbamate adducts from BMAA and bicarbonate is similar to the formation of carbamate adducts from non-proteinogenic amino acids. Structural, chemical, and biological information related to non-proteinogenic amino acids provide insight into the formation of and possible neurological action of BMAA. This article reviews the carbamate formation of BMAA in the presence of bicarbonate ions, with a particular focus on how the chemical equilibrium of BMAA carbamate adducts may affect the molecular mechanism of its function. Highlights of nuclear magnetic resonance (NMR)-based studies on the equilibrium process between free BMAA and its adducts are presented. The role of divalent metals on the equilibrium process is also explored. The formation and the equilibrium process of carbamate adducts of BMAA may answer questions on their neuroactive potency and provide strong motivation for further investigations into other toxic mechanisms.

  6. Laboratory studies of 235U enrichment by chemical separation methods

    International Nuclear Information System (INIS)

    Daloisi, P.J.; Orlett, M.J.; Tracy, J.W.; Saraceno, A.J.

    1976-01-01

    Laboratory experiments on 235 U enrichment processes based on column redox ion exchange, electrodialysis, and gas exchange chromatography performed from August 1972 to September 1974 are summarized. Effluent from a 50 to 50 weight mixture of U +4 and U +6 (as UO 2 2+ ), at a total uranium concentration of 5 mg U per ml in 0.25N H 2 SO 4 -0.03N NaF solution, passing through a 100 cm length cation exchange column at 0.5 ml/min flow rates, was enriched in 235 U by 1.00090 +- .00012. The enriched fraction was mostly in the +6 valence form while the depleted fraction was U +4 retained on the resin. At flow rates of 2 ml/min, the enrichment factor decreases to 1.00033 +- .00003. In the electrodialysis experiments, the fraction of uranium diffusing through the membranes (mostly as +6 valence state) in 4.2 hours is enriched in 235 U by 1.00096 +- .00012. Gas exchange chromatography tests involved dynamic and static exposure of UF 6 over NaF. In dynamic tests, no significant change in isotopic abundance occurred in the initial one-half weight cut of UF 6 . The measured relative 235 U/ 238 U mole ratios were 1.00004 +- .00004 for these runs. In static runs, enrichment became evident. For the NaF(UF 6 )/sub x/-UF 6 system, there is 235 U depletion in the gas phase, with a single-stage factor of 1.00033 at 100 0 C and 1.00025 at 25 0 C after 10 days of equilibration. The single-stage or unit holdup time is impractically long for all three chemical processes

  7. Study of spatially extended dynamical systems using probabilistic cellular automata

    International Nuclear Information System (INIS)

    Vanag, Vladimir K

    1999-01-01

    Spatially extended dynamical systems are ubiquitous and include such things as insect and animal populations; complex chemical, technological, and geochemical processes; humanity itself, and much more. It is clearly desirable to have a certain universal tool with which the highly complex behaviour of nonlinear dynamical systems can be analyzed and modelled. For this purpose, cellular automata seem to be good candidates. In the present review, emphasis is placed on the possibilities that various types of probabilistic cellular automata (PCA), such as DSMC (direct simulation Monte Carlo) and LGCA (lattice-gas cellular automata), offer. The methods are primarily designed for modelling spatially extended dynamical systems with inner fluctuations accounted for. For the Willamowskii-Roessler and Oregonator models, PCA applications to the following problems are illustrated: the effect of fluctuations on the dynamics of nonlinear systems; Turing structure formation; the effect of hydrodynamic modes on the behaviour of nonlinear chemical systems (stirring effects); bifurcation changes in the dynamical regimes of complex systems with restricted geometry or low spatial dimension; and the description of chemical systems in microemulsions. (reviews of topical problems)

  8. Molecular beam studies of adsorption dynamics

    International Nuclear Information System (INIS)

    Arumainayagam, C.R.; McMaster, M.C.; Madix, R.J.

    1991-01-01

    We have investigated the trapping dynamics of C 1 -C 3 alkanes and Xe on Pt(111) using supersonic molecular beams and a direct technique to measure trapping probabilities. We have extended a one-dimensional model based on classical mechanics to include trapping and have found semiquantitative agreement with experimental results for the dependence of the initial trapping probability on incident translational energy at normal incidence. Our measurements of the initial trapping probability as a function of incident translational energy at normal incidence are in agreement with previous mean translational energy measurements for Xe and CH 4 desorbing near the surface normal, in accordance with detailed balance. However, the angular dependence of the initial trapping probability shows deviations from normal energy scaling, demonstrating the importance of parallel momentum in the trapping process and the inadequacy of one-dimensional models. The dependence of the initial trapping probability of Xe on incident translational energy and angle is quite well fit by three-dimensional stochastic classical trajectory calculations utilizing a Morse potential. Angular distributions of the scattered molecules indicate that the trapping probability is not a sensitive function of surface temperature. The trapping probability increases with surface coverage in quantitative agreement with a modified Kisliuk model which incorporates enhanced trapping onto the monolayer. We have also used the direct technique to study trapping onto a saturated monolayer state to investigate the dynamics of extrinsic precursor adsorption and find that the initial trapping probability onto the monolayer is higher than on the clean surface. The initial trapping probability onto the monolayer scales with total energy, indicating a highly corrugated interaction potential

  9. 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

  10. Toxicity studies of drugs and chemicals in animals: An overview

    OpenAIRE

    S. Saganuwan

    2017-01-01

    Toxicity study is the investigation of either short or long-term toxic effects of a drug or chemical on animals. The toxicity is dose-dependent as asserted by Paracelsus over 500 years ago. However, short-term toxic effect is determined using median lethal dose (LD50) first introduced by Trevan in 1927 and revised many times. Presently there is a growing preponderance of rejection of scientific papers on acute toxicity study, simply because of the belief that in the current hazard and safety ...

  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. Dynamics of liquids, molecules, and proteins measured with ultrafast 2D IR vibrational echo chemical exchange spectroscopy.

    Science.gov (United States)

    Fayer, M D

    2009-01-01

    A wide variety of molecular systems undergo fast structural changes under thermal equilibrium conditions. Such transformations are involved in a vast array of chemical problems. Experimentally measuring equilibrium dynamics is a challenging problem that is at the forefront of chemical research. This review describes ultrafast 2D IR vibrational echo chemical exchange experiments and applies them to several types of molecular systems. The formation and dissociation of organic solute-solvent complexes are directly observed. The dissociation times of 13 complexes, ranging from 4 ps to 140 ps, are shown to obey a relationship that depends on the complex's formation enthalpy. The rate of rotational gauche-trans isomerization around a carbon-carbon single bond is determined for a substituted ethane at room temperature in a low viscosity solvent. The results are used to obtain an approximate isomerization rate for ethane. Finally, the time dependence of a well-defined single structural transformation of a protein is measured.

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

    International Nuclear Information System (INIS)

    Soorkia, Satchin

    2008-09-01

    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 + CH 3 F. 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 (X 2 Δ) 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-CH 3 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 a 3 F → z 3 F in the metal. This transition is forbidden from the ground state a 3 F 2 of zirconium but allowed from the a 3 F 4 state. Complexation of the metal atom with a CH 3 F molecule allows coupling of these two states to occur which ensures the optical transition from the ground state of the complex. (author)

  14. Dynamics, Chemical Abundances, and ages of Globular Clusters in the Virgo Cluster of Galaxies

    Science.gov (United States)

    Guhathakurta, Puragra; NGVS Collaboration

    2018-01-01

    We present a study of the dynamics, metallicities, and ages of globular clusters (GCs) in the Next Generation Virgo cluster Survey (NGVS), a deep, multi-band (u, g, r, i, z, and Ks), wide-field (104 deg2) imaging survey carried out using the 3.6-m Canada-France-Hawaii Telescope and MegaCam imager. GC candidates were selected from the NGVS survey using photometric and image morphology criteria and these were followed up with deep, medium-resolution, multi-object spectroscopy using the Keck II 10-m telescope and DEIMOS spectrograph. The primary spectroscopic targets were candidate GC satellites of dwarf elliptical (dE) and ultra-diffuse galaxies (UDGs) in the Virgo cluster. While many objects were confirmed as GC satellites of Virgo dEs and UDGs, many turned out to be non-satellites based on their radial velocity and/or positional mismatch any identifiable Virgo cluster galaxy. We have used a combination of spectral characteristics (e.g., presence of absorption vs. emission lines), new Gaussian mixture modeling of radial velocity and sky position data, and a new extreme deconvolution analysis of ugrizKs photometry and image morphology, to classify all the objects in our sample into: (1) GC satellites of dE galaxies, (2) GC satellites of UDGs, (3) intra-cluster GCs (ICGCs) in the Virgo cluster, (4) GCs in the outer halo of the central cluster galaxy M87, (5) foreground Milky Way stars, and (6) distant background galaxies. We use these data to study the dynamics and dark matter content of dE and UDGs in the Virgo cluster, place important constraints on the nature of dE nuclei, and study the origin of ICGCs versus GCs in the remote M87 halo.We are grateful for financial support from the NSF and NASA/STScI.

  15. [Study on the chemical constituents of Buddleja davidii].

    Science.gov (United States)

    Peng, Xue-Jing; Zeng, Yong; Luo, Jian-Jun; Chang, Xiao-Li; Xie, Qin-Jian; Wang, Ting; Li, Chong; Zhao, Lei

    2012-12-01

    To study the chemical constituents of Buddleja davidii. The constituents were isolated and purified by silica gel column chromatography, polyamide column chromatography and macroporous adsorption resin and their structures were identified by spectroscopic analysis. Eight compounds were elucidated as : Cranioside A (1), Eutigoside A (2), 1-O-4-Dimethoxyphenylethyl-4-O-3,4-dimethoxyphenylethy-beta-D-glucopyranoside (3), Isomartynoside (4'), 4"-O-Acetylmartynoside (5), Stigmasterol glueoside (6), beta-Sitosterol (7), Daucosterol (8). All these compounds are obtained from this plant for the first time.

  16. An electrochemical study of natural and chemically controlled eumelanin

    Directory of Open Access Journals (Sweden)

    Ri Xu

    2017-12-01

    Full Text Available Eumelanin is the most common form of the pigment melanin in the human body, with functions including antioxidant behavior, metal chelation, and free radical scavenging. This biopigment is of interest for biologically derived batteries and supercapacitors. In this work, we characterized the voltammetric properties of chemically controlled eumelanins produced from 5,6-dihydroxyindole (DHI and 5,6-dihydroxyindole-2-carboxylic acid (DHICA building blocks, namely, DHI-melanin, DHICA-melanin, and natural eumelanin, extracted from the ink sac of cuttlefish, Sepia melanin. Eumelanin electrodes were studied for their cyclic voltammetric properties in acidic buffers including Na+, K+, NH4+, and Cu2+ ions.

  17. Study to establish cost projections for production of Redox chemicals

    Science.gov (United States)

    Walther, J. F.; Greco, C. C.; Rusinko, R. N.; Wadsworth, A. L., III

    1982-01-01

    A cost study of four proposed manufacturing processes for redox chemicals for the NASA REDOX Energy Storage System yielded favorable selling prices in the range $0.99 to $1.91/kg of chromic chloride, anhydrous basis, including ferrous chloride. The prices corresponded to specific energy storage costs from under $9 to $17/kWh. A refined and expanded cost analysis of the most favored process yielded a price estimate corresponding to a storage cost of $11/kWh. The findings supported the potential economic viability of the NASA REDOX system.

  18. An experimental study of steam explosions involving chemically reactive metal

    International Nuclear Information System (INIS)

    Cho, D.H.; Armstrong, D.R.; Gunther, W.H.; Basu, S.

    1997-01-01

    An experimental study of molten zirconium-water explosions was conducted. A 1-kg mass of zirconium melt was dropped into a column of water. Explosions took place only when an external trigger was used. In the triggered tests, the extent of oxidation of the zirconium melt was very extensive. However, the explosion energetics estimated were found to be very small compared to the potential chemical energy available from the oxidation reaction. Zirconium is of particular interest, since it is a component of the core materials of the current nuclear power reactors. This paper describes the test apparatus and summarizes the results of four tests conducted using pure zirconium melt

  19. An electrochemical study of natural and chemically controlled eumelanin

    Science.gov (United States)

    Xu, Ri; Prontera, Carmela Tania; Di Mauro, Eduardo; Pezzella, Alessandro; Soavi, Francesca; Santato, Clara

    2017-12-01

    Eumelanin is the most common form of the pigment melanin in the human body, with functions including antioxidant behavior, metal chelation, and free radical scavenging. This biopigment is of interest for biologically derived batteries and supercapacitors. In this work, we characterized the voltammetric properties of chemically controlled eumelanins produced from 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) building blocks, namely, DHI-melanin, DHICA-melanin, and natural eumelanin, extracted from the ink sac of cuttlefish, Sepia melanin. Eumelanin electrodes were studied for their cyclic voltammetric properties in acidic buffers including Na+, K+, NH4+, and Cu2+ ions.

  20. Towards the use of dynamic growing seasons in a chemical transport model

    Science.gov (United States)

    Sakalli, A.; Simpson, D.

    2012-12-01

    Chemical transport models (CTMs), used for the prediction of, for example, nitrogen deposition or air quality changes, require estimates of the growing season of plants for a number of reasons. Typically, the growing seasons are defined in a very simplified way in CTMs, using fixed dates or simple functions. In order to explore the importance of more realistic growing season estimates, we have developed a new and simple method (the T5 method) for calculating the start of the growing season (SGS) of birch (which we use as a surrogate for deciduous trees), suitable for use in CTMs and other modelling systems. We developed the T5 method from observations, and here we compare with these and other methodologies, and show that with just two parameters T5 captures well the spatial variation in SGS across Europe. We use the EMEP MSC-W chemical transport model to illustrate the importance of improved SGS estimates for ozone and two metrics associated with ozone damage to vegetation. This study shows that although inclusion of more realistic growing seasons has only small effects on annual average concentrations of pollutants such as ozone, the metrics associated with vegetation risk from ozone are significantly affected. This work demonstrates a strong need to include more realistic treatments of growing seasons in CTMs. The method used here could also be suitable for other types of models that require information on vegetation cover, such as meteorological and regional climate models. In future work, the T5 and other methods will be further evaluated for other forest species, as well as for agricultural and grassland land covers, which are important for emissions and deposition of reactive nitrogen compounds.

  1. Intermolecular dynamics studied by paramagnetic tagging

    Energy Technology Data Exchange (ETDEWEB)

    Xu Xingfu; Keizers, Peter H. J. [Leiden University, Institute of Chemistry (Netherlands); Reinle, Wolfgang; Hannemann, Frank; Bernhardt, Rita [Universitaet des Saarlandes, Naturwissenschaftlich-Technische Fakultaet III, Institut fuer Biochemie (Germany); Ubbink, Marcellus [Leiden University, Institute of Chemistry (Netherlands)], E-mail: m.ubbink@chem.leidenuniv.nl

    2009-04-15

    Yeast cytochrome c and bovine adrenodoxin form a dynamic electron transfer complex, which is a pure encounter complex. It is demonstrated that the dynamic nature of the interaction can readily be probed by using a rigid lanthanide tag attached to cytochrome c. The tag, Caged Lanthanide NMR Probe 5, induces pseudocontact shifts and residual dipolar couplings and does not perturb the binding interface. Due to the dynamics in the complex, residual dipolar couplings in adrenodoxin are very small. Simulation shows that cytochrome c needs to sample a large part of the surface of adrenodoxin to explain the small degree of alignment observed for adrenodoxin. The applied method provides a simple and straightforward way to observe dynamics in protein complexes or domain-domain mobility without the need for external alignment media.

  2. Intermolecular dynamics studied by paramagnetic tagging

    International Nuclear Information System (INIS)

    Xu Xingfu; Keizers, Peter H. J.; Reinle, Wolfgang; Hannemann, Frank; Bernhardt, Rita; Ubbink, Marcellus

    2009-01-01

    Yeast cytochrome c and bovine adrenodoxin form a dynamic electron transfer complex, which is a pure encounter complex. It is demonstrated that the dynamic nature of the interaction can readily be probed by using a rigid lanthanide tag attached to cytochrome c. The tag, Caged Lanthanide NMR Probe 5, induces pseudocontact shifts and residual dipolar couplings and does not perturb the binding interface. Due to the dynamics in the complex, residual dipolar couplings in adrenodoxin are very small. Simulation shows that cytochrome c needs to sample a large part of the surface of adrenodoxin to explain the small degree of alignment observed for adrenodoxin. The applied method provides a simple and straightforward way to observe dynamics in protein complexes or domain-domain mobility without the need for external alignment media

  3. Molecular dynamics studies of superionic conductors

    International Nuclear Information System (INIS)

    Rahman, A.

    1979-01-01

    Over the last fifteen years computer modeling of liquids and solids has become a useful method of understanding the structural and dynamical correlations in these systems. Some characteristics of the method are presented with an example from work on homogeneous nucleation in monoatomic liquids; the interaction potential determines the structure: a Lennard--Jones system nucleates a close packed structure while an alkali metal potential nucleates a bcc packing. In the study of ionic systems like CaF 2 the Coulomb interaction together with the short range repulsion is enough to produce a satisfactory model for the motion of F - ions in CaF 2 at approx. 1600 0 K. Analysis of this motion shows that F - ions reside at their fluorite sites for about 6 x 10 -12 s and that the diffusion is mainly due to F - jumps in the 100 direction. The motion can be analyzed in terms of the generation and annihilation of anti-Frenkel pairs. The temperature dependence of the F - diffusion constant at two different densities has also been calculated. The computer model does not correspond with experiment in this regard

  4. Prolactin secretion: the impact of dynamic studies

    International Nuclear Information System (INIS)

    L'Hermite, M.; Degueldre, M.; Caufriez, A.; Delvoye, P.; Robyn, C.

    1975-01-01

    Human prolactin blood levels were determined by radioimmunoassay in basal condition and in response to various inhibiting and/or stimulating agents (levodopa, water overload, insulinic hypoglycaemia, synthetic TRH, sulpiride) in cases of disturbed hypothalamo-pituitary axis (failure to lactate, prolactin-secreting pituitary adenomas, acromegaly, other pituitary tumours, clinical panhypopituitarism). A blunted prolactin response to suckling was evidenced in 2 post-partum women who were unable to breast feed. Hyperprolactinaemia, whether related to the existence of a prolactin-producing adenoma or not was associated with the disappearance of the normal circadian pattern of prolactin secretion and with a blunted relative response to TRH; the latter phenomenon occurred also in acromegaly regardless of the basal prolactinaemia, and during the last trimester of pregnancy. Water overload was unsuccessful to suppress prolactin during the last trimester of pregnancy while the acute administration of levodopa was quite effective in about half of the patients with pituitary tumour. Therefore none of the dynamic tests presently studied allowed to attribute a hyperprolactinaemia to a pituitary tumour rather than to a functional disturbance. On the contrary, stimulation tests can help to locate the level of a defect in cases of hypopituitarism [fr

  5. Microbial dynamics during and after in situ chemical oxidation of chlorinated solvents

    NARCIS (Netherlands)

    Sutton, N.B.; Atashgahi, S.; Wal, van der J.; Wijn, G.; Grotenhuis, J.T.C.; Smidt, H.; Rijnaarts, H.

    2015-01-01

    In situ chemical oxidation (ISCO) followed by a bioremediation step is increasingly being considered as an effective biphasic technology. Information on the impact of chemical oxidants on organohalide respiring bacteria (OHRB), however, is largely lacking. Therefore, we used quantitative PCR (qPCR)

  6. Does the QCD vacuum build up a colour chemical potential dynamically?

    International Nuclear Information System (INIS)

    Sailer, K.; Greiner, W.

    1998-01-01

    The one-loop effective theory is found for QCD assuming an overcritical homogeneous gluon vector potential background that corresponds to a non-vanishing colour chemical potential. It is found that the vacuum is unstable against building up a non-vanishing colour chemical potential for sufficiently large number of flavours. (author)

  7. 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.

