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Sample records for theoretical kinetic study

  1. Theoretical Studies Of Nucleation Kinetics And Nanodroplet Microstructure

    International Nuclear Information System (INIS)

    Wilemski, Gerald

    2009-01-01

    The goals of this project were to (1) explore ways of bridging the gap between fundamental molecular nucleation theories and phenomenological approaches based on thermodynamic reasoning, (2) test and improve binary nucleation theory, and (3) provide the theoretical underpinning for a powerful new experimental technique, small angle neutron scattering (SANS) from nanodroplet aerosols, that can probe the compositional structure of nanodroplets. This report summarizes the accomplishments of this project in realizing these goals. Publications supported by this project fall into three general categories: (1) theoretical work on nucleation theory (2) experiments and modeling of nucleation and condensation in supersonic nozzles, and (3) experimental and theoretical work on nanodroplet structure and neutron scattering. These publications are listed and briefly summarized in this report.

  2. Theoretical Studies in Chemical Kinetics - Annual Report, 1970.

    Science.gov (United States)

    Karplus, Martin

    1970-10-01

    The research performed includes (a) Alkali-Halide, Alkali-Halide (MX, M?X?) Exchange Reactions; (b) Inversion Problem; (c) Quantum Mechanics of Scattering Processes, (d) Transition State Analysis of Classical Trajectories, (e) Differential Cross Sections from Classical Trajectories; and (f) Other Studies.

  3. Size dependence of adsorption kinetics of nano-MgO: a theoretical and experimental study

    International Nuclear Information System (INIS)

    Wang, Shuting; Wen, Yanzhen; Cui, Zixiang; Xue, Yongqiang

    2016-01-01

    Nanoparticles present tremendous differences in adsorption kinetics compared with corresponding bulk particles which have great influences on the applications of nanoparticles. A size-dependent adsorption kinetic theory was proposed, the relations between adsorption kinetic parameters, respectively, and particle size of nano-adsorbent were derived theoretically, and the influence mechanism of particle size on the adsorption kinetic parameters was discussed. In experiment, nanoscale magnesium oxide (nano-MgO) with different diameters between 11.5 and 41.4 nm with narrow size distribution and low agglomeration were prepared, and the kinetic parameters of adsorption of benzene on nano-MgO in aqueous solution were obtained. Then the influence regularities of the particle size on the adsorption kinetic parameters were obtained. The experimental results are consistent with the nano-adsorption kinetic theory. With particle size decreasing, the adsorption rate constant increases; the adsorption activation energy and the adsorption pre-exponential factor decrease. Furthermore, the logarithm of adsorption rate constant, the adsorption activation energy, and the logarithm of adsorption pre-exponential factor are linearly related to the reciprocal of particle diameter, respectively. The mechanism of particle size influence on the kinetic parameters is that the activation energy is influenced by the molar surface enthalpy of nano-adsorbent, the pre-exponential factor by the molar surface entropy, and the rate constant by both the molar surface enthalpy and the molar surface entropy

  4. An experimental and theoretical kinetic study of the reaction of OH radicals with tetrahydrofuran

    KAUST Repository

    Giri, Binod

    2016-06-24

    Tetrahydrofuran (CHO, THF) and its alkylated derivatives of the cyclic ether family are considered to be promising future biofuels. They appear as important intermediates during the low-temperature oxidation of conventional hydrocarbon fuels and of heavy biofuels such as long-chain fatty acid methyl esters. The reaction of tetrahydrofuran with OH radicals was investigated in a shock tube, over a temperature range of 800-1340 K and at pressures near 1.5 bar. Hydroxyl radicals were generated by the rapid thermal decomposition of tert-butyl hydroperoxide, and a UV laser absorption technique was used to monitor the mole fraction of OH radicals. High-level CCSD(T)/cc-pV(D,T)Z//MP2/aug-cc-pVDZ quantum chemical calculations were performed to explore the chemistry of the THF+OH reaction system. Our calculations reveal that the THF+OH (R1) reaction proceeds via either direct or indirect H-abstraction from various sites, leading to the formation of tetrahydrofuran-2-yl (THF-R2) or tetrahydrofuran-3-yl (THF-R3) radicals and water. Theoretical kinetic analysis revealed that both channels are important under conditions relevant to combustion. To our knowledge, this is the first direct experimental and theoretical kinetic study of the reaction of tetrahydrofuran with OH radicals at high temperatures. The following theoretical rate expressions (in units of cmmols) are recommended for combustion modeling in the temperature range 800-1350 K: . k1(T)=4.11×1040.16em0ex(TK)2.69exp(1316.80.16em0exKT)2.em0ex0.16em0ex(THF+OH→Products) . k2(T)=6.930.16em0ex×10110.16em0ex(TK)0.41exp(-106.80.16em0exKT)2.em0ex0.16em0ex(THF+OH→THF-R20.16em0ex+H2O) . k3(T)=4.120.16em0ex×1030.16em0ex(TK)3.02exp(456.90.16em0exKT)2.em0ex0.16em0ex(THF+OH→THF-R30.16em0ex+H2O) . .

  5. Theoretical Kinetic Study of the Formic Acid Catalyzed Criegee Intermediate Isomerization: Multistructural Anharmonicity and Atmospheric Implications

    KAUST Repository

    Monge Palacios, Manuel

    2018-01-29

    We performed a theoretical study on the double hydrogen shift isomerization reaction of a six carbon atom Criegee intermediate (C6-CI), catalyzed by formic acid (HCOOH), to produce vinylhydroperoxide (VHP), C6-CI+HCOOH→VHP+HCOOH. This Criegee intermediate can serve as a surrogate for larger CIs derived from important volatile organic compounds like monoterpenes, whose reactivity is not well understood and are difficult to handle computationally. The reactant HCOOH exerts a pronounced catalytic effect on the studied reaction by lowering the barrier height, but the kinetic enhancement is hindered by the multistructural anharmonicity. First, the rigid ring-structure adopted by the saddle point to facilitate simultaneous transfer of two atoms does not allow formation of as many conformers as those formed by the reactant C6-CI. And second, the flexible carbon chain of C6-CI facilitates the formation of stabilizing intramolecular C–H···O hydrogen bonds; this stabilizing effect is less pronounced in the saddle point structure due to its tightness and steric effects. Thus, the contribution of the reactant C6-CI conformers to the multistructural partition function is larger than that of the saddle point conformers. The resulting low multistructural anharmonicity factor partially cancels out the catalytic effect of the carboxylic acid, yielding in a moderately large rate coefficient, k(298 K) = 4.9·10-13 cm3 molecule-1 s-1. We show that carboxylic acids may promote the conversion of stabilized Criegee intermediates into vinylhydroperoxides in the atmosphere, which generates OH radicals and leads to secondary organic aerosol, thereby affecting the oxidative capacity of the atmosphere and ultimately the climate.

  6. Theoretical study of thin metallic deposit layers: from electronic structure to kinetics

    International Nuclear Information System (INIS)

    Senhaji, Abdelali

    1993-01-01

    We have studied the relation between the equilibrium surface segregation in an alloy A c B 1-c and the kinetics of dissolution of a few metallic layers of A (or B) deposited on a B (or A) substrate. We used an energetic model derived from the electronic structure (T.B.I.M.) allowing us to study the surface segregation both in disordered and in ordered alloys. Moreover we have developed a kinetic model (K.T.B.I.M.) consistent with the TBIM energetic model to study the kinetics both of segregation and dissolution. This process has been applied to the Cu-Pt system for which Auger, LEED and photoemission experiments are in progress at L.U.R.E. Concerning the equilibrium surface segregation in the ordered state we have studied all the possible terminations for the (111) and (100) faces in the various ordered structures occurring on the F.C.C. lattice (L1 0 , L1 1 - L1 2 and L'). In particular we have determined the domain of (meta)stability of each termination, which is very useful to understand the competition between single and double steps in ordered alloys. Studying the kinetics of dissolution of a few layers of Cu (or Pt) deposited on the (111) or (100) face of a Pt (or Cu) substrate, we have shown the formation of surface compounds with a great variety of behaviours depending on the face or on the temperature. All these behaviours can be rationalized with the local equilibrium concept, which we have defined accurately within our model and which allows to connect the dissolution mode with the equilibrium segregation. (author) [fr

  7. Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Jorge, Nelly Lidia [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain); Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Romero, Jorge Marcelo [Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Grand, Andre [INAC, SCIB, Laboratoire ' Lesions des Acides Nucleiques' , UMR CEA-UJF E3, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Hernandez-Laguna, Alfonso, E-mail: ahlaguna@ugr.es [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain)

    2012-01-17

    Highlights: Black-Right-Pointing-Pointer Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. Black-Right-Pointing-Pointer Gas chromatography and computational potential energy surfaces were performed. Black-Right-Pointing-Pointer A mechanism in steps looked like the most probable mechanism. Black-Right-Pointing-Pointer A spin-orbit coupling appeared at the singlet and triple diradical open structures. Black-Right-Pointing-Pointer A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463-503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 {+-} 0.8 kcal/mol and 5.2 Multiplication-Sign 10{sup 13} s{sup -1}, respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G{sup Asterisk-Operator Asterisk-Operator} level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin-orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.

  8. Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms

    International Nuclear Information System (INIS)

    Jorge, Nelly Lidia; Romero, Jorge Marcelo; Grand, André; Hernández-Laguna, Alfonso

    2012-01-01

    Highlights: ► Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. ► Gas chromatography and computational potential energy surfaces were performed. ► A mechanism in steps looked like the most probable mechanism. ► A spin–orbit coupling appeared at the singlet and triple diradical open structures. ► A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463–503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 ± 0.8 kcal/mol and 5.2 × 10 13 s −1 , respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G ∗∗ level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin–orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.

  9. Study of hydrogen mobility by hydrogen-deuterium exchange. II. Theoretical kinetic study in alkyl and amino-alkyl pyrimidines

    International Nuclear Information System (INIS)

    Pompon, Alain

    1975-01-01

    Alkyl groups bound to the pyrimidine ring can be deuterium substituted on the carbon adjacent to the ring, in acidic D 2 O; kinetic equations corresponding to various exchange mechanism hypothesis are established. It is shown that theoretical and experimental results can be compared in order to precise the mechanism and to measure the characteristic parameters of the exchange reaction [fr

  10. Theoretical study of the reaction kinetics of atomic bromine with tetrahydropyran

    KAUST Repository

    Giri, Binod; Lo, John M H; Roscoe, John M.; Alquaity, Awad; Farooq, Aamir

    2015-01-01

    A detailed theoretical analysis of the reaction of atomic bromine with tetrahydropyran (THP, C5H10O) was performed using several ab initio methods and statistical rate theory calculations. Initial geometries of all species involved in the potential

  11. Theoretical and experimental study demonstrates kinetic control in chalcone-flavanone transformation of naphthalene derivatives

    Science.gov (United States)

    Gasque, Laura; Álvarez-Idaboy, J. Raul; Flores-Álamo, Marcos; Guzmán-Méndez, Óscar; Campos-Cerón, Juan M.

    2018-04-01

    The condensation of 1‧-hydroxy-2‧-acetonaphthone with 1- or 2-naphthaldehyde produced the corresponding stable chalcones: C1 or C2. However, the condensation product of either naphthaldehyde with 2‧-hydroxy-1‧-acetonaphthone yielded chalcones that convert to flavanones- F1 and F2- upon recrystallization. Crystal structures for C1, F1 and F2 are described. Transition state theory estimated rate constants, based on the calculated DFT M052X/6-311 + G(d,p) Gibbs Free energies, show that the rate delimiting step is the cyclization of the chalconate in protic polar solvent. The thermodynamically preferred product is always the flavanone, therefore, the yielding of one or other product is kinetically controlled.

  12. Kinetic Adsorption Study of Silver Nanoparticles on Natural Zeolite: Experimental and Theoretical Models

    Directory of Open Access Journals (Sweden)

    Alvaro Ruíz-Baltazar

    2015-12-01

    Full Text Available In this research, the adsorption capacity of Ag nanoparticles on natural zeolite from Oaxaca is presented. In order to describe the adsorption mechanism of silver nanoparticles on zeolite, experimental adsorption models for Ag ions and Ag nanoparticles were carried out. These experimental data obtained by the atomic absorption spectrophotometry technique were compared with theoretical models such as Lagergren first-order, pseudo-second-order, Elovich, and intraparticle diffusion. Correlation factors R2 of the order of 0.99 were observed. Analysis by transmission electron microscopy describes the distribution of the silver nanoparticles on the zeolite outer surface. Additionally, a chemical characterization of the material was carried out through a dilution process with lithium metaborate. An average value of 9.3 in the Si/Al ratio was observed. Factors such as the adsorption behavior of the silver ions and the Si/Al ratio of the zeolite are very important to support the theoretical models and establish the adsorption mechanism of Ag nanoparticles on natural zeolite.

  13. A theoretical and shock tube kinetic study on hydrogen abstraction from phenyl formate.

    Science.gov (United States)

    Ning, Hongbo; Liu, Dapeng; Wu, Junjun; Ma, Liuhao; Ren, Wei; Farooq, Aamir

    2018-06-12

    The hydrogen abstraction reactions of phenyl formate (PF) by different radicals (H/O(3P)/OH/HO2) were theoretically investigated. We calculated the reaction energetics for PF + H/O/OH using the composite method ROCBS-QB3//M06-2X/cc-pVTZ and that for PF + HO2 at the M06-2X/cc-pVTZ level of theory. The high-pressure limit rate constants were calculated using the transition state theory in conjunction with the 1-D hindered rotor approximation and tunneling correction. Three-parameter Arrhenius expressions of rate constants were provided over the temperature range of 500-2000 K. To validate the theoretical calculations, the overall rate constants of PF + OH → Products were measured in shock tube experiments at 968-1128 K and 1.16-1.25 atm using OH laser absorption. The predicted overall rate constants agree well with the shock tube data (within 15%) over the entire experimental conditions. Rate constant analysis indicates that the H-abstraction at the formic acid site dominates the PF consumption, whereas the contribution of H-abstractions at the aromatic ring increases with temperature. Additionally, comparisons of site-specific H-abstractions from PF with methyl formate, ethyl formate, benzene, and toluene were performed to understand the effects of the aromatic ring and side-chain substituent on H-abstraction rate constants.

  14. Theoretical Study of the Kinetics of the Pyrolytic Elimination Reaction of Ethyl Chloride

    Directory of Open Access Journals (Sweden)

    Isaiah Ajibade Adejoro

    2010-01-01

    Full Text Available The products of the gas-phase elimination of ethyl chloride are hydrogen chloride and ethane. Using AM1, MNDO and PM3 Hamiltonians of quantum mechanical computer code called MOPAC, a procedure for the kinetics and computation of the Arrhenius parameters for the pyrolytic elimination reaction of ethyl chloride was devised in order to evaluate the predictive ability of the three Hamiltonians used. The first-order rate coefficient for the three Hamiltonians are 1.15x10-8s-1, 4.55x10-15s-1 and 5.36x10-4s-1 for AM1, MNDO and PM3 respectively. The results obtained showed that the rate constant for the computed Arrhenius parameters compare well with the experimental values in the literature, thus showing that the computational procedure adequately simulates experimental results; also the semi-empirical AMI calculation has the best predictive ability with experiment followed by PM3 while MNDO has the least.

  15. Theoretical study of the reaction kinetics of atomic bromine with tetrahydropyran

    KAUST Repository

    Giri, Binod

    2015-02-12

    A detailed theoretical analysis of the reaction of atomic bromine with tetrahydropyran (THP, C5H10O) was performed using several ab initio methods and statistical rate theory calculations. Initial geometries of all species involved in the potential energy surface of the title reaction were obtained at the B3LYP/cc-pVTZ level of theory. These molecular geometries were reoptimized using three different meta-generalized gradient approximation (meta-GGA) functionals. Single-point energies of the stationary points were obtained by employing the coupled-cluster with single and double excitations (CCSD) and fourth-order Møller-Plesset (MP4 SDQ) levels of theory. The computed CCSD and MP4(SDQ) energies for optimized structures at various DFT functionals were found to be consistent within 2 kJ mol-1. For a more accurate energetic description, single-point calculations at the CCSD(T)/CBS level of theory were performed for the minimum structures and transition states optimized at the B3LYP/cc-pVTZ level of theory. Similar to other ether + Br reactions, it was found that the tetrahydropyran + Br reaction proceeds in an overall endothermic addition-elimination mechanism via a number of intermediates. However, the reactivity of various ethers with atomic bromine was found to vary substantially. In contrast with the 1,4-dioxane + Br reaction, the chair form of the addition complex (c-C5H10O-Br) for THP + Br does not need to undergo ring inversion to form a boat conformer (b-C4H8O2-Br) before the intramolecular H-shift can occur to eventually release HBr. Instead, a direct, yet more favorable route was mapped out on the potential energy surface of the THP + Br reaction. The rate coefficients for all relevant steps involved in the reaction mechanism were computed using the energetics of coupled cluster calculations. On the basis of the results of the CCSD(T)/CBS//B3LYP/cc-pVTZ level of theory, the calculated overall rate coefficients can be expressed as kov.,calc.(T) = 4.60 × 10

  16. A combined high-temperature experimental and theoretical kinetic study of the reaction of dimethyl carbonate with OH radicals

    KAUST Repository

    Khaled, Fathi; Giri, Binod; Szőri, Milá n; Mai, Tam V.-T.; Huynh, Lam K.; Farooq, Aamir

    2017-01-01

    The reaction kinetics of dimethyl carbonate (DMC) and OH radicals were investigated behind reflected shock waves over the temperature range of 872-1295 K and at pressures near 1.5 atm. Reaction progress was monitored by detecting OH radicals at 306.69 nm using a UV laser absorption technique. The rate coefficients for the reaction of DMC with OH radicals were extracted using a detailed kinetic model developed by Glaude et al. (Proc. Combust. Inst. 2005, 30(1), 1111-1118). The experimental rate coefficients can be expressed in Arrhenius form as: kexpt'l = 5.15 × 10(13) exp(-2710.2/T) cm(3) mol(-1) s(-1). To explore the detailed chemistry of the DMC + OH reaction system, theoretical kinetic analyses were performed using high-level ab initio and master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) calculations. Geometry optimization and frequency calculations were carried out at the second-order Møller-Plesset (MP2) perturbation level of theory using Dunning's augmented correlation consistent-polarized valence double-ζ basis set (aug-cc-pVDZ). The energy was extrapolated to the complete basis set using single point calculations performed at the CCSD(T)/cc-pVXZ (where X = D, T) level of theory. For comparison purposes, additional ab initio calculations were also carried out using composite methods such as CBS-QB3, CBS-APNO, G3 and G4. Our calculations revealed that the H-abstraction reaction of DMC by OH radicals proceeds via an addition elimination mechanism in an overall exothermic process, eventually forming dimethyl carbonate radicals and H2O. Theoretical rate coefficients were found to be in excellent agreement with those determined experimentally. Rate coefficients for the DMC + OH reaction were combined with literature rate coefficients of four straight chain methyl ester + OH reactions to extract site-specific rates of H-abstraction from methyl esters by OH radicals.

  17. Field-theoretic calculation of kinetic helicity flux

    Indian Academy of Sciences (India)

    Given all these practical aspects, kinetic helicity is an important quantity to study in fluid turbulence. Turbulence involves millions of interacting modes. It is very difficult to analyze these modes theoretically as well as numerically. In recent times, a new numeri- cal procedure called 'large eddy simulations' (LES) has become ...

  18. A combined high-temperature experimental and theoretical kinetic study of the reaction of dimethyl carbonate with OH radicals

    KAUST Repository

    Khaled, Fathi

    2017-02-08

    The reaction kinetics of dimethyl carbonate (DMC) and OH radicals were investigated behind reflected shock waves over the temperature range of 872-1295 K and at pressures near 1.5 atm. Reaction progress was monitored by detecting OH radicals at 306.69 nm using a UV laser absorption technique. The rate coefficients for the reaction of DMC with OH radicals were extracted using a detailed kinetic model developed by Glaude et al. (Proc. Combust. Inst. 2005, 30(1), 1111-1118). The experimental rate coefficients can be expressed in Arrhenius form as: kexpt\\'l = 5.15 × 10(13) exp(-2710.2/T) cm(3) mol(-1) s(-1). To explore the detailed chemistry of the DMC + OH reaction system, theoretical kinetic analyses were performed using high-level ab initio and master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) calculations. Geometry optimization and frequency calculations were carried out at the second-order Møller-Plesset (MP2) perturbation level of theory using Dunning\\'s augmented correlation consistent-polarized valence double-ζ basis set (aug-cc-pVDZ). The energy was extrapolated to the complete basis set using single point calculations performed at the CCSD(T)/cc-pVXZ (where X = D, T) level of theory. For comparison purposes, additional ab initio calculations were also carried out using composite methods such as CBS-QB3, CBS-APNO, G3 and G4. Our calculations revealed that the H-abstraction reaction of DMC by OH radicals proceeds via an addition elimination mechanism in an overall exothermic process, eventually forming dimethyl carbonate radicals and H2O. Theoretical rate coefficients were found to be in excellent agreement with those determined experimentally. Rate coefficients for the DMC + OH reaction were combined with literature rate coefficients of four straight chain methyl ester + OH reactions to extract site-specific rates of H-abstraction from methyl esters by OH radicals.

  19. Theoretical Kinetic Study of the Unimolecular Keto–Enol Tautomerism Propen-2-ol ↔ Acetone. Pressure Effects and Implications in the Pyrolysis of tert- and 2-Butanol

    KAUST Repository

    Grajales Gonzalez, Edwing

    2018-03-21

    The need for renewable and cleaner sources of energy has made biofuels an interesting alternative to fossil fuels, especially in the case of butanol isomers, with its favorable blend properties and low hygroscopicity. Although C4 alcohols are prospective fuels, some key reactions governing their pyrolysis and combustion have not been adequately studied, leading to incomplete kinetic models. Enols are important intermediates in the combustion of C4 alcohols, as well as in atmospheric processes. Butanol reactions kinetics is poorly understood. Specifically, the unimolecular tautomerism of propen-2-ol ↔ acetone, which is included in butanol combustion kinetic models, is assigned rate parameters based on the tautomerism vinyl alcohol ↔ acetaldehyde as an analogy. In an attempt to update current kinetic models for tert- and 2-butanol, a theoretical kinetic study of the titled reaction was carried out by means of CCSD(T,FULL)/aug-cc-pVTZ//CCSD(T)/6-31+G(d,p) ab initio calculations, with multistructural torsional anharmonicity and variational transition state theory considerations in a wide temperature and pressure range (200-3000 K; 0.1-108 kPa). Results differ from vinyl alcohol ↔ acetaldehyde analogue reaction, which shows lower rate constant values. It was observed that decreasing pressure leads to a decrease in rate constants, describing the expected falloff behavior. Tunneling turned out to be important, especially at low temperatures. Accordingly, pyrolysis simulations in a batch reactor for tert- and 2-butanol with computed rate constants showed important differences in comparison with previous results, such as larger acetone yield and quicker propen-2-ol consumption.

  20. Theoretical Kinetic Study of the Unimolecular Keto–Enol Tautomerism Propen-2-ol ↔ Acetone. Pressure Effects and Implications in the Pyrolysis of tert- and 2-Butanol

    KAUST Repository

    Grajales Gonzalez, Edwing Javier; Monge Palacios, Manuel; Sarathy, Mani

    2018-01-01

    The need for renewable and cleaner sources of energy has made biofuels an interesting alternative to fossil fuels, especially in the case of butanol isomers, with its favorable blend properties and low hygroscopicity. Although C4 alcohols are prospective fuels, some key reactions governing their pyrolysis and combustion have not been adequately studied, leading to incomplete kinetic models. Enols are important intermediates in the combustion of C4 alcohols, as well as in atmospheric processes. Butanol reactions kinetics is poorly understood. Specifically, the unimolecular tautomerism of propen-2-ol ↔ acetone, which is included in butanol combustion kinetic models, is assigned rate parameters based on the tautomerism vinyl alcohol ↔ acetaldehyde as an analogy. In an attempt to update current kinetic models for tert- and 2-butanol, a theoretical kinetic study of the titled reaction was carried out by means of CCSD(T,FULL)/aug-cc-pVTZ//CCSD(T)/6-31+G(d,p) ab initio calculations, with multistructural torsional anharmonicity and variational transition state theory considerations in a wide temperature and pressure range (200-3000 K; 0.1-108 kPa). Results differ from vinyl alcohol ↔ acetaldehyde analogue reaction, which shows lower rate constant values. It was observed that decreasing pressure leads to a decrease in rate constants, describing the expected falloff behavior. Tunneling turned out to be important, especially at low temperatures. Accordingly, pyrolysis simulations in a batch reactor for tert- and 2-butanol with computed rate constants showed important differences in comparison with previous results, such as larger acetone yield and quicker propen-2-ol consumption.

  1. Borosilicate nuclear waste glass alteration kinetics theoretical basis for the kinetic law of nuclear glass alteration

    International Nuclear Information System (INIS)

    Jegou, Ch.; Gin, St.; Advocat, Th.; Vernaz, E.

    1997-01-01

    Work carried out since the early 1980's to predict the long-term behavior of nuclear containment glasses has revealed the inadequacy of existing models, notably in accounting for the fundamental mechanisms involved in some complex systems (e.g. glass-water-clay), inciting us to examine and discuss the theoretical basis for the hypotheses generally assumed in our models. This paper discusses the theoretical basis for the Aagaard-Helgeson law and its application to nuclear glasses. The contribution of other types of kinetic laws is also considered to describe the alteration kinetics of nuclear glasses. (authors)

  2. An Experimental and Theoretical Study on the Kinetic Isotope Effect of C2H6 and C2D6 Reaction with OH

    KAUST Repository

    Khaled, Fathi; Giri, Binod; Szőri, Milá n; Viskolcz, Bé la; Farooq, Aamir

    2015-01-01

    We report experimental and theoretical results for the deuterated kinetic isotope effect (DKIE) of the reaction of OH with ethane (C2H6) and deuterated ethane (C2D6). The reactions were investigated behind reflected shock waves over 800–1350 K by monitoring OH radicals near 306.69 nm using laser absorption. In addition, high level CCSD(T)/cc-pV(T,Q)Z//MP2/cc-pVTZ quantum chemical and statistical rate theory calculations were performed which agreed very well with the experimental findings. The results reported herein provide the first experimental evidence that DKIE for alkanes asymptotes to a value of 1.4 at high temperatures.

  3. An Experimental and Theoretical Study on the Kinetic Isotope Effect of C2H6 and C2D6 Reaction with OH

    KAUST Repository

    Khaled, Fathi

    2015-10-30

    We report experimental and theoretical results for the deuterated kinetic isotope effect (DKIE) of the reaction of OH with ethane (C2H6) and deuterated ethane (C2D6). The reactions were investigated behind reflected shock waves over 800–1350 K by monitoring OH radicals near 306.69 nm using laser absorption. In addition, high level CCSD(T)/cc-pV(T,Q)Z//MP2/cc-pVTZ quantum chemical and statistical rate theory calculations were performed which agreed very well with the experimental findings. The results reported herein provide the first experimental evidence that DKIE for alkanes asymptotes to a value of 1.4 at high temperatures.

  4. Kinetic and theoretical studies of novel biodegradable thermo-sensitive xerogels based on PEG/PVP/silica for sustained release of enrofloxacin

    Science.gov (United States)

    Ebadi, Azra; Rafati, Amir Abbas; Bavafa, Sadeghali; Mohammadi, Masoumah

    2017-12-01

    This study involves the synthesis of a new silica-based colloidal hybrid system. In this new hybrid system, poly (ethylene glycol) (PEG) and thermo-sensitive amphiphilic biocompatible poly (vinyl pyrrolidone) (PVP) were used to create suitable storage for hydrophobic drugs. The possibility of using variable PVP/PEG molar ratios to modulate drug release rate from silica nanoparticles was a primary goal of the current research. In addition, an investigation of the drug release kinetic was conducted. To achieve this, silica nanoparticles were synthesized in poly (ethylene glycol) (PEG) and poly (vinyl pyrrolidone) (PVP) solution incorporated with enrofloxacin (EFX) (as a model hydrophobic drug), using a simple synthetic strategy of hybrid materials which avoided waste and multi-step processes. The impacts of PVP/PEG molar ratios, temperature, and pH of the release medium on release kinetic were investigated. The physicochemical properties of the drug-loaded composites were studied by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). In vitro drug release studies demonstrated that the drug release rate, which was evaluated by analyzing the experimental data with seven kinetic models in a primarily non-Fickian diffusion-controlled process, aligned well with both Ritger-Peppas and Sahlin-Peppas equations.

  5. Torsional energy levels of CH3OH+/CH3OD+/CD3OD+ studied by zero-kinetic energy photoelectron spectroscopy and theoretical calculations

    International Nuclear Information System (INIS)

    Dai, Zuyang; Gao, Shuming; Wang, Jia; Mo, Yuxiang

    2014-01-01

    The torsional energy levels of CH 3 OH + , CH 3 OD + , and CD 3 OD + have been determined for the first time using one-photon zero kinetic energy photoelectron spectroscopy. The adiabatic ionization energies for CH 3 OH, CH 3 OD, and CD 3 OD are determined as 10.8396, 10.8455, and 10.8732 eV with uncertainties of 0.0005 eV, respectively. Theoretical calculations have also been performed to obtain the torsional energy levels for the three isotopologues using a one-dimensional model with approximate zero-point energy corrections of the torsional potential energy curves. The calculated values are in good agreement with the experimental data. The barrier height of the torsional potential energy without zero-point energy correction was calculated as 157 cm −1 , which is about half of that of the neutral (340 cm −1 ). The calculations showed that the cation has eclipsed conformation at the energy minimum and staggered one at the saddle point, which is the opposite of what is observed in the neutral molecule. The fundamental C–O stretch vibrational energy level for CD 3 OD + has also been determined. The energy levels for the combinational excitation of the torsional vibration and the fundamental C–O stretch vibration indicate a strong torsion-vibration coupling

  6. Torsional energy levels of CH₃OH⁺/CH₃OD⁺/CD₃OD⁺ studied by zero-kinetic energy photoelectron spectroscopy and theoretical calculations.

    Science.gov (United States)

    Dai, Zuyang; Gao, Shuming; Wang, Jia; Mo, Yuxiang

    2014-10-14

    The torsional energy levels of CH3OH(+), CH3OD(+), and CD3OD(+) have been determined for the first time using one-photon zero kinetic energy photoelectron spectroscopy. The adiabatic ionization energies for CH3OH, CH3OD, and CD3OD are determined as 10.8396, 10.8455, and 10.8732 eV with uncertainties of 0.0005 eV, respectively. Theoretical calculations have also been performed to obtain the torsional energy levels for the three isotopologues using a one-dimensional model with approximate zero-point energy corrections of the torsional potential energy curves. The calculated values are in good agreement with the experimental data. The barrier height of the torsional potential energy without zero-point energy correction was calculated as 157 cm(-1), which is about half of that of the neutral (340 cm(-1)). The calculations showed that the cation has eclipsed conformation at the energy minimum and staggered one at the saddle point, which is the opposite of what is observed in the neutral molecule. The fundamental C-O stretch vibrational energy level for CD3OD(+) has also been determined. The energy levels for the combinational excitation of the torsional vibration and the fundamental C-O stretch vibration indicate a strong torsion-vibration coupling.

  7. Theoretical study on the mechanism and kinetics of the reaction of 2,2‧,4,4‧-tetrabrominated diphenyl ether (BDE-47) with OH radicals

    Science.gov (United States)

    Cao, Haijie; He, Maoxia; Han, Dandan; Sun, Yanhui; Xie, Ju

    2011-03-01

    The mechanism and kinetic properties of OH-initiated gas-phase reaction of 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) have been studied at the MPWB1K/6-311 + G(3df,2p)//MPWB1K/6-31G(d) level of theory. Two types of reactions including hydroxyl addition and hydrogen abstraction have been considered. The calculation results indicate that addition reactions except for the bromo-substituted addition reaction have lower energy barriers than hydrogen abstraction reactions. Hydroxyl radical is most likely to be added to non-substituted C atoms (C(3), C(5), and C(6) atoms). Moreover, for all the reactions with OH radical, the bromo-substituted C atoms encountered the highest barrier compared to that of the rest C atoms. The rate constants and product branching ratios of each pathway have been deduced over a wide range of 200-1000 K using canonical variational transition state (CVT) theory with small curvature tunneling (SCT) contribution. This study can be regarded as an attempt to investigate the OH-initiated photochemical reaction mechanism of polybrominated diphenyl ethers (PBDEs).

  8. Ab Initio Theoretical Studies on the Kinetics of Hydrogen Abstraction Type Reactions of Hydroxyl Radicals with CH3CCl2F and CH3CClF2

    Science.gov (United States)

    Saheb, Vahid; Maleki, Samira

    2018-03-01

    The hydrogen abstraction reactions from CH3Cl2F (R-141b) and CH3CClF2 (R-142b) by OH radicals are studied theoretically by semi-classical transition state theory. The stationary points for the reactions are located by using KMLYP density functional method along with 6-311++G(2 d,2 p) basis set and MP2 method along with 6-311+G( d, p) basis set. Single-point energy calculations are performed by the CBS-Q and G4 combination methods on the geometries optimized at the KMLYP/6-311++G(2 d,2 p) level of theory. Vibrational anharmonicity coefficients, x ij , which are needed for semi-classical transition state theory calculations, are computed at the KMLYP/6-311++G(2 d,2 p) and MP2/6-311+G( d, p) levels of theory. The computed barrier heights are slightly sensitive to the quantum-chemical method. Thermal rate coefficients are computed over the temperature range from 200 to 2000 K and they are shown to be in accordance with available experimental data. On the basis of the computed rate coefficients, the tropospheric lifetime of the CH3CCl2F and CH3CClF2 are estimated to be about 6.5 and 12.0 years, respectively.

  9. 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.

  10. Theoretical Kinetic Study of the Unimolecular and H-Assisted Keto-Enol Tautomerism Propen-2-ol ↔Acetone. Pressure Effects and Implications in the Pyrolysis and Oxidation of tert- And 2-Butanol

    KAUST Repository

    Grajales Gonzalez, Edwing Javier

    2018-05-01

    The need for renewable and cleaner sources of energy has made biofuels an interesting alternative to fossil fuels, especially in the case of butanol isomers, with their favorable blend properties and low hygroscopicity. Although C4 alcohols are prospective fuels, some key reactions governing their pyrolysis and combustion have not been adequately studied, leading to incomplete kinetic models. Butanol reactions kinetics is poorly understood. Specifically, the unimolecular and H-assisted tautomerism of propen-2-ol to acetone, which are included in butanol combustion kinetic models, are assigned rate parameters based on the analogous unimolecular tautomerism vinyl alcohol ↔ acetaldehyde and H addition to the double bound of iso-butene, respectively. In an attempt to update current kinetic models for tert- and 2-butanol, a theoretical kinetic study of the unimolecular and H-assisted tautomerism, i-C3H5OH⟺CH3COCH3 and i-C3H5OH+Ḣ⟺CH3COCH3+Ḣ, was carried out by means of CCSD(T,FULL)/aug-cc-pVTZ//CCSD(T)/6-31+G(d,p) and CCSD(T)/aug-cc-pVTZ//M062X/cc-pVTZ ab initio calculations, respectively. For H-assisted tautomerism, the reaction takes place in two consecutive steps: i-C3H5OH+Ḣ⟺CH3ĊOHCH3 and CH3ĊOHCH3⟺CH3COCH3+Ḣ. Multistructural torsional anharmonicity and variational transition state theory were considered in a wide temperature and pressure range (200 K – 3000 K, 0.1 kPa – 108 kPa). It was observed that decreasing pressure leads to a decrease in rate constants, describing the expected falloff behavior for both isomerizations. Results for unimolecular tautomerism differ from vinyl alcohol ↔ acetaldehyde analogue reactions, which shows lower rate constant values. Tunneling turned out to be important, especially at low temperatures. Accordingly, pyrolysis simulations in a batch reactor for tert- and 2-butanol with computed unimolecular rate constants showed important differences in comparison with previous results, such as larger acetone yield and

  11. Kinetic study on Iranian furfural extract hydrocracking

    Energy Technology Data Exchange (ETDEWEB)

    Zarkesh, J.; Akbarnejad, M. M. [NIOC Research Institute of Petroleum Industry, Tehran (Iran, Islamic Republic of); Khorasheh, F. [Sharif Univ. of Technology, Tehran (Iran, Islamic Republic of); Badakhshan, A. [Calgary Univ., AB (Canada)

    1998-05-01

    Upgrading heavy crude oil to light crude oil is one of the most important refining processes. Familiarity with the kinetics and related kinetic models is one of the important aspects of developing expertise in this field. This joint study between the NIOC Institute of Research of the Petroleum Industry and Sharif University was undertaken to determine the most appropriate upgrading process for Iranian heavy feed stock and to predict the conversion and product distribution in commercial hydrocracking units. The study involved the evaluation of stoichiometry of the hydrocracking process, focusing on the catalytic hydrocracking of furfural extract (a by-product of the lubricating oil plant) of the Tehran refinery. A pilot plant reactor was used. Good correspondence between model predictions and theoretical values was obtained.

  12. Studies of combustion kinetics and mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Gutman, D. [Catholic Univ. of America, Washington, DC (United States)

    1993-12-01

    The objective of the current research is to gain new quantitative knowledge of the kinetics and mechanisms of polyatomic free radicals which are important in hydrocarbon combustion processes. The special facility designed and built for these (which includes a heatable tubular reactor coupled to a photoionization mass spectrometer) is continually being improved. Where possible, these experimental studies are coupled with theoretical ones, sometimes conducted in collaboration with others, to obtain an improved understanding of the factors determining reactivity. The decomposition of acetyl radicals, isopropyl radicals, and n-propyl radicals have been studied as well as the oxidation of methylpropargyl radicals.

  13. Study on platelet kinetics

    International Nuclear Information System (INIS)

    Yui, Tokuo

    1981-01-01

    Fundamental study: Factors influencing the labeling on human platelets were evaluated and optimal labeling conditions were chosen. Then, platelet survival times were measured and organ distribution of labeled platelets was observed in rat by four different methods. These results were compared with each other. Based on the findings of those studies, the protocol of human platelet labeling with 111 In-oxine for clinical use was established. Clinical study: In normal cases, a platelet survival time and a platelet turnover rate were quite similar to the results from 51 Cr method. In gamma camera imaging, a radioactivity on the heart decreased with the lapse of time, while that on the spleen and liver gradually increased. In patients with idiopathic thrombocytopenic purpura, platelet survival time was markedly shortened and both a platelet turnover rate and an effective production increased. In patient with congestive splenomegaly, a platelet survival time was normal, whereas a platelet pooling on the spleen markedly increased. In patients who were implanted dacron-graft for abdominal aortic aneurysm, a radioactivity accumulated to the graft and a platelet survival time shortened. In a patient with myocardial infarction, the camera imaging clearly showed the thrombus in the left ventricular aneurysm. In three patients with mitral stenosis, thrombi in left atrium were observed at the camera images. Imaging of a platelet distribution and measurement of platelet survival time using 111 In-oxine labeled platelets are considered to be an excellent method for the diagnosis and decision of treatment on various disorders with thrombocytopenia and thrombosis. (J.P.N.)

  14. 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.

  15. THEORETICAL RESEARCH ON THE MULTI-CHANNEL REACTION MECHANISM AND KINETICS OF HNCS WITH OH-

    Directory of Open Access Journals (Sweden)

    Li-Jie Hou

    Full Text Available We presented a theoretical study on the detailed reaction mechanism and kinetics of the HNCS molecule with the OH-. The barrierless minimum energy path and the most favorable entrance channel have been determined by study the thermodynamic and kinetic characters of the channel with low energy barrier. The B3LYP/6-311++G** method was employed for all the geometrical optimizations and a multi-level extrapolation method based on the G3 energies was employed for further energy refinements. In addition, the analysis of the combining interaction between hydroxide ion and HNCS was performed by natural bond orbitals (NBO analysis. The calculation results indicated that the reaction of OH- with HNCS had four channels, and the channel of H-atom in HNCS direct extraction to OH- (OH-+HNCS→IM1→TS3→IM4→P2(SCN- +H2O in singlet state was the main channel with the low potential energy and high equilibrium constant and reaction rate constant. SCN- and H2O were main products.

  16. THEORETICAL ASPECTS OF FILMMUSIC STUDY

    Directory of Open Access Journals (Sweden)

    Egorova Tatiana K.

    2014-04-01

    Full Text Available In this article, author analyzes the theoretical aspects of the film music study taking into account with modern realities in the development of world film-process and attempts to its scientific understanding. Need for innovation in this area is long overdue, because the existing on this topic nonfiction no longer meets the new aesthetic and art-practical achievements and innovations in the film music development at the XXI century. Related to the phenomenon of music in screen arts a number of new terms and concepts require a certain adjustment as well. Their range of action is not yet fully defined. Author of the article offered her version of their content-semantic interpretation (largely experimental designed to promote new research methods for the film music study.

  17. Diffusion in liquids a theoretical and experimental study

    CERN Document Server

    Tyrrell, H J V

    1984-01-01

    Diffusion in Liquids: A Theoretical and Experimental Study aims to discuss the principles, applications, and advances in the field of diffusion, thermal diffusion, and thermal conduction in liquid systems. The book covers topics such as the principles of non-equilibrium thermodynamics; diffusion in binary and multicompetent systems; and experimental methods of studying diffusion processes in liquids. Also covered in the book are topics such as the theoretical interpretations of diffusion coefficients; hydrodynamic and kinetic theories; and diffusion in electrolyte systems. The text is recommen

  18. Dual-Mode Measurement and Theoretical Analysis of Evaporation Kinetics of Binary Mixtures

    Science.gov (United States)

    Song, Hanyu; He, Chi-Ruei; Basdeo, Carl; Li, Ji-Qin; Ye, Dezhuang; Kalonia, Devendra; Li, Si-Yu; Fan, Tai-Hsi

    Theoretical and experimental investigations are presented for the precision measurement of evaporation kinetics of binary mixtures using a quartz crystal resonator. A thin layer of light alcohol mixture including a volatile (methanol) and a much less volatile (1-butanol) components is deployed on top of the resonator. The normal or acoustic mode is to detect the moving liquid-vapor interface due to evaporation with a great spatial precision on the order of microns, and simultaneously the shear mode is used for in-situ detection of point viscosity or concentration of the mixture near the resonator. A one-dimensional theoretical model is developed to describe the underlying mass transfer and interfacial transport phenomena. Along with the modeling results, the transient evaporation kinetics, moving interface, and the stratification of viscosity of the liquid mixture during evaporation are simultaneously measured by the impedance response of the shear and longitudinal waves emitted from the resonator. The system can be used to characterize complicated evaporation kinetics involving multi-component fuels. American Chemical Society Petroleum Research Fund, NSF CMMI-0952646.

  19. Kinetics of heterogeneous chemical reactions: a theoretical model for the accumulation of pesticides in soil.

    Science.gov (United States)

    Lin, S H; Sahai, R; Eyring, H

    1971-04-01

    A theoretical model for the accumulation of pesticides in soil has been proposed and discussed from the viewpoint of heterogeneous reaction kinetics with a basic aim to understand the complex nature of soil processes relating to the environmental pollution. In the bulk of soil, the pesticide disappears by diffusion and a chemical reaction; the rate processes considered on the surface of soil are diffusion, chemical reaction, vaporization, and regular pesticide application. The differential equations involved have been solved analytically by the Laplace-transform method.

  20. Studies in theoretical particle physics

    International Nuclear Information System (INIS)

    Kaplan, D.B.

    1991-01-01

    This proposal focuses on research on three distinct areas of particle physics: (1) Nonperturbative QCD. I tend to continue work on analytic modelling of nonperturbative effects in the strong interactions. I have been investigating the theoretical connection between the nonrelativistic quark model and QCD. The primary motivation has been to understand the experimental observation of nonzero matrix elements involving current strange quarks in ordinary matter -- which in the quark model has no strange quark component. This has led to my present work on understanding constituent (quark model) quarks as collective excitations of QCD degrees of freedom. (2) Weak Scale Baryogenesis. A continuation of work on baryogenesis in the early universe from weak interactions. In particular, an investigation of baryogenesis occurring during the weak phase transition through anomalous baryon violating processes in the standard model of weak interactions. (3) Flavor and Compositeness. Further investigation of a new mechanism that I recently discovered for dynamical mass generation for fermions, which naturally leads to a family hierarchy structure. A discussion of recent past work is found in the next section, followed by an outline of the proposed research. A recent publication from each of these three areas is attached to this proposal

  1. Cyclotron tubes - a theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Mourier, G

    1980-12-01

    The introduction presents a general discussion of electron cyclotron masers (ECM): resonance, relativistic effects, elementary quantum aspects, the classical relativistic bunching and the optimum value of the electric field. The practical structure - in particular that of the gyrotron - is specified only insofar as it is useful for understanding the following chapters. The main parameters are discussed. Section 2 develops a nonlinear adiabatic or orbital theory of electron motion which alleviates calculations considerably while keeping numerical errors low enough for many practical cases. Its results are compared to a rigorous integration in one case. Other cases show the importance of the electric field profile inside the resonant cavity. Section 3 is devoted to space charge phenomena, and, for the most part, to a linear theory with space charge. In its limited range of validity (low-energy electrons), the theory indicates a strong impact of space charge for low a.c. fields and exhibits a pure beam instability. Section 4 is devoted to circuit equations with emphasis on the special features of cavities consisting of a long waveguide near cutoff. The conclusion indicates some trends of gyrotron development and corresponding theoretical problems.

  2. Kinetic studies on leucite precursors

    Czech Academy of Sciences Publication Activity Database

    Mrázová, M.; Kloužková, A.; Kohoutková, Martina

    2009-01-01

    Roč. 7, č. 2 (2009), s. 205-210 ISSN 1895-1066 R&D Projects: GA MPO 2A-1TP1/063 Institutional research plan: CEZ:AV0Z40320502 Keywords : leucite * crystallization kinetics * hydrothermal Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.065, year: 2009

  3. Theoretical and experimental investigation of the thermodynamic and kinetic nitrogen absorption by liquid alloys

    Energy Technology Data Exchange (ETDEWEB)

    Grigorenko, G.M.; Pomarin, Yu.M.; Orlovsky, V.Yu. [Natsional' na Akademyiya Nauk Ukrayini, Kiev (Ukraine). E.O. Paton Inst. of Electrical Welding

    1999-07-01

    The work was performed within the framework of the Ukrainian-French program of cooperation in the field of metal of high inclusion and was dedicated to joint fundamental investigation of thermodynamics and kinetics of nitrogen absorption by the Ni-20%Cr liquid alloy. The comparative investigations of kinetic absorption of nitrogen from the gas phase were performed by the method of levitation melting within the temperature range of 1600-1800 C in the atmosphere of pure nitrogen. Using the method of mathematical statistics and experimental Cp values at the different temperatures, the temperature dependence of the equilibrium constant of nitrogen solution reaction in the Ni-20%Cr alloy was obtained (lgK{sub N}=1284/T-1.94). Theoretical and graphical analysis of the experimental data allowed to make the conclusion that the absorption nitrogen process is controlled by the general kinetic equation of the first degree. Using of the aforementioned results the mass transfer factors were calculated with the different temperature and were obtained their mathematical description ({beta}{sub N}{sup Ni-Cr}=-454/T+0.285). (orig.)

  4. Diffusion-controlled interface kinetics-inclusive system-theoretic propagation models for molecular communication systems

    Science.gov (United States)

    Chude-Okonkwo, Uche A. K.; Malekian, Reza; Maharaj, B. T.

    2015-12-01

    Inspired by biological systems, molecular communication has been proposed as a new communication paradigm that uses biochemical signals to transfer information from one nano device to another over a short distance. The biochemical nature of the information transfer process implies that for molecular communication purposes, the development of molecular channel models should take into consideration diffusion phenomenon as well as the physical/biochemical kinetic possibilities of the process. The physical and biochemical kinetics arise at the interfaces between the diffusion channel and the transmitter/receiver units. These interfaces are herein termed molecular antennas. In this paper, we present the deterministic propagation model of the molecular communication between an immobilized nanotransmitter and nanoreceiver, where the emission and reception kinetics are taken into consideration. Specifically, we derived closed-form system-theoretic models and expressions for configurations that represent different communication systems based on the type of molecular antennas used. The antennas considered are the nanopores at the transmitter and the surface receptor proteins/enzymes at the receiver. The developed models are simulated to show the influence of parameters such as the receiver radius, surface receptor protein/enzyme concentration, and various reaction rate constants. Results show that the effective receiver surface area and the rate constants are important to the system's output performance. Assuming high rate of catalysis, the analysis of the frequency behavior of the developed propagation channels in the form of transfer functions shows significant difference introduce by the inclusion of the molecular antennas into the diffusion-only model. It is also shown that for t > > 0 and with the information molecules' concentration greater than the Michaelis-Menten kinetic constant of the systems, the inclusion of surface receptors proteins and enzymes in the models

  5. Kinetic and theoretical studies on the protonation of [Ni(2-SC6H4N){PhP(CH2CH2PPh2)2}]+: nitrogen versus sulfur as the protonation site.

    Science.gov (United States)

    Petrou, Athinoula L; Koutselos, Andreas D; Wahab, Hilal S; Clegg, William; Harrington, Ross W; Henderson, Richard A

    2011-02-07

    The complexes [Ni(4-Spy)(triphos)]BPh(4) and [Ni(2-Spy)(triphos)]BPh(4) {triphos = PhP(CH(2)CH(2)PPh(2))(2), 4-Spy = 4-pyridinethiolate, 2-Spy = 2-pyridinethiolate} have been prepared and characterized both spectroscopically and using X-ray crystallography. In both complexes the triphos is a tridentate ligand. However, [Ni(4-Spy)(triphos)](+) comprises a 4-coordinate, square-planar nickel with the 4-Spy ligand bound to the nickel through the sulfur while [Ni(2-Spy)(triphos)](+) contains a 5-coordinate, trigonal-bipyramidal nickel with a bidentate 2-Spy ligand bound to the nickel through both sulfur and nitrogen. The kinetics of the reactions of [Ni(4-Spy)(triphos)](+) and [Ni(2-Spy)(triphos)](+) with lutH(+) (lut = 2,6-dimethylpyridine) in MeCN have been studied using stopped-flow spectrophotometry, and the two complexes show very different reactivities. The reaction of [Ni(4-Spy)(triphos)](+) with lutH(+) is complete within the deadtime of the stopped-flow apparatus (2 ms) and corresponds to protonation of the nitrogen. However, upon mixing [Ni(2-Spy)(triphos)](+) and lutH(+) a reaction is observed (on the seconds time scale) to produce an equilibrium mixture. The mechanistic interpretation of the rate law has been aided by the application of MSINDO semiempirical and ADF calculations. The kinetics and calculations are consistent with the reaction between [Ni(2-Spy)(triphos)](+) and lutH(+) involving initial protonation of the sulfur followed by dissociation of the nitrogen and subsequent transfer of the proton from sulfur to nitrogen. The factors affecting the position of protonation and the coupling of the coordination state of the 2-pyridinethiolate ligand to the site of protonation are discussed.

  6. Linear and nonlinear kinetic-stability studies in tokamaks

    International Nuclear Information System (INIS)

    Tang, W.M.; Chance, M.S.; Chen, L.; Krommes, J.A.; Lee, W.W.; Rewoldt, G.

    1982-09-01

    This paper presents results of theoretical investigations on important linear kinetic properties of low frequency instabilities in toroidal systems and on nonlinear processes which could significantly influence their impact on anomalous transport. Analytical and numerical methods and also particle simulations have been employed to carry out these studies. In particular, the following subjects are considered: (1) linear stability analysis of kinetic instabilities for realistic tokamak equilibria and the application of such calculations to the PDX and PLT tokamak experiments including the influence of a hot beam-ion component; (2) determination of nonlinearly saturated, statistically steady states of three interacting drift modes; and (3) gyrokinetic particle simulation of drift instabilities

  7. Theoretical studies in nuclear physics

    International Nuclear Information System (INIS)

    Landau, R.H.; Madsen, V.A.

    1991-01-01

    This report discusses research in nuclear theory in the following areas: Isospin effects and charge exchange; inelastic and charge exchange scattering; momentum space proton scattering; pion scattering from nuclei; and antiproton studies. 14 refs

  8. Theoretical studies in nuclear physics

    International Nuclear Information System (INIS)

    Landau, R.H.; Madsen, V.A.

    1990-01-01

    This report discusses: microscopic imaginary optical potential; isospin effects and charge exchange; multistep inelastic and charge exchange scattering; momentum space proton scattering; pion scattering from nuclei; antiproton studies; antikaons-nucleon interactions; and quantum mechanics. 11 refs

  9. Theoretical studies of unconventional superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Groensleth, Martin Sigurd

    2008-07-01

    This thesis presents four research papers. In the first three papers we have derived analytical results for the transport properties in unconventional superconductors and ferromagnetic systems with multiple broken symmetries. In Paper I and parts of Paper II we have studied tunneling transport between two non-unitary ferromagnetic spin-triplet superconductors, and found a novel interplay between ferromagnetism and superconductivity manifested in the Josephson effect as a spin- and charge-current in the absence of an applied voltage across the junction. The critical amplitudes of these currents can be adjusted by the relative magnetization direction on each side of the junction. Furthermore, in Paper II, we have found a way of controlling a spin-current between two ferromagnets with spin-orbit coupling. Paper III considers a junction consisting of a ferromagnet and a non-unitary ferromagnetic superconductor, and we show that the conductance spectra contains detailed information about the superconducting gaps and pairing symmetry of the Cooper-pairs. In the last paper we present a Monte Carlo study of an effective Hamiltonian describing orbital currents in the CuO2 layers of high-temperature superconductive cuprates. The model features two intrinsically anisotropic Ising models, coupled through an anisotropic next-nearest neighbor interaction, and an Ashkin-Teller nearest neighbor fourth order coupling. We have studied the specific heat anomaly, as well as the anomaly in the staggered magnetization associated with the orbital currents and its susceptibility. We have found that in a limited parameter regime, the specific heat anomaly is substantially suppressed, while the susceptibility has a non-analytical peak across the order-disorder transition. The model is therefore a candidate for describing the breakup of hidden order when crossing the pseudo-gap line on the under-doped side in the phase diagram of high-temperature superconductors. (Author) 64 refs., figs

  10. Theoretical studies in nuclear structure

    International Nuclear Information System (INIS)

    Marshalek, E.R.

    1991-11-01

    In this period, the work has centered on two topics. The first is the study of a novel type of collective rotation in which an atomic nucleus with an inversion-symmetric shape rotates uniformly about an axis that is not a principal axis of the quadrupole tensor of the density distribution. This mode is referred to as tilted rotation. By using the cranking model together with higher-order corrections, it was shown that tilted rotation is indeed possible, not only within a microscopic framework, but also within the framework of collective models such as the IBM. The maximum tilt angle of π/4 is realized for a certain class of states in the U(5) limit. The second topic, which actually was suggested during the course of the first investigation, is concerned with a new way of representing collective harmonic-oscillator algebras using boson-mapping techniques. In this approach, the many-phonon eigenvectors of a 2λ+1-dimensional oscillator having good angular momentum are represented by simple products of boson operators acting on a vacuum. This representation may simplify the calculation of reduced matrix elements of arbitrary operators in collective models, but more work needs to be done

  11. Liquefaction chemistry and kinetics: Hydrogen utilization studies

    Energy Technology Data Exchange (ETDEWEB)

    Rothenberger, K.S.; Warzinski, R.P.; Cugini, A.V. [Pittsburgh Energy Technology Center, PA (United States)] [and others

    1995-12-31

    The objectives of this project are to investigate the chemistry and kinetics that occur in the initial stages of coal liquefaction and to determine the effects of hydrogen pressure, catalyst activity, and solvent type on the quantity and quality of the products produced. The project comprises three tasks: (1) preconversion chemistry and kinetics, (2) hydrogen utilization studies, and (3) assessment of kinetic models for liquefaction. The hydrogen utilization studies work will be the main topic of this report. However, the other tasks are briefly described.

  12. Kinetic study of the alkaline metals oxidation by dry oxygen

    International Nuclear Information System (INIS)

    Touzain, Ph.

    1967-06-01

    The oxidation of lithium, sodium, potassium, rubidium, cesium and sodium-potassium alloys by dry oxygen is studied at several temperatures and in the oxygen pressure range 40 to 400 mmHg. One distinguishes three different oxidation behaviours (inflammation, ignition and slow combustion) whose zones are precised in function of the temperature. The slow oxidation kinetic laws, the composition of oxides and the motive of oxides colorations are determined. At least, the experimental data are construed theoretically. (author) [fr

  13. Theoretical study of fractal growth and stability on surface

    DEFF Research Database (Denmark)

    Dick, Veronika V.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2009-01-01

    We perform a theoretical study of the fractal growing process on surface by using the deposition, diffusion, aggregation method. We present a detailed analysis of the post-growth processes occurring in a nanofractal on surface. For this study we developed a method which describes the internal...... dynamics of particles in a fractal and accounts for their diffusion and detachment. We demonstrate that these kinetic processes are responsible for the formation of the final shape of the islands on surface after the post-growth relaxation....

  14. Kinetic Study of Curcumin on Modal Fabric

    Directory of Open Access Journals (Sweden)

    Abu Naser Md. Ahsanul Haque

    2018-03-01

    Full Text Available A kinetic study of curcumin on modal fabric was carried out using an initial dye concentration of 1 g/L at three different temperatures, 70 °C, 85 °C and 100 °C, at pH 7 and an material to liquor ratio of 1:20. Pseudo first-order and pseudo second-order kinetics were applied, and it was found that the adsorption kinetics of curcumin on modal fabric matched the pseudo second-order kinetic model. The activation energy was found to be equal to 71.14 kJ/mol, while the enthalpy and entropy of activation were 68.16 kJ/mol and –66.02 J/molK respectively.

  15. Theoretical Study of the Diastereofacial Isomers of Aldrin and Dieldrin

    Directory of Open Access Journals (Sweden)

    Zoran Zdravkovski

    2006-02-01

    Full Text Available The Diels-Alder reaction of hexachlorocyclopentadiene with norbornadiene givesaldrin but theoretically three other diastereofacial isomers are possible. On oxidation theseisomers can generate eight adducts one of which is known as dieldrin. All these, as well asthe corresponding reactions with hexafluorocyclopenadiene were studied by semiempirical(AM1 and PM3 and hybrid density functional (B3LYP methods. Besides the energy levels,the transition states were calculated for the reactions leading to the diastereofacial isomers ofaldrin, which indicate that aldrin is the favored product of the reaction both fromthermodynamic and kinetic point of view.

  16. 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.

  17. Surfactants, interfaces and pores : a theoretical study

    NARCIS (Netherlands)

    Huinink, H.

    1998-01-01

    The aim of this study was to investigate the behavior of surfactants in porous media by theoretical means. The influence of curvature of a surface on the adsorption has been studied with a mean field lattice (MFL) model, as developed by Scheutjens and Fleer. An analytical theory has been

  18. EXPERIMENT AL AND THEORETICAL STUDY OF PRECAST ...

    African Journals Online (AJOL)

    EXPERIMENT AL AND THEORETICAL STUDY OF PRECAST BEAM-SLAB. CONSTRUCTION. Girma Zerayohannes and Adil Zekaria. Department of Civil Engineering. Addis Ababa University. ABSTRACT. The use of partially precast beam elements ivith shear connectors in slab construction relieves the requirement of ...

  19. A combined experimental and theoretical study

    Indian Academy of Sciences (India)

    A combined theoretical and experimental study was also performed, which demonstrated that the clus- ters 1–3 with ... silica gel TLC plates (MERCK TLC Plates). The NMR .... tronic μ3-Se and maintains the same number of clus- ter valance ...

  20. Theoretical and simulation studies of seeding methods

    Energy Technology Data Exchange (ETDEWEB)

    Pellegrini, Claudio [Univ. of California, Los Angeles, CA (United States)

    2017-12-11

    We report the theoretical and experimental studies done with the support of DOE-Grant DE-SC0009983 to increase an X-ray FEL peak power from the present level of 20 to 40 GW to one or more TW by seeding, undulator tapering and using the new concept of the Double Bunch FEL.

  1. Lithium hydride hydrolysis: experimental and kinetic study

    International Nuclear Information System (INIS)

    Charton, S.; Maupoix, C.; Brevet, A.; Delaunay, F.; Heintz, O.; Saviot, L.

    2006-01-01

    In this work has been studied the contribution of various analyses techniques in the framework, on the one hand of revealing the mechanisms implied in lithium hydride hydrolysis, and on the other hand of studying the kinetics of hydrogen production. Among the methods recently investigated, Raman spectroscopy, XPS and SIMS seem to be particularly attractive. (O.M.)

  2. Kinetic studies of anomalous transport

    International Nuclear Information System (INIS)

    Tang, W.M.

    1990-11-01

    Progress in achieving a physics-based understanding of anomalous transport in toroidal systems has come in large part from investigations based on the proposition that low frequency electrostatic microinstabilities are dominant in the bulk (''confinement'') region of these plasmas. Although the presence here of drift-type modes dependent on trapped particle and ion temperature gradient driven effects appears to be consistent with a number of important observed confinement trends, conventional estimates for these instabilities cannot account for the strong current (I p ) and /or q-scaling frequently found in empirically deduced global energy confinement times for auxiliary-heated discharges. The present paper deals with both linear and nonlinear physics features, ignored in simpler estimates, which could introduce an appreciable local dependence on current. It is also pointed out that while the thermal flux characteristics of drift modes have justifiably been the focus of experimental studies assessing their relevance, other transport properties associated with these microinstabilities should additionally be examined. Accordingly, the present paper provides estimates and discusses the significance of anomalous energy exchange between ions and electrons when fluctuations are present. 19 refs., 3 figs

  3. Kinetic Study on Channelling of Protons in Metallic Carbon Nanotubes

    International Nuclear Information System (INIS)

    Dan, Zhao; Yuan-Hong, Song; You-Nian, Wang

    2008-01-01

    Based on the kinetic model and the dielectric response theory, a theoretical model is put forward to describe the transport of protons along nanotube axes. With the introduction of electron band structure for different nanotubes like zigzag and armchair nanotubes of metallic properties, the collective excitation of electrons on the cylinders induced by the incident ions is studied, showing several distinct peaks in the curves of the energy loss function. Furthermore, the stopping power and the self-energy are calculated as functions of ion velocities, especially taking into account the influence of damping coefficients. It is conceivable from the results that, in the kinetic formulation, plasmon excitation plays a major role in the stopping. And as the damping increases, the peaks of the stopping power shift to the lower velocities, with the broadening of the plasmon resonance. (condensed matter: structure, mechanical and thermal properties)

  4. Prompt radiation activation analysis, (1) Theoretical study

    International Nuclear Information System (INIS)

    EL Barouni, A. M.; Araddad, S. Y.; Mosbah, D. S.; Elfakhri, S. M.; Rateb, J. M.; Benghzail, M. A.

    2004-01-01

    The measurement of the prompt γ following neutron capture in the reaction has been extensively developed. In this method the gamma-ray intensity is depended only upon the radiative capture cross-section and not upon the half-life of the product nucleus. The prompt gamma-ray activation analysis method stems from the radiative capture process which results in the decay of the compound nucleus by the emission of characteristic gamma radiation, either as a single photon with kinetic energy equal to the excitation energy less the recoil energy or, more likely, by a cascade of two or more photons with the same energy. The equations and the computer program required to calculate the yield, the intensity and the K χ emission probability per disintegration, are given in this study.(author)

  5. Kinetic catalytic studies of scorpion's hemocyanin

    International Nuclear Information System (INIS)

    Queinnec, E.; Vuillaume, M.; Gardes-Albert, M.; Ferradini, C.; Ducancel, F.