  8. Molecular dynamics of TBP and DBP studied by neutron transmission

    International Nuclear Information System (INIS)

    Salles Filho, J.B.V.; Refinetti, M.E.; Fulfaro, R.; Vinhas, L.A.

    1984-04-01

    Differences between the properties of TBP and DBP, concerning the uranium extraction processes, may be related to certain characteristics of the molecular dynamics of each compound. In order to investigate the dynamical behaviour of hydrogen in these molecules, neutron transmission of TBP and DBP has been measured as a function of neutron wavelenght in the range 4.0 - 6.0 A, at room temperature. Scattering cross sections per hydrogen atom have been obtained. From the comparison with results previously obtained for n-butanol, similar dynamical behaviour of butyl radicals in these compounds could be observed. This similarity indicates that the presence of two or three butyl radicals in butylphosphate molecules does not exert influence in the hydrogen motion of methyl and methylene groups. This suggests that the different chemical behaviour between TBP and DBP is related to the dynamics of the hydrogen directly bound to the DBP phosphate group.(Author) [pt

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

    Directory of Open Access Journals (Sweden)

    S. ACATINCĂI

    2008-10-01

    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.

  10. Thermal transpiration: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    T, Joe Francis [Computational Nanotechnology Laboratory, School of Nano Science and Technology, National Institute of Technology Calicut, Kozhikode (India); Sathian, Sarith P. [Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai (India)

    2014-12-09

    Thermal transpiration is a phenomenon where fluid molecules move from the cold end towards the hot end of a channel under the influence of longitudinal temperature gradient alone. Although the phenomenon of thermal transpiration is observed at rarefied gas conditions in macro systems, the phenomenon can occur at atmospheric pressure if the characteristic dimensions of the channel is less than 100 nm. The flow through these nanosized channels is characterized by the free molecular flow regimes and continuum theory is inadequate to describe the flow. Thus a non-continuum method like molecular dynamics (MD) is necessary to study such phenomenon. In the present work, MD simulations were carried out to investigate the occurance of thermal transpiration in copper and platinum nanochannels at atmospheric pressure conditions. The mean pressure of argon gas confined inside the nano channels was maintained around 1 bar. The channel height is maintained at 2nm. The argon atoms interact with each other and with the wall atoms through the Lennard-Jones potential. The wall atoms are modelled using an EAM potential. Further, separate simulations were carried out where a Harmonic potential is used for the atom-atom interaction in the platinum channel. A thermally insulating wall was introduced between the low and high temperature regions and those wall atoms interact with fluid atoms through a repulsive potential. A reduced cut off radius were used to achieve this. Thermal creep is induced by applying a temperature gradient along the channel wall. It was found that flow developed in the direction of the increasing temperature gradient of the wall. An increase in the volumetric flux was observed as the length of the cold and the hot regions of the wall were increased. The effect of temperature gradient and the wall-fluid interaction strength on the flow parameters have been studied to understand the phenomenon better.

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

    International Nuclear Information System (INIS)

    Mota Vieira, V.; Oliveira, C.C. de

    2015-01-01

    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)

  12. Chemical Oscillations

    Indian Academy of Sciences (India)

    IMTECH),. Chandigarh. Praveen Kumar is pursuing his PhD in chemical dynamics at. Panjab University,. Chandigarh. Keywords. Chemical oscillations, autoca-. talYSis, Lotka-Volterra model, bistability, hysteresis, Briggs-. Rauscher reaction.

  13. Chemical exchange in novel spirobicyclic zwitterionic Janovsky complexes using dynamic 1H NMR spectroscopy.

    Science.gov (United States)

    Culf, A S; Cuperlović-Culf, M; Ouellette, R J

    2009-02-01

    Highly coloured Janovsky complexes have been known for over 120 years, being used in many colourimetric analytical procedures. In this present study, two novel and stable nitrocyclohexadienyl spirobicyclic, zwitterionic Janovsky anionic hydantoin sigma-complexes, rac-1,3-diisopropyl-6-nitro-2,4-dioxo-1,3-diazaspiro[4.5]deca-6,9-dien-8-ylideneazinate, ammonium internal salt (1) and 1,3-diisopropyl-2,4-dioxo-1,3-diazaspiro[4.5]deca-6,9-dien-8-ylideneazinate, ammonium internal salt (2) have been prepared and characterised by NMR, electrospray ionization mass spectrometry (ESI-MS) and UV/visible methods. For the p-mononitro-substituted complex (2), we discovered chemical exchange behaviour using 1D saturation transfer and 2D exchange spectroscopy (EXSY) (1)H NMR techniques. The coalescence temperature was determined to be 62 degrees C in d(3)-acetonitrile. Analysis of these data provided a Gibbs free energy of activation, DeltaG double dagger, of + 67 kJ mole(-1), a rate constant, k, coalescence of 220 Hz and an equilibrium constant, K(eqm), of 0.98 as estimates of the exchange process in this solvent. Of the two mechanisms proposed for this fluxional behaviour, ring opening to a substituted benzene or proton exchange, a further theoretical modelling study of 1D (1)H NMR spectra was able to confirm that simple proton exchange between the two nitrogen sites of the hydantoin ring provided an accurate simulation of the observed experimental evidence. Interestingly, the o,p-dinitro-substituted complex (1) did not show any chemical exchange behaviour up to 150 degrees C in d(3)-acetonitrile (to 75 degrees C) and d(6)-dimethyl sulfoxide (DMSO). Molecular modelling at the MM2 level suggests that steric collisions of an N-acyl isopropyl substituent of the hydantoin ring with the ortho-nitro group of the spirofused cyclohexadienyl ring prevents the proposed proton exchange mechanism occurring in this case. 2008 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.

  14. Dynamical interactions between solute and solvent studied by nonlinear infrared spectroscopy

    International Nuclear Information System (INIS)

    Ohta, K.; Tominaga, K.

    2006-01-01

    Interactions between solute and solvent play an important role in chemical reaction dynamics and in many relaxation processes in condensed phases. Recently third-order nonlinear infrared (IR) spectroscopy has shown to be useful to investigate solute-solvent interaction and dynamics of the vibrational transition. These studies provide detailed information on the energy relaxation of the vibrationally excited state, and the time scale and the magnitude of the time correlation functions of the vibrational frequency fluctuations. In this work we have studied vibrational energy relaxation (VER) of solutions and molecular complexes by nonlinear IR spectroscopy, especially IR pump-probe method, to understand the microscopic interactions in liquids. (authors)

  15. Final report for NIF chamber dynamics studies

    International Nuclear Information System (INIS)

    Burnham, A; Peterson, P F; Scott, J M

    1998-01-01

    The National Ignition Facility (NIF), a 1.8 MJ, 192 laser beam facility, will have anticipated fusion yields of up to 20 MJ from D-T pellets encased in a gold hohlraum target. The energy emitted from the target in the form of x rays, neutrons, target debris kinetic energy, and target shrapnel will be contained in a 5 m. radius spherical target chamber. various diagnostics will be stationed around the target at varying distances from the target. During each shot, the target will emit x rays that will vaporize nearby target facing surfaces including those of the diagnostics, the target positioner, and other chamber structures. This ablated vapor will be transported throughout the chamber, and will eventually condense and deposit on surfaces in the chamber, including the final optics debris shields. The research at the University of California at Berkeley relates primarily to the NIF chamber dynamics. The key design issues are the ablation of the chamber structures, transport of the vapor through the chamber and the condensation or deposition processes of those vaporized materials. An understanding of these processes is essential in developing a concept for protecting the fina optics debris shields from an excessive coating (> 10 A) of target debris and ablated material, thereby prolonging their lifetime between change-outs. At Berkeley, we have studied the physical issues of the ablation process and the effects of varying materials, the condensation process of the vaporized material, and design schemes that can lower the threat posed to the debris shields by these processes. The work or portions of the work completed this year have been published in several papers and a dissertation [l-5

  16. 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.

  17. 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

  18. Action-Derived Molecular Dynamics in the Study of Rare Events

    Energy Technology Data Exchange (ETDEWEB)

    Passerone, Daniele; Parrinello, Michele

    2001-09-03

    We present a practical method to generate classical trajectories with fixed initial and final boundary conditions. Our method is based on the minimization of a suitably defined discretized action. The method finds its most natural application in the study of rare events. Its capabilities are illustrated by nontrivial examples. The algorithm lends itself to straightforward parallelization, and when combined with ab initio molecular dynamics it promises to offer a powerful tool for the study of chemical reactions.

  19. Action-Derived Molecular Dynamics in the Study of Rare Events

    International Nuclear Information System (INIS)

    Passerone, Daniele; Parrinello, Michele

    2001-01-01

    We present a practical method to generate classical trajectories with fixed initial and final boundary conditions. Our method is based on the minimization of a suitably defined discretized action. The method finds its most natural application in the study of rare events. Its capabilities are illustrated by nontrivial examples. The algorithm lends itself to straightforward parallelization, and when combined with ab initio molecular dynamics it promises to offer a powerful tool for the study of chemical reactions

  20. Effects of N-glycosylation on protein conformation and dynamics: Protein Data Bank analysis and molecular dynamics simulation study.

    Science.gov (United States)

    Lee, Hui Sun; Qi, Yifei; Im, Wonpil

    2015-03-09

    N-linked glycosylation is one of the most important, chemically complex, and ubiquitous post-translational modifications in all eukaryotes. The N-glycans that are covalently linked to proteins are involved in numerous biological processes. There is considerable interest in developments of general approaches to predict the structural consequences of site-specific glycosylation and to understand how these effects can be exploited in protein design with advantageous properties. In this study, the impacts of N-glycans on protein structure and dynamics are systematically investigated using an integrated computational approach of the Protein Data Bank structure analysis and atomistic molecular dynamics simulations of glycosylated and deglycosylated proteins. Our study reveals that N-glycosylation does not induce significant changes in protein structure, but decreases protein dynamics, likely leading to an increase in protein stability. Overall, these results suggest not only a common role of glycosylation in proteins, but also a need for certain proteins to be properly glycosylated to gain their intrinsic dynamic properties.

  1. Assessing the chemical contamination dynamics in a mixed land use stream system

    DEFF Research Database (Denmark)

    Sonne, Anne Thobo; McKnight, Ursula S.; Rønde, Vinni

    2017-01-01

    Traditionally, the monitoring of streams for chemical and ecological status has been limited to surface water concentrations, where the dominant focus has been on general water quality and the risk for eutrophication. Mixed land use stream systems, comprising urban areas and agricultural production......, are challenging to assess with multiple chemical stressors impacting stream corridors. New approaches are urgently needed for identifying relevant sources, pathways and potential impacts for implementation of suitable source management and remedial measures. We developed a method for risk assessing chemical...... stressors in these systems and applied the approach to a 16-km groundwater-fed stream corridor (Grindsted, Denmark). Three methods were combined: (i) in-stream contaminant mass discharge for source quantification, (ii) Toxic Units and (iii) environmental standards. An evaluation of the chemical quality...

  2. Raman spectroscopic study of reaction dynamics

    Science.gov (United States)

    MacPhail, R. A.

    1990-12-01

    The Raman spectra of reacting molecules in liquids can yield information about various aspects of the reaction dynamics. The author discusses the analysis of Raman spectra for three prototypical unimolecular reactions, the rotational isomerization of n-butane and 1,2-difluoroethane, and the barrierless exchange of axial and equatorial hydrogens in cyclopentane via pseudorotation. In the first two cases the spectra are sensitive to torsional oscillations of the gauche conformer, and yield estimates of the torsional solvent friction. In the case of cyclopentane, the spectra can be used to discriminate between different stochastic models of the pseudorotation dynamics, and to determine the relevant friction coefficients.

  3. Coupled sulfur isotopic and chemical mass transfer modeling: Approach and application to dynamic hydrothermal processes

    International Nuclear Information System (INIS)

    Janecky, D.R.

    1988-01-01

    A computational modeling code (EQPSreverse arrowS) has been developed to examine sulfur isotopic distribution pathways coupled with calculations of chemical mass transfer pathways. A post processor approach to EQ6 calculations was chosen so that a variety of isotopic pathways could be examined for each reaction pathway. Two types of major bounding conditions were implemented: (1) equilibrium isotopic exchange between sulfate and sulfide species or exchange only accompanying chemical reduction and oxidation events, and (2) existence or lack of isotopic exchange between solution species and precipitated minerals, parallel to the open and closed chemical system formulations of chemical mass transfer modeling codes. All of the chemical data necessary to explicitly calculate isotopic distribution pathways is generated by most mass transfer modeling codes and can be input to the EQPS code. Routines are built in to directly handle EQ6 tabular files. Chemical reaction models of seafloor hydrothermal vent processes and accompanying sulfur isotopic distribution pathways illustrate the capabilities of coupling EQPSreverse arrowS with EQ6 calculations, including the extent of differences that can exist due to the isotopic bounding condition assumptions described above. 11 refs., 2 figs

  4. A stochastic chemical dynamic approach to correlate autoimmunity and optimal vitamin-D range.

    Science.gov (United States)

    Roy, Susmita; Shrinivas, Krishna; Bagchi, Biman

    2014-01-01

    Motivated by several recent experimental observations that vitamin-D could interact with antigen presenting cells (APCs) and T-lymphocyte cells (T-cells) to promote and to regulate different stages of immune response, we developed a coarse grained but general kinetic model in an attempt to capture the role of vitamin-D in immunomodulatory responses. Our kinetic model, developed using the ideas of chemical network theory, leads to a system of nine coupled equations that we solve both by direct and by stochastic (Gillespie) methods. Both the analyses consistently provide detail information on the dependence of immune response to the variation of critical rate parameters. We find that although vitamin-D plays a negligible role in the initial immune response, it exerts a profound influence in the long term, especially in helping the system to achieve a new, stable steady state. The study explores the role of vitamin-D in preserving an observed bistability in the phase diagram (spanned by system parameters) of immune regulation, thus allowing the response to tolerate a wide range of pathogenic stimulation which could help in resisting autoimmune diseases. We also study how vitamin-D affects the time dependent population of dendritic cells that connect between innate and adaptive immune responses. Variations in dose dependent response of anti-inflammatory and pro-inflammatory T-cell populations to vitamin-D correlate well with recent experimental results. Our kinetic model allows for an estimation of the range of optimum level of vitamin-D required for smooth functioning of the immune system and for control of both hyper-regulation and inflammation. Most importantly, the present study reveals that an overdose or toxic level of vitamin-D or any steroid analogue could give rise to too large a tolerant response, leading to an inefficacy in adaptive immune function.

  5. A stochastic chemical dynamic approach to correlate autoimmunity and optimal vitamin-D range.

    Directory of Open Access Journals (Sweden)

    Susmita Roy

    Full Text Available Motivated by several recent experimental observations that vitamin-D could interact with antigen presenting cells (APCs and T-lymphocyte cells (T-cells to promote and to regulate different stages of immune response, we developed a coarse grained but general kinetic model in an attempt to capture the role of vitamin-D in immunomodulatory responses. Our kinetic model, developed using the ideas of chemical network theory, leads to a system of nine coupled equations that we solve both by direct and by stochastic (Gillespie methods. Both the analyses consistently provide detail information on the dependence of immune response to the variation of critical rate parameters. We find that although vitamin-D plays a negligible role in the initial immune response, it exerts a profound influence in the long term, especially in helping the system to achieve a new, stable steady state. The study explores the role of vitamin-D in preserving an observed bistability in the phase diagram (spanned by system parameters of immune regulation, thus allowing the response to tolerate a wide range of pathogenic stimulation which could help in resisting autoimmune diseases. We also study how vitamin-D affects the time dependent population of dendritic cells that connect between innate and adaptive immune responses. Variations in dose dependent response of anti-inflammatory and pro-inflammatory T-cell populations to vitamin-D correlate well with recent experimental results. Our kinetic model allows for an estimation of the range of optimum level of vitamin-D required for smooth functioning of the immune system and for control of both hyper-regulation and inflammation. Most importantly, the present study reveals that an overdose or toxic level of vitamin-D or any steroid analogue could give rise to too large a tolerant response, leading to an inefficacy in adaptive immune function.

  6. Dynamic Aperture Studies for SPEAR 3

    International Nuclear Information System (INIS)

    Nosochkov, Yuri

    1999-01-01

    The SSRL is investigating an accelerator upgrade project to replace the present 130 nm.rad FODO lattice with an 18 nm.rad double bend achromat lattice: SPEAR 3. In this paper, we review the methods used to maximize the SPEAR 3 dynamic aperture including optimization of linear optics, betatron tune, chromaticity and coupling correction, and effects of machine errors and insertion devices

  7. Excess water dynamics in hydrotalcite: QENS study

    Indian Academy of Sciences (India)

    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 transla- tional jump diffusion model. The observed increase in translational diffusivity with increase in the amount of excess water is attributed to the ...

  8. Chemoproteomics Reveals Chemical Diversity and Dynamics of 4-Oxo-2-nonenal Modifications in Cells.

    Science.gov (United States)

    Sun, Rui; Fu, Ling; Liu, Keke; Tian, Caiping; Yang, Yong; Tallman, Keri A; Porter, Ned A; Liebler, Daniel C; Yang, Jing

    2017-10-01

    4-Oxo-2-nonenal (ONE) derived from lipid peroxidation modifies nucleophiles and transduces redox signaling by its reactions with proteins. However, the molecular interactions between ONE and complex proteomes and their dynamics in situ remain largely unknown. Here we describe a quantitative chemoproteomic analysis of protein adduction by ONE in cells, in which the cellular target profile of ONE is mimicked by its alkynyl surrogate. The analyses reveal four types of ONE-derived modifications in cells, including ketoamide and Schiff-base adducts to lysine, Michael adducts to cysteine, and a novel pyrrole adduct to cysteine. ONE-derived adducts co-localize and exhibit crosstalk with many histone marks and redox sensitive sites. All four types of modifications derived from ONE can be reversed site-specifically in cells. Taken together, our study provides much-needed mechanistic insights into the cellular signaling and potential toxicities associated with this important lipid derived electrophile. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  9. Study on microwave assisted process in chemical extraction

    International Nuclear Information System (INIS)

    Amer Ali; Rosli Mohd Yunus; Ramlan Abd Aziz

    2001-01-01

    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)

  10. Phyto chemical study of the flavonoids of khaya senegalensis

    International Nuclear Information System (INIS)

    Shakir, S. H.

    2005-03-01

    Phyto chemical screening of the leaves of Khaya senegalensis revealed the presence of flavonoids. Crushed air-dried leaves of Khaya senegalensis were extracted at ambient temperature with ethanol. The crude product obtained after removal of the solvent was subjected to chromatographic fractionation. Using silica gel and the solvent system: butanol: acetic acid: water (3:1:6 ; V:V:V) a pure flavonoid was isolated. The colour reactions and the UV spectra of the isolated flavonoid clearly indicated that it is a flavone. The hydroxylation pattern of the isolated flavone was studies using shift reagents. The structural features were further elucidated via IR, NMR and Mass spectrophotometry. The following tentative structure was proposed.(Author)

  11. Statistical study of chemical additives effects in the waste cementation

    International Nuclear Information System (INIS)

    Tello, Cledola C.O. de; Diniz, Paula S.; Haucz, Maria J.A.

    1997-01-01

    This paper presents the statistical study, that was carried out to analyse the chemical additives effect in the waste cementation process. Three different additives from two industries were tested: set accelerator, set retarder and super plasticizers, in cemented pates with and without bentonite. The experiments were planned in accordance with the 2 3 factorial design, so that the effect of each type of additive, its quantity and manufacturer in cemented paste and specimens could be evaluated. The results showed that the use of these can improve the cementation process and the product. The admixture quantity and the association with bentonite were the most important factors affecting the process and product characteristics. (author). 4 refs., 9 figs., 4 tabs

  12. Vibrational spectroscopic studies of Isoleucine by quantum chemical calculations.

    Science.gov (United States)

    Moorthi, P P; Gunasekaran, S; Ramkumaar, G R

    2014-04-24

    In this work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of Isoleucine (2-Amino-3-methylpentanoic acid). The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments, thermodynamics properties, NBO analyses, NMR chemical shifts and ultraviolet-visible spectral interpretation of Isoleucine have been studied by performing MP2 and DFT/cc-pVDZ level of theory. The FTIR, FT-Raman spectra were recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1) respectively. The UV-visible absorption spectra of the compound were recorded in the range of 200-800 nm. Computational calculations at MP2 and B3LYP level with basis set of cc-pVDZ is employed in complete assignments of Isoleucine molecule on the basis of the potential energy distribution (PED) of the vibrational modes, calculated using VEDA-4 program. The calculated wavenumbers are compared with the experimental values. The difference between the observed and calculated wavenumber values of most of the fundamentals is very small. (13)C and (1)H nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method and compared with experimental results. The formation of hydrogen bond was investigated in terms of the charge density by the NBO calculations. Based on the UV spectra and TD-DFT calculations, the electronic structure and the assignments of the absorption bands were carried out. Besides, molecular electrostatic potential (MEP) were investigated using theoretical calculations. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Dynamics of shearing force and its correlations with chemical compositions and in vitro dry matter digestibility of stylo (Stylosanthes guianensis) stem.

    Science.gov (United States)

    Zi, Xuejuan; Li, Mao; Zhou, Hanlin; Tang, Jun; Cai, Yimin

    2017-12-01

    The study explored the dynamics of shearing force and its correlation with chemical compositions and in vitro dry matter digestibility (IVDMD) of stylo. The shearing force, diameter, linear density, chemical composition, and IVDMD of different height stylo stem were investigated. Linear regression analysis was done to determine the relationships between the shearing force and cut height, diameter, chemical composition, or IVDMD. The results showed that shearing force of stylo stem increased with plant height increasing and the crude protein (CP) content and IVDMD decreased but fiber content increased over time, resulting in decreased forage value. In addition, tall stem had greater shearing force than short stem. Moreover, shearing force is positively correlated with stem diameter, linear density and fiber fraction, but negatively correlated with CP content and IVDMD. Overall, shearing force is an indicator more direct, easier and faster to measure than chemical composition and digestibility for evaluation of forage nutritive value related to animal performance. Therefore, it can be used to evaluate the nutritive value of stylo.

  14. Real-time nonlinear feedback control of pattern formation in (bio)chemical reaction-diffusion processes: a model study.

    Science.gov (United States)

    Brandt-Pollmann, U; Lebiedz, D; Diehl, M; Sager, S; Schlöder, J

    2005-09-01

    Theoretical and experimental studies related to manipulation of pattern formation in self-organizing reaction-diffusion processes by appropriate control stimuli become increasingly important both in chemical engineering and cellular biochemistry. In a model study, we demonstrate here exemplarily the application of an efficient nonlinear model predictive control (NMPC) algorithm to real-time optimal feedback control of pattern formation in a bacterial chemotaxis system modeled by nonlinear partial differential equations. The corresponding drift-diffusion model type is representative for many (bio)chemical systems involving nonlinear reaction dynamics and nonlinear diffusion. We show how the computed optimal feedback control strategy exploits the system inherent physical property of wave propagation to achieve desired control aims. We discuss various applications of our approach to optimal control of spatiotemporal dynamics.

  15. Dynamic Aperture Studies for SPEAR 3

    International Nuclear Information System (INIS)

    Corbett, William

    1998-01-01

    The Stanford Synchrotron Radiation Laboratory is investigating an accelerator upgrade project that would replace the present 130 nm rad FODO lattice with an 18 nm rad double bend achromat (DBA) lattice: SPEAR 3. The low emittance design yields a high brightness beam, but the stronger focusing in the DBA lattice increases chromaticity and beam sensitivity to machine errors. To ensure efficient injection and long Touschek lifetime, an optimization of the design lattice and dynamic aperture has been performed. In this paper, we review the methods used to maximize the SPEAR 3 dynamic aperture including necessary optics modifications, choice of tune and phase advance, optimization of sextupole and coupling correction, and modeling effects of machine errors, wigglers and lattice periodicity

  16. Dynamic aperture studies for SPEAR 3

    International Nuclear Information System (INIS)

    Nosochkov, Y.; Corbett, J.

    1999-01-01

    The Stanford Synchrotron Radiation Laboratory is investigating an accelerator upgrade project that would replace the present 130 nm·rad FODO lattice with an 18 nm·rad double bend achromat (DBA) lattice: SPEAR 3. The low emittance design yields a high brightness beam, but the stronger focusing in the DBA lattice increases chromaticity and beam sensitivity to machine errors. To ensure efficient injection and long Touschek lifetime, an optimization of the design lattice and dynamic aperture has been performed. In this paper, we review the methods used to maximize the SPEAR 3 dynamic aperture including necessary optics modifications, choice of tune and phase advance, optimization of sextupole and coupling correction, and modeling effects of machine errors, wigglers and lattice periodicity

  17. Sensitivity case study in dynamic reliability

    International Nuclear Information System (INIS)

    Kopustinskas, V.

    2001-01-01

    Recent trends in the risk assessments of the complex industrial plants show increased interest in dynamical models arising from the coupling of the probabilistic and deterministic approaches. Conventionally used static system models, represented by the fault/event trees can not reflect dynamic behaviour of the system and complex interaction between the process variables, components and human actions. The nature of the most complex industrial systems, like nuclear power plants (NPP) suggests that Markov type stochastic differential equations (SDEs) consisting of jump and drift components can be successfully used to represent and analyze the phenomena. This paper discuss possible applications of the SDEs in reliability problems. In particular, Accident Localization System (ALS) of the Ignalina NPP was analyzed as a benchmark for further investigations in this area. (author)

  18. 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...

  19. Application of iterative reconstruction in dynamic studies

    International Nuclear Information System (INIS)

    Meikle, S.R.

    1998-01-01

    Full text: The conventional approach to analysing dynamic tomographic data (SPECT or PET) is to reconstruct projections corresponding to each time interval separately and then fit a suitable tracer kinetic model to the dynamic sequence (method 1 ) . This approach assumes that the tracer distribution remains static during any given time interval and, for practical reasons, filtered back-projection (FBP) is the preferred reconstruction algorithm. However, alternative approaches exist which lend themselves to iterative algorithms, such as EM. One approach is to fit the model directly to the projection data, followed by EM reconstruction of the parameter estimates (method 2). This requires that the tracer model can be expressed as a linear function of the unknown model parameters. A third alternative is to incorporate the tracer model into the reconstruction algorithm (method 3). Such an extension was described during the early development of the EM algorithm, referred to as the EM parametric image reconstruction algorithm (EM-PIRA). We have investigated these various strategies for analysing dynamic data and their relative pros and cons. Tracer modelling was performed using a general model, referred to as spectral analysis, which makes no restriction on the number of physiological compartments and satisfies the linearity requirement of method 2. A kinetic software phantom was created and used to test the convergence and noise properties of the different approaches. In summary, method 2 is the most practical as it reduces the number of reconstructions by at least an order of magnitude and provides improved signal-to-noise ratios compared with method 1. EM-PIRA allows greater flexibility in the choice of parametric images and appears to have a regularising effect on convergence. Methods 2 and 3 are also better suited to dynamic scanning with a rotating camera, as they can potentially account for changes in tracer distribution between projections

  20. CHEMICAL ABUNDANCES IN NGC 5053: A VERY METAL-POOR AND DYNAMICALLY COMPLEX GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico [Astronomy Department, Indiana University, Bloomington, IN 47405 (United States)

    2015-05-10

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin–Indiana–Yale–NOAO–Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ∼ 75–90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of −2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na–O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  1. Chemical Abundances in NGC 5053: A Very Metal-poor and Dynamically Complex Globular Cluster

    Science.gov (United States)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2015-05-01

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin-Indiana-Yale-NOAO-Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ˜ 75-90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of -2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na-O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  2. Modeling heat dissipation at the nanoscale: an embedding approach for chemical reaction dynamics on metal surfaces.

    Science.gov (United States)

    Meyer, Jörg; Reuter, Karsten

    2014-04-25

    We present an embedding technique for metallic systems that makes it possible to model energy dissipation into substrate phonons during surface chemical reactions from first principles. The separation of chemical and elastic contributions to the interaction potential provides a quantitative description of both electronic and phononic band structure. Application to the dissociation of O2 at Pd(100) predicts translationally "hot" oxygen adsorbates as a consequence of the released adsorption energy (ca. 2.6 eV). This finding questions the instant thermalization of reaction enthalpies generally assumed in models of heterogeneous catalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Iteration scheme for implicit calculations of kinetic and equilibrium chemical reactions in fluid dynamics

    International Nuclear Information System (INIS)

    Ramshaw, J.D.; Chang, C.H.

    1995-01-01

    An iteration scheme for the implicit treatment of equilibrium chemical reactions in partial equilibrium flow has previously been described. Here we generalize this scheme to kinetic reactions as well as equilibrium reactions. This extends the applicability of the scheme to problems with kinetic reactions that are fast in regions of the flow field but slow in others. The resulting scheme thereby provides a single unified framework for the implicit treatment of an arbitrary number of coupled equilibrium and kinetic reactions in chemically reacting fluid flow. 10 refs., 2 figs

  4. Studies on lipid peroxidation and anti-LPO chemicals

    International Nuclear Information System (INIS)

    Wang Chongdao; Qiang Yizhong; Lao Qinhua

    1995-02-01

    The contents of lipid peroxides (LPO) in sera and tissues were determined by the modified spectrophotometry of TBA, and the effects of three chemicals on lipid peroxidation induced by radiation were observed. The items studied included: (1) the normal values of LPO of sera in rats and adults: (2) the normal values in some tissues of rats; (3) the changes of LPO levels of sera in patients with some mental diseases and patients with malignant tumours before and after local gamma irradiation exposure; (4) the changes of LPO contents of some tissues in rats after whole-body gamma irradiation exposure; (5) the changes of LPO contents of some tissues in mice after internal exposure by Th(NO 3 ) 4 solution; (6) the effects of chinonin, tannic acid and squalene on lipid peroxidation induced by irradiation. The results were as follows: (1) the LPO contents in patients with some mental diseases dramatically increased; (2) there was marked difference between the LPO levels before and after local gamma irradiation exposure in patients with malignant tumours; (3) the LPO contents in some tissues of rats remarkably increased after whole-body gamma irradiation exposure; (4) the LPO contents in some tissues of mice dramatically increased and their protein contents markedly reduced after internal exposure, showing a negative correlation between them; (5) a gradual increase in LPO contents in some tissues of mice appeared with increasing dosage of whole-body gamma irradiation exposure at dose range from 0 to 4 Gy. A linear relationship between the dose and the LPO contents was observed; (6) all three chemicals could reduce the LPO levels in liver, spleen and kidney of the irradiated mice. The efficacy of chinonin was better than that of tannic acid and squalene. (5 tabs., 1 fig.)

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

    International Nuclear Information System (INIS)

    Hilmy, N.; Suwirma, S.; Harsoyo; Suhadi, F.

    1987-01-01

    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 7x10 8 per g during the rainy season and 7x10 6 up to 1.3x10 8 per g during the dry season, while coliform fecal Streptococcus and Pseudomonas were found to be 1.6x10 4 to 1.0x10 7 , 3x10 5 , and 5x10 3 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

  6. Comparative study of the chemical properties of palm oil extracted ...

    African Journals Online (AJOL)

    The chemical properties of oil samples determined were free fatty acid, acid value, saponification value, peroxide value, iodine value and moisture content. The experimental design adopted was 3 x 2 x 2 factorial randomized complete block design in three replicates. The data of chemical properties of extracted palm oil ...

  7. LOSS OF ORGANIC CHEMICALS IN SOIL: PURE COMPOUND TREATABILITY STUDIES

    Science.gov (United States)

    Comprehensive screening data on the treatability of 32 organic chemicals in soil were developed. Of the evaluated chemicals, 22 were phenolic compounds. Aerobic batch laboratory microcosm experiments were conducted using two soils: an acidic clay soil with <1% organic matter and ...

  8. Integrating atomistic molecular dynamics simulations, experiments and network analysis to study protein dynamics: strength in unity

    Directory of Open Access Journals (Sweden)

    Elena ePapaleo

    2015-05-01

    Full Text Available In the last years, we have been observing remarkable improvements in the field of protein dynamics. Indeed, we can now study protein dynamics in atomistic details over several timescales with a rich portfolio of experimental and computational techniques. On one side, this provides us with the possibility to validate simulation methods and physical models against a broad range of experimental observables. On the other side, it also allows a complementary and comprehensive view on protein structure and dynamics. What is needed now is a better understanding of the link between the dynamic properties that we observe and the functional properties of these important cellular machines. To make progresses in this direction, we need to improve the physical models used to describe proteins and solvent in molecular dynamics, as well as to strengthen the integration of experiments and simulations to overcome their own limitations. Moreover, now that we have the means to study protein dynamics in great details, we need new tools to understand the information embedded in the protein ensembles and in their dynamic signature. With this aim in mind, we should enrich the current tools for analysis of biomolecular simulations with attention to the effects that can be propagated over long distances and are often associated to important biological functions. In this context, approaches inspired by network analysis can make an important contribution to the analysis of molecular dynamics simulations.

  9. Mobility and Attenuation Dynamics of Potentially Toxic Chemical Species at an Abandoned Copper Mine Tailings Dump

    Directory of Open Access Journals (Sweden)

    Wilson Mugera Gitari

    2018-02-01

    Full Text Available Large volumes of disposed mine tailings abound in several regions of South Africa, as a consequence of unregulated, unsustainable long years of mining activities. Tailings dumps occupy a large volume of valuable land, and present a potential risk for aquatic systems, through leaching of potentially toxic chemical species. This paper reports on the evaluation of the geochemical processes controlling the mobility of potentially toxic chemical species within the tailings profile, and their potential risk with regard to surface and groundwater systems. Combination of X-ray fluorescence (XRF, X-ray diffraction (XRD, and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS techniques, show that the tailing profiles are uniform, weakly altered, and vary slightly with depth in both physical and geochemical properties, as well as mineralogical composition. Mineralogical analysis showed the following order of abundance: quartz > epidote > chlorite > muscovite > calcite > hematite within the tailings profiles. The neutralization of the dominant alumino-silicate minerals and the absence of sulfidic minerals, have produced medium alkaline pH conditions (7.97–8.37 at all depths and low concentrations of dissolved Cu (20.21–47.9 µg/L, Zn (0.88–1.80 µg/L, Pb (0.27–0.34 µg/L, and SO42− (15.71–55.94 mg/L in the tailings profile leachates. The relative percentage leach for the potentially toxic chemical species was low in the aqueous phase (Ni 0.081%, Cu 0.006%, and Zn 0.05%. This indicates that the transport load of potentially toxic chemical species from tailings to the aqueous phase is very low. The precipitation of secondary hematite has an important known ability to trap and attenuate the mobility of potentially toxic chemical species (Cu, Zn, and Pb by adsorption on the surface area. Geochemical modelling MINTEQA2 showed that the tailings leachates were below saturation regarding oxyhydroxide minerals, but oversaturated with Cu

  10. A dynamical study on extrasolar comets

    Science.gov (United States)

    Loibnegger, B.; Dvorak, R.

    2017-09-01

    Since the detection of absorption features in spectra of beta Pictoris varying on short time scales it is known that comets exist in other stellar systems. We investigate the dynamics of comets in two differently build systems (HD 10180 and HIP 14810). The outcomes of the scattering process, as there are collisions with the planets, captures and ejections from the systems are analysed statistically. Collisions and close encounters with the planets are investigated in more detail in order to conclude about transport of water and organic material. We will also investigate the possibility of detection of comets in other planetary systems.

  11. Structure and dynamics of photosynthetic proteins studied by neutron scattering and molecular dynamic simulation

    International Nuclear Information System (INIS)

    Dellerue, Serge

    2000-01-01

    Understand the structure-dynamics-function relation in the case of proteins is essential. But few experimental techniques allow to have access to knowledge of fast internal movements of biological macromolecules. With the neutron scattering method, it has been possible to study the reorientation dynamics of side chains and of polypeptide skeleton for two proteins in terms of water or detergent and of temperature. With the use of the molecular dynamics method, essential for completing and interpreting the experimental data, it has been possible to assess the different contributions of the whole structure of proteins to the overall dynamics. It has been shown that the polypeptide skeleton presents an energy relaxation comparable to those of the side chains. Moreover, it has been explained that the protein dynamics can only be understood in terms of relaxation time distribution. (author) [fr

  12. 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

  13. Alternative Enhanced Chemical Cleaning Basic Studies Results FY09

    International Nuclear Information System (INIS)

    Hay, M.; King, W.

    2010-01-01

    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

  14. 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

  15. 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...

  16. A Chemical Study of 47 Tucanae (NGC 104)

    Science.gov (United States)

    Cordero, Maria J.; Pilachowski, C. A.; Johnson, C. I.; Simmerer, J. A.

    2013-01-01

    47 Tuc (NGC 104) is a nearby, metal-rich globular cluster often used as a benchmark when studying dwarf spheroidal galaxies. We present chemical abundances for a sample of nearly 100 red giants whose spectra were obtained with the moderate resolution Blanco 4M telescope and Hydra multifiber specrograph, using two wavelength regions, 6140-6350 Å and 6500-6750 Å, with signal-to-noise (S/N) ranging from 70-120. Abundances for O, Na, Al, Si, Ca, Ti, Fe, Ni, La, and Eu have been determined using either equivalent width measurements or spectrum synthesis together with the LTE line analysis code MOOG and ATLAS 9 model atmospheres. We found [Fe/H]=-0.68 ± 0.06, which is consistent with previous studies. Additionally, we found a star-to-star variation in Na, Al, and O abundances and a first-to-second generation ratio of 36/64. Furthermore, alpha-elements (Si, Ca, and Ti) are overabundant with respect to Fe, and Ni presents a solar value.

  17. 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

  18. A molecular dynamics simulation study of chloroform

    Science.gov (United States)

    Tironi, Ilario G.; van Gunsteren, Wilfred F.

    Three different chloroform models have been investigated using molecular dynamics computer simulation. The thermodynamic, structural and dynamic properties of the various models were investigated in detail. In particular, the potential energies, diffusion coefficients and rotational correlation times obtained for each model are compared with experiment. It is found that the theory of rotational Brownian motion fails in describing the rotational diffusion of chloroform. The force field of Dietz and Heinzinger was found to give good overall agreement with experiment. An extended investigation of this chloroform model has been performed. Values are reported for the isothermal compressibility, the thermal expansion coefficient and the constant volume heat capacity. The values agree well with experiment. The static and frequency dependent dielectric permittivity were computed from a 1·2 ns simulation conducted under reaction field boundary conditions. Considering the fact that the model is rigid with fixed partial charges, the static dielectric constant and Debye relaxation time compare well with experiment. From the same simulation the shear viscosity was computed using the off-diagonal elements of the pressure tensor, both via an Einstein type relation and via a Green-Kubo equation. The calculated viscosities show good agreement with experimental values. The excess Helmholtz energy is calculated using the thermodynamic integration technique and simulations of 50 and 80 ps. The value obtained for the excess Helmholtz energy matches the theoretical value within a few per cent.

  19. Chemical dynamics simulations of X- + CH3Y → XCH3 + Y- gas-phase S(N)2 nucleophilic substitution reactions. Nonstatistical dynamics and nontraditional reaction mechanisms.