    1991-01-01

    Hemocyanins are copper proteins which function as oxygen carriers in the haemolymph of Molluscs and Arthropods. They possess enzymatic properties: peroxidatic and catalatic activities, although they have neither iron nor porphyrin ring at the active site. The kinetics of the catalytic reaction is described. The reaction of superoxide anion with hemocyanin has been studied using pulse radiolysis at pH 9. The catalytic rate constant is 3.5 X 10 7 mol -1 .l.s -1 [fr

  6. CO oxidation on gold nanoparticles: Theoretical studies

    DEFF Research Database (Denmark)

    Remediakis, Ioannis; Lopez, Nuria; Nørskov, Jens Kehlet

    2005-01-01

    We present a summary of our theoretical results regarding CO oxidation on both oxide-supported and isolated gold nanoparticles. Using Density Functional Theory we have studied the adsorption of molecules and the oxidation reaction of CO on gold clusters. Low-coordinated sites on the gold...... nanoparticles can adsorb small inorganic molecules such as O2 and CO, and the presence of these sites is the key factor for the catalytic properties of supported gold nanoclusters. Other contributions, induced by the presence of the support, can provide parallel channels for the reaction and modulate the final...

  7. Theoretical Investigation of Kinetic Processes in Small Radicals of Importance in Combustion

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, Millard [Univ. of Maryland, College Park, MD (United States). Dept. of Chemistry and Biochemistry; Dagdigian, Paul J. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Chemistry

    2017-12-12

    Our group studies inelastic and reactive collisions of small molecules, focusing on radicals important in combustion environments. The goal is the better understanding of kinetic processes that may be difficult to access experimentally. An essential component is the accurate determination and fitting of potential energy surfaces (PESs). After fitting the ab initio points to obtain global PESs, we treat the dynamics using time-independent (close-coupling) methods. Cross sections and rate constants for collisions of are determined with our Hibridon program suite . We have studied energy transfer (rotationally, vibrationally, and/or electronically inelastic) in small hydrocarbon radicals (CH2 and CH3) and the CN radical. We have made a comparison with experimental measurements of relevant rate constants for collisions of these radicals. Also, we have calculated accurate transport properties using state-of-the-art PESs and to investigate the sensitivity to these parameters in 1-dimensional flame simulations. Of particular interest are collision pairs involving the light H atom.

  8. The mechanism for the rhodium-catalyzed decarbonylation of aldehydes: A combined experimental and theoretical study

    DEFF Research Database (Denmark)

    Fristrup, Peter; Kreis, Michael; Palmelund, Anders

    2008-01-01

    that similar mechanisms are operating. A DFT (B3LYP) study of the catalytic cycle indicated a rapid oxidative addition into the C(O)-H bond followed by a rate-limiting extrusion of CO and reductive elimination. The theoretical kinetic isotope effects based on this mechanism were in excellent agreement...

  9. Theoretical pluralism in psychoanalytic case studies.

    Science.gov (United States)

    Willemsen, Jochem; Cornelis, Shana; Geerardyn, Filip M; Desmet, Mattias; Meganck, Reitske; Inslegers, Ruth; Cauwe, Joachim M B D

    2015-01-01

    The aim of this study is to provide an overview of the scientific activity of different psychoanalytic schools of thought in terms of the content and production of case studies published on ISI Web of Knowledge. Between March 2013 and November 2013, we contacted all case study authors included in the online archive of psychoanalytic and psychodynamic case studies (www.singlecasearchive.com) to inquire about their psychoanalytic orientation during their work with the patient. The response rate for this study was 45%. It appears that the two oldest psychoanalytic schools, Object-relations psychoanalysis and Ego psychology or "Classical psychoanalysis" dominate the literature of published case studies. However, most authors stated that they feel attached to two or more psychoanalytic schools of thought. This confirms that the theoretical pluralism in psychoanalysis stretches to the field of single case studies. The single case studies of each psychoanalytic school are described separately in terms of methodology, patient, therapist, or treatment features. We conclude that published case studies features are fairly similar across different psychoanalytic schools. The results of this study are not representative of all psychoanalytic schools, as some do not publish their work in ISI ranked journals.

  10. Theoretical pluralism in psychoanalytic case studies

    Science.gov (United States)

    Willemsen, Jochem; Cornelis, Shana; Geerardyn, Filip M.; Desmet, Mattias; Meganck, Reitske; Inslegers, Ruth; Cauwe, Joachim M. B. D.

    2015-01-01

    The aim of this study is to provide an overview of the scientific activity of different psychoanalytic schools of thought in terms of the content and production of case studies published on ISI Web of Knowledge. Between March 2013 and November 2013, we contacted all case study authors included in the online archive of psychoanalytic and psychodynamic case studies (www.singlecasearchive.com) to inquire about their psychoanalytic orientation during their work with the patient. The response rate for this study was 45%. It appears that the two oldest psychoanalytic schools, Object-relations psychoanalysis and Ego psychology or “Classical psychoanalysis” dominate the literature of published case studies. However, most authors stated that they feel attached to two or more psychoanalytic schools of thought. This confirms that the theoretical pluralism in psychoanalysis stretches to the field of single case studies. The single case studies of each psychoanalytic school are described separately in terms of methodology, patient, therapist, or treatment features. We conclude that published case studies features are fairly similar across different psychoanalytic schools. The results of this study are not representative of all psychoanalytic schools, as some do not publish their work in ISI ranked journals. PMID:26483725

  11. Theoretical study of rock mass investigation efficiency

    International Nuclear Information System (INIS)

    Holmen, Johan G.; Outters, Nils

    2002-05-01

    The study concerns a mathematical modelling of a fractured rock mass and its investigations by use of theoretical boreholes and rock surfaces, with the purpose of analysing the efficiency (precision) of such investigations and determine the amount of investigations necessary to obtain reliable estimations of the structural-geological parameters of the studied rock mass. The study is not about estimating suitable sample sizes to be used in site investigations.The purpose of the study is to analyse the amount of information necessary for deriving estimates of the geological parameters studied, within defined confidence intervals and confidence level In other words, how the confidence in models of the rock mass (considering a selected number of parameters) will change with amount of information collected form boreholes and surfaces. The study is limited to a selected number of geometrical structural-geological parameters: Fracture orientation: mean direction and dispersion (Fisher Kappa and SRI). Different measures of fracture density (P10, P21 and P32). Fracture trace-length and strike distributions as seen on horizontal windows. A numerical Discrete Fracture Network (DFN) was used for representation of a fractured rock mass. The DFN-model was primarily based on the properties of an actual fracture network investigated at the Aespoe Hard Rock Laboratory. The rock mass studied (DFN-model) contained three different fracture sets with different orientations and fracture densities. The rock unit studied was statistically homogeneous. The study includes a limited sensitivity analysis of the properties of the DFN-model. The study is a theoretical and computer-based comparison between samples of fracture properties of a theoretical rock unit and the known true properties of the same unit. The samples are derived from numerically generated boreholes and surfaces that intersect the DFN-network. Two different boreholes are analysed; a vertical borehole and a borehole that is

  12. Theoretical studies on aerosol agglomeration processes

    Energy Technology Data Exchange (ETDEWEB)

    Lehtinen, K.E.J. [VTT Energy, Espoo (Finland). Energy Use

    1997-12-31

    In this thesis, theoretical modeling of certain aerosol systems has been presented. At first, the aerosol general dynamic equation is introduced, along with a discretization routine for its numerical solution. Of the various possible phenomena affecting aerosol behaviour, this work is mostly focused on aerosol agglomeration. The fundamentals of aerosol agglomeration theory are thus briefly reviewed. The two practical applications of agglomeration studied in this thesis are flue gas cleaning using an electrical agglomerator and nanomaterial synthesis with a free jet reactor. In an electrical agglomerator the aerosol particles are charged and brought into an alternating electric field. The aim is to remove submicron particles from flue gases by collisions with larger particles before conventional gas cleaning devices that have a clear penetration window in the problematic 0.1-1{mu}m size range. A mathematical model was constructed to find out the effects of the different system parameters on the agglomerator`s performance. A crucial part of this task was finding out the collision efficiencies of particles of varying size and charge. The original idea was to use unipolar charging of the particles, and a laboratory scale apparatus was constructed for this purpose. Both theory and experiments clearly show that significant removal of submicron particles can not be achieved by such an arrangement. The theoretical analysis further shows that if the submicron particles and the large collector particles were charged with opposite polarity, significant removal of the submicron particles could be obtained. The second application of agglomeration considered in this thesis is predicting/controlling nanoparticle size in the gas-to-particle aerosol route to material synthesis. In a typical material reactor, a precursor vapor reacts to form molecules of the desired material. In a cooling environment, a particulate phase forms, the dynamics of which are determined by the rates of

  13. Theoretical studies on aerosol agglomeration processes

    Energy Technology Data Exchange (ETDEWEB)

    Lehtinen, K E.J. [VTT Energy, Espoo (Finland). Energy Use

    1998-12-31

    In this thesis, theoretical modeling of certain aerosol systems has been presented. At first, the aerosol general dynamic equation is introduced, along with a discretization routine for its numerical solution. Of the various possible phenomena affecting aerosol behaviour, this work is mostly focused on aerosol agglomeration. The fundamentals of aerosol agglomeration theory are thus briefly reviewed. The two practical applications of agglomeration studied in this thesis are flue gas cleaning using an electrical agglomerator and nanomaterial synthesis with a free jet reactor. In an electrical agglomerator the aerosol particles are charged and brought into an alternating electric field. The aim is to remove submicron particles from flue gases by collisions with larger particles before conventional gas cleaning devices that have a clear penetration window in the problematic 0.1-1{mu}m size range. A mathematical model was constructed to find out the effects of the different system parameters on the agglomerator`s performance. A crucial part of this task was finding out the collision efficiencies of particles of varying size and charge. The original idea was to use unipolar charging of the particles, and a laboratory scale apparatus was constructed for this purpose. Both theory and experiments clearly show that significant removal of submicron particles can not be achieved by such an arrangement. The theoretical analysis further shows that if the submicron particles and the large collector particles were charged with opposite polarity, significant removal of the submicron particles could be obtained. The second application of agglomeration considered in this thesis is predicting/controlling nanoparticle size in the gas-to-particle aerosol route to material synthesis. In a typical material reactor, a precursor vapor reacts to form molecules of the desired material. In a cooling environment, a particulate phase forms, the dynamics of which are determined by the rates of

  14. ENZYMATIC KINETIC STUDY HYDROLASE FROM CITRUS

    Directory of Open Access Journals (Sweden)

    Israel Hernández

    2015-09-01

    Full Text Available In this paper the degrading activity of enzymes derived from orange peels (Citrus x sinensis, grapefruit (Citrus paradise and pineapple (Ananas comosus on the organic matter in wastewater is evaluated. This activity is measured indirectly by quantifying the biochemical oxygen demand (COD before and after degradation process based on a period of time using the HACH DR / 2010, and then the kinetic study was performed by the differential method and integral with the experimental data, obtaining a reaction order of 1 to pectinase (orange, and order 2 for bromelain (pineapple.

  15. Systems identification: a theoretical method applied to tracer kinetics in aquatic microcosms

    International Nuclear Information System (INIS)

    Halfon, E.; Georgia Univ., Athens

    1974-01-01

    A mathematical model of radionuclide kinetics in a laboratory microcosm was built and the transfer parameters estimated by multiple regression and system identification techniques. Insight into the functioning of the system was obtained from analysis of the model. Methods employed have allowed movements of radioisotopes not directly observable in the experimental systems to be distinguished. Results are generalized to whole ecosystems

  16. Theoretical study of defect properties in metals

    International Nuclear Information System (INIS)

    Sindzingre, P.

    1987-01-01

    Several characteristic properties (formation and migration enthalpies and volumes, dipole tensors, effects on shear elastic constants) of several point defects (vacancy, divacancy, interstitial, di-interstitial) in different metals: f.c.c. metals (Al, Cu, Ag, Au), h.c.p. metals (Be, Mg, Zn, Cd, Na, Co, Ti, Zr), b.c.c. metals (Li, Na, K, Rb, Cs) have been calculated. The calculated properties are evaluated from static computations performed with pair potentials derived from pseudo-potential theory (for simple or noble metals) or deduced empirically. Results are compared with available experimental data with previous theoretical works. The first part of this work where we have studied point defects properties in f.c.c. metals lead us to suggest a more convincing interpretation of X-ray scattering and elastic relation measurements concerning interstitials in Al and Cu, and a new interpretation for X-ray scattering measurements concerning di-interstitials in Al. In the second part, devoted to h.c.p. metals we are brought to propose for each studied metal the interstitial configurations which yield the best agreement with experimental results. The third part, devoted to the study of point defects in alkalin b.c.c. metals lead us to interpret self-diffusion in these metals with the assumption of a simultaneous contribution of monovacancies, divacancies and interstitials [fr

  17. Theoretical and experimental studies of elementary physics

    International Nuclear Information System (INIS)

    Bodek, A.; Ferbel, T.; Melissinos, A.C.; Slattery, P.; Tipton, P.; Das, A.; Hagen, C.R.; Rajeev, S.G.; Okubo, S.; Orr, L.

    1993-01-01

    The various components of the high-energy physics research program at the University of Rochester are presented. (I)Fixed-target experimentation at FNAL includes studies of direct photon production by p and π on H, Be, and Cu, and hybrid mesons and other physics issues in Coulomb excitation at high energies. (II)The status of the GEM (Gammas, Electrons, and Muons) Experiment at the SSC is given. (III)The D-Zero experiment at FNAL is reviewed. (IV)Deep inelastic lepton--nucleon scattering experiments are summarized: electron scattering experiments at SLAC, FNAL neutrino quad triplet runs, FNAL neutrino sign selected experiments, and SDC cosmic ray test and test beam calibration. (V)Studies of nonlinear QED at SLAC concentrated on a study of QED at critical field strength in intense laser--high-energy electron collisions. (VI)Development work on the Collider Detector at Fermilab (CDF) emphasized the CDF silicon vertex detector, the end plug calorimeter, and the SDC tile/fiber calorimetry. (VII)The theoretical physics effort is sketched

  18. Experimental and theoretical investigations on the carbon dioxide gas hydrate formation kinetics at the onset of turbidity regarding CO2 capture and sequestration processes

    International Nuclear Information System (INIS)

    ZareNezhad, Bahman; Mottahedin, Mona; Varaminian, Farshad

    2013-01-01

    The carbon dioxide gas hydrate formation kinetics at the onset of turbidity is experimentally and theoretically investigated. It is shown that the time-dependent heterogeneous nucleation and growth kinetics are simultaneously governing the hydrate formation process at the onset of turbidity. A new approach is also presented for determination of gas hydrate-liquid interfacial tension. The CO 2 hydrate-liquid interfacial tension according to the suggested heterogeneous nucleation mechanism is found to be about 12.7 mJ/m 2 . The overall average absolute deviation between predicted and measured CO 2 molar consumption is about 0.61%, indicating the excellent accuracy of the proposed model for studying the hydrate-based CO 2 capture and sequestration processes over wide ranges of pressures and temperatures

  19. Stochastic optimization-based study of dimerization kinetics

    Indian Academy of Sciences (India)

    To this end, we study dimerization kinetics of protein as a model system. We follow the dimerization kinetics using a stochastic simulation algorithm and ... optimization; dimerization kinetics; sensitivity analysis; stochastic simulation ... tion in large molecules and clusters, or the design ..... An unbiased strategy of allocating.

  20. Theoretical and observational studies of stellar activity

    International Nuclear Information System (INIS)

    Schmitt, J.H.M.M.

    1984-01-01

    In the theoretical part of this thesis, doubly-diffusive MHD instabilities are studied as a means of breaking up a diffuse magnetic field at the bottom of the solar convection zone. The analysis is linear and local, and assumes short meridional wavelengths; the effects of rotation and diffusion of vorticity, magnetic fields and heat are included. Results show that the instability depends sensitively on the temperature stratification, but rather insensitively on the assumed magnetic field configuration; instability time scales considerably less than the solar cycle period can be easily obtained. In the observational part of the thesis, results are reported of a survey of the x-ray emission of stars with shallow connection zones to study the onset of convection and dynamo activity along the main sequence. Complications arising from stellar multiplicity are discussed extensively; it is demonstrated that binaries have statistically higher x-ray luminosities; and it is shown that physical parameters can only be deduced from single stars. It is further shown that the x-ray luminosities of stars with spectral type in the color range 0.1 less than or equal to B. V less than or equal to 0.5 increase rapidly, whereas stars with B. V approx. 0.0 appear to have no intrinsic x-ray emission at presently detectable levels

  1. Theoretical and experimental study of thermoacoustic engines

    Science.gov (United States)

    Raspet, Richard; Bass, Henry E.; Arnott, W. P.

    1992-12-01

    A three year study of thermoacoustic engines operating as prime movers and refrigerators was completed. The major thrust of this effort was the use and theoretical description of ceramic honeycomb structures as the active element in thermoacoustic engines. An air-filled demonstration prime mover was constructed and demonstrated at Acoustical Society of America and IEE meetings. A helium-filled test prime mover was designed and built an is being employed in studies of the threshold of oscillation as a function of temperature difference and pressure. In addition, acoustically based theories of the thermoacoustic engine have been developed and tested for a parallel plate stack at the Naval Postgraduate School and for a honeycomb stack at the University of Mississippi. Most of this work is described in detail in the attached publications. In this report we will give an overview of the research completed to date and its relationship to work performed at the Naval Postgraduate School and to future work at the University of Mississippi.

  2. Studies In Theoretical High Energy Particle Physics

    Energy Technology Data Exchange (ETDEWEB)

    Keung, Wai Yee [Univ. of Illinois, Chicago, IL (United States)

    2017-07-01

    This is a final technical report for grant no. DE-SC0007948 describing research activities in theoretical high energy physics at University of Illinois at Chicago for the whole grant period from July 1, 2012 to March 31, 2017.

  3. Kinetic studies on the hafnium nad deuterium

    International Nuclear Information System (INIS)

    Bing Wenzeng; Long Xinggui; Zhu Zuliang

    2009-04-01

    Through the method of reaction rate analysis in a constant volume reactor, the time dependence of the pressure drop of the hafnium deuteride formation are studied over a temperature range 573-873 K on a metal hydride thermodynamic and kinetic parameters measuring apparatus. The rate constants of the hafnium deuteride formation, which are 0.0530 s -1 , 0.0452 s -1 , 0.0319 s -1 , 0.0261 s -1 , are calculated at a serial temperatures of 573 K, 673 K, 773 K, 873 K and the initial pressure of 13 kPa. The activation energy of the reaction is (-10.1±1.5) kJ·mol -1 . Comparing the above results with those of titanium deuteride formation on the same measuring apparatus, the kinetic mechanism of the deuteride formation of hafnium and titanium is considered different. It is concluded that the reaction rate of hafnium absorbing deuterium may be controlled by phase transformation and surface oxidation. (authors)

  4. Theoretical Foundations of Study of Cartography

    Science.gov (United States)

    Talhofer, Václav; Hošková-Mayerová, Šárka

    2018-05-01

    Cartography and geoinformatics are technical-based fields which deal with modelling and visualization of landscape in the form of a map. The theoretical foundation is necessary to obtain during study of cartography and geoinformatics based mainly on mathematics. For the given subjects, mathematics is necessary for understanding of many procedures that are connected to modelling of the Earth as a celestial body, to ways of its projection into a plane, to methods and procedures of modelling of landscape and phenomena in society and visualization of these models in the form of electronic as well as classic paper maps. Not only general mathematics, but also its extension of differential geometry of curves and surfaces, ways of approximation of lines and surfaces of functional surfaces, mathematical statistics and multi-criterial analyses seem to be suitable and necessary. Underestimation of the significance of mathematical education in cartography and geoinformatics is inappropriate and lowers competence of cartographers and professionals in geographic information science and technology to solve problems.

  5. Sibutramine characterization and solubility, a theoretical study

    Science.gov (United States)

    Aceves-Hernández, Juan M.; Nicolás Vázquez, Inés; Hinojosa-Torres, Jaime; Penieres Carrillo, Guillermo; Arroyo Razo, Gabriel; Miranda Ruvalcaba, René

    2013-04-01

    Solubility data from sibutramine (SBA) in a family of alcohols were obtained at different temperatures. Sibutramine was characterized by using thermal analysis and X-ray diffraction technique. Solubility data were obtained by the saturation method. The van't Hoff equation was used to obtain the theoretical solubility values and the ideal solvent activity coefficient. No polymorphic phenomena were found from the X-ray diffraction analysis, even though this compound is a racemic mixture of (+) and (-) enantiomers. Theoretical calculations showed that the polarisable continuum model was able to reproduce the solubility and stability of sibutramine molecule in gas phase, water and a family of alcohols at B3LYP/6-311++G (d,p) level of theory. Dielectric constant, dipolar moment and solubility in water values as physical parameters were used in those theoretical calculations for explaining that behavior. Experimental and theoretical results were compared and good agreement was obtained. Sibutramine solubility increased from methanol to 1-octanol in theoretical and experimental results.

  6. Theoretical studies of binaries in astrophysics

    Science.gov (United States)

    Dischler, Johann Sebastian

    This thesis introduces and summarizes four papers dealing with computer simulations of astrophysical processes involving binaries. The first part gives the rational and theoretical background to these papers. In paper I and II a statistical approach to studying eclipsing binaries is described. By using population synthesis models for binaries the probabilities for eclipses are calculated for different luminosity classes of binaries. These are compared with Hipparcos data and they agree well if one uses a standard input distribution for the orbit sizes. If one uses a random pairing model, where both companions are independently picked from an IMF, one finds too feclipsing binaries by an order of magnitude. In paper III we investigate a possible scenario for the origin of the stars observed close to the centre of our galaxy, called S stars. We propose that a cluster falls radially cowards the central black hole. The binaries within the cluster can then, if they have small impact parameters, be broken up by the black hole's tidal held and one of the components of the binary will be captured by the black hole. Paper IV investigates how the onset of mass transfer in eccentric binaries depends on the eccentricity. To do this we have developed a new two-phase SPH scheme where very light particles are at tire outer edge of our simulated star. This enables us to get a much better resolution of the very small mass that is transferred in close binaries. Our simulations show that the minimum required distance between the stars to have mass transfer decreases with the eccentricity.

  7. Computational and theoretical studies of globular proteins

    Science.gov (United States)

    Pagan, Daniel L.

    Protein crystallization is often achieved in experiment through a trial and error approach. To date, there exists a dearth of theoretical understanding of the initial conditions necessary to promote crystallization. While a better understanding of crystallization will help to create good crystals suitable for structure analysis, it will also allow us to prevent the onset of certain diseases. The core of this thesis is to model and, ultimately, understand the phase behavior of protein particles in solution. Toward this goal, we calculate the fluid-fluid coexistence curve in the vicinity of the metastable critical point of the modified Lennard-Jones potential, where it has been shown that nucleation is increased by many orders of magnitude. We use finite-size scaling techniques and grand canonical Monte Carlo simulation methods. This has allowed us to pinpoint the critical point and subcritical region with high accuracy in spite of the critical fluctuations that hinder sampling using other Monte Carlo techniques. We also attempt to model the phase behavior of the gamma-crystallins, mutations of which have been linked to genetic cataracts. The complete phase behavior of the square well potential at the ranges of attraction lambda = 1.15 and lambda = 1.25 is calculated and compared with that of the gammaII-crystallin. The role of solvent is also important in the crystallization process and affects the phase behavior of proteins in solution. We study a model that accounts for the contribution of the solvent free-energy to the free-energy of globular proteins. This model allows us to model phase behavior that includes solvent.

  8. Theoretical Studies of Nanoclusters (Briefing Charts)

    Science.gov (United States)

    2015-07-23

    nanoclusters. However, scanning transmission electron microscopy ( STEM ) measures show cluster inversion occurred to produce MgyCux(!) a) copper atoms b...methane (née CLL -1) as a potential explosive ingredient: a theoretical study”, Propellants, Explosives, Pyrotechnics 38, 9-13 (2013). Jesus Paulo L

  9. Theoretical Studies in Elementary Particle Physics

    Energy Technology Data Exchange (ETDEWEB)

    Collins, John C.; Roiban, Radu S

    2013-04-01

    This final report summarizes work at Penn State University from June 1, 1990 to April 30, 2012. The work was in theoretical elementary particle physics. Many new results in perturbative QCD, in string theory, and in related areas were obtained, with a substantial impact on the experimental program.

  10. Ab initio and kinetic modeling studies of formic acid oxidation

    DEFF Research Database (Denmark)

    Marshall, Paul; Glarborg, Peter

    2015-01-01

    A detailed chemical kinetic model for oxidation of formic acid (HOCHO) in flames has been developed, based on theoretical work and data from literature. Ab initio calculations were used to obtain rate coefficients for reactions of HOCHO with H, O, and HO2. Modeling predictions with the mechanism...

  11. Theoretical and experimental study of non-monotonous effects

    International Nuclear Information System (INIS)

    Delforge, J.

    1977-01-01

    In recent years, the study of the effects of low dose rates has expanded considerably, especially in connection with current problems concerning the environment and health physics. After having made a precise definition of the different types of non-monotonous effect which may be encountered, for each the main experimental results known are indicated, as well as the principal consequences which may be expected. One example is the case of radiotherapy, where there is a chance of finding irradiation conditions such that the ratio of destructive action on malignant cells to healthy cells is significantly improved. In the second part of the report, the appearance of these phenomena, especially at low dose rates are explained. For this purpose, the theory of transformation systems of P. Delattre is used as a theoretical framework. With the help of a specific example, it is shown that non-monotonous effects are frequently encountered, especially when the overall effect observed is actually the sum of several different elementary effects (e.g. in survival curves, where death may be due to several different causes), or when the objects studied possess inherent kinetics not limited to restoration phenomena alone (e.g. cellular cycle) [fr

  12. Theoretical Studies of Elementary Hydrocarbon Species and Their Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Wesley D. [University of Georgia, Department of Chemistry and Center for Computational Quantum Chemistry; Schaefer, Henry F. [University of Georgia, Center for Computational Quantum Chemistry

    2018-04-08

    The research program supported by this DOE grant carried out both methodological development and computational applications of first-principles theoretical chemistry based on quantum mechanical wavefunctions, as directed toward understanding and harnessing the fundamental chemical physics of combustion. To build and refine the world’s database of thermochemistry, spectroscopy, and chemical kinetics, predictive and definitive computational methods are needed that push the envelope of modern electronic structure theory. The application of such methods has been made to gain comprehensive knowledge of the paradigmatic reaction networks by which the n- and i-propyl, t-butyl, and n-butyl radicals are oxidized by O2. Numerous ROO and QOOH intermediates in these R + O2 reaction systems have been characterized along with the interconnecting isomerization transition states and the barriers leading to fragmentation. Other combustion-related intermediates have also been studied, including methylsulfinyl radical, cyclobutylidene, and radicals derived from acetaldehyde and vinyl alcohol. Theoretical advances have been achieved and made available to the scientific community by implementation into PSI4, an open-source electronic structure computer package emphasizing automation, advanced libraries, and interoperability. We have pursued the development of universal explicitly correlated methods applicable to general electronic wavefunctions, as well as a framework that allows multideterminant reference functions to be expressed as a single determinant from quasiparticle operators. Finally, a rigorous analytical tool for correlated wavefunctions has been created to elucidate dispersion interactions, which play essential roles in many areas of chemistry, but whose effects are often masked and enigmatic. Our research decomposes and analyzes the coupled-cluster electron correlation energy in molecular systems as a function of interelectronic distance. Concepts

  13. Methane production from cellulosic wastes: kinetic studies

    Energy Technology Data Exchange (ETDEWEB)

    Goma, G; De La Torre, I; Maugheri, F; Yameogo, T

    1979-09-01

    The anaerobic fermentation is studied on lignocellulosic materials and sucrose as substrate. With the lignocellulosic material cellulolysis is rate limiting. The reducing sugar concentration in the fermentation broth is less than 15 mgl/sup -1/. With rumen bacteria, 50% of the initial polyoside are used and 12% of the lignin is solubilized. With sucrose studies on the kinetic behaviour of the mixed population responsible of the acidogenesis step permite to find the optimal temperature (40/sup 0/C) feed substrate concentration (50 gl/sup -1/) residence time (60 hours) and pH (5,5 - 6). The better technology is a plug flow fermentor with cell recycling. Modeling of the behaviour of this reactor was performed. The use of this reactor for the selection of acido resistant bacteria is discussed. For methanogenesis, in continuous culture, the ideal technology seems to be an association of two reactors. In the first step, a plug flow reactor must be used for acidogenesis, and in the second step a well mixed reactor permit the conversion of organic acids in methane.

  14. Theoretical studies in elementary particle physics

    International Nuclear Information System (INIS)

    Collins, J.

    1994-01-01

    This is a report on research conducted at Penn State University under grant number DE-FG02-90ER-40577, from November 1992 to present. The author is a member of the CTEQ collaboration (Coordinated Theoretical and Experimental Project on Quantitative QCD). Some of the work in CTEQ is described in this report. Topics which the authors work has touched include: polarized hard scattering; hard diffraction; small x and perturbative pomeron physics; gauge-invariant operators; fundamental QCD; heavy quarks; instantons and deep inelastic scattering; non-perturbative corrections to τ decay

  15. Studies in theoretical high energy particle physics

    International Nuclear Information System (INIS)

    Aratyn, H.; Brekke, L.; Keung, Wai-Yee; Sukhatme, U.

    1993-01-01

    Theoretical work on the following topics is briefly summarized: symmetry structure of conformal affine Toda model and KP hierarchy; solitons in the affine Toda and conformal affine Toda models; classical r-matrices and Poisson bracket structures on infinite-dimensional groups; R-matrix formulation of KP hierarchies and their gauge equivalence; statistics of particles and solitons; charge quantization in the presence of an Alice string; knotting and linking of nonabelian flux; electric dipole moments; neutrino physics in gauge theories; CP violation in the high energy colliders; supersymmetric quantum mechanics; parton structure functions in nuclei; dual parton model. 38 refs

  16. Combustion Kinetic Studies of Gasolines and Surrogates

    KAUST Repository

    Javed, Tamour

    2016-11-01

    Future thrusts for gasoline engine development can be broadly summarized into two categories: (i) efficiency improvements in conventional spark ignition engines, and (ii) development of advance compression ignition (ACI) concepts. Efficiency improvements in conventional spark ignition engines requires downsizing (and turbocharging) which may be achieved by using high octane gasolines, whereas, low octane gasolines fuels are anticipated for ACI concepts. The current work provides the essential combustion kinetic data, targeting both thrusts, that is needed to develop high fidelity gasoline surrogate mechanisms and surrogate complexity guidelines. Ignition delay times of a wide range of certified gasolines and surrogates are reported here. These measurements were performed in shock tubes and rapid compression machines over a wide range of experimental conditions (650 – 1250 K, 10 – 40 bar) relevant to internal combustion engines. Using the measured the data and chemical kinetic analyses, the surrogate complexity requirements for these gasolines in homogeneous environments are specified. For the discussions presented here, gasolines are classified into three categories: (i)\\tLow octane gasolines including Saudi Aramco’s light naphtha fuel (anti-knock index, AKI = (RON + MON)/2 = 64; Sensitivity (S) = RON – MON = 1), certified FACE (Fuels for Advanced Combustion Engines) gasoline I and J (AKI ~ 70, S = 0.7 and 3 respectively), and their Primary Reference Fuels (PRF, mixtures of n-heptane and iso-octane) and multi-component surrogates. (ii)\\t Mid octane gasolines including FACE A and C (AKI ~ 84, S ~ 0 and 1 respectively) and their PRF surrogates. Laser absorption measurements of intermediate and product species formed during gasoline/surrogate oxidation are also reported. (iii)\\t A wide range of n-heptane/iso-octane/toluene (TPRF) blends to adequately represent the octane and sensitivity requirements of high octane gasolines including FACE gasoline F and G

  17. Study of internal oxidation kinetics of molybdenum base alloys

    International Nuclear Information System (INIS)

    Krushinskij, Yu.Yu.; Belyakov, B.G.; Belomyttsev, M.Yu.

    1989-01-01

    Metallographic and microdurometric method as well as new technique were used to study kinetics of internal oxidation (IO). It is shown that study of IO kinetics on the base of metallographic measurements of layers depth is not correct because it is related with insufficient sensitivity of the method. IO kinetics under conditions of formation of molybdenum oxide layer on saturated material surface as well as IO of alloy with high carbon content were investigated. Oxide film formation does not affect the IO kinetics; decarburization observed along with oxidation increases the apparent activation energy and K exponent on time dependence of diffusion layer depth

  18. Theoretical model based on the memory effect for the strange photoisomerization kinetics of diarylethene derivatives dispersed on polymer films

    International Nuclear Information System (INIS)

    Seki, Kazuhiko; Tachiya, M.

    2007-01-01

    In the present paper the authors present a theoretical model to explain the kinetics involving the induction period observed by Irie et al. [Nature (London) 420, 759 (2002)] for photoisomerization of diarylethene derivatives dispersed on polymer films at a single molecular level. In the model we assume that both ground state and excited state free energy landscapes which result from the interaction between the photochromic molecule and the surrounding polymer are rugged and have several local minima along the pathway to the critical point at which isomerization actually occurs. We assume that after one photoexcitation a fraction of the photochromic molecule moves to a new local minimum and stays there, although the other fraction returns to the original local minimum. The former effect is referred to as the memory effect. After repeated photoexcitations the photochromic molecule moves gradually from one local minimum to another in the pathway to the isomerization point. It finally reaches the isomerization point, where isomerization occurs. Their model successfully reproduces the kinetics of photoisomerization of diarylethene derivatives dispersed on polymer films observed experimentally

  19. Theoretical prediction of crystallization kinetics of a supercooled Lennard-Jones fluid

    Science.gov (United States)

    Gunawardana, K. G. S. H.; Song, Xueyu

    2018-05-01

    The first order curvature correction to the crystal-liquid interfacial free energy is calculated using a theoretical model based on the interfacial excess thermodynamic properties. The correction parameter (δ), which is analogous to the Tolman length at a liquid-vapor interface, is found to be 0.48 ± 0.05 for a Lennard-Jones (LJ) fluid. We show that this curvature correction is crucial in predicting the nucleation barrier when the size of the crystal nucleus is small. The thermodynamic driving force (Δμ) corresponding to available simulated nucleation conditions is also calculated by combining the simulated data with a classical density functional theory. In this paper, we show that the classical nucleation theory is capable of predicting the nucleation barrier with excellent agreement to the simulated results when the curvature correction to the interfacial free energy is accounted for.

  20. Solar pond conception - experimental and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Kurt, Huseyin [Zonguldak Karaelmas Univ., Technical Education Faculty, Karabuk (Turkey); Halici, Fethi [Sakarya Univ., Mechanical Engineering Dept., Adapazari (Turkey); Binark, A. Korhan [Marmara Univ., Technical Education Faculty, Istanbul (Turkey)

    2000-07-01

    A one dimensional transient mathematical model for predicting the thermal performance of the salt gradient solar pond is developed and presented. In this paper, the natural solar ponds and different artificial solar pond systems found in the literature are introduced. Necessary modifications are made on the experimental stand located in Istanbul Technical University, the experimental stand is introduced and natural phenomena produced in the pond by the different solar pond variations under natural conditions are observed. In the theoretical work based on a one dimensional unsteady state heat conduction model with internal heat generation, the energy and mass balance equations for the upper convective zone, the non-convective zone and the lower convective zone, all of which form the solar pond, are written in terms of differential equations. These equations are solved analytically and numerically. The results obtained from the analysis are compared with the experimental results. The temperature and the concentration profiles are separately presented in the figures. (Author)

  1. Studies in Theoretical and Applied Statistics

    CERN Document Server

    Pratesi, Monica; Ruiz-Gazen, Anne

    2018-01-01

    This book includes a wide selection of the papers presented at the 48th Scientific Meeting of the Italian Statistical Society (SIS2016), held in Salerno on 8-10 June 2016. Covering a wide variety of topics ranging from modern data sources and survey design issues to measuring sustainable development, it provides a comprehensive overview of the current Italian scientific research in the fields of open data and big data in public administration and official statistics, survey sampling, ordinal and symbolic data, statistical models and methods for network data, time series forecasting, spatial analysis, environmental statistics, economic and financial data analysis, statistics in the education system, and sustainable development. Intended for researchers interested in theoretical and empirical issues, this volume provides interesting starting points for further research.

  2. Kinetic study of solid-state processes

    International Nuclear Information System (INIS)

    Malek, Jiri; Mitsuhashi, Takefumi

    2003-01-01

    A simple method for kinetic analysis of solid-state processes has been developed and the criteria capable of classifying different processes are explored. They provide a useful tool for the determination of the most suitable kinetic model. The method has been applied to the analysis of calorimetric data corresponding to the crystallization processes in amorphous ZrO 2 . It is found that the crystallization kinetics of amorphous powder sample exhibits a complex behavior under non-isothermal conditions. A two-parameter model provides a satisfactory description of the crystallization process for isothermal and non-isothermal conditions. This enables better control of crystallization extent in fine ZrO 2 powders that is important for preparation of zirconia ceramics with defined properties. (author)

  3. Combustion Kinetic Studies of Gasolines and Surrogates

    KAUST Repository

    Javed, Tamour

    2016-01-01

    . These measurements were performed in shock tubes and rapid compression machines over a wide range of experimental conditions (650 – 1250 K, 10 – 40 bar) relevant to internal combustion engines. Using the measured the data and chemical kinetic analyses, the surrogate

  4. Theoretical Semi-Empirical AM1 studies of Schiff Bases

    International Nuclear Information System (INIS)

    Arora, K.; Burman, K.

    2005-01-01

    The present communication reports the theoretical semi-empirical studies of schiff bases of 2-amino pyridine along with their comparison with their parent compounds. Theoretical studies reveal that it is the azomethine group, in the schiff bases under study, that acts as site for coordination to metals as it is reported by many coordination chemists. (author)

  5. Theoretical & Experimental Studies of Elementary Particles

    Energy Technology Data Exchange (ETDEWEB)

    McFarland, Kevin [Univ. of Rochester, NY (United States)

    2012-10-04

    Abstract High energy physics has been one of the signature research programs at the University of Rochester for over 60 years. The group has made leading contributions to experimental discoveries at accelerators and in cosmic rays and has played major roles in developing the theoretical framework that gives us our ``standard model'' of fundamental interactions today. This award from the Department of Energy funded a major portion of that research for more than 20 years. During this time, highlights of the supported work included the discovery of the top quark at the Fermilab Tevatron, the completion of a broad program of physics measurements that verified the electroweak unified theory, the measurement of three generations of neutrino flavor oscillations, and the first observation of a ``Higgs like'' boson at the Large Hadron Collider. The work has resulted in more than 2000 publications over the period of the grant. The principal investigators supported on this grant have been recognized as leaders in the field of elementary particle physics by their peers through numerous awards and leadership positions. Most notable among them is the APS W.K.H. Panofsky Prize awarded to Arie Bodek in 2004, the J.J. Sakurai Prizes awarded to Susumu Okubo and C. Richard Hagen in 2005 and 2010, respectively, the Wigner medal awarded to Susumu Okubo in 2006, and five principal investigators (Das, Demina, McFarland, Orr, Tipton) who received Department of Energy Outstanding Junior Investigator awards during the period of this grant. The University of Rochester Department of Physics and Astronomy, which houses the research group, provides primary salary support for the faculty and has waived most tuition costs for graduate students during the period of this grant. The group also benefits significantly from technical support and infrastructure available at the University which supports the work. The research work of the group has provided educational opportunities

  6. Theoretical Studies of Hydrogen Storage Alloys.

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, Hannes

    2012-03-22

    Theoretical calculations were carried out to search for lightweight alloys that can be used to reversibly store hydrogen in mobile applications, such as automobiles. Our primary focus was on magnesium based alloys. While MgH{sub 2} is in many respects a promising hydrogen storage material, there are two serious problems which need to be solved in order to make it useful: (i) the binding energy of the hydrogen atoms in the hydride is too large, causing the release temperature to be too high, and (ii) the diffusion of hydrogen through the hydride is so slow that loading of hydrogen into the metal takes much too long. In the first year of the project, we found that the addition of ca. 15% of aluminum decreases the binding energy to the hydrogen to the target value of 0.25 eV which corresponds to release of 1 bar hydrogen gas at 100 degrees C. Also, the addition of ca. 15% of transition metal atoms, such as Ti or V, reduces the formation energy of interstitial H-atoms making the diffusion of H-atoms through the hydride more than ten orders of magnitude faster at room temperature. In the second year of the project, several calculations of alloys of magnesium with various other transition metals were carried out and systematic trends in stability, hydrogen binding energy and diffusivity established. Some calculations of ternary alloys and their hydrides were also carried out, for example of Mg{sub 6}AlTiH{sub 16}. It was found that the binding energy reduction due to the addition of aluminum and increased diffusivity due to the addition of a transition metal are both effective at the same time. This material would in principle work well for hydrogen storage but it is, unfortunately, unstable with respect to phase separation. A search was made for a ternary alloy of this type where both the alloy and the corresponding hydride are stable. Promising results were obtained by including Zn in the alloy.

  7. Experimental and theoretical studies of cylindrical Hall thrusters

    International Nuclear Information System (INIS)

    Smirnov, Artem; Raitses, Yegeny; Fisch, Nathaniel J.

    2007-01-01

    The Hall thruster is a mature electric propulsion device that holds considerable promise in terms of the propellant saving potential. The annular design of the conventional Hall thruster, however, does not naturally scale to low power. The efficiency tends to be lower and the lifetime issues are more aggravated. Cylindrical geometry Hall thrusters have lower surface-to-volume ratio than conventional thrusters and, thus, seem to be more promising for scaling down. The cylindrical Hall thruster (CHT) is fundamentally different from the conventional design in the way the electrons are confined and the ion space charge is neutralized. The performances of both the large (9-cm channel diameter, 600-1000 W) and miniaturized (2.6-cm channel diameter, 50-300 W) CHTs are comparable with those of the state-of-the-art conventional (annular) design Hall thrusters of similar sizes. A comprehensive experimental and theoretical study of the CHT physics has been conducted, addressing the questions of electron cross-field transport, propellant ionization, plasma-wall interaction, and formation of the electron distribution function. Probe measurements in the harsh plasma environment of the microthruster were performed. Several interesting effects, such as the unusually high ionization efficiency and enhanced electron transport, were observed. Kinetic simulations suggest the existence of the strong fluctuation-enhanced electron diffusion and predict the non-Maxwellian shape of the electron distribution function. Through the acquired understanding of the new physics, ways for further optimization of this means for low-power space propulsion are suggested. Substantial flexibility in the magnetic field configuration of the CHT is the key tool in achieving the high-efficiency operation

  8. Theoretical studies of controlled fusion. Final report

    International Nuclear Information System (INIS)

    Krall, N.A.

    1986-01-01

    Transport in FRC was studied analytically and numerically. The physics considered included lower-hybrid-drift turbulence, rapid convection along closed magnetic field lines, nonadiabaticity, and large particle orbits. The study also extended conventional modeling procedures by developing nonlocal models of stability and transport and determined the relation between such models and the more widely used local models

  9. Theoretical studies of controlled fusion: Final report

    International Nuclear Information System (INIS)

    Krall, N.A.

    1987-01-01

    This report summarizes the results of a study of low frequency stability in the Field Reversed Configuration (FRC), with emphasis on the transport resulting from this stability behavior. 11 refs., 5 figs., 2 tabs

  10. Theoretical Studies of Small-System Thermodynamics in Energetic Materials

    Science.gov (United States)

    2016-01-06

    SECURITY CLASSIFICATION OF: This is a comprehensive theoretical research program to investigate the fundamental principles of small-system thermodynamics ...a.k.a. nanothermodynamics). The proposed work is motivated by our desire to better understand the fundamental dynamics and thermodynamics of...for Public Release; Distribution Unlimited Final Report: Theoretical Studies of Small-System Thermodynamics in Energetic Materials The views, opinions

  11. Global Leadership Study: A Theoretical Framework

    Science.gov (United States)

    Perkins, Anne W.

    2009-01-01

    Traditional leadership theory and research courses do not adequately prepare students for cross-cultural leadership. This article notes six premises of Western theories and demonstrates the limitations of these premises in non-Western settings. A framework for the study of cross-cultural leadership, The Global Leadership-Learning Pyramid, is…

  12. Polymeric nanoparticles stabilized by surfactants: kinetic studies

    Czech Academy of Sciences Publication Activity Database

    Pánek, Jiří; Filippov, Sergey K.; Koňák, Čestmír; Steinhart, Miloš; Štěpánek, Petr

    2011-01-01

    Roč. 32, č. 8 (2011), s. 1105-1110 ISSN 0193-2691 R&D Projects: GA ČR GAP208/10/1600 Institutional research plan: CEZ:AV0Z40500505 Keywords : nanoparticles * solvent shifting * time-resolved SAXS Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.560, year: 2011

  13. Theoretical and experimental studies of elementary particles

    International Nuclear Information System (INIS)

    Bodek, A.; Ferbel, T.; Melissinos, A.C.; Olsen, S.L.; Slattery, P.; Tipton, P.; Das, A.; Hagen, C.R.; Rajeev, S.G.; Okubo, S.

    1991-01-01

    This report discusses: Fixed target experimentation at Fermilab; the D-zero collider experiment at Fermilab; deep inelastic lepton nucleon scattering; non-accelerator experiments and non-linear QED; the AMY experiment at TRISTAN and other activities at KEK; the collider detector at Fermilab; laser switched linac; preparations for experiments at the SSC; search for massive stable particles; and the Advanced Study Institute on techniques and concepts of high energy physics

  14. Isothermal, kinetic and thermodynamic studies on basic dye sorption ...

    African Journals Online (AJOL)

    Isothermal, kinetic and thermodynamic studies on basic dye sorption onto tartaric acid esterified wheat straw. ... African Journal of Biotechnology ... esterified wheat straw (EWS), was originally prepared by solid phase thermochemistry method.

  15. Kinetic Studies of Catalytic Oxidation of Cyclohexene Using ...

    African Journals Online (AJOL)

    acer

    Kinetic Studies of Catalytic Oxidation of Cyclohexene Using Chromium VI Oxide in. Acetic Acid ... respect to the oxidant using pseudo-order approximation method. .... making the concentration of the cyclohexene in ..... on Titanium Silicate.

  16. kinetic studies of colour and phenol removal from wastewater using

    African Journals Online (AJOL)

    user

    Kinetic studies by batch technique were carried out using activated carbon prepared from mango seed ... and the rate controlling steps of sorption which ... as follows (Lagergren, 1898): … ... plot of t /qt against t of Equation (6) should give a.

  17. Kinetics of ethylcyclohexane pyrolysis and oxidation: An experimental and detailed kinetic modeling study

    KAUST Repository

    Wang, Zhandong; Zhao, Long; Wang, Yu; Bian, Huiting; Zhang, Lidong; Zhang, Feng; Li, Yuyang; Sarathy, Mani; Qi, Fei

    2015-01-01

    species were evaluated, and good agreement was observed between the PIMS and GC data sets. Furthermore, a fuel-rich burner-stabilized laminar premixed ECH/O2/Ar flame at 30Torr was studied using synchrotron VUV PIMS. A detailed kinetic model for ECH high

  18. Fragmentation of atomic clusters: A theoretical study

    International Nuclear Information System (INIS)

    Lopez, M.J.; Jellinek, J.

    1994-01-01

    Collisionless fragmentation of nonrotating model n-atom metal clusters (n=12, 13, and 14) is studied using isoergic molecular-dynamics simulations. Minimum-energy paths for fragmentation are mapped out as functions of the distance between the centers of mass of the fragments. These paths provide information on the fragmentation energies for the different fragmentation channels. Fragmentation patterns (distributions of the fragmentation channel probabilities) and global and channel-specific fragmentation rate constants are computed and analyzed as functions of the internal energy and of the size of the clusters. The trends derived from the dynamics are compared with those obtained using the RRK and TST statistical approaches. The dynamics of the fragmentation process is analyzed in terms of characteristic quantities such as the distance between the centers of mass of the fragments, their relative translational energy, and their interaction energy, all considered as functions of time

  19. A theoretical study of hydrodynamic cavitation.

    Science.gov (United States)

    Arrojo, S; Benito, Y

    2008-03-01

    The optimization of hydrodynamic cavitation as an AOP requires identifying the key parameters and studying their effects on the process. Specific simulations of hydrodynamic bubbles reveal that time scales play a major role on the process. Rarefaction/compression periods generate a number of opposing effects which have demonstrated to be quantitatively different from those found in ultrasonic cavitation. Hydrodynamic cavitation can be upscaled and offers an energy efficient way of generating cavitation. On the other hand, the large characteristic time scales hinder bubble collapse and generate a low number of cavitation cycles per unit time. By controlling the pressure pulse through a flexible cavitation chamber design these limitations can be partially compensated. The chemical processes promoted by this technique are also different from those found in ultrasonic cavitation. Properties such as volatility or hydrophobicity determine the potential applicability of HC and therefore have to be taken into account.

  20. Theoretical studies of controlled fusion: Final report

    International Nuclear Information System (INIS)

    Krall, N.A.

    1987-01-01

    This report summarizes the results of a study of low frequency stability in the Field Reversed Configuration (FRC), with emphasis on the transport resulting from this stability behavior. Anomalous transport plays an obvious role in the confinement physics of the Field Reversed Configuration. Other anomalies are also observed, including an apparent absence of MHD instability and, in some cases, of lower-hybrid-drift instability. In current FRC experiments at LANL and Spectra Technology, particle, energy, and magnetic flux loss are observed to differ from classical prediction, both in size and in scaling. Early models proposed to explain that transport properties were based on anomalous radial loss of plasma particles in the vicinity of the separatrix between closed and open field lines produced by lower-hybrid instabilities. Our present work has shown that low frequency drift waves were also unstable in FRC, and produce energy and flux loss consistent with observation. 11 refs., 5 figs., 2 tabs

  1. 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

  2. Experimental and theoretical study of reflux condensation

    Energy Technology Data Exchange (ETDEWEB)

    Bakke, Knut

    1997-12-31

    This thesis studies the separation of gas mixtures in a reflux condenser. also called a dephlegmator. Reflux condensation is separation of a gas mixture, in reflux flow with condensing liquid, under continuous heat removal. A numerical model of a dephlegmator for binary mixtures was developed. The model may readily be extended to multi-component mixtures, as the solution method is based on a matrix solver. Separation of a binary mixture in a reflux condenser test rig is demonstrated. The test facility contains a single-tube test section that was designed and built as part of the project. Test mixtures of propane and n-butane were used, and a total of 15 experiments are reported. Limited degree of separation was achieved due to limited heat transfer area and narrow boiling point range of the test mixture. The numerical model reproduces the experimental data within reasonable accuracy. Deviation between calculated and measured properties is less than 6% of the measured temperature and less than 5% of the measured flow rate. The model is based on mechanistic models of physical processes and is not calibrated or tuned to fit the experimental data. The numerical model is applied to a number of separation processes. These case studies show that the required heat transfer area increases rapidly with increments in top product composition (light component). Flooding limits the amount of reflux liquid. The dephlegmator is suitable for separation of feed mixtures that are rich in light components. The gliding temperature in the dephlegmation process enables utilization of top product as refrigerant, with subsequent energy saving as a result. 61 refs., 50 figs., 34 tabs.

  3. Contributions to the study of positive ion kinetics in gases

    International Nuclear Information System (INIS)

    Popescu, A.

    1978-01-01

    Extensive studies on cesium ion kinetics in cesium and cesium-noble gas mixtures were performed. The obtained data are correlated with the measured parameters of the thermionic diodes. The mobility of atomic and molecular cesium ions at low electric fields, including zero electric field, in cesium and cesium krypton mixtures were measured using the time of flight method and a special thermionic ion detector. The atomic ion conversion into molecular ions is theoretically considered in the diffusion equation of the charged particles and the obtained analytical relation is in good agreement with the experimental cesium measured data. The reaction rate of the ion conversion in cesium is considered from these measurements. Measurements on the diffused plasma through the anode (provided with holes) of the cesium thermionic diode supply data on the anode sheath, the ratio of electronic and ionic current, electron temperature and the nature of the cesium ions (atomic or molecular) for various modes of the low voltage arc discharge. The obtained data have been used for the optimization of the thermionic diode parameters, as well as for the development of a new type of device for the detection of impurities in the air. (author)

  4. Theoretical studies of homogeneous catalysts mimicking nitrogenase.

    Science.gov (United States)

    Sgrignani, Jacopo; Franco, Duvan; Magistrato, Alessandra

    2011-01-10

    The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen 'fixation' via an iron molybdenum cofactor (FeMo-co) under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N₂ to various degrees. However, to date Mo(N₂)(HIPTN)₃N with (HIPTN)₃N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N₂. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

  5. Theoretical Studies of Homogeneous Catalysts Mimicking Nitrogenase

    Directory of Open Access Journals (Sweden)

    Alessandra Magistrato

    2011-01-01

    Full Text Available The conversion of molecular nitrogen to ammonia is a key biological and chemical process and represents one of the most challenging topics in chemistry and biology. In Nature the Mo-containing nitrogenase enzymes perform nitrogen ‘fixation’ via an iron molybdenum cofactor (FeMo-co under ambient conditions. In contrast, industrially, the Haber-Bosch process reduces molecular nitrogen and hydrogen to ammonia with a heterogeneous iron catalyst under drastic conditions of temperature and pressure. This process accounts for the production of millions of tons of nitrogen compounds used for agricultural and industrial purposes, but the high temperature and pressure required result in a large energy loss, leading to several economic and environmental issues. During the last 40 years many attempts have been made to synthesize simple homogeneous catalysts that can activate dinitrogen under the same mild conditions of the nitrogenase enzymes. Several compounds, almost all containing transition metals, have been shown to bind and activate N2 to various degrees. However, to date Mo(N2(HIPTN3N with (HIPTN3N= hexaisopropyl-terphenyl-triamidoamine is the only compound performing this process catalytically. In this review we describe how Density Functional Theory calculations have been of help in elucidating the reaction mechanisms of the inorganic compounds that activate or fix N2. These studies provided important insights that rationalize and complement the experimental findings about the reaction mechanisms of known catalysts, predicting the reactivity of new potential catalysts and helping in tailoring new efficient catalytic compounds.

  6. Theoretical study of cisplatin adsorption on silica

    Energy Technology Data Exchange (ETDEWEB)

    Simonetti, S., E-mail: ssimonet@uns.edu.ar [Departamento de Fisica and IFISUR, Universidad Nacional del Sur-CONICET, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Departamentos de Ciencias Basicas e Ingenieria Mecanica, Universidad Tecnologica Nacional, 11 de Abril 461, 8000 Bahia Blanca (Argentina); Company, A. Diaz; Brizuela, G.; Juan, A. [Departamento de Fisica and IFISUR, Universidad Nacional del Sur-CONICET, Av. Alem 1253, 8000 Bahia Blanca (Argentina)

    2011-11-15

    The adsorption of cisplatin and its complexes, cis-[PtCl(NH{sub 3}){sub 2}]{sup +} and cis-[Pt(NH{sub 3}){sub 2}]{sup 2+}, on a SiO{sub 2}(1 1 1) hydrated surface has been studied by the Atom Superposition and Electron Delocalization method. The adiabatic energy curves for the adsorption of the drug and its products on the delivery system were considered. The electronic structure and bonding analysis were also performed. The molecule-surface interactions are formed at expenses of the OH surface bonds. The more important interactions are the Cl-H bond for cis-[PtCl{sub 2}(NH{sub 3}){sub 2}] and cis-[PtCl(NH{sub 3}){sub 2}]{sup +} adsorptions, and the Pt-O interaction for cis-[Pt(NH{sub 3}){sub 2}]{sup 2+} adsorption. The Cl p orbitals and Pt s, p y d orbitals of the molecule and its complexes, and the s H orbital and, the s and p orbitals of the O atoms of the hydrated surface are the main contribution to the surface bonds.

  7. GLOBAL SOURCING: A THEORETICAL STUDY ON TURKEY

    Directory of Open Access Journals (Sweden)

    Aytac GOKMEN

    2010-07-01

    Full Text Available Global sourcing is to source from the global market for goods and services across national boundaries in order to take advantage of the global efficiencies in the delivery of a product or service. Such efficiencies are consists of low cost skilled labor, low cost raw materials and other economic factors like tax breaks and deductions as well as low trade tariffs. When we assess the case regarding to Turkey, global sourcing is an effective device for some firms. The domestic firms in Turkey at various industries are inclined to global source finished or intermediate goods from the world markets, finish the production process in Turkey and export. Eventually, on the one hand the export volume of Turkey increases, but on the other hand the import of a considerable volume of finished or intermediate goods bring about a negative trade balance and loss of jobs in Turkey. Therefore, the objective of this study is to assess the concept of global sourcing transactions on Turkey resting on comprehensive publications.

  8. Theoretical studies on sRNA-mediated regulation in bacteria

    Science.gov (United States)

    Chang, Xiao-Xue; Xu, Liu-Fang; Shi, Hua-Lin

    2015-12-01

    Small RNA(sRNA)-mediated post-transcriptional regulation differs from protein-mediated regulation. Through base-pairing, sRNA can regulate the target mRNA in a catalytic or stoichiometric manner. Some theoretical models were built for comparison of the protein-mediated and sRNA-mediated modes in the steady-state behaviors and noise properties. Many experiments demonstrated that a single sRNA can regulate several mRNAs, which causes crosstalk between the targets. Here, we focus on some models in which two target mRNAs are silenced by the same sRNA to discuss their crosstalk features. Additionally, the sequence-function relationship of sRNA and its role in the kinetic process of base-pairing have been highlighted in model building. Project supported by the National Basic Research Program of China (Grant No. 2013CB834100), the National Natural Science Foundation of China (Grant Nos. 11121403 and 11274320), the Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Grant No. Y4KF171CJ1), the National Natural Science Foundation for Young Scholar of China (Grant No. 11304115), and the China Postdoctoral Science Foundation (Grant No. 2013M541282).

  9. Theoretical studies of solar pumped lasers

    Science.gov (United States)

    Harries, Wynford L.

    1990-01-01

    One concept for collecting solar energy is to use large solar collectors and then use lasers as energy converters whose output beams act as transmission lines to deliver the energy to a destination. The efficiency of the process would be improved if the conversion could be done directly using solar pumped lasers, and the possibility of making such lasers is studied. There are many applications for such lasers, and these are examined. By including the applications first, the requirements for the lasers will be more evident. They are especially applicable to the Space program, and include cases where no other methods of delivering power seem possible. Using the lasers for conveying information and surveillance is also discussed. Many difficulties confront the designer of an efficient system for power conversion. These involve the nature of the solar spectrum, the method of absorbing the energy, the transfer of power into laser beams, and finally, the far field patterns of the beams. The requirements of the lasers are discussed. Specific laser configurations are discussed. The thrust is into gas laser systems, because for space applications, the laser could be large, and also the medium would be uniform and not subject to thermal stresses. Dye and solid lasers are treated briefly. For gas lasers, a chart of the various possibilities is shown, and the various families of gas lasers divided according to the mechanisms of absorbing solar radiation and of lasing. Several specific models are analyzed and evaluated. Overall conclusions for the program are summarized, and the performances of the lasers related to the requirements of various applications.

  10. Theoretical studies of Anderson impurity models

    International Nuclear Information System (INIS)

    Glossop, M.T.

    2000-01-01

    A Local Moment Approach (LMA) is developed for single-particle excitations of a symmetric single impurity Anderson model (SIAM) with a soft-gap hybridization vanishing at the Fermi level, Δ I ∝ vertical bar W vertical bar r with r > 0, and for the generic asymmetric case of the 'normal' (r = 0) SIAM. In all cases we work within a two-self-energy description with local moments introduced explicitly from the outset, and in which single-particle excitations are coupled dynamically to low-energy transverse spin fluctuations. For the soft-gap symmetric SIAM, the resultant theory is applicable on all energy scales, and captures both the spin-fluctuation regime of strong coupling (large-U), as well as the weak coupling regime where it is perturbatively exact for those r-domains in which perturbation theory in U is non-singular. While the primary emphasis is on single-particle dynamics, the quantum phase transition between strong coupling (SC) and local moment (LM) phases can also be addressed directly; for the spin-fluctuation regime in particular a number of asymptotically exact results are thereby obtained, notably for the behaviour of the critical U c (r) separating SC/LM states and the Kondo scale w m (r) characteristic of the SC phase. Results for both single-particle spectra and SG/LM phase boundaries are found to agree well with recent numerical renormalization group (NRG) studies; and a number of further testable predictions are made. Single-particle spectra are examined systematically for both SC and LM states; in particular, for all 0 ≤ r 0 SC phase which, in agreement with conclusions drawn from recent NRG work, may be viewed as a non-trivial but natural generalization of Fermi liquid physics. We also reinvestigate the problem via the NRG in light of the predictions arising from the LMA: all are borne out and excellent agreement is found. For the asymmetric single impurity Anderson model (ASIAM) we establish general conditions which must be satisfied

  11. Theoretical and Experimental Studies in Accelerator Physics

    Energy Technology Data Exchange (ETDEWEB)

    Rosenzweig, James [Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy

    2017-03-08

    . We note also that PBPL graduates remain as close elaborators for the program after leaving UCLA. The UCLA PBPL program is a foremost developer of on-campus facilities, such as the Neptune and Pegasus Laboratories, providing a uniquely strong environment for student-based research. In addition, the PBPL is a strong user of off-campus national lab facilities, such as SLAC FACET and NLCTA, and the BNL ATF. UCLA has also vigorously participated in the development of these facilities. The dual emphases on off- and on-campus opportunities permit the PBPL to address in an agile way a wide selection of cutting-edge research topics. The topics embraced by this proposal illustrate this program aspect well. These include: GV/m dielectric wakefield acceleration/coherent Cerenkov radiation experiments at FACET (E-201) and the ATF; synergistic laser-excited dielectric accelerator and light source development; plasma wakefield (PWFA) experiments on “Trojan horse” ionization injection (FACET E-210), quasi-nonlinear PWFA at BNL and the production at Neptune high transformer ratio plasma wakes; the inauguration of a new type of RF photoinjector termed “hybrid” at UCLA, and application to PWFA; space-charge dominated beam and cathode/near cathode physics; the study of advanced IFEL systems, for very high energy gain and utilization of novel OAM modes; the physcis of inverse Compton scattering (ICS), with applications to e+ production and γγ colliders; electron diffraction; and advanced beam diagnostics using coherent imaging techniques. These subjects are addressed under the leadership of PBPL director Prof. James Rosenzweig in Task A, and Prof. Pietro Musumeci in Task J, which was initiated following his OHEP Outstanding Junior Investigator award.

  12. KrF laser kinetics studies

    International Nuclear Information System (INIS)

    Mandl, A.; Klimek, D.; Parks, J.H.

    1984-01-01

    A series of measurements characterizing an e beam pumped KrF* laser was carried out using a 200-nsec e-beam pulse having a rise time of 25 nsec at current densities up to 50 A/cm 2 . These pump conditions are relevent for inertial confinement fusion laser drivers. The measurements include fluorescence efficiency, sidelight suppression of the fluorescence during lasing, and laser energy output over a wide range of laser parameters including: total density 0.5--2.0 amagats, temperature 300--400 K, fluorine density 0.15%--0.5%, current density 38--50 A/cm 2 and various mirror transmissions. This data was used to verify and refine a model of KrF* kinetics which was then used to estimate the performance of an angular multiplexed power amplifier suitable for laser fusion applications

  13. Experimental and theoretical studies of bombardment induced surface morphology changes

    International Nuclear Information System (INIS)

    Carter, G.; Nobes, M.J.; Williams, J.S.

    1980-01-01

    In this review results of experimental and theoretical studies of solid surface morphology changes due to ion bombardment are discussed. An attempt is undertaken to classify the observed specific features of a structure, generated by ion bombardment [ru

  14. Theoretical Studies of Elementary Hydrocarbon Species and Their Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Wesley D. [Univ. of Georgia, Athens, GA (United States). Dept. of Chemistry. Center for Computational Quantum Chemistry; Schaefer, III, Henry F. [Univ. of Georgia, Athens, GA (United States). Dept. of Chemistry. Center for Computational Quantum Chemistry

    2015-11-14

    This is the final report of the theoretical studies of elementary hydrocarbon species and their reactions. Part A has a bibliography of publications supported by DOE from 2010 to 2016 and Part B goes into recent research highlights.

  15. Theoretical Kinetics Analysis for Ḣ Atom Addition to 1,3-Butadiene and Related Reactions on the Ċ4H7 Potential Energy Surface.