    Science.gov (United States)

    Manikandan, Paranjothy; Zhang, Jiaxu; Hase, William L

    2012-03-29

    Extensive classical chemical dynamics simulations of gas-phase X(-) + CH(3)Y → XCH(3) + Y(-) S(N)2 nucleophilic substitution reactions are reviewed and discussed and compared with experimental measurements and predictions of theoretical models. The primary emphasis is on reactions for which X and Y are halogen atoms. Both reactions with the traditional potential energy surface (PES), which include pre- and postreaction potential energy minima and a central barrier, and reactions with nontraditional PESs are considered. These S(N)2 reactions exhibit important nonstatistical atomic-level dynamics. The X(-) + CH(3)Y → X(-)---CH(3)Y association rate constant is less than the capture model as a result of inefficient energy transfer from X(-)+ CH(3)Y relative translation to CH(3)Y rotation and vibration. There is weak coupling between the low-frequency intermolecular modes of the X(-)---CH(3)Y complex and higher frequency CH(3)Y intramolecular modes, resulting in non-RRKM kinetics for X(-)---CH(3)Y unimolecular decomposition. Recrossings of the [X--CH(3)--Y](-) central barrier is important. As a result of the above dynamics, the relative translational energy and temperature dependencies of the S(N)2 rate constants are not accurately given by statistical theory. The nonstatistical dynamics results in nonstatistical partitioning of the available energy to XCH(3) +Y(-) reaction products. Besides the indirect, complex forming atomic-level mechanism for the S(N)2 reaction, direct mechanisms promoted by X(-) + CH(3)Y relative translational or CH(3)Y vibrational excitation are possible, e.g., the roundabout mechanism.

  20. Dimensionless study on dynamics of pressure controlled mechanical ventilation system

    International Nuclear Information System (INIS)

    Shi, Yan; Niu, Jinglong; Cai, Maolin; Xu, Weiqing

    2015-01-01

    Dynamics of mechanical ventilation system can be referred in pulmonary diagnostics and treatments. In this paper, to conveniently grasp the essential characteristics of mechanical ventilation system, a dimensionless model of mechanical ventilation system is presented. For the validation of the mathematical model, a prototype mechanical ventilation system of a lung simulator is proposed. Through the simulation and experimental studies on the dimensionless dynamics of the mechanical ventilation system, firstly, the mathematical model is proved to be authentic and reliable. Secondly, the dimensionless dynamics of the mechanical ventilation system are obtained. Last, the influences of key parameters on the dimensionless dynamics of the mechanical ventilation system are illustrated. The study provides a novel method to study the dynamic of mechanical ventilation system, which can be referred in the respiratory diagnostics and treatment.

  1. Dimensionless study on dynamics of pressure controlled mechanical ventilation system

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yan; Niu, Jinglong; Cai, Maolin; Xu, Weiqing [Beihang University, Beijing (Korea, Republic of)

    2015-02-15

    Dynamics of mechanical ventilation system can be referred in pulmonary diagnostics and treatments. In this paper, to conveniently grasp the essential characteristics of mechanical ventilation system, a dimensionless model of mechanical ventilation system is presented. For the validation of the mathematical model, a prototype mechanical ventilation system of a lung simulator is proposed. Through the simulation and experimental studies on the dimensionless dynamics of the mechanical ventilation system, firstly, the mathematical model is proved to be authentic and reliable. Secondly, the dimensionless dynamics of the mechanical ventilation system are obtained. Last, the influences of key parameters on the dimensionless dynamics of the mechanical ventilation system are illustrated. The study provides a novel method to study the dynamic of mechanical ventilation system, which can be referred in the respiratory diagnostics and treatment.

  2. Biodegradation of HT Agent from an Assembled Chemical Weapons Assessment (ACWA) Projectile Washout Study

    National Research Council Canada - National Science Library

    Guelta, Mark A

    2006-01-01

    In this study, HT agent, removed from a chemical round similar to the current stockpile stored at Pueblo Chemical Depot, was neutralized and the hydrolysate treated in a laboratory scale Immobilized Cell Bioreactor (ICB...

  3. Model for the dynamic study of AC contactors

    Energy Technology Data Exchange (ETDEWEB)

    Corcoles, F.; Pedra, J.; Garrido, J.P.; Baza, R. [Dep. d' Eng. Electrica ETSEIB. UPC, Barcelona (Spain)

    2000-08-01

    This paper proposes a model for the dynamic analysis of AC contactors. The calculation algorithm and implementation are discussed. The proposed model can be used to study the influence of the design parameters and the supply in their dynamic behaviour. The high calculation speed of the implemented algorithm allows extensive ranges of parameter variations to be analysed. (orig.)

  4. 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.

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

    Directory of Open Access Journals (Sweden)

    Daniel F. Miranda

    2014-05-01

    Full Text Available 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-aminopropyltriethoxysilane. 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.

  6. Kinetic calorimetry in the study of the mechanism of low-temperature chemical reactions

    Science.gov (United States)

    Barkalov, I. M.; Kiryukhin, D. P.

    schemes are described [1-5]. However, despite the high working characteristics of modern calorimeters (Perkin-Elmer, Du Pont, LKB, etc.), all of them have one principal disadvantage: a cell with a sample is placed in them at room temperature. In cryochemical investigation, when the sample has metastable formations, the loading is made `from nitrogen to nitrogen', i.e. the sample prepared at 77 K should be loaded into a calorimeter at 77 K. Besides, the existing installations do not allow measurements at the temperatures Cryochemistry and Radiation Chemistry at the Institute of Chemical Physics in Chernogolovka has created original calorimetric techniques which allow: (1) the carrying out phase analysis and the determination of the main thermodynamic characteristic of individual substances and complicated systems in the temperature range 5 300 K. Sample loading can be conducted at 77 K that allows us to study the systems containing: tetrafiuoroethylene, hexafluoropropylene, ethylene, carbon monoxide, nitrogen, methane, hydrogen, oxygen, ozone, formaldehyde and many other gaseous substances; (2) the study of the dynamics of chemical reactions and to measure the main kinetic parameters of the processes-the elementary rate constants and the activation energies. The experiment can be conducted both under direct action of radiation and UV light and in the post-effect mode [5,6].

  7. Methodological issues in human studies of endocrine disrupting chemicals.

    Science.gov (United States)

    Lee, Duk-Hee; Jacobs, David R

    2015-12-01

    Possible harm from endocrine disrupting chemicals (EDCs) in humans is speculated based on two types of evidence; 1) increasing trends of suspected diseases in ecological studies of populations and 2) findings from traditional epidemiological studies of individuals. However, ecological findings are not regarded as direct human evidence of the relation between EDCs and disease, while the evidence among epidemiological studies of individuals is often inconsistent. Thus, a criticism is that linking EDCs and health in human is naively presumed without solid evidence. However, human studies of EDCs are methodologically complex and understanding methodological issues will help to interpret findings from existing human studies and to properly design optimal human studies. The key issues are low reliability of exposure assessment of EDCs with short half-lives, EDC mixtures, possibility of non-monotonic dose-response relationships, non-existence of an unexposed group, difficulties in measuring exposure during critical periods, and interactions with established risk factors. Furthermore, EDC mixtures may affect human health through other mechanisms than traditional endocrine disruption, for example glutathione depletion or mitochondrial dysfunction. Given this complexity, the most plausible scenario in humans is that exposure to EDC mixtures leads to increasing risk of related diseases at the ecological level, but inconsistent associations would be expected in traditional epidemiological studies. Although epidemiologists have long relied on Bradford Hill's criteria to objectively evaluate whether associations observed in epidemiology can be interpreted as causal, there are challenges to use these criteria for EDCs, particularly concerning consistency across studies and the findings of linear dose-response relationships. At the individual level, compared to EDCs with short half-lives, epidemiological studies of EDCs with long half-lives among populations with a relatively low

  8. Dynamical Timescale of Pre-collapse Evolution Inferred from Chemical Distribution in the Taurus Molecular Cloud-1 (TMC-1) Filament

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yunhee; Lee, Jeong-Eun [School of Space Research, Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104 (Korea, Republic of); Bourke, Tyler L. [Square Kilometre Array Organisation, Jodrell Bank Observatory, Lower Withington, Cheshire SK11 9DL (United Kingdom); II, Neal J. Evans, E-mail: yunhee.choi@khu.ac.kr, E-mail: jeongeun.lee@khu.ac.kr [Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States)

    2017-04-01

    We present observations and analyses of the low-mass star-forming region, Taurus Molecular Cloud-1 (TMC-1). CS ( J = 2–1)/N{sub 2}H{sup +} ( J = 1–0) and C{sup 17}O ( J = 2–1)/C{sup 18}O ( J = 2–1) were observed with the Five College Radio Astronomy Observatory and the Seoul Radio Astronomy Observatory, respectively. In addition, Spitzer infrared data and 1.2 mm continuum data observed with Max-Planck Millimetre Bolometer are used. We also perform chemical modeling to investigate the relative molecular distributions of the TMC-1 filament. Based on Spitzer observations, there is no young stellar object along the TMC-1 filament, while five Class II and one Class I young stellar objects are identified outside the filament. The comparison between column densities calculated from dust continuum and C{sup 17}O 2–1 line emission shows that CO is depleted much more significantly in the ammonia peak than in the cyanopolyyne peak, while the column densities calculated from the dust continuum are similar at the two peaks. N{sub 2}H{sup +} is not depleted much in either peak. According to our chemical calculation, the differential chemical distribution in the two peaks can be explained by different timescales required to reach the same density, i.e., by different dynamical processes.

  9. Study and interpretation of the chemical characteristics of natural water

    Science.gov (United States)

    Hem, John David

    1985-01-01

    The chemical composition of natural water is derived from many different sources of solutes, including gases and aerosols from the atmosphere, weathering and erosion of rocks and soil, solution or precipitation reactions occurring below the land surface, and cultural effects resulting from human activities. Broad interrelationships among these processes and their effects can be discerned by application of principles of chemical thermodynamics. Some of the processes of solution or precipitation of minerals can be closely evaluated by means of principles of chemical equilibrium, including the law of mass action and the Nernst equation. Other processes are irreversible and require consideration of reaction mechanisms and rates. The chemical composition of the crustal rocks of the Earth and the composition of the ocean and the atmosphere are significant in evaluating sources of solutes in natural freshwater.

  10. Physico-chemical and toxicological studies on Afzelia africana seed ...

    African Journals Online (AJOL)

    USER

    2010-03-29

    Mar 29, 2010 ... Table 2. Physico-chemical characteristics of Afzelia africana seed oil*. Property .... The moisture level of the seeds of A. africana is low resulting in low acid .... Keay RWJ, Onochie CFA, Stanfield DP (1964). Nigerian Trees, 2.

  11. Dynamical study of symmetries: breaking and restauration

    International Nuclear Information System (INIS)

    Schuck, P.

    1986-09-01

    First symmetry breaking (spontaneous) is explained and the physical implication discussed for infinite systems. The relation with phase transitions is indicated. Then the specific aspects of symmetry breaking in finite systems is treated and illustrated in detail for the case of translational invariance with the help of an oversimplified but exactly solvable model. The method of projection (restauration of symmetry) is explained for the static case and also applied to the model. Symmetry breaking in the dynamical case and for instance the notion of a soft mode responsible for the symmetry breaking is discussed in the case of superfluidity and another exactly solvable model is introduced. The Goldstone mode is treated in detail. Some remarks on analogies with the breaking of chiral symmetry are made. Some recent developments in the theory of symmetry restauration are briefly outlined [fr

  12. 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.

  13. The Lewis Chemical Equilibrium Program with parametric study capability

    Science.gov (United States)

    Sevigny, R.

    1981-01-01

    The program was developed to determine chemical equilibrium in complex systems. Using a free energy minimization technique, the program permits calculations such as: chemical equilibrium for assigned thermodynamic states; theoretical rocket performance for both equilibrium and frozen compositions during expansion; incident and reflected shock properties; and Chapman-Jouget detonation properties. It is shown that the same program can handle solid coal in an entrained flow coal gasification problem.

  14. 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.

  15. 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.

  16. Human immunotoxicologic markers of chemical exposures: preliminary validation studies.

    Science.gov (United States)

    Wartenberg, D; Laskin, D; Kipen, H

    1993-01-01

    The circulating cells of the immune system are sensitive to environmental contaminants, and effects are often manifested as changes in the cell surface differentiation antigens of affected populations of cells, particularly lymphocytes. In this investigation, we explore the likelihood that variation in the expression of the surface markers of immune cells can be used as an index of exposure to toxic chemicals. We recruited 38 healthy New Jersey men to study pesticides effects: 19 orchard farmers (high exposure); 13 berry farmers (low exposure); and 6 hardware store owners (no exposure). Immunophenotyping was performed assaying the following cell surface antigens: CD2, CD4, CD8, CD14, CD20, CD26, CD29, CD45R, CD56, and PMN. Data were analyzed using univariate and multivariate methods. There were no significant differences among the groups with respect to routine medical histories, physical examinations, or routine laboratory parameters. No striking differences between groups were seen in univariate tests. Multivariate tests suggested some differences among groups and limited ability to correctly classify individuals based on immunophenotyping results. Immunophenotyping represents a fruitful area of research for improved exposure classification. Work is needed both on mechanistic understanding of the patterns observed and on the statistical interpretation of these patterns.

  17. Quantitative chemical exchange saturation transfer with hyperpolarized nuclei (qHyper-CEST): sensing xenon-host exchange dynamics and binding affinities by NMR.

    Science.gov (United States)

    Kunth, M; Witte, C; Schröder, L

    2014-11-21

    The reversible binding of xenon to host molecules has found numerous applications in nuclear magnetic resonance studies. Quantitative characterization of the Xe exchange dynamics is important to understand and optimize the physico-chemical behavior of such Xe hosts, but is often challenging to achieve at low host concentrations. We have investigated a sensitive quantification technique based on chemical exchange saturation transfer with hyperpolarized nuclei, qHyper-CEST. Using simulated signals we demonstrated that qHyper-CEST yielded accurate and precise results and was robust in the presence of large amounts of noise (10%). This is of particular importance for samples with completely unknown exchange rates. Using these findings we experimentally determined the following exchange parameters for the Xe host cryptophane-A monoacid in dimethyl sulfoxide in one type of experiment: the ratio of bound and free Xe, the Xe exchange rate, the resonance frequencies of free and bound Xe, the Xe host occupancy, and the Xe binding constant. Taken together, qHyper-CEST facilitates sensitive quantification of the Xe exchange dynamics and binding to hydrophobic cavities and has the potential to analyze many different host systems or binding sites. This makes qHyper-CEST an indispensable tool for the efficient design of highly specific biosensors.

  18. Paper spray mass spectrometry applied in the monitoring of a chemical system in dynamic chemical equilibrium: the redox process of methylene blue.

    Science.gov (United States)

    de Paula, Camila Cristina Almeida; Valadares, Alberto; Jurisch, Marina; Piccin, Evandro; Augusti, Rodinei

    2016-05-15

    The monitoring of chemical systems in dynamic equilibrium is not an easy task. This is due to the high rate at which the system returns to equilibrium after being perturbed, which hampers the possibility of following the aftereffects of the disturbance. In this context, it is necessary to use a fast analytical technique that requires no (or minimal) sample preparation, and which is capable of monitoring the species constituting the system in equilibrium. Paper spray ionization mass spectrometry (PS-MS), a recently introduced ambient ionization technique, has such characteristics and hence was chosen for monitoring a model system: the redox process of methylene blue. The model system evaluated herein was composed of three cationic species of methylene blue (MB), which coexist in a dynamic redox system: (1) [MB](+) of m/z 284 (cationic MB); (2) [MB + H + e](+•) of m/z 285 (the protonated form of a transient species resulting from the reduction of [MB](+) ); (3) [MB + 2H + 2e](+) or [leuco-MB + H](+) of m/z 286 (the protonated leuco form of MB). Aliquots of a MB solution were collected before and after the addition of a reducing agent (metallic zinc) and directly analyzed by PS-MS for identification of the predominant cationic species at different conditions. The mass spectra revealed that before the addition of the reducing agent the ion of m/z 284 (cationic MB) is the unique species. Upon the addition of the reducing agent and acid, however, the solution continuously undergo discoloration while reduced species derived directly from cationic MB (m/z 285 and 286) are detected in the mass spectra with increasing intensities. Fragmentation patterns obtained for each ionic species, i.e. [MB](+) , [MB + H + e](+•) and [leuco-MB + H](+) , shown to be consistent with the proposed structures. The PS-MS technique proved to be suitable for an in situ and 'near' real-time analysis of the dynamic equilibrium involving the redox of MB in aqueous medium. The data clearly

  19. Study of a spur gear dynamic behavior in transient regime

    Science.gov (United States)

    Khabou, M. T.; Bouchaala, N.; Chaari, F.; Fakhfakh, T.; Haddar, M.

    2011-11-01

    In this paper the dynamic behavior of a single stage spur gear reducer in transient regime is studied. Dynamic response of the single stage spur gear reducer is investigated at different rotating velocities. First, gear excitation is induced by the motor torque and load variation in addition to the fluctuation of meshing stiffness due to the variation of input rotational speed. Then, the dynamic response is computed using the Newmark method. After that, a parameter study is made on spur gear powered in the first place by an electric motor and in the second place by four strokes four cylinders diesel engine. Dynamic responses come to confirm a significant influence of the transient regime on the dynamic behavior of a gear set, particularly in the case of engine acyclism condition.

  20. Dynamic and Progressive Control of DNA Origami Conformation by Modulating DNA Helicity with Chemical Adducts.

    Science.gov (United States)

    Chen, Haorong; Zhang, Hanyu; Pan, Jing; Cha, Tae-Gon; Li, Shiming; Andréasson, Joakim; Choi, Jong Hyun

    2016-05-24

    DNA origami has received enormous attention for its ability to program complex nanostructures with a few nanometer precision. Dynamic origami structures that change conformation in response to environmental cues or external signals hold great promises in sensing and actuation at the nanoscale. The reconfiguration mechanism of existing dynamic origami structures is mostly limited to single-stranded hinges and relies almost exclusively on DNA hybridization or strand displacement. Here, we show an alternative approach by demonstrating on-demand conformation changes with DNA-binding molecules, which intercalate between base pairs and unwind DNA double helices. The unwinding effect modulates the helicity mismatch in DNA origami, which significantly influences the internal stress and the global conformation of the origami structure. We demonstrate the switching of a polymerized origami nanoribbon between different twisting states and a well-constrained torsional deformation in a monomeric origami shaft. The structural transformation is shown to be reversible, and binding isotherms confirm the reconfiguration mechanism. This approach provides a rapid and reversible means to change DNA origami conformation, which can be used for dynamic and progressive control at the nanoscale.

  1. Multi-fractal characterization of bacterial swimming dynamics: a case study on real and simulated Serratia marcescens

    OpenAIRE

    Koorehdavoudi, Hana; Bogdan, Paul; Wei, Guopeng; Marculescu, Radu; Zhuang, Jiang; Carlsen, Rika Wright; Sitti, Metin

    2017-01-01

    To add to the current state of knowledge about bacterial swimming dynamics, in this paper, we study the fractal swimming dynamics of populations of Serratia marcescens bacteria both in vitro and in silico, while accounting for realistic conditions like volume exclusion, chemical interactions, obstacles and distribution of chemoattractant in the environment. While previous research has shown that bacterial motion is non-ergodic, we demonstrate that, besides the non-ergodicity, the bacterial sw...

  2. Role of tip chemical reactivity on atom manipulation process in dynamic force microscopy

    Czech Academy of Sciences Publication Activity Database

    Sugimoto, Y.; Yurtsever, A.; Abe, M.; Morita, S.; Ondráček, Martin; Pou, P.; Perez, R.; Jelínek, Pavel

    2013-01-01

    Roč. 7, č. 8 (2013), s. 7370-7376 ISSN 1936-0851 R&D Projects: GA ČR(CZ) GPP204/11/P578 Grant - others:GA AV ČR(CZ) M100101207 Institutional support: RVO:68378271 Keywords : noncontact atomic force microscopy * atomic manipulation * force spectroscopy * chemical interaction force * DFT simulations * nudged elastic band Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 12.033, year: 2013 http://pubs.acs.org/doi/abs/10.1021/nn403097p

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

    International Nuclear Information System (INIS)

    Hussein, H. A. S.

    2012-07-01

    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. Molecular dynamics studies of displacement cascades

    International Nuclear Information System (INIS)

    Averback, R.S.; Hsieh, Horngming; Diaz de la Rubia, T.

    1990-02-01

    Molecular-dynamics simulations of cascades in Cu and Ni with primary-knock-on energies up to 5 keV and lattice temperatures in the range 0 K--700 K are described. Interatomic forces were represented by either the Gibson II (Cu) or Johnson-Erginsoy (Ni) potentials in most of this work, although some simulations using ''Embedded Atom Method'' potentials, e.g., for threshold events in Ni 3 Al, are also presented. The results indicate that the primary state of damage produced by displacement cascades is controlled by two phenomena, replacement collision sequences during the collisional phase of the cascade and local melting during the thermal spike. As expected, the collisional phase is rather similar in Cu and Ni, however, the thermal spike is of longer duration and has a more pronounced influence in Cu than Ni. When the ambient temperature of the lattice is increased, the melt zones are observed to both increase in size and cool more slowly. This has the effect of reducing defect production and enhancing atomic mixing and disordering. The implications of these results for defect production, cascade collapse, atomic disordering will be discussed. 34 refs., 7 figs., 2 tabs

  5. Ozone decay in chemical reactor for ozone-dynamical disintegration of used tyres

    International Nuclear Information System (INIS)

    Golota, V.I.; Manuilenko, O.V.; Taran, G.V.; Dotsenko, Yu.V.; Pismenetskii, A.S.; Zamuriev, A.A.; Benitskaja, V.A.

    2011-01-01

    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.

  6. Dynamical study of a polydisperse hard-sphere system

    KAUST Repository

    Nogawa, Tomoaki; Ito, Nobuyasu; Watanabe, Hiroshi

    2010-01-01

    We study the interplay between the fluid-crystal transition and the glass transition of elastic sphere system with polydispersity using nonequilibrium molecular dynamics simulations. It is found that the end point of the crystal-fluid transition

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

    International Nuclear Information System (INIS)

    Gilath, Ch.

    1983-01-01

    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)

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

    International Nuclear Information System (INIS)

    Shen Xiaoyao

    2012-01-01

    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)

  9. [Studies on chemical constituents from leaves of Vaccinium bracteatum].

    Science.gov (United States)

    Li, Zeng-Liang; Zhang, Lin; Tian, Jing-Kui; Zhou, Wen-Ming

    2008-09-01

    To investigate the chemical constituents from the leaves of Vaccinium bracteatum. Many column chromatographic techniques were used for the isolation and separation of chemical constituents. Their structures were elucidated on the basis of spectral analysis and chemical evidences. Twelve compounds were isolated from the plant, and they were identified as chrysoeriol (1), scopoletin (2), trans-p-hydroxycinnamic acid (3), trans-p-hydroxycinnamic acid ethyl ester (4), cafeic acid ethyl ester (5), beta-sitosterol (6), iuteolin (7), quercetin (8), esculetin (9), cafeic acid (10), isolariciresinol-9-O-beta-D-xyloside (11), 10-O-trans-p-coumaroylsandoside (12). Compounds 4, 5, 11, 12 were isolated from the genus Vaccinium for the first time, and compounds 1, 2, 9, 10 were isolated from this plant for the first time.

  10. Benzene: a case study in parent chemical and metabolite interactions.

    Science.gov (United States)

    Medinsky, M A; Kenyon, E M; Schlosser, P M

    1995-12-28

    Benzene, an important industrial solvent, is also present in unleaded gasoline and cigarette smoke. The hematotoxic effects of benzene in humans are well documented and include aplastic anemia and pancytopenia, and acute myelogenous leukemia. A combination of metabolites (hydroquinone and phenol for example) is apparently necessary to duplicate the hematotoxic effect of benzene, perhaps due in part to the synergistic effect of phenol on myeloperoxidase-mediated oxidation of hydroquinone to the reactive metabolite benzoquinone. Since benzene and its hydroxylated metabolites (phenol, hydroquinone and catechol) are substrates for the same cytochrome P450 enzymes, competitive interactions among the metabolites are possible. In vivo data on metabolite formation by mice exposed to various benzene concentrations are consistent with competitive inhibition of phenol oxidation by benzene. In vitro studies of the metabolic oxidation of benzene, phenol and hydroquinone are consistent with the mechanism of competitive interaction among the metabolites. The dosimetry of benzene and its metabolites in the target tissue, bone marrow, depends on the balance of activation processes such as enzymatic oxidation and deactivation processes such as conjugation and excretion. Phenol, the primary benzene metabolite, can undergo both oxidation and conjugation. Thus, the potential exists for competition among various enzymes for phenol. However, zonal localization of Phase I and Phase II enzymes in various regions of the liver acinus regulates this competition. Biologically-based dosimetry models that incorporate the important determinants of benzene flux, including interactions with other chemicals, will enable prediction of target tissue doses of benzene and metabolites at low exposure concentrations relevant for humans.

  11. Chemical sensors and microsystems for pollution abatement. Brief study

    International Nuclear Information System (INIS)

    Drost, S.; Aberl, F.; Endres, H.E.

    1994-01-01

    The demand for chemical sensors and microsystems is assessed on the basis of the substances which the pollution regulations identify as air and water pollutants in accordance with defined immission standards. Microsystems technology can do away with the disadvantages of environmental analysis. Chemical sensors offer many advantages but must be improved as regards their measuring accuracy and service life. These sensors must be developed further (transducers and coatings) and be combined into multisensor systems. Special sensor signal processing methods (pattern recognition) must be developed for the latter as microsystems technology advances. (orig./EF) [de

  12. Study about chemical and radiological toxicity of rare earths

    International Nuclear Information System (INIS)

    Goncalez, O.L.

    1987-02-01

    The maximum permissible concentration in workplace air for an admixture of rare earths is calculated to be 1.47 mg/m 3 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/m 3 , showing that the chemical toxity of these products is predominant. (Author) [pt

  13. 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.

  14. Dynamics of catalytic tubular microjet engines: dependence on geometry and chemical environment.

    Science.gov (United States)

    Li, Jinxing; Huang, Gaoshan; Ye, Mengmeng; Li, Menglin; Liu, Ran; Mei, Yongfeng

    2011-12-01

    Strain-engineered tubular microjet engines with various geometric dimensions hold interesting autonomous motions in an aqueous fuel solution when propelled by catalytic decomposition of hydrogen peroxide to oxygen and water. The catalytically-generated oxygen bubbles expelled from microtubular cavities propel the microjet step by step in discrete increments. We focus on the dynamics of our tubular microjets in one step and build up a body deformation model to elucidate the interaction between tubular microjets and the bubbles they produce. The average microjet velocity is calculated analytically based on our model and the obtained results demonstrate that the velocity of the microjet increases linearly with the concentration of hydrogen peroxide. The geometric dimensions of the microjet, such as length and radius, also influence its dynamic characteristics significantly. A close consistency between experimental and calculated results is achieved despite a small deviation due to the existence of an approximation in the model. The results presented in this work improve our understanding regarding catalytic motions of tubular microjets and demonstrate the controllability of the microjet which may have potential applications in drug delivery and biology.

  15. Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

    Science.gov (United States)

    Spezia, Riccardo; Jeanvoine, Yannick; Hase, William L.; Song, Kihyung; Largo, Antonio

    2016-08-01

    We show, by means of direct dynamics simulations, how it is possible to define possible reactants and mechanisms leading to the formation of formamide in the interstellar medium. In particular, different ion-molecule reactions in the gas phase were considered: NH3OH+, NH2OH{}2+, H2COH+, and NH4 + for the ions and NH2OH, H2CO, and NH3 for the partner neutrals. These calculations were combined with high level ab initio calculations to investigate possible further evolution of the products observed. In particular, for formamide, we propose that the NH2OH{}2+ + H2CO reaction can produce an isomer, NH2OCH{}2+, that, after dissociative recombination, can produce neutral formamide, which was observed in space. The direct dynamics do not pre-impose any reaction pathways and in other reactions, we did not observe the formation of formamide or any possible precursor. On the other hand, we obtained other interesting reactions, like the formation of NH2CH{}2+. Finally, some radiative association processes are proposed. All of the results obtained are discussed in light of the species observed in radioastronomy.

  16. Radiative Properties, Dynamics, and Chemical Evolution of the Smoke from the 1991 Kuwait Oil Fires.

    Science.gov (United States)

    Herring, John Allan

    The oil fields in Kuwait were the scene of a massive conflagration during much of 1991 that was started by Iraqi forces during the Gulf War. At this time, approximately 4 to 5 million barrels of oil were burning each day. The climatic impacts of the fires were limited by the fact that the smoke was generally confined to the lower 6 km of the atmosphere, where its removal by precipitation processes limited its lifetime. The optical properties of the smoke were such that it was an efficient absorber of solar radiation, with a single-scattering albedo of {~ }0.6. This led to rapid warming of the plume during the daytime. Instantaneous heating rates were calculated to be up to {~}90 K day ^{-1}. Because of the vertical distribution of the heating in the plume, the upper part of the plume became unstable and a turbulent mixed-layer developed. Conversely, the lower part of the plume became stably stratified due to the heating. This led to a general decoupling of the lower boundary layer, preventing the heating experienced by the plume from reaching the ground. The general warming of the plume led to mesoscale vertical transport of the plume as a whole. This mode of vertical transport was limited because of the large horizontal extent of the region of buoyant smoke. The mesoscale vertical transport occurred at roughly the same rate as the upward mixing of smoke due to smaller-scale turbulent motions. This vertical transport, however, did not occur rapidly enough to loft the smoke into the upper troposphere before it was dispersed by wind shear and the mixing caused by solar heating of the smoke. The chemical evolution of the plume was generally somewhat slow, due to the lack of ultraviolet radiation to initiate photochemistry within the smoke plume and to the generally low concentrations of nitrogen oxides, which act as catalysts for photochemical chain reactions. Heterogeneous chemical reactions between gases and black carbon particles produced by the fires were also not

  17. Molecular Dynamic Studies of the Complex Polyethylenimine and Glucose Oxidase.

    Science.gov (United States)

    Szefler, Beata; Diudea, Mircea V; Putz, Mihai V; Grudzinski, Ireneusz P

    2016-10-27

    Glucose oxidase (GOx) is an enzyme produced by Aspergillus, Penicillium and other fungi species. It catalyzes the oxidation of β-d-glucose (by the molecular oxygen or other molecules, like quinones, in a higher oxidation state) to form d-glucono-1,5-lactone, which hydrolyses spontaneously to produce gluconic acid. A coproduct of this enzymatic reaction is hydrogen peroxide (H₂O₂). GOx has found several commercial applications in chemical and pharmaceutical industries including novel biosensors that use the immobilized enzyme on different nanomaterials and/or polymers such as polyethylenimine (PEI). The problem of GOx immobilization on PEI is retaining the enzyme native activity despite its immobilization onto the polymer surface. Therefore, the molecular dynamic (MD) study of the PEI ligand (C14N8_07_B22) and the GOx enzyme (3QVR) was performed to examine the final complex PEI-GOx stabilization and the affinity of the PEI ligand to the docking sites of the GOx enzyme. The docking procedure showed two places/regions of major interaction of the protein with the polymer PEI: (LIG1) of -5.8 kcal/mol and (LIG2) of -4.5 kcal/mol located inside the enzyme and on its surface, respectively. The values of enthalpy for the PEI-enzyme complex, located inside of the protein (LIG1) and on its surface (LIG2) were computed. Docking also discovered domains of the GOx protein that exhibit no interactions with the ligand or have even repulsive characteristics. The structural data clearly indicate some differences in the ligand PEI behavior bound at the two places/regions of glucose oxidase.

  18. Molecular Dynamic Studies of the Complex Polyethylenimine and Glucose Oxidase

    Directory of Open Access Journals (Sweden)

    Beata Szefler

    2016-10-01

    Full Text Available Glucose oxidase (GOx is an enzyme produced by Aspergillus, Penicillium and other fungi species. It catalyzes the oxidation of β-d-glucose (by the molecular oxygen or other molecules, like quinones, in a higher oxidation state to form d-glucono-1,5-lactone, which hydrolyses spontaneously to produce gluconic acid. A coproduct of this enzymatic reaction is hydrogen peroxide (H2O2. GOx has found several commercial applications in chemical and pharmaceutical industries including novel biosensors that use the immobilized enzyme on different nanomaterials and/or polymers such as polyethylenimine (PEI. The problem of GOx immobilization on PEI is retaining the enzyme native activity despite its immobilization onto the polymer surface. Therefore, the molecular dynamic (MD study of the PEI ligand (C14N8_07_B22 and the GOx enzyme (3QVR was performed to examine the final complex PEI-GOx stabilization and the affinity of the PEI ligand to the docking sites of the GOx enzyme. The docking procedure showed two places/regions of major interaction of the protein with the polymer PEI: (LIG1 of −5.8 kcal/mol and (LIG2 of −4.5 kcal/mol located inside the enzyme and on its surface, respectively. The values of enthalpy for the PEI-enzyme complex, located inside of the protein (LIG1 and on its surface (LIG2 were computed. Docking also discovered domains of the GOx protein that exhibit no interactions with the ligand or have even repulsive characteristics. The structural data clearly indicate some differences in the ligand PEI behavior bound at the two places/regions of glucose oxidase.

  19. Challenges to studying the health effects of early life environmental chemical exposures on children's health.

    Science.gov (United States)

    Braun, Joseph M; Gray, Kimberly

    2017-12-01

    Epidemiological studies play an important role in quantifying how early life environmental chemical exposures influence the risk of childhood diseases. These studies face at least four major challenges that can produce noise when trying to identify signals of associations between chemical exposure and childhood health. Challenges include accurately estimating chemical exposure, confounding from causes of both exposure and disease, identifying periods of heightened vulnerability to chemical exposures, and determining the effects of chemical mixtures. We provide recommendations that will aid in identifying these signals with more precision.

  20. An Analytical Study of Prostate-Specific Antigen Dynamics.

    Science.gov (United States)

    Esteban, Ernesto P; Deliz, Giovanni; Rivera-Rodriguez, Jaileen; Laureano, Stephanie M

    2016-01-01

    The purpose of this research is to carry out a quantitative study of prostate-specific antigen dynamics for patients with prostatic diseases, such as benign prostatic hyperplasia (BPH) and localized prostate cancer (LPC). The proposed PSA mathematical model was implemented using clinical data of 218 Japanese patients with histological proven BPH and 147 Japanese patients with LPC (stages T2a and T2b). For prostatic diseases (BPH and LPC) a nonlinear equation was obtained and solved in a close form to predict PSA progression with patients' age. The general solution describes PSA dynamics for patients with both diseases LPC and BPH. Particular solutions allow studying PSA dynamics for patients with BPH or LPC. Analytical solutions have been obtained and solved in a close form to develop nomograms for a better understanding of PSA dynamics in patients with BPH and LPC. This study may be useful to improve the diagnostic and prognosis of prostatic diseases.

  1. Dynamic transition in the structure of an energetic crystal during chemical reactions at shock front prior to detonation.

    Science.gov (United States)

    Nomura, Ken-Ichi; Kalia, Rajiv K; Nakano, Aiichiro; Vashishta, Priya; van Duin, Adri C T; Goddard, William A

    2007-10-05

    Mechanical stimuli in energetic materials initiate chemical reactions at shock fronts prior to detonation. Shock sensitivity measurements provide widely varying results, and quantum-mechanical calculations are unable to handle systems large enough to describe shock structure. Recent developments in reactive force-field molecular dynamics (ReaxFF-MD) combined with advances in parallel computing have paved the way to accurately simulate reaction pathways along with the structure of shock fronts. Our multimillion-atom ReaxFF-MD simulations of l,3,5-trinitro-l,3,5-triazine (RDX) reveal that detonation is preceded by a transition from a diffuse shock front with well-ordered molecular dipoles behind it to a disordered dipole distribution behind a sharp front.

  2. Semiclassical theory of electronically nonadiabatic chemical dynamics: Incorporation of the Zhu-Nakamura theory into the frozen Gaussian propagation method

    International Nuclear Information System (INIS)

    Kondorskiy, A.; Nakamura, H.

    2004-01-01

    The title theory is developed by combining the Herman-Kluk semiclassical theory for adiabatic propagation on single potential-energy surface and the semiclassical Zhu-Nakamura theory for nonadiabatic transition. The formulation with use of natural mathematical principles leads to a quite simple expression for the propagator based on classical trajectories and simple formulas are derived for overall adiabatic and nonadiabatic processes. The theory is applied to electronically nonadiabatic photodissociation processes: a one-dimensional problem of H 2 + in a cw (continuous wave) laser field and a two-dimensional model problem of H 2 O in a cw laser field. The theory is found to work well for the propagation duration of several molecular vibrational periods and wide energy range. Although the formulation is made for the case of laser induced nonadiabatic processes, it is straightforwardly applicable to ordinary electronically nonadiabatic chemical dynamics

  3. Physico-chemical characterization and cytotoxicity studies of seed ...

    African Journals Online (AJOL)

    The seeds of Khaya senegalensis were extracted using petroleum ether and methanol with the aim of determining the physico-chemical properties of the seed oil and the cytotoxicity of the two extracts. The refractive index of the oil was found to be 1.458, while the relative density was 0.953. The iodine and saponification ...

  4. Structural studies of chemical constituents of Thithonia Tagetiflora Desv (Asteraceae)

    DEFF Research Database (Denmark)

    Ngoc Huynh, Vinh; Nguyen Thi Hoai, Thu; Phi Phung Nguyen, Kim

    2013-01-01

    Tithonia tagetiflora Desv. (Asteraceae) is a widespread plant in Vietnam, and the species of Tithonia are known as plants containing many biologically active compounds. However, T. tagetiflora's chemical composition remains mostly unknown. Therefore, we now report the structural elucidation of tw...

  5. Experimental and quantum chemical studies on corrosion inhibition ...

    Indian Academy of Sciences (India)

    the metal surface and form barrier film. .... with time may be attributed to the formation of a barrier film, which prevents the ..... high chemical activity and low kinetic stability and is termed ... Physical adsorption of the organic inhibitor on the metal.

  6. Short Communication: Studies of antimicrobial activity and chemical ...

    African Journals Online (AJOL)

    Chemical constituents of the extract were also determined. The extract of was active against the test organisms including Escherischia coli, Pseudomonas aeruginosa and Candida albicans. Tannins, flavonoids, alkaloids, saponins, anthrax-quinones, starch, general glycosides and bitter principles were found to be present ...

  7. Studies on the chemical constituents, antioxidants and membrane ...

    African Journals Online (AJOL)

    The chemical constituents, antioxidant and membrane stability activities of Hibiscus rosa sinensis Linn. (Malvaceae) flower were determined. The total anthocyanin was 165 mg / kg with about 6 % reduction due to fermentation. Tannin, ascorbic acid, and total polyphenol were 11.8 g / kg; 478 mg / kg; and 14.4 mg / g, ...

  8. Comparative Studies of Physico-chemical Properties of Some ...

    African Journals Online (AJOL)

    Akorede

    cement (As, Br, De and Sk) sold in Nigerian market using standard methods; due to the persistent collapse of buildings. ... important factors for chemical control in cement (Nasir and .... and mixed for 90s; this was allowed to stop at every 15s in.

  9. Experimental and quantum chemical studies on corrosion inhibition ...

    Indian Academy of Sciences (India)

    Abstract. The corrosion inhibition effect of fluconazole (FLU) was investigated on steel in 1 M hydrochloric acid solution. Weight loss measurements and atomic force microscope analysis were utilized to investigate the corrosion inhibition properties and film formation behaviour of FLU. Quantum chemical approach was also ...