    Science.gov (United States)

    Li, Yang; Klippenstein, Stephen J; Zhou, Chong-Wen; Curran, Henry J

    2017-10-12

    The oxidation chemistry of the simplest conjugated hydrocarbon, 1,3-butadiene, can provide a first step in understanding the role of polyunsaturated hydrocarbons in combustion and, in particular, an understanding of their contribution toward soot formation. On the basis of our previous work on propene and the butene isomers (1-, 2-, and isobutene), it was found that the reaction kinetics of Ḣ-atom addition to the C═C double bond plays a significant role in fuel consumption kinetics and influences the predictions of high-temperature ignition delay times, product species concentrations, and flame speed measurements. In this study, the rate constants and thermodynamic properties for Ḣ-atom addition to 1,3-butadiene and related reactions on the Ċ 4 H 7 potential energy surface have been calculated using two different series of quantum chemical methods and two different kinetic codes. Excellent agreement is obtained between the two different kinetics codes. The calculated results including zero-point energies, single-point energies, rate constants, barrier heights, and thermochemistry are systematically compared among the two quantum chemical methods. 1-Methylallyl (Ċ 4 H 7 1-3) and 3-buten-1-yl (Ċ 4 H 7 1-4) radicals and C 2 H 4 + Ċ 2 H 3 are found to be the most important channels and reactivity-promoting products, respectively. We calculated that terminal addition is dominant (>80%) compared to internal Ḣ-atom addition at all temperatures in the range 298-2000 K. However, this dominance decreases with increasing temperature. The calculated rate constants for the bimolecular reaction C 4 H 6 + Ḣ → products and C 2 H 4 + Ċ 2 H 3 → products are in excellent agreement with both experimental and theoretical results from the literature. For selected C 4 species, the calculated thermochemical values are also in good agreement with literature data. In addition, the rate constants for H atom abstraction by Ḣ atoms have also been calculated, and it is

  16. Theoretical evidence of the observed kinetic order dependence on temperature during the N(2)O decomposition over Fe-ZSM-5.

    Science.gov (United States)

    Guesmi, Hazar; Berthomieu, Dorothee; Bromley, Bryan; Coq, Bernard; Kiwi-Minsker, Lioubov

    2010-03-28

    The characterization of Fe/ZSM5 zeolite materials, the nature of Fe-sites active in N(2)O direct decomposition, as well as the rate limiting step are still a matter of debate. The mechanism of N(2)O decomposition on the binuclear oxo-hydroxo bridged extraframework iron core site [Fe(II)(mu-O)(mu-OH)Fe(II)](+) inside the ZSM-5 zeolite has been studied by combining theoretical and experimental approaches. The overall calculated path of N(2)O decomposition involves the oxidation of binuclear Fe(II) core sites by N(2)O (atomic alpha-oxygen formation) and the recombination of two surface alpha-oxygen atoms leading to the formation of molecular oxygen. Rate parameters computed using standard statistical mechanics and transition state theory reveal that elementary catalytic steps involved into N(2)O decomposition are strongly dependent on the temperature. This theoretical result was compared to the experimentally observed steady state kinetics of the N(2)O decomposition and temperature-programmed desorption (TPD) experiments. A switch of the reaction order with respect to N(2)O pressure from zero to one occurs at around 800 K suggesting a change of the rate determining step from the alpha-oxygen recombination to alpha-oxygen formation. The TPD results on the molecular oxygen desorption confirmed the mechanism proposed.

  17. Kinetics of ethylcyclohexane pyrolysis and oxidation: An experimental and detailed kinetic modeling study

    KAUST Repository

    Wang, Zhandong

    2015-07-01

    Ethylcyclohexane (ECH) is a model compound for cycloalkanes with long alkyl side-chains. A preliminary investigation on ECH (Wang et al., Proc. Combust. Inst., 35, 2015, 367-375) revealed that an accurate ECH kinetic model with detailed fuel consumption mechanism and aromatic growth pathways, as well as additional ECH pyrolysis and oxidation data with detailed species concentration covering a wide pressure and temperature range are required to understand the ECH combustion kinetics. In this work, the flow reactor pyrolysis of ECH at various pressures (30, 150 and 760Torr) was studied using synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS) and gas chromatography (GC). The mole fraction profiles of numerous major and minor species were evaluated, and good agreement was observed between the PIMS and GC data sets. Furthermore, a fuel-rich burner-stabilized laminar premixed ECH/O2/Ar flame at 30Torr was studied using synchrotron VUV PIMS. A detailed kinetic model for ECH high temperature pyrolysis and oxidation was developed and validated against the pyrolysis and flame data performed in this work. Further validation of the kinetic model is presented against literature data including species concentrations in jet-stirred reactor oxidation, ignition delay times in a shock tube, and laminar flame speeds at various pressures and equivalence ratios. The model well predicts the consumption of ECH, the growth of aromatics, and the global combustion properties. Reaction flux and sensitivity analysis were utilized to elucidate chemical kinetic features of ECH combustion under various reaction conditions. © 2015 The Combustion Institute.

  18. Crossed beam studies related to gas kinetics

    International Nuclear Information System (INIS)

    Buss, R.J.; Lee, Y.T.

    1979-01-01

    Recent advances in methods of quantum mechanical calculations, electronic computer capabilities, and microscopic experimental methods have put us in a position to understand, evaluate, and extend our current knowledge of elementary chemical reactions. It is certain that, in the future, information derived from first principles will become more important in understanding chemical processes, although chemistry will remain largely an experimental science. Microscopic experiments, such as molecular beam methods, are not the general means for obtaining precise data on rate constants. They are designed not only to reveal detailed information on reaction dynamics with which to gain a clear understanding of macroscopic phenomena, but also to provide a benchmark for the future development of quantum chemical methods for solving the problems of chemical kinetics. Actually, collection of rate constants alone is not sufficient to understand many chemical phenomena. For example, in the modeling of chemical lasers, it is necessary to have detailed information on reaction dynamics. We will discuss contributions which crossed molecular beams have made to our understanding of elementary chemical reactions. It is likely that the advancement of crossed beam methods will make it an important tool for obtaining new chemical information in the future

  19. Kinetic Uptake Studies of Powdered Materials in Solution

    Directory of Open Access Journals (Sweden)

    Mohamed H. Mohamed

    2015-06-01

    Full Text Available Challenges exist for the study of time dependent sorption processes for heterogeneous systems, especially in the case of dispersed nanomaterials in solvents or solutions because they are not well suited to conventional batch kinetic experiments. In this study, a comparison of batch versus a one-pot setup in two variable configurations was evaluated for the study of uptake kinetics in heterogeneous (solid/solution systems: (i conventional batch method; (ii one-pot system with dispersed adsorbent in solution with a semi-permeable barrier (filter paper or dialysis tubing for in situ sampling; and (iii one-pot system with an adsorbent confined in a semi-permeable barrier (dialysis tubing or filter paper barrier with ex situ sampling. The sorbent systems evaluated herein include several cyclodextrin-based polyurethane materials with two types of phenolic dyes: p-nitrophenol and phenolphthalein. The one-pot kinetics method with in situ (Method ii or ex situ (Method iii sampling described herein offers significant advantages for the study of heterogeneous sorption kinetics of highly dispersed sorbent materials with particles sizes across a range of dimensions from the micron to nanometer scale. The method described herein will contribute positively to the development of advanced studies for heterogeneous sorption processes where an assessment of the relative uptake properties is required at different experimental conditions. The results of this study will be advantageous for the study of nanomaterials with significant benefits over batch kinetic studies for a wide range of heterogeneous sorption processes.

  20. Theoretical study of nuclear physics with strangeness at Nankai University

    International Nuclear Information System (INIS)

    Ning Pingzhi

    2007-01-01

    Theoretical study of nuclear physics with strangeness from the nuclear physics group at Nankai university is briefly introduced. Theoretical calculations on hyperon mean free paths in nuclear medium have been done. The other 4 topics in the area of strangeness nuclear physics are the effect of different baryon impurities in nucleus, the heavy flavored baryon hypernuclei, the eta-mesons in nuclear matter and the properties of kaonic nuclei. (authors)

  1. Theoretical and experimental study of an energy-reinforced braking radiation photon beam

    International Nuclear Information System (INIS)

    Bertin, Pierre-Yves

    1966-01-01

    This research thesis reports the theoretical study of a photon beam raised towards high energies, its experimental implementation, the definition of a gamma spectrometry method which aimed at checking various hypotheses used in the beam theoretical study. After a presentation of the theory of phenomena of electron braking radiation, of materialisation of photons into positon-negaton pair, and of issues related to multiple Coulomb diffusion, the author reports the study of the different solutions which allow a photon beam to be obtained. A braking radiation of mono-kinetic electron has been used. This braking radiation is reinforced by absorption of low energy protons in a column of lithium hydride. The author describes how the beam is built up, and the experimental approach. He describes how raw data are processed to get rid of the influence of the multiple Coulomb diffusion and of the braking radiation. Experimental results are compared with those obtained by convolution of photon spectra and differential cross section

  2. Experimental, theoretical, and numerical studies of small scale combustion

    Science.gov (United States)

    Xu, Bo

    Recently, the demand increased for the development of microdevices such as microsatellites, microaerial vehicles, micro reactors, and micro power generators. To meet those demands the biggest challenge is obtaining stable and complete combustion at relatively small scale. To gain a fundamental understanding of small scale combustion in this thesis, thermal and kinetic coupling between the gas phase and the structure at meso and micro scales were theoretically, experimentally, and numerically studied; new stabilization and instability phenomena were identified; and new theories for the dynamic mechanisms of small scale combustion were developed. The reduction of thermal inertia at small scale significantly reduces the response time of the wall and leads to a strong flame-wall coupling and extension of burning limits. Mesoscale flame propagation and extinction in small quartz tubes were theoretically, experimentally and numerically studied. It was found that wall-flame interaction in mesoscale combustion led to two different flame regimes, a heat-loss dominant fast flame regime and a wall-flame coupling slow flame regime. The nonlinear transition between the two flame regimes was strongly dependent on the channel width and flow velocity. It is concluded that the existence of multiple flame regimes is an inherent phenomenon in mesoscale combustion. In addition, all practical combustors have variable channel width in the direction of flame propagation. Quasi-steady and unsteady propagations of methane and propane-air premixed flames in a mesoscale divergent channel were investigated experimentally and theoretically. The emphasis was the impact of variable cross-section area and the flame-wall coupling on the flame transition between different regimes and the onset of flame instability. For the first time, spinning flames were experimentally observed for both lean and rich methane and propane-air mixtures in a broad range of equivalence ratios. An effective Lewis number

  3. Spectroscopic and kinetic study of bismuth dimers

    Science.gov (United States)

    Franklin, Robert Eugene

    1997-08-01

    The spectroscopy of high rotational levels in Bi2 X(0g+) and A(0u+) was investigated for 2/le v/prime'/le5 and 0/le v/sp/prime/le4 by observing total fluorescence from laser excitation with a scanning, continuous wave, narrow linewidth ring laser. Rotational levels with J/le211 were accessed. Dunham coefficients were derived that fit all observed rotational lines to within 0.01 cm-1. From these coefficients, Franck-Condon factors were calculated that accurately reflect a set of experimentally determined Franck-Condon factors originating from the initially populated levels 0/le v/sp/prime/le5. Vibrational energy transfer in the low-lying vibrational levels (v/sp/prime/le4) of the A(0u+) state of Bi2 was investigated using spectrally resolved, continuous wave laser induced fluorescence. Spectrally resolved emissions from collisionally populated Bi2(A) vibrational levels were observed for rare gas collision partners. Vibrational transfer promoted rapid thermalization of the excited A state molecules. Landau- Teller scaling of vibrational transfer rates was found to be an acceptable model for the scaling of transfer rates with vibrational quantum number. Fundamental transfer rate coefficients ranged from kv(1,0)=5.29/pm0.73×10-12/ [ cm]3/molec-sec for helium to kv(1,0)=2.38/pm0.36×10-12/ [ cm]3/molec-sec for krypton. Electronic quenching and multi-quantum transfer rates were found to be approximately an order of magnitude slower than the corresponding single quantum transfer rates. Rotational energy transfer in high rotational levels of the A state of Bi2 was also investigated by spectrally resolved, continuous wave laser induced fluorescence. Spectrally resolved emissions from collisionally populated Bi2(A) rotational levels were observed for collisions with helium, neon and argon after laser excitation of J/sp/prime=171,201,231. Rotational energy transfer was the most efficient kinetic process in Bi2(A) and is adequately modeled by the energy based statistical

  4. Kinetic and Related Determinants of Plasma Triglyceride Concentration in Abdominal Obesity: Multicenter Tracer Kinetic Study.

    Science.gov (United States)

    Borén, Jan; Watts, Gerald F; Adiels, Martin; Söderlund, Sanni; Chan, Dick C; Hakkarainen, Antti; Lundbom, Nina; Matikainen, Niina; Kahri, Juhani; Vergès, Bruno; Barrett, P Hugh R; Taskinen, Marja-Riitta

    2015-10-01

    Patients with obesity and diabetes mellitus have increased risk of cardiovascular disease. A major cause is an atherogenic dyslipidemia related primarily to elevated plasma concentrations of triglyceride-rich lipoproteins. The aim of this study was to clarify determinants of plasma triglyceride concentration. We focused on factors that predict the kinetics of very-low density lipoprotein 1 (VLDL1) triglycerides. A multicenter study using dual stable isotopes (deuterated leucine and glycerol) and multicompartmental modeling was performed to elucidate the kinetics of triglycerides and apoB in VLDL1 in 46 subjects with abdominal obesity and additional cardiometabolic risk factors. Results showed that plasma triglyceride concentrations were dependent on both the secretion rate (r=0.44, Ptriglycerides and VLDL1-apoB. Liver fat mass was independently and directly associated with secretion rates of VLDL1-triglycerides (r=0.56, Ptriglycerides (r=0.48, Ptriglyceride concentrations in abdominal obesity are determined by the kinetics of VLDL1 subspecies, catabolism being mainly dependent on apoC-III concentration and secretion on liver fat content. Reduction in liver fat and targeting apoC-III may be an effective approach for correcting triglyceride metabolism atherogenic dyslipidemia in obesity. © 2015 American Heart Association, Inc.

  5. An Activity Theoretical Approach to Social Interaction during Study Abroad

    Science.gov (United States)

    Shively, Rachel L.

    2016-01-01

    This case study examines how one study abroad student oriented to social interaction during a semester in Spain. Using an activity theoretical approach, the findings indicate that the student not only viewed social interaction with his Spanish host family and an expert-Spanish-speaking age peer as an opportunity for second language (L2) learning,…

  6. Kinetic study on UV-absorber photodegradation under different conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bubev, Emil, E-mail: ebubev@my.uctm.edu [University of Chemical Technology and Metallurgy, Department of Physical Chemistry (Bulgaria); Georgiev, Anton [University of Chemical Technology and Metallurgy, Department of Organic Chemistry (Bulgaria); Machkova, Maria [University of Chemical Technology and Metallurgy, Department of Physical Chemistry (Bulgaria)

    2016-09-12

    The photodegradation kinetics of two benzophenone derivative UV-absorbers (UVAs)-BP-4 (benzophenone-4) and 4-HBP (4-hydroxybenzophenone), as additives in polyvinyl acetate (PVAc) films, were studied. Solution-processed PVAc films were irradiated in different environments in order to study oxygen and atmospheric humidity influence on UVA photodegradation. Photodegradation was traced by absorption intensity loss via UV–vis spectroscopy. Both UVAs exhibited excellent photostability in an inert atmosphere. Rate constants showed that BP-4 has better permanence in absence of oxygen. Both film types experienced rapid absorption loss, when irradiated in an oxygen containing atmosphere. UVA degradation was treated as a two-stage process. The photodegradation kinetics in the first stage agreed with the adopted complex rate law, but the second stage was best described by pseudo-first order kinetics. BP-4 exhibited better stability. Oxygen was established as the main accelerating factor for photodegradation of benzophenone derivatives UV-absorbers in thin PVAc films.

  7. Theoretical and Methodological Perspectives on Designing Video Studies of Interaction

    Directory of Open Access Journals (Sweden)

    Anna-Lena Rostvall

    2005-12-01

    Full Text Available In this article the authors discuss the theoretical basis for the methodological decisions made during the course of a Swedish research project on interaction and learning. The purpose is to discuss how different theories are applied at separate levels of the study. The study is structured on three levels, with separate sets of research questions and theoretical concepts. The levels reflect a close-up description, a systematic analysis, and an interpretation of how teachers and students act and interact. The data consist of 12 hours of video-recorded and transcribed music lessons from high school and college. Through a multidisciplinary theoretical framework, the general understanding of teaching and learning in terms of interaction can be widened. The authors also present a software tool developed to facilitate the processes of transcription and analysis of the video data.

  8. Studies on the kinetics and intraparticle diffusivities of BOD, colour ...

    African Journals Online (AJOL)

    Therefore, this study reveals that boiler fly ash can effectively be used as an adsorbent for POME treatment and also established the kinetic and mechanisms of the sorption process. Also, the results of this study could serve as effective design parameters for a treatment plant to further reduce BOD, colour and TSS from ...

  9. Kinetic-energy functionals studied by surface calculations

    DEFF Research Database (Denmark)

    Vitos, Levente; Skriver, Hans Lomholt; Kollár, J.

    1998-01-01

    The self-consistent jellium model of metal surfaces is used to study the accuracy of a number of semilocal kinetic-energy functionals for independent particles. It is shown that the poor accuracy exhibited by the gradient expansion approximation and most of the semiempirical functionals in the lo...... density, high gradient limit may be subtantially improved by including locally a von Weizsacker term. Based on this, we propose a simple one-parameter Pade's approximation, which reproduces the exact Kohn-Sham surface kinetic energy over the entire range of metallic densities....

  10. Theoretical nuclear reaction and structure studies using hyperons and photons

    International Nuclear Information System (INIS)

    Cotanch, S.R.

    1991-01-01

    This report details research progress and results obtained during the 12 month period from January 1991 through 31 December 1991. The research project, entitled ''Theoretical Nuclear Reaction and Structure Studies Using Hyperons and Photons,'' is supported by grant DE-FG05-88ER40461 between North Carolina State University and the United States Department of Energy. In compliance with grant requirements the Principal Investigator, Professor Stephen R. Cotanch, has conducted a research program addressing theoretical investigations of reactions involving hyperons and photons. The new, significant research results are briefly summarized in the following sections

  11. Theoretical studies in nuclear reactions and nuclear structure

    International Nuclear Information System (INIS)

    Wallace, S.J.

    1991-05-01

    This report discusses topics in the following areas: Hadronic structure; hadrons in nuclei; hot hadronic matter; relativistic nuclear physics and NN interaction; leptonic emissions from high-Z heavy ion collisions; theoretical studies of heavy ion dynamics; nuclear pre-equilibrium reactions; classical chaotic dynamics and nuclear structure; and, theory of nuclear fission

  12. A theoretical study of absorption equilibria in silicon CVD

    NARCIS (Netherlands)

    Gardeniers, Johannes G.E.; Giling, L.J.; de Jong, F.; van der Eerden, J.P.

    1990-01-01

    As part of a theoretical study of adsorption processes in the chemical vapour deposition of silicon, thermochemical data are derived for the adsorption of Si-H species on the Si(111) and the dimer-reconstructed Si(001)-(2 x 1) surfaces. Essential contributions to the heats of adsorption appear to be

  13. Theoretical studies of transition metal complexes with nitriles and isocyanides

    International Nuclear Information System (INIS)

    Kuznetsov, Maksim L

    2002-01-01

    Theoretical studies of transition metal complexes with nitriles and isocyanides are reviewed. The electronic structures and the nature of coordination bonds in these complexes are discussed. The correlation between the electronic structures of transition metal complexes with nitriles and isocyanides and their structural properties, spectroscopic characteristics, and reactivities are considered. The bibliography includes 121 references.

  14. A theoretical study on interaction of proline with gold cluster

    Indian Academy of Sciences (India)

    with Au3 (Pakiari and Jamshidi 2007) and interaction of. ∗. Author for correspondence (harjinder.singh@iiit.ac.in) small gold clusters with xDNA base pairs (Sharma et al. 2009) have motivated us to carry out a theoretical study on interaction of proline with gold nanoparticles. Proline is unique among the natural amino acids ...

  15. Theoretical study of catalytic hydrogenation of oxirane and its methyl ...

    African Journals Online (AJOL)

    C3H6O) is its methyl derivative. Theoretical studies on catalytic hydrogenation of both compounds, in presence of aluminium chloride (AlCl3) catalyst, are carried out. The products of reactions are ethanol and propan-1-ol from oxirane and ...

  16. Theoretical study of n-alkane adsorption on metal surfaces

    DEFF Research Database (Denmark)

    Morikawa, Yoshitada; Ishii, Hisao; Seki, Kazuhiko

    2004-01-01

    The interaction between n-alkane and metal surfaces has been studied by means of density-functional theoretical calculations within a generalized gradient approximation (GGA). We demonstrate that although the GGA cannot reproduce the physisorption energy well, our calculations can reproduce the e...

  17. DSC and curing kinetics study of epoxy grouting diluted with furfural -acetone slurry

    Science.gov (United States)

    Yin, H.; Sun, D. W.; Li, B.; Liu, Y. T.; Ran, Q. P.; Liu, J. P.

    2016-07-01

    The use of furfural-acetone slurry as active diluents of Bisphenol-A epoxy resin (DGEBA) groutings has been studied by dynamic and non-isothermal DSC for the first time. Curing kinetics study was investigated by non-isothermal differential scanning calorimetries at different heating rates. Activation enery (Ea) was calculated based on Kissinger and Ozawa Methods, and the results showed that Ea increased from 58.87 to 71.13KJ/mol after the diluents were added. The furfural-acetone epoxy matrix could cure completely at the theoretical curing temperature of 365.8K and the curing time of 139mins, which were determined by the kinetic model parameters.

  18. Kinetic Studies of Catalytic Oxidation of Cyclohexene Using ...

    African Journals Online (AJOL)

    Cyclohexene was oxidized using chromium (VI) oxide (CrO3) in pure acetic acid medium. The products of oxidation were analysed using simple qualitative analysis, IR spectroscopy and Gas chromatography-Mass spectrometry (GC/MS). Kinetics studies were carried out to determine the order of reaction, rate constant and ...

  19. Kinetic and Thermodynamic Studies on Adsorption of Sulphate from ...

    African Journals Online (AJOL)

    DELL USER

    22, No. 1, 2017. 39. Kinetic and Thermodynamic Studies on Adsorption of Sulphate from Aqueous Solution by. Magnetite ... poison catalysts, and affect the .... C for 1 h in a stainless steel reactor placed in a furnace ... N2 gas for 30 min. 50 ml of ...... adsorption for designing and evaluating the ... is the equilibrium liquid-phase.

  20. Dissociation of the Phenylarsane Molecular Ion: A Theoretical Study

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sun Young; Choe, Joong Chul [Dongguk University, Seoul (Korea, Republic of)

    2010-09-15

    The potential energy surfaces (PESs) for the primary and secondary dissociations of the phenylarsane molecular ion (1a) were determined from the quantum chemical calculations using the G3(MP2)//B3LYP method. Several pathways for the loss of H· were determined and occurred though rearrangements as well as through direct bond cleavages. The kinetic analysis based on the PES for the primary dissociation showed that the loss of H{sub 2} was more favored than the loss of H·, but the H· loss competed with the H{sub 2} loss at high energies. The bicyclic isomer, 7-arsa-norcaradiene radical cation, was formed through the 1,2 shift of an α-H of 1a and played an important role as an intermediate for the further rearrangements in the loss of H· and the losses of As· and AsH. The reaction pathways for the formation of the major products in the secondary dissociations of [M-H]{sup +} and [M-H{sub 2}]{sup +·} were examined. The theoretical prediction explained the previous experimental results for the dissociation at high energies but not the dissociation at low energies.

  1. Bench-scale Kinetics Study of Mercury Reactions in FGD Liquors

    Energy Technology Data Exchange (ETDEWEB)

    Gary Blythe; John Currie; David DeBerry

    2008-03-31

    This document is the final report for Cooperative Agreement DE-FC26-04NT42314, 'Kinetics Study of Mercury Reactions in FGD Liquors'. The project was co-funded by the U.S. DOE National Energy Technology Laboratory and EPRI. The objective of the project has been to determine the mechanisms and kinetics of the aqueous reactions of mercury absorbed by wet flue gas desulfurization (FGD) systems, and develop a kinetics model to predict mercury reactions in wet FGD systems. The model may be used to determine optimum wet FGD design and operating conditions to maximize mercury capture in wet FGD systems. Initially, a series of bench-top, liquid-phase reactor tests were conducted and mercury species concentrations were measured by UV/visible light spectroscopy to determine reactant and byproduct concentrations over time. Other measurement methods, such as atomic absorption, were used to measure concentrations of vapor-phase elemental mercury, that cannot be measured by UV/visible light spectroscopy. Next, a series of bench-scale wet FGD simulation tests were conducted. Because of the significant effects of sulfite concentration on mercury re-emission rates, new methods were developed for operating and controlling the bench-scale FGD experiments. Approximately 140 bench-scale wet FGD tests were conducted and several unusual and pertinent effects of process chemistry on mercury re-emissions were identified and characterized. These data have been used to develop an empirically adjusted, theoretically based kinetics model to predict mercury species reactions in wet FGD systems. The model has been verified in tests conducted with the bench-scale wet FGD system, where both gas-phase and liquid-phase mercury concentrations were measured to determine if the model accurately predicts the tendency for mercury re-emissions. This report presents and discusses results from the initial laboratory kinetics measurements, the bench-scale wet FGD tests, and the kinetics modeling

  2. A kinetic study of solar wind electrons

    International Nuclear Information System (INIS)

    Lie-Svendsen, Oeystein; Leer, Egil

    1996-01-01

    The evolution of the distribution function for a test population of electrons in an isothermal electron-proton corona has been studied using a Fokker-Planck description. The aim is to investigate whether a suprathermal tail forms due to the energy dependence of the Coulomb cross section. We find that a Maxwellian test population, injected into this background close to the coronal base with a temperature equal to that of the background electrons, maintains its shape throughout the transition from collision-dominated to collisionless flow. No significant suprathermal tail in the electron distribution function is seen in the outer corona

  3. COMBINED THEORETICAL AND EXPERIMENTAL INVESTIGATION OF MECHANISMS AND KINETICS OF VAPOR-PHASE MERCURY UPTAKE BY CARBONACEOUS SURFACES; ANNUAL

    International Nuclear Information System (INIS)

    Radisav D. Vidic; Eric V. Borguet; Karl J. Johnson

    2000-01-01

    The overall goal of this research program is to gain fundamental understanding of the important chemistry and physics involved in mercury adsorption on carbonaceous surfaces. This knowledge will then be used to optimize adsorption processes and operating conditions to maximize the uptake of mercury within the required contact time. An additional long-term benefit of this research is the basic understanding of the Hg adsorption process, which may facilitate the design of new adsorbents for more efficient and cost-effective removal of Hg from a variety of effluent streams. Molecular modeling of the adsorption of Hg on carbonaceous surfaces will greatly increase the insight into the physics of the adsorption process and combined with in situ rate measurements of mercury adsorption and desorption (conventional and pulsed laser) on graphite using linear and nonlinear optical probes with real time optical resolution have the potential to provide fundamental insight into the process of mercury uptake by carbonaceous surfaces. Besides accurate assessment of key parameters influencing adsorption equilibrium, fundamental understanding of the kinetics of mercury adsorption, desorption, and diffusion will be developed in this study. These key physical and chemical processes postulated through molecular modeling efforts and verified by in situ measurements will be utilized to select (or develop) promising sorbents for mercury control, which will be tested under dynamic conditions using simulated flue gas

  4. Kinetic Studies on Trichoderna Viride Cellulase

    International Nuclear Information System (INIS)

    Saw Aung; Oo Aung; Aung Myint

    2002-02-01

    Studies on cellulase enzyme (EC 3.2.1.4), which catalyzes the hydrolysis of. cellulose to yield glucose, were made. Cellulase from a fungus source, Trichoderma viride was cultivated on Czapek's agar medium and enzyme production broth medium was employed for parameter tests. The microscopic examination and cellulase hydrolysis test on subcultured fungi were applied to confirm the T. viride species. A calibration curve for standard glucose was plotted by using visible spectroscopy. Dinitrosalicylic acid was used as enzyme reaction inhibitor and the colour intensity was measured in a UV-visible spectrophotometer at a λ max of 570 nm. The parameters such as optimum pH, optimum temperature, effect of substrate concentration, effect, of enzyme concentration, enzyme unit (EU), reaction order (n), maximum velocity (V max ), Michaelis-Menten constant (K m ) using various substrates, viz., carboxy methylcellulose, cotton fibre and filter paper determined. (author)

  5. Theoretical Analysis of the Relative Significance of Thermodynamic and Kinetic Dispersion in the dc and ac Voltammetry of Surface-Confined Molecules

    KAUST Repository

    Morris, Graham P.; Baker, Ruth E.; Gillow, Kathryn; Davis, Jason J.; Gavaghan, David J.; Bond, Alan M.

    2015-01-01

    © 2015 American Chemical Society. Commonly, significant discrepancies are reported in theoretical and experimental comparisons of dc voltammograms derived from a monolayer or close to monolayer coverage of redox-active surface-confined molecules. For example, broader-than-predicted voltammetric wave shapes are attributed to the thermodynamic or kinetic dispersion derived from distributions in reversible potentials (E0) and electrode kinetics (k0), respectively. The recent availability of experimentally estimated distributions of E0 and k0 values derived from the analysis of data for small numbers of surface-confined modified azurin metalloprotein molecules now allows more realistic modeling to be undertaken, assuming the same distributions apply under conditions of high surface coverage relevant to voltammetric experiments. In this work, modeling based on conventional and stochastic kinetic theory is considered, and the computationally far more efficient conventional model is shown to be equivalent to the stochastic one when large numbers of molecules are present. Perhaps unexpectedly, when experimentally determined distributions of E0 and k0 are input into the model, thermodynamic dispersion is found to be unimportant and only kinetic dispersion contributes significantly to the broadening of dc voltammograms. Simulations of ac voltammetric experiments lead to the conclusion that the ac method, particularly when the analysis of kinetically very sensitive higher-order harmonics is undertaken, are far more sensitive to kinetic dispersion than the dc method. ac methods are therefore concluded to provide a potentially superior strategy for addressing the inverse problem of determining the k0 distribution that could give rise to the apparent anomalies in surface-confined voltammetry.

  6. Theoretical Analysis of the Relative Significance of Thermodynamic and Kinetic Dispersion in the dc and ac Voltammetry of Surface-Confined Molecules

    KAUST Repository

    Morris, Graham P.

    2015-05-05

    © 2015 American Chemical Society. Commonly, significant discrepancies are reported in theoretical and experimental comparisons of dc voltammograms derived from a monolayer or close to monolayer coverage of redox-active surface-confined molecules. For example, broader-than-predicted voltammetric wave shapes are attributed to the thermodynamic or kinetic dispersion derived from distributions in reversible potentials (E0) and electrode kinetics (k0), respectively. The recent availability of experimentally estimated distributions of E0 and k0 values derived from the analysis of data for small numbers of surface-confined modified azurin metalloprotein molecules now allows more realistic modeling to be undertaken, assuming the same distributions apply under conditions of high surface coverage relevant to voltammetric experiments. In this work, modeling based on conventional and stochastic kinetic theory is considered, and the computationally far more efficient conventional model is shown to be equivalent to the stochastic one when large numbers of molecules are present. Perhaps unexpectedly, when experimentally determined distributions of E0 and k0 are input into the model, thermodynamic dispersion is found to be unimportant and only kinetic dispersion contributes significantly to the broadening of dc voltammograms. Simulations of ac voltammetric experiments lead to the conclusion that the ac method, particularly when the analysis of kinetically very sensitive higher-order harmonics is undertaken, are far more sensitive to kinetic dispersion than the dc method. ac methods are therefore concluded to provide a potentially superior strategy for addressing the inverse problem of determining the k0 distribution that could give rise to the apparent anomalies in surface-confined voltammetry.

  7. Cell kinetic studies on radiation induced leukemogenesis

    International Nuclear Information System (INIS)

    Nakao, Isamu; Suzuki, Gen; Imai, Yasufumi; Kawase, Yoshiko; Nose, Masako; Hirashima, Kunitake; Bessho, Masami

    1989-01-01

    The purpose of this study was threefold: (1) to determine the clonal origin of radiation-induced thymic lymphoma in mice with cellular mosaicism for phosphoglycerate kinase; (2) to determine the incidence and latent period of myeloid leukemia and thymic lymphoma induced by whole-body exposure to median doses (3.0 Gy or less) in RFM/MsNrs-2 mice; and (3) to examine the influence of human recombinant interleukin-2 (hrIL-2). Thymic lymphoma was of a single cell origin. The incidence of radiation-induced myeloid leukemia and thymic lymphoma in RFM mice increased in a dose dependent fashion. Mean latent periods of both myeloid leukemia and thymic lymphoma after irradiation became shorter in proportion to radiation doses. When hrIL-2 was injected to RFM mice receiving 3.0 Gy, mean survivals were shorter in thymoma-bearing mice than the control mice. This suggested that hrIL-2 shortens the promotion step of thymoma. Administration of hrIL-2 failed to alter the incidence of myeloid leukemia or the mean survival of mice having myeloid leukemia, indicating that the protocol of hrIL-2 administration was not so sufficient as to alter the myeloid leukemogenesis. (Namekawa, K)

  8. Kinetic study and thermal decomposition behavior of viscoelastic memory foam

    International Nuclear Information System (INIS)

    Garrido, María A.; Font, Rafael; Conesa, Juan A.

    2016-01-01

    Highlights: • The thermal degradation has been studied under three different atmospheres. • Pyrolysis and combustion kinetic models have been proposed. • Evolved products under different atmospheres have been analyzed by TG-FTIR and TG-MS. - Abstract: A systematic investigation of the thermal decomposition of viscoelastic memory foam (VMF) was performed using thermogravimetric analysis (TGA) to obtain the kinetic parameters, and thermogravimetric analysis coupled to Fourier Transformed Infrared Spectrometry (TGA-FTIR) and thermogravimetric analysis coupled to Mass Spectrometry (TGA-MS) to obtain detailed information of evolved products on pyrolysis and oxidative degradations. Two consecutive nth-order reactions were employed to correlate the experimental data from dynamic and isothermal runs performed at three different heating rates (5, 10 and 20 K/min) under an inert atmosphere. On the other hand, for the kinetic study of the oxidative decomposition, the data from combustion (synthetic air) and poor oxygen combustion (N_2:O_2 = 9:1) runs, at three heating rates and under dynamic and isothermal conditions, were correlated simultaneously. A kinetic model consisting of three consecutive reactions presented a really good correlation in all runs. TGA-FTIR analysis showed that the main gases released during the pyrolysis of VMF were determined as ether and aliphatic hydrocarbons, whereas in combustion apart from the previous gases, aldehydes, amines and CO_2 have also been detected as the main gases. These results were confirmed by the TGA-MS.

  9. Kinetic Modelling and Experimental Study of Small Esters: Methyl Acetate and Ethyl Acetate

    KAUST Repository

    Ahmed, Ahfaz; Mehl, Marco; Lokachari, Nitin; Nilsson, Elna J.K.; Konnov, Alexander A.; Wagnon, Scott W.; Pitz, William J.; Curran, Henry J.; Roberts, William L.; Sarathy, Mani

    2017-01-01

    A detailed chemical kinetic mechanism comprising methyl acetate and ethyl acetate has been developed based on the previous work by Westbrook et al. [1]. The newly developed kinetic mechanism has been updated with new reaction rates from recent theoretical studies. To validate this model, shock tube experiments measuring ignition delay time have been conducted at 15 & 30 bar and equivalence ratio 0.5, 1.0 and 2.0. Another set of experiments measuring laminar burning velocity was also performed on a heat flux burner at atmospheric pressure over wide range of equivalence ratios [~0.7-1.4]. The new mechanism shows significant improvement in prediction of experimental data over earlier model across the range of experiments.

  10. Kinetic Modelling and Experimental Study of Small Esters: Methyl Acetate and Ethyl Acetate

    KAUST Repository

    Ahmed, Ahfaz

    2017-12-14

    A detailed chemical kinetic mechanism comprising methyl acetate and ethyl acetate has been developed based on the previous work by Westbrook et al. [1]. The newly developed kinetic mechanism has been updated with new reaction rates from recent theoretical studies. To validate this model, shock tube experiments measuring ignition delay time have been conducted at 15 & 30 bar and equivalence ratio 0.5, 1.0 and 2.0. Another set of experiments measuring laminar burning velocity was also performed on a heat flux burner at atmospheric pressure over wide range of equivalence ratios [~0.7-1.4]. The new mechanism shows significant improvement in prediction of experimental data over earlier model across the range of experiments.

  11. Study on the agglomeration kinetics of uranium peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, M.; Mojica Rodriguez, L.A. [CEA, Centre de Marcoule, Nuclear Energy Division, RadioChemistry and Process Department, 17171, Bagnols-sur-Ceze 30207 (France); Muhr, H.; Plasari, E. [Reaction and Process Engineering Laboratory, CNRS, University of Lorraine. 1 rue Grandville, BP 20451, Nancy 54001 (France); Auger, F. [Areva Mines/SEPA. 2 route de Lavaugrasse, Bessines-sur-Gartempe 87250 (France)

    2016-07-01

    Considering the previous study dealing with thermodynamic and kinetic phenomena (nucleation and crystal growth) during the uranium peroxide precipitation, this work focuses on the agglomeration mechanism. It provides the results obtained from the experiments carried out in a mixed suspension - mixed product removal (MSMPR) mixer operating at steady state. The influence of the operating parameters on the uranium peroxide agglomerates was studied in order to identify the agglomeration kernel. The method is based on the resolution of the population balance equation using the method of moments and the experimental particle size distributions. The results lead to a size-independent kernel directly proportional to the crystal growth rate. Under the stirring conditions studied, the agglomeration appears to be significantly reduced by mixing which results in a kernel inversely proportional to the average shear rate. The agglomeration kinetic law obtained in this study will be used for the process modelling in a further study. (authors)

  12. Study on the agglomeration kinetics of uranium peroxide

    International Nuclear Information System (INIS)

    Bertrand, M.; Mojica Rodriguez, L.A.; Muhr, H.; Plasari, E.; Auger, F.

    2016-01-01

    Considering the previous study dealing with thermodynamic and kinetic phenomena (nucleation and crystal growth) during the uranium peroxide precipitation, this work focuses on the agglomeration mechanism. It provides the results obtained from the experiments carried out in a mixed suspension - mixed product removal (MSMPR) mixer operating at steady state. The influence of the operating parameters on the uranium peroxide agglomerates was studied in order to identify the agglomeration kernel. The method is based on the resolution of the population balance equation using the method of moments and the experimental particle size distributions. The results lead to a size-independent kernel directly proportional to the crystal growth rate. Under the stirring conditions studied, the agglomeration appears to be significantly reduced by mixing which results in a kernel inversely proportional to the average shear rate. The agglomeration kinetic law obtained in this study will be used for the process modelling in a further study. (authors)

  13. Theoretical Studies on Photoionization Cross Sections of Solid Gold

    International Nuclear Information System (INIS)

    Ma Xiaoguang; Sun Weiguo; Cheng Yansong

    2005-01-01

    Accurate expression for photoabsorption (photoionization) cross sections of high density system proposed recently is used to study the photoionization of solid gold. The results show that the present theoretical photoionization cross sections have good agreement both in structure and in magnitude with the experimental results of gold crystal. The studies also indicate that both the real part ε' and the imaginary part ε'' of the complex dielectric constant ε, and the dielectric influence function of a nonideal system have rich structures in low energy side with a range about 50 eV, and suggest that the influence of particle interactions of surrounding particles with the photoionized particle on the photoionization cross sections can be easily investigated using the dielectric influence function. The electron overlap effects are suggested to be implemented in the future studies to improve the accuracy of theoretical photoionization cross sections of a solid system.

  14. A Study on the Kinetic Characteristics of Transmutation Process Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Chang Hyun; You, Young Woo; Cho, Jae seon; Huh, Chang Wook; Kim, Doh Hyung [Seoul National University, Seoul (Korea, Republic of)

    1997-07-01

    The purpose of this study is to examine the transient heat transfer characteristics of liquid mental as the coolant used in accelerator-driven transmutation process reactor which is related the disposal of high-level radioactive nuclide. At current stage, the accelerator-driven transmutation process is investigated as the most appropriate method among many transmutation process methods. In this study, previous research works are investigated especially about the thermal hydraulics and kinetic behavior of coolant material including heat transfer of coolant in transmutation process reactor. A study on the heat transfer characteristics of liquid metal is performed based on the thermal hydraulic kinetic characteristics of liquid metal reactor which uses liquid metal coolant. Based on this study, the most appropriate material for the coolant of transmutation reactor will be recommended. 53 refs., 15 tabs., 33 figs. (author)

  15. Kinetic resolution of α-bromoamides: Experimental and theoretical investigation of highly enantioselective reactions catalyzed by haloalkane dehalogenases

    NARCIS (Netherlands)

    Westerbeek, Alja; Szymanski, Wiktor; Wijma, Hein J.; Marrink, Siewert; Feringa, Ben L.; Janssen, Dick B.

    2011-01-01

    Haloalkane dehalogenases from five sources were heterologously expressed in Escherichia coli, isolated, and tested for their ability to achieve kinetic resolution of racemic alpha-bromoamides, which are important intermediates used in the preparation of bioactive compounds. To explore the substrate

  16. A kinetic study of pyrolysis in pitch impregnated electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kocaefe, D.; Charette, A.; Ferland, J.; Couderc, P.; Saint-Romain, J.L. (Universite du Quebec a Chicoutini, Chicoutini, PQ (Canada))

    1990-12-01

    A study was conducted on carbon electrodes which were impregnated with three different pitches. The focus of the study was to investigate the pyrolysis of pitch impregnated electrodes. For the purposes of the research an experimental technique and calculation procedure were developed. A kinetic model was used to interpret the data, comparison of model predictions and experimental data showed good agreement. 17 refs., 10 figs., 2 tabs.

  17. Charging/discharging processes in nanocrystaline MOS structures - Theoretical study

    International Nuclear Information System (INIS)

    Tanous, D; Mazurak, A; Majkusiak, B

    2016-01-01

    We present the study of impact of some parameters of the metal-insulator-semiconductor structure with nanocrystals embedded in the insulator layer on the current-voltage and capacitance-voltage characteristics with the bias voltage ramp rate as a parameter. The developed model is used as a tool for theoretical understanding the physics behind charging and discharging processes in the considered structures. (paper)

  18. Theoretical studies of fusion physics. Volume I. Summary. Final report

    International Nuclear Information System (INIS)

    1983-01-01

    Theoretical studies were performed on each of the following topics: (1) absorption of waves near the cyclotron frequency by relativistic electrons in EBT, (2) power balance in a stable, adiabatic hot electron annulus, (3) whistler instability in a relativistic electron annulus, (4) adiabatic limits on electron temperature in the EBT annulus, and (5) summary of a model of the EBT ring heating/loss process

  19. A theoretical and experimental study of microshield circuits

    Science.gov (United States)

    Dib, Nihad I.; Drayton, Rhonda F.; Katehi, Linda P. B.

    1993-05-01

    The novel type of monolithic planar transmission line presently studied theoretically and experimentally operates without via-holes or ground-equalizing air bridges; it also radiates less than conventional coplanar waveguides and furnishes a wide range of impedances in virtue of its many design parameters. The space-domain integral equation method is used to analyze several discontinuities of the proposed line. It is shown that the proposed line discontinuities radiate less than the corresponding coplanar waveguide cases.

  20. Theoretical study on the first kind of density wave instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Zuying, Gao; Jincai, Li; Baocheng, Xu; Zuoyi, Zhang; Cheng, Gao [Institute of Nuclear Energy and Technology, Tsingua Univ., Beijing (China)

    1997-09-01

    The present paper summarizes the theoretical studies carried out by INET (Institute of Nuclear Energy Technology) of Tsinghua University on the first kind of density wave instabilities (DWIs) of natural circulation systems. The analysis methods of DWI and mathematical models of drift flux are presented. Based on the general excess entropy production criterion of non-equilibrium thermodynamics, an energy principle of DWI is established. (author). 10 refs, 16 figs.

  1. An experimental and theoretical study of reaction steps relevant to the methanol-to-hydrocarbons reaction

    Energy Technology Data Exchange (ETDEWEB)

    Svelle, Stian

    2004-07-01

    The primary objective of the present work is to obtain new insight into the reaction mechanism of the zeolite catalyzed methanol-to-hydrocarbons (MTH) reaction. It was decided to use both experimental and computational techniques to reach this goal. An investigation of the n-butene + methanol system was therefore initiated. Over time, it became apparent that it was possible to determine the rate for the methylation of n-butene by methanol. The ethene and propene systems were therefore reexamined in order to collect kinetic information also for those cases. With the development of user-friendly quantum chemistry programs such as the Gaussian suite of programs, the possibility of applying quantum chemical methods to many types of problems has become readily available even for non-experts. When performing mechanistic studies, there is quite often a considerable synergy effect when combining experimental and computational approaches. The methylation reactions mentioned above turned out to be an issue well suited for quantum chemical investigations. The incentive for examining the halomethane reactivity was the clear analogy to the MTH reaction system. Alkene dimerization was also a reaction readily examined with quantum chemistry. As discussed in the introduction of this thesis, polymethylbenzenes, or their cationic counterparts, are suspected to be key intermediates in the MTH reaction. It was therefore decided to investigate the intrinsic reactivity of these species in the gas-phase by employing sophisticated mass spectrometric (MS) techniques in collaboration with the MS group at the Department of Chemistry, University of Oslo The data thus obtained will also be compared with results from an ongoing computational study on gas phase polymethylbenzenium reactivity. 6 papers presenting various studies are included. The titles are: 1) A Theoretical Investigation of the Methylation of Alkenes with Methanol over Acidic Zeolites. 2) A Theoretical Investigation of the

  2. An experimental and theoretical study of reaction steps relevant to the methanol-to-hydrocarbons reaction

    Energy Technology Data Exchange (ETDEWEB)

    Svelle, Stian

    2004-07-01

    The primary objective of the present work is to obtain new insight into the reaction mechanism of the zeolite catalyzed methanol-to-hydrocarbons (MTH) reaction. It was decided to use both experimental and computational techniques to reach this goal. An investigation of the n-butene + methanol system was therefore initiated. Over time, it became apparent that it was possible to determine the rate for the methylation of n-butene by methanol. The ethene and propene systems were therefore reexamined in order to collect kinetic information also for those cases. With the development of user-friendly quantum chemistry programs such as the Gaussian suite of programs, the possibility of applying quantum chemical methods to many types of problems has become readily available even for non-experts. When performing mechanistic studies, there is quite often a considerable synergy effect when combining experimental and computational approaches. The methylation reactions mentioned above turned out to be an issue well suited for quantum chemical investigations. The incentive for examining the halomethane reactivity was the clear analogy to the MTH reaction system. Alkene dimerization was also a reaction readily examined with quantum chemistry. As discussed in the introduction of this thesis, polymethylbenzenes, or their cationic counterparts, are suspected to be key intermediates in the MTH reaction. It was therefore decided to investigate the intrinsic reactivity of these species in the gas-phase by employing sophisticated mass spectrometric (MS) techniques in collaboration with the MS group at the Department of Chemistry, University of Oslo The data thus obtained will also be compared with results from an ongoing computational study on gas phase polymethylbenzenium reactivity. 6 papers presenting various studies are included. The titles are: 1) A Theoretical Investigation of the Methylation of Alkenes with Methanol over Acidic Zeolites. 2) A Theoretical Investigation of the

  3. A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhu

    2006-08-31

    Currently, DOE is conducting pilot CO{sub 2} injection tests to evaluate the concept of geological sequestration. One strategy that potentially enhances CO{sub 2} solubility and reduces the risk of CO{sub 2} leak back to the surface is dissolution of indigenous minerals in the geological formation and precipitation of secondary carbonate phases, which increases the brine pH and immobilizes CO{sub 2}. Clearly, the rates at which these dissolution and precipitation reactions occur directly determine the efficiency of this strategy. However, one of the fundamental problems in modern geochemistry is the persistent two to five orders of magnitude discrepancy between laboratory measured and field derived feldspar dissolution rates. To date, there is no real guidance as to how to predict silicate reaction rates for use in quantitative models. Current models for assessment of geological carbon sequestration have generally opted to use laboratory rates, in spite of the dearth of such data for compositionally complex systems, and the persistent disconnect between laboratory and field applications. Therefore, a firm scientific basis for predicting silicate reaction kinetics in CO2 injected geological formations is urgently needed to assure the reliability of the geochemical models used for the assessments of carbon sequestration strategies. The funded experimental and theoretical study attempts to resolve this outstanding scientific issue by novel experimental design and theoretical interpretation to measure silicate dissolution rates and iron carbonate precipitation rates at conditions pertinent to geological carbon sequestration. In the second year of the project, we completed CO{sub 2}-Navajo sandstone interaction batch and flow-through experiments and a Navajo sandstone dissolution experiment without the presence of CO{sub 2} at 200 C and 250-300 bars, and initiated dawsonite dissolution and solubility experiments. We also performed additional 5-day experiments at the

  4. A kinetic study of the electrochemical hydrogenation of ethylene

    International Nuclear Information System (INIS)

    Sedighi, S.; Gardner, C.L.

    2010-01-01

    In this study, we have examined the kinetics of the electrochemical hydrogenation of ethylene in a PEM reactor. While in itself this reaction is of little industrial interest, this reaction can be looked upon as a model reaction for many of the important hydrogenation processes including the refining of heavy oils and the hydrogenation of vegetable oils. To study the electrochemical hydrogenation of ethylene, several experimental techniques have been used including polarization measurements, measurement of the composition of the exit gases and potential step, transient measurements. The results show that the hydrogenation reaction proceeds rapidly and essentially to completion. By fitting the experimental transient data to the results from a zero-dimensional mathematical model of the process, a set of kinetic parameters for the reactions has been obtained that give generally good agreement with the experimental results. It seems probable that similar experimental techniques could be used to study the electrochemical hydrogenation of other unsaturated organic molecules of more industrial significance.

  5. Kinetic Study on Pyrolysis of Oil Palm Frond

    International Nuclear Information System (INIS)

    Soon, V S Y; Chin, B L F; Lim, A C R

    2016-01-01

    The pyrolysis of oil palm frond is studied using thermogravimetric analysis (TGA) equipment. The present study investigates the thermal degradation behaviour and determination of the kinetic parameters such as the activation energy (E A ) and pre-exponential factor (A) values of oil palm frond under pyrolysis condition. The kinetic data is produced based on first order rate of reaction. In this study, the experiments are conducted at different heating rates of 10, 20, 30, 40 and 50 K/min in the temperature range of 323-1173 K under non-isothermal condition. Argon gas is used as an inert gas to remove any entrapment of gases in the TGA equipment. (paper)

  6. The pressure distribution for biharmonic transmitting array: theoretical study

    Science.gov (United States)

    Baranowska, A.

    2005-03-01

    The aim of the paper is theoretical analysis of the finite amplitude waves interaction problem for the biharmonic transmitting array. We assume that the array consists of 16 circular pistons of the same dimensions that regrouped in two sections. Two different arrangements of radiating elements were considered. In this situation the radiating surface is non-continuous without axial symmetry. The mathematical model was built on the basis of the Khokhlov - Zabolotskaya - Kuznetsov (KZK) equation. To solve the problem the finite-difference method was applied. On-axis pressure amplitude for different frequency waves as a function of distance from the source, transverse pressure distribution of these waves at fixed distances from the source and pressure amplitude distribution for them at fixed planes were examined. Especially changes of normalized pressure amplitude for difference frequency were studied. The paper presents mathematical model and some results of theoretical investigations obtained for different values of source parameters.

  7. THEORETICAL AND EXPERIMENTAL STUDY OF STRUCTURES SUBJECTED TO EARTHQUAKES

    Energy Technology Data Exchange (ETDEWEB)

    Soubirou, A.

    1967-12-31

    The object of the study was the investigation of the behaviour of structures subject to earthquakes. After .describing and analysing seismic movements, useful concepts for earthquake-proofing structures are lintroduced. Then, the dynamic behaviour of systems with n degrees of freedom was studied in order to evolve the theoretical computation of seismic behaviour, a typical application being reticulated structures. The next stage was showing the computational procedure for seismic spectra and the natural frequencies of buildings, an attempt being made to define earthquake-proofing criteria for a special type of reinforced-concrete construction. . The last matter dealt with is elastoplastic behaviour of structures, a study of increasingly growing importance.

  8. Stochastic theory of interfacial enzyme kinetics: A kinetic Monte Carlo study

    International Nuclear Information System (INIS)

    Das, Biswajit; Gangopadhyay, Gautam

    2012-01-01

    Graphical abstract: Stochastic theory of interfacial enzyme kinetics is formulated. Numerical results of macroscopic phenomenon of lag-burst kinetics is obtained by using a kinetic Monte Carlo approach to single enzyme activity. Highlights: ► An enzyme is attached with the fluid state phospholipid molecules on the Langmuir monolayer. ► Through the diffusion, the enzyme molecule reaches the gel–fluid interface. ► After hydrolysing a phospholipid molecule it predominantly leaves the surface in the lag phase. ► The enzyme is strictly attached to the surface with scooting mode of motion and the burst phase appears. - Abstract: In the spirit of Gillespie’s stochastic approach we have formulated a theory to explore the advancement of the interfacial enzyme kinetics at the single enzyme level which is ultimately utilized to obtain the ensemble average macroscopic feature, lag-burst kinetics. We have provided a theory of the transition from the lag phase to the burst phase kinetics by considering the gradual development of electrostatic interaction among the positively charged enzyme and negatively charged product molecules deposited on the phospholipid surface. It is shown that the different diffusion time scales of the enzyme over the fluid and product regions are responsible for the memory effect in the correlation of successive turnover events of the hopping mode in the single trajectory analysis which again is reflected on the non-Gaussian distribution of turnover times on the macroscopic kinetics in the lag phase unlike the burst phase kinetics.

  9. Theoretical studies on core-level spectra of solids

    International Nuclear Information System (INIS)

    Kotani, Akio

    1995-01-01

    I present a review on theoretical studies of core-level spectra (CLS) in solids. In CLS, the dynamical response of outer electrons to a core hole is reflected through the screening of core hole potential. Impurity Anderson model (IAM) or cluster model is successfully applied to the analysis of X-ray photoemission spectra (XPS) and X-ray absorption spectra (XAS) in f and d electron systems, where the f and d electron states are hybridized with the other valence or conduction electron states. The effect of the core-hole potential in the final state of XPS and XAS plays an important role, as well as the solid state hybridization and intra-atomic multiplet coupling effects. As typical examples, the calculated results for XPS of rare-earth compounds and transition metal compounds are shown, and some discussions are given. As a subject of remarkable progress with high brightness synchrotron radiation sources, I discuss some theoretical aspects of X-ray emission spectra (XES) and their resonant enhancement at the X-ray absorption threshold. Some experimental data and their theoretical analysis are also given. (author)

  10. Theoretical study for solar air pretreatment collector/regenerator

    Energy Technology Data Exchange (ETDEWEB)

    Peng Donggen; Zhang Xiaosong; Yin Yonggao [School of Energy and Environment, Southeast Univ., Nanjing (China)

    2008-07-01

    A new liquid regeneration equipment - solar air pretreatment collector/regenerator for liquid desiccant cooling system is put forward in this paper, which is preferable to solution regeneration in hot and moist climate in South China. The equipment can achieve liquid regeneration in lower temperature. When the solution and the air are in ''match'' state in collector/ regenerator, a match air to salt mass ratio ASMR* is found by theoretical study in which there is the largest theoretical storage capacity SC{sub max}. After two new concepts of the effective solution proportion (EPS) and the effective storage capacity (ESC) are defined, it is found by theoretical calculation that when ESP drops from 100% to 67%, ESC raises lowly, not drops and liquid outlet concentration C{sub str} {sub sol} increases from 40% to 49% in which its increment totals to 90%. All these data explain fully that air pretreatment liquid regeneration equipment enables to improve the performance of liquid desiccant cooling system. (orig.)

  11. Micro sociological study of family relationships: heuristic potential theoretical principles

    Directory of Open Access Journals (Sweden)

    O. P. Zolotnyik

    2015-03-01

    Full Text Available This article is devoted to demonstrate the heuristic potential of theoretical principles by microsoсiological analysis of one of the indicators of family – family relations. Theoretical analysis of the interaction experience is quite large, but there is the question about it’s possibility to describe the specifics of that relationship that arise in family interaction. The study of family relationships requires an integrated approach to the comprehension of many related components: system of spouses value orientations, family life cycle, socio­economic living conditions of couple. However, the accentuation exactly on action­behavioral aspect allows to make assumptions about correlations between: success of family interaction and microclimate in the family; satisfaction level of interpersonal interaction and overall satisfaction with marriage, familiarity of family interaction and density of childbearing, and so on. The presentation of microsoсiological theoretical achievements will be carried out of sociological schools, orientations and their members that are the most popular references in this area. this paper will presents the theory of exchange, supporters of symbolic interactionism, dramatic and etnometodological approach and family systems theory.

  12. Kinetic study of enzymatic hydrolysis of potato starch

    Directory of Open Access Journals (Sweden)

    Óscar Fernando Castellanos Domínguez

    2004-01-01

    Full Text Available This article describes the kinetic study of potato starch enzymatic hydrolysis using soluble enzymes (Novo Nordisk. Different assays divided into four groups were used: reaction time (with which it was possible to reduce the 48-72 hour duration reported in the literature to 16 hours with comparable productivity levels; selecting the set of enzymes to be used (different types were evaluated - BAN and Termamyl as alfa-amylases during dextrinisation stage, and AMG, Promozyme and Fungamyl for sacarification reaction- identifying those presenting the best performance during hydrolysis.Reaction conditions were optimised for the process's two stages (destrinisation and sacarification. Enzyme dose, calcium cofactor concentration, pH, temperature and agitation speed were studied for the first stage. Enzyme ratio, pH and agitation speed were studied for sacarification; the latter parameter reported values having no antecedents in the literature (60 rpm and 30 rpm for first and second reactions, respectively. Michaelis Menten kinetics were calculated once conditions had been optimised, varying substrate from 10-50% P/V, obtaining km and Vmax kinetic parameters for each reaction. A kinetic model was found according to local working conditions which was able to explain potato starch conversion to glucose syrup, achieving 96 dextrose equivalents by the end of the reaction, being well within the maximum range reported in the literature (94-98.Laboratory equipment was constructed prior to carrying out assays which was able to reproduce and improve the conditions reported in the literature, making it a useful, reliable tool for use in assays returning good results.

  13. Theoretical and Experimental Study on Electromechanical Coupling Properties of Multihammer Synchronous Vibration System

    Directory of Open Access Journals (Sweden)

    Xin Lai

    2016-01-01

    Full Text Available Industrial simulation of real external load using multiple exciting points or increasing exciting force by synchronizing multiple exciting forces requires multiple vibration hammers to be coordinated and work together. Multihammer vibration system which consists of several hammers is a complex electromechanical system with complex electromechanical coupling. In this paper, electromechanical coupling properties of such a multihammer vibration system were studied in detail using theoretical derivation, numerical simulation, and experiment. A kinetic model of multihammer synchronous vibration system was established, and approximate expressions for electromechanical coupling strength were solved using a small parameter periodic averaging method. Basic coupling rules and reasons were obtained. Self-synchronization and frequency hopping phenomenon were also analyzed. Subsequently, numerical simulations were carried out and electromechanical coupling process was obtained for different parameters. Simulation results verify correctness of the proposed model and results. Finally, experiments were carried out, self-synchronization and frequency hopping phenomenon were both observed, and results agree well with theoretical deduction and simulation results. These results provide theoretical foundations for multihammer synchronous vibration system and its synchronous control.

  14. Experimental studies of caesium iodide aerosol condensation: theoretical interpretation

    International Nuclear Information System (INIS)

    Beard, A.M.; Benson, C.G.; Horton, K.D.; Buckle, E.R.

    1990-07-01

    Caesium iodide is predicted to be a significant source of fission product aerosols during the course of a severe accident in a pressurised water reactor (PWR). The nucleation and growth of caesium iodide aerosols have been studied using a plume chamber and the results compared with theoretical values calculated using the approach developed by Buckle for aerosol nucleation. The morphology of the particles was studied using scanning electron microscopy (SEM) and transmission optical microscopy (TOM), whilst the particle size distributions were determined from differential mobility (DMPS) and aerodynamic (APS) measurements. (author)

  15. Kinetic study of lithium-cadmium ternary amalgam decomposition

    International Nuclear Information System (INIS)

    Cordova, M.H.; Andrade, C.E.

    1992-01-01

    The effect of metals, which form stable lithium phase in binary alloys, on the formation of intermetallic species in ternary amalgams and their effect on thermal decomposition in contact with water is analyzed. Cd is selected as ternary metal, based on general experimental selection criteria. Cd (Hg) binary amalgams are prepared by direct contact Cd-Hg, whereas Li is formed by electrolysis of Li OH aq using a liquid Cd (Hg) cathodic well. The decomposition kinetic of Li C(Hg) in contact with 0.6 M Li OH is studied in function of ageing and temperature, and these results are compared with the binary amalgam Li (Hg) decomposition. The decomposition rate is constant during one hour for binary and ternary systems. Ageing does not affect the binary systems but increases the decomposition activation energy of ternary systems. A reaction mechanism that considers an intermetallic specie participating in the activated complex is proposed and a kinetic law is suggested. (author)

  16. DEFLUORIDATION OF DRINKING WATER BY ELECTROCOAGULATION/ELECTROFLOTATION - KINETIC STUDY

    Directory of Open Access Journals (Sweden)

    Bennajah Mounir

    2010-06-01

    Full Text Available A variable order kinetic (VOK model derived from the langmuir-freundlish equation was applied to determine the kinetics of fluoride removal reaction by electrocoagulation (EC. Synthetic solutions were employed to elucidate the effects of the initial fluoride concentration, the applied current and the initial acidity on the simulation results of the model. The proposed model successfully describes the fluoride removal in Airlift reactor in comparison with the experimental results. In this study two EC cells with the same capacity (V = 20 L were used to carry out fluoride removal with aluminum electrodes, the first is a stirred tank reactor (STR the second is an airlift reactor (ALR. The comparison of energy consumption demonstrates that the (ALR is advantageous for carrying out the defluoridation removal process.

  17. Evaluation of dilatometric techniques for studies of sintering kinetics

    International Nuclear Information System (INIS)

    El-Sayed Ali, M.; Toft Soerensen, O.

    1985-04-01

    The kinetics of the initial sintering stage of CeO 2 is evaluated by three different techniques: constant heating rate dilatometry, constant shrinkage rate dilatometry and a new technique recently introduced by the authors called Stepwise Isothermal Dilatometry (SID). Comparative measurements with these techniques showed that too high activation energies were obtained with the two first techniques, both of which can be termed as nonisothermal, whereas activation energies comparable to those reported for cation diffusion in other fluorite oxides were obtained with the latter technique. Of the three techniques SID is thus considered to be the most accurate for studies of the sintering kinetics. In contrast to the two nonisothermal techniques SID has the further advantage that both the controlling mechanism and its activation energy can be determined in a single experiment. From the SID-measurement it was concluded that the initial sintering stage of CeO 2 is controlled by grain-boundary diffusion. (author)

  18. Theoretical studies of Pt-Ti nanoparticles for potential use as PEMFC electrocatalysts.

    Science.gov (United States)

    Jennings, Paul C; Pollet, Bruno G; Johnston, Roy L

    2012-03-07

    A theoretical investigation is presented of alloying platinum with titanium to form binary Pt-Ti nanoalloys as an alternative to the expensive pure platinum catalysts commonly used for Proton Exchange Membrane Fuel Cell cathode electrocatalysts. Density Functional Theory calculations are performed to investigate compositional effects on structural properties as well as Oxygen Reduction Reaction kinetics and poisoning effects. High symmetry A(32)-B(6) clusters are studied to investigate structural properties. From these structures binding energies of hydroxyl and carbon monoxide are studied on a range of sites on the surface of the clusters. Promising results are obtained suggesting that the bimetallic Pt-Ti nanoalloys may exhibit enhanced properties compared to pure platinum catalysts.