  10. Physical, Chemical and Periphyton/Phytoplankton Study of Onah ...

    African Journals Online (AJOL)

    physico-chemical parameter, viz: ionic conductivity factor contributed 26.07%, nutrient factor contributed 40.61% while dissolved oxygen factor contributed 33.32%. Three divisions, eight families and ten species of periphyton were encountered. The most abundant periphyton species recorded are Closterium spp. (26.37%) ...

  11. Experimental and quantum chemical studies on corrosion inhibition

    Indian Academy of Sciences (India)

    The corrosion inhibition effect of fluconazole (FLU) was investigated on steel in 1 M hydrochloric acid solution. Weight loss measurements and atomic force microscope analysis were utilized to investigate the corrosion inhibition properties and film formation behaviour of FLU. Quantum chemical approach was also used to ...

  12. 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.

  13. Flux Decoupling and Chemical Diffusion in Redox Dynamics in Aluminosilicate Melts and Glasses (Invited)

    Science.gov (United States)

    Cooper, R. F.

    2010-12-01

    Measurements of redox dynamics in silicate melts and glasses suggest that, for many compositions and for many external environments, the reaction proceeds and is rate-limited by the diffusive flux of divalent-cation network modifiers. Application of ion-backscattering spectrometry either (i) on oxidized or reduced melts (subsequently quenched before analysis) or (ii) on similarly reacted glasses, both of basalt-composition polymerization, demonstrates that the network modifiers move relative to the (first-order-rigid) aluminosilicate network. Thus, the textures associated with such reactions are often surprising, and frequently include metastable or unstable phases and/or spatial compositional differences. This response is only possible if the motion of cations can be decoupled from that of anions. In many cases, decoupling is accomplished by the presence in the melt/glass of transition-metal cations, whose heterovalency creates distortions in the electronic band structure resulting in electronic defects: electron “holes” in the valence band or electrons in the conduction band. (The prevalence of holes or electrons being a function of bulk chemistry and oxygen activity.) These electronic species make the melt/glass a “defect semiconductor.” Because (a) the critical issue in reaction dynamics is the transport coefficient (the product of species mobility and species concentration) and (b) the electronic species are many orders of magnitude more mobile than are the ions, very low concentrations of transition-metal ions are required for flux decoupling. For example, 0.04 at% Fe keeps a magnesium aluminosilicate melt/glass a defect semiconductor down to 800°C [Cook & Cooper, 2000]. Depending on composition, high-temperature melts can see ion species having a high-enough transport coefficient to allow decoupling, e.g., alkali cations in a basaltic melt [e.g., Pommier et al., 2010]. In this presentation, these ideas will be illustrated by examining redox dynamics

  14. Effects of stochastic time-delayed feedback on a dynamical system modeling a chemical oscillator

    Science.gov (United States)

    González Ochoa, Héctor O.; Perales, Gualberto Solís; Epstein, Irving R.; Femat, Ricardo

    2018-05-01

    We examine how stochastic time-delayed negative feedback affects the dynamical behavior of a model oscillatory reaction. We apply constant and stochastic time-delayed negative feedbacks to a point Field-Körös-Noyes photosensitive oscillator and compare their effects. Negative feedback is applied in the form of simulated inhibitory electromagnetic radiation with an intensity proportional to the concentration of oxidized light-sensitive catalyst in the oscillator. We first characterize the system under nondelayed inhibitory feedback; then we explore and compare the effects of constant (deterministic) versus stochastic time-delayed feedback. We find that the oscillatory amplitude, frequency, and waveform are essentially preserved when low-dispersion stochastic delayed feedback is used, whereas small but measurable changes appear when a large dispersion is applied.

  15. Predicting in vivo effect levels for repeat-dose systemic toxicity using chemical, biological, kinetic and study covariates.

    Science.gov (United States)

    Truong, Lisa; Ouedraogo, Gladys; Pham, LyLy; Clouzeau, Jacques; Loisel-Joubert, Sophie; Blanchet, Delphine; Noçairi, Hicham; Setzer, Woodrow; Judson, Richard; Grulke, Chris; Mansouri, Kamel; Martin, Matthew

    2018-02-01

    In an effort to address a major challenge in chemical safety assessment, alternative approaches for characterizing systemic effect levels, a predictive model was developed. Systemic effect levels were curated from ToxRefDB, HESS-DB and COSMOS-DB from numerous study types totaling 4379 in vivo studies for 1247 chemicals. Observed systemic effects in mammalian models are a complex function of chemical dynamics, kinetics, and inter- and intra-individual variability. To address this complex problem, systemic effect levels were modeled at the study-level by leveraging study covariates (e.g., study type, strain, administration route) in addition to multiple descriptor sets, including chemical (ToxPrint, PaDEL, and Physchem), biological (ToxCast), and kinetic descriptors. Using random forest modeling with cross-validation and external validation procedures, study-level covariates alone accounted for approximately 15% of the variance reducing the root mean squared error (RMSE) from 0.96 log 10 to 0.85 log 10  mg/kg/day, providing a baseline performance metric (lower expectation of model performance). A consensus model developed using a combination of study-level covariates, chemical, biological, and kinetic descriptors explained a total of 43% of the variance with an RMSE of 0.69 log 10  mg/kg/day. A benchmark model (upper expectation of model performance) was also developed with an RMSE of 0.5 log 10  mg/kg/day by incorporating study-level covariates and the mean effect level per chemical. To achieve a representative chemical-level prediction, the minimum study-level predicted and observed effect level per chemical were compared reducing the RMSE from 1.0 to 0.73 log 10  mg/kg/day, equivalent to 87% of predictions falling within an order-of-magnitude of the observed value. Although biological descriptors did not improve model performance, the final model was enriched for biological descriptors that indicated xenobiotic metabolism gene expression, oxidative stress, and

  16. Applications of Neutron Scattering in the Chemical Industry: Proton Dynamics of Highly Dispersed Materials, Characterization of Fuel Cell Catalysts, and Catalysts from Large-Scale Chemical Processes

    Science.gov (United States)

    Albers, Peter W.; Parker, Stewart F.

    The attractiveness of neutron scattering techniques for the detailed characterization of materials of high degrees of dispersity and structural complexity as encountered in the chemical industry is discussed. Neutron scattering picks up where other analytical methods leave off because of the physico-chemical properties of finely divided products and materials whose absorption behavior toward electromagnetic radiation and electrical conductivity causes serious problems. This is demonstrated by presenting typical applications from large-scale production technology and industrial catalysis. These include the determination of the proton-related surface chemistry of advanced materials that are used as reinforcing fillers in the manufacture of tires, where interrelations between surface chemistry, rheological properties, improved safety, and significant reduction of fuel consumption are the focus of recent developments. Neutron scattering allows surface science studies of the dissociative adsorption of hydrogen on nanodispersed, supported precious metal particles of fuel cell catalysts under in situ loading at realistic gas pressures of about 1 bar. Insight into the occupation of catalytically relevant surface sites provides valuable information about the catalyst in the working state and supplies essential scientific input for tailoring better catalysts by technologists. The impact of deactivation phenomena on industrial catalysts by coke deposition, chemical transformation of carbonaceous deposits, and other processes in catalytic hydrogenation processes that result in significant shortening of the time of useful operation in large-scale plants can often be traced back in detail to surface or bulk properties of catalysts or materials of catalytic relevance. A better understanding of avoidable or unavoidable aspects of catalyst deactivation phenomena under certain in-process conditions and the development of effective means for reducing deactivation leads to more energy

  17. Backtracing neutron analysis in the fusion-fission dynamics study

    International Nuclear Information System (INIS)

    Brennand, E. de Goes; Hanappe, F.; Stuttge, L.

    2001-01-01

    A new method for the analysis of multi parametric experimental data is used in the study of the dynamics of the fission process for the compound system 126 Ba. We apply this method to obtain the correlation between thermal energy related to the neutron total multiplicity and the correlation between pre-scission neutron and pos-scission neutron multiplicities. The results obtained are interpreted into the framework of a dynamical model. From this interpretation we have access to the following information: the friction intensity which drives the dynamical evolution of the system; the initial deformation of the compound system; the barrier evolution with temperature and angular momentum, and fission times. (author)

  18. 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.

  19. NASA plan for international crustal dynamics studies

    Science.gov (United States)

    1979-01-01

    The international activities being planned as part of the NASA geodynamics program are described. Methods of studying the Earth's crustal movements and deformation characteristics are discussed. The significance of the eventual formalations of earthquake predictions methods is also discussed.

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

    Science.gov (United States)

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

    2016-01-21

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

  1. Chemical dynamics between wells across a time-dependent barrier: Self-similarity in the Lagrangian descriptor and reactive basins.

    Science.gov (United States)

    Junginger, Andrej; Duvenbeck, Lennart; Feldmaier, Matthias; Main, Jörg; Wunner, Günter; Hernandez, Rigoberto

    2017-08-14

    In chemical or physical reaction dynamics, it is essential to distinguish precisely between reactants and products for all times. This task is especially demanding in time-dependent or driven systems because therein the dividing surface (DS) between these states often exhibits a nontrivial time-dependence. The so-called transition state (TS) trajectory has been seen to define a DS which is free of recrossings in a large number of one-dimensional reactions across time-dependent barriers and thus, allows one to determine exact reaction rates. A fundamental challenge to applying this method is the construction of the TS trajectory itself. The minimization of Lagrangian descriptors (LDs) provides a general and powerful scheme to obtain that trajectory even when perturbation theory fails. Both approaches encounter possible breakdowns when the overall potential is bounded, admitting the possibility of returns to the barrier long after the trajectories have reached the product or reactant wells. Such global dynamics cannot be captured by perturbation theory. Meanwhile, in the LD-DS approach, it leads to the emergence of additional local minima which make it difficult to extract the optimal branch associated with the desired TS trajectory. In this work, we illustrate this behavior for a time-dependent double-well potential revealing a self-similar structure of the LD, and we demonstrate how the reflections and side-minima can be addressed by an appropriate modification of the LD associated with the direct rate across the barrier.

  2. Study on Human-structure Dynamic Interaction in Civil Engineering

    Science.gov (United States)

    Gao, Feng; Cao, Li Lin; Li, Xing Hua

    2018-06-01

    The research of human-structure dynamic interaction are reviewed. Firstly, the influence of the crowd load on structural dynamic characteristics is introduced and the advantages and disadvantages of different crowd load models are analyzed. Then, discussing the influence of structural vibration on the human-induced load, especially the influence of different stiffness structures on the crowd load. Finally, questions about human-structure interaction that require further study are presented.

  3. Dynamic scintigraphic studies after oesophageal reconstruction

    International Nuclear Information System (INIS)

    Maliska, C.M.; Maliska, C.; Pinto, E.; Castro, L.; Fonseca, L.B.E; Miranda, M.

    1997-01-01

    Full text: We have studied the oesophageal transit and gastric emptying in the monitoring of the effect of oesophageal reconstruction surgery. Oncologic patients were evaluated after oesophageal reconstruction surgery with gastric (14 patients) or colonic (5 patients) tube and they were compared with 15 healthy volunteers, using scintigraphic method with liquid food (S-colloid-Tc99m). In the oesophageal transit studies there were no significant statistical differences among the three groups, when we have just considered to two superior (of the three) segments, as oesophagus, showing that the distal neo-tube works just like the stomach of normal volunteers

  4. Theoretical analysis of dynamic chemical imaging with lasers using high-order harmonic generation

    International Nuclear Information System (INIS)

    Van-Hoang Le; Anh-Thu Le; Xie Ruihua; Lin, C. D.

    2007-01-01

    We report theoretical investigations of the tomographic procedure suggested by Itatani et al. [Nature (London) 432, 867 (2004)] for reconstructing highest occupied molecular orbitals (HOMOs) using high-order harmonic generation (HHG). Due to the limited range of harmonics from the plateau region, we found that even under the most favorable assumptions, it is still very difficult to obtain accurate HOMO wave functions using the tomographic procedure, but the symmetry of the HOMOs and the internuclear separation between the atoms can be accurately extracted, especially when lasers of longer wavelengths are used to generate the HHG. Since the tomographic procedure relies on approximating the continuum wave functions in the recombination process by plane waves, the method can no longer be applied upon the improvement of the theory. For future chemical imaging with lasers, we suggest that one may want to focus on how to extract the positions of atoms in molecules instead, by developing an iterative method such that the theoretically calculated macroscopic HHG spectra can best fit the experimental HHG data

  5. Factors associated with chemical burns in Zhejiang province, China: An epidemiological study

    Directory of Open Access Journals (Sweden)

    Jiang Rui M

    2011-09-01

    Full Text Available Abstract Background Work-related burns are common among occupational injuries. Zhejiang Province is an industrial area with a high incidence of chemical burns. We aimed to survey epidemiological features of chemical burns in Zhejiang province to determine associated factors and acquire data for developing a strategy to prevent and treat chemical burns. Methods Questionnaires were developed, reviewed and validated by experts, and sent to 25 hospitals in Zhejiang province to prospectively collect data of 492 chemical burn patients admitted during one year from Sept. 1, 2008 to Aug. 31, 2009. Questions included victims' characteristics and general condition, injury location, causes of accident, causative chemicals, total body surface area burn, concomitant injuries, employee safety training, and awareness level of protective measures. Surveys were completed for each of burn patients by burn department personnel who interviewed the hospitalized patients. Results In this study, 417 victims (87.61% got chemical burn at work, of which 355 victims (74.58% worked in private or individual enterprises. Most frequent chemicals involved were hydrofluoric acid and sulfuric acid. Main causes of chemical injury accidents were inappropriate operation of equipment or handling of chemicals and absence of or failure to use effective individual protection. Conclusions Most chemical burns are preventable occupational injuries that can be attributed to inappropriate operation of equipment or handling of chemicals, lack of employee awareness about appropriate action and lack of effective protective equipment and training. Emphasis on safety education and protection for workers may help protect workers and prevent chemical burns.

  6. Studies on marine toxins: chemical and biological aspects

    International Nuclear Information System (INIS)

    Stonik, Valentin A; Stonik, Inna V

    2010-01-01

    The structures and mechanisms of biological action of the best known representatives of the main groups of marine toxins are presented. It is shown that many compounds have complex chemical structures and possess extremely high toxicities. Characteristic features of isolation, structure determination and syntheses of these compounds using the achievement of modern organic chemistry are discussed. The methods of identification and quantitative analysis of marine toxins are briefly reviewed.

  7. Archaeological recording and chemical stratigraphy applied to contaminated land studies.

    Science.gov (United States)

    Photos-Jones, Effie; Hall, Allan J

    2011-11-15

    The method used by archaeologists for excavation and recording of the stratigraphic evidence, within trenches with or without archaeological remains, can potentially be useful to contaminated land consultants (CLCs). The implementation of archaeological practice in contaminated land assessments (CLAs) is not meant to be an exercise in data overkill; neither should it increase costs. Rather, we suggest, that if the excavation and recording, by a trained archaeologist, of the stratigraphy is followed by in-situ chemical characterisation then it is possible that much uncertainty associated with current field sampling practices, may be removed. This is because built into the chemical stratigraphy is the temporal and spatial relationship between different parts of the site reflecting the logic behind the distribution of contamination. An archaeological recording with chemical stratigraphy approach to sampling may possibly provide 'one method fits all' for potentially contaminated land sites (CLSs), just as archaeological characterisation of the stratigraphic record provides 'one method fits all' for all archaeological sites irrespective of period (prehistoric to modern) or type (rural, urban or industrial). We also suggest that there may be practical and financial benefits to be gained by pulling together expertise and resources stemming from different disciplines, not simply at the assessment phase, but also subsequent phases, in contaminated land improvement. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Quantum chemical studies on the some inorganic corrosion inhibitors

    International Nuclear Information System (INIS)

    Sayin, Koray; Karakaş, Duran

    2013-01-01

    Highlights: •Some quantum chemical parameters are important to determine inhibition efficiency. •Quantum chemical calculations were performed on six inorganic inhibitors. •Five experimental reports were used to explain the theoretical results. •Atomic charges and %contributions were used to determine the atom at protonation process. •For inorganic inhibitors, the best method and basis set were investigated. -- Abstract: Some quantum chemical parameters were calculated by using Hartree–Fock (HF) approximation, Density Functional Theory (DFT/B3LYP) and Møller Plesset perturbation theory (MP3) methods at LANL2DZ, LANL2MB and SDD levels in gas phase and water for dichromate (Cr 2 O 7 2- ), chromate (CrO 4 2- ), tungstate (WO 4 2- ), molybdate (MoO 4 2- ), nitrite (NO 2 - ) and nitrate (NO 3 - ) which are used as inorganic corrosion inhibitors. All theoretical results and experimental inhibition efficiencies of inhibitors were subjected to correlation analyses. In a summary, MP3/SDD level in water was found as the best level. In this level, the inhibition efficiency ranking was found as CrO 4 2- >WO 4 2- >MoO 4 2- >Cr 2 O 7 2- >NO 2 - ≈NO 3 -

  9. Fundamental study of dynamic ECT by dual detector gammacamera system

    International Nuclear Information System (INIS)

    Kakegawa, M.; Matsui, S.; Maeda, H.; Takeda, K.; Nakagawa, T.

    1982-01-01

    The improvement of image quality of reconstructed image by the simple pre-processing of projections is studied. Using the improved algorithm and dual detector gammacamera system, the possibility of dynamic ECT is studied. As shown in clinical examples, renal flow study using Tc-99m-DTPA, dynamic ECT imaging is possible with measuring time of 1 or 2 minutes. By this method cortex and medulla are separately imaged and each function can be analyzed more precisely. Using high sensitive collimator it will be possible to take ECT images every 30 sec. with little resolution loss quantitative three dimensional time activity analysis is under study

  10. Clinical application of cerebral dynamic perfusion studies

    International Nuclear Information System (INIS)

    DeLand, F.H.

    1975-01-01

    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)

  11. Conformational fluctuation dynamics of domain I of human serum albumin in the course of chemically and thermally induced unfolding using fluorescence correlation spectroscopy.

    Science.gov (United States)

    Yadav, Rajeev; Sengupta, Bhaswati; Sen, Pratik

    2014-05-22

    The present study elucidates the involvement of conformational fluctuation dynamics during chemically and thermally induced unfolding of human serum albumin (HSA) by fluorescence correlation spectroscopic (FCS) study, time-resolved fluorescence measurements, and circular dichroism (CD) spectroscopic methods. Two fluorescent probes, tetramethylrhodamine-5-maleimide (TMR) and N-(7-dimethylamino-4-methylcoumarin-3-yl) iodoacetamide (DACIA) were used to selectively label the domain I of HSA through the reaction with cys-34 for these studies. The guanidine hydrochloride (GnHCl) induced global structural change of HSA is monitored through its hydrodynamic radius (r(H)) and CD response, which is found to be two step in nature. In FCS experiment, along with the diffusion time component we have observed an exponential relaxation time component (τ(R)) that has been ascribed to the concerted chain dynamics of HSA. Unlike in the global structural change, we found that the τ(R) value changes in a different manner in the course of the unfolding. The dependence of τ(R) on the concentration of GnHCl was best fitted with a four state model, indicating the involvement of two intermediate states during the unfolding process, which were not observed through the CD response and r(H) data. The fluorescence lifetime measurement also supports our observation of intermediate states during the unfolding of HSA. However, no such intermediate states were observed during thermally induced unfolding of HSA.

  12. The General Laws of Chemical Elements Composition Dynamics in the Biosphere

    Science.gov (United States)

    Korzh, Vyacheslav D.