  19. Kinetic study of ozonation of molasses fermentation wastewater

    International Nuclear Information System (INIS)

    Coca, M.; Pena, M.; Gonzalez, G.

    2007-01-01

    A kinetic study of molasses wastewater ozonation was carried out in a stirred tank reactor to obtain the rate constants for the decolorization reaction and the regime through which ozone is absorbed. First, fundamental mass transfer parameters such as ozone solubility, volumetric mass transfer coefficients and ozone decomposition kinetics were determined from semi-batch experiments in organic-free solutions with an ionic composition similar that of industrial wastewater. The influence of operating variables such as the stirring rate and gas flow rate on the kinetic and mass transfer parameters was also studied. The application of film theory allows to establish that the reactions between ozone and colored compounds in wastewater take place in the fast and pseudo-first-order regime, within the liquid film. The decolorization rate constants were evaluated at pH 8.7 and 25 deg. C, varying from 0.6 x 10 7 to 3.8 x 10 7 L mol -1 s -1 , depending on the stirring rate and the inlet gas flow

  20. Theoretical and experimental studies on emissions from wood combustion

    Energy Technology Data Exchange (ETDEWEB)

    Skreiberg, Oeyvind

    1997-12-31

    This thesis discusses experiments on emissions from wood log combustion and single wood particle combustion, both caused by incomplete combustion and emissions of nitric and nitrous oxide, together with empirical and kinetic NO{sub x} modelling. Experiments were performed in three different wood stoves: a traditional stove, a staged air stove and a stove equipped with a catalytic afterburner. Ideally, biomass fuel does not give a net contribution to the greenhouse effect. However, incomplete combustion was found to result in significant greenhouse gas emissions. Empirical modelling showed the excess air ratio and the combustion chamber temperature to be the most important input variables controlling the total fuel-N to NO{sub x} conversion factor. As the result of an international round robin test of a wood stove equipped with a catalytic afterburner, particle emission measurements were found to be the best method to evaluate the environmental acceptability of the tested stove, since the particle emission level was least dependent of the national standards, test procedures and calculation procedures used. In batch single wood particle combustion experiments on an electrically heated small-scale fixed bed reactor the fuel-N to NO conversion factor varied between 0.11-0.86 depending on wood species and operating conditions. A parameter study and homogeneous kinetic modelling on a plug flow reactor showed that, depending on the combustion compliance in question, there is an optimum combination of primary excess air ratio, temperature and residence time that gives a maximum conversion of fuel-N to N{sub 2}. 70 refs., 100 figs., 26 tabs.

  1. Full-dimensional analytical potential energy surface describing the gas-phase Cl + C2H6 reaction and kinetics study of rate constants and kinetic isotope effects.

    Science.gov (United States)

    Rangel, Cipriano; Espinosa-Garcia, Joaquin

    2018-02-07

    Within the Born-Oppenheimer approximation a full-dimensional analytical potential energy surface, PES-2017, was developed for the gas-phase hydrogen abstraction reaction between the chlorine atom and ethane, which is a nine body system. This surface presents a valence-bond/molecular mechanics functional form dependent on 60 parameters and is fitted to high-level ab initio calculations. This reaction presents little exothermicity, -2.30 kcal mol -1 , with a low height barrier, 2.44 kcal mol -1 , and intermediate complexes in the entrance and exit channels. We found that the energetic description was strongly dependent on the ab initio level used and it presented a very flat topology in the entrance channel, which represents a theoretical challenge in the fitting process. In general, PES-2017 reproduces the ab initio information used as input, which is merely a test of self-consistency. As a first test of the quality of the PES-2017, a theoretical kinetics study was performed in the temperature range 200-1400 K using two approaches, i.e. the variational transition-state theory and quasi-classical trajectory calculations, with spin-orbit effects. The rate constants show reasonable agreement with experiments in the whole temperature range, with the largest differences at the lowest temperatures, and this behaviour agrees with previous theoretical studies, thus indicating the inherent difficulties in the theoretical simulation of the kinetics of the title reaction. Different sources of error were analysed, such as the limitations of the PES and theoretical methods, recrossing effects, and the tunnelling effect, which is negligible in this reaction, and the manner in which the spin-orbit effects were included in this non-relativistic study. We found that the variation of spin-orbit coupling along the reaction path, and the influence of the reactivity of the excited Cl( 2 P 1/2 ) state, have relative importance, but do not explain the whole discrepancy. Finally, the

  2. Theoretical and experimental study of fenofibrate and simvastatin

    Science.gov (United States)

    Nicolás Vázquez, Inés; Rodríguez-Núñez, Jesús Rubén; Peña-Caballero, Vicente; Ruvalcaba, Rene Miranda; Aceves-Hernandez, Juan Manuel

    2017-12-01

    Fenofibrate, an oral fibrate lipid lowering agent, and simvastatin, which reduces plasma levels of low-density lipoprotein cholesterol, are active pharmaceutical ingredients (APIs), currently in the market. We characterized these APIs by thermal analysis and conducted X-ray powder diffraction techniques. Studies should be carried out in the formulation stage before the final composition of a polypill may be established. Thus, it was found in thermochemical studies that both compounds present no chemical interactions in an equimolar mixture of solid samples at room temperature. Theoretical studies were employed to determine possible interactions between fenofibrate and simvastatin. A very weak intramolecular hydrogen bond is formed between the hydroxyl group (O5H5) of the simvastatin with chlorine and carbonyl group (C11O4, C1O2) of the fenofibrate molecule. These weak energy hydrogen bonds have no effect on the chemical stability of the compounds studied. The results were obtained using Density Functional Theory methods; particularly the BPE1BPE and B3LYP functional and 6-31++G** basis set. The values of energy show good approximation when are compared with similar calculations previously reported. Infrared spectra of monomers and dimers were obtained via theoretical calculations.

  3. Theoretical studies of ionic conductivity of crosslinked chitosan membranes

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, Ernesto Lopez [Programa de Ingenieria Molecular y Nuevos Materiales, Universidad Autonoma de la Ciudad de Mexico, Fray Servando Teresa de Mier 92, 1er. Piso, Col Centro, Mexico D.F. CP 06080 (Mexico); Oviedo-Roa, R.; Contreras-Perez, Gustavo; Martinez-Magadan, Jose Manuel [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte 152, Col. San Bartolo Atepehuacan, CP 07730 Mexico D.F. (Mexico); Castillo-Alvarado, F.L. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional, Edificio 9 de la UPALM, Colonia Lindavista, Mexico D.F. CP 07738 (Mexico)

    2010-11-15

    Ionic conductivity of crosslinked chitosan membranes was studied using techniques of molecular modeling and simulation. The COMPASS force field was used. The simulation allows the description of the mechanism of ionic conductivity along the polymer matrix. The theoretical results obtained are compared with experimental results for chitosan membranes. The analysis suggests that the conduction mechanism is portrayed by the overlapping large Polaron tunneling model. In addition, when the chitosan membrane was crosslinked with an appropriate degree of crosslinking its ionic conductivity, at room temperature, was increased by about one order of magnitude. The chitosan membranes can be used as electrolytes in solid state batteries, electric double layer capacitors and fuel cells. (author)

  4. Theoretical study on perylene derivatives as fluorescent sensors for amines

    Science.gov (United States)

    Lathiotakis, Nektarios N.; Kerkines, Ioannis S. K.; Theodorakopoulos, Giannoula; Petsalakis, Ioannis D.

    2018-01-01

    A theoretical study is presented on perylene diimide (PDI) and perylene monoimide (PMI) and their action as sensors of amines in solution. Density functional theory (DFT) and Time dependent DFT (TDDFT) calculations are carried out on complexes of PDI and PMI with aniline in THF solution. The optimized geometries for the complexes have aniline lying parallel above the perylene at 3.15 Å and with binding energy of 0.53 eV in the ground state. The results on the excited states are consistent with a photoinduced electron transfer (PET) mechanism. The effective aniline-perylene distance resulting from a Mulliken's approach is 3.61 Å.

  5. Theoretical comparison of performance using transfer functions for reactivity meters based on inverse kinetic method and simple feedback method

    International Nuclear Information System (INIS)

    Shimazu, Yoichiro; Tashiro, Shoichi; Tojo, Masayuki

    2017-01-01

    The performance of two digital reactivity meters, one based on the conventional inverse kinetic method and the other one based on simple feedback theory, are compared analytically using their respective transfer functions. The latter one is proposed by one of the authors. It has been shown that the performance of the two reactivity meters become almost identical when proper system parameters are selected for each reactivity meter. A new correlation between the system parameters of the two reactivity meters is found. With this correlation, filter designers can easily determine the system parameters for the respective reactivity meters to obtain identical performance. (author)

  6. Experimental and theoretical studies of manganite and magnetite compounds

    International Nuclear Information System (INIS)

    Srinitiwarawong, Chatchai

    2002-01-01

    In the recent years interest in the transition oxide compounds has renewed among researchers in the field of condensed matter physics. This thesis presents the studies of the two families of the transition oxides, the manganite and magnetite compounds. Manganite has regained the interest since the discovery of the large magnetoresistance around its Curie temperature in 1990s. Magnetite on the other hand is the oldest magnetic material known to man however some of its physical properties are still controversial. The experimental works address some basic properties of these compounds when fabricated in the form of thin films. These include the resistivity measurements and magnetic measurements as well as the Hall effect. The various models of transport mechanism have been compared. The magnetic field and the temperature dependence of magnetoresistance have also been studied. Simple devices such as an artificial grain boundary and bilayers thin film have been investigated. The second part of this thesis concentrates on the theoretical aspects of the fundamental physics behind these two compounds. The problem of electrons tunnelling between the magnetite electrodes has been addressed taking into account the surface effect with distortion. The last chapter presents a theoretical study of the spinless-Hubbard model which is the simplest approximation of the conduction electrons in magnetite and manganite. The results are obtained from the Hartree-Fock and the Hubbard-I approximations as well as the exact diagonalisation method. (author)

  7. Theoretical study of near-threshold electron-molecule scattering

    International Nuclear Information System (INIS)

    Morrison, M.A.

    1989-01-01

    We have been engaged in carrying out a foundation study on problems pertaining to near-threshold nuclear excitations in e-H 2 scattering. The primary goals of this study are: to investigate the severity and nature of the anticipated breakdown of the adiabatic-nuclei (AN) approximation, first for rotation only (in the rigid-rotator approximation), and then for vibration; to determine a data base of accurate ab initio cross sections for this important system; to implement and test accurate, computationally-tractable model potentials for exchange and polarization effects; and to begin the exploration of alternative scattering theories for near-threshold collisions. This study has provided a well-defined theoretical context for our future investigations. Second, it has enabled us to identify and quantify several serious problems in the theory of near-threshold electron-molecule scattering that demand attention. And finally, it has led to the development of some of the theoretical and computational apparatus that will form the foundation of future work. In this report, we shall review our progress to date, emphasizing work completed during the current contract year. 17 refs., 5 figs., 1 tab

  8. Strong correlation effects in theoretical STM studies of magnetic adatoms

    Science.gov (United States)

    Dang, Hung T.; dos Santos Dias, Manuel; Liebsch, Ansgar; Lounis, Samir

    2016-03-01

    We present a theoretical study for the scanning tunneling microscopy (STM) spectra of surface-supported magnetic nanostructures, incorporating strong correlation effects. As concrete examples, we study Co and Mn adatoms on the Cu(111) surface, which are expected to represent the opposite limits of Kondo physics and local moment behavior, using a combination of density functional theory and both quantum Monte Carlo and exact diagonalization impurity solvers. We examine in detail the effects of temperature T , correlation strength U , and impurity d electron occupancy Nd on the local density of states. We also study the effective coherence energy scale, i.e., the Kondo temperature TK, which can be extracted from the STM spectra. Theoretical STM spectra are computed as a function of STM tip position relative to each adatom. Because of the multiorbital nature of the adatoms, the STM spectra are shown to consist of a complicated superposition of orbital contributions, with different orbital symmetries, self-energies, and Kondo temperatures. For a Mn adatom, which is close to half-filling, the STM spectra are featureless near the Fermi level. On the other hand, the quasiparticle peak for a Co adatom gives rise to strongly position-dependent Fano line shapes.

  9. A theoretical and experimental study of the thermal degradation of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Groenli, Morten G.

    1996-12-31

    This thesis relates to the thermal degradation of biomass covering a theoretical and experimental study in two parts. In the first part, there is presented an experimental and modeling work on the pyrolysis of biomass under regimes controlled by chemical kinetics, and the second part presents an experimental and modeling work on the pyrolysis of biomass under regimes controlled by heat and mass transfer. Five different celluloses, and hemicellulose and lignin isolated from birch and spruce have been studied by thermogravimetry. The thermo grams of wood species revealed different weight loss characteristics which can be attributed to their different chemical composition. The kinetic analysis gave activation energies between 210 and 280 kJ/mole for all the celluloses, and a model of independent parallel reactions was successfully used to describe the thermal degradation. In the second part of the thesis there is presented experimental and modeling work on the pyrolysis of biomass under regimes controlled by heat and mass transfer. The effect of heating conditions on the product yields distribution and reacted fraction was investigated. The experiments show that heat flux alters the pyrolysis products as well as the intra particle temperatures to the greatest extent. A comprehensive mathematical model which can simulate drying and pyrolysis of moist wood is presented. The simulation of thermal degradation and heat transport processes agreed well with experimental results. 198 refs., 139 figs., 68 abs.

  10. Experimental, computational and theoretical studies of δ′ phase coarsening in Al–Li alloys

    International Nuclear Information System (INIS)

    Pletcher, B.A.; Wang, K.G.; Glicksman, M.E.

    2012-01-01

    Experimental characterization of microstructure evolution in three binary Al–Li alloys provides critical tests of both diffusion screening theory and multiparticle diffusion simulations, which predict late-stage phase-coarsening kinetics. Particle size distributions, growth kinetics and maximum particle sizes obtained using quantitative, centered dark-field transmission electron microscopy are compared quantitatively with theoretical and computational predictions. We also demonstrate the dependence on δ′ precipitate volume fraction of the rate constant for coarsening and the microstructure’s maximum particle size, both of which remained undetermined for this alloy system for nearly a half century. Our experiments show quantitatively that the diffusion-screening theoretical description of phase coarsening yields reasonable kinetic predictions, and that useful simulations of microstructure evolution are obtained via multiparticle diffusion. The tested theory and simulation method will provide useful tools for future design of two-phase alloys for elevated temperature applications.

  11. We need theoretical physics approaches to study living systems

    Science.gov (United States)

    Blagoev, Krastan B.; Shukla, Kamal; affil="3" >Herbert Levine,

    2013-08-01

    Living systems, as created initially by the transition from assemblies of large molecules to self-reproducing information-rich cells, have for centuries been studied via the empirical toolkit of biology. This has been a highly successful enterprise, bringing us from the vague non-scientific notions of vitalism to the modern appreciation of the biophysical and biochemical bases of life. Yet, the truly mind-boggling complexity of even the simplest self-sufficient cells, let alone the emergence of multicellular organisms, of brain and consciousness, and to ecological communities and human civilizations, calls out for a complementary approach. In this editorial, we propose that theoretical physics can play an essential role in making sense of living matter. When faced with a highly complex system, a physicist builds simplified models. Quoting Philip W Anderson's Nobel prize address, 'the art of model-building is the exclusion of real but irrelevant parts of the problem and entails hazards for the builder and the reader. The builder may leave out something genuinely relevant and the reader, armed with too sophisticated an experimental probe, may take literally a schematized model. Very often such a simplified model throws more light on the real working of nature....' In his formulation, the job of a theorist is to get at the crux of the system by ignoring details and yet to find a testable consequence of the resulting simple picture. This is rather different than the predilection of the applied mathematician who wants to include all the known details in the hope of a quantitative simulacrum of reality. These efforts may be practically useful, but do not usually lead to increased understanding. To illustrate how this works, we can look at a non-living example of complex behavior that was afforded by spatiotemporal patterning in the Belousov-Zhabotinsky reaction [1]. Physicists who worked on this system did not attempt to determine all the relevant chemical intermediates

  12. Experimental kinetic study and modeling of calcium oxide carbonation

    International Nuclear Information System (INIS)

    Rouchon, L.

    2012-01-01

    Anthropogenic carbon dioxide (CO 2 ) emissions, major contributors to the greenhouse effect, are considered as the main cause of global warming. So, decrease of CO 2 emitted by large industrial combustion sources or power plants, is an important scientific goal. One of the approaches is based on CO 2 separation and capture from flue gas, followed by sequestration in a wide range of geological formations. In this aim, CO 2 is captured by sorbents like calcium oxide (CaO) in multi-cycle process of carbonation/de-carbonation. However, it was shown that the most important limitations of such process are related to the reversibility of reaction. CaO rapidly loses activity towards CO 2 , so the maximum extent of carbonation decreases as long as the number of cycles increases. In order to well understand the processes and parameters influencing the capture capacity of CaO-based sorbents, it appears important to get details on the kinetic law governing the reaction, which have not been really studied up to now. To investigate this reaction, CaO carbonation kinetics was followed by means of thermogravimetric analysis (TGA) on divided materials. Special care was given to the validation of the usual kinetic assumptions such as steady state and rate-determining step assumptions. The aim was to obtain a model describing the reaction in order to explain the influence of intensive variables such as carbonation temperature and CO 2 partial pressure. TGA curves obtained under isothermal and isobaric conditions showed an induction period linked to the nucleation process and a strong slowing down of the reaction rate once a given fractional conversion was reached. Both phenomena were observed to depend on carbonation temperature and CO 2 partial pressure. To explain these results, the evolution of texture and microstructure of the solid during the reaction was regarded as essential. Reaction at the grain scale induces a volume increase from CaO to CaCO 3 which causes a change in the

  13. Theoretical study of the ionization of B2H5

    International Nuclear Information System (INIS)

    Curtiss, L.A.; Pople, J.A.

    1989-01-01

    Ab initio molecular orbital calculations at the G1 level of theory have been carried out on neutral B 2 H 5 radical, doubly bridged B 2 H + 5 cation, and the first triplet excited state of B 2 H + 5 . Singly bridged B 2 H 5 is 4.0 kcal/mol (without zero-point energies) more stable than doubly bridged B 2 H 5 . Based on this work and previous theoretical work on triply bridged B 2 H + 5 , ionization potentials (vertical and adiabatic) are determined for B 2 H 5 . The adiabatic ionization potentials of the two B 2 H 5 structures are 6.94 eV (singly bridged) and 7.53 eV (doubly bridged). A very large difference is found between the vertical and adiabatic ionization potentials (3.37 eV) of the singly bridged B 2 H 5 structure. The first triplet state of B 2 H + 5 is found to be 4.55 eV higher in energy than the lowest energy B 2 H + 5 cation (triply bridged). The results of this theoretical study support the interpretation of Ruscic, Schwarz, and Berkowitz of their recent photoionization measurements on B 2 H 5

  14. Theoretical Studies of Strongly Interacting Fine Particle Systems

    Science.gov (United States)

    Fearon, Michael

    Available from UMI in association with The British Library. A theoretical analysis of the time dependent behaviour of a system of fine magnetic particles as a function of applied field and temperature was carried out. The model used was based on a theory assuming Neel relaxation with a distribution of particle sizes. This theory predicted a linear variation of S_{max} with temperature and a finite intercept, which is not reflected by experimental observations. The remanence curves of strongly interacting fine-particle systems were also investigated theoretically. It was shown that the Henkel plot of the dc demagnetisation remanence vs the isothermal remanence is a useful representation of interactions. The form of the plot was found to be a reflection of the magnetic and physical microstructure of the material, which is consistent with experimental data. The relationship between the Henkel plot and the noise of a particulate recording medium, another property dependent on the microstructure, is also considered. The Interaction Field Factor (IFF), a single parameter characterising the non-linearity of the Henkel plot, is investigated. These results are consistent with a previous experimental study. Finally the results of the noise power spectral density for erased and saturated recording media are presented, so that characterisation of interparticle interactions may be carried out with greater accuracy.

  15. THEORETICAL ANALYSIS STUDY OF FORMATION OF FUTURE LEGAL LAWYERS

    Directory of Open Access Journals (Sweden)

    Eugene Stepanovich Shevlakov

    2015-09-01

    Full Text Available The article deals with topical issues of formation of legal consciousness of future lawyers in high school. Obtained kinds of legal consciousness of future lawyers, determined its structure. Dedicated components of justice are mutually reinforcing, and provide an opportunity for further development of the personality of the future specialist, their personal growth.The purpose: to carry out theoretical analysis of the problem of formation of legal consciousness of future lawyers.The novelty is based. On the analysis of theoretical appro-aches of pedagogy, psychology, law, the notion of «lawfulness of the future of the law student», which is regarded as a form of social consciousness, which is a set of legal views and feelings, expressing the attitude to the law and legal phenomena that have regulatory in character and which includes know-ledge of legal phenomena and their evaluation from the point of view of fairness and justice, formed in the process of studying in the University.Results: this article analyzes different approaches to understanding the content and essence of the concept of legal consciousness of the legal profession. Define the types and structure of legal consciousness of future lawyers.

  16. Experimental and theoretical understanding of the gas phase oxidation of atmospheric amides with OH radicals: kinetics, products, and mechanisms.

    Science.gov (United States)

    Borduas, Nadine; da Silva, Gabriel; Murphy, Jennifer G; Abbatt, Jonathan P D

    2015-05-14

    Atmospheric amides have primary and secondary sources and are present in ambient air at low pptv levels. To better assess the fate of amides in the atmosphere, the room temperature (298 ± 3 K) rate coefficients of five different amides with OH radicals were determined in a 1 m(3) smog chamber using online proton-transfer-reaction mass spectrometry (PTR-MS). Formamide, the simplest amide, has a rate coefficient of (4.44 ± 0.46) × 10(-12) cm(3) molec(-1) s(-1) against OH, translating to an atmospheric lifetime of ∼1 day. N-methylformamide, N-methylacetamide and propanamide, alkyl versions of formamide, have rate coefficients of (10.1 ± 0.6) × 10(-12), (5.42 ± 0.19) × 10(-12), and (1.78 ± 0.43) × 10(-12) cm(3) molec(-1) s(-1), respectively. Acetamide was also investigated, but due to its slow oxidation kinetics, we report a range of (0.4-1.1) × 10(-12) cm(3) molec(-1) s(-1) for its rate coefficient with OH radicals. Oxidation products were monitored and quantified and their time traces were fitted using a simple kinetic box model. To further probe the mechanism, ab initio calculations are used to identify the initial radical products of the amide reactions with OH. Our results indicate that N-H abstractions are negligible in all cases, in contrast to what is predicted by structure-activity relationships. Instead, the reactions proceed via C-H abstraction from alkyl groups and from formyl C(O)-H bonds when available. The latter process leads to radicals that can readily react with O2 to form isocyanates, explaining the detection of toxic compounds such as isocyanic acid (HNCO) and methyl isocyanate (CH3NCO). These contaminants of significant interest are primary oxidation products in the photochemical oxidation of formamide and N-methylformamide, respectively.

  17. Study of kinetics of extraction of actinides in processes of reprocessing of nuclear fuels

    International Nuclear Information System (INIS)

    Lamotte, Claude

    1978-01-01

    This research thesis reports a bibliographical study on extraction kinetics. After some generalities on solvent-based extraction, and on the chemistry of actinides in solution, on the methods of kinetics study which are generally used and their mathematical treatments, the author compares the published results for the extraction kinetics of nitric acid, uranium VI, uranium IV, neptunium IV and plutonium IV [fr

  18. A study of calculation methodology and experimental measurements of the kinetic parameters for source driven subcritical systems

    International Nuclear Information System (INIS)

    Lee, Seung Min

    2009-01-01

    This work presents a theoretical study of reactor kinetics focusing on the methodology of calculation and the experimental measurements of the so-called kinetic parameters. A comparison between the methodology based on the Dulla's formalism and the classical method is made. The objective is to exhibit the dependence of the parameters on subcriticality level and perturbation. Two different slab type systems were considered: thermal one and fast one, both with homogeneous media. One group diffusion model was used for the fast reactor, and for the thermal system, two groups diffusion model, considering, in both case, only one precursor's family. The solutions were obtained using the expansion method. Also, descriptions of the main experimental methods of measurements of the kinetic parameters are presented in order to put a question about the compatibility of these methods in subcritical region. (author)

  19. Kinetic study of an alcoholic fermentation, using honey like substrate

    International Nuclear Information System (INIS)

    Gomez, Jose Angel; Castano, Hader Ivan; Arias Mario

    1997-01-01

    The paper describes a kinetic study of an alcoholic fermentation using honey like substrate; for this effect they were carried out nine fermentations in discontinuous process with a volume, of 10 L, following the behavior of the substrate concentrations, biomass and product in the time. It was evaluated the convenience of factors like the agitation and the addition of nutritious, also, it was observed the effect of the initial concentrations of substrate and inoculate and the type of honey looking for the best conditions of the process for the obtaining of an alcoholic drink

  20. Kinetic Studies on Microbial Production of Tannase Using Redgram Husk

    OpenAIRE

    S. K. Mohan; T. Viruthagiri; C. Arunkumar

    2015-01-01

    Tannase (tannin acyl hydrolase, E.C.3.1.1.20) is an important hydrolysable enzyme with innumerable applications and industrial potential. In the present study, a kinetic model has been developed for the batch fermentation used for the production of tannase by A.flavus MTCC 3783. Maximum tannase activity of 143.30 U/ml was obtained at 96 hours under optimum operating conditions at 35oC, an initial pH of 5.5 and with an inducer tannic acid concentration of 3% (w/v) for a fe...

  1. The theoretical study of the optical klystron free electron laser

    International Nuclear Information System (INIS)

    Yang Zhenhua

    2001-01-01

    The work of the theoretical study and numerical simulation of optical klystron free electron laser is supported by National 863 Research Development Program and National Science Foundation of China. The object of studying UV band free electron laser (FEL) is to understand the physical law of optical klystron FEL and to gain experience for design. A three-dimensional code OPFEL are made and it is approved that the code is correct completely. The magnetic field of the optical klystron, the energy modulation of the electron beam, the density modulation of the electron beam, spontaneous emission of the electron beam in optical klystron, the harmonic super-radiation of the electron beam, and the effects of the undulator magnetic field error on modulation of the electron beam energy are simulated. These results are useful for the future experiments

  2. A Combined Theoretical and Experimental Study for Silver Electroplating

    Science.gov (United States)

    Liu, Anmin; Ren, Xuefeng; An, Maozhong; Zhang, Jinqiu; Yang, Peixia; Wang, Bo; Zhu, Yongming; Wang, Chong

    2014-01-01

    A novel method combined theoretical and experimental study for environmental friendly silver electroplating was introduced. Quantum chemical calculations and molecular dynamic (MD) simulations were employed for predicting the behaviour and function of the complexing agents. Electronic properties, orbital information, and single point energies of the 5,5-dimethylhydantoin (DMH), nicotinic acid (NA), as well as their silver(I)-complexes were provided by quantum chemical calculations based on density functional theory (DFT). Adsorption behaviors of the agents on copper and silver surfaces were investigated using MD simulations. Basing on the data of quantum chemical calculations and MD simulations, we believed that DMH and NA could be the promising complexing agents for silver electroplating. The experimental results, including of electrochemical measurement and silver electroplating, further confirmed the above prediction. This efficient and versatile method thus opens a new window to study or design complexing agents for generalized metal electroplating and will vigorously promote the level of this research region.

  3. Theoretical study of liquid droplet dispersion in a venturi scrubber.

    Science.gov (United States)

    Fathikalajahi, J; Talaie, M R; Taheri, M

    1995-03-01

    The droplet concentration distribution in an atomizing scrubber was calculated based on droplet eddy diffusion by a three-dimensional dispersion model. This model is also capable of predicting the liquid flowing on the wall. The theoretical distribution of droplet concentration agrees well with experimental data given by Viswanathan et al. for droplet concentration distribution in a venturi-type scrubber. The results obtained by the model show a non-uniform distribution of drops over the cross section of the scrubber, as noted by the experimental data. While the maximum of droplet concentration distribution may depend on many operating parameters of the scrubber, the results of this study show that the highest uniformity of drop distribution will be reached when penetration length is approximately equal to one-fourth of the depth of the scrubber. The results of this study can be applied to evaluate the removal efficiency of a venturi scrubber.

  4. A Combined Theoretical and Experimental Study for Silver Electroplating

    Science.gov (United States)

    Liu, Anmin; Ren, Xuefeng; An, Maozhong; Zhang, Jinqiu; Yang, Peixia; Wang, Bo; Zhu, Yongming; Wang, Chong

    2014-01-01

    A novel method combined theoretical and experimental study for environmental friendly silver electroplating was introduced. Quantum chemical calculations and molecular dynamic (MD) simulations were employed for predicting the behaviour and function of the complexing agents. Electronic properties, orbital information, and single point energies of the 5,5-dimethylhydantoin (DMH), nicotinic acid (NA), as well as their silver(I)-complexes were provided by quantum chemical calculations based on density functional theory (DFT). Adsorption behaviors of the agents on copper and silver surfaces were investigated using MD simulations. Basing on the data of quantum chemical calculations and MD simulations, we believed that DMH and NA could be the promising complexing agents for silver electroplating. The experimental results, including of electrochemical measurement and silver electroplating, further confirmed the above prediction. This efficient and versatile method thus opens a new window to study or design complexing agents for generalized metal electroplating and will vigorously promote the level of this research region. PMID:24452389

  5. Optical and theoretical studies of giant clouds in spiral galaxies

    International Nuclear Information System (INIS)

    Elmegreen, B.G.; Elmegreen, D.M.

    1980-01-01

    An optical study of four spiral galaxies, combined with radiative transfer models for transmitted and scattered light, has led to a determination of the opacities and masses of numerous dark patches and dust lanes that outline spiral structure. The observed compression factors for the spiral-like dust lanes are in accord with expectations from the theory of gas flow in spiral density waves. Several low density (10 2 cm -3 ) clouds containing 10 6 to 10 7 solar masses were also studied. These results are discussed in terms of recent theoretical models of cloud and star formation in spiral galaxies. The long-term evolution of giant molecular clouds is shown to have important consequences for the positions and ages of star formation sites in spiral arms. (Auth.)

  6. Theoretical study of excitonic complexes in semiconductors quantum wells

    International Nuclear Information System (INIS)

    Dacal, Luis Carlos Ogando

    2001-08-01

    A physical system where indistinguishable particles interact with each other creates the possibility of studying correlation and exchange effect. The simplest system is that one with only two indistinguishable particles. In condensed matter physics, these complexes are represented by charged excitons, donors and acceptors. In quantum wells, the valence band is not parabolic, therefore, the negatively charged excitons and donors are theoretically described in a simpler way. Despite the fact that the stability of charged excitons (trions) is known since the late 50s, the first experimental observation occurred only at the early 90s in quantum well samples, where their binding energies are one order of magnitude larger due to the one dimensional carriers confinement. After this, these complexes became the subject of an intense research because the intrinsic screening of electrical interactions in semiconductor materials allows that magnetic fields that are usual in laboratories have strong effects on the trion binding energy. Another rich possibility is the study of trions as an intermediate state between the neutral exciton and the Fermi edge singularity when the excess of doping carriers is increased. In this thesis, we present a theoretical study of charged excitons and negatively charged donors in GaAs/Al 0.3 Ga 0.7 As quantum wells considering the effects of external electric and magnetic fields. We use a simple, accurate and physically clear method to describe these systems in contrast with the few and complex treatments s available in the literature. Our results show that the QW interface defects have an important role in the trion dynamics. This is in agreement with some experimental works, but it disagrees with other ones. (author)

  7. Isotherm, kinetic, and thermodynamic study of ciprofloxacin sorption on sediments.

    Science.gov (United States)

    Mutavdžić Pavlović, Dragana; Ćurković, Lidija; Grčić, Ivana; Šimić, Iva; Župan, Josip

    2017-04-01

    In this study, equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin concentration, temperature and ionic strength on the sorption process were studied. The K d parameter from linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin-Radushkevich (D-R) sorption models were applied to describe the equilibrium isotherms by linear and nonlinear methods. The estimated K d values varied from 171 to 37,347 mL/g. The obtained values of E (free energy estimated from D-R isotherm model) were between 3.51 and 8.64 kJ/mol, which indicated a physical nature of ciprofloxacin sorption on studied sediments. According to obtained n values as measure of intensity of sorption estimate from Freundlich isotherm model (from 0.69 to 1.442), ciprofloxacin sorption on sediments can be categorized from poor to moderately difficult sorption characteristics. Kinetics data were best fitted by the pseudo-second-order model (R 2  > 0.999). Thermodynamic parameters including the Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to estimate the nature of ciprofloxacin sorption. Results suggested that sorption on sediments was a spontaneous exothermic process.

  8. Study of water vapour adsorption kinetics on aluminium oxide materials

    Science.gov (United States)

    Livanova, Alesya; Meshcheryakov, Evgeniy; Reshetnikov, Sergey; Kurzina, Irina

    2017-11-01

    Adsorbents on the basis of active aluminum oxide are still of demand on the adsorbent-driers market. Despite comprehensive research of alumina adsorbents, and currently is an urgent task to improve their various characteristics, and especially the task of increasing the sorption capacity. In the present work kinetics of the processes of water vapours' adsorption at room temperature on the surface of desiccant samples has been studied. It was obtained on the basis of bayerite and pseudoboehmite experimentally. The samples of pseudoboehmite modified with sodium and potassium ions were taken as study objects. The influence of an adsorbent's grain size on the kinetics of water vapours' adsorption was studied. The 0.125-0.25 mm and 0.5-1.0 mm fractions of this sample were used. It has been revealed that the saturation water vapor fine powder (0.125-0.25 mm) is almost twofold faster in comparison with the sample of fraction 0.5-1.0 mm due to the decrease in diffusion resistance in the pores of the samples when moving from the sample of larger fraction to the fine-dispersed sample. It has been established that the adsorption capacity of the pseudoboehmite samples, modified by alkaline ions, is higher by ˜40 %, than for the original samples on the basis of bayerite and pseudoboehmite.

  9. Experimental and theoretical study of solid solution stability under irradiation

    International Nuclear Information System (INIS)

    Cauvin, Richard.

    1981-08-01

    The behavior of dilute alloys (Al-Zn, Al-Ag, Al-Si, Al-Ge and Al-Mg) under 1 MeV electron irradiation has been studied in a high voltage electron microscope. A phenomenon of homogeneous precipitation induced by irradiation in undersaturated solid solutions (Al-Zn, Al-Ag and Al-Si) has been discovered; the observed precipitates are either coherent or incoherent, but never associated with point defect sinks. The solubility limit is a function of irradiation temperature and flux; but, under irradiation, it does not behave as a true thermal solubility limit (without irradiation). The existing theories (kinetic or strictly thermodynamic) do not account for this phenomenon. It is shown that the irreversibility of the mutual recombination between trapped vacancies and mixed interstitials is the driving force of this homogeneous precipitation. Using a dilute solid solution model, we show that, under irradiation, the homogeneous stationary state, stable from a strictly thermodynamic point of view, can be unstable when the recombination reaction is taken into account. The solubility limit under irradiation is calculated with a nucleation-growth model taking account for this effect; it is proportional to the thermal solubility limit without irradiation. This model explains all the experimental observations [fr

  10. A Theoretical Study of Microwave Beam Absorption by a Rectenna

    Science.gov (United States)

    Ott, J. H.; Rice, J. S.; Thorn, D. C.

    1981-01-01

    The theoretical operational parameters for the workable satellite power system were examined. The system requirements for efficient transmission and reception of an environmentally benign microwave beam were determined.

  11. Mechanical properties of jennite: A theoretical and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Juhyuk, E-mail: juhyuk.moon@stonybrook.edu [Civil Engineering Program, Department of Mechanical Engineering, Stony Brook University, NY 11794 (United States); Yoon, Seyoon [School of Engineering, Kings College, University of Aberdeen, Aberdeen AB24 3UE (United Kingdom); Monteiro, Paulo J.M. [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

    2015-05-15

    The objective of this study is to determine the mechanical properties of jennite. To date, several hypotheses have been proposed to predict the structural properties of jennite. For the first time as reported herein, the isothermal bulk modulus of jennite was measured experimentally. Synchrotron-based high-pressure x-ray diffraction experiments were performed to observe the variation of lattice parameters under pressure. First-principles calculations were applied to compare with the experimental results and predict additional structural properties. Accurately measured isothermal bulk modulus herein (K{sub 0} = 64(2) GPa) and the statistical assessment on experimental and theoretical results suggest reliable mechanical properties of shear and Young's modulus, Poisson's ratio, and elastic tensor coefficients. Determination of these fundamental structural properties is the first step toward greater understanding of calcium–silicate–hydrate, as well as provides a sound foundation for forthcoming atomic level simulations.

  12. Theoretical and Experimental Study of Plasmonic Polymer Solar Cells

    DEFF Research Database (Denmark)

    Mirsafaei, Mina; Adam, Jost; Madsen, Morten

    The organic bulk hetero-junction solar cell has remarkable advantages such as low cost, mechanical flexibility and simple process techniques. Recently, low-band gap photoactive materials have obtained a significant attention due to their potential to absorb a wider range of the solar spectrum...... to attain higher power conversion efficiencies. Many low-band gap photoactive materials, however, still show a relatively low external quantum efficiency of less than 60% [1]. One possible approach to improve the device performance is to increase the light absorption in the active layer. This may, amongst...... other approaches, be achieved by using nano- or micro-structures that trap light at specific wavelengths [2], or by using the localized surface plasmon resonance effect of metal nanoparticles in the devices. In this work, we theoretically studied planar polymer solar cell based on finite-difference time...

  13. A theoretical-experimental study of backup bearings

    DEFF Research Database (Denmark)

    Lampe Linhares da Fonseca, Cesar Augusto

    of two types of backup bearings, which are investigated experimentally and theoretically. The first type is a conventional ball bearing commonly used in industrial applications. The second is an unconventional bearing that, which contains pins inside the clearance for the rotor to impact on. The main...... both types of bearings for further investigation. Also, a full failure of the control and a rotor drop on the ball bearing as backup bearing is investigated by removing the magnetic forces. The nonlinear features of the dynamics of the rotor are assessed for different levels of unbalance. It has been...... radial forces. Remaining in this condition, it may lead to permanent damage or total failure of the machine. This is why the backup bearing design has to be carefully planned and investigated as to whether it helps to protect the integrity of the machine. This PhD thesis provides a comprehensive study...

  14. Electrochemistry of chlorogenic acid: experimental and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Namazian, Mansoor [Department of Chemistry, Yazd University, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)]. E-mail: namazian@yazduni.ac.ir; Zare, Hamid R. [Department of Chemistry, Yazd University, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)

    2005-08-10

    Cyclic voltammetry, chronoamperometry and rotating disk electrode voltammetry as well as quantum chemical methods, are used for electrochemical study of chlorogenic acid, as an important biological molecule. The standard formal potential, diffusion coefficient, and heterogeneous electron transfer rate constant of chlorogenic acid in aqueous solution are investigated. Acidic dissociation constant of chlorogenic acid is also obtained. Quantum mechanical calculations on oxidation of chlorogenic acid in aqueous solution, using density functional theory are presented. The change of Gibbs free energy and entropy of oxidation of chlorogenic acid are calculated using thermochemistry calculations. The calculations in aqueous solution are carried out with the use of polarizable continuum solvation method. Theoretical standard electrode potential of chlorogenic acid is achieved to be 0.580 V versus standard calomel electrode (SCE) which is in agreement with the experimental value of 0.617 V obtained experimentally in this work. The difference is consistent with the values we previously reported for other quinone derivatives.

  15. Theoretical Study of Irradiation Effects in Close Binaries

    Directory of Open Access Journals (Sweden)

    Srinivasa Rao, M.

    2009-06-01

    Full Text Available The effect of irradiation is studied in a close binary systemassuming that the secondary component is a point source, moving in a circularorbit. The irradiation effects are calculatedon the atmosphere of the primary component in a 3-dimensional Cartesiancoordinate geometry. In treating the reflection effect theoretically, the totalradiation $(S_mathrm{T}$ is obtained as the sum of the radiation of 1 the effect ofirradiation on the primary component which is calculated by using onedimensional rod model $(S_mathrm{r}$ and 2 the self radiation of the primarycomponent which is calculated by using the solution of radiative transferequation in spherical symmetry $(S_mathrm{s}$. The radiation field is estimated alongthe line of sight of the observer at infinity. It is shown how the radiationfield changes depending on the position of the secondary component.

  16. Theoretical study of asymmetric super-rotors: Alignment and orientation

    Science.gov (United States)

    Omiste, Juan J.

    2018-02-01

    We report a theoretical study of the optical centrifuge acceleration of an asymmetric top molecule interacting with an electric static field by solving the time-dependent Schrödinger equation in the rigid rotor approximation. A detailed analysis of the mixing of the angular momentum in both the molecular and the laboratory fixed frames allows us to deepen the understanding of the main features of the acceleration process, for instance, the effective angular frequency of the molecule at the end of the pulse. For the case of the SO2 molecular super-rotor, we show numerically that it rotates around one internal axis and that its dynamics is confined to the plane defined by the polarization axis of the laser, in agreement with experimental findings. Furthermore, we consider the orientation patterns induced by the dc field, showing the characteristics of their structure as a function of the strength of the static field and the initial configuration of the fields.

  17. Experimental and theoretical studies of buoyant-thermo capillary flow

    International Nuclear Information System (INIS)

    Favre, E.; Blumenfeld, L.; Soubbaramayer

    1996-01-01

    In the AVLIS process, uranium metal is evaporated using a high power electron gun. We have prior discussed the power balance equation in the electron beam evaporation process and pointed out, among the loss terms, the importance of the power loss due to the convective flow in the molten pool driven by buoyancy and thermo capillarity. An empirical formula has been derived from model experiments with cerium, to estimate the latter power loss and that formula can be used practically in engineering calculations. In order to complete the empirical approach, a more fundamental research program of theoretical and experimental studies have been carried out in Cea-France, with the objective of understanding the basic phenomena (heat transport, flow instabilities, turbulence, etc.) occurring in a convective flow in a liquid layer locally heated on its free surface

  18. Theoretical and experimental study of a thruster discharging a weight

    Science.gov (United States)

    Michaels, Dan; Gany, Alon

    2014-06-01

    An innovative concept for a rocket type thruster that can be beneficial for spacecraft trajectory corrections and station keeping was investigated both experimentally and theoretically. It may also be useful for divert and attitude control systems (DACS). The thruster is based on a combustion chamber discharging a weight through an exhaust tube. Calculations with granular double-base propellant and a solid ejected weight reveal that a specific impulse based on the propellant mass of well above 400 s can be obtained. An experimental thruster was built in order to demonstrate the new idea and validate the model. The thruster impulse was measured both directly with a load cell and indirectly by using a pressure transducer and high speed photography of the weight as it exits the tube, with both ways producing very similar total impulse measurement. The good correspondence between the computations and the measured data validates the model as a useful tool for studying and designing such a thruster.

  19. Phosphonic drugs: Experimental and theoretical spectroscopic studies of fosfomycin

    Science.gov (United States)

    Chruszcz-Lipska, Katarzyna; Zborowski, Krzysztof K.; Podstawka-Proniewicz, Edyta; Liu, Shaoxuan; Xu, Yizhuang; Proniewicz, Leonard M.

    2011-02-01

    pH and time-dependant changes of fosfomycin molecular structure in an aqueous solution are studied by Raman, NMR, and generalized 2D correlation spectroscopies. Interpretation of the experimental spectra is based on the assumption of formation of different species running on applied physicochemical conditions. Geometries of all possible structures were entirely optimized with the 6-311++G(2df,p) basis set at the B3LYP theoretical level using procedures implemented in the Gaussian '03 set of programs. Harmonic frequency calculations verified the nature of the studied structures and allowed to simulate obtained Raman spectra. The theoretical NMR shielding was calculated using the GIAO method at the same computational level. In addition, in some cases PCM model was used to monitor the influence of water molecules on the NMR spectra. It is shown that in the pH range of 1-2 of fosfomycin aqueous solution oxirane ring is open sequent to nucleophilic attack and forms 1,2-dihydroxyphosphonic acid with small content of its monodeprotonated species. On the other hand, in pH 7 and higher it appears either as 1,2-epoxypropylphosphonic or 1,2-dihydroxyphosphonic dianion depending upon whether hydrolysis took place or not. It is also discussed that Raman marker bands originating from the individual species of fosfomycin can be used to detect and/or to monitor this antibiotic in an aqueous medium (for example urine samples). Hence, depending upon the structure found in urine one can tell about metabolic processes of this antibiotic in the body.

  20. Theoretical study of turbulent channel flow - Bulk properties, pressure fluctuations, and propagation of electromagnetic waves

    Science.gov (United States)

    Canuto, V. M.; Hartke, G. J.; Battaglia, A.; Chasnov, J.; Albrecht, G. F.

    1990-01-01

    In this paper, we apply two theoretical turbulence models, DIA and the recent GISS model, to study properties of a turbulent channel flow. Both models provide a turbulent kinetic energy spectral function E(k) as the solution of a non-linear equation; the two models employ the same source function but different closures. The source function is characterized by a rate n sub s (k) which is derived from the complex eigenvalues of the Orr-Sommerfeld (OS) equation in which the basic flow is taken to be of a Poiseuille type. The O-S equation is solved for a variety of Reynolds numbers corresponding to available experimental data. A physical argument is presented whereby the central line velocity characterizing the basic flow, U0 sup L, is not to be identified with the U0 appearing in the experimental Reynolds number. The theoretical results are compared with two types of experimental data: (1) turbulence bulk properties, and (2) properties that depend strongly on the structure of the turbulence spectrum at low wave numbers. The only existing analytical expression for Pi (k) cannot be used in the present case because it applies to the case of a flat plate, not a finite channel.

  1. Theoretical study on the photoionization of metanal and fluoromethane

    International Nuclear Information System (INIS)

    Tanaka, Helder Kenji; Silveira, Tiago Rodrigues; Nascimento, Edmar Moraes do

    2011-01-01

    Full text. The photoionization study of biological interest molecules has increased last few years due to the basic interest in the fundamental nature of electronic structures and scattering molecular processes. It was considered to this study hypothesis in that simple molecules would give birth to more complex molecules through photochemical reactions induced by interstellar radiation. This paper shows a theoretical study over photoionization of the valence shells of some biological interest molecules. Cross sections and parameters of asymmetry are set due to ab initio, using the continued fractions method to determine the scattering matrix and wave functions of the continuum. Results will be presented to the valence shell photoionization of formaldehyde (CH 2 O) and fluoromethane (CH 3 F). This work is part of a larger project to study of biological interest molecules, motivated by the hypothesis that based on these simple molecules, physicochemical processes may have given origin to more complex molecules responsible for the production of terrestrial life. The formamide, for example, has been subject of interest between researchers as a possible material from which can be created RNA bases. In this case has been studied the production of guanine from the formamide heated while irradiated by ultraviolet radiation

  2. Action of Molecular Switches in GPCRs - Theoretical and Experimental Studies

    Science.gov (United States)

    Trzaskowski, B; Latek, D; Yuan, S; Ghoshdastider, U; Debinski, A; Filipek, S

    2012-01-01

    G protein coupled receptors (GPCRs), also called 7TM receptors, form a huge superfamily of membrane proteins that, upon activation by extracellular agonists, pass the signal to the cell interior. Ligands can bind either to extracellular N-terminus and loops (e.g. glutamate receptors) or to the binding site within transmembrane helices (Rhodopsin-like family). They are all activated by agonists although a spontaneous auto-activation of an empty receptor can also be observed. Biochemical and crystallographic methods together with molecular dynamics simulations and other theoretical techniques provided models of the receptor activation based on the action of so-called “molecular switches” buried in the receptor structure. They are changed by agonists but also by inverse agonists evoking an ensemble of activation states leading toward different activation pathways. Switches discovered so far include the ionic lock switch, the 3-7 lock switch, the tyrosine toggle switch linked with the nPxxy motif in TM7, and the transmission switch. The latter one was proposed instead of the tryptophan rotamer toggle switch because no change of the rotamer was observed in structures of activated receptors. The global toggle switch suggested earlier consisting of a vertical rigid motion of TM6, seems also to be implausible based on the recent crystal structures of GPCRs with agonists. Theoretical and experimental methods (crystallography, NMR, specific spectroscopic methods like FRET/BRET but also single-molecule-force-spectroscopy) are currently used to study the effect of ligands on the receptor structure, location of stable structural segments/domains of GPCRs, and to answer the still open question on how ligands are binding: either via ensemble of conformational receptor states or rather via induced fit mechanisms. On the other hand the structural investigations of homo- and heterodimers and higher oligomers revealed the mechanism of allosteric signal transmission and receptor

  3. The kinetic study of oxidation of iodine by hydrogen peroxide

    International Nuclear Information System (INIS)

    Cantrel, L.; Chopin, J.

    1996-01-01

    Iodine chemistry is one of the most important subjects of research in the field of reactor safety because this element can form volatile species which represent a biological hazard for environment. As the iodine and the peroxide are both present in the sump of the containment in the event of a severe accident on a light water nuclear reactor, it can be important to improve the knowledge on the reaction of oxidation of iodine by hydrogen peroxide. The kinetics of iodine by hydrogen peroxide has been studied in acid solution using two different analytical methods. The first is a UV/Vis spectrophotometer which records the transmitted intensity at 460 nm as a function of time to follow the decrease of iodine concentration, the second is an amperometric method which permits to record the increase of iodine+1 with time thanks to the current of reduction of iodine+1 to molecular iodine. The iodine was generated by Dushman reaction and the series of investigations were made at 40 o C in a continuous stirring tank reactor. The influence of the initial concentrations of iodine, iodate, hydrogen peroxide, H + ions has been determined. The kinetics curves comprise two distinct chemical phases both for molecular iodine and for iodine+1. The relative importance of the two processes is connected to the initial concentrations of [I 2 ], [IO 3 - ], [H 2 O 2 ] and [H + ]. A rate law has been determined for the two steps for molecular iodine. (author) figs., tabs., 22 refs

  4. Kinetic studies of ICF target dynamics with ePLAS

    Science.gov (United States)

    Mason, R. J.

    2016-10-01

    The ePLAS code was recently used1 to show that a modeling change from artificial to real viscosity can result in a decrease of the predicted performance of ICF targets. This code typically follows either fluid or PIC electrons with fluid ions in self-consistent E - and B - fields computed by the Implicit Moment Method2. For the present study the ions have instead been run as PIC particles undergoing Krook-like self-collisions. The ePLAS collision model continually redistributes the ion particle properties toward a local Maxwellian, while conserving the mean density, momentum and energy. Whereas the use of real viscosity captures large Knudsen Number effects as the active target dimensions shrink below the ion mean-free-path, the new kinetic modeling can manifest additional effects such as collisional shock precursors3 from the escape and streaming of the fastest particle ions. In 2D cylindrical geometry we will explore how such kinetic shock extensions might affect shell and core compression dynamics in ICF target implosions.

  5. Kinetics study of antimony adsorption on Si(1 1 1)

    International Nuclear Information System (INIS)

    Lapena, L.; Mueller, P.; Quentel, G.; Guesmi, H.; Treglia, G.

    2003-01-01

    In this paper, we use mass spectrometry (MS) and reflection high-energy electron (RHEED) to study the kinetics of adsorption of Sb on Si(1 1 1) surface and its relation to the corresponding surface structure. At high temperature (T>800 deg. C) all the impinging Sb 4 molecules completely dissociate at the silicon surface and a 2D gas of Sb monomers reversibly adsorbs on the (1x1) surface. At low temperature (T 4 molecules act as precursors and can be partially reflected or desorbed while a 2D stable layer of Sb monomers irreversibly adsorbs. The surface continuously shifts from a blurred (7x7) surface to a (1x1) structure near completion of the 2D layer. In the intermediate range (600 deg. C< T<800 deg. C) provided that the coverage is large enough (θ ∼ 2/3) the condensation of the 2D gas leads to a 2D (5√3 x 5√3) reconstruction. We show that introducing the formation of a condensed phase in a kinetics model allows us to reproduce our experimental data. Finally, we determine the adsorption geometry from ab initio calculations: Sb is adsorbed on top positions, somewhat passivating the Si surface dangling bonds

  6. Experimental and Theoretical Studies of Atmosphereic Inorganic Chlorine Chemistry

    Science.gov (United States)

    Sander, Stanley P.; Friedl, Randall R.

    1993-01-01

    Over the last five years substantial progress has been made in defining the realm of new chlorine chemistry in the polar stratosphere. Application of existing experimental techniques to potentially important chlorine-containing compounds has yielded quantitative kinetic and spectroscopic data as well as qualitative mechanistic insights into the relevant reactions.

  7. Kinetic study of hydrolysis of coconut fiber into glucose

    Science.gov (United States)

    Muhaimin, Sudiono, Sri

    2017-03-01

    Kinetic study of hydrolysis of coconut fiber into glucose has been done. The aim of this research was to study of the effect of time and temperature to the glucose as the result of the conversion of coconut fiber. The various temperature of the hydrolysis process were 30 °C, 48 °C, 72 °C and 95 °C and the various time of the hydrolysis process were 0, 15, 30, 60, 120, 180, 240, 300 minutes. A quantitative analysis was done by measured the concentration of the glucose as the result of the conversion of coconut fiber. The result showed that the rate constant from the various temperature were 3.10-4 minute-1; 8.10-4 minutees-1; 84.10-4 minute-1, and 205.10-4 minute-1, and the energy activation was 7,69. 103 kJ/mol.

  8. Thermodynamic properties and solidification kinetics of intermetallic Ni7Zr2 alloy investigated by electrostatic levitation technique and theoretical calculations

    International Nuclear Information System (INIS)

    Li, L. H.; Hu, L.; Yang, S. J.; Wang, W. L.; Wei, B.

    2016-01-01

    The thermodynamic properties, including the density, volume expansion coefficient, ratio of specific heat to emissivity of intermetallic Ni 7 Zr 2 alloy, have been measured using the non-contact electrostatic levitation technique. These properties vary linearly with temperature at solid and liquid states, even down to the obtained maximum undercooling of 317 K. The enthalpy, glass transition, diffusion coefficient, shear viscosity, and surface tension were obtained by using molecular dynamics simulations. Ni 7 Zr 2 has a relatively poor glass forming ability, and the glass transition temperature is determined as 1026 K. The inter-diffusivity of Ni 7 Zr 2 alloy fitted by Vogel–Fulcher–Tammann law yields a fragility parameter of 8.49, which indicates the fragile nature of this alloy. Due to the competition of increased thermodynamic driving force and decreased atomic diffusion, the dendrite growth velocity of Ni 7 Zr 2 compound exhibits double-exponential relationship to the undercooling. The maximum growth velocity is predicted to be 0.45 m s −1 at the undercooling of 335 K. Theoretical analysis reveals that the dendrite growth is a diffusion-controlled process and the atomic diffusion speed is only 2.0 m s −1

  9. Theoretical studies of growth processes and electronic properties of nanostructures on surfaces

    Science.gov (United States)

    Mo, Yina

    Low dimensional nanostructures have been of particular interest because of their potential applications in both theoretical studies and industrial use. Although great efforts have been put into obtaining better understanding of the formation and properties of these materials, many questions still remain unanswered. This thesis work has focused on theoretical studies of (1) the growth processes of magnetic nanowires on transition-metal surfaces, (2) the dynamics of pentacene thin-film growth and island structures on inert surfaces, and (3) our proposal of a new type of semiconducting nanotube. In the first study, we elucidated a novel and intriguing kinetic pathway for the formation of Fe nanowires on the upper edge of a monatomic-layer-high step on Cu(111) using first-principles calculations. The identification of a hidden fundamental Fe basal line within the Cu steps prior to the formation of the apparent upper step edge Fe wire produces a totally different view of step-decorating wire structures and offers new possibilities for the study of the properties of these wires. Subsequent experiments with scanning tunneling microscopy unambiguously established the essential role of embedded Fe atoms as precursors to monatomic wire growth. A more general study of adatom behavior near transition-metal step edges illustrated a systematic trend in the adatom energetics and kinetics, resulted from the electronic interactions between the adatom and the surfaces. This work opens the possibility of controlled manufacturing of one-dimensional nanowires. In the second study, we investigated pentacene thin-films on H-diamond, H-silica and OH-silica surfaces via force field molecular dynamics simulations. Pentacene island structures on these surfaces were identified and found to have a 90-degree rotation relative to the structure proposed by some experimental groups. Our work may facilitate the design and control of experimental pentacene thin-film growth, and thus the development

  10. Status of the theoretical study of microwave heating in EBT

    International Nuclear Information System (INIS)

    Batchelor, D.B.

    1978-09-01

    The basic strategy of the theoretical study of microwave heating in the ELMO Bumpy Torus (EBT) is outlined and the current status of the various aspects of the study is described. There are four broad areas which are being investigated: (1) heating and wave damping mechanisms, (2) the geometrical optics of microwave propagation in EBT, (3) reflection and mode conversion effects at regions such as cutoff and resonances where the geometrical optics approximation breaks down, and (4) nonlinear effects such as ponderamotive effects and parametric decay. Details are given of the geometrical optics code which has been developed to do ray tracing in arbitrary three dimensional (3-D) plasma equilibria. Examples are given for plasma parameters characteristic of EBT-I and EBT-II. Details are also given of the stochastic heating model currently in use with the 1-D transport code and of the linear wave damping model used in the ray tracing code. The most pressing problems of physics yet to be addressed and the directions for future work are indicated

  11. Thermochemistry of sarcosine and sarcosine anhydride: Theoretical and experimental studies

    International Nuclear Information System (INIS)

    Amaral, Luísa M.P.F.; Santos, Ana Filipa L.O.M.; Ribeiro da Silva, Maria das Dores M.C.; Notario, Rafael

    2013-01-01

    Highlights: ► Study on the Energetics of the sarcosine and sarcosine anhydride. ► Experimental and computational thermochemistry of sarcosine and its anhydride. ► Ab initio calculations for two amino acid derivatives by G3(MP2)//B3LYP method. -- Abstract: The standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of sarcosine, −(388.0 ± 1.0) kJ · mol −1 , and sarcosine anhydride, −(334.5 ± 1.6) kJ · mol −1 , were calculated by combining, for each compound, the standard molar enthalpy of formation, in the crystalline phase, and the standard molar enthalpy of sublimation, derived from measurements of the standard massic energies of combustion by static bomb combustion calorimetry, and from measurements of vapour pressures by the Knudsen mass-loss effusion method, respectively. The standard (p o = 0.1 MPa) molar enthalpies, entropies and Gibbs functions of sublimation, at T = 298.15 K, were also calculated. A theoretical study at the G3 and G4 levels has been carried out, and the calculated enthalpies of formation have been compared with the experimental ones

  12. Experimental and theoretical studies on a novel helical architecture ...

    Indian Academy of Sciences (India)

    aKey Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory ... bInstitute for Computation in Molecular and Material Science, School of Chemical Engineering, Nanjing ... mental and theoretical points of view is still largely.

  13. Theoretical Study of the Compound Parabolic Trough Solar Collector

    OpenAIRE

    Dr. Subhi S. Mahammed; Dr. Hameed J. Khalaf; Tadahmun A. Yassen

    2012-01-01

    Theoretical design of compound parabolic trough solar collector (CPC) without tracking is presented in this work. The thermal efficiency is obtained by using FORTRAN 90 program. The thermal efficiency is between (60-67)% at mass flow rate between (0.02-0.03) kg/s at concentration ratio of (3.8) without need to tracking system.The total and diffused radiation is calculated for Tikrit city by using theoretical equations. Good agreement between present work and the previous work.

  14. Kinetic Study of Denatonium Sorption to Smectite Clay Minerals.

    Science.gov (United States)

    Crosson, Garry S; Sandmann, Emily

    2013-06-01

    The denatonium cation, as a benzoate salt, is the most bitter cation known to modern society and is frequently added to consumer products to reduce accidental and intentional consumption by humans and animals. Denatonium can enter the environment by accidental discharges, potentially rendering water supplies undrinkable. Interactions of denatonium with soil components ( i.e. , smectite minerals) ultimately control the environmental fate of denatonium, but the current literature is devoid of studies that evaluate denatonium sorption to smectite minerals. This study investigated the mechanism and kinetics of denatonium sorption to smectite clay minerals as a function of smectite type, temperature, pH and ionic strength. Uptake by synthetic mica montmorillonite (Syn-1), Wyoming montmorillonite (SWy-2), and Texas montmorillonite (STx-1b) at 305K was rapid, with equilibrium being reached within 2 min for all clays. Complete removal of denatonium was observed for STx-1b at pH 6.9, while partial removal was observed for Syn-1 and SWy-2. Kinetic behavior of SWy-2 and Syn-1 is consistent with a pseudo-second-order model at 305K. An activation energy of +25.9 kJ/mol was obtained for sorption to Syn-1 and was independent of temperature between 286K and 338K. Activation-free energy (Δ G *), activation enthalpy (Δ H *), and activation entropy (Δ S *) for Syn-1 were found to be +62.91 kJ/mol, +23.36 kJ/mol, and -0.130 kJ/(K·mol), respectively. Sorption capacities at pH 3.6, 6.9, and 8.2 were constant at 1.3×10 -2 g denatonium/g clay; however, the kinetic rate constant increased by 56%, going from acidic to basic solution conditions. Distribution coefficients were negatively correlated with ionic strength, suggesting cation exchange. Collectively, results suggested that smectite minerals can serve as efficient sinks for denatonium cations. This is much-needed information for agencies developing regulations regarding denatonium usage and for water treatment professionals

  15. Thermogravimetric kinetic study of agricultural residue biomass pyrolysis based on combined kinetics.

    Science.gov (United States)

    Wang, Xun; Hu, Mian; Hu, Wanyong; Chen, Zhihua; Liu, Shiming; Hu, Zhiquan; Xiao, Bo

    2016-11-01

    Pyrolytic kinetic of an agricultural residue (AR) feedstock, a mixture of plants (cotton, wheat, rich, corn) stems, was investigated based on combined kinetics. The most suitable mechanism for AR one-step pyrolysis was f(α)=(1-α)(1.1816)α(-1.8428) with kinetic parameters of: apparent activation energy 221.7kJ/mol, pre-exponential factor 4.17E16s(-1). Pyrolysis of AR feedstock could not be described by one-step reaction attributes to heterogeneous features of pyrolysis processes. Combined kinetics three-parallel-reaction (CK-TPR) model fitted the pyrolysis experimental data very well. Reaction mechanisms for pseudo hemicelluloses, cellulose, lignin in CK-TPR model was f(α)=(1-α)(1.6244)α(-0.3371)[-ln(1-α)](-0.0515), f(α)=(1-α)(1.0597)α(-0.6909)[-ln(1-α)](0.9026) and f(α)=(1-α)(2.9577)α(-4.7719), respectively. Apparent activation energy of three pseudo components followed the order of Elignin(197.3kJ/mol)>Ecellulose(176.3kJ/mol)>Ehemicelluloses (151.1kJ/mol). Mechanism of hemicelluloses pyrolysis could be further expressed as f(α)=(1-α)(1.4). The pyrolytic mechanism of cellulose met the Nucleation well. However, mechanism of lignin pyrolysis was complex, which possibly was the combined effects of Nucleation, Diffusion, Geometrical contraction, and Power law. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Kinetic study of the reaction of chlorine atoms with hydroxyacetone in gas-phase

    Science.gov (United States)

    Stoeffler, Clara; Joly, Lilian; Durry, Georges; Cousin, Julien; Dumelié, Nicolas; Bruyant, Aurélien; Roth, Estelle; Chakir, Abdelkhaleq

    2013-12-01

    function of temperature (233-298 K) were performed by Dillon et al. [7]. An experimental (laser photolysis/FIL) and theoretical approach (quantum calculation) were realized. This study showed that the oxidation of HA by OH-radicals has a negative temperature coefficient which is explained by an intermediate complex formation. Another study as a function of temperature was conducted by Butkovskaya et al. using the technique of a turbulent flow reactor coupled with a mass spectrometer chemical ionization [8]. This work was purely mechanistic and it shows that the mechanism of this reaction changes with temperature: a temperature increase favors the production yields of methanoic and ethanoic acids and reduces the formation yield of methylglyoxal [8]. Our work is motivated by the fact that the kinetic studies of the reaction of HA with chlorine radicals are rare in comparison with the kinetic studies of the reaction of HA with OH radicals. So far, only one such kinetic study is reported in the literature. It has been carried out by Orlando et al. at 294 K [6]. To the best of our knowledge, this reaction has not yet been studied as a function of temperature. Therefore, to enrich kinetic data concerning this compound, the study of HA with Cl atoms reaction as a function of temperature has been undertaken. Experiments are carried out using the relative technique in a simulation chamber coupled with an infrared Fourier transform (FTIR) spectrometer and a quantum cascade laser in external cavity (ECQCL) at 1 bar with the temperature ranging 277-350 K. Using both FTIR and ECQCL techniques allows comparing the measurements sensitivity and improving the kinetic precision determination. The FTIR spectroscopy is widely used to perform kinetic measurements whereas the ECQCL spectrometer is quite original in kinetic studies. Laser spectrometry indeed presents advantages such as high sensitivity, high resolution, and fast acquisition time compared to the FTIR spectrometer. The ECQCL

  17. Kinetics studies of solvent extraction of rare earths into DEHPA

    International Nuclear Information System (INIS)

    Lim, T.M.; Tran, T.