    2013-04-01

    The key point of investigation of the specificity of the biosphere elemental composition formation is determination of patterns of redistribution of elemental average concentrations among various phases, like solid - liquid ( the lithosphere - the hydrosphere), which occurs as a result of a global continuous processing of inert matter by living substances. Our task here is to investigate this process in the system "lithosphere - hydrosphere" in view of the integrated involvement of living material in it. This process is most active in biogeochemical barriers, i.e. in places of "the life condensation" and runs under a nonlinear regularity that has been unknown before. It is established that this process results in a general relative increase in concentrations of chemical elements in the solid phase in proportion as their prevalence in the environment is reduced. This process running in various natural systems has practically the same parameter of nonlinearity (v) approximately equal to 0.7. For proto-lithosphere -"living material" - soil v = 0.75. For river - "living material" - ocean v = 0.67. For the contemporary factual awareness level these estimations of nonlinearity indices are practically negligible. Hence, it is for the first time that the existence of a universal constant of nonlinearity of elemental composition evolution in the biosphere has been proved and its quantitative evaluation has been made. REFERENCES 1. Korzh V.D. 1974. Some general laws governing the turnover of substance within the ocean-atmosphere-continent-ocean cycle. // Journal de Recherches Atmospheriques. Vol. 8. P. 653-660. 2. Korzh V.D. 2008. The general laws in the formation of the elemental composition of the Hydrosphere and Biosphere.// J. Ecologica, Vol. XV, P. 13-21. 3. Korzh V.D. 2012. Determination of general laws of elemental composition in Hydrosphere // Water: chemistry & ecology, Journal of water science and its practical application. # 1, P.56-62.

  13. Dynamic Modeling and Plantwide Control of a Hybrid Power and Chemical Plant: An Integrated Gasification Combined Cycle Coupled with a Methanol Plant

    Science.gov (United States)

    Robinson, Patrick J.

    simulators Aspen Plus and Aspen Dynamics. This dissertation first presents a simple approximate method for achieving the objective of having a gasifier model that can be exported into Aspen Dynamics. Limitations in the software dealing with solids make this a necessary task. The basic idea is to use a high molecular weight hydrocarbon that is present in the Aspen library as a pseudo fuel. For many plantwide dynamic studies, a rigorous high-fidelity dynamic model of the gasifier is not needed because its dynamics are very fast and the gasifier gas volume is a relatively small fraction of the total volume of the entire plant. The proposed approximate model captures the essential macro-scale thermal, flow, composition and pressure dynamics. This paper does not attempt to optimize the design or control of gasifiers, but merely presents an idea of how to dynamically simulate coal gasification in an approximate way. This dissertation also presents models of the downstream units of a typical IGCC. Dynamic simulations of the H2S absorption/stripping unit, Water-gas Shift (WGS) reactors, and CO2 absorption/stripping unit are essential for the development of stable and agile plantwide control structures of this hybrid power/chemical plant. Due to the high pressure of the system, hydrogen sulfide is removed by means of physical absorption. SELEXOLRTM (a mixture of the dimethyl ethers of polyethylene glycol) is used to achieve a gas purity of less than 5 ppm H2S. This desulfurized synthesis gas is sent to two water gas shift reactors that convert a total of 99% of carbon monoxide to hydrogen. Physical absorption of carbon dioxide with Selexol produces a hydrogen rich stream (90 mol% H2) to be fed into combustion turbines or to a methanol plant. Steady-state economic designs and plantwide control structures are developed in this dissertation. A steady-state economic design, control structure, and successful turndown of the methanol plant are shown in this dissertation. The Plantwide

  14. A New Theoretical Approach to Single-Molecule Fluorescence Optical Studies of RNA Dynamics

    International Nuclear Information System (INIS)

    Zhao Xinghai; Shan Guangcun; Bao Shuying

    2011-01-01

    Single-molecule fluorescence spectroscopy in condensed phases has many important chemical and biological applications. The single-molecule fluorescence measurements contain information about conformational dynamics on a vast range of time scales. Based on the data analysis protocols methodology proposed by X. Sunney Xie, the theoretical study here mainly focuses on the single-molecule studies of single RNA with interconversions among different conformational states, to with a single FRET pair attached. We obtain analytical expressions for fluorescence lifetime correlation functions that relate changes in fluorescence lifetime to the distance-dependent FRET mechanism within the context of the Smoluchowski diffusion model. The present work establishes useful guideline for the single-molecule studies of biomolecules to reveal the complicated folding dynamics of single RNA molecules at nanometer scale.

  15. Microscopic study on dynamic barrier in fusion reactions

    International Nuclear Information System (INIS)

    Wu Xizhen; Tian Junlong; Zhao Kai; Li Zhuxia; Wang Ning

    2004-01-01

    The authors briefly review the fusion process of very heavy nuclear systems and some theoretical models. The authors propose a microscopic transport dynamic model, i.e. the Improved Quantum Molecular Dynamic model, for describing fusion reactions of heavy systems, in which the dynamical behavior of the fusion barrier in heavy fusion systems has been studied firstly. The authors find that with the incident energy decreasing the lowest dynamic barrier is obtained which approaches to the adiabatic static barrier and with increase of the incident energy the dynamic barrier goes up to the diabatic static barrier. The authors also indicate that how the dynamical fusion barrier is correlated with the development of the configuration of fusion partners along the fusion path. Associating the single-particle potentials obtained at different stages of fusion with the Two Center Shell Model, authors can study the time evolution of the single particle states of fusion system in configuration space of single particle orbits along the fusion path. (author)

  16. Studies of Beam Dynamics in Cooler Rings

    International Nuclear Information System (INIS)

    Dietrich, J.; Stein, J.; Meshkov, I.; Sidorin, A.; Smirnov, A.

    2006-01-01

    This report describes the numerical simulation of the crystalline proton beam formation in COSY using BETACOOL code. The study includes the description of experimental results at NAP-M storage ring where the large reduction of the momentum spread was observed for first time. The present simulation shows that this behavior of proton beam can not be explained as ordered state of protons. The numerical simulation of crystalline proton beams was done for COSY parameters. The number of protons when the ordering state can be observed is limited by value 106 particles and momentum spread less then 10-6. Experimental results for the attempt to achieve of ordered state of proton beam for COSY is presented. This work is supported by RFBR grant no. 05-02-16320 and INTAS grant no. 03-54-5584

  17. RF quadrupole beam dynamics design studies

    International Nuclear Information System (INIS)

    Crandall, K.R.; Stokes, R.H.; Wangler, T.P.

    1979-01-01

    The radio-frequency quadrupole (RFQ) linear accelerator structure is expected to permit considerable flexibility in achieving linac design objectives at low velocities. Calculational studies show that the RFQ can accept a high-current, low-velocity, dc beam, bunch it with high efficiency, and accelerate it to a velocity suitable for injection into a drift-tube linac. Although it is relatively easy to generate a satisfactory design for an RFQ linac for low beam currents, the space-charge effects produced by high currents dominate the design criteria. Methods have been developed to generate solutions that make suitable compromises between the effects of emittance growth, transmission efficiency, and overall structure length. Results are given for a test RFQ linac operating at 425 MHz

  18. 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.

  19. Structural, dynamical, and electronic properties of amorphous silicon: An ab initio molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Car, R.; Parrinello, M.

    1988-01-18

    An amorphous silicon structure is obtained with a computer simulation based on a new molecular-dynamics technique in which the interatomic potential is derived from a parameter-free quantum mechanical method. Our results for the atomic structure, the phonon spectrum, and the electronic properties are in excellent agreement with experiment. In addition we study details of the microscopic dynamics which are not directly accessible to experiment. We find in particular that structural defects are associated with weak bonds. These may give rise to low-frequency vibrational modes.

  20. Molecular dynamics studies of the dynamics of supercooled Lennard-Jones liquids

    International Nuclear Information System (INIS)

    De Leeuw, S.W.; Brakkee, M.J.D.

    1990-01-01

    Results are presented of molecular dynamics experiments, in which the Lennard-Jones liquid is cooled isobarically into the metastable temperature region below the freezing temperature. The variation of the density-density and transverse current correlation functions with temperature is studied. We observed a power-law behaviour for the temperature dependence of dynamical properties (viscosity and coefficienty of self-diffusion) with an exponent in good agreement with prediction of mode coupling theories and recent experimental results. (author). 23 refs, 5 figs

  1. Protein Dynamics in Organic Media at Varying Water Activity Studied by Molecular Dynamics Simulation

    DEFF Research Database (Denmark)

    Wedberg, Nils Hejle Rasmus Ingemar; Abildskov, Jens; Peters, Günther H.J.

    2012-01-01

    In nonaqueous enzymology, control of enzyme hydration is commonly approached by fixing the thermodynamic water activity of the medium. In this work, we present a strategy for evaluating the water activity in molecular dynamics simulations of proteins in water/organic solvent mixtures. The method...... relies on determining the water content of the bulk phase and uses a combination of Kirkwood−Buff theory and free energy calculations to determine corresponding activity coefficients. We apply the method in a molecular dynamics study of Candida antarctica lipase B in pure water and the organic solvents...

  2. Studies of Fundamental Particle Dynamics in Microgravity

    Science.gov (United States)

    Rangel, Roger; Trolinger, James D.; Coimbra, Carlos F. M.; Witherow, William; Rogers, Jan; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    This work summarizes theoretical and experimental concepts used to design the flight experiment mission for SHIVA - Spaceflight Holography Investigation in a Virtual Apparatus. SHIVA is a NASA project that exploits a unique, holography-based, diagnostics tool to understand the behavior of small particles subjected to transient accelerations. The flight experiments are designed for testing model equations, measuring g, g-jitter, and other microgravity phenomena. Data collection will also include experiments lying outside of the realm of existing theory. The regime under scrutiny is the low Reynolds number, Stokes regime or creeping flow, which covers particles and bubbles moving at very low velocity. The equations describing this important regime have been under development and investigation for over 100 years and yet a complete analytical solution of the general equation had remained elusive yielding only approximations and numerical solutions. In the course of the ongoing NASA NRA, the first analytical solution of the general equation was produced by members of the investigator team using the mathematics of fractional derivatives. This opened the way to an even more insightful and important investigation of the phenomena in microgravity. Recent results include interacting particles, particle-wall interactions, bubbles, and Reynolds numbers larger than unity. The Space Station provides an ideal environment for SHIVA. Limited ground experiments have already confirmed some aspects of the theory. In general the space environment is required for the overall experiment, especially for cases containing very heavy particles, very light particles, bubbles, collections of particles and for characterization of the space environment and its effect on particle experiments. Lightweight particles and bubbles typically rise too fast in a gravitational field and heavy particles sink too fast. In a microgravity environment, heavy and light particles can be studied side-by-side for

  3. 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

  4. Chemical evolution coefficients for the study of galactic evolution

    Energy Technology Data Exchange (ETDEWEB)

    Mallik, D C.V. [Indian Inst. of Astrophysics, Bangalore

    1980-05-01

    A new evaluation of chemical evolution coefficients has been made using recent stellar evolution and nucleosynthesis data. The role of the low and intermediate mass stars in galactic nucleosynthesis has been emphasized. A significant amount of /sup 4/He, /sup 12/C and neutron-rich species is found to be contributed by these stars. Comparison with observed abundances suggests a primary origin of /sup 14/N. The simple model of galactic evolution with the new coefficients has been used to derive the ratio of helium to heavy element enrichment in the Galaxy. The new stellar evolution data do not explain the large value of this ratio that has been determined observationally.

  5. Chemical evolution coefficients for the study of galactic evolution

    International Nuclear Information System (INIS)

    Mallik, D.C.V.

    1980-01-01

    A new evaluation of chemical evolution coefficients has been made using recent stellar evolution and nucleosynthesis data. The role of the low and intermediate mass stars in galactic nuclosynthesis has been emphasized. A significant amount of 4 He, 12 C and neutron-rich species is found to be contributed by these stars. Comparison with observed abundances suggests a primary origin of 14 N. The simple model of galactic evolution with the new coefficients has been used to derive the ratio of helium to heavy element enrichment in the Galaxy. The new stellar evolution data do not explain the large value of this ratio that has been determined observationally. (orig.)

  6. Physico-chemical studies on samarium soaps in solid state

    International Nuclear Information System (INIS)

    Mehrotra, K.N.; Chauhan, M.; Shukla, R.K.

    1989-01-01

    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)

  7. [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.

  8. Study on magnetite nanoparticles synthesized by chemical method

    International Nuclear Information System (INIS)

    Pei Wenli; Kumada, H.; Natusme, T.; Saito, H.; Ishio, S.

    2007-01-01

    Magnetite nanoparticles with controlled size were synthesized by chemical method. Higher deposition temperature and a rapid-raising temperature procedure are favorable to particle size distribution and fabrication of monodisperse nanoparticles. The larger nanoparticles can be synthesized by the two-step method. The large nanoparticle (up to 25 nm) without agglomeration was successfully produced. The saturation magnetization of 11 nm magnetite particles was 45 emu/g at room temperature, which is smaller than that of bulk magnetite due to surface effect. Hysteresis of the magnetite nanoparticle was very small, indicating superparamagnetic behavior. The magnetic domains of the 11 nm magnetite nanoparticles were successfully observed by MFM

  9. Human volunteer studies with non-pharmaceutical chemicals: metabolism and pharmacokinetic studies.

    Science.gov (United States)

    Wilks, M F; Woollen, B H

    1994-06-01

    1. Human volunteer studies are an essential part of drug development but their use in the area of non-pharmaceutical chemicals has so far been very limited. Such studies can have considerable value in the assessment and improvement of the safe use of chemicals. 2. Once metabolic pathways and target metabolites have been identified in volunteers this information can be used in studies in the workplace or in the general population. Studies should be performed selectively only if there is both a toxic hazard and a significant exposure potential. In addition, they should only be carried out if the required information cannot be obtained in any other way. 3. Volunteer studies with non-pharmaceuticals have become increasingly acceptable in the light of established international guidelines, no-fault compensation, improvements in study design and technical developments which allow the use of very low dose levels. The final decision on whether to carry out a study must always rest with an independent ethical committee. 4. The practical aspects of the study should be specified in a detailed protocol conforming with the principles of good clinical practice. The safety of volunteers must be of paramount concern throughout. Depending on the nature of the chemical and the study, it may be advisable to carry out studies in a clinical facility where equipment is available for the treatment of any emergencies that might occur. 5. Numerous investigators have now shown that human volunteer studies are ethically acceptable, practicable and yield important information. The risk to volunteers is minimal and this approach can lead to an improved foundation for occupational hygiene standards, more accurate risk assessment and thus better protection of the workforce and the general population.

  10. Application of single photon ECT for dynamic study

    International Nuclear Information System (INIS)

    Mukai, T.; Ishii, Y.; Tamaki, N.

    1982-01-01

    Feasibility of dynamic study in a form of ECT using a rotating gamma camera was evaluated. Since it takes longer one around time sampling, application for the dynamic study is limited under following conditions; 1) physiological gated process, 2) slow clearance process, 3) physiological steady state process. The gated study was applicated for heart pumping action synchronized with ECG. The ECG gated heart ECT either of blood pool or myocardium was useful to reveal a subtle wall motion abnormalities in a tomographic plane, even when a planar imaging failed to reveal it. As for slow dynamic process of tracer, an excretion process of hepatobiliary agent, was subjected to be analyzed in order to calculate clearance rate at each pixel. As for steady state process, an ECT of regional celebral blood flow (rCBF) was investigated during continuous infusion into intracarotid artery. All of these technique were proved to have a clinical feasibility and to potentiate usefulness of the single photon ECT (SPECT)

  11. Chemical studies on some radionuclides in industrial wastes

    International Nuclear Information System (INIS)

    Ibrahim, M.F.A.

    2006-01-01

    in this thesis, there is much concern about the technologically enhanced-naturally occurring radioactive materials (TE-NORM) associated with phosphate fertilizers and chemical materials production in abu Zaabal Company, Egypt. the phosphogypsum (PG)wastes associated with the phosporic acid produced was found to contain high concentrations of radioactivity than that exists naturally (i.e., background). this chapter includes sufficient information about the different sources of the environmental radioactivities as well as TE-NORM associated with phosphate fertilizers and oil and gas production facilities . it includes also, information about the history, methods used in detection and measurements, limits, trials of TE-NORM treatment . it contains some aspects on the chemistry and radiochemistry of radium and radon. also, this chapter includes the aim of the present work.this chapter includes preparation of all required samples for analysis, as well as chemicals and reagents used in the experimental work .it includes also, description of the different spectroscopic instruments used. which are: HPGe γ-ray spectrometry,α-spectrometry, X-ray diffraction(XRD), x-ray fluorescence (XRF), and IR-spectrometry. the energy and efficiency calibrations of both γ and α-spectrometry are also presented

  12. 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…

  13. Study on Physical Properties and Chemical Composition of Some Myanmar Gems

    International Nuclear Information System (INIS)

    Kyaw Myint Htoo; Tun Khin; Sein Htoon

    2004-05-01

    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

  14. Study of beam dynamics at cooler synchrotron TARN-II

    International Nuclear Information System (INIS)

    Watanabe, S.; Katayama, T.; Watanabe, T.; Yoshizawa, M.; Tomizawa, M.; Chida, K.; Arakaki, Y.; Noda, K.; Kanazawa, M.

    1992-08-01

    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)

  15. 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.

  16. An infrared free electron laser system for the proposed Chemical Dynamics Research Laboratory at LBL based on a 500 MHz superconducting linac

    International Nuclear Information System (INIS)

    Kim, K.J.; Byrns, R.; Chattopadhyay, S.; Donahue, R.; Edighoffer, J.; Gough, R.; Hoyer, E.; Leemans, W.; Staples, J.; Taylor, B.; Xie, M.

    1992-09-01

    We describe a new design of the Infrared Free Electron Laser (IRFEL) for the proposed Chemical Dynamics Research Laboratory (CDRL) at LBL. The design and choice of parameters are dictated by the unique requirements of the CDRL scientific program. The accelerator system is based on the 500 MHz superconducting cavity technology to achieve a wavelength stability of 10 -4

  17. Influence of radioprotectors of various chemical compounds on the dynamic performance capacity and carbohydrate metabolism

    International Nuclear Information System (INIS)

    Vladimirov, V.G.; Golubentsev, D.A.; Merkina, T.N.; Smirnova, S.M.

    1978-01-01

    Studied is the effect of the most effective radiotectors (gammaphos, cystamine and mexamine) on some factors of carbohydrate metabolism and working capacity of rats. In the effect of preparations studied great differences are established. Decrease of glycogen storage in liver and museles increase of lactate and pyruate level in blood as compared to control, decrease of animal working capacity are observed at introducing cystamine into rats when in rest and while dosed muscular loadings. Mexamine causes great shifts in carbohydrate exchange (in combination with physical loadings), and decreases animal strength. Gammaphos does not influence carbohydrate metabolism and does not decrease animal working capacity

  18. Study of virgin olive oil clarification by settling under dynamic conditions.

    Science.gov (United States)

    Gila, Abraham; Bejaoui, Mohamed Aymen; Beltrán, Gabriel; Aguilera, María Paz; Jiménez, Antonio

    2018-04-16

    Vertical centrifugation is the main method for virgin olive oil (VOO) clarification. However, in recent years, settling tanks are also being used to clarify the oils from decanters. They can operate under static or dynamic conditions. In this work, vertical centrifugation and settling under dynamic conditions for VOO clarification and their effects on VOO characteristics were compared. VOO quality parameters were not affected by the clarification systems studied. The vertical centrifugal separator (VCS) showed higher clarification efficiency, giving clarified oils with higher phenol content and better sensory characteristics. VOOs clarified by dynamic settling showed notable losses of phenols and worse sensory characteristics, since the tank purge system was not efficient, with most of the impurities remaining in the tanks. The VCS with minimal water addition is a quick operation with low water consumption and is a better option to produce VOOs of improved quality, especially in terms of longer shelf life and preservation of positive sensory notes. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

  19. Elastic properties of amorphous boron suboxide based solids studied using ab initio molecular dynamics

    International Nuclear Information System (INIS)

    Music, Denis; Schneider, Jochen M

    2008-01-01

    We have studied the correlation between chemical composition, structure, chemical bonding and elastic properties of amorphous B 6 O 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

  20. Adsorption study of copper (II) by chemically modified orange peel

    International Nuclear Information System (INIS)

    Feng Ningchuan; Guo Xueyi; Liang Sha

    2009-01-01

    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.