    1996-01-01

    The kinetics of rare earth solvent extraction into di(2-ethylhexyl) phosphoric acid have been studied using radiotracers ( 141 Ce, 152 Eu, 153 Gd, 160 Tb and 88 Y) in a modified Lewis cell. The experimental procedure involved continuous monitoring of both aqueous and organic phases using an automated γ- counting system. Using this method, highly reproducible results were obtained without chemical analysis or disturbance of the system. The initial rate extraction was first order with respect to individual rare earth concentration. At low acidities ([H+] < 0.01 M), the extraction rates of rare earths were equal and independent of pH. However, at high acidities, the extraction rate was strongly dependent on pH and varied between the rare earths. Similarly, differences in the extraction rate of individual rare earths were apparent at low DEHPA concentration. (authors)

  18. Carbohydrate deficient transferrin (CDT) in alcoholic cirrhosis: a kinetic study

    DEFF Research Database (Denmark)

    Henriksen, Jens Henrik; Grønbaek, M; Møller, Søren

    1997-01-01

    BACKGROUND/AIMS: Carbohydrate deficient transferrin has been introduced as a marker of excessive alcohol intake. The present study was undertaken in order to measure the circulating level of carbohydrate deficient transferrin in patients with alcoholic cirrhosis and to assess arteriovenous kinetics...... of carbohydrate deficient transferrin in liver and kidney. METHODS/RESULTS: The median value of serum carbohydrate deficient transferrin was 16.0 U/l in patients with alcoholic cirrhosis (n = 41), and this value was not significantly different from that of a normal control group (median 17.4 U/l, n = 55, ns......). Carbohydrate deficient transferrin was significantly higher in patients with cirrhosis and high current alcohol intake than in abstaining patients (20 vs. 14 U/l, p 50 g/day) had a significantly higher carbohydrate deficient transferrin...

  19. Prospects in the Study of Stem-Cell Kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Till, J. E. [Department of Medical Biophysics, University of Toronto (Canada); Ontario Cancer Instute, Toronto, ON (Canada)

    1968-08-15

    The recent rapid progress in the field of stem-cell kinetics has been due in large part to the development of reliable in-vivo assays for the functions of haemopoietic stem cells. As a direct result of the availability of these assays, several novel and interesting phenomena have been described. What is now needed is not so much further search for new phenomena as an understanding of the phenomena that have already been uncovered. It is postulated that new approaches will be required for the analysis of these phenomena, and that future progress in the field will be strongly dependent on the development of methods suitable for the detailed study of the growth and differentiation of populations of haemopoietic cells in culture systems. (author)

  20. Study of kinetics of the tetroxane thermolysis by UV spectrophotometry

    International Nuclear Information System (INIS)

    Jorge, N.L.; Leiva, L.C.; Castellanos, M.G.; Cafferata, L.F.R.; Gomez V, M.E.

    2002-01-01

    The 3,3,6,6-tetramethyl-1,2,4,5-tetroxane (ACDP) in methanol solution shows an absorbance peak at low wave length in UV spectrum and follows the Lambert Beer law until 10-2 M concentration at 209 nm. The ACDP thermal decomposition have been studied by the UV spectroscopy like an alternative method to find out the kinetic parameters from the thermolysis of these compounds. The rate constants at the temperatures and initial concentration ranges of 130-166 and 0,003-0,013 mol / L, respectively, and the activation parameters were similar to the corresponding values found by other methodology, verifying this analytic technique. Acetone produced during reaction no interference in ACDP quantification by UV analysis. (Author)

  1. A study of butyl acetate synthesis. 4-reaction kinetics

    Directory of Open Access Journals (Sweden)

    Álvaro Orjuela Londoño

    2006-05-01

    Full Text Available This work was aimed at studying liquid-phase acetic acid and butyl alcohol esterification reaction (P atm =0.76 Bar,using an ion exchange resin (Lewatit K-2431 as catalyst. The effect of the absence of internal and external mass transport on catalyst particles was established in the research conditions used here. A set of assays to determine the effect of catalyst load (0.5%, 1%, 2% w/w temperature (73°C, 80°C, 87°C and molar ratio (1:2, 1:1, 2:1 acid/alcohol on reaction rate was carried out and both LHHW and pseudo-homogeneous kinetic expressions were obtained, these being in good agreement with the experimental data.

  2. In vitro studies of ante-mortem proliferation kinetics

    International Nuclear Information System (INIS)

    McBride, W.H.; Withers, H.R.

    1986-01-01

    Using K562 human erythroblastoid cells, it was concluded that dose fractionation has no discrepant effect on the ante-mortem proliferation kinetics of doomed cells as opposed to clonogenic cell survival and that effects on ante-mortem proliferation kinetics cannot be solely responsible for the differences in fractionation response between early and late responding tissues. (UK)

  3. Analytical and computational study of magnetization switching in kinetic Ising systems with demagnetizing fields

    DEFF Research Database (Denmark)

    Richards, H.L.; Rikvold, P.A.

    1996-01-01

    particularly promising as materials for high-density magnetic recording media. In this paper we use analytic arguments and Monte Carlo simulations to quantitatively study the effects of the demagnetizing field on the dynamics of magnetization switching in two-dimensional, single-domain, kinetic Ising systems....... For systems in the weak-field ''stochastic region,'' where magnetization switching is on average effected by the nucleation and growth of a single droplet, the simulation results can be explained by a simple model in which the free energy is a function only of magnetization. In the intermediate......-field ''multidroplet region,'' a generalization of Avrami's law involving a magnetization-dependent effective magnetic field gives good agreement with the simulations. The effects of the demagnetizing field do not qualitatively change the droplet-theoretical picture of magnetization switching in highly anisotropic...

  4. A theoretical study for thorium monocarbide (ThC)

    International Nuclear Information System (INIS)

    Aydin, S.; Tatar, A.; Ciftci, Y.O.

    2012-01-01

    Highlights: ► We focused on high pressure behavior of ThC. ► ThC is metallic, and mechanically stable. ► The obtained results agree with the other available values. ► ThC is hard material, and hardness increases properly with pressure. - Abstract: The structural, mechanical, electronic and thermodynamic properties of thorium monocarbide (ThC) with NaCl-type structure have been investigated by using first-principles plane wave density functional calculations with GGA, LDA and LDA + U functionals. It is shown that calculated equilibrium structural parameters of ThC are in agreement with the experimental results. It is seen from calculated single-crystal elastic constants that ThC with NaCl-type structure is mechanically stable. And from calculated density of states and band structure, it is observed that ThC is metallic. After the properties at 0 GPa are clarified, pressure dependency of the structural parameters, the elastic properties and related mechanical properties, density of states (DOS) and hardness are studied. Furthermore, the thermodynamic properties of ThC are obtained from the quasi-harmonic Debye model (QHM) over high pressure and temperature ranges for three functionals. The results are compared to each other, and the available experimental and theoretical data.

  5. A theoretical study for thorium monocarbide (ThC)

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, S.; Tatar, A. [Gazi University, Department of Physics, Teknikokullar 06500, Ankara (Turkey); Ciftci, Y.O., E-mail: yasemin@gazi.edu.tr [Gazi University, Department of Physics, Teknikokullar 06500, Ankara (Turkey)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer We focused on high pressure behavior of ThC. Black-Right-Pointing-Pointer ThC is metallic, and mechanically stable. Black-Right-Pointing-Pointer The obtained results agree with the other available values. Black-Right-Pointing-Pointer ThC is hard material, and hardness increases properly with pressure. - Abstract: The structural, mechanical, electronic and thermodynamic properties of thorium monocarbide (ThC) with NaCl-type structure have been investigated by using first-principles plane wave density functional calculations with GGA, LDA and LDA + U functionals. It is shown that calculated equilibrium structural parameters of ThC are in agreement with the experimental results. It is seen from calculated single-crystal elastic constants that ThC with NaCl-type structure is mechanically stable. And from calculated density of states and band structure, it is observed that ThC is metallic. After the properties at 0 GPa are clarified, pressure dependency of the structural parameters, the elastic properties and related mechanical properties, density of states (DOS) and hardness are studied. Furthermore, the thermodynamic properties of ThC are obtained from the quasi-harmonic Debye model (QHM) over high pressure and temperature ranges for three functionals. The results are compared to each other, and the available experimental and theoretical data.

  6. Theoretical Study of Triatomic Systems Involving Helium Atoms

    International Nuclear Information System (INIS)

    Suno, H.; Hiyama, E.; Kamimura, M.

    2013-01-01

    The triatomic 4 He system and its isotopic species 4 He 2 3 He are theoretically investigated. By adopting the best empirical helium interaction potentials, we calculate the bound state energy levels as well as the rates for the three-body recombination processes: 4 He + 4 He + 4 He → 4 He 2 + 4 He and 4 He + 4 He + 3 He → 4 He 2 + 3 He. We consider not only zero total angular momentum J = 0 states, but also J > 0 states. We also extend our study to mixed helium-alkali triatomic systems, that is 4 He 2 X with X = 7 Li, 23 Na, 39 K, 85 Rb, and 133 Cs. The energy levels of all the J ≥ 0 bound states for these species are calculated as well as the rates for three-body recombination processes such as 4 He + 4 He + 7 Li → 4 He 2 + 7 Li and 4 He + 4 He + 7 Li → 4 He 7 Li + 4 He. In our calculations, the adiabatic hyperspherical representation is employed but we also obtain preliminary results using the Gaussian expansion method. (author)

  7. A theoretical and spectroscopic study of conformational structures of piroxicam

    Science.gov (United States)

    Souza, Kely Ferreira de; Martins, José A.; Pessine, Francisco B. T.; Custodio, Rogério

    2010-02-01

    Piroxicam (PRX) has been widely studied in an attempt to elucidate the causes and mechanisms of its side effects, mainly the photo-toxicity. In this paper fluorescence spectra in non-protic solvents and different polarities were carried out along with theoretical calculations. Preliminary potential surfaces of the keto and enol forms were obtained at AM1 level of theory providing the most stable conformers, which had their structure re-optimized through the B3LYP/CEP-31G(d,p) method. From the optimized structures, the electronic spectra were calculated using the TD-DFT method in vacuum and including the solvent effect through the PCM method and a single water molecule near PRX. A new potential surface was constructed to the enol tautomer at DFT level and the most stable conformers were submitted to the QST2 calculations. The experimental data showed that in apolar media, the solution fluorescence is raised. Based on conformational analysis for the two tautomers, keto and enol, the results indicated that the PRX-enol is the main tautomer related to the drug fluorescence, which is reinforced by the spectra results, as well as the interconvertion barrier obtained from the QST2 calculations. The results suggest that the PRX one of the enol conformers presents great possibility of involvement in the photo-toxicity mechanisms.

  8. Experimental and theoretical study of Co sorption in clay montmorillonites

    Science.gov (United States)

    Gil Rebaza, A. V.; Montes, M. L.; Taylor, M. A.; Errico, L. A.; Alonso, R. E.

    2018-03-01

    Montmorillonite (MMT) clays are 2:1 layered structures which in natural state may allocate different hydrated cations such as M-nH2O (M = Na, Ca, Fe, etc) in its interlayer space. Depending on the capability for ion sorption, these materials are interesting for environmental remediation. In this work we experimentally study the Co sorption in a natural Na-MMT using UV-visible spectrometry and XRD on semi-oriented samples, and then analyze the sorption ability of this clay by means of ab initio calculation performed on pristine MMT. The structural properties of Na-MMT and Co-adsorbed MMT, and the hyperfine parameters at different atomic sites were analyzed and compared with the experimental ones for the first, and for the case of the hyperfine parameters, presented for the first time for the last. The theoretical predictions based on total energy considerations confirm that Co incorporation replacing Na is energetically favorable. Also, the basal spacing d001 experimentally obtained is well reproduced.

  9. Strategic Step for Environmental Rescue: A Theoretical Legal Studies

    Directory of Open Access Journals (Sweden)

    Bambang Sutrisno

    2014-01-01

    Full Text Available Indonesia is among the developing countries that are struggling to develop in the field of industrial development. The logical consequence of any development process, especially industrial development is the emergence of associated impacts that greatly affect the durability and sustainability of the environment. Developing the equitable industry in order to create public welfare is important. However, maintaining the security and preservation of the environment is also very important, because it is only with the availability of a good environment and healthy living that human beings can perform daily living. The availability of good and healthy environment is the constitutional responsibility of the government, as well as part of the human rights of all citizens which must be given by the State. Efforts to create a good environment and healthy living will be effective if controlled by State government and institutions who understand the objective conditions on the ground. In this regard, the granting of the authority on environmental control to regional government autonomously is the right, very smart policy choice. How To Cite: Sutrisno, B. (2016. Strategic Step for Environmental Rescue: A Theoretical Legal Studies. Rechtsidee, 1(1, 27-58. doi:http://dx.doi.org/10.21070/jihr.v1i1.98

  10. Theoretical studies of potential energy surfaces and computational methods

    Energy Technology Data Exchange (ETDEWEB)

    Shepard, R. [Argonne National Laboratory, IL (United States)

    1993-12-01

    This project involves the development, implementation, and application of theoretical methods for the calculation and characterization of potential energy surfaces involving molecular species that occur in hydrocarbon combustion. These potential energy surfaces require an accurate and balanced treatment of reactants, intermediates, and products. This difficult challenge is met with general multiconfiguration self-consistent-field (MCSCF) and multireference single- and double-excitation configuration interaction (MRSDCI) methods. In contrast to the more common single-reference electronic structure methods, this approach is capable of describing accurately molecular systems that are highly distorted away from their equilibrium geometries, including reactant, fragment, and transition-state geometries, and of describing regions of the potential surface that are associated with electronic wave functions of widely varying nature. The MCSCF reference wave functions are designed to be sufficiently flexible to describe qualitatively the changes in the electronic structure over the broad range of geometries of interest. The necessary mixing of ionic, covalent, and Rydberg contributions, along with the appropriate treatment of the different electron-spin components (e.g. closed shell, high-spin open-shell, low-spin open shell, radical, diradical, etc.) of the wave functions, are treated correctly at this level. Further treatment of electron correlation effects is included using large scale multireference CI wave functions, particularly including the single and double excitations relative to the MCSCF reference space. This leads to the most flexible and accurate large-scale MRSDCI wave functions that have been used to date in global PES studies.

  11. Optical activity in planar chiral metamaterials: Theoretical study

    International Nuclear Information System (INIS)

    Bai, Benfeng; Svirko, Yuri; Turunen, Jari; Vallius, Tuomas

    2007-01-01

    A thorough theoretical study of the optical activity in planar chiral metamaterial (PCM) structures, made of both dielectric and metallic media, is conducted by the analysis of gammadion-shaped nanoparticle arrays. The general polarization properties are first analyzed from an effective-medium perspective, by analogy with natural optical activity, and then verified by rigorous numerical simulation, some of which are corroborated by previous experimental results. The numerical analysis suggests that giant polarization rotation (tens of degrees) may be achieved in the PCM structures with a thickness of only hundreds of nanometers. The artificial optical activity arises from circular birefringence induced by the structural chirality and is enhanced by the guided-mode or surface-plasmon resonances taking place in the structures. There are two polarization conversion types in the dielectric PCMs, whereas only one type in the metallic ones. Many intriguing features of the polarization property of PCMs are also revealed and explained: the polarization effect is reciprocal and vanishes in the symmetrically layered structures; the effect occurs only in the transmitted field, but not in the reflected field; and the polarization spectra of two enantiomeric PCM structures are mirror symmetric to each other. These remarkable properties pave the way for the PCMs to be used as polarization elements in new-generation integrated optical systems

  12. Theoretical studies of the reactions of HCN with atomic hydrogen

    International Nuclear Information System (INIS)

    Bair, R.A.; Dunning, T.H. Jr.

    1985-01-01

    A comprehensive theoretical study has been made of the energetics of the important pathways involved in the reaction of hydrogen atoms with hydrogen cyanide. For each reaction ab initio GVB-CI calculations were carried out to determine the structures and vibrational frequencies of the reactants, transition states, and products; then POL-CI calculations were carried out to more accurately estimate the electronic contribution to the energetics of the reactions. The hydrogen abstraction reaction is calculated to be endoergic by 24 kcal/mol [expt. ΔH (0 K) = 16--19 kcal/mol] with a barrier of 31 kcal/mol in the forward direction and 6 kcal/mol in the reverse direction. For the hydrogen addition reactions, addition to the carbon atom is calculated to be exoergic by 19 kcal/mol with a barrier of 11 kcal/mol, while addition to the nitrogen center is essentially thermoneutral with a barrier of 17 kcal/mol. Calculations were also carried out on the isomerization reactions of the addition products. The cis→trans isomerization of HCNH has a barrier of only 10 kcal/mol with the trans isomer being more stable by 5 kcal/mol. The (1,2)-hydrogen migration reaction, converting H 2 CN to trans-HCNH, is endoergic by only 14 kcal/mol, but the calculated barrier for the transfer is 52 kcal/mol. The energy of the migration pathway thus lies above that of the dissociation--recombination pathway

  13. Kinetic study and syngas production from pyrolysis of forestry waste

    International Nuclear Information System (INIS)

    Hu, Mian; Wang, Xun; Chen, Jian; Yang, Ping; Liu, Cuixia; Xiao, Bo; Guo, Dabin

    2017-01-01

    Highlights: • Pyrolysis process can be divided into three stages using differential DTG method. • A modified discrete DAEM model fitted experimental data well. • Fe/biochar catalyst showed a good performance on catalytic reforming process. - Abstract: Kinetic study and syngas production from pyrolysis of forestry waste (pine sawdust (PS)) were investigated using a thermogravimetric analyzer (TGA) and a fixed-bed reactor, respectively. In TGA, it was found that the pyrolysis of PS could be divided into three stages and stage II was the major mass reduction stage with mass loss of 73–74%. The discrete distributed activation energy model (DAEM) with discrete 200 first-order reactions was introduced to study the pyrolysis kinetic. The results indicated that the DAEM with 200 first-order reactions could approximate the pyrolysis process with an excellent fit between experimental and calculated data. The apparent activation energies of PS ranged from 147.86 kJ·mol −1 to 395.76 kJ·mol −1 , with corresponding pre-exponential factors of 8.30 × 10 13 s −1 to 3.11 × 10 25 s −1 . In the fixed-bed reactor, char supported iron catalyst was prepared for tar cracking. Compared with no catalyst which the gas yield and tar yield were 0.58 N m 3 /kg biomass and 201.23 g/kg biomass, the gas yield was markedly increased to 1.02 N m 3 /kg biomass and the tar yield was decreased to only 26.37 g/kg biomass in the presence of char supported iron catalyst. These results indicated that char supported iron catalyst could potentially be used to catalytically decompose tar molecules in syngas generated via biomass pyrolysis.

  14. Theoretical analysis and experimental study of spray degassing method

    International Nuclear Information System (INIS)

    Wu Ruizhi; Shu Da; Sun Baode; Wang Jun; Li Fei; Chen Haiyan; Lu YanLing

    2005-01-01

    A new hydrogen-removal method of aluminum melt, spray degassing, is presented. The thermodynamic and kinetic analysis of the method are discussed. A comparison between the thermodynamics and kinetics of the spray degassing method and rotary impellor degassing method is made. The thermodynamic analysis shows that the relationship between the final hydrogen content of the aluminum melt and the ratio of purge gas flow rate to melt flow rate is linear. The result of thermodynamic calculation shows that, in spray degassing, when the ratio of G/q is larger than 2.2 x 10 -6 , the final hydrogen content will be less than 0.1 ml/100 g Al. From the kinetic analysis, the degassing effect is affected by both the size of melt droplets and the time that melt droplets move from sprayer to the bottom of the treatment tank. In numerical calculation, the hydrogen in aluminum melt can be degassed to 0.05 ml/100 g Al from 0.2 ml/100 g Al in 0.02 s with the spray degassing method. Finally, the water-model experiments are presented with the spray degassing method and rotary impellor degassing method. Melt experiments are also presented. Both the water-model experiments and the melt experiments show that the degassing effect of the spray degassing method is better than that of the rotary impeller method

  15. The kinetic study of oxidation of iodine by hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Cantrel, L [Institut de Protection et de Surete Nucleaire, IPNS, CEN Cadarache, Saint Paul lez Durance (France); Chopin, J [Laboratoire d` Electrochimie Inorganique, ENSSPICAM, Marseille (France)

    1996-12-01

    Iodine chemistry is one of the most important subjects of research in the field of reactor safety because this element can form volatile species which represent a biological hazard for environment. As the iodine and the peroxide are both present in the sump of the containment in the event of a severe accident on a light water nuclear reactor, it can be important to improve the knowledge on the reaction of oxidation of iodine by hydrogen peroxide. The kinetics of iodine by hydrogen peroxide has been studied in acid solution using two different analytical methods. The first is a UV/Vis spectrophotometer which records the transmitted intensity at 460 nm as a function of time to follow the decrease of iodine concentration, the second is an amperometric method which permits to record the increase of iodine+1 with time thanks to the current of reduction of iodine+1 to molecular iodine. The iodine was generated by Dushman reaction and the series of investigations were made at 40{sup o}C in a continuous stirring tank reactor. The influence of the initial concentrations of iodine, iodate, hydrogen peroxide, H{sup +} ions has been determined. The kinetics curves comprise two distinct chemical phases both for molecular iodine and for iodine+1. The relative importance of the two processes is connected to the initial concentrations of [I{sub 2}], [IO{sub 3}{sup -}], [H{sub 2}O{sub 2}] and [H{sup +}]. A rate law has been determined for the two steps for molecular iodine. (author) figs., tabs., 22 refs.

  16. Theoretical study of incoherent φ photoproduction on a deuteron target

    International Nuclear Information System (INIS)

    Sekihara, T.; Martinez Torres, A.; Jido, D.; Oset, E.

    2012-01-01

    We study the photoproduction of φ mesons in deuteron, paying attention to the modification of the cross-section from bound protons to the free ones. For this purpose we take into account Fermi motion in single scattering and rescattering of φ to account for φ absorption on a second nucleon as well as the rescattering of the proton on the neutron. We find that the contribution of the double scattering for φ is much smaller than the typical cross-section of γp→φp in free space, which implies a very small screening of the φ production in deuteron. The contribution from the proton rescattering, on the other hand, is found to be not negligible compared to the cross-section of γp→φp in free space, and leads to a moderate reduction of the φ photoproduction cross-section on a deuteron at forward angles if the LEPS set-up is taken into account. The Fermi motion allows contribution of the single scattering in regions forbidden by phase-space in the free case. In particular, we find that for momentum transfer squared close to the maximum value, the Fermi motion changes drastically the shape of dσ/dt, to the point that the ratio of this cross-section to the free one becomes very sensitive to the precise value of t chosen, or the size of the bin used in an experimental analysis. Hence, this particular region of t does not seem to be the most indicated to find effects of a possible φ absorption in the deuteron. This reaction is studied theoretically as a function of t and the results are contrasted with recent experiments at LEPS and Jefferson Lab. The effect of the experimental angular cuts at LEPS is also discussed, providing guidelines for future experimental analyses of the reaction. (orig.)

  17. Fibrin related antigens: assay development, clinical and kinetic studies

    Energy Technology Data Exchange (ETDEWEB)

    Kruskal, J B

    1987-08-01

    This thesis describes an assay which is able to measure and to determine the proportions of fibrin- and fibrinogen-related antigens (FRA) present in clinical samples. No assay exists at present which is capable of distinguishing between fibrin and fibrinogen degradation products concurrently and in a clinical setting. The assay may be used as a tool with which to gain further insight to pathophysiology of disorders characterized by activation of the coagulation and fibrinolytic pathways. This study provides and analysis of the FRA profiles in patients with disorders characterised by possible enhanced fibrinolytic activity. Studies have been undertaken on patients with acute and chronic liver diseases, on patients with the various syndromes of coronary artery disease and on patients with insulin-dependent diabetes mellitus with and without evidence of microvascular disease. Certain observations made it evident that further studies were required in order to explain previously undocumented fibrinolytic abnormalities in certain patient groups. Data obtained from patients with liver disease provided information compatible with the activation of their fibrinolytic pathways. The initial scope of this study was then extended to further investigate the deranged haemostatic mechanisms in patients with severe liver diseases. Kinetic studies were performed which required the development of specific technology to be able to measure certain previously undertermined parameters. Mathematical models describing the rates of fibrin formation and lysis were developed for human studies. Fibrin-derived D-dimer was radiolabelled and its validity as and intravenous tracer and maker of fibrin degradation established.

  18. Study of the kinetics parameters for subcritical media driven by source

    International Nuclear Information System (INIS)

    Lee, S.M.; Maiorino, J.R.

    2009-01-01

    This paper presents a theoretical study of reactor kinetics focusing on the methodology of calculation and the experimental measurements of the so-called kinetic parameters. A comparison between the methodology based on the Dulla's formalism and the classical method is made. The objective is to exhibit the dependence of the parameters on sub criticality level and perturbation. Two different slab type systems were considered: thermal one and fast one, both with homogeneous media. One group diffusion model was used for the fast reactor, and for the thermal system, two group diffusion model, considering, in both case only one precursor's family. For reason of simplicity, several additional assumptions were made for calculation of two group method: no up-scattering, fission reaction occurring only in thermal group, etc. The solutions for subcritical systems were obtained using the expansion method, and for critical systems, the methods presented in classical textbooks of reactor physics were applied. The numerical results presented their dependence on sub criticality level and perturbation. (author)

  19. Theoretical Study of the Compound Parabolic Trough Solar Collector

    Directory of Open Access Journals (Sweden)

    Dr. Subhi S. Mahammed

    2012-06-01

    Full Text Available Theoretical design of compound parabolic trough solar collector (CPC without tracking is presented in this work. The thermal efficiency is obtained by using FORTRAN 90 program. The thermal efficiency is between (60-67% at mass flow rate between (0.02-0.03 kg/s at concentration ratio of (3.8 without need to tracking system.The total and diffused radiation is calculated for Tikrit city by using theoretical equations. Good agreement between present work and the previous work.

  20. Theoretical study on device efficiency of pulsed liquid jet pump

    International Nuclear Information System (INIS)

    Gao Chuanchang; Lu Hongqi; Wang Shicheng; Cheng Mingchuan

    2001-01-01

    The influence of the main factors on device efficiency of pulsed liquid jet pump with gas-liquid piston is analysed, the theoretical equation and its time-averaged solution of pulsed liquid jet pump device efficiency are derived. The theoretical and experimental results show that the efficiency of transmission of energy and mass to use pulsed jet is greatly raised, compared with steady jet, in the same device of liquid jet pump. The calculating results of time-averaged efficiency of pulsed liquid jet pump are approximately in agreement with the experimental results in our and foreign countries

  1. In-Situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes

    Science.gov (United States)

    2010-12-28

    DATES COVERED (From - To) 1/29/10-9/30/10 4. TITLE AND SUBTITLE In situ optical studies of oxidation/reduction kinetics on SOFC cermet anodes 5a...0572 In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Department of Chemistry and Biochemistry Montana State University...of Research In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Principal Investigator Robert Walker Organization

  2. Powder X-ray diffraction studies of structural and kinetic aspects of polymorphism

    International Nuclear Information System (INIS)

    Chan, F.C.

    1999-01-01

    Polymorphism is a poorly understood phenomenon that is of considerable technological interest to the pharmaceutical industry. The polymorph selected can influence the bioavailability, processing and stability of the pharmaceutical dosage form. In this study structural, kinetic and thermodynamics aspects of polymorphism and polymorphic phase transformations have been examined using powder X-ray diffraction (PXRD). The compound sulphathiazole is a well-studied model in the investigation of polymorphism and crystal growth. There are five known polymorphic forms and the structure of form V was unknown until this study. The difficulty has been that it has not been possibly to prepare crystals of appropriate size and quality for single crystal diffraction. Furthermore, structure solution from powder data for organic molecules is almost impossible. Despite the challenge the structure of sulphathiazole form V have been solved ab initio from powder data using direct methods. With 16 non-hydrogen atoms in the molecule and two molecules in the asymmetric unit, this structure represents a significant advance in terms of the complexity of an organic structure solved from PXRD data. The structural data should be invaluable for rationalizing experimental observations and the development of theoretical ideas regarding polymorphism and crystal growth. The second part of the study, has examined kinetics of polymorphic phase transformations as a function of pressure combined with temperature using real-time synchrotron PXRD. The significance of pressure arises from the fact that phase transitions can be induced in pharmaceuticals during tabletting. The phase transformation behaviour of rubidium iodide (chosen as a simple test model) has been investigated as a function of isobaric pressure at ambient and elevated temperatures. The kinetics have been characterized by using the Johnson-Melil-Avrami equation. The effect of successive cycling across the transition pressure was also

  3. a Theoretical Study of Coherent Structures in Nonneutral Plasma Columns

    Science.gov (United States)

    Lund, Steven M.

    A ubiquitous feature of experimental and computer simulation studies of magnetically confined pure electron plasmas in cylindrical confinement devices is the formation of nonaxisymmetric (partial/partial theta ne 0) rotating equilibria. In this dissertation, nonaxisymmetric rotating equilibria are investigated theoretically for strongly magnetized, low-density (omega_sp{pe} {2}/omega_sp{ce}{2 } guiding-center model in the cold-fluid limit (the continuity and Poisson equations) that treats the electrons as a massless fluid (m_{e} to 0) with E times B flow velocity V _{e} = -(c/B_0)nablaphi times {bf e}_{z}. Within this model, general rotating equilibria with electron density (n_{e} equiv n_{R}(r,theta-omega _{r}t) and electrostatic potential phi equiv phi_{R }(r,theta-omega_{r}t) have the property that the electron density is functionally related to the streamfunction psi _{R} = -ephi_{R} + omega_{r}(eB_0/2c)r^2 by n_{R} = n_{R }(psi_{R}). The streamfunction psi_{R} satisfies the nonlinear equilibrium equation nabla ^2psi_{R} = -4pi e^2n _{R}(psi_{R}) + 2omega_{r}eB_0/c with psi_{R} = omega _{r}(eB_0/2c)r_sp{w }{2} equiv psi_{w } = const. on the cylindrical wall at r = r_{w}. A general methodology for the solution of this equilibrium system is presented and several properties of rotating equilibria are analyzed. Following this analysis, two classes of nonaxisymmetric equilibria are investigated. These two classes of equilibria can have large amplitude (strongly nonaxisymmetric). First, a class of vortex-like rotating equilibria is analyzed that is characterized by a structured density profile that fills a confinement geometry with an inner conducting cylinder at radius r = r_{I} Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).

  4. Theoretical and spectroscopic studies of a tricyclic antidepressant, imipramine hydrochloride

    Science.gov (United States)

    Sagdinc, S. G.; Azkeskin, Caner; Eşme, A.

    2018-06-01

    Imipramine hydrochloride ([H-IMI]Cl), C19H24N2.HCl, is the prototypic tricyclic antidepressant (TCA) inhibitor of norepinephrine and serotonin neuronal reuptake. The molecular structure, molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis, linear and non-linear optical (NLO) properties of [H-IMI]Cl have been investigated using the density functional theory (DFT) calculations with the B3LYP level at the 6‒311++G(d,p) basis set. The UV-Vis spectra for [H-IMI]Cl were experimentally studied in water and methanol. TD‒DFT calculations in water and methanol were employed to investigate the absorption wavelengths (λ), excitation energies (E), and oscillator strengths (f) for the UV-Vis analysis and the major contributions to the electronic transitions. From NBO analysis, the orbitals with the stabilization energy E(2) of 192.15 kcal/mol are π*(C5sbnd C18) as donor NBO and π*(C19sbnd C20) as acceptor NBO. The FT‒IR (4000‒400 cm-1) and FT‒Raman (3500-50 cm-1) spectra have been measured and analyzed. The assignment of bands observed vibrational spectra have been made by comparison of its calculated theoretical vibrational frequencies obtained using the DFT/B3LYP/6‒311++G(d,p) method. The detailed vibrational assignments were performed with the DFT calculation, and the potential energy distribution (PED) of [H-IMI]Cl was obtained by the Vibrational Energy Distribution Analysis 4 (VEDA4) program. The scaled frequencies resulted in good agreement with the observed spectral patterns.

  5. A Theoretical Framework for Studying Adolescent Contraceptive Use.

    Science.gov (United States)

    Urberg, Kathryn A.

    1982-01-01

    Presents a theoretical framework for viewing adolescent contraceptive usage. The problem-solving process is used for developmentally examining the competencies that must be present for effective contraceptive use, including: problem recognition, motivation, generation of alternatives, decision making and implementation. Each aspect is discussed…

  6. Experimental and theoretical study of magnetohydrodynamic ship models.

    Directory of Open Access Journals (Sweden)

    David Cébron

    Full Text Available Magnetohydrodynamic (MHD ships represent a clear demonstration of the Lorentz force in fluids, which explains the number of students practicals or exercises described on the web. However, the related literature is rather specific and no complete comparison between theory and typical small scale experiments is currently available. This work provides, in a self-consistent framework, a detailed presentation of the relevant theoretical equations for small MHD ships and experimental measurements for future benchmarks. Theoretical results of the literature are adapted to these simple battery/magnets powered ships moving on salt water. Comparison between theory and experiments are performed to validate each theoretical step such as the Tafel and the Kohlrausch laws, or the predicted ship speed. A successful agreement is obtained without any adjustable parameter. Finally, based on these results, an optimal design is then deduced from the theory. Therefore this work provides a solid theoretical and experimental ground for small scale MHD ships, by presenting in detail several approximations and how they affect the boat efficiency. Moreover, the theory is general enough to be adapted to other contexts, such as large scale ships or industrial flow measurement techniques.

  7. Experimental and theoretical study of magnetohydrodynamic ship models.

    Science.gov (United States)

    Cébron, David; Viroulet, Sylvain; Vidal, Jérémie; Masson, Jean-Paul; Viroulet, Philippe

    2017-01-01

    Magnetohydrodynamic (MHD) ships represent a clear demonstration of the Lorentz force in fluids, which explains the number of students practicals or exercises described on the web. However, the related literature is rather specific and no complete comparison between theory and typical small scale experiments is currently available. This work provides, in a self-consistent framework, a detailed presentation of the relevant theoretical equations for small MHD ships and experimental measurements for future benchmarks. Theoretical results of the literature are adapted to these simple battery/magnets powered ships moving on salt water. Comparison between theory and experiments are performed to validate each theoretical step such as the Tafel and the Kohlrausch laws, or the predicted ship speed. A successful agreement is obtained without any adjustable parameter. Finally, based on these results, an optimal design is then deduced from the theory. Therefore this work provides a solid theoretical and experimental ground for small scale MHD ships, by presenting in detail several approximations and how they affect the boat efficiency. Moreover, the theory is general enough to be adapted to other contexts, such as large scale ships or industrial flow measurement techniques.

  8. Coordination to transition metal surfaces : a theoretical study

    NARCIS (Netherlands)

    Santen, van R.A.

    1985-01-01

    A theoretical framework is developed that describes the chemisorption of CO to transition metal surfaces analogous to the HOMO-LUMO concept of MO theory. An explanation is given for the exptl. observation that CO adsorbs on top at the (111), face of Pt, but bridge at the (111) face of Ni. One is due

  9. Theoretical study of diaquamalonatozinc(II) single crystal for ...

    Indian Academy of Sciences (India)

    MITESH CHAKRABORTY

    2017-11-28

    Nov 28, 2017 ... 2Laser and Spectroscopy Laboratory, Department of Applied Physics, Indian Institute of ... The aim of the present paper is to employ theoretical methods to investigate the zero field splitting .... using quantum chemistry computational models has ..... The authors are grateful to the Science and Engineer-.

  10. Thermodynamics of Macromolecular Association in Heterogeneous Crowding Environments: Theoretical and Simulation Studies with a Simplified Model.

    Science.gov (United States)

    Ando, Tadashi; Yu, Isseki; Feig, Michael; Sugita, Yuji

    2016-11-23

    The cytoplasm of a cell is crowded with many different kinds of macromolecules. The macromolecular crowding affects the thermodynamics and kinetics of biological reactions in a living cell, such as protein folding, association, and diffusion. Theoretical and simulation studies using simplified models focus on the essential features of the crowding effects and provide a basis for analyzing experimental data. In most of the previous studies on the crowding effects, a uniform crowder size is assumed, which is in contrast to the inhomogeneous size distribution of macromolecules in a living cell. Here, we evaluate the free energy changes upon macromolecular association in a cell-like inhomogeneous crowding system via a theory of hard-sphere fluids and free energy calculations using Brownian dynamics trajectories. The inhomogeneous crowding model based on 41 different types of macromolecules represented by spheres with different radii mimics the physiological concentrations of macromolecules in the cytoplasm of Mycoplasma genitalium. The free energy changes of macromolecular association evaluated by the theory and simulations were in good agreement with each other. The crowder size distribution affects both specific and nonspecific molecular associations, suggesting that not only the volume fraction but also the size distribution of macromolecules are important factors for evaluating in vivo crowding effects. This study relates in vitro experiments on macromolecular crowding to in vivo crowding effects by using the theory of hard-sphere fluids with crowder-size heterogeneity.

  11. Preparation of theoretical scanning tunneling microscope images of adsorbed molecules: a theoretical study of benzene on the Cu(110) surface

    International Nuclear Information System (INIS)

    Shapter, J.G.; Rogers, B.L.; Ford, M.J.

    2003-01-01

    Full text: Since its development in 1982, the Scanning Tunneling Microscope (STM) has developed into a powerful tool for the study of surfaces and adsorbates. However, the utility of the technique can be further enhanced through the development of techniques for generating theoretical STM images. This is particularly true when studying molecules adsorbed on a substrate, as the results are often interpreted superficially due to an inadequate understanding of the orbital overlap probed in the experiment. A method of preparing theoretical scanning tunneling microscope (STM) images using comparatively inexpensive desktop computers and the commercially available CRYSTAL98 package is presented through a study of benzene adsorbed on the Cu(110) surface. Density Functional Theory (DFT) and Hartree-Fock (HF) methods are used to model clean Cu(110) slabs of various thicknesses and to simulate the adsorption of benzene onto these slabs. Eight possible orientations of benzene on the Cu(110) surface are proposed, and the optimum orientation according to the calculations is presented. Theoretical STM images of the Cu(110) surface and benzene adsorbed on the Cu(110) surface are compared with experimental STM images of the system from a published study. Significant differences are observed and are examined in detail

  12. A computational study on kinetics, mechanism and thermochemistry ...

    Indian Academy of Sciences (India)

    level procedure employing the optimization at .... for a better understanding of mechanistic pathways, kinetics and thermochemistry we must rely on quantum chemical methods. The aim of this paper is to have .... The search was made along.

  13. Kinetic Study of Calcination of Jakura Limestone Using Power Rate ...

    African Journals Online (AJOL)

    National Research Institute for Chemical Technology, P.M. B 1052, Zaria, ... calcination of Jakura limestone was also found to be first order reaction with respect to CaCO3 ... Keywords: Jakura, limestone, calcination, kinetics, power law model.

  14. Study of growth kinetic and modeling of ethanol production by ...

    African Journals Online (AJOL)

    ... coefficient (0.96299). Based on Leudking-Piret model, it could be concluded that ethanol batch fermentation is a non-growth associated process. Key words: Kinetic parameters, simulation, cell growth, ethanol, Saccharomyces cerevisiae.

  15. COMBINED THEORETICAL AND EXPERIMENTAL INVESTIGATION OF MECHANISMS AND KINETICS OF VAPOR-PHASE MERCURY UPTAKE BY CARBONACOUES SURFACES

    Energy Technology Data Exchange (ETDEWEB)

    Radisav D. Vidic

    2002-05-01

    The first part of this study evaluated the application of a versatile optical technique to study the adsorption and desorption of model adsorbates representative of volatile polar (acetone) and non-polar (propane) organic compounds on a model carbonaceous surface under ultra high vacuum (UHV) conditions. The results showed the strong correlation between optical differential reflectance (ODR) and adsorbate coverage determined by temperature programmed desorption (TPD). ODR technique was proved to be a powerful tool to investigate surface adsorption and desorption from UHV to high pressure conditions. The effects of chemical functionality and surface morphology on the adsorption/desorption behavior of acetone, propane and mercury were investigated for two model carbonaceous surfaces, namely air-cleaved highly oriented pyrolytic graphite (HOPG) and plasma-oxidized HOPG. They can be removed by thermal treatment (> 500 K). The presence of these groups almost completely suppresses propane adsorption at 90K and removal of these groups leads to dramatic increase in adsorption capacity. The amount of acetone adsorbed is independent of surface heat treatment and depends only on total exposure. The effects of morphological heterogeneity is evident for plasma-oxidized HOPG as this substrate provides greater surface area, as well as higher energy binding sites. Mercury adsorption at 100 K on HOPG surfaces with and without chemical functionalities and topological heterogeneity created by plasma oxidation occurs through physisorption. The removal of chemical functionalities from HOPG surface enhances mercury physisorption. Plasma oxidation of HOPG provides additional surface area for mercury adsorption. Mercury adsorption by activated carbon at atmospheric pressure occurs through two distinct mechanisms, physisorption below 348 K and chemisorption above 348 K. No significant impact of oxygen functionalities was observed in the chemisorption region. The key findings of this study

  16. 3D studies of coarserning kinetics of individual grains

    DEFF Research Database (Denmark)

    Poulsen, Stefan Othmar

    Techniques for fast, non-destructive characterization of the microstructure of materials using synchrotron X-ray radiation have in recent years become an important tool in materials science. The non-destructive nature of the techniques allows for time-resolved characterization of three-dimensiona......Techniques for fast, non-destructive characterization of the microstructure of materials using synchrotron X-ray radiation have in recent years become an important tool in materials science. The non-destructive nature of the techniques allows for time-resolved characterization of three......-dimensional microstructures, i.e. direct probing of the evolution of specific microstructural features. Synchrotron X-ray radiation techniques have in the present work been employed for experimental characterization of microstructural evolution in individual grains during isothermal annealing: For a study of individual...... grains during recrystallization, where the recrystallization kinetics of individual grains and the temperature dependence of the recrystallization rate is examined, and for a study of grain structure and grain growth, where growth predictions are put forth in terms of the grain size and topology...

  17. Spectroscopic Analysis of Neurotransmitters: A Theoretical and Experimental Raman Study

    Science.gov (United States)

    Alonzo, Matthew

    Surface-enhanced Raman spectroscopy (SERS) was applied to investigate the feasibility in the detection and monitoring of the dopamine (DA) neurotransmitter adsorbed onto silver nanoparticles (Ag NPs) at 10-11 molar, a concentration far below physiological levels. In addition, density functional theory (DFT) calculations were obtained with the Gaussian-09 analytical suite software to generate the theoretical molecular configuration of DA in its neutral, cationic, anionic, and dopaminequinone states for the conversion of computer-simulated Raman spectra. Comparison of theoretical and experimental results show good agreement and imply the presence of dopamine in all of its molecular forms in the experimental setting. The dominant dopamine Raman bands at 750 cm-1 and 795 cm-1 suggest the adsorption of dopaminequinone onto the silver nanoparticle surface. The results of this experiment give good insight into the applicability of using Raman spectroscopy for the biodetection of neurotransmitters.

  18. Theoretical study of reaction dynamics in radiation chemistry

    International Nuclear Information System (INIS)

    Tachiya, Masanori

    2008-01-01

    The period from late 1950's to early 1970's was golden age of radiation chemistry. During this period the hydrated electron was discovered, various new phenomena were found in ionic processes in liquid hydrocarbons, and the trapped electron and electron tunneling were discovered in organic glasses. In those days radiation chemistry was a vast treasure-house of theoretical problems. We could find not only problems special to radiation chemistry but also many problems interesting as general physical chemistry. In this review I explain how some theoretical problems discovered in the field of radiation chemistry have evolved into those of general physical chemistry, with special emphasis on my own work. (author)

  19. An Experimental and Theoretical Study on Cavitating Propellers.

    Science.gov (United States)

    1982-10-01

    34 And Identfyp eV &to" nMeeJ cascade flow theoretical supercavitating flow performance prediction method partially cavitating flow supercavitating ...the present work was to develop an analytical tool for predicting the off-design performance of supercavitating propellers over a wide range of...operating conditions. Due to the complex nature of the flow phenomena, a lifting line theory sirply combined with the two-dimensional supercavitating

  20. Experimental and theoretical studies of the thermal behavior of titanium dioxide-SnO2 based composites.

    Science.gov (United States)

    Voga, G P; Coelho, M G; de Lima, G M; Belchior, J C

    2011-04-07

    In this paper we report experimental and theoretical studies concerning the thermal behavior of some organotin-Ti(IV) oxides employed as precursors for TiO(2)/SnO(2) semiconducting based composites, with photocatalytic properties. The organotin-TiO(2) supported materials were obtained by chemical reactions of SnBu(3)Cl (Bu = butyl), TiCl(4) with NH(4)OH in ethanol, in order to impregnate organotin oxide in a TiO(2) matrix. A theoretical model was developed to support experimental procedures. The kinetics parameters: frequency factor (A), activation energy, and reaction order (n) can be estimated through artificial intelligence methods. Genetic algorithm, fuzzy logic, and Petri neural nets were used in order to determine the kinetic parameters as a function of temperature. With this in mind, three precursors were prepared in order to obtain composites with Sn/TiO(2) ratios of 0% (1), 15% (2), and 30% (3) in weight, respectively. The thermal behavior of products (1-3) was studied by thermogravimetric experiments in oxygen.

  1. Hydrodenitrogenation mechanism of aromatic amines. Kinetic study and simulation

    International Nuclear Information System (INIS)

    D'Araujo, P.A.P.

    1994-06-01

    The decomposition of model molecules reacting alone or in competition was studied in a fixed bed reactor at 623 K and 7 MPa over a sulfided NiMo/Al 2 O 3 catalyst. The inhibiting effect of H 2 S and some nitrogen molecules, namely quinoline type compounds plays a major role in the transformation of anilines intermediates. On the other hand H 2 S acts as a cocatalyst and promote carbon-nitrogen bond cleavage, specially at low H 2 S partial pressure. When the H 2 S partial pressure is greater than the nitrogen compound partial pressure an inhibiting effect of H 2 S occurs and its promoting effect on carbon-nitrogen bond cleavage is cancelled. Hydrogen has a positive but moderate effect in hydrogenation steps. The mechanism of carbon-nitrogen bond scission depends on the structure of the nitrogen molecule namely on the hybridization of the carbon atom bearing the nitrogen atom. If the carbon a with respect to the nitrogen is monosubstituted the mechanism is essentially a nucleophilic substitution. When the degree of substitution increases the elimination mechanism becomes more important and the two mechanisms are in competition. With a sulfided catalyst, H 2 S from the gas phase doesn't change the importance of each mechanism, it just increases the rate of the reaction. In the presence of an oxide catalyst the contribution of the two mechanisms change. This result shows the importance of the sulphur species from the surface. Using isotopic exchange we could demonstrate that the sites able to dissociate H 2 S and H 2 are the same, and that the dissociation is of heterolytic nature. The kinetic modeling of hydrotreatment reactions using the CHEMKIN/SURFACE CHEMKIN package seems to be a convenient method in order to understand the kinetic and mechanistic phenomena in hydrodenitrogenation. The preliminary simulations in the case of 2.6 diethylaniline showed that only one type of site is not sufficient in order to account for the experimental results. Further simulations

  2. Detailed kinetic modeling study of n-pentanol oxidation

    KAUST Repository

    Heufer, Karl Alexander; Sarathy, Mani; Curran, Henry J.; Davis, Alexander C.; Westbrook, Charles K.; Pitz, William J.

    2012-01-01

    To help overcome the world's dependence upon fossil fuels, suitable biofuels are promising alternatives that can be used in the transportation sector. Recent research on internal combustion engines shows that short alcoholic fuels (e.g., ethanol or n-butanol) have reduced pollutant emissions and increased knock resistance compared to fossil fuels. Although higher molecular weight alcohols (e.g., n-pentanol and n-hexanol) exhibit higher reactivity that lowers their knock resistance, they are suitable for diesel engines or advanced engine concepts, such as homogeneous charge compression ignition (HCCI), where higher reactivity at lower temperatures is necessary for engine operation. The present study presents a detailed kinetic model for n-pentanol based on modeling rules previously presented for n-butanol. This approach was initially validated using quantum chemistry calculations to verify the most stable n-pentanol conformation and to obtain C-H and C-C bond dissociation energies. The proposed model has been validated against ignition delay time data, speciation data from a jet-stirred reactor, and laminar flame velocity measurements. Overall, the model shows good agreement with the experiments and permits a detailed discussion of the differences between alcohols and alkanes. © 2012 American Chemical Society.

  3. Kinetic study of uranium carburization by different carbonated gases

    International Nuclear Information System (INIS)

    Feron, Guy

    1963-01-01

    The kinetic study of the reaction U + CO 2 and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO 2 → UO 2 + 2 CO U + CO 2 → UO 2 + C The reaction with carbon monoxide leads to a mixture of dioxide UO 2 , dicarbide UC 2 and free carbon. The main reaction can be written. U + CO → 1/2 UO 2 + 1/2 UC 2 The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO 2 and UC 2 can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO 2 and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [fr

  4. Kinetic Study of Nonequilibrium Plasma-Assisted Methane Steam Reforming

    Directory of Open Access Journals (Sweden)

    Hongtao Zheng

    2014-01-01

    Full Text Available To develop a detailed reaction mechanism for plasma-assisted methane steam reforming, a comprehensive numerical and experimental study of effect laws on methane conversion and products yield is performed at different steam to methane molar ratio (S/C, residence time s, and reaction temperatures. A CHEMKIN-PRO software with sensitivity analysis module and path flux analysis module was used for simulations. A set of comparisons show that the developed reaction mechanism can accurately predict methane conversion and the trend of products yield in different operating conditions. Using the developed reaction mechanism in plasma-assisted kinetic model, the reaction path flux analysis was carried out. The result shows that CH3 recombination is the limiting reaction for CO production and O is the critical species for CO production. Adding 40 wt.% Ni/SiO2 in discharge region has significantly promoted the yield of H2, CO, or CO2 in dielectric packed bed (DPB reactor. Plasma catalytic hybrid reforming experiment verifies the reaction path flux analysis tentatively.

  5. Kinetic studies on a repetitively pulsed fast reactor

    International Nuclear Information System (INIS)

    Das, S.

    1982-01-01

    Neutronic analysis of an earlier proposed periodically pulsed fast reactor at Kalpakkam (KPFR) has been carried out numerically under equilibrium and transient conditions using the one-point model of reactor kinetics and the experimentally measured total worth of reactivity modulator, the parabolic coefficient of reactivity of the movable reflector and the mean prompt neutron lifetime. Results of steady-state calculations - treated on the basis of delayed neutron precursor and energy balances during a period of operation - have been compared with the analytical formulae of Larrimore for a parabolic reactivity input. Empirical relations for half-width of the fast neutron pulse, the peak pulse power and the power at first crossing of prompt criticality have been obtained and shown to be accurate enough for predicting steady-state power pulse characteristics of a periodically pulsed fast reactor. The concept of a subprompt-critical reactor has been used to calculate the fictitious delayed neutron fraction, β of the KPFR through a numerical experiment. Relative pulse height stability and pulse shape sensitivity to changes of maximum reactivity is discussed. With the aid of new safety concepts, the Power Amplification Factor (PAF) and the Pulse Growth Factor (Rsub(p)), the dynamics KPFR under accidental conditions has been studied for step and ramp reactivity perturbations. All the analysis has been done without taking account of reactivity feedback. (orig.)

  6. Aqueous photodegradation of antibiotic florfenicol: kinetics and degradation pathway studies.

    Science.gov (United States)

    Zhang, Ya; Li, Jianhua; Zhou, Lei; Wang, Guoqing; Feng, Yanhong; Wang, Zunyao; Yang, Xi

    2016-04-01

    The occurrence of antibacterial agents in natural environment was of scientific concern in recent years. As endocrine disrupting chemicals, they had potential risk on ecology system and human beings. In the present study, the photodegradation kinetics and pathways of florfenicol were investigated under solar and xenon lamp irradiation in aquatic systems. Direct photolysis half-lives of florfenicol were determined as 187.29 h under solar irradiation and 22.43 h under xenon lamp irradiation, respectively. Reactive oxygen species (ROS), such as hydroxyl radical (·OH) and singlet oxygen ((1)O2) were found to play an important role in indirect photolysis process. The presence of nitrate and dissolved organic matters (DOMs) could affect photolysis of florfenicol in solutions through light screening effect, quenching effect, and photoinduced oxidization process. Photoproducts of florfenicol in DOMs solutions were identified by solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) analysis techniques, and degradation pathways were proposed, including photoinduced hydrolysis, oxidation by (1)O2 and ·OH, dechlorination, and cleavage of the side chain.

  7. KINETIC MODELS STUDY OF HYDRODESULPHURIZATION VACUUM DISTILLATE REACTION

    Directory of Open Access Journals (Sweden)

    AbdulMunem A. Karim

    2013-05-01

    Full Text Available    This study deals with  kinetics of hydrodesulphurization (HDS reaction of vacuum gas oil (611-833 K which was distillated from Kirkuk crude oil and which was obtained by blending the fractions, light vacuum gas oil (611 - 650 K, medium vacuum gas oil (650-690 K, heavy vacuum gas oil (690-727 K and very heavy vacuum gas oil (727-833 K.   The vacuum gas oil was hydrotreated on a commercial cobalt-molybdenum alumina catalyst presulfied at specified conditions in a laboratory trickle bed reactor. The reaction temperature range (583-643 K,liquid hourly space velocity range (1.5-3.75 h-1 and hydrogen pressure was kept constant at 3.5 MPa with hydrogen to oil ratio about 250 lt/lt.           The conversion results for desulphurization reaction appeared to obey the second order reaction. According to this model, the rate constants for desulphurization reaction were determined. Finally, the apparent activation energy (Ea, enthalpy of activation ( H* and entropy ( S* were calculated based on the values of rate constant (k2 and were equal 80.3792 KJ/mole, 75.2974 KJ/mole and 197.493 J/mole, respectively.

  8. Kinetic study of ultrasonic antisolvent crystallization of sirolimus

    Energy Technology Data Exchange (ETDEWEB)

    Gandhi, P.J. [Chemical Engineering Department, S. V. National Institute of Technology, Surat 395007, Gujarat (India); Concept Medical Research Pvt. Ltd., Ground Floor, Narayan Darshan, Nr. Rupam Cinema, Salabatpura, Surat 395003, Gujarat (India); Murthy, Z.V.P.

    2010-03-15

    Sirolimus, generally used in organ transplantation, is derived from bacterium Streptomyces hygroscopicus. Mass transfer controlled ultrasonic antisolvent method was used for determining the precipitation kinetics of sirolimus. The effect of temperature was determined on the particles size, percentage recovery, critical radius of nucleus, mass transfer coefficient, etc. for sirolimus dissolved in methanol and antisolvent water using ultrasonic treatment. The study was done using classical nucleation theory, which can also be applied to precipitation processes. Experiments were carried out at various temperatures; viz: 45, 50, 60 and 70 C and the percentage recoveries of sirolimus were found to be 90.74, 91.5, 92.64 and 93.61%, respectively, for initial amount of 8 mg dissolved in 1 mL of solvent and further introduced into 12 mL of HPLC water. The final average diameters of crystals observed for the temperatures were 1371, 1287, 1063 and 863 nm, respectively. The systems were found to be mass transfer controlling and that the mass diffusivities were found to be about 3.97 x 10{sup -9}, 4.00 x 10{sup -9}, 3.01 x 10{sup -9} and 1.92 x 10{sup -9} m{sup 2}/s, respectively. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Studies on drying kinetics of olive foot cake

    Directory of Open Access Journals (Sweden)

    Hamlat, M. S.

    2002-06-01

    Full Text Available The olive foot cake is a very important by-product of olive oil industry since it can contain until 12 % of oil which can be extracted using solvent. The used solvent is often immiscible with water. This is the reason why its effect is limited by the moisture of olive foot cake making its drying imperative. In this paper, we present the behaviour of olive foot cake subjected to convective drying. The experimental results show that the drying rate versus moisture presents only one period of decreasing rate. The influence of the main parameters on drying kinetics is studied.El orujo es un importante subproducto de la industria del aceite de oliva ya que puede contener hasta el 12 % del aceite, el cual puede ser extraído usando un disolvente apropiado. El uso del disolvente es a menudo inmiscible con el agua. Esta es la razón por la que su efecto está limitado por la humedad del orujo, haciendo su secado imperativo. En este artículo se presenta el comportamiento del orujo sometido a un secado por convección. Los resultados experimentales mostraron que la velocidad de secado frente a la humedad, presenta un solo período de disminución de dicha velocidad. Se ha estudiado la influencia de los principales parámetros sobre la cinética de secado.

  10. Kinetic study of seawater reverse osmosis membrane fouling

    KAUST Repository

    Khan, Muhammad

    2013-10-01

    Reverse osmosis (RO) membrane fouling is not a static state but a dynamic phenomenon. The investigation of fouling kinetics and dynamics of change in the composition of the foulant mass is essential to elucidate the mechanism of fouling and foulant-foulant interactions. The aim of this work was to study at a lab scale the fouling process with an emphasis on the changes in the relative composition of foulant material as a function of operating time. Fouled membrane samples were collected at 8 h, and 1, 2, and 4 weeks on a lab-scale RO unit operated in recirculation mode. Foulant characterization was performed by CLSM, AFM, ATR-FTIR, pyrolysis GC-MS, and ICP-MS techniques. Moreover, measurement of active biomass and analysis of microbial diversity were performed by ATP analysis and DNA extraction, followed by pyro-sequencing, respectively. A progressive increase in the abundance of almost all the foulant species was observed, but their relative proportion changed over the age of the fouling layer. Microbial population in all the membrane samples was dominated by specific groups/species belonging to Proteobacteria and Actinobacteria phyla; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age. © 2013 American Chemical Society.

  11. Kinetic studies following state-selective laser excitation

    International Nuclear Information System (INIS)

    Keto, J.W.

    1992-01-01

    We have made measurements of state-to-state deactivation cross sections and radiative lifetimes for Xe*(6p,6p',7p) and Kr*(5p) states in xenon and krypton buffer gases. These results are relevant to kinetic models and both excimer lasers and the infrared xenon laser; and they are a significant improvement in the precision of the known radiative lifetimes. This type of experiment can now be compared with recent calculations of state-to-state collisional relaxation in rare-gases by Hickman, Huestis, and Saxon. We have also made significant progress in the study of the electronic spectra of small molecules of the rare gases. Spectra have been obtained for Xe 2 , Xe 3 , Xe 4 , and larger clusters. As guidance for the larger clusters of the rare gases we have obtained the first multiphoton spectra for excitons in condensed xenon. In collaboration with research on the multiphoton spectra of the rare gases, we have continued experiments using synchrotron radiation in collaboration with the University of Hamburg. In experiments there we have observed excitation and fluorescence spectra for single xenon atoms at the surface, within the second layer, and within the bulk of large argon clusters

  12. Detailed kinetic modeling study of n-pentanol oxidation

    KAUST Repository

    Heufer, Karl Alexander

    2012-10-18

    To help overcome the world\\'s dependence upon fossil fuels, suitable biofuels are promising alternatives that can be used in the transportation sector. Recent research on internal combustion engines shows that short alcoholic fuels (e.g., ethanol or n-butanol) have reduced pollutant emissions and increased knock resistance compared to fossil fuels. Although higher molecular weight alcohols (e.g., n-pentanol and n-hexanol) exhibit higher reactivity that lowers their knock resistance, they are suitable for diesel engines or advanced engine concepts, such as homogeneous charge compression ignition (HCCI), where higher reactivity at lower temperatures is necessary for engine operation. The present study presents a detailed kinetic model for n-pentanol based on modeling rules previously presented for n-butanol. This approach was initially validated using quantum chemistry calculations to verify the most stable n-pentanol conformation and to obtain C-H and C-C bond dissociation energies. The proposed model has been validated against ignition delay time data, speciation data from a jet-stirred reactor, and laminar flame velocity measurements. Overall, the model shows good agreement with the experiments and permits a detailed discussion of the differences between alcohols and alkanes. © 2012 American Chemical Society.

  13. SYSTEMATIC THEORETICAL STUDY ON THE INTERSTELLAR CARBON CHAIN MOLECULES

    Energy Technology Data Exchange (ETDEWEB)

    Etim, Emmanuel E.; Arunan, Elangannan [Inorganic and Physical Chemistry Department, Indian Institute of Science Bangalore, 560012 (India); Gorai, Prasanta; Das, Ankan [Indian Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata 700 084 (India); Chakrabarti, Sandip K., E-mail: ankan.das@gmail.com [Department of Chemical Sciences, Federal University Wukari,  Katsina-Ala Road, P.M.B. 1020 Wukari, Taraba State (Nigeria)

    2016-12-01

    In an effort to further our interest in understanding the basic chemistry of interstellar molecules, here we carry out an extensive investigation of the stabilities of interstellar carbon chains; C{sub n}, H{sub 2}C{sub n}, HC{sub n}N and C{sub n}X (X = N, O, Si, S, H, P, H{sup −}, N{sup −}). These sets of molecules account for about 20% of all the known interstellar and circumstellar molecules. Their high abundances, therefore, demand serious attention. High-level ab initio quantum chemical calculations are employed to accurately estimate the enthalpy of formation, chemical reactivity indices, global hardness and softness, and other chemical parameters of these molecules. Chemical modeling of the abundances of these molecular species has also been performed. Of the 89 molecules considered from these groups, 47 have been astronomically observed, and these observed molecules are found to be more stable with respect to other members of the group. Of the 47 observed molecules, 60% are odd-numbered carbon chains. Interstellar chemistry is not actually driven by thermodynamics, but it is primarily dependent on various kinetic parameters. However, we found that the detectability of the odd-numbered carbon chains could be correlated due to the fact that they are more stable than the corresponding even-numbered carbon chains. Based on this aspect, the next possible carbon chain molecule for astronomical observation in each group is proposed. The effect of kinetics in the formation of some of these carbon chain molecules is also discussed.

  14. Kinetic Study of Crystallization Process in Fe32Ni36Cr14P12B6 Metallic Glass

    International Nuclear Information System (INIS)

    Lad, Kirit; Pratap, Arun; Rao, T. L. Shanker

    2010-01-01

    Kinetics of crystallization process in a Fe-based metallic glass 2826A (Fe 32 Ni 36 Cr 14 P 12 B 6 ) has been studied with the help of differential scanning calorimetry(DSC). It is found that the 2826A metallic glass exhibits two overlapping crystallization peaks. The activation energy for crystallization (E) and the Avrami exponent (n) for the two crystallization peaks have been obtained using the Kolmogorov-Jhonson-Mehl-Avrami (KJMA) equation. The so-obtained values of E and n have been utilized to derive normalized heat flow curves. It has been observed that the theoretical heat flow curves obtained using KJMA equation show large deviations from the experimental curves for the first peak whereas the curves are in very close agreement for the second peak. This suggests that kinetics of crystallization process during the first peak cannot be described correctly in KJMA formalism.