  1. [Chemical study on fruiting bodies of Boletus vioaceo-fuscus].

    Science.gov (United States)

    Ma, Bing-ji; Ruan, Yuan; Liu, Ji-kai

    2007-09-01

    To investigate the chemical constituents of Boletus vioaceo-fuscus. The compounds were isolated with column chromatography. The structures were determined by spectroscopic techniques. Six compounds were isolated from the fruiting bodies of Boletus vioaceo-fiuscus. They were identified as ergosta-5, 7, 22-triene-3beta-ol (1), dihydrofuran-2, 5-dione (2), (22E, 24R)-5alpha, 6alpha-epoxyergosta-8, 22-diene-3beta, 7alpha-diol (3), (22E, 24R)-5alpha, 6alpha-epoxyergosta-8 (14), 22-diene-3beta, 7alphadiol (4), cerebroside B (5) and adenosine (6), respectively. All the Compounds were obtained from the fruiting bodies of Boletus vioaceo-fiscus for the first time.

  2. Physico- chemical study of Ceratitis capitata rearing diet

    International Nuclear Information System (INIS)

    El Sghiri, Mohamed Ali; Maddouri Fakri

    2005-01-01

    The inhibition of the microbial growth in the rearing diet of ceratitis capitata made it possible to increase the productivity in pupae. The follow-up of the microbial load and the physicochemical parameters of the diets used with varous microbial inhibitors (potassium sorbate in combination with sodium benzoate with varous amounts, on the one hand, and of another share, nipagine in combination with sodium benzoate also with varous amounts) during a rearing of ceratitis capitata on the laboratory scale made it possible to select the diet D as being the most favorable diet. Indeed, a stability of the physico chemical parameters as well as a weak evolution of the microbial load are noted in this diet. (author). 16 refs

  3. Chemical effects in materials studies using Auger analysis

    International Nuclear Information System (INIS)

    Rye, R.R.

    1985-01-01

    Core-valence-valence Auger spectra (AES) afford a unique local view of valence electron structure. The direct involvement in the Auger process of both core and valence states means that the transition matrix element will have a large value only for that portion of the valence electron density which covers the same spatial extent as the core wave function. Thus, the information content of AES is local to the atomic site containing the initial core hole. Our approach in understanding the local information content of AES has been mainly experimental through the intercomparison of model systems, both molecular and solid. The use of molecules in this regard is particularly useful since the vast array of molecular species of known geometric and electronic structures allows one to both vary these properties in a systematic fashion to observe trends and to choose a molecule to probe a specific chemical question

  4. Studies of coupled chemical and catalytic coal conversion methods

    Energy Technology Data Exchange (ETDEWEB)

    Stock, L.M.

    1990-01-01

    This report concerns our research on base-catalyzed coal solubilization and a new approach for hydrogen addition. The work on base-catalyzed, chemical solubilization is continuing. this report is focused on the hydrogenation research. Specifically it deals with the use of arene chromium carbonyl complexes as reagents for the addition of dideuterium to coal molecules. In one phase of the work, he has established that the aromatic hydrocarbons in a representative coal liquid can be converted in very good yield to arene chromium carbonyl compounds. In a second phase of the work directly related to our objective of improved methods for catalytic hydrogenation, he has established that the aromatic constituents of the same coal liquid add dideuterium in the presence of added napththalene chromium carbonyl.

  5. Effects of sample injection amount and time-of-flight mass spectrometric detection dynamic range on metabolome analysis by high-performance chemical isotope labeling LC-MS.

    Science.gov (United States)

    Zhou, Ruokun; Li, Liang

    2015-04-06

    The effect of sample injection amount on metabolome analysis in a chemical isotope labeling (CIL) liquid chromatography-mass spectrometry (LC-MS) platform was investigated. The performance of time-of-flight (TOF) mass spectrometers with and without a high-dynamic-range (HD) detection system was compared in the analysis of (12)C2/(13)C2-dansyl labeled human urine samples. An average of 1635 ± 21 (n = 3) peak pairs or putative metabolites was detected using the HD-TOF-MS, compared to 1429 ± 37 peak pairs from a conventional or non-HD TOF-MS. In both instruments, signal saturation was observed. However, in the HD-TOF-MS, signal saturation was mainly caused by the ionization process, while in the non-HD TOF-MS, it was caused by the detection process. To extend the MS detection range in the non-HD TOF-MS, an automated switching from using (12)C to (13)C-natural abundance peaks for peak ratio calculation when the (12)C peaks are saturated has been implemented in IsoMS, a software tool for processing CIL LC-MS data. This work illustrates that injecting an optimal sample amount is important to maximize the metabolome coverage while avoiding the sample carryover problem often associated with over-injection. A TOF mass spectrometer with an enhanced detection dynamic range can also significantly increase the number of peak pairs detected. In chemical isotope labeling (CIL) LC-MS, relative metabolite quantification is done by measuring the peak ratio of a (13)C2-/(12)C2-labeled peak pair for a given metabolite present in two comparative samples. The dynamic range of peak ratio measurement does not need to be very large, as only subtle changes of metabolite concentrations are encountered in most metabolomic studies where relative metabolome quantification of different groups of samples is performed. However, the absolute concentrations of different metabolites can be very different, requiring a technique to provide a wide detection dynamic range to allow the detection of as

  6. Model reduction for dynamic real-time optimization of chemical processes

    NARCIS (Netherlands)

    Van den Berg, J.

    2005-01-01

    The value of models in process industries becomes apparent in practice and literature where numerous successful applications are reported. Process models are being used for optimal plant design, simulation studies, for off-line and online process optimization. For online optimization applications

  7. Quantum chemical studies on structural, vibrational, nonlinear optical properties and chemical reactivity of indigo carmine dye

    Science.gov (United States)

    El-Mansy, M. A. M.

    2017-08-01

    Structural and vibrational spectroscopic studies were performed on indigo carmine (IC) isomers using FT-IR spectral analysis along with DFT/B3LYP method utilizing Gaussian 09 software. GaussView 5 program has been employed to perform a detailed interpretation of vibrational spectra. Simulation of infrared spectra has led to an excellent overall agreement with the observed spectral patterns. Mulliken population analyses on atomic charges, MEP, HOMO-LUMO, NLO, first order hyperpolarizability and thermodynamic properties have been examined by (DFT/B3LYP) method with the SDD basis set level. Density of state spectra (DOS) were calculated using GaussSum 3 at the same level of theory. Molecular modeling approved that DOS Spectra are the most significant tools for differentiating between two IC isomers so far. Moreover, The IC isomers (cis-isomer) have shown an extended applicability for manufacturing both NLO and photovoltaic devices such as solar cells.

  8. Groundwater hydrology study of the Ames Chemical Disposal Site

    International Nuclear Information System (INIS)

    Stickel, T.

    1996-01-01

    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

  9. Study of blast wave overpressures using the computational fluid dynamics

    Directory of Open Access Journals (Sweden)

    M. L. COSTA NETO

    Full Text Available ABSTRACT The threats of bomb attacks by criminal organizations and accidental events involving chemical explosives are a danger to the people and buildings. Due the severity of these issues and the need of data required for a safety design, more research is required about explosions and shock waves. This paper presents an assessment of blast wave overpressures using a computational fluid dynamics software. Analyses of phenomena as reflection of shock waves and channeling effects were done and a comparison between numerical results and analytical predictions has been executed, based on the simulation on several models. The results suggest that the common analytical predictions aren’t accurate enough for an overpressure analysis in small stand-off distances and that poorly designed buildings may increase the shock wave overpressures due multiple blast wave reflections, increasing the destructive potential of the explosions.

  10. Plant-symbiotic fungi as chemical engineers: multi-genome analysis of the clavicipitaceae reveals dynamics of alkaloid loci.

    Directory of Open Access Journals (Sweden)

    Christopher L Schardl

    Full Text Available The fungal family Clavicipitaceae includes plant symbionts and parasites that produce several psychoactive and bioprotective alkaloids. The family includes grass symbionts in the epichloae clade (Epichloë and Neotyphodium species, which are extraordinarily diverse both in their host interactions and in their alkaloid profiles. Epichloae produce alkaloids of four distinct classes, all of which deter insects, and some-including the infamous ergot alkaloids-have potent effects on mammals. The exceptional chemotypic diversity of the epichloae may relate to their broad range of host interactions, whereby some are pathogenic and contagious, others are mutualistic and vertically transmitted (seed-borne, and still others vary in pathogenic or mutualistic behavior. We profiled the alkaloids and sequenced the genomes of 10 epichloae, three ergot fungi (Claviceps species, a morning-glory symbiont (Periglandula ipomoeae, and a bamboo pathogen (Aciculosporium take, and compared the gene clusters for four classes of alkaloids. Results indicated a strong tendency for alkaloid loci to have conserved cores that specify the skeleton structures and peripheral genes that determine chemical variations that are known to affect their pharmacological specificities. Generally, gene locations in cluster peripheries positioned them near to transposon-derived, AT-rich repeat blocks, which were probably involved in gene losses, duplications, and neofunctionalizations. The alkaloid loci in the epichloae had unusual structures riddled with large, complex, and dynamic repeat blocks. This feature was not reflective of overall differences in repeat contents in the genomes, nor was it characteristic of most other specialized metabolism loci. The organization and dynamics of alkaloid loci and abundant repeat blocks in the epichloae suggested that these fungi are under selection for alkaloid diversification. We suggest that such selection is related to the variable life histories

  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. Treatment Tank Corrosion Studies For The Enhanced Chemical Cleaning Process

    International Nuclear Information System (INIS)

    Wiersma, B.

    2011-01-01

    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

  13. Dynamics of polymers in a good solvent - a molecular dynamics study using the Connection Machine

    International Nuclear Information System (INIS)

    Shannon, S.R.; Choy, T.C.

    1996-01-01

    In recent times the use of molecular dynamics simulations has become an important tool in modelling and understanding the dynamics of interacting many-body systems. With recent advances in computing power it is now feasible to perform modelling of systems which contain a large number of interacting particles, and thus to simulate the behaviour of real systems reasonably. Our earlier discoveries of anomalous corrections to scaling behaviour of the Edward's polymer were applied to study the dynamical behaviour of two dimensional polymer systems - either a single chain immersed in a fluid, a pure polymer melt, or with any concentration of polymers in the fluid. By choosing a suitable interaction potential between the fluid particles and the monomers, we are able to study the experimentally observable time dependent structure factor of polymers in a good solvent. Simulations were performed using the Connection Machine CM5 supercomputer at the Australian National University which due to its fast multi- processor nearest neighbour communications facility, enables us to easily model large systems of at least 3000 fluid plus monomer particles. Our study is based on a finite difference solution of Newton's equations of motion i.e. the Verlet algorithm, and the results are used to test current theories of polymer dynamics, which were based primarily on the earlier models proposed by Rouse (1953) and Zimm (1956). In particular dynamical scaling predictions is scrutinised to examine the effects due to the anomalous corrections-to-scaling behaviour found in an earlier work using finite-size scaling analysis of Monte-Carlo data and now understood via a new perturbation concept

  14. Dynamic chemical communication between plants and bacteria through airborne signals: induced resistance by bacterial volatiles.

    Science.gov (United States)

    Farag, Mohamed A; Zhang, Huiming; Ryu, Choong-Min

    2013-07-01

    Certain plant growth-promoting rhizobacteria (PGPR) elicit induced systemic resistance (ISR) and plant growth promotion in the absence of physical contact with plants via volatile organic compound (VOC) emissions. In this article, we review the recent progess made by research into the interactions between PGPR VOCs and plants, focusing on VOC emission by PGPR strains in plants. Particular attention is given to the mechanisms by which these bacterial VOCs elicit ISR. We provide an overview of recent progress in the elucidation of PGPR VOC interactions from studies utilizing transcriptome, metabolome, and proteome analyses. By monitoring defense gene expression patterns, performing 2-dimensional electrophoresis, and studying defense signaling null mutants, salicylic acid and ethylene have been found to be key players in plant signaling pathways involved in the ISR response. Bacterial VOCs also confer induced systemic tolerance to abiotic stresses, such as drought and heavy metals. A review of current analytical approaches for PGPR volatile profiling is also provided with needed future developments emphasized. To assess potential utilization of PGPR VOCs for crop plants, volatile suspensions have been applied to pepper and cucumber roots and found to be effective at protecting plants against plant pathogens and insect pests in the field. Taken together, these studies provide further insight into the biological and ecological potential of PGPR VOCs for enhancing plant self-immunity and/or adaptation to biotic and abiotic stresses in modern agriculture.

  15. Study on the Flare Load Estimation of the Deethanizer using Dynamic Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Kyungtae; Won, Wangyun [GS EC, Seoul (Korea, Republic of); Shin, Dongil [Myongji University, Yongin (Korea, Republic of)

    2014-10-15

    A flare system is a very important system that crucially affects on the process safety in chemical plants. If a flare system is designed too small, it cannot prevent catastrophic accidents of a chemical plant. On the other hand, if a flare system is designed too large, it will waste resources. Therefore, reasonable relief load estimation has been a crucial issue in the industry. American Petroleum Institute (API) suggests basic guidelines for relief load estimation, and a lot of engineering companies have developed their own relief load estimation methods that use an unbalanced heat and material method. However, these methods have to involve lots of conservative assumptions that lead to an overestimation of relief loads. In this study, the new design procedure for a flare system based on dynamic simulation was proposed in order to avoid the overestimation of relief loads. The relief load of a deethanizer process was tested to verify the performance of the proposed design procedure.

  16. Role of quantitative and dynamic radioactive studies in renal testing

    International Nuclear Information System (INIS)

    Raynaud, C.

    1977-01-01

    Many dynamic and quantitative radioactive tests are at present used in studying renal function. Whether involving dynamic morphological tests such as sequential images, dynamic quantitative tests such as the renogram or quantitative static tests such as radioactive clearances, their effective and original contribution is rather unimportant. Only one provides original data, the Hg renal uptake test but it is generally avoided due to the radiation dose absorbed by the kidney in children. A study of the causes of this lack of effectiveness leads to the observation that such tests are not well adapted to the needs of kidneys specialists. They are for the most part based on replacing a 'cold' indicator by radioactive indicator and the advantages anticipated from using radionuclide are not evident. In fact, they are often cancelled by the shortcomings of external detection. For the future, it seems indispensable to abandon some traditional concepts which lead us to consider that the only exploitable renal function is represented by excretion. The kidney has other functions; one of the most interesting seems to be the function of uptake of heavy metals and toxic substances, a study of which is only possible using radionuclides. A new generation of radioactive tests based on a study of uptake and also on a study of other renal functions may provide dynamic or quantitative data which physician urgently need

  17. Combining NMR ensembles and molecular dynamics simulations provides more realistic models of protein structures in solution and leads to better chemical shift prediction

    International Nuclear Information System (INIS)

    Lehtivarjo, Juuso; Tuppurainen, Kari; Hassinen, Tommi; Laatikainen, Reino; Peräkylä, Mikael

    2012-01-01

    While chemical shifts are invaluable for obtaining structural information from proteins, they also offer one of the rare ways to obtain information about protein dynamics. A necessary tool in transforming chemical shifts into structural and dynamic information is chemical shift prediction. In our previous work we developed a method for 4D prediction of protein 1 H chemical shifts in which molecular motions, the 4th dimension, were modeled using molecular dynamics (MD) simulations. Although the approach clearly improved the prediction, the X-ray structures and single NMR conformers used in the model cannot be considered fully realistic models of protein in solution. In this work, NMR ensembles (NMRE) were used to expand the conformational space of proteins (e.g. side chains, flexible loops, termini), followed by MD simulations for each conformer to map the local fluctuations. Compared with the non-dynamic model, the NMRE+MD model gave 6–17% lower root-mean-square (RMS) errors for different backbone nuclei. The improved prediction indicates that NMR ensembles with MD simulations can be used to obtain a more realistic picture of protein structures in solutions and moreover underlines the importance of short and long time-scale dynamics for the prediction. The RMS errors of the NMRE+MD model were 0.24, 0.43, 0.98, 1.03, 1.16 and 2.39 ppm for 1 Hα, 1 HN, 13 Cα, 13 Cβ, 13 CO and backbone 15 N chemical shifts, respectively. The model is implemented in the prediction program 4DSPOT, available at http://www.uef.fi/4dspothttp://www.uef.fi/4dspot.

  18. Combining NMR ensembles and molecular dynamics simulations provides more realistic models of protein structures in solution and leads to better chemical shift prediction

    Energy Technology Data Exchange (ETDEWEB)

    Lehtivarjo, Juuso, E-mail: juuso.lehtivarjo@uef.fi; Tuppurainen, Kari; Hassinen, Tommi; Laatikainen, Reino [University of Eastern Finland, School of Pharmacy (Finland); Peraekylae, Mikael [University of Eastern Finland, Institute of Biomedicine (Finland)

    2012-03-15

    While chemical shifts are invaluable for obtaining structural information from proteins, they also offer one of the rare ways to obtain information about protein dynamics. A necessary tool in transforming chemical shifts into structural and dynamic information is chemical shift prediction. In our previous work we developed a method for 4D prediction of protein {sup 1}H chemical shifts in which molecular motions, the 4th dimension, were modeled using molecular dynamics (MD) simulations. Although the approach clearly improved the prediction, the X-ray structures and single NMR conformers used in the model cannot be considered fully realistic models of protein in solution. In this work, NMR ensembles (NMRE) were used to expand the conformational space of proteins (e.g. side chains, flexible loops, termini), followed by MD simulations for each conformer to map the local fluctuations. Compared with the non-dynamic model, the NMRE+MD model gave 6-17% lower root-mean-square (RMS) errors for different backbone nuclei. The improved prediction indicates that NMR ensembles with MD simulations can be used to obtain a more realistic picture of protein structures in solutions and moreover underlines the importance of short and long time-scale dynamics for the prediction. The RMS errors of the NMRE+MD model were 0.24, 0.43, 0.98, 1.03, 1.16 and 2.39 ppm for {sup 1}H{alpha}, {sup 1}HN, {sup 13}C{alpha}, {sup 13}C{beta}, {sup 13}CO and backbone {sup 15}N chemical shifts, respectively. The model is implemented in the prediction program 4DSPOT, available at http://www.uef.fi/4dspothttp://www.uef.fi/4dspot.

  19. Time-resolved resonance fluorescence spectroscopy for study of chemical reactions in laser-induced plasmas.

    Science.gov (United States)

    Liu, Lei; Deng, Leimin; Fan, Lisha; Huang, Xi; Lu, Yao; Shen, Xiaokang; Jiang, Lan; Silvain, Jean-François; Lu, Yongfeng

    2017-10-30

    Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al 2 O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al 2 O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O 2 chemistry in air.

  20. Computer simulation of chemical nucleation

    International Nuclear Information System (INIS)

    Turner, J.S.

    1979-01-01

    The problem of nucleation at chemical instabilities is investigated by means of microscopic computer simulation. The first-order transition of interest involves a new kind of nucleation arising from chemical transformations rather than physical forces. Here it is the chemical state of matter, and not matter itself, which is spatially localized to form the nucleus for transition between different chemical states. First, the concepts of chemical instability, nonequilibrium phase transition, and dissipative structure are reviewed briefly. Then recently developed methods of reactive molecular dynamics are used to study chemical nucleation in a simple model chemical reactions. Finally, the connection of these studies to nucleation and condensation processes involving physical and chemical interactions is explored. (orig.)