  15. Kinetic Study of Crystallization Process in Fe32Ni36Cr14P12B6 Metallic Glass

    Science.gov (United States)

    Lad, Kirit; Rao, T. L. Shanker; Pratap, Arun

    2010-06-01

    Kinetics of crystallization process in a Fe-based metallic glass 2826A (Fe32Ni36Cr14P12B6) has been studied with the help of differential scanning calorimetry(DSC). It is found that the 2826A metallic glass exhibits two overlapping crystallization peaks. The activation energy for crystallization (E) and the Avrami exponent (n) for the two crystallization peaks have been obtained using the Kolmogorov-Jhonson-Mehl-Avrami (KJMA) equation. The so-obtained values of E and n have been utilized to derive normalized heat flow curves. It has been observed that the theoretical heat flow curves obtained using KJMA equation show large deviations from the experimental curves for the first peak whereas the curves are in very close agreement for the second peak. This suggests that kinetics of crystallization process during the first peak cannot be described correctly in KJMA formalism.

  16. A study of redox kinetic in silicate melt

    International Nuclear Information System (INIS)

    Magnien, V.

    2005-12-01

    The aim of this thesis is to understand better iron redox reactions and mechanisms in silicate glasses and melts. Particular interest has been paid to the influence of temperature and chemical composition. For this purpose, the influence of alkali element content, iron content and network formers on the kinetics of redox reactions has been determined through XANES and Raman spectroscopy experiments performed either near the glass transition or above the liquidus temperature. As a complement, electrical conductivity and RBS spectroscopy experiments have been made to characterize the diffusivity of the species that transport electrical charges and the reaction morphology, respectively. Temperature and composition variations can induce changes in the dominating redox mechanism. At a given temperature, the parameters that exert the strongest influence on redox mechanisms are the presence or lack of divalent cations and the existing decoupling between the mobility of network former and modifier elements. Near Tg, the diffusion of divalent cations, when present in the melt, controls the kinetics of iron redox reactions along with a flux of electron holes. Composition, through the degree of polymerization and the silicate network structure, influences the kinetics and the nature of the involved cations, but not the mechanisms of the reaction. Without alkaline earth elements, the kinetics of redox reactions are controlled by the diffusion of oxygen species. With increasing temperatures, the diffusivities of all ionic species tend to become similar. The decoupling between ionic fluxes then is reduced so that several mechanisms become kinetically equivalent and can thus coexist. (author)

  17. Adsorptive removal of Auramine-O: Kinetic and equilibrium study

    International Nuclear Information System (INIS)

    Mall, Indra Deo; Srivastava, Vimal Chandra; Agarwal, Nitin Kumar

    2007-01-01

    Present study deals with the adsorption of Auramine-O (AO) dye by bagasse fly ash (BFA) and activated carbon-commercial grade (ACC) and laboratory grade (ACL). BFA is a solid waste obtained from the particulate collection equipment attached to the flue gas line of the bagasse fired boilers of cane sugar mills. Batch studies were performed to evaluate the influences of various experimental parameters like initial pH (pH 0 ), contact time, adsorbent dose and initial concentration (C 0 ) for the removal of AO. Optimum conditions for AO removal were found to be pH 0 ∼ 7.0 and equilibrium time ∼30 min for BFA and ∼120 min for activated carbons. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 2 g/l, respectively. Adsorption of AO followed pseudo-second order kinetics with the initial sorption rate for adsorption on BFA being the highest followed by those on ACL and ACC. The sorption process was found to be controlled by both film and pore diffusion with film diffusion at the earlier stages followed by pore diffusion at the later stages. Equilibrium isotherms for the adsorption of AO on BFA, ACC and ACL were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin isotherm equations using linear correlation coefficient. Langmuir isotherm gave the best correlation of adsorption for all the adsorbents studied. Thermodynamic study showed that adsorption of AO on ACC (with a more negative Gibbs free energy value) is more favoured. BFA which was used without any pretreatment showed high surface area, pore volume and pore size exhibiting its potential to be used as an adsorbent for the removal of AO

  18. Theoretical and Shock Tube Study of the Rate Constants for Hydrogen Abstraction Reactions of Ethyl Formate

    KAUST Repository

    Wu, Junjun; Khaled, Fathi; Ning, Hongbo; Ma, Liuhao; Farooq, Aamir; Ren, Wei

    2017-01-01

    We report a systematic chemical kinetics study of the H-atom abstractions from ethyl formate (EF) by H, O(3P), CH3, OH, and HO2 radicals. The geometry optimization and frequency calculation of all the species were conducted using the M06 method and the cc-pVTZ basis set. The one-dimensional hindered rotor treatment of the reactants and transition states and the intrinsic reaction coordinate analysis were also performed at the M06/cc-pVTZ level of theory. The relative electronic energies were calculated at the CCSD(T)/cc-pVXZ (where X = D, T) level of theory and further extrapolated to the complete basis set limit. Rate constants for the tittle reactions were calculated over the temperature range of 500‒2500 K by the transition state theory (TST) in conjunction with asymmetric Eckart tunneling effect. In addition, the rate constants of H-abstraction by hydroxyl radical were measured in shock tube experiments at 900‒1321 K and 1.4‒2.0 atm. Our theoretical rate constants of OH + EF → Products agree well with the experimental results within 15% over the experimental temperature range of 900‒1321 K. Branching ratios for the five types of H-abstraction reactions were also determined from their individual site-specific rate constants.

  19. Theoretical and Shock Tube Study of the Rate Constants for Hydrogen Abstraction Reactions of Ethyl Formate

    KAUST Repository

    Wu, Junjun

    2017-08-03

    We report a systematic chemical kinetics study of the H-atom abstractions from ethyl formate (EF) by H, O(3P), CH3, OH, and HO2 radicals. The geometry optimization and frequency calculation of all the species were conducted using the M06 method and the cc-pVTZ basis set. The one-dimensional hindered rotor treatment of the reactants and transition states and the intrinsic reaction coordinate analysis were also performed at the M06/cc-pVTZ level of theory. The relative electronic energies were calculated at the CCSD(T)/cc-pVXZ (where X = D, T) level of theory and further extrapolated to the complete basis set limit. Rate constants for the tittle reactions were calculated over the temperature range of 500‒2500 K by the transition state theory (TST) in conjunction with asymmetric Eckart tunneling effect. In addition, the rate constants of H-abstraction by hydroxyl radical were measured in shock tube experiments at 900‒1321 K and 1.4‒2.0 atm. Our theoretical rate constants of OH + EF → Products agree well with the experimental results within 15% over the experimental temperature range of 900‒1321 K. Branching ratios for the five types of H-abstraction reactions were also determined from their individual site-specific rate constants.

  20. Theoretical and experimental study of carburisation and decarburisation of a meta-stable austenitic steel

    Directory of Open Access Journals (Sweden)

    Charles West

    2005-12-01

    Full Text Available Metastable austenitic stainless steels are known to undergo a partial transformation of austenite to martensite as a consequence of plastic deformation. In the case of cyclic loading, a certain level of plastic strain must be exceeded, and phase formation takes place after an incubation period, during which the necessary amount of plastic deformation is accumulated. The susceptibility of the austenitic phase to deformation-induced martensite formation is strongly affected by the temperature of loading and the stability of austenite, which itself depends on the chemical composition. A key element in this regard is carbon which stabilizes the austenitic phase. It is shown in this study that the carbon concentration can be analysed systematically and reproducible by means of annealing treatments, if the parameters of these treatments are carefully defined on the basis of advanced theoretical thermodynamic and kinetic considerations. First results on the effect of carbon concentration and temperature of fatigue testing on the austenite/martensite transformation are presented, in order to illustrate the significance of these parameters on the martensite formation rate.

  1. Theoretical and numerical study of the equations of Vlasov-Maxwell in the covariant formalism

    International Nuclear Information System (INIS)

    Back, A.

    2011-11-01

    A new point of view is proposed for the simulation of plasmas using the kinetic model which links the equations of Vlasov for the distribution of particles and the equations of Maxwell for the electromagnetic contribution of fields. We use the following principle: the equations of Physics are mathematical objects which put in relation geometrical objects. To preserve the geometrical properties of the various objects in an equation, we use, for the theoretical and numerical study, the differential geometry. All the equations of Physics can be written with differential forms and this point of view is not dependent on the choice of coordinates. We propose then a discretization of the differential forms by using B-Splines. To be coherent with the theory, we also propose a discretization of the various operations of the differential geometry. We test our scheme, first on the equations of Maxwell with several boundary conditions and since it does not depend on the system of coordinates, we also test it when we change coordinates. Finally, we apply the same method to the equations of Vlasov-Poisson in one-dimension and we propose several numerical schemes. (author)

  2. Kinetic Studies on Ni-YSZ Composite Electrodes

    DEFF Research Database (Denmark)

    Njodzefon, Jean-Claude; Sudireddy, Bhaskar Reddy; Hjelm, Johan

    2015-01-01

    AC and DC techniques were applied to investigate the electrochemical reaction kinetics of porous composite Ni/8-mol% yttria-stabilized zirconia (Ni/8YSZ) solid oxide cell (SOC) electrodes using a novel pseudo-3-electrode cell geometry. From OCV impedance spectra an activation energy Ea of 1.13 e......V, prefactor yan of 3.7·105·T, hydrogen and steam partial pressure dependencies a and b respectively of -0.07 and 0.22 were determined. DC current density vs. overpotential curves compared with those predicted using the determined kinetic parameters. Apparent Butler-Volmer charge transfer coefficients α were...... branch and the need for different α values for each branch suggests that a simple BV model of the measured electrode kinetics is insufficient and/or different reaction mechanisms might be occurring in anodic vs cathodic polarization....

  3. The Study of a Simple Redox Reaction as an Experimental Approach to Chemical Kinetics.

    Science.gov (United States)

    Elias, Horst; Zipp, Arden P.

    1988-01-01

    Recommends using iodide ions and peroxodisulfate ions for studying rate laws instead of the standard iodine clock for kinetic study. Presents the methodology and a discussion of the kinetics involved for a laboratory experiment for a high school or introductory college course. (ML)

  4. Kinetic and equilibrium study for the sorption of Pb(II) ions from ...

    African Journals Online (AJOL)

    Kinetic and equilibrium study for the sorption of Pb(II) ions from aqueous phase by water hyacinth ( Eichhornia crassipes ) ... Bulletin of the Chemical Society of Ethiopia ... Abstract. This paper reports the kinetic and equilibrium studies of Eichhornia crassipes root biomass as a biosorbent for Pb(II) ions from aqueous system.

  5. Theoretical study of a melting curve for tin

    International Nuclear Information System (INIS)

    Feng, Xi; Ling-Cang, Cai

    2009-01-01

    The melting curve of Sn has been calculated using the dislocation-mediated melting model with the 'zone-linking method'. The results are in good agreement with the experimental data. According to our calculation, the melting temperature of γ-Sn at zero pressure is about 436 K obtained by the extrapolation of the method from the triple point of Sn. The results show that this calculation method is better than other theoretical methods for predicting the melting curve of polymorphic material Sn. (condensed matter: structure, thermal and mechanical properties)

  6. Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

    Science.gov (United States)

    Phatak, C.; Petford-Long, A. K.; Beleggia, M.; De Graef, M.

    2014-06-01

    Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift computation for a uniformly polarized prolate ellipsoid with varying aspect ratio in the absence of screening charges.

  7. Theoretical and experimental study on broadband terahertz atmospheric transmission characteristics

    International Nuclear Information System (INIS)

    Guo Shi-Bei; Zhong Kai; Wang Mao-Rong; Liu Chu; Xu De-Gang; Yao Jian-Quan; Xiao Yong; Wang Wen-Peng

    2017-01-01

    Broadband terahertz (THz) atmospheric transmission characteristics from 0 to 8 THz are theoretically simulated based on a standard Van Vleck–Weisskopf line shape, considering 1696 water absorption lines and 298 oxygen absorption lines. The influences of humidity, temperature, and pressure on the THz atmospheric absorption are analyzed and experimentally verified with a Fourier transform infrared spectrometer (FTIR) system, showing good consistency. The investigation and evaluation on high-frequency atmospheric windows are good supplements to existing data in the low-frequency range and lay the foundation for aircraft-based high-altitude applications of THz communication and radar. (paper)

  8. Theoretical study of Cherenkov radiation emission in anisotropic uniaxial crystals

    Energy Technology Data Exchange (ETDEWEB)

    Delbart, A; Derre, J

    1996-04-01

    A theoretical review of the Cherenkov radiation emission in uniaxial crystals is presented. The formalism of C. Muzicar in terms of energetic properties of the emitted waves are corrected. This formalism is used to simulate the Cherenkov radiation emission in a strongly birefringent sodium nitrate crystal (NaNO{sub 3}) and to investigate the consequences of the slight anisotropy of sapphire (Al{sub 2}O{sub 3}) on the design of the Optical Trigger. (author). 12 refs. Submitted to Physical Review, D (US).

  9. Study of the oxidation kinetics of the MA 956 superalloy

    International Nuclear Information System (INIS)

    Garcia-Alonso, M.C.; Gonzalez-Carrasco, J.L.; Escudero, M.L.

    1998-01-01

    This work deals with the oxidation kinetics of the MA 956 superalloy in the temperature range of 800-1,200 degree centigree for up to 200 h exposure. During oxidation the alloy develops a fine, compact and very well adhered α-alumina layer, the thickness of which increases with increasing time and temperature. The oxidation kinetics obeys a sub parabolic type behaviour. The scale growth seems to occur by two different oxidation mechanisms; above 1,050 degree centigree, the oxidation process would be controlled by α-alumina, and below 900 degree centigree by γ-alumina. (Author) 17 refs

  10. Protonation of caffeine: A theoretical and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Bahrami, Hamed [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Tabrizchi, Mahmoud, E-mail: m-tabriz@cc.iut.ac.ir [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Farrokhpour, Hossein [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2013-03-29

    Highlights: ► Protonation of caffeine was examined by ion mobility spectrometry equipped with two ionization sources. ► Experimental and theoretical evidence was collected to assign the observed peaks to caffeine related ionic species. ► A new concept of “internal proton affinity”, the protonation tendency for each atom in a molecule, was defined. - Abstract: Protonation of caffeine was examined by ion mobility spectrometry equipped with two ionization sources, corona discharge (CD) and UV photoionization. Three peaks were observed in ion mobility spectrum by simultaneously running the two ionization sources. Experimental and theoretical evidence was collected to link the observed peaks to caffeine related ionic species. One peak was attributed to the M{sup +} ion while the other two were assigned to different protonated isomers of caffeine. In the case of CD ionization source, it was observed that different sites of caffeine compete for protonation and their relative intensities, depends on the sample concentration as well as the nature of the reactant ions. The new concept of “internal proton affinity” (IPA) was defined to express the tendency of holding the added proton for each atom in a molecule.

  11. Protonation of caffeine: A theoretical and experimental study

    International Nuclear Information System (INIS)

    Bahrami, Hamed; Tabrizchi, Mahmoud; Farrokhpour, Hossein

    2013-01-01

    Highlights: ► Protonation of caffeine was examined by ion mobility spectrometry equipped with two ionization sources. ► Experimental and theoretical evidence was collected to assign the observed peaks to caffeine related ionic species. ► A new concept of “internal proton affinity”, the protonation tendency for each atom in a molecule, was defined. - Abstract: Protonation of caffeine was examined by ion mobility spectrometry equipped with two ionization sources, corona discharge (CD) and UV photoionization. Three peaks were observed in ion mobility spectrum by simultaneously running the two ionization sources. Experimental and theoretical evidence was collected to link the observed peaks to caffeine related ionic species. One peak was attributed to the M + ion while the other two were assigned to different protonated isomers of caffeine. In the case of CD ionization source, it was observed that different sites of caffeine compete for protonation and their relative intensities, depends on the sample concentration as well as the nature of the reactant ions. The new concept of “internal proton affinity” (IPA) was defined to express the tendency of holding the added proton for each atom in a molecule

  12. Crystal growth, characterization and theoretical studies of 4-aminopyridinium picrate

    Science.gov (United States)

    Aditya Prasad, A.; Muthu, K.; Rajasekar, M.; Meenatchi, V.; Meenakshisundaram, S. P.

    2015-01-01

    Single crystals of 4-aminopyridinium picrate (APP) were grown by slow evaporation of a mixed solvent system methanol-acetone (1:1, v/v) containing equimolar quantities of 4-aminopyridine and picric acid. Structure is elucidated by single crystal XRD analysis and the crystal belongs to monoclinic system with four molecules in the unit cell (space group P21/c) and the cell parameter values are, a = 8.513 Å (±0.015), b = 11.33 Å (±0.02), c = 14.33 Å (±0.03) and β = 104.15° (±0.019), V = 1340 A3 (±6) with refined R factors R1 = 0.0053 and wR2 = 0.0126. The electron density mapping is interpreted to find coordinates for each atom in the crystallized molecules. The various functional groups present in the molecule are confirmed by FT-IR analysis. UV-visible spectral analysis was used to determine the band gap energy of 4-aminopyridinium picrate. Powder X-ray diffraction pattern reveals the crystallinity of the as-grown crystal and it closely resembles the simulated XRD from the single crystal XRD analysis. Scanning electron microscopy reveals the surface morphology of the grown crystal. Optimized geometry is derived by Hartree-Fock theory calculations and the first-order molecular hyperpolarizability (β), theoretically calculated bond length, bond angles and excited state energy from theoretical UV-vis spectrum were estimated.

  13. Influencing factors and kinetic studies of imidacloprid degradation by ozonation.

    Science.gov (United States)

    Chen, Shi; Deng, Jing; Deng, Yang; Gao, Naiyun

    2018-03-02

    Batch kinetic tests in ozonation of imidacloprid from water were performed in this study. The pseudo-first-order rate constant of imidacloprid degradation was increased from 0.079 to 0.326 min -1 with the increasing pH from 6.02 to 8.64 at an average ozone dose of 1.149 mg L -1 . When the alkalinity was increased from 0 to 250 mg L -1 NaHCO 3 , the pseudo-first-order rate constants decreased from 0.121 to 0.034 min -1 . These results suggested that the predominant oxidant gradually switched from ozone to hydroxyl radicals ([Formula: see text]) with the increase in solution pH. The secondary rate constant [Formula: see text] (10.92 ± 0.12 M -1 s -1 ) for the reaction of imidacloprid and molecular ozone was determined at pH 2.0 and in the presence of 50 mM ter-butyl alcohol (p-chlorobenzoic acid, pCBA), respectively. An indirect competition method was used to determine the secondary rate constant for [Formula: see text] oxidation of imidacloprid in the presence of pCBA as the reference compound. The rate constants [Formula: see text] were estimated to range 2.65-3.79 M -1 s -1 at pH 6.02-8.64. Results obtained from this study demonstrate that ozonation appears to be an effective method to remove imidacloprid from water.

  14. Theoretical and experimental assessment of the kinetic properties of N-isopropyl-p-[{sup 123}I]iodoamphetamine in the human brain

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Kentaro; Nakajima, Keiji; Maeda, Minoru [Juntendo Univ., Shizuoka (Japan). Izunagaoka Hospital

    1993-12-01

    The effect of the loss of radioactivity from the human brain on the measurement of regional cerebral blood flow (rCBF) using N-isopropyl-p-[{sup 123}I]iodoamphetamine (IMP) was evaluated by measuring rCBF in 10 normal male volunteers from 0.5 to 30 minutes after intravenous administration. rCBF was calculated by the operational equation, which assumes no product loss. Brain tissue and arterial blood concentration data were plotted according to a multiple-time/graphic evaluation technique. Data were fitted to the kinetic three-compartment model to estimate four kinetic rate constants to evaluate activity loss from the brain. These studies showed that loss of activity from the brain is negligible during the first 5 minutes, but after 7.5 minutes the loss becomes significantly higher with time. The present study corroborates the necessity for using single photon emission computed tomographic images measured within 5 minutes of IMP injection to quantify rCBF. (author).

  15. Theoretical studies of acrolein hydrogenation on Au20 nanoparticle

    Science.gov (United States)

    Li, Zhe; Chen, Zhao-Xu; He, Xiang; Kang, Guo-Jun

    2010-05-01

    Gold nanoparticles play a key role in catalytic processes. We investigated the kinetics of stepwise hydrogenation of acrolein on Au20 cluster model and compared with that on Au(110) surface. The rate-limiting step barrier of CC reduction is about 0.5 eV higher than that of CO hydrogenation on Au(110) surface. On Au20 nanoparticle, however, the energy barrier of the rate-determining step for CC hydrogenation turns out to be slightly lower than the value for the CO reduction. The selectivity difference on the two substrate models are attributed to different adsorption modes of acrolein: via the CC on Au20, compared to through both CC and CO on Au(110). The preference switch implies that the predicted selectivity of competitive hydrogenation depends on substrate model sensitively, and particles with more low-coordinated Au atoms than flat surfaces are favorable for CC hydrogenation, which is in agreement with experimental result.

  16. Studies on the kinetics and intraparticle diffusivities of BOD, colour ...

    African Journals Online (AJOL)

    EJIRO

    The kinetics and intraparticle diffusivities of BOD, TSS and colour reduction from palm oil mill effluent (POME) using ... discharged (Asia et al., 2006). The oil palm ... biological treatment methods, anaerobic digestion is often the most ... and lower capital cost. ... was then rinsed with distilled water and air dried, ready for the.

  17. Kinetic modelling and thermodynamic studies on purification of ...

    African Journals Online (AJOL)

    Adsorbent capacities have been determined by mathematical fitting of equilibrium data using the most common isotherms: Freundlich isotherm and Langmuir isotherm. Several kinetic models have been applied to the process. Thermodynamic parameters: △So, △Ho, △Go and Ea (kJ/mol) have been determined.

  18. Kinetic, Equilibrium and thermodynamic studies on the biosorption ...

    African Journals Online (AJOL)

    The kinetics, equilibrium and thermodynamics of the biosorption of Cd (II) from aqueous solution by the leaf biomass of Calotropis procera popularly known in western Nigeria as 'bom bom'and genrally known as Sodom apple were investigated at different experimental conditions. Optimum conditions of pH, contact time, ...

  19. Penicillin Hydrolysis: A Kinetic Study of a Multistep, Multiproduct Reaction.

    Science.gov (United States)

    McCarrick, Thomas A.; McLafferty, Fred W.

    1984-01-01

    Background, procedures used, and typical results are provided for an experiment in which students carry out the necessary measurements on the acid-catalysis of penicillin in two hours. By applying kinetic theory to the data obtained, the reaction pathways for the hydrolysis of potassium benzyl penicillin are elucidated. (JN)

  20. Kinetic study on anaerobic oxidation of methane coupled to denitrification.

    Science.gov (United States)

    Yu, Hou; Kashima, Hiroyuki; Regan, John M; Hussain, Abid; Elbeshbishy, Elsayed; Lee, Hyung-Sool

    2017-09-01

    Monod kinetic parameters provide information required for kinetic analysis of anaerobic oxidation of methane coupled to denitrification (AOM-D). This information is critical for engineering AOM-D processes in wastewater treatment facilities. We first experimentally determined Monod kinetic parameters for an AOM-D enriched culture and obtained the following values: maximum specific growth rate (μ max ) 0.121/d, maximum substrate-utilization rate (q max ) 28.8mmol CH 4 /g cells-d, half maximum-rate substrate concentration (K s ) 83μΜ CH 4 , growth yield (Y) 4.76gcells/mol CH 4 , decay coefficient (b) 0.031/d, and threshold substrate concentration (S min ) 28.8μM CH 4 . Clone library analysis of 16S rRNA and mcrA gene fragments suggested that AOM-D reactions might have occurred via the syntrophic interaction between denitrifying bacteria (e.g., Ignavibacterium, Acidovorax, and Pseudomonas spp.) and hydrogenotrophic methanogens (Methanobacterium spp.), supporting reverse methanogenesis-dependent AOM-D in our culture. High μ max and q max , and low K s for the AOM-D enrichment imply that AOM-D could play a significant role in mitigating atmospheric methane efflux. In addition, these high kinetic features suggest that engineered AOM-D systems may provide a sustainable alternative to nitrogen removal in wastewater treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Kinetic study of sphingomyelin hydrolysis for ceramide production

    DEFF Research Database (Denmark)

    Zhang, Long; Hellgren, Lars; Xu, Xuebing

    2008-01-01

    in cosmetic and pharmaceutical industries such as in hair and skin care products. The enzymatic hydrolysis of sphingomyelin has been proved to be a feasible method to produce ceramide. The kinetic performance of sphingomyelin hydrolysis in the optimal two-phase (water:organic solvent) reaction system...

  2. Kinetic studies of alkaline phosphatase extracted from rabbit (Lepus ...

    African Journals Online (AJOL)

    user

    activity, and the kinetic constants-maximum enzyme velocity (Vmax) and Michealis-Menten constant (Km) were evaluated. ... the enzyme a readily available parameter for diagnostic and research .... procedure while treatment means were separated by the least .... mammalian enzymes are responsible for this increase in ...

  3. Theoretical Advanced Study Institute in Elementary Particle Physics

    CERN Document Server

    2017-01-01

    The program will consist of a pedagogical series of lectures and seminars. Lectures will be given over a four-week period, three or four lectures per day, Monday through Friday. The audience will be composed primarily of advanced theoretical graduate students. Experimentalists with a strong background in theory are also encouraged to apply. Some post-doctoral fellows will be admitted, but preference will be given to applicants who will not have received their Ph.D. before 2017. The minimum background needed to get full benefit of TASI is a knowledge of quantum field theory (including RGEs) and familiarity with the Standard Model. Some familiarity with SUSY would be helpful. We hope to provide some subsidy, but students will need partial support from other sources. Rooms, meals, and access to all facilities will be provided at reasonable rates in beautifully located dormitories at the University of Colorado.

  4. Supplement to final report for ''Theoretical studies in tokamaks''

    International Nuclear Information System (INIS)

    McBride, J.B.

    1992-07-01

    In a previous report we summarized the results obtained for Task I of Contract Number AC03-88ER53270 for the two-year period of performance of the work supported by the contract. That report constituted the final report for Task 1. Since then, the contract was extended and the funding for Task I was incremented with $35K of new funds. The purpose for incrementing the contract was to begin a collaboration with the PBX-M group at Princeton Plasma Physics Laboratory (PPPL) in the area of ion Bernstein wave (IBW) effects in the PBX-M experiment. This report summarizes the initial results of that collaboration obtained under the incremental continuation funding. In the intervening period, experimental and theoretical program directions changed so that no further funds were committed to Task 1

  5. Excitons in van der Waals Heterostructures: A theoretical study

    DEFF Research Database (Denmark)

    Latini, Simone

    )electronics devices, e.g. light emitting diodes, solar cells, ultra-fast photodetectors, transistors etc., have been successfully fabricated. It is well established that for isolated 2D semiconductors and vdWHs the optical response is governed by excitonic effects. While it is understood that the reduced amount...... of electronic screening in freestanding 2D materials is the main origin of extraordinarily strongly bound excitons, a theoretical understanding of excitonic effects and of how the electronic screening is affected for the more complex case of multi-layer structures is still lacking due to the computational...... in a generalized hydrogenic model to compute exciton binding energies in isolated, supported, or encapsulated 2D semiconductors. The non-locality of the dielectric screening is inherently included in our method and we can successfully describe the non-hydrogenic Rydberg series of low-dimensional systems...

  6. A theoretical study on a convergence problem of nodal methods

    Energy Technology Data Exchange (ETDEWEB)

    Shaohong, Z.; Ziyong, L. [Shanghai Jiao Tong Univ., 1954 Hua Shan Road, Shanghai, 200030 (China); Chao, Y. A. [Westinghouse Electric Company, P. O. Box 355, Pittsburgh, PA 15230-0355 (United States)

    2006-07-01

    The effectiveness of modern nodal methods is largely due to its use of the information from the analytical flux solution inside a homogeneous node. As a result, the nodal coupling coefficients depend explicitly or implicitly on the evolving Eigen-value of a problem during its solution iteration process. This poses an inherently non-linear matrix Eigen-value iteration problem. This paper points out analytically that, whenever the half wave length of an evolving node interior analytic solution becomes smaller than the size of that node, this non-linear iteration problem can become inherently unstable and theoretically can always be non-convergent or converge to higher order harmonics. This phenomenon is confirmed, demonstrated and analyzed via the simplest 1-D problem solved by the simplest analytic nodal method, the Analytic Coarse Mesh Finite Difference (ACMFD, [1]) method. (authors)

  7. Road Surfaces And Earthquake Engineering: A Theoretical And Experimental Study

    International Nuclear Information System (INIS)

    Pratico, Filippo Giammaria

    2008-01-01

    As is well known, road surfaces greatly affect vehicle-road interaction. As a consequence, road surfaces have a paramount influence on road safety and pavement management systems. On the other hand, earthquakes produce deformations able to modify road surface structure, properties and performance. In the light of these facts, the main goal of this paper has been confined into the modelling of road surface before, during and after the seismic event. The fundamentals of road surface texture theory have been stated in a general formulation. Models in the field of road profile generation and theoretical properties, before, during and after the earthquake, have been formulated and discussed. Practical applications can be hypothesised in the field of vehicle-road interaction as a result of road surface texture derived from deformations and accelerations caused by seismic or similar events

  8. Modeling Exoplanetary Atmospheres using BART, TEA, and Drift-RHD; Theoretical studies and Observational Implications

    Science.gov (United States)

    Dobbs-Dixon, Ian

    numerous published papers, further work is needed to couple them self-consistently. Our theoretical studies focus on a number of objectives. We will start by incorporating our kinetic, non-equilibrium cloud model within BART, allowing us to obtain a consistent solution for cloud characteristics. We will further test simple parameterizations against the full solution to explore the reliability of simpler models. Utilizing Drift-RHD, we will explore the role of horizontal advection on cloud distribution, investigate the validity of 1D retrievals by comparing them to selfconsistently generated 3D models, and develop a retrieval framework for wavelengthdependent phase-curves. TEA will be enhanced with additional databases and the inclusion of condensates, providing realistic initial cloudy-model for retrievals. To explore the importance of equilibrium chemistry and exclude non-plausible chemical compositions (often the outcome of many retrieval approaches) we will relax the assumption of non-equilibrium chemistry by utilizing an analytical chemical equilibrium approach in BART. To address observations, our OBS suit for generating synthetic observations will be adapted to interface with our models, allowing us to both compare to existing observations and make predictions for future observations. With these tools, we are particularly well suited to understand discriminants between classes of models and identifying which particular set of observations could most readily distinguish cloud constituents and temperature features. The proposed research is directly relevant to the Planetary Science and Astrophysics goals through furthering our understanding of compositions, dynamics, energetics, and chemical behaviors of exoplanetary atmospheres. In addition, to maximize NASA's investment and encourage open access, we have and will continue to make all of our codes public and available to the community throughout the course of the research.

  9. Novel swirl-flow reactor for kinetic studies of semiconductor photocatalysis

    NARCIS (Netherlands)

    Ray, A.K; Beenackers, A.A C M

    1997-01-01

    A new two-phase swirl-flow monolithic-type reactor was designed to study the kinetics of heterogeneous photocatalytic processes on immobilized semiconductor catalysts. True kinetic rate constants for destruction of a textile dye were measured as a function of wavelength of light intensity and angle

  10. Oxidation of L-cystine by chromium(VI) - a kinetic study | Kumar ...

    African Journals Online (AJOL)

    The kinetics of the title reaction was studied spectrophotometrically in HClO4 medium at 380 nm. The data suggested that the order with respect to cystine is fractional, whereas chromium(VI) follows first order kinetics. The reaction was second order in [H+]. Cysteic acid was found to be the main product of oxidation.

  11. Biomarker kinetics in the prediction of VAP diagnosis: results from the BioVAP study

    NARCIS (Netherlands)

    Póvoa, Pedro; Martin-Loeches, Ignacio; Ramirez, Paula; Bos, Lieuwe D.; Esperatti, Mariano; Silvestre, Joana; Gili, Gisela; Goma, Gema; Berlanga, Eugenio; Espasa, Mateu; Gonçalves, Elsa; Torres, Antoni; Artigas, Antonio

    2016-01-01

    Prediction of diagnosis of ventilator-associated pneumonia (VAP) remains difficult. Our aim was to assess the value of biomarker kinetics in VAP prediction. We performed a prospective, multicenter, observational study to evaluate predictive accuracy of biomarker kinetics, namely C-reactive protein

  12. Synthesis, structural investigation and kinetic studies of uranyl(VI) unsymmetrical Schiff base complexes

    Czech Academy of Sciences Publication Activity Database

    Asadi, Z.; Asadi, M.; Zeinali, A.; Ranjkeshshorkaei, M.; Fejfarová, Karla; Eigner, Václav; Dušek, Michal; Dehnokhalaji, A.

    2014-01-01

    Roč. 126, č. 6 (2014), s. 1673-1683 ISSN 0974-3626 R&D Projects: GA ČR(CZ) GAP204/11/0809 Institutional support: RVO:68378271 Keywords : uranyl schiff base complexes * kinetic study * kinetics of thermal decomposition * X-ray crystallography * cyclic voltammetry Subject RIV: CA - Inorganic Chemistry Impact factor: 1.191, year: 2014

  13. Correction: Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review

    Directory of Open Access Journals (Sweden)

    Kleinstreuer Clement

    2011-01-01

    Full Text Available Abstract Correction to Kleinstreuer C, Feng Y: Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review. Nanoscale Research Letters 2011, 6:229.

  14. Theoretical study of isomerization and decomposition of propenal

    International Nuclear Information System (INIS)

    Chin, Chih-Hao; Lee, Shih-Huang

    2011-01-01

    We investigated the dynamics of isomerization and multi-channel dissociation of propenal (CH 2 CHCHO), methyl ketene (CH 3 CHCO), hydroxyl propadiene (CH 2 CH 2 CHOH), and hydroxyl cyclopropene (cyclic-C 3 H 3 -OH) in the ground potential-energy surface using quantum-chemical calculations. Optimized structures and vibrational frequencies of molecular species were computed with method B3LYP/6-311G(d,p). Total energies of molecules at optimized structures were computed at the CCSD(T)/6-311+G(3df,2p) level of theory. We established the potential-energy surface for decomposition to CH 2 CHCO + H, CH 2 CH + HCO, CH 2 CH 2 /CH 3 CH + CO, CHCH/CH 2 C + H 2 CO, CHCCHO/CH 2 CCO + H 2 , CHCH + CO + H 2 , CH 3 + HCCO, CH 2 CCH + OH, and CH 2 CC/cyclic-C 3 H 2 + H 2 O. Microcanonical rate coefficients of various reactions of trans-propenal with internal energies 148 and 182 kcal mol -1 were calculated using Rice-Ramsperger-Kassel-Marcus and Variational transition state theories. Product branching ratios were derivable using numerical integration of kinetic master equations and the steady-state approximation. The concerted three-body dissociation of trans-propenal to fragments C 2 H 2 + CO + H 2 is the prevailing channel in present calculations. In contrast, C 3 H 3 O + H, C 2 H 3 + HCO and C 2 H 4 + CO were identified as major channels in the photolysis of trans-propenal. The discrepancy between calculations and experiments in product branching ratios indicates that the three major photodissociation channels occur mainly on an excited potential-energy surface whereas the other channels occur mainly on the ground potential-energy surface. This work provides profound insight in the mechanisms of isomerization and multichannel dissociation of the system C 3 H 4 O.

  15. An experimental and theoretical kinetic study of the reaction of OH radicals with tetrahydrofuran

    KAUST Repository

    Giri, Binod; Khaled, Fathi; Szőri, Milá n; Viskolcz, Bé la; Farooq, Aamir

    2016-01-01

    by the rapid thermal decomposition of tert-butyl hydroperoxide, and a UV laser absorption technique was used to monitor the mole fraction of OH radicals. High-level CCSD(T)/cc-pV(D,T)Z//MP2/aug-cc-pVDZ quantum chemical calculations were performed to explore

  16. Theoretical Kinetic Study of the Formic Acid Catalyzed Criegee Intermediate Isomerization: Multistructural Anharmonicity and Atmospheric Implications

    KAUST Repository

    Monge Palacios, Manuel; Rissanen, Matti Petteri; Wang, Zhandong; Sarathy, Subram Mani

    2018-01-01

    intermediate can serve as a surrogate for larger CIs derived from important volatile organic compounds like monoterpenes, whose reactivity is not well understood and are difficult to handle computationally. The reactant HCOOH exerts a pronounced catalytic

  17. Theoretical and numerical studies on the transport of transverse beam quality in plasma-based accelerators

    International Nuclear Information System (INIS)

    Mehrling, Timon Johannes

    2014-11-01

    This work examines effects, which impact the transverse quality of electron-beams in plasma-based accelerators, by means of theoretical and numerical methods. Plasma-based acceleration is a promising candidate for future particle accelerator technologies. In plasma-based acceleration, highly intense laser beams or high-current relativistic particle beams are focused into a plasma to excite plasma-waves with extreme transverse and longitudinal electric fields. The amplitude of these fields exceed with 10-100 GV/m the ones in today's radio-frequency accelerators by several orders of magnitude, hence, in principle allowing for accordingly shorter and cheaper accelerators based on plasma. Despite the tremendous progress in the recent decade, beams from plasma accelerators are not yet achieving the quality as demanded for pivotal applications of relativistic electron-beams, e.g. free-electron lasers (FELs).Studies within this work examine how the quality can be optimized in the production of the beams and preserved during the acceleration and transport to the interaction region. Such studies cannot be approached purely analytical but necessitate numerical methods, such as the Particle-In-Cell (PIC) method, which can model kinetic, electrodynamic and relativistic plasma phenomena. However, this method is computationally too expensive for parameter-scans in three-dimensional geometries. Hence, a quasi-static PIC code was developed in connection with this work, which is significantly more effective than the full PIC method for a class of problems in plasma-based acceleration.The evolution of the emittance of beams which are injected into plasma modules was studied in this work by means of theoretical and the above numerical methods. It was shown that the beam parameters need to be matched accurately into the focusing plasma-channel in order to allow for beam-quality preservation. This suggested that new extraction and injection-techniques are required in staged plasma

  18. Electrochemical and theoretical complexation studies for Zn and Cu with individual polyphenols

    International Nuclear Information System (INIS)

    Esparza, I.; Salinas, I.; Santamaria, C.; Garcia-Mina, J.M.; Fernandez, J.M.

    2005-01-01

    Zn and Cu interactions with three selected flavonoids (catechin, quercetin and rutin) have been electrochemically monitored. It has been shown that catechin takes one atom of metal per molecule; quercetin takes two atoms, and rutin is able to take up to three atoms. Not all ligands bind metals equally strong, and weakly bonded metals can be distinguished. Zn shows a sluggish kinetics and, at the same time, the highest conditional formation constants. The method could be applied to a real sample. Theoretical models are proposed for the most favourable compounds

  19. Atmospheric degradation of 3-methylfuran: kinetic and products study

    Directory of Open Access Journals (Sweden)

    A. Tapia

    2011-04-01

    Full Text Available A study of the kinetics and products obtained from the reactions of 3-methylfuran with the main atmospheric oxidants has been performed. The rate coefficients for the gas-phase reaction of 3-methylfuran with OH and NO3 radicals have been determined at room temperature and atmospheric pressure (air and N2 as bath gases, using a relative method with different experimental techniques. The rate coefficients obtained for these reactions were (in units cm3 molecule−1 s−1 kOH = (1.13 ± 0.22 × 10−10 and kNO3 = (1.26 ± 0.18 × 10−11. Products from the reaction of 3-methylfuran with OH, NO3 and Cl atoms in the absence and in the presence of NO have also been determined. The main reaction products obtained were chlorinated methylfuranones and hydroxy-methylfuranones in the reaction of 3-methylfuran with Cl atoms, 2-methylbutenedial, 3-methyl-2,5-furanodione and hydroxy-methylfuranones in the reaction of 3-methylfuran with OH and NO3 radicals and also nitrated compounds in the reaction with NO3 radicals. The results indicate that, in all cases, the main reaction path is the addition to the double bond of the aromatic ring followed by ring opening in the case of OH and NO3 radicals. The formation of 3-furaldehyde and hydroxy-methylfuranones (in the reactions of 3-methylfuran with Cl atoms and NO3 radicals confirmed the H-atom abstraction from the methyl group and from the aromatic ring, respectively. This study represents the first product determination for Cl atoms and NO3 radicals in reactions with 3-methylfuran. The reaction mechanisms and atmospheric implications of the reactions under consideration are also discussed.

  20. A unified theoretical and experimental study of anisotropic hardening

    International Nuclear Information System (INIS)

    Boehler, J.P.; Raclin, J.

    1981-01-01

    The purpose of this work is to develop a consistent formulation of the constitutive relations regarding anisotropic hardening materials. Attention is focused on the appearance and the evolution of mechanical anisotropies during irreversible processes, such as plastic forming and inelastic deformation of structures. The representation theorems for anisotropic tensor functions constitute a theoretical basis, allowing to reduce arbitrariness and to obtain a unified formulation of anisotropic hardening. In this approach, a general three-dimensional constitutive law is developed for prestrained initially orthotropic materials. Introduction of the plastic behavior results in the general forms of both the flow-law and the yield criterion. The developed theory is then specialized for the case of plane stress and different modes of anisotropic hardening are analyzed. A new generalization of the Von Mises criterion is proposed, in considering a homogeneous form of order two in stress and employing the simplest combinations of the basic invariants entering the general form of the yield condition. The proposed criterion involves specific terms accounting for the initial anisotropy, the deformation induced anisotropy and correlative terms between initial and induced anisotropy. The effects of prestrainings result in both isotropic and anisotropic hardening. An adequate experimental program, consisting of uniaxial tensile tests on oriented specimens of prestrained sheet-metal, was performed, in order to determine the specific form and the evolution of the anisotropic failure criterion for soft-steel subjected to different irreversible prestrainings. (orig.)

  1. Theoretical studies in medium-energy nuclear and hadronic physics

    International Nuclear Information System (INIS)

    Horowitz, C.J.; Macfarlane, M.H.; Matsui, T.; Serot, B.D.

    1993-01-01

    A proposal for theoretical nuclear physics research is made for the period April 1, 1993 through March 31, 1996. Research is proposed in the following areas: relativistic many-body theory of nuclei and nuclear matter, quasifree electroweak scattering and strange quarks in nuclei, dynamical effects in (e,e'p) scattering at large momentum transfer, investigating the nucleon's parton sea with polarized leptoproduction, physics of ultrarelativistic nucleus endash nucleus collisions, QCD sum rules and hadronic properties, non-relativistic models of nuclear reactions, and spin and color correlations in a quark-exchange model of nuclear matter. Highlights of recent research, vitae of principal investigators, and lists of publications and invited talks are also given. Recent research dealt primarily with medium-energy nuclear physics, relativistic theories of nuclei and the nuclear response, the nuclear equation of state under extreme conditions, the dynamics of the quark endash gluon plasma in relativistic heavy-ion collisions, and theories of the nucleon endash nucleon force

  2. Theoretical and Experimental Studies of Elementary Particle Physics

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Harold G [Indiana University; Kostelecky, V Alan [Indiana University; Musser, James A [Indiana University

    2013-07-29

    The elementary particle physics research program at Indiana University spans a broad range of the most interesting topics in this fundamental field, including important contributions to each of the frontiers identified in the recent report of HEPAP's Particle Physics Prioritization Panel: the Energy Frontier, the Intensity Frontier, and the Cosmic Frontier. Experimentally, we contribute to knowledge at the Energy Frontier through our work on the D0 and ATLAS collaborations. We work at the Intensity Frontier on the MINOS and NOvA experiments and participate in R&D for LBNE. We are also very active on the theoretical side of each of these areas with internationally recognized efforts in phenomenology both in and beyond the Standard Model and in lattice QCD. Finally, although not part of this grant, members of the Indiana University particle physics group have strong involvement in several astrophysics projects at the Cosmic Frontier. Our research efforts are divided into three task areas. The Task A group works on D0 and ATLAS; Task B is our theory group; and Task C contains our MINOS, NOvA, and LBNE (LArTPC) research. Each task includes contributions from faculty, senior scientists, postdocs, graduate and undergraduate students, engineers, technicians, and administrative personnel. This work was supported by DOE Grant DE-FG02-91ER40661. In the following, we describe progress made in the research of each task during the final period of the grant, from November 1, 2009 to April 30, 2013.

  3. Experimental and theoretical studies of 3-benzyloxy-2-nitropyridine

    Science.gov (United States)

    Sun, Wenting; Cui, Yu; Liu, Huimin; Zhao, Haitao; Zhang, Wenqin

    2012-10-01

    The structure of 3-benzyloxy-2-nitropyridine has been investigated both experimentally and theoretically. The X-ray crystallography results show that the nitro group is tilted out of the pyridine ring plane by 66.4(4)°, which is mainly attributed to the electron-electron repulsions of the lone pairs in O atom of the 3-benzyloxy moiety with O atom in nitro group. An interesting centrosymmetric π-stacking molecular pair has been found in the crystalline state, which results in the approximate coplanarity of the pyridine ring with the benzene ring. The calculated results show that the dihedral angle between the nitro group and pyridine ring from the X3LYP method is much closer to the experimental data than that from the M06-2X one. The existing two conformational isomers of 3-benzyloxy-2-nitropyridine with equal energy explain well the disorder of the nitro group at room temperature. In addition, the vibrational frequencies are also calculated by the X3LYP and M06-2X methods and compared with the experimental results. The prediction from the X3LYP method coincides with the locations of the experimental frequencies well.

  4. Heat conduction in graphene: experimental study and theoretical interpretation

    International Nuclear Information System (INIS)

    Ghosh, S; Nika, D L; Pokatilov, E P; Balandin, A A

    2009-01-01

    We review the results of our experimental investigation of heat conduction in suspended graphene and offer a theoretical interpretation of its extremely high thermal conductivity. The direct measurements of the thermal conductivity of graphene were performed using a non-contact optical technique and special calibration procedure with bulk graphite. The measured values were in the range of ∼3000-5300 W mK -1 near room temperature and depended on the lateral dimensions of graphene flakes. We explain the enhanced thermal conductivity of graphene as compared to that of bulk graphite basal planes by the two-dimensional nature of heat conduction in graphene over the whole range of phonon frequencies. Our calculations show that the intrinsic Umklapp-limited thermal conductivity of graphene grows with the increasing dimensions of graphene flakes and can exceed that of bulk graphite when the flake size is on the order of a few micrometers. The detailed theory, which includes the phonon-mode-dependent Gruneisen parameter and takes into account phonon scattering on graphene edges and point defects, gives numerical results that are in excellent agreement with the measurements for suspended graphene. Superior thermal properties of graphene are beneficial for all proposed graphene device applications.

  5. Optical gain coefficients of silicon: a theoretical study

    Science.gov (United States)

    Tsai, Chin-Yi

    2018-05-01

    A theoretical model is presented and an explicit formula is derived for calculating the optical gain coefficients of indirect band-gap semiconductors. This model is based on the second-order time-dependent perturbation theory of quantum mechanics by incorporating all the eight processes of photon/phonon emission and absorption between the band edges of the conduction and valence bands. Numerical calculation results are given for Si. The calculated absorption coefficients agree well with the existing fitting formula of experiment data with two modes of phonons: optical phonons with energy of 57.73 meV and acoustic phonons with energy of 18.27 meV near (but not exactly at) the zone edge of the X-point in the dispersion relation of phonons. These closely match with existing data of 57.5 meV transverse optical (TO) phonons at the X4-point and 18.6 meV transverse acoustic (TA) phonons at the X3-point of the zone edge. The calculated results show that the material optical gain of Si will overcome free-carrier absorption if the energy separation of quasi-Fermi levels between electrons and holes exceeds 1.15 eV.

  6. Experimental and numerical studies of burning velocities and kinetic modeling for practical and surrogate fuels

    Science.gov (United States)

    Zhao, Zhenwei

    continues to predict the earlier validation experiments as well as the newly acquired laminar flame speed data and other recently published shock tube ignition delay measurements. A high temperature decomposition and oxidation model based on a hierarchical nature of reacting systems to reflect the new development in the small molecule and radical kinetics and thermochemistry and to evaluate recent measurements of DME laminar flame speeds is developed. The, thermal decomposition of DME was studied theoretically by using the RRKM/master equation approach and the high temperature model was then compared with the literature experimental data. The new model predicts well high temperature flow reactor data, high temperature shock tube ignition delays, and the species profiles from the burner-stabilized flames. Predictions of laminar flame speed and jet-stirred reactor data also reasonably agree with the available experimental data. The remaining uncertainties that need to be addressed for further model improvement will also be discussed. This thesis also presents a novel temperature-dependent feature sensitivity analysis methodology for combustion modeling. The obtained information is demonstrated to be of critical relevance in optimizing complex reaction schemes against multiple experimental targets. Applications of the presented approach are not limited to sensitivities with respect to reaction rate coefficients; the method can also be used to investigate any temperature-dependent property of interest (such as binary diffusion coefficients). This application is also demonstrated in this thesis.

  7. A study of kinetic friction: The Timoshenko oscillator

    Science.gov (United States)

    Henaff, Robin; Le Doudic, Gabriel; Pilette, Bertrand; Even, Catherine; Fischbach, Jean-Marie; Bouquet, Frédéric; Bobroff, Julien; Monteverde, Miguel; Marrache-Kikuchi, Claire A.

    2018-03-01

    Friction is a complex phenomenon that is of paramount importance in everyday life. We present an easy-to-build and inexpensive experiment illustrating Coulomb's law of kinetic friction. The so-called friction, or Timoshenko, oscillator consists of a plate set into periodic motion through the competition between gravity and friction on its rotating supports. The period of such an oscillator gives a measurement of the coefficient of kinetic friction μk between the plate and the supports. Our prototype is mainly composed of a motor, LEGO blocks, and a low-cost microcontroller, but despite its simplicity, the results obtained are in good agreement with values of μk found in the literature (enhanced online).

  8. Hydroxylamine nitrate self-catalytic kinetics study with adiabatic calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Liu Lijun [Mary Kay O' Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas A and M University System, College Station, TX 77843-3122 (United States); Wei Chunyang [BASF Corporation, Wyandotte, MI 48192 (United States); Guo Yuyan; Rogers, William J. [Mary Kay O' Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas A and M University System, College Station, TX 77843-3122 (United States); Sam Mannan, M. [Mary Kay O' Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas A and M University System, College Station, TX 77843-3122 (United States)], E-mail: mannan@tamu.edu

    2009-03-15

    Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine compound family with applications that include equipment decontamination in the nuclear industry and aqueous or solid propellants. Due to its instability and autocatalytic behavior, HAN has been involved in several incidents at the Hanford and Savannah River Site (SRS) [Technical Report on Hydroxylamine Nitrate, US Department of Energy, 1998]. Much research has been conducted on HAN in different areas, such as combustion mechanism, decomposition mechanism, and runaway behavior. However, the autocatalytic decomposition behavior of HAN at runaway stage has not been fully addressed due to its highly exothermic and rapid decomposition behavior. This work is focused on extracting HAN autocatalytic kinetics and analyzing HAN critical behavior from adiabatic calorimetry measurements. A lumped autocatalytic kinetic model for HAN and associated model parameters are determined. Also the storage and handling critical conditions of diluted HAN solution without metal presence are quantified.

  9. Hydroxylamine nitrate self-catalytic kinetics study with adiabatic calorimetry

    International Nuclear Information System (INIS)

    Liu Lijun; Wei Chunyang; Guo Yuyan; Rogers, William J.; Sam Mannan, M.

    2009-01-01

    Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine compound family with applications that include equipment decontamination in the nuclear industry and aqueous or solid propellants. Due to its instability and autocatalytic behavior, HAN has been involved in several incidents at the Hanford and Savannah River Site (SRS) [Technical Report on Hydroxylamine Nitrate, US Department of Energy, 1998]. Much research has been conducted on HAN in different areas, such as combustion mechanism, decomposition mechanism, and runaway behavior. However, the autocatalytic decomposition behavior of HAN at runaway stage has not been fully addressed due to its highly exothermic and rapid decomposition behavior. This work is focused on extracting HAN autocatalytic kinetics and analyzing HAN critical behavior from adiabatic calorimetry measurements. A lumped autocatalytic kinetic model for HAN and associated model parameters are determined. Also the storage and handling critical conditions of diluted HAN solution without metal presence are quantified

  10. Chemical kinetics studies at high temperatures using shock tubes

    OpenAIRE

    Rajakumar, B; Anandraj, D; Reddy, KPJ; Arunan, E

    2002-01-01

    Shock tube is an unique facility to create temperature gradients exceeding million degrees Kelvin per second. We have established two shock tubes for measuring the kinetic reaction rates at high temperatures with two different but complementary detection techniques. The first one is a single pulse shock tube, in which the reflected shock is used to heat the molecules. The equilibrated products are analyzed by gas chromatograph and infrared spectrometer. The second one uses laser-schlieren sys...

  11. Kinetic studies following state-selective laser excitation

    International Nuclear Information System (INIS)

    Keto, J.W.

    1991-01-01

    During the past year, we have made measurements of state-to-state energy transfer cross sections and radiative lifetimes for Xe*(6p,6p',7p) and Kr*(5p) states in xenon and krypton buffer gases. These results are relevant to kinetic models of both excimer lasers and the infrared xenon laser; and they are a significant improvement in the precision of the known radiative lifetimes. 3 refs., 2 figs., 2 tabs

  12. An experimental and kinetic modeling study of glycerol pyrolysis

    International Nuclear Information System (INIS)

    Fantozzi, F.; Frassoldati, A.; Bartocci, P.; Cinti, G.; Quagliarini, F.; Bidini, G.; Ranzi, E.M.

    2016-01-01

    Highlights: • Glycerol pyrolysis can produce about 44–48%v hydrogen at 750–800 °C. • A simplified 452 reactions kinetic model of glycerol pyrolysis has been developed. • The model has good agreement with experimental data. • Non condensable gas yields can reach 70%. - Abstract: Pyrolysis of glycerol, a by-product of the biodiesel industry, is an important potential source of hydrogen. The obtained high calorific value gas can be used either as a fuel for combined heat and power (CHP) generation or as a transportation fuel (for example hydrogen to be used in fuel cells). Optimal process conditions can improve glycerol pyrolysis by increasing gas yield and hydrogen concentration. A detailed kinetic mechanism of glycerol pyrolysis, which involves 137 species and more than 4500 reactions, was drastically simplified and reduced to a new skeletal kinetic scheme of 44 species, involved in 452 reactions. An experimental campaign with a batch pyrolysis reactor was properly designed to further validate the original and the skeletal mechanisms. The comparisons between model predictions and experimental data strongly suggest the presence of a catalytic process promoting steam reforming of methane. High pyrolysis temperatures (750–800 °C) improve process performances and non-condensable gas yields of 70%w can be achieved. Hydrogen mole fraction in pyrolysis gas is about 44–48%v. The skeletal mechanism developed can be easily used in Computational Fluid Dynamic software, reducing the simulation time.

  13. Differences in kinetic variables between injured and noninjured novice runners : A prospective cohort study

    NARCIS (Netherlands)

    Bredeweg, Steef W.; Kluitenberg, Bas; Bessem, Bram; Buist, Ida

    Objectives: This prospective study examined differences in kinetic variables between injured and noninjured novice female and male runners and their potential contribution to RRIs. Design: A prospective cohort study. Methods: At baseline vertical ground reaction forces were assessed with an

  14. First principle chemical kinetics in zeolites: the methanol-to-olefin process as a case study.

    Science.gov (United States)

    Van Speybroeck, Veronique; De Wispelaere, Kristof; Van der Mynsbrugge, Jeroen; Vandichel, Matthias; Hemelsoet, Karen; Waroquier, Michel

    2014-11-07

    To optimally design next generation catalysts a thorough understanding of the chemical phenomena at the molecular scale is a prerequisite. Apart from qualitative knowledge on the reaction mechanism, it is also essential to be able to predict accurate rate constants. Molecular modeling has become a ubiquitous tool within the field of heterogeneous catalysis. Herein, we review current computational procedures to determine chemical kinetics from first principles, thus by using no experimental input and by modeling the catalyst and reacting species at the molecular level. Therefore, we use the methanol-to-olefin (MTO) process as a case study to illustrate the various theoretical concepts. This process is a showcase example where rational design of the catalyst was for a long time performed on the basis of trial and error, due to insufficient knowledge of the mechanism. For theoreticians the MTO process is particularly challenging as the catalyst has an inherent supramolecular nature, for which not only the Brønsted acidic site is important but also organic species, trapped in the zeolite pores, must be essentially present during active catalyst operation. All these aspects give rise to specific challenges for theoretical modeling. It is shown that present computational techniques have matured to a level where accurate enthalpy barriers and rate constants can be predicted for reactions occurring at a single active site. The comparison with experimental data such as apparent kinetic data for well-defined elementary reactions has become feasible as current computational techniques also allow predicting adsorption enthalpies with reasonable accuracy. Real catalysts are truly heterogeneous in a space- and time-like manner. Future theory developments should focus on extending our view towards phenomena occurring at longer length and time scales and integrating information from various scales towards a unified understanding of the catalyst. Within this respect molecular

  15. Theoretical Studies of Spectroscopic Line Mixing in Remote Sensing Applications

    Science.gov (United States)

    Ma, Q.

    2015-12-01

    The phenomenon of collisional transfer of intensity due to line mixing has an increasing importance for atmospheric monitoring. From a theoretical point of view, all relevant information about the collisional processes is contained in the relaxation matrix where the diagonal elements give half-widths and shifts, and the off-diagonal elements correspond to line interferences. For simple systems such as those consisting of diatom-atom or diatom-diatom, accurate fully quantum calculations based on interaction potentials are feasible. However, fully quantum calculations become unrealistic for more complex systems. On the other hand, the semi-classical Robert-Bonamy (RB) formalism, which has been widely used to calculate half-widths and shifts for decades, fails in calculating the off-diagonal matrix elements. As a result, in order to simulate atmospheric spectra where the effects from line mixing are important, semi-empirical fitting or scaling laws such as the ECS and IOS models are commonly used. Recently, while scrutinizing the development of the RB formalism, we have found that these authors applied the isolated line approximation in their evaluating matrix elements of the Liouville scattering operator given in exponential form. Since the criterion of this assumption is so stringent, it is not valid for many systems of interest in atmospheric applications. Furthermore, it is this assumption that blocks the possibility to calculate the whole relaxation matrix at all. By eliminating this unjustified application, and accurately evaluating matrix elements of the exponential operators, we have developed a more capable formalism. With this new formalism, we are now able not only to reduce uncertainties for calculated half-widths and shifts, but also to remove a once insurmountable obstacle to calculate the whole relaxation matrix. This implies that we can address the line mixing with the semi-classical theory based on interaction potentials between molecular absorber and

  16. Theoretical and computational studies of excitons in conjugated polymers

    Science.gov (United States)

    Barford, William; Bursill, Robert J.; Smith, Richard W.

    2002-09-01

    We present a theoretical and computational analysis of excitons in conjugated polymers. We use a tight-binding model of π-conjugated electrons, with 1/r interactions for large r. In both the weak-coupling limit (defined by W>>U) and the strong-coupling limit (defined by Wparticle models. We compare these to density matrix renormalization group (DMRG) calculations, and find good agreement in the extreme limits. We use these analytical results to interpret the DMRG calculations in the intermediate-coupling regime (defined by W~U), most applicable to conjugated polymers. We make the following conclusions. (1) In the weak-coupling limit the bound states are Mott-Wannier excitons, i.e., conduction-band electrons bound to valence-band holes. Singlet and triplet excitons whose relative wave functions are odd under a reflection of the relative coordinate are degenerate. Thus, the 2 1A+g and 1 3A-g states are degenerate in this limit. (2) In the strong-coupling limit the bound states are Mott-Hubbard excitons, i.e., particles in the upper Hubbard band bound to holes in the lower Hubbard band. These bound states occur in doublets of even and odd parity excitons. Triplet excitons are magnons bound to the singlet excitons, and hence are degenerate with their singlet counterparts. (3) In the intermediate-coupling regime Mott-Wannier excitons are the more appropriate description for large dimerization, while for the undimerized chain Mott-Hubbard excitons are the correct description. For dimerizations relevant to polyacetylene and polydiacetylene both Mott-Hubbard and Mott-Wannier excitons are present. (4) For all coupling strengths an infinite number of bound states exist for 1/r interactions for an infinite polymer. As a result of the discreteness of the lattice and the restrictions on the exciton wave functions in one dimension, the progression of states does not follow the Rydberg series. In practice, excitons whose particle-hole separation exceeds the length of the polymer

  17. A Correlational Study of Students' Theoretical and Practical

    African Journals Online (AJOL)

    Galadanci & Mukhtar

    Science World Journal Vol 12(No 2) 2017 ... Scores in Computer Applications Courses in Bayero University Kano. A CORRELATIONAL STUDY OF STUDENTS ... Physics, Chemistry and Biology, where the course of study has a substantial ...

  18. Theoretical study of electronic transfer current rate at dye-sensitized solar cells

    Science.gov (United States)

    AL-Agealy, Hadi J. M.; AlMaadhede, Taif Saad; Hassooni, Mohsin A.; Sadoon, Abbas K.; Ashweik, Ahmed M.; Mahdi, Hind Abdlmajeed; Ghadhban, Rawnaq Qays

    2018-05-01

    In this research, we present a theoretical study of electronic transfer kinetics rate in N719/TiO2 and N719/ZnO dye-sensitized solar cells (DSSC) systems using a simple model depending on the postulate of quantum mechanics theory. The evaluation of the electronic transition current rate in DSSC systems are function of many parameters such that; the reorientation transition energies ΛSe m D y e , the transition coupling parameter ℂT(0), potential exponential effect e-(E/C-EF ) kBT , unit cell volume VSem, and temperature T. Furthermore, the analysis of electronic transfer current rate in N719/TiO2 and N719/ZnO systems show that the rate upon dye-sensitization solar cell increases with increases of transition coupling parameter, decreasing potential that building at interface a results of different material in this devices and increasing with reorientation transition energy. On the other hand, we can find the electronic transfer behavior is dependent of the dye absorption spectrum and mainly depending on the reorientation of transition energy. The replacement of the solvents in both DSSC system caused increasing of current rates dramatically depending on polarity of solvent in subset devices. This change in current rate of electron transfer were attributed to much more available of recombination sites introduced by the solvents medium. The electronic transfer current dynamics are shown to occurs in N719/TiO2 system faster many time compare to ocuures at N719/ZnO system, this indicate that TiO2 a is a good and active material compare with ZnO to using in dye sensitized solar cell devices. In contrast, the large current rate in N719/TiO2 comparing to ZnO of N719/ZnO systems indicate that using TiO2 with N719 dye lead to increasing the efficiency of DSSC.

  19. Theoretical study of chain transfer to solvent reactions of alkyl acrylates.

    Science.gov (United States)

    Moghadam, Nazanin; Srinivasan, Sriraj; Grady, Michael C; Rappe, Andrew M; Soroush, Masoud

    2014-07-24

    This computational and theoretical study deals with chain transfer to solvent (CTS) reactions of methyl acrylate (MA), ethyl acrylate (EA), and n-butyl acrylate (n-BA) self-initiated homopolymerization in solvents such as butanol (polar, protic), methyl ethyl ketone (MEK) (polar, aprotic), and p-xylene (nonpolar). The results indicate that abstraction of a hydrogen atom from the methylene group next to the oxygen atom in n-butanol, from the methylene group in MEK, and from a methyl group in p-xylene by a live polymer chain are the most likely mechanisms of CTS reactions in MA, EA, and n-BA. Energy barriers and molecular geometries of reactants, products, and transition states are predicted. The sensitivity of the predictions to three hybrid functionals (B3LYP, X3LYP, and M06-2X) and three different basis sets (6-31G(d,p), 6-311G(d), and 6-311G(d,p)) is investigated. Among n-butanol, sec-butanol, and tert-butanol, tert-butanol has the highest CTS energy barrier and the lowest rate constant. Although the application of the conductor-like screening model (COSMO) does not affect the predicted CTS kinetic parameter values, the application of the polarizable continuum model (PCM) results in higher CTS energy barriers. This increase in the predicted CTS energy barriers is larger for butanol and MEK than for p-xylene. The higher rate constants of chain transfer to n-butanol reactions compared to those of chain transfer to MEK and p-xylene reactions suggest the higher CTS reactivity of n-butanol.

  20. Kinetic study of UV-irradiated amorphous sulfur by EPR spectroscopy

    International Nuclear Information System (INIS)

    El Mkami, H.; Smith, G.M.

    2005-01-01

    Electron paramagnetic resonance (EPR) spectroscopy is used to investigate UV-irradiation damage in amorphous sulfur by examining post-irradiation kinetics as a function of UV-exposure time. The kinetic study is described by first-order concurrent reactions where the sulfur, as reactant, undergoes two parallel processes leading to the formation of two distinct defects called S 1 * and S 2 *. The temperature dependence of the EPR intensities of the signals, related to these defects, is used in the kinetic study

  1. Study of the stochastic point reactor kinetic equation

    International Nuclear Information System (INIS)

    Gotoh, Yorio

    1980-01-01

    Diagrammatic technique is used to solve the stochastic point reactor kinetic equation. The method gives exact results which are derived from Fokker-Plank theory. A Green's function dressed with the clouds of noise is defined, which is a transfer function of point reactor with fluctuating reactivity. An integral equation for the correlation function of neutron power is derived using the following assumptions: 1) Green's funntion should be dressed with noise, 2) The ladder type diagrams only contributes to the correlation function. For a white noise and the one delayed neutron group approximation, the norm of the integral equation and the variance to mean-squared ratio are analytically obtained. (author)

  2. Derivation of kinetic coefficients by atomistic methods for studying defect behavior in Mo

    International Nuclear Information System (INIS)

    Insepov, Z.; Rest, J.; Yacout, A.M.; Kuksin, A.Yu.; Norman, G.E.; Stegailov, V.V.; Starikov, S.V.; Yanilkin, A.V.

    2012-01-01

    Highlights: ► A multiscale concept couples molecular dynamics (MD) with ab initio and kinetic rate theory. ► Evolution of a system of self-interstitial atoms and vacancies in Mo is studied by MD. ► Formation of di-SIA clusters and SIA–vacancy recombination is analyzed. ► 1D diffusion of self-interstitials at various temperature and defect concentrations were studied. ► This paper provides a powerful predictive tool for simulating irradiation of nuclear materials. - Abstract: A multiscale concept for irradiated materials simulation is formulated based on coupling molecular dynamics simulations (MD) where the potential was obtained from ab initio data of energies of the basic defect structures, with kinetic mesoscale models. The evolution of a system containing self-interstitial atoms (SIAs) and vacancies in crystalline molybdenum is investigated by means of MD. The kinetics of formation of di-SIA clusters and SIA–vacancy recombination is analyzed via approaches used in the kinetic theory of radiation ageing. The effects of 1D diffusion of SIAs, temperature, and defect concentrations on the reaction rates are also studied. This approach can validate both the kinetic mechanisms and the appropriate kinetic coefficients, offering the potential to significantly reduce the uncertainty of the kinetic methodology and providing a powerful predictive tool for simulating irradiation behavior of nuclear materials.

  3. Heavy leptons: theoretical study of the implications of their existence

    International Nuclear Information System (INIS)

    Ragiadakos, C.

    1978-01-01

    The following points are studied: the possibility of an internal structure of heavy leptons and its manifestation; a study of the production of neutral heavy leptons in e + -e - collisions; consequences of the lumaton (heavy lepton having strong interactions) hypothesis; the introduction of a muon number violating mechanism in gauge theories. A gauge model characterized by the symmetries: left-right and quarks-leptons is also studied. A general review of the heavy leptons is given [fr

  4. A Study on the Pyrolysis of Peanut Shells at Different Isothermal Conditions and Determination of the Kinetic Parameters

    Directory of Open Access Journals (Sweden)

    Şeyda Taşar

    2015-12-01

    Full Text Available The pyrolysis process, which is applied for the aim of producing energy and raw materials which are implemented for the chemical industry from biomass sources, is a thermal conversion process. Determination of the pyrolysis kinetic parameters are important In order to suitable equipment and process design. In this target, in the study the pyrolysis of peanut shells was conducted in a muffle furnace at static atmosphere with temperatures ranging from 300-700 °C. The effects of various parameters on the rate of thermal decomposition rate and the solid yield were determined. The parameters of interest were temperature 300-700 °C, particle size 4-50 mesh, pelletizing, and pelletizing pressure 1.103-5.103 kgf/cm2. Regression coefficients for the total decomposition step were obtained using the thermographs were obtained as a result of the pyrolysis of the peanut shells, and 20 different theoretical model equations that represented the degradation by the Coast-Redfern method. According to regression coefficients of the theoretical model equations, we determined the kinetic model that best represented the degradation. Using this model to represent the degradation, the activation energy (Ea and Arhenius frequency factor ln(A for the total reaction were calculated to be 38.245 kJ/mol and 8.124, respectively.

  5. Theoretical studies of Elmo Bumpy Torus. Annual report

    International Nuclear Information System (INIS)

    1984-01-01

    The work was divided into four basic areas. Studies of the effect of waves on stability and transport considered the possibility of using radio frequency waves to stabilize interchange modes, as well as the general problem of influencing plasma transport by wave absorption. Studies related to wave heating of plasmas considered nonlinear effects such as mode conversion and parametric absorption, along with studies of the structure of ion cyclotron waves in a strongly bumpy geometry. Ring physics studies added nonadiabaticity and whistler instabilities to the model, producing a fairly realistic picture of energy balance, power requirements, and scaling for hot electron rings. Finally, studies analyzing EBT transport data were performed, with emphasis on testing various hypotheses for apparent anomalies in the EBT

  6. Experimental and Chemical Kinetic Modeling Study of Dimethylcyclohexane Oxidation and Pyrolysis

    KAUST Repository

    Eldeeb, Mazen A.; Jouzdani, Shirin; Wang, Zhandong; Sarathy, Mani; Akih-Kumgeh, Benjamin

    2016-01-01

    A combined experimental and chemical kinetic modeling study of the high-temperature ignition and pyrolysis of 1,3-dimethylcyclohexane (13DMCH) is presented. Ignition delay times are measured behind reflected shock waves over a temperature range

  7. Stable isotope studies of nicotine kinetics and bioavailability

    International Nuclear Information System (INIS)

    Benowitz, N.L.; Jacob, P. III; Denaro, C.; Jenkins, R.

    1991-01-01

    The stable isotope-labeled compound 3',3'-dideuteronicotine was used to investigate the disposition kinetics of nicotine in smokers, the systemic absorption of nicotine from cigarette smoke, and the bioavailability of nicotine ingested as oral capsules. Blood levels of labeled nicotine could be measured for 9 hours after a 30-minute intravenous infusion. Analysis of disposition kinetics in 10 healthy men revealed a multiexponential decline after the end of an infusion, with an elimination half-life averaging 203 minutes. This half-life was longer than that previously reported, indicating the presence of a shallow elimination phase. Plasma clearance averaged 14.6 ml/min/kg. The average intake of nicotine per cigarette was 2.29 mg. A cigarette smoke-monitoring system that directly measured particulate matter in smoke was evaluated in these subjects. Total particulate matter, number of puffs on the cigarette, total puff volume, and time of puffing correlated with the intake of nicotine from smoking. The oral bioavailability of nicotine averaged 44%. This bioavailability is higher than expected based on the systemic clearance of nicotine and suggests that there may be significant extrahepatic metabolism of nicotine

  8. Kinetic study of oil extraction from olive foot cake

    Directory of Open Access Journals (Sweden)

    Lamrous, O.

    2006-06-01

    Full Text Available The kinetics of oil extraction from olive foot cake can be explained by a model based on two stages. The first step corresponds to a simple washing of the oil from the particle surface. In the second step, the extraction is controlled by two mechanisms: slow diffusion from broken cells and very slow diffusion from intact cells.The kinetic coefficients of this mathematical model are calculated using the experimental results obtained from hexane and commercial ethyl alcohol for different particle sizes.La cinética de extracción de aceite de orujo puede ser explicada por un modelo basado en dos etapas. La primera etapa corresponde a un simple lavado del aceite de la superficie de las partículas. En la segunda etapa, la extracción esta controlada por dos mecanismos: difusión lenta desde las células rotas y difusión muy lenta desde las células intactas.Los coeficientes cinéticas de este modelo matemático se calculan usando los resultados experimentales obtenidos con hexano y alcohol etílico comercial para diferentes tamaños de partícula.

  9. Freezing of bentonite. Experimental studies and theoretical considerations

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2010-01-15

    During its lifetime, a KBS-3 repository will be subject to various ambient temperatures. Backfilled tunnels, shafts and investigation bore holes closest to ground level will experience periods of temperature below 0 deg C. From a safety assessment perspective, it is therefore essential to understand the behavior of compacted bentonite below 0 deg C. A theoretical framework for predicting the pressure response in compacted water saturated bentonite due to temperature changes has been developed based on thermodynamics and a single pore-type. This model predicts an approximately linear temperature dependence of swelling pressure P{sub s}(w,DELTAT) = P{sub s}(w,0 deg C) + DELTAs(w)DELTAT/nu{sub clay}(w) where DELTAT denotes a temperature difference from 0 deg C, DELTAs(w) is the difference in partial molar entropy between clay water and bulk water, nu{sub clay} (w) is the partial molar volume of the clay water and w denotes the water/solid mass ratio of the clay. As bulk water changes phase at 0 deg C, DELTAs(w) has a different value dependent on whether DELTAT is negative or positive. Above 0 deg C DELTAs(w) is a small value for all relevant densities which means that the pressure response due to temperature changes is small. A further consequence of this fact is that DELTAs(w) is a large positive number below 0 deg C when the external water phase is transformed to ice. Consequently, the model predicts a large drop of swelling pressure with temperature below 0 deg C, in the order of 1.2 MPa/deg C. Specifically, the swelling pressure is zero at a certain (negative) temperature T{sub C}. T{sub C} also quantifies the freezing point of the bentonite sample under consideration, as ice formation in the bentonite does not occur until swelling pressure is lost. A large set of laboratory tests have been performed where fully water saturated samples of bentonites have been exposed to temperatures in the range -10 deg C to +25 deg C. The swelling pressure response has been

  10. Mechanistic and kinetic study on the catalytic hydrolysis of COS in small clusters of sulfuric acid.

    Science.gov (United States)

    Li, Kai; Song, Xin; Zhu, Tingting; Wang, Chi; Sun, Xin; Ning, Ping; Tang, Lihong

    2018-01-01

    The catalytic hydrolysis of carbonyl sulfide (COS) and the effect of small clusters of H 2 O and H 2 SO 4 have been studied by theoretical calculations. The addition of H 2 SO 4 could increase the enthalpy change (ΔHhydrolysis reaction changed from an endothermic reaction to an exothermic reaction. Further, H 2 SO 4 decreases the energy barrier by 5.25 kcal/mol, and it enhances the catalytic hydrolysis through the hydrogen transfer effect. The (COS + H 2 SO 4 -H 2 O) reaction has the lowest energy barrier of 29.97 kcal/mol. Although an excess addition of H 2 O and H 2 SO 4 increases the energy barrier, decreases the catalytic hydrolysis, which is consistent with experimental observations. The order of the energy barriers for the three reactions from low to high are as follows: COS + H 2 SO 4 -H 2 O hydrolysis of COS both kinetically and thermodynamically. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Glass-crystal transformation under non-isothermal conditions: Kinetic analysis of the Ag{sub 0.16}As{sub 0.38}Se{sub 0.46} glassy alloy by using a new theoretical method based on nucleation and growth processes, which depend on time as a power law

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez, J., E-mail: jose.vazquez@uca.e [Departamento de Fisica de la Materia Condensada, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, 11510, Puerto Real (Cadiz) (Spain); Cardenas-Leal, J.L.; Garcia-G Barreda, D.; Gonzalez-Palma, R.; Lopez-Alemany, P.L.; Villares, P. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, 11510, Puerto Real (Cadiz) (Spain)

    2010-11-01

    A theoretical method, which we have published in two previous works, has been applied to the study of the glass-crystal transformation of the Ag{sub 0.16}As{sub 0.38}Se{sub 0.46} semiconductor glass under non-isothermal conditions. This method allows one to obtain an evolution equation with temperature for the actual volume fraction, to calculate the kinetic parameters of the quoted transformation, to establish the thermal process type, to determine the dimensionality of the crystal growth and to evaluate the exponents of the power laws of the time-dependence both for the nucleation frequency and for the crystal growth rate in non-isothermal transformations. The quoted method assumes the concept of extended volume of the transformed material, the condition of randomly located nuclei and the supposition of mutual interference of regions growing from separated nuclei, considering moreover the case presented in the practice of a kinetic exponent with a value larger than 4. To study the quoted case it is proposed that both the nucleation frequency and the crystal growth rate depend on time as a power law. The above-mentioned Ag{sub 0.16}As{sub 0.38}Se{sub 0.46} glassy alloy presents two exothermic peaks. The second peak gives for the kinetic exponent a value large enough than 4 and it is necessary to resort to the hypotheses of the considered method to justify the unexpectedly high value of the kinetic exponent. Following the quoted method it has been found that the thermal process type is continuous nucleation with three-dimensional growth for the two peaks of crystallization of the studied alloy. Moreover, the experimental curve of the transformed fraction shows a satisfactory agreement with the theoretical curve corresponding to the considered method, confirming the reliability of the quoted method in order to analyze the transformation kinetics of the above-mentioned alloy.

  12. Theoretical and Experimental Studies of Magneto-Rayleigh-Taylor Instabilities

    International Nuclear Information System (INIS)

    Lau, Yue Ying; Gilgenbach, Ronald

    2013-01-01

    Magneto-Rayleigh-Taylor instability (MRT) is important to magnetized target fusion, wire-array z-pinches, and equation-of-state studies using flyer plates or isentropic compression. It is also important to the study of the crab nebula. The investigators performed MRT experiments on thin foils, driven by the mega-ampere linear transformer driver (LTD) facility completed in their laboratory. This is the first 1-MA LTD in the USA. Initial experiments on the seeding of MRT were performed. Also completed was an analytic study of MRT for a finite plasma slab with arbitrary magnetic fields tangential to the interfaces. The effects of magnetic shear and feedthrough were analyzed

  13. Theoretical and Experimental Studies of Magneto-Rayleigh-Taylor Instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Yue Ying [University of Michigan, Ann Arbor, MI (United States); Gilgenbach, Ronald [University of Michigan, Ann Arbor, MI (United States)

    2013-07-07

    Magneto-Rayleigh-Taylor instability (MRT) is important to magnetized target fusion, wire-array z-pinches, and equation-of-state studies using flyer plates or isentropic compression. It is also important to the study of the crab nebula. The investigators performed MRT experiments on thin foils, driven by the mega-ampere linear transformer driver (LTD) facility completed in their laboratory. This is the first 1-MA LTD in the USA. Initial experiments on the seeding of MRT were performed. Also completed was an analytic study of MRT for a finite plasma slab with arbitrary magnetic fields tangential to the interfaces. The effects of magnetic shear and feedthrough were analyzed.

  14. Applied and theoretical study of textural and structural evolution of pure and doped zircon powders

    International Nuclear Information System (INIS)

    Methivier, A.

    1992-02-01

    Using different preparation methods, undoped zircon constituted of quadratic and monoclinic phases, and quadratic phase zircon doped with lanthanum, magnesium or silicon were obtained and characterized. An applied kinetic study of the influence of the gaseous phase, and of the doping on pre-sintering shows an accelerating effect of water vapour, an important stabilization effect of lanthanum or silicon additions and a little effect of magnesium additions. This kinetic study leads to a model giving two parallel types of matter transport: one using water vapour catalytic effect, and the other oxygen diffusion

  15. Theoretical and numerical study of highly anisotropic turbulent flows

    NARCIS (Netherlands)

    Biferale, L.; Daumont, I.; Lanotte, A.; Toschi, F.

    2004-01-01

    We present a detailed numerical study of anisotropic statistical fluctuations in stationary, homogeneous turbulent flows. We address both problems of intermittency in anisotropic sectors, and the relative importance of isotropic and anisotropic fluctuations at different scales on a direct numerical

  16. Theoretical study of the mechanism of proton transfer in tautomeric ...

    Indian Academy of Sciences (India)

    Semiempirical SCF-MO studies of tautomerism in alloxan preclude the ... However, in aqueous solution, the activation barrier reduces appreciably, not ... which stabilize the transition state to a greater extent due to its higher dipole moment.

  17. A combined electrochemical and theoretical study of pyridine-based ...

    Indian Academy of Sciences (India)

    PARUL DOHARE

    2018-02-01

    Feb 1, 2018 ... diamine (DAP-3) were synthesized, characterized, and their corrosion inhibition performance was studied on ... inhibition efficiencies of various organic compounds on ...... 5 alkyl 1,3,4 thiadiazole compounds on the corrosion ...

  18. Joint Experimental and Theoretical Study on Vibrational Excitation Cross Sections for Electron Collisions with Diacetylene

    Czech Academy of Sciences Publication Activity Database

    Čurík, Roman; Paidarová, Ivana; Allan, M.; Čársky, Petr

    2014-01-01

    Roč. 118, č. 41 (2014), s. 9734-9744 ISSN 1089-5639 R&D Projects: GA ČR GAP208/11/0452; GA MŠk LD14088 Institutional support: RVO:61388955 Keywords : diacetylenes * electron collision * theoretical study Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.693, year: 2014

  19. Experimental and theoretical study of heterogeneous iron precipitation in silicon

    OpenAIRE

    Haarahiltunen, Antti; Väinölä, Hele; Anttila, O.; Yli-Koski, Marko

    2007-01-01

    Heterogeneous iron precipitation in silicon was studied experimentally by measuring the gettering efficiency of oxide precipitate density of 1×10exp10cm−3. The wafers were contaminated with varying iron concentrations, and the gettering efficiency was studied using isothermal annealing in the temperature range from 300 to 780°C. It was found that iron precipitation obeys the so called s-curve behavior: if iron precipitation occurs, nearly all iron is gettered. For example, after 30 min anneal...

  20. Experimental and Theoretical Studies in Hydrogen-Bonding Organocatalysis

    Directory of Open Access Journals (Sweden)

    Matej Žabka

    2015-08-01

    Full Text Available Chiral thioureas and squaramides are among the most prominent hydrogen-bond bifunctional organocatalysts now extensively used for various transformations, including aldol, Michael, Mannich and Diels-Alder reactions. More importantly, the experimental and computational study of the mode of activation has begun to attract considerable attention. Various experimental, spectroscopic and calculation methods are now frequently used, often as an integrated approach, to establish the reaction mechanism, the mode of activation or explain the stereochemical outcome of the reaction. This article comprises several case studies, sorted according to the method used in their study. The aim of this review is to give the investigators an overview of the methods currently utilized for mechanistic investigations in hydrogen-bonding organocatalysis.

  1. Theoretical provisions for the discharge at TJ-1 (Preliminary study)

    International Nuclear Information System (INIS)

    Guasp, J.

    1981-01-01

    Using the transport code PLASMATOR a numerical study about the TJ-1 discharge (a Tokamak close to be installed at JEN) has been made, observing the behaviour under huge variations on the transport coefficients as well as on density and current. Noteworthy a scaling law of the kind τ E ∼n θ has been contested at not too high density, The model insensibility upon the initial values has been confirmed and the effects of variations on the recycling coefficient and the rate rise of current studied too. Finally comparisons with alternative models have been accomplished. (Author) 29 refs

  2. Theoretical and experimental study of mixed solvent electrolytes

    International Nuclear Information System (INIS)

    Cummings, P.T.; O'Connell, J.P.

    1990-01-01

    In the original proposal to study mixed solvent electrolyte solutions, four major goals were formulated: fundamental modeling of mixed solvent electrolytes using numerically solved integral equation approximation theories; evaluation of intermolecular pair potential models by computer simulation of selected systems for comparison with experiment and the numerical integral equation studies; development of fundamentally based correlations for the thermodynamic properties of mixed solvent electrolyte solutions using analytically solvable statistical mechanical models; and extension of experimental database on mixed solvent electrolytes by performing vapor-liquid equilibrium measurements on selected systems. This paper discusses the progress on these goals

  3. A Theoretical Study of Subsurface Drainage Model Simulation of ...

    African Journals Online (AJOL)

    A three-dimensional variable-density groundwater flow model, the SEAWAT model, was used to assess the influence of subsurface drain spacing, evapotranspiration and irrigation water quality on salt concentration at the base of the root zone, leaching and drainage in salt affected irrigated land. The study was carried out ...

  4. Platinum and palladium on carbon nanotubes : Experimental and theoretical studies

    NARCIS (Netherlands)

    Adjizian, J. J.; De Marco, P.; Suarez-Martinez, I.; El Mel, A. A.; Snyders, R.; Gengler, R. Y. N.; Rudolf, P.; Ke, X.; Van Tendeloo, G.; Bittencourt, C.; Ewels, C. P.

    2013-01-01

    Pristine and oxygen plasma functionalised carbon nanotubes (CNTs) were studied after the evaporation of Pt and Pd atoms. High resolution transmission electron microscopy shows the formation of metal nanoparticles at the CNT surface. Oxygen functional groups grafted by the plasma functionalization

  5. Connecting theoretical and empirical studies of trait-mediated interactions

    Czech Academy of Sciences Publication Activity Database

    Bolker, B.; Holyoak, M.; Křivan, Vlastimil; Rowe, L.; Schmitz, O.

    2003-01-01

    Roč. 84, č. 5 (2003), s. 1101-1114 ISSN 0012-9658 Institutional research plan: CEZ:AV0Z5007907 Keywords : community models * competition * empirical study Subject RIV: EH - Ecology, Behaviour Impact factor: 3.701, year: 2003

  6. Theoretical study of bone sialoprotein in bone biomineralization

    CSIR Research Space (South Africa)

    Yang, Y

    2011-05-01

    Full Text Available , highly conserved across several vertebrates, are the proposed active sites. We selected one of these sites, i.e. (Sp) 2 E 8 , where Sp represents a phosphoserine as a model peptide to study the role of BSP. We used molecular dynamics simulations...

  7. Theoretical Study of Spin Crossover in 30 Iron Complexes

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2016-01-01

    Spin crossover was studied in 30 iron complexes using density functional theory to quantify the direction and magnitude of dispersion, relativistic effects, zero-point energies, and vibrational entropy. Remarkably consistent entropy−enthalpy compensation was identified. Zero-point energies favor...

  8. A theoretical parametric study of Water Flooding | Ohirhian | Journal ...

    African Journals Online (AJOL)

    A multidimensional mathematical model derived by combining equation of continuity and Darcy's law and solved using the strongly implicit procedure (SIP) has been used to study the effects of permeability distribution, shape of the relative permeability and capillary pressure curves, ratio of water to oil viscosity, and amount ...

  9. THEORETICAL STUDY (AB INITIO AND DFT METHODS) ON ...

    African Journals Online (AJOL)

    ng reaction mechanisms that involve hydrogen atom transfer/proton-coupled. 5]. For these ... f theory have been extensively employed to the study of acidities and the compared with the .... evidence for the second deprotonation of XO. Also, as ...

  10. Theoretical studies on rapid fluctuations in solar flares

    International Nuclear Information System (INIS)

    Vlahos, L.

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins, e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed

  11. Theoretical studies on rapid fluctuations in solar flares

    Science.gov (United States)

    Vlahos, Loukas

    1986-01-01

    Rapid fluctuations in the emission of solar bursts may have many different origins e.g., the acceleration process can have a pulsating structure, the propagation of energetic electrons and ions can be interrupted from plasma instabilities and finally the electromagnetic radiation produced by the interaction of electrostatic and electromagnetic waves may have a pulsating behavior in time. In two separate studies the conditions for rapid fluctuations in solar flare driven emission were analyzed.

  12. Theoretical study of adsorption of lithium atom on carbon nanotube

    OpenAIRE

    Senami, Masato; Ikeda, Yuji; Fukushima, Akinori; Tachibana, Akitomo

    2011-01-01

    We investigate the adsorption of lithium atoms on the surface of the (12, 0) single wall carbon nanotube (SWCNT) by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsiv...

  13. Biological and Theoretical Studies of Adaptive Networks: The Conditioned Response.

    Science.gov (United States)

    1992-06-30

    suggest experimental tests and provide direction for physiological studies. 14 SU~la TIPO ~IS- NIJUMS Of PAGIS 17. @1d-ftA ITY CLASSIPtCATICON...mancte suditioned inhibition of the rabbit’s nictitating membrane response, CI tasks require the active suppression of CRs in the Bull . Psychon. Soc., 20... Bull ., 84 (1977) encephalon and mesencephalon26. 690-711. Several lines of evidence suggest that the septal and 8 Evans,J.A.C. and Thornton, E.W

  14. Dynamic behavior of hybrid sodium bearings. Theoretical and experimental studies

    International Nuclear Information System (INIS)

    Guidez, J.; Juignet, N.; Queval, M.

    1981-08-01

    The primary sodium pump shaft lower section of a fast breeder reactor is guided by a hydrostatic sodium bearing. This recess type bearing is supplied via orifices restrictors. Sodium is sampled at hight pressure at the diffuser outlet and is then centrifuged towards the orifices restrictors. Bearing stiffness and damping data is essential for the study of rotor dynamic behavior. Two points in particular may then be studied: - calculation of rotor instability ranges and critical speeds, - dynamic behavior of the rotor in the event of an earthquake. As regards the bearing design, the problem is to obtain the pressure fields in the liquid film. The integration of these pressure fields will then give the stiffness coefficients. The damping coefficients can then be obtained by the same calculation after slight displacement. The Reynolds equation can be used to study the liquid film (under any conditions for the turbulent and inertia effects). Then the computer code DELPAL is explained that solves the modified Reynolds equation using a finite element method. The presentation of tests conducted in 1981 on the Super-Phenix 1 full scall bearing (diameter 850 mm) in water is made. In conclusion this paper describes a method for calculating the stiffness and damping matrices of a hydrostatic bearing using the DELPAL calculation code and shows the loop of behavior tests on a bearing with sinusoidal excitation. The results, obtained by calculation and by testing, are indispensable when calculating the dynamic behavior of the shaft line

  15. Ignition characteristics of 2-methyltetrahydrofuran: An experimental and kinetic study

    KAUST Repository

    Tripathi, Rupali

    2016-10-15

    The present paper elucidates oxidation behavior of 2-methyltetrahydrofuran (2-MTHF), a novel second-generation biofuel. New experimental data sets for 2-MTHF including ignition delay time measurements in two different combustion reactors, i.e. rapid compression machine and high-pressure shock tube, are presented. Measurements for 2-MTHF/oxidizer/diluent mixtures were performed in the temperature range of . 639-1413 K, at pressures of 10, 20, and 40 bar, and at three different equivalence ratios of 0.5, 1.0, and 2.0. A detailed chemical kinetic model describing both low-and high-temperature chemistry of 2-MTHF was developed and validated against new ignition delay measurements and already existing flame species profiles and ignition delay measurements. The mechanism provides satisfactory agreement with the experimental data. For identifying key reactions at various combustion conditions and to attain a better understanding of the combustion behavior, reaction path and sensitivity analyses were performed.

  16. Theoretical study of adsorption of lithium atom on carbon nanotube

    Directory of Open Access Journals (Sweden)

    Masato Senami

    2011-12-01

    Full Text Available We investigate the adsorption of lithium atoms on the surface of the (12,0 single wall carbon nanotube (SWCNT by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsive force between lithium atoms destabilizes a system for the large number of lithium atoms.

  17. Theoretical Studies of Optical Properties of Silver Nanoparticles

    International Nuclear Information System (INIS)

    Ye-Wan, Ma; Zhao-Wang, Wu; Li-Hua, Zhang; Jie, Zhang

    2010-01-01

    Optical properties of silver nanoparticles such as extinction, absorption and scattering efficiencies are studied based on Green's function theory. The numerical simulation results show that optical properties of silver nanoparticles are mainly dependent on their sizes and geometries; the localized plasmon resonance peak is red shifted when the dielectric constant of the particle's surrounding medium increases or when a substrate is presented. The influences of wave polarizations, the incident angles of light, the composite silver and multiply-layers on the plasmon resonance are also reported. The numerical simulation of optical spectra is a very useful tool for nanoparticle growth and characterization. (fundamental areas of phenomenology(including applications))

  18. A theoretical study on free monopolar spacial change

    International Nuclear Information System (INIS)

    Camargo, P.C. de.

    1975-01-01

    Assuming planar symmetry and an arbitrary charge distribution that spreads through the sample, the one-carrier free-space-charge motion is studied in insulators solids. Using the method of characteristics we can reduce the problem to the resolution of a system of two ordinary first order differential equations. Results are applied to linear, exponential and S.C.L. current charge distributions, under short-circuit conditions. The charge distribution for several times and the discharge currents are presented. The results are compared with those from an approximated method, based on variational principles. (author) [pt

  19. Role of hot electron transport in scintillators: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Huihui [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, Key Lab. of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen Univ. (China); Li, Qi [Physical Sciences Division, IBM TJ Watson Research Center, Yorktown Heights, NY (United States); Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Lu, Xinfu; Williams, R.T. [Department of Physics, Wake Forest University, Winston Salem, NC (United States); Qian, Yiyang [College of Engineering and Applied Science, Nanjing University (China); Wu, Yuntao [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN (United States)

    2016-10-15

    Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab-initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte-Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Atmospheric reaction of Cl + methacrolein: a theoretical study on the mechanism, and pressure- and temperature-dependent rate constants.

    Science.gov (United States)

    Sun, Cuihong; Xu, Baoen; Zhang, Shaowen

    2014-05-22

    Methacrolein is a major degradation product of isoprene, the reaction of methacrolein with Cl atoms may play some roles in the degradation of isoprene where these species are relatively abundant. However, the energetics and kinetics of this reaction, which govern the reaction branching, are still not well understood so far. In the present study, two-dimensional potential energy surfaces were constructed to analyze the minimum energy path of the barrierless addition process between Cl and the C═C double bond of methacrolein, which reveals that the terminal addition intermediate is directly formed from the addition reaction. The terminal addition intermediate can further yield different products among which the reaction paths abstracting the aldehyde hydrogen atom and the methyl hydrogen atom are dominant reaction exits. The minimum reaction path for the direct aldehydic hydrogen atom abstraction is also obtained. The reaction kinetics was calculated by the variational transition state theory in conjunction with the master equation method. From the theoretical model we predicted that the overall rate constant of the Cl + methacrolein reaction at 297 K and atmospheric pressure is koverall = 2.3× 10(-10) cm(3) molecule(-1) s(-1), and the branching ratio of the aldehydic hydrogen abstraction is about 12%. The reaction is pressure dependent at P pressure limit at about 100 Torr. The calculated results could well account for the experimental observations.

  1. Influence of rapid changes in cytosolic pH on oxidative phosphorylation in skeletal muscle: theoretical studies.

    Science.gov (United States)

    Korzeniewski, Bernard; Zoladz, Jerzy A

    2002-07-01

    Cytosolic pH in skeletal muscle may vary significantly because of proton production/consumption by creatine kinase and/or proton production by anaerobic glycolysis. A computer model of oxidative phosphorylation in intact skeletal muscle developed previously was used to study the kinetic effect of these variations on the oxidative phosphorylation system. Two kinds of influence were analysed: (i) via the change in pH across the inner mitochondrial membrane and (ii) via the shift in the equilibrium of the creatine kinase-catalysed reaction. Our simulations suggest that cytosolic pH has essentially no impact on the steady-state fluxes and most metabolite concentrations. On the other hand, rapid acidification/alkalization of cytosol causes a transient decrease/increase in the respiration rate. Furthermore, changes in pH seem to affect significantly the kinetic properties of transition between resting state and active state. An increase in pH brought about by proton consumption by creatine kinase at the onset of exercise lengthens the transition time. At intensive exercise levels this pH increase could lead to loss of the stability of the system, if not compensated by glycolytic H+ production. Thus our theoretical results stress the importance of processes/mechanisms that buffer/compensate for changes in cytosolic proton concentration. In particular, we suggest that the second main role of anaerobic glycolysis, apart from additional ATP supply, may be maintaining the stability of the system at intensive exercise.

  2. Experimental and theoretical study of cascade solar stills in Iran

    International Nuclear Information System (INIS)

    Tabrizi, F.F.; Sharak, A.Z.

    2009-01-01

    Due to low annual rainfall, most of Iran is dominated by arid and semi-arid areas. The solar radiation intensity is extremely high in most of the country. The need to produce fresh water from brackish water is considerably high, especially in dry regions. Desalination of brackish water may become a competitive potential water resource to meet potable water demand, and as the price of oil goes higher, using solar energy for water desalinisation becomes more economical. This paper presented a study that involved mathematical modeling of the first solar still in Iran. The cumulative fresh water production and water temperature were calculated as a function of time. The obtained results were verified by one month daily-based experimental data. The paper also provided background information on the Koshk village, situated in the south part of Iran near Badar Abbas city. Various investigations regarding meteorological conditions, economical considerations, and technical and operational appropriateness demonstrated that the cascade solar still is suitable for desalination of brackish water. 100 solar stills were installed at the site to provide potable water for a nearby village. It was concluded that the model could be used to simulate and optimize the effective design parameters in future studies. 6 refs., 7 figs

  3. Hydroxyl radical induced transformation of phenylurea herbicides: A theoretical study

    International Nuclear Information System (INIS)

    Mile, Viktória; Harsányi, Ildikó; Kovács, Krisztina; Földes, Tamás; Takács, Erzsébet; Wojnárovits, László

    2017-01-01

    Aromatic ring hydroxylation reactions occurring during radiolysis of aqueous solutions are studied on the example of phenylurea herbicides by Density Functional Theory calculations. The effect of the aqueous media is taken into account by using the Solvation Model Based on Density model. Hydroxyl radical adds to the ring because the activation free energies (0.4–47.2 kJ mol −1 ) are low and also the Gibbs free energies have high negative values ((−27.4) to (−5.9) kJ mol −1 ). According to the calculations in most of cases the ortho- and para-addition is preferred in agreement with the experimental results. In these reactions hydroxycyclohexadienyl type radicals form. In a second type reaction, when loss of chlorine atom takes place, OH/Cl substitution occurs without cyclohexadienyl type intermediate. - Highlights: • Attack of • OH to aniline, phenol, fenuron, monuron, diuron was studied by DFT. • Ortho-para directing is suggested with –NH 2 , –OH and –NHCON(CH 3 ) 2 groups. • • OH addition to the ring gives hydroxycyclohexadienyl radical. • Attack at C-Cl leads to • OH/Cl substitution without cyclohexadienyl intermediate.

  4. Theoretical study of reactions at the electrode-electrolyte interface

    International Nuclear Information System (INIS)

    Halley, J.W.

    1994-01-01

    Electron transfer rates are predicted by numerical methods, in collaboration with ANL. Emphasis is on electron transfer involving ions known to be important in enhancing stress corrosion cracking in light water reactors and on electron transfer at oxide surfaces. We have completed studies of the ferrous-ferric electron transfer rate in which effects of electric field, entropic effects in the free energy and quantum effects are included for the first time in the calculation of the rate of an electrochemical (heterogeneous) reaction rate. These new results confirm assumptions made in earlier calculations. The ferric ion has been modelled in a dissociable polarizable model showing the six-fold coordination of this ion in aqueous solution is stabilized by the three body interactions arising from the polarizability of water. In our studies of oxides, we have completed a Hartree self consistent calculation of the electronic structure of fayalite. The calculation utilizes a new method which takes phenomenological account of local electron correlations which have plagued electronic structure calculations of oxides for a long time. No electronic structure calculation of fayalite has been previously reported to our knowledge. Similar methods have been used to calculate the electronic structure of a vacancy in rutile (TiO 2 ). Results show that the screening donor electrons are anisotropically distributed around the vacancy

  5. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Science.gov (United States)

    Morales, Javier; Günther, Germán; Zanocco, Antonio L; Lemp, Else

    2012-01-01

    Detection of singlet oxygen emission, λ(max) = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T), and the reactive reaction rate constant, k(r), for the reaction between singlet oxygen and several flavonoids. Values of k(T) determined in deuterated water, ranging from 2.4×10(7) M(-1) s(-1) to 13.4×10(7) M(-1) s(-1), for rutin and morin, respectively, and the values measured for k(r), ranging from 2.8×10(5) M(-1) s(-1) to 65.7×10(5) M(-1) s(-1) for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  6. Singlet Oxygen Reactions with Flavonoids. A Theoretical – Experimental Study

    Science.gov (United States)

    Morales, Javier; Günther, Germán; Zanocco, Antonio L.; Lemp, Else

    2012-01-01

    Detection of singlet oxygen emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, kT, and the reactive reaction rate constant, kr, for the reaction between singlet oxygen and several flavonoids. Values of kT determined in deuterated water, ranging from 2.4×107 M−1s−1 to 13.4×107 M−1s−1, for rutin and morin, respectively, and the values measured for kr, ranging from 2.8×105 M−1s−1 to 65.7×105 M−1s−1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid. PMID:22802966

  7. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Directory of Open Access Journals (Sweden)

    Javier Morales

    Full Text Available Detection of singlet oxygen emission, λ(max = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T, and the reactive reaction rate constant, k(r, for the reaction between singlet oxygen and several flavonoids. Values of k(T determined in deuterated water, ranging from 2.4×10(7 M(-1 s(-1 to 13.4×10(7 M(-1 s(-1, for rutin and morin, respectively, and the values measured for k(r, ranging from 2.8×10(5 M(-1 s(-1 to 65.7×10(5 M(-1 s(-1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  8. Kinetic study of formation of sodalite from a kaolin waste of Jari river - PA, Brazil

    International Nuclear Information System (INIS)

    Silva, L.N. da; Paz, S.P.A. da; Angelica, R.S.; Neves, R.F.

    2011-01-01

    Zeolites are materials with a wide industrial application, which has motivated the development of a large number of scientific papers on this topic. This work presents a kinetic study of the formation process of sodalite produced from the reaction of the kaolin waste in the presence of sodium hydroxide solution (5M) performed at temperatures of 80, 100, 120 and 150 ° C. The process was conducted in batch, static, and autoclaves lined with Teflon, and monitoring the kinetics was performed by ex situ XRD analysis of the materials obtained in the time interval from 2 to 24 hours. The kinetic model that best describes this transformation is zero-order homogeneous reaction. Finally, we conclude that the technique of X-ray diffraction is a powerful tool to study the kinetics of phase transformation ex situ. (author)

  9. Flow-Based Systems for Rapid and High-Precision Enzyme Kinetics Studies

    Directory of Open Access Journals (Sweden)

    Supaporn Kradtap Hartwell

    2012-01-01

    Full Text Available Enzyme kinetics studies normally focus on the initial rate of enzymatic reaction. However, the manual operation of steps of the conventional enzyme kinetics method has some drawbacks. Errors can result from the imprecise time control and time necessary for manual changing the reaction cuvettes into and out of the detector. By using the automatic flow-based analytical systems, enzyme kinetics studies can be carried out at real-time initial rate avoiding the potential errors inherent in manual operation. Flow-based systems have been developed to provide rapid, low-volume, and high-precision analyses that effectively replace the many tedious and high volume requirements of conventional wet chemistry analyses. This article presents various arrangements of flow-based techniques and their potential use in future enzyme kinetics applications.

  10. Structure–kinetic relationship study of CDK8/CycC specific compounds

    Science.gov (United States)

    Schneider, Elisabeth V.; Böttcher, Jark; Huber, Robert; Maskos, Klaus; Neumann, Lars

    2013-01-01

    In contrast with the very well explored concept of structure–activity relationship, similar studies are missing for the dependency between binding kinetics and compound structure of a protein ligand complex, the structure–kinetic relationship. Here, we present a structure–kinetic relationship study of the cyclin-dependent kinase 8 (CDK8)/cyclin C (CycC) complex. The scaffold moiety of the compounds is anchored in the kinase deep pocket and extended with diverse functional groups toward the hinge region and the front pocket. These variations can cause the compounds to change from fast to slow binding kinetics, resulting in an improved residence time. The flip of the DFG motif (“DMG” in CDK8) to the inactive DFG-out conformation appears to have relatively little influence on the velocity of binding. Hydrogen bonding with the kinase hinge region contributes to the residence time but has less impact than hydrophobic complementarities within the kinase front pocket. PMID:23630251

  11. A Initio Theoretical Studies of Surfaces of Semiconductors

    Science.gov (United States)

    Wang, Jing

    1993-01-01

    The first semiconductor which we study with these techniques is the archetypal elemental semiconductor, silicon. We present the first extensive study of point defects on Si(100). We identify the principal defects and two primary mechanisms responsible for their dominance: the need to eliminate dangling bonds on the surface and the need to compensate the strain induced by topological effects. Furthermore, we present evidence that the presence of point defects on the Si(100) surface is not intrinsic to the ground state of the surface as a stress relieving mechanism but rather is due merely to thermal fluctuations. We address materials issues associated with the identification of the lowest energy surfaces of GaAs and the determination of the geometric structure of a GaAs crystallite growing freely in three dimensions. The fracture energies associated with (110), (100) and (111) interface planes are calculated and a Wulff construction indicates that an ideal stoichiometric GaAs crystal should be terminated with (110) surfaces. We investigate the more complex issues that arise on surfaces when aspects of these two semiconductors are mixed. We investigate the problem of growing GaAs on the Si(100) surface and demonstrate how and why the most fundamental properties of the resulting bulk GaAs material, such as its crystalline orientation, may depend sensitively on the interplay between growth conditions such as temperature and the properties of the Si surface. For stepped Si(100) -As, we show that the growth of As directly on top of the Si surface produces a metastable state, while the replacement of the original top Si layer leads to a lower energy configuration, with the rearrangement of the surface driven by the relaxation of stress by surface steps. Finally, we study delta -doping, where one attempts to grow a single layer of Si on a GaAs surface before continuing with the growth of bulk GaAs. We shall employ a slightly different modality of the ab initio approach. We

  12. Theoretical study about L-arginine complexes formation with thiotriazolin

    Directory of Open Access Journals (Sweden)

    L. I. Kucherenko

    2017-02-01

    Full Text Available Brain vascular diseases are one of the leading causes of morbidity, mortality and disability of population in the industrialized countries of the world. An important element of this problem’s solution is the creation of new highly effective and safe drugs, which would lead to mortality reduction, to increase in life expectancy and quality of life. Therefore it is interesting to create a new combined drug based on L-arginine and thiotriazolin. Purpose of the study: to consider the possible structure and energy characteristics of complexes formed by L-arginine, 3-methyl-1,2,4-triazolyl-5-thioacetate (MTTA and morpholine. Calculation method. The initial approximation to the complex geometry was obtained using molecular docking with the help of AutoDock Vina program. The obtained ternary complexes were pre-optimized by semi-empirical PM7 method with modeling the impact of the environment by COSMO method. The calculations were carried out using MOPAC2012 program. Then they were optimized by B97-D3/SVP + COSMO (Water dispersion-corrected DFT-D with geometrical spreading correction on insufficiency of gCP basis set. A more accurate calculation of the solvation energy was conducted by SMD. The calculations by density functional method were carried out using the ORCA 3.0.3 software. Energy complex formation in solution was calculated as the difference of the Gibbs free energy of the solvated complex and its individual components. Results. Quantum chemical calculations show, that thiotriazolin and L-arginine are able to form ternary complexes, where molecules are linked by multiple hydrogen bonds. The calculation data suggest, that studied complexes are thermodynamically unstable in solution. The energies of them are positive, but rather low despite charge gain of a number of intermolecular hydrogen bonds. Finding. Based on the results of the conducted quantum-chemical study of a three components system (MTTA, morpholine, and L-arginine it is possible

  13. Theoretical Study of Watershed Eco-Compensation Standards

    Science.gov (United States)

    Yan, Dandan; Fu, Yicheng; Liu, Biu; Sha, Jinxia

    2018-01-01

    Watershed eco-compensation is an effective way to solve conflicts over water allocation and ecological destruction problems in the exploitation of water resources. Despite an increasing interest in the topic, the researches has neglected the effect of water quality and lacked systematic calculation method. In this study we reviewed and analyzed the current literature and proposedatheoretical framework to improve the calculation of co-compensation standard.Considering the perspectives of the river ecosystems, forest ecosystems and wetland ecosystems, the benefit compensation standard was determined by the input-output corresponding relationship. Based on the opportunity costs related to limiting development and water conservation loss, the eco-compensation standard was calculated.In order to eliminate the defects of eco-compensation implementation, the improvement suggestions were proposed for the compensation standard calculation and implementation.

  14. 1,2-Propanediol. Comprehensive experimental and theoretical study

    International Nuclear Information System (INIS)

    Verevkin, Sergey P.; Emel'yanenko, Vladimir N.; Nell, Gernot

    2009-01-01

    The standard (p 0 =0.1MPa) molar enthalpy of formation at the temperature 298.15 K of the liquid 1,2-propanediol was measured using combustion calorimetry. Molar enthalpies of vaporization of isomeric 1,2-propanediols were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. Thermochemical investigations of 1,2-ethanediol and 1,2-propanediol available in the literature were collected and combined with own experimental results. This collection together with the new experimental results reported here has helped to resolve contradictions in the available sublimation enthalpies data and to recommend consistent and reliable set of vaporization and formation enthalpies for both diols under study. Ab initio calculations of gaseous molar enthalpy of formation of 1,2-ethanediol and 1,2-propanediol have been performed using the G3MP2 method and results are in excellent agreement with the selected experimental data.

  15. Theoretical study of the elastic properties of titanium nitride

    Institute of Scientific and Technical Information of China (English)

    Jingdong CHEN; Yinglu ZHAO; Benhai YU; Chunlei WANG; Deheng SHI

    2009-01-01

    The equilibrium lattice parameter, relative volume V/Vo, elastic constants Cij, and bulk modulus of titanium nitride are successfully obtained using the ab initio plane-wave pseudopotential (PW-PP) method within the framework of density functional theory. The quasi-harmonic Debye model, using a set of total energy vs molar volume obtained with the PW-PP method, is applied to the study of the elastic properties and vibrational effects. We analyze the relationship between the bulk modulus and temperature up to 2000 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonously with increasing pressure and decreases with increasing temperature. Moreover, the Debye temperature is determined from the non-equilibrium Gibbs func-tions.

  16. Theoretical study of short pile effect in tunnel excavation

    Science.gov (United States)

    Tian, Xiao-yan; Liu, Jing; Gao, Xiao-mei; Li, Yuan

    2017-09-01

    The Misaki Sato Go ideal elastoplastic model is adopted and the two stage analysis theory is used to study the effect of tunnel excavation on short pile effect in this paper. In the first stage, the free field vertical displacement of the soil at the corresponding pile location is obtained by using empirical formula. In the second stage, the displacement is applied to the corresponding pile location. The equilibrium condition of micro physical differential equation settlement of piles. Then through logical deduction and the boundary condition expressions of the settlement calculation, obtain the pile side friction resistance and axial force of the week. Finally, an engineering example is used to analyze the influence of the change of main parameters on their effects.

  17. Theoretical and computational studies in intermediate energy nuclear physics

    International Nuclear Information System (INIS)

    Elster, C.

    1993-08-01

    The research includes applications of many-body scattering theory to nuclear systems and studies of few-body systems described by effective hadronic field theories. Progress was made in bringing all first-order effects into the nonrelativistic elastic nucleon-nucleus scattering in a consistent fashion. This work is directed towards completely and reliably calculating the first-order term in a Watson expansion including a modification through the nulear medium. The research effort in few-body physics was concentrated on nucleon-nucleon (NN) scattering below pion production threshold, where recent measurements indicated that the backward-angle neutron-proton (np) differential cross section may show sensitivity to the size of the pion-nucleon coupling constant

  18. Theoretical study of lithium clusters by electronic stress tensor

    International Nuclear Information System (INIS)

    Ichikawa, Kazuhide; Nozaki, Hiroo; Komazawa, Naoya; Tachibana, Akitomo

    2012-01-01

    We study the electronic structure of small lithium clusters Li_n (n = 2 ∼ 8) using the electronic stress tensor. We find that the three eigenvalues of the electronic stress tensor of the Li clusters are negative and degenerate, just like the stress tensor of liquid. This leads us to propose that we may characterize a metallic bond in terms of the electronic stress tensor. Our proposal is that in addition to the negativity of the three eigenvalues of the electronic stress tensor, their degeneracy characterizes some aspects of the metallic nature of chemical bonding. To quantify the degree of degeneracy, we use the differential eigenvalues of the electronic stress tensor. By comparing the Li clusters and hydrocarbon molecules, we show that the sign of the largest eigenvalue and the differential eigenvalues could be useful indices to evaluate the metallicity or covalency of a chemical bond.

  19. On flaw tolerance of nacre: a theoretical study

    Science.gov (United States)

    Shao, Yue; Zhao, Hong-Ping; Feng, Xi-Qiao

    2014-01-01

    As a natural composite, nacre has an elegant staggered ‘brick-and-mortar’ microstructure consisting of mineral platelets glued by organic macromolecules, which endows the material with superior mechanical properties to achieve its biological functions. In this paper, a microstructure-based crack-bridging model is employed to investigate how the strength of nacre is affected by pre-existing structural defects. Our analysis demonstrates that owing to its special microstructure and the toughening effect of platelets, nacre has a superior flaw-tolerance feature. The maximal crack size that does not evidently reduce the tensile strength of nacre is up to tens of micrometres, about three orders higher than that of pure aragonite. Through dimensional analysis, a non-dimensional parameter is proposed to quantify the flaw-tolerance ability of nacreous materials in a wide range of structural parameters. This study provides us some inspirations for optimal design of advanced biomimetic composites. PMID:24402917

  20. Exergy performance of different space heating systems: A theoretical study

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Shukuya, Masanori; Olesen, Bjarne W.

    2016-01-01

    , the effects of floor covering resistance on the whole system performance were studied using two heat sources; a natural gas fired condensing boiler and an air-source heat pump. The heating systems were also compared in terms of auxiliary exergy use for pumps and fans. The low temperature floor heating system......Three space heating systems (floor heating with different floor covering resistances, radiator heating with different working temperatures, warm-air heating with and without heat recovery) were compared using a natural gas fired condensing boiler as the heat source. For the floor heating systems...... performed better than other systems in terms of exergy demand. The use of boiler as a heat source for a low-exergy floor heating system creates a mismatch in the exergy supply and demand. Although an air-source heat pump could be a better heat source, this depends on the origin of the electricity supplied...

  1. Theoretical nuclear reaction and structure studies using hyperons and photons

    International Nuclear Information System (INIS)

    Cotanch, S.R.

    1992-01-01

    Research in three principal areas is summarized: (1) Work in elementary hadron structure seeks to further the understanding of hadron structure within the framework of quantum chromodynamics (QCD) and QCD-based models. A comparative study of meson properties employed three relativistic models: an extended Dziembowski model, a generalized light-front approach, and a completely covariant null plane approach. (2) Work on the electromagnetic production of strangeness addressed systems involving the strange quark (hyperons) and hyperon electromagnetic production and radiative capture processes. (3) In the work on medium-energy photonuclear reactions, a large-scale continuum shell-model calculation was performed for (γ,N) and (N,γ) reactions at low and medium energies spanning the Δ isobar region

  2. Theoretical Study of Sodium-Water Surface Reaction Mechanism

    Science.gov (United States)

    Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro

    Computational study of the sodium-water reaction at the gas (water) - liquid (sodium) interface has been carried out using the ab initio (first-principle) method. A possible reaction channel has been identified for the stepwise OH bond dissociations of a single water molecule. The energetics including the binding energy of a water molecule on the sodium surface, the activation energies of the bond cleavages, and the reaction energies, have been evaluated, and the rate constants of the first and second OH bond-breakings have been compared. It was found that the estimated rate constant of the former was much larger than the latter. The results are the basis for constructing the chemical reaction model used in a multi-dimensional sodium-water reaction code, SERAPHIM, being developed by Japan Atomic Energy Agency (JAEA) toward the safety assessment of the steam generator (SG) in a sodium-cooled fast reactor (SFR).

  3. Theoretical study of sodium-water surface reaction mechanism

    International Nuclear Information System (INIS)

    Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro

    2012-01-01

    Computational study of the sodium-water reaction at the gas (water) - liquid (sodium) interface has been carried out using the ab initio (first-principle) method. A possible reaction channel has been identified for the stepwise OH bond dissociations of a single water molecule. The energetics including the binding energy of a water molecule on the sodium surface, the activation energies of the bond cleavages, and the reaction energies, have been evaluated, and the rate constants of the first and second OH bond-breakings have been compared. It was found that the estimated rate constant of the former was much larger than the latter. The results are the basis for constructing the chemical reaction model used in a multi-dimensional sodium-water reaction code, SERAPHIM, being developed by Japan Atomic Energy Agency (JAEA) toward the safety assessment of the steam generator (SG) in a sodium-cooled fast reactor (SFR). (author)

  4. Theoretical and experimental studies for optimization of PCRV top closures

    International Nuclear Information System (INIS)

    Ottosen, N.S.; Andersen, S.I.

    1975-01-01

    The results from the remaining part of the parameter study and the preparations for the verification of an optimized design are presented. Three models have been made in the same scale and with the same depth to span ratio α as the low LM-3 model from the first investigation, i.e. α=0.35. The model LM-5 was provided with reinforcement in the tensile zone, the upper part of the closure. This reinforcement did not influence the stresses and strains in the load carrying concrete, and the dome failed at the same pressure as in the unreinforced model LM-3. However, the closure did not disintegrate, but failed due to large overall deformations causing seal leakage. In the model LM-6, the inverted dome, which is formed at higher loads as demonstrated in LM-3, was reinforced perpendicular to the supposed middle surface. This reinforcement proved to be effective, giving the dome a higher ultimate load capacity. The LM-6 test stopped due to a circumferential crack in the flange. Finally, the unreinforced LM-7 closure was tested to failure. Apart from minor changes in the flange, LM-7 was identical to LM-3 except for the excavated upper part of the concrete, which in LM-3 formed the heavily cracked tensile zone. The ultimate load and the failure mode observed for this closure were the same as for the LM-3. The experimental results are compared to finite element calculations, in which plasticity and cracking of the concrete are taken into account, and the influence of different material models for the concrete is investigated. A unique failure criterion, which includes failure of the concrete for both tensile and compressive stresses in the same mathematical expression, is proposed. Based on the results obtained from the parameter study, a new closure design is proposed, which is optimized with respect to the requirements at service conditions and ultimate load

  5. A theoretical study of cylindrical ultrasound transducers for intracavitary hyperthermia

    International Nuclear Information System (INIS)

    Lin, W.-L.; Fan, W.-C.; Yen, J.-Y.; Chen, Y.-Y.; Shieh, M.-J.

    2000-01-01

    Purpose: The purpose of this paper was to examine the heating patterns and penetration depth when a cylindrical ultrasound transducer is employed for intracavitary hyperthermia treatments. Methods and Materials: The present study employs a simulation program based on a simplified power deposition model for infinitely long cylindrical ultrasound transducers. The ultrasound power in the tissue is assumed to be exponentially attenuated according to the penetration depth of the ultrasound beam, and a uniform attenuation for the entire treatment region is also assumed. The distribution of specific absorption rate (SAR) ratio (the ratio of SAR for a point within the tissue to that for a specific point on the cavity surface) is used to determine the heating pattern for a set of given parameters. The parameters considered are the ultrasound attenuation in the tissue, the cavity size, and the transducer eccentricity. Results: Simulation results show that the ultrasound attenuation in the tissue, the cavity size, and the transducer eccentricity are the most influential parameters for the distribution of SAR ratio. A low frequency transducer located in a large cavity can produce a much better penetration. The cavity size is the major parameter affecting the penetration depth for a small cavity size, such as interstitial hyperthermia. The heating pattern can also be dramatically changed by the transducer eccentricity and radiating sector. In addition, for a finite length of cylindrical transducer, lower SAR ratio appears in the regions near the applicator's edges. Conclusion: The distribution of SAR ratio indicates the relationship between the treatable region and the parameters if an appropriate threshold of SAR ratio is taken. The findings of the present study comprehend whether or not a tumor is treatable, as well as select the optimal driving frequency, the appropriate cavity size, and the eccentricity of a cylindrical transducer for a specific treatment

  6. Theoretical study of hydrogen-bridged beryllium compounds

    International Nuclear Information System (INIS)

    Hashimoto, Kenro; Osamura, Yoshihiro; Iwata, Suehiro

    1986-01-01

    Ab initio closed-shell SCF method, combined with the energy gradient technique, was applied to study the molecular structures and the stability of (i) beryllium dihydride and its polymers (BeH 2 ) n (n = 1 to 5), and of (ii) monosubstituted beryllium hydrides HBeX (X = BH 2 , CH 3 , NH 2 , OH, F and Cl). Basis set dependence on the geometries and the force constants of BeH 2 and (BeH 2 ) 2 was carefully examined. The minimal basis set gives us a qualitative picture for chemical bonding of beryllium, though at least the split-valence type basis set is needed to obtain quantitative results. The effect of the electron correlation on the dimerization energy of BeH 2 was studied with SDCI and MP3 methods and was not so important as on the dimerization energy of Be atom. The dimer formation of BeH 2 results from the strong orbital interaction between a σ orbital (HOMO) of one of BeH 2 and a vacant 2p π orbital (LUMO) of the other. The energy gain from (BeH 2 ) n to (BeH 2 ) n+1 was almost constant for n = 2, 3, and 4 (about 120 kJ/mol) and it is larger than that from BeH 2 to (BeH 2 ) 2 (about 80 kJ/mol). This result means that in the chemical bonding of Be atom the sp 3 hybridization is more favorable than the sp 2 hybridization, and the sp 2 is more than the sp hybridization. With STO-3G and 3 - 21G basis sets the molecular structures of a series of monosubstituted beryllium hydrides and their dimers were determined, and the vibrational frequencies were evaluated for them. Bond lengths between a Be atom and a neighboring atom become shorter as the electronegativity of the neighboring atom increases. In particular, the bonding with oxygen is found to be very strong. These hydrides tends to dimerize, and the dimerization energy is about 60 ∼ 100 kJ/mol, when the bridged atoms are hydrogen atoms, irrespective of the terminal substituents. (author)

  7. Theoretical study of the relativistic molecular rotational g-tensor

    Energy Technology Data Exchange (ETDEWEB)

    Aucar, I. Agustín, E-mail: agustin.aucar@conicet.gov.ar; Gomez, Sergio S., E-mail: ssgomez@exa.unne.edu.ar [Institute for Modeling and Technological Innovation, IMIT (CONICET-UNNE) and Faculty of Exact and Natural Sciences, Northeastern University of Argentina, Avenida Libertad 5400, W3404AAS Corrientes (Argentina); Giribet, Claudia G.; Ruiz de Azúa, Martín C. [Physics Department, Faculty of Exact and Natural Sciences, University of Buenos Aires and IFIBA CONICET, Ciudad Universitaria, Pab. I, 1428 Buenos Aires (Argentina)

    2014-11-21

    An original formulation of the relativistic molecular rotational g-tensor valid for heavy atom containing compounds is presented. In such formulation, the relevant terms of a molecular Hamiltonian for non-relativistic nuclei and relativistic electrons in the laboratory system are considered. Terms linear and bilinear in the nuclear rotation angular momentum and an external uniform magnetic field are considered within first and second order (relativistic) perturbation theory to obtain the rotational g-tensor. Relativistic effects are further analyzed by carrying out the linear response within the elimination of the small component expansion. Quantitative results for model systems HX (X=F, Cl, Br, I), XF (X=Cl, Br, I), and YH{sup +} (Y=Ne, Ar, Kr, Xe, Rn) are obtained both at the RPA and density functional theory levels of approximation. Relativistic effects are shown to be small for this molecular property. The relation between the rotational g-tensor and susceptibility tensor which is valid in the non-relativistic theory does not hold within the relativistic framework, and differences between both molecular parameters are analyzed for the model systems under study. It is found that the non-relativistic relation remains valid within 2% even for the heavy HI, IF, and XeH{sup +} systems. Only for the sixth-row Rn atom a significant deviation of this relation is found.

  8. Theoretical study on onset of cubic distortion product otoacoustic emissions

    Science.gov (United States)

    Vencovský, Václav; Vetešník, Aleš

    2018-05-01

    The distortion product otoacoustic emissions (DPOAEs) are generated when the cochlea is stimulated by two pure tones with different frequencies f1 and f2. Onset of the DPOAE amplitude may have a nonmonotonic complex shape when the f2 is pulsed during a stationary f1 input. Observed complexities have been explained as (1) due to the secondary source of the DPOAE at the distortion product (DP) characteristic site, and (2) due to the spatial distribution of DP sources with different phases. There is also a third possibility that the complexities are due to the suppression of the f1 basilar membrane (BM) response during the f2 onset. In this study, a hydrodynamic cochlea model is used to examine influence of f1 suppression on the time course of DPOAE onset. In particular, a set of simulations was performed for frequency ratio f2/f1 = 1.26 and various levels of the primary tones (L1 and L2=30-70 dB SPL) to determine the relationship between time dependencies of the DPOAE onset and the suppression of the f1 BM response. The model predicts that suppression of the f1 BM response can cause suppression of DPOAE amplitude during the onset period.

  9. Theoretical study of the relativistic molecular rotational g-tensor

    International Nuclear Information System (INIS)

    Aucar, I. Agustín; Gomez, Sergio S.; Giribet, Claudia G.; Ruiz de Azúa, Martín C.

    2014-01-01

    An original formulation of the relativistic molecular rotational g-tensor valid for heavy atom containing compounds is presented. In such formulation, the relevant terms of a molecular Hamiltonian for non-relativistic nuclei and relativistic electrons in the laboratory system are considered. Terms linear and bilinear in the nuclear rotation angular momentum and an external uniform magnetic field are considered within first and second order (relativistic) perturbation theory to obtain the rotational g-tensor. Relativistic effects are further analyzed by carrying out the linear response within the elimination of the small component expansion. Quantitative results for model systems HX (X=F, Cl, Br, I), XF (X=Cl, Br, I), and YH + (Y=Ne, Ar, Kr, Xe, Rn) are obtained both at the RPA and density functional theory levels of approximation. Relativistic effects are shown to be small for this molecular property. The relation between the rotational g-tensor and susceptibility tensor which is valid in the non-relativistic theory does not hold within the relativistic framework, and differences between both molecular parameters are analyzed for the model systems under study. It is found that the non-relativistic relation remains valid within 2% even for the heavy HI, IF, and XeH + systems. Only for the sixth-row Rn atom a significant deviation of this relation is found

  10. Theoretical studies of superconductivity in doped BaCoSO

    Science.gov (United States)

    Qin, Shengshan; Li, Yinxiang; Zhang, Qiang; Le, Congcong; Hu, Jiangping

    2018-06-01

    We investigate superconductivity that may exist in the doped BaCoSO, a multi-orbital Mott insulator with a strong antiferromagnetic ground state. The superconductivity is studied in both t-J type and Hubbard type multi-orbital models by mean field approach and random phase approximation (RPA) analysis. Even if there is no C 4 rotational symmetry, it is found that the system still carries a d-wave like pairing symmetry state with gapless nodes and sign changed superconducting order parameters on Fermi surfaces. The results are largely doping insensitive. In this superconducting state, the three {t_{{2_g}}} orbitals have very different superconducting form factors in momentum space. In particular, the intra-orbital pairing of the {d_{{x^2} - {y^2}}} orbital has an s-wave like pairing form factor. The two methods also predict very different pairing strength on different parts of Fermi surfaces. These results suggest that BaCoSO and related materials can be a new ground to test and establish fundamental principles for unconventional high temperature superconductivity.

  11. Canister displacement in KBS-3V. A theoretical study

    International Nuclear Information System (INIS)

    Boergesson, Lennart; Hernelind, Jan

    2006-02-01

    The vertical displacement of the canister in the KBS-3V concept has been studied in a number of consolidation and creep calculations using the FE-program ABAQUS. The creep model used for the calculations is based on Singh-Mitchell's creep theory, which has been adapted to and verified for the buffer material MX-80 in earlier tests. A porous elastic model with Drucker-Prager plasticity has been used for the consolidation calculations. For simplicity the buffer has been assumed to be water saturated from start. In one set of calculations only the consolidation and creep in the buffer without considering the interaction with the backfill was studied. In the other set of calculations the interaction with the backfill was included for a backfill consisting of an in situ compacted mixture of 30% bentonite and 70% crushed rock. The motivation to also study the behaviour of the buffer alone was that the final choice of backfill material and backfilling technique is not made yet so that set of calculations simulates a backfill that has identical properties with the buffer. The two cases represent two extreme cases, one with a backfill that has a low stiffness and the lowest allowable swelling pressure and one that has the highest possible swelling pressure and stiffness. The base cases in the calculations correspond to the final average density at saturation of 2,000 kg/m 3 with the expected swelling pressure of 7 MPa in a buffer. In order to study the sensitivity of the system to loss in bentonite mass and swelling pressure seven additional calculations were done with reduced swelling pressure down to 80 kPa corresponding to a density at water saturation of about 1,500 kg/m 3 . The calculations included two stages, where the first stage models the swelling and consolidation that takes place in order for the buffer to reach force equilibrium. This stage takes place during the saturation phase and the subsequent consolidation/swelling phase. The second stage models the

  12. Canister displacement in KBS-3V. A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Boergesson, Lennart [Clay Technology AB, Lund (Sweden); Hernelind, Jan [FEMTech AB, Vaesteraas (Sweden)

    2006-02-15

    The vertical displacement of the canister in the KBS-3V concept has been studied in a number of consolidation and creep calculations using the FE-program ABAQUS. The creep model used for the calculations is based on Singh-Mitchell's creep theory, which has been adapted to and verified for the buffer material MX-80 in earlier tests. A porous elastic model with Drucker-Prager plasticity has been used for the consolidation calculations. For simplicity the buffer has been assumed to be water saturated from start. In one set of calculations only the consolidation and creep in the buffer without considering the interaction with the backfill was studied. In the other set of calculations the interaction with the backfill was included for a backfill consisting of an in situ compacted mixture of 30% bentonite and 70% crushed rock. The motivation to also study the behaviour of the buffer alone was that the final choice of backfill material and backfilling technique is not made yet so that set of calculations simulates a backfill that has identical properties with the buffer. The two cases represent two extreme cases, one with a backfill that has a low stiffness and the lowest allowable swelling pressure and one that has the highest possible swelling pressure and stiffness. The base cases in the calculations correspond to the final average density at saturation of 2,000 kg/m{sup 3} with the expected swelling pressure of 7 MPa in a buffer. In order to study the sensitivity of the system to loss in bentonite mass and swelling pressure seven additional calculations were done with reduced swelling pressure down to 80 kPa corresponding to a density at water saturation of about 1,500 kg/m{sup 3}. The calculations included two stages, where the first stage models the swelling and consolidation that takes place in order for the buffer to reach force equilibrium. This stage takes place during the saturation phase and the subsequent consolidation/swelling phase. The second stage

  13. Thermochemical study of cyanopyrazines: Experimental and theoretical approaches

    International Nuclear Information System (INIS)

    Miranda, Margarida S.; Morais, Victor M.F.; Matos, M. Agostinha R.

    2006-01-01

    The standard (p - bar =0.1MPa) molar energy of combustion, at T=298.15K, of crystalline 2,3-dicyanopyrazine was measured by static bomb calorimetry, in oxygen atmosphere. The standard molar enthalpy of sublimation, at T=298.15K, was obtained by Calvet Microcalorimetry, allowing the calculation of the standard molar enthalpy of formation of the compound, in the gas phase, at T=298.15K: Δ f H m - bar (g)=(518.7+/-3.4)kJ.mol -1 . In addition, the geometries of all cyanopyrazines were obtained using density functional theory with the B3LYP functional and two basis sets: 6-31G* and 6-311G**. These calculations were then used for a better understanding of the relation between structure and energetics of the cyanopyrazine systems. These calculations also reproduce measured standard molar enthalpies of formation with some accuracy and do provide estimates of this thermochemical parameter for those compounds that could not be studied experimentally, namely the tri- and tetracyanopyrazines: the strong electron withdrawing cyano group on the pyrazine ring makes cyanopyrazines highly destabilized compounds

  14. Theoretical and experimental studies of a magnetically actuated valveless micropump

    International Nuclear Information System (INIS)

    Ashouri, Majid; Shafii, Mohammad Behshad; Moosavi, Ali

    2017-01-01

    This paper presents the prototype design, fabrication, and characterization of a magnetically actuated micropump. The pump body consists of three nozzle/diffuser elements and two pumping chambers connected to the ends of a flat-wall pumping cylinder. A cylindrical permanent magnet placed inside the pumping cylinder acts as a piston which reciprocates by using an external magnetic actuator driven by a motor. The magnetic piston is covered by a ferrofluid to provide self-sealing capability. A prototype composed of three bonded layers of polymethyl-methacrylate (PMMA) has been fabricated. Water has been successfully pumped at pressures of up to 750 Pa and flow rates of up to 700 µ l min −1 while working at the piston actuation frequency of 4 and 5 Hz, respectively. 3D numerical simulations are also carried out to study the performance of the pump. The best experimental and numerical volumetric efficiency of the pump are about 7 and 8%, respectively, at the piston speed of 0.03 m s −1 . The contactless external actuation feature of the design enables integration of the pump with other PMMA-based microfluidic systems with low cost and disposability. (paper)

  15. Theoretical study of bismuth-doped cadmium telluride

    Science.gov (United States)

    Menendez-Proupin, E.; Rios-Gonzalez, J. A.; Pena, J. L.

    Cadmium telluride heavily doped with bismuth has been proposed as an absorber with an intermediate band for solar cells. Increase in the photocurrent has been shown recently, although the overall cell efficiency has not improved. In this work, we study the electronic structure and the formation energies of the defects associated to bismuth impurities. We have performed electronic structure calculations within generalized density functional theory, using the exchange-correlation functional HSE(w) , where the range-separation parameter w has been tuned to reproduce the CdTe bandgap. Improving upon previous reports, we have included the spin-orbit interaction, which modifies the structure of the valence band and the energy levels of bismuth. We have found that interstitial Bi (Bii) tends to occupy Cd vacancies, cadmium substitution (BiCd) creates single donor level, while tellurium substitution (BiTe) is a shallow single acceptor. We investigate the interaction between these point defects and how can they be combined to create a partially filled intermediate band. Supported by FONDECYT Grant 1130437, CONACYT-SENER SUSTENTABILIDAD ENERGETICA/project CeMIE-Sol PY-207450/25 and PY-207450/26. JARG acknowledges CONACYT fellowship for research visit. Powered@NLHPC (ECM-02).

  16. Theoretical and numerical study of heat transfer deterioration in HPLWR

    International Nuclear Information System (INIS)

    Palko, D.; Anglart, H.

    2007-01-01

    A numerical investigation of the Heat Transfer Deterioration (HTD) phenomena is performed using the low-Re k - ω turbulence model. Steady state Reynolds-averaged Navier-Stokes equations are solved together with equations for the transport of enthalpy and turbulence. Equations are solved for the supercritical water flow at different pressures, using water properties from the standard IAPWS tables. All cases are extensively validated against experimental data. The influence of buoyancy on the HTD is demonstrated for different mass flow rates in the heated pipes. Numerical results prove that the RANS low-Re turbulence modeling approach is fully capable to simulate the heat transfer in pipes with the water flow at supercritical pressures. A study of buoyancy influence shows that for the low mass flow rates of coolant, the influence of buoyancy forces on the heat transfer in heated pipes is significant. For the high flow rates, buoyancy influence could be neglected and there are clearly other mechanisms causing the decrease in heat transfer at high coolant flow rates. (author)

  17. Theoretical study of the properties of BH3NH3

    International Nuclear Information System (INIS)

    Binkley, J.S.; Thorne, L.R.

    1983-01-01

    Borane monoammoniate (BH 3 NH 3 ) has been studied using several ab initio electronic structure methods and Gaussian basis sets. Equilibrium geometries have been computed at the Hartree--Fock level and, using the electron-correlated Moller--Plesset perturbation method, carried out to third order (MP3) with double-zeta polarized quality basis sets. The computed MP3 geometry is in close agreement with recent microwave data; electron correlation is found to be necessary for a proper description of the B--N distance. Hartree--Fock dipole moments and harmonic vibrational frequencies are presented and discussed. Moller--Plesset perturbation theory carried out to fourth order with triple-zeta plus polarization basis sets is used to compute a B--N dissociation energy of 34.7 kcal mol -1 and a (Hartree--Fock zero-point corrected) rotational barrier of 2.065 kcal mol -1 , which is in excellent agreement with the experimental value. Analysis of the dissociation energy as a function of perturbation order indicates that terms involving triple and quadruple substitutions are required in the dissociation energy

  18. Theoretical study for the interlamellar aminoalcohol functionalization of kaolinite

    International Nuclear Information System (INIS)

    Hou, Xin-Juan; Li, Huiquan; Liu, Qinfu; Cheng, Hongfei; He, Peng; Li, Shaopeng

    2015-01-01

    Graphical abstract: - Highlights: • The results indicated that aminoalcohols exist with a mixing of intercalation and grafting. • Aminoalcohols can form strong hydrogen bonds with Al octahedral sheet. • The interaction between aminoalcohols and Si tetrahedral sheet are mainly attributed by vdW force. • Aminoalcohols grafting or intercalating on kaolinite have strong reactivity as electron donors. - Abstract: Fundamental problems related to aminoalcohols intercalating on kaolinite were investigated by using density functional theory method. This study examines the adsorption modes of diethanolamine and triethanolamine on kaolinite, the role of hydrogen bonds and van der Waals (vdW) forces between aminoalcohols and interlayer of kaolinite, and the change of molecular orbital occupancies of functionalized kaolinite. Results show that functionalized kaolinite is physically intercalated and covalently grafted by aminoalcohols. Non-covalent interaction analysis provides a visualized description that intercalated aminoalcohols form strong hydrogen bonds with Al octahedral sheet, and the interaction between aminoalcohols and Si tetrahedral sheet is mainly attributed to weak vdW force. The analysis of molecular orbital occupancies for kaolinite complex showed that the functionalized kaolinite has strong chemical reactivity as electron donors on the sites of grafted or intercalated aminoalcohols for further chemical reaction with other materials

  19. Theoretical study of impurity effects in iron-based superconductors

    Science.gov (United States)

    Navarro Gastiasoro, Maria; Hirschfeld, Peter; Andersen, Brian

    2013-03-01

    Several open questions remain unanswered for the iron-based superconductors (FeSC), including the importance of electronic correlations and the symmetry of the superconducting order parameter. Motivated by recent STM experiments which show a fascinating variety of resonant defect states in FeSC, we adopt a realistic five-band model including electronic Coulomb correlations to study local effects of disorder in the FeSC. In order to minimize the number of free parameters, we use the pairing interactions obtained from spin-fluctuation exchange to determine the homogeneous superconducting state. The ability of local impurity potentials to induce resonant states depends on their scattering strength Vimp; in addition, for appropriate Vimp, such states are associated with local orbital- and magnetic order. We investigate the density of states near such impurities and show how tunneling experiments may be used to probe local induced order. In the SDW phase, we show how C2 symmetry-breaking dimers are naturally formed around impurities which also form cigar-like (pi,pi) structures embedded in the (pi,0) magnetic bulk phase. Such electronic dimers have been shown to be candidates for explaining the so-called nematogens observed previously by QPI in Co-doped CaFe2As2.

  20. Enhanced piezoelectricity of monolayer phosphorene oxides: a theoretical study.

    Science.gov (United States)

    Yin, Huabing; Zheng, Guang-Ping; Gao, Jingwei; Wang, Yuanxu; Ma, Yuchen

    2017-10-18

    Two-dimensional (2D) piezoelectric materials have potential applications in miniaturized sensors and energy conversion devices. In this work, using first-principles simulations at different scales, we systematically study the electronic structures and piezoelectricity of a series of 2D monolayer phosphorene oxides (POs). Our calculations show that the monolayer POs have tunable band gaps along with remarkable piezoelectric properties. The calculated piezoelectric coefficient d 11 of 54 pm V -1 in POs is much larger than those of 2D transition metal dichalcogenide monolayers and the widely used bulk α-quartz and AlN, and almost reaches the level of the piezoelectric effect in recently discovered 2D GeS. Furthermore, two other considerable piezoelectric coefficients, i.e., d 31 and d 26 with values of -10 pm V -1 and 21 pm V -1 , respectively, are predicted in some monolayer POs. We also examine the correlation between the piezoelectric coefficients and energy stability. The enhancement of piezoelectricity for monolayer phosphorene by oxidation will broaden the applications of phosphorene and phosphorene derivatives in nano-sized electronic and piezotronic devices.

  1. Benchmark thermodynamic properties of methylanisoles: Experimental and theoretical study

    International Nuclear Information System (INIS)

    Emel’yanenko, Vladimir N.; Zaitseva, Ksenia V.; Agapito, Filipe; Martinho Simões, José A.; Verevkin, Sergey P.

    2015-01-01

    Highlights: • Thermochemistry of 2-, 3-, and 4-methylanisoles was studied. • Liquid state enthalpies of formation were measured by calorimetry. • Vaporisation enthalpies were derived from by transpiration method. • Ab initio enthalpies of formation are in excellent agreement with experiment. • A new paradigm for obtaining thermochemistry of liquid compounds was suggested. - Abstract: Accurate standard molar enthalpy of formation values in the liquid phase can be obtained by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporisation. The procedure is illustrated for 2-, 3-, and 4-methyl-anisoles. Using the W1-F12 and G4 quantum-chemical methods, the gas-phase enthalpies of formation of these compounds at T = 298.15 K were computed. Molar enthalpies of vaporisation for these isomers were measured by the transpiration method. Combining the experimental and the high-level ab initio values, the standard molar enthalpies of formation in the liquid phase for all three isomers were derived and compared with those determined for 2- and 4-methyl-anisoles by using combustion calorimetry

  2. Experimental and theoretical studies of metal vapor atoms

    International Nuclear Information System (INIS)

    Whitfield, S.B.; Wehlitz, Ralf; Martins, Michael

    2004-01-01

    Employing electron spectrometry in conjunction with tuneable synchrotron radiation, we will present a detailed examination of the photoionization dynamics of selected metal vapor atoms. In particular, this paper will focus on the relative partial cross sections of the atomic Li K-shell main and satellite (ionization with excitation) photoelectron lines in the region of the strong 1snln'l' autoionizing transitions, the atomic Sc 3d, 4s main and satellite photoelectron lines in the region of the 3p→3d giant resonance, and also the atomic Fe 3d, 4s main and satellite photoelectron lines in the same resonance region. Our experimental data for Sc and Fe will be compared to our state-of-the-art calculations based on the superposition of configuration method developed by Cowan (The Theory of Atomic Structure and Spectra. University of California Berkeley Press, Berkeley and Los Angeles, 1981). Our partial cross section measurements for Li and Sc will be complemented with measurements of the angular distribution parameter, β. In addition, our Li data will also be compared with recent R-matrix calculations (Phys. Rev. 57 (1998) 1045). In the case of Fe, we will also address the term dependent behavior of the partial cross sections on resonance. These results will highlight what can be achieved with today's technology and point the way towards future endeavors in the study of the photoionization dynamics of open-shell metal vapor atoms

  3. Theoretical design study of the MSFC wind-wheel turbine

    Science.gov (United States)

    Frost, W.; Kessel, P. A.

    1982-01-01

    A wind wheel turbine (WWT) is studied. Evaluation of the probable performance, possible practical applications, and economic viability as compared to other conventional wind energy systems is discussed. The WWT apparatus is essentially a bladed wheel which is directly exposed to the wind on the upper half and exposed to wind through multiple ducting on the lower half. The multiple ducts consist of a forward duct (front concentrator) and two side ducts (side concentrators). The forced rotation of the wheel is then converted to power through appropriate subsystems. Test results on two simple models, a paper model and a stainless steel model, are reported. Measured values of power coefficients over wind speeds ranging from 4 to 16 m/s are given. An analytical model of a four bladed wheel is also developed. Overall design features of the wind turbine are evaluated and discussed. Turbine sizing is specified for a 5 and 25 kW machine. Suggested improvements to the original design to increase performance and performance predictions for an improved WWT design are given.

  4. Study of kinetics and mechanism of diazo compound reactions using nuclear chemical polarization

    International Nuclear Information System (INIS)

    Gragerov, I.P.; Levit, A.F.; Kiprianova, L.A.; Buchachenko, A.L.; Sterleva, T.G.

    1975-01-01

    It has been established that at the rate-determining steps of the radical reactions in which aniline interacts with isoamyl nitrite and substituted diazo salts interact with sodium methylate, tertiary fatty amines, or phosphinic acid, no transfer of a single electron occurs. The processes of single electron transfer do not seem to play a decisive role in the kinetics of most transformations of diazo compounds. Chemical nuclear polarization is shown to be suitable for kinetic studies of fast radical processes

  5. Gravimetric and conductometric studies of the sedimentation kinetics in aqueous dispersions of kaoline

    International Nuclear Information System (INIS)

    Bulavyin, L.A.; Khrapatij, S.V.; Koval'chuk, V.Yi.; Klepko, V.V.; Lebovka, M.Yi.

    2006-01-01

    Using gravimetric and conductometric methods, the sedimentation kinetics in aqueous suspensions of Alekseev kaoline has been studied for pH value range from 4 to 10. It has been found that pH increasing leads to the decreasing of mean radii of flocks linearly. We found that sedimentation kinetics for intermediate pH values can be described by scaling equations that crossover time defined transition from a gravitational mechanism of deposition to the diffusion one

  6. A study of sodium oxide crystallization mechanisms and kinetics in cold traps

    International Nuclear Information System (INIS)

    Latge, C.

    1984-04-01

    After showing up the present lack of data on crystallization mechanisms and kinetics, a number of tests were conducted on a sodium test loop equipped with two experimental cold traps. The effects of several geometric and thermohydraulic parameters on purification efficiency were also studied. The test results were used to develop a simulation model. An optimization code based on the model can be used to determine the nucleation and growth kinetics

  7. Disclosure of minor mental health problems: an exploratory theoretical study.

    Science.gov (United States)

    Williams, B; Healy, D

    2001-07-01

    The aim of this study was to explore people's experiences, concerns and beliefs about disclosing minor mental health problems by focusing on the ways in which such disclosures are interpreted. Approximately half of people with mental health problems do not seek help. The decision to consult represents just one aspect of the process of revealing one's illness to others. People with mental health problems are known to be reluctant to reveal the existence of those problems through fear of how others might then view them. A qualitative approach was employed. In-depth interviews were carried out with 47 users and nonusers of community mental health services. Interviews were tape-recorded, transcribed and analysed. The data suggest that when people reveal minor mental health problems others interpret these in relation to a number of perceived contextual factors. These include perceptions of the severity and duration of any possible causes, the inner 'strength' of the person, the expected ability of the person to either solve or suppress the experience, and the form and context of the expression itself. The data presented included individuals who were seeking help for relatively 'minor' mental health problems (primarily depression and anxiety) and individuals who had no current mental health problems but routinely managed expressions of their own emotions. Throughout the data there appeared to be no distinct difference between these two groups other than one of the severity of psychological experience. The key elements involved in the interpretation of people's expressions of sadness were essentially the same as those involved in the interpretation of expressions of depression. An appreciation of these contextual factors influencing the interpretation and disclosure of minor mental health problems may aid the development of more person-centred mental health services and inform the content of health education in the mental health field.

  8. Theoretical studies in nuclear reactions and nuclear structure. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    1992-05-01

    Research in the Maryland Nuclear Theory Group focusses on problems in four basic areas of current relevance. Hadrons in nuclear matter; the structure of hadrons; relativistic nuclear physics and heavy ion dynamics and related processes. The section on hadrons in nuclear matter groups together research items which are aimed at exploring ways in which the properties of nucleons and the mesons which play a role in the nuclear force are modified in the nuclear medium. A very interesting result has been the finding that QCD sum rules supply a new insight into the decrease of the nucleon`s mass in the nuclear medium. The quark condensate, which characterizes spontaneous chiral symmetry breaking of the late QCD vacuum, decreases in nuclear matter and this is responsible for the decrease of the nucleon`s mass. The section on the structure of hadrons contains progress reports on our research aimed at understanding the structure of the nucleon. Widely different approaches are being studied, e.g., lattice gauge calculations, QCD sum rules, quark-meson models with confinement and other hedgehog models. A major goal of this type of research is to develop appropriate links between nuclear physics and QCD. The section on relativistic nuclear physics represents our continuing interest in developing an appropriate relativistic framework for nuclear dynamics. A Lorentz-invariant description of the nuclear force suggests a similar decrease of the nucleon`s mass in the nuclear medium as has been found from QCD sum rules. Work in progress extends previous successes in elastic scattering to inelastic scattering of protons by nuclei. The section on heavy ion dynamics and related processes reports on research into the e{sup +}e{sup {minus}} problem and heavy ion dynamics.

  9. Theoretical studies in nuclear reactions and nuclear structure

    Energy Technology Data Exchange (ETDEWEB)

    1992-05-01

    Research in the Maryland Nuclear Theory Group focusses on problems in four basic areas of current relevance. Hadrons in nuclear matter; the structure of hadrons; relativistic nuclear physics and heavy ion dynamics and related processes. The section on hadrons in nuclear matter groups together research items which are aimed at exploring ways in which the properties of nucleons and the mesons which play a role in the nuclear force are modified in the nuclear medium. A very interesting result has been the finding that QCD sum rules supply a new insight into the decrease of the nucleon's mass in the nuclear medium. The quark condensate, which characterizes spontaneous chiral symmetry breaking of the late QCD vacuum, decreases in nuclear matter and this is responsible for the decrease of the nucleon's mass. The section on the structure of hadrons contains progress reports on our research aimed at understanding the structure of the nucleon. Widely different approaches are being studied, e.g., lattice gauge calculations, QCD sum rules, quark-meson models with confinement and other hedgehog models. A major goal of this type of research is to develop appropriate links between nuclear physics and QCD. The section on relativistic nuclear physics represents our continuing interest in developing an appropriate relativistic framework for nuclear dynamics. A Lorentz-invariant description of the nuclear force suggests a similar decrease of the nucleon's mass in the nuclear medium as has been found from QCD sum rules. Work in progress extends previous successes in elastic scattering to inelastic scattering of protons by nuclei. The section on heavy ion dynamics and related processes reports on research into the e{sup +}e{sup {minus}} problem and heavy ion dynamics.

  10. Absorption heat cycles. An experimental and theoretical study

    International Nuclear Information System (INIS)

    Abrahamsson, K.

    1993-09-01

    A flow sheeting programme, SHPUMP, was developed for simulating different absorption heat cycles. The programme consists of ten different modules which allow the user to construct his own absorption cycle. The ten modules configurate evaporators, absorbers, generators, rectifiers, condensers, solution heat exchangers, pumps, valves, mixers and splitters. Seven basic and well established absorption cycles are available in the configuration data base of the programme. A new Carnot model is proposed heat cycles. Together with exergy analysis, general equations for the Carnot coefficient of performance and equations for thermodynamic efficiency, exergetic efficiency and exergy index, are derived, discussed and compared for both absorption heat pumps and absorption heat transformers. Utilizing SHPUMP, simulation results are presented for different configurations where absorption heat cycles are suggested to be incorporated in three different unit operations within both pulp and paper and oleochemical industries. One of the application studies reveled that an absorption heat transformer incorporated with an evaporation plant in a major pulp and paper industry, would save 18% of the total prime energy consumption in one of the evaporation plants. It was also concluded that installing an absorption heat pump in a paper drying plant would result in steam savings equivalent to 12 MW. An experimental absorption heat transformer unit operating with self-circulation has been modified and thoroughly tested. A reference heat transformer plant has been designed and installed in a major pulp and paper mill where it is directly incorporated with one of the evaporation plants. Preliminary plant operation data are presented. 72 refs, 63 figs, 33 tabs

  11. Theoretical Study of Amplitude Modulation Application during Radio Frequency Electrocoagulation

    Directory of Open Access Journals (Sweden)

    V. A. Karpuhin

    2015-01-01

    Full Text Available This article concerns the investigation results of influence of the amplitude-modulated acting signal parameters on the thermoelectric characteristics of biological tissues for a specified geometry of the working electrode section during RF mono-polar electrocoagulation. The geometric model ‘electrode - a biological tissue’ was suggested to study the distribution of power and temperature fields in biological tissue during mono-polar coagulation. The model of biological tissue is represented as a cylinder and the needle electrode is an ellipsoid immersed in the biological tissue. The heat and quasi-electrostatics equations are used as a mathematical model. These equations are solved in Comsol Multiphysics environment.As a result, we have got the following findings: the technique of calculating parameters of the PAM acting signal which has a fixed carrier frequency for the needle electrode of a specified geometry and the immersion depth in biological tissues is suggested. Parameters of PAM signal are determined for this electrode geometry. These parameters provide a 60 ... 80°C heating range of biological tissues near the working part of the tool for different amplitudes of acting signal during RF coagulation. It has been found out that both the temperature and the relaxation frequency of biological tissue depend on exposure time for the needle electrode of a specified geometry and immersion depth of the working part of tool into biological tissue.It is shown that the relaxation frequency of the biological tissue, subjected to the radiofrequency pulses, linearly depends on its heating temperature and can be used as a numerical criterion for maintaining the specified temperature conditions. It is found that the relaxation frequency of the biological tissue depends on the contact area of the tool working part and biological tissues. To reduce this dependence it is necessary to provide automatic current control of the output action.

  12. Theoretical studies in nuclear reactions and nuclear structure

    International Nuclear Information System (INIS)

    1992-05-01

    Research in the Maryland Nuclear Theory Group focusses on problems in four basic areas of current relevance. Hadrons in nuclear matter; the structure of hadrons; relativistic nuclear physics and heavy ion dynamics and related processes. The section on hadrons in nuclear matter groups together research items which are aimed at exploring ways in which the properties of nucleons and the mesons which play a role in the nuclear force are modified in the nuclear medium. A very interesting result has been the finding that QCD sum rules supply a new insight into the decrease of the nucleon's mass in the nuclear medium. The quark condensate, which characterizes spontaneous chiral symmetry breaking of the late QCD vacuum, decreases in nuclear matter and this is responsible for the decrease of the nucleon's mass. The section on the structure of hadrons contains progress reports on our research aimed at understanding the structure of the nucleon. Widely different approaches are being studied, e.g., lattice gauge calculations, QCD sum rules, quark-meson models with confinement and other hedgehog models. A major goal of this type of research is to develop appropriate links between nuclear physics and QCD. The section on relativistic nuclear physics represents our continuing interest in developing an appropriate relativistic framework for nuclear dynamics. A Lorentz-invariant description of the nuclear force suggests a similar decrease of the nucleon's mass in the nuclear medium as has been found from QCD sum rules. Work in progress extends previous successes in elastic scattering to inelastic scattering of protons by nuclei. The section on heavy ion dynamics and related processes reports on research into the e + e - problem and heavy ion dynamics

  13. Experimental and theoretical studies of d-dot

    International Nuclear Information System (INIS)

    Ishida, Takekazu; Fujii, Masaki; Abe, Taiji; Yamamoto, Masuo; Miki, Shigehito; Kawamata, Shuichi; Satoh, Kazuo; Yotsuya, Tsutomu; Kato, Masaru; Machida, Masahiko; Koyama, Tomio; Terashima, Takahito; Tsukui, Shigeki; Adachi, Motoaki

    2006-01-01

    We propose the idea of d-dot, where a d-wave superconducting dot is embedded in s-wave matrix. Spontaneous half vortices should appear in the four corners of the d-dot [M. Kato, M. Ako, M. Machida, T. Koyama, T. Ishida, Physica C 412-414 (2004) 352; M. Ako, M. Kato, M. Machida, T. Koyama, T. Ishida, Physica C 412-414 (2004) 544; M. Fujii, T. Abe, H. Yoshikawa, S. Miki, S. Kawamata, K. Satoh, T. Yotsuya, M. Kato, M. Machida, T. Koyama, T. Terashima, S. Tsukui, M. Adachi, T. Ishida, Physica C 426-431 (2005) 104]. Symmetric geometry and the fourfold symmetry of the d-dot would be suitable as a building block for constructing the novel physical systems. The phase dynamics of a closed 0-π junction, which can be realized in a small d x 2 -y 2 -dot, is mapped on a quantum two-level system when the system size is small enough. Using two-component Ginzburg-Landau equation, we study the physical properties of d-dots systematically. We prepare epitaxial YBa 2 Cu 3 O 7 (YBCO) films of thickness 100nm on SrTiO 3 substrates using a laser ablation apparatus. The d-dot is fabricated by a photolithography, electron beam lithography EB and an electron cyclotron resonance (ECR) etching, a focused ion beam microscope, and a lift-off technique. Local vortex profile is investigated using a SQUID microscope when d-dot is cooled in zero field

  14. Experimental and theoretical study of radon levels in a house

    International Nuclear Information System (INIS)

    Ameon, R.; Dupuis, M.; Marie, L.; Diez, O.; LionS, J.; Tymen, G.

    2006-01-01

    Full text of publication follows: Radon being a radioactive gas of natural origin is omnipresent everywhere at the surface of earth. It is created by the radium decay issued from the uranium contained in the earth crust and more specifically in granitic and volcanic subsoils. Because of the dilution due to air masses, its concentration in open air is low. On the other hand, radon may accumulate in the confined atmosphere of buildings and achieve high concentration levels. Across France, it has been estimated that 300 000 individual dwellings present concentration higher than the French reference level of 400 Bq.m -3 and that 60 000 other ones would exhibit concentration above 1 000 Bq.m -3 , the French warning threshold. Indoor radon concentration may vary significantly for various reasons, including design of buildings, radium content and texture of the soil in contact with the building's slab and walls, the under pressure value between the inside and outside and the fresh air supply rate. These considerations have led the I.R.S.N. to develop a code called R.A.D.O.N. 2 for conducting simple and methodical studies of indoor radon concentrations, to take into account the above-mentioned factors. But, the achievement of an effective diagnosis and risk management -aiding tool requires to first check its validity on the phenomenological model at the origin of the code. A 3-year experimental follow-up was, thus, conducted within an unoccupied house built on an uranium-bearing geological formation. After characterization of the subsoil, the instrumentation was implemented on site to continuously monitor the following parameters: - the radon source term in the building (exhalation rate of 222 Rn at the ground/building interface and at soil surface, radon concentration at the soil and in outdoor air), - the radon penetration by advection (differential pressure in the house basement), - the driving mechanisms for natural ventilation in the house (weather conditions, indoor

  15. Experimental and theoretical study of radon levels in a house

    Energy Technology Data Exchange (ETDEWEB)

    Ameon, R.; Dupuis, M.; Marie, L.; Diez, O.; LionS, J. [Institute for Radiological Protection and Nuclear Safety, Fontenay-aux-roses (France); Tymen, G. [LARAAH, Universite de Bretagne Occidentale, Brest (France)

    2006-07-01

    Full text of publication follows: Radon being a radioactive gas of natural origin is omnipresent everywhere at the surface of earth. It is created by the radium decay issued from the uranium contained in the earth crust and more specifically in granitic and volcanic subsoils. Because of the dilution due to air masses, its concentration in open air is low. On the other hand, radon may accumulate in the confined atmosphere of buildings and achieve high concentration levels. Across France, it has been estimated that 300 000 individual dwellings present concentration higher than the French reference level of 400 Bq.m{sup -3} and that 60 000 other ones would exhibit concentration above 1 000 Bq.m{sup -3}, the French warning threshold. Indoor radon concentration may vary significantly for various reasons, including design of buildings, radium content and texture of the soil in contact with the building's slab and walls, the under pressure value between the inside and outside and the fresh air supply rate. These considerations have led the I.R.S.N. to develop a code called R.A.D.O.N. 2 for conducting simple and methodical studies of indoor radon concentrations, to take into account the above-mentioned factors. But, the achievement of an effective diagnosis and risk management -aiding tool requires to first check its validity on the phenomenological model at the origin of the code. A 3-year experimental follow-up was, thus, conducted within an unoccupied house built on an uranium-bearing geological formation. After characterization of the subsoil, the instrumentation was implemented on site to continuously monitor the following parameters: - the radon source term in the building (exhalation rate of {sup 222}Rn at the ground/building interface and at soil surface, radon concentration at the soil and in outdoor air), - the radon penetration by advection (differential pressure in the house basement), - the driving mechanisms for natural ventilation in the house (weather

  16. Centrifugation. A theoretical study of oxygen enrichment by centrifugation

    Energy Technology Data Exchange (ETDEWEB)

    Kierkegaard, P.; Raetz, E.

    1998-12-01

    In the present paper we first investigate what happens if we fill a cylinder with air, close it and rotate it. The results show that no matter which peripheral speed is used, it is not possible by means of the radial separation effect alone, to enrich the oxygen concentration from the previous 21% to more then 23.3%, which is of no practical value. In case of a too low enrichment in one centrifuge, the wanted material from this centrifuge can be used as an input for a second centrifuge and so on, in this way forming a cascade of centrifuges. Oxygen will be enriched in each step, until the desired concentration is reached. Cascading was the technology in the very beginning by enrichment plants for uraniumhexaflouride, used for atomic weapons and nuclear power plants. In this study we try to avoid cascading by aiming for higher separation factors. Therefore, we next investigate the possibilities of using a countercurrent centrifuge where in principle the enriched gas is subjected to several centrifugation in the same centrifuge. The calculations show, that in this way it is possible to produce nearly a 100% pure oxygen (polluted with some heavier molecules like argon) in one machine. Our third step was to calculate the amount of oxygen produced per hour. Using a countercurrent centrifuge of the Zippe type, 100 cm high and 20 cm in diameter, it is or will be possible in the near future to produce 17 g enriched air per hour enriched to 50% oxygen. That corresponds to processing 1 m{sup 3} atmospherical air in the period of approximately 24 hours. This is not very impressive. Our fourth step was to estimate the amount of power used for producing this amount of oxygen. A rough, but complicated, estimate shows that the power consumption at the production level will be about the double of the consumption used today. The overall conclusion is, that centrifugation as a production method for oxygen (or nitrogen) will not be competitive with the currently used method in the

  17. Theoretical Study of Spin Crossover in 30 Iron Complexes.

    Science.gov (United States)

    Kepp, Kasper P

    2016-03-21

    Iron complexes are important spin crossover (SCO) systems with vital roles in oxidative metabolism and promising technological potential. The SCO tendency depends on the free energy balance of high- and low-spin states, which again depends on physical effects such as dispersion, relativistic effects, and vibrational entropy. This work studied 30 different iron SCO systems with experimentally known thermochemical data, using 12 different density functionals. Remarkably general entropy-enthalpy compensation across SCO systems was identified (R = 0.82, p = 0.002) that should be considered in rational SCO design. Iron(II) complexes displayed higher ΔH and ΔS values than iron(III) complexes and also less steep compensation effects. First-coordination sphere ΔS values computed from numerical frequencies reproduce most of the experimental entropy and should thus be included when modeling spin-state changes in inorganic chemistry (R = 0.52, p = 3.4 × 10(-3); standard error in TΔS ≈ 4.4 kJ/mol at 298 K vs 16 kJ/mol of total TΔS on average). Zero-point energies favored high-spin states by 9 kJ/mol on average. Interestingly, dispersion effects are surprisingly large for the SCO process (average: 9 kJ/mol, but up to 33 kJ/mol) and favor the more compact low-spin state. Relativistic effects favor low-spin by ∼9 kJ/mol on average, but up to 24 kJ/mol. B3LYP*, TPSSh, B2PLYP, and PW6B95 performed best for the typical calculation scheme that includes ZPE. However, if relativistic and dispersion effects are included, only B3LYP* remained accurate. On average, high-spin was favored by LYP by 11-15 kJ/mol relative to other correlation functionals, and by 4.2 kJ/mol per 1% HF exchange in hybrids. 13% HF exchange was optimal without dispersion, and 15% was optimal with all effects included for these systems.

  18. Theoretical study of ultraviolet induced photodissociation dynamics of sulfuric acid

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Tatsuhiro; Ohta, Ayumi; Suzuki, Tomoya; Ikeda, Kumiko [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Danielache, Sebastian O. [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan); Earth-Life Science Institute (ELSI), Tokyo Institute of Technology (Japan); Department of Environmental Science and Techonology, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yoohama 226-8502 (Japan); Nanbu, Shinkoh, E-mail: shinkoh.nanbu@sophia.ac.jp [Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-Cho, Chiyoda-ku, Tokyo 102-8554 (Japan)

    2015-05-01

    Highlights: • Photodissociation dynamics of H{sub 2}SO{sub 4} at low-lying electronically excited states were investigated. • Photochemical processes were simulated by on-the-fly ab initio MD. • Sulfuric acid after the excitation to the S{sub 1} state dissociated to HSO{sub 4}(1{sup 2}A″) + H({sup 2}S). • Sulfuric acid after the excitation to the S{sub 2} state dissociated to HSO{sub 4}(2{sup 2}A″) + H({sup 2}S). • The energy region of the UV spectra where NMD fractionation may occur is predicted. - Abstract: Photodissociation dynamics of sulfuric acid after excitation to the first and second excited states (S{sub 1} and S{sub 2}) were studied by an on-the-fly ab initio molecular dynamics simulations based on the Zhu–Nakamura version of the trajectory surface hopping (ZN-TSH). Forces acting on the nuclear motion were computed on-the-fly by CASSCF method with Dunning’s augmented cc-pVDZ basis set. It was newly found that the parent molecule dissociated into two reaction-channels (i) HSO{sub 4}(1{sup 2}A″) + H({sup 2}S) by S{sub 1}-excitation, and (ii) HSO{sub 4}(2{sup 2}A″) + H({sup 2}S) by S{sub 2}-excitation. The direct dissociation dynamics yield products different from the SO{sub 2} + 2OH fragments often presented in the literature. Both channels result in the same product and differs only in the electronic state of the HSO{sub 4} fragment{sub .} The trajectories running on S{sub 2} do not hop with S{sub 0} and a nonadiabatic transition happens at the S{sub 2}–S{sub 1} conical intersection located at a longer OH bond-length than the S{sub 1}–S{sub 0} intersection producing an electronic excited state (2{sup 2}A″) of HSO{sub 4} product.

  19. Experimental and Theoretical Study of Microturbine-Based BCHP System

    International Nuclear Information System (INIS)

    Fairchild, P.D.

    2001-01-01

    On-site and near-site distributed power generation (DG), as part of a Buildings Cooling, Heating and Power (BCHP) system, brings both electricity and waste heat from the DG sources closer to the end user's electric and thermal loads. Consequently, the waste heat can be used as input power for heat-activated air conditioners, chillers, and desiccant dehumidification systems; to generate steam for space heating; or to provide hot water for laundry, kitchen, cleaning services and/or rest rooms. By making use of what is normally waste heat, BCHP systems meet a building's electrical and thermal loads with a lower input of fossil fuel, yielding resource efficiencies of 40 to 70% or more. To ensure the success of BCHP systems, interactions of a DG system-such as a microturbine and thermal heat recovery units under steady-state modes of operation with various exhaust back pressures-must be considered. This article studies the performance and emissions of a 30-kW microturbine over a range of design and off-design conditions in steady-state operating mode with various back pressures. In parallel with the experimental part of the project, a BCHP mathematical model was developed describing basic thermodynamic and hydraulic processes in the system, heat and material balances, and the relationship of the balances. to the system configuration. The model can determine the efficiency of energy conversion both for an individual microturbine unit and for the entire BCHP system for various system configurations and external loads. Based on actual data Tom a 30-kW microturbine, linear analysis was used to obtain an analytical relationship between the changes in the thermodynamic and hydraulic parameters of the system. The actual data show that, when the backpressure at the microturbine exhaust outlet is increased to the maximum of 7 in. WC (0.017 atm), the microturbine's useful power output decreases by from 3.5% at a full power setting of 30 kW to 5.5% at a one-third power setting (10

  20. A Theoretical and Experimental Study of DNA Self-assembly

    Science.gov (United States)

    Chandran, Harish

    The control of matter and phenomena at the nanoscale is fast becoming one of the most important challenges of the 21st century with wide-ranging applications from energy and health care to computing and material science. Conventional top-down approaches to nanotechnology, having served us well for long, are reaching their inherent limitations. Meanwhile, bottom-up methods such as self-assembly are emerging as viable alternatives for nanoscale fabrication and manipulation. A particularly successful bottom up technique is DNA self-assembly where a set of carefully designed DNA strands form a nanoscale object as a consequence of specific, local interactions among the different components, without external direction. The final product of the self-assembly process might be a static nanostructure or a dynamic nanodevice that performs a specific function. Over the past two decades, DNA self-assembly has produced stunning nanoscale objects such as 2D and 3D lattices, polyhedra and addressable arbitrary shaped substrates, and a myriad of nanoscale devices such as molecular tweezers, computational circuits, biosensors and molecular assembly lines. In this dissertation we study multiple problems in the theory, simulations and experiments of DNA self-assembly. We extend the Turing-universal mathematical framework of self-assembly known as the Tile Assembly Model by incorporating randomization during the assembly process. This allows us to reduce the tile complexity of linear assemblies. We develop multiple techniques to build linear assemblies of expected length N using far fewer tile types than previously possible. We abstract the fundamental properties of DNA and develop a biochemical system, which we call meta-DNA, based entirely on strands of DNA as the only component molecule. We further develop various enzyme-free protocols to manipulate meta-DNA systems and provide strand level details along with abstract notations for these mechanisms. We simulate DNA circuits by

  1. For a new dialogue between theoretical and empirical studies in evo-devo

    Directory of Open Access Journals (Sweden)

    Giuseppe eFusco

    2015-08-01

    Full Text Available Despite its potentially broad scope, current evo-devo research is largely dominated by empirical developmental studies, whereas comparably little role is played by theoretical research. I argue that this represents an obstacle to a wider appreciation of evo-devo and its integration within a more comprehensive evolutionary theory, and that this situation is causally linked to a limited exchange between theoretical and experimental studies in evo-devo. I discuss some features of current theoretical work in evo-devo, highlighting some possibly concurring impediments to an effective dialogue with experimental studies. Finally, I advance two suggestions for enhancing fruitful cross-fertilization between theoretical and empirical studies in evo-devo: i to broaden the scope of evo-devo beyond its current conceptualization, teaming up with other variational approaches to the study of evolution, and ii to develop more effective forms of scientific interaction and communication.

  2. Thermogravimetric analysis and kinetic study of formation of lithium titanate by solid state route

    International Nuclear Information System (INIS)

    Sonak, Sagar; Jain, Uttam; Sahu, Ashok Kumar; Kumar, Sanjay; Krishnamurthy, Nagaiyar

    2015-01-01

    The kinetics of formation of lithium titanate from the solid state reaction of lithium carbonate and titanium oxide was studied using non-isothermal thermogravimetric technique. Thermogravimetric data for the reaction of lithium carbonate and titanium oxide was obtained at various heating rates. The methods such as Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose were used to estimate the kinetic parameters from the obtained thermogravimetric data. The average activation energy for the formation of lithium titanate by solid state route was found to be 243 kJ/mol K. The reaction mechanism was determined by the method given by Malek. It was found that the three dimensional diffusion model best describes the reaction kinetics. A kinetic equation describing the reaction is proposed and reaction mechanism is discussed

  3. Kinetic Study on the Esterification of Palm Fatty Acid Distillate (PFAD) Using Heterogeneous Catalyst

    Science.gov (United States)

    Rofiqah, U.; Djalal, R. A.; Sutrisno, B.; Hidayat, A.

    2018-05-01

    Esterification with heterogeneous catalysts is believed to have advantages compared to homogeneous catalysts. Palm Fatty Acid Distillate (PFAD) was esterified by ZrO2 -SO4 2-/natural zeolite at temperature variation of 55°C, 60°C, and 65°C to produce biodiesel. Determination of reaction kinetics was done by experiment and modeling. Kinetic study was approached using pseudo-homogeneous model of first order. For experiment, reaction kinetics were 0.0031 s-1, 0.0054 s-1, and 0.00937 s-1 for a temperature of 55 °C, 60 °C and 65 °C, respectively. For modelling, reaction kinetics were 0.0030 s-1, 0.0055 s-1, and 0.0090 s-1 for a temperature of 55°C, 60°C and 65°C, respectively. Rate and conversion of reaction are getting increased by increasing temperature.

  4. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    Science.gov (United States)

    Al-Rubaiey, Najem A.; Walsh, Robin

    2017-03-01

    Silylenes (silanediyls) have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD) of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2) are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas) at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using Lindemann

  5. Time resolved spectroscopic investigation of SiD2 + D2: kinetic study

    Directory of Open Access Journals (Sweden)

    Al-Rubaiey Najem A.

    2017-01-01

    Full Text Available Silylenes (silanediyls have made an important impact on organosilicon chemistry even if it is of more recent foundation than carbenes in organic chemistry and much less complete. These species are highly reactive intermediates. They play a central role in the chemical vapour deposition (CVD of various silicon-containing thin films which have a technological importance in microelectronics as well as in the dry etching processes of silicon wafers. Spectroscopic methods have been developed to observe these species, a necessary pre-requisite to their direct monitoring. In this work, deuterated phenylsilane precursor, PhSiD3 was chosen for SiD2 because its analogue phenylsilane, PhSiH3 proved to be a good precursor for SiH2 and the high quality decay signals observed revealed that SiD2 be readily detected from PhSiD3 and that if other decomposition pathways (e.g. PhSiD + D2 are occurring, they do not effect measurements of the rate constants for SiD2. The absorption spectrum of SiD2 formed from the flash photolysis of a mixture of PhSiD3 and SF6 at 193nm were found in the region 17384-17391 cm-1 with strong band at 17387.07 cm-1. This single rotational line of pQ1 was chosen to monitor SiD2 removal. Time-resolved studies of SiD2 have been carried out to obtain rate constants for its bimolecular reactions with D2. The reactions were studied over the pressure range 5-100 Torr (in SF6 bath gas at four temperatures in the range 298-498K. Single decay from 10 photolysis laser shots were averaged and found to give reasonable first-order kinetics fits. Second order kinetics were obtained by pressure dependence of the pseudo first order decay constants and substance D2 pressures within experimental error. The reaction was found to be weakly pressure dependent at all temperatures, consistent with a third-body mediated association process. In addition, SiH2+ H2 reaction is approximately ca. 60% faster than SiD2+D2 reaction. Theoretical extrapolations (using

  6. Heparin kinetics

    International Nuclear Information System (INIS)

    Swart, C.A.M. de.

    1983-01-01

    The author has studied the kinetics of heparin and heparin fractions after intravenous administration in humans and in this thesis the results of this study are reported. Basic knowledge about the physico-chemical properties of heparin and its interactions with proteins resulting in anticoagulant and lipolytic effects are discussed in a review (chapter II), which also comprises some clinical aspects of heparin therapy. In chapter III the kinetics of the anticoagulant effect are described after intravenous administration of five commercial heparin preparations. A mathematical model is presented that fits best to these kinetics. The kinetics of the anticoagulant and lipolytic effects after intravenous injection of various 35 S-radiolabelled heparin fractions and their relationship with the disappearance of the radiolabel are described in chapter IV. Chapter V gives a description of the kinetics of two radiolabels after injection of in vitro formed complexes consisting of purified, 125 I-radiolabelled antithrombin III and various 35 S-radiolabelled heparin fractions. (Auth.)

  7. Theoretical studies in nuclear reaction and nuclear structure. Final report, January 1, 1975--June 30, 1976

    International Nuclear Information System (INIS)

    Banerjee, M.K.; Griffin, J.J.

    1977-07-01

    Progress in theoretical research is reported under the following readings: (1) few nuclear reactions, Eikonal approximations, and optical models; (2) pion reactions; (3) nuclear structure by reaction studies; (4) nuclear dynamics

  8. Studies of the kinetics of radiation induced spurs

    International Nuclear Information System (INIS)

    Green, N.J.B.

    1982-12-01

    This thesis addresses two major unresolved problems of diffusion-controlled reaction kinetics: diffusion and reaction in a system containing a small number of particles and the geminate recombination of ions. The few particle system is approached from the assumption that all pair distances evolve independently. From this assumption a Master equation is set up with which the discrete nature of the reaction process in removing particles in pairs is described. The independent pairs assumption gives an expression for the time-dependent rate of transition between states of the process. The model is compared with direct Monte Carlo simulations of the diffusion-reaction process for systems where the initial distribution of particles is Gaussian. Several gross effects are accounted for quantitatively. Minor discrepancies are resolved by further comparison with a Monte Carlo formulation of the independent pairs model which accounts for all initial correlations. Several extensions of the model are discussed, in particular the extensions to systems of charged particles and scavenging reactions. In order to make the extension to account for Coulomb forces, the recombination of a geminate charged pair must be analysed. The analysis is made in terms of the mathematical theory of diffusion. (author)

  9. Study on the numerical analysis of nuclear reactor kinetics equations

    International Nuclear Information System (INIS)

    Yang, J.C.

    1980-01-01

    A two-step alternating direction explict method is proposed for the solution of the space-and time-dependent diffusion theory reactor kinetics equations in two space dimensions as a special case of the general class of alternating direction implicit method and the truncation error of this method is estimated. To test the validity of this method it is applied to the Pressurized Water Reactor and CANDU-PHW reactor which have been operating and underconstructing in Korea. The time dependent neutron flux of the PWR reactor during control rod insertion and time dependent neutronic power of CANDU-PHW reactor in the case of postulated loss of coolant accident are obtained from the numerical calculation results. The results of the PWR reactor problem are shown the close agreement between implicit-difference method used in the TWIGL program and this method, and the results of the CANDU-PHW reactor are compared with the results of improved quasistic method and modal method. (Author)

  10. Theoretical Studies on the Physical and Environmental Factors Which Govern the Thermal Fading of Thermoluminescence Signal

    International Nuclear Information System (INIS)

    Rasheedy, M.S.; El-Sherif, M.A.; Hefni, M.A.

    2008-01-01

    Thermoluminescence solid-state detector is widely used to determine the dose in personnel and environmental monitoring for radiation protection purposes, for instance in the field of nuclear power production, medicine and research. However, thermal fading is a limiting factor for a long-term application, especially where temperature is changing significantly during the accumulation period. This paper studied the influence of temperature and duration of storage after irradiation on the thermal fading of the TL signal. Also, this paper discussed the dependence of the thermal fading on the trap parameters of TL glow peak. The most important parameters, which were considered here include the order of kinetics b, the depth of the trap level E (eV) and the frequency factor S (s-1). The dependence of the thermal fading on thermal stability parameters, namely trap depths and frequency factors for the glow peaks is discussed. The variation of the thermal fading as a function of the order of kinetics is demonstrated. In addition, this paper discussed the dependence of the thermal fading on the absorbed dose in case of first-, second- and general-order kinetics. The above-mentioned studies were arranged considering the models of first-, second- and general-order of kinetics

  11. A kinetic study on the development of porosity in porcelain stoneware tile sintering

    Directory of Open Access Journals (Sweden)

    Jazayeri, S. H.

    2007-02-01

    Full Text Available The aim of this work is to develop a mathematical model to study the mechanism of elimination of total porosity as a function of soaking time using the Navier-Stokes. Then, parameters of the model such as kinetic constants and apparent activation energy are calculated on the basis of experimental data for a standard porcelain stoneware tile composition. The theoretical data calculated from the model are in good agreement with the experimental data. Using the model developed, it is possible to estimate the best soaking time to obtain minimum total porosity at a given firing temperature . The effects of nepheline on sintering process of porcelain stoneware tile is investigated. It was found that when the nepheline syenite content of the starting mix was increased to 10%, the constant kp of the kinetic equation also increased. The results showed that addition of nepheline to composition of porcelain stoneware bodies was influenced remarkably suitable soaking time to obtain the minimum total porosity and increased shrinkage and bulk density while total and closed porosity fall down.

    El propósito de este trabajo es desarrollar un modelo matemático tipo Navier-Stokes para estudiar el mecanismo de eliminación de la porosidad en función del tiempo de maduración en cocción. Los parámetros del modelo tales como las constantes cinéticas y la energía de activación aparente se calcularon a partir de datos experimentales para una composición de gres porcelánico estándar. Los datos teóricos obtenidos a partir del modelo están en buena concordancia con los datos experimentales. Se investigaron los efectos de la nefelina en el gres porcelánico, encontrado que cuando se aumenta el contenido hasta un 10%, la constante de la ecuación cinética kp aumenta. Empleando el modelo desarrollado, es posible estimar el tiempo de maduración en cocción para obtener la porosidad mínima (se alcanza la eliminación de la porosidad debido a la presi

  12. Pyrolysis of Waste Castor Seed Cake: A Thermo-Kinetics Study

    Directory of Open Access Journals (Sweden)

    Abdullahi Muhammad Sokoto

    2018-03-01

    Full Text Available Biomass pyrolysis is a thermo-chemical conversion process that is of both industrial and ecological importance. The efficient chemical transformation of waste biomass to numerous products via pyrolysis reactions depends on process kinetic rates; hence the need for kinetic models to best design and operate the pyrolysis. Also, for an efficient design of an environmentally sustainable pyrolysis process of a specific lignocellulosic waste, a proper understanding of its thermo-kinetic behavior is imperative. Thus, pyrolysis kinetics of castor seed de-oiled cake (Ricinus communis using thermogravimetric technique was studied. The decomposition of the cake was carried out in a nitrogen atmosphere with a flow rate of 100mL min-1 from ambient temperature to 900 °C. The results of the thermal profile showed moisture removal and devolatilization stages, and maximum decomposition of the cake occurred at a temperature of 200-400 °C. The kinetic parameters such as apparent activation energy, pre-exponential factor, and order of reaction were determined using Friedman (FD, Kissinger-Akahira-Sunose (KAS, and Flynn-Wall-Ozawa (FWO kinetic models. The average apparent activation energy values of 124.61, 126.95 and 129.80 kJmol-1 were calculated from the slopes of the respective models. The apparent activation energy values obtained depends on conversion, which is an evidence of multi-step kinetic process during the pyrolytic decomposition of the cake. The kinetic data would be of immense benefit to model, design and develop a suitable thermo-chemical system for the conversion of waste de-oil cake to energy carrier.

  13. Experimental and Chemical Kinetic Modeling Study of Dimethylcyclohexane Oxidation and Pyrolysis

    KAUST Repository

    Eldeeb, Mazen A.

    2016-08-30

    A combined experimental and chemical kinetic modeling study of the high-temperature ignition and pyrolysis of 1,3-dimethylcyclohexane (13DMCH) is presented. Ignition delay times are measured behind reflected shock waves over a temperature range of 1049–1544 K and pressures of 3.0–12 atm. Pyrolysis is investigated at average pressures of 4.0 atm at temperatures of 1238, 1302, and 1406 K. By means of mid-infrared direct laser absorption at 3.39 μm, fuel concentration time histories are measured under ignition and pyrolytic conditions. A detailed chemical kinetic model for 13DMCH combustion is developed. Ignition measurements show that the ignition delay times of 13DMCH are longer than those of its isomer, ethylcyclohexane. The proposed chemical kinetic model predicts reasonably well the effects of equivalence ratio and pressure, with overall good agreement between predicted and measured ignition delay times, except at low dilution levels and high pressures. Simulated fuel concentration profiles agree reasonably well with the measured profiles, and both highlight the influence of pyrolysis on the overall ignition kinetics at high temperatures. Sensitivity and reaction pathway analyses provide further insight into the kinetic processes controlling ignition and pyrolysis. The work contributes toward improved understanding and modeling of the oxidation and pyrolysis kinetics of cycloalkanes.

  14. Equilibrium, kinetic and thermodynamic studies of uranium biosorption by calcium alginate beads

    International Nuclear Information System (INIS)

    Bai, Jing; Fan, Fangli; Wu, Xiaolei; Tian, Wei; Zhao, Liang; Yin, Xiaojie; Fan, Fuyou; Li, Zhan; Tian, Longlong; Wang, Yang; Qin, Zhi; Guo, Junsheng

    2013-01-01

    Calcium alginate beads are potential biosorbent for radionuclides removal as they contain carboxyl groups. However, until now limited information is available concerning the uptake behavior of uranium by this polymer gel, especially when sorption equilibrium, kinetics and thermodynamics are concerned. In present work, batch experiments were carried out to study the equilibrium, kinetics and thermodynamics of uranium sorption by calcium alginate beads. The effects of initial solution pH, sorbent amount, initial uranium concentration and temperature on uranium sorption were also investigated. The determined optimal conditions were: initial solution pH of 3.0, added sorbent amount of 40 mg, and uranium sorption capacity increased with increasing initial uranium concentration and temperature. Equilibrium data obtained under different temperatures were fitted better with Langmuir model than Freundlich model, uranium sorption was dominated by a monolayer way. The kinetic data can be well depicted by the pseudo-second-order kinetic model. The activation energy derived from Arrhenius equation was 30.0 kJ/mol and the sorption process had a chemical nature. Thermodynamic constants such as ΔH 0 , ΔS 0 and ΔG 0 were also evaluated, results of thermodynamic study showed that the sorption process was endothermic and spontaneous. -- Highlights: • Equilibrium, kinetics and thermodynamics of uranium sorption by CaAlg were studied. • Equilibrium studies show that Langmuir isotherm better fit with experimental data. • Pseudo-second-order kinetics model is found to be well depicting the kinetic data. • Thermodynamic study shows that the sorption process is endothermic and spontaneous

  15. Theoretical Study on the Flow of Refilling Stage in a Safety Injection Tank

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jun Sang [Halla Univ. Daejeon (Korea, Republic of)

    2017-10-15

    In this study, a theoretical analysis was performed to the flow of refilling stage in a safety injection tank, which is the core cooling system of nuclear power plant in an emergency. A theoretical model was proposed with a nonlinear governing equation defining on the flow of the refilling process of the coolant. Utilizing the Taylor-series expansion, the 1st - order approximation flow equation was obtained, along with its analytic solution of closed type, which could predict accurately the variations of free surface height and flow rate of the coolant. The availability of theoretical result was confirmed by comparing with previous experimental results.

  16. Kinetics of corneal epithelium turnover in vivo. Studies of lovastatin

    International Nuclear Information System (INIS)

    Cenedella, R.J.; Fleschner, C.R.

    1990-01-01

    The authors developed a direct chemical approach for estimating the rate of turnover of the corneal epithelium in vivo. The method was used to examine the effects of lovastatin, a potent inhibitor of cholesterol biosynthesis, on proliferation and turnover of the epithelium. Corneal DNA was labeled by pulse injection (IP) of the rat with 3H-thymidine, and 3H-labeled DNA was recovered from peripheral and central corneas over the next 15 days. Only the epithelium became labeled, and the loss of label by cell desquamation began 3 days after injection. The loss of 3H-DNA from the cornea (peripheral plus central region) followed first-order kinetics. The half-life of the disappearance was about 3 days. The peripheral cornea became more highly labeled than the central cornea and began to lose 3H-DNA before the central cornea. These observations support the possibility of a higher mitotic rate in the peripheral region and the centripetal movement of a population of peripheral epithelial cells in the normal cornea. The half-lives of the disappearance of 3H-DNA from peripheral and central corneas measured between days 5 and 15 postinjection were identical, both at 3 days. Complete turnover of the corneal epithelium would, therefore, require about 2 weeks (4-5 half-lives). Treatment of the rat with lovastatin had no obvious effects upon the proliferation or turnover of the corneal epithelium. Although lovastatin inhibited corneal 3-hydroxy-3-methylglutaryl coenzyme A reductase, the key regulatory enzyme of cholesterol synthesis, the cornea compensated by induction of this enzyme so that there was no net inhibition of cholesterol synthesis in the cornea

  17. An in-depth analysis of theoretical frameworks for the study of care coordination

    Directory of Open Access Journals (Sweden)

    Sabine Van Houdt

    2013-06-01

    Full Text Available Introduction: Complex chronic conditions often require long-term care from various healthcare professionals. Thus, maintaining quality care requires care coordination. Concepts for the study of care coordination require clarification to develop, study and evaluate coordination strategies. In 2007, the Agency for Healthcare Research and Quality defined care coordination and proposed five theoretical frameworks for exploring care coordination. This study aimed to update current theoretical frameworks and clarify key concepts related to care coordination. Methods: We performed a literature review to update existing theoretical frameworks. An in-depth analysis of these theoretical frameworks was conducted to formulate key concepts related to care coordination.Results: Our literature review found seven previously unidentified theoretical frameworks for studying care coordination. The in-depth analysis identified fourteen key concepts that the theoretical frameworks addressed. These were ‘external factors’, ‘structure’, ‘tasks characteristics’, ‘cultural factors’, ‘knowledge and technology’, ‘need for coordination’, ‘administrative operational processes’, ‘exchange of information’, ‘goals’, ‘roles’, ‘quality of relationship’, ‘patient outcome’, ‘team outcome’, and ‘(interorganizational outcome’.Conclusion: These 14 interrelated key concepts provide a base to develop or choose a framework for studying care coordination. The relational coordination theory and the multi-level framework are interesting as these are the most comprehensive.

  18. Kinetic Monte Carlo Study of Li Intercalation in LiFePO4.

    Science.gov (United States)

    Xiao, Penghao; Henkelman, Graeme

    2018-01-23

    Even as a commercial cathode material, LiFePO 4 remains of tremendous research interest for understanding Li intercalation dynamics. The partially lithiated material spontaneously separates into Li-poor and Li-rich phases at equilibrium. Phase segregation is a surprising property of LiFePO 4 given its high measured rate capability. Previous theoretical studies, aiming to describe Li intercalation in LiFePO 4 , include both atomic-scale density functional theory (DFT) calculations of static Li distributions and entire-particle-scale phase field models, based upon empirical parameters, studying the dynamics of the phase separation. Little effort has been made to bridge the gap between these two scales. In this work, DFT calculations are used to fit a cluster expansion for the basis of kinetic Monte Carlo calculations, which enables long time scale simulations with accurate atomic interactions. This atomistic model shows how the phases evolve in Li x FePO 4 without parameters from experiments. Our simulations reveal that an ordered Li 0.5 FePO4 phase with alternating Li-rich and Li-poor planes along the ac direction forms between the LiFePO 4 and FePO 4 phases, which is consistent with recent X-ray diffraction experiments showing peaks associated with an intermediate-Li phase. The calculations also help to explain a recent puzzling experiment showing that LiFePO 4 particles with high aspect ratios that are narrower along the [100] direction, perpendicular to the [010] Li diffusion channels, actually have better rate capabilities. Our calculations show that lateral surfaces parallel to the Li diffusion channels, as well as other preexisting sites that bind Li weakly, are important for phase nucleation and rapid cycling performance.

  19. Theoretical and experimental studies on electric field and confinement in helical systems

    International Nuclear Information System (INIS)

    Sanuki, H.; Itoh, K.; Todoroki, J.; Ida, K.; Idei, H.; Iguchi, H.; Yamada, H.

    1994-06-01

    The present study consists of two parts. The first part is oriented to a theoretical model of selfconsistent analysis to determine simultaneously the electric field and loss cone boundary in heliotron/torsatron configurations under the influence of nonclassical particle losses. The second part is referred to the analysis on NBI heated and ECH plasmas in Compact Helical System (CHS) device. A comparison is made between theoretical results and experimental observations. (author)

  20. Toward a Theoretical Framework for Studying Climate Change Policies: Insights from the Case Study of Singapore

    Directory of Open Access Journals (Sweden)

    Ai Sian Ng

    2017-07-01

    Full Text Available The world decided in December 2015 to take actions to reduce global warming. To contribute toward this goal, this research examines possible policy levers for inclusion in the climate change ratification plan. A case study of the measures taken by the Republic of Singapore, a low-lying 719.2 km2 island without natural resources in Asia, is conducted. Being vulnerable to climate change impact and yet having to balance her people’s needs and economic progress with limited resources, the measures taken by this small country could offer policy insights for small states and states without access to alternative energy sources. This research analyzes the online policy documents posted by eleven organizations to answer the main research question of identifying policy levers as theoretical constructs to form a framework that can be used to study climate change policies. A qualitative data analysis software, QSR NVivo 10, is used to classify the proposed nodes developed by the researchers using a system perspective integrating the insights from the key international climate change frameworks with the theoretical concepts from the model of pro-environmental behavior. The findings can offer insights toward developing a new contextual influence framework, which can help strengthen policy development and outcome measurement